GB2292994A

GB2292994A - Self-closing/time-delay valve cartridge for a water supply tap

Info

Publication number: GB2292994A
Application number: GB9518191A
Authority: GB
Inventors: Michael Rice
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-09-07
Filing date: 1995-09-07
Publication date: 1996-03-13
Anticipated expiration: 2015-09-07
Also published as: GB9518191D0; GB2292994B

Abstract

A self-closing/time-delay valve cartridge for a water supply tap comprises a valve body 1, a valve seat 5 and an axially slidable spindle 13 which is movable against the bias of a spring 15 to lift a valve seal 21 from the seat 5. Spindle sealing is effected by a bellows having a first end element 31 sealing around the spindle and movable therewith and a second end element 33 in sealing engagement with the body 1 and/or an end cap 25 on the body. Delayed closing is provided by a lip seal, formed integrally with the element 31 and engaging a bore 7 in the body 1, together with a restricted by-pass groove 51 in the bore 7. Alternatively, the groove may be replaced by a restricted passage through the spindle. In a further modification (Fig. 3, not shown), a dashpot chamber is defined between an actuating knob (170) and the valve body and includes a lip seal (155) and an adjustable vent (167) to atmosphere. <IMAGE>

Description

TITLE: Self-closing/time delay valve assembly and water supply tap DESCRIPTION The present invention relates to a selfclosing/time delay valve assembly for a water supply tap and to a self-closing/time delay water supply tap.

Self-closing/time delay water supply taps are being increasingly specified in the interests of water conservancy. One known purpose-designed push-operated self-closing water tap comprises a sleeve which is threaded to fit into a tap body and received slidably within the sleeve is a spindle which is sealed with respect to the bore of the sleeve and which projects from opposite ends of the sleeve. The spindle passes sealingly through a port ring disposed at the lower end of the sleeve and the spindle has an internal bore and spaced axial ports intersecting with the internal bore.

In the closed position the water access to the lower inlet port is closed by the port ring seal. On axial displacement of the spindle the inlet port is uncovered and water can enter the port and pass to the other side of the seal via the internal bore in the spindle. The lower end of the spindle carries a lip seal which is received slidably as a close fit in a blind bore except that the wall of the bore has a small chordal flat with a shallow axial groove therealong. On axial displacement of the spindle against a return spring water is displaced from the blind bore past the lip seal and movement in the reverse direction is resisted by a suction effect within the blind bore such that water has to bleed past the lip seal. This is made possible by the groove running down the chordal flat.

The arrangement results in delayed closing of the valve.

A disadvantage with this known construction resides in the plurality of component parts and difficulties of insuring a satisfactory water shut-off.

Another push-operated self-closing tap which is intended to convert normal screw-operated taps comprises a sleeve adapted to be screwed into the tap body and a valve disposed slidably within the sleeve having sealing means for closing a valve seat at the lower end of the sleeve. The valve is moved against resilient biasing and a seal intermediate opposite ends of the valve stem mates with an internal bore of the sleeve. On axial displacement of the valve in the opening direction water passes through a bore in a flange in the spindle and past a loose rubber washer into a chamber to the trailing side of said seal. Movement in the opposite direction under the spring pressure is resisted as the presence of water on the trailing side of the seal acts on the rubber washer to close off the bore and water can only bleed from the chamber via a bleed bore in the spindle.The size of the bore can be adjusted. The construction is complicated and expensive to manufacture and difficult to assemble. A plurality of O-ring seals are provided to seal the spindle with respect to the sleeve and this creates a large frictional effect making it difficult to the move the valve. In order to overcome friction a stronger return spring is required. The number of component parts used and the number of seals makes the adapter expensive and problematic.

It is an aim of the present invention to overcome the problems with the prior art devices, especially the problems caused by seal friction.

Accordingly, one aspect of the present invention provides a self-closing/time delay valve assembly for a water supply tap comprising a valve body adapted to fit in a water supply tap body, the valve body having a valve seat around a water inlet passage and receiving an axially slidably valve member having means to close off the water inlet passage in a closed position, the valve being movable against resilient biasing, an end cap securable to the valve body and having an aperture through which an end of the spindle projects for actuation purposes, and wherein sealing of the valve spindle with respect to at least the end cap is by sealing means comprising a first element disposed in surrounding sealing engagement with the valve spindle and movable therewith, a second element disposed in sealing engagement with at least one of the valve body or end cap, and a third sealing element surrounding the valve stem and connecting the first and second elements and being in the form of a bellows to allow axial movement of the spindle.

The above-described invention is advantageous since there is virtually no resistance to movement of the valve spindle. This is in marked contrast to the prior art constructions in which utilises a sliding seal, ie. where the spindle has to slide through the seal.

A particularly advantageous construction results if the second element forms a seal between the valve body and the end cap, as this eliminates the need for a separate seal. It is preferred if the second element has a peripheral bead which is received in an end groove of the valve body and which is held in place by the end cap. It is further preferred if the second element has an annular portion which mates with a boss of the end cap which surrounds the aperture through which the valve spindle passes.

The above-described sealing means is preferably moulded in one piece and hereinafter will be referred to as a bellows seal for ease of reference. There are now described alternative embodiments of self-closing valve in which various means are provided for controlling the rate of closing of the valve. In at least one of those embodiments, the first element further comprises a lip seal which makes contact with a bore in the valve body and is employed in a water control system as described hereinafter.

Thus, in one embodiment, the above-described lip seal is slidable the bore in the valve body and defines a metering chamber from which the flow of water is restricted in the closing direction of the valve to give a delayed closing action. Movement in the opening direction is substantially unrestricted as water can flow past the lip seal. In one embodiment, a longitudinal groove is disposed in the bore to allow water to leak past the lip seal. In another embodiment, there is a leakage passageway through the spindle to allow water to pass from one side of the lip seal to the other. The inlet to the passageway from the chamber on the side remote from the water inlet valve, is through the wall of the first element so that sealing with respect to the spindle is maintained.An adjustable flow restrictor may be provided in this leakage In a further embodiment, a lip seal may be provided primarily for a damping function, and the rate of closing controlled by other means, for example by a pneumatic system by providing a peripheral lip seal between the valve body and an actuating cap of the valve spindle.

According to another aspect of the invention there is provided a self-closing/time delay valve assembly for a water supply tap comprising a valve body adapted to fit in a water supply tap body, the valve body having a valve seat around a water inlet passage and receiving an axially slidable valve member having means to close off the water inlet passage in a closed position, the valve being movable against resilient biasing, a chamber within the valve body and sealing means disposed upstream of the valve seat and carried by the valve to be movable therewith and engageable with a bore of the chamber in a valve body, and wherein the sealing means is such as to allow water past the seal without undue restriction when the spindle is moved in an opening direction to pass water to the trailing side of the sealing means and wherein flow of water past the seal in the reverse direction is restricted to give a delayed closing action.

Yet another aspect of the invention provides a water supply tap incorporating any of the above described self-closing/time delay valve assemblies.

More particularly the water inlet passage is disposed to the lower end of the sleeve and conveniently comprises a cylindrical bore providing a guide surface for a spindle of the valve member. The means for sealing the inlet passage may comprise a suitable valve face to mate with the aforesaid valve seat, but more preferably comprises an O-ring seal or washer.

Conveniently the O-ring seal is received on a reduced diameter portion of the valve spindle and retained thereon by a locking nut threaded onto the end of the valve spindle or other suitable fixing device. Part of the valve spindle is dimensioned to be received in said cylindrical bore of the water inlet passage.

Conveniently the spindle has one or more grooves in its periphery and running axially. On opening of the valve the water can pass by way of said one or more grooves into said chamber of the valve body. Conveniently the valve spindle has a flange intermediate its end and resilient biasing comprises a spring acting between a lower end of the valve body and said flange.

The sealing means comprises a lip seal to make engagement with the bore of said chamber. An end closure cooperates sealingly with the upper end of the valve body and has the valve spindle extending therethrough. In order to avoid having to provide a separate seal between the end cap and the valve spindle the sealing means further comprises an axially expandable and contractible portion between the lip seal portion and an end seal portion providing the aforesaid sealing engagement between the end cap and the valve body. More particularly, said axially expandable and contractible portion comprises a bellows portion. Thus, water to the trailing side of the sealing means (relative to the direction of opening of the tap), actually the trailing side of the lip seal, is received in a chamber defined between the sealing element and the bore of the valve body.

In order to control the closing stroke of the tap, water is permitted to "leak" from the trailing side of the lip seal (ie. from said chamber) back to the leading side. In one embodiment this is achieved by the provision of one or more shallow grooves in the wall of said chamber such that water leaks past the lip seal where it contacts the chamber wall.

In an alternative embodiment, the spindle includes a bleed passage which extends between the leading end trailing sides of the lip seal, communication with said chamber being by way of one or more holes in the sealing means where it makes contact with the spindle. Conveniently adjustable valve means is provided to control the flow through the bleed passage. Advantageously it comprises a screw threaded adjustable member, and more preferably still acts on a distortable resilient plug.

The lower end of the valve body chamber is apertured to permit passage of water to the outlet of the tap. The apparatus further comprises an actuation cap fitting to the spindle where it projects from the end cap. The valve body is typically received in the body of the tap by way of a screw threaded connection.

Adapters may be provided to suit different sizes of valve tap body.

In the afore-described embodiments, the sealing means is such as to allow water past the seal without undue restriction when the valve member is moved in the opening direction to pass water to the trailing side of the sealing means, but the flow of water past the seal in the reverse direction is restricted to give a delayed closing action. The restriction is conveniently achieved by providing an axial groove in the wall of the valve body contacted by the sealing means.

An alternative means of controlling movement of the valve member in the closing direction, and preferably employing the afore-described bellows seal, is described hereinafter and constitutes yet another aspect of the invention. Accordingly there is provided a self-closing/time delay valve assembly for a water supply tap comprising a valve body adapted to fit in a water supply tap body, the valve body having a valve seat around a water inlet passage and receiving an axially slidable valve member having means to close off the water inlet passage in a closed position, the valve is movable against resilient biasing, one end of the valve member extends sealingly from the valve body and carries an actuating plunger which makes sealing engagement with the valve body to define an air chamber between the plunger and the valve body from which air is expelled during an opening movement of the valve and wherein the admission of air to the chamber is restricted to control the rate of closing.

This alternative is conveniently used with the afore-described bellows seal, and is further described hereinafter.

By relying on an air chamber to control the rate of closing the performance of the valve is not affected by the build up of limescale which can be a problem with prior art devices in which closing is controlled by water flow to give the desired delayed closing.

Advantageously there is an adjustable bleed passage between the chamber and the external air (eg.

atmosphere) by which the rate of air ingress can be adjusted and thereby adjust the rate of closing. The rate at which air is admitted into the chamber may be variable or constant throughout the stroke of the valve, but it is advantageous if the rate is increased just before closing takes place. More particularly, it is advantageous if a rapid pressured equalisation takes place just before closing. This has the effect of accelerating valve closure to cut off the water supply sharply and thereby avoid incomplete closure which could result in a dripping tap. The rapid pressure equalisation can be conveniently achieved by strategic positioning of a port or passageway to breach the sealing arrangement of the plunger with the valve body at a predetermined position in the closing movement.

Conveniently this can take the form of a groove cut in the actuating plunger. Conveniently the sealing of the actuating plunger with the valve body is provided by an annular lip seal with the lip inclined to make sealing contact under the influence of the vacuum within said chamber. The actuating plunger may be received in a bore of the valve body, but preferably the actuating plunger comprises a sleeve or bonnet carried by the end of a spindle of the movable valve member which projects from the valve body in sealing contact with the outer periphery of the valve body. The annular sealing element is conveniently mounted on the valve body.

Advantageously the bonnet is releasably connectable with the spindle, which connection is sealed.

Advantageously, the sealing of the valve member with respect to the valve body where the end of the valve member extends from the valve body incorporates a low friction seal so as to avoid increasing the resistance to closing. Preferably the sealing means comprises a first part received sealingly on the movable valve member and connected by way of axially flexible portion (eg. axially expandable and compressible) to a second part sealingly engaged with the valve body.

Conveniently, the axially flexible portion comprises a bellows portion. Optionally, said first portion includes an annular sealing lip which makes engagement with an internal bore of the valve body. Said annular sealing lip is disposed upstream of the valve seat and carried by the valve member and engageable with the bore in the valve body and defines a chamber within the valve body and upstream of the annular lip seal of said first part. Conveniently said annular lip seal of the sealing means is apertured to allow water past the seal when the spindle is moved to pass water between the leading and trailing sides of the annular lip seal.

This gives rise to a damping or smoothing action of the valve.

Another aspect of the invention provides a water supply tap incorporating the above-described selfclosing/time delay valve assembly and pneumatic closing control mechanism.

An end closure cooperates sealingly with the upper end of the valve body and has the valve spindle extending therethrough. The need for a separate seal between the end cap and the valve spindle is avoided by the provision of the aforesaid axially expandable and contractible portion between said first part of the seal portion and the end seal portion providing the aforesaid sealing engagement between said first part of the end cap and the valve body. As previously mentioned said axially expandable and contractible portion comprises a bellows portion. Thus, in a preferred embodiment, water to the trailing side of the sealing means (relative to the direction of opening of the tap), actually the trailing side of the lip seal, is received in said chamber defined between the sealing element and the bore of the valve body.

The lower end of the valve body chamber is apertured to permit passage of water to the outlet of the tap. The valve body is typically received in the body of the tap by way of a screw threaded connection.

Adapters may be provided to suit different sizes of valve tap body.

The present invention will now be described further, by way of example only, with reference to the accompanying drawing, in which: Figure 1 is a cross-section view through a valve assembly and showing part of a valve tap body for illustrative purposes and embodying the invention, Figure 2 is a fragmentary cross-sectional view showing an alternative construction for controlling closing of the valve, and Figure 3 is a cross-section view through a valve assembly and showing part of a valve tap body for illustrate and embodying the invention.

Referring to the drawing of Figure 1, a valve assembly comprises a valve body 1, a bore 3 to the lower end of which forms a water inlet passage and has an annular valve seat 5 to the end thereof. The valve body in the illustrated embodiment has second and third stepped diameter bores 7, 9 respectively. Water outlet passages 11 are provided in the walls of the valve body.

A valve spindle 13 is disposed within the valve body and arranged to be axially slidable with respect thereto against resilient biasing of coil spring 15 acting between a shoulder of the valve body at a lower end and a flange 17 carried by a spindle of the valve and disposed intermediate its ends. The spindle is slidably guided within the bore 3 and in the illustrated embodiment the periphery of the spindle has three circumferentially spaced axially extending grooves 18.

A lower end of the spindle is of reduced diameter and threaded as at 19 and carries an O-ring seal 21 retained on the threaded portion 19 by a lock nut 23.

The water inlet passage is sealed by mating engagement of the O-ring seal 21 with the valve seat 5.

It will be apparent that Figure 1 shows the valve assembly in its fully closed position. An end cap 25 is threaded onto the upper end of the valve body and has a bore through which an upper end 27 of the valve spindle projects. An actuating cap 30 is secured to the valve spindle by any suitable means, conveniently using a circlip washer (not illustrated) received in retention groove 27a.

Sealing means is generally indicated at 29, and in the illustrated embodiment comprises a lip seal portion 31, an end seal 33 and a flexible bellows portion 35 connecting the lip seal and the end seal.

The lip seal is carried sealingly on the valve spindle between flange 17 and a smaller flange 37. The tip of the lip seal makes engagement with the bore 7 of the valve body. The end seal 33 is trapped between the end cap 25 and the end of the valve body 1. Thus a chamber 39 is formed to the trailing side of the lip seal between the valve body and the seal 29.

When the valve assembly is inserted into a tap body shown generally at 41 a sealing washer 43 is trapped between an abutment 45 of the valve body and an abutment 47 of the tap body. The valve body may be directly threaded into the tap body or an intermediate adapter employed such as that shown at 49 in the illustrated embodiment.

In operation of the valve assembly the force exerted by a spring 15 displaces the valve spindle upwardly so that the seal 21 makes sealing engagement with the valve seat 5. On actuation of the valve by pushing on the cap 30 to displace it axially downwards as viewed in the illustration, water from the supply side is admitted to the grooves 18 and so passes into the chamber within the valve body outwardly of the valve spindle. The water may then pass through ports 11 to be dispensed from the tap outlet.

The movement of the valve spindle axially downwardly in conjunction with the water pressure causes water to be displaced past the lip seal 31 and into the chamber 39. Maximum axial movement of the valve spindle is limited by engagement of flange 17 with the abutment surface 7a at the end of bore 7. Because water is noncompressible the presence of water behind the lip seal provides a potential bar to return movement as it forces the lip seal into engagement with the bore 7. This can only be overcome by arranging for controlled leakage past the lip seal. This can be conveniently achieved by providing a metering groove along with length of the bore 7. In the illustrated embodiment this is shown as line 51. It extends over the working range of movement of the valve spindle. The cross-sectional area of the valve groove will determine the speed of leakage.More than one groove may be provided. The area may be uniform or non-uniform.

Figure 2 illustrates a modification to the above described embodiment, in which the speed of closing is controlled by an alternative construction. According to this construction, the spindle 27 has an internal blind bore 61 extending in from its upper end and to a position beyond the position of seal 31. Ports 63, 65 are provided to opposite sides of the flange 17 between the internal bore 61 and the outer periphery of the spindle. Conveniently, the spindle has a groove 67 around its periphery aligned with one or more ports 63.

The sealing means 29 has one or more through holes 69 aligned with the groove 67. An adjusting valve 71 is received within the spindle and is in threaded connection therewith for adjustment of its axial position to vary the flow of liquid between ports 63 and 65. The valve 71 is sealed with respect to the bore 61 using an annular seal element 73. In the illustrated embodiment the end of the adjusting valve acts on a plug 75 which is conveniently made of rubber, or a material having similar properties, such that the leakage path is obstructed to a lesser or greater extent depending on the load applied to it by the adjusting valve 71. The rubber plug may extend over port 65 or over both ports 63 and 65. Thus in this embodiment, a controlled leakage path is provided via the spindle and the aforedescribed grooves 51 would usually be omitted.

The valve spindle and the valve body and any adapter are conveniently made from plastics material, preferably PTFE, or alternatively may be cast from a suitable metal. It will be noted that according to the invention only two sealing elements are required as part of the valve assembly and the design avoids using O-ring seals in circumstances which require sliding contact with an O-ring seal which is disadvantageous.

Where the self-closing valve is to be applied to a purpose-designed tap rather than intended as an adapter for an ordinary screw action tap, the aforementioned valve body may be formed by the tap body.

Referring to Figure 3 of the drawings, a valve assembly comprises a valve body 101, a bore 103 to the lower end of which forms a water inlet passage and has an annular valve seat 105 to the end thereof. The valve body in the illustrated embodiment has second and third stepped diameter bores 107, 109 respectively. Water outlet passages 111 are provided in the walls of the valve body. A valve spindle 113 is disposed within the valve body and arranged to be axially slidable with respect thereto against resilient biasing of coil spring 115 acting between a shoulder of the valve body at a lower end and a flange 117 carried by a spindle of the valve and disposed intermediate its ends. The spindle is slidably guided within the bore 103 and in the illustrated embodiment the periphery of the spindle has three circumferentially spaced axially extending grooves 118.A lower end of the spindle is of reduced diameter and threaded as at 119 and carries an O-ring seal 121 retained on the threaded portion 119 by a lock nut 123.

The water inlet passage is sealed by mating engagement of the O-ring seal 121 with the valve seat 105.

It will be apparent that Figure 3 shows the valve assembly in its fully closed position. An end cap 125 is threaded onto the upper end of the valve body and has a bore through which an upper end 127 of the valve spindle projects. An actuating cap 130 is secured to the valve spindle by any suitable means, conveniently using a circlip washer 128 received in retention groove 127a.

End cap 125 carries an annular lip seal 155 received in a groove 157 of the end cap 125. The annular lip seal makes sealing contact with the inner bore 159 of the actuating cap or bonnet 130. The connection of the spindle 127 to the actuating cap 130 is sealed from the atmosphere conveniently by way of a sealing bezel 130 or alternatively by way of a O-ring between the end of the spindle and the end wall of the actuating cap. The lowermost end of the actuating cap 130 has at least one axial groove 161 extending from the lower end thereof a prescribed distance and functions as described further hereinafter.

Sealing means is generally indicated at 129, and in the illustrated embodiment comprises a first seal portion 131, an end seal 133 and a flexible bellows portion 135 connecting the first seal portion and the end seal. The first seal is carried sealingly on the valve spindle between flange 117 and a smaller flange 137. The end seal 133 is trapped between the end cap 125 and the end of the valve body 1. By this means water is denied access to the spindle where it passes through the end cap 125.

In the illustrated embodiment the first seal portion 131 is extended to form an annular lip seal 163 which contacts the bore 107 and effectively defines a chamber 139 to the trailing side thereof between the valve body and the remainder of the seal 129. The lip seal incorporates one or more through bores 165 to provide a liquid flow passage between the leading and trailing sides of the lip seal 163. This allows liquid to flow between the two sides of the seal and acts as a damping means.

The end cap 125 incorporates a threaded bore 167 for receiving a threaded bleed screw 169. A chamber 170 is defined within the actuating cap or bonnet 130 sealed from the atmosphere by the lip seal 155, the end cap seal 130 and from the water supply by the seal 129. The bleed screw 169 and its associated bore together with the threaded connection 171 between the end cap 125 and the valve body constitutes a bleed passage controlling the flow of air between the atmosphere and chamber 170.

When the valve assembly is inserted into a tap body shown generally at 141 a sealing washer 143 is trapped between an abutment 145 of the valve body and an abutment 147 of the tap body. The valve body may be directly threaded into the tap body or an intermediate adapter employed such as that shown at 149 in the illustrated embodiment.

In operation of the valve assembly, the force exerted by a spring 115 displaces the valve spindle upwardly so that the seal 121 makes sealing engagement with the valve seat 105. On actuation of the valve by pushing on the cap 130 to displace it axially downwards as viewed in the illustration, water from the supply side is admitted to the grooves 118 and so passes into the chamber within the valve body outwardly of the valve spindle. The water may then pass through ports 111 to be dispensed from the tap outlet.

The movement of the valve spindle axially downwardly causes air to be displaced from the chamber 170 past the lip seal 155 to atmosphere. Maximum axial movement of the valve spindle is limited by engagement of flange 117 with the abutment surface 107a at the end of bore 107.

On releasing pressure on the actuating cap 130 the spring 115 attempts to urge the valve in the closing direction. However, since the chamber 170 has been evacuated the pressure differential between the chamber 170 and the atmosphere applies a restraining force restricting movement in the return direction. The vacuum draws the lip seal 155 into contact with the bore 159. However, the bleed path comprising the threads 171, bore 167 and bleed valve 169 allows a leakage path from atmosphere to the chamber 170 which gradually equalises the pressure and therefore reduces the resistance to movement under the influence of the spring 115. When the lip seal reaches the edge of groove 161 rapid pressure equalisation occurs and the valve closes quickly.

Because water is non-compressible the presence of water behind the lip seal 163 provides a potential bar to return movement as it forces the lip seal into engagement with the bore 107. This is overcome by providing the ports 165 which allow water past the lip seal whilst providing a damping function. The lip may be eliminated from the first element.

In the above-described embodiments various means are employed to control the closing of the valve, but all share the use of the bellows seal in its basic form which provides a substantially frictionless seal between the valve stem and at least the end cap - also the valve body in the illustrated embodiment. The frictionless seal is advantageous as it makes control of valve closing easier using the above-described embodiments.

Claims

1. A self-closing/time delay valve assembly for a water supply tap comprising a valve body adapted to fit in a water supply tap body, the valve body having a valve seat around a water inlet passage and receiving an axially slidably valve member having means to close off the water inlet passage in a closed position, the valve being movable against resilient biasing, an end cap securable to the valve body and having an aperture through which an end of the spindle projects for actuation purposes, and wherein sealing of the valve spindle with respect to at least the end cap is by sealing means comprising a first element disposed in surrounding sealing engagement with the valve spindle and movable therewith, a second element disposed in sealing engagement with at least one of the valve body or end cap, and a third sealing element surrounding the valve stem and connecting the first and second elements and being in the form of a bellows to allow axial movement of the spindle.

2. A valve assembly as claimed in claim 1 in which the second element forms a seal between the valve body and the end cap.

3. A valve assembly as claimed in claim 1 or 2 in which the second element has a peripheral bead which is received in an end groove of the valve body and which is held in place by the end cap.

4. A valve assembly as claimed in any one of claims 1, 2 or 3 in which the second element has an annular portion which mates with a boss of the end cap which surrounds the aperture through which the valve spindle passes.

5. A valve assembly as claimed in any one of claims 1 to 4 in which sealing means is moulded in one piece.

6. A valve assembly as claimed in any one of claims 1 to 5 in which the first element further comprises a lip seal which makes contact with a bore in the valve body.

7. A valve assembly as claimed in any one of claims 1 to 6 and further comprising means for controlling the rate of closing of the valve.

8. A valve assembly as claimed in claim 7 when appendant to claim 6 in which the lip seal is slidable in the bore in the valve body and defines a metering chamber from which the flow of water is restricted in the closing direction of the valve to give a delayed closing action, and in which movement in the opening direction is substantially unrestricted.

9. A valve assembly as claimed in claim 8 in which a longitudinal groove is disposed in the bore to allow water to leak past the lip seal.

10. A valve assembly as claimed in claim 8 in which there is a leakage passageway through the spindle to allow water to pass from one side of the lip seal to the other.

11. A valve assembly as claimed in claim 10 in which the inlet to the passageway from the chamber on the side remote from the water inlet valve, is through the wall of the first element so that sealing with respect to the spindle is maintained.

12. A valve assembly as claimed in claim 11 in which an adjustable flow restrictor is provided in the leakage passageway.

13. A valve assembly as claimed in claim 7 in which the means for controlling the rate of closing of the valve comprises a pneumatic system.

14. A valve assembly as claimed in claim 13 in which the pneumatic control system comprises a peripheral lip seal between the valve body and an actuating cap of the valve spindle, and an associated leakage path controlling the closing movement.

15. A self-closing/time delay valve assembly for a water supply tap comprising a valve body adapted to fit in a water supply tap body, the valve body having a valve seat around a water inlet passage and receiving an axially slidable valve member having means to close off the water inlet passage in a closed position, the valve being movable against resilient biasing, a chamber within the valve body and sealing means disposed upstream of the valve seat and carried by the valve to be movable therewith and engageable with a bore of the chamber in a valve body, and wherein the sealing means is such as to allow water past the seal without undue restriction when the spindle is moved in an opening direction to pass water to the trailing side of the sealing means and wherein flow of water past the seal in the reverse direction is restricted to give a delayed closing action.

16. A valve assembly as claimed in any one of the preceding claims in which the water inlet passage is disposed to the lower end of the valve body and comprises a cylindrical bore providing a guide surface for the spindle of the valve member.

17. A valve assembly as claimed in claim 16 in which the means for sealing the inlet passage comprises an O- ring seal or washer to mate with the aforesaid valve seat.

18. A valve assembly as claimed in claim 17 in which the O-ring seal is received on a reduced diameter portion of the valve spindle and retained thereon by a locking nut threaded onto the end of the valve spindle.

19. A valve assembly as claimed in any one of claims 16, 17 or 18 in which part of the valve spindle is dimensioned to be received in said cylindrical bore of the water inlet passage.

20. A valve assembly as claimed in any one of the preceding claims in which the spindle has one or more grooves in its periphery and running axially whereby on opening of the valve the water can pass by way of said one or more grooves into said chamber of the valve body.

21. A valve assembly as claimed in any one of the preceding claims in which the valve spindle has a flange intermediate its end and resilient biasing comprises a spring acting between a lower end of the valve body and said flange.

22. A self-closing/time delay valve assembly for a water supply tap comprising a valve body adapted to fit in a water supply tap body, the valve body having a valve seat around a water inlet passage and receiving an axially slidable valve member having means to close off the water inlet passage in a closed position, the valve is movable against resilient biasing, one end of the valve member extends sealingly from the valve body and carries an actuating plunger which makes sealing engagement with the valve body to define an air chamber between the plunger and the valve body from which air is expelled during an opening movement of the valve and wherein the admission of air to the chamber is restricted to control the rate of closing.

23. A valve assembly as claimed in claims 13 or 14 or claim 22 in which there is an adjustable bleed passage between the chamber and the external air (eg.

atmosphere) by which the rate of air ingress can be adjusted and thereby adjust the rate of closing.

24. A valve assembly as claimed in claim 23 in which the rate at which air is admitted into the chamber is increased just before closing takes place.

25. A valve assembly as claimed in claim 24 in which rapid pressure equalisation is achieved by strategic positioning of a port or passageway to breach the sealing arrangement of the plunger with the valve body at a predetermined position in the closing movement.

26. A self-closing/time delay valve assembly constructed and arranged substantially as hereinbefore described with reference to any one of the accompanying drawings.