Abstract:
A sewing machine comprises: a head portion having a sewing needle driven to vertically reciprocate; a lower shaft having a shuttle connected thereto which is driven to rotate synchronized with the vertical movement of the sewing needle cooperating to form stitches; a table positioned above the lower shaft; a retainer positioned above the table to retain a material for forming stitches thereon; a holding frame placed parallel to the table, the head portion being mounted at a position on the holding frame; and supporting posts adapted to support opposite ends of the holding frame for positioning the holding frame above the table. The sewing machine allows a material to be sewn, which is retained retainer, to be easily mounted or removed.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a sewing machine with improved structure and constitution, and more particularly to a sewing machine in which a retainer adapted to retain a material to be sewn can move along an X-axis and a Y-axis.  
         [0003]     2. Description of the Prior Art  
         [0004]     When it is necessary to extend the sewing range of conventional sewing machines, in particular in the Y-axis direction (forward or backward direction), the arm on which the head portion of the sewing machine is installed had to be elongated forward. This causes a problem in that the elongated arm occupies a considerable space.  
         [0005]     Moreover, when the arm is elongated, the center of gravity of the sewing machine is positioned at a front portion thereof This makes it difficult to maintain the balance of the sewing machine. Accordingly, there has been a request for a construction capable of reducing the space occupied by the sewing machine while easily maintaining the balance of the sewing machine.  
         [0006]     An example of such conventional sewing machines is given in  FIG. 1 .  FIG. 1  shows a side elevation view of a conventional sewing machine disclosed in Korean Patent Application No. 1999-0015717, the content of which is incorporated herein for reference (reference numerals presented hereinafter to explain  FIG. 1  apply to  FIG. 1  only). Referring to  FIG. 1 , the conventional sewing machine has a head portion  202  elongated toward the front side of its body  203  by means of an arm  201 . The longer the material to be sewn is in the Y-axis direction (forward or backward direction) as retained on a retainer  204  atop a table  200 , the longer the arm  201  needs to be.  
         [0007]     As the arm  201  becomes longer, the head portion  202  becomes farther from the body  203 . This makes the center of gravity of the sewing machine positioned at the front portion thereof Consequently, the body  203 , having the arm  201  connected thereto, is subject to additional weight and torsion due to the lengthened arm  201 . It results in a problem in strength of the machine. Therefore, there has existed a demand for a sewing machine making it possible to minimize or eliminate the length of an aim  201  for the purpose of avoiding any damage to its body  203  and, at the same time, to extend the sewing area in the X-axis direction (leftward or rightward direction) and/or Y-axis direction of the sewing machine.  
         [0008]     Meanwhile, conventional sewing machines employ single driving motor to drive both a needle and a shuttle race body, as shown in  FIG. 2 . Referring to  FIG. 2 , a single driving motor  230  is adapted to drive an upper shaft  210  for driving a needle  205 , as well as a lower shaft  220  for driving a shuttle race body (not shown in the drawing).  
         [0009]     The driving motor  230  is connected in a line with the upper shaft  210 . The lowershaft  220  is positioned below a table  200  and is parallel to the upper shaft  210 . A rotation transfer means  240 , such as a timing belt, is used to enable the single driving motor  230  to drive both the upper and lower shafts  210  and  220 .  
         [0010]     Such a simultaneous driving of the upper and lower shafts  210  and  220  necessitates the interconnection and coupling of them within the arm  201  and the body  203 . When the arm  201  and the body  203  need to be removed to extend the sewing area in the Y-axis direction, as mentioned above, the simultaneous driving of the upper and lower shafts  210  and  220  cannot be implemented. Therefore, it is necessary to solve such problem and, at the same time, to provide an improved construction accordingly.  
       SUMMARY OF THE INVENTION  
       [0011]     Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a sewing machine having a feeding device which can move a retainer, on which a material to be sewn is reained, in the X-axis or Y-axis direction so that sewing can be performed in an extended sewing area regardless of the position of its head portion.  
         [0012]     Another object of the present invention is to provide a sewing machine having an arm lifting device which can move its head portion in the upward or downward direction so that a material to be sewn, which is retained on a retainer, can be easily mounted or removed.  
         [0013]     Still another object of the present invention is to provide a sewing machine having an upper shaft driving motor and a lower shaft driving motor for driving its upper and lower shafts, respectively, as a result of having removed its arm and body so that the upper and lower shafts can be driven in accordance with its improved constitution.  
         [0014]     In order to accomplish this object, there is provided a sewing machine comprising: a head portion for mounting a needle for sewing thereon; a table for accommodating a material to be sewn thereon; a holding frame for mounting the head portion thereon; and supporting posts for supporting and positioning the holding frame above the table.  
         [0015]     According to a feature of the present invention, the holding frame is positioned horizontally in the X-axis direction and the supporting posts are adapted to support the opposite ends of the holding frame vertically.  
         [0016]     According to another feature of the present invention, the sewing machine further comprises a retainer for retaining a material to be sewn and an X-axis feeding means for moving the retainer leftward or rightward in the X-axis direction.  
         [0017]     According to another feature of the present invention, the X-axis feeding means comprises: an X-axis flame elongated in the leftward and rightward direction; a guide rail installed or formed in the X-axis flame; a holding portion coupled with the guide rail and adapted to move in the leftward or rightward direction while holding the retainer, and an X-axis driving motor for moving the holding portion.  
         [0018]     According to another feature of the present invention, the sewing machine further comprises a retainer for retaining a material to be sewn and a Y-axis feeding means for moving the retainer forward or backward in the Y-axis direction.  
         [0019]     According to another feature of the present invention, the Y-axis feeding means comprises: a moving portion for moving the retainer in the forward or backward direction; and a Y-axis driving motor for moving the moving portion.  
         [0020]     According to another feature of the present invention, the sewing machine further comprises a Y-axis feeding means for moving the X-axis feeding means forward or backward in the Y-axis direction.  
         [0021]     According to another feature of the present invention, the Y-axis feeding means comprises: a moving portion for moving the X-axis feeding means in the forward or backward direction; and a Y-axis driving motor for moving the moving portion.  
         [0022]     According to another feature of the present invention, the moving portion comprises a belt moved by the Y-axis driving motor.  
         [0023]     According to another feature of the present invention, the sewing machine further comprises an arm lifting device coupled to the holding frame together with the head portion for moving the head portion upward or downward.  
         [0024]     According to another feature of the present invention, the arm lifting device comprises: a guide plate held on the holding frame; and a feeder held on the head portion, wherein the feeder is adapted to move upward or downward in accordance with the guide plate.  
         [0025]     According to another feature of the present invention, the arm lifting device is moved upward or downward by hydraulic pressure, pneumatic pressure, or a mechanical structure utilizing the rotation of a screw structure.  
         [0026]     According to another feature of the present invention, the sewing machine further comprises: an upper shaft driving motor connected to an upper shaft for driving the sewing needle of the head portion; and a lower shaft driving motor connected to the lower shaft for driving a shuttle race body. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0028]      FIG. 1  shows a side elevation view of a conventional sewing machine;  
         [0029]      FIG. 2  shows a side sectional view of a conventional sewing machine;  
         [0030]      FIG. 3  shows a perspective view of a sewing machine according to the present invention;  
         [0031]      FIG. 4  shows a front view of a sewing machine according to the present invention;  
         [0032]      FIG. 5  shows a side elevation view of a sewing machine according to the present invention;  
         [0033]      FIG. 6  shows a top view illustrating an X-axis feeding means and Y-axis feeding means according to the present invention;  
         [0034]      FIG. 7  shows an exploded perspective view of an arm lifting device according to the present invention;  
         [0035]      FIG. 8   a  shows a side sectional view illuraing a head portion lowered by an arm lifting device according to the present invention; and  
         [0036]      FIG. 8   b  shows a side sectional view illustrating a head portion lifted by an arm lifting device according to the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0037]     Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. In the following description and drawings, the same reference numerals are used to designate the same or similar components, and so repetition of the description on the same or similar components will be omitted.  
         [0038]      FIG. 3  shows a perspective view of a sewing machine according to the present invention. Referring to the drawing, a head portion  40  is positioned above a table  10 . The head portion  40  performs a sewing operation on a material retained on a retainer  50 .  
         [0039]     The table  10  is a square plate on which the material to be sewn is placed. The table  10  is provided with guide holes  12  elongated in the forward and backward director along its opposite sides. The guide holes  12  are adapted to transmit the movement of a Y-axis feeding means  70  ( FIG. 4 ), positioned below the table  10 , to a retainer  50 , positioned above the table  10 .  
         [0040]     Supporting posts  22  are formed vertically on the opposite ends of the table  10 . A holding frame  20  is supported between the supporting posts  22  in the horizontal direction. The holding frame  20  is preferably made of a rectangular steel tube and has a head portion  40  extending forward from its center portion. An arm lifting device  30  is preferably provided between the head portion  40  and the holding frame  20  to move the head portion  40  upward or downward.  
         [0041]     The sewing machine according to the present invention makes it possible to sew a material in an extended area while the head portion  40  is held, because the retainer  50  is adapted to move in the X-axis and Y-axis direction. For this, the holding frame  20  is positioned horizontally for openness in the forward and backward direction, opposite ends of which being supported by the supporting post  22 , so that the head portion  40  is held in a bridge-like fashion.  
         [0042]     FIGS.  3  to  5  show an arrangement for moving the retainer  50  in the X-axis or Y-axis direction.  
         [0043]     An upper shaft driving motor  39  is provided behind the holding frame  20  to drive an upper shaft (not shown) within the head portion  40 . The upper shaft driving motor  39  is connected to the upper shaft (not shown), but not to a lower shaft (not shown) for driving a shuttle race body (not shown).  
         [0044]      FIG. 4  shows a front view of a sewing machine according to the present invention. Referring to the drawing, an X-axis feeding means  60  is provided above the table  10  and extends in the X-axis direction. Multiple Y-axis feeding means  70  are provided below the table  10  and extend in the Y-axis direction.  
         [0045]     The X-axis feeding means  60  comprises an X-axis frame  62  elongated in the X-axis direction, a guide rail  64  installed or formed on the X-axis frame  62 , and a holding portion  66  adapted to move leftward or rightward in accordance with the guide rail  64 . The retainer  50 , on which a material to be sewn is retained, is coupled to the holding portion  66 . As the holding portion  66  can move leftward or rightward, it is possible to sew a material in an extended area in the X-axis direction without any movement of the head portion  40 .  
         [0046]     The Y-axis feeding means  70  enable movement of the retainer  50  in the Y-axis direction, that is, in the forward or backward direction. The Y-axis feeding means  70  extend in the forward and backward direction and have moving portions  72  adapted to move in the forward or backward direction.  
         [0047]     The moving portions  72  are preferably made of belts  72   a  adapted to move in the forward or backward direction. Holders  72   b  are coupled on top of the belt  72   a  and protrude upward. The holders  72   b  are displaced forward or backward in accordance with the movement of the belts  72   a.    
         [0048]     Each of the Y-axis feeding means  70 , positioned on opposite sides of the table  10 , is provided with its own holder  72   b  in parallel orientation. The guide holes  12  of the table  10  expose the holders  72   b  upward. The X-axis frame  62  is connected to the holders  72   b.  When the X-axis feeding means  60  is not coupled, direct connection could be possible using additional extensions from the retainer  50  in the leftward and rightward direction.  
         [0049]     As the holders  72   b  move forward or backward in accordance with the movement of the moving portions  72 —i.e. the belts  72   a —the retainer  60 , which is connected to the X-axis frame  62 , is displace forward or backward accordingly. This makes it possible to sew a material in an extended area in the Y-axis direction without any movement of the head portion  40 .  
         [0050]     A lower shaft driving motor  39  is positioned below the table  10  to transmit power to a lower shaft (not shown), which is adapted to drive a shuttle race body (not shown). According to the inventive sewing machine, the upper and lower shafts should each be driven separately because, unlike in the prior art, the head portion  40  is held in a bridge-like fashion.  
         [0051]     More specifically, a prior sewing machine has a body  203  ( FIGS. 1 and 2 ) positioned in its center portion and a single driving motor  230  for driving the upper and lower shafts  210  and  220  simultaneously. However, the inventive sewing machine has an additional lower shaft driving motor  89  for separate driving of the shafts. A control unit (not shown) controls the driving operation of the upper and lower shafts  38  and  39 .  
         [0052]      FIG. 5  shows a side elevation view of a sewing machine according to the present invention. Referring to the drawing, each of the X-axis feeding means  60  has an X-axis feeding motor  68  and the Y-axis feeding means  70  extend in the forward and backward direction along the side.  
         [0053]     The X-axis feeding means  60  is positioned above the table  10  and is connected to the retainer  50 . The Y-axis feeding means  70  is positioned below the table  10  and is connected to the X-axis feeding means  60  through the guide hole  12 . Reference numeral  42  denotes a needle.  
         [0054]      FIG. 6  shows a top view illustrating an X-axis feeding means and Y-axis feeding means according to the present invention. Referring to the drawing, the X-axis feeding means  60  has an X-axis driving motor  68  provided on a side thereof for driving movement in the leftward or rightward direction The Y-axis feeding means  70  have a Y-axis driving motor  74  for driving movement in the forward or backward direction.  
         [0055]     The X-axis driving motor  68  rotates a driving pulley  68   b  coupled to a driving shaft  68   a  which faces forward. This rotation moves a belt  69  leftward or rightward, which is wound around the driving pulley  68   b.  As the belt  69  is moved, a holding portion  66  connected thereto is moved accordingly. As a result, the retainer  50 , which is coupled to the holding portion  66 , is displaced A following pulley (not shown), which is provided on an end opposite from the end on which the driving pulley  68   b  is provided, winds the belt  69 .  
         [0056]     The Y-axis driving motor  74  is connected, via driving shafts  74   a,  to the rear portions of the Y-axis feeding means  70 , which extend in the forward and backward direction along opposite sides of the table. As the Y-axis driving motor  74  is rotated, the belts  72   a  which are wound around driving pulleys (not shown) are moved forward or backward accordingly.  
         [0057]     Holders  72   b  are coupled on top of the belts  72   a  and protrude upward. The holders  72   b  move the X-axis feeding means  60  horizontally forward or backward in accordance with the movement of the belts  72   a . The belts  72   a  are wound around driving pulleys (not shown) at their rear portions, as well as around following pulleys (not shown) at their front portions.  
         [0058]      FIG. 7  shows an exploded perspective view of an arm lifting device according to the present invention. Referring to the drawing, a guide plate  32 , which is fixedly coupled to the holding frame  20 , engages a feeder  34 , which is fixedly coupled to the head portion  40 , within the arm lifting device  30 .  
         [0059]     The guide plate  32  is in the shape of a bar elongated in the upward and downward direction and is hollow in its center portion, as in the case of a rail used in the railway. The feeder  34  has rear ends defining a narrowed space between them so that the guide plate  32  can be fitted from above or below into the space. The hollow portion of the guide plate  32  is fitted with the rear ends of the feeder  34 . As a result, the feeder  34  can slide upward or downward relative to the guide plate  32 , but cannot move laterally, i.e., in the forward or backward directions.  
         [0060]     Movement of the arm lifting device  30  in the upward or downward direction can be realized, for example, by means of a pneumatic or hydraulic cylinder or via a mechanical structure, such as the rotation of a screw structure, but the means for movement is not limited thereby.  
         [0061]     More specifically, the arm lifting device  30  is supported by the holding frame  20  and the head portion  40  is connected to the arm lifting device  30 . A control box (not shown) controls the upward and downward movement through a structure using a pneumatic or hydraulic cylinder or a mechanical structure using a screw.  
         [0062]      FIGS. 8   a  and  8   b  show side sectional views illustrating a head portion lowered and lifted respectively by an arm lifting device according to the present invention. Referring to the drawing, the feeder  34 , which is integrated and moved together with the head portion  40 , is displaced upward or downward in accordance with the guide plate  32 , which is integrated to the holding frame  20 .  
         [0063]     When the arm lifting device  30  applies pneumatic pressure through an upper pneumatic pressure opening (not shown), the lifting plate  36  within the arm lifting device  30  is pushed down from above and lowered accordingly. This makes the feeder  34  descend along the guide plate  32  and, as a result, the head portion  40  is moved downward  
         [0064]     When the head portion  40  is to be moved upward, on the other hand, pneumatic pressure is discharged through a lower pneumatic pressure opening (not shown). The lifting plate  36  within the arm lifting device  30  is then lifted. This makes the feeder  34  ascend along the guide plate  32  and, as a result, the head portion  40  is moved upward.  
         [0065]     If the head portion  40  has finished its operation, the arm lifting device  30  lifts the head portion  40  to facilitate removal of the sewn material. If another material is placed in position to be sewn, the head portion  40  is lowered for sewing so that the needle  42  can approach the material.  
         [0066]     This behavior makes it possible to use the retainer  50  in the sewing machine more efficiently and to sew thicker materials, although only materials the thicknesses of which are below a determined value can be sewn with prior sewing machines.  
         [0067]     The present invention eliminates any coupling portion between an arm and a bed, as used in prior sewing machines. Instead, the inventive sewing machine has a holding frame supported by support posts, a head portion mounted on the holding frame, and a means for driving its upper shaft separately. Due to an arch-shaped arrangement positioned on its center portion without any structure for connecting upper and lower portions, sewing area is substantially increased in the Y-axis direction. Accordingly, it is possible to sew materials with unlimited length, such as a long cloth, without any interruption.  
         [0068]     In addition, the retainer can be lifted when sewing is started or finished and the head portion can be moved up and down. This makes it possible to easily place and remove the material to be sewn and to process materials with various thicknesses, although only thin materials can be sewn with conventional sewing machines.  
         [0069]     The inventive sewing machine separately drives its upper and lower shafts using separate driving motors. This avoids any overloading to single motor adapted to drive upper and lower shafts simultaneously via, for example, a timing belt.  
         [0070]     Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.