GB2263755A

GB2263755A - Mixer valve for showers

Info

Publication number: GB2263755A
Application number: GB9301781A
Authority: GB
Inventors: Colin Mcmaster-Christie
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-01-30
Filing date: 1993-01-29
Publication date: 1993-08-04
Also published as: GB9301781D0; GB9201978D0

Abstract

A mixer valve (1) has a valve plate in the form of a bar (6) formed with elongate hot and cold water openings (10, 11) and with rack teeth (14) meshed with a drive pinion (15). The bar (6) is a loose fit in a bore (7) in a housing (2), and controls the proportions of hot and cold water flowing from hot and cold water inlets (3, 4) to a mixed water outlet (5). There are no seals between the housing and the bar (6); instead non-return valves (12, 13) are provided in the hot and cold water inlet passages (3, 4) of the housing. Servo-control systems are described in which a thermistor (28, Fig 7) is used to monitor the temperature of the mixed water, the signal produced being used to control the position of the bar (6). The valve may be used in a shower and positioned outside the shower cubicle. <IMAGE>

Description

SHOWER WATER SUPPLY APPARATUS This invention relates to a shower water supply apparatus and particularly to such apparatus of the kind which incorporates a pump.

Pumped systems have well-known advantages that the pressure of the water supply or supplies to the apparatus can be relatively low, and that a relatively large flow rate of water to the shower head can be achieved if desired.

Pumped systems have usually employed a twin-impeller pump, the respective impellers being arranged to pump hot and cold water to the respective inlets of a mixer valve, the outlet of which is connected to the shower head.

One problem with that arrangement is that cavitation can readily occur in the hot water chamber of the pump if air is picked up from a hot water cylinder which is supplying the hot water.

This problem can be overcome by arranging for mixing of the water to take place prior to the water entering the pump, which need then have only a single impeller.

A mixing valve is known in which a valve plate provided with a hot water opening and a cold water opening is slidable relative to fixed hot and cold water supply ports whereby one port is progressively opened as the other port is progressively closed on movement of the valve plate, thereby to alter the proportions of hot and cold water being mixed. Seals are provided around the respective ports to seal the ports to the valve plate. Such seals increase the resistance to movement of the valve plates and would necessitate the provision of a relatively powerful actuator if the valve plates were to be remotely controlled rather than manually operated by a mechanical drive from a control knob.

Another problem with seals in that arrangement is that the seals could take on a permanent set if the valve plates were to be left between use of the shower in a condition in which the seal overlapped with one of the supply ports. To avoid this it would be necessary to return the mixing valve to an off condition in which the seals both co-operate with blanking portions of the valve plate.

If an actuator was employed a special circuit function would be needed to return the valve to the off condition.

We have realised that, in accordance with one aspect of the invention, it is possible to dispense with seals between the inlet ports and the valve plate by providing one-way valves in the supplies to the respective ports.

According to one aspect of the invention a mixer valve assembly for a shower water supply apparatus comprises a valve housing formed with a hot water inlet, a cold water inlet and a water outlet, a valve plate movable in a chamber in the housing, the chamber being exposed to hot and cold water supply ports which communicate respectively with the hot and cold water inlets respectively through respective one-way valves, which valves both operate to permit water flow from the respective inlet to the respective port but to close against reverse flow, the valve plate being formed with a hot water opening and a cold water opening for overlapping with the hot and cold water supply ports, no effective seals being provided between the ports and the valve plate.

It does not then matter that there may be some 'leakage' between one inlet port and the other inlet port. The valve plate can be made a relatively loose fit in the mixer valve body, and so it becomes possible to control the movement of the valve plate more easily.

Also, the lack of need for precision results in reduced costs.

It should be appreciated that the valve plate may be arranged to move linearly or arcuately, depending upon the construction of the mixer valve.

A second aspect of the invention is a shower water supply assembly comprising a pump having the inlet of the pump connected to the water outlet of a mixer valve assembly in accordance with the first aspect of the invention.

The pump is preferably a centrifugal pump.

According to a third aspect of the invention, a mixer valve assembly comprises an elongate valve plate in the form of an elongate bar provided with elongate hot and cold water openings extending transversely therethrough, and the plate is formed with rack teeth meshed with a drive pinion. The drive pinion may be manually operated but is preferably driven by a suitable actuator, such as a stepper motor.

The rack is preferably positioned towards one end of the plate, the elongate openings being longitudinally spaced-apart along the plate.

The use of an elongate plate with rack teeth towards one end thereof facilitates the provision of relatively large rack and pinion teeth which can therefore be made relatively strong and durable.

The use of elongate openings enables the total area of the valve openings overlapping with the inlet ports to be relatively large so as to match more closely the flow output area of the shower head holes. We consider this to be desirable for close control of the mixing operation.

A position transducer may be associated with the drive to the drive pinion to provide a signal corresponding to the position of the plate relative to the mixer valve housing.

The position transducer signal can then be employed to provide a plate position feedback signal in a servo-control system controlling the position of the plate in response to a command signal, which signal is preferably influenced by a water temperature sensor responsive to the temperature of the mixed water.

When a water temperature sensor is provided the sensor is preferably positioned in the water at a position adjacent to the pump.

Since a thermistor as the temperature sensor can be used in a simple balance circuit which incorporates the variable output provided by the position transducer and, since thermistors are inexpensive, a relatively inexpensive thermostatic control can be provided.

According to a fourth aspect of the invention a shower water supply apparatus comprises a mixer valve having a hot water inlet, a cold water inlet, and a mixed water outlet, a mixer valve member controlling the proportions of hot and cold water flowing from the inlets to the outlet, drive means operative to drive the mixer valve member, a position transducer associated with the drive means or mixer valve member to provide a position signal indicative of the position of the valve member relative to the valve housing, a pump having an inlet connected to the outlet of the mixer valve, a temperature sensor sensing the temperature of water downstream of the mixer valve member or pump, a temperature setting means for setting the desired water temperature, and a controller controlling the position of the mixer valve member in response to the temperature setting means and the temperature sensing means.

The temperature setting means can be located in the shower cubicle but, advantageously, the pump and mixer valve can be located outside the shower cubicle, and even outside the bathroom or shower room.

The temperature setting means can operate on a low voltage, such as 9 volts, to improve safety, whereas the pump can still operate on mains voltage.

Various embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which: Figure 1 is a schematic transverse cross-section of a mixer valve assembly, Figure 2 is a perspective view of the valve plate of the valve assembly of Figure 1, Figure 3 is a side elevation of a practical mixer valve assembly, Figure 4 is a view from the right in Figure 3, Figure 5 is a section on the line 5-5 of Figure 4, Figure 6 is a plan view of the assembly of Figure 3, Figure 7 is a layout of a shower water supply system incorporating a mixer valve assembly similar to that of Figures 3 to 6, and Figure 8 is a layout of a modified system similar to that of Figure 7 and including a block diagram of the control system.

In Figure 1 a mixer valve assembly 1 comprises a housing 2 provided with a hot water inlet 3, a cold water inlet 4 and a water outlet 5.

An elongate valve plate 6 is axially slidable with clearance in a transverse bore 7 in the housing 2, hot and cold water supply ports 8 and 9 respectively opening into the bore 7 for control by hot and cold water openings 10 and 11 respectively extending transversely through the valve plate 6.

The openings 10 and 11 in the valve plate 6 are of elongate shape, in transverse cross-section, as are the ports 8 and 9. Ports 8 and 9 communicate respectively with the inlets 3 and 4 through respective one-way valves 12 and 13 respectively which are arranged to close against any tendency for fluid to flow out of an inlet port.

It should be noted that no measures are taken to seal the valve plate 6 to the walls bounding ports 8 and 9.

A rack 14 is provided on one end portion of the valve plate 6 and is meshed with a drive pinion 15. The shape of the openings 10, 11 leads to a relatively long rack 14 which can therefore be provided with teeth of robust dimensions. The teeth can extend for the full width of the valve plate, as shown. This is particularly advantageous when the valve plate is moulded from a plastics materi al.

The assembly of Figures 3 to 6 is similar to that of Figure 1 but a valve plate of reduced length is employed, the upper end 61 of the valve plate controlling the flow from inlet 3 to outlet 5, only one aperture 11 being provided in the plate 6. (The one-way valves 12, 13 have not yet been installed in the assembly of Figures 3 to 6.) Figure 7 shows one system incorporating the mixer valve assembly 1 in which the valve assembly 1 is mounted with a centrifugal single stage, single inlet and outlet, impeller pump 16 in a position external to a bathroom in which a shower cubicle 17 is located, the control panel 18 for the shower being located in the cubicle and receiving water from the pump outlet 19 through a pipe 20.The on/off control knob 24 operates firstly an on/off valve behind the panel 18 which controls the flow from a panel inlet 21 to a panel outlet 22 leading to a shower head 23, secondly a main switch on the power supply transformer output, and thirdly an initiation switch for the control circuitry.

A temperature control knob 25 operates a low-voltage circuit for providing an actuator control signal on an electrical lead 26 to an actuator 27, such as a stepper motor, driving the pinion 15.

Since the pump 16 is located externally of the bathroom the pump motor can be a mains voltage motor and without there being any mains voltage in the panel 18.

A water temperature sensor in the form of a thermistor 28 is positioned in the mixed water supply in the pump outlet 19 to provide a feedback signal on line 29. The control circuitry for the actuator 27 can compare the temperature demand signal on line 26 with the actual temperature signal on line 29 and adjust the axial position of the valve plate 6 accordingly.

The pump 16 could be replaced by a pump having a plurality of stages, but still having only one inlet and one outlet.

In a modification, not shown, the water pipe 20 is connected directly to the shower head 23, and an on/off valve remote from panel 18 is controlled by the knob 24. The knob 24 is connected to an on/off switch as well as to a potentiometer. The on/off switch operates said remote valve, and the potentiometer controls the flow rate, by varying the pump speed, for example, using a thyristor.

In a further modification, the panel 18 and the actuator 27 can be DC units. A battery backup may then be incorporated, to enable temperature control of the water to be maintained in the event of a mains power cut. Alternatively it can be arranged that, in the event of a mains power cut, the battery backup drives the valve plate 6 to the cold condition.

The system of Figure 8 is similar to that of Figure 7 and corresponding reference numerals have been applied to corresponding parts.

In the system of Figure 8 the thermistor 28 has been positioned in the water passage between the outlet 5 of the mixer valve assembly 1 and the inlet of the pump 16.

The control unit 35 is preferably housed in a position external to the bathroom or shower room, conveniently adjacent to the valve assembly 1.

Control unit 35 receives a temperature demand signal on line 36 from the temperature control 25, and on line 37 a flow on/off control signal from the on/off control 24. A mixed water temperature signal is provided to the control unit 35 on line 38 from the thermistor 28. Valve actuator 27 incorporates a potentiometer to provide to the control unit 35 on line 39 an actuator feedback signal indicative of the position of the valve plate 6. On line 40 a thermistor can provide a switch-off signal to switch off pump 16 in the event of sensing an excessive water temperature in mixer valve unit 2.

An actuator motor control signal is provided to actuator 27 on line 41, and a pump motor control signal on line 42.

Claims

1. A mixer valve assembly for a shower water supply apparatus comprising a valve housing formed with a hot water inlet, a cold water inlet and a water outlet, a valve plate movable in a chamber in the housing, the chamber being exposed to hot and cold water supply ports which communicate respectively with the hot and cold water inlets respectively through respective one-way valves, which valves both operate to permit water flow from the respective inlet to the respective port but to close against reverse flow, the valve plate being formed with a hot water opening and a cold water opening for overlapping with the hot and cold water supply ports, and there being no effective seals provided between the ports and the valve plate.

2. A mixer valve assembly as claimed in claim 1 in which the valve plate is in the form of an elongate bar, the hot and cold water openings extending transversely through the bar and being elongated in the longitudinal direction of the bar.

3. A mixer valve assembly as claimed in claim 1 or claim 2 in which the valve plate is formed with rake teeth meshed with a drive pinion which is adapted to be rotated for controlling the position of the valve plate relative to the housing.

4. A mixer valve assembly as claimed in claim 3 in which the rack teeth are disposed adjacent to one end of the valve plate.

5. A mixer valve assembly as claimed in any of the preceding claims comprising an electro-mechanical actuator so arranged as to be capable of adjusting the position of the valve plate relative to the housing to adjust the proportions of hot and cold water flowing to the water outlet.

6. A mixer valve assembly as claimed in any of the preceding claims comprising a position transducer so arranged as to provide a position signal corresponding to the position of the valve plate relative to the housing.

7. A mixer valve assembly as claimed in claim 6 and comprising a servo-control means which is so arranged as to control said position of the valve plate in response to a command signal.

8. A mixer valve assembly as claimed in claim 7 in which the command signal is influenced by the output of a water temperature sensor so arranged as to be responsive to the temperature of the mixed water.

9. A shower water supply assembly comprising a pump having a pump inlet connected to the water outlet of a mixer valve assembly as claimed in any of the preceding claims.

10. A shower water supply assembly as claimed in claim 9 as appended to claim 8 in which the temperature sensor is located adjacent to the pump.

11. A shower water supply assembly as claimed in claim 9 or claim 10 in which the pump is located externally of a shower cubicle and is adapted to be operated by a mains voltage, and comprising a manually operable temperature setting means adapted to be positioned within the shower cubicle, the temperature setting means operating on a voltage which is substantially lower than mains voltage.

12. A shower water supply apparatus comprising a mixer valve having a hot water inlet, a cold water inlet, and a mixed water outlet, a mixer valve member controlling the proportions of hot and cold water flowing from the inlets to the outlet, drive means operative to drive the mixer valve member, a position transducer associated with the drive means or mixer valve member to provide a position signal indicative of the position of the valve member relative to the valve housing, a pump having an inlet connected to the outlet of the mixer valve, a temperature sensor sensing the temperature of water downstream of the mixer valve member or pump, a temperature setting means for setting the desired water temperature, and a controller controlling the position of the mixer valve member in response to the temperature setting means and the temperature sensing means.

13. A mixer valve assembly comprising an elongate valve plate in the form of an elongate bar provided with elongate hot and cold water openings extending transversely therethrough, the plate being formed with rack teeth meshed with a drive pinion.

14. A shower mixer valve assembly substantially as described herein with reference to Figures 1 and 2 of the accompanying drawings.

15. A shower mixer valve assembly substantially as described herein with reference to Figures 3 to 6 of the accompanying drawings.

16. A shower water supply assembly substantially as described herein with reference to Figure 7 of the accompanying drawings.

17. A shower water supply assembly substantially as described herein with reference to Figure 8 of the accompanying drawings.