US2581069A - Apparatus for producing airlaid fibrous webs - Google Patents

Description

Jan. 1, 1952 E. C. BERTOLET, JR

2,581,069 APPARATUS F'OR PRODUCINC AIRLAID FIBROUS WEBS Filed Sept. v24, 1945 5 Sheets-Sheet l Janl, 1952 E. c. BERToLE-r, .1R 2,581,069

' APPARATUS FOR PRODUCING AIRLAID FIBROUS WEBS lFilec Sept. 24, 1945 5 Sheets-Sheet 2 0 -f in .w

I I 00 l N N (ql I l 'v m g I L 1 R Jan. 1, 1952 E. C. BEQTOLET, JR 2,581,069

APPARATUS FOR PRODUCING AIRLAID FIBROUS WEBS 5 Sheets-Sheet 3 Filed Sept. 24, 1945 lygfgwf JML- l, 1952 v E. c. BERTOLET, JR I 2,581,069

APPARATUS FOR PRonucING AIRLAID FIBRoUs WEBS 5 Sheets-Sheet 4 Filed Sept. 24, 1945 Jan. 1, 1952 E. c. BERTOLET, JR

APPARATUS FOR PRODUCING AIRLAID FIBROUS WE Bib Filed sept. 24, 1945 5 Sheets-Sheet 5 Patented Jan. l, 1952 APPARATUS FOR PRODUCIN G AIRLAID FIBROUS Elmer C. Bertolet, Jr., Manheim, Pa., assignor to Raybestos-Manhattan, Inc., Passaic, N. J., a corporation of New Jersey Application September 24, 1945, Serial No. 618,247

6 Claims.

This invention relates to improvements in alr- Iaid fibrous web and to methods and apparatus for producing same. More particularly, this invention is concerned with the production of continuous self-sustaining fibrous sheets of predetermined uniform thickness formed from organic and/or inorganic fibers disposed in random orientation.

This invention further contemplates the provision of improved methods and apparatus for producing felt or paper like sheets from relatively long asbestos bers known in this art as spinning grade fibers, and without the necessity of admixing thereto certain percentages of organic fibers of the type usually employed for the purpose of carrying the fibers through conventional textile equipment such as carding machines. However, it is contemplated that various percentages of organic and/or inorganic fibers may admixed with the asbestos fibers for the purpose of modifying the end product for the following reasons:

1. To make les's expensive products through use of lower cost organic and/or inorganic bers.

2. To make a product with a lower specific gravity where light weight is an important factor.

3. The addition of organic fibers to add strength to the formed web to aid in processing.

4. The addition of fibers capable of coalescing and forming a bonded product either through activation by heat and/or solvents.

5. The addition of high tenacity bers which improve the physical properties of the finished product.

6. To make a product having improved electrical properties due to the use of bers having better electrical characteristics than absestos.

7. The use of asbestos in small quantities for of increasing bonding strength of laminates formed principally of high strength bers having poor bonding characteristics.

amide, or soy bean fibers such as Nylon and Soylon), alginates, casein Aralac," etc.

Web or sheet material produced by the meth- WEBS tively thin.

This invention further contemplates the provision of methods and apparatus adapted to pro- This invention further contemplates the promethod and apparatus emvarying the thickness In the use of other become aky due to choking up of the card clothing.

This invention embodies panying drawings wherein:

Fig.. 1 is a diagrammatic view, partly in side Fig. 6 is a diagrammatic view, partly in side elevation and partly in section, showing another modified form of apparatus for producing airlald fibrous web.

Fig. 7 is a diagrammatic view, partly in section and partly in elevation, showing another modified form of apparatus for forming airlald fibrous web.

Fig. 8 is a diagrammatic view, partly in section and partly in side elevation, showing another modified form of apparatus provided with means for spraying fibers prior to arranging same in the form of an airlald fibrous web.

Referring now to the drawings and more particularly to Figs. 1. 2 and 3 therein for a better understanding of this invention, one form of apparatus for producing airlaid fibrous web is shown as comprising a hopper I I adapted to contain the fibers prior to forming same into an airlaid web. The fibers are delivered from the hopper II to a conventional weighing pan I2 by means of a suitable conveyor I3. A feed conveyor I4 is disposed under the weighing pan I2 to receive and deliver the fiber between a pair of feed rolls I6. The rolls I6 deliver the fibers to a picker wheel I1 provided with teeth I3 which coact with mote knives I9 to open up the fibers and direct same into a deposition chamber I5 in the form of a mass of light fluffy fibers. The picker wheel I1. feed roll I6 and feed conveyor I4 are ldriven at suitable predetermined speeds by means of a motor 20 through suitable belts 2i, 22 and 23, and variable speed mechanism I for feed rolls and feed table.

'Ihe deposition chamber I5 is preferably in the form of an enclosed housing of gradually increasing area for the passage of the light iiuffy fibers. At the far end of the deposition chamber I from the picker wheel I1 is provided a sealed section of an air permeable conveyor belt 26, The conveyor belt 26 may be formed of any suitable material such as Fourdrinier wire, window screening, cloth, thin perforated metal, or other flexible air permeable material adapted to permit passage of air and to prevent the passage of entrained fibers.

A primary discharge hopper 21 is disposed below the picker wheel I1 to receive relatively heavy particles of material such as incompletely opened fibers, rocks, sand, and other foreign material having a specific gravity great enough to move downwardly through an upwardly flowing stream I of air entering the hopper through a plurality of air inlet openings 28. A suitable rotary discharge valve 29 is provided at the bottom of the hopper for discharging foreign material therefrom, and is driven by means of a motor 3| through a belt 32. A secondary discharge hopper 33 is provided within the deposition cham-ber I5 below the sealed portion of. the air permeable conveyor belt 26 to receive relatively heavy particles of material having a suiciently high specific gravity to fall downwardly out of an air stream passing through the sealed portion of the air permeable conveyor belt 26. This secondary discharge hopper 33 is also provided with a rotary discharge valve 34 driven by a motor 36 through a beit 31 for discharging accumulations of material from the hopper.

On the far side of the air permeable conveyor belt 26 from the .deposition chamber i5 is provided a subatmospheric air chamber 36 of sufficient size to produce an even and uniform velocity of air to be drawn through the sealed portion of the conveyor belt 26 when same is running free of fibrous material. Preferably the transverse sectional area of the sub-atmospheric chamber 3l should be at least double the area of the nozzle portion 39. In order to reduce turbulence in the air stream passing through the nozzle 39, said nozzle may be provided with vertically and horizontally arranged partitions 4| to provide a plurality of relatively small air passages 42 leading from the belt 26 to the chamber 38. If desired, suitable control dampers 43 may be pivotally mounted at the outlet ends of said passages 42 to further control passage of air through selected portions of the air permeable conveyor belt 26.

An air conduit 44 leads from the sub-atmospheric chamber 36 to an exhaust fan 45 driven by a motor 46 through a beit 41 and variable speed pulleys 50. The sealed portion of the conveyor belt 26 is enclosed at the sides by means of sealing strips 48 which may be formed of sheet rubber or rubberized material having their edges secured at 49 to the adjacent side walls of the deposition chamber I5 and nozzle 39, and having their free edges disposed in sliding engagement with conveyor belt 26.

Two pairs of rubber rolls 5I and 52 serve as end seals for the sealed portion of the conveyor belt 26. Rolls 5I and 52 are preferably formed of soft rubber to prevent the leakage of air into the interior of the deposition chamber I5 or nozzie 39.

The conveyor belt 26 extends from the rubber rolls 5I and 52 around suitable idler rolls 53, a driving roll 54. and a guide mechanism of the conventional type employed in the paper industry for'guiding Fourdrinier belts. The driving roll 54 is driven by a motor 56 through a belt 51, variable speed drive 58, and a belt 59. A rotary brush driven by a motor M is used to remove extraneous fibers adhering to belt on its return run.

In forming airlald fibrous web by means of the apparatus thus shown and described, the fibers are delivered from the hopper II to the weighing pan I2 by means of the conveyor I3. vThe fibers are distributed from the weighing pan I2 onto the conveyor I4 for delivery to and through the feed rolls I6 for iiberizing and iiuiiing action by the picker wheel I1 and mote knives I9. By means of the exhaust fan 45. air is drawn through the vents 28 upwardly through the primary discharge chamber 21, the deposition chamber I5, thence through the sealed portion of the conveyor belt 26, nozzle 39, sub-atmospheric chamber 38, and conduit 44 to be exhausted to the atmosphere through the outlet port of the exhaust fan 45.

Relatively heavy particles of material, such as incompletely opened fibers. rocks, grit, etc., are adapted to move downwardly through the primary discharge chamber 21 and discharge therefrom by means of the rotary valve 29. The relatively light fluffed up fibers are adapted to be carried by the air stream from the picker wheel I1 into contact with the sealed portion of the conveyor belt 26, and it will be noted that the deposition chamber I5 should be of suiiicient length to prevent turbulence within the air stream in order to prevent "hailing" or entanglement of the suspended fibers prior to their engagement against the conveyor belt 26. A secondary discharge chamber 33 is provided below the sealed portion of the conveyor belt 26 to receive relatively heavy particles of incompletely opened fibers, dirt or other foreign material falling from the air stream. which foreign material is discharged from the chamber by means of the rotary valve 34.

During the operation of the apparatus, the sub-atmospheric pressure within the chamber 38 a lweb of heterogeneously arranged fibers for transfer onto a porous conveyor belt 6|. By careful control of the velocity of the air stream passing through the deposition chamber I5, it will be noted that only fibers of the desired openness will be deposited upon the conveyor belt 26. It will also be noted that this apparatus is adapted to produce a fibrous web consisting of the rnost` completely opened fibers.

In the use of this apparatus, airlaid fibrous web 25 may be formed of the desired thickness by merely changing the linear speed of the conveyor belt 26. It is also possible to vary the thickness of the web by changing the exhaust fan speed with resultant change of air velocity, air volume. and static pressure. It may at times be found desirable to vary both the fan speed and the speed of the conveyor belt 36 in order to obtain the desired thickness of web. These changes however are relatively simple to accomplish and may be made while the apparatus is in operation.

It will be noted that a change in the linear speed of the conveyor belt 26 results in a variation in the interval of time during which a selected point on the sealed portion of the belt is exposed to receive fibers carried in the air stream. In this manner of adjustment, production speed on a weight basis remains relatively constant as In the use of carding machinery there is a re1- atively fixed speed for the withdrawal of a smooth web as the Withdrawal has to be synchronized with the speed of formation of the web. Therefore a reduction in withdrawal speed usually requires a decrease in feed of the uncarded asbestos fibers. In addition. it is necessary to make careful adjustment of the feed in order to obtain different weights or thicknesses of aweb from a card. The range of thicknesses in weights of fibrous web from a card are also limited as webs below .002 or .003 inch are diicult to handle due to their lacy structure, and brous webs above .005 or .006 inch have a tendency to become flaky due to choking up of the card clothing which results in poorly carded fiber.

It has been determined that the ultimate thickness of the web formed at a definite speed and at predetermined static pressure is also dependent upon the mesh size or air spaces provided in the conveyor belt 26. The degree of openness of sultant decrease in attraction of the fibers toward the conveyor belt 26. When the conveyor belt 26 travels at a reduced speed to allow an equilibrium condition to be obtained, the web will build up to a thickness commensurate with the available static pressure in the sub-atmospheric chamber 38, after which little or no additional fiber will be added to the web. In other words, for a given quality of fiber, the thickness of the web can be governed by measurement of the static pressure in the subatmospheric chamber 38.

The airlaid fibrous web is delivered from the air permeable conveyor belt 26 onto an endless porous saturator belt 6I which may be formed of woolen felt, wire mesh or the like. The belt 6| carries the fibrous web around a cylindrical mold roll 62 disposed within a trough-shaped solution pan 63 and thence around a couch roll 64 for delivery between a pair of compression rolls 66 and 61. The compression roll 66 is driven from the motor 56 by means of a belt 68. The trough shaped pan 63 is filled with a suitable sizing or bonding solution to be applied to the fibrous web, and the excess vsizing or bonding material is removed from the saturated fibrous web during its passage between compression rolls 66 and 61. The roll 66 is preferably formed of semi-hard rubber, and the roll 61 is preferably formed of steel or other hard-surfaced material. These compression rolls thus act to remove the excess sizing or bonding solution from the fibrous web without crushing or distorting same, due to the slight resiliency afforded by the rubber surfaced roll 66.

The sizing or bonding solution preferably comprises a dilute water solution or suspension of boiled (swollen) tapioca flour, although other types of starches, dextrines, glues, resinous suspensions or solutions such as polyvinyl alcohol, methylv cellulose, melamine formaldehyde, urea formaldehyde, phenol formaldehyde, latex (natural or synthetic), sodium silicates, and the like may be used depending on the properties desired for bonding and sizing, although solutions up to 5% (by weight) concentration may be employed when greater stiffness and less porosity of the sheet is desired. In the use of other binders, the concentration of the solution may vary considerr ably from those given above for tapioca flour,

the concentration used being determined by the qualities of the sizing or adhesive as well as the properties desired in the finished product.

Where tapioca flour is used in 1/2% to 1% solution for sizing, the resultant sheet (after evaporation of the water carrier) is compact. densiled, self-sustaining, and also of good absorptive characteristics with the fibers heterogeneously arranged in accordance with the method herein set forth. The product differs from waterlaid papers in that long fibers are present, which it is believed has not heretofore been possible on paper making equipment due to balling up or entanglement of the fibers in the beater or other slurry making equipment. The present product also differs from carded webs in that there is no parallelism of the fibers in the finished sheet. While thermore, a web formed of relatively long asbestos fibers by means of the present method and apparatus also differs from a carded asbestos web in that the organic fibers usually employed to carry the asbestos fibers through the process are omitted. This feature results in a material having higher heat resistance and lower moisture absorption due to its completely inorganic fibrous base.

After the sizing and bonding solution has been applied to the fibrous web, and the excess bonding or sizing material has been removed from the web by means of the compression rolls 66 and 61, thegweb is transferred to a plurality of rolls 69 formingpart of a drier for removing the solvent from the sizing or bonding adhesive provided on the fibrous sheet. The drier may be of any conventional type such as steam heated drums, a convection type oven, a forced convection oven. infra-red drier, or the like. The drier preferably embodies dry-cans of the type used in the textile industry. After the sheet has been passed through the drier, it is rolled up around a roll 1 I.

After a fibrous web has been formed on the type of apparatus illustrated in Fig. l, it may be passed through additional chambers of the same or similar construction for the deposition of other fibers upon the surface of the web by means of the apparatus illustrated in Fig. 4 of the drawings. For example, these additional fibers may consist of very short asbestos fibers for filling all surface irregularities in the web to provide a finished product having a smooth surface approximating a surface of conventional waterlaid asbestos paper. By employing the type of apparatus illustrated in Fig. 4, it is also possible to build up laminae of different classifications of fibers. For example, a primary web of cotton may be formed on the foraminous belt 26 within the first deposition chamber, and then a rayon web deposited on the surface of the primary cotton web within the second deposition chamber. In Fig. 4, the primary web forming apparatus is designated as A and the secondary web forming apparatus is designated as B. The primary web forming apparatus A is shown as comprising a feed conveyor lla to receive and deliver the fiber between a pair of feed rolls lGa which act to direct the fibers to a picker wheel IIa provided with teeth which coact with mote knives lSa to open up the fibers and to direct same into a deposition chamber |50. in the form of a mass of light, fluffy fibers. At the far end of the deposition chamber l5a from the picker wheel Ila is provided a sealed section of an air permeable conveyor belt 26a, the belt being formed of any suitable material adapted to permit passage of air and to prevent the passage of entrained fibers.

A primary discharge hopper 21a is disposed below the picker wheel Ha to receive relatively heavy particles of material, such as incompletely opened fibers. sand, etc. having a specific gravity great enough to move downwardly through an upwardly-flowing stream of air entering the hopper through a plurality of air inlet openings 28a. A lsecondary discharge hopper 33a is provided within the deposition chamber |5a below the sealed portion of the belt 26a to receive relatively heavy particles of material falling by gravity downwardly out of the air stream as the latter passes through the sealed portion of the conveyor 26a. A subatmospheric air chamber 38a is provided to produce an even and uniform velocity of air through the sealed portion of the conveyor belt 26a when the latter is running free of fibrous material. Two pairs of rubber rolls 51a and 52a serve as end seals for the sealed portion of the conveyor belt 26a. The air inlet side of the chamber 38a is preferably provided with a plurality of relatively small air passages 42a provided with suitable control dampers 43a.

The secondary web forming apparatus B is shown as comprising a feed conveyor Hb to receive and deliver the fiber between a pair of feed rolls 1Gb which act to direct the fibers to a picker wheel IIb provided with teeth which coact with mote knives lSb to open up the fibers and to direct same into a deposition chamber 15b in the form of a mass of light, fiuiy fibers. At the far end of the deposition chamber ISb from the picker wheel llb is provided a sealed section of the air permeable conveyor belt 26a.

.A primary discharge hopper 21h is disposed below the picker wheel lib to receive relatively heavy particles of material, such as incompletely opened fibers, sand, etc., having a specific gravity great enough to move downwardly through an upwardly-flowing stream of air entering the hopper through a plurality of air inlet openings 28h. A secondary discharge hopper 33h is provided within the deposition chamber l5b below the sealed portion of the belt 26a to receive relatively heavy particles of material falling by gravity downwardly out of the air stream as the latter passes through the sealed portion of the conveyor 26a. A subatmospheric air chamber 38h is provided to produce an even and uniform velocity of air through the sealed portion of the conveyor belt 28a when the latter is running free of fibrous material. Two pairs of rubber rolls Sib and 52h serve as end seals for the sealed portion of the conveyor belt 26a. The air inlet side of the chamber 38h is preferably provided with a plurality of relatively small air passages 42h provided with suitable control dampers 43h.

It will further be noted that the process and apparatus shown and described in connection with Fig. i of the drawings is also adaptable for use in cleaning fibrous materials. By embodying the principles of this invention, fibers of desired openness may be selectively deposited on the endless conveyor belt 26, free of dirt, splints, open particles, etc., to provide a fibrous web of well opened fibers suitable for textile uses such as carding, spinning, and drafting into yarns of high quality. When the apparatus disclosed in Fig. 1 of the drawings is employed in the manner thus described, the fibrous web will not, of course, be transferred to the saturating equipment shown in Fig. 2 of the drawings.

Fig. 5 illustrates a, modified form of this invention which is similar to the form heretofore described in connection with Fig. 1, but in which the secondary dirt discharge chamber 33 is omitted from the apparatus. This form of the invention is shown as comprising a feed conveyor Mc to deliver fiber between a pair of feed rolls ISc which act to transfer the fiber to a picker wheel llc provided with teeth to coact with mote knives l9c to open up the bers and direct same into a deposition chamber 16. An air permeable conveyor belt 26o is provided at the f ar end of the deposition chamber from the picker wheel llc, the belt being formed of flexible, air permeable material such as cloth, window screening, or the like. adapted to permit the passage of air therethrough and to prevent the passage of fibers. A discharge hopper 21e is disposed below the picker wheel |1c to receive foreign material such as incompletely opened fibers, rocks, sand, etc. The hopper 21o is provided with a plurality of air inlet openings 28e to direct air upwardly through the hopper. A subatmospheric air chamber 38o is provided on the far side of the belt 26e from the deposition chamber I6 to 75 produce an even and uniform velocity of air through the sealed portion of the conveyor belt 28e when the latter is running free of fibrous In order to reduce turbulence in the air stream passing through the nozzle portion of the chamber 38e, the nozzle may be provided with a plurality of relatively small air passages 2c provided with control dampers 43e. Two pairs of rubber rolls 5| c and 52e are provided to engage the conveyor belt 26e and to prevent leakage of air into the interior of the deposition chamber 16 or the chamber 38e. In this form of the invention. all of the bers carried by the air stream passing through the deposition chamber 16 are deposited uponA the enclosed portion of the foraminous conveyor belt 26o. Apparatus of this type is adapted for use in producing a ings 28d are provided at the upper end of the vertically disposed portion 18. This form of the invention is shown as comprising a feed conveyor Hd to deliver bers between a pair of feed rolls IGd, the rolls acting to direct the bers to a picker A discharge hopper 21d is disposed below the picker wheel I'Id to receive relatively heavy particles of material such as incompletely opened bers. rocks, sand, and other foreign material having a belt 26d is provided at the lower end of the vertical portion 18 of the deposition chamber to receive `the bers passing downwardly therethrough and is engaged between two pairs of rubber seating rolls 5l e and 52e. Below the endbrous material. The chamber 38d is provided with relatively small air passages 42d controlled by suitable dampers 43d. In this form of the invention, it will be noted that the ber is deposited upon the upper surface of the conveyor belt 26d by gravity, with a suction applied to the underside of the conveyor belt to aid in directing the fibers to the thinner spots of the web during formation of same. Due to the omission of the secondary discharge chamber illustrated at 33 in of apparatus heretofore shown and described in connection with Fig. l in the drawings.

Fig. 7 illustrates another modmed form ol this invention in which the fiber isv directed through a.

relatively heavy particles of material, such as lncompletely opened bers, rocks, sand. and other foreign material having a specific gravity The chamber 38e is provided with small air passageways 42e controlled by dampers 43e. In this form of the invention, a plurality This form of apparatus will have the lowest production rate as it utilizes the lowest percentage of bers fed into the apparatus.

made with standard short fibered waterlaid asbestos paper absorbs approximately 0.80% water in 24 hours. A standard woven asbestos cloth laminate absorbs approximately 1.00% water in 24 hours. A web formed in accordance with the present invention absorbs approximately 0.25% to 0.30% water in 24 hours with an increase to approximately 0.60% absorption after ten days of immersion in water at room temperature. The moisture stability of the present sheet material appears to far exceed that of other well known same is subjected to heat and high pressures it embodies excellent flow characteristics to allow the molding of parts with uneven contours and variable cross section without the necessity for maceratlng the sheet as is ordinarily necessary with long iibered molding fillers of woven structure.

Another use for the present type of sheet material resides in impregnation of the basic sheet with various varnishes and/or resinous materials to form electrical insulating tapes. Tapes of this type may be produced so that the relatively small voids between the longer fibers are filled with shorter fibers, thus resulting in a tape of uniform and smooth surface appearance and, after impregnation, results in a tape of good electrical properties, high heat resistance, low moisture absorption, and other desirable characteristics.

Fig. 8 in the drawings illustrates another modified form of this invention in which the apparatus is constructed for use in spraying the individually suspended fibers with a suitable resin of the thermo-setting type to obtain coated fibers containing from 30% to 60% by weight of resin. This form of the invention is shown as comprising an endless feed conveyor I4] tc deliver fibers between a pair of feed rolls which act to direct the fibers to a picker wheel Il! provided with teeth which coact with mote knives I9] to open up the fibers and direct same into a deposition chamber 9|. The apparatus illustrated comprises a horizontally disposed passage 9i leading from the picker wheel llf to anI inverted U- shaped conduit 92. A stream of airis drawn into the passage 9| through air vents B3 provided in a primary dirt discharge chamber 94 to draw the fluied up material from the picker wheel through the passage 9|, and thence through the passage 92 for distribution onto a oraminous conveyorbelt 95. A secondary dirt discharge chamber 95 is provided at one end of the conduit 92 and provided with shutters `lllll for controlling air openings 91. The air is drawn through the openings S3 and 91 for passage through the conduit 92, the roraminous conveyor belt 95, the sub-atmospheric chamber 38f and conduit by means of the type of power driven blower 45 illustrated in Fig. 2 of the drawings. During downward movement of the fibers through the conduit 92, they are sprayed with a suitable resin of the thermo-setting type, the liquefied resin being directed through conduit 98 and outwardly through a suitable spray nozzle S9. After the fibers have been coated with the resin, they are deposited upon the foraminous conveyor belt 95, dried by means of oven |02, and discharged therefrom into a suitable storage container IM. The oven |02 may embody any suitable type of heating means such as steam heating coils, infra-red circulating convection type, etc. A scraper or doctor blade |03 aids in removing resin coated fibers from the belt. Resinous coated fibers of this type, when subjected to predetermined heat and pressures, form a strong compact plastic mass somewhat similar to that obtained through molding of the impregnated sheets as heretofore set forth. Resinous coated fiber of this type is adapted for such practical uses as straight plastics molding, or for incorporation into friction materials where the fiber coating serves to increase frictional characteristics or wearing qualities. In the operation of this apparatus, it may be found to be desirable to provide adjustable shutters 90 for controlling the passage of air through the air inlet openings 53. It is contemplated that the use of adjustable shutters 30 may prove to be desirable for controlling the flow of air through the air inlet openings 28 illustrated in Figs. l, 4, 5, 6 and 7. Two pairs of rubber rolls 5|! and 52j serve as end wheels for the conveyor belt B5. The subatmospheric chamber 30j is also preferably provided with relatively small air passages 421* provided with control shutters 43j.

While this invention has been shown in several forms, it is obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit and scope of the claimed invention.

I claim as my invention:

l. In an apparatus for forming airlaid fibrous web, a pair of deposition chambers having air inlet and outlet openings, a continuous foraminous conveyor belt for movement past the air outiet openings of said deposition chambers, blower means for drawing a stream of air through each deposition chamber and said conveyor belt, fiber- 'izing means disposed at the air inlet ends of each of said deposition chambers for opening the fibrous material and projecting same into their respective air streams in a fluffed-up condition for distribution upon said conveyor belt as same vmoves past the respective air outlet openings of said deposition chambers, a dirt discharge chamber formed in each deposition chamber below said iiberizing means to receive relatively heavy particles of material dropping by gravity from a fiber charged air stream, said air inlet openings for said deposition chambers being formed in the side walls defining the dirt discharge chambers.

2. In an apparatus for forming airlaid brous web, a pair of deposition chambers having air inlet and outlet openings, a continuous foraminous conveyor belt for movement past the air outlet openings of said deposition chambers, blower means for drawing a stream of air through each deposition chamber and said conveyor belt, flberizing means disposed at the air inlet ends of each of said deposition chambers for opening the fibrous material and projecting same into their respective air streams in a fiuffed-up condition for distribution upon said conveyor belt as same moves past the respective air outlet openings of said deposition chambers, a dirt discharge chamber formed in each deposition chamber below said iiberizing means to receive relatively heavy particles of material dropping by gravity from a ber charged air stream, safd air inlet openings'for said deposition chambers being formed in the side walls dening the dirt discharge chambers, and means for controlling the ow of air through said air inlet openings.

3. In an apparatus for forming airlaid brous web, a pair of deposition chambers having air inlet and outlet openings, a continuous foraminous conveyor belt for movement past the air outlet openings of said deposition chambers, blower means for drawing a stream of air through each deposition chamber and said conveyor belt, fibereach of said deposition chambers for opening the brous material and projecting same into their respective air streams in a fiuiTed-up condition for distribution upon said conveyor belt as same moves past the respective air outlet openings of said deposition chambers, a dirt discharge chamber formed in each deposition chamber below said berizing means to receive relatively heavy particles of material dropping by gravity from a ber charged air stream, and a secondary dirt discharge chamber formed in each of said deposition chambers below their respective air outlet openings to receive relatively heavy particles of material dropping by gravity from their respective fiber charged air streams.

their respective air streams in a fiuiTed-up condition for distribution upon said conveyor belt as same moves past the respective air outlet openings of said deposition chambers, a dirt discharge material dropping by gravity from their respective ber charged air streams, and a sub-atmospheric chamber for creating a sub-atmospheric pressure condition between each of the air outlet openings oi said deposition chambers and said blowermeans.

5. In an apparatus for forming airlaid fibrous web, a deposition chamber having an inlet and ous conveyor belt having an air-sealed portion thereof interposed between said deposition champlurality of passageways at the inlet end of said sub-atmospheric chamber, control means assoelated with each of said passageways to selectively control the iiow of air therethrough, iiberizing means for opening the fibrous material and projecting same laterally into the upper end of said dirt discharge chamber to cause the open fibers to be carried upwardly and thence laterally by said air stream for passage through said deposition chamber, whereby said open bers will be distributed in heterogeneous interlocking arrangement upon the air-sealed portion of said conveyor belt, said dirt discharge chamber being formed to receive relatively`heavy particles of incompletely open bers and foreign material falling thereinto from the ber-charged air stream.

6. In an apparatus for forming airlaid brous web, a deposition chamber having inlet and outlet openings, said deposition chamber having a dirt discharge chamber leading downwardly from said deposition chamber inlet opening, a continuous foraminous conveyor belt for movement past the outlet opening of said deposition chamber, blower means for drawing a stream osition chamber and conveyor belt, fiberizing means disposed at the juncture of said dirt discharge chamber and the inlet end of said depcharge chamber to cause the open bers to be carried upwardly and thence laterally for distribution upon the portion of the conveyor belt openings of said dirt discharge chamber, a subatmospheric chamber for creating a sub-atmospheric pressure condition between the outlet opening of the deposition chamber and said blower means, means dening a plurality of pas- ELMER C. BERTOLET, JR.

REFERENCES CITED The following references are oi' record in the le of this patent:

UNITED STATES PATENTS Number Name Date 258,397 Faulkner May 23, 1882 304,527 Jarrell Sept. 2, 1884 480,588 Kellner Aug. 9, 1892 593,620 Sweet Nov. 16, 1897 1,026,432 Dey May 14, 1912 1,284,922 O'Connell Nov. 12, 1918 1,761,493 Rogers June 3, 1930 1,886,044 Quinn et al. Nov. 1, 1932 2,086,592 Williams July 13, 1937 2,122,472 Hurst et al July 5, 1938 2,152,901 Manning Apr. 4, 1939 2,222,633 Sheesley Nov. 26, 1940 2,389,024 Brownlee Nov. 13, 1945 FOREIGN PATENTS Number Country Date 376,598 Germany May 31, 1923 422,226 Great Britain Jan. 8, 1935

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