| 摘要 |
1. An hydraulic pump having at least one reciprocably movable piston, each piston being associated with an inlet valve which is urged towards the closed position by a return spring, characterised by the fact that said return spring (16) is associated with a pusher element (15) actuated cyclically by a cam (21) driven by the pump drive shaft (1) ; such that, when the pusher element (15) is actuated by the cam (21), the action of the spring (16) on the valve (11) is nullified during the inlet phase and re-established at the end of said phase, which has the result that the valve (11) is free during this period and opens only if the inlet pressure is greater than the residual pressure prevailing in the cylinder (6) associated with said valve. |
