Patent ID: 7070583

Claim:
A medical bevel needle ( 1 , 11 ) having an open bevel end surface ( 3 , 13 ) on the front-end portion ( 2 , 12 ) thereof, CHARACTERIZED IN THAT, when the needle axis is held horizontal with said open bevel end surface ( 3 , 13 ) facing upward, said bevel needle ( 1 , 11 ) comprises: (A) right and left front ground surfaces ( 5 , 15 ), disposed on said front-end portion ( 2 , 12 ), respectively positioned right and left with respect to a vertical plane containing said needle axis, said right and left front ground surfaces ( 5 , 15 ) crossing each other at the front end of said front-end portion ( 2 , 12 ) of said bevel needle ( 1 , 11 ), extending diagonally rearwardly and symmetrically with respect to said vertical plane; and (B) right and left rear ground surfaces ( 6 , 16 ), disposed on said front-end portion ( 2 , 12 ), said right and left rear ground surfaces ( 6 , 16 ) respectively succeeding said right and left front ground surfaces ( 5 , 15 ) at a longitudinal position where the lateral width between said right and left front ground surfaces ( 5 , 15 ) reaches a specified length, said right and left rear ground surfaces ( 6 , 16 ) extending diagonally rearwardly and symmetrically with respect to said vertical plane at an angle smaller than the angle of said right and left front ground surfaces ( 5 , 15 ) with respect to said vertical plane, said right and left rear ground surfaces ( 6 , 16 ) respectively having a tilt angle of 5π/12 to π/2 radians (75 to 90 degrees) with respect to the horizontal plane; said right and left rear ground surfaces ( 6 , 16 ) limiting the maximum lateral width between cutting edges ( 9 , 19 ), said cutting edges ( 9 , 19 ) being formed either by said right and left front ground surfaces crossing the external circumferential surface ( 4 , 14 ) of said bevel needle ( 1 ) or by said right and left front ground surfaces crossing said open bevel end surface; said right and left rear ground surfaces ( 6 , 16 ) respectively succeed said right and left front ground surfaces ( 5 , 15 ) at a longitudinal position where the lateral width between said right and left front ground surfaces ( 5 , 15 ) reaches a length equal to, or slightly smaller than, the radius of said bevel needle ( 1 , 11 ).