SANDWICH CONSTRUCTION BUILDING MATERIALS

Abstract: Sandwich construction building materials (10) are produced using conventional facings or plywood, fiberboard, particle board, mineral board, wood, metal, plastic, etc. on both faces (12, 14) of the building material (10), in the inner core (16) therebetween being made from natural wood veneer, veneer made from wood fibers or shavings bound by synthetic resin, etc., shaped into elongate strips (18) of angular, corrugated or undulating configuration or rolled into hollow cylindrical tubes. The strips (18) or tubes may be cut transversely into sections of equal height and assembled proximately or contiguously to form an inner core layer (16) having an openwork pattern. Openwork may be filled with insulation or strengthening materials, and core elements may be coated. The resulting building products (10) may be modular, lightweight, strong and suitable for use as plywood, flooring, walls, beams, joists, trusses and posts.

Description: SANDWICH CONSTRUCTION BUILDING MATERIALS Field of the Invention This invention is concerned with sandwich construction building materials, specifically with novel openwork core layers in sandwich construction building products useful in a broad variety of structural applications. Background of the Invention Sandwich construction building materials have been in use for many years. The "honeycomb" type core sandwiched between two facing elements was developed during the second World War especially for use in aircraft to gain a greater strength- to-weight advantage over solid structural materials. Today, the prior art technology widely employs sheets of cloth, metal and paper as the honeycomb core material formed into various geometric shapes. A broad survey of general prior art practices in structural sandwich technology may be found in "Wood Handbook: Wood as an Engineering Material", prepared by Forest Products Laboratory, Forest Service, U.S. Department of Agriculture, 1988, pages 12-2 through 12-8. The principal object of this invention is to provide novel core layers for sandwich construction building materials of superior strength-to-weight ratios and of wider application at lower cost, using readily available environmentally favorable raw materials. Another object of the invention is to provide sandwich construction building materials of greater adaptability and versatility to be used for flooring, walls, posts, columns, beams, joists, trusses, arches, etc. Summary of the Invention Structural "honeycomb" sandwich construction materials of this invention are faced with conventional outer layers of plywood, metal, plastic, various composition boards, cements and laminations of any combination of these. The central inner core layer within the outer facings is composed of core elements formed from natural wood veneer, veneer formed from wood fibers or shavings combined with synthetic resins, wood shavings, into selected geometric shapes, or formed from bamboo into rings by transverse cutting of branches thereof. When assembled, these core elements are positioned within, and perpendicular to, conventional parallel or encompassing facings, and arranged contiguously or proximately to each other in such a way that the core layer assumes an overall openwork pattern. The core elements may be secured to the outer facing layers into a unitary structural material, and may be reinforced by a synthetic resin-based coating which may contain dispersed fibers therethrough for enhanced strengthening. The core elements may be made from natural or resin-bound wood veneer, preferably with their fibers aligned with their height, shaped into angular, corrugated or undulating shapes, or rolled into hollow tubes, then selectively cut transversely into strips or hollow rings to a height corresponding to the desired thickness of the core layer. Similarly, bamboo stalks may be cut into hollow rings to serve as core elements. Shaped strips arranged in staggered relationship, or hollow tube rings, form the core's openwork or "honeycomb" pattern and may have some or all the geometrically shaped spaces created thereby filled with insulation or strengthening materials (lightweight cement or concrete) during assembly of the structural sandwich construction building material. The resulting building products, varying widely in core thickness, core height and overall strength to meet specific use requirements, may be lightweight, strong, relatively inexpensive, and suitable for use advantageously as modified plywood, flooring, walls trusses, poles, and assembled into beams, joists, posts, columns, structural modules, etc. Brief Description of the Drawings Details of illustrative but not limiting preferred embodiments will now be disclosed and explained in connection with the accompanying drawings, wherein: FIGURE 1 is a top plan view, with parts broken away, of a unit of sandwich construction building material assembled in accordance with this invention; FIGURES 2 and 3 are partial sectional views taken along lines 2-2 and 3-3, respectively, of FIGURE 1; FIGURES 4A, 4B and 4C are diagrammatic plan views of veneer strips shaped into geometric patterns and assembled in the openwork "honeycomb" core layer arrangement of this invention; FIGURE 5 is a plan view partially broken away of another embodiment of the invention, illustrating a finished building material module; FIGURES 6 and 7 are partial sectional views taken through other preferred embodiments; FIGURE 8A is a partial top perspective view of a piece of natural wood veneer in the process of being shaped to form one of the geometric core element configurations of this invention; FIGURE 8B is a partial top perspective view of a veneer formed from wood fibers embedded in synthetic resin; FIGURES 9, 10 and 11 are plan views of hollow wood veneer tubes formed in various ways; FIGURE 12 is a top perspective view of a hollow veneer tube perforated over its entire surface; FIGURE 13 is a top perspective view of a length of bamboo; FIGURE 14 is a top perspective view of an assembly of veneer hollow tubes formed before being cut into core layers; FIGURE 15 is a top perspective view of a coiled wood shaving core element; FIGURE 16 is a sectional view taken transversely through a hollow wood veneer tube, the inner and outer walls of which being lined with fine wire mesh; FIGURE 17 is a partial transverse sectional view taken though a core layer of veneer hollow tube rings filled with cement and surrounded by a circular facing; FIGURE 18 is a partial transverse sectional view taken through a core layer of veneer hollow tube rings with an interposed length of solid wood, the hollow rings being partly filled with insulation; FIGURE 19 is a partial transverse sectional view taken through a core layer of hollow wooden rings positioned in spaced relationship with each other, being held in place by having each end thereof embedded in a layer of lightweight cement; FIGURE 20 is a partial vertical sectional view of the embodiment of FIGURE 19; FIGURE 21 is a top perspective view of the structural module of FIGURE 5; FIGURES 22 and 23 are partial elevational views of horizontal and vertical assemblies, respectively, of modular building units corresponding to the module of FIGURE 21; FIGURE 24 is a partial elevational view of an assembly of arcuate modules forming an arched structure; FIGURE 25 is a vertical sectional view of a truss made in accordance with this invention; and FIGURE 26 is a top plan view of the truss of FIGURE 25. Detailed Description of the Preferred Embodiment The sandwich construction building material 10 shown in FIGURES 1-3 has upper plywood facing 12 and lower plywood facing 14 covering core layer 16, made from longitudinally extending angularly shaped veneer strips 18 coated and secured to each other and to facings 12, 14 by resin adhesive 20. Strips 18 may be of natural wood veneer, veneer formed from wood fibers or shavings in combination with synthetic resin or wood shavings, and are arranged in alternating or staggered nonnesting relationship to each other so that diamond-shaped spaces 22 provide an openwork or "honeycomb" pattern to core layer 16. In FIGURE 4 A, core layer 16a is assembled from wood veneer strips 18a formed into longitudinally extending undulating or corrugated shapes arranged in staggered relationship so that substantially elliptical spaces 22a are generated; FIGURE 4B shows inner core layer 16b with veneer strips 18b shaped in right-angled wave form creating rectangular spaces 22b; and FIGURE 4C's core layer 16c has veneer strips 18c in angled configuration to form hexagonal spaces 22c. Another sandwich construction building material embodiment 24 is shown in FIGURE 5, wherein top facing plywood layer 26 and bottom facing plywood layer 28 cover inner core layer 30. In addition, building material 24 is enclosed by plywood side covers 32 and 34 as well as plywood end covers 36 and 38 to complete a modular unit exemplifying this invention. Core layer 30 here is composed of hollow wood veneer tubes 40, optionally coated with, and attached to, facings 26, 28, sides 32, 34, ends 36, 38, and each other by resin adhesive 42. Tubes 40 create an openwork pattern of circular spaces 44 for core layer 30. FIGURES 6 and 7 illustrate modifications of the building material embodiment of FIGURE 5, each having the same core layer 30 fashioned from tubes 40. In FIGURE 6, facing layers 46 and 48 are laminations of metal sheeting 50 covered with paper outer facing 52; in FIGURE 7, core layer 30 is covered with plastic facing 54 on its upper side, as shown, and with wood facing 56 on its opposite side. Wood veneer sheet 58 in FIGURE 8 A is shown at the start of being bent in the direction of arrow A to form any of the shapes 18, 18a-c, 40 and 40a-c previously described. It may be noted that veneer sheet 58, or any shapes formed therefrom, may be treated by conventional methods at any stage of the formation of the core layers of this invention, to facilitate bending or shaping as well as to provide resistance to fire, moisture, decay and insect attack. FIGURE 8B illustrates veneer 60, formed by embedding wood fibers 62 in synthetic resin matrix 64. Wood fibers 62 are preferably aligned in one direction for greater veneer strength, and may be replaced in the resin-bound veneer by wood shavings. Veneer 60 may be shaped, bent and treated in much the same way as veneer 58 of FIGURE 8 A. Depending on the use and strength requirements of the structural sandwich construction building materials produced from veneers 58 and 60, core elements such as 18, 18a-c, 40 and 40a-d may vary in thickness from less than l/64th inch to more than l/4th inch while the height of these elements, corresponding to the desired thickness of the resulting core layer, may range from l/16th inch to telephone pole height. FIGURES 9-11 illustrate three different ways of adhesively securing veneer 58 or 60 after forming either veneer into a hollow cylindrical tube; in FIGURE 9, tube 40a is joined at butt joint 66; tube 40b of FIGURE 10 is scarf-jointed at 68; and tube 40c of FIGURE 11 is helically wound to form a double-layered tube structure. The hollow tube 40d of FIGURE 12 is shown with perforations 72 covering its outer and inner surfaces to promote the adhesion of any substance applied thereto, including resin adhesive, coatings, lightweight cement, etc. Dot-dash lines represent cutting planes for dividing tube 40d into hollow rings 76 of equal height for use in a core layer of this invention. Similarly, FIGURE 13's hollow wooden tube is a length of natural bamboo, to be divided into equally sized core hollow ring elements 78 cut along lines 80. In contrast to the embodiments of FIGURES 12 and 13, tubes 40 in FIGURE 14 have been joined adhesively into assembly 82 before being cut into core layers along cutting planes 84. Still another core element embodiment 86 is shown in FIGURE 15 made from a strip of wood shaving 88 loosely coiled into helical form and coated with resin adhesive 20. In FIGURE 16, both inner surface 90 and outer surface 92 of hollow tube 40 are provided with fine wire mesh screening 94, covering the surfaces to enhance adhesion of any substances applied thereto and to add strength to core element ring 40. As an example, inner surface 90 and wire mesh 94 are shown with a layer of of lightweight cement 96 applied thereto. It is apparent that cement or similar material may be applied to outer surface 92 of hollow tube ring 40 or used to fill completely space 44 thereof. Core layer 98 of FIGURE 17 comprises adhesively connected hollow veneer tube rings 40, which have been selectively filled with lightweight cement 100 and surrounded by facing 101 to form post or column 103. FIGURE 18 is of a construction similar to that of FIGURE 17, but shows core layer 102 with some of its tube rings 40 filled with insulation material 104, and also having solid wood beam 106 interposed among rings 40 for added rigidity and strength, and as a convenient anchorage for fastening the assembled sandwich construction building material to any other structural element. FIGURES 19 and 20 illustrate another core element embodiment 108 wherein hollow tubes 40 are not contiguous but are positioned in spaced proximate relationship with each other and held in place by the ends thereof being embedded in lightweight cement facing 110. Tubes 40 are herein covered with resin adhesive coating 20a containing fibrous threads 112 dispersed throughout to increase tube strength. Strands 112 may be glass fibers, wood fibers, natural cloth fibers and synthetic fibers. It may be noted that in this embodiment, spaces 114 between tubes 40, as well as spaces 44 within the tubes, may be filled optionally with insulation or the like. The resulting product may be used as a construction material directly or may have further facings added as desired. The hollow cylindrical tubes 40 illustrated and described thus far have all been shown to be uniform in material and size for each embodiment disclosed. It is envisioned, however, that tubes 40 of widely differing lengths, diameters and thicknesses may be mixed and combined in any one building material, that tubes or tube assemblies may be fixedly attached to each other in lengthwise fashion to form an elongate core of telephone pole length, or even that core elements 18, 18a-c may be mixed with hollow tubes 40, 40a-e in any one structural component, all being within the concepts of this invention. FIGURE 21 is a top perspective view of building unit 24 shown in FIGURE 5, emphasizing its unitary modular character; FIGURE 22 shows an assembly of modules 24 arranged in horizontal overlapping and staggered rows to achieve wall 116; and FIGURE 23 has modules 24 stacked in a vertical pile and held in place by side walls or facings 118, forming vertical column or pole 120. The arched modular structure 122 in FIGURE 24 has been assembled from modules 24a, each arcuately formed from a core layer 30 composed of hollow cylindrical tubes 40, covered by upper and lower parallelly curved facings 26a and 28a, and enclosed by side facings 32a and 34a. Each module 24a is provided with a male element 124 on one side and female element 126 oppositely positioned for interlockingly connecting each module securely to its adjacent modules 24a. FIGURES 25 and 26 illustrate joist 128 made in accordance with the concepts of this invention. Hollow cylindrical tubes 40 are aligned and adhesively connected to each other as well as to top facing 130, bottom facing 132, end facings 134 and 136 and side facings 138 and 140.

Claims: The preferred embodiments of this invention as now contemplated have been described. It will be evident to those skilled in the art that a wide variety of novel and useful building materials may be advantageously made and used in accordance with the concepts herein disclosed, and many more products may be derived and conceived therefrom and from modifications, combinations and substitutions without exceeding the scope of these concepts, which are defined and limited only by the ensuing claims, wherein what is claimed is: 1. Sandwich construction building material which comprises: at least one facing element forming each outer covering of the sandwich construction building material, said at least one facing element on each face having been made from a substance selected from the group consisting of: plywood, fiberboard, particle board, mineral board, wood, metal, synthetic resin, cement, cement combined with wire mesh, laminates and any combination of the above; and an interior core layer fixedly mounted perpendicular to, and on the inner surface of each said at least one facing element, said core layer comprising at least one core element shaped into a preselected geometric configuration, said at least one core element being formed from a unitary piece of material selected from the group consisting of: natural wood veneer, veneer formed from wood fibers combined with synthetic resin and veneer formed from wood shavings combined with synthetic resin, said at least one core element being positioned to form an overall openwork pattern in said core layer, the opposite edges of each said geometrically shaped core element each being substantially uniplanar and parallel to each other, said opposite edges each being secured to one said at least one facing element on each face of the sandwich construction building material. 2. Building material as defined in Claim 1, wherein said at least one core element further comprises a coating applied to at least one surface thereof, said coating being selected from the group consisting of: synthetic resin coatings, adhesives, coatings having fibrous threads dispersed therethrough, wire mesh, lightweight cement and wire mesh combined with lightweight cement. 3. Building material as defined in Claim 1, wherein said core layer comprises a plurality of said at least one core element, each shaped into a longitudinally extending and recurring shape, said plurality of shapes being assembled in proximate offset relationship to each other to form a succession of spaces therebetween, the shape of said spaces having been selected from the group consisting of: polygonal, elliptical and circular configurations, said veneer core element having been cut transversely to a height equal to the desired thickness of said core layer at a time selected from the group consisting of: before assembly and after assembly of said plurality of core elements into said interior core layer. 4. Building material as defined in Claim 1, wherein said at least one core element has been formed into a hollow cylindrical tube selected from the group consisting of: butt-jointed veneer, scarf-jointed veneer and overlapping veneer, said at least one hollow cylindrical tube having been cut transversely into tube sections of a height equal to the desired thickness of said core layer. 5. Building material as defined in Claim 1, wherein said veneer core layer comprises a plurality of said at least one core element, said plurality of core elements being arranged in a position selected from the group consisting of: contacting contiguous relationship and proximate but spaced relationship with each other. 6. Building material as defined in Claim 5, wherein one end of each of said plurality of core elements has been embedded and secured in said at least one facing element during the formation of said facing element. 7. Building material as defined in Claim 1, further comprising: said at least one core element having been given at least one of the treatments selected from the group consisting of: perforating said core element's surface for greater adhesion thereto, adding resistance to fire, resistance to moisture, resistance to decay and resistance to insect attack; and spaces in said openwork pattern in said core layer may be filled selectively with at least one substance selected from the group consisting of: thermal insulating material, sound insulating material, lightweight cement and at least one solid wooden member interposed among, of equal height to, and extending along at least one dimension of said interior core layer. 8. Building material as defined in Claim 1, wherein said at least one core element may range in height from 1/16 inch to 8 feet, and may range in thickness from l/64th inch to 1/4 inch. 9. Building material as defined in Claim 1, wherein said outer facing elements are used to enclose at least one of the otherwise exposed edges of the building material where necessary to produce building modules suitable for assembly into building structures, said assembly being selected from the group consisting of: piling said modules into stacks vertically to form posts and columns, and attaching said modules in horizontal rows, each said row being positioned in overlapping offset relationship to its adjacent rows. 10. Building material as defined in Claim 9, wherein said building modules have said at least one facing element on each face arcuately shaped, said interior core layer correspondingly arcuately shaped, and further comprising means for locking said arcuately shaped modules together in side-by-side relationship to form an arched structure. 11. Building material as defined in Claim 4, wherein said interior core layer comprises a plurality of said at least one hollow cylindrical tube, said plurality of tubes being assembled in multiple lengthwise extension as well as being attached in side-by- side relationship, said at least one facing element being shaped to encompass and surround said interior core layer and thus to form elongate structures suitable for use as poles, posts and columns. 12. In combination with known conventional facing elements for sandwich construction building materials, an interior core layer fixedly mounted perpendicular to, and on the inner surface of, each said facing element, said interior core layer comprising at least one core element formed from a unitary piece of material selected from the group consisting of: wood shavings and hollow rings transversely cut from bamboo branches, said at least one core element being arranged and positioned to form an overall openwork pattern in said interior core layer.

Inventors: SING PETER, SING, PETER
Applicants: SING PETER, SING, PETER
Application year: 1995
Main classification: B32B3
IPC codes: B32B3, E04B1, E04C2, G10K11