Patent Publication Number: US-9410274-B2

Title: Sewing machine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2014-029595 filed on Feb. 19, 2014, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a sewing machine. 
     2. Related Art 
     A sewing machine has conventionally been known which sews an embroidery pattern based on embroidery data. This type of sewing machine includes a storage device storing embroidery data of a plurality of embroidery patterns. A user selects a desirable one of the embroidery patterns. The sewing machine reads the embroidery data of the selected embroidery pattern and instructs a transfer mechanism to transfer an embroidery pattern holding a workpiece cloth while a needle bar with a needle attached thereto is being moved up and down by an up-down moving mechanism. The embroidery pattern is sewn on the workpiece cloth by the operation. 
     The above-described sewing machine includes a type added with a boring function which makes cuts in the workpiece cloth. More specifically, a boring knife (a cutting needle) is attached to the needle bar, instead of the needle. Boring data is stored in a storage device. The boring data is indicative of cut positions in the workpiece cloth. The sewing machine reads the boring data and transfers the embroidery frame while the needle bar with the cutting needle being attached thereto is being moved up and down. Successive cuts are formed on the workpiece cloth by this operation, so that the workpiece cloth is cut into a predetermined configuration. 
     SUMMARY 
     The sewing machine constructed as described above can form a cut pattern with a predetermined configuration on the workpiece cloth based on the boring data. However, the user sometimes wishes to cut the workpiece cloth into an arbitrary configuration, instead of a cut pattern of a predetermined configuration. In this case, for example, boring data to cut the arbitrary configuration needs to be generated using a dedicated data generator. The generation of boring data takes a lot of trouble and is cumbersome. 
     Therefore, an object of the disclosure is to provide a sewing machine which can easily form a cut pattern desired by the user on the workpiece cloth. 
     The disclosure provides a sewing machine including a detection unit configured to detect a moving direction of an object to be processed when the object placed on a sewing machine bed is moved in any direction, a cutting needle having a distal end formed with a blade edge and configured to form a cut in the object, an up-down drive mechanism configured to reciprocate the cutting needle in an up-down direction, a rotational drive mechanism configured to rotate the cutting needle about a rotation axis line of the cutting needle, and a control device configured to control the up-down drive mechanism and the rotational drive mechanism based on a result of detection by the detection unit so that an orientation of the blade edge is changed according to the moving direction of the object and the cutting needle is reciprocated to form the cut in the object with the blade edge being in the changed orientation. 
     The disclosure also provides a sewing machine including a detection unit configured to detect a moving direction and a movement amount of an object to be processed when the object placed on a sewing machine bed is moved in any direction, a cutting needle having a distal end formed with a blade edge and configured to form a cut in the object, an up-down drive mechanism configured to reciprocate the cutting needle in an up-down direction, a rotational drive mechanism configured to rotate the cutting needle about a rotation axis line of the cutting needle, a first pitch setting unit configured to set a pitch length to a first pitch length, said pitch length being an interval between cuts formed in the object by an up-down movement of the cutting needle, and a control device configured to control the up-down drive mechanism and the rotational drive mechanism based on a result of detection by the detection unit so that an orientation of the blade edge is changed according to the moving direction of the object and the cutting needle is reciprocated to form the cut in the object at the first pitch length with the blade edge being in the changed orientation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a perspective view of an entire sewing machine according to a first embodiment together with an attachment; 
         FIG. 2  is a left side view of a sewing machine head, showing an arrangement of a camera; 
         FIGS. 3A and 3B  are a plan view and a bottom view of the attachment together with a moving table respectively; 
         FIG. 4  is a cross-sectional view of the attachment, showing an inner structure thereof; 
         FIG. 5  is a longitudinal section of the attachment; 
         FIGS. 6A, 6B and 6C  are a plan view, a front view and a right side view of a cutting unit respectively; 
         FIG. 7  is a front view of the cutting unit, showing an inner structure thereof; 
         FIG. 8  is a left side view of the cutting unit; 
         FIG. 9  is a partially broken rear view of the cutting unit, showing the inner structure thereof; 
         FIG. 10  is a block diagram showing an electrical arrangement of the sewing machine; 
         FIG. 11  is an illustration diagram showing the relationship between a still image of workpiece cloth and a rotational angle of a cutting needle; 
         FIGS. 12A and 12B  are an enlarged side view and an enlarged front view of the blade edge side of the cutting needle respectively; 
         FIG. 13  is a flowchart showing cutting control under a free motion mode; 
         FIGS. 14A, 14B and 14C  are diagrams exemplifying the relationship among a moving direction of the workpiece cloth, the rotational angle of the cutting needle and a cut position; 
         FIG. 15  is a view similar to  FIG. 13 , showing a second embodiment; 
         FIG. 16  is a view similar to  FIG. 13 , showing a third embodiment; 
         FIGS. 17A, 17B and 17C  are diagrams exemplifying a cut pattern by the cutting needle; and 
         FIG. 18  is a view similar to  FIG. 13 , showing a fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A first embodiment will be described with reference to  FIGS. 1 to 14C . The first embodiment is directed to a household sewing machine which is capable of sewing an embroidery pattern and which will hereinafter be referred to as “sewing machine M.” 
     Referring to  FIG. 1 , the sewing machine M includes a bed  1  extending in a right-left direction, a pillar standing upward from a right end of the bed  1  and an arm  3  extending leftward from an upper part of the pillar  2 , all of which are integrally formed with the sewing machine M. A main shaft (not shown) and a sewing machine motor  4  (see  FIG. 10 ) are provided in the arm  3 . The main shaft extends in the right-left direction. The sewing machine motor  4  is provided in the pillar  2  to rotate the sewing machine shaft. 
     In the following description, the side where a user is located relative to the sewing machine M will be referred to as “front” of the sewing machine, that is, the front of the sewing machine is the side where switches and a display unit both of which will be described later are located in the sewing machine M. The side located opposite the front will be referred to as “rear.” The side where the pillar  2  is located in the sewing machine M will be referred to as “right” and the distal end side of the arm  3  will be referred to as “left.” The front-back direction is a Y direction and the direction perpendicular to the Y direction is an X direction. 
     A sewing machine head  3   a  is provided at the distal end side of the arm  3  as shown in  FIG. 2 . A needle bar  5   a  and a presser bar  6   a  are provided on the sewing machine head  3   a . The needle bar  5   a  has a lower end to which a sewing needle  5  is attached. The presser bar  6   a  has a lower end on which a presser foot  6  is mounted. In the arm  3  are provided a needle bar drive mechanism, a needle bar swinging mechanism, a take-up lever drive mechanism, a presser bar drive mechanism and the like, none of which are shown. The needle bar drive mechanism moves the needle bar  5   a  up and down by rotation of the main shaft. The needle bar swinging mechanism swings the needle bar  5   a  in a right-left direction. The take-up lever drive mechanism moves a take-up lever up and down in synchronization with the up-and-down motion of the needle bar  5   a . The presser bar drive mechanism moves the presser bar  6   a  up and down. 
     The bed  1  has a top on which a needle plate  1   a  is mounted. In the bed  1  are provided a cloth feed mechanism, a rotating shuttle, a thread cutting mechanism and the like, all of which are located below the needle plate  1   a  and none of which are shown. The cloth feed mechanism moves a feed dog in the up-down direction and the front-back direction. The rotating shuttle houses a bobbin and forms stitches in cooperation with the sewing needle  5 . The thread cutting mechanism cuts the needle thread and the bobbin thread. 
     A switching lever (not shown) is provided on a rear surface of the bed  1  to switch the feed dog between an operative state and a non-operative state. When in the operative state, the feed dog appears above and disappears below the needle plate  1   a  thereby to feed a workpiece cloth. When in the non-operative state, the feed dog remains below the needle plate  1   a . The switching lever is configured to switch the feed dog from the operative state to the non-operative state in conjunction with the attaching of an attachment  10  to the sewing machine M although the switching will not be described in detail. The attachment  10  will be described later. 
     Various switches including a start/stop switch  8   a , and a speed adjusting knob  8   b  are mounted on a front of the arm  3 . The start/stop switch  8   a  instructs start and stop of a sewing operation of the sewing machine M. The speed adjusting knob  8   b  is operated to set a sewing speed, that is, a rotating speed of the main shaft. A display  9  is mounted on a front of the pillar  2 . The display  9  displays various sewing patterns including practical patterns and embroidery patterns, various names of functions to be executed in a sewing work, various messages and the like. A touch panel  9   a  (see  FIG. 10 ) is mounted on a front of the display  9 . The touch panel  9   a  has a plurality of touch keys comprising transparent electrodes. When the user touches one or more touch keys, a desirable sewing pattern can be selected, functions can be instructed and parameters can be set. 
     The attachment  10  shown in  FIG. 3A  is detachably attached to a left part of the bed  1 . The bed  1  includes a part located on the left of a substantially central part thereof although the part is not shown in detail. The part of the bed  1  is formed into a generally quadrangular prism extending leftward. This part will be referred to as “free arm bed.” When the attachment  10  has been attached to the bed  1 , a fitting part  20   a  (see  FIG. 3A ) of the attachment  10  is fitted with the free arm bed, as will be described in detail later. 
     The attachment  10  has a function of an embroidering device which transfers an embroidery frame (not shown) holding the workpiece cloth in the X direction and the Y direction over upper sides of the bed  1  and the attachment  10 . The attachment  10  also has a function of a support device which supports a moving table  11  (see  FIG. 1 ) so that the moving table  11  is movable in the X direction and the Y direction, when the moving table  11  is attached, instead of an embroidery frame. The moving table  11  will be described later. The attachment  10  further has a cutting function of forming a cut in the workpiece cloth. 
     The attachment  10  will be described with reference to  FIGS. 3A to 5 . The attachment  10  includes a body  12  and a moving part  13 . An upper surface of the body  12  is on a level with an upper surface of the bed  1  when the attachment  10  has been attached to the bed  1 . The moving part  13  is mounted on the upper surface of the body  12  to be movable in the X direction. 
     The body  12  of the attachment  10  includes a body cover  20  formed into a generally rectangular box shape as a whole as shown in  FIG. 3A . The fitting part  20   a  having an upper opening is provided on a right part of the body cover  20  so as to be located in the middle of the body cover  20  in the front-back direction. The fitting part  20   a  is fitted with the free arm bed while the body  12  is being slid rightward relative to the bed  1 , so that the attachment  10  is attached to the bed  1 . The body cover  20  has aright end provided with a connector  20   b . When the attachment  10  is attached to the sewing machine M, the connector  20   b  is connected to a connector at the sewing machine M side, with the result that the attachment  10  is electrically connected to a control device  39  (see  FIG. 10 ) of the sewing machine M. 
     The moving part  13  is provided with a carriage  14  (see  FIGS. 4 and 5 ). The carriage  14  is movable in the Y direction. An embroidery frame or the moving table  11  is attached to the carriage  14 . The moving table  11  attached to the carriage  14  is supported so as to be movable in the X direction and the Y direction on the upper surfaces of the bed  1  and the body  12 . 
     A fixing frame  16  extending in the right-left direction is mounted inside the body  12  as shown in  FIGS. 4 and 5 . An X-direction guide shaft  15  extending in the right-left direction is fixed to the fixing frame  16 . A moving frame  17  includes a first frame  17   a  and a second frame  17   b . The first frame  17   a  is supported on the X-direction guide shaft  15  so as to be movable. The second frame  17   b  is connected to an upper part of the first frame  17   a . As a result, the moving frame  17  is supported on the X-direction guide shaft  15  so as to be movable in the X direction. The first frame  17   a  is housed in the body cover  20 . The second frame  17   b  is covered by a moving part cover  13   a.    
     A Y-direction guide shaft  18  extending in the front-back direction is fixed to the second frame  17   b . The carriage  14  is supported by the Y-direction guide shaft  18  to be movable in the Y direction. The carriage  14  has an applied part  4   a  formed therein. The moving table  11  has an attaching part  11   a  which is detachably attached to the applied part  14   a  as will be described later. The above-described attachment  10  functions as a support device which movably support the moving table  11 . 
     The moving table  11  is formed into the shape of a rectangular frame as a whole as shown in  FIG. 3A . The moving table  11  has a thin frame-shaped body  11   b  and an attaching part  11   a  formed on a left edge of an outer periphery of the body  11   b . The body  11   b  and the attaching part  11   a  are formed integrally with the moving table  11 . The body  11   b  has a rectangular opening  11   c  formed thereinside. The opening  11   c  has an inner region where a workpiece cloth can be cut when a free motion cutting is carried out. The attaching part  11   a  is attached to the applied part  14   a  of the carriage  14 . The workpiece cloth is placed on four sides of the body  11   b  so as to overlay the body  11   b , so that the workpiece cloth can be moved in the X direction and the Y direction together with the moving table  11 . 
     The attachment  10  is provided with a first displacement detection mechanism  21   a  and a second displacement detection mechanism  21   b . The first displacement detection mechanism  21   a  detects a displacement of the moving table  11  in the X direction. The second displacement detection mechanism  21   b  detects a displacement of the moving table  11  in the Y direction. The first displacement detection mechanism  21   a  includes an X-axis motor  22 , an encoder  25  and an X-axis transmission mechanism  23 . More specifically, the X-axis motor  22  and a reduction gear mechanism  24  are enclosed in the body cover  20  of the attachment  10  so as to be located on the right side of the fixing frame  16  as shown in  FIGS. 4 and 5 . The X-axis motor  22  is fixed to the underside of the fixing frame  16  and has a rotating shaft  22   a  extending through the fixing frame  16 . A gear  24   a  brought into mesh engagement with the reduction gear mechanism  24  is secured to an upper part of the rotating shaft  22   a . An X-axis encoder  25  (see  FIG. 5 ) is mounted on a lower part of the X-axis motor  22 . The reduction gear mechanism  24  is provided with a pulley  26  (see  FIG. 4 ), and another pulley  27  is rotatably mounted on a left part of the fixing frame  16 . An endless timing belt  28  extends between the pulleys  26  and  27 . The timing belt  28  is connected to the first frame  17   a  of the moving frame  17 . 
     When the moving table  11  is moved in the X direction, the motion of the moving table  11  is transmitted via the moving frame  17  and the timing belt  28  to the pulley  26 , so that the reduction gear mechanism  24  is rotated. The X-axis motor  22  is rotated by the reduction gear mechanism  24 . The X-axis transmission mechanism  23  is thus constituted by the reduction gear mechanism  24 , the gear  24   a , the pulleys  26  and  27 , the timing belt  28  and the like. 
     The second displacement detection mechanism  21   b  includes a Y-axis motor  29 , a Y-axis encoder  33  and a Y-axis transmission mechanism  30 . More specifically, the Y-axis motor  29  is enclosed in the body cover  20  of the attachment  10  so as to be located under the first frame  17   a . The reduction gear mechanism  31  is enclosed in the moving part cover  13   a  of the moving part  13  so as to be located on an upper face of the second frame  17   b . The Y-axis motor  29  has a rotating shaft  29   a  extending through the first and second frames  17   a  and  17   b  in the up-down direction. A gear  31   a  brought into mesh engagement with the reduction gear mechanism  31  is secured to an upper part of the rotating shaft  29   a . A Y-axis encoder  33  is mounted on a lower part of the Y-axis motor  29 . Another pulley  34  is mounted on the reduction gear mechanism  31 . A pulley  35  (see  FIG. 4 ) is rotatably mounted on a rear part of the second frame  17   b . An endless timing belt  36  extends between the pulleys  34  and  35 . The timing belt  36  is connected to the carriage  14 . 
     When the moving table  11  is moved in the Y direction, the motion of the moving table  11  is transmitted via the carriage  14  and the timing belt  36  to the pulley  34 , so that the reduction gear mechanism  31  is rotated. The Y-axis motor  29  is rotated by the reduction gear mechanism  31 . The Y-axis transmission mechanism  30  is thus constituted by the reduction gear mechanism  31 , the pulleys  34  and  35 , the timing belt  36  and the like. The X-axis transmission mechanism  23  and the Y-axis transmission mechanism  30  double as a transfer mechanism which transfers an embroidery frame attached to the carriage  14  in the X direction and the Y direction by driving the X-axis motor  22  and the Y-axis motor  29  respectively. 
     The X-axis encoder  25  is an optical rotary encoder comprising a rotating disc  25   a  and a photointerrupter  25   b . The rotating disc  25   a  is fixed to a lower part of the rotating shaft  22   a  of the X-axis motor  22 . The rotating disc  25   a  has a number of slits formed circumferentially at regular intervals. The photointerrupter  25   b  includes a light-emitting element and a light receiving element located opposite each other with the slits of the rotating disc  25   a  being interposed therebetween. The photointerrupter  25   b  supplies an A-phase signal and a B-phase signal to the control device  39 . These A-phase and B-phase signals have respective phases shifted from each other. Thus, the X-axis encoder  25  detects an amount of rotation and a rotational direction of the X-axis motor  22 . 
     The Y-axis encoder  33  is an optical rotary encoder comprising a rotating disc  33   a  and a photointerrupter  33   b  as the X-axis encoder  25 . The rotating disc  33   a  is fixed to a lower part of the rotating shaft  29   a  of the Y-axis motor  29  and slit. The photointerrupter  33   b  supplies an A-phase signal and a B-phase signal to the control device  39 . Thus, the Y-axis encoder  33  detects an amount of rotation and a rotational direction of the Y-axis motor  29 . The control device  39  calculates amounts of rotation and rotational directions of the moving table  11  in the X direction and the Y direction, based on the detection signals of the encoders  25  and  33 . A calculating manner will be described later. The control device  39 , the encoders  25  and  33  and the like constitute a detection unit which detects an amount of movement and a moving direction of the workpiece cloth placed on the moving table  11 . 
     The sewing machine M further includes a camera  38  provided in the head  3   a  as shown in  FIG. 2 . The camera  38  is an imaging unit comprising a CMOS image sensor and images the workpiece cloth placed on the bed  1 . Images of the workpiece cloth are loaded as still images at predetermined intervals into the control device  39 . The control device  39  compares the latest still image with a last one, thereby specifying an amount of movement and a moving direction of the workpiece cloth. The control device  39 , the camera  38  and the like constitute a detection unit in the case where the moving table  11  is not used. 
     The attachment  10  is provided with a cutting unit  40  to form a cut in the workpiece cloth. A compartment  41  for housing the cutting unit  40  is formed in a right rear of the body cover  20  of the attachment  10 . The compartment  41  defines a space by an upper surface  20   c  and a peripheral wall  41   a . The cutting unit  40  is housed in the space. The cutting unit  40  is formed into a substantially trapezoidal shape in a planar view as shown in  FIG. 6A . The compartment  41  is formed into a shape matching to the trapezoidal shape of the cutting unit  40  as shown in  FIGS. 3A and 3B . Accordingly, when housed in the compartment  41 , the cutting unit  40  is regulated in the orientation in the front-back direction thereby to be housed in the compartment  41  in a correct orientation. 
     The upper surface  20   c  of the compartment  41  has bosses  41   b  and  41   c  which are located at a forward corner and formed integrally with the compartment  41 , as shown in  FIG. 3A . The bosses  41   b  and  41   c  are formed into a right-and-left pair and a columnar shape. The bosses  41   b  and  41   c  protrude downward from the upper surface  20   c  and have lower ends formed with screw holes (not shown) extending in the up-down direction respectively. The upper surface  20   c  of the compartment  41  is formed with a circular hole  41   d  in a forward part thereof. The circular hole  41   d  is formed so as to be located in the rear of a needle location of the needle  5  when the attachment  10  has been attached to the bed  1 . 
     The cutting unit  40  will now be described with reference to  FIGS. 6A, 6B and 6C . The cutting unit  40  includes an enclosure case  51  which is made of resin and formed into a horizontally long box shape. The enclosure case  51  is formed into a substantially trapezoidal shape in a planar view. The enclosure case  51  is mounted by screws (not shown) to a unit frame  56  which will be described later. The enclosure case  51  includes an upper part having stepped parts  51   a  and  51   b  at right and left ends thereof respectively. The stepped parts  51   a  and  51   b  are formed with through holes  51   c  and  51   d  respectively. 
     An extending part  51   e  is formed on a lower part of the enclosure case  51 . The extending part  51   e  extends downward in accordance with a base plate  55  (see  FIG. 8 ) which will be described later. A connector opening  51   f  is formed in a right side of the extending part  51   e . The enclosure case  51  has a substantially cylindrical needle case  53  formed on the left stepped part  51   a . The needle case  53  includes an upper smaller-diameter part  53   a  and a lower larger-diameter part  53   b . The smaller-diameter part  53   a  is fitted into the circular hole  41   d  of the compartment  41 . The enclosure case  51  is set to a height H such that an upper surface of the smaller-diameter part  53   a  is coplanar with the upper surface  20   c  of the body cover  20  when housed in the compartment  41 . Further, the smaller-diameter part  53   a  has an upper surface  53   c  formed with a hole  53   d  (see  FIG. 6A ). A cutting needle  60  as shown in  FIG. 7  comes out of and into the hole  53   d.    
     The inner structure of the cutting unit  40  will now be described with reference to  FIGS. 7 to 9 . Note that the base plate  55  in the enclosure case  51  is eliminated and the inner structure of the cutting unit  40  is partially broken in the rear view of  FIG. 9 . The unit frame  56  is provided in the enclosure case  51 . The unit frame  56  has a standing wall  56   d , a left upper edge  56   a , a right upper edge  56   b  and a lower edge  56   c , all of which are formed integrally therewith. The standing wall  56   d  extends in the up-down direction. The left upper edge  56   a  extends forward from a left upper end of the standing wall  56   d . The right upper edge  56   b  extends forward from a right upper end of the standing wall  56   d . The lower edge  56   c  extends forward from a lower end of the standing wall  56   d . The left upper edge  56   a  is formed with a through hole  57   a  as shown in  FIG. 7 . The right upper edge  56   b  is also formed with a through hole  57   b . The holes  57   a  and  57   b  are located to correspond to the through holes  51   c  and  51   d  of the enclosure case  51  respectively. The holes  57   a  and  57   b  are formed so that bosses  41   b  and  41   c  are fittable with the holes  57   a  and  57   b  respectively. The lower edge  56   c  is formed with through holes  57   c  and  57   d  which are located to correspond to the screw holes formed in the distal ends of the bosses  41   b  and  41   c  respectively. The holes  57   c  and  57   d  have outer diameters which are smaller than outer diameters of the bosses  41   b  and  41   c . The enclosure case  51  includes a lower part formed with through holes (not shown) which are located to correspond to the holes  57   c  and  57   d  respectively. The through holes of the enclosure case  51  have respective outer diameters equal to outer diameters of the holes  57   c  and  57   d.    
     The following describes the case where the cutting unit  40  is housed in (or attached to) the compartment  41 . As the cutting unit  40  is inserted into the compartment  41 , the bosses  41   b  and  41   c  are inserted through the holes  51   c  and  51   d  of the enclosure case  51  and the holes  57   a  and  57   b  respectively. The distal (lower) ends of the bosses  41   b  and  41   c  then abut against an upper surface of the lower edge  56   c . As a result, the unit frame  56  is positioned in the up-down direction with the result that the cutting unit  40  is positioned in the up-down direction. In this state, two screws as shown in  FIG. 3B  are inserted through the holes of the lower part of the enclosure case  51  and the holes  57   c  and  57   d  to be screwed into the screw holes of the bosses  41   b  and  41   c , respectively. The screws  52  have heads having respective outer diameters larger than the outer diameters of the holes of the lower part of the enclosure case  51 . Accordingly, the enclosure case  51  and the unit frame  56  are fixed to the bosses  41   b  and  41   c . Thus, the cutting unit  40  is housed and fixed in the compartment  41 . The screws  52  are loosened when the cutting unit  40  housed in the compartment  41  is detached. 
     A cutting needle support  61  is mounted on a left part of the unit frame  56  so as to extend through the left upper edge  56   a . The cutting needle support  61  has the cutting needle  60 . The cutting needle support  61  includes a support bar extending in the up-down direction, amounting cylindrical part  62  mounted on an upper part of the support bar  63  and a connecting part  64  mounted on a lower part of the support bar  63 . The cutting needle  60  has a haft  60   b  (see  FIG. 9 ) serving as a base and formed into a substantially round bar shape and a blade  60   a  constituting a distal end (an upper end) of the cutting needle  60 , both of which are formed integrally with the cutting needle  60 . The blade  60   a  has a blade edge having a predetermined width W (2 mm, for example) as shown in an enlarged view of  FIG. 12A . In a stricter sense, the blade  60   a  is formed so that two widthwise ends  59   b  are slightly higher than a central part  59   a . When the blade  60   a  forms a cut in the workpiece cloth CL, the ends  59   b  firstly come into contact with and cut into the workpiece cloth CL. Accordingly, the cut is formed by the blade  50   a  without displacement of the blade  60   a  relative to the workpiece cloth CL. The haft  60   b  has an outer periphery including a planar part  60   c  (see  FIG. 9 ) although the planar part  60   c  is not shown in detail. As a result, the haft  60   b  has a D-cut shape, that is, a D-shaped cross-section perpendicular to the lengthwise direction thereof. The planar part  60   c  is formed to extend in a direction perpendicular to the direction (the right-left direction in  FIG. 12 ) in which the blade  60   a  (the blade edge) extends. 
     The support bar  63  includes a first smaller diameter part  63   a  constituting an upper part thereof as shown in  FIG. 9 . The support bar  63  also includes a second smaller diameter part  63   b  constituting a lower part thereof. The first smaller diameter part  63   a  is formed with an insertion groove  62   b  extending in the up-down direction. The insertion groove  62   b  has two sidewalls and an inner wall although these walls are not shown in detail. The insertion groove  62   b  has a generally U-shaped cross-section perpendicular to a lengthwise direction thereof. The insertion groove  62   b  has a width (a dimension between the sidewalls) that is slightly larger than an outer diameter of the haft  60   b . The haft  60   b  of the cutting needle  60  is inserted into the insertion groove  62   b . In this case, the planar part  60   c  of the haft  60   b  is brought into face-to-face contact with the inner wall of the insertion groove  62   b . The mounting cylinder  62  for fixing the cutting needle  60  is attached to cover the first smaller diameter part  63   a  to be fixed to the first smaller diameter part  63   a . The mounting cylinder  62  has aside (a rear surface in  FIG. 9 ) formed with a screw hole (not shown), into which a screw  65  is screwed. When the screw  65  is tightened, a distal end of the screw  65  abuts against the haft  60   b  of the cutting needle  60  to press the haft  60   b . Thus, the planar part  60   c  is pressed against the inner wall of the insertion groove  62   b  with the result that the cutting needle  60  is fixed to the first smaller diameter part  63   a . The cutting needle  60  is thus mounted on the support bar  63  with the blade  60   a  being directed upward. The cutting needle  60  and the support bar  63  are configured so that a central axis line C of the cutting needle  60  corresponds with a central axis line of the support bar  63 . The blade  60   a  has a widthwise central position located on the central axis line C. 
     The support bar  63  extends in the up-down direction through a through hole  57   e  (see  FIG. 9 ) of the left upper edge  56   a  of the unit frame  56 . Further, the support bar  63  is supported on a bearing member  66  so as to be movable up and down and rotatable. The bearing member  66  is fixed to the underside of the left upper edge  66   a  and has a left-half fixing part  66   a  and a right-half bearing part  66   b  both of which are formed integrally with the bearing member  66 , as shown in  FIG. 7 . The fixing part  66   a  is fixed to the left upper edge  56   a  by a screw  67 . The bearing part  66   b  supports the support bar  63  so that the support bar  63  is rotatable about the central axis line C. The fixing part  66   a  is formed with an insertion hole  66   c  having an inner diameter substantially equal to the outer diameter of the boss  41   b . The boss  41   b  is inserted through the insertion hole  66   c  so as to be fitted therein almost without gap. More specifically, when the cutting unit  40  is housed in the housing part  41 , the boss  41   b  is fitted into the insertion hole  66   c , and the boss  41   c  is inserted into the insertion hole  57   b  of the right upper edge  56   b  so as to be fitted with the front and rear portions of the insertion hole  57   b . Thus, the cutting unit  40  is positioned correctly relative to the body cover  20  of the attachment  10  with respect to the front-back direction and the right-left direction. 
     The support bar  63  has a middle part in the direction of the central axis line C. The middle part is formed with an elongate hole  63   c  extending in the direction of the central axis line C. A pin  69  which will be described later is inserted through the hole  63   c  so as to be movable up and down. A first gear  68  is rotatably supported by the middle part of the support bar  63 . The first gear  68  is disposed between the left upper edge  56   a  of the unit frame  56  and the bearing part  66   b . The first gear  68  has an inner periphery formed with a groove  68   a  as shown in  FIG. 9 . The groove  68   a  is open at the underside of the first gear  68 . The pin  69  is fitted in the groove  68   a  and inserted through the hole  63   c  of the support  63 . As a result, the first gear  68  rotated via the pin  69  together with the support bar  63  and allows up-and-down motion of the support bar  63 . The hole  63   c  is formed to extend in a direction perpendicular to an inner wall of the insertion groove  62   b . Accordingly, the pin  69  has a central axis line having a direction corresponding to the direction in which the blade  60   a  (the blade edge) extends. 
     A connecting part  64  is provided under the support bar  63 . The connecting part  64  is connected to a first engagement pin  82   a  of a swing link  80  which will be described later. The connecting part  64  has a cylindrical portion  64   a  and a pair of flanges  64   b  and  64   c  all of which are formed integrally therewith, as shown in  FIG. 8 . The cylindrical portion  64   a  is inserted into the second smaller diameter portion  63   b  of the support bar  63 . The flanges  64   b  and  64   c  are formed on upper and lower ends of the cylindrical portion  64   a  respectively. The second smaller diameter portion  63   b  has a lower end formed with a screw hole (not shown) extending in the up-down direction. The connecting part  64  is fixed by a screw  73  screwed into the screw hole from below the second smaller diameter portion  63   b  while inserted in the second smaller diameter portion  63   b . The flanges  64   b  and  64   c  are each formed into a disc shape such that the flanges  64   b  and  64   c  hold the first engagement pin  82   a  vertically therebetween. A distance between the flanges  64   b  and  64   c  is set to be slightly larger than an outer diameter of the first engagement pin  82   a . Accordingly, the connecting part  64  is maintained in engagement with the first engagement pin  62   a  even when rotated together with the support bar  63 . 
     The following will describe the construction for driving the cutting needle support  61  up and down. A first motor  75  is mounted on the standing wall  56   d  of the unit frame  56  backward so as to be located at a slightly upper rightward position. The first motor  75  is a stepping motor, for example and has an output shaft to which a smaller diameter driving gear  75   a  is fixed, as shown in  FIG. 9 . Further, a gear shaft  76  extending rearward is mounted on the standing wall  56   d  so as to be located at a centrally upper rightward position. A larger diameter driven gear  77  is rotatably mounted on the gear shaft  76 . The driven gear  77  is brought into mesh engagement with the driving gear  55   a . The driven gear  77  has a grooved cam  77   a  formed in a front thereof as shown in  FIG. 7 . The grooved cam  77   a  has an annular shape eccentric to the gear shaft  76 . The grooved cam  77   a  engages a first engagement pin  81   a  of a swing link  80  which will be described later. 
     On the other hand, the driven gear  77  has a rear provided with a first arc portion  78   a  and a second arc portion  78   b  formed integrally therewith, as shown in  FIG. 9 . The first and second arc portions  78   a  and  78   b  are concentric and are each formed into the shape of a thin rib protruding rearward. The base plate  55  is opposed to the standing wall  56   d  of the unit frame  56  and disposed in the rear of the first and second arc portions  78   a  and  78   b . The base plate  55  includes vertical position sensors  79   a  and  79   b  corresponding to the first and second arc portions  78   a  and  78   b  respectively. The vertical position sensors  79   a  and  79   b  detect rotation angles of circumferential ends of the first and second arc portions  78   a  and  78   b  respectively. The vertical position sensors  79   a  and  79   b  are comprised of photointerrupters respectively. Rotation angles of the first and second arc portions  78   a  and  78   b  are detected by the vertical position sensors  79   a  and  79   b  respectively, whereby a horizontal position of the first engagement pin  81   a  engaging the grooved cam  77   a  is determined. Thus, the control device  39  detects a vertical position of a second engagement pin  82   a  which will be described later. A vertical position of the cutting needle  60  is determined based on the determination of the vertical position of the second engagement pin  82   a . Thus, the control device  39  detects the vertical position of the cutting needle  60  based on the detection of rotational angles of the first and second arc portions  78   a  and  78   b  by the vertical position sensors  79   a  and  79   b.    
     The swing link  80  is disposed along a front surface of the standing wall  56   d  in the unit frame  56  as shown in  FIG. 7 . In this case, the swing link  80  is located between the driven gear  77  and the connecting part  64  of the cutting needle support  61 . Further, a frontwardly extending pivotably-supporting shaft  83   a  is mounted on a lower central part of the standing wall  56   d . The swing link  80  is pivotably supported by the shaft  83   a  so as to be swingable. The swing link  80  is constructed of a plate-shaped member and includes an upwardly extending upper arm  81  and a leftwardly extending left arm  82  both of which are formed into an inverted L-shape. The swing link  80  further includes a supported part (a proximal end) which is folded back to the front side thereby to be formed into a U-shape in a side view as shown in  FIG. 8 . The supported part is provided with a folded piece  83  having a through hole (not shown) through which the shaft  63   a  extends. 
     The upper arm  81  has an upper end from which a first engagement pin  81   a  protrudes. The engagement pin  81   a  is located at a rear surface side facing an upper cutout  56   e  (see  FIG. 7 ). The first engagement pin  81   a  is inserted into the grooved cam  77   a  of the driven gear  77  thereby to be in engagement with the grooved cam  77   a . On the other hand, the left arm  82  has a left end from which a second engagement pin  82   a  protrudes. The second engagement pin  82   a  is located at the front surface side so as to be aligned with the connecting part  64 . The second engagement pin  82   a  is held between the flanges  64   b  and  64   c  of the connecting part  64  to be in engagement with the flanges  64   b  and  64   c.    
     Upon drive of the first motor  75 , the driven gear  77  is rotated via the driving gear  75   a . The first engagement pin  81   a  engaging the grooved cam  77   a  is moved in the right-left direction (reciprocal movement) with the result that the swing link  80  is swung about the shaft  83   a . The swing of the swing link  80  moves the second engagement pin  82   a  in the up-down direction (reciprocal movement). The connecting part  64  is moved in the up-down direction by the second engagement pin  82   a  moved in the up-down direction. Thus, the cutting needle support  61  is moved up and down by driving the first motor  75 , so that the cutting needle  60  is moved reciprocally between a top dead point and a bottom dead point. When the cutting needle  60  is located at the top dead point, the blade  60   a  projects from the top  53   c  of the enclosure case  51  (the upper surface  20   c  of the embroidery frame transfer device  13 ). When the cutting needle  60  is located at the bottom dead point, the blade  60   a  is located below the top  20   c . An amount of projection of the blade  60   a  is set to, for example, 5 mm when the cutting needle  60  is located at the top dead point. A cutting needle up-down motion mechanism  86  moving the cutting needle  60  up and down are thus constructed of the first motor  75 , the gears  75   a  and  77 , the grooved cam  77   a , the swing link  80 , the cutting needle support  61  and the like. 
     The cutting unit  40  includes a rotating mechanism  87  which rotates the cutting needle  60  about the central axis line C. In more detail, a second motor  90  is mounted on the left upper edge  56   a  of the unit frame  56  to a downward direction so as to be located in the right of the cutting needle support  61 . The second motor  90  is a stepping motor, for example. The second motor  90  has an output shaft to which a smaller diameter driving gear  90   a  is fixed. A downwardly extending gear shaft  91  is mounted on the left upper edge  56   a  of the unit frame  56  so as to be located between the cutting needle support  61  and the second motor  90 . A driven gear  92  is rotatably mounted on the gear shaft  91 . 
     The driven gear  92  has a cylindrical part through which the gear shaft  91  is inserted, a first gear  92   a  mounted on an upper end of the cylindrical part and a sectorial part  92   b  formed in a lower end of the cylindrical part, all of which are formed integrally with the driven gear  92 , as shown in  FIG. 7 . The sectorial part  92   b  is formed into the shape of a plate with an arc-shaped outer periphery in a planar view. A rotation angle sensor  93  (shown only in  FIG. 10 ) is provided on the standing wall  56   d  of the unit frame  56 . The rotation angle sensor  93  detects a rotation angle of a circumferential end of the sectorial part  92   b . The rotation angle sensor  93  is configured of a photointerrupter. The control device  39  detects a rotation angle of the blade  60   a  of the cutting needle  60  based on a detection signal of the rotation angle sensor  93 . 
     The first gear  92   a  of the driven gear  92  is brought into mesh engagement with both the driving gear  90   a  of the second motor  90  and the first gear  48  of the cutting needle support  61 . The first gear  92   a  has gear teeth the number of which is equal to that of the second gear  68 . The driving gear  90   a , the first gear  92   a  and the second gear  48  constitute a gear train constructed by combining the three spur gears. Accordingly, the driving gear  90   a  has a rotation direction that is the same as a rotation direction of the second gear  68 . When the second motor  90  is driven for normal rotation or for reverse rotation, the first gear  92   a  is rotated via the driving gear  90   a . The second gear  68  is rotated together with the cutting needle support  61  with rotation of the first gear  92   a . Further, the first gear  92   a  has the gear teeth the number of which is equal to that of the second gear  68  as described above. When the first gear  92   a  is rotated one turn, the second gear  68  is also rotated one turn accordingly. Therefore, a rotation angle of the second gear  68  is detected by detecting a rotation angle of the first gear  92   a . The rotation angle of the second gear  68  accordingly corresponds to a rotation angle of the blade  60   a  of the cutting needle  60 . 
     Thus, the second motor  90 , the gears  68 ,  90   a  and  92   a  and the like constitute a rotating mechanism  87  which rotates the cutting needle  60  about the central axis line C. The up-down motion mechanism  86 , the rotating mechanism  87  and the like are assembled to the unit frame  56  to constitute one unit housed in the enclosure case  51  together with the cutting needle  60 , that is, the cutting unit  40 . 
     In attaching the cutting unit  40 , the user puts the cutting unit  40  into the compartment  41  from the underside of the attachment  10  while the cutting unit  40  is oriented so that the needle case  53  side is located upward (see  FIG. 3A ). The cutting unit  40  is fixed by the screws  32 . Thus, the cutting unit  40  is attached to the compartment  41  of the attachment  10  with the blade  60   a  of the cutting needle  60  being directed upward. Further, when the cutting unit  40  has been attached to the compartment  41 , the cutting needle  60  is moved up and down at a location spaced rearward from the needle location  1   b  of the needle  5  by distance G (see  FIG. 3A ). 
     A connector  94  is mounted in a right lower part of the base plate  35  in the cutting unit  40  (see  FIGS. 6C and 7 ). The connector  94  faces the connector opening  51   f  of the enclosure case  51 . When the cutting unit  40  has been attached to the compartment  41 , a cable (not shown) connected to the connector  94  is further connected to a connector (not shown) provided on the rear or the right side of the sewing machine M. As a result, electrical components such as the motors  75  and  90  and the sensors  79   a ,  79   b  and  93  in the cutting unit  40  are electrically connected to the control device  39  of the sewing machine M. 
     The control system of the sewing machine M will now be described with reference to  FIG. 10 . The control device  39  is configured to be microcomputer-centric and includes a CPU  101 , a ROM  102  and a RAM  103 . To the control device  39  are connected the start/stop switch  8   a , the speed adjusting knob  8   b , the touch panel  9   a , the X-axis encoder  25 , the Y-axis encoder  33  and the camera  38 . To the control device  39  are also connected drive circuits  104 ,  105 ,  106  and  107  driving the sewing machine motor  4 , the X-axis motor  22 , the Y-axis motor  29  and the display  9  respectively. Further, the vertical position sensors  79   a  and  79   b  and the rotation angle sensor  93  are connected to the control device  39 . Drive circuits  108  and  109  driving the first motor  75  and the second motor  90  are connected to the control device  39  respectively. 
     The ROM  102  stores embroidery data of various types of embroidery patterns, cutting data, a sewing control program, cutting control program and the like. The embroidery data specifies a needle location for every stitch to sew an embroidery pattern on the workpiece cloth using the sewing needle  5  as well known in the art. More specifically, an X-Y coordinate system is defined in the sewing machine M. The X-Y coordinate system has an origin which is a location where a central point (not shown) of a sewable region automatically set according to a type of the embroidery frame corresponds with the needle location  1   b . The embroidery data has coordinate data based on which the sewing needle  5  is caused to drop sequentially, as needle location data defined by the X-Y coordinate system (embroidery coordinate system) and indicative of an amount of transfer of the embroidery frame in the X direction and the Y direction. The control device  39  controls the sewing machine motor  4 , the X-axis motor  22  and the Y-axis motor  29  based on the embroidery data thereby to automatically perform an embroidery sewing operation for the workpiece cloth. 
     The cutting data is provided for forming a predetermined cut pattern by the cutting needle  60  on the workpiece cloth held on the embroidery frame. The cutting data includes cut position data and angle data. The cut position data is indicative of an amount of transfer of the embroidery frame in the X direction and the Y direction thereby to denote a cut position for every vertical reciprocal movement of the cutting needle  60 . The angle data is set to correspond to the cut position data and denotes a rotation angle (a cut angle) for every vertical movement of the cutting needle  60 . The control device  39  controls the X-axis motor  22 , the Y-axis motor  29 , the first motor  7  and the second motor  90  based on the cutting data, thereby automatically performing a cutting operation for the workpiece cloth. 
     The rotation angle is indicative of a rotation angle of the cutting needle  60  about a central axis line C and is represented by an angle θ made by the cutting needle  60  and the X direction (see  FIG. 11 ). In this case, the central axis line C is perpendicular to the plane of paper of  FIG. 11 . The rotation angle θ in the figure is positive (+) in the counterclockwise direction and negative (−) in the clockwise direction. Further, in the aforesaid XY coordinate system, the direction from left to right of the sewing machine M (rightward on the paper of  FIG. 11 ) is indicated by the positive (+) direction on the X axis, and the direction from front to back (upward on the paper of  FIG. 11 ) is indicated by the negative (−) direction on the Y axis. 
     The sewing machine M is configured to perform a plurality of operation modes including a practical sewing mode, an embroidery sewing mode, a cutting mode and a free motion mode. In the practical sewing mode, sewing is performed while the feed dog is moved forward and backward with the attachment  10  being unattached. On the other hand, in the embroidery sewing mode and the cutting mode, the workpiece cloth held by the embroidery frame is sewn or cut with the attachment  10  being attached, although detailed description of both modes will be eliminated. In the free motion mode, the workpiece cloth is sewn or cut with the attachment  10  being attached and without attachment of the embroidery frame while the user moves the workpiece cloth in any direction. The sewing performed while the user moves the workpiece cloth in any direction is referred to as “free motion stitching.” For example, the configuration disclosed by Japanese patent application publication, JP-A-2009-189626, the application of which was filed by the applicant of the present application, may be employed regarding the free motion stitching, although detailed description will be eliminated. Further, the cutting performed while the user moves the workpiece in any direction is referred to as “free motion cutting.” 
     In the free motion cutting, the control device  39  specifies a moving direction of the workpiece cloth in the case where the user moves the workpiece cloth in any direction, and the control device  39  controls a rotating mechanism  87  so that the direction of the blade  60   a  is changed according to the specified moving direction. The up-down drive mechanism  86  is driven to vertically reciprocate the cutting needle  60 , thereby forming a cut in the workpiece cloth according to a moving direction of the workpiece cloth by the blade  60   a  of the cutting needle  60 . The moving direction of the workpiece cloth is specified based on an image of the workpiece cloth taken by the camera  38  or detection signals generated by the encoders  25  and  33  in the case where the moving table  11  is moved with the workpiece cloth being placed on the moving table  11 . In the following description of the working, the moving direction is to be specified based on an image of workpiece cloth taken by the camera  38 . A fourth embodiment will describe a manner of specifying the moving direction of the workpiece cloth using the moving table  11 . 
     When the free motion cutting is carried out, the user attaches the attachment  10  with the cutting unit  40  to a free arm bed of the bed  1 . The embroidery frame or the moving table  11  is not set on the carriage  14 . The user then places a workpiece cloth as an object to be processed on the bed  1 . The user further operates the touch panel  9   a  to select the cutting control in the free motion mode. As a result, the control device  39  starts the cutting control in the free motion mode. 
     Referring to  FIG. 13  showing processing procedure on a cutting control program in the free motion mode, when determining that the start/stop switch  8   a  has been operated by the user (YES at step S 1 ), the control device  39  detects a rotation angle of the cutting needle  60  based on the detection signals of the rotation angle sensor  93  (step S 2 ). Data of the detected rotation angle is stored in a rotation angle storage area of a RAM  103  by the control device  39 . The control device  39  then controls the camera  38  so that the workpiece cloth on the bed  1  is imaged. In this case, the control device  39  reads an image of the workpiece cloth CL as shown in  FIG. 11  as a still image A, storing the image in a first image storage area of the RAM  103  (step S 3 ). Subsequently, the control device  39  stands by for a predetermined time (0.2 seconds, for example) and controls the camera  38  so that the workpiece cloth CL is again imaged by the camera  38  (steps S 4  and S 5 ). The obtained image of the workpiece cloth CL is stored as a still image B in a second image storage area of the RAM  103 . The control device  39  then specifies a moving direction of the workpiece cloth CL based on the still images A and B, performing a process of obtaining a rotation angle of the cutting needle  60  (step S 6 ). 
     More specifically, the still images A and B are read at predetermined time intervals. Accordingly, when the workpiece cloth CL is moved by the user during the time interval, displacement of the image occurs according to an amount of movement (see symbols ΔX and ΔY in  FIG. 11 ). The control device  39  then measures displacements in the X direction and the Y direction by the number of pixels with respect to pixels composing the still images A and B. Since a known method can be employed for measurement of displacements of the image, a detailed description of the measuring manner will be eliminated. The control device  39  further converts the numbers of pixels in the X direction and the Y direction, measured as the displacements into values corresponding to amounts of movement of the workpiece cloth CL on the bed  1  in the X direction and the Y direction respectively. When symbols, ΔX and ΔY denote converted movement amounts in the X direction and the Y direction respectively, a movement direction θ 1  of the workpiece cloth CL is calculated from the following equation (1), for example:
 
θ1=tan −1 (Δ Y/ΔX )  (1)
 
     The control device  39  then calculates the difference Ψ (=θ 1 −θ 0 ) between θ 1  obtained from equation (1) and the rotation angle θ 0  of the cutting needle  60  obtained at step S 2 . The control device  39  drives the rotational drive mechanism  87  to rotate the cutting needle  60  with the calculated difference Ψ serving as a rotation angle, changing the rotation angle from θ 0  to θ 1  (step S 7 ). The control device  39  further updates the rotation angle in the rotation angle storage area of the RAM  103  from θ 0  to θ 1  added with the difference Ψ (step S 8 ). 
     When determining that the start/stop switch  8   a  has not been operated by the user (NO at step S 9 ), the control device  39  drives the up-down drive mechanism  86  to vertically reciprocate the cutting needle  60  once (step S 10 ). At this time, the cutting needle  60  is moved upward from below, so that the blade  60   a  penetrates through the workpiece cloth CL from below thereby to form a cut L 1 . After having formed the cut L 1 , the cutting needle  60  is moved downward from above thereby to be spaced downward from the workpiece cloth CL. The cut L 1  shown in  FIG. 14A  has a length corresponding to the width W of the blade  60   a  and has an angle θ 1  made along the moving direction (curved line shown by arrow in  FIG. 14A ) of the workpiece cloth CL at the cut position P 1 . Subsequently, the control device  39  stores (updates) the still image A in the first image storage area of the RAM  103  (step S 11 ), returning to step S 5 . 
     The control device  39  causes the camera  38  to image the workpiece cloth CL again. The control device  39  then stores an obtained image of the workpiece cloth CL in a second image storage area of the RAM  103  as a still image B (step S 5 ). The control device  39  further calculates X-direction and Y-direction movement amounts ΔX and ΔY of the workpiece cloth CL, based on the still image A in the first image storage area and the still image B in the second image storage area, obtaining a moving direction θ 2  of the workpiece cloth CL. The control device  39  further calculates the difference Ψ (=θ 2 −θ 1 ) between the movement direction θ 2  and the rotation angle θ 1  stored in the RAM  103 . The control device  39  then drives the rotational drive mechanism  87  to rotate the cutting needle  60  with the result that the rotation angle of the cutting needle  60  is changed from θ 1  to θ 2  (step S 7 ). The rotation angle in the rotation angle storage area of the RAM  103  is updated from θ 1  to θ 2  (step S 8 ). 
     When determining that the start/stop switch  8   a  has not been operated by the user (NO at step S 9 ), the control device  39  drives the up-down drive mechanism  86  to reciprocate the cutting needle  60  once. As a result, a second cut L 2  is formed at a cut position P 2  as shown in  FIG. 14A  and has an angle θ 2  made along the moving direction of the workpiece cloth CL (step S 10 ). Subsequently, the control device  39  proceeds to step S 11  to write the still image B onto a first image storage area of the RAM  103  to store the still image B as the still image A, returning to step S 5 . Steps S 5  to S 11  are thus executed repeatedly, so that cuts L 2 , L 4 , . . . having angles θ 3 , θ 4 , . . . in the moving direction of the workpiece cloth CL are formed at third and subsequent cut positions P 3 , L 4 , . . . respectively. The control device  39  completes the process (END) when determining at step S 9  that the start/stop switch  8   a  has been operated (YES). 
     A time period between the reciprocation of the cutting needle  60  and re-reciprocation of the cutting needle  60  (that is, a time period required for execution of steps S 5  to S 11 ) is 0.2 seconds, for example. The cuts L 1 , l 2 , . . . are formed at this time intervals. Accordingly, when the user moves the workpiece cloth CL at a relatively slower speed (a first speed), the intervals (pitch lengths) between adjacent cut positions P 1 , P 2 , . . . are rendered longer, as shown in  FIG. 14A . In other words, when the workpiece cloth CL is moved at the first speed, the movement amount of the workpiece cloth CL for a unit time is increased with the result of an increase in the pitch length, so that a perforated (dashed) cut pattern CP 1  is formed. 
     Further, the pitch length is rendered longer when the user moves the workpiece cloth CL at a speed (a second speed) further slower than the first speed, as shown in  FIG. 14B . In other words, when the workpiece cloth CL is moved at the second speed, the movement amount of the workpiece cloth CL for the unit time is reduced with the result that the pitch length becomes equal to or shorter than the width W of the blade  60   a , so that a cut pattern CP 2  is formed by continuous cuts L 1 , L 2 , . . . . Further, when the user moves the workpiece cloth CL at a speed still further slower than the second speed, the movement amount of the workpiece cloth CL for the unit time is further reduced, as shown in  FIG. 14C . Accordingly, the pitch length is rendered still further shorter with the result that a cut pattern CP 3  is formed by densely continuous cuts L 1 , L 2 , . . . . When the user keeps the workpiece cloth CL still without movement, the movement amounts ΔX and ΔY become zero and a rotation angle as the difference Ψ also becomes zero, with the result that the cutting needle  60  repeats the vertical movement at the same cut position. 
     The sewing machine M as described above includes the control unit which controls the up-down movement of the cutting needle  60  by the up-down drive mechanism  86  and rotation of the cutting needle  60  by the rotational drive mechanism  87 . Based on the results of detection by the detection unit, the control unit controls the rotational drive mechanism  87  so that the direction of the blade  60   a  is changed according to the moving direction of the workpiece cloth CL. 
     According to the above-described configuration, the moving direction of the workpiece cloth CL is detected by the detection unit when the user moves the workpiece cloth CL on the bed in any direction. In this case, the cutting needle  60  is rotated by the rotational drive mechanism  87  so that the direction of the blade  60   a  is changed according to the moving direction of the workpiece cloth CL based on the results of detection by the detection unit. When the up-down drive mechanism  86  is driven to reciprocate the cutting needle  60  in the up-down direction, a cut can be formed in the workpiece cloth CL by the blade  60   a  of the cutting needle  60  according to the moving direction of the workpiece cloth CL. Thus, the rotation and the up-down movement of the cutting needle  60  are repeated while the workpiece cloth CL is moved in any direction, so that a plurality of cuts is formed along the moving direction of the workpiece cloth CL. Thus, the workpiece cloth CL can be cut in a desired cut pattern by the free motion. 
     The detection unit includes the imaging unit which images the workpiece cloth CL placed on the bed. The imaging unit images the workpiece cloth CL every reciprocation of the cutting needle  60 . The detection unit detects the movement amounts ΔX and ΔY and the moving direction of the workpiece cloth CL every reciprocation of the cutting needle  60 , based on two images (the still images A and B) obtained before and after one reciprocation of the cutting needle  60 . According to this configuration, the movement amounts ΔX and ΔY and the moving direction of the workpiece cloth CL are detected every reciprocation of the cutting needle  60 , so that the direction of blade  60   a  can be oriented to the moving direction θ. Consequently, the workpiece cloth CL can be formed with a clearer cut pattern. Further, the movement amounts ΔX and ΔY and the moving direction θ of the workpiece cloth CL can be detected by a simple configuration using the images obtained by the imaging unit. 
     The cutting unit  40  includes the cutting needle  60 , the up-down drive mechanism  86  and the rotational drive mechanism  87  and is mounted on the attachment  10 . According to this configuration, the cutting function by the cutting needle  60  can easily be added to the attachment  10  in addition to a function as an original embroidering device. 
       FIG. 15  illustrates a second embodiment. Only the differences between the first and second embodiments will be described. Identical or similar parts in the second embodiment will be labeled by the same reference symbols as those in the first embodiment. In the first embodiment, the pitch length of the cuts can optionally be changed according to the movement amount (moving speed) of the workpiece cloth CL as shown in  FIGS. 14A to 14C . However, when the movement amount is not constant, the pitch length varies to become irregular with the result that the cuts look unattractive. 
     In view of the foregoing, the cutting control program employed in the second embodiment includes a default on the pitch length. The default is a set value usable to set the intervals of cuts formed in the workpiece cloth CL, namely, the pitch length to a predetermined first pitch length (2 mm, for example). A setting screen (not shown) to set the first pitch length may be displayed on the display  9  so that the first pitch length is set to an optional value by touch operation onto the touch panel  9   a . The control device  39  executing the cutting control program in the second embodiment, the touch panel  9   a , the display  9  and the like constitute a first pitch setting unit which sets the pitch length to the first pitch length. 
     Referring to  FIG. 15 , the processing flow of the cutting control program in the second embodiment is shown. Substantially the same processing as steps S 1  to S 11  in the first embodiment is carried out at all the steps except step S 30 , that is, steps S 21  to S 29 , S 31  and S 32  in the second embodiment. More specifically, when the start/stop switch  8   a  has been operated (YES at step S 21 ), the control device  39  detects a rotation angle of the cutting needle  60  (step S 22 ) as described above. The control device  39  then obtains still images A and B of the workpiece cloth CL (steps S 23  to S 25 ). Based on the still images A and B, the control device  39  specifies a moving direction of the workpiece cloth CL and performs processing to obtain a rotation angle of the cutting needle  60  (step S 26 ). In this case, the control device  39  calculates a movement amount of the workpiece cloth CL as a movement distance r as shown in  FIG. 11  based on the still images A and B. The movement distance r can be obtained from the x-direction movement amount ΔX and the Y-direction movement amount ΔY:
 
 r =(Δ X   2   +ΔY   2 ) 1/2   (2)
 
     The control device  39  further calculates the difference Ψ between the movement direction θ 1  obtained from the equation (1) and the rotation angle θ 0  of the cutting needle  60  obtained at step S 22 . As a result, the control device  39  drives the rotational drive mechanism  87  to rotate the cutting needle  60  with the difference Ψ serving as a rotation angle (step S 27 ). The control device  39  then updates the rotation angle θ 0  to θ 1  (step S 28 ). 
     When the start/stop switch  8   a  has not been operated (NO at step S 29 ) and the movement amount of the workpiece cloth CL has reached the first pitch length, the control device  39  reciprocates the cutting needle  60  once. More specifically, the control device  39  determines at step S 30  whether or not the movement distance r equals the first pitch length commensurate with the width W of the blade  60   a . When the movement distance r is not equal to the first pitch length, that is, shorter than the first pitch length (NO at step S 30 ), the control device  39  repeats steps S 25  to S 30 . As a result, the control device  39  sets the cutting needle  60  to a rotation angle according to the moving direction of the workpiece cloth CL based on the latest still image B. When determining that the movement distance r equals the first pitch length (YES at step S 30 ), the control device  39  drives the up-down drive mechanism  86  to reciprocate the cutting needle  60  once (step S 31 ). Subsequently, the control device  39  stores the still image B in the RAM  103  as the still image A at step S 31 , returning to step S 25 . 
     Thus, the repeated steps S 25  to S 32  produce a cut pattern (not shown) on the workpiece cloth CL, which cut pattern has the pitch length equal to the width W of the blade  60   a  and is composed of continuous cuts.  FIG. 17A  shows a cut pattern CP 4  having the first pitch length set to a value smaller than the width W of the blade  60   a .  FIG. 17B  shows a cut pattern CP 5  having the first pitch length set to a value larger than the width W. Each one of the cut patterns CP 4  and CP 5  includes a plurality of cuts having an orientation according to the moving direction of the workpiece cloth CL and a constant pitch length. The cuts adjacent to one another are continuous in the cut pattern CP 4 . On the other hand, the cut pattern CP 5  is composed of the cuts separate from one another thereby to be formed into a perforated (dashed) cut pattern. 
     As described above, the sewing machine M of the second embodiment includes the first pitch setting unit which sets to the first pitch length the interval of cuts formed on the workpiece cloth CL by the up-down movement of the cutting needle  60 , that is, the pitch length. The control unit controls the up-down drive mechanism  86  based on the detection results of the detection unit, so that cuts having the first pitch length set by the first pitch setting unit are formed on the workpiece cloth CL. The control unit further controls the rotational drive mechanism  87  so that the orientation of the blade  60   a  is changed according to the moving direction of the workpiece cloth CL. 
     According to the above-described configuration, when the user moves the workpiece cloth CL placed on the bed in any direction, the detection unit can detect a movement amount and a moving direction of the workpiece cloth CL. Consequently, the cutting needle  60  is rotated based on the results of detection by the detection unit so that the orientation of the blade  60   a  is changed according to the moving direction of the workpiece cloth CL. The cutting blade is moved up and down by the up-down drive mechanism  86  so that cuts are formed which have the first pitch length set on the basis of the results of detection by the detection unit. Thus, when the rotation and the up-down movement of the cutting needle  60  are repeated while the workpiece cloth CL is moved in any direction, a plurality of cuts having the first pitch length can be formed along the moving direction of the workpiece cloth CL. This can easily form a good-looking clear cut pattern composed of cuts oriented according to the moving direction of the workpiece cloth CL and having a uniform pitch length. 
     Further, in the second embodiment, the movement distance r and the moving direction θ of the workpiece cloth CL are detected every reciprocation of the cutting needle  60 , so that the orientation of the blade  60   a  is accorded with the moving direction θ and set to a constant pitch length, with the result that a further clearer cut pattern can be formed. 
       FIG. 16  illustrates a third embodiment. Only the differences between the second and third embodiments will be described. Identical or similar parts in the third embodiment will be labeled by the same reference symbols as those in the second embodiment. In the third embodiment, a cut pattern CP 6  can be formed as exemplified in  FIG. 17C . The cut pattern CP 6  is a combination of the cut pattern CP 4  and the cut pattern CP 5 . The cutting control program employed in the third embodiment includes a default a on the pitch length. The default a is a set value usable to set the pitch length to a predetermined second pitch length (1 mm, for example). The default a corresponds to a length of discontinuities (a part between cuts L 5  and L 6  and a part between cuts L 10  and L 11 ) of cuts L 1 , L 2 , . . . in the cut pattern CP 6 , as exaggeratingly shown in  FIG. 17C . Thus, the pitch lengths between the cuts L 5  and L 6  and cuts L 10  and L 11  of a plurality of cuts L 1 , l 2 , . . . composing the cut pattern CP 6  are set to a second pitch length obtained by adding the default a to the width W of the blade  60   a.    
     Further, in the third embodiment, a number setting screen (not shown) is displayed on the display  9  in starting the free motion cut. The number setting screen is provided for setting the number of reciprocation of the cutting needle  60  to a predetermined number of times. More specifically, the user sets the number of reciprocation of the cutting needle  60  by the touch operation onto the touch panel  9   a  in order to optionally set a cut position of the second pitch length (discontinuities of cuts in the cut pattern). In this case, a setting screen (not shown) to set the second pitch length may be displayed on the display  9 , so that the second pitch length may be set to any value by the touch operation on the touch panel  9   a . The control device  39 , the touch panel  9   a , the display  9  and the like constitute a second pitch setting unit which sets the pitch length to the second pitch length and a number setting unit which sets the number of reciprocation of the cutting needle  60  to the predetermined number of times. 
     Referring to  FIG. 16 , the processing flow of the cutting control program in the third embodiment is shown. Substantially the same processing as steps S 21  to S 32  in the second embodiment is carried out at all the steps except steps S 30 , S 43 , S 51 , S 54 , S 56  and S 57 . More specifically, the control device  39  causes the display  9  to display the number setting screen and obtains the reciprocation number n supplied by touch operation (step S 40 ). When the start/stop switch  8   a  has been operated (YES at step S 41 ), the control device  39  detects a rotation angle of the cutting needle  60  (step S 42 ). The control device  39  resets a counter counting the number of reciprocation of the cutting needle  60  to 0 thereby to initialize the counter. The control device  39  further loads the supplied reciprocation number (five times, for example) and the default a to store them in the RAM  103  (step S 43 ). 
     The control device  39  further obtains the still images A and B of the workpiece cloth CL (steps S 44  to S 46 ), specifies the moving direction of the workpiece cloth CL based on the still images A and B and performs processing to obtain the rotation angle of the cutting needle  60  (step S 47 ). In this case, the control device  39  calculates a movement amount of the workpiece cloth CL as the movement distance r based on the still images A and B. The control device  39  further calculates the difference Ψ between the movement direction θ 1  obtained from the equation (1) and the rotation angle θ 0  of the cutting needle  60  obtained at step S 42 . As a result, the control device  39  drives the rotational drive mechanism  87  to rotate the cutting needle  60  with the difference Ψ serving as a rotation angle (step S 48 ). The control device  39  then updates the rotation angle θ 0  to θ 1  (step S 49 ). 
     The control device  39  reciprocates the cutting needle  60  once when the start/stop switch  8   a  has not been operated (NO at step S 50 ) and the count value is less than the reciprocation number n (NO at step S 51 ) and the movement amount of the workpiece cloth CL has reached the width W of the blade  60   a . More specifically, when the current count value is 0 (NO at step S 51 ), the control device  39  determines whether or not the movement distance r equals the width W of the blade  60   a  (step S 52 ). When determining that the movement distance r equals the width W of the blade  60   a  (YES), the control device  39  drives the up-down drive mechanism  86  to reciprocate the cutting needle  60  once (step S 53 ). Subsequently, the control device  39  increments the counter (step S 54 ) and stores (updates) the still image B in the RAM  103  as the still image A (step S 55 ), returning to step S 46 . 
     Thus, when the repeated steps S 46  to S 55  produce five cuts L 1  to L 5 , the control device  39  determines at step S 51  that the count value of the counter is equal to or larger than the reciprocation number n (=5) (YES). In this case, the control device  39  determines whether or not the movement distance r of the workpiece cloth CL is equal to the addition of the width W of the blade  60   a  and the default a (that is, the second pitch length) (step S 56 ). When determining that the movement distance r of the workpiece cloth CL is less than the second pitch length (NO), the control device  39  repeats steps S 46  to S 51  and S 56 . As a result, the control device  39  sets the cutting needle  60  to a rotation angle according to the moving direction of the workpiece cloth CL based on the latest still image B. 
     When determining that the movement distance r of the workpiece cloth CL is equal to the second pitch length (YES at step S 56 ), the control device  39  resets the counter to 0 (step S 57 ). The control device  39  then drives the up-down drive mechanism  86  to reciprocate the cutting needle  60  once (step S 53 ). The sixth cut L 6  formed to have the second pitch length is further formed to be spaced from the cut L 5  adjacent thereto (see  FIG. 17C ). The control device  39  thus counts as a counting unit the reciprocation number of the cutting needle  60  and sets the pitch length of the next cuts L 6 , L 11 , and . . . to the second pitch length every time the count reaches 5. As a result, discontinuities of the cuts are formed in the cut pattern CP 6 . 
     The reciprocation number n set on the number setting screen may optionally be set according to preference of the user. Further, the object placed on the bed  1  should not be limited to the workpiece cloth CL but may be a paper or resin sheet or the like. Accordingly, the reciprocation number n and the default a may be set to respective appropriate values according to a material of the object. 
     In the third embodiment, the second pitch setting unit sets the pitch length to the second pitch length that is longer than the width W of the blade  60   a . When the reciprocation number of the cutting needle  60  counted by a count unit has reached the predetermined number set by the number setting unit, the control unit controls the up-down drive mechanism  86  so that the cuts are formed on the workpiece cloth W so as to have the second pitch length set by the second pitch setting unit. The control unit further resets the reciprocation number of the cutting needle  60  by the count unit. According to this configuration, the reciprocation number of the cutting needle  60  is set by the number setting unit, so that the discontinuities of the cuts can be formed in the cut pattern according to the set number. 
       FIG. 18  illustrates a fourth embodiment. Only the differences between the first and fourth embodiments will be described. Identical or similar parts in the fourth embodiment will be labeled by the same reference symbols as those in the first embodiment. In the fourth embodiment, encoders  25  and  33  of the attachment  10  are used as the detection units which detect the movement amount and moving direction of the workpiece cloth CL. The moving table  11  is attached to the carriage  14  of the attachment  10  so that the workpiece cloth CL is placed on the moving table  11 . When the free motion mode is selected by the touch operation onto the touch panel  9   a , the cutting control is started in the free motion mode. 
     Referring to  FIG. 18 , the processing flow of the cutting control program in the fourth embodiment is shown. Firstly, at step S 60  of initializing process, the control device  29  de-energizes the X-axis motor  22  and the Y-axis motor  29  when these motors are energized. As a result, the moving table  11  is freely movable in the X direction and the Y direction, that is, braking forces of both motors  22  and  29  are not applied to the moving table  11 . The control device  39  further initializes count values (default=0) which will be described later. The control device  39  then receives detection signals from the X-axis encoder  25  and the Y-axis encoder  33  to start counting. In this case, the count value (X-phase count value) is incremented or decremented every time the control device  39  receives a detection signal from the X-axis encoder  25 , and the count value (Y-phase count value) is incremented or decremented every time the control device  39  receives a detection signal form the Y-axis encoder  33 . The control device  39  calculates a current position of the moving table  11  based on these count values. 
     When determining, in the above-described state, that the start/stop switch  8   a  has been operated by the user (YES at step S 61 ), the control device  39  detects a rotation angle of the cutting needle  60  and stores the detected rotation angle in a rotation angle storage area of the RAM  103  (step S 62 ). The control device  39  further reads the coordinate of the current position of the moving table  11  as a read-out value Ae and stores the read-out value in a first read-out value storage area of the RAM  103  (step S 63 ). Subsequently, the control device  39  stands by for the predetermined time period (0.2 seconds, for example) and then reads a coordinate of current position of the moving table  11  as a read value Ae to store the read value Ae in the second read value storage area of the RAM  103  (steps S 64  and S 65 ). Based on the read values Ae and Be, the control device  39  specifies the moving direction of the workpiece cloth, obtaining the rotation angle of the cutting needle  60  (step S 66 ). 
     More specifically, since the user manually moves the workpiece cloth CL in any direction together with the moving table  11  in the fourth embodiment, the X-direction and Y-direction movement amounts can be obtained from the read values of Ae and Be of the X-axis and Y-axis encoders  25  and  33 . When the coordinate of the read value Ae is represented as (X1, Y1) and the coordinate of the read value Be is represented as (X2, Y2), the X-direction and Y-direction movement amounts ΔX and ΔY can be calculated by the following equations (3) and (4) respectively:
 
Δ X=X 2− X 1  (3)
 
Δ Y=Y 2− Y 1  (4)
 
     The moving direction θ 1  of the workpiece cloth CL is obtained when the movement amounts ΔX and ΔY are substituted in the equation (1). The control device  39  then calculates the difference Ψ (=θ 1 −θ 0 ) between θ 1  obtained from equation (1) and the rotation angle θ 0  of the cutting needle  60  obtained at step S 62 . The control device  39  further drives the rotational drive mechanism  87  to rotate the cutting needle  60  with the obtained difference Ψ serving as the rotation angle (step S 67 ). The control device  39  still further updates the rotation angle θ 0  in the rotation angle storage area of the RAM  103  to θ 1  (step S 68 ). 
     When determining that the start/stop switch  8   a  has not been operated by the user (NO at step S 69 ), the control device  39  drives the up-down drive mechanism  86  to reciprocate the cutting needle  60  once (step S 70 ). In this case, the cut L 1  is formed at an angle θ 1  according to the moving direction of the workpiece cloth CL in the same manner as in the first embodiment. Subsequently, the control device  39  stores the read value Be in the first read value storage area of the RAM  103  as the read value Ae (step S 71 ), returning to step S 65 . Thus, steps S 65  to S 61  are repeated so that the cut patterns CP 1  to CP 3  according to the movement amount of the moving table  11  can be formed on the workpiece cloth CL (see  FIGS. 14A to 14C ). 
     The sewing machine M of the fourth embodiment as described above uses the encoders  25  and  33  as the detection unit to detect the movement amounts ΔX and ΔY and the moving direction θ in the case where the workpiece cloth CL placed on the moving table  11  on the bed is moved together with the moving table  11 . According to this configuration, the fourth embodiment can achieve the same advantageous effect as the first embodiment, for example, a plurality of cuts can be formed along the moving direction of the workpiece cloth CL. 
     The foregoing embodiments should not be restrictive but may be modified or expanded as follows. The sewing machine M may be configured to be capable of selectively performing the processing contents of the flowcharts in the first to fourth embodiments. 
     In each of the second and third embodiments, the encoders  25  and  33  may be used as the detection units which detect the movement amount and moving direction of the workpiece cloth CL. More specifically, in the second embodiment, too, step S 60  is carried out as the initialization process and steps S 63 , S 65 , S 66  and S 71  are carried out instead of steps S 23 , S 25 , S 26  and S 32  in  FIG. 15 . This can move the workpiece cloth CL together with the moving table  11  with the moving table  11  being attached to the carriage  14  and further form a cut pattern having cuts oriented in the moving direction and having an equal pitch length. 
     In the third embodiment, step S 60  may be carried out as the initializing process, and steps S 63 , S 65 , S 66  and S 71  may be carried out instead of steps S 44 , S 46 , S 47  and S 55  in  FIG. 16 . As a result, the work piece CL can be moved together with the moving table  11  with the moving table  11  being attached to the carriage  14 , and various types of perforations can be formed on the workpiece cloth. 
     The detection unit should not be limited to the camera  38  and the encoders  25  and  33  but may be at least capable of detecting the moving direction of the object such as the workpiece cloth CL placed on the bed. For example, an imaging device (imaging unit) of the type that is used in an optical mouse provided with a digital signal processor (DSP) may be provided on the attachment  10 . As a result, the movement amount and the moving direction of the object may be detected with images obtained by the imaging device serving as still images A and B. Further, an oscillator may be provided on the movable side moving table  11 , for example. A receiver may be provided on the fixed side attachment  10 . Ultrasonic waves oscillated from the oscillator may be received by the receiver, whereby the movement amount and moving direction of the moving table  11  (the object to be processed) may be detected. 
     The cutting unit  40  should not be limited to the application to the sewing machine M but may be applied to various types of sewing machines. Further, the cutting unit  40  should not be limited to provision on the bed but may be provided in the sewing machine head  3   a . An auxiliary table can be attached to the bed  1 , instead of the attachment  10 . The auxiliary table is a known attachment for enlarging a surface on which the object is placed. When the auxiliary table is attached to the bed  1 , an upper surface of the auxiliary table is substantially coplanar with the upper surface of the bed  1 , thereby serving as the surface on which the workpiece cloth CL is placed. The auxiliary table may be provided with a housing part which detachably houses the cutting unit  40 . The housing part may have the same configuration as the compartment  41  of the attachment  10 . Alternatively, the up-down drive mechanism  86  and the rotational drive mechanism  87  may directly be assembled to the machine frame in the auxiliary table. In this construction, too, the cutting needle  60  can be in an upward direction such that the cutting needle  60  forms a cut in the object with upward movement from below, with the result that the same advantageous effects as the foregoing embodiments can be achieved. 
     The first pitch length, the second pitch length, the width W of the blade  60   a , the default a and the line should not be limited to respective exemplified values but may appropriately be changed. 
     The foregoing description and drawings are merely illustrative of the present disclosure and are not to be construed in a limiting sense. Various changes and modifications will become apparent to those of ordinary skill in the art. All such changes and modifications are seen to fall within the scope of the appended claims.