GB1320341A - Windscreen wipers - Google Patents

Abstract

1320341 Control of DC motors INVICTA PLASTICS Ltd 19 April 1971 [17 Feb 1970 7457/70 Heading H2J [Also in Division H3] A control system for providing intermittent operation of a windscreen wiper motor comprises a relay CR having normally open switching contacts CS1, CS2, an electronic delay cricuit TC to control the energization of the relay, a power supply circuit which includes a rectifier bridge R connected across said switching contacts and arranged to supply to the delay circuit in use a power supply of a specific polarity whilst said contacts are open, the delay circuit being adapted on being supplied with power, to energize the relay and thereby close the switching contacts after a predetermined delay and to maintain the contacts closed for a predetermined dwell time. The system is intended to be connected in parallel with the parking switch of a windscreen wiper system so that on closing a switch SW1 the delay circuit is energized and when contacts CS1, CS2 close after the predetermined delay current by passes main and parking switches MS, PS to start wiper motor M. When movement of the parking switch cam closes the parking switch, current flows through the parking switch circuit to make the wipers sweep once across the windscreen before reaching the parking position and stopping as usual. This short circuits the delay circuit until the parking switch again opens when the delay circuit is again activated and after the predetermined delay closes the contacts CS1, CS2 to begin another cycle. When switch SW1 is closed with parking and main switches, PS, MS, open power is supplied to cayacitor C1 in time delay circuit TC. After an interval controlled by variable resistor R1 transistor T1 stops conducting, conductor T2 is switched on and current flows through relay CR to close contacts CS1 and CS2. Current flows while capacitor C2 discharges. Diode D1 is stated to discharge the timing circuit while motor M is running to prepare the circuit for another cycle. Contacts C23, C24 are normally closed contacts opened by relay CR simultaneously with contacts CS1, CS2 closing. In use they are connected in the braking circuit of the motor M (Figs. 2, 3, not shown).