Automatic temperature and humidity regulation – Mixing fluid of dissimilar temperature – Mixing valve with temperature motive means
Reexamination Certificate
2002-01-30
2003-10-07
Tapolcai, William E. (Department: 3744)
Automatic temperature and humidity regulation
Mixing fluid of dissimilar temperature
Mixing valve with temperature motive means
C236S09300A, C236S09300A
Reexamination Certificate
active
06629645
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a water mixing valve apparatus and, more particularly, to improvements in the control system of a water mixing valve apparatus having a servo controlled mixing valve.
2. Description of the Related Art
Previously it was known to provide an electronically controlled mixing valve for mixing hot and cold water to provide outlet water of a desired temperature. The apparatus was provided with a control loop having a temperature sensor in the outlet of the mixing valve so that the mixing valve could be adjusted to provide a desired outlet temperature. It was also known to provide the mixing valve apparatus as part of a shower, e.g. for washing.
This known mixing valve apparatus has a problem when it is installed in a non-linear environment. For instance, where a mixing valve is installed in a water system having a higher pressure cold water supply, the first part of movement of the mixing valve will have little effect in raising the outlet temperature and the outlet temperature will be very sensitive to movement of the valve in a later small range.
OBJECTS AND SUMMARY OF THE INVENTION
To overcome this problem, it is possible to adapt the mixing valve for a particular pressure system, for instance by inserting restrictors in the inlet pipes. However, the installation of such restrictors is not a trivial matter and, unless the nature of a water system is known in advance, it is necessary to use trial and error to determine the correct restrictor. Furthermore, it is necessary to produce and stock a selection of different restrictors for different types of water system.
It is also possible to use a control loop which adjusts dynamically according to sensed operating conditions. However, this is unduly complicated and requires the control loop to reconfigure itself when the valve is moved between different portions of a stable, but non-linear environment.
According to the present invention, there is provided a mixing valve apparatus including:
a mixing valve for mixing water from a cold water inlet and a hot water inlet and supplying the mixed water to a water outlet, the water inlets and outlets being for connection to an external water system;
a valve servo for moving the position of the valve;
a control system for operating the valve servo and thereby controlling at least the temperature at the water outlet; wherein
the control system characterises he external water system in which the mixing valve is connected and optimizes control of the valve according to he characterisation.
In this way, it is not necessary for different mixing valves to be provided for different installations or to provide additional parts to adapt the mixing valve for different installations. The control system can adapt the way it controls the mixing valve according to the properties of the external water system In particular, for a given temperature change at a particular point in the temperature range, the control system can move the mixing valve by a different amount according to how the external water system has been characterised. Where the control system uses an outlet temperature sensor with a control loop, it can optimise control of the valve by varying, according to the characterisation, the amount of movement of the valve to correct a difference between actual and desired temperature as detected by the temperature sensor. In other words, the control loop in effect employs a gain which varies through the valves range according to the characterisation.
However, for the particular characterization, appropriate gains are known for positions throughout the operating range and there is no need for the system to dynamically change the gain on the basis of sensed conditions. A respective characterization represents an entire operating range.
Preferably, the characterisation takes account of at least one of inlet water flows, pressures and temperatures. This enables the mixing valve apparatus to be optimised for a wide variety of external water systems.
The characterisation used by the control system can be selected by the user, for instance by means of an input selector. In this way, the user merely preselects the type of external water system in which the mixing valve apparatus is installed or changes the selection until an optimum response is observed.
On the other hand, the control system could automatically determine the characterisation on the basis of operating conditions of the valve.
In this way, the control system determines the characterisation of the external water system on the basis of the properties of the water at the outlet of the mixing valve compared to the controlled position of the valve to produce those properties.
Hence, the operating conditions may include the mixed temperature at the outlet and the position of the mixing valve. Furthermore, they may include the cold water inlet temperature or an estimation thereof. Similarly, the operating conditions can include a measure of the change of position of the mixing valve with respect to a change in the actual mixed water temperature at the outlet.
By additionally considering the cold water inlet temperature, the control system only requires data relating to two other operating positions to characterise the external system.
The operating conditions may additionally include the temperature of the input hot water.
In this way, the control system only requires data relating to one intermediate position of the valve to characterise the external system.
Thus, by using the input cold and/or hot water temperatures, the control system is able to characterise the external system more quickly and easily.
Preferably the control system is continuously adaptive such that, should the properties of the external system change, the characterisation will also change. In other words, the applicable response or gain for the operating range will change. However, in addition, the control system may also determine the characterisation of the external water system with respect to time. In this way, the control system can predict conditions where the properties of the external water system change over time. For instance, the control system could compensate for the temperature of the hot water inlet decreasing over time as the temperature in a hot water supply tank decreases. Similarly, the control system could compensate for dead leg in supply pipes according to time since the mixing valve was last used and/or changes as the temperature of a supply pipe comes up to the temperature of the water it carries.
Preferably, upon stat up, the control system makes use of the characterisation to move the valve to a position predicted to produce the required temperature at the water outlet.
Indeed, according to the present invention, there is provided a mixing valve apparatus including:
a mixing valve for mixing water from a cold water inlet and a hot water inlet and supplying the mixed water to a water outlet, the inlets and outlets being for connection to an eternal water system;
a valve servo for moving the position of the valve; and
a control system for operating the valve servo and thereby controlling flow from the water outlet; wherein
the control system stores information relating position of the valve and valve servo to temperature at the outlet such that, upon start-up, when a desired temperature is selected the valve servo is initially operated to move the valve to the position stored for the selected temperature.
Where the control system uses a temperature sensor in the outlet together with a control loop, the control system positions the valve without using the control loop for a short predetermined period of time. In this way, when the control loop is again used, the valve position and the actual temperature should be close to the required position and temperature such that the required temperature can be reached more quickly and with less oscillation in temperature.
Often mixing valves will be used in systems which are shut down and restarted within a short period of time. For
Cox Micheal John
Flicos Daniel James
Langford Jocelin
Mountford Colin Lander
Newcombe Paul John
Ali Mohammad M.
Aqualisa Products Limited
Glenn Michael A.
Glenn Patent Group
Tapolcai William E.
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