Abstract:
A sewing machine frame drive device capable of precisely conveying on an X-Y coordinate plane a frame, on which an article being sewn is set, comprising X-direction drive units ( 6 ) and Y-direction drive units ( 7 ) for imparting driving forces to a frame ( 5 ) of various types, on which an article being sewn is set, the units being composed of screw rods ( 11 ) rotatingly driven by motors ( 23 ) in alternate directions, and moving bodies ( 12 ) threaded on the screw rods ( 11 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates to a sewing machine frame drive device, more particularly, to a device for freely conveying on an X-Y coordinate plane a frame, on which an article being sewn is set. 
     DESCRIPTION OF THE RELATED ART 
     Generally known as a sewing machine frame drive device of the type is a drive unit comprising two timing pulleys disposed with a predetermined spacing therebetween, a timing belt extended between the timing pulleys in an endless fashion, and a driving force transmitting member mounted on the linear running portion of the timing belt. With the drive unit, a shaft of one of the timing pulleys is rotatingly driven by a motor, whereby the timing belt is made to run alternately to move a frame, by which an article being sewn is supported, through the driving force transmitting member provided on the belt. 
     In the above-described drive unit of the prior art, the timing belt generates elongation when the unit is driven, and an error in movement is caused by backlash when the timing pulleys are reversed. Therefore, it is difficult to perform precise control of movement of the frame, on which an article being sewn is supported. Accordingly, in some cases, correction control of various types is needed for compensation of the above-mentioned disadvantage. 
     SUMMARY OF THE INVENTION 
     The present invention has been proposed to preferably solve the disadvantage inherent in the above-mentioned prior art, and provides as its object a sewing machine frame drive device capable of precisely conveying on an X-Y coordinate plane a frame, on which an article being sewn is set. 
     To overcome the above-mentioned problem and to preferably attain the intended object, a sewing machine frame drive device, according to the present invention, comprises X-direction drive units and Y-direction drive units for imparting driving forces to a frame of various types, on which an article being sewn is set, at least one of the drive units being composed of screw rods rotatingly driven by a motor in alternate directions, and moving bodies threaded on the screw rods. 
     Further, the frame driving unit is composed of a screw rod and a moving body threaded on the screw rod to eliminate any contracting and extending element from a driving force transmitting system and to involve less influence due to backlash, so that the frame can be precisely driven. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view showing the appearance of an embroidery sewing machine, to which a sewing machine frame drive device according to a first embodiment of the invention is applied. 
     FIG. 2 is a partially cutaway plan view showing the embroidery sewing machine of FIG.  1 . 
     FIG. 3 is a plan view showing a state of pairs of drive units being connected. 
     FIG. 4 is a cross sectional view taken along the line A—A in FIG.  3 . 
     FIG. 5 is a partially cutaway perspective view showing a state, in which the drive units are connected to a frame. 
     FIG. 6 is a plan view showing a state, in which the respective pairs of drive units are connected in a different fashion. 
     FIG. 7 is a plan view showing a state, in which the respective pairs of drive units are further connected in a different fashion. 
     FIG. 8 is an illustration as viewed from a direction of the line B—B. 
     FIG. 9 is a partially cutaway plan view showing an embroidery sewing machine according to a second embodiment. 
     FIG. 10 is a partially cutaway perspective view showing a state, in which drive units in the second embodiment are connected to a frame. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     (First Embodiment) 
     A sewing machine frame drive device according to the present invention will be described hereinbelow with reference to the accompanying drawings, giving a preferred embodiment, in which it is applied to a multi-head embroidery sewing machine. FIG. 1 is a perspective view showing a multi-head embroidery sewing machine having four heads. A frame  4  is mounted horizontally above a sewing machine table  1 , and four sewing machine heads  2  in total are arranged on the front sure of the frame  4 . Mounted on the underside of the sewing machine table  1  below the respective serving machine heads  2  are shuttle bases (not shown), which support shuttles. The top surfaces of the respective shuttle bases are covered by throat plates  3  mounted on the sewing machine table  1 . Placed on the sewing machine table  1  is a rectangular-shaped embroidery frame  5 , and arranged on the underside of the sewing machine table  1  are two X-direction drive units  6 ,  6  and two Y-direction drive units  7 ,  7 . The embroidery frame  5  is connected to the X-direction drive units  6  and the Y-direction drive units  7 , respectively, through slits  8   a  formed in covers  8 , which cover the upper surface of the sewing machine table  1 . 
     The X-direction drive units  6  and the Y-direction drive units  7  are mainly composed of a screw rod  11  (commonly called ball screw), which is rotatably supported in a frame member  10  having a C-shaped cross section, and a nut member  12  adapted to be threaded on the ball screw  11  to function as a moving body, as shown in FIGS. 3 and 4. The ball screw  11  extends lengthwise in the frame member  10  and is supported by bearings  15 ,  15 , respectively, fixed on both ends of the frame member  10 . As clearly shown in FIG. 4, linear guides  16 ,  16  are correspondingly fixed to both sides of the nut member  12  threaded on the ball screw  11 . The respective linear guides  16 ,  16  are correspondingly fixed on and supported by linear rails  17 , which are mounted on inner sides of the frame member  10  to be in parallel to the ball screw  11  and function to stop rotation of the nut member  12 . A support stud  18  is provided vertically upwardly on the top surface of the nut member  12 , and a roller  20  is supported on an upper end of the support stud  18  to be rotatable on a horizontal plane. 
     As shown in FIG. 3, one ends of the ball screws  11  in the X-direction drive units  6  (and the Y-direction drive units  7 ) are extended from the bearings  15 , timing pulleys  21  are fitted on specific ends of the ball screws, and a timing belt  22  is extended between the timing pulleys  21 . Connected to an end of one of the ball screws  11  via a coupling member (not shown) is an output shaft  25  of a motor  23 . Accordingly, when the motor  23  is activated, the pair of ball screws  11  are rotated in the same direction through the timing belt  22 , and the two nut members  12  are correspondingly moved in the same direction. 
     The rollers  20  provided on the respective support studs  18  of the X-direction drive units  6  and of the Y-direction drive units  7  extend above the sewing machine table  1  through slits  8   a  of the covers  8  on the sewing machine table  1  shown in FIG. 2, and are substantially closely fitted in an engagement groove  5   a  formed on the underside of the embroidery frame  5  placed on the sewing machine table (see FIG.  5 ). In this case, both the rollers  20 ,  20  in the X-direction drive units  6  are correspondingly fitted in the engagement groove  5   a  in a right hand piece  5 A of the embroidery frame  5 , and both the rollers  20 ,  20  in the Y-direction drive units  7  are correspondingly fitted in the engagement groove  5   a  in a right hand piece  5 B of the embroidery frame  5  (see FIG.  2 ). 
     Thus the sewing machine frame drive device according to this embodiment is constructed in the above manner, and the motor  23  allotted to the X-direction drive units  6  and the motor  23  allotted to the Y-direction drive units  7  are activated to drive the pair of drive units so that the embroidery frame  5  is controlled to be freely movable in the X-Y coordinates. Since no extending and contracting elements in a transmitting mechanism in the prior art are provided in the respective drive units  6 ,  7 , transmission of driving forces by the motors  23  is extremely precisely performed. 
     In the case where the number of sewing machine heads provided in the embroidery sewing machine is great, the embroidery frame  5  in the embodiment shown in FIG. 2 is larger in the X direction. Thus, in order to stably perform driving of the embroidery frame  5  in the Y direction, there is involved a need for increasing the number of the Y-direction drive units  7 . FIG. 6 shows a modification of a manner of connecting the respective Y-direction drive units  7  in such a case. In the case where four of the Y-direction drive units  7  are connected as in the modification, two of the Y-direction drive units  7  disposed on opposite sides are connected to each other by a timing belt  30 . Further, a motor  33  disposed in a middle position is connected to two of the Y-direction drive units  7 , respectively, disposed inward by timing belts  34 ,  34 . Thus two timing pulleys  36 ,  37  are mounted on an output shaft  35  of the motor  33 , and timing pulleys  38 ,  39  are mounted on shaft ends of the two Y-direction drive units  7  disposed inward. The timing belts  34 ,  34  are extended between the timing pulleys  36 ,  38  and between the timing pulleys  37 ,  39 . Accordingly, all the Y-direction drive units  7  are driven synchronously when the motor  33  is activated. 
     FIGS. 7 and 8 show another way of connection in the case where a multiplicity of Y-direction drive units  7  are provided, like the modification described above. More specifically, a drive shaft  40  is arranged in a position spaced a predetermined distance from and below timing pulleys  21 , which are mounted on shaft ends of ball screws  11  in the respective Y-direction drive units  7 , and is made perpendicular to the ball screws  11 . The drive shaft  40  mounts thereon timing pulleys  41  disposed immediately below the respective timing pulleys  21 , and timing belts  43  are twisted 90 degrees and extended between the respective timing pulleys  41  and the timing pulleys  21  disposed thereabove. The drive shaft  40  is connected at its end to an output shaft  46  of a motor  45  through a connection member (not shown). 
     (Second Embodiment) 
     FIGS. 9 and 10 show a preferred second embodiment of the invention. This embodiment is different from the first embodiment in that driving forces are transmitted indirectly to the embroidery frame  5  from the respective Y-direction drive units  7 . In addition, the same elements as those in the first embodiment are designated by the same reference numerals, and an explanation thereof is omitted. A Y-direction driven body  50 , which is longer than a rear side piece  5 B of the embroidery frame  5 , is arranged on the upper surface of the sewing machine table  1  to be rearwardly of and in parallel to the rear side piece  5 B. As shown in FIG. 10, spacers  51  in place of the rollers  20  in the first embodiment are fixed to nut members  12  on the Y-direction drive units  7 , and the top surfaces of both spacers  51  project upward through the slits  8   a  formed in the covers  8 , which cover the upper surface of the sewing machine table  1 . The Y-direction driven body  50  is mounted on the top surfaces of these spacers  51 . The Y-direction driven body  50  and the rear side piece  5 B of the embroidery frame  5  are connected to each other so that the rear side piece  5 B of the embroidery frame  5  is movable relative to the Y-direction driven body  50  in the X direction. Such a connection method can employ roller pairs, and various other known connection methods. 
     In the second embodiment, transmission of driving forces to the embroidery frame  5  from the respective Y-direction drive units  7  is performed via the Y-direction driven body  50 . Since driving forces in the Y direction can be uniformly exerted on the embroidery frame  5  even in any position where the embroidery frame  5  is moved, there is produced an advantage that the embroidery frame  5  is moved without generation of distortion. In the second embodiment, the embroidery frame  5  is driven by the Y-direction driven body  50  only in the Y direction, but a similar construction may be employed in the X direction. More specifically, an X-direction driven body is connected directly to both X-direction drive units  6 ,  6  so that driving forces in the X direction are transmitted to the embroidery frame  5  through the X-direction driven body. In this case, the embroidery frame  5  can be more precisely moved by arranging both X-direction drive units  6 ,  6  between both Y-direction drive units  7 , and positioning respective ends of the Y-direction driven body  50  and the X-direction driven body so as not to have them overhanging outside the respective rows of the drive units. Of course, the X-direction driven body may be provided for the X-direction drive units. 
     (Other Embodiments) 
     (1) In the embodiments described above, a so-called “material cloth fabrics frame”, which directly holds material cloth fabrics and holds small-sized embroidery frames of various types corresponding to respective sewing machine heads, is illustrated as an embroidery frame, but the present invention is not limited thereto. It is understood that a frame body recited herein indicates a comprehensive concept including all frame members driven in a direction of X-Y coordinates, for example, a base frame holding a bag frame, a cap frame or the like. 
     (2) In the embodiments described above, a timing belt or belts for connection of a pair or pairs of drive units are referred to as an example, but the present invention is not limited thereto. For example, other connecting means such as wire connection, gear connection or the like may be employed. 
     (3) In the embodiments described above, a pair or pairs of drive units are connected to each other and driven by a common motor, but individual motors may be provided for respective drive units to be subjected to synchronous control. 
     (4) Vertical load from the embroidery frame is not exerted on the nut members provided on the drive units in the embodiments described above. Accordingly, it is unnecessary to use the guide member composed of the linear rail and the linear guide in the illustrated examples provided that measures is effectively employed for inhibiting rotation of the nut members. 
     (5) The embodiments described above employ the constitution, in which the screw rod and the moving body threaded onto the screw rod are combined to drive both of the X-direction drive unit and the Y-direction drive unit. The combination of the screw rod and the moving body may be used only for either of the drive units. 
     As described above, the sewing machine frame drive device according to the present invention enables performing precise control of movements of the frame, so that an article being sewn can be conveyed in accordance with sewing data even when additional correction control is not implemented, and so a useful effect is obtained in achieving precise sewing.