US 2720005 A
Description (OCR text may contain errors)
Oct. 11, 1955 J D A. CLARK E'T'AL 2,720,005
AIR SCRABBLER SYSTEM FOR FIBER DEPOSITION IN THE MANUFACTURE OF FIBROUS STRUCTURES Filed 001.. 6, 1952 2 Sheets-Sheetl ATTORNEYS.
Oct. 11, 1955 J. D A. CLARK ETAL AIR SCRABBLER SYSTEM FOR FIBER DEPOSITION IN THE MANUFACTURE OF FIBROUS STRUCTURES 2 Sheets-SheetZ Filed Oct. 6, 1952 jzzcfion Fan FIG 5 6 m mob NSC 2 mm am m WJ B United States Patent AIR SCRABBLER SYSTEM FOR FIBER DEPOSITION IN THE MANUFACTURE oF FIBRoUs STRUC- TURES James dA. Clark, Longview, Wash., and Bror E. Anderson, Park Ridge, Ill., assignors to A. B. Dick Company, Niles, 11]., a corporation of Illinois Application October 6, 1952, Serial No. 313,316
16 Claims. (Cl. 19-156) This invention relates to the air deposition of dry fibers to produce new and improved fibrous structures and more particularly to an improvement in the method and apparatus described and claimed in the copending application of James dA. Clark, Ser. No. 61,674, filed on November 23, 1948, wherein a new and improved method and apparatus are described for the fabrication of structures by the air deposition of dry fibers.
An object of this invention is to provide a further improvement in the method and apparatus for the air deposition of fibers in the manufacture of fibrous structures.
Another object is to provide a method and apparatus for the air deposition of fibers wherein a constant stream of air having fibers entrained therein is caused to move over a foraminous separating wall in a manner to make use of a shower-head principle for the transmission of uniform volumes of both air and fiber through the separating wall for deposition as a fibrous structure on a spaced collecting wall.
A further object is to provide a method and apparatus embodying means therein for maintaining a desired turbulence for fiber separation and entrainment in an air stream while causing uniform amounts of dry fiber and air to pass through a foraminous separating wall and form a fibrous structure on a closely spaced foraminous collecting wall.
These and other objects and advantages of this invention will hereinafter appear, and for purposes of illustration, but not of limitation, embodiments of the invention will be shown in the accompanying drawings in which- Figure l is a schematic sectional elevational view of a fiber depositing system embodying features of this invention; n
Figure 2 is a perspective view, partially in section, of a form of air nozzle illustrated in Figure 1 of the drawing;
Figure 3 is a schematic sectional elevational view of a modification in a fiber depositing system embodying features of this invention, and I Figure 4 is a sectional elevational view of a fiber depositing system embodying a further modification.
Figure 5 is a schematic. elevational view of an assembly illustrating the elements employed in the practice of this invention.
In the copending application of James dA. Clark, Ser. No. 61,674, filed on November 23, 1948, of which this application is an improvement, description is made of a method and apparatus for the manufacture of fibrous structures by air deposition. As described therein, the apparatus comprises a housing which may be cylindricalin shape, as shown in Figures 1 and 4, or ellipsoidal. The housing is provided on the underside with a separating wall having openings therein dimensioned to limit passage to separated fibers. A collecting wall, preferably in the form of a moving belt, is positioned in closely spaced apart substantially parallel relation with the separating wall and is provided with openings dimensioned to permit passage of air but to separate out the fibers from the ice air stream on the surface thereof. The cylindrical housing has a rotating drum with a plurality of scrabbler blades extending radially from the periphery thereof for rotational movement in slightly spaced apart relation from the inner surface of the separating wall, mechanically to impart rotational movement to the fiber and air contained within the housing.
Air or other gaseous medium is introduced into the housing in sufiicient volume to provide for a linear speed of 1000 to 5000 feet per minute as the air passes through the openings in the separating wall, thereby to nullify any gravitational effects. An amount of air slightly greater than the volume introduced into the housing is withdrawn from the underside of the collecting wall whereby the deficiency is made up by a slight inflow of air from the atmosphere surrounding the space between the separating and collecting walls. As a result, it has been possible for the first time to permit the area to remain open to the atmosphere without blowing fibers out into the air or disrupting the linear flow of fibers from the separating wall to the collecting wall.
Separated fibers are entrained in the air stream introduced into the housing and the scrabbler blades operate mechanically to cause fibers and air in excess of that capable of immediately passing through the separating Wall to travel under positive pressure as a moving layer over the face of the separating wall. The cooperative relation between the scrabbler blades and the moving layer of air and fibers keeps the openings of the separating wall sufficiently free to permit uniform volumes of air and fiber to pass through the openings of the separating wall to the collecting wall for the separation of the fibers in interfelted relation on the surfaces thereof.
It has been found that dispersal of fibers, especially long fibers, in the air stream becomes a matter of difliculty because of the tendency of such fibers rapidly to interfelt and intertwine upon contact. Some of the fibers which catch onto the ends of the scrabbler blades or other moving elements combine with other fibers upon contact and form strings or pellets. in the case of long fibers, this formation of aggregates presents a serious problem of disposal and handicaps the rapid and efiicient production of a uniform fibrous structure of substantially separated fibers.
It is also believed that the reaction between the ends of the scrabbler blades and the walls of the housing in closely spaced relation therewith causes the fibers therebetween to be rolled and formed into balls or rice which resist further separation. While such pellets and rice can be removed during operation of the machine as described in the copending application of James dA. Clark, Serial No. 114,942, filed on September 10, 1949, the formation thereof unnecessarily lowers the efficiency of the machine and causes waste of fibrous material.
In accordance with the practice of this invention, the formation of pellets or aggregates is greatly reduced and in most cases stopped by the elimination of mechanical means for generating fiber dispersal in the air stream and for causing the fibers and air in excess of that capable of passing through the separating wall to move as a transient layer over the face of the separating wall in a manner to bring into operation the desired shower-head principle. Instead, fiber dispersal and the desired movement of fibers and air over the face of the separating wall is achieved by the use of a high velocity stream or streams of air introduced substantially tangentially into a cylindrical housing at an angle to cause the air and fibers to move in a circular path about the housing while maintaining sufficient turbulence to cause and maintain fiber separation and avoid the formation of fiber aggregates.
The function of the mechanical scrabblers in the apparatus of the aforementioned copending application for air fiber dispersion are thus replaced by a new and improved air scrabbler means capable of achieving fiber separation and movements of air and fibers without causing fiber agglomeration or ricing thereby markedly improving the efficiency and operation of the fiber depositing system.
For illustration, reference will now be made to the drawings showing apparatus embodying features of this invention. As shown in Figure 1, represents a dcpositing' head in the form of an elongate cylindrical housing 11. Across the upper portion of the housing is an inlet opening 12 of substantial dimension extendingacross the housing and provided with a feed chute 13 through which substantially separated or loosely associated fibers are admitted to the interior of the housing at a predetermined rate. The bottom side of the housing, and preferably offset opposite the direction of movementof the air stream, is provided with a separating wall 14 having a plurality of openings 15 through which the fibers entrained in the air stream are able to pass. Th6 Openings in the separating wall may be dimensioned and spaced in accordance with the limitations described in the aforementioned copending application, but it has been found that such limitations with respect to the size, shape, and the spacing of the openings are not so important in the air scrabbler system described and claimed herein. The openings may be in the form of slots extending substantially continuously in spaced apart relation across the separating wall or they may be in the form of closely spaced separate openings, corresponding to a screen or the like. While it is possible to form the separating wall as an integral part of the cylindrical housing, it is preferred to have the separating wall as a separate plate having its inner surface substantially flush with the inner wall of the housing and conforming to the curvilinear shape thereof to provide a continuous surface over which the layer of fibers and air is able to move without interferences. By the use of a removable plate, the separating wall can be easily changed to provide openings designed for most efficient use with specific types of fibers and lengths of fibers.
The foraminous separating wall is spaced a distance from a collecting wall 16, having foramens therein dimensioned to permit free passage of the air stream therethrough but to filter out the fibers to form a fibrous structure on the surfaces thereof. In the fiber depositing zone 17, the underside of the collecting wall is positioned over an inlet 18 preferably of adjustable length and position formed by supporting walls 19 and 20 and duct work (not shown) in communication with an exhaust means for withdrawing air through the collecting wall whereby a suction is created to hold the separated fiber onto the surface of the collecting wall. It is preferred to withdraw a volume of air larger than that which is supplied or passes through the separating wall. The balance between the amount of air withdrawn through the collecting wall as compared to the amount of air passing through the separating wall is made up by a slight inflow of air from the surrounding atmosphere into the space between the separating wall and collecting wall. This relationship permits the elimination of enclosures usually positioned about the area between the separating wall and the collecting wall to prevent fibers from being blown out into the atmosphere and to prevent such turbulence and interference as would militate against a desired linear movement of fibers from the separating wall to the collecting wall as would be necessary for uniform fiber deposition.
As illustrated in Figure 1, the collecting wall 16 may comprise a stationary foraminous member but it is preferred to make use of a wall in the form of an endless screen or other flexible foraminous member mounted to travel continuously over a supporting structure to form a continuous fibrous web. It will be evident that the finished basis weight of the web formed will depend upon the rate of fiber passage and the linear rate of travel of the collecting wall. The maximum rate at which the fibers may be fed to and deposited from the head will depend on the character of the fibers as well as the number and dimensions of the openings in the separating wall.
The desired movement of air and fibers within the cylindrical housing 11 is achieved by introducing high velocity streams of air chiefly in a substantially tangential direction into the housing to cause the air and fibers therein to travel about the housing in a circular path. Frequently sufficient turbulence is imparted thereby to maintain and/or cause fiber separation. However, it is usually desirable to introduce air streams into the housing, less tangentially and more radial to the housing as shown by 26 in Figure l. The purpose for so doing is to more effectively break up clumps or aggregate of fibers than if all the jets were, strictly speaking, tangential. It is also desirable to be able to adjust the axis of the jets both radially and axially to the housing. To avoid interference with the layer of air and fibers moving over the surface of the separating wall it is desirable to avoid directing the air streams so that they impinge on the separating wall. Otherwise fiber aggregate will tend to be blasted through the openmgs.
it is preferred to make use of a plurality of air nozzles for introducing jets of air into the housing for effecting the circulating movements and it is possible to make use of a substantially continuous nozzle in the form of an air blade extending substantially continuously across the housing at the desired angular relationship. In such a case, the blade should be provided with means to adjust the volume of air along its length as by adjusting screws.
As illustrated in Figure l, the housing is provided with an elongate inlet opening 21 located just beyond the feed chute opening 12. The inlet opening is fitted with an air nozzle in the form of an elongate nose piece 22 on the end of a header 23 connected by passage 24 to a source of air under pressure. The nose piece 22 is provided with an elongate substantially continuous transverse slot 25 for passage of air under high velocity from the header into the interior of the housing. The air nozzle is arranged in the inlet opening to direct the air blade toward a portion of the housing Wall slightly in advance of the separating wall thereby to cause the air and fibers in the housing to circulate rapidly in the counterclockwise direction. In order to minimize non: uniform spread of the slotted openings under the pressure conditions existing, it is desirable to construct the nose piece 22 with heavy cross section or else to sub.- divide the slotted openings to provide for occasional stifiening.
In operation, fibers are fed at a rate sufiicient to maintain an excess of that capable of immediately passing through the openings 15 of the separating wall 14. For best operation, fibers should be fed at a rate to maintain the concentration of fibers in the head which is about 1.5-4 times the amount of fiber delivered through the separating wall per minute, depending of course on the type of fiber and the lengths thereof. Air under pressure is continuously admitted through the nozzle whereby the fibers become entrained in the air stream and are caused to circulate together with the air about the housing. The effect thereof is to cause the openings in the separating wall to remain free of clogging fibers and to maintain a moving layer of air and fibers under substantially positive pressure over the surface of the separating wall. As a result, substantially uniform volumes of air and fibers pass through each of the openings of the separating wall to the collecting wall. 'I'he air passes through the collecting wall but the fibers separate on the Surfaces thereof in interfelted relationto form a fibrous structure. i t
As further illustratedinFigurel, turbulence of the.
air within the housing without preventing the circulating movement thereof may be achieved by a separate means for introducing air at high velocity in a radial direction. Such means may include an air nozzle system 26, corresponding to the means previously described. for, introducing air streams in a radial direction. The effect of this auxiliary source of air is to subject the fiber. ag-
gregates to a blast of air at a substantial angle to their direction of movement and thus tend to disrupt them and reduce the tendency of the fibers to agglomerate or rotate about the housing in masses or in beats. As a aratingwall, may be located in advance of the fiber feed opening 12, in the upper Wall portion ofthe cylindrical wall. Under such circumstances, a broader range is available for angular adjustment because theseparating wall is positioned about diametrically thereto.
By way of still further modification, it is possible to make use of more than one air inlet arranged to introduce tangential streams of air into the housing. As shown in Figure 4, one inlet 30 may be located beyond the fiber feedopening, as illustrated in Figure 1, while another inlet 30 may be located in advance of the fiber feed opening, as in Figure 3. As illustrated in this modification,inlet 30 may be angularlyadjusted to direct. its stream of air beyond the feed opening 12 to impart circulating movement to the fiber dispersed air stream, while at the same time functioning as an aspirator to generate subatmospheric conditions in the feed inlet whereby the fibers are drawn into the housing. Instead of being directed to bear upon a portion of the housing wall in advance of the separating wall, the other inlet 20 can be positioned to direct its air stream in a direction to bear upon the wall portion beyond the separating wall but in advance of the wall portion diametrically opposite.
It will be evident that the apparatus described herein provides for a new and improved method for the air deposition of dry fibers without embodying the difficulties resulting from the formation of fiber agglomerates or balls in amounts characteristic of the use of mechanical means for generating the desired air movements and fiber transmission through the separating wall. The utilization of air for generating the desired conditions for fiber separation and transmission in uniform quantities through the separating wall for deposition in interfelted relation on the collecting wall provides for a more efii cient and low cost operation wherein the fiber properties most suitable for deposition to form fibrous structures are caused to exist.
It will be understood that changes may be made with respect to the velocity of the air streams introduced into the housing, the dimensions of the openings in the separating wall and the cooperative relation between the separating wall and the collecting wall, as defined in the aforementioned copending application, without departing from the spirit of the invention, especially as defined in the following claims.
1. Apparatus for the air deposition of dry fibers in the manufacture of fibrous structures comprising a substantially cylindrical housing having an inlet, an outlet in a portion of the circumference in the form of a foraminous separating wall, a collecting wall spaced a short distancefrom the separating wall having foramens therein dimensioned to prevent passage of fibers, means for feeding dry fibers into the housing, and means for introducing high velocity streams of air tangentially into the housing to cause the fibers to become entrained and to become carried with the air circumferentially as a moving layer of air and fibers over. the face of the separating wall whereby fibers pass in substantially uniform concentration with the air through the separating wall for deposition onto the collecting wall.
2. Apparatus for the air deposition of dry fibers in the manufacture of fibrous structures comprising a fiber depositing head including a substantially cylindrical housing having a fiber feed opening, a foraminous separating wall forming a portion of the housing wall, a collecting wall spaced a short distance from the separating wall having foramens therein dimensioned to prevent passage of fibers, means for feeding fibers into the housing, and an air nozzle for introducing a high velocity stream of air tangentially into the housing to cause the fibers to become entrained therein and to be carried with the air circumferentially about the housing to form a moving layer of air and fibers over the separating wall whereby fibers pass in substantially uniform concentration with the air through the separating wall to the collecting wall.
3. Apparatus for the air deposition of dry fibers as claimed in claim 1 in which the means for introducing the streams of .air into the housing comprises air nozzles positioned to direct the stream of air into the housing at an angle less than, radial.
4. Apparatus for the air deposition of dry fibers in the manufacture offibrous structures as claimed in claim 2 in which the air nozzle is positioned to direct the air stream into the housing at an angle less than degrees -;from normal.
Apparatus for. the air deposition of fibers in the manufacture of fibrous structures as, claimed in claim 2 which includes means for withdrawing air from the underside of the collecting wall whereby a suction is generated to anchor the separated fibers onto the collecting wall.
6. Apparatus for the air deposition of dry fibers as claimed in claim 2 including means for withdrawing larger volumes of air through the collecting wall than passes through the separating wall so as to cause a slight inflow of air from the surrounding atmosphere into the space between the separating wall and the collecting wall.
7. Apparatus for the air deposition of fibers as claimed in claim 2 in which the collecting wall comprises an endless member and means for moving the endless member in one direction to form a continuous web of fibers separated thereon.
8. Apparatus for the air deposition of dry fibers in the manufacture of fibrous structures as claimed in claim 2 which includes additional air inlets positioned to direct streams of air radially into the housing to increase the turbulence and disintegrate aggregates.
9. In the method of producing fibrous structures of the type described, the steps of introducing separated fibers into a housing having a foraminous separating wall and a separate collecting wall in closely spaced relation with the separating wall having foramens dimensioned to prevent the passage of fibers therethrough, directing a high velocity stream of air tangentially into the housing to cause the fibers to become entrained therein and travel as a moving layer with the air over the separating wall during circulation about the housing whereby some of the air and fibers pass through the separating wall to the collecting wall for separation thereon to form a fibrous structure.
10. In the method of producing fibrous structures of the type described, the steps of introducing separated fibers into a substantially cylindrical housing having a foraminous separating wall and a separate collecting wall zpmow in" closely spaced relzitio'n -withl the separating wall haw ing foram'ens dimensioned to preventthe passage' of fibers therethioughiydirectingqhigh' vel'ocity"streams' of' ain tan gentiall? into the hbusing 1 at an angl'e less than =radialto cause the ain stre'am to cir'culate' abour the 'hbusing and" entrain the fihers" therein which" move as a-"layen'with the air over the separating wall whereby air antl fiB'er in-s substantially" uniformconcentration. pass thio'ugh the openings of-ith'eseparatin'g Wall to the collecting walli 11. The method as claimed in-cla'im 10 which includes the'additionalstep of withdrawing air from the=underside of 'the collecting wall to createa suction whichanchors K the fibers separateditrom the air stream ontothe surface of sthe collecting wa'll.
12L Th'e meth'od as claimed'in claim *l which incllides the additional; step of 'withdfawifig a volume of air through the collecting -wall-" sli'ghtly' larger than the :volume' ofetiair passing through the 1 separating '-wall' soas; to cause a slight inflow- 0f air' from the surrounding atmos-- phere "into" thespace between the-separating wallandthe collectihg wall.
13; Themeth'od "as claimed in claim 10which includes the additional steps-of-withdrawing avol1ime of 'air' through the collecting-wall slightly larger than the volume of air passing through"the-separating=wall soasto cause a slight inflow of air from the surrounding atmosphere into the'--space"between-the separating wall' and thecollecting Wall, andin'troducing separate streams" ofair radially into" the housing to" generateturbulence and more uniform distribution of fibersinthe' air streamcirculating thereabouti- I v 14'.- Apparatusas claimed in claim" '2 in"whi'ch"'the air nozzle comprisesa header "corresponding to the width of the housing-and a substantially"continuous sldt communi= eating the header with the interior of the housing-to forma substantially continuous'air bladeextendingacross the housing and positioned to :direct atangential stream'of'air into the housing:
15. Apparams;fdr-the air depositiomofiseparated fibers v in the manufacture of fibrous strl'lctlires comprising 'a subtantially cylindrical housing' having an inlet 1 and an outlet: a:portionof the housing inithe form of -a -for- I aminous *separating \wal-lg a colleetiiig wall spaced ffom=' the separating wva'll having -'foramens' thereinsdiinensioned to prevent passage "of fibers, 1 means for feeding separated fibers into "the-housing; and means fo'r introducing high" velocity' stre'ams of airatan'angleless than radial into the housing 'to-causethe fibers tobecOme-entrainedtherein and carried eircumfe'rentially as 'a moving layerof air and filiers over the-face of the separating wall'= wherebyfibers 'pass"in subst'antially uniform concentration with" the air throughthe separating' wall for deposition onto the colleetihgv w'alll' 16. Irithe method of producingfibrous" structures of the'type described; thestepsof'introdueing"separated* fiher's' into a"-substantia1l cylindricaFhousing "having a foraminous separating wall and' a separate collecting wall spacedfrom the separatih'g'wall havingforamens 'dimen-' sione dto'prevent passage of'fibers thereth'rough,directing, high velocity streams ofair' into the housing 'at'an' angle tionpass through the -:openingsiof' the separating wall to the collecting jwa'l'l.
References-Cited in' the file'of this patent UNITED STATES PATENTS 2,338,739 Mutchl. Jan. 11,; 1944 2,491,877 SChug; Dec; 20,, 1949 2600:8315 Boyerr. JunerlZ; 1952!v 2,632,923
Nisbet vMatt. 31,. 1953