GB2472121A

GB2472121A - Valve head assembly

Info

Publication number: GB2472121A
Application number: GB0921246A
Authority: GB
Inventors: Robin Charles Morewood; Erling Arnum Freudendahl
Original assignee: AVK Holding AS
Current assignee: AVK Holding AS
Priority date: 2009-07-24
Filing date: 2009-12-03
Publication date: 2011-01-26
Also published as: WO2011010122A3; WO2011010122A2; GB0921246D0

Abstract

A valve head assembly comprises an inlet 3, an outlet 4 and a valve disc 20. The valve disc 20 is operatively moveable from a closed position in which it engages the inlet 3 so as to close it against the passage of liquid, and an open position in which it is disengaged from the inlet 3 so as to allow the passage of liquid from the inlet 3 to the outlet 4. The inlet 3 and outlet 4 are substantially aligned so as to form a substantially straight chamber 10. In the open position of the valve disc 20, it is substantially completely withdrawn from the chamber 10 between the inlet 3 and outlet 4 so as to allow free passage from the inlet 3 to the outlet 4.

Description

I

Through Bore Valve The present invention relates a new design of valve such as a fire hydrant, and more particularly to a valve having a straight through bore.

Valves heads are generally known having a straight through bore between the inlet and the outlet with a valve closure member disposed therebetween for shutting off the flow between the inlet and outlet. Different valve configurations are known enabling forced opening and closing of the valve again the flow through the valve, or enabling one-way flow only through the system. However, typically, the valve closure member, even in the open position, will still extend partially into the through bore so as to effect some constriction in the flow path.

Hydrants such as fire hydrants are a particular type of valve head assembly and are used to enable access to water supplies at outside locations. The most common use for hydrants is by emergency services such as the fire services to provide a high pressure supply of water for use in fighting fired. A hydrant is secured to the top of a riser pipe connected directly to the water main, and is usually located in a chamber beneath a cover plate so as to protect against damage and tampering. Figure 1 shows a conventional hydrant design having a lower inlet which is connected to the top of the riser pipe in a fluid tight manner. The upper surface of the inlet forms a valve seat against which is engageable a valve closure member in order to close the inlet and stop the flow of water from the water main out of the hydrant.

The valve closure member is carried on a valve stem which extends substantially coaxially with the inlet and links to caps which is operated to move the valve closure member and hence open and close the inlet. The whole valve assembly is mounted on a bonnet which is secured to the top of the hydrant above the inlet.

The hydrant further has an outlet in its upper surface which is offset from the inlet and is linked thereto by a chamber. The outlet is closed off by a screw cap. Opening of the valve allows water to pass through the inlet, through the chamber and to the outlet. A suitable attachment such as a fire hose is secured to the outlet by means of the thread.

Although primarily designed to allow water to be taken from water main, the direct connection of the riser pipe to the main and the frequency of hydrants have the potential to enable access to the water main, for example for servicing purposes, such as for inspection of the pipe using cameras, or remote repair, with necessitating excavation of the pipe which is time consuming, costly and inconvenient. However, the conventional hydrant design has the problem that due to the offset of the inlet and outlet, access to the riser pipe and water main is difficult. For example, a camera must be manoeuvred from the outlet, through the chamber to and through the inlet into the riser pipe. The must be done against the water pressure and also past the valve closure member, which will not have sufficient clearance from the valve seat to allow a typical camera to pass into the riser pipe.

According to the present invention there is further provided a valve head assembly comprising an inlet, an outlet and a valve member operatively moveable from a closed position in which it engages the inlet so as to close it against the passage of liquid therethrough and an open position in which it is disengaged from the inlet so as to allow the passage of liquid from the inlet to the outlet, wherein the inlet and outlet are substantially aligned so as to form a substantially straight chamber therebetween, and wherein the valve member, in its open position, is substantially completely withdrawn from the chamber between the inlet and outlet so as to allow free passage from the outlet to the inlet.

According to the present invention there is further provided a hydrant comprising a lower inlet, an upper outlet and a valve member operatively moveable from a closed position in which it engages the inlet so as to close it against the passage of liquid therethrough and an open position in which it is disengaged from the inlet so as to allow the passage of liquid from the inlet to the outlet, wherein the inlet and outlet are substantially aligned so as to form a substantially straight chamber therebetween, and wherein the valve member, in its open position, is substantially completely withdrawn from the chamber between the inlet and outlet so as to allow free passage from the outlet to the inlet.

A hydrant in accordance with the invention has the advantage that the alignment of the inlet and outlet allows easy passage of articles such as a camera through the hydrant and into the water main via the riser pipe.

Preferably the valve head assembly or hydrant is formed by a body in which the inlet and outlets are formed and by a bonnet assembly which is removably attached to the body so as to close a bonnet opening formed in the body. A valve assembly including the valve member is then preferably mounted in the bonnet so as to form a unitary assembly therewith which is attachable to and removable from the body as a single assembly.

In one embodiment of the invention, the valve member is mounted in the hydrant so as to be pivotally moveable between its open and closed positions. More particularly, the valve member is preferably formed as a hinged valve disc which, in its closed position, sealing engages a valve seat formed by an annular closure surface inside the body so as to close the inlet. In the case of a hydrant, the annular closure surface is preferably proximate to and surrounding the inlet so as to close the inlet. In the case of a valve head assembly, the valve disc preferably extends obliquely across the chamber between the inlet and outlet so as to block the flow therebetween. A notch may be formed in the chamber in which the valve disk engages when closed, but this may be omitted in order to maintain a smooth bore to avoid trapping of dirt.

The valve assembly preferably then includes an actuating arm, an end of which is associated with the valve disc and is moveable between an extended position in which it presses the valve disc against the valve seat and a retracted position associated with opening of the valve.

More particularly, in one embodiment, the said end of the actuating arm is connected to the valve disc for pivotal movement only relative thereto. Movement of the end towards its retracted position thereby actively pulls the valve disc away from the valve seat and thereby opens the valve. This has the advantage of enabling both forced opening and forced closing of the valve However, in a preferred embodiment, a lost motion coupling is provided between the valve disc and actuating means for opening and closing the valve such that, upon operation of the actuating means in an opening sense, the actuating means is moveable completely independently of the valve disc. In this way, the actuating means is operable to forcibly close the valve but does not forcibly open it. Instead, it relies on water pressure on the face of the valve disc to pivot it away from the valve seat and thereby open the valve when the actuator is moved to its open position. In the application as a valve head assembly, this has the advantage of providing a non-return valve configuration in a very simple manner, and, indeed, the valve can be switched between a forced open/forced closes configuration and a non-return configuration by simply adjusting the coupling between the end of the actuating arm and the valve disc, for example by tightening the coupling to lock against lost motion.

This has the advantage that when the pressure is insufficient to effect opening movement of the valve disc, or the pressure drops after the valve disc has moved to its open position, the valve disc will automatically return to its closed position, either under its own weight or optionally helped by provision of biasing means such as a spring. This prevents the possibility of backflow from the outlet into the inlet when water pressure is too low, which backflow could, in the case of a hydrant, contaminate the water supply.

Preferably, in the embodiment in which a lost motion coupling is provided, manual override means is provided which can used manually to open and/or lock the valve disc in an open position valve when there is insufficient water pressure for automatic opening to take place.

In a preferred embodiment, the manual override means comprises means such as a handle for manually rotating a pivot shaft to which the valve disc is mounted for pivotal movement between its open and closed positions. In particular, the pivot shaft advantageously extends

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exteriorly of the had assemblyiydrant and has a handle formed directly thereon, latching means preferably being provided on the outside of the body which co-operates with the pivot shaft to lock it against rotation and hence lock the valve disc in position.

The lost motion coupling advantageously takes the formed of a pin and slot coupling between the actuating means and the valve disc, the pin pressing against an end of the slot upon movement of the actuating means in a closing sense so as to move the valve disc to its closed position, and the pin being retracted from said end upon movement of the actuating means in an opening sensor so as to allow the valve disc to pivot away from its closed position.

The actuating means preferably takes the form of a rotating threaded shaft which may have a worm gearing and on which is mounted a nut which is constrained to move longitudinally along the shaft upon rotation of the shaft, a link member extending between and being pivotally attached to each of the nut and the valve disc, the end of the link member associated with the valve disc being extended towards and retracted away from the inlet upon operation of the actuating means. The pin and slot coupling is then advantageously formed between the link member and at least one of the nut and the valve disc. The lost motion coupling may alternatively be formed between the nut and the rotating shaft.

Rotation of the threaded shaft may be achieved by an actuator non-rotatably attached to and coaxial with the threaded shaft, which is located outside of the body. However, the the actuator may instead have it axis perpendicular to the axis fo the shaft and rotate a shaft which is connected to the threaded shaft by a bevel gearing or the like so as to translate rotation about the axis of the actuator into rotation about the axis of the threaded shaft.

In a still further embodiment, the valve disc may be connected to the rotating shaft without a lost motion coupling by means of a pivot only coupling between each end of the link member and the valve disc and nut respectively. Such a system then provides a forced open and forced closed operating system for the valve disc.

Instead of a hinged valve member, a translating valve member may be provided in the form of a valve wedge which moves laterally between an extended position in which it completely overlies the inlet and thereby closes it and a retracted position in which it is completely withdrawn from between the inlet and outlet.

Preferably, the translating valve member is mounted on a valve stem which is operatively attached to a cam mechanism having a rotatable actuator, the cam mechanism translating rotation of the actuator into longitudinal movement of the stem so as to slide the valve member back and forth, for example by means of a rack and pinion system, or even by a pivot linkage mechanism of the type described above in relation to the hinged valve member embodiments.

In order that the invention may be well understood, there will now be described some embodiments thereof, given by way of example, reference being made to the accompanying drawings, in which: Figure 1 is a sectional side view of a conventional hydrant according to the prior art; Figure 2 is a sectional side view of a hydrant according to a first embodiment of the invention; Figure 3 is a perspective view of the hydrant of Figure 2; Figure 4 is a sectional side view of a hydrant according to a second embodiment of the invention; Figure 5 is a perspective cut-away view of a hydrant according to a third embodiment of the invention; Figure 6 is a sectional side view of a further embodiment of the invention in the form of a forced open and forced closed valve head assembly; and Figure 7 is a sectional side view of a valve head assembly corresponding to the embodiment of Figure 6 but a non-return variant.

A hydrant 1 according to a first embodiment of the invention is shown in Figures 1 and 2 which includes back-flow prevention as described below. The hydrant 1 comprises a body 2 having a lower end 2a in which is formed an inlet 3, an upper end 2b in which is formed an outlet 4, and a through chamber 10 extending between the inlet 3 and outlet 4. As clearly shown in Figure 2, the inlet and outlet are coaxial so as to allow straight passage from the inlet to the outlet and vice-versa. A flange 5 is formed on the bottom of the body 2 around the inlet by means of which the hydrant may be secured to a rise pipe in conventional and well-known fashion, for example using bolts passing through anchoring holes 5a. A flange 6 is similarly formed on the top of the body 2 around the outlet by means of which an outlet coupler 7 may be removably attached to the body 2 by means of bolts (not shown). A suitable seal 8 will typically be provided between the body and the outlet coupler 7 to ensure a water tight connection.

The body 2 furthermore includes a side opening 12, to which is removably attached a valve bonnet assembly, generally indicated at 13. The bonnet assembly is sealingly attached to the body 12 by means of bolts or the like (not shown) is a fluid tight fashion. The bonnet assembly 12 includes a complete valve assembly as a removable unit by means of which flow the inlet 3 of the body 2 may be closed in order to prevent liquid flow to the outlet as described hereinafter.

The valve assembly comprises a valve disc 20 which is engageable with a valve closure face 16 formed inside the body 2 around the inlet 3 so as to seal the inlet 3 against the passage of liquid therethrough into the chamber 10. The valve disc 20 is mounted on a pivot arm 21 which is hingedly mounted to the body 2 on a hinge pin 22 for rotational movement about the longitudinal axis 22a of the hinge pin 22 between a lowered, closed position as shown in Figure 2 and a raised, open position. The hinge pin 22 is rotationally fast with the pivot arm 21 so as to rotate therewith as the pivot arm moves, and is rotatably mounted in the body 2 to allow for the movement of the pivot arm 21. The hinge pin 22 furthermore extends through the body 2 so as to be accessible externally of the body 2 and includes a cross bar 22b by means of which it may be manually rotated as described below.

The pivot arm 21 also has an arcuate lever 23 formed on it which extends upwards and towards the bonnet, an arcuate slot 24 being formed in the lever 23 extending longitudinally therealong.

A threaded actuator shaft 25 is mounted in the bonnet so as to extend substantially parallel to the axis of the inlet and outlet. The shaft extends through bearings 26 in the bonnet 13 so as to be freely rotatable relative to the bonnet 13 about is longitudinal axis and extends out of the top of the bonnet 13 where it terminates in an operating nut 26 which is rotationally fast with the actuator shaft. The operating nut 26 is therefore accessible from outside the hydrant and can be turned, for example using a spanner in or to rotate the actuator shaft 25 relative to the bonnet 13 and hence the body 2. A nut 27 is mounted on the actuator shaft 25 inside the bonnet assembly 13 and is constrained to be on-rotatable not longitudinally moveable relative to the bonnet. The nut 27 therefore acts as a cam follower for the thread on the actuator shaft 25, the nut 27 moving upwards and downwards along the shaft 25 parallel to the axis of the inlet 3 and outlet 4 when the shaft 25 is rotated.

A link member 30 is pivotally attached at one end 30a to the nut 27 and at the other end 30b carries of pin 31 which engages in the slot 24 of the arcuate lever 23 so as to be slidable back and forth therealong which at the same time allow the link member 30 to pivot relative to the lever 23. When the nut 27 moved down the actuator shaft 25 to its lowermost position thereon as indicated by the solid line in Figure 2, the pin 31 is pressed along the slot 24 towards the valve disc into engagement with the left hand end of the slot 24 closest to the valve disc 20 as illustrated in Figure 12. The engagement of the pin 31 with the end of the slot 24 forces the pivot arm 21 to rotate anti-clockwise so as to press the valve disc 20 against with the valve closure face 16 of the body, thereby prevent liquid flow through the inlet, and holds it in this closed position against the pressure of the water in the riser pipe acting against the underside of the valve disc 20.

In order to open the valve, the operating nut 26 is rotated so as to move the nut 27 upwards in the bonnet. This causes the pin 31 to move relative to the body 2 away from the inlet 3 and thereby release the closing pressure on the valve disc 20. As the pin 31 retracts away from the inlet 3, the water pressure in the riser pipe causes the valve disc 20 to pivot about the hinge 22 away from the closure face 16 and thereby allow liquid to pass through the inlet 3 into the chamber 10. When the nut 27 has been moved to it upper most position shown in dotted line in Figure 2, the pin 31 is moved to its fully withdrawn position, allowing the valve disc 20 to pivot fully upwards to the position shown in broken line in Figure 2 in which is it moved completely out of the path between the inlet and outlet, thereby allowing free passage of tools through the outlet, the inlet and into the riser pipe.

By virtue of the slot and pin link between the lever 23 and the link member 30, a lost motion coupling is formed with the valve disc 20. The valve disc 20 is therefore not directly opened by the valve assembly but instead relies on the water pressure to lift the valve disc when the operating nut 26 is rotated towards its open position. This system protects against backflow into the inlet from the outlet in that if the water pressure in the riser pipe drop below a level sufficient to hold the weight of the valve disc 20, the valve disc will automatically pivot back towards the closure face 16 of the body, thereby automatically closing the inlet 3 to prevent unwanted passage of material from the outlet into the riser pipe which might pollute the water in the main. Cross bar 22b formed on the hinge pin 22 then enables the valve disc 20 manually to be opened to still allow access to the riser pipe through the outlet even when there is insufficient pressure in the riser pipe to lift the valve disc 20. A suitable latch system (not shown) may be provided externally of the body to manually lock the valve disc in its open position.

The valve disc 20 may be made of rubber, be rubber faced or the like in order to ensure an effective liquid tight seal with the closure face 16 of the body.

It will be appreciated that the attachment of the bonnet assembly to a side opening in the body 2 enables the whole valve assembly easily to be inserted into and removed from the body as a unitary assembly, thereby facilitating servicing and repair.

Although the embodiment of Figure 2 includes a lost motion coupling between the link member 30 and pivot arm 23 so as to provide backflow protection, the lost motion coupling may instead be formed between the closure nut 27 and the link member 30 or even between the closure nut 27 and the actuator shaft 25. It will be understood that backflow protection is not essential for all aspects of the invention. The link member 30 could instead have a simply pivot connection with the pivot arm so that operation of the operating nut 26 both forcible opens and forcibly closes the valve disc without providing backflow protection.

Although not shown, a torsion spring may be mounted on the hinge pin 22 which cooperates with the body 2 to help urge the valve disc 20 into a closed position.

Referring now to Figure 4, there is shown a second embodiment of the invention which is slightly modified from the embodiment shown in Figures 2 and 3. In this case, the closure face 116 on the body 102 is inclined to the axis of the inlet 103 rather than being perpendicular to it as in the first embodiment. As a result, the angular movement of the valve disc 120 between the closed position and open position is reduced and hence the valve is faster opening, requiring smaller rotation of the operating nut 126. Furthermore, the location of the axis 1 22a of the hinge pin 122 is raised relative to the actuator shaft 125 so that the actuating position of the nut 127 is reversed -the closed position now being when the nut 127 is fully upwards as shown in Figure 4 and the open position when fully downwards as indicated by the feint line in Figure 4. In all other respects the construction and operation of the embodiment of Figure 4 is identical to that of Figures 2 and 3.

Referring now to Figure 5, there is shown a third embodiment of the invention which uses an alternative valve mechanism. In this embodiment, the pivoting valve is replaced by a slide or wedge gate valve 220, which is operatively moveable perpendicular to the axis of the inlet 203 between an extended, closed position in which the valve member 220 completely overlies the inlet and thereby closes it, and a retracted, open position, as illustrated in Figure 5, in which the valve member 220 is completely withdrawn into a side passage 240 in the body 202 so as to be completely withdrawn from the chamber 210 linking the inlet 203 to the outlet 204 and thereby allow clear access to the inlet from the outlet.

The valve member 220 is mounted on the end of a valve stem 221 which is slidably mounted in the bonnet 213 by means of a bearing and is drivingly connected to an operating nut 226 located on the top of the bonnet 213 by means of a suitable cam mechanism which converts rotational movement of the operating nut 226 into translational movement of the valve stem 221. Such mechanisms are well known to the skilled person and will not be described here in detail. It will be recognised that because the direction of operative movement of the valve member 220 is perpendicular to the line of action of the force exerted on the valve member 220 by the water pressure in the riser pipe, the water pressure which not automatically open the valve as in the case of the first two described embodiments and hence the embodiment of Figure 5 does not provide any back-flow protection.

As with the previous embodiments, the valve assembly of Figure 5 is formed as a unitary assembly which is connected to and therefore removable with the bonnet assembly 213 so as to facilitate servicing and repair.

Referring next to Figure 6, there is shown an embodiment of the invention in the form of valve head assembly 300 for use in controlling fluid flow between an inlet 303 and an outlet 304. The assembly is mechanically very similar to the hydrant of Figure 2 except that the inlet and outlet are disposed along a horizontal axis and is typically position in-line in a pipe system. It will, though, be understood that the assembly may be tilted to suit the orientation of any particular pipe.

An inclined groove 305 is formed around the internal periphery of the pipe forming a seat against which valve disc 320 engages to close the flow between the inlet and the outlet. The valve disc 320 is pivotally moveable as with the earlier embodiments by is connected to closure nut 327 by a fixed link member 33Owhich is connected to the closure nut and valve disc respectively for rotational movement only -no lost motion coupling is provided.

Rotation of actuator shaft 325 is effected by means of rotating an operating nut 326 orientated perpendicularly to the axis of the actuator shaft 325. By means of suitable bevel gearing or the like (not shown) rotation of the operating nut 326 about its axis effects rotation of the actuator shaft 325 about its axis, causing the closure nut 327 to translate along the actuator shaft 325 and therefore either forceably open or forceably close the valve.

Figure 7 shows a variant of the assembly of Figure 6 configured for non-return operation.

The rotation only coupling between the link member 330 and the valve disc 320 in the embodiment of Figure Figure 6 is replaced by a lost motion coupling in the form of an arcuate lever 423 carried on the back of the valve disc 420 having an arcuate slot 424 formed therein in which a pin 431 carried on the end of link member 43Oslidably engages so as to provide a lost motion system identical with that described in connection with the embodiment of Figure 2.

In this way, the valve may either be forcibly closed or set in a a non-return configuration in which flow in one direction (left to right in Figure 7) is prevent whilst flow in the opposite direction of sufficient force is allowed.

If the distance of travel of the closure nut 427 along the actuator shaft 425 is sufficient, the valve of Figure 7 may also then be moved to a forced open position by, once the pin 431 reaches the upper end of the slot 424, the closure nut 427 being moved further along th shaft 425 50 as to pull the arcuate lever 423 with it and thereby forceably open the valve.

In the embodiments of both Figure 6 and Figure 7, a closure spring is preferably utilised in connection with the valve disc in order to bias the valve into the closed position.

Claims

Claims 1. A valve head assembly comprising an inlet, an outlet and a valve member operatively ji moveable from a closed position in which it engages the inlet so as to close it against the passage of liquid therethrough and an open position in which it is disengaged from the inlet so as to allow the passage of liquid from the inlet to the outlet, wherein the inlet and outlet are substantially aligned so as to form a substantially straight chamber therebetween, and wherein the valve member, in its open position, is substantially completely withdrawn from the chamber between the inlet and outlet so as to allow free passage from the outlet to the inlet.
2. A valve head assembly according to claim 1, including a body in which is formed a bonnet opening as well as the inlet and outlets, and a bonnet assembly which is removably attached to the body so as to close the bonnet opening.
3. A valve head assembly according to claim 2, wherein the valve member is mounted *..* in the bonnet so as to form a unitary assembly therewith which is attachable to and *S***S * removable from the body as a single assembly. ** * * * *S*

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4. A valve head assembly according to any of the preceding claims, wherein the valve *: :: member is mounted so as to be pivotally moveable between its open and closed positions. S.
5. A valve head assembly according to claim 4, wherein the valve member is formed as a hinged valve disc which, in its closed position, sealing engages a valve seat formed by an annular closure surface inside the body so as to close the inlet.
6. A valve head assembly according to claim 5, further including an actuating arm, an end of which is associated with the valve disc and is moveable between an extended position in which it presses the valve disc against the valve seat and a retracted position associated with opening of the valve.
7. A valve head assembly according to claim 6, wherein said end of the actuating arm is connected to the valve disc for pivotal movement only relative thereto, such that movement ij' of the said end towards its retracted position actively pulls the valve disc away from the valve seat and thereby opens the valve.
8. A valve head assembly according to any of claims 1 to 6, wherein a lost motion coupling is provided between the valve disc and actuating means for opening and closing the valve such that, upon operation of the actuating means in an opening sense, the actuating means is moveable completely independently of the valve disc.
9. A valve head assembly according to claim 8, wherein the coupling between the end of the actuating arm and the valve disc is adjustable to allow only relative rotational movement, such that the valve can be switched between a forced openlforced closes configuration and a non-return configuration by simply adjusting the coupling between the end of the actuating arm and the valve disc. * * 0sSsS

*..SSS *
10. A valve head assembly according to claim 8 or claim 9, wherein manual override means is provided which is operable manually to open and/or lock the valve disc in an open *. position. * S.

* :
11. A valve head assembly according to claim 10, wherein the manual override means S..comprises means for manually rotating a pivot shaft with which the valve disc is rotationally fast and about the longitudinal axis of which the valve disc rotates for movement between its open and closed positions.
12. A valve head assembly according to claim 11, wherein the pivot shaft extends exteriorly of the head assembly and has a handle formed directly thereon, latching means preferably being provided on the outside of the body which co-operates with the pivot shaft to lock it against rotation and hence lock the valve disc in position.S
13. A valve head assembly according to any of claims 8 to 12, wherein the lost motion coupling takes the formed of a pin and slot coupling between the actuating means and the valve disc, the pm pressing against an end of the slot upon movement of the actuating means in a closing sense so as to move the valve disc to its closed position, and the pin being retracted from said end upon movement of the actuating means in an opening sensor so as to allow the valve disc to pivot away from its closed position.
14. A valve bead assembly according to any of the preceding claims, wherein the actuating means comprises a rotating threaded shaft and on which is mounted a nut, the nut being constrained to move longitudinally along the shaft upon rotation of the shaft, a link member extending between and being pivotally attached to each of the nut and the valve disc, the end of the link member associated with the valve disc being extended towards and retracted away from the inlet upon operation of the actuating means.
15. A valve head assembly according to claim 14, wherein the pin and slot coupling is S..formed between the link member and at least one of the nut and the valve disc.

* S. *e* * S *
16. A valve head assemblt according to claim 14 or claim 15, wherein rotation of the *:. threaded shaft is effected by an actuator which is located outside of the body and which is *: non-rotatably attached to and coaxial with the threaded shaft. 5S
17. A valve head assembly according to claim 14 or claim 15, wherein rotation of the threaded shaft is effected by an actuator which is located outside of the body and which has its axis perpendicular to the axis of the threaded shaft, the actuator being operate to rotate a shaft which is connected to the threaded shaft by a bevel gearing or the like so as to translate rotation about the axis of the actuator into rotation about the axis of the threaded shaft.
18. A valve head assembly according to any of claims 1 to 3, wherein the valve member is a translating valve member in the form of a valve wedge which moves laterally between an extended position in which it completely overlies the inlet and thereby closes it and a retracted position in which it is completely withdrawn from between the inlet and outlet.

* ji
19. A valve head assembly according to claim 18, wherein the translating valve member is mounted on a valve stem which is operatively attached to a cam mechanism having a rotatable actuator, the cam mechanism translating rotation of the actuator into longitudinal movement of the stem so as to slide the valve member back and forth.
20. A valve head assembly according to any of claims 5 to 19, wherein the valve member, in its closed position, extends obliquely across the chamber between the inlet and outlet so as to block the flow therebetween.
21. A valve head assembly according to claim 20, wherein a notch is formed in the chamber in which the valve disk engages when closed.
22. A valve head assembly according to any of claims 5 to 19, wherein the annular *.IS * closure surface is proximate to and surrounds the inlet. * .
23. A hydrant incorporating a valve head assembly according to any of the preceding *. claims, wherein the inlet is below the outlet. * S.

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24. A valve head assembly substantially as herein desribed with reference to the accompanying drawings.
25. A hydrant substantially as herein described with reference to the accompanying drawings.