| 摘要 |
756,935. Shears &c. WILKINSON SWORD CO., Ltd., and RANDOLPH, H. B. March 26, 1954 [April 1, 1953], No. 9081/53. Class 30. The cutting edge of at least one blade of shears &c. is convexly curved over a portion near the fulcrum the remainder of that edge being straight and the cutting edge of the cooperating blade being straight or convexly curved over a corresponding portion so that over that arc of opening during which the point of intersection of the cutting edges lies on the curved portion the angle of intersection between the cutting edges remains substantially constant. As shown, the cutting edges of blades 10 are recessed near the fulcrum 11 to form convex portions 10b, the angle of opening of the blades remaining substantially constant while the point of intersection of the cutting edges is on the part XY of the bisector 13 and being less than the angle of opening for straight edged blades 10c which intersect at W spaced farther from the fulcrum with consequent loss of mechanical advantage. Slipping of the material to be cut is avoided by forming the curvature so that the angle between the curved edge and the bisector is less than the friction angle for the material. In order to increase the rigidity of the blades they may be hollow forged as disclosed in Specification 756,928. According to the Provisional Specification toothed blade edges are provided as disclosed in Specification 706,296. |
