Patent GB-613321-A (GB)
Title: Thread-case and carrier therefor for lock-stitch sewing machines
IPC: D05B73/12
Filed: 1946-06-18
Abstract: 613,321. Sewing-machines. SINGER MANUFACTURING CO. June 18, 1946, No. 18330. Convention date, Aug. 21, 1945. [Class 112] Lock-stitching-A loop-taker thread-case and its carrier, particularly for a rotary hook as used in the straight buttonhole sewing-machine described in Specification 419,923, are designed so that the case is latched to the carrier at widely-spaced points, to minimise shake of the case during operation ; a lever attached to the latch for withdrawal thereof is also adapted to be used as a handle for the case. The thread-case is designed for alternative use with the usual bobbin, unwinding from the outside, or a cop unwinding from the inside. An improved variabletension device on the bobbin-case comprises a flat spring pressing the thread against an adjustable shoe. The carrier is formed with a guard flange to keep the thread out of contact with the bearing-rib, and a plate to guide the needle loop over the rotation-preventing means and to control this loop while it is being drawn up after being cast off. In the form shown, the wall 23 Fig. 4, of the thread-case carrier is made conical, and its edge is of greater diameter than the bearing-rib 15 and is spaced therefrom to clear the gib which completes the raceway in the rotary hook body ; the needle thread is thus kept from contact with the lubricant on the bearing rib. The thread-case carrier is prevented from rotation with the hook by a pair of projections 18 which engage between stops which are adjustable on the machine frame transversely of the hook-shaft axis ; the needle-loop is guided clear of the projections 18, and is controlled while it is being pulled up after being cast off by a curved plate 30 shaped to merge into the conical wall 23 and having its pointed end projecting into a small hole in the wall 23. A notch 25 is provided to receive the usual vibrating member which opens a thread space between the rear projections 18 and its stop member at each stitch. The wall of the carrier is formed with a needle-slot 20, of which the sides serve to guide the needle and its thread-loop. The bobbin-case, Fig. 10, comprises a base 34, with a central thread hole 37 for use with a cop unwinding from the inside. and a cylindrical wall 35 with a thread slot 38, with threading-slit 39, for use with the usual bobbin. The case is secured in the carrier by a spring- pressed latch 40 sliding in undercut guides 41 and engaging at 44 and 45 with notches 46, 47, Fig. 4, in the carrier, the edges of the outer walls of these notches being chamfered as shown to allow the latch to snap into engagement when the case is pressed home. A cam lever 51, pivoted to the latch by a pin 52, engages a recess 54 in the base of the case to disengage the latch when lifted, and serves as a handle for withdrawal of the thread-case ; the travel of the latch is limited by a stop-screw 56 engaging in a notch 57. The screw 56 also serves to secure a spring member 58 which, when the latch is disengaged, presses against the periphery of the bobbin or cop to keep it in the case on withdrawal of the latter. A flat spring member 60, secured by a screw through its lower end and engaging a pin 64, bears against a shoe 61 which floats on the pin 64 and by means of a pin engaging a hole in the member 60 and is held up to the spring by an adjusting screw 69 to produce an adjustable tension in a thread passing between the members 60, 61. The thread is guided from the aperture 37 or 38 through the tension device over a guiding pin (not shown) and through a hole 74 in the rotation-preventing lug 63 which fits between the projections 18 on the threadcase carrier ; the thread is inserted into the hole 74 by way of a slit 72 and is held therein by being passed under a spring. The thread may be engaged by a pull-off member working in the notches of the members 18, 63.