GB863696A - Thread tensioning device in sewing machines - Google Patents

Abstract

863,696. Sewing machines. SINGER MANUFACTURING CO. Jan. 29, 1959 [Feb. 14, 1958], No. 3300/59. Class 112 A sewing machine comprises a rotary take-up, a thread-tensioning unit disposed under the takeup, a check spring anchored to the tensioning unit and having a looped extremity for engaging the thread extending between the tensioning unit and the take-up, a thread guide for engaging the thread between the tensioning unit and the take-up, and a check spring guard member secured to the tensioning unit and having a finger extending across the looped extremity of the check spring at a point disposed between the thread guide and the path of the periphery of the take-up. A thread-tensioning unit comprises a stud 30 carrying a hollow collar 35 formed with a peripheral groove 36 fixable by means of a set screw in the head 10 of a sewing machine. A thread-engaging wheel 49, disposed between friction washers 48, 51, is journalled on stud 30. Washer 48 abuts a guard disc 42 keyed to roller 35. Washer 51 abuts a pressure disc 52 slidably but non-rotatably mounted on stud 30. A spring 55, interposed between a nut 56 and the disc 52, applies pressure to the latter. Disc 42 is formed over half its periphery with an axiallyextending flange 45. A threading slot 46 extends peripherally from one end of flange 45 at the base thereof, and a finger 47 extends axially from the other end of flange 45. A check spring 22, keyed to stud 30 within collar 35, has a portion 59 which extends radially through a slot 38 in collar 35 and is bent into a loop 60 which extends across the periphery of the guard disc 42 in the gap between the ends of flange 45, the free end 61 of loop 60 being bent to extend inwardly beyond the outer face of disc 52. The thread tensioning unit is used in conjunction with a thread guide 19 carried on the presser bar 17, and a rotary take-up 13 journalled at 12 in the head 10 of the sewing machine. The tensioning unit is located immediately under the take-up and in a position such that stud 30, the guard finger 47 and the pivot 12 are substantially aligned. In threading the tensioner, the thread is drawn through the slot 46 which directs the thread on to the peripheral channel in the wheel 49. The thread is then looped around the latter till its free end assumes the position A, when the thread is disposed under both the finger 47 and the spring 61. The thread is then moved in the reverse direction, when it is guided by the flange 45 over the end 61 to enter the loop 60. The thread is then passed downwardly through the guide 19, and is then moved reversely to the position B, prior to being threaded through the take-up 13. In position B the thread extends over the finger 47, and the latter thus prevents the thread from re-entering the check spring loop 60.