Overlock sewing machine with movable cutter

An overlook sewing machine having a movable cutter which is activated in association with rotation of a main drive shaft to cooperate with a fixed cutter provided in the same plane with an upper surface of a needle plate, to thereby cut a work while the work is being stitched, said overlook sewing machine comprising:

• a drive link having one end swingably connected to a fixed mount and an opposite end connected to said movable cutter;
• a swingable link having opposite ends and a central axis between said opposite ends, around which said swingable link is swingable, said swingable link having an arcuate guide groove extending between said central axis and one of said opposite ends thereof;
• reciprocation movement generating means including an eccentric cam secured to said main drive shaft for rotation therewith and a transmission link having one end engaging said eccentric cam and the opposite end connected to the other of said opposite ends of said swingable link, thereby to normally swing said swingable link around said central axis thereof as said main drive shaft is rotated;
• an intermediate link having opposite ends, one of which is turnably connected to a central part between said opposite ends of said drive link;
• operating means including an operating shaft having one end portion extending through the other of said opposite ends of said intermediate link and being in engagement with said arcuate guide groove of said swingable link, said operating means further including an operating knob mounted on said operating shaft, said operating knob operated to move said one end portion of said operating shaft alone said arcuate guide groove of said swingable link, thereby to move said other end of said intermediate link between said central axis and said one end of said swingable link, said intermediate link enabling said drive link to swingingly reciprocate to activate said movable cutter when said other end of said intermediate link is moved to said one end of said swingable link, said intermediate link rotatingly move said drive link to move said movable cutter to an inoperative position below said needle plate where said movable cutter is held at standstill when said other end of said intermediate link is moved to said central axis of the swingable;
• further comprising positioning means including a positioning plate secured to said swingable link and having a guide slot provided thereon, said guide slot being substantially of the same shape with that of said guide groove of said swingable link and having opposite enlarged circular portions provided at the opposite ends thereof and being axially in alignment with said guide groove of said swingable link, so that said operating knob may be operated to engage either of said opposite enlarged circular portions to position said other end of said intermediate link at either of said opposite ends of said guide groove of said swingable link.