Residual load relief system for hydraulic compactors having rotary pumps

A hydraulic compactor automatic residual load relief system comprising:

• the combination of a rotary pump powered by a motor, first and second one-way suction check valves, a one-way flow check valve, a one-way, normally-open, pilot operated check valve, a cylinder comprising a reciprocating piston, the piston defining a disk void and an annular void within the cylinder, first and second cylinder ports, first and second supply ports, first and second tank return ports, and a tank, all connected in fluid communication by conduits, with a first conduit segment extending between the first supply port and the one-way flow check valve and a second conduit segment extending between the one-way flow check valve and the first cylinder port, and with the one-way, normally-open, pilot operated check valve in operational communication through a pilot line with the first conduit segment and in fluid communication with the second conduit segment;
• whereby during a compaction stroke the motor rotates the rotary pump in a first direction such that hydraulic fluid, comprising fluid returned from the annular void of the cylinder and fluid drawn as needed from tank through the second suction check valve, passes through the first supply port, the first conduit segment, the flow check valve, the second conduit segment and the first cylinder port into the disk void of the cylinder;
• whereby the normally-open pilot operated check valve in communication with the first conduit segment through the pilot line is closed in response to the pressurized flow in the first conduit segment creating sufficient pressure in the pilot line to maintain the pilot operated check valve in the closed position, thereby preventing fluid delivered from the pump through the flow check valve from being returned to the tank through the pilot operated valve;
• and further whereby upon cessation of the compaction stroke and during a retraction stroke the motor rotates the pump in the opposite direction from the rotation of the compaction stroke, such that fluid drawn from the tank through the first suction check valve is forced through the second supply port and second cylinder port into the annular void of the cylinder:
• whereby the fluid forced from the cylinder disk void by the retracting piston passes through the first cylinder port into the second conduit segment and is diverted by the one-way flow check valve to the pilot operated check valve, which is in fluid communication with the second conduit segment, said pilot operated check valve now being open as there is now low pressure in the first conduit segment, such that the hydraulic fluid dispelled from the cylinder disk void is returned to the tank through second tank return port and is precluded from passing into the rotary pump.