GB1361550A - Double chain stitch sewing machines - Google Patents

Abstract

1361550 Sewing machines PFAFF INDUSTRIEMASCHINEN GmbH 21 Feb 1972 [22 Feb 1971] 7861/72 Heading D1G A two thread chain stitch sewing machine in which work is fed by a feed dog and by needle swing has mechanism for varying the stitch length so arranged that when the needle and looper are in the loop seizing position adjustment of the linkage to effect that variation does not move the needle or looper. Thus the loop engaging action is not affected by such variation. A shaft 59, Fig. 2, driven from the armshaft carries eccentrics 74, 66, 79 and 57 which respectively oscillate the looper 72; feed dog lifting mechanism 67, 69, 68, 70, 71; loop spreader 77; and feed advance block 53 about its pivot 52. A block 50, selectively positioned in an arcuate slot 51 in block 53 by lever 54 and link 55, is connected by a link 48 to a crank 47 on the feed advance shaft 45 connected to the feed bar 63, with its integral feed dog, by a crank 64 and connected to the shaft 41 by link 44 and crank 43 to oscillate the needle bar gate 38. The centre of curvature of slot 51 lies on the pin 49 to achieve the object specified. In a second embodiment (Fig. 3) the shaft 45 is oscillated by a crank 95 connected at 96 to a link 94 embracing a pin 90 coupled to the rod 93 of an eccentric 92 on the arm shaft 33. Pin 90 is connected at 89 to the arms 87 of a yoke 86 by links 88. When parts 89 and 96 are aligned no motion is transmitted from the eccentric 92 to the shaft 45, parts 88 and 90 merely swinging about the common axis of 89 and 96. Rotation of the yoke by shaft 85 separates those axes and oscillation of shaft 45, with consequent feed motion results. Here shaft 85 is coaxial with pin 90 when the looper and needle are in the loop seizing position.