GB2192504A - Motor apparatus for a control valve - Google Patents

Abstract

A motor is connected to a reversing switching and a rechargeable electrical energy storage device such as a high value capacitor (SC1, SC2). On application of power to the apparatus (ie. during normal operation), the motor can be driven in forward and reverse directions to drive a valve, and on removal of power from the apparatus, charge stored in the storage means drives the motor to bring the valve to a rest position. The apparatus is self-contained, and avoids the need for an over dimensioned motor which would be necessary to drive against the normal self-return spring. <IMAGE>

Description

SPECIFICATION Motor apparatus for a control valve This invention relates to a motor apparatus for a control valve, particularly for a control valve for a domestic heating system.

In domestic heating systems, it is common to have a motor operated control valve which is controlled by signals from thermostats. Such a valve may be, for example, a two-way or a three-way valve connecting the boiler to the central heating supply pipe and/or the hot water tank supply pipe. Such valves are commonly biased to one position so that if the electrical supply to the valve should be cut off, then the valve will return to a preferred position. In the case of the three-way valve, the preferred position is generally the one which connects the boiler to the hot water tank. Valves of this type are biased by means of a spring which needs to be quite strong in order to overcome the resistance of the valve, especially since the resistance increases with age.Consequently, the motor to drive the valve needs to be sufficiently powerful not only to overcome the resistance of the valve but also to load the spring. In other words, the motor is about twice as powerful as would be necessary if no spring was involved.

A major aim in the design of these devices is the minimising of the overall dimensions of the housing containing the motor. To reduce the overall size of the device, it would be desirable to enable a less powerful motor to be used. This would have the further advantage of reducing the power consumption.

According to the present invention, a motor apparatus is provided for a control valve, comprising a motor connected to reversing switching means, electrical energy storage means and a housing containing the motor and the storage means, the motor and storage means being arranged such that on application of power to the apparatus (normal operation), the motor can be driven in forward and reverse directions to drive the valve and on the removal of power from the apparatus, charge stored in the storage means drives the motor to bring the valve to a rest position.

The storage means may be rechargable cell or battery or a capacitor.

If the storage means is rechargable, then during normal operation, charge may be stored in it to subsequently drive the motor when power is removed from the apparatus. Preferably the storage means is placed at a point in the circuit at which it will be charged while power is applied and at which it will discharge, when power is removed, through the same circuit as that which is used to drive the motor during normal operation.

The storage means is preferably a capacitor having a capacitance sufficient to drive the motor for five seconds or more. The capacitance may be 0.125 Farads or more but is preferably 0.5 Farads or more, for example about 1.65 Farads. Preferably the motor is a DC motor and the reversing switching means is a polarity reversing switch which is biased in one direction. Voltage regulating means may be provided for regulating the voltage from the storage means to drive the motor when power has been removed from the circuit.

According to the present invention, there is also provided an apparatus as described above, when mounted on a two-way or a three-way valve.

It has been found that the invention enables a substantially smaller motor to be used and this can be reflected in a reduced housing size.

Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a circuit diagram of a valve actuator circuit for a two-port valve; Figure 2 is a circuit diagram of an actuator circuit for a three-port valve; Figure 3 is a circuit diagram of an alternative actuator circuit for a three-port valve.

In the diagrams, standard signs are used to represent standard components, as can readily be understood by one skilled in the art.

Referring to Figure 1, the components used are designated in Table 1 TABLE 1 BR1,BR2 1A,600PIV ZD1 12V,2W ZD2 3.9V, 1.3W C1 33 microfarads C2 1.5 microfarads R1 1 Megaohm R2 15 ohms SC1, SC2 3.3F, 1.8V D1 lN40p2 RLA1 G6A DPDT MS1,2 OMRON SS10 RS TH-3 The motor M drives the shaft of a two-way valve, via a gearbox having a ratio of 1500:1. The valve is valve type 420202 manufactured by the Applicants, which opens and closes through 90" of arc. The microswitches MS1 and MS2 are actuated by a cam mounted on the gearbox output shaft. In the diagram, the microswitches and relays are shown in their relaxed positions.

The motor gearbox is provided with a slipping clutch to enable manual operation.

The operation of the circuit is as follows. When the thermostat (not shown) calls for heat, a 240 volts AC signal is applied to the line labelled "sensor". This signal is rectified by bridges BR1 and BR2. The rectified signal from BR1 activates relay RLA1, which closes contacts RLA1A and RLA1 B. The rectified signal from bridge BR2 causes two things to happen: (1) it charges up supper-capacitors SC1 and SC2 (total capacitance 1.65 Farads) to approximately 3.4 volts; and (2) it activates the motor M which opens the valve. As the spindle of the valve turns, microswitch MS1 closes, thus supplying power to the boiler. When the spindle of the valve has turned to 90 , MS2 switches over, thus removing power from the motor M.This disconnection of power is important in preventing the motor from being stalled against an endstop for long periods of time, thus protecting its life.

When the signal to the "sensor" line is removed, relay RLA1 relaxes, and switches RLA1A and RLA1 B return to the positions shown in the Figure. In this position, motor M draws current from the super-capacitors SC1 and SC2 and rotates in the reverse direction, thus closing the valve. In doing so, microswitch MS2 returns to the position shown, and when the valve is almost closed, microswitch MS1 opens. The motor M takes about 20 seconds to close, and there is ample charge on the super-capacitors to drive the motor for this period. With the super-capacitors charged to approximately 3.4 volts, there is sufficient charge to power the motor for substantially more than thirty seconds.

Termistor RS and resistor R2 are provided to reduce surge currents.

Referring now to Figure 2, the part of circuit A shown within the dotted line, is similar to that of Figure 1, except that relay RLA3 in this case operates a switch in the boiler power circuit, and there is no microswitch in the direct connections to the motor.

In this circuit, there are four bridge rectifiers BR1-4 and the circuits of BR1, BR3 and BR4, with their respective relays, are identical. The reversing switches to the motor are operated by relays RLA4 and RLA5 separately.

The motor drives a three-port valve, which has its three ports arranged in the form of a T. The spindle of the valve has two paddles, arranged at 900 to each other. The actuator and valve are intended to be arranged such that in the relaxed position of the valve, the centre port, which is connected to the boiler, is in connection with the hot water tank, through the valve. In this position, the residual heat in the boiler is most quickly dissipated.

When the spindle of the valve turns through 45 , the paddle blocking the third port (the central heating supply port) uncovers that port and the supply from the boiler is free to flow to both the hot water tank and the central heating. With a further 450 turn, the other paddle of the valve blocks the port to the hot water tank, and the supply from the boiler is fed entirely to the central heating.

The microswitches are shown in the positions taken up when the valve is turned to the hot water supply port. As the valve turns, the microswitches are operated in the following order: after the first few degrees of turn, MSl 2A and MS12B switch over; after approximately 45" of turn, MS1 1A siwtches, followed by MSl 1 B; after a further 45" of turn, MS12A and MS12B switch back again simultaneously.

The supply for the circuit comes from conventional thermostats providing 240 volts AC through a four core mains cable. The AC signals are rectified to DC by one or more of the four bridge rectifiers as determined by the particular signal and the position of the valve at any given time. Thus, for example, with the valve in the rest position, if a signal is applied to "central heating" input line, this is rectified by bridges BR3 and BR4, which switch relays RLA4 and RLA5. The signal is also rectified by BR2, which powers the motor, to turn the valve towards the centre position. On reaching the centre position, microswitch MS11A switches over, thus removing power from BR3 and causing relay RLA5 to return, whereupon the motor stops. If at this point, a signal is also applied to the input line "H.W.OFF", then this signal is rectified by BR3 and the motor continues to turn the valve, whereupon switch MS11 B switches over, and when the motor has turned until the hot water supply port is closed, switch MSl 2A (and MS12B) opens, thus starving bridge BR4 of power and switching RLA5. At this point the motor stops.

When there is no signal applied to either BR3 or BR4, the motor is powered by the super-capacitors and the valve returns to the rest position.

Referring now to Figure 3, an alternative actuator circuit for a three-port valve is shown.

The part of the diagram enclosed within the dotted line will be described in detail. The remainder of the circuit is new and may also have inventive features.

Capacitors CXl and CX2 are super-capacitors of one Farad each, such as are manufactured by Matsushita Electronics Components Co., Ltd., referred to as "Gold Capacitors". Z23 is a zener diode having a threshold voltage of 4.7 volts. The motor drives the shaft of a three-wayvalvevia a gearbox having a ratio of 180-90:1.

The micro-switch is actuated by a cam mounted on the gearbox output shaft, being switched at the centre position of the valve.

The operation of the circuit is as follows. The leads labelled grey, brown, blue and orange are connected to mains, thermostat, neutral and boiler, respectively, as is standard in the art. The brown and grey A.C. signals are rectified by bridges BR21 and BR22 and the resulting DC voltage is applied through zener diodes Z21 and Z22, to result in a voltage at point X, this voltage being 4.7 volts as determined by Z23. During normal operation, there will always be a voltage at point X. This voltage charges capacitors CX1 and CX2 via protective diodes D21 and D22. Two capacitors have been used, because the capacitors chosen have a rating of only 1.8 v each, while the voltage developed across the capacitors is 3.4v. This voltage is regulated by means of transistors Q1 and Q2 and preset resistor VR, to result in a voltage of 1.1v at the connections to the motor.Relay contacts RL.B and RL.C make up a polarity reversing switch, the state of which is determined by the signals from the thermostats and by the micro-switch.

If, for any reason, the AC signals supplied to the leads should fail, and the power supply to the circuit thus be removed, the affect is as follows. Capacitors CX1 and CX2, which together are charged to 3.4v, discharge through the voltage regulating circuits comprising Q1, Q2 and VR, and then through the motor. Because relays RL.B and RL.C are not energised by signals from the thermostats, they are in their relaxed positions, as shown.

The discharging of the capacitors activates the motor which turns the valve towards the hot water tank pipe, thus connecting the boiler and the hot water tank.

With a motor which draws 25-30mA, it has been found that there is sufficient charge in the super-capacitors to drive the motor for about 30 seconds. The minimum closing time of the valve is considered to be about 5 seconds and a more usual time is about 8 seconds, so there is a sufficient safety factor within the charge stored to ensure that the valve will close, even as it stiffens with age. Should a lighter valve be used, then it is considered that a quarter of this capacitance, ie. 0.125 Farads, would be the minimum practical size.

It should be understood that the above description is made by way of example only. For example, the necessary capacitor for storing charge to drive the motor could be arranged in many different ways, provided it can store enough charge to carry out its function. The size of capacitor or capacitors necessary to do this will depend upon the particular arrangement. Further modifications of detail can likewise be made within the scope of the invention.

Claims (10)

1. A motor apparatus for a control valve comprising a motor connected to reversing switching means and rechargable electrical energy storage means and a housing containing the motor and the storage means, the motor and storage means being arranged such that on application of power to the apparatus, the motor can be driven in forward and reverse directions to drive the valve, and on the removal of power from the apparatus, charge stored in the storage means drives the motor to bring the valve to a rest position.

2. An apparatus according to claim 1 wherein the storage means is rechargable and is placed in a point in the circuit at which it will be charged while power is applied and at which it will discharge, when power is removed, through the same circuit as that which is used to drive the motor during normal operation.

3. An apparatus according to either of claims 1 and 2 wherein the storage means is a capacitor.

4. An apparatus according to claim 3 wherein the capacitor has a capacitance sufficient to drive the motor for five seconds or more.

5. An apparatus according the either of claims 3 and 4 wherein the capacitor has a capacitance of 0.125 Farads or more.

6. An apparatus according to claim 5 wherein the capacitor has a capacitance of 0.5 Farads or more.

7. An apparatus according to any one of the previous claims wherein the motor is a DC motor and the reversing switching means is a polarity reversing switch which is biased in one direction.

8. An apparatus according to any one of the previous claims provided with one or more switching means responsive to movement of the motor and arranged to stop the motor until power is removed from the apparatus.

9. An apparatus according to any one of the previous claims when mounted on a two-way or a three-way valve.

10. An apparatus substantially as herein before described and as shown in any one of the accompanying drawings.