US2863168A - Embossing hardboard - Google Patents

Description

J. BUCKLEY ET Al.

EMBOSSING HARDBOARD Filed July 20, 1953 INVEN TOR. JOHN L. bZ/C'KAEV ATTOPA/EVS Unite States Patent 2,863,168 EMBOSSING HARDBOARD John L. Buckley and Lawrence G. Buckley, Seattle, Wash. Application July 20, 1953, Serial No. 368,854 9' Claims. c1. 18-10) For many years various materials have been embossed for many and varied purposes. Thin, flexible materials, such as artificial leather, wall paper, or doilies, have been embossed in relief from one surface through to the other surface; solid pieces of wooden molding, plain or covered with a flexible surfacing material, have been embossed on a single surface; more recently rigid, cut-to-size wall panels have been embossed on one surface, principally when made of plywood. The present invention relates primarily to such wall panels or panels of similar nature, but to such panels made of hardboard, as hereinafter defined, and to the embossment thereof on one surface.

It is self-evident that thin, flexible materials, whether or not laminated, are readily embossed through and through, but that the problems arising in their embossment are quite different from the problems which arise in the embossment on a single surface of heavy, stiff, thick, resistant, materials, such assolidwood, plywood, or hardboard. Also, as will appear more fully hereinafter, the problems involved in the embossment of solid wooden pieces, or of plywood formed of thin laminations of wood veneer, are rather different from the problems involved in the embossment of hardboard. The solid wood is difficult to depress, and so in practice the embossment thereof can only be in narrow Zones, or in somewhat isolated, areas, due to the difficulty of applying sufficient pressure and heat without crushing and ruining the piece, in the embossed area. Also, in plywood there is a tendency for the pressure employed, particularly if all-over embossment of the area of a large panel is required, to splinter out the back side of the panel, for such embossment can only be done by passing the panel between two rollers, an embossing roller and a backing roller, betweenwhich the pressure is heavily concentrated along a very narrow traveling Zone in very thin face plies, and the tendency is to crush and break loose the grain layers and to cause grain separation and splintering in at least the underface of the plywood panel. The application of Lawrence G. Buckley, one of the inventors herein, Serial No. 143,932, filed February 13,1950, and now abandoned, deals with this latter problem.

Aside from these technical difficulties of embossment of plywood panels, whereas plywood for many years was plentifully available in good grades and at reasonable prices, and so the embossed plywood was readily available and in good demand, more recently even veneer faces have been patched and of lower grade, mostly unsuitable for embossment, and so the unavailability of sound, first grade veneer, whether for plain or embossed panels (and only such grades can be used in embossing) has added to ,the cost. of such panels of embossed ply-f wood, and indeed .hasincreasedthe cost and reduced the availability of high grade plywood for any purpose, wherefore, it hasbeenattempted recently to emboss hardboard, ,which has tended recently toreplaceplywood as a ,buildingmaterial. Hardboard in the sense thus used iii is a built-up fiberboard of substantially density, strength and rigidity, in which the wood fibers are felted and more or less compressed together, in random disposition and with little residual compressibility, all bonded together by a binder usually consisting of or incorporating a thermosetting resin. Such hardboard is usually manu-. factured by forming individual panels in the fiat in a mold, sometimes by a cold process, but usually by a hot press process, the heat and moderate pressure being used to effect thermosetting of the resinous binder.

Attempts have been made heretofore to emboss various hardboard panels in the process of their manufacture, and particularly, in the hot press process, in the final pressing stage of the manufactured form. To a certain degree such embossment has been successful, but with very great limitations. eight feet, or more, in size. The pressure required in this hot press completion of a hardboard panel is of a value far'less per unit area than is required to emboss other than the very shallowest of patterns, and then usually only in a depressed area limited to a small percentage of the total surface area. In consequence all embossment of hardboard in the hot press, or in any analogous all-over fiat embossment, has resulted only in a very shallow pattern of limited area or extent. Such patterns can consist primarily only of depressed narrow lines, rather than an over-all embossed pattern. These considerations limit the pattern to one which cannot be painted, for paint will almost obliterate, the shallow pattern and fill the narrow depressed lines. This is a very serious drawback, inasmuch as the hardboard in its natural color has a somewhat unattractive or unfinished appearance which makes painting very desirable. Due to these limitations of embossed hardboard as heretofore embossed, the product has been satisfactory only as a novelty rather than as an overall panel for finishing walls.

Roller embossing of hardboard, by which. pressure can be concentrated in a narrow, traveling pressure zone, has been attempted heretofore, but employment of the processes normal to the roller embossment of plywood panels, namely the passing of the panel between a heated patterned embossing roller and a backing roller, have not been wholly successful. The pattern can only thus be deeply impressed into the surface of the hardboard, but the natural resilient characteristics of the felted fibers of a hardboard panel which has been completely formed and set when thus embossed, including its lack of a crushable wood cells and of grain structure, cause the depressions to spring back, in contrast to the crushing effect on the wood cells in the thin veneer face laminations in plywood, and this, plus the obliterating or obscuring effect which is inherent in the somewhat mottled appearance of the surface of a hardboard panel, tends to eliminate to a high degree the fine details of roller embossment of finished hardboard panels.

In the attempt to eliminate these difiiculties, we have heretofore proposed to effect embossment of a hardboard panel at the time of, or subsequent to, the application of a paper facing to the embossed surface of the panel, such process being disclosed in our application Serial No. 298,774 filed July 14, 1952, now abandoned. Embossing performed according to the process therein disclosed results in a retention by the resin-impregnated paper facing, of the embossed pattern, even though the hardboard itself does not receive and retain the pattern to any higher degree than if the paper facing were'not' present. In other words, the paper facing is more readily receptive of, and retentive of, the embossed pattern, than the hardboard, and-thereby the lack of retention of thepattern by thefibers and upon the surface of the hard-" board itself is overlooked. The paper facing being of Patented Dec. 9, 1958" Such panels are usually four feet. by

more uniform appearance per se, its presence also eliminates the obliterating effect of the surface appearance of the hardboard itself. The hardboard itself, embossed according to the process of our said application, does not per se retain the fine details of the embossed pattern, and without the paper facing such a panel would be' no different than. an unfaced hardboard panel embossed by the roller method. The application of the paper facing adds an element of cost, and since the paper is subject to damage, it is still desirable to. provide a 1 method of embossing a persisting and adequately deep and sharp over-all pattern directly upon a hardboard panel, andv particularly of embossing a pattern such as is of an over-all extent, including grooves of random width, dcpth and shape, and of appreciable depth where desired, and of having the hardboard itself retain that embossed pattern so that it may be painted or otherwise finished, and so that the pattern so embossed will not be obscured or obliterated by the painting. The provision of a. method and of apparatus. to effect that desired end is the principal object of this invention.

One important drawback of hardboard as a wall panel is that it expands rather appreciably with absorption of moisture, to any extent up to A3 inch across the width of-afour foot panel. While this drawback is not peculiar to hardboard panels alone, it is present in hardboard panels and means that such panels must be applied to a wall with rather wide and unsightly gaps between them, so, as to accommodate subsequent expansion, or that if twofsuch panels are placed in close edge-abutting relationship such gaps 'will develop if the panels shrink, or will cause buckling of the panels later if the panels swell with access of moisture. In view of such gaps and the necessity to camouflage them, or to reduce their obviousness in the wall, it is highly desirable that any pattern embossed on hardboard wall panels should be of considerable depth, and in the form of straight line or parallel ridges and grooves of random width, depth and shape, so that the gaps will blend into the embossed pattern and tend to obscure the presence of the gaps. This, then, is another reason for desiring to emboss an overall pattern of this type on hardboard panels, and for reasons given above, it has been impossible to do this by any flat pressing method, and it has been impossible to do it heretofore in such a way as to obtain and retain the depth and sharpness of the pattern even when embossed by rollers. It is an object of this invention to provide a method and apparatus to carry out the same whereby a pattern of this nature and for such a purpose canbe: applied practically and economically to a finished hardboard panel, so that such panels may be used as a wall surface and Will hide the scams or gaps between panels.

The present invention concerns the method by which roller, embossm-ent of a hardboard panel of the nature and having the characteristics indicated above may be accomplished, and concerns also the apparatus by which such a method is carried out.

In the accompanying drawings the invention is illustrated in connection with two forms'of the apparatus, anclthe several variations possible in the method will be morefully brought out hereinafter.

Figure 1 is a longitudinal sectional view, on a vertical plane, through a complete machine arranged for carrying out the method according to one proposedprocedure, and Figure 2 is a similar view showing the apparatus arranged for carrying out the method according to a somewhat modified procedure.

In the drawings P1 represents a panel which is substantially completely embossed and-which is emerging from between the embossing rollers. P2 indicates a panel which, is' in process of being preliminarily treated and which is aboutto pass between the embossing rollers, and P3 designates a panel which is about to be fed into the machine, and upon which the processing is about to begin. Each such hardboard panel (being usually of a size four feet by eight feet, or if not pretrimmed, slightly wider and longer than that) is fed face down from a feed table 9 between two feed rolls 81 and 82. The roll 81 is preferably driven, as by drive means indicated at 80, from a motor 8, and the roll 82 is urged toward the roll 81 but held from it by suitable adjustable pressure means indicated diagrammatically at 83. The motor 8 also drives the embossing roller 1 at the exit end of the machine, the peripheral rate of these two rollers 1 and 81 being kept the same through the respective drive means to them. A backing roller 10 is located above the patterned embossing roller 1, and is pressed toward the latter with heavy pressure (perhaps 200,000 pounds across a four foot panel), by pressure means typified at 11. The feed rolls 81, 82 are spaced longitudinally from the embossing roller 1 and its companion backing roller 10 by a distance slightly less than the length of the panel, although they could be more widely spaced if desired, in which latter case the feed of a given panel would be by pushing of a following paneluntil the' leading panel comes into the nip between the rollers 1 and 10.

Preferably the rolls 81, 82 are housed within a casing 2, which defines agenerally elongated oven space 20,= wherein are located horizontal guide channels 21 out standing from the sides of the housing to receive and guide the side edges of the panels, as they pass through the oven. Inasmuch as the panels such as P2 are thus of the full width of the oven, they in turn subdivide the oven space into a lower compartment 22 and an upper compartment 23, with one side or portion of each compartment being defined by and coincidingwith the planar surfaces of the panel. The patterned embossing roller, whereon the pattern is engraved or cut preferably as a series of parallel ridges and grooves'of random shape, width and depth, is preferably located in the lower com partment 2..

Means are provided to heat the patterned emb'oss'in'g' roller 1, and to this end a conduit or header 4' for a cornbustible gas may be provided with a number of longitudinally spaced apertures constituting burning jets, whereby the pipe 4 constitutes a bank of burners playing upon the under side of the roller 1 to heat it to the desired temperature. Such a bank of burners is preferably housed within the oven space 20 at the exit end thereof, so that the hot gases fill the lower chamber 22, and serve to-heat the under side of the panels P2 which divide the oven, this under side being the'surface which is to be embossed. Such gases may exit at the far or entrance end of the oven, and in this manner theyprogressively heat the'panel, so that its temperature is highest at' the point where'it enters the nip between the rollers land 10.

In. addition to heating the panel, one of the essential features of. the process is that the under surface, at least, of the panel must be moistened at about the time that the panel enters the oven, so that the moistened surface isheated, and the moisture is caused by the beat to penetrate somewhat deeply into the under surface of the panel. In order to achieve these results a moistening roller 3 is located in the vicinity'of the entrance 24 to the oven, preferably just within that entrance or just past the feed rolls 81, 82. This moistening roller may be felt-covered, and dips into a trough 31 which is kept filled with a liquid 30, which is absorbed by'the periphery of the roller 3 and is applied by the latter to the under surface of'the panel P2 as the panel is passing over the roller. A hold-down roller 32 may be employed above the panel and in conjunction with the moistening roller, to insure even application of moisture to the panels under surface. Preferably these rollers 3, 32am not driven rollers.

It may be that-the moistening conditions the cells of the wood particles incorporated in the hardboard, much as a steamed wooden rib or plank can be permanently bent or deformed in boat-building, but this is not advanced as the explanation, merely as a possible theory. Again, it may be that the moistening swells the wood fibers, making them less dense and more susceptible to deformation.

The liquid at 30 may be no more than water, or a like moistening liquid, but preferably it contains a synthetic resin dissolved in the water. Preferably such resin is of the thermoplastic, thermosetting type. While the concentration of the solution is not critical, best results have been obtained from a solution of 20% of such synthetic resin in water. Proportions from to 25% have been found reasonably satisfactory.

Such a resin solution, applied in the manner indicated to the under side of a panel adjacent the entrance to the oven, is caused to be heated and to penetrate this under surface of the panel by the heat which is applied to the under surface of the panel during its passage through the oven. In this passage, which will require approximately forty-five seconds to one minute, the resin, which penetrates the panels under surface, plasticizes the surface to an adequate depth by the time the panel reaches the embossing roller 1. It has by then achieved a temperature preferably of approximately 325 F., during the passage of the panel through the oven. The embossing roller 1 is preferably at the same temperature of 325 F., so that the embossing roller may deeply impress the plasticized under surface of the panel, and the plastic, which has penetrated this surface of the panel, is in a thermosetting condition when it issues from between the embossing rolls onto the oifbearing table 7. A hold-down guide 70 cooperates with the offbearing table 7 to hold the panel down, and the better to prevent it from curling as it issues in a some what thermoplastic or pliable condition and before it has fully set. The panel upon issuing cools down fairly rapidly, and can be readily handled in removing it from the oifbearing table.

If the panel has not previously been trimmed to width, trim saws 6, placed at proper spacing at its opposite edges and supported from the offbearing table 7, will effect the edge-trimming of the panel, and it is thus assured that the trimmed edges will be precisely parallel to the ridges and grooves of the embossed pattern.

As has been indicated above, the oven may be longer, for example sixteen feet instead of eight feet approximately, but if longer the feed-through rate should be increased correspondingly, so that the panel is subjected in any event to the effect of heat and moisture for only about the same time, that is, approximately one minute or less.

The panel, when finally cooled, has the resin contained in its embossed surface thermoset by the heat and pressure of the embossing roll, leaving a hard, moistureresistant embossed surface.

The heat applied to the panel and the heat applied to the embossing roller, either or both, may be other than the heated gas, the gas of combustion described above. For example, in Figure 2 a steam pipe is represented at 5, with a control valve at 50, leading to the interior of the embossing roller 1 through its journal at one end, and this steam, after heating the embossing roller, issues through the opposite journal and into a discharge pipe 52, which preferably is directed within the lower portion 22 of the oven, where this steam, passing out at the entrance 24 opposite the embossing roller, heats the under side of the panel and moistens it in passing.

The embossing roller might be heated, by means common in the art and other than those specifically described above, for example, by embedded electrical heating elements. In such a case other means to heat the under side of the panel as it passes through the oven would be desirable, and could be supplied by such means as infrared lamps playing upon the under side of the panel,

in its passage, as is common for heating in various arts.

We claim as our invention:

l. A method for embossing a single surface of a thick, dense, and substantially rigid panel of hardboard such as contains a previously set binder, which method comprises continuously advancing successive panels endwise in a single plane, applying a liquid thermosetting resinous moistening and penetrating agent to the surface to be embossed, passing the panel, at a distance in its path from the liquid-applying station, between a patterned embossing roller applied to the moistened surface, and a paired backing roller applied to its opposite surface thereby embossing said moistened surface, continuously subjecting the surface to be embossed, from a point in the vicinity of the liquid-applying station to a point in the vicinity of the embossing station, to temperatures whch progressively increase as. any. given point on that surface approaches the embossing station, to effect penetration of the panel by the applied liquid, and cooling the panels embossed surface promptly after it passes the embossing station, to set the applied resinous moistening agent.

2. A method as in claim 1, including continuously heating the embossing roller by playing thereon a bank of flames, and conducting the gases of combustion from said flames across the moistened surface of the panel, to the vicinity of the liquid-applying station, as the heating medium for such surface.

3. A process of embossing a sharply detailed overall pattern upon a single planar surface of a hardboard panel of the character described, which comprises moistening the surface of the hardboard panel which is to be embossed with a water solution of a thermosetting resin, and heating the so-moistened surface to a temperature to soften such surface and to cause the mostening agent to penetrate at least to the depth of the pattern to be applied, and to soften the surface, but insufiicient to set the resin; passing the panel while so heated and moistened between a patterned roller applied to the moistened surface and a backing roller'applied to its opposite surface, the pressure between the two rollers being sufficient to impress the pattern deeply into the softened surface of the panel, and the temperature of thevembossing roller being sufficient to set the resin in the moistened surface, for retention of the pattern impressed.

4. A process as set forth in claim 3, wherein the heat ing of the panels surface is accomplished by directing a hot gas onto such surface during its advance towards the embossing roller.

5. A process as set forth in claim 4, wherein the hot gas is the product of combustion of a gas.

6. A process as set forth in claim 3, wherein the heating and embossing is accomplished in a period of time not exceeding about one minute.

7. A process as set forth in claim 4, wherein the heating and embossing is accomplished in a period not exceeding about one minute.

8. Mechanism for embossing a single surface of a thick, dense and substantially rigid panel of hardboard, such as contains a previously set binder, said mechanism comprising means to advance successive panels endwise in a single and generally horizontal plane, means defining an elongated compartment having a portion coinciding with said plane, means located adjacent one end of said compartment to apply, to the planar surface of said panel adjacent said compartment, a liquid resinous moistening and penetrating agent, a patterned embossing roller and a paired opposed backing roller having a nip therebetween, located adjacent the other end of said compartment in positions to engage the surfaces of the passing panel, at least a portion of said embossing roller adjacent the nip of said rollers being within said compartment, and means to supply a gaseous heating medium within the compartment, at a location adjacent the embossing roller and for exit of said medium at said one end of the compartment, to heat slich s'nrfa'c'e' adjacent sai cl'c'cirflpai'tm'nf td' p'rdgress'ivelyhigher temper'atures' as it approaches theembossing roller, and to facilitate p'ene tfa'tidn l'iyth liquid'agent.

M'eeh'afnisIiias" in claim 8, wherein the embossing roller is Idcat'ed' Completely within the compartment, and including a bank of burners extending lengthwise of and directed n'pbn the embossing roller to heat the same, whef'e'by' the" gases of combustion from said burners c'o'n's'titu'te' the g'aSeous heating medium, and exit from the c'dmpartmenf through said one end thereof, and one shrfakie 'of'the p'anel issuc'cessijvely moistened with the liqiiid'r'esi'ndu's' agent, heated and embossed.

Refei'e'nc'esCit'ed in the file ofthis patent UNITED STATES PATENTS 8 Fischer Aug. 13, Ldngren OCT. 23;. Bl o'n'son Apr; 1 8, Zinser Ocjt. 8, Jenett Feb; 11', France Oct." 29 Smith Jan; 14, Lundstrom Sept. 11, Va'rner Jan. 1, Getchell' Sept. 9, Collins' Oct; 13; Brown Nov. 22,

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