Dual-cylinder piston pump

Abstract

The invention relates to a hydraulically actuated dual-cylinder piston pump ( 1 ), with a first differential cylinder ( 22 ), with a head-end chamber ( 51 ) and a rod-end chamber ( 53 ), which actuates a first delivery piston ( 4 ) via a first piston rod ( 6 ), and also with a second differential cylinder ( 23 ), with a head-end chamber ( 52 ) and a rod-end chamber ( 54 ), which actuates a second delivery piston ( 5 ) via a second piston rod ( 7 ), and with a switching device ( 14 ) which by switching the hydraulic oil flow to the chambers ( 51, 52, 53, 54 ) of the differential cylinders ( 22, 23 ) establishes a head-end or rod-end operating mode of the dual-cylinder piston pump ( 1 ), wherein the switching device ( 14 ) is arranged on the bottoms ( 48, 49 ) of the head-end chambers ( 51, 52 ) of the differential cylinders ( 22, 23 ) as a bridge-forming connection between the differential cylinders ( 22, 23 ). The invention is distinguished by the fact that the switching device ( 14 ) comprises through-passages ( 28, 29 ) for the hydraulic oil for actuating the differential cylinders ( 22, 23 ), via which the head-end chambers ( 51, 52 ) of the differential cylinders ( 22, 23 ) are connected to the switching device ( 14 ) without hydraulic oil lines. The object of the invention is also a method for operating a hydraulically actuated dual-cylinder piston pump according to the invention.

1 . Hydraulically actuated dual-cylinder piston pump comprising:
 a first differential cylinder, with a head-end chamber and a rod-end chamber, which actuates a first delivery piston via a first piston rod,   a second differential cylinder, with a head-end chamber and a rod-end chamber, which actuates a second delivery piston via a second piston rod,   a switching device which by switching the hydraulic oil flow to the chambers of the differential cylinders establishes a head-end or rod-end operating mode of the dual-cylinder piston pump, wherein the switching device is arranged on the bottoms of the head-end chambers of the differential cylinders as a bridge-forming connection between the differential cylinders,   characterized in that   the switching block comprises through-passages for the hydraulic oil for actuating the differential cylinders, via which the head-end chambers of the differential cylinders are connected to the switching device without hydraulic oil lines.   
     
     
         2 . Hydraulically actuated dual-cylinder piston pump according to  claim 1 , characterized by flanges, arranged on the differential cylinders, by means of which the differential cylinders are fastened, preferably screwed, to the switching device. 
     
     
         3 . Hydraulically actuated dual-cylinder piston pump according to  claim 1 , characterized by-adapter flanges which are arranged between the switching device and the bottoms of the differential cylinders. 
     
     
         4 . Hydraulically actuated dual-cylinder piston pump according to  claim 3 , characterized in that the adapter flanges are inserted into close-fitting seats which are introduced into the bottoms of the differential cylinders. 
     
     
         5 . Hydraulically actuated dual-cylinder piston pump according to  claim 2 , characterized in that the expansion sleeves are arranged on the flanges for accommodating screws. 
     
     
         6 . Hydraulically actuated dual-cylinder piston pump according to  claim 1 , characterized in that-the switching device comprises an inlet for a control line for the switching over of the operating mode. 
     
     
         7 . Hydraulically actuated dual-cylinder piston pump according to  claim 6 , characterized by a pilot valve for switching over the operating mode of the switching device, which can be controlled by the control line. 
     
     
         8 . Hydraulically actuated dual-cylinder piston pump according to  claim 7 , characterized by a latching device which holds the pilot valve in its switched position when the control line is shut down. 
     
     
         9 . Switching device for establishing the operating mode of the hydraulically actuated dual-cylinder piston pump according to  claim 1 . 
     
     
         10 . Method for operating the hydraulically actuated dual-cylinder piston pump according to  claim 1 , characterized in that before startup of the dual-cylinder piston pump the last established operating mode is determined a check is carried out as to whether the last established operating mode is to be used for startup of the pump, and in that in dependence of this the operating mode is maintained or switched over before the pump is started. 
     
     
         11 . Method according to  claim 10 , characterized in that the last established operating mode is specified as the operating mode during startup of the pump. 
     
     
         12 . Method for operating a hydraulically actuated dual-cylinder piston pump according to  claim 1 , characterized in that during the operation of the dual-cylinder piston pump the pump pressure is detected; it is determined whether the detected pump pressure lies within a specified tolerance for the established operating mode, and a check is carried out as to whether the operating mode is to be maintained, and in that in dependence of the result of the check the operating mode is maintained or switched over.