JP5693045B2 - Valve device with integrated mixer element - Google Patents

Description

  The present invention relates to a valve device that discharges a liquid medium supplied through a fluid passage and includes a heating element that heats a wall of the fluid passage.

  In modern manufacturing processes, it is often necessary to deposit a minimum amount of media on a workpiece or product. Such media may include oils, greases or adhesives in the field of mechanics, cleaning or sterilizing means in the medical or pharmaceutical field, paints, fluxes, coatings in the electronics industry, etc. Food contents may also be included.

  In weighing technology, two different approaches have been proposed for the ejection of a minimum amount of media. On the one hand, a so-called injection valve is used to apply a drop or stream of medium to the workpiece. In this case, high pressure is used so that the desired amount of media is fired onto the workpiece through the outlet or nozzle of the valve head. On the other hand, a metering valve with a metering needle is known, but in this case a relatively low pressure is used because the medium is simply pushed out of the tip of the needle rather than being fired by the injection method. In this case, the needle tip is brought close to the workpiece so that the medium flowing out of the needle is applied directly to the workpiece.

  However, high-viscosity fluids such as one-part epoxy resin, silicone, and other adhesives, as well as some greases and oils, that flow through the valve's supply pipes, typically adhere to the wall surface Indicates. In these surface regions, the flow rate is much slower than the center of the tube. Near the wall of the tube, the flow rate can even be nearly zero.

  Thus, for example, in a tubular fluid passage of a discharge valve, the fluid to be discharged has the highest flow velocity at the center of the fluid passage diameter and almost zero velocity at the fluid passage wall (s) to which the fluid layer adheres. Have This effect leads to several drawbacks. First, if a low or stable fluid viscosity is desired to obtain proper discharge conditions, heat energy must be put into the liquid. This can be done by an electrical heating element placed close to the fluid passage so as to heat the metal tube and the adhering boundary layer of the fluid adhering thereto to a regulated temperature. However, since the liquid portion in this surface region does not flow or flows very slowly, the time affected by the temperature is very long. This can increase the viscosity of thermoset adhesives or premixed two-part adhesives that have a limited pot life (the useful life of the adhesive that has been mixed and then stored in the bucket). Second, the adhesive surface layer on the fluid passage wall of the valve acts as a thermal insulation for the fluid flowing in the center of the fluid passage. If the fluid flow rate is high (eg, at high discharge or jet frequencies), this insulation will not be able to heat the material passing through the center of the fluid path fast enough, so this insulation will cause temperature non-uniformity of the discharge fluid Can cause. Thirdly, fluids containing dispersed solid particles, such as silicone containing phosphor fillers for encapsulating light emitting diodes (LEDs), are due to the long residence time of the fluid in the surface region of the fluid path, The sedimentation of the filler is shown.

  It is an object of the present invention to improve heat transfer from the heating element to the liquid in the fluid passage so as to increase the uniformity of the radial temperature distribution.

  This object is achieved by the features of claim 1.

  Thus, the proposed mixing element introduces a radial flow component to improve the radial mixing of the fluid in the valve fluid passage. Thereby, a uniform radial temperature distribution can be obtained even with a very high viscosity fluid. Furthermore, mixing allows fluid to move to any area of the fluid passage leaving only a very thin surface area on the wall of the fluid passage. Since all the fluid is in contact with the heated wall, an improvement in heat transfer is obtained, resulting in a high throughput with little temperature difference within the fluid. Furthermore, the mixing element helps prevent particle settling because the cross-section of the fluid passage can be reduced, the fluid velocity can be increased, and the radial mixing effect helps stabilize the dispersion. Achieving improved particle dispersion is important for obtaining stable ejection results. Note that the cross section of the fluid passage need not be circular. This can have any non-circular shape, where the radial flow component described above is understood as a transverse or transverse flow component.

  According to an exemplary embodiment, the mixing element may comprise at least one stationary static mixer element having a predetermined obstacle to the fluid flow of the liquid medium. As a more specific example, the static mixer element may include at least one spiral mixer having at least one helical element.

  Further, the fluid passage may be defined by a metal tube. In this case, the metal tube can be heated by a heating element arranged nearby.

  The liquid medium can be, for example, an adhesive, grease, or oil. Of course, the present invention can be applied to other types of fluids.

  The discharge valve may comprise a piezoelectric drive that controls at least one nozzle.

  Next, the present invention will be described in more detail based on an embodiment with reference to the accompanying drawings.

The side sectional view of the discharge valve by an embodiment is shown. An example of a mixing element that can be used in the first embodiment is shown.

  Next, a first embodiment will be described based on a piezoelectric drive type discharge valve 20 as shown in a side sectional view of FIG.

  The discharge valve 20 includes a piezoelectric driving device 22. The piezoelectric driving device 22 may be composed of a piezo stack to which an electrical signal is supplied via the plug 10 and the connection cable. The movement of the piezoelectric driving device 22 can be controlled by an applied electrical signal. When this movement is transmitted to the rod 26, the rod 26 is moved up and down in the vertical direction of FIG. A sealing sphere 23, which can be made of resistive ceramic, is fixed to the lower end of the rod 26. When the sealing ball 23 is lifted, the liquid medium to be discharged can flow out of the discharge valve 20 through the nozzles of the nozzle plate 27.

  The medium to be discharged can be supplied via an inlet 25, which leads to a fluid passage in which a mixing element 29 is inserted. The fluid passage can be heated by a heating element 28 that can also be powered through the plug 10 and connecting cable.

  As shown in FIG. 1, the mixing element 29 can be arranged as a rod or tube with a static mixer element and incorporated into the fluid passage of the discharge valve 20, usually near the heating element 28. The static mixer element of the mixing element 29 is configured to allow radial mixing of the material flowing through the fluid passage of the discharge valve 20. Thereby, even when a fluid having a very high viscosity is used as the discharge material, the thickness of the laminar boundary layer can be reduced in order to obtain a more uniform radial temperature distribution.

  Further, the static mixer element of the mixing element 29 may be configured to force fluid from the surface area of the fluid path toward the center of the fluid path and vice versa. Thus, the fluid travels as plug flow through all areas of the fluid passage leaving only a very thin surface area on the walls of the fluid passage. As a result, the entire portion of the fluid to be discharged is brought into contact with the heated wall of the fluid passage, and a high throughput can be obtained without much temperature difference in the fluid due to improved heat transfer.

  In addition, the static mixer element of the mixing element 29 helps to prevent particle settling. This is achieved by reducing the cross section of the fluid passage. The fluid velocity increases and the radial mixing effect helps stabilize the dispersion. This leads to an improvement in particle dispersion, for example important for the uniformity of the spectral irradiance (ie when pouring the adhesive containing the phosphor converter into the LED) to obtain a stable ejection result.

  The improved heat transfer achieved by the mixing element 29 results in higher throughput of the discharge valve 20 at lower heater temperatures. Further, the risk of clogging of the discharge valve 20 due to early curing of the thermosetting adhesive is minimized, and sedimentation of fluid containing solid particles (eg, filler) at the discharge valve is reduced.

  In the following, some examples of mixing element structures that can be used in the discharge valve 20 of FIG. 1 will be described in more detail. It should be noted that the mixing element 29 may comprise an additional tube that is inserted into the liquid passage or may consist solely of a mixer element that is inserted directly into the liquid passage.

  A stationary or static mixer that can be used for the mixing element 29 serves to mix liquids, particularly high viscosity materials, and to contact different phases to facilitate heat and mass transfer. These are flow regulating inserts that can be incorporated into tubes, conduits, or containers such as the liquid passages of the discharge valve 20. The mixing element 29 or its mixer element does not move itself, but moves by creating a predetermined flow pattern and / or random movement using the pressure difference or kinetic and potential energy of the material being processed. It causes velocity differences in various parts of the material inside, and thus relative displacement. In the fluid, the static mixer element of the mixing element 29 serves to cause the various parts of the fluid or discharged material to be split, moved, sheared, rotated, accelerated, decelerated and / or recombined. Thus, static mixer elements are beneficial in that they do not require a direct motive force, drive motor, and electrical connection (s) to eliminate the need for mechanical stirrers and the like. The flow of material in the liquid passage can be induced by gravity, by pressure difference, or by using existing potential energy or kinetic energy. Thus, the small space requirement allows a compact design of the mixing element 29. Furthermore, the mounting is easy and quick, for example by simple replacement of a part of the tube of the fluid passage or by fixing the insert in the fluid passage.

  Static mixer elements are available in a number of different types, shapes, and geometric shapes made from a wide variety of materials. Thus, the mixing element 29 can be easily adapted to process requirements and process material characteristics. Physical properties such as flow behavior, particle size, mechanical strength, wear effects, such as food industry and pharmaceutical industry safety regulations can be taken into account by appropriate design of the mixer elements of the mixing element 29.

  Several different types of static mixer elements are available. In the following, two suitable types of such mixer elements will be described with reference to FIG.

  FIG. 2 shows a spiral mixer consisting of a heating element 29 or a cylindrical pipe with a long fluid passage, containing a plurality of helical elements 294 which are twisted 180 degrees alternately in the left-right direction perpendicular to the flow direction. Adjacent elements are provided with a 90 ° offset in the radial direction. Thus, the exit edge of a given element and the entrance edge of the next element are perpendicular to each other. A smooth helical surface directs the flow of material back to the pipe wall and back to the center by secondary vertices induced by twisting of the spiral form of the flow path. Additional velocity reversal and shunting results from shearing of the material along the tube cross section between adjacent elements. Systematic division of the flows and their recombination in another form enhance the mixing effect. In fluid or multiphase flows, in addition to excellent radial mixing, a relatively short residence time is ensured. The smooth and gently curved surface of the spiral element 294 provides very little pressure loss along the spiral mixer, while providing continuous and thorough mixing and radial temperature, speed, and composition gradients. Disappear.

  As a modification of the above spiral mixer, the individual helical elements can be inclined with respect to the tube axis and tapered along their length. This has the advantage that the gap between the mixer element and the tube wall is slightly increased so that there are no corners or contact points between them. Therefore, there is no dead zone and neither deposition nor clogging can occur. On the other hand, the cross-section of the flow path on the two sides of the mixer element continues to change along its length. Due to the tangential flow in the wall and the pressure difference between the two sides, a strong cross flow occurs between adjacent channels. These features improve mixing efficiency, reduce pressure loss with proper cross-sectional turbulence, and more uniform radial and tangential velocity fields. The higher the velocity and the greater the turbulence near the tube, the greater the heat transfer coefficient and the cleaner the surface. In addition to this self-cleaning action, the absence of corners facilitates cleaning of different materials. Therefore, in the spiral mixer thus improved, higher mixing efficiency per unit length of the mixer is obtained, and the risk of clogging is reduced.

  By using the mixer type in the mixing element 29 of the embodiment of FIG. 1, radial mixing of the discharge material in the fluid passage of the discharge valve 20 can be performed. Of course, depending on the type and size of the particular application, other static mixer types such as low pressure loss (LDP) or SMX mixers may also be used.

  Thus, it should be noted that the present invention is not limited to the specific embodiment of FIG. 1 and can be used with any valve device having a heated fluid passage or flow path for the material to be dispensed.

Claims (4)

A valve device (20) for discharging a liquid medium supplied via a fluid passage,
The valve device (20) includes a heating element (28) for heating the wall of the fluid passage,
Wherein is inserted into the fluid passage, and the liquid medium have at least one mixing element is configured (29) to introduce a radial flow component to the liquid medium when flowing the fluid passageway ,
The mixing element (29) comprises a stationary static mixer element (294) having a predetermined obstacle to the flow of liquid medium;
The static mixer element comprises at least one spiral mixer comprising at least one helical element (294);
The valve device characterized in that the at least one helical element (294) is inclined with respect to the axis of the fluid passage and is tapered along the length of the at least one helical element (294). . The valve device according to claim 1 , wherein the fluid passage is defined by a metal tube. The liquid medium, adhesives, grease, or a valve apparatus according to claim 1 or 2 which is an oil. The valve device according to any one of claims 1 to 3 , wherein the valve device (20) comprises a piezoelectric drive device (22) for controlling at least one nozzle of the valve device (20).

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