Patent GB-915794-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B49/02
Filed: 1961-11-02
Abstract: 915,794. Sewing - machines. UNION SPECIAL MACHINE CO. Nov. 2, 1961 [Nov. 21, 1960], No. 39232/61. Class 112. In a single-thread blindstitch sewing-machine the thread tension is released during a portion of each stitch-forming cycle. The machine comprises an upper arm 12 containing a main shaft 15, a work-supporting arm 13 spaced beneath and forwardly of arm 12, and an arm 14 extending downwardly from arm 12 and containing a shaft 19 which is oscillated from shaft 15. A crank-arm 18 on shaft 19 carries a curved needle 17. A presser foot 22 fixed to the end of arm 14 co-operates with a pair of upwardly-biased work-supports 23 (24) mounted at the end of arm 13. A work bender 26, carried by an oscillating shaft 27 in arm 13, operates through a slot in the presser foot 22. A forked looper 20 operates from a horizontal loop-seizing position to the right of the work bender, to a vertical position to the left of the work bender in which it passes through a slot 25 in the presser foot to present the taken thread loop to the next needle stroke. The work is fed by an upper feeding foot 21. Shaft 27 is journalled in a cradle 28 pivoted at 29 and 30 in arm 13. A spring 31 biases cradle 28 against a screw 33 for adjusting the height of the work bender 26. Cradle 28 is pivotally connected to an arm 37 on a sleeve 38 journalled on an eccentric 39 fixed to a shaft 40. A second arm 41 on sleeve 38 is connected by a link 43 to a variable throw eccentric 45 on shaft 15. A shaft 47 carries a gear 48 meshing with a gear 49 on shaft 40. A spring 46a acts on a segment 46 rigid with shaft 47 to bias an abutment 53 rigid with shaft 40 against a cam 52 controlled by a rotatable disc 50, for adjusting the angular position of eccentric 39 and thereby the field of movement of the work bender 26. A shaft 55 is biased by a spring 56 to move a knee press 54 on shaft 55 towards the right knee of an operator. An arm 59 rigid with shaft 55 is connected by a link 61 to an arm 63 rigid with a shaft 64. When the knee press 54 is operated, link 61 moves downwardly and a nose 65 thereon engages a stud 66 on gear 48 to rotate the latter. Eccentric 39 is also thereby rotated to alter the position of cradle 28 for lowering the work bender 26 beneath the work-supporting surface, Fig. 10. The work-supports 23 (24) are carried by respective curved arms 68 pivoted in alignment with shaft 64 and acted upon by springs 69 to bias the work supports upwardly. When the knee press 54 is operated, an abutment 71 on shaft 64 engages abutments 70 on the arms 68 to pivot the latter and thereby lower the work supports. The thread 72 passes to the needle via a thread lock 73, a thread tensioner 74, and thread guides 75 and 76. Thread lock 73 is carried by a detachable plate 85 and comprises discs 86, 87 biased together by a spring 89 but normally held apart by a vertical rod 91, the lower end of which engages an abutment 93 on shaft 55, whereby a collar 94 on rod 91 is biased by spring 50 into engagement with the lower surface of a fixed abutment 92. When the knee press 54 is operated to permit of work insertion or removal, abutment 93 moves away from rod 91 to allow spring 89 to clamp the thread between the discs 86, 87. The thread tensioner 78 comprises a pair of discs 98, 99 biased together by a spring 101 but adapted to be separated, for releasing the thread tension during a part of each stitchforming cycle, by a rod 103, which co-operates with a cam 104 on shaft 15. The arrangement is such that the thread tension is released from at least the instant that the point of the needle is withdrawn from the work to the instant at which the needle is fully retracted. U.S.A. Specifications 2,109,014, 2,588,274, 2,632,416 and 2,679,814 are referred to.