Patent GB-664575-A (GB)
Title: Improvements in or relating to windscreen wipers
IPC: B60S1/10
Filed: 1949-10-24
Abstract: 664,575. Gaseous pressure engines; valve gear. TRICO PRODUCTS CORPORATION. Oct. 24, 1949 [Nov. 4, 1948], No. 27305/49. Classes 122(ii) and 122(iii) [Also in Groups XXIII and XXIV] Relates to a gaseous pressure motor and valve gear therefor, for operating a windscreen-wiper mechanism (see Group XXIII). The motor 5, Fig. 3, preferably operable by a super-atmospheric gaseous pressure, comprises a chamber 6 and a multi-part piston having spaced heads 7, 8 joined by a body 9 on which a rack 11 is formed which rack is connected to the wiper mechanism. The piston is slidable back and forth over a gaseous pressure supply pipe 29 communicating with a chamber 30 within the piston. The piston is also formed with an inlet through-passage 28 and an outlet-through passage 27. The passage 28, which communicates with the chamber 30 through a port 32 has two valve seats 23 and an inlet valve 20 which is alternately engagable with the seats by means of opposed rods 24 carried by shift plates 25 slidably supported on the opposite ends of the piston by means of one or more studs 26. The passage 27, which communicates with the chamber 6 through a vent port 34, Fig. 4 (not shown), is provided with two valve seats 21 and two outlet valves 19 between which a spacer rod 22 is interposed to cause one valve to unseat when the other is seated. The valves 19 are operated by the shift plates 25 which overlie them. When the piston is moving to the left, Fig. 3, the right hand valve 19 is seated and the valve 20 is seated on its left hand seat 23. As the piston, comes to the end of its stroke the left hand plate 25 compresses a spring 31 until sufficient energy is stored in the spring to overcome the pressure holding the right hand valve 19 and the valve 20 on their seats whereupon the plate is moved to the right to seat the left hand valve 19 and to seat the valve 20 on the right hand seat 23, which positions are indicated in Fig. 3. The gaseous pressure is now applied to the piston head 7 so that the piston moves to the right. At the end of this stroke the .piston and the right hand plate 25 will compress a second spring 33 to reverse the valves to allow the piston to move to the left again. During operation air in advance of the moving piston will exhaust through the passage 27, vent port 34 and a vent port 35, Fig. 2 in the chamber 6. For parking the wiper when the motor is arrested the coil spring 33 is retracted so that it does not effect the reversal of the valves. The spring 33 is mounted on an auxiliary piston 36 slidable in a chamber 37 communicating through a pipe 39 and a control valve, Figs. 1 and 5 (not shown), with the source of gaseous pressure. When pressure is supplied to the chamber 37 in one position of the control valve the spring 33 is retained in the valve operating position. When the control valve is in the other position the chamber 37 is vented to atmosphere and the spring 33 is pushed by the encasing piston into the chamber 37, the piston head 8 then engaging a stop 40 in the chamber 6. The piston is then locked by the gaseous pressure acting on the piston head 7, the supply to the motor being independent of the control valve. A handle 44 is provided on the shaft 13 to permit of. manual movement of the wiper.