US3601860A

US3601860A - Method of and apparatus for forming a web of fibrous material

Info

Publication number: US3601860A
Application number: US802592*A
Authority: US
Inventors: Heinz Keib
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-03-07
Filing date: 1969-02-26
Publication date: 1971-08-31
Anticipated expiration: 1988-08-31
Also published as: GB1256571A; DK133117C; FR2003397A1; SE364939B; BE729503A; DK133117B; RO56673A; FI44575B; AT320478B; NO122359B

Abstract

A method of an an apparatus for forming a nonwoven web of fibrous material. A pervious supporting surface travels in a predetermined direction. One or more spray pipes are arranged above and spaced from the supporting surface either in parallelism with or inclined to the direction of travel of the surface. Liquid is sprayed from the spray pipes as a liquid curtain or curtains downwardly towards the supporting surface. A supply arrangement advances a stream of staple fibers into the path of the liquid curtain or curtains so that the staple fibers are entrained by the liquid and deposited on the pervious supporting surface in the form of a fibrous web.

Description

United States Patent Primary Examiner- Dorsey Newton Attorney-Michael S. Striker ABSTRACT: A method of an an apparatus for forming a nonwoven web of fibrous material. A pervious supporting surface travels in a predetermined direction. One or more spray pipes are arranged above and spaced from the supporting surface either in parallelism with or inclined to the direction of travel of the surface. Liquid is sprayed from the spray pipes as a liquid curtain or curtains downwardly towards the supporting surface. A supply arrangement advances a stream of staple fibers into the path of the liquid curtain or curtains so that the staple fibers are entrained by the liquid and deposited on the pervious supporting surface in the form of a fibrous web PATENTED A1183] IS?! sum 2 BF 2 INVEN'I'OR.

Ham. 1 err} n, i y Misriiou or nnlujsri titarus rots romaine A was U1? iliilROUS MATlEftlllhL I BACKGROUND or THE INVENTION The present invention relates generally to the production of nonwoven webs from fibrous material, and more particularly to thef'production 'of webs of substantially unifonn density. Still more specifically the invention relates to a method of forming such a web of fibrous material, and to an apparatus for earnin out the method.

The :manufactureof nonwoven webs or mats from fibrous materials, particularly from staple fibers, isof course well known. Accordingly, there exist many methods and apparatuses for this purpose. The resulting product, that is the web, mat or otherwise configurated body of fibrous material, may have a variety of applications as a carrier or a reinforcing means in bituminous material, in synthetic plastic materials, or in rubber; or for other purposes.

None of the known approaches, however, have been found to be entirely satisfactory. They all have in common-the disadvantage that the resulting fibrous body, that is the web, mat, or

the like, either cannot be made to have uniformly high tensile strength and uniform distribution of the fibers, or that these characteristics can be provided only at great expense and with considerable technological expenditures. Attempts at overcoming these problems at lesser expense have included experimentation with fibers of different lengths. This has not been successful either. if one uses relativelylong'staple fibers it is possible to produce a fibrous body having a high tensile strength but in which the fibers are distributed nonuniformly. The use of short staple fibers, on the other hand-results in the production of a fibrous body of substantially uniform fiber distribution but having only a low tensile strength. Although the former characteristic is highly important for the industry, because it provides a fibrous body of uniform porosity which is thus capable of undergoing uniform impregnation, the absence of the latter characteristic is evidently highly disadvantageous. The-currently used compromise solution in the production of such fibrous bodies, with which it is possible to obtain afibrous body having significant tensile strength as well as significantly uniform fiber distribution, utilizes a mixture of long and short staple fibers. Even this solution, however, fails far short of what-theindustry considers desirable.

Among the various approaches which have been proposed for obtaining a fibrous material having the desired charac-' teristics, is that taught in US. Pat. No. 2,931,421 which proposes todeposit fibers on an inclined sieve wall by advancing them thereagainst suspended in a stream of air, and to continuously withdraw the deposited fibers from the lower edge of the inclined wall in form of a mat. The fibers are supplied by a drum-type arrangement provided at one lateral side of the conveyor. belt which serves to withdraw the mat from the inclined wall.

To increase the rate of output,U.S. Pat. Nos. 2,996,102 and 3,220,811 all have proposed to arrange a plurality of fiberproducing devices at opposite lateral sides of a conveyor belt in such a manner that the fibers produced by these devices are deposited in form of a mat on the conveyor belt in a direction transversely to the advancement of the belt. This is accomplished by the use of traversing distributing or depositing heads. This approach has been found to be very economical.

However, the use of fibrous bodies produced from fibrous materials increases constantly as new applications are discovered or developed. Accordingly, the speed of production must be increased concomitantly in order to enable industry to keep pace with the increased requirements. This, on the other hand, requires an increase in the advancing speed of the surface on which the fibers are deposited to form the fibrous body. Of course, to obtain an increase in production it is not only necessary to increase the advancing speed of the supporting surface but also to increase the output of the fiber-producing devices. In an arrangement as taught in US. Pat. No.

2,996,102 it is also necessary, under these circumstances, to increase the traversing speed of the distributing heads because this speed must be maintained at a predetermined relationship with reference to the speed of advancement of the supporting surface if uniformity of fiber deposition is to be maintained. It will be appreciated that the fibers are deposited in zigzag form as a thin veil of fibers which results from the reciprocatory movement of the distributing head associated with the respective fiber-producing device and movable above the fiber-supporting surface. Increases in the speed of traversal of the distributing heads are subject to mechanical limitations, however, because of the necessary directional reversal of the masses which must be accelerated and decelerated. Furthermore, it will be appreciated that the distributing heads are located relatively closely to the fiber-supporting surface and that an increase in their traversing speed beyond a predetermined point brings with it the development of eddies in the air above the surface which negatively influence the desired uniform deposition of the fibers. Furthermore, the impossibility of avoiding, with the aforementioned arrangement, a nonuniform distribution of fibers in a given fiber veil of the type discussed above, has led to a tendency to provide as many of such fiber veils as possible in order to compensate in this manner with the overlapping veils for irregularities which occur in any given veil. This, however, means that the traversing speed of the distributing heads is greatly dependent upon the output of the fiber-producing devices as expressed in lcg./h., and upon the weight of the fibrous body being produced as expressed in g./mi in practical application, the output of such an arrangementin terms of the finished fibrous material is limited to a maximum of 35 mF/min. because of the aforementioned limitation imposedlby the masses to be accelerated and decelerated.

Beyond this, there are other problems to be considered. The widthof the fibrous bodywhich is being produced, for instance a fibrous nonwoven web is of importance because the airm'ass and the air pressure are the more difficult to maintain constant ,-tbe longer the traversing paths of the distributing heads, this distance being of course dependent upon the width of the fibrous article which is to be produced. Such changes, however, may result in fluctuations in the weight of the deposited fiberquantities, fluctuations which may amount to :25 percent of the nominal weight per unit area, for example per l(i( cm? Furthermore, fluctuations in the weight bring with them fluctuations in the porosity and in the tensile strength of the finished product. A further disadvantage which may arise, depending upon the ultimate use for which the finished product is intended, is the fact that an uneven distribution in the tensile strength of the finished product may occur, based upon the ratio of the advancing speed of the supporting surface to the traversing speed of the distributing heads. it has been found that such a product will have a higher tensile strength in longitudinal direction than in transverse direction. Tests have shown values of ltiilkbo percent for these two factors.

Also, the use of air to transport the fibers to the fiber-supporting surfaces requires very large quantities of air which must be conditioned as well as advanced. There are two reasons for this, namely on the one hand the fact that the fibers are maintained in position on the fiber-supporting surface only by the underpressure which exists directly below the fiber-supporting surface, and on the other hand because during their production and transport the fibers are subjected to electrostatic charging which would result in lumping' of the fibers if the charges were not removed or significantly reduced through conditioning of the air.

It is thus a general object of the present invention to provide a method and an apparatus which are not subject to the afore mentioned disadvantages.

' A more specific object of the present invention is to con-.

tinuously deposit staple fibers, in particular, long staple fibers, on a supporting surface in such a manner that the fibers, which may be supplied in large quantities and at high production speed, are distributed very evenly and uniformly and that the resulting fibrous material has a high tensile strength and a uniform high porosity.

A concomitant object of the invention is to assure that the fibrous material being produced may be provided at will with portions of greater or lesser fiber'density but of substantially uniform fiber distribution.

SUMMARY OF THE INVENTION 7 In accordance with the aforementioned objects, and others the predetermined path so as to form in this portion a fibrous web of substantially uniform density.

Thus the fibers are deposited inthe portion of the predetermined path, which latter is defined by the moving pervious fiber supporting surface, for instance the surface of a conveyor belt, and they are weighted by contact with the liquid particles which, it must be noted, also serve to destroy any lumping" of fibers which may have occurred in the incoming stream of fibers.

By resorting to my invention it is possible to produce a web of fibrous material having a uniformity of fiber distribution which has heretofore not been'attained. Moreover, this is achieved not only with shortstaple fibers, but also with long and very long staple fibers which could not heretofore be deposited in form of a uniform web with the knownprocesses and apparatus as the term uniform web" refers here to a fibrous web wherein the fibers are uniformly distributed ,over the entire web surface. Long or very long staple fibers may have a length ranging up to 200 or 300 cm. but usually they have a length of between 25 and 100 cm. During their advancement in a stream towards the supporting surface, and even more so during their deposition on the surface, they have atendency to form lumps. If, now, the fibers are for example produced by the so called drum method which is widely used in the industry, then their length will vary considerably.

- The present invention is generally suitable for the deposition of staple fibers but will hereafter be discussed, for the sake of better understanding, withmeference' toglass fibers which term is not to be considered limiting. The invention is also suitable for use with fiber-supporting surfaces of all types,

for instance perforated drums, stationery sieves, or the like,

although hereafter, and again for the sake of convenienceand better understanding, it will be assumed that fiber deposition is being made on pervious conveyor belts. p

Generally speaking the fiber-air'mixture known heretofore, as well as the novel fiber-water mixture, may be considered as dispersed systems and it must be kept in mind that such a system is at its most stable if the component parts thereof are at least substantially identical in their'specific weights. The following comparison of the specific weights, airzglass fibers #watenglass fibers w v 0.00129 2,54 kp Jdm. #10 2.54 kp./dm.

indicates that the approximation of the specific weights in the fiber-water mixture is significantly better than in a fiber-air mixture; this 'means thata mass of fibers can be deposited better and more precisely by the useof liquid than by'the use of air. While it is true that in the above comparison the percentage of air contained in the fiber-water mixture has not been considered, this does not significantly influence the various factors involved because the proportion of air in the stream of liquid which entrains and deposits the fibers is very small. I

As pointed out earlier, the known approaches to the problem have utilized a stream of air as a carrier medium. This stream of air, and the fibers therein, are usually guidedv in a This is advantageous as far as the tensile strength of the finished fibrous web is concerned, but is disadvantageous for achieving uniformity of distribution. By resorting to the present invention, however, I obtain a surprisingly uniform distribution of the fibers despite even if the same are of the long or very long type,and despite the fact that if the fibers are produced by the drum method, they may vary considerably in length and are supplied in great quantities per time unit. The uniformity of distribution obtained by resorting to my invention appears to result from the fact that the liquid carrier spray, which may advantageously be water, serves to separate and distribute fiber agglomerations or lumps of fibers either during transport or during deposition of the fibers on the supporting surface, it being understood that the sprays of carrier liquid'a'ct upon the stream of fibers with constant force and in a direction which is unvarying per unit of time. Even significant agglomerations of fibers, such as sometimes occur from improper functioning of the fiber-producing device wherein the stream of incoming fibers is nonuniform, are distributed by the water spray while being carried in direction towards the fiber-supporting surface. This serves to prevent the fibers from intertwining into a fibrous veil prior to their deposition on the fiber-supporting surface.

guide channel whose outlet is located-proximal tothe supporting surface. On leaving this outlet the air expands very rapidly, which makes it difficult'to aim the fibers properlyfor depositionpurposes. Use of a stream of liquid, however, overcomes this problem because the stream of liquid isof considerably I higher density which barely decreases intermediate the point from which the liquid issues and the fiber-supporting surface. An'additional advantage of the use of liquid is the fact that the individual fibers, for instance glass fibers,are deposited on the supporting surface in stretched condition, unlike the situation where air is used in which case a matting and intertwining of small quantities of fibers occurs already in the airstream prior to deposition of the fibers on the fiber-supporting surface. It has been found in the method according to the present invention that the stretched and uniform deposition of fibers improves as the water pressure increases and as the quantity of water and thickness of each spray decreases. it follows from this that to obtain a web of fibrous material according'to the present invention and having the aforementioned desired characteristics, it is not necessary to provide a large quantity of water but to provide water which is finely distributed in sure created, the fibers deposited in accordance with the present invention are maintained by the relatively high proportion of water by which they have been entrained and which serves to in effect-hold them in position. However, it is possible to create underpres'sure in addition,-so as to further fix the position of the fibers, particularly during transporting'of the deposited fibrous web, and this under-pressure may also serve to withdraw a part of the moisture from the deposited web. If the web of fibrous material is to consist of fibers which are deposited without predetermined orientation, this can be attained by utilizing a sieve-type conveyor belt having a mesh of approx. 1.5 mm. and a free cross section of approximately 50 percent whereby a good and uniform fiber deposition is obtained, as tests have shown.

Furthermore, the web may be given any desired structure or orientation of fibers by a simple selection of the mesh arrangement, or by varying the mesh density, or by providing the mesh with a desired pattern. This makes it possible to'so control the deposition of fibrous material on the supporting surface that fiber-ing globerations occur in form of longitudinally or transversely extending continuous or discontinuous strips which form a longitudinally extending, a transversely extending or even a lattice-type reinforcing structure. This is for example shown in Canadian Pat. No. 612,990 and it will be appreciated that such measure will increase the tensile strength in longitudinal and transverse direction of the fibrous web. This may be of particular importance if not only a high longitudinal tensile strength, but a similar transverse tensile strength is required of the finished fibrous web. In certain applications such characteristics are necessary, for instance if the fibrous web is to be used as the carrier for bituminous roofing material and is to be coated in a high-speed coating machine. In this case high tensile strength in longitudinal direction of the fibrous web is necessary during coating, whereas in actual use of the finished produce high tensile strength in transverse direction is additionally required. A further example is found in the so-called corrosion-protective bandages which are wound about tubes and pipes because the high tensile stresses acting on such bandages in longitudinal direction during winding are joined by similar tensile stresses acting transversely because of the spiral made of winding. This possibility of influencing the deposition, structure and fiber orientation of the fibrous web by patterning the supporting surface is novel and the result obtained is assumed to be caused by the fact that those fibers or portions of fibers which initially contact the raised portions of the supporting surface are washed off these, either completely or partially, into the recessed or depressed portions by the impinging water to form denser pockets. In addition it is possible, by varying the suction produced below the previous supporting surface or by suitably selecting this suction, to obtain any desired porosity in the web of fibrous material.

In connection with such suction or underpressure it should also be kept in mind that in the methods used heretofore, where this suction was the only means serving to maintain the deposited fibers on the supporting surface, it was necessary to provide for high air turnover which required expensive installations. For instance, in a relatively large installation air turnover of up to 300,000 mi /h. was required, and this necessitated the provision of a basement below the housing for the installation. In addition to this, and as pointed out before, it was necessary to condition these quantities of air and to also subject them to a cleaning operation so as to prevent or at least reduce the formation of fiber agglomerations, and to eliminate or reduce electrostatic charges which result in such agglomerations. Evidently, the present invention eliminates the need for this because it entrains and deposits the fibers with a stream of water, and retains the fibers securely on the supporting surface because of the high proportion of water contained in the deposited fibrous web. Furthermore, and in the event that fiber deposition as well as fiber production occur in one and the same room, the moist atmosphere result ing from the use of water for the fiber deposition eliminates the electrostatic charging which occurs during production and initial transport of the fibers.

Finally, an additional advantage of the present invention is the fact that the lateral zones of a web produced in this manner are of the same or substantially the same thickness as the remainder of the web. Heretofore, ,the lateral zones were always thinner than the remainder of the web and had to be cut off and discarded. This waste is thus also eliminated by resorting to my invention.

The novel features which are considered as characteristic for the invention are set forth in particular in theappendeo claims. The invention itself, however, both as to apparatus and method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. l is a schematic front-elevational view of an apparatus for carrying out the present invention, in one simplified embodiment;

FIG. 2 is a view similar to FIG. 11 but illustrating an apparatus according to a further embodiment;

FIG. 3 is a view similar to FIG. l, but showing yet an additional embodiment of the invention;

FIG. 4 is a schematic end-elevational view of still a further embodiment of the invention;

FIG. 5 is a top plan view of yet another embodiment of the invention; and

FIGS. 6-9 are diagrammatic explanatory-detail views illustrating various features of the disclosed embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawing all embodiments are illustrated in highly simplified manner and schematically. It is to be understood that the various embodiments are shown by way of example only and are not to be considered limiting. It is also to be understood that the manner in which the fibers are produced and conveyed to the vicinity of the supporting surface is immaterial. For instance, conveyance may be mechanical or pneumatic.

Discussing now the drawing in detail, and firstly FIG. 1 thereof, it is assumed that fibers are produced at a remote location and are advanced by means of a conveyor belt 2 guided on rollers 3 and provided with projecting portions 3 for entraining the fibers to be transported. The conveyor belt 2 terminates above one lateral edge 4 of an advancing belt 5 whose surface constitutes the fiber-supportingsurface. It will be appreciated that when the belt 2 is driven with sufficient speed, the fibers 6 being carried thereon are projected in form of a fiber-air stream 7 in the direction towards the surface of the belt 5 as shown in the drawing.

Provided above the belt 5 extending in the direction of travel of the same is an arrangement which produces directed streams of water in form of a water curtain. In the exemplary embodiment of FIG. 1 this arrangement comprises a tube 8 having a longitudinally extending row of apertures or nozzles. The tube 8 is supplied with water under pressure through a conduit 9 and a flexible hose member 11 which connects the conduit 9 with the inlet tube 10. A suitable mechanism of simple construction, for instance a chain drive with cardioid control, serves to turn the tube 8 in the direction of the arrows A and B in such a manner that the water curtain 12 produced by the tube 8 will traverse through an angle D from one lateral edge 4 of the belt 5 to the other lateral edge 4' and back. The speed of traversal in the directions A-B must be related to the speed of advancement of the belt 5 in order to obtain a web of predetermined thickness. However, it is not difficult to produce such traversal at high speed because the masses being accelerated are rather small. It should be noted that in FIG. 1 the diameter of the tube 8 with respect to the width of the belt 5 is shown much larger than it would be in actual fact, so as to provide a clear illustration. Actually, the tube will be much smaller and, assuming that the belt 5 has a width of cm., a tube having an outer diameter of 5 cm. and arranged approximately cm. above the fibersupporting surface of the belt 5 will suffice.

The fibers of the fiber stream 7 are entrained on contact with the water curtain l2 and are accelerated thereby to subsequently be deposited on the fiber-supporting surface of the belt 5. Of course, once entrained the fibers will move with the curtain of water as the same traverses from side to side; this means that the fibers which contact the liquid curtain 12 in the position 12a thereof are predominantly deposited in the rightof-center region of the belt 5, and the fibers which are higher in the stream 7 are deposited in the position 12b of the water curtain l2 predominantly in the left-of-center portion of the belt 5. Because they are accelerated towards the surface of the belt 5 and impinge thereon with significant force, they are stretched to a greater or lesser extent by an impingement.

Because a weakening of the liquid curtain 12, resulting from clogging of one of the openings or nozzlesin the tube 8, would permit the passage through the weakened portion of fibers which'are not entrained and which would thus be deposited in uncontrolled manner, it may be advantageous to provide the tube 8 with two parallel rows of openings or nozzles, so arranged that each opening or nozzle of one row is located in the space between two consecutive openings or nozzles of the other row so that the spray cones of the respective openings or nozzles overlay. These spray cones should be relatively narrow.

As also shown in FIG. 1, there are provided sidewalls 13 extending upwardly from the fiber-supporting surface of the belt 5. The purpose of these sidewalls 13 is to prevent the water curtain 12 from extending laterally beyond the width of the fibrous web which it is intended to produce. In accordance with the invention the walls 13 may be provided at the upper edges, or in the region thereof, with spray tubes 14 from which water may run in form of a low-pressure or nonpressure sheet 15 over the inner sides of the walls 13 so as to remove therefrom any fibers which may have adhered thereto, and to convey them towards the fiber-supporting surface of the belt 5. Arranged below the belt are suction channels 16 through which the water is removed. Additionally, an exhauster 17 may be provided for producing an area of underpressure below the 'belt 5. The suction channels 16 are arranged in such a manner that the water entering thereinto is removed through an outlet conduit 18 with or without a valve, and with or without a suitable filter, so as to be recirculated to the pressure conduit 9.

The embodiment illustrated in FIG. 2 is intended for the production of a fibrous web which is wider than the one which can be produced with the embodiment of FIG. 1. The term wider here implies webs having a width in excess of approximately 1,200-1500 mm; In this embodiment it is assumed that the fibers are supplied through fiber guide and

supply conduits

20a, 20b, located at opposite lateral sides of the advancing belt 19 provided with the previous fiber-supporting surface. Thus, a fiber-air stream issues from each of the

supply conduits

20a, 20b. Arranged at or adjacent the respective outlet slots 21a, 21b of the

channels

20a, 20b are

waterspray tubes

22a, 22b. The water sprays or. water curtains thus produced are inclined downwardly in direction towards the belt 19, and these water curtains are identified with reference numerals 23a a'nd 23b and shown in broken lines. They intersect the fiber-air streams issuing from the

channels

20a, 20b and thus entrain the fibers thereof. Additionally, there are provided water spray tubes 24 which are mounted for reciprocatory movement in the direction of the arrows C-D, for example by means of schematically illustrated chain drive 25, and which produce water curtains 26 which are directed normal to the fiber-supporting surface of the belt 19. These water curtains 26 effect the deposition of the fibers suspended in the

water curtains

23a, 23b, by causing these fibers to move towards the surface of the belt 19 and to become deposited thereon.

Sidewalls 27 correspond to the ones identified with reference numeral 13 in FIG. 1. The spray tubes 28 provided on the sidewalls 27 correspond to the ones identified with reference numeral 14 in FIG. 1.

Coming now to the embodiment of FIG. 3 it will be seen that this differs from those of FIGS. 1 and 2 in that the watercurtain producing tube 35 extends not in the direction of travel of the belt 29 having the fiber-supporting surface, but rather transversely thereof. The direction of travel of the belt 29 is identified in FIG. 3 with reference symbol E, and the water-producing tube 35 which may otherwise correspond to the tube 8 shown in FIG. 1 and which may similarly be traversed, extends in the illustrated embodiment normal to the direction of travel. A guide conduit 30 is provided from which a fiber-air stream issues. In this embodiment, however, the fiber-air stream is supplied so as to travel in the direction of movement of the belt 29. It will be appreciated that two or more of the guide channels 31 may be arranged side by side,

depending upon' the width 05:17:32 29. A guide fiap 32, tiltable about an axis 31, in the direction of the double-headed arrow F-G, serves to direct the fiber-air stream as desired. The

' fibers in this stream are again entrained when they move into the area of the water curtain 33 produced by the traversing tube 35 and are deposited on that advancing portion of the belt 29 which is located between the walls 34. It will be appreciated without requiring detailed discussion that the walls 34 and the collecting channel corresponding to the one identified with reference numeral 16 in FIG. 1, will be so arranged as not to interfere with the movement of the belt 29 and/or the fibrous nonwoven web deposited on the fiber-sup porting surface of the belt.

In accordance with the invention the flap 32 may either be arranged fixedly, or it may be moved about the axis 31 in the direction of the arrow F-G in dependence upon the changes of traversal of the tube 35. In the latter case it will constitute closure means which can be made movable between a closure position closing the conduit outlet and an open position opening the outlet. How this can be accomplished will be readily apparent to those skilled in the art and the details of the mechanism required for this purpose do not constitute a part of the invention. It will also be understood that it is possible to provide the tube 35 itself on the flap 32, for instance on the free end thereof, but in this case it is of course necessary that the flap 32 move in the directions F-G at all times so that it cannot be arranged stationarily.

In the embodiment shown in FIG. 4, the belt is identified with reference numeral and corresponds to the belt 5 ,of FIG: 1. Here, however, the fibers are introduced into a supply conduit 36 and advanced through the same into and through a discharge conduit 38 in the direction of the arrow H, for instance by blowing a stream of air in this direction through the

conduits

36 and 38 in a blower 37 or air analogous device. The cross-sectional configuration of the conduits can be selected in accordance with prevailing requirements; that of conduit 36 is advantageously rectangular. 7

Discharge conduit 38 has an outlet opening 39 which is located midway between the sides of the belt 40 and upwardly spaced from the latter. Arranged adjacent the opposite lateral sides of the outlet opening 39 are pipes or

tubes

43a, 43b identical with or analogous to the tube 8 of FIG. 1. The

tubes

43a, 43b are tumable about their respective longitudinal axes in the direction of the double-headed arrow l-K, in the same manner as tube 8 and for the same purpose.

Additionally, and to protect the fiber-air stream issuing from opening 39 against immediate contact with the liquid curtains 44a, 44b which are respectively projected by the.

tubes

43a, 43b in direction towards the surface of belt 40, each of the tubes carries a flap or shield member 42a, 42b which thus turns with its associated tube. The flap members 42a, 42b are so arranged as to define between themselves a gap 41 which communicates both with the opening 39 and with the space between the liquid curtains 44a, 44b.

Turningof the

tubes

43a, 43b in the indicated manner results in traversal of the liquid curtains 44a, 44b, which one shown in one end position, in the direction arrow I-K to and from their other illustrated end position which is identified with reference numerals 44a and 44b. Evidently, during such traversal the liquid curtains will contact and entrain the fiberair stream downstream of the gap 41 and deposit the fibers on the belt 40 in the manner described earlier. Because in this embodiment the fiber-air stream is introduced between the two liquid curtains, both of which are accelerated towards the belt 40 at high speed, the fibers are entrained particularly well and deposited'on the surface of the belt 40 with exceptionally good regularity of distribution.

In this embodiment, reference numeral 45 identifies sidewalls corresponding, for example, to the sidewalls 13 of FIG. 1 and having the same purpose as those. Reference numeral 46 identifies spray pipes corresponding to the pipes 14 in FIG. 1. Additionally, I may provide upper cover members 47 as protection against undesired outside influences.

While the liquid curtains serve to deposit the fibers evenly distributed onto the belt db, they can do at least to the extent of uniformity which it is desired to obtain only if the fibers are supplied in a constant regular stream from fiber lumps and agglomerations. This, in turn, requires that the agglomeration of fibers in the gap ill and on the inwardly directed sides of the flaps d211, d2!) be prevented. It is therefore desirable to prevent wetting of these inwardly directed sides to avoid adhering of fibers thereto, and in accordance with another concept of my invention this is accomplished by providing baffles dila, dbl; each of which is associated with one of the flaps Mia, lib. These baffles are slightly spaced from their associated flaps and, more specifically, from the outwardly directed side of their associated flaps. Advantageously the baffles ib a, d-fib are somewhat shorter than the associated flaps 42a, d217, as shown in H6. ii. Liquid which becomes deposited on the outwardly directed sides of the baffles dfia, 4 811, that is the sides which face the respective tubes 43a, 4317, creeps" around the free edges of the baffles and into the gap between the respective baffle and the associated flap, thus being ltept away from the inwardly directed sides of the flaps. It will be appreciated that in the absence of the baffles dda, dbl; such liquid would become deposited on the outwardly directed sides of the flaps 32a, 42b themselves and would then creep" around their free edges to the respective inwardly directed sides of the flaps 42a, 42b.

The embodiment of FIG. 5, finally, utilizes an advancing belt 50, guided over the rollers 49 (one shown). Arranged vertically above the fibersupporting surface of the belt 50, and inclined at an angle to the direction of travel of the same, is a tube fill provided with the openings or nozzles 52 which face the surface of the belt fill. Contrary to the preceding embodiments the tube fill is fixed, that is it does not perform traversing movement. The streams of fibers and air in this embodiment are supplied through the

supply conduits

53a, 53b in the direction of the arrows lL-M, respectively. in other words, the streams of fibers which are identified with reference nu merals Eda, Sdb, advance in direction normal or substantially normal to the elegation and the travel of the belt 50, as

inill

12 or 33, that it has a higher speed of traversal when it is closer to the point of issuance of the fiber-air stream than when it is farther spaced therefrom. Suitable control means for this purpose is also well known in the art and is not believed to require detailed discussion, particularly because the mechanical arrangement itself does not form a part of the invention.

FIG. 6 shows detail of the circulating means for the liquid. While the figure is thought to be self-explanatory it is pointed out that liquid received from conduit 18 passes through filter so from where it is advanced by pump fill into a reservoir 62.

Pump oil then circulates the liquid from the reservoir through conduit 9 to the spray nozzles or the like.

FIG. 7 shows a detail of the traversing means for the conduits. Again, in conjunction with the description of FIGS. 2 and 3 this figure is self-explanatory. A chain is trained about the sprockets 70 and carries a pin 7ll. A rotary shaft 72 carries a rotary cam '73 with a recess of which the pin 71 engages. Conduits .M are mounted on chain 25. Cam '72 rotates alternately in opposite direction as shown by the doubleheaded arrow and takes along chain 25 via pin 711.

In FIG. til i have shown details of the structure for the pivoting or traversing in unison of two parallel conduits dIla and 3312. The figure is clear in conjunction with the description of dicated by the arrows. A water curtain is projected in a downwardly direction from the tube M and serves to entrain and deposit the fibers of the streams 5dr: and Ed!) on the supporting surface of the belt 5% in the manner already described. The angle B included between the axis of the tube 51 and the direction of advancement of the belt 5b depends upon the length of the tube 51, as well as upon the width of the belt and the width of the mat of fibrous material which is to be produced. it can be readily determined by those skilled in the art. Sidewalls are provided for the purpose discussed with respect, for example, to the sidewalls 13 of F llG. ll.

it is clear that it is well within the purview of the present invention to add to the liquid, for instance the water which entrains the fibers, additional substances such as binders, impregnating agents, dyes or the like. Of course, excess quantities of these additive substances must berecovered. If this is not practical or not desired, then moisture may be withdrawn in the aforediscussed manner from the wet mat of fibrous material at one or several places along its direction of travel whereupon at another place a binder substance, an impregnating substance, a dye or the like may be added, for instance by passing the completely or partially dried web or mat of fibrous material through a bath of the substance, by spraying the substance on the web, or in other suitable and well-known manner.

Under certain circumstances it is possible, particularly in the embodiments of H63. ii and 3, that the

water curtain

12 or 33 entrains more fibers and deposits more fibers on the fiber-supporting surface when it is relatively close to the point at which the fiber-air stream issues, and will entrain and deposit fewer fibers when it has traversed to a position where it is farther removed therefrom. To counteract this it may be advantageous to so vary the traversing speed of the

respective tube

3 or 35, and accordingly of the respective water curtains MG. 4. A rod hill is pivoted at 81 to rods 32 whose lower ends in turn are each pivoted at $3 to conduits 33a and MN), respectively. The pivots M are stationary so that the conduits are displaced in arcuate paths when the rod is reciprocated in the direction of the double-headed arrow.

Finally, FIG. 9 shows in a bottom view how the nozzles or apertures 48a, dbl) in the two parallel conduits 43a, 4312 are ar ranged so that each nozzle 48a of conduit 43a is located intermediate two nozzles 4l8b of conduit 43b, and vice versa.

it will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in an arrangement for forming a web of fibrous material, it is not intended to be limited to the details shown, since various modification and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Lettcrs Patent is set forth in the appended:

l. A method of forming a nonwoven web of fibrous material along a predetermined path of predetermined width and defined by a pervious surface, comprising the steps of showering particles of a liquid carrier over at least substantially the entire width of a portion of said path in form of two liquid curtains originating at two transversely spaced locations and diverging from one another in direction towards said pervious surface, and traversing said liquid curtains between opposite lateral sides of said pervious surface; and advancing a stream of staple fibers into the path of the liquid particles intermediate said transversely spaced locations toward said pervious surface so that the fibers are entrained downstream of said spaced locations on contact with the traversing liquid curtains, whereby the thus entrained staple fibers are caused by the liquid particles to enter said portion of said predetermined path so to become deposited on said pervious surface and form thereon a fibrous web of substantially uniform density.

2. A method as defined in claim ll, wherein said liquid curtains are traversed in unison.

3. A method as defined in claim 1, wherein said liquid particles advance against said portion of said predetermined path at a speed which is greater than the speed at which said stream of staple fibers advances into the path of the liquid particles.

4. A method as defined in claim 1; and further comprising the step of varying the speed of traversal of said liquid curtains.

5. A method of forming a nonwoven web of fibrous material along a predetermined path of predetermined width and defined by a pervious surface, comprising the steps of showering particles of a liquid carrier in form of a liquid curtain against a portion of said pervious surface over substantially the entire width thereof; advancing a stream of staple fibers into the path of the liquid particles from a predetermined location for entrainment by said liquid particles traversing said liquid curtain toward and away from said predetermined location; and varying the speed of such traversal by increasing the speed with increasing proximity of the traversing liquid curtain to said predetermined location, and decreasing the speed with decreasing proximity of the traversing liquid curtain to said predetermined location, whereby the entrained staple fibers are deposited by the liquid particles on said portion of said pervious surface so as to form thereon a fibrous web of substantially uniform density.

6. A method as defined in claim 5, wherein said stream of staple fibers is advanced in direction towards said pervious surface.

7. Apparatus for forming a nonwoven web of fibrous material of substantially uniform density, comprising, in combination, first means comprising a conveyor belt having a pervious supporting surface and travelling in a predetermined direction; second means operative for propelling at least one stream of particles of a liquid carrier under pressure against said pervious supporting surface and comprising discharging means including elongated liquid-discharging conduit means above said surface extending in said predetermined direction centrally of and at least substantially parallel to said surface for discharging and propelling said liquid particles, recovering means below said pervious surface for receiving at least the major part of the discharged liquid particles, and circulating means for recirculating the recovered liquid particles to said discharging means; and third means operative for advancing a stream of staple fibers into the path of such liquid particles, whereby said staple fibers are forcibly entrained by said liquid particles and forcibly deposited on said pervious surface as a fibrous web.

8. Apparatus as defined in claim 7, said liquid-discharging conduit means comprising at least one conduit having an axis, and said second means further comprising traversing means associated with said conduit and operative for traversing the same about said axis.

9. Apparatus as defined in claim 8, said liquid-discharging means comprising an additional conduit also having an axis and being transversely spaced from said one conduit so as to define a narrow gap therewith; and wherein said traversing means is associated with both of said conduits and is operative for traversing the same about their respective axes.

10. Apparatus as defined in claim 9, said traversing means being operative for traversing both of said conduits in unison.

11. Apparatus as defined in claim 9, further comprising a guide flap carried by each of said conduits at the side thereof facing the other conduit, said guide flaps bounding the opposite lateral sides of said narrow gap against intrusion of liquid particles; and wherein said third means comprises at least one guide channel for said fibers having an outlet registering with said narrow gap so as to discharge said stream of fibers through said gap and towards said pervious surface.

12. Apparatus as defined in claim 11; and further comprising baffle means respectively provided on said conduits parallel to and slightly spaced from the outwardly directed sides of said guide flaps for intercepting liquid particles and preventing deposition thereof on said guide flaps.

13. Apparatus as defined in claim 12, said guide flaps projecting from said conduits towards said pervious surface by a predetermined distance, and said baffle means projecting from said conduits towards said pervious surface by a distance slightly smaller than said predetermined distance.

14. Apparatus for forming a nonwoven web of fibrous material of substantially uniform density, comprising, in combination, first means including a conveyor belt having a pervious supporting surface and travelling in a predetermined direction; second means operative for propelling at least one stream of particles of a liquid carrier under pressure against said pervious supporting surface and comprising discharging means including at least one elongated liquid-discharging conduit above said surface in at least substantial parallelism therewith and having an axis, recovering means below said pervious surface for receiving at least the major part of the discharged liquid particles, and circulating means for recirculating the recovered liquid particles to said discharging means; traversing means for traversing said conduit about said axis; and third means including at least one guide channel for said staple fibers having an outlet located upwardly of said supporting surface and operative for advancing a stream of staple fibers into the path of such liquid particles, and said discharging means comprising at least one additional liquid-discharging conduit proximal to said outlet and being constructed and arranged for propelling additional liquid particles in form of a liquid curtain intersecting the stream of staple fibers from above and being inclined downwardly toward said supporting surface in direction other-than-normal to the latter, the firstmentioned conduit propelling said liquid particles in form of a shower of liquid from above through said stream of staple fibers and said liquid curtain toward said, supporting surface substantially normal to the same, whereby said staple fibers are forcibly entrained by said liquid particles and forcibly deposited on said pervious surface as a fibrous web.

15. Apparatus for forming a nonwoven web of fibrous material of substantially uniform density, comprising, in combination, first means including a conveyorbelt having a pervi ous supporting surface and travelling in a predetermined direction; second means operative for propelling at least one stream of particles of a liquid carrier under pressure against said pervious supporting surface and comprising discharging means including at least one elongated liquid-discharging conduit above said surface in at least substantial parallelism therewith and having an axis, recovering means below said pervious surface for recovering at least the major part of the discharged liquid particles, and circulating means for recirculating the recovered liquid particles to said discharging means;

transversing means for traversing said conduit about said axis in a predetermined pattern; and third means operative for advancing a stream of staple fibers into the. path of such liquid particles, said third means including at least one guide channel for said staple fibers having an outlet for the same, and closure means movable between a closure position closing said outlet and an open position opening said outlet and directing the stream of fibers issuing therefrom, said closure means being movable between said closure position and said open position in correspondence with the predetermined pattern of traversal of said conduit, whereby said staple fibers are forcibly entrained by said liquid particles and forcibly deposited on said pervious surface as a fibrous web.

16. Apparatus as defined in claim 15, said conduit being provided on said guide channel at said outlet of the same.

17. Apparatus as defined in claim 15, said conduit being provided with a plurality of discharge apertures distributed along said conduit.

18. Apparatus as defined in claim 17, said apertures being arranged in two substantially parallel rows extending in lon' gitudinal direction of said conduit 19. Apparatus as defined in claim 18, wherein each aperture of one of said rows is located intermediate two consecutive apertures of the other of said rows.

20. Apparatus as defined in claim 15, and further comprising a pair of sidewalls extending along opposite lateral sides of said supporting surface upwardly from the latter for delimiting the lateral extent of the fibrous nonwoven web being formed on said supporting surface.

21. Apparatus as defined in claim 20, and further compris- 22. Apparatus as defined in claim 21, said fiber-removing ing fiber-removing means for removing fibers adhering to the means including at least one liquid-discharging tube asinner faces of said sidewalls which face inwardly towards said sociated with each of said sidewalls extending along said inner supporting surface. faces of the same.

Claims

1. A method of forming a nonwoven web of fibrous material along a predetermined path of predetermined width and defined by a pervious surface, comprising the steps of showering particles of a liquid carrier over at least substantially the entire width of a portion of said path in form of two liquid curtains originating at two transversely spaced locations and diverging from one another in direction towards said pervious surface, and traversing said liquid curtains between opposite lateral sides of said pervious surface; and advancing a stream of staple fibers into the path of the liquid particles intermediate said transversely spaced locations toward said pervious surface so that the fibers are entrained downstream of said spaced locations on contAct with the traversing liquid curtains, whereby the thus entrained staple fibers are caused by the liquid particles to enter said portion of said predetermined path so as to become deposited on said pervious surface and form thereon a fibrous web of substantially uniform density.

2. A method as defined in claim 1, wherein said liquid curtains are traversed in unison.

14. Apparatus for forming a nonwoven web of fibrous material of substantially uniform density, comprising, in combination, first means including a conveyor belt having a pervious supporting surface and travelling in a predetermined direction; second means operative for propelling at least one stream of particles of a liquid carrier under pressure against said pervious supporting surface and comprising discharging means including at least one elongated liquid-discharging conduit above said surface in at least substantial parallelism therewith and having an axis, recovering means below said pervious surface for receiving at least the major part of the discharged liquid particles, and circulating means for recirculating the recovered liquid particles to said discharging means; traversing means for traversing said conduit about said axis; and third means including at least one guide channel for said staple fibers having an outlet located upwardly of said supporting surface and operative for advancing a stream of staple fibers into the path of such liquid particles, and said discharging means comprising at least one additional liquid-discharging conduit proximal to said outlet and being constructed and arranged for propelling additional liquid particles in form of a liquid curtain intersecting the stream of staple fibers from above and being inclined downwardly toward said supporting surface in direction other-than-normal to the latter, the first-mentioned conduit propelling said liquid particles in form of a shower of liquid from above through said stream of staple fibers and said liquid curtain toward said supporting surface substantially normal to the same, whereby said staple fibers are forcibly entrained by said liquid particles and forcibly deposited on said pervious surface as a fibrous web.

15. Apparatus for forming a nonwoven web of fibrous material of substantially uniform density, comprising, in combination, first means including a conveyor belt having a pervious supporting surface and travelling in a predetermined direction; second means operative for propelling at least one stream of particles of a liquid carrier under pressure against said pervious supporting surface and comprising discharging means including at least one elongated liquid-discharging conduit above said surface in at least substantial parallelism therewith and having an axis, recovering means below said pervious surface for recovering at least the major part of the discharged liquid particles, and circulating means for recirculating the recovered liquid particles to said discharging means; transversing means for traversing said conduit about said axis in a predetermined pattern; and third means operative for advancing a stream of staple fibers into the path of such liquid particles, said third means including at least one guide channel for said staple fibers having an outlet for the same, and closure means movable between a closure position closing said outlet and an open position opening said outlet and directing the stream of fibers issuing therefrom, said closure means being movable between said closure position and said open position in correspondence with the predeterminEd pattern of traversal of said conduit, whereby said staple fibers are forcibly entrained by said liquid particles and forcibly deposited on said pervious surface as a fibrous web.

18. Apparatus as defined in claim 17, said apertures being arranged in two substantially parallel rows extending in longitudinal direction of said conduit .

19. Apparatus as defined in claim 18, wherein each aperture of one of said rows is located intermediate two consecutive apertures of the other of said rows.

21. Apparatus as defined in claim 20, and further comprising fiber-removing means for removing fibers adhering to the inner faces of said sidewalls which face inwardly towards said supporting surface.

22. Apparatus as defined in claim 21, said fiber-removing means including at least one liquid-discharging tube associated with each of said sidewalls extending along said inner faces of the same.