Patent ID: 6929454

Claim:
A thick matter pump comprising: two delivery cylinders ( 10 ) containing drive cylinders ( 24 ′, 24 ″), which cylinders respectively open into a material feed basin ( 14 ) via openings ( 12 ) situated at one end; two hydraulic drive cylinders ( 24 ′, 24 ″) containing drive pistons ( 30 ′, 30 ″), each piston having a rod side and a head side, said cylinders connected to a reversible hydraulic pump ( 42 ) via piston rod-side or piston head-side pump connections ( 34 ′, 34 ″; 36 ′, 36 ″); a swing oil line ( 44 ) interconnecting the ends of the drive cylinders which are opposite to the pump connections; piston rods ( 28 ) rigidly pair-wise connecting the drive pistons ( 30 ′, 30 ″) of the drive cylinders ( 24 ′, 24 ″) and the delivery pistons ( 26 ) of the delivery cylinders ( 10 ) respectively; equalizing lines ( 48 ) connected in the area of the piston head ends of the two drive cylinders ( 24 ′, 24 ″) and forming a bridge between the head side and the rod side of the respective drive pistons ( 30 ′, 30 ″) when said drive pistons are at their respective end positions, said equalizing lines each containing a check valve ( 46 ); and two position sensors ( 52 ′, 52 ″), wherein one of these position sensors is provided a defined distance from the rod-side end of each drive cylinder ( 24 ′, 24 ″), and connected to a control device ( 51 ) and emitting an end position signal in response to the passing by of a drive piston ( 30 ′, 30 ″) for controlling the reversal of the hydraulic pump, such that the sensing of the piston by the position sensor triggers a reversing of the direction of the pistons, wherein, in addition, a correcting sensor ( 54 ) is arranged at a defined distance from the piston head-side end of one of the drive cylinders ( 24 ′), wherein said control device temporarily activates said correcting sensor ( 54 ) such that said correcting sensor is used in place of the rod-side position sensor ( 52 ″) of the other drive cylinder ( 24 ″) in order to initiate the piston reversing process, whereby a condition of piston stroke being too short or too long due to excess or insufficient hydraulic fluid is corrected by transfer of hydraulic fluid between the piston side and rod side of a piston near the correcting sensor via the equalizing line ( 48 ).