GB1005253A - Electro-hydraulic device - Google Patents

Abstract

1,005,253. Hydraulic apparatus. RECHERCHES ETUDES PRODUCTION R.E.P. May 31, 1963 [June 2, 1962], No. 21921/63. Heading F1P. [Also in Division F2] In an electrohydraulic device having a piston rod T for controlling e.g. a cut-off valve, the piston 4 thereof is provided with automatic locking means at the ends of its stroke and is actuated in one direction or the other by a reversible pump 8 driven by a two-way motor M which when started causes the piston to be unlocked by the action of hydraulic pressure before commencing its stroke, the automatic locking at the end of the stroke causing the motor to stop. The locking of the piston at the ends of its stroke operates contact makers 6a, 6b to stop the motor. The pump 8 draws liquid from one side of the piston 4 and supplies it to the other side of the piston through conduits 7a, 7b which include a pair of valves 9a, 9b which compensate for the effect of the difference in effective volume of the chambers 2a, 2b on opposite sides of the piston 4 and are operable in response to pressure variations to allow return or withdrawal of liquid to the device through a conduit 13 connected to a reservoir. Connected in the conduits 7a, 7b are two pressure relief valves 14a, 14b and two retaining valves 18a, 18b which are both normally kept open by a cam 17, but one or other of which may be closed when an emergency hand pump 15 connected through conduits 15a, 15b to the conduits 7a, 7b is in use. A high pressure relief valve 19 controls the pressure created by the hand pump 15. The piston rod T is connected to the piston 4 through a spring formed by a stack of resilient rings 5. In Fig. 1 (not shown) all the components apart from the piston and its cylinder are combined in a single unit which can be orientated with respect to the piston and cylinder in two plane at right angles.