CA1322838C - Ductless webber - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A lickerin and feed mechanism create a supply of individual short fibers which follow the rotation of the lickerin. These fibers are deflected from the lickerin in the form of a stream by means of a plate arranged parallel to the lickerin. A conveying screen intercepts the stream of fibers and accumulates them into a web without the use of a high pressure stream of air to doff the fibers from the lickerin or to capture fibers on the conveyor. Further, the housing for the apparatus is opened so that there are no seals to compress the web after it is produced. A feed tray located next to the lickerin can be used to include other particulate materials (fiber or granules) in the main fiber stream and a tapering of the deflector plate can separate the component of the blended fiber-particulate material stream into layers in the resulting web distinguished by particle weight.

Description

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Technical_Field The present invention relates to methods and apparatus for forming non-woven structures of fibers and, more par-ticularly, to the efficient formation of uniform webs from short fiber materials, such as pulp board stock.

Background_Art Non-woven fabrics are structures consisting of ac-cumulations of ~ibers typically in the form of a web. Such fabrics have found great use in disposable i~ems, such as hand towels, table napkins, curtains, hospital caps, draperies, etc., because they are far less expensive to make than conven-tional textile fabrics made by weaving and knitting prbcesses.
There exist many different processes for forming non-woven structures. The processes, however, when used to generate uniform pulp fluf~ structures from pulp board stock, generally involve introducing the individualized pulp fibers into an air ~tream, such that the fibers are conveyed at high velocity and high dilution rates to a moving condensing screen upon which the fibers are accumulated in the ~orm of a con-tinuous web. The individualized pulp fibers may be generated through the use of YariOus hammer mills. As an alternative, the fibers may be generated by using a lickerin or wire-wound roll to grind or shred pulp board. An air stream is tangen~
tially passed over the fiber-laden Iickerin, or about the mill, ' ~ d ~,1 ( ) ' i ' J

to doff or remove the fibers and entrain them in the air stream. Typically the air stream with the ~ibers is contained within a duct from the point of grinding to the point of deposition upon the condenser screen. In order to maintain the air streams in the duct at velocities high enough to ensure a uniform flow and deposition of the fibers upon the condensing screen, as well as to assure that the fibers do not adhere to the duct walls, it is necessary to employ a fan or other suction device beneath the condensing screen to create a pressure of at least 20 inches of water, and often up to 100 inches of water.
U.S. Patent No. 3,512,218 of Langdon discloses ap-paratus for forming non-woven webs with two lickerins. The fibers are doffed from the lickerins by a single air stream formed by a suction box below the condensing screen. U.S.
Patent No. 3,535,187 of Woods discloses a similar arrangement wherein two air streams are used to doff the fibers from the lickerin. According to U.S. Patent No. ~,772,739 of Lovgren both pulp fibers and longer textile fibers are individualized 2n and blended in apparatus using high speed lickerins rotating at different speeds. As in the other references, the individual-ized fibers are doffed ~rom their respective lickerins by separate air streams produced by a suction fan located in the condenser section of the apparatus. A baffle plate inserted between two lickerins for controlling the degree of mixing of fibers doffed by air streams passing over separate lickerins is described in U.S. Patent No. 3,768,118 of Ruffo et al. and U.S.
Patent No. 3,740,797 of Farrington.
In these references, and generally in the prior art, the high speed aix streams impel the fibers against the moving condenser screen at such a speed that there is a compression of the resulting web. In addition, the particles, after leaving the lickerin, are conducted to the condensing screen by a duct structure whi~h confines their travel and, due to the air pres-sure, accelerates their travel. In order to assure that theair pressure is not reduced, seal means are provided where the duct structure engages the moving condenser scxeen. This may be in the fo~n of floating or rolling seals, which further act to compress the fiber web as it is withdrawn from the condenser on the moving screen.
Because of the substantial pressure which must be generated in order to create the high speed air streams, the prior art methods of producing pulp webs require a great deal of energy. In addition, the resulting web is compressed both by the air stream and the seals that are used to maintain the pressure for the air stream. Thus it would clearly be ad-vantageous to the production of fluff fiber structures, if theycould be created with much less energy and with less compres-sion, i.e. much greater loft.

Disclosure of the Inventlon The present invention i5 directed to a method and ap-paratus for ~1) forming high loft short fiber structures without the use of high speed air streams and duct structure, such that much less energy is needed and a more lofty web is formed, and t2) blending other fibers or particulate matt~r into the fiber structure.
In an illustrative embodiment of the invention a frame structure is used which has an endless conveyor screen in its lower section. This screen enters the frame structure at one end and exists it at the other. At the locations where the conveyor screen enters and leaves the frame, the frame is open to the atmosphere.
At an upper portion of the frame there is a feeding means for feeding short fiber stock, e.g. pulp stock, into engagement with a high speed rotating lickerin. The feeding means essentially comprises a feed roller, which forces the stock against the licXerin, and a nose bar that holds the stock in place as its end is shredded by the wire projections of the lickerin.
It has been found that in the absence of a high speed air stream, the individualized shsrt fibers created by the lickerin tend to follow the peripheral direction of the lickerin. However, if a deflector plate is positioned parallel ~ 3 2 ~ ~J~3)~

to the axis of the lickerin, but closely spaced from its peripheral surface, the fibers are directed from the lic~erin in a stream towards the conveyor screen located in the lower portion of the frame.
~t the conveyor screen, the individual particles are accumulated into a non-woven fiber structure. As the screen is moved, a continuous fiber structure is formed, which structure extends out of the open end of the frame to other processing equipment.
If dasired, a relatively low air pressure may be created in a suction chamber below the screen. This acts to keep dust particles at a minimum and to improve the lateral placement of the fibers in forming the web. However, this low pressure is insufficient to doff the individual fibers from the lickerin. In particular, the suction pressures can be less than 5 inches of water, and are preferably in the range of 1/2 to 1 inch of water, as opposed to 20 to 100 inches of water as in prior art processes.
Pulp webs formed by this new process are typically more lofty than webs formed using a conventional process because of the lower compression effect resulting from the elimination of the high velocity depositing stream and the absence of seals positioned at the exit of the conveyor screen from the frame.
Other materials can be blended with the fibrous stream deflected from the lickerin. This is accomplished by mounting a feed tray beneath and parallel to the nose bar. The rotation of the lickerin creates a high velocity airstream in proximity to the rotating surface which draws particulate or fibrous materials in a tray toward the lickerin, where it is blended with the fiber stream. This results in the creation of uniqu~
blended non-woven fiber products.
When two materials of diff~rent densities are combined through the use of a feed tray, it is also possible to control the relativ~ positioning of the two components in the resulting fiber structure by varying the shape of the discharge edge of the deflector plate. A sharp-edged, straight plate will yield a uniformly blended web. How~ver, a discharge edge that is 5 ~ 3 anyled or curved away frorn the normal direction of flow, will create a wall attachment effect that causes lightweight particles to follow the contour of the wall, while heavy parti.cles, under inertial influence, contlnue in a straight line. The result is a preponderance of heavy particles in -the lower layers of the fiber structure, and light particles in the upper layers.
According to a b:road aspect of the present invention, there is provided a web forming apparatus which comprises feeding means for feeding fiber stock to a fiberizing station. A rokatlng toothed cylinder mounted such that a portion of the cylinder's outer periphery is adjacent the feeding means at the fiberizing station. The rotating toothed cylinder creates induced air streams and the cylinder is engageable with fiber stock fed to the fiberizing station. Means is also providPd for rotating the cylinder with respect to the stock fed to the flberizing station so as to open the stock and produce individual short fibers moving with the cylinder. Deflector means is provided for deflecting the indiv.idual fibers as a fiber stream from the cylinder at a preselected location along the periphery o the cylinder. The deflector means is free of means of introducin~ further air streams o'cher than the induced air streams ~or doffing fibers from the cylinder and being in the foxm of a plate positioned such that the deflector means is parallel to the axis of the cylinder and adjacent to, but out of contact with, the cylinder periphery.
The plate is at a location spaced from the fiberizing station in the direction of rotation of the cylinder. Fiber ~collecting means is provided adjacent the cylinder for interceptiny the stream of individual fibers accumulating the fibers to form a ' ~2~33~
5a web. The fiber collecting means is free of structural members for confining the stream of individual fibers.
Brief Description of the Drawinqs The foregoing and other feàtures of the present lnvention will be more readily apparent from the following detailed description and drawings of illustrative embodiments o~ the invention in which:
Fig. 1 is a schematic illustration of apparatus for carrying out the present invention, but with the frame removed;
Fig. 2 is a schematic illustration of a side view, partially broken away, of apparatus for practicing the present invention, including the frame thereofi Fig. 3 is a perspective view of one end of a product made according to the embodiment of Fig.
l;
Fig. 4 is a perspective view of the apparatus of Fig. 1 equipped with a feed tray;
Fig. 5 is a side sectional view of the apparatus of Fig. ~ showing two feed trays and the effect of angling the deflector plate; and Figs. 6A and 6B are cross section views of products made by the apparatus of Fig. 5.
Description of an Illustrative Embodiment In Fig. 1 there is shown the lower portion of a frame structure for carrying out the pre3ent invention. Th.is structure includes a low vacuum chamber 10 which creates vacuum ~orces on a convayor mesh screen 12. This screen is moved by a motor (not shown) such that it travels from the right of Fig. 1 to the left, as shown by arrow A. Because the screen 12 is co~tinuous, it passes about a roller 13, under the vacuum chamber lQ, over a roller 15 and back into the ~rame o the ~i , , , ,J?,) jJ

appa:ratus over th~ top o~ vacuum cham~er 10. The pe~foratiorls in conveyor screen 12 allow suction force which is less than 5 inches of wa~er, and preferably in the range of 1/2 to 1 inch of water, to be created across the screen where the screen is over openings in the vacuum chamber 10. This low vacuum is created in chamber 10 by suction in a conduit 19, shown extending from a side of the housing. The conveyor screen 12 intersects stream 20 of lndividualized short fibers, e.g. pulp ~ibers, and accumulates them to form the non-woven structure or web of material 20.
One of the desirable features of this device is that it allows the non-woven structure 22 to be formed on a porous substrate 26. This ~ubstrate ~6 may be tissue paper or a similar porous thin web material. It may be ~sd from a roll 27 and carried into the ~rame by screen 12. Such a substrate will generally have a uni~orm width that i5 the same or greater than that of the formed web 22. However, in Fig. 1, the substrate 26 is shown partially broken away to reveal the screen 12.
Tha raw material for creating the fibers is typically derived from pulp board stock 30. Such pulp boards come in varyin~ thicknesses and lengths and are a ready source of "short fibers". The terms "short fibers" typically re~ers to paper making ~ibers, such as wood pulp ~iber~ or cotton linters, having a length less than about l/4 inch. These ~ibers are generally inexpensive and absorbent, and thus are greatly used ~or making non-woven products. In addition to pulp boards, short fi~ers may be obtained from various types of wood, asbestos, glass fibers and the like.
~ndividual short fibers are created in the example of Figs. l and 2, from the pulp hoard 30 by means of feed roller 32, nose bar 34 and lickerin 36~ In particular, the ~eed roller 32 i5 rotated by motors (not shown) to drive the pulp board 30 against the wire projections o~ lickerin 36. Because the pulp hoard is flexible, it must be held rigid at its end such that the projections o~ the lickerin can open or separate the ~ibers ~rom the board. ~This is accomplish~d by the nose bar 34.

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The speed- of the feed roller 32 controls the rate at which the pulp board is fed against khe lickerin, and thus af-fects the thickness of the web which is formed at any par-ticular speed for the conveyor screen 12. The spacing of the nose bar from the feed roller and the lickerin is optimized for the particular pulp board 30 being utilized, such that it can be assured that complete separation of the fibers is accom-plished. In addition, the speed of the lickerin is set to optimize the ~iberization process. For example, a 9 inch diame~er lickerin may be rotated at from about 4,000 to 6lO00 r.p.m.
As the fibers are separated from board 30 they become entrained ln an air stream created by the high speed rotaticn o~ lickerin 36. As a result, the fibers tend to ~ollow the contour o~ the periphery o~ the lickerin. In order to do~f these ~ibers ~rom the lic~erin, a de~ector plate 40 is posi-tioned at a particular location along the peripheral direction o~ rotation o~ lickerin 36. The ef~ect of this de~lector plate i9 to separate the stream o~ individual ~ibers ~rom the lickerin and to direct it onto the conveyor screen. The de~lector plate ~ 5 not in contact with the lickerin. However, it is believed that it acts to separate the ~ibers from the lickerin by de~lecting the air stream created by the lickerin rotation towards the conveyor screen, so that the fibers, which are entrained in this air stream, follow the air stream onto the conveyor.
In Fig. 2, a ~rame 50 ~or the apparatus is illustrated.
The ~rame has no top, but it has side plates 52 which are shown broken away 50 that the interior o~ the structure can be seen.
These side plates 52 act to support feed roll 32, nose bar 34 and lickerin 35.
The end plates 53 and 54 at the exit and entrance to the apparatus, respectively, stop at some distance above the conveyor screen 12. Thus, the interior o~ ~he frame is open to thQ atmosph~re and cannot be under a high vacuum. Further, ~he end walls 53, 54 do not contain any sealing rollers or ~loating seal~ to maintain a vacuum. The absence of such a seal at end ~1 .

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plate 54, assures that the natural loft of the web created by the present invention is not compressed.
As shown in Fig. 2, a motor 56 is connected to a belt 57 and acts to turn the lickerin at the proper speed for optimum individuali~ation of the fibers.
A device according to the present invention is capable of forming uniform low density pulp webs at speeds in excess of 300 linear feet per minute. At a speed of 300 feet per minute webs of weights o e up to 2 ounces per square yard can be achieved. At slower speeds, the apparatus can produce webs in excess of 20 ounces per squaxe yard.
In a preferred embodiment, a cover 59 extends from the deflector plate 40 to the feed roll 32 on the side o~ the lick-erin away from the fiber stream 20. This additionally acts to prevent the air stream from completely circling the lickerin and carrying individual ~ibers beyond the deflector plate 40.
While typically a single fiber board 30 would be fed to the lickerin, it is also possible to feed simultaneously separ-ate boards 3Oa, 3Ob and 30c (Fig. 1) to the apparatus.
Further, it is possible to form unitary boards having three different segments. These segments 30a, 30b, 30c may be distinguished by a difference in composition or merely a difference in color. When such an arran~ement is used, the cross-sectional composition of the web produced is as shown in Fig. 3. In particular, there will be three separate lateral zones in the X direction of Fig. 3 forming the web material.
The web is continuous in the longitudinal or Y diraction and can be severed as desired to produce products of a particular length. The height of the product (i.e. in the Z direction) depends on the speed of the conveyor (greater height for a slower speed) and the speed of the feed roller 32 (greater height for a faster spe~d).
Products produced by th2 present invention have more loft than conventional products. It is believe that this re-sults because a greater proportion of the individual pulpfibers are deposited in the present invention such that their axes are generally perpendicular to the conveyor screen, than 3 .~` ') in prior high vacuum type systems. This results in more resiliency in the web perpendicular to the screen (i.e. in the Z direction) and a product that has better fluid uptaks. When a strong suction force is used below the screen, the ~ibers tend to flatten out, which removes the resiliency perpendicular to the screen and the natural channels for conducting fluids across the thickness of the web.
In conventional dual rotor machines, such as that de-scribed in Patent No. 3,740,797 of Farrington, when a 40 inch long lickerin is used there is a loss o~ between 8 and 12 pounds of pulp per hour due to the high suction. ~ith the present invention, however, there is only about 1/3 of a pound per hour lost. Thus, there is less material which is wasted and less clean up is required in the vicinity of the machine.
In a ductless device according to the present inven-tion, the stream of material has a greater fiber to air ratio than in a machine like that of the Farrington patent. However, fibers are deposited at a slower velocity. These two effects tend to cancel each other so that the ductless webber has the same throughput as a conventional weber. Also, in the conven-tional webber there tends to be an overlapping of fibers, which creates a shingle ef~ect in the machine or conveyor screen direction. This may cause the web to separate. However, this shingle effect is absent from products produced according to ~5 the present invention.
It may be desirable to blend other materials in the non-woven structure created by the apparatus o~ the present invention. This can be accomplished by installing an open feed tray 60 beneath the nose bar 34 as shown in Fig. 4.
Individualized short fibers, e.g. from a hammer mill, or other fine particulate materials, e.g. superabsorbent powders, are placed in or metered into the tray. The high velocity air stream created in proximity to the lickerin surface due to its rGtation, draws the fine particulate material (e.g. either ~ibers or granules3 in the tray toward the lickerin. The material is drawn to the lickerin because the high speed rotation o~ the lickerin creates a low static 10 ~ JIJ
pressure zone at its periphery~
At the lickerin the particles from the feed tray blend with the fibers following the lickerin and create a generally uniform blend of fibers and particles. This blend is deflected ~rom the lickerin as a blended fiber stream by the deflector plate 40. The result is a blended product such as that shown in Fig. 6A.
As shown in Fig. 4, the tray may have longitudinal dividers 61 within it. Differen-t particulate material may be located in each section of the tray formed by the dividers.
These different materials will tend to be drawn to the portion of the lickerin immediately in front of the portion of the tray where they are located and then deflected to the corresponding portion of the forming web. If materials A, B, and C are spaced evenly in the tray, this material will be blended in the web product as shown in Fig. 3. The difference from the prior description of Fig. 3, however, is that the pulp ~ibers will be uniform and the variation in material will be in the concentra-tion of particles mixed with the pulp.
Instead of a single feed tray, one or more additional trays may also be used. As shown in Fig. 5, a second tray 64 is located above the first tray 60 and supplies an additional source of particulate matter to the fiber stream. As with tray 60, tray 64 may have a number of dividers with different types of particulate materials in each section of the tray. These materials in tray 64 will not only blend with the short fibers, but will also blend with the particulate matter in tray- 60 which is adjacent the same section of the lickerin. As a result, strips of uniquely blended combinations of two or more particles and short fiber~ can be formed along the continuously forming fiber structure.
Generally the deflector plate 40 is straight and the fiber stream is directed straiyht down on to the conveyor as shown by th~ solid arrows in Fig. 5. This results in a uniform blend of short fibers and particles as shown in Fig. 6A.
However, if the edge of the deflector adjacent the fiber stream is angled (as shown in dotted line3 or given a radius curve, ~' 2 ~ J ~
light particles, e.g. pulp fibers, will follow the curve or angle sf the deflector plate due to the wall attachment or Coanda effect. Thus these fibers are deposited at a different angle as shown by the dashed arrows in Fig. 5. The heavy particles, e.g. thermoplastic bonding particles, will continue in the straight line under the influence of inertia. The angled deflector plate results in the heavy particles being laid down mainly toward the bottom of the web and the light particles toward the top of the web as shown in Fig. 6B.
In one example of the present invention, individual pulp fibers can be generated by the lickerin by engagement with the pulp fiber board. Superabsorbent powder can be drawn to the lickerin from the first feed tray and thermoplastic bonding particles (e.g. polyethylene granules) from the second tray.
Depending on the type of deflector, these particles can be uniformly blended or laid down in layers predominated by one of these materials. Subsequently, the web can be heated so the fiber and superabsorbent particles are stabilized by the thermo~bonding material and retain their position in the structure.
While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art, that various changes in form and details may be made therein without depar-ting from the spirit and scope of the invention.

Claims (14)

1. Web forming apparatus comprising:
feeding means for feeding fiber stock to a fiberizing station;
a rotating toothed cylinder mounted such that a portion of said cylinder's outer periphery is adjacent said feeding means at the fiberizing station, said rotating toothed cylinder creating induced air streams and said cylinder is engageable with fiber stock fed to the fiberizing station;
means for rotating said cylinder with respect to the stock fed to said fiberizing station so as to open the stock and produce individual short fibers moving with the cylinder;
deflector means for deflecting the individual fibers as a fiber stream from the cylinder at a preselected location along the periphery of the cylinder, said deflector means being free of means of introducing further air streams other than said induced air streams for doffing fibers from the cylinder and being in the form of a plate positioned such that said deflector means is parallel to the axis of the cylinder and adjacent to, but out of contact with, the cylinder periphery, said plate being at a location spaced from the fiberizing station in the direction of rotation of the cylinder; and fiber collecting means adjacent said cylinder for intercepting the stream of individual fibers accumulating the fibers to form a web, said fiber collecting means being free of structural members for confining the stream of individual fibers.

2. Web forming apparatus as claimed in claim 1, wherein said feeding means includes a feed roller extending parallel to the cylinder and a nose bar parallel to the feed roller such that fiber stock may be fed between the feed roller and the nose bar into engagement with the cylinder.

3. Web forming apparatus as claimed in claim 1 further including a cylindrical cover extending from said deflector means to said feeding means about said cylinder on the side away from the stream of fibers.

4. Web forming apparatus as claimed in claim 1, wherein said fiber collecting means includes an endless conveyor positioned below said cylinder so as to intercept the stream of fibers, and means for moving said conveyor so as to create a continuous web delivered at the end of the conveyor.

5. Web forming apparatus as claimed in claim 4, wherein said conveyor is a screen mesh having perforations extending therethrough, and further including a low vacuum chamber located below said conveyor at the point where said conveyor intercepts the fiber stream, said low vacuum chamber creating a suction force through said conveyor screen mesh.

6. Web forming apparatus as claimed in claim 5, wherein said low vacuum chamber creates a pressure of less than 5 inches of water through said conveyor screen mesh.

7. Web forming apparatus as claimed in claim 6, wherein said pressure is in the range of 1/2 to 1 inch of water.

8. Web forming apparatus as claimed in claim 4, further including means for positioning a supply of porous substrate material positioned so that said substrate material covers and travels with the conveyor such that the web is formed on the substrate.

9. Web forming apparatus as claimed in claim 1, further including at least a first feed tray with an open top and an open front wall, said first feed tray being positioned with its open front wall adjacent the periphery of said cylinder between the feed means and the deflector plate, said tray being adapted to channel a supply of particulate material to the lickerin due to the air flow induced by the cylinder rotation.

10. Web forming apparatus as claimed in claim 9, wherein there are first and second feed trays positioned one above the other with their open front ends adjacent the periphery of the cylinder between the feed means and the deflector plate in the direction of rotation of the cylinder, both said trays containing particulate material.

11. Web forming apparatus as claimed in claim g, wherein the deflector plate has an end remote from the cylinder and the fiber stream is guided along a front surface of said deflector plate, the remote end of the deflector plate being tapered away from the front surface so as to guide lightweight particles by a wall effect, away from the direction of the surface, but to permit heavier particles to follow in the direction of the surface.

12. The web forming apparatus as claimed in claim 1, wherein said fiber stock is short fiber stock.

13. The web forming apparatus as claimed in claim 12, wherein said fiber stock is wood pulp.

14. The web forming apparatus as claimed in claim 13, wherein said rotating cylinder is a lickerin.