Green-wood Fibrating Means And Method

Abstract

A process and apparatus for converting solid pieces of timber into slender, splinter-like strands of wood fiber of more or less uniform thickness. Timber first passes through a series of rolls revolving at uniform or variable controlled speeds. The rolls have varying thread-like configurations and are vertically activated under controlled pressure of such magnitude as to cause the solid wood to be separated into splinter-like strands along the grain. The spongy mass of loosely matted fiber strands are then passed through a scrubbing device to be pulled apart.

Description

My invention relates to a novel approach for the utilization of substantially all portions of poorest quality timber such as logs, bolts, and cants, into physical forms eminently suitable for producing wooden particle board products. More particularly, my invention relates to a method and means wherein substantially 100 percent of such logs, bolts, etc., are converted into physical form suitable for the production of wood particle products whereby the heretofore approximately 40 percent loss of the peeled log to mill residue and sawdust is substantially eliminated. Still more particularly my invention is directed to a novel means and method whereby round bolts, round logs, half round pieces, square-edge cants or thick flitches of wood of any species and poor quality may be readily crushed into a sponge-like mat of long wooden splinters loosely held together as mats, which mats are subsequently broken apart into splinters of more or less uniform thickness and random lengths, whereby substantially 100 percent of the low-quality logs, etc. acted upon are converted into said splinters of more or less uniform thickness and length, which splinters after drying and refining can be used either in particle board or hard board manufacture or more desirably may be prepared for molding into products which can be more economically substituted for presently derived low grades of lumber.

Traditionally, the building industry, particularly that segment related to the construction of single-family residences, has relied upon construction utilizing substantial amounts of structural wood as its mainstay. Since the early 1950's the wood-using industries have been called upon to meet increasing demands for wood products. At the present time, it is projected that in this country alone some 50 million dwelling units.sup.1 Frank S. Kristof, "Urban Housing Needs Through the 1980's: An Analysis and Projection," National Commission of Urban Problems, Research Rept. 10, Washington 1968, p.6) will need to be constructed over the next 2 decades to house the expanding population and to replace many dwellings which may be either unsatisfactory or substandard. This, of course, offers a challenge to both timber growers and wood-using industries to supply a ready market of wood products without seriously depleting the forest capital. Conversion of poorest quality timber, heretofore uneconomic, into high-valve wood products in strong demand meets this challenge.

As is commonly known, only upwards of about 60 percent of products of logging operations from only the better quality trees can be utilized by present-day methods in the production of useful lumber, with the other 40 percent ending up as solid residue and sawdust. Under current practices, about 25 of all peeled logs end up in the form of solid residue, all of which can be used as chippable material. Up to the present time, the challenge to the timber growers and wood-using industries for complete utilization of the wood has resulted in extended efforts to convert the great proportion of the solid residue into useful forms or into useful materials either by chemical methods, such as for example, extracting wood sugars, alcohols, and the like from wood residues or by converting such wood residues into pulp and paper products. Alternatively, the mechanical approach for utilization of low-quality timber and the solid wood residue has been in efforts to convert such timber and residues into useful forms for the production of cement fiber boards, particle boards, hard boards, and the like, whereby such timber and solid residue is chipped, shaved, or otherwise mechanically worked on to render the product from such processes in a form whereby they can be utilized, as just mentioned.

I have now discovered a new approach, means, and method for the utilization of substantially all of a peeled, small, low-quality log, whereby same is converted into a form eminently suitable for the production of wood products fully equivalent or superior to the lumber products heretofore recoverable from such logs. In my process, I utilize essentially all of the peeled log, or the like, for the ultimate production of the lumber equivalent product, as contrasted to the art heretofore practiced wherein only upwards to about 60 percent of such logs can be so utilized. In my process, there is no sawdust by product, nor are there any substantial amounts of wood residue produced. In my process, substantially all of the stumpage ultimately is useful in the end product as a full equivalent and substitute for conventional lumber as heretofore utilized and relied upon by the building industry generally, and the furniture industry, specifically. Basically, my invention comprises a method for disintegrating a log or any portion thereof into splinter-like strands of wood substance of more or less uniform width and thickness and reduced moisture content from the original moisture content of the solid piece. The wood strands are subsequently formed into fiber board or panels having structural strength equal to or superior to the strength of flake board panels of the same size.

Further, I have found that, in carrying out my process, the wood products made in accordance therewith contains all of the inherent characteristic and properties of the original timber, except that some of the free moisture will have been removed and the knots eliminated. Inasmuch as the original log or piece, in my process, is subjected to pressure and forces which exceed the maximum crushing strength of the timer, and solid structure of the timber is caused to disintegrate along the direction of the grain into varying length splinter-like strands of woody material which takes the form of a mat, which mat is subsequently broken apart into splinters of more or less uniform thickness and random lengths. These splinters, when subsequently molded into the desired shapes and cemented together, yield a material which derives substantially all of its strength from the inherent strength of the wood splinters themselves, rather than from the cementing material. Thus, molded panel boards will be at least as strong and in many instances stronger than similar boards which are being made from flakes or other particles with the added advantage that substantially all of the low-quality log may be so utilized rather than only upwards to about 60 percent under heretofore practiced conventional sawmill procedures.

It is therefore an object of the present invention to disintegrate a log or any portion thereof into splinters of more or less uniform thickness and random lengths, a reduced moisture content from the original content of the log, or portion thereof, whereby substantially 100 percent of said log or portion thereof may be ultimately utilized in the production of wood products of at least the full equivalent, and in many instances, far superior, to products made from wood particles of varying geometry.

Another object of the present invention is to disintegrate a low-quality log or any portion thereof, into splinters of more or less uniform thickness and random lengths, and reduced moisture content from the original content of the log, or portion thereof, whereby substantially 100 percent of said log or portion thereof may be ultimately utilized in the production of formed wood products of at least the full equivalent, and in many instances, far superior to the products resulting from present-day sawmill practice, and whereby the heretofore approximate 40 percent of wood residue and sawdust resulting from said sawmill practice is substantially eliminated thereby.

Still another object of the present invention is to disintegrate a log, or any portion thereof, into splinters of more or less uniform thickness and random lengths, and reduced moisture content from the original content of the log, or portion thereof, whereby substantially 100 percent of said log or portion thereof may be ultimately utilized in the production of formed wood products of at least the full equivalent, and in many instances, for superior to the products resulting from present-day sawmill practice, by a process wherein aid log or portion thereof is acted upon by forces which exceed:

1. the maximum crushing strength of the timber in compression; parallel and perpendicular to the grain;

2. the maximum shearing strength in shear parallel to the grain; and

3. maximum cleavage or load to cause splitting.

A further object of the present invention is to disintegrate a log, or any portion thereof, into splinters of more or less uniform thickness and random lengths, and reduced moisture content from the original content of the log, or portion thereof, whereby substantially 100 percent of said log or portion thereof may be ultimately utilized in the production of formed wood products of at least the full equivalent, and in many instances, far superior to the products resulting from present-day sawmill practice, by a process wherein said log or portion thereof is acted upon by forces which exceed:

1. the maximum crushing strength of the timber in compression; parallel and perpendicular to the grain;

2. the maximum shearing strength in shear parallel to the grain; and

3. maximum cleavage or load to cause splitting;

and wherein said forces in addition to yielding the desired physical material reduce the original moisture content thereof by literally squeezing some of the free moisture from the cell cavities exposed to such forces whereby is acquired the liquid material squeezed from the timer, which is subsequently processed by appropriate chemical engineering principles and methods so as to salvage such extractive substances as may be contained in the wood naturally, including such substances as tannin from the oak species, oils and their derivatives from the cedar species, and resins and their derivatives from the pine species.

A still further object of the present invention is to disintegrate a log, or any portion thereof, into splinters of more or less uniform thickness and random lengths, and reduced moisture content from the original content of the log or portion thereof, whereby substantially 100 percent of said log or portion thereof may be ultimately utilized in the production of formed wood products of at least the full equivalent, and in many instances, far superior to the products resulting from present-day sawmill practice, whereby will be promoted a more extensive utilization of the low-quality timber not economically feasible to convert, under existing technology and conventional methods of manufacture, into useful solid wood products, thereby contributing materially to the conservation and wise use of our nation's timber resources and capital.

Still further and more general objects and advantages of the present invention will appear from the more detailed description set forth below, it being understood however that this more detailed description is given by way of illustration and explanation only and not by way of limitation since various changes therein may be made by those skilled in the art without departing from the true spirit and scope of my invention.

My invention, together with further objects and advantages thereof will be better understood from a consideration of the following description taken in connection with the accompanying drawing in which:

FIG. 1 is an isometric schematic illustration of the preferred embodiment of a log defibrating apparatus used in accordance with the practice and teachings of my invention.

FIGS. 2 and 3 are depictions drawn approximately to scale of the splinters resulting from my invention as operated under two different sets of parameters whereby in FIG. 2 it was desired to have relatively short wood splinters of more or less uniform lengths and diameters whereas in FIG. 3 are depicted wood splinters of longer lengths.

FIG. 4 is an illustration of typical wood chips prepared by conventional means from solid wood residues, which chips are intended for use in the production of pulp and paper.

FIG. 5 is a depiction of just one of many typical shavings resulting from a particular planer setting for producing flakes by conventional means intended for use in the production of particleboard by conventional methods.

FIG. 6 depicts both a typical green plank and a half log illustrative of the low quality timber or stumpage which may be expediently utilized according to the instant invention.

FIG. 7 is an illustration of what the solid wood plank or half log from FIG. 6 looks like when processed according to my invention into the spongy-like mat of long, splinter-like wood fiber strands more or less firmly enough held together to remain as a unit mass of material prior to treatment with my scrubber apparatus.

FIG. 8 is a schematic illustration of the detail of the top rolls in the first series of rollers having the cylindrical portions of their cylindrical surface in the form of screw threads, said screw threads being left handed from about the horizontal midpoint of said rolls and extended to the right hand horizontal terminus thereof, and said screw threads being right handed from about the horizontal midpoint of said rolls to the left hand terminus thereof when viewed along the axis of the long portion of said L-shaped frame from a direction from said first series of top rolls to said second series of top rolls. As will be noted in later discussion, the thread depth on rolls 2, 3, and 4 may vary from one-fourth to three-fourths inch and the thread pitch may vary from one-half inch up to 2 inches. In addition, FIG. 8 depicts the thread type on said rolls as being of the buttress type, which is a thread type commonly used wherein motion or thrust is required in but a single direction such as in the breech of large guns, in jack stands, and the like.

FIG. 9 is a schematic illustration of one type of drive means for operably engaging the top platen for imparting thereto in the vertical plane and egg-shaped, elliptical orbit with the larger of the two radii of said egg-shaped elliptical orbit disposed toward the corner portion of the L-shaped frame member. As may be seen from the detail in FIG. 9, driving the two shafts at identical speeds produces the desired elliptical orbit of the upper platen due to the action of the two different size cam. For the sake of convenience, the driving machinery for said shafts and the supporting structures are not shown.

FIG. 10 is a depiction not to scale of the cylindrical portions of the peripheral surfaces of the second series of bottom rolls which may be serrated with the grooves of the serration thereof being parallel to the axes of the second series of bottom rolls.

Referring now more specifically to FIG. 1, there is shown a preferred embodiment of apparatus which I have had constructed and operated for carrying out the objectives of my invention. As may be seen, the apparatus comprises a sturdy L-shaped frame upon which are mounted two series of roll sets 2-2a, 3-3a, 4-4a, and 8-8a, 9-9a, 10-10a and 11-11a. Each of the aforementioned roll sets consists of a companion upper and lower roll. Lower rolls, 2a, 3a, 4a, and 8a, 9a, 10and 11a, are rigidly supported by the lower frame of the machine to withstand the crushing load imposed upon the log by upper rolls 2, 3, 4, and 8, 9, 10, and 11. The wood pieces, i.e., log, half log, flitch, cant, or whatever to be processed according to my invention, are fed into my apparatus by means of roller table 1 whereby said pieces are first acted upon by roll set 2-2a.

The cylindrical surfaces of upper rolls 2, 3, and 4 are in the form of screw threads right and left hand from the center of the rolls to their ends. The thread form and pitch on each roll is that which is most suited to the purpose of tearing apart and spreading the wood fibers into a mat under pressure. As indicated, upper rolls 2, 3, and 4, in addition to being rotated by variable speed motor-reducer 26, can be moved vertically. Vertical movement is accomplished by hydraulic cylinders 25 so arranged and controlled as to operate in unison, and capable of exerting the required crushing force upon the log. The rotational and vertical drives for these upper rolls are independent of each other. Wood material passing through roll sets 2-2a and 3-3a to roll set 4-4a is supported by platens 5 and 6.

Surfaces of bottom rolls 2a, 3a, and 4a are smooth or they may be serrated with grooves parallel to the axes of the rolls. Speed of bottom rolls 2a, 3a, and 4a is restrained by a dynamic braking system utilizing motor-reducer 22 as a regenerative electric brake so that the speed of the wood mass or log through my apparatus is less than the peripheral speed of upper rolls 2, 3, and 4. Crushed wood mass or logs leave roll set 4-4a as a mat supported and guided into roll set 8-8a by platen 7. Likewise platens 12, 13, and 14 disposed between roll sets 8-8a, 9-9a, 10a, and 11-11a, as well as the platens shown numbered as 5 and 6 on drawing and as noted above disposed between roll sets 2-2a, 3-3a, and 4-4a support the wood mat as it is formed and spread out progressively through the apparatus mounted on the longer portion of the L-shaped frame. Surfaces of upper rolls 8, 9, 10, and 11 are smooth while the surfaces of lower rolls 8a, 9a, 10a, and 11a, although not shown, are, in my most preferred embodiment, serrated with grooves parallel to the axis of said rolls. I have observed that the serration of these lower roll surfaces, although not absolutely essential to the carrying out of my process, produces a more desirable mat form. The peripheral speed of the lower rolls 8a through 11a is identical to the speed of lower rolls 2a, 3a, and 4a.

Upper rolls 8 through 11 are provided with hydraulic cylinders, 23 for activating them vertically and also independently of each other. One or more of the upper rolls 8 through 11 may be oscillated vertically by controlled, repeated action of hydraulic cylinders 23, to provide a beating action. Platens 12, 13, and 14 support the fiber mat through roll sets 8-8a through 11-11a. The fiber mat, mat, as it leaves roll set 11-11a, is supported and guided to transfer table 16 by roller table 15. For convenience, one type of mechanism for actuating transfer table 16 is shown removed from therebeneath consisting of hydraulic cylinder 16a for providing reciprocal motion in a horizontal plane and rocker arms 16a for transferring the impulses from cylinder 16a to transfer table 16. From transfer table 16 the fiber mat proceeds into the fiber scrubber 17. Scrubber 17 is essentially a machine consisting of fixed lower platen 18 and movable upper platen 19, together with drive means not shown necessary to cause upper platen 19 to travel in an egg-shaped, elliptical orbit, as indicated on the drawing. Both upper platen 19 and lower platen 18 are grooved or serrated across their juxtaposed surfaces with the grooves parallel to the alignment of wood fibers as they pass through scrubber 17. As shown in FIG. 1, the serrations or grooves in the top surface of the lower platen 18 and the lower surface of the top platen 19 are generally in the form of teeth-like members whose bite is in the direction from the corner of the L-shaped frame toward the exit of the scrubber. Thus, the wood mat leaving roller table 15 is moved via transfer table 16 into the mouth of the scrubber jaws which work on the mat bundle to pull, shred, roll, and otherwise work the individual strands from the mat to be discharged for further processing and molding into the desired forms. Such further processing requires varying degrees of further drying of the individual wood strands and, if desired, screening or sizing thereof.

The loosely separated fiber strands, when discharged from the fiber scrubber 17, drop onto belt conveyor 20 as a new geometric form of wood resource ready for a variety of manufacturing processes.

Trough 21 catches liquids squeezed from the logs and drains the liquid to a suitable tank for subsequent chemical processing.

As should now be apparent, the instant invention provides an arrangement by means of which low quality round bolts, round logs, half round pieces, square edge cants or thick flitches of any wood species may be readily crushed into a sponge-like mat of long wood splinters loosely held together, and as the mats are formed, are acted upon by a first series of rotating sets of rolls containing screw-thread-like configurations which, under pressure, cause further disintegration of the wood into a mat of thin splinter-like strands. Further action by a second series of rotating sets of rolls having smooth and/or serrated surfaces (serrations parallel to axis of the rolls) causes compression and spreading of the mat. Further and subsequent action by the scrubber element causes the resulting compressed and spread woody fiber mat to be broken apart into individual splinters of more or less uniform and random lengths. Actually, the individual elongated wood splinters are themselves composed of almost hair-like individual strands held together in their natural state as produced in the tree.

It should be appreciated that the thread sizes on rolls 2, 3, and 4 and their configuration, of course, might be varied over substantial range; however, based on my experience with the apparatus I have developed, I have found that the operable ranges are as follows:

thread depth -- one-fourth inch to three-fourth inch

thread pitch -- one-half inch to 2 inches

thread lead -- same as pitch for single thread and twice the pitch for double thread

A buttress type thread is the one used on rolls 2, 3, and 4 in the apparatus shown in FIG. 1, and my experience has shown that this appears to be thread configuration most suited to splitting and spreading the wood mass.

The maximum range of pressures is, of course, controlled by the maximum force available to the machine. The pressure on any given thread form will depend upon the type and size of the thread and the total area of contact of the thread with the wood. Thus, in my device the initial pass of a log or the like will, in my most preferred embodiment, be through a roll with a large pitch thread and succeeding passes through rolls with progressively smaller pitch threads.

In the apparatus depicted in FIG. 1, the maximum pressure available on the hydraulic system as I used same was 3,000 p.s.i. With this maximum pressure, the compressive force available at the top rolls is about 93,000 pounds. Assuming that the initial penetration of the threads has taken place such that a 2-inch length of crest on two threads is in contact with wood, the pressure exerted thereby is about 370,000 p.s.i. Assuming that the threads are embedded to their full depth, the maximum pressure on the projected area parallel to the surface of the top roll is then 34,000 p.s.i. As the crushing proceeds, the mass of wood spreads out into a spongy-like mat of increasing width and decreasing thickness. With a 10-inch spread of wood mat, pressure exerted is about 3100 p.s.i. With a mat spread of 20 inches, the pressure is reduced by about one-half to about 1,550 p.s.i. At this stage, i.e., a mat spread of about 20 to 22 inches, crushing is complete, the integrity of the solid wood mass is completely destroyed, and the mat is ready to pass through scrubber 17 for separation into thin individual splinters or strands.

Because of the inherent properties of wood, green wood lends itself to the above-described process quite readily and has advantages of processing in addition to being processed immediately after harvesting. Wood in the green state contains a considerable amount of moisture, varying from about 30 to 40 percent (based on the weight of the dry wood) in the heartwood of some of the pines to over 200 percent in the sapwood of some other species. Part of this moisture is held absorbed by the cell walls and part is held within the cell cavities as water is held in a container. As wood dries, the cell cavities must first be emptied of all their moisture before the adjacent cell walls start to release their moisture. The condition in which the cell walls are fully saturated and the cell cavities empty is known as the "fiber saturation point." It varies between species from approximately 25 to 30 percent moisture content.

Strength begins to increase when the cell walls start to lose moisture; that is, after drying continues below the fiber saturation point. From this point on, most strength properties increase rapidly as drying progresses. To illustrate, for the strength properties most involved in this log defibrating process, the following figures show the average variation of strength properties of wood with change in moisture content: The percentages show the average increase (or decrease) in value effected by lowering (or raising) the moisture content 1 percent:

Maximum crushing strength in compression parallel to grain -- 6percent

Fiber stress at proportional limit in compression perpendicular to grain -- 5-1/2 percent.

Shearing strength parallel to grain -- 3percent

As a restriction for optimum operating conditions, it is therefore stipulated that the timbers should be in the green state or at a minimum moisture content of 30 percent, based on the oven-dry weight of the wood.

A further stipulation for optimum operation of the process involves temperature. It is known that tests in compression parallel to the grain have shown strength values for green wood at temperatures near the boiling point about one-fifth as great as at normal room temperature. It is therefore stipulated that optimum defibration conditions require that timbers, in addition to being in the green state, also could best be defibrated if temperatures are raised somewhat above room temperature and upwards. This could mean that all timbers would undergo immersion in heated water vats prior to defibrating.

In order that those skilled in the art may be better understand how the present invention can be practiced, the following examples of the methods I have used in disintegrating logs and other portions of timber for producing the desired wood splinters and in some instances the subsequent formation and molding of same into desired structural members and board products are given by way of illustration and not by way of limitation.

EXAMPLE I

Suppose it is desired to defibrate a green plank or a half log as shown in FIG. 6, or any other shaped solid piece of timber. The underlying idea of the instant invention is to completely crush the solid wood plank or log into a spongy-like mat of long, splinter-like wood fiber strands more-or-less firmly enough held together to remain as a unit mass of material as shown in FIG. 7. This is accomplished through roll sets 2, 3, and 4 within a range of pressures between 1,500 and 3,000 p.s.i. As the spongy mass passes through roll sets 8, 9, 10, and 11, the mass of more-or-less firmly held together splinter-like wood fiber strands are more finely divided and separation becomes more complete due to the action of the changed configuration of threads on roll sets 8, 9, 10, and 11. Final separation of the then more-or-less loosely held together mass is then accomplished through scrubber 17 by its crushing, rolling, and pulling action of the woody mass between the serrated top and bottom platens.

Another general embodiment of the instant invention deals with the variability that can be encountered in the separation or defibration process due to the grain of wood. Grain of wood in this instance is defined as the arrangement and direction of alignment of wood elements when considered en masse. Three type of grain are recognized as basic wood grain structure; although they do occur in combination: (1) Straight grain -- grain in which the direction of the fiber alignment is straight or nearly so; grain in which the fiber alignment is vertical or nearly so in the standing tree. Defibration is quick and nearly complete resulting in long strands of more-or-less uniform thickness. (2) Spiral grain -- grain in which the fibers are aligned spirally in the standing tree. Defibration is more difficult resulting in shorter strands due to cutting action across the grain by the threaded roll sets 2, 3, and 4. More of the separation must be effected by scrubber 17. (3) Interlocked grain -- grain in which the direction of the fiber alignment alternates at intervals. Defibration is most difficult with wood of this nature, but fortunately species of trees with this inherent characteristic are in the minority. Defibration is most difficult and requires more of the cutting action of the fine thread configuration on roll sets 8, 9, 10, and 11, and the additional scrubbing effect of scrubber 17. The resulting splinter-like strands are the shortest of the three kinds of grain but, since various length of strands is an asset in envisioned product development, use of wood of this nature poses no series problem.

Another general example, exemplifying the idea of the instant invention deals with the recovery of liquid (free moisture contained in the cell cavities of the wood) squeezed from the timber under pressure. Collection of the varying amounts of liquid due to species of wood and greenness of the wood entering the machine is provided for by trough 19.

EXAMPLE II

A specific example of the instant invention portrays results of the defibrating process under systemmatic test. Twenty-four black oak (Quercus velutina Lam.) planks 3 .times. 5 .times. 7 were defibrated to obtain optimum operating ranges of the equipment. Controlling variables in the defibrating process are pressure, speeds of top and bottom rolls and thread configuration on top rolls. Best results were obtained with pressures between 1,550 and 1,950 p.s.i.; top and bottom roll speeds of 24.8 and 9 rpm's respectively and a buttress type, single acting thread. After three passes through a single roll set, average width and the thickness of the original 5 -inch wide by 3 -inch thick plank was 16.5 inches wide by 2 inches thick. The integrity of the wood was completely destroyed resulting in a mat of more-or-less loosely held together splinter-like strands of wood as shown in FIG. 7.

Another specific example of the instant invention deals with the measured loss of moisture from the 3 .times. 5 ' 7 test planks which were in their natural green condition at the time of the test. Average moisture content (MC) before defibration was 83 percent (based on oven dry -- O.D. -- weight): after defibration it was 75 percent. The measured moisture loss due to defibration ranged between 0.24 and 2.64 lbs. per cubic foot of wood and averaged 1-3/4 lbs. per cubic foot. Assuming a standard cord of black oak wood to contain 72 cubic feet of solid wood, an average of approximately 15-3/4 gallons of liquid per cord would be salvaged for chemical processing.

EXAMPLE III

Three sheathing-type boards were experimentally made at the United States Department of Agriculture's Forest products Laboratory, Madison, Wisconsin. Using 2- to 3 -inch long splinters produced by the present invention, three sheathing-type boards were made to the following "basic" specifications:

Board size: 1/2 .times. 24 .times. 28 inches Board density: 40 pounds per cubic foot Resin type and content: Phenolic, 3 percent (solids basis) Additives: 1 percent emulsion (solids basis) Press cycle: 10 minutes at 350.degree. F, pressed to 1/2 -inch thickness in 1 minute

Two boards, A and B were made from splinters as produced by the invention. The third board, C, was made from splinters produced by the invention after they were hammermilled. The splinters were fed through a small agricultural hammermill without screen.

Board B had a moisture content of 15 percent, whereas boards A and C had moisture contents of 10 percent. It was the hope of the product development engineers that the boards with the higher mat moisture content would have surfaces with fewer voids. However, little difference was noticed.

Engineering test results on three critical properties of the new sheathing-type board products are given below:

The results of the modulus of rupture, modulus of elasticity, and nail tests are:

Board Lateral Nail No. M.O.R. M.O.E. Nail Pull Withdrawal __________________________________________________________________________ (p.s.i.) (1,000 (Lbs.) (Lbs.) p.s.i.) A 1260 190 261 .sup.1 24 .sup.2 128 B 890 150 169 .sup.1 24 .sup.2 140 C 1320 210 338 .sup.1 28 .sup.2 125 __________________________________________________________________________

In addition to strength tests, an ovendry to vacuum-pressure-soak dimensional movement test was made on each board with the following results:

Board Length Change From Thickness Change No. O.D. to V.P.S. from O.D. to V.P.S. __________________________________________________________________________ A 0.92 percent 58.1 percent B 1.15 percent 62.6 percent C 1.04 percent 48.7 percent __________________________________________________________________________

While I have shown and described particular embodiments of my invention, modifications and variations thereof will appear to those skilled in the art. I wish it to be understood, therefore, that the appended claims are intended to cover such modifications and variations which are within the true scope and spirit of my invention.

Claims

What we claim as new and desired to secure by Letters Patent of the United States is

1. In a device, for forming small splinter-like strands of wood of relatively uniform lengths and diameters and having the axes thereof substantially parallel along the grain of wood pieces from which said strands are formed, said strands formed from solid forms of low-quality wood selected from the group consisting of round logs, semi-round logs, square edge cants, thick flitches and mixtures thereof, and said strand eminently suitable for use in forming and molding lumber products including structural members having strength characteristics equal or superior to commercially available wood members; a frame, said frame being generally L-shaped in a horizontal plane and having later mentioned (a) roller means about the longer portion of said L-shaped frame (b) scrubber means about the shorter portion of said L-shaped frame and (c) transfer table means mounted about the corner portion of said L-shaped frame, a first and second series of bottom rolls rigidly supported on said L-shaped frame juxtaposed the longer portion thereof for rotation thereon in a plane substantially parallel with the long axes of said frame, braking means operably engaging said first and second series of bottom rolls for restraining the peripheral speed thereof, a first and second series of top rolls mounted on said L-shaped frame with the axes thereof parallel to the axes of said first and second series of bottom rolls and each roll in said first and second series of top rolls being in vertical alignment with its corresponding and companion bottom roll, means operably engaging each roll in said first and second series of top rolls for imparting thereto rotational movement about its axis at a predetermined peripheral speed, means operably engaging each roll in said first and second series of top rolls for imparting thereto vertical reciprocating movement, said means for imparting both said rotational and said reciprocating vertical movement to each roll in said first and second series of top rolls, being operably independent, said means for imparting rotational movement to each roll in said first and second series of top rolls adapted to impart thereto a peripheral speed greater than the peripheral speed of the companion bottom roll aligned vertically therebeneath, said top rolls in said first series having the cylindrical portions of their peripheral surfaces in the form of screw threads, said screw threads being left handed from about the horizontal midpoint of said rolls and extending to the right hand horizontal terminus thereof and said screw threads being right handed from about the horizontal midpoint of said rolls to the left hand terminus thereof when viewed along the axis of the long portion of said L-shaped frame from a direction from said first series of top rolls to said second series of top rolls; transfer means mounted on said L-shaped frame ahead of said first series of companion bottom and top rolls for introducing and carrying into said rolls said solid wood forms; transfer means disposed between each roll in both said first and said second series of said bottom rolls for effecting mechanical transfer of the wood mat resulting from passage thereover, transfer means disposed beyond said second series of companion top and bottom rolls for effecting movement of the resulting wood mat onto said transfer table means; drive means in association with said transfer table means for changing the direction of travel of said wood mat entering thereupon to substantially 90.degree. from its original direction of travel to a direction of travel substantially parallel with and in a direction along the shorter portion of said L-shaped frame while maintaining the alignment of the individual splinters in said wood mat in a direction parallel with the axis of the long portion of said L-shaped frame, wood splinter scrubber means juxtaposed said transfer table means mounted on said L-shaped frame and disposed along the short portion thereof, said scrubber means having a fixed lower platen and a moveable upper platen the top surface of said lower platen and the bottom surface of said upper platen being serrated with the grooves from said serrations being substantially parallel to the long axis portion of said L-shaped frame member, said serrations on the surfaces of both said lower and said upper platen being in the form of teeth-like members, the direction of bite thereof being in a direction away from the corner of said L-shaped frame and toward the terminus of the short portion thereof, and drive means operably engaged said movable top platen for imparting thereto in the vertical plane an egg-shaped eliptical orbit with the larger of the two minor radii of said egg-shaped eliptical orbit disposed toward the corner portion of said L-shaped frame member.

2. The device claimed in claim 1 wherein the screw thread type on the cylindrical portion of the peripheral surfaces of said top rolls in said first series are of the buttress type.

3. The device claimed in claim 2 wherein said buttress-type thread has a depth in the range from about one-fourth inch to about three-fourths inch and has a pitch in the range from about one-half inch to 2 inches.

4. The device claimed in claim 3 wherein the cylindrical portion of the surfaces of said first series of bottom rolls is relatively smooth and the cylindrical portions of the peripheral surfaces of said second series of bottom rolls are serrated with the grooves of the serrations thereof being parallel to the axis of said second series of bottom rolls.

5. The device claimed in claim 4 wherein said transfer means mounted on said L-shaped frame ahead of said first series of companion bottom rolls and top rolls and said transfer means disposed beyond said second series of companion top and bottom rolls are roller tables, and wherein said transfer means disposed between each roll of said first and second series of said bottom rolls are platens disposed in substantially a horizontal plane.

6. The device claimed in claim 5 including liquid restraining means disposed vertically beneath both said first and second series of bottom rolls for recovery of liquids removed from said solid forms of wood passed thereover.