Multiple ply composite veneer laminate with improved dimensional stability

The present invention is a veneer laminate comprising a first veneer sheet as one surface, a second veneer sheet as the other surface of the laminate with its grain running substantially parallel to the grain of the first sheet, and a sheet of paper of a width of substantially the same width as the first and second veneer sheets bonded to the inner surface of each of the veneer sheets. The fibers of the veneer sheets in a direction substantially normal to the grain of said veneer sheets are broken at spaced intervals sufficient to permit the flexing of the laminate about a tight radius of an object of less than about 90.degree..

FIELD OF THE INVENTION 
The invention relates to wood panels and, more particularly, to multiple 
ply wood veneer laminates adapted to be used to cover furniture and the 
like. 
BACKGROUND OF THE INVENTION 
Wood veneer is highly desirable for many purposes including the covering of 
furniture with wood of appropriate grain and coloring. Because the veneer 
sheets are thin, difficult to handle without breakage, subject to warping 
and delamination when adhered due to environmental considerations, it is 
desirable to give the sheet stability by bonding the sheets to a 
substrate. Composite veneer laminates, i.e., veneer sheets bonded to a 
substrate, come in many forms such as paper backed veneer laminates in 
which the veneer sheet is glued directly to a paper substrate. The paper 
itself can have varying thicknesses as desired. Another common laminate is 
a fabric backed veneer laminate in which the veneer sheet is glued to a 
fabric of selected stiffness. An early composite laminate is found in U.S. 
Pat. No. 1,387,101 in which the veneer sheet is adhered to a box board 
paper intermediate layer and wire mesh reinforcement. An example of a wood 
to wood composite laminate is found in U.S. Pat. No. 2,356,625 that 
describes two sheets of veneer being bonded together with a matrix of saw 
dust and adhesive. Notably the sheets in this patent have their grains 
running in parallel directions. To provide stability to the composite, 
strips of veneer with the grains running perpendicular to the grain of the 
sheets were adhered thereto. 
An important improvement to the aforementioned laminate is described in 
U.S. Pat. No. 4,569,873 describing a composite laminate in which three 
veneer sheets are used. Two of the sheets are the face plies of the 
composite laminate while the third sheet is the center ply. The grains of 
the outer plies run in parallel directions. An adhesive is used to bond 
the three sheets. To provide structural integrity the center sheet has the 
grain running perpendicular to the grain of the outer face plies. 
Still another type of composite laminate is the phenolic backed veneer 
sheet which has found great acceptance in the industry. In this case the 
integrity of the sheet is maintained by supplying a thick paper sheet 
impregnated with glue. The laminate is then adhered to a surface gluing 
the phenolic backing directly the article being covered. Phenolic backed 
laminates are characterized by durability but not flexibility and 
dimensional stability. 
One problem with the composite laminates discussed above and others in the 
prior art is maintaining the appropriate balance between durability and 
flexibility. When fabricating composite laminates in an attempt to gain 
durability and dimensional stability under various atmospheric conditions, 
the result is generally a stiff laminate that is rigid. It is extremely 
difficult to post the laminate around articles to be covered without 
damaging the laminate itself. It is generally necessary to cut the 
laminate when reaching the edge of a corner and to start again with 
another piece of the laminate around the corner. The internal composition 
of the laminate will be readily apparent and be manifested in the form of 
a black line. To obscure or otherwise camouflage the black line, artisans 
often use moldings and the like that may not be suitable in many 
applications. Yet the additional wood ply or phenolic resin backing is 
required to provide the aforementioned stability and/or durability. 
It is therefore a paramount object of the present invention to provide for 
a new composite veneer laminate made substantially of wood having good 
stability and durability which can be bent around tight radii of the 
structure to be covered and additionally does not display the dark line 
evidenced by prior art composite laminates even when cut and the edge 
thereof is exposed. 
It is still another important object of the present invention to provide a 
method for making composite veneer laminates having improved stability, 
durability and flexibility and which minimize the visibility of internal 
construction of the laminate when viewed on edge. 
SUMMARY OF THE INVENTION 
In accordance with one embodiment of the present invention, a composite 
veneer laminate comprises a pair of veneer sheets as the outward facing 
surfaces of the laminate and a sheet of paper sandwiched therebetween, the 
paper sheet having a thickness of not greater than about 5 mils. The 
veneer sheets are bonded to the paper sheet by an appropriate adhesive. 
Additionally, the veneer sheets are positioned so that the grains are 
running parallel with one another. The fibers of the veneer sheets lying 
across the grain are broken at predetermined intervals so as to provide 
further flexibility across the grain of the veneer sheets and permit 
posting of the veneer about tight radius applications such as the corners 
of furniture, profiles of molding and the like. 
In accordance with another embodiment of the present invention, a process 
for making a composite veneer laminate comprises supporting a first sheet 
of veneer in a substantially horizontal position, laying a sheet of paper 
having adhesive on both sides thereof on the first sheet of veneer, laying 
a second sheet of veneer on the paper sheet with the grain thereof running 
substantially parallel to the grain of the first veneer sheet, applying a 
predetermined amount of pressure to the laminate and simultaneously 
heating the laminate at predetermined temperature for a time period 
sufficient to cause the veneer sheets to bond to the paper sheet lying 
across the grain, and thereafter breaking the fibers of the veneer sheets 
of the composite laminate at predetermined intervals. 
Still other objects of the present invention will become readily apparent 
to those skilled in the art from the following description wherein there 
is shown and described a preferred embodiment of this invention. As it 
will be realized, the invention is capable of being modified in various, 
obvious aspects all without departing from the invention. Accordingly the 
drawings and descriptions will be regarded as illustrative in nature and 
not as restrictive.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Reference is made to FIG. 1 which illustrates a cubic structure 10 covered 
by a phenolic backed veneer laminate 12 typical of the veneer laminates 
used extensively today. Because the laminate has a relative thick backing 
made of paper and a phenolic based glue penetrating the paper, the 
sectional view shown along the edges of cubic structure easily displays 
the characteristic black line denoted by the character numeral 14 of this 
type of laminate. These type of laminates lack the ability to "post" (flex 
about a tight radius) around corners. Thus, it is necessary to cut the 
laminate to fit along the edge and start anew on the adjacent 
perpendicular surface. The side of the laminate is therefore exposed and 
the backing is clearly visible as a line. Multiple veneer laminates using 
a central wood veneer ply with cross grain positioning also would show the 
internal structure when cut along the edges. 
To camouflage the line those skilled in the art often use molding or other 
materials to hide the line. However, many applications cannot use such 
techniques or the structure of the object to be covered requires veneer 
sheet to be tailored such that the edges thereof are exposed. Thus, the 
line, undesirable as it may be, remains exposed. Typical prior art paper 
backed laminates, while not having the disadvantage of a highly visible 
black line, lack the structural integrity to withstand continuous moisture 
exposure and handling, often resulting in warping of the material or 
delamination in situ. 
The cubic structure 18 of FIG. 2 is identical in all respects to that of 
FIG. 1 except for the sheets of composite veneer laminate 20 covering the 
surface of the structure. It is important to note that even where the 
edges of the veneer laminate are exposed no discernible line is evident. 
As will be discussed below, since the width of the paper sheet bonding the 
veneer sheets together is relative small, the edge thereof is almost 
invisible. Essentially the composite laminate is almost completely 
composed of wood and has both good flexibility and dimensional stability 
as discussed below. Thus, the composite laminate of the present invention 
allows one to produce unbroken corner edges without resorting to the 
camouflaging techniques of the prior art even when the edge is exposed. In 
many instances because of the excellent flexibility characteristics of the 
composite laminate of the present invention, the laminate can be posted 
around a tight radius and there is not need to cut or otherwise have a 
discontinuous laminate surface in situ. 
A composite laminate 22 in accordance with the present invention is 
illustrated in FIG. 3. For clarity, the thicknesses of the various plies 
are exaggerated and are not to scale. Laminate 22 comprises generally two 
layers of veneer sheets 24, 26 bonded together by flexible paper sheet 28 
having adhesive on both sides thereof. As can be seen in FIG. 3, sheet 28 
has substantially the same width of veneer sheets 24, 26. The sheets 24 
and 26 are positioned such that the grains run in parallel directions as 
indicated by the directional arrows 30 and 32. Finally, the entire 
laminate is "tenderized" by breaking the fibers lying across the grain of 
the veneer sheets at predetermined intervals allowing significantly 
improved flexibility across the grain. 
Composite laminates of the present invention may be constructed from a 
large number of species of wood, available domestically or abroad, such as 
birch, elm, sugar maple, ash, red, white and pin oak, mahogany and teak. 
The thickness of the veneer sheets used in the composite of the present 
invention varies depending upon the application but is generally between 
about 0.036 inches (0.09 centimeters) and 0.02 inches (0.051 centimeters). 
The paper used as the central ply is a thermoset paper, double coated with 
adhesive, having a thickness of between about 0.005 inches (0.013 
centimeters) to 0.015 inches (0.038 centimeters), preferably about 0.01 
inches (0.025 centimeters). Such thermoset paper is commonly available and 
may, for example, be purchased from Kimberly Clark as paper number C64233. 
To provide flexibility suitable for posting and the like, the fibers are 
broken at intervals of between about 0.125 inches (0.31 centimeters) and 
0.06 inches (0.16 centimeters). The breaking of the fibers lying across 
the grain of the veneer sheets allows the laminate of the present 
invention to be flexed across the grain when the composite is wrapped in a 
small radius, i.e., around a corner or an angle of 90.degree. or less. It 
additionally promotes durability as the composite will not tend to 
delaminate or warp over a period of time due to atmospheric conditions. 
When exposed to moist air the cells of the wood tend to swell due to 
moisture penetration and the fibers attempt to bend back into original 
position. Breaking the fibers adds dimensional stability to the composite, 
thus minimizes warping and delamination from the surface of the object 
covered by the composite laminate. 
The laminate of the present invention can be fabricated in accordance with 
the steps set forth in outline,form in FIG. 4. The first step 40 comprises 
the positioning of a sheet of selected wood and thickness such as, for 
example, a sheet of ash veneer of about 1/28th of an inch on a horizontal 
support. Step 42 is the placement of a sheet of thermoset paper having a 
thickness, for example, of about 5 mils and coated with an adhesive on at 
least the side to abut the first veneer sheet. The adhesive should be a 
thermosetting type of adhesive as discussed above. The sheet then may be 
coated on the up-face as shown in step 44 with the adhesive to accept the 
second veneer sheet. Alternatively, the paper sheet may be precoated with 
adhesive on both sides before placing on the first veneer sheet as 
desired. 
Step 46 is the positioning of the second veneer sheet over the paper sheet. 
Preferably the second sheet is of the same species and thickness as the 
first sheet to promote dimensional stability. However, there may be 
instances when it is appropriate to use sheets of different species and 
thicknesses. The grain of the second sheet is positioned parallel to the 
grain of the first sheet. In the next step 48, the intermediate composite 
laminate is next subjected to pressure and heat for a predetermined time 
period until the adhesive is completely bonded to the veneer sheets. The 
pressure and temperature needed to accomplish bonding varies depending 
mainly upon the type of wood composing the veneer sheets, the paper and 
the adhesive employed. However, typical pressures are between about 100 to 
120 psi, preferably about 110 psi, and the temperatures range from about 
280.degree. F. to 340.degree. F., preferably about 310.degree. F. The time 
duration for applying pressure and heat at any of the temperatures and 
pressures is generally short, depending on the nature of the constituent 
parts of the laminate. Typical time periods are between about one to ten 
minutes, and preferably about two minutes when using the example thickness 
and species above at the preferred pressure and temperature. The pressure 
and temperature can be supplied by a hot hydraulic press. For efficient 
manufacture of the composite laminates, the laminates may be stacked in 
sheets as high as eight when applying the pressure and heat. 
The final step 50 involves the breaking of the fibers in the laminate 
across the grain at predetermined intervals. This step can be accomplished 
by causing the laminate composite to move around a tight radius such as a 
roller under pressure to ensure the sheet follows the curvature. The sheet 
should be moved in a direction substantially perpendicular to the 
direction of the grain. It has been found that the breaking should occur 
at about 0.06 inches (0.16 centimeters) to 0.125 inches (0.32 centimeters) 
for the best flexibility performance. To accomplish appropriate breakage, 
the roller about which the composite laminate is moved should have a 
radius of between about 0.250 to 0.125 inches. To prevent damage to the 
wood veneer the roller may be covered with a rubber or elastomeric 
covering. 
The foregoing description of a preferred embodiment of the invention has 
been presented for purposes of illustration and description. It is not 
intended to be exhaustive or limiting with respect to the precise form 
disclosed. Obvious modifications or variations are possible in light of 
the above teachings. The embodiments were chosen and described to provide 
the best illustration of the principles of the invention and its practical 
application to thereby enable one of ordinary skill in the art to utilize 
the invention in various embodiments and with various modifications as are 
suited to the particular use contemplated. All such modifications and 
variations are within the scope of the invention as determined by the 
appended claims when interpreted in accordance with the breadth to which 
they are fairly, legally and equitably entitled.