JP7724171B2 - Shaft seal - Google Patents

Description

The present invention relates to shaft seals, particularly those that include resin packing.

"Shaft seal" is a general term for components used to seal the gap between the opening of the casing of a fluid equipment and the movable shaft, i.e., to prevent fluid leakage from the gap or the intrusion of foreign matter into the gap. Some shaft seals, in particular, include packing packed into a stuffing box (see, for example, Patent Documents 1-6). A stuffing box is a cylindrical member fitted inside the casing opening, surrounding the movable shaft and forming an annular space, or packing chamber, between its inner circumferential surface and the outer circumferential surface of the movable shaft. "Packing" is a flexible member, either string-like or annular, and multiple packings are generally packed into the packing chamber. Within the packing chamber, multiple packings are arranged side by side along the movable shaft, wrapped around the movable shaft if string-like, or with the movable shaft threaded through the inside if annular, to form a cylindrical structure surrounding the movable shaft. When compressed axially by an annular member called a "packing gland," this cylindrical structure expands radially, adhering tightly to the inner circumferential surface of the stuffing box and the outer circumferential surface of the movable shaft. As a result, the packing chamber is closed, sealing the gap between the casing opening and the movable shaft.

The pressure of the packing against the inner surface of the stuffing box and the outer surface of the movable shaft, i.e., the sealing pressure, is the result of increased radial stress caused by axial compression of the packing. Therefore, when stress relaxation occurs, a phenomenon in which stress decreases in the packing due to creep deformation, wear, temperature drop, etc., the sealing pressure decreases. To prevent an increase in fluid leakage due to this decrease, work is required to increase the pressure of the packing gland against the packing, i.e., retightening. One known technique for reducing the frequency of retightening and easing the maintenance burden related to shaft seals is to attach a spring to the stuffing box or packing gland that applies axial pressure to the packing (see, for example, Patent Documents 3-6). When the packing reduces its axial stress due to stress relaxation, the spring pressure further compresses it in the axial direction. This increases the radial stress of the packing, offsetting the reduction due to stress relaxation, making it less likely to reduce sealing pressure.

Japanese Utility Model Application Laid-Open Publication No. 02-084062 JP 2016-020711 A Japanese Patent Application Publication No. 11-344123 Japanese Patent Application Laid-Open No. 2005-220832 Japanese Patent Application Laid-Open No. 2009-215905 Patent No. 5820793

Resins are often chosen as packing materials. Fluoropolymers such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and polyvinylidene fluoride (PVDF) are particularly popular due to their high heat resistance, excellent chemical stability against fluids, and low coefficient of friction against moving shafts. However, compared to metals, which are commonly used for moving shafts and stuffing boxes, resins, especially fluoropolymers, have a thermal shrinkage rate that is about 10 times higher. This means that using resin packing for shaft seals poses the following problems. Note that "thermal shrinkage rate" refers to the rate at which an object thermally shrinks, i.e., the rate at which an object's volume or length decreases as its temperature drops, and is actually equal to the object's thermal expansion coefficient.

When fluid equipment handles low-temperature fluids (below -100°C), such as liquefied natural gas (LNG, boiling point approximately -160°C), liquid nitrogen (boiling point -196°C), liquid hydrogen (boiling point -253°C), and liquid helium (boiling point -269°C), the fluid cools not only the moving shaft but also the shaft seal to low temperatures. Compared to moving shafts and stuffing boxes, which are generally made of metal, resin packings have a higher thermal shrinkage rate. Therefore, as the temperature drops from room temperature (above -10°C or below -10°C) to low temperatures (hereinafter referred to as "low-temperature"), the radial width of the packing shrinks more than the inner radial dimension of the packing chamber. As a result, sealing pressure decreases, especially on the outer periphery of the packing. Furthermore, because there is a large difference in thermal shrinkage rate between the packing chamber and the packing, the decrease in sealing pressure due to low-temperature conditions is significantly greater than the decrease due to stress relaxation at room temperature, such as creep deformation and wear.

Even if the packing is pressurized with a spring, as in the shaft seals disclosed in Patent Documents 3-6, the spring pressure is only sufficient to prevent a decrease in sealing pressure due to stress relaxation in the packing at room temperature, and is insufficient to prevent a decrease in sealing pressure due to low temperatures. However, pressurizing the packing with a stronger spring is difficult for reasons such as requiring a stronger or larger stuffing box or packing gland structure. Even if a sufficiently strong spring were attached to the stuffing box, the spring pressure exceeds the required level at room temperature, causing the packing's sealing pressure to increase excessively. This results in excessively rapid wear of the packing and excessively high sliding resistance of the packing against the movable shaft. To avoid these problems, it is necessary to devise a way to reduce the spring pressure at room temperature compared to low temperatures. However, such a design is difficult.

The object of the present invention is to solve the above problems, and in particular to provide a shaft seal that can maintain a sufficiently high seal pressure at low temperatures without excessively increasing the packing seal pressure at room temperature.

One aspect of the present invention provides a shaft seal for sealing the gap between a movable shaft and a stuffing box of a fluid device, and includes a resin packing and a support. The packing is packed into the gap between the movable shaft and the stuffing box by axial pressure from the packing gland. The support is an annular structure surrounding the movable shaft, with one axial side in contact with one axial end of the packing and the other side in contact with the stuffing box or the packing gland. The support includes a clamping region in at least a portion of the axial direction. The outer periphery of the clamping region has a higher thermal shrinkage rate than the inner periphery, and as the temperature drops, the outer periphery clamps the inner periphery. The support is configured so that this clamping force is transmitted from the clamping region to the packing as axial pressure.

The specific configuration of the support body is diverse. For example, the support body may have a clamping ring and a pressing ring. The clamping ring is an annular member that surrounds the movable shaft and includes a tapered inner circumferential surface on the side closer to the packing in the axial direction. The tapered inner circumferential surface is inclined so that the diameter narrows from the end to the center in the axial direction. The pressing ring is an annular member that surrounds the movable shaft and has a lower thermal shrinkage rate than the clamping ring and includes a tapered outer circumferential surface on the side farther from the packing in the axial direction. The tapered outer circumferential surface is inclined so that the diameter narrows from the center to the end in the axial direction. In the clamping region, the tapered inner circumferential surface of the clamping ring contacts the tapered outer circumferential surface of the pressing ring.

In addition to the above, the support may have a pressing ring and a stationary ring. The pressing ring is an annular member that surrounds the movable shaft and includes a tapered inner peripheral surface on the side farther from the packing in the axial direction. The tapered inner peripheral surface is inclined so that the diameter increases from the center to the end in the axial direction. The stationary ring is an annular member that surrounds the movable shaft and has a lower thermal shrinkage rate than the pressing ring and includes a tapered outer peripheral surface on the side closer to the packing in the axial direction. The tapered outer peripheral surface is inclined so that the diameter increases from the end to the center in the axial direction. In the clamping region, the tapered inner peripheral surface of the pressing ring contacts the tapered outer peripheral surface of the stationary ring.

The packing may be a V-packing. Furthermore, the support may have a male adapter that contacts one axial end of the packing. "V-packing" refers to a lip packing with a V-shaped cross section, i.e., a molded packing (a packing in which the material is molded in a mold) that includes a protruding portion called a "lip." In a V-packing, the two upper ends of the V-shaped cross section correspond to the lips. A "male adapter" refers to a member that supports the V-packing from its lip side.

In the shaft seal of the present invention, the support is sandwiched axially between the packing gland and the packing, or between the packing and the stuffing box. At room temperature, the support transmits the axial pressure from the packing gland or stuffing box, which is associated with the connection between the packing gland and the stuffing box, to the packing essentially as is. On the other hand, at low temperatures, the support not only transmits the axial pressure from the packing gland, etc. to the packing, but also generates its own axial pressure on the packing in the following manner.

When a low-temperature fluid flows through the casing of a fluid equipment, not only the packing but also the support body becomes colder. As a result, the support body transmits the force of the outer periphery of the clamping area clamping against the inner periphery to the packing as axial pressure. There are various specific configurations for the support body, including, for example, the combination of (1) a clamping ring and a pressing ring, and (2) a combination of a pressing ring and a stationary ring, as described above.

(1) The pressure ring is sandwiched axially between the packing and the clamp ring, with its tapered outer peripheral surface in contact with the tapered inner peripheral surface of the clamp ring. When the pressure ring is clamped by the clamp ring as the temperature drops, the tapered outer peripheral surface is subjected to pressure from the tapered inner peripheral surface. The tapered outer peripheral surface and the tapered inner peripheral surface are inclined so that their diameters increase as they approach the packing, so the pressure the tapered outer peripheral surface receives from the tapered inner peripheral surface is inclined relative to the radial direction. Therefore, axial stress is generated within the pressure ring, which is transmitted from the pressure ring to the packing as axial pressure. Meanwhile, the reaction force received by the tapered inner peripheral surface from the tapered outer peripheral surface is also inclined relative to the radial direction, so axial stress is also generated within the clamp ring, which is transmitted from the clamp ring to the stuffing box or packing gland as axial pressure. However, because both the stuffing box and the packing gland have sufficiently high rigidity, they are not substantially deformed or displaced by the axial pressure from the clamp ring. As a result, the clamping ring cannot be displaced axially, so the pressure of the pressing ring against the packing is high.

(2) The pressure ring is sandwiched axially between the packing and the stationary ring, with its tapered inner peripheral surface in contact with the tapered outer peripheral surface of the stationary ring. As the temperature drops, the pressure ring tightens the stationary ring, causing the tapered inner peripheral surface to apply pressure to the tapered outer peripheral surface. The tapered inner peripheral surface and the tapered outer peripheral surface are inclined so that their diameters narrow as they approach the packing, so the pressure applied by the tapered inner peripheral surface to the tapered outer peripheral surface is inclined relative to the radial direction. Therefore, the reaction force to this pressure is also inclined relative to the radial direction, generating axial stress within the pressure ring, which is transmitted from the pressure ring to the packing as axial pressure. Meanwhile, the pressure applied by the tapered inner peripheral surface to the tapered outer peripheral surface also generates axial stress within the stationary ring, which is transmitted from the stationary ring to the stuffing box or packing gland as axial pressure. However, because both the stuffing box and the packing gland are sufficiently rigid, they are not substantially deformed or displaced by the axial pressure from the stationary ring. As a result, the stationary ring cannot be displaced axially, so the pressure of the pressing ring against the packing is high.

Thus, at low temperatures, the packing is subjected not only to axial pressure associated with the bond between the packing gland and stuffing box, but also to axial pressure associated with thermal contraction of the clamping area of the support. Consequently, the packing is further compressed in the axial direction, increasing radial stress. This increase offsets the decrease in radial stress associated with the packing's low temperature, making it possible to maintain a sufficiently high packing sealing pressure even at low temperatures. Thus, the shaft seal according to the present invention is able to maintain a sufficiently high packing sealing pressure at low temperatures without excessively increasing it at room temperature.

When the packing is a V-packing and the support includes a male adapter, the support is located on the lip side of the V-packing. Therefore, the axial pressure from the pressure ring, which increases with the temperature, not only compresses the V-packing in the axial direction, but also opens the lip of the V-packing even more, pressing it more firmly against the stuffing box and movable shaft. As a result, the packing's sealing ability at low temperatures is further improved.

1A is a cross-sectional view of a shaft seal according to a first embodiment of the present invention, and FIG. 1B is a partially enlarged view of the packing shown in FIG. 1A and its vicinity. FIG. 2 is an exploded view of the shaft seal shown in FIG. 1. 1A is a schematic diagram showing the force transmitted from the clamping ring to the pressing ring and then to the packing as the temperature drops, and FIG. 1B is a schematic diagram showing the deformation of the packing and the displacement of the pressing ring as the clamping ring thermally shrinks. FIG. 4 is a cross-sectional view of a modified example of the shaft seal according to the first embodiment of the present invention. 10A is a cross-sectional view of a shaft seal according to a second embodiment of the present invention, and FIG. 10B is a partially enlarged view of the packing and its vicinity shown in FIG. FIG. 6 is an exploded view of the support shown in FIG. 1A is a schematic diagram showing the force transmitted from the pressing ring to the stationary ring and the packing as the temperature drops, and FIG. 1B is a schematic diagram showing the displacement of the pressing ring and the deformation of the packing as the pressing ring thermally shrinks.

A shaft seal according to an embodiment of the present invention is used, for example, to seal the gap between the opening of a valve casing and the stem. The "casing," also known as the "valve box," is a housing that houses a flow path inside. The "stem," also known as the "valve rod," is a rod-shaped member that transmits power to the valve element of the valve by rotating around its central axis or by reciprocating along the central axis. Since the power is transmitted to the flow path inside the casing, an opening is essential in the casing to allow the stem to pass through. The shaft seal according to an embodiment of the present invention reduces the amount of fluid leaking from this opening.
First Embodiment

(a) in Figure 1 is a cross-sectional view of a shaft seal 100 according to a first embodiment of the present invention. The shaft seal 100 seals the gap between the valve stem 510 and the opening 551 of the casing 550. The cross section shown in (a) in Figure 1 includes the central axis of the stem 510. In (a) in Figure 1, the central axis of the stem 510 is parallel to the left-right direction, with the flow path 540 inside the casing 550 located on the right side and the external space 560 of the casing 550 extending to the left side, generally open to the outside air. Hereinafter, the right side of any part shown in (a) in Figure 1 (i.e., the side closer to the flow path 540) will be referred to as the "fluid side," and the left side (i.e., the side farther from the flow path 540) will be referred to as the "atmosphere side."

A stuffing box 520 is fitted inside the opening 551 of the casing 550. The stuffing box 520 is a cylindrical member made of metal such as brass, bronze, steel, or cast iron, and coaxially surrounds the stem 510. The fluid-side end 521 (the right end in Figure 1(a)) of the stuffing box 520 faces the flow path 540 inside the casing 550, and the atmosphere-side end 522 (the left end in Figure 1(a)) protrudes outside the casing 550. The inner surface 523 of the stuffing box 520 forms a cylindrical packing chamber between itself and the outer surface 511 of the stem 510. An annular rib 524 protrudes from the fluid-side end 521 of the stuffing box 520 toward the outer surface 511 of the stem 510, separating the flow path 540 from the packing chamber.

Inside the atmosphere-side end 522 (left end in FIG. 1 ) of the stuffing box 520, a packing gland 530 closes the opening on the atmosphere side (left side in FIG. 1 ) of the packing chamber at its fluid-side end 531 (right end in FIG. 1 ). The packing gland 530 is a circular member made of a metal such as brass, bronze, steel, or cast iron, and coaxially surrounds the stem 510. An annular flange 533 projects outward from the atmosphere-side end 532 (left end in FIG. 1 ) of the packing gland 530. Multiple bolts 534 penetrate the flange 533 parallel to the stem 510 (left-right direction in FIG. 1 ), securing the flange 533 to the atmosphere-side end 522 of the stuffing box 520.
[Shaft seal structure]

The shaft seal 100 is a group of parts for sealing the packing chamber, and includes a packing 120, a female adapter 140, and support bodies 150 and 160.
-rubber seal-

Figure 1(b) is a partially enlarged view of the packing 120 shown in Figure 1(a) and its vicinity (the area surrounded by the dashed line in Figure 1(a)), and Figure 2 is an exploded view of the shaft seal 100. The packing 120 is a V-packing, and is composed of, for example, four V-rings 121. "V-ring" refers to a V-packing that forms a single ring shape. In the following, to avoid confusion with "V-rings," "V-packing" will only be used as the overall term for the V-rings packed into the packing chamber.

Each V-ring 121 is an annular molded packing made of fluororesin such as PTFE, and its cross section (a cross section taken along a plane including the central axis of the annular shape) is V-shaped, with the axial direction of the V-ring 121 as the up-down direction. The two upper ends of this V-shape, i.e., lips 122 and 123, extend to one side of the V-ring 121 in the axial direction (the right side in FIG. 1 ) and are connected circumferentially around the V-ring 121 to form two concentric rings. The inner lip 122 has a minimum inner diameter equal to or smaller than the diameter of the stem 510, while the outer lip 123 has a maximum outer diameter equal to or larger than the diameter of the inner circumferential surface 523 of the stuffing box 520. Due to the flexibility of their materials, the lips 122 and 123 can be bent to increase or decrease the opening of the V-shape (the vertical distance in FIG. 1 ). The lower end 124 of the V-shape (hereinafter referred to as the "heel") protrudes axially away from the lips 122, 123 (to the left in FIG. 1 ) of the V ring 121 and extends circumferentially around the V ring 121 to form a single ring. The cross section of the heel 124 is tapered in the axial direction of the V ring 121, with the inner diameter widening and the outer diameter narrowing toward the tip. The four V rings 121 are pressed into the packing chamber with the lips 122, 123 facing the fluid side (to the right in FIG. 1 ) and the stem 510 coaxially passing through the inside, and are arranged side by side along the stem 510. At this time, the heel 124 of another V ring 121 adjacent to the fluid side (to the right in FIG. 1 ) is fitted between the lips 122, 123 of each V ring 121. This integrates the four V rings 121 into a single cylindrical structure, i.e., the V packing 120.
-Female adapter-

The female adapter 140 is a circular ring member made of metal such as bronze or aluminum bronze, and is adjacent to the atmospheric side (left side in Figure 1) of the V-packing 120, coaxially surrounding the stem 510. The female adapter 140 has an inner diameter slightly larger than the diameter of the stem 510, and an outer diameter slightly smaller than the diameter of the inner circumferential surface 523 of the stuffing box 520. This ensures that the sliding resistance of the female adapter 140 relative to the stem 510 is sufficiently low, and it can slide along the stem 510.

The term "female adapter" originally refers to a component that supports the V-packing from its heel side. The female adapter 140 also supports the V-packing 120 from the heel 124 side of each V-ring 121, i.e., the atmosphere side (left side in FIG. 1 ). In fact, the annular surface 141 on the atmosphere side (left side in FIG. 1 ) of the female adapter 140 contacts the fluid-side end (right end in FIG. 1 ) 531 of the packing gland 530. Meanwhile, the annular surface on the fluid side (right side in FIG. 1 ) of the female adapter 140, i.e., the side that contacts the V-packing 120, has a circumferentially extending annular recess 142. The heel 124 of the V-ring 121 located closest to the atmosphere (left side in FIG. 1 ) is fitted into the recess 142. In particular, the entire outer surface of the heel 124 is in close contact with the entire inner surface of the recess 142. Since the female adapter 140 is more rigid than the V-ring 121, its close contact with the heel 124 transmits the pressure from the packing gland 530 evenly to the entire circumference of the heel 124, and suppresses excessive deformation and protrusion of the heel 124 caused by friction with the stem 510 or fluid pressure.
-Support-

Figure 2 includes an exploded view of the supports 150 and 160. The supports are composed of a pressure ring 150 and a clamping ring 160. The pressure ring 150 is a circular ring member made of a metal such as bronze or aluminum bronze, and coaxially surrounds the stem 510 adjacent to the fluid side (right side in Figure 1) of the V-packing 120. The pressure ring 150 has an inner diameter slightly larger than the diameter of the stem 510 and an outer diameter slightly smaller than the diameter of the inner circumferential surface 523 of the stuffing box 520, so that the sliding resistance against the stem 510 is sufficiently low and it can slide along the stem 510. The clamping ring 160 is a circular ring member made of a fluororesin such as PTFE, and coaxially surrounds the stem 510 adjacent to the fluid side (right side in Figure 1) of the pressure ring 150. The tightening ring 160 has an inner diameter larger than the diameter of the stem 510, so it does not provide sliding resistance to the stem 510, while its outer diameter is equal to or greater than the diameter of the inner circumferential surface 523 of the stuffing box 520, so it is fixed to that inner circumferential surface 523 by press-fitting.

The pressure ring 150 functions as a male adapter for the V-packing 120. A series of annular protrusions 151 protrude from the annular surface of the pressure ring 150 on the atmosphere side (left side in Figure 1), i.e., the side that contacts the V-packing 120. The protrusions 151 are fitted between the lips 122 and 123 of the V-ring 121 located closest to the fluid side (right side in Figure 1). Meanwhile, the pressure ring 150 has a tapered outer peripheral surface 152 on its fluid side (right side in Figure 1). The tapered outer peripheral surface 152 is inclined so that its diameter narrows from the center of the pressure ring 150 axially toward the fluid-side end (right end in Figure 1). The tapered outer peripheral surface 152 contacts the clamping ring 160 (see below for details). This allows the pressure ring 150 to be supported by the inner peripheral surface 523 and ribs 524 of the stuffing box 520 via the clamping ring 160. Because the pressure ring 150 is more rigid than the V-ring 121, it transmits the axial pressure from the rib 524 of the stuffing box 520 that occurs when the stuffing box 520 and packing gland 530 are joined evenly to the entire circumference of the V-ring 121, particularly to both lips 122 and 123, while also preventing excessive deformation and protrusion of the lips 122 and 123 due to friction with the stem 510 or fluid pressure.

The clamping ring 160 includes a tapered inner peripheral surface 161 on the side that contacts the pressure ring 150, i.e., the atmosphere side (left side in FIG. 1 ). The tapered inner peripheral surface 161 is inclined so that its diameter narrows from the atmosphere side end (left end in FIG. 1 ) of the clamping ring 160 toward the center in the axial direction. The maximum diameter of the tapered inner peripheral surface 161, i.e., the inner diameter at the atmosphere side end (left end in FIG. 1 ) of the clamping ring 160, is larger than the minimum diameter of the tapered outer peripheral surface 152 of the pressure ring 150, i.e., the outer diameter at the fluid side end (right end in FIG. 1 ) of the pressure ring 150. Therefore, the tapered inner peripheral surface 161 contacts the tapered outer peripheral surface 152. Meanwhile, the annular surface 162 on the fluid side (right side in FIG. 1 ) of the clamping ring 160 is in close contact with the annular surface 525 on the atmosphere side (left side in FIG. 1 ) of the rib 524 of the stuffing box 520. As a result, the pressing ring 150 is supported by the inner peripheral surface 523 and the ribs 524 of the stuffing box 520 via the tightening ring 160 .
[Sealing action of shaft seal]

When the flange 533 of the gland 530 is pressed against the atmosphere-side end 522 of the stuffing box 520 by the axial force of the bolt 534, the fluid-side end 531 (left end in FIG. 1) of the gland 530 applies axial (rightward in FIG. 1) pressure to the atmosphere-side (left side in FIG. 1) annular surface 141 of the female adapter 140. This pressure is transmitted by the recess 142 of the female adapter 140 to the heel 124 of the V-ring 121 closest to the atmosphere (left side in FIG. 1), and then by the lips 122, 123 of that V-ring 121 to the heel 124 of the V-ring 121 closest to the fluid (right side in FIG. 1). Similar pressure transmission is repeated among the remaining V-rings 121, causing the lips 122, 123 of the V-ring 121 closest to the fluid (right side in FIG. 1) to apply axial (rightward in FIG. 1) pressure to the protrusion 151 of the pressure ring 150. This pressure is applied by the tapered outer peripheral surface 152 of the pressing ring 150 to the tapered inner peripheral surface 161 of the clamping ring 160, causing the clamping ring 160 to be pressed against the inner peripheral surface 523 and ribs 524 of the stuffing box 520.

Because the stuffing box 520 is fixed to the casing 550 and has high rigidity, it is not substantially displaced or deformed by the pressure from the clamping ring 160. Therefore, the clamping ring 160 receives a strong axial (leftward in Figure 1) reaction force from the inner circumferential surface 523 and ribs 524 of the stuffing box 520. Furthermore, this reaction force is applied to the V-packing 120 from the clamping ring 160 through the pressure ring 150. As a result, the V-packing 120 is compressed axially (left-right in Figure 1) and expands radially (up-down in Figure 1) by both this reaction force and the pressure from the packing gland 530. Furthermore, the lips 122, 123 of each V-ring 121 are pushed apart by the convex portion 151 of the pressure ring 150 or the heel 124 of the V-ring 121 on the fluid side (rightward in Figure 1), widening the V-shape (the vertical spacing in Figure 1). As a result, the inner lip 122 of each V-ring 121 fits tightly against the outer peripheral surface 511 of the stem 510, and the outer lip 123 fits tightly against the inner peripheral surface 523 of the stuffing box 520. Therefore, only a very small amount of fluid can penetrate into the gap between the inner peripheral surface of the V-packing 120 and the outer peripheral surface 511 of the stem 510, and into the gap between the outer peripheral surface of the V-packing 120 and the inner peripheral surface 523 of the stuffing box 520. In this way, the gap between the stem 510 and the rib 524 of the stuffing box 520 is sealed.

The lips 122, 123 of the V-ring 121 also have a self-sealing effect. When fluid is filled in the gap between the pressure ring 150 and the V-ring 121, and further in the gaps between the V-rings 121, the pressure of the fluid presses the inner lip 122 further against the outer peripheral surface 511 of the stem 510, and presses the outer lip 123 further against the inner peripheral surface 523 of the stuffing box 520. This further increases the sealing pressure at the lips 122, 123, particularly at their tip ends, and therefore the sealing performance of the V-packing 120 is high.
[Preventive effect against reduction in sealing pressure due to low temperatures]

When a valve handles low-temperature fluids such as LNG or liquid nitrogen, at temperatures below 100°C, the stem 510 and the shaft seal 100 both cool while the low-temperature fluid flows through the flow path 540 in the casing 550. Compared to the stem 510 and stuffing box 520, the V-packing 120 experiences greater thermal contraction due to the drop in temperature than the packing chamber. However, in the shaft seal 100, the pressure ring 150 and the clamping ring 160 also cool. As a result, despite the large difference in thermal contraction between the packing chamber and the V-packing 120, a decrease in seal pressure due to the drop in temperature is prevented as follows:

Figure 3(a) is a schematic diagram showing the force transmitted from the clamping ring 160 to the pressing ring 150 and then to the V-ring 121 as the temperature drops. The clamping ring 160, like the V-ring 121, is made of fluororesin, and therefore has a thermal shrinkage rate that is at least as high as that of the V-ring 121. In contrast, the pressing ring 150 is made of metal, and therefore has a thermal shrinkage rate that is lower than that of either the V-ring 121 or the clamping ring 160, specifically only about 1/10 of that of the V-ring 121 and the clamping ring 160. Therefore, in the region where the tapered inner peripheral surface 161 of the clamping ring 160 contacts the tapered outer peripheral surface 152 of the pressing ring 150 (hereinafter referred to as the "clamping region"), the tapered inner peripheral surface 161 clamps the tapered outer peripheral surface 152 due to thermal shrinkage caused by the drop in temperature. In particular, the stress SS in the inner circumferential direction within the clamping ring 160 is transmitted from the tapered inner peripheral surface 161 to the tapered outer peripheral surface 152 as pressure PA. The tapered inner peripheral surface 161 and tapered outer peripheral surface 152 are inclined so that the diameter increases as they approach the V-ring 121 (toward the left in Figure 3(a)), so the pressure PA is inclined relative to the radial direction (vertical direction in Figure 3(a)). Therefore, axial stress (leftward in Figure 3(a)) is generated within the pressure ring 150, and this is transmitted as axial pressure PB (leftward in Figure 3(a)) from the convex portion 151 of the pressure ring 150 to the lips 122, 123 of the V-ring 121, which are located closest to the fluid (rightmost in Figure 3(a)).

Meanwhile, the reaction force that the tapered inner peripheral surface 161 receives from the tapered outer peripheral surface 152 is also inclined relative to the radial direction, so axial stress (to the right in Figure 3(a)) is generated within the clamping ring 160, and this stress is transmitted as axial pressure from the clamping ring 160 to the rib 524 of the stuffing box 520. However, because the rib 524 has sufficiently high rigidity, it is not substantially deformed or displaced by the axial pressure from the clamping ring 160. Therefore, because the clamping ring 160 cannot substantially displace in the axial direction, the pressure PB of the pressing ring 150 against the V-ring 121 is sufficiently high.

This pressure PB is transmitted by the heel 124 of the V-ring 121 to the lips 122, 123 of the adjacent V-ring 121 on the atmosphere side (left side in Figure 3(a)). Similar transmission of pressure PB is repeated among the remaining V-rings 121, and pressure PB is transmitted from the V-ring 121 located closest to the atmosphere side (leftmost side in Figure 3(a)) to the female adapter 140. Because the female adapter 140 is supported by the packing gland 530, it cannot be substantially displaced by the pressure PB. Furthermore, because the female adapter 140 is made of metal and has higher rigidity than the V-ring 121, it is not substantially deformed by the pressure PB. Therefore, each V-ring 121 is displaced toward the female adapter 140 (to the left in Figure 3(a)) by the pressure PB, and is further compressed axially due to the reaction force from the female adapter 140 against the pressure PB.

Figure 3(b) is a schematic diagram showing the deformation of the V ring 121 and the displacement of the pressing ring 150 due to thermal contraction of the clamping ring 160. The axial displacement of the V ring 121 is greater the closer the V ring 121 is to the pressing ring 150 (located to the right in Figure 3(b)). In response to the displacement of the V ring 121, the pressing ring 150 also displaces toward the V-packing 120 (to the left in Figure 3(b)). At this time, due to the inclination of the tapered outer peripheral surface 152 and the tapered inner peripheral surface 161, the inner diameter of the clamping ring 160 shrinks in response to the displacement of the pressing ring 150. Therefore, the clamping area is maintained, i.e., the tapered inner peripheral surface 161 continues to contact the tapered outer peripheral surface 152, so the pressing ring 150 continues to receive pressure PA from the clamping ring 160, maintaining pressure PB on the V-packing 120. As a result, the axial compression of each V ring 121 is sufficiently large.

Since each V-ring 121 increases its radial stress (vertical direction in FIG. 3B) as it is compressed in the axial direction, this offsets the decrease in radial stress that occurs with lower temperatures. Furthermore, the lips 122, 123 of each V-ring 121 are expanded by the convex portion 151 of the pressure ring 150 or the heel 124 of the V-ring 121 on the fluid side (right side in FIG. 3B). Therefore, regardless of lower temperatures, the inner lip 122 maintains a sufficiently high sealing pressure PI against the outer peripheral surface 511 of the stem 510, and the outer lip 123 maintains a sufficiently high sealing pressure PO against the inner peripheral surface 523 of the stuffing box 520.
[Advantages of the First Embodiment]

In the shaft seal 100, the pressure ring 150 is fitted as a male adapter onto the lip side of the V-packing 120 and is supported by the inner circumferential surface 523 and rib 524 of the stuffing box 520 via the clamping ring 160. Therefore, at room temperature, the pressure ring 150 and the clamping ring 160 transmit the axial pressure from the stuffing box 520, which occurs when the stuffing box 520 and the packing gland 530 join together, to the V-packing 120 essentially as is. This compresses the V-packing 120 axially, increasing the desired sealing pressure. Meanwhile, at low temperatures, the clamping ring 160 thermally contracts to tighten the pressure ring 150, which in turn presses the V-packing 120 axially. This pressure PB further compresses the V-packing 120 axially, increasing radial stress. This ensures that the sealing pressure of the V-packing 120 remains sufficiently high, even at low temperatures. In this way, the shaft seal 100 can maintain the sealing pressure of the V-packing 120 at a sufficiently high level at low temperatures without excessively increasing it at room temperature.

Like the V-packing 120, the clamping ring 160 is also made of fluororesin, so the thermal shrinkage rate of the clamping ring 160 is equal to or greater than that of the V-packing 120. As a result, as the thermal shrinkage of the V-packing 120 increases significantly, the pressure PB of the pressing ring 150 increases due to the thermal shrinkage of the clamping ring 160. This effectively prevents a decrease in the sealing pressure of the V-packing 120 due to lower temperatures.

Because the pressing ring 150 is made of metal, it has high rigidity against the pressure PA that the tapered outer peripheral surface 152 receives from the tapered inner peripheral surface 161 of the clamping ring 160, and is substantially undeformed even when subjected to that pressure PA. Therefore, the pressing ring 150 can slide along the stem 510 as smoothly at low temperatures as it does at room temperature, efficiently converting the pressure PA from the tapered inner peripheral surface into axial pressure PB on the V-packing 120.

The pressure ring 150 and the clamping ring 160 are located on the lip 122, 123 side of each V-ring 121. Therefore, the axial pressure PB of the pressure ring 150, which increases with the temperature, opens the lips 122, 123 of the V-ring 121 even wider, pressing them more firmly against the outer surface 511 of the stem 510 and the inner surface 523 of the stuffing box 520. As a result, the sealing performance of the V-packing 120 at low temperatures is further improved.

The pressing ring 150 and the clamping ring 160 are located on the opposite side of the packing gland 530 with respect to the V-packing 120. In this case, the pressure PB of the pressing ring 150, which increases with the temperature drop, is weakened by friction between each V-ring 121 and its periphery 510, 110 before reaching the packing gland 530. Therefore, it is unlikely that the bolt 534 will be unable to withstand the pressure PB from the pressing ring 150 and loosen, and the packing gland 530 can return a sufficiently strong reaction force against the pressure PB. Therefore, each V-ring 121 is sufficiently compressed by this reaction force and the pressure PB from the pressing ring 150, so that a sufficiently high sealing pressure is maintained.
[Modification]

(1) The shaft seal 100 is used to seal the gap between the opening 551 of the casing 550 of a valve and the stem 510. However, shaft seals according to embodiments of the present invention may also be used to seal the gap between the opening of the casing and the movable shaft of other fluid equipment. "Fluid equipment" includes not only devices that mechanically control fluid flow, such as valves, but also devices that use power to change fluid pressure, such as pumps, and devices that generate power from fluid pressure, such as generators. "Casing" refers to a housing that houses a flow path inside, such as the main body of a pump, and "movable shaft" refers to a rod-shaped member, such as a pump drive shaft, that transmits power by rotating around a central axis or by reciprocating motion along the central axis. When the destination of the power transmission is located in a flow path within the casing, such as a pump impeller or piston, an opening is essential in the casing to allow the movable shaft to pass through. Shaft seals according to embodiments of the present invention can also be used to reduce the amount of fluid leakage from this opening.

(2) The packing 120 is a V-packing made up of four V-rings 121. However, the present invention is not limited to this, and the number of V-rings 121 may be other than four, and spacer rings or V-rings made of a resin other than fluororesin may be inserted between the V-rings 121. All of the V-rings 121 may be made of a resin other than fluororesin. Also, although the packing 120 is a V-packing, the present invention is not limited to this, and the packing may be another lip packing such as a U-packing, or a gland packing.

(3) The pressure ring 150 is made of metal. However, the present invention is not limited to this. The pressure ring may be made of a material other than metal, such as resin, as long as its thermal contraction rate is sufficiently lower than that of the clamping ring. Furthermore, it is desirable that the rigidity of the pressure ring is sufficiently high to withstand the pressure received from the clamping ring as the clamping ring thermally contracts. Furthermore, although the pressure ring 150 also functions as a male adapter for the V-packing 120, the present invention is not limited to this. The support body may include another annular member between the pressure ring and the V-packing that functions as a male adapter.

(4) The pressure ring 150 and the tightening ring 160 are located on the opposite side of the packing gland 530 from the V-packing 120. However, the present invention is not limited to this, and the pressure ring 150 and the tightening ring 160 may be located between the V-packing 120 and the packing gland 530. It is sufficient that the packing gland 530 is fixed to the stuffing box 520 firmly enough that it does not substantially displace even when subjected to axial pressure from the pressure ring 150 due to low temperatures.

(5) The pressing ring 150 and the tightening ring 160 are located on the opposite side of the V-packing 120 from the packing gland 530. In this case, a spring may be incorporated into the packing gland 530 to prevent the V-packing 120 from reducing its sealing pressure due to stress relaxation at room temperature.

Figure 4 is a cross-sectional view of a modified shaft seal 200 according to embodiment 1. This modified shaft seal 200 differs from the shaft seal 100 shown in Figure 1 only in that it includes a spring 210. The other elements are common to the elements of the shaft seal 100, so the explanation for embodiment 1 will be used for those elements.

The packing gland 530 is fixed to the atmospheric end (left end in FIG. 4) 522 of the stuffing box 520 by bolts 534 that pass through the flange 533 parallel to the stem 510 (left-right in FIG. 4). The springs 210 are, for example, coil springs, and one spring is arranged for each bolt 534, coaxially surrounding the bolt 534. They are pressed against the flange 533 by the axial force of nuts 535 threaded onto the bolts 534.

Even if the axial stress of the V-packing 120 decreases due to stress relaxation at room temperature, such as creep deformation or wear, the packing gland 530 continues to apply axial pressure to the V-packing 120 due to the elasticity of the spring 210. Therefore, the axial pressure from the packing gland 530 further compresses the V-packing 120 in the axial direction, increasing the radial stress. This offsets the decrease in radial stress due to stress relaxation, and the sealing pressure of the V-packing 120 is maintained high.

The pressing ring 150 and the clamping ring 160 are located on the opposite side of the packing gland 530 with respect to the V-packing 120. In this case, the pressure PB of the pressing ring 150, which increases with the temperature drop, is weakened by friction between each V-ring 121 and its peripheries 510 and 110 before reaching the packing gland 530. Therefore, it is unlikely that the spring 210 will be unable to withstand the pressure PB from the pressing ring 150 and will further compress, and the packing gland 530 can return a sufficiently strong reaction force against the pressure PB. Therefore, each V-ring 121 is sufficiently compressed by this reaction force and the pressure PB from the pressing ring 150, so that a sufficiently high sealing pressure is maintained.
Second Embodiment

Fig. 5(a) is a cross-sectional view of a shaft seal 300 according to a second embodiment of the present invention, Fig. 5(b) is a partially enlarged view of the packing 120 shown in Fig. 5(a) and its vicinity (the area surrounded by the dashed line in Fig. 5(a)), and Fig. 6 is an exploded view of supports 350, 360, and 370. The shaft seal 300 differs from the shaft seal 100 shown in Figs. 1 and 2 only in the configuration of the supports. The other elements are common to the elements of the shaft seal 100, so the explanation of the first embodiment will be used for those elements.
-Support-

The support is composed of a male adapter 370, a pressing ring 350, and a stationary ring 360. The male adapter 370 is a circular member made of a metal such as bronze or aluminum bronze, and coaxially surrounds the stem 510 adjacent to the fluid side (right side in Figure 5) of the V-packing 120. The male adapter 370 has an inner diameter slightly larger than the diameter of the stem 510 and an outer diameter slightly smaller than the diameter of the inner circumferential surface 523 of the stuffing box 520, so that sliding resistance against the stem 510 is sufficiently low and it can slide along the stem 510. The pressing ring 350 is a circular member made of a fluororesin such as PTFE, and coaxially surrounds the stem 510 adjacent to the fluid side (right side in Figure 5) of the male adapter 370. The inner diameter of the pressure ring 350 is larger than the diameter of the stem 510, so it does not provide sliding resistance to the stem 510, while its outer diameter is smaller than the diameter of the inner circumferential surface 523 of the stuffing box 520, so it can move along the stem 510. The immobile ring 360 is a circular member made of a metal such as bronze or aluminum bronze, and is adjacent to the fluid side (right side in Figure 5) of the pressure ring 350, coaxially surrounding the stem 510. The inner diameter of the immobile ring 360 is slightly larger than the diameter of the stem 510, so it provides sufficiently low sliding resistance to the stem 510, while its outer diameter is equal to or greater than the diameter of the inner circumferential surface 523 of the stuffing box 520, so it is fixed to the inner circumferential surface 523 by press-fitting.

A series of annular protrusions 371 protrude from the annular surface of the male adapter 370 on the atmosphere side (left side in Figure 5), i.e., the side that comes into contact with the V-packing 120. The protrusions 371 are fitted between the lips 122, 123 of the V-ring 121 located closest to the fluid (right side in Figure 5). Because the male adapter 370 is more rigid than the V-ring 121, it transmits the axial pressure from the rib 524 of the stuffing box 520 associated with the connection between the stuffing box 520 and the packing gland 530 evenly to the entire circumference of the V-ring 121, particularly to both lips 122, 123, while suppressing excessive deformation and extrusion of the lips 122, 123 due to friction with the stem 510 or fluid pressure.

A tapered inner peripheral surface 352 is located on the inner periphery of the pressure ring 350 on the fluid side (right side in Figure 5). The tapered inner peripheral surface 352 is inclined so that the diameter increases from the center of the pressure ring 350 in the axial direction toward the fluid-side end (right end in Figure 5). The tapered inner peripheral surface 352 contacts the stationary ring 360 (see below for details). As a result, the pressure ring 350 is supported by the inner peripheral surface 523 and ribs 524 of the stuffing box 520 via the stationary ring 360.

The stationary ring 360 includes a tapered outer peripheral surface 361 on the side that contacts the pressure ring 350, i.e., the atmosphere side (left side in FIG. 1 ). The tapered outer peripheral surface 361 is inclined so that its diameter increases from the atmosphere side end (left end in FIG. 5 ) of the stationary ring 360 toward the center in the axial direction. The minimum diameter of the tapered outer peripheral surface 361, i.e., the inner diameter at the atmosphere side end (left end in FIG. 5 ) of the stationary ring 360, is smaller than the maximum diameter of the tapered inner peripheral surface 352 of the pressure ring 350, i.e., the outer diameter at the fluid side end (right end in FIG. 5 ) of the pressure ring 350. Therefore, the tapered outer peripheral surface 361 contacts the tapered inner peripheral surface 352. Meanwhile, the annular surface 362 on the fluid side (right side in FIG. 5 ) of the stationary ring 360 is in close contact with the annular surface 525 on the atmosphere side (left side in FIG. 5 ) of the rib 524 of the stuffing box 520. As a result, the pressing ring 350 is supported by the inner peripheral surface 523 and the ribs 524 of the stuffing box 520 via the stationary ring 360 .
[Sealing action of shaft seal]

Similar to the supports 150 and 160 of the first embodiment, the supports 350, 360, and 370 receive axial pressure (to the right in FIG. 5 ) from the packing gland 530 through the V-packing 120, transmit it to the inner circumferential surface 523 and ribs 524 of the stuffing box 520, and return a strong axial (to the left in FIG. 5 ) reaction force from them to the V-packing 120. As a result, the V-packing 120 is compressed in the axial direction (left-right direction in FIG. 5 ) and expands in the radial direction (up-down direction in FIG. 5 ), causing the lips 122 and 123 of each V-ring 121 to tightly contact the outer circumferential surface 511 of the stem 510 and the inner circumferential surface 523 of the stuffing box 520. In this way, the gap between the stem 510 and the ribs 524 of the stuffing box 520 is sealed.
[Preventive effect against reduction in sealing pressure due to low temperatures]

7A is a schematic diagram showing the force transmitted between the supports 350, 360, and 370 and then to the V-ring 121 as the temperature drops. Like the V-ring 121, the pressing ring 350 is made of fluororesin, and therefore has a thermal shrinkage rate that is at least as high as that of the V-ring 121. In contrast, the stationary ring 360 and the male adapter 370 are both made of metal, and therefore have a thermal shrinkage rate that is lower than that of either the V-ring 121 or the pressing ring 350, specifically only about 1/10 of that of either the V-ring 121 or the pressing ring 350. Therefore, in the region where the tapered inner peripheral surface 352 of the pressing ring 350 contacts the tapered outer peripheral surface 361 of the stationary ring 360 (hereinafter referred to as the "clamping region"), thermal contraction caused by the temperature drop causes the tapered inner peripheral surface 352 to clamp the tapered outer peripheral surface 361. In particular, the stress SS in the inner circumferential direction within the pressing ring 350 is transmitted from the tapered inner peripheral surface 352 to the tapered outer peripheral surface 361 as pressure PA. The tapered inner peripheral surface 352 and tapered outer peripheral surface 361 are inclined so that their diameters narrow as they approach the V ring 121 (toward the left in Figure 7A), and therefore both the pressure PA and the corresponding reaction force PR from the tapered outer peripheral surface 361 are inclined relative to the radial direction (vertical direction in Figure 7A). Therefore, axial stress (leftward in Figure 7A) is generated within the pressing ring 350, causing the pressing ring 350 to press the male adapter 370 axially (leftward in Figure 7A). This pressure is transmitted from the convex portion 371 of the male adapter 370 to the lips 122, 123 of the V ring 121, which are located closest to the fluid (rightmost in Figure 7A), as axial pressure PB (leftward in Figure 7A).

Meanwhile, the pressure exerted by the tapered inner peripheral surface 352 on the tapered outer peripheral surface 361 generates axial stress within the stationary ring 360 (to the right in Figure 7(a)). This stress is transmitted from the stationary ring 360 to the rib 524 of the stuffing box 520 as axial pressure. However, because both the stationary ring 360 and the rib 524 are sufficiently rigid, they do not substantially deform or displace. Therefore, the pressure PB of the male adapter 370 on the V-ring 121 is sufficiently high. This pressure PB is transmitted to the female adapter 140 through each V-ring 121. Because the female adapter 140 does not substantially displace or deform under the pressure PB, each V-ring 121 is displaced toward the female adapter 140 (to the left in Figure 7(a)) by the pressure PB, and is further compressed axially by the reaction force from the female adapter 140 against the pressure PB.

Figure 7(b) is a schematic diagram showing the displacement of the pressure ring 350 and the deformation of the V ring 121 due to thermal contraction. The axial displacement of the V ring 121 is greater the closer the V ring 121 is to the male adapter 370 (located to the right in Figure 7(b)). In response to the displacement of the V ring 121, both the male adapter 370 and the pressure ring 350 displace toward the V packing 120 (to the left in Figure 7(b)). At this time, due to the inclination of the tapered inner peripheral surface 352 and the tapered outer peripheral surface 361, the inner diameter of the pressure ring 350 contracts in response to the displacement of the pressure ring 350. Therefore, the clamping region is maintained, i.e., the tapered inner peripheral surface 352 continues to contact the tapered outer peripheral surface 361. Therefore, the pressure ring 350 continues to receive a reaction force PR against the pressure PA from the stationary ring 360, and the male adapter 370 maintains pressure PB on the V packing 120. As a result, the axial compression of each V-ring 121 is sufficiently large.

Each V-ring 121 increases its radial stress (vertical direction in FIG. 7B) as it is compressed in the axial direction, offsetting the decrease in radial stress that occurs with lower temperatures. Furthermore, the lips 122, 123 of each V-ring 121 are pushed apart by the convex portion 371 of the male adapter 370 or the heel 124 of the V-ring 121 on the fluid side (right side in FIG. 7B). Therefore, regardless of lower temperatures, the inner lip 122 maintains a sufficiently high sealing pressure PI against the outer peripheral surface 511 of the stem 510, and the outer lip 123 maintains a sufficiently high sealing pressure PO against the inner peripheral surface 523 of the stuffing box 520.
[Advantages of Embodiment 2]

In the shaft seal 300, the pressure ring 350, together with the male adapter 370, is fitted onto the lip side of the V-packing 120 and is supported by the inner surface 523 and rib 524 of the stuffing box 520 via the stationary ring 360. Therefore, at room temperature, the pressure ring 350 and stationary ring 360 transmit the axial pressure from the stuffing box 520, which occurs when the stuffing box 520 and the packing gland 530 join together, to the V-packing 120 essentially as is. This compresses the V-packing 120 axially, increasing the sealing pressure to the desired level. Meanwhile, at low temperatures, the pressure ring 350 tightens the stationary ring 360 due to thermal contraction, and the corresponding reaction force PR from the stationary ring 360 causes the pressure ring 350 to press the male adapter 370 axially. This pressure PB further compresses the V-packing 120 in the axial direction, increasing radial stress, so the sealing pressure of the V-packing 120 is maintained sufficiently high regardless of low temperatures. In this way, the shaft seal 300 can maintain the sealing pressure of the V-packing 120 sufficiently high at low temperatures without excessively increasing it at room temperature.

Like the V-packing 120, the pressure ring 350 is also made of fluororesin, so the thermal shrinkage rate of the pressure ring 350 is equal to or greater than that of the V-packing 120. As a result, as the thermal shrinkage of the V-packing 120 increases significantly, the pressure PB associated with the thermal shrinkage of the pressure ring 350 also increases. This effectively prevents a decrease in the sealing pressure of the V-packing 120 due to lower temperatures.

Since the stationary ring 360 is made of metal, it has high rigidity against the pressure PA that the tapered outer peripheral surface 361 receives from the tapered inner peripheral surface 352 of the pressing ring 350, and does not substantially deform even when subjected to that pressure PA. Therefore, the tapered inner peripheral surface 352 can slide smoothly along the tapered outer peripheral surface 361, efficiently converting the pressure PA from the tapered inner peripheral surface 352 into axial pressure PB on the V-packing 120.

The pressing ring 350 and the stationary ring 360 are located on the lip 122, 123 side of each V-ring 121. Therefore, the axial pressure PB of the pressing ring 350, which increases with the temperature, causes the lips 122, 123 of the V-ring 121 to open further, pressing them more firmly against the outer surface 511 of the stem 510 and the inner surface 523 of the stuffing box 520. As a result, the sealing performance of the V-packing 120 at low temperatures is further improved.

The pressing ring 350 and the stationary ring 360 are located on the opposite side of the packing gland 530 with respect to the V-packing 120. In this case, the pressure P B of the pressing ring 350, which increases with the temperature drop, is weakened by friction between each V-ring 121 and its surroundings 510, 110 before reaching the packing gland 530. Therefore, it is unlikely that the bolt 534 will be unable to withstand the pressure P B from the pressing ring 350 and loosen, and the packing gland 530 can return a sufficiently strong reaction force to the pressure P B. Therefore, each V-ring 121 is sufficiently compressed by this reaction force and the pressure P B from the pressing ring 350, so that a sufficiently high sealing pressure is maintained.
[Modification]

Embodiment 2 can also be modified in the same way as embodiment 1. Furthermore, if the rigidity of the pressing ring 350 is sufficiently high, the male adapter 370 can be removed, and instead the end of the pressing ring 350 on the atmosphere side (the left end in Figure 5) can be in direct contact with the V-ring 121 closest to the fluid side (the rightmost end in Figure 5).

100 Shaft seal 120 Packing 121 V-ring 122 Inner lip 123 Outer lip 124 Heel 140 Female adapter 141 Atmosphere-side annular surface of female adapter 142 Fluid-side concave portion of female adapter 150 Press ring 151 Atmosphere-side convex portion of press ring 152 Tapered outer surface of press ring 160 Clamp ring 161 Tapered inner surface of clamp ring 162 Fluid-side annular surface of clamp ring 510 Stem 511 Outer surface of stem 520 Stuffing box 521 Fluid-side end of stuffing box 522 Atmosphere-side end of stuffing box 523 Inner surface of stuffing box 524 Rib 525 Atmosphere-side annular surface of rib 530 Packing gland 531 Fluid side end of packing gland 532 Atmospheric side end of packing gland 533 Flange 534 Bolt 535 Nut 540 Flow path 550 Casing 551 Casing opening 560 Casing exterior space

Claims (4)

A shaft seal for sealing a gap between a movable shaft of a fluid device and a stuffing box,
a resin packing that is filled into the gap by axial pressure from a packing gland;
a support member which is an annular structure surrounding the movable shaft and has one axial side in contact with one end of the packing in the axial direction and the other side in contact with the stuffing box or the packing gland,
The support body has at least a portion in the axial direction.
The outer circumferential side has a higher thermal shrinkage rate than the inner circumferential side, and includes a tightening region in which the outer circumferential side tightens the inner circumferential side as the temperature drops;
The support body is configured such that the contact surface between the outer circumferential side and the inner circumferential side in the clamping region is inclined relative to the radial direction, so that the force with which the outer circumferential side clamps the inner circumferential side is transmitted from the clamping region to the packing as axial pressure. A shaft seal for sealing a gap between a movable shaft of a fluid device and a stuffing box,
a resin packing that is filled into the gap by axial pressure from a packing gland;
a support member which is an annular structure surrounding the movable shaft and has one axial side in contact with one end of the packing in the axial direction and the other side in contact with the stuffing box or the packing gland;
Equipped with
The support is
a clamping region located at least in a part in the axial direction, the clamping region having a higher thermal shrinkage rate on the outer circumferential side than on the inner circumferential side, and the outer circumferential side clamping the inner circumferential side as the temperature drops;
a clamping ring which is an annular member surrounding the movable shaft and includes, on a side closer to the packing in the axial direction, a tapered inner circumferential surface which is inclined so that the diameter narrows from the end toward the center in the axial direction;
a pressing ring which is an annular member surrounding the movable shaft, has a thermal shrinkage rate lower than that of the clamping ring, and includes, on a side farther from the packing in the axial direction, a tapered outer peripheral surface which is inclined so that the diameter narrows from the center toward the end in the axial direction;
The support is
In the clamping region, the tapered inner peripheral surface contacts the tapered outer peripheral surface,
The force with which the outer circumferential side clamps the inner circumferential side is transmitted from the clamped area to the packing as axial pressure.
It is configured as follows:
A shaft seal characterized by: A shaft seal for sealing a gap between a movable shaft of a fluid device and a stuffing box,
a resin packing that is filled into the gap by axial pressure from a packing gland;
a support member which is an annular structure surrounding the movable shaft and has one axial side in contact with one end of the packing in the axial direction and the other side in contact with the stuffing box or the packing gland;
Equipped with
The support is
a clamping region located at least in a part in the axial direction, the clamping region having a higher thermal shrinkage rate on the outer circumferential side than on the inner circumferential side, and the outer circumferential side clamping the inner circumferential side as the temperature drops;
a pressing ring which is an annular member surrounding the movable shaft and includes, on a side farther from the packing in the axial direction, a tapered inner circumferential surface which is inclined so that the diameter increases from the center toward the end in the axial direction;
a stationary ring which is an annular member surrounding the movable shaft, has a thermal shrinkage rate lower than that of the pressing ring, and includes, on a side closer to the packing in the axial direction, a tapered outer peripheral surface which is inclined so that the diameter increases from the end toward the center in the axial direction;
The support is
In the clamping region, the tapered inner peripheral surface contacts the tapered outer peripheral surface,
The force with which the outer circumferential side clamps the inner circumferential side is transmitted from the clamped area to the packing as axial pressure.
It is configured as follows:
A shaft seal characterized by: The packing is a V-packing,
The support is
a male adapter that contacts one end of the packing in the axial direction;
The shaft seal according to claim 2 or 3.