GB899978A - Thread tension device for sewing machines - Google Patents

Abstract

899,978. Sewing machines. FAIRWEATHER, H. G. C. (Singer Manufacturing Co.). May 31, 1960, No. 19300/60. Class 112 In a sewing machine thread tension device the knob which is turnable to vary the spring force on the tension discs is releasably mounted on its rod to allow the tension discs to be removed. The thread tensioning device comprises a rod 4 mounted in a boss 2 in a sewing machine head 1 and rotatable in the boss by a knob 10 the nut 23 then moving along a threaded portion of the rod to vary the compression of a spring 31 urging a sleeve 29 outwardly to press together the tension discs 32. Rotation of the nut 23 is prevented by ears thereon which enter slots 25 in a barrel 26. The barrel is slidable within a bore 3 in the head 1 and is engaged at 36 by one end of a first order lever 33 connected to the presser-bar lifting-lever 45 so as to be rockable about its pivot 34. When the foot is raised the barrel 26 is moved to the position shown, together with the sleeve 29, to release the discs 32 from the spring pressure and release the thread tension. In another embodiment (Figs. 5 and 6, not shown) the spring 8 is replaced by a bifurcated leaf spring engaging a groove in the shaft 4. In both embodiments the knob 10, discs 32 and rod 4 may be moved and replaced without disturbing the other parts of the device contained within the bore 3. The check spring is separated from the tension device. The check spring arbor 55 is secured in an angularly adjustable position in a boss 54. The check spring is coiled around an enlarged portion 57 of the arbor and has one end anchored in a selected one of a number of grooves 58 provided in the portion 57. A spacer 61 having a threading groove 62 and a guide plate 63 having a thread guide and stop for the free end 64 of the check spring are secured to the free end of the arbor 55. Specification 800,727 is referred to.