US2544133A - Edge-gluing of veneer - Google Patents

Description

March 6, 1951 A. c. cARLsoN EDGE-GLUING 0F VENEER 5 Sheets-Sheet 1 Filed Nov. 20, 1946 I m L m E E E h E ME 1 E M E E E 1 AM/ MA A E. i n l t. u I E A E 45V E J5. L. 9 Q w W W M E E f a F E ,9 LE E F E E 3 L M E E R 1 P r E E m c II. II

ZZZ "j Gttomegs March 6, 1951 A. c. CARLSON EDGE-GLUING 0F VENEER 5 Sheets-Sheet 2 Filed Nov. 20, 1946 March 6, 1951 c, c Lso 2,544,133

EDGE-GLUING OF VENEER Filed Nov. 20, 1946 5 Sheets-Sheet 3 f I w I V ow Qr Q X if Joya.

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N I I E 3 N b h 3nventor ARTHUR C. CARLSON Cittornegs March 6, 1951 A. c. cAFLsoN 2,544,133

EDGE-GLUING 0F VENEER Filed Nov. 20, 1946 5 Sheets-Sheet 4 d M: wk

3m entor ARTHUR C. CARLSON March 6, 1951 A. C. CARLSON EDGE-GLUING OF VENEER Filed Nov. 20, 1946 5 Sheets-Sheet 5 3nventor ARTHUR C. CARLSON Patented Mar. 6, 1951 EmGE-GLWG @F VENEER Arthur 0. Barlson, Anacortes, Wash, assignor, by

mesne assignments, to American Manufacturing Company, Inc., Tacoma, Wash, a corporation of Washington Application November 29, 19M, fierial No. illidifli (i. MHz) I c tiililz i The present invention concerns the edge-gluing of two strips of wood veneer which have their edges abutting, with a glue, usually a thermosetting glue, therebetween. Such wood veneer strips have a definite grain that runs the long Way of the strips. Each is thin and flexible, and is subject to wrinkling and warping which produces irregularities in their edges to an extent to prevent proper matching or registry of the edges when abutted. More particularly, two such strips by reason of their irregularities of surface have not heretofore been made to lie both in one smooth common surface, thereby to join smoothly along their abutted edges, by mechanism suited to the quick-setting characteristics of glue which sets by high frequency heating, and without halting of the strips beneath a heavy press.

Veneer comes from the green chains in strips of varying widths, for it is the practice to clip out imperfections, and after drying and edgejointing to edge-glue the strips together, for the purpose of making up plies in plywood manufacture, and in order that the continuous strip so formed can be clipped into uniform widths of panel size. Such veneer is difficult to handle, for it is thin, (usually or in thickness) and even before drying it is subject to localized.

stresses of one sort and another, which cause it to wrinkle, to warp, and to undulate to some extent in localized areas, the crests and valleys of which wrinkles or undulations extend generally lengthwise of the grain; after drying such stresses and the resultant irregularities are much more pronounced. Always it tends to buckle if pushed ahead transversely of its grain by a following strip. Such crests and valleys of course, are not uniform throughout the length of the veneer strips, and are not similarly located in any two strips, with the result that the edges which are to be abutted undulate in such fashion that they cannot be made to register unless they are forced into a common line. The usual way to effect such registry of the edges in edge-gluing veneer strips is to press'the/abutted edges, or the glue line, between two platens urged by heavy pressure toward one another, in this way to attempt to iron them, as it were, into a common plane; see, for instance, the patents to Black, No. 1,698,185, dated January 8, 1929, to Meyercord, No. 1,397,489, dated November 15, 1921, and to Weber, No. 1,702,185, dated February 12, 1929. Extremely heavy pressure is required, and the process does not lend itself conveniently to rapid production, since it is necessary to halt the veneer sheet and the strip to be joined thereto while such pressing is being accomplished and the glue is setting. Neither is it suited to high frequency heating, to dry in a few seconds, for such high frequency platens usually require discontinuity of surface, yet continuity of the platens surface is required for holding the edges smoothly joined throughout.

It has been proposed also, in the patents to Miller, Nos. 2,290,761 and 2,290,762, dated July 21, 1942, to bring the strips successively into edge-abutting relationship to the rear edge of a continuously advancing sheet, and while the sheet is proceeding slowly about a large heated drum, to pull the strips closely adjacent the periphery of the drum, by such means attempting to hold the strip and the sheet flat against the drums periphery. The apparatus to this end is large and expensive, and the rate of production is still slow, though the operation is a continuous one, and, moreover, it is not feasible to use sufiicient inward pressure, nor to apply it so at such close spacings, as to make sure that all the local edge irregularities are ironed out, and that the edges being thus glued are perfectly straight throughout their length, that is, without local undulations above or below the general plane of the sheet. Nor is this mechanism suited for use with high frequency glue setting, hence is much slower.

The primary object of the present invention, then, as it concerns the edge-gluing of veneer strips, is to provide a means and a method whereby, during the glue setting operation, the strip edges which are abutting are so stressed overall as to overcome the locally distorting stresses, and

to take an altered but uniform and controlled formation, so that both are maintained in perfect registry; additionally, by such stressing the tendency to buckle is overcome.

In the general field of edge-gluing work pieces,

as illustrated by the patent to Jones, No. 1,693,606,

dated December 4, 1928, as well as in the specialized portion of that field which deals with the edge-gluing of veneer strips, there is need of a method and apparatus for effecting the gluingof such pieces or strips continuously and rapidly, without long holding under edgewise pressure, and without interruption in the forward advance of the pieces and of the sheet formed by precedingly joined pieces. The provision of satisfactory mechanism and a method to this end is an important object of this invention. Additionaly, the accomplishment of this end is greatly facilitated by the use of a thermosetting glue, subjected, while the edges between which it is interposed are abutted, to the influence of a 3 high frequency electrical field, which effects an adequate degree of setting of proper types of glue in a matter of a few seconds. The patent to Linquist, No. 2,317,281 dated April 20, 1943, discloses such an operation.

Diillculty has been experienced, however, in employing such high frequency glue setting, and particularly in the edge-joining of thin pieces, like veneer, due to the fact that the platens between which the high frequency discharge passes should be, in effect. in contact with the opposite surfaces of the pieces to be joined, yet when the platens are thus closely disposed for edge-gluing veneer strips or similar thin strips there is so small a dielectric air gap between them that the operation of the device is seriously affected, and its efllciency is reduced. It is necessary for the building up of adequate capacitance between the platens to maintain a minimum discontinuity or spacing between them which is considerably greater than the thickness of the veneer strips.

Accordingly, it is a further object of the present invention to provide apparatus and a method by means of which high frequency glue-setting mechanism may be employed, and yet the platens, being maintained always at a suflicient or adequate dielectric spacing, will yet effect proper contact with the opposite surfaces of thin veneer strips, without interference with their proper operation and their full efllciency.

Associated with the latter object it is a further object so to control and localize the application of the high frequency field, and to cause it in effect to shift along the glue line, rather than to attempt to set the glue along all portions of the glue line simultaneously, to the end that the current strength may be reduced to a minimum, yet without loss of 'but rather a gain in efliciency and uniformity of application.

There are many other objects accomplished by the present invention, such as localizing the effect of the glue setting in sectional portions of the glue line and causing this localization to progress until the entire glue line has been acted upon by such a localized application of the glue setting field, and such as the adjustability of the device to accommodate different thicknesses of veneer, as well as many others, which will appear as better understanding of the invention is obtained from study of the drawings and of this specification, and it is not deemed necessary to enumerate them at this point, as suflicient has been said to indicate the general objects of the invention.

The invention, as will now be evident, concerns the apparatus shown in the accompanying drawings, and the method which, with the apparatus, will be more fully explained in the following specification and defined by the claims which terminate the same.

In the accompanying drawings the invention is shown in an elemental or diagrammatic form, it being understood that various details of construction have been omitted or merely suggested, and that various additions or changes may be made in the construction of the device, or of certain parts thereof, within the skill of one familiar with this art.

Figure l is a general plan view of the mechanism in the region of the glue-setting station, various parts being broken away to show better the construction of parts beneath them.

Figure 2 is a longitudinal sectional view, taken in part along the edge of the machine and in part along the crown of the table's curvature, the portion illustrated corresponding to that shown in Figure 1.

Figure 3 is a general diagrammatic view in side elevation of the complete machine, and Figure 4 is a similar diagrammatic view, illustrating the drive arrangement, and being in effect a side elevational view.

Figures 5, 6;. and '7 are successive transverse sectional views, taken substantially along the lines indicated at 5-5, 66, and ll, respectively, of Figure 2.

Figure 8 is a sectional view edgewise of the glue-setting platens, Figure 9 is an end view thereof, illustrating the manner of adjusting the spacing of the platens, and Figure 10 is a detail sectional view alongthe line Ill-l0 of Figure 8.

Figures 11 and 12 are diagrammatic views, illustrating successive stages in the progress of a glue line through the platen, in one form of the latter.

Figure 13 is an enlarged view of an edge of the platens, with a veneer strip therebetween, the viewpoint being indicated by the line l3-l3 of Figure 11.

Figure 14 is a detail view, illustrating the effect of inclining the corrugations relative to the length of the platen, the viewpoint being indicated at I l-I4 of Figure 11.

Figure 15 is an isometric view of a portion of one of the platens, in this instance the lower one.

It has already been pointed out above that wood veneer strips, because of non-uniformity of water content, or the nature of the grain or fiber, are subject to localized stresses which cause their edges (both end edges and those side edges which extend lengthwise of their grain), to wrinkle, or undulate, that is, to depart from the general plane of the strip. Yet when two abutted side edges are to be joined, it is essential that they abut uniformly along a common line, usually thought of as a straight line, and the only way in which this has been accomplished heretofore has been by applying very great pressure so distributed along the entire length of the glue line, normal to the surface of the strips, and of such magnitude, that the edges are pressed flat against a platen or similar support. I have discovered, however, that such edges maybe caused to come into registry if both strips are so stressed otherwise than by pressing, to such an extent that the local stresses are overcome or dominated by an overriding internal stress from end to end of the edge, and I have also discovered how such stressing may be readily produced, with a minimum of applied external force, namely, by bowing or bending the veneer strips lengthwise of their grain, and usually in a smooth, continuous curve of progressively (lengthwise of the table) decreasing radius, about a table or form. As such bending progresses the wrinkles gradually disappear and each bowed edge lies in a plane disposed radially of such curved edge, that is, transversely of the bowed strip. While the strips are thus bent to a common curvature by the stress endwise of the grain, they may be held in edge-abutting relationship, and thermosetting glue previously applied therebetween may be set by passing them through a thermosetting zone, or otherwise subjecting them to glue-setting conditions. This glue-setting is readily accomplished while the strips are advancing at a constant rate, and without interruption of their advance, through the space between two separated platens, between which a high frequency field is established, the platens during their passage being held, thus bent, and

' in edge-abutting relationship.

Care must be taken that the stress is not so 18 great nor so abruptly applied that the fibers are broken down or the strips cracked transversely of their grain. This can readily be accomplished by bending the strips progressively, by moving them transversely of their grain, along arcuate guide means, such as a table or similar support, which is progressively more sharply curved until the curvature from end to end is suflicient to produce the intended stress throughout the length of the grain of each strip as it reaches this most curved portion of the table. By holding this curvature while the glue line is passing through the glue-setting zone, the glue is set, and it is only necessary now to take care that the curvature is not so abruptly released, nor released in such manner, that the joint breaks apart upon reestablishment of the local stresses. This may be done by gradually decreasing the curvature of the sheet formed from such strips, so joined, and in particular by retaining the side edges of the sheet formerly the ends of the strips, substantially at their former depressed level, and permitting the elevated crown of the strip to drop down gradually to the level of the edges of the sheet.

The table which receives the strips to be joined may start out as a plane table, such as might be defined by the rollers Ia upon the shafts lIIa supported in bearings II upon any convenient framework 9. In this instance feed tapes I2 extend between the rollers Ia and the next series of rollers Ib (see Figure 3). This series of rollers lb is arranged somewhat on a slight transverse curve. Beyond the rollers lb are further series of rollers Ic, Id, etc., terminating in four series of rollers I7, I10, Im, and In, though further rollers Ip and Iq constitute in effect an extension of the table. These rollers are supported on corresponding shafts, such as the shafts We in Figure 6 and the shaft Illq in Figure 7, and each of the series of rollers from In through at least to I7, and normally through to In, is of increasing curvature lengthwise of the strips of veneer, or transversely of the table. The shafts, IUb to Iflq, inclusive, are provided with universal joints I3 at intervals, for these shafts are driven shafts, as is indicated by the sprocket gears Me, ltd, l lq, etc., and idlers my; a common drive chain It, driven by the motor I lr, accomplishes rotation of these successive series of rollers. As will be evident in Figure 4, these sprocket gears are progressively of different size, at least to include the sprocket gear My, but the sprocket wheels My, I 2k, Him, and Itn are preferably all of one size; the purpose for so doing will be pointed out later. The sprocket gears Mp and Mq are of the same size, but preferably are slightly larger than the gears M7, to Itn, in order to insure that the newly joined glue lines are not pulled apart.

The series of supporting and progressively transversely curved bottom rollers define a definite and progressively sharper curvature, and topor hold-down rollers are employed in order to insure that all strips will be bowed alike. These top rollers are designated I5b, I5c, etc.,and are supported upon shafts I6, likewise having universal joints I3, so that the curvature of each series of hold-down rolls may correspond to the curvature of the supporting rolls beneath it with which they cooperate, such two series of rollers thus forming coacting arched upper and lower guide means spaced apart a distance approximately equal to the thickness of the veneer. The hold-down rolls are driven each from its series of supporting rolls by the intermeshing gears II. For further support of the strips as they advance along the table thus constituted there may be provided narrow strips or skids 90, disposed in the general direction of the advance of the strips; see Figure 7.

The hold-down rollers of the 15 series and their shafts I6 are permitted to rise and fall slightly by guiding them for vertical movement between stakes 9i, depending from an overhead framework 92, which constitutes part of the supporting framework.

Just beyond the rollers In and Itn are the spaced-apart platens, which with the means to establish a high frequency electrical field between them, constitute the glue-setting means. These platens may take various forms, as the mechanical or the electrical requirements may dictate, hence while the form now to be described will serve to illustrate the principles involved, it is not to be taken as constituting, per se, the only nor necessarily the best form of construction.

The upper platen 2 is divided longitudinally into two halves 2a and 2b, while the lower platen 20 is continuous. The purpose of the division is to form an adequate dielectric air gap between the two halves 2a and 2b, so that the terminals of the high frequency device 29 may be connected to these two halves of the upper platen. Whereas the lower platen 20 is spaced below the upper platen to an extent sufficient to constitute an adequate dielectric air gap, yet under operating conditions the current discharges include the lower platen 20 in their path, and in the field, intermediate the platen halves 2a and 2b. Care must be taken, of course, to afford these conductive elements adequate insulation, and the upper platen is supported upon an insulating framework 2I, and the lower platen 22 upon a similar framework 22. The upper framework 2I is mounted for adjustment vertically relative to the lower platen 2, the means to this end being shown best in Figures 8 and 9, and including the worm pinion 23 on the transverse shaft 22 in mesh with the worm gear 25, to operate a screw jack elevator 21. The framework 2I is supported from the elevator 27 through a compression spring 2%, which absorbs a considerable part of the weight of the framework 2I and the upper platen 2, so that this platen does not rest heavily upon the strips as they pass beneath it.

The supporting rollers Ip and I q are beyond the platens from the last series of feed rollers In, I512, and with their hold-down rollers I51) and Itq these rollers constitute in effect oifbearing rolls. Their transverse curvature is substantially the same as the transverse curvature of the last series In, I5n, so that the sheet of joined veneer strips, as it emerges from between the platen, retains the same curvature to avoid the possibility of disturbing the preceding strips until there has been a chance for the glue to become set in its passage between the platens. However, in order to prevent breaking down of this joint by altering. that is, lessening, the curvature of the sheet prematurely, the table, as may best be seen in Figure 3, beyond the rollers lp and Iq changes its transverse curvature gradually in the section 93. However, even here it is preferred that the change be not a raising of the edges of the section 93 to the level of the crown thereof, but rather a dropping away of the crown towards the level of the edges. There may be some slight raising of the edges, but preferably the change in curvature is primarily accomplished by dropping the crown gradually to the level of the edges of the sheet. When finally the sheet is flattened out again, it may be delivered to offbearing rolls and tapes or chains 94.

Individual veneer strips, previously edge-jointed and having a suitable glue, usually a thermosetting glue, applied to at least one edge thereof, are laid up upon the feed tapes I2 or in advance thereof, to be advanced thereby edgewise and transversely of their grain, and in somewhat random spaced disposition, until they reach the feed rollers Ib and the corresponding hold-down rollers I5b, collectively constituting elongated arcuate guide means through which the veneer strips are advanced transversely of segmental planes passing through such arcuate guide means. In their passage along the tapes I2 their ends are permitted to sag or drop down somewhat, until by the time they arrive at the first feed rollers each strip has acquired some curvature lengthwise of its grain. Engaged between the rollers Ib and I5 b, the strip is now positively fed and retained in this curved position, and its speed of advance may be decreased slightly. As it passes to successive series of rollers its speed of advance is further decreased, and likewise its curvature lengthwise of its grain is further increased, at least until such time as it arrives at the feed rollers I7 and I57. If prior to the time it reaches the latter rollers its leading edge has caught up with the trailing edge of the strip in advance of it, its speed of advance, of course, is not further decreased relative to the strip ahead of it. However, its curvature does increase, at least until it reaches the rollers I y and I57, and, preferably, its curvature increases further until it passes between the rollers In and I511.

As may be seen in Figure 5, where the strip V is viewed edgewise, and not stressed, but is held more or less in a fiat plane, its edge may have a number of undulations U. As its curvature lengthwise of the grain is increased (see Figure 6), these edge undulations decrease, since the undulations having crests and valleys extending lengthwise of the grain that cause them are dissipated increasingly by the internal over-all stress caused by bending the strips, until, by the time the strip has reached the last rollers In and I5n, the edge and surface undulations both have disappeared, and the veneer strip V, as may be seen in Figure 7, is bent to a uniform or predetermined curvature, and its edge follows the smooth predetermined curve defined by these rollers and by the skids 90. In addition, and for a purpose which will shortly appear, there may be flexible hold-down strips 96 beyond the rollers Ii'm, or intermediate any preceding series of rollers.

The platens 2 and are of the same curvature as the last rollers In and I5n, and consequently the strips, by now brought into edge-abutting relationship each witlzghe strip that preceded it, enter the space betw n the platens, and in passing through the platen space or any other gluesetting device at this location, the glue is set while the strips continue their advance. When they emerge they are engaged between the offbearing rollers Ip and Hip, Iq and I5q, turning at the same rate or slightly slower than the final four series of feed rollers, and the strip is thus advanced over the table 93, where its curvature.

the off-bearing chains 94. What happens to it thereafter is not part of the present invention,

is gradually reduced, and finally is delivered to 8 but normally it would pass a clipper and be clipped into widths of standard panel size.

The platens 2 and 20, as is clearly shown in Figure 1, are inclined somewhat with respect to the direction of advance of the strip V, and with respect to the glue line G between two such edgeabutted strips. One purpose of so doing is to avoid the possibility of interference between a strip edge and the entrance to the interplaten face, and to guide the edge by a progressive shifting of the point of engagement with the platen lengthwise of the latter. A further and quite important purpose, however, concerns the employment of the high frequency electrical field and the current strength to produce the same, and its distribution or concentration. This will appear shortly.

There are serious disadvantages to the location of two platens, between which a high voltage, high frequency field is established, so closely together as would be required to effect their surface contact with the opposite surfaces of thin veneer strips. Unless a minimum dielectric spacing of about one-half inch is left, or the voltage is undesirably decreased, leakage results, the capacitance can not build up sufilciently, and also the field is localized in certain areas, causing too great application of heat in those areas and too little in other areas. the platens are substantially in contact with the opposite surfaces of the thin strips, usually not thicker than /8", and in particular with spaced points along the glue line, proper thermosetting conditions cannot be produced within the glue lines, certainly not within the period of a few seconds. Thus apparently there are two incompatible requirements, the one for sufficient spacing to preserve an adequate dielectric air gap, and the other for close approach to contact opposite surfaces of thin work pieces. The solution, according to the present invention, is to provide veneer strip engaging rib or ridge elements disposed in alternate arrangement'at opposite faces of the strips, such as by corrugating the platens (see Figures 13, 14, and 15) complementally so that the ridges or spaced lines of contact of one platen are opposite the valleys of the other, and vice versa, and so that the general surface defined by the ridges of one platen approaches closely the general surface defined by the ridges of the opposite platen, and yet at all points the metal of the two platens is maintained at an adequate dielectric spacing. Thus the spacing SI in Figure 13 is identical with the spacing S2, yet the ridges of the platens approach closely enough a common plane that they contact the opposite surfaces of the thin veneer strip V, which is passing between them.

Moreover, these corrugations are preferably so inclined relative to the direction of advance D (see Figure 1) that the ridges of the corrugations define between them inter-ridge sections of the glue line G. and as the glue line advances, due to the inclination of the corrugations, this point of contact of any given ridge will swee the length of the inter-ridge section of the glue line, so that by the time passage of the glue line through the interplaten space is completed, all parts of the glue line will have been swept by at least one ridge of a corrugation. The effect of this is seen in Figure 14. Additionally, the corrugations by their light pressure produce progressive slight undulations, which serve further to iron out any remaining wrinkles.

On the other hand, unless The eflect of the inclination of the platens as a whole relative to the direction of advance D is illustrated by comparison of Figures 11 and 12. In Figure 11 the lower part of the glue line G is just entering between the platens, and since the glue line affords the best discharge path, all the field tends to localize now in the region of the entering glue line. veneer strips continues, a condition illustrated in Figure 12 is reached, and by now the portion of the glue line which was shown entering in Figure 11 has passed beyond the platens, with the result that the concentration of the electrical field has progressed lengthwise oi the platens and will finally localize in the opposite end of the glue line, after traversing the entire length of such line. The concentration at the ends of the glue line is advantageous, for it is here that the greatest danger of separation occurs, until the set of the glue is complete. Furthermore, since it is not necessary to provide current of such strength that it can be distributed throughout the entire length of the glue line at one time, this length being normally somewhat in excess of eight feet, the current strength employed may be somewhat less than were simultaneous distribution throughout the entire length of the glue line to be required. Surges and excessive loads are thus avoided.

It will be understood, of course, that the platens might be heated by means such as electrical resistance elements or steam, to supply such heat by conduction to the glue, or infra-red or other radiation heat sources might be provided, and if such were the case, the corrugations and their arrangement, as described, would still be advantageous. The corrugations are not only valuable for more even distribution of the electrical field, but have an important advantage in that they lessen the friction of the stressed strips as they are pushed between and are held to their curvature by the platens. For such purposes the corrugations would be desirable, even though the work pieces to be joined were not stressed or bowed, as are the veneer strips, or even if the platens were of a type which would raise from and lower upon a glue strip, as in a common type of platen press. Additionally, the valleys of the corrugations serve to collect exuded glue, keeping the ridges clear thereof.

The arrangement shown will provide smooth edge joints, continuously and without interruption of production, and at a rapid rate, for only a matter of seconds is required to effect the setting of the glue in such a thin joint, and this can be accomplished during the passage of the glue line through the narrow platens.

I claim as my invention:

1. A machine for continuously edge-gluing individual veneer strips into a continuous sheet, comprising upper and lower platens spaced apart for edgewise passage therebetween of such strips, and constituting glue-setting means, said platens being materially curved, lengthwise of such strips, to stress the strips fibers, and means to guide and advance strips edgewise to said glue-settingmeans, to arrive there in edge-abutting relationship, the strip-contacting faces of said platens being corrugated, to engage the strips only along a plurality of spaced zones, in their passage through the glue-setting means, and the corrugations being inclined relative to the direction of the strips advance, and closely enough spaced that each section of the glue line is wiped pro- However, as advance of the g-ressively lengthwise by at least one such corrugation.

2. A machine for. continuously edge-gluing individual veneer strips into a continuous sheet, comprising upper and lower platens spaced apart for edgewise passage therebetween of such strips, and constituting glue-setting means, said platens being materially curved, lengthwise-of such strips, to stress the strips fibers, and means to guide and advance strips edgewise to said glue-setting means,- to arrive there in edge-abutting relationship, said platens being inclined relative to the passing strip edges, to advance each gl-ue line progressively lengthwise between the platens, the strip-contacting faces of said platens being corrugated, to engage the strips only along a plurality of spaced zones, in their passage through the glue-setting means, and the corrugations being inclined relative to the direction of the strips advance, and closely enough spaced that each section of the glue line is wiped progressively lengthwise by at least one such corrugation.

3. Means for edge-gluing edge-abutting veneer strips comprising two fixedly positioned, superposed, electrically conductive platens spaced apart at all points by an air gap constituting an adequate dielectric spacing under conditions of use, means to establish a high frequency field between said two platens, means to advance edgeabutting strips edgewise between said platens, the strip-contacting surfaces of the platens being corrugated, each complementally to the other, to maintain such dielectric spacing, but the surfaces defined by the ridges of the respective platens being of lesser spacing, to correspond to the thickness of said strips, the platens being bowed, lengthwise of the strips, to an extent to stress the fibers along the glue line during its passage between the platens, and the corrugations being inclined, relative to the direction of advance and their spacing, and to the width of the platens, that each inter-ridge section of the glue line is swept from end to end by at least one corrugation, in its passage between the platens.

4. The process of edge-joining two elongated wood veneer strips each of which has its longitudinal edges extending lengthwise of its grain, which comprises bending the two veneer strips lengthwise of their grain, thereby bowingtheir longitudinal edges, and thus dissipating all local undulations having their crests or valleys extending lengthwise oi the grain, abutting a longitudinal edge of one strip with a longitudinal edge of the other strip, and, while maintaining the veneer strips thus bent with their bowed edges abutted, bonding together and thereby joining such bowed, abutted edges, and subsequent to such edge-joining operation unbending such strips in edge-joined condition forming a substantially flat composite veneer sheet.

5. The process of edge-joining elongated wood veneer strips each of which has its longitudinal edges extending lengthwise of its grain, which comprises moving successive veneer strips edgewise and transversely of their grain, during such movement abutting adjacent longitudinal edges of adjacent veneer strips with adhesive therebetween, during such edgewise movement bending such strips lengthwise of their grain and thereby bowing such longitudinal edges and dissipating all local undulations having their crests or valleys extending lengthwise of the grain, while maintainin the veneer strips thus bent and with their bowed, longitudinal edges abutted, setting wise and transversely of their grain, during such movement abutting adjacent longitudinal edges of adjacent veneer strips with adhesive therebetween, as suchedgewise movement progresses bending increasingly sharply such strips lengthwise of their grain and thereby bowing such longitudinal edges and dissipating all local undulations having their crests or valleys extending lengthwise of the grain, while maintaining the veneer strips thus bent continuing their edgewise movement with their bowed, longitudinal edges abutted through an adhesive-setting zone and thereby joining such bowed, abutted edges, and subsequent to such edge-joining operation unbending such veneer strips in edge-joined condition forming a substantially fiat composite veneer sheet.

7. A machine for edge-gluing elongated wood veneer strips, each of which has its longitudinal edges extending lengthwise of its grain, into a continuous sheet, comprising arcuate guide means of a circumferentiaLextent corresponding to the length of such veneer strips, and adapted to engage opposite sides of the veneer strips, conveying means movable in a direction transversely of segmental planes passing through said arcuate guide means and operable to move such veneer strips'bent lengthwise of their grain through said arcuate guide means edgewise transversely of the grain of the strips and into edge-abutting relationship, bonding means operable to set adhesive between the abutting edges of the veneer strips in their bent shape to form a composite sheet, and means at the discharge side of said bonding means engageable with the veneer sheet and operable to support the veneer sheet in bowed form.

8. The machine for edge-gluing wood veneer strips defined in claim 7, in which the arcuate guide means incorporate upper arched guide means and lower arched guide means spaced apart a distance approximately equal to the thickness of the veneer.

9. The machine for edge-gluing wood veneer strips defined in claim 8, each arched guide means including a plurality of veneer-engaging rollers, and mounting means for said rollers sunporting those for the upper arched guide means with their lower peripheries conjointly defining the portion of the upper arched guide means contactin the veneer strips and supporting those for the lower arched guide means with their upper peripheries conjointly defining the portion of the lower arched guide means contacting the veneer strips.

10. A machine for edge gluing wood veneer strips into a continuous sheet, comprisin elongated arcuate guide means of a circumferential extent corresponding to the length of such veneer strips, of progressively sharper curvature lengthwise in the direction of veneer strip movement, and adapted to engage opposite sides of the veneer strips. conveying means movable in a direction transversely of segmental planes passing through said arcuate guide means and operable to move such veneer strips through said arcuate guide means edgewise and into edge-abutting relationship and transversely of the grain of the strips, and thereby bending such strips lengthwise of their grain, bonding means operable to set adhesive between the abutting edges of the veneer strips in their bent shape to form a composite sheet, and means at the discharge side of said bonding means engageable with opposite sides of the veneer sheet and operable to flatten the veneer sheet.

ARTHUR C. CARLSON.

REFERENCES oI'rEn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,010,846 Black Dec. 5, 1911 40 1,338,564 Elmendorf Apr. 27, 1920 1,410,879 Bither Mar. 28, 1922 1,578,020 Elmendorf Mar. 23, 1926 2,035,682 Wikle Mar. 31, 1936 2,074,854 Owens Mar. 23, 1937 2,084,676 Friz June 22, 1937 2,231,457 Stephen Feb. 11, 1941 2,290,762 Miller July 21, 1942 2,324,068 Crandell July 13, 1943 2,379,258 Smith June 26, 1945 2,407,833 Jablonsky Sept. 17, 1946 2,434,573 Mann Jan. 13, 1948 2,457,498 Russell Dec. 28, 1948 FOREIGN PATENTS Number Country Date 517,126 Great Britain Jan. 22 1940

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