Patent GB-639877-A (GB)
Title: Improvements relating to hydraulically operated windscreen wipers
IPC: B60S1/12
Filed: 1947-11-01
Abstract: 639,877. Windscreen cleaners. DUNLOP RUBBER CO., Ltd., and TREVASKIS, H. W. Nov. 1, 1947, Nos. 29199/47 and 1508/48. [Class 138 (i)] [Also in Group XXIX] In a hydraulic windscreen wiper system comprising a wiper unit and a two-throw pump, the wiper unit comprises a pair of cylinders and a pair of single-acting pistons connected to a pair of racks, each rack engaging at the opposite end of a diameter of a pinion mounted in the wiper unit on a shaft adapted to carry the wiper blade so that alternate supply of liquid under pressure to the cylinders causes the wiper blade to be oscillated, means being provided for returning to the pump excess liquid pumped to the cylinders. A windscreen wiper unit housing 1, Fig. 1, has a pinion 7 rotatably mounted therein and meshing with racks 4 connected to single-acting pistons 3 in cylinders 2, each of which cylinders has a port 12 each communicating with passageways 11. The two cylinders 2 and the passageways 11 are connected to a twothrow pump, Fig. 3, by pipes 13, 14 and 15 respectively. The pump has a casing 17 housing two cylinders 21 which are connected by the pipes 13, 14 to the cylinders 2 of the wiper unit. Each pump cylinder 21 has a port connecting with the bottom of the casing 17 which casing is connected by the pipe 15 to the passageways 11 in the wiper unit. Two pistons 19, one for each pump cylinder, are coupled by a cradle-like component 20 and are driven by a crank-shaft 18, rotatably mounted in the casing 17, driven by an electric motor through reduction gearing. Liquid is introduced into the four cylinders and the pipes in any convenient manner. In operation, e.g. the right pump piston 19 moves to the right thereby covering the port in the cylinder 21 and expels liquid by the pipe 14 to the right-hand cylinder 2 and thus raises the piston 3 and rack 4 to turn the pinion 7. The left-hand rack 4 and piston 3 are moved in the opposite direction by the pinion 7 to expel liquid in the left-hand cylinder 2 via the pipe 13 to the left-hand cylinder 21 of the pump which cylinder is then in communication with the casing 17 by its uncovered port. When the right piston 3 uncovers the port 12 excess liquid passes to the passageway 11 and returns to the pump casing 17 by the pipe 15. Further rotation of the crank-shaft 18 causes periodic reversals of this operation. The wiper unit housing is provided with apertures 16 to facilitate its fixing. The upper end of the passageways 11 may be provided with a valve which is normally open to allow egress of air and which is automatically closed to prevent loss of liquid should the wiper unit be inverted. In a modification one cylinder of the two-throw pump has a capacity, eg. approximately 10 per cent greater than the other cylinder, which latter cylinder has a capacity equal to each of the wiper unit cylinders 29, Fig. 4. The smaller capacity pump cylinder is connected by a pipe 38 to the left-hand cylinder 29 which has a piston 27 incorporating a chamber 28a having a seating 30 for a ball 31, which chamber communicates with the upper side of the piston by holes 29a. The ball is retained in the chamber by an annular member 32 having a central hole 33 and an upper face with radial slots 34. The larger capacity pump cylinder is connected by a pipe 39 to the right cylinder 29 having a plain piston 28 and a port 36 communicating with the upper end of the left-hand cylinder 29. Excess liquid supplied by the larger capacity pump cylinder to the right-hand cylinder 29 returns to the pump by the port 36, upper end of the lefthand cylinder 29, through holes 29a, chamber 28a, radial slots 34 and hole 33 to the pipe 38. When liquid is supplied to the left-hand cylinder the ball-valve automatically closes so that the piston 27 can be raised. In both embodiments a further pair of pump pistons can be operated from the pump crank-shaft which pistons are reciprocable in cylinders connected to a second wiper unit.