Patent GB-631561-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B51/00
Filed: 1947-11-05
Abstract: 631,561. Sewing-machines. NEWTON, E. P. (International Button Hole Sewing Machine Co.). Nov. 5, 1947, No. 29526. [Class 112] In order to control the thread during the formation of the first stitch in an operating cycle, so that the thread pulled off for this stitch is not slackened to make the stitch loose, there are provided a thread tension movable with the needle, a thread clamp, and a device acting on the thread between the clamp and the tension to draw thread through the clamp while the latter is open and to give up thread to the needle tension when the clamp is closed. Button-attaching machines; governing needle-thread in stitch-forming and otherwise. In the arrangement shown, in a machine for attaching flat buttons by means of an eyed needle 19 co-operating with a pair of oscillating loopers and loop-spreaders beneath the work, the thread passes to the needle via a tension device 38, a slot 53 in a lug on an arm 50, a thread clamp 40, an eye on a member 55 adjustably fixed to the arm 50, a fixed eye 46, and a light tension device 39 on the needle-bar, with intermediate guide pins 41. The arm 50 is fixed to a shaft 51, with a spring biasing it in an anti-clockwise direction, and another arm 59 on the shaft has a pin adapted to be engaged by a notch in a spring-biased pivoted latch 62 ; the arm 59 is connected by a link with a transverse lever 68 arranged for engagement with a cam 71 on the needle-bar shaft 37. At the end of a stitching operation, the needle is at the top of its stroke and the arm 50 is also in its highest position, being held by the latch 62 ; the thread is central in the slot 53 and is drawn out to the maximum by the member 56. When the button clamp is lifted by mechanism including a lever on a spindle 29, a transverse pin 66 in this spindle engages a pin on the latch 62 to make it free the arm 59, which rises to the position shown, lifting the lever 68 into contact with the cam 71. This cam, during the first needle descent of a new cycle of operation, allows the arm 50 to descend further, drawing thread from the supply and giving up thread below the clamp as the needle requires it, and then raises it again while the clamp is opened for a time by another cam, to release thread through the clamp ; the thread below the clamp is tensioned slightly during the last part of the needle descent to ensure the casting of a loop during the ascent of the needle. The thread end is drawn in to some extent during the ascent of the needle by the action of the looper and spreader, and also by deflection of the thread between the eye 46 and the needle, the tension 39 being ineffective to draw thread through the work. Near,the top of the needle stroke the cam 71 returns the arm 50 to the highest position, this movement pulling the thread slightly to bring the end below the button. The thread hardly moves in the needle eye during this first needle stroke ; subsequently the needle draws thread as required during the time the clamp is open, while the arm 50 is latched out of action. Specifications 476,079, 476,080, 476,081 and 476,082 are referred to.