JP7840903B2 - non-return valve - Google Patents

Description

This invention relates to a check valve that allows fluid flow in one direction and prohibits fluid flow in the opposite direction.

In the medical field, check valves are sometimes used that allow fluid flow in one direction (forward flow) and prohibit fluid flow in the opposite direction (reverse flow). For example, when administering intravenous fluids such as infusions, a check valve may be installed in the fluid path connecting the container holding the medication (e.g., an IV bag) to the indwelling needle inserted into the patient's vein to prevent backflow of the medication.

Patent Document 1 describes a check valve that can be used for medical purposes. This check valve comprises a housing that combines a first housing with an inlet passage and a second housing with an outlet passage. A valve body is positioned in the hollow portion (cavity) between the inlet and outlet passages within the housing. The valve body is made of a disc-shaped elastic body. In the initial state, when the fluid pressure on the inlet passage side and the fluid pressure on the outlet passage side are balanced relative to the valve body, the outer peripheral region of the valve body is in annular contact with the inner surface of the first housing. When fluid flows from the inlet passage into the hollow portion, the fluid pressure on the inlet passage side increases. The valve body elastically bends and deforms toward the second housing, and the outer peripheral region of the valve body separates from the inner surface of the first housing. As a result, the fluid can flow in the forward direction from the inlet passage to the outlet passage. On the other hand, when fluid flows from the outlet passage into the hollow portion, the fluid pressure on the outlet passage side increases, and the outer peripheral region of the valve body adheres tightly to the inner surface of the first housing around its entire circumference. As a result, fluid flow in the reverse direction from the outflow channel to the inflow channel is prohibited.

Japanese Patent Publication No. 2021-156406 Japanese Patent Publication No. 2016-056902

For a fluid to flow forward through a check valve, the fluid pressure on the inflow side of the valve body (upstream pressure) must rise to a threshold pressure required to bend and deform the valve body. For example, in intravenous fluid administration in a NICU (Neonatal Intensive Care Unit), because patients are small, medications are administered at a low flow rate using syringe pumps. If a check valve is installed downstream of the syringe pump, it takes time for the upstream pressure to exceed the threshold after the syringe pump starts operating. Therefore, there is a long time lag between the start of the syringe pump operation and the actual inflow of the medication through the check valve to the patient. Furthermore, when the upstream pressure gradually rises and exceeds the threshold, the valve body bends and deforms, and the medication flows through the check valve all at once. As a result, the medication is administered in a bolus, making it difficult to administer the medication at a constant low flow rate even when using a syringe pump. Such time lags in drug administration and bolus administrations should be avoided, as they can affect the patient's hemodynamics depending on the drug being administered.

Generally, the time lag and bolus administration described above are affected by the valve opening characteristics (ease of opening of the valve body) of the check valve. If the valve body bends and deforms at relatively low upstream pressures, problems with time lag and bolus administration are less likely to occur.

However, improving the opening ability of a check valve reduces its check valve performance, which is the ability to prevent fluid flow in the reverse direction. There is a trade-off between opening ability and check valve performance, and with conventional check valves, it has been difficult to improve opening ability while maintaining check valve performance.

The object of this invention is to provide a check valve with improved opening performance while maintaining check valve performance to a level that is not problematic for practical use.

The check valve of the present invention comprises a housing having a cavity communicating with a first passage and a second passage, and a valve body disposed within the cavity. The housing is configured by joining a first housing, which is provided with the first passage, and a second housing, which is provided with the second passage, such that the cavity is formed between the first housing and the second housing. The valve body comprises a projection that fits into a fixed portion provided at the opening end of the second passage of the second housing, and an elastic membrane that extends radially outward from the projection and is capable of elastic bending deformation. The check valve changes between an open state in which a gap is formed between the first surface of the elastic membrane and the first housing so as to allow fluid flow from the first passage to the second passage, and a closed state in which the first surface of the elastic membrane contacts the first housing in an annular manner so as to prohibit fluid flow from the second passage to the first passage. In the initial state where the fluid pressure on the first flow path side and the fluid pressure on the second flow path side are balanced relative to the valve body, the outer peripheral region of the first surface of the elastic membrane contacts the first housing in an annular manner. In this initial state, the distance from the central axis of the check valve, defined by the fixing portion, to the inner end of the outer peripheral region changes in the circumferential direction.

When the check valve of the present invention is in its initial state, the outer peripheral region of the first surface of the elastic membrane of the valve body contacts the first housing in an annular manner. The distance from the central axis of the check valve to the inner end of the outer peripheral region changes in the circumferential direction. Therefore, the elastic membrane can undergo localized elastic bending deformation at relatively low upstream pressures. Accordingly, the present invention provides a check valve with improved opening performance while maintaining check valve performance to a level that is not problematic for practical use.

Figure 1 is a cross-sectional view of a check valve according to Embodiment 1 of the present invention in its initial state. Figure 2A is an exploded perspective view of the check valve according to Embodiment 1 of the present invention, as seen from the first housing side. Figure 2B is an exploded perspective view of the check valve according to Embodiment 1 of the present invention, as seen from the second housing side. Figure 3A is a bottom view of the first housing used in the check valve according to Embodiment 1 of the present invention. Figure 3B is a top view of the valve body used in the check valve according to Embodiment 1 of the present invention. Figure 4 is a cross-sectional view of a comparative example check valve in its initial state. Figure 5A is a bottom view of the first housing used in the comparative example check valve. Figure 5B is a top view of the valve body used in the comparative example check valve. Figure 6 is a cross-sectional view of a comparative example check valve in the open state. Figure 7 is a cross-sectional view of a check valve according to Embodiment 1 of the present invention in the open state. Figure 8 is a cross-sectional view of a check valve according to Embodiment 1 of the present invention, in which liquid flows in the reverse direction. Figure 9 is a cross-sectional view of a check valve according to Embodiment 2 of the present invention in its initial state. Figure 10A is a bottom view of the first housing used in the check valve according to Embodiment 2 of the present invention. Figure 10B is a top view of the valve body used in the check valve according to Embodiment 2 of the present invention. Figure 11 is a cross-sectional view of a check valve according to Embodiment 3 of the present invention in its initial state. Figure 12 is a perspective view from below of the first housing used in the check valve according to Embodiment 3 of the present invention. Figure 13A is a bottom view of the first housing used in the check valve according to Embodiment 3 of the present invention. Figure 13B is a top view of the valve body used in the check valve according to Embodiment 3 of the present invention. Figure 14 is a cross-sectional view of a check valve according to Embodiment 4 of the present invention in its initial state. Figure 15 is a perspective view from below of the first housing used in the check valve according to Embodiment 4 of the present invention. Figure 16A is a bottom view of the first housing used in the check valve according to Embodiment 4 of the present invention. Figure 16B is a top view of the valve body used in the check valve according to Embodiment 4 of the present invention.

(1) The check valve of the present invention comprises a housing having a cavity communicating with a first passage and a second passage, and a valve body disposed within the cavity. The housing is configured by joining a first housing having the first passage and a second housing having the second passage, such that the cavity is formed between the first housing and the second housing. The valve body comprises a projection that fits into a fixed portion provided at the opening end of the second passage of the second housing, and an elastic membrane that extends radially outward from the projection and is capable of elastic bending deformation. The check valve changes between an open state in which a gap is formed between the first surface of the elastic membrane and the first housing so as to allow fluid flow from the first passage to the second passage, and a closed state in which the first surface of the elastic membrane contacts the first housing in an annular manner so as to prohibit fluid flow from the second passage to the first passage. In the initial state where the fluid pressure on the first flow path side and the fluid pressure on the second flow path side are balanced relative to the valve body, the outer peripheral region of the first surface of the elastic membrane contacts the first housing in an annular manner. In this initial state, the distance from the central axis of the check valve, defined by the fixing portion, to the inner end of the outer peripheral region changes in the circumferential direction.

In this invention, "the distance from the central axis to the inner edge of the outer peripheral region changes in the circumferential direction" means that the distance from the central axis to the inner edge of the outer peripheral region is not constant in the circumferential direction; that is, when viewed along the central axis, the inner edge of the outer peripheral region is not a circular shape concentric with the central axis.

(2) In the check valve described in item (1) above, when viewed along the central axis, the shape of the inner end of the outer peripheral region may include a part of an ellipse. This embodiment is advantageous for simplifying the configuration of a check valve in which the distance from the central axis to the inner end of the outer peripheral region changes in the circumferential direction.

(3) In the check valve described in item (1) or item (2) above, when viewed along the central axis, the inner end of the outer peripheral region may have a shape combining a semicircle and a semiellipse. Such an embodiment is advantageous for improving the opening performance of the check valve with a simple configuration.

(4) In the check valve described in item (1) or item (2) above, the inner circumferential end of the outer peripheral region may be elliptical when viewed along the central axis. This configuration is advantageous for simplifying the structure of a check valve in which the distance from the central axis to the inner circumferential end of the outer peripheral region changes in the circumferential direction.

(5) In the check valve described in item (1) above, the shape of the inner end of the outer peripheral region may be a substantially regular polygon when viewed along the central axis. This configuration is advantageous for achieving a good balance between the opening and check valve performance of the check valve. In this invention, "substantially regular polygon" includes both exact regular polygons and deformed polygons in which substantially circular arcs (including parts of circular arcs and ellipses) are provided at the vertices of the regular polygon.

(6) In the check valve according to any one of the above items (1) to (5), when viewed along the central axis, the shape of the inner end of the outer peripheral region may include a substantially circular arc and a convex portion connected to the substantially circular arc, which protrudes radially outward or radially inward from the substantially circular arc. Such an embodiment is advantageous for further improving the opening performance of the check valve without requiring significant design changes.

The present invention will be described in detail below, with reference to preferred embodiments. However, it goes without saying that the present invention is not limited to the following embodiments. For the sake of clarity, the drawings referenced in the following description show simplified representations of the main components constituting the embodiments of the present invention. Therefore, the present invention may include any components not shown in the following drawings. Furthermore, within the scope of the present invention, components shown in the following drawings may be modified or omitted. In the drawings referenced in the description of each embodiment, components corresponding to those shown in the drawings referenced in a prior embodiment are denoted by the same reference numerals as those used in the drawings of the prior embodiment. For such components, redundant explanations are omitted, and the descriptions of the prior embodiments should be considered as appropriate.

(Embodiment 1)
Figure 1 is a cross-sectional view of a check valve 1 according to Embodiment 1 of the present invention, in a plane including the central axis 1a. The check valve 1 comprises a housing 30 having a cavity 31 formed inside, and a valve body 50 disposed within the cavity 31. The housing 30 is constructed by joining a first housing 10, which is provided with a first passage 11, and a second housing 20, which is provided with a second passage 21, such that a cavity 31 is formed between the first housing 10 and the second housing 20. The cavity 31 communicates with the outside world of the check valve 1 only through the first passage 11 and the second passage 21. In this example, the first passage 11, the second passage 21, and the valve body 50 are arranged coaxially, and the axis common to them is the central axis 1a of the check valve 1.

In this invention, the direction along a straight line perpendicular to the central axis 1a is referred to as the "radial direction." Within the radial direction, the side closer to the central axis 1a is referred to as the "inner" side, and the side further from the central axis 1a is referred to as the "outer" side. The direction of rotation around the central axis 1a is referred to as the "circumferential direction." The direction parallel to the central axis 1a is referred to as the "vertical direction." Within the vertical direction, the side of the first flow path 11 is referred to as the "upper" side, and the side of the second flow path 21 is referred to as the "lower" side. The direction parallel to a plane perpendicular to the central axis 1a is referred to as the "horizontal direction." However, the terms "vertical direction" and "horizontal direction" are for convenience in explaining this invention and do not represent the actual orientation of the check valve 1 during use.

As will be explained in detail later, the check valve 1 is configured to allow the fluid to flow in the order of the first passage 11, cavity 31, and second passage 21, and conversely, to prohibit the fluid from flowing in the order of the second passage 21, cavity 31, and first passage 11. In this invention, the direction of fluid flow from the first passage 11 to the second passage 21 is called the "forward direction," and the direction of fluid flow from the second passage 21 to the first passage 11 is called the "reverse direction." Furthermore, regardless of the direction of fluid flow, the side of the valve body 50 facing the first passage 11 is sometimes referred to as the "upstream side," and the side facing the second passage 21 as the "downstream side."

Figure 2A is an exploded perspective view of the check valve 1, seen from the first housing 10 side. Figure 2B is an exploded perspective view of the check valve 1, seen from the second housing 20 side.

As shown in Figures 1 and 2B, the inner surface 15 defining the cavity 31 of the first housing 10 includes a first inner surface 13 extending from the opening of the first flow path 11 on the cavity 31 side, and a second inner surface 14 adjacent to the first inner surface 13 on its outer surface. The first inner surface 13 is a concave curved surface inclined radially outward to approach the second housing 20. In this embodiment 1, the second inner surface 14 is a flat surface parallel to the radial direction and is continuous in an annular manner in the circumferential direction, surrounding the first inner surface 13. A joint portion (first joint portion) 18 is formed on the outer surface of the second inner surface 14, which is joined to the second housing 20. The joint portion 18 may, but is not limited, include an annular convex (projection) or concave (groove) continuous in the circumferential direction.

As shown in Figures 1 and 2A, the opening end of the second housing 20 on the cavity 31 side of the second flow path 21 constitutes a fixed portion 23 that holds the valve body 50. When viewed along the central axis 1a, the fixed portion 23 is along a circle concentric with the central axis 1a. The inner surface defining the cavity 31 of the second housing 20 includes a convex curved surface 25 that slopes radially outward from the fixed portion 23, away from the first housing 10. The convex curved surface 25 is not limited, but may be, for example, a frustoconical surface (the side surface of a frustocone). A plurality of grooves 24 are formed in the convex curved surface 25 along the radial direction. The plurality of grooves 24 are arranged at equal angular intervals with respect to the central axis 1a. The grooves 24 communicate with the second flow path 21 and extend to the outer peripheral end of the convex curved surface 25, dividing the fixed portion 23 and the convex curved surface 25 in the circumferential direction. The grooves 24 can serve as fluid passages for fluid flowing forward through the check valve 1 (i.e., from the first passage 11 to the second passage 21). While there are three grooves 24 in this embodiment 1, the present invention is not limited to this, and there may be more or fewer grooves. A joint portion (second joint portion) 28, which is joined to the first housing 10, is formed on the outside of the convex curved surface 25. The joint portion 28 is not limited, but may include annular grooves or projections that are continuous in the circumferential direction.

The first housing 10 and the second housing 20 preferably have mechanical strength (rigidity) such that they are not substantially deformed by external forces. Specifically, the materials for the first and second housings 10 and 20 are preferably resins such as polypropylene, acrylonitrile-butadiene-styrene copolymer, polycarbonate, polyacetal, polystyrene, polyamide, polyethylene, and rigid polyvinyl chloride, with polypropylene being particularly preferred. Each of the first and second housings 10 and 20 can be manufactured integrally as a single part using the above-mentioned resin by injection molding or the like. The first housing 10 and the second housing 20 may be made of the same material, or they may be made of different materials.

The joint 18 of the first housing 10 and the joint 28 of the second housing 20 are joined such that a liquid-tight seal is formed between them. For example, a protrusion on the joint 18 is fitted into a recess on the joint 28, and/or a protrusion on the joint 28 is fitted into a recess on the joint 18. There are no limitations on the method of joining the joint 18 and the joint 28; known methods can be used, taking into account the materials of the first and second housings 10 and 20. For example, welding (e.g., laser welding, ultrasonic welding), adhesive bonding (e.g., solvent bonding), or simple fitting (e.g., tapered fitting) can be used.

A valve body 50 is positioned within the cavity 31. The valve body 50 has a generally thin, disc-like shape, with a substantially circular shape in plan view (viewed along the central axis 1a). A first projection 51 and a second projection 52 are provided at the center of the valve body 50, projecting in the thickness direction (vertical direction, i.e., along the central axis 1a). The first projection 51 projects toward the second housing 20 (see Figure 2B). The second projection 52 projects toward the first housing 10 (see Figure 2A). The shapes of the first and second projections 51 and 52 are not limited, but may be substantially conical or frustoconical in shape, with the diameter decreasing towards the tip.

An elastic membrane 60 extends radially outward from projections 51 and 52 (more precisely, from the bases of projections 51 and 52). The elastic membrane 60 is continuous in the circumferential direction. The elastic membrane 60 has a first surface 60a (see Figure 2A) facing the first housing 10 and a second surface 60b (see Figure 2B) facing the second housing 20. Both the first surface 60a and the second surface 60b are flat surfaces aligned horizontally. The thickness of the elastic membrane 60 (dimension in the direction of the central axis 1a) is constant.

The valve body 50 is made of an elastic (or flexible or soft) material (so-called elastomer) that can be deformed relatively easily by external force and immediately return to its pre-deformation state (initial state) when the external force is removed. Specifically, the material of the valve body 50 is preferably rubber such as silicone rubber, isoprene rubber, or butyl rubber; thermoplastic elastomers such as styrene-based elastomers, olefin-based elastomers, or polyurethane-based elastomers; or soft polyvinyl chloride, with silicone rubber being particularly preferred. The valve body 50 can be manufactured integrally as a single component using the above materials.

As shown in Figure 1, the valve body 50 is mounted on the second housing 20 with its first projection 51 fitted into the fixed portion 23, which is the opening end of the second flow path 21. The valve body 50 is aligned vertically and horizontally with respect to the second housing 20 by the fit of the side surface (e.g., conical surface) of the first projection 51 into the fixed portion 23. The first housing 10 is joined to the second housing 20 on which the valve body 50 is mounted. The first surface 60a of the elastic membrane 60 contacts the second inner surface 14 of the first housing 10 in the vertical direction. The fixed portion 23 and the second inner surface 14 work together to correct the tilt of the valve body 50.

The valve body 50 divides the cavity 31 into two parts, upper and lower: a first cavity 31a on the first housing 10 (or first flow path 11) side and a second cavity 31b on the second housing 20 (or second flow path 21) side. The state in which the fluid pressure in the first cavity 31a (upstream pressure) and the fluid pressure in the second cavity 31b (downstream pressure) are balanced (equilibrium) is called the "initial state." Figure 1 shows the check valve 1 in the initial state. In the initial state, the elastic membrane 60 contacts the inner surface 15 (particularly the second inner surface 14) of the first housing 10, but does not substantially bend or deform, and extends along the horizontal direction (parallel to the plane perpendicular to the central axis 1a).

Figure 3A is a bottom view of the first housing 10 as seen from the valve body 50 side. The X and Y axes, shown by the dashed lines, both extend along a plane perpendicular to the central axis 1a and are perpendicular to each other at the central axis 1a. From the central axis 1a outward in the radial direction, the first flow path 11, the first inner surface 13, the second inner surface 14, and the joint 18 are arranged in this order. The shape of the inner circumferential end (or the opening end of the first flow path 11) 13a of the first inner surface 13 is a circle concentric with the central axis 1a. On the other hand, the shape of the inner circumferential end (i.e., the boundary between the first inner surface 13 and the second inner surface 14) 14a of the second inner surface 14 is non-circular. More specifically, the inner circumferential end 14a of the second inner surface 14 follows a circle concentric with the central axis 1a to the left of the Y axis, and follows an ellipse with the X axis as its major axis to the right of the Y axis. The radius of the circle and the minor axis of the ellipse are the same. The distance from the central axis 1a to the inner circumference end 14a is constant on the left side of the Y-axis, but changes circumferentially on the right side of the Y-axis, maximizing along the X-axis. The first inner surface 13 is a concave curved surface that smoothly connects the circular inner circumference end 13a of the first inner surface 13 to the non-circular inner circumference end 14a of the second inner surface 14.

Figure 3B is a top view of the valve body 50 as seen from the first housing 10 side. The X and Y axes in Figure 3B correspond to the X and Y axes in Figure 3A, respectively. As described above, in the initial state, the second inner surface 14 of the first housing 10 contacts the first surface 60a of the elastic membrane 60 in the vertical direction (see Figure 1). The area of the first surface 60a of the elastic membrane 60 marked with numerous dots is the outer peripheral region 61 that contacts the second inner surface 14 of the first housing 10 in the initial state. The outer peripheral region 61 is continuous in an annular shape along the outer circumference of the first surface 60a of the elastic membrane 60. The inner circumferential end 61a of the outer peripheral region 61, shown by the dashed line, corresponds to the inner circumferential end 14a of the second inner surface 14 of the first housing 10 (see Figure 3A). When viewed along the central axis 1a, the inner circumferential end 61a of the outer peripheral region 61 is non-circular. More specifically, the inner circumferential end 61a of the outer circumferential region 61 follows a circle concentric with the central axis 1a on the left side of the Y-axis, and follows an ellipse with the X-axis as its major axis on the right side of the Y-axis. The radius of this circle and the minor axis of this ellipse are the same. The distance from the central axis 1a to the inner circumferential end 61a is constant on the left side of the Y-axis, but varies circumferentially on the right side of the Y-axis, maximizing along the X-axis. When viewed along the central axis 1a, the outer circumferential end 60c of the elastic membrane 60 is a circle concentric with the central axis 1a. Therefore, the radial width of the outer circumferential region 61 is constant on the left side of the Y-axis, but varies circumferentially on the right side of the Y-axis, maximizing along the X-axis.

When fluid flows forward through the first passage 11 into the check valve 1 in its initial state (see Figure 1), the fluid pressure (upstream pressure) in the first cavity 31a increases. The fluid in the first cavity 31a presses the valve body 50 toward the second housing 20. The center of the valve body 50 (first projection 51) is supported by the fixed portion 23 of the second housing 20. Therefore, the fluid in the first cavity 31a elastically bends and deforms the elastic membrane 60 so that, in a radial cross-section as shown in Figure 1, the outer peripheral end of the elastic membrane 60 is displaced toward the second housing 20.

In the initial state, the fluid pressure (upstream pressure) within the first cavity 31a acts on the region inside the inner circumferential end 61a of the outer peripheral region 61 of the valve body 50 (this is referred to as the "pressurized region"). In this embodiment 1, the distance from the central axis 1a to the inner circumferential end 61a of the outer peripheral region 61 (this is referred to as the "pressurized region radius") changes in the circumferential direction. Therefore, the bending load that attempts to bend the elastic membrane 60 toward the second housing 20 in the initial state is relatively larger on the side with a larger pressurized region radius.

To facilitate understanding the operation of the check valve 1 of this embodiment 1, consider the comparative example check valve 900 shown in Figure 4. The check valve 900 is the same as the check valve 1 of embodiment 1, except for the first housing 910. Figure 5A is a bottom view of the first housing 910 constituting the check valve 900, as seen from the valve body 50 side. Similar to the first housing 10 of embodiment 1, the first flow path 11, the first inner surface 913, the second inner surface 914, and the joint 18 are arranged in this order radially outward from the central axis 1a. The shape of the inner circumferential end (or the opening end of the first flow path 11) 13a of the first inner surface 913 is a circle concentric with the central axis 1a. The shape of the inner circumferential end (i.e., the boundary between the first inner surface 913 and the second inner surface 914) 914a of the second inner surface 914 is also a circle concentric with the central axis 1a. The first inner surface 913 is a conical surface (concave surface) that smoothly connects the inner circumferential end 13a of the circular first inner surface 913 and the inner circumferential end 914a of the circular second inner surface 914. Figure 5B is a top view of the valve body 50 used in the check valve 900. The valve body 50 of the comparative example is the same as the valve body 50 of Embodiment 1. When the check valve 900 is in its initial state, the second inner surface 914 of the first housing 910 contacts the outer peripheral region 961 of the first surface 60a of the elastic membrane 60. The inner circumferential end 961a of the outer peripheral region 961, shown by the dashed line, corresponds to the inner circumferential end 914a of the second inner surface 914 of the first housing 910 (see Figure 5A). When viewed along the central axis 1a, the shape of the inner circumferential end 961a of the outer peripheral region 961 is a circle concentric with the central axis 1a. Except as stated above, the check valve 900 is the same as the check valve 1 in Embodiment 1. In Figures 4, 5A, and 5B, the components (or elements) corresponding to those shown in Figures 1, 3A, and 3B are denoted by the same reference numerals as in Figures 1, 3A, and 3B.

The check valve 900 shown in Figure 4 is in an initial state where the fluid pressure in the first cavity 31a (upstream pressure) and the fluid pressure in the second cavity 31b (downstream pressure) are balanced. When fluid flows into the check valve 900 in the forward direction through the first flow path 11 in the initial state, the fluid pressure in the first cavity 31a (upstream pressure) increases. The upstream pressure acts on the region inside the inner circumferential end 961a of the outer peripheral region 961 of the valve body 50 (pressurized region). The distance from the central axis 1a to the inner circumferential end 961a of the outer peripheral region 961 (radius of the pressurized region) is constant in the circumferential direction. The entire elastic membrane 60 is made of the same material. Therefore, when the upstream pressure exceeds a certain threshold, as shown in Figure 6, the outer peripheral region 961 of the elastic membrane 60 separates almost simultaneously from the second inner surface 914 of the first housing 910 over its entire circumference. The bending deformation of the elastic membrane 60 is constant in the circumferential direction. The vertical dimension of the gap 935 formed between the outer peripheral region 961 of the elastic membrane 60 and the second inner surface 914 of the first housing 910 is constant in the circumferential direction. Thus, the check valve 900 is in the "open state". The fluid flows from the first cavity 31a through the gap 935 to the second cavity 31b, and then flows through the second flow path 21. In this way, the fluid can flow through the check valve 900 from the first flow path 11 to the second flow path 21. In Figure 6, arrows 41 and 42 indicate the direction of fluid flow in the forward direction through the first flow path 11 and the second flow path 21, respectively.

The upstream pressure (threshold) required to separate the outer peripheral region 961 from the second inner surface 914 of the first housing 910 depends on the bending stiffness of the elastic membrane 60 and the distance from the central axis 1a to the inner circumferential end 961a of the outer peripheral region 961 (radius of the pressurized region). Here, the "bending stiffness" of the elastic membrane 60 refers to the resistance of the elastic membrane 60 to bending deformation within a cross-section along the thickness direction of the elastic membrane 60 (for example, the cross-section in Figure 4), and is affected by the material and thickness of the elastic membrane 60. If the bending stiffness of the elastic membrane 60 is constant, the threshold increases as the radius of the pressurized region decreases, and the outer peripheral region 961 of the elastic membrane 60 will not separate from the second inner surface 914 of the first housing 910 until the upstream pressure increases. Such a check valve 900 has poor opening properties. When fluid flows into the check valve 900 with poor opening properties at a low velocity in the forward direction through the first flow path 11, the following problems occur, similar to those of the conventional check valve described above. Firstly, the time lag between the initial state of the check valve 900, when the fluid begins to flow in the forward direction through the first channel 11, and when the fluid flows out of the check valve 900 through the second channel 21, becomes longer. Secondly, when the elastic membrane 60 separates from the second inner surface 914 of the first housing 910, the high-pressure fluid in the first cavity 31a flows all at once. Therefore, if the check valve 900 is installed in the fluid infusion channel, the fluid will be administered in a bolus.

In the comparative example check valve 900, increasing the radius of the pressurized area makes it possible to separate the elastic membrane 60 from the second inner surface 914 of the first housing 910 at a relatively low upstream pressure. This improves the opening performance of the check valve 900 and can eliminate problems of time lag and bolus administration. However, if fluid flows into the check valve 900 in the reverse direction through the second passage 21, the pressure of the fluid in the second cavity 31b (downstream pressure) may cause the elastic membrane 60 to deform abnormally, potentially allowing the fluid to flow from the second cavity 31b to the first cavity 31a. This leads to a decrease in the check valve performance of the check valve 900, as it prohibits the flow of fluid from the second passage 21 to the first passage 11.

Therefore, it is difficult to improve the opening performance of the comparative example check valve 900 while maintaining its check valve performance.

The operation of the check valve 1 of this embodiment 1 will now be explained.

In this embodiment 1, as described above, the distance from the central axis 1a to the inner circumferential end 61a of the outer peripheral region 61 (the radius of the pressurized region) changes in the circumferential direction. Figure 1 shows the check valve 1 in its initial state. The cross-section of Figure 1 includes the central axis 1a and the X-axis (see Figures 3A and 3B). Therefore, in Figure 1, the radius of the pressurized region is larger to the right of the central axis 1a than to the left of the central axis 1a.

When fluid flows into the first flow path 11 of the check valve 1 in the forward direction 41 at a low flow velocity (see Figure 7), the fluid pressure (upstream pressure) in the first cavity 31a gradually increases. The fluid in the first cavity 31a presses the valve body 50 toward the second housing 20. The cross-section in Figure 7, like in Figure 1, includes the central axis 1a and the X-axis (see Figures 3A and 3B). The radius of the pressurized area is relatively large to the right of the central axis 1a in Figure 7, and is maximum on the X-axis. Therefore, shortly after the upstream pressure begins to rise, the elastic membrane 60 is locally bent and deformed so that the outer peripheral region 61 separates from the second inner surface 14 of the first housing 10 near the point on the inner peripheral end 61a where the radius of the pressurized area is maximum. A gap 35 is formed between the elastic membrane 60 and the first housing 10. The check valve 1 becomes "open". On the side where the radius of the pressurized area is relatively small (to the left of the central axis 1a in Figure 7), the outer peripheral region 61 is still in contact with the second inner surface 14. The fluid flows from the first cavity 31a through the gap 35 into the second cavity 31b, and then flows further through the second flow path 21 in the direction of arrow 42. In this way, the fluid can flow through the check valve 1 from the first flow path 11 to the second flow path 21.

In this embodiment 1, the outer peripheral region 61 near the portion on the inner peripheral end 61a with a large pressurized area radius separates from the second inner surface 14 at a relatively lower upstream pressure than the other outer peripheral regions 61. The upstream pressure required to change the check valve 1 from the initial state (see Figure 1) to the open state (see Figure 7) is lower than the upstream pressure required to change the check valve 900 of the comparative example to the open state (see Figure 6). The check valve 1 has improved opening performance compared to the check valve 900 of the comparative example. Even if the flow velocity of the fluid flowing forward into the check valve 1 is small, the check valve 1 changes to the open state as soon as the upstream pressure begins to rise. For this reason, the time lag from when the fluid begins to flow forward into the check valve 1 through the first passage 11 to when the fluid flows out of the check valve 1 through the second passage 21 is short. Since the check valve 1 changes from the initial state to the open state at a relatively low upstream pressure, the upstream pressure does not rise abnormally. Therefore, if check valve 1 is installed in the fluid infusion path, the fluid will not be administered as a bolus.

In this embodiment 1, when fluid flows into the first flow path 11 of the check valve 1 in the forward direction at a high flow velocity, the fluid pressure (upstream pressure) in the first cavity 31a increases. Therefore, in addition to the outer peripheral region 61 near the portion on the inner circumferential end 61a with a large pressurized area radius, other outer peripheral regions 61 also separate from the second inner surface 14. For example, as the upstream pressure increases, the outer peripheral region 61 near the portion on the inner circumferential end 61a with a large pressurized area radius separates from the second inner surface 14 first, forming a small gap 35 (see Figure 7). Subsequently, starting from this small gap 35, the remaining portions of the outer peripheral region 61 sequentially separate from the second inner surface 14. Thus, the portion with a relatively large pressurized area radius provides a starting point for the outer peripheral region 61 to separate from the second inner surface 14. This is advantageous for improving the opening performance of the check valve 1. Although not shown in the diagram, as the upstream pressure increases, the outer peripheral region 61 separates from the second inner surface 14 of the first housing 10 along its entire circumference, and the gap between the outer peripheral region 61 and the second inner surface 14 of the first housing 10 expands. The elastic membrane 60 may bend and deform significantly to the point where its second surface 60b contacts the convex curved surface 25 of the second housing 20. The fluid can then flow through the check valve 1 from the first channel 11 to the second channel 21 at a larger flow rate.

Figure 8 shows the initial state of the check valve 1, where for some reason, fluid has flowed into the second passage 21 in the reverse direction 45. The inflow of fluid in the reverse direction 45 increases the fluid pressure (downstream pressure) in the second cavity 31b. The fluid in the second cavity 31b presses the valve body 50 toward the first housing 10. The first surface 60a of the elastic membrane 60 comes into close contact with the inner surface 15 of the first housing 10. In Figure 8, the outer peripheral region 61 of the first surface 60a is in contact with the second inner surface 14 of the first housing 10, but this is just one example. If the fluid pressure in the second cavity 31b increases, the first projection 51 may move upward away from the fixing part 23, and the valve body 50 may deform into a dome shape so that it protrudes toward the first cavity 31a. In this case, the first surface 60a may come into contact with the first inner surface 13 of the first housing 10. In any case, the first surface 60a of the elastic membrane 60 contacts the inner surface 15 of the first housing 10 in an annular manner, forming an annular, liquid-tight seal between them. The check valve 1 enters a "closed state" where the valve body 50 blocks communication between the second flow path 21 and the first flow path 11. The fluid in the second cavity 31b cannot flow through the elastic membrane 60 and the first housing 10 to the first cavity 31a. In this way, the fluid is prevented from flowing from the second flow path 21 to the first flow path 11 through the check valve 1.

Generally, as the radius of the pressurized area increases, the check valve's check-stopping performance decreases. In this embodiment 1, when fluid flows into the check valve 1 in the reverse direction 45 through the second flow path 21, the pressure of the fluid in the second cavity 31b (downstream pressure) may cause abnormal deformation of the portion of the elastic membrane 60 that has a relatively large pressurized area radius. However, by optimizing the circumferential change in the pressurized area radius (as shown in Figure 3B, when the inner circumferential end 61a of the outer circumferential region 61 is composed of a semicircle and a semiellipse, the radius of the semicircle and the semi-major axis of the semiellipse), it is possible to suppress abnormal deformation of the elastic membrane 60 due to downstream pressure, thereby ensuring the check-stopping performance of the check valve 1, which prohibits the flow of fluid in the reverse direction.

Therefore, the check valve 1 of this embodiment 1 has improved opening performance while maintaining check valve performance to a level that is not problematic in practical use.

The following explains how to use check valve 1, using its use in intravenous fluid administration such as drip infusion as an example.

The check valve 1 may constitute an infusion set used when administering intravenous fluids. There are no restrictions on the configuration of the infusion set. Although not shown in the illustration, one example of an infusion set includes a flexible first tube connected to a first tube 12 (see Figure 1) that constitutes a first flow path 11, and a flexible second tube connected to a second tube 22 (see Figure 1) that constitutes a second flow path 21. The first tube is provided with a clamp for opening and closing the flow path within the first tube. An indwelling needle, to be inserted into the patient, is provided at the downstream end of the second tube.

With the clamp on the first tube closed, the upstream end of the first tube is connected to a container (e.g., an infusion bag) containing a liquid (e.g., a drug solution). Next, the clamp is opened to prime the infusion set (i.e., the first tube, check valve 1, the second tube, and the indwelling needle) by introducing the liquid from the container. Afterward, the clamp is closed to stop the flow of liquid into check valve 1. The pressure of the liquid in the first cavity 31a (upstream pressure) and the pressure of the liquid in the second cavity 31b (downstream pressure) are balanced, and check valve 1 is in its initial state (see Figure 1). In this initial state, as described above, the outer peripheral region 61 of the valve body 50 (see Figure 3B) is in annular contact with the second inner surface 14 of the first housing 10. Communication between the first flow path 11 and the second flow path 21 is blocked by the valve body 50.

Next, the indwelling needle is inserted into the patient. Then, the clamp on the first tube is opened, and infusion is started. As shown in Figure 7, the liquid flows into the first cavity 31a through the first channel 11 in the direction of arrow 41 (forward direction). The pressure inside the first cavity 31a (upstream pressure) increases. The liquid inside the first cavity 31a presses against the valve body 50. The outer peripheral region 61 of the elastic membrane 60 separates from the second inner surface 14 of the first housing 10, and the check valve 1 becomes "open". The liquid can flow from the first channel 11 to the second channel 21 through the check valve 1. Alternatively, a syringe pump may be used to introduce the liquid into the first channel 11 at a low flow rate. In this case, the time lag between starting the syringe pump and the liquid passing through the check valve 1 and actually flowing into the patient is short. Furthermore, the liquid can be administered to the patient at the desired low flow rate without bolus administration.

When the clamp on the first tube is closed (or the syringe pump is stopped), the flow of liquid into the first channel 11 stops. The elastic membrane 60 recovers its elasticity, and the check valve 1 returns to its initial state. Infusion is stopped.

If, for some reason, liquid flows into the second channel 21 in the reverse direction 45 (see Figure 8), the pressure of the liquid in the second cavity 31b (downstream pressure) increases. As described above, even though the elastic membrane 60 has a large pressurized area radius to improve valve opening, an annular liquid-tight seal is formed between the first surface 60a of the elastic membrane 60 and the inner surface 15 of the first housing 10. The check valve 1 becomes "closed." Liquid flow from the second channel 21 to the first channel 11 through the check valve 1 is prohibited.

In this embodiment 1, when viewed along the central axis 1a, the shape of the inner circumferential end 61a of the outer peripheral region 61 includes a part of an ellipse (see Figure 3B). This is advantageous for simplifying the configuration of the check valve 1, where the distance from the central axis 1a to the inner circumferential end 61a (the radius of the pressurized region) changes in the circumferential direction.

More specifically, when viewed along the central axis 1a, the inner circumferential end 61a of the outer circumferential region 61 has a shape that combines a semicircle and a semiellipse (see Figure 3B). The distance from the central axis 1a to the inner circumferential end 61a is maximum on the semielliptical side. Therefore, in the initial state of the check valve 1, when the fluid pressure (upstream pressure) in the first cavity 31a begins to rise, the outer circumferential region 61 first separates from the second inner surface 14 of the first housing 10 on the semielliptical side with respect to the center of the valve body 50 (or central axis 1a) (see Figure 7). This simple configuration allows for improved valve opening performance of the check valve 1.

In Figures 3A and 3B, when viewed along the central axis 1a, the inner circumferential end 14a of the second inner surface 14 and the inner circumferential end 61a of the outer peripheral region 61 both have a shape that combines a semicircle concentric with the central axis 1a on the left side with respect to the Y-axis and a semiellipse with the X-axis as its major axis on the right side with respect to the Y-axis. However, the present invention is not limited to this. Although not shown in the illustration, for example, the semiellipse on the right side with respect to the Y-axis may be a semiellipse with the Y-axis as its major axis. The semi-major axis of this semiellipse is the same as the radius of the semicircle on the left side with respect to the Y-axis. In this case, the distance from the central axis 1a to the inner circumferential ends 14a and 61a is constant on the left side with respect to the Y-axis (semicircle side), but changes to be minimized on the X-axis on the right side with respect to the Y-axis (semiellipse side). In the initial state of the check valve 1, when the fluid pressure (upstream pressure) in the first cavity 31a begins to rise, the outer peripheral region 61 initially separates from the second inner surface 14 of the first housing 10 on the semicircular side with respect to the center (or central axis 1a) of the valve body 50. Even in this case, as in the example above, the opening performance of the check valve 1 can be improved with a simple configuration.

In the above example, when viewed along the central axis 1a, the shape of the inner circumferential end 14a of the second inner surface 14 and the inner circumferential end 61a of the outer peripheral region 61 both had a shape that combined a semicircle (i.e., a circular arc with a central angle of 180 degrees) and a semiellipse. However, the present invention is not limited to this. For example, when viewed along the central axis 1a, the inner circumferential ends 14a and 61a may have a shape that combines a circular arc with a central angle greater than or less than 180 degrees and a part of an ellipse connecting both ends of the circular arc. In this case as well, since the distance from the central axis 1a to the inner circumferential end of the outer peripheral region changes in the circumferential direction, the opening performance of the check valve can be improved.

(Embodiment 2)
Figure 9 is a cross-sectional view of the check valve 2 according to Embodiment 2 of the present invention in its initial state. The check valve 2 is the same as the check valve 1 of Embodiment 1, except for the first housing 210. The check valve 2 and the first housing 210 of Embodiment 2 will be described below, focusing on the differences from Embodiment 1.

Figure 10A is a bottom view of the first housing 210 as seen from the valve body 50 side. The X and Y axes both extend along a plane perpendicular to the central axis 1a and are perpendicular to each other at the central axis 1a. Similar to the first housing 10 of Embodiment 1 shown in Figure 3A, the first flow path 11, the first inner surface 213, the second inner surface 214, and the joint 18 are arranged in this order radially outward from the central axis 1a. The shape of the inner circumferential end (or the opening end of the first flow path 11) 13a of the first inner surface 213 is circular and concentric with the central axis 1a. On the other hand, the shape of the inner circumferential end (i.e., the boundary between the first inner surface 213 and the second inner surface 214) 214a of the second inner surface 214 is non-circular. More specifically, when viewed along the central axis 1a, the inner circumferential end 214a of the second inner surface 214 is elliptical with the X axis as its major axis. The distance from the central axis 1a to the inner circumferential end 214a varies circumferentially such that it is minimum on the Y-axis and maximum on the X-axis. The first inner surface 213 is a concave curved surface that smoothly connects the inner circumferential end 13a of the circular first inner surface 213 to the inner circumferential end 214a of the elliptical second inner surface 214. The second inner surface 214, similar to the second inner surface 14 in Embodiment 1, is a flat surface parallel to the radial direction and is continuous in an annular manner in the circumferential direction, surrounding the first inner surface 213.

Figure 10B is a top view of the valve body 50 used in the check valve 2, as seen from the first housing 210 side. The X and Y axes in Figure 10B correspond to the X and Y axes in Figure 10A, respectively. Similar to Embodiment 1, in the initial state, the second inner surface 214 of the first housing 210 contacts the first surface 60a of the elastic membrane 60 in the vertical direction (see Figure 9). The area of the first surface 60a of the elastic membrane 60 marked with numerous dots is the outer peripheral region 261 that contacts the second inner surface 214 of the first housing 210 in the initial state (see Figure 9). The outer peripheral region 261 is continuous in an annular shape along the outer circumference of the first surface 60a of the elastic membrane 60. The inner circumferential end 261a of the outer peripheral region 261, shown by the dashed line, corresponds to the inner circumferential end 214a of the second inner surface 214 of the first housing 210 (see Figure 10A). The inner circumferential end 261a of the outer peripheral region 261 is non-circular. More specifically, when viewed along the central axis 1a, the inner circumferential end 261a of the outer circumferential region 261 is elliptical with the X-axis as its major axis. The distance from the central axis 1a to the inner circumferential end 261a (the radius of the pressurized region) varies circumferentially such that it is minimum on the Y-axis and maximum on the X-axis. When viewed along the central axis 1a, the outer circumferential end 60c of the elastic membrane 60 is circular and concentric with the central axis 1a. Therefore, the radial width of the outer circumferential region 261 varies circumferentially such that it is maximum on the Y-axis and minimum on the X-axis.

In the initial state of the check valve 2 of this embodiment 2 (see Figure 9), when the fluid pressure (upstream pressure) in the first cavity 31a begins to rise, the upstream pressure acts on the region inside the inner end 261a of the outer peripheral region 261 of the valve body 50 (the pressurized region). The distance from the central axis 1a to the inner end 261a of the outer peripheral region 261 (the radius of the pressurized region) is maximum on the X-axis. Therefore, initially, the outer peripheral region 261 separates from the second inner surface 214 of the first housing 210 at both ends in the X-axis direction. Even with relatively low upstream pressure, the check valve 2 changes to an open state. The check valve 2, having an elliptical pressurized region, has improved valve opening performance.

As the upstream pressure increases further, the outer peripheral region 261 separates from the second inner surface 214 of the first housing 210 along its entire circumference, and the gap between the outer peripheral region 261 and the second inner surface 214 of the first housing 210 expands.

Generally, as the radius of the pressurized area increases, the check valve's check-stopping performance decreases. That is, when fluid flows into the check valve 2 through the second flow path 21, the pressure of the fluid in the second cavity 31b (downstream pressure) may cause abnormal deformation of the elastic membrane 60 in the portion with a large pressurized area radius. However, by optimizing the aspect ratio (major axis/minor axis, or the flattening ratio of the ellipse) of the ellipse along the inner circumferential end 261a of the outer circumferential region 261 (and furthermore, the inner circumferential end 214a of the second inner surface 214), abnormal deformation of the elastic membrane 60 due to downstream pressure can be suppressed, thereby ensuring the check-stopping performance of the check valve 2, which prohibits the flow of fluid in the reverse direction.

Therefore, the check valve 2 of this embodiment 2 has improved opening performance while maintaining check valve performance to a level that is not problematic in practical use.

In this second embodiment, when viewed along the central axis 1a, the inner circumferential end 261a of the outer circumferential region 261 is elliptical (see Figure 10B). This is advantageous for simplifying the configuration of the check valve 2, where the distance from the central axis 1a to the inner circumferential end 261a (the radius of the pressurized region) changes in the circumferential direction.

In the above example, the shape of the inner circumferential end 214a of the second inner surface 214 and the shape of the inner circumferential end 261a of the outer circumferential region 261 were both elliptical, but the present invention is not limited to this. The shapes of the inner circumferential ends 214a and 261a may be any shape having a major axis and a minor axis, such as the shape of an athletics track formed by connecting two parallel lines with two semicircles (or semi-ellipses). Preferably, the center of gravity of the shape coincides with the central axis 1a.

This second embodiment is the same as the first embodiment, except as described above. For configurations or elements in this second embodiment that are common to both the first and second embodiments, the description of the first embodiment applies to this second embodiment as well.

(Embodiment 3)
Figure 11 is a cross-sectional view of the check valve 3 according to Embodiment 3 of the present invention in its initial state. The check valve 3 is the same as the check valve 1 of Embodiment 1, except for the first housing 310. The check valve 3 and the first housing 310 of Embodiment 3 will be described below, focusing on the differences from Embodiment 1.

Figure 12 is a perspective view of the first housing 310 seen from below. Figure 13A is a bottom view of the first housing 310 seen from the valve body 50 side. In Figure 13A, the X and Y axes both extend along a plane perpendicular to the central axis 1a and are perpendicular to each other at the central axis 1a. Similar to the first housing 10 of Embodiment 1 shown in Figure 3A, the first flow path 11, the first inner surface 313, the second inner surface 314, and the joint 18 are arranged in this order radially outward from the central axis 1a. The shape of the inner circumferential end (or the opening end of the first flow path 11) 13a of the first inner surface 313 is circular and concentric with the central axis 1a. On the other hand, the shape of the inner circumferential end (i.e., the boundary between the first inner surface 313 and the second inner surface 314) 314a of the second inner surface 314 is non-circular. More specifically, when viewed along the central axis 1a, the inner circumferential end 314a of the second inner surface 314 is approximately square. The four sides of the approximately square are parallel to the X-axis or Y-axis. The diagonals of the approximately square intersect at the central axis 1a and are inclined at a 45-degree angle to the X-axis and Y-axis. Circular arcs are provided at the four corners of the approximately square. The distance from the central axis 1a to the inner circumference end 314a changes circumferentially such that it is minimum on the X-axis and Y-axis and maximum on the diagonal axis of the approximately square. The first inner surface 313 is a concave curved surface that smoothly connects the inner circumference end 13a of the circular first inner surface 313 to the inner circumference end 314a of the approximately square second inner surface 314. The second inner surface 314, similar to the second inner surface 14 of Embodiment 1, is a flat surface parallel to the radial direction and is continuous in a ring shape circumferentially, surrounding the first inner surface 313.

Figure 13B is a top view of the valve body 50 used in the check valve 3, as seen from the first housing 310 side. The X and Y axes in Figure 13B correspond to the X and Y axes in Figure 13A, respectively. Similar to Embodiment 1, in the initial state, the second inner surface 314 of the first housing 310 contacts the first surface 60a of the elastic membrane 60 in the vertical direction (see Figure 11). The area of the first surface 60a of the elastic membrane 60 marked with numerous dots is the outer peripheral region 361 that contacts the second inner surface 314 of the first housing 310 in the initial state (see Figure 11). The outer peripheral region 361 is continuous in an annular shape along the outer circumference of the first surface 60a of the elastic membrane 60. The inner circumferential end 361a of the outer peripheral region 361, shown by the dashed line, corresponds to the inner circumferential end 314a of the second inner surface 314 of the first housing 310 (see Figure 13A). The inner circumferential end 361a of the outer circumferential region 361 is non-circular. More specifically, when viewed along the central axis 1a, the inner circumferential end 361a is approximately square. The four sides of the approximately square are parallel to the X-axis or Y-axis. The diagonals of the approximately square intersect at the central axis 1a and are inclined at a 45-degree angle with respect to the X-axis and Y-axis. Circular arcs are provided at the four corners of the approximately square. The distance from the central axis 1a to the inner circumferential end 361a (the radius of the pressurized area) varies circumferentially such that it is minimum on the X-axis and Y-axis and maximum on the diagonal axis of the approximately square. When viewed along the central axis 1a, the outer circumferential end 60c of the elastic membrane 60 is a circle concentric with the central axis 1a. Therefore, the radial width of the outer circumferential region 361 varies circumferentially such that it is maximum on the X-axis and Y-axis and minimum on the diagonal axis of the approximately square.

In the initial state of the check valve 3 of this embodiment 3 (see Figure 11), when the fluid pressure (upstream pressure) in the first cavity 31a begins to rise, the upstream pressure acts on the region inside the inner circumferential end 361a of the outer circumferential region 361 of the valve body 50 (the pressurized region). The distance from the central axis 1a to the inner circumferential end 361a of the outer circumferential region 361a (the radius of the pressurized region) is maximum on the diagonal axis of the approximately square. Therefore, initially, the outer circumferential region 361 separates from the second inner surface 314 of the first housing 310 at four points on the diagonal axis. Even with a relatively low upstream pressure, the check valve 3 changes to an open state. The check valve 3, having an approximately square pressurized region, has improved valve opening performance.

As the upstream pressure increases further, the outer peripheral region 361 separates from the second inner surface 314 of the first housing 310 along its entire circumference, and the gap between the outer peripheral region 361 and the second inner surface 314 of the first housing 310 expands.

Generally, as the radius of the pressurized area increases, the check valve's check-stopping performance decreases. That is, when fluid flows into the check valve 3 through the second flow path 21, the pressure of the fluid in the second cavity 31b (downstream pressure) may cause abnormal deformation of the elastic membrane 60 in the portion with a large pressurized area radius. However, by optimizing the approximately square shape (diagonal axis dimension / X-axis (or Y-axis) dimension) along which the inner circumferential end 361a of the outer circumferential region 361 (and furthermore, the inner circumferential end 314a of the second inner surface 314) follows, abnormal deformation of the elastic membrane 60 due to downstream pressure can be suppressed, thereby ensuring the check-stopping performance of the check valve 3, which prohibits the flow of fluid in the reverse direction.

Therefore, the check valve 3 of this embodiment 3 has improved opening performance while maintaining check valve performance to a level that is not problematic in practical use.

In the above example, the shape of the inner circumference end 314a of the second inner surface 314 and the shape of the inner circumference end 361a of the outer circumference region 361 were both approximately square, but the present invention is not limited to this. The shapes of the inner circumference ends 314a and 361a may be regular polygons such as equilateral triangles or regular pentagons. Preferably, the centroid of the regular polygon coincides with the central axis 1a. At the vertices of the regular polygon, arbitrary curves (preferably curves projecting radially outward) such as circular arcs similar to the above-mentioned approximately square or parts of ellipses may be provided.

In this embodiment 3, when viewed along the central axis 1a, the shape of the inner circumferential end 361a of the outer circumferential region 361 is a substantially regular polygon. The number of portions of the outer circumferential region 361 that selectively separate from the second inner surface 314 of the first housing 310 when the upstream pressure increases depends on the number of vertices (corners) of the substantially regular polygon. By changing the number of vertices, the opening and check-stopping performance of the check valve can be adjusted. Therefore, the check valve of this embodiment 3, having a substantially regular polygonal pressurized region, is advantageous for achieving a good balance between opening and check-stopping performance.

This third embodiment is the same as the first embodiment, except as described above. For configurations or elements in this third embodiment that are common to the first embodiment, the description of the first embodiment applies to this third embodiment as well.

(Embodiment 4)
Figure 14 is a cross-sectional view of the check valve 4 according to Embodiment 4 of the present invention in its initial state. The check valve 4 is the same as the check valve 1 of Embodiment 1, except for the first housing 410. The check valve 4 and the first housing 410 of Embodiment 4 will be described below, focusing on the differences from Embodiment 1.

Figure 15 is a perspective view of the first housing 410 from below. Figure 16A is a bottom view of the first housing 410. In Figure 16A, the X and Y axes both extend along a plane perpendicular to the central axis 1a and are perpendicular to each other at the central axis 1a. Similar to the first housing 10 of Embodiment 1 shown in Figure 3A, the first flow path 11, the first inner surface 413, the second inner surface 414, and the joint 18 are arranged in this order radially outward from the central axis 1a. The shape of the inner circumferential end (or the opening end of the first flow path 11) 13a of the first inner surface 413, and the shape of the inner circumferential end (i.e., the boundary between the first inner surface 413 and the second inner surface 414) 414a of the second inner surface 414 are both circular and concentric with the central axis 1a. The first inner surface 413 is a frustoconical surface (side surface of a frustocone) connecting the inner circumferential end 13a of the circular first inner surface 413 and the inner circumferential end 414a of the circular second inner surface 414. The second inner surface 414 is a flat surface parallel to the radial direction, similar to the second inner surface 14 in Embodiment 1, and is continuous in an annular manner in the circumferential direction so as to surround the first inner surface 413. Multiple recesses (six in this example) 416 are provided on the inner circumferential end 414a. The multiple recesses 416 are arranged at equal angular intervals with respect to the central axis 1a. Each recess 416 extends radially from the first inner surface 413 to the second inner surface 414, intersecting the circular inner circumferential end 414a. The multiple recesses 416 divide the circular inner circumferential end 414a into multiple arcs. As shown in Figure 14, in the initial state, the recess 416 forms a gap between the first housing 410 and the elastic membrane 60 of the valve body 50, which is continuous with the first cavity 31a.

Figure 16B is a top view of the valve body 50 used in the check valve 4, as seen from the first housing 410 side. The X and Y axes in Figure 16B correspond to the X and Y axes in Figure 16A, respectively. Similar to Embodiment 1, in the initial state, the second inner surface 414 of the first housing 410 contacts the first surface 60a of the elastic membrane 60 in the vertical direction (see Figure 14). The area of the first surface 60a of the elastic membrane 60 marked with numerous dots is the outer peripheral region 461 that contacts the second inner surface 414 of the first housing 410 in the initial state (see Figure 14). The outer peripheral region 461 is continuous in an annular shape along the outer circumference of the first surface 60a of the elastic membrane 60. The shape of the inner circumferential end 461a of the outer peripheral region 461, shown by the dashed line, is approximately circular overall, with a plurality of protrusions 461c that locally protrude radially outward. More specifically, the inner circumferential end 461a of the outer circumferential region 461 is composed of a plurality of circular arcs 461b concentric with the central axis 1a and a plurality of protrusions 461c projecting radially outward from the circular arcs 461b. The circular arcs 461b and protrusions 461c are arranged alternately in the circumferential direction. The protrusions 461c connect adjacent circular arcs 461b in the circumferential direction. The circular arcs 461b correspond to the circular inner circumferential end 414a of the second inner surface 414 of the first housing 410 (see Figures 15 and 16A), and the protrusions 461c correspond to the recesses 416 of the first housing 410 (see Figures 15 and 16A). In this example, the protrusions 461c are circular arcs having a smaller radius of curvature than the circular arcs 461b. The distance from the central axis 1a to the inner circumferential end 461a (the radius of the pressurized area) is constant in the arc 461b and changes circumferentially, becoming larger at the convex portion 461c. When viewed along the central axis 1a, the outer circumferential end 60c of the elastic membrane 60 is a circle concentric with the central axis 1a. Therefore, the radial width of the outer circumferential region 461 is maximum in the arc 461b and minimum at the convex portion 461c, changing circumferentially.

In the initial state of the check valve 4 of this embodiment 4 (see Figure 14), when the fluid pressure (upstream pressure) in the first cavity 31a begins to rise, the upstream pressure acts on the region inside the inner circumferential end 461a of the outer peripheral region 461 of the valve body 50 (the pressurized region). The distance from the central axis 1a to the inner circumferential end 461a of the outer peripheral region 461 (the pressurized region radius) is maximum at the convex portion 461c. Therefore, initially, the outer peripheral region 461 separates from the second inner surface 414 of the first housing 410 near the convex portion 461c. Even with a relatively low upstream pressure, the check valve 4 changes to an open state. The check valve 4, having a pressurized region where the pressurized region radius is locally increased at the convex portion 461c, exhibits improved valve opening performance.

As the upstream pressure increases further, the outer peripheral region 461 separates from the second inner surface 414 of the first housing 410 along its entire circumference, and the gap between the outer peripheral region 461 and the second inner surface 414 of the first housing 410 expands.

Generally, as the radius of the pressurized area increases, the check valve's check-stopping performance decreases. That is, when fluid flows into the check valve 4 through the second flow path 21, the pressure of the fluid in the second cavity 31b (downstream pressure) may cause abnormal deformation of the elastic membrane 60 in the portion with a large pressurized area radius. However, by optimizing the number of protrusions 461c on the inner circumferential end 461a of the outer circumferential region 461, the circumferential dimensions of the protrusions 461c, and the radial outward projection length of the protrusions 461c relative to the arc 461b, it is possible to suppress abnormal deformation of the elastic membrane 60 due to downstream pressure, thereby ensuring the check valve 4's ability to prevent reverse fluid flow.

Therefore, the check valve 4 of this embodiment 4 has improved opening performance while maintaining check valve performance to a level that is not problematic in practical use.

In the example above, the number of protrusions 461c on the inner circumferential end 461a of the outer circumferential region 461 was six, but the present invention is not limited to this, and it is sufficient that at least one protrusion 461c is provided on the inner circumferential end 461a. The shape and dimensions (circumferential dimension, radial outward projection length relative to the arc 461b) of the protrusions 461c can be arbitrarily set. The recess 416 provided in the first housing 410 is appropriately modified so that the desired protrusions 461c are formed.

A protrusion similar to the protrusion 461c in this embodiment 4 may be provided on the inner circumferential ends 61a, 261a, and 361a of the outer circumferential regions 61, 261, and 361 in embodiments 1 to 3. In this case, it is preferable to provide the protrusion at a position where the distance from the central axis 1a to the inner circumferential ends 61a, 261a, and 361a is maximized. This is advantageous for further improving the opening performance of the check valve. Recesses similar to the recess 416 are provided on the second inner surfaces 14, 214, and 314 so that the desired protrusions are formed on the inner circumferential ends 61a, 261a, and 361a.

Generally, it is preferable that the protrusions are connected to substantially circular arcs (including parts of arcs and ellipses) that constitute the inner circumferential ends (61a, 261a, 361a, 461a) of the outer circumferential region (61, 261, 361, 461), such that they protrude radially outward from the substantially circular arcs. Preferably, the protrusions include substantially circular arcs (including parts of arcs and ellipses) that protrude radially outward. Preferably, the radius of curvature of the substantially circular arc of the protrusion is smaller than the radius of curvature of the substantially circular arc to which the protrusion is connected.

To provide a protrusion on the inner circumferential ends (61a, 261a, 361a, 461a) of the outer circumferential region (61, 261, 361, 461), it is sufficient to provide a recess in the first housing that divides the inner circumferential ends (14a, 214a, 314a, 414a) of the second inner surface (14, 214, 314, 414). Furthermore, if a recess is provided at the inner circumferential end 914a (see Figure 5A) of the second inner surface 914 of the first housing 910 in the comparative example described above, a protrusion that locally increases the pressurized area radius can be formed at the inner circumferential end 961a (see Figure 5B) of the outer circumferential region 961, similar to this embodiment 4. Therefore, this embodiment 4 is advantageous for further improving the opening performance of the check valve without significantly redesigning the existing first housing.

In the above example, the inner circumferential end 461a of the outer circumferential region 461 was composed of a plurality of circular arcs 461b concentric with the central axis 1a and a plurality of protrusions 461c projecting radially outward from the circular arcs 461b. However, the protrusions 461c may be replaced with protrusions projecting radially inward (hereinafter referred to as "inward protrusions"). In this case, the distance from the central axis 1a to the inner circumferential end 461a of the outer circumferential region 461a (the pressurized region radius) is constant in the circular arcs 461b and decreases in the inward protrusions, changing in the circumferential direction. When the fluid pressure in the first cavity 31a (upstream pressure) begins to rise in the initial state of the check valve, the outer circumferential region 461 first separates from the second inner surface 414 of the first housing 410 in the circular arcs 461b. Therefore, similar to the above example, the opening performance of the check valve can be improved while maintaining the check valve performance to a level that is not problematic for practical use. The inward-facing protrusion can be formed on the first housing 410 by forming a protrusion (projection) on the first housing 410 that projects radially inward from the inner circumferential end 414a of the second inner surface 414, and has a flat surface continuous with the second inner surface 414. Similar to the check valve in the above example where the inner circumferential end 461a of the outer circumferential region 461 has a protrusion 461c, a check valve where the inner circumferential end 461a of the outer circumferential region 461 has an inward-facing protrusion also improves valve opening performance without significantly redesigning the existing first housing. Similar to the protrusion 461c, the number, shape, and dimensions (circumferential dimension, radial inward projection length relative to the arc 461b) of the inward-facing protrusions can be arbitrarily set. Furthermore, the inward-facing protrusions may be provided on the inner circumferential ends 61a, 261a, and 361a of the outer circumferential regions 61, 261, and 3611 of Embodiments 1 to 3.

This fourth embodiment is identical to the first embodiment except for the features described above. For configurations or elements in this fourth embodiment that are common to the first embodiment, the description of the first embodiment applies to this fourth embodiment as well.

The embodiments described above (1-4) are merely illustrative. The present invention is not limited to these embodiments and can be modified as appropriate.

The valve body 50 of Embodiments 1 to 4 had a first projection 51 and a second projection 52 that were arranged coaxially with the central axis 1a and had the same shape (see Figures 2A and 2B). The valve body 50 is rotationally symmetrical twice with respect to any axis perpendicular to the central axis 1a. That is, when the valve body 50 is inverted, its shape matches that of the original valve body. This makes it possible to manufacture the check valve of the present invention by fitting the second projection 52 into the fixing portion 23 of the second housing 20. In the manufacture of the check valve, it is unnecessary to distinguish between the upper and lower surfaces of the valve body 50. Therefore, the manufacture of the check valve is simplified. However, the present invention is not limited to this. For example, the valve body 50 does not need to have the second projection 52.

In embodiments 1 to 4 described above, the first flow path 11, the second flow path 21, the fixed portion 23, and the valve body 50 were arranged coaxially, but the present invention is not limited thereto. For example, the first flow path 11 and/or inner surface 15 may be eccentric with respect to the second flow path 21, the fixed portion 23, and the valve body 50. In this case, the central axis 1a of the check valve of the present invention is defined by the fixed portion 23.

In the embodiments 1 to 4 described above, the inner circumferential ends (61a, 261a, 361a, 461a) of the outer peripheral region (61, 261, 361, 461a) were not perfectly circular when viewed along the central axis 1a in order to vary the distance (pressurized region radius) from the central axis 1a to the inner circumferential ends (61a, 261a, 361a, 461a) of the outer peripheral region (61, 261, 361, 461a) in the circumferential direction. However, the present invention is not limited to this. In the present invention, for example, the inner circumferential ends of the outer peripheral region, which have a perfectly circular shape when viewed along the central axis 1a, may be eccentric with respect to the central axis 1a (fixed portion 23). In this case as well, similar to embodiments 1 to 4 described above, the distance (pressurized region radius) from the central axis 1a of the check valve to the inner circumferential ends of the outer peripheral region changes in the circumferential direction in the initial state. In the initial state of the check valve, when the fluid pressure (upstream pressure) in the first cavity 31a begins to rise, the outer peripheral region of the elastic membrane 60 initially separates from the second inner surface of the first housing on the side where the radius of the pressurized area is maximum. Therefore, it is possible to improve the valve opening performance while maintaining a level of check valve performance that is not problematic for practical use. The inner circumferential end of the outer peripheral region, which is eccentric with respect to the central axis 1a, can be obtained, for example, by making the inner circumferential end of the second inner surface of the first housing 10 eccentric with respect to the central axis 1a.

In embodiments 1 to 4 described above, the elastic membrane 60 of the valve body 50 extended horizontally in the initial state, but the present invention is not limited thereto. The check valve of the present invention may include a so-called umbrella-type valve body, such as that described in Patent Document 2, which has an elastic membrane inclined radially outward toward the second housing 20. Depending on the configuration of the valve body, the shape of the inner surfaces defining the cavity 31 (for example, the inner surface 15 of the first housing 10, the convex curved surface 25 of the second housing 20) can be appropriately modified.

While embodiments 1 to 4 described the use of a check valve in an infusion circuit, the applications of the check valve of the present invention are not limited to this. The check valve of the present invention can be applied to any fluid flow path where backflow prevention is required. The fluid flowing through the check valve is not limited, but is generally a liquid. The type of liquid is not a factor.

The application fields of the check valve of the present invention are not limited, but it is preferably used in the medical field, for example, in infusion circuits and hemodialysis circuits. Of course, the check valve of the present invention can also be widely used in fields other than medicine, such as chemistry and food processing, where check valves are required.

1, 2, 3, 4 Check valve 1a Check valve central axis 10 First housing 11 First flow path 13 First inner surface of first housing 14 Second inner surface of first housing 15 Inner surface of first housing 20 Second housing 21 Second flow path 23 Fixing part 30 Housing 31 Cavity 35 Gap between elastic membrane and first housing 50 Valve body 51 Projection (first projection)
60 Elastic film 60a First surface of elastic film 60b Second surface of elastic film 61, 261, 361, 461 Outer peripheral region 61a, 261a, 361a, 461a Inner peripheral end of outer peripheral region 461b Arc 461c Convex portion

Claims (6)

A check valve comprising a housing having a cavity formed therein that communicates with a first flow path and a second flow path, and a valve body disposed within the cavity,
The housing is configured such that a first housing provided with the first flow path and a second housing provided with the second flow path are joined together such that the cavity is formed between the first housing and the second housing.
The valve body comprises a projection that fits into a fixed portion provided at the opening end of the second flow path of the second housing, and an elastic membrane that extends radially outward from the projection and is capable of elastic bending deformation.
The aforementioned check valve is
An open state in which a gap is formed between the first surface of the elastic membrane and the first housing so as to allow fluid flow from the first channel to the second channel,
The first surface of the elastic membrane changes to a closed state in which it makes annular contact with the first housing so that the flow of fluid from the second channel to the first channel is prohibited.
In the initial state in which the pressure of the fluid on the first flow path side and the pressure of the fluid on the second flow path side are balanced relative to the valve body, the outer peripheral region of the first surface of the elastic membrane is in annular contact with the first housing.
A check valve characterized in that, in the initial state, the distance from the central axis of the check valve defined by the fixed portion to the inner end of the outer peripheral region changes in the circumferential direction. The check valve according to claim 1, wherein, when viewed along the central axis, the shape of the inner end of the outer peripheral region includes a portion of an ellipse. The check valve according to claim 1, wherein, when viewed along the central axis, the inner circumferential end of the outer circumferential region has a shape combining a semicircle and a semiellipse. The check valve according to claim 1, wherein, when viewed along the central axis, the inner circumferential end of the outer circumferential region is elliptical. The check valve according to claim 1, wherein, when viewed along the central axis, the shape of the inner end of the outer peripheral region is substantially a regular polygon. The check valve according to claim 1, wherein, when viewed along the central axis, the shape of the inner end of the outer peripheral region includes a substantially circular arc and a convex portion connected to the substantially circular arc, the convex portion projecting radially outward or radially inward from the substantially circular arc.