GB2303685A - Hot and cold water mixer control - Google Patents

Abstract

A mixer control comprises a mixing chamber at which thermostatically controlled valve means is provided for controlling mixture of hot and cold water for an adjustable discharged water temperature selectable by manual operation of the valve means, an outlet by way of which mixed water from the mixing chamber passes to be discharged from the mixer control, and a temperature responsive shut-off valve at the outlet which is normally open but which is operated automatically to close the outlet when the temperature of water from the mixing chamber exceeds a predetermined value. The predetermined value will normally be at or just above the maximum permitted operating temperature of the mixer control. The shut-off valve provides a back-up for the thermostatically controlled valve means to cut-off water discharge should the valve means not respond, or not respond quickly enough, to an increase in the discharged water temperature to an undesirable level.

Description

HOT AND COLD WATER MIXER CONTROL This invention relates to a hot and cold water mixer control for mixing and controlling supply of mixed hot and cold water at a selectable temperature. The invention has particular, though not exclusive, application to showering or bathing, and may especially find use in installations in hospitals, care and residential homes, hotels, leisure centres, schools and institutional premises.

Other possible applications include heating and refrigeration circuits.

Mixer controls commonly are adjustable to control the relative proportions in which hot and cold water are received into a mixing chamber to be mixed so as to provide a selected discharged water temperature for a user, and include a thermostat which automatically adjusts a valve to maintain the selected discharged water temperature substantially constant. There may be control of both temperature and flow rate of discharged water.

Mixer controls used in showering and/or bathing installations such as referred to above are subject to strict requirements for providing safe operating temperature. For example, the thermostat should control the discharged water temperature accurately at any setting in the available range for use, the controls should provide a maximum operating temperature of 38"C for showering and 430C for bathing, and in the event of water supply failure the controls should safely shut down to prevent scalding or shock of the user. However, the mixer controls can at times be subjected to appreciable variations in water supply pressures while they are in use which can produce sudden variations in discharged water temperature from a selected temperature before their thermostats can respond to cause the necessary valve adjustment to correct the discharge temperature.Variations may only be momentary, but sharp increases in temperature may cause scalding and are undesirable. A failure of a part of the valve means, for example a spring, or a build up of scale may also result in temperature increases.

The present invention is aimed at dealing with undesirable temperature increases.

According to the present invention a mixer control is provided which comprises a mixing chamber at which thermostatically controlled valve means is provided for controlling mixture of hot and cold water in the mixing chamber for an adjustable discharged water temperature selectable by manual operation of the valve means, an outlet by way of which mixed water from the mixing chamber passes to be discharged from the mixer control, and a temperature responsive shut-off valve at the outlet which is normally open but which is operated automatically to close the outlet when the temperature of water from the mixing chamber exceeds a pre-determined value.

Thus if for any reason the temperature of water leaving the mixing chamber when the mixer control is in use exceeds the pre-determined value the shut-off valve will automatically operate to prevent the discharge of water from the mixer control. The predetermined temperature will normally be at or just above the maximum permitted operating temperature of the mixer control, depending upon whether it is intended for showering or bathing or other application. It may be, say, 480C. Accordingly the shut-off valve provides a back-up for the thermostatically controlled valve means at the mixing chamber to cut off water discharge from the mixer control in the event that the valve means does not respond, or does not respond quickly enough, to an increase in the discharged water temperature to an undesirable level.

The shut-off valve may be controlled by a thermostat of similar kind to the thermostat of the valve means at the mixing chamber. The thermostat may, for example, be of the well-known wax element type.

Preferably the shut-off valve is arranged to be held in the outlet-closing position until it is able to be re-set manually in the open position again.

The valve preferably prevents re-setting until the temperature of water at the outlet has dropped below the pre-determined value. A re-setting element of the shut-off valve may be caused to be projected externally of the mixer control when the valve closes the outlet so as to be clearly visible and readily accessible for re-setting the valve in the open position.

The shut-off valve may have a detent which holds the valve in the outlet closing position when once the valve has taken up that position, and which has to be released by manual actuation before the valve can open the outlet again. In one embodiment, the shut-off valve has a detent acting on a normally contracted wax element connected to a closure member. Normally the closure member is held in an open position against spring-loading so that the outlet is open. When the wax element is subjected to a temperature of the pre-determined value it expands, enabling the spring loading on the closure member to move the closure member to its outlet closing position, and moving the detent to a position in which retention means co-operates with the detent to hold it against return movement.

Whilst the detent is so held it holds the closure member in the outlet closing position. The retention means has to be released manually but the closure member cannot return to its open position until the wax element has contracted again.

Preferably the mixer control is arranged to be set to a test condition to allow water to pass to the outlet from the mixing chamber at a higher temperature than is normally available in the selectable discharged water temperature range. This is for testing from time to time that the shut-off valve is able to function correctly. A special operative movement of a member for setting the mixer control in the test condition should be provided for in order to prevent unintentional setting.

The mixer control may have hot and cold inlets comprising connector parts which are adjustable relative to the body of the control so as to allow for connection of hot and cold water supplies to the control from more than one direction, for example from above, below or behind the positions in which the control is mounted for use. Whilst the mixer control may have the hot and cold inlets arranged for "left" and "right" supply of hot and cold water respectively to the mixing chamber, in accordance with the accepted convention, the mixer control may be of a structurally symmetrical design enabling the connection of the hot and cold water supplies to the inlets to be reversed, if necessary.

Inlet valves are preferably provided at the hot and cold water inlets for controlling water flow to the mixing chamber. They are conveniently connected for operation by a common control, for example a hand wheel or paddle, for simultaneous manual opening and closing of the inlets, closing isolating the hot and cold water supplies before they reach the mixing chamber. In a preferred embodiment the inlet valves are of the dual piston, neutral pressure, type. The pistons of each inlet valve cooperate with twin ports from the respective inlet to the mixing chamber, and the pistons are subjected to equal pressure from water entering the inlet so that no movement of the pistons relative to the ports is induced by the pressure of water at the inlet while the inlet valves are open or closed.

Non-return, check, valves may also be provided at both the hot and cold inlets to prevent any possibility of cross flow between the hot and cold water supplies through the mixer control, and contamination of a potable water supply.

Flow regulators may be included at the hot and cold inlets to optimise performance of the mixer control in high or uneven inlet water pressure conditions.

Water flow through the mixer control can be opened, adjusted and closed by means of the aforesaid inlet valves at the inlets. Where a common control such as a hand wheel or paddle is provided for operating the inlet valves the full range of operation of the inlet valves from closed to fully open positions is preferably achieved within 3/4 to 1 revolution of the hand wheel or paddle, stop means defining the limits of the turning movement. The flow control can be quite independent of the temperature control of mixed water discharged from the mixer control.

A thermostatically controlled valve at the mixing chamber may be manually set as desired by a separate actuator, for example a knob, for a desired discharged water temperature within the available working temperature range of the mixer control. The actuator may control spring tension on a thermostat of the wax element type acting on a piston which varies the proportional mixing of hot and cold water in the mixing chamber, according to any discharged water temperature selected at the actuator. The thermostat acts to cause the piston to close off hot water supply to the mixing chamber in the event of the water temperature in the mixing chamber exceeding a pre-determined value.

It is this thermostat which normally prevents discharge from the mixer control if a pre-determined maximum working temperature is exceeded. However, if for any reason it should fail to respond to a temperature increase above the pre-determined maximum temperature the shut-off valve at the outlet will close off the outlet to prevent discharge from the mixer control.

Preferably the mixer control is so constructed that its component parts can be readily removed for servicing or replacement. It is also desirable that the thermostatically controlled valve means should be contained in a cartridge or module which can be removed from the body of the inner control to enable periodic cleaning and sterilisation of the body and other parts for the avoidance of any possible contamination. For this to be done, the hot and cold water supplies to the installed mixer control should have service valves to enable the supplies to be isolated from the mixer control The shut-off valve may be contained in a cartridge which may be readily fitted and removed for temperature control in installations for showering, bathing or other purposes.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a partly sectioned underneath plan view of a mixer control in accordance with the present invention; Figure 2 is a partly sectioned front view of the mixer control; Figure 3 is a section on line 3-3 of Figure 2; Figure 4 is an exploded perspective view of a body and cartridge housing of the mixer control; and Figure 5 is an enlarged axial section through a modified shut-off valve of the mixer control.

The mixer control of this embodiment may be used for showering or bathing purposes. It is of a modular construction, has dual control for separate control of flow and discharge water temperature of mixed water and is of the single point type having a single outlet for the discharge of mixed water for an individual shower, bath, wash basin, bidet or other such a ablutionary facility.

As shown in the drawings, the mixer control comprises a base dry, cylindrical chamber body 1, made conveniently as a brass casting with, for example, a polished chrome finish. In a back wall 1' are apertures for concealed fixing of the chamber body 1 by screws 2 to a suitable mounting surface. In Figure 1 mounting on a wall surface 3 is shown and, as an alternative, mounting in a wall recess 4 over which an escutcheon plate 5 is secured, embracing a shroud 6, for example of stainless steel, on the front of the chamber body 1, to conceal the body. On a circumferential wall of the body are two similar diametrically opposed, integral, inlet bosses 1'',1''' which open coaxially through the wall and have elbow fittings 7 rotatably retained to them, with seals, by high shear split snap rings 8, for connection respectively to hot and cold water supply pipes, not shown.The elbow fittings 7 can be swivelled through 3600 relative to the inlet bosses 1'',1''' to enable them to be connected to supply pipes extending downwards, upwards or from the rear to the installed mixer control. Following the accepted convention, a hot water supply would be connected to the left hand inlet boss 1'', as viewed in the drawings, and a cold water supply would be connected to the right hand inlet boss 1'''. For convenience, therefore, the bosses will be individually referred to respectively as hot inlet boss 1'' and cold inlet boss 1'''. Removably located in the elbow fittings 7 are filters or strainers 9 and non-return valves 10, Figures 1 and 2, respectively for protection of the mixer control from foreign matter in the hot and cold water supplies and to prevent cross flow of hot and cold water through the inlets of the chamber body 1.At diametrically opposite positions perpendicular to the axis of the inlet bosses 1'',1''' are two further co-axial bosses 11,12 integral with and opening through the circumferential wall of the body. One of these forms an outlet boss 11 which may, for example, connect to a shower hose. A shut-off valve 13 is housed in the chamber body adjacent to the outlet boss. The other boss 12 is shown plugged but it may be fitted with a drain device, if desired. This boss 12 may also provide a convenient connection for purging the interior of the mixer control with disinfectant, if required, in the course of maintenance.An integral inner wall 14, Figure 3, of the body 1 spaced from the back wall 1' defines between it and the back wall a channel 15 extending between and communicating with the two bosses 11,12, and has a recess 16 opening to the front of the chamber body 1 from which a central aperture 17 communicates with the channel 15. The shut-off valve 13 is operable to close and open the communication between the channel 1 5 and the outlet boss 11, as will be described below. A short cylindrical seating 18 on the inner wall 14 surrounds the central aperture 17 in the recess 16.

Located in the chamber body 1 is a removable cartridge 19 which can be taken out, for example, for servicing and purging purposes. The removable cartridge 19 is an assembly of valves, as will be described below, contained in a two-part housing comprising inner and outer components 20 and 21 respectively. Both housing components, best seen in Figure 4, are conveniently formed as castings of brass. The outer housing component 21 may be a moulding of a suitable plastics material, which may be glass filled. Inner housing component 20 seats, with a sealing ring 22, on the seating 18 in the recess 16 and has a tubular portion 23 which projects through the central aperture 17 of the inner wall 14 of the chamber body.It contains a mixing chamber 24 in which is a mixing valve 25 and thermostat 26, and diametrically spaced, hot and cold, inlets 27, 27' which communicate with the nonreturn valves 10 in the elbow fittings 7 and each have a location 28 for a respective inlet valve 29.

Ports 30, 30' at the hot and cold inlets 27, 27' open to the mixing chamber 24. Outer housing component 21 has an annular plate section 31 and a tubular section 32 which extends co-axially forwards from the inner perimeter of the annular plate section. The plate section 32 seats on the inner housing component 20 and on an annular shoulder 33, Figure 3, on the front of the chamber body surrounded by an annular lip 34, so as to close off the front of the chamber body. Fixing screws, not shown, engaged in holes, not shown, in the plate section 32 and tightened into blind tapped holes 35, Figure 2, in the inner housing component, secure the two housing components together. Further fixing screws, not shown, engaged in holes, not shown, in the plate section 32 and tightened into blind tapped holes 36 in the chamber body, secure the cartridge 19 to the chamber body.

The shroud 6 surrounds a rearward part of the outer housing component 21 adjacent to the chamber body 1 and seats on the outer edge of the plate section 31 immediately inside the lip 34. It is fixed on an inner sleeve 37, Figure 3, secured by screws 38 at an internal flange 39 to the plate section 31.

In front of the shroud 6 a hand wheel 40, for example made as a plastics moulding, is rotatably mounted on the tubular section 32 of the outer housing component. The hand wheel 40 is removable for access to the screws 38 and to the fixing screws by which the cartridge is secured to the chamber body, and also the fixing screws connecting the two housing components 20, 21 together. When in position on the tubular section 32 the hand wheel is restrained from axial movement relative to the tubular section. In a frontal hollow 41 of the hand wheel 40 a temperature indicating ring 42 is fixed on the tubular section 32.A temperature setting knob 43 set inside and projecting forwards from the temperature indicating ring 42 is secured to the forward end of a tubular spindle 44 which is rotatably located in, but is normally restrained from axial movement relative to, the forward end of the tubular section 32. The temperature indicating ring, knob 43 and spindle 44 may all be plastics mouldings.

The various valves of the mixer control referred to above will now be described in more detail.

Shut-off valve 13, Figure 3, is temperature responsive. It comprises a valve member 45 slidably located in a valve body 46 sealed in a confined chamber 47 formed in the chamber body 1 adjacent to the outlet boss 11 which opens from that chamber.

The channel 15 opens into the rear of the chamber 47. Valve member 45 has an enlarged cylindrical bell part 48 which is open at a rear end 49, has a tubular stem 50 extending co-axially from a forward end and opposed ports 51 in its circumferential wall which are registrable with ports 52 in the valve body 46. A closed forward end 53 of the stem 50 is fitted with a knob 54 which protrudes through an opening 55 in the front of the shroud 6. A helical compression spring 56 bearing on a seat 57 at the rear of the chamber 47, adjacent the channel 15, extends inside the bell 48 of the valve member 45 and acts on the forward end of the bell. This urges the valve member towards a closed position in which its ports 51 are out of register with the ports 52 of the valve body, so that water cannot pass from the channel to the outlet boss.

However, balls 58 in an annular groove 59 of the valve body 46 engage in complementary diameter holes 60 in the stem 50 to resist the action of the compression spring 56, so as to hold the valve member 45 normally in an open position in which the ports 51, 52 of the valve member and valve body are fully in register. Located inside the bell 48 is a thermostat 61, of the known thermo-responsive wax element type, which projects into the stem 50. A piston rod 62, which is an integral part of the wax element, abuts a detent piston 63 in the stem which has an annular, release, groove 64 and is slidable in the stem. A helical compression return spring 65 acts between the detent piston 63 and the closed forward end 53 of the stem, its effect being to urge the piston rod 62 of the wax element, through the detent piston, to a retracted position.The detent piston 63 is normally held with its release groove 64 axially spaced rearwardly of the balls 58.

This piston serves to hold the balls in engagement with the annular groove 59 of the valve body.

Typically the thermostat is arranged to respond to water at a temperature at and above 480C, Until such a temperature is reached the wax element remains dormant and the valve member occupies its open position. When water in contact with the thermostat reaches 480C its piston rod 62 is projected, forcing the detent piston 63 forwards along the stem and compressing the return spring 65 until the release groove 64 is opposite the balls 58. The balls then disengage from the groove 59 of the valve body 46 and enter the release groove. This leaves the valve member free to be moved forwards, relative to the valve body, under the action of the compression spring 56, to its closed position, thereby closing the outlet of the mixer control. The knob 54 of the valve member is projected from the shroud where it is clearly conspicuous and can be manually pushed in subsequently to re-set the valve member in the open position, but only when the wax element of the thermostat 61 allows its piston rod 62 to be returned to the retracted position.

A modified form of the shut-off valve is shown in Figure 5. In this case the valve body is shortened, projects rearwards only part-way across the chamber 47 and is fitted with a soft sealing ring 66 around its rearward end. The valve member does not have the bell 48. Instead there is a separate tubular gate 67 with crossed webs 68 on which the thermostat 61 seats. The gate 67 is slidable, and sealed by a sealing O-ring 69, in a bore 70 connecting the rear of the chamber 47 to the channel 15. Compression spring 56 acts between the back wall 1' of the chamber body and the crossed webs 68 normally to urge the gate 67 towards a closed position bearing on the soft-sealing ring 66.

However, as before, the valve is normally set so that the gate is in an open position spaced from the sealing ring 66 enabling water to pass from the channel and through the gate to the outlet boss.

When the thermostat is operated, as before, by water at or above a pre-determined temperature, the detent piston 63 causes the stem 50 to be released from the valve body to be projected forwards by the compression spring 56 acting on the gate 67. The gate is thus moved to its closed position and remains there, closing the outlet of the mixer control, until the valve member can be manually reset to open the valve again.

The shut-off valve may be provided in a cartridge form.

The mixing valve 25 comprises two co-axial, spaced annular, rear and front seats 71, 72 respectively and a piston 73 positioned with axial spacing, between the seats. Rear seat 71 is sealed in the tubular portion 23 of the inner housing compartment 20. The front seat 72 is sealed in the rear end of the tubular section 32 of the outer housing compartment 21 and projects into the mixing chamber 24. There are two annular channels 74, 75 in the mixing chamber 24, one, 74, adjacent the front seat 72, with which the port 30' from the cold inlet 27' communicates, and the other channel 75 adjacent the rear seat 71 with which the port 30 from the hot inlet 27 communicates. Between the channels 74,75 the mixing chamber 24 has an annular rib 76 in which the piston 73 is sealed and is axially slidable between the two seats 71 72.The piston 73 is tubular, of corresponding diameter to adjacent bearing faces of the seats 71, 72 with which the piston can co-operate, and has an apertured web 79 across its bore. A helical compression spring 80 located at one end on an optional cup-shaped mixing baffle 81 held in the rear seat 71 bears on the apertured web 79 of the piston normally to urge the piston towards the forward seat.

Thermostat 26 of the mixing valve 25 is also of the wax element type. It is positioned co-axially between the rear seat 71 and the piston 73 and is anchored in an axial bore 82 in the apertured web 79, its piston rod 83 extending forwards to the front seat 72. The piston rod 83 is connected to a pusher 84 slidably sealed in an axial bore 85 of the front seat and slidably retained in the rearward end of a tubular return-spring carrier 86 guided for axial sliding movement in, and restrained from rotation relative to, the tubular section 32 of the outer housing component 21. A helical compression return spring 87 acts on the pusher 84 to urge it rearwardly relative to the carrier 86. The return spring 87 bears on an adjustable bias screw 88 engaged with an internal screw thread 89 in the carrier.A forward end of the carrier 86 has a multi-start screw-threaded connection with the tubular spindle 44 of the temperature setting knob 43. Rotation of the knob 43 moves the carrier axially of the tubular section 32 causing axial adjustment of the piston 73, against the spring loaded pusher 84, relative to the two seats 71, 72.

Adjustment of the axial position of the piston 73 relative to the seats varies its spacing from the seats, and so varies the amount of water that can enter into the mixing valve from the annular channels 74, 75 of the mixing chamber 24 connected to the cold and hot inlets 27', 27. The proportions in which the water from the annular channels is mixed determines the temperature of water leaving the valve by way of the rearward seat to pass into the channel 15, and hence to the outlet boss 11.

The temperature required by a user is set by turning the knob 43 to a desired temperature on the temperature indicating ring 42. Maximum and minimum safe temperature settings are defined by interengagement of the knob 43 with a stop ring 90 fixed on the forward end of the tubular section 32 of the outer housing component 21. The thermostat 26 automatically adjusts the piston 73 to even out temperature variations of water entering the mixing chamber, so that the discharged water is maintained substantially constant at the required set temperature.

In the event of a sudden increase in the temperature of water entering into the mixer valve above the safe maximum temperature, the thermostat 26 reacts to allow the piston to close onto the rear seat 71, which causes the hot water supply to the outlet to be shut off. In the case of the mixer control being used with a shower the safe maximum temperature to which the thermostat responds to shut off the hot water supply will normally be 380C, and when used with a bath the safe maximum temperature will normally be 430C.

The two inlet valves 29 are similar. Each is of the dual piston, neutral pressure type. Their axially spaced pistons 91 are on integral piston rods 92 extending parallel to the central axis of the mixer valve. Forward end portions of the piston rods 92 are slidably sealed in bearings 93 formed at the plate section 31 of the outer housing equipment 21, and are connected at their ends to opposite ends of a connecting bridge 94 concealed behind the hand wheel 40. The connecting bridge 94 has a course pitch, multi-start, screw-threaded connection to a tubular wheel carrier 95 rotatable on, but restrained from axial movement on, the tubular section 32 of the outer housing component.

The wheel carrier 95 is connected to the hand wheel 40. Rotation of the hand wheel moves the connecting bridge 94 axially along the tubular section 32 to move the pistons 91 between closed and open positions. In their closed positions the pistons 91 sealingly engage in seats 96 replaceably held in the locations 28 of the inner housing component 20. Flow rate of the hot and cold water into the mixer control is set by the extent to which the pistons 91 are opened by the user's turning of the hand wheel. Neutral axial pressure is maintained on piston rods 92, independent of supply pressures, providing low effort and smooth operation of hand wheel 40.

In all the valves component parts may be made of metal or suitable plastics materials, and they are readily replaceable. Preferably all metal component parts with which water comes into contact in the mixer control are coated with a friction reducing material such as p.t.f.e.

Provision is made in the mixer control for testing that the shut-off valve 13 is able to function. This is enabled by a special setting of the temperature setting knob 43. The knob is urged to a normal, forward, operating position by a helical compression spring 97 fitted around the tubular spindle 44 and bearing on the knob and front end of the tubular section 32 of the outer housing component. In order to check that the shut-off valve can function the knob can be pushed rearwards against spring 97 to a release position clear of engagement with the stop ring 90 in which it can be rotated further, whilst still being pushed, to open the mixer valve more widely for a greater proportion of hot water to enter so as to increase the temperature of mixed water passing to the outlet boss. An additional stop ring 98 is fixed on the tubular section 32 to set the higher maximum temperature limit for the mixed water. Typically this temperature limit is 480C. If the shut-off valve is effective its thermostat 61 responds to the higher test temperature and the valve is caused to close the outlet of the mixer valve. Opposite rotation of the temperature setting knob 43 to the release position clear of engagement with stop ring 90 enables the spring 97 to restore the knob to its normal operating position again.

It will be understood from the foregoing that a user of the mixer control turns the hand wheel 40 to operate the two inlet valves 29 both to open hot and cold water flow into the mixer control and set the rate of flow as desired, the user also sets the discharged water temperature as required independently of the flow by turning the temperature setting knob 43 to the appropriate temperature on the temperature indicating ring 42. The flow and temperature may, of course, be varied during use, if desired. Normally the mixer valve thermostat 26 maintains the discharged water temperature substantially constant at the user's set temperature. If there is temperature increase above the safe maximum temperature the thermostat 26 will normally cut off the hot water supply into the mixer control. However, if for any reason the mixer valve thermostat 26 fails to respond to the increased temperature the shut-off valve will be closed by its thermostat 61 to close the outlet of the mixer valve.

For maintenance purposes, and cleaning of the mixer control, the cartridge 19 can be readily removed once the hot and cold water supplies to the mixer control have been turned off by separate upstream service valves.

Claims (1)

1. A mixer control comprising a mixing chamber at which thermostatically controlled valve means is provided for controlling mixture of hot and cold water in the mixing chamber for an adjustable discharged water temperature selectable by manual operation of the valve means, an outlet by way of which mixed water from the mixing chamber passes to be discharged from the mixer control, and a temperature responsive shut-off valve at the outlet which is normally open but which is operated automatically to close the outlet when the temperature of water from the mixing chamber exceeds a pre-determined value.

2. A mixer control according to claim 1, in which the predetermined value of the temperature is at or just above a maximum permitted operating temperature of the mixer control.

3. A mixer control according to claim 1 or claim 2, in which the predetermined value of the temperature is 480C.

4. A mixer control according to any preceding claim, in which the shut-off valve is controlled by a thermostat of similar kind to the thermostat of the valve means at the mixing chamber.

5. A mixer control according to claim 4 in which the thermostat is a wax element type thermostat.

6. A mixer control according to any preceding claim, in which the shut-off valve is arranged to be held in an outlet-closing position until it is able to be reset manually in an open position again.

7. A mixer control according to claim 6, in which the shut-off valve prevents resetting until the temperature of water at the outlet has dropped below the pre-determined value.

8. A mixer control according to claim 6 or claim 7, in which a resetting element of the shutoff valve is caused to be projected externally of the mixer control when the shut-off valve closes the outlet so as to be clearly visible and readily accessible for resetting the shut-off valve in the open position.

9. A mixer control according to any of claims 6 to 8, in which the shut-off valve has a detent which holds the shut-off valve in the outlet-closing position when once the shut-off valve has taken up that position and which has to be released by manual actuation before the shut-off valve can open the outlet again.

10. A mixer control according to claim 9, in which the detent acts on a normally contracted wax element connected to a closure member, and when the wax element is subjected to a temperature of the predetermined value the element expands enabling spring loading on the closure member to move the closure member to the outlet-closing position and moving the detent to a position in which retention means co operate with the detent to hold it against return movement, the closure member being held by the detent in the outlet-closing position, and wherein the retention means have to be released manually and the closure member cannot return to its open position until the wax element has contracted again.

11. A mixer control according to any preceding claim, in which the mixer control is arranged to be set to a test condition to allow water to pass through the outlet from the mixing chamber at a higher temperature than is normally available in the selectable discharged water temperature range.

12. A mixer control according to claim 11, in which the mixer control has an operating member which is movable from a normal operating position to an alternative position for setting the mixer control in the test condition.

13. A mixer control according to any preceding claim, in which the mixer control has hot and cold inlets comprising connector parts which are adjustable relative to the body of the control so as to allow for connection of hot and cold water supplies to the control from more than one direction.

14. A mixer control according to claim 13, which is of a structurally symmetrical design enabling the connection of the hot and cold water supplies to the inlets to be reversed.

15. A mixer control according to claim 13 or claim 14, in which inlet valves are provided at the hot and cold inlets for controlling water flow to the mixing chamber.

16. A mixer control according to claim 15, in which the control of water flow is independent of the control of the temperature of mixed water discharged from the mixer control.

17. A mixer control according to claim 15 or claim 16, in which the inlet valves are connected for operation by a common control for simultaneous manual opening and closing of the inlets, closing isolating the hot and cold water supplies before they reach the mixing chamber.

18. A mixer control according to claim 17, in which the common control is a hand wheel or paddle and a full range of operation of the inlet valves from closed to fully open positions is preferably achieved within three quarters to one revolution of the hand wheel or paddle, and wherein stop means define the limits of the turning movement.

19. A mixer control according to any of claims 15 to 18, in which the inlet valves are of the dual piston, neutral pressure type.

20. A mixer control according to claim 19, in which the pistons of each inlet valve co-operate with twin ports from the respective inlet to the mixing chamber, and the pistons are subjected to equal pressure from water entering the inlet so that no movement of the pistons relative to the ports is induced by pressure of the water at the inlet while the inlet valves are open or closed.

21. A mixer control according to any of claims 15 to 20, in which non-return, check valves are provided at both the hot and cold inlets to prevent any possibility of cross flow between the hot and cold water supplies through the mixer control.

22. A mixer control according to any preceding claim, in which flow regulators are included at hot and cold inlets, or at the hot and cold inlets, to optimise performance of the mixer control in high or uneven inlet water pressure conditions.

23. A mixer control according to any preceding claim, in which the thermostatically controlled valve means at the mixing chamber is manually set as desired by a separate actuator for a desired discharged water temperature within the available working temperature range of the mixer control.

24. A mixer control according to claim 23, in which the actuator controls spring tension on the thermostat of a wax element type acting on a piston which varies the proportional mixing of hot and cold water in the mixing chamber according to any discharged water temperature selected at the actuator.

25. A mixer control according to claim 24, in which the thermostat acts to cause the piston to close off hot water supply to the mixing chamber in the event of the water temperature in the mixing chamber exceeding the predetermined value.

27. A mixer control according to any preceding claim, which is so constructed that its component parts can be readily removed for servicing or replacement.

28. A mixer control according to any preceding claim, in which the thermostatically controlled valve means is contained in a cartridge or module which can be removed from a body of the mixer control to enable periodic cleaning and sterilisation of the body and other parts.

29. A mixer control according to claim 28, in combination with service valves adapted to be fitted to hot and cold water supplies to the installed mixer control so as to enable the supplies to be isolated from the mixer control.

30. A mixer control according to any preceding claim adapted for mixing and controlling supply of mixed hot and cold water at a selectable temperature for showering or bathing.

31. A mixer control substantially as described herein with reference to Figures 1 to 4 of the accompanying drawings.

32. A mixer control substantially as described herein with reference to Figures 1 to 4 as modified by Figure 5 of the accompanying drawings.