US3155558A - Method and means for patching veneer and manufacturing paper-overlaid veneer - Google Patents

Description

Nov. 3, 1964 c. c. cLAPP METHOD AND MEANS FOR PATCHING VENEER AND MANUFACTURING PAPER-OVERLAID VENEER 2 Sheets-Sheet 1 Filed April 6, 1959 xom 295mm mwoiomu Q\ INVENTOR. (7/4565? C. (ZAP/ NOV. 3, 1964 c, c CLAPP 3,155,558

METHOD AND MEANS FOR PATCHING VENEER AND MANUFACTURING PAPER-OVERLAID VENEER Filed April 6, 1959 '2 Sheets-Sheet 2 INVENTOR. 644E155 C, (ZAP/9 A r role/vfl United States Patent 3,155,558 METHOD Ahll) MEANS FQR PATCHING VENEER AND MANUFACTURENG PAPER OVERLAID VENEER Qharles C. Clapp, Tacoma, Wash, assignor to Weyerhaenser Company, Tacoma, Wash, a corporation of Washington Filed Apr. 6, i959, Ser. No. soaaaz (Ilaims. (Cl. 15694) This invention relates to a new and improved process and apparatus for patching or plugging holes in wood veneer and to an improved process for manufacturing veneer in which such patching arangernents are employed to unique advantage. The invention is herein illustratively described by reference to the presently preferred form and mode of operation thereof; however, it will be recognized that certain modifications and changes therein with respect to details may be made without departing from the underlying features involved.

In the manufacture of veneer and similar products using wood veneer as the base and using paper, fabric or other sheet material as a cover layer, usually on both faces, it is important that a grade of veneer be chosen having no large knots or unfilled knotholes. If the over-all diameter of a knot and immediately surrounding region of very dense grain exceeds about one inch it is very difficult to achieve a good adhesive bond between the wood and the overlay sheet in that area. This is particularly so with thermoactive cements, as used in most case. Therefore, in order to upgrade reject or inferior veneer satisfactorily for this and similar applications, it is necessary to remove the large knots and immediately surrounding dense grain regions, and then to fill the resulting holes, as well as to fill any other holes in the veneer. T o be most economical and practical the patching should be executed in a rapid and substantially continuous machine operation, and in this case one which is readily integrated into a veneer production system. The filler material used should produce in the completed product a strong and durable patch which adheres well both to the surrounding hole edges and to the adhesively coated overlay sheets. In the final product the patch, though concealed by the cover, must nevertheless possess a substantial degree of hardness, with toughness and a certain flexiblity so that it will compare favorably with the characteristics of the surrounding Wood making up the veneer core. The raw materials used in patching should, of course, be readily available as well as inexpensive materials.

In broad terms the invention is concerned with the attainment of the foregoing objectives. In so doing, however, it is particularly concerned with avoiding certain difficulties which develop in connection with a prior proposal for machine patching of veneer. In that proposal finely particulated thermoactive material in a powdery and almost dustlike readily airborne state was partially blown by air and partially drawn and held by suction, against a carrier screen or backing supporting the veneer itself, in order to fill the holes or openings in the veneer sheet. It was necessary to substantially overfill or heap material in and upon the cavities in each instance in order to obtain the necessary density and solidity of the final patches which resulted when the material was compacted to the level of the veneer surface and activated by heat. One difiiculty with such a process was that of preventing excessive spreading and overflow of the powdery and readily shiftable material beyond the hole edges, aggravated or caused by transferal of the veneer onto a succeeding conveyor prior to any substantial activation or setting of the fill material.

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The unavoidable result, therefore, was the presence of lumps and ridges surrounding the patches themselves, thereby impairing the quality of the product or necessitating subsequent sanding or scraping operations to remove the excess following curing of the patches. Uniform patches were difficult to achieve with that proposed process and the same is not Well suited for integration into a rapid and continuous machine patching operation nor into a production system for veneer.

It is a further and more specific object of the in- Vention to provide a machine patching apparatus and process generally overcoming the above-mentioned and other difficultiesand limitations in the prior proposals and particularly the problem of lumps or ridges left adjacent the hole edges by overflow patching material. Also the invention is concerned with improving the patch characteristics and attaining high rates of production of patched veneer and of vener incorporating the patched veneer.

Another object is to provide such a process and apparatus wherein certain operations are combined in order to save space, and the cost of components as well as the cost of thermal energy. Thus final activation of the patch material and activating of the adhesive coating on the paper or other covering layers as the latter is being applied to the patched veneer are combined to particular advantage. While with the method disclosed surface projections of patch material resulting from the initial phases of the patching operation are minimal, and occur if at all substantially within the projected outlines of the holes or openings being filled, the same are readily eliminated in a combined process of heat-bonding the paper overlay sheets and at the same time remolding and ironing out the patches.

In accordance with additional features of the invention thermoactive, preferably thermoplastic patch material is utilized and is partially cured or set by heat before leaving the suction field of the carrier screen, particularly so that the surface or side of the patch opposite the screen is activated to form a retaining crust. In the process thereof it is found that the material shrinks somewhat in volume, within the projected outline of the patch hole edges, and substantially closer to the contiguous surface level of the veneer. Because of relatively dense granulated type of material is used in the first instance, requiring very little overfilling of the hole in order to produce the requisite patch density upon compaction to surface level there is no appreciable spreading or spilling of the material beyond the hole edges to cause objectionable lumps and ridges on the surface of the veneer. The opposite side or surface of the patch upon leaving the field of the suction carrier screen is already substantiaily at veneer surface level because of the coplanar relationship between the two caused by their contact with a common backing surface, namely the screen. Consequently, as the preliminarily secured patch advances into a subsequent or final curing operation which in the preferred instance is the cover paper application, there is no appreciable problem with spillage or overflow of patch material, yet adequate patch material is present in all of the holes for final curing when the thermoactive paper-coating adhesive itself is cured for bonding the paper to the veneer. Such a process and apparatus avoids serious problems of cleaning the suction carrier screen because of the fact that the patching material in contact with the screen is not cured or activated while on the screen, but after leaving it. With the invention, knotholes and any other openings or gaps between adjoining sheets of veneer are uniformly and rapidly filled automatically as the veneer sheets are crowded in successive edge-abutted relationship to the apparatus in a continuous production line flow. Heated rolls are preferably used as the heat and pressure applying means bonding the paper to the veneer surfaces and remolding and finally curing the patches in conjunction with the assembly of the veneer layers -to produce a strong, smooth-surfaced, durable and high quality product, starting with normal reject or waste veneer stock.

These and other features, objects and advantages of the invention including the details of the preferred and illustrated embodiment thereof will become more fully evident from the following description by reference to the accompanying drawings.

FIGURE 1 is a simplified side elevation view illustrating the process and the preferred form of apparatus for patching veneer and manufacturing veneer in accordance with this invention.

FIGURE 2 is a side elevation view of a preferred form of a portion of the machine illustrated in a practical working form.

FIGURE 3 is a top view of the same machine.

FIGURE 4 is an enlarged longitudinal sectional view of that portion of the machine by which the granulated material is initially applied to the holes to be patched.

FIGURE 5 is an enlarged sectional end view showing a side portion of the machine and supplementing the showing of FIGURE 4 of the patching material applicator, the view being taken in a vertical plane through the applicator bin parallel to the applicator shaft.

Referring to the drawings, particularly to FIGURE 1 at the outset, cut veneer strips V are delivered in rapid succession by a feed conveyor 60 to a crowder conveyor comprising a plurality of parallel conveyor chains 10a encircling sprockets 10b. Slightly overlapping the discharge end of the crowder conveyor 10, is the receiving end of the suction-screen or patching conveyor 12 comprising the wide, endless wire mesh screen belt 12:: encircling the driving and driven guide rolls 12b and 12c spaced apart in parallel relationship along the desired direction of conveyance. The lineal speed of the crowder conveyor chains 1011 are caused to slightly exceed that of the patching conveyor belt 12a so as to permit the crowder conveyor to advance the oncoming sheets into tightly edge-abutted relationship with those which immediately precede them in reaching the lower surface of the lower stretch of the patching conveyor screen belt, which is its active conveying surface.

Within the space defined and encircled by the patching conveyor 12 is an enclosed suction box 14 having a perforate lower side serving as a backing and guide for the lower stretch of the belt. Openings 14a in the perforate lower side of the suction box are distributed more or less uniformly over its surface. Suction is applied to the interior of the suction box 14 through a suction tube 14b from a source (not shown), the suction tube 14b joining the suction box 14 through a widened throat 14b which assures substantially uniform distribution of suction over the openings 14a. Once the veneer sheet comes into overlap with the suction box and into the field of suction communicated and evenly distributed through the screen mesh, the veneer is held flatly against the screen as a result of the vacuum. It remains suspended horizontally in this manner until it is deposited or transferred into supported contact on the lower sheet of paper or other covering material 16:: being continuously supplied and drawn from the supply roll 16, as shown.

Just beyond the discharge end of the crowder conveyor 10 is situated a patching material applicator 18 by which a shower of granulated patching composition is thrown in quantity against the lower surface of the veneer with substantially uniform density across its entire width, as it advances on the conveyor screen belt 12a beneath the suction box 14. Where this particulated material strikes solid areas on the veneer, it simply falls back into the container of the applicator 18. However, due to the suction applied through the multiply apertured lower plate of the suction box 14 and distributed uniformly by the metal belt 12a, the material which is thrown into an opening or hole in the veneer is held there and accumulates to overfill the hole. To assure complete filling of all of the holes and openings, an excess quantity of material is, of course, projected against the veneer. The excess actually accumulated as fill in each hole or opening in the veneer is removed and the pile leveled off by a scraper 18a as the veneer in its advance passes beyond the edge of the applicator. In fact, as later explained more fully, with the type of fill material preferably used in the process very little excess fill is required beyond the thickness of the veneer itself in order, when compacted and activated, to form an ultimately solid and durable patch. During the further advance of the veneer the resulting proper measure of fill material is held by the suction in each opening to be patched as long as the veneer sheets are carried on the patching conveyor and are within the field of suction.

Prior to leaving the field of suction established by the suction box through the distributive action of the screen, and in accordance with an important feature of the invention, the lower side or surface region of each fill is activated and thereby solidified or semi-solidiied, as by passing the veneer over a heat source 20. The amount of heat applied is preferably sufiicient to form a retentive crust on the lower surface of the granulated material fills so as to retain the remainder of the material in the patch openings. Excess heat is avoided so as to prevent activating the upper surface regions and causing fusion and sticking of the material to the screen itself which could plug the screen and create serious cleaning problems as well as pulling needed fill material from the patch openings. Application of heat from the source 20 not only sets up a solid or semi-solid crust on the lower side of the body of granulated filler material occupying the openings or holes in the veneer but causes a certain substantial amount of shrinkage of that material which will draw much of it up into the confines of the hole and closer to the lower surface plane of the veneer itself.

In the veneer application disclosed, upon leaving the heater 20 and upon discharge from the field of suction the sheets, with at least partially set or solidified patches, continue their advance onto a continuously fed bottom surfacing sheet of paper 16a which passes through an ad hesive spreader consisting of a glue trough 9, a pick-up roll 8, an applicator roll 7 and a backup roll 6, and slides on a guide platen 22. A top surfacing sheet of paper 24a unwinding from a supply roll 24 is fed through a similar adhesive spreader consisting of a glue trough 9a, a pickup roll 8a, an applicator roll 7a and a backup roll 6a, and into contact with the upper surface of the advancing veneer sheets. The veneer, covered on both sides by the paper sheets, then passes between means to fully activate and solidify the patches and preferably at the same time activate the adhesive coating on the paper and press the latter into bonding contact with the veneer surfaces. The compressor rolls 26 .and 28, at least one of which is heated and one of which is preferably driven, accomplish this in highly simple and effective manner. The upper roll may be mounted on a suitable support permitting the weight thereof to provide the necessary pressure. At this time any irregularities or excesses of granulated fill material projecting beyond the surface planes of the sheet within the hole outlines are ironed out by the applied heat and pressure to impart an externally smooth and flat, finished surface effect.

It will be evident that in this manner the openings or holes H in the veneer sheets though occurring in varying sizes, shapes and locations will be treated alike and uniformly patched. In a continuous edge-abutted run of the sheets as in the illustrated veneer manufacturing arrangeswans ment any unevenness or jogs in the edges 1, which would otherwise form gaps in the veneer core, will also be patched along with the holes formed by knots and from other causes.

For convenience in maintaining the desired tension in the wire screen belt 12a the idler roll 12c thereof is mounted on pillow blocks 30 which may be moved lengthwise of the machines, toward and from the axle 32 carrying the opposing driven roller 12b. Take-up-adjustment is effected by means of the positioning bolts 34 and nuts 36 which bear against a fixed support 33 comprising part of the machine frame. The suction box 14 is mounted between frame bars 40 by anchor bolts 4?. which may be loosened in order to permit raising or lowering the suction box any necessary amount for a close adjustment of its position in relation to the desired guide plane for the lower, active stretch of the conveyor screen. To this end the frame side bars 40 have vertical slots 44 which accommodate the bolts 42.

A geared motor unit 46 having an output gear 48 provides the drive power for the complete conveyor system. A drive chain 50 passing around the drive gear 48 also engages a pinion 52 on the drive shaft 32 of roll 12b and passes around a pinion 54 drivingly connected to the sprocket shaft for the crowder conveyor 10. Finally such chain completes its drive circuit in passing around the sprocket 56 on the drive shaft of the heated compression roller 28 as shown. The appropriate speed ratios are achieved by selecting proper sprocket sizes and the appropriate relative directions of turn of the driven shafts are determined by the manner in which the chain engages the associated sprockets. Preferably the veneer sheets are supplied to the crowder conveyor from any suitable input conveyor such as the chain conveyor 60 shown in FIGURES 2 and 3.

The fill material applicator 18, which throws the material against the veneer preferably comprises a mechani cal type device as distinguished from a type relying solely on air currents, since relatively dense and heavy particulated fill material is used in the preferred technique of the invention. As shown in FIGURE 4 the illustrated applicator comprises an elongated hopper or bin 64 which extends the full width of the machine or of the veneer and contains a supply of the granulated fill material G. An agitator or flinger unit is mounted for rapid rotation in this hopper on a horizontally disposed shaft 66 extending transversely to the line of conveyance. The shaft 66 is driven at relatively high speed by a suitable drive source (not shown), acting in this instance through a V-belt 75 and pulley '78. Paddles or arms 66a are mounted at longitudinal intervals and at circumferentially spaced points on the shaft 66 and pick up quantities of the material and throw it against the under side of the advancing veneer sheet so that the openings H therein will be filled as shown at F. Slight forward curvature or canting of the outer end portions of these arms in the direction of rotation increases their efiiciency to pick up the material from the bottom of the bin and carry it upwardly for discharge against the veneer. The bin is constantly or intermittently supplied with fresh granulated material from a suitable feed source (not shown) through the duct or ducts 68. With agitator arms approximately two inches long (i.e., overall diameter of approximately four inches) a shaft speed of approximately 290 rpm. proves to be satisfactory. Speeds much below this value cause the fine size particles to produce some clogging of the screen and reduce the amount of material that could be held by suction in the veneer openings. At this speed and with the materials Yo be described the machine proves capable of patching at a rate of 35 to 40 feet per minute which is ade quate since it somewhat exceeds the usual rate at which veneer can be satisfactorily fed to the crowder conveyor 10.

As previously mentioned, with relatively dense and incompressible fill material only a slight excess of fill beyond the actual thickness of the veneer itself is required in order to form the patches. The precise amount required is gauged by close adjustment of the scraper 18a which projects upwardly from the down-travel side of the bin 64. This scraper preferably comprises a somewhat flexible member such as a rubber blade which will not catch or hang up a veneer sheet and stop its advance in case it accidentally carries a projecting burr or the like. This blade is adjusted to the desired height in relation to the lower surface elevation of the veneer which in a typical case will allow about one-sixteenth of an inch overfill with three-sixteenths inch thick veneer, and in approximately the same proportion on thicker or thin ner veneers depending upon the fill materials used and the heats and pressures applied. The scraper blade also incidentally serves as a seal minimizing escape of particles beyond the confines of the bin at the discharge side of the bin. A rubber wiper blade 72 on the input side of the bin performs a similar function at that location, so that very little of the material is wasted. A screw 74 and clamp strip 76 holds the scraper 18a in position and the screw may be loosened in order to permit vertical adjustment of the scraper, as by providing vertical slots (not shown) in the hopper wall at the location of each of the screws 74. A similar arrangement is provided in connection with the wiper 72.

With reference to the suction box 14, the sizes and locations of the openings or apertures 14a in the bottom plate thereof are not particularly critical in view of the effect of the wire screen belt 12a in distributing and equalizing the force of suction applied throughout the area of the screen belt in contact with the veneer sheets. The interstices in the wire screen provide this function while at the same time the flexible screen backed by the rigid bottom panel of the suction box maintains a substantially rigid and flat backing surface against which the veneer is held by the suction during the patching operation. A suction of the order of six inches of water is considered adequate to perform the functions required.

The carrier screen belt 12a may be of a suitable wire or equivalent mesh material having a mesh opening size which will prevent passage of fill material particles into the suction box, yet provide the desired distribution of suction over the surface of the veneer. In a typical case the wire screen used has 0.008 inch warp and 0.0095 inch filler wire diameter with open spaces of 0.0063 inch times 0.0084 inch. Excessively heavy gauge wire presents problems in tearing due to fatigue failure as the wire continues to travel in a bend around the rollers over a long period of use. In another case a 55 mesh (0.01075 inch wire diameter) times 40 mesh (0.012 inch wire diameter) bronze Fourdrinier wire screen with pin seam proved successful.

The principal or pre-cure heater unit 20 may assume different forms and in its preferred form, intended for high rates of production wherein the veneer sheets advance quite rapidly through the heating zone, preferably relies, primarily at least, on heated air currents to fuse or set the lower portions of the patch fills. One suitable heating arrangement for this purpose is represented by the insulating casing or shield 20:: which prevents excessive heat radiation against the bin 18, for example, where it would prematurely set up the stored granular fill material, and also confines the heat to the working area. Calrod electrical heater units 20!: are mounted in this casing and openings 200 are afforded in the bottom thereof to permit air to rise into contact with these units. Baffles 20d prevent direct radiation of heat against the veneer and insure the maximum conversion of energy into the heating of the rising air currents which thereafter flow into contact with the material. This assures shallow but quick surface heating of the patch fills in order to form the desired crust at the bottom thereof without excessive penetration to the upper regions in contact with the carrier screen. Thermostatically controlled air, heated in this manner to about 220 degrees Fahrenheit proved effective to heat and fuse the lower portions of the patches with the material used as hereinafter described. A suitable thermostatic control (not shown) controls the air temperature. Radiant heating methods may be used if desired but more exact and critical control thereof is usually necessary to assure effective and sufficient heating of the lower surface region of the patches without fusing the upper regions thereof so as to cause the material to stick to the screen.

As previously indicated, the initial heat application effected while the veneer fills are still in the suction field not only assures the eventual confinement of the granulated and unfused portions of the patch material in the openings to be patched but causes some contraction of the excess which projected beyond the plane of the veneers lower face. Consequently the fill material will not tend to shift or sift out of place and initial contact of the lower side of the fills with the paper 16a overlying the platen 22 will not press and spread out the granulated material beyond the edges of the opening at the lower side of the sheet nor will it displace the fills upwardly in relation to the veneer and cause the material to spill over the sides of the opening at the top face to cause eventual lumps or ridges on the veneer surface. If desired, prior to contacting the top surfacing paper sheet, thermoactivation of the upper regions of the fill material may be effected by suitable means such as a radiant source means represented by the battery of infrared lights 25 stationed just beyond the patching conveyor 12 and ahead of the point of introduction of the top cover sheet 24a as shown (FIG. 1).

It is usually desirable, despite the minimal tendency to activate fill material in contact with the carrier screen 12a to provide some means assuring that the screen will be kept quite clean of accumulations of granulated patching material. One effective arrangement for this purpose comprises a suction hood 80 overlying the upper or return stretch of the screen with a rotary bristle brush 82 constantly rubbing against the screen in order to dislodge or loosen any adhered particles. A force jet or jets 84 situated directly beneath the screen blows upwardly into the suction hood 89 the loosened particles where they are carried away through the suction conduit 86 connected to any suitable source of suction.

The patching compound or composition selected for the purpose should have certain desirable characteristics as mentioned above including that of forming a good adhesive bond with the veneer hole edges and with the bonding adhesive which is used to bond the cover sheets 16a and 24a to the veneer itself. Moreover, such material is preferably thermoplastic as distinguished from thermosetting so that even the preliminarily encrusted or set lower portions of the patches may be remolded if and as necessary when the paper covers are being pressed and heated in contact with the veneer. This capability of softening again under heat assures a smoother exterior surface finish free of lumps and also assures obtaining a stronger bond between the patch material and the paper which covers it on both sides. A preferred material for this use comprises a mixture of thermoplastic substance such as a resin with a suitable extender such as a bark fraction extender. Successful results have been achieved with a composition mixture of 45% by weight of a hard, brittle, dark-colored, non-crystalline thermoplastic resin which is 60% gasoline insoluble, which has a melting point of 187 F. and a flash point of 410 F., which has an acid number of 119 and a specific gravity of 1.138 at 20 C., and which is soluble in ethyl acetate, alcohol, acetone, aromatic hydrocarbons, and is partly soluble in aliphatic hydrocarbons, carbon tetrachloride, and is compatible with ethyl cellulose, and 55% of a selected Douglas fir bark powder fraction having as constituents, lignin like polyphenols with tannins, natural waxes, and resins present in fair quantity. Intermixed, the bark extender and resin are heated and rolled out as a thin sheet, then cooled. This hard sheet is then ground to form particles similar to ground coffee or sand and screened to take out the extremely coarse and fine particles. The overly coarse or excessive fine particles are of course reusable in the forming of subsequent sheets to be ground for achieving the desired particle size acceptable for use in the disperser bin. Preferably the usable particle sizes are those in the range which will pass an approximately 14 mesh screen and not a 50 or 60 mesh screen.

Other wood resins which may be used for the purpose would include a black soda-treated rosin which has a melting point of 76 C. using the ball and ring method, an acid number of 1.07, a saponification number of 135, and has 22.5% unsaponifiable matter. The bark extender and the thermoplastic material used have a variety of suitable substitutes which may be used in their place but in choosing materials, economy should, of course, be considered, as well as the necessary physical characteristics desired for the disclosed application. For example, experiments with some success have been conducted with a mixture of sand and rosin, another dense and substantially homogeneous mixture which requires little compaction in order to form a solid patch. Coffee grounds proved usable though not as satisfactory as the preferred materials named. The step of fusing the material into a base stock which is subsequently comminuted assures an initial relatively high-density and low-compressibility fill which requires very little compacting or compression in volume in order to produce a strong and solid filler patch despite the fact that very little excess is left in the process of passing the veneer by the scraper blade 18a. Foamed plastic beads, such as expandable polystyrene beads, may be used as the patching compound. It has been found desirable in using such materials to pre-expand and dry the beads. It is also advantageous to use an expandable bead compound having a bulk density of 6 to 10 pounds per cubic foot after expansion.

The invention has thus been set forth in its preferred embodiment as a new and useful advance in the art of veneer patching and veneer manufacture. It will be recognized, however, that the disclosure is necessarily based on examples which, taken alone, should not be considered as delimitative of the scope of the novel features and aspects represented.

I claim as my invention:

1. A continuous method of patching veneer to plug a hole therein comprising the steps of applying a perforate external backing surface to the upper face of said veneer,

applying a suction to said veneer through said external backing surface to maintain said veneer in contact with said backing surface, propelling particulate thermoactive material upwardly from beneath said veneer to fill said hole in said veneer with enough of said material to completely fill said hole when said material has been activated,

heating said material on the lower face of the veneer during the application of said suction to effect at least partial solidification thereof at said lower face and to a limited depth terminating short of said upper face in contact with said surface, removing said heat from said lower face, continuing said suction during formation of a retentive crust on said material, continuing said suction until said veneer is deposited onto a lower support,

removing said suction and said perforate backing surface from said veneer, and

further heating said material to activate said material in said hole, whereby a substantially solid plug is formed in such hole.

2. A continuous method of patching veneer to plug a hole therein comprisinng the steps of applying a perforate external backing surface to the upper face of said veneer,

applying a suction to said veneer through said external backing surface to maintain said veneer in contact with said backing surface,

propelling particulate thermoplastic material upwardly from beneath said veneer to fill said hole in said veneer with enough of said material to completely fill said hole when said material has been softened,

heating said material on the lower face of the veneer during the application of said suction to effect at least partial solidification thereof at said lower face and to a limited depth terminating short of the upper face in contact with said surface,

removing said heat from said lower face,

continuing said suction during formation of a retentive crust on said material, continuing said suction until said veneer is deposited onto a lower support,

removing said suction and said perforate backing surface from said veneer, and

thereupon heating said material and pressing the veneer and the material between external surfaces to activate and move the material at both sides of the veneer, whereby substantially solid flush plugs are formed in said hole.

3. A continuous method of patching veneer to plug a hole therein comprising the steps of applying a perforate external backing surface to the upper face of said veneer,

applying a suction to said veneer through said external backing surface to maintain said veneer in contact with said backing surface, propelling particulate thermoactive material upwardly from beneath said veneer to fill said hole in said veneer with enough of said material to completely fill said hole when said material has been activated,

heating said material on the lower face of the veneer during the application of said suction to effect at least partial solidification thereof at said lower face and to a limited depth terminating short of said upper face in contact with said surface, removing said heat from said lower face, continuing said suction during formation of a reten tive crust on said material, continuing said suction until said veneer is deposited onto a lower support,

removing said suction and said perforate backing surface from said veneer, and

further heating said material to activate said material in contact with said surface, whereby a substantially solid plug is formed in such hole,

applying therrnoactive adhesive coated top and bottom surfacing sheets to said veneer, and

thereupon heating the fills and sheet and pressing the same between external surfaces to bind the sheets to the veneer and to activate and smooth the fill material therein.

4. The method of claim 3 in which said thermoactive filling material is a thermoplastic material.

5. Apparatus for patching holes in veneer with particulated thermoactive fill material, comprising support means including an endless screen belt conveyor having a generally horizontal stretch and means mounted above said stretch of screen to apply suction through the same to draw and hold the veneer sheet into contact with the lower side thereof over a surface area on the veneer including the area of holes to be patched, said suction applying means comprising a hood overlying the generally horizontal lower stretch of the screen and having a bottom side surface slidably contacted by said lower stretch and having suction openings therein distributed over a substantial portion of the length and width thereof superimposed on said stretch of screen, the screen mesh openings being smaller effectively than the size of said particulate material, applicator means for fill material stationed beneath said screen stretch and operable for applying particulated fill material to the veneer sheet to fill any holes in the veneer, said applicator comprising a bin containing fill material extending transversely substantially the width of the screen, an agitator means in said .bin including a rotatable shaft extending transversely of the screen and having arms thereon dipping into the fill material in the bin and flinging such material upwardly in a steady shower against the lower surface of the veneer as the shaft rotates accompanying advance of the veneer on the conveyor screen, heater means stationed beneath and spaced from said screen stretch at a relative location olfset from said applicator means to heat the fills in the veneer superficially in the lower side thereof while held by suction on said screen, means to move the screen and thereby the veneer successively past said applicator means and heating means, auxiliary veneer support means stationed adjacent said conveyor screen and olfset from said heater means for receiving the veneer on transferral from the latter, and heating means associated with said auxiliary support means further to heat and cure the preliminarily heated fills, including the upper sides thereof, to activate and substantially solidify the fill material therein.

6. The apparatus defined in claim 5, wherein the firstmentioned heating means comprises a heat source, shield means surrounding said heat source having openings at top and bottom for passage of rising air currents through said shield means to heat the veneers lower face in passing over said shield means and thereby heat the fills superficially.

7. The apparatus defined in claim 5, wherein the second-mentioned heating means and auxiliary support means comprise rollers at least one of which is heated, between which the filled veneer sheets pass on leaving the conveyor screen.

8. The apparatus of claim 5 further comprising laminating conveyor means stationed beyond the screen belt conveyor and beyond said heating means and including means applying thermoactive-adhesive-coated covering sheets progressively to the veneer sheets emerging from the screen belt conveyor,

said laminating conveyor means comprising means applying heat and pressure to the covering sheets and veneer sandwiched therebetween, thereby to activate the bonding adhesive and the thermoactive fill material.

9. The apparatus defined in claim 8, wherein the laminating conveyor means comprises rollers between which the assembled veneer and covering sheets pass and are pressed, and means applying heat to the veneer and covering sheets in conjunction with pressing the same together between such rollers.

10. Apparatus for patching holes in veneer with particulated thermoactive fill material, comprising support means including a veneer conveyor screen having a generally horizontal stretch and means mounted above said stretch of screen to apply suction through the same to draw and hold the veneer sheet into contact with the lower side thereof over a surface area on the veneer including the area of holes to be patched, the screen mesh openings being smaller effectively than the size of said particulate material, applicator means for fill material stationed beneath said screen stretch and operable for applying particulated fill material to the veneer sheet to fill any holes in the veneer, said applicator means comprising a ,bin containing fill material extending substantially the width of the screen, an agitator means in said bin including a rotatable shaft extending transversely of the screen and having arms thereon dipping into the fill material in the bin and flinging such material upwardly in a steady shower against the lower surface of the veneer as the shaft rotates accompanying advance of the veneer on the conveyor screen, heater means stationed beneath and spaced from said screen stretch at a relative location offset from said applicator means to heat the fills in the veneer superficially in the lower side thereof while held by suction on said screen, means to move the screen and thereby the veneer successively past said applicator means and heating means, auxiliary veneer support means stationed adjacent said conveyor screen and offset from said heater means for reciving the veneer on transferral from the latter, and heating means associated With said auxiliary support means further to heat and cure the preliminarily heated fills, including the upper sides thereof, to activate and substantially solidify the fill material therein.

Merritts et al Mar. 14, 1905 Valtat Oct. 7, 1930 1 Carlson Nov. 19, 1940 Welch Apr. 29, 1947 Lambert et a1 as. 13, 1949 Elrnendorf Apr. 22, 1952 McCullough et al. Mar. 3, 1953 Hogg Oct. 11, 1955 Seymour Nov. 29, 1955 Grangaard et a1 Nov. 13, 1956 Runton Dec. 10, 1957 Works et a1 Nov. 18, 1958

Claims (1)

1.A CONTINUOUS METHOD OF PATCHING VENEER TO PLUG A HOLE THEREIN COMPRISING THE STEPS OF APPLYING A FERFORATE ETERNAL BACKING SURFACE TO THE UPPER FACE OF SAID VENEER, APPLYING A SUCTION TO SAID VENEER THROUGH SAID EXTERNAL BACKING SURFACE TO MAINTAIN SAID VENEER IN CONTACT WITH SAID BACKING SURFACE, PROPELING PARTICULATE THERMOACTIVE MATERIAL UPWARDLY FROM BENEATH SAID VENEER TO FILL SAID HOLE IN SAID VENEER WITH ENOUGH OF SAID MATERIAL TO COMPLETELY FILL SAID HOLE WHEN SAID MATERIAL HAS BEEN ACTIVATED, HEATING SAID MATERIAL ON THE LOWER FACE OF THE VENEER DURING THE APPLICATION OF SAID SUCTION TO EFFECT AT LEAST PARTIAL SOLIDIFICATION THEREOF AT SAID LOWER FACE AND TO A LIMITED DEPTH TERMINATING SHORT OF SAID UPPER FACE IN CONTACT WITH SAID SURFACE, REMOVING SAID HEAT FROM SAID LOWER FACE, CONTINUING SAID SUCTION DURING FORMATION OF A RETENTIVE CRUST ON SAID MATERIAL CONTINUING SAID SUCTION UNTIL SAID VENEER IS DEPOSITED ONTO A LOWER SUPPORT, REMOVING SAID SUCTION AND SAID PERFORATE BACKING SURFACE FROM SAID VENEER, AND FURTHER HEATING SAID MATERIAL TO ACTIVATE SAID MATERIAL IN SAID HOLE, WHEREBY A SUBSTANTIALLY SOLID PLUG IS FORMED IN SUCH HOLE.

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