Patent Abstract:
A work machine includes: a bed having a table positioned on the upper surface thereof; sidewalls positioned to the left and right of the bed and projecting to the rear of the rear surface of the bed; support members for each supporting the bed in relation to a floor surface by using two points on the sidewalls to the left and right of the bed, and using at least one other point; a vertically moving body for moving along a pair of left and right vertical guides positioned in the vertical direction down to the vicinity of the floor surface on the rear surface of the bed; and a vertical drive means for moving the vertically moving body as one of the abovementioned relative movements, and having a pair of left and right feed screws positioned in parallel with the vertical guides.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Phase patent application of PCT/JP2012/066180, filed on Jun. 25, 2012, which is hereby incorporated by reference in the present disclosure in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a machine tool for processing a workpiece by moving a tool attached to a spindle and the workpiece attached to a table relative to each other. 
       BACKGROUND OF THE INVENTION 
       [0003]    Generally, in machine tools, there are various types of configuration for moving a spindle and a tale in X-, Y- and Z-axes. Depending on the configuration, X-, Y- and Z-axes moving bodies, X-, Y- and Z-axes guides, X-, Y- and Z-axes feeding drives and a chip remover are appropriately arranged. 
         [0004]    In a machine tool of Patent Document 1, the respective moving bodies movable in X-, Y- and Z-axes directions are disposed on a rear face of a base. A feeding mechanism for vertically moving a body along guide rails is disposed over the base. This feeding mechanism includes a pair of parallel ball screws providing vertical feed screws and a pair of feed motors for rotationally driving the ball screws separately. 
         [0005]    Patent Document 1: Japanese Unexamined Patent Publication No. 2007-75926 
       SUMMARY OF THE INVENTION 
       [0006]    In the machine tool of Patent Document 1, the base defines a discharge hole extending from the front face to the rear face of the base, and therefore the feed screws are disposed above the base. Further, feed motors must be attached to the top ends of the ball screws because a space must be secured above the base for the movement of the vertically moving body. Accordingly, the gravity center of the machine tool becomes higher, because the relatively heavy feed motors are disposed at a point higher than the tool, and the guide rails for the vertically moving body are disposed above the discharge hole. As a result, the stability of the machine tool is degraded and the over-all height is increased by the feed motors mounted to the top of the machine. Further, the volume of the machine tool is increased, because the elements for supporting the feed motors must be manufactured to have a higher rigidity so as to bear the load acting on the supports. 
         [0007]    The invention is directed to solve the above-described problems of the prior art, and the objective of the invention is to provide a highly rigid and compact machine tool which has gravity center set to a lower point compared with the prior art so as to increase the stability of the machine tool. 
         [0008]    In order to solve the above-described problem, according to the invention, there is provide a machine tool for machining a workpiece, which is attached to a table, by moving a tool attached to a spindle and the workpiece relative to each other, comprising: 
         [0009]    a bed providing a base and defining a top to which a table is disposed; 
         [0010]    supporting members for supporting the bed at three or more points on a floor; 
         [0011]    a vertically moving body moving vertically along a pair of left-right vertically extending guides mounted to the rear side of the bed or to the rear lateral sides of the bed so as to extend near the floor; and 
         [0012]    vertically driving means for moving the vertically moving body, the vertically driving means having at least one feed screw, which is disposed over the supporting means, located at the rear of the bed, and parallel to the vertically extending guides, and a feed motor, connected to the lower end of the feed screw, for rotationally driving the feed screw. 
         [0013]    According to the invention, the arrangement of the feed screw of the vertically driving means disposed over the supporting means for supporting the bed on the floor, and the feed motor connected to the lower end of the feed screw allows the supporting means to receive directly the downward force acting on the bearing element of the feed screw and the motor bracket. Accordingly, the rigidity of the machine tool is increased. If the feed screw and the supporting means are apart from each other, a highly rigid and heavy bed is necessary. However, the above-described arrangement of the invention enables the bed to maintain the rigidity if its weight is reduced. Further, by disposing the relatively heavy feed motor at a lower portion of the machine tool, the gravity center is lowered and the overall height of the machine tool is reduced, resulting in a high stability. The increase in the rigidity and the stability of the machine tool allows the feed axes to move at a higher speed and accuracy. Furthermore, it contributes to downsizing of the machine tool. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a side view schematically showing the configuration of a machine tool according to an embodiment of the invention. 
           [0015]      FIG. 2  is a rear view of the machine tool in the direction of arrows  2 - 2  in  FIG. 1 . 
           [0016]      FIG. 3  is a perspective view of the exterior of the machine tool with a splashguard enclosing the machine tool. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    With reference to the drawings, an embodiment of the invention will be described below.  FIG. 1  is a side view schematically showing the structure of a machine tool according to an embodiment of the invention.  FIG. 2  is a rear view of the machine tool viewing in the direction of arrows  2 - 2  in  FIG. 1 .  FIG. 3  is a perspective view schematically showing the exterior of the machine tool with a splashguard. In this specification, a front side of the machine tool is defined by the direction of the tip of a tool attached to the end of a spindle as described below. 
         [0018]    In this embodiment, as an example, a machine tool  10  may be a four-axis horizontal machining center having liner feed axes extending in three orthogonal X-, Y- and Z-axes directions and a B-axis providing a rotary feed axis. The left-right direction (perpendicular to the plane of  FIG. 1 ) of the machine tool  10  is defined as the X-axis, the vertical direction is defined as the Y-axis, and the front-rear direction (the left-right direction in  FIG. 1 ) is defined as the Z-axis. The B-axis is a rotary feed axis about a vertical axis parallel to the Y-axis. The machine tool  10  may be, instead of a four-axis horizontal type, for example, a five-axis machine, a vertical type machining center, a milling machine, an electric discharge machine, etc. 
         [0019]    The machine tool  10  comprises a bed  12  providing a base supported on a floor of a factory. The bed  12  comprises a bed body  13  in the form of a hollow substantially rectangular column and a pair of side walls  14  rearwardly extending in Z-axis direction from a rear face of the bed body  13 . The bed  12  is supported by a plurality of, in this embodiment three height-adjustable leveling blocks as supporting members. In particular, the bed  12  is supported by a front leveling block  11   a , disposed at the front side center of the bed body  13 , and rear leveling blocks  11   b  disposed at the respective rear ends of the pair of side walls  14 . 
         [0020]    On the top surface of the bed body  13 , a table  15  is arranged. The table  15  is driven by a B-axis servomotor  15   a,  incorporated in the bed body  13  to rotate about a rotational axis, i.e., B-rotary feed axis, parallel to the Y-axis. On the table  15 , a double-faced workpiece mount  16  is fastened. The double-faced workpiece mount  16  includes oppositely defined mounting faces  16   a  and  16  for mounting workpiece W. 
         [0021]    The machine tool  10  comprises a vertically moving body  21  disposed for linear reciprocal movement in the vertical direction along the Y-axis at the back of the bed body  13 . At the top of the vertically moving body  21 , a left-right moving body  23  is mounted for liner reciprocal movement in the left-right direction along the X-axis. A front-rear moving body  24  is mounted to the left-right moving body  23  for liner reciprocal movement in the front-rear direction along the Z-axis. Mounted to the front-rear moving body  24  is a spindle head  25  for supporting a spindle  26  for rotation about a rotational axis O parallel to the Z-axis. A tool  27  is detachably attached to the end of the spindle  26  so as to face the workpiece W mounted to one of the double-faced workpiece mount  16 . 
         [0022]    Mounted to the rear side of the bed body  13  are Y-axis guide rails  28 , providing a pair of left-right guides extending in the Y-axis direction (vertical direction), and Y-axis ball screws  35 , providing a pair of vertical feed screws, disposed outside the Y-axis guide rails  28  so as to extend in the Y-axis direction. Further, brackets  31  are disposed in the rear side of the bed body  13 . In this embodiment, the brackets  31  are integrally formed with the side walls  14  so as to extend from the inner side surfaces of the side walls  14 . Y-axis servomotors  30 , as vertically feed motors, are mounted to and the Y-axis ball screws  35  are rotationally supported by the brackets  31 . Brackets  31  define through holes  32  extending in the Y-axis direction from the top surface to the bottom surface, wherein the Y-axis servomotors  30  are mounted to the bottom surfaces of the brackets  31  so that their output shafts  30   a  extends upwardly through the respective through holes  32 . The output shafts  30   a  are connected to the lower ends of the Y-axis ball screws  35  by couplings  34 . Y-axis ball screws  35  are disposed as possible as near the rear leveling blocks  11   b.    
         [0023]    The vertically moving body  21  comprises a pair of left-right legs  22  which are apart from each other or formed into a bifurcated fork downwardly extending in the Y-axis direction. Y-axis guide blocks  29  are mounted to the vertically moving body  21 . The vertically moving body  21  is supported on the Y-axis guide rails  28  through the Y-axis guide blocks  29  for sliding along the Y-axis guide rails  28 . As shown in  FIG. 2 , the Y-axis guide blocks  29  are position so that the Y-axis guide rails  28  are overlapped by the pair of legs  22  when the vertically moving body  21  is mounted to the rear side of the bed body  13 . In particular, the vertically moving body  21  is provided with a pair of top and bottom Y-axis guide blocks  29  for each of the pair of Y-axis guide rails  28  whereby at least one of the Y-axis guide blocks  29  of each of the pairs is always disposed on each of the pair of legs  22 . 
         [0024]    Further, mounted to the vertically moving body  21  are nuts  36  for engaging the Y-axis screws  36 . When the 
         [0025]    Y-axis servomotors  30  are rotated, the vertically moving body  21  is vertically driven in accordance with the direction and the amount of the rotation of the Y-axis servomotors  30 . In this connection, the Y-axis servomotors  30  and the Y-axis ball screws  35  provide vertically moving means of the invention. Provision of at least one of the Y-axis ball screws  35  may be sufficient. The left-right size of the vertically moving body  21  may be a minimum length allowing the vertically moving body to accommodate the guide blocks  29  whereby the vertically moving body may have laterally extending portions for mounting the nuts  36  to reduce its weight. 
         [0026]    Mounted to the top of the vertically moving body  21  are X-axis guide rails  37 , providing a pair of left-right guides extending in the X-axis direction, and an X-axis ball screw  41 , providing a left-right feed screw disposed between the pair of the X-axis guide rails  37  so as to extend in the X-axis direction. X-axis guide blocks  38  are mounted to the left-right moving body  23 . The left-right moving body  23  is supported on the X-axis guide rails  37  through the X-axis guide blocks  38  for sliding along the X-axis guide rails  37  in the left-right direction. An X-axis servomotor  39  is mounted to the vertically moving body  21  as a left-right feed motor. Output shaft (not shown) of the X-axis servomotor  39  is connected to the X-axis ball screw  41  by a coupling (not shown). A nut  42 , engaging the X-axis ball screws  41 , is mounted to the left-right moving body  23  whereby when the X-axis servomotor  39  is rotated, the left-right moving body  23  is driven in the left-right direction in accordance with the direction and the amount of the rotation of the X-axis servomotor  39 . The X-axis servomotor  39  and the X-axis ball screw  41  provide left-right driving means of the invention. 
         [0027]    Mounted to the top of the left-right moving body  23  are Z-axis guide rails  43 , providing a pair of front-rear guides extending in the Z-axis direction, and a Z-axis ball screw  46 , providing a front-rear feed screw disposed between the pair of the Z-axis guide rails  43  so as to extend in the Z-axis direction. Z-axis guide blocks  44  are mounted to the front-rear moving body  24 . The front-rear moving body  24  is supported on the Z-axis guide rails  43  through the Z-axis guide blocks  44  for sliding along the Z-axis guide rails  43  in the front-rear direction. A Z-axis servomotor  45  is mounted to the left-right moving body  23  as a front-rear feed motor. An output shaft (not shown) of the Z-axis servomotor  45  is connected to the Z-axis ball screw  46  by a coupling (not shown). Nut  42 , engaging the Z-axis ball screw  46 , is mounted to the front-rear moving body  24  whereby when the 
         [0028]    Z-axis servomotor  45  is rotated, the front-rear moving body  24  is driven in the front-rear direction in accordance with the direction and the amount of the rotation of the Z-axis servomotor  45 . The Z-axis servomotor  45  and the Z-axis ball screw  46  provide front-rear driving means of the invention. 
         [0029]    A built-in type spindle motor (not shown) is incorporated in the spindle head  25 . The spindle  26  and tool  27  are rotationally driven by the spindle motor about the rotational axis O. The tool  27  is moved relative to the workpiece W by the linear motion of the left-right moving body  21  and the front-rear moving body  24  in the X-, Y- and Z-axes directions. The relative movement is controlled by an NC device (not shown) incorporated in the machine tool  10 . The rotating tool  27  contact the workpiece W at a machining point when the tool  27  and the workpiece W move relative to each other. Accordingly, the workpiece is machined into a desired shape. 
         [0030]    As shown in  FIG. 1 , the bed body  13  defines an upwardly opening cavity  51 . A chute  52  is defined in the inner wall of the cavity  51  under the table  15 . The rear side of the bed body  13  defines an opening  13   a  as an outlet for chips. The chute  52  is defined by a slope lowering from the front side of the bed body  13  rearwardly toward the opening  13   a  and downwardly inclined surfaces defined by the left and right inner walls. The chips generated during the machining of the workpiece W and the machining liquid injected to machining areas in the workpiece W will fall from around the table  15  into the cavity  51 , then move toward the opening  13   a  along the chute  52 . 
         [0031]    A chip removing duct  53 , for removing the chips and the machining liquid outside the machine tool, i.e., outside the cavity  51  of the bed body  13 , is mounted to the rear side of the bed body  13 . The chip removing duct  53  extends rearwardly from the rear side of the bed body  13  to pass between the legs  22  of the vertically moving body  21 . The chip removing duct  53  is mounted at one end thereof to the rear side of the bed body  13  by for example screws bolts so as to enclose the opening  13   a . The other end  53   b  of the duct  53  is configured to be connected to a chip receptacle  56 . The chip receptacle  56  is a member in the form of an upwardly opening shallow tray having a meshed bottom wall (now shown). A machining liquid reservoir  54  is placed under the chip receptacle  56 . The chip removing duct  53  is downwardly inclined, i.e., closing the floor, from the chute  52  toward the machining liquid reservoir  54 . Thus, the chips and the machining liquid, discharged outside the machine tool through the opening  13   a,  are directed to the chip receptacle  56  by the chip removing duct  53 . In the chip receptacle  56 , the machining liquid will fall into the machining liquid reservoir  54  after it is filtered by the meshed bottom wall of the chip receptacle  56  whereby only the chips are deposited on the bottom wall of the chip receptacle  56 . The chips remaining in the chip receptacle  56  will be periodically collected by an operator. 
         [0032]    The machining liquid reservoir  54  contains the machining liquid from the chute  52  through chip removing duct  53 . A pump  55  is mounted to the machining liquid reservoir  54 . The pump  55  directs the machining liquid, contained in the machining reservoir  54 , to the machining areas in the workpiece W. A filter (not shown) may be provided in the machining liquid reservoir  54  in order to further remove fine chips before the supply to the machining areas. Thus, the machining liquid is reused. 
         [0033]    The machine tool  10  is provided with a splashguard  61  in the form of for example a box containing all of the above-described components. The splashguard  61  a front panel  62 , left and right side panels  63   a  and  63   b  and a top panel  64 , respectively covering a front lower part, the sides and the top and rear side of the machine tool  10 . A front upper part of the machine tool  10 , in particular the space where the double-faced workpiece mount  16  is disposed, is covered by slid doors  65  and  66 . The slide doors  65  and  66  include rectangular monitoring windows  65   a  and  66   a.  Transparent glass plates are fitted in the monitoring windows. 
         [0034]    A control panel  68  is incorporated in the right side panel  63   b.  The control panel  68  is connected to the above-described NC device. In the control panel  68 , a display panel, displaying the operation states of the above-described components, and a various input buttons are disposed. An operator of the machine tool  10  can input a machining program and a various machining parameters to the NC device. A machining program may be input through a communication network, such as a LAN in a factory. 
         [0035]    As described above, in the machine tool  10  according to the embodiment, the pair of vertically extending left-right Y-axis guide rails  28  are disposed adjacent the either sides of the bed body  13  in the rear side of the bed body  13 , and the vertically moving body  21 , having the pair of downwardly extending legs  22  in the form of a bifurcated fork, is mounted to the bed  13  for vertical movement along the pair of left-right Y-axis guide rails  28 . The pair of left-right vertically extending Y-axis ball screws  35  is disposed, as a vertically driving means for vertically driving the vertically moving body  21 , parallel to each other adjacent the pair of left-right Y-axis guide rails  28 , and the vertically moving body  21  is provided with the nuts  36  engaging the Y-axis ball screws  35 . The pair of left-right Y-axis guide rails  28  is positioned so as to be overlapped by the pair of downwardly extending legs  22  in the form of a bifurcated fork, when the vertically moving body  21  is mounted to the rear side of the bed body  13 . The arrangement of the legs  22  in the form of a bifurcated fork, the Y-axis guide rails  28  and the Y-axis ball screws  35  allows the chip removing duct  53 , for discharging the chips and the machining liquid outside the machine, to be positioned at the center of the rear side of the bed  13  in the left-right direction and to extend rearward from the rear side of the bed body  13  between the bifurcated legs  22  of the vertically moving body  21 . This enables the larger sectional areas of the opening  13  as a discharge outlet and the chip removing duct  53 , ensuring the discharge of the chips and the machining liquid effectively. 
         [0036]    Further, in the machine tool  10  according to the embodiment, the pair of left-right Y-axis ball screws  35  is disposed parallel to and adjacent to the pair of left-right Y-axis guide rails  28 , and the Y-axis servomotors  30  are connected to the lower end of the Y-axis ball screws  35 . The Y-axis servomotors  30  are mounted to the brackets  31 , and the brackets  31  are integrally formed with the side walls  14  so as to extend from the inner surface of the side walls  14 . In the side walls  14 , adjacent the brackets  31 , i.e., adjacent the Y-axis servomotors  30 , the leveling blocks  11   b , for supporting the rear part of the machine tool  10 , are disposed. In this manner, the disposition of the Y-axis ball screws  35 , for vertically driving the vertically moving body  21  which is the heaviest moving body of the machine tool  10 , adjacent the rear leveling blocks  11   b , which is disposed at the side walls  14 , increases the over-all rigidity of the machine tool  10 , enabling high speed and high accuracy motion of vertically moving body  21 . 
         [0037]    Further, the Y-axis servomotors  30  and the Y-axis ball screws  35  are disposed rear side of the bed body  13 , and the Y-axis servomotors  30  are connected to the lower ends of the Y-axis ball screws  35 . In the embodiment, the Y-axis guide rails  28 , the Y-axis servomotors  30  and the Y-axis ball screws  35  are disposed below the spindle head  25 . In particular, the Y-axis guide rails  28  extend so that their lower ends are positioned near the floor, and the servomotors  30  are also disposed adjacent the floor. As a result, the gravity center of the machine tool  10  can be lowered compared with conventional machine tools. Furthermore, higher stability of the machine tool  10  than ever before is realized by forming the vertically moving body  21  to have the bifurcated legs  22 , which accommodate the chip removing duct  53 , and by disposing guide blocks  29  to the legs  22  so as to support and guide the vertically moving body  21  with relatively long vertical span. Accordingly, the machining accuracy of the machine tool  10  can be increased. Further, the over-all height of the machine tool  10  can be reduced because the Y-axis servomotors  30  must not be disposed on the top of the machine tool  10 . 
         [0038]    The vertically moving body  21  may be configured to slide vertically along a pair of Y-axis guide rails  28  which may be disposed to extend vertically along the rear lateral sides of the bed  12 , which does not have the left and right side walls  14  extending rearwardly from the rear side of the bed body  13 , instead of the rear side of the bed body  13 . 
       REFERENCE SIGNS LIST 
       [0000]    
       
           10  Machine Tool 
           11   a  Front Leveling Block 
           11   b  Rear Leveling Block 
           12  Bed 
           13   a  Opening 
           14  Side Wall 
           15  Table 
           21  Vertically Moving Body 
           22  Leg 
           23  Left-Right Moving Body 
           24  Font-Rear Moving Body 
           25  Spindle Head 
           26  Spindle 
           27  Tool 
           28  Y-axis Guide Rail 
           29  Y-axis Guide Block 
           30  Y-axis Servomotor 
           30   a  Output Shaft 
           31  Bracket 
           35  Y-axis Ball Screw 
           36  Nut 
           37  X-axis Guide Rail 
           43  Z-axis Guide Rail 
           52  Chute 
           53  Chip Removing Duct 
           54  Machining Liquid Reservoir 
           56  Chip Receptacle

Technology Classification (CPC): 8