Patent Publication Number: US-2005120932-A1

Title: Cloth cutting devices for use with sewing machines

Description:
This application claims priority to Japanese patent application serial number 2003-357837, the contents of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to cutting devices for cutting a cloth along a feeding direction of the cloth during a sewing operation.  
      2. Description of the Related Art  
      In order to cut cloths during a sewing operation, various types of cutting devices have been proposed for attaching to sewing machines. For example, Japanese Laid-Open Patent Publication No. 2002-18170 teaches a cutting device that has a swing member pivotally mounted on a machine head of a sewing machine. A cutter is mounted on one end of the swing member, so that the cutter can move between a storage position within the sewing head and an operational position adjacent to a table of the sewing machine on which the cloth to be sewn is placed.  
      However, because the swing member pivots relative to the sewing head, a large space is required in order to permit the swinging movement of the cutter between the storage position and the operational position.  
     SUMMARY OF THE INVENTION  
      It is accordingly an object of the present invention to teach improved cloth-cutting devices that require a small space for the movement of a cutter between a storage position and an operational position.  
      According to one aspect of the present teachings, cloth-cutting devices are taught that are attached to a sewing machine for cutting a cloth along a feeding direction of the cloth during a sewing operation. The cloth-cutting device includes a mount member mounted to the sewing machine on the side of the sewing head, an extendable member linearly vertically extendable from the mount member, and a cutter disposed at a lower end of the extendable member. The cutter is movable between a storage position on the side of a sewing head of the sewing machine and an operational position on the side of a table of the sewing machine as the extendable member moves between an upper position and a lower position.  
      Because the cuter moves linearly vertically together with the extendable member, the moving paths of the cutter and the extendable member are positioned on a vertical linear line. Therefore, a space required for the movement of the cutter and the extendable member is minimized. As a result, the cutting device can be easily mounted to the sewing machine.  
      In another aspect of the present teachings, the cloth cutting devices further include a lock device for locking the extendable member in the upper position and the lower position, a lock releasing device for releasing the lock device, and two grip portions disposed on the lower and front side of the extendable member. The lock device is released by the lock releasing member when the operator grasps the grip portions. The operator vertically moves the extendable member with the grip portions grasped by the operator. The lock device is operable to lock the extendable member when the operator releases the grip portions while the extendable member is located at the upper position and the lower position.  
      Because the two grip portions for releasing and locking the extendable member are disposed on the lower and front side of the extendable member, the operator can easily grasp the grip portions to operate the lock device. In addition, grasping the grip portions allows the operator to easily cause the vertical movements of the extendable member. After grasping the grip portions and vertically moving the extendable member away from the upper position and the lower position, the grip portions may be released. The extendable member may continue to be moved to the upper position and the lower position where the lock may be automatically reapplied.  
      In another aspect of the present teachings, the extendable member includes a fixed member and a movable member. The fixed member has a positioning portion disposed at a lower portion of the fixed member. The positioning member is positioned relative to the table of the sewing machine when the extendable member is located in the lower position.  
      Therefore, the positioning member can be easily positioned relative to the table when the extendable member has been extended or withdrawn downward to the lower position. Because the extending direction of the extendable member and the direction for locating the positioning member relative to the table are the same as one another, the positioning member may have a relatively simple construction.  
      In another aspect of the present teachings, the cutting devices further include a driven device that is driven by the needle bar. The movable member has a connecting portion that is connected to the driven device when the extendable member is positioned in the lower position. The connecting portion is disposed at an upper portion of the movable member.  
      Therefore, when the extendable member is positioned in the lower position to configure the cutter in an operational position, the movable member reciprocates to cut the cloth by the cutter as the needle bar reciprocates.  
      In another aspect of the present teachings, the cutter includes a fixed knife mounted to the lower end of the fixed member and a movable knife mounted to the lower end of the movable member.  
      In another aspect of the present teachings, the lock releasing device for releasing the lock device also serves to connect and disconnect between the connecting portion of the movable member and the driven device.  
      Because the same device can be used as the lock releasing device and as the device for connect and disconnect the movable member and the driven device, the number of parts of the cutting device can be reduced or minimized and the cutting device may have a simple construction.  
      In another aspect of the present teachings, the lock releasing device includes a lock operation member pivotally mounted to the fixed member about a pivotal axis. The lock operation member has a first grip portion disposed on the lower side of the pivotal axis of the lock operation member. The fixed member has a second grip portion. The lock operation member is pivoted about the pivotal axis to release the lock device when an operator grasps the first grip portion and the second grip portion. In this way, the lock operation member serves as the lock release device.  
      In another aspect of the present teachings, the lock operation member further includes a contact portion in a position on the upper side of the pivotal axis in order to contact with the movable member. The contact portion urges the movable member to pivot so as to disconnect between the connecting portion and the driven device when the lock operation member is pivoted to release the lock device. In this way, the operation member also serves as the device for connecting and disconnecting between the connecting portion and the driven device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic perspective view as viewed from the front side of a sewing machine to which a first representative cloth cutting device is mounted; and  
       FIG. 2  is a cross sectional view taken along line II-II in  FIG. 1 , in which a lock operation member is omitted for the purpose of illustration; and  
       FIG. 3  is a rear view in a storage position of the cloth cutting device; and  
       FIG. 4  is a view similar to  FIG. 2  with an extendable member and its related parts omitted for the purpose of illustration; and  
       FIG. 5  is a rear view of parts of the cutting device mounted to a sewing head of the sewing machine, together with the extendable member and its related parts; and  
       FIG. 6  is an exploded left side view of the extendable member and its related parts; and  
       FIG. 7  is a view similar to  FIG. 2 , but showing an operational position of the cutting device; and  
       FIG. 8  is a view similar to  FIG. 3 , but showing the operational position of the cutting device; and  
       FIG. 9  is a view similar to  FIG. 2 , but showing a second representative cloth cutting device; and  
       FIG. 10  is a view similar to  FIG. 5 , but showing the second representative cutting device; and  
       FIG. 11  is a view similar to  FIG. 4 , but showing the second representative cutting device; and  
       FIG. 12  is an exploded left side view of the extendable member and its related parts of the second representative cutting device. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Each of the additional features and teachings disclosed above and below may be utilized separately or in conjunction with other features and teachings to provide improved cloth cutting devices. Representative examples of the present invention, which examples utilize many of these additional features and teachings both separately and in conjunction with one another, will now be described in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Moreover, various features of the representative examples and the dependent claims may be combined in ways that are not specifically enumerated in order to provide additional useful embodiments of the present teachings.  
     FIRST REPRESENATIVE EMBODIMENT  
      A first representative embodiment will now be described with reference to FIGS.  1  to  8 . Referring to  FIG. 1 , a sewing machine  10  has a table  12 , a substantially inverted L-shaped arm  15  extending over the table  12 , and a sewing head  11  disposed on the left end of the arm  15 . The table  12  has a throat plate  13  attached to the table  12  and a feed dog  19  disposed within the table  12  in order to feed a cloth to be sewn (not shown). A motor (not shown) is mounted within the arm  15 . A needle bar  14  and a presser bar  17  extend vertically downward from the sewing head  11  toward the table  12 . The needle bar  14  is linked to the motor via a link mechanism (not shown), so that the needle bar  14  vertically reciprocates when the motor is energized. A presser foot  18  is attached to the lower end of the presser bar  17 .  
      As shown in  FIG. 1 , a cutting device  1  is mounted to the sewing head  11 . As shown in  FIG. 2 , the cutting device  1  includes a mount member  2  mounted within the sewing head  11 , an extendable member  30  extendable linearly downward relative to the mount member  2 , and a cutter  6  mounted on the lower end of the extendable member  30 . The cutting device  1  further includes a driven mechanism ( 20 ,  21 ,  22 , and  23 ) that is linked to the needle bar  14 .  
      As shown in  FIG. 4 , the mount member  2  has mount portions  2   a  and  2   b  that are mounted on a framework  16  of the sewing machine. Rail members  2   c  and  2   d  are mounted on the mount member  2  and extend parallel to each other to define a guide portion  2   e  therebetween.  
      As shown in  FIG. 4 , the driven mechanism ( 20 ,  21 ,  22 , and  23 ) includes a pivotal support member  23 , two link members  21  and  22 , and an upper connecting member  20 . The needle bar  14  pivotally supports the lower end of the link member  22  via the pivotal support member  23 . The upper end of the link member  22  is pivotally connected to the link member  21 . The left end (as viewed in  FIGS. 2 and 4 ) of the link member  21  is pivotally connected to the link member  22 . The right end of the link member  21  is pivotally mounted to the rail member  2   d.  A slot  21   c  is formed in the right side section of the middle portion of the link member  21  and is elongated in the lengthwise direction of the link member  21 .  
      The upper connecting member  20  has an elongated plate-like configuration and is movable in the vertical direction under the guide of the guide portion  2   e.  A first connecting pin  20   a  is secured to one side of the upper portion of the upper connecting member  20  and extends into the slot  21   c  of the link member  21 . In this way, the upper connecting member  20  is connected to the needle bar  14  via the link member  21  and  22 , so that the upper connecting member  20  reciprocates vertically as the needle bar  14  reciprocates. As shown in  FIG. 4 , the upper connecting member  20  has a second connecting pin  20   b  that is connected to the connecting portion  4   d  of the extendable member  4  ( FIGS. 7 and 8 ).  
      As shown in  FIG. 4 , a positioning member  7  that also serves a lock member is disposed within the sewing head  11 . The positioning member  7  extends perpendicularly from the rail member  2   d  and has two engaging recesses  7   a  and  7   b  as shown in  FIG. 5 . The engaging recesses  7   a  and  7   b  are adapted to engage an engaging pin  5   e  secured to an operation member  5  connected to the extendable member  30  as will be explained later. When the engaging pin  5   e  engages the engaging recess  7   a  as shown in  FIG. 3 , the extendable member  30  may be locked in a storing position. On the other hand, when the engaging pin  5   e  engages the engaging recess  7   b  as shown in  FIG. 8 , the extendable member  30  may be locked in an operational position.  
      As shown in  FIG. 6 , the extendable member  30  has a fixed member  3  and a movable member  4 . The fixed member  3  has a plate-like configuration and extends in the vertical direction. A recess  3   a  is formed in the upper end of the fixed member  3 . A fixed knife  60  is fixedly attached to the lower end of the fixed member  3 . A grip portion  3   d  is formed on the front side (right side as viewed in  FIG. 6 ) of the fixed member  3 . Also, an uprising portion  3   b  is formed on the front edge of the fixed member  3  and extends perpendicular to the fixed member  3 . As shown in  FIG. 2 , the width of the fixed member  3  is substantially the same as the width of the guide portion  2   e.  Therefore, the fixed member  3  is prevented from being tilted in the forward and rearward directions. As shown in  FIG. 5 , the fixed member  3  is positioned between the mount member  2  and the upper connecting member  20 . Therefore, the fixed member  3  is also prevented from being tilted in the light and left directions, i.e., the direction of thickness of the fixed member  3 . In this way, the fixed member  3  can stably move vertically relative to the mount member  2 .  
      As shown in  FIG. 6 , the movable member  4  also has a plate-like configuration and extends in the vertical direction. As shown in  FIG. 8 , the movable member  4  is arranged parallel to the fixed member  3  in the direction of thickness. As shown in  FIG. 6 , the movable member  4  has an uprising portion  4   a,  a connecting portion  4   d,  and a mount portion  4   c.  The uprising portion  4   a  extends perpendicular to the movable member  4  and has a through-hole through which one end of a wire spring  50  is inserted, as will be explained later. The connecting portion  4   d  is configured as a through hole formed in the upper portion of the movable member  4  in order to removably receive the second connecting pin  20   b  as shown in  FIG. 8 . The mount portion  4   c  is disposed at the lower end of the movable member  4 . A movable knife  61  is pivotally mounted to the mount portion  4   c.    
      As shown in  FIG. 6 , the cutter  6  includes the fixed knife  60  and the movable knife  61 . As noted previously, the fixed knife  60  is fixedly attached to the lower end of the fixed member  3 . The fixed knife  60  has a mount portion  60   c,  a positioning portion  60   a,  and a knife-edge  60   d.  The positioning portion  60   a  is disposed at the lower end of the fixed knife  60  and extends downwardly therefrom. As shown in  FIG. 7 , the positioning portion  60   a  is inserted into an insertion hole  13   a  formed in the throat plate  13  so as to be fixed in position relative to the table  12 . The mount portion  60   c  is formed in the rear portion of the fixed knife  60 . The mount portion  61   a  of the movable knife  61  is pivotally mounted to the mount portion  60   c.    
      As shown in  FIG. 6 , the movable knife  61  extends in substantially forward and rearward directions. The rear portion of the movable knife  61  is pivotally mounted to the fixed knife  60 . The front portion of the movable knife  61  is pivotally mounted to the mount portion  4   c  of the movable member  4 . Therefore, as the movable member  4  vertically reciprocates, the movable knife  61  pivots about the mount portion  60   c,  so that a knife-edge  61   b  of the movable knife  61  vertically reciprocates relative to the knife-edge  60   d  of the fixed knife  60 .  
      As shown in  FIG. 6 , the cutting device has a lock operation member  5  disposed on the side of the extendable member  30 . Also, the lock operation member  5  has a plate-like configuration and extends in the vertical direction. The lock operation member  5  has a mount portion  5   c  disposed in a substantially middle portion in the longitudinal direction. The mount portion  5   c  is configured as a through-hole extending throughout the thickness of the lock operation member  5 . The mount portion  5   c  is pivotally mounted to the uprising portion  3   b  of the fixed member  3  via a support member  31 . Thus, the lock operation member  5  is positioned to be perpendicular to the fixed member  3  as shown in  FIG. 8 , and the lock operation member  5  can pivot relative to the fixed member  3  in the right and left directions (i.e., the direction of thickness of the fixed member  3 ).  
      As shown in  FIG. 6 , a contact portion  5   h  is formed on the upper end of the lock operation member  5 . As shown in  FIG. 8 , the contact portion  5   h  extends to a position between the movable member  4  and the fixed member  3 , so that the movable member  4  may move away from the fixed member  3  by the contact portion  5   h  when the lock operation member  5  is pivoted. As shown in  FIG. 6 , the contact portion  5   h  has a tilting movement preventing portion  5   j  that serves to prevent the movable member  4  from being pivoted in the forward and rearward directions.  
      As shown in  FIG. 6 , a grip portion  5   g  is formed on the lower end of the lock operation member  5 . The grip portion  5   g  extends forwardly from the lock operation member  5 . In the assembled state shown in  FIG. 8 , the grip portion  5   g  and the grip portion  3   d  of the fixed member  3  extend parallel to each other in the forward direction. If the operator grasps the grip portions  3   d  and  5   g  with his or her hand, the grip portion  5   g  may be moved toward the grip portion  3   d,  so that the lock operation member  5  pivots about the mount portion  5   c.    
      As shown in  FIG. 5 , two wire springs  50  and  51  are mounted to the lock operation member  5 . The wire spring  51  extends between the lock operation member  5  and the fixed member  3  in order to bias the lower portion of the lock operation member  5  in a counterclockwise direction as viewed in  FIG. 5 . The wire spring  50  extends between the lock operation member  5  and the movable member  4  in order to bias the upper portion of the lock member  5  also in the counterclockwise direction (the direction on the side of the contact portion  5   h ).  
      As shown in  FIG. 5 , the engaging pin  5   e  positioned on the upper portion of the lock operation member  5   e  is forced to engage the engaging recess  7   a  or  7   b  (see  FIGS. 3 and 8 ) by the biasing force applied to the operation member  5  via the wire spring  51 . Thus, the engaging pin  5   e  can be reliably held in engagement with the engaging recess  7   a  or  7   b.  This condition will be hereinafter called a “lock condition.” In order to disengage the engaging pin  5   e  from the engaging recess  7   a  or  7   b,  operator may simply grasps the grip portions  3   d  and  5   g,  so that the lock operation member  5  pivots against the biasing force of the wire spring  51  to remove the engaging pin  5   e  from the engaging recess  7   a  or  7   b.  This condition will be hereinafter called a “lock releasing condition.” 
      As shown in  FIG. 8 , the wire springs  50  and  51  bias the movable member  4  toward the fixed member  3  via the lock operation member  5 . Therefore, the connecting portion  4   d  of the movable member  4  is forced toward the second connecting pin  20   b,  so that the connecting portion  4   d  can be reliably held in engagement with the connecting pin  20   b.  This condition will be hereinafter called a “connecting condition.” In order to disengage the connecting portion  4   d  from the connection pin  20   b,  the operator may simply grasps the grip portions  3   d  and  5   g,  so that the lock operation member  5  is pivoted against the biasing force of the wire spring  51  and the contact portion  5   h  contacts or engages the movable  4  to pivot the movable member  4 . As a result, the connecting portion  4   d  is removed from the second connecting pin  20   b.  This condition will be hereinafter called a “disconnecting condition.” 
      Further, in the storage position of the extendable member  30 , as shown in  FIG. 3 , the connecting pin  20   b  and the connecting portion  4   d  are offset from each other in the vertical direction. Thus, the connecting pin  20   b  and the connecting portion  4   d  are held in the disconnecting condition while in the storage position. In addition, in the storage position, the engaging pin  5   e  engages the engaging recess  7   a,  so that the movable member  4  is held in the pivoted position. As a result, the movable member  4  can be further prevented from contacting with the connecting pin  20   b.    
      As shown in  FIGS. 6 and 8 , a leaf spring  40  is mounted to the lower portion of the fixed member  3  via a mount base  41  and serves to bias the movable member  4  toward the fixed member  3 . Therefore, the movable knife  61  mounted to the movable member  4  is pressed by a large force to contact with the fixed knife  60  mounted to the fixed member  3 . Therefore, the movable knife  61  can reliably cut the cloth due to cooperation with the fixed knife  60 .  
      The operation for moving the extendable member  30  from the storage position to the operational position will now be described. First, the operator grasps the grip portions  3   d  and  5   g  (see  FIGS. 2 and 3 ) in order to disengage the engaging pin  5   e  from the engaging recess  7   a.  Subsequently, with the grip portions  3   d  and  5   g  grasped, the operator pulls or withdraws the extendable member  30  downward and inserts the positioning portion  60   a  into the insertion hole  13   a  as shown in  FIG. 7 . In this way, the lower end of the fixed member  3  is positioned relative to the table  12 . Thereafter, the operator releases the grip portions  3   d  and  5   g,  so that the engaging pin  5   e  engages the engaging recess  7   b  and the connecting portion  4   d  of the movable member  4  engages the connecting pin  20   b  of the upper connecting member  20 . In this condition, the movable member  4  can vertically reciprocate as the needle bar  14  reciprocates.  
      In order to move the extendable member  30  from the operational position to the storage position, the operation may grasp the grip portions  3   d  and  5   g  (see  FIG. 8 ), so that the engaging pin  5   e  is disengaged from the engaging recess  7   b  and the connecting portion  4   d  is disengaged from the connecting pin  20   b.  Subsequently, with the grip portions  3   d  and  5   g  grasped, the operator lifts the extendable member  30 . Thereafter, the operator releases the grip portions  3   d  and  5   g,  so that the engaging pin  5   e  engages the engaging recess  7   a  as shown in  FIG. 3 .  
      According to the representative embodiment, the cutter  6  moves linearly upward and downward together with the extendable member  30  relative to the mount member  2  as shown in  FIGS. 2 and 7 . Consequently, the paths of the upward and downward movements of the cutter  6  and the extendable member  30  are positioned along a linear line. Therefore, the space required for the movement of the cutter  6  and the extendable member  30  is minimized. In other words, the cutting device  1  can be easily and compactly mounted to the sewing machine  10 .  
      In addition, according to the representative embodiment, the lock operation member  5  also serves as a lock releasing device, and the positioning member  7  and the engaging pin  5   e  constitute a lock device. Consequently, the lock releasing device ( 5 ) is configured to release the lock device ( 7 ,  5   e ) via the grip portions  3   d  and  5   g.  Because the grip portions  3   d  and  5   g  are disposed on the lower front side of the extendable member  30 , the operator of the sewing machine can readily grasp the grip portions  3   d  and  5   g  to operate the lock device. In addition, while the grip portions  3   d  and  5   g  are grasped, the operator can easily move the extendable member  30  in the upward and downward directions.  
      Further, as shown in  FIGS. 6 and 7 , the extendable member includes the fixed member  3  and the movable member  4 . The cutter  6  includes the fixed knife  60  and the movable knife  61  respectively mounted to the fixed member  3  and the movable member  4 . The positioning member  60   a  is disposed at the lower end of the fixed member  3  and is positioned relative to the table  12  of the sewing machine  10 .  
      Therefore, the positioning member  60   a  can be easily positioned relative to the table  12  as the fixed member  3  moves in the downward direction, i.e., withdrawing direction from sewing head  11 . In contrast, the cloth-cutting device of Japanese Laid-Open Patent Publication No. 2002-18170 has a positioning means disposed at a lower end of a swing member that pivots relative to the sewing machine. In addition, the positioning means is extended from the lower end of the swing member after the swing member has been swung or pivoted to an operational position. Thus, the moving direction of the swing member and the moving direction of the positioning means are different from one another. According to the representative embodiment, the moving direction of the positioning member  60   a  for positioning relative to the sewing machine is the same as the extending direction of the extendable member  30 . Therefore, the positioning member  60   a  may have a simple construction. In other words, the positioning member  60   a  is not necessary to extend and retract relative to the extendable member.  
      Furthermore, as shown in  FIG. 8 , the upper connecting member  20  serves as a driven device that is driven by the needle bar  14 . The lock releasing device ( 5 ) is configured to enable the connecting portion  4   d  of the movable member  4  to be connected to or disconnected from the driven device ( 20 ). In this way, the lock releasing device ( 5 ) also serves to connect and disconnect between the connecting portion  4   d  and the driven device ( 20 ), so that the same parts can be commonly used for different functions. Therefore, the construction of the cutting device  1  can be simplified. In addition, in the storage position shown in  FIG. 3 , the movable member  4  is disconnected from the driven device ( 20 ). Therefore, it is possible to minimize the waste of energy of the sewing machine.  
      Thus, the lock operation member  5  can pivot relative to the fixed member  3  in order to release the lock device ( 7 ,  5   e ) and to disengage or disconnect the connecting portion  4   d  from the driven device ( 20 ).  
     SECOND REPRESENTATIVE EMBODIMENT  
      A second representative embodiment will now be described with reference to FIGS.  9  to  12 . The second representative embodiment is a modification of the first representative embodiment. Therefore, in FIGS.  9  to  12 , like members are given the same reference numerals as in the first representative embodiment and the explanation of these members may not be repeated.  
      As shown in  FIG. 9 , a cloth cutting device  101  according to the second representative embodiment includes an extendable member  130 , a cutter  106 , a driven device ( 120 ,  121 ,  122 ,  23 ), and a positioning member  107  in addition to the mount member  2 . The cutting device  101  also has a lock operation member  105  (see  FIG. 12 ). The extendable member  130  includes a fixed member  103  and a movable member  104 .  
      As shown in  FIG. 9 , the driven device includes a first link member  122  pivotally mounted to the needle bar  14  and a second link member  121  pivotally connected to the first link member  122 . As shown in  FIG. 11 , the driven device further includes an upper connecting member  120 . A first connecting pin  120   a  is mounted to the upper portion of the upper connecting member  120  and is inserted into an elongated slot  121   c  formed in the second link member  121 . A second connecting pin  120   b  is mounted to the lower portion of the upper connecting member  120 . The second connecting pin  120   b  is adapted to engage a connecting portion  104   d  formed in the movable member  104  of the extendable member  130  when the movable member  104  has been extended downward or withdrawn downward.  
      A cutout portion  103   a  is formed in the upper portion of the fixed member  103 . A fixed knife  160  is mounted to the lower end of the fixed member  103 . The fixed knife  160  includes a mount portion  160   c,  a positioning portion  160   a,  a knife edge  160   d,  and a grip portion  103   d.  The grip portion  103   d  extends on the front side of the fixed member  103  and a grip member  103   e,  preferably made of resin, is fitted on the grip portion  103   d.    
      As shown in  FIG. 12 , a contact portion  104   a  is formed on the upper end of the movable member  104 . A movable knife  161  is pivotally mounted to the lower end of the movable member  104 . A mount portion  161   a  is disposed at the rear portion of the movable knife  161  and is pivotally mounted to the mount portion  160   c  of the fixed knife  160 . Consequently, the front portion of the movable knife  161  pivots about the mount portion  104   c  of the movable member  104 .  
      As shown in  FIG. 9 , the contact portion  104   a  extends in the right side direction (perpendicular to the sheet of  FIG. 9 ), so that the contact portion  104   a  contacts with an extension  107   a  formed on the upper end of the positioning member  107  when the extendable member  130  is located in a storage position as shown in  FIG. 9 . Therefore, the position of the movable member  104  relative to the fixed member  103  can be determined by the contact portion  104   a,  so that the pivotal position of the movable knife  161  is held in a position as shown in  FIG. 9 , where the movable knife  161  and the fixed knife  160  are substantially overlaid with one another. Therefore, the knife edges of the movable knife  161  and the fixed knife  160  have only a minimum area exposed to the outside when the extendable member  130  is located in the storage position.  
      As shown in  FIG. 12 , a mount base  141  is fixedly mounted to the fixed member  103 . The mount base  141  has a mount plate  141   a  for mounting to the fixed member  103 , an uprising plate  141   b  extending perpendicular to the mount plate  141   a,  and a turn-back plate  141   c  bent to be turned back from the upper portion of the uprising plate  141   b.  A leaf spring  140  has an upper end that is secured to the turn-back plate  141   c.  The lower end of the leaf spring  140  contacts the mount portion  104   c  of the movable member  104  in order to bias the fixed knife  160  against the movable knife  161 . Consequently, the fixed knife  160  is pressed against the movable knife  161  so that the fixed knife  160  reliably cooperates with the movable knife  161  in order to cut the cloth.  
      As shown in  FIG. 12 , a contact portion  105   h,  a tilting movement preventing portion  105   j,  and an engaging pin  105   e,  are formed on the upper portion of the lock operation member  105 . A grip portion  105   g  is formed on the lower end of the lock operation member  105 . A mount portion  105   c  is formed in substantially the middle position in the longitudinal direction of the lock operation member  105 . The mount portion  105   c  is pivotally mounted to the uprising plate  141   b  of the mount base  141  via the support member  31 . The grip portion  105   g  extends forwardly from the lock operation member  105 . A grip member  105   k,  preferably made of resin, is fitted on the grip portion  105   g.  In addition, the grip member  105   k  is received within a recess  103   e   1  formed in the grip member  103   e  of the fixed member  103 . The grip member  105   k  is movable within the recess  103   e   1  in the direction of the depth of the recess  103   e   1 . Therefore, when the operator grasps the grip members  103   e  and  105   k,  the grip member  105   k  moves toward the grip member  103   e,  so that the lock operation member  105  pivots about the mount portion  105   c.    
      As shown in  FIGS. 10 and 12 , a wire spring  151  is attached between the lock operation member  105  and the fixed member  103 , so that the wire spring  151  biases the lock operation member  105  in a counterclockwise direction as viewed in  FIG. 10 . A wire spring  150  is attached between the lock operation member  105  and the movable member  104 , so that the wire spring  150  biases the movable member  104  toward the contact portion  105   h  of the lock operation member  105 .  
      With the second representative embodiment, substantially the same operation and advantages can be attained as the first representative embodiment.