Abstract:
Machine tool having a bed, a table arranged on the bed, a first saddle provided free to travel back and forth, a second saddle supported on the first saddle and provided free to travel side to side, a spindle head provided free to travel perpendicularly on the second saddle, a main spindle situated above the table and by the spindle head supported free to rotate on its center axis, a front cover provided on the front side of the bed and furnished with doors that open and close sideways, and top covers configured with one end sideways shiftably connected to the front side of the first saddle, and with another end connected extensibly/retractably to the top of the front-cover doors, therein being configured for permitting back-and-forth-directed movement of the first saddle.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Technical Field  
         [0002]     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 to rotate freely on its center axis; a feed mechanism for shifting the table and the main spindle relatively to each other along three orthogonal axes within the machining area, and a cover for covering the machining area.  
         [0003]     2. Description of the Related Art  
         [0004]     Such machine tools known to date include the example composed of, primarily: a bed made up of a rectangular base, two sidewalls provided standing along respective right and left sides of the base and opposing each other across an interval; a table on which a workpiece is carried and which is disposed on the base portion of the bed; a cross beam made from a long beam disposed lengthwise between the sides with the longitudinal end parts of the cross beam supported on top of the side walls of the bed so that the cross beam can move freely within a horizontal plane along the front-to-back orientation of the bed; a saddle that is supported to move freely horizontally side-to-side (right-to-left) on the front of the cross beam; a spindle head that is supported to move freely vertically on the front of the saddle; and a main spindle that holds a tool and is supported by the bottom end portion of the spindle head so that the axis of the main spindle is vertical and the main spindle can rotate freely on the main spindle axis above the table.  
         [0005]     This machine tool also has a first feed mechanism for moving the cross beam back and forth, a second feed mechanism for moving the saddle side to side, a third feed mechanism for moving the spindle head vertically, a rotational drive mechanism for rotating the main spindle on the main spindle axis, and a cover that encloses the machine tool and has doors that open by sliding side-to-side at the front (the front of the bed).  
         [0006]     A workpiece held on the table is processed by the tool held by the main spindle as a result of the first feed mechanism moving the cross beam back and forth, the second feed mechanism moving the saddle side-to-side, the third feed mechanism moving the spindle head vertically, and the rotational drive mechanism rotating the main spindle on the main spindle axis. Chips, swarf, and other waste produced during machining, and cutting fluid supplied as needed to the point of contact between the tool and the workpiece flies outside the machining area but is prevented from exiting the machine tool by the cover.  
         [0007]     When the workpiece is relatively small and light, the operator can load and unload the workpieces from the table, but when the work is heavy and large a crane or other type of hoist must be used to place the workpiece in and remove the workpiece from the machine tool. In this situation, however, the doors of this cover may not afford an opening that is large enough to carry the workpiece in and out of the machine tool, thus requiring removing part of the cover. This prevents efficiently changing the workpiece on the table.  
         [0008]     Japanese Unexamined Utility Model App. Pub. No. H06-24847 discloses a machine tool having a cover comprising a front cover, a first top cover, a second top cover, and a third top cover. The front cover has a door that slides side-to-side to open, and is disposed in front of the base portion of the bed to cover the space enclosed between the two side walls of the bed. The first top cover is disposed between the side walls on both sides of the bed and covers the top of the space between the side walls. The second top cover is disposed covering the top of this space between the left side of the spindle head, the left side wall of the bed, the front of the cross beam, and the first top cover. The third top cover is disposed covering the top of this space between the right side of the spindle head, the right side wall of the bed, the front of the cross beam, and the first top cover.  
         [0009]     The first top cover is an extensible/retractable sheet that shifts back and forth and allows the spindle head (cross beam) to move back and forth. One end of the first top cover is connected to the top of the cover so that the first top cover can be freely disconnected, and the other end is connected to the front of the spindle head.  
         [0010]     The second top cover and third top cover are also extensible/retractable sheets that can move side-to-side and allow the spindle head (saddle) to move side-to-side. One end of the second top cover is connected to the top of the left side wall of the bed, and the other end is connected to the left side of the spindle head. One end of the third top cover is connected to the top of the right side wall of the bed, and the other end is connected to the right side of the spindle head.  
         [0011]     The other end part of the first top cover is connected to the spindle head so that the spindle head can move vertically and side-to-side, and the one end of the second and third top covers is connected to the left wall and right wall, respectively, of the bed so that the top covers can move back and forth with the cross beam.  
         [0012]     When a crane or other hoist mechanism is used to carry workpiece into or remove workpiece from this machine tool having a front cover, first top cover, second top cover, and third top cover, the one end of the first top cover is disconnected from the front cover and rolled up toward the spindle head. Thus rolling up the first top cover and opening the door of the front cover efficiently forms the opening needed to move workpiece into and out from the machine tool, and therefore enables efficiently changing the workpiece.  
         [0013]     A problem with the machine tool disclosed in Utility Model App. Pub. No. H6-24847, however, is that in order to roll the first top cover to the spindle head and open the part covered by the first top cover, the one end of the first top cover must be disconnected from the front cover and rolled toward the spindle head. After the workpiece is changed, the first top cover must then be unrolled and the one end reattached to the front cover. This is tedious and time-consuming.  
       BRIEF SUMMARY OF THE INVENTION  
       [0014]     An object of the present invention is therefore to solve this problem by making available a machine tool that enables the operator to easily open and close the top cover without trouble.  
         [0015]     To achieve this object, a machine tool according to the present invention has a bed; a table which is disposed on the bed and on which work is held; a moving component disposed on the bed and provided free to travel at least on a horizontal first axis that is front-to-rear oriented; a main spindle which is supported by the moving component to rotate freely on the main spindle axis and holds a tool; a feed mechanism for moving the table and the moving component relatively on three perpendicular axes including the first axis, and moving the table and main spindle relatively in a machining area; and a cover for covering the machining area by means of a front cover covering a front side of the machining area and first top covers covering a top side of the machining area. The front cover is disposed on the front side of the bed and is furnished with doors that open and close moving on a horizontal second axis perpendicular to the first axis. The first top covers have one end connected to the front side of the moving component to enable movement on the second axis, and the other end connected to the top part of the door of the front cover to extend and retract freely on the first axis and allow the moving component to move on the first axis.  
         [0016]     Work can be processed by this machine tool as a result of the feed mechanism moving the table and moving component relatively on three perpendicular axes including the first axis (aligned side-to-side, that is, left-to-right), moving the table (the work on the table) and main spindle (the tool held by the main spindle) relative to each other in the machining area, and a rotational drive mechanism driving the main spindle rotationally on the main spindle axis.  
         [0017]     The first top cover does not interfere with movement of the moving component on the first axis because the first top cover can extend and retract freely on the first axis when the moving component moves on the first axis.  
         [0018]     Furthermore, by covering the machining area with a cover comprising a front cover covering the front of the machining area and first top covers covering the top of the machining area, chips and other waste from the machining process and cutting fluid supplied appropriately to where the tool contacts the workpiece are also prevented from flying outside the machine tool during the machining process.  
         [0019]     When the machining process ends and the worker moves the doors of the front cover on the second (side-to-side) axis to open in order to replace the workpiece on the table, the first top covers also move with the doors along the second axis because one end of each top cover is connected movably along the second axis to the front of the moving component and the top of the machining area is thus opened. Conversely, when the doors of the front cover are moved on the second axis (side-to-side) and closed, the first top covers also move with the doors on the second axis and the top of the machining area is closed.  
         [0020]     A worker can thus easily open and close the top of the machining area by simply opening and closing the doors of the machine tool according to the present invention because the first top cover is rendered movably along the second axis together with the doors when the doors of the front cover open and close. Work can therefore be efficiently loaded and unloaded from the table using a crane or other hoist mechanism.  
         [0021]     Preferably, the machine tool also has linkage members disposed above or below the first top covers with one end connected to the one end of a first top cover and the other end connected to a top part of a door of the front cover. The linkage members can extend and retract on the first axis and enable the moving component to move on the first axis.  
         [0022]     By rendering the first top covers to extend and retract freely on the first axis, the rigidity of the covers may be low depending on how the covers are constructed. As a result, even if the other end of the first top covers moves on the second axis when the doors open and close, the one end of the first top covers may not move at the same time.  
         [0023]     However, by providing linkage members connecting the one end of the first top covers to the doors, the one end of the first top covers can be moved in conjunction with the doors opening and closing (that is, in conjunction with moving the other end of the first top covers). This prevents damaging the first top covers and prevents the first top covers from not opening or closing completely.  
         [0024]     Yet further preferably, the bed has a rectangular base and two opposing side walls rising vertically from both second-axis sides of the base with a gap therebetween; the moving component is supported freely movably along the first axis on top portions of both side walls of the bed; and the first top covers are disposed above the top of both side walls of the bed. This machine tool also has second top covers disposed between both side walls of the bed and the first top covers to close the gaps between the side walls and the first top covers. The second top covers have one end connected to the front of the moving component, and the other end connected to the top part of the front cover to extend and retract freely along the first axis and allow movement of the moving component on the first axis.  
         [0025]     If the bed has a rectangular base and two opposing side walls rising vertically from both sides of the base along the second axis with a gap therebetween, and the first top covers are disposed above the tops of the side walls of the bed in order to increase the size of the opening afforded by the first top covers more than a predetermined size, to open the first top covers without interfering with the side walls of the bed, or to increase the height at which the first top covers are located, a gap may result between the side walls and the first top covers, and waste and cutting fluid may escape through this gap outside the machine tool.  
         [0026]     The machine tool according to the invention prevents waste and cutting fluid from exiting through this gap, however, by providing second top covers having one end connected to the front of the moving component and the other end connected to the top part of the front cover so that the second top covers extend and retract freely along the first axis and close the gap between the side walls on both sides of the bed and the first top covers.  
         [0027]     By connecting one end of first top covers that extend and retract freely along a first axis to the front side of a moving component so that the first top covers can move on a second axis, and connecting the other end of the first top covers to the top part of the doors of the front cover so that the first top covers move along the second axis together with the doors, a machine tool according to the present invention enables easily opening and closing the first top covers by simply opening and closing the doors. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0028]      FIG. 1  is an oblique schematic view of a machine tool according to a preferred embodiment of the invention.  
         [0029]      FIG. 2  is an oblique schematic view of a machine tool according to a preferred embodiment of the invention.  
         [0030]      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.  
         [0031]      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.  
         [0032]      FIG. 5  is a front view showing a part of a machine tool according to a preferred embodiment of the invention.  
         [0033]      FIG. 6  is a section view through line A-A in  FIG. 5 .  
         [0034]      FIG. 7  is a plan view showing a part of the top cover in a preferred embodiment of the invention.  
         [0035]      FIG. 8  is a plan view showing a part of the top cover in a preferred embodiment of the invention.  
         [0036]      FIG. 9  is a section view through line B-B in  FIG. 7 .  
         [0037]      FIG. 10  is a section view through line C-C in  FIG. 8 .  
         [0038]      FIG. 11  is a front schematic view of a machine tool according to another embodiment of the invention.  
         [0039]      FIG. 12  is a section view through line D-D in  FIG. 11 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0040]     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 , a 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 .  
         [0041]     The machine tool unit  10  comprises a bed  11 , a first saddle  16  that is disposed on the bed  11  and moves freely back and forth in a horizontal plane (along the Y-axis), a second saddle  17  that is disposed on 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 on 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 on 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.  
         [0042]     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, an 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 rotation 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.  
         [0043]     The bed  11  comprises a base  12  that is rectangular when seen in plan view, left and right side walls  13  and  14  (left side wall  13  on the front left side and right side wall  14  on the front right side) disposed vertically on both sides of the base  12  with a gap therebetween on the X-axis, and a side wall  15  (back side wall) disposed vertically to the base  12  at the back between the right and left side walls  13  and  14 .  
         [0044]     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 side wall  13  and the base portion of the right side wall  14  decline into the opening to the waste removal hole  12   a.    
         [0045]     A tool changing opening  13   a  is formed through from the outside to the inside of the left side wall  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 side walls  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 side wall  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 side walls  13 ,  14 ,  15 ) when the pallet changing device  45  changes the pallet P.  
         [0046]     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 back side wall  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 side walls  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 .  
         [0047]     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.  
         [0048]     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 side wall  13  and right side wall  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 .  
         [0049]     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.  
         [0050]     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 .  
         [0051]     The Y-axis guide mechanism  21  comprises guide rails  21   a  aligned with the Y-axis on the top of the left side wall  13  and right side wall  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.    
         [0052]     The Y-axis feed mechanism  24  comprises drive motors  24   a  disposed on the top of left side wall  13  and right side wall  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 side wall  13  and right side wall  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.    
         [0053]     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 .  
         [0054]     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.    
         [0055]     The X-axis feed mechanism  25  comprises a drive motor  25   a  disposed on one longitudinal side portion 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.    
         [0056]     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 .  
         [0057]     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).  
         [0058]     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).  
         [0059]     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).  
         [0060]     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 side wall  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 side wall  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 side wall  13  and supports the tool changing arm  42 , and causes the tool changing arm  42  to rotate horizontally and move vertically.  
         [0061]     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 side wall  13 .  
         [0062]     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 .  
         [0063]     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 side wall  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.  
         [0064]     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 workpiece W is mounted on the pallet P.  
         [0065]     The pallet changing device  45  replaces the pallet P to replace the work W on the table  20  in this embodiment of the invention, but the invention is not so limited. If the work W is small or light, a worker can manually replace the work W on the table  20 . If the work W is large or heavy, however, a crane or other type of hoist can be used to directly load and unload the work W on the table  20 . Work can proceed efficiently even if a hoist is used to load and unload the work W in a machine tool  1  according to this embodiment of the invention because opening the doors  61   a  and  61   b  of the first cover  61  to the sides also opens the first left top cover  76  and first right top cover  77  to the sides as further described below.  
         [0066]     The waste recovery device  50  comprises a discharge mechanism  51 , a storage tank  54 , a collection box  55 , a plurality of nozzles  56 , and a supply pump (not shown in the figures).  
         [0067]     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 of 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 back side wall  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.  
         [0068]     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 .  
         [0069]     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.  
         [0070]     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 .  
         [0071]     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 .  
         [0072]     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 base portions where the left side wall  13  and right side wall  14  meet the base  12 , and covers not shown disposed appropriately in the space enclosed by the side walls  13 ,  14 ,  15 , and drop from this waste removal hole  12   a  onto the conveyor belt  52 , which is driven circularly 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 .  
         [0073]     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.  
         [0074]     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 side walls  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 (not shown in the figures) for closing the tool changing opening  13   a  in the left side wall  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 side wall  14  of the bed  11 .  
         [0075]     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 .  
         [0076]     The first cover  61  comprises a left door  61   a  that opens by sliding to the left side wall  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 side wall  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 .  
         [0077]     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.    
         [0078]     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 a 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  76  and a first right top cover  77  with the front and back end portions connected to the tops of the doors  61   a  and  61   b  of the first cover  61  and to the moving members  72  and  73 ; a second left top cover  74  and a second right top cover  75  disposed below the first left top cover  76  and first right top cover  77 ; and a left linkage member  78  and a right linkage member  79  disposed above the first 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 to the moving members  72  and  73 .  
         [0079]     The first 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 first 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 first 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 .  
         [0080]     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 on each of the first 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 to 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 to the right moving member  73 .  
         [0081]     The second top covers  74  and  75  are telescopic covers that enable movement of the first saddle  16  on the Y-axis. The second left top cover  74  is disposed with the bottom part attached to the top of the left side wall  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 second left top cover  74  thus closes the gap between the top of the left side wall  13  and the first left top cover  76 .  
         [0082]     The first right top cover  75  is disposed with the bottom part attached to the top of the right side wall  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 second right top cover  75  thus closes the gap between the top of the right side wall  14  and the first right top cover  77 .  
         [0083]     The second 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 side walls  13  and  14  of the bed  11 .  
         [0084]     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 on the inside of the side walls  13 ,  14 ,  15  of the bed  11 , close the space (machining area) contained within the side walls  13 ,  14 ,  15 , and prevent waste and cutting fluid from flying outside.  
         [0085]     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 first 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.  
         [0086]     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 .  
         [0087]     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 .  
         [0088]     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 side wall  13  of the bed  11 .  
         [0089]     When the first saddle  16  moves on the Y-axis, the first top covers  76  and  77 , second top covers  74  and  75 , and linkage members  78  and  79  do not interfere with movement of the first saddle  16  on the Y-axis because the first top covers  76  and  77 , second top covers  74  and  75 , and linkage members  78  and  79  can also move freely extending and retracting along the Y-axis.  
         [0090]     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 on 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 .  
         [0091]     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 side wall  14  of the bed  11 .  
         [0092]     When a worker opens and closes the doors  61   a  and  61   b  of the first cover  61  of a machine tool  1  according to this embodiment of the invention, the first 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 , and thus open and close together with the doors  61   a  and  61   b.    
         [0093]     A worker can therefore easily open and close the top of the machining area of a machine tool  1  according to this embodiment of the invention by simply opening and closing the doors  61   a  and  61   b , and work W can therefore be efficiently mounted on and dismounted from the table  20  using a crane or other hoist mechanism, for example.  
         [0094]     By rendering the first top covers  76  and  77  as telescopic bellows that can extend and retract freely on the Y-axis, the rigidity of the covers is low. Even if the front part of the first top covers  76  and  77  moves on the X-axis when the doors  61   a  and  61   b  are opened and closed, the back part of the first top covers  76  and  77  may not move with the front part due to the low rigidity of the covers. However, by providing linkage members  78  and  79  connecting the back part (the moving members  72  and  73 ) of the first top covers  76  and  77  to the doors  61   a  and  61   b  of this machine tool  1 , the back part of the first top covers  76  and  77  can be moved in conjunction with opening and closing the doors  61   a  and  61   b  (that is, in conjunction with moving the front part of the first top covers  76  and  77 ). This prevents damaging the first top covers  76  and  77  and prevents the first top covers  76  and  77  from not opening or closing completely.  
         [0095]     Furthermore, if the first top covers  76  and  77  are disposed above the tops of the right and left side walls  13  and  14  of the bed  11  in order to increase the size of the opening afforded by the first top covers  76  and  77  more than a predetermined size, to open the first top covers  76  and  77  without interfering with the right and left side walls  13  and  14  of the bed  11 , or to increase the height at which the first top covers  76  and  77  are located, a gap may result between the side walls  13  and  14  and the first top covers  76  and  77 , and waste and cutting fluid may escape through this gap outside the machine tool  1 . The machine tool  1  according to this embodiment of the invention effectively prevents waste and cutting fluid from exiting through this gap, however, by providing second top covers  74  and  75  closing this gap.  
         [0096]     In addition, because the table  20  is disposed inside the space enclosed by the three side walls  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 side walls  13  and  14  of the bed  11  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 , the first saddle  16 , the second saddle  17 , and the spindle head  18  can also be disposed above the top of the table  20 .  
         [0097]     This makes it 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). 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.  
         [0098]     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 , the spindle head  18  is disposed inside a through-hole  17   b  formed vertically through the second saddle  17 , and a support structure for the saddle and spindle head that projects from the front is thus not used. Deflection and other deformation of the bed  11 , first saddle  16 , and second saddle  17  are therefore prevented, and work W can be machined with high precision.  
         [0099]     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).  
         [0100]     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 .  
         [0101]     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.  
         [0102]     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 side wall  13  side of the bed  11  and changes tools through a tool changing opening  13   a  in the left side wall  13 , and the pallet changing device  45  is disposed on the right side wall  14  side of the bed  11  and changes the pallets through a pallet changing opening  14   a  in the right side wall  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 .  
         [0103]     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 .  
         [0104]     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  on the B-axis to invert the work W on the pallet P, and cutting fluid is then discharged from the nozzles  56  to effectively and efficiently remove any waste on the support unit  20   b , the pallet mounting unit  20   a , the pallet P, and the work W. Waste can therefore be efficiently removed, and waste and cutting fluid are prevented from being removed from the machine tool unit  10 .  
         [0105]     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.  
         [0106]     The cover  60  according to the present invention can be applied to a machine tool  80  such as shown in  FIG. 11  and  FIG. 12 , for example. In this arrangement the cover  60  includes a front cover  90  disposed on the front side of the bed  81 , and a first left top cover  91 , second left top cover  92 , first right top cover  93 , and second right top cover  94  disposed above the tops of the side walls  81   b  of the bed  81 .  
         [0107]     This machine tool  80  has a bed  81  composed of a rectangular base  81   a  and two opposing side walls  81   b  rising vertically from the left and right sides of the base  81   a  with a gap between the walls, a table  82  which is disposed on top of the base  81   a  of the bed  81  and on which work W is held, a cross beam  83  made from a long beam disposed lengthwise between the right and left sides with the longitudinal end parts of the cross beam supported on top of the side walls  81   b  of the bed  81  so that the cross beam  83  can move freely in a horizontal plane in the front-to-back direction of the bed, a saddle  84  that is supported to move freely horizontally side-to-side (right-to-left) in front of the cross beam  83 , a spindle head  85  that is supported to move freely vertically in front of the saddle  84 , and a main spindle  86  that holds a tool T and is supported by the bottom end portion of the spindle head  85  so that the axis of the main spindle is vertical and the main spindle  86  can rotate freely on the main spindle axis above the table  82 .  
         [0108]     The front cover  90  has a left door  90   a  and a right door  90   b  that slide to the left and right sides to open. The front cover  90  is disposed in front of the base  81   a  of the bed  81  in order to close the front of the space between the side walls  81   b  of the bed  81 .  
         [0109]     The first left top cover  91  and first right top cover  93  can extend and retract freely back and forth, allowing the spindle head  85  (cross beam  83 ) to travel back and forth. The back part of the first left top cover  91  is connected freely movably side-to-side to a guide member (not shown in the figures) that is appropriately disposed in the side-to-side direction to the front of the cross beam  83  with the spindle head  85  between the guide member and the cross beam  83 , and the front part of the first left top cover  91  is connected to the top part of the left door  90   a . The back part of the first right top cover  93  is connected freely movably side-to-side to the same guide member (not shown in the figures), and the front part is connected to the top part of the right door  90   b.    
         [0110]     The second left top cover  92  and the second right top cover  94  can extend and retract freely in the side-to-side direction, allowing the spindle head  85  (saddle  84 ) to move side-to-side. The second left top cover  92  is suitably supported by the left side of a cover (not shown in the figures) covering the spindle head  85  and the front of the cross beam  83 , and covers the gap between the left side of the spindle head  85 , the side wall  81   b  on the left side of the bed  81 , the front of the cross beam  83 , and the first left top cover  91 . The second right top cover  94  is suitably supported by the right side of a cover (not shown in the figures) covering the spindle head  85  and the front of the cross beam  83 , and covers the gap between the right side of the spindle head  85 , the right side wall  81   b  of the bed  81 , the front of the cross beam  83 , and the first right top cover  93 .  
         [0111]     This arrangement enables opening and closing the first left top cover  91  and first right top cover  93  by opening and closing the doors  90   a  and  90   b , and thus affords the same effect described above. In addition, the top covers  91 ,  92 ,  93 , and  94  do not interfere with the back-and-forth, side-to-side, or vertical movement of the spindle head  85 .  
         [0112]     A vertical machining center is used herein as an example of a machine tool  1 ,  80  according to the present invention, but the first cover  61 , front cover  90 , and top covers  70 ,  91 ,  92 ,  93 , and  94  described in these embodiments can obviously be adapted for use with a horizontal machining center. The structure of the bed and the arrangement of the moving bodies (saddles  16 ,  17 , and  84 , spindle heads  18  and  85 , and cross beam  83 ) are also not limited to these examples and can obviously be modified in many ways.  
         [0113]     Furthermore, the arrangement of the doors  61   a ,  61   b ,  90   a , and  90   b  of the first cover  61  and front cover  90  are also not limited to these embodiments. The arrangement of the extensible/retractable covers  74 ,  75 ,  76 ,  77 ,  91 ,  92 ,  93 ,  94  is also not limited to a telescopic bellows-like cover as described above. These covers can be rendered as sheets that can be rolled down and rolled up, for example.