Abstract:
Machine tool simplifying maintenance, reducing manufacturing costs, and enabling high precision machining. The machine tool is equipped with: a bed furnished with a rectangular base, right and left sidewalls provided standing either side of the base, and a rear sidewall provided standing along the back of the base; a table disposed in the space surrounded by the three sidewalls; a first saddle shaped in the form of a rectangular frame shape, provided free to shift back and forth supported on the tops of the left and right sidewalls; a second saddle penetrated by a perpendicular through-hole and arranged free to shift sideways inside the first saddle frame; and a spindle head arranged free to shift perpendicularly inside the through-hole in the second saddle; and a main spindle arranged over the table and supported by the spindle head free to rotate centered on its axis.

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The present invention relates to machine tools furnished with: a bed; a table on which a workpiece is carried and which is disposed on the bed; a main spindle for retaining a tool, and provided, with its axis disposed perpendicularly, to rotate freely centered on the axis; and a feed mechanism for shifting the table and the main spindle relatively to each other along three orthogonal axes. 
   2. Description of the Related Art 
   Such machine tools known to date include the example disclosed in Japanese Unexamined Patent App. Pub. 2001-87964. This machine tool primarily is made up of: a bed; a column arranged on the bed; a saddle that is supported on the front of the column and is shiftable horizontally (along the X-axis); a spindle head that is supported on the saddle and is shiftable vertically (along the Z-axis); a main spindle for retaining a tool and being supported by the spindle head so that the axis of the main spindle is perpendicular and the main spindle is rotatable about the main spindle axis; and a table on which a workpiece is carried, the table being arranged on the upper face of the bed and provided below the main spindle, provided to be shiftable along an axis (the Y-axis) that is orthogonal in the horizontal plane to the course along which the saddle shifts. 
   This machine tool also has a rotational drive mechanism for rotating the main spindle on the main spindle axis, an X-axis guide mechanism for guiding movement along the X-axis of the saddle, a Z-axis guide mechanism for guiding movement along the Z-axis of the spindle head, a Y-axis guide mechanism for guiding movement along the Y-axis of the table, an X-axis feed mechanism for moving the saddle on the X-axis, a Z-axis feed mechanism for moving the spindle head on the Z-axis, a Y-axis feed mechanism for moving the table on the Y-axis, a machine tool cover that is attached to the bed and surrounds the machine tool, an X-axis cover disposed in front of the cover, a Z-axis cover disposed in front of the cover, a Y-axis cover disposed above the bed, and a guide cover disposed above the bed on both sides of the table on the X-axis. 
   The X-axis guide mechanism comprises a first X-axis guide surface formed along the X-axis in front of the column, and a second X-axis guide surface formed behind the saddle so that the second X-axis guide surface connects with the first X-axis guide surface. The Z-axis guide mechanism comprises a first Z-axis guide surface formed along the Z-axis in front of the saddle, and a second Z-axis guide surface formed behind the spindle head so that the second Z-axis guide surface connects with the first Z-axis guide surface. The Y-axis guide mechanism comprises a first Y-axis guide surface formed along the Y-axis above the bed, and a second Y-axis guide surface formed below the table so that the second Y-axis guide surface connects with the first Y-axis guide surface. 
   The X-axis feed mechanism comprises an X-axis drive motor disposed to the column, an X-axis ball screw disposed along the X-axis in front of the column and axially rotated by the X-axis drive motor, and an X-axis nut that is affixed to the back of the saddle and screws onto the X-axis ball screw. The Z-axis feed mechanism comprises a Z-axis drive motor disposed to the saddle, a Z-axis ball screw disposed along the Z-axis in front of the saddle and axially rotated by the Z-axis drive motor, and a Z-axis nut that is affixed to the back of the spindle head and screws onto the Z-axis ball screw. The Y-axis feed mechanism comprises a Y-axis drive motor disposed to the bed, a Y-axis ball screw disposed along the Y-axis above the bed and axially rotated by the Y-axis drive motor, and a Y-axis nut that is affixed to the bottom of the table and screws onto the Y-axis ball screw. 
   The X-axis cover is a telescopic cover disposed in front of the column to allow movement of the saddle along the X-axis with both side portions and the top portion of the cover connected to the inside of the machine tool cover. The Z-axis cover is a roll-up cover disposed in front of the saddle covering the Z-axis guide mechanism and the Z-axis feed mechanism to allow movement of the spindle head along the Z-axis. The Y-axis is a telescopic cover disposed above the bed covering the Y-axis guide mechanism and Y-axis feed mechanism to allow movement of the table along the Y-axis, and is rendered so that the top of the Y-axis cover declines to both sides from the middle portion of the Y-axis cover on the X-axis. The covers prevent chips, swarf and other cutting waste and cutting fluid from flying outside the machine tool and from entering the X-axis guide mechanism and X-axis feed mechanism, the Z-axis guide mechanism and Z-axis feed mechanism, and the Y-axis guide mechanism and Y-axis feed mechanism. 
   The guide cover is disposed below the X-axis cover, the Z-axis cover, and the Y-axis cover, and guides waste and cutting fluid into a collection box located below drain holes appropriately formed in the bed along the X-axis on both sides of the table. 
   When the X-axis drive motor in this machine tool rotates the X-axis ball screw and the X-axis nut moves along the X-axis ball screw, the saddle moves along the X-axis guided by the first X-axis guide surface and the second X-axis guide surface. When the Z-axis drive motor rotates the Z-axis ball screw and the Z-axis nut moves along the Z-axis ball screw, the spindle head moves along the Z-axis guided by the first Z-axis guide surface and the second Z-axis guide surface. When the Y-axis drive motor rotates the Y-axis ball screw and the Y-axis nut moves along the Y-axis ball screw, the table moves along the Y-axis guided by the first Y-axis guide surface and the second Y-axis guide surface. The rotational drive mechanism drives the main spindle rotationally on the main spindle axis. The workpiece held on the table is thus processed by the tool held in the main spindle as the saddle, spindle head, and table move on their respective axes while the main spindle rotates on the main spindle axis. 
   Waste produced by machining the workpiece and cutting fluid supplied appropriately to the point of contact between the tool and the workpiece during processing are also prevented from entering the X-axis guide mechanism and X-axis feed mechanism, the Z-axis guide mechanism and Z-axis feed mechanism, and the Y-axis guide mechanism and Y-axis feed mechanism by the X-axis cover, the Z-axis cover, and the Y-axis cover, respectively, and from flying outside the machine tool by the machine tool cover. 
   In addition, waste and cutting fluid also fall down along the inside surface of the machine tool cover, the X-axis cover, and the Z-axis cover, and are guided downward to both sides along the X-axis by the inclined surface of the top of the Y-axis cover. The waste and cutting fluid then fall onto the top of the guide cover whereby they are guided towards the collection box and exit. 
   With this conventional machine tool, the Y-axis guide mechanism that guides table movement and the Y-axis feed mechanism that moves the table are located below the top of the table, and waste and cutting fluid always flow over the top of the Y-axis cover. Waste and cutting fluid can therefore enter the Y-axis guide mechanism and Y-axis feed mechanism more easily than the X-axis guide mechanism and X-axis feed mechanism or the Z-axis guide mechanism and Z-axis feed mechanism. As a result, the Y-axis cover requires frequent maintenance, or requires using a complicated and costly construction. 
   Another problem with the conventional technology is that the heavy saddle is supported at the front of the column and the similarly heavy spindle head is supported at the front of the saddle with the saddle and spindle head protruding to the front of the machine tool. This results in deflection or deformation of the column or saddle and thus prevents high precision machining. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention is directed to solving these problems, and an object of the invention is to provide a machine tool that affords easy maintenance, reduces manufacturing cost, and enables high precision processing. 
   To achieve this object, a machine tool according to a preferred aspect of the invention comprises: a bed comprising a rectangular base, two sidewalls rising vertically from opposing left and right sides of the base across an interval between the sidewalls, and a rear sidewall disposed at the back vertically to the base between the right and left sidewalls; a table disposed to the bed in a space surrounded by the three sidewalls of the bed; a first saddle having a rectangular frame shape with both lengthwise end parts supported by a top portion of the left and right sidewalls of the bed, and disposed freely movably back and forth in a horizontal plane; a second saddle disposed freely movably side-to-side in a horizontal plane inside the frame of the first saddle, and comprising a vertical through-hole; a spindle head disposed freely movably vertically inside the through-hole of the second saddle; a main spindle disposed above the table with the main spindle axis vertical and the main spindle supported by the spindle head freely rotatably on the main spindle axis; a first guide mechanism for guiding the first saddle back and forth; a second guide mechanism for guiding the second saddle side-to-side; a third guide mechanism for guiding vertical movement of the spindle head; a first feed mechanism for moving the first saddle back and forth; a second feed mechanism for moving the second saddle side-to-side; a third feed mechanism for moving the spindle head vertically; and a first rotation drive mechanism for rotating the main spindle on the main spindle axis. 
   With the machine tool according to this aspect of the invention the first saddle is guided by the first guide mechanism and moved back and forth by the first feed mechanism, the second saddle is guided by the second guide mechanism and moved side-to-side by the second feed mechanism, the spindle head is guided by the third guide mechanism and moved vertically by the third feed mechanism, the main spindle is driven rotationally on its axis by the first rotation drive mechanism, and the work held on the table is thus machined by the tool held by the main spindle. 
   In a machine tool according to this aspect of the invention the table is disposed inside the space enclosed by the three sidewalls of the bed, both ends of the long sides of the first saddle are supported and move freely back and forth on top of the right and left sidewalls of the bed, the second saddle is disposed movably side-to-side (right and left) inside the frame of the first saddle, and the spindle head is disposed to move vertically inside the through-hole in the second saddle. As a result, the first saddle, the second saddle, and the spindle head can also be disposed above the top of the table. 
   A machine tool according to this invention therefore makes it more difficult for waste and cutting fluid to enter the first feed mechanism and first guide mechanism, the second feed mechanism and second guide mechanism, and the third feed mechanism and third guide mechanism when compared with a prior art machine tool in which the feed mechanism for moving the table and the guide mechanism for guiding table movement are disposed below the top of the table. The manufacturing cost and construction of the cover that prevents waste and cutting fluid from entering the slide and guide mechanisms can thus be reduced, and cover maintenance can be simplified. 
   Furthermore, the first saddle is rendered with a rectangular frame shape, the second saddle is disposed inside the frame of the first saddle, and the spindle head is disposed inside a through-hole formed vertically through the second saddle. Unlike the prior art machine tool, the saddle therefore does not project from the front and a support structure for the spindle head is not needed. Deflection and other deformation of the bed, first saddle, and second saddle are thus prevented, and work can be machined with high precision. 
   Furthermore, by rendering a recess at the front outside surface between the ends of the long sides of the first saddle, the front outside surface of the first saddle can be prevented from striking a worker working at the front of the bed when the first saddle moves to the front side of the bed. 
   In another aspect of the invention the table is supported by the rear sidewall of the bed, can rotate freely on an axis of rotation perpendicular to the top surface of the table, and can swivel freely on a swivel axis parallel to the direction of first saddle movement. In addition, the machine tool further comprises: a second rotation drive mechanism for rotating the table on the axis of rotation and indexing the table to a specific rotational angle position; and a swivel drive mechanism for swiveling the table on the swivel axis and indexing the table to a specific swivel angle position. 
   The table can be rotated on the axis of rotation and indexed to a specific rotational angle position by means of the second rotation drive mechanism, and can be rotated on the swivel axis and indexed to a specific swivel angle position by means of the swivel drive mechanism, to index the work on the table to an appropriate position. The work therefore needs to be mounted on the table only once in order to complete a processing sequence including machining the outside of the work, thus improving efficiency and machining precision. 
   In a machine tool according to another aspect of the invention the bed comprises a tool changing opening passing from the outside to the inside through any one of the right, left, and rear sidewalls, and the machine tool further comprises a tool changing device for carrying tools in and out through the tool changing opening, and replacing a tool held in the main spindle with a new tool. 
   Tools can thus be changed efficiently by means of the tool changing device replacing the tool held by the main spindle with a new tool. Furthermore, because the desired new tool can be delivered through the tool changing opening rendered in any one of the sidewalls of the bed, and the replaced tool that was held by the main spindle can be removed through the tool changing opening, the tool changing device does not interfere with the performance of a worker working at the front of the bed. 
   In a machine tool according to another aspect of the invention the bed comprises a pallet changing opening passing from the outside to the inside through any one of the right, left, and rear sidewalls, and the machine tool further comprises a pallet changing device for carrying pallets in and out through the pallet changing opening, and replacing a pallet holding processed work on the table with a new pallet holding unprocessed work. 
   Pallets can thus be changed efficiently by means of the pallet changing device replacing the pallet holding processed work on the table with a new pallet holding unprocessed work. Furthermore, because the new pallet can be delivered through the pallet changing opening rendered in any one of the sidewalls of the bed, and the replaced pallet that was held on the table can be removed through the pallet changing opening, the pallet changing device does not interfere with the performance of a worker working at the front of the bed. 
   In a machine tool according to another aspect of the invention the bed comprises a pallet changing opening passing from the outside to the inside through any two of the right, left, and rear sidewalls, and the machine tool further comprises a pallet changing device for carrying pallets in from one pallet changing opening and out through the other pallet changing opening, and replacing a pallet holding processed work on the table with a new pallet holding unprocessed work. 
   This arrangement enables delivering the new pallet through one of the two pallet changing openings rendered in any two of the sidewalls of the bed, and removing the replaced pallet fixed to the table from the other pallet changing opening. As a result, pallets can be changed efficiently by means of the pallet changing device and the pallet changing device does not interfere with the performance of a worker working at the front of the bed. 
   A machine tool according to another aspect of the invention also has a discharge means disposed below the table for discharging fluid toward the table, and a fluid supply means for supplying and discharging the fluid from the discharge means. The swivel drive mechanism can swivel the table in at least one table swiveling direction between a first swivel angle position where the top of the table is horizontal and a second swivel angle position where the table top is swiveled 90 degrees or more from the first swivel angle position, and the discharge means discharges fluid supplied from the fluid supply means toward the table swiveled to the second swivel angle position by the swivel drive mechanism. 
   When processing the work is finished, the swivel drive mechanism swivels the table to the second swivel angle position rotated 90 degrees or more from the first swivel angle position, and fluid is then supplied by the fluid supply means and discharged from the discharge means. 
   The direction in which the fluid is discharged from the discharge means is toward the table after the table has been swiveled to the second swivel angle position by the swivel drive means, and waste left on the table or on the work held on the table is removed by the fluid discharged from the discharge means. This causes the waste to fall so that it can be efficiently removed. Production costs can also be reduced because a special device for removing waste accumulated on or adhering to the work is not needed. 
   Alternatively, the discharge means can be rendered to discharge the fluid supplied from the fluid supply means toward the table after the table is swiveled by the swivel drive mechanism to a swivel angle position of 90 degrees or more from the first swivel angle position, and the fluid supply means can be rendered to supply the fluid to the discharge means while the table is being swiveled by the swivel drive mechanism from a swivel angle position of 90 degrees or more toward the second swivel angle position. 
   In this aspect of the invention the fluid is discharged from the discharge means while the table is swiveling and the table swivels through the streams of discharged fluid. Swiveling the table and removing waste by discharging fluid thus proceed in parallel, and the waste can be remove in less time and more efficiently. 
   In another aspect of the invention the bed has a waste discharge opening of which one end opens to the top of the base and the other end opens to the outside of the bed, and the machine tool further comprises a waste recovery means disposed inside the waste discharge opening for recovering waste falling from the open portion in the top of the base of the bed. 
   Waste can thus be efficiently discharged from the one end of the waste discharge opening rendered below and around the table in the top of the base of the bed, and can be recovered into the waste recovery means. 
   A machine tool according to the present invention thus renders the first saddle, second saddle, and spindle head movable in respective specific slide directions at a position above the top of the table, thus making it difficult for waste and cutting fluid to enter the first feed mechanism and first guide mechanism, the second feed mechanism and second guide mechanism, and the third feed mechanism and third guide mechanism. The construction and manufacturing cost of covers used to prevent such unwanted penetration of waste and cutting fluid can therefore be reduced and cover maintenance can be simplified. 
   Furthermore, because the second saddle is rendered inside the frame of the first saddle and the spindle head is disposed in a through-hole in the second saddle, the first saddle and second saddle are more resistant to deflection and other deformation, thus affording high precision machining. 
   From the following detailed description in conjunction with the accompanying drawings, the foregoing and other objects, features, aspects and advantages of the present invention will become readily apparent to those skilled in the art. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       FIG. 1  is an oblique schematic view of a machine tool according to a preferred embodiment of the invention. 
       FIG. 2  is an oblique schematic view of a machine tool according to a preferred embodiment of the invention. 
       FIG. 3  is an oblique schematic view showing the machine tool, a tool changing device, and a pallet changing device according to a preferred embodiment of the invention. 
       FIG. 4  is an oblique schematic view showing the machine tool, a tool changing device, and a pallet changing device according to a preferred embodiment of the invention. 
       FIG. 5  is a front view showing a part of a machine tool according to a preferred embodiment of the invention. 
       FIG. 6  is a section view through line A-A in  FIG. 5 . 
       FIG. 7  is a plan view showing a part of the top cover in a preferred embodiment of the invention. 
       FIG. 8  is a plan view showing a part of the top cover in a preferred embodiment of the invention. 
       FIG. 9  is a section view through line B-B in  FIG. 7 . 
       FIG. 10  is a section view through line C-C in  FIG. 8 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A preferred embodiment of the invention is described below with reference to the accompanying figures wherein  FIG. 1  and  FIG. 2  are oblique schematic views of a machine tool according to a preferred embodiment of the invention, and  FIG. 3  and  FIG. 4  are oblique schematic views showing the machine tool, a tool changing device, and a pallet changing device according to this preferred embodiment of the invention.  FIG. 5  is a front view showing a part of a machine tool according to this preferred embodiment of the invention, and  FIG. 6  is a section view through line A-A in  FIG. 5 .  FIG. 7  and  FIG. 8  are plan views showing a part of the top cover in this preferred embodiment of the invention,  FIG. 9  is a section view through line B-B in  FIG. 7 , and  FIG. 10  is a section view through line C-C in  FIG. 8 . 
   As shown in  FIG. 1  to  FIG. 6 , a machine tool  1  according to this embodiment of the invention has a machine tool unit  10  of a type known as a vertical machining center, a tool changing device  40 , pallet changing device  45 , and a waste recovery device  50  attached to the machine tool unit  10 , and a cover  60  covering at least the machine tool unit  10 , tool changing device  40 , and pallet changing device  45 . 
   The machine tool unit  10  comprises a bed  11 , a first saddle  16  that is disposed to the bed  11  and moves freely in a horizontal plane in the front-rear direction (along the Y-axis), a second saddle  17  that is disposed to the first saddle  16  and moves freely in a horizontal plane side to side (along the X-axis), a spindle head  18  that is disposed to the second saddle  17  and moves freely vertically (along the Z-axis), a main spindle  19  that holds a tool T and is supported by the spindle head  18  to rotate freely on the main spindle axis, and a table  20  on which a pallet P is mounted. Work W is fixed on top of the pallet P. The table  20  is disposed to the bed  11  and can swivel freely on an axis of rotation (B-axis) parallel to the Y-axis and rotate freely an axis of rotation (C axis) perpendicular to the top surface of the pallet P. 
   The machine tool unit  10  also comprises a Y-axis guide mechanism  21  for guiding movement of the first saddle  16  along the Y-axis, a X-axis guide mechanism  22  for guiding movement of the second saddle  17  along the X-axis, a Z-axis guide mechanism (not shown in the figures) for guiding movement of the spindle head  18  along the Z-axis, a Y-axis feed mechanism  24  for moving the first saddle  16  along the Y-axis, an X-axis feed mechanism  25  for moving the second saddle  17  along the X-axis, a Z-axis feed mechanism  26  for moving the spindle head  18  along the Z-axis, a main spindle rotational drive mechanism (not shown in the figures) for rotating the main spindle  19  on its axis, a first table rotation drive mechanism (not shown in the figures) for swiveling the table  20  on the B-axis for indexing to a specific rotational angle position, and a second table rotation drive mechanism (not shown in the figures) for rotating the table  20  on the C axis for indexing to a specific rotational angle position. 
   The bed  11  comprises with a rectangular base when seen in plan view, left and right sidewalls  13  and  14  (left sidewall  13  on the front left side and right sidewall  14  on the front right side) disposed vertically on both sides of the base  12  across an interval therebetween on the X-axis, and a sidewall  15  (rear sidewall) disposed vertically to the base  12  at the back between the right and left sidewalls  13  and  14 . 
   The base  12  has a waste removal hole  12   a  of which one end opens to the top center portion of the base  12  and the other end opens to the back outside surface of the base  12 . The top of the base  12  and the base portion of the left sidewall  13  and the base portion of the right sidewall  14  decline into the opening to the waste removal hole  12   a.    
   A tool changing opening  13   a  is formed through from the outside to the inside of the left sidewall  13  so that a tool T can be delivered into and removed from the inside of the machine tool unit  10  (the space enclosed by sidewalls  13 ,  14 ,  15 ) when the tool changing device  40  changes the tool T. A pallet changing opening  14   a  is formed through from the outside to the inside of the right sidewall  14  so that a pallet P can be delivered into and removed from the inside of the machine tool unit  10  (the space enclosed by sidewalls  13 ,  14 ,  15 ) when the pallet changing device  45  changes the pallet P. 
   The table  20  comprises a pallet mounting unit  20   a  on which a pallet P is mounted, and a support unit  20   b  which is supported on the inside of the rear sidewall  15  of the bed  11  to swivel freely on the B-axis and supports the pallet mounting unit  20   a  to rotate freely on the C axis. The table  20  is located in the space enclosed by the sidewalls  13 ,  14 ,  15  so that the pallet P mounted on the pallet mounting unit  20   a  is substantially positioned above the waste removal hole  12   a , and there is a constant gap between the bottom of the support unit  20   b  and the top of the base  12 . 
   The pallet mounting unit  20   a  is rotated on the C axis by the second table rotation drive mechanism (not shown in the figures) and indexed to a specific rotational angle position, and the support unit  20   b  is swiveled on the B-axis by the first table rotation drive mechanism (not shown in the figures) and indexed to a specific rotational angle position. The work W on the pallet P can thus be indexed to a desired angular position by rotating the support unit  20   b  on the B-axis to swivel the pallet P on the B-axis, and by rotating the pallet P with the pallet mounting unit  20   a  on the C axis. 
   A pallet P on the pallet mounting unit  20   a  can be swiveled both to the right and to the left on the B-axis by the first table rotation drive mechanism (not shown in the figures) to any position on the B-axis between a position where the top of the pallet P is horizontal and facing up (with the pallet P at a swivel angle of 0 degrees) to a position where the top of the pallet P is horizontal and facing down (with the pallet P at a swivel angle of 180 degrees). 
   The first saddle  16  has a rectangular frame shape with the transverse side parallel to the X-axis and the longitudinal side parallel to the Y-axis. The end portions of the long transverse sides are supported to move freely along the Y-axis on the top of the left sidewall  13  and right sidewall  14  of the bed  11 . A recess  16   a  is formed in the front outside surface between both ends of the long side of the first saddle  16 . As shown in  FIG. 6 , when the first saddle  16  moves toward the front of the bed  11 , the recess  16   a  prevents the front outside surface of the first saddle  16  from striking a worker S working at the front side of the bed  11 . 
   The second saddle  17  comprises a shoulder  17   a  extending to each side in the Y-axis direction, and a through-hole  17   b  passing vertically through the second saddle  17 . The second saddle  17  is disposed within the frame of the first saddle  16  with the shoulders  17   a  supported by the top of the transverse portions of the first saddle  16  so that the second saddle  17  can move freely on the X-axis. 
   The spindle head  18  is supported to move freely on the Z-axis inside the through-hole  17   b  in the second saddle  17 . The main spindle  19  is disposed above the table  20  with the main spindle axis parallel to the Z-axis and the main spindle  19  freely rotatably supported by the bottom portion of the spindle head  18 . 
   The Y-axis guide mechanism  21  comprises guide rails  21   a  aligned with the Y-axis on the top of the left sidewall  13  and right sidewall  14  of the bed  11 , and sliders  21   b  that are affixed to the bottom of both long end parts of the first saddle  16  and engage and move freely on the guide rails  21   a.    
   The Y-axis feed mechanism  24  comprises drive motors  24   a  disposed on the top of left sidewall  13  and right sidewall  14  of the bed  11 , ball screws  24   b , and nuts  24   c . The ball screws  24   b  are disposed aligned with the Y-axis on the top of the left sidewall  13  and right sidewall  14  of the bed  11 , and are axially rotated by the corresponding drive motors  24   a . The nuts  24   c  are affixed to the outside surfaces of the longitudinal portions of the first saddle  16 , and screw onto the matching ball screws  24   b.    
   When the drive motors  24   a  of this Y-axis feed mechanism  24  are driven and the ball screws  24   b  thus turn axially, the nuts  24   c  move along the ball screws  24   b  and the first saddle  16  thus moves on the Y-axis guided by the guide rails  21   a  and sliders  21   b  of the Y-axis guide mechanism  21 . 
   The X-axis guide mechanism  22  comprises guide rails  22   a  disposed aligned with the X-axis on the top of the transverse side portions of the first saddle  16 , and sliders  22   b  that are affixed to the bottoms of the shoulders  17   a  of the second saddle  17  and engage and move freely on the guide rails  22   a.    
   The X-axis feed mechanism  25  comprises a drive motor  25   a  disposed to one longitudinal side portion of the of the first saddle  16 , a ball screw  25   b  that is disposed on the X-axis inside the frame of the first saddle  16  and is axially rotated by the drive motor  25   a , and a nut (not shown in the figures) that is affixed to the second saddle  17  and screws onto the ball screw  25   b.    
   When the drive motor  25   a  of this X-axis feed mechanism  25  is driven and the ball screw  25   b  turns axially, the nut moves along the ball screw  25   b  and the second saddle  17  thus moves along the X-axis guided by the guide rails  22   a  and sliders  22   b  of the X-axis guide mechanism  22 . 
   The Z-axis guide mechanism (not shown in the figures) comprises guide rails (not shown in the figures) aligned with the Z-axis on the inside of both X-axis sides of the through-hole  17   b  of the second saddle  17 , and sliders (not shown in the figures) that are affixed to the outside of both X-axis sides of the spindle head  18  and engage and move freely on these guide rails (not shown in the figures). 
   The Z-axis feed mechanism  26  comprises drive motors  26   a  disposed on the top of both X-axis sides of the second saddle  17 , ball screws (not shown in the figures) that are disposed aligned with the Z-axis on the inside of both X-axis sides of the second saddle  17  and are axially rotated by the drive motors  26   a , and nuts (not shown in the figures) that are affixed to the outside of both X-axis sides of the spindle head  18  and screw onto the ball screws (not shown in the figures). 
   When the drive motors  26   a  of this Z-axis feed mechanism  26  are driven and the ball screws (not shown in the figures) turn axially, the nuts (not shown in the figures) move along the ball screws so that the spindle head  18  moves on the Z-axis guided by the guide rails (not shown in the figures) and sliders (not shown in the figures) of the Z-axis guide mechanism (not shown in the figures). 
   The tool changing device  40  comprises a tool magazine  41 , a tool changing arm  42 , and a drive mechanism unit  43 . The tool magazine  41  is supported on the outside of the left sidewall  13  of the bed  11 , and has a plurality of holding units  41   a  each holding a tool T. The tool changing arm  42  swivels horizontally, grips the tool T held in the main spindle  19  on one end, and is inserted from the tool magazine  41  through the tool changing opening  13   a  in the left sidewall  13  to the inside of the machine tool unit  10  to grip the (next) tool T positioned at a predetermined position with the other end. The drive mechanism unit  43  is supported on the inside surface of the left sidewall  13  and supports the tool changing arm  42 , and causes the tool changing arm  42  to rotate horizontally and move vertically. 
   The tool changing device  40  replaces the tool T on the main spindle  19  with the next tool T set to a predetermined position (indicated by the imaginary line in  FIG. 3  and  FIG. 4 ) as a result of the horizontal rotation and vertical movement of the tool changing arm  42  driven by the drive mechanism unit  43 , and introduces and removes the tools T through the tool changing opening  13   a  in the left sidewall  13 . 
   The pallet changing device  45  has pallet moving table  46  and a pallet moving mechanism  47 . The pallet moving table  46  has a plurality of pallet tables  46   a  on top of which the pallets P are placed, and rotates the pallet tables  46   a  on a vertical axis of rotation in the direction of the arrows shown in  FIG. 3  and  FIG. 4 . The pallet moving mechanism  47  is located between the machine tool unit  10  and the pallet moving table  46 , and moves a pallet P between the pallet table  46   a  rotated to a predetermined position by the pallet moving table  46  and the table  20  inside the machine tool unit  10 . 
   The pallet moving mechanism  47  has a conveyance member  47   a  that can move to and away from the table  20  through the pallet changing opening  14   a  in the right sidewall  14  of the bed  11 . When moving a pallet P, the conveyance member  47   a  moves to the table  20  to place or remove a pallet P on the table  20  through the pallet changing opening  14   a , and thus replaces the pallet P carrying the processed work W on the table  20  with a new pallet P carrying unprocessed work W. 
   Loading and unloading work W on a pallet P is done by a worker, for example, after the pallet moving table  46  has rotated the pallet table  46   a  (pallet P) to a predetermined rotational position where the processed work W is removed from the pallet P and an unprocessed work W is mounted on the pallet P. 
   The waste recovery device  50  comprises a discharge mechanism  51 , a storage tank  54 , a collection box  55 , a nozzles  56 , and a supply pump (not shown in the figures). 
   The discharge mechanism  51  conveys cutting waste resulting from processing the work W in a specific transportation direction and removes the waste from the machine tool unit  10 . The storage tank  54  is disposed below the discharge mechanism  51  on the upstream side in the waste transportation direction, and stores the cutting fluid. The collection box  55  is disposed below the discharge mechanism  51  at the downstream end of the transportation direction. A plurality of nozzles  56  are disposed inside the waste removal hole  12   a  at the top of the opening in the base  12 , and on the rear sidewall  15  at the top of the waste removal hole  12   a  in the base  12 . The supply pump (not shown in the figures) supplies cutting fluid from the storage tank  54  to the plural nozzles  56  for discharge to the work W. 
   The discharge mechanism  51  comprises a conveyor belt  52  composed of a plurality of plates connected in an endless loop for carrying cutting waste to the collection box  55 , and a support unit  53  that houses and enables the conveyor belt  52  to move freely in a loop. The support unit  53  has a horizontal portion  53   a  disposed inside the waste removal hole  12   a , and an incline portion  53   c  disposed outside the machine tool  1 . The discharge mechanism  51  also has a drive motor (not shown in the figures) that causes the conveyor belt  52  to move in the direction of the arrows shown in  FIG. 6 . 
   The horizontal portion  53   a  of the support unit  53  is open on the top and bottom. Waste and cutting fluid drop from this open portion  53   b  onto the conveyor belt  52 , and cutting fluid that drops onto the conveyor belt  52  flows down through this open portion  53   b  into the storage tank  54  as further described below. The bottom of the downstream end part of the incline portion  53   c  of the support unit  53  is open, and waste conveyed by the conveyor belt  52  drops through this opening (not shown in the figures) into the collection box  55  below. 
   The storage tank  54  is located below the horizontal portion  53   a  of the support unit  53  and collects the cutting fluid that drops from the conveyor belt  52 . 
   The nozzles  56  are arranged to discharge cutting fluid supplied by the supply pump (not shown in the figures) through supply tubes not shown upward toward the pallet P on the table  20 , which has been swiveled 180 degrees on the B-axis to the upside down position by the first table rotation drive mechanism (not shown in the figures). 
   With this waste recovery device  50 , waste and cutting fluid are guided into the waste removal hole  12   a  by the inclined top of the base  12 , the inclined based portions where the left sidewall  13  and right sidewall  14  meet the base  12 , and covers not shown disposed appropriately in the space enclosed by the sidewalls  13 ,  14 ,  15 , and drop from this waste removal hole  12   a  onto the conveyor belt  52 , which is driven in a circle by a drive motor (not shown in the figures). The cutting waste is then conveyed outside the machining center by the conveyor belt  52 , falls into the collection box  55  located below the downstream end of the conveyor belt  52 , and is recovered. The cutting fluid drops from the conveyor belt  52  and is collected in the storage tank  54 . 
   As shown in  FIG. 5  and  FIG. 6 , the support unit  20   b  of the table  20  is swiveled 180 degrees on the B-axis by the first table rotation drive mechanism (not shown in the figures) so that the support unit  20   b  and the work W on the pallet P attached to the pallet mounting unit  20   a  are upside down. Cutting fluid is then supplied from the supply pump (not shown in the figures) and discharged from the nozzles  56  to remove any cutting waste left on the support unit  20   b , the pallet mounting unit  20   a , the pallet P, and the work W, for example. The waste thus removed drops onto the conveyor belt  52  from the waste removal hole  12   a , and is conveyed outside the machine tool unit  10  and recovered. 
   The cover  60  includes a first cover  61  covering the outside of the machine tool unit  10  and the tool changing device  40 ; a second cover  62  that is connected to the first cover  61  and covers the pallet changing device  45 ; a top cover  70  that is connected to the first cover  61  and covers the top of the opening enclosed by the sidewalls  13 ,  14 ,  15  of the bed  11 ; a telescopic third cover  63  that is rendered inside the frame of the first saddle  16  of the machine tool unit  10  to enable movement of the second saddle  17  on the X-axis; a tool changer door for closing the tool changing opening  13   a  in the left sidewall  13  of the bed  11 ; and a pallet changer door (not shown in the figures) for closing the pallet changing opening  14   a  in the right sidewall  14  of the bed  11 . 
   The tool changer door (not shown in the figures) can be opened as needed during the tool changing operation of the tool changing device  40 , and the pallet changer door (not shown in the figures) can be opened as needed during the pallet changing operation of the pallet changing device  45 . 
   The first cover  61  comprises a left door  61   a  that opens by sliding to the left sidewall  13  of the bed  11  at the front of the machine tool unit  10 , and a right door  61   b  that slides to the right sidewall  15  to open. The opened doors  61   a  and  61   b  are housed in pockets  61   c  rendered in the front of the first cover  61 . 
   The second cover  62  comprises doors  62   a  that slide to the right and left to open similarly to the first cover  61 . Work W can be placed on and removed from the pallets P on the pallet moving table  46  of the pallet changing device  45  through the opening afforded by these doors  62   a.    
   The top cover  70  comprises a guide rail  71  disposed on the front top portion of the first saddle  16  and aligned with the X-axis; a left moving member  72  and right moving member  73  having sliders  72   a  and  73   a  that engage and move freely on the guide rail  71 ; a first left top cover  74  and a first right top cover  75  disposed below the guide rail  71 ; a second left top cover  76  and a second right top cover  77  disposed above the first top covers  74  and  75  with the front and back end parts of the covers  76  and  77  connected to the top inside surface of the doors  61   a  and  61   b  of the first cover  61  and the moving members  72  and  73 ; and a left linkage member  78  and a right linkage member  79  disposed above the second top covers  76  and  77  with the end parts connected to the top inside of the doors  61   a  and  61   b  of the first cover  61  and the moving members  72  and  73 . 
   The first top covers  74  and  75  are telescopic covers that enable movement of the first saddle  16  on the Y-axis. The first left top cover  74  is installed with the bottom part attached to the top of the left sidewall  13  of the bed  11  inside of the guide rails  21   a  of the Y-axis guide mechanism  21 , the back part below the guide rail  71  at the front left end part of the long side of the first saddle  16 , and the front part attached to the top inside part of the first cover  61 . The first right top cover  75  is installed with the bottom part attached to the top of the right sidewall  14  of the bed  11  inside of the guide rails  21   a  of the Y-axis guide mechanism  21 , the back part below the guide rail  71  at the front right end part of the long side of the first saddle  16 , and the front part attached to the top inside part of the first cover  61 . 
   The first top covers  74  and  75  do not cover the Y-axis guide mechanism  21  and Y-axis feed mechanism  24  because the bottom part of the covers is disposed inside of the guide rails  21   a  at the top of the sidewalls  13  and  14  of the bed  11 . 
   The second top covers  76  and  77  are bellows-like covers enabling movement of the first saddle  16  on the Y-axis. The front part of the second left top cover  76  is attached to the top inside part of the left door  61   a , and the back part is attached to the left moving member  72 . The front part of the second right top cover  77  is attached to the top inside part of the right door  61   b , and the back part is attached to the right moving member  73 . 
   The linkage members  78  and  79  comprise a pantograph mechanism enabling movement of the first saddle  16  on the Y-axis, and two linkage members are disposed to each of the second top covers  76  and  77 . The ends of the left linkage member  78  are affixed to the top inside part of the left door  61   a  and the left moving member  72 , and the ends of the right linkage member  79  are affixed to the top inside part of the right door  61   b  and right moving member  73 . 
   The first cover  61 , third cover  63 , top cover  70 , tool changer door (not shown in the figures), and pallet changer door (not shown in the figures) of the cover  60 , and the covers (not shown in the figures) appropriately disposed to the inside of the sidewalls  13 ,  14 ,  15  of the bed  11 , close the space (machining area) contained within the sidewalls  13 ,  14 ,  15 , and prevent waste and cutting fluid from flying outside. 
   When the doors  61   a  and  61   b  of the first cover  61  open and close as shown in  FIG. 1 ,  FIG. 2 ,  FIG. 7 , and  FIG. 8 , the second top covers  76  and  77  are guided by the guide rail  71  and sliders  72   a  and  73   a  and move on the X-axis together with the linkage members  78  and  79  and moving members  72  and  73 . As a result, opening and closing the doors  61   a  and  61   b  opens and closes the top part of the working area. 
   With the machine tool  1  according to this embodiment of the invention the first saddle  16  is guided by the Y-axis guide mechanism  21  and moved along the Y-axis by the Y-axis feed mechanism  24 , the second saddle  17  is guided by the X-axis guide mechanism  22  and moved along the X-axis by the X-axis feed mechanism  25 , the spindle head  18  is guided by the Z-axis guide mechanism (not shown in the figures) and moved along the Z-axis by the Z-axis feed mechanism  26 , and the main spindle  19  is driven rotationally on its axis by the main spindle rotation drive mechanism (not shown in the figures), and the work W held on the pallet P placed on the table  20  is thus machined by the tool T held on the main spindle  19 . 
   Waste produced by machining and cutting fluid supplied appropriately to where the tool T and work W contact drop from the waste removal hole  12   a  onto the conveyor belt  52 . The waste is conveyed by the conveyor belt  52  and recovered in the collection box  55 , and the cutting fluid flows down and off the conveyor belt  52  into the storage tank  54  located below the conveyor belt  52 . 
   The pallet mounting unit  20   a  of the table  20  is rotated on the C axis and indexed to a predetermined rotational angle position by the second table rotation drive mechanism (not shown in the figures), and the support unit  20   b  of the table  20  is swiveled on the B-axis by the first table rotation drive mechanism (not shown in the figures) and indexed to a predetermined rotational angle position, to index the pallet P (the work W on the pallet P) to a specific rotational angle position on the C axis and a specific rotational angle position on the B-axis for processing. The tool changing device  40  also changes the tool T as needed through the tool changing opening  13   a  in the left sidewall  13  of the bed  11 . 
   When the machining process is completed, the first table rotation drive mechanism (not shown in the figures) swivels the support unit  20   b  of the table  20  on the B-axis to turn the work W on the pallet P upside down, and cutting fluid is then discharged from the nozzles  56  to remove any waste from the support unit  20   b , the pallet mounting unit  20   a , the pallet P, or the work W, for example. The removed waste drops through the waste removal hole  12   a  onto the conveyor belt  52  whereby the waste is conveyed out from the working area and recovered into the collection box  55 . 
   The first table rotation drive mechanism (not shown in the figures) then again swivels the support unit  20   b  of the table  20  on the B-axis to the upright horizontal position, and the pallet changing device  45  changes the pallet P through the pallet changing opening  14   a  in the right sidewall  14  of the bed  11 . 
   In a machine tool  1  according to this embodiment of the invention the table  20  is disposed inside the space enclosed by the three sidewalls  13 ,  14 ,  15  of the bed  11 , both ends of the long sides of the first saddle  16  are supported on top of the right and left sidewalls  13  and  14  to move freely on the Y-axis, the second saddle  17  is disposed movably on the X-axis inside the frame of the first saddle  16 , and the spindle head  18  is disposed movably on the Z-axis inside the through-hole  17   b  of the second saddle  17 . As a result, the first saddle  16 , the second saddle  17 , and the spindle head  18  can also be disposed above the top of the table  20 . 
   A machine tool  1  according to this embodiment of the invention makes it more difficult for cutting waste and cutting fluid to enter the Y-axis feed mechanism  24  and Y-axis guide mechanism  21 , the X-axis feed mechanism  25  and X-axis guide mechanism  22 , and the Z-axis feed mechanism  26  and Z-axis guide mechanism (not shown in the figures) when compared with a prior art machine tool in which the feed mechanism for moving the table and the guide mechanism for guiding table movement are disposed below the top of the table. Waste and cutting fluid can therefore be prevented from entering the Y-axis, X-axis, and Z-axis feed mechanisms  24 ,  25 ,  26  and the Y-axis, X-axis, and Z-axis guide mechanisms  21  and  22  using only the top cover  70  and third cover  63 , and separate covers for the Y-axis, X-axis, and Z-axis feed mechanisms  24 ,  25 ,  26  and the Y-axis, X-axis, and Z-axis guide mechanisms  21  and  22  are not needed. As a result, the parts count and the manufacturing cost of the cover  60  can be reduced, and maintenance of the cover  60  can be simplified. 
   The first saddle  16  is also rendered with a rectangular frame shape, the second saddle  17  is disposed inside the frame of the first saddle  16 , and the spindle head  18  is disposed inside a through-hole  17   b  formed vertically through the second saddle  17 . Unlike the prior art machine tool, the saddle therefore does not project from the front and a support structure for the spindle head is not needed. Deflection and other deformation of the bed  11 , first saddle  16 , and second saddle  17  are thus prevented, and work W can be machined with high precision. 
   Play and a change in attitude can also be prevented when moving the first saddle  16  and spindle head  18 , and high precision machining is thus afforded, by driving both long-end portions of the first saddle  16  by means of a Y-axis feed mechanism  24  comprising two drive motors  24   a , ball screws  24   b , and nuts  24   c , and driving both ends of the spindle head  18  by means of a Z-axis feed mechanism  26  comprising two drive motors  26   a , ball screws (not shown in the figures), and nuts (not shown in the figures). 
   Yet further, by rendering a recess  16   a  at the front outside surface between the ends of the long sides of the first saddle  16 , the front outside surface of the first saddle  16  can be prevented from striking a worker S working at the front of the bed  11  when the first saddle  16  moves to the front side of the bed  11 . 
   A pallet P on the table  20  can be swiveled and indexed on the B-axis by means of a first table rotation drive mechanism (not shown in the figures) and can also be rotated and indexed on the C axis by means of a second table rotation drive mechanism (not shown in the figures). The work W (pallet P) therefore needs to be mounted on the table  20  only once in order to complete a processing sequence, including machining the outside of the work W, thus improving efficiency and machining precision. 
   The tool changing device  40  and pallet changing device  45  also enable more efficient tool changing and pallet changing, the tool changing device  40  is disposed on the left sidewall  13  side of the bed  11  and changes tools through a tool changing opening  13   a  in the left sidewall  13 , and the pallet changing device  45  is disposed on the right sidewall  14  side of the bed  11  and changes the pallets through a pallet changing opening  14   a  in the right sidewall  14 . Thus rendering the tool changing device  40  and pallet changing device  45  on the sides prevents interference with tasks performed by a worker S at the front of the bed  11 . 
   Furthermore, when processing the work W is finished, the first table rotation drive mechanism (not shown in the figures) swivels the support unit  20   b  on the table  20  180 degrees on the B-axis to invert the work W on the pallet P, and cutting fluid is then discharged towards the pallet P from nozzles  56  located below the table  20  to effectively and efficiently remove any waste accumulated on or clinging to the support unit  20   b , the pallet mounting unit  20   a , the pallet P, and the work W. Waste and cutting fluid are thus prevented from being removed with the pallet P and work W from the machine tool unit  10 . The processing cost can also be reduced because dedicated equipment for removing waste adhering to the work W is not needed. 
   A waste removal hole  12   a  is rendered as an opening in the top of the base  12  of the bed  11 , and a waste recovery device  50  is disposed inside the waste removal hole  12   a . Waste and cutting fluid can thus be efficiently discharged from the opening of the waste removal hole  12   a  in the base  12  and recovered by the waste recovery device  50 . 
   A preferred embodiment of the present invention is described above, and it will be obvious to one with ordinary skill in the related art that the invention is not limited to this embodiment. 
   A tool changing device  40  and pallet changing device  45  are disposed to the machine tool unit  10  in this embodiment of the invention, but the invention is not so limited as the machine tool unit  10  could be equipped with only the tool changing device  40  or only the pallet changing device  45 . In such an arrangement only the corresponding tool changing opening  13   a  or pallet changing opening  14   a  is rendered in one of the three sidewalls  13 ,  14 ,  15  of the bed  11 . 
   The arrangement of the tool changing device  40  and pallet changing device  45  is also not limited to the preferred embodiment described above. For example, a pallet changing opening  14   a  can be rendered in any two of the three sidewalls  13 ,  14 ,  15  of the bed  11  so that the pallet changing device  45  delivers a pallet P from one pallet changing opening  14   a  and removes the pallet P from the other pallet changing opening  14   a , thereby replacing the pallet P holding the processed work W on the table  20  with a new pallet P carrying unprocessed work W. 
   Yet further, cutting fluid is discharged from each of plural nozzles  56  in this preferred embodiment of the invention, but the invention is not so limited and the nozzles  56  could instead discharge compressed air. Furthermore, the nozzles  56  only need to be located below the table  20 , and are not limited to being located directly below the table  20 . The construction of the table  20  and the construction of the machine tool unit  10  are also not limited to this embodiment of the invention. 
   The rotational angle position of the table  20  when the cutting fluid is discharged from the nozzles  56  is also not limited to the 180 degree inverted position described above, and can be any angle of 90 degrees or more. In addition, discharging the cutting fluid from the nozzles  56  is not limited to after the table  20  has been swiveled 180 degrees on the B-axis, and the cutting fluid can be discharged while the table  20  is swiveling. In this situation the table  20  crosses the streams of discharged cutting fluid while the table  20  swivels. Swiveling the table  20  and removing waste by discharging cutting fluid are thus parallel operations, and the waste can be removed in less time and more efficiently. 
   Furthermore, pallets P (work W) are changed by the pallet changing device  45  in this embodiment of the invention, but a crane or other type of hoist device can be used to load the work W on the table  20  instead of using a pallet changing device  45 . Work W can be efficiently loaded and unloaded from the table  20  in this arrangement because the top cover  70  opens together with the doors  61   a  and  61   b  of the first cover  61 .