Patent GB-804854-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B15/04
Filed: 1955-07-14
Abstract: 804,854. Sewing machines BRITISH UNITED SHOE MACHINERY CO., Ltd. (United Shoe Machinery Corporation). July 13, 1956 [July 14, 1955], No. 20358/55. Class 112 Stitching by locking thread loops with free loops of thread. A loop lock-switch sewing machine for sewing soles to footwear comprises a curved hooked needle 2, Fig. 17, curved awl 4, a work support and a pressure foot 14 'for co-operation therewith, a loop spreader 6 for opening the needle thread loop to triangular form, a locking thread carrying finger 26 arranged to carry a loop of locking thread 60 through the loop of needle thread 57, and a detaining finger 28 for engaging the loop of locking thread during the withdrawal of the locking thread carrying finger. The two fingers are mounted and arranged so as to partake of the heightwise variations of the position of the presser foot due to variations in thickness of the work. A take-up is provided to give up needle thread to the needle as it retracts from the work and a locking thread controlling means is provided to withdraw locking thread from a supply and give it up while the take-up sets each stitch. Feeding of the work is effected by a swinging carriage 30, Figs. 6 and 10, to which the work support 12 is secured and to which a lever 32 carrying the presser foot is pivoted at 34. The presser foot releases the work during backward movement of the carriage. Alternatively, the invention may be applied to a machine in which feeding is effected by the awl. The finger 26 is provided with a guide sleeve 58 for the thread and is adjustably secured in a split clamp 44 bolted at 45 to an arm 46 on a pin 48 rotatable in a lug at the forward end of a carrier 50 clamped to a stud 52 mounted in a bearing on the bracket 41. The movement of the finger to and from the needle-thread loop is effected by a cam-actuated lever 68 mounted on a shaft 70 and coupled by a link 64 to an arm 54 mounted on the pin 48 and adjustably clamped to the arm 46 by a screw 56. A bar 82 on the carrier 50 slidingly engages a slot 84 in the lever 32 carrying the presser foot so that the heightwise position of the finger 26 corresponds with that of the presser foot. The detaining finger 28 is carried by a rod 92 clamped in a bar 94 which is clamped in an arm 96 fixed to a shaft 98 mounted in bearings in the lever carrying the presser foot. The finger is moved to and from the work by a cam-actuated lever 108 mounted on the shaft 70 and connected by a link 104 to an arm 100 on the shaft 98. The finger 28 has a rounded point 88, Fig. 12, which forms a definite indentation in the work, and has an enlargement 90 which ensures withdrawal of sufficient locking thread. before the needle thread loop is drawn into the work. The lower end of the loop spreader 6, Fig. 17, is forked to provide a hook portion 122 to effect loop spreading when moving in one direction, and a thumb portion 124 to cast the needle loop off the needle hook when moving in the other direction. The needle-thread take-up is associated with thread-measuring mechanism which automatically ensures the provision of more or less thread dependent upon the heightwise position of the presser foot. The thread is presented to the needle by a looper 8, Fig. 6. The supply of locking thread 60 is controlled by an arm 126 mounted on the loop spreader shaft 116 and carrying a flanged roll 128 which swings between the arm 132 of a W-shaped guide plate having guide eyes through which the thread passes. Thread is thus first pulled from a source of supply and is then released to the finger 26. Specifications 23478/10 and 532,026 [Class 112] are referred to.