Tough pump serves tough applications

Hydraulic piston pumps and motors reduce design cost and increase productivity in shredders and waste reducers.

Drives for heavy-duty shredders must be able to withstand frequent reversals in direction and stalling without damage. Unlike electromechanical drives, this poses no great challenge to hydrostatic drives.

The Gold Cup series of hydraulic piston pumps and motors, from Parker Hannifin Corp., can reduce the total design cost while also increasing the productivity of shredders and waste reducers used to process difficult materials. Whether itÕs tires, debris, appliances, or furniture, heavy-duty shredders must operate with high torque and at high speed to rip through these materials quickly.

Gold Cup closed-circuit hydrostatic drives incorporate features that are often add-on items — integral servo and replenishing pumps, replenishing check valves, and stroking control mechanisms — in shredder/reducer designs. This selfcontained drive package can help OEMs achieve a smaller system envelope and potentially lessen the complexity of other external components, ultimately equating to a lower total design cost.

Many control options are offered for customizing in specific applications. The result is a more efficient hydraulic system that, in turn, will be cost effective for the end user to operate and maintain.

“To transmit low-speed, high-torque power for shredding applications, a gearbox could be used to reduce speed from an electric motor and multiply torque,” notes Doug Krantz, senior product engineer at Parker’s, Hydraulic Pump Div., Marion, Ohio. “Our Gold Cup technology is a natural fit for systems with gearboxes and those that use high-torque, low-speed motors as a direct drive.”

To ensure reliable delivery of hydraulic power, Gold Cup pumps are widely used to drive the cutter shafts on shredders, where a series of rotating cutters pulls debris through small openings to shear and reduce its bulk. These pumps have a maximum continuous operating pressure of 5000 psi and a maximum theoretical flow of up to 234 gpm at 1800 rpm. Typically, the pump feeds two pairs of hydraulic motors, with each pair mounted to either end of a cutter shaft. The Gold Cup hydrostatic drive offers capabilities such as reversing and stall, which are critical to the shredding process. These capabilities are also a big reason why hydraulics outperforms electromechanical drives in this application. Finally, in some designs, output from Gold Cup pumps can be used to power track drives and hydraulic fan drives to manage the engine’s thermal load.

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Details about the pump

The Parker Gold Cup series of large-displacement, closed-circuit axial piston pumps features a proprietary barrel-bearing design that produces high stability when the pump runs at high speeds and pressures. It can also be instrumental in lowspeed, high-torque applications. Gold Cup modes of operation include:

• Closed hydraulic circuit with a variable pump and fixed motor. This combination provides a constant torque output at a fixed maximum pressure over the pump’s full speed range. Speed and direction are controlled with a variable-displacement over-center pump. Power from over-running loads is regenerated back into the pump prime mover. Motor speed is limited to the maximum speed permitted by full pump displacement.
• Variable pump with a variable motor. This combination provides an extended range of motor speeds. At full displacement, the motor delivers maximum torque while its speed and direction respond to displacement changes of the crossover center pump. Power is proportional to motor speed.
• High-torque, low-speed start-up. The transmission system can provide constant torque and rising power until the pump reaches full displacement and full power at high speeds as motor displacement and torque are reduced.