Patent ID: 6422165
Filing Date: 2002-07-23
Classification: D05B

Abstract:
An apparatus for preventing raveling of a seam, which is constructed to be mounted in a sewing machine for sewing a product by allowing a looper which advances from the right side to the left side of a needle drop point to pass through a loop of a needle thread formed at the needle drop point to force the looper thread held by the looper to the twine around the needle thread, said apparatus comprising:a looper thread hanging hook arranged on the right rear side of the needle drop point to advance or retreat and catch the looper thread in the vicinity of the advance end of the looper at the time of the advance thereof; a needle thread cutting hook arranged on the right side of the needle drop point to advance or retreat and catch the needle thread being inserted into the loop of the needle thread at the time of the advance thereof; a needle thread knife slidably contacting the needle thread cutting hook at the time of the retreat of the hook, the knife cutting the needle thread which is caught at the time of the advance of the needle thread cutting hook; a looper thread cutting hook arranged on the right side of the needle drop point to advance or retreat and catch the looper thread caught by the looper thread hanging hook at the time of the advance thereof; a looper thread knife slidably contacting the looper thread cutting hook at the time of the retreat thereof, the knife cutting the looper thread caught at the time of the advance of the loop thread cutting hook; and means for controlling an operation of preventing the raveling of the seam, the means causing the sewing machine to temporarily suspend the sewing operation before the end of the sewing in the state in which the looper advances followed by forcing the looper thread hanging hook to advance to catch the looper thread and then forcing the hook to retreat, then forcing the sewing machine to conduct the sewing operation for one stitch in this state, which is then followed by forcing the needle thread cutting hook and the looper thread cutting hook to advance and retreat thereby cutting the needle thread and the looper thread with the needle thread knife and the looper thread knife respectively.