Fiber chopper and method of controlling force

A method of separating long lengths of unwound item(s) selected from the group consisting of fibers, fiber strands, string, yarn, wire, tape and ribbon into short pieces comprising feeding one or more items in an unwound form into a chopper comprising a frame, a rotatable backup roll outboard of one side of the frame, the backup roll having a peripheral elastomeric working layer, a rotatable blade roll outboard of the side of the frame, the blade roll having a plurality of blades residing in slots in a second elastomer, the second elastomer having a Shore A hardness greater than that of the elastomer working layer of the backup roll, the plurality of blades being spaced apart around its periphery for contact with and penetration of said items and into the peripheral elastomeric working layer of the backup roll and a biasing system for biasing the blades of the blade roll and the backup roll together, the biasing system comprising a mechanical jack that extends and retracts as an element of the mechanical jack is rotated first in one direction to extend and in the opposite direction to retract, and a motor assembly for rotating said element, and operating the chopper,

• the improvement comprising using a biasing system comprising an assembly for biasing the blade roll and the backup roll together with a force, the magnitude of the force being that which will cause the blades to penetrate the peripheral elastomeric working layer of the backup roll to a desired distance to separate the unwound items, said assembly comprising one or more strain gauges or load cells providing data for bias control using input from the one or more strain gauges or load cells and an output for the motor assembly to maintain the desired magnitude of biasing force during the separating of the unwound items.