GB414291A - Self-opening screw-cutting die head - Google Patents

Abstract

414,291. Die - heads. HAENGGI, C., 22, Neuweilerstrasse, Basle, Switzerland. Jan. 3, 1934, No. 241. Convention date, Jan. 7, 1933. [Class 83 (iii).] In a self-opening die-head a divided die R, Fig. 1, each part of which has two or more cutting edges r, is carried by two levers C mounted by means of a common pivot C<1> on a body B, Fig. 4, which is axially slidable within a holder A. The pivot C<1> is so positioned eccentrically to the plane of symmetry of the die that all the cutting edges r will leave the work simultaneously on opening of the head. The levers C are retained in the closed positions shown in Fig. 1 by means of pins h thereon engaging slots i, Fig. 3, in nuts d mounted on a right and left handed screw c. The nuts are square in section and are prevented from rotating by the flange on the holder A and the flat top of the body B. A conical screw e, located in a block a attached to the holder A, locks the screw c in any position to which it has been rotated in order to vary the cutting diameter of the dies. The dies are biassed towards the open position by springs t, Fig. 9, acting on pins t<1> which are axially slidable within sleeves m mounted in the levers C and attached to plates n slidable in slots in the holder A. These plates act as guides for the levers C and are adjusted to take up wear by means of screws p screwing in the sleeves m, rotation of the sleeves being prevented by feathers p<1>. In operation, the levers C are brought together by projections V thereon, operated by hand or automatically by a part of the machine, the pins h sliding along inclined surfaces on the nuts d until they snap into the slots i. Springs within the pins and abutting on plates k allow axial movement of the pins, the plates k also serving to prevent rotation of the pins. The saddle carrying the die-head is then pushed against the work, and after the required length of thread has been cut, further advance of the saddle is prevented by a stop on the machine. The screwing action then draws forward the body B relatively to the holder A, against the pressure of a spring g, Fig. 4, until the pins h have been pulled clear of the recesses i, whereupon the springs t open the levers C. Should the springs t fail to act, inclined surfaces w on the pins and recesses cause a gradual opening of the head to draw the dies positively away from the threads on the work. A flange f on the body B limits the axial movement of the body in the holder. Dies.-The parts of the divided die R have outer bevelled edges coacting with bevelled surfaces q, Fig. 4, in the levers C and are drawn into these surfaces, with clearance at the base, by means of screws s.