Patent ID: 9551362
Date: 2017-01-24
CPC Classifications: E01C,F15B

Claim:
1. An apparatus comprising: (a) first and second delivery cylinders containing respectively first and second delivery pistons and first and second end-side openings; (b) a delivery line alternately connected to the first and second delivery cylinders during a respective pressure stroke of the first and second delivery pistons; (c) first and second hydraulic drive cylinders containing respectively first and second drive pistons connected to the first and second delivery pistons via first and second common piston rods, respectively; (d) drive hydraulics comprising a reversing pump actuating and controlling the first and second drive pistons; (e) a placing boom; (f) boom hydraulics actuating and controlling the placing boom; and (g) motor-driven first and second primary pumps; wherein the drive hydraulics and the boom hydraulics form a common primary circuit having a tank at atmospheric pressure for accommodating hydraulic oil; wherein the primary circuit comprises the first primary pump, the first primary pump being charged with the hydraulic oil via a first suction line, wherein the primary circuit is connected at a first outlet side to at least one first return line, and has a suction/return filter communicating at the first outlet side with the first suction line and being charged at an inlet side with returned oil from the at least one first return line, wherein a branch line branches off from the first suction line and issues into the tank via a preload valve; wherein the apparatus further comprises a secondary circuit comprising a motor-driven secondary pump charged with the hydraulic oil via a second suction line; wherein the motor-driven secondary pump is connected at a second outlet side to at least one second return line; wherein the second suction line communicates with the tank directly or via a suction filter ( wherein the first suction line communicates with the tank via a separate replenishment suction line and the suction filter, and wherein a replenishment suction valve preloaded toward the suction filter is arranged in the replenishment suction line.