Hydraulic pump with automatic hydro-mechanical torque control

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Eaton Corporation is adding a hydro-mechanical torque control option and several performance upgrades to its 420 open circuit piston pump product line. The 420 pump with hydro-mechanical torque control automatically senses heavy loads and adjusts hydraulic fluid flow accordingly.

It is intended for moderate-flow, medium-pressure mobile applications such as compact wheel loaders, telehandlers, rough terrain forklifts, telescopic booms, sweepers, backhoe loaders and refuse trucks operating up to 280bar continuously.

To accommodate the new torque control, the pump housing was redesigned and a case-to-inlet check valve was added to improve cold weather operation and provide added protection to the seals and rotating group. The new torque control works in parallel with the standard compensator, using a special mechanism to replace the control piston. Other design changes have decreased airborne noise to a typical 76dBA at 1800rpm and 207bar, providing an environmental benefit both to the operator and those working around the vehicle.

John Taylor, Product Manager for power products at Eaton, states: "In compact and mid-size equipment, torque almost always needs to be controlled. Limiting the torque at the pump shaft across a wide range of engine speeds provides operators with the benefits of increased productivity, greater efficiency and fewer engine stalls. The result is lower engine emissions and improved fuel economy.

"Productivity is enhanced by increasing the speed with which the vehicle function is performed due to flow rate changes made by the torque control system. For example, raising a heavy load with a set of forks on a telehandler places a significant amount of demand on the hydraulic pump and system. To prevent engine stalls without limiting the telehandler's lifting capacity, manufacturers not using torque control would be forced to use a smaller-displacement pump that significantly slows the operation of the forks. Torque control automatically senses heavy loads and adjusts flow accordingly. Limiting the flow in high-pressure situations limits the torque the pump can apply to the engine and, as a result, avoids the corner horsepower point and prevents the engine from stalling. It also allows for higher flow and quicker operation when the set of forks is empty, which means higher productivity."

Eaton's 420 pumps are claimed to offer outstanding power density that is not compromised by the use of torque control.

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