PAPER TRIMMING KNIFE SYSTEM

A rotary cutting knife for trimming signatures of multiple thicknesses of paper, such as folded press products, said knife having sharply pointed teeth around the periphery thereof, one surface of each tooth being planar, within the plane of one surface of said knife, and the edges of said teeth being beveled from the opposite surface at an acute angle to said one surface of said knife to provide camming surfaces on said teeth operable to engage a plurality of superimposed sheets of paper, including especially sheets folded upon themselves, and prevent the same from moving away from said planar surfaces of said teeth while shearing such paper by coaction of said teeth with a rotary bed knife having a planar face slidable in shearing relationship with said planar surfaces of said teeth on said cutting knife. During a rotary shearing operation, leading teeth of said cutting knife engage and progressively pierce the adjacent surfaces of said sheets of paper to maintain an intended line of cut accurately in alignment with the planar surface of said cutting knife and such penetrating movement into said paper continuing at least to the full depth of said teeth for shearing coaction with said rotary bed knife and thereby form a smoothly sheared accurate edge along one side of said paper.