Patent ID: 6068448
Filing Date: 2000-05-30
Classification: F04B

Abstract:
A high pressure hydraulic pump apparatus comprising:inlet means adapted to be connected to a reservoir containing a liquid;outlet means adapted to be connected to a load;first reciprocating pump means for alternately sucking and delivering the liquid with a predetermined first displacement per unit stroke length;second reciprocating pump means for alternately sucking and delivering the liquid with a second displacement per unit stroke length which is smaller than said first displacement;drive means for synchronously driving said first and second reciprocating pump means with an equal stroke length for each other such that said second reciprocating pump means performs a suction stroke when said first reciprocating pump means is on a delivery stroke and vice versa;a supply line for connecting said first reciprocating pump means to said inlet means when said first reciprocating pump means is on the suction stroke;a connecting line for directing the liquid discharged from said first reciprocating pump means to said second reciprocating pump means when said first reciprocating pump means is on the delivery stroke and said second reciprocating pump means is on the suction stroke;a delivery line for directing the liquid discharged from said second reciprocating pump means to said outlet means when said second reciprocating pump means is on the delivery stroke; andpressure control means connected to said connecting line for hydraulically controlling the pressure of the liquid in said connecting line,wherein said supply line includes a first check valve for permitting the flow of the liquid directed to said first reciprocating pump means from said inlet means and for blocking the reverse flow,wherein said connecting line includes a second check valve for permitting the flow of the liquid directed to said second reciprocating pump means from said first reciprocating pump means and for blocking the reverse flow, andwherein said pressure control means is adapted to suck an excess amount of flow which is delivered from said first reciprocating pump means and which exceeds an amount of flow sucked by said second reciprocating pump means, at a predetermined lower pressure in the vicinity of a predetermined target pressure of said load.