Background of the invention Valves of this type to which this invention applies are often referred to as tempering valves and are increasingly used, interposed between storage water heaters and bathrooms or en- suite bathrooms to guard against any possibility of people being scalded by excessively hot water accidentally delivered to a shower or bath. In certain types of washing facilities, such as in homes for very aged people, such tempering valves are already mandatory. The embodiments of the present invention, as will be described, are particularly suitable for domestic application.

The economy, compactness and fail-safe qualities of valves according to the invention may lead to greater consumer acceptance of tempering valves for domestic installation and thereby lead to beneficial reduction in the number of reported scalding accidents related to taking baths and showers. Scalding accidents are infrequent, yet some are regularly reported by the population at large in home accident statistics.

The seriousness of a hot water scald burn is directly dependent on the temperature of the water and the length of contact time. There is a significant difference in the time that it takes to suffer a serious, third degree, scald at different temperatures. A third degree burn is one that affects the full thickness of skin and is likely to require surgery.

For water temperatures less than 50° C there is a substantial safe contact time before third degree burns occur. At 50° C the safe contact time for adults and children is 5 minutes.

Table 1 below shows how this time is substantially reduced at higher temperatures. ............................................................ ............................................................ ............................................................ ........................................................ :' ! ............ 5 minutes 5 minutes ............... 55 30 seconds 7 seconds 60 5 seconds 1 second 70 1 second 0.5 seconds Table 1. Time taken to produce third degree burns from hot water

The following patents, located in a specific purpose search but not representing common general knowledge in this field, describe inventions having some elements in common with the present one.

US patent 5032992, Bergmann, assigned to American Standard Inc, entitled"Electronic temperature control system", primary US Class 364/550.

US patent 4875623, Garris, assigned to Memrysafe, Inc, entitled"Valve control", primary US Class 236/12.12 US patent 5927332, Richard, entitled"Fluid dispensing device including at least one remote-controlled motor", particularly a water mixing valve, primary US Class 137/625.4.

US patent 4696428, Shakalis, entitled"Electronic fluid temperature flow control system", primary US Class 236/12.12.

United States Patent 5,341,987, Ackroyd, assigned to Watts Investment Company, entitled"Temperature control flow valve", primary U. S. Class 236/12. 21. This patent discloses a temperature control flow valve with a body defining conduits for connection to cold and hot water and a chamber for mixing the water but discloses, in a particularly preferred form, a thermostat element filled with a copper powder/wax mixture in the mixing chamber that exchanges heat with the mixed water and expands or contracts accordingly to move a valve member for maintaining the temperature of the mixed water at or below a predetermined maximum temperature. The cold and hot water inlet streams are therefore combined through a mixing valve in a ratio adjusted continuously by means of the thermostat element to provide the mixed water at the predetermined temperature. Valves of this type, when they fail, do not fail in a safe mode; rather the thermostat element causes the valve to fail wide open to hot water flow, which will of course lead to water typically hotter than 70° C being delivered to a shower or bath outlet, with potential to cause scalding.

Summary of the invention The invention consists of a temperature control flow valve comprising: a body defining a first conduit having a cold water inlet adapted for attachment to a source of cold water, a second conduit having a hot water inlet adapted for attachment to a source of hot water, the first conduit having a cold water outlet for flow of cold water into a first mixing chamber, the second conduit having a hot water outlet for flow of hot water into the first

mixing chamber and a mixed water outlet adapted for attachment to a third conduit for delivery of mixed water to one or more points of use; a mixing valve assembly comprising a mixing valve element in the first mixing chamber directly coupled to a stepper motor for axial movement of the element within the first mixing chamber in a manner to adjust the ratio of hot water and cold water flowing into the first mixing chamber; an electronic control logic module for interfacing between a flow sensor and a temperature sensor located in a second mixing chamber; wherein the second mixing chamber communicates with the first mixing chamber and receives partially mixed fluids from the first mixing chamber and the second mixing chamber contains a flow sensor comprising as a single entity a rotary turbine with plural blades, each blade carrying magnetic means for effecting a signalling pulse each time it passes a magnetic sensor means fixed to an outside surface of the second mixing chamber near the turbine, the turbine simultaneously mixing the hot and cold fluid streams to effect complete temperature uniformity of the mixed fluid stream in the second mixing chamber; and wherein the. temperature sensing element is adapted to react to change of temperature of the mixed water in a manner to interface with the stepper motor to adjust the position of the mixing valve element in the first mixing chamber, thereby to maintain the temperature of mixed water leaving the second mixing chamber and entering the third conduit below a predetermined maximum.

Preferably, the moveable element comprises a threaded member that moves axially in the first mixing chamber by being rotated by the stepper motor. Preferably the mixing valve assembly further comprises a cold water mixing valve seat; a hot water mixing valve seat; and the mixing valve element disposed in the first mixing chamber comprises a first mixing valve member opposed to and disposed for near approach to the first mixing valve seat and a second

water valve element further comprises a hot water plug element defining a surface exposed to hot water supply pressure acting in a second direction generally opposed to the first direction.

The temperature control flow valve preferably further comprises a non-return valve in at least the first conduit, connected to the cold water inlet.

The temperature control flow valve preferably further comprises a non-return valve in the second conduit, connected to the hot water inlet.

The temperature control flow valve preferably comprises a tapered surface on the hot water valve plug to prevent loss of control as a result of pressure imbalance up to at least about 250kPa (37psi).

Brief description of the drawings Embodiments of the invention will now be described, by way of example only, with reference to the following illustrations in which: Fig 1 is a schematic circuit diagram showing a tempering valve location in hot water supply system; Fig 2 is a tempering valve according to the invention location in a portion of a hot water supply system; Fig 3 is a touch-pad temperature radio frequency remote controller used with the tempering valve and controller of Fig 2; Fig 4 is an exploded view of the complete tempering valve of Fig 2; Fig 5 is a section through valve body of Fig 4; Fig 6 is a valve spindle from the valve of Fig 4; Fig 7 is a spindle housing incorporating a cold water seat that houses the spindle of Fig 6 and is housed in valve body of Fig 5; Fig 8 is a valve spindle and hot water seat in, closed position; Fig 9 is a valve spindle and hot water seat in open position; Fig 10 is the first portion of a flow chart of a valve start-up sequence control algorithm; Fig 11 is the second portion of a valve start-up sequence control algorithm which joins to the first portion in Fig 10 at A and B;

Fig 12 is the third portion of a valve start-up sequence control algorithm which joins to the second portion in Fig 11 at C and J; Fig 13 is the fourth portion of a valve start-up sequence control algorithm which joins to the first portion in Fig 10 at D; Fig 14 is the fifth portion of a valve start-up sequence control algorithm which joins to the third portion in Fig 12 at E and to the fourth portion in Fig 13 at F, G and H.

Detailed description of the embodiments Fig 1 shows a valve 10 to produce a mixed stream of water, installed to produce a tempered water supply system 11 for a bathroom. The component parts of the system 11 include: a hot water storage tank 12, a cold water supply 14, a manual shut-off tap 16, a non- return valve 18, a pressure reducing valve 20, a storage water heater 22, a non-return valve 26, a pressure reducing valve 28, a cold water inlet port 40 to the valve 10, a hot water inlet port 42 to the valve 10, a mixed flow outlet port 46, a manual tap (faucet) 34 in a bathroom and an outlet 36 such as a shower rose or other spout.

Fig 2 shows, in larger scale, part of the tempered water supply system 11 of Fig 1 showing greater detail associated with the valve 10. Like-numbered parts as included in Fig 1 are repeated in Fig 2 and, as well, there is illustrated a power supply cord 50 for powering an electronic logic control system in the valve. The system is powered from a 240V AC (or other mains voltage available) transformed and rectified to 5V DC by power pack 48.

Fig 3 shows a touch pad temperature setting and controlling module 52 for setting the temperature of the water delivered at the mixed water outlet of valve 10. The module 52 includes a temperature set point display 54 for the mixed water at the outlet 46, as well as manually operable buttons 56 and 58 for lowering and raising (respectively) the set-point temperature in 1 Celsius degree increments. The touch pad 52 is installed, for example, in the bathroom to be within reach of a person using the tempered water supply, whether from a shower, spout or other outlet 36used for washing. The touch pad 52 is powered by an enclosed battery (not visible) to send radio frequency signals encoding the set point temperature during normal use and, during installation, to send other requirements and resetting parameters to the electronic control module 52 inside the valve 10.

Fig 4 shows the component parts of the water mixing valve 10 of Figs 1 & 2. The component parts included are: a cold water inlet port 40, a hot water inlet port 42, a mixed

water outlet port 46, inlet strainers (quantity 2) 60, a valve spindle 62, twin O-ring seals 63, a spindle spline 64, a spindle housing 66, an 0-ring seal 68, a stepper motor 70, an electronic logic controller module 72, an electronics housing 74, valve cover plates (quantity 2) 76, a first mixing chamber 78, a second mixing chamber 80, a mixing chambers housing 82, an axial flow sensing and mixing turbine 84, a turbine retaining clip 86, a magnetic sensor 88, a thermistor 90, a thermistor-sealing 0-ring 92, a thermistor mounting opening 94, thermistor mounting clips 96,98 and components of the electronic control logic mounted on printed circuit board 100. The electronics mixing chambers housing 74 is moulded from a high grade engineering thermoplastics resin having high hot water resistance, such as polyphenylene sulphide (PPS) and, upon assembly, is sealed entirely separately from the mixing chamber housing 82. The two housings, 74 and 82 are sandwiched together as an assembly by connection to the valve cover plates 76. Twin O-ring seals 63 on the valve spindle 62 deter any transference of water from the first mixing chamber 78 to the electronics housing 74.

Fig 5 shows the mixing chambers housing 82 of Fig 4 in cross-section including the water inlets, 40 and 42, the mixed flow outlet 46, the first and second mixing chambers 78 and 80, respectively. The housing 82 (excluding the three hexagonal pipe fitting nuts 110) is injection moulded as a single-piece from a thermoplastics material such as PPS. The view in Fig 5 shows the hot water seat 112 of the valve, which is tapered.

Fig 6 shows the valve spindle 62, removed from the first mixing chamber 78 (in Fig 5) for clarity. The spindle 62 is a single piece injection moulding also made from a hot water resistant thermoplastics material such as PPS and has a longitudinal axial shaft with a spline 64 at its upper end for mating with the drive of the stepper motor 70 and at its lower end a tapered plug 114, for mating with the seat 112 (Fig 5). The spindle 62 also has a plug 116 intermediate the upper and lower ends of the shaft, two plain bearing shoulders 118 and a male-threaded portion 120 intermediate the shoulders 118 and spline 64.

Fig 7 shows the spindle housing 66 introduced in Fig 4, which again is a single piece injection moulded part of PPS resin or the like. The housing 66 has a hollow bore extending axially from top to bottom of the housing and at the top end of the bore is a female threaded length for mating with the male threaded portion 120 of the valve spindle 62 (Fig 5). The spindle and housing are inter-assembled by screwing the housing 66 over the spindle 62 before that sub-assembly is inserted in the first mixing chamber 78 of the housing 82, from the top end.

The spindle housing 66 further comprises four flow openings 124 symmetrically arranged and or equi-spaced around the housing, each separated from its adjacent opening by a solid finger

126. Also the housing 66 has two grooves 128 for containing O-rings (not shown) for sealing the housing 66 in the bore of the first mixing chamber 78.

At the lower end of the housing 66 an opening 130 is provided in which the plug 116 (Fig 6) engages as a clearance fit to throttle cold water flow into the first mixing chamber 78.

The housing 66 also comprises a flange 132 for locating in a matching recess 113 of the mixing chambers housing 82. As evident from Fig 4, the flange 132 of housing 66 is non- circular to enable alignment and attachment means to properly locate and fix the sub-assembly of the housing 66 with the spindle 62 to the housing 82.

Figs 8 and 9 show a portion of the fully assembled valve 10 in a closed and open position, respectively, to show how the spindle 62 engages with the bore of the first mixing chamber and translates axially in that chamber to adjust the ratio of incoming cold and hot water entering the first mixing chamber during use.

Figs 8 and 9 show the cold water inlet 40 entering the first mixing chamber 78 of the valve section from the left, the hot water inlet 60 entering vertically upwardly and the second mixing chamber 80 on the right. The flow-sensing and fluid-mixing turbine 84 introduced in Fig 4 is not shown in Figs 8 & 9 but it is to be understood that the turbine 84 occupies the space immediately to the right of an opening 134 which communicates the first mixing chamber 78 with the second mixing chamber 80. Rotation of the spindle by the stepper motor 70 (Fig 4), which is coupled to the shaft of the spindle at the spline 64, advances or retracts the hot water plug 114 towards or away from the hot water seat 112, depending on the direction of rotation of the motor.

The incoming cold water fills an annular space 136 between the spindle housing 66 and the bore of the first mixing chamber 78 at its upper end, where the annular space is sealed by a pair of 0-rings (not shown) in the pair of grooves 128. However, cold water flow can take place from the annular space 136 to the first mixing chamber 78 through the four openings 124 at a rate of flow dependent upon the degree of opening of the cold water plug 116 relative to the cold water opening 130 (Fig 7).

The taper of the hot water plug 114 and its matching seat 112 (suitably 30°) provides the hot entry side of the valve with an opening valve characteristic favourable to fine control of the hot water pressure should it for any abnormal reason tend to exceed the cold water supply pressure.

The valve copes with a variety of conditions that may occur in different hot water installations and it may be attached to any storage water heating system. To cope with different kinds of installations the control module follows a strategy that ensures safe operation regardless of unexpected variables.

The mode of normal mechanical operation of the valve 10 in the water supply system is now explained with reference to Figs 1 to 9, deferring detailed explanation of the electronic control logic.

The valve 10 is opened and closed by rotation of the stepper motor 70 under control of the electronic logic controller 100. The valve 10 is normally installed in a conventional mains- pressure hot water system 11 where the inlet and outlet water pressures are balanced but the valve 10 is provided with features enabling it to cope with at least 250kPa (approximately 37 psi) imbalance. The object of the valve 10 is to prevent water hotter than 52° being deliverable to an outlet used for washing (or 48° C when installed in pre-schools and kindergartens). The actual maximum temperature for a given installation can be programmed as required, as described below.

The mixed water outlet 46 is connected to either a single outlet tap (i. e., faucet) or the hot tap where both a hot and cold tap is provided. The tap 34, Fig 1, is plumbed to serve a water outlet such as a bath, shower, sink, tub or basin in the normal way. Where the valve 10 is retro- fitted to a two-tap-with-single-mixer outlet service, the mixed water outlet 46 from the valve 10 is connected to the former hot tap, whilst the former cold tap is retained but need no longer be used to temper the hot water to a safe, comfortable or required temperature.

The initiating action for the valve 10 to function is the opening of a tap 34 downstream, such as at a shower 36 to allow flow of at least 2 litres per min (L/min). The electronic control logic 100 treats any lower flow rate as zero flow. The opening of the downstream tap 34 initially permits only cold water to enter the valve 10. The cold water enters at cold water inlet 40, where it passes through the four openings 124 (Fig 8) in the spindle housing 66, through the annular gap between the open cold water opening 130 and the cold water plug 116. As soon as that cold water begins to flow through the second mixing chamber 80 of the valve 10 it rotates the turbine 84, causing a magnetic sensor 88, attached to the outside of the second mixing chamber 80, to send a string of electrical pulses to the electronic controller 100. In known manner, the number of pulses per unit of time provides a signal related to flow rate. Until this cold water flows at 2L/min or more, the stepper motor 70 is not powered to move the valve spindle 62 to admit any hot water into the valve 10.

When cold water flow is proved by the turbine 84 rotating at a sufficient speed the stepper motor rotates the valve spindle 22 thereby simultaneously lifting the hot water plug 114 from the hot water seat 112 while moving the cold water plug 116 towards the cold water opening 130. The stepper motor 70 is programmed to rotate in predetermined increments.

Depending on the required water temperature set at the touch pad 52 (Fig 3), the initial rotation is in the range of 10° to 15°. The touch pad 52 sends an appropriately encoded radio frequency signal to a receiver associated with the electronic logic controller (ECL) 100 forming part of the valve 10, which generally should be no more than about 30 metres from the touch pad 52 to successfully receive that signal. The thermistor 90 immediately downstream of the turbine 84 in the second mixing chamber 80 senses the temperature of the mixed water as it leaves the valve at outlet 46 and the ECL 100 positions the valve spindle 62 accordingly to deliver mixed water at the desired temperature regardless of fluctuations in temperature or flow rate upstream of the valve 10.

The turbine 84 mixes the incoming hot and cold streams very efficiently in as little as 2 to 3 pipe diameters from its downstream end, enabling the thermistor 90 to respond very quickly to transient temperature changes without responding to spurious apparent changes in temperature caused by imperfect mixing, a defect in some known valves of the same general type. Accordingly the valve responds quickly to minor variations in either or both hot or cold water supplies to the valve 10 and provides a correcting response. Thus in the hot water tempering valve 10 as illustrated, having 15mm and 20mm port sizes as is typical, it is adequate that the overall length of hot water flow dimension of the valve from the opening 42 where the hot water stream first enters the valve to the valve outlet 46, be as small as 100 mm. The valve also displays a very short response time to signals from a user requesting a change in temperature of the water in use via the touch pad 52.

Figs 10 to 14 show the logic algorithm for a start-up sequence as processed between the control components, namely the stepper motor 70, the thermistor 90 and the ECL 100. When the valve 10 is first operated the energy content of the hot water tank 22, distance from the tank to the valve 10, water pressure imbalances and the like are all unknown and the start-up sequence is designed to sequence events so that these unknowns and their possible range of variations are duly taken into account.

Where, in the following description, repeated mention is made of a component by name and there is only one part of that name, which has been already listed above, the reference number is not repeated.

The sequence starts with an initial predetermined"trial"rotation of the stepper motor, which is directly coupled to the spindle of the valve, without any gearing. The initial angle of rotation is variable, a function of the set-point temperature and is between 15° and 20° in the direction which increases the opening between the hot water plug and seat 112. The program maintains the spindle in this position until the temperature stabilises, that is, until the rate of increase of temperature falls below a predetermined threshold value. Then, the instantaneous value of temperature is stored in an electronic memory as Initial Temperature Toe The sequence continues by rotating the spindle in up to five 12° increments (at the rate of one per second) and measuring the resultant temperature. So long as the resultant temperature has increased by at least 0.4°C this temperature is made the To value for a Proportional Integral Differential (PID) algorithm and normal regulation (as will be described below) is applied. For each rotational increment (up to 5) the resultant temperature at the thermistor fails to increase by at least 0.4°C the spindle is rotated forward another 12 degrees.

If the mixed water temperature does not increase by at least 0.4°C after 5 successive rotations of 12°, a time delay of 5 seconds without further spindle rotation is applied to verify a potential reason that it is only the fact of a combination of low flow rate and/or a relatively long distance pipe run between the valve 10 and the tank that is the cause of no observed threshold temperature increase at the outlet 46.

If after this 5 second time delay the temperature has increased by at least 0.4° C, the actual temperature is set as the To value for the PED algorithm and normal regulation is applied.

If the temperature does not comply with the above condition after expiration of 5 seconds a potential reason may be that the hot water storage tank may contain only cold water due to a malfunction. Another possibility is that the pressure is higher at the cold inlet 60 and does not allow hot water to enter the valve 10. The control sequence now rotates the valve for another 35 degrees (cumulative total between 130° and 140°) and again tests for a temperature rise of at least 0.4°C, failing which the programmed assumption is that no hot water is available in the tank and the spindle remains at this position as long as the turbine senses continuance of flow.

If, instead, the temperature does increase, the control sequence reverse rotates the valve spindle 90 degrees rapidly in a non-stop series of steps and continues with the normal PID regulation. The reason for the rapid reverse rotation is that it might be possible in some particular locations that the distance between the valve 10 and the tank is sufficient that first 10- 15 seconds would be insufficient for hot water to reach the valve's hot water inlet. Assuming

for this case that pressure imbalance between hot and cold supplies has not been present, a spindle rotation of 130 to 140 ° may produce an output temperature range that is much higher than is safe.

In all possible start-up routines whenever the arrival of warmer water at the outlet is sensed by the thermistor, further control of temperature is via the PID algorithm, which starts regulation by using the last temperature sample as the initial condition To. After every iteration, the control logic calculates the rate of rise of temperature and once it falls below the threshold value (0. 4°C), the latest temperature sample is entered as initial condition for the next iteration.

When monitoring the temperature gradient change during start-up or normal PID regulation while in steady state use, the ECL applies a correction regulation sequence in the event of certain predicted modes of malfunction. One is if the temperature quickly approaches the set-point temperature (that is, during the start-up sequence) and a second is if, during normal operation, the outlet temperature begins and continues to depart from the set point, either increasing or decreasing.

Another programmed response of the ECL is to identify and react to any tendency to hysteresis of the delivered water temperature, that is, if the temperature were to begin oscillating in the range of 0.4°C from the set temperature. Such a fluctuation could be felt by a person showering and may be considered undesirable. Should this happen, the normal PID sequence would be interrupted and the ECL would stop regulating the valve to break the hysteresis loop.

If the thermistor registers a temperature exceeding 52°C due to external transients of any kind the ECL immediately decreases hot water flow by a 30° reverse rotation of the stepper motor. If this fails to produce any temperature reduction the motor is further reversed to close the hot water inflow at the hot water seat and an over-temperature message is issued, as will be explained later. If the thermistor communicates to the ECL over-temperature flow when the valve is fully shut, the ECL will continue with regulation of the set-point temperature but this time using different control parameters to be able to cope with excessive transients and possible pressure excess on the hot supply side.

The user interface with the system is by way of a combination of the water tap to set the tempered water flow rate and the remote radio frequency (RF) touch-pad, kept within reach of the user so that adjustments to temperature can be requested as desired. With the touch-pad, the user can set the maximum setting temperature, the set-point temperature as well as to calibrate the system if necessary. The range of the touch-pad is approximately 30 metres and it may vary

in particular locations. During initial set up of an installation, to enable assurance that the signal sent from the transmitter in the touch-pad is received by the controller, a green light emitting diode (LED) is provided on the controller, which illuminates briefly each time the controller receives the new set-point temperature. If the touch-pad fails during normal use, the valve opening is maintained at the last entered set-point. If the system operates without touch-pad, it will use the default set-temperature of 40°C.

The stepper motor is driven by using half-step increments to improve the resolution of the spindle movement. The motor contains two Hall effect sensors that signal the start position.

The ECL software utilises information from these two sensors but it also performs calculation of the angular position of the valve by other means. If the valve drifts from the set position during operation, it may be possible that the motor may not reach the"close"Hall effect sensor when the valve is fully closed, in which case the control logic disconnects the motor ten seconds after it started closing the valve.

For verifying correct installation and operation, a red LED is provided on the control board to indicate power, liquid flow and control logic faults. When the valve is closed (flow switch does not sense a flow) the red light will blink on-off. As soon as the flow turbine senses flow above 2L/min the red LED remains illuminated continuously.

If the thermistor output is sensed by the control logic as being above the permissible safe temperature for the application (e. g. 52° or 48°C) the red LED flashes on-off when the mixed- water flow stops but it will remain off when the flow resumes. The LED remaining off during the operation of the valve indicates that an over-temperature event has occurred and has been memorised by the ECL. To reset the memory it is necessary to switch off the power to the control board and then to switch it on.

One of the causes of over-temperature may be the failure of the cold water supply. If this occurs the ECL shuts the valve and, for further safety, rotates the valve another 30° after it passes through the"close"Hall effect sensor.

There are four latched errors that the ECL reports by an error number of N successive pulses of the red LED, separated by a pause (where N is the error code number as listed below).

Error 6-Reverse inlet connection: ECL fully opens the valve Error 4-Sensor is not connected or failed as open circuit Error 7-Communication error

Error 8-Communication error or the touch-pad is not matched with the receiver.

When error 6 occurs the ECL responds by fully opening the valve. For all other errors, the ECL shuts the valve.

All errors are latched and require manual intervention (reset of the controller) to enable the valve to operate again.

It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

The foregoing describes embodiments of the present invention and modifications, obvious to those skilled in the art can be made thereto, without departing from the scope of the present invention.