Patent GB-940078-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B23/00
Filed: 1961-07-31
Abstract: 940,078. Sewing-machines. G.M.PFAFF A. G. July 31, 1961 [Aug. 27, 1960], No. 27649/61. Heading D1G. Labels, attacking by stitching; feed by foot. To permit a label to be sewn on to material by a closed seam a sewing machine has its work engaging plate suspended from a carrier by a cranked shaft rotatably journalled in the carrier. The sewing machine includes a control disc 6 provided on opposite faces with cam grooves 7 and 8. The groove 8 engages a lever 12 adjustably connected at 15 to a post 16 on a slide 17 and imparts to the slide movements along the axis of the bed 1. A lever 11 engaged by the groove 7 is connected to one arm of a bell crank lever pivoted within the bed, the other arm being connected to the slide 17 to impart transverse movement to it. A member 19 secured at one end to the slide 17 carries at its other end a presser plate holder 21 which can be moved vertically against the leaf spring 22 by the lifting rod 40. A carrier 23 attached to the holder 21 carries a sliding member 30 biased to the right, as seen in Fig. 1, by a spring 35. The cranked shaft 25 is journalled at one end in the carrier and supports the presser plate 26 rotatably suspended from its other end. One of the crank webs has an extension 27, a pin 28 extending therefrom engaging with a cam surface on the sliding member 30 to hold the crank over to the right, as seen in Fig. 1, at the start of a label sewing operation, the needle axis then passing between the crank cheeks. The cranked shaft remains in this position until the last stages of the sewing cycle. The carrier 23 and its presser plate is moved by the member 19, after an initial advance and retraction to lock the beginning of the seam, so that the needle sews around the perimeter of the presser plate. Towards the end of the seam, as the crank 25 approaches the needle again a nose 37 on the slide 30 engages one end 38 of a lever 41 pivoted to the lifting rod 40, the slide then moving relatively to the carrier against the spring 35 to cause the cam surface engaging pin 28 to rotate the crank away from the approaching needle, which then enters between the crank cheeks to complete and close the seam. When the rod 40 and plate 26 are raised by the lever 58 and the other end 43 of the lever 41 engages the head 4 of the machine to move the end 38 clear of the nose 37 to allow the slide 30 and the cranked shaft to be returned to their previous position by the spring 35. In a modification, (see Fig. 6) the crank-shaft is provided with a pinion engaged by a sector rack 71 pivoted to the holder at 70 and spring biased to move crank into the starting position. Towards the end of the stitching cycle a pin 71a on the rack engages a nose 75 on the rod 40 to rotate the crank as before. Starting and stopping. To prevent starting of the machine unless the rod 40 has been raised to permit the crank to assume its starting position, the starting lever 47 is connected by a link 46 (see Fig. 5) to a safety lever 45 pivoted at 44 to the machine and provided with a slidable locking plate 48 biased upwards by a spring 53. In the position shown the lever 47 and hence the lever 45 cannot be moved to the starting position as the element 59 on the lifting lever 58 lies in the path of the raised plate 48 on the lever 45. Actuation of the lever 58 to lift the presser plate engages element 59 with stop 57 to depress the plate 45, the plate end 51 engaging the spring 56 to hold the plate down against its spring. The levers may then be moved to the starting position, when the elements 51, 56 disengage.