Multi-thread chain stitch sewing machine with seam ravel preventing apparatus

Abstract

A needle plate base in a multi-thread chain stitch sewing machine with a seam ravel preventing apparatus is divided into a left needle plate base for attaching a needle plate thereto and supporting a swinging support shaft of a thread hanging hook; and a right needle plate base for fixedly supporting a stopper member and a thread handling air cylinder and a stopper air cylinder. The right needle plate base is fastened to a sewing machine bed. The left needle plate base is fastenably and unfastenably fastened to an upper surface of the bed via screw members. Adjustment of stitch performation, and maintenance, e.g., replacement of various kinds of components stored inside the bed, can extremely easily and simply be carried out without having much trouble and requiring labor and time, and therefore, the stitch performation and predetermined ravel preventing function can be constantly surely reproduced.

I claim:  
     
         1 . A multi-thread chain stitch sewing machine with a seam ravel preventing apparatus wherein the multi-thread chain stitch sewing machine comprises a needle having a drop position moving up and down while holding a needle thread; a looper which is movable forward and backward while holding a looper thread in a direction substantially orthogonal to a vertical movement path of the needle, and catches a needle thread loop formed below a needle plate by the needle during a forward movement; and a needle plate base having the needle plate attached thereto and being attached to an upper surface of a sewing machine bed, and wherein the multi-thread chain stitch sewing machine forms multi-thread chain stitch seams on a fabric by allowing the looper to catch the needle thread loop formed below the needle plate by the needle, and then by interlooping the needle thread with the looper thread held by the looper, the multi-thread chain stitch sewing machine with the seam ravel preventing apparatus comprising:
 a needle thread holding mechanism comprising (i) a thread hanging hook which is approachable and departable with respect to the looper, and swings around a vertically extending support shaft in a plane substantially parallel to the needle plate between a standby position away from the looper and a thread hooking position close to the looper, and (ii) a hook actuator for drivingly swinging the thread hanging hook to the standby position and the thread hooking position;   a stopper mechanism comprising (iii) a stopper member disposed at a position farther away from the needle plate than the thread hanging hook of the needle thread holding mechanism, and permits temporary suspension and unsuspension of a swing of the thread hanging hook from the thread hooking position to the standby position so that the needle thread loop caught by the thread hanging hook at the thread hooking position is held at a hold position between the thread hooking position and the standby position, and (iv) a stopper actuator for performing the suspension and the unsuspension of the stopper member;   a connecting member for interlockingly connecting the thread hanging hook of the needle thread holding mechanism and the stopper member of the stopper mechanism; and   a control section for controlling the needle thread holding mechanism and the stopper mechanism in association with a vertical movement of the needle, forward and backward movements of the looper, and feed of the fabric, so that the looper is moved forward after a normal sewing is terminated, the thread hanging hook of the needle thread holding mechanism is brought near the looper, the needle thread loop caught at the thread hooking position is moved to the hold position, a resulting state is maintained until the needle descends through the needle thread loop caught by the looper, and thereafter, a sewing action for at least one stitch is performed, wherein   the needle plate base is divided into two sections: a left needle plate base for attaching the needle plate thereto and supporting a swinging support shaft of the thread hanging hook; and a right needle plate base for fixedly supporting the stopper member and the hook actuator and the stopper actuator, and wherein   the right needle plate base is fastened to the sewing machine bed, and the left needle plate base is fastenably and unfastenably fastened to an upper surface of the sewing machine bed via screw members.   
     
     
         2 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 1 , further comprising:
 a feed reducing mechanism for feeding the fabric at a lower feed rate than during a normal sewing under an operation command provided from the control section, in the sewing action for the at least one stitch.   
     
     
         3 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 1 , further comprising:
 a looper thread restraining mechanism for restraining feed of the looper thread to the looper under an operation command provided from the control section, after the looper thread is positioned ahead of or behind the drop position of the needle.   
     
     
         4 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 1 , wherein the stopper mechanism comprises:
 the stopper member directly connected to the hook actuator and moves linearly reciprocally;   a swing lever engageable with and disengageable from a part of the stopper member;   a spring for swingingly energizes the swing lever in a direction in which the thread hanging hook is positioned at the standby position; and   the stopper actuator for disengaging the swing lever from the part of the stopper member against an energizing force of the spring.   
     
     
         5 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 4 , wherein the swing lever in the stopper mechanism is attached to a movable base attached laterally position-adjustably to the right needle plate base. 
     
     
         6 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 4 , wherein the hook actuator of the needle thread holding mechanism and the stopper actuator of the stopper mechanism are fixedly supported on a lower surface of the right needle plate base in a vertical two-stage fashion. 
     
     
         7 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 1 , further comprising:
 a looper thread holder which holds the looper thread extending from the looper to the fabric at a more forward position than the drop position of the needle by swinging together with the thread hanging hook of the needle thread holding mechanism around the support shaft in a plane substantially parallel to the needle plate, between the thread hooking position, the hold position, and the standby position; and   an actuator for swinging the looper. thread holder.   
     
     
         8 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 1 , wherein the looper thread holder is fastened together with the thread hanging hook of the needle thread holding mechanism to swing integrally with the thread hanging hook around the swinging support shaft in the plane substantially parallel to the needle plate, between the thread hooking position, the hold position, and the standby position. 
     
     
         9 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 8 , wherein the looper thread holder is attached position adjustably to the thread hanging hook. 
     
     
         10 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 1 , wherein the hook actuator of the needle thread holding mechanism and the stopper actuator of the stopper mechanism are both air cylinders. 
     
     
         11 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 1 , further comprising a pin protruding upwardly from a connection end portion of the connecting member, and a connection end portion of the thread hanging hook is provided with a connecting hole that is insertable into the pin from above the pin, and is drawable in an upward direction. 
     
     
         12 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 1 , wherein the left needle plate base or the sewing machine bed comprise protruding knock pins for positioning the left needle plate base to the sewing machine bed at a plurality of positions away from a plurality of fixedly connecting portions and connection release portions by the screw members, and wherein the sewing machine bed or the left needle plate base is provided with pin holes engageable with the knock pins. 
     
     
         13 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 1 , wherein a target sewing machine is a horizontal tube type single needle multi-thread chain stitch sewing machine. 
     
     
         14 . The multi-thread chain stitch sewing machine with the seam ravel preventing apparatus according to  claim 1 , wherein a target sewing machine is a horizontal tube type multi-needle multi-thread chain stitch sewing machine.