Patent GB-723347-A (GB)
Title: Windscreen wiper apparatus and differential fluid pressure motors therefor
IPC: B60S1/10
Filed: 1952-04-18
Abstract: 723,347. Compressed-air engines; vacuum engines. O'SHEI, W. E. April 20, 1953 [April 18, 1952; April 25, 1952; April 25, 1952; May 22, 1952], Nos. 9808/52, 10491/52, 10492/52 and 12989/52. Classes 110 (2), 122 (2) and 122 (3). A windscreen-wiper system, Fig. 1, comprises two motors A, B, each of which is provided with a piston 1 actuating a semi-rotary valve 3, ports 4, 5, 6 and sealing-off members 7, 8 adapted to register with valve cups 9, 10 respectively. The rocker shaft 14 of each motor is provided with a conventional kicker 15 or an arm rigid therewith; the valves 3, 31 being positively pushed to their limiting positions. The motors are operatively interconnected as shown, the arrangement being such that, with the valves 13, 131 open, one piston is held stationary until the other piston executes a movement in one direction only. The motor B may be of smaller size than the motor A and serve as an auxiliary motor therefor or both motors may be of the same size and each drive a wiper blade. Motor A can be parked by closing valve 13 and leaving valve 131 open and to this end valve 13 can be provided with a push-button-controlled by-pass, if so desired. Parking can be effected by closing off one of the pipes 11, 12 with an appropriate valve or by associating a pair of pipes 11 and 12 with a changeover valve such that the connections between the ports 4 and 6 and the cups 91 and 101 will be interchanged. In a modification, Fig. 2, the ports 25, 26, 27 are so arranged that when the piston 22 reaches the limit of its stroke the valve 23 will have moved into a neutral position so that vacuum is cut off from both sides of the piston. The valve is moved beyond its neutral position to reverse the movement of the piston by an auxiliary motor comprising a pair of interconnected pistons 36 which slide in a bore 37 in the motor housing. A semi-rotary valve 31 is mounted on the rocker shaft 24 and is associated with ports 32, 33, 34 for controlling the movement of the piston. The delay before reversal of the piston can be effected is controlled by a manually operable valve 46, Fig. 3 (not shown). The stroke of the piston may terminate at the seatings 44 or near thereto, in which case the piston is provided with a manual parking control valve. Again, the motor may be constructed for parking at one or both ends of its stroke. In a modification of the embodiment described with reference to Fig. 2, the first valve is arranged to vent both sides of the piston 22 to atmosphere when in its neutral position. In a further modification, both valves may be incorporated in a single valve structure. The valve mechanism and auxiliary motor can be located remote from the main motor. The valve mechanism can be actuated by a wiper arm spindle as described in Specification 679,469, [Group XXIII]. The motors can be operated by compressed air or other fluids. The second motor B may be embodied in the motor A and comprise pistons, plungers or diaphragms accommodated in appropriate bores or chambers in the body of the motor A. Means may be provided for adjusting the speed of movement of the wiper blade independent of the means for changing the dwell during reversal. Specifications 557,377, 685,554 and 699,233 are referred to.