Knife for cutting out clippings

Claim 1

A knife for cutting out clippings from a sheet of paper, comprising a knife blade of generally planar shape and having a contact surface substantially perpendicular to the plane of the blade for sliding contact with a surface of the paper and a cutting edge disposed in the vicinity of said contact surface and extending beyond the contact surface by a cutting depth distance, said contact surface having a contour of a convex fair curve, when viewed in the direction perpendicular to the plane of the blade, of a large radius of curvature, the relationship between the dimensions and shapes of said contact surface and the cutting edge being so selected that the depth of cut of the cutting edge into the paper can be adjustably varied by varying the angular attitude of the knife blade relative to the paper, said contact surface having a contour of a convex fair curve formed by an edge surface of a bulbous projection extending rearwardly with respect to the cutting direction of the knife, the blade piece in planar view having two long sides and at least one short side at an acute angle to one of the long sides, the short side forming a straiGht cutting edge with a cutting tip at the vertex of the acute angle, the contact surface being parallel to the cutting edge for a major portion of the length of the cutting edge then rising arcuately from a point slightly forwardly of the cutting tip with respect to cutting advance of the knife and extending rearwardly of the cutting tip along the arc progressively departing thereby from the straight line portion parallel to the cutting edge, the cutting edge extending beyond the contact surface along the parallel portion by a cutting depth distance corresponding to the small thickness of a single sheet of paper, whereby when the knife is held at an angle to the surface of the paper with the parallel portion of the contact surface in contact with the paper, the cutting edge is limited by said contact surface portion to cut the paper only to a depth substantially equal to its thickness, the arcuate portion of the contact surface being such that for varying thicknesses of single sheets of paper the knife may be tilted progressively rearwardly to cut increasing thicknesses of single sheets of paper, the use of the knife in upright attitude to the paper positioning a portion of the arcuate portion of the contact surface in sliding contact with the paper at a point rearwardly of the cutting tip with respect to cutting advance of the knife.