WO1997032147A1

WO1997032147A1 - Mixing valve responsive to inlet pressure conditions

Info

Publication number: WO1997032147A1
Application number: PCT/AU1997/000116
Authority: WO
Inventors: Gary Sutherland Hay
Original assignee: Gsa Industries (Aust.) Pty. Ltd.
Priority date: 1996-02-29
Filing date: 1997-02-28
Publication date: 1997-09-04
Also published as: AUPN836196A0; ZA971780B

Abstract

A mixing valve for blending incoming streams of hot and cold water and controlling the temperature of the mixed flow passing through an outlet (4) of the valve. Hot and cold water streams enter a mixing chamber (5) through respective inlets (3a, 2a) and the valve includes a valve member (7) which is mounted within the valve body (1) for movement relative to a cold water inlet seat (34a) and a hot water inlet seat (6). The arrangement is such that the valve member (7) is engageable with either of those valve seats (34a, 6) and moves towards one while moving away from the other. An outward shoulder (23) is formed on the valve member (7) so as to be exposed to the incoming hot water stream such that the prevailing conditions of that stream impose a closing force on the valve member (7) which urges the member (7) towards the hot water inlet seat (6). A mixing tube (24) communicates with the mixing chamber (5) and is provided with transverse openings (31) through which hot water enters the mixed water flow passing through the interior of the tube (24) from the mixing chamber (5). The valve can be arranged to close either inlet (2a, 3a) while leaving the other open, or to close both inlets (2a, 3a) if the temperature responsive element (16) fails, for example.

Description

MIXING VALVE RESPONSIVE TO INLET PRESSURE CONDITIONS

BACKGROUND OF THE INVENTION This invention is concerned with mixing valves as used in fluid reticulation systems to regulate the temperature or other condition of a mixture comprising two or more fluids received from different sources. The invention will be hereinafter described with particular reference to the mixing of hot and cold water so as to regulate the temperature of water delivered to an outlet, but it is to be understood that the invention has wider application.

A dangerous situation can develop if the cold water flow to a mixing valve ceases or reduces significantly in pressure. It is necessary for the valve to respond to that changed condition to avoid delivery of excessively hot water to the outlet, but prior to the present invention many mixing valves did not possess satisfactory fail-safe characteristics for that purpose. Furthermore, the prior mixing valves have not been entirely satisfactory in providing thorough mixing of the hot and cold water such as to ensure that the outlet flow is of substantially stable temperature.

Mixing valves which regulate the temperature of an outlet flow generally include an element which controls the flow of hot and cold water streams into a mixing chamber and which responds to temperature changes within that chamber to reduce or increase the flow of either the cold water or the hot water stream. In the event of failure of the temperature responsive element it is important to shut-off the hot water flow, at least, with minimum delay, but prior mixing valves have not been entirely satisfactory in that regard.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mixing valve having improved fail-safe characteristics. It is a further object of the invention to provide a mixing valve which ensures thorough mixing of the fluids received by that valve. It is still another object of the invention to provide a valve having both of the aforementioned characteristics. Yet another object of the invention is to provide a mixing valve cartridge which can be inserted into an existing valve housing to create a valve having improved fail-safe and/or mixing characteristics. A mixing valve according to one aspect of the present invention is characterised in that it includes a mixing chamber, an outlet and a first inlet each of which communicates with the mixing chamber, a second inlet capable of communicating with the mixing chamber, a valve seat, a valve member which is movable relative to the valve seat and is engageable with that seat to prevent communication between the second inlet and the mixing chamber, and a surface area of the valve member which is exposed to incoming flow through the second inlet so that the prevailing conditions of that flow impose a closing force on the valve member tending to move that member towards the valve seat. In such an arrangement the flow imposed closing force causes or assists rapid engagement of the valve member and the valve seat in circumstances where there is no flow or relatively little flow through the first inlet.

In accordance with another aspect of the invention there is provided a mixing valve cartridge which is insertable into a valve body having at least two inlets and an outlet, and the cartridge includes a mixing chamber, a valve seat, a valve member which is movable relative to the valve seat and is engageable therewith, and a surface area of the valve member which when the cartridge is in use is exposed to the conditions of incoming flow through one of the valve inlets so that the valve member is subjected to a flow imposed closing force which tends to move that member towards the valve seat. The cartridge is adapted to cooperate with the valve body in such a way that engagement between the valve member and the valve seat prevents communication between the mixing chamber and the aforementioned one inlet.

In one particular application of the invention the mixing valve is of the thermostatic type having a temperature responsive element exposed to the mixing chamber and connected to the valve member so as to move that member towards the valve seat when the temperature within the mixing chamber rises above a predetermined level. In such an arrangement the incoming flow which influences closing movement of the valve member may be hot water flow and the other valve inlet is adapted to receive cold water flow. The arrangement is such that under some circumstances the closing force imposed on the valve member by the hot water flow conditions dominates over the closing influence of the temperature responsive element and causes the valve to close more rapidly than would otherwise occur.

The valve, or a cartridge for use with a valve, may include a mixing tube which forms at least part of the mixing chamber or is included in that chamber. In the case of a thermostatic valve the mixing tube is preferably arranged to receive at least part of the temperature responsive element in such a way that a flow passage exists between that element and an inner surface of the tube.

The flow passage communicates with the valve outlet and is arranged to receive incoming flow from both inlets when the valve is open so that those flows thoroughly mix and the combined flow has direct contact with the temperature responsive element.

In accordance with a further aspect of the invention there is provided a mixing valve having a mixing chamber, an outlet and a first inlet each of which communicates with the mixing chamber, a second inlet capable of communicating with the mixing chamber, isolating means operable to prevent communication between the second inlet and the mixing chamber, and a mixing tube which forms part of the mixing chamber or communicates with the mixing chamber. The mixing tube is arranged to receive incoming flow from each of the inlets so as to promote thorough mixing of those flows prior to exhaust of the combined flow through the outlet. If the valve is of the thermostatic type adapted to mix hot and cold water flows, a temperature responsive element may be arranged so that at least part of that element is contained within the tube and a flow passage which receives each of the two incoming flows is formed between that element part and an inner surface of the tube, and that flow passage communicates with the valve outlet. The isolating means may include a valve seat and a relatively movable valve member which is engageable with the valve seat.

According to yet another aspect of the invention there is provided a cartridge for use in a mixing valve and which includes the mixing chamber, isolating means and mixing tube as referred to in the preceding paragraph. Such a cartridge is adapted to be insertable in a valve body having two inlets and an outlet as referred to in the preceding paragraph. ln accordance with still another aspect of the invention, there is provided a valve including, a mixing chamber, first and second inlets through which respective streams of fluid can flow into said chamber, an outlet through which fluid can leave said chamber, a valve member movable relative to said inlets and being operable to close either one of said inlets or both of said inlets and thereby prevent communication between said chamber and one or both respectively of said inlets, said valve member being operative to close said first inlet and leave said second inlet open when moved in one direction and to close said second inlet and leave said first inlet open when moved to a first position in a direction opposite to said one direction, said valve member being operative to close both said inlets when moved in said opposite direction beyond said first position to a second position, a temperature responsive element exposed to said mixing chamber and being connected to said valve member so as to be operative to control the position of the valve member relative to said inlets in accordance with the temperature conditions existing within said mixing chamber, and biasing means urging said valve member in said opposite direction and being operative to move said valve member to said second position in response to failure of said temperature responsive element.

In accordance with a still further aspect of the invention, there is provided a valve cartridge assembly for use within a valve body having first and second inlet ports and an outlet port, said assembly including, a mixing chamber, first and second inlets through which respective streams of fluid can flow into said chamber from said first and second ports respectively, an outlet through which fluid can leave said chamber, a valve member movable relative to said inlets and being operable to close either one of said inlets or both of said inlets and thereby prevent communication between said chamber and one or both respectively of said inlets, said valve member being operative to close the first said inlet only when moved in one direction and to close said second inlet only when moved to a first position in a direction opposite to said one direction, said valve member being operative to close both said inlets when moved in said opposite direction beyond said first position to a second position, a temperature responsive element exposed to said mixing chamber and being connected to said valve member so as to be operative to control the position of the valve member relative to said inlets in accordance with the temperature conditions existing within said mixing chamber, and biasing means urging said valve member in said opposite direction and being operative to move said valve member to said second position in response to failure of said temperature responsive element.

It will be convenient to hereinafter describe the invention with particular reference to a thermostatic mixing valve arranged to receive hot and cold water flows, but as previously stated the invention has wider application. Embodiments of the invention are described in detail in the following passages of the specification which refer to the accompanying drawings. The drawings, however, are merely illustrative of how the invention might be put into effect, so that the specific form and arrangement of the various features as shown is not to be understood as limiting on the invention. BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Figure 1 is a cross-sectional view of a mixing valve in accordance with one embodiment of the invention.

Figure 2 is an enlarged view of part of the valve shown in Figure 1 and showing the hot water inlet closed.

Figure 3 is a still further enlarged view of part of the valve arrangement shown in Figure 2.

Figure 4 is a view similar to Figure 2 but showing the hot water inlet open. Figure 5 is a cross-sectional view of a valve according to another embodiment of the invention.

Figure 6 is a side elevation view of a valve according to still another embodiment of the invention.

Figure 7 is a cross-sectional view taken along line VII-VII of Figure 6. Figure 8 is a cross-sectional view of yet another embodiment of the invention. Figure 9 is an enlarged view of part only of a mixing tube according to one embodiment of the invention.

Figure 10 is a view similar to Figure 9 but showing another form of mixing tube. Figure 11 is a view similar to Figure 9 and showing still another form of mixing tube.

Figure 12 is a view similar to Figure 9 showing yet another form of mixing tube.

Figure 13 is a view similar to Figure 9 showing a further form of mixing tube.

Figure 14 is a cross-sectional view of another embodiment of the invention.

Figure 15 is an enlarged view of part only of the valve shown in Figure

14 and which shows the valve in one condition of operation. Figure 16 is a view similar to Figure 15 but showing the valve in another condition of operation.

Figure 17 is a view similar to Figure 15 and showing the valve in still another condition of operation.

Figure 18 is a cross-sectional view of yet another embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The particular valve shown by Figure 1 includes a hollow body 1 having a cold water inlet port 2, a hot water inlet port 3 and an outlet port 4, each of which communicates with a mixing chamber 5 when the valve is in an open condition as shown by Figure 1. The cold water port 2 communicates with the mixing chamber 5 by way of a valve controlled inlet 2a, and the hot water port

3 communicates with the mixing chamber 5 by way of a valve controlled inlet

3a. Isolating means is operable to close off communication between the inlet port 3 and the mixing chamber 5 under conditions hereinafter described, and in the particular arrangement shown that isolating means includes a valve seat 6 and a valve member 7 which is movable relative to the valve seat 6 and is engageable with the valve seat 6 so as to close the inlet 3a and thereby isolate the mixing chamber 5 from the hot water inlet port 3. Figure 2 shows the valve in that closed condition.

In the particular arrangement shown the valve member 7 is in the form of an open ended cylindrical tubular member which is slidable axially within an internal wall 8 of the valve body 1. When the valve is in the closed condition as shown by Figure 2 the wall 8 serves to provide a separation between cold and hot water passages 9 and 10 formed within the body 1. As will be apparent from Figure 2 the cold water passage 9 remains in communication with the chamber 5 and the outlet port 4, whereas the passage 10 is cut-off from such communication when the valve is closed as shown by Figure 2.

The valve member 7 may cooperate with the seat 6 in any appropriate manner to effect closure of the valve inlet 3a, but one particularly satisfactory arrangement is shown. As best seen in Figure 3 the valve seat 6 includes a resilient O-ring 11 or other resilient member retained within a holder 12. The cooperable part of the valve member 7 comprises a relatively fine edge 13 formed at the junction of two relatively sloping surfaces 14 and 15 (Figure 3). The edge 13 tends to press into the resilient O-ring 11 so as to thereby achieve a fluid tight seal between the member 7 and the seat 6. It will be appreciated that other arrangements could be adopted. By way of example, the resilient member could form part of the member 7 rather than the seat 6 in which event a relatively rigid cooperable member would form part of the seat.

In the arrangement shown a temperature responsive element 16 is located within the body 1 so as to be capable of coacting between part of the body 1 and the valve member 7. It is preferred that the element 16 is connected to the valve member 7 in such a way that the member 7 moves relative to the valve seat 6 in response to extension or contraction of the element 16 as hereinafter described. The element 16 may be of a known kind including a wax or other material which expands with increasing temperature, and a plunger 17 responds to such expansion so as to increase the effective length of the element 16. In the example shown a collar 18 of the element 16 bears against a surface of a sleeve 19 which is biased by a spring 20 to move away from the valve seat 6. Such arrangements are well known and do not need to be described in detail at this time. The sleeve 19 may be connected to the valve member 7 in any appropriate fashion to achieve the aforementioned connection between the element 16 and the valve member 7.

It is preferred as shown that the plunger 17 bears against a cap member 21 which is adjustable relative to the valve body 1 towards and away from the valve seat 6. Such adjustment permits the valve to be calibrated in a known manner so that the element 16 operates to close the valve at a predetermined temperature.

As previously stated the valve member 7 is mounted within the body 1 for relatively sliding movement towards and away from the valve seat 6, and because of the connection with the element 16 the direction of that movement is the same as the direction of movement of the element 16 when that element extends or contracts. The member 7 is preferably biased away from the seat 6 by appropriate means such as a spring 22 which tends to hold the valve in an open condition as shown by Figure 1.

It is a feature of the particular construction shown that a radially outwards step or shoulder 23 is formed on the valve member 7 adjacent its lower end. The step 23 forms an upwardly facing surface against which water flowing inwards through the inlet port 3 impinges to impose a closing force on the valve member 7. When the flow of cold water through the inlet port 2 ceases or reduces significantly the hydraulic thrust imposed on the step 23 by the incoming hot water flow becomes a dominant force and promotes rapid movement of the valve member 7 against the valve seat 6. That is, the hydraulic thrust on the step 23 augments the closing influence imposed on the valve member 7 by the element 16 and therefore assists in avoiding a dangerous situation which might arise if the hot water flow through the valve was not halted quickly. In that regard the element 16 requires time to respond to increase in temperature and that response may not be quick enough in some circumstances. In the event of failure or partial failure of the cold water flow the valve member 7 will be maintained in engagement with the valve seat 6 until the cold water flow is re-established. The mixing chamber 5 of the embodiment shown is preferably formed at least in part by an open ended tube 24 which is substantially coaxial with the valve member 7 and contains at least part of the probe portion 25 of the element 16. The probe 25 includes the wax or other heat responsive medium and consequently is best located within the environment which the valve is intended to control. In the arrangement shown the tube 24 extends into the valve member 7 so that an annular passage 26 is formed between the inner and outer surfaces 27 and 28 of the valve member 7 and the tube 24 respectively (Figure 4). A further annular passage 29 is formed between the probe 25 and the inner surface 30 of the tube 24, and one or more openings 31 may be provided through an upper end portion of the tube 24 to promote communication between the passages 26 and 29 (Figure 4).

When the valve is open as shown by Figures 1 and 4 and cold and hot water flows through the inlet ports 2 and 3 respectively, the cold and hot water streams enter the chamber 5 from different directions and thorough mixing of the two flows is thereby promoted. The cold water in the passage 9 enters into the top of the chamber 5 by passing through the inlet 2a formed between adjacent surfaces of the valve member 7 and a closure member 34. Cold water may also flow through small openings 32 (Figure 1 ) formed in an upper part of the valve member 7, but such openings may not be provided in some circumstances. The hot water flow passes from the passage 10 through the inlet 3a formed between the valve member edge 13 and the seat 6, and then flows upwards through the passage 26. Part of the hot water flow passes through the openings 31 and enters laterally into the passage 29 to mix with the downwardly flowing cold water within that passage. The hot water stream flowing upwards through the passage 26 meets with the downwardly flowing cold water at or adjacent the top of the tube 24 and the combined flow moves downwardly through the passage 29 and thereby passes over the probe 25. Thorough mixing of the hot and cold water flows therefore occurs around the probe 25 so that the environment around that probe accurately reflects the temperature of the combined flow which emerges at the delivery point to which the valve is connected. It follows that the element 16 is able to respond effectively to changing conditions so as to maintain a substantially stable temperature in the flow at the delivery point.

It will be apparent from the foregoing description that the valve member

7 will move further away from the seat 6 if the temperature within the mixing chamber 5 falls below the predetermined temperature for which the valve has been calibrated. That is, the valve will automatically adjust to enable a larger flow of hot water into the chamber 5. In the event that the hot water flow into the valve fails or reduces significantly the top edge of the valve member 7 may be moved against a valve seat 34a (Figure 4) formed by or at the adjacent lower edge of the closure member 34. Under those circumstances the arrangement may be such that flow of cold water into the chamber 5 is stopped or reduced significantly, perhaps to something in the order of 5% of the flow which would be otherwise permitted. Various other arrangements could be adopted to achieve the same effect. Figure 5 shows an embodiment similar to that of Figures 1 to 4 in which the valve member 7, valve seat 6 and mixing tube 24 form part of a cartridge assembly 33 which can be installed in a pre-existing valve body 1. Such installation may be achieved by removing the closure 34 to expose an opening in the valve body 1 opposite the outlet 4. The element 16 and associated members 19 and 21 are removed with the closure 34 and are replaced after the cartridge assembly 33 has been installed. In the arrangement shown the cartridge assembly 33 includes a casing 35 which contains the valve seat holder 12 at the lower end of a counter-bored section 36. The valve member 7 is also located within the counter-bored section 36 and is retained against separation from the casing 35 by a retaining ring 37 which is attached to the upper end of the casing 35 by a screw thread or other appropriate means. The valve member 7 slides axially within the ring 37 and the ring 37 seals against the internal wall 8 of the valve body 1 to separate the cold and hot water passages 9 and 10. It is preferred but not essential that the casing 35 is connected to or formed integral with the closure 34, and in that event the element 16 and associated members 19 and 21 form part of the cartridge assembly 33. A valve including the assembly 33 functions in substantially the same manner as the valve of Figures 1 to 4.

Figures 6 and 7 show yet another embodiment of the invention which is substantially the same as that of Figures 1 to 4, but includes two outlets 4 each of which is connectable to any number of delivery points. The valve of Figures 6 and 7 is therefore particularly useful in water reticulation systems in hospitals and other establishments having a large number of locations requiring delivery of water at a controlled temperature.

Figure 8 shows another embodiment of the invention which is similar to that of Figure 5 and which includes another form of cartridge assembly 33 suitable for use with a pre-existing valve body 1.

The mixing tube 24 as used in any valve in accordance with the invention may be provided with turbulence inducing means so as to promote mixing of the cold and hot water streams, particularly at the inside of the tube 24. Openings 31 as previously referred to serve to induce turbulence in the mixed stream flowing down the inside surface of the tube 24, but alternative or additional turbulence inducing means could be adopted. Preferably, the turbulence inducing means includes discontinuities, projections, recesses, or two or more of such features, at the inner surface of the tube 24.

Figure 9 illustrates one possible form of turbulence inducing means which includes a series of tabs 40 punched or pressed out of the wall of the tube 24 so as to project beyond the inner surface 41 of that wall. Openings 42 are thereby formed through the tube wall and they also contribute to generation of turbulence within the tube 24. The tabs 40 are shown as triangular, but could be of any shape. Figure 10 shows another type of turbulence inducing means including a number of crossed helical grooves 43 formed in the inner surface 41 of the tube 24. In a variation of that arrangement, a series of circumferential grooves may be arranged to cross with a series of axially extending grooves.

In another arrangement as shown by Figure 11 the turbulence inducing means includes a number of circumferentially extending grooves 44, whereas in the Figure 12 arrangement a number of circumferentially extending ribs 45 function as the turbulence inducing means, or as part of that means. A combination of such grooves and ribs could be used in another tube arrangement.

Figure 13 shows yet another arrangement involving the use of alternating projections 41 and recesses 47. A series of such projections and recesses may extend over the entire inner surface of the tube 24 or over only part of that surface.

It will be apparent that other forms of turbulence inducing means could be adopted. Also, any of the arrangements shown in Figures 9 to 13 could include openings 31 as previously described in addition to the particular features illustrated by those figures. The same applies to any other form of turbulence inducing means as may be adopted. It also needs to be understood that turbulence inducing means could also be provided on the outside of the tube 24. By way of example, in the Figure 13 arrangement that could be achieved by forming the tube wall so that a recess lies behind each projection 46 and an outward projection lies behind each recess 47.

Figure 14 shows yet another form of valve incorporating an aspect of the invention which is not included in the prior described valve constructions. The valve shown by Figure 14 does not include a feature equivalent, in either form or function, to the step 23 of the valve constructions previously described. It is to be understood however, that such a step, or a functional equivalent, could be included in a variation of the valve shown by Figure 14. Furthermore, although the Figure 14 valve does not include a mixing tube similar to the tube 24 of the previously described valves, such a tube could be included in a variation of the valve shown by Figure 14. Components and features of the Figure 14 valve which correspond to components and features of the previously described valves will be given like reference numerals except they will be in the number series 100 to 199.

The valve body 101 has a cold water inlet port 102, a hot water inlet port 103, and an outlet port 104. The inlet ports 102 and 103 communicate with a mixing chamber 105 in a manner similar to the previously described valves, but there are differences in detail as hereinafter explained because the valve member 107 has a function additional to the function of the valve member of the previously described valves.

It is a feature of the Figure 14 valve that the valve member 107 can adopt any one of the following conditions:

(1) A condition, as shown by Figure 14, in which both the inlet ports 102 and 103 communicate with the mixing chamber 105.

(2) A condition in which one of the inlet ports 102 or 103 communicates with the mixing chamber 105 and the other port is prevented from communicating with that chamber (see Figures 15 and 16).

(3) A condition in which both inlet ports 102 and 103 are prevented from communicating with the mixing chamber 105 (see Figure 17).

The valve arrangement shown by Figure 14 enables each of the aforementioned conditions to be adopted as hereinafter explained, but it is to be understood that the same functional result can be achieved with other valve arrangements. In the particular arrangement shown by Figure 14 the valve member 107 has an upper part 150 which is in the form of a cylindrical tube, and a lower part 151 which is also of cylindrical tubular form but of similar diameter than the part 150. The parts 150 and 151 are interconnected through a web 152 having one or more openings 153 to permit the passage of water from the mixing chamber 105 to the outlet port 104. At least one transverse opening 154 is formed through the wall of the upper part 150 at a location and for a purpose hereinafter described. A plurality of openings 154 preferably extends in circumferentially spaced relationship around the port 150, and the size of each opening 154 may be related to the size and location of the hot water inlet referred to below.

The valve member 107 is slidable axially within an internal wall 155 of the valve, and in the particular arrangement shown that wall 155 is formed by a cylindrical tubular skirt depending from and forming part of a closure 134. A cold water inlet 102a and a hot water inlet 103a are formed through the wall 105 as shown. Each of those inlets may comprise a plurality of openings of suitable shape and size arranged in circumferentially spaced relationship around the wall 155. Also, as shown, the inlets 102a and 103a are preferably positioned adjacent the top and bottom respectively of the wall 155.

In the particular arrangement shown circumferentially continuous seals 156 and 157 are provided on the inside of the wall 155 at locations above and below respectively the inlet 103a. Those seals function as valve seats as hereinafter described. Similar seals 158 and 160, each of which also functions as a valve seat, are provided above and below the inlet 102a as shown. It is to be understood that other forms of valve seats may be adopted to achieve the functional result hereinafter described.

A temperature responsive element 116 of a known kind is located within the valve body 101 so as to be exposed to the mixing chamber 105, and the element 116 is connected to the valve member 107 so as to be operative to control the axial position of that member relative to the inlets 102a and 103a. That connection can be achieved in any suitable manner, including an abutting relationship which, by way of example, is retained by means of a spring or other biasing means. Alternatively, the connection could be of a permanent nature, or of a releasable nature such as that achieved through engagement of cooperable screw threads.

In the particular arrangement shown by Figure 14 a biasing spring 159 acts between the valve body 101 and the element 116 so as to urge the element 116, and consequently the connected valve member 107, upwards. The valve shown by Figure 14 functions in the following manner. In the condition shown by Figure 14, both incoming cold and hot fluid streams can enter the mixing chamber 105 by way of the respective inlets 102a and 103a. If the temperature of the mixed flow passing over the element 116 exceeds a predetermined temperature the element 116 will respond by extending its effective length in a known manner and thereby push the valve member 107 downwards against the action of the biasing spring 159. A situation can then arise as shown by Figure 15 at which the inlet 103a is closed by a non-apertured part of the valve member 107 engaging both the seals 156 and 157, whereas the inlet 102a remains open. As a result, hot water is prevented from entering the chamber 105, but cold water entry continues so as to reduce the temperature of the outflow through the outlet port 104. Alternatively, the Figure 15 situation might arise if the cold water supply fails or is substantially reduced, in which event closure of the hot water inlet 103a is an important safety measure.

Assuming the temperature of the mixed stream flowing over the element 116 falls below another predetermined temperature, the length of the element

116 will reduce to an extend such that the spring 159 urges the valve member

107 upwards to the position shown by Figure 16. At that position the cold water inlet 102a is closed because a non-apertured part of the valve member

107 engages both the seals 156 and 160, whereas the hot water inlet 102a remains open. As a consequence the hot water flow is able to raise the temperature within the chamber 105 to an acceptable level.

In the event that the hot water supply fails, it is preferred that the valve is so arranged that the spring 159 forces the valve member 107 further upwards to the position shown by Figure 17 at which both inlets 102a and 103a are closed because each of the seals 156, 157, 158 and 160 is engaged by a non-apertured part of the valve member 107. That has the benefit of preventing excessively cold flow through the outlet port 104, which in some circumstances could be dangerous or at least uncomfortable to a person receiving water from the outlet 104. The Figure 17 condition will also be achieved if the element 116 ruptures or otherwise fails.

Figure 18 shows another valve which is in many respects the same as that of Figure 14, but employs the cartridge type of construction as described above in connection with Figures 5 and 8. As in the Figure 5 arrangement the cartridge assembly 133 includes a casing 135 which may be formed integral with or connected to the closure 134. In the Figure 18 arrangement, the internal wall 154 forms part of the casing 135.

The Figure 18 valve also differs from that of Figure 14 in that it includes a mixing tube 124. That tube can be constructed and arranged as herein described in connection with any one of Figures 1 to 13.

Operation of the Figure 18 valve is essentially the same as described in connection with the Figure 14 valve. It will be apparent from the preceding description that the present invention provides a mixing valve which is effective in operation and which minimises the possibility of dangerous situations arising because of failure, or partial failure, of one of the incoming flows to the valve. The provision of a cartridge assembly which incorporates the beneficial characteristics of the invention enables the invention to be adapted with minimum cost in pre¬ existing valve bodies.

Various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention as defined by the appended claims.

Claims

1. A mixing valve including, a mixing chamber, first and second inlets through which respective streams of fluid can flow into said chamber, an outlet through which fluid can leave said chamber, a valve seat, a valve member movable relative to said seat and which is engageable with that seat to thereby prevent communication between said chamber and said first inlet, a temperature responsive element exposed to said mixing chamber and being connected to said valve member so as to be operative to control the position of the valve member relative to the valve seat in accordance with the temperature conditions existing within said mixing chamber, and a surface area of said valve member exposed to said first inlet and arranged so that the prevailing conditions of said first inlet stream impose a closing force on said valve member which urges that member towards said valve seat.

2. A mixing valve according to claim 1 , wherein said first inlet is an inlet for relatively hot fluid and said second inlet is an inlet for relatively cold fluid.

3. A mixing valve according to claim 1 or 2, wherein said valve seat forms a first valve seat, said valve member is engageable with a second valve seat to thereby prevent communication between said chamber and said second inlet, and said first and second valve seats are spaced apart and arranged so that said valve member moves away from one said seat as it moved towards the other.

4. A mixing valve according to any preceding claim, wherein said surface area is formed by a step in a side surface of said member.

5. A mixing valve according to any preceding claim, wherein said valve member is in the form of a tubular member which is open at least at one end thereof, said movement of the valve member is in the direction of the longitudinal axis of that member, and said surface area is formed by a surface of said valve member which extends transverse to said longitudinal axis and faces away from said valve seat.

6. A mixing valve according to claim 5, wherein said transverse surface is a substantially annular surface.

7. A mixing valve according to claim 5 or 6, wherein said tubular valve member is open at both ends thereof, at least part of said mixing chamber is formed within said tubular valve member, and said first and second inlet streams enter into said mixing chamber part through a lower end and an upper end respectively of said tubular valve member.

8. A mixing valve according to claim 5 or 6, wherein at least part of said mixing chamber is formed within said tubular valve member, and both said first and second inlet streams enter into said mixing chamber part through a lower end of said tubular valve member.

9. A mixing valve according to claim 7 or 8, wherein an open ended mixing tube is arranged substantially coaxial with said tubular valve member and is located within a lower region of that valve member so as to receive mixed fluid flow from said chamber, and a flow passage is formed between said mixing tube and said tubular valve member whereby at least one said fluid stream is directed towards an upper region of said valve member.

10. A mixing valve according to claim 9, wherein at least one opening is formed through said mixing tube transverse to the axial direction of that tube to provide communication between said flow passage and the interior of said tube.

11. A mixing valve according to claim 9 or 10, wherein said temperature responsive element includes an elongate probe which is arranged substantially coaxial with said mixing tube, and a flow passage for a mixed fluid stream is formed between said probe and said mixing tube and extends in the axial direction of said probe.

12. A mixing valve according to any one of claims 9 to 11 , wherein the or each said flow passage is a substantially annular passage.

13. A mixing valve according to any preceding claim, wherein two said outlets are provided and each is connected to said mixing chamber.

14. A mixing valve cartridge assembly for use within a valve body having first and second inlet ports and an outlet port, said assembly including a mixing chamber, first and second inlets through which respective streams of fluid can flow into said chamber from said first and second parts respectively, a valve seat, a valve member movable relative to said seat and which is engageable with that seat so as to thereby close said first inlet, a temperature responsive element exposed to said mixing chamber and being connected to said valve member so as to be operative to control the position of the valve member relative to the valve seat in accordance with the temperature conditions existing within said mixing chamber, and a surface area of said valve member exposed to said first inlet and arranged so that the prevailing conditions of said first inlet stream impose a closing force on said valve member which urges that member towards said valve seat.

15. A mixing valve including, a mixing chamber, first and second inlets through which respective streams of fluid can flow into said chamber, an outlet through which fluid can leave said chamber, a valve seat, a valve member movable relative to said seat and which is engageable with that seat to thereby prevent communication between said chamber and said first inlet, a temperature responsive element exposed to said mixing chamber and being connected to said valve member so as to be operative to control the position of the valve member relative to the valve seat in accordance with the temperature conditions existing within said mixing chamber, said valve member is in the form of a tubular member which is open at least at one end thereof, an open ended mixing tube arranged substantially coaxial with said tubular valve member and is located within a lower region of that valve member so as to receive mixed fluid flow from said chamber, and a flow passage is formed between said mixing tube and said tubular valve member whereby at least one said fluid stream is directed towards an upper region of said valve member.

16. A mixing valve according to claim 15, wherein at least one opening is formed through said mixing tube transverse to the axial direction of that tube to provide communication between said flow passage and the interior of said tube.

17. A mixing valve according to claim 15 or 16, wherein said temperature responsive element includes an elongate probe which is arranged substantially coaxial with said mixing tube, and a flow passage for a mixed fluid stream is formed between said probe and said mixing tube and extends in the axial direction of said probe.

18. A mixing valve cartridge assembly for use within a valve body having first and second inlet ports and an outlet port, said assembly including a mixing chamber, first and second inlets through which respective streams of fluid can flow into said chamber from said first and second ports respectively, a valve seat, a valve member movable relative to said seat and which is engageable with that seat so as to thereby close said second inlet, a temperature responsive element exposed to said mixing chamber and being connected to said valve member so as to be operative to control the position of the valve member relative to the valve seat in accordance with the temperature conditions existing within said mixing chamber, said valve member is in the form of a tubular member which is open at least at one end thereof, an open ended mixing tube arranged substantially coaxial with said tubular valve member and is located within a lower region of that valve member, and a flow passage is formed between said mixing tube and said tubular valve member whereby at least one said fluid stream is directed towards an upper region of said valve member.

19. A valve including, a mixing chamber, first and second inlets through which respective streams of fluid can flow into said chamber, an outlet through which fluid can leave said chamber, a valve member movable relative to said inlets and being operable to close either one of said inlets or both of said inlets and thereby prevent communication between said chamber and one or both respectively of said inlets, said valve member being operative to close said first inlet and leave said second inlet open when moved in one direction and to close said second inlet and leave said first inlet open when moved to a first position in a direction opposite to said one direction, said valve member being operative to close both said inlets when moved in said opposite direction beyond said first position to a second position, a temperature responsive element exposed to said mixing chamber and being connected to said valve member so as to be operative to control the position of the valve member relative to said inlets in accordance with the temperature conditions existing within said mixing chamber, and biasing means urging said valve member in said opposite direction and being operative to move said valve member to said second position in response to failure of said temperature responsive element.

20. A valve according to claim 19, wherein each said inlet is formed by at least one opening provided through an internal wall of said valve.

21. A valve according to claim 20, wherein said internal wall is a cylindrical wall within which said valve member is slidably mounted, and said inlets are spaced apart in the axial direction of the cylindrical wall.

22. A valve according to claim 20 or 21 , wherein said valve member is in the form of a tubular member which is open at least at one end thereof, and said movement of the valve member is in the axial direction thereof.

23. A valve cartridge assembly for use within a valve body having first and second inlet ports and an outlet port, said assembly including, a mixing chamber, first and second inlets through which respective streams of fluid can flow into said chamber from said first and second ports respectively, an outlet through which fluid can leave said chamber, a valve member movable relative to said inlets and being operable to close either one of said inlets or both of said inlets and thereby prevent communication between said chamber and one or both respectively of said inlets, said valve member being operative to close the first said inlet only when moved in one direction and to close said second inlet only when moved to a first position in a direction opposite to said one direction, said valve member being operative to close both said inlets when moved in said opposite direction beyond said first position to a second position, a temperature responsive element exposed to said mixing chamber and being connected to said valve member so as to be operative to control the position of the valve member relative to said inlets in accordance with the temperature conditions existing within said mixing chamber, and biasing means urging said valve member in said opposite direction and being operative to move said valve member to said second position in response to failure of said temperature responsive element.