GB1006150A - Bobbin thread pull-off for sewing machines - Google Patents

Abstract

1,006,150. Sewing machines. SINGER CO. May 11, 1964 [May 14, 1963], No. 19502/64. Heading D1G. In a lockstitch sewing machine comprising a rotary looptaker, rotation of the bobbin is frictionally braked to impart tension to the thread drawn therefrom, and a bobbin thread pull-off device, arranged adjacent the feed bar, is actuated by the means for inparting feed lift movement to the feed bar to move in a substantially constant path relatively to the feed bar for drawing from the bobbin once during each needle reciprocation only a portion of the bobbin thread required for the next stitch. A vertical axis rotary hook 17 houses a bobbin case 63 containing a bobbin 72 having an upper flange 71 which is supported by an annular surface 70 on the bobbin case. Flange 71 is pressed against surface 70 by a spring-biased arm 75, pivoted to the bobbin case, for tensioning the bobbin thread. The feed bar 33 is pivoted by a bolt 34 to a crank 35 on a feed advance shaft 36. An arm 43 depending from the feed bar is connected by a pivotal link 44 to a crank 45 on a feed lift shaft 46. A feed dog 32 is fixed to a rectangular boss 93 formed on the feed bar above arm 43. A bobbin thread pull-off member 90 has an upper flange 91 which is supported by the feed bar, and is formed with a slot slidably embracing boss 93. A slot 98 in member 90 embraces bolt 34. An arm 96 depending from member 90 is connected by a pivotal link 99 to a crank 102 on the feed lift shaft 46. Member 90 thereby rises and falls with the feed bar, and has reciprocating movement of constant amplitude. Thread from the bobbin passes beneath a rib 28 on the bobbin case, over an inclined surface 79 on the latter, and through an aperture 94 in member 90. The arrangement is such that as the needle and feed dog commences to descend, member 90 is shifted to the left to pull from the bobbin a length of thread somewhat less than the amount required for the smallest stitch.