Patent GB-507318-A (GB)
Title: Tension-releaser for sewing machines
IPC: D05B3/08
Filed: 1939-02-15
Abstract: 507,318. Sewing-machines. SINGER MANUFACTURING CO. Feb. 15, 1939, No. 4942. Convention date, April 26, 1938. [Class 112] In a buttonhole-sowing machine having rapid-feed moans to produce relative movement of the work and stitch-forming devices between the cutting and stitching positions, the needlethread tension is released at all times when stitching is not in progress by means controlled conjointly with the rapid-feed clutch, so that the tension - release operation requires no separate adjustment. The actuating force for the tension release is derived from the rapidfeed shaft, thus minimizing the load on the stitching stop mechanism. In the machine shown, the work-clamp 16, 17 is laterally slidable on a frame 27 which is longitudinally movable on the machine bed, the movements of the work-clamp being derived from an interchangeable pattern cam on a cross-shaft 34 and a feed-cam 12 geared to the shaft 34; the cam 12 is driven during stitching from the main shaft 13, which operates the stitchforming devices, through a train of gears including a pin and star-wheel connection giving step-by-step motion, and the shaft 34 is driven from the continuously-running rapidfeed shaft 36 through a worm-gear and a clutch which is controlled by an arm on a sliding transverse rod 42, Fig. 4, the clutch being normally held disengaged by a spring 54. The rod 42 carries a pin 43, for engagement with an operating member 48, and a latch-block 44 for engagement with a keeper 54<1> adjustable on a lever 55 which is pressed upwards by a spring 57 ; the member 48 is reciprocated by a crank 48<1> on the shaft 36 by means of a bell-crank 46, and is normally held in the position shown, against the action of a spring 49, by a latch 51, Fig. 8, which is actuated by an arm 64 on a rock-shaft 63. The take-up lever 78, Fig. 7, is pivoted at 77 on the top of the machine standard to work in a horizontal plane, and is actuated by a roller 79 engaging a groove 80 in a cam driven from the needle-bar shaft. The needle-thread passes through a guide 87 to the tension device 88 of the usual form, then through guides 89, 90, take-up eye 82, thread nipper 91, Fig. 1, and guide 92 to the hollow needle-bar 76. The tension-release rod 99 is actuated by a lever 100 which is pivoted at 101 and formed with a lug 103 for engagement by a screw in the upper end of a lever 105 pivotally mounted at 106 ; the lower end of the lever 105 has a face 110 for engagement with a cam-block 111 carried by the longitudinally-moving work-frame 27, and has adjustably fixed to it an extension 108 of which the end is adapted to be engaged by the pin 43 on the rod 42. The tension is held released by the cam 111 when the machine is at rest. When the machine is started, a lever 20, having a pin 24 which is engaged with a cam groove in a continuously-running free pulley 22 for one revolution and is then disengaged and latched out, receives from this cam an impulse causing it to close the work-clamp 17 ; on its return the lever 20 actuates a rod 113 to trip into operation a one-revolution clutch which drives the shaft 23 to operate the cutter blades, one of which is shown at 70. At the end of the revolution of the cutter shaft 23 a cam 66 thereon operates an arm 65 on the rock-shaft 63 to trip the latch 51, thus allowing the member 48 to rise during its reciprocation so that a notch in it engages the pin 43 and moves the rod 42 to the right, engaging the rapid-feed clutch; the pin 43 engages the member 108 to hold the tension released when the cam 111 moves clear of the part 110 during the movement of the work, and the rod 42 is latched in the right-hand position by the member 54<1>, while the member 48 is depressed on its return movement to be re-engaged by the latch 51. When the work reaches the position for sewing, a tripping point 61, Fig. 8, on the pattern wheel actuates a lever 62 to depress the lever 55, carrying the keeper 54<1> clear of the latch-block 44 to allow the rod 42 to spring to the left, thus throwing out the rapid feed and releasing the member 108 to allow the thread-tensioning device 88 to become operative ; the stop mechanism S is actuated at the same time by a cam on the pattern wheel to set the stitch-forming devices in motion. At the completion of the sewing, the pattern-wheel cam actuates the stop mechanism S to stop the stitching, and this movement of the mechanism raises a pawl 69 to operate a third arm 68 on the shaft 63 to recommence rapid feed and release the tension.