Patent GB-757813-A (GB)
Title: Improvements in windscreen wiper actuator mechanisms
IPC: B60S1/08
Filed: 1954-03-23
Abstract: 757,813. Windscreen cleaners. GENERAL MOTORS CORPORATION. March 23, 1954 [April 6, 1953], No. 8401/54. Class 138(1)  A windscreen wiper actuator mechanism comprises a compound linkage 21, 22 Fig. 1 fixed at one end to a rotatable driven member 15 and at its other end pivotally connected tb a' connecting rod 20 linked to a driving member 18 rotated by a motor 10 so as to oscillate the driven member 15 and an adjustable linkage 25, 27 which upon movement of a control member 33 is movable to vary the amplitude of oscillation of the driven member and automatically discontinues the drive of the driven member when the amplitude is increased. Rotary motion of the electric motor 10 .Figs. 2 and 3 causes oscillation of a shaft 15 through the agency of a worm 11, worm wheel 18, connecting rod 20 pivoted at one end to the wheel 18 at 19, an arcuate link 22 pivoted at 23 to the other end of the rod 20 and a link 21 pivoted at 24 to the link 22 and secured to the shaft 15. The shaft 15 oscillates a coupling member 16 connected by cables to the usual wiper blades. Also pivoted to the connecting rod 20 at 23 is a bell-crank shaped arm 25 provided with a movable pivot 26. The pivot 26 is carried by one end of an arm 27 mounted on a fixed pivot 28, the other end of which arm engages the plunger 32 of an electric parking switch 31. A spring 30 urges the pivot 26 and arm 27 to a position such that the switch 31 is normally closed. When the wiper mechanism is  operating normally the shaft 15 and arm 25 are oscillated between the limits shown in Figs. 2 and 3. In order to park the wipers in positions outside the limits of their normal arcs of wiping a cam portion 35 of the arm 25 is caused to engage an axially movable roller 33. This roller is normally urged by a spring 36, Fig. 5, to a position as shown in Fig. 2 where it cannot engage the cam 35. When however the roller is moved axially to a position in which it will be engaged by the arm 35, the pivot 26 will be moved to the position shown in Fig. 1 whereby the plunger 32 of the switch 31 can move under the urge of a spring (not shown) to open the switch. At the same time the movement of the pivot 26 will cause the effective length of the connecting rod 20 to be increased whereby the shaft 15 will be oscillated beyond its normal limit shown in Fig. 2. The roller 33, Fig. 5, is movable axially by manually operating the switch arm 56, Fig. 6 of a control switch 52 for the motor which arm 56 is connected by a Bowden cable 41, Fig. 5, to a lever 39 mounted on a fixed pivot 40, which lever enages an end abutment 37 of the roller 33. In the position of the switch arm 56 shown in Fig. 6 the contacts 53, 54 of the switch 31 are broken and the wipers are parked. On rotating the arm 56 clockwise the roller 33 is released from the cam 35 and the motor 10 is energized through bus-bars 51, 57 and its speed controlled by a resistor 58 in the shunt field 61. If the arm 56 is moved so as to connect the bus-bar 57 with a contact 55 and cause the movement of the roller 33 against its spring 36 the motor will continue to operate until the switch 31 is broken by movement of the pivot 26, when the cam 35 engages the roller. The inertia of the motor ensures that the wipers move to parked positions.