Patent Publication Number: US-2005139054-A1

Title: High flow/high pressure cutting table

Description:
CROSS REFERENCE TO A RELATED APPLICATION  
      Applicant claims priority based on U.S. provisional application No. 60/507,026 filed Sep. 29, 2003 and entitled “High Flow/High Pressure Cutting Table”, the disclosure of which is incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      This invention relates to the art of apparatus for performing operations including cutting sheet material such as cloth, and more particularly to a new and improved table for supporting and holding sheet material during such operations.  
      Vacuum tables have been proposed for supporting and holding down sheet material such as cloth during cutting of the sheet material into desired shapes. Such tables include, briefly, a table top provided with apertures there through, a plenum below the tabletop in communication with the apertures, a vacuum blower and a plumbing system placing the blower in communication with the plenum. In operation, sheet material on the top of the table is held down by the vacuum or suction created by operation of the blower which draws air from the apertures in the table top through the plenum and the plumbing system.  
      It has been determined according to this invention that certain types of sheet material, such as open woven fabrics, require high flow/high pressure conditions for efficient handling in tables for supporting and holding the sheet material during operations such as cutting.  
     SUMMARY OF INVENTION  
      It is, therefore, an object of this invention to provide a new and improved table for supporting and holding sheet material during operations such as cutting.  
      It is a more particular object of this invention to provide such a table for efficient handling of open weave fabric and like materials.  
      It is a further object of this invention to provide such a table with high flow/high pressure operation.  
      The invention provides a high flow/high pressure table for supporting and holding sheet material during operations such as cutting which table includes a rigid air plenum structure providing extremely flat surface tolerances for cutting and having high volume cross-flow capability. The plenum structure includes a supporting framework of interlocking strips with air passages therein that determines table strength, flatness and flow capacity. The table configuration includes straight section, large diameter tubes feeding a high pressure/high flow vacuum source. There is also provided zonable low pressure-loss risers for transitioning between tubes and plenum. The plenum structure includes extrusions that provide rigidity for the cutting surface and attachment means for racks and rails to support and guide a gantry assembly associated with the table.  
      The following detailed description of the invention, when read in conjunction with the accompanying drawings wherein the same reference numerals denote the same or similar parts throughout the several views, is in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains, or with which it is mostly nearly connected, to make and use the invention. The foregoing and additional advantages and characterizing features of the invention will become clearly apparent upon a reading of the ensuing detailed description together with the included drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       FIG. 1  is a perspective view of a high flow/high pressure cutting table according to the invention;  
       FIG. 2  is a developed perspective view of the table of  FIG. 1 ;  
       FIG. 3  is a developed perspective view of a plenum assembly of the table of  FIG. 1 ;  
       FIG. 4  is an enlarged, perspective view showing a partially assembled supporting framework for the plenum assembly of  FIG. 3 ;  
       FIG. 5  is an enlarged, perspective view of a portion of the framework of  FIG. 4 ;  
       FIG. 6  is an enlarged, perspective view of another portion of the framework of  FIG. 4 ;  
       FIG. 7  is an enlarged, fragmentary perspective view of one of the strip components of the framework of  FIG. 4 ;  
       FIG. 8  is a perspective view of a valve assembly of the table of  FIG. 1 ;  
       FIG. 9  is an enlarged, perspective view showing the arrangement of guide racks and rails for the gantry assembly on the table of  FIG. 1 ;  
       FIG. 10  is an enlarged, fragmentary perspective view of a portion of the arrangement of  FIG. 9 ;  
       FIG. 11  is an enlarged, fragmentary perspective view showing the guide racks and rails in  FIGS. 9 and 10 ;  
       FIGS. 12 and 13  are diagrammatic views further illustrating operation of the high flow/high pressure table according t the invention; and  
       FIG. 14  is a diagrammatic perspective view of the table of the invention incorporated in a conveyor arrangement. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      A basic vacuum table for holding down sheet material during cutting includes an apertured table top, a plenum below the table top in communication with the apertures and a vacuum blower and a plumbing system placing the blower in communication with the plenum. In operation, sheet material on the top of the table is held down by the vacuum or suction created by operation of the blower which draws air from the apertures in the table top through the plenum and the plumbing system.  
      Certain types of open woven/open cell material require high flow/high pressure conditions for efficient handling in vacuum tables of the foregoing type. In particular, the openings in such open woven/open cell materials define an interstitial or lattice-like structure. A high flow at high pressure is needed from around the solid regions or boundaries outlining the openings and then through the openings to create a force to hold down the material on the surface of the table top.  
      Some prior art cutting tables have structures supporting the cutting surface which would cause pressure loss under high flow conditions. For example, table plenums have been created using honeycomb materials sandwiched between two surfaces. This provides desired flatness and rigidity but severely limits high cross-flow. Some arrangements have opened air paths provided by holes drilled in the honeycomb permitting some amount of cross-flow, but this still is very limited. Other prior art cutting tables have plumbing components that create pressure drops in high flow or long length configurations. In particular, all known prior cutting tables which employ pipes or tubes in the plumbing system do not have high flow capacity. Any known prior tables having high flow capacity are based on large vacuum chambers.  
      Accordingly it is an object of this invention to provide a flat/rigid table surface for performing operations such as cutting on various materials in sheet form while at the same time eliminating pressure loss in the structure supporting the cutting surface under high flow conditions needed for operations on open woven/open cell materials. It is a further object to eliminate plumbing components that create pressure drops in high flow or long length table configurations. It is an additional object to give the table the capability to provide vacuum zones for optimizing material-holding pressure. It also is an object to provide convenient and easy attachment of guide racks and rails to the table structure.  
      A high flow/high pressure cutting table according to the present invention is shown in  FIGS. 1-11 . It has a rigid air plenum structure providing extremely flat surface tolerances for cutting. It includes an air plenum structure with high volume cross-flow capability. The plenum structure includes a supporting framework of interlocking strips that determines table strength, flatness and flow capacity. The table configuration includes straight section, large diameter tubes feeding a high pressure/high flow vacuum source. There is also provided zonable low pressure-loss risers for transitioning between tubes and plenum. The plenum structure includes extrusions that provide rigidity for the cutting surface and attachment means for racks and rails to support and guide a gantry assembly associated with the table.  
      Referring to  FIG. 1 , the table  10  according to the invention includes an air-permeable top surface  12  which in the present illustration is divided into a plurality of sections extending lengthwise along the table. Preferably a plurality of apertures  14  are provided in surface  12  for communication with a plenum (not show in  FIG. 1 ) located beneath the surface. The particular number of apertures  14  shown in  FIG. 1  is for convenience in illustration, a greater number of apertures per unit of table surface area being provided in an actual table. By way of example, in an illustrative table, apertures  14  comprise 0.026 inch diameter holes arrayed in a 0.25 inch by 0.25 inch pattern. Illustrative materials for an apertured supporting surface  12  include polyurethane surface belting material or thin plastic sheet material such as Lexan. Alternatively, a non-apertured material with sufficient porosity to provide a vacuum-creating air flow can be employed, such as the porous material commercially available under the designation POREX. In any event, surface  12  must allow sufficient air flow therethrough while at the same time providing a solid surface on which the sheet material can be cut.  
      A gantry  16  carrying tooling for operating on sheet material, such as a cutter for operating on cloth, is supported by and movable along table  10  in a known manner. Table  10  is supported by a series of vertical legs  20  which rest on a floor or other supporting surface.  
      The developed view of  FIG. 2  shows a series of plenum assemblies  26  located beneath each section of the table top surface  12 . A corresponding series of valved riser assemblies  30 , one for each plenum assembly, is provided for placing each plenum in controlled fluid communication with a pipe or conduit  34  which, in turn, is converted to a blower unit  38 . A pair of end panels  40  and  42  close off the ends of pipe  34  as well as supporting the same, the panels  40 ,  42  being joined to pairs of the table legs  20 .  
      One of the plenum assemblies  26  is shown in detail in  FIG. 3 . The plenum top surface is defined by a rigid sheet  50 , preferably of metal, which is provided with a series of apertures  51 . The particular number of apertures  51  is shown in  FIG. 3  for convenience in illustration. In an actual plenum, a greater number of apertures per unit of table surface area typically is provided, for example apertures of about 0.25 inch diameter closely spaced to allow a substantial flow of air therethrough. Furthermore, various patterns of apertures can be employed. The plenum assembly  26  also includes a base  54  in the form of a rigid sheet, preferably of metal, of substantially the same shape and dimensions of top sheet  50  and preferably of substantially the same thickness. Base  54  is solid with the exception of a central opening (not shown) for connection to a corresponding one of the valved riser assemblies  30  in a manner which will be described. In the completed plenum assembly  26 , top sheet  50  and base  54  are disposed in spaced apart substantially parallel planes.  
      The plenum assembly  26  further includes a supporting framework  60  between top sheet  50  and base  54 . Supporting framework  60  comprises a grid-like arrangement of orthogonally disposed strips each having a series of openings along the length thereof as will be described in further detail presently. The supporting framework  60  is located within a peripheral frame  66  having substantially parallel side members  68  joined to substantially parallel end members  70 . Frame  66  is of rigid material such as metal or plastic and preferably is extruded.  
      The plenum assembly  26  is illustrated in further detail by the partially-completed assembly shown in  FIG. 4 . The upper half as viewed in  FIG. 4  is a completed framework comprising spaced-apart laterally-extending strips  74  which are interconnected with spaced-apart longitudinally extending strips  76  in an orthogonal arrangement. Strips  74  and  76  are stamped or otherwise formed from thin sheet material such as metal or plastic. In the framework illustrated in  FIGS. 3 and 4 , the longitudinal and lateral spacings between strips are substantially equal thereby defining substantially square-shaped open regions between adjacent strips. Each of the strips has a series of closely spaced openings or windows along the length thereof, i.e. the openings  78  in the laterally extending strips  74  and the openings  80  in the longitudinally extending strips  76 . The opposite ends of each of the laterally extending strips  74  abut the frame members  68 , and the opposite ends of each of the longitudinally extending strips  76  abut the frame members  70  in a completed plenum assembly. The laterally extending strips  74  and longitudinally extending strips  76  are interconnected by means of co-operating slits or notches in each of the strips. In the lower half of the assembly as viewed in  FIG. 4 , where only the laterally extending strips are shown, the slits or notches  84  in those strips can be seen. In particular, slits  84  are provided at equally-spaced intervals along the length of each strip, the spacing determining the distance between the longitudinally extending strips. In the arrangement shown, the slits  84  extend from the upper edge of each strip  74  as viewed in  FIG. 4  to a point about halfway down the width of the strip. Co-operating slits are provided in the longitudinally extending strips to provide an interlocked arrangement in a manner which will be described. The completed framework of longitudinally and laterally extending strips may be viewed as an egg carton-like assembly.  
      By virtue of the many openings or windows in the laterally and longitudinally extending strips and the open regions defined by the intersections of the strips, there is provided an air plenum structure with high volume, cross-flow capability. The supporting framework of interlocking strips provides table strength and flatness together with flow capacity. The rigid air plenum structure  26  provides extremely flat surface tolerances for cutting.  
       FIG. 5  is an enlarged view of the upper left-hand corner of the assembly of  FIG. 4  and shows in further detail the structure of the interlocking lateral  74  and longitudinal  76  strips.  FIG. 6  is an enlarged view of the lower left-hand corner of the assembly of  FIG. 4  and shows in further detail the laterally-extending strips  74  including the openings  78  and slits  84  therein.  FIG. 7  shows in detail one of the longitudinally extending strips  76  including the openings  80  and slits  90  therein. The slits  90  are provided at equally spaced intervals along the length of each strip. In the arrangement shown, the slits  90  extend from the bottom edge of each strip  76  as viewed in  FIG. 7  to a point about halfway up the width of the strip. The spacings between slits  90  in strips  76  are equal to the spacings between slits  84  in strips  74  so as to provide the square-shaped open regions between adjacent strips previously described. In assembling the framework, the slits  90  of a longitudinally extending strip  76  are aligned with the series of slits  84  of the plurality of laterally extending strips  74  and then the strip  76  is fitted onto the plurality of strips  74  to provide an interlocked assembly. This is repeated for each of the longitudinally extending strips  76 . This procedure could be done after the laterally extending strips  74  are located within frame  66 , or the framework of strips  74  and  76  could be assembled first and then placed in frame  66  thereafter.  
      By way of example, in an illustrate table, each plenum assembly has a width, measured longitudinally of table  10 , of about 48 inches and a height of about 3 inches. The plenum length, measured laterally of table  10 , is determined by the width of the sheet material being cut or otherwise operated on. A typical plenum length is about 86 inches. Each of the windows or openings  78  and  80  in strips  74  and  76 , respectively, has a size of about 2.5 inches by 2.5 inches. The windows or openings are spaced along the corresponding strips in an arrangement of two windows or openings every 6 inches. Strips  74  are spaced 6 inches from each other and, likewise, strips  76  are spaced 6 inches from each other.  
      The plenum assembly  26  shown in  FIGS. 3-7  is one of a plurality of such assemblies included in the table of the invention. Six such plenum assemblies  26  are shown in the illustrative table  10  of  FIG. 1 , but the actual number will vary depending on the length of a particular table. Each plenum assembly  26  is placed individually in controlled fluid communication with pipe  34 , and thus ultimately with blower unit  38 , by a corresponding valved riser assembly  30 . One such assembly is illustrated in  FIG. 8 . It includes a housing  100  having a peripheral lip  102  which is attached to the base  54  of the corresponding plenum assembly  26  for placing the interior of the plenum assembly in fluid communication with the interior of the riser housing  100 . A movable valve element  104  controls fluid communication between the interior of riser housing  100  and a duct-like structure  106  leading from riser housing  100  to an opening in pipe  34 . The valve element  104  is of the butterfly type, being fixed to a shaft  110  operated by a controlled valve motor  112 . By virtue of the provision of a plurality of plenum assemblies  26  and corresponding valved riser assemblies  30 , table  10  is given the capability to provide vacuum zones for optimizing material-holding capability. All or some of the plenum assemblies  20  can be placed in fluid communication with pipe  34  and blower unit  38  by selective operation of the valved riser assemblies  30 . The combination of plenum assemblies  26 , valved riser assemblies  30 , pipe  34  and blower unit  38  eliminates the prior art plumbing components that created pressure drops in high flow or long length table configurations. By way of example, in an illustrative table, blower  38  can be a 7.5 HP blower. The foregoing illustrative table can operate, for example, at a maximum flow from the pump at 3000 cfm and at a maximum pressure of 18 inches of water.  
       FIGS. 9-11  show in further detail the arrangement for guiding movement of gantry  16  along table  10 . Gantry  16  carries an appropriate tool for operations on the sheet material, such as a cutter, router, drill, marker or the like. As gantry  16  moves longitudinally along table  10 , the tool is moved along gantry  16  and thus laterally of table  10 . Such operation is well-known to those skilled in the art. Gantry  16  is provided with a linear bearing  120  or the like which co-operates with a guide rail  122  which extends along the side of table  10  and is attached to the series of plenum assembly frame members  68  located along the length of table  10 . Gantry  16  is moved along table  10  by engagement between a motor driven gear (not shown) on gantry  16  and a rack  124  which extends along table  10  in spaced relation to guide rail  122 . Rack  124  is attached to one flange of an angle member  126 , the other flange of which is attached to the series of plenum assembly frame members  68  along the length of table  10 . The arrangement of plenum assembly frame members along the length of table  10  provides a convenient and easy attachment of guide racks and rails to the table structure.  
      In the operation of table  10 , a sheet of material on which operations such as cutting are to be performed is placed on the table top overlaying the top surfaces  12  of the plenum structures  26 . Operation of blower  38  draws air through the sheet material, apertures  14 , the plenum framework  60 , risers  30  and through pipe  34  to blower  38 . The high flow at high pressure from around the solid regions or boundaries outlining the openings in the sheet material and then through these openings onto surface  12  and through apertures  14  creates a force to hold down the sheet material on the table top. Gantry  16  can move along the table and the tool carried thereby can operate effectively on the sheet material. The supporting framework  60  of the plenum structures  26  provides table strength and flatness while at the same time having high volume, cross-flow capability. The risers  30  and pipe  34  avoid the losses associated with prior art plumbing arrangements characterized by small passages or openings leading from plenums.  
      It has been determined that not only does the high flow help hold down open/porous materials, but it also provides additional hold-down on the edge of all materials being cut. When cutting, if the cutting blade causes the edge of the material to move or lift, the accuracy will be impacted. In tables heretofore available, the vacuum pressure on the entire table has very little effect on the edge if the edge is lifted, since atmospheric pressure is present at the cutting location. However, if there is a significant air flow velocity under the edge being cut, this velocity will create additional pressure to hold the material edge in place. The foregoing is illustrated in  FIG. 12  which shows sheet material  150  being cut and resting on the air permeable supporting surface  12 ′. A corner  152  of the material is lifted for purposes of illustration. The high velocity air flow under the sheet material is represented by arrows  154 , and the high flow through the surface  12 ′ is represented by the arrows  156 . This velocity can also be amplified by utilizing a cutting surface on the table which consists of a solid material with small holes drilled in it. The smaller the diameter of the holes, the greater the velocity. The foregoing is illustrated in  FIG. 13  wherein components similar to those shown in  FIG. 13  are designated by the same reference numerals, with a prime or double prime indication and wherein the holes or apertures are designated  14 ′.  
       FIG. 14  shows a table  10 ′ according to the present invention provided with a conveyor for moving the sheet material along the top surface  12 ′″. One of the plenum assemblies has been removed for purposes of illustration. The previously described table legs  20 ′ are part of a frame structure generally designated  160 . The conveyor arrangement can include a pair of end rollers  162 ,  164  at opposite ends of the table and rotatably supported in frame  160 . A series of additional conveyor rollers  166 ,  168 ,  170  and  172  can be provided beneath the series of plenums and rotatably supported in frame  160 . The conveyor belt, a portion of which is shown at  180 , is of suitable air-permeable material, and extends around all the rollers and along the top surface  12 ′″ beneath the sheet material for conveying the material along surface  12 ′″. A suitable conveyor drive arrangement (not shown) would be provided. For a more detailed description of an exemplary conveyor for use in vacuum-hold down apparatus for cutting sheet material, reference may be made to U.S. Pat. No. 6,520,057 issued Feb. 18, 2003 and entitled “Continuous System And Method For Cutting Sheet Material”, the disclosure of which is incorporated by reference.  
      If desired, an overlay of suitable thin sheet material can be placed over the sheet material being cut or otherwise operated on. Such an overlay controls the flow to direct and distribute the air flow across the apertured table top surface. The air permeability of the overlay is the control parameter. The table of the invention is usable with various open weave materials and open cell materials such as open woven cloth and fabric, woven fiberglass, open cell foam material, etc. A variety of tools can be used for operation on the sheet material, such as knives, routers and drills to mention a few. On extremely long tables, the valves in selected risers can be operated to close and shut off sections of the table not in use.  
      It is therefore apparent that the invention accomplishes its intended objectives. While an embodiment of the invention has been described in detail, that has been done for the purpose of illustration, not limitation.