US 3772739 A
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United States Patent [1 1 Lovgren Nov. 20, 1973  Assignee: Johnson & Johnson, New
 Filed: Jan. 21, 1971  Appl. No.: 108,547
Ernest G. Lovgren, Palos Park, Ill.
 U.S. Cl. 19/156.3  Int. Cl D0lg 25/00  Field of Search 19/155, 156, 156.4, 19/205, 88, 89, 105
[5 6] References Cited UNITED STATES PATENTS 1,810,675 6/1931 Nuttall et al 19/89 X 2,150,040 3/1939 Seigle et al. 19/155 X 2,451,915 10/1948 .Buresh 19/105 X 2,911,684 11/1959 Hunter 19/205 X 3,052,928 9/1962 Charlton, Jr. et al.. l9/156.3 3,512,218 5/1970 Langdon 19/156 3 3,535,187 10/1970 Wood 19/156.4 UX 3,579,744 5/1971 Menzies, .Ir..... 19/105 FOREIGN PATENTS OR APPLICATIONS 545,638 6/1942 Great Britain 19/89 Primary Examiner-Dorsey Newton Att0rney-Michael Q. Tatlow, Harolw L. Warner and Robert L. Minier  ABSTRACT An apparatus for forming an air-laid non-woven web wherein a pair of parallel lickerins are positioned adjacent one another with the lickerins being rotated in opposite directions, so that when a first supply of iibrous material is fed to one lickerin and a second supply of fibrous material is fed to the other lickerin, separate supplies of individualized fibers are produced that are entrained in separate air streams impelled toward one another and toward a mixing zone between the lickerins. The individualized fibers are doffed from lickerins by the separate air streams and centrifugal force, and the doffed fibers are given an initial trajectory, whereby the inertia of the fibers is sufficient to allow at least a portion of the fibers from each supply to become homogeneously blended as the air streams are impelled against one another. A suction actuated fiber condensing means is positioned in communication with the mixing zone, and the separate air streams are combined into a common air stream that directs the fibers through the mixing zone and toward the condensing means where the fibers are deposited to produce a web comprised of randomly oriented fibers. When the material fed to the first lickerin includes relatively long fibers, such as textile length fibers, and the material fed to the second lickerin contains relatively short fibers, such as papermaking fibers, a web of randomly arranged fibers can be produced having a dispersion of different length fibers in more or less uniform intermixtnres, to create a web having desired properties.
8 Claims, 24 Drawing Figures United States Patent [1 1 [111 3,772,739
Lovgren [451 Nov. 20, 1973 PATENIEU Nov 20 I975 sum 8 CF 8 1 WEB FORMING APPARATUS This invention relates generally to air-laid nonwoven materials, and more particularly to air-laid monwoven webs consisting of a more or less uniform intermixture of randomly oriented fibers. Preferably, the web comprises a substantially homogeneous blend of long and short fibers; i.e., textile length and papermaking fibers.
Fibers are usually classified according to length, with relatively long or textile length fibers being longer than about one-fourth inch and generally between one-half and two and one-half inches in length. The term long fibers as used herein, refers to textile fibers having a length greater than one-fourth inch, and the fibers may be of natural or synthetic origin. The term short fibers," as used herein, refers to papermaking fibers, such as wood pulp fibers or cotton linters having a length less than about one-fourth inch. While it is recoghized that short fibers are usually substantially less costly than long fibers, it is also recognized in many instances that it is desirable to strengthen a short fiber product by including a blend of long fibers therein.
In the recent past, nonwoven fabrics have met with increasing commercial acceptance because such fabrics can be made with physical properties, and appearance, more or less comparable with the more expensive woven fabrics. In general, these fabrics are structures consisting of a random assemblage or web of fibers which are joined together with a binder to provide the desired strength.
It is well known to produce nonwoven webs of textile length fibers by a conventional carding process, and this results in an anisotropic web wherein the fibers are aligned predominantly in the machine direction. It is also known to produce a nonwoven web by a garnetting process, and while webs produced by this technique have less fiber orientation than carded webs, the garnetted webs are generally of unsatisfactory uniformity and also are limited to textile length fibers. Furthermore, the rate at which webs can be produced by either of these techniques is limited, and these techniques do not lend themselves for use in making the very low cost nonwoven fabrics, especially those embodying the use v of the relatively low cost wood pulp fibers.
It is also known to eliminate directionality in carded or garnetted webs by replacing the doffing cylinder used in these processes with an air duct leading to an air condenser. in one arrangement, known as the Duo-Form technique, a carding lickerin individualizes fibers from pre-opened textile length stock, and an intermediate doffing and transfer cylinder feeds the opened fibers to a second lickerin for further opening. The fibers removed from the second lickerin are carried by an air stream and deposited on a screen cage where the web is formed. The Duo-Form process is limitedto the production of a web having textile length fibers, and the successful operation of the process requires thorough pre-opening of the fibrous stock.
Another machine that has been proposed for eliminating directionality in carded or garnetted webs consists of two traveling flat cards having doffers which confront one another. Rapidly rotating needle cylinders remove the fibers from the card doffers and transport them in an essentially inverted .l-shaped path through the converging upper branches of a generally Y-shaped duct system. The lower branch of the duct system is traversed by a horizontally moving screen upon which the fibers are condensed. This latter apparatus is, of course, limited to textile length materials, and even though the output of two cards is combined, the total production rate is still unsatisfactory.
The velocities of the air streams flowing through the converging branches of the generally Y-shaped duct system of the machine just referred to is, of necessity, quite limited. These low velocities are required to avoid upsetting the web on the doffing cylinders of the cards prior to removal of the fibers by the rotating needle cylinders. Also, while this machine ultimately combines the output of two cards into a single duct, because of the necessity of having low air velocities and thus eliminating the possibility of turbulent flow conditions, in the event that two different textile length fibers were fed into the converging branches of the duct system of the machine, little or no blending of the different fibers would take place, and instead a web of an essentially laminar arrangement of fibers would result with a marked interface between the layers of fibers.
Nonwoven webs have also been produced by feeding filamentary material downwardly between oppositely rotating beater blades which break up or rupture the filaments to form long fibers as the filaments are fed between the beater blades. The thus formed fibers are subsequently deposited on a screen or other condenser to form a web, and while such webs may have the textile length fibers randomly arranged, the process is limited to use with tow or other continuous filament material as the source of the fibers.
A further process for producing a random web of textile length fibers is known as the Rando-Webber process, and is practiced upon apparatus available from the Curlator Corporation of East Rochester, New York. In this process, pre-opened textile length fibrous material is fed to a supply device, which further opens and delivers the fibrous material as a loose mat to a web forming unit. The mat is compressed and fed over a nose bar where it is brought into contact with a lickerin, and the teeth of the lickerin remove fibers from the mat and introduce them into a high velocity, low pressure air stream in the reduced cross section throat of a duct. The fibers are subsequently deposited in random fashion on a condensing screen to produce a substantially isotropic web. While this process and apparatus have functioned generally staisfactorily to produce a relatively uniform random web of textile length fibers, it is generally not suitable for use with short fibers nor with blends of short and long fibers. Furthermore, throughputs with this type of apparatus are limited.
It has recently been proposed to produce a random fiber web consisting entirely of short fibers, and one such process is known as the Texpa process that is practiced upon apparatus also available from the Curlator Corporation of East Rochester, New York. This apparatus consists essentially of two adjacent, generally vertically disposed foraminous belts that converge downwardly and that are positioned in communication with a duct carrying short fibers. A pair of oppositely rotating opening cylinders are positioned in close adjacency to one another beneath the converging belts, and a suction actuated fiber condensing means is positioned below the opening cylinders. Suction is applied to the foraminous belts to withdraw fibers from the conveying duct thereabove, and the belts convey the fibers downwardly where they are compressed into a single mat at the point of convergence of the two belts. The single mat is fed downwardly to the opening cylinders, one of which is rotating at a faster speed than the other. The cylinders have oppositely disposed teeth, so that as the mat is fed downwardly between the cylinders, the downwardly facing teeth of one cylinder carry the fiber through the nip between the cylinders, while the upward facing teeth of the other cylinder hold the fibers back. This action tears the mat into individual fibers which are then carried by an air stream onto a condenser belt to form a random web. The Texpa" process is generally not suitable for use with long fibers, or blends of long and short fibers, and the throughputs obtained with this process are limited.
The desirability of, and need for, a web comprised of a mixture of long and short fibers is well understood by those skilled in the art. In general, the desired characteristics of the nonwoven end product as well as its utility dictate the type of fibers and the relative proportions of long and short fibers to be used. Thus, for example, the product may require one or more characteristics such as tear resistance, abrasion resistance, washability and stretchability, burst strength, absorption or nonabsorption to different liquids, heat sealability, ability to resist delamination, etc., all of which will influence the type of fiber or mixture of fibers to be used. Thus, by way of specific example, absorbent products requiring strength characteristics may be a combination of two or more different fibers such as wood pulp fibers and rayon or similar fibers in varying percentages.
Likewise, again depending on the nature of the product desired, the product may have to possess substantially random characteristics as opposed to oriented fiber characteristics in order to provide for balanced properties in both the machine and cross direction for most uses. For example, in the case of products intended for surgical or similar uses requiring absorbency characteristics, such as a sanitary napkin or a portion thereof, absorbent surgical drapes, etc., mixtures of randomly oriented short and long fibers are required to provide improved mechanical characteristics; while in the case of nonwoven materials suitable for use as disposable items in the field of diapers, short fibers are generally employed.
Typical of the short fibers are wood pulp fibers from various types of woods, cotton linters, asbestos fibers, glass fibers and the like; with wood pulp fibers being those which find most frequent use in a large variety of products due to their ready availability and economical attributes. Typical of the long or staple length fibers are synthetic fibers such as cellulose acetate fibers, vinyl chloride-vinyl acetate fibers (e.g. the product marketed under the trademark VINYON), polyamide fibers such as NYLON 6, NYLON 66, etc., viscose staple rayon, cupra-ammonium rayon or other regenerated cellulose fibers including saponified ester fibers, cellulose ester fibers such as cellulose acetate and cellulose triacetate, acrylic fibers, polyester fibers, polyvinyl chloride fibers, polyolefin fibers such as polyethylene and polypropylene, fluorocarbon fibers such as TEF- LON" and natural fibers such as cotton, flax, jute, wool, silk, ramie or rag, or protein fibers such as VlCARA Combinations of any of the short and staple or long fibers may be employed in this invention. The denier of the fibers used may vary over a wide range and may be from one-half to 100 depending on the type of fiber employed and the requirements of the nonwoven material. Commonly, when using staple fibers such as rayon, the denier will vary from 0.75 to 5 or 6 denier.
Conventionally, the shorter type of fibers such as wood pulp fibers are commerically available for airlaying processes in the form of pulp boards, which are compressed sheets of fibers in intimate contact with each other. The pulp boards come in varying thicknesses and lengths, typical thicknesses being from onesixteenth of an inch to three-sixteenths of an inch, and sometimes more. If desired, the starting material such as pulp boards may be comprised of a mixture of two or more different fibers, preferably of approximately the same length. Thus, by way of example, in place of utilizing a conventional wood pulp board, a board may be of a mixture of wood pulp fibers and cotton linters, asbestos fibers, glass fibers, etc. Thus, different properties may be imparted to the product by employing various combinations of fibers.
In the case of staple or longer length fibers, such as rayon, for example, they are normally commerically available in bale form in various fiber lengths; and for use in the present invention, they are generally employed in a pre-opened oriented condition, termed a carded web or carded batt in the art. To this end, baled rayon can be formed into a carded lap according to conventional techniques known to those skilled in the art, which, briefly summarized, first involves form ation of a picker lap wherein the fibers are formed into a uniform batt of generally constant weight, whereafter they are carded to orient and open and comb the fibers, and thus form the carded batt. If desired, in place of using a carded batt of only rayon, a mixture of rayon and other fiber or fibers, or for that matter a mixture of any two or more different long fibers can be employed, thereby providing a product having different fibers and with them the different properties they impart to the ultimate nonwoven fabric. It is not necessary that the staple length fibers be used in the form of a carded batt but these fibers may be presented to the machine of the present invention by other means well known to those skilled in the art, such as chute feeding, CMC even feed, or directly from a card, for example.
Those skilled in the art have recognized the long felt need for providing a process and apparatus for producing a web of homogeneously blended short and long fibers, as described above, with substantially all of the fibers being randomly disposed. Various systems have been proposed in the past, but none have met with wide commercial success because of the failure to either get satisfactory randomnization, satisfactoy homogenization, or a satisfactory production rate.
For example, it has been proposed to individualize short fibers by a milling device, such as a hammer mill or a fitz mill, and to entrain the individualized short fibers in an air stream into which individualized long fibers are fed. In one known technique, the individualized short fibers are transported in a horizontal duct, with a lickerin rotating at a narrowed throat portion of the duct and combing individual fibers from a long fiber web or mat and introducing them into the short fiber air stream traveling therebelow. It has been proposed to form a web by depositing the airborne fibers on a foraminous condenser that intersects the duct, or by allowing the duct to feed fibers into a gravity settling box, where they settle by gravity on a foraminous conveyor. In either technique, because the long fibers are introduced into the air stream above the short fibers, the resulting webs have a tendency toward stratification, with the long fibers predominating at the top of the web, and the short fibers predominating at the bottom of the web. This lack of complete homoginization has made such processes generally unsatisfactory.
Webs of blended short and long fibers that have been produced by such prior art techniques have not only exhibited a marked different in properties from one side to the other, but also have shown a definite tendency to strip or separate at the line of demarcation between the layers. While such webs have been satisfactory for certain products, particularly where the web is an internal layer that is not visible to the consumer, such webs have not been completely satisfactory for other products, particularly where strength is required and, also, where the web is exposed to view by the consumer.
One of the major problems in connection with blended fibrous webs formed by prior art techniques is in the proper opening of the fibrous materials at high speeds to substantially completely individualize the fibers without damaging them. For example, a single lickerin has been used to simultaneously open both long and short fiber materials, and it has been found that lickerin speeds that are suitable to open the short fiber material in a high speed commercial operation have caused excessive damage to the fibers of the long fiber material.
In webs produced by prior art techniques, it is common to find a relatively large percentage of incompletely opened clumps of fibers and it is also common to find a relatively large percentage of salt like hardened particles that are formed by compressing individual fibers during the fiberizing step. Such webs have not been visually acceptable and suitable for use as an exposed layer in an end product, since they are not uniform in appearance. Furthermore, in webs having clumps of fibers, or hardened particles of broken and/or compacted fibers, the functional characteristics of the web are not uniform. For example, the presence of clumps of fibers or compacted fibers causes the web to be of variable weight, strength, cohesiveness, fluid absorbtiveness and uneven in color when dye is used. Webs having a high percentage of salt-like particles, are completely unsatisfactory for many uses, such as surgical towels and dressings, because of the tendency of these particles to flake off the web.
To obviate such problems, it has been necessary to rotate the lickerin at a compromise speed, which is not suitable for commercial production. Other techniques that have been proposed in the past have the same or similar problems.
In accordance with the process and apparatus of the present invention, a nonwoven web of substantially completely open fibers, preferably randomly oriented, is produced wherein at least a portion of the web consists of a homogeneous blend of fibers from two separate and distinct supplies of fibers. The present invention utilizes a pair of parallel lickerins that are rotated in opposite directions to individualize fibers from each supply. When the web is to include a blend of long and short fibers, the lickerin for the short fibers is rotated at a faster speed than the lickerin for the long fibers. A backing member is provided for each fibrous source adjacent its respective lickerin, and different and optimum opening relationships may be established between each lickerin and the nose bar portion of its associated backing member.
The fibers are doffed from the lickerins substantially immediately after individualization by separate gaseous streams flowing adjacent each lickerin, and by centrifugal force, which tends to throw the fibers into their respective gaseous streams. The supplies of indivualized fibers are entrained in the separate gaseous streams, and the streams are impelled toward one another and toward a generally centrally disposed mixing zone, where the fibers intermix.
The supplies of individualized fibers are combined in a common gaseous stream flowing downwardly through the mixing zone, in an exemplary form of the invention. The common air stream may be produced by the cooperative action of a suction actuated fiber condensing means at the terminal end of the mixing zone and by the air generated by the rotary action of the oppositely rotating lickerins.
In the process of the present invention, the fibers entrained in the separate gaseous streams have a trajectory including a component directed toward one another, as well as a component directed toward the mixing zone. Although the fibers are transported by the separate gaseous streams through the mixing zone, the fibers have sufficient kinetic energy by virtue of their mass and velocity that the fibers continue to travel generally in the direction of their initial trajectory because of their inertia. The component of motion of the fibers toward one another causes them to combine in an intimate mixture of fibers as the gaseous streams are impelled against one another and combined into the common'stream. The combined stream transport the mixed and blended fibers through the mixing zone to a condensing means where the fibers are deposited to build up a web of the desired thickness.
The blending action may be regulated by controlling certain machine parameters, such as the rate of fiber input, the volume and/or velocity of the air flowing through the machine, the speeds of the lickerins, type of lickerin teeth and the winding of the clothing, and the geometry of the ducting system. For example, at relatively low air volumes, when producing a web comprised of homogeneously blended short and long fibers, since the short fiber lickerin is rotating at a higher speed than the long fiber lickerin, a differential velocity is created in the common gaseous stream, with the portion of the gaseous stream on the short fiber side of the machine having a greater velocity (and hence a lower pressure) than the portion of the gaseous stream on the long fiber side of the machine. Therefore, the individualized long fibers are accelerated and drawn into the faster moving zone of air, and the acceleration of the individualized long fibers keeps them under tension substantially until they are deposited on the fiber condensing means. The suction or drawing action created by the faster rotating short fiber lickerin enhances the intimate admixure of the long fibers with the individualized short fibers.
Also, by having relatively higher gas volumes, with an appropriately shaped ducting system, the gas passing through the machine can be retained in a turbulent condition, which also enhances the degree of blending of the long and short fibers.
In one embodiment of the invention a variable nose bar-lickerin relationship is provided for each supply of fibrous material, so that these realtionships can be individually adjusted and controlled for different materials to produce a lickerin action that will substantially completely open the respective fibrous materials.
The relationship of the fiber condensing means to the fiber mixing zone is also adjustable in an illustrative embodiment of the invention, so that by establishing a desired relationship between the mixing zone and condensing means, the directioning of the individual fibers of the resulting web can be varied and controlled between a completely randomized orientation, and an orientation wherein a majority of the fibers extend either lengthwise or crosswise of the web.
The process and apparatus of the present invention produces a web having at least a portion comprised of a homogeneous admixture of long and short fibers; and in webs where all of the fibers are homogeneously blended, such webs are not only uniform in external appearance, but also have uniform functional characteristics including weight, thickness, etc.
DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevational view, partly in section, of a web forming apparatus constructed in accordance with the present invention;
FIG. 2 is a side elevational view, partly in section and partly broken away, of the apparatus illustrated in FIG.
FIG. 3 is an enlarged sectional view taken generally along line 33 of FIG. 2;
FIGS. 4l2 are enlarged, fragmentary sectional views of modified configurations for the mixing zone of the apparatus illustrated in FIGS. 13;
FIG. 13 is a central sectional view through a further embodiment of the web forming apparatus, and FIG. 13 is taken generally along line l313 of FIG. 14;
FIG. 14 is a front elevational view of the apparatus illustrated in FIG. 13;
FIG. 15 is a fragmentary perspective view illustrating details of the condensing screen of the embodiment of FIGS. 13 and 14;
FIG. 16 is an enlarged sectional view taken generally along line 16-16 of FIG. 15;
FIGS. 17-19 are schematic representations of the apparatus illustrated in FIGS. 13-16, and illustrate the baffle in different positions;
FIGS. 20-23 illustrate in cross section various webs that can be produced by the apparatus of FIGS. 13-16 and FIG. 24 is an enlarged schematic view illustrating the profile of the lickerin teeth used in the apparatus of the present invention.
DETAILED DESCRIPTION OF THE INVENTION While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail only preferred embodiments of the invention and modifications thereof, with the understanding that the present invention is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments illustrated. The scope of the invention will be pointed out in the appended claims.
Referring now to the drawings in detail, and particularly to FIGS. 1-3, an exemplary embodiment of the apparatus of the present invention is indicated generally at 20, and the apparatus 20 includes frame means 22 supporting first and second fiberizing means 24 and 26 adjacent the upper end thereof, and supporting a suction actuated fiber receiving means 28 therebelow, as will hereinafter be described in detail. Fiberizing means 24 and 26 are operative on separate sources of fibrous material to substantially completely open the material and create separate supplies of individualized fibers that are entrained and conveyed in separate gaseous streams directed toward each other and toward a common mixing zone 25 therebetween. The individual fibers are doffed from the fiberizing means 24 and 26 by centrifugal force and by the separate gaseous streams moving relative to the fiberizing means. The separate gaseous streams are impelled against one another, and are combined into a common high speed gaseous stream flowing through the mixing zone 25 toward the fiber receiving means 28. The fibers are given an initial trajectory in the doffing direction, and the kinetic energy imparted to the fibers by virtue of their mass and velocity enables them to have substantial inertia and continue to have a significant component of motion toward the other supply of fibers. This allows at least a portion of the fibers of each supply to become homogeneously blended and further mixing can take place in the mixing zone 25 by adjusting certain machine conditions, as is hereafter explained. The entrained fibers are then directed to, and deposited upon, receiving means 28 by the common air stream to build up a web W. A doffing roll 27 is supported upon frame means 22 adjacent receiving means 28 for removing web W therefrom and transferring it to a conveyor 29 therebelow.
The apparatus of the present invention includes frame means 22 defined in part by upright members 30 that are connected to one another by upper crossrails 32 and lower crossrails 34. A subframe 36 is mounted upon upper crossrails 32, and subframe 36 includes a pair of spaced side plates 38 that are stabilized by transversely extending tie rods 40. Fiberizing means 24 and 26 are supported between side plates 38 at first and second fiberizing stations, respectively.
In order to be able to change the characteristics of web W, as by varying the direction and pattern in which the individualized fibers are deposited on the fiber receiving means 28, in the embodiment illustrated in FIGS. 1-3, the position of the fiber receiving means 28 relative to the mixing zone 25 can be varied, and for this purpose, a pair of transversely extending frame members 42 are adjustably connected to uprights 30. A vertical adjustment means is provided by plates 44 that are fixed to opposite ends of each frame member 42, with the plates 44 each including spaced, vertical slots 46. Locking bolts 48 impale slots 46 and are threaded into internally threaded openings in uprights 30, so that the frame members 42 can be moved vertically when the locking bolts 48 are loosened, and positively retained in the desired position relative to mixing zone 25 when locking bolts 48 are tightened.
Fiber receiving means 28 includes side plates 50 at opposite ends thereof, and horizontally or lateral adjustment of the fiber receiving means 28 is effected by mounting bolts 52 that are slidably mounted in elongate slots 54 in the upper flange 56 of frame member 42. As can be seen in FIG. 1, bolts 52 extend through openings in mounting feet 58 that extend laterally from the lower ends of side plates 50, and nuts 60 are threaded upon bolts 52 to retain the fiber receiving means 28 in the desired position of lateral adjustment relative to mixing zone 25. While the position of the fiber receiving means 28 is variable in the illustrated embodiment of the invention, it should be understood, that the adjustability feature is not critical to the present invention, when, in use, a given type of web is to be continuously produced on the machine.
A mass of long or textile length fibers 62 of the type described above, is fed to fiberizing means 24 by a cylindrical feed roll 64. The opposite ends of feed roll 64 are rotatably supported upon mounting plates 38, and the feed roll 64 is positively rotated by conventional means, not shown, to control the rate and amount of long fiber material that is fed to the fiberizing means 24.
The present invention includes adjustment means 66 for varying the position of the feed roll 64 relative to a nose bar assembly 68 for accommodating different thicknesses of long fiber material. The adjustment means 66 includes a mounting block 70 adjacent each side plate 38, and each block 70 is generally T-shaped in cross section with an offset portion being slidably mounted in an inclined slot 72 in the adjacent mounting plate 38. Each block 70 includes a recess 74 that positions a further mounting block 76 for movement perpendicularly to slots 72. Mounting blocks 76 include a boss 78 having the ends of the feed roll 64 rotatably mounted therein, and elongate slots 80 at each side of blocks 76 are impaled by clamping bolts 82 that are threaded into blocks 70-to allow the blocks 76 to be adjusted at right angles to slots 72. In this manner, the clearance between the feed roll 64 and nose bar assembly 68 can be set at an optimum gap for the particular type and thickness of the fibrous source 62.
Feed roll 64 is retained in a positive material feeding relationship with the nose bar assembly 68, and to this end, feed roll 64 is urged toward the nose bar assembly 68 by springs 84 that act between a recess in one end of each block 70 and an aligned recess in an abutment plate 86 that is secured to each side plate 38. Elongate guide slots 88 are provided in each corner of blocks 70, and clamping bolts 90 impale slots 88 and are threaded into openings in side plates 38. The ends of slots 88 limit the movement of feed roll 64 toward the nose bar assembly 68 and provide a minimum clearance therebetween, it being understood that the bolts 90 can be .tightened to positively secure the feed roll 64 in a selected position of adjustment. By virtue of the abovedescribed adjustment means 66, it will be appreciated that feed roll 64 can be located in any of a plurality of locations relative to the nose bar assembly 68. However, in a situation where the fibrous source 62 will always be substantially the same, it should be understood that the adjustment means 66 can be eliminated or greatly simplified.
In order to provide a first supply of individualized fibers, a material opening cylinder 92 is mounted for rotation in a clockwise direction between side plates 38 below feed roll 64, and opening cylinder 92 preferably takes the form of a lickerin having spirally wound toothed clothing 94 thereon. The teeth of the rayon lickerin usually have a lower tooth height and pitch than the pulp lickerin. The pitch and height of the teeth used on the lickerin for the rayon may vary, ggod results being obtained with a tooth pitch of about oneeighth inch to about one-fourth inch and a tooth height of about one-eighth inch to about one-fourth inch. The
angle of the teeth of the lickerin for the rayon may also vary, generally within the limits of about -l0 to about The teeth 96 may have only a slight positive rake, or even a slight negative rake, to facilitate doffing of the short fibers from the lickerin 92.
Adjustment means 98 is provided for varying the position of the nose bar assembly 68 relative to the lickerin 92, so as to provide optimum conditions for substantially fully opening the long fiber material 62 without damaging the fibers thereof. The nose bar assembly 68 includes a holder 100 that extends between side plates 38, and holder 100 supports a nose bar 102 thereon that has a curved material supporting surface facing feed roll 64. Holder 100 is mounted for movement toward and away from lickerin 92 in inclined slots 104 in side plates 38, and the position of holder 100 is adjusted by screws 106 that are threaded into holder 100, with screws 106 reacting against saddle members 108 that are secured to side plates 38. A support block 110 is secured to each side plate 38, and clamping 7 plates 112 fixed to holder 100 are tightened against support blocks 110 by screws 114 to positively retain holder in the selected positions of adjustment, it being understood that clearance slots 116 are provided in blocks to allow the holder 100 to move relative thereto. Should it be desired to always include substantially the same type of long fibers in the end product, the aforementioned adjustment means 98 may become unnecessary.
The long fiber material 62 is presented to the teeth of the rapidly rotating lickerin 92 at approximately 11 oclock position, and the lickerin teeth comb out and individualize the long fibers as the teeth move past the nose bar 102.
In order to be abe to vary and control the mixing characteristics of the long and short fibers as their individual carrier streams are combined, as will hereinafter appear, the width of the throat of the mixing zone 25, i.e., the distance between the fiberizing means 24 and 26, can be varied, and adjustment means 118 is provided for moving lickerin 92 in and out in a horizontal plane. The axle 122 of lickerin 92 is mounted in slide members 124 that ride in horizontal slots in side plates 38, and adjustment means 1 18 is provided by adjusting screws 126 that are threaded into slide members 124 for varying the position of lickerin 92. Adjusting screws 126 react against plates 128 that are secured to side plates 38.
Lickerin 92 is rotated in a clockwise direction, as shown by the directional arrow in FIG. 3, and to this end, the output shaft 132 (FIG. 1) of a motor is connected to lickerin 92 by a belt drive system including a sheave 134 on shaft 132, a sheave 136 on axle 122, and an endless belt 138 trained over sheaves 134 and 136. Motor 132 can be bolted to an upright 30 of a main frame, as illustrated, or it can be mounted on the floor, and the motor mounting means may be adjustable, so that the position of the motor 130 can be changed when theposition of the lickerin 92 is changed. Motor 130 rotates lickerin 92 at a high speed that allows the teeth 96 to comb out and individualize the long fibers from supply 62 at a rapid rate, and for purposes of illustration, a rotational speed of 2,400 rpm has been found to be satisfactory to produce a desired quantity of individualized rayon fibers from picker lap fiber source without damage to the fibers. Lickerin 92 can be rotated at higher speeds for greater throughput, if desired.
The rotation of lickerin 92 generates a stream of gas, e.g., air, as indicated by the directional arrow 139 in FIG. 3, that flows under the nose bar assembly 68, to initiate a fiber doffing action, in cooperation with the centrifugal forces acting on the fibers, substantially immediately after the fibers are combed from source 62. Since doffing is initiated substantially immediately following fiber individualization, i.e. at about the 12 O- clock position, a large number of the fibers are given an initial trajectory having a significant component of motion toward the oncoming fibers from fiberizing means 26. As the fibers are accelerated and entrained in the stream 139 they possess substantial kinetic energy because of their mass and velocity, and the inertia of the fibers tends to keep them moving along a path generally in the direction of their initial trajectory.
A further gas stresm, represented by the directional arrow 140 in FIG. 3, flows generally vertically downwardly through the mixing zone 25 toward the fiber collecting means 28 adjacent the periphery of lickerin 92, and any undoffed fibers are removed from the lickerins by the stream 140. Stream 140 serves as a common carrier stream for the fibers doffed from both lickerins as will hereinafter appear. The gas stream 140 can be generated in part from a separate source 142, such as a commercially available air knife, or the gas stream can be generated by the combined action of the separate carrier streams and the suction actuated condenser means 28, as will hereinafter be explained. In any event, the common stream 140 receives the oncoming fibers and partially, but not completely (as will hereafter appear), overcomes their inertia to change their trajectory and direct them to the condensing means 28.
In the event that an air knife is used, adjustment means 144 (FIG. 1) may be provided for positioning the air knife in an optimum position relative to the mixing zone 25 to get the desired type of directionalized air flow. Adjustment means 144 is arranged to move the air knife 142 both vertically and angularly, if desired. To this end, the air knife 42 includes laterally extending support portions 146 at each end thereof having internally threaded vertically extending openings therein. Frame members 148 are secured to side plates 38, and adjusting screws 150 adjacent each side plate 38 extend through the threaded openings in support portions 146 and through aligned bores in frame members 148 so that the air knife 142 can be vertically adjusted. A worm wheel 152 is provided at each end of air knife 142, and angular adjustment of the air knife is accomplished by worm gears 154 on adjusting screws 156 that are mounted for horizontal movement in horizontal bores in frame members 148. By appropriate adjustment of adjusting screws 150 and 156 the direction of the air stream emanating from the orifice at the lower end of the air knife can be varied and controlled.
A mass of short fibers 162, such as pulpboard or linters board in sheet form, is fed to fiberizing means 26 by a cylindrical feed roll 164, which is positively rotated by conventional means, not shown, to control the rate and amount of short fiber material that is fed to the fiberizing means 26. The opposite ends of feed roll 164 are rotatably mounted in support arms 166 that are pivotally connected between side plates 38 by pivot members 167. Feed roll 164 is biased towards a nose bar assembly 168 by springs 169 that bear against support arms 166, and springs 169 urge the support arms in a counterclockwise direction about pivots 167. Springs 169 react between support arms 166 and a nut 170 on spring retention members 172 that are pivotally connected to side plates 138, it being understood that the members 172 pass through clearance openings in the support arms 166. Spring holding members 172 include a stop surface 174 for limiting the pivotal movement of the support arms 166, thereby establishing a minimum clearance between the mass 162 of short fibers and the nose bar assembly 168.
A material opening cylinder 176 is mounted for rotation in a counterclockwise direction between side plates 38 below feed roll 164, and opening cylinder 176 preferably takes the form of a lickerin having spirally wound toothed clothing 178 thereon. As is evident from FIGS. 1 and 3, lickerins 92 and 176 are positioned in parallelism with one another and are preferably of the same diameter. In an exemplary embodiment of the invention, lickerins 92 and 176 have an outer diameter of approximately 9 a and a length of approximately 40 inches. The individual teeth 180 of clothing 178 are selected to optimize the opening or grinding conditions for the short fiber material 162. The pitch and height of the teeth used on the lickerin for the pulpboard may vary, good results being obtained with a tooth pitch or about three thirty-second inch to about one-half inch and a tooth height of about three thirty-second inch to about one-half inch. The rake angle of the individual teeth 180 of clothing 176 is selected to give the optimum opening characteristics for the specific material being fed to the lickerin. The angle of the teeth of the lickerin for the pulpboard may also vary, generally within the limits of about l0 to about +10. To facilitate doffing the teeth may preferably have a negative rake.
Optimum conditions for substantially completely opening the short fiber material 162 may be further established by virtue of an adjustment means 182 which varies the position of the nose bar assembly 168 relative to the lickerin 176. The nose bar assembly 168 includes a holder 184 having a nose bar 186 at the lower end thereof that faces feed roll 164. The nose bar 186 preferably has a straight or flat material engaging surface for supporting the short fiber pulp material 162 in position to have the material combed and the fibers individualized by lickerin 176. Plates 188 (FIG. 1) are secured to opposite ends of the holder 184, and plates 188 are generally T-shaped in cross section, with the offset portion of each plate 188 riding in an inclined slot 190 in one side plate 38. The adjustment means 182 is provided by adjusting screws 192 that are threaded into openings in plates 188, with the screws 192 reacting against saddle members 194 that are fixed to the side plates 38. Plates 188 include a plurlaity of elongate slots 196 (FIG. 1) therein, and clamping bolts 198 that are threaded into side plates 38 impale slots 196, it being understood that the bolts 198 are tightened to positively retain the holder 184 in the selected position of adjustment relative to lickerin 176.
The nose bar holder 184 can also be adjusted angularly relative to the feed roll 164 and the teeth on lickerin 176, and to this end, a block 200 on one side of the holder 184 is pivotally mounted on a shaft 202 that the extends transversely between plates 188. Further clamping plates 204 are affixed to the ends of shaft 202, and arcuate slots 206 in clamping plates 204 are impaled by clamping bolts 198, that are tightened to positively retain the holder 184 in the selected position of angular adjustment. lf should be understood that the adjustment means for either or both of the nose bar assemblies is not critical to the process of the present invention, and fixed lickerin-nose bar relationships may be established for both supplies of fibers, particularly if each lickerin and nose bar is to always open material having substantially the same characteristics, but the adjustability feature adds flexibility to the machine making capable of use with materials having different characteristics.
As is mentioned briefly above in connection with lickerin 92 a preselected spacing between the lickerins 92 and 176 can be established by virtue of an adjustment means 210 for varying the position of lickerin 176 relative to the mixing zone and lickerin 92 acting in combination with the adjustment means 118 for lickerin 92. To this end, the axle 212 of lickerin 176 is mounted in slide members 214 that ride in horizontal slots 216 in side plates 38. Lickerin 176 is moved in and out by adjusting screws 218 that are threaded into slide members 214, with screws 218 reacting against plates 220 that are secured to the side plates 38. By virtue of the adjustment means 118 and 210, the width of the throat portion of the mixing zone 25 between the lickerins 92 and 176 can be varied and controlled. The distance between the lickerins will, to a certain extent, be determinative of the volume of fibers that are entrained in gas stream 140 and ultimately deposited upon receiving means 28. A spacing of approximately .25 inches has been found to give excellent results although smaller gaps, and larger gaps up to 1.5 inches have also given satisfactory results.
Lickerin 176 is rotated in a counterclockwise direction, as shown by the directional arrow in FIG. 3, and to this end, the output shaft 222 (FIG. 1) of a motor 224 is connected to lickerin 176 by a belt drive system including a sheave 226 on shaft 222, a sheave 228 on axle 212, and an endless belt 230 trained over sheaves 226 and 228. Lickerin 176 may be rotated at a speed substantially faster than the rotational speed of lickerin 92 when lickerin 176 is opening short fiber material and lickerin 92 is opening long fiber material. For purposes ofexample, a rotational speed of 4,000 rpm has been found satisfactory to produce a desired quantity of high quality individualized pulp fibers from a pulp board. Faster rotational speeds for lickerin 175 can be used if greater throughput is desired. Like motor 130, motor 224 is illustrated as being secured to an upright of the main frame, although it may be mounted on the floor, and the mounting for motor 224 may also be adjustable.
In order to improve the opening action of lickerins, an arcuate cover plate 233 (shown only for lickerin 92) may be positioned over the portion of the lickerin between the nose bar and the upper end of the mixing zone. The end of cover plate 233 is spaced from the nose bar 102, so that the rotation of the lickerin 92 will draw in a stream of gas, e.g. air, between the cover plate 233 and nose bar 102 that will force the fibers against the lickerin 92, while at the same time force the fibers cooling the cover plate and helping to convey fibers. A gap of one-half inch between the cover plate 233and nose bar 102 has proven to be effective in providing a stream that forces the upper layer of fibers into the teeth of lickerin 92 for additional working.
Because of the relatively high rotational speeds of lickerins 92 and 176, each lickerin creates a zone of gas, e.g. air, moving circumferentially therearound. As is mentioned above, lickerin 92 generates gas stream 139 that initiates doffing of the individualized fibers from lickerin 92. Likewise, lickerin 176 generates a gas stream, represented by directional arrow 231, that passes under nose bar assembly 168 and in conjunction with centrifugal force and tooth configuration initiates a fiber doffing action substantially immediately after the fibers have been combed from source 162. As is evident from FIG. 3, the short fiber material is presented to the teeth on lickerin 175 at approximately a l oclock position. Since a large number of the fibers are doffed from lickerin 176 substantially immediately following individualization, i.e. at about a 12 oclock position, the fibers are given an initial trajectory having a significant component of motion toward the oncoming fibers from lickerin 92. As the fibers are accelerated into stream 231, because of their inertia, they will tend to continue to move in their initial direction.
Since the lickerins 92 and 176 are rotating in opposite directions, the zones of air generated thereby cooperate to produce at least a portion of the common high speed stream that is directed downwardly between the lickerins through the mixing zone 25 toward the fiber receiving means 28. It is has been found that with rotational speeds of the aforementioned magnitude, i.e., 2,400 rpm for lickerin 92 and 4,000 rpm for lickerin 176, and with the tooth-to-tooth spacing of the lickerins being inthe aforementioned range, the lickerins can produce a substantial portion of the velocity of stream 140, depending of course on the presence or absence of air knife 142 and the magnitude of the suction drawn by fiber receiving means 28.
It has been found that at the lickerin rotational speeds mentioned above and with condensing means 28 pulling approximately 400 cfm, the combined air stream 140 has an average volumetric flow rate of approximately 500 cfm. This flow rate gives the individual streams 139 and 231 and the common stream 140 sufficient velocity to effect the desired fiber doffing and blending, so that a separate gas source, such as air knife 142 is not necessary.
As has been mentioned above, the fibers entrained in gaseous streams 139 and 231 posess substantial kinetic energy, and their inertia tends to keep them moving in the initial doffing direction. As the separate gaseous streams 139 and 231 merge into the common gaseous stream 180, the combined forces of gravity and the suction applied by the fiber receiving means tend to cause the fibers to assume a more downward trajectory, but the momentum of thefibers is such that as the streams 139 and 231 are impelled against one another, a substantial portion of the long and short fibers become intermixed. The position at which the streams 139 and 231 are brought together, and the degree of blending of the long and short fibres can be controlled by varying certain machine parameters such as the volume and/or velocity of gas flowing through the machine, the speed of the lickerins, the rate of fiber input, the geometry of the ducting system, and the position of the fiber receiving means.
In one mode of operation, at relatively low gas volumes, in forming a web of blended long and short fibers, since lickerin 178 is rotating at a substantially greater speed than lickerin 92, a zone of lower pressure is created in the common high speed stream 140 in mixing zone 25 between and below the lickerins 92 and 176. The individualized long fibers from the lickerin 92 are accelerated toward the zone of low pressure and retained substantially under tension until the fibers are deposited upon the fiber receiving means 28. The drawing of the long fibers into the zone of low pressure and the aforementioned inertial impelling of the fibers together, cause the long and short fibres to be homogeneously blended in the mixing zone 25.
Also, as is explained in detail in the commonly assigned, concurrently filed application Ser. No. 108,545 of A. Farrington, the geometry of the ducting of the machine, may be configured to insure that the gaseous streams will have turbulent flow characteristics from the point of doffing to the point of deposit of the fibers. This, together with the interposition ofa baffle between the separate gaseous streams can result in the production of various different webs, including a web comprised of homogeneously blended long and short fibers. Furthermore, as is explained in the commonly assigned, concurrently filed Ruffo et al. application Ser. No. 108,546, at increased gas-to-fiber volume ratios, various high quality webs can be produced at high production rates.
The lower portion of the mixing zone 25, i.e., the portion between the lickerins 92 and 176 and the fiber receiving means 28 is preferably closed by deflector plates 232 and 234 that are secured between side plates 38. Because the lower portion of the mixing zone 25 is wider than the throat portion between the lickerins 92 and 176, the stream 140 having the intimate admixture of long and short fibers therein tends to decelerate as it approaches the fiber receiving means 28, and hence it is desirable that the fiber receiving means 28 be positioned sufficiently closely to the lickerins 92 and 176 that deceleration of the rayon fibers in the stream is minimized. While the receiving means 28 is illustrated substantially immediately below lickerins 92 and 176 in FIG. 3, the present invention does not require that the fiber receiving means be positioned this close to the lickerins, and satisfactory webs have been produced withh the distance between the center line to center line spacing between the lickerins and receiving means being as much as 16 inches.
The fiber receiving means 28 is defined by a suction actuated fiber condensing drum 236 having a foraminous fiber supporting surface formed by a radially open honeycomb network 238 (FIG. 3) that has at least one fine mesch screen 240 thereover. In an exemplary embodiment of the invention, drum 236 has an outer diameter of approximately 12 inches. Drum 236 is rotated (clockwise in the illustrated embodiment as indicated by the directional arrow in FIG. 3) by a motor 242 through a chain drive (FIG. 1) including a sprocket 244 fixed to the output shaft 246 of the motor 242, a sprocket 248 fixed to the drum 236, and an endless chain 250. The fiber receiving means 28 further includes a stationary central portion 252 having flanges 254 that extend radially outwardly into sealing engagement with the drum 236. In the embodiment of FIGS. 1-3, one flange 254 is positioned in substantial alignment with deflector plate 232, while the other flange 254 is circumferentially beyond deflector plate 234. A conduit 256 (FIG. 2) is connected to stationary portion 252 and to a suitable source of negative pressure for applying a suction to drum 236 between the flanges 254. It will be appreciated that the suction of the fiber receiving means 28 cooperates with the air streams created by the oppositely rotating lickerins 92 and 176 to provide a pressure gradient across the mixing zone 25 which draws the individualized and homogeneously blended long and short fibers onto the drum 236 to build a web. The stream 140 that is produced by the conjoint action oflickerins 92 and 176 and the negative pressure of the fiber receiving means 28 is retained at a large enough velocity that a sufficient means interstitial spacing between the fibers is maintained in the mixing zone which allows the fibers to remain intermixed without agglomeration prior to deposition on the fiber receiving means.
In a typical example of the practice of the invention disclosed herein, lickerins 92 and 176 of the size set forth above were rotated at the above mentioned speeds, and 555 pounds of fibers per hour were fed to the lickerins, with percent of the fibers being pulp fibers, and 25 percent of the fibers being rayon fibers. The tooth-to-tooth spacing between the lickerins was 0.25 inches, and deflector plates 232 and 234 were parallel with one another and spaced by .625 inches. The air stream had an average volumetric flow rate of 500 cubic feet per minute (2,250 pounds per hour), and there was a feed ratio of about 4.05 pounds of air per pound of fiber. The average volume ratio of air to fiber was approximately 5,000 to l. Pitot readings were taken at various positions between deflector plates 232 and 234, and these readings indicated that stream 140 had a high velocity zone adjacent deflector plate 234. Visual observations confirmed that a large number of fibers were entrained in the high velocity portion stream 140, and that a majority of the fibers were condensed on the screen adjacent deflector plate 234. With the conveyor 29 operating at a web take away speed of 200 feet per minute, it was found that an extremely satisfactory web W was produced having an average weight of about 900 grains per square yard.
It will be understood, of course, that conveyor 29 is intended to transport the web W to a further processing zone, such as a bonding zone where a bonding agent may be applied to the web.
The nonwoven webs obtained by the process of the present invention may be post-treated by any suitable conventional technique, to bond the web and provide the required strength and coherency characteristics for a given product. The particular type of bonding technique chosen will depend on various factors wellknown to those skilled in the art, e.g., the type of fibers, the particular use of the products, etc. To this end, typical of the conventional techinques are web saturation bonding, suction bonding, foam bonding, print bonding, fiber bonding, fiber interlocking, spring bonding, solvent bonding, scrim bonding, viscose bonding, mercerization, etc.
In the case of web saturation bonding, the nonwoven web is generally soaked with a solution or emulsionbinder, and thereafter, the excess fluid is removed usually by mechanical means (e.g. squeeze rollers and/or vacuum), followed by evaporation. In the case of suction bonding, a web is treated with a suitable binder by soaking and the excess removed by means ofa vacuum apparatus. In foam bonding, which is a variation of saturation bonding and is particularly useful for products requiring good bulk and through-bonding, a foam binder is employed. In print bonding, generally employed where softness and absorbency is required, a bonding agent will be printed onto the web by, e.g. gravure type rolls. The web can be wet or dry when printed and generally the binder is a water, solvent or plastisol based one.
In fiber bonding techniques, employed where a percentage of the fibers in the web are semi-soluble in certain solvents, e.g. hot water, the web may be bonded by adhesive or by treating the web with a suitable solvent e.g. polyvinyl alcohol. In a variation of this procedure, if the web includes thermoplastic fibers such as polypropylene, VINYON or low melting polyester, hot roll embossing calendars may be employed. Still further, 'in other case, a low melting spun bonded web may be placed between higher melting fiber webs and hot calendered. Thermoplastic powders may also be used in this technique.
In the case of mechanical interlocking bonding techniques, needle looms are employed in bonding soft fiber webs. Boards of needles with barbs downwardly pointed perforate the web and entangle the layers. A variation of this type of bonding technique is stitch bonding with yarn, as may be accomplished by using an ARACHNE apparatus or with the fibers of the web itself.
As the name implies, spray bonding techniques spray a binder onto the web which is subsequently passed into a drying chamber. This type of bonding is particularly useful where high loft is required in products, e.g. which are suitable for use as air filters. Solvent bonding employs a solvent which is applied to the web to soften the fiber surface and render it adhesive. Typical solvent bonding employs the use of chloral hydrate of DMSO (dimethylsulfoxide).
ln scrim bonding, a scrim layer or yarn layer act as carriers for a wet or thermoplastic adhesive used to laminate the nonwoven webs to one or more layers of a substrate, e.g. tissue. In viscose bonding, which is a special case of print or saturation bonding, cellulose xanthate is regenerated to pure cellulose on the inner sections of the fibers forming the nonwoven web. in a like manner, acid solutions of nylon may be regenerated in situ.
in mercerization bonding techniques, nonwoven webs are bonded using the uncurling manner of caustic solutions, e.g. caustic soda on all-cotton nonwoven webs. The fibers unwind to entangle each other and, thereafter, the resulting product is thoroughly washed.
The above list of bonding techniques is not intended to be exhaustive as others known to those skilled in the art may be employed, e.g. bonding with the use of high pressure streams of water or other fluids directed onto the nonwoven web to cause the fibers to interlace; or still further, using ultrasonic waves and laser beams.
in any of the above dry bonding techniques, the binder areas may be of any suitable shape and size and may be continuous or discontinuous straight, sinuous, curved, or wavy lines; rows of polygons, circles, annuli, or other regular or irregularly shaped geometric figures; all of which normally extend across the width of the nonwoven fabric at various angles to the long direc tion thereof. Specific examples of such binder areas are noted in US. Pats. Nos. 2,705,688, 2,705,687, 2,705,498 and 3,009,822.
The amount of binder employed will depend on the type of bonding technique used and depend on the type and quality of product desired i.e. the amount of binder add-on to the nonwoven web maybe varied according to the technique employed and will vary within relatively wide ranges, depending to a large extent upon the intended use of the nonwoven fabric, upon its type, weight and thickness, as well as upon the specific binder employed. Typically, the binder areas should not exceed a substantial amount of the total surface of the nonwoven fabric, if a soft hand, drape and other textile-like properties and characteristics are desired or required. in cases where a somewhat different hand and drape is acceptable, increased binder coverages of up to almost any value, say 50 percent or even 75 percent, are useful. For some binders, as low as from about 2 percent to about 20 percent by weight has been found sufficient; for others, as high as from about 40 percent to about percent or more by weight has been found preferable. Within the more commercial aspects of the present invention, however, binder add-ons of from about 3 percent to about 40 percent by weight are known in the art to be satisfactory.
The particular type of binder used may be selected from a large group of binders now known in the industry for such purposes. Non-migratory binders, such as hydroxyethyl cellulose and regenerated cellulose, are preferred inasmuch as they yield sharp and clear boundaries of bonded areas and unbonded areas. Water-insoluble or water-insensitive binders, such as melamine-formal-dehyde, urea formaldehyde, or the acrylic resins, notably the self-cross-linking acrylic ester resin, are also preferred inasmuch as they are capable of completely resisting a subsequent aqueous reararanging treatment. Other binders, however, are also of use and would include polyvinyl acetate, polyvinyl chloride, copolymers thereof, polyvinyl acrylate, acrylate, polyethyl methacrylate, polyvinyl butyral, cellulose acetate, ethyl cellulose, carboxymethyl cellulose, etc.
Following bonding, the nonwoven webs may be treated again according to conventional procedures for any further desired purpose, such as for decorative reasons.
Still further, the nonwoven webs may be treated with various types of resinous coatings according to conventional techniques, or alternatively by bonding the nonwoven web to various substrates to provide laminates.
The products obtained by the process of the present invention, following bonding, find use in various and diverse fields. Moreover, the random nonwoven webs will now have greater utility because of their greater availability, and may be used to replace oriented nonwoven webs where improved machine and cross direction strength ratios are required. Typical of the uses to which the products can be put include limited-wear garments such as dresses, medical and industrial apparel, caps, hospital uses such as for surgical products, e.g. bandages, alcohol preparation, towelling, surgical pad covers, sanitary products such as napkins, absorbent products such as diapers and diaper facings, polishing and buffing cloths, wash cloths, wiping cloths, etc., consumer products such as table cloths and place mats, serviettes, book jackets, labels and tags, mop covers, cosmetic pads, filtration uses such as air filtration media as well as liquid filtration media in the chemical and food industries, etc. This is not exhaustive and many different uses are well known to those skilled in the art.
lt should also be understood that while the persons and apparatus of the present invention have been described in terms of producing a web that has at least a portion that consists of homogeneously blended long and short fibers, the present invention comprehends that the web may be formed entirely either of short fibers or long fibers. Furthermore, while adjustment means have been illustrated for varying the positions of the lickerins, the nose bars, the fiber receiving means, and the feed rolls, these mechanisms may also be positioned at fixed locations, on the frame in instances where the apparatus will continuously be operating upon fibrous materials having the same characteristics.
Also, the web formation characteristics and the dry strength of the resulting web can be improved by selecting both machine and fiber materials which produce an appropriate electrostatic attraction and/or repulsion of one fiber to another and their relationship to the machine itself. During transport of the fibers through the mixing zone to the condensing screen, it is desirable to maintain the voltages between the fibers to reduce coalescence. This can be accomplished by selecting fibers and machine components that produce fibers with like charges so as to eletrostatically repel one another when they are transported in the common air stream. In some instances, to optimize the buildup of web W on the condensing screen, fibers can be chosen that will be electrostatically attracted to one another, and this phenomenon can be especially important in retaining the air laid web as a unitary mass during transport from the condensing screen to a further processing station wherein a binder is applied to the web. It is also a factor in how the fibers line up relative to one another.
Instead of merely having outwardly diverging deflector plates, such as 232 and 234, at the lower end of the mixing zone 25, many different arrangements can be utilized, and several of these are illustrated in FIGS. 4-12. It will be understood that with the various arrangements illustrated in FIGS. 4-12, the air flow patterns at the lower end of the mixing zone can be modified to control the manner in which the airborne fibers are accumulated on drum 236. While several different arragements have been illustrated, these arrangements have been selected for purpose of example only, and in no way should they be construed as limiting the invention as defined in the appended claims.
In the embodiment of FIG. 4, deflector plates 260 and 261 at the lower end of the mixing zone 25 are arranged so that the intermediate portion of the mixing zone is a narrow channel. Deflector plate 261 may have rounded portions 261a and 26lb at the upper and lower ends thereof, respectively, to guide the large number of fibers traveling in the high velocity portion of stream 140, assuming that low gas volumes are flowing through the machine, as described above. A sealing roll 262 is carried upon an arm 263 that is pivotally mounted to the frame of the machine, and sealing roll 262 is driven by conventional means, not shown, with the sealing roll being positioned in alignment with one flange 254 of the internal portion 252 of drum 236. A baffle 264 is positioned below deflector plate 260, and includes an inclined portion 265 that extends tangentially with respect to the periphery of drum 236. An extension plate 267 is pivotally connected to the lower end of deflector plate 260, and the lower end of plate 267 is spaced from the periphery of drum 236 between the flanges 254.
With the arrangement of FIG. 4, the fibers are deposited on drum 236 essentially between roll 262 and plate 267, with the fibers being guided around the rounded portion 26lb of deflector plate 261. A generally triangularly shaped blocking element B may be positioned above lickerins 96 and 176 to prevent any dense particles that are thrown off the lickerins by centrifugal force from entering the mixing zone. The dense particles collected on blocking element B preferably are continuously removed from the machine by means, not shown, such as an air stream, or a screw conveyor or other means.
In many instances it is desired to concentrate the highest portion of the suction from the condensing means over a relatively narrow area in the fiber accumulating zone, and several arrangements for accomplishing this are illustrated in FIGS. 5-9. In the embodiment of FIG. 5, the internal portion 252 of the fiber receiving means is angularly adjustable, and the sealing flanges 254 are spaced apart by an angle slightly in excess of A pair of flanges 266 extend inwardly of the internal portion 252 of drum 236, and baffles 267 are fixed thereto. Baffles 267 includes parallel portions 268 that extend vertically upwards toward the mixing zone, so that the fibers are deposited on the drum 236 in a relatively narrow area with high velocity as determined by the distance between the baffle portions 268. The thus laid fibers are retained on the screen by the low velocity and low suction areas outwardly of baffle portions 268 to firmly hold the web on the screen as it moves out of the fiber condensing zone. The lower portion of the mixing zone 25 in the embodiment of FIG. 5 includes deflector plates 260 and 261 similar to those illustrated in FIG. 4; and a plate 267a, similar to plate 267 in FIG. 4, is pivotally connected to the lower end of deflector plate 260, with plate 267a extending vertically downwardly into engagement with drum 236. As is evident from FIG. 5, the internal baffles 268 on drum 236 are positioned in alignment with plate 267a and sealing roll 262. With the arrangement of FIG. 5, even though the sealing flanges 254 on drum 236 may be positioned more than 90 from one another, the fibers are deposited on the drum in an extremely narrow zone determined by the spacing between baffles 268.
In the embodiment of FIGS. 6 and 7, the sealing flanges 254 of the condensing drum 236 are positioned relatively closely to one another, and a narrow area of suction application is obtained by a straight baffle member 271 that is positioned in close proximity to one of the sealing flanges 254. In the embodiment of FIG. 6, a stationary tube 272 extends transversely across the frame of the machine below deflector plate 260, and in alignment with one sealing flange 254. In the arrangement of FIG 7, the condensing drum 236 is offset laterally (to the left) relative to lickerins 92 and 176. A plate 273 is pivotally connected to the lower end of deflector plate 260, and bears against the periphery of drum 236 in alignment with one flange 254, while sealing roll 262 is positioned in alignment with the other flange 254. As is evident from FIG 6, the internal baffle 271 on drum 236 is substantially parallel to the deflector plates 260 and 261, while in the embodiment of FIG. 7, the baffle 271 is positioned at an angle with respect to the deflector plates 260 and 261.
In the embodiment of FIG. 8, like the embodiment of FIG. 7, the condensing drum 236 is offset to the left relative to the vertical center line of the mixing zone. De-