Thread cutter and drive unit for a chain stitch sewing machine

A drive unit for a multi-head sewing machine which is provided with a plurality of machine heads each including a main machine head, a needle bar cam and a cloth pressing cam fixed to said main machine shaft so that the needle bar cam and the cloth pressing cam rotate together with said main machine shaft, a needle bar driving lever and a cloth pressing member driving lever which repeat a reciprocating movement over a predetermined range in response to rotation of said needle bar cam and rotation of said cloth pressing cam so that a needle bar and a cloth pressing member move up and down, and a retracting mechanism for rotating said needle bar driving lever and said cloth pressing member driving lever upward beyond said predetermined range so that said needle bar and said cloth pressing member retract upward, and where said main machine shaft penetrates said plurality of machine heads so that it is driven for rotation, characterized in that:

• an actuator for driving a corresponding retracting mechanism is individually arranged in a corresponding machine head;
• and
• when said retracting mechanism of one of said plurality of machine heads is operated to retract said needle bar and said cloth pressing member, an interlocked relation between said needle bar cam and said needle bar driving lever and an interlocked relation between said cloth pressing cam and said cloth pressing member driving lever are cut off in said one of the plurality of machine heads.