HYDRAULIC DRIVE FOR LIFTING DEVICE Russian patent published in 1996 - IPC

FIELD: mechanical engineering. SUBSTANCE: pistons secured at the ends of a rod form four spaces inside a tandem cylinder. The pump and drain are connected with a tank from one side and with a hydraulic dispenser from the other side. The dispenser is connected with one of the under-piston spaces of the tandem cylinder. One above-piston space is air-operated and in communication with a vessel filled with a compressed gas. The second under-piston space is connected with the under-piston space of the working cylinder whose above-piston space is in communication with the hydraulic dispenser. A make-up unit is made up as working cylinder that is mounted inside the piston of the working cylinder of the controllable check valve. The control space of the valve is made to permit its interaction with the plunger secured to the tandem cylinder cover. The by-pass valve is mounted in the cross-piece of the tandem cylinder whose inlet is in communication with the second under-piston space. The stop member of the valve is kinematically connected with one piston of the tandem cylinder. EFFECT: enhanced reliability. 3 cl, 2 dwg