Method and sewing machine for forming single-thread locked handstitches

A method forming single-thread locked handstitches, comprising the steps of:

• forming a handstitch on a front surface and a locked stitch on a back surface of a fabric workpiece as a skip stitch set by cooperation of an open eye needle which is provided with a thread capturing open eye laterally, a rotary hook which is composed by a rocking bobbin casing which is loaded at a rotative outer rotary hook and a thread draw out actuator,
• setting a stitch length feed quantity of a stitch length feed and an inter-stitch pitch feed quantity of an inter-stitch pitch feed respectively, when the stitch length feed of said fabric workpiece for said handstitch is performed by a feed mechanism in a first stroke of said open eye needle, and the inter-stitch pitch feed of said fabric workpiece for the inter-handstitch is performed by said feed mechanism in a second stroke of said open eye needle,
• changing over to each fabric workpiece feed mode corresponding to said stitch length feed and said inter-stitch pitch feed respectively every one skip stitch set in sequence,
• transmitting said set stitch length feed quantity and inter-stitch pitch feed quantity to a feed drive mechanism in each fabric workpiece feed mode respectively, and
• feeding said fabric workpiece by said feed mechanism.

A single-thread locked handstitch sewing machine, comprising:

• an open eye needle, which is provided with a thread capturing open eye laterally which captures a thread in a first stroke which performs a linear reciprocating motion vertically by coming down from the upper dead center, piercing the fabric workpiece which is placed on a throat plate, slipping out from said fabric workpiece from the lower dead center, going up when coming down from an upper dead center, piercing a fabric workpiece, and going up from a lower dead center, and which releases the captured thread when coming down from the upper dead center, piercing said fabric workpiece, and going up from the lower dead center in a second stroke,
• a rotary hook, which is the rotary hook which contacts circumferentially on an open eye needle and tightens a thread which is drawn out from a thread exit by rocking the thread exit of a bobbin case which houses a bobbin that the thread which is incorporated in a bobbin casing is wound by rocking the bobbin casing which is loaded in the rotative outer rotary hook of the rotary hook positioned under a throat plate by the time the open eye needle goes up from the brink of reaching a lower dead center, and that said fabric workpiece is fed with one stitch length while said open eye needle slips out from said fabric workpiece, goes up and passes through the upper dead center in said first stroke, and that the open eye needle has a loop-taker point of the rotative outer rotary hook for scooping the thread which is captured by said thread capturing open eye when said open eye needle comes down from the upper dead center, pierces said fabric workpiece, and goes up from the lower dead center in the second stroke, and that the captured thread is released from said thread capturing open eye by the rotation of said rotary hook, and the released thread which is scooped by the loop-taker point of said rotary hook is guided in to said rotary hook by the further rotation of said rotary hook and is interlaced to the thread which is wound in said bobbin,
• a thread draw out actuator, which tightens the thread which guides out from said rotary hook by the further rotation of said rotary hook,
• a feed mechanism, which feeds said fabric workpiece with one stitch length while said open eye needle slips out from said fabric workpiece, goes up, and passes through the upper dead center in said first stroke, and feeds said fabric workpiece with one inter-stitch pitch while said open eye needle slips out from said fabric workpiece, goes up, and passes through the upper dead center in the second stroke, and thereby
• a handstitch on a front surface and a locked stitch on a back surface of said fabric workpiece are formed respectively.