In an effort to reduce the stresses put on the operators of compact machinery, HydraForce, the Lincolnshire, Ill.-headquartered specialist in hydraulic cartridge valves, manifolds and electronic controls, has developed a new pressure-balanced boom suspension system designed to dampen the movements of booms and lifting arms and thereby removing one of the significant causes of shock loads and vibration to the operator.
The HydraForce pressure-balanced boom suspension system incorporates a pump connection to maintain the accumulator charge without borrowing oil from the boom cylinder. “This means no sudden load drops or pops on activation,” said Schmidt. “No leaking down, no clunks of the boom dropping onto the stops, and no mushy digging performance. It simply performs the way the operator wants it to.”
The system is based on HydraForce’s patented PB08-E40 pressure-balanced accumulator charging valve, an externally piloted reducing/relieving valve designed to regulate accumulator pressure. With connections to both pump and tank, it is engineered to balance pressure in the pilot port, even when the system is disengaged. This, HydraForce said, provides pressure-balanced accumulator charging and ensures that the load does not move when the system is activated. The system is charged using pump flow and discharge flow to the reservoir. And as valves used to set and maintain the accumulator pressure generally all have some amount of leakage — which can lead to load creep — the HydraForce system incorporates leakdown protection.
The system’s hydraulic valve manifold, which can be mounted close to the boom or integrated into a complete vehicle hydraulic system manifold, has connections for pump, tank, accumulator, boom cylinder rod and boom cylinder base. Solenoid valves enable suspension operation by connecting the cylinder base to the accumulator and the cylinder rod to the tank. The pressure-balanced accumulator charging valve regulates pressure in the accumulator based on a pilot signal from the boom cylinder base. This pilot connection is designed to allow accumulator charging even when the suspension is disengaged.
Any of the orifices in the system can be changed to tune performance characteristics such as accumulator charge/discharge rate, pilot circuit damping and cylinder rod-end metering.
Read the full story in October Diesel Progress.