US3841933A

US3841933A - Process and apparatus for the production of continuous random webs

Info

Publication number: US3841933A
Application number: US00283298A
Authority: US
Inventors: H Fleissner
Original assignee: Vepa AG
Current assignee: Vepa AG
Priority date: 1968-02-28
Filing date: 1972-08-24
Publication date: 1974-10-15
Anticipated expiration: 1991-10-15

Abstract

1. A process for the production of a continuous random web of continuous endless filaments which comprises feeding a plurality of individual continuous endless filaments downwardly by free fall onto the curved rotating surface of a first sieve drum means subjected to a suction draft sufficient to maintain said filaments thereon, the feeding speed of the filaments being higher than the conveying speed of the rotating sieve drum means, thereby depositing said filaments in a plaited, random arrangement across the curved surface of said sieve drum means to form a random continuous random web on said curved surface, passing the continuous random web from the sieve drum means directly onto a subjacent planar conveying surface which supports said web in its random arrangement and which introduces the random web into a heated treatment chamber and onto a curved rotating surface of a second sieve drum means subjected to a suction draft sufficient to maintain said web in its random arrangement thereon, said conveying surface extending in a horizontal plane located between said curved surface of the first sieve drum means being interrupted immediately prior to passing the continuous random web from the first sieve drum means whereby said random web is released in its random arrangement onto said planar conveying surface, applying a bonding agent to said endless filaments before the random web enters said heated chamber, drawing a heated gaseous treatment medium through the random web on the curved surface of said second sieve drum means to consolidate and bond the web in its random arrangement and thereafter removing said consolidated and bonded web of continuous endless filaments from the treatment chamber.

Description

PROCESS AND APPARATUS FOR THE; PRODUCTION O1 Oct. 15,1974 H. FLEISSN4ER 3,841,933-

CONTINUOUS RANDOM WEBS Original Filed Feb. 27, 1969 //7 V912 for x/z/nz flax/vi;

United States Patent O M US. Cl. 156-148 14 Claims ABSTRACT OF THE DISCLOSURE The present disclosure is directed to a process and apparatus for the production of a continuous random web of filaments which comprises introducing a plurality of individual filaments on to the surface of a sieve subjected to a suction draft, the feeding speed of the filaments being higher than the conevying speed of the sieve, thereby depositing the said filaments in a random manner on said sieve, passing the continuous random web from the sieve and laying it on a conveying surface which introduces said web into a treatment chamber and on the surface of at least one sieve drum means subjected to a suction draft, drawing a hot treatment medium through the material being treated to mechanically or chemically consolidate said web, and removing said consolidated web from the treatment chamber.

This is a continuation of application Ser. No. 802,975 filed Feb. 27, 1969, now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to a process and apparatus for the production of continuous random webs of filaments which are mechanically and/ or chemically bonded after web laying.

Continuous random webs of staple fibres are well known. These webs are generally floated in a liquid bowl and condensed to a web on a wire mesh belt or a sieve drum subjected to a suction draft. Subsequently, the web is bonded, generally by impregnating it with a bonding agent dispersion. However, it is also well known to add melt fibres to the web wherein one fibre component has a lower softening and/or melting point than the remaining fibre components. Furthermore, it is well known to spray a bonding agent dispersion on a web or to apply a bonding agent in powder form to said web. The web is then bonded by heating it in a convection dryer.

It is also well known to form a web by blowing loose fibrous material onto a sieve drum subjected to a suction draft. The bonding of such a web is accomplished in the same manner as described above. The strength of such continuous random webs depends essentially on the bonding agent content and/or on the melt fibre content. However, a high bonding agent content renders the web relatively hard, whereas a low bonding agent content produces a soft, textile-like web. However, in the latter case, the fibres in the web are not as substantially fixed as in the former situation, so that said fibres tend to detach from the web and accordingly fluifs tend to form on the web.

SUMMARY OF THE INVENTION An object of the present invention is to avoid the prior art disadvantages in the production of continuous random webs.

Another object of the present invention is to provide an improved process and apparatus for the production of continuous random webs which possess a high strength with the use of a relatively small amount of bonding agent.

3,841,933 Patented Oct. 15, 1974 A further object of the present invention is to provide an improved process and apparatus for the production of continuous random webs wherein the formation of fluffs on the web is substantially eliminated.

Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Pursuant to the present invention, it has been found that the above mentioned disadvantages may be eliminated and a much improved process and apparatus for the production of continuous random webs may be obtained by having a plurality of filaments freely fall in a random manner with an overfeed onto the surface of a sieve subjected to a suction draft, for example a wire mesh belt or a sieve drum, and by subsequently bonding the web on the sieve and/ or subsequent treatment device.

A uniform application of the bonding agent can be achieved in an effective manner by spraying and/ or blowing the liquid or pulverous bonding agent against the filaments before depositing them on the sieve. However, it is also possible to apply the bonding agent to the filaments by means of an impregnating device, for example a padder, before the continuous web is formed.

Furthermore, the continuous random web can be consolidated and/or pre-consolidated by means of needling. In many cases in which a dense web is desired, it is advantageous to condense the web before bonding, for example by means of squeezing. A web which has been pre-consolidated by means of needling may also be passed through a padder for the application of the bonding agent.

For consolidating the continuous random web, it is advantageous to pass hot air and/or steam through the continuous random web, so that it is heated up uniformly, and that a migration of the bonding agent to the surfaces, as it occurs with jetting, is avoided.

Furthermore, it is advantageous if filaments with different melting and/or softening points are used for producing a continuous random web, so that the bonding of the web can be effected by softening and/or melting one of the fibre components.

It is also advantageous to consolidae a continuous random web by high-frequency heating. Also, an absolutely uniform heating and thus consolidation throughout the thickness of the continuous random web is obtained. The bonding agent, and thus the continuous random web, can also be consolidated by heating it up through the use of infrared radiation and possibly also by convection of a gaseous and/ or vaporous treatment medium.

The apparatus for carrying out the present process comprises a filament feeding unit which is arranged above a sieve subjected to a suction draft, for example a wire mesh belt or a sieve drum and a driving mechanism which permits a feeding speed which is about 3 to 20 times higher than the speed of the sieve and/or the speed of the continuous random web. For applying the bonding agent, an impregnating and/or spraying device may be provided in front of and/ or behind the sieve.

For laying the web, a sieve drum subjected to a suction draft may be arranged above and/or in front of the inlet belt of the consolidating device. The filaments fall on the drum subjected to a suction draft and are deposited on said drum in a random manner. By the suction draft the tangle of the fibres is condensed into a web and is passed to the subsequent inlet belt. However, it is also possible to work without a sieve drum and to deposit the filaments directly on to the inlet belt of the consolidating plant. For this purpose, the inlet belt is designed as a wire mesh and is provided with a suction box, so that the surface on which the material is deposited may be subjected to a suction draft.

A spraying device may be correlated to the inlet belt or may be arranged above the inlet belt or the wire mesh belt may be passed together with the continuous random web through an impregnating device. The particular elements utilized depend upon the viscosity and the nature of the bonding agent which is chosen. If the web has a high strength transversely to the operating direction, it is advantageous to use a folding device, for example a folding funnel for laying the web. The folding device plaits the filaments transversely to the direction of material passage, said folding device being arranged above the sieve subjected to a suction draft. In this case, the driving mechanism is to be designed in such a way that the folding motion of the folding device is about 3 to 20 times slower than the speed at which the filaments are deposited. However, it is also possible to use an air and/or a liquid jet which is moved to and fro over the width of the filament length being fed as a plaiting device instead of the folding funnel. In this case, a particularly irregular positioning of the filaments is obtained. Together with the air jet, a pulverous bonding agent can be applied to the filament group and/or the liquid jet may consist of a liquid bonding agent.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become more fully understood from the detailed description given hereinbelow and the acompanying drawings which are given by way of illustration only and thus are not limitative of the present invention and wherein,

FIG. 1 is a longitudinal section of the apparatus according to the present invention;

FIG. 2 is a longitudinal section of another embodiment of the apparatus of the present invention; and

FIG. 3 is a plan view of the web laying device according to FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, wherein like reference numerals are used throughout the various views to designate like parts, the apparatus of the present in- 'vention comprises the devices shown in FIGS. 1 to 3 in the present application. A plurality of individual filaments 1, which are preferably arranged in parallel at a desired distance from each other, are drawn off a bobbin creel (not shown) by means of a pair of rollers 2. The pair of rollers 2 is located above a sieve drum 3 subjected to a suction draft, so that the filaments fall freely onto said sieve drum. The feeding speed of the filaments 1 is substantially higher than the conveying speed of the sieve drum 3. In this manner the filaments 1 are deposited in a random manner on the sieve drum 3 subjected to a suction draft and form a continuous random web 4. The thickness of the web results from the difference between the feeding speed of the filaments 1 and the speed of the sieve drum 3. At that portion of the sieve drum 3 which is not covered with the material being treated, the suction draft is interrupted by means of a baffie 5 which is aranged in the sieve drum. The continuous random web is passed from the sieve drum 3 to a conveyor belt 6 and from the conveyor belt to a sieve drum 7 subjected to a suction draft. As in the well known sieve drum dryers and heat-setting plants, the sieve drum 7 is arranged in a heat-insulated housing 8. The fans for the sieve drums 3 and 7 are arranged at one or at both faces of the sieve drum. They draw the treatment medium out of the sieve drum and blow it ofi to the atmosphere, as in the case of sieve drum 3, or they return it into the treatment chamber, as in the case of sieve drum 7.

To improve the flow conditions, perforated sheets 9 are provided above and below the sieve drums 7.

In the housing 8, a hot air atmosphere, a steam atmosphere or a steam-air atmosphere may be maintained. As the treatment medium is intensely drawn through the material, the continuous random web is heated up uniform ly, and if a liquid treatment medium is used, the treatment medium is dried and consolidated. If melt fibres are used, the continuous random web is heated up to the melting point of one of the fibre components, so that a consolidation takes place due to the melting of the fibre component with the lower melting point.

As shown in FIG. 1, the bonding agent may be sprayed 7 onto the filaments 1 by means of jets 10 before the continuous random web is formed or it may be applied by means of one or several jets 11 after the continuous random web 4 has been laid. After the consolidation, the continuous random web 4 is passed out of the chamber on a discharge belt '12. This belt 12 may possibly also be designed as a wire mesh belt and may be subjected to a suction draft in order to obtain a rapid cooling-down of the continuous random web 4. At high production speeds, it is expedient to provide a separate cooling drum.

The apparatus according to FIG. 2 is similar in design to that of FIG. 1. However, in this device the filaments 1 are deposited on the sieve drum 3 transversely to the direction of passage of the continuous random web by means of a folding funnel 13. However, the filaments may also be folded in the direction of the passage of the continuous random web.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from. the spirit and scope of the invention, and all such modifications as would be apparent to one skilled in the art are intended to be included.

It is claimed: 1

1. A process for the production of a continuous random web of continuous endless filaments which comprises feeding a plurality of individual continuous endless filaments downwardly by free fall onto the curved rotating surface of a first sieve drum means subjected to a suction draft sufiicient to maintain said filaments thereon, the feeding speed of the filaments being higher than the conveying speed of the rotating sieve drum means, thereby depositing said filaments in a plaited, random arrangement across the curved surface of said sieve drum means to form a random continuous web thereon, maintaining the continuous random web on said curved surface with said suction draft until said web is turned over by the the rotation of said curved surface, passing the continuous random web from the sieve drum means directly onto a subjacent planar conveying surface which supports said Web in its random arrangement and which introduces the random web into a heated treatment chamber and onto a curved rotating surface of a second sieve drum means subjected to a suction draft sufficient to maintain said web in its random arrangement thereon, said conveying surface extending in a horizontal plane located between said curved surfaces, the suction draft applied to the curved surface of the first sieve drum means being interrupted immediately prior to passing the continuous random web from the first sieve drum means whereby said random web is released in its random arangement onto said planar conveying surface, applying a bonding agent to said endless filaments before the random web enters siad heated chamber, drawing a heated gaseous treatment medium through the random web on the curved surface of said second sieve drum means to consolidate and bond the web in its random arrangement and thereafter removing said consolidated and bonded web of continuous endless filaments from. the treatment chamber.

2. The process of claim '1 wherein the individual filaments are introduced onto the current surface of the sieve in substantanial parallel relationship with respect to each other.

3. The process of claim 1 wherein the treatment medium is selected from the group consisting of hot air, steam and a steam/air mixture.

4. The process of claim 1 wherein a bonding agent is applied to the filaments before they are deposited on a sieve drum means.

5. The process of claim 4 wherein the bonding agent is sprayed onto the filaments.

6. The process of claim 4 wherein the filaments are impregnated by the bonding agent in a padder.

7. The process of claim 4 wherein the continuous random web is pre-consolidated by means of needling prior to the application of the bonding agent.

8. The process of claim 1 wherein the web is condensed by squeezing before it is consolidated.

9. The process of claim 1 wherein the filaments are added to the sieve about 3 to 20 times faster than the speed of said sieve.

10. The process of claim 1 wherein the random web being treated is removed from the treatment chamber on a conveying surface subjected to a suction draft for the rapid cooling-down of the continuous random web.

11. The process of claim 1 wherein the filaments are deposited on the sieve transversely to the direction of the web.

12. The process of claim 1 wherein the filaments are folded in the direction of travel.

13. A process for the production of a continuous random web of continuous endless filaments which comprises feeding a plurality of individual continuous endless filaments downwardly by free fall onto the curved rotating surface of a first sieve drum means subjected to a suction draft sufficient to maintain said filaments thereon, at least some of said filaments having a different melting point than the other filaments, and the feeding speed of the filaments onto the first sieve drum means being higher than the conveying speed of the first sieve drum means thereby depositing said filaments in a plaited, random arrangement on the curved surface of said sieve drum means to form a random web thereon; maintaining said random web on the curved rotating surface until the web is turned over by the rotation of said curved surface; passing the continuous random web from the first sieve drum means directly onto a subjacent planar conveying surface which supports said web in its random arrangement and which introduces the random web into a heated treatment chamber and onto a curved rotating surface of a second sieve drum means subjected to a suction draft suflicient to maintain said web thereon, said conveying surface extending in a horizontal plane located between said curved surfaces, the suction draft applied to the curved surface of the first sieve drum means being interrupted immediately prior to passing the continuous random web from the first sieve drum means whereby said random web is released in its random arrangement onto said planar conveying surface, thereafter consolidating and bonding the web in its random arrangement by drawing a heated treatment medium therethrough while the Web is conveyed on the surface of the second sieve drum means subjected to a suction draft suflicient to maintain said web thereon; consolidation and bonding of the continuous random web being achieved by melting the low melting filaments within said web.

'14. A process for the production of a continuous random web of continuous filaments which comprises feeding a plurality of individual continuous endless filaments downwardly by free fall onto the curved rotating surface of one sieve drum means subjected to a suction draft, the feeding speed of the filaments being higher than the conveying speed of the sieve drum means, thereby depositing said filaments in a plaited, random arrangement on the curved surface of said sieve drum means to form a continuous random web thereon; maintaining the continuous random web on said rotating curved surface with said suction draft until said web is turned over by the rotation of said curved surface; passing the continuous random web directly from the sieve drum means while maintaining the web in its random arrangement, applying a bonding agent to said web of said endless filaments and thereafter consolidating and bonding the web in its random arangement by drawing a heated gaseous treatment therethrough while the web is conveyed on the curved rotating surface of another sieve drum means subjected to a suction draft sufiicient to maintain the web on said curved surface.

References Cited UNITED STATES PATENTS 2,306,347 12/1942 Slayter. -3 3,242,702 3/1966 Fleissner 68-177 3,030,245 4/ 1962 Greiner et al 156167 2,897,874 4/1959 Stalego et al. 65-3 2,794,759 4/1957 Dildilian 15662.2 3,295,942 1/1967 Smock et a1 156--181 3,328,23 6/1967 Levecque et a1 161150 3,595,7 I 7/1971 Davies et al. 161150 3,341,394 9/1967 Kinney 156-167 DANIEL J. FRITSCH, Primary Examiner US. Cl. X.R.