Patent GB-815657-A (GB)
Title: Improvements in or relating to windscreen wiper actuator mechanisms
IPC: B60S1/16
Filed: 1956-09-12
Abstract: 815,657. Windscreen cleaners. GENERAL MOTORS CORPORATION. Sept. 12, 1956 [Sept. 23, 1955], No. 27861/56. Class 138(1). A windscreen wiper actuator mechanism comprises a crank arm 65 interconnecting an oscillatory output shaft 22 for actuating the wiper, and a driven element 53 eccentrically mounted on a rotary element 50; the arrangement being such that the driven element may be rotated on the rotary element and so vary the throw of the crank arm 65, and thus vary the arc of oscillation of the output shaft. As described, a worm 45, which is rotated by an electric motor 20, engages worm wheel 46 fixed upon a rotatable shaft 49 and having a cam projection 47. A disc 50 having a lug 51 and an eccentric hub 52 is rotatably mounted on the shaft 49; and a dished spring washer, inserted between and frictionally engaging the disc 50 and the worm wheel 46, establishes driving connection between these members. A cam member 53 having a crank pin 55 is mounted upon the eccentric hub 52 and is constrained to rotate with the worm wheel 46 by a yoke member 57 rigidly mounted on the shaft 49 and having a radial slot 56 which embraces the crank pin 55. The crank pin is pivoted to one end of a connecting rod 65 which in turn is connected to an oscillatory output shaft 22 by crossed links 66, 67. A manually operated toggle arm 75 moves the latch arm 73 by snap action, and also controls the electric motor switch, not shown. If the mechanism is initially in the parked position, as in Fig. 2, operation of the toggle arm energises the motor and also tends to move the arm 73 out of engagement with the lug 51. Engagement is maintained, however, by pressure of the lug 51 on the shoulder 79 of the arm 73 due to the frictional driving connection between the disc 50 and the wheel 46 which is now rotating. The crank pin 55 is moved radially inwardly as it rotates about the stationary eccentric hub 52, and thus the crank throw is reduced to a minimum, Fig. 4 (not shown), at which time the cam 47 engages the shoulder 79 and moves the latch arm 73 out of engagement with the lug 51. The mechanism continues to operate with a reduced crank throw until the toggle arm is operated thereby snapping the latch arm into engagement with the disc 50 and breaking the switch to the electric motor which is now controlled by a parking switch, not shown. The latch projection 78 engages the lug 51, the cam 47 continues to rotate and bears against the shoulder 79 thereby disengaging the arm 73 from the disc 50 which then rotates until the lug 51 is engaged by the shoulder 79. Continued rotation of the worm wheel causes the crank pin to move radially outwards as it rotates about the eccentric hub 52, thus increasing the throw of crank arm 65, and thereby causing output shaft 22 to move through a greater arc to carry the wiper blades into a parked position, the parking switch then being opened by a lever connected to the output shaft. In another embodiment, the latch projection 78 is absent and the shoulder 79 engages a second lug formed on the disc 50, Figs. 12 and 13 (not shown).