ATWO-SPEED PUMP ASSEMBLY

摘要

A hand or foot operated hydraulic press tool has an actuating plunger 56 fast with a low pressure piston 82 and a high pressure piston 162 mounted concentrically within the piston 82. The plunger 56 is reciprocated, and the pistons operate in unison to draw liquid from a reservoir 80 through respective check valves 128 and 174 and deliver liquid under pressure to an output device through a conduit 88. As pressure increases the low pressure pump is effectively disabled by a pressure relief valve 90 and further liquid under pressure is then delivered by the high pressure pump working alone up to a limit set by a high pressure relief valve 112. When the required pressure has been achieved, relief is effected by operating a manual release valve 116.