Patent GB-879225-A (GB)
Title: Improvements in threading implements
IPC: B21H3/04
Filed: 1957-10-16
Abstract: 879,225. Rolling screw-threads. NATIONAL ACME CO. Oct. 16, 1957 [Oct. 17, 1956], No. 32341/57. Class 83 (4). Thread-forming means, relatively rotatable with respect to a workpiece to be threaded, include a shank, a thread forming tool or tools, gear means interconnecting the tool or tools and the shank to move the tool, at the completion of the threading operation, from a thread forming position, in which it is lockable, laterally outward away from the workpiece, and a friction clutch for re-engaging the lock means to re-set the head for a further threading operation. A thread rolling head 11 includes a shank 12, adapted to be gripped in the machine with which the head is to be used, and a frame 13 coaxial with the shank and carrying three thread-forming rolls 17, 18, 19 each journalled on an eccentric portion 34 of a slightly skew spindle 33 journalled in the frame. In operation a workpiece threaded by the rolls, on relative rotation between the workpiece and the frame 13, is fed forward by the' rolls until it engages the end 52, of an adjustable stop 51 on the shank 12 to move the shank 12 axially relatively to the frame 13, against the action of a spring 41 connecting the frame 13 and shank 12 until a dog clutch 44 formed between the frame and shank is disengaged. The relative rotation of the tool 11 relative to the work is counterclockwise, as viewed in Fig. 1, during threading. The spring 41 besides urging the frame 13 and shank 12 together, on account of its initially conical form; also tends to turn the frame counter-clockwise relative to the shank. Thus, as soon as the clutch 44 is disengaged the spring 41 turns the frame 13, counterclockwise, about 60 degrees relative to the shank 12 until steps on the clutch engage. This causes pinions 36 fixed on the ends of the roll spindles 33 to roll on a central gear 37 slidably splined on the shank 12. The spindles 33 turn and the eccentrics 34 thus rock the rolls away from the work, the axis 21 of the eccentric 34 of the lower roll 19, for example, moving counter-clockwise, as viewed in Fig. 1, around the axis 20 of the spindle 33 from a ten o'clock, work-engaging, position as shown in Fig. 1, to a seven o'clock position. The roll 19 in its withdrawal from the work, in. view of the skewness of its axis and the initial and final angular positions of the eccentric 34, moves slightly axially in the same direction as the relative axial movement of the head 11 with respect to the work during the thread rolling operation. To close the rolls, a cam handle 55 actuated by machine or by hand rotates the frame 13 clockwise 60 degrees relative to the shank 12. When the head 11 is used as a rotating head a friction yoke 59 may engage a tapered shoulder 58 formed on the frame 13 to, effect such relative rotation or the inertia of the frame 13 may be used, the shank 12 being decelerated and then decelerated by a motor controlled by a switch tripped by axial movement of the die head. Two rolls instead of three or other thread-forming tools instead of rolls may be used. Specification 705,754 is referred to.