Rotary knife paper trimmer with long life shearing surfaces for trimming thick and shingled paper products

Claim 1

In a paper trimming system having two substantially circular knives rotatable about respective axes of rotation and mounted to overlap over an arc at a shearing station for receiving, transporting, and shearing a multiple sheet paper product, the improvement for reducing cutting blade wear; reduction of friction, heat and power; and for better cutting action with thick paper products comprising, a rotary bed knife with a substantially cylindrical outer circumferential portion upon which the paper product rides and a substantially planar cutting surface disposed substantially normally to its axis of rotation, rotary bed knife holder means for rotatably mounting said bed knife to present an outer circumferential arc at said shearing station, a cutting knife blade comprising a circular annular disc with cutting teeth on the outer circumference for presenting a substantially planar circumferential cutting surface for mating with the cutting surface of the bed knife in a sliding relationship at said shearing station, rotary cutting knife blade holder means for rotatably mounting said cutting knife blade to overlap the rotary bed knife in said arc at the shearing station in sliding contact, and clamping means for changing the configuration of said cutting knife blade from an initial configuration to a generally frustro-conical dished configuration which is different than the initial configuration and for holding the cutting knife blade on the rotary cutting knife blade holder means in the frustro-conical dished configuration deflected inwardly from the outer circumference in a direction away from the bed knife, thereby to engage the cutting surface of the bed knife only at a narrow circumferential band about the cutting knife to reduce friction and heat, said cutting knife blade having a ground circumferential surface band which slidably engages the cutting surface on said rotary bed knife and a bevel surface which intersects said ground circumferential surface band and is disposed on a side of said cutting knife blade opposite from said ground circumferential surface band, said rotary cutting knife blade holder means having a support surface which engages said cutting knife blade at a location adjacent to an inner edge of the bevel surface to resist deflection of the cutting blade away from its sliding contact with said bed knife in the presence of paper products being cut.