Title:
APPARATUS FOR SPLAYING AND DEPOSITING NONWOVEN FILAMENTARY STRUCTURES
United States Patent 3734803
Abstract:
An apparatus of augmenting dispersal and improving deposition of a plurality of continuous filaments onto a continuously moving surface whereby random distribution of the filaments is provided for the production of uniformly distributed nonwoven webs. A splaying device comprising a completely enclosed channel with open ends, the exit end of which is in the form of a slot having an effective shorter dimension less than 25 percent of an effective longer dimension, is positioned near the exit of an aspirator so as to spread the filaments in substantially all directions and to provide greater openness and greater random laydown of filaments.
US Patent References:
/3692618.html
Dorschner et al. - September 1972 - 3692618
/3655862.html
Dorschner et al. - April 1972 - 3655862
Sheets of randomly distributed continuous filaments
Kinney - September 1967 - 3341394
PROCESS FOR THE PRODUCTION OF A NONWOVEN WEB OF A CONTINUOUS FILAMENT YARN
Davies et al. - January 1969 - 3423266
Fibrous mats and production thereof
Frickert, Jr. - February 1956 - 2736676
/3692618.html
Dorschner et al. - September 1972 - 3692618
/3655862.html
Dorschner et al. - April 1972 - 3655862
Sheets of randomly distributed continuous filaments
Kinney - September 1967 - 3341394
PROCESS FOR THE PRODUCTION OF A NONWOVEN WEB OF A CONTINUOUS FILAMENT YARN
Davies et al. - January 1969 - 3423266
Fibrous mats and production thereof
Frickert, Jr. - February 1956 - 2736676
Inventors:
Lipscomb, Walter Peter (Chesterfield County, VA)
Shelburne Sr., Eli Bently (Chesterfield County, VA)
Shelburne Sr., Eli Bently (Chesterfield County, VA)
Application Number:
05/184421
Publication Date:
05/22/1973
Filing Date:
09/28/1971
View Patent Images:
Export Citation:
Assignee:
Allied Chemical Corporation (New York, NY)
Primary Class:
Other Classes:
156/167, 19/299, 156/497, 156/433, 425/83.100, 156/181
International Classes:
B29C70/30; D04H3/03; B29C70/04; D04H3/02; D04H3/00
Field of Search:
156/167,181,433,436,441,497 264/103 425/83
Primary Examiner:
Fritsch, Daniel J.
Claims:
What is claimed is
1. In an apparatus for depositing filaments onto a moving receiving surface in a randomly dispersed manner to form a nonwoven web of randomly disposed filaments substantially uniformly distributed throughout said web, said apparatus comprising an aspirating means for forwarding the filaments at high velocity to the moving receiving surface, the improvement comprising a splaying means for augmenting spreading of the filaments while advancing said filaments from said aspirating means to said moving receiving surface, said splaying means consisting of an enclosed open-ended channel, one upper, entry end thereof formed and positioned so as to accept passage of said filaments from the exit of said aspirating means without any substantial leakage of the aspirating medium from between said aspirating means exit and said entry end of said splaying means, the other lower, exit end forming a slot having an effective shorter dimension not more than 25 percent of an effective longer dimension, said entry end having an effective minimum dimension of a magnitude at least as great as the magnitude of said effective shorter dimension of said exit end, said channel having side walls to connect said entry end to said exit end, said side walls sloping from said entry end to said exit end of said channel in a manner such that the slope makes an angle with the center-line axis of the exit passageway of said aspirating means not exceeding approximately 45° at any point on the interior side walls of said channel from said entry end to said exit end, said side walls terminating at said exit end in side walls being substantially parallel to said center-line axis.
2. The apparatus of claim 1 wherein said splaying means augments filament spreading in substantially all directions from said aspirating means exit.
3. The apparatus of claim 2 wherein the cross-section of said exit end restriction has said effective shorter dimension ranging from 70 to 150 percent of the effective diameter of said aspirating means exit passageway and from 7 to 15 percent of said effective longer dimension.
4. The apparatus of claim 3 wherein said splaying means is positioned such that said shorter dimension is substantially in the direction of motion of said moving receiving surface.
5. The apparatus of claim 4 wherein a distance along the center-line of said splaying means from said entry end to said exit end ranges from 10 times to 25 times said shorter dimension.
6. The apparatus of claim 5 wherein the orifice of said aspirating means exit passageway is approximately at or immediately below said entry end.
7. The apparatus of claim 6 wherein said shorter dimension is approximately 88 percent of the diameter of said aspirating means exit passageway and approximately 11 percent of said longer dimension.
1. In an apparatus for depositing filaments onto a moving receiving surface in a randomly dispersed manner to form a nonwoven web of randomly disposed filaments substantially uniformly distributed throughout said web, said apparatus comprising an aspirating means for forwarding the filaments at high velocity to the moving receiving surface, the improvement comprising a splaying means for augmenting spreading of the filaments while advancing said filaments from said aspirating means to said moving receiving surface, said splaying means consisting of an enclosed open-ended channel, one upper, entry end thereof formed and positioned so as to accept passage of said filaments from the exit of said aspirating means without any substantial leakage of the aspirating medium from between said aspirating means exit and said entry end of said splaying means, the other lower, exit end forming a slot having an effective shorter dimension not more than 25 percent of an effective longer dimension, said entry end having an effective minimum dimension of a magnitude at least as great as the magnitude of said effective shorter dimension of said exit end, said channel having side walls to connect said entry end to said exit end, said side walls sloping from said entry end to said exit end of said channel in a manner such that the slope makes an angle with the center-line axis of the exit passageway of said aspirating means not exceeding approximately 45° at any point on the interior side walls of said channel from said entry end to said exit end, said side walls terminating at said exit end in side walls being substantially parallel to said center-line axis.
2. The apparatus of claim 1 wherein said splaying means augments filament spreading in substantially all directions from said aspirating means exit.
3. The apparatus of claim 2 wherein the cross-section of said exit end restriction has said effective shorter dimension ranging from 70 to 150 percent of the effective diameter of said aspirating means exit passageway and from 7 to 15 percent of said effective longer dimension.
4. The apparatus of claim 3 wherein said splaying means is positioned such that said shorter dimension is substantially in the direction of motion of said moving receiving surface.
5. The apparatus of claim 4 wherein a distance along the center-line of said splaying means from said entry end to said exit end ranges from 10 times to 25 times said shorter dimension.
6. The apparatus of claim 5 wherein the orifice of said aspirating means exit passageway is approximately at or immediately below said entry end.
7. The apparatus of claim 6 wherein said shorter dimension is approximately 88 percent of the diameter of said aspirating means exit passageway and approximately 11 percent of said longer dimension.
Description:
CROSS-REFERENCE TO RELATED APPLICATIONS
The invention herein set forth is related to the inventions described in copending applications Ser. No. 184,420 entitled "Two-Planar Deflector For Dispersing And Depositing Nonwoven Filamentary Structures," filed on Sept. 28, 1971 in the name of Walter P. Lipscomb and Garland L. Turner and Ser. No. 184,422 entitled "Foraminal Apparatus For Splaying And Depositing Nonwoven Filamentary Structures," filed on Sept. 28, 1971 in the name of Walter P. Lipscomb and Garland L. Turner, wherein different apparatus for improving the dispersal and deposition of a plurality of continuous filaments onto a continuously moving surface are disclosed.
BACKGROUND OF THE INVENTION
This invention relates to an apparatus for improving the dispersal and deposition of filaments. In particular, it relates to an apparatus for augmenting the dispersal of continuous filaments onto a receiving surface so as to form a nonwoven web of randomly disposed filaments.
Nonwoven webs formed from continuous filamentary materials which have been laid in a random configuration are well known in the art. In the formation of such webs, great care is frequently taken to ensure that the filaments are maintained apart from each other and that interfilamentary entanglement and the formation of filament aggregates are avoided.
Nonwoven webs comprising multi-filaments are commonly formed by withdrawing the filaments from a source of supply, such as a melt spinnerette and then depositing the filaments at high velocity onto a moving surface by means of an aspirator. In the production of nonwoven webs having a substantial width, there must be provided either a plurality of aspirators for depositing a plurality of filamentary bundles in a random manner upon the moving surface or there must be provided a means, normally unduly complicated and cumbersome, to move the aspirator over the width of the nonwoven web to be produced.
When depositing filaments from a conventional aspirator onto a collecting surface, the filaments will spread out within the confines of the aspirator boundary. However, the filament distribution in the jet stream is not always uniform and random and is often restricted to a small laydown area; for example, a web width normally does not exceed 8 inches when a fixed aspirator jet is situated at a distance of 1 to 3 feet from the receiving surface.
Some of these deficiencies have been overcome by impinging the filaments against a single deflecting surface before the filaments are massed in web form. The intermixing which is normally attendant with the deflection promotes a filament interaction which tends to integrate but also to aggregate the product. Also, there is normally an accompanying bulkiness or uneven filament distribution, a twisting pattern or roping, a tendency toward sagging or a loss of strength, each of which is undesirable for many end uses of the web material.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to provide an apparatus for augmenting dispersal of a plurality of filaments which are thereafter deposited onto a receiving surface so as to form a web. It is a further object of this invention to provide a simple, reliable, inexpensive, and easily constructed apparatus for more expeditiously spreading filaments and thereby for producing superior nonwoven webs having high strength and integrity. A further object of this invention is the provision of a filament splaying means that spreads the filaments in substantially all directions. A still further object of this invention is the provision of a filament splaying and depositing means that is readily adaptable for usage with conventional aspirating means used in the production of nonwoven webs. Further objects and advantages of the present invention will become apparent by reference to the following specification and drawings.
In attaining the foregoing objects, this invention features an apparatus for spreading while depositing filaments onto a moving receiving surface in a randomly dispersed manner to form a nonwoven web. Such apparatus comprises, in combination, an aspirator to forward filaments at a high velocity and a splaying device to separate widely the filaments exiting from such aspirator and to forward the filaments onto the moving receiving surface. The splaying device is affixed near the exit of the aspirator so as to accept passage of substantially all the filaments exiting from such aspirator. The splaying device comprises an enclosed, open-ended channel. The entry end of such channel is connected to the aspirator exit by an extension which provides an effective air-tight seal around and envelops the aspirator exit. The opposite exit end of the channel forms a slot which has an effective shorter dimension less than 25 percent of an effective longer dimension and is, preferably, generally elliptical or rectangular in form. Preferably, the effective shorter dimension of the channel exit end ranges from 70 to 150 percent of the effective diameter of the aspirator exit passageway and from 7 to 15 percent of the longer dimension. The minimum effective dimension of the channel entry end is at least the magnitude of the effective shorter dimension of the channel exit end. The channel has side walls to connect the two open ends and to completely enclose the remainder of the channel. Such side walls slope from the entry end to the exit end of the channel in a manner such that the slope makes an angle with the center-line axis of the aspirator exit passageway not exceeding approximately 45° at any point on the internal side walls of the channel from the entry end to the exit end. The slope changes from the entry end to the exit end of the channel in order to form side walls at such exit end which are substantially parallel to such center-line axis of the aspirator exit passageway. The internal surface of the channel has a surface which facilitates passage of the filaments through the channel. Preferably, a distance along the center line of the splaying device from the entry end to the exit end ranges from 10 to 25 times, more preferably from 15 to 20 times, the magnitude of the effective shorter dimension of the exit end.
In a preferred embodiment, the exit end of the splaying device has a substantially uniformly wide shorter dimension, being approximately 88 percent of the aspirator exit passageway diameter and approximately 11 percent of a substantially uniformly wide longer dimension.
A feature of this invention is its quick and easy adaptability for use with many conventional aspirators, i.e., aspirator jets, in dispersing while depositing filamentary materials onto a moving receiving surface.
Advantageously, the combination of the splaying device with the aspirator may be reciprocated above a moving receiving surface in a direction substantially transverse to the forward motion of the receiving surface. Further advantageously, this combination may be made a part of a plurality of substantially similar combinations and then may be reciprocated at essentially the same rate and stroke in a pattern such that filaments from a given combination overlap those of the next adjacent combination so as to further increase web width.
The method utilizing the apparatus of this invention comprises, in general, the utilization of the above described splaying device in combination with an aspirator whereby filaments, preferably forwarded from a spinnerette of a spinning mechanism and thereafter from a drawing mechanism, are forwarded through a high velocity fluid jet of the aspirator. Subsequent thereto, the aspirator jet stream propels the filaments onto the splaying device of this invention whereby the filaments are deflected onto a continuously moving, preferably foraminous, surface to form a uniform nonwoven web comprising randomly disposed, substantially uniformly distributed filaments. Deposition of the filaments may be aided by a suction chamber located underneath the moving surface.
The described apparatus can be readily used for dispersion of filaments or, alternately, of strands, yarns, slivers, or other similar forms of material, or mixtures thereof. Such materials include any fiber-forming thermoplastic polymer from which filaments can be obtained. These materials include: polyamides, for example, poly(epsilon-caprolactam) (hereinafter nylon 6) and poly(hexamethylene adipamide) (hereinafter nylon 66); linear polyesters, for example, poly(ethylene terephthalate); acrylonitrile polymers and copolymers; olefinic polymers, for example, polyethylene, polypropylene and polyvinyl chloride; and cellulose acetates. Preferred materials include nylon 6, nylon 66 and poly(ethylene terephthalate).
The invention will be more clearly understood and additional objects and advantages will become apparent upon reference to the discussion below and to the figures which are given for illustrative purposes.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a schematic perspective view depicting a preferred embodiment of the apparatus employed for carrying out the invention;
FIG. 2 is a sectional view of the apparatus of FIG. 1, taken on line 2--2 thereof;
FIG. 3 is a bottom view of the apparatus of FIG. 2, taken on line 3--3 thereof.
FIG. 4 is a side elevation of the splaying device turned 90° clockwise from the position of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings and particularly to FIG. 1, a bundle of freshly formed filaments 12 enter inlet aperture 57 of an aspirator such as aspirating jet 19. The filaments were formed from the spinnerette of a melt spinning apparatus (not shown). Subsequent to spinning, the filaments may also be attenuated and oriented on a drawing apparatus (also not shown). Filament bundles having a broad range of denier, i.e., 30 to 3,400 total denier, may be used in the apparatus of this invention. Within the aspirating jet 19, the filaments are acted upon by a high velocity fluid medium such as air, which is supplied through the inlet conduit 35. Aspirating jet 19 comprises an air nozzle 9, a collar 10 and a diffuser 11. The filament bundle 12 is forwarded via the high velocity fluid medium from the jet exit 17 into the splaying device 22 whereby the filaments of the bundle 12 are splayed onto receiving surface 20. Air stream restriction and its attendant turbulence spreads and opens the filament bundle 12 at the splaying device exit. Splaying device 22 is attached to the exit end of jet 14 via extension 18. Extension 18 is preferably molded from the same material as splaying device 22 to assure a smooth internal surface and is attached to the jet exit end so as to form a close seal thereon. This seal must be effective in preventing air leaks which enhance clogging of the filaments near any area of such air leaks. On receiving surface 20, preferably a foraminous continuously moving conveyor with a suction chamber 21 provided beneath that portion of conveyor 20 on which the filaments are being laid down, the filaments are deposited in a random manner to form web 23. Upon passing from receiving surface 20, web 23 is forwarded to further processing units 24 (not shown), such as fusion rolls to bond the web 23.
In FIG. 2, the aspirating jet 19 comprises: a hollow air nozzle 9 which is externally threaded at each end and which has an air inlet conduit 35 attached to its upper end; a hollow collar 10 which is internally threaded at both ends so as to connect air nozzle 9 with diffuser 11 and which has an inlet aperture 57 for receiving filament bundle 12; and a hollow diffuser 11 which is externally threaded at its upper end and through which the filaments and high velocity air are propelled into splaying device 22 and thereafter onto a receiving surface. The annular internal aperture 57 is arranged to direct the filaments entering therein downwards, i.e., in the direction of air flow. The internal dimensions of collar 10 and of diffuser 11 are arranged so as to minimize twisting, knotting and entanglement of the filaments passing therein. By way of example only, the diameter of nozzle passageway 51 is preferably from 20 percent to 33 percent of the nozzle passageway length. Also, the cross-sectional area of nozzle passageway 51 is preferably from 25 percent to 35 percent of the cross-sectional area of diffuser passageway 54. Further, the diameter of diffuser passageway 54 is preferably from 2 to 10 percent of the length thereof. Still further, the maximum diameter of diffuser entrance passageway 53, which is conical in shape, is most preferably approximately two times the diameter of the diffuser chamber 54. The cross-sectional area of diffuser passageway 54 is designed such that the cross-sectional area of filament bundle 12 passage therein ranges from 0.1 to 5 percent, preferably from 0.2 to 1.5 percent, of the diffuser passageway cross-sectional area. The respective lengths and diameters of air nozzle entrance chamber 50 and of collar chamber 52 are not critical. However, such lengths and diameters should be used as are practical; i.e., compatible with the overall operation of the present process.
Referring now to FIGS. 3 and 4 as well as to FIG. 2, the splaying device 22 is characterized by an enclosed hollow channel 17, the upper, entry end 15 of splaying device 22 is generally of the same internal dimensions as extension 18 which is formed so as to fit tightly over the aspirator exit. Entry end 15 is designed to accept and to facilitate passage of the filament bundle 12 from the aspirator exit. We have found that smooth, effective filament passage occurs when the aspirator exit orifice is approximately at or just below entry end 15. The lower, exit end 16 of splaying device 22 is designed so as to restrict filament flow substantially in one direction and thereby to spread the filaments to a greater degree, especially in the transverse direction, subsequent to filament departure from exit end 16. Accordingly, the exit end 16 is in the form of a slot having an effective shorter dimension not more than 25 percent of the effective longer dimension. The dimension of exit end 16 in the restricted direction, characterized by the effective shorter dimension, should be of a value which is sufficient to effect a high degree of filament spreading, so that the economics of this invention may be realized. The splaying device 22 exhibits such a high degree of filament spreading when such effective shorter dimension S ranges preferably from approximately 70 percent to approximately 150 percent of the effective dimension of the aspirator exit in the direction of forward motion of the moving receiving surface, i.e., the aspirator exit diameter, and from approximately 7 percent to approximately 15 percent of the effective longer dimension, as depicted by L in FIG. 3. With values of S less than approximately 7 percent of L, the exiting filaments tend to become plugged at the exit end of the splaying device when used with conventional-sized aspirators. With values of S greater than approximately 15 percent of L, the degree of filament spreading and randomness is not significantly greater than that obtained through the use of the aspirator alone without the splaying device 22. An exact determination of the effective shorter dimension S is dependent on such variables as the type of polymer from which the filaments are made, the physical properties of the filaments which contact the splaying device, the speed of filaments at the point of entry to the splaying device, the desired properties of the nonwoven web product, and the desired filament laydown pattern. The minimum effective dimension, e.g., the diameter of the entry end of the splaying device, which dimension is dependent on the cross-sectional dimensions, i.e., diameter, of the aspirator, also is generally at least as great as and preferably substantially greater than the effective shorter dimension S of the splaying device exit end. Subject to the above expressed limitations on the shorter dimension, the greater the differential between such minimum effective dimension of the entry end and such shorter dimension S, generally the greater the quality and degree of filament spreading and the randomness of distribution that occurs during exiting of the filaments from the splaying device.
The side walls of splaying device 22 are constructed of any material which is substantially rigid and is not detrimental to the filaments which contact it, i.e., stainless steel or brass tubing. The side walls connect entry end 15 to exit end 16 and completely enclose the channel between these two ends. The internal surface of side walls should have a finish which facilitates passage of the filaments through the channel, i.e., a polished finish. It is important for effective and wide filament dispersal having a minimum amount of filament entanglement that the side walls slope from the entry end to the exit end of the channel in a manner such that the slope makes an angle with the center-line axis of the aspirator jet passageway not exceeding approximately 45 degrees at any point on the internal side walls of the splaying device from the entry end to the exit end. Further, the slope should change gradually from the entry end to the exit end of the channel in order to terminate in side walls at such exit end which walls are substantially parallel to the center-line axis of the aspirator jet passageway. Such change in slope is preferably gradual, positive and continuous. Experience has shown that a center-line distance along the effective center line of the splaying device from the entry end 15 to the exit end 16 ranging preferably from 10 to 25 times, more preferably from 15 to 20 times, the effective shorter dimension S has yielded satisfactory results.
Filaments exiting the splaying device of this invention are deposited generally in a swirl pattern which effectively augments the formation of widely and randomly dispersed, substantially uniformly distributed filaments in the resultant product. Because of such relative uniformity of filament dispersal, the splaying device may be positioned such that the shorter dimension is in any direction with reference to the direction of motion of the moving receiving surface. However, highly effective filament dispersal occurs when the shorter dimension of the splaying device is substantially in the direction of motion of the moving receiving surface.
Although the splaying device 22 works especially compatibly with the preferred aspirating jet 19 as described in FIG. 2 and as described in greater detail in patent application Ser. No. 184,542 entitled "Process And Apparatus For Production Of A Nonwoven Web," filed on Sept. 28, 1971 in the name of Walter P. Lipscomb and Garland L. Turner, it has been designed to work compatibly with many conventional aspirators. In general, such conventional aspirators are especially suitable for use with the apparatus of this invention if these aspirators forward the filament bundle into splaying device 22 at a high velocity, generate sufficient pull within the aspirator to maintain the filaments under minimum tension, open and separate the filament bundle during the exiting of the filaments from the aspirators, and prevent filaments from undergoing any substantial twisting, knotting or entanglement.
In operation, the aspirating medium, which may be a pressurized fluid such as air, is introduced from a supply source, not shown, into chamber 50, at a pressure preferably ranging from 30 to 100 psig. Such media enters and flows through nozzle passageway 51 and exits therefrom as a high velocity stream. The pressurized state of the aspirating media is contingent upon several conditions and thus may be varied to meet the specified circumstances. Some factors which influence operating pressures are the aspirating jet design, aspirating media pressure consumed, type and nature of filament-forming polymer, degree of orientation to which filaments have been subjected, and the resulting properties of the nonwoven product. The high velocity fluid stream exiting nozzle passageway 51 engages filaments 12 entering the aperture 57 with sufficient energy to propel the filaments through collar chamber 52 into the diffuser 11, which is characterized by an initially diverging chamber 53. Subsequently, the propelled filaments are forwarded into splaying device 22 and are dispersed therefrom in a wide and random manner. Then the filaments are deposited on a receiving surface which normally takes the form of a conveyor belt moving at a predetermined constant speed and at a predetermined distance from the exit end 16 of splaying device 22. The receiving surface should be placed below the splaying device 22 at a distance such that efficiency of random dispersal of filaments thereon in a uniform manner is achieved.
We have found that it is especially advantageous in the process utilizing this invention to fix the combination of the splaying device with the aspirating means, or a plurality of such combinations in parallel, on a reciprocating bar or similar mechanism and to reciprocate such combination or plurality of combinations in a direction substantially transverse to the direction of forward motion of said moving receiving surface. Preferably, a plurality of such combinations are reciprocated at a rate and stroke in such a pattern that the filaments from a given combination overlap those from adjacent combinations. A suitable means of reciprocation is described in greater detail in the aforementioned patent application, Ser. No. 184,242 entitled "Process And Apparatus For Production Of A Nonwoven Web," filed on Sept. 28, 1971 in the name of Walter P. Lipscomb and Garland L. Turner.
The following example is provided as further illustrative of the present invention. The enumeration of details therein however should not be considered as restrictive of the scope of this invention.
In an example, nylon 6 is melt spun into a 70-filament bundle 12 of 125 denier. The filament bundle 12 is subsequently introduced into aspirating jet 19 via aperture 57. The jet is reciprocated at 62 cycles per minute at a stroke of 10 inches. In collar chamber 52, the filaments are subjected to air as the aspirating medium at a pressure of 40 psig. The filaments 12 are forwarded to and through diffuser passageway 54 by he aspirating jet stream. The diameter of diffuser passageway 54 is 0.072 inches. Thereafter, the filaments 12 exit from jet 19 into splaying device 22. Splaying device 22 is made of stainless steel tubing and has a diameter of entry end 15 of approximately three-eights inch, a substantially rectangularly shaped exit end 16 with a shorter dimension S of approximately one-sixteenth inch and a longer dimension L of approximately nine-sixteenths inch, and a distance from entry end 15 to exit end 16 of approximately 1 inch. Extension 18 has a length of approximately three-fourths inch and a diameter of approximately three-eights inch. Upon exiting from splaying device 22, filaments 12 open up considerably and are deposited on continuously moving, foraminous horizontal conveyor 20 which is moving at a speed of 16 feet per minute and is at a distance of 13 inches from the closest portion of splaying device 22. Suction chamber 21 is provided beneath conveyor 20.
Nonwoven webs produced in a process using the splaying device of this invention are characterized by a random filament distribution throughout the web. The appearance of webs is uniform, and it is essentially free of filament aggregates. The improvements of yarn randomness, openness and cover are such that approximately one-half the usual layers may give as even a web as with the aspirating jet alone.
The nonwoven web or other useful construction processed from a coherent filament bundle prepared in accordance with this invention may serve a variety of useful purposes, particularly in the manufacture of nonwoven products, such as carpet backing, wall covering, insulation, coating substrates, interfacing, filters, fabric applications, and the like.
While an exemplary embodiment of this invention has been described, the true scope of the invention is to be determined from the following claims.
The invention herein set forth is related to the inventions described in copending applications Ser. No. 184,420 entitled "Two-Planar Deflector For Dispersing And Depositing Nonwoven Filamentary Structures," filed on Sept. 28, 1971 in the name of Walter P. Lipscomb and Garland L. Turner and Ser. No. 184,422 entitled "Foraminal Apparatus For Splaying And Depositing Nonwoven Filamentary Structures," filed on Sept. 28, 1971 in the name of Walter P. Lipscomb and Garland L. Turner, wherein different apparatus for improving the dispersal and deposition of a plurality of continuous filaments onto a continuously moving surface are disclosed.
BACKGROUND OF THE INVENTION
This invention relates to an apparatus for improving the dispersal and deposition of filaments. In particular, it relates to an apparatus for augmenting the dispersal of continuous filaments onto a receiving surface so as to form a nonwoven web of randomly disposed filaments.
Nonwoven webs formed from continuous filamentary materials which have been laid in a random configuration are well known in the art. In the formation of such webs, great care is frequently taken to ensure that the filaments are maintained apart from each other and that interfilamentary entanglement and the formation of filament aggregates are avoided.
Nonwoven webs comprising multi-filaments are commonly formed by withdrawing the filaments from a source of supply, such as a melt spinnerette and then depositing the filaments at high velocity onto a moving surface by means of an aspirator. In the production of nonwoven webs having a substantial width, there must be provided either a plurality of aspirators for depositing a plurality of filamentary bundles in a random manner upon the moving surface or there must be provided a means, normally unduly complicated and cumbersome, to move the aspirator over the width of the nonwoven web to be produced.
When depositing filaments from a conventional aspirator onto a collecting surface, the filaments will spread out within the confines of the aspirator boundary. However, the filament distribution in the jet stream is not always uniform and random and is often restricted to a small laydown area; for example, a web width normally does not exceed 8 inches when a fixed aspirator jet is situated at a distance of 1 to 3 feet from the receiving surface.
Some of these deficiencies have been overcome by impinging the filaments against a single deflecting surface before the filaments are massed in web form. The intermixing which is normally attendant with the deflection promotes a filament interaction which tends to integrate but also to aggregate the product. Also, there is normally an accompanying bulkiness or uneven filament distribution, a twisting pattern or roping, a tendency toward sagging or a loss of strength, each of which is undesirable for many end uses of the web material.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to provide an apparatus for augmenting dispersal of a plurality of filaments which are thereafter deposited onto a receiving surface so as to form a web. It is a further object of this invention to provide a simple, reliable, inexpensive, and easily constructed apparatus for more expeditiously spreading filaments and thereby for producing superior nonwoven webs having high strength and integrity. A further object of this invention is the provision of a filament splaying means that spreads the filaments in substantially all directions. A still further object of this invention is the provision of a filament splaying and depositing means that is readily adaptable for usage with conventional aspirating means used in the production of nonwoven webs. Further objects and advantages of the present invention will become apparent by reference to the following specification and drawings.
In attaining the foregoing objects, this invention features an apparatus for spreading while depositing filaments onto a moving receiving surface in a randomly dispersed manner to form a nonwoven web. Such apparatus comprises, in combination, an aspirator to forward filaments at a high velocity and a splaying device to separate widely the filaments exiting from such aspirator and to forward the filaments onto the moving receiving surface. The splaying device is affixed near the exit of the aspirator so as to accept passage of substantially all the filaments exiting from such aspirator. The splaying device comprises an enclosed, open-ended channel. The entry end of such channel is connected to the aspirator exit by an extension which provides an effective air-tight seal around and envelops the aspirator exit. The opposite exit end of the channel forms a slot which has an effective shorter dimension less than 25 percent of an effective longer dimension and is, preferably, generally elliptical or rectangular in form. Preferably, the effective shorter dimension of the channel exit end ranges from 70 to 150 percent of the effective diameter of the aspirator exit passageway and from 7 to 15 percent of the longer dimension. The minimum effective dimension of the channel entry end is at least the magnitude of the effective shorter dimension of the channel exit end. The channel has side walls to connect the two open ends and to completely enclose the remainder of the channel. Such side walls slope from the entry end to the exit end of the channel in a manner such that the slope makes an angle with the center-line axis of the aspirator exit passageway not exceeding approximately 45° at any point on the internal side walls of the channel from the entry end to the exit end. The slope changes from the entry end to the exit end of the channel in order to form side walls at such exit end which are substantially parallel to such center-line axis of the aspirator exit passageway. The internal surface of the channel has a surface which facilitates passage of the filaments through the channel. Preferably, a distance along the center line of the splaying device from the entry end to the exit end ranges from 10 to 25 times, more preferably from 15 to 20 times, the magnitude of the effective shorter dimension of the exit end.
In a preferred embodiment, the exit end of the splaying device has a substantially uniformly wide shorter dimension, being approximately 88 percent of the aspirator exit passageway diameter and approximately 11 percent of a substantially uniformly wide longer dimension.
A feature of this invention is its quick and easy adaptability for use with many conventional aspirators, i.e., aspirator jets, in dispersing while depositing filamentary materials onto a moving receiving surface.
Advantageously, the combination of the splaying device with the aspirator may be reciprocated above a moving receiving surface in a direction substantially transverse to the forward motion of the receiving surface. Further advantageously, this combination may be made a part of a plurality of substantially similar combinations and then may be reciprocated at essentially the same rate and stroke in a pattern such that filaments from a given combination overlap those of the next adjacent combination so as to further increase web width.
The method utilizing the apparatus of this invention comprises, in general, the utilization of the above described splaying device in combination with an aspirator whereby filaments, preferably forwarded from a spinnerette of a spinning mechanism and thereafter from a drawing mechanism, are forwarded through a high velocity fluid jet of the aspirator. Subsequent thereto, the aspirator jet stream propels the filaments onto the splaying device of this invention whereby the filaments are deflected onto a continuously moving, preferably foraminous, surface to form a uniform nonwoven web comprising randomly disposed, substantially uniformly distributed filaments. Deposition of the filaments may be aided by a suction chamber located underneath the moving surface.
The described apparatus can be readily used for dispersion of filaments or, alternately, of strands, yarns, slivers, or other similar forms of material, or mixtures thereof. Such materials include any fiber-forming thermoplastic polymer from which filaments can be obtained. These materials include: polyamides, for example, poly(epsilon-caprolactam) (hereinafter nylon 6) and poly(hexamethylene adipamide) (hereinafter nylon 66); linear polyesters, for example, poly(ethylene terephthalate); acrylonitrile polymers and copolymers; olefinic polymers, for example, polyethylene, polypropylene and polyvinyl chloride; and cellulose acetates. Preferred materials include nylon 6, nylon 66 and poly(ethylene terephthalate).
The invention will be more clearly understood and additional objects and advantages will become apparent upon reference to the discussion below and to the figures which are given for illustrative purposes.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a schematic perspective view depicting a preferred embodiment of the apparatus employed for carrying out the invention;
FIG. 2 is a sectional view of the apparatus of FIG. 1, taken on line 2--2 thereof;
FIG. 3 is a bottom view of the apparatus of FIG. 2, taken on line 3--3 thereof.
FIG. 4 is a side elevation of the splaying device turned 90° clockwise from the position of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings and particularly to FIG. 1, a bundle of freshly formed filaments 12 enter inlet aperture 57 of an aspirator such as aspirating jet 19. The filaments were formed from the spinnerette of a melt spinning apparatus (not shown). Subsequent to spinning, the filaments may also be attenuated and oriented on a drawing apparatus (also not shown). Filament bundles having a broad range of denier, i.e., 30 to 3,400 total denier, may be used in the apparatus of this invention. Within the aspirating jet 19, the filaments are acted upon by a high velocity fluid medium such as air, which is supplied through the inlet conduit 35. Aspirating jet 19 comprises an air nozzle 9, a collar 10 and a diffuser 11. The filament bundle 12 is forwarded via the high velocity fluid medium from the jet exit 17 into the splaying device 22 whereby the filaments of the bundle 12 are splayed onto receiving surface 20. Air stream restriction and its attendant turbulence spreads and opens the filament bundle 12 at the splaying device exit. Splaying device 22 is attached to the exit end of jet 14 via extension 18. Extension 18 is preferably molded from the same material as splaying device 22 to assure a smooth internal surface and is attached to the jet exit end so as to form a close seal thereon. This seal must be effective in preventing air leaks which enhance clogging of the filaments near any area of such air leaks. On receiving surface 20, preferably a foraminous continuously moving conveyor with a suction chamber 21 provided beneath that portion of conveyor 20 on which the filaments are being laid down, the filaments are deposited in a random manner to form web 23. Upon passing from receiving surface 20, web 23 is forwarded to further processing units 24 (not shown), such as fusion rolls to bond the web 23.
In FIG. 2, the aspirating jet 19 comprises: a hollow air nozzle 9 which is externally threaded at each end and which has an air inlet conduit 35 attached to its upper end; a hollow collar 10 which is internally threaded at both ends so as to connect air nozzle 9 with diffuser 11 and which has an inlet aperture 57 for receiving filament bundle 12; and a hollow diffuser 11 which is externally threaded at its upper end and through which the filaments and high velocity air are propelled into splaying device 22 and thereafter onto a receiving surface. The annular internal aperture 57 is arranged to direct the filaments entering therein downwards, i.e., in the direction of air flow. The internal dimensions of collar 10 and of diffuser 11 are arranged so as to minimize twisting, knotting and entanglement of the filaments passing therein. By way of example only, the diameter of nozzle passageway 51 is preferably from 20 percent to 33 percent of the nozzle passageway length. Also, the cross-sectional area of nozzle passageway 51 is preferably from 25 percent to 35 percent of the cross-sectional area of diffuser passageway 54. Further, the diameter of diffuser passageway 54 is preferably from 2 to 10 percent of the length thereof. Still further, the maximum diameter of diffuser entrance passageway 53, which is conical in shape, is most preferably approximately two times the diameter of the diffuser chamber 54. The cross-sectional area of diffuser passageway 54 is designed such that the cross-sectional area of filament bundle 12 passage therein ranges from 0.1 to 5 percent, preferably from 0.2 to 1.5 percent, of the diffuser passageway cross-sectional area. The respective lengths and diameters of air nozzle entrance chamber 50 and of collar chamber 52 are not critical. However, such lengths and diameters should be used as are practical; i.e., compatible with the overall operation of the present process.
Referring now to FIGS. 3 and 4 as well as to FIG. 2, the splaying device 22 is characterized by an enclosed hollow channel 17, the upper, entry end 15 of splaying device 22 is generally of the same internal dimensions as extension 18 which is formed so as to fit tightly over the aspirator exit. Entry end 15 is designed to accept and to facilitate passage of the filament bundle 12 from the aspirator exit. We have found that smooth, effective filament passage occurs when the aspirator exit orifice is approximately at or just below entry end 15. The lower, exit end 16 of splaying device 22 is designed so as to restrict filament flow substantially in one direction and thereby to spread the filaments to a greater degree, especially in the transverse direction, subsequent to filament departure from exit end 16. Accordingly, the exit end 16 is in the form of a slot having an effective shorter dimension not more than 25 percent of the effective longer dimension. The dimension of exit end 16 in the restricted direction, characterized by the effective shorter dimension, should be of a value which is sufficient to effect a high degree of filament spreading, so that the economics of this invention may be realized. The splaying device 22 exhibits such a high degree of filament spreading when such effective shorter dimension S ranges preferably from approximately 70 percent to approximately 150 percent of the effective dimension of the aspirator exit in the direction of forward motion of the moving receiving surface, i.e., the aspirator exit diameter, and from approximately 7 percent to approximately 15 percent of the effective longer dimension, as depicted by L in FIG. 3. With values of S less than approximately 7 percent of L, the exiting filaments tend to become plugged at the exit end of the splaying device when used with conventional-sized aspirators. With values of S greater than approximately 15 percent of L, the degree of filament spreading and randomness is not significantly greater than that obtained through the use of the aspirator alone without the splaying device 22. An exact determination of the effective shorter dimension S is dependent on such variables as the type of polymer from which the filaments are made, the physical properties of the filaments which contact the splaying device, the speed of filaments at the point of entry to the splaying device, the desired properties of the nonwoven web product, and the desired filament laydown pattern. The minimum effective dimension, e.g., the diameter of the entry end of the splaying device, which dimension is dependent on the cross-sectional dimensions, i.e., diameter, of the aspirator, also is generally at least as great as and preferably substantially greater than the effective shorter dimension S of the splaying device exit end. Subject to the above expressed limitations on the shorter dimension, the greater the differential between such minimum effective dimension of the entry end and such shorter dimension S, generally the greater the quality and degree of filament spreading and the randomness of distribution that occurs during exiting of the filaments from the splaying device.
The side walls of splaying device 22 are constructed of any material which is substantially rigid and is not detrimental to the filaments which contact it, i.e., stainless steel or brass tubing. The side walls connect entry end 15 to exit end 16 and completely enclose the channel between these two ends. The internal surface of side walls should have a finish which facilitates passage of the filaments through the channel, i.e., a polished finish. It is important for effective and wide filament dispersal having a minimum amount of filament entanglement that the side walls slope from the entry end to the exit end of the channel in a manner such that the slope makes an angle with the center-line axis of the aspirator jet passageway not exceeding approximately 45 degrees at any point on the internal side walls of the splaying device from the entry end to the exit end. Further, the slope should change gradually from the entry end to the exit end of the channel in order to terminate in side walls at such exit end which walls are substantially parallel to the center-line axis of the aspirator jet passageway. Such change in slope is preferably gradual, positive and continuous. Experience has shown that a center-line distance along the effective center line of the splaying device from the entry end 15 to the exit end 16 ranging preferably from 10 to 25 times, more preferably from 15 to 20 times, the effective shorter dimension S has yielded satisfactory results.
Filaments exiting the splaying device of this invention are deposited generally in a swirl pattern which effectively augments the formation of widely and randomly dispersed, substantially uniformly distributed filaments in the resultant product. Because of such relative uniformity of filament dispersal, the splaying device may be positioned such that the shorter dimension is in any direction with reference to the direction of motion of the moving receiving surface. However, highly effective filament dispersal occurs when the shorter dimension of the splaying device is substantially in the direction of motion of the moving receiving surface.
Although the splaying device 22 works especially compatibly with the preferred aspirating jet 19 as described in FIG. 2 and as described in greater detail in patent application Ser. No. 184,542 entitled "Process And Apparatus For Production Of A Nonwoven Web," filed on Sept. 28, 1971 in the name of Walter P. Lipscomb and Garland L. Turner, it has been designed to work compatibly with many conventional aspirators. In general, such conventional aspirators are especially suitable for use with the apparatus of this invention if these aspirators forward the filament bundle into splaying device 22 at a high velocity, generate sufficient pull within the aspirator to maintain the filaments under minimum tension, open and separate the filament bundle during the exiting of the filaments from the aspirators, and prevent filaments from undergoing any substantial twisting, knotting or entanglement.
In operation, the aspirating medium, which may be a pressurized fluid such as air, is introduced from a supply source, not shown, into chamber 50, at a pressure preferably ranging from 30 to 100 psig. Such media enters and flows through nozzle passageway 51 and exits therefrom as a high velocity stream. The pressurized state of the aspirating media is contingent upon several conditions and thus may be varied to meet the specified circumstances. Some factors which influence operating pressures are the aspirating jet design, aspirating media pressure consumed, type and nature of filament-forming polymer, degree of orientation to which filaments have been subjected, and the resulting properties of the nonwoven product. The high velocity fluid stream exiting nozzle passageway 51 engages filaments 12 entering the aperture 57 with sufficient energy to propel the filaments through collar chamber 52 into the diffuser 11, which is characterized by an initially diverging chamber 53. Subsequently, the propelled filaments are forwarded into splaying device 22 and are dispersed therefrom in a wide and random manner. Then the filaments are deposited on a receiving surface which normally takes the form of a conveyor belt moving at a predetermined constant speed and at a predetermined distance from the exit end 16 of splaying device 22. The receiving surface should be placed below the splaying device 22 at a distance such that efficiency of random dispersal of filaments thereon in a uniform manner is achieved.
We have found that it is especially advantageous in the process utilizing this invention to fix the combination of the splaying device with the aspirating means, or a plurality of such combinations in parallel, on a reciprocating bar or similar mechanism and to reciprocate such combination or plurality of combinations in a direction substantially transverse to the direction of forward motion of said moving receiving surface. Preferably, a plurality of such combinations are reciprocated at a rate and stroke in such a pattern that the filaments from a given combination overlap those from adjacent combinations. A suitable means of reciprocation is described in greater detail in the aforementioned patent application, Ser. No. 184,242 entitled "Process And Apparatus For Production Of A Nonwoven Web," filed on Sept. 28, 1971 in the name of Walter P. Lipscomb and Garland L. Turner.
The following example is provided as further illustrative of the present invention. The enumeration of details therein however should not be considered as restrictive of the scope of this invention.
In an example, nylon 6 is melt spun into a 70-filament bundle 12 of 125 denier. The filament bundle 12 is subsequently introduced into aspirating jet 19 via aperture 57. The jet is reciprocated at 62 cycles per minute at a stroke of 10 inches. In collar chamber 52, the filaments are subjected to air as the aspirating medium at a pressure of 40 psig. The filaments 12 are forwarded to and through diffuser passageway 54 by he aspirating jet stream. The diameter of diffuser passageway 54 is 0.072 inches. Thereafter, the filaments 12 exit from jet 19 into splaying device 22. Splaying device 22 is made of stainless steel tubing and has a diameter of entry end 15 of approximately three-eights inch, a substantially rectangularly shaped exit end 16 with a shorter dimension S of approximately one-sixteenth inch and a longer dimension L of approximately nine-sixteenths inch, and a distance from entry end 15 to exit end 16 of approximately 1 inch. Extension 18 has a length of approximately three-fourths inch and a diameter of approximately three-eights inch. Upon exiting from splaying device 22, filaments 12 open up considerably and are deposited on continuously moving, foraminous horizontal conveyor 20 which is moving at a speed of 16 feet per minute and is at a distance of 13 inches from the closest portion of splaying device 22. Suction chamber 21 is provided beneath conveyor 20.
Nonwoven webs produced in a process using the splaying device of this invention are characterized by a random filament distribution throughout the web. The appearance of webs is uniform, and it is essentially free of filament aggregates. The improvements of yarn randomness, openness and cover are such that approximately one-half the usual layers may give as even a web as with the aspirating jet alone.
The nonwoven web or other useful construction processed from a coherent filament bundle prepared in accordance with this invention may serve a variety of useful purposes, particularly in the manufacture of nonwoven products, such as carpet backing, wall covering, insulation, coating substrates, interfacing, filters, fabric applications, and the like.
While an exemplary embodiment of this invention has been described, the true scope of the invention is to be determined from the following claims.