US2747232A - Process for decorticating fibrous materials - Google Patents

Description

May 29, 1956 ARMSTRQNG 2,747,232

PROCESS FOR DECORTICATING FIBRO-US MATERIALS Filed July 5, 1952 4 Sheets-Sheet l COLE/VCHYMH P/ 7/1 {PHRENCH YMH ENE Y" May 29, 1956 B. ARMSTRONG 2,747,232

PROCESS FOR DECORTICATING FIBROUS MATERIALS Filed July 5, 1952 4 Sheets-Sheet 2 INVENTOR. BRUCL' fle/wsma 5 T'TORNE Y" y 1956 B. ARMSTRONG 2,747,232

PROCESS FOR DECORTICATING FIBROUS MATERIALS Filed July 5, 1952 4 Sheets-Sheet 5 INVEN TOR. 19/90:: #RW: TAO/V6 May 29, 1956 B. ARMSTRONG PROCESS FOR DECORTICATING FIBROUS MATERIALS 4 Sheets-Sheet 4 Filed July 3 INVENTOR.

BRUCE file/14$ mom;

PROCESS FOR DEfiORTICATKNG FIERGUS MATERIALS Bruce Armstrong, Saginaw, Mich assignar to Saclrscn (2;; Church Company, Saginaw, Mich a corporation or Michigan Application July 3, 1952, Serial No. 297,078

6 Claims. (Cl. 199) This invention relates to a process for decorticating fibrous vegetable materials such as flax, bagasse, kenaf, ramie or jute, and particularly to a type thereof which effects such decortication by repeated bending of bundles of said fibers at high rates of speed and at high frequencies.

In the presently known processes for separating vegetable fibers from each other, and for separating same from the material, usually pith, comprising the heart of stalks containing said fibers, principal reliance is placed upon striking such material a large number of times per second by blunt instruments wherein the shock of such blows, as in a common hammer mill, breaks down the structure of the material holding said fibers together and leaves such fibers free to separate. However, such methods also tend to break the fibers themselves, or at least materially to weaken same, due to the pounding thereof and it is desired to find a method for effecting such fiber separation Without such undesirable weakening thereof.

Further, in such methods of separating fibers, the material comprising the heart of the stalks containing the desired fibers is, particularly if such material is somewhat dry, so pulverized that it is extremely difiicult to handle and hence is usually lost. Thus, such material, though often containing valuable elements, and from which such products as cattle feed may often be advantageously made, is lost and an economic waste consequently occurs.

The fibers upon which the present process is particularly intended to operate are those fibers which occur somewhat as a sheath located near the surface of a vegetable stalk and surrounding a central zone of relatively short fibers constituting the pith. These fibers are commonly termed bast fibers and are relatively long, flexible and tough. The fibers constituting the pith, or parenchyma, are relatively short and brittle, as are also other fibrous layers immediately adjacent to and surrounding the bast fibers. Therefore, if the vegetable stalk is subjected to rapid and repeated bending, the stresses set up within the stalk will break apart these shorter and more brittle fibers and separate them from the bast fibers but will not materially affect the bast fibers themselves excepting to separate them from each other. In this way, it is possible, by subjecting the vegetable material to rapid and repeated bending to break the bonds that exist between the bast fibers themselves and between the bast fibers and the surrounding shorter fibers, particularly the parenchyma, and convert the vegetable stalk into a mass of substantially unbroken and unshortened bast fibers, wherein each thereof is substantially thoroughly separated from other bast fibers in the massand is well cleaned of other fibers occurring in the vegetable stalk, and wherein the pith and other associated fibers are scattered loosely through the mass in a su-fficiently broken and shattered form as to be readily separable by any convenient shaking or blowing methods and yet without the same being so small as to render them useless for such by-product purposes as cattle feed.

For the purpose of clarity in reference, the term de- 2,747,232 Patented May 29, 1956 corticate will hereinafter be used'to refer to that portion of the process which consists of breaking the bond between the bast fibers themselves and between the bast fibers and the surrounding shorter fibers. The term separation or cleaning will refer to the steps by which the scattered particles of pith and other short fibers which are scattered through the fibrous mass at the end of the decortication process are ultimately removed therefrom and the bast fibers obtained free and clean of all other materials.

It therefore is an object of this invention to provide a method for disconnecting from each other the fibers 0f fibrous material, particularly of a cellulosic form, withou unduly weakening or shortening said fibers.

A further object of said invention is to provide a method for breaking the bond between the bast fibers themselves and between the bast fibers and the adjacent shorter fibers, particularly pith, associated therewith, which is particularly adaptable to materials having a center composed of relatively short fibers, such as corn stalks, sugar cane, flax and many others.

A further object of the invention is to provide a method for breaking the bond between the bast fibers themselves and between the bast fibers and the adjacent shorter fibers, particularly pith, associated therewith, as aforesaid, which will not unduly pulverize or otherwise comminute the material comprising the heart of such stalks but rather will preserve such heart of material largely in chunks of appreciable size and thereby render it possible to handle same by mechanical methods.

A further object of the invention is to provide a method for breaking the bond between the bast fibers themselves and between the bast fibers and the adjacent shorter fibers, particularly pith, associated therewith, as aforesaid, which has material in the heart thereof comprising nutrient components and so preserving the physical structure of such heart material sufficiently to make it possible to make animal food therefrom. I

A further "object of the invention is to provide a method for decorticating fibers of fibrous materials which will not noticeably shorten or weaken said fibers.

A further object of the invention is to provide a method, as aforesaid, which method may be carried out by a substantially continuously operating means.

A further object of the invention is to provide a method, as aforesaid, which is capable of being practiced by relatively inexpensive means and yet -means which can handle a large volume of such fibrous material.

Other objects and purposes of the invention will be apparent to persons acquainted with processes of this general type upon a reading of the following specification and inspection of the accompanying drawings.

in the drawings:

Figure 1 represents a side view of a segment of fibrous material which has been chopped into a convenient length for handling, such as 2 or 3 inches. Fig. la indicates an end view of said segment with the important parts of the stalk indicated for purposes of reference.

Figure 2 shows a central section of a fiber when same is bent in one direction.

Figure 3 represents the bundle of fibrous material shown in Figure 2 when subjected to bending in the opposite direction.

Figure 4 represents a schematic illustration of a portion of a device for'practicing saidrmethod and showing two bundles of fibers therein.

Figure 5 represents a section taken on the line 55 of Figure 4.

Figure 6 is a view in vertical section of a machine capable of practicing the process.

Figure 7 is a plan View of one of the rotating plates of said machine.

Figure 8 is a section taken on the line 88 of Figure 7.

Figure 9 is an oblique view of an alternate plate for use with said machine and showing in broken lines a bundle of fibers ther eon and two teeth on the cooperating plate. Figure 10 is a section taken on the line 1010 of Figure 9.

Figure 11 shows a central longitudinal section of another machine capable of carrying out the same process. Figure 12 is a section taken on the line 12-42 of Figure 11.

' General description The method herein disclosed contemplates (1) suspending a bundle of fibrous material in a fluid stream, and while so suspended therein, (2) contacting thereof by suitably spaced fingers which will effect a bending of said bundle and a prompt release thereof, followed by the immediate engagement of said bundle by other fingers which again bend and release it, the bending and releasing occurring in progressively shorter segments of the bundles.

Detailed description In meeting the objectives of the invention, recognition is made of the fact that as an elongated bundle of fibers is bent transversely of the direction of said fibers, said fibers will be caused to slip upon each other and will thereby be caused to separate. So long as the bending is carried out without excessive hammering or beating, such slippage and consequent separation of fibers can be effected without seriously damaging or weakening the fibers and, in the case of materials having a substantial amount of pith, such operations can be carried out without reducing the pith to unreasonably small pieces.

Turning now to Figures 1 to 3, it will be well understood that the central plane or neutral plane, indicated at 3 will, when the segment is subjected to bending, constitute a neutral plane and will be under no stress at all but that all portions above said neutral plane and indicated by the numeral 1 (Figure 2 only) will be in compression and all portions below said neutral plane indicated by the numeral 2 will be in tension. Further, it will be understood that, considering the portion 2 by way of example, the tension stresses will be the greatest at the lower extremity of the section and will progressively diminish to zero toward the neutral plane 3. Thus, any two radially adjacent fibers lying between the lower extremity 4 and the neutral plane 3 will be under different tensile stress and will therefore have a tendency to slip with respect to each other. When the fibers are in reverse position (Figure 3) the tension and compression stresses will be reversed.

This tendency of radially adjacent fibers to slip with respect to each other, together with the lesser capacity of the short fibers to withstand tensile stresses as compared to the corresponding capacity of the bast fibers indicated at and 16, will tend to break said short fibers apart in an axial direction and tend to separate them from each other and from the bast fibers in a radial direction. Thus, repeated bending of a given fibrous stalk a great many times and in many different directions will result in the short fibers surrounding the bast fibers being broken into relatively small pieces and broken loose from said bast fibers. Further, said bast fibers will for the same reasons be thoroughly broken loose from each other.

It will be recognized that as each segment of the vegetable stalk breaks longitudinally in response to the shear forces set up by the bending thereof, each part thereof then becomes a new bundle to be bent and again split in the same manner as the original segment.

It will be appreciated, however, that, due to the irregular nature of most vegetable products, such cleavage as takes place along any given longitudinal plane will not take place uniformly. That is, cleavage will occur at some points along said plane and at other points the fibers, or the fibers and pith, will remain fastened together. Therefore, further steps must be provided in the process to assure that cleavage occurs throughout the full length of all fibers. This is accomplished by progressively diminishing the length of the segment subjected to bending. Thus, in the beginning of the process a relatively long segment, as indicated by A in Figure 3, is subjected to the bending force and said length is then progressively iminished to a much shorter length, as the length 13 which is subjected to bending force near the end of the process. Thus, the shearing stress is placed upon all portions of all of the segments and full separation is attained.

In devising a series of mechanical steps by which this broad process may be effected automatically, I have provided a first plurality of spaced teeth extending into a zone bounded in any convenient manner and I have provided also a second plurality of spaced teeth extending between the teeth of said first plurality of teeth and also within said zone. By moving said teeth in opposite directions with respect to each other in said zone, and by causing said bundles of fiber to move through said zone transversely to the direction of movement of said teeth in response to the movement of a fluid therethrough, I am able to suspend said bundles in said fluid in such positions that as they move through said zone they will be repeatedly held by two teeth of one set and engaged intermediate said two teeth by a tooth of the other set and thereby caused to bend, as illustrated in Figure 4. As tooth 5 moves in the direction indicated by the arrow C adjacent same and between the teeth 6 and 7 the fiber bundle will be subjected to a sharp bending. When said tooth 5 moves past said teeth 6 and 7, the fiber bundle will then be released and in the turbulence of the fluid stream, resulting from the rapid passage of the said teeth through said stream, will be caused to somewhat rotate on its own axis before again being engaged by the same or other teeth. The spacing between any pair of said teeth may be progressively diminished during said process or, if more convenient from the standpoint of particular means used, a plurality of teeth may be provided in which different teeth are provided for carrying out the latter part of the process than those which initiate it and the teeth carrying out the latter part of the process are spaced more closely together than the teeth initiating the process.

Further understanding of the process may be had by reference to one specific means for practicing same, it being understood, however, that this particular means is only illustrative of the process and that the process may, as already indicated, be carried out by a variety of specific apparatus.

Referring now to Figures 6 and 7, there is shown a device which is disclosed and described in detail in my co-pending application Serial No. 204,039, now Patent No. 2,716,926 to which reference is hereby made. However, for the purposes of convenience, a brief description thereof will be set forth herein. A base 13 supports a lower housing 12 which supports a spaced upper housing 11. Depending from the lower housing 12 is an internal housing 22 supporting a lower closure plate 24. A hollow boss 19 depends from the lower housing 12 for the reception of the upper end of the sleeve 29 and a hollow boss 34 depends from the lower plate 24 for the reception of the lower end of the sleeve 29. Means indicated generally at 23 support the spring 39 by which the sleeve 29 is resiliently supported in a vertically adjustable position. Said sleeve in turn supports the bearings 32 and 33 which, in turn, rotatably support the shaft 28. Said shaft is driven by any convenient means, as the sheave 31, and drives a lower rotating plate 57. An upper non-rotating plate 68 is fastened to the upper housing 11 by any convenient means. Each of said plates have teeth thereon extending towards the other plate and said teeth closely intermesh with each other. Said teeth are conveniently provided on inserts which in turn are fastened, as by bolting, to the upper non-rotating plate 68 and to the lower rotating plate 57. For example, the lower insert 66 is fastened to the lower rotating plate 57 by bolts of which one is shown at 67 (Figure 6).

Figure 7 illustrates a plan view of said teeth 72 taken from a portion of the lower rotating insert 66. It is understood that the teeth on the upper plate are similar therewith excepting that their radial spacing is such as to permit them to enter in between the teeth on the lower plate as shown. Said teeth, as appearing in Figure 7, are relatively large and widely spaced at the centerward portion thereof and become progressively smaller and more closely spaced both radially and circumferentially as they approach the periphery. Material is fed to said plate through the central opening 17 (Figure 6) in the upper housing 11 and after passing between said teeth escapes through the opening 13 defined between said upper and lower housings. The clearance between said teeth is determined by vertical adjustment of the lower rotating plate 57 and will, of course, be suiiicient that the particular fibers being handled by the machine in a given instance will be merely bent between said teeth and will not be cut or broken.

in Figure 9 there appears an oblique view of a difierent design for said plates wherein the teeth constitute a plurality of pegs mounted in said plates and extending from the opposed surfaces of each thereof toward the other of said plates. manner, as by welding or as indicated in Figure 10. in this instance, the teeth are all of the same size but they are so arranged on the plate as to be of substantially diminishing spacing as they progress from the inner portion thereof toward the periphery.

The vanes 65 (Figure 6) are positioned on the periphery of the lower rotating plate 57 in order to increase the air flow from the entrance 17 to the exit 13 and thereby both improve the strength of the air stream by which the fibrous material is carried through the teeth and effect a strong air stream for carrying said fibrous material away from the machine. It will be recognized that the rapid passage of the several teeth through the zone between the plates 57 and 63 will effect a vigorous turbulence in said air stream which, while not interfering with its radially outward flow, will nevertheless agitate the bundles of fiber carried by said fluid stream, keep same in suspension and keep same in constant motion with respect to each other.

The annular zone bounded on the upper and lower sides by the said plates and beginning at the inner edge 80 of the top non-rotating plate 68 and ending at the periphery of said plates thus constitutes the zone in which the decortication of the vegetable stalks takes place and hence may be geferred to as the decorticating Zone.

As fibrous material is received into said machine through the entrance 17 and enters into the decorticating zone,,it is first engaged bytheinner rows of teeth, for example, as indicated by the broken lines at 9 in Figure 9. Said fiber bundle is then engaged by a tooth moving in theopposite direction as indicated at 5 in Figures 4 and 9. and the fiber. bundleis caused to bend as the tooth 5 urges it between the teeth 6 and 7.

As said fiber bundle is momentarily released after it passes between teeth 6 and 7 it will move a short distance toward the periphery of the plates as indicated by the arrow D before being engaged by another set of teeth 25, 26 and 27 and during such movement the turbulence of the air between said plates 57 and 68 will cause it to rotate somewhat on its own axis and thus the next bending thereof may be expected to be in a different direction.

It will be appreciated that the strong air stream thus moving the fibers spirally outwardly will keep them some- The teeth are mounted in any convenient 6 what aligned to prevent their becoming entangled upon the several teeth.

As said fibers move toward the periphery of the plates and into the region where the teeth are progressively closer together, it will be recognized that the bending will be imposed over progressively shorter segments of a given fiber bundle and thereby the complete separation above set forth will be obtained.

However, it is important that the teeth be spaced sufiiciently apart from each other that the bundle can pass between same as a bundle and without being subjected to transverse cutting or breaking. This is indicated in somewhat an exaggerated manner in Figure 4. By this providing of sufiicient space between said teeth to prevent the occurence of substantial cutting or breaking, the fiber bundles are subjected to bending only and their length is not thereby impaired. Further, any pith material which may come into the process with the fiber bundles will not be pulverized but will pass through the machine in chunks of substantial size and will thereby be obtained in a condition which is more conducive to easy handling than it would be if the pith were pulverized and it will be of more commercial value for a variety of purposes, such as for cattle feed in the case of corn or sugar cane operations.

Turning to Figures 11 and 12 for another type of device for practising the process of this invention, there is shown an external cylindrical housing 35 having a hopper 36 at one end thereof and an outlet 37 at the' 'surface of the drum 42, of similarly progressively diminished spacing and extending between the teeth 43. A plurality of air inlets 47 are placed substantially opposite to, and around the full circumferential extent of, the zone between the cylindrical housing 35 and the cylindrical drurn 42. Fan blades 46 are located at the discharge end of the drum 42. Thus, as fiber bundles to be decorticated are introduced into the hopper 36 and they are caused to pass from said hopper through the throat 48, an air stream carries them into the decorticating zone where they are bent, turned and rebent, and such bending is carried out with progressively diminishing segments, and are finally discharged through the opening 37. It will be appreciated that, although an entirely different mechanism is used than that above illustrated as preferable, the same process will be carried out.

After the decorticating operations are completed, it is then relatively easy to separate the broken particles of pith, and other short fibers, from the mass of bast fibers by any of many conventional steps. Such cleaning steps will normally involve moving of the mass along an inclined plane and may also include concurrent treatment thereof with a flowing stream of air or water, such as shown in United States Patent Number 2,200,472. As in conventional practice, agitation may be provided by shaking the screen or by delivering the fluid stream in a pulsating manner, the latter also being shown in United States Patent No. 2,200,472. Alternatively, the separation may be effected by any of the various kinds of pulp screens and screening mechanism illustrated and described between pages 726 and 749 of Pulp and Paper Manufacture, volume I, 1950, McGraw-Hill Book Co., inc, or by any of the well known forms of rotating inclined screens with counter flowing fluid or by vertical flow air separators of conventional sort as shown in United States Patent Numbers 1,650,727 or 1,085,921. Where temperature control of the decorticating process 7 is required, it will, in view of the foregoing, be obviously possible to provide the apparatus illustrated and described above with suitable heat exchange means, such as conventional water jacketing of means defining the decorticating chamber, through which either hot or cold heat exchange fluid, as water, may be circulated.

Accordingly, I have set forth a process by which the above named objects and purposes may be carried out. In actual experimentation with a wide variety of vegetable materials, this process has been found to be effective, 1

forth as illustrative only and that various modifications may be made therein without departing from the broader aspects thereof and that the hereinafter appended claims should be construed to cover such modifications excepting as by their own terms they expressly limit otherwise.

I claim:

1. In a method for decorticating bundles of fibrous vegetable material, which bundles consist of relatively long, flexible and tough fibers bonded together with natural bonding agents, the steps comprising: suspending said bundles independently of each other in a fluid stream and conducting said stream and bundles suspended therein through a decorticating zone; applying a bending moment to said bundles while same remain suspended in said fluid stream, said bending moment being applied to said respective bundles over a predetermined length thereof;

repeatedly applying subsequent bending moments to said bundles and progressively diminishing the distance over which said bending moment is applied as said fluidsupported bundles move through said decorticating zone; conducting said fluid and the decorticated material supported thereby out from said zone.

2. In a method for decorticating bundles of fibrous vegetable material, the steps comprising: suspending said bundles independently of each other in a fluid stream and conducting said stream and bundles suspended therein through a decorticating zone; applying a bending moment to said bundles while same remain suspended in said fluid stream; said bending moment being applied to said bundles over a predetermined length thereof; repeatedly applying subsequent bending moments to said bundles and progressively diminishing the distance over which said bending moment is applied as said fluid supported bundles move through said decorticating zone; creating a turbulence within said fluid and utilizing said turbulence to rotate said bundles on an axis substantially parallel with the direction of said fibers between said applications of bending moment.

3. In a method for decorticating bundles of fibrous vegetable material, the steps comprising: suspending said bundles independently of each other in a fluid stream and conducting said stream and bundles suspended therein' through a decorticating zone; imposing a bending moment upon said bundles while suspended in said fluid stream by means projecting into said zone and engaging said bundles, said bending moment being applied over a predetermined length of said fiber bundles; utilizing said means for creating a turbulence within said zone whereby to rotate said bundles on axes parallel to the length of said fibers; repeatedly imposing further bending moments upon said fibers, said bending moments being of progressively shorter length as said fibers progress through said zone; conducting said fluid and decorticated fibers supported thereby out from said zone.

4. In a method for decorticating bundles of fibrous vegetable material, the steps comprising: suspending said bundles independently of each other in a fluid stream and conducting said stream and bundles suspended therein through a decorticating zone; applying a bending moment to said bundles while same remain suspended in said fluid stream, said bending moment being applied to said respective bundles over a predetermined length thereof; repeatedly applying subsequent bending moments to said bundles and progressively diminishing the distance over which said bending moment is applied as said fluid-supported bundles move through said decorticating zone; conducting fluid and decorticated material supported thereby out from said zone; and subsequently separating the bast fibers from the pith fibers.

5. In a method of decorticating bundles of fibrous materials, which bundles consist of relatively long, flexible and tough fibers bonded together with natural bonding agents, said bundles being elongated in an axial direction, the steps comprising: suspending said bundles independently of each other in a fluid stream, passing said stream and bundles suspended therein between a pair of spaced obstacles in a direction generally transverse to a plane including said two obstacles, said obstacles being spaced apart a distance less than the axial length of said bundles but greater than a distance that would cause the fibers in said bundles to break, the bundles being disposed in said stream so that the longitudinal axis thereof is generally transverse to the direction of travel of said stream when said bundles pass between said obstacles, said bundles being bent by engaging and passing between said obstacles without being cut.

6. The method of claim 5, including the step of subsequently passing said stream and bundles suspended therein between other pairs of spaced obstacles, said other pairs of obstacles being spaced a progressively lesser distance apart than said first-named pair of obstacles.

References Cited in the file of this patent UNITED STATES PATENTS 443,037 Coles Dec. 16, 1890 1,215,936 Holtzclaw Feb. 13, 1917 1,641,119 Cook Aug. 30, 1927 1,802,249 Goldberg Apr. 21, 1931 2,090,925 Wilkinson et a1 Aug. 24, 1937 2,161,502 Brown June 6, 1939 2,208,287 Cochrane July 16, 1940 2,222,793 Burkardt Nov. 26, 1940 2,263,591 Patterson Nov. 25, 1941 2,391,977 Johansen Ian. 1, 1946

Claims (1)

1. IN A METHOD FOR DECORTICATING BUNDLES OF FIBROUS VEGETABLE MATERIAL, WHICH BUNDLES CONSIST OF RELATIVELY LONG, FLEXIBLE AND TOUGH FIBERS BONDED TOGETHER WITH MATURAL BONDING AGENTS, THE STEPS COMPRISING: SUSPENDING SAID BUNDLES INDEPENDENTLY OF EACH OTHER IN A FLUID STREAM AND CONDUCTING SAID STREAM AND BUNDLES SUSPENDED THEREIN THROUGH A DECORTICATING ZONE; APPLYING A BENDING MOMENT TO SAID BUNDLES WHILE SAME REMAIN SUSPENDED IN SAID FLUID STREAM, SAID BENDING MOMENT BEING APPLIED TO SAID RESPECTIVE BUNDLES OVER A PREDETERMINED LENGTH THEREOF; REPEATEDLY APPLYING SUBSEQUENT BENDING MOMENTS TO SAID BUNDLES AND PROGRESSIVELY DIMINISHING THE DISTANCE OVER WHICH SAID BENDING MOMENT IS APPLIED AS SAID FLUIDSUPPORTED BUNDLES MOVE THROUGH SAID DECORTICATING ZONE; CONDUCTING SAID FLUID AND THE DECORTICATED MATERIAL SUPPORTED THEREBY OUT FROM SAID ZONE.

Images