GB1391126A - Hydraulic devices - Google Patents

Abstract

1391126 Hydraulic reciprocating motors FABBRICA ITALIANA MAGNETI MARELLI SpA 28 July 1972 [31 July 1971] 35454/72 Heading F1A Pistons 12,72 of a device for oscillating vehicle windscreen wipers (not shown) are reciprocated in synchronism in cylinders 10,72 by liquid alternately supplied to working chambers M 1 ,M p2 by a distributor valve T, the changeover of the valve T being controlled by a device K responsive to the fall of pressure in the opposed working chambers M 2 ,M P1 which occurs when one or other of relief valves 22,84 is opened by a respective pin 26,88 at the end of each working stroke. In the position of the device shown, the pistons are completing their rightward strokes under the action of liquid directed by the valve T to the chamber M 1 , the liquid being supplied to the valve T from a source Ma via a stop valve R 1 and a throttling valve D. When the pin 88 opens the valve 84, liquid in the chambers M 2 ,MP 1 and a connecting conduit 104 are connected to an outlet Sc via passages 76,78,80 in the piston 72. The resulting fall in pressure in the conduit 104 is detected in a chamber K2 of the pressure responsive device K the chamber being partly defined by a diaphragm 124. A spring 126 thus moves the diaphragm and a rod 135, thereby to effect, via a toggle mechanism 138, 140 leftward movement of the valve T. This causes the pressurization of chamber M P2 and the exhaust, via a check valve V 1 , of chamber M 1 . A return stroke is therefore initiated provided a pin 28 is in the position shown. If, on the contrary, the pin 28 displaced to the left by moving a valve R 2 to a position in which liquid causes operation of an actuator piston 150, the consequentially increased opening of a relief valve 24 prevents pressure building up in the chamber M P2 and the pistons remain in their positions shown. In a second embodiment, Fig.1 (not shown), the pressure responsive device (B) controls a valve member (32) which operates in conjunction with a piston actuated commutator valve C to cause hydraulic changeover of the distributor valve T. Two by-pass passages around a valve (R 2 ) for stopping the device by cutting off the liquid supply are under the control, respectively, of a valve (34) operated by the pressure responsive device (B) and a valve land (42) of the commutator valve (C).