Patent GB-915672-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B3/24
Filed: 1961-11-01
Abstract: 915,672. Sewing-machines. GRITZNERKAYSER A.G. Nov. 1, 1961 [Nov. 9, 1960], No. 39028/61. Class 112. In a zig-zag sewing-machine a rotary shaft carrying means for appropriately controlling the stitch width, stitch position and work feed in order to sew a buttonhole, is moved step-bystep to successive positions by manuallyoperated means and a ratchet disc. The pivoted needle-bar gate 2 is connected by a link 4 to a block 6 slidable in a bar 5. The upper end of the latter is connected by a link 8 to one arm of a lever 9 on a shaft 10 provided with a handle 11, manipulation of which thereby serves to vary the stitch position. The other arm of lever 9 is formed with notches 12 engageable with a spring detent 13. The lower end of bar 5 is pivoted to one arm of a lever 7, the other arm of which is connected by a link 14 to a pivoted frame 15. A follower 18, mounted on frame 15, is biased by a spring 21 into engagement with a cam 19 on a driven shaft 20 for imparting oscillation to gate 2 via bar 5. A shaft 22 carries a cam 23 which co-operates with a follower pin 24 on a bar 26, one end of which is forked to embrace shaft 22 and the other end of which is connected by a bell-crank lever 27 and pin 28 to a member 30 rigid with link 4. Shaft 22 may be turned by a knob 58, thereby to shift block 6 in bar 5 for varying the stitch width in accordance with a scale 59 on knob 58. A spring 31 maintains pin 24 engaged with cam 23. A pivoted slide 39, the inclination of which controls the work feed, carries a pin 40 which is biased by a spring 42 into engagement with one end of a lever 38 having at its other end a feed-adjusting handle 41. Spring 42 also biases a projection 37 on lever 38 against one. end of a bell-crank lever 34, the other end of which carries a follower pin 33 which is thereby engaged with a cam 32 on shaft 22. Cam 32 is inoperative while knob 58 is turned through scale 59. A cam 43 on shaft 22 co-operates with a follower stud 45 on frame 15, and is formed with a single projection 44. A ratchet disc 48 on shaft 22 is formed with four notches 49. A plate 51, pivoted on shaft 22, carries a pawl 50 biased by a spring 52 against ratchet disc 48. A plate 53 on plate 51 engages a slot in one arm of a lever 55, the other arm of which has a handle 56 biased to a raised position by a spring 57. For buttonhole sewing, handle 11 is adjusted to set the stitch position fully to the right, and knob 58 is adjusted to a mark 60 to set the cams 23, 32, 43 and the ratchet disc 48 at position A. Pawl 50 then engages the first notch 49, cam 32 establishes forward feed, and cam 23 sets the stitch for maximum width, but projection 44 engages follower stud 45 to restrict the stitch to the left half of this width. The left side of the buttonhole is thereby sewn. Handle 56 is then depressed to set the controls at position B, when pawl 50 engages the second notch, cam 32 reduces the feed to zero, cam 23 retains the full width position, and projection 44 moves off stud 45 to establish full width sewing for producing the top barring stitches. When handle 56 is next depressed to set the controls at position C, cam 32 establishes reverse feed and cam 23 reduces the stitch to half width for producing the right side of the buttonhole. The next depression of the handle 56 sets the controls at position D, when feed is reduced to zero and the stitch width is increased to its maximum for producing the bottom barring stitches. At the final depression of handle 56 the controls are set at position E for zero feed and stitch width, to make the final locking stitches. Pawl 50 is now disengaged from the notches 49 and the machine is thus under normal manual control.