Patent GB-819802-A (GB)
Title: Improvements in windscreen wiper actuator mechanisms
IPC: B60S1/16
Filed: 1955-12-21
Abstract: 819,802. Windscreen cleaners. GENERAL MOTORS CORPORATION. Dec. 21, 1955 [Jan. 14, 1955], No. 36616/55. Addition to 787,133. Class 138(1) A windscreen wiper actuator mechanism comprises a rotatable driving member 31, Fig. 1, yieldably coupled to a rotatable driven member 41 by a spring biased pawl 44 carried by the member 41 and operable to engage the member 31, the members 31, 41 and a driven oscillatory wiper actuator member 60 being interconnected by mechanism which includes a linkage 61, 64, 65 and 68 of variable effective length, relative roatation between the members 31, 41 about the axis of the member 31 being adapted to vary the effective length of the linkage and thereby vary the angular movement imparted to the wiper actuator member 60. The wiper actuator mechanism comprises a motor 26 driving a worm 30 meshing with the member 31 in the form of a worm wheel which in turn imparts rotation to a crank pin 54 the latter oscillating the member 60 in the form of a wiper actuating shaft through a connecting rod 68, crossed links 64, 65 and a rocker arm 61, as described in the parent Specification. Referring to Figs. 6 and 10 the worm wheel 31 is secured by rivets (not shown) to a plate 36 on a shaft 37 ournalled at one end in the housing 20 Fig. 1, of the actuator mechanism. The other end of the shaft 37 is provided with flats 38, 39 and an annular groove 40. The shaft 37 passes through an axial aperture 32 in the worm wheel 31. Also rotatable on the shaft 37 is the member 41 in the form of a plate having a concentric sleeve portion 42 fitting into the aperture 32. On the same side of the plate 41 as the sleeve 42 is the pawl 44 pivoted on a pin 45 and having at one end a cam follower 47 and at its other end a notch 46. The pawl 44 is urged in an anticlockwise direction by a hairpin spring 48 one leg of which engages the sleeve 42 and the other leg of which engages the follower 47. The plate 41 has on its other side an eccentric sleeve portion 43. Rotatably mounted on the sleeve 43 is a crank plate 51 having an aperture 52, a cam projection 53 and the crank pin 54 which is guided for radial movement relative to the shaft 37 by means of a radial slot 55 in a yoke member 56 having a rectangular opening 57 received by the flats 38, 39 on the shaft 37. The assembly is restrained from axial movement on the shaft 37 by a washer 58 and a snap ring 59, Fig. 1, which is located in the annular groove 40. The cam follower 47 on the pawl engages with a concentric cam surface 34 on the wheel 31 which surface has a notched portion 35 to receive the follower when the pawl is retracted. In the extended position of the pawl, i.e. when the follower is engaging the concentric surface 34 the notch 44 can engage a pivoted latch arm 70. The latch arm 70 is snapped either to the position shown in Fig. 1, or the position shown in dotted lines in Fig. 3, by a toggle arm 75 operable manually and is limited in its movements by a pin 78 on the housing 20 engaging in a larger aperture 72 in the arm 70, all as described in the parent Specification. In the position shown in Fig. 1, the mechanism is in the parked position of the shaft 60 and the crank pin 54 is in its outermost position in the slot 55. When the motor is energized by a manual slider, the toggle arm 75 is snapped in an anticlockwise direction but the arm 71 does not pivot clockwise since it is engaged by the pawl notch 46. However worm wheel 31 drives the yoke 56 clockwise and thus the cam plate 51 and owing to the stationary plate 41 and its sleeve 43 the pin 54 is caused to move inwardly of the slot 55. In the position shown in Fig. 3, the cam projection 53 engages the end of the latch arm 70 and moves it to the dotted line position. However the pawl is still in its extended position until the parts have rotated through approximately another 165 degrees, when the spring 48 moves the follower 47 into the cam notch 35 and thus retracts the pawl 44 out of contact with the arm 70. At this stage the crank pin 54 is in its innermost position in the slot 55, being adjacent the low point on the eccentric 43. The mechanism will thus continually oscillate the wiper shaft 60 through its normal arc 91, 92, Fig. 1. When the manual control is moved to the " off " position the toggle arm 75 will be moved to the position shown in Fig. 1. The arm 70 then engages the retracted pawl and when the pawl notch 44 engages the end of the arm 70 rotation of the plate 41 will be restrained and the follower 47 will move out of the notch 35 and thus the crank plate 57 will rotate about the eccentric sleeve and cause the shaft 60 to move to the " park " position 90, Fig. 1. At this time a parking switch (not shown) de-energizes the motor which is then dynamically braked. Reference has been directed by the Comptroller to Specification, 650,016.