Patent GB-1511252-A (GB)
Title: Motor driven control valves
IPC: F16K31/04
Filed: 1975-07-28
Abstract: 1511252 Valves APPLIANCE COMPONENTS Ltd 28 July 1975 [30 July 1974] 33648/74 Heading F2V [Also in Division H2] A motor driven multiway control valve comprisss a valve unit with a valve member moveable between at least three predetermined positions, an electric motor for driving the valve member between said positions, and a motor control circuit including first and second electrical switches connected between an electrical supply line and the motor and operable to demand first and second positions for the valve member, and a triac connected in parallel with one of the switches and arranged such that when both switches are demanding different positions for the valve member it controls electrical supply to the motor to cause the valve member to be moved to a third position. A shown in Fig. 1, the valve is a three part valve having an inlet 2, an outlet 3 for a water heating system and an outlet 4 for a central heating system, and the valve member 7 is spring biased to close port 4. The switches comprises a water system thermostat 13 and a room temperature thermostat 14 connected in a circuit with the triac 22 and the motor 8 between supply lines 20, 21 as shown. A pair of cam operated switches 11, 12 are also provided. In operation, if the thermostat 13 operates, contact 16 is made and power is supplied to a control unit 19 which causes hot water to be supplied to the inlet port 2 with the valve member 7 in the position shown. However, if the thermostat 14 operates, contact 18 is made, the unit 19 is again energized and power is supplied to the motor 8 via terminal 20, thermostat 14, thermostat 13, motor 8 and terminal 21. The valve member is thus moved to open port 4 and close port 3. If in this position, thermostat 13 is also operated to make contact 16, power is removed from the motor and the valve member starts to return to its position shown under spring action. When it reaches its mid-position, switch 12 is opened and half-wave rectified current is caused to pass through the gate 2 of triac 22. This current causes permanent magnetism in the motor, locking the rotor against the action of the spring, thereby stopping the valve member in its mid-position. If in this position the thermostat 14 becomes satisfied, the triac will become non-conductive, thereby unlocking the motor which allows the member 7 to return to the position shown. If now the thermostat 14 is again operated, the triac becomes conductive on both half cycles to drive the motor 8 until the member 7 reaches its mid-position when switch 11 closes to cause half-wave rectified current to pass through the gate of the triac again locking the motor. If now thermostat 13 becomes satisfied, the supply is connected directly across the motor to drive the member 7 to close port 3. In Fig. 2, the valve is a rotating valve having a shoe 31, 32 for closing ports 34, 35. A cam 37 having a notch is driven with the shoe and co-operates with three switches 38, 39, 40 each having a central blade and two contacts and mounted in the circuit of the motor 41, triac 56 and thermostats 48, 51, as shown. Switch 38 coincides with the position where shoe 31 covers port 34, switch 40 with the position where shoe 31 covers port 35, and switch 39 with the midposition. Thus when one or other of the thermostats operates, power is supplied directly to the motor until switch 38 or 40 operates. However, when both thermostats operate, motor 41 is controlled by triac 56 until switch 39 operates.