Abstract: A rotary shear type shredder for shredding a wide range of materials, including flat and sheet materials has a plurality of spaced, intermeshed coacting cutter discs mounted for counterrotation on a parallel shaft. Each disc has a single cutter hook and a single rectangular cutter block fixedly mounted on opposite circumferential sides thereof. The hooks and blocks are arranged to form a spiral of cutters and hooks mounted on each shaft a 180 degrees apart and positioned so that blocks on one shaft feed material to hooks on the other shaft. The cutter blocks have a pair of right-angle cutter edges on both front and back sides for coacting with discs and hooks when rotated in a forward direction and coacting with cleaning fingers when reversed.

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.

Abstract: A hydraulic drive arrangement for a shear-type shredder includes an electrically operable control circuit, including a jam sensor external to the hydraulic fluid circuit, for sensing jamming conditions in the shredder and reversing the flow in the fluid circuit only when a true jamming condition is sensed. The jam sensor is located in the electrical power circuit to the electric motor driving the hydraulic fluid pump for sensing the load on the motor. An electric discriminator circuit responds to the sensor to distinguish between load changes due to true and momentary jamming conditions in the shredder. An actuator responsive to the discriminator actuates a flow-reversing valve in the hydraulic circuit to reverse fluid flow therein to reverse the shredder and thereby clear the jamming condition.