GB813229A - Thread-controlling means for sewing machine - Google Patents

Abstract

813,229. Sewing machines. SINGER MANUFACTURING CO. April 29, 1957 [May 24, 1956], No. 13509/57. Class 112 A check-spring device for taking up slack in the needle thread in a sewing machine comprises a mandrel formed with a reduced diameter neck, and a checkspring arm carrying a thread eyelet and adapted to pivot about the mandrel, the arrangement being such that said eyelet and the limb of thread extending from the latter to said neck pivot about substantially the same centre, whereby the thread passing through the eyelet is subjected to a minimum of abrasion on pivoting of the arm. In Figs. 7, 8 the check-spring device is combined with a disc-type thread tensioner. A mandrel 119 is fixed at one end in a cup-like member 116 secured by a grub screw 117 in the head 118 of a sewing machine. A check-spring has a coiled portion 125 mounted on the mandrel, the spring at one end of the coiled portion being anchored in a longitudinal groove 121 in the mandrel, and at the other end of the mandrel extending as a radial arm 123 ending in a thread-securing eyelet 124. An inner tensioning disc 127 abuts a shoulder 126 on the mandrel and is secured non- rotatably to the latter by a pin 138. A sector-shaped opening 141, subtending an angle of 80 degrees, is provided in disc 127. The outer tensioning disc 128 is pressed against disc 127 by a spring 133 mounted between a nut 132 on the end of the mandrel and a diameter-bar washer 131 which abuts disc 128. The thread 144 is gripped at a point 146 between the discs, and after passing over a reduced neck portion 137 of the mandrel, extends in a limb through the opening 141 to the eyelet 124 which is aligned with the neck 137. The latter is of small diameter, whereby the said thread arm which extends from a point 147 on the neck, and the eyelet which pivots about the centre of the mandrel, have substantially the same pivotal axis. Moreover, since the coiled portion 125 is loosely contained in the cup 116, said portion can distort when the spring relaxes on arm 123 moving upwardly, whereby the centre of pivoting of the latter moves slightly downwards and thus into closer agreement with point 147. The tension may be released by means of a rod 129. The check-spring device may be mounted separately from the thread tension device, the latter then, as shown in Fig. 6, being of the normal disc type adapted to grip the thread at two points. A mandrel 58 is screwed into the machine head 34. A cup 62 is gripped between the latter and a flange 64 on the mandrel. An inner disc 57 is supported on said cup and flange, and an outer disc 56 is pressed against disc 57 by a spring 68 interposed between a nut 67 and a diameter-bar washer 63 abutting disc 56. A rod 61 slidable in head 34, has an inner end which projects through a longitudinal bore in the mandrel and is adapted to engage washer 63 for releasing the spring pressure. The outer end 72 of rod 61 is adapted to be engaged by a cam surface 73 on a finger 74 carried by the presser-foot-lifting lever 79, whereby, when the latter is operated to lift the presser foot, rod 61 is moved inwardly against the bias of a spring 76 to engage washer 63.