Thread cutter for a zig-zag sewing machine

摘要

A thread cutter for a zig-zag sewing machine which has a needle which swings transversely to the material feed direction to form a zig-zag seam of predetermined width while the needle is reciprocated to pierce material to be sewn in cooperation with a revolving looper as the material being sewn is moved transverse to the swing direction and includes a cutting knife which cooperates with a movable catcher which is moved in time relationship to the rotation of the looper. The catcher is a plate-like member having an end terminating in the tip and a lateral edge on each side of the tip with one lateral edge having a first barb for engaging one leg of the needle thread loop and an opposite lateral edge having a second barb for engaging another leg of the needle thread loop, the one leading directly to the needle. The catcher is movable with the engaged thread portions into association with the knife to sever the threads so as to obtain a free length of thread ends independent of the piercing position of the needle. The second barb is advantageously staggered relative to the first barb by an amount which is less than the maximum width of the zig zag seam. The thread guide surface is provided next to the second barb which extends toward the catcher tip. The thread catcher may also have a third barb on the same side as the second barb which is provided for each half of the overstitch range for the leg of the thread which leads directly to the needle. The spacing between the barbs are equal to the maximum width of the zig-zag seam.