Patent GB-447454-A (GB)
Title: Screw-cutting die-heads
IPC: B23G5/12
Filed: 1935-06-17
Abstract: 447,454. Screwing die-heads. HERBERT, SIR A., LLOYD, A. H., DRANE, H. A., and MALLINSON, H., c/o. Alfred Herbert, Ltd., Canal Road, Edgwick, Coventry. June 17, 1935, No. 17370. [Class 83 (iii)] In a screw-cutting die-head having a body carrying pivoted chasers and slidable axially on a support to allow opening of the head to be effected, the body carrying an adjusting ring and a closing ring and the support carrying a locking ring provided with pins coacting with the closing ring, the support consists of a ring portion mounted with slight clearance on a shank portion so as to float thereon and the ring portion, which carries the locking ring, has a firm axially slidable engagement with the body, towards which it is biassed. As applied to a non-rotary die-head, the body 11 has apertures for the trunnions 20 of pivoted die-carriers 13 which are oscillated by pins on a closing ring 14 rotatable on the body. An adjusting ring 16 is rotatable on the body by means of a tangential worm therein engaging teeth 32 on the body and the ring 14 is biassed to the open position by means of a tangential spring in the ring 16 engaging an axial projection on the ring 14. Provision is made for the spring to operate for either right or left-hand threading. A supporting ring 34 is mounted on a spigot 54 of the shank 49 with slight clearance and bevelled surfaces 55 are provided to allow the ring to float relatively to the shank. The body 11 carries a spigot 27 which is a firm fit in the ring 34. A locking ring 35 is slidable on the ring 34, forward motion being limited by a flange 36, and is provided with diametrically opposite locking pins 41 engageable with hardened bushes 42 in the closing ring 14 and passing through holes in the ring 16. Two driving pins 47 slidably engage holes in the body 11 and the supporting ring 34 and pass into clearance holes in the flange 50. Washers 22 are forced into the body 11 adjacent the ends of the trunnions 20 and the latter are secured by nuts 24. A plate 26 is mounted on the spigot 27, with shims between it and the washers 22 if necessary, and is secured to the body by axial screws. The supporting ring 34 is pressed against the plate 26 by string springs surrounding screws attached to the body, and the locking ring 35 is pressed against the adjusting ring 16 by light springs 40 on similar screws 39, Fig. 6. The ring 34 is pressed away from the flange 50 by light springs 51, this motion being limited by the heads of screws 52 in the ring engaging the flange. A flange 37 on the ring 16 covers the gap between this ring and the ring 35, as shown in Fig. 6, to prevent the ingress of cuttings &c. In operation, the die-head is fed towards the rotating work and when the desired length of thread has been cut, further feed of the head is prevented. The dies then draw the body and rings 14, 16 forward relatively to the flange 50 and rings 34, 35, thereby freeing the pins 41 from the bushes 42 and allowing the tangential spring to rotate the ring 14 to open the head. When the chasers are clear of the work the body and rings 14, 16 are moved backwards by the strong springs to engage the ring 34 and the closing ring 14 pushes back the pins 41 and ring 35 to the position shown in Fig. 6. On rotating the closing ring 14 either manually or otherwise the springs 40 reset the ring 35 to the locking position shown in Fig. 1. As applied to a rotary head the pins 41 are replaced by pointed pins 41<1>, Fig. 7, which lock the ring 14 by engagement of their cylindrical portions with the bushes 42. The locking ring 35 is allowed a larger movement by omission of the springs 40 from the screws 39 and this movement is effected by the closing ring 14 acting on the conical pins 411, which never lose contact with the bushes 42 so that on rearward movement of the head after automatic opening an abutment may engage the ring 35 to force it forwards and rotate the ring 14 to cutting position, in which it is again locked by the pins 41<1> springing forward. The rotary head has less floating motion than the stationary one this being controlled by omitting the springs 51, Fig. 1, and inserting springs 59, Fig. 7, around the screws 52, these springs biassing the flange 50 and ring 34 towards each other. The ring 34 may in this case be locked relatively tightly to the flange 50 by the screws 52. The stationary head of Fig. 1, may be changed readily into the rotary form of Fig. 7.