Patent Publication Number: US-6981458-B2

Title: Sewing machine with work edge cutting mechanism

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a sewing machine and more particularly relates to an overolock sewing machine having a cutter mechanism for cutting the edge of work while the work is to sewn, wherein a blade which is activated may be kept stopped and held as placed under the needle plate in case a stitching operation is performed without use of the cutter mechanism. 
   It is generally known that the overlock sewing machine is provided with a work edge cutting mechanism including a movable blade which may be operatively disconnected from a drive source in case the stitching operation is performed without use of the work edge cutting mechanism. This type of sewing machine is disclosed in the Japanese patent application laid open Hei.11-235489. The sewing machine is described as follows; An upper blade  16  is operated in association with a link  28  which is vertically reciprocated by rotation of an eccentric cam  27 , because the vertical reciprocation of the link  28  is transmitted to the upper blade  16  through a first arm  29 , a second arm  30 , a blade holder  22  and a holder guide  23 . The upper blade  16  may be disconnected from the vertically reciprocating link  28  by manipulation of a changeover lever  38  in case the stitching operation is performed without use of the work edge cutting mechanism, the changeover lever  38  being operated to pull out a connecting pin  34  from an operative position to disconnect the first arm  29  and the second arm  30  from each other. 
   According to the sewing machine, the work edge cutting mechanism is so formed as to keep the upper blade as is stopped in a region where the upper blade is operated in case the upper blade is disconnected from a drive source. In the operative region, the upper blade is vertically moved to cut the work edge between an upper position and a lower position where the upper blade is partly located above the needle plate where the work is handled by the user to be sewn. The upper blade is, therefore, something in the way in the stitching operation in case the stitching operation is performed without use of the upper blade. It is, therefore, an object of the invention to eliminate the defects and disadvantages of prior art. More precisely, it is an object of the invention to disconnect the upper blade from the drive source and move the same into a retreat position where the upper blade is not in the way of stitching operation in case the stitching operation is performed without use of the upper blade, and to connect the upper blade to the drive source and revert the same into the operative region in case the stitching operation is performed with use of the upper blade. 
   SUMMARY OF THE INVENTION 
   The inventers have made efforts to solve the problems of prior art and succeeded in providing a sewing machine with work edge cutting mechanism having a main drive shaft which is rotated to vertically reciprocate a machine needle, the sewing machine substantially comprising: a cutting means for cutting the work edge while the work is stitched, the cutting means including a lower blade fixed to a place adjacent a needle plate of the sewing machine and an upper blade which is located in an upper operative position as is protruded up from the needle plate, the upper blade being operated in association rotation of the main drive shaft to cut the edge of work while the work is stitched; a transmission means for transmitting the rotation of the main drive shaft to the upper blade such that the upper blade may be vertically reciprocated relative to the lower blade; a transmission intercepting means for intercepting the transmitting operation of the transmission means; an operating means which is manipulated to activate the intercepting means; a retreating means operated in association with the operating means to retreat the upper blade from the upper operative position to a retreat position where said upper blade is inoperative. 
   According to the invention, the mechanism is simple and may be easily operated to disconnect the upper blade from the drive source and to retreat the same into the inoperative position outside of the operative region so that the upper blade may be not in the way of work stitching operation in case the stitching operation is performed without use of the upper blade. The upper blade may be easily connected to the drive source to revert the same to the operative position where the upper blade is operated to cut the edge of work while the work is stitched. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     
       FIG. 1 
     
     (a) is a front elevational view of the work edge cutting mechanism of the invention shown as is in operative condition. 
     (b) is a plan elevational view of an essential part of (a) shown partly in section and showing the upper blade of the work edge cutting mechanism operatively connected to a drive source. 
     
       FIG. 2 
     
     (a) is a front elevational view of the work edge cutting mechanism of the invention shown as is inoperative condition. 
     (b) is a plan elevational view of an essential part of (a) shown partly in section and showing the upper blade of the work edge cutting mechanism operatively disconnected from the drive source. 
     
       FIG. 3 
     
     (a) is a plan elevational view of an essential part of the work edge cutting mechanism of the invention showing the operating section moved to a first position for holding the mechanism operative. 
     (b) is a plan elevational view of the essential part of the work edge cutting mechanism of the invention showing the operating section moved to a second position for holding the mechanism inoperative. 
     
       FIG. 4 
     
     (a) is a perspective view of an essential part of the operating section of the work edge cutting mechanism. 
     (b) is an exploded view of an essential part of (a). 
     
       FIG. 5 
     
     (a) is a side elevtional view of an essential part of  FIG. 4  showing a reverting lever operated to render the work edge cutting mechanism into inoperative condition. 
     (b) is a side elevtional view of an essential part of  FIG. 4  showing the reverting lever operated to render the work edge cutting mechanism into operative condition. 
       FIG. 6  is a front elevtional view of an essential part of the work edge cutting mechanism showing a transmission mechanism moved between an operative position and an inoperative position. 
     
       FIG. 7 
     
     (a) is a perspective view of an essential part of the work edge cutting mechanism. 
     (b) is an exploded perspective view of a part of (a). 
     (c) is an exploded perspective view of another part of (a). 
     (d) is an exploded perspective view of another part of (a). 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The invention will be described in detail in reference to the preferred embodiments as shown in the attached drawings. The invention is substantially composed of a drive mechanism moving an upper blade section  13  in a vertical plane, a transmission mechanism for transmitting the movement of the drive mechanism to the upper blade section  13 , a mechanism for intercepting the transmission of the transmission mechanism and a mechanism which is manually operated to act on the intercepting mechanism. 
   The drive mechanism includes a main rotation shaft  2  of sewing machine, an eccentric cam  3  mounted to the main rotation shaft  2  and a transmission rod  4  having the upper end being in engagement with the eccentric cam  3  so that the transmission rod  4  may be vertically reciprocated when the main rotation shaft  2  is rotated. The transmission mechanism includes a first crank  5  having one end connected to the rod  4 , a second crank  6  and a swingable arm  7 . The transmission intercepting mechanism includes a connection  52  between the first crank  5  and the second crank  6 . The manually operated mechanism includes the section as designated by a letter A. 
   A lower blade section  1  including a lower blade  1   a  is secured to a base  1   b  which is provided below a needle plate  30 , the lower blade  1   a  having the edge provided at the upper side thereof An upper blade section  13  including an upper blade  13   a  is provided in connection with the lower blade  1   a,  such that the upper blade  13   a  may be vertically moved relative to the lower blade  1   a.    
   The upper blade  13   a  is mounted to an upper blade holder  13   b  which is mounted to a connecting arm  13   c  as shown in  FIG. 7(   c ). Precisely, the upper blade holder  13   b  is composed of a holder portion  13   b   1  and a holder shaft  13   b   2 . The upper blade  13   a  is secured to the holder portion  13   b   1  by a screw or the like, and the holder shaft  13   b   2  is inserted into a cylinder base portion  13   c   1  of the connecting arm  13   c  which has an arm portion  13   c   2 . 
   A spring  13   d  is provided between a stopper  13   e  and the holder shaft  13   b   2  of the upper blade holder  13   b  to normally pressing the upper blade  13   a  toward the lower blade  1   a,  the pressure being required for the upper blade  13   a  to cut off the thread in cooperation with the lower blade  1   a.    
   The upper blade connecting arm  13   c  is connected to a transmission link  8  by means of a connecting shaft  15 . The base  1   b  of the lower blade  1   a  is secured to a mount  1   c  which is provided under the needle plate  30 , so that the lower blade  1   a  may be located in a same plane with the needle plate  30 , and so that the lower blade  1   a  may be located forward of the place where there are a needle drop hole and feed dogs. In  FIGS. 1 and 2 , a machine needle  31  is shown, and the first crank  5  has one end rotationally connected to the lower end of the transmission rod  4  by means of a pin  5   c.  The first crank  5  has the opposite end is rotationally connected to the second crank  6 . 
   The axial reciprocation of the transmission rod  4  is transmitted to the first crank  5 . As shown in  FIG. 7(   b ), the first crank  5  has a central through hole  5   a  formed thereat. The second crank  6  has a through hole  6   a  formed at one end portion thereof and has a connecting shaft  6   b  provided at the opposite end thereof The first and second cranks  5 , 6  are connected by means a connecting shaft  51  which is inserted into the through hole  6   a  and the central through hole  5   a,  so that the first and second cranks  5 , 6  may be swingingly moved around the connecting shaft  51  as shown in  FIGS. 1 and 2 . The second crank  6  may be moved axially of the connecting shaft  51  and relative to the first crank  5 . 
   With manual operation of the operating section A which will be described in detail hereinlater, the second crank  6  may be pressed against or spaced from the first crank  5  as shown in  FIG. 1(   b ) and  FIG. 2(   b ). Namely the second crank  6  may be moved toward and away from the first crank  5 . Further as shown in  FIG. 1(   b ),  FIG. 2(   b ),  FIG. 3  and  FIG. 7 , there is provided a connecting means  52  including a hole  52   a  formed on the first crank  5  at the opposite end thereof between the through hole  6   a  and the connecting shaft  6   b  of the second crank  6 , and a projection  52   b  formed on the second crank  6  at the opposite end thereof. In case the projection  52   a  engages the hole  52   b  as the second crank  6  is moved toward the first crank  5 , the first and second cranks  5 , 6  are operatively connected. On the other hand, in case the projection  52   a  disengages from the hole  52   b  as the second crank  6  is moved away from the first crank  5 , the first and second cranks  5 , 6  are operatively disconnected. 
   When the first and second cranks  5 , 6  are operatively connected, the second crank  6  may be reciprocated in the axial direction thereof by the first crank  5 . The is second crank  6  is normally pressed toward the second crank  6  by a torsion spring  18  which is arranged between the second crank  6  and a part of machine housing (not shown). The torsion spring  18  may be replaced by a coil spring. 
   Thus the first crank  5  and the second crank  6  are operatively connected by the connecting portion  52  when the projection  52   a  of the second crank  6  is inserted into the hole  52   b  of the first crank  5 . On the other hand, the first crank  5  and the second crank  6  are operatively disconnected when the projection  52   a  of the second crank  6  is moved back from the hole  52   b  of the first crank  5 . The connecting means  52  may be optionally modified in any ways other than the present embodiment. 
   With rotation of the upper rotation shaft  2 , the eccentric cam  3  is rotated and the transmission rod  4  is vertically reciprocated as shown in  FIG. 1(   a ). As the result, the first and second cranks  5 , 6  are swingingly moved around the connecting shaft  51  in case the first and second cranks  5 , 6  are operatively connected by the projection  52   a  of the second crank  6 . The swinging movement of the first and second cranks  5 ,  6  is transmitted to the upper blade  13   a  through the swingable arm  7  which is connected to the opposite end of the second crank  6 . 
   The swingable arm  7  is swingable around a shaft  53  which supports the swingable arm  7  at the center  7   a  thereof and is mounted to a machine housing (not sown). The swingable arm  7  has one end connected to the opposite end of the second crank  6  by means of a connecting shaft  6   b  which is secured to the opposite end of the second crank  6  as shown in  FIGS. 1 ,  2  and  FIG. 7(   a ). 
   Precisely, the swingable arm  7  has a triangular slide groove  7   b  formed at one end thereof A triangular slide block  7   d  is fitted into the triangular slide groove  7   b  such that the former may be slidingly moved in the latter. The triangular slide block  7   d  has a central hole  7   d   1  formed thereat. The swingable arm  7  is connected to the second crank  6  by the connecting shaft  6   b  which is inserted into the central hole  7   d   1  of the triangular slide block  7   d,  so that the swinging movement of the second crank  6  may be smoothly transmitted to the swingable arm  7  through the triangular slide block  7   d.    
   The swingable arm  7  has an opposite end  7   c  operatively connected to a lower end of a transmission link  8 . The transmission link  8  has an upper end operatively connected to the connecting arm  13   c.  The upper blade  13   a  is normally pulled down by a tension spring  19 ,so that the upper blade  13   a  may be moved down to below the needle plate  30  in case the second crank  6  is operatively disconnected from the first crank  5 . 
   Precisely, as shown in  FIG. 1(   a ),  FIG. 2(   a ) and  FIG. 7(   a ), the transmission link  8  is connected to the fixed base  1   b  of the lower blade  1   a  by means of a first link  9  and a second link  10  which are arranged in parallel with each other. The longitudinal length of the first and second links  9 , 10  is slightly different so that the upper blade  13   a  may be vertically moved as is slightly swingingly moved in the vertical plane. The tension spring  19  has one end hung to the second link  10  and has the opposite end anchored to the machine housing (not shown). Thus the upper blade  13   a  is normally pulled down by the tension spring  19 . 
   The manually operating section A includes a changeover lever  16 , a transmission member  23  and a reverting lever  24  as shown in  FIG. 3  and  FIGS. 4(   a ), ( b ). The changeover lever  16  is substantially of a T-shape including an operating arm  16   a  and an activating arm  16   b  which is generally normal to the operating arm  1 . 
   The changeover lever  16  is mounted to a machine housing (not shown) such that the same may be swingable around the center axis  16   e  thereof in the horizontal plane. A knob  17  is secured to one end of the operating arm  16   a  and is protruded out of the machine housing so that the same may be accessible at he outside of sewing machine. With operation of the knob  17 , the changeover lever  16  is swingingly moved around the center axis  16   e.  The swinging movement of the lever  16  causes the second crank  6  to move and disconnect and disconnect toward and away from the first crank  5 , thereby to connect and disconnect the former to and from the latter as will be described in detail hereinlater. 
   As shown in  FIGS. 3(   a ), ( b ), the knob  17  may be moved between two positions where the knob  17  may be held by a holder  20  which is composed of a fixing portion  20   a  and a fixing spring  20   b.  The fixing portion  20   a  is provided on the operating arm  16   a  of the changeover lever  16  and the fixing spring  20   b  is provided on the machine frame. The fixing portion  20   a  is formed with two holes  20   a   1 ,  20   a   1  which are laterally spaced from each other. 
   The fixing spring  20   b  may be a plate spring  20   b   1  which is bent at the free end thereof to provide a projection  20   b   2 . The projection  20   b   2  is adapted to engage either of the holes  20   a   1 ,  20   a   1  of the fixing portion  20   a  as the changeover lever  16  is swinginly moved while the knob  17  is between the two positions as shown in  FIGS. 3(   a ) and ( b ). Thus the changeover lever  16  may be held in the two positions. In one of the positions, the first and second cranks  5 , 6  are connected and in the other of the positions, the first and second cranks  5 , 6  are disconnected. In this connection, the changeover lever  16  is normally urged in one direction by a tension spring  25 . The tension spring  25  has one end connected to the operating arm  16   a  of the changeover lever  16  and has the opposite end anchored to the connecting shaft  51 . Namely the second crank 6  is normally urged in the direction to be disconnected from the first crank  5 . 
   Precisely, the activating arm  16   b  of the changeover lever  16  has a projection  16   c  which is in engagement with a hole  16   d  formed at the underside of the second crank  6  so that the second crank  6  may be moved axially of the connecting shaft  51 toward and away from the first crank  5  with swinging movement of the changeover lever  16 . 
   The free end of the activating arm  16   b  of the changeover lever  16  is connected to one end  23   a  of the transmission member  23 . The transmission member  23  has a projection  23   b   2  provided at the opposite end  23   b   1  thereof which is bent up as shown in  FIGS. 4(   a ), ( b ). The projection  23   b   2  is in engagement with a forked portion  24   a  provided at the lower end of the reverting lever  24  which is mounted to the machine frame so as to be swingable around the swing center  24   c  thereof. 
   The reverting lever  24  is further provided with a projection  24   b  which is adapted to press down the swingable arm  7  in the counterclockwise direction in  FIG. 6  as the reverting lever  24  is swingingly moved as shown in  FIGS. 5(   a ), ( b ) and  FIG. 6 . With the operation of the reverting lever  24 , the connection and disconnection between the first and second cranks  5 , 6  may be easily and smoothly made through the hole  52   a  and the projection  52   b.    
   Precisely, in the condition that the second crank  6  is disconnected from the first crank  5  with the projection  52   b  is pulled out of the hole  52   a  of the first crank  5 , it is designed that the projection  52   b  is located outside of the swing region of the first crank  5  which is defined by the swing angle θ of the first crank  5  as shown in  FIG. 2 , wherein the upper blade  13   a  and the transmission  8  are normally urged in the lower direction by the tension spring  19  and the swingable arm  7  is swingingly moved in the clockwise direction and the connecting point between the second crank  6  and the swingable arm  7  is moved to the upper position. In this condition, the swinging movement of the first crank  5  will not cause the hole  52   a  to interfere with the projection  52   a  of the second crank  6 . 
   In order to connect the second crank  6  to the first crank  5 , the knob  17  of the operating section A is manually operated to swing the reverting lever  24  in the counterclockwise direction as shown in  FIGS. 5(   a ), ( b ) through the transmission member  23 . Then the projection  24   b  of the reverting lever  24  moves the swingable lever  7  in the counterclockwise direction as shown in  FIG. 6  so that the second crank  6  may be moved in the clockwise direction into the swing region of the first crank  5  wherein the torsion spring  18  moves the second crank 6  axially of the connecting shaft  51  toward the first crank  5 . In this condition, the projection  52   b  of the second crank  6  may enter the hole  52   a  of the first crank  5  as the hole  52   a  comes in alignment with the projection  52   b.    
   Thus the first and second cranks  5 ,  6  connected in one body transmits the vertical reciprocating movement of the transmission rod  4  to the upper blade  13   a  through the swingable arm  7  and the transmission link  8 . The upper blade  13   a,  therefore, may be operated while the sewing machine is operated. 
   In case the stitching operation of sewing machine is performed without requiring the operation of the work edge cutting mechanism, the knob  17  of the operating section A is manually moved from the position as shown in  FIG. 3(   a ) to the position as shown  FIG. 3(   b ). Then the changeover lever  16  is turned in the clockwise direction. Simultaneously the projection  16   c  of changeover lever  16  moves the second crank  6  away from the first crank  5  axially of the connecting shaft  51  and against the action of the torsion spring  18 . The projection  52   a  of the second crank  6  is disengaged from the hole  52   b  of first crank  5 . Thus the second crank  6  is disconnected from the first crank  5 . 
   In the condition that the second crank  6  is disconnected from the first crank  5 , the second crank  6  is turned in the counterclockwise direction around the axis  51  in  FIG. 2(   a ) by the swingable arm  7  which is normally urged in the clockwise direction around the axis  53  by the tension spring  19  through the connecting link  10  and the transmission link  8 . Thus the projection  52   a  of the second crank  6  is held at an upper position that is out of the swing region of the first crank  5 . Simultaneously the upper blade  13   a  is retreated from the upper operative position as shown in  FIG. 1(   a ) to the lower inoperative position where the upper blade  13   a  is located under the needle plate  30  as shown in  FIG. 2 , by the transmission link  8  which is normally urged in the lower direction by the tension spring  19 . 
   In this instance, the projection  52   a  of the second crank  6  is located out of the swing locus of the hole  52   b  of the first crank  5 . Therefore, the projection  52   a  will not engage the hole  52   b  in any way. This disconnected condition is maintained by the holder  20 , wherein one of the holes  20   a   1 ,  20   a   1  of the fixing portion  20   a  is in engagement with the projection  20   b   2  of the plate spring  20   b   1  as shown in  FIG. 3(   b ). Thus the upper blade  13   a  is held in the inoperative position below the needle plate  30 . 
   As is apparent from the foregoing description of the invention, the upper blade  13   a  may be easily disconnected from the drive mechanism and may be simultaneously retreated to the inoperative position below the needle plate  30  where the upper plate  13   a  is not in the way of stitching operation in case the sewing machine is driven without necessity of operation by the work edge cutting mechanism. 
   The invention thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all modifications are intended to be included within the scope of the following claims.