GB859999A - Improvements in or relating to sewing machines - Google Patents

Abstract

859,999. Sewing machines. MEFINA S.A. Feb. 12, 1957 [Feb. 18, 1956], No. 4742/57. Class 112 In a zig-zag sewing machine wherein lateral movements of the needle bar are imparted directly by the profile of a cam capable of controlling at each revolution a cyclic number of stitches, and an adjusting member permits of varying the amplitude of said movements, a device is provided comprising at least one auxiliary cam and capable of varying cyclically, during a cyclic number of 'stitches higher than the original cyclic number, the amplitude of the lateral movements of the needle bar. A machine generally similar to that described in Specification 683,291 is modified by the provision of an attachment, enabling the manually operated stitch width and needle centering adjustment means to be controlled automatically by cam means. The original pattern cam 1, driven by a rotary shaft 13, co-operates with a follower pin 2 carried at one end of an arm 3 the other end of which is pivoted at 4 to one arm 5 of a bell crank lever 5, 19 pivoted at 6 to the machine frame 7. A surface 8 on arm 3 is engaged by a roller 9 on a bar 10 which is pivoted to the needle bar gate. An extension 11 of the pivot of roller 9 is embraced by a forked member 12 which is pivoted on shaft 13 and has a handle 16, whereby roller 9 may be shifted from a position at the end of arm 3 to produce stitches of maximum width to a position coincident with pivot 4 to produce straight stitching. A pin 20 on the end of arm 19 is biased by a spring 24 into engagement with a spiral cam 21 formed internally of a wheel 22, rotation of which, by pivoting lever 5, 19, serves to adjust the neutral position of the needle bar. To convert the machine to automatic control, cam 1 is removed and a support 39 is secured to frame 7, said support carrying a sleeve 41 which fits over shaft 13. Journalled on the lower end of sleeve 41 is a cam 1a having nine identical lobes, and journalled on the upper end of sleeve 41 is a ratchet wheel 44 formed with ninety ratchet teeth 52. A pawl 42 engages the latter to prevent counterclockwise turning of the ratchet wheel. One arm 48 of a lever pivoted at 47 to support 39 carries a pin 49 biased into engagement with cam 1a by a spring 58. The other arm 50 is formed with a slot 54 having three notches 55 in one of. its edges. A pin 53, carrying a pawl 51 adapted to engage the teeth 52, is held in any one of said notches by a spring 56. The arrangement is such that when pin 53 occupies the notch nearest the pivot 47, pawl 51 engages successive teeth 52 on rotation of cam 1a, when pin .53 is in the intermediate notch pawl 51 engages every second tooth, and when pin 53 is in the farthest notch pawl 51 engages every third tooth. Pawl 51 may be retracted from teeth 52 by manipulation of a lever 62, one arm of which has a cam surface 65 adapted to co-operate with a surface 66 on arm 48. Lever 62 is held in adjusted position by friction at its pivot 61. A set of three cams 67, 98, 107 is supported by wheel 44 and is coupled to the latter by a pin 45. A follower finger 68 engages cam 67 for the automatic control of stitch width. Finger 68 is formed on one arm of a lever 69 pivoted.on a fixed pin 70. The other arm of lever 69 carries a plate 72 formed with a cam edge 73. One end 74 of a link 75 bears against edge 73 and. the other end is pivoted at 85 to a member 86 slidable axially in a cylinder 87. End 74 is pivoted at 92 to one end of a link 76, the other end of which is pivoted at 77 to a plate 78 journalled on the sleeve 41. An arm 79 on plate 78 is acted on by a spring 84 to hold end 74 against edge 73, and a plate 81 carried by arm 79 is formed with a notch 82 adapted to fit over the stitch width-adjusting lever 16. A spindle 90 screwed into slide 86 carries a knob 91, rotation of which serves to shift end 74 along edge 73, the position of end 74 being indicated by the position of a pin 95 on slide 86 in a graduated slot 94. End 74 in its innermost position transmits maximum displacement to arm 79 on oscillation of lever 69. When end 74 is shifted outwardly to align pivots 70 and 92, and pin 95 is positioned opposite the zero graduation, no movement is transmitted to arm 79. End 74 may be shifted temporarily to zero adjustment by pulling knob 91 outwardly against the bias of a spring 88. A nose 106 is adapted to co-operate with cam 98 for controlling the neutral position of the needle. Nose 106 is provided on an arm 99 pivoted on the pivot pin 4 of arm 3. A resilient plate 100, fixed to arm 99, is formed with a pair of spaced holes 104, 105, either of which may be engaged with a pin 103 on arm 5 for respectively engaging and disengaging nose 106 and cam 98. Cam 107 cooperates with a nose 33 on a lever 31 for automatic control of the feed. The machine may be modified for sewing buttonholes. For semi-automatic control, cam 67 is of the form shown in Fig. 6, and has an outer portion 108 corresponding to the sides 109 of the buttonhole and a notched portion 111 corresponding to the ends 112, 113. Needle centering and feed are controlled manually. For fully automatic control, a second notch 111a is provided for end 113, and suitable cams 98, 107 control the needle centering and feed. Specification .779,038 and U.S.A. Specification 2,682,845 also are referred to.