ES347163A1 - Hydraulic antishock device - Google Patents

Abstract

In a double acting hydraulic jack 101, Fig.1, supplied by an electric motor driven pump P which delivers through an open control three-position distributing valve 111 controlled by solenoids EA, ER and also through a pressure regulating valve 119 upstream of valve 111 and discharging directly into a return line 113 and also through a solenoid actuated master control valve 120 to said return line as disclosed in patent Specification 1, 55, 865, the electric circuit for stopping and starting the pump motor M and for energizing solenoids EA, ER and solenoid EP of valve 120 comprises two first double switches 133, 134 having contacts 133a, 133b and 134a, 134b open and closed alternately and actuated by mechanical link between each switch and the solenoid on the remote side of the valve 111 the contacts 133a, 134a being in circuits U2, U3, Fig. 2 of solenoids EA, ER respectively so as to prevent energization of one solenoid whilst the other is energized whereas the contacts 133b, 134b are in circuit U4 of solenoid EP, and the circuit also comprises a second double switch 139 actuated by a mechanical link between the switch and the master distributer 120 and having two sets of contacts 139a, 139b which close simultaneously and are respectively in series with contacts 134a, 133a, and the circuit further comprises two double end of travel switches 141, 142 of opposite ends of the jack so as to be actuated by the piston rod 103a, 103b and having sets of contacts 141a, 141b and 142a, 142b which open and close alternately, contacts 141a, 142a, being circuit U4 of solenoid EP whilst contacts 141b, 142b are respectively in series with contacts 134a, 133a in circuits U3, U2 of solenoids ER, EA. The system is designed to prevent pressure surges on either side of the jack piston 102 when valve 111 is moved from its central neutral position shown. In operation and with pump motor switch D2 closed, a manual switch Dc is closed which excites solenoid EA resulting in movement of valve 111 to the right and low-pressure pump delivery being fed to jack chamber 105. Movement of valve 111 is transmitted to solenoid ER and a lever 132 which opens contacts 134a and closes 134b resulting in excitation of solenoid ER which moves valve 120 so as to progressively block the by-pass line 121 and allow build-up of pump delivery pressure to jack chamber 105 as described in Specification 1, 055, 865, contacts 139a are now closed to prepare a feed path for excitation of solenoid ER and contacts 139b are closed so that manual switch DC may be released. At the right hand end position of jack piston 102 contacts 141a are opened and contacts 141b closed by a cam 103c resulting in de-energizing of solenoid EP whereby the valve 120 is returned by its spring 124 to the position in which pump delivery is progressively returned to reservoir 114 and contacts 139b are opened resulting in de-energizing of solenoid EA and return of valve 111 to neutral by springs 115, 116. In this neutral position of valve 111 contacts 134a are closed and since contacts 141b are closed solenoid ER is energized to reverse valve 111 to initiate leftward movement of the piston 102. The mechanical link opens contacts 133a and closes contacts 133b and with contacts 142a still closed solenoid EP is energized resulting in progressive closing of valve 119 and progressive increase of pump delivery pressure to jack space 104. At the left hand position of piston 102 solenoid EP is de-energized, valve 119 is returned to its open by-pass position and valve 111 to its central neutral position. The jack piston 102 remains in this L.H. position providing a manual switch Im in circuit U2 remains open, however if Im is closed the cycle recommences. The piston may be stopped at any position by opening a manual switch AC in the circuit U4 of solenoid EP.