GB876273A - Improvements in or relating to hydraulic actuating mechanisms - Google Patents

Abstract

876,273. Hydraulic apparatus. POWER JACKS Ltd. June 21, 1960 [June 20, 1959], No. 21248/59. Class 69 (2). An hydraulic actuating mechanism comprises a pair of double-acting rams 10, 11 coupled by a flexible cable 12 so as to rotate a drum 13, one end of each ram being connected through a control valve 17 to a source 21 of hydraulic pressure, and the other ends of the rams being hydraulically coupled in a closed circuit. When the control valve is moved to connect the hydraulic pressure to the ram 10 to move the piston 10a to the right, the other ram 11 then being connected to a reservoir 20, the movement of the piston displaces fluid through a pipe 14 into the cylinder of the vane 11 to move its piston 11a to the left, thus maintaining the cable 12 taut. The pistons may be formed with one-way valves 10d, 11d which open when their respective pistons are in their extreme right-hand positions to permit make-up fluid to pass into the circuit between the pistons. In an alternative arrangement, fluid may be supplied through a one-way valve in a pipe connected directly to the source and to the pipe 14 between the rams. Springs in the rams may assist in maintaining the tension in the cable and the pistons may have dummy rods on their left-hand sides so as to have opposite faces of equal area. The control valve is provided with a neutral position in which the rams are locked, and a further valve may be incorporated in the pipe 14 to assist the locking action.