GB611877A - Improvement in thread-trimming and pull-off mechanisms for sewing machines - Google Patents

Abstract

611,877. Sewing-machines. SINGER MANUFACTURING CO. May 13, 1946, No. 14343. Convention date, Aug. 21, 1945. [Class 112] The bobbin-thread of a buttonhole sewing machine is trimmed, when the workclamp is opened, by a pair of moving blades, of which one is oscillated by a rack and toothed segment and the other receives a movement perpendicular to its plane, in addition to its cutting movement, so that it can lie normally clear of other moving parts. A bobbin-thread pull-off finger is carried by the same member as the oscillating trimmer-blade, and the rotationrestricting finger of the bobbin-case carries a resilient thread-controlling member. Thread-cutters.-An oscillating bobbinthread-trimming blade 43, Fig. 4 (underneath plan), is fixed to a carrier 44 which is mounted on a stud beneath the workclamp and is pressed upwards by a resilient member 47 fixed to the clamp base; the carrier 44 has teeth engaging a rack-bar 61 which is reciprocated across the clampbase when the treadle opening the workclamp is depressed. The bar 61 carries a leger blade 58, by means of an arm 60 formed on the latter, for co-operation with the blade 43; the blade member 58, 60 is resilient, and the blade is normally housed in a groove in the work-clamp base, as shown in Fig 10, so as to be clear of a thread pull-off finger 42 mounted on the carrier 44, being pressed downwards into operative position, as it moves towards the blade 43, by a fixed cam member 74 engaging the arm 60. A guiding lip 57 on the blade 43 prevents the blade 58 from moving downwards too far. Stitch-forming devices.-The bobbinthread is pulled off when the end is cut, to provide a sufficient length for the first stitch of the next buttonhole, by a finger 42, Fig. 4, fitting on the stud 45 in a recess in the trimmer-blade carrier 44. and adjustably secured.thereto by a clamping screw 53. The rotation-resisting finger 12 of the rotary-hook bobbin-case 11, which engages stops carried by the machine frame, carries a resilient thread-controlling member 15, Fig. 10.