US 2714081 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
July 26, 1955 w. J. BURGoN 2,714,081
PROCESS OF FORMIN FIBROUS SHEETS Filed March 17, 1950 INVENTOR. WIN/'am rf. Burgo/7 BY ufm M4 cavia.
2,714,08l Patented July 26, 1955 ice PROCESS F FORMING FHBRQUS SHEETS William J. Burgen, New Westminster, British Columbia, Canada, assignor of fifty-one per cent to William H. Rambo, Portland, Greg.
Application March 17, 1950, Serial No. 150,204
3 Claims. (Cl. 154-101) The present invention comprises a method and apparatus for forming brous sheets such as berboards, brous core stock, ber insulating pads and similar items of a self-sustaining nature, being particularly concerned with ber articles of a planular form and of a density of about .7 or less. Material formed in the apparatus and by the method of my present invention may later be subjected to heat and pressure to form hard berboard of a density in the range of 1.0 by any of the known processes and utilizing any known apparatus, and I do not intend to exclude from the purposes of my invention the thought of forming articles of such hardness but am limiting the disclosure and claims of this application to the inventive features involved in the formation of a sheet of bers of an intermediate or low density utilizable either as the end product or as an intermediate product in the formation of articles of high density.
The invention relates to the formation of medium or low density products by the use of lignocellulosic materials reduced to a nely divided or brous condition and rendered plastic, immediately upon rendering the bers plastic rather than at a later stage as is the case with all processes with which I am at present acquainted. The art of making brous sheet materials as presently practiced comprises the reduction of lignocellulosic materials to a brous condition and the rendering of the same to a plastic state in the presence-of hot water or steam, by means of equipment and processes such as disclosed, for example, in the patents to Asplund 2,008,892, July 23, 1935, and 2,145,851, February 7, 1939, or in the patents to Mason 1,578,609, March 30, 1926, and 1,586,159, May 25, 1926, or in the patents to Mason 1,663,503, 1,663,504, 1,663,505 and 1,663,506, all of March 20, 1928. In all of these prior art processes the hot, plasticized bers are subjected to further treatment in which they lose their plasticity and become inert, hardened, or relatively cool bers incapable of cohering to each other until they are again brought back to a condition of plasticity by the further application of heat. All such processes involve the mixing of the bers with sufcient water to permit pumping the mixture from place to place; and nally the dense pulp is mixed with water vat a temperature insufcient to plasticize the bers and in such large quantity as to form a slurry having the flowing characteristics of water. The slurry is agitated to maintain the bers in suspension while the water is brought into contact with a screen through which the Water is drained while a mat of cold bers is deposited upon the screen. The so-called white Water drained from the bers contains recoverable valuable substances such as bers themselves or chemicals such as llers, sizes, resins and the like which have been mixed with the pulp or the slurry at some stage in the process preceding the screening operation, hence the White water has to be recaptured and the valuable components recovered by some means. The so formed mat of bers usually contains a large quantity of economize on the heat required to reheat the bers to a condition of plasticity in a subsequent heating and pressing operation where the mat is reduced to a self-sustaining sheet of the desired characteristics, the amount of pressure, the amount of heat applied and the duration of application of either or both being regulated to determine the density and other characteristics of the resulting sheet. All such steps subsequent to the initial formation of the plastic bers require far greater expenditure of energy, far greater equipment and far greater manhours of labor than that required initially to reduce lignocellulosic bers to a disintegrated, plastic condition. It is the principal object of the present invention to eliminate all such intermediate steps and apparatus and to form self-sustaining sheet material directly from the plastic bers created in such equipment as an Asplund debrator or other equipment for producing plastic bers.
f numerals refer to like parts throughout, while the features of novelty will be more distinctly pointed out in the appended claims.
ln the drawing,
Fig. l discloses one type of equipment which may be utilized to receive the output of a plastic ber producing mechanism and form self-sustaining ber sheets therefrom; and
Fig. 2 illustrates a second form which may be utilized.
The drawing schematically discloses two types of equipment which may be utilized in carrying out my process, the two types having general characteristics in common and being merely exemplary of many difierent forms which the apparatus may assume Without departing from my invention.
Referring to Fig. l, there is disclosed at 10 a box exemplifying equipment for forming plastic lignocellulosic bers, which equipment may be as disclosed in the above-identied Mason patents, but which is preferably of the type disclosed in the above-identied Asplund patents because the Asplund equipment produces a more nearly continuous ow of hot, plasticized bers. In the Asplund equipment wood chips or the like are continuously fed to internal mechanism for beating, rub-V bing or agitating the chips after they have been subjected to steam at such temperatures and pressures as substantially to plasticize the bers in a relatively short time, the mechanical agitation or beating thereupon readily disintegrating the chips or the like and separating the individual bers in an envelopment of steam. The apparatus may be of the continuous flow type in which pressure is maintained by an outlet restriction, or may be of the substantially continuous ow type in which continuity of flow is established while maintaining high pressures within the equipment by intermittently opening and closing a valve at the output end of the equipment, each opening of the valve resulting in the discharge of a plug of plasticized bers under steam pressure such that the steam may be utilized to convey the bers to other equipment. The box 10 may exemplify any other type of equipment from which a relatively continuons ow of bers in an environment or envelopment of steam is emitted into a discharge pipe 11. The box 10 may, for example, represent a plasticizer which receives the output of other debratng equipment such as mechanical free water which is removed from the mat so as to The box 10 may represent an Asplund machine receiving theutput'of 'some yother type of disintegrating equip-1 ment such 'as wood "gr'ind'efsr the Ilike. My "invention therefore comprises a closed vessel 10 in which fibers are renderedL plastic` by subjecting them to steam at such temperatures pressures and f`or`s`u'ch lengths of time 'as fma'y be requiredfby the characteristics ,of the fibers. 'A'sis 'well known in the art and 'thoroughly eX- pla'ined in y the `above-'ir'le'ntined Asplund patent 2,008,892, the 'steam maybe at or nearthe boiling point of: water but is preferably at a higher temperature achieved by 'holding the vpressure at greater than atmosphe'lr'hic.` vBe's'tfre's'ults are'obtained `*when the temperature isjmaintindbetweea 250 Rand 360 F. The temperaturefshouldfriot be materially above 400 F. as suchelevated temperatures V'do not ymaterially facilitate the disintegrf'tien"orplasticizirig 4offthe bers Aand charting or discloratin'of'the fibers usually takes'place at elevated fempepramres-jfthe'rar'f 450 F. to 500 F. 'rn an finachine Jvvoodxiibers subjected to temperatures between `300 F. arid340 F. for some twenty to forty seconds, depending upon the voriginal moisture content and .temperature ofthe wood, will be reduced to substantially individual bers Vor bundles yof tibers of such size as to be suitable for the 4forr'nation of boardlike materials'in the equipment and will be ejected therefrom in a plastic state in anenvironment of steam under pressure.
4Instead of 4conducting the steam-borne'fibers to a cyclone or other equipment in whichthe lfibers are separated from the steam and dropped into storage or treating vats where it is allowed to cool and is mixed with diluting water, my invention contemplates the provision of arelatively thin, wide discharge spout 12 directly connected to a short outlet pipe 11 from the equipment 10, the orifice '1'3"of the flaring outlet being located in the angle of convergence between a supported, traveling sereen`1`4 and an opposed driven, heated roll 15. In the embodiment disclosed in Fig. 1 the screen 1`4'is supported upon aperforated cylinder 16 of relatively large diameter, and a'spaced stretcher 'roll 17 of any suitable diameter. The "roll Y'1S may have any desired diameter provided that the surface speed thereof is the same as the surface speed of the sereenf1n4. The distance between the rolls and '16 is such that a layer of fibers inhot, plastic condition envelopedkin steam will be deposited upon the screenbetween 'the two rolls. The speed of movement of the screen andthe opposed roll 15`should be such as to cause aplu'g of fibers` continuously to'form at the oritice 13 or in Vspout 12 behind Athe orifice 13, thus holding the Vsteam pressure in theoutlet and creating a uniform layer 'eliminating Athepulsations of discharge from the equipment 10. r The plugwill not be of Vsuch density as to prevent the continuous escape of 'steam therefrom so that theiibersare compacted and interlaced with each otherin'the 'longitudinal Vdirection of the layer being deposited upon the traveling screen.
a The screen 14 may be of any Ysuitable Vtype developed in the ypulp and' paper'industries and nmay lcomprise a woven wire screen or other foraininous member such vvas wa perforated, exible sheet. The drum 16 preferably hasperforatioris of larger diameter but still of relatively small size and 4closely spaced throughout so that upon the application ofrsuction to the'interior 'of-the drum'the steam will'be uniformly withdrawn from the hot mat.
rThe mat whilesusvtained upon the drum is successively compressed and released vbythe application of rolling pressure thereto through the rnedium of a "serieswof heated pressing rolls 1'8, 19 'and 20 which may be disposed 'at successively decreasing distances from the surface of the wire or may be uniformly spaced therefrom, depending upon thedensity and other characteristics of the sheet to be formed. While being alternately compressed and released frompressure the mat is subjected to suction by the application of suctionto the interior of the drum so that the s teamis rapidly withdrawn from the bers after the intial'compressio'n applied by roll rl5, andheated airis drawn through the fibers to maintain them in somewhat `plasticized condition While the "subsequent 'pressing opera- Y of the fiber may thus be more gradually reduced, vlending greater effect to the compressing action of the second roll 13. A further function may be provided in that one of the pipes, such as thepipe 23 maybe utilized for the injection of steam and the other pipe utilized for the application of some foreign chemical such as an insect poison, antifungus chemical, sizing material, resin, or coloring mattert It is'to lbe V,appreciated that no binder need be added, butthat resin binders orthe like may be added for special purposes. Preferably the pipe '23 would be utilized for introducing such Vforeign substances, and the pipe/24 utilized for'the introduction ofsteam-serving to drive the chemical or foreign substance into more intimate contact with the fibers and distribute the same more evenly through the mat. a
The drum 16 is preferably of the type driven through end bells or the like so that therinterior may be subdivided into stationary compartments to which suction may be individually applied, the partitions being such as disclosed at 226`a`nd127 providing a pair of interior suction chambers 28 and 29 toi which suction may be applied individuallythrough pipes 3Q and 31. The partition 25 may be arranged to permit drainage of condensed steam or other. liquid material to a low point so that water will not remain in the chamber 28 and so that any chemical which may be carried through thermat may be salvaged. A furtherfunction isachieved in this fashion in that the steam which is substantially entirely withdrawn from the mat in the space between thepp'oints of contact of rolls 18 and 15 may be utilized initially to heat the Vlignocellulosic material, thus further reducing fuel consumption.
The drum 16 should be of suchl relatively large diameter thatrthe uponleaving the surface of the drum and following ther stretch of wire between the drum 16 and stretcher roll 17 will not crack to any appreciable extent along its lower or Wire surface. However, there might be ja 'multiplicity of line checks or cracksin the lower surface of the sheet, kand for this purpose a succeeding pair of pressure rolls 32 and 33l further compact the mat as it travels toward the stretcher rolll'l, this'action taking place while the fibers Vare still in somewhatfplastic condition and before theybecome permanently set. Further pressure is preferably provided by a roll 34opposing the stretcher roll 17. At this point the mat would be selfsustaining Vand in condition to travel straight ahead while the screen separates therefrom around the stretcher roll 17, and'would be carried `from the forming equipment by suitable means such as the carrier lrolls 35. The sheet may be conducted by thecarrier rolls intoany desired finishing equipment.
lt isV to be appreciated that at this point a self-sustaining, continuous sheet of medium or low density is formed. This sheet 'is cut into smallerjsheets which may be conducted to a storage space and may be Vutilized in their existing shape as insulatingmaterial,pads, acoustic surfacing or Vcore stock. However, if denser or smoother boards are desired, they may be removed from'the storage space, or conducted directly from the forming equipment, and placed in or passed through equipment adapted to apply heatand pressure to create hardboard or other sheet material offgreater density'or otherwise finish the material, asV is welll known in theart.
Iniorder todemonstrate that thel present invention is not limited to Ya particular type ofl equipment; and inl order to illustrate a type of equipment in which it will be certain that no checking or cracking of the wire surface of the sheet will occur, I have illustrated a second form in Fig. 2. In this form the fibers are plasticized in equipment indicated at and conducted through pipe 41 and a flaring outlet 42 to an orifice 43 in the angle of convergence between the upper flight of a traveling screen 44, entrained about end rolls 45 and 46, and a first heated pressure roll 47. The upper fiight of the wire is supported upon a grid or perforated plate 48 beneath which is positioned suction means such as a first suction box 49 and a second suction box 50. The suction box 49 is preferably coextensive with the space between the point of contact of the first presser roll 47 and a second presser roll 51.
The space between rolls 47 and S1 is formed into a chamber 52 by a sealing roll 53, and a pair of pipes 54 and SS may introduce steam and/ or other materials into the chamber so as to be sucked through the mat into the box 49 and salvaged through the suction pipe 56. A plurality of other heated presser rolls 57, 58 and 59 successively apply rolling pressure to the mat while on the screen, the rolls being spaced to permit the passage of air therebetween upon the application of suction to the box through the pipe 60. By the time the mat passes from the opposed rolls 46 and 59 a self-sustaining sheet of medium or low density will be formed and may be transported away from the forming apparatus by carrier rolls 61. In this instance I have illustrated further treating equipment such as a pair of opposed pressing rolls 62 and 63 which are preferably heated and which further compact the sheet and exemplify other equipment which may be utilized to produce a finshed product of high density.
It is to be appreciated that the apparatus herein disclosed is schematically illustrated. For example, no details are given of equipment which may be utilized to synchronize the feeding movement of thev screen with the rate of production of the fibers. For example, means may be supplied at or near the orifice of the conduit conducting the fibers to the screen for sensing the volume of fibers being ejected or for sensing the thickness of the mat at the point of formation and controlling the speed of the screen and rolls accordingly, thereby continuously to assure uniformity of the mat being formed. Under normal conditions such would not be necessary since the equipment for forming the plasticized fiber would be of such capacity as to be capable of producing plasticized fibers at a rate t0 insure the formation of a uniform layer at the desired constant rate of movement of the screen, the initial compressing roll ironing our irregularities in a lateral direction and holding back a plug within the flaring tube. Sensing equipment may be placed in,-or arranged in conjunction with, the flaring outlet tube to regulate the speed of operation of the plasticizing equipment so as to insure the formation of a uniform mat. It is to be appreciated that the present invention may be utilized in the formation of mats from fibers created in any suitable manner provided that they are rendered plastic and fed to the screen in a hot, plastic condition in a gaseous environment rather than in liquid suspension. By the term steam I mean to imply the usual definition thereof as water in a gaseous state, with or without the addition of other impurities such as would be present in the lignocellulosic materials or which may have been added 'in the treatment thereof.
Having illustrated and described preferred embodiments of my invention, it should be apparent to those skilled in the art that the invention permits of modification in arrangement and detail. I claim as my invention all such modifications as come within the true spirit and scope of the appended claims.
l. The process of making fiber boards comprising subjecting lignocellulosic fibers to steam in a high pressure zone until the fibers are plasticized, permitting the continuous escape of steam to a zone of steam at lower pressure and utilizing the steam to entrain fibers in hot, plasticized condition, resisting movement of the entrained fibers at the point of release from the zone of high pressure so as to build up a wall of interlaced fibers between the two Zones of pressure, continuously and mechanically withdrawing the built-np wall of fibers through the zone of lower pressure steam so as to form a continuous mat of plasticized fibers interlaced in the longitudinal direction of the mat, and compressing the mat into a self-sustaining sheet while moving the same away from association with steam.
2. The process of making fiber boards or similar fibrous sheets comprising subjecting lignocellulosic bers to steam under pressure in a confined space until the fibers are plasticized, continuously releasing the plasticized fibers from the confined space in a relatively thin, wide stream under pressure of steam escaping from the confined space, mechanically moving the fibers away from the point of release from the confined space at a rate such that pressure is maintained in the confined space and a continuous mat of fibers is formed, and subjecting the moving mat to transverse compression until the fibers lose plasticity.
3. The process of making fiber boards or similar fibrous sheets comprising subjecting lignocellulosic fibers to steam under pressure in a confined space until the fibers are plasticized, continuously releasing the plasticized fibers from the confined space in a relatively thin, wide stream under pressure of steam escaping from the confined space, mechanically moving the fibers away from the point of release from the confined space at a rate such that pressure is maintained in the confined space and a continuous mat of fibers is formed, and transversely compressing the moving mat While subjecting the mat to suction applied to at J least one surface thereof to hasten the Withdrawal 0f steam therefrom.
References Cited in the file of this patent UNITED STATES PATENTS