Thick matter pump
In a thick matter pump, especially for delivering concrete, comprising two delivery cylinders, it is known to provide two position sensors in one of the two cylinders for control of the pistons. However, leakage of hydraulic fluid can lead to an imbalance of the two cylinders. In the invention two position sensors ( 52′, 52 ″) are provided, which are arranged at a defined distance from one of the ends of the drive cylinders and which respond to a drive piston ( 30′, 30 ″) that is passing by. To prevent the formation of concrete clots inside the delivery cylinders ( 10 ) and to prevent the occurrence of a slamming when the drive pistons ( 30′, 30 ″) reach their end of travel, the invention provides that both position sensors ( 52′, 52 ″) are arranged at a distance from the piston rod-side ends of both drive cylinders ( 24′, 24 ″) and, 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 ′). This correcting sensor can be temporarily activated for initiating a reversing process overruling the rod-side position sensor ( 52 ″) of the other drive cylinder ( 24 ″).
1. 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 ).
2. A thick material pump according to claim 1 , wherein the correction sensor ( 54 ) is activateable respectively for one reversal process in defined time intervals.
3. A thick material pump according to claim 1 , wherein the control device ( 51 ) includes a delay circuit or a processor with delay software for activation of the correction sensor ( 54 ).
4. A thick material pump according to claim 3 , wherein the delay circuit or the delay software have a time constant, which corresponds to at least twice the stroke time of the drive piston.
5. A thick material pump according to claim 3 , wherein the delay circuit is triggered by the absence of an end position signal of the correction sensors ( 54 ) and presence of an end position signal of the oppositely lying drive cylinder ( 24 ″) associated position sensor ( 52 ″) and is resettable upon occurrence of end position signal of the correction sensor.
6. A thick material pump according to claim 3 , wherein the delay circuit is a re-triggerable time delay.
7. A thick material pump according to claim 1 , wherein respectively two redundant piston rod-sided position sensors ( 52 ′, 52 ″) are provided.
8. A thick material pump according to claim 1 , the position sensors ( 52 ′, 52 ″) and the correction sensor ( 54 ) are proximity switches or magnetic switches for detecting bypassage of the associated drive piston ( 30 ′, 30 ″) in the direction of the end position.
9. A thick material pump according to claim 1 , wherein position sensors ( 52 ′, 52 ″) and the correction sensor ( 54 ) are signal emitters emitting end position signals during the passage by of the respective drive piston ( 30 ′, 30 ″) in the direction towards the end position.
10. A thick material pump according to claim 1 , the hydraulic pump is in a reversing pump ( 42 ), in particular a slant disc axial piston pump.
11. A thick material pump according to claim 1 , wherein hydraulic pump ( 42 ) conveys unidirectionally and that the pump connections ( 36 ′, 36 ″) of the drive cylinder ( 24 ′, 24 ″) are connected with the hydraulic pump ( 42 ) via a directional valve ( 58 ).
12. A thick material pump according to claim 1 , wherein at least two parallel connected hydraulic pumps ( 42 ) are provided.