Patent GB-821216-A (GB)
Title: Improvements in or relating to windscreen wiper actuator mechanisms
IPC: B60S1/16
Filed: 1958-04-03
Abstract: 821,216. Windscreen wipers. GENERAL MOTORS CORPORATION. April 3, 1958 [April 18, 1957], No. 10795/58. Class 138(1). In a windscreen wiper actuator mechanism, a rotary drive member has rotatably journalled thereon an eccentric on which is rotatably journalled a crank, said drive member being operatively connected to said crank for rotation of the crank by the drive member and said eccentric being restrained against rotation during normal operation of the wiper but being rotatable to effect a variation in the throw of the crank. As shown, a worm drive 41 on the shaft 40 of a reversible motor 35 engages a worm wheel 42 attached by bushing 43 to a knurled portion 44 of shaft 45 carried in bearings 46 and 47. At one end of shaft 45 is journalled a plate 54 which includes an axially extending eccen. tric hub 55 with stops 56 and 57 on a radially extending flange. Stop 56 or 57 engages tang 51 affixed to plate 48 according to the direction of rotation of gear 42. A drive arm 62 with a slot 63 at its end is driven by shaft 45 and drives pin 64 on crank arm 58 which rotates about the centre of eccentric 55. A spring washer 59 between crank arm 58 and eccentric 55 maintains stop 56 or 57 in contact with tang 51. Thus the reversal of the direction of rotation of shaft 45 causes plate 54 with cam 55 to rotate through 180 degrees and change the axis of rotation of crank arm 58 enabling the wiper blades to be parked beyond their normal wiping arcs by means of conventional linkage. A second crank arm 70 actuates a second wiper in the same way as the components so far described but it is distinguished by the provision thereon of a cam surface 72 which actuates a plunger 73 serving to break the supply to the motor when the wiper blades reach the parked position. Motor 35 is connected by leads 105 and 106 to centre contacts 88, 86 ; thereby a means is provided for reversing the direction of current through the motor without affecting the field current so that the direction of rotation is reversed by the up and down movement of armature 75. When bridging member 111 is set to the "Low" position coil 81 is energised and armature 75 moves downwards causing the motor to rotate in the operative direction, slowly, because both shunt and series field windings are in circuit. In the "High" speed position the shunt field is out of circuit. In the "Off" position current ceases to flow through coil 81 releasing armature 75, which, under the influence of spring 85, moves upwards and causes engagement of its movable contacts 86, 87, 88 with contacts 91, 94, 93 respectively, to reverse the direction of the flow of current through the motor. The motor now runs in the reverse direction, eccentrics 55 and 55<SP>1</SP> rotate through 180 degrees and change the axes of rotation of pins 64 and 641 to the new centres of the eccentrics. When cam 72 engages pin 73 the armature 75 is moved to an intermediate position where its contacts 86, 87, 88 are disengaged, so breaking off all connection to the motor and the wipers come to rest in a parked position.