| 摘要 |
A hydraulic system for operating support legs comprises a directional valve (2), a non-return valve (3) and a hydraulic cylinder (4) with a piston (5) dividing the cylinder into first and second chambers (8, 9). Between these and the directional valve extend first and second oil conduits (10, 11). The non-return valve (3) contains a pilot piston (29) which can lift a ball (25) in the valve. The second conduit (11) contains a valve means (32) dividing the conduit into two portions (11', 11"), of which a first portion (11') can be maintained pressurised while the other portion (11") is substantially unpressurised. The conduit system also comprises a drain passage (36) enabling drainage of a secondary portion (10") of the first conduit (10). The inventive device makes it possible to reliably maintain the piston (5) in a given position without any tendency to uncontrolled motions as a result of leak flows in the directional valve. |
