GB2176575A

GB2176575A - Fluid control valve

Info

Publication number: GB2176575A
Application number: GB08514105A
Authority: GB
Inventors: John Few
Original assignee: Edward Barber and Co Ltd
Current assignee: Edward Barber and Co Ltd
Priority date: 1985-06-04
Filing date: 1985-06-04
Publication date: 1986-12-31
Also published as: GB8514105D0

Abstract

A valve for the control of fluid flow comprises a valve seat (5), a valve member (7,8) co-operating with the valve seat to open and close a flow path through the valve, which valve member comprises first (8) and second (7) mutually telescopically slideable elements defining a variable volume chamber and means defining a bleed path for fluid to said chamber, a valve operating mechanism (14,15,16) connected to the first element of the valve member and adapted to produce linear movement of the first element between valve opening and valve closed positions, the arrangement being such that in said valve closed position of the first element, the second element is constrained to close the valve seat and upon movement of the first element to the valve opening position the second element is constrained initially to move away from the valve seat but upon flow of liquid into said chamber through said bleed path the second element returns to close the valve seat, wherein the valve operating mechanism comprises an operating member (15) rotatable about the line of movement of the first element and rotary cam means (14) adapted to translate rotation of the operating member into said linear movement of the first element for opening and closing of the valve. <IMAGE>

Description

SPECIFICATION Fluid control valve The present invention relates to valves for the control of fluid flow such as valves for use as taps intended to present waste of liquids such as water.

British Patent specification No. 997599 describes a tap of this general kind having an operating handle linked to a valve member so that movement of the operating handle raises the valve member off a valve seat to allow flow of liquid through the tap. The valve member is in two parts and a part of the valve member lifted from the valve seat by operation of the handle moves back towards the valve seat at a predetermined rate even when the handle is held down in the valve opening position so that the flow of water through the tap ceases after a predetermined amount of water has been passed whether or not the operating lever is held in the open position.

Taps as described in specification 997599 have proved useful in practice and their design has changed relatively little. A common feature of the design of such taps is that the valve member is lifted by a cam finger carried by a rotatable shaft running crosswise of the line of movement of the valve member. Because such an arrangement necessarily produces forces acting on the valve member tending to cause it to tilt, it is necessary that the mechanism be made carefully and to fairly close tolerances and include means for guiding the valve member to prevent it tilting. Any tilting of the valve member when lifted will prevent the sealing plug of the valve member from making a good seal with the valve seat when it falls to close off the flow.

This has meant in practice that the whole of the operating mechanism of the tap needs to be made out of a material such as brass which can be shaped with precision and which resists corrosion. Also, the mechanism involved is generally complex and relatively expensive.

The present invention seeks to overcome the problems implicit in the use of the crosswise operating shaft and cam finger characteristic of all previous designs.

The present invention relates to a valve for the control of fluid flow comprising: a valve seat, a valve member co-operating with the valve seat to open and close a flow path through the valve, which valve member comprises first and second mutually telescopically slideable elements defining a variable volume chamber and means defining a bleed path for fluid to said chamber, a valve operating mechanism connected to the first element of the valve member and adapted to produce linear movement of the first element between valve opening and valve closed positions, the arrangement being such that in said valve closed position of the first element, the second element is constrained to close the valve seat and upon movement of the first element to the valve opening position the second element is constrained initially to move away from the valve seat but upon flow of liquid into said chamber through said bleed path the second element returns to close the valve seat, wherein the valve operating mechanism comprises an operating member rotatable about the line of movement of the first element and rotary cam means adapted to translate rotation of the operating member into said linear movement of the first element for opening and closing of the valve.

Preferably, the rotary cam means is provided by engaged male and female screw threads.

These are preferably multi-start quick acting threads. For instance, the threads may be such that the full range of movement of the first element is obtained by a quarter to a half turn of the operating member, preferably a quarter turn.

Preferably, a first of said threads is provided on the operating member and a second of the threads is provided on the first element.

Suitably, the male thread is provided on the operating member and the female thread on the first element.

The first element is preferably prevented from rotating, for instance by being keyed to the valve body or by having a periphery which is non-circular, for instance hexagonal, and which is received in a correspondingly shaped guideway in the valve body.

Preferably, said linear movement is substantially vertical in use and the return movement of the second element is downward. The return movement is preferably produced by gravity but additional means may be provided to urge the second element to move to close the valve seat.

The bleed path is preferably provided by an axially running groove in the surface of the second element. The second element is preferably in the nature of a plug moving as a piston in a cylinder defined by the first element.

By virtue of the nature of the valve mechanism and in particular the avoidance of forces tending to produce tilting of the valve member, there will generally be less wear between the first element and the guideway in the valve body. This in turn will lead to the second element continuing to return accurately to close the valve seat during heavy use of the tap, increasing the working life of the resilient washer.

The invention will be illustrated by the following description of a preferred embodiment with reference to the accompanying drawings in which Figure 1 is a side elevation of a valve according to the invention with one half shown in section, the valve being in the normal closed position; Figure 2 is a similar view of the same valve in the open position; and Figure 3 is a similar view of the same valve in the self-closed position.

As shown in Fig. 1, a valve according to the invention is provided by a tap having a casing 1 having an inlet 2 and an outler nozzle 3. The interior of the casing is divided into compartments by a partition 4 having an aperture into which is screwed a seat member 5 which is associated with a valve member for controlling liquid flow through the tap.

The valve member comprises a piston member 7 loosely and slideably accommodated in a cup-shaped chamber formed at one end of a first element 8 of the valve member. The piston comprises the second element of the valve member.

At the lower end of the piston 7 is provided a washer 6 for closing the valve seat 5.

Washer 6 is retained on the end of the piston 7 by a retaining cap 9.

As best seen in Fig. 3, piston 7 is provided with an axially running groove 10 for allowing liquid flow into and out of a variable volume chamber 11 defined betwen the upper end of the piston and the interior of the cup of the first element 8 of the valve member. The first element 8 of the valve member is tubular having an upper cylindrical reduced diameter portion and a lower enlarged diameter portion having an external hexagonal section, the portions being separated externally by an annular shoulder 12 and internally by a partition wall 13. The cup receiving the piston 7 is defined by the enlarged diameter portion of the first element 8. A female fast acting multi-start screw thread 14 is formed on the interior of the reduced diameter portion of the first element 8.

A corresponding male thread is provided on an operating member in the form of a shaft 15 which carries a hand wheel 16 for rotation of the operating member 15. Operating member 15 passes through a plug 17 threaded into the upper part of the casing 1. Suitable O-ring seals are provided to seal the operating member 15 in the plug 17 and to seal the plug 17 to the casing 1.

A compression coil spring 18 is provided extending between the plug 17 and the annular shoulder 12 of the first element 8.

An annular rib 19 is provided on the operating member 15 immediately below the plug 17 to prevent axial movement of the operating member 15.

In order to prevent rotation of the first element 8 in use, an insert 20 is provided in the valve casing immediately below the inlet 2 having a hexagonal bore provided in each of two opposed interior faces with an axially running slot forming a waterway. The exterior of the enlarged diameter portion of the first element 8 is provided with a corresponding hexagonal section so as to lock the first element 8 against rotation but allow it to slide freely longitudinally.

A quarter turn of the hand wheel 16 serves to bring the parts of the valve into the position shown in Fig. 2. It can be seen that the rotation of the screw thread has carried the firest element 8 upwardly to its maximum extent against the compression spring 18. The piston 7 constituting the second element of the valve member has been carried upwardly with the first element opening the valve seat 5 for liquid flow through the nozzle 3.

Piston 7 is urged to descend by gravity and a flow of fluid into the chamber 11 through the groove 10 allows the gradual descent of the piston 7 to the position shown in Fig. 3 in which it once again closes the valve seat 5.

The maximum amount of liquid allowed to pass through following each opening operation of the tap depends upon the flow rate permitted through the groove 10 in relation to the lift of the piston 7 off the valve seat 5 but can be set to any desired value, for instance about 10 litres of water.

In order to again raise the piston 7 and allow further liquid to pass through the tap, it is necessary to rotate the hand wheel 16 in the opposite direction to bring the valve back to the position shown in Fig. 1. This serves to drive liquid out of the chamber 11 through the groove 10. This action is assisted by the spring 18 which may be made sufficiently powerful to cause the handle to rotate and to cause the valve to revert to the position shown in Fig. 1 as soon as the handle is released.

As can be seen, the forces acting on the valve member constituted by the first and second elements 7, 8 are directly along the line of movement desired. There is therefore a greatly lessened risk of the valve member becoming cocked and causing the piston to fail to make an adequate seal on the valve seat.

The general construction of the valve illustrated is considerably simpler than the known valves, leading to a considerable decrease in the cost of materials involved in constructing the valve.

Whilst the invention has been described with reference to a particular embodiment thereof, many modifications and variations are possible within the scope of the invention.

Claims

1. A valve for the control of fluid flow comprising: a valve seat, a valve member co-operating with the valve seat to open and close a flow path through the valve, which valve member comprises first and second mutually telescopically slideable elements defining a variable volume chamber and means defining a bleed path for fluid to said chamber, a valve operating mechanism connected to the first element of the valve member and adapted to produce linear movement of the first element between valve opening and valve closed positions, the arrangement being such that in said valve closed positions of the first element, the second element is constrained to close the valve seat and upon movement of the first element to the valve opening position the second element is constrained initially to move away from the valve seat but upon flow of liquid into said chamber through said bleed path the second element returns to close the valve seat, wherein the valve operating mechanism comprises an operating member rotatable about the line of movement of the first element and rotary cam means adapted to translate rotation of the operating member into said linear movement of the first element for opening and closing of the valve

2. A valve as claimed im claim 1 wherein the rotary cam means is provided by engaged male and female screw threads.

3. A valve as claimed in claim 2 wherein said screw threads are multi-start quick acting threads.

4. A valve as claimed in claims 2 or claim 3 wherein a first of said threads is provided on said operating member and a second of said threads is provided upon said first element.

5. A valve as claimed in claim 4 wherein the male thread is provided on the operating member.

6. A valve as claimed in any preceding claim wherein means are provided for preventing rotation of the first element.

7. A valve as claimed in any preceding claim wherein use said linear movement is substantially vertical and said return movement of the second element is downwards.

8. A valve as claimed in any preceding claim wherein the said bleed path is provided by an axially running groove in the surface of the second element.

9. A valve as claimed in any preceding claim wherein the body of the valve is of cast brass.

10. A valve substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.