GB630639A - Improvements in or relating to thread tension devices - Google Patents

Abstract

630,639. Sewing-machines. BRITISH UNITED SHOE MACHINERY CO. (United Shoe Machinery Corporation) Ltd. June 13, 1947, No. 15590. [Class 112] In a thread-tensioning device, particularly for shoe-sewing machines, of the kind in which a member is rotated by the thread against the resistance of braking means, this means comprises a resilient friction element having a plurality of turns round a member coupled to the rotating member ; this arrangement secures more uniform thread tension in spite of variations in the coefficient of friction in the braking-means, since an increased grip on some coils of the friction element will cause slight unwinding of other coils to compensate. Means are provided for moving one end of the friction element to vary the friction during the stitch-forming cycle, and to relieve the friction when the machine stops. The device is described in connection with a chainstitch shoe-inseam sewing machine. Thread-tensioning devices.-The thread, on its way to the auxiliary take-up 10 and take-up 8, passes round a wheel 16 comprising a pair of toothed discs on a spindle 18, the rotation of which is resisted by a round-wire spring 23 coiled round a slightlyenlarged end of the spindle and provided with ends formed as shown to allow yielding : the left-hand end is adjustably secured at 26 to the frame of the machine, and the right-hand end to a link 32. Chain-stitching by barbed needles.-The link 32 is adjustably pivoted to a member 38 adjustably secured to the take-up arm 8, so that the element 23 is tightened round the spindle 18, to increase the thread-tension, while the arm 8 is taking up thread. Stopping-gear.-When the machine stops, an arm 58 is rocked slightly anti-clockwise, as described in Specification 548,344, and a member 48 rigid with this arm engages the left-hand end of the spring 23 to uncoil the spring slightly, and thus relieve the friction on the tension-wheel spindle 18. The arm 58 is held in the tension-releasing position by a latch 62 until the latter is withdrawn by a latch 66 engaging a notch in the hub of the take-up 8 when the machine starts.