GB1370351A - Windscreen wiper control systems - Google Patents

Abstract

1370351 Control of D.C. motors JOSEPH LUCAS (INDUSTRIES) Ltd 12 Jan 1972 [20 Jan 1971] 2744/71 Heading H2J A windscreen wiper control system capable of operating with a delay between each wipe, includes a wiper motor 13, a switch 14 controlled by motor 13 and having a parking position 16 in which the motor circuit through said switch is broken, and an operative position 15 in which the motor circuit is completed; a capacitor 24 connected in circuit with said switch 14 so that the capacitor 24 is charged through said switch 14 when in its parking position 16; a relay 17 which is energized when the capacitor 24 has charged, and has contacts 18, 21 which then operate the motor 13 so that switch 14 moves from its parking position 16 to its operating position 15; the said capacitor 24 provides the required delay between wipes and the system further includes means 27 for maintaining said capacitor charged while the switch 14 is moving from position 16 to position 15, whereupon the capacitor discharges and the relay is de-energized. As shown positive and negative terminals 11 and 12 are provided and the capacitor 24 charges via diode 26 and variable resistor 25 until N-P-N transistor 22 is turned on, energizing relay 17 to make the motor 13 run. When switch 14 reaches position 15 the emitter and base of transistor 22 are both connected to terminal 11, the transistor is thus turned off and capacitor 24 discharges. The means 27 comprises a resistor which maintains the connection of the emitter and capacitor to terminal 12 until switch 14 reaches position 15 and thus prevents chattering of relay contact 18.