GB2417058A

GB2417058A - Water mixing valve

Info

Publication number: GB2417058A
Application number: GB0417904A
Authority: GB
Inventors: Kevin Norman White Gibbons
Original assignee: Aqualisa Products Ltd
Current assignee: Aqualisa Products Ltd
Priority date: 2004-08-11
Filing date: 2004-08-11
Publication date: 2006-02-15
Anticipated expiration: 2024-08-11
Also published as: GB2417058B; GB0417904D0

Abstract

A water mixing valve for mixing hot water from a combi-boiler with cold water from a cold-water supply, the water mixing valve including a hot-water flow controller defining a hot-water flow path 32 of variable cross-section and a cold-water flow controller defining a cold-water flow path 34 of variable cross-section. A temperature controller 24 simultaneously operates the hot and cold-water flow controllers to provide a user-selectable outlet water temperature. The hot and cold-water flow controllers operate in tandem so that, for a mid-range portion of operation, the total through-flow of water is substantially constant. However, the hot-water flow controller operates at at least one end of the range of operation to vary the total through-flow of water and, hence, extends the temperature range achievable by the water mixing valve.

Description

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L- at., . ,, _,,, ,, , _,, _, At, _,,, , ,, ,_, : it, _1! , _ r. = . -! -A- _. 1 V I. I { t_ W - I I K I r \. I r r _ In the summer months, with relatively high ambient water temperatures, the user will only require the mixing valve to mix a small flow of hot water with a relatively large flow of cold water. However, unfortunately, often the required flow rates through the combi-boiler are then below the predetermined minimum such that the combi- boiler will shut off completely.

On the other hand, in the winter months, the user may require the mixing valve to provide very little or no cold water. In these conditions, the through-flow for the hot water is at a maximum and the combi-boiler may not have sufficient power to raise adequately the water temperature of the relatively cold ambient inlet water.

It is known for plumbers to insert various restrictors in the water supplies to overcome the problems experienced for one particular season. However, unfortunately, these restrictors will then have the effect of heightening problems in the opposite season.

It is an object of the present invention to provide a method and water mixing valve which provides improved water-outlet temperature performance.

According to the present invention there is provided a water mixing valve for mixing hot water from a combi- boiler with cold water from a cold-water supply, the water mixing valve including: a hot-water flow controller defining a hot-water flow path of variable cross-section; r r a cold-water flow controller defining a cold- water flow path of variable cross-section; and a temperature controller for simultaneously operating the hot and cold-water flow controllers to provide a user-selectable outlet water temperature; wherein the water mixing valve has a range of operation In which outlet water IS provided, the range of operation having a midrange portion between two end portions; the hot and cold-water flow controllers operate in tandem such that, for said midrange portion, the total through-flow of water is substantially constant; and the hot-water flow controller operates at at least one end of said range of operation to vary the total through-flow of water and, hence, extend the temperature range achievable by the water mixing valve.

By varying the total through-flow of water, for the extreme ends of operation of flow, it is possible to improve performance and extend the temperature range of the valve. In particular, at the high-temperature end of operation, having reduced the cold flow to a minimum, by then reducing the total through-flow by reducing the hot- water flow, the water passes through the combi-boiler at a lower rate and, hence, is raised to a higher temperature. On the other hand, at the low temperature end of operation, by increasing the total through-flow by maintaining the hot-water flow constant whilst increasing the cold-water flow, it is possible to provide further temperature selection for the user without the combi- boiler shutting off completely and the outlet water reverting to only the cold-water flow.

Preferably, through the range of operation, the cross- section of the hot-water flow path defined by the hot- water flow controller is always above a predetermined minimum cross- section.

In this way, it is ensured that the combi-boiler has enough through-flow to remain active. At the cold end of operation of the mixing valve, this is most important and allows the combi-boiler to remain active while outlet water temperature is controlled by varying the amount of cold water mixed with the constant hot-water flow.

Hence, preferably, the predetermined minimum cross- section allows sufficient through-flow of water for operation of a combi- boiler.

Of course, at the hot end of operation, the cross-section of the hotwater flow path should also remain above this minimum cross-section to prevent the combi-boiler shutting off and the water mixing valve thus failing to maintain its operation of providing outlet water.

Preferably, at the cold end of the range of operation, while the coldwater flow controller increases the cross section of the cold-water flow path, the hot-water flow controller maintains the cross-section of the hot-water flow path at the predetermined minimum cross-section.

Thus, as a user selects lower temperatures, increased cold-water flow is mixed with the constant hot-water flow.

Preferably, at the hot end of the range of operation, after the cold-water controller has reduced the cross- section of the cold-water flow path to zero, use of the temperature controller to increase the outlet water temperature causes the hot-water flow controller progressively to reduce the cross-section of the hot- water flow path.

In other words, as the user selects higher and higher temperatures through the mid-range portion, the mixing valve provides increasing flows of hot water with decreasing flows of cold water. Once the valve is providing a flow of only hot water, it would seem that further increases in temperature would not be possible.

However, by then reducing the cross-section of the hot- water flow path, the hot-water through-flow is reduced not only through the valve, but also the combi-boiler.

This has the effect of causing the combi-boiler to produce higher hotwater temperatures.

Preferably, the hot-water flow controller progressively reduces the crosssection of the hot-water flow path to the predetermined minimum crosssection.

At this cross-section, the combi-boiler is providing the maximum temperature allowable.

Of course, the water-mixing valve may additionally be arranged such that the temperature controller operates the hot and cold-water flow controllers to reduce the hot and cold-water flow paths simultaneously to cross- sections of zero. This has the effect of bringing the water-mixing valve to a state outside the range of operation and in which no through-flow occurs.

Preferably, the hot-water flow controller includes a hot water inlet and a first part defining a generally tapered orifice moving across the hotwater inlet, the cold-water flow controller includes a cold-water inlet a second part defining a second generally tapered orifice movable across the cold-water inlet and the temperature controller is arranged to move the first and second parts relative to the hot and cold water inlets so as to vary the flow from the hot and cold water inlets to provide the user-selectable outlet water temperature.

It will be appreciated that the first orifice defines with the hot-water inlet the cross-section of the hot- water flow path and, similarly, the second orifice defines with the cold- water inlet the cross-section of the cold-water flow path. Since the orifices are generally tapered, by moving them relative to the inlets, the defined cross-sections change accordingly.

This arrangement provides a simple and effective way of controlling water flows.

The first and second parts could be independently movable and controllable. The effects described above could be achieved by moving the first and second parts independently so as to provide the hot and coldwater through-flows as required. Indeed, in this respect, any form of controllable valve could be provided on the respective hot and cold-water supplies and controlled together to cause the required effect.

However, the present invention is particularly advantageous when embodied such that the first and second parts are arranged together whereby the temperature controller provides only one control movement.

In one example, the first and second parts could be provided as separate plates that have a common drive mechanism that moves the plates in a ganged relationship.

Preferably, the first and second parts are formed in a single plate member.

The first and second generally tapered orifices could be aligned in a generally parallel orientation and then moved back and forth in a parallel direction.

However, in a preferred embodiment, the plate member is rotatable about an axis substantially perpendicular to the plane of the plate member and the first and second generally tapered orifices extend in a circumferential direction with respect to the axis.

The orifices may extend along the same or different circumferences.

In this way, the temperature controller need only rotate the plate member (or alternatively inlets relative to the plate member) in order to provide the complete range of outlet temperatures.

Preferably, each of the generally tapered orifices extends from a respective narrow end having a narrow width to a respective wide end having a wide width.

For the mid-range portion, the widths of the generally tapered orifices change substantially proportionally along their lengths.

In this way, when the first and second generally tapered orifices are moved together by the same amount relative to their respective hot and cold-water inlets, the cross- section defined for one flow path increases proportionally as the cross- section for the other flow path decreases correspondingly. Hence, for the mid-range portion, a substantially constant total through-flow is provided.

Preferably, the narrow end of the first generally tapered orifice includes a length having substantially constant width such that, at the cold end of the range of operation, movement of the first and second generally tapered orifices relative to the hot and cold inlets causes no change in water flow through the hot-water flow path.

In other words, since the length at the narrow end of the first generally tapered orifice has a substantially constant width, movement of that orifice relative to the hot-water inlet will not cause any change in the hot- water flow path cross-section. This allows the second generally tapered orifice to move relative to the cold inlet so as to increase the cross-section of the cold- water flow path. Thus, a single continuous movement of the temperature controller causing corresponding continuous relative movement of both generally tapered orifices still allows the mixing valve to move from the mid-range portion where hot and cold-water flows are both - 9 - changed proportionally to the cold-end portion where hot- water flow stays constant and the outlet temperature is controlled by varying the cold-water flow.

In a preferred embodiment, at at least the narrow end of the first generally tapered orifice, the width of the hot-water flow path defined by the overlap of the first generally tapered orifice and the hot-water inlet is smaller than the width of the first generally tapered orifice at that point.

In practice, it may be difficult to provide the first generally tapered orifice with a sufficiently small width. For instance, there may be problems of manufacture in moulding. However, the cross-section for the hot-water flow path is defined by the overlap of the first generally tapered and the hot-water inlet. Hence, the required small cross-section can be achieved by having some of the width of the first generally tapered orifice positioned beyond the periphery of the hot-water inlet. The water mixing valve can be arranged such that movement of the first generally tapered orifice through the range of operation results in lateral relative movement (relative to the length of the tapered orifice) such that, in the mid-range portion, the first generally tapered orifice is generally central with respect to hot- water inlet, but at the cold end of operation it overlaps one side edge of the hot-water inlet.

Alternatively or in addition, the inlets can have a non- uniform (for instance non-square or rectangular) cross section. In particular, the spacing across the inlet can vary in the lengthwise direction (with respect to the length of the corresponding generally tapered orifice) at different positions across the width. For instance, the inlets could be circular.

By arranging for the generally tapered orifices to move laterally relative to their respective inlets as described above, it is possible to produce variations in the available through-flow cross-section. For instance, movement of a generally tapered orifice towards the periphery of a circular inlet will result in a reduced length of the inlet overlapping with the orifice and, hence, a reduced overlapping cross- section.

Preferably, at the hot-end of the range of operation, for increasing mixed-water temperature, the hot-water flow path defined by the overlap of the first generally tapered orifice and the hot-water inlet decreases so as to decrease the cross-section of the hot-water flow path.

The first generally tapered orifice may include a particular width profile at the wide end which reduces in width in a direction extending away from the narrow end.

However, it is sufficient for the temperature controller merely to move the first generally tapered orifice such that the hot-water inlet extends partially beyond the wide end of the first generally tapered orifice and the overlapping cross-section is thereby reduced.

Preferably, at the hot end of the range of operation, the cold-water inlet is beyond the narrow end of the second generally tapered orifice such that the cross-section of the cold-water flow path is zero.

In this way, the water-mixing valve, in the mid-range portion, reduces cold-water flow as hot-water flow is proportionally increased. The position where cold-water flow has just ceased and hot-water flow is at a maximum marks the divide between the mid-range portion and the hot-end portion of operation. By then reducing the cross-section of the hot-water flow path, further increases in temperature are possible.

The water mixing valve could merely be manually operated.

Only a single temperature controller is required for the user to adjust temperatures from cold to hot while still achieving the advantages discussed above. However, the water mixing valve could be provided with a thermostatic controller for operating the hot and cold-water flow controllers in conjunction with the temperature controller.

With a temperature sensor, for instance at the outlet, it would be possible mechanically or electronically to control the hot and cold-water flow controllers to achieve a desired temperature. Again, since only one movement of control is required for the entire temperature range, the present invention provides significant advantages.

The water mixing valve may be provided in a domestic shower system.

The invention will be more clearly understood from the following description, given by way of example only, with reference to the accompanying drawings In which: t Figure 1 illustrates a shower system embodying the present invention; Figure 2 illustrates a valve embodying the present invention; Figure 3 illustrates a cross-section of the valve of Figure 2; Figure 4 illustrates the temperature controller of Figure 2; Figure 5 illustrates the temperature controller of Figure 4 in conjunction with hot and cold-water inlets; and Figures 6(a) to (h) illustrate schematically profiles of orifices in a plate usable with the valve of Figures 2 to 5.

Figure 1 illustrates a typical shower system in which a water mixing valve of the present invention could be embodied.

A water mixing valve 2 is connected to a cold water supply 4 and combi-boi.ler 6. As illustrated, the combi- boiler 6 is also connected to the cold-water supply 4 and provides hot water, as required, to the mixing valve 2.

In the illustrated embodiment, the water mixing valve has an outlet 8 for supplying a shower handset 10, such that the valve 2 forms part of a domestic shower system. l

A water mixing valve is illustrated in Figure 2. This includes a coldwater supply 12, a hot-water supply 14, an outlet 16, a housing 18, a temperature sensor 20 and a motor 22. The generally arrangement of this device is described in further detail in EP 1 128 105.

As shown in Figure 3, within the housing 18, there is provided a rotatable temperature controller 24. In the illustrated embodiment, this is rotatable by means of the motor 22 under the control of a thermostatic controller using the temperature sensed by the temperature sensor 20. However, it will be appreciated that, in place of the motor 22, a manual actuator, such as a rotatable knob could be provided.

As illustrated in Figure 4, the temperature controller 24 supports a plate 30 having a first generally tapered orifice 32 and a second generally tapered orifice 34.

As illustrated in Figures 3 and 5, the plate 30 is positioned adjacent the hot-water inlet 42 and cold-water inlet 44. By rotating the temperature controller 24, the generally tapered orifices 32 and 34 are moved relative to the hot and cold-water inlets 42 and 44 so as to define variable cross-section flow paths into a mixing chamber 50, which, in this embodiment, is positioned within the temperature controller 24.

For this embodiment, the position, shape and size of the generally tapered orifices 32 and 34, in particular the first generally tapered orifice 32 used for controlling hot-water flow, provide the invention with its advantages.

Figure 6(a) illustrates a plate embodying the present invention. A narrow end 32a for the cold end of operation of the valve extends for a length with a substantially constant width. A wide end 32b extends relatively further titan the opposite narrow end 34a of the second generally tapered orifice.

Figure 6(b) illustrates schematically the hot-water inlet 12 and coldwater inlet 14 positioned adjacent the first and second generally tapered orifices 32 and 34 respectively. In this embodiment, the hot and coldwater inlets 12 and 14 are positioned generally diametrically oposed to one another with respect to the axis of rotation of the plate 30. However, with different arrangements of the generally tapered orifices 12 and 14, different positions for the hot and cold-water inlets 12 and 14 are also possible. Indeed, whereas for the illustrated embodiment, the first and second generally tapered orifices 32 and 34 extend generally around a common circumference, it is possible for such orifices to be positioned extending around different circumfences.

In this case, the two orifices and inlets could be positioned side by side.

In Figure 6(b), the plate 30 is orientated relative to the hot and coldwater inlets 12 and 14 such that the device is operating in a mid-range portion of the operating range. Thus, as viewed in Figure 6(b), clockwise rotation of the plate 30 will result in the cross-sectional area defined by the hot-water inlet 12 and the first generally tapered orifice to reduce whilst the cross-sectional area defined by the overlap of the / cold-water inlet 14 and the second generally tapered orifice 34 increases.

In the preferred embodiment, the tapered profiles of the first and second generally tapered orifices are such that the total cross-sectional area available for through-flow in the device remains substantially constant with movement of the plate 30 in the mid-ranqe portion.

Figure 6(c) illustrates the relative orientation where the device is at the divide between the mid-range portion of operation and the hot-end range of operation. At this position, the hot-water inlet 12 is adjacent the wide end 32b of the first generally tapered orifice 32 so as to allow maximum flow of water through the hot-water inlet 12. In the preferred embodiment, the wide end 32b provides no obstruction to the hot-water inlet 12 such that the cross-sectional area available for through-flow is defined only by the cross-section of the hot-water inlet 12. However, other embodiments are possible where the hot-water inlet 12 is larger than the width of the wide end 32b of the first generally tapered orifice 32, but still defines a maximum hot-water through-flow for the device.

At this position, the cold-water inlet 14 has just moved past the narrow end 34a of the second generally tapered orifice 34. Hence, the cold-water inlet 14 is completely closed by the plate 30 and the cross-sectional area available for cold-water flow is zero.

In this way, Figure 6(c) illustrates the position at the extreme end of the mid-range portion where maximum flow of hot water is provided with a minimum flow of cold water.

Figure 6(d) illustrates an orientation of the device where the plate 30 has been moved beyond the position of Figure 6(c) and where the device is operating in the hot- end portion of the range of operation.

In the hot-end portion, the cold-water inlet 14 continues to be closed by the plate 30, such that there is no flow of cold water. On the other hand, the hot-water inlet continues to define with the wide end 32b of the first generally tapered orifice 32 a cross-section for through- flow of hot water. However, as the hot-water inlet 12 moves over the end boundary 36 of the first generally tapered orifice 32 away from the first generally tapered orifice 32, the cross-sectional area defined by the overlap of the water inlet 12 and the first generally tapered orifice 32 reduces.

In this way, the through-flow of hot water is reduced and, hence, the combi-boiler 6 heats the hot water to higher temperatures.

In the preferred embodiment, further relative movement of the plate 30 results in the device being brought beyond its range of operation to the position illustrated in Figure 6(e) where both the hot-water inlet 12 and the cold-water inlet 14 are closed and the device provides no throughflow of water.

Figure 6(f) illustrates the relative orientation of the plate 30 where the device is positioned at the boundary between the mid-range portion of operated and the cold- end range of operation. Further movement of the plate 30 beyond this position (relative clockwise rotation of the plate 30 as illustrated in Figure 6(f)) causes the cross sectional area defined by the overlap between the cold- water inlet 14 and the second generally tapered orifice 34 to increase, thereby increasing the through- flow of cold water. As illustrated in the Figures, in the preferred embodiment, the wide end 34b of the second generally tapered orifice 34 has a tapered profile which is a continuation of the tapered profile for the mid- range portion such that relative movement in the cold-end portion of the range of operation causes similar increasing or decreasing flows of cold water.

As mentioned above, the narrow end 32a of the first generally tapered orifice is arranged as a length having generally constant width.

Figure 6(g) illustrates an orientation of the plate 30 for a position within the cold-end portion of the range of operation.

Since the hot-water inlet 12 is adjacent the constant width narrow end 32a of the first generally tapered portion 32, relative movement of the plate 30 will not result in any change in the cross-sectional area defined by the overlap of the hot-water inlet 12 with the first generally tapered orifice 32, such that there will be a constant flow of hot water. On the other hand, the cok1- water inlet will move relative to the tapered wide end 34b of the second generally tapered orifice 34, such that the cross-sectional area defined by the overlap of r the cold-water inlet 14 and the second generally tapered orifice 34 will vary. In this way, in the cold-end portion of the range of operation, the flow of hot water will remain small but constant, while the cold flow of water will be varied. This allows a user to have improved control over cold-water temperatures, without the flow of hot water reducing to a level at which the combi-boiler 6 shuts off.

It will be appreciated that a wide range of different profiles could be used whilst achieving the same effect.

It would be possible for the first and second generally tapered orifices 32 and 34 to be positioned with their centre lines along a circumference. However, as illustrated in Figure 6(h), in the preferred embodiment, towards the narrow ends 32a and 34a, the first and second generally tapered orifices 32 and 34 move away from the circumference. This results in the overlap between the inlets 12 and 14 and the first and second generally tapered orifices 32 and 34 being defined by edge portions of the hot and cold-water inlets 12 and 14, rather than their central portions. Using circular hot and cold- water inlets as illustrated, the edge portions have reduced cross- sectional areas as compared to their central portions. In this way, it is possible for the cross-sectional area defined by the overlap to be reduced.

In manufacturing plate 30, there can be a problem in forming the narrow ends 32a and 34a with sufficiently reduced width. By arranging the generally tapered orifices as discussed above, it is possible to produce sufficiently small cross-sectional area overlaps with widths of the generally tapered orifices which are larger than would otherwise be required.

It is also possible for the narrow ends 32a and 34a of the generally tapered orifices to move away from the circumference such that they overlap only partly with the hold and cold-water inlets. This also allows the use of reduced cross-sectional area overlaps with relatively large width for the generally tapered orifices.

As described above, the preferred embodiment includes a single plate including both first and second generally tapered orifices. As an alternative to the described embodiment, the single plate could be moved linearly, rather than rotationally, with the generally tapered orifices extending in the direction of movement. Other similar alternative arrangements are also possible.

Indeed, the first and second generally tapered orifices could be provided in separate respective plates which are moved together.

Many benefits of the present invention could also be achieved using separately controllable valves of any design. By ensuring that the hotwater flow does not drop below a predetermined minimum whilst the coldwater flow is varied, improved cold-end performance may be achieved. Similarly, by reducing hot-water flow after the cold-water flow has been shut off, hot-end performance can be improved.

Claims

Claims 1. A water mixing valve for mixing hot water from a combi-boiler

with cold water from a cold-water supply, the water mixing valve including: a hot-water flow controller defining a hot-water flow path of variable cross-section; a cold-water flow controller defining a cold-water flow path of variable cross-section; and a temperature controller for simultaneously operating the hot and cold-water flow controllers to provide a user-selectable outlet water temperature; wherein the water mixing valve has a range of operation in which outlet water IS provided, the range of operation having a midrange portion between two end portions; the hot and cold-water flow controllers operate in tandem such that for said midrange portion, the total through-flow of water is substantially constant; and the hot-water flow controller operates at at least one end of said range of operation to vary the total through-flow of water and, hence, extend the temperature range achievable by the water mixing valve.
2. A water mixing valve according to claim 1 wherein, through said range of operation, the cross-section of the hot-water flow path defined by the hot-water flow controller is always above a predetermined minimum cross section.
3. A water mixing valve according to claim 2 wherein the predetermined minimum cross-section allows sufficient through-flow of water for operation of a combi-boiler. fir
4. A water mixing valve according to claim 2 or 3 wherein, at the cold end of said range of operation, while the cold-water flow controller increases the cross section of the cold-water flow path, the hot-water flow controller maintains the cross-section of the hot-water flow path at the predetermined minimum cross-section.
5. A water mixing valve according to any preceding claim wherein, at the hot end of said range of operation, after the cold-water controller has reduced the cross section of the cold-water flow path to zero, use of the temperature controller to increase the outlet water temperature causes the hot-water flow controller progressively to reduce the cross-section of the hot water flow path.
6. A water mixing valve according to 5 when appendant on claim 2 wherein the hot-water flow controller progressively reduces the cross-section of the hot-water flow path to the predetermined minimum cross-section.
7. A water mixing valve according to any preceding claim wherein, outside said range of operation, the temperature controller operates the hot and cold water flow controllers to reduce the hot and cold-water flow paths simultaneously to cross-sections of zero.
8. A water mixing valve according to any preceding claim wherein, the hotwater flow controller includes a hot-water inlet and a first part defining a first generally tapered orifice movable across the hot water inlet; 1, 1 the cold-water flow controller includes a cold-water inlet and a second part defining a second generally tapered orifice movable across the cold-water inlet; and the temperature controller is arranged to move the first and second parts relative to the hot and cold inlets so as to vary the flow from the hot and cold inlets to provide the user- selectable outlet water temperature.
9. A water mixing valve according to claim 8 wherein the first and second parts are arranged to move together such that the temperature controller provides only one control movement.
10. A water mixing valve according to claim 8 or 9 wherein the first and second parts are formed in a single plate member.
11. A water mixing valve according to claim 10 wherein the plate member is rotatable about an axis substantially perpendicular to the plane of the plate member and the first and second generally tapered orifices extend in a circumferential direction with respect to the axis.
12. A water mixing valve according to any one of claims 8 to 11 wherein each of the generally tapered orifices extends from a respective narrow end having a narrow width to a respective wide end having a wide width.
13. A water mixing valve according to claim 12 wherein, for said midrange portion, the widths of the generally tapered orifices change substantially proportionally along their lengths.
14. A water mixing valve according to any one of claims 8 to 13 wherein the narrow end of the first generally tapered orifice includes a length having substantially constant width, such that, at the cold end of said range of operation, movement of the first and second generally tapered orifices relative to the hot and cold inlets causes no change in water flow through the hot-water flow path.
15. A water mixing valve according to claim 14 wherein, at at least the narrow end of the first generally tapered orifice, the width of the hotwater flow path defined by the overlap of the first generally tapered orifice and the hot-water inlet is smaller than the width of the first generally tapered orifice at that point.
16. A water mixing valve according to any one of claims 8 to 15 wherein, at the hot-end of said range of operation, for increasing mixed-water temperature, the hot-water flow path defined by the overlap of the first generally tapered orifice and the hot-water inlet decreases so as to decrease the cross-section of the hot- water flow path.
17. A water mixing valve according to claim 16 wherein, at the hot end of said range of operation, the cold-water inlet is beyond the narrow end of the second general! tapered orifice such that the cross-section of the cold- water flow path is zero.
18. A water mixing valve according to any preceding claim including a thermostatic controller for operating the hot and cold-water flow controllers in conjunction with the temperature controller.
19. A domestic shower system including a water mixing valve according to any preceding claim.
20. A water mixing valve constructed and arranged substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.
21. A domestic shower system constructed and arranged substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.