HYDRAULIC JACK WITH LIMITED TRAVEL

摘要

The hydraulic jack has an inner cylinder (2) which houses a piston (4) fitted with a lip seal (5). The piston has a limited axial movement on the extension (17) of the piston rod (6). A flat sealing ring (21) is fitted in an annular groove on the upper face of the piston. A passageway (23,24) connects the upper end of the inner cylinder (2) with the reserve tank (13) formed by the outer cylinder (11). When the piston reaches the top of its stroke, its upper face abuts against the shoulder (27) of the end cover (8). Any further rise in pressure in the cylinder (2) moves the piston rod relative to the piston. Oil in the inner cylinder can then flow through the piston rod clearance (18) over the sealing ring (21) and out through the passage into the outer cylinder thus relieving the pressure in the inner cylinder.