US3485428A - Method and apparatus for pneumatically depositing a web - Google Patents

Description

Dec. 23. 1969 R, c, JACKSQN 3,485,428

METHOD AND APPARATUS FOR PNEUMATI CALLY DEPOSITING A WEB Filed Jan. 27, 1967 nnM INVENTOR. ROBERT C. JACKSON BY W ATTORNEY United States Patent 3,485,428 METHOD AND APPARATUS FOR PNEUMAT- ICALLY DEPOSITING A WEB Robert C. Jackson, Dayton, Ohio, assiguor to Monsanto Company, St. Louis, Mo., a corporation of Delaware Filed Jan. 27, 1967, Ser. No. 612,154 Int. Cl. B65h 17/18 US. Cl. 226-97 4. Claims ABSTRACT OF THE DISCLOSURE A combination aspirator and traverse mechanism utilizing fluid dynamic principles of operation for orienting, forwarding, and traversing a plurality of continuous filaments onto a continuously moving surface whereb random distribution of the filaments is provided for the production of uniformly dense nonwoven webs.

Nonwoven webs comprising multifilament yarns or strands, hereinafter referred to as strands, are commonly formed by withdrawing said strands from a source of supply, for example the spinnerette of a spinning machine or feed rolls and supply bobbins, by means of an aspirating jet and then depositing the strand at high velocity onto a moving surface. In the production of nonwoven products having a substantial width there must be provided either a plurality of aspirators for depositing a plurality of strands in a random manner upon the moving surface or there must be provided a means to traverse the aspirator jet over the Width of the product to be produced.

When depositing yarn from a conventional aspirator onto a collecting surface, the filaments will spread out within the confines of the aspirated free air jet boundary. However, the filament distribution in the jet stream is not uniform, probably due to the v locity distribution generated by the aspirator. Consequently, a web deposited on a moving surface from a fixed position aspirator is parabolic in section with more filaments being deposited in the center thereof.

In the conventional practice a fixed aspirator jet situated a distance of one to three feet from the collecting surface normally provides a web width of from 2 to 8 inches even though the filaments may have been previously given a static charge to facilitate dispersion. Thus, it can be seen that to produce a nonwoven web having a width of several feet would require several fixed aspirators having individual sources of supply strands. To obviate the necessity of utilizing a large number of jets it b comes necessary to mechanically traverse the aspirating means. However, when the aspirator means is mechanicab ly traversed the mechanism required to facilitate traversal is unduly complicated and cumbersome with attendant difficulty in achieving the requisite uniform traversing velocity and instantaneous reversals of the mechanism mass at the traverse end points. Traversing the aspirator jet also results in a continuous change in the angle of the multifilament strand with respect to the entrance aperture of the aspirator which adv rsely affects the product quality.

With the above cited problems in mind it is therefore an object of the instant invention to provide, in combination, a fluid operated aspirating and traversing mechanism.

Another object of this invention is the provision of a method for producing uniform nonwoven products.

Yet another object of this invention is the provision of a strand forwarding and traversing means employing no moving parts.

Still another object of this invention is the provision of a strand drawing, forwarding, and traversing apparatus utilizing fluid dynamic principles of operation.

One embodiment contemplated for this invention comprises, in combination, a fluid operated aspirating and traversing means for drawing, forwarding, and traversing a multifilament strand positioned above a continuously moving surface for depositing said strand in a random manner whereby uniform nonwoven products having predetermined Widths and thicknesses may be obtained.

The method of this invention comprises, in general, the utilization of the combination aspirating and traversing means whereby a strand, preferably forwarded from the spinnerette of a spinning machine, is drawn by the high velocity fluid jet of the aspirator. Subsequent thereto the the aspirating jet stream forwards the yarn into the traversing zone of the apparatus wherein the fluid jet stream envelops the strand whereby the high velocity stream upon discharge from the aspirating zone systematically deflects the yarn in a reciprocating manner by means of two diametrically opposed control fluid jets, and whereby the strand is propelled onto a continuous y moving foraminous surface in the form of a uniform nonwoven web comprising randomly disposed, drawn continuously filaments. Deposition of the yarn may preferably be aided by a suction chamber located underneath the moving surface.

The specific nature of the invention, as well as other objects, uses and advantages thereof, will clearly be evident from the following description and the accompanying drawing in which:

FIGURE 1 is a pictorial view depicting the preferred embodiment of the nonwoven web forming apparatus employed for carrying out the invention,

FIGURE 2 is a sectional view through the combination aspirator and traverse mechanism showing a particular arrangement of the elements taken along the line 22 of FIGURE 1,

FIGURE 3 is a bottom plan view of the apparatus showing a configuration of the traversing means taken along line 33 of FIGURE 1; and

FIGURE 4 is a sectional view through the aspirating zone taken along the line 4-4 of FIGURE 2.

Referring now to the drawings, and particularly FIG- URES 2, 3 and 4, there is shown a particular embodiment of the combination aspirating and traversing mechanism which comprises a housing body 10 having provided integrally therein an annular chamber 12 and a diverging cavity 13 which are interconnected by passageway 14. The vertical length of the diverging wall of chamber 13 is preferably approximately 4 to 6 times the diameter of passageway 14. The chamber 12 is enclosed by a body cap 15 which is provided with a hollow stem 16 that extends to within close proximity of the entrance to passageway 14. An element 17 is concentrically disposed about the stem '16 in chamber 12. The bott m portion of chamber 12 is flared to provide a chamber 18 between element 17 and passageway 14. The body cap 15 is secured in a sealed relationship to the body member 10 by a screw 19 and gasket 20. The thickness of the gasket also controls the throat size 21 and thereby functions as a means for adjusting the distance between passageway 14 and stem 16.

The closure cap 15 is provided with a passageway 22 which is in alignment with passageway 14 for receiving a strand 24. The passageway 22 has a flared portion 23 to facilitate string up of the strand 24. In order to prevent false twisting of the strand, the element 17 is provided with a plurality of passageways concentrically arranged around the strand 24 and are parallel therewith.

The aspirating media, which may be a pressurized gas or liquid, is introduced from a supply source, not shown,

into chamber 12 by means of pipe 26 and hole 27. Said media enters chamber 12 and flows through .the plurality of passageways 25 of element 17 in a streamline manner exiting through throat 21 as a high velocity stream. The pressurized state of the aspirating media is contingent upon several conditions and thus may be varied to suit the particular situation. Some factors which influence operating pressures are the degree of drawing required on the multifilaments of the strand, the type of polymer from which the filaments are made, whether the strand has previously been subjected to an orientation step and the resulting properties of the nonwoven product. The high velocity fluid stream emanating throat 21 engages strand 24 with sufiicient energy to draw the strand and forward same through passageway 14 into the traversing zone of the apparatus which is characterized by a diverging cavity 13.

Traversing of the multifilament strand 25 is accomplished by sequentially controlling a low pressure fluid media that is supplied to diverging cavity 13, from a source not shown, by means of ports 28 and 29, and pipes 30 and 31. A programmed rotating valve of a well known type may be advantageously utilized in series with pipes 30 and 31 to divert the control fluid media in an alternating manner prescribed by the desired traversing frequency. Alternatively to utilizing the programmed rotary valve, a fluid oscillator of the type disclosed in US. Patent No. 3,016,066 may be interconnected between ports 28 and 29 to generate self-excited oscillations to directionally control the reciprocatory action of the aspirated jet stream. However, this necessitates different length tubes for different traverse frequencies but coincident therewith obviates the need for a separate source of supply for the control fluid media.

The included angle ,8 of diverging cavity 13 is determined by the desired length of the traverse stroke at the point of filament deposition, the distance residing between the traversing means and the deposition surface, and the degree of filament separation from the air stream at the deposition surface. The included angle 13 may range between approximately and 90 degrees depending upon length of traverse stroke desired. Expen'ence has shown that a distance of one to three feet between the diverging cavity 13 and the deposition surface has yielded satisfactory results.

FIGURE 1 depicts the arangement of the apparatus utilized for the production of nonwoven webs wherein the combination aspirator and traverse mechanism assembly 40, indicated by the arrowed leader, is shown in a fixed relationship above a foraminous continuous belt 32. Belt 32 is mounted for rotation by means of rolls 33, 34, and 35 with roll 33 being driven by a variable speed drive, not shown. A suction box 36 is provided directly below belt 32 and the line of traverse to insure that the randomly dispersed filaments retain their respective position after deposition. Evacuation of suction box 36 is accomplished by means of a pipe 37 and a vacuum source, not shown.

In an example, polyhexamethylene adipamide polymer was melt-spun into a 15 filament strand of 342 as-spun denier, said filaments were subsequently introduced into the combination aspirating and traversing mechanism assembly 40 wherein the strand 24 was subjected to air as the aspirating medium at a pressure of 90 p.s.i.g. The filaments were attenuated 3.8x to a total drawn denier of and were simultaneously forwarded into the traversing zone by the aspirating jet stream. The control fluid pressure, also air, entering alternately through ports 28 and 29 was 30 p.s.i.g., said fluid being sequentially supplied to provide a traverse rate of 10 strokes per minute. The traverse zone divergence angle [3 was 90 and the fixed distance residing between the traversing means and the continuous foraminous belt was approximately one foot. This provided for a traverse stroke length of 17 inches which yielded a web width of 17%. inches. The rotational speed of belt 32 was 18 inches per minute.

The nonwoven web produced was characterized by having a random filament distribution throughout. Physical testing of testing of strips of the nonwoven web revealed that isotropism did not exceed 10 percent.

It is to be understood that the above example is for illustrative purposes only and is not to be construed as limiting the invention for it is contemplated that a strand having 1X10 total denied could be processed into webs by this invention. Too, it is contemplated that the aspirating streamline element 17 could be provided with a plurality of passageways 25 selectively arranged which would enable imparting a false twist to the multifilament strand 24 such that a coherent yarn bundle could be produced for processing into constructions other than nonwoven webs.

I claim:

1. Apparatus for traversing and depositing a strand onto a moving collection surface in a randomly dispersed manner to deposit the strand in the form of a nonwoven web structure having uniform density and directional properties, wherein the improvement comprises:

(a) a member having a chamber therein for receiving a pressurized fluid,

(b) a first passageway connecting said chamber with a portion of the member having outwardly diverging walls to form a traversing chamber,

(c) a second passageway coextensively aligned with said first passageway for receiving a strand,

(d) means for introducing into the chamber a pressurized fluid which envelops the strand within the first passageway and exits through the portion having diverging walls, and

(e) oppositely disposed means in the diverging walls for sequentially introducing a lower pressure control fluid whereby the strand is deflected by said control fluid.

2. The apparatus of claim 1 in which the chamber is provided with an element having a plurality of holes concentrically arranged and parallel to the strand for communication between the opening into the chamber and the first passageway to insure that false twist is not imparated to the strand.

3. The apparatus of claim 1 in which the included angle 5 of divergence is between 15 and 90 degrees.

4. The apparatus of claim 3 in which the length of the traversing chamber is from 4 to 6 times greater than the diameter of the first passageway.

References Cited UNITED STATES PATENTS 3,259,952 7/1966 Caines 28l.4 3,279,024 10/1966 Sakai et a1 28l.4

ALLEN N, KNOWLES, Primary Examiner

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