Thread trimmer system for in-line chain stitch cylinder bed sewing

Abstract

Apparatus and method for severing the needle and looper threads of a chain stitch formed by a cylinder bed sewing machine having an in-line looper system is disclosed. The cylinder bed sewing machine has a needle plate and a needle carrying the needle thread through the material and the needle plate to form a needle loop of needle thread therebelow that has a needle side running to the needle. The apparatus comprises a device operating as a dual needle plate holder and knife slide base, a stationary knife positioned below the needle plate, a spring positioned below said stationary knife, a movable knife positioned on the knife slide base and slidably mounted between the stationary knife and the spring for yieldingly urging the movable knife thereagainst. The movable knife has one penetrating end with a pair of axially offset barbs, a lagging barb and a leading barb closer to the penetrating end of the movable knife than the lagging barb. Finally, the apparatus includes actuating means, connected to the other end of the movable knife, for extending the penetrating end through the needle loop so that the leading barb hooks the needle side of the needle loop and the lagging barb hooks the looper thread and retracts the penetrating end. These elements cooperate to hook and sever the needle side of the needle loop and the looper thread below the needle plate of the cylinder bed sewing machine and prepare the looper thread for the next stitch.