US3622077A

US3622077A - Apparatus for air-laying wet fibers

Info

Publication number: US3622077A
Application number: US702364A
Authority: US
Inventors: Donald E Wiegand
Original assignee: Conwed Corp
Current assignee: Leucadia Inc
Priority date: 1968-02-01
Filing date: 1968-02-01
Publication date: 1971-11-23
Anticipated expiration: 1988-11-23
Also published as: NL6901561A; BE727767A; FR2001155A1; LU57878A1; DE1904856A1

Abstract

In an apparatus for mixing an air-fiber stream with a liquid spray and dispersing the same, the outlet creates a vena contracta in the air-fiber stream and the nozzles for the liquid spray are thin and have steeply sloped upstream edges to prevent ''''hang-up'''' of fiber and any resulting clots.

Description

United States Patent [72] inventor Donald E. Wiegand Minneapolis, Minn.

[2| Appl. No. 702,364

[22] Filed Feb. 1, 1968 [45] Patented Nov. 23, 197 l l 73] Assignee Conwed Corporation St. Paul, Minn.

[54] APPARATUS FOR AIR-LAYING WET FIBERS 4 Claims, 8 Drawing Figs.

52 [1.5. CI..' 239/336, 239/424 [51 Int. Cl 1305b 7/06 [50] Field oi Search 222/194,

i [56] References Cited UNITED STATES PATENTS 2,288,095 6/1942 Lindsay et al 264/121 FOREIGN PATENTS 955,744 1/1957 Germany 222/145 Primary Examiner- Roben B. Reeves Assistant Examiner-John P. Shannon, .lr. Attorney-Gunnar A. Gustafson, .lr.

ABSTRACT: In an apparatus for mixing an air-fiber stream with a liquid spray and dispersing the same, the outlet creates a vena contracta in the air-fiber stream and the nozzles for the liquid spray are thin and have steeply sloped upstream edges to prevent hang-up of fiber and any resulting clots.

PATENTED NOV 2 3 l9?! SHEET 1 OF 2 FIG. 3

INVIJNTOR. DONALD E. W/EGA/VD H/S ATTORNEY PATENTEUunv 23 I9?! SHEET 2 OF 2 INVIINTOR. DONALD E. W/EGAND H/S ATTOR/V APPARATUS FOR AIR-LAYING WET FIBERS In my copending U.S. applications Ser. No. 702,365, filed Feb. 1, I968, and Ser. No. 702,363, filed Feb. I, I968, I have disclosed various means of improving the mixing of an airfiber stream with a binder carrying liquid spray by spraying the liquid from within the air-fiber stream. As disclosed in said above mentioned copending United States applications, the mixing is enchanced by restricting the air-fiber streams either within the dispersing mechanism itself or within a vena contracta created just beyond the outlet of the disperser and the spraying of a flaring liquid spray into the air-fiber stream from a nozzle orifice located within the air-fiber stream at or adjacent to the point where the air-fiber stream is contracting.

While the spraying of the liquid into the air-fiber stream from within the same as disclosed in my copending cases creates excellent mixing, with improved mat formation, and while the methods and apparatus disclosed in said applications decrease considerably the formation of festoons" or clots of fibers, there are occasions when some fiber hang-up" with attendant clots will occur, particularly with longer fibers such as textile fibers and synthetic fibers.

The object of this invention is to retain the advantages of internal spraying of liquid into an air-fiber stream from within the same as disclosed in my said copending cases and to achieve substantially total elimination of the problem of fiber hang-up and the attendant unevenness of mat.

Another specific object of this invention is to prevent fiber hang-up" by the specific design of the liquid spray nozzle or nozzles.

These and other advantages will be apparent to those skilled in the art from the following description of the invention and the accompanying drawings in which:

FIG. 1 is a schematic showing of a felting apparatus incorporating the invention.

FIG. 2 is an enlarged prospective view of the felting head portion of FIG. 1 taken upwardly from beneath the head.

FIG. 3 is an enlarged cross-sectional view of the head shown in FIG. 1 taken along the line 3-3.

FIG. 4 is a still further enlarged cross-sectional view of a portion of FIG. 1.

FIG. 5 is a prospective view of one of the nozzles of my invention.

FIGS. 6 and 7 show cross sections comparable generally to FIG. 3 of modified forms of the head shown in FIGS. 1-4.

FIG. 8 is a top plan view taken along the line 88 in FIG. 1.

In FIG. 1, a felting apparatus is shown as including a fan 12 driven by the motor 14 and having an air and fiber inlet conduit I6 for fiber or fibrous material fed to the apparatus from supply 18, for example, in the manner set forth in US. Pat. No. 2,646,381. The air-fiber stream from fan 12 is conveyed through cylindrical outlet duct 22 to and through elbow 23, a transition section 42, another elbow 43, and finally the felting head generally indicated at 10. The fibrous mat is then formed upon and collected by any suitable means such as indicated generally at 20.

The collecting means 20 is essentially conventional and, as shown in FIG. 1, is located at a suitable distance from the felting head 10. As shown, there is an endless conveyor screen 24 running over roll 32 and over a suction box 26 connected by conduit 28 to a suction means (not shown). A felted mat 34 of adhesive-carrying fibers is shown building up on the conveyor 24.

The felted mat 34 forming upon the conveyor 24 is created the the impingement upon the screen 24 and the forming mat 34 of an air-fiber stream generally indicated at 36 which has mixed therewith and mixing therewith a liquid spray as more fully discussed hereinafter.

Since the felting head is rectangular in cross section, as best shown in FIG. 3, and since the conduit 22 is cylindrical, the transition section 42 is provided to change the cross-sectional shape of the conduit from cylindrical to rectangular. As best shown in FIGS. I and 8, the transition section 42 narrows in one direction and widens in the other direction, cross-sectionally considered. As shown in FIG. 1, the

walls

45 and 47 of the transition portion 42 taper toward each other, from right to left, from the cylindrical elbow 23 toward the rectangular elbow 43. In FIG. 8, as shown, the

opposite walls

49 and 51 taper away from each other from the cylindrical elbow 23 toward the rectangular elbow 43. While the apparatus shown in FIG. I incorporates

elbows

23 and 43 in the conduit system, it is obvious that either one or both of these elbows may be dispensed with. Indeed, it is known that it is generally preferable to avoid as many changes in direction of the air-fiber stream as is possible under any given circumstances of space and equipment. The construction shown in FIG. 1 with the

elbows

23 and 43 is shown merely for compactness and convenience of illustration. The transition section 42 could as well as be attached directly at one end to the conduit 22 and at the other end directly to the felting head 10, thus avoiding the

elbows

23 and 43.

The felting head 10 is rectangular in cross section, as best shown in FIGS. 2 and 3. The felting head 10 comprises an upper rectangular portion 38 with straight parallel sides and a lower portion 40 which has its two

longer sides

44 and 48 tapering toward each other in the direction of the outlet 58. The other

narrow sides

46 and 53 are not similar tapered but, rather, are straight continuations from the upper section 38.

The cross-sectional area of the upper portion 38 is dimensioned to be approximately the same as the cross-sectional area of the conduit 22 in order to maintain substantially the same velocity of the air-fiber stream. Some slight difference in cross-sectional area of the upper portion 38 over the crosssectional area of the conduit 22 is permissible; however, it has been found advantageous to keep the two cross-sectional areas substantially the same. The transition portion 42 is very gradual, and it is known that an included angle between the

sides

49 and 51 of 6 to l I minimizes shock loss, with 6 being preferred in this environment. The

other walls

45 and 47 can converge (in the direction of flow) at any angle that will preserve the flow velocity. If the width of the fibrous mat to be formed is quite large, say 8 in width or larger, then the felting head 10 must similarly be of approximately that width. In such circumstances, it may be necessary to use a plurality of airfiber stream feeding mechanisms, including a plurality of fans 12, infeeds l6 and 18, and a plurality of ducts 22 leading to a single felting head through a plurality of transition portions 42. In such construction, the cross-sectional area of the portion 38 of the felting head 10 should be kept approximately the same as the total cross-sectional area of all of the conduits 22.

The lower

tapered walls

44 and 48 of the tapered section 40 of the felting head create a vena contracta in the exiting airfiber stream 36. The vena contracta will be from only the two longitudinal sides of the airstream, since only the two

longer sides

44 and 48 of the lower portion 40 of the felting head are tapered to create the two-sided vena contracta.

Since the

opposite walls

46 and 53 are straight and parallel, there will be no constriction or vena contracta in that direction. As shown in FIG. 4, the exiting airstream 36 constricts in the portion 52 forming a vena contracta or a maximum constricted portion 50, and then expands in the portion 54. As such, the air-fiber stream within the felting head is first contracting within the lower portion 40 and therebeyond in the area indicated at 52 until it reaches the point or area of maximum contraction 50, and from thence it expands as indicated at 54. Arranged within the lower portion 40 of the felting head are a plurality of nozzles 30 positioned to create a flaring spray 56 of liquid particles, which spray 56 is flaring outwardly from within the air-fiber stream is contracting. Thus, as the air-fiber is contracting and the liquid spray 56 is expanding, the two are converging as indicated in my copending application Ser. No. 702,365, filed Feb. 1, I968. As indicated, the tapered lower portion 40 will produce a pronounced vena contracta in the fiber stream beyond the outlet 58 of the felting head. By means of the vena contracta thus created, the velocity of the air-fiber stream is increased to a maximum and its direction is controlled to impinge more effectively inwardly toward the outwardly flaring liquid spray 56. Thus, greatly improved interrnixing of the liquid spray and air-fiber stream is achieved, with excellent uniformity of deposition of liquid particles upon fibers. The orifices 60 of the nozzles 30 are located such that the spray 56 produced by the nozzles 30 is largely or entirely outside the outlet 58 of the felting head such that the liquid spray 56 will be within the airfiber stream and located vertically substantially at the vena contracta or slightly thereabove. The location of the orifices 60 of the nozzles 30 may vary between two extremes. The orifices 60 of the nozzles 30 should not be placed so far downstream that the flaring liquid spray 56 from the orifices 60 begins beyond the vena contracta, since the best mixing is achieved when the air-fiber stream is necking down to form the vena contracta at about the point or area where the liquid spray or sprays 56 are flaring outwardly, thus crating a convergence of the two streams. On the other hand, if the nozzles 30 are arranged too far upstream within the lower portion 40 of the head, the liquid spray or sprays 56 from the orifices 60 will have an opportunity to reach the

inside walls

44, 46, 48, and 53 of the lower portion 40 of the felting head and thus form festoons or clots of fiber and liquid (which liquid usually includes a sticky binder) which will tend to fall into the mat, creating uneven areas. Accordingly, the orifices 60 should be far enough downstream (though they may actually physically still be within the felting head as shown) that it will be impossible for the spray or sprays 56 emerging therefrom to strike the inside of the walls of the felting head. Conversely, as indicated above, the orifices 60 must be sufficiently upstream with respect to the air-fiber stream that the flaring liquid spray or sprays 56 will be expanding in the area 52 of the formation of the vena contracta and throughout the length of the formation of the vena contracta. It will be appreciated that within these two extremes there is considerable latitude for the location of the orifices 60 and the nozzles 30. The particular location and the degree of the vena contracta can be controlled by the degree of the taper in the portion 40 of the felting head and other facts indicated hereinafter. It will be seen that by proper adjustment of the velocities, volumes, and dimensions of the liquid spray or sprays with respect to the air-fiber stream, the air-fiber stream will serve to form an envelope or air curtain to contain the liquid spray within the confines of the air-fiber stream. If the liquid spray is too strong or too large in cross section for the particular air-fiber stream velocity and force, the liquid spray will break through the air-fiber stream and spray fugitive liquid particles outside of the air-fiber stream and downwardly upon the mat being formed. Conversely, if the liquid spray is of inadequate dimension, velocity, and force with respect to the associated particular air-fiber stream, the liquid spray will not satisfactorily mix with the outermost portions of the air-fiber stream. All of these variables can be readily adjusted for the given fiber concentration, and liquid being sprayed. In many instances, the spray will consist of a liquid binder for the fibers carried in the air-fiber stream. One example of this is a starch solution. In other instances, the binder may consist of a dry particulate matter incorporated in the air-fiber stream which is then activated by the water or other liquid of the liquid spray. In both instances, suitably uniform mixing of the liquid and the fiber is essential. As indicated, this mixing may required adjustments in positioning and velocities for different fibers and binders as well as for different rates of mat formation.

The details of the nozzles 30 are shown best in FIG. 4, in which one ofthe nozzles 30 is shown in cross section as including two horizontal conduits 62 and 64 bored therein. Adjacent the inner end of the conduit 64 is bored a crossing vertical conduit 68 opening to said conduit 64 on one end and to the outside at the lower edge 72 of the nozzle 30 at the other end. At the inner end ofthe conduit 62 a smaller diameter bore 66 extends downwardly and intersects the bore 64 and is concentric with the bore 68. Within the bore 68 is a tube 74 extending from or from close to the bore 64 downwardly beyond the lower edge 72 of the nozzle 30 to form the orifice 60 of the spray nozzle 30. While this tube 74 is not absolutely essential, it does provide for replacement of the tube with tubes of different internal diameter as may be required for different mixtures ofliquid and air. Within the bore 66 is a smaller diameter tube 76 which extends from or from close to the conduit 62 downwardly through the tube 74 and concentric therewith and terminating at about the same plane as the bottom edge of the tube 74, thus to form therewith the orifice 60. The outer tube 74 may be soldered in place as indicated at 78. The tube 76 is preferably held in place merely by friction fit within the bore 66.

The conduits 62 and 64 are connected by

conventional means

82 and 84 respectively to sources of supply of liquid and air respectively, which fluids are provided under pressure in a conventional manner.

The nozzles 30 are mounted tightly against the

walls

44 and 48 by means of screws 86 tapped into the nozzles 30 through nontapped openings 88 through the

walls

44 and 48 of the lower portion 40 of the felting head 10.

Of critical importance is the shape and dimension of the nozzles 30. Since these structures protrude into the air-fiber stream, it is important that they be so designed as to avoid retaining any fiber that may impinge thereupon. This shape becomes even more critical when dealing with longer textile fibers or synthetic fibers such as cotton waste, other cotton fibers, and the various synthetic fibers such as rayon, nylon, and other synthetics. Textile fibers and synthetic fibers are generally of considerable length as compared to, say, wood fibers such as aspen fibers or sulfite fibers which are quite short. Such long fibers tend to hang-up" on the least projection in the felting head or in the conduits carrying the air-fiber stream. The instant invention incorporates nozzles 30 which completely prevent the hang-up" of even the longest fibers and other fibers prone to such hang-up." The inner edge of the nozzles 30 comprises two portions 90 and 92. The vertical and innermost edge 92, of course, will not tend to obstruct fibers since it is parallel to the general direction of the air-fiber stream. The edge 90 is at a considerable angle to the direction of the air-fiber stream. Any fibers striking the edge 90 will either fall 05 to one side or the other of the nozzle 30 or will tend to slide downwardly along the edge 90 and drop off from the nozzle 30 at the point 94, where the edges 90 and 92 intersect. In this way, no fiber buildup or hang-up will develop. The angle between the edge 90 and the vertical centerline 96 of the felting head which will achieve the desired results is, in part, determined empirically for any given fiber, texture, and length; however, it has been found that an angle of 45 between the edge 90 and the centerline 96 serves the purposes for most common fibers encountered. Of course, any increase over this 45 will tend to enhance the possibility offiber hangup and any lessening of this angle of 45 will tend to decrease the possibility of any fiber hang-up.

In order to further reduce any possibility of fiber hang-up, the edges 90 and 92 are rounded as shown in FIG. 5 and polished smooth. Additionally, the corner 80, where the edge 90 meets the inside of the

walls

44 and 48, is carefully constructed to provide a smooth juncture with no sharp comers to catch fibers.

Since in normal commercial practice it will be necessary to form a mat 34 of considerable width (as, for example, from about 30 inches on up to and including l3 feet), the felting head 10 is shown as being rectangular and arranged transversely of the collecting mechanism 20. This construction requires a plurality of nozzles 30. It has been found that the preferred arrangement in order to provide balance and evenness in the air-fiber stream and the resulting air-fiber and liquid mixture is to stagger or alternate the nozzles 30 in the manner shown in FIGS. 2 and 3. As shown, the nozzles 30 extend outwardly from their

walls

44 and 48 beyond the centerline 96 of the felting head 10. This permits the arrangement of the orifices 60 with their centers of the centerline 96 of the felting head, with all of the orifices 60 in rectilinear alignment. The particular number of nozzles will be determined by the requirements in any given situation, but it has been found that from five to eleven nozzles are satisfactory with a 30 inch width of felting head 10.

In FIG. 6 a modified felting head 100 is shown, which felting head 100 is cylindrical. With this construction, the wall 98 tapers frustoconically downwardly to the outlet orifice 102 of the felting head 101). With this construction, only a single nozzle 104 is required. The nozzle 104 is identical in construction to the nozzle 30 described above. The orifice 106 in the nozzle 104 is arranged concentrically with the cylindrical outlet orifice 102 to provide even distribution of the liquid outwardly in all directions within the contracting air-fiber stream.

In FIG. 7, an additional modification of the felting head is shown in which the felting head 110 has a tapering frustoconical wall 108 terminating in an outlet orifice 112. In this instance, there are a plurality of nozzles 114 arranged around the innerside of the wall 108. In this instance, however, the nozzles 114 are somewhat shorter, since they do not reach to the center of the outlet orifice 112. In this instance, the spray orifices 116 in the nozzles 1 14 are arranged in a circular alignment, which circle is concentric with the outlet orifice 112 for the fiber head 110.

It will be appreciated that cylindrical heads such as shown in FIG. 6 and FIG. 7 have limitations with respect to the width of mat that can be produced, since if they are made of too large a diameter (in order to produce a wider mat) ultimately the head will become to large in diameter and produce an air-fiber stream of too great a diameter to permit adequate mixing from the liquid orifice or orifices. While this problem can be alleviated somewhat by the additional of a plurality of orifices as shown in FIG. 7, there still remain ancillary problems of overapplying the liquid spray in the center and similar problems. Accordingly, the rectangular configuration as described above with respect to FIGS. 1 through 5 is preferred; however, in certain applications the head shown in FIGS. 6 or 7 may be more economical to produce and utilize and their limitations can be partly or wholly overcome by oscillating the head back and forth transversely of the collecting screen 24 of the collecting mechanism 20.

The mats formed as disclosed herein (when the binder is suitably set as by drying or heating) are suitable for a number of end uses, including furniture cushioning, furniture padding, packaging, and the like. They may also be used (with subsequent operations such as pressing) to form boards and boardlike materials.

One example of the use of the apparatus disclosed herein is the production of suitable upholstery cushioning materials from refined sulfite fibers and a starch solution as a binder for the fibers. The formed mat is then oven dried to form the final bonded product. It has been found that about 6 percent to 8 percent starch solids by weight with respect to the weight of fibers in the final mat produces an excellent and uniform blanket, with no clots coming from festoons, with no clots of fibers resulting from fiber hang-up in the felting head, and with excellent distribution of binder upon the fibers.

It will be appreciated that the directions of the liquid spray and the air-fiber stream are not straight line as shown in the drawings and are shown as such convenience of illustration only. Actually, there will be some curvature to the directions of the spray and the air-fiber stream created by the merging and interrelation of the spray and the stream on each other.

Iclaim:

1. In an apparatus having means for forming and discharging a stream of air containing fibers, including a conduit means, a plurality of nozzle means having an outlet orifice positioned within said stream for spraying a liquid into and along said stream from its position within said stream, the improvement comprising each of said nozzle means extending inwardly from a wall of said conduit toward the center of said conduit, each of said nozzle means being a vanelike member having an edge abutting said wall, said vanelike nozzles each having a second edge inward of said wall and substantially parallel to the direction of flow of said stream, said vanelike nozzles each having a third edge extending from the upper end of said second edge at an angle thereto and terminating at its other end at said first edge, alternate ones of said nozzle means extending from the same wall of said conduit and the others of said nozzle means extending inwardly from an opposite wall.

2. The apparatus of claim 1 in which said conduit is generally rectangular in cross section, said alternate ones of said nozzle means extend inwardly from one of the longer walls of said conduit and the others of said nozzle means extend inwardly from the opposite wall.

3. The apparatus of claim 2 in which the innermost ends of said nozzle means extend beyond the longitudinal centerline of the cross section of said conduit and said outlet orifices are arranged substantially on said centerline.

4. An apparatus having means for forming and discharging a stream of air containing fibers, including a conduit means, said conduit means having an outlet and being so shaped at and adjacent said outlet as to produce a vena contracta in said stream downstream of said outlet, nozzle means having outlet orifice means positioned within said stream for spraying a flaring liquid spray into and along said stream, said outlet orifice being so positioned with respect to said conduit means that the flaring liquid spray therefrom avoids striking said conduit means, said outlet orifice also being so positioned with respect to the vena contracta of said stream that the liquid spray is flaring outwardly within said stream where said stream is contracting to form said vena contracta, said nozzle means extending inwardly from a wall of said conduit toward the center of said conduit, said nozzle means having upstream edge means abutting said wall at one end thereof and said edge means sloping steeply downstream from said one end, whereby mixing of the liquid spray and the fibers in said stream is accomplished and accumulation of fibers on said nozzle means is prevented.