METHOD FOR MAKING A DIAL TABLE

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

[0001] This patent application claims the benefit of U.S. Provisional Patent Application No. 60/659,262, filed March 7, 2005.

FIELD OF THE INVENTION

[0002] This invention generally relates to techniques for constructing a dial table and, in particular, a technique for constructing a carbon fiber dial table.

BACKGROUND OF THE INVENTION

[0003] Dial tables are commonly used in assembly manufacturing. The dial table effectively holds pieces of everyday items (e.g., printed circuit boards, tooling bits, and the like) while machines above the dial table perform tasks on those items. To make the process more efficient, each time a particular task is performed by a certain machine, the dial table is rotated such that another machine can perform a different task on the item. This sequential process of working on an item and rotating the dial table can be continued a number of times, depending on how many workstations are provided to the dial table.

[0004] Conventional dial tables can be three, four, five, and up to twelve feet in diameter and range from several inches to more than a foot in thickness. Unfortunately, because dial tables that are used in the manufacturing industry are predominately formed from steel, aluminum, and other metals, the dial tables are extremely heavy and very expensive. Thus, a dial table that is lighter and less expensive than the conventional steel or aluminum dial table, yet comparably strong, would be desirable. The invention provides such a dial table. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.

BRIEF SUMMARY OF THE INVENTION

[0005] In one aspect, the invention provides a dial table comprising a top assembly, a base assembly, a foam layout, and a resin. The top assembly includes a first segmented carbon fiber layout therein and the base assembly includes a second segmented carbon fiber layout therein. The foam layout is interposed between the base assembly and the top assembly. The resin is infused into the base assembly, the top assembly, and the foam layout.

[0006] In another aspect, the invention provides a method of making a dial table. A foam layout is interposed between a base assembly and a top assembly to form a composite layout. The base assembly includes a first segmented carbon fiber layout therein and the top assembly includes a second segmented carbon fiber layout therein. A caul plate is placed adjacent to the composite layout. The caul plate includes a plurality of caul plate apertures. A vacuum is generated proximate the composite layout. A resin is drawn through the plurality of caul plate apertures using the generated vacuum until the composite layout is infused with the resin. The caul plate is removed from adjacent the composite layout. The resin-infused composite layout is cured thereby forming the dial table.

[0007] In yet another aspect, a method of making a dial table is provided. Selected ones of a plurality of carbon fiber segments are arranged to form a first segmented carbon fiber layout. The first segmented carbon fiber layout is interposed between first and second glass cloth layouts to form a base assembly. Selected ones of a plurality of carbon fiber segments are arranged to form a second segmented carbon fiber layout. The second segmented carbon fiber layout is interposed between third and fourth glass cloth layouts to form a top assembly. The top assembly, the foam layout, and the base assembly are sequentially placed into a mold such that the foam layout is interposed between the top assembly and the bottom assembly to form a composite layout. A caul plate is placed adjacent to the composite layout. The caul plate includes a plurality of caul plate apertures. A vacuum is generated proximate the composite layout. A resin is drawn through the plurality of caul plate apertures using the generated vacuum until the composite layout is infused with the resin. The caul plate is removed from proximate the composite layout. The resin-infused composite layout is baked thereby curing the resin and forming the dial table.

[0008] Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention, hi the drawings:

[0010] FIG. 1 is a side elevation view of an exemplary embodiment of a composite dial table constructed in accordance with the teachings of the present invention;

[0011] FIG. 2 is a top plan view of a carbon fiber segment template used in constructing the dial table of FIG. 1;

[0012] FIG. 3 is top plan view of the template of FIG. 2 placed upon unidirectional carbon fiber fabric;

[0013] FIG. 4 is a top plan view of one of a plurality of carbon fiber segments used in the dial table of FIG. 1 and made with the carbon fiber segment template of FIG. 2;

[0014] FIG. 5 is a top plan view of a plurality of glass-cloth layouts used in the dial table of FIG. 1;

[0015] FIG. 6 is a top plan view of a plurality of carbon twill weave layouts used in the dial table of FIG. 1;

[0016] FIG. 7 is a top plan view of a capping strip used in the dial table of FIG. 1;

[0017] FIG. 8 is a side elevation view of a base assembly constructed from the carbon fiber segments of FIG. 4, the glass cloth layouts of FIG. 5, and a carbon twill weave layout of FIG. 6;

[0018] FIG. 9 is a top plan view of a carbon fiber segment layer formed using the carbon fiber segments of FIG. 4;

[0019] FIG. 10 is a fragmentary perspective view of two of the carbon fiber layers of FIG. 9 stacked upon each other;

[0020] FIG. 11 is a side elevation view of a top assembly constructed from the carbon fiber segments of FIG. 4, the glass cloth layouts of FIG. 5, and a carbon twill weave layout of FIG. 6;

[0021] FIG. 12 is a top plan view of the top assembly of FIG. 11 with a plurality of serrating cuts therein;

[0022] FIG. 13 is a side elevation view of a foam layout used in the dial table of FIG. 1, the foam layout having the capping strip of FIG. 7 thereon and including a plurality of infusion slots and holes therein;

[0023] FIG. 14 is a top plan view of a caul plate used in the construction of the dial table of FIG. 1;

[0024] FIG. 15 is a top plan view of another embodiment of a caul plate used in the construction of the dial table of FIG. 1;

[0025] FIG. 16 is a side elevation view of a mold or mold arrangement used to construct the dial table of FIG. 1, the mold having a washer and a sleeve therein;

[0026] FIG. 17 is a front elevation view of the sleeve of FIG. 16, the sleeve forming a part of the dial table of FIG. 1;

[0027] FIG. 18 is a side elevation view of the top assembly of FIG. 11 in the mold of FIG 16 and upon the washer of illustrated in FIG. 16;

[0028] FIG. 19 is a side elevation view of the foam layout of FIG. 13 stacked upon the top assembly of FIG. 18;

[0029] FIG. 20 is a side elevation view the base assembly of FIG. 8 stacked upon the foam layout of FIG. 18 and a peripheral portion of the top assembly folded over a peripheral portion of the base assembly to form a composite layout, the base assembly including another washer thereon;

[0030] FIG. 21 is a side elevation view of a caul plate from either of FIGS. 14-15 placed over the composite layout of FIG. 20, a resin deliver device placed over the caul plate, and a vacuum producing device placed proximate a central aperture in the composite layout; and

[0031] FIG. 22 is a perspective view of the arrangement detailed in FIG 21.

[0032] While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

[0033] Referring to FIG. 1, a composite dial table 10 is illustrated. In the exemplary embodiment of FIG. 1, the composite dial table comprises a top assembly 12, a foam layout 14, a capping strip 16, a base assembly 18, washers 20, 22, a sleeve 24. The dial table also includes therein a central aperture 26. The composite dial table 10, otherwise known as a Basic Carbon Dial Table (BCDT), is preferably annularly-shaped. As such, the composite dial table can, for example, have a diameter of between six inches and twelve feet and an approximate thickness of one or several inches. The composite dial table 10 of FIG. 1 is assembled and constructed as outlined by the following paragraphs.

[0034] To begin the process of making the dial table 10, a generally triangular template 28 as shown in FIG. 2 is provided. In a preferred embodiment, the template 28 resembles an isosceles triangle having an acute angle 30 that forms an outer edge 32. In one embodiment, the acute angle 30 is approximately ten degrees. However, depending on the size of the dial table 10, the eventual use of the dial table, and other such considerations, the acute angle 30 can be varied from ten degrees. For example, when constructing a dial table 10 having a diameter of about six inches, the acute angle 30 of the template 28 will be about two to three degrees. Likewise, when manufacturing a dial table 10 having a diameter of ten feet or more, the acute angle 30 of the template will be about twenty-five degrees. Therefore, as the overall size of the dial table 10 increases, the acute angle 30 also generally increases in size.

[0035] The outer edge 32 can be straight or can be arcuate, beveled, and the like as shown in FIG. 2. Moving to FIG. 3, the template 28 is placed over a carbon fiber fabric 34. In a preferred embodiment, the carbon fiber fabric 34 is "unidirectional" or "single- direction" fabric as known in the art. In an exemplary embodiment, the carbon fiber fabric 34 is Zoltek PANEX ^® carbon fiber fabric commercially available from Zoltek Corporation of St. Louis, Missouri. As illustrated, when the template 28 is laid upon or placed proximate to the carbon fiber fabric 34, the apex 36 of the template 28 is aligned with the fiber orientation arrows 38 and generally points in the same direction as the lower of the two fiber direction arrows 38 as oriented in FIG. 3. In other words, the unidirectional carbon fibers 40 are generally transverse to the outer edge 32 when that edge is straight.

[0036] After appropriately positioning the template 28 over the carbon fiber fabric 34, a number of carbon fiber segments 42 are cut or formed using the template. In a preferred embodiment, since the acute angle 30 is ten degrees, a total of thirty-six carbon fiber

segments 42 are made for use within the top assembly 12 such that, by suitably arranging the segments, a complete three hundred sixty degree circle can be formed. In similar fashion, an additional thirty-six of the carbon fiber segments, having an acute angle 30 of ten degrees, are made for use within the base assembly 18. Again, if the additional thirty- six segments are suitably arranged, a further complete three hundred sixty degree circle can be formed from these segments. If desired, numerous further segments 42 can be formed using template 28. Additionally, other segments possessing some other angle can be cut or formed using another template. Notably, as illustrated in FIG. 4, the orientation of the unidirectional fibers 40 is preferably approximately radial with respect to the apex 44 of the individual carbon fiber segment 42 as depicted in FIG. 4.

[0037] Next, as shown in FIG. 5, a plurality of round discs 46 are cut or formed from a carbon fiber fabric 48. In a preferred embodiment, five discs 46 are fashioned from a bidirectional carbon fiber fabric such as, for example, glass-cloth. In an exemplary embodiment, the carbon fiber fabric 48 is a Hexcel Plain Weave Volan Glass-Cloth fabric commercially available from Hexcel Corporation of Pleasanton, California, hi a further preferred embodiment, each of the washers 20, 22 and the sleeve 24 (FIG. 1) are also formed from a carbon fiber fabric. In this further embodiment, the carbon fiber fabric, like above, can comprise a glass-cloth carbon fiber fabric such as, for example, the Hexcel Plain Weave Volan Glass-Cloth fabric.

[0038] Referring now to FIG. 6, once again, a plurality of discs 50 are cut from a carbon fiber fabric 52. In a preferred embodiment, two of the discs 50 are fashioned from a carbon fiber fabric 52 such as, for example, a carbon fiber twill weave (a.k.a., carbon fiber twill) that is commercially available from several manufacturers.

[0039] Next, as shown in FIG. 7, a capping strip 16 is fashioned from, for example, a carbon fiber fabric 56. In preferred embodiment, the carbon fiber fabric 56 used for the capping strip 16 is the Zoltek PANEX ^® carbon fiber fabric. The capping strip 16 has a length that corresponds to and generally follows along with the periphery of the composite dial table 10 as will be more fully explained below. The capping strip 16 also has a width that is approximately the same as the thickness of the foam layout 14 which, in the embodiment of FIG. 1, is approximately one inch.

[0040] Each of the carbon fiber segments 42, the plurality of discs 46, the plurality of discs 50, and the capping strip 16 all have small thicknesses compared to the foam layout 14. For example, in an exemplary embodiment, while the foam layout 14 has a thickness of approximately one inch (1.0"), each of the carbon fiber segments 42 has a thickness of approximately twenty-three thousandths of an inch (0.023"), each of the glass-cloth discs 46

has a dry thickness of approximately six thousandths of an inch (0.006"), each of the carbon fiber twill weave discs 50 has a dry thickness of about six thousandths of an inch (0.006"), and the carbon fiber capping strip 16 has an approximate dry thickness of twenty-two thousandths of an inch (0.022"). Despite the large dry thickness disparity between the carbon fiber segments 42, the layers 46, 50, and the capping strip 16 in relation to the dry thickness of the foam layout 14, to aid in the illustration and understanding of the invention, the dry thickness of the fiber layers has been exaggerated in the drawing figures.

[0041] To construct the base assembly 18 of FIG. 1 , the plurality of carbon fiber segments 42 are arranged into a carbon fiber segment layer 60 and placed upon, adjacent to, and/or proximate one of the plurality of glass-cloth discs 46 as shown in FIG. 8. The carbon fiber segments are, in a preferred embodiment, arranged as generally shown in FIG. 9 with the carbon fibers 40 extending in a generally radial direction. As illustrated, the carbon fiber segments 42 are assembled such that their respective outer edges 32 form a generally constant periphery and their respective apexes all meet at a central point 58. Therefore, the carbon fiber segments 42 form a carbon fiber segment layer 60. In an exemplary embodiment, to maintain the position of adjacent carbon fiber segments 42 relative to each other when those segments are assembled as the carbon fiber segment layer 60 and placed upon the glass-cloth layer 46, an adhesive is employed. In a preferred embodiment, a weak spray adhesive is employed for this task. The weak adhesive, which is applied to one or more edge 62 of the plurality of carbon fiber segments 42, has little bonding strength compared to a resin (which is more fully described below). Even so, the weak adhesive provides enough support to the carbon fiber segment layer 60 to permit the layer to be transported and to keep the individual segments 42 from moving relative to each other. In an exemplary embodiment, an AIRTAC II rubber spray adhesive, which is commercially available from AirTech, Inc., of Huntington Beach, California, is employed for this purpose.

[0042] In one embodiment, as shown in FIG. 10, two or more of the carbon fiber segment layers 60, 60' are stacked upon and/or placed adjacent and proximate to each other. For instance, when a dial table 10 having a diameter of about four feet is constructed, two of the segment layers 60, 60' are stacked together. Similarly, when a dial table 10 having a diameter of about six feet is made, three of the segment layers are employed. Likewise, when a dial table 10 having a diameter of about ten feet is formed, six of the segment layers can be used. Generally, as the diameter of the dial table 10 increases, so to does the number of stacked segment layers used in that dial table.

[0043] Since each of the carbon fiber segments 42 is, in an earlier mentioned preferred embodiment approximately ten degrees, it is correspondingly preferable that the stacked

carbon fiber segment layers 60, 60' are offset about five degrees or about two and a half degrees. The exact amount of offset can be adjusted to a variety of differing degrees. As will be recognized by those skilled in the art, such offset can depend on the number of carbon fiber segment layers 60, 60' that are arranged in this fashion, the acute angle 30 of each of the carbon fiber segments 42, the diameter of the dial table 10, and the like.

[0044] Referring back to FIG. 8, after the carbon fiber segments 42 have been assembled into a carbon fiber segment layer 60 (or layers 60, 60'), the layer or layers are preferably placed on the glass-cloth disc 46. Hereinafter, for clarity, a single carbon fiber segment layer 60 will be referenced despite multiple layers (e.g., 60, 60', and the like) being employable. After the layer 60 is placed on the disc 46, one of the carbon fiber twill discs 50 is stacked upon and/or adjacent to the carbon fiber segment layer 60. Continuing, a further glass cloth disc 46 is placed upon and/or adjacent to the carbon fiber twill disc 50. hi other words, the carbon fiber segment layer 60 and the carbon fiber twill disc 50 are interposed between two of the glass-cloth discs 46. Thereafter, a base aperture 64 is formed through the stacked layers as shown in FIG. 8 to complete the base assembly 18.

[0045] After the base assembly 18 is constructed, the same or similar procedure is employed to form the top assembly 12 as shown in FIG. 11. While the base assembly 18 and top assembly 12 are, or can be, quite similar, in a preferred embodiment, the top surface assembly has a larger overall diameter. The top surface assembly 12 includes top aperture 66.

[0046] After the top surface assembly is constructed, a plurality of serrating cuts 68 are formed in the top assembly 12. These serrating cuts 68 are generally oriented radially inwardly toward the center of the top assembly 12. hi a preferred embodiment, seventeen of these serrating cuts are formed around a top assembly periphery 70, are angled slightly so as not to be oriented directly radially inwardly, and are about one inch (1.0") deep.

[0047] Referring to FIG. 13, the foam layout 14 is illustrated. The foam layout 14 includes a pair of opposing recesses 72, 74, and a central aperture 76. The recesses 72, 74, are formed in the foam layout 14 and dimensioned to receive and/or accommodate the washers 20, 22 as shown in FIG. 1. Preferably, the foam layout 14 also includes a plurality of resin infusion promoting features 78 such as infusion slots 80 and infusion holes 82. Likewise, in a preferred embodiment, a radius portion 84 is formed upon the foam layout 14 proximate the foam layout periphery 86 such that the foam layout has smooth, rounded ends. After the recesses 72, 74 and aperture 76 have been formed, the capping strip 16 (FIG. 7) is adhered to the foam layout 14 proximate the foam layout periphery 86.

[0048] The foam layout 14 can, if desired, be formed from a single large piece of foam. However, since the composite dial table can be several feet in diameter, the foam layout 14 must often be manufactured and/or assembled from several smaller pieces or portions of foam that are either stacked upon each other and/or placed side-by-side to attain a desired thickness, height, and/or width for the foam layout 14. In one embodiment, two or more portions of foam, having a glass scrim covering one surface, are employed to create the foam layout 14. In such an embodiment, foam portions are positioned such that the glass scrim portions are in an abutting relationship. As will be recognized by those skilled in the art, the foam layout 14 can be constructed in a variety of ways and can include materials therein.

[0049] The foam layout 14 can vary in thickness as the diameter of the dial table 10 increases. For example, when a dial table 10 that has a diameter of six inches is made, the foam layout 14 has a thickness of about one-quarter inch (0.25") while when constructing a dial table that has a diameter often feet or more the foam layout has a thickness of about two and a half inches (2.5").

[0050] Referring now to FIG. 14, a caul plate 88 is shown. The caul pate includes central caul plate aperture 90 and a plurality of caul plate apertures 92. The caul plate apertures 92 are disposed proximate a periphery 94 of the caul plate 88 and, in the embodiment illustrated in FIG. 14, are arcuate apertures. As shown in an alternative embodiment in FIG. 15, the caul plate 88' includes central aperture 90', caul plate apertures 92', and periphery 94'. While the caul plate 88' is similar to the caul plate 88, the caul plate apertures 92' as shown in FIG. 15 are circular. The caul plate apertures (e.g., 92, 92') can be sized, dimensioned, and oriented in a variety of different configurations (e.g., oval, rectangular, elliptical, arcuate, and the like) depending on the application and the dial table 10 to be constructed. No matter which configuration of caul plate 88, 88' is chosen, the caul plate is preferably coated with a mold release. In an exemplary embodiment, the mold release applied to the caul plate is CHEMLEASE commercially available from Chem-Trend America of Howell, Michigan. For clarity, hereinafter only caul plate 88 will be referenced.

[0051] Referring now to FIG. 16, a mold 96 for assembling the composite dial table 10 (FIG. 1) is illustrated. As shown in this embodiment, the mold 96 includes a tooling plate 98, a shim 100, and a supporting block 102. The supporting block 102 abuts the shim 100 on one side while a bead 104, preferably a silicon rubber bead, abuts the shim from the other side. A mold release such as, for example, the mold release described above is applied to one or more of the tooling plate 98, the shim 100, the supporting block 102, the

bead 104, and an outer side 106 of the sleeve 24. Thereafter, the washer 20 is placed in the mold 96 such that the washer is proximate to the sleeve 24.

[0052] As shown in FIG. 17, the sleeve 24, on an inner side 108, includes a plurality of infusion grooves 110 and an infusion port 112. In a preferred embodiment, the sleeve 24 includes four infusion grooves 110, each measuring approximately one hundredth of an inch (0.01 "), and four infusion ports 112, each having a diameter of approximately twenty- five hundredths of an inch (0.25").

[0053] As shown in FIG. 18, the top assembly 12 is placed within the mold such that a portion of the top assembly lays over and/or upon the washer 20, abuts and/or is adjacent to the sleeve 24, bends upwardly (as oriented in FIG. 18) at the bead 104 and extends along an inner surface of the shim 100. Thereafter, as shown in FIG. 19, the foam layout 14 is disposed within the mold and, preferably, upon the top assembly 12. Continuing, as shown in FIG. 20, the base assembly 18 is disposed upon the foam layout 14 such that the foam layout is interposed between the top assembly 12 and the base assembly 18. With the foam layout 18 interposed between a top assembly 12 and a base assembly 18, a composite layout 114 is formed.

[0054] In a preferred embodiment, a top assembly periphery portion 116 is folded over a base assembly periphery portion 118. The task of folding is made considerably easier as a result of the serrating cuts 68 (FIG. 12) that were previously formed in the top assembly periphery 70. With the foam layout interposed between the top assembly 12 and the base assembly 18, and the periphery portions 116, 118 engaged with one another, the washer 22 can be disposed upon or adjacent to the base assembly 18. In a preferred embodiment, washer 20 is positioned on the top assembly 12 proximate recess 74 (FIG. 13) of foam layout 14. Likewise, in a preferred embodiment, the washer 22 is disposed on or adjacent to base assembly 18 proximate recess 72 (FIG. 13) of foam layout 14. In this arrangement, each of the washers 20, 22 are generally transverse to, and in abutting relationship with, sleeve 24.

[0055] After assembling the composite layer 114 with the washers 20, 22 and the sleeve 24 thereon, the caul plate 88 (or 88') as shown in FIG. 14 (or FIG. 15), is placed over and/or upon the composite layer 114 such that the caul plate generally extends from the folded over top assembly periphery portion 116 to the washer 22 as shown in FIGS. 21 and 22. Thereafter, a resin delivery device such as, for example, a circular tube 120 is placed on the caul plate 88 such that the caul plate apertures 92 are covered. The resin that the circular tube 120 delivers can be a variety of resins known in the art such as, for example, a room temperature cured resin, a resin that requires baking, and the like.

[0056] After the caul plate 88 and the circular tube 120 have been positioned relative to the composite layout 114, a vacuum producing device 122 is placed in and/or adjacent to central aperture 26 (FIG. 1) that is formed by the outer sides 106 of the sleeve 24. When the vacuum producing device 122 is activated, a vacuum (i.e., a low pressure and/or a negative pressure) is produced proximate the central aperture 26 and, preferably, within the infusion ports 112 and/or infusion grooves 110 in the sleeve 24.

[0057] As and after the vacuum is created, the circular tube is permitted to release the resin such that the resin is introduced into the composite layout 114 and the mold 96 in general via the caul plate apertures 92. In other words, the base assembly 18, the foam layout 14, and the top assembly 12 are infused with the resin. The resin also preferably coats all or a portion of one or more of the washers 20, 22 and the sleeve 24. Because of the low pressure created by the vacuum producing device 122, the resin generally migrates from the circular tube 120 towards the infusion ports 112. In an exemplary embodiment, one or more of the serrating cuts 68 in the top assembly 12, the infusion slots 80 and the infusion holes 82 in the foam layout 14, and the infusion grooves 110 in the sleeve 24 promote distribution of the resin within the composite layout 114 and about the washers 20, 22 and the sleeve 24.

[0058] After a predetermined amount of time and/or after a predetermined amount of the resin has penetrated and/or been infused into the composite layer 114, as well as around the washers 20, 22 and the sleeve 24, each of the caul plate 88, the circular tube 120, and the vacuum producing device 122 is removed. Thereafter, the entire resin-infused assembly (e.g., the composite layout 114, the washers 20, 22, and the sleeve 24) is cured, either in or out of the mold 96, to harden the resin. In a preferred embodiment, the resin is cured by baking. In an exemplary embodiment, the entire assembly is baked for four hours at approximately one hundred fifty degrees Fahrenheit.

[0059] After the resin has been cured and has sufficiently hardened, the assembly can, if not already, be removed from the mold 96. Thus, the composite dial table 10 of FIG. 1 has been constructed. As would be appreciated by those skilled in the art, the dial table 10 can be supplied and/or configured with a plurality of workstations thereon. Likewise, further accessories and/or components can be affixed to or placed upon the dial table 10 so that it can be used in, for example, operations particularly suited to automotive, semiconductor, welding, and other manufacturing industries. Advantageously, the composite dial table 10 has a strength that is comparable to steel and/or aluminum. In particular, the composite dial table 10 has a stiffness in the radial direction that rivals that of steel. However, the

composite dial table 10 is much lighter than steel and, at the present price of steel, much less expensive.

[0060] All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0061] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non- claimed element as essential to the practice of the invention.

[0062] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.