GB1495487A - Window wiping apparatuses - Google Patents

Abstract

1495487 Vehicle window wipers MOORE REED & CO Ltd 10 June 1976 24116/76 Heading A4F [ Also in Division H2] Window wiping apparatus comprises a stepper motor driving a window wiper and being energized by signals from a drive circuit. The apparatus is particularly applicable to a vehicle (for example a military one) fitted with a radio receiver, since the stepper motor does not produce interference therewith. In the circuit shown, a four phase stepper motor 12 is directly coupled to a wiper arm 10 and is supplied from power amplifiers 20 receiving driving signals from a phase splitter 18 fed from an oscillator 16, whose frequency is adjustable continuously or stepwise to vary the motor speed. The motor is reversed at each extreme position of the arm 10 by a counter 22 and reversing circuit 24, which are responsive to a predetermined number of output signals from the phase splitter 18, corresponding to movement of the motor to one or other position, to cause the phase splitter to reverse its signals. When the motor is de-energized, means (not shown) cause it to continue to rotate until an extreme position is reached. In a modification, Fig. 2 (not shown), the movable contact (40) of a changeover switch moves with the arm 10 and engages a fixed contact (36, 38) at the extreme positions thereof, the fixed contacts being connected to the inputs of a bistable circuit (42) controlling the phase splitter 18, whereby the signals of the latter are reversed when the movable contact engages the fixed contacts.