US3002849A

US3002849A - Method and apparatus for forming nonwoven fabric

Info

Publication number: US3002849A
Application number: US589697A
Authority: US
Inventors: Harmon Carlyle; Charles H Plummer; Joseph H Smith
Original assignee: Chicopee Manufacturing Corp
Current assignee: Chicopee Manufacturing Corp
Priority date: 1956-06-06
Filing date: 1956-06-06
Publication date: 1961-10-03
Anticipated expiration: 1978-10-03
Also published as: DE1288056B

Description

Oct. 3, 1961 c. HARMON ET A1. 3,002,849

METHOD AND APPARATUS FOR FORMING NoNwovEN FABRIC Filed June 6, 1956 3 Sheets-Sheet l w 'A l\ t\ N A A w MWI- R \9 *u o o ATTORNEY Oct. 3, 1961 c. HARMoN ET AL 3,002,849

METHOD AND APPARATUS FOR FORMING NoNwovRN FABRIC 5 Sheets-Sheet 2 Filed June 6, 1956 N Q S CARI-YLE H INVE. N'TOF? S ARMON CHARLES H- PLUMA/IER JO SEFH H- SM VTI-i BYMQM ATTORNEY METHOD AND APPARATUS FOR FORMING NONWOVEN FABRIC Filed June 6, 1956 Oct. 3, 1961 c. HARMON ET AL 3 Sheets-Sheet 5 CARLYLE HARMON CHARLES H- FLLJMME JO SEPI-1 H SM l 'T H ATTO? NEY IIIA tes

This invention relates to methods for producing nonwoven fabrics, i.e., fabrics produced directly from fibers without the use of conventional spinning, weaving, knitting, or felting operations. More particularly, it is concerned with methods and apparatus for producing such fabrics from relatively loosely assembled fibrous Webs by bonding the fibers together with an adhesive material deposited in the Web according to a predetermined pattern.

Such fabrics conventionally are manufactured at the present time by producing a more or less tenuous Web or layer of loosely associated fibers, preferably of textile length or over, using any one of a variety of well-known procedures or techniques and then distributing an adhesive material in the layer in a predetermined pattern designed to adhere the individual fibers together while providing some measure of textile-like properties in the fabric. In general, webs or thin layers formed by carding, garnetting, air laying, papermaking methods, or the like, are bonded individually, or a plurality of such layers are laminated and then bonded. Bonding has been effected by printing the bonding material in spaced areas of thefibrous layer or web to be bonded. Binders in the form of aqueous dispersions, solutions, plastisols, melts, and the like have been employed for this purpose.

` Considerable difficulty has been experience due to the processing and web handling problems which arise in attempting to apply a viscous, adhesive, or sticky bonding material to a layer of loosely assembled fibers. In order to facilitate web handling and minimize sticking, with most materials it has been necessary to Wet the fibrous layer, either during or before the printing step. If the binder is in a Wet system, i.e., a dispersion, solution, orv

the like, it tends to migrate or spread in the Wet web beyond the areas in which it originally was applied, thereby decreasing the sharpness of the pattern and detracting from fabric qualities such as softness and drape. While sharper patterns may be obtained with hot melts or fused bonding material, many web handling plroblems must be overcome and the choice of bonding materials which may be applied satisfactorily in melt form is somewhat limited.

This invention contemplates a process and apparatus by which the bonding material is applied in a pattern to a web or fibrous layer in solid particulate, or powder form, and in a substantially nonadhesve state. The bonding particles then are activated to` form bonds with the fibers in the web areas covered by the pattern. particles are dispersed substantially uniformly in a gaseous medium such as air and streams of the gas carrying the particles are passed through a web or layer of relatively loosely assembled overlapping, intersecting fibers to cause the fibers to filter the particles from the streams and form deposits of particles in areas of the web corresponding to the arrangement of streams striking the Web. Preferably, the streams are formed and their arrangement is determined by foraminous distributing means, such as an apertured plate or drum, at one side of the layer.

According to one embodiment of the invention, a gas carrying the particles is passed through the foramina or apertures in the distributing means to form the streams before striking the layer, with the result that the pattern Solid binderarent O l dlt Patented 9ct. 3, 1961 in which the binder is deposited is determined by the shape and arrangement of openings in the distributing means. It is preferred that the fibrous layer be held closely against the distributing means by porous or foraminous backing means, such as woven screening so that the distributing means and the backing means form a sandwich with the layer between them. The gas carrying the particles may be moved toward the sandwich with suliicient velocity to cause the streams to pass through the layer, or the gas may advance at a lower velocity with a vacuum underneath the backing means assisting liow through the sandwich.

According to another embodiment of the invention, the apertured distributing means is positioned underneath the fibrous layer and a relatively high vacuum is applied under the distributing means. This causes the gas carrying the particles approaching the layer from above to iiow through the layer in specified areas and then through the apertures in the distributing means. The particles are filtered out on the layer from the gas in a pattern corresponding roughly to the pattern of the apertures in the distributing means.

A thermoplastic bonding material is preferred since it may be softened vor fused and caused to penetrate through the web by the application of heat and pressure without the necessity of moistening the web or treating the binder or the Web further. When an extremely soft fluffy product is desired, it is advantageous that the web remain substantially dry to retain a maximum of its original tlufliness and soft handle, although under some conditions, as described more fully hereinafter, it may be advantageous to wet the web, either during or before distributing the particles therein, particularly if the web initially is relatively compacted. It also is preferred that enough heat be applied to fuse the thermoplastic binder particles so that the bonding material will penetrate through the web during the application of pressure to surround and imbed the fibers in the bonding areas. A solvent activated bonding material may be used, in which case, only enough solvent need be added to the web carrying the binder particles to soften these particles to the extent necessary for bonding. Sufficient solvent may be added to the web without materially decreasing its llufiiness and loft by passing it through a fog chamber or by spraying a small amount of solvent directly on the web, while supporting it by means such as a traveling belt. In addition, some heat may be advantageous to assist the solvent in softening the binder particles.

The process of this invention has many advantages. The solid binder particles remain substantially within the arcas in which they originally are deposited in the web to provide a relatively sharp pattern of binder distribution. This is advantageous since variousproperties, including textile-like softness and drape, may be designed in the fabric by virtue of the relatively sharply defined binder patterns which may be obtained. Since the particles are applied to the fibrous layer in a nonadhesive condition, sticking and the like are minimized so that processing and web `handling are facilitated greately. A Wide range of both thermoplastic and solvent activatable bonding materials may be employed and deposited in a variety of patterns. Also, the binder may be applied and the web may be treated dry, or without wetting the web, With all of the advantages which may flow therefrom.

Other features and advantages of the invention will be apparent to one skilled in the art from the following description and claims, taken together with the drawings, wherein:

FIG. l is a top plan View of apparatus according to one embodiment of the invention.

FIG. 2 is a view in side elevation of the apparatus of FIG. 1.

FIG. 3 is an enlarged view along the line 3-3 of FIG. 1, partly in section and partly in elevation.

FIG. 4 is a fragmental view partly in section and partly in elevation taken along the line 4-4 of FIG. 3.

FIG. l5 is a very greatly enlarged schematic sectional View of a portion of the sandwich formed by the apertured distributing drum, the foraminous backing screen, and the fibrous layer between them in the area wherein particles are first deposited in the layer according to the embodiment of FIGS. l-3.

FIG. 5A is a very greatly enlarged developed plan view of a fragment of the drum of FIG. 5 showing the holes in the drum as they appear from its inside surface.

FIG. 6 -is a view similar to FIG. 5 of a portion ofthe drum, screen, layer sandwic as the screen carrying the fibrous layer separates from the drum.

FIG. 7 is an enlarged schematic plan view of a portion of a nonwoven fabric formed according to one embodiment of the invention.

FIG. 8 is a very greatly enlarged schematic sectional view along the line 8 8 of FIG. 7.

FIG. 9 is a View partly in section and partly in elevation taken along the axis of the distributing drum to show a somewhat different embodiment of means for distributing the binder particles and conveying them to the inside surface of the drum.

FIG. 10 is a schematic view partly in section and partly in elevation showing apparatus for wetting the fibrous layer before it reaches the printing drum.

FIG. 11 is a schematic sectional view of a portion of apparatus according to a somewhat different embodiment of the invention.

FIG. 12 is a more greatly enlarged schematic sectional view showing the deposition of particles in spaced areas of a fibrous layer according to the embodiment of FIG. l1.

Referring in particular to FIG. 3 and FIGS. 5-6 there is shown a portion of apparatus according to one embodiment of the invention wherein a sandwich comprising a distributing drum 14 having apertures 15, a fibrous layer 16, and a flexible foraminous backing screen 17 is passed under a transfer duct 1.8 through which there is passing an air stream carrying binder particles 19. The particles 19 are solid and relatively nonadhesive and are suspended substantially uniformly in the stream. As the air carrying the particles approaches or strikes the sandwich it forms into a large number of individual streams 2 1 which pass first through the apertures 15 in the drum 14 and then through the fibrous layer 16 and the backing screen 17. The particles are filtered out of the air by the fibers to form piles or deposits 22 of the particles in areas in the layer corresponding to the arrangement of the apertures 15 in the drum. As shown in FIG. 5A the apertures 15 may be spaced from one another and arranged in a regular pattern in the drum or distributing means 14.

A somewhat different embodiment of apparatus according to this invention is shown in FIGS. 11 and 12` In these figures the backing screen `is removed, and the air carrying the particles approaches the fibrous layer itself from the outside of the drum 14. A relatively high vacuum is applied through the apertures 15 in the drum and thence through the fibrous layer 16 to attract particles 19 to the layer and cause them to flow in spaced individual streams Z3 to pass through areas of the layer roughly corresponding to the shape and arrangement of the apertures in the drum. As described in connection with FIGS. 3, and 5-6, the particles 19 are filtered from the air passing through the layer to form particulate deposits Z2Y in the layer roughlyin accordance with the pattern of holesor apertures in the drum.

As shown in FIGS. 6 and 12 prior to the formation ofY bonds, thebinder particles restfmoreror less on one side of the brous layer 16 in pilesV 22,1of roughlythesame shape astheY apertures in the' distributing drum.y Preparatoryt'o bondingfthe particles are activated to a softfor adhesive state, preferably being fused in the case of thermoplastic particles. It also -is preferred that pressure be applied to the layer 16, either during or just after the application of heat or other activation, to cause the softened or fused binder material to penetrate through the fibrous layer and surround and imbed the bers. Referring to FIGS. 7 and 8, there is shown a fabric 25 formed by this technique wherein the particles have been fused and caused to penetrate through the layer from surface to surface, surrounding and imbedding the fibers passing through the bonding. areas or bonds 26. The bonding areas '26 are spaced from one another in a regular pattern and are relatively sharply defined with very little spreading of the binder material, or fuzziness, at the edges of the bonds.

A wide variety of gases may be employed to convey the particles and deposit them in the fibrous layer. For various reasons, air is preferred. However, it may be desirable to convey certain types of binders in an atmosphere of carbon dioxide, nitrogen, exhaust engine gas, or the like.

The fibrous layer 16 must be permeable to the gas employed to carry the particles. On the other hand, it must have sufcient body to act uniformly as a filter to remove the particles from the gas passing through the layer and hold them in spaced or discrete deposits. As mentioned hereinbefore, the web or layer may be formedv by any one of a number of conventional techniques for depositing or arranging fibers in a layer. These techniques include carding, garnetting, air laying, papermaking methods, and the like. Individual webs or thin layers formed by one or more of these techniques may be laminated to provide a thicker layer for conversion into a fabric. In general, in such a layer the fibers are not compacted, in the plane of the web, but instead are relatively loosely assembled forming myriad small interstices between them. In this type of web, the fibers extend in various directions in general alignment with the major plane of the fabric overlapping, intersecting, and supporting one another to form a relatively open porous structure.

VIt is preferred that the average weight of the fibrous layer 16 be between about 150 vand 1200 grains/sq. yd., although under certain conditions webs as light as l0() grains or as heavy as 2000 grains/sq. yd. may be used. An optimum weight range for card web laminates comprising all viscose rayon fibers has been found to be betweenabout 200 land 500 grains/sq. yd.

Generally speaking, fibers of almost any material and of almost any size and length may be employed in practicing this invention. Fibers possessing particular qualities may be employed to contribute the same or related properties to the resulting fabric. Natural bers of animal or vegetable origin and artificial fibers, whether of materials such as regenerated cellulose, or true synthetics, such as nylon or the like, maybe employed. Fiber size, ie., denier or diameter, may be varied somewhat with the thickness of the layer to provide the desired permeability and filtering capacity. For instance, for layers 16 ,at the lower end of the web weight range, fibers having a denier in the order of 1.5 are preferred, while for much heavier weight webs, at the upper end of the web weight range, fibers in the order of three to five denier may 'be advantageous from the standpoint of permeability.

The mesh size of the binder particles may vary over a wide range. In referring to particles by mesh, we mean that the particles will pass through a standard screen of that mesh size. Particles, as small as 300 mesh or smaller may be employed, and even very large particles also may be used. In general, particles laccording to this invention are macroscopic in size, preferably no smallerthan about 300 mesh,v as opposed to smoke particles or those an aqueous, emulsion, for instance, which are much smaller and generally, microscopic or4 semimicroscopic insizc.

The particles should be large enough that they can be filtered out of the individual air streams and held in position by the fibers in the relatively open and porous starting layer described above in order that a relatively sharp binder pattern may be obtained. In theory, the particles may be almost as large as the apertures in the distributing means, and inthe oase of the embodiment of FIGS. ll and 12, even somewhat larger. However, when the particles are first dispersed in an air stream, for example, and then distributed in the fibrous layer as described hereinbefore in connection with FIGS. 3 and 5-6, they must be small enough that they can be distributed and suspended substantially uniformly in the air stream and conveyed in this condition to the web. Particles ranging between about 80 and 200 mesh in size have been found to give particularly good results in practicing this invention according to the embodiment of FIGS. 1-6.

Referring again to FIGS. 1-6, the apertured distri-but ting drum 14 is shown mounted to run against a pair of

positioning rollers

23 and 29 spaced from one another inside the drum and between the rollers and the flexible backing screen 17. The screen is tensioned around

guide rollers

31 and 32 spaced slightly below and outwardly of the

positioning rollers

28 and 29, respectively, so that the drum 14 is supported by the screen 17 and held by the screen against the positioning rollers 2S and 29. Mounted inside the drum 14 above the

positioning rollers

23 and 29 is a pair of axial guide rollers 33 for determining the position of the drum in the direction of its axis. The rollers 33 are rotatably mounted 'in fixed axial positions adjacent opposite ends of the drum 14 on a xed shaft 34 adjacent the top of the drum. -Flanges 35 affixed to and extending around the inner surface of the drum at opposite ends thereof enter into and are guided by annular grooves 36 in the rollers 33, with lche result that the axial position o-f the drum 14 is determined by the axial position of the rollers 33.

The

positioning rollers

28 and 29 and the

guide rollers

31 and 32 are rotatably mounted cantilever fashion on fixed

shafts

37 and 38 respectively, extending from the triangular footings 39 and 41 which are bolted to a horizontal foundation girder 42. The shaft 34 carrying the axial guide rollers 33 also is mounted cantilever fashion on a mounting plate structure extending upwardly from the horizontal foundation girder `42 (FIG. 9). This structure comprises a vertical mounting plate 43, upstand- -ing flanges 44 and a horizontal reinforcing bracket 45 behind the plate. The shaft 34 may be secured through the mounting plate 43 by a nut 46 and bolt 47 and then locked in position by welded llets 48, as shown in PIG. 4.

The horizontal foundation girder 42 is supported by two of four vertical framing members or uprights 51 which support the main foundation structure of the ernbodiment of FIGS. 1 6. The uprights 5l directly supporting the foundation girder 42 are spaced at opposite ends of the girder slightly (beyond one end of the drum 14, while the other twouprights 5l are arranged in the same way beyond the opposite end of the drum. Longitudinal stilfening beams yS2. extend horizontally between the uprights 51 at each end of the drum. Brackets 53 are employed to stiffen the structure between the stiftening beams 52 and the uprights 51. Extending outwardly from the uprights 51 on one side of the drum is a cantilever bearing support structure which comprises slotted beams 54 extending horizontally from each of the uprights 51, brackets 55 between the beams and t-he uprights, and a connecting beam 56 extending across the ends of the horizontally slotted beams. Extending outwardly from the upper end of each of the uprights 51 at the opposite side of the drum 14 is a horizontal cantilever beam 57 supported by Ia bracket 58 extending to the upright 51.

The backing screen 17 turns around the first guide roller 31, a portion of the apertured drum 14, and the second guide roller 32 and then passes around a horizontal turning roller 61 mounted for rotation in bearings 62 xed in the outer ends of each of the horizontal beams 57. The screen 17 then passes over a guide roller 63 mounted in bearings 64 depending from the horizontal beams 57, and downwardly at an angle and under a centrally positioned guide roller 64a mounted in bearings 65 bolted to the stiifening beams 52. From the guide roller 64 the screen 17 passes upwardly at an angle and around a tensioning roller 66 positioned in t-he aforementioned slotted beams 54 of the cantilever bearing support, and thence back to the rst guide roller 31 and around the drum 14. The tensioning roller is fixed to a shaft 67 mounted for rotation -in bearing supports 63 which are positioned in the slotted beams 54 for adjustment along their length. Adjusting screws 69 extend through the connecting beam 56 to collars 71 at each end of the shaft 67 beyond the bearing supports 68 for moving the tensioning roller 66 inwardly or outwardly in the slotted beams to adjust the tension of the backing screen 17.

On :the inlet side of the drum 14, a pair of supply rolls 72 and '73 of sheet material to make up the fibrous layer 16 to be bonded are supported on brackets 74 fixed at the top of the cantilever bearing support members 54'. Brackets 74 present vertical slots 7S to accommodate mandrels on which rolls 72 and 73 are wound, the slots being sufficiently deep to permit appropriate adjustment in the height of the rolls.

On the other side of the drum 14 is a table having a horizontal rectangular top 77 supported by legs 7S and 79* extending downwardly from each of its corners to the main `foundation structure below. The two longer outermost legs 7 8 are mounted near the ends of the horizontal beams S7, and the two shorter innermost legs 79 connect to an extension 81 of the main foundation structure. 'Ihe legs 78 and 79 are secured to the extension 81 of the main foundation structure and the beams 57 by bolts or the like. Both the inner legs 79 and outer legs 78 have teeth 82 on one side which act as racks for holding a vertically adjustable heater frame 83 extending between them. The frame 83, which carries a bank of six radiant heaters 84 extending transversely of the apparatus, is mounted on the racks through gears 35 at each end of the frame. The frame includes a reinforcing plate 83a at one end thereof.

The heaters 84 may be adjusted toward and away from the fibrous layer 16 containing the binder material by operating an adjusting lever 87 at one end of the frame 83. Between adjustments, `the frame is held in position on the racks by a suitable ratchet or locking device 83 which is adapted to enter into the teeth `82 of the legs 78 a-t the same end of the frame as the lever.

A feeding arrangement for supplying the solid binder particles 19 to the apparatus is mounted on the table top 77. Extending transversely over the table with its delivery outlet positioned roughly along the center line of the `apparatus is a conventional vibratory particle or powder feeder 89, such as is made by the Jelrey-Traylor Co., and called a vibratory feeder. As shown in FIG. 2, a curtain or strip 91 of particles falls from the end of the feeder into the intake 92 of a supply duct 93. Inserted in the end of the supply duct is an air nozzle or air jet device 94 which is arranged to project a stream or jet of air into one edge of the strip 91 of binder particles as they are falling and longitudinally through the strip to hurl the particles in a direction substantially normal to their fall and disperse them substantially uniformly in the supply duct 93.

The air nozzle 94 is mounted in a clamp 95 on the end of a vertical member 96 extending upwardly from the table top. One end of the supply duct intake 92 is supported from the vertical member 96 through an adjustable supporting device 97. Air under pressure is '7 supplied to the nozzle from a suitable source, not shown, through an 4air supply hose 98 attached to one end of the nozzle.

The supply duct 93 extends downwardly to the top of the drum 14 to which it is sealed by a exible wiping ange 99 attached to the lower end of the duct (FIGS. l, 2, and 3). This flange, which may be of a suitable resilient durable material, maintains resilient contact with the drum as it rotates to assure sealing between the duct 93 and the drum 14. The aforementioned transfer duct 18 extends between the top and the bottom inside surfaces of the drum 14 and is supported in this position by a horizontally disposed bracket 101 secured at one end to the vertical mounting plate 43 and which extends inwardly into the drum for connection at its other end with the duct 1S. The transfer duct 18 is located with its top end directly underneath the supply duct 93 to act as a continuation thereof, and with its lower end directly above the central portion of the sandwich formed by the drum 14, the screen 17, and the fibrous layer 16. A flexible wiping flange 102 and 103 at each end of the :transfer duct seals its ends with the inside surface of the drum, as described'above in connection with the wiping iiange 99 and the supply duct 93. Positioned directly under the lower end of the transfer duct but at the outside of the sandwich, there is la vacuum duct 104 which is con nected to a suitable source of vacuum, such as a vacuum pump, not shown, and mounted on brackets 105 bolted to the horizontal girder 42. A similar flexible wiping flange 106 in contact with the backing screen .17 is secured to the upper end of the vacuum duct 104 to provide a seal with the sandwich In FIGS. l and 2 there is shown a bonding unit beyond the beams 57 which comprises a pair of electrically heated calenders or bonding rollers 107 pneumatically urged together to form a pressure nip between them. The bonding rollers 107 may be connected to any suitable electrical power source, not shown, for supplying current to heating coils or the like, also not shown, within the rollers. The rollers are fixed on shafts 108 journaled at their ends for rotation in bearings 109 which are adjustably held in horizontal supporting frames 111. The supporting frames 111 are mounted cantilever fashion at the ends of vertical columns 1'12 where structural brackets 113 extend between the frames and the columns to provide support for the frames.

The calenders 107 are positioned along the supporting frames 111 by adjusting screws 114 between the bearings themselves and between the bearings and the ends of the frames 111. The nip is opened and closed pneumatically by air cylinders 115 mounted on the columns and connected to the innermost bearings. Air under pressure is supplied to the air cylinders through air lines 116 from a pressure source, not shown.

Positioned beneath the heated calenders l107 are forked shaft supports 117 for supporting a wind-up or storage roll 118 of the fabric after it leaves the bonding step. A guide roller 121 for leading the fabric around the last calender and then down tothe storage roll 118 is mounted near the ends of the horizontal supporting frames 111 on brackets 122 fixed to and depending from the frames. The roller 121 is carried on a horizontal shaft A123 journaled at its ends in the brackets 122.

The apertured drum 14 and associated parts are driven through contact with the backing screen 17 which in turn is driven by contact with the turning roller 61 positioned at one end of the main foundation structure. The turning roller 61 is driven from an electric power source through a driving chain 124 which engages a sprocket 125 at one end of the roller. The chain is connected for driving by an electric driving motor 126 through gear boxes 127. The driving chain 124 also passes around a guiding sprocket 128 fixed to one of the vertical columns 112, around a sprocket 129 at one end of the innermost ofgtheheated calenders 107, and'then upgand around the '8 sprocket 12S at the end of Vthe turning roller 61. Thus, the calenders 107 also are driven from the electric motor 126 through the aforesaid chain drive. The wind-up roll 118 is connected to the driven calender 107 by a belt or chain 131 which in turn drives the wind-up roll 118.

In operation, layers 133 of superimposed card webs are unrolled from the supply rolls 72 and 73 and plied together to form a starting brous layer 16 which is passed between the apertured drum 14 and the backing screen 17 to form the aforesaid drum, screen, layer sandwich. The travel of the belt 17 moves the sandwich as a unit between the transfer duct 18 and the vacuum duct 104 to cause the deposition of binder powder in spaced areas of the layer, as described hereinbefore.

Relatively nontacky thermoplastic binder particles 19 are dispersed substantially uniformly in the supply duct 93 by the vibratory feeder 89 operating in conjunction with the air jet 94. The particles 19, suspended in the rapidly moving air stream formed by the jet, are carried through the supply duct 93 to the top of the drum 14, and then through the drum 14, and into the transfer duct 18. At this point, the drum acts as a baffle for improving the distribution of the binder particles uniformly across the transfer duct. The air stream carrying the particles 19 moves rapidly toward the bottom of the drum where it strikes the aforesaid sandwich and splits into a plurality of individual streams 21 in order to pass again through the holes 15 in the drum. The particles are filtered from the streams passing through the sandwich by the fibrous layer 16 and are deposited in the layer in a pattern corresponding roughly to the pattern of holes 15 in the drum. The vacuum provided by the vacuum duct 104 underneath the sandwich helps draw the air carrying the particles 19 through the sandwich in relatively sharply defined individual streams 21, thereby improving the sharpness of the pattern in which the particles are deposited in the fibrous layer.

Some of the particles v19 may stick on the inside surface of the drum 14, instead of passing through the apertures 15 therein. A brush 135 for cleaning these particles from the drum is positioned against its inside surface approximately 90 away from the point where the drum rotates between the transfer duct 18 and the vacuum duct 104. The brush is mounted in a holder 136 which, in turn, is supported on a bracket 137 attached to the vertical mounting plate 43.

The binder particles 19 may be deposited in the layer 16 in areas which are quite small and closely spaced from one another. For instance, the apertures in the drum 14 quite commonly may range between 0.027 and 0.062 inch in diameter with to 300 holes per square inch accounting for about 17 to 23 percent of the area of the drum, and the particles may be deposited in the fibrous layer in a corresponding pattern. This data merely is illustrative since apertures which are considerably larger or smaller may be used.

As illustrated in FIGS. 5 and 6, the particles are deposited in little piles 22 on the fibrous layer 16. While the particles do penetrate the layer to some extent initially, they predominately are filtered out on its top surface. It is preferred that the layer be separated from the drum in such a way that it moves in an approximately horizontal direction to prevent the piles from spilling or the particles from falling therefrom into those portions of the layer which are outside the desired pattern areas. The fibrous layer 16 normally is compressed somewhat while it is held in the sandwich between the drum 14 and the backing screen 17. In FIG. 6 the layer 16 is shown regaining some of its original thickness as the drum 14 and the backing screen 17 separate.

The backing screen 17 carrying the fibrous layer 16 with the binder arranged in spaced areas thereof passes from the drum underneath the bank of six radiant heaters 84. binder particles sufficiently to fix them in position in the The radiant heaters are adjusted to activate thev fibrous layer as the layer passes below them.

Additional rollers

138 and 139 are mounted to rotate in a vertical frame 141 extending upwardly from the inner ends of the horizontal supporting frames 111 beyond the heaters 84. The layer 16, with the binder fixed in position therein, then is plied with a similar fibrous laminate 142 of approximately equal weight coming from the

rolls

138 and 139 in such a way that the side of the rst layer 16 carrying the particles 19 is in contact with the second layer 142. The resulting two-ply structure then is passed through the nip between the heated calenders 197 where suliicient heat and pressure are applied to fuse the binder particles 19 and cause penetration of the fused binder substantially through the two-ply fibrous laminate to surround and imbed the fibers passing through the binder areas and form a nonwoven fabric 25 as illustrated in FIGS. 7 and 8. Since the binder particles 19 were positioned between the two

plies

16 and 142 before passing between the calenders 107, the resulting bonds 26 are somewhat fuller half way between the fabric surfaces than at the surfaces. Thus, plying in this way concentrates binder inwardly of the fabric surfaces where it may be most needed. The resulting fabric 25 also may be advantageously soft due to the absence of binder concentrations at or on its surfaces.

Although the additional fibrous layer 142 may be advantageous for the reasons mentioned above, excellent results may be achieved by applying heat and pressure directly to the layer 16 carrying the particles 19 to fuse the particles and imbed the fibers passing through the binder areas.

, Various methods may be employed for dispersing binder particles and suspending them in an air stream for passage through the sandwich. However, a vibratory feeder of the type described is preferred. In addition, it is preferred that an air jet be employed in conjunction with the feeder to disperse the particles uniformly and suspend them in the air or gaseous carrier stream in such a way that uniformity of flow is provided, i.e., the number and spacing of particles are substantially uniform along the length and width of the stream and do not vary appreciably with time.

An alternate embodiment of apparatus for feeding particles 19 through one side of the drum 14, rather than through the top of the drum, is illustrated in FIG. 9. Here a transfer duct 143 extends at an angle through one side of the drum from a feeder 89-air jet 94 combination such as described in connection with FIGS. 1-6 and which may be suitably mounted in the position shown. The duct 143 is supported from the vertical mounting plate 43, by a bracket 144 bolted to the plate. The angle of the jet 94 is adjusted vertically to strike the curtain 91 of particles 19 falling from the vibratory feeder in such a way that the air stream carrying the particles is properly positioned with respect to the center line of the duct 143. A trough 145 may be positioned under the jet to assist in suspending the particles in the air stream. As describedV in connection with FIGS. 1 6, a flexible wiping flange, not shown, may be positioned at the lower end of the duct 143 between the duct and the inner surface of the drum 14 to minimize air leakage into the duct at this point. A vacuum duct or similar means, also not shown, may be employed underneath the drum to facilitate particle deposition.

In the event that it is desired to wet the fibrous layer 16 prior to particle deposition, the structure shown in FIG. l may be employed. In FIG. l0 there is shown a conventional wet-out nip where a lower ro'll 147 dips into a pan containing a wet-out fluid 149, such as water, and carries the fluid in a film along its surface as it rotates into contact with the fibrous layer 16 passing between the lower roll 147 and a pressure roll 151 cooperating therewith to form the nip. The upper or pressure roll 151 is adjustable towards and away from the lower roll 147 by an air cylinder 152 connected to bearings, not shown, at the ends of the roll. The lair cylinder 152 may be con- 10' nected to a suitable pressure source, also not shown. The wet-out unit may be mounted on stanchions 153 positioned at the entrance side of the apertured drum 14 to wet the fibrous layer 16 just before it enters between the drum 14 and the backing screen 17.

With relatively uniform and compact fibrous webs such as long fiber paper webs of the type which may be used for tea bags, or the like, wetting the web may be advantageous since a clearer binder pattern may be obtained. Also, the binder particles tend to remain more readily in a moist web and are not easily dislodged therefrom or disturbed in handling.

As described hereinbefore, a somewhat different ern-y bodiment of apparatus according to this invention is shown in FIGS. l1 and l2. In these figures the vacuum duct 104 is positioned inside the drum 114 underneath the supply duct 93, the backing screen is removed, and the fibrous layer 16 passes over the drum between the supply duct 93 and the vacuum duct 104. To prevent leakage around the supply duct sealing rollers 155' are provided between the duct 93 and the drum 14. These rollers may be mounted in suitable brackets 156 extending from the duct 93 and are positioned in such a way as not to disturb materially the arrangement of the particles 19 on the brous layer. Preferably, the duct 93 is about as wide, or wider, than the fibrous layer 16 so that flexible wiping flanges 157, of the type described hereinbefore, may extend from the sides of the duct to the drum 14. Preferably, also, the lower edge of each wiping flange 157 is shaped to fit the surface of the drum 14, as shown in FIGURE ll. On the opposite side of the drum the flexible wiping flange 166 is positioned around the vacuum duct 104 between the duct and the drum 14 for sealing purposes. Since as described hereinbefore a higher vacuum m-ay be necessary to form fabrics according to this embodiment as compared with the embodiment of FIGS. 1-6, it is particularly advantageous to have effective sealing between the drum 14 and the vacuum duct 104 in FIG. 11.

According to this invention, the drum 14 may be made of any desirable material, for example, plastic, metal, rubber, or any other self-sustaining material capable of retaining the desired perforations or foramina therein, It is preferred that the drum be of metal, preferably stainless steel or other suitable material capable of withstanding corrosion. The thickness of the drum may vary rather widely, and in general, it is preferred that it be characterized by rigidity.

The backing screen 17 may be made of any suitable material. Screen belts in woven form give excellent results. However, a woven belt is not essential since the belt may have the openings punched or etched in the material. The belt, in screen form, may be made of stainless steel, bronze, copper, alloy, nylon, synthetic resinous fibrous materials such as fibers sold by the E. I. du Pont C-o. under the trademark Orlon, or the like. It can be in the form of a punched plate or sheet of steel, plastic or any other material which is sulliciently permeable to allow the gas to pass fairly easily therethrough. Of course, where the belt 17 carrying the fibrous layer is exposed to heat as from the heaters 84 in the embodiment of FIGS. 1 6, it must be capable of withstanding the required amount of heat during use.

The apertured distributing means may be in the form of a flexible foraminous distributing belt having apertures shaped and arranged to determine the desired binder pattern, in which case, the distributing belt may substitute for the apertured drum 14 in either of the embodiments of FIGS. l-6 or FIGS. ll and l2. A sandwich formed by the flexible distributing belt, the backing screen, and the fibrous layer between them may be passed around suitable supports, such as spaced table rollers, not shown, of the type commonly used in the paper industry and a particle carrying gas may be passed through the apertures in the belt and thence through the sandwich to deposit the binder particles in the fibrous layer as' described in connection with FIGS. 1-6. v The `backing screen may be II removed and the particles applied from the web side of the opened sandwich with a source of vacuum on the other side of the belt to deposit particles as described in con. nection with FIGS. l1 and l2.

The apertured belt may be of any one of a number of suitable materials such as punched metal or plastic sheet ing, open woven fabrics, orA the like. The material employed should be capable of defining and retaining the desired apertures in accordance with the sharpness of definition required for the .binder areas in the resulting fabric.

One of the major advantages of the process and apparatus of this invention lies in the wide variety of binder materials which may be employed. Almost any particulate material, which exists in a relatively nontacky state and which may be Iactivatedto anadhesive or bond forming state, may be used. Typical materials include ethyl cellulose, various nylons, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl formal, cellulose acetates, and the like.

Having now described the invention in specific detail and exemplified the manner in which it may be carried into practice, it will befreadily apparent to those skilled in the art that innumerable variations, modifications, applications, and extensions of the basic principles involved may be made without departing from its spirit and scope.

The invention claimed is:

l. The method of forming a nonwoven fabric from a relatively loosely assembled layer of overlapping and intersecting fibers, which comprises positioning distributing means at one side of the layer, said distributing means having a multiplicity of apertures therethrough, dispersing in a gas macroscopic solid particles of bonding material in a substantially nonadhesive state, passing the gas carrying the particles into the layer in streams arranged in a pattern determined by said apertures, said particles being ltered from the streams by said bers in areas of the layer corresponding to said pattern, and activating the particles to render them bond forming and forming bonds with the bers in said areas.

2. The method of forming a nonwoven fabric from a relatively loosely assembled layer of overlapping and intersecting bers, which comprises positioning distributing means at one side of the layer, said distributing means having a multiplicity of apertures therethrough, passing a gas carrying solid particles of thermoplastic bonding material in a substantially non-adhesive state through said apertures and into the layer in streams arranged in a pattern determined by said apertures, said particles being filtered from the streams by said fibers in areas of the layer corresponding to said pattern, and heating the layer to soften Ithe particles and form bonds with the bers in said areas.

3. The method of forming a nonwoven fabric according to claim 2 wherein the thermoplastic bonding material is fused and suicient pressure is applied to the layer to cause the fused bonding material to surround and embed the fibers in the areas of the layer corresponding to said pat-tern.

4. The method of forming a nonwoven fabric from a relatively loosely assembled layer of overlapping and intersecting bers, which comprises positioning distributing means at one side of the layer, said distributing means having a multiplicity of apertures therethrough, exposing the side of the layer. opposite to said distributing means to a gas carrying macroscopic solid particles of bonding material in a substantially non-adhesive state, applying a vacuum through said apertures to the opposite side of the layer to cause said gas to ow through the layer and the apertures in streams arranged in a pattern determined by the apertures, said particles being filtered from the streams by said bers in areas of the layer corresponding to said pattern, andsactivating the particles to render them bond forming and forming bonds with the bers in said areas.

5. The methodof formingf a nonwoven fabric from 12 a relatively loosely assembled layer of'overlapping and intersecting fibers, which comprises positioning the layerV between forarninous backing means and distributing means having apertures arranged in a predetermined pattern,

' passing a gas carrying macroscopic solid particles of bonding material 'in a substantially non-adhesive state through said apertures and thence through the layer and said backing means, said particles being filtered from the gas passing through said apertures by said fibers in areas of the layer corresponding to said pattern, and activating said particles to render 'them bond forming and forming bonds with the bers in said areas.

6. The method of lforming a nonwoven fabric from a relatively loosely assembled layer of overlapping and intersecting fibers, which comprises positioning the layer between foraminous backing means and distributing means having apertures arranged in a predetermined pattern, passing a gas carrying solid thermoplastic particles of bonding material in a substantially non-adhesive state through said apertures and thence through the layer land said backing means, said particles being macroscopic in size and being ltered from the gas passing through said apertures by said fibers in areas of the layer corresponding to said pattern, and applying heat and pressure to said areas to activate the particles and form bonds with the fibers in said areas.

7. The method of forming a nonwoven fabric from a relatively loosely assembled layer of overlapping and intersecting fibers, which comprises positioning the layer between foraminous backing means `and distributing means having apertures arranged in a predetermined pattern, dispersing macroscopic solid particles of bonding material substantially uniformly in a gaseous stream, passing the stream carrying the particles through said apertures and thence through the layer and said backing means, said particles being filtered from the gas passing through said apertures by said fibers in areas of the layer corresponding to said pattern, and activating said particles to render them bond forming and forming bonds with the bers in said areas.

8. The method of forming a nonwoven fabric from a relatively loosely assembled layer of overlapping and intersecting fibers, which comprises positioning the layer snugly between foraminous backing means and distributing means having apertures arranged in a predetermined pattern, ldispersing solid particles of bonding material substantially uniformly in a gaseous stream, passing the stream carrying the particles through said apertures and thence through the layer and said backing means while applying a vacuum to the side of said backing means opposite to said layer, said particles being filtered from the gas passing through said apertures by said bers in areas of the layer corresponding to said pattern, and activating said particles to render them bond forming and forming bonds with the fibers in said areas.

9. The method of forming a nonwoven fabric according to claim 8, wherein the fibers are textile bers and the layer of fibers weighs between about 200 and 1200 grains per square yard.

10. A machine for forming a nonwoven fabric from a layer of bers, which comprises distributing means on one side of said layer having apertures arranged in a pattern, foraminous backing means on the other side of said layer, means on the side of said distributing means opposite to said layer for supplying a gas carrying solid particles of bonding material through said apertures to said layer, means for applying a vacuum to the side of said backing means opposite to said layer, whereby said gas passes through the layer and then through said backing means and the particles are filtered from the gas in areas of the layer corresponding to said pattern, and means for activating said particles to render them bond forming and for forming bonds with the bers in said areas.

11. A machine for forming a nonwoven fabric from` a layer of bers, which comprises a distributing plate on one side of said layer having apertures arranged in a pattern, a foraminous backing screen on the other side of said layer, means on the side of said distributing plate opposite to said layer for supplying a gas carrying solid particles of bonding material through said apertures to said layer, whereby said gas passes through the layer and then through said backing screen and the particles are iltered from the gas in areas of the layer corresponding to said pattern, and heat and pressure applying means for activating said particles to form bonds with the fibers in said areas.

1'2. A machine for forming a nonwoven fabric from a layer of fibers, which comprises a distributing drum on one side of said layer having apertures arranged in a pattern, foraminous backing means on the other side of said layer for holding said layer against said drum, means inside the drum for supplying a gas carrying solid particles of bonding material to said layer through the apertures in said drum, means for applying a vacuum to the side of said backing means opposite to said layer, whereby said gas passes through the layer and then through said backing means and the particles are iiltered from the gas in areas of the layer corresponding to said pattern, and means for activating said particles to render them bond forming and for forming bonds with the fibers in said areas.

13. A machine for forming a nonwoven fabric from a layer of fibers, which comprises a distributing drum on one side of said layer having apertures arranged in a pattern, foraminous backing means on the other side of said layer for holding said layer against said drum, means for dispersing solid particles of bonding material substantially uniformly in a gaseous carrier stream, means for supplying the gas carrying the particles to the inside surface of the drum and then through the apertures to said layer, means for applying a vacuum to the side of said backing means opposite to said layer whereby said gas passes through the layer and then through said backing means and the particles are ltered from the gas in areas of the layer corresponding to said Pattern, and means for activating said particles to render them bond forming and for forming bonds with the fibers in said areas.

References Cited in the le of this patent UNITED STATES PATENTS 1,448,203 Cumfer et al. n Mar. 13, 1923 2,341,130 Unsworth Feb. 8, 1944 2,550,686 Goldman May 1, 1951 2,671,496 Chavannes et al. Mar. 9, 1954 2,698,574 Dougherty et al. Ian. 4, 1955 2,736,362 Slayter et al Feb. 28, 1956 2,862,251 Kalwaites Dec. 2, 1958 FOREIGN PATENTS 328,714 France May 8, 1903

Claims

1. THE METHOD OF FORMING A NONWOVEN FABRIC FROM A RELATIVELY LOOSELY ASSEMBLED LAYER OF OVERLAPPING AND INTERSECTING FIBERS, WHICH COMPRISES POSITIONING DISTRIBUTING MEANS AT ONE SIDE OF THE LAYER, SAID DISTRIBUTING MEANS HAVING A MULTIPLICITY OF APERTURES THERETHROUGH, DISPERSING IN A GAS MACROSCOPIC SOLID PARTICLES OF BONDING MATERIAL IN A SUBSTANTIALLY NONADHESIVE STATE, PASSING THE GAS CARRYING THE PARTICLES INTO THE LAYER IN STREAMS ARRANGED IN A PATERN DETERMINED BY SAID APERTURES, SAID PARTICLES BEING FILTERED FROM THE STREAMS BY SAID FIBERS IN AREAS OF THE LAYER CORRESPONDING TO SAID PATTERN, AND ACTIVAT-