Patent GB-862946-A (GB)
Title: Thread-chain cutter for sewing machines
IPC: D05B65/00
Filed: 1959-05-12
Abstract: 862,946. Sewing machines. SINGER MANUFACTURING CO. May 12, 1959 [May 26, 1958], No. 16207/59. Class 112 [Also in Group XXX]. Thread-cutters; driving; feed by clamps; lifting presser bars; work holders. In a sewing machine a thread chain extending between the stitching point and a stitched work piece is severed by engagement with an electrically heated wire. As shown, Fig. 4, a plunger 55, carrying a heated wire 59, is projected upwardly through an opening in the bedplate 5 of the machine at the end of a sewing operation, whereby the thread chain C extending to a work piece mounted on a clamp moved mechanically over the bedplate to produce a seam S, automatically engages the wire 59. The bedplate 5 of the sewing machine 2 is carried by a fixed table 1. The machine is driven, via a belt 9, by a continuously running motor 10 coupled to the machine when a clutch solenoid 14 is energized, and uncoupled when a brake solenoid 13 is energized. The sewing machine presser foot 21 is lifted, via a lever 23, when a solenoid 24 is energized. The work is clamped to a supporting plate 36, slidable on the bedplate 5, by a clamping bar 37 pivoted to plate 36 and biased downwardly by a spring 38. Plate 36 is fixed to a table 25 mounted for universal movement in a horizontal plane by means of wheels running on tracks 28 carried by a wheeled frame 27 which in turn runs on tracks 26 carried by a fixed table 3 and disposed at right angles to tracks 28. An arm 39, fixed to the clamping bar 37, is connected by a cord 40 to one arm 41 of a bell crank lever pivoted on table 25. When the latter approaches table 1, the other arm 43 is raised by engagement with a bar 44 carried by table 1 to lift the clamp bar 37. When table 25 moves away from table 1, bar 44 raises arm 41 to permit the spring 38 to lower the clamp bar 37. A motor 29, mounted on table 25, is connected by a belt 30 and gearbox 31 to a vertical spindle 32 carrying at its lower end a gear pinion 33 meshing with a toothed track 34 mounted on table 1. An operation of motor 29, table 25 will be traversed through a path defined by the track 25 to produce the seam S. The work is loaded on to and unloaded from plate 36 by a mechanism comprising a sleeve 45 slidable on a fixed rod 46. Sleeve 45 is moved by a reversible motor 47 coupled by an endless belt 49 to an arm 52 on sleeve 45. A fresh workpiece is transferred from table 1 to plate 36 by engagement with arm 52, and a sewn workpiece is simultaneously removed from plate 36 by the attraction between an electromagnet 53 on sleeve 45 and a metallic insert embedded in a work-holding element having upper and lower plates between which the workpiece is sandwiched. The plunger 55 carries at its upper end the thread-severing wire 59, and is connected at its lower end to the armature of a solenoid 70, current being supplied to the wire via leads 66, 69. The motor 11 is operated by high voltage leads 75, and the remainder of the apparatus via low voltage leads 73, 74. To initiate an operation, a solenoid-actuated starting switch 76 is momentarily energized via a lead 77 to close a solenoid - actuated holding switch 78, whereby motor 29 is energized via a normally closed stop switch 79, carried by table 25, to traverse the latter. A cam 85 on table 25 then moves away from a switch 86 to allow the latter to close for de-energizing the presser foot-lifting solenoid 24, and a double acting switch 81, carried by table 25, moves off a fixed cam 82, whereby the brake solenoid 13 is de-energized and the clutch solenoid 14 is energized for driving the sewing machine 2. At the end of the stitching cycle, switches 81 and 86 are again operated for stopping the sewing machine and raising the presser foot. Near the end of the traversing cycle switch 79 is momentarily opened by passing engagement with a fixed cam 80 to stop the motor 29, and a switch 83, carried by the table 25, is also momentarily closed by passing engagement with a fixed cam 84. Closure of switch 83 energizes the solenoids of solenoidactuated switches 87 and 93 via a limit switch 89. Switch 93 thereby closes to energize the workremoval magnet 53, and in switch 87 a pair of normally closed contacts opens and two pairs of normally open contacts close, whereby the forward rotation coil 90 of motor 47 is energized to initiate movement of sleeve 45. The workshifting arm 52 on the latter thereupon allows a limit switch 88 to close, whereby switches 87 and 93 continue to be energized after switch 83 opens. At the end of the forward movement of sleeve 45, an arm 92 on the latter opens the limit switch 89 and the switches 87 and 93 are thus de-energized, whereby the reverse rotation coil 91 of motor 47 is energized via switch 88 and the normally closed contacts of switch 87. When sleeve 45 returns to its initial position, arm 52 opens switch 88 to stop motor 47. When switch 81 is reversed at the beginning of the stitching cycle, a solenoid 102 is also energised to close a pair of contacts 101 after a time delay determined by a dashpot 103. Closure of contacts 101 serves to energize a solenoid 99 to close a pair of contacts 97 in the primary coil of a transformer 96, the secondary coil of which serves to heat the thread-severing wire 59. At the end of the stitching cycle, when switch 81 is reversed on energizing cam 82, solenoid 102 is de-energized, but the opening of contacts 97 is delayed by a dashpot 100. On initial forward movement of sleeve 45, an arm 94 thereon closes a switch 95 to energize solenoid 70, whereby plunger 55 is moved upwardly to position the heated wire 59 in the path of the thread chain C.