GB893925A - Screw thread cold-rolling machine - Google Patents

Abstract

893,925. Rolling screw-threads. SOC. INDUSTRIELLE DE DELLE. June 10, 1960 [June 18, 1959; Nov. 17, 1959], No. 20578/60. Class 83 (4). In a machine for cold-rolling screw-threads comprising two threaded rolls mounted on parallel spindles rotating in the same direction at different tangential speeds, at least one of the rolls is mounted on a spindle so as to be capable of slight angular oscillation relative to a plane perpendicular to the spindle and is associated with elastically-yieldable biasing means for returning the roll to a mean position and means are provided for feeding the blanks between the rolls by gravity. To attain the differential tangential speed for moving the blank through the pass, the rolls may differ in diameter or have differing angular speeds of rotation or may have both differing diameters and angular speeds. One of the rolls is adjustable in the plane of the spindles to vary the pass. When a blank enters the pass, under the influence of its own weight, for example, the blank is rolled immediately if the rolls happen to be in phase. If, however, the rolls are not in phase the roll A impresses shallow furrows in the blank, while the roll B tends to slide over the smooth surface of the blank due to insufficient feed pressure until such time as the rolls come into phase at which point the crests of the thread on the roll B enter the furrows formed by the roll A and rolling proper commences. The rolls A, B may be fixed relative to their axes of rotation or if precise screw threads are required provision is made for slight angular movement of one or both of the rolls relative to a plane perpendicular to the spindles. The maximum movement at the periphery corresponds to one pitch of the thread if only one roll is movably mounted; the amount of movement may be halved if both rolls are so mounted. Figs. 7 and 8 show different methods of mounting the rolls A and B for angular movement relative to the plane of rotation. In Fig. 7, spherical seatings 40, 41 attached to the roll-body permit angular movement under the restraint of rubber washers 47, 48 which return the roll to a mean position. Clearances J1-J4 permit the movement. The roll is driven through a pin 39. In Fig. 8, the arrangement is similar but the seatings 40, 41 are replaced by a swivel rollerbearing 56. The rolls are cleaned by brushes 11 and jets of lubricating and cooling oil are directed on to the rolls. Metal screws, wood screws, self-tapping screws, coach screws and worms may be threaded with single or multiple start.