Abstract: A needle bar actuating device for double chain stitch and/or overlock sewing machines provided with a driving crank, one crank pin of which has three angularly differentiated reference surfaces in order to define an equal number of positions and lengths for said driving crank with respect to its axis of rotation; to each of said positions and lengths corresponding a different predetermined stroke length of the needle bar.

Abstract: A looper operating device for sewing machines in which the looper is provided with forward movement and the machine's needle possesses work feeding movement which is synchronized and caused to perform its intended function simultaneously with the machine's feed dog. The device includes a lever member having an upper fulcrum to which actuating linkage for the looper are connected. The opposite end of the lever member includes a lower fulcrum 25 connected to a lever element mounted on a shaft that is operatively connected to and simultaneously actuates both the feed dog and needle. This lever element is stationary when the stitch length is zero or is oscillating with an amplitude proportional to the stitch length.

Abstract: An apparatus for controlling movement of a looper while forming zig-zag stitches in a sewing machine. The apparatus is provided with a first drive device for moving and maintaining the looper in alignment with the machine's needle and a second drive device for causing the looper to travel in planes which are parallel when moving to cooperate with the needle in each of its stitch forming positions.