GB1007698A - Chain stitch device for lock stitch sewing machines - Google Patents

Abstract

1,007,698. Sewing machines. SINGER CO. Aug. 4, 1964 [Aug. 7, 1963], No. 31661/64. Heading D1G. A lock stitch sewing machine, modified to produce chain stitching, comprises a work support formed with a needle aperture, a rotary looptakes disposed beneath said support, a bobbin-supporting case journalled in the looptaker and constrained from rotation therewith, a stationary thread loop engaging finger carried by the machine frame and disposed beneath the work support in advance of the needle aperture and parallel to the path of needle reciprocation, opposed spring and abutment means arranged between the frame and bobbin case in advance of the thread loop engaging finger for resiliently constraining passage of thread loops from the looptaker to said finger until the loops are tightened by the needle thread take-up, and a reciprocating element disposed between the needle aperture and said finger for stripping the thread loops from the latter when the needle penetrates the needle aperture. A conventional lock stitch sewing machine comprising a vertical axis rotary hook 32 formed with a loop-seizing beak 33 and journalling a bobbin case 34 constrained from rotation by a spring 36, is fitted with a modified throut plate 52 formed in its under surface with a recess 72 in which a bar 70 and a leaf spring 76 are severed by a screw 71. A finger 74 depending from bar 70 engages a leaf spring 80 fixed by a saw 81 to the bobbin case 34, and a protrusion 79 on spring 80 engages an abutment 82 on the bobbin case. Needle thread loops seized by beak 33 are transferred in succession from the looptaker to finger 74. As the needle 19 descends through the needle aperture, which is elongated in the direction of work feed, to carry a fresh loop TsTw through the previous loop Tl held on finger 74, the feed dog 49 also descends, whereby a web 50 thereon engages loop Tl to strip the latter from finger 74. Loop TsTw, when shed by the looptaker, is initially retained between protrusion 79 and abutment 82 until tightened by the take-up to overcome the resistance of spring 76 and thereby engage finger 74. The bobbin thread is concatenated with the needle thread loops, but lies on the undersurface of the work and may be readily drawn out of the seam.