Loop forming device used for a chainstitch sewing machine

Abstract

Disclosed is a chainstitch sewing machine having a plurality of needles having needle threads which are moved up and down through needle holes of a throat plate, a looper having a looper thread, which is reciprocatively moved in a direction orthogonal to a cloth feeding direction under the throat plate, guide holes provided in the throat plate for guiding loops formed by the needle threads and a looper thread by the cooperation of the needles and the looper, to a rear part in a cloth feeding direction, and a main feed dog, disposed at a part closer to a rear than the guide hole, for feeding the loops in the cloth feeding direction. Improvement is made such that the upper end edge of the needle hole located at a rear part as viewed in the cloth feeding direction, takes a planar shape configured such that a part thereof located closer to the forward movement end of the looper is gradually varied toward the needles with respect to a straight line orthogonal to a cloth feed direction, and a thread guide surface, which is chamfered off to become thin in the forward direction of the looper and toward the lower surface of the throat plate, is provided on the upper edge of the guide hole.

Dependencies are inferred from the claim text.