IL33332A - A non-woven fibrous pad,method of and apparatus for producing the same - Google Patents

Description

ι¾**»»> )p no»s> ,iiis 'ΐ »«ι A KQJi-ViOW TOlM PAD» OSS!!GD OF AliD A^ ARASfS FOR PRODUCE <2HE βΔΜΒ This invention relates generally to the art of non-woven fibrous structures and more particularly to non-woven resilient padding.

In the past, various procedures have been developed for making non-woven, lofted, fibrous batts; and it is known in the art to counteract the general physical weakness of thes products by incorporating adhesive binders and the like for locking the individual fibers together into a stronger, more integral material. Where cushioning applications are contemplated, the air lay procedure produces a reasonably resilient product at moderate web speeds; and while a batt of greater resiliency can be produced in a carded batt by the needle punching procedure, the latter method is characterized by low web speeds and an undesirable loss in the loft of the fibers.

Accordingly, it is an important object of the present invention to provide a new, non-woven, fibrous pad which has improved resiliency and which can be produced at high machine speeds.

Another object of the invention is to provide a non-woven, fibrous pad which is characterized by an unusually high resiliency per pound of fiber.

Still another object of the invention is to provide a ηόη-woven, fibrous pad which has a greater over-all volume and a greater surface area than the web from which it is produced.

And still another object of the invention is to provide a pad of the type described which is amenable to the addition of high levels of binder.

It is also known in the prior art to texture a fibrous sheet product, as by embossing; but these procedures tend to compress the material making it lees resilient, and actually weaken the material with respect to its ability to store compressive loads by thinning the material in those sections run therefore a further object of the present invention to provide a non-woven, fibrous pad in which the fibers are selectively distributed in dome-shaped structures having a lesser concentration of fibers in the dome caps than in the remainder of the structure.

A yet further object of the invention is to provide such a pad in which the fibers in the dome sidewalls are selectively oriented to resist compressive loads applied to the face of the pad.

It is also an object of the invention to provide advantageous methods and apparatus for the production of a resilient pad of the type described.

These and other objects and features of the invention will become more apparent from a consideration of the following descriptions.

Brief Description of the Drawings In the drawing: Fig. 1 is a perspective view of a piece of non-woven, fibrous padding constructed and produced in compliance with the present invention; Fig. 2 is an enlarged elevational view taken in cross-section along the line 2-2 of Fig. 1 and showing the undulating elevations and depressions as well as the general orientation of the fibers in the pad of Fig. 1; Fig. 3 is a schematic elevational view of apparatus arranged to produce the fibrous pad of the invention; Fig. 4 is an enlarged front elevational view of the cogged, fiber-orienting rolls or cylinders used in the apparatus of Fig. 3; Fig. 5 is an end elevational view in cross-section showing the preforming or bulking rolls used in the apparatus Fig. 6 is a fragmentary view somewhat similar to the showing of Fig. 5 but illustrating the alternate arrangement of the cog teeth; Fig. 7 is an elevational view of one type of fiber- orienting apparatus useful for producing the fibrous pad of the invention; Fig. 8 is a schematic view of a modified form of apparatus for producing the fibrous pad of the invention; Fig. 9 is a chart of one example showing the relation of the resiliency of the pad to fiber orientation and the amount of working to which the pad is subjected in processing; and Figs. 10 and 11 are perspective views of the cogged cylinders used in the apparatus of Fig. 3 and arranged with conveyor belt elements to deliver a carded web to the cylinders and to strip a processed web therefrom.

Detailed Description of the Invention Referring now in detail to the drawings, specifically to Figs. 1 and 2, a non-woven fibrous pad constructed in compliance with the present invention is indicated generally by the reference numeral 20. The pad 20 comprises a three-dimensional network of individual fibers 22 that form a surface which is textured with a pattern of undulating elevations 24, elevations 24 being separated by a respective pattern of undulating depressions 26. The individual fibers are bonded where they cross and contact each other, as by droplets of a suitable adhesive 28. The elevations 24 comprise dome-shaped structures whereas the depressions 26 comprise corresponding, inverted dome-shaped structures; and as compared with an ordinary carded web, the pad 20 exhibits an enhanced total surface area and increased resiliency. While the pad 20, like conventional non-woven materials, has a degree of translucense, it ordinarily has no Each of the domes comprising the elevations 24 and the depressions 26 includes a cap wall 30 and a surrounding sidewall 32; and in compliance with the features of the present invention, the fibers making up the domes are distributed in greater concen- tration in the sidewalls than in the cap walls. More specifically, the fibers in the pad 20 are arranged so that the ratio of cap wall unit weight to the average web unit weight is less than 1.0; and in further accord with the invention, this ratio of cap wall unit weight to the average web unit weight is controlled to be greater than about 0.2, the precise figure for this lower limit being governed by the physical properties which are acceptable in each given situation and selected to be such that no appreciable perforation of the pad is developed. In addition, the individual fibers in the sidewalls 32 are advantageously oriented generally parallel with the thickness dimension of the pad 20. The described arrangement achieves a high degree of resiliency per pound of fiber used and is more readily penetrated by bonding liquids than the starting web.

A wide variety of fibers may be used in the pad 20; and at the present time, cut staple fiber having a crimp or fibrils to encourage mechanical interlocking is preferred. However, expanded tow may also be employed. The fibers may be natural fibers such as hogs hair, cotton, sisal and hemp, or they may be synthetic fibers such as nylon, rayon acetate, poly-ester, acrylonitrile polymers, polypropylene, and polyvinylidene chloride-polyvinyl chloride copolymers. Inorganic fibers such as glass fibers may also be used, and any of these various fibers may be used alone or in admixture with others .

Great latitude is also available in the selection of the binder; and while substantially any binder which is compatible with the fiber may be employed, exemplary binders include Binder may be added in quantities varying from 10% to 100% of the weight of fiber utilized. Furthermore, bonding of the fibers may also be achieved by momentarily heating thermoplastic fibers to their softening point.

The individual elevations 24 and depressions 26 may take various shapes such as ellipsoidal (as shown) , round, elliptical, or nearly square for example. In the embodiment illustrated in Figs. 1 and 2, which is shown approximately to scale the vertical projection of an individual elevation or depression is a rectangle measuring approximately one cm. by one-half cm. Elevations and depressions of other sizes may also be employed. In addition, the one-hundred-and-eighty degree phase relationship between adjacent rows of elevations and depressions need not be adhered to, and other phase relationships may be used. It is also possible to fill the depressions on one side of the pad 20 as with the same ot a dissimilar fiber or with a foamed resin.

According to the method aspects of the present invention, a resilient non-woven product, such as the pad 20, is produced by reorienting the fibers of a lofted web in successive stages while the fibers themselves are in a substantially dry state. The "massaging", rubbing or wiping action of smooth, partially intermeshing cog teeth serves to relocate generally the horizontally disposed fibers from the incipiently forming dome caps of the undulating elevations and depressions to the more vertically disposed sections of the dome sidewalls.

Whether the fibers in the initial web are oriented to produce iso tropic properties or anisotropic properties is immaterial to the practice of the present invention since a reorientation and re-distribution of the fibers is achieved.

Referring to Fig. 3, a carded web 34 of cut staple subjected to successive forming operations between partly meshing, multiply cogged work members, specifically first stage forming rolls 38 and second stage forming rolls 40. Only two forming stages are suggested In Fig. 3 for simplicity of illustration; and it is to be recognized that the optimum number of forming operations will vary with such factors as the type and length of the fibers in the web 34, the thickness and density of the starting web and the depth of the cog teeth on the work members 38 and 40. In reorienting the fibers in the starting web 34, it is advantageous that the depth of the cog teeth in the subsequent work members be substantially the same as the depth of the cog teeth in the preceding work members, although under certain circumstances it is desirable that the subsequent work members have a greater cog tooth depth or that the subsequent work members be meshed to a greater degree than the preceding work members. In any event, engagement of the various work members with the web being processed is synchronized as by means of the mechanical interlock achieved through common drive gearing 42.

The processing which the web 34 receives at station 36 produces an orientation of the fibers of the type generally illustrated in Figs. 1 and 2, and this process step bulks the structure and generates a high percentage of load bearing fibers without deliberately breaking them, such as occurs during needling for example. A dry, unbonded web 44 formed with patterns of undulating elevations and depressions exits from the station 36; and frictional effects between the fibers, arising due to the high individual fiber crimp or fibril-interlock, are relied upon initially to maintain integrity of the structure. Subsequent bonding achieves permanency of the web. In order to accommodate high machine speeds, it is advantageous to apply the bonding structures. Accordingly, a light coating, on the order of 0.1 - 0.2 ounces per square yard may be applied to one or both surfaces of the web 44 by spray nozzles 46 or other suitable means. The bonding agent applied by means of the nozzles 46 is suitably dissolved or dispersed in a solvent for ease of application and to promote penetration into the web 44. In order to develop structural strength and stability in the processed web, the bond ing agent is dried or cured in a drier 48; and upon leaving the drier 48, the web can be treated with less care and concern.

Additional binder material is then supplied by a surface spray station or saturator 50 and the web is heated to cure or dry the binder in a drier 52 where the web is advantageously festooned. The finished web 54 emerges from the drier 52 from whence it can be directed for further processing or wound up in a roll 56 for shipment.

Turning to a consideration of Figs. 4-6 for a more detailed description of the cogged work members 38 and 40, each of these elements is similarly fabricated to comprise a central drum or shaft 58 upon which is mounted a plurality of cog rings 60. Each of the cog rings 60 carries a suitable number of cog teeth 62; and to produce spacing of the cog teeth 62 axially of the shaft or drum 58, the cog rings 60 are provided with lateral shoulders 64, best seen in Fig. 4. As will also be seen in Fig. 4, spacing of paired shafts 58, while taking into considera* tion the length of the cog teeth 62, is selected to provide a relatively deep but only partly meshed engagement of the cog teeth of the upper and lower rolls whereby to accommodate the fibrous web therebetween without excessive compression. Furthermore, the lateral faces, of the cog teeth 62 are tapered in order to cooperate with the axial spacing afforded by shoulders 64 in accommodating the material of the fibrous web. The shape of to correspond with the vertical projection of the elevations and undulations to be formed in the fibrous web, and the preliminary work members 38 may be considered as bulking rolls in that the pattern of undulations is well established even in a single pass, as is shown in Fig. 5. The subsequent work members may be correspondingly considered as fiber-orienting rolls which redistribute the individual fibers into the desired configuration described hereinabove.

In order to distribute the undulating elevations and de-pressions across the width of the fibrous web, the cog rings 60 of each work drum are mounted with a relative angular displacement as described hereinabove and as shown in Fig. 6. However, precise intermeshing registration is maintained between each cogged work member and its intermeshing element. As illustrated in the drawings, the cog teeth 62 are alternated with the corresponding cog spaces across the face of the roll or drum. However, it is to be recognized that the cog teeth may be staggered by a fractional pitch other than one-half pitch in either direction The cog teeth are fabricated to be smooth surfaced and with rounded corners and edges in order to prevent catching individual fibers from the processed web. In addition, the cog teeth and even the cog rings themselves are preferably fabricated from an elastomeric material such as an unfoamed polyruethane material of about 90 durometer hardness on the Shore A scale. So fabricated, intrusion of a hard foreign object between the relatively deeply engaged cog teeth is prevented from fracturing the teeth or overloading the bearings for the work cylinders .

Some polyurethanes of a moldable nature are also of advantage for manufacture of the cog teeth and cog rings since they possess a low coefficient of friction and exhibit good wear resistance.

As stated hereinabove, the optimum number of forming fabricated pad varies with such factors as the type and cut length of the fibers, the thickness and density of the starting web and the depth of the individual cog teeth. Turning to Fig. 7, a processing machine, indicated generally at 66, is particularl arranged to accommodate a selected number of plural forming operations from two to seven. More specifically, a primary rotatable work member 68 is mounted on a horizontal shaft 70 and includes a tubular hub 72 which rotatably receives the shaft 70, an outer cylindrical drum 74, and radial spokes or arms 76 which attach cylinder 74 to the hub 72. The outer surface of cylinder 74 is provided with a pattern of cog teeth 78 similar to the cog teeth described with reference to Figs. 4-6 hereinabove; and advantageously, the drum 74 is arranged to have a relatively large diameter in order that the height of the cog teeth will be small compared with the circumference of the drum for ease in stripping the processed web. Arcuately spaced about the periphery of cylinder 78 are seven, smaller diameter satellite rolls or drums 80. Each of the satellite drums 80 is suitably rotatably mounted on a radially adjustably positionable bracket 82 which is secured to a machine frame, a portion of which is indicated at 82, by means of adjustment screws 84. In addition, the satellite drums 80 are individually provided with multiply cog toothed outer surfaces whichare suitably arranged to mesh with the cogged surface of the primary cylinder 74.

In order to synchronize the rotation of primary cylinder 74 and the satellite drums 80, a sprocket wheel 86 is secured to the work member 68 for rotation therewith; and correspondingly, an individual sprocket wheel 88 is secured to each of the satellite drums 80 for rotation therewith. A sprocket chain 90 is trained over the sprocket wheel 86 and over the individual satellite drum sprocket wheels 88; and in order to insure proper 92 are radially adjustably mounted on the machine frame 83 by means of brackets 94 and adjustment screws 96. In the event that one or more of the satellite drums 80 is repositioned either into or out of meshed engagement with the primary work member 68, one or more of the idler sprockets 92 will be appropriately repositioned to take up or provide, as the case may be, slack in the sprocket chain 90. Rotary driving force may be applied at the central shaft 70 or at one of a pair of outlying sprocket wheels 98.

In order to conduct a web 34 through the several work stations established in the machine 66, an endless infeed aid stripper belt arrangement 100 is directed e er a system of fixed rollers 102 and positionally adjustable roller 104. The rollers 104 are rotatably mounted on brackets 106 which are, in turn, swingably mounted to the machine frame 83 by pivots 108, the brackets 106 being arcuately slotted to pass the shanks of adjustment screws 110. Thus, the rollers 104 may be moved in respective arcuate paths and positioned to apply a selected degree of tension in the stripper belt arrangement 100. The infeed and stripper belt arrangement 100 is trained through the enmeshed, cog toothed work members in a manner to be described more fully hereinafter with respect to Figs. 10 and 11; but continuing with reference to Fig. 7, an endless helper belt 112 is driven by a suitably powered drive roll 114 and guided by an idler roll 116 to aid in delivering the carded web 34 to the cogged work members. The processed web 44 is passed from the machine 66 and guided by an idler roller 118 to further processing stations.

In order to optimize uniformity of the fiber orientation in the elevations and depressions of the resilient pad of the invention, it may be desirable to perform a first series of work operations principally with respect to one side of the web to the opposite side of the web. Apparatus generally arranged for achieving this result is suggested in Fig. 8 where two machines similar to the machine 66 described with reference to Fig. 7 are arranged in tandem, one of the machines being inverted in order that the respective work members or satellite drums may engage that side of the web which is opposite to that engaged by the satellite drums of the other machine. Since the tandemized processing machines of Fig. 8, designated respectively by the reference numerals 66a and 66b, are constructed similarly to the processing machine 66 of Fig. 7, like numerals have been used to designate like parts with the suffix letters "a" and "b" being employed to distinguish the respective machine elements found in the apparatus of Fig. 8.

It is to be recognized that, in operation, the process-ing machine 66, as well as its counterparts in the tandem machine arrangement of Fig. 8, is fashioned to support an incoming web of fibers on the cogged surface of primary drum 74 while the cogged surfaces of one or more satellite drums are rotated in synchronism with the primary drum in partly meshed engagement therewith so that the cog teeth of the satellite drum or drums wipe into the web to form respective patterns of depressions and elevations. Subsequently, one or more of the cooperatively cogged satellite drums are rotated in correspondence with the primary drum in partly meshed engagement therewith so that the cog teeth of the subsequent drum or drums engage the previously formed depressions and elevations to relocate fibers from the respective crest and root regions thereof to the sidewall regions. After the infed web is processed in this manner in a substantially dry state, the fibers are bonded together as pre-viously described so as to produce a resilient fibrous pad of the character of pad 20 described hereinabove.

The effect of utilizing a multiplicity of forming operations in accordance with the principles of the present invention is clear from the data graphically presented in Fig. 9. These data represent work conducted on eight denier rayon viscose and constitute a first working example of the invention. Actual values are set forth as plotted points and generalized relationships are suggested in the form of curves. A carded web having an average fiber weight of 2.2 ounces per square yard was employed as the starting material, and uniform amounts of binder were added to the respective samples after processing. The binder itself was made up of equal parts of polyvinyl chloride latex and acrilonitrile-butadiene latex. In determining the amount of fiber translocation, slugs having a diameter of about 0.6 cms. were punched out of the cap area of the undulating eleva-tions of each specimen. The elevations themselves had a vertical projected area that measured approximately 1 cm. by 0.5 cm.; and ten slugs were extracted from each sample and their weight averaged for the determination.

From an examination of the upper portion of the chart, it will be apparent that the unit work load is optimized for this particular starting web and this particular machine setting at between seven and twelve forming operations. The upper curve also shows a rapid rise of properties from the unprocessed web to a maximum at about ten forming operations followed by a rapid decay to approximately sixteen forming operations. Comparing the lower curve, it will be apparent that the foregoing change in physical properties was accompanied by a thinning out of the web in the center or cap area of the dome from one hundred per cent to forty-five per cent of the average web weight. Be-yohd sixteen forming operations, the weight ratio stabilized, as did the physical properties, representing the built in clearances foregoing studies, that shaping of the web into the pattern of undulating elevations and depressions was substantially complete, to within seven per cent of maximum height, after one or two forming operations.

Turning to a consideration of Figs. 10 and 11, variote elements of the work station 36, described with reference to Figs. 3-6, are shown arranged with an infeed and stripper belt arrangement 120 of the general type suggested for use with the processing machines of Figs. 7 and 8. It has been found that the formed web has some tendency to cling to one of the cogged members, and it is ordinarily desirable to peel the formed web gently and progressively and without distortion from that member, stripper belts being one advantageous means for accomplishing this objective. Use of stripper belt arrangements is of particular advantage with lightweight webs on the order of 1.0 ounces per square yard or less in weight. The stripper belt arrangement 120 specifically comprises a plurality of laterally spaced-apart belts 122 which run between the individual cog rings 60 at the root of the space between the cog teeth of the lower work element or drum. As is shown in Fig. 4, the cog rings 60 are fashioned with inwardly sloping surfaces at the shoulders 64 to define grooves 124, the location of individual stripper belts 122 in these grooves 124 being suggested in Fig. 4. The individual stripper belts 122 may comprise such things as monofilament nylon, nylon rope, solid rubber strands of circular cross-section, and coiled wire or garter spring belting. The latter material is of particular advantage because of its rough surface and ease of splicing. Under some circumstances, as for example when the cog teeth a re at other than one-half pitch spacing axially of the work drums, it is advantageous to include a second series of belt elements 126, as suggested in Fig. 11, the second set and connected thereto at points of contact whereby to form a mesh.

In order to describe the invention more fully, the following additional specific examples are given without, however, limiting the invention to the precise details and conditions set forth.

A number of resilient pads were made incompliance with the principles of the invention using two separate cut staple fiber base carded webs, specifically a rayon viscose of fifteen denier and a staple length of one and nine-sixteenths inches and a rayon viscose of eight denier and one inch cut staple length. A single binder was employed at different levels of addition, the binder in each case being equal parts of Geon 580 (polyvinyl chloride latex) arid Hycar 1552 (acrylonitrile-butadiene latex) .

Processing of the carded webs was achieved on a work fixture in which the forming cog teeth were based on a linear pitch distance of 0.392 inches and a transverse spacing of 0.31 inches. Alternate cog rings were staggered one-half pitch, and the pitch diameter was chosen to be 4.50 inches. Webs were processed in four forming operations, and products were treated at linear web speeds of up to about 180 f.p.m. The different examples produced in this way and their resultant physical properties are set forth in Table 1 below: TABLE I Example No. 2 3 4 5 6 7 8 9 Fiber Denier 15 15 15 15 8 8 8 8 Fiber Batt Weight Ounces per sq. Yd. 3.085 3.63 2.14 2.1 3.94 3.4 2.26 2.37 Binder add-on ounces per sq. yd. 1.7 .575 1.57 .90 1.87 .99 1.73 .89 % Solids in binder (measure of penetration) 44 25 25 44 25 44 44 25 Compression (lbs.) 33 34.5 25 14.5 45.5 30.5 22 22 Work absorbed in Compr. inch-lbs. 2.85 3.26 2.42 1.10 4.52 2.29 1.71 1.88 Breaking strength, lbs. (Ave. of 2 directions) 19 11 not ob-9.5 22 12 21.5 15.5 tained % Elongation @I (Ave. of 2 directions) 63 45 not ob-70 tained Having now described the invention in specific detail and exemplified the manner in which it may be carried into practice, it will be readily apparent to those skilled in the art that innumerable variations, applications, modifications and extensions of the basic principles involved may be made without departing from the spirit and scope of the invention. Thus, the fibrous resilient pads of the present invention may be laminated with various fabrics, with paper or with other materials, to be employed in numerous ways that will be readily apparent to the skilled artisan, such as for example in lightweight resilient or insulating structures and padded garments.

Claims (16)

WHAT IS CLAIMED IS:

1. A non-woven fibrous pad comprising: a three-dimensional network of individual fibers forming a surface textured with a pattern of undulating elevations separated by a respective pattern of undulating depressions, each of said elevations comprising a structural dome in which the ratio of cap wall unit weight to the average web unit weight is less than 1.0; and bonding means interconnecting said fibers where they cross and contact each other.

2. A non-woven fibrous pad according to claim 1 wherein the fibers in the sidewalls of said domes are oriented substantially parallel with the thickness dimension of said pad.

3. A non-woven fibrous pad according to claim 1 wherein said fibers have interlocking means.

4. A non-woven fibrous pad according to claim 3 wherein said interlocking means are crimped portions.

5. A non-woven fibrous pad according to claim 3 wherein said interlocking means are laterally extending fibrils.

6. A non-woven fibrous pad according to claim 1 wherein said ratio is greater than about 0.2.

7. A non-woven fibrous pad according to claim 1 wherein each of said depressions comprises an inverted structural dome in which the ratio of cap wall unit weight to the average web unit weight is less than 1.0.

8. A non-woven fibrous pad according to claim 7 wherein said ratios are greater than about 0.2.

9. A method of producing fibrous pad claimed in claim 1, iwhicH"comprises forming in an unbonded web of mechanically engaged fibers a pattern of undulating elevations separated by a respective pattern of undulating depression by relocating fibers from the areas of desired elevation and depression to the sidewalls thereof and then bonding said formed pad to lock said fibers in the new con iguration.

10. A method according to claim 9 wherein said relocation of fiber is done; with the web in a substantially dry state.

11. A method according to claim 9 wherein said relocation of film is done first from one side of the web and then from the other side.

12. A method according to any of claims 9, 10 or 11 which comprises supporting said web on a cogged surface; rotating a first correspondingly cogged drum means in partly meshed engagement with said surface, the cog teeth of said drum means wiping into said web to form said depressions and elevations; rotating a second correspondingly cogged drum means in partly meshed engagement with said surface and subsequent to said first drum means, the cog teeth of said second drum means engaging said depressions and elevations to relocate fibers from the respective crest and root regions thereof to the sidewall regions; and bonding said formed web to lock said fibers in their reoriented relationship,, the,

13. Apparatus for producing (m non-woven fibrous pad clai in any one of the claims 1 to 8 Comprising: first fiber orienting means including means forming a traveling cog surface; second fiber orienting means including a plurality of synchronized cog means meshing successively with said cog surface, one of said first and second fiber orienting means including a plurality of closely laterally spaced cog elements having channel means therebetween running generally in the direction of travel of said cog surface; and conveyor belt means disposed partly in said channel means and diverging from a meshed region of said first and second fiber orienting means for feeding a fibrous web into said fiber orienting means or stripping a processed web therefrom.

14. Apparatus according to claim 9 wherein said cog surface is arranged on the periphery of a cylindrical drum0

15. Apparatus according to claim 9 wherein said conveyor belt means includes laterally spaced belt elements running generally parallel with the direction of travel of said cog surface.

16. Apparatus according to claim $ wherein said conveyor belt means includes first belt elements running generally parallel with the direction of travel of said cog surface and second belt elements running transversely of said first belt elements and connected thereto forming a mesh.