Hydraulic pump with spring valves - springs delay suction valve opening until after start of suction stroke

摘要

The plunger-type hydraulic pump has suction and delivery valves spring-loaded shut for each plunger. The force tending to open the suction valve in opposition to the spring is less than the force of the latter during delivery and greater than it during part at least of the suction stroke. The valve does not open until the residual delivery pressure, due to compression of the fluid, in the clearance volume has fallen below a predetermined level, resulting from the start of the suction stroke.