GB744610A - Needle positioning device for sewing machines - Google Patents

Abstract

744,610. Sewing-machines. SINGER MANUFACTURING CO. Jan. 21, 1953 [Jan. 30, 1952], No. 1720/53. Class 112. [Also in Group XXIV] A sewing-machine has primary and secondary (slow-speed) driving mechanisms, the latter including a continuously-rotating electric motor, with control means for bringing the needle to a predetermined position by means of the secondary mechanism. The invention is described in connection with a machine which is driven through a clutch element 34 slidable on its shaft 26, which also carries a cam 59 to open contacts a, b when the needle is in its lower and upper positions respectively. The element 34 is normally spring-pressed into engagement with a pulley 29 belt-driven through the usual clutch and brake arrangement on the shaft of an electric motor controlled by a treadle 77 so that when this treadle is depressed the machine is driven by the motor, and when the treadle is released the drive is held stationary and the pulley 29 acts as a brake on the machine. The treadle 77 is connected to the clutch-operating lever 69 through an arm 75 pivoted on the lever and biased to a position midway between stops 78 by a spring 80. When the treadle is released from the running position to stop the drive, the arm 75 closes a switch 81 to energize, through contact b, an electromagnetic clutch element 44 which is continuously rotated at slow speed by a secondary electric motor ; the element 34 is thus drawn away from the stationary pulley 29 into engagement with the element 44 and the machine is thus driven at a low speed until the contact b is opened when the needle reaches its upper position, the electromagnet being then de-energized to allow the element 34 to return into engagement with the pulley 2a and thus stop the machine. If it is desired to stop the machine with the needle in its lowest position, the treadle is " heeled " to operate a changeover switch 83 to bring the electromagnet under the control of the contact a, a further reversal then being possible by a change-over switch 85 actuated by moving a presser-lifting knee-lever 87 beyond its presser-lifting position. Slow stitching may be performed by oscillating the treadle between the neutral and " heeled " positions to produce successive half-revolutions of the machine. In a modified arrangement, Fig. 8 (not shown), the switch 85 is replaced by a double-pole manual reversing switch (113) and the switch 83 by a similar switch (110) actuated by a knee-lever, and a manual switch (114) is provided to connect the two sides of the reversing switch, so that the electromagnet is fed through both contacts a, b and continuous slow running is thus obtained until the switch 114 or switch 81 is opened. The switch 81 may be placed on the mains side of the rectifier 92. Specifications 694,769; 744,652 and 744,660 are referred to.