GB827883A - Improvements in or relating to stop motion devices for power-driven sewing machines - Google Patents

Abstract

827,883. Sewing machines. JOHNSTON, ALLEN & CO. Ltd. Jan. 7, 1958 [Jan. 15, 1957], No. 1488/57. Class 112 [Also in Group XXXVII] Stopping, alarms. A stop motion device in a sewing machine comprises a pair of fixed contacts, a corresponding pair of movable contacts, a pulley adapted to be driven by the upper thread being drawn from a supply source, a cranked member mounted eccentrically on said pulley and adapted, when the latter rotates, to move, in turn, the movable contacts away from the fixed contacts, the arrangement being such that if the thread breaks or the pulley rotates below a predetermined speed, one or other of the movable contacts engages the corresponding fixed contact and closes a circuit to stop the drive. A pulley 34 is rotated by needle thread 36 and carries a cranked pin formed with portions 38, 40 adapted to engage alternately the free ends of arms 41 pivoted at their other ends as at 42, so as to raise contacts 43 on said arms from corresponding fixed contacts 42. Each arm is provided at its pivot with a fin 44 which dips into viscous liquid in a container 45 to damp the fall of the arm. If the pulley stops or slows down, one or other of the pairs of contacts closes to complete an electrical circuit adapted to stop the machine, preferably by disengaging a driving clutch. A signal lamp 32, is simultaneously lighted. In a modification the arms are pivoted intermediate their lengths. Governing threads. The device is mounted in a casing 10 fixed to a hollow vertical post 11 carried by a base 12. A thread cone 13 is carried by a sprocket 14 journalled on post 11 and rotated to feed off the thread 36. The latter passes over a hook 16 at the top of post 11, through a tensioner 33, around pulley 34, and from thence passes to the needle.