GB2418970A - Dispensing valve - Google Patents

Abstract

A dispensing valve has a resiliently deformable sleeve (35) mounted between a valve closure member (28) and a portion of the valve housing (10). The sleeve is located around a tubular actuating rod (72) connected to an actuating piston (70) which is movable by means of fluid pressure. The actuating rod (72) and the tubular sleeve (35) are both mounted around a valve actuating rod (38) connected to the valve closure member (28) and which is itself secured to a valve actuating piston (40) which also forms the cylinder for the actuating piston (70). By coordinating the movement of the actuating piston (70) and the valve actuating piston (40), a narrowed waisted portion (35w) of the tubular sleeve can be expanded radially outwardly by an enlarged head portion (72a) of the tubular rod (72) to reduce the effective diameter of a valve chamber (C). In this way the valve can be closed with the sleeve (35) in its expanded condition. The sleeve can then be allowed to contract radially inwardly when the valve is closed in order to apply a partial vacuum to the valve outlet (20) to prevent formation of drips.

Description

24 1 8970

DESCRIPTION

DISPENSING VALVE

The present invention relates to dispensing valves and in particular, but not exclusively, to precision dispensing valves for use with sensitive fluids.

When dispensing fluids, a precise shut-off is often not required as the occasional drip falling into the main body of the fluid often has no effect on the process. I lowever, this is not always the case as some processes require extremely accurate amounts of fluids to be dispensed and in such cases an unwanted drip can cause major problems.

Different fluids and conditions can cause different reasons for drips. For example, heat creates expansion in most fluids and trapped air/gas entrained in viscous fluids re-expands after pumping. In particular, when pumping viscous fluids the high pressure required causes the tiny pockets of air/gas normally entrained in the fluid during production to be compressed. As the quantity of entrained air/gas is very small it would normally have little effect on the process and since it is not able readily to re-expand, it does not create any significant safety issues. However, once the pressure has been removed, the air/gas does gradually overcome the resistance of the fluid to regain its original volume, which frequently leads to drips after the control valve has closed.

To prevent this situation, the control valve should ideally be situated as close as possible to the actual exit of the fluid, but often due to size and space limitations the valve has to be situated remotely and a hose and nozzle used to direct the fluid to the actual dispense point. Unfortunately, the large volume of fluid after the control valve expands as the air/gas expands and so causes drips.

To prevent the formation of such drips, a combination control valve with a "drawback" can be used which creates a partial vacuum between its seal area and the dispense point as it closes. As an alternative to this, a separate device to the control valve can be used to create a vacuum after the control valve has closed, but the sequence must be organized so that the "drawback" only operates after the control valve is closed. Under some circumstances the "drawback" device could even be made from a diaphragm which would avoid sliding surfaces, but if any serious back pressure is produced it could lead to rupture of the diaphragm.

All known combination control valves with "drawback" rely on sliding shafts passing through seals and bearings to form the valve seals. The further withdrawal of the shaft from the volume between the valve and the dispense point is used to create the vacuum for the "drawback". However, some materials are sensitive to the mechanical meshing of components within these conventional valves, which can lead to the alteration of their properties. I?or example, some materials such as UV paste ink (a viscous ink which is set by means of ultra-violet light) can even turn from a fluid into a solid and so block the valve or seize its components together.

It is an object of the present invention to provide a dispensing valve which creates a void on the downstream side of the seal to allow the fluid to expand into it to prevent drips forming at the dispense point.

In accordance with the present invention, a dispensing valve comprises a valve housing, a valve inlet, a valve outlet, a valve chamber, within the valve housing between the valve inlet and the valve outlet, a valve seat, a valve closure member displaceable into engagement with the valve seat in order to close the valve and displaceable away from the valve seat in order to open the valve, a resiliently deformable member exposed to the valve chamber, a support for the resiliently deformable member and means for displacing the support when the valve is closed to adjust the projection of the resiliently deformable member into the valve chamber and thereby control the effective volume of the valve chamber.

By using a resiliently deformable member which is in contact with the valve chamber, it is possible to adjust the effective volume of the chamber without using any sliding or intermeshing components which could cause alterations of the properties of sensitive fluids, as discussed above. However, by providing a support for the resiliently deformable member, it can be ensured that high fluid pressures within the valve chamber can be tolerated.

Preferably, the support for the resiliently deformable member is always in supporting contact with the resiliently deformable member.

More preferably, the support for the resiliently deformable member is substantially rigid.

Conveniently, the resiliently deformable member is tubular and displacement of the support changes the radial dimensions of the resiliently deformable member.

Preferably, one end of the tubular resiliently deformable member is attached to the valve closure member and the opposite end is fixed with respect to the valve housing.

By coordinating the displacement of the support with respect to the position of the valve closure member, it is possible to expand the tubular support radially outwardly while the valve is closed, thereby reducing the effective volume of the valve chamber. The valve can then re- open to allow fluid to flow through the valve and then closed with the tubular member still in the expanded state. Once the valve is closed, the support can then be displaced to allow the tubular member to retract inwardly, thereby increasing the effective volume of the valve chamber and applying a partial vacuum to the valve outlet, which prevents the formation of drips.

Preferably, the support for the tubular resiliently deformable member comprises an elongate member located within the resiliently deformable member and which is slidably disposed with respect to the valve housing.

The valve preferably further comprises biassing means acting between the valve closure member and the elongate member which urge the elongate member to a position in which the portion of the tubular resiliently deformable member is displaced outwardly into the valve chamber.

Preferably, the support comprises a portion which is engageable with a 1 S portion of the resiliently deformable member of smaller diameter, in order to expand the resiliently deformable member radially outwardly.

Preferably, the elongate member comprises an enlarged portion.

The elongate member is preferably connected to an actuating piston which is displaceable by means of fluid pressure.

Preferably, the valve further comprises a valve actuating rod connected to the valve closure member, the rod being connected to a valve actuating piston which is displaceable within the housing by means of fluid pressure, the valve actuating rod passing through the elongate member and through the piston to which the elongate member is connected.

Preferably, biassing means extend between the valve housing and the valve actuating piston for urging the valve towards the closed condition.

Conveniently, the piston to which the elongate support members connect is slidably disposed in the valve actuating piston.

Preferably, the valve comprises a first inlet in the housing for ingress of pressurised fluid for displacing the valve actuating piston in a closing direction and restrictor means for additionally applying said pressurised fluid to the other piston at a restricted flow rate.

] O Preferably, the restrictor means a bore passing through a wal] of the valve actuating piston.

By way of example only, specific embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Fig. I is a longitudinal cross-section through a first embodiment of valve in accordance with the present invention, shown in a first, fully closed condition; Fig. 2 is a longitudinal cross-section of the valve of Fig. 1 shown in an intermediate condition just after, or just before, the condition shown in Fig. 1; Fig. 3 is a longitudinal cross- section of the valve of Fig. 1, shown in a fully open condition; Fig. 4 is a longitudinal cross-section through a second embodiment of valve in accordance with the present invention; Fig. 5 is a longitudinal cross- section through a third embodiment of valve in accordance with the present invention; and Fig. 6 is a longitudinal cross-section through a fourth embodiment of valve in accordance with the present invention.

Referring to Figs. 1 to 3, a first embodiment of valve comprises a valve housing formed from a valve chamber housing 10 and an actuator housing 12, which are separated by a support plate 14, the two housings and the support plate being secured together by a plurality of bolts 16, only one of which is visible in the figures.

The valve chamber housing defines a valve chamber C and has a fluid inlet port 18 at one end and a fluid outlet port 20 formed in its side wall, each of the ports screw threadedly receiving a respective nozzle 22, 24 for connection to a fluid conduit (not shown). The fluid inlet port 18 is also formed into a frusto-conical valve seat 26 with which a valve closure member 28 is releasably sealingly engagable. A filter screen 29 is also retained between the fluid inlet port 18 and the nozzle 22.

T he valve closure member 28 comprises an elastomeric frusto-conical valve cap 30 which is carried on a metal support 32. The face of the metal support remote from the valve cap 30 is provided with an upstanding peripheral flange 34 which receives one end of a tubular elastomeric sleeve 35 and a tubular sleeve support 36, to be described in m. ore detail hereafter.

The valve closure member 28 and sleeve support 36 are threadedly engaged with a threaded end of an actuator rod 38, the opposite end of which is secured to a main actuator piston 40 which is slidably disposed within the actuator housing 12.

The actuator piston 40 is provided with an upstanding peripheral tubular flange 42 and is sealingly slidable within the actuator housing by means of a tubular main piston bearing 44 which is secured to the main piston by means of six bolts 46 spaced equally around the periphery of the piston. A tubular spring locating boss 48 is sealingly secured to the face ol'the main piston opposite to the peripheral tubular flange 42 by means of six cap head screws 50. One end of a helical compression spring 52 is located over the locating boss 48 and the opposite end of the spring bears against an outer end wall 54 of the actuator housing 12. The spring 52 urges the main piston 40 in the closing direction of the valve member 28 (i.e. to the left as illustrated in Figs 1 to 3). The main piston 40 may be further urged in the closing direction of the valve by application of compressed air to a first air inlet port 56 located in the outer end wall 54 of the actuator housing and may be urged in the opposite direction by application of compressed air to a second air inlet port 58 located in a side wall of the actuator housing.

The main piston is movable between a first extreme position, shown in Fig. 1, which corresponds to a closed condition of the valve and in which the peripheral flange 42 of the piston is located adjacent to an inner wall 60 of the actuator housing, and a second extreme position, shown in Fig. 3, which corresponds to an open condition of the valve and in which the main piston 40 is displaced rightwards (as shown in Fig. 3) against the restoring force of the coil spring 52.

The peripheral tubular flange 42 of the main piston 40 also forms the cylinder wall for a secondary piston 70. A tubular displacement rod 72 is secured to the secondary piston by means of four cap head screws 74 and is slidably mounted around the actuator rod 38. The Alar displacement rod 72 also passes sealingly through a tubular support and bearing collar 76 which forms a bearing for the = displacement rod 72 and a support _or the end of the tubular elastomeric sleeve 35 remote from the valve closure member 28.

The internal bore of the portion 78 of the displacement rod 72 remote from the secondary piston 70 is of an enlarged diameter and receives a further helical compression spring 80 which extends between a first tubular spring guide 82 in contact with the inner face of the tubular sleeve support 36 and a second tubular spring guide 84 in contact with shoulder 86 formed at the inner end of the enlarged bore portion 78. The end 72a of the displacement rod 72 remote from the secondary piston 70 is also of increased external diameter, corresponding to the inner diameter of the tubular sleeve support 36 within which it is slidably received.

The secondary piston 70 is urged by the second compression spring 80 in a direction away from the valve closure member 28. The secondary piston may be further urged in the same direction by application of compressed air to the second air inlet port 58 located in the side wall of the tubular housing. Conversely, the secondary piston may be urged in the opposite direction by application of compressed air to the first air inlet port 56 located in the outer end wall 54 of the actuator housing via a connecting bore 88 drilled through the main piston 40, which forms a restriction for the application of compressed air pressure to the secondary piston 70.

The elastomeric sleeve 35 is generally tubular and is formed from a tough, resiliently deformable material such as polyurethane. It comprises an inwardly directed peripheral securing rib 35a, 35b located at each of its ends, for engagement with the tubular sleeve support 36 and the support and bearing collar 76 respectively.

The end 35' of the sleeve 35 is of increased external diameter, corresponding to the internal diameter of the peripheral flange 34 of the metal support 32 of the valve closure member 28 and the central part of the sleeve is formed into a narrowed, waisted portion 35w. The resilient sleeve is therefore supported by the rigid sleeve support at all times, which enables the sleeve to withstand high pressures within the valve chamber C without rupturing.

The above valve operates in the following manner.

Referring firstly to Fig. 1, the valve is shown in the fully-closed position with high pressure fluid being supplied to the valve inlet 18 and with air pressure supplied to the first air inlet port 56. The combination of the air pressure applied to inlet port 56 and the force applied by the first helical spring 52, both to the main piston 40, urges the valve closure member 28 into sealing engagement with the frusto-conical valve seat 26.

In order to open the valve, the air pressure is removed from the first air inlet port 56 and is instead applied to the second air inlet port 58. This causes the secondary piston 70 and the displacement rod 72 to be displaced away from the valve inlet 18 (to the right as shown in Fig. 2), in which they are assisted by the second helical compression spring 80. The secondary piston 70 moves away from the valve inlet until, as illustrated in Fig. 2, it abuts the main piston 40. The main piston 40 is held in position, with the valve closure member 28 engaging the valve seat 26 by means of the first compression spring 52.

As the displacement rod 72 is displaced in this way, its enlarged head portion 72a begins to withdraw from the tubular sleeve support 36 and engages the narrowed waist 35w of the tubular elastomeric sleeve and displaces the sleeve radially outwardly, thereby reducing the effective volume of the valve chamber C. Once the secondary piston 70 engages the primary piston 40, further application of air pressure to the second air inlet port 58 causes the main piston 40 and secondary piston 70 to be displaced away from the valve inlet 18 against the restoring force of the first helical spring 52, until the spring locating boss 48 engages the wall of the actuator housing 12, as illustrated in Fig. 3. As shown in Fig. 3, this movement of the main piston 40 withdraws the valve closure member 28 out of engagement with the valve seat 26 and allows fluid to flow through the fluid inlet port 18, into the valve chamber C and out through the fluid outlet port 20.

In order to close the valve, the air pressure is removed from the second air inlet port 58 and is applied to the first air inlet port 56. The application of air pressure to the first air inlet port 56, in combination with the force applied by the first helical spring 52 causes the main piston 40 to be displaced towards the valve inlet 18 until the valve closure member 28 sealingly engages the frusto-conical valve seat 26.

At this stage, the secondary piston 70 remains in contact with the main piston 40, since the air pressure applied to the first air inlet port 56 must pass through the restriction formed by bore 88 through the main piston 40 before it is applied to the secondary piston 70. The valve is at this stage in the configuration shown in Fig. 2, in which the valve is closed but the valve chamber has a reduced volume due to the outwardly expanded elastomeric sleeve 35.

Continued application of air pressure to the first air inlet 56 eventually causes the secondary piston 7() to be displaced away from the main piston 40, towards the fluid inlet 18, against the resisting force of the second helical spring 80 to the position shown in Fig. 1. This in turn causes the enlarged head portion of the tubular displacement rod to move away from the narrowed waist portion 35w of the tubular elastomeric sleeve, which thereby resumes its normal diameter and increases the effective volume of the valve chamber C, thereby applying a partial vacuum to the outlet port 20 of the valve. Thus, any fluid in communication with the valve outlet 20 will be subjected to this partial vacuum, and will thereby be drawn back towards the valve, thereby preventing the formation of drips.

Further embodiments of the present invention are shown in Figs 4 to 6. These are variations of the first embodiment and the variations relate to the connections made to the outlet port 20. The construction and operation of the further embodiments are otherwise identical to the first embodiment.

The second embodiment of the present invention is illustrated in Fig. 4. This embodiment is virtually identical to the first embodiment, the only difference being the replacement of the nozzle 24 with an extended outlet nozzle 24'. This construction has the advantage that the partial vacuum created within the valve pulls the fluid back inside the extended outlet nozzle, where a meniscus forms. As the fluid re-expands the fluid is pushed further back down the nozzle but not far enough for it to break the meniscus to form a drip.

The third embodiment, illustrated in Fig. 5, is again virtually identical to the f rst embodiment and again only differs in the replacement of the outlet nozzle 24 with a spring-loaded non-drip nozzle 24" connected to the outlet port 20. Such spring-loaded non-drip nozzles are relatively common and comprise a frusto-conical valve closure member 100 which is engageable with a frusto-conical annular valve seat] 02 formed at the upper end of a cylindrical housing 104. The valve closure member 100 is connected to a longitudinally-extending shaft 106 carrying an annular collar 108 by means of which a helical compression spring] 10 urges the valve closure member l 00 into sealing engagement with the valve seat 102 (as shown at "id" in Fig. 5).

Such nozzles are normally of limited use, since as the fluid within the nozzle starts to expand it pushes the valve closure member off the valve seat l 02, thereby allowing the nozzle to drip. However, when used with a valve in accordance with the present invention, as described, as there is no pressure created by fluid expansion there is no reason for the nozzle to drip.

The fourth embodiment of the present invention is virtually identical to the third embodiment, except that the non-drip valve is situated remotely from the outlet port 20, to which it is connected by means of a hose 1 12. If the valve did not have the "draw-back" created by the partial vacuum, the fluid trapped in the hose between the valve and the non-drip nozzle would continue to re-expand after the controller was closed, which would eventually result in drips from the outlet nozzle 24".

The invention is not restricted to the details of the foregoing embodiments.

Claims (16)

< ,' ''(. I CLAIMS

1. A dispensing valve comprising a valve housing, a valve inlet, a valve outlet, a valve chamber, within the valve housing between the valve inlet and the valve outlet, a valve seat, a valve closure member displaceable into engagement with the valve seat in order to close the valve and displaceable away from the valve seat in order to open the valve, a resiliently deformable member exposed to the valve chamber, a support for the resiliently deformable member and means for displacing the support when the valve is closed to adjust the projection of the resiliently deformable member into the valve chamber and thereby control the effective volume of the valve chamber.

2. A dispensing valve as claimed in claim 1, wherein the support for the resiliently deformable member is always in supporting contact with the resiliently deformable member.

3. A dispensing valve as claimed in claim I or claim 2, wherein the support for the resiliently deformable member is substantially rigid.

4. A dispensing valve as claimed in any of claims 1 to 3, wherein the resiliently deformable member is tubular and displacement ofthe support changes the radial dimensions of the resiliently deformable member.

5. A dispensing valve as claimed in claim 4, wherein one end of the tubular resiliently deformable member is attached to the valve closure member and the opposite end is fiend with respect to the valve housing.

6. A dispensing valve as claimed in claim 4 or claim 5, wherein the support for the tubular resiliently deformable member comprises an elongate member located within the resiliently deformable member and which is slidably disposed with respect to the valve housing.

7. A dispensing valve as claimed in claim 6, further comprising biassing means acting between the valve closure member and the elongate member which urge the elongate member to a position in which a portion of the tubular resiliently deformable member is displaced outwardly into the valve chamber.

8. A dispensing valve as claimed in claim 6 or claim 7, wherein the support comprises a portion which is engageable with a portion of the resiliently deformable member of smaller diameter to expand the resiliently deformable member radially l O outwardly.

9. A dispensing valve as claimed in claim 8, wherein the elongate member comprises an enlarged portion.

10. A dispensing valve as claimed in claim 9, wherein the elongate member is connected to an actuating piston which is displaceable by means of fluid pressure.

l I. A dispensing valve as claimed in claim 10, further comprising a valve actuating rod connected to the valve closure member, the rod being connected to a valve actuating piston which is displaceable within the housing by means of fluid pressure, the valve actuating rod passing through the elongate member and through the piston to which the elongate member is connected

l 2. A dispensing valve as claimed in claim 11, further comprising biassing means extending between the valve housing and the valve actuating piston for urging the valve towards the closed condition.

13. A dispensing valve as claimed in claim 12, wherein the piston to which the elongate support member is connected is slidable disposed in the valve actuating piston.

14. A dispensing valve as claimed in claim 13, comprising a first inlet in the housing for ingress of pressurized fluid for displacing the valve actuating piston in a closing direction and restrictor means for additionally applying said pressurized fluid to the other piston at a restricted flow rate.

15. A dispensing valve as claimed in claim 14, wherein the restrictor means comprises a bore passing through a wall of the valve actuating piston.

16. A dispensing valve substantially as herein described with reference to, and as illustrated in, the accompanying drawings.