Patent GB-263215-A (GB)
Title: Improvements in and relating to screw-cutting die heads
IPC: B23G5/12
Filed: 1925-09-16
Abstract: 263,215. Westerheide, W. Sept. 16,1925. Screwing ; die-head.-In a self-opening screwcutting die-head capable of cutting taper threads the dies 43, Fig. 8, are mounted for radial movement in a. body 42 and are adjusted by rotary motion of a cam plate 38 having eccentric slots engaging bolts 40 on the die-carriers. The cam plate is attached by a sleeve 37 to an annular casing 34 rotatable on the body 42 and enclosing two spiral springs 35 which tend to rotate the casing and cam in the opening direction. Normally rotation of the cam is prevented by a pin 33 engaging a radial groove 32 in the casing 34, but when the latter is drawn forward axially relatively to the head by the work, the pin is disengaged and the dies are free to open. A central interchangeable member 25 urged forward by a spring 57 carries a. plug 56 for engagement by the end of the work as it is drawn into the head by the dies, the member having an axial inclined groove 26, Fig. 9, coacting with a pin 27 in contact with a lever 29 which carries the pin 33. In operation the work is fed between the dies and as it is drawn forward the member 25 is pushed back so that the pin 27 may move inwardly, allowing the lever 29 to oscillate and the cam plate to rotate slightly and move the dies to cut a tapered thread. For cutting parallel threads the member 25 is replaced by one having a groove 26 parallel to the head axis. When a nut 44 on the spindle 45 of the member 25 meets an adjustable internal stop 46, Fig. 8, further progress of the work is arrested and the dies screw themselves forward and draw with them the casing 34 and the body 42, releasing the groove 32 from the pin 33 and allowing the springs 35 to open the dies. Should the dies fail to open immediately, further forward movement of the body 42 releases clutch teeth 48 through which the body is rotated by its driving spindle. Rotation of the dies is consequently asserted momentarily until a dog 49 on the rotating spindle engages a shoulder 50, Fig. 9, on the casing 34 so as to give further compression to the springs 35 and ensure the opening of the dies. A spring 52 rotates the body in the reverse direction when the dies are free to allow the clutch teeth 48 to re-engage through the axial pressure of springs 47. To reset the die-head a brake acting on a groove in the sleeve 37 restrains its rotation until the pin 33 snaps into the groove 32. To adjust the cutting diameter of the dies a screw 28 is provided in the lever 29, abutting against the pin 27. If threads of unlimited length are to be cut the members 56, 25 and 46 are removed and the pin 27 is replaced by a closing plug. A screwing machine embodying the die-head is described in which the work is gripped between lever jaws 1, Fig. 6, actuated by a right and left hand screw 2 and a hand lever 7, a clutch 8 being provided which may be locked by a screw 7a to prevent the jaws from being loosened by vibration during securing. A spring- pressed pivoted dog 14 on a rod 12 adjustably secured to the work carriage is adapted to coact with a projection on the end of a lever 15 attached to a shaft 18 carrying two opposed cams 20, the action being such that as the shaft 18 is rocked by movement of the work towards the die head, the cams 20 force together two shoes 22 against the pressure of a spring 23 and so draw together the ends of the brake band which closes the die head. The work carriage is traversed by a rack 11 thereon and a pinion operated from a handle 9 on the machine bed. The die head is rotated from a main shaft through cone pulleys d, e, Fig. 2, and two sets of gearing f, a clutch g controlled by a hand lever h determining the direction of rotation. Specifications 26969/98 and 253,690 are referred to.