GB897563A - Thread cutting mechanisms for sewing machines - Google Patents

Abstract

897,563. Sewing machines. SINGER MANUFACTURING CO. June 22, 1960 [June 24, 1959], No. 21928/60. Class 112. Thread-severing means in a sewing machine comprise two relatively movable assemblies one of which has a thread-engaging finger and the other a thread-nipping finger biased against an abutment element, the thread-engaging finger being directed between the nipping finger and abutment element during relative movement of the assemblies in one direction, and not passing therebetween during relative movement of the assemblies in the opposite direction. The device is incorporated in a buttonholesewing machine. One of the assemblies is mounted on a movable bar 43 and comprises a blade 46 formed with a cutting edge 50, a threadengaging finger 47 formed with a thread-receiving notch 52, and a blade 48 formed with a threaddeflecting edge 53. The other and fixed assembly comprises a blade 62 formed with a cutting edge 65, a blade 63 formed with a lateral threadnipping finger 67, and a spring blade 69 having a lateral finger 71 which bears upon finger 67 to bias the latter against blade 62. Bar 43 is operated by the stopping mechanism at the end of a sewing operation, when a bevel 51 on blade 46 engages a forwardly-projecting guide finger 66 on blade 62, and the bobbin thread B is defected by edge 53 into notch 52. Blade 47 is also deflected by the bevelled outer edge of finger 67 to move between the latter and blade 62, Fig. 5, and thread B, thus pressed against blade 62, is held taut while being severed by the edges 50, 65. Towards the end of its inward travel blade 47 drops behind finger 67, Fig. 6, and the thread is then nipped between the latter and blade 62. The inner edges of blade 47 and finger 67 are so bevelled that blade 47 in its outward movement passes between fingers 67 and 71, whereby the thread is wrapped around finger 67, Fig. 7, and is pressed thereagainst by finger 71. When the machine is stationary a dimple 70 on spring blade 69 lies in a depression 75 in a work-feeding bar 16. After a predetermined number of stitches have been formed in a new operation, bar 16 moves to position dimple 70 on a land between depression 75 and a longer depression 76. The blade 69 is thereby depressed to release the thread, which will then be drawn off the finger 67. Dimple 70 subsequently passes into the depression 76. Specifications 225,748 and 226,133 are referred to.