Patent ID: 6299416
Filing Date: 2001-10-09
Classification: F04B

Abstract:
A bulk material pump device, comprising;an oil tank;an oil pump for producing pressurized oil;first and second hydraulic cylinders each having a cylinder housing with an axial bore and a drive piston with a piston rod, the drive piston of the respective drive cylinder slidably received in the axial bore to divide it into a base chamber and a head chamber, the base chamber of the second drive cylinder coupled to the oil pump via a second fluid line, the head chamber of the first drive cylinder being in fluid communication with the head chamber of the second drive cylinder;first and second pump cylinders each having a pumping barrel and a pumping piston slidably received in the pumping barrel, the pumping piston of the first pump cylinder affixed to the piston rod of the first drive cylinder for unitary movement therewith, the pumping piston of the second pump cylinder attached to the piston rod of the second drive cylinder for unitary movement therewith;a head bypass line for allowing the pressurized oil in the base chamber of the first drive cylinder to be admitted into the head chamber thereof at the end of retracting movement of the drive piston of the first drive cylinder;a base bypass line for allowing the pressurized oil in the head chamber of the first drive cylinder to be admitted into the base chamber thereof only at the end of extending movement of the drive piston of the first drive cylinder; anda cartridge valve operatively connected to the base bypass line via a pilot line in such a manner that the cartridge valve can be closed or opened by the fluid pressure developed in the base chamber of the first drive cylinder.