Patent GB-902346-A (GB)
Title: Improvements in or relating to sewing machines
IPC: D05B/
Filed: 1961-03-15
Abstract: 902,346. Sewing-machines. NECCHI S.p.A. March 15, 1961 [March 28, 1960], No. 9485/61. Class 112. In a zig-zag sewing machine adapted to sew buttonholes, the fabric feed and the lateral movement of the needle are controlled by cams driven through clutch means by a rotary shaft, means are provided for disengaging the clutch means to arrest the cams in predetermined angular positions corresponding to settings of the control means for sewing the respective sides of the buttonhole, and for engaging the clutch means for driving the cams to sew the respective end barring stitches, the clutch means being operable by a lever arranged to be actuated alternatively either by a lever adapted for automatic displacement by stops provided on a slide movable by the work being sewn, or by a manually operable lever. A sleeve 32, releasably fixed to a rotatably driven shaft 6, journals a cam block 40 formed with cams 13, 14, 15 adapted to control the mean lateral position of the needle 3, the stitch width and the work feed respectively, via cam follower levers 9, 10, 11 pivoted on a fixed pin 12. Block 40 is releasably coupled to sleeve 32 by a torsion spring 35, the free end of which abuts a finger 42 disposed with clearance in a recess in block 40 and rigid with a disc 36 journalled on sleeve 32. Holding disc 36 from rotation thereby serves to uncouple block 40 from sleeve 32. Disc 36 is formed with three shoulders 46a, 46b, 46c separated by surfaces 45a, 45b, 45c. A pawl 48, adapted to engage the shoulders, is fixed to the upper end of a hollow pivoted shaft 49, the lower end of which carries a lever arm 53. A spring 50 acts on shaft 49 to bias pawl 48 against disc 36. A presser foot support 57, fixed to the presser bar 55 by a screw 56, has a base 58 on which is slidably mounted a presser foot 59 having a serrated under surface 60 so that it can be displaced by the work. A bracket 61 rigid with the presser foot has adjustably fixed thereto, by means of a screw 64 passing through a slot 63, an inclined end stop 62. A second end stop 65 is rigid with bracket 61. A lever 67, pivoted at 68 on support 57, carries at one end 66 a pin 70 which normally rides on the upper edge 71 of bracket 61. End 66 is adapted to ride up the respective stops 62, 65, whereby lever 67 is swung in the direction W and its other end 69 engages the lever arm 53 to move pawl 48 away from disc 36. A shaft 96, journalled in shaft 49, carries a manually-operable lever arm 97 which lies between fixed stops 100, 101 and is normally biased against stop 100 by a spring 104. A cam follower lever 108, pivoted on pin 12, co-operates with a cam 114 rigid with cam block 40, whereby one end of lever 108 is adapted to be moved against the bias of a spring 109 to operate the button 106 of a micro-switch 105, mounted on lever 97, for stopping the machine. A manually-operable lever 23, when moved in the direction X is adapted, via a lever 20, to shift the cam follower levers 9, 10, 11, 108 away from the cam block 40. At the commencement of a buttonhole, pawl 48 engages shoulder 46c, lever 108 is depressing button 105, and end 66 is adjacent stop 62. To start the machine lever 97 is moved momentarily against stop 101 to release button 105 and also to shift pawl 48 away from disc 36 via a lug 115 on lever 97. Pawl 48 then rides on surface 45a and a portion 51a of the right-hand side of the buttonhole is sewn until pawl 48 engages shoulder 46a to arrest disc 36 while the remainder 52a of the right-hand side is completed. When end 66 engages stop 65 to release pawl 48, the latter then rides on surface 45b, whereby the feed is reversed and the bottom barring stitching 51b is produced until pawl 48 engages shoulder 46b for producing the left-hand stitching 52b. When end 66 engages stop 62, pawl 48 is released and then rides on surface 45c, whereby the feed is reversed and the upper barring stitching 51a is produced. When pawl 48 engages shoulder 46c, the needle swing and the work feed are both stopped, while follower lever 108 operates button 106 to switch off the driving motor. The inertia of the machine, however, enables the final locking stitches 52c to be inserted. A lamp 76 is provided to illuminate the work. In a modification, lever 67 is adapted to displace a spring-biased lever arm, whereby light from lamp 76 passes through an aperture in a fixed plate and falls upon a photo-electric cell which thereby operates a relay to energize a solenoid adapted to move pawl 48 away from disc 36.