THREAD CUTTING DEVICE AND THREAD CUTTING METHOD FOR DOUBLE CHAIN-STITCH SEWING MACHINE

摘要

PROBLEM TO BE SOLVED: To provide a thread cutting device and a thread cutting method for a double chain-stitch sewing machine capable of improving the appearance of a sewing object after finishing of sewing by cutting a needle thread part and a looper thread part on the back side of a sewing fabric so as to shorten the residual thread lengths without requiring troublesome hand work upon finishing of sewing.SOLUTION: In a movable knife 5 of a thread cutting device, there are formed: a blade part 5e for pushing and cutting a needle thread part projected to the back side of a sewing fabric when the movable knife 5 is moved by forward driving from an outside position close to one side of a needle location toward an outside position close to the other side of the needle location; and a looper thread catching part 10 for hooking and catching a looper thread part projected to the back side of the sewing fabric when the movable knife 5 is moved by backward driving from the outside position close to the other side of the needle location toward the outside position close to the one side of the needle location. A fixed knife 6 for cutting the looper thread part caught by the looper thread catching part 10 and a looper thread holding member 7 for holding a looper thread end part after cutting between the movable knife 5 and itself are arranged at positions closest to the needle location within a range such that the tips thereof do not enter the vertical reciprocating motion path of a needle.