US 2770556 A
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METHOD OF PATCHING AN OPENING IN A PLANE MEMBER Filed Jan. 22, 1.95;
D. H. GRANGAARD ETAL 2 Sheds-Sheet l frzvenfirs/ florwld H Grarggmrd and Gri /22:47 Z1). Pl MEW NWV 13, 1956 GRANGAARD ETAL 2,770,556
METHOD OF PATCHING AN OPENING IN A PLANE MEMBER Filed Jan. 22, 1953 2 Sheets-Sheet 2 QrZ /iur Z0. Plummer W YW United States Patent 1 2,770,556 METHOD OF PATCI-IING AN OPENING IN A PLANE MEMBER Donald H. Grangaard, Appleton, and Arthur W. Plummer, Neenah, Wis., assignors, by mesne assignments, to Kimberly-Clark Corporation, a corporation of Delaware Application January 22, 1953, Serial No. 332,694 3 Claims. (Cl. 1172) The present invention is concerned with a method and apparatus for patching surface discontinuities such as holes, splits, and cracks in wood veneer.
As wood veneer strips are cut from logs, a wide variation in quality occurs in the strips produced, even in strips cut from the same log. Some lengths of veneer will be found to have practically no surface defects, and these strips are immediately suitable as facing sheets for the manufacture of plywood of high quality. Other strips, however, have so many knotholes, splits, and cracks that they are rendered practically useless as surface veneers for the better grades of plywood and in many instances even for cross-banding, and consequently command only a far smaller price than the strips free from such defects.
The Douglas Fir Plywood Association grades Douglas fir plywood veneer into four classes. Type A veneers are those which have a smooth surface free from knots, splits, pitch pockets, and other open defects. Type B veneers are those which have a solid surface and are free of open defects. They may contain some neatly made patches and small amounts of discoloration. Knots up to one inch in diameter may be present if the knots are sound and tight. Similarly, tight splits or a slightly rough or ruptured grain and minor sanding and patching defects may be found in this veneer. Both type A and type B veneers are considered suitable for surfacing use in the manufacture of the better grades of plywood.
The next lower grade, type C, are those which may contain knotholes up to one inch in diameter, pitch pockets not wider than one inch, and splits no wider than inch, provided the splits taper to a point. Such veneers may also have worm or borer holes whose dimensions may be no greater than /8 inch by 1 /2 inches.
The lowest grade, type D, are those which may contain knotholes up to 2 /2 inches in diameter, and pitch pockets up to 2 inches by 4 inches. Such veneers may also contain splits, provided the splits taper to a point. The maximum width of such splits is designated as /2 inch if the split extends to a quarter of the panel length, 4 inch if it extends to a half of the panel and m; inch if it extends the full length of the panel. C and D veneers are used primarily for the internal plies, except for low grade products.
As an overall average, Douglas fir plywood veneers cut in the United States average about 25 percent type A, 5 percent type B, 30 percent type C, and 40 percent typeD. Thus, more than half of the veneers are undergrade for many purposes.
Veneer strips require patching for reasons otherthan,
are manufactured, it has been necessary to specify that.
the outermost plies consist of type A or type B veneer. Naturally, this raises the cost of these products because one must supply a high grade veneer of good appearance for a use in which appearance is not of primary importance. This practice depletes the supply of grade Patented Nov. 13, 1956 and B veneers for uses where the use of these grades is essential.
The patching of veneers has heretofore been carried out as a more or less manual operation requiring the services of reasonably skilled workmen. In one method commonly used for patching veneers, surface discontinuities such as knotholes are punched out of the sheet by means of a machine leaving a circular hole in the sheet. This hole is then plugged with a so-called cookie patch which consists of a circular piece of veneer, this patch being wedged into the previously cut hole. This type of patching was not always effective to present a completely flat surface and had the distinct disadvantage that it required an operation which was. both costly and time consuming.
Somewhat better patches are obtained with the socalled boat patch method, in which the veneer surrounding the defect is sawed out in the shape of a boat, i. e., an elongated, doubly convex shape having tapered ends. The boat patch is beveled at its edges and adhesive is applied to these beveled edges. The boat patch is then inserted into the cut and the assembly is pressed between heated platens to set the adhesive and anchor the patch in the cut.
The need still remains for an efiicient method for patching low grade veneers in order to provide a smooth, flat surface. The ideal patch method would involve a continuous operation with a minimum of supervision in which any surface discontinuities would be located and filled automatically. The provision of such a method and various types of apparatus for performing this method are the main objects of the present invention.
Other objects of the present invention include the provision of a method for continuously patching wood veneer with a bonding composition and completely filling surface discontinuities in the sheet regardless of their location or configuration. Another object of the invention is to provide a method for patching wood veneer with a readily available, inexpensive filler material such as comminuted wood particles and a binder. Another object of the invention is to provide a method for automatically depositing controlled amounts of a filler into surface discontinuities of a wood veneer.
The present invention provides a continuous means for applying a filler material into surface discontinuities of a moving sheet of veneer and is based upon the maintenance of a pressure diiferential across the veneer sheet to control the amount of filler material retained in the holes or other discontinuities. The most convenient means for accomplishing this purpose is to provide a continuously circulating, gaseous stream in a confined path, and dispersing in this stream a particulated mixture of comminuted filler and a resinous binder. The flow characteristics of the main stream are so adjusted to suspend the filler material uniformly in the air stream. The pressure drop across the discontinuity is so adjusted that the stream when passing into a discontinuity is in .a condition of laminar flow.
One of the characteristic features of a stream in laminar flow is the fact that the pressure drop between two spaced points in the stream is a linear function of the velocity of the stream, and this characteristic is used to advantage in the practice of our method.
The amount of material deposited, for example, in a knothole under such conditionsis the product of the concentration of filler composition per unit volume, in the stream and the total volume of the stream. passing through the hole. Hence, the material deposited. in a given hole can be represented by the equation: r
- M1=C0Q1 where M1 is the quantity of material deposited in the existing across the sheet, and similar factors.
3 hole,- Cu is-the concentration of material per unit volume in the stream, and Q1 is the total volume of the stream through the hole. For anothervhole, the same relationship applies -sothat:
where'Mz is .the amount of material=deposited in the second hole, C is the concentrationof filler material per unit volume in the stream and Q2 is thetotalvolume of the material through the second hole. In the present system, the total quantity of filler circulatingin the stream is high with respect to the amount deposited from 'thestream at any given time, and this small amount of depletion'may beignored'because it has a negligibleeffect upon the concentration of material, Co. 7
From the above, the ratio between theamounts of materialdeposited in the two holes may be expressed as follows:
but since C0 cancels'out of the equation and the discharge velocities are the products of the areas of the holes and the linear velocity of'the stream through'the holes, the
above equation maybe written:
M1/Mz=V1A1/V2A2 where V1 and V2 are the velocities through the respective holes and A1 and A2 are the areas of the holes. However, as previously brought out, the system is operated under a substantially constant pressure differential, in substantiallylaminar flow, so the velocity V1 will equal the velocity V2, and the final equation may be written:
Hence, the amount of material deposited in the surface discontinuities in this process is directly proportional to the area involved.
The present invention thereby provides an automatic means for determining the amount of filler introduced into a surface discontinuity. As the filler material builds 'upin the surface discontinuity, a point of equilibrium will he reached depending upon the velocity of the stream, the
size and density of the particles, the pressure differential Once .this equilibrium is reached, there'is no appreciable additional depositionon the filler material alreadydeposited'in'the space. Hence, by adjustment of the variables'mentioned, the proper amount of filler material will be deposited automatically in the surface discontinuity. 'Since'the filler material has a far lower bulk density than theveneer', the tiller will be deposited in volumetric excess of the volume of thehole, leaving a mound of filler material completely covering the hole. Any excess filler material which becomes deposited upon the veneer in its passage through the z oneof deposition can be convenientlyremoved,
whereupon the filled sheet can be passed into a pressure means which consolidates the material, making the filler essentially flush with the surface of the sheet.
' The preferred filler in the process of the'present invent'ionconsits of comminuted wood particles and apowdered'resin. The method described is, however, equally applicable to the use of numerous types of filler particles, such as ground bark, finely divided straw,'mica, and the like. As will appear from a subsequent discussion, partic le's of this type can be combined-witha'resin having adhesive properties to provide a filler which adheres Well "mechanism;
become deposited in the screen.
Figure 2 is a fragmentary, enlarged, cross-sectional view of a piece of veneer shortly after it has been contacted with the stream of filler;
Figure 3 is a view similar toFigure 2, and illustrates the same piece of veneer shortly after the time illustrated in Figure 2;
Figure 4 is a view similar to- Figure 2, and illustrates the piece of veneer at a still later time;
Figure 5 is a view similar to Figure 2, and illustratesthe veneer after the excess patching material has been re moved from the edges of thedefect;
Figure 6 is a schematic view of another form of apparatus; and Figure 7 is a schematic view of a still further modified form of apparatus.
In the assembly shown in Figure 1, reference numeral '19 indicates generally'a housing consisting of-a suction box it and a deposition chamber 12. The suction box 11 has a perforated upper plate 13 which has an end portion 13a extending somewhat beyond the 'end of the deposition chamber 12. An endless belt consisting of a foraminous member in the form of a wire screen14-of relatively fine mesh for example, one having twenty-four wires per'inch, is trained about a pair of rolls'16 and 1 7 which are journalled for rotation on shafts 18, and 19, respectively. a
The suction box 11 is connected by meansof a con duit 21 to the inlet end of a blower 22 of relatively high capacity. The flow of air through the conduit 21 is controlled by a blast gate 25. The'blower 22 should be sufficiently large so that changes in vacuum in the suction box 11 due tovariation in the number of discontinuities in the veneer sheets being treated does not change the preferably both are maintained under subatmospheric pressure conditions. 'Forexample, the suction box may be maintained at a vacuum of about 9-inches of water while the deposition chamber 'lZ'maybe at a negative pressure of /2 to 1 inch of water. 7
Outside the'suction box 11, the wire'14 travels over a perforated pipe 24 which directs a'stream of air to the wire mesh to clean out 'anywood powder which has Within the deposition chamber 12, means are provided to regulate the flow characteristics'of the'air stream carrying' the comminuted particles and *the resinous binder. These means may include a plurality ofbattles 26, 2'7,
and 28, each of which is vertically'adjustable by meansof wing nuts 29,30, and 31 which secure each 'ofthebaffles in a selected vertical position. i
The comminuted mixture'of wood particles and'resin binder is introduced into the system from a hopper 32 provided with a. worm feeding "mechanism 33. The
hopper "32 introduces the particulated mixture into an inlet conduit 34 which delivers the material "into-the blower 22 to be discharged therefrom into an outlet conduit 36. Theparticle laden air is then introduced into the'topof a cyclone separator "37 andafterpassing "through the latter, enters the "deposition chamber 12 through an orifice 38 provided with an adjustable series of jbafiles 39. The velocitypfthe air'strea'mcan be controlled byJrneans of a blast" gate 41 disposed 'imme'diately above'the hopper 32'in the inlet-line 34.
As a veneer1panel43 is introduced into' the deposition chamber12bn the wire 14,'it moves 'into 'contact with a constantly flowing gaseous stream containing the fillcr particles and resin in suspension. The path of the stream is essentially confined to flow through the orifice -38,
"c'eeds substantially normal to't-he surface of the veneer '43. This condition "is illustrated 3 in Figure 2 Where ta together.
knothole 46 is shown substantially filled with a resinfiller mixture 44. Within a short time, an equilibrium condition is reached in which a mound 44a is built up over each of the surface discontinuities 46 present in the veneer 43. This point is illustrated in Figure 3. At this point, the path or" least resistance for the air stream is along lines which are more radial than normal, and deposition of the filler then becomes greater along the edges of the surface defect and usually results in a relatively heavy buildup 44b (Figure 4) of filler along edges of the mound 44.
As the veneer 43 proceeds through the deposition chamber 12 it passes under the depending baffle 27 and is then subjected to the action of a cleaning air stream, as for example, from a perforated pipe 47. The baffle 28 controls the direction of the air stream from the pipe 47 and together with the baflle 27 provides a channel for the removal of excess filler. The material being continuously removed by the cleaning air stream is then directed into the conduit 34 associated with the blower 22.
In place of the perforated pipe 47 it is possible to employ a soft brush or a series of brushes as the means for brushing ofi excess material from the veneer. However, the air stream is much more convenient to use than a soft brush and is therefore preferred. The term brushing as used in this specification shouldbe applied to various suitable means for removing excess powdered material, Whether by mechanical brushing means or by an air brush. After the excess filler material has been removed from the veneer sheet, the filler deposit will have been reduced, as illustrated in Figure 5. The exact size and shape of the remaining material will depend primarily on the size of the filler particles and the pressure differential existing across the deposit 44 at the time the excess was removed.
The veneer 43 is then subjected to a slight pressing action by means of a slack rubber belt 48 supported between a soft rubber-covered press roll 49 and small roll 50. It should be noted that at all times during the removal of surface filler material the veneer 43 is still subjected to suction from the suction box 11 and this condition exists until the veneer sheet has traveled beyond the press roll 49.
The patched sheet is then received on a highly polished transfer plate 51 which is preferably cooled so as to prevent the resinous component of the filler from becoming tacky and sticking to it.
The transfer plate 51 guides the veneer between a pair of vertically adjustable belt supporting rolls 52 and 53. A narrow spring arm 54 serves to prevent vertical movement of the veneer in its passage between the rolls.
The roll 52 and a second roll 56 are both supported on a support 57 which is pivoted to a frame by means of a pivot 53. A flexible metal belt 59 extends between the rolls 52 and 56, the belt 59 being heated by means of radiant heaters 60 supported above the rolls 52 and 56. The lower assembly, consisting of rolls 53 and 61, is mounted on a support 62 in spaced relation with the rolls 52 and 56, the nip pressure between rolls 56 and 61 being adjustable by means of a spring assembly 63 associated with a spacer rod 64 between the supports 62 and 57.
A flexible metal belt 65 extends between the rolls 53 and 61 and is heated by radiant heaters 66 disposed beneath the rolls.
The various rolls are driven by means of belts or gears from shafts 67 and 68 which themselves are geared The shaft 67 is associated with a chain driven gear 69 driven from a drive system generally indicated at 71 and powered by a motor 72.
The temperature conditions to which the veneer is subjected in passing through the heated roll assembly will vary with the type of resin employed, the amount of resin, and the subsequent processing to which the veneer is to be put. Where the veneer panel is to be heat bonded to other veneer panels in the manufacture of plywood, then the temperature conditions need only be sufficient to partially melt the resin to cause the filler particles to adhere together as the subsequent plywood making step will effectively cure the resin completely. However, if desired, the complete cure can be carried out in this stage.
The pressure on the veneer sheets applied by the belts 59 and 65, in passing between the rolls 56 and 61, is sufiicient to press the filler material flush with the surface of the veneer, thereby forming a relatively high density plug in each of the surface discontinuities.
Numerous different types of thermosetting and thermoplastic resins can be employed for the purposes of the present invention. Phenol-formaldehyde, urea-aldehyde, melamine-aldehyde resins, and natural thermoplastic resins are among those resins which may be employed. For those thermosetting resins which have some thermoplastic properties in their unset condition, the filler mixture may include merely the comminuted particles such as sander dust or sawdust and the thermosetting resin.
However, for those resins which do not have sufiicient thermoplasticity, it is often desirable to add a thermoplastic resin having adhesive properties to the mix.
If the patched veneer is to be secured to other plies in a cold gluing process, then the resinous binder may be a thermoplastic resin alone. Where a hot pressing operation is to be employed, then the use of some thermosetting resin would be indicated. Where the filler particles are used with either the thermosetting or thermoplastic resin alone, best results are obtained where 5 to 50 parts of the resin are added to every parts of the comminuted material. Where both types of resins are included, from 5 to 50 parts of thermoplastic resin in combination with 2.5 to 10 parts of the thermosetting resin for every 100 parts of filler particles may be employed. As the thermoplastic resin, we prefer to use an inexpensive, natural resin known commercially as Vinsol resin. This material is a hard, brittle, dark colored thermoplastic resin derived from pine trees and containing phenol, aldehyde, and ether groups. A typical sample has a specific gravity of 1.2 to 1.3, a melting point of 230 to 240 F., and an acid number of between 90 and 100. Other suitable low melting thermoplastic resins include methacrylate polymers and polyethylene resins.
Various specific examples for filler mixtures are given below:
Example I 1500 parts sander dust 500 parts Vinsol parts Durez 14184 (powdered thermosetting phenolic resin) Example 11 500 parts sander dust 55 parts Bakelite QR 18615 (powdered thermosetting phenolic resin) Example III 450 parts sander dust 50 parts powdered melamine-formaldehyde condensation product Example IV 1500 parts sander dust 500 parts Vinsol Example V 90 parts sawdust 5 parts Vinsol 5 parts Durez 14184 Example Vl 90 parts sawdust Example VII 80 parts sander dust 20 parts polymerized n-butyl methacrylate (Hypalon Example VIII 80 parts sander dust 20 'parts polyethyleneresin ('Alathon GP-1000) Example 1X '80 parts sander dust 20 parts polyethylene resin parts phenolicresin Various changes can be made in'the specific examples mentioned above depending upon the type and density of the 'filler desired. In-general, as a coarser filler is used, the relative amount (percentagewise) of resin can be decreased.
The amount of resin can be changed for various reasons. For example, if the filled veneer is to be used as a facing strip for plywood, it is desirable to use a relatively large amount of resin in the mix to provide more water resistance, more abrasive resistance, or more surface hardness.
Other systems of apparatus for distributing the filler material onto the veneer have been illustrated in Figures 6 and 7 of the drawings. Figure 6 illustrates a system in which a hopper 77 containing the powdered filler material 78 applies a more or less uniform layer 79 of fil'ler material over a-traveling veneer sheet 80 supported on a moving endless wire screen 81. The screen 81 is driven by a pair of rolls 82 and 83. As the filler material 78 is distributed along'the veneer 80, it will loosely fill surface discontinuities such as knotholes 80a in the veneer'80. The veneer. sheet 80 advances over a suction box'84 over which it travels until'it is subjected to the action of an air stream from a source of pressured air such as a perforated pipe 86. The air stream fromthe pipe 86' blows away the excess material but the previously applied suction from the suctionbox-84 retains the deposited filler in the surface defects such as knotholes 80b. The loosely filled veneer can be passed to heating and pressing apparatus which consolidates the excess filler into a plug 'flush with the surface of the veneer.
In the system of Figure 7, a veneer sheet 90 is carried along an endless wire screen 91 supported between a pair of rolls 92 and 93. A suction box 94 provides the suction to hold the sheet 90 against the screen 91. As the veneer 90 passes over the housing 95, it is contacted with an air stream containing the resin-filler mixture 96 circulating within the housing 95 by the action of a pump .1101. In this type ofsystem, the cleaning air stream may be eliminated in some cases. As the veneer 90 travels beyond the end of the suction" box 94,.it is gently transferred to the surface of a metallic belt 100 trained about a roll 97.
The veneer 90 travels onthe belt100 into contact with a heated belt 98 trained about a roll 99. Preferably, both the belts 100 and 98 are heated to effect softening of the resin binder in the filler. The belts 100 and 98 then deliver the veneer 90 to press rolls wherew'the material is heated and consolidated into aself-sustaining mass.
The present system provides a convenient means for patching veneers in an automatic manner. The necessity of providing machines for cutting outsurface defects and replacing them with special patches has been eliminated by the system of the present invention. A i
It Will be evident thatvario'us modifications can be made to the described processesand apparatus'without departing from the scope of the present invention.
We claim: 1
1. The method of patching an opening extending through a generally plane member, which comprises providing a constantly flowing gaseous stream containing comminuted solid filler particles, supporting said plane member on a foraminous member-in a position generally parallel to the directionof flow-of the gaseous stream and in surface contact with the constantly flowing gaseous stream, said foraminous member being disposed onthe side of said plane member opposite that which is in contact'with said gaseous stream, and-providing suction on the side of said plane memberopposite the gaseous stream,
thereby drawingfiller particles from thestream only into said opening through said plane member and filling-said opening at least -to the level of the opposite surfaces of said-plane member.
2. The method of patching an opening extending through a generally plane member, which comprises providing a constantly flowing gaseous stream containing comminuted solid filler particles having a lower density than the density of said generally plane member, supporting said planemember on a foraminous member ina position generally parallel to the direction of flow of the gaseous stream and in surface contact with the constantly flowing gaseous stream, said foraminous member being disposed on the side of-said plane member opposite that which is in contact with said gaseous stream, and providing suction on the side of said plane member opposite the gaseous stream, thereby drawing filler particlesfrom the stream only into said opening through said plane member and filling said opening, with'said suction beingcorrelated with the density of said fillerparticles and with the characteristics of said gaseous strearn'so that thevolume of filler particles drawn into saidopening exceeds the volume of saidopening and forms a mound offiller material completely covering said opening.
3. The method of patchingaplurality of spaced-apart openings extending through a generally plane member, which comprisesproviding azconstantly flowing gaseous stream containing comminuted solid fillerparticles having a lower density than the density of saidgenerally plane member, supporting \saidplane member on a forarninous member in a position underlying. said gaseous stream and generally .parallelatolthe direction of flow; thereof, there- :byplacing 'saidiplane memberin surface contact with the .gaseousstream, said foraminous member being .dis-
posed beneath said .plane member, and providing .suc- 7 .tion on;the bottom side.of;said'plane member, thereby drawing filler particles from the stream. into each;of:the openings in said plane :member. that .aretdisposed between the flowing gaseous stream'and the suction and. filling :the. area of each opening and so thateach of said volumes offiller particles exceed the volume of the opening filled thereby and formsa mound of filler material completely covering the opening, said volumes of filler particles being such' that upon compression the openings. are filled to the level of the opposite surfaces of said plane member and the density of thematerial ineach opening isessentially the same as the density of said plane. member.
ReferencescCited intheifile of this patent UNITED STATES PATENTS