GB2087793A - Corrugated building panel and method of manufacturing same - Google Patents

Abstract

A corrugated building panel formed of two plies of paperboard or chipboard, is make steaming the two plies 12 applying an adhesive 16 to a facing side of one of the plies, subjecting the plies to corrugation, followed immediately by bonding of the plies. The laminated structure may be heat set, trimmed into individual panels, asphalt impregnated, and, as desired, surface coated or painted. <IMAGE>

Description

SPECIFICATION Corrugated building panel and method of manufacturing same Corrugated panels, due to the inherent strength thereof, have found ready acceptance in the building trades. Such panels will most frequently be found in use as exterior wall paneling or roofing in "corrugated buildings" which can range in size from garden sheds to manufacturing of storage facilities covering great areas. Corrugated paneling is also finding ready acceptance in the home market, used as patio covers and the like.

Traditionally, corrugated panels have been formed of sheet metal, which includes a full range of strengths and weights for substantially any application, from thin aluminum panels to heavy steel panels.

More recently, plastic or fiberglass reinforced resin panels have come into common usage. Such panels, because of inherent advantages, such as the possibility of being made translucent, being readily cut and drilled, and the like, are preferred under some circumstances, particularly in the home improvement market.

Corrugated building panels of other materials, while not as widely used, are also known. In this regard, attention is directed to patent US 2,236,932, issued to G. J. Arenstsen on April 1, 1941. This patent discloses a corrugated construction board of asbestos-cement, the board being formed by introduction thereof, while still in a plastic state, between sets of converging rollers. Corrugated cylinders receive and pull the corrugated asbestos-cement board as it discharges from the corrugation-forming rollers.

Another known form of corrugated panel is formed from saturated and treated sheets of the wood or woody constituents of fibrous vegetable material. Such a construction is shown in US patent 2,058,334, issued to W. H. Mason on October 20, 1936. In Mason, the sheet from which the panel is formed, after the extensive treatment to which it is subjected, is corrugated by a series of pipes which initiate the pressing at the middle of the treated sheet and proceeds outwardly toward the sides thereof. Mason also proposes introducing a further structural rigidity or stability into the single corrugated sheet by planing the apices of the corrugations off flat and gluing flat surface plates, also of vegetable-fiber board, thereto.

The corrugation of paperboard, primarily as a means for increasing the strength thereof, is also a known expedient, primarily utilized in the formation of boxes, shipping containers, and the like. In connection therewith, the following patens are considered of interest: Rosati US 3,002,876 Kellicutt US 3,425,888 Tisdale US 3,178,494 and 3,676,263 Rosati and Kellicutt illustrate procedures for forming panels incorporating multiple layers of corrugated and planar sheets.

The Tisdale patents set forth a procedure whereby a corrugated laminated panel is formed by initially gluing together a multiplicity of flat webs of paper and subsequently forming the glued webs into a corrugated panel prior to hardening the glue. The glue, upon hardening, apparently locks the structure together in the corrugated configuration.

The present invention is concerned with a new form of roofing or wall panel, as well as the specific method of making same. The proposed panel is considered a viable substitute for the more conventional metal or plastic panels, is the functional equivalent thereof and offers substantial advantages including cost economies, ease of construction and availability of materials.

Basically, the panel is formed of a pair of corrugated sheets adhesively laminated together into a unitary construction. The sheets, rather than being of the thickness normally encountered in corrugated boxes or the like, on the order of .009", are substan tiallythicker and generally in the range of .035 to .052" in thickness.

Panels formed from the corrugation and lamination of as few as two of such sheets, in accordance with the method of the present invention, have been found to be of superior construction, providing an economical, functional equivalent to corrugated panels of more conventional construction.

In constructing the panels of the present invention, fully formed sheets of paperboard are utilized, thus taking advantage of the greatly enhanced strength achieved by the tensioning, pressing, and the like which occurs during the final drying procedures associated with conventional paperboard construction. This in itself differs from presently known procedures involved in the formation of corrugated paperboard in that corrugating is normally done using the wet lap at the end of a paper machine as the wet lap exists therefrom prior to final strengthening and drying.

The fully prepared paperboard sheets used in the procedures ofthe present invention are normally supplied in large rolls to enable a continuous forming operation with the finished panels being severed to length after completion of the lamination procedure. The sheets, discharging from two separate rolls, are first subjected to steam to increase the flexibility or workability thereof and thus facilitate corrugation. Immediately prior to entering the combined corrugating and laminating apparatus, one of the facing surfaces has an appropriate adhesive applied thereon. The two sheets then enter an assembly of elongated cylindrical rods or pipes provided in upper and lower tiers individually formed of horizontally spaced pipes.These tiers are widely spaced at the sheet receiving ends thereof and subsequently converge, laterally and vertically, and interdigitate toward the discharge end. The spacing of the tiers is such that the inwardly moving sheets are initially separately engaged by the upper and lower tiers and the corrugating thereof commences immediately prior to converging movement of the sheets into adhesive bonding engagement with each other. The movement of the sheets into bonding engagement with each other occurs substantially simultaneously with advancement of the sheets into their final corrugated configuration.By corrugating the sheets generally simultaneously with an adhesive lamination of these sheets to each other, a highly stable construction is produced with the sheets themselves tending to maintain the formed corrugated configuration, rather than relying merely on the strength and set of the bonding adhesive.

The laminated construction thus formed is drawn forward from the corrugating assembly by interfitting corrugated rollers which also function as means to ensure a uniform final corrugated configuration.

The continually traveling formed construction then proceeds along a series of straight heated pipes which conform to the upper and lower troughs of corrugations and provide both additional setting time and additional drying for the laminated construction. Beyond the heating pipes, the laminated construction is trimmed along the sides to the final panel width. Pull rollers, positioned forward of the side trimming apparatus, continue to forwardly draw the laminated construction. These pull rolls will normally consist of an upper roll formed of steel discs and a bottom roll of urethane.

The laminated construction then enters a final section wherein the construction is transversely cut to the desired panel iengths by a traveling blade shear with a corrugated shaped cutting blade and a corrugated shaped back-up. It is contemplated that the cutting blades be designed with somewhat lower amplitude than the panel corrugations to prevent cutting all the laminated construction at one time and yet obtain a clean cut without distorting the corrugations.

Ultimately, the sized corrugated panels are batch treated with a roofing grade asphalt. This can be effected by, as an example, apparatus of the type shown in US Patent 3,601,090, issued to Roger Vallon on August 1971. In the final step, if so desired, the treated sheets can be painted with an appropriate polymeric material, such as acrylic based paint, using commercially available curtain coaters and high velocity hot air drying ovens.

Other objects and advantages may become apparent from the following more detailed consideration of the invention wherein reference is had to the accompanying drawings forming a part hereof. The invention will be described with reference to the accompanying drawings.

Figure l is a perspective view of a portion of a corrugated building panel constructed in accordance with the present invention; Figure 2 is an enlarged sectional detail view of a portion of the panel of Figure 1; Figure 3 is a schematic side elevational view of the apparatus used in the process of forming panels in accordance with the present invention; and Figure 4 is a schematic plan view of the apparatus assembly of Figure 3.

Referring now more specifically to the drawings, reference numeral 10 is used to generally designate the corrugated building panel constructed in accord ance with the present invention. This panel 10, comprising a pair of corrugated paperboard sheets 12, laminated or bonded together by an interposed adhesive layer 14, is in itself considered to constitute a significant advance in the art, both because of the constructional details thereof, and the procedures involved in the formation thereof.

Of particular significance with regard to the structure of the building panel, is the formation of the panel from plural fully formed sheets of paperboard.

Such sheets have been subjected to the complete paperboard forming process, including the significant final steps of tensioning and pressing the paperboard sheet in a drying machine, thus giving a final sheet its maximum strength.

While, as shall be explained subsequently, the sheets 12, in the process of making the panel, are subjected to steam to increase the moisture content thereof and the formability of the sheets, this has little effect on the inherent strength built into the individual sheets by an initial full forming thereof, achieved to a large degree, as indicated above, by a subjecting of the sheets to the conventional final drying procedure. While it is not inconceivable the sheets could be formed or corrugated directly from the wet lap as it exits from a paperforming machine and without subjecting the lap to the drying procedure, the resulting product would clearly lack the strength and stability obtained by the use of fully formed sheets as proposed.This in turn is considered quite critical in that maximum strength is highly desirable if an effective use is to be made of paperboard in the formation of building panels, which will of necessity be subjected to a variety of load and weathering conditions.

Also considered of particular significance is the proposed formation of building panels using at least two sheets laminated into a unitary structure, as opposed to a single "thick" paperboard sheet. In regard thereto, in the conventional manufacture of paperboard, the rate of drainage of the pulp slurry is a major factor determining the rate of productivity.

One way to produce very heavy weight paperboard without loss of productivity is to form the board at high consistency which results, on a conventional machine, in poor formation with the board having lower strength properties. In other words, the heavier the board, the lumpier the formation with resultant weak spots and streaks. Adequate strength in thick or heavyweight paperboard can be developed by refining. Refining is an operation whereby wet fibers are "worked" to soften them in their wet state, develop microfibrils on their surface, and otherwise prepare them so that they will have sufficient fiber-to-fiber contact area to provide the bonding needed for the increased strength. However, refining also substantially slows the drainage rate of the pulp, and thus adversely affects the rate of production. Thus, "thick" paperboard can be produced economically only if the forming consistency is high, which hurts the strength, and there is a low level of refining, which also hurts strength development. The present invention avoids the above problems and produces a finished panel of a thickness commensurate with its use as a building panel, in an economically feasible manner, by the lamination and substantially simultaneous corrugation of two sheets of high strength paperboard into a unitary structure. While two sheets have been referred to, and in fact will be referred to hereinafter, it is to be appreciated that the laminated panel may in fact incorporate more than two sheets, although this, in normal circumstances, will not be necessary.

It should also be noted that the individual sheets as used herein, while sufficiently thin to allow for economical production thereof without strength loss, are of a substantially greater thickness than a conventional "carton box cardboard". It is contemplated that the sheets of the present invention preferably be on the order of .052 inches, although they may be as thin as .035 inches, in each instance as compared to a thickness of .009 inches for conventional cardboard.

The building panel 10 has the inherent strength thereof, resulting from the nature of the basic paperboard sheets utilized, enhanced by a corrugation of the panel 10. This in itself is achieved in a unique manner, whereby an initial corrugation of the individual sheets is commenced priorto a positive adhesive bonding of the sheets, with the bonding of the sheets being effected generally simultaneously with the final corrugating thereof. Proceeding thusly, the adhesive is not subjected to disruptive shearing forces, as would occur were the flat sheets bonded and then corrugated. In addition, at least the initial corrugating of the sheets, prior to the full bonding thereof, produces more stable laminated panel, both more readily formed and less resistant to distortion.

Once the corrugating procedure has been completed, it is contemplated that the adhesive be appreciably stronger than the sheets bonded thereby, thus adding further strength to the completed panel.

Turning now to the specific method involved in the formation of the panel 10 of the present invention, attention is directed to Figures 3 and 4, wherein both the steps involved in the production of the panel, and the associated apparatus, have been schematically illustrated.

The sheets 12, initially flat, are drawn continuously from rolls 16 of fully formed paperboard, preferably on the order of approximately .035 to .052 inches.

The sheets, in vertically spaced, generally parallel planes, are directed over a series of guide rolls 18, which introduce the sheets into the actual panel forming apparatus. The sheets 12, immediately beyond the initial series of guide rollers 18, are each individually directed over vertically spaced, transversely elongated steam grids 20, which moisten, heat and soften the sheets to the degree necessary to form the corrugations without the introduction of damaging stresses thereto. Immediately beyond the steam grids 20, upper and lower sets of guide bars 22, direct the sheets 12 through adhesive application apparatus 24. This apparatus, of generally conventional construction, will normally adhesively coat one facing surface of one of the sheets. However, if so desired, provisions can be made for coating the facing surfaces of both sheets.

The adhesive application apparatus 24 is followed by the forming section 26. The forming section 26 consists of a plurality of heated pipes 28 arranged in upper and lower tiers with the pipes in the upper and lower tiers being laterally offset from each other along the full length thereof. The upper and lower tiers of pipes, at the entry end of the forming section 26, are relatively widely spaced whereby the upper and lower sheets 12 can be received therebetween, respectively contacting the inner surfaces of the upper and lower pipes. The upper and lower pipes converge, ultimately interdigitate, and then extend in a generally common plane for a substantial distance.Noting Figure 4 in particular, the heated pipes 28 of each of the upper and lower tiers also laterally converge inwardly as the tiers converge toward each other, thus acommodating the decrease in overall width of the sheets as the corrugations are formed therein. In this manner, there is a substantially greater tendency for the corrugations to form without the introduction of undesirable stresses in the sheets themselves.

It is to be appreciated that the sheets 12, as they enter the open inlet end of the forming section 26, are individually contacted by the pipes of the spaced upper and lower tiers, whereby an initial corrugation of the upper and lower sheets is effected prior to a fully bonded engagement of the sheets with each other. There is thus no resistance, by the adhesive, to at least the initial corrugated forming of the sheets. Rather, the bonding adhesive interengagement of the sheets takes place only as the sheets are brought toward their corrugated configuration. In this manner, a more positive corrugated configuration and stable product is achieved.

Immediately beyond the forming section 26, and receiving the now assembled panel, is a set of upper and lower corrugated rolls which insure that the proper corrugated configuration has been achieved, provide additional pressure to insure proper adhesion between the panels, and act in the manner of pull rollers to advance the panel.

The corrugated rollers 30 are followed by a setting or drying section 32 formed of a series of elongated straight heated pipes which are configured to closely conform, both above and below the panel, to the corrugations. This section 32 provides for both additional setting time and additional drying to properly set the laminating adhesive and dry, and therefore harden, the paperboard of the panel.

The panel, which at this point is continuous, is trimmed along the opposed side edges thereof by appropriate rotating blades 34. Immediately beyond the trimming blades 34 are a series of pull rolls 38.

These pull rolls 38 will preferably consist of upper rows of steel discs and lower urethane back-up rolls.

Appropriate drive means will be provided.

In the final section 40, the continuously formed panel is cut to length preferably using a vertical blade shear 42 with a corrugated cutting blade and a corrugated back-up blade. These blades are designed with a somewhat lower amplitude than the panel to prevent cutting all of the panel at one time, and yet obtain a clean cut without flattening the corrugations.

After formation of the panels in the above described manner, the panels will normally be loaded into a treating rack and batch treated in roofing grade asphalt. The treated panels can then be coated with a polymeric material, such as acrylic based paint, and oven dried.

From the foregoing, it will be appreciated that a unique corrugated building panel and method of making same have been defined. The panel incorporates a degree of structural integrity and strength heretofore not deemed practical when utilizing a paperboard or chipboard product. In turn, the unique structural nature of the final product is, to a large degree, attributable to the particular procedures used in defining the final product.

The foregoing is considered illustrative of the principles of the invention which are deemed to encompass all suitable modifications and variations which can be considered to fall within the scope of the invention as claimed.

Claims (12)

1. A method of forming a corrugated building panel utilizing multiple formed paperboard sheets; said method comprising the steps of introducing multiple sheets from independent sources of indeterminate length, treating each sheet to enhance the formability thereof, advancing the sheets in a converging direction, applying an adhesive to selected ones of said sheets prior to contact therebetween and in a manner whereby the adhesive is provided between each pair of contacting sheets, commencing corrugation of each sheetpriorto bonding contact with the other sheet, and, in conjunction with the continuing corrugation of the sheets, bringing the sheets into adhesive bonding contact with each other to define a unitary corrugated panel.

2. The method of claim 1 wherein the treating of each sheet to enhance the formability thereof comprises subjecting of the sheets to steam.

3. The method of claim 2 wherein two paperboard sheets are used.

4. The method of claim 3 wherein each sheet is on the order of approximately .035 to .052 inches.

5. The method of claim 2 wherein the unitary corrugated panel is subjected to heat to encourage the drying of the panel forming sheets and setting of the adhesive.

6. The method of claim 5 wherein the unitary corrugated panel is treated with asphalt.

7. The product produced by the method of claim 1.

8. A corrugated building panel when produced by the method of claim 1 comprising two fully formed sheets of paperboard substantially simultaneously corrugated, laminated and adhesively bonded into a unitary panel.

9. The corrugated building panel of claim 8 wherein the panel is treated with asphalt.

10. The corrugated building panel of claim 9 wherein the panel is coated with a polymeric material.

11. The corrugated building panel of claim 8 wherein each sheet has an initial thickness of approximately .035 to .052 inches.

12. Acorrugated building panel substantially as as described with reference to the accompanying drawings.