ES315449A1 - Apparatus for controlling the operation of fluid operated jacks required to be moved in synchronism - Google Patents

Abstract

A hoisting apparatus comprises two hydraulic jacks V1, V2 whose pistons P1, P2 are fixed to the ground in a vertical position and whose cylinders C1, C2 are supplied with pressure liquid through pipes a1, a2. A load supporting platform is represented by a crossmember T attached to the cylinders C1, C2 by pin joints A1, A2. In order to cause the jacks to move together so as to keep the crossmember T horizontal each cylinder C1, C2 comprises a bleed pipe b1, b2, respectively, connected to a valve 1 fixed to the cylinder C1. The valve 1 consists of a body 6 with a bore 7 into which extend ducts 8, 9, 10, 101. A slide member 11 extended by a rod 12 is connected by a rod 3 and pivoted lever 4 to the cross-member T. If the jack V1 rises more rapidly than the jack V2 the lever 4 is pivoted clockwise by the tilting of the cross-member T so that the slide member 11 moves to the left to connect the bleed orifice b 1 to tank through the duets 8, 101 to slow down the jack V1. On descent the system operates in the same way, the bleed orifice of the lagging jack being connected to tank to accelerate its descent. The means sensitive to the relative movement of the jacks V1, V2 may be two micro-contactors (13), (14), Fig. 3 (not shown): a mercury contactor (15), Fig.4 (not shown) photo-sensitive cells (26), (27), Fig. 5 (not shown), or an arm (28), Fig. 6 (not shown), may act directly on micro-contactors. In a platform raised by four jacks (not shown) the horizontality of the platform may be maintained by combining the jacks in pairs, each jack being provided with two synchronizing devices, one of which controls the tilt of a transverse cross member, and the other the tilt of a longitudinal cross-member.