US3325906A

US3325906A - Process and apparatus for conveying continuous filaments

Info

Publication number: US3325906A
Application number: US431691A
Authority: US
Inventors: Ralph A Franke
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1965-02-10
Filing date: 1965-02-10
Publication date: 1967-06-20
Anticipated expiration: 1984-06-20

Description

R. A. FRANKE June 26, 1967 5 Sheets-Sheet 1 Filed Feb. 10, 1965 R. A. FRANKE June 20, 1967 PROCESS AND APPARATUS FOR CONVEYING CONTINUOUS FILAMENTS 3 Sheets-Sheet 5;

Filed Feb. 10, 1965 R. A. FRANKE June 20, 1967 PROCESS AND APPARATUS FOR CONVEYING CONTINUOUS FILAMENTS 3 Sheets-Sheet 5 Filed Feb. 10, 1965 United States Patent 3,325,906 PROCESS AND APPARATUS FOR CONVEYING CONTiNUOUS FILAMENTS Ralph A. Franke, Nashville, Tenn., assignor to E. l. du

Pont de Nemours and Company, Wilmington, DeL, a

corporation of Delaware Filed Feb. 10, 1965, Ser. No. 431,691 6 Claims. (Cl. 3410) This invention relates to an improved process and apparatus for forwarding strands of textile filaments and particularly to the forwarding of filaments by means of a high-velocity fluid stream flowing through an enclosed channel.

The forwarding of filaments by means of a high-velocity fluid stream in a jet device is well known in the textile art and is an especially valuable technique for use in a recently developed process for the manufacture of nonwoven fabrics composed of continuous synthetic organic filaments. In this process, which is described in British Patent 932,482, a multifilament strand of continuous filaments under tension is electrostatically charged by known techniques, for example by triboelectric charging or by passing the filaments through a corona discharge zone; the charged filaments are then forwarded by means of a jet device toward a web-laydown zone; the tension on the filaments is released as they exit the jet device thereby permitting them to separate due to the repelling effect of the applied electrostatic charge; and the filaments, while thus separated, are collected as a nonwoven web. The filaments are randomly and uniformly distributed throughout the web so obtained and are essentially free from filament aggregates or bunches. This arrangement of the filaments is highly desired since it yields an isotropic web with outstanding uniformity of opacity and full utilization of the strength of the constituent filaments.

The foregoing process, however, makes severe demands upon the jet device used to apply the forwarding tension. In various operating procedures within the scope of the above-described process, the jet device provides the forwarding tension to (1) draw the filaments as they are extruded from a spinneret, (2) pull the filaments from yarn packages or (3) strip the filaments from a mechanical drawing apparatus, for example, draw rolls. The jet device must not only apply adequate tension to forward the strand of filaments, it must do so while avoiding excessively turbulent fluid flow which would lead to filament entanglements and undesirable bunching of the filaments. Furthermore, as the filaments leave the jet, the tension must be rapidly removed to permit the filaments to separate.

The foregoing demands on the performance of the jet are further increased by the requirements of commercial manufacture, namely, the production of a wide nonwoven web and economical operation. Thus the high number of filaments forwarded by each jet device in commercial operation, which may amount to 700 to 800 or more, accentuates the need for uniform velocity profile in the jet device. The need for the preparation of wide webs requires that the output from a multiplicity of jet devices be combined. This in turn is most satisfactorily and most economically accomplished when the output from each jet forms a wide area of deposition at the web-laydown zone and when there is a uniform concentration of filaments throughout the area of deposition.

It is the purpose of this invention to provide a process for forwarding filaments by a high-velocity fluid stream with a minimum of filament entanglement and bunching.

It is another purpose to forward filaments by a highice form expansion of a stream of fluid containing a strand of filaments moving cocurrently with the fluid stream.

An additional purpose is to provide a jet device which uses a high-velocity fluid stream to impart a forwarding tension to a multifilament strand of continuous filaments and in which the fluid stream has a uniform velocity profile.

A further purpose is to provide a diffuser section for a filament-forwarding jet device which spreads the filaments uniformly.

These and other purposes are attained in accordance with this invention by forwarding continuous filaments by means of a high-velocity fluid flowing through a confining channel and withdrawing a portion of the boundary layer, i.e., the fluid adjacent to the walls of the channel. This Withdrawal of fluid from the body of a filamentforwarding jet device improves the uniformity of the filament stream passing through the device. Withdrawal of fluid from the diffuser section as indicated, spreads the filaments uniformly.

The channels referred to above can have a circular or rectangular cross section and can have a constant, increasing or decreasing cross-sectional area. Divergence angles of up to about 6 may be used in the body of filament-forwarding jet devices while a divergence considerably greater than 6 is normally used in the diffuser section. The filament passageway defined by the diffuser section becomes wider in the downstream direction. The diffuser section can either be an integral part of the jet device or an attachment at the exit of the jet device.

With the jet devices having a circular cross section the withdrawal of fluid to regulate the boundary layer is usually confined to the diffuser section. With slot jet devices, that is, jet devices with a rectangular cross section. e.g.', the type described in the copending and coassigned application to Cope, et al. Ser. No. 425,839 filed on Ian. 15, 1965: the withdrawal of fluid is used in either or both the body of the jet device and diffuser section. Boundary layer regulation by withdrawal of a portion of the fluid is especially valuable in the case of slot jets with a high aspect ratio (ratio of the length to the width of the rectangular cross section). With slot jets, fluid is withdrawn from the narrow walls of the jet device. In the body section of the jet device withdrawal of a portion of the fluid through the narrow walls leads to greatly improved uniformity in the velocity profile of the fluid stream.

In the diffuser section of the jet device the wide walls increase in dimension in the direction of flow of the fluid stream sufficiently rapidly that the narrow walls spread outwardly at an angle greater than 6. By withdrawing a portion of the fluid through these narrow walls, the fluid stream and the filaments contained therein expand smoothly and uniformly to give a wide area of deposition at the web laydown zone and uniform concentration of walls of the jet device. This can lead to inhomogeneities in the nonwoven web and frequently to plugging of the jet device.

Further, in certain applications the jet devices are also used to effect heat treatment of the filaments, for example, to generate the property of spontaneous elongation as described in Kitson and Reese, US. Patent 2,952,879.

This places additional demands on the jet device since the hot filaments are more prone to stick to the Walls of the jet device on contact therewith thus increasing the chance of filament aggregates in the nonwoven web and plugging of the jet device. In order to avoid these problems, the jet device may be designed and operated to minimize contact of the filaments with the walls of the jet device.

To accomplish this for example, the boundary layers along the wide walls of the diffuser section of a slot jet are augmented in order to create a thick turbulent layer which prevents filament contact with the walls. This thicker layer can be created by roughening the interior of the wide walls by blasting with abrasives, by coating, or by other suitable means. Stepped increases in the internal cross-sectional area create a turbulent boundary after the step. Another and preferred technique is to introduce additional fluid into the jet device at a small angle with the flow of the primary fluid stream in the device. This additional fluid may be introduced under pressure or by aspiration into the primary fluid stream at the point where the diffuser section of the jet device begins or along the wide Walls in the body of the jet device. These methods of boundary layer augmentation are the subject of a copending and coassigned application to Jose P. de Guzman, Ser. No. 431,637, filed on even date herewith.

The invention will be further understood by reference to the drawings in which:

FIGURE 1 is a sketch which shows schematically the velocity profile of a fluid stream flowing through an enclosed channel and the growth of the boundary layer;

FIGURE 2 is a sketch as in FIGURE 1 showing the effect of filaments contained in the fluid stream on the velocity profile of the fluid stream as well as the nonuniform distribution of filaments in the stream.

FIGURE 3 illustrates the effect on the velocity profile of the filament-containing fluid streams in FIGURE 2. by

withdrawal of a portion of the fluid layer adjacent to the.

boundaries of the channel in accordance with this invention;

FIGURE 4 is a sketch which shows schematically the path of a high-velocity fluid stream and cocurrently moving filaments contained therein as they pass through a diffuser'having a divergence angle greater than 6;

FIGURE 5 is a sketch similar to FIGURE 4 showing the effect of removal of a portion of the boundary layer on the expansion of the fluid stream and the filaments contained therein;

FIGURE 6 is a side view of a specific embodiment of a diffuser of this invention attached at the exit of a jet device, with a part broken away to show the interior construction; and

FIGURE 7 is an end view along line AA of FIG- URE 6.

In the foregoing discussion the term fluid stream is intended to encompass both liquid and gas streams. The preferred fluid for forwarding filaments is air. It will be understood that the primary air or air supplied to the jet is high pressure air entering the jet device at an angle to and in the direction of the filament stream and which applies tension to forward the filaments. This is to be distinguished from aspirated air or air supplied for augmentation of boundary layers as discussed below.

In FIGURE 1 the velocity profiles of a stream of air moving through a narrow enclosed channel with a high aspect ratio are shown at 1, 2, and 3. Dotted lines 4 indicate the growth of the boundary layer along the narrow side walls 5 of the channel as the air moves in the direction indicated by the arrowv When this fast-moving stream of air contains slower-moving filaments, the velocity of the main stream of air is reduced and the velocities near the narrow sides are accelerated. This is indicated in FIG- URE 2 by velocity profiles 6, 7, and S. The filaments 9 migrate toward the high velocity peaks causing a high concentration at the edges of the group of filaments issuing from the exit of the channel. The laydown of a nonwoven web from such a group of filaments leads to a blotchy nonwoven web with aggregates of filaments.

FIGURE 3 shows the surprising flattening effect on the velocity profiles and the uniform distribution of the filaments across the channel when a portion of the air in the boundary layer is withdrawn through perforations 10 in walls 5 into suction chambers 11, 12, 13, and 14. Multiple chambers along each side wall as shown in FIGURE 3 are generally preferred in order to provide for better regulation of the amount of air withdrawn at various locations in the channel. Single chambers on each side are operable, however. The side walls are foraminous members such as perforated metal plates, sintered glass, or similar porous structures.

A further application of this invention is illustrated in FIGURES 4 and 5. FIGURE 4 shows the exit of filaments from diffuser section 15 having walls that diverge at an included angle greater than 6 from the channel walls 5. As indicated in FIG. 4, the diffuser is ineffective for serving its desired purpose, namely to spread the strand of filaments 9.

In FIGURE 5 a portion of the air adjacent to the walls of the diffuser is removed through perforations 16 in the walls 15 into the suction chambers 17 and 18. The smooth and uniform expansion of the stream of air is indicated by the paths taken by the filaments 9 contained in the stream. The filaments exiting from the diffuser are found to wander laterally as individual filaments, rather than to move sinuously in bundles or groups of filaments as is characteristic of the behavior without an effective diffuser. Thus nonuniformities caused by the sinuous movements of the filament bundle are minimized and the uniformity of the resulting web is greatly improved.

Although a diffuser section attached at the exit of a slot channel is highly effective for uniformly spreading a strand of filaments, when equipped as in FIGURE 5 to remove a portion of the boundary layer adjacent to the diffuser walls, it will not completely counteract large velocity peaks such as shown in FIGURE 2. Accordingly, the most preferred jet devices will have provision for removing a portion of the boundary layers in both the body and the diffuser section of the device.

FIGURES 6 and 7 illustrate an embodiment of a diffuser which employs the present invention and which is designed for attachment at the exit of a filament-forwarding jet device having a rectangular cross section.

The diffuser housing is formed by side members 19 and end members 20. Side members 19 are positioned adjacent to each other and form the wide walls of the filament passageway 21, corresponding to the long sides of the rectangular cross section. The filament passageway between these walls diverges at a small angle of the order of about 2 or less. The edges of the side members spread outwardly at an angle greater than 3 and coact with the end members to form a filament passageway having an include-d angle between the end members of greater than 6. Vacuum chambers 22 in the end members are formed by housings 23 and perforated plates 24. Plates 24, form the narrow walls of the filament passageway correponding to the short sides of the rectangular cross section.

The perforations 25 in plate 24 are positioned, as shown best in FIGURE 7, to open into the filament passageway. Air is withdrawn from the filament passageway through the perforations by means of a vacuum applied to chamber 22 through inlet 26. The diffuser section is attached at the exit of the jet device, shown fragmentarily in FIG- URES 6 and 7, by means of screws 27 through flanges 28 and 29 on the end plates 30 of the jet device and the end members 20 of the diffuser section, respectively.

The preferred embodiment of the diffuser section shown in FIGURES 6 and 7, permits withdrawal of a portion of the air in the boundary layers adjacent to the narrow walls of the filament passageway and the augmentation of the boundary layers adjacent to the wide walls of the filament passageway by aspiration of additional air into the filament passageway. Thus both spreading of the filaments and the prevention of contact of the filaments with the diffuser walls can be accomplished if desired. This can be achieved by the arrangement of the apparatus in FIGURES 6 and 7. The position of the diffuser section, in particular the side members 19, relative to the effuser plates 31, is adjusted by means of washers 32. The slot openings 33 between the effuser plates 31 and the side members 19 permit the aspiration of air into the filament passageway and the formation of a thick boundary layer of air along the interior surfaces of the side members 19. The augmented boundary layer is particularly desirable where heat relaxation is performed along with filament forwarding as in Example l-B below. The width of the slot openings is normally adjusted to be in the range of 0.010 to 0.070 inch (0.025 to 0.178 cm.).

Example 1 This example illustrates the use of boundary layer regulation in the diffuser section of a filament-forwarding slot jet device.

(A) Poly(ethylene terephthalate) filaments are spun from a spinneret with 250 holes (0.009 in. diameter x 0.012 in. long) (0.23 cm. x 0.030 cm.), quenched with air at 18 C., drawn as a ribbon of filaments from the spinneret by means of 2 draw rolls operating at a surface speed of 3850 yd./min. (3520 m./min.), electrostatically charged to a level of 66,000 c.g.s. electrostatic units (esu) per m2 of filament surface with 2 corona discharge devices of the type described in Di Sabato and Owens, US. Patent 3,163,753, located between the spinneret and the draw rolls, and then passed into a 5-in. (12.7-cm.) wide slot jet which strips the filaments from the last draw roll. The slot jet is of the type described in the aforementioned application of Cope et al. and has an exit of 5 in. x 0.130 in. (12.7 cm. x 0.330 cm.). The jet is supplied with 93 s.c.f.m. (2630 l./min.) of air at room temperature.

Filaments of a 79/21 copolymer of poly(ethylene terephthala-te)/poly(ethylene isophthalate) are spun from a spinneret with 54 holes (0.009 in. diameter x 0.012 in. long) (0.023 cm. x 0.030 cm.), quenched 'With air at 18 C., and elect-rostatically charged to a level of 66,000 esu. per square meter of filament surface by the same method as used for the poly(ethylene terephthalate) filaments. The copolymer filaments are spread by means of convex guides into a ribbon having the same width as the ribbon of poly(ethylene terephthalate) filaments and the two ribbons are combined on the first draw roll to give a uniform distribution of the copolymer filaments throughout the composite ribbon. The composite ribbon has a width of 4.25 in. (10.8 cm.).

A diffuser as illustrated in FIGURES 6 and 7 is attached at the exit of the slot jet. The diffuser has an entrance of 5 in. x 0.140 in. (12.7 cm. x 0.356 cm.), an exit of 6.5 in. x 0.280 in. (16.5 cm. x 0.712 cm.), and is 4.75 in. (12.1 cm.) long. A slot, 0.050 in. (0.127 cm.) wide, is provided at the juncture between the jet and diffuser along each of the wide walls, as indicated by the numeral 33 in FIGURES 6 and 7. The slot makes a 15 angle with the center line of the diffuser. Air is aspirated into these slots to create boundary layers which prevent the filaments from contacting the wide walls. The included angle formed by the two narrow walls at the diffuser exit is 30.8". The walls are formed to the shape of a segment of a circle with a radius of 17.5 in. (44.5 cm.). There are 28 perforations of 0.0625 in. (0.159 cm.) diameter in each of the narrow walls providing an open area of 13%. By application of suction, corresponding to 45 in. (114 cm.) of water, to the perforations, 5 s.c.f.m. (140 l./min.) of air is removed and boundary layer build-up and separation of the air stream from the walls is prevented. A 16-in.

6 (41-cm.) wide area of deposition of filaments is obtained on a laydown belt positioned 18.75 in. (47.6 cm.) below the exit of the diffuser and provided with a suction chamber, having an area of 1.8 ft. (0.167 m throu h which 1000 s.c.f.m. (28,000 l./min.) of air is removed.

(B) Part A is repeated except that the air supplied to the slot jet is at 240 C. to provide for heat relaxation of the poly(ethylene terephthalate) filaments thereby developing the property of spontaneous elongation as described in Kitson and Reese, US. Patent 2,952,879. The following additional changes from Part A are made: the air flow to the jet is 78 s.c.f.m. (2200 l./min.); the draw roll speed is 3920 yd./min. (3580 m./min.); and the suction applied to the perforations in the diffuser corresponds to 20 in. (51 cm.) of water. Since the copolyester filaments shrink more than the poly(ethylene terephthalate) filaments during the relaxation step, thereby causing a greater concentration of electrostatic charge on the copolymer filaments, the charging of the filament ribbons is individually controlled before they are combined so that all the filaments will have the same charge level, 66,000 esu. per square meter of filament surface, when they exit from the diffuser.

Under the conditions described above, a suction corresponding to only 20 in. (51 cm.) of water, is required to prevent separation of the air stream from the narrow walls of the diffuser. Two s.c.f.m. (57 l./min.) of air is removed at this suction level. The air being aspirated into the slots at the diffuser entrance keeps the ribbon of filaments separated from the wide diffuser walls by 0.03 in. (0.08 cm.). When the slots are closed, the filaments touch the hot walls, and stick to them, eventually causing plugging of the diffuser.

(C) Part B is repeated using different levels of suction applied to the perforations in the narrow walls of the diffuser and the widths of the areas of deposition of the filaments on a laydown belt located 19.25 in. (49 cm.) below the exit of the diffuser are determined, The results are summarized below:

Level of Suction Width of area of deposition Inch of Cm. 01' Inch Cm.

water water 0 0 4 10 20 51 Variable (D) Part C is repeated using 3 diffuses having various amounts of open area in the narrow walls. The results are summarized below:

Level of Suction Width of Area of Deposition Wall open area In. of Cm. of In. Cm. water water 1 15 s.c.f.1n. (420 l./min.) of air removed.

Example 2 This example illustrates the removal of air from the boundary layers in the body portion of a slot jet and the effect this has on the level of suction which must be applied in the diffuser section to achieve maximum Width and uniformity of web laydown.

A diffuser section of the general type used in Example 1 and having provision for removing a portion of the air I in the boundary layers adjacent to the narrow walls of the diffuser, is attached at the exit of a 12-in. (31-cm.) long slot jet having a width of in. (12.7 cm.). The narrow walls of the jet downstream from the primary 8 Example 4 This example illustrates the removal of boundary layers from a diffuser whose cross-sectional area decreases from entrance to exit.

air inlets are prepared from photo-etched platescontain- 5 ing 10,000 holes (0.005 in. diameter) Per square inch A lortg asplator/ 2 t [1550 holes (0.0127 cm. diameter) per square centitype g gg g copgndmg x g g ifi meter]. A single suction chamber is supplied along of the i 3i 3 P to t 5 g ed g narrow walls to permit the withdrawal of air through the 1 now i an avmg an of 6 in. x 1.125 in. (6.75 111. (15.2 cm. x 2.86 cm.)

perforations of the. photo-etched plates. 2 7 6 I l f A ribbon of continuous filaments as in Example 1 is (436 used to stflp 2 p0 i flaments fed into the jet which is supplied with 32 s.c.f.m. (910 l./ at a Speed Of 870 y /u (795 m./min.) from the last min.) of air through the primary air inlets. Various levels draw You of a mechanical drawmg apparatus P f f Suction are applied to the porous ll i the d heated feed rolls and two draw ro-lls. An exit a1r velocity portion and diffuser section of the jet as indicated in 15 0f160fL/See- 111/ is Provided y the 390 Table I. The effect of these variations on the maximum Ihhh) of air pp to the j and 75 width and uniformity of the nonwoven web obtained by (2100 0f pp to the j and 75 collecting the filaments exiting from the jet on a moving A diff h n entrance of 6 X 1375 laydown belt is summarized in Table I. in?) (15.2 cm. X 3.49 cm.) (53.2 cm?) and an exit of TABLE I Level of Suction Maximum Web Width Uniformity of web, Body portion of jet Diffuser section =l=percent of average Inch Cm. web weight 1 Inch of Cm. of Inch of Cm. of water water water water A 2.5 6.4 5.0 12.7 23 5s +s,-7. B 51 23.5 60 +9,-14. C 102 18 46 +13, 10.

1 Webs have an average weight of about 2 oz./yd. (68 g./m. 1 Suction chambers closed to atmosphere.

These results indicate that removal of air from the 7.5 in. x 1 in. (7.5 in?) (19.1 cm.X 2.54 cm.) (84.4 cm?) boundary layers adjacent to the narrow walls in' the body is used at the exit of the jet. The narrow divergent walls portion of the jet reduces the level of suction needed to 40 are formed to the shape of a segment of a circle with remove air from the boundary layers in the diffuser seca radius of 13 in. (33 cm.). Suction is applied to perforation in order to obtain satisfactory levels of web width and tions placed down the length of the narrow walls. A high uniformity. The improvement in uniformity is evidence air velocity is maintained through the diffuser, permitthat bunching of filaments, as illustrated schematically in ting operation with a suction level of less than 4 in. (10 FIGURE 2, is decreased by removal of air from the cm.) of water. A 22-in. (56 cm.) wide laydown is proboundary layer in the body portion. duced on a laydown belt positioned 25 in. (64 cm.) from the exit of the diffuser. Example 3 By the use of this type of diffuser having converging This example illustrates the removal of air from the Wide walls and diverging narrow walls, the ribbon of filaboundary layers along the narrow walls ofa diffuser which ments can be spread without having a larger cross-sechas parallel wide walls. tional area at the exit of the diffuser than at the entrance.

A l2-in. (31 cm.) long slot jet with a 4 in. x 0.140 By utilizing a constant or a decreasing cross-sectional X 0356 eXit area, the air velocity can be maintained at a high level is used to 'tP 363 p p py filaments at a Speed through the diffuser. This high velocity can be an ad- Of 933 y TIL/111th) from the tfh of a vantage when operating with the diffuser walls at a temmechamcal filament-attenuation apparatus utl llllllg two perature below the Sticking point of the filaments being hefated feed rolls and two dr aw rollsgnw Jet 15 supphefi processed. Since some filament contact with the walls can Wlth j (187.0 of an through be tolerated under these conditions, the high air flows are mary dlffuser wlth l entrance of 4 X able to overcome adequately the electrostatic attraction 0.140111. (0.561n.-) (10.2 cm. x0556 cm.) (3.62 0111. bt th t t 11 h d fil d h and an exit of 5.6 in. X 0.140 in. (0.783 in?) 14.2 cm. x e Ween e "1 C arge t 6 0.356 cm.) (5.06 cm?) is attached at the exit of the jet of Jet devlce' Thls greatly. reduces the.1evel of with 0.060 in. (0.162 cm.) aspiration slots at the juncture suftlon t be used to achleve the issued web between the Wide Walls of the diffuser and jet. The slots width and unifonmty' make an angle of 15 with the main stream of air passing 5 By the of asymmetric suctlon dlffusers that is, through the jet. The narrow walls of the diffuser are use of Suctloh on only one of the narrow Walls, and by formed to the shape of a segment of a circle with a radius Varying the cross'seetional Shape of the diffuser eXit, Variof 13 in. (33 cm.). Each narrow wall has 9 perforations ettohs in the Profile of the nonwoven web Produced y 0.031 in. (0.079 cm.) in diameter. By application of suc- Collecting the filaments exiting from the diffuser On 3 tion to the perforated Walls at a level corresponding to 7 laydown belt can be obtained. These methods may be 4 in. (10.2 cm.) of water, the ribbon of polypropylene used to control the profile of the web laid down by the filaments is maintained in a stable configuration and a layterminal jet devices when a row of jets is used to produce down zone 22 in. (56 cm.) Wide is produced on a laya wide nonwoven web. In this manner, it is possible to down belt positioned 26.3 in. (67 cm.) below the exit of reduce the amount of edge trimming that is required to the diffuser. obtain a uniform web.

What is claimed is:

1. In a method wherein a multifilament strand of continuous filaments is forwarded by means of a high-velocity fluid stream through a confining channel with minimum filament entanglement and bunching, the improvement comprising spreading the filaments of the strand uniformly across the confining channel by withdrawing a portion of the fluid adjacent the wall of the channel as the fluid carrying the filaments passes through.

2. In the passage of a plurality of continuous filaments by means of a high-velocity fluid stream through a filament-forwarding slot jet device having a diffuser section with a rectangular passageway, the improvement comprising withdrawing a portion of the fluid adjacent to the narrow sides of the rectangular passageway of the difluser section, to spread the filaments uniformly across the diffuser section.

3. In a process wherein a multifilament strand of continuous synthetic organic filaments are electrostatically charged while under tension and then forwarded by means of a high-velocity fluid stream through a jet device toward a web-laydown zone and collected thereon as a nonwoven web, the said jet device having a diflFuser section to achieve a wide area of laydown, the improvement comprising withdrawing a portion of the fluid adjacent the walls of difluser thereby increasing the area of laydown.

4. The process of claim 3 wherein the filament passageway in the diffuser is rectangular and the fluid is removed through the narrow Walls.

5. In a jet device suitable for the forwarding of filaments under tension, having means defining a filament passageway therethrough and means for providing high pressure gas at an angle to and in the direction of filament travel and a diffuser section defining a filament passageway that becomes wider in the downstream direction, the improvement comprising means for withdrawing gas through the wall of the diffuser section defining the filament passageway, to spread the filaments uniformly across the passageway of the diffuser section.

6. The jet device of claim 5 wherein the filament pas sageway defined by the diffuser section is rectangular and gas withdrawing means are provided only at the narrow sides of the passageway.

References Cited UNITED STATES PATENTS 2,956,328 10/1960 Faw.

FREDERICK L. MATTESON, JR., Primary Examiner. D. A. TAMBURRO, Assistant Examiner.

Claims

1. IN A METHOD WHEREIN A MULTIFILAMENT STRAND OF CONTINUOUS FILAMENTS IF FORWARDED BY MEANS OF A HIGH-VELOCITY FLUID STREAM THROUGH A CONFINING CHANNEL WITH MINIMUM FILAMENT ENTANGLEMENT AND BUNCHING, THE IMPROVEMENT COMPRISING SPREADING THE FILAMENTS OF THE STRAND UNIFORMLY