Patent GB-334948-A (GB)
Title: Improvements in screw threading means for automatic lathes
IPC: B23B11/00
Filed: 1929-06-14
Abstract: 334,948. Bariquand, G. June 14, 1929. Screwing-dies and die-heads. - In screwcutting die-heads of the kind wherein the opening of the head is caused by rotation of the front part of the head under the action of transverse springs when the screw-threaded workpiece exerts a pull on the chasers and disengages the front part from locking pins, the locking pins and conically pointed setting pins are mounted on separate members, the setting pins being carried by a ring and guided by another ring which carries the large locking pins with a minimum of play between the parts. The chaser carriers, (not shown), are provided with trunnions 5<1> rotatable within holes 5 in the body 4 which is slidable on the shank 1 and is driven during securing by two pins 9 carried by a flange 10 on the shank. The chasers are operated by a rotary ring 6 having radial slots 7 engaging pivoted blocks on the chaser-carriers and an outer ring 8 prevents ingress of cuttings &c. to the slots 7. The ring 6 is locked in the closed position by one or more square ended pins 13 on an adjusting ring 14 which is prevented from moving axially on the shank but is rotatably adjusted to vary the effective diameter of the diehead by means of a tangential cam 25 therein engaging teeth on the periphery of the flange 10. The ring 14 is locked in the adjusted position by brake shoes 26. The closing ring 6 is rotated to the closed position by a conically ended setting pin 15 co-operating with a bush 17 in the ring and attached to a ring 18 slidable on a collar 19 attached to the flange 10 by screws 20. The ring 18 is normally pushed rearwards by springs 24, Fig. 2, into contact with a flange 32 on the collar 19. A flanged ring 21 is secured to the flange 10 by the bolts 20 and is graduated on its peripheral portion 22 to facilitate adjustment by the worm 25. The sliding movements of the ring 18 are guided by a pin 16 which is shorter than the pin 15 and does not pass beyond the front face of the ring 14. In operation, the diehead in the closed position is pushed against the work and is then drawn forwards bv the screwing action of the chasers. When the desired length of thread has been cut further motion of the shank 1 is stopped and the body 4, together with the chasers and the ring 6 moves forwards until the locking pin 13 is disengaged from its recess in the ring 6. A spring. (not shown), situated in a recess 14<1>, Fig. 2, in the ring 14 then rotates the ring 6 to disengage the chasers from the work. On withdrawing the die-head from the work, an abutment B engages the ring 18 and forces it to the forward position shown in Fig. 1, whereby the conical setting pin 25 rotates the ring 6 until the locking pin 13 is opposite its recess in the ring 6, whereupon the body 4 and ring 6 are retracted to the position shown in Fig. 1, by means of springs surrounding the headed pins 9', Fig. 2. On advancing the die-head towards a new work-piece the - springs 24 force back the ring 18 and pins 15, 16 as the ring recedes from the abutment 13, the length of the pin 15 being such that when the ring 18 is again in contact with the flange 23 the extreme end of the pin protrudes slightly beyond the end of the locking pin 13 so as to preserve engagement with the socket 17.