Patent GB-775685-A (GB)
Title: Windscreen wiper system
Inventor: HARPER THOMAS WILLIAM
IPC: B60S1/12
Filed: 1954-07-15
Abstract: 775,685. Windscreen cleaners. DUNLOP RUBBER CO., Ltd. July 5, 1955 [July 15, 1954], No. 20639/54. Class 138(1) A windscreen wiper system comprises an oscillatable shaft 8, Fig. 1, for the wiper blade 2 fluid pressure operated means 1 to oscillate the shaft upon energization of electric means 3a supplying pressure-fluid thereto, a second fluid pressure operating means 9 associated with the shaft and adapted to rotate the shaft in one direction to a predetermined angular position upon the de-energization of the electric means 3a, and electrically operated 'valve means 20 operable, upon energization of the electric means supplying pressure-fluid to the means 1, to prevent flow of pressurefluid to the second means 9, and operable upon de-energization thereof to supply fluid-pressure to the second means 9 whereby to rotate the shaft 8 to, and retain it in, the predetermined angular position. Three panels of an aircraft windscreen are each cieaned by a wiper blade 2, Fig. 1, oscillated by a hydraulic motor unit 1 supplied with pressure liquid from a twothrow pump 3 driven by an electric motor 3a. The motor 1, Fig. 2, has a pair of cylinders 5 for pistons 4 connected to racks - engaging a pinion 7 on the wiper actuating shaft 8. The arrangement of the motor 1 and the pump 3 is similar to that described in Specification 639,877 which is referred to. The shaft 8 also carries a pinion 13, which is received in an opening 12 in a housing 9, Fig. 3, bolted to the motor 1 and meshes with a rack 16 movable in a tubular extension 14 and a passage 14a aligned with the extension. A piston plunger 15 is slidable in the extension 14 and contacts the rack 16. Hydraulic pressure liquid can be supplied to the plunger 15, to move the rack 16, through a connection 17. Referring to Fig. 1, the three liquid connections 17 are connected through hydraulic pressure relays 20a and a four-way connection 19 with an electric solenoid-operated control valve mechanism 20 which is connected to a hydraulic pump and reservoir (not shown). The relays 20a are of the type described in Specification 701,973 [Group XXIX] which is referred to. As shown in Fig. 4, the mechanism 20 comprises a housing having two chambers 21, 22, the chamber 21 being connected to the hydraulic pump (not shown) and through a valve seat 24 with the connections 17 and also with the chamber 22, whilst the latter is connected by a valve seat 24 to the liquid reservoir (not shown). The chamber 21 has a valve 23 normally urged away from the seat 24 by a spring and closed when its solenoid is energized, whilst the chamber 22 has a valve 23 normally seated on the seat 24 by a spring and opened when its solenoid is energized. When the motors 3a are energized the left-hand valve 23, Fig. 4, is closed and the right-hand valve 23 opened by the solenoids, so that the hydraulic pump connected to the mechanism 20 is cut-off from the connections 17 which latter are then connected to the reservoir. When, however, the motors 3a are de-energized, the solenoids are likewise de-energized and the valves 23 adopt the positions shown in Fig. 4, whereby pressure-liquid is placed in communication with the connections 17 to, operate the pistons 15 and racks 16 to move the wiper blades to their parked positions. At the same time the liquid reservoir is sealed off from the connections 17.