Patent GB-909225-A (GB)
Title: Improvements in roll heads
IPC: B21H3/04
Filed: 1959-10-09
Abstract: 909,225. Rolling screw-threads; drilling ; chucks. NATIONAL ACME CO. Oct. 9, 1959 [March 9, 1959], No. 34290/59. Classes 83 (3) and 83 (4). A rolling head having several working rolls arranged about an axis is provided with a dogclutch having a cam surface which during axial separation of the clutch parts permits relative rotation thereof so that through intermediate means progressive radial movement of the working rolls is effected to form the work with variable diameters. In rolling the external surface of a tubular workpiece, the bore is resized with a drill having a reverse cutting edge and a chamfering tool forms the end of the work. A rolling head 15 comprises a shank 16 and a coaxial frame 18. The frame 18 includes front and rear plates 21, 22 and a housing 23 for a spiral spring 41, the three parts of the frame being bolted together, the bolts passing through slotted holes in the housing 23 for angular adjustment. Annularlygrooved thread rolls 31 are mounted on eccentric portions 34 of angularly adjustable shafts 35 which are arranged at a slight skew angle to the axis of the work 32 during rolling. Pinions 36 attached one to each shaft 35 mesh with a gear 37 which is journalled in the plate 22 and splined to the shank 16. Relative axial motion between the work 32 and the head causes a stop 55 and a slidable shaft 50 carrying a collar 44 to retract against a spring 51 to progressively disengage a clutch part 43 on the collar 44 from a clutch part 42 on the housing 23. The engaging surfaces of the clutch are inclined so that during progressive axial disengagement relative rotation of the rollcarrying frame 18 and the spindle 16 results under the bias of the spring 41. This relative rotation effects through gearing 37, 36 a rotation of the eccentric 34 so that the roll pass is progressively opened to form a tapered thread on the work. Disengagement of the clutch may be effected by a yoke attached to the work 32 acting on a disc 60 fixed to the clutch-collar 44. Either the head or the work may rotate and either the head or the work may be axially movable. On completion of the thread-forming operation the clutch disengages for 60 degrees rapid relative rotation during which the rollers are rapidly withdrawn radially of the work. The head is reset by rotation of the frame against the spring 41 using either manual, braking or inertial force. The surface 53 of clutch part 43 may take any form except axially parallel and can for example comprise two stepped formations for rolling threads of different diameters with a shoulder between. In a modified head for rolling tapered threads on a tubular workpiece a drill 70 and a chamfering tool 74 are fixed in the shank 16. In operation, the drill 70 enters the work 32A without cutting before the thread-rolling commences. The action of the rollers in rolling a tapered thread reduces the internal diameter of the work and at the completion of the threadrolling operation the end of the work is chamfered by the tool 74 and during withdrawal the drill 70 resizes the bore. Coolant is passed to the cutting tools axially through the shank 16 to emerge through a hole 86 in the tool 70. Swarf is removed through apertures 87 in the plate 21A. Specification 705,754 is referred to.