US3161267A

US3161267A - Building wall

Info

Publication number: US3161267A
Application number: US853790A
Authority: US
Inventors: Robert R Keller
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-11-18
Filing date: 1959-11-18
Publication date: 1964-12-15
Anticipated expiration: 1981-12-15
Also published as: GB929307A

Description

R. R. KELLER BUILDING WALL Dec. 15, 19 4 3 Sheets-Sheet 1 Filed NOV. 18, 1959 Dec. 15, 1964 R. R. KELLER 3, 6

BUILDING WALL Filed Nov. 18, 1959 3 Sheets-Sheet 2 R. R. KELLER Dec. 15, 1964 BUILDING WALL 3 Sheets-Sheet 3 Filed NOV. 18, 1959 United States Patent Ofifice 3,151,2h7 Patented Dec. 15, 1964 3,161,267 BUILDING WALL Robert R. Keller, 150 Milford Sn, Manchester, Nli. Filed Nov. 18, 1959, Ser. No. 853,790 1 Claim. (Cl. l89--34-) This invention relates to building walls and more particularly to wall panels having large continuous surface areas, for use as outer and inner walls of buildings and for partitions. The application is a continuation-in-part of my copending application, now issued as Patent No. 2,931,468.

The existence of thin, high-grade sheet materials, plastics, fibers, minerals and metals, has caused hope that bricks, lumber and concrete would be replaced by more economical building walls which are highly improved in appearance, much lighter and hence easier to erect and which require little or no maintenance throughout a long life. But, in addition to remaining less expensive, conventional materials have been regarded as more reliable in appearance and in resistance to impact loading.

Lightweight panels made from available highgrade thin sheet materials have generally had an unsightly, unevenly dished appearance. Such panels placed side by side have not presented a consistent appearance, but rather uneven shadow effects have occurred, due to the unevenly dished nature of surfaces of the panels. Such panels have also had low impact resistance being damaged in appearance by impinging impact loads and frequently in structure as well. Stiff high-grade sheet materials (e.g., high-density cement-asbestos) have had such low resistance to impact loading as to have been completely unusable for walls in ofiice buildings and others, where long life and good appearance are important factors. Panels without at least one of these defects have not been i economically competitive with conventional materials, and have, therefore, found application only where expense has been of little importance.

The principal object of this invention is, therefore, to produce improved building wall panels of high-grade, thin sheet materials.

Another object is to provide wall panels having a consistent, even appearance. Panels following the invention can have glossy, smooth, highly polished outer skin surcan, undished and completely planar.

Another object is to provide panels having very thin surface skin members with high impact resistance.

A still further object is to provide lightweight wall panels constructed with a minimum of expensive materials, having a large span between stiffener members.

Achievements of the invention include the provision of prefabricated building panels having good insulation and sound absorption features and which provide fire barriers.

The invention comprises an interior, low-density sheet member having a mutual extent with and bonded continuously to the inner surface of a continuous high-grade skin member, but having spaced-apart elongated interruptions, and spaced-apart, elongated rigid stiffener members bonded directly to the skin member at the interruptions. Where the panels comprise structural members, and not mere curtain walls, a second skin is bonded on the other side of the stiiftfener members.

The low-density thick backing sheet material must have the following characteristics: It must be relatively thick, a thickness of and upwards to 1", preferably between /2" and A". It must have a non-friable face directed toward the high-grade skin member, non-friable being used in the sense that surface material must not rub off or otherwise separate from the general mass of lowdensity material. This non-friable surface must conform to the matching surface of the skin member. The lowdensity sheet must have substantial structural stability and stiffness. Where the sheet is fibrous, affected by moisture to become less stiff, upon the face opposite from the bonded skin there must be a vapor barrier, preferably a very thin impermeable sheet such as polyethylene or aluminum coated paper, laminated thereto.

Skin members according to the invention must be continuous weather and wear resistant sheets of a thickness generally less than /8", in many preferred embodiments less than .080" and must be high-grade: highly compact with hard and non-friable surfaces and having a relatively high internal strength with a tensile yielding point generally above 1000 p.s.i. where thicknesses around 4;" are employed, and proportionately higher specific strengths for thinner members. The high-grade material may be fairly brittle as is high-density cement-asbestos, but not extremely brittle as in glass.

A continuous film of flexible adhesive must bond together the matching surfaces of the interrupted lowdensity sheet and the skin member throughout their mutual extent.

The rigid, elongated stiffener members fitting the interruptions in the low-density sheet have non-friable conforming surfaces directed towards the inner surface of the continuous skin member. A film of high-grade adhesive material is interposed, directly bonding each stiffener member to the skin. In structural panels a second continuous skin member, also of high-grade material is generally parallel to the first skin member, separated therefrom by the stiifeners and is bonded through mtaching non-friable surfaces to them. Where both sides of a structural panel are exposed to impact loads and to view, a low-density sheet member is bonded to each of its skin members.

The invention is further amplified in the following detailed description including illustration of a number of preferred embodiments in the drawings wherein:

FIG. 1 is a perspective, exploded view of a typical prefabricated structural wall panel constructed according to the teachings of this invention;

FIG. 2 is a section of the panel of FIG. 1 along line 2-2;

FIG. 3 is a perspective partially cut-away view of another preferred embodiment of a prefabricated structural wall panel;

FIG. 4 is a section of the panel of FIG. 3 taken on lines 44;

FIG. 5 is another section of the panel of FIG. 3 along line 5-5 thereof showing in particular the construction of the core;

FIG. 6 is a section similar to that of FIG. 5 of another preferred embodiment of the invention;

FIG. 7 is a section similar to FIG. 4 of another preferred structural panel of the invention for use where both surfaces are exposed to view and to impact loads;

FIG. 8 is a fragmentary perspective of a large prefabricated curtain wall panel in which plastic stiffeners are employed; and

FIG. 9 is a magnified, partially cut-away perspective of an embodiment wherein a moisture barrier is employed.

Thickness of the skins and the films of adhesive and clearances between low-density sheet interruptions and stiffener members are generally exaggerated for the purposes of illustration.

As noted above there exists a number of high-grade materials produced in very thin continuous sheets.

Skin walls of many of these high-grade materials yield slightly at varying rates across the surface thereof in response to heating, cooling, wind conditions and other factors, dishing in irregular amounts across the surface, forming a very undesirable dished appearance. In the case of planar panelsthis dishing is characterized as a non-planar irregular surface with high points appearing at points of attachment of the skins and irregular depth .low points across the surface between. Increase in thickvness of the skin decreases'the dishing tendency-but such improvement is made only by greatly increasing the cost .per unit .areaof the wall, and theweight thereof. The invention eliminates dishing in a panel surf-ace so that instead of increasing the thickness of the expensive high- .grade sheetmater-ial, it is possible to utilize much thinner skin memberspermitting substantial savings.

The invention, in addition, permits great-increases in the impactresistance-of skins. This impact. resistance concerns the withstanding of such concentrated loads as may occur when stones or baseballs are thrown against .a building wall; when air rifles are discharged thereagainst; andfrom impacts from kicking or 'scufling or moving furniture thereagainst. To be acceptable, walls mustwithstand such impact loads, not only without structural failure, but without surface changes such as crack- :ing, ,denting, pitting and crazing.

Following the invention relatively brittle materials,

heretofore unsuitable because of cracking and failure under low impact loads (e.g. high-density cement-asbestos), can now be utilized in permanent structures, .e.g., as outer walls of oflice buildings; denting by local stretching beyond the elastic limit as in extremely thin metal sheets isavoided; and crazing as occurs in plastic sheets is eliminated. 7

All of this is accomplished while providing a structure in which center distancesbetween elongated stiffener membersare unusually great, providing a minimization of .relatively heavy and expensive stiffener material.

- 4 the interior of this second skin is bonded low-density bagasse board 15 interrupted and bonded as is sheet 14. The structural panel thickness may range up to 8", thickness between 1 /2 and 4 being presently most common.

The preferred embodiment of FIGS. 3, 4 and 5 is a prefabricated structural panel having a height of 20 feet and a width of 4feet. The panel 40 comprises an open stiffener frame 42 comprised of I

section core elements

43, 43" and 45 of rigid structural material providing oppositely directed bonding areas bonded directly to outer high-gradeskins 44, 46 with high-grade bonding material 48. Skin 44,.is a high-grade continuous wear resistant sheet (stainless steel of a thickness of about .020) extending across the entire width'and length of the panel; skin 46 is also a high-grade continuous sheet (high-density cement-asbestos of -a thickness of about /sn). I

An interrupted, interior low-density thick and stiff backing sheet material 50 (low-density asbestos board) with a thickness of between /2 andv has a non- .friable surface geometrically conforming with the interior surface of skin 44. The'interruptions of thislowdensity sheet 50 receive the stiffener members, but the low-density sheet 50 is not bonded to them. A layer of flexible bonding material 52, continuous and-coterminous with the low-density sheet portions is interposed between the matching surface of the low-density sheet 50 and the interior surface of skin. 44. To the interior of the skin 46, bonded thereto in a like manner, is an interrupted low-density fiberboard 51 of /2" thickness, formed from reclaimed newspapers. V

The stiffener structure of this embodiment also follows my copending application, as shown in FIG. 5. It will been seen that a longitudinal groove 60 is provided along the abutted side of an, abutted element 43. A projection means at the end of .the abutting element 45,. here oppositely directed cars. 49, is twisted into this groove preventing endwise' removal of element 45 away fi'om Q element 43.

polyester plastic, but may obviously be formed of other 7 such plastics, e.-g. vinyls, Bakelites (phenolic) and acrylics reinforced where necessary with paper, wire, glass, and the like.

Upon the interior area .of this skin is a low-density thick and stiff backing sheet material 14 .of fiberboard formed from reclaimed newspapers, with a thickness of about /2" having a non-friable face towards the skin and having spaced-apart

elongated interruptions

16, 18. The low-density sheet covers the entire inner area of the skin except for the interruptions, and is bonded thereto with acontinuous film 20 of aflexible bonding agent, e.g., a plastic or rubber base adhesive.

Elongated rigid stiffener members 22, .24 fitting the interruptions are inserted therein. These stiffener members provide non-friable bonding areas conforming with the inner surface .of the skin member, and a high-strength bonding material 26 is interposed between the stiffener members and the matching skin area, effecting a highstrength direct bond therebetween. The

rigid stiffener members

22, 24 are strong and lightweight. In this embodiment the stiffener members 24 are box shaped with I shaped members 22 having spaced-apart longitudinal slides 23 in which end projections 25 of abutting, members 22 interlock for sliding engagement following the teachings of my abovementioned copending application, and flanges of

members

24 and 22 oppositely directed from skin member 12 are bonded to a second wear resistant skin member 30 generally parallel to the first. This second skin, a high-grade sheet, is of higlrdensity melamine sheet .060 thick and is separated from the first by the stiffeners interposed therehetween. To

I In FIG. 6 are flanged'stiifener members ofanothe'r preferred embodiment which, while not offering the rigidity of structure of those of FIG. 5, are suitable in instances where the skin members offer substantial strength. An abut-ted element 61 is abutted by abutting element 62. A longitudinal seating portion 64 (the inside surfiace of a flange) is provided along the abutted side of the abutted element 60. A projection means 66 is provided at anend portion of the abutting element for slidably engaging the seating portion, while maintaining the outer'flange surfaces of abutted and abutting elements in common planes.

During assembly, with slidable connections as shown in FIGS. 1 through 6, as taught in my copending application, the abutting members may be selectively positioned along the sides of abutted'members so to fit within the elongated interruptions in the low-density sheet.

Other advantageous embodiments of my present invention do notem'ploy my novel connection between stiffenermernbers.

Referring to FIG. 7 this prefabricated structural panel has a narrow width and is useful for curved walls. Both of the oppositely directed skin Wall surfaces have extremely high impact resistance and resistance to dishing, and the panel is, therefore, useful to define both inner and outer walls of a gymnasium. Parallel opposed stiffener members '70 and 72 have opposed U crosssections with oppositely directed flange bonding areas lying in parallel spaced-apart planes. High-grade continuous wear

resistant skin members

74 and 76, each high-density cement-asbestos with a vitrified outer surface, thickness Vs", extend across the panel, one in each plane 'being bonded intimately to the flanges with high- 'strength adhesives 78. On the" inside surface of one "ness, and to the other sheet member 82 is a low-density asbestos board thick, each of which extends continuously across the area of its skin member with elongated interruptions only at the periphery for the stiffeners 70 and 72. A film of flexible bonding material 73 is interposed between the mutual extent of each skin member and its low-density sheet member.

Referring to FIG. 8 a curtain wall comprised of a network of rigid, rectangular cross-sectioned

plastic stiffener members

84 and 86 notched for egg crate assembly are bonded to a high-grade weather resistant skin 90 of aluminum of .015 thickness. To the entire inside area of sheet S0, interrupted only at the stiffeners, is bonded low-density thick and stiff backing sheet material hl, pressed paper sheet of a thickness of Referring to FIG. 9 a sheet of low-density sheet material conforming to the requirements of the invention is shown. This sheet has a thickness of /z". The under surface A is non-friable and conforms to a skin member E to which it is bonded with a flexible bonding agent D. The thick and stiff low-density sheet has a mutual extent with the skin member except for elongated interruptions F. This sheet of low-density material is formed of compressed fibers and although stiff is subject to becoming flexible when subjected to moisture. Laminated to surface B, facing opposite from non-friable surface A is a vapor barrier layer C comprised of a thin plastic sheet laminated thereto. Vapor barrier material is also applied to the edges of the low-density sheet. Rigid Wooden and plastic stiffeners with an ordinary rectangular cross-section may be used to advantage in some instances to provide oppositely directed or single bonding areas.

To withstand varying wind loading, construction han dling and head loads, it is imperative that the rigid stiifeners have non-friable surfaces so as to withstand differential expansion and contraction and must be compatibly bonded to the high-grade skin sheet, at intervals directly thereto. This high-grade bond must be stronger than the permissible flexible bond existing between the interior low-density sheet and the skin sheet as it must transfer stress and aiford support, and stiffness currently achieved only by the use of extremely expensive bonding agents. An example of such an adhesive is synthetic rubber base phenolic material. The comparatively narrow nature of the stiifener bonding areas permits the use of such high-grade bonding agents in competitive structures.

The following is a table of some advantageous combinations of high-grade skins and low-density sheet material, combined, according to the teachings of the invention, with the stiffener members, to comprise panels economically competitive with conventional materials. The thick and stiif low density backing sheet in every instance is upwards of A2" in thickness, preferably within the range of /2" to The face of this low-density sheet bonded to the skin is non-friable. It has substantial structural stability and stiffness, not highly pliable, and is provided with a vapor barrier where subject to softening Water stiifener members G are bonded directly to the skin memvapors.

EXAMPLES OF COMBINATIONS FOR BUILDING PANELS High-Grade Skins Low-Density Sheet Added Advantages Stainless Steel 0.040" thick Asllgiztos fliggard is thick, weight Fire Barrier.

oz. Fiber Glass reinforced Polyester Bagasse (Pressed Sugar Cane Fiber) Extremely Light.

sheet .030 thick, weight 9 oz./it. High-density Cement Asbestos is thick, weight 20 oZ./ft.

Pressed Exploded Fiberboard 0.125

thick, weight 12% 01../it. Plywood 3-ply laminations,

thick over-all.

Anodized Aluminum 0.015 thick.

Enameled Steel 0.015 thick over-alL.

High-density Cement Asbestos Pt thick, weight 20 oz.,/ft

Aluminum 0.015 thick Fire Barrier, High Insulation Value.

High Sound Absorbency, Ideal Interior Partition.

High Insulation Value.

Very lightweight.

Inexpensive Permanence.

Inexpensive Medium Life.

Feather weight.

ber, conforming to the interruptions F of the low-density sheet.

As indicated in the drawings, FIGS. 1-7, some preferred forms of the invention are structural panels, which are selfasupporting over large areas and which can withstand wind loadings and head loads without additional support. For these structural panels to resist buckling under such loads it is important that the sandwich be relatively deep, i.e. that the opposite skin sheets be spaced apart as high as 8". The depth provides substantial stiffener material spaced from theneutral axis of the panel. The panel acts as a sturdy column, and is, therefore, not subject to buckling failure.

Other preferred embodiments, e.g., P16. 8, comprise a single continuous Weathering wear resistant skin mem- High-density plastic, aluminum and steel are examples of non-friable surfaced material which may be so utilized.

N0 dishing occurs with the above structures. Each combination has extremely high impact resistance. Of course, other combinations of materials under the limitations set forth also achieve improved building panels. Among these are light-transmitting compact plastic facings, backed with light-transmitting slightly expanded plastic foam sheets in a light-diffusing structural panel.

Although low-density sheet materials are pound-forpound much less desirable from a structural tension and compression standpoint than the high-grade skin materials, they permit decrease in skin thickness to the point that the total weight of the panels is not greatly increased while dishing is prevented. Thus an unbacked skin panel of a given construction and weight which dishes badly and irregularly can be of about equal weight with a panel according to the invention, of similar construction, which does not dish. The reason for this is that the thickness of the interior sheet material as defined provides a substantial amount of rather stiff material spaced apart from any possible bending axis of the interior low-density sheet, preventing bending thereof and thus supporting a thinner skin from dishing either in or out.

The low-density sheet has a much poorer surface facing, more subject to damage under impact loading, such as cracking, scratching and denting, as compared with the high-density skin material. But it greatly improves impact resistance of the high=g rade skin sheets furnishing in bonded combination with the skin, characteristics lacking in the thin Thin highgrade skin members (compact, hard, non-friable surfaced, strong, not extremely brittle) standing alone,ha've anumb'er of impact resistance deficiencies found in differing degrees from material to material. ductile and subject to permanent denting and wrinkling; harder plastics are subject to surface pitting and crazing when impact loads impinge thereupon. High-grade skin members less susceptible to these, are inversely much more brittle and subject to cracking and breakage, one example or this sort of material beingrthe thin, highdensity cement-asbestos sheet. All high-grade thin skins will have their impact resistance Substantially increased by this invention. The improvement :in impact resistance is primarily due to the combined effects of distributiono'f impact loads throughout substantial skin area' and impact absorbency.

(A) Impact Spreading in Skin 7 As described above, the low-density sheet material must not be pliable but rather must have structural stability and stiffness, of course, a function of the thickness of the material as well as its particular internal structure. With this degree of stiffness, upon a concentrated impact blow the force tending to deform the skin is transferred through the impact point on the skin member to a much larger area of the interior low-density sheet. In turn,'these dispersed forces upon the interior low-density sheet, tending to depress it, are restrained by the adjacent portions of the bonded skin member at points spaced apart from the point of impact, tending to draw those portions of the skin in the direction of impact. A substantial area of the skin is thus slightly deflected and does the work of resisting a concentrated impact blow with no portion of the skin being subjected to stresses in excess of the elastic limit of the material.

(B) Impact i lbsorlieitcy Impact resistance,'especially for those skins which are relatively brittle, lies also in the absorption characteristics of the backing sheet. Cracking and breaking of brittle skins is due in large part to responsive vibrations in the brittle sheet. With the low-density sheet of the invention, the impact shock is transferred into the low-density sheet and is d ampenethand cracking and shattering are prevented.

Elasticity of the low-density sheet inherent in its stiffness, is imparted to the high-density sheet, achieving v greater impact absorption without yielding.

(C) Decrease in Prestress In many previous structures skin members have been prestressed across stiffener members, in order to attempt to prevent dishing. When an impact load occurred, sufficient deflection of the skin to absorb the blow greatly increased the tension stressed at the point of impact, exceeding the elastic limit and causing damage. With the instant'invention, however, prestressing to eliminate dishing is not needed and damage is avoided. v r

It must be appreciated that not one of these efiects alone explains the full advantages of the invention in any one embodiment, but there is a cooperation of eflects difficult to analyze. 7

To achieve the surface bond between the inner skin area and the matching low-density sheet adequate to provide the resistance to impact loading it is imperative that each surface be continuous and non-friable, so that a bond therebetween effects a lasting union between the mass of the low-density sheet and the skinto withstand differential expansion and contraction and to give impact resistance. The bonding material m'ust'be flexible so that the portions can flex in response to concentrated impacts.

.ND numerical weight limits are employed herein in Metals and some plastics in thin sheets are are 1,12 6? 8 defining the low-density of the thick and stiff backing sheet member without reference to specific material because avery loose composition formed of a material *having high molecular weight would not have a non friable surface, stitfnes's 'or structural stability, but would have a higher Weight per unit area thanfor instance, a satisfactory pressed fiber board of the'same thickness. What is generally intended by low=den'sity sheet which has structural stability and stiffness, is a'she'et of material having a strong rigid bridged network, but with substantial air space, and, therefore, being capable of being further compacted to a substantial amo'unt during its manufacture. Of course, to be useful herein, the sheet must have a non-friable surface.

As an example, presently known polyurethane expanded foarn having a density upwards of 15 lb./ft. in sheets of thickness has a sufliciently strong, rigid bridged network to serve -as the lowdensity sheet, while such foams of lower density arefinadequate for the purpose having, for instance, insufi icient :stability and stifiness for use in the instant invention as well as an inadequate surface. I I

The specific stiffness of the low-density material (modulus of elasticity and theelastic limit) is not specified with numerical limits 'in defining low density of the sheet first, because the over-all stiffness of a sheet is a function of the thickness of the sheet which may be varied within the teachings of the invention over a substantial range as well as the specific stiffness. Secondly, the required amount of over-all stiifness depends upon the particular application. As an example, for a backing for skins of fiber glass reinforced plastics, dishing is the greatest problem to be combatted because the reinforced plastic has a comparatively favorable impact resistance apart from impact crazing, due ,to the high elasticity of the fiber glass. Thus, although the backing material serves both important functions of increasing impact resistance and decreasing dishing, the nature of the required stiffness of the low-density sheet is that the material be rigid but need not have a very high elastic limit. Ctintraste'd with this are skins of extremely thin sheets of steel, more ductile than fiber glass reinforced plastic, being particularly subject to permanent impact denting' and wrinkling by yielding, as well as dishing.

These thin sheets of steel require not only a stifi interior backing member, but also one having elasticity over a widerange, providing elastic return and efficient spreading 'of stress to a wide area of the skin relative to the area of impact. High-density cement-asbestos sheet skin members, in further contrast, is weakest from an impact loading standpoint, and absorption of shock being very important, the low-density sheet must have low compaction, and while stiff, is not required to have as high a degree of stiffness as is necessary in some of the other situations.

b The teachings herein serve as a complete guide to the assemblyrnan who will find many combinations obvious, following the teachings herein, using other analogous materials than the examples herein within the spirit and teachings of the invention.

What is claimed is:

A prefabricated building'panel comprising a grid formed of a multiplicity of rigid grid members mechanically connected together, each of said grid members having a web and flanges at each edge thereof extending at an angle to said web, the outer surfaces of each of said flanges being substantially fiat and parallel to each other, the grid members extending in two directions and defining a multiplicity of open spaces surrounded by said grid members, said flanges at one edge of. said webs defining a first set of bonding surfaces, said bonding'surfaces being aligned in a single plane, a first outer sheet member extending in said plane over said grid, said first *sheet member having an outer wearresistant surface and bonded with a layer of adhesive face-to-face to said first set of bonding surfaces, said layer of adhesive lying directly between the cooperating bonding surfaces of said first sheet member and said first set of bonding surfaces, said first sheet member extending continuously over all of said open spaces, a multiplicity of stitf, pre-forrned backing sheet members one fitted in each of said open spaces in said grid, each backing sheet member having an area substantially corresponding to the area of said first sheet member lying over said open space, each backing sheet member having a planar bonding surface bonded by a layer of flexible adhesive face-toface to said first sheet member substantially throughout said area, said backing sheet members each being thicker than said first sheet member and structurally of lesser density than said first sheet member and said grid members, the outer surfaces of said flanges on the other edge of said webs defining a second set of bonding surfaces, said second set of bonding surfaces being aligned in a single plane, a second outer sheet member adhesively secured to said 19 second set of bonding surfaces, said second set of bonding surfaces locating said second sheet member in a spaced apart relationship to said backing sheet members, the smallest dimension of each of said open spaces parallel to said planes being substantially greater than the spacing between said planes.

References fitted in the file of this patent UNITED STATES PATENTS 887,912 Bokor May 19, 1908 1,540,542 Carhart June 2, 1925 1,637,497 ODowd Aug. 2, 1927 2,160,066 Frische May 30, 1939 2,302,586 Thelen Nov. 17, 1942 2,757,116 Clements July 31, 1956 2,890,977 Bayer et al June 16, 1959 FOREIGN PATENTS 723,621 Great Britain Feb. 9, 1955