Abstract:
A machine tool loading apparatus is adapted to register the sheets being loaded directly in the workclamps of the machine tool. A four bar linkage is utilized to control the position of the sheet as the loader removes it from the supply stack and brings it into the workclamps. The four bar linkage is provided with a controlled amount of compliance which is released as the sheet is brought into the workclamps. The sheet is thus allowed a limited ability to be repositioned as the loading mechanism guides it into the workclamps, so that a registered position is achieved before the workclamps are closed. The preferred loader apparatus can be used to unload large parts from the machine tool. The loader apparatus may be adapted to the machine tool in conjunction with a material storage tower.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS  
       [0001]    This patent application claims the benefit of U.S. provisional patent application 60/283,300, filed Apr. 12, 2001. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention generally relates to machine tools, more particularly relates to apparatus for automatically loading machine tools, and in particular to an apparatus for automatically loading machine tools which operate on sheet or plate including a CNC punch press machine tool, a CNC punch press machine tool having a thermal cutting apparatus such as a plasma torch or a laser, a plasma cutting machine tool or a laser cutting machine tool.  
         BACKGROUND OF THE INVENTION  
         [0003]    [0003]FIGS. 1 and 2 are provided for background, and show a well-known type of punch press with thermal cutting capability, associated with a loader mechanism. The punch press is representative of the broad range of machine tools with which a loader according to the present invention can be associated. In greater detail, FIG. 1 shows machine tool  1 , a CNC punch press having a loading apparatus  2 . CNC punch press  1  has an X-axis  3  based on a rail  3 ′ supported by bracket  4  and pedestals  5  and  5 ′, carrying a translatable table  6 .  
           [0004]    Translatable table  6  is driven by a servomotor and ballscrew that cannot be seen and carries two workclamps  7  and  7 ′ for gripping the work, and several sets of punching tools  8 . The Y-axis is defined by a frame  9  carrying a translatable punching cylinder  10  and a translatable die support  11 . Punching cylinder  10  is driven via a servomotor  200  connected by coupling  201  to ballscrew  202 . At the left side and connected to the mounting plate of punching cylinder  10  is a plasma torch  203  for cutting large holes and the outer boundary of parts from workpiece  17 . Below and to the immediate left of torch  203  is a drop leaf table apparatus  204  for removal of small parts after they have been cut from material  17 . An electrical cabinet houses the CNC  12  along with other electrical controls, and operator station  13  provides the man/machine interface for machine tool  1 . Worktable  14  on the right side of frame  9  and worktable  15  on the left side of frame  9  and drop leaf table  204  are adapted with ball transfers  16  to support the material  17  to be processed. Material  17  is flat, rectangular metal sheet and plate.  
           [0005]    In operation, material  17  is gripped by workclamps  7  and  7 ′ and moved and positioned under CNC control along X axis  3  while punching cylinder  10  and die support  11  are moved and positioned under CNC control along the Y-axis. The work is positioned and tools are selected according to a part program processed by the CNC  12 . At commanded positions the CNC  12  cycles punching cylinder  10  to punch a hole in the work. After all holes have been punched the CNC  12  in like manner positions the plasma torch  203  to commanded positions, lowers plasma torch  203  to the work  17 , ignites plasma torch  203  then coordinates the velocity and motion of the X and Y axes to move plasma torch  203  along a described path to create a hole or to cut a part from material  17 . Small parts cut from the material are unloaded via drop leaf table  204  and large parts are removed manually, with the assist of a hoist or crane, or by other means.  
           [0006]    A supply of material  17  is staged on loading apparatus  2  at the right side of machine tool  1 . Loading apparatus  2  typically includes a base  77 ′ having a freestanding column  18  supporting a power driven cantilevered beam  19 , pivotable at the proximal end of cantilevered beam  19  about supporting point  20 . Cantilevered beam  19  is often further strengthened by a support rod  21 , connected to cantilevered beam  19  at  22  and pivotally connected to column  18  directly above and inline with supporting point  20 . Carried at the distal end of cantilevered beam  19  is a pivotable member  23 , which is pivotable about bearing  24 . In the illustrated embodiment two bearings  24  are mounted to plates  24 ′ bolted to the distal end of beam  19 , one attached to the upper side of beam  19  and one to the bottom side of beam  19 . The angular position of pivotable member  23  relative to machine tool I is fixed by a four bar linkage to stabilize the pivotable member  23  so as to maintain the long side of rectangular material  17  generally parallel to the X axis  3  of machine tool  1 .  
           [0007]    The first bar of the four bar linkage is attachment plate  25 , which is connected to freestanding column  18 . The second bar is bar  26  pivotally connected to attachment plate  25  and pivotally connected to pivotable member  23 . The third bar is bar  27  pivotally connected to attachment plate  25  and pivotally connected to pivotable member  23 . The fourth bar is the pivotable member or extension  23 .  
           [0008]    In the present embodiment, part handling apparatus generally indicated at  29   a  include mast  28  which is carried by and connected to pivotable member  23 , and is adapted to support and vertically translate load beam  29  via cylinder  30 . Bars  31  are adjustably connected to load beam  29  and are adapted with vacuum cups  31  ′ to pick up material  17 .  
           [0009]    The powered drive for the cantilevered beam  19  is shown as a cylinder  32 , which is pivotally connected at  33  to a plate  34  attached to freestanding column  18 , and pivotally connected to cantilevered beam  19  at  35 . Curved line  36  traces the path of the center of the mast as cantilevered beam  19  is pivoted by cylinder  32 . Line  37  generally traces the path of the front edge of material  17  as it is transferred from the staging position to worktable  14  and workclamps  7  and  7 ′ of machine tool  
           [0010]    When commanded to load a sheet of material, cylinder  30  lowers the vacuum cups to the supply of material  17 . A sensor detects the presence of a sheet for pickup. The vacuum cups are engaged to grip the top sheet, cylinder  30  lifts the load beam picking up the top sheet of material, cylinder  32  pivots cantilevered beam  19  clockwise until the sheet is over worktable  14 , cylinder  30  lowers the load beam and attached sheet to the surface of worktable  14 , cylinder  32  pivots cantilevered beam clockwise to urge the sheet into the workclamps and toward workclamp registration surfaces  39 ′ and  39 . Sensors associated with workclamp registration surfaces detect the sheet is loaded and cause the workclamps to grip the sheet. Then the vacuum cups release the sheet, cylinder  30  lifts the load beam and vacuum cups above the sheet, and cylinder  32  pivots cantilevered beam  19  counterclockwise positioning it once more over material  17  at the staging area.  
           [0011]    While loader apparatus  2  can reliably deliver sheets of material to worktable  14  of machine tool  1 , it cannot reliably load the material into workclamps  7  and  7 ′ in a registered orientation. If the sheet  17  in the supply stack is perfectly aligned with the X-axis of the machine tool, the four bar linkage is designed to deliver the sheets to the workclamps in parallel alignment with the X-axis as desired. But very often the sheet in the supply stack is not perfectly aligned, and therefore delivery into the workclamps is not reliably accomplished.  
           [0012]    [0012]FIG. 2 is an enlarged drawing of the material loading side of machine tool  1  showing a fragment of machine tool  1 . Like objects are identified with the same numbers as in FIG. 1. Workpiece  17 , FIG. 2, is shown residing in an angular relationship to the X-axis of machine tool  1 . Such conditions can occur several ways. The sheet may have been improperly stacked in preparation, the stack of material may have been jostled during transport, or the stack may have been improperly loaded on the loader staging station.  
           [0013]    Workpiece  17 ′, FIG. 2, represents workpiece  17  after it is loaded on worktable  14 . Note that the left end of sheet  17 ′ is in contact with registration surface  39 ′ while the right end is not in contact with registration surface  39 . Loader  2  is a typical machine tool quality device with typical machine tool accuracy and repeatability, and it therefore lacks adequate compliance to successfully load the angular sheet. Loader apparatus  2  will stall at the position shown in which the sheet is not fully registered with the workclamps.  
           [0014]    The problem exemplified in FIG. 2 is but one example of a condition that can cause failure of an automatic load cycle. Any condition in which the sheet is angularly rotated relative to the X-axis of machine tool  1  can cause similar load failure.  
         SUMMARY OF THE INVENTION  
         [0015]    It is an objective of the invention to add controlled compliance to a loader, such that it can automatically and reliably load a sheet or plate into the workclamps of a CNC machine tool such as a punch press, while minimizing additional hardware and cost to do so.  
           [0016]    Broadly, it is an object of the invention to provide an automated loader for a machine tool which cooperates with the machine tool to load the sheet or plate in a position which is registered along at least one axis. Such automated loading is accomplished without the need to move the workclamps along that axis during the loading operation.  
           [0017]    It is a further objective of the invention to automatically gauge or position the loaded sheet such that the sheet can be processed by the CNC machine tool.  
           [0018]    It is a feature of the invention that controlled compliance is added to a loader by providing a releasable four bar linkage.  
           [0019]    It is a further feature of the invention to make one link of a four bar linkage pivotable and to provide a mechanism to alternately lock the link in position and release to the link such that it is free to pivot.  
           [0020]    In that regard, a further feature is to restrict the range of motion of the releasable link of the four bar mechanism when it is in the released position.  
           [0021]    A further objective of the invention is to provide a releasable four bar linkage that is easily adapted to other embodiments of loading or loading/unloading apparatuses.  
           [0022]    Another objective of the invention is to provide a preferred embodiment of a loading device that can also be used to unload completed parts from a machine tool. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    [0023]FIG. 1, provided for background, is a plan view of a machine tool having a loader apparatus adapted with a fixed four bar linkage.  
         [0024]    [0024]FIG. 2, provided for background, is an enlarged drawing of the material loading side of machine tool  1  showing a fragment of machine tool  1 , and showing the top sheet of the supply of material  17  in an angular relationship to the X-axis of machine tool  1 .  
         [0025]    [0025]FIG. 3 is a drawing of a releasable four bar linkage.  
         [0026]    [0026]FIG. 4 is an enlarged section view taken through  4 - 4  of FIG. 3  
         [0027]    [0027]FIG. 5 is the same as FIG. 3 except it embodies the locking mechanism in an alternate form.  
         [0028]    [0028]FIG. 6 is the same as FIG. 3 except it embodies the locking mechanism in an alternate form.  
         [0029]    [0029]FIG. 7 is similar to FIG. 3 except it embodies a different pivoting apparatus at the distal end of beam  19  and it embodies a locking mechanism in another alternate form.  
         [0030]    [0030]FIG. 8 a  is an exploded perspective showing the lock/release mechanism of FIG. 7.  
         [0031]    [0031]FIGS. 8 b  and  8   c  are assembled partial views showing the lock/release mechanism of FIG. 7 in the released and locked position respectively.  
         [0032]    [0032]FIG. 9 shows the loading apparatus of FIG. 2 embodied with the releasable four bar linkage of FIGS. 3 and 4, making the loader suitable to load sheets directly into the workclamps.  
         [0033]    [0033]FIG. 10 is a preferred embodiment of a loading apparatus, having a four bar lock/release apparatus in preferred form, and that can also unload finished parts from the machine tool.  
         [0034]    [0034]FIG. 11 is an enlarged view of the four bar lock/release mechanism of FIG. 10.  
         [0035]    [0035]FIG. 12 is a machine tool embodied with the loader/unloader of FIG. 10.  
         [0036]    [0036]FIG. 13 is an alternate form of a CNC punch press having a plasma torch thermal cutting apparatus and adapted such that the workpiece moves in both the X and Y-axis and adapted with the loader/unloader of FIGS. 10 and 11.  
         [0037]    While the invention is susceptible of various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention as defined by the appended claims. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0038]    Turning now to the drawings, FIG. 3 shows a four bar linkage similar to that of FIGS. 1 and 2 but adapted, in accordance with the invention, to be lockable and releasable. Items equivalent to those of FIGS. 1 and 2 are identified with same numbers. Column  18 , mast  28  and load beam  29  have been omitted to focus on the four bar linkage and lock/release mechanism. In this example the cantilevered beam  19  of FIG. 3 does not have an additional support rod  21 . The configuration of attachment plate  125  has been changed. It is no longer one of the bars of the four bar linkage but instead pivotably supports one of the bars of the four bar linkage as will be described. The attachment plate  125  has a leftward projection  40  having cylinder mounting bracket  41  for cylinder  42 . Cylinder  42  has a cylinder rod  43  extending through mounting bracket  41  and connected to locking wedge  44 .  
         [0039]    Attachment plate  125  also has an upward projecting stub shaft  45  threaded into it as best seen in FIG. 4 and configured for limited pivotable support of one bar of the four bar linkage. The first bar of the four bar linkage in this arrangement is bar  46  which, in the illustrated example, has a bronze flanged bearing  47 , and is pivotable about stub shaft  45 . Bar  46  is retained on stub shaft  45  by a washer  48  and a nut  49 . To provide for limited amount of controlled compliance, pivotable bar  46  has a vee notch  50  at its left end, FIG. 3, for accepting locking wedge  44 . The distance the locking wedge  44  is pulled out toward the left sets space  51 , which is predetermined by design. Space  51  determines the compliance of pivotable extension  23  by determining how much pivotable extension  23  can rotate when bar  46  is released. When cylinder  42  is extended, cylinder rod  43  pushes locking wedge  44  into notch  50  of bar  46 , eliminating space  51  and locking pivotable bar  46  in position.  
         [0040]    The second bar of the four bar linkage is bar  26 , which is pivotally connected to pivotable bar  46  by rod end bearing  52  and pivotally connected to pivotable member  23  by rod end bearing  53 . The third bar is bar  27 , which is pivotally connected to pivotable bar  46  by rod end bearing  54  and pivotally connected to pivotable member  23  by rod end bearing  55 . The fourth bar is the pivotable member  23 .  
         [0041]    The locking apparatus and vee notch  50  can be located at either end of pivotable bar  46  and achieve intended function. Likewise, pivotable bar  46  and associated lock/release apparatus can be adapted at either end of bars  26  and  27  and perform the same function.  
         [0042]    It is noted that the currently preferred position for the releasable element of the four bar linkage is in the bar mounted on or otherwise associated with attachment plate  125  or its equivalent. However, the invention is equally applicable to a releasable bar of the four bar linkage mounted at the opposite end of the linkage, that is rotatably connected to pivotable member  23  or its equivalent. Unless otherwise indicated, both alternatives are intended to be encompassed by the appended claims.  
         [0043]    [0043]FIG. 5 is the same as FIG. 3 except it embodies the locking mechanism and compliance-limiting feature in an alternate form. Items equivalent to those of FIGS.  3  are identified with the same numbers. Cylinder  42  of FIG. 5 has a longer stroke, sufficient to pull locking wedge  44  fully from vee notch  50  in the left end of pivotable bar  46 . Further, bar  56  has been fixed to plate  125  parallel to pivotable bar  46 , when bar  46  is in locked position, at space  51  ′ for the purpose of limiting the range of travel of pivotable bar  46  when pivotable bar  46  is released. The left end of bar  56  limits the clockwise pivoting of bar  46  while the right end of bar  56  limits counterclockwise pivoting of bar  46  thus determining the amount of compliance or rotation of pivotable bar  46  and thus of pivotable extension  23 .  
         [0044]    [0044]FIG. 6 is the same as FIG. 3 except it embodies the locking mechanism in an alternate form. Items equivalent to those of FIGS.  3  are identified with same numbers. Shown in released position, cylinder  42  drives, via cylinder rod  43 , a vee notched locking block  57  to engage a wedge shaped end  58  of pivotable bar  59 , to lock the first bar  59  of a four bar linkage. Space  51  determines the compliance of pivotable extension  23  by determining how much pivotable bar  59  can rotate when pivotable bar  59  is released. When cylinder  42  is extended, cylinder rod  43  pushes locking block  57  over wedge shaped end  58  of bar  59  eliminating space  51  and locking pivotable bar  59  in position. The locking apparatus and wedge shaped end  58  can be located at either end of bar  59  and achieve intended function. Likewise, pivotable bar  59  and associated lock/release apparatus can be adapted at either end of bars  26  and  27  and perform the same function.  
         [0045]    [0045]FIG. 7 is similar to FIG. 3 except it embodies a different pivoting member at the distal end of beam  19  and it embodies a locking mechanism in another alternate form. Items equivalent to those of FIGS.  3  are identified with same numbers. At the distal end of pivotable beam  19 , supported by two bearings  24 , one bearing above beam  19  and one bearing below beam  19 , is shaft  60 . Plate  61 , connected to the lower end of shaft  60 , is a pivotable member in the form of a mounting plate, for attaching a platen of a loading apparatus, pivotable about bearings  24 .  
         [0046]    The lock/release mechanism of FIG. 7 is best understood by concurrent reference to FIG. 7 and FIGS. 8 a - 8   c.  Below leftward projection  40  of attachment plate  125  there is a cylinder mounting plate  62 , and a vertically mounted cylinder  63  having a cylinder rod  64  connected to locking wedge  65 . The lock/release mechanism is shown with the locking wedge  65  in its raised, locked position in FIG. 8 c.  FIG. 8 b  shows the wedge  65  retracted to release the mechanism for limited controlled compliance as will now be described. Locking wedge  65  in released position resides in a rectangular hole  67  having radiused corners and is guided by the sides  68  and  68 ′ of rectangular hole  67 . First bar  69  of a four bar linkage has a reversed, vertical “C” shaped slot  70  through its left end, has a bronze flange bearing  47 , and is pivotable about stub shaft  45 . Space  71  between locking wedge  65  in released position and pivotable bar  69 , established by design, determines the amount of compliance or range of rotation of pivotable bar  69  and thus of mounting plate  61  (FIG. 7). A downward directed “C” shaped support block  72  mounted to the leftward of projection  40  of attachment plate  125  such that the inner surface of the “C” shape is proximate to the upper surface of bar  69 , supports pivotable bar  69  when the locking wedge is driven by cylinder  63  to its raised locking position  66 . Space  73  between bar  69  and inner downward legs of “C” shaped support bar  72  is greater than space  71  allowing space  71  to control the amount of compliance.  
         [0047]    In alternate form, space  73  could be made smaller than space  71  such that space  73  would control the amount of compliance. The lock/release mechanism of FIG. 8 could be embodied at either end of bar  69  and accomplish intended function. Also the mechanism could easily be embodied with the cylinder mounted above bar  69 . Further it could be easily embodied such that the cylinder locks on the pull stroke and releases on the extend stroke. Further, pivotable bar  69  and associated lock/release apparatus can be adapted at either end of bars  26  and  27  and perform the same function.  
         [0048]    In another alternate form of the locking mechanism of FIGS. 7 and 8, locking wedge  65  can be in the form of a pin having a tapered end, the reversed, vertical “C” shaped slot  70  can be in the form of a round hole proximate the left end of pivotable bar  69 , the downward directed “C” shaped support block  72  could be spaced slightly to the immediate left or right of the locking pin, and space  71  can be the space between the tapered end of the pin and the inner hole diameter  70  when the locking pin is retracted. Such a form can be adapted in any of the configurations previously described.  
         [0049]    [0049]FIG. 9 is the loading apparatus of FIG. 2 embodied with the releasable four bar linkage of FIGS. 3 and 4, making the loader adequately compliable to load sheets directly into workclamps  7  and  7 ′. Items equivalent to those of FIGS.  2  are identified with same numbers. Lock/release mechanism  74  is shown in the locked position. Workpiece  17  is shown residing in an angular relationship to X-axis  3  of machine tool  1 . Workpiece  17 ′ shows workpiece  17  loaded on worktable  14  and in contact with workclamp registration surfaces  39 ′ and  39  of workclamps  7 ′ and  7 .  
         [0050]    Operation of the loader of FIG. 9 is as follows. A supply of material  17  is staged on loading apparatus  2  at the right side of machine tool  1 . The releasable four bar linkage  74  of loader  2  is locked. When commanded to load a sheet of material, cylinder  30  lowers the vacuum cups  31  to the supply of material  17 . A sensor detects the presence of a sheet for pickup, and thereafter vacuum cups  31  ′ are engaged to grip the top sheet. Cylinder  30  lifts the load beam  29  picking up the top sheet of material, cylinder  32  pivots cantilevered beam  19  clockwise until the sheet  17 ′ is over worktable  14 . Cylinder  30  lowers the load beam  29  and attached sheet  17 ′ to the surface of worktable  14  and the releasable four bar linkage  74  of loader  2  is released. Cylinder  32  pivots cantilevered beam  19  clockwise to urge sheet  17 ′ against workclamp registration surfaces  39  and  39 ′. Since one of the bars of the four bar linkage is free for limited pivotable movement, the sheet can be slightly reoriented as it engages the workclamps so that it is loaded in registration with both workclamps. Sensors associated with workclamp registration surfaces  39  and  39 ′ detect the sheet is loaded and cause the workclamps  7  and  7 ′ to grip the sheet. Vacuum cups  31 ′ release the sheet, cylinder  30  lifts the load beam  29  and vacuum cups  31 ′ above the sheet, releasable four bar linkage  74  is locked and cylinder  32  pivots cantilevered beam  19  counterclockwise positioning it once more over the staging area.  
         [0051]    It is noted that cylinder  32  can be adapted as multiple cylinders. In one form, two single acting cylinders  32  can be adapted, one on each side of cantilevered beam  19 , such that each cylinder causes pivotable motion by being operated in one direction, either by extension or by retraction. In another form, multiple cylinders mounted end to end can be adapted on one side of cantilevered beam  19 . In this form, the stroke of each cylinder is sufficient to pivot cantilevered beam  19  to a predetermined position.  
         [0052]    [0052]FIG. 10 is a drawing of a loader/unloader apparatus  75  in preferred form having a releasable four bar linkage  76  in preferred form. Loader/unloader  75  is sometimes referred to as loader  75 . FIG. 11 is an enlarged view of the lock/release apparatus of releasable four bar linkage  76 .  
         [0053]    Loader/unloader  75  has a base  77  adapted with several angle brackets  78  adapted with leveling screws  79  and spacer plates  80  for leveling loader/unloader  75  and securing it to the floor. Leveling screws  70  have a hole axially through their center suitable for passage of an anchor bolt (not shown) for securing loader/unloader  75  to the floor.  
         [0054]    Freestanding column  81  is attached to base  77 . The connection of freestanding column  80  to base  77  is strengthened by several gussets  81 . A way mounting plate  82  is attached to one face of freestanding column  80 . Attached to way mounting plate  82  are two linear ways  83  having linear guide bearings  84 . Attached to linear guide bearings  84  is a mounting plate  85 . Attached to mounting plate  85  is a pair of brackets  86  and  86 ′ for supporting and pivotally connecting cantilevered beam  87 . Servomotor  88  is adapted to drive the input shaft of gear reducer  89  that is mounted to the upper surface of supporting bracket  86 ′. Gear reducer  89  is adapted to horizontally pivot cantilevered beam  87 .  
         [0055]    At the upper end of mounting plate  85  is a “C” shaped bracket  90  pivotally connecting an attachment block  91  about shaft  92 . Shaft  92  is concentric with the output shaft of gear reducer  89  for pivoting cantilevered beam  87 . “U” shaped bracket  93  is pivotally connected to attachment block  91  by bolt  94 . The upper end of support rod  95  is attached to “U” shaped bracket  93 . The lower end of support rod  95  is attached to “U” shaped bracket  93 ′ pivotally connected to “U” shaped bracket  96  by bolt  94 ′. “U” shaped bracket  96  is attached to the distal end of cantilevered beam  87 .  
         [0056]    Below mounting plate  82 , attached to column  81 , is a bracket  97  for supporting gear reducer  98  driven by motor  99 . Gear Reducer  98  is connected via coupling  100  to the drive shaft of ballscrew  101 . Bearing housing  102  supports the lower end of ballscrew  101 , a translation screw. Ballnut  103  of ballscrew  101  is connected to the lower end of mounting plate  85 . Motor  99  via reducer  98  and coupling  100  drives ballscrew  101  to raise or lower mounting plate  85  and attached apparatus guided by linear bearings  84 . Brake  104  holds mounting plate  85  in position when motor  99  is de-energized. Other types of translation screws can be used in place of ballscrew  101 .  
         [0057]    The cantilevered beam  87  carries at its distal end a pivotable member including plate  109  which in turn supports part handling apparatus generally indicated at  107 . More particularly, inverted “V” shaped ring  105  is attached to the lower end of bracket  106 , which is attached to the underside of the distal end of cantilevered beam  87 . Load beam  107 , sometimes called a platen, is connected by spacers  108  to plate  109  and pivotally supported about inverted “V” ring  105  by “V” flanged wheels  110  attached to the upper side of plate  109 . Platen  107  is equipped with programmable permanent magnets  111  having variable magnetic attraction force. Permanent magnets  111  are adapted such that the magnetic field strength can be varied or reduced to zero by passing a current through a winding about the magnet. This is a safety feature such that, in event of a power failure, the magnets will not drop a carried part.  
         [0058]    A dedicated Programmable Logic Controller, PLC,  112 , controls magnets  11   1 . PLC  112 , considered a smart device, in response to signals from a CNC control, turns on or off selected magnets  111 , controls the magnetic field strength of each magnet  111  and monitors the operation of each magnet.  
         [0059]    Pivotable plate  109  is the fourth bar of a releasable four bar linkage. Bar  113 , the second bar of the releasable four bar linkage, is pivotally attached to pivotable plate  109  by rod end bearing  1   14  and pivotally attached proximate the left end of bar  115  (FIG. 11) by rod end bearing  114 ′.  
         [0060]    Bar  116 , the third bar of the releasable four bar linkage, is pivotally attached to pivotable plate  109 , in like manner as bar  113  but to the opposite side of plate  109 , by rod end bearing  117  and pivotally attached proximate the right end of bar  115  by another rod end bearing that cannot be seen.  
         [0061]    Pivotable bar  115 , the first bar of the releasable four bar linkage, is pivotally connected to bracket  118 . The pivotable connection of bar  115  cannot be seen but is similar to that shown in FIGS. 4 and 6 with the pivot center equally spaced from the pivotable connection points of bars  113  and  116 . Bracket  118 , attached to the lower end of mounting plate  85 , supports pivotable bar  115  and lock/release apparatus  76 .  
         [0062]    Cylinder  119  is flange mounted to plate  120 , which is attached to the left end of bracket  118 . Rod  121  of cylinder  119  is connected to “V” shaped block  122  to pull it away from bar  115  to release the releasable four bar linkage and push it against bar  115  to lock the releasable four bar linkage. Bars  123  and  123 ′ are attached to the upper side of bracket  118 , parallel to pivotable bar  115 , when bar  1   15  is in the locked position, and proximate each side of “V” shaped block  122  to slideably guide “V” shaped block  122  when locking pivotable bar  115 . The left end of pivotable bar  115  is adapted with a wedge shaped end  124  matching that of “V” shaped bock  122 . “V” shaped block  122  and wedge shaped end of pivotable bar  115  of FIG. 10 and  11  are similar to vee notched locking block  57  and wedge shaped end  58  of pivotable bar  59  shown in FIG. 6.  
         [0063]    Platen  107  is adapted with a sensor apparatus  150  to detect when material is present for pick up and to sense when a sheet picked up and carried by platen  107  has been set on a worktable.  
         [0064]    While loader/unloader  75  of FIG. 10 has been shown with a platen  107  adapted with programmable magnets  111 , having variable magnetic force, controlled by PLC  112  in response to a Computer Numerical Control, CNC, platen  107  could be adapted with programmable vacuum cups. In such an apparatus, which vacuum cups are turned on or off could be controlled by a PLC in response to the CNC or by the CNC itself.  
         [0065]    [0065]FIG. 12 is a plan view of a machine tool  126  embodied with the preferred loader/unloader  75  of FIGS. 10 and 11. Machine tool  126 , a CNC controlled punch press, is like machine tool  1  of FIGS. 1 and 2, except that the punching tool sets  8  of FIGS. 1 &amp; 2 are not shown. Several items equivalent to those of FIGS. 1 and 2 are identified with same numbers. Some items equivalent to those of FIGS. 1 and 2 are not identified to eliminate excessive redundancy.  
         [0066]    Alternate embodiments of machine tool  1  and machine tool  126  can be adapted to be a CNC punching machine without a thermal cutting attachment or a thermal cutting machine such as a plasma torch or a laser not having a punching tool. Reference to machine tool  1  and machine tool  126  is intended to apply inclusively to such machines unless the context clearly indicates otherwise.  
         [0067]    Alternate embodiments of machine tool I and machine tool  126  can be adapted with the thermal cutting attachment on the side opposite that shown or with the loading apparatus on the side opposite that shown. The invention is intended to apply inclusively to such embodiments unless the context clearly indicated otherwise.  
         [0068]    Machine tool  126  is adapted to have punching tool sets distributed along the translatable X-axis translatable table  6  in predetermined and numbered positions.  8 ′ of is one of the pockets for holding punching tool sets. The position of the work clamps and punching tool sets can be interchanged. A workclamp can be moved to a position occupied by a punching tool set and the punching tool set can be moved to the position previously occupied by the workclamp.  
         [0069]    Upon machine power up or after a change in machine setup the machine operator must run a machine setup program before the machine is used to produce parts. The setup program moves the X-axis table  6  carrying the workclamps  7  and  7 ′ and punching tool sets  8  such that the workclamps  7  and  7 ′ pass over a sensor that detects the position numbers that hold a workclamp. The workclamp positions are stored for future use. Safety zones are then established for each workclamp to prevent collision of a workclamp with the punching cylinder or plasma torch.  
         [0070]    Worktable  127  located to the right of frame  9 , FIG. 12, is different from worktable  14  of FIGS. 1 and 2. Worktable  127  is described in co-pending patent application of William B. Scott, Joachim Mayer and Michael Dixon, the teachings and disclosure of which are hereby incorporated in their entirety by reference thereto. Worktable  127 , also called a scrap table or a scrap table apparatus, is adapted to unload skeletal remnants from machine tool  1  such that they fall through scrap table  24  such that they are stacked on blocks  28  resting on or proximate the floor.  
         [0071]    Proximate in front of punching cylinder  10  are two cylinders  207 , called reposition cylinders, mounted on the bottom surface of the mounting plate of punching cylinder  10 . The function of cylinders  207  is to clamp the sheet or plate being processed by machine tool  126  such that the sheet will not move in the event that the workclamps must be opened and repositioned relative to the sheet.  
         [0072]    Behind machine tool  126  is a plasma power pack  129  for operating plasma torch  203  and a dust collector  128  for collecting smoke and dust from operation of plasma torch  203 . To the immediate rear of frame  9  is hydraulic power unit  130  of machine tool  126 .  
         [0073]    The magnetic platen  107  of loader/unloader  75  has it&#39;s own PLC  112 . The CNC of machine tool  126  communicates with PLC  112  telling it which magnets to use and what magnetic field strength to employ. PLC  112  activates and deactivates magnets  111  accordingly and monitors their operation.  
         [0074]    Left of workclamp  7 ′ is a bracket  206  attached to stationary X-axis rail  3 ′. Photo switch  205  is mounted to bracket  206 . Photo switch  205  is of a type like Cutler Hammer E58-30DP150-ELPB. The function of photo switch  205  is to find the left edge of a plate loaded into the workclamps. The description of how this is accomplished will follow later. The CNC has a “fixture offset” position associated to the position of photo switch  205 . The CNC also has a “modifier” position associated with photo switch  205  such that the switch does not have to be installed exactly at the “fixture offset” position. The CNC adds the positive or negative “modifier” and the “fixture offset” position to determine exactly where photo switch  205  is installed relative to the X-axis “0”.  
         [0075]    A smart drive assembly programmed in statement language, such as a VLT 5000 series voltage vector control drive manufactured by Danfoss, positions the Z-axis of loader/unloader  75 , driven by motor  99 . Motor  99  and associated components are named the Z-Axis because they raise and lower magnetic platen  107 . The smart drive closes the motor position loop accomplishing control of the axis independently from the CNC.  
         [0076]    The pivoting motion of loader/unloader  75  driven by servomotor  88  and gear reducer  89  is named the W-axis. The pivoting motion is controlled directly by the CNC of machine tool  126 . This control scheme is used because of availability within the CNC system of a control function allowing a commanded move to be terminated before reaching the end point of the move and for the remaining move distance to be abandoned or skipped.  
         [0077]    To the left rear of machine tool  126  is a material storage tower  131  for storage of various thickness of raw material to be processed. Material storage tower  131  has a loading side  132  and a material staging station  133 . Loading side  132  is equipped with an elevator apparatus to store and retrieve pallets of material from the storage tower. The material staging table contains magnetic sheet fanners to assist separation of steel sheets. Material  17  is removed from the storage tower  131  by the elevator then moved by a pallet transfer apparatus to the staging station  133  for loading by loader/unloader  75  to worktable  15 , into workclamps  7  and  7 ′, against registration surfaces  39  and  39 ′, for processing by machine tool  126 .  
         [0078]    In preferred form, material storage tower  131  is controlled by a stand alone PLC. The elevator drive for material storage tower  131  is controlled by a smart drive programmed in statement language, such as a VLT 5000 series voltage vector control drive manufactured by Danfoss. Such a smart drive closes the motor position loop accomplishing control of the axis independently from the PLC. The PLC communicates with the smart drive. These communications request the elevator drive to position the elevator to specified shelf locations. The material storage tower PLC controls the movement of pallets in and out of the shelves of the tower. The material staging apparatus, which moves a pallet from the material tower elevator to the material staging position, is also controlled by the PLC. The CNC of machine tool  126  communicates with the material storage tower PLC requesting a specific action such as delivery of 0.5-inch thick material to the staging position  133 . The PLC initiates the action and signals the CNC when that action has been accomplished.  
         [0079]    In alternate form, the CNC of machine tool  126  controls material storage tower  131  in place of the stand alone PLC. The elevator drive for material storage tower  131  remains a smart drive programmed in statement language. The CNC communicates with the smart drive. These communications cause the elevator drive to position the elevator to a requested shelf. The CNC controls movement of pallets in and out of the shelves of the material tower  131 . The material staging apparatus, which moves a pallet from the material storage tower elevator to the raw material staging position  133  for loading, is also controlled by the CNC via input/output logic.  
         [0080]    After a pallet is positioned at the material staging position the CNC communicates with the PLC  112  of magnet platen  107 . This communication informs PLC  112  which magnets to activate and what magnetic field strength to develop to ensure a single sheet is picked up.  
         [0081]    Once this transmission has been completed between the CNC and the PLC  112 , the CNC of machine tool  126  initiates a load cycle. Following is a description of that cycle.  
         [0082]    (1) The Z-axis of loader  75  moves to full up position such that magnet platen  107  will clear the rail  3 ′ of X-axis  3 .  
         [0083]    (2) The X-axis moves the workclamps to a calculated plate load position ((((“X”−1)*10.236)+7.244)+28.0) where “X” contains the tool pocket number of the second workclamp (workclamp  7 ), 10.236 is the distance between tool pockets, 7.244 is the distance from the centerline of the first tool pocket to the centerline of machine tool  126 , and 28.0 is an approximate minimum position required to assure the second workclamp (workclamp  7 ) is in a position to clamp the material. The 28.0 position can be changed to suit installation conditions. Simultaneously, the Y-axis moves the punching cylinder  10  and plasma torch  203  to a safe location out of the way of the loading cycle. Simultaneously, the W axis moves over the material staging position and all magnets  111  are fully de-energized to have no attraction to metal.  
         [0084]    (3) When material clamps  7  and  7 ′ reach load position they open.  
         [0085]    (4) When the loader W-axis is over the material staging position  133 , the loader Z-axis moves down until material  17  is contacted, then stops. Sensor apparatus  150  indicates to the CNC contact with material.  
         [0086]    (5) Upon receipt of the contact with material signal, the CNC will command platen PLC  112  to perform all of it&#39;s internal checks. All other signals to PLC  112  are off. PLC  1   12  activates all previously selected magnets at specified magnetic field strength, and all other magnets to the off or fully deactivated magnetic field strength level. This allows the platen to lift one and only one plate. When PLC  112  verifies that all magnets are properly seated and energized to specified magnetic field strength, PLC  112  communicates an “ok to go”signal to the CNC.  
         [0087]    (6) Upon receipt of the “ok to go” signal, the CNC commands the smart drive of loader  75  to move the Z-axis up. At a pre-designated time, when magnet platen  107  is far enough away from the top of the material stack that switching all magnets to high power will not cause the platen to pick up a second sheet, the CNC commands PLC  112  to energize all magnets to full magnetic field strength. Tentatively, the time is set to three seconds after the start of the up move. If the Z-axis reaches full up position before the magnets have been energized to full field strength, the CNC commands PLC  112  to energize all magnets to full magnetic field strength at full up position.  
         [0088]    (7) With platen  107  at full up position, sensor apparatus  150  communicating that the sheet is held by the platen, and PLC  112  communicating that all magnets are at full field strength, the CNC moves the loader W-axis to a position over worktable  15  such that the rear edge of the sheet is forward of workclamps  7  and  7 ′ then stops.  
         [0089]    (8) The CNC commands the smart drive of loader  75  Z-axis to lower platen  107 . Z-axis motion stops when the sensor apparatus  150  indicates the material has reached the surface of worktable  15  or when the distance to the table has been traveled.  
         [0090]    (9) The CNC releases locking apparatus  76  of loader  75  to allow the sheet to align with workclamps  7  and  7 ′ against sensors  39  and  39 ′ and moves the loader W-axis toward the open workclamps.  
         [0091]    (10) When sensors  39  and  39 ′ detect the material is against the registration surfaces of workclamps  7  and  7 ′ W axis motion is halted and workclamps  7  and  7 ′ are closed.  
         [0092]    (11) When the clamps have closed the CNC commands platen PLC  112  to de-energize all magnets  111  to zero magnetic field strength to release the plate.  
         [0093]    (12) PLC  112  communicates to the CNC that all magnets are at zero magnetic field strength then the CNC commands the smart drive of loader  75  Z-axis to move to the full up position. This full up position, above worktable  15  is the standby position of loader/unloader  75 .  
         [0094]    (13) The smart drive of loader  75  Z-axis signals the CNC that the Z-axis is at the full up position, then the CNC commands PLC  112  to energize all magnets to fall strength to conserve power and the CNC will initiate finding the leading edge of the material loaded in workclamps  7  and  7 ′.  
         [0095]    (14) The CNC moves the X-axis table  6  carrying the workclamps  7  and  7 ′ and the clamped sheet or plate in a series of incremental moves such that the position of the left edge of the sheet relative to X “0” is accurately determined by sensor  205 . If photo sensor  205  detects the plate, the first of the series of moves is to the right, X minus, until photo sensor  205  loses the plate. If photo sensor  205  does not detect the plate, the first of the series of moves is to the left, X plus, until photo sensor  205  detects the plate. The CNC then reverses the direction of travel of the X-axis, reduces the move velocity and reduces the move increment to a smaller step such that photo sensor  205  changes state. This process is repeated several times with direction changes and smaller increment steps until the location of the edge of the sheet in the X-axis is accurately determined.  
         [0096]    (15) The CNC then calculates the position of the edge of the plate relative to the X-axis zero position. The CNC uses this calculated position to reposition the workclamps relative to the plate.  
         [0097]    (16) The CNC moves the X and Y-axes to a position such that reposition cylinders  207  can clamp the sheet during repositioning of the workclamps.  
         [0098]    (17) The CNC initiates reposition cylinders  207  to clamp the plate.  
         [0099]    (18) The CNC initiates opening workclamps  7  and  7 ′ thereby releasing the plate from the X-axis.  
         [0100]    (19) The CNC moves the X-axis to reposition workclamps  7  and  7 ′ such that when the work clamps are closed and the X-axis is moved to X “0”, the edge of the sheet is accurately positioned relative to the X centerline of punching cylinder  10 .  
         [0101]    (20) The CNC initiates closure of workclamps  7  and  7 ′ to grip the plate.  
         [0102]    (21) The CNC initiates reposition cylinders  207  to retract to their full up position.  
         [0103]    (22) The sheet or plate is now fully gauged and ready for processing by machine tool  126 .  
         [0104]    Machine tool  126  processes the sheet such that all punching operations are performed; then any larger holes are cut with the plasma torch. Afterward, the plasma torch cuts individual parts from the sheet. Small parts are unloaded from the machine via drop leaf table  204 . Parts too large for the drop leaf table are unloaded by loader/unloader  75 .  
         [0105]    An unloading zone  208 , FIG. 12 outlines an area for unloaded large parts. The unloading function can stack parts on a table or on pallets or drop parts into containers located within zone  208 .  
         [0106]    When a part too large for drop leaf table  204  is cut out by plasma torch  203  the CNC moves the W-axis of loader  75  to position platen  107  over worktable  15  such that magnets  111  are over the large part to be removed then stops. The CNC commands PLC  112  to reduce the magnetic field of all magnets to “0”. When PLC  112  signals the CNC that all magnets are at “0” magnetic field strength the CNC commands the smart drive of loader  75  to move the Z-axis of loader  75  down until sensor apparatus  150  indicates to the CNC that the material has been contacted. The CNC instructs PLC  112  which magnets to energize and what magnetic field strength to employ. PLC  112  energizes the requested magnets then sends an “ok to go” signal to the CNC. Upon receipt of the “ok to go” signal, the CNC commands the smart drive of loader  75  to move the Z-axis up. At a pre-designated time, when magnet platen  107  has been raised above the material and if the magnetic fields are not already at full strength, the CNC commands PLC  112  to energize the previously selected magnets  111  to full magnetic field strength. Tentatively, the time is set to two seconds after the start of the up move. If the Z-axis reaches full up position before the magnets have been energized to full field strength, the CNC commands PLC  112  to energize the previously selected magnets to full magnetic field strength at full up position. With platen  107  at full up position, sensor apparatus  150  communicating that the part is held by the platen, and PLC  112  communicating that the selected magnets are at full field strength, the CNC moves the loader W-axis to a commanded position over unloading zone  208  then stops. When the part has been moved horizontally clear of worktable  15 , the CNC restarts processing the part program controlling machine tool  126 . The CNC will either drop the part into a container or stack the part on a table or pallet.  
         [0107]    If the command is to drop the part, the CNC will command PLC  112  to reduce the magnetic field strength of the selected magnets  111  to “0”. When the CNC receives a signal from PLC  112  that the magnetic field strength is at “0” and receives confirmation from sensor apparatus  150  that magnets  111  no longer hold the part, the CNC commands PLC  112  to energize all magnets to fall strength, to conserve power, and moves the loader W-axis back to the standby position over worktable  15 .  
         [0108]    If the command is to stack the part, the CNC commands the smart drive of loader  75  Z-axis to lower platen  107 . Z-axis motion stops when the sensor apparatus  150  indicates the material has reached the surface of the pallet, table, or stack. Upon receipt of the contact signal, the CNC will command platen PLC  112  to reduce the magnetic field strength of the selected magnets to “0”. When the CNC receives a signal from PLC  112  that the magnetic field strength of all magnets is at “0” magnetic field the CNC commands the smart drive of loader  75  Z-axis to move to the full up position. The smart drive of loader  75  Z-axis signals the CNC that the Z-axis is at the full up position then the CNC commands PLC  112  to energize all magnets to full magnetic field strength to conserve power and moves the loader W-axis back to the standby position over worktable  15 .  
         [0109]    [0109]FIG. 13 is an alternate form of a CNC punch press  210  having a plasma torch thermal cutting apparatus  211  and adapted such that the workpiece moves in both the X and Y-axis and adapted a loader/unloader  75  like that of FIGS. 10 and 11. Some items equivalent to those of FIGS. 10 and 1  1  are identified with same numbers. Some components associated with CNC punch press  210  are not shown as they are not important to the invention. For example a power island, electrical cabinet, plasma power pack and dust collector are not shown.  
         [0110]    CNC punch press  210  has a frame  212  shaped somewhat like a rectangular letter “0” when viewed from the side. Frame  212  has a lower base member to which is attached linear ways, which cannot be seen, which carry translatable worktables  213  on the right and  213 ′ on the left, driven by two ballscrews  214  and  214 ′ driven by servomotors  215  and  215 ′. Attached to the upper rear of worktables  213  and  213 ′ is a X-axis rail  216  to which is attached a linear way, which cannot be seen, carrying a translatable X-axis table  217  carrying workclamps  218  and  218 ′. X-axis table  217  is driven by a ballscrew, which cannot be seen, which is driven by servomotor  219 . Workclamps  218  and  218 ′ have registration surfaces for locating a workpiece in the Y-axis and sensors adapted to sense when a workpiece is loaded against the registration surfaces.  
         [0111]    To the right of translatable worktable  213  is a fixed worktable  220 . To the left of translatable worktable  213 ′ is a fixed worktable  221 . Proximate the center of frame is a fixed worktable  222 . Worktables  213 ,  213 ′,  220 ,  221 , and  222  are adapted with ball transfer bearings  223 ,  224 , and  225 . Ball transfer bearings  225  are spring loaded such that they retract when depressed by a workclamp. Ball transfer bearings  223  and  224  are fixed in place.  
         [0112]    CNC punch press  210  is adapted such that the Y-axis carries the X-axis. A workpiece, gripped by workclamps  218  and  218 ′ is positioned in the X-axis  233  by servomotor  219  and is carried, at least partially, on translatable worktables  213  and  213 ′ as it is positioned in the Y-axis  234  by servomotors  215  and  215 ′.  
         [0113]    CNC punch press  210  is adapted with a punching cylinder  226  and a robotic tool changer  227  that moves tool sets between the punching cylinder and storage areas  228  arrayed on shelves  229 . Proximate in front and to each side of punching cylinder  226  are two reposition cylinders  207 . To the left of plasma torch  211  is a drop leaf table  230 . Drop leaf table  230  unloads small parts after they are cut from a workpiece by plasma torch  211 .  
         [0114]    To the left of workclamp  218 ′ is a bracket  206  attached to X-axis rail  216 . Photo switch  205  is mounted to bracket  206 . Photo switch  205  is of a type like Cutler Hammer E58-30DP150-ELPB. The function of photo switch  205  is to find the left edge of a plate loaded into the workclamps.  
         [0115]    Operator station  13  provides the man/machine interface for machine tool  210 .  
         [0116]    Loader/unloader  75  is adapted with a material staging station  231  and large parts unload area  232 . Material staging station  231  can be a material staging station of a material storage tower.  
         [0117]    Operation of the system is similar to that previously described. The CNC of punch press  210  positions the X and Y-axis to a “load position”. The X and Y-axis remain stationary while the workpiece is loaded into workclamps  218  and  218 ′. Loader  75  loads a workpiece on worktables  213  and  221  and into the registration surfaces of workclamps  218  and  218 ′. The workclamps close gripping the workpiece then the loader releases the part and returns to “standby position”. The CNC moves the workpiece in the X-axis such that photo switch  205  finds the location of the left edge of the workpiece then positions the workpiece under reposition cylinders  207 . Reposition cylinders  207  grip the workpiece while the workclamps are repositioned such that the workpiece is fully registered and ready for processing by machine tool  210 .  
         [0118]    The large part unloading cycle functions as previously described.  
         [0119]    While loader apparatuses with releasable four bar linkages have been described for use with a CNC punch press machine tool, similar loaders with releasable four bar linkages can be adapted to load different types of machine tools where the part must be aligned with an axis, table or fixture of the machine tool during loading. The requirement is that the axis, table, or fixture has a surface to set the material, part, or some portion of the loading platen apparatus against to align the part to the axis.  
         [0120]    It can now be seen by one of ordinary skill in the art that the present invention provides a new and improved machine tool loading apparatus. Means to add compliance to a loader with a releasable four bar linkage and several forms of four bar lock/release apparatuses have been described. A loading cycle has been described, which is capable of automatically picking up a single sheet from a staging station, loading the sheet into the workclamps of the machine tool, locating the position of the sheet on one axis of the machine tool, moving the sheet to the processing area of the machine tool, and repositioning the workclamps of the machine tool relative to the sheet such that the sheet or plate is fully gauged and ready for automatic processing by the machine tool. An unloading cycle has been described such that the loader can also be used to unload large parts from the machine tool. The preferred loader/unloader apparatus has been shown adapted to two types of CNC punch presses. Such adaptations may or may not include a material storage tower apparatus.