Patent Publication Number: US-6698369-B2

Title: Embroidery machine

Description:
BACKGROUND OF THE INVENTION 
     1. Technical field 
     The present invention relates to an embroidery machine, more particularly to X-axis and Y-axis driver units for driving an embroidery frame and interlocking units of the embroidery machine. 
     2. Description of the Prior Art 
     In general, an embroidery machine is a two-axis positioning control device in which an embroidery frame into which a raw cloth is fixed moves horizontally in X or Y direction, while a needle holder of a sewing machine moves up and down. 
     In such an embroidery machine, the precision in movement and constant speed of the embroidery frame is closely involved with the quality of the embroidery because an embroidery frame fixed with raw cloth is configured to embroider the cloth while moving in X and Y directions. 
     Accordingly, a servo motor, or an induction motor which can control speed is used as a power source for driving the needle holder of the embroidery machine up and down, a stepping motor which has an excellent positioning function and is easy to control is used as a power source for driving the embroidery machine in X and Y directions. 
     The prior art is described below with reference to the FIG. 22 to FIG.  24 . First, there is provided a rectangular table  102 , an embroidery frame  104  installed above the table  102  for fixing a cloth on which various patterns are embroidered, a head  106  including a plurality of needles for embroidering the cloth and installed above the embroidery frame  104 , and a hook  108  installed below the table  102  opposite to the head  106  for feeding a lower thread. 
     In this case, an upper shaft  403  and a lower shaft  142  for transmitting power are coupled to the head  106  and the hook  108  respectively. The upper shaft  403  and lower shaft  142  are coupled to a main-shaft driver unit  401  which provides power to the shafts. 
     An X-axis driver unit  110  is provided on one end portion of the embroidery machine  104 . The X-axis driver unit  110  is described below. A connector frame A  112  is coupled with one side of the embroidery frame  104  with slippingly placed on the table  102 , and a slider  114  which is located below the table  102  and move back and forth is coupled with the lower part of the connector frame A  112 . A front face of the timing belt for transmitting power is coupled with lower end portion of the slider  114 , driver timing pulley  116  and follower timing pulley  118  are coupled with one end portion and other end portion of the timing belt respectively, and a shaft  120  for transmitting power is coupled with the driver timing pulley  116 . 
     An X-axis driver motor  122  for providing power is coupled with one end portion of the shaft  120 , a control unit, not shown, for transmitting commands is coupled with the X-axis driver motor  122 . In addition, a guide rail  115  which serves as a guide is coupled with a lower part of the slider  114 , and the driver timing pulley  116  and follower timing pulley  118  are installed rotatably at respective leading end portion and trailing end portion of the guide rail  115 . 
     At the rear part of the embroidery frame  104  there is provided a Y-axis driver unit  120 . In the Y-axis driver unit  120 , a connector frame B  126  is placed on and coupled slippingly in X direction with the table  102 , in the rear end portion of the embroidery frame  104 , and a slider  128  moving back and forth is coupled with a lower part of the connector frame B  126 . 
     Also, a front face of the timing belt is coupled with a lower end portion of the slider  128 , and a driver timing pulley  130  and a follower gear  132  are coupled with respective leading end portion and trailing end portion of the timing belt. 
     A shaft  134  is coupled with the driver timing pulley  130 , an Y-axis driver motor  136  for providing power is coupled with the shaft  134 , then a control unit for transmitting commands is coupled with Y-axis driver motor  136 . 
     In addition, a guide rail  138  which serves as a guide is slippingly coupled with a lower part of the slider  128 , and the driver timing pulley  130  and the follower gear  132  are installed rotatably at respective leading end portion and trailing end portion of the guide rail  138 . 
     In the meanwhile, a thread-cut drive unit  140  for cutting unnecessary threads from the head  106  and the hook  108  is located below the table  102 , and the structure of the thread-cut drive unit  140  is as follows. 
     First, in the thread-cut drive unit  140 , a driver sprocket  144  is mounted on the lower shaft  142  while winding one side of a chain  146 , and a follower sprocket  148  is coupled with a shaft B  152  installed inside a case  150  in other side of the chain  146 . 
     In addition, a cam  154  is coupled with the shaft B  152 , a roller  156  is coupled slidingly with the cam  154 , and a front end portion of a lever  158  is coupled with the roller  156 . 
     Also, a hinge shaft  160  defining an axis of rotation is coupled with the center of the lever  158 , and a solenoid, not shown, for applying force to attach the roller  156  to the cam  154  or to detach the roller  156  from the cam  154  is installed at the lower end portion of the hinge shaft  160 . 
     Further, a pusher  162  for transmitting the force is vertically coupled with the rear end portion of the lever  158 , a rod  164  moving back and forth is coupled with the lower end portion of the pusher  162 , in this case, the rod  164  extends outwardly through the case  150 . 
     A thread-cut shaft  166  rotating positive or reverse direction by the power transmitted at the time of moving back and forth is installed on the rod  164 , a cutter A  168  rotating with the shaft  166  is coupled with the upper end portion of the thread-cut shaft  166  above the hook  108 , and a cutter B  170  is located crosswise at the front end portion of the cutter A  168 . At this time, the cutter B  170  is fixed to a hook base  172 . 
     In addition, a front end portion of a shaft C  174  which transmits power is coupled to the hook  108 , a follower gear  176  formed with helical gear is engaged with the rear end portion of the shaft C  174 , a driver gear  178  formed with helical gear is installed at the lower shaft  142  in gear engagement with the follower gear  176 . 
     In the meanwhile, a color-change drive unit  180  for adjusting the head to embroider in various colors is located at one end portion of the head  106  as shown in FIG. 25, the color-change drive unit  180  comprises a rod  182  moving back and forth and coupled with the one end portion of the head  106  at the same time, a block  184  moving back and forth with the rod  182  is coupled with a rear end portion of the rod  182  inside a housing  186 . 
     Also, guide rods  188  that serve as a guide for moving back and forth are coupled slippingly with upper and lower parts of the block  184 , and front and rear end portions of the guide rod  188  are coupled with the housing  186  walls respectively. 
     A sensor pointer  190  configured to check the range of movement of the head  106  is installed at the front part of the block  184 , a roller  192  is rotatably coupled with the block  184  rear part. 
     While, the roller  192  is mounted in a threaded groove of a cam shaft  194  which transmits force for moving the block  184  back and forth, the cam shaft  194  is installed transversely inside the housing  186 , the front and rear end portions of the cam shaft  194  are coupled rotatably with walls of the housing  186  respectively, a follower gear  196  for receiving power is coupled with a rear part of the cam shaft  194 . 
     In addition, a driver gear  198  is coupled with a follower gear  196  in gear engagement, the driver gear  198  is coupled with a shaft  202  of a step motor  200  which provides power, and a control unit for transmitting commands is coupled with the step motor  200 . In addition, a panel which is not shown is coupled with a front face of the housing  186 , a plurality of sensors which are used to determine whether the color of a lower thread has changed or not by sensing the position of the sensor pointer  190  are installed on the panel, the control unit is connected to the sensors. 
     Next, the structure of the head is described below with reference to the FIG.  26 . 
     First, the head  106  is coupled slippingly with an upper front face of an arm  409  through which an upper shaft  403  connected with a main-shaft driver unit  401  passes. At this time, a driver cam  413  formed with a cam groove  411  in front face thereof is mounted on the arm  409 , a cam roller  415  installed on a rotating driver lever  417  is placed in the cam groove  411 . 
     Next, a driver gear  419  is coupled with a front end portion of the driver lever  417 , a thread-snatch unit  421  for drawing a single thread located above the driver gear  419  is coupled to the driver gear  419  with its rear part in gear engagement and is installed at the head  106   
     Further, a rear end portion of a rotating driver lever  423  is mounted on a rear face of the driver cam  413 , a slider  425  is coupled with the front end portion of the driver lever  423 , and a control block  427  which actuates repeatedly upward and downward is coupled with the slider  425 . A needle holder shaft  429  which serves as a guide is coupled slippingly with the control block  427  and mounted vertically at the arm  409 . 
     In addition, a fixed bracket  431  is detachably coupled with the front end portion of the control block  427  and installed at the head  106 , and a needle holder  433  which is configured to move a single thread from the thread-snatch unit  421  onto the cloth and to embroider the cloth is coupled with the fixed bracket  431  and installed vertically movably at the head  106 . 
     The operation of the prior art having such composition is described as follows. 
     First, operation items are inputted in the operating panel in order to embroider various patterns on a cloth, then the control unit transmits commands to the X-axis and Y-axis driver motors  122 ,  136  and the main-shaft driver unit. 
     When the X-axis driver motor  122  operates according to a command from the control unit, the driver timing pulley  116  is rotated by the positive or reverse rotation of the shaft  120 , accordingly the slider  114  is moved by the timing belt which is engaged partly with the driver timing pulley  116 . 
     The connector frame A  112  pushes or pulls the embroidery frame when the slider  114  moves back and forth as described above, at the same time, the rear part of the embroidery frame  104  moves slidingly in the connector frame B  126  which remains in a fixed position. 
     When the embroidery frame  104  moves like that, the driver cam  413  is rotated by a part of power transmitted through the upper shaft  403  and provided from the main-shaft driver unit  401 , consequently, cam roller  415  located in the cam groove  411  of the driver cam is rotated and is moved by a width in left and right. 
     Therefore, the driver lever  417  is rotated to move the thread-snatch unit up and down which is coupled with the driver gear  419  in gear engagement, thereby the thread-snatch unit  421  draws a single thread above the embroidery frame  104  and feeds the single thread. 
     At the same time, the driver cam  413  rotates other driver lever  423 , and slides the slider  425  and control block  427  up and down repeatedly on the needle holder shaft  429 . 
     Consequently, the control block  427  causes the fixed bracket  431  and needle holder shaft  429  to move up and down together, and the single thread from the thread-snatch unit  421  to move onto the cloth and to embroider the cloth. 
     Further, in case the position is needed to be changed when embroidering the cloth, the Y-axis driver motor  136  is operated by a command from the control unit, then the driver timing pulley  130  is rotated in a positive or reverse direction by the rotation of the shaft  134 , as a result, the timing belt which winds the driver timing pulley  130  in part moves the slider  128 . 
     Therefore, the slider  128  pushes and pulls the connector frame B  126 , and causes the embroidery frame  104  to move forward or backward, at the same time the one end portion of the embroidery frame  104  slides on the connector frame A  112  located in a fixed position 
     When the embroidery frame  104  moves in such a way, needles provided identically in the head as described above move up and down, to embroider on the cloth. 
     At the same time, a part of the power from the main-shaft driver unit  401  is transmitted through the lower shaft  142  and rotates the driver sprocket  144 , thereby the power is transmitted through the chain  146  and rotates the follower sprocket  148 . 
     Further, when the follower sprocket  148  rotates and causes the shaft B  152  and the cam  154  to rotate together, the roller  156  and the shaft B  152  are in idle state because the control unit does not transmit the operating commands to the solenoid yet and accordingly the roller  156  is not engaged with the cam  154 . Therefore, the rod  164  remains at an original position and the cutter A  168  is in stationary state. 
     At the same time, the driver gear  178  is rotated by the rotation of the lower shaft  142  and causes the follower gear  176  which is in gear engagement with the driver gear  178  together with the shaft C  174  to rotate, so that the hook  108  coupled with the front end portion of the shaft C  174  can be rotated. 
     In the meanwhile, in case a single thread of other colors might be provided while embroidering the cloth, the lower thread provided previously should be cut. At this time, when an operating command is transmitted from the control unit to the solenoid, the hinge shaft  160  is raised with the lever  158  and causes the roller  156  to couple with the cam  154 . 
     As a result of this, the roller  156  is coupled with the cam which has been in idle state, and thereby the cam  154  moves within a predetermined range and causes the lever  158  to move toward a center of the hinge shaft  160 . 
     Therefore, when the pusher  162  installed at the rear end portion of the lever  158  moves leftward and rightward and causes the rod  164  to move forward and backward, then the thread-cut shaft  166  is rotated by the rod  164  and causes the cutter A  168  to rotate. At this time, the cutter A  168  pushes an upper thread near the needle outwardly, and draws upper and lower threads near the cloth toward the cutter B  170  and cuts the threads when returning to the previous position. 
     When the cutting operation is over as described above, the control unit transmits a command to the step motor  200  in the color-change driver unit  180 . 
     When the step motor  200  is rotated in a positive or reverse direction by a command received as above and causes the follower gear  196  to rotate through the driver gear  198 , then the follower gear  196  rotates the cam shift  194  and pushes or pulls the roller  192  so as to move the block  184  forward or backward on the guide rod  188 . 
     Accordingly, the rod  182  moves forward and backward by the block and causes the head  106  to move to a position into which an upper thread of corresponding color is fed. 
     At this time, the center pointer  180  mounted on the front face of the block  184  is checked by any one of the plurality of sensors mounted on the panel, the information with respect to result is transmitted to the control unit and stops the operation of the step motor  200 , thereby the head  106  reaches and stops at the position where the color of the upper thread is changed. 
     Further, while the control unit transmits the operating command to the X-axis and Y-axis driver motors so as to move the embroidery frame  104  forward and backward as described above, and at the same time causes the needle provided in the head  106  to move up and down so as to embroider the cloth. 
     The above-described prior art generates great vibration and noise due to its intricate construction in the interlocking units which constitutes X-axis and Y-axis driver units, and a problem in expensive production cost due to the complicated mechanical structure. 
     There is another problem of the low quality of the embroidery because the power transmission is performed through several steps and thereby it is not possible to control the embroidery frame precisely. 
     SUMMARY OF THE INVENTION 
     The present invention is designed to overcome the above problems of the prior art. Therefore, it is a first object of the invention to reduce the vibration and noise in the embroidery machine by simplifying the construction of the interlocking units which constitutes X-axis and Y-axis driver units, and to improve the productivity by reducing the production cost. 
     It is a second object of the invention to provide a more space-efficient embroidery machine by simplifying the construction of the interlocking units which constitutes X-axis and Y-axis driver units, and reducing the space required for the X-axis and Y-axis driver units. 
     It is a third object of the invention to simplify a power transmission procedure by installing a vertical driver unit inside each head so as to drive needles separately according to each head. 
     It is a fourth object of the invention to simplify a power transmission procedure and reduce operating errors of a needle holder and a hook by installing a vertical driver unit inside each head and, in addition, constructing the hook interlocked with the vertical driver unit to be driven separately from the unit. 
     It is a fifth object of the invention to simplify interlocking units and to reduce vibration and noise by constructing not only a needle holder and a hook but also an embroidery frame to be driven separately. 
     It is a sixth object of the invention to simplify interlocking units, to reduce significantly the vibration and noise of the entire embroidery machine and to perform various embroidery operations with one embroidery machine so as to maximize the effectiveness of operation and at the same time to make mass production of the embroideries possible, by disposing an embroidery frame in each head group, simplifying the construction of X-axis and Y-axis driver unit which drives the embroidery frame of each head group, and separately driving a vertical driver unit for moving a needle holder of the head, a hook, and the embroidery frame respectively. 
     The first object of the invention is accomplished by an embroidery machine comprising: a table; an embroidery frame placed on the table; a head located above the embroidery frame, the head having a plurality of needles; a hook installed below the table, the hook being opposite to the head; an X-axis driver unit for providing power to move the embroidery frame forward and backward in X direction; an Y-axis driver unit for providing power to move the embroidery frame forward and backward in Y direction; and a control unit for being connected to the X-axis driver unit and Y-axis driver unit. 
     The second object of the invention is accomplished by an embroidery machine comprising: a table; an embroidery frame slippingly placed on the table; a head located above the embroidery frame, the head having a plurality of needles; and a hook installed below the table, the hook being opposite to the head, wherein an XY system for providing power to move the embroidery frame in X and Y directions is mounted on a central portion of a rear side of the embroidery frame, a control unit is coupled to the XY system. 
     In addition, the second object of the invention is accomplished by an embroidery machine comprising: a table; an embroidery frame slippingly placed on the table; a head located above the embroidery frame, the head having a plurality of needles; and a hook installed below the table, the hook being opposite to the head, wherein an XY table for providing power to move the embroidery frame in X and Y directions is mounted on a central portion of a rear side of the embroidery frame, a control unit is coupled to the XY table. 
     The third object of the invention is accomplished by an embroidery machine comprising: a plurality of heads installed above a working table; a needle holder installed inside each head and slidingly movable up and down; a vertical driver unit for moving the needle holder up and down, the vertical driver unit being installed inside each head; and a controller for controlling a plurality of the vertical driver units. 
     The fourth object of the invention is accomplished by an embroidery machine comprising: a plurality of heads installed above a working table; a needle holder mounted inside each head and slidingly movable up and down; a vertical driver means mounted on one side of each head and causing the needle holder to move up and down; a plurality of hooks installed at a lower part of the needle holder and vertically opposite to the needle holder; a small-sized motor mounted at a rotatory shaft of each hook; and a controller for controlling a plurality of vertical driver means and a plurality of small-sized motors. 
     The fifth object of the invention is accomplished by an embroidery machine comprising: a plurality of heads installed above a working table and spaced apart each other; a needle holder installed inside each head and slidingly movable up and down; a plurality of hooks installed at a lower part of each needle holder and vertically opposite to the needle holder; a plurality of embroidery frames installed between the needle holder and the hook, and movable in X or Y direction; a guide rail disposed in X direction of each embroidery frame; an X-axis driver linear motor for moving the embroidery frame in X direction while moving along the guide rail; a guide rail disposed in Y direction of each embroidery frame; an Y-axis driver linear motor for moving the embroidery frame in Y direction while moving along the guide rail; and a controller for controlling a plurality of X-axis and Y-axis driver linear motors. 
     The sixth object of the invention is accomplished by an embroidery machine comprising: a plurality of heads installed in groups above a working table and spaced apart each other; a needle holder installed inside each head and slidingly movable up and down; a vertical driver means mounted on one side of each head and causing the needle holder to move up and down; a plurality of hooks installed at a lower part of each needle holder and vertically opposite to the needle holder; a small-sized motor mounted on a rotatory shaft of each hook; a plurality of embroidery frames installed on an upper surface of the working table according to each head group, and movable in X or Y direction; a guide rail disposed in X direction of each embroidery frame; an X-axis driver linear motor for moving the embroidery frame in X direction while moving along the guide rail; a guide rail disposed in Y direction of each embroidery frame; an Y-axis driver linear motor for moving the embroidery frame in Y direction while moving along the guide rail; and a controller for controlling the plurality of vertical driver means, the plurality of small-sized motors, and the plurality of X-axis and Y-axis driver linear motors. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, append portioned claims, and accompanying drawings, in which like components are referred to by like reference numerals. In the drawings: 
     FIG. 1 shows a front view of an embroidery machine according to an embodiment of the invention; 
     FIG. 2 shows a plan view of the embroidery machine according to the embodiment of the invention; 
     FIG. 3 shows a fragmentary perspective view of an X-axis driver unit according to the embodiment of the invention; 
     FIG. 4 shows a section view of the X-axis driver unit in combination according to the embodiment of the invention; 
     FIG. 5 shows a fragmentary perspective view of a Y-axis driver unit according to the embodiment of the invention; 
     FIG. 6 shows a section view of the Y-axis driver unit in combination according to the embodiment of the invention; 
     FIG. 7 shows a schematic plan view of an embroidery frame into which a mono-axis table is installed according to another embodiment of the invention; 
     FIG. 8 shows a perspective view of the mono-axis table according to the embodiment of the invention; 
     FIG. 9 shows a schematic plan view of an embroidery frame into which an XY-system is installed according to still another embodiment of the invention; 
     FIG. 10 shows a perspective view of the XY-system according to the embodiment of the invention; 
     FIG. 11 shows a perspective view of the XY-table according to still another embodiment of the invention; 
     FIG. 12 shows a plan view of a thread-cut unit according to an embodiment of the invention; 
     FIG. 13 shows a perspective view of the thread-cut unit according to the embodiment of the invention; 
     FIG. 14 shows a plan view in which another embodiment of the invention is installed into a thread-cut unit; 
     FIG. 15 shows a plan view of a power transmission unit of a hook of the invention; 
     FIG. 16 shows a perspective view of a head according to the embodiment of the invention; 
     FIG. 17 shows an installed state in which the embodiment of the invention is installed into a color-change driver unit; 
     FIG. 18 shows an installed state in which a mono-axis table according to another embodiment of the invention is installed into the color-change driver unit; 
     FIG. 19 shows a section view of a head of the invention; 
     FIG. 20 shows a front view illustrating an entire appearance of a multi-head embroidery machine of an independent-drive type according to another embodiment of the invention; 
     FIG. 21 shows a plan view illustrating an entire appearance of a multi-head embroidery machine of an independent-drive type according to another embodiment of the invention; 
     FIG. 22 shows a plan view of an embroidery machine according to a prior art; 
     FIG. 23 shows an internal construction illustrating a head and a hook driver unit of the embroidery machine according to the prior art. 
     FIG. 24 shows a plan view of a thread-cut unit according to the prior art; 
     FIG. 25 shows a installation view of a color-change driver unit according to the prior art; and 
     FIG. 26 shows an internal construction of a head in the embroidery machine according to the prior art. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
     As shown in FIG.  1  and FIG. 2, an embroidery machine of the invention comprises a rectangular table  2  and an embroidery frame  4  located above the table  2 . An X-axis slot  6  which guides the embroidery frame  4  so as to move in X direction is formed in a certain distance along a longitudinal direction on one side of the table, and a Y-axis slot  8  which guides the embroidery frame  4  so as to move in Y direction is formed in a certain distance along the longitudinal direction on a rear part of the table  2 . 
     A beam  10  extends from one end portion to the other end portion of the table  2  in the center above the embroidery frame  4 , a desired number of heads  12  including a plurality of needles are arranged apart in a constant distance each other on the beam  10 , a main-shaft driver unit  16  which is located on the other side below the table  2  and provides power is coupled with the head  12 . 
     In addition, an X-axis driver unit  17  for providing power to move the embroidery frame  4  forward and backward in X direction is mounted on one end portion of the embroidery frame as shown in FIGS. 3 and 4, and the X-axis driver unit  17  is described in detail below. 
     First, the X-axis driver unit  17  comprises a roller  18  mounted rotatably on one end portion of the embroidery frame  4 , and a front part of a connector frame A  20  coupled with the roller  18  for moving the embroidery frame  4  in X direction. A guide groove  22  for guiding the roller  18  to move slidingly in Y direction is formed on a front face of the connector frame A  20  along the longitudinal direction. 
     An upper end portion of a supporter  24  which slides in the X-axis slot  6  is coupled with the lower part of the connector frame A  20 , a linear motor  26  for providing power to move the embroidery frame  4  in X direction is mounted on the lower end portion of the supporter  24 , and a control unit  28  for transmitting commands is connected to the linear motor  26 . While, the control unit  28  is installed below the table  2 . 
     An operating panel  30  provided for selecting menus to embroider various colors and patterns is connected to the control unit  28 . 
     The linear motor  26  includes various types, though, a structure of the linear motor  26  of the most appropriate type for the embodiment of the invention is as follows. 
     First, the linear motor  26  comprises a rack base  34  having a magnet  32  along the longitudinal direction, each rail  36  which serves as a guide is mounted on both sides of the rack base  34  respectively, and a slider  38  moving back and forth is mounted slippingly on the rail  36 . In addition, a coil, not shown, for generating a magnetic field by the provided current is installed on the bottom of the slider  38  and opposite to the magnet. 
     It is also possible to install the X-axis driver unit  17  constructed as such at the other side of the embroidery frame  4  as necessary. 
     In the mean while, a Y-axis driver unit  39  for moving the embroidery frame  4  forward and backward in Y direction is installed on the rear part of the embroidery frame  4  as shown in FIG.  5  and FIG. 6, the structure of the Y-axis  39  is as follows. 
     The Y-axis driver unit  39  comprises a connector frame B  40  installed at the rear part of the embroidery frame  4 , and a slide rib  42  formed vertically on the rear face of the connector frame B  40  along the longitudinal direction. 
     A supporter  44  moving forward and backward along the Y-axis slot  8  is located at the lower end portion of the connector frame B  40 , two guide rollers  46  which slippingly contact with the slide rib  42  and serve as a guide are mounted on both sides of the upper end portion of the supporter  44 , a support roller  48  for supporting the lower end portion of the slide rib  42  and serving as a guide is installed between the guide rollers  46 . 
     In addition, a linear motor  50  for providing power to move the embroidery frame  4  in Y direction is installed at the lower end portion of the supporter  44 , while the structure of the linear motor  50  is the same as that of the above-mentioned linear motor  26 . 
     In the meanwhile, it is possible to install the Y-axis driver unit  39  constructed as such at the front end portion of the embroidery frame  4  as necessary. 
     In another embodiment to move the embroidery frame  4  in X and Y directions, mono-axis tables  77 (model HS of NSK Co., in Korea) with a structure different from the linear motors  26 ,  50  can be installed in the X-axis driver unit  17  and the Y-axis driver unit  39  at one side and rear part of the embroidery frame  4  as shown in FIG.  7 . 
     The structure of the mono-axis table  77  installed as such is described below with reference to the FIG.  8 . 
     First, the mono-axis table  77  comprises a base  79  fixed to the table  2 , two beds  82  mounted respectively on the both sides of the base  79  along the longitudinal direction for serving as a guide, and a palette  83  moving forward and backward and mounted slidingly on the bed  81 . 
     In addition, a screw  85  engaging with the lower part of the palette  83  is installed between the beds  81 , a motor  87  for providing power is coupled with the rear end portion of the screw  85 , and the control unit  28  for controlling the operation of the motor  87  is connected to the motor  87 . 
     In still another embodiment to move the embroidery frame  4  in X and Y directions, XY-system  89 (model JTM-C type of JUSTEK Co.) can displace other units at the central portion of the rear face of the embroidery frame  4  as shown in FIG. 9, the structure of the XY-system  89  is described below with reference to the FIG.  10 . 
     First, the XY-system  89  comprises an X-axis linear motor  91  which is fixed on the table  2  and provides power to move the embroidery frame  4  in X direction, and a Y-axis linear motor  93  installed above the X-axis linear motor  91  for providing power to move the embroidery frame  4  in Y direction. And the embroidery frame  4  is located on the Y-axis linear motor  93 . 
     The control unit  28  for transmitting commands is connected to the XY-system  89 . 
     Further, in still another embodiment to move the embroidery machine  4  in X and Y directions, XY-table  95 (model HD of NSK Co., in Korea) can displace other units at the central portion of the rear face of the embroidery frame  4  as shown in FIG. 11, the structure of the XY-table  95  is described below with reference to the FIG.  11 . 
     First, the XY-table  95  comprises a lower base  97  fixed on the table, each bed  99  serving as a guide is mounted respectively on the both sides of the lower base  97 , and an upper base  101  moving slidingly along the longitudinal direction of the bed  99  is slippingly mounted on the bed  99 . 
     In addition, a screw A  103  engaging with the lower part of the upper base  101  is installed between the beds  99 , a Y-axis motor  105  for providing power is coupled with the rear end portion of the screw A  103 . 
     Furthermore, each bed  107  serving as a guide is mounted on both sides of the upper base  101  along the longitudinal direction, and a palette  109  sliding on the beds is installed on the beds  107 . A screw B  111  engaging with the lower part of the palette  109  is installed between the beds  107 , an X-axis motor  113  for providing power is coupled with the rear end portion of the screw B  111 . 
     Also, the control unit  28  for transmitting commands is connected to the X-axis motor  113  and Y-axis motor  105  respectively. 
     A thread-cut unit  52  for cutting an unnecessary lower thread fed from the head  12  and the hook  14  is located below the table, the structure of the thread-cut unit  52  is described below with reference to the FIG.  12  and FIG.  13 . 
     First, there is provided a shaft  54  rotated by the power transmitted from the main-shaft driver unit  16 , a rear part of a hook base  56  is coupled with the shaft  54  below the table  2  where the heads are arranged, and a driver gear  58  formed with a helical gear is located inside the hook base  56  and engages with the shaft  54 . 
     Then, a follower gear  60  coupled with the driver gear  58  in gear engagement is engaged with a shaft  62  which is installed rotatably at the hook base  56 , the hook  14  is coupled with the front end portion of the shaft  62  so as to rotate together, a cutter  64  for holding the unnecessary lower thread to be cut has a blade at its front end portion and is installed at a plate  66  mounted on the hook base  56 , above the hook  14 . 
     Also, a cutter  68  for cutting the lower thread while rotating has a blade at its front end portion and is located crosswise, a power transmission unit  70  for providing power to cut the lower thread is installed at the cutter  68 , while a thread-cut shaft  72  constituting the power transmission unit  70  is installed vertically at the rear end portion of the cutter  68 . 
     The lower part of the thread-cut shaft  72  is rotatably coupled to a lug  74  installed inside the hook base  56 , link  76  and link  78  which transmit rotatory force are rotatably coupled with the lower end portion of the thread-cut shaft  72  in sequence, and a upper end portion of a clamp  80  is coupled with the rear end portion of the link  78 . 
     A thread-cut driver unit  52  for providing power for the cutter  68  to perform the cutting operation is installed at the rear part of the rod  82 , the thread-cut driver unit  52  comprises a linear motor  84  having the same structure as the linear motor  26  installed at the above-mentioned X-axis driver unit  17  and Y-axis driver unit. Also, the control unit  28  for transmitting commands is connected to the linear motor  84 . 
     On the contrary, the mono-axis table  121  which will be described below can be installed at the thread-cut driver unit  52  instead of the linear motor  84 . 
     In the structure of the mono-axis table  121  shown in FIG. 14, two beds  123  are mounted on both sides of the base along the longitudinal direction, a palette  127  is slidingly mounted on the beds  125 , the rod  82  is coupled with the front face of the palette  127 . Further, a screw  129  is screwed into the rear face of the palette  127 , a motor  231  for providing force is coupled with the rear end portion of the screw  129 , a control unit  28  for transmitting commands is connected to the motor  231 . 
     Alternatively, another embodiment to rotate the hook  14  is described below with reference to the FIG.  15 . 
     First, a hook  14  is installed inside the hook base  56  as described above, a front end portion of a shaft B  62  for transmitting power is coupled with the hook  14 , a small-sized motor for providing power is coupled with the rear part of the shaft B  62 , the control unit  28  for transmitting commands is connected to the small-sized motor  13 . 
     In the meanwhile, a plurality of arms  88  are mounted on the front face of the beam  10  and spaced apart each other, a shaft C  90  rotated by the power provided from the main-shaft driver unit  16  is coupled with the arm  88  as shown in FIG. 16, a rail  86  serving as a guide is installed at the front upper end portion of the arm  88 . Also, a head  12  moving transversely is slidingly coupled with the rail  86 . 
     In addition, a front end portion of the rod  92  for transmitting force so as to move the head  12  leftward and rightward is coupled with one end portion of the head  12 , a color-change driver unit  94  for adjusting the head so as to embroider in various colors is installed at the rear end portion of the rod  92  as shown in FIG.  17 . 
     The color-change driver unit  94  comprises a housing  96  fixed to the beam  10 , a linear motor  98  with the same structure as the above-mentioned linear motor  26  is installed inside the housing  96 . A rear end portion of the rod  92  is coupled with the linear motor  98 , and the control unit  28  for transmitting commands is connected to the linear motor  98 . 
     Alternatively, the above-mentioned mono-axis table  131  can be installed inside the housing  96  instead of the linear motor  98 . 
     In the structure of the mono-axis table  131  shown in FIG. 18, each bed  135  is mounted respectively on both sides of the base  133  along the longitudinal direction, a palette  137  is mounted on the beds  135 , the rod  92  is coupled with the front end portion of the palette  137 . 
     In addition, a screw  139  is screwed into the rear face of the palette, a motor  141  for providing power is installed at the rear end portion of the screw  139 , and the control unit  28  for transmitting commands is connected to the motor  141 . 
     While, an arm  302  fixed to the front face of the beam  10 , and a head  304  slidingly coupled to the upper part of the head and transversely movable are installed in the head such as those shown in FIG.  19 . And, the constitution of the invention for feeding a single thread to the thread is as follows. 
     First, an inner frame  306  with a guide rail  307  at its front face is installed inside the arm  302 , a linear motor  308 , i.e. vertical driver means connected to the control unit  28  is installed at the front face of the inner frame  306 . A slider  310  which moves up and down and is coupled with a needle holder control block  314  is installed at the linear motor  308 , a needle holder shaft  312  serving as a guide is slippingly coupled with the needle holder control block  314  and installed vertically at the arm  302 . 
     A fixed bracket  316  which can be inserted or removed is installed at the center of the needle holder control block  314 , and a needle holder  318  is coupled with fixed bracket  316  so as to move up and down therewith. At this time, the needle holder  318  is installed so as to move up and down within the head  304 . 
     In addition, a reversible motor  320  which provides power and is connected to the control unit  28  is installed at the upper end portion of the inner frame  306 , a driver lever  322  with a sector gear at its one end portion is installed at the reversible motor  320 , and a driver gear  324  is engaged with the sector gear of the driver lever  322  and rotatably installed at the head  304 . A thread-snatch unit  326  that pulls a thread located above the needle holder  318  and feeds the thread to the needle holder  318  is coupled with the driver gear  324 . 
     Next, another embodiment of the invention is described below with reference to the FIG.  20  and FIG.  21 . 
     First, five heads  334  connected to controllers  337  respectively form a head group and are installed at the upper part of a working plate  332 . 
     Also, it is possible to set the number of the head  334  in a head group or set the head groups according to embroidery operation items. A single embroidery frame  336  is disposed in each head group. 
     A fixed bracket  338  is installed at one end portion of each embroidery frame  336 , a linear motor  342  for providing power so as to move the embroidery frame  336  in X direction is installed at the fixed bracket  338 , and the linear motor  342  is connected to the controller  337 . 
     Next, a fixed bracket  340  is installed at the rear part of each embroidery frame  336 , a linear motor  344  for providing power to move the embroidery frame  336  in Y direction is installed at the fixed bracket  340 , and the linear motor  344  is connected to the controller  337 . 
     The operation of the invention constructed as such is as follows. 
     First, operation items are inputted through the operating panel  30  in order to embroider various patterns on a cloth, then the control unit  28  transmits commands to the linear motors  26 ,  50 , the main-shaft driver unit  16  and the like. 
     Accordingly, the control unit  28  makes the linear motor  50  remain a stationary state, and at the same time transmits an operation command to the other linear motor  26  when the embroidery frame  4  is required to move in X direction. Then, the slider  38  moves forward or backward along the rail  36  together with the supporter  24 , thereby the supporter  24  moves along inside the X-axis slot  6  and causes the connector frame A  20  to move therewith. 
     When the connector frame A  20  moves forward or backward, then the roller  18  coupled with the guide groove  22  is pulled or pushed, thereby the embroidery frame  4  is moved in X direction on the table  2 . 
     At the same time, the slide rib  42  moves between the guide rollers  46  at the upper end portion of the supporter  44  of the linear motor  50  and over the support roller  48 , because the connector frame B  40  at the rear part of the embroidery frame  4  is at a fixed position, as a result of this, the embroidery frame  4  is guided and moved forward or backward in X direction. 
     The power transmitted from the main-shaft driver unit  16  when the embroidery frame moves forward and backward is transmitted to the shaft C  90  and causes the needle at the head  12  to move up and down so as to embroider the cloth. 
     Further, in case the embroidery frame  4  is required to change the position when embroidering as above, then the control unit  28  transmits a ‘stop command’ to the linear motor  26 , and at the same time, transmits an ‘operation command’ to the other linear motor  50 . 
     Accordingly, the linear motor  50  moves forward or backward and causes the supporter  44  to move, thereby one face of the slide rib  42  located between the guide rollers  46  is pushed or pulled and moved in Y direction together with the connector frame B  40 , and at the same time the embroidery frame  4  is moved slidingly on the table  2 . 
     When the embroidery frame  4  is moved in Y direction as such, the roller  18  located at one end portion of the embroidery frame  4  is rotated and moved in Y direction along the guide groove  22  formed on the front face of the connector frame A  20 . 
     At this time, the connector frame A  20  remains stationary because the operation of the other linear motor  26  is stopped. 
     When the embroidery frame  4  moves as such, the needle at the head  12  moves up and down constantly and embroiders on the cloth as described above. 
     Alternatively, when the motor  87  in the mono-axis table  77  installed at the one side and rear part of the embroidery frame  4 , with different structures respectively, receives a command from the control unit  28  for operation, the screw  85  is rotated and causes the palette  83  to move so that the palette  83  can slide along the bed  81 . 
     Further, when the embroidery frame  4  is required to move in both X and Y directions, the control unit  28  transmits selectively a command to the motors  87  located respectively at one side and a rear part of the embroidery frame  4 , so that the embroidery frame  4  is moved on the table  2  to embroider on the cloth as described above. 
     In addition, when the XY-system  89  which has a structure different from those in the above and is installed at the rear face of the embroidery frame  4  receives a command from the control unit  28 , the XY-system  89  causes the embroidery frame  4  to move in X and Y directions according to a desired embroidering position. At this time, when the control unit  28  transmits a command to the X-axis linear motor  91  so as to move the embroidery frame  4  in X direction, then the Y-axis linear motor  93  in stationary state is moved forward and backward on the table  2  together with the embroidery frame  4 . 
     Alternatively, when the control unit  28  transmits an operation command to a Y-axis linear motor  93 , which causes the stationary X-axis linear motor  91  to remain current position and causes the embroidery frame  4  to move forward and backward in Y direction. 
     In addition, when the XY-table  95  which has a structure different from those in the above and is installed at the rear face of the embroidery frame  4  receives a command from the control unit  28 , the XY-table  95  causes the embroidery frame  4  to move in X and Y directions according to the desired embroidering position. 
     At this time, the control unit  28  transmits an operation command to the X-axis motor  113  in order to move the embroidery frame  4  in X direction, then the screw B  111  is rotated leftwards or rightwards by the X-axis motor  113  and causes the palette  109  to move forward or backward, as a result of this, the palette  109  slides along the beds  107  and causes the embroidery frame  4  to move forward or backward in X direction on the table  2 . 
     Alternatively, when the control unit  28  transmits an operation command to the Y-axis motor  105 , the screw A  103  is rotated leftwards or rightwards and causes the upper base  101  to move forward or backward, so that the upper base  101  slides along the beds  99  together with the palette  109 . Accordingly, the embroidery frame  4  located above the palette  109  is caused to move forward or backward on the table. 
     In the meanwhile, a part of the power transmitted to the shaft C  90  is transmitted to the shaft A  54  in turn and causes the driver gear  58  to rotate, so that the follower gear  60  engaged with the driver gear  58  is rotated with the shaft B  62  and causes the hook  14  to rotate. 
     As a result, the hook  14  is rotated and feeds a single thread upward, so that the single thread can be tied to another single thread moving downward along the head  12 . At this time, the cutter B  68  remains stationary because the cutter B  68  did not receive the force through the power transmission unit  70 . 
     On the contrary, in the method for rotating the hook  14  directly without the power from the main-shaft driver unit  16 , when the small-sized motor  13  receives an operation command from the control unit  28 , the shaft B  62  is rotated and causes the hook  14  to rotate so as to feed a single thread as described above. 
     In the step of embroidering on the cloth fixed to the embroidery frame  4 , when a single thread of another color is required to be fed so as to form various patterns, the previously fed single thread should be cut. At this time, the control unit  28  transmits an operation command to the linear motor  84 , then the rod  82  is moved forward together with the clamp  80  by the force. 
     Therefore, the links A and B  76 ,  78  are rotated by the moving clamp  80  and cause the thread-cut shaft  72  to rotate, so as to rotate the cutter B  68  therewith and push the necessary single thread away. On the contrary, when the control unit  28  transmits a command to the linear motor  84  again and causes the rod  82  to move backward, the clamp  80  is moved together with the rod  82  and causes the links A and B  76 ,  78  to rotate in the direction opposite to that described above. 
     Accordingly, the thread-cut shaft  72  is rotated reversely and returns the cutter B  68  to its original position, as a result of this, an upper thread near the needle and located outward the cutter B  68  is protected and returned to its original position, and unnecessary upper thread and lower thread near the cloth are moved toward the cutter A  64  and cut. 
     After the upper and lower threads are cut as such, the control unit  28  transmits a stop command to the linear motor  84  so that the cutter B  68  can be in a stationary state. 
     Alternatively, the operation procedure of the mono-axis table  121  coupled with the rod  82  is as follows. 
     First, when the motor  231  receives an operation command from the control unit  28 , the screw  129  is rotated by the motor  231  and causes the palette  127  to move forward and backward, thereby the rod  82  is moved forward and backward by the palette  127  and causes the cutter B  68  to rotate as described above so as to perform the cutting operation. 
     After the cutting operation of the upper and lower threads near the cloth as such, when the color of the single thread is required to be changed, the control unit  28  transmits an operation command to the linear motor  98  and causes the rod  92  to move forward or backward so as to push the head  12  away. 
     At this time, the range of the movement in which the operating linear motor  98  moves the rod forward or backward corresponds to the position of the needle into which an upper thread of the color corresponding to the one selected in the operating panel  30  is fed, and the linear motor  98  is operated so as to move the rod forward and backward within the range. 
     Accordingly, the head  12  is moved slidingly along the rail  86  installed the upper part of the arm  88  by the rod  92  moving forward or backward as such, at the same time a part of the power provided from the main-shaft driver unit  16  is transmitted to the shaft C  90  and causes the needle which feeds a single thread of corresponding color to move up and down so as to embroider on the cloth installed to the embroidery frame  4 . 
     Alternatively, the operation procedure of the mono-axis table  131  coupled with the rod  92  is as follows. 
     First, when the motor  141  receives an operation command from the control unit  28 , the screw  139  is rotated leftward and rightward by the motor  141  and causes the palette  137  to move forward and backward, thereby the rod  92  is moved forward and backward by the palette  137  and pushes or pulls the head  12  so as to change the color of the single thread. 
     The operation according to the embodiment of the invention for feeding a single thread to the cloth fixed to the embroidery frame  4  is as follows. 
     First, when the reversible motor  320  is operated by the command from the control unit  28 , the driver lever  322  is rotated repeatedly and causes the driver gear  324  engaged with the sector gear to rotate in positive or reverse direction. Accordingly, the thread-snatch unit  326  coupled with the driver gear  324  is moved up and down repeatedly and pulls the single thread located above the embroidery frame downward. 
     In the step of feeding the single thread as such, when the linear motor  308  is operated up and down by the command from the control unit  28 , the needle holder control block  314  coupled with the slider  310  slides along the needle holder shaft  312  and operates up and down repeatedly. 
     As a result of this, the fixed bracket  316  inserted into the central portion of the needle holder control block  314  is moved up and down together with the needle holder  318 , and feeds the single thread from the thread-snatch unit  326  to the cloth fixed to the embroidery frame  4 . 
     In the meanwhile, the operation according to another embodiment of the invention is as follows. 
     First, when the controller  337  transmits an operation command to a head group comprising a plurality of head  334 , or several head groups, the operation of the head group(s) is as follows. 
     When one pattern is required to embroider on the cloth in the embroidery frame  336  in order to produce the embroideries in small quantities according to the product characteristics, the controller  337  transmits operation commands to respective heads  334  constituting each head group located on the working plate  332 . 
     In addition, when the controller  337  transmits operation commands to the linear motors  342 ,  344  respectively installed at one side and the rear part of the embroidery frame  336  in order to form the embroidery patterns, the embroidery frame  336  moves in X or Y direction on the working platen  332 . 
     Alternatively, when two kinds of embroidery patterns or a medium-amount of production is required, the controller  337  transmits respective commands to two head groups so as to operate the linear motor  342 ,  344 , so as to cause the embroidery frame  336  to move in X or Y direction. At this time, the controller  337  can be set so that one pattern or two patterns can be embroidered on the cloth of the embroidery frame  336 . 
     In another way, when a mass production is required, the controller  337  transmits respective commands to the linear motor  342  constituting the three head groups so as to move the embroidery frame  336  in X or Y direction. At this time, the controller  337  can be set so that one pattern to three patterns can be embroidered on the cloth of the embroidery frame  336 . Accordingly, various patterns are embroidered on the cloth at the same time, and mass production of the embroidery product is possible when the three head groups are operated simultaneously. 
     The present invention has been described in detail. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.