Abstract:
The devices and systems encompass the provision of a plurality of supports specially designed to closely support a work piece immediately adjacent the edge being worked, ground or polished. The top surfaces of the supports are machineable in place on the working table to insure that all are brought to exactly the same height to prevent adjacent supports from creating uneven support and adjacent shear forces. The top members of the supports are a hardened plastic which will not enable the work piece to displace downwardly but which will provide a vacuum downward force. The hardened plastic top of the edge hold down are machineable without losing the ability to act as a vacuum hold down. The shape of the hardened plastic top portions of the edge hold downs are complementary to each other and provide gently interlocking support and can be placed closely enough to eliminate the possibility of any significant amount of work piece area exposure which could produce shear forces. The gently interlocking shape of the edge supports facilitates their arrangement in a shape matching complex edge shapes of the work piece, including sharp corners and the like.

Description:
FIELD OF THE INVENTION 
     The present invention relates to improvements in the field of work piece holding devices for machines. More specifically, the present invention relates to a vacuum hold down device which is machineable upon installation and provides center and edge support needed for working thinner materials, especially for downward beveling grinding forces without failure or with extremely reduced incidence of failure. 
     BACKGROUND OF THE INVENTION 
     In many instances, it is necessary to locate, position and support a work piece which is to be milled, sanded, ground, etc. The precision and stability of the positional device is important, as is the ability to re-position the positional device. Positive location of a work piece is described in U.S. patent application Ser. No. 09/108,792 now U.S. Pat. No. 6,186,567 entitled “Automatic Clamping and Placement Holder” and which describes the use of an air and vacuum driven work piece holder which uses the positioning locator of a milling machine to locate the holder. The Automatic Clamping and Placement Holder works in conjunction with a system described in U.S. Pat. No. 5,562,276 entitled “Locator and Hold Down system for a Machine” which describes an integrated system for using holders. Both of these systems are incorporated herein by reference. 
     Most of the equipment described in the above references is sufficient for work pieces thicker than about 0.5 inches, even where downward forces are applied. For materials which are less than about 0.5 inches and especially for material which is less than 0.25 inches, the support of the material at the situs where the grinding tool operates on the work piece is a severe problem, especially where downward force is used. In larger pieces, support by a series of round vacuum hold downs located 2-3 inches from the outer edge has worked well. 
     In the thicker materials, the forces produced by the grinding tool at the edge of the work piece, are easily resisted in the volume of the work piece extending between the hold down and the worked edge. However, in thinner materials, a work piece support which is spaced 1-2 inches from the edge typically has a material strength that cannot withstand a bending moment on the length of material between the edge and the support. 
     Given the materials cost and the average amount of work time which goes into a work piece at failure, each failure has a significant cost in both materials cost, machine time, and labor required to clean up the breakage debris and re-load the machine. 
     Larger supports are simply not designed for the close-in location and spacing which would be needed to provide the close-in support, at the work piece edge to drastically reduce the material failure during the manufacturing process. Another reason that the larger supports are not utilizable is that their vacuum hold-down capability is usually achieved against a surface which is soft and therefore height variable, as well as frictionally deficient. Most hold downs have isolated circular or rectangular projections to form the support for the work piece. A vacuum is introduced around a cup surrounding the upper periphery of the support. The downward force is generated by the area of the upper periphery of the support which is evacuated, and limited only by the isolated circular projections. The rubber cup provides vacuum within its periphery but it does not provide support, even at its periphery. Thus even where grinding were to occur at the outer edge of a large vacuum support, which would be unadvisable and unsafe and too close to the rubber cup, a downward bending force over a one to two inch length of the material would still exist. Further, since most major supports are round and have a diameter of from about six to eight inches, there would be little coverage available between the main supports along a straight edge. 
     Another problem with close support of a work piece at its edge relates to the need to exactly control the height of closely spaced supports. Where one support is slightly taller or shorter than an adjacent support, the support itself can exert a harmful shear force on the material of the work piece and actually cause it to be more prone to failure during the grinding and polishing operation. 
     What is therefore needed is a support specially formulated to closely support a thin work piece near its edge, eliminating the rubber cut over extension seen in main supports, and which can provide even, secure support to a work piece. 
     SUMMARY OF THE INVENTION 
     The devices and systems of the present invention encompass the provision of a plurality of supports specially designed to closely support a work piece immediately adjacent the edge being worked, ground or polished, but especially an edge which is being beveled or some other type of material process where downward force is applied to the edge of the workpiece. The top surfaces of the supports are machineable in place on the working table to insure that all are brought to exactly the same height to prevent adjacent supports from creating uneven support and adjacent shear forces. The top members of the supports are a hardened plastic, such as polyvinylchloride (PVC), or a super hard rubber, or any other suitable machineable material which will not enable the work piece to displace downwardly but which will provide a vacuum downward force. The hardened plastic top of the edge hold down are machineable without losing the ability to act as a vacuum hold down. The shape of the hardened plastic top portions of the edge hold downs are complementary to each other and provide gently interlocking support and can be placed closely enough to eliminate the possibility of any significant amount of work piece area exposure which could produce shear forces. The smaller supports which are placed closely adjacent each other in conformance to the edge of the work piece provide additional support. In addition, the use of a gently partially interlocking shapes of the edge supports facilitates their arrangement in a shape matching complex edge shapes of the work piece, including sharp corners and the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention, its configuration, construction, and operation will be best further described in the following detailed description, taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a perspective exploded view looking up at a vacuum support of the invention; 
     FIG. 2 is a perspective view looking down on the vacuum support seen in FIG. 1; 
     FIG. 3 is a sectional view of the vacuum support for supporting the edge of a work piece seen in FIGS. 1 &amp; 2 taken along line  3 — 3  of FIG. 2; 
     FIG. 4 is a top view of the supports seen in FIGS. 1-3 and illustrated with different machineable support members having shapes which cooperate and partially interfit with each other including a double concave shape, a round shape and a concave-convex shape; 
     FIG. 5 is a perspective view of a two columnar support operable from vacuum fittings supported by a single one of the columnar supports; 
     FIG. 6 is a bottom perspective view of the support seen in FIG. 5; 
     FIG. 7 is a top view of the support of FIGS. 5 and 6 to show the relative position of the vacuum distribution grooving and top support surfaces on either side of the vacuum distribution grooving; 
     FIG. 8 is a top view of a curved version of a two columnar support similar to the support of FIGS. 5-7 for comparison to FIG. 7; 
     FIG. 9 is a top view of a curved version of a three columnar support similar to the support of FIG. 8; 
     FIG. 10 is a perspective view of a circular support utilizable as a main support for thin work pieces and having a machineable top material having vacuum distribution grooves and an outer rubber cup; 
     FIG. 11 is a bottom view of the support seen in FIG. 10; 
     FIG. 12 is a top view of an edge support similar to that of FIGS. 9 and 7 but in which the machinable edge support member is straight, and for which sits atop columnar members supported by an expanded base to provide additional vacuum holding support; 
     FIG. 13 is a top view of a support having an enlarged base  207  which projects laterally in one direction, and 
     FIG. 14 is a plan view overlooking a work setup shown as a kidney shaped glass piece to be cut or polished about its periphery as a representative of a complex shape and which has a combination of the types and shapes of both main supports and edge supports seen in the previous Figures and employed to conform to the kidney shape to provide closely toleranced holding force for the glass table while it is being worked, machined, polished, etc. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The description and operation of the invention will be best described with reference to prior art FIG. 1, which is a bottom perspective exploded view of an edge vacuum hold down support  21 . Support  21  includes a base  23  having a lower surface  25  including a downwardly directed groove  27  extending about the lower surface  25  adjacent an outer peripheral edge. A pair of through bores  29  and  31  are formed in the base  23  and are useful for facilitating the formation of the support  21 . Bore  31  is sealed off with a simple threaded plug  33 . Bore  29  carries a chamfered surface  35  to accommodate an angled head of a hollow threaded member  37 . Threaded member  37  has an internally located bore  39  which opens into a hexagonal opening  41  used to interfit a hex wrench or the like. A continuous “o” ring (not shown) fits within the downwardly directed groove  27 . 
     At the left, a washer fitting  45  has a rubber inside and a metal outside and fits within a counterbore  47  about a threaded bore  49  of a columnar support  51 . Into the columnar support  51 , a lower threaded aperture  53  supports a threaded hose insertion fitting  53  which is in fluid pressure communication with the threaded bore  49 . An upper threaded aperture  55  supports a threaded hose insertion fitting  57 . In a partial sectional cutaway, the columnar support  51  can be seen as having a threaded bore  59  which is in fluid pressure communication with threaded hose insertion fitting  57 . 
     Above columnar support  51 , another washer fitting  45  underlies a round, re-dressable, machinable vacuum support member  61  having a bore  63 , and a cylindrical side wall  65 . Note that the base  23  is larger in one direction and configured to lend support to the relatively smaller re-dressable, machinable vacuum support member  61 , yet base  23  is configured so that it can be positioned closely adjacent other supports  21  to both avoid interference with the beveling operation and adjacently located supports  21 . The diameter of the re-dressable, machinable vacuum support member  61  is such that it can fit anywhere about an edge of a work piece. The diameter of the re-dressable, machinable vacuum support member  61  is about the same as or larger than the width of the base  23  to enable maximum vacuum holding force of the base  23 . An important aspect of the invention is that the vacuum area of engagement of the base  23  should be larger then vacuum area of engagement of the re-dressable, machinable vacuum support member  61 , but without interfering with the ability to place the supports  21  closely together along the edge of a work piece. Other configurations which meet this requirement are contemplated by the invention disclosed herein. The criticality of the invention For the vast majority of applications of the support  21  of the invention, a simple round machinable vacuum support member  61  will sufficiently support the edge of a work piece under beveling or other conditions where the edge receives downward bearing forces. A further threaded member  37  also having an internally located bore  39  opening into a hexagonal opening  41  is seen. 
     Referring to FIG. 2, a view of the support  21  is seen in assembled position and from an upper perspective. Hoses  67  connect to hose insertion fittings  55  &amp;  57 . Now seen is a top surface  69  of vacuum support member  61 . Between the threaded member  37  and top surface  69 , a chamfered surface  71  is partially seen. The chamfered surface  71  enables the head of threaded member  37  to complementarily engage the vacuum support member  61  and enables the head of the threaded member  37  to seat at a low enough position that there is plenty of material on the machinable vacuum support member  61  to be milled off for leveling several times over the life of the hold down support  21 . If the amount of material removed from the top surface  69  brings the level of the top surface  69  too close to the top of the threaded member  37 , the machinable vacuum support member  61  can simply be replaced by removing the threaded member  37  and adding a new support member  61 . By the same fashion, vacuum support members  61  of other shapes can be interchanged atop the edge vacuum hold down support  21 . However, frequent changing of the support member  61  in close tolerance demanding applications will require a re-milling or re-dressing of the substituted edge support  21 , and frequent interchange is not recommended. 
     Referring to FIG. 3, a side sectional view taken along line  3 — 3  of FIG. 2 illustrates the vacuum hold down edge support  21  with respect to a flat table surface  73  and illustrates an “o” ring  75  located within the downwardly directed groove  27 . The fluid communication between the threaded hose insertion fitting  57  and bottom of the support  21  and between the threaded hose insertion fitting  57  and edge support member  61  is seen. Edge support member  61  is preferably made of a hardened plastic. Since the top surface  69  will be milled to a flat finish and since the edge support  21  typically works in a wet environment, the material of the edge support need not be soft to maintain and vacuum and in fact should rigid to insure that it provides a common level of support with edge supports  21  located next adjacent to it, it must have a constantly even and rigid support capability and to prevent a work piece from deflecting. FIG. 3 also illustrates the flat surface  69  with respect to a milling head which rotates and approaches the surface  69  to perform exacting milling material removal. 
     Referring to FIG. 4 a top view of several of the supports  21  placed side by side illustrate how different shaped edge supports, such as edge support member  61  actually interfit loosely and interact. The use of different shaped edge supports enable a chain-like distribution when viewed from the top. The direction in which the base  23  extends with respect to the columnar support  51  is also optional, and dictated by the space available on a work table. In FIG. 4, the support  21  having edge support member  61  is seen in the middle. Adjacent and to the left is a support  21  having a machineable vacuum support member  77  having pair of oppositely oriented parallel side surfaces  79  and  81 , as well as a pair of oppositely oriented concave side surfaces  83  and  85 . The top surface of member  77  is still referred to with the numeral  69 . Round edge support  61  has a cylindrical side surface  65  which complementarily fits adjacent to concave surface  85  of edge support member  77 . To the extent that there is some overlap, not of the edge supports member  61  and  77 , but of a crossing of a line between adjacent supports  21 , an edge of a material to be worked at a given point may be supported by two edge supports member  61  and  77 . 
     To the right of support member  61  is a support  21  having an edge support  89  having a pair of parallel sides  91  and  93 , and a concave curved side  95  opposite a convex curved side  97 . Convex curved side  97  has about the same curvature as the round side of support member  61  and can complementarily fit against side  65  of support member  61 . 
     Referring to FIG. 5 a corner shaped support member  99  has a pair of concave curved side surfaces  95  which are angled approximately 90° apart. A pair of flat sides  79 , as were seen in FIG.  4 ,are also oriented at 90° apart. The orientation of the support member  99  can be rotationally varied with respect to the base  23  where necessary. Support  21  having support member  99  in combination with a pair of supports  21  having support members  99  can provide a general corner support which can provide slightly more interstitital support than a set of three supports  21  having support members  61 . 
     Referring to FIG. 6, a support  101  having two columnar supports  103  and  105  on a base  107  illustrates that only one columnar support, in this case columnar support  103  is necessary to supply vacuum both downwardly to hold the support  101  down, and upwardly to hold the work piece in place. An upper fitting  111  is in vacuum communication with hexagonal opening  41  of hollow threaded member  37 . A lower fitting  113  is in vacuum communication with the bottom of base  107  in the same manner as that seen for support  21 . At the top of the columnar supports  103  and  105 , a common plate  115  evenly supports a long edge support  117  having chamfered surfaces  119  leading to openings, one of which accommodates hollow threaded member  37  which sits atop columnar support  103 . A solid bodied threaded member  121  sits atop columnar support  105 . No vacuum is pressurably transmitted through columnar support  105 . A vacuum distribution groove  123  extends into the chamfered surfaces  119  to enable vacuum developed at the hollow threaded member  37  to be distributed to the area over the solid bodied threaded member  121 . A top support surface  125  lies within the vacuum distribution structures  119  and  123 , while a top support surface  127  lies peripherally outside of vacuum distribution structures  119  and  123 . Thus, the top surface area of long edge support  117  is either providing a space in which vacuum is distributed or a surface which is utilized by a work piece to gather edge support. 
     Referring to FIG. 7, a bottom perspective of the support  101  illustrates that at the bottom, the hollow threaded member  37  is all that is necessary to introduce a source of vacuum from the lower fitting  113  into the space bounded by the “o” ring  83 . Beneath columnar support  105 , the solid bodied threaded member  121  is used. 
     Referring to FIG. 8, a top reduced view of support  101  is seen. Referring to FIG. 9, a top reduced view of a curving support  131  is seen, with the same top surface features, but having a curved shape, including a gently curved long edge support  133 . Although not seen in FIG. 8, the structures corresponding to the common plate  115  and base  107  of FIG. 6 are similarly curved with respect to support  131 . 
     Similarly, and referring to FIG. 10 a top reduced view of support  141  which is gently curving as was support  131 , but having three columnar supports (not seen) is seen. A gently curved long edge support  143  is seen. Again, only one of the columnar supports nee be available to supply a source of vacuum to the bottom of the base and top of the gently curved long edge support  143 . Only one hollow threaded member  37  need be present. The other structures of the gently curved long edge support  143  are numbered in accord with that seen in FIG. 9. A similar support as that seen for support  141  could be made with a straight shape as was seen in FIG. 7 for support  101 , but with three columns. Other multiple column and multiple shapes are possible. 
     As has been recited, the hold downs for thin work pieces which are not of exacting common heights will create :problems. A hold down with a reduced frictional area can introduce unwanted slip for a given level of friction in the material. A hold down which has a support height which is not precise could on its own create breakage of material. A main hold down is usually placed near the center or a series of centroid locations of the work piece. It is usually meant to stabilize the work piece, but where edge supports are employed, a central support which is not similarly machined to similar tolerances could create breakage problems. Further, even where milling of the modest area portions of the main hold downs is possible, simple downward pressure at the middle of a work piece is not likely to provide the necessary resistance to movement especially needed by a thin work piece. 
     Referring to FIG. 11, a central support  151  includes a base  153 , columnar supports  155 ,  157 ,  159  and member  61  arranged in a square pattern. Columnar support  155  supports a lower threaded hose insertion fitting  163  and an upper threaded hose insertion fitting  165 . Columnar supports  155 ,  157 ,  159  and member  61  support an upper support plate  167  having a space  169  into which a plate  171  fits. Plate  171  has a thickness of machineable material  173  adhered thereto. 
     Machineable material  173 , which preferably is a very hard rubber material, includes vacuum distribution channels  175  connecting four main apertures  177  in the machineable material  173  which overlie 4 chamfered apertures in the plate  171  for engagement with three solid bodied threaded member  121  and one hollow threaded member  37 . The upper support plate  167  is surrounded by an over fitting rubber cup  181  which sits generally lower than the machineable material  173  in order that vacuum may be effectively transmitted to it through the radially positioned vacuum distribution channels  175 . A raised rim  183  about the outermost periphery of the rubber cup  181  is positioned to engage a work piece, seal against it and provide a peripheral seal against air entering the cup  181 . Since nearly all of the area within the raised rim  183  is evacuated, a large downward force is produced. The machineable material  173  includes a relatively large area including a main central expanse  185  and a series of curved expanses  187 . Expanses  185  and  187  provide the surface area of friction and proper machined height to hold a work piece level in immovable. In the machining operation, the removable cup  181  is removed, especially since its rim  183  typically rests in an upwardly urged position. 
     Referring go FIG. 12, a bottom view of support  151  illustrates a bottom surface  191  with four chamfered apertures  193  into which fit three solid bodied threaded member  121  and one hollow threaded member  37 . A peripherally extending “o” ring  193  rests within a groove  195  to provide a seal to enable vacuum introduced through the hollow threaded member  37  to hold the support  151  down to a work table surface. 
     Referring to FIG. 13, a support  201  has a straight edge support  203 , and vacuum distribution grooves  205 . However, support  201  has an enlarged base  207  which projects laterally in one direction. Enlarged base  207  is nothing more than an expansion to provide increased resistance to pushing of a work piece. Although shown generally as rectangular, the support  201  could have an overall curvature, along with a curvature of the edge support  203   
     Referring to FIG. 14, a top view looking down onto a working surface  81  illustrates a typical set up for beveling the edge of a kidney shaped glass work piece  211  shown over a motley selection of supports assembled to follow as closely as possible to the edge of the glass work piece  211 . All of the supports  21  may have round support member  61 . To illustrate, a significant part of the periphery of the kidney shaped glass work piece  211  is supported solely by round support members  61 . The vacuum hoses  73  are eliminated, as are a more detailed numbering which would obscure FIG. 13 if all of the structures shown were numbered. Larger units, such as support  141  and  131  should be utilized where possible for ease of positioning and reduced handling of the relatively smaller supports  21 . 
     While the present invention has been described in terms of a device and system used in conjunction with securing work pieces for all types of process machinery, and in particular with machinery for the milling, edging and machining of materials including glass, granite, marble, stone, and the like, one skilled in the art will realize that the structure and techniques of the present invention can be applied to many appliances. The present invention may be applied in any situation where the position of relatively less thick work pieces is desired to be precisely secured to reduce breakage and to reduce lost time. 
     Although the invention has been derived with reference to particular illustrative embodiments thereof, many changes and modifications of the invention may become apparent to those skilled in the art without departing from the spirit and scope of the invention. Therefore, included within the patent warranted hereon are all such changes and modifications as may reasonably and properly be included within the scope of this contribution to the art.