GB1101441A - Improvements in windscreen wipers - Google Patents

Abstract

1,101,441. Control of motors. KEMPSTON ELECTRICAL CO. Ltd., and L. A. TIMBRELL. 15 March, 1966 [5 March, l965], No. 9469/65. Heading H2J. [Also in Division A4] In a windscreen wiper system having means for producing intermittent operation of a wiper motor the closing of two switches 81, S2 causes charging of a condenser C through a variable resistor R1 to render a transistor TR1 conductive and thereby energize a relay RL. Relay contacts RL1 then close to discharge the condenser through a resistor R2 so that the relay becomes de-energized and the cycle is repeated, each energization of the relay RL also closing contacts RL3 to energize the wiper motor intermittently. The circuit also includes a moisture detector D comprising interlaced metal strips (M 1 , M 2 , Fig. 2, not shown), on an insulating base (B) mounted on the vehicle exterior so that when rain water collects thereon the strips are bridged to complete a circuit through a resistor R3. This causes a second transistor TR2 to conduct to energize the relay RL. A heater H controlled by relay contacts RL2 dries the detector D sufficiently during light rain or drizzle to render the transistor TR2 inoperative. The wiper motor then operates intermittently under the control of the transistor TR1, but during heavy rain the wiper motor is operated continuously under the control of the transistor TR2 and the detector D. Preferably, a windscreen washer is brought automatically into operation when the detector D energizes the wiper motor. When switch S is open and switch S2 is closed the wiper motor is controlled only by the detector D. A further system is described in which a relay (R, Fig. 5, not shown), controlling the wiper motor is in a circuit containing three resistors, two being associated with a resistance-capacity time delay system and the other being associated with a moisture detector.