Abstract:
A pneumatic die transfer system for a press machine comprises at least two primary roller rails and at least two secondary roller rails set in respective T-slots in a bolster. The primary roller rails are perpendicular to the secondary roller rails. Airbags below each roller rail are selectively inflated to elevate either the primary or the secondary roller rails above the bolster face. The secondary roller rails each have a plurality of discontinuities configured to receive the primary roller rails and their associated airbags in an intersecting fashion. As a result, the bolster can be easily fabricated with intersecting T-slots and relatively few roller rails are needed to achieve fully orthogonal conveyance of a heavy die over the face of a bolster.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to Provisional Patent Application No. 62/126,953 filed Mar. 2, 2015, the entire disclosure of which is hereby incorporated by reference and relied upon. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates generally to self-loading or unloading vehicles for conveyor devices where a load is guided or supported by at least one roller that can be raised and lowered, and more particularly to a die transfer system for a press machine. 
       Description of Related Art 
       [0003]    Relatively heavy stamping, forging, die casting and plastic injection molding dies often present a handling problem when such dies are assembled with or removed from the bolster of a press machine. For example, U.S. Pat. No. 5,947,676 to Richard, issued Sep. 7, 1999, discloses a die lift system that uses a silicone airbag in conjunction with a specially configured compressed air manifold, like that illustrated in  FIG. 1 . A series of parallel channels, in the form of T-slots, are formed in the bolster. An airbag is placed in at least two channels and each are connected to a source of compressed air via a manifold. Roller rails are placed in the channels over the airbags to be raised/lowered in conjunction with inflation/deflation of the respective airbags. When a die is affixed to the bolster during normal operation of the press machine, the airbags are deflated and the roller rails retracted below the face of the bolster so as not to interfere with the secure placement of the die. However, when it is desired to move the die off the bolster, the airbags are simultaneously inflated thereby elevating the bottom of the die above the bolster face by the several roller elements in each of the roller rails. Suspended by the roller elements, the die can then be easily moved in a path parallel to the roller rails. The Richard &#39;676 patent is assigned to the assignee of the present invention, and the entire disclosure thereof is hereby incorporated by reference and relied upon. Other examples of T-slot and airbag type die lift systems may be found in U.S. Pat. Nos. 4,498,384, 4,691,554 and 4,700,624 to Murphy, the disclosures of which are also incorporated by reference and relied upon. 
         [0004]    Sometimes, it is desirable for a technician or millwright to be able to manually move a die in two orthogonal directions on a bolster, for example forward-to-backward and left-to-right. The prior art has offered some examples of die lift systems that will enable a technician or millwright to be able to manually move a die in two orthogonal directions on a bolster, but all have shortcomings. For example, U.S. Pat. No. 3,011,665 to Wise, issued Dec. 5, 1961, discloses a roller conveyor system that is capable of transferring objects in two perpendicular directions (i.e., in the X and Y directions of a horizontal plane). The Wise &#39;665 system is designed with rollers carried in trays that are held in channels in the system bed. All of the channels in the bed are parallel, and all of the roller trays are likewise arranged parallel to one another. Half of the roller trays have rollers that are supported on axles so as to transfer objects in the “X” direction. The rollers in the other half of the roller trays are supported on axles so as to transfer objects in the “Y” direction. The “X” direction trays are alternated between the “Y” direction trays. Air bladders are placed under the roller trays. The air bladders are selectively inflatable to raise all of the “X” direction trays in unison while the “Y” direction trays remain low. Alternatively, the air bladders underneath the “Y” direction trays can be inflated in unison while the “X” direction trays remain low. In this manner, objects can be moved in either the “X” or “Y” direction depending upon which set of roller trays are raised. A relatively large number of channels and rails need to be provided in the bolster for smooth rolling transfer in the directions perpendicular to the channels. That is to say, the Wise &#39;665 system requires significantly more than two roller rails for conveying dies perpendicular to the channels. 
         [0005]    In another example, U.S. Pat. No. 4,819,554 to Fleischer et al., issued Apr. 11, 1989, describes a roller conveyor system that is capable of transferring objects in two perpendicular directions (X-Y). The rollers are held in trays, which in turn are located in channels in the system bed. Air bladders are placed under the roller trays, and are selectively inflatable to raise all of the “X” direction (or alternatively the “Y” direction) trays in unison while the other trays remain low. In the embodiment of Fleischer&#39;s  FIG. 3 , the channels are formed so that the “X” direction channels do not intersect the “Y” direction channels. And likewise, the “X” &amp; “Y” roller trays do not intersect. This complicates fabrication of the bolster, and also complicates installation of the roller tray system and its air connections. 
         [0006]    German Patent No. DE3109219 to Streit, published Jul. 8, 1982, shows yet another example of a material handling system that is capable of transferring objects in two perpendicular directions (X-Y). In this system, large primary (live) rollers do not raise or lower; they are fixed in position. Smaller transverse rollers are raised or lowered below the tops of the large live rollers in order to switch between “X” and “Y” direction transfers. The system is therefore ill-suited to many forms of modern-day press machine operations. 
         [0007]    There is therefore a need in the art for an improved die transfer system that retains the functionally flawless performance of the Richard &#39;676 patent, but yet allows a technician or millwright to manually move a die in two orthogonal directions on the bolster. The improved system must be relatively low-cost, easy to install and maintain, and robust. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    According to a first aspect of this invention. A pneumatic die transfer system for a press machine comprises at least two primary roller rails disposed parallel to one another. Each primary roller rail comprises an elongated U-channel supported over a primary base plate. Each primary base plate includes a pair of laterally extending primary flanges. A lateral measurement across the primary flanges comprises a primary flange width. The height of the primary flanges comprises a primary flange thickness. At least two elongated first airbags are provided. Each first airbag is disposed below a respective one of the primary roller rails. Each first airbag is configured to inflate to an inflated height in response to an admittance of compressed air and thereby elevate the respective primary roller rail. At least two secondary roller rails are disposed parallel to one another. Each secondary roller rail comprises an elongated U-channel supported over a secondary base plate. At least two elongated second airbags are provided. Each second airbag is disposed below a respective one of the secondary roller rails. Each second airbag is configured to inflate in response to an admittance of compressed air and thereby elevate the respective secondary roller rail. Each secondary roller rail includes a plurality of discontinuities in the U-channel thereof. Each discontinuity corresponding to a respective one of the primary roller rails. Each discontinuity is under-girded by the secondary base plate. Each discontinuity has a longitudinal gap spacing. The longitudinal gap spacing is at least as large as the primary flange width in order to receive in the discontinuity and above the under-girded secondary base plate a transversely oriented one of the primary rails together with the respective first airbag, whereby the at least two primary roller rails intersect the at least two secondary roller rails in a grid pattern while remaining selectively operable by the respective first and second airbags to facilitate manual transfer of a forming die in the linear direction of either the primary or secondary roller rails. 
         [0009]    According to another aspect of this invention, a combination die transfer system and press machine is provided. The press machine includes a bolster having a generally horizontal face. A plurality of T-slots are formed in the face of the bolster, each with opposing undercut sections that establish shoulder stop features. Each T-slot has a respective length. The T-slots comprise at least two shallow T-slots and at least two deep T-slots. The shallow T-slots are disposed parallel to one another. The deep T-slots are parallel to each other, and perpendicularly intersect the shallow T-slots. A primary roller rail is disposed in each of the shallow T-slots, and each primary roller rail has a length generally corresponding to the length of the respective shallow T-slots and/or to the required die travel requirements. Each primary roller rail comprises an elongated U-channel supported over a primary base plate. Each primary base plate includes a pair of laterally extending primary flanges. A lateral measurement across the primary flanges comprises a primary flange width. The height of the primary flanges comprises a primary flange thickness. The primary flanges are fitted within the opposing undercut sections of the shallow T-slots. Vertical movement of each primary roller rail within the respective shallow T-slot is constrained by the shoulder stops. An elongated first airbag is disposed within each shallow T-slot, and is disposed below a respective primary roller rail. Each first airbag is configured to inflate to an inflated height in response to receiving a supply of compressed air and thereby elevate the respective primary roller rail within the associated shallow T-slot so that the plurality of roller elements protrude above the bolster face. An elongated second airbag is disposed within each deep T-slot. Each second airbag is disposed below the respective secondary roller rail, and is configured to inflate in response to receiving a supply of compressed air so as to elevate the respective secondary roller rail within the associated deep T-slot. A secondary roller rail is disposed in each of the deep T-slots. Each secondary roller rail comprises an elongated U-channel supported over a secondary base plate. Each secondary roller rail includes a plurality of discontinuities in the U-channel. Each discontinuity corresponds to a respective one of the primary roller rails, and is under-girded by the secondary base plate. Each discontinuity has a longitudinal gap spacing that is at least as large as the primary flange width in order to receive therein a transversely oriented primary rail together with its first airbag. 
         [0010]    The present invention enables an improved die transfer system that retains the functionally flawless performance of the Richard &#39;676 patent, but yet allows a technician or millwright to manually move a die in two orthogonal directions on the bolster. The present invention can be constructed at relatively low-cost, is easy to install and maintain, and is robust. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0011]    These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein: 
           [0012]      FIG. 1  is a perspective view of a prior art die lifting system integrated into the bolster portion of a press machine, and further depicting an exemplary forming die resting on the bolster; 
           [0013]      FIG. 2  is a perspective view of a novel die transfer system according to one embodiment of the present invention shown fitted in a bolster which is depicted in phantom lines and schematically connected to a supply of compressed air; 
           [0014]      FIG. 3  is a top view of a bolster in which are formed orthogonally intersecting T-slots to accommodate the die transfer system of the present invention; 
           [0015]      FIG. 4  is a front view of the bolster as taken generally along lines  4 - 4  of  FIG. 3 ; 
           [0016]      FIG. 5  is an end view of the bolster as taken generally along lines  5 - 5  of  FIG. 3 ; 
           [0017]      FIG. 5A  is an enlarged view of the area circumscribed at  5 A in  FIG. 5  and calling out various dimensional attributes of a T-slot; 
           [0018]      FIG. 6  is a front elevation view of a primary roller rail according to one exemplary embodiment of the invention; 
           [0019]      FIG. 7  is a top view of the primary roller rail as taken generally along lines  7 - 7  of  FIG. 6 ; 
           [0020]      FIG. 8  is an end view of the primary roller rail as taken generally along lines  8 - 8  of  FIG. 6 ; 
           [0021]      FIG. 9  is a top view of a secondary roller rail according to one exemplary embodiment of the invention; 
           [0022]      FIG. 10  is a front elevation view of the secondary roller rail as taken generally along lines  10 - 10  of  FIG. 9 ; 
           [0023]      FIG. 10A  is an enlarged view of the area circumscribed at  10 A in  FIG. 10  and calling out various dimensional attributes of a specially configured discontinuity in the secondary roller rail; 
           [0024]      FIG. 11  is an end view of the secondary roller rail as taken generally along lines  11 - 11  of  FIG. 10 ; 
           [0025]      FIG. 12  is an enlarged fragmentary cross-sectional view of a bolster taken generally along lines  12 - 12  in  FIG. 2 , and showing both a primary roller rail and a secondary roller rail in retracted, non-inflated positions so that a forming die thereabove rests in surface-to-surface contact against the face of the bolster; 
           [0026]      FIG. 13  is a view as in  FIG. 12 , but showing the primary roller rail elevated by inflating the underlying first airbag to lift the forming die by the primary roller elements; and 
           [0027]      FIG. 14  is a view as in  FIG. 12 , but showing the secondary roller rail elevated by inflating the underlying second airbag to raise the forming die by the secondary roller elements. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    Referring to the figures, wherein like numerals indicate like or corresponding parts throughout the several views, a die transfer system for a press machine  18  is generally shown at  20 . The term press machine  18  is used herein broadly to describe any type of industrial machine used to cut and/or shape a working material, such as metal or plastic, between two tool parts. When configured as a stamping press, for example, the press machine  18  shapes and/or cuts metal by deforming the metal between two dies. Alternatively, a press machine  18  configured for injection molding forms plastic products in a cavity between two dies. 
         [0029]    The typical press machine  18  has a bolster  22  and a ram (not shown). The ram is moveable vertically in relation to the bolster  22  and provides the stroke (up and down movement). The bolster  22  (also known as a bolster plate or bed) is often a large block of stationary metal having a generally horizontal face, as perhaps best shown in  FIG. 3 . A plurality of T-slots are cut into the bolster  22 . Preferably, but not necessarily, the T-slots extend from edge-to-edge of the bolster  22 , such that the length of each T-slot corresponds to the length or width of the bolster  22  according to its respective orientation. In order to accommodate the die transfer system  20  of the present invention as depicted in  FIG. 2 , the T-slots will comprise at least two shallow T-slots  24  and at least two deep T-slots  26 . The two shallow T-slots  24  are disposed parallel to one another. Similarly the two deep T-slots  26  are disposed parallel to one another. These T-slot sets  24 ,  26  are oriented orthogonally to one another, so that the two shallow T-slots  24  perpendicularly intersect the two deep T-slots  26 . It will be understood that the bolster  22  may include more than two shallow T-slots  24  and/or more than two deep T-slots  26 . However, for convenience the description will make reference to the minimum numbers only—i.e., two each. 
         [0030]      FIGS. 3-5  illustrate an exemplary bolster  22  supporting a minimum number of T-slots  24 ,  26  to implement the die transfer system  20  of this invention. Both the shallow  24  and deep  26  T-slots share many common attributes. An enlarged view of a deep T-slot  26  is provided in  FIG. 5A , and will serve as a representative to explain some of the common T-slot attributes. In particular, each T-slot  24 ,  26  comprises a throat section  28  that opens into the face of the bolster  22 . A pair of recessed undercut sections  30  are formed at the bottom of the throat section  28 . These features  28 ,  30  take the shape of a generally inverted T when viewed in cross-section or in profile as in  FIG. 5A . The horizontal interface between each undercut section  30  and the adjacent throat section  28  comprises a shoulder stop  32 . The throat section  28  opens upwardly into the bolster  22  face in the form of an elongated slot. In the illustrated embodiments, the depth of the shallow T-slots  24  may be generally equal to the throat section  28  depth of the deep T-slots  26 . In this manner, the overall depth of the shallow T-slots  24  is less than the overall depth of the deep T-slots. For the sake of clarity, the overall depth is indicated by reference dimension A in  FIG. 5A , and the depth of the throat section  28  is indicated by reference dimension B. It should be appreciated that the adjectives “shallow” and “deep” are intended mainly to distinguish the T-slots  24 ,  26  one from the other in the accompanying illustrations, rather than impose strict definitional limitations. That is to say, it is possible that the shallow T-slots  24  could be designed to have an equal or greater depth in the bolster  22  than the deep T-slot formations  26 . 
         [0031]    A forming die  34  is disposed on top of the bolster  22 , i.e., between bolster  22  and the ram, for forming work-parts to shape according to the type of press machine  18  in which it is operating. The forming die  34 , depicted in the prior art example of  FIG. 1 , includes a lower die member  36 . The lower die member  36  has a generally flat bottom surface configured to rest in surface-to-surface contact against the face of the bolster  22 , and is there held fast using various methods like clamps or magnets (not shown) engaged through ancillary T-slots (like that shown in  FIG. 1 ) in the traditional manner. A mounting flange  38  may be provided, at least partially surrounding the bottom surface of the lower die member  36 , to provide convenient clamping methods. Therefore, using any suitable method, the lower die member  36  is held immobile on the bolster  22  during a forming operation. A fragmentary portion of a lower die member  36  is visible in  FIGS. 12-14 . The forming die  34  also commonly includes an upper die member  40  affixed to the ram and moveable therewith so as to reciprocate against the lower die member  36  to shape work-parts therebetween. 
         [0032]    Turning now to  FIGS. 6-8 , a primary roller rail, generally indicated at  42 , is disposed in each shallow T-slot  24 . In many cases each primary roller rail  42  will have a length generally equal to the length of the respective shallow T-slots  24 . That is, the primary roller rail  42  may substantially fill the full length of its host shallow T-slot  24 . Of course, there may be applications where the length of the primary roller rail  42  is shorter or longer than the length of its respective T-slot  24 . Each primary roller rail  42  comprises an elongated U-channel  44  supported over a primary base plate  46 . The primary base plate  46  is shown as an integral formation with the U-channel  44 . That is to say, both features may be milled or extruded from a common piece of stock. Alternatively, the primary base plate  46  and U-channel  44  could be separately formed as loose pieces and subsequently attached as by welding or fasteners. The U-channel  44  fits within the throat section  28  of the host shallow T-slot  24 , whereas the primary base plate  46  is contained within the opposing undercut sections  30 . Each primary base plate  46  includes a pair of laterally extending primary flanges  48 . A lateral measurement across the primary flanges  48  comprises a primary flange width C. The height of the primary flanges  48  comprises a primary flange thickness D. Vertical movement of each primary roller rail  42  within its respective shallow T-slots  24  is constrained by the shoulder stops  32 . That is to say, the primary flanges  48  are free to move vertically a limited distance within the opposing undercut sections  30 , because the height of the undercut sections  30  is greater than the primary flange thickness D. A plurality of primary roller elements  50  are spaced in generally equal longitudinal increments along the length of each primary roller rail  42 . The primary roller elements  50  are supported on pins or bearings or bushings or in some other manner within the U-channel  44  to enable free rotation about generally horizontal axes. The overall height E of the primary roller rail  42  is smaller than the overall depth A of the shallow T-slots  24 . 
         [0033]      FIGS. 2 and 12-14  show an elongated first airbag  52  disposed within each shallow T-slot. The first airbags  52  are located below respective primary roller rail  42 , in a manner similar to that shown and described in the aforementioned U.S. Pat. No. 5,947,676. Any suitable material can be used to construct the first airbags  52 , including but not limited to spun polyester lined with a thermoplastic polyurethane (TPU) material. The first airbags  52  are configured to be inflated to an inflated height in response to receiving a supply of compressed air. In so doing, the overlying primary roller rail  42  is elevated within the associated shallow T-slots  24 . As will be described below in connection with  FIGS. 12-14 , the roller elements  50  protrude above the bolster  22  face when its associated first airbag  52  is inflated, and conversely the roller elements  50  retract below (or at least generally flush with) the bolster  22  face when its associated first airbag  52  is deflated. 
         [0034]    A secondary roller rail is generally indicated at  54  in  FIGS. 9-11 . One secondary roller rail  54  is disposed in each deep T-slot  26 . Like the primary roller rails  42 , the deep T-slots  26  may or may not have a length that is generally equal to the length of its host deep T-slots  26 . Each secondary roller rail  54  has an elongated U-channel  56  supported over a secondary base plate  58 . The secondary base plate  58  is shown attached to the U-channel  44  using fasteners. As previously suggested in connection with the primary base plate  46  and U-channel  44 , the secondary base plate  58  and U-channel can be separately formed as loose pieces and subsequently attached as by welding or other methods. Alternatively, the primary base plate  46  and U-channel  44  can be formed as a monolithic structure from a common piece of stock. The secondary base plate  58  includes a pair of laterally extending secondary flanges  60  that nest within the opposing undercut sections  30  of the deep T-slots  26 . Each secondary roller rail  54  includes a plurality of secondary roller elements  62  spaced in generally equal longitudinal increments along the length thereof. The secondary roller elements  62  are supported within the U-channel  56  for free rotation about generally horizontal axes. The overall height E of the secondary roller rail  54  is smaller than the overall depth A of the deep T-slots  26 . Vertical movement of each secondary roller rail  54  within its host deep T-slot  26  is constrained by the secondary flanges  60  interacting with the shoulder stops  32 . 
         [0035]    Unlike the primary roller rails  42 , each secondary roller rail  54  includes a plurality of discontinuities  64  in the U-channel, as perhaps best shown in  FIGS. 10 and 10A . The number of discontinuities  64  corresponds to at least the number of primary roller rails  42 . If the die transfer system  20  utilizes two primary roller rails  42  (the minimum number), then each secondary roller rail  54  will have at least two discontinuities. If, in another example, the die transfer system  20  utilizes four primary roller rails  42  then each secondary roller rail  54  will have at least four discontinuities, and so forth. Each discontinuity  64  corresponding to a respective one of the primary roller rails. Each discontinuity  64  is under-girded by the secondary base plate  58 . That is to say, the secondary base plate  58  is generally continuous along the length of the secondary roller rail  54  and thus spans the discontinuities  64 . Each discontinuity  64  has a longitudinal gap spacing F. The longitudinal gap spacing F is at least as large as the primary flange width C in order to receive a transversely oriented primary roller rail  42  in the discontinuity  64 . The first airbags  52  must also fit within the longitudinal gap spacing F. Opposing cantilever sections  66  of the U-channel  56  project into each discontinuity  64  to form a generally inverted T-shaped negative space clearly visible in the enlarged elevation view of  FIG. 10A . The distance G between the secondary base plate  58  and the overhang of the cantilever sections  66  is generally equal to or greater than the inflated height of the first airbag  52  plus the primary flange thickness D, as shown in  FIG. 13 . 
         [0036]    An elongated second airbag  68  is disposed in each deep T-slot  26 , below a respective secondary roller rail  54 . The second airbags  68  can be fabricated from any suitable material, including but not limited to spun polyester lined with a thermoplastic polyurethane (TPU). Like the first airbags  52 , the second airbags  68  are configured to inflate in response to receiving a supply of compressed air and thereby elevate their respective secondary roller rails  54  within the associated deep T-slots  26  so that the secondary roller elements  62  protrude above the face of the bolster  22 . See  FIG. 14 . 
         [0037]    Returning to  FIG. 2 , a schematic representation of an air manifold  70  is shown in fluid communication with a supply of compressed air  72 . The air manifold  70  is operatively connected to each of the first  52  and second  68  airbags to selectively admit air into either the first airbags  52  or into the second airbags  68 . In this manner, the first  54  and second  68  are to alternately inflate so that their associated primary  42  and secondary  54  roller rails lift above the face of the bolster  22 . End caps  74  may be used to retain the primary roller rails  42  in their respective shallow T-slots  24 , in much the same way illustrated in the prior art example of  FIG. 1 . The end caps  74  shown in  FIG. 1  at least partially cover the longitudinal ends of each T-slot  24 ,  26 , thereby allow access for the air supply but inhibiting egress of the components from their host T-slots  24 ,  26 . 
         [0038]    An exemplary installation process may take the following sequence. The second airbags  68  are slid or otherwise placed into the bottom of the deep T-slots  26 . Next, the secondary roller rails  54  are slid into the respective deep T-slots  26 , overtop of the second airbags  68 . Care is taken to align the discontinuities  64  with the intersecting shallow T-slots  24 . Although not shown, buffers can of course be placed between airbags and roller rails if desired. Next, the first airbags  52  are placed into the respective shallow T-slots  24 . At the intersection of the deep T-slots  26 , the first airbags  52  overlay the secondary base plates  58  of the secondary roller rails  54 . The primary roller rails  42  can then be inserted into their respective shallow T-slots  24  over the first airbags  52 . Air connections can be made to the manifold  70  to enable air from the source  72  to selectively fill the airbags  52 ,  68 . End caps  74  (as in  FIG. 1 ) can be installed to the bolster  22  to retain the roller rails  42 ,  54  in the respective T-slots  24 ,  26 . 
         [0039]    Operation of the die transfer system will be described according to the illustrated exemplary embodiment.  FIG. 12  represents a fragmentary section taken through the bolster  22  generally along the lines  12 - 12  in  FIG. 2 . A primary roller rail  42  appears in cross-section along with an intersecting portion of a secondary roller rail  54 . The lower die member  36  of a forming die  34  is shown resting on the face of the bolster  22 , as may be the case when the forming die  34  is secured in place and in use shaping or cutting workparts. In this condition, both of the primary  42  and secondary  54  roller rails are lowered in their respective T-slots  24 ,  26  such that their respective roller elements  50 ,  62  are recessed below the face of the bolster  22 . The roller elements  50 ,  62  have no affect or interaction with the forming die  34  in this condition. 
         [0040]    When it is desired to move the forming die  34  from its seated position in  FIG. 12 , an operator will disable any clamps or other fastening elements that may be locking the forming die  34  to the bolster  22 . Next, the operator activates the air manifold  70  to selectively admit air into either the first airbag  52  or into the second airbag  68 . It is not expected that air would be admitted to both airbags  52 ,  68  simultaneously, however it is possible that is some alternative constructions that may be desirable. However, in normal usage, the operator will choose to energize only the first airbag  52  if it is desired to move the forming die  34  in the longitudinal direction of the shallow T-slots  24 . Alternatively, the operator will choose to energize only the second airbag  68  if it is desired to move the forming die  34  in the longitudinal direction of the deep T-slots  26 . 
         [0041]      FIG. 13  represents the situation where the operator wants to move the forming die  34  in the longitudinal direction of the shallow T-slots  24 . In this case, the operator manipulates the control valve features of the air manifold  70  to admit compressed air (from source  72 ) into all of the first airbags  52 , which simultaneously deflates (either actively or passively) the second airbags  68 . The influx of compressed air causes the first airbags  52  to inflate, upwardly pushing the associated primary roller rails  42 . The uppermost tangential edges of the primary roller elements  50  will press into the bottom of the lower die member  36 , causing the entire forming die  34  to lift above the face of the bolster  22 . Once raised out of frictional contact with the bolster  22 , the forming die  34  is easily moved along the primary roller elements  50  by human power alone. In this manner, the operator can re-position the forming die  34  on the bolster  22 , or move the forming die  34  onto an adjacent waiting bolster extension (not shown) or transfer cart (not shown). 
         [0042]    Of particular note in  FIG. 13  is the interaction between the primary  42  and secondary  54  roller rails. Because the first airbags  52  extend over top of the secondary base plates  58 , when inflated the secondary roller rails  54  are pushed down with forces exerted on the primary roller rails  42 . This initially helps to retract or push the secondary roller rails  54  toward the bottoms of their respective deep T-slots  26 , forcefully expelling any residual air contained within the second airbags  68 . However, when the primary flanges  48  are raised to the point of contacting the cantilever sections  66 , the downward forces are immediately counter-balanced and the upward travel of the primary roller rails  42  arrested at an upper limit. Depending on tolerances and design specifications, in some embodiments the upward travel of the primary roller rails  42  may be limited by the shoulder stops  32  in the respective host shallow T-slots  24  rather than by the cantilever sections  66 . 
         [0043]      FIG. 14  represents the situation where the operator wants to move the forming die  34  in the longitudinal direction of the deep T-slots  26 . To accomplish this, the operator manipulates the control valve features of the air manifold  70  to admit compressed air into all of the second airbags  68 , which concurrently enables deflation of the first airbags  52 . The influx of compressed air causes the second airbags  68  to inflate, upwardly pushing the associated secondary roller rails  54 . The uppermost tangential edges of the secondary roller elements  62  will press into the bottom of the lower die member  36 , causing the entire forming die  34  to lift above the face of the bolster  22 . Now, the forming die  34  is easily moved along the secondary roller elements  62  by human power alone for re-positioning or service to the forming die  34 . 
         [0044]    Unlike prior art systems that require a large number of roller rails to accomplish die movement in perpendicular directions, or that require complicated bolster fabrications and/or complicated installation procedures, or that in some other way are generally ill-suited to modern-day press machine operations, the die transfer system  20  of the present invention can be constructed at relatively low-cost, is easy to install and maintain, and is robust in operation. 
         [0045]    The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and fall within the scope of the invention. Furthermore, particular features of one embodiment can replace corresponding features in another embodiment or can supplement other embodiments unless otherwise indicated by the drawings or this specification.