GB2389674A

GB2389674A - Valve control system for mixing liquids

Info

Publication number: GB2389674A
Application number: GB0213325A
Authority: GB
Inventors: Christopher Terrell
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-06-11
Filing date: 2002-06-11
Publication date: 2003-12-17
Also published as: GB0213325D0

Abstract

Hot and cold water 308, 306 are fed via regulator valves 309, 307 to mixing chamber 302. The temperature of the mixed water is measured by thermistor 315, and along with the pressure in at least the cold water feed is used to adjust at least valve 307 to control the water temperature. Determination of water pressure improves compensation for changes in water supply pressure. Regulator gate valves 307, 309 may be in the form of a paddle 1413, 1416 operated by a threaded rod 1419, 1420 and having triangular apertures 1414, 1415, 1417, 1418 in the paddle. Paddle 1413 controls the overall flow rate from the system, and paddle 1416 controls the temperature of the mixed water. The system may supply a shower 1409.

Description

( Valve Control System The present invention relates to a valve control

system, in particular a shower valve control system.

Shower units having built in temperature control systems are known.

For example, a temperature control system may operate to prevent potentially scalding water from reaching a showering person, or to maintain a steady temperature of water flowing through a shower head into a shower cubicle. to In a known type of shower unit, hot water and cold water is supplied via separate inlets, in adjustable proportions, to a mixing chamber. The water mixes together in the mixing chamber and is then supplied, at a moderated temperature, to an outlet leading to a shower head.

A problem with this style of shower unit is that the unit is often 15 plumbed inline with other water outlets in the home, for example sink taps and toilets. Thus, when an upstream outlet is opened, there is a change in the proportions of cold water and hot water supplied via the inlets to the shower unit, which in turn affects the moderated temperature of the mixed water in the mixing chamber, and therefore the temperature of the water no supplied to the shower head.

A particular problem is a drop in the supply of cold water to the shower unit, for example as a result of a toilet being flushed. This event can cause an undesirable rapid increase in the temperature of the water being supplied to the shower head.

z A known way of overcoming this problem is the incorporation of an emergency shut off function into the shower unit, which shuts down the unit

when the temperature of the water being supplied to the shower head is detected as being too high. A technique for achieving this function is to compare readings from a temperature detector located downstream of the mixing chamber, with predetermined criteria which, if exceeded, initiates a 5 routine to shut down the shower unit.

A more sophisticated known method of temperature regulation, also using a temperature detector downstream of the mixing chamber, is to use temperature readings to adjust flow control gates on each inlet to the mixing chamber, thereby controlling the mixing ratio of the inlets, and hence the to moderated temperature at which the mixed water is supplied to the shower head. Thus, if the temperature of the outlet water is detected as being too high, the gates are adjusted to effect an increase in the inflow of cold water, a decrease in the inflow of hot water, or both.

However, a problem that arises with both of the above described s temperature control systems is that temperature detection is downstream of the mixed water. Thus, if the moderated temperature of mixed water is detected as exceeding an acceptable temperature range' then although adjustments can be made to higher or lower the moderated temperature of future mixed water, the existing mixed water will continue to flow through the go outlet leading to the shower head. Thus, these systems have an inherent time delay between detecting outlet water at a temperature that will be uncomfortable to a showering person, and reacting to prevent that water from reaching the shower head.

According to a first aspect of the present invention there is provided s A valve control system for mixing liquids comprising a mixing chamber having a plurality of inlets and at least one outlet, at least one adjustable

( flow rate regulator configured to regulate flow through at least one inlet into said mixing chamber, flow rate regulator adjusting means configured to adjust at least one flow rate regulator, a mixing control circuit, temperature detecting means configured to detect temperature of mixed liquid and to supply an input signal to said mixing control circuit; said mixing control circuit configured to supply an output signal to said flow rate regulator adjusting means; wherein said valve control system further comprises pressure detecting means configured to detect pressure in at least one inlet and to supply an input signal to said mixing control circuit.

10 The invention will now be described by way of example, with reference to the accompanying drawings of which: Figure A shows a schematic of a prior art shower unit;

Figure B is a graph showing outlet water flow against time for the prior art shower unit shown in Figure A; Figure C is a graph showing outlet water temperature against time for the prior art shower unit shown in Figure A;

Figure 1 shows a shower cubicle fitted with a shower unit incorporating a valve control system according to a first embodiment of the present invention; 20 Figure 2 shows the shower-user interface of the shower unit shown in Figure 1 in more detail; figure 3 is a schematic diagram of a valve control system according to a first embodiment of the present invention; Figure 4 is a front view of internal components of the shower unit 25 shown in Figure 1; Figure 5 is an enlarged view of a region of Figure 4;

( Figure 6 shows an upper region of flow rate regulator adjusting means within the shower unit shown in Figure 1; Figure 7 shows a lower region of the flow rate regulator adjusting shown in Figure 6; Figure 8 shows flow rate regulator position detecting means within the shower unit shown in Figure 1; Figure g shows pressure detecting means mounted upon a water inlet to the shower unit shown in Figure 1; Figure 10 is a circuit diagram according to a first described to embodiment of the valve control system shown in Figure 3; Figure 11 is a flow chart of a program executed during operation of the circuit shown in Figure 10; Figure 12 shows a battery source located within the shower-user interface shown in Figure 2; Figure 13 shows a power generator mounted upon two water inlets to the shower unit shown in Figure 1; Figure 14 shows a shower unit incorporating a valve control system according to a second embodiment of the present invention; Figure 15 shows a variant of the shower unit shown in Figure 14; no Figure 16 shows a hand basin incorporating a valve control system according to the present invention.

Figare A Figure A shows a prior art shower unit A01 (shown not in operation)

2s mounted to wall A02. Shower unit A01 comprises a mixing chamber A03 having a cold water inlet And, a hot water inlet Age, and a mixed water

( outlet A06 leading to shower head A07. Shower unit A01 further comprises a starVstop lever Age, cold water adjustable flow control gate AO9, which is aligned with cold water inlet A04, and hot water adjustable flow control gate A10, which is aligned with hot water inlet A05. Means for adjusting cold s water adjustable flow control gate AO9 and hot water adjustable flow control gate A10 are not shown.

As can be seen from Figure A, mixing chamber A03 is mounted to one side of wall A02, and mixed water outlet A06 and starVstop lever A08 extend from mixing chamber A03 through wall A02 to the other side.

to Attached to starVstop lever is ceramic disc AO9 which has a cold water disc aperture A10 and a hot water disc aperture All defined therein.

Cold water disc aperture A10 and hot water disc aperture All are each elongate and taper in opposite directions to each other. Cold water disc aperture A10 and hot water disc aperture All extend circumferentially s within disc AO9 and are aligned with the ports to cold water inlet A04 and hot water inlet A05 respectively. The geometry of cold water disc aperture A10 and hot water disc aperture All is such that the maximum potential volume flow rate of water through prior art shower unit A01 increases as

disc AO9 is rotated in one direction, and decreases as disc AO9 is rotated in go the opposite direction. Disc AO9 controls the maximum potential volume flow rate of water supplied from mixing chamber A03 to shower head A07.

In operation, cold water flows through cold water inlet A04 in the direction of arrow A12 and hot water flows through hot water inlet A05 in the direction of arrow A13. Water flowing into mixing chamber A03 mixes as together such that the temperature of the water is moderated before being supplied to mixed water outlet A06, flowing in the direction of arrow A14.

( Thus, the temperature of the mixed water supplied to shower head A07 is dependent upon the temperature of the water flowing through cold water inlet A04 and hot water inlet A05 into mixing chamber A03.

Figure A shows cold water adjustable flow control gate A15 in the closed position, so as to restrict the flow of cold water into mixing chamber A03. Hot water adjustable flow control gate A16 is shown in the open position, such that the flow of hot water into mixing chamber A03 is unrestricted. This arrangement represents a problem arising during use of prior art shower unit A01, this being that when the cold water supply is

to diminished, for example when an upstream toilet (not shown) is flushed, or other upstream cold water outlet (not shown) is opened, the water flowing through mixed water outlet A06 to shower head A07 comprises a greater proportion of water originating from hot water inlet A05 than the proportion of water originating from cold water inlet A04. Thus, when the cold water s supply suddenly drops, the temperature of the mixed water supplied to shower head A07 suddenly increases, and vice versa. This relationship is illustrated graphically in Figures B and C. Figure B zo Figure B is a graph showing outlet volume flow rate(l/min) axis B01 for shower unit A01, versus time(s) axis B02 for a sample period of 50 seconds. The sample period is taken after shower unit A01 has settled into normal operation after start-up. It can be seen between O and 20 seconds, and between 40 and 50 seconds, that outlet volume flow rate line B03 s remains at an approximately zero gradient, ignoring individual fluctuations.

Between the aforementioned time intervals, the variation in the supply of

( water to the cold water inlet A04 and the hot water inlet A05 is negligible However, when a toilet (not shown) is flushed at approximately 20 seconds, thus diminishing the cold water supply to cold water inlet A04, outlet volume flow rate line B03 turns into a negative gradient, levels at a minimum and turns into a positive gradient at approximately 30 seconds, and turns into an approximately zero gradient again by approximately 40 seconds. Thus, the outlet volume flow rate from prior art shower system A01 is dependent

upon the volume flow rate of water supplied to cold water inlet A04 and to hot water inlet A05.

Figure C Figure C is a graph showing an outlet water flow temperature( c) axis C01 for shower unit A01, versus a time(s) axis C02 for the same sample period of 50 seconds as that shown in Figure B. It can be seen 5 between 0 and 20 seconds, and between 40 and 50 seconds, that outlet water temperature line C03 remains at an approximately zero gradient.

However, outlet water temperature line C03 turns into a positive gradient at approximately 20 seconds, levels at a maximum and turns into a negative gradient at approximately 30 seconds, and turns into an approximately zero 20 gradient again by approximately 40 seconds.

Through comparison of Figures B and C, it can be seen that there is an inverse relationship between outlet water flow line B03 and outlet water temperature line C03 during the sample period of normal operation of prior art shower unit A01; during which the aforementioned toilet (not shown) is z5 flushed. Thus, the temperature of the mixed water supplied to shower head A07 is also dependent upon the ratio of water supplied through cold water

( inlet A04 and hot water inlet A05 to mixing chamber A03.

Figure 1 Figure 1 illustrates a shower cubicle 101 fitted with a shower unit 102 5 (shown not in operation) incorporating a valve control system according to a first embodiment of the present invention. Showering person 103 is standing underneath shower head 104 with her hand 105 upon shower user interface 106, in preparation for the ebullient outflow of water from shower head 104, when she manually turns on shower unit 102.

Figure 2 Shower-user interface 106 is shown in more detail in Figure 2. Hand 105 of showering person 103 is placed upon starVstop lever 201, which is in the off position, in which symbol 202 is visible. StarVstop lever 201 is s rotatable through 180 and comprises a disc (not shown) similar to disc AO9 of prior art shower unit A01. Start/stop lever 201 is configured such that the

further it is turned in the clockwise direction from symbol 202, the greater the maximum potential volume flow rate of water from shower head 104.

When shower unit 102 is on, display 203 displays a desired no temperature 204, which in Figure 2 is shown to be 38.0 c. Preferably, display 203 also displays an actual temperature value, described In further detail below. Display 203 is a low energy consumption display, preferably an LCD negative dot matrix, seven segment or hybrid design display.

Desired temperature 204 is pre-settable through shower-user 25 interface 106. However, when shower unit 102 is in operation, desired temperature 204 is also manually variable by pressing increase desired

( temperature button 205 or decrease desired temperature button 206. Each press of increase desired temperature button 205 or decrease desired temperature button 206, increases or decreases desired temperature 204 respectively by one pre-determined increment, and the display of desired 5 temperature 204 on display 203 is correspondingly updated.

Figure 3 Figure 3 shows a schematic of a valve control system 301 according to a first embodiment of the present invention, which is incorporated into to shower unit 102.

A primary function of valve control system 301 is to maintain the temperature of the outlet water flowing through shower head 104 at desired temperature 204.

Typically, a domestic water supply will supply cold water at a s temperature between 10 c and 20 c, and hot water at a temperature between 50 c and 70 c. A temperature "comfort zone" for outlet water being supplied to an average human, such as showering person 103, varies between 28 c and 40 c with a normal range being between 32 c and 36 c. However, an average human can detect temperature fluctuations of + 20 1 c. Valve control system 301 comprises a mixing chamber 302 having a cold water inlet 303, a hot water inlet 304 and a mixed water outlet 305 leading to shower head 104. Cold water inlet 303, hot water inlet 304 and mixed water outlet 305 are rotatably connected to mixing chamber 302, 2s preferably being rotatable through 360 c, to facilitate the installation of shower unit 102 into shower cubicle 101.

( During operation, the flow of water through cold water inlet 303, in the direction of arrow 306, into mixing chamber 302 may be restricted by means of cold water adjustable flow rate regulator 307. Similarly, the flow of water through hot water inlet 304, in the direction of arrow 308, into mixing chamber 302 may be restricted by means of hot water adjustable flow rate regulator 309 The flow of water from mixing chamber 302 into mixed water outlet 305, flowing in the direction of arrow 310, may be adjusted between zero volume flow rate and a maximum potential volume flow rate by means of 10 adjustable outlet flow regulator 311.

According to the first embodiment of the present invention, adjustable outlet flow regulator 311 is a disc (not shown) similar to disc AO9, connected to start/stop lever 201. Thus, in the first embodiment, adjustable outlet flow regulator 311 is manually adjustable. However, cold water flow rate regulator 307 and hot water flow rate regulator 309 are controlled by control circuit 312 via flow rate regulator adjusting means 313, described in more detail below with reference to Figures 4-6, and position detecting means 314, described in more detail 'belong with reference to Figures 5 and 8.

20 Valve control system 301 also comprises temperature detecting means 315 and pressure detecting means 316.

According to the first embodiment of the present invention, temperature detecting means 315 is configured to detect the temperature of mixed water supplied from mixing chamber 302 to mixed water outlet 305.

z Temperature detecting means 315 is described in more detail below, with reference to Figures 4, 10 and 11.

In addition, pressure detecting means 316 is configured to detect pressure variations within cold water inlet 303. Pressure detecting means 316 is described in more detail below, with reference to futures 9-11.

Temperature detecting means 315 and pressure detecting means 5 316 are configured to provide an input signal to control circuit 312, which in response provides an output signal to flow rate regulator adjusting means 313. In addition, position detecting means 314 provides an input signal to control circuit 312, which is indicative of the position of cold water to adjustable flow rate regulator 307 with respect to the port of cold water inlet 303, with which cold water adjustable flow rate regulator 307 is aligned.

Position detecting means 314 enables valve control system 301 to return cold water adjustable flow rate regulator 307 to a pre-determined position when valve control system 301 is powered down from an active state into a stand-by state.

According to the first embodiment of the present invention, when valve control system 301 is in the stand-by state, cold water adjustable flow rate regulator 307 and hot water adjustable flow rate regulator 309 are in a central position, thus allowing a restricted level of water to flow through cold zo water inlet 303 and hot water inlet 304 into mixing chamber 302. However, when valve control system 301 is in the stand-by state, adjustable outlet flow regulator 311 is in the fully closed position, thus preventing the flow of water from mixing chamber 302 into mixed water outlet 305.

With this arrangement, pressure is exerted on adjustable outlet flow 25 regulator 311 by static upstream water remaining in mixing chamber 302, cold water inlet 3Q3 and hot water inlet 304. Thus, when showering person

( 103 turns shower unit 102 on, thus opening adjustable outlet flow regulator 311, the aforementioned static water flows into mixed water outlet 305 resulting in a pressure drop, which is detected by pressure detecting means 316. In response, pressure detecting means 316 supplies an input signal to s control circuit 312, which in response, wakes up valve control system 301 from the stand-by state to the active state.

Valve control system 301 is powered by power source 317, which is described in more detail below with reference to Figures 12 and 13.

o Figure 4 Figure 4 shows the arrangement of internal components of shower unit 102. Within region 401, there is arranged flow rate regulator adjusting means 313 and position detecting means 314, which are described in more detail below with reference to Figures 5-8.

1s Connected to the flow rate regulator adjusting means 313 is cold water adjustable flow rate regulator 307, which is mounted in housing 402, and hot water adjustable flow rate regulator 309, which is mounted in housing 403. Cold water adjustable flow rate regulator 307 and hot water adjustable flow rate regulator 309, which are described in more detail with 20 reference to Figure 8, are shown obscuring cold water inlet 303 and hot water inlet 304 from view.

As can be seen from Figure 4, mixed water outlet 305 is positioned below cold water inlet 303 and hot water inlet 304, so as to effectively utilise the pressure gradient within mixed water present in mixing chamber 302 to 25 supply water to mixed water outlet 305. The arrangement shown in Figure 4 also facilitates the supply of mixed water to mixed water outlet 305 when

( there is a low level of mixed water present within mixing chamber 302.

According to the first described embodiment, temperature detecting neons 315 comprises a rapid response glass encapsulated thermistor 404, suspended in a central position within mixed water outlet 305 by three supporting struts 405, 406, and 407. Rapid response glass encapsulated thermistor 404 provides an output signal to control circuit 312, which is indicative of temperature, accurate to the nearest 0.2 c.

Figure 5 lo An enlarged view of region 401 is shown in Figure 5. Flow rate regulator adjusting means 313 and pressure detecting means 316 are arranged within a supporting structure 501 and are mechanically sealed from the pressurised working regions of shower unit 102. Affixing flow rate regulator adjusting means 313 and pressure detecting means 316 to s supporting structure 501, thus creating a separate module, facilitates the construction and replacement of components within valve control system 301. Gearing system 502, which is actuated by do motor 503, is shared by flow rate regulator adjusting means 313 and position detecting means 20 314.

Figure 6 Figure 6 shows components of flow rate regulator adjusting means 313. It can be seen from Figure 6, that gearing system 502 drives first rod 2s 601, which is connected to cold water adjustable flow rate regulator 307 and second rod 602 which is connected to hot water adjustable flow rate

( regulator 309. Gearing system 502 is configured such that first rod 601 is moved in contra-rotation to second rod 602. Cold water adjustable flow rate regulator 307 and hot water adjustable flow rate regulator 309 are simultaneously moved in opposite directions.

5 DC motor 503 produces linear motion and can be driven in forward or reverse by an output signal from control circuit 312; described in more detail with reference to Figures 10 and 11.

figure 7 lo Figure 7 shows paddle section 701 of cold water adjustable flow rate regulator 307. Paddle section 701 extends from first rod 601, and comprises a thread 702 about which a closure member 703 is mounted.

Paddle section 701 is mounted within housing 402 such that closure member 703 is prevented from rotating when first rod 601 is rotated. Thus, when first rod 601 is rotated in a clockwise direction, closure member 704 is moved upwards along first rod 601 and similarly when first rod 601 is rotated in an anti-clockwise direction, closure member 704 is moved downwards along first rod 601.

zo Figure 8 According to the first embodiment of the present invention, position detecting means 314, which detects the position of cold water flow rate regulator 307 with respect to the port of cold water inlet 303, comprises an optical disc encoder 801, shown in Figure 8.

s Optical disc encoder 801 comprises disc 802 and sensor 803. Disc 802 has a cut away portion along its radius, between edge 803 and edge

( 804, such that light can reach sensor 803 when a section of the cut away portion is positioned between jaw 805. Valve control system 301 comprises a light source for optical disc encoder 801, which is described in more detail with reference to Figure 10.

5 Optical disc encoder 801 is configured such that edge 804 corresponds to one extreme position of cold water adjustable flow rate regulator 307 e.g. the fully open position, and edge 805 corresponds to the other extreme position of cold water adjustable flow rate regulator 307 e.g. the fully closed position. Thus, optical disc encoder 801 is configured to to provide an indication of the position of cold water adjustable flow rate regulator 307, which by means of the configuration of gearing system 502, also provides an indication of the position of hot water flow rate regulator 309 with respect to the port of hot water inlet 304.

5 Figure 9 According to the first embodiment of the present invention, pressure detecting means 316 comprises a pressure transducer 901, shown in Figure 9. Pressure transducer 901 is mounted upon cold water inlet 303 by clamp 902. It can be seen from Figure 9 that clamp 902 holds pressure zo transducer 901 against the external wall of cold water inlet pipe 903, in alignment with an aperture 904 extending between the external wall and the internal wall of cold water inlet pipe 903. Thus, pressure transducer 901 is configured to directly detect pressure within cold water inlet 303, from which changes in pressure within cold water inlet 303 can be determined.

Q5 Variations in pressure within cold water inlet 303 are indicative of variations in the volume flow rate of water supplied to cold water inlet 303,

( for example when the supply of water to cold water inlet 303 is diminished due to the flushing of an upstream toilet (not shown).

In response to inputs from temperature detecting means 315 and pressure detecting means 316, control circuit 312 provides an output signal 5 to flow rate regulator adjusting means 313 to adjust the position of cold water flow rate regulator 307 and hot water flow rate regulator 309 to vary the mixing ratio of cold water and hot water in mixing chamber 302. This operation functions to counteract predicted resultant fluctuations in the temperature of water being supplied to mixed water outlet 305.

to Pressure detecting means 316 supplies an input signal to control circuit 312 that is indicative of a characteristic of water flowing upstream of mixing chamber 302, whilst temperature detecting means 315 supplies an input signal to control circuit 312 that is indicative of a characteristic of water flowing downstream of mixing chamber 302. Valve control system 301 utilises feed forward input signals from pressure detecting means 316, in combination with input signals from temperature detecting means 315, within a closed loop control circuit in which the actual temperature of water supplied to mixed water outlet 305 is compared against the current desired temperature 204, and output signals are supplied from control circuit 312 to so flow rate regulator adjusting means 313 in response.

Figure 10 Figure 10 is a schematic of control circuit 312, according to the first embodiment of the present invention. In addition to the already described 2s components, valve control system 301 comprises a 28-pin microprocessor 1001, such as a Microchip Corporation PIC 16F870 having an onboard

( analogue to digital converter, to which 8MHz resonator 1002 is connected.

Microprocessor 1001 executes a program, described in more detail below with reference to Figure 11.

Valve control system 301 also comprises a sound generator 1003, such as a piezoelectric buzzer, which activates an audible signal when a steady state_temperature of water supplied to mixed water outlet 305 reaches the current desired temperature 204 for the first time. Valve control system 301 may be configured such that sound generator 1003 is activated during execution of an emergency override function, described in more to detail below with reference to Figure 11.

Sound generator 1003 may comprise a speaker, and thus may provide aural indications of the operation of valve control system 301, which is advantageous for persons suffering with sight difficulty. Sound generator 1003 may also comprise a microphone, preferably with amplification s means, which provides a means of communication between showering person 103 and a third party. This feature is advantageous, for example, if shower unit 102 is installed in a care home. In addition, valve control system 301 may be configured to provide wireless communication between showering person 103 and a third party.

So As previously mentioned, pressure detecting means 316 provides an input signal to control circuit 312 that is indicative of shower unit 102 being switched on. In response, power switch 1004 is activated to power up valve control system 301 from a stand-by state to an active state. Power switch 1004 is also used to power down valve control system 301 from the active 25 state to the stand-by state, and may be configured to be directly activated and deactivated. Power switch 1004 is preferably a magnetic reed switch or

( a non-electric switch.

The input signal from pressure transducer 901 is input into solid state bridge driver 1005 to produce an input signal which is proportional to the differential changes in pressure in cold water inlet 303 with respect to 5time. In place of solid state bridge driver 1005, a potential divider may be used. The input signal from rapid response glass encapsulated thermistor 404 is input into operational amplifier 1006 for amplification. The sensitivity and scale of rapid response glass encapsulated thermistor 404 may be to adjusted using potentiometers.

An input signal is also supplied by optical disc encoder 801. A dedicated source of light for optical disc encoder 801 is provided by LED 1 007.

In addition to an increase desired button 205 and a decrease desired s temperature button 206, shower-user interface 106 may also comprise a mode switch 1008. Mode switch 1008 may be used to navigate around a menu system, for example to input or alter a number of desired temperature settings corresponding to a number of users of shower unit 102. This feature provides for a personal temperature setting for a number of different zo users of shower unit 102. Mode switch 1008 may be also used to select other functions, for example to change the language of the display, to include or modify courtesy messages, to change the display of temperature values between imperial or metric systems, to display instructions or to change the display of characters between static, flashing, scrolling etc. zip Preferably, increase desired temperature button 205, decrease desired temperature button 206 and mode switch 1008 are digital push buttons, but

alternatively may be mechanical rotary dials.

Microprocessor 1001 supplies an output signal to do motor 601. This output signal comprises pulses of equal amplitude but varying width. The determination of the pulse width is described in more detail below, with 5 reference to Figure 11.

Figure 1 1 Figure 11 is a flow chart illustrating steps involved in program 1101 executed by microprocessor 1001, which is coded using an assembler 1 0 language.

Program 1101 starts at step 1102, following activation of valve control system 301. At step 1103, an analogue input signal from pressure transducer 901 is received, which at step 1104 is converted into a digital signal. The value of this digital pressure signal is indicative of the pressure within cold water inlet 303, and at step 1105 is compared to a pre programmed pressure value that is indicative of a normal pressure within cold water inlet 303 during normal operation of shower unit 102. A pressure difference variable Predicative of the difference in magnitude between the aforementioned digital pressure signal and pre- programmed pressure value go is stored in program 1101 for use in the algorithm executed at step 1109.

At step 1103, an analogue input signal from rapid response glass encapsulated thermistor 404 is received, which at step 1107 is converted into a digital signal. The value of this digital temperature signal is indicative of the temperature of the water supplied to mixed water outlet 305, and at z step 1108 is compared to the current value of desired temperature 204, which is stored as a variable in program 1101. A temperature difference

( variable indicative of the difference in magnitude between the aforementioned digital temperature signal and the current value of desired temperature 204 is stored in program 1101 for use in the algorithm executed at step 1109.

At step 1109, the pressure difference variable stored at step 1105 and the temperature difference variable determined at step 1108 are input into an algorithm executed at step 1109, which combines both the temperature difference value and the pressure difference value to provide a predicted temperature value for use at step 1110. For example, the to algorithm may add or subtract the pressure difference value to or from the temperature difference value, depending on an empirical relationship between variations in pressure within cold water inlet 303, and resultant downstream fluctuations in the temperature of water supplied to mixed water outlet 305.

The predicted temperature value determined at step 1109 is indicative of the temperature of the water supplied to mixed water outlet 305 in the future, after a time delay from calculation. Delays in valve control system 301 are introduced by, for example, the physical inertia of do motor 503, cold water flow rate regulator 307, and hot water flow rate regulator 20 309, the mechanical heat capacitance of rapid response glass encapsulated thermistor 404, and the velocity of the water flowing through shower unit 102. For example, a 50% pressure drop within cold water inlet 303 may result in a 7 c rise in the temperature of water flowing into mixed water outlet 305, after a delay of approximately 2 seconds. Valve control :s system 301 is configured such_that an input signal from pressure transducer 901 is received by control circuit 312 within this time delay, after

( approximately 20 milliseconds, that is indicative of the pressure variation within cold water inlet 303. Furthermore, valve control system 301 is configured such that in response, control circuit 312 supplies an output signal to flow rate regulator adjusting means 313, also within the aforementioned time delay, to adjust the volume flow rate of water through cold water inlet 303 and hot water inlet 304, to counteract the predicted temperature increase in water flowing into mixed water outlet 305.

At step 1110, the predicted temperature value determined at step 1109 is compared to the current desired temperature 204, resulting in one 10 of three possible outcomes. If the predicted temperature value is determined to be higher than the current desired temperature 204, then an output signal is supplied to do motor 503, to the effect that at step 1111, do motor 503 is rotated left, or clockwise, such that cold water adjustable flow rate regulator 307 is opened further, and at the same time hot water adjustable flow rate regulator 309 is closed further. If the predicted temperature value is determined to be lower than the current desired temperature 204, then an output signal is supplied to do motor 503, to the effect that at step 1112, do motor 503 is rotated right, or anticlockwise, such that cold water adjustable flow rate regulator 307 is closed further, and 20 at the same time hot water adjustable flow rate regulator 309 is opened further. The length of the pulse width in the output signal to do motor 503 is dependent upon the magnitude of the difference between the actual temperature value and desired temperature 204. According to the preferred embodiment, program 1101 elects one of three duty factors of 10%, 30% z and 80% for each output signal. The duty factors selectable at step 1110 are pre-determined with respect to the arrangement and operational

( characteristics of cold water adjustable flow rate regulator 307, hot water adjustable flow rate regulator 309 and flow rate regulator adjusting means 313. Program 1101 may include more selectable duty factors, but each additional duty factor will introduce an associated program execution delay.

5 Alternatively, the predicted temperature value may equal the current desired temperature 204, and no output signal to do motor 503 is supplied.

At step 1113, an output signal derived from the digital temperature signal determined at step 1107 is supplied to display 203, which updates the actual temperature value displayed to showering person 103. Display to 203 can display temperature values in increments of 0.1 c.

At step 1114, a question is asked as to whether shower unit 102 is switched on. If the question is answered in the affirmative, program 1101 loops back to step 1103. If the question is answered in the negative, then at step 1115, cold water adjustable flow rate regulator 307 and hot water adjustable flow rate regulator 309 are reset to a pre-determined position, which in this described embodiment in the central position. The central position may be biased towards cold water inlet 303 or hot water inlet 304 to compensate for any pressure difference between these inlets. At step 1116, valve control system 301 is powered down from the active state to no the stand-by state and execution of program 1101 ceases.

Valve control system 301 may also comprise an emergency override function. For example, program 1101 may comprise a function wherein in the event that the temperature difference value determined at step 1108 exceeds a pre-determined temperature override value, then hot water 25 adjustable flow rate regulator 309 may be moved into the closed position, after a predetermined time delay, to shut off the supply from hot water inlet

304. For example, the temperature override value may be set at 10 c and the time delay may be set at 5 seconds, however, both may be adjustable.

The emergency override function may prevent normal operation of shower unit 102 until pre-determined criteria are satisfied, for example, until valve 5 control system 301 detects normal pressure in cold water inlet 303 and hot water inlet 304. In addition, on activation of the emergency override function, an emergency message may be displayed on display 203 and sound generator 1002 may be activated in response.

Valve control system 301 may also comprise a time out function. For to example, program 1101 may comprise a function to power down valve control system 301 into the stand-by state after a pre-determined time delay from being powered up into the active state. The pre-determined time out period, which may be adjustable, functions to reduce water wastage.

Figure 12 Figure 12 shows shower-user interface 106 with start/stop lever 201 removed, such that battery source 1201 is visible. Battery source 1201 provides power for valve control system 301, upon power up from the stand-by state to the active state.

zo According to the first described embodiment, battery source 1201 comprises three Nickel Metal Hydride (NiMH) rechargeable M batteries, which are widely available. Battery source 1201 is located behind start/stop lever 201, which is removable, to facilitate the construction of valve control system 301 and for convenient replacement of battery source 1201.

Figure 13 Battery source 1201 is recharged by means of power generation module 1301, shown in Figure 13. Power generation module 1301 comprises four thermo-electric generators, producing between 3 and 5 volts 5 utilising the Seebeck-Peltier Effect. Power generation module 1301 is mounted about cold water inlet 303 and hot water inlet 305 such that the aforementioned thermo-electric generators are disposed between cold water inlet 303 and hot water inlet 304. Thus, the output voltage from power generation module 1301 is dependent upon the temperature differential to between cold water inlet 303 and hot water inlet 304.

Power generator module 1301 is configured to recharge battery source 1201 from a temperature differential of 24 c. However, with a normal water domestic supply of hot water at 60 c and ambient cold water at 18 c in summer, or 6 c in winter, temperature differentials of 38 c and 54 c respectively are achievable.

The output from power generation module 1301 is input into a buck boost circuit which provides a uniform output of 5 volts, and which also serves as a current limiter during the recharging of battery source 1201.

According to the first embodiment of the present invention, the 20 provision of a rechargeable battery source 1201, rechargeable by means of power generation module 1301, advantageously enables shower unit 102 to be operated without deriving power from a domestic power supply. This feature is advantageous in environments in which water is present, and also simplifies the installation of shower unit.

( Figure 14 Figure 14 shows a shower unit 1401 (shown in operation) incorporating a valve control system according to a second embodiment of the present invention. The second embodiment of the present invention provides a valve control system that is scaleable with respect to water pressure and volume flow rate of water.

The valve control system incorporated into shower unit 1401 comprises basic components 302-305, 307, 309 and 311-317 of valve control system 301, shown schematically in Figure 3. In operation, the to directional flow of water through shower unit 1401 is similar to the flow of water through shower unit 102, wherein cold water flows through cold water inlet 1402 in the direction of arrow 1403 and hot water flows through hot water inlet 1404 in the direction of arrow 1405, into mixing chamber 1406.

Water in mixing chamber 1406 is supplied at a moderated temperature to mixed water outlet 1407, flowing in the direction of arrow 1408 towards shower head 1409.

According to the second embodiment of the present invention, temperature detecting means 315 comprises a rapid response glass encapsulated thermistor 1410, suspended within mixed water outlet 1407.

so Rapid response glass encapsulated thermistor 1410 is configured to provide an input signal into control circuit 312.

According to the second embodiment, pressure detecting means 316 comprises a cold water pressure transducer 1411, which is mounted upon cold water inlet 1402 and is configured to directly detect pressure and Q changes In pressure within cold water inlet 1402; and also comprises a hot water pressure transducer 1412, which is mounted upon hot water inlet

( 1404 and is configured to directly detect pressure and changes in pressure within hot water inlet 1404.

Both cold water pressure transducer 1411 and hot water pressure transducer 1412 are configured to supply an input signal to control circuit 5 312. Thus, according to the second embodiment of the present invention, pressure detecting means 316 supplies hvo input signals to control circuit 312. According to the second embodiment of the present invention, adjustable outlet flow regulator 311 comprises an outlet flow control slider to 1413. Preferably, outlet flow control slider 1413 is an elongate rectangular member having two apertures defined therein; a cold water aperture 1414 and a hot water aperture 1415. As can be seen from Figure 14, cold water aperture 1414 and hot water aperture 1415 are shaped as isosceles triangles and are aligned with cold water inlet 1402 and hot water inlet 1404 s respectively. Cold water aperture 1414 and hot water aperture 1415 are arranged within outlet flow control slider 1413 such that as outlet flow control slider 1413 is moved upwards and downwards via flow rate regulator adjusting means 313, there is a proportional relationship between the amount of cold water aperture 1414 appearing at the port of cold water go inlet 1402 and the amount of hot water aperture 1415 appearing at the port of hot water inlet 1404, at the same time. Thus, the flow of water from mixing chamber 1402 to flow mixed water outlet 1405 may be adjusted between zero volume flow rate and a maximum potential volume flow rate by means of outlet flow control slider 1413.

25 In contrast to the first embodiment of the present invention, cold water adjustable flow rate regulator 307 and hot water flow rate regulator

( 309 are combined within a single inlet flow control slider 1416. Preferably, inlet flow control slider 1416 is an elongate rectangular member having two apertures defined therein; a cold water aperture 1417 and a hot water aperture 1418. As can be seen from Figure 14, cold water aperture 1417 and hot water aperture 1418 are shaped as isosceles triangles and are aligned with cold wafer inlet 1402 and hot water inlet 1404 respectively.

Cold water aperture 1417 and hot water aperture 1418 are arranged within inlet flow control slider 1416 such that as inlet flow control slider 1416 is moved upwards and downwards via flow rate regulator adjusting means to 313, there is an inverse relationship between the amount of cold water aperture 1417 appearing at the port of cold water inlet 1402 and the amount of hot water aperture 1418 appearing at the port of hot water inlet 1404, at the same time.

Thus, the maximum volume flow rate of water supplied to mixing 15 chamber 1402 from cold water inlet 1402 and hot water inlet 1404 is controlled by inlet flow control slider 1416 With this preferred configuration of outlet flow control slider 1413 and inlet flow control slider 1414, cold water adjustable inlet flow regulator 307, hot water adjustable flow regulator 309 and adjustable outlet flow regulator so 311 are scaleable to fit any size of showering unit. This feature advantageously reduces manufacturing costs.

According to the second embodiment, flow rate regulator adjusting means 313 comprises two do motors that can be driven in forward and reverse; an inlet flow control slider motor 1419 and an outlet flow control :5 slider motor 1420. Inlet flow control slider motor 1419 is actuated by an output signal from control circuit 312 and outlet flow control slider motor

( 1420 is actuated manually by means of a spring biased switch on the shower-user interface. Inlet flow control slider motor 1419 and outlet flow control slider motor 1420 drive outlet flow control slider 1413 and inlet flow control slider 1416 respectively via a screw and nut system. Alternatively, 5 outlet flow control slider 1413 may be actuated via a lever on the shower user interface and a rack and pinion system.

During power down from the active to the stand-by state, in which outlet flow control slider 1413 is in the fully closed position, inlet flow control slider 1416 is moved to a pre-determined position, for example the open to position. The position of inlet flow control slider 1416 is determined by means of position detecting means 314, which, similar to the first I embodiment, comprises a geared optical disc encoder; the ratio of the gears being dependent upon the pitch of the nuts connected to inlet flow control slider 1416. The type, function and operation of the aforementioned geared optical disc encoder, is similar to optical disc encoder 801, described above with reference to Figure 8.

In accordance with the second embodiment of the present invention, control circuit 312 and program 1101 are correspondingly adapted to! receive an additional input signal from pressure detecting means 316 and go to supply an additional output signal to flow rate regulator adjusting means 313. According to the present embodiment, power source 317 is I derived from a domestic electricity supply; regulated using high frequency switching circuits, double wound transformers and residual current 25 breakers, to provide a source of low voltage and current limited electricity.

This source of power provides an increased amount of power with which

( valve control system 301 may be operated. Thus, valve control system 301 may be fully remote control, with servomechanism actuation of both outlet flow control slider 1413 and inlet flow control slider 1416, and may comprise a more sophisticated display. Furthermore, deriving power from a domestic electricity supply provides a greater degree of flexibility with respect to the type and arrangement of components in valve control system 301, for example, the location and available volume of sound generator 1003.

Figure 15 10 Figure 15 shows shower unit 1401, shown in Figure 14, with a first additional shower head 1501 and a second additional shower head 1502. Valve control system 301 is suitable for use in shower units having a plurality of shower heads per shower cubicle. Alternatively, valve control system 30t is suitable for use with showering systems having a single 1s shower unit and a single shower head per shower cubicle, for example sports showers, such as those typically found in a public swimming baths.

Valve control system 301 provides for central control of the desired temperature 204 of outlet water with such a showering system.

20 Figure 16 Figure 16 shows a hand basin 1601 incorporating a valve control system according to the present invention. Hand basin 1601 operates according to an automatic activation system, wherein a sensor, for example an infra-red detector, detects the presence of hands 1602 and 1603 within as hand basin 1601, and in response activates an outlet flow of water. Such a type of hand basin 1601 may be found in, for example, public wash rooms

( or factories. Thus, valve control system 301 is suitable for use with domestic and business water supply units.

Preferably, components of valve control system 301 that will be in contact with water are fabricated from plastic or ceramic. These materials 5 help reduce wear and the build up of water deposits, and thus prolong the working life of the system. Referring to the second described embodiment of the present invention, outlet flow control slider 1413 and inlet flow control slider 1416 are preferablyfabricated from ceramic or silicon carbide. These materials, when combined with others, can be flattened and polished to to provide a tight seal and facilitate shut down under adverse water conditions, for example water hardness and deposits. A ceramic-to-ceramic contact is known to provide a tight seal. However, inlet flow control slider 1416 may be fabricated from plastic if a watertight seal is achieved by outlet flow control slider 1413.

Valve control system 301 is suitable for use in low pressure water supply environments and high pressure water supply environments, and is also suitable for use with shower units providing an outlet volume flow rate in the range 2-20 I/min.!

Claims

( Claims

1. A valve control system for mixing liquids comprising a mixing chamber having a plurality of inlets and at least one outlet, 5 at least one adjustable flow rate regulator configured to regulate flow through at least one inlet into said mixing chamber, flow rate regulator adjusting means configured to adjust at least one flow rate regulator, a mixing control circuit, to temperature detecting means configured to detect temperature of mixed liquid and to supply an input signal to said mixing control circuit; said mixing control circuit configured to supply an output signal to - said flow rate regulator adjusting means; wherein said valve control system further comprises pressure detecting 5 means configured to detect pressure in at least one inlet and to supply an input signal to said mixing control circuit.

2. A valve control system according to claim 1 wherein said pressure detecting means comprises a pressure transducer.

3. A valve control system according to claim 1 or claim 2 wherein said temperature detecting means comprises a thermistor.

4. A valve control system according to any preceding claim :s wherein said plurality of inlets comprises a hot water inlet and a cold water inlet.

( 5. A valve control system according to claim 4 wherein said pressure detecting means is configured to detect pressure in said cold water inlet.

6. A valve control system according to any preceding claim wherein at least one adjustable flow rate regulator comprises a paddle mounted upon a threaded section of a rod.

10 7. A valve control system according to any of claims 1-5 wherein at least one adjustable flow rate regulator comprises a rectangular member having two apertures.

8. A valve control system according to claim 7 wherein at least 15 one of said apertures is a triangle.

9. A valve control system according to claim 6 wherein said paddle is fabricated from plastic or ceramic.

20 10. A valve control system according to any claim 7 or claim 8 wherein said rectangular member is fabricated from plastic, ceramic or silicon carbide. 3 11. A valve control system according to claim 1 wherein at least :s one adjustable flow rate regulator is scaleable with respect to liquid pressure or volume flow rate.

( 12. A shower system comprising a valve control system according to any preceding claim.

13. A shower valve control system substantially as herein described with reference to and as shown in Figures 1-16.