US3243327A

US3243327A - Method of making a pressed plate

Info

Publication number: US3243327A
Application number: US194449A
Authority: US
Inventors: Hoppeler Walter
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-05-16
Filing date: 1962-05-14
Publication date: 1966-03-29
Anticipated expiration: 1983-03-29
Also published as: BE615433A; CH398072A; DE1194570B; AT242935B; GB972868A

Description

March 29, 1966 w. HoPPELr-:R

METHOD oF MAKING A PREssED PLATE Filed May 14, 1962 INVENTOR. Mil,l Wale www: f #ff/w www United States Patent O 3,243,327 METHOD F MAIHNG A PRESSED PLATE Walter Hoppeler, Haus Lampitschen, Klosters, Graubnden, Switzerland Filed May 14, 1962, Ser. No. 194,449 Claims priority, application Germany, May 16, 1961, H 42,610 11 Claims. (Cl. 156-622) The present invention relates to a pressed plate and a method of making the same, and more particularly to the type of pressed plates which are produced of wood particles and binder material in plate presses at elevated pressure. The present invention is also concerned with the use of the thus produced pressed plates.

Several types of fabricated sheets or compound cornpressed plates made of layers of pieces of wood and binder materials are known in the art and described in a number of U.S. patents, for instance in U.S. Patents 2,642,371 and 2,686,143. For brevity, such compressed wooden boards of fabricated sheets or compressed plates made of layers of Wood and binder material are referred to therein as pressed plates.

Up to now, pressed plates formed by compression in plate presses customarily were made from Wood particles which had been produced for this purpose, as well as additional wood particles which might have accrued in other manufacturing processes, such as the Wood shavings which accrue in the planing of Wood. In order to obtain a very smooth surface, pressed plates were subjected on one or both of their surfaces to a grinding operation, the wood our formed in such grinding operation could not be reused as part of the raw material for producing pressed plates, due to its iineness and the relatively large surface of such wood flour which would require unduly large proportions of binder material and thus would make the production of pressed plates therefrom or partly consisting thereof relatively uneconomical. Thus, the grinding of the surface of previously pressed plates will result in wood iiour as a waste material which could not be reworked and consequently utilized only as fuel. To form the desired plane :surface of pressed plates by other methods than grinding appeared impossible until recently, due to the fact that the hardness of the pressed plate prevented planing of the surface thereof in the manner in which for instance the surface of a board of natural wood could be planed.

There exists one prior art method according to which shaped bodies consisting partially of Wood are produced by compression of a mixture of wood particles with synthetic resin binders at elevated temperatures and according to which 50% or somewhat more of wood particles are mixed with thermoplastic synthetic resins, softeners, gelatinizing agents, lubricating agents and acid-binding compounds so that the pH of the mixture during processing of the same will remain in the vicinity of pH 7. According to this method, the thermoplastic synthetic resins, softeners, etc. are mixed to the wood particles in pulverulent form and the mixture is then subjected in a suitable press to temperatures of between 150 and 210 C. Waste formed during the nal shaping of the thus produced plates can be reintroduced into the process so that the method can be carried out substantially Without accrual of useless waste products. However, according to this method, the proportion of non-Wood constituents has to 3,243,327 Patented Mar. 29, 1966 ICC be relatively `high so that the finished product will contain up to somewhat more than 50% wood. Thus, the product obtained according to the last mentioned method is entirely different from the pressed plates with which the present invention is concerned and which contain much larger proportions of wood particles.

Thus, the problem remained up to recently that pressed plates containing a relatively large proportion of wood could not be planed prior to the final grinding of the surface thereof, since due to the relatively high resin content of the surface portion of such pressed plate, the surface portion becomes too hard and working of the surface portion with planing tools such as hard metal knives was economically not feasible. Furthermore, no planing machines were in existence which would permit vibrationfree planing of pressed plates having a lateral extension of more than 1500 mm. In addition, noplaning machines existed which were capable of planing warm pressed plates accurately to a desired thickness which would vary only within extremely close tolerances.

Recently, a planing machine and method has been described in U.S. patent application Serial No. 86,744 which will permit the planing of pressed plates having a width of more than 1500 mrn., in an economically feasible manner. No provision was made, however, for reusing the shavings which would accrue upon the planing of freshly produced pressed plates while the same are still at an elevated temperature.

It is therefore an object of the present invention to overcome the difficulties and disadvantages of the prior methods of producing pressed plates.

It is a further object of the present invention to provide a method of producing pressed plates which can be carried out so as to more completely utilize the Wood material and without creating any substantial quantities of Wood waste unsuitable for incorporation into subsequently produced pressed plates.

It is still another object of the present invention to provide a pressed plate which due to the fact that shavings cut from previously pressed plates, i.e. pressed shavings, are incorporated therein, will be of a quality which may be superior to that of pressed plates which are produced without the incorporation of pressed wood material.

Other objects and advantages of the present invention will become apparent from a further reading of the description and of the appended claims.

With the above and other objects in view, the present invention contemplates a pressed plate consisting essentially of wood particles and binder material, the plate including a significant portion of pressed shavings formed by planing previously produced pressed plates while the same are maintained at an elevated temperature.

The present invention is also concerned with a method of producing pressed plates by hot pressing a mixture consisting essentially of wood particles and hardenable binder material, and particularly with the improvement of such method which consists in planing the freshly pressed plates while still hot, thereby separating pressed shavings from the plates, forming a mixture of Wood particles and hardenable binder material including at least a portion of the pressed shavings, and subjecting the thus formed mixture to hot pressing so as to form pressed plates thereof.

According to the preferred embodiment, the present invention includes in a method of producing pressed plates by hot pressing mixtures consisting essentially of wood particles and hardenable binder material, the improvement which consists in planing the freshly pressed plates while still hot thereby-separating pressed shavings from the plate, forming a first mixture of wood particles and hardenable binder material including at least a portion of the pressed shavings, forming a second mixture of wood particles and hardenable binder material, subjecting the rst and second mixtures in superposed position to hot pressing so as to form pressed plates thereof in such a manner that the first mixture will form at least one face of the thus formed pressed plates, and subjecting the thus formed pressed plates to planing while still in hot condition, allowing the plates to cool, thereafter subjecting at least one face of the planed pressed plates to grinding, and incorporating the ground plate in a plywood structure.

Thus, the pressed plate according to the present invention has incorporated therein shavings which were produced by planing previously pressed plates while still in hot condition. It is important to note that these shavings were cut from a pressed plate and thus consist of a material which had been subjected to compression.

According to the method of the present invention, the pressed plates are planed while in warm or hot condition and the thus formed shavings are at least partly recycled so as to be incorporated in the mixture of which the pressed plates or certain portions thereof, such as a core portion or a surface portion, are formed. In a further embodiment, the present invention is also concerned with the use of pressed plates produced in accordance therewith for the manufacture of plywood. The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, tgether with additional objects and advantages thereof,

. will be best understood from the following description of specific embodiments when read in connection withV the accompanying drawings, in which the figure is a schematic illustration of an arrangement for producing pressed plates in accordance with the present invention.

The invention will now be described in the following example with reference to the drawing:

Wood, for instance inthe form of logs of 1 meter length is conveyed in any desired manner to endless chain conveyer 1 and passes therefrom to band saw 2.

The logs which were cut by band saw 2 to the desired length and which are now in condition to be chipped, are conveyed to rotary drum 3 which is arranged in the vicinity and equidistant of wood chippers 4 and 5. While in rotary drum 3, the better pieces of wood are selected and placed into wood chipper 4 while wood pieces of lesser quality are passed to wood chipper 5. The chips produced in wood chipper 4 will eventually form the surface layer of the pressed plate, while the chips of lesser quality produced in wood chipper 5 will eventually form the core portion of the pressed plate. The thickness of the chips can be varied rby a suitable adjustment of the knives of chippers 4 and 5. The dimensions of the chips are dependent on the distance of the coring knives and the size of the wood portions introduced into chippers 4 and 5.

The thickness of the chips which will form the surface layer of a multi-layer plate preferably will be between 0.15 and 0.3 mm. and most preferably about 0.2 mm. The desire'd size of the chips will be determined by a mill through which the chips pass after leaving the chipper. The length and width of the chips depends on the specific chipping and milling conditions, for instance, the chips might have ldimensions so as to permit passage of the same through screens having an aperture of 3 mm., or flat chips of such length and width that their flat pressed plate generally are not subjected to milling after passing the chipper and will retain the average dimensions to which they were comminuted in chipper 5. The thickness of these chips preferably will be between 0.3 and 1 mm. and most preferably about 0.4 mm.

However, the dimension of the chips may vary within very broad ranges, from about 10 X 40 mrn. down to nearly the fineness of sawdust. The average dimensions of the chips for the core layer may be such as to allow passage through a screen of 8 mm. mesh width.

From chippers 4 and 5, two parallel lines with substantially identical machinery lead. to distributor 13, whereby one line, namely line Il serves for processing of the chips which will form the surface layer, while the other line, namely line I serves for processing the chips for the core layer of the pressed plate.

After passage through mill 6, which mill might be omitted in line I, the chips are conveyed into the socalled wet hoppers 7.1 From wet hoppers 7, the chips pass continuously and at an even rate over screen 8 having a mesh Width of between 2-4 mm., whereby between about 3 and,10% preferably about 5% of the smallest chips are separated Land withdrawn as fuel material, while the coarser chip portion representing between 90 and 97% thereof are passed through dryer 9. Screen 8 generally is required only in line I.

While passing through dryers 9, the chips are dried to a water content of about between 2 and 6%, preferably about 3.5% and thereafter the chips are conveyed to dry chip hoppers 10. Hoppers 10 in which the chips will rest for some length of time will serve to further equalize the moisture content of the chips and in addition will assure continuous operation of the press by holding a reserve quantity of chips which may be used faces, respectively represent an area of about 1 cm?, may v up in case introduction of additional chips into hoppers 10 is interrupted, or the rate of introduction is temporarily reduced to below the Vrate of withdrawal of chips from hopper 10. The chips then pass over scales 11 into mixing devices 12 in which an aqueous suspension of a synthetic resin binder is sprayed onto the chips. This suspension preferably will consist of between 38 and 55% per Weight of pulverulent synthetic binder, the balance being water, and most preferably, the suspension will contain about 50% of pulverulent synthetic resin binder. Based on the dry substance of the chips, the amount of dry binder which is thus applied to the chips which are to serve for forming the cover or surfacerlayer of the pressed plate, generally will equal between 5 and 15% per weight, in the present case not more than 10% per weight. As such binder a synthetic-resin cement will be used, e.g. on a base of urea formaldehyde, a phenolic resin or melamine resin. The water of the suspension is absorbed by the dry chips, while the suspended synthetic resin particles will adhere to the surface of the chips. Thus, the chips will not become adhesive but will only appear to be somewhat more moist, however, the thus treated chips still form a owable mass.

Thechips now pass to distributor 13 and are placed continuously on conveyer sheets 14. The chips fall onto conveyer sheets 14 as a thin veil having a width of for instance 1.75 meters. Several layers of chips are formed on sheets 14, namely first a cover or surface layer 15, then two core layers 16 and 17 and on top thereof again a cover or surface layer 1S. Spacers 19 are interposed between adjacent metal sheets 14. The respective chip type will fall downwardly between adjacent sheets 14 and can then be collected and reused. The loosely poured composite layer on sheets 14 has a bulk or apparent density of between 0.06 gr./crn.3 and 0.25 gr./cm.3, preferably of about 0.15 gr./cm.3, and the sheets with the composite layer thereon pass then over scale 49, and then, one sheet 14 at a time, through press 20 wherein 1Wet hoppers 7 serve t0 equalize the moisture of the wood to between l5 and 75 preferably 40% in weight per unit 0L' completely dry wood.

the composite layer of chips is subjected to a pressure of about 3 and 12 atmospheres, preferably 5 atmospheres above atmospheric pressure. The thus preliminarily pressed composite layer of chips is then subjected to further pressure in a heated multilayer press 21 at a pressure above atmospheric pressure of between 5 and 20 atmospheres, preferably between l2 and 16 atmospheres and a temperature of between 120 and 180 C., preferably about 140 C., or in certain cases about 170 C. Pressing is carried out for a period of between 0.3 and 1.0 minute for each millimeter thickness of the crude pressed plates, preferably, pressing per millimeter thickness will last for between 0.4 and 0.6 minute. The thickness of the crude pressed plates will vary between 8 and 80 mm. and thus, for instance in the case of a crude plate having a thickness of 10 mm., pressing might be carried out for about 5 minutes.

The crude plates in warm condition are then laterally trimmed to standard widths in contact with automatic circular saw 22. The plates which now will still have a temperature of at least 100 C., are passed directly into

planing machines

23 and 24 in which both faces of the plates are planed. The layer which is removed by planing has a thickness of up to 2 mm. and the shavings produced by planing equal between 2 and 12% of the weight of the plate.

The shavings may have for instance the following sizes:

Percent, by weight Up to 1 mm 48.6 Between l and 3 mm 36.2 Between 3 and 5 mm. 12.8

Above 5 mm. 2.4

A turning device 23 is arranged between

planing machines

23 and 24. The shavings which accrue during the planning of the hot pressed plate are directly returned to dry chip hoppers 10, preferably to the dry chip hopper 10 associated with line II, i.e. the line through which the chips pass which will eventually form the cover or surface layers of the pressed plate.

After passing through planing machine 24, the pressed plates are placed into a temporary storage 25 and allowed to rest there for between 3 and 8 days, preferably for about 5 days, depending on the weight of the plates and the temperature to which the plates were exposed in press 21. Thereafter, both faces of the plate are ground in

grinders

26 and 27. Turning device 2S is interposed between the two grinders. Y

The grinding of the planed plates will reduce the thickness of the same by between 0.5 and 1 mm., depending on the type of chips forming the surface layers of the plates and the specific weight of the same. On the other hand, if plates are to be ground which have not been planed according to the present invention, then any diferences in thickness of the plates must be equalized by grinding and thus it is necessary to grind so as to reduce the total thickness of the plates by between about 1.2 and 2.5 mm., which frequently will be equal to between about 0.1 and 0.14% of the width of the plates. It can be readily seen that by interposing the hot planing, about 40-60% of the wood our which previously was produced by grinding will accrue in the form of shavings which may be reused for forming additional pressed plates, particularly the surface portion thereof and, in this connection, it should be remembered that the shavings which are formed during passage of the plates through

planing machines

23 and 24 represent pressed material and thus will improve the quality of the subsequently produced plates which contain such shavings. After passing through grinder 27, the now linished plates are placed into warehouse 29.

Thus, from wood chippers 4 5 to distributor 13, two parallel lines of chips are processed, whereby on line l1 chips for forming the cover or `surface layers are treated, while on line I `the chips for the core layer are prepared.

From distributor 13 on, the lines unite into a forming line which passes through rst press or pre-'pressing arrangement 20 and hot press 21 as well as circular saws 22 and

planing machines

23 and 24.

In arrangements according to the prior art, the plates pass from hot press 21 directly to intermediate storage 25 for cooling, and only after cooling of the plates, the same were laterally trimmed and then ground, whereby the entire material taken off the faces of the plates would accrue in the form of wood ilo-ur or dust substantially suitable only as fuel.

The wood shavings which are taken olf the pressed plates in planing

machines

23 and 24, are of such quality that they may be used as they are for forming the cover or surface layers `of subsequently produced plates. The shavings accruing in the

planing machines

23 and 24 preferably are conveyed by means of pneumatic conveyer 35 back into dry-chip hopper 10 of line II, i.e. the line for the chips forming the surface layers of the pressed plate. The pneumatically conveyed shavings are separated in centrifugal separator 36.

Since the excess thickness of the plates which is required in order to allow for loss of `thickness by planing and grinding need not be greater than that required up to now for the conventional grinding alone, the reuse of the surface layer shavings will represent a saving of wood which usually will amount to between labout 4 and 10% of the total wood consumption, the actual percentage depending on the quality of lthe plates and the thickness of the same.

The planing of the pressed plates has the following additional advantages:

(1) The plates can be produced to very small tolerances :such as il mm. maximum difference between plates.

(2) Within an individual plate thickness tolerance may -be as small `as .a maximum of i005 mm.

(3) The surface of 'the planed plates after subsequent grinding of the same is considerably smoother and quieter since the chips of the cover layers which are located in the surface plane of the plate have an opportunity to expand after planing in hot condition and, wherever they are not firmly interlocked, to rise outwardly of the surface plane.

Subsequent grinding then results in an absolutely smooth quiet surface.

(4) Due to the fact that by planing of the plates as described above, the accruing shavings are recovered and thus an allowance mu'st be made only for the grinding loss, such allowance becomes a constant figure and therefore also the corresponding accounting position is no more a variable figure which make it difficult to have the budget made, but a constant value in the budget.

(5) The vertical upright of the plates is better as these plates repose for cooling and hardening absolutely at on the staple of raw-plates.

(6) For manufacturing the raw-plates higher tolerances in plate-thickness can be accepted.

For the manufacture of veneered pressed plates the planed surface is ideal. Planing is more precise, quicker and more economic than grinding and lshavings are pneumatically conveyed in a cleaner, better and cheaper manner than grinding-dust.

By returning these shavings back into the manufacturing of the pressed plates the problem of handling these shavings is solved at the same time.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications with-out omitting Ifeatures that, `from the standpoint of prior art, fairly constitute essential characteristics of the generic or specic aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning .and range of equivalence of the following claims.

What is claimed as new and desired to besecured by Letters Patent is:

1. In a method of producing compressed plates by hot pressing a mixture consisting essentially of Wood particles and pulverulent synthetic Ibinder material, the improvement which consists in forming a stream comprising wood particles and pulverulent synthetic binder material-adapted to become actively adhesive when heated to a predetermined elevated temperature; compressing successive portion-s of said stream while heated to at least said predetermined elevated temperature so as to form hot compressed plates; planing said compressed plates while still hot, thereby removing hot compressed shavings from said plates; and reintroducing at least a portion of said removed hot compressed `shavings while the same are still hot into said stream comprising wood particles and binder material before compressing the Isame so that the compressed plates contain also removed compressed shavings.

2. In a method of producing compressed plates by hot pressing a mixiture consisting essentially of wood particles and pulverulent lsynthetic: binder material, the improvement which consists in forming a stream comprising wood panticles 1an-d pulverulent synthetic binder material adapted to become actively adhesive when heated to a predetermined elevated temperature; compressing successive portions of said stream while heated to at least said predetermined elevated temperature so as to form hot compressed plates; planing said compressed plates while still hot, thereby removing hot compressed shavings from said plates; and reintroducing substantially all of said removed hot compressed shavings while the same are still hot into said stream comprising wood particles and binder material before compressing the same so that the compressed plates contain also removed compressed shavings.

3. A method according to claim 1 wherein said removed hot compressed shavings are reintroduced into said stream in such a manner that at least one of the opposite face portions of the compressed plates formed by compressing portions of said stream will include a greater proportion of said removed compressed shavings than the core portion of said compressed plates.

4. In a method of producing compressed plates by hot pressing a mixture consisting essentially of wood particles and pulverulent synthetic binder material, the improvement which consists in forming a lirst stream and a second stream comprising Wood particles and pulverulent synthetic binder material adapted to become actively adhesive when heated to predetermined elevated temperature; compressing successive portions of said iirst and second stream in superposed position and while heated to at least said predetermined elevated temperature so as to form hot compressed plates at least one face of which will be formed of said first stream; planing Said compressed plates while still hot, thereby removing hot compressed shavings from said plates; and reintroducing at leasty a portion of said removed hot compressed shavings while the same are still hot into said iirst stream comprising wood particles and binder material before compressing the same so that said one face of said compressed plates contains also removed compressed shavings.

5. In a method of producing compressed plates by hot pressing a mixture consisting essentially of Wood particles and pulverulent synthetic binder material, the improvement which consists in forming a iirst stream and a second stream comprising Wood particles and pulverulent synthetic binder materialvadapted to become actively adhesive when heated to a predetermined elevated temperature; compressing successive portions of said irst and second stream in superposed position and while heated to at least said predetermined elevated temperature so as to form hot compressed plates at least one face of which will be formed of said stream; planing said compressed plates while still hot, thereby removing hot compressed shavings from said plates; and reintroducing a major portion of said removed hot compressed shavings while the same are still hot into said first stream comprising wood particles and binder material and a minor portion of said removed hot compressed shavings while the same are still hot into said second stream comprising Wood particles and binder material before compressing said streams so that said one face of said compressed plates contains also a major portion of said removed compressed shavings.

6. In a method of producing compressed plates by hot pressing a mixture consisting essentially of wood particles and pulverulent synthetic binder material, the improvement which consists in forming a iirst stream and a second stream comprising wood particles and pulverulent synthetic binder material adapted to become actively adhesive when heated to a predetermined elevated temperature; compressing successive portions of said first and second stream in superposed position and while heated to at least said predetermined elevated temperature so as to form hot compressed plates the face portions of which will be formed of said iirst stream and the core portion of which will be formed of said second stream; planing said compressed plates while still hot, thereby removing hot compressed shavings from said plates; and reintroducing at least a portion of said removed hot compressed shavings while the same are still hot into said first stream comprising Wood particles and binder material before compressing the same so that said face portions of said compressed plates contain also removed compressed shavings.

7. In a method of producing compressed plates by hot pressing a mixture consisting essentially of Wood particles and pulverulent synthetic binder material, the improvement which consists in forming a first stream and a second stream comprising wood particles and pulverulent synthetic binder material adapted to become actively adhesive When heated to a predetermined elevated temperature; compressing successive portions of said first and second stream in superposed position and While heated to at least said predetermined elevated temperature so as to form hot compressed plates the face portions of which Will be formed of said first stream and the core portion of which will be formed of said second stream; planing said compressed plates while still hot, thereby removing hot compressed shavings from said plates; and reintroducing at least a portion of said removed hot compressed shavings while the same are still hot into said second stream comprising Wood particles and binder material before compressing the same so that the core of said compressed plates contains also removed compressed shavings.

8. A method according to claim 1 wherein at least one face of said compressed plates after planing and removal of hot compressed shavings therefrom is subjected to grinding.

9. A method according to claim 8 and including the step of applying a Wood veneer to the thus formed ground face.

10. In a method of producing compressed plates by hot pressing a mixture consisting essentially of Wood particles and pulverulent synthetic binder material, the improvement which consists in forming a stream comprising Wood particles and pulverulent synthetic binder material adapted to become actively adhesive when heated to predetermined elevated temperature; compressing successive portions of said stream while heated to at least said predetermined elevated temperature so as to form hot compressed plates; planing at least one face of said compressed plates while still hot, thereby removing hot compressed shavings from said plates; reintroducing at least a portion of said removed hot compressed shavings while the same are still hot into said stream comprising wood particles and binder material before compressing the same so that the compressed plates contain also removed compressed shavings; and applying a wood veneer to the planed face of said compressed plates.

11. In a method of producing compressed plates by hot pressing a mixture consisting essentially of wood particles and pulverulent synthetic binder material, the improvement which consists in forming a stream comprising Wood particles and pulverulent synthetic binder material adapted to become actively adhesive when heated to a predetermined elevated temperature; compressing successive portions of said stream While heated to at least said predetermined elevated temperature so as to form hot compressed plates; planing said compressed plates while still hot, thereby removing hot compressed shavings from said plates; and reintroducing at least a portion of said removed `compressed shavings into said stream comprising Wood particles and binder material before compressing the same so that the compressed plates contain also removed compressed shavings.

References Cited bythe Examiner UNITED STATES PATENTS 1,019,407 3/1912 Baekeland.

5 2,697,254 12/1954 Gordon 264--13 X 2,743,758 5/1956 Uschmann 264-113 X 2,912,041 11/1959 Boggs 156-372 X 2,925,117 2/1960 Moore et al. 156-375 10 2,947,654 8/ 1960 Chapman 156-267 X 2,992,152 7/1961 Chapman 264-113 X EARL M. BERGERT, Primary Examiner.

15 P. R. WYLIE, I. MATHEWS, Assistant Examiners.

Claims

1. IN A METHOD OF PRODUCING COMPRESSED PLATES BY HOT PRESSING A MIXTURE CONSISTING ESSENTIALLY OF WOOD PARTICLES AND PULVERULENT SYNTHETIC BINDER MATERIAL, THE IMPROVEMENT WHICH CONSISTS IN FORMING A STREAM COMPRISING WOOD PARTICLES AND PULVERULENT SYNTHETIC BINDER MATERIAL ADAPTED TO BECOME ACTIVELY ADHESIVE WHEN HEATED TO A PREDETEMINED ELEVATED TEMPERATURE; COMPRESSING SUCCESSIVE PORTIONS OF SAID STGREAM WHILE HEATED TO AT LEAST SAID PREDETERMINED ELEVATED TEMPERATURE SO AS TO FORM HOT COMPRESSED PLATES; PLANING SAID COMPRESSED PLATES WHILE STILL HOT, THEREBY REMOVING HOT COMPRESSED SHAVINGS FROM SAID PLATES; AND REINTRODUCING AT LEAST A PORTION OF SAID REMOVED HOT COMPRESSED SHAVINGS WHILE THE SAME ARE STILL HOT INTO SAID STREAM COMPRISING WOOD PARTICLES AND BINDER MATERIAL BEFORE COMPRESSING THE SAME SO TGHAT THE COMPRESSED PLATES CONTAIN ALSO REMOVED COMPRESSED SHAVINGS.

8. A METHOD ACCORDING TO CLAIM 1 WHEREIN AT A LEAST ONE FACE OF SID COMPRESSED PLATES AFTER PLANING AND REMOVAL OF HOT COMPRESSED HAVINGS THEREFROM IS SUBJECTED TO GRINDING.

9. A METHOD ACCORDING TO CLAIM 8 AND INCLUDING THE STEP OF APPLYING A WOOD VENEER TOTHE THUS FORMED GROUND FACE.