Abstract: A method for preventing seam ravel of multi-thread chain stitches is provided. After normal sewing is terminated with a looper set in a forward movement state, a state in which a needle thread loop caught by the looper is subjected to position-holding at a position closer to a forward movement end of the looper than a descent position of a needle is maintained until the needle descends through the needle thread loop caught by the looper. Thereafter, the position-holding of the needle thread loop is released to permit a sewing action for at least one stitch, thereby allowing the needle thread loop to be self-looped with a needle thread held by the needle. This surely strongly prevents the seam ravel of multi-thread chain stitches formed by the single needle, irrespective of the dimension of tension applied to the needle thread and the looper thread.

Abstract: Apparatus for reinforcing or attaching composite structural materials by chain-stitching. A reciprocating head is powered to alternate between outward and return motions. A needle is mounted for outward and return movement with the head, the needle having a material piercing end and a notch adjacent the material piercing end. A cast off has a first portion configured to overlie the notch, to maintain a thread within a notch, and a second portion configured to expand a loop in the thread on release of the thread from the notch. The needle pierces the material on outward motion of the head and withdraws through the material, with the thread in the needle notch, during the return motion of the head. The cast off first portion overlies the needle notch during a part of the needle return movement and moves in trailing relation to the needle during a part of the needle outward movement. A pressure foot may also be commonly driven, with the needle and cast off, by the head.

Abstract: A chainstitch machine has an edge trimmer knife driven in vertical chopping motion adjacent the needle by a linkage actuated by an oscillating shaft that operates synchronously relative to stitch-forming components. The linkage includes a bracket oscillated by the shaft and a joint movable along the bracket between a first position, in which the axis of the joint is offset from the axis of the shaft to communicate oscillating movement to the knife, and a second position, in which the axis of the joint is concentric with the shaft and transmits no oscillatory movement. In the second position, the knife is retracted by the linkage to a location above the region through which work pieces move, but in the first position, the linkage moves the knife down so that part of the knife extends through the plane of the throat plate and is pressed against an edge of a throat plate insert by a small pressure slide entirely within a notch in the insert and guided by juxtaposed edges of the notch.