Patent ID: 6814015
Filing Date: 2004-11-09
Classification: D05B

Abstract:
A looper drive mechanism for sewing machine in which using an upper thread which is made to pass through a needle which performs an upward and downward movement drawing a trace vertically relative to a throat plate and a lower thread accommodated in a rotary hook, the upper thread which is made to pass through the needle performing the reciprocating movement in the vertical direction and passing through a work mounted on the throat plate every one stitch feed of the work is, at the time of elevating the upper thread from a lowermost position of the needle, intercepted by a loop-taker point of the rotary hook which accommodates the lower thread below the throat plate and performs the rotational movement so as to make the upper thread and the lower thread interlace each other thus forming a lockstitch portion made of a stitch parallel to a surface of the work and a stitch perpendicular to the surface of the work, and an over-edge stitch portion is formed by an upper looper thread and a lower looper thread which are respectively made to pass through an upper looper which performs a reciprocating movement drawing a substantially arcuate trace extending above and below the throat plate and intersects the trace of the needle above the throat plate and a lower looper which draws a substantially arcuate trace below the throat plate and intersects the trace of the needle and the trace of the upper looper respectively,the improvement being characterized in that the looper drive mechanism for sewing machine further includes a looper drive portion having a constitution in which the upper looper and the lower looper are respectively disposed below the throat plate, respective loop-taker points thereof are arranged in the same direction such that the loop-taker points pass a front side of the needle as seen in the stitching direction, the upper looper and the lower looper are driven such that the upper looper and the lower looper perform movements having traces on planes substantially parallel to each other, the upper looper thread which is made to pass through the upper looper which performs the reciprocating movement drawing the arcuate trace which intersects the trace of the needle above the throat plate and passes through the throat plate is intercepted by the needle descending from an uppermost position when the upper looper is descended from an uppermost position, the lower looper thread which is made to pass through the lower looper which performs the reciprocating movement drawing the trace which intersects the trace of the needle and the trace of the upper looper below the throat plate is intercepted by the descending needle below the throat plate when the lower looper is moved from one end to the other end of the trace, and the lower looper thread is intercepted by the upper looper elevating from the lowermost position when the lower looper is moved to the other end, whereby the upper looper thread and the lower looper thread are interlooped each other at the edge portion of the work and, at the same time, the upper looper thread is interlooped with the lockstitch portion through the upper surface of the work, and the lower looper thread is interlooped with the lockstitch portion through the lower surface of the work thus forming the over-edge stitch portion.