Patent ID: 9636734
Date: 2017-05-02
CPC Classifications: B21D,B21J,B21K,B60N

Claim:
1. A method during which is produced, in an outer wall of a tube extending along a longitudinal axis, through guiding punches in a working plane and in a working direction concurrent with the longitudinal axis of the tube, at least one notch comprising at least one locking flank, the method comprising the following steps: guiding a first punch in the working direction, a preforming tooth of the first punch extending from one end of the first punch and parallel to the working plane, an intersection of a leading end of the preforming tooth with the working plane forming a straight line, an intersection of said leading end of the preforming tooth with a plane parallel to the longitudinal axis of the tube forming a convex curve, exerting a preforming force onto the first punch so as to cause the preforming tooth to penetrate into the wall of the tube until obtaining a protuberance of material on both sides of the leading end of the preforming tooth, a solid cylindrical mandrel being positioned inside the tube, guiding a second punch in the working direction, a punching tooth of the second punch extending from one end of the second punch and parallel to the working plane, a leading end of the punching tooth having a shape complementary to a shape of the notch to be produced, and exerting a punching force on said second punch so as to cause the punching tooth to penetrate into the wall of the tube by a radial distance equal to the depth of the notch to be produced, a punching mandrel being positioned inside the tube, said punching mandrel having, near to a notching area, a groove containing a material displaced during the displacement of the second punch.