CA1156813A - System for full width feeding of lightly compacted uniform batts of non-bonded fibers to a flow control and separating mechanism in a system for forming an air-laid web of dry fibers - Google Patents

Abstract

ABSTRACT
Methods and apparatus for pre-forming and feeding a lightly compacted batt of individualized fibers having a controlled cross-directional profile directly to a rotary fiber orienting and screening mechanism across the full width thereof so as to maintain a controlled cross-directional profile in an air-laid web of dry fibers formed in a high speed dry web forming system.

Description

This application is related to Applicant's copending Canadian Patent Application filed December 19, 1980 under Serial Nu~ber 367~268O
~CKGROUND OF THE INVENTION
The present invention relates in general to methods for forming non-woven fabrics; andl m.ore particularly, to improved methods for forming ar air-laid web of dry fibers having a controlled cross-directional profile on -~ igh-speed production basis wherein the f.ibrous materials mput to the system are first for~ed into a lightly compacted feed mat having a controlled cross-directional profile with such feed mat then being fed directly to the forming head without being pre-opened and conveyed to the forming head in an air/fiber stream; yet, wherein the web being Eormed is characterized by a random dispersion of essentially undamaged, ~mcurledr individualized -fibers disposed i.n a controll.ed cross-directional profile and is substantially devoid of nits, pills~ rice and other aggregated fiber masses so as to result in a web of aesthetically pleasing appearance and increased tensile strength irrespective o~ the basis we~ght of the web which can range from at least as low as 13 ~s./2880 ft.2 suitable for bath tissue or the like to heavier webs suitable for facial tissues~
components for feminine napkins, diaper fillers, toweling, wipes~ non-woven fabrics, saturating paper, paper webs, paperboard, et cetera.
Conventionally, materials suitable for use as disposable tissue and towel products ha~e been :formed on paper~making equipment by water la~ing a wDod pulp fibrous sheet. ~onceptional~y~ such equipment has been designed so that the configuration of the resulting sheet approaches a planar structureO This allows continuous operation at high sFeeds; and, such sheets may be fonmed at speeds cf 3,000 to 4,000 feet per mimlteO Indeed, recent developments have allowed ~`'

2 -sustained production at speeds of up to 5,000 feet per minute.
Followiny formation of the sheet, the water is removed either by drying or by a combination of pressing and drying.
As water is re~oved during formation, surface tension forces of very great magnitude develop which press the fibers into contact with one ano~her, resulting in overall hydrogen bonding at substantially all fiber intersections; and a thin, essentially planar sheet is formed. It is the hydrogen bonds between fibers which provide sheet strength and, such bonds are produced even in the absence of extensive additional pressing. Due to this overall bonding phenomenon, cellulosic sheets prepared by water-laid ~ethods inherently possess very unfavorable tactile properties (e.g., harshness, stiffness, low bulk, and poor overall softness-) and, addition-ally, possess poor absorbency characteristics rendering suchshe~ts generally unsuitable for use as sanitary wipes, bath and facial tissues, and toweling.
To improve these unfavorable properties, water-laid sh~ets are typically crepad from the ~ryer roll--i.e., the paper is scraped from a dryer roll with a doctor blade.
Creping reforms the flat sheet into a corrugated-like structure~
thereby increasing its bulk and simultaneously breaking a significant portion of the ~iber bonds, thus artifically improving the tactile and absorbency properties of the material. But creping raises several proble~sO Conventional creping is only effective on low basis weight webs (e~
webs having basis weights less than about 15 lbs./2800 ft.2), and higher basis weight webs, after creping, remain guite stiff and are generally unsatisfactory for uses such as quality facial tissues. Because of this, it is conventional practice to employ at least two plies of creped low basis ~5~

weight paper sheets for such uses. Only by doing this can a sufficiently bulky product with acceptable softness be prepared. However, even this process does not completely overcome the detrimental effects of the initial overbonding in a water~laid paper sheet.
Sanford et al. U.S. Pat. No. 3,301,~46 proposes improving the tactile properties of water-laid sheets by thermally predrying a sheet to a fiber consistency substantially in excess of that norMally applied to the dryer surface of a paper machine and then imprinting the partially dried sheet with a knuckle pattern of an imprinting fabric. The sheet is thereafter dried without disturbing the imprinted knuckle-pattern bonds. While this method may somewhat improve the softness, bulk and absorbency of the resulting sheet, the spaces between the knuckle bonds are still appreciably compacted by the surface-tension forces developed during water removal/ and consider~ble fiber bonding occurs.
Creping is still essential in order o realize the maximum advantage of the propose~ process; and, for many uses, two plies are still necessary.
As will be apparent from the foregoing discussion, conventional paper-making methods utilizing water are geared towards the high speed formation of essentially planar sheets; yet, such methods inherently possess the inefficient attribute of initial "overbonding," which then necessitates a creping step to partially "debond~ the sheet to enhance the tactile properties~ Also, the extreme water requirements limit the locations where paper-making operations may be carried out. Such operations require removing a large quantity of the water used as the carrier, and the used process water can create an associated water pollution problem. Still furtherl the essential drying procedures consume tremendous amounts of energy.
Air forming of wood pulp fibrous webs has been carried out for many years; however, the resulting webs have been used for applications where either little strength is required, such as for absorbent products--i.e. r pads--or applications where a certain minimum strength is required but the tactile and absorbency properties are unimportant~-i.e., various specialty papers. U.S. Pat. No. 2,447,161 to Coghill, ~.S. Pat. No. 2,810,940 to Mills, and British Pat.
No. 1,088,991 illustrate various air-forming techniques for such applications.
In the late 1940's and early 1950's, work by James D'A~
Clark resulted in the issuance of a series of patents directed to systems employing rotor blades mounted within cylindrical fiber "disintegrating and dispersing chamber"
wherein air-suspended,fibers were fed to the chamber and discharged from the chamber through a screen onto a forming wire~-viz., J.D'A. Clark U.S. Pat. Nos. 2,748,429, 2,751,633 and 2,931,076. E~owever, Claxk and his associates encountered serious problems with these types of forming systems as a result of disintegration of the fibers by mecllanical co~action of the rotor blades with the cha~ber wall and/or the screen ~ounted therein which caused fibers to be '~rolled and formed into balls or rice which resist separation'7--a ph~nomenon more commonly referred to today as ~pilling". These problems, inter alia! and proposed solutions thereto, are described in, for example: J.D'A. Clark U.S. Pat. No. 2,8~7,668, J.D'A. Clark et al. U~S. Pat. Nos. 2,714,749 and 2,720,005;
Anderson U.S. Pat. No. 2,738;556; and, Anderson et al. U.S.
Pat. No. 2,738,557. However, prior to the advent oE the present - _5_ ~ ~.5~

invention, it is not believed that systems of the type disclosed by J.D'A. Clark and his associates which employed cylindrical fiber disintegrating and dispersing mechanisms with and/or without rotors, have been suitable for use in production type, air-laid, dry fiber, web forming systems, principally because problems of pilling have not been resolved, and because of severe fiber damage due to the disintegrating action of the rotor in Clark's cylindrical chamber.
P~ second type of sys~m for forming air-laid webs of dry cellulosic fibers which has found limited commercial use has been developed by Karl Kristian Kobs Kroyer and his associates as a result of work performed in Denmark.
Certain of these systems are described in: Kroyer U.S. Pat.
Nos. 3,575,749 and 4,014,635; Rasmussen U.S. Pat. Nos. 3JS81,706 and 3,669,773; Rasmussen et al. U.S. Pat. No. 3,769,115;
Attwood et al. U.S. Pat. No. 3,976,412; Tapp 11.S. Pat.
No. 4,060,36~; and, Hicklin et al. U.S~ Pat. No. 4,074,393.
In genexal, these systerns employ a fiber sifting chamber or head having a planar sifti~g screen which is ~ounte~ over a forming wire. Fibers are fed into the sifting chamber where they are mechanically agitated by means of a plurality of mechanically driven rotors mounted or rotation about vertical axes. Each rotor has an array of symmetrical blades which rotate in close proximity to the surface of the sifting screen. The systems described in the aforesaid Kroyer and related patents generally employ two, three, or more side-by-side rotors mounted in a suitable forming head.
This type of sifting equipment suffers from poor productivity and other inherent disadvantages, especially when making tissue-weight webs. For example, the rotor action concentrates most of the incoming material at the periphery of the blades where the velocity is at a maximum.
Most of the sifting action is believed to take place in these peripheral zones, while other regions of the sifting screen are either covered with more slowly moving material or are bare. Thus, a large percentage of the sifting screen area is poorly utilized and the system productivity is low.
Moreover, fibers and agglomerates tend to remain in the forming head for extended periods of time, especially in the lower velocity, inner regions beneath the rotor blades.
This accentuates the tendency of fibers to roll up into pills. Conse~uently, if the forming head is to be cleared of agglomeratea material, it is necessary to r~move 10% or more by weight o~ the incoming material from the forming head for subsequent reprocessing or for use in less critical end products. The separating method used (See, e.g., the aforesaid Kroyer U.S~ Pat. No. 4,014,635) entrains a large number of good fibers with the agglomerates leaving the forming head. The severe mechanical action of the hammermills in the secondary processing syste~ damages and shortens such otherwise good fibers, while breaking up the agglomerates.
Another inherent shortcoming of these systems is a tendency to form webs having a non-uniform weight profile across their width. (See, e.g~, the aforesaid Tapp U.S. Pat.
No. 4,060,360). This is a condition which is very difficult to overcome. It is especially troublesome when making webs in the towelling and lightweight tissue ranges.
The inventor has found that, when using high quality fibers--i.e., long, straight fibers, in a sifting type system--the above difficulti s were aggravated. The rate of pill formation increased and it was necessary to remove and ~5~3 recycle more -than 50% by weight of the incoming fibrous rr~terial to produce good quali-ty tissue-weight webs. Productivity was unacceptabiy low and excessive da~nage was done to otherwise good fibers during -the secondary harrmerrnilling s-tep. The -tensile strength of the webs produced was decreased. Moreover, the circular movemen-t of the rotors above the screen causes oorresponding air and fiber rnovement in the forming region below the screen. ~;trong, unstable cross-flow forces are present and contribute to non-uniform formation of the web. Efforts to corrpensate for the low throughput.of sifting type systems involve increasing the area of the screens and the forming surface. Thus, fiber is more thinly distributed over the forming surface and is not held in place as firmly by the suction box. The fibers are easily disturbed at hi.gher speeds and wave patterns are formed. Fibers are also disturbed by the seal rollers which are required to rraintain the forming region at sub-atmospheric pressure. The difEiculties described above compound each other and are especially -troublesorrR when forming lightweight webs at acceptable production speeds.
In an effort to overcome the productivity problem, compleY
.production systen~C have been devised utilizing multiple forrr~ng heads--for e~Yample, up to eight separate spaced fo.rn~lng heads associated with multiple hammerrrills ~nd each errploying two or three side-by-side rotors. The n~st recent sifting type systems employing on the order of eighteen, twen-ty or more rotors per forrQing head, still require up to three separate forming heads in order to operate a-t satisfactory production speeds--that is, the sys-terrs employ up to :fif-ty--Eour to sixty, or more, separate rotors with all of the attendant complex drive systems, feed arrangements, recycling quipment and hammermill equipment.
Mor~over, it has been found that the foregoing sifting systems are also deficient in that there is only limited control of cross-directional uniformity OL the web being produced--sce, e.g., the afore~aid Tapp V.S. Pat. No. 4,060,360--thereby imposing severe constraints when attempting to scale the equipment up to make webs of 96 inches, 120 inches, 200 inches, or more, in width. The tensile properties of the web may suffer as a result of excessive mechanical action in the forming heads and non uniformities in web weight and formation. The aesthetic appearance of the webs is often less than optimum as a result of wave patterns on the web surface resulting from the closely spaced rotor blades which are rotatin~ in a horizontal plane just above the forming wire and the other factors described above. To date, the foregcing problems have been so significant that this type of sif~ing system has been found totally unsuitable for makin~ relatively light weight webs at acceptable production speeds-~e.g., webs having basis weights of from 13 lbs./2880 ft.2 to 1~ lbs./2880 ft.2 suitable for use as bath or facial tissues~-although such equipment can produce low basis weight webs at low forming wire speeds. Rather, the equipment has generally found application in forming heavier basis weight webs suitable for use in making towels or paperboard where the web imperfections inherently produced can be either tolerated or masked because of the bulk and thickness of the web.
During the 1970's a series of patents were issued to C.E. Dunning and his associates which have been assigned to the assignee of the present invention; such patents describing yet another approach to the formation of air-laid dry fiber webs. Such paten~s include, f ~ Dunning U.S. Pat.
Nos. 3,692,622, 3,733,234 and 3,764,451; and, Dunning et al.
U.s. Pat. Nos. 3,776,807 and 3,825,3~1. This development has been found to xesolve a number of the problems that have heretofore plagued the industry. For example, high productivity rates have been achieved and fiber webs can easily be formed at high machine speeds. However, the system requires preparation of pre-formed rolls of fi~ers having high cross-directional uni~ormity and is not suitable for use with bulk or baled fibrous materials. Because of this, problems are experienced when attempting to scale the equipment up to produce wide webs--i.e., webs on the ord~r of 120 inches in width or greater--and the requirement for pre- ormed special web lS rolls having the requisite uniformity in cross-directional profile has been such that, to date, the system has found only limited commercial application.
Indeed, heretofore it has not been believed that air-forming techniques can be advantageously used in high speed production Operations to prepare cellulosic sheet material that is su~iciently thin, and yet has adequate strength, together with softness and absorbency, to serve in applications such as bath tissues, facial tissues and light weight toweling.

SUMMARY OF THE INVENTION
It is a general aim of the present invention to provide methods sr*-~ppQr~ which overcome all of the foregoing disadvantages which are characteristic of the prior art, which eliminate the need to feed fibrous materials suspended in an air stream to a dry orming system and, therefore, which are economical and require only minimal capital ~6~;~3 investment .
In one of its aspects, it is an object of the invention to provide improved methods for feeding fibers to a 2-dimensional dry forming system which reliably maintain the fibers in a pre-established controlled state in terms of cross-directional profile and which permit air deposition of dry fibers to form webs having any selected one of a wide range of basis weights and wherein the speed of web formation is no longer the limiting constraint in the n~nufacture of finished products.
In a further aspect of the invention -there is provided improved dry air-laid web forming methods characterized by their simplicity, yet which permit of high capacity operation with fiber throu~hput and wherein the product prod~ced is characterized by in~roved properties in terms of strength, tactile properties, f.reedom from nitsr uniformity, and general aesthetic appearallce. It is a more specific object to provide nethods and apparatus capable of producing high-quality webs at speeds in the range of 300 to 2,000 feet per minute andr even at speeds in excess of 2,000 feet per minute. :
In ~et a further aspect of the invention there is provided improved dry air-laid web forming rllethods wherein a feed mat having a controlled cross-directional profile is formed at a location remote from the 2-dimens.ional forming head and is lightly compacted to facilitate delivery of fibrous materials directly to the forming head in ligh-tly com~acted, non-bonded fo~m and which, the.refore, result in substantial savings in terms of space requirements, energy consump-tion, and environmental pollution.

~6~

In accordance with the present invention there is provided a method of forming a quality web of air-laid dry Eibers on a high speed production basis comprising the steps of: a) forming a feed mat of fibers having a con-trolled cross-directional profile; b) lightly compacting the feed mat to provide sufficient mat integri-ty to permi-t delivery to a remote point yet without sufficlent compaction as to cause hydrogen bonding of the fibers; c) delivering the lightly compactecd reed mat to a forming head positioned over a forming surface;
d) dispersing the dry fibrous materials comprising the feed mat uniformly throughout forming head in a rapidly moving aerated bed of individualized fi~ers, soft fiber flocs and aggregated fiber masses and in an environment maintained substantial]y free of fiber grindihg and disintegrating forces; e) continuously separating a substantial portion of those fibrous materials deliverecl to the Eormlng head havirly a bulk density in excess of .2g./cc. from the aerated bed so as to separate a subs-tantial portion oE the aggregated fiber masses from the aerated bed; f) discharging such separa-ted fibrous ma-terials including the aggregated fiber masses contained therein from the forming head;
g) conveying the individualized fibers and soft fiber flocs from the forming head at a ~lber throughput rate anywhere in the range of .5 Ibs./
hr./in. to at least l.S0 lbs.~hr./in. -through an enclosed forming zone towards the moving foraminous forming surface in a rapidly moving air stream, h) air-laying the individualized fibers and soft fiber flocs on the moving forarninous forming surface so as to form an air-laid web of randomly orientea dry indiv,i,dualized fibers and soft fiber flocs on the forming surface; and, i) moving the foraminous forming surface at a con-trolled and selected speed so as to produce an air-laid web having and any specific desired basis weigh-t in lbs./2880 ft. ranging from at least as lo~ as 13 lbs./2880ft. to in excess of 40 lbs./2880ft. .

DESCRIPTION OF ~'HE DRAWINGS
These and other objects and advantages of the present invention wi.ll become more readily apparent upon reading the following detailed description and upon reference to the at-tached drawings, in which:
~ IGURE 1 is a schematic view, in side elevation, of one form of apparatus which has been employed for the air deposition of dry fibers to form a web continuum;
FIG. 2 is a schematic view here illustrating an exempl.ary air-laid, dry fiber, web forming system utilizing two substantially identical cylindrical flow control and forming heads disposed in side-by-side relationship above the foraminous forming wire;
FIG. 3 is an oblique view, partially cut away, here schematically illustrating detail.s of an exemplary fiber feed, eductor, flow controlJ screening, and fiber forming arrangement;
FIG. 4 is a fragmen-tary front elevational view, partly in section, of -the rotor assembly shown in FIG. 3;
FIG. 5 is an end view of a modified rotor assembly ~ 5~ ~ 3 t similar to that shown in FIG. 3, but here depicting a rotor employing only four rotor bars;
FIG. 6 is a diagramatic plan view indicating in schematic, idealized fashion fiber movement through a conventional woven square-mesh screen under the influence of air movement and rotor action;
FIG. 7 is a view similar to FIG. 6, but here depicting movement of fibers through a high capacity slotted screen in which the slots are oriented parallel to the axis of the rotor;
FIG. 8 is a view similar to FIG. 7, but here illustrating the undesirable plugging action that occurs when the slots of a slotted screen are oriented in a direction generally perpendicular to a plane passing through the axis of the rotori FIG. 9 is a photograph illustrating the plug~ing of a slotted screen that occurs when the slots are oriented at an angle of approximately 45 to a plane passing through the axis of the rotor;
FIGu 10 is an enlarged, fragmentary side elevational view here depicting in diagramatic form the air/fiber stream as it moves through the xotor housing where an annular moving aexated bed of fibers is created and maintained and r thereafter, as it moves through the screening means and forming zone and is air-laid on the forming wire to form an air-laid web of fibers and, further, depicting the pressure relationships and the air velocity and rotor bar velocity relationships that are believed to exist when operating the system of the present invention at a desired one of several selectable sets of adjustable parameters in terms of ratio of air-to-~iber supply, rotor speed, and recycle balance;

~14-6~

FIG. 11 is a highly enlarged view of a pcrtion of the system shown diagramatically in FIG~ 10 here depicting how the differential relative velocities of the rotor bars and air strea~ serve to generate a rapidly moving full-width zone of negative pressure in the wake of each rotor bar, thereby lifting fibrous materials off the screen in the region beneath the moving negative pressure zone, whlle permittin~ individual fibers to dive axially or end-wise through the openings in the screen in those regions of positive pressure drop across the screen between successive negative pressure zones;
FIG. 12 is a vi~w similar to the rotor chamber portion of FIG. 1, bu~ here depicting an arxangement in which a lightly compacted feed mat of non-bonded fibers is fed directly into the rotor chamber in accordance with the present invention as contrasted with the system shown in FIGS. 1 and 3 wherein the fibers are pre-opened and fed into the chamber suspended in an air stream;
FIG. 13 is a view similar to that of FIG. 12, here illustrating another modi~ied system for feeding lightly compacted mats of non-bonded fibers and which is suitable or use with the present invention;
FIGo 14 is a view similar to FIGo 13, but here il-lustrating a modified system for converting fibers in a lightly compacted feed mat to individualized fibers fed to the rotary flow control and separating chamber in an air-suspended fiber delivery system;
FIG. 15 is a graphic representation of a typical set of curves indicative of the functional relationships existing with air-laid web forming systems embodying features of the present invention between fiber throughput for specific representatlve screen designs and rotor asscmbly operating parameters~-viz., rotor RPM and the number of r~tor bars employed;
FIG. 16 is a graphic representation of the functional relationships existing between nit levels in a finished air-laid web made in accordance with the present invention, fiber throughput, and the percentage of fibrous materials separated and/or recycled prior to deposition on a moving forming wire; and, FIGS. 17 through 23 are photographs of exemplary air-laid fiber webs having increasing nit levels suitable for subjectively evaluating and rating web quality in accordance with subjective visual standards as to product acceptability established by the assignee of the present invention.
While the invention is susceptible of various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the intention is to co~er all modifications, equivalents and alternatives falling within the spirit and scope of the in-vention as expressed in the appended claimsO

DETAILED DESCRIPTION
A. Definitions To facilitate an understanding of the ensuing description and the appended claims, definitions of certain selected terms and phrases as used throughout the specification and claims are set forth below.
The phrase "pulp lump" ls herein used to descrlbe a dense, bonded clump of fibers in the incoming fiberized supply ~hich is most conventionally caused by hard pressing, non-uniform application of debonding agents, and/or inadequate opening or hammermilling. Pulp lumps are present in ordinary S commercial grades of pulp.
The words "pill" and/or "rice n are herein each used to describe a dense/ rolled up bundle of fibers, often including bonded fibers, which are generally formed by mechanical action during fiber transport or in a rotor chamber wher~
the fibers are commonly, and often intentionally, subjected to mechanical disintegrating action.
The word "nit" is herein used to generically refer to pulp lumps, pills and/or rice. Nits are considered to be an unacceptable defect in light-weight tissues such as bath and facial tissues having basis weights of from 13 lbs./2880 ft.2 to 18 lbs./2880 ft.2, and generally result in decreased tensile strength in webs of these, or even of heavier, basis weights.
The terms "floc" and "soft floc" are herein used to describe soft, cloud-like accumulations of fibers which behave like individualized fibers in air; i.e., they exhibit relatively high co-efficients of drag in air.
The phrase "agyregated fiber masses" is herein used to generically embrace pulp lumps, pills, rice and/or nits, and to describe aggregations of bonded and/or ~echanically entangleA fibers generally having a bulk density on the order of greater than .2 grams per cubic centimeter (g./cc.~.
Aggregated fiber masses are to be distinyuished from flocs and/or soft flocs whose bulk density is generally less than .2 g./cc. ~creover, aggregated fiber masses have a relatively low coefficient of drag in air.

"Bulk density" is the weight in grams of an uncompressed sample divided by its volume in cubic centimeters.
The phrase "semi-cylindrical" is used herein to describe a portion of the rotor chamber wall and~or forming screen, and is intended to mean that wall portion from the upstream leading edge of the screen to and including the full-width separator slot. In the various exemplary embodiments herein described, the phrase "semi-cylindrical'l embraces a peripheral wall portion having an included angle of less than 180.
However, such phrase is used herein in a descriptive sense and is not intendPd to be construed in a limiting sense since those skilled in the art will appreciate as the ensuing description proceeds that the rotor chamber cvuld be cylindrical, or substantially cylindrical, in which event the phrase "semi-cylindrical n would be intended to embrace peripheral wall portions having an included angle of greater than 180.
The phrase "2-dimensional" is used to d~scribe a system for forming a web wherein: i) the cross-section of the svstem and the flows of air and fiber therein are the same at all sections a&ross the width of the system; and ii), where each increment of system width behaves essentially the same as every other increment of system width; thereby permitting the system to be scaled up or down to produce high quality webs of any suitable and commercially useful widths on a high-speed production basis and wherein a web's cross-directional profile in terms of basis weight can be controlled and, preferably, can be maintained uniform.
The phrase "coefficient of variation'l is used herein to describe variations in the cross-directional basis weight profile of both the web being formed and the lightly compacted feed mat input to the system, and comprises the standard deviation (CJ) expressed as a percent of the mean. The coefficient of variation should not vary more than 5% and, preferably, should vary less than 3% in the cross-machine direction. The basis weight profile in the cross-machine direction of the web bein~ formed may, for example, be determined by weighing strips of the web which are three inches in width (3" C.D.) by seven inches in length l7"
M.D.)-The phrases "uniform cross-directional profile", "uniform Mass quantum of fibers in the cross-machine ~irection", and similar phrases, are herein used to describe a condition in the web bein~ formed, as well as in the lightly compacted feed mat delivered to the forming apparatus, wherein the coefficient of variation does not vary more than 5% and, preferably, varies less than 3~ in the cross-machine direction.
The phrases "controlled cross-directional deposition", "controlled cross-directional profile", "controlled mass quantum of fibers in the cross-machine direction", and similar phrases, are herein used to describe a condition wherein the cross-directional profiles of the lighly compacted feed mat and the web being formed are not necessarily uniform but, rather, may intentionally be non-unifor~; and, because the system is substantially devoid of cross-directional flows, the cross-directional profile of the finished web is controlled so as to be similar in profile to thc cross-directional profile of the feed mat-- 9., if the feed mat has twice the mass quantum of fibers at its center as it does along its marginal edges, the basis-weight of the web produced will also be approximately twice as great at its center than at lts marginal edges when viewed in cross~

directional profile. While the invention will herein be described in large part in terms of a lighly compacted feed mat input to the system wherein the coefficient of variation is not more than 5% and, preferably, 7 S less than 3~, and the formation of air-laid webs having a uniform cross-directional profile ~ith a coefficient of variation of not more than 5~ and, preferably, of less than 3%, since there is presently a significant demand for such products--~articularly in the case of relatively low basis weight webs on the order of 13 lbs./2880 ft.2 to 18 lbs./2880 ft.2__ it should be understood that the invention is not limited to the formation of webs having uniform cross-directional profiles but, rather, is equally useful in the manufacture of webs having controlled cross-directional profile~, both unifor~ and non-uniform~

The term "throughput" and the phrase "rate of web formation" are herein used generally interchangeably and are to be distinguished fro~ the phrase "rate of fiber delivery".
Thus, the phrase-"rate o~ ~iber delivery" is intended to mean the mass quantum or weight rate of feed of the lighly compacted feed mat delivered _ the forming head, and may be expressed, for example, in units of pounds per hour per inch of former width llbS./hr./in.), pounds p~r minute per foot of former width (lbs./min./ft.), or in any other suitable units. "Throughput", on the other hand, is intended to describe the screening rate for fibrous materials discharged from the forming head--i.e., the mass quantum or weight rate of fiber delivery through the fo;emer screen per unit area of screen surface-~and may be expressed, for example, in units 30 of pounds per hour per square inch of effective screen surface area (lbs.~hr.~in. ~, p~unds pcr minute per square ~r/~ 3 foo-t of effective screen surface area (lbs./min./ft. ), or any other sui-table units. The fiber "throughput" achieved is reflected directly in the "rate of web formation" and may be calculated by multiplication of fiber thro~lghput by the effective length of the former screen. "Rate of web formation"--i.e., the rate at which the air-laid web is formed on the moving forming wire or other forming surface--may be expressed, for example, in units of pounds per hour per inch of former width (~bs./hr./in.), pounds per minute per foot of former width (lbs./min./ft.), or in any other suitable units.
lo The words "up", "down", "above" and/or "below" are used in a relative, non-limiting sense to describe, merely ~ y of example, a relationship of one structural element to a forming wire or to another structural element.
B. Overall System Description Briefly, and referring first to FIG. 1, there has been illustrated an exemplary system for forming an air-laid web 60 of dry fibers, such system here comprising: a fiber metering section, generallv indicated at 65; a fiber transport or eductor section, generally indicated at 70; a forming head, generally indicated at 75, where provision is made for controlling air and fiber flow, and where I individual fibers are screened from undesirable aggregated fiber masses and, thereafter, are air-laid on a foraminous forming wire 80; a suitable bonding station, general:Ly indicated at 85, where the web is bonded -to provide strength and integr;ty; a drying sta-tion, generally indicated at 87, where the bonded web 60 is dried prior to storage; and, a take-up or reel-type storage s-tationr generally ,~

~S~ 3.

indicated at 90, where the air-laid web 60 of dry fibers is, after bonding and'drying, formed into suitable rolls 95 for storage prior to delivery to som~ subseguent processing operation (not shown) where the web 60 can be formed into specifically desired consumer products.
In the exemplary system, the forming head 75 includes a separator system, generally indicated at 76, for continuous 'removal of aggregated fiber masses. Such separated aggregated fiber masses and individualized fibers entrained therewith are preferably removed from the forming area by means of a suitable conduit 77 maintained at a pressure level lower than the pressure within the forming head 75 by means of a suctio.n fan (not shownJ. The conduit 77 may onvey the masses to some other area (not shown) for use in inferior products, for scrap, or, alternatively, the undesirable aggregated fiber,masses may be recycled via conduit 78 to a hammermill, generally indicated at 100, where the'masses.are subj~cted to secondary mechanical disintegration prior ~o reintroduction into fiber meter 65. Finally, the forming head 75 also includes a forming chamber, generally indicated at 79, position~d immediately above the foraminous forming wire 80. Thus, the arrangement is such that individual fibers and soft fiber flocs pass through the forming chamber 79 and are deposited or air-laid on the forming wire 80 to form a web 60 cha.racteri2ed by its controlled cross-directional profile'and basis weight.
C. Fiber Metering Section While various types of commercially available fiber metering systems can, with suitable modifications, be employed with equipment embodying the features of the present invention, one system which has been found suitable and which permits of the necessary modifying adaptations is a RANDO-FEEDER~ (a registered trademar~ of the manufacturer, Rando Machine Corporation, Macedon, New York). The fiber metering section 65 shown by way of example in FIG. 1 is such a system. Indeed, a RANDO-FEEDER3 is ideally suited for use with the present invention when att~mpting to work with synthetic fibers.
As here shown, the fib r metering section 65 is mounted on the mezzanine floor le~el 101 of a suitable paper mill. Fibers may be fed to the fiber separator hopper 102 in any of a variety of conventional ways. For example, pr~-opened fibers may be manually introduced in bulk through inlet chute 103 which is provided with a closure member 104 so as to maintain an enclosed chamber. Alternatively, batts or other compacted fibers may be introduced through inlet 105 of hammermill 100 (which is here shown only in diagrammatic block-and-line form and may take any well known conventional form). The compacted batts are fibe:rized within the hammer-mill and, after fiberization, the individualized fibers are . ..
delivered to the fiber separator hopper 102 via inlet 106.

A fan 107 is provided for removing excess air from th~ fiber separator hopper 102, thereby permitting the fibers to form a loose fiber bed 108 at the bottom o~ the hopper 102. Thus, the fan 107 functions to withdraw excess air from the hopper 102 and such excess air, together with some escaping fibrous materials, are thereafter discharged into a suitable waste air filter or cyclone separator (not shown). If desired, a conventional pre-feeder and opener-blender (not shown) can be used to feed indi~idualized fibers to the fiber meter 65.
In operation, fibers fall from the fiber separator hopper 102 and form a loose bed 108 of open fibers carried by a floor apron conveyor 109. An anti-static spray system 110 may be p~ovided to minimize adherence of the fibers to portionC~ of the system. The fibers arc conveyed by the floor apron conveyor 109 to an elevating apron conveyor 111 having conventional pins and slats (not shown). Fibers are carried upwardly by the elevator apron conveyor to a rotatin~
stripper apron 112 which serves to remove excess fibèr stock and return such excess stocX to the bed 108. The arrangement is such that a controlled, metered ~uantity of small opened tufts of fiber remains on the pins of elevator apron conveyor 111 and is carried over the top thereof uniformly across the entire width of apron 111 into an area 113 known as an air bridge.
Fibers delivered to the air bridge 113 are doffed from the pins on apron 111 by means of air flow under the control of a suitable air volume controller 114. As a result of the flow rate of air movement, a controllable quantity of fibers--uniform throughout the full width of aix bridge 113--are deposited on a rotating condenser screen 115, thus .orming a full-wldth uniform feed mat 116 conveyed by roller conveyor 118 to a feed plate 119. The arrangement is such that as the feed mat 116 takes shape, the resistanc~ o the mat on condensor screen 115 serves to reduce air flow through the screen and, consequently, proportionally less doffing occurs at apron 111 until a condition of equilibrium is reached. At the equilibrium point, a sufficient quantity of fibers are doffed to form a continuous uniform fecd mat 116, with the balance of unused fibers being returned by the pins on elevator convcyor 111 to the fiber bed 108.
The full-width uniform feed mat 116 may then be conveyed over feed plate 119 by means of feed roller 120 and into the path of teeth formed on an opening roll or lickerin 121. The lic~erin 121 serves to comb individual fibers from the feed mat 116 with the individualized fibers being picked 5 up and carried by a full-width air stream passing under feed plate 119 and generated by fan 124 and eductor 70. From this point, the entrained stream of individualized air-suspended fibers is introduced into the main air supply stream generated by fan 124 and carried through eductor 70 and the forming head 75, with the fibers exiting the forming head 75 passing through the forming chamber 79 and being uniformly deposited across the full-width of forming wire 80 in a uniform, but completely random, fiber pattern, thereby forming web 60.
D. Web Forming, Compacting, Bondin ~yin~ & Storage Section As heretofore indicated, fibers are air-laid on the foraminous forming wire 80 at the forming station by means of an air stream generated primarily by fan 124. In addition, a vacuum box 1~6 positioned immediately below the forming wire 80 and the web forming s~ction 79 serves to maintain a positive downwardly moving stream of air which assists in collecting the web 60 on the moving wire 80. If desired, a second supplementary vacuum box 128 may be provided beneath the forming wire at the point where the web 60 exits from beneath the forming chamber 79, thereby insuring that the web is maintained flat against the forming wire.
After formation, the web 60 is passed through calender rclls 129 to lightly compact the weh and give it sufficient integrity to permit ease of transportation to conveyor belt 130. A light water spray can be applied from nozzle 131 in order to counteract static attraction between the web and the wire. An air shower 132 and vacuum box 134 serve to clean loose fibers from the wire 80 and thus prevent fiber build-up.
After transfer to the belt 130, the web 60 may be bonded in any known conventional manner such, ~ y b~ way _ example, as i) spraying with adhesives such as latex, ii) overall calendering to make a saturating base paper--i.e., a -bulky web with a controlled degree of hydrogen bonding--iii~
adhesive print pattern bonding, or other suitahle process.
1~ Such bonding processes do not form part of the present invention and, therefore, are neither shown nor described in detail herein, but, such processes are well known to those skilled in the art of non-woven fabric manufacture. For exa~ple, the web 60 may be pattern bonded in the manner described in greater detail in the aforesaid Dunning U.S.
Pat. No. 3,692,62~ assigned to the assignee of the present invention. ~riefly, in this bonding process, the moisture content of the web is adjusted to 6~ to 35% by a water spray 135 and, thereafter, the web is bonded by passing it through the nip between a small hard roll 136 and a patterned steel roll 138. Su~sequently, the bonded web 60 is transferre~ to conveyor belt 139 and transported thereby through the dryin~
station 87 to the storage station 90 where the web 60 is taken up on a driven reel 140 to form roll 95 which may thereafter be either stored for subseguent use or unwound at a subsequent web processing station (not shown~ to form any desired end product. The drying station 87 may take any suitable conventional form such, for example, as a pair of closely spaced heated plates 88, 89, or an oven or heated roll (not shown).
Referrinq to FIG. 2, there has been diagrammatically ~5~
illustrated a typical system employing multiple forming heads Eor increasing overall productivity of the air-laid dry fiber web forming system. As here shown, multiple forming heads 75A - 75N are posi-tioned over the foraminous forming wire 80~ with each forming head being supplied with a full-wid-th uniform supply of air-suspended fibers fed from respective ones of a multipllcity of hammermills and fiber meters (not shown in FIG. 2, but respectively similar to the hammermill lO0 and fiber meter 65 shown in FIG. l). Of course, while only t~
forming heads 75A and 75N have been shown for illustrative purposes in FIG. 2, those skilled in the art will appreciate that any desired number of forminy heads could be used dependent upon the productivity desired in terms of the web's basis weight, forming wire speed, and the speed at which ~he bonding station can be effectively operated.
l'hus, it will be appreciated tha-t the air-laid web 60 is formed by a first layer of fibers 60A deposited by forming head 75A, and n (where n - any whole integer) successive layer(s) 60N deposited by n downstream forming head~s) 75N. As a conseg~lence of this construction, the s~eed of the forming wire may be increased by a multlple of the number of forming heads employed to form a composite web 60 of a selected basis weight for a given forming wire speed.
E. Full-Width Me-tered Fiber Feed In previous systems, provision is made for forming a full-width feed mat of fibers having a controlled cross-directional profile in terms of the mass quantum of fibers constituting the mat.
To this end, and as best illustrated in FIG. 3, feed mat 116 may be formed in the manner previously described ~5~

in connection with the fiber metering section 65 shown by way of example in FIG. 1. Such feed mat 116 has been found to meet the preferred conditions of full-width uniformity in terms of the m~ss quantum of fibers forming the mat and the coefficient of variation of the fibrous materials input to the system. The mat thus formed--2 g., mat 116~-may then be fed across feed plate 119 by ~eans of a feed roller 120 into the teeth on lickerin 121 which serves to disaggregate the fibers defining the mat by combing such fibers (along with any pulp lumps, nits and other aggregated fiber masses which are present~ out of the mat and feeding such materials directly into a high volume air stream generated by fan 124 (FIG~ 1~ and eductor 70 ~FIGS~ 1 ancl 3~.
The air-to-fiber ratio preferably employed when working with cellulosic wood fibers is on the order of 200-600 cubic feet of air (at standard temperature and atmospheric pressure conditions) per pound of fiber--viz.l 200-600 ft.3~1b.
Moreover, when employing the exemplary equipment herein described such air is supplied at relatively high volumes which vary dependent upon the operational speed of the rotor assembly and the types of fibers being worked with--i.e~, volumes ranging from 1,000 to 1,800 ft.3~min./ft. of for~er width are conventional when working with cellulosic wood fibers. For ex~ple, when employin~ an 8-bar rotor operating at 1432 RP~I, the volume of air supplied is preferably on the order of 1500-1650 ft.3/min./ft. of former width. On the other hand, when workins with synthetic fibers or cotton linters, for example, considerably higher volumes of air per pound of fiber may be employed--e.s.~ the air-to-fiber ratio may range from 1,000 to 3,000 ft.3/lb., or even higher.
In operation, the air-suspended fiber stream is conveyed ~28-through a suitable fiber transport duct 170 (FIG. 3) from the full-width eductor 70 to a full-width inlet slot 171 for~ed in the upper surface of, and extending fully across, a gencrally cylindrical housing 172 which here defines the 2-dimensional flow control, screening and separating zone 75. To insure that full-width mass quantum fiber control is maintained, the exemplary duct 170 is preferably subdivided into a plurality of side-by-side flow channels separated by partitions 174 extending the full length of the duct. It has been found that the desired coefficient of variation constraint in the web being formed can be obtained by spacing the partitions 174 apart by approximately ~our inches so as to form a plurality of adjacent flow channels extending across the full axial length of housing 172.
F. Flow Control, Screening and Separation _ _ . _ _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ In carrying out the present invention, a 2-dimensional cylindrical rotor former is p.rovided which serves to control flow of an air-suspended fiber stream through a separation zone while minimizing mechanical disintegration of fibrous materials, and which is designed to provide an acceptable level of fine scale air turbulence while insuring that the system is substantially devoid of eddy currents and other undesired cross-flow forces so as to maintain a control~ed mass quantum of fibers across the full width of the forming head 75. To accomplish this, the exemplary forming head 75 includes a rotor assembly, generally indicated at 175 in FIGS. 3 and 4, mounted for rotation within housing 172 about a hoxizontal axis defined by shaft 176. The arrangement is such that fibrous materials introduced into housing 172 are conveyed by co-action of the air strea~ introduced through inlet slot 171 and the rotor assPmbly 175 through the housing -29~

~5~ 3 ~`

172 for controlled and selective discharge either a) through a full width discharge opening, generally, indicated at 178 in FIG. 3, and into forming zone 79 for ultimate, air-laid deposition on for,ning wire 80 or, alternatively, b) through a full-width tangential separator slot 179 ~ormed in housing 172 downstream of the discharge opening 178. The separator slot 179, which here forms part of the separation and/or recycle zone 76 (FIGS. 1 and 3), is preferably on the order of from 3/16" to 3/8" in circumferential width when working with wood fibers and, if desired, may be adjustable in any conventional manner (not shown) so as to per~it circumferential widening or narrowing of the slot 179 to optimize separation conditions.
To permit controlled~ selective discharge of individuali~ed fiber~ and soft fiber flocs through opening 178 and into forming æone 79, while at the same time precluding discharge of nits and other undesired aggregated fiber masses ther through, suitable screening means, generally indicated at 180 in FIG. 3, is mounted within discharge opening 178. Such screening means 180 may simply take the form of a conventional woven s~uare-mesh wire ~creen of the type shown at 180A in FIG. ~ and having openings sized to preclude passage of aggregated fiber masses--e.~., the screen may take the form of an 8x8 mesh screen having 64 openings per square inch, a lOxlO mesh screen, a 12x12 mesh screen, or other commonly available woven mesh screens; provlded only that the screen openings do not exceed 0.1" open space from wire-to-wire in at least one direction and have between 30% and 55~ open area and, preferably, between 38~ and 46% open area. As best shown in FIG. 3, screening means 180 is formed with the same radius of curvature as the semi-cylindrical portion of ~5~ 3 housing 172 within which discharge opening 178 is formed.
In carrying out this aspect of the invention, and as best illustrated by reference to FIGS. 3 and 4 conjointly, rotor assembly 175 comprises a plurality of transversely extending rotor bars 181, each fixedly mounted on the outer periphery of a plurality of closely spaced spiders 18~. The spiders 182 are, in turn, fixedly mounted on shaft 176 which is journalled for rotation in outboard bearing housings lB3, 184 tFIG. 4) and which i5 coupled to drive shaft 185 driven by any sultable means (not shown). The arrangement is such that the high volume air stream passing through duct 170 is introduced radially into housing 172 through inlet slot 171 and such stream tends to pass across the rotationally driven rotor bars 181- viz., the bars 181 move through the radially entering air stream. As a result of rotor bar movement and the high velocity movement of the air stream, the air and fibrous materials introduced into housing 172 tend to move outwardly towards the wall of housing 172, thus for~ing an annular, rotati4g, aerated bed of fibrous materials, best illustrated at 186 in FIG. 10. Such annular aerated bed 186 of fibrou~ materials is believed to be on the order of one-half inch to one and one-half inches thick tdependent upon actual operating parameters), and is believed to be moving rotationally at about half the speed of the rotor bars 1~1.
F example, in a cylindrical former having an inside housing diameter of 24" where the rotor assembly 175 is being driven at 1432 RPM, the tip velocity of the rotor bars 181 i5 on the order of 150 f.p.s. tfeet/~econd) and, consequentl~, it is believed that the velocity of the aerated bed 186 is on the order of 80 f.p.s. Thus, since the rotor bars 181 are moving at 150 f.p.s. through an aerated bed of fibers moving ~ ~56~
in the same direction at approximately 80 f.p.s., -the relative velocity between the aera-ted bed 186 of fibers and the rotor bars 181 is on the order of 70 f.p.s FIBER DELIVERY IN ACoORD2~CE Wq ~
Thus far, the envi.ronment of the invention has been described in connection with a fiber delivery system wherein fibrous materials are n~etered to form a feed mat 116 (FIGS. 1 and 3) having a controlled cross-directional profile and which is then pre-opened by means of a lickerin 121 which serves to disaggregate the fibers defining the mat by combing such fibers (along with any pulp lumps, nits and other aggregated fiber masses r~hich are present) out of the mat and feeding such materials directly into a high volume air stream generated by fan 124 (FIG. 1) and eductor 70 (FIGS. 1 and 3). In such a system, it is then necessary to convey the air-suspended fiber stream to the forming head 75, often over considerable distances, while insuring that cross-flow forces are eliminated wi-thin the air-suspended f.iber delivery system so as to ensure mainta:inence of the controlled c.ross-directional profile of the fibrous materials combed out of the feed mat 116. This ty~e of arrangement places some limiting constraints on the location .of the fiber metering equipment 65 (FIG. 1) relative to the forming head 75.
In accordar.ce with -the present invention, provision is .made for forming a lightly compacted feed mat of non-bonded fibers having a controlled cross-directional profile at any desirable ren~te location and, thereaf-ter, conveying such ,i ., .

~6~3~3 feed mat in its lightly compacted form directly to the forming head 75, and introducing the feed mat into the forming head where the fibrous materials comprising the mat are instantaneously dispersed in a rapidly moving annular aerated fiber bed 186 by action of the rotor assembly 175 and the high volume air stream generated by fan i24 and introduced to the forming head 175 through inlet slot 171. In carrying out this aspect of the invention, the feed mat initially formed may be formed by an known conventional mat forming system capable of metering fibers to form a mat having a controlled cross-directional profile such, for example, as a conventionalmultiple scarfing system (not shown) or the fiber metering system 65 ~hown in FIG. 1.
G. Alternative Li~htly Compacted Feed Mat Delivery Systems Turning to FIG. 12, there has been illustrated one form of system for feeding a lightly compacted feed mat having a controlled C.D. coefficient of variation--e.g., he feed mat 116 formed in the manner shown in FXGS. 1 and 3--directly into a forming head 75 in accordance with the present invention.
~s here shown, a feed mat such as that shown at 116 in FIGS.
1 and 3 is first conveyed between a pair of full-width compacting rolls 234, 235 which serve to lightly compact the web 116 so as to form a feed mat 236 characterized by its full-width uniformity and having a coefficient of variation of 5% or less. The compacting rolls 234, 235 are hardened steel rolls and are adjusted so as to provide sufCicient web compaction to form a feed mat 236 having enough integrity to permit subseguent handling; yet, not sufficient co~paction as to cause hydrogen bonding of individual fibers. For example, when working with Northern Softwood Kraft (NSWK) fibers, it has been found that the requisite degree of ~33-~5~ 13 compaction can be achieved with compacting forces on the order of 200 to 800 p.l.i. (pounds per lineal inch) when using two equal diameter hardened steel rolls 234, 235, each 6" in diameter.
In carrying out this aspect of the present invention, the lig~tly compacted feed mat 236 of non-bonded fibers thus formed is fed through a remotely located full-width feed inlet 244 radially into rotor housing 172 by means of a feed roll 245. The feed inlet 244 is preferably positioned downstream of air inlet 171 and upstream of discharge opening 178. The arrangement is such that as the feed mat 236 enters housing 172, it radially intersects the aerated bed 186 of fibers which is moving at a relatively high velocity--e.g., on the order of 80 f.p.s.--and, as a result of movement of the high velocity air stream and the rotor bars 181 which are moving at approximately twice the speed of the aerated bed 186 of fibers, the non-bonded, lightly compacted fibers constituting f~ed mat 236 are instantaneously and uniformly dispersed into the rapidly xotating aerated bed 186 of fibers.
The fibrous materials are, thereafter, selectively passed through screening means 180 disposed in outlet 178 or, alternatively, through full width tangential separator slot 179, in the manner hereinafter described. Those fibers passing through screening means 180 are conveyed through forming zone 79 and are air-laid on foraminous forming wire 80 to form web 60~ It will be noted that in this arrangement, those fibers freshly introduced into the housing 172 through inlet 244 wili, at least initially, be pxincipally located within the radially o~termost regions of the aerated bed 186 and, consequently, will be in close proximity to the screenin~
means 180; whereas those fibers not discharged through the ~56~ t screen 180 on the first pass will tend to be principally located in ~he radially innermost regions of the aerated bed 186 o~ fibers. Consequently, it is believed that this arrangement will permit relatively high forming capacity s since a high mass quantum of fibers are dispersed in the outermost xegions of the aerated bed just upstream OL the screening ~eans 180 where they will have immediate access to the screenin~ means.
Referring to FIG. 13, there has been illustrated a slightly modified system for introducing a lightly compacted feed mat 236 of non-bonded fibers into a 2-dimensional orming head 75 embodying the features of the present invention. As here shown, the system is essentially identical to that shown in FIG. 12 except that the feed mat 236 is fed into housing 172 tangentially rather than radially, with the mat entering just ~pstream of screen:ing means 180. Such an arrangement is believed to be highly advanta~eous to high capacity forming operations since the freshly infed fibers are afforded ~ax1mum screen access as they.are first entrained in the rotating aerated bed 186 of fibers.
While lightly compacted feed mat~ 236 of unbonded fibers may be fed directly into the for~ing head 75 of the present invention in the manner herein df~scribed in connection with FIGS. 12 and 13, those skilled in the art will appreciate that the fibers constituting the feed mat 236 can, if desired, be pre-opened and fed into the forming head in an air/fiber stream. Thus, as shown in FIG. 14, the lightly compacted feed mat 236 of non-bonded fibers is fed into the teeth on a full-width opening roll or lickerin 121 located at the lower end of full-width air conduit 170' and just above the inlet 171 to forming head 75~ The individualized fibers are combed out of the feed rnat 236 and entrained in the high velocity air stream immediately upstream of their entry point into housing 172; thereby eliminating the need for partitioned ducts of the type sho~n at 170 in FIG. 3 since th fibers are introduced into the 2~dimensional forming head 75 immediately after being combed out of the feed mat.
Thus, those skilled in the art will appreciate that the alternative arranqements described above in connection with FIGS. 12-14 will readily permit th~ formation of a feed mat having a contrclled cross-directional profile at any suitable re~ote location and in any known conventional manner and, thereafter, lightly compacting the feed mat to give it sufficient integrity to permit handling thereof and delivery to a remotely located 2-dimensional formin~ head 75 without disturbing the cross-directional profile of the feed mat, yet wherein the fibers are not compacted suf iciently to cause hydroge~n bonding thereof. As a consequence of attaining the foregoing objectives of the present invention, it is possible to locate multiple formin~ heads--e.g., the forming heads 75A-75N shown in FIG. 2--in relatively close, side-by-side proximity, thereby shortening foraminous ~orming wire runs. At the same time, it is not necessary to provide complex air-suspended fiber delivery systems which require special precautions to preclude generation of cross-flow forces.
In carrying out the invention, the rotox assembly 175 is preferably designed a) to minimize pumping action which tends to reduce the relative speed differential between the rotor bars 181 and the aerated bed 186, thus causing the fibers to move over and beyond the screening means 180, and ~ ~ 5~

b) so as to minimize mechanical action between the rotor bars 181 and both the housing 172 and screening means 180, which action tends to disintegrate fibers and aggregated fiher masses carried in the air stream and to generate pills. To this end, the rotor bars 181 are generally o~
relatively small cross-section--e ~ in the casc of the exemplary rectangular bars shvwn in FIG. 10, such bars are on the order 3/4" in radial height by 3/8" in thickness, such thickness dimension being desired only for purposes of structural integrity--and are mounted so as to provide a clearance between the outer edges of the bars 181 and the inner wall surface of the housing 172 and screening means 180 of from 0.10 inches to 0.25 inches and, preferably, from 0.18 inches to 0.20 inches, at least during transit of the rotor bars from the upstream edge 188 of screening means 180 through separator slot 179. In terms of "pumping action", therefore, the signficant bar area .is only 3/4" times the width in i~nches of the for~ing head 75. To avoid generation of cross-flow forces, it is important that the rotor bars 181 are continuous, extend the full width o~ the rotor chamber, and are oriented parallel to the axis of the rotor assembly 175.
In carrying out this aspect of the invention, the rotor housing 172 is preferably semi-cylindrical in cross-section 2S throughout at least the arcuate span ranging from the upstrea~ edge 188 of screening means 180 through the tangential separator slot 179, thereby insuring proper clearance between the rotor bars 181 and the inner periphery of both the screening means 180 and housing 172 as the rotor assembly 175 is driven rotationally. The remaining upper segment of the housing 172 may be of any desired shape, including P~ 3 s~bstantially semi-cylindrical, but is preferably relieved immediately adjacent the downstream edge of the inlet slot 171 as indicated at 183, thereby preventing the tendency of those fibers passing the separator slot 179 from impinging against the vertical edge 190 of inlet slot 171 and causing consequent blockage, or partial blockage, of the inlet slot.
Referring again to FIGS. 3, 12, 13 and 14, it will be apparent from the description as thus far set forth, that as fibers are introduced into the rotor housing 172--viz., in either lightly compacted form as shown in FIGS. 12 and 13 where the fibers comprising the mat are instantaneously individualized and dispersed upon entry into housin~ 172, or through inlet slot 171 in the form of an air-suspended fiber stream as shown in FIGS. 3 and 14-- the fibers are moved rapidly through the housing under the influenc~ of the air stream and movement of the rotor bars 181, thus forming the moving annular aerated bed 186 of fibers (FIG. 10) about the inner periphery of the housing wall. As the aerated bed--which contains individualized fibers, soft fiber flocs, nits and other aggregated fiber masses--passes over the screening means 180, some, but not al~, of the individualized fibers and soft fiber flocs pass through the screening ~eans into the for~ing zone 79, while the balance of the individualized fibers and soft fiber ~locs, together with nits and other aggregated fiber masses, pass over the screen without exiting from the rotor housing 172. The undesired pills, rice and nits- i.e., aggregated fiber masses--have a bulk density generally in excess of .2 g./cc. and tend to be separated along with some individualized fibers and soft fiher flocs from the aerated bed 186 at the tangential separator slot 179, with those separated materials being centrifugally expelled through th~ slot 179 where they are entrained in a recycle or separating air stream generated by any suitable means (not shown) coupled to manifold 191 with the air-suspended separated particles moving outward through a full-width discharge passage 192 coupled to separator slot 179 and, ultimately, to conduit 77 (FIG. 1). Such separation is aided by a positive air outflow fro~ housing 172 throuyh separator slot 179.
In keeping with the present invention, provision is made for insuring positive separation of undesired nits and aggregated fiber masses from individualized fibers and soft ~iber flocsl and for preventing movement of the latter through separator slot 179 to the full extent possible, thereby insuring that individualized fibers and soft fiber flocs are retained within rotor housing 172 and move with the aerated bed 186 back to the area of screening means 180 where such desirable materials have successive opportunities to pass through the screening means 180 into the forming zone 79. To accomplish this, a full-width classifying air jet 194 is pxovided upstream of the separator slot 179 and downstream of screening means 180; such air jet being positioned to introduce a full-width air stream generated by any conventional source (not shown) radially into rotor hou~ing 172 just ahead of the separator slot 173. As a 2~ consequence, the positive classifying air stream introduced radially into housing 172 through air jet 194 tends to divert individualized fibers and soft fiber flocs within the aerated bed 186 radially inward as a result of the relatively high drag coeLficients of such materials and their relatively low bulk density (whi.ch is generally on the order of less than .2 g~/cc.). Since the nits and aggregated fiber masses have a relatively high bulk density in excess of .2 g./cc.
and relatively low drag coefficients, the classifying air stream introduced through the full-width air jet 194 does not divert such materials to any significant extent and, therefore/ such undesired m~terials tend to be centrifugally expelled through the tangential separator slot 179. It has been found that the introduction of classifying air through the full-width classifying air jet 194 into housing 172 at pressures on the order of from 50" to 100" H2O and at volumes ranging from 1.5 to 2.5 ft.3/min./in. is adeguate for deflecting a siynificant portion of the individualized fibers and soft fiber flocs. The energy level of the classifying air jet is most conventiently controlled by adjusting its pressure.
In operation, it has been found that excellent results are obtained by limiting the amount of fibrous material removed from the system through separator slot 179 to less than 10% by weight and, preferably, to between 1% and 5% by weight, of the fibrous material introduced into the housin~
172 through inlet slot 171. Stated diLferently, at least 90% of the fibrous materials introduced and, preferably between 95~ and 99% thereof, ul~imately pass through screening means 180 into the forming zone 79 and are air-laid on the foraminous forming wire 80 without requiring any secondary hammer~illing operations and without being subjected to any significant mechanical disintegrating forces. The quantity of material separated may be controlled by the operator by varying the volume of recycle air supplied through manifold 191 and/or by adjusting the circumferential extent of full-width separator slot 179 in any suitable manner (not shown)O
Although the present invention has thus far been described in connection with the use of a conventional woven ' square-mesh screen 180A (E'IG. 6) for the screeni.ng means 180 shown diagra~natically in FIG. 3, it is preferred -that the screening means 180 take -the form of a high capacity slotted screen 180B--~
of the type shown in FIG~ 7. When utilizing a slotted type screen 180B with a 2-dimensional rotor assembly 175 mounted for rotation about a horizon-tal axis, it has heen found essential that the screen slots be oriented with their long dimensions parallel to the axis of the rotor assembly. When so oriented, individualized fibers tend to move through the screen slots while nits and aggregated fiber masses~e.g., the aggregated fiber masses 195 shown in FIG. 7--are precluded from passing through the screen since they are generally larger in size then the narrow dimensions of the slots which, preferably, do not exceed 0.1" open sPace from wire-to-wire in at least one direction.
However, when the slo-ts of a slotted screen 180B are oriented with their long dimensions perpendicular to a plane passing through the rotor axis as shown in FIG. 8, it has been :Eound that the screen -tends to rapidly plug--indeed, when operating under commercial production conditions, it has been found that the screen tends to becom~e completely plugged al~ost instantaneously. It is believed that such plugging acti.on results from the tendency of individual fibers to "staple" or "hair-pin" and othe~wise hang up or collect within the narrow confines at the end of each slot as best indicated at 196 in the lower right-hand corner of FIG. 8; and, as soon as a fe~ fibers have collec-ted, other .E.ibers and aggregated Eiber masses 195 a~r~ost instantaneously agglomerate on the screen as depicted in the balance of FIG. 8. This plugging phenomenon is more clearly visible upon reference to the photograph reproduced as FIG. 9--such photograph illustrating a slotted screen 180B wherein the slots are oriented at an angle of 45 to a plane passing through the rotor axis--and, under these conditions, the screen 180B plugged almost completely and instantaneously~
On the other hand, it has been found that a conventional woven square mesh screen of the type shown at 180A in FI~. 6, and a slotted screen 180B with the slots oriented as shown in FIG. 7, exhibit little or no tendency to plug under normal operating conditions. Rather, while individualized fibers still have a tendency to "staple" or "hair-pin", as indicated at 197 in FIGS. 6 and 7, there seems to be adequate time and room for the suspended fibers to disengage themselves from the screen; whereas in the arrangements shown in FIGS. 8 and 9, the suspended fibers tend to catch and congregate in the closely proximate confined corners of the screen slot and, as a result, ot:her fibers and aggregated fiber masses 195 xapidly accumulatel thus plugging the screen and rendering the system inoperative.
The exemplary system herein described has been depicted in F~GS. 3 and 4 as incl~lding a rotor assembly 175 having eight rotor bars 181. However, the number and/or shape of the rotor bars may be varied, provided that such modifications are consistent with mechanical stability and low rotor "pumping" action. That is, the rotor assembly 175 must be a dynamically balanced assembly and, therefore, it must include at least two rotor bars. However, it will be appreciated that it can include fewer or more than the eight bars illustrated in FIGS. 3 and 4--for exa~ple, excellent results have been achieved with a 4-bar rotor assembly of ~ii6~3 the type indicated at 175' in FIG. 5. On the other hand, care must be taken to insure that the nllmber of rotor bars employed--e.g., n rotor bars where n equals any whole integer greater than "1"--and the shape of the rotor bars are such that pumping action is minimized. Otherwise, the rotor assembly 175 will tend to sweep the aerated fiber bed 186 over and beyond the screening means 180 rather than permitting and, indeed, assisting fiber movement through the screening ~eans.
In the illustrative form of the invention, the ro~or bars 181 have a rectangular cross-section, and pumping action is minimized by keeping the effective rotor bar area relatively small--e.g., 3/4" times the length of the bars which extend across the full width of the rotor housing 172--and by spacing the bars apart circumferentially by 45 (there being eight egually spaced bars) and from the housing 172 by on the order of 0.18" to 0.20n~ However, the rotor bars 181 need not be rectangular in cross-section. Rather, they can be circular, vane-shaped, or of virtually any other desired cross-sectional configuration not inconsistent with the objective of minimizinq rotor pumping action. For example, rotor bars having a circular cross-section would, because of their shape, be even more effective than rectangular bars in t rms of minimizing rotor pumping action. However, the primary function of the rotor assembly as employed in the present invention is, as more fully described in Section I, page 49 et seq., infra~ of this specification, to lift individualized fihers, soft fiber flocs, and aggregated fiber masses off the surface of the former screening means and, thereby, to prevent plugging of the screen, to prevent layering of fibers on the screen, and to reopen apertures in the screen so as to permit passage of the air-suspended fiber stream therethrough. This desirable result is achieved by the negative pressure zones created in the wakes of the moving rotor bars; and, the negative pressure æones in the wakes of rotor bars having a rectangular cross-section have been found to be as effective for this purpose as those created by rotor bars of circular cross-section.
It is significant to a complete understanding of the present invention that one understand the difference between the primary function of the rotor assembly here provided--viz., to lift fibrous materials upwardly and off the screen or, stated differently, to momentarily disrupt passage of the air-suspended fiber stream through the screen--and that stated for conventional cylindrical rotor systems of the type disclosed, for ~ in the aforesaid J.D'A~ Clark patents where the rotor chamber functions as a "disintegrating and dispersing chamber" (See, e.~., col. 4, line 53, J~D'A. Clark U.S. Pat. No. 2,931,076)--viz., where the rotor blades mechanically act upon the fibrous materials to "disintegrate"
such materials and propel them hrough the screen.
H Forming Zone In keeping with the present invention, provision is made for insuring that individualized fibers passing through the screening means 180 shown in FIG. 3 are permitted to move directly to the foraminous forming wire 80 without being subjected to cross~flow forces, eddy currents or the like, thereby maintaining cross-directional control of the mass quantum of fibers delivered to the forming wire through the full width of forming zone 79. To accomplish this, provision i5 made for insuring that the upstream, downstream and side edges of the forming zone -i.e., the boundaries of _g~_ ~ ~5~

the zone 79 -are formed so as to define an enclosed forming zone and to thereby preclude intermixing of ambient air with the air/fiber stream exiting housing 172 through screening means 180. It has been found that the air/fiber stream exiting from housing 172 through screening means 180 does not exit radially but, rather, at an acute angle or along chordal lines or vectors which, on average, tend to intersect a line tangent to the mid-point of the screening means 180 at an included angle C~. In the exemplary forrn of the in~ention where the screening means 180 covers an arc of approximately 86--i.e., an arc extending clockwise as viewed in FIG. 3 from a point (indicated at 198 in FIG. 3) approximately 159 from the center of inlet slot 171 to a point 188 approximately 245 from the center of inlet slot 171--and, where an 8 bar rotor is be:ing op~rated at a rotor speed on the order of 1400 1450 RPM, it has been found that the angle CY is generally on the order of 11.
Consequently, the for~ing zone 79 is preferably provided with sidewalls (a portion of one such sidewall is shown at 199 in FIG. 3), a full-width downstream forming wall 200, and a generally parallel full-width upstream forming wall 201, which are respectively connected to rotor housing 172 at the downstream and upstream edges of screening means 180, and whicn xespectively lie in parallel planes which intersect a line tangent to the mid-point of the screening means 180 at included angles on the order of llQ. The upstrearn end of forming wall 201 is bent as indicated at 201A, 201B so as to form a shaped portion which genexally accommodates the air/fiber flow pattern exiting the upstream portion of screening means 180~ The walls 199, 200 and 201 serve to enclose the forming zone 79 and to thereby preclude disruption ~ ~ 5 ~ 3 of the air/fiber stream as a result of mixing between ambient air and the air/fiber stream. The enclosed forming zone 79 is preferably maintained at or near atmospheric pressure so as to prevent inrush and outrush of air and to thereby assist in precluding generation of cross-flow forces within the formin~ zone. Those skilled in the art will appreciate that angle C~ can vary with changes in oper~ting parameters such, for example, as changes in ro~or RPM. However, for operation at or near optimum conditions, it is believed that the angle __ will generally lie within the range of 5 to 20 and, preferably, will lie within the range of 8 to 15~
The lower edges of forming walls 200, 201 terminate slightly above the surface of foraminous ~orming wire 80--generally terminating on the order of from one-quarter inch to one and one-~uarter inches above the wire.
In the exemplary system shown in FIG. 3, when the angle CY
is on the order of 11 and when the forming zone 79 is positioned ov~r a horizontal forming ~urface 80, the upstream and downstream forming walls lie in planes which intersect the horizontally disposed forming surface 80 at included acute angles @ where ~ is on the order of 33. Howe~er, those skilled in the art will appreciate that the angular value of @ is not critical and can vary over a wide range dependant only upon the orientation of the forming surface 80 relative to the forming zone 79. For example, one advantage to positioning the forming 5urface 80 in a hoxizontal plane as shown in FIG. 3 is that an acute angle @ of approximately 33 tends to opti~ize the fiber deposition surface area of the forming surface 80. That is, assuming the forming walls 200, 201 to be parallel and spaced apart by approximately 9"
as measured in a direction normal to the walls, and assuming -46~

an angle ~ on the order of 33, the lower edges of the forming walls will be on the order of 16" apart in a horizontal plane just above the forming surface 80~ thereby providing a total fiber deposition area egual to 16l' times the width of the forming zone 79. Moreover, fiber deposition is optimized by virtue of the fact that the fibers approach the forming surface 80 at an acute angle @ of about 33 while moving in the direction of forming surface movement.
As the angle @ is increased--e.g., towards an angle of 90--the area of fiber deposition is reduced, approaching a total deposition surface area equal to only 9" times the width of the forming zone 79 under the assumed conditions;
and, at the same time, the vector component of fiber movement in the direction of movement of the forming sur~ace 80 is also reduced until at an angle ~ of 90, the fibers have no component of movement in the direction of forming surface movement. Such an increase in the angle ~ can be readily achieved by the simple expedient of mounting the forming surface 80 in an inclined plane -viz., inclined upwardly and towards the right as viewed in FIG. 30 Converslyr reduction in the angle ~ below 33 tends to further increase the total area of fiber de~osition on the forming surface 80.
~owever, it is believed that optimum results are attained where angle @ is on the order of 33 when angle Cr is on the order of 11.
The foregoing arrangement insures that the upstream and downstream boundaries of forming zone 79 generally coincide with the upstream and downstream boundaries of the air/fiber stream exiting the rotor housing 172 through screening means 180, consequently preventing mixing of ambient or room air with the moving air/fiber stream, minimizing impingement of l3 the air/fiber stream on the walls of the forming zone and, thereby preventing the setting up of eddy currents or other gross cross-flow forces which would interfere with the cross-directional mass quantu~ dispersion of fibers being conveyed through the forming zone 79 in the air strea~
across the full-width of the system. Moreover, since constraining walls 200, 201 are parallel, there is no tendency to decelerate the flow (as would be the case where the walls diverge). This fact aids in preventing eddy currents and other unwanted cross-flow forces~ There is, of course, some deceleration of the air/fiber stream as it exits the housing 172 through screening means 180; but, such deceleration occurs immediately upon exit from the screening means and produces only a fine scale turbulence effect which does not induce gross eddy currents or cross-flow forces.
The forming zone is preferably dimensioned so that under normal adjustment of variable system operating parameters, the velocity of the fiber/air stream through the for~ing zone is at least 20 f.p.s. and the fibers are capable of trav~rsing the entire length of the formlng zone 79 fro~
screen 180 to fo~ming wire 80 in not more than .1 second.
While the forming zone 79 in the exemplary form of the invention has been depicted as including physical walls 199, 2G0 and 201, those skilled in the art will appreciate that the boundary layer confining means could take other forms if desired without departing from the scope of the invention--for example, the confining boundary walls could take the form of air curtains (not shown). Moreover, in some cases it might be desirable to have the walls 200, 201 converge slightly so as to accelerate and, therefore, stabilize the flow.

~5i6~3 ~

I. Overall System Operation .._ Numerous system parameters may be varied i~l the operation of a forming system embodying thP features of the pre~ent invention in order to form an air-laid web of dry fibers having specific desired characteris~ics. Such variable parameters include, for ~ air-to-fiber ratio in aerated fiber bed 186 (which is, preferably 200-600 ft. /lb.
when working with cellulosic wood fibers/ and preferably 1000 to 3000 ft.3/lb., and perhaps higher, when working with cotton linters and relatively long synthetic fibers); air pressure within housing 172 (which preferably varies from +0.5" to +3.0" B2O); rotor speed (which preferably varies from 800 to 1800 RPM); the number, orientation and shape of rotor bars employed; the quantity of air supplied per foot of former width (which is, preferably, on the order of 1500 to 1650 ft.3/min. with an 8~bar rotor operating at 1432 RPM); the energy level of classifying air supplied (which preferably ranges from 1.5 to 2.5 Et.3/min./in. or, stated in term~ of pressure, preferably ranges from 50" to 100"
2Q H2O); recycle or separation balance (which is less than 10%
by weight of the fiber supplied and, pr~ferably, from 1% to 5~ by weight of the fiber suppliedj; screen design--viz., whether the screen is a woven squaxe-mesh screen or a slotted screen, the size of the screen openings (which range between .02" and 0.1" wire-to-wire open space in at least one direction and, preferably, range between .045" and .085" wire-to-wire open space in at least one direction), the wire diameter used tWhich preferably varies from on the order of .023" to .064") and, the percentage of open screen area (which is between 30% and 55% and, preferably, varies from 3~% to 46%); air pressure within the enclosed forming zone 79 (which is preferably atmospheric); as well as the physical dimensions of the forming head 75 (which, in the exemplary form of the invention, comprises a generally cylindrical hou~ing 172 having an inside diameter of 24").
Moreover, the rate of production of the web being formed can also be varied by altering numerous other system parameters such, ~ by ~ of example, as the number of forming heads 75 used, the position of the forming head relative to the forming wire-- e., whether the forming head is mounted in the cross~direction, the machine-direction, or at some angle therebetween--forming wire speed, and the type of fibers used~ Still other variable parameters under the control of the operator include the cross-directional profile of the feed mat delivered to the forming head 75. Thus, where it is desired to produce a web having a uniform cross-directional profile with an acceptable coefficient of variation, the lightly compacted feed mat--e.g.' feed mat 236 in FIGS. 12, 13 and 14 -preferably will have a uniform cross-directional profile in ter~s of the mass quantum of fibers present. On the ~her hand, if one desires to produce an air-laid web having a specific non-uniform cross-directional profile--e.g., an absorbent filler web having a central portion with a relatively high basis weight and ~arginal edges of relatively low basis weights~-it is merely necessary to form either a singla lightly compacted feed mat or multiple side-by-side lightly compacted feed mats having the requisite cross-directional profile and, ~ince the present system is substantially devoid of cross-directional forces, the cross-directional profile of the input feed mat(s~ will control the cross-directional profile of the air-laid web.
Recognizing the foregoing, let it be assumed that the operator wishes to fonn an air-laid web 60 one foot (1') in width (all ensuing assumptions are per one foot of width of thc forming head 75) ha~ing a controlled uniform cross-directional profile and a hasis weight of 17 lbs./2880 ft.2 Assume further:
a~ Air-to-fiber ratio within the aerated bed 186 of fibers equals 350 ft.3/lb.
b) Inlet slot 171 is 5 in circumferential width--i.e., the dimension from edge 190 (FrG. 3) to edge 2020 c) Rotor housing 172 is 24 I.D.
d) Rotor assembly 175 employs eight equally spaced rectangular rotor ~ars 181, each 3/4 in radial height by 3/8 in circumferential thickness and extending parallel to the axis of the rotor assembly continuously throughout the full width of rotor housing 172 and, each spaced from the rotor housing 172 by 0.18 .
e) Rotor assembly 175 is driven at 1432 RPM.
f) Rotor bar 181 tip velocity equals 150 f.p.s.
g) Relative velocity between the rotor bars 181 and the aerated bed 185 is approximately 70 f.p.s.
h) Screening means 180 defines an arc or 86, and has 40~ open area.
i) Separation and/or recycle through separator slot 179 comprises 5% ~y weight of fibrous materials supplied through inlet slot 171.
j) The quantity of classifying air introduced through air jet 194 is between 1.5 and 2.5 ft.3/minO/in. at pressures between 50" and ,~oo" H20.
k~ Forming walls 200, 201 are parallel and spaced 9" apart in a direction normal to the parallel walls 200, 201 and 16l' apart in a horizontal just above thc plane of the forming wire 80.
l) Forming wire speed equals 750 f.p.m.
All of the foregoing operating parameters are either fixed and known, or can be pre-set by the operator, exce~
for the relative velocity betw~en the rotor bars lB1 and the aerated bed 186 of fibers within the rotor housing 172. The actual speed of the aerated bed 186 is not known with certainty;
but, it is belie~ed to be substantially less than the rotor bar tip velocity of 150 f.p.s.; and, more particularly, it is believed to be on the order of half the tip velocity of the rotor bars 181. For convenience, it is here assumed to be approximately 80 f.p.s., an assumption believed to be reasonably accurate based upon observation of overall system behavior, thereby resulting in a relative velocity between the rotor bars 181 and the aerated bed 186 of approximately 70 f.p~s. (see assumption "g", ~E~
~ Accordingly, supply and velocity relationships within the foregoing exemplary system can be readily calculated as follows; and, such relationships ha~re been illustrated in FIG. 10:
17 x 750 = 4.43 lbs./min. -Rate of formation [I]
2880 of web 60.
4.43 x 1.05 = 4.65 lbs./min.--Rate of fiber [II]
supply through fiber inlet slot 2440 4.65 x 350 - 1627 ft. /min.-~Vol. of air sup- ~III]
plied through air inlet slot 171.
2 ~r x B6 = 1.5 ft.--Scre~n circumference. [IV~

1.5' x 1' x = 216 in.2--Screen area. [V]
144 in.2/ft.2 ~ 5~ ~a3 4.43 x 60 min.= 1.23 lbs./hr./in.2--Fiber [VI]
216 in.2 throughput of former screen 180.

1.5ft.2x 40~ = 0.6 ft. --Amount of open area in [VII]
screen 180.

1627 = 65 f.p.s.--Velocity of air stream [VIII]
55/12 x 60 entering rotor housing 172 through inlet slot 171.

1627= 18 f.p.s.--Velocity approaching [IX]
1.5 x 60the screen 180 (i.e., normal to the screen).

1627 = 45 f.p.s.--Velocity through screen [X]
0.6 x 60 openings.

10 1627 _= 36 f.p.s.--Velocity in forming ~XI]
9/12 x 60 zone 79.

1627- 20 f.p.s.--Velocity normal to [XII~
16712-x 60forming wire 80.

lS0 - 70= 80 f.p.s. -Velocity vector [XIII~
parallel to the scxeen 180.

~ o2 ~ l82 = 82 f.p.s.--Air velocity vector [XIV]
composite withln housing 172.
4.65 - 4.43 = .22 lbs./min.---~mount of fiber [XV]
removed through separator slot 179.
Ke~ping the foregoing supply and velocity relationships in mind, and upon consideration of FIGS. 10, 12, 13 and 14, it will be appreciated that the individualized fibers, soft fiber flocs, and any aggregated fiber masses present in the lightly compacted feed mat 236 tFIGS. 12, 13 and 14) will be instantaneously dispersed within the aerated bed 186 of fibers (FIG. 10) with esscntially the same cross-directional mass guantum relationship as they occupied in the lightly compacted feed mat 236. Under the assumed conditions, the air stream enters rotor housing 172 (FIG. 3) at approximately 65 f.p.s. ~Eg. VIII]~ while the ibers enter housing 172 (FIGS. 12, 13 and 14) at a fiber feed rate of 4.65 lbs./min.
~E~. II]. The vo~ume of air supplied to rotor housing 172--vlz., 1,627 ft. /min. [Eq. III] -is such that a positive pressure of approximately 1.5" H20 is maintained within the housing 1720 Since the forming zone 79 is maintained at atmospheric pressure, there exists a pressure drop on the order of 1.5" H20 across the screening means 180 through which the air-suspended fibers pass.
Although the air stream entering rotor housing 172 through inlet slot 171 i5 moving radially initially, rotation of the rotor assembly 175 (counterclockwise as viewed in FI~S. 3 and 103 tends to divert the fibers introduced through lG either inlet 244 (FIGS. 12 and 13) or inlet 171 (FIG. 14~

outwardly towards the periphery of housing 172 so as to form an annular aerated bed of fibers, as best illustrated at 186 in FIG. 10. Movement of the rotor bars 181 through the annular aerated bed 186 of fibers at a rotor bar tip velocity of 150 f.p.s. tends to accelerate the air stream from its entry velocity of 65 f.p.s. [Eq. VIII] to approximately 80 f.p.s., thus resulting in a relative velocity of 70 f.p.s.
between the rotor bars 181 and the aerated bed 186 of fibers.
However, because of the clearance of 0.18" between the rotor bars 181 and housing 172, and the relatively small effective area of the rotor bars, only minimal pumping action occurs and there is little or no tendency to roll fibers between the rotor bars 181 and either housing 172 or screening means 180. Therefore, there is little or no tendency to form pills; and, since only minimal mechanical disintegrating action occurs, curling or shortening of individualized fibers is essentially precluded. Rather, the rotor bars 181 sweep through the aerated bed 186 and across screening means 180, thus causing at least certain of the individuali7ed fibers and soft fiber flocs within the aerated bed 186 to move through the screening means--such air-suspended fibers -5~-~5~

have a velocity vector normal to the screening means 180 of approximately 18 f~p.s. [Eq. IX] and a composite velocity vector of approximately 82 f.p.s. [Eq. XIV] directed towards screening means 180 at an acute angle--while, at the same time, sweeping nits and aggregated fiber masses over and beyond the screening means 180.
Since the rotor bars 181 are moving through the aerated bed 186 of fibexs at a relative speed 70 f.p.s. faster than movement of the aerated bed, a negative suction zone ~f 1.7"
H2O is generated in the wake of each rotor bar 181, as best illustrated at 204 in FIG~ 10. Each such negative suction zone extends the full-width of the rotor housing 172 and is parallel to the axis oE the rotor assembly 175. In the case oF rotor bars having a circular cross-section (not shown), the negative suction generated would be on the order of 3O0ll H2O. In either case, the negative suction generated is suffic.ient to momentarily overcome the pressure drop of approximately 1.5" H2O across the screening means 180 and, as a c~nsequence, normal flow of the air/fiber stream through screening means 180 ceases momentarily in the region of the screen beneath the negative suction zone 204. The full-width negative suction zones 204 are, of course, also sweeping across the screening means 180 at the same velocity as the rotor bars 181--vi~., 150 f.p.sO-~and, as a consequence, the rapidly moving spaced, full-width negative s~ction zones 204 tend to establish spaced full-width lifting forces which serve two important functions--viz., the generated lifting forces i~ tend to lift individualized fibers and soft fiber flocs off screening means 180 in the wakes of the rotor bars across the full-width of rotor housing 172, thus preventing layering of fibers on the screen which tends to plug the screen openings and thus inhibits free move~ent of fibers through the screen; and ii), tend to lift nits and other aggregated fiber masses off the screening means 180 so as to facilitate their peripheral movement over and beyond the screening means and towards the full-width separator slot 1790 Such peripheral movement xesults from the movement of the annular aerated bed 186 and the sweeping action of the rotor bars 181.
It will be apparent that in the exemplary case employing an 8-bar rotor assembly 175 moving at 1432 RPM with a rotor bar tip veloci~y of approximately 150 f.p~s., approximately one hundred and ninety-one spaced full-width negative pressure zones 204 or negative impulsQs are generated per second, each of which sweep across the surface of the screening means 180 throughout the full-width thereof at a velocity equal to that of the rotor bars which generated such zones--vLz., 150 f.p.s. Moreover, each full-width negative pressure zone 204 persists over an arcuate span on the order of severai times the height of the rotor bars 181; although the actual distance through which the negative pressure zones 204 persist will vary dependent upon the specific operating parameters selected such, for example, as rotor speed, the relative speed differential between the rotor bars 181 and the aerated bed 186 of fibers, and the actual pressure conditions established. However, assuming a full-width negative pressure zone 204 persisting on the order of three times the height of the rotor bars 181 (which are here 3/4"
in height), then the arcuate extent x (FIG. 10) of the negative pressure zone 204 will be on the order of 2.25".
That is, each negative pressure zone 204 will span approximately 24~ of the circumferential space of approxi~ately 9.3"

between two adjacent rotor bars 181 (assuming an 8-bar rotor assembly 175 with an outside diameter of 23.54"--i.e., 24"
I.D. for housing 172 minus 2 x .18" clearance). Therefore, the balance of the circumferential region from the trailing edge of each zone 204 to the next succeeding rotor bar 181--viz., a circumferential arc ~ (FIG. 10) spanning approximately 76% of the circumferential distance between two adjacent rotor ~ars 181, or a distance of approximately 7"--constitutes a region of positive pressure drop of approximately 1.5" H2O.
Thus, it will be appreciated that in operation, approximately one hundred and ninety-one full-width negative pressure zones 204 alternating with an equal number of full-width zones of positive pressure drop which are each on the order of three times as extensive in duration (i.e., y - 3x), will sweep across screening means 180 each second. As indicated above, in those xapidly sweeping regions beneath the negative pressure zones 204, flow of the air/fiber stream through screening means 180 at 45 f.p.s. [Eq. X] ceases momentarily and, the fibrous material in those regions tends to be lifted off the screening means. Considering any given fixed area of th~ screening means 180, immediately upon passage of each ne.gative pressure zone 204, the positive pressure drop conditions of approximately 1.5" H2O are restored until the next rotor bar 181 passes thereover; thus permitting the individualized fibers and soft fiber flocs to again move toward the screening means 180 at a velocity of 18 f.p.s.
[Eg. IX3 normal to the screen and at a composite velocity vector of 82 f.p.s. [Eq. XIV] directed towards the screen at an acute angle and, ultimately, through the screen openings at approximately 45 fop~s~ [Eq. X]. Thus, the arrangement is such that plugging of the screen is effectively precluded, -57~

while individuali~ed fibers tend to dive end-wise through the screen openings in the regions of positive pressure drop, as best illustrated in FIG. 11~ e., in those regions between the trailing end of each full~width negative pressure zone 204 and the next succeeding rotor bar 181.
Those individualized fibers, soft fiber flocs, and aggregated fiber masses within the aerated bed 186 of fibers which do not pass through the screening means 180 the first time they are presented thereabove are swept over and beyond the screening means 180 and, thereafter, past classifying air jet 194 (FIG. 3). Under the assumed conditions, the individuali~ed fibers and soft fiber flocs tend to be diverted radially inward by the clas~ifying air jet ~94, while the undesired aggregated fiber masses are centrifugally and tangentially separated from the aerated bed 186 through full-width separator slot 179 at the rate of .22 lbs./min.
[Eq. XV]. Those individualized fibers and soft fiber flocs remaining in the aerated bed 186 after transit of separator slot 179 are then returned to the region overlying screening means 180, where thPy are ~uccessively acted upon by the rapid succession of pressure reversal conditions from full-width neqative ~ressure zones 204 alternatin~ with full-w~dth zones of positive pressure drops until all sucl~ materials pass through the screening means 180 into forming zone 79.
The air/fiber stream tends to exit from housing 172 non-radially throuyh screening means 180--indeed, as previously indicated, under the assumed operating conditions the aix/fiber stream tends to exi~ at an acute angle which, on average over the full extent of discharge opening 178, intersects a line tangent to the midpoint of screening means 180 at an included anyle CYof from 5 to 20 and, preferably, on the order of 11. The exiting air/Eiber stream decelerates almost immediately to approximately 36 f.p.s. [Eq. XIj within forming zone 79 and moves through the forming zone toward the foraminous forming wire 80 which is here moving at 750 ft./min. The fibers are air-laid or deposited on forming wire 80 at the rate of 4.43 1bs./min. ~Eq. I]--i.e., the difference between the rate of fiber supplied [Eq. II~
and the 5% of fibrous materials supplied which are separated and removed through separating slot 179--to form web 60.
The fibers deposited on the forming wire 80 are held firmly in position thereon as a result of suction box 126 (FIG~ 3) and its associated suction fan and ducting which serve to accomodate and remove the high volume of air supplied.
Following formation of web 60 on fora~inous forming wire 80 in the manner above described, the web, carried by foxming wire 80 at a speed of 750 ft./min., exits from beneath forming zone 79. An auxiliary suction box 128 may, i desixed, be pro~ided to insure ~hat the web remains flat on the forming wire as it exits from beneath forming zolle 79 where the web has been subjected to the holding action provided by suction box 126 which accomodates the ~ain air stream. The thus formed web 60 may then be further processed in the m~nner previously described in detail in Section D, pages 25-27, supra, of this specification. That is, and as best illustrated in FIG. 1, the web 60 is preferabl~
passed through calender rolls 129 where it is compacted lightly, and is then transferred to a conveyor belt 130.
The web is thereafter bonded in any suitablP bonding station 85, dried at a drying station 87, and formed into a storage roll 95 at a suitable storage station 90.
Those skilled in the art will appreciate that there has herein been described a typical set of operating parameters for foxming an air-laid web 60 of dry fibers at a reiatively high production speed--viz., 750 ft./min.--utilizing only a single forming head 75 (FIGS. 1 and 3). The exemplary web thus formed has a basis weight of 17 lbs./2883 ft.2 and is essentially devoid of nits and other aggregated fiber masses which have been removed through separator slot 179. Because the foxming head 75 and forming zone 79 have been designed so as to essentially preclude induced cross-flow forces and/or eddy c~rrents therein, the controlled mass quantum dispersion of fibers remains substantially unchanged throughout the system, thereby permitting the system to be scaled up or down to form air-laid webs of virtually any desired width and with a controlled coefficient of variation.
The web 60 deposited on forming wire 80 has more than adeguate integrity to permit rapid movement of the forming wire. Indeed, if one desires to furt;her increase productivity, n additional forming heads 75A-75N (FIG. 2--where n eguals any whole integerj may be utilized and the speed of fora~inous forming wire 80 may be increased by a factor equal to the number of separate orming heads used--e.g., under the assurned operating conditions, two heads would permit operation at 1,500 f.p.m.; three heads would permit operation at 2,250 f.p.m.; et cetera. Indeed, with the present invention, forming wire speed is no longer limited by the speed of web formation but, rather, by the speed of such subsequent processing steps as bonding in the web bonding station 85 (FIG. 1).
~xperimentation with air-laid, dry fiber, web forming systems embodying the features of the present invention has indicated that a wide range of results are attainable dependent upon the particular operating parameters selected.
Particularly important are such desiqn and operating parameters as: i3 rotor design; ii) rotor speed; iii) recycle or separation percentage, iv) screen design; and v), air-to-fiber ratio.
Of the foregoing, rotor design and screen design represent fixed parameters which, once selected, are not normally subject to operator control; whereas the remaining parameters may be varied over wide ranges to provide virtuall~ an infinite range of possible permutatlons and combinations which can~ and will, affect the characteristics of both the web produced and the rate of web productivity.
For example, as indicated in Section G at pages 42-43, of this specification, the rotor assembly 175 may be formed with n rotor bars 181 where n equals any whole integer greater than "1". However, it has been ascertained that fiber throughput--a limiting constraint when atte~pting to maximize productivity--is a function of rotor speed multiplied by the square root of the number of rotor bars employed--i.e., fiber throughput: J (RPM x ~k~ rotor bars 181). This relationship will, of course, vary with the particular screen employed; and, has been graphically illustrated in ~IG. 15 wherein fiber throughput in lbs./in./hr. tthe ordinate) has been plotted at various rotor speeds for each of a 2-bar, 4-bar, and 8-bar rotor assembly (the abscissa) when using both a coarse wire screen (lOx2.75; .047" wire dia.;
.059" screen opening; and 46.4% open screen area) and a fine wire screen (16x4; .035" wire dia.; .032" screen opening;
and 38.8% open screen area). As here shown, the circular points 205 are each representative of fiber throughput at a given rotor speed multiplied by the square root of "2" and are, therefore, indicative of throughput for a 2-bar rotor.

~5~ 3 Similarly, the triangular points 206 are each indicative of fiber throughput for a 4-bar rotor, while the square points 208 are indicative of fiber throughput or an 8-bar rotor.
Thus, the line 209 (FIG. 15) represents the Regressor, or "line-o~ best-fit", from which functional relationships between throughput and rotor speed can be determined when using a coarse wire screen of the type described above.
Similarly, the line 210 represents the same functional relationships when using a fine wire screen of the type described above. ~he data thus corroborates experimental findings that rotor RPM can be reduced while fiber throughput is maintained, or even increased, by going, ~or example, fxom a 4-bar rotor assembly 175' (FIG. 5) to an 8-bar rotor assembly 175 (FIG. 3). However, when using an 8-bar rotor assembly 175, the forming system seems to be less tolerant of mismatches between forming air and rotor speed; and, where such mismatches occur, fibers tend to accumulate on the sidewalls 193 o~ the forming zone 79. This is readily corrected by reducing rotor speed, normally by less than 10~, while maintaining forming air constant.
It has further been discovered that both nit le~els in the air-laid web 60, and fiber throughput in lbs./hr./in.2, are a function of the percentage o fibrous materials removed from ~he aerated bed 186 ~FIG. 1~) through the full~
width separator slot 179 (FIG. 3). Thus, referring to FIG. 16, line 211 graphically portrays the decreasing relationship nf nit level (the ordinate~ with increasing separation/recycle percentages (the abscissa); whiler at the same time, incr~asin~ separation/recycle percentages are accompanied by increased flber throughput in lbs./hr~/in.2 The graph is here representative o a system in which the -~2-6~3~ 3 rotor assembly 175'--a 4-bar rotor assembly--was driven at 1700 RPM and fibers were introduced into the rotor housing 172 ~FIGS. 3 and 14) in an air strea~ supplying air at approximately 106 ft.3/min./in. ~en the percentage of fibrous material separated tnrough separator slot 179 was 1%, fiber throughput was 0.62 lbsO/hr./in.2, and the air-laid web 60 exhibi$ed a nit level of "3"--a level deemed to be "poor", or border-line between acceptable and non-acceptable~
As hereinafter described in more detail, numerical nit levels range from l0" ("excellent"), to "1" ("good"), to "2"
("adequate"), to "3" ~"poor"~, to ~4" through "6" ("inadequate"
to "non-acceptable"). Such numerical ratings are subjective ratings based upon visual inspectio~ of the formed web 60 and subjective comparison thereof with pre-established 1~ standards.
As the pressure of ~he recycle air supplied thxough manifold 191 (FIG. 3) is decreased and~or as separator slot 17g is widened, thereby modulating the pressure conditions within discharge conduits 192 ~FIG~ 3) ~nd 77 (FIG. 1) which are maintained at a pressure level below that within the forming head 75 by means of a suction fan (not shown), the amount of fibrous material removed from rotor housing 172 through separator slot 179 is increased. Other means such, for exarnE~eL as venturi passeageways (not shown) could also be used to insure a controlled outflow of ~aterials through separator slot 179.
As the percentage of fibrous materials separated and/or recycled increases, nit level in the for~ed web 60 decxeases.
At the operating conditions under which FIG. 16 was prepared, when the separation percentage was increased to approximately 2.5%, a web having a nit level of "2" (i.e., an "adequate"

i6~3 nit level rating) was produced; at a separation percentage of 3%, the web's nit level decreased to approximately "1.6"
(i.eO ~ approximately midway between "adequate" and "good");
at a separation percentage of approximately 3.8%, nit level dropped to "1" ("good"); and, at a separation percentage of 5%, nit level dropped to approximately "0" ("excellent").
FIG. 19 also shows that the throughput of the forming system was increased from .62 lbs./hr./in.2 to .96 lbs./hr./in.2 while at the same time improving web quality from "poor" to "excellent". The total amount of fiber delivered to the forming system was increased by an even greater percentage to compensate for th~ increased removal of fiber and aggregate for recyclying. Productivity of the forming system was thus increased about 55% even though the screen was more heavily loaded with fiber; a very significant improvement These comparisons were made while running good quality pulp (Northern Softwood Xraft) having a low content of pulp lumps and being well fiberized in the hammermill. Poorer quality pulps or less effective fiberizatlon would require highex recycle rates of up to 10% to maintain an acceptable nit level in the web being formed. When making less critical webs or thick batts, nit level and recycle rate become less critical.
, Those skilled in the ar~ will, of course, appreciate that the experimental data set forth in FIG. 16 is only representative for one given set of operating parameters;
and, such data will vary with changes in, e.g., air-to-fiber ratio, type of fiber used, rotor speed, rotor design, air supply, and/or screen characteristics. However, experiments have indicated that recycle percentage is critical and, for cellulosic fibers, should exceed 1%, is preferably between about 1% and 5~, and should be less than on the order of 10~ .
It has been found that a 2-dimensional air-laid web forming system embodying features of the present invention will, when operating at a proper balance of fiber supply, forming air supply, and rotor speed, not only deliver maximum fiber throughput with minimum recycle, but, moreover, will exert a "healing effect'l on basis weight non-uniformities entering the forming head 75 (FIG. 3). That is, the screen 180, when prcperly loaded with a moving or transient aerated bed 186 of fibers (FIG. 10), acts as a membrane which tends to equalize or even out the passage of fibers through adjacent incremental widths of the screen. Such "healing effect" is only operative over distances of six inches (6"~ or less.
The "healing effect" will not function to even out gross irregularities in fiber basis weight over a wide expanse of former widths. Stated differently, a forming head 75 embodying the features of the present invention can even out either low or high non-uniformities of up to approximately three inches in widthl but it cannot even out gross non-uniformities of eight, twelve, or more, inches in width. It has further been found that if insufficient fiber loading occurs--i.e., if,the air-to-fiber ratio increases to substantially-abov~
600 ft.3/lb. when working, for example, with cellulosic wood fibers--then, i) the aerated bed 186 tends to be starved of fibers; ii) the 'healing effect" is reduced because of an inadequate transient membrane over the screen 180; and iii), input non-uniformities tend to be replicated in the finished web 60, thus deleteriously affecting the coefficient of variation of the finished web.
Standards have been established by the assignee of the present invention for subjectively classifying the nit :~56t~:~3 levels in air-laid webs formed of dry fibers. Such subjective standards are based upon visual inspection of the webs and comparison thereof with existing webs having differing nit levels which have been subjectively rated as "0", "1", "2", 5 1l3n ~ ~4~, "5" and "6 n . Photographs representative of webs having nit levels of "0", "1", "2", "3", "4", "5" and "6"
are here reproduced as FIGS. 17-23, respectively. FIG. 17 portrays a web having a nit level of lO" which is indicative of a web rated "excellent" and which is essentially free of nits and can, therefore, be u.sed for the highest quality tissue products. FIG. 18 portrays a web having a nit level of "1" which is indicative of a high ~uality web having only a minimal level cf nits and which is classified as "good".

Again, such a web is suitable for use in pre~ium grade, quality bath and~or facial tissues. FIG. 19 photoqraphically depicts a web having a nit level of "2" which is indicative of a web having a higher percentage of nits; yet which is "acceptable" for usage in quality bath and/or facial tissues.

FIG. 20 comprises a photograph of a web having a nit level of "3" which is considered "poor"~ but which is suitable for occasional usage in quality tissues or for usage in medium grade tissue products. FIGS. 21-23 photographically portray we~s having nit levels of "4", "5" and l'6", respectively, and are indicative of webs of inferior quality which are generally not suitable for usage in bath and/or facial tissues.
It will be appreciated by those skilled in the art that the present invention is uniguely suited for forming high quality webs having virtually any desired basis weight in lbs./2880 ft. at relatively high forming wire speeds.

Indeed, such extremely high productlvity rates may be readily set forth as follows: A web having a basis weight of (_~ (17 lbs./2880 ft.2) where "x" is equal to any desired whole or fractional value, can be produced at a forming wire 80 speed of 750 f.p.m. divided by "_"; or, (x) (17 lbs./2880 ft.2) = forming wire speed (750 f-p-m-) [XVI]
Similarly, where N forming heads 75A-75N are used (See, e.g., FIG. 2), the fore~oing relationship of web basis weight to forming wire 80 speed may be expressed as follows:

(_) (17 lbs./2880 ft.2) = forrni~g wire speed - [XVII]
Based on the experimental data reported herein it is evident that dramatic improvements in fiber throughput capacity for the forming head can be obtained irrespective of whether fibrous materials are delivered -to the forming head in bulk air-suspended form or~ as with the present invention, in the form of a lightly compacted feed rrat. Thus, fiber throughputs ranging from approximately .5 lbs./hr./in. 2 to in excess of 1.50 Lbs./hr./in.Z have been obtained when working with cellulosic wood fibers and a former 75 24" in diameter. Moreover, it should be noted that the foregoing range of from .5 lbs./hr./in. 2 to at least 1.50 lbs./hr./in. 2 reflects efforts made to form high quality, lightweight tissue and/or towel grade products. Where product quality in terms of, for example, nit level can be accepted at lower quality levels, it can be expected that fiber throughput will exceed, and may substantially exceed, the level of 1.50 lbs./hr./in.2. Similarly, when actual production experience has been acquired, it can be expected that fiber throughputs will be regularly achieved which do exceed the level of 1.50 lbs./hr./in.2, and such improved results may also be achieved when the system is scaled up in size--e.g., to rotor assemblies on the order of 36" in diameter. Therefore, the phrase "to at leact 1.50 lbs./hr./in.2" as used herein and in the appended claims is not intended to place an upper limit on throughput capacity.
Those skilled in the art will appreciate that there has herein been described a novel web forming system characteri~ed by its simplicity and lack of co~plex, space-consuming, fiber handling equipment; yetr which is effective in forming air laid webs of dry fibers at commercially acceptable production speeds irrespective of the basis weight of the web being formed. At the same time, the absence of cross-flow forces insures that the finished web possesses thedesired controlled C.D. profile which may be either uniform or non-uniform.

Claims (9)

1. The method of forming a quality web of air-laid dry fibers on a high speed production basis comprising the steps of:
a) forming a feed mat of fibers having a controlled cross-directional profile;
b) lightly compacting the feed mat to provide sufficient mat integrity to permit delivery to a remote point yet without sufficient compaction as to cause hydrogen bonding of the fibers;
c) delivering the lightly compacted feed mat to a forming head positioned over a forming surface;
d) dispersing the dry fibrous materials comprising the feed mat uniformly throughout forming head in a rapidly moving aerated bed of individualized fibers, soft fiber flocs and aggregated fiber masses and in an environment maintained substantially free of fiber grinding and disintegrating forces;
e) continuously separating a substantial portion of those fibrous materials delivered to the forming head having a bulk density in excess of .2g./cc. from the aerated bed so as to separate a substantial portion of the aggregated fiber masses from the aerated bed;
f) discharging such separated fibrous materials including the aggregated fiber masses contained therein from the forming head;
g) conveying the individualized fibers and soft fiber flocs from the forming head at a fiber throughput rate anywhere in the range of .5 lbs./hr./in.2 to at least 1.50 lbs./hr./in.2 through an enclosed forming zone towards the moving foraminous forming surface in a rapidly moving air stream;
h) air-laying the individualized fibers and soft fiber flocs on the moving foraminous forming surface so as to form an air-laid web of randomly oriented dry individualized fibers and soft fiber flocs on the forming surface; and, i) moving the foraminous forming surface at a controlled and selected speed so as to produce an air-laid web having and any specific desired basis weight in lbs./2880 ft.2 ranging from at least as low as 13 lbs./2880ft.2 to in excess of 40 lbs.2890 ft.2.

2. The method as set forth in claim 1 further characterized in that the individualized fibers and soft fiber flocs air-laid on the moving forming surface in step (h) are conveyed from the forming head in step (g) at a rate on the order of 1.23 lbs./hr./in.2, and the forming surface is moved at a control led and selected speed in step (i) so as to produce an air-laid web having a specific basis weight in lbs./
2880 ft.2 in accordance with the following set of operating parameters: (x) (17 lbs./2880 ft.2) at a forming surface speed on the order of (where x equals any whole or fractional number).

3. The method as set forth in claim 1 further characterized in that from 1% to 10% of the fibrous materials in the lightly compacted feed delivered in step ( c ) are separated from the aerated bed in step (e) and discharged from the forming head in step (f) and the air-laid web formed in step (h) has a nit level of from "0" to "3".

4. The method as set forth in claim 1 further characterized in that steps (d), (e), (g) and (h) are carried out in an environment essentially devoid of cross-flow forces so as to maintain cross directional control of the mass quantum of fibers being processed and of the cross-directional profile of the air-laid web produced.

5. The method as set forth in claim 2 further characterized in that steps (d), (e), (g) and (h) are carried out in an environment essentially devoid of cross-flow forces so as to maintain cross-directional control of the mass quantum of fibers being processed and of the cross-directional profile of the air-laid web produced.

6. The method as set forth in claim 4 further characterized in that the mass quantum dispersion of fibrous materials in the lightly compacted feed mat delivered to the forming head in step (c) is essentially uniform in cross-directional profile and the air-laid web produced has a cross-directional coefficient of variation in the range of zero to 5%.

7. The method as set forth in claim 5 further characterized in that the mass quantum dispersion of fibrous materials in the lightly compacted feed mat delivered to the forming head in step (c) is essentially uniform in cross-directional profile and the air-laid web produced has a cross-directional coefficient of variation in the range of zero to 5%.

8. The method as set forth in claim 5 further characterized in that the fibrous materials in the lightly compacted feed mat delivered in step (c) are pre-opened adjacent the forming head and are delivered into the forming head suspended in an air stream.

9. The method as set forth in claim 5 further characterized in that the fibrous materials in the lightly compacted feed mat delivered in step (c) are dispersed from the feed mat within the forming head.