TECHNICAL FIELD

The variable geometry core structure relates generally to structural members and more specifically to core structures capable of supporting loads and distributing stresses in such a manner as to closely approximate stress distribution in a solid panel. Such stress distribution is instrumental in forming a panel of a high strength to weight ratio and has applications in numerous fields of construction. The endeavors in this field usually result in designing a core structure that takes advantage of voids in the interior of a panel to reduce weight while maintaining sufficient and appropriately oriented structures within to distribute the forces to an area of the panel that is more efficient in carrying those forces. The instant invention is in that specific category, but expands its applicability through and by means of the inherent flexibility of the design used.

BACKGROUND ART

Numerous structural members have been provided in prior art that are adapted to support loads and resist stresses. For example, U.S. Patent Nos. 3,086,899; 3,108,924; 3,849,237; 3,906,571; 4,348,442 and more recently 4,495,237 are all illustrative of such prior art. Figge, e.g., with U.S. Patent Number 4,348,442 was speculative in the field, in that it possibly alludes, without definition, to some of the art defined by the instant invention. . While . each of these inventions may be suitable for the particular purpose which they address, they have certain limitations in utility and flexibility. Even U.S. Patent Number 4,495,237, which is held by applicant, does not address the flexibility of the instant invention and it is not apparent from prior art. The flexibility and varied applications made possible by the variable geometry core structure are new. Although the instant invention is to some extent the progeny of all other core structures including the venerable honeycomb, it is not an extension or modification of any of them.

In all prior instances, except U.S. Patent Number

4,495,237, one or more of the properties of the instant invention were omitted. None were capable of assuming global shapes in the finished product. The latter did allude to the ability of of the core structure so described as being capable of forming in such a manner, but did not proceed to incorporate the appropriate design properties for those global shapes.

The unique design criteria for attaining those global shapes will be included in the following sections entitled "Disclosure of Invention" and "Description of the drawings", which will readily point out the unique advantages of the instant invention.

DISCLOSURE OF INVENTION

The primary purpose of the instant invention is to provide a simple and cost effective means of enhancing the strength to weight ratio of a wide variety of materials and using them in the construction of practically all physical shapes. The configurations made possible can be extended to virtually all shapes and may have varying thicknesses across the sections. Another goal of such a consideration is to lower the cost associated with the use of extremely expensive materials in construction, e.g., graphite composites. The instant invention is the embodiment of a geometric concept to attain those engineering goals.

These goals are met by providing a variable geometry core structure which is capable of being formed into each of the desired shapes based on a series of hollow quadrilateral pyramids (described in the following sections) in which the bases, altitudes, face angles, bevels, truncations and channels of the hereinafter described concept may be varied in each individual pyramid provided. The geometry of such a core structure is normally obtained by the "embossment" of the pyramids in a series of rows and columns on each of two sheets forming the core structure in such a manner as to allow the mating of the two panels across the bevels of all pyramids with the truncations attaching at the intersection of the channels between the pyramids. The core structure described is based solely on the geometry obtained. Each individual use

may require any number of different methods of attaining the geometry desired. It must be remembered in all of the descriptions of uses made of the panel, that the features that comprise the core structure may be varied to the extent necessary and as limited by the type of construction used. By use of certain changes of the face angles, base vertex angles, bevels, truncations or channels, other shapes may be formed which do not, at first inspection, appear to meet the criteria of a quadrilateral pyramid, but on deeper inspection do indeed present a special case of such a form, e.g., if the base angle required at one vertex were to become 180 degrees, then the resultant pyramid would be a triangular based pyramid. In the extreme, such variability might lead to a conical shape or the inverse, a star shaped figure. Such figures would produce less than optimum results in all but the most esoteric design, as the embodiment herein described derives a great part of its strength from the combination of a crossed truss and a stressed skin structure. Face angles may be acute or obtuse and bevels or channels may vary in width along the pyramids ' vertices and bases thereby allowing for smoothly curved embodiments. The truncation may also become a concave or convex curve. In certain uses, particularly when ending a panel, the resulting pyramid may assume the form of a dimensionally flat surface.

The single sheet of "embossed" pyramids is inversely mated to a second sheet of pyramids that is designed so as to provide mating between the bevels of each adjacent pyramid. The truncations are normally attached to the channels at the point of intersection between pyramids. The face angles, base dimensions and orientation, as well as the altitude of the pyramids of the opposing panel are determined by the pyramid apex and channel intersection to which each attaches. The structure so formed provides both a stressed skin and truss type reinforcement in the core structure. The stressed skin occurs where the bevels attach and form a skin along the faces of the pyramids to form interlocking "V" channels across the panel approximately normal to each other. The truss type reinforcement occurs along the bevels and is formed in two directions approximately 45 degrees from the stressed skin and

approximately normal to each other. The combination of these stress carrying members result in a high strength to weight ratio, with three dimensional stability and a decreased effect of local failure on the overall structure formed. The bases of the pyramids may take on certain required curvature so that the core may be evenly bonded to one or more sheets used for surfacing the entire panel so as to provide a continuous and smooth surface for the desired shape, and to provide additional stress carrying capability.

Further investigation shows that the panel has the attribute of continuation, meaning that by attaching the next series of pyramids to the preceding set, large panels can be formed f om a number of smaller ones. Although this attribute is of particular importance in the case of a flat uniform thickness panel, it is applicable to any shape. It is also particularly important in the formation of objects comprising or similar to spherical shapes, in that the inherent problems of converting such a shape to a two dimensional embodiment make it practically impossible to form the desired shape in one series of core structures without undesirable distortions and loss of strength. One of the simplest means of overcoming this limitation is to produce the spherical structure in a minimum of six pieces, and then join them by means of continuation as described below. The larger the spherical like shape being constructed (in relation to its thickness), the larger the number of separate panels, joined in continuation, may be desired. It must be remembered that only certain combinations of numbers of pyramids can be appropriately fitted in the continuation and for many applications great care must be taken to ensure the correct configuration of the pyramids. Such choices are left to the engineer, as proposing every possible case would be tiresome and of no benefit to the instant disclosure.

Orientation of the rows and columns of the pyramids will be frequently at 45 degrees to what would be considered to be a normal orientation of rows and columns in prior attempts at a strong core structure. The reasons are not evident other than through close inspection based upon the teachings of this description. Where such panels are to be used in suspended

horizontal construction, such an orientation will aid in controlling the resulting shear forces. Corner attachment becomes much simpler in multi-dimensional uses of adjoining construction panels and such an orientation facilitates the ending of a panel in a solid manner without resorting to some of the more difficult and less efficient, albeit cheaper, manners of so doing. The foregoing specifically relates, inter alia, to the ease of simply placing a continuous planar sheet at the corner attachment surface and attaching each panel to it. The requirements of orientation of the rows and columns may be of the utmost concern where loading is discontinuous and may vary from the 45 or 90 degree arrangement in various applications. Further, the rows and columns may vary from the basic orientation of being normal to each other, e.g., a diamond-like configuration of the pyramidal base pattern may be desirable.

It is desirable and sometimes required that the orientation of the pyramids be changed to another angle. E.g., it is usually more effective and simple to end a panel with a 45 degree orientation, whereas other considerations may require a 90 degree orientation for the rest of the panel. The opposite case is obvious. In such cases, the change in orientation can normally be carried out on separate sets of panels and then "continued" with various panels of diverse sizes. Other uses for change of orientation are too numerous to list, but as one becomes familiar with the particular flexibilities of the panels, it becomes obvious that all are of this generic case.

Other requirements dictate that two or more of . the above described core structures be anchored at angles to each other, with or without separating panels. It is obvious,, in such instances, that the preferred embodiment would be that of having the bases of the pyramids in such multiple members arranged in such a manner as to result in continuation of the stress carrying capacity of the panel along the maximum number of the bevels (trusses) of both panels. However, it must be remembered that continuity of both the stressed skin and the truss arrangement should be followed to the extent possible.

Although flow of fluids or the intrusion of mechanical

ducts through the faces of the pyramids may be required in certain applications, it is necessary to the extent possible to maintain the integrity of the stressed skin. Sections of the panel taken at practically any angle will reveal complex stress carrying paths and discontinuities may be critical and result in the success or failure of the panel in its desired application. The crossed stressed skin structure carries the loading along the trusses in all directions and. therefore care should be taken to ensure that sufficient integrity remains. The crossed trusses likewise reinforce the stressed skin component.

It should be noted that the core structure merely provides the means by which forces are transmitted to the surface or surfaces of the panel being formed. In certain instances it is apparent that no extra surfacing panel is necessary. In others, one or two panels are required for facing the core structure. Other applications require the use of multiple layers of the core structure of possibly varying shapes and which may or may not be separated by other surfacing panels. Some applications may require the use of compressible or non-compressible materials inserted in the voids. One envisioned use would require that the voids be filled with helium. Still other uses may dictate that a series of "shells" be constructed and each succeeding shell may require different pressures. Such applications would normally be associated with the usage of the core structure in applications in which a large change of pressure between the inside and outside surface must be withstood, e.g., space or deep sea usage. Various methods of separating the shells may be used. Many other uses of these geometric arrangements are possible and the foregoing is only descriptive of the advantages of the variable geometry core structure and in no way should be assumed as definitive of the limits of the applicability of the instant invention.

Depending on the type of material used and the configuration of the finished panel, any type of bonding may be used for the attachment of the sheets of the core as well as the sheet(s) attached to the core to provide the final result (if a requirement) of a smooth surface. Modern bonding

techniques allow the use of different materials for each member of the panel. Most applications do require that complete bonding along the bevels and truncations occurs. The requirements for attachment are more fully discussed in the section entitled "Modes For Carrying Out The Invention".

It is obvious that in certain materials which have no inherent strength in tension, that some other means must be provided that allows the geometry to be used. An inherent feature of mating the pyramids to form a core structure is that in so doing, a tetrahedron is formed in the adjacent hollow spaces. This allows one to use very light weight materials to appropriately form "voids" of the pyramidal and tetrahedronal shapes and attach them to the appropriate reinforcement so as to allow the low tensile strength material to be inserted into the spaces remaining. This approach provides the means of transmitting the compressive forces across the panel so formed and preventing the distortion of the reinforceing material and thereby to enhance and take advantage of the tensile strength of the reinforcement. Such an approach is of particular use when designing long span cementitious type structures, where dead load is particularly a problem.

Another feature of the variable geometry core structure that enhances its flexibility is that the core or any surfacing panel may be varied in thickness as the engineering requirements of the panel being formed dictate, e.g., where extra support is required in mid-span, those variables can be addressed and incorporated to form a structure capable of supporting a larger load at the interface with the column or beam and thereby appropriately overcoming the shear stresses associated with such a configuration. This feature coupled with the curvature allowed by the core structure may also be used to integrate the columns into the overall architectural design for aesthetic purposes. Additional support may be required or desirable in certain usages and the variable geometry core structure is equally applicable to providing a means of forming box channels, "I" beams and other similar support methods. The flexibility of the variable geometry core structure permits such additional reinforcement to take

on other than normally used shapes, e.g., additional support may take on the form of a flowing curve and blend with the architectural effect being sought, without resort to facades covering the stress bearing panels.

In very large structures such as ships, it may be desirable to form the pyramids by means of welding each pyramidal face,truncation,etc. , in place, as the panel is formed. The means of attaching a sufficiently thick skin could take advantage of many currently used methods, such as riveting, or welding as the core structure is built.

Further objects of the variable geometry core structure are to provide a panel that has three dimensional stability which can withstand local failure without probable destruction of the entire panel and of ending the panel in a uniform continuous manner thereby preventing loss of "stiffness" or strength at such terminus.

Corner attachment of the panel is a sometimes difficult task. One method is obvious in that the pyramids may be attached "face to face" , but the inherent stability desired suffers from such a treatment, particularly in uses in which the stresses carried by one panel may be advantageously carried over the "corners". One method of accomplishing this goal is presented in the "Drawings" and description thereof. This is one approach that results in providing two or more stressed skins for direct mating. As with other characteristics of the instant invention, the "corner" does not necessarily mean a square corner or the point of joining flat plates and may prove desirable over continuation in certain applications. This approach is particularly important where the structure must have a large stress carrying capacity at the "corners". This approach will become more apparent in the "Description of the Drawings" and the "Drawings" themselves.

The flexibility of the variable geometry core structure allows an additional capability, namely a method of attaching panels at a mid-point on another panel. The depiction is shown in the "Drawings", and is very close to that of corner attachment in usage and variability. Both structures are normally formed separately and added by means of attachment

through "continuation", except where additional stress carrying constraints are applicable or where only a singl dimensioned structure is contemplated.

It is obvious that one can take the panels formed by the variable geometry core structure and make a larger core structure based on the same principles. Every individual variable geometry core structure may be considered to be a solid panel in its own right, and using the correct formulae to determine its strength will allow it to be used to make progressively larger constructions, e.g., it may be desirable to construct very large ships or rigid airships by using the variable geometry core structure as the basis for a larger variable geometry core structure. The number of repetitions is dictated by the usage.

Toward the accomplishment of the above and related objects, this invention may be embodied in the forms illustrated in the accompanying drawings and their description. Attention is called to the fact that the drawings are illustrative only and that changes may be made in the specific configurations illustrated and described within the scope of the "Claims", and any other obvious embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

As the variable geometry core structure relates to the geometric structure capable of attaining the goals hereinbefore related and thickness of the particular members of the structure and any desired or required skin or surfacing of the core structure is dictated by the particular uses to which the architect or the engineer puts them, the thicknesses, and the depictions of the bevels, channels and truncations of the panels so formed will normally be ommitted except where necessary for clarity.

Details of the Drawings are presented under the sub-title "Modes For Carrying Out The Invention". The figures in the drawings are briefly described as follows:

(a) Figure 1 is an exploded view of the invention in a flat uniform thickness sheet. It is oriented at 45 degrees from the panel edges and shows the preferred embodiment for ending such a construction in a continuous manner.

(b) Figure 2 is an inverted view of the top core sheet taken through the line 2-2 in figure 1, as depicted.

(c) Figure 3 is a top view of the bottom core sheet taken through the line 3-3.

(d) Figure 4 is a cross sectional view taken through the apexes of a row of pyramids in the lower illustrated embossment on line 4-4 in figure 1 showing the invention assembled.

(e) Figure 5 is a cross section view taken through the apexes of a row of pyramids in the upper illustrated embossment on line 5-5 in figure 1 showing the invention assembled.

(f) Figure 6 is a cross sectional view taken on the line 6-6 in figures 4 and 5.

(g) Figures 7 through 11 are depictions of the invention in a 90 degree oriention to the panel edge and correspond to figures 1 through 6, except that figure 9 incorporates the aspects of figures 2 and 3. Figures 8 and 9 additionally depict the normal manner of ending a panel of this orientation. No cross sectional view through plane 11-11 is presented, as figure 6 adequately represents the concept.

(h) Figure 11 is an exploded perspective view of a method of changing from a 90 degree pyramid orientation to a 45 degree orientation.

(i) Figure 12 depicts the embodiment used in a uniform thickness spherical configuration and relates to sheets 12 and 14 in figure 1.

(j) Figures 13 and 14 depict a section and a plan view of a compound curve of variable thickness panel, based on a wing section, and showing the ease with which the opposing sheet of the construction may be derived for any given curvature.

(k) Figure 15 depicts an exploded view of a hypothetical supercritical wing, constructed using the variable geometry core structure.

(1) Figures 16 and 17 depict two methods of mid-panel attachment, useful in many areas where shear forces need to be converted into torsion and then skin stress forces.

(m) Figure 18 depicts corner attachment of the panel in three spatial dimensions, using the 45 degree orientation. It should be obvious that that in use of a 90 degree orientation that the preferred method would be to simply join the pyramids face to face, normally with a strip of material joining them along the line of their attachment for added stability. MODES FOR CARRYING OUT THE INVENTION

Due to the flexibility of the instant invention, including the universality of shapes and configurations attainable, the materials that are adaptable to usage and the applicability of the geometry presented; there is no one best method of carrying out the invention. An effort will be made to present a representative array of possible methods of achieving the goals and capabilities of the variable geometry core structure. Many obvious ones will be omitted. A detailed description of the drawings will be presented at the end of this section, but a general overview of the total concept is necessary prior to that description.

The primary mode for carrying out the invention and the one which has the broadest aplicability is by means of appropriately embossing the required pyramidal shapes of the appropriate geometry in a continuous manner in rows and columns on two sheets of the chosen material and then mating them by appropriate means to form a core structure. The forming is usually done by means of rotary compression forming,vacuum forming or some other means such as an extrusion process. The mating is achieved by the use of appropriate means for the material(s) being used. This could be solvent cements, glues, welding by electrical or other means or attachment in a mechanical manner, e.g., serrations along the bevels of the pyramids formed which would be held in place once the below described skin was installed. Other various means for such bonding will be determined by the materials and usage to which they are put for the core structure, size and configuration of the panel and be dictated by those usages.

The core structure, so constructed, would normally be bonded to at least one sheet and in most instances to two sheets of an appropriate material, thereby attaching a smooth skin to the core. This results in increased strength in most applications and facilitates the utility of the panel formed. It should be noted that certain applications might dictate that each of the core sheets and each of the facing (or surfacing) sheets be made of different materials and of different thicknesses. The variations allowed are only limited by the availability of suitable bonding and forming methods. Further, it should be noted that the panels so formed may contain embossments on the external faces simulating any number of aesthetic effects, e.g., wood grain, rock like embossments and artistic designs such as murals or any other feature that add color or texture to the finished panel.

The construction of very large panels using the foregoing techique will req uire that the aspect of continuation mentioned in the subtitle "Disclosure of Invention" be used to mate succeeding panels in order to provide the size of the product being constructed or to add edge panels as depicted in Figure 7 of the drawings. Many other uses will be obvious for this aspect. It should be remembered that each pyramid is capable of having it's own individual dimensions and the core design can be made to fit the required continuation, whether the configuration of the product panel is curved, flat or of variable thickness. The dimensions of the pyramids at the continuation can therefore be independent of the normal configuration of the pyramids throughout the remaining core structure.

Using this mode of carrying out the invention further allows multiple layers of core structure as described in the "Disclosure of Invention". Multiple layered core structures are particularly important in embodiments of the invention which require good thermal insulation or buoyancy qualities. Further uses of this mode include formation of panels embodying the concept of offset orientation in which adjoining cores would have different orientation of the rows and columns of the pyramids. Use of these methods is not limited to flat plate embodiments.

Another mode of carrying out the invention is to di stamp the individual sheets and mate them appropriately. This mode would normally be reserved for metal like materials, although requirements for precision may make die stamping applicable to other material usage. Formation of complex shapes may also be best carried out using die stamping. An example of such a structure would be the formation of an aircraft wing or wing section. The precision required, the complexity of the design and the reliance on easily calculable strength and aerodynamic properties in structures of this type, demand processes not normally required or attainable by means of other processes.

Other methods of producing the geometry required in sheet material type construction are available and need not be elaborated as their uses would be dictated by the type of structure being produced and the material required. The core structure, inter alia, may be produced by means of rolled thermal molding, rolled extrusions, die casting, injection molding, compression molding, vacuum forming, blow molding, dip forming, accretion of materials to a substrate and any other means developed for the formation of this structure or others. The listing, included in the subtitle "Industrial Applicability", is included for example only and is by no means intended as an exhaustive treatment of the objectives of constructions contemplated.

In all instances of sheet forming, it must be remembered that certain usages may require the introduction of reinforcement, either embedded in the sheet material or placed along and bonded to certain of the individual features of the variable geometry core structure, e.g., reinforcement may be required only along the channels or bevels of some or all of the pyramids in a sheet. Additionally, there may be a requirement for only local reinforcement, as in where exceptional stresses are localized in the panel. Examples are: where a column is required, wall attachment or corners occur, or windows, doors or other openings in the panel are required.

The applicability of the geometry to a cementitious type material or any other material with low tensile strength dictates an entirely different approach, from those described

above, in order to take advantage of the strength to weight ratios - offered by this invention. The "Disclosureof Invention" section provides the mode of construction required to utilize the geometry provided. Basically, such types of materials inherently require the use of reinforcing material to carry the tension loading; then the material itself prevents distortion or deformation of the reinforcing (other than in tension) and carries the compressive and shear forces, with shear and torsional forces being carried to some extent by both. The variable geometry core structure provides a realistic method of constructing such products (which would normally be associated with the building construction industry, including public works such as bridges).

Indeed, in all modes of construction this core structure serves its purposes to some extent by the "V" channel, stressed skin reinforcement providing stability to the trusses and vice-versa. The voids formed in cementitious type construction provide an excellent visualization of the overall concept, even though malleable and high tensile strength material provide many more paths for stress distribution. With this in mind, it becomes readily apparent that the structure formed after appropriate attachment becomes a unified structure with appropriate voids, thereby deleting unnecessary, costly and burdensome material. Again attention is called to the necessity of limiting voids in the faces of the pyramids and tetrahedrons formed by the cementitious material, however, it becomes less critical to the overall strength of the core structure in this usage, due to the type of forces carried by the material.

This feature of the core structure allows the same principle of stress distribution to be used to form a panel of ther relatively heavy yet low tensile strength material, thereby permitting greater free span distance. To accomplish the construction of such a panel, e.g., an elevated parking garage floor, a bridge, a building wall, or even a complex curve shape such a building constructed in the form of a hyperbolic paraboloid; the builder installs within the appropriately designed reinforcing structure, very light weight pyramids and tetrahedrons of the geometry required to void the useless material, while leaving the required space

for the cementitious type material for the transmission o stresses, stabilization of the reinforcement and obtaining o the shape which is desired. It is obvious that th reinforcing cage and the required forms must be able t support themselves and the amount of cementitious materia inserted, until setup has occurred. After installing th required reinforcement, any required mechanical ducts (such a conduits, water pipes, etc.) and light weight voids (ligh weight solidified foam, other light weight solids or hollo construction of some other material may be used, as required), the cementitious type material is then placed in the remainin space and allowed to set up to its final configuration. Panels may be pre-poured, pre-stressed and then post-tensioned as desired. The effects of post-tensioning have not been explored. However, the linearity of performance of test panels indicate that it is feasible to use such a procedure with some modification of the fully formed panel. It may, however, be proven to be more effective to vary the geometry of the core structure than use such an approach.

The surfaces (skin) in such construction may or may not be desired or required. If so, they may be an integral part of the pour and contain their- own reinforcing. Such structures may utilize other types of materials appropriately attached (including those of variable geometry core structure) for such surfacing. The exposed light weight materials may be removed or remain in place, depending on the aesthetics and engineering requirements of the construction. In certain instances, especially where the core structure is to be left exposed or a different type of skin is to be emplaced, it may be desirable to remove the voiding material and reuse it in succeeding forms or later construction. In most uses for horizontal surfaces, the "bottom" surfacing sheet would not be used as the most efficient means of carrying the tension loading is in the internal reinforcement. The cost efficiency factors will be different form any given application and as they dictate the approach in most instances. Any preference of method must be left to the architect, engineer and ultimately to the builder.

In all instances, it must be remembered that the instant invention relates to the geometry of the design and not to

any specifics of manner or mode of construction, although examples are provided thoughout for purposes of visualization and as a means of illuminating the flexibility of the design.

Details of the Drawings

The "Brief Description of the Drawings" and the foregoing are inadequate to present the drawings and concept completely, therefore the following detailed description is included. Reference characters denote similar elements throughout the several views and the several drawings. A number of the drawings are "line" drawings and do not depict the various aspects of bevels, channels, truncations and thicknesses of the sheets as to do so would serve no purpose.

The general depictions shown are as follows. Figures 1 through 10 illustrate various aspects of the variable geometry core structure in a uniform thickness flat panel configuration. They feature the two normal orientations of 45 and 90 degrees in sufficient detail to allow elimination of many drawings of particular embodiments and permit some of the special features to be displayed by means of line ' drawings only. Figure 11 depicts a means of transition from one orientation to another for use in those instances where particular requirements call for different stress carrying capability at different points in the structure. Figure 12 depicts a portion of a uniform thickness spherical structure. It should be easy for one trained in the art to produce any other global shape from that depiction and those of Figures 13 and 14. Figure 13 depicts a section through a panel of variable thickness and curvature. Figure 14 is a plan view of the same panel showing the ease with which the opposing pyramids can be deduced. Figure 15 is an exploded view of a portion of a hypothetical wing - depicting a possible application of the core structure. Figures 16 and 17 show two methods of mid-panel attachment, hereinbefore described. Figure 16 depicts such an attachment for a 45 degree orientation and figure 17 for a 90 degree orientation. Figure 18 is a line drawing of a method of attaching panels of three separate dimensional planes at a common corner. The facing sheets in figure 18 are omitted due to the fact that such attachment should be obvious and it ,is a practical

impossibility of presenting them without destroying an possibility of understanding the attachment.

From these drawings, descriptions and the othe disclosures of this application, it is possible to visualiz the flexibility inherent in the instant invention, perceiv the wide range of usage and extrapolate to most of the usefu embodiments, including the limited listing under "Industria Appplications" .

Figure 1 is illustrative of the general concept, eve though it is limited to a flat plate. It uses various type of pyramids 20 and results in an intergral panel endin without voids. Each sheet 12 and 14 usually has continuou (except as otherwise noted) hollow pyramid shapes 20 embosse in both the longitudinal and latitudinal directions or at 45 degeees thereto with narrow channels 22 between them. Each o the pyramid shapes 20 have slightly beveled edges 24 and a slightly truncated top 26. In most flat, uniform thickness applications, sheet 12 and 14 are identical and sheet 12 can be inverted and mated to sheet 14 along the bevels 24 with the truncations 26 mating at the intersection of opposing channels 29. This is true even when ending the panel in a continuous manner as depicted in figure 1, but care must be taken in design to insure the appropriate number of rows and columns of pyramids 20 are used so that the appropriate size core structure 28 is formed. When used, sheets 16 and 18 are in engagement with the exterior surfaces 30 and 32 formed by the interior channels 22. The resulting panel 10, after appropriate bonding as described above then provides a simple, cost effective means of constructing a high strength to weight ratio panel for any given material used.

Figures 7 through 10 generally relate to figures 1 through 6 with the exceptions that the core structure 28 is not ended in a continuous manner and as sheets 12 and 14 are identical, figure 8 represents figures 2 and 3. Further the figure represented by the plane 11-11 is not shown as it is adequately represented by figure 6. It is noted that although not shown, the primary means of ending a panel such as figure 7 is by means of making one of the sheets 12 or 14 have the outside row of pyramids attain a 90 degree face angle with the opposing sheet wrapping around at that point to form a smooth

core ending.

Figure 11 is particularly representative of the variability of the instant core structure, in that it presents a number of individual pyramids with several of the varying configurations possible under the concept on a two dimensional or flat plate presentation. Primarily, figure 11 presents a method of changing orientations of the pyramidal alignment of the core structure 28 in cases where stresses change at critical areas of the panel. In this depiction, there are five different embodiments of the pyramids used in a flat plane, uniform thickness of the embodiment. When engineering criteria dictate uses other than the 45 and 90 degree orientation presented in the drawings, it should become obvious that the variations can be numerous in a flat plate embodiment. Compound curves and variable thicknesses increase the variation even further.

Figure 12 has already been explained in the lead in to this description, yet it again should be remembered that due to the variability of the concept, the drawing is illustrative only, and meets the same requirements as figure 1, so far as the mating of the various components of the core structure 28 apply.

The importance of figures 13 and 14 to this application is that they together illustrate in an appropriate manner the ease with which the geometry of the opposing sheets 12 and 14 can be determined in attaining the geometry required for successful use of this concept. Numerous details have been omitted as redundent in these drawings.

Figure 15 is a possible embodiment of the Variable Geometry Core Structure. From the detail presented, it should be obvious to one versed in the art, how the various individual constructions of the pyramids and tetrahedrons combine to form the myriad shapes and structures presented.

Figures 16 and 17 should be self explanatory from the introduction to this section. It is obvious that in each case, the mating core structure translates forces from a shear stress to a torsional stress, which in turn is translated into a tension force on the attaching panel. Although these drawings are presented in a perspective in which the panels are presented as being normal to each other, it should be

obvious that a certain degree of latitude in the angula orientation is allowed.

Figure 18 presents the before described "corner", i which three separate dimensional planes meet. Corners, as defined herein need not be of plates normal to each other no of flat plates, but are where a discontinuity arises. typical use would be in the construction of a non-curved containment with high internal forces. As previously stated, only one sheet of each of the core structure is presented due to confusion possible in the drawing. It is obvious that in order to attain this attribute of the core structure, one must resort to the variability of the core structure and in this case arrive at a symetrical arrangement in which each sheet will contain one side with a closed end (180 degree face angle) and the other edge having a normal full quadridlateral base with the bevel angles designed for the appropriate corner angles. Corner attachment of panels having a 90 degree orientation is simply a matter of placing the pyramids of the exterior sheets face to face with an additional flat member of approprita- size placed along the intersections. In a three dimensional embodiment, these approaches work perfectly well, however, when the numbers of sheets meeting at a corner exceed this number, it may be necessary to resort to other aspects of the Variable Geometry Core Structure. E.g., integration of these panels in multi-faceted structures, such as the geodesic dome will require the engineer to use the teachings contained herein to derive the necessary variations in the pyramidal core to attain the optimum mating at said corners. It is obviously impossible to depict all practicle embodiments.

As stated thoughout this treatise, the face angles 36, base vertex angles 38, the pyramid altitude 40, the bevels 24, the channels 22 and the truncations 26 are variable over a wide range to produce the desired structure. The bevels 22 should, to the extent possible, be designed so as to allow a continuous unbroken "V" channel to be formed in each direction to achieve optimum utility. The trusses will then also be formed of the optimum shape (normally a square bar) . The face angles 36 may even become obtuse in certain applications and base vertex angles 38 may become or even exceed 180 degrees. Even though there is, at present, no envisioned use for

exceeding ^' -said 180 degrees, a 180 degree base angle 38 (usually associated with a face angle 36 of 90 degrees) has wide spread use as evidenced by the "Drawings". The channels 22 may require changing width and may assume a curved surface 30 or 32 to accomodate embodiments other than flat plate panels. Likewise, the truncations 26 may require a concave or convex surface to facilitate complete bonding. This feature allows the formation of complex curves of variable thickness. Certain uses may even require that the faces of the individual pyramids assume a slight curvature. To accomodate other engineering requirements associated with the use of the panel, the thickness of any member may also be varied.

Several features of the Variable Geometry Core Structure to which mention has been made, have been omitted from the drawings. Of particular importance is the aspect of continuation and that should be simple to visualize from the word picture. All other allusions to aspects of the core structure herein described, should be obvious to one versed in the art and are thereby omitted from the "Drawings". For instance the ability to increase the local area strength by the simple expediant of increasing the face angles and " the altitude of the pyramids are obvious, as is attaining the same ^' objective by merely increasing the thicknesses of the members comprising the core structure. Other uses and means of accomplishing the end result should be obvious from the word picture contained herein. INDUSTRIAL APPLICABILITY

Due to the fact that the variable geometry pyramidal core structure is specifically presented as a geometric embodiment capable of being formed from a variety of materials and in such usage is further capable of transmitting stresses along numerous paths thereby embodying such structures with enhanced strength to weight ratios over a global range of shapes; industrial applicability is virtually unlimited within the constraints of cost effectiveness and material adaptability.

The following is a brief list of concepts currently being explored by the inventor. It is by no means exhaustive of the possibilities of usage in industry and is presented for illustration only. No particular weight or priority is given to any one usage other than certain applications are less

critical in the sphere of design and are therefore capable of enhancing the learning curve for design and production of machinery and processes for the assembly of the basic structure, and therefore lead to the perfection of more esoteric and exotic uses.

Aircraft Structures

Airships

Automobile Structures

Boats, Canoes and other pleasure craft

Bridges, Fixed and Portable

Cantilevered Construction

Cementitious Type Construction

Construction Requiring Expensive Material

High Strength, Light Weight Doors

Housing

Hydrofoils

Interior Partitions

Light weight Furniture

Long Span Suspended Structures

Oil Drilling Platforms

Packing, Crating and Dunnage for High Value Items

Portable Runways

Railroad Cars

Recreational Vehicles

Ships

Sound and Temperature Insulation

Space Craft and Structures

Stadium Domes

Structures Requiring Variable Geometry

Submersibles

Surface Effect Machines

Truck Beds and Bodies

Underwater Tunnels

Utility Buildings