GB976275A - Improvements in or relating to thread cutting or trimming mechanism for sewing machines - Google Patents

Abstract

976,275. Sewing machines. G.M.PFAFF A.G. April 23, 1963 [April 26, 1962], No. 15883/63. Addition to 954,734. Heading D1G. In a sewing machine having a device which is adapted to catch the needle and looptaken threads and to feed these simultaneously to a stationary cutter, is of armate shape in conformity with the periphery of the looptaker, and is mounted between the looptaker and the feed dog on a carrier which is co-axial with the looptaker and which is in disengageable driving connection with the looptaker shaft, a control shaft parallel with the looptaker shaft comprises two coupled parts, one of which is connected to the thread-catching device, and the other of which is axially displaceable by a spring into operative engagement with rotary drive means associated with the looptaker shaft, one end of the spring abutting a member fixed to the displaceable part, and the other end abutting a sleeve which is displaceable on the displaceable part by foot or hand operated means. The looptaker 15 is carried by a shaft 14 coupled by gearing 12,13 to a shaft 11 coupled by a resilient belt 9 to the arm shaft 5. The thread catcher 17, similar to the thread catcher described in Specification 954,734, is connected by a link 23 to a crank 24 on a shaft 27. A bar 30, axially projecting from shaft 27, slidably engages a slotted collar 31 fast with an axially displaceable shaft 28 to couple the shafts rotatably together. A spring 32 biases bar 30 against a fixed stud 33 to retain the catcher 17 in an inoperative position. An arm 48 has an end which is journalled on shaft 11 and is biased by a spring 49 into engagement with a friction disc 52 fast with shaft 11, whereby arm 48 engages the end face 47 of a collar 46 fast with shaft 28 to maintain a follower pin 42, on a crank 41 on shaft 28, out of engagement with a cam groove in a cam disc 43 fast with shaft 11. A spring 35 is positioned between a collar 34 fast with shaft 28 and a sleeve 36 slidable on the latter. A lever 38 has one end forked to engage sleeve 36, and the other end connected by a link 40 to a treadle, depression of which, while the machine is running, serves to stress spring 35. When the machine stops, dissipation of the energy stored in belt 9 turns shaft 11 momentarily in the reverse direction, whereby arm 48 moves clear of collar 46, and spring 35 moves shaft 38 axially to engage follower 42 with cam 43. When the machine is re-started, shafts 27 and 28 are thereby rotated to operate the thread-severing device. On release of the treadle, shaft 28 is moved axially by a spring 44 to disengage the follower pin 42. It is stated that arm 48 may, alternatively, be operated positively by any suitable means. When shaft 28 moves in the cam-engaging direction, an inclined surface 54 on collar 46 cooperates with a pin 55 on one arm of a lever 57 for turning the latter to release the tension in a thread-tensioner 62 via a linkage 59, 60, 61.