Sewing stitch length adjustment mechanisms

Abstract

The length of a sewing machine stitch is adjustable by varying the effective length of a first bar of a multi-bar linkage operably secured to a feed dog of the sewing machine. The effective length of the first bar is defined between an anchor point and a pivot point, with the pivot point being secured to a slider configured for movement along the length of the first bar. The slider comprises a pinion gear configured to engage a gear rack of the first bar, such that rotation of the pinion gear causes movement of the slider and the pivot point relative to the anchor point. Moreover, to accommodate the adjustable stitch length, the sewing machine additionally comprises an adjustable looper thread eyelet configured to adjust the length of the looper thread path to accommodate increased tension or slack in the looper thread due to the changed stitch length.

That which is claimed: 
     
         1 . A sewing machine looper thread mechanism comprising:
 a reciprocating looper arm configured to tie a locking stitch with a looper thread and a needling thread; and   an adjustable take-up eyelet secured relative to an exterior surface of the sewing machine;   wherein the adjustable take-up eyelet is configured to redirect a looper thread from a first thread direction extending from a looper thread source to a second thread direction extending to the reciprocating looper arm; and   wherein the adjustable take-up eyelet is configured for movement to adjust the length of the looper thread path between the looper thread source and the reciprocating looper arm.   
     
     
         2 . The sewing machine looper thread mechanism of  claim 1 , wherein the looper thread path extends at least substantially linearly from the reciprocating looper arm to a distal end of the adjustable take-up eyelet, and wherein the adjustable take-up eyelet is configured for movement to adjust a linear distance between the distal end of the adjustable take-up eyelet and the reciprocating looper arm. 
     
     
         3 . The sewing machine looper thread mechanism of  claim 1 , wherein the adjustable take-up eyelet comprises:
 an elongated planar medial portion having a face surface and defining a linear adjustment slot extending through the face surface, wherein the adjustment slot is configured to slide relative to one or more fasteners securing the adjustable sewing machine looper thread take-up eyelet relative to the sewing machine;   an angled base portion on a base end of the elongated planar medial portion, wherein the angled base portion has a base guide hole extending therethrough, and the angled base portion is angled relative to the face surface; and   a skew distal end portion on a distal end of the elongated planar medial portion, wherein the skew distal end portion has a distal guide hole extending therethrough, and the skew distal end portion is skewed about an axis at least substantially aligned with the length of the elongated planar medial portion.   
     
     
         4 . The sewing machine looper thread mechanism of  claim 3 , wherein a linear portion of the looper thread path extends between the base guide hole and the distal guide hole. 
     
     
         5 . The sewing machine looper thread mechanism of  claim 4 , wherein the looper thread path turns between the linear portion of the looper thread path extending between the base guide hole and the distal guide hole to a second at least substantially linear portion extending between the distal guide hole and the reciprocating looper arm. 
     
     
         6 . The sewing machine looper thread mechanism of  claim 4 , wherein the adjustable take-up eyelet is movable in a direction parallel with the linear portion of the looper thread path. 
     
     
         7 . An adjustable sewing machine looper thread take-up eyelet comprising:
 an elongated planar medial portion having a face surface and defining a linear adjustment slot extending through the face surface, wherein the adjustment slot is configured to slide relative to one or more fasteners securing the adjustable sewing machine looper thread take-up eyelet relative to a sewing machine;   an angled base portion on a base end of the elongated planar medial portion, wherein the angled base portion has a base guide hole extending therethrough, and the angled base portion is angled relative to the face surface; and   a skew distal end portion on a distal end of the elongated planar medial portion, wherein the skew distal end portion has a distal guide hole extending therethrough, and the skew distal end portion is skewed about an axis at least substantially aligned with the length of the elongated planar medial portion.   
     
     
         8 . The adjustable sewing machine looper thread take-up eyelet of  claim 7 , wherein a linear looper thread path extends between the base guide hole and the distal guide hole.