WO1990000694A1

WO1990000694A1 - Fluid flow control apparatus

Info

Publication number: WO1990000694A1
Application number: PCT/GB1989/000803
Authority: WO
Inventors: Stephen Richard Heneker
Original assignee: Stephen Richard Heneker
Priority date: 1988-07-13
Filing date: 1989-07-13
Publication date: 1990-01-25
Also published as: EP0424450A1; GB8816699D0; AU3968989A

Abstract

A safety shut-off device is disclosed which acts to shut-off the supply of hot water in a pipe when a predetermined temperature threshold is achieved. The device includes a valve seat (8) and a valve member (24) moveable into and out of contact with the valve seat (8). The valve member (24) is supported by a membrane (22) which closes the lower end of a cylindrical chamber (20). The chamber has an opening which is coupled to the flow upstream of the valve seat (8). The valve member (24) has a bore (24C) which extends from the chamber to a location downstream of guide legs (24B) which engage the valve seat to guide the valve member (24) into and out of engagement with the valve seat (8). A bimetallic disc (28) is supported by the legs (24B) on the underside of the valve member (24). When the temperature of the water flowing through the valve seat (8) exceeds a predetermined threshold, the bimetallic disc (28) snaps into a position to close the bore (24C). As a result pressure in the chamber (20) builds up to cause the valve member (24) to close against the valve seat (8).

Description

FLUID PIOW CONTROL APPARATUS

The present invention relates to fluid flow- control apparatus.

Domestic water systems supply hot water to the domestic user. Such systems include mixer taps which mix both hot and cold water usually such systems are adjusted manually to provide water at the right temperature. Mechanical heat responsive apparatus is known which automatically varies the ratio at which hot and cold water are supplied (by means of a bimetallic element for example) in a sense to maintain the mixed water at a constant predetermined temperature.

Such apparatus tends to be slow to react and for short periods of time the temperature of the water can exceed the predetermined temperature.

In the case of single hot water taps there is generally little control available over the water dispensed other than on the very crude temperature control system at the water heater. Thus there is always the danger of the taps issuing scalding water which can produce severe burns on the unwary user.

It is an object of the present invention to provide apparatus which inhibits the flow of fluid through a conduit when the temperature of the fluid reaches a predetermined level.

According to the present invention there is provided a fluid flow control apparatus comprising an inlet conduit, an outlet conduit, a valve seat providing communication between the inlet and outlet conduits, a valve member moveable into and out of contact with the valve seat to open and close communication between the inlet and outlet conduits, a pressurisable chamber having an opening closed by a membrane, said membrane supporting said valve member, - 2 - whereby when the pressure in said chamber is increased the valve member acts to close the valve seat and when the pressure in said chamber is reduced the valve member acts to open the valve seat, and temperature responsive means located in the flow path of fluid through said apparatus, said temperature responsive means being responsive to the fluid achieving a predetermined threshold to cause the fluid in said inlet conduit to act in a sense to increase the pressure in said chamber to a level at which the valve member closes said valve seat.

According to the present invention the is further provided a fluid flow control apparatus comprising a valve seat, a chamber located adjacent the valve seat, a flexible membrane forming part of the chamber wall and carrying a valve member moveable towards or away from the valve seat to open and close the valve seat, means providing communication between the chamber and a location upstream of the valve seat, an opening in said valve member to provide communication between the chamber and a location downstream of the valve seat, and a bimetallic element mounted on the valve member and responsive to the temperature of fluid flow through the valve seat to open and close the opening in dependance thereon.

According to the present invention there is still further provided a fluid flow control apparatus comprising a valve seat defining an outlet port, a valve member, a membrane supporting the valve member for movement towards and away from the valve seat to control the flow of fluid through the port, means for supplying fluid under pressure to the valve member over a part of the face of the valve - 3 - member not shielded by the valve seat, first control means responsive to a command, to vary the pressure on the opposite side of the membrane so as, to allow the fluid pressure on the 5 one side of the membrane to displace the valve member away from the valve seat by a predetermined extent to achieve a predetermined flow from the port, second control means responsive to variations of pressure in the fluid supplied to the

10 port to adjust the pressure on the said opposite side of the diaphragm in a sense and by an amount to tend to maintain the rate of flow from the outlet substantially constant over a predetermined range of pressure variations in the fluid supplied,

15 and temperature responsive means responsive to. the temperature of the fluid flowing though the valve seat and operable when a predetermined threshold is achieved to vary the pessure across the diaphragm in a sense to cause the valve member to

20 close the valve seat.

According to the present invention there is yet further provided a valve assembly comprising: a housing defining a chamber, a diaphragm located in the housing to divide the chamber into two separate 25 sections, a common source of fluid, means defining a main flow path connected to one section, means defining a control flow path having an intermediate portion connected to the other section, both the main . and control flow paths being arranged to be connected

¹ 30 to the common source of fluid, a valve member supported by the diaphragm and moveable in response to relative changes in pressure between the two _'. sections to open and close the main flow path, i an inlet and outlet control valve mounted

35 in the control flow path respectively upstream and - 4 - downstream of the said portion of the flow control path, the two control valves being independently operable to change the pressure in said other section and thereby controlling the opening and closing of the main flow path by said valve member, the two control valves being both closed under any steady state flow condition in the main path, means defining a passage extending from said common source of fluid to the intermediate portion of the flow path, and temperature responsive means normally holding said passage close but operable in response to the temperature of the fluid flow from said source achieving a predetermined - threshold to open said passage and thereby cause said valve member to close the main flow path.

Plow control apparatus embodying the present invention will now be described,, by way of example, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a longitudinal section through the apparatus with a bimetallic element in an operative mode;

Figure 2 is a detail of the apparatus of Figure 1 shown to an enlarged scale with the bimetallic element in its normal state;

Figure 3 is a longitudinal section of a hot water tap incorporating a fluid flow control apparatus; and

Figure 4 is a longitudinal section of a controllable water supply valve.

The hot water flow control apparatus to be described, is intended to be installed in an existing hot water supply pipe (for example a copper pipe) and is arranged to cut off the supply of hot water along - 5 - the pipe when the temperature of the water flowing through the apparatus exceeds a predetermined level.

^'' It will be apparent to the skilled reader that the apparatus can readily be adapated to shut off the supply of water when the temperature drops below a predetermined level.

As shown in Figure 1 the apparatus comprises a body 2 with an inlet conduit 4 and an outlet conduit

6 extending along a common axis from opposite sides of the body 2. The free end portions of the inlet and the outlet conduits 4 and 6 are each externally screw threaded to enable the apparatus to be installed in a copper pipe, for example using conventional compression fittings. Instead the free end portions may be coupled into a copper pipe using conventional lead soldering techniques well known to plumbers. The body 2 is generally cylindrical and has an axis which extends at right angles to the common axis of the conduits 4 and 6. Rising within the cylindrical body 2 is a cylindrical valve seat defining a channel of generally circular cross- section that communicates with the outlet conduit 6. The valve seat has an axis which extends parallel to but lies spaced from the axis of the body. Also located within the body 2 and lying to one side of the valve seat 8 is an inlet orifice 10 which provides communication with the inlet conduit 4- The upper rim of the body 2 is externally screw threaded. The upper rim of the body 2 is closed by a cap member 12 having at its lower end, a radially and inwardly directed flange 16 which rests on the axial end face of the upper rim. A sealing washer 14 is interposed between the upper rim and the flange 16. A clamping nut 18 encircling the cap member 12 screw threadedly engages the upper rim of the body 2 and can be - 6 - tightened to clamp the flange 16 and the washer 14 against the end face of the upper rim. A cylindrical member 20 is located within the cap member 12 extending downwardly from the roof thereof. The cylindrical member 20 is of smaller diameter than that of the cap member and has a wall which is at one point contiguous with the wall of the cap member 12. Thus the axis of the cylindrical member 20 is parallel to but spaced from the axis of the cap member 12. In fact the axis of the cylindrical member 20 is arranged to be generally coaxial with the axis of the valve seat when the cap member 12 is clamped to the rim by the clamping nut 18.

^'The lower end face of the cylindrical member 20 is closed by a flexible diaphragm 22, which is secured to the lower face by welding, adhesive or any other well known^' method. The diaphragm 22 carries a valve member 24 having an upper support portion 24A which supports a central region of the diaphragm 22 to move an annular portion of the diaphragm 22 into and out of sealing engagement with the valve seat 8.

The valve member 24 has four downwardly depending legs 24B equiangularly spaced about the central axis of the member 24. The legs 24B are of arcuate cross-section and engage the valve seat to guide the movement of the valve member 24 along the axis of the valve seat 8.

. The valve member 24 has a central bore 24C which is coaxial with the axis of the valve seat 8 and which provides communication between the chamber defined by the cylindrical member 20 and the channel defined by the valve seat. Located directly below the bore 24C is an elastomeric closure member 26 which is moveable into and out of engagement with the valve member 24 to open and close the bore 24C. The closure member 26 is supported centrally on an arcuate bimetallic dome shaped disc 28 having its outer perimeter embedded in or otherwise secured to, the inner faces of the legs 24B. The disc 28 may be perforated or otherwise provided with apertures or cutouts to improve the flow of water there past. Otherwise flow will take place through the spacings between adjacent legs. The wall of the cylindrical member 20 is provided with an aperture 30 having a smaller cross- sectional area to that of the bore 24C.

In operation it will be assumed that the hot water passing through the apparatus has exceeded the predetermined temperature and that the bimetallic disc 28 has responded by adopting the convex configuration shown in Figure 1 to cause the closure member 26 to close the bore 24C.

In this state water entering the inlet conduit 4 will pass into the body 2 to act on the underside of the diaphragm. At the same time water will enter the chamber defined by the cylindrical member 20 through the aperture 30. As the chamber fills up it will force the diaphragm 22 downwardly to bring it into contact with the valve seat 8. The area on the underside of the diaphragm 22 now exposed to pressure by water entering into the body 2 is now reduced by the area of the valve seat while the area of the diaphragm within the chamber exposed to pressure remains unchanged. As a result there is a significant pressure differential across the diaphragm which acts to hold the valve seat closed.

As the temperature of the bimetallic disk drops below the predetermined value a point will be reached at which the bimetallic disk snaps back into - 8 - a concave mode. When this occurs the closure member 26 is pulled away from the bore 24C and water will start to flow through the bore 24C. Since the rate of flow of water through the bore 24C is greater than the rate of flow of water entering the aperture 30 by virtue of their relative sizes, the pressure within the chamber will drop and the pressure of water acting on the underside of the diaphragm 22 will now be greater than the pressure on the opposite side. As a result the diaphragm will be displaced upwardly to be lifted off the valve seat 8. Water will now flow through the valve seat 8 and out through the outlet conduit. When the temperature of this water flow again exceeds the predetermined temperature, the bimetallic disk will snap into a convex mode again causing the closure member 26 to close the bore 24C. This allows pressure to build up again in the chamber and as the pressure builds up the diaphragm is once again forced downwardly to close the valve seat. It will be appreciated that the legs 24B not only provide a support for the bimetallic disc but also act to guide the valve member and diaphragm in their movements towards and away from the valve seat.

The apparatus may be generally fabricated of brass or plastics material such as an acetal copolymer. The diaphragm is advantageously of a melt processable elastomer having little resilience and the bimetallic disk is tin plated or otherwise treated with a corrosion resistant material. It will be appreciated that while the invention has been described in connection with a water shut off device on its own it can be incorporated in other valves and taps where the opening and closing of the valve of the tap is assisted by the pressure of the water. -. 9 - For example in US Patent No. 4,725,038 the subject matter of which is incorporated herein by reference, the pillar tap described can be modified to cause the water to be shut off automatically when the temperature of the water exceeds a predetermined level.

The modification is shown in Figure 3« The pillar tap or faucet shown in Figure 3 includes an inlet 121 which, in use, is arranged to be coupled to the domestic water supply system. The body of the faucet defines a generally cylindrical chamber 123 which communicates both with the inlet 121 and a spout 120 which defines an outlet duct. The spout 120 has an upstream portion defining an annular valve seat 124 extending into the lower end of the chamber 123 and a downstream portion terminating in a discharge port 125-

A diaphragm 126 located in the chamber separates the chamber in a liquid-tight manner into upper and lower sections. The diaphragm 126 supports a valve 127 in the form of a plug and constrains it for movement within the chamber towards and away from the valve seat. The under side of the plug carries a projecting guide which is arranged to engage the inner wall of the valve seat so as to guide the plug on to the valve seat. The guide has a stepped or fluted profile so that as the valve is progressively opened, the flow rate through the valve will increase in a non-linear manner; very slowly at first and then progressively faster.

An upper chamber 119 located above the generally cylindrical chamber 123 is in communication with the inlet 121 via a channel 122. A valve member 128 in the channel 122 controls the flow of water through the cahnnel 122. The upper chamber 119 is in - 10 - communication with the cylindrical chamber 123 through openings in the roof of the chamber 123. Another channel 137 provides communication between the upper chamber 119 and the downstream portion of the spout 120. A valve member 129 located in the channel 137, opens and closes the flow to the channel.

A lever 131 supported by a shaft 134 is housed in the upper chamber 119- The shaft 134 projects through an opening in the roof of the upper chamber 119- An 0-ring seal 133 between the shaft 134 and the roof not only provides a liquid-tight seal between the wall and the shaft 134, but also pivotally supports the shaft on the roof. The two valve members 128 and 129 are each provided with a respective control rod. Each control rod has a central portion of reduced cross-section. The ends of opposite arms of the control lever 131 are bifurcated and sliάably engage the reduced cross- section portions or respective ones of the control rods. In this way there is a degree of lost motion in the coupling between the lever and the control rods of the two valve members. The lower end of the valve member 28 carries a frusto conical valve which is arranged to engage a valve seat, when the valve member 1 8 is urged into the raised position by an arm of the lever 131 pivoting in a clockwise sense to engage the axial end face of an upper step in the control rod of the valve member 128. When the arm is pivoted in an anti¬ clockwise sense (with the valve closed) it will engage the axial end face of the lower step in the rod and displace the rod downwardly to open the valve. The diameter of the rod of each valve - 11 - member 128 and 129 where it lies within the bore is slightly smaller than the bore so as to allow the rod to slide easily along the bore and to allow water to flow between the bore and the rod. Preferably the rod is provided with grooves or slots to increase the rate of flow of water through the bore.

The upper axial end of the rod of the valve member 129 carries a rubber washer of considerably lesser diameter than the bore but which can engage an annular valve seat at the upper end of the bore to close off the flow of water to the bore 137. The other arm of the lever 131 is arranged to control the upward and downward movement of the rod by engaging the axial end face of the upper and lower steps in the rod. Pivotal movement of the lever 131 in an anti-clockwise sense moves the rod upwards to cause the washer to engage the annular seat and so close the valve 129- Pivotal movement of the lever 131 in a clockwise sense moves the rod downwards to open the valve 129-

The shaft 134 carries a lever 110 at its upper end. A pair of ON" "OFF" push buttons 135 and 136 are located above the lever 110, one adjacent each of the two arms of the lever 110. Each push button 135 and 136 is spring- loaded away from the lever 110 but has a respective actuating pin extending towards the lever, to engage and tilt the lever 110 upon depression of the corresponding button. In operation with the faucet or tap in the

OFF condition, depression of the ON button will cause the water flow to increase progressively. Release of the ON button will prevent further increase in the water flow rate, and the water flow through the faucet will continue at a constant rate. Depression - 12 - of the OFF button turns the faucet OFF, preventing water flow through the faucet. If the ON button is only partially depressed, a small flow is established which will automatically be shut off as soon as the ON button is released. When a flow through the faucet has been established and it is required to reduce this flow without turning the faucet OFF, a partial depression of the OFF button will achieve this. When the flow rate from the faucet has been reduced to the desired rate, releasing the OFF button will cause the flow to remain constant again.

In Figure 3 the faucet is shown in the OFF condition. In this state the valve 128 is maintained open by the force of gravity. Instead the valve is biased into its open state by other means. A detent mechanism (not shown) is provided to hold the valve in its open state until forcibly returned to its closed state. Water pressure from the faucet inlet 121 communicates with the upper portion of the chamber 123 through the upper chamber 119, the channel 122 and the inlet valve 128. The outlet valve 129 in the passage leading from the upper chamber 119 is maintained closed by a spring 130. In this condition, both sides of the diaphragm 126 are subjected to the same pressure from the supply. However, as there is a greater surface area under pressure above the diaphragm than below it, there will be a greater force acting on the upper surface of the diaphragm and so the diaphragm will urge the plug 127 against its valve seat 124 to block any flow of water from the lower section of the chamber 123 to the spout 120.

Depression of the ON button tilts the lever 110 and therefore the shaft 134 about its 0-ring seal 131_* This in turn displaces the lever 131 to open - 13 - the valve 129 and to close the valve 128. The valve 128 is then maintained against its valve seat by water pressure from the inlet 121. A small volume of water now flows from the outlet valve 129, into the faucet outlet 120 via channel 137. This reduces the pressure in the upper part of the chamber 123 and so the diaphragm 126 will slowly rise by an amount corresponding to the volume of water lost through outlet valve 129- The plug 127 is lifted by the water pressure and flow of water from inlet 121 via the lower section of the chamber 123 to outlet 120 can now take place. The longer that the ON button 1 5 is held depressed the greater will be the amount of water discharged through the valve-and consequently the greater the flow through the faucet. The increase in flow rate through the faucet may be arrested at any point during the opening cycle by releasing the ON button. With the ON button released, water will flow through the faucet at the required constant rate until altered by depression of either the ON or OFF buttons.

With the faucet running at a constant rate, but not at maximum flow, an increase in the flow rate through the faucet is achieved by further depressing the ON button until the flow has increased to the desired rate. Once the desired rate has been achieved, the ON button is released and once more, water will flow through the faucet at a constant but now increased rate. To reduce the rate of waτer flow without turning the faucet off altogether, the mechanism operates in the following manner: It should first be noted that the OFF button has two operating pressures. The first pressure is when the button is partially depressed and the second .pressure is when - 14 - the button is fully depressed. To reduce the faucet water flow without turning the faucet OFF, the OFF button is partially depressed to its first operating pressure. This opens the inlet valve 128 partially, while leaving the outlet valve 129 closed. In this condition, water flows into the chamber 123 above the diaphragm effecting a downward displacement of the plug 127- The water flow through the faucet is therefore reduced. As valve 128 is only partially opened, hydraulic pressure in the passage 122 will cause inlet valve 128 to be lifted against its seat as soon as the OFF button is released, thereby preventing any further closing of the faucet. The flow of water from the faucet will then remain constant until altered by a subsequent depression of either the ON or OFF button.

To stop all flow -from the outlet 120, with the faucet running at a steady rate, the OFF button is depressed to its second pressure position. This tilts the lever 131 to open the inlet valve 128. The lost motion built into the outlet valve 1 9 between its operating shoulders allows the lever 131 to rise without displacing the outlet valve 129 and so the outlet valve 129 remains closed. With inlet valve 128 fully open, the chamber 119 and the upper section of chamber 123 will fill rapidly causing the faucet to close rapidly. The inlet valve is so profiled that the flow of water past it tends to hold it open. When the faucet is closed and no further flow passes the inlet valve, it will open under gravitational force. However, when the faucet is open and there is no flow past the inlet valve, the valve will close as will be enplained hereinafter.

'With the faucet closed, a very small flow may be established by partially depressing the ON - 15 - button. This has the effect of opening the outlet valve 129 but the inlet valve 128 will remain fully open. With the inlet valve still open, the diaphragm holds the plug in its closed state, but with the outlet valve 129 open, a small flow is created through the outlet channel 137 to the main faucet outlet 120. This gives a drip control facility to the faucet for the dispensing of small volumes of water. Releasing the ON button automatically closes the faucet in this instance, without the need for depressing the OFF button, because the inlet valve will return to its fully open position while the outlet valve will close again.

The hot water SHUT-OFF modification includes a channel 138 extending from the inlet 121 to the upper chamber 119- A bimetallic strip 139 has its lower end rigidly secured to the linear face of the inlet 121 and carries at its opposite end a closure pad 140. The pad 140 is positioned to face the entrance to the channel 138 and when the water temperature in the inlet lies below the predetermined temperature level the bimetallic strip is tensioned to urge the pad 140 to close the entrance to the channel. In this position the faucet or tap operates normally and as hereinbefore described. As soon as the temperature of the water in the inlet 121 exceeds the predetermined temperature the bimetallic strip 139 reacts to become tensioned in the opposite sense. The pad 140 is pulled away from the entrance to the channel 138 and water under pressure enters the chamber -123• As described hereinbefore when the inlet 121 communicates with the chamber 123 the plug 127 is forced downwardly to close off the supply of water to the discharge port 125• Accordingly shut off is automatically effected when the water - 16 - temperature exceeds the predetermined temperature. When the water has cooled sufficiently to allow the bimetallic strip to close off the chan-nel 138 the faucet or tap can resume normal operation and water flow is initiated by pressing the ON button 136.

In another example in European Patent Specification No. 0 268 358 (corresponding to US Patent Application No. 07/099 397) the subject matter of which is incorporated herein by reference, a flow stabiliser is provided which once set maintains the flow of fluid therethrough substantially constant.

In the modification shown in Figure 4 a valve incorporating a flow stabiliser, has a housing 150, an inlet conduit 152 leading to a control chamber 151, a valve seat 154 in a housing defining a control chamber, and an outlet conduit 155 leading from the valve 1 4-

Housed within the chamber 151 is an elongate closed container 153 filled with water. The lower rim of the container 153 is supported on a land in the bottom of the chamber 151, which land extends generally about the valve seat 154-

The underside of the container 153 is closed by a flexible membrane 156 which in turn supports a centrally located valve member 157 for vertical movement. The vertical axis of movement of the valve member 1 7 is in alignment with the axis of the valve seat 154. The roof 158 of the container 153 is of undulating profile to allow it to flex more readily. A rigid rod 159 is attached to a central portion of the roof 158 and passes through an opening in the roof of the housing 150. An 0-ring 160 is provided to provide a water tight seal between the rod 159 and the housing 150 at the point at which the - 17 - rod 159 passes through the housing 150.

The container 153 has four side walls; one pair of opposite walls and being of arcuate configuration and conforming to the inner surface of the housing 150 to hold the container rigidly in position within the chamber, a third wall being rigid and planar, and a fourth wall (not shown) being of undulating profile so as to enable it to flex more readily. The container 153 is of an acetal copolymer and is such that upon flexure of any wall it will resile. The membrane 156 is made of a melt- processable elastomer for example Santoprene (Registered Trade Mark) having little or no resilience.

As can be seen, the profiles of the container 153 and the chamber 151. are such that water entering the inlet conduit 1 2 will pass through the gap between the wall and the housing 1 0, over the roof of the container, through the gap between the wall and the housing to the underside of the membrane. When the valve member is lifted off the valve seat 154, water will then flow through the valve seat and out along the outlet conduit 1 5- In operation with the rod 159 held in its depressed state, the roof will be bowed inwardly and so the incompressible liquid in the container will act on the membrane 156 to displace the valve member 157 into engagement with the valve seat 54. In this position a central area of the membrane 156 is shielded from the water pressure. Since the roof has a greater area subjected to water pressure than the unshielded part of the membrane 1 6 there will be a net force on the container acting to urge it towards the valve seat 154 and since the contents of the - 18 - container are incompressible this net force will be the force acting on the valve member 157 to maintain it closed.

To open the valve member 157 the rod 159 is raised. This will pull the roof upwardly increasing the volume inside the upper portion of the container 153- This now allows the pressure on the underside of the unshielded part of the membrane to displace the valve member 154 upwardly thus releasing water from the chamber 151 into the outlet conduit 155-

The extent of upward movement of the valve member 157 will depend upon the extent to which the volume in the upper part of the chamber has been increased and this in turn will depend upon the upward movement of the rod 159* Thus the flow rate through the valve will vary as a function of the displacement of the rod 159-

When a required flow rate is achieved, this flow rate will remain constant so long as the pressure of the water in the inlet conduit 152 remains constant. If the pressure were to increase the flow rate would tend to increase and vice versa. However, the provision of an undulating resilient wall acts to compensate for variations in pressure. The undulating wall is arranged to have a greater surface area than that of the unshielded part of the membrane 156 and thus if the pressure inside the chamber rises, the wall will be bowed inwardly by this increase in pressure and the displaced liquid in the container 153 will act on the membrane 156 to displace the membrane 156 downwardly.

This has the effect of moving the valve member 157 towards the valve seat 154.

It will thus be seen that an increase in water pressure will tend to increase the flow rate - 19 - through the valve but the consequent reduction in the gap between the valve member 157 and the valve seat 154 will tend to reduce the flow rate and so the net result is that the flow rate remains unchanged. Similarily any reduction in water pressure will allow the resilient wall to return towards its unstressed state under its own resilience and thus will allow the valve member 157 to rise to increase the gap between the valve member 157 and its seat 154.

The reduction in pressure accompanied by the slight corresponding opening of the valve will tend to maintain the flow rate through the valve unchanged. The hot water SHUT-OFF modification includes an opening 162 in the planar rigid wall of the container 153. A bimetallic strip 163 has one end rigidly fixed to the planar rigid wall and carries at its 'free end portion a closure pad 164 positioned to face the opening 162. When the temperature of the water flowing through the valve is less than the predetermined level then the bimetallic strip 163 is tensioned to urge the pad 164 against the opening 162 to close the opening. In this state the valve operates as already described. However, as soon as the water temperature exceeds the predetermined temperature the bimetallic strip will pull the pad away from the opening 162 to admit water under pressure to the interior of the container 53- As pressure in the container 153 increases it will act on the membrane to urge the plug 157 against the valve seat 154 and so shut off the water to the outlet conduit 155-

Wherithe temperature of the water drops below the predetermined temperature the bimetallic - 20 - strip will flex to cause the pad 164 to close the opening 162. Water flow can then be resumed by raising the rod 159 again.

After a series of shut off's the volume of water within the container will have built up progressively and so further scope for lifting the rod 1 9 may not be possible. In this event the rod 159 is driven down under pressure until the pressure water in the container 153 displaces the pad 164 away from the opening 162 and a certain volume of water is expelled. Thereafter the normal operation of the valve can be resumed.

It will be appreciated that the described applications relate primarily to domestic water supply devices and the temperature at which the devices will close for domestic hot water systems is likely to be about 60 degrees Celsius. The invention may equally be used in other applications to control the flow of other fluids. It should also be appreciated that while the devices described above close when the inlet supply fluid temperature exceeds a certain value, by using a bimetallic spring or other temperature sensitive device that deflects in the manner described above when the inlet supply fluid temperature falls below a certain value. For example, in an application where the supply temperatures of a fluid must not fall below a certain value, such an apparatus would close as the supply fluid temperature drops below a specified value.

Claims

- 21 - CLAIMS

1. Fluid flow control apparatus comprising an inlet conduit, an outlet conduit, a valve steat providing communication between the inlet and outlet conduits, a valve member moveable into and out of contact with the valve seat to open and close communication between the inlet and outlet of conduits, a pressurisable chamber having an opening closed by a membrane, said membrane supporting said valve member,whereby when the pressure in said chamber is increased the valve member acts to close the valve seat and when the pressure in said chamber is reduced the valve member acts to open the- valve seat, and temperature responsive means located in the flow path of fluid through said apparatus, said temperature responsive means being responsive to the fluid achieving a predetermined threshold to cause the fluid in said inlet conduit to act in a sense to increase the pressure in said chamber to a level at which the valve member closes said valve seat.

2. Apparatus according to Claim 1 wherein said chamber includes a first aperture which is permanently open to said inlet conduit, and a second aperture which provides communication from the chamber to the outlet conduit, said temperature responsive means comprising means for opening and closing the second aperture.

3« Apparatus according to Claim 2 wherein said second aperture is defined by a passage in said valve member leading from said chamber to said outlet conduit.

4« Apparatus according to any preceding claim wherein said temperature responsive means comprises a - 22 - bimetallic member located downstream of said valve seat and carrying a fluid flow closure element.

5- Apparatus according to Claim 3 wherein said temperature responsive means comprises a dome-shaped bimetallic disc mounted on the valve member and carrying a closure member moveable into and out of contact with the second aperture in response to flexure of said disc.

6. Apparatus according to any preceding claim including a plurality of guides legs rigid with said valve member and engaging said valve seat to guide the valve member along a predetermined axis with respect to the axis of the valve seat.

7. Apparatus according to Claim 6- dependent upon Claim 5 wherein the periphery of said disc is rigidly supported by said guide legs.

8. Apparatus according to Claim 2 or any one of Claims 3 to 7 as dependent upon Claim 2 wherein the cross-sectional area of the second aperture is substantially larger than that of said first aperature.

9- Fluid flow control aperatus comprising a valve seat, a chamber located adjacent the valve seat, a flexible membrane forming part of the chamber wall and carrying a valve member moveable towards or away from the valve seat to open and close the valve seat, means providing communication between the chamber and a location upstream of the valve seat, an opening in said valve member to provide communication between the chamber and a location downstream of the valve seat, and a bimetallic element mounted on the valve member and responsive to the temperature of fluid flow through the valve seat to open and close the opening in dependance thereon. - 23 -

10. Fluid flow control apparatus comprising a valve seat defining an outlet port, a valve member, a membrane supporting the valve member for movement towards and away from the valve seat to control the flow of fluid through the port, means for supplying fluid under pressure to the valve member over a part of the face of the valve member not shielded by the valve seat, first control means responsive to a command, to vary the pressure on the opposite side of the membrane so as to allow the fluid pressure on the one side of the membrane to displace the valve member away from the valve seat by a predetermined extent to achieve a predetermined flow from the port, and second control means responsive to variations of pressure in the fluid supplied to the port to adjust the pressure on the said opposite side of the diaphragm in a sense and by an amount to tend to maintain the rate of flow from the outlet substantially constant over a predetermined range of pressure variations in the fluid supplied, and temperature responsive means responsive to the temperature of the fluid flowing though the valve seat and operable when a predetermined threshold is achieved to vary the pressure across the diaphragm in a sense to cause the valve member to close the valve seat.

11. Apparatus according to Claim 10 wherein said first control means comprises means defining a tubular enclosure closed at one end by a side of said membrane remote from the valve seat, a carrier supported for movement along said tubular member, - 24 - and a diaphragm supported by the carrier and in sliding sealing engagement with the inner wall of the carrier to define a sealed chamber, and a substantially incompressible fluid filling said chamber, and wherein said temperature responsive means comprises means for opening said sealed chamber to admit further fluid therein.

12. A valve assembly comprising: a housing defining a chamber, a diaphragm located in the housing to divide the chamber into two separate sections, a common source of fluid, means defining a main flow path connected to one section, means defining a control flow path having an intermediate portion connected to the other section, both the main and control flow paths being arranged to be connected to the common source of fluid, a valve member supported by the diaphragm and moveable in response to relative changes in pressure between the two sections to open and close the main flow path, an inlet and and outlet control valve mounted in the control flow path respectively upstream and downstream of the said portion of the flow control path, the two control valves being independently operable to change the pressure in said other section and thereby controlling the opening and closing of the main flow path by said valve member, the two control valves being both closed under any steady state flow condition in the main path, means defining a passage extending from said common source of fluid to the intermediate portion of the flow path, and temperature responsive means normally holding said passage close but operable in response to the temperature of the fluid - 25 - flow from said source achieving a predetermined threshold to open said passage and thereby cause said valve member to close the main flow path.

13. An assembly, according to Claim 12, including: means defining an outlet duct having an upstream end projecting into said one section of the chamber and defining a seat for the valve member, the duct, when the valve is seated thereon, acting to reduce the surface area of the diaphragm in said one section to which fluid pressure is applied and thereby enabling a net force to be exerted on the diaphragm, in a sense to hold the valve member in a closed state.