HYDRAULIC CONTROL UNIT FOR RECIPROCATING DOUBLE-ROW CYLINDER TYPE POSITIVE DISPLACEMENT PUMP

摘要

PURPOSE:To keep off any surge pressure as well as to secure such a hydraulic control unit as being longevity in service life, by attaching a pilot valve to both push and pull stroke end positions of a power cylinder at one side, while connecting a pilot port to a return oil system in a controlling valve. CONSTITUTION:Both push and pull stroke positions of a power cylinder 11 at one side are provided with each of pilot valves 15' and 16'. A pipe line 38 ranging from a pilot port H of a controlling valve 19B is connected to a port B of a power cylinder 19A, while a pipe line 41 ranging from a pilot port G is connected to a port A. With this constitution, in time of a piston 13 being in its push stroke, pressure oil inside the power cylinder 11 passes through the pipe line 38 from a port Q and then pushes a spool 23 at the pilot port H. At this time, oil at the opposite side of the spool 23 passes through each of pipe lines 41 and 43 from the port G and then returns to a tank running past a port A-T by way of a check valve 44.