US3578522A - Veneer defect filling method - Google Patents

Abstract

THE PRESENT INVENTION AND APPARATUS COVERS A TWOSTAGE METHOD FOR PATCHING SURFACE DISCONTINUITIES IN WOOD PANELS SUCH AS VENEERS AND THE LIKE. IN AN INITIAL STAGE, AGGREGATE IS ADDED TO THE DISCONTINUITY BY MEANS OF A VACUUM. THE AGGREGATE IS THEN COMPACTED. IN A SECOND STAGE ADDITIONAL AGREGATE IS ADDED IN THE VOIDS OF THE AGGREGATE ADDED IN THE INITIAL STAGE BY IMPOSING A VACUUM THROUGH SAID VOIDS.

Description

May 11, 1971 A. H. RAUCH vENEER- DEFECT FILLING METHOD Filed July 6, 1966 m. Samus, Q

` INVENTOR AUGUST H'. RAUCH- www AT TORNEY,

United States Patent 3,578,522 VENEER DEFECT FILLING METHOD August H. Rauch, Lebanon, Oreg., assignor to U.S. Plywood-Champion Papers Inc., New York, N.Y. Filed July 6, 1966, Ser. No. 563,268 Int. Cl. B32b 19/08, 35/00 U.S. Cl. 156-94 8 Claims ABSTRACT OF 'I'HE DISCLOSURE The present invention is broadly concerned with an improved method and apparatus for upgrading wood veneers by patching surface discontinuities such as cracks, knot holes, splits, and the like. In accordance with the present invention, improved veneers are secured by a double filling technique wherein a portion of the discontinuity is first filled in an initial stage or phase, initially processed, and finally filled in a second stage then finally processed. While very desirable and beneficial results are achieved when using the present technique on top side processing, the technique and process are particularly adapted wherein the split or hole discontinuity is treated from the down or under side of the veneer.

It is known in the art that wood veneer strips as cut vary appreciably in quality and texture. Some lengths of the strips have no surface defects and are of the highest quality. These veneers, free of defects, may be utilized Iwithout any further processing as facing sheets for the manufacture of high quality plywood or lumber. Other veneer strips have slight defects and it is necessary that these surface splits, holes, and the like be repaired if they are to be used in the production of plywood panels or veneered lumber. Other strips are of a poor quality and are generally used as cross bands.

Veneer strips also particularly require patching if they are to be utilized as substrates or supports for plastic films and the like. For example, in the manufacture of a film covered plywood product, it is essential that the outermost ply to which the film sheet is bonded be fiat and substantially completely free from surface cavities, discontinuities, and the like. Thus, when such film bonded wood products are manufactured, it has been necessary that the surface plies be of the highest quality and be free of cavities, holes, and the like. Furthermore, there are many end uses wherein it is essential that the solid inner ply or crossband be initially free of defects or processed and patched so as to render it defect free.

One method of patching plies and repairing surface discontinuities such as knots and knotholes, is to punch out the remaining knot, thus completely clearing the hole. This hole is then plugged with a circular piece of veneer which is securely wedged into the cut hole. However, this method of patching is not completely effective in producing a satisfactory flat surface. This method also has the distinct disadvantage that it requires an operation which is both costly and time consuming.

Another technique used is the boat patch in which the veneer surrounding the defect is sawed out in the shape of a boat, i.e., pointed. The boat patch is beveled on its side edges, i.e., its thickness, and is inserted into the prepared cut. The assembly is pressed between heated platens to set the adhesive and to anchor the patch in the veneer. These methods also have not been entirely satisfactory for upgrading low grade veneers in order to produce the desired smooth uniform, and fiat surface. Typical processes and apparatuses for patching veneers are described in Pats. 1,549,691, 1,703,890, 2,336,703, 2,536,665 and 2,649,869.

The present invention is concerned with a novel technique and apparatus for upgrading veneers containing defects and producing high quality veneers free of open defects and discontinuities and having the desired and essential smooth fiat surfaces. The present method may be adapted for continuously patching wood veneers with a bonding composition and completely filling open voids or discontinuities in the sheets regardless of shapes or locations. Also, by the utilization of the present method, inexpensive filler materials, such as comminuted wood particles, and a binder may be readily and effectively utilized. In accordance with the present invention, a double filling and processing technique is utilized to secure a very high quality product. As mentioned heretofore, it is preferred to use the technique on the down side of the panel.

In accordance with the present invention, which may be readily understood by reference to the diagrammatic drawing illustrating one embodiment of the same, in a first stage or phase, dry aggregate is introduced by suitable means into the voids on the bottom or under side of a piece of veneer moving along a conveyor such as on a Fourdrinier type wire screen passing over vacuum suction boxes. In passing over the filler application area, filling material is drawn into the void or open defect areas, with the excess aggregate or filling material falling off and being recovered by a return conveyor. An appreciable buildup occurs around the edges.

The filled void is then nip rolled for compaction and shaved or brushed off down to the veneer surface. After compaction and shaving, or brushing off, the filler aggregate (remaining) in the knothole or other open defect, is of a thickness equal to that of the surrounding veneer. These level filled defects in a second stage are then passed over a second filling section where additional aggregate is introduced to the surface of the veneer. The suction box or means at this second section picks up a second layer of aggregate in the previously completely void areas due to some air passing through the porous aggregate already in the hole. The aggregate picked up at this point is channeled directionally into the remaining voids left from the first stage through which the suction air is passing. Due to this controlled directional liow the second application of aggregate results in very little, if any, buildup of aggregate around the edge of the hole. As discussed, this is apparently due to the fact that restriction of air flow and suction occurs which is controlled by material which has been introduced into the hole in the first stage. The result is a buildup of aggregate in the second stage of sufficient depth to give the density desired in the final patch upon further compaction. The buildup of aggregate on the second pass is confined to the void area being repaired rather than extending over the veneer face surrounding the edge of the patch.

The double filled, or processed, patch is then finally vacuumed or shaved from the bottom side to give the desired depth of aggregate to secure the density desired in the finished patch. The patch is nip rolled again to physically compact the filling aggregate to the desired density in the void areas. The veneer is then passed from the filling machines to the presses for bonding of the respective plies, While various operating conditions may be used, one method is to use a continuous belt type of press and apply about 50 p.s.i. at 350 for 10 to 20 3 seconds. The se conditions may be varied appreciably as a function of other operating conditions. This heat sealing operation functions to retain the patch for handling the plies through the layup process with the nal patch cure occurring in pressing of the plywood panel.

The described double fill procedure is very desirablesince, when using known techniques, problems existed with respect to an excess, ledge or, button of aggregate around the edge of the repaired void due to the overhang of the applied aggregate. This was very troublesome when patching both small and large knotholes simultaneously because if an adjustment were made to get minimum overhang on large knotholes, then the small knotholes would be starved or deficient as to the required aggregate. On the other hand, if the adjustment were made -to secure the required amount of aggregate for the small knot-holes, then a considerable excess of overhang `of aggregate would occur around the larger holes. The present double fill process completely overcomes this problem and produces rapid and efficient repair of all deficiencies in a panel, irrespective of the sizes of the deficiencies.

Referring specifically to the drawing, wood veneers and 20 are passed by means of a suitable conveyor along the processing line. A number of discontinuities 1 to 6 are illustrated in veneer 10. In the illustration, discontinuity or void 1 has passed through a number of treating stages or operations as hereinafter described and is fully repaired in a manner to produce a very high quality product. Discontinuity 6 is moving through the first stage or first fill stage of the process while discontinuities 2 to S have passed through intermediate processing steps including the second fill stage. Thus, the operation will be described sequentially and it is understood that repaired defect 1 has passed through stages 6 to 2 as will be described.

Defect 6 comprising a hole or a split is first filled in an initial filling stage with a filling material 11 by means of a suitable conveyor assembly 12. The material is drawn into defect or hole 6` by means of an airstream passing through the defect secured by imposing a vacuum above the panel 10 in the assembly line. The desired vacuum conditions may be secured by any suitable means and apparatus (not shown). Aggregate is prevented from passing the defect by a fine mesh screen 26 which rotates around the rolls 25 and 24. This screen is positioned on the top surface of the panel while the same is being processed. The filled void having excess aggregate is passed through suitable. rollers 13 and 14 wherein the aggregate is compacted to the desired density. The initially compacted material as illustrated at 5, is passed through an element or means designed to remove the excess aggregate therefrom. This element may comprise a stiff bristle brush 15, a suitable scraper element or equivalent means.

The patch after passing by the scraper element 15 as illustrated at 4, has a thickness equal to that of the panel. The patch or repair area 4 passes by a secondary feeder roller 1'6 assembly wherein additional 'filler material or aggregate 17 is applied to the patch 4. As pointed out heretofore, the suction applied in this secondary filling stage picks a second layer of aggregate due to air passing through the voids of aggregate already in the hole. Due to the directional controlled flow of the air stream, very little buildup of aggregate will occur around the edge of the hole. This is due to the restriction of air flow controlled by the material already introduced into the hole in the initial filling stage. The vacuum imposed in this area may be secured by any suitable arrangement of elements. Excess material is removed by means of a shaver element 18 or other equivalent means. Unused or excess filler applied in each stage is collected in aggregate return units 19 and 21 and is recycled to the operation. The patch containing the correct amount of aggregate passes through nip rolls 22 and 23 which produces the desired compaction to secure the correct density. Rolls 24 and 25 serve to introduce and remove the respective veneers to the processing elements.

In order to illustrate the invention the following example is given.

EXAMPLE In one operation a 1A veneer knothole 21/2: x 21/2 in size was filled with an aggregate using a conventional single pass technique and downside process. The aggregate was found to weigh eight grams and measure 2%" x 31/2" on the filling or overhang side. In another operation a similar but larger hole in the same veneer measuring 2% x 3" was filled using the double pass application technique of the present invention with the same settings on the machine. In the latter ope-ration the aggregate was found to weight nine grams and measure 2% x 3%" on the filling side. Thus surprisingly, there is considerably less overhang and equivalent, or better, weight with the double pass technique.

It is to @be understood that the composition of the filling aggregate may be varied appreciably in carrying out the present technique. The aggregate used in the eX- ample had the following composition:

FORMULATION A Sawdust (from sash gang through l0 mesh) 1-871/2 i.e.,

-90 parts by weight Asbestos fibers (Johns-Manville 7-D) 2 5, i.e., 3-6 parts by weight Monsanto 575 (liquid phenolic resin) 3 5, i.e., 3-6 parts by solid basis Emulsified petroleum wax 4-25, i.e., 2-10 parts by solid basis 1 Through 10 mesh results in a beautiful patch texture and the desired degree of fiuftiness. Sash gang refers to gang saws mounted in a sash, i.e., frame or gate.

2J*M7D is Group 7, Grade D of milled asbestos according to the Quebec Standard Testing Method. Fibers are Segregated on this test as follows: on 10 mesh-3,1%; through 10 mesh-69%, Fibers generally range up to about 3/9 in length with the bulk of them being 1A or less in length, pref enably having a length from 1&4" tto 1A.

3 Monsanto 575 is 1a thermosetting `aqueous `phemol-formaldehyde resin with a pH of 9.4 to 10.3, a viscosity of about 450 to 700 centipoises, a solids content of about 45% and a specie gravity of about 1.140 to 1.155.

dtParacol 404N is a paraffin wax emulsion, by weight, 46% solids, Wax, wax melting point 125 F. to 135 F., emulsion pH 6.0-6.5, Weight per gal. 8 lbs., average particle size 1-2 microns.

Other compositions may be used but with less effective results. Among these are the compositions set forth in my prior copending application, Ser. No. 102,145, filed Apr. 1l, 1961, entitled Veneer Filling Compound which is incorporated herein in its entirety by reference.

As a result of further tests it was determined that the internal bond of single pass patches made by the single pass technique average about 40 to 50 pounds per square inch, whereas the double application techniquel as described produces internal bond averages of from about 70 to 100 pounds per square inch. This unexpected greatly increased patch strength, as Well as the minimized overhang secured by the double fill technique is of extreme value and is critical to the success of veneer filling processes in Order to secure high grade veneers.

The present invention is also particularly adaptable for cold press patching techniques especially when using a latex additive formation. Under these conditions the patching operations may be conducted at temperatures in the range from about 65 to 180 F. particularly in the range from about to about 160 F. The cold patching operation utilizing nip rolls produces an excellent quality product. The cold or warm patching has the distinct economic advantage of requiring very little or no cooling as is necessary to prevent further cure in the stack when using the hot-set procedure described in last paragraph of Column 2. The cold set patch would, of course, be finally cured in hot pressing of the plywood panels.

The above compositions set forth in my prior copending application Ser. No. 102,145, filed Apr. 11, 1961, entitled Veneer Filling Compound, now abandoned (see corresponding Canadian Pat. No. 690,395, page 11) in part, are as follows:

FORMULATION B Parts by weight Sawdust (sash gang thru mesh) 80 Asbestos fiber (Iohns-Manville 7-D) 5 Monsanto 575 (liquid phenolic resin) 5 Goodyear 2000 (synthetic rubber latex) 1 10 1 Goodyear 2000 is butadiene styrene synthetic latex (50/ 50) of 41% solids and a pH of about 11.0. It has a viscosity of 11S centipoises and a surface tension of 46 dynes per centime er.

The preferable order of addition is as listed. However, under certain conditions, the resin and latex may be added simultaneously, Other latices such as natural or butadiene-acrylonitrile and butadiene-styrene of other monomer ratios may be used but the butadiene styrene latex is preferred due to its excellent performance.

Another desirable formulation utilizing a dry, powdered resin binder is as follows:

FORMULATION C Parts by Weight Sawdust (sash gang thru 10 mesh) 821/2 Asbestos fiber (Johns-Manville 7-D) 5 Hot wax (Standard Oil Petrolatum 110) 21/2 Vareum 1462 (Reichhold Chemicals Powdered Phenolic Resin) 10 In general, it is preferred that the compositions comprise from about l to parts by weight of asbestos fiber, the preferred compositions containing from about 21/2 to 5 parts of asbestos fiber. The amount of sawdust with respect to the asbestos fiber may be adjusted accordingly.

The amount of phenolic resin may vary in the range from about 1 to 15 parts, preferably from about 4 to 6 parts while the amount of rubber latex may vary from 21/2 to 15 parts, preferably from about 5 to 10 parts by weight.

What is claimed is:

1. Method for the repair of a hole in a ligno-cellulose board which comprises, (1) filling the hole in an initial stage with ligno-cellulose aggregate by vacuum means under conditions to have an excess of aggregate above the surface of said board, (2) compacting the aggregate by suitable means, (3) removing excess aggregate above said surface, (4) thereafter in a second stage by vacuum means imposed through the voids in the aggregate positioned in said lfirst stage adding more aggregate thereto into said voids, and (5) compacting the same, and adding a resin and wax in combination at a temperature range from about 150 to 190 F. onto tumbling sawdust having a moisture content less than 15% and thereafter adding to said mixture asbestos fiber having a moisture content of approximately 1%.

2. A method as defined in claim 1 wherein a rubber latex is added with said resin and petroleum wax.

3. A method as defined in claim 2 wherein the amount of wax present is in the range from about 1% to 5% by weight and wherein the amount of rubber latex present is in the range from about 5% to 10% by weight.

4. A method as defined by claim 3 wherein the quantity of asbestos fiber present is in the ran-ge from 1 to 15 by weight.

S. Method for the repair of a hole in a ligno-cellulose board which comprises, (1) lfilling the hole in an initial stage with ligne-cellulose aggregate by vacuum means under conditions to have an excess of aggregate above the surface of said board, (2) compacting the aggregate by suitable means, (3) removing excess aggregate above said surface, (4) thereafter in a second stage by vacuum means imposed through the voids in the aggregate positioned in said first stage adding more aggregate thereto into said voids, and (5) compacting the same, and including the initial step of mixing -90 parts by weight of sawdust, approximately 3-6 parts by weight of asbestos fibers, 3-6 parts by solid basis of liquid phenolic resin, a small quantity of latex, and approximately 2-10 parts by solid basis of petroleum wax to form the ligno-cellulose aggregate.

6. Method for the repair of a hole in a ligno-cellulose board which comprises, 1) lling the hole in an initial sta-ge with ligno-cellulose aggregate by vacuum means under conditions to have an excess of aggregate above the surface of said board, (2) compacting the aggregate by suitable means, 3) removing excess aggregate above said surface, (4) thereafter in a second stage by vacuum means imposed through the voids in the aggregate positioned in said first stage adding more 'aggregate thereto into said voids, and (5) compacting the same, and comprising the additional step of mixing sawdust from a sash gang saw through 10 mesh which gives effective patch texture and the desired flufliness; mixing asbestos fibers 31% on #10 mesh and 69% through #10 mesh, and said asbestos being in length to less than 1A" in length; mixing phenolic resin of the type being a thermosetting phenol formaldehyde resin with a pH of 9.4 to 10.3, a viscosity of about 450 to 700 centipoises, a solids content of about 45% and a specific gravity of about 1.140 to 1.155; and mixing petroleum wax of a paraffin wax emulsion, by weight, 46% solids, 100% wax, wax melting point 125 F, to F., emulsion pH 6.0-6.5, weight per gal, 8 lbs. average particle size 1-2 microns.

7. Method for the repair of a hole in a ligne-cellulose board which comprises, (l) filling the hole in an initial stage with ligno-cellulose aggregate by vacuum means -under conditions to have an excess of aggregate above the surface of said board, (2) compacting the aggregate by suitable means, (3) removingexcess aggregate above said surface, (4) thereafter in a second stage by vacuum means imposed through the voids in the aggregate positioned in said first stage adding more aggregate thereto into said voids and (5 compacting the same, and comprising the initial step of mixing asbestos fibers, sawdust, and a binder, wherein the amount by weight, in which the asbestos fibers present largely range in length from about 3744" to 1A" and in the range from about 21%% to 5%, and in which the amount of phenolic binder present ranges from about 4 to 6%, and a small amount of rubber latex, and the remain-der sawdust from a sash gang saw.

8. Method for the repair of a hole in a ligno-cellulose board which comprises, (1) -iilling the hole in an initial stage with ligno-cellulose aggregate by vacuum means under conditions to have an excess of aggregate above the surface of said board, (2) compacting the aggregate by suitable means, (3) removing excess aggregate above said surface, (4) thereafter in a second stage by vacuum means imposed through the voids in the aggregate positioned in said first stage adding more aggregate thereto into said voids, and (5) compacting the same, and comprising the initial step of mixing asbestos fibers and sawdust, and adding thereto a 'binder of about 5 to 10% by weight of latex.

References Cited UNITED STATES PATENTS 2,635,976 4/ 1953 Meiler et al. 260-17.2X 2,652,373 9/ 1953 Avedikian 260-17.2 3,155,558 11/1964 Clapp 156-94 JOHN T. GOOLKASIAN, Primary Examiner H. F. EPSTEIN, Assistant Examiner U.S. Cl. X.R.

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