US 4,793,561 AGranted

Speed-responsive reversing hydraulic drive for rotary shredder

AssigneeMAC Corporation of America

InventorDan S. Burda

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Abstract

A hydraulic drive for a rotary shredder includes a rotation-actuated electric reversing control. Such control includes a rotation sensor positioned on one of the rotational elements of the drive: one of the cutter shafts, the hydraulic drive motor shaft or the hydraulic pump motor shaft. An RPM monitor circuit receives a signal from the rotation sensor and measures rotational speed to determine existence of a stoppage or slowing of the shaft corresponding to a jamming condition. This circuit monitors shaft speed over discrete time intervals and discriminates between momentary jamming conditions by determining the duration of low shaft speed conditions. The circuit transmits a jam signal to a reversal actuator circuit upon detection of a subnormal shaft speed persisting longer than the predetermined time interval. The reversal actuator circuit includes a timer and reverse and forward solenoids on a flow-reversing valve for briefly reversing fluid flow to the hydraulic motor when a jam signal is received. Monitoring rotation at the pump motor enables the hydraulic fluid circuit, including a pressure relief valve, and the pump motor to filter out brief changes in rotation due to momentary jamming conditions and thereby aid in discriminating between true and momentary jamming conditions.

Claims8

Dependent claims

A drive arrangement for a rotary shear-type shredder including shredding means, said arrangement comprising:

a hydraulic fluid-pumping means;
a first rotational drive means operatively connected to said fluid-pumping means for undirectionally driving the latter;
a reversible hydraulic motor means;
a second rotational drive means operatively-connected to said hydraulic motor means for bidirectionally driving said shredding means;
a hydraulic fluid drive circuit means including the hydraulic fluid-pumping means and the reversible hydraulic motor means for transmitting power from the first drive means in a downstream direction to the second drive means and transmitting changes in a load in the shredder means upstream to the first drive means, the first drive means being responsive to an increase in load to operate at a reduced speed;
a flow-reversing means for reversing a fluid flow in the hydraulic circuit to the hydraulic motor means to reverse said motor means and thus said shredding means;
and
an electrically operable reversing control means for actuating the flow-reversing means upon detecting an increase in load corresponding to a jamming condition during shredding operation, including:
jam-sensing means connected to the first drive means upstream of the fluid circuit means and operable to sense the speed of said first drive means and responsive to a predetermined minimum speed thereof corresponding to a jamming condition in the shredding means to produce an electrical signal;
and
electrically reversal operable actuation means responsive to the reversal signal for actuating the flow-reversing means to reverse flow in the fluid circuit means for a predetermined time interval.

8 more elements

Dependencies are inferred from the claim text.