EP0000222A1

EP0000222A1 - Method and apparatus for continuously forming an airlaid web

Info

Publication number: EP0000222A1
Application number: EP78200043A
Authority: EP
Inventors: Kenneth Barclay Buell
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1977-06-27
Filing date: 1978-06-15
Publication date: 1979-01-10
Also published as: DE2860461D1; BE868480A; CA1095214A; BR7804070A; AT365682B; ATA466578A; US4141772A; MX148662A; GB1588210A; IT7850025A0; JPS5438982A; GR63111B; ES471132A1; IT1156838B; ES476107A1; EP0000222B1

Abstract

A continuous in-line method for forming an airlaid fibrous fluff web adjacent the uppermost and lowermost surfaces of a substantially planar internal reinforcing ply having substantially the same width as said fibrous web, said ply being substantially impervious to the passage of fibers from one surface thereof to the other, in a continuous fiber deposition zone is disclosed. In a preferred embodiment, a unique tissue folding board is employed to permit continuous formation of an airfelt web having a wet strength tissue reinforcing member located approximately mid-way between its uppermost and lowermost surfaces, In the apparatus for forming the web, two adjacent vacuum chambers (26,27) are preferably employed in the continuous forming zone to compensate forthe increased airflow restriction encountered when forming the uppermost fibrous web position over the reinforcing ply and the lowermost fibrous web portion. In a particularly preferred embodiment, the portion of the internal ply (20) relative to the uppermost and lowermost surfaces of the resultant pad may be adjusted by advancing or retarding the position of the folding board (1) within the fiber deposition zone (12).

Description

Absorbent fibrous structures comprised of low strength absorbent materials such as airlaid wood pulp fibers are well known in the disposable absorbent bandage art. In certain of these prior art fibrous pad structures it has been found desirable to employ one or more internally located plies of tissue paper or other web materials which are substantially impervicus to the passage of fibers to act, for example, as a reinforcing agent, as a fluid baffle to distribute absorbed fluids within the absorbent fluff structure, as a partitioning agent or the like. Addition of such internal plies which have a width substantially equal to that of the absorbent fibrous webs located on the uppermost and lowermost surfaces thereof has typically been provided by utilizing a multiplicity of discrete forcing zones with a separate fiber supply source for each zone. However, the multiple forming zone approach typically employed by such prior art systems requires considerable converting line space and involves a duplication of disintegrating and air laying equipment for each absorbent fibrous layer employed in the resultant structure. Furthermore, altering the position of the internal ply relative to the uppermost and lowermost surfaces of the finished absorbent pad typically requires a complex adjustment procedure for each fiber deposition zone in the system.
Accordingly, it is an object of the present invention to provide method and apparatus for forming an airlaid fibrous fluff web adjacent the uppermost and lowermost surfaces of a substantially planar, fiber-impervious internal reinforcing ply having substantially the same width as said fibrous web in a continuous fiber deposition zone.
It is another object of the present invention to provide method and apparatus for easily altering the position of the internal ply relative to the uppermost and lowermost surfaces of the absorbent pad in question.
It is yet another object of the present invention to provide method and apparatus for forming an airlaid fibrous fluff web adjacent the uppermost and lowermost surfaces of a substantially planar fiber-impervious internal reinforcing ply having-substantially the same width as said fibrous web in a continuous fiber deposition zone having an.overall length no greater than the required to form an identical absorbent pad of the comparable basis weight without said center ply.

SUMMARY OF THE INVENTION

In simplest terms, the present invention accomplishes the aforementioned objectives by carrying out the steps of:

(a) continuously feeding a substantially planar reinforcing ply in a first direction in a first plane;
(b) introducing said moving reinforcing ply to a fiber deposition zone while oriented so that the direction of fiber flow is substantially parallel to the width of said ply to form the portion of said airlaid fibrous fluff web adjacent the lowermost surface of said reinforcing ply;
(c) guiding said moving reinforcing ply into contact with a first equal length leg portion of the trailing surface of a first planar isosceles right triangle, said right triangle having the second of its equal length legs oriented perpendicular to said first direction of travel of said moving ply;
(d) wrapping said moving reinforcing ply about opposite surfaces of said planar right triangle by passing said ply about the hypotenuse thereof;
(e) restoring said moving ply to said first direction of travel by passing said moving ply about the second of said equal length legs, thereby causing said ply to assume a planar condition in a second plane perpendicular to said first plane;
(f) exposing the uppermost surface of said moving reinforcing ply to said fiber deposition zone while in a planar condition to form the portion of said airlaid fibrous fluff web adjacent the uppermost surface of said reinforcing ply; and
(g) removing said ply from said fiber deposition zone.

In a particularly preferred embodiment, said planar isoceles right triangle may be advanced or retarded in the machine direction within the fiber deposition chamber to alter the final position of the reinforcing ply relntive to the uppermost and lowermost surfaces of the resultant absorbent fibrous pad.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as forming the present invention, it is believed that the invention will be better understood from the following description taken in connection with the accompanying drawings in which:

Figure 1 is a simplified cross-sectional illustration of a pad forming mechanism employing a preferred embodiment of the present invention taken along Section Line 1-1 in Figure 2;
Figure 2 is : complete side elevation view of che pad forming mechanism illustrated in cross-section Figure 1.
Figure 3 is an enlarged cross-sectional illustration taken along Section line 3-3 in Figure 2;
Figure 4 is a simplified perspective view of the pad forming mechanism illustrated in Figures 1-3;
Figure 5 is a simplified schematic illustration of the folding board portion of the mechanism utilized in a preferred embodiment of the present invention;
Figure 6 is a discharge end view of the folding board illustrated in Figure 5;
Figure 7 is a plan view of the folding board illustrated in Figure 5; and
Figure 8 is a simplified perspective view of yet another folding board suitable for use in the present invention

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 is a plan view of a preferred embodiment of the present invention wherein a wet.strength tissue ply 20 is incorporated intermediate the uppermost and lowermost surfaces of an absorbent pad for a disposable absorbent article to improve its in use integrity. As can be seen more clearly from Figure 2, the wet strength tissue ply 20 is directed about a folding board mechanism 1 prior to entry of the tissue ply into a fiber deposition chute 12 wherein a lowermost layer of absorbent airfelt 21 is formed beneath the surface of the tissue ply 20 and an uppermost layer of airfelt 22 is formed adjacent its uppermost surface. In a particularly preferred embodiment of the present invention, a layer of wet strength tissue paper 23 is employed adjacent the lowermost surface of the layer of airfelt 21, and an uppermost layer of tissue paper 24 is employed adjacent the uppermost surface of the layer of airfelt 22.
In the embodiment illustrated in Figures 1 and 2 the folding board 1 comprises a pair of identical planar isosceles triangles 2, 4 having an included angle of approximately 90° or their respective apexes, connected to one another at their altitudes by means of a vertical planar member 3. A layer of reinforcing wet strength tissue paper 20 having a width W substantially equal. to that of the airfelt layers 21, 22 is preferably fed in the same direction and at the same velocity V as the. foraminous supporting surface 11. The tissue ply 20 is caused to alter its path of travel from a horizontal direction to a vertical direction by virtue of being wrapped about direction changing roller 5 located near the base of the isosceles right triangle 2 forming a portion of the folding board 1. While the centerline of the moving tissue ply 20 is caused to coincide with the altitude of the isosceles right triangle 2 in the illustrated embodiment, the lateral edge portions of the ply are caused to remain in contact with both the leading and trailing surfaces of the triangle by virtue of angular guides 7, 8 located adjacent the interior corners formed between vertical planar member 3 and the planar triangle 2. When the tissue ply 20 is forced to resume its original direction of travel about the apex of the isoceles right triangle 2, the angular guide members /. 8 force the tissue ply 20 to assume an inverted U-shape as illustrated in the cross-section of Figure 3. While the vertical planar member 3 does conveniently serve to maintain planar isosceles triangles 2, 4 in longitudinal alignment with one another, its presence is not essential to guide the inverted U-shaped tissue ply 20 intermediate the triangls 2, 4. The inverted U-shaped shroud 28 which connects angins 9, 10 to one another serves to prevent fibers within the deposition chute 12 from collecting on the inverted U-shaped tissue ply 20 prior to passage of the ply through the limited clearance corners formed between angles 9, 10, triangle 4 and vertical planar member 3. Collection of fibers on the inverted U-shaped tissue ply 20 could cause jamming or tearing at these points.
The tissue ply 20 is introduced into the fiber deposition chute 12 while in the inverted U-shape in order to permit formation of a substantially planar lowermost layer of airfelt 21 which lies adjacent the lowermost surface of the tissue ply 20 in the finished absorbent pad embodiment. Internal airflow baffling techniques well known in the art may be employed within the vacuum chamber 26 to minimize any discontinuities in the cross-machine direction uniformity of the airfelt layer 21 which might otherwise occur due to the minor obstruction presented by the thin U-shaped shroud 23. In a particularly preferred embodiment, the lowermost layer of airfelt 21 is formed directly over a layer of envelope tissue 23 similar to that utilized as the reinforcing ply 20 in the forwardmost portion 3 of the fiber deposition chute 12. As can be seen in Figure 2, the vacuum chamber 25 located adjacent the lowermost surface of the moving foraminous support member 11 is preferably divided into two distinct segments 26, 27 by means o an adjustable dividing wall 19 which may be advanced or re arded in the machine direction. The vacuum chamber 25 is preferably segmented as outlined above in order to perm t the application of differing vacuum levels between the leading portion 13 of the fiber deposition chute 12 and the trailing portion 14, since the trailing portion encounters more resistance to air flow than the leading portion due to the presence of the fibrous layer 21 and the reinforcing tissue ply 20 during formation of the uppermost layer of airfelt 22.
As is apparent from Figures 1 and 2, the tissue, ply 20 is-maintained in an inverted U-configuration until the desired thickness of airfelt layer 21 has been obtained. The relative and total thickness of the respective airfelt layers 21 and 22 is controllable not only by the rate of fiber deposition within the chute 12, but also by the level. of vacuum applied beneath the moving foraminous support. member 11 in vacuum chamber segments 26 and 27, the machine direction positioning of the segmenting wall 19 within the vacuum chamber 25, and the machine direction positioning of the planar isosceles right triangle 4 connected to vertical planar member 3. Furthermore, baffle plates 15 and 16 which extend across the entire width of the fiber deposition chute 12, and which may be adjusted about pivot points 17 and 18, may also be employed to direct the flow of fibers toward either the leading portion 13 or the trailing portion 14 of the deposition chute 12, depending upon the desired. split between uppermost layer 22 and lowermost layer 21.
Angular guides 9 and 10 force the tissue ply 20 to remain in contact with the leading surface of isosceles right triangle 4 which is identical in size and shape to the isoceles right triangle 2 as the centerline of a tissue ply 20 is directed about the apex of triangle 4. This in turn forces the tissue ply 20 to.resume a planar configuration as it passes the base portion of the trailing surface of the triangle 4. Direction changing roll 6 restores the tissue ply 20 to its original direction of travel and exposes the uppermost surface of the ply to the deposition of fibers in the downstream portion 14 of the fiber deposition chute 12. A fibrous airlaid web 22 is thus formed adjacent the uppermost surface of the tissue ply 20 prior to passage of the assemblage from the fiber deposition chute 12. A wet strength tissue ply 24 is preferably thereafter brought into contact with the uppermost surface of the absorbent airfelt layer 22 about direction changing roller 30 as shown in Figure 2 to form a reinforced fibrous structure encapsulated on both sides by wet strength tissue plies 23, 24.
As has been pointed out earlier herein, the relative position of the internally located tissue ply 20 may be adjusted intermediate the uppermost and lowermost surfaces of the resultant absorbent pad structure by advancing or retarding the position of the folding board 1 and the direction changing rollers 5, 6 which are preferably mounted thereto within the fiber deposition chute 12. This of course necessitates a corresponding adjustment of angular guides 7, 8, 9 and 10 and shroud 28 in order to maintain the tissue ply 20 in contact with the surfaces of triangles 2,4. The U-shaped shroud 28 illustrated in cross-section in Figure 3 is preferably employed in the practice of the present invention to avoid the collection of fibers on the uppermost surfaces of the wet strength tissue ply 20 prior to direction of the ply intermediate angular guides 9 and 10 located at the interior corners formed between isosceles triangle 4 and vertical planar member 3. This is necessary to avoid hangup or jamming of the ply within the relatively tight clearances provided intermediate the guides 9 and 10 and the interior corners formed by triangle 4 and vertical planar member 3. As will thus be apparent to those skilled in the art, the shroud 28 must also be adjustable such that adjustment of the triangle 4 in the machine direction will not result in exposure of the inverted U-shaped tissue ply 20 to the stream of fibers present in the leading portion 13 of fiber deposition chute 12. In a most preferred embodiment of the present invention, separating wall 19 in vacuum chamber 25 - is adjustable so as to vertically coincide with the position : ultimately assumed by isosceles triangle 4 within the deposition chute 12.
Figure 4 is a simplified perspective illustration of the embodiment of the present invention illustrated in Figures 1-3. Selected portions of the fiber deposition chute 12 have been broken away to illustrate with maximum clarity the present pad forming operation.
The geometry of the folding board 1 illustrated in Figures 1-4.is more clearly set forth in Figures 5-7. While it is not essential that the folding board 1 be comprised of solid sheet stock as illustrated in Figure 5, the folding board preferably comprises a pair of planar isoceles right triangles 2, 4 connected to one another by means of a vertical planar member 3 corresponding in height to the altitude of each isosceles triangle. In order to minimize the vertical height requirement for a folding board of the present invention, it is preferable that the centerline of the tissue ply 20 be made to coincide with the altitude of both triangles during its passage over the folding board. Thus, in the simple embodiment illustrated in Figure 4 the included right angle α of triangle 2 is surrounded by equal length legs 42, 43 while the included right angle α of identical triangle 4 is surrounded by equal length legs 45, 46. The base 44 of isosceles triangle 2 and the base 47 -of isosceles triangle 4 connect the respective equal length leg segments of the triangles. Lines 40 and 41 illustrated in Figure 5 represent the altitudes of right triangles 2 and 4, respectively. Thus, the angle β in each case amounts to 90 degrees, and the included right angle α of each triangle is bisected by its respective altitude. The angle between the altitude 40 of right triangle 2 and the base of vertical planar member 3 and the angle. δ between the altitude 41 of triangle 4 and the base of vertical planar member 3 in the illustrated embodiment are also equal to 90 degrees.
The principle upon which the folding board 1 illustrated in Figures 1-7 operates is that each point on the incoming ply 20 must travel the same linear distance in traversing the surface of the forming board from entry thereon near the base 44 of isosceles right triangle 2 until its exit therefrom near the base 47 of isosceles right triangle 4. The paths followed by a pair of corresponding points located on opposite sides of the ply centerline is represented by lines 48 and 49 in Figure 5. The principle is further illustrated in Figure 6 which is a'discharge end view of the folding board 1 illustrated in Figure 5. The sum of any given pair of lines An + B_n must be constant, where An is any line parallel to the altitude 41 of the triangle and B_n is the corresponding horizontal distance of the line A_n from the altitude 41.
As should be clear from Figure 7 which is a plan view of the folding board 1 illustrated in Figure 5; the lowermost layer of absorbent fibers 21 is formed while the ply 20 is.in the inverted U-configuration intermediate triangles 2, 4. As will be appreciated by those skilled in the art, it is desirable to minimize the width occupied by the ply 20 as it passes through the fiber deposition chute 12 in the inverted U-configuration in order to minimize any cross-machine direction non-uniformity in the lowermost airlaid web 21 formed adjacent its lowermost surface.
While it should be observed that the angle θ formed between triangle 2 and vertical planar member 3 and the angle φ formed between triangle 4 and vertical planar member 3 amounts to 90 degrees in the embodiment illustrated in Figures 1-7, it should be noted that the angles θ and φ need not equal one another, nor is it required that either angle be a right angle. The angle of infeed and outfeed of the tissue ply 20 may be varied as desired, provided only that the angles employed permit the tissue ply to be maintained in substantial surface contact with the triangles at'the inside corners formed between triangles 2, 4 and vertical planar member 3. It should further be noted that vertical planar member 3 is not an essential portion of the present folding board 1, but rather is employed in a preferred embodiment of the present invention as a means of securing the triangles in longitudinal alignment with one another, a feature which is critical to the practice of the present invention.
It is possible to substitute other suitable means of maintaining the tissue ply 20 in contact with the inside corners formed between triangles 2, 4 and vertical planar member 3 for the angular guides 7, 8, 9 and 10 illustrated in Figures 1 and 2. Thus, rods, rolls, or any other suitable mechanism may be employed, provided only that the overall distance traveled by any given point on the tissue-ply remain substantially constant across the width of the ply. In this regard, it should be noted that sharp edges are preferably removed from portions of the folding board 1 where stress concentrations are particularly high in order to avoid cutting or tearing of the tissue ply by the tensional forces to which it is subjected as it is drawn through the folding board. In this regard, a slight relief is preferably provided at the leading and trailing surfaces of the triangl 2, 4 at. their respective apexes. While this causes a very slight deviation in the theoretical constant length criteria described above, the practical and beneficial effect is to minimize the tendency of the ply 20 to rip or tear at points of stress concentration.
Figure 8 represents yet another particularly preferred eabodiment of a folding board 50 which may be employed in the practice of the present invention in a system similar to that illustrated in Figures 1 and 2. In the embodiment illustrated in Figure 8, a vertical support member 57 is joined to one of the equal length leg segments 58 of an isoceles right triangle 52 having its included right angle ψ located intermediate equal length legs 58, 56. The triangle 52 preferably forms an angle Ω of 90 degrees with vertical planar member 57. In practice, a ply of reinforcing tissue 20' having a width W' is fed in a vertical plane in a direction parallel to the direction of travel of the foraminous support member 11 illustrated in Figures 1 and 2. The incoming ply 20' is wrapped about leg 58 of the isoceles right triangle 52 such that it contacts the trailing surface of the triangle and its borders parallel the equal length leg 56. The ply 20' is thereafter directed about the hypotenuse 54 of the planar triangle 52 and dcwnwardly in a direction parallel to leg 58 while in contact with the leading surface of the triangle. The ply 20' is finally . directed about equal length leg 56 of the triangle and thereafter continues in a manner similar to that illustrated in Figures 1 and 2. The particular embodiment illustrated in Figure 8 offers the advantage that the tissue ply 20' does not require the use of any external guides to hold it is intimate contact with the surfaces of the isoceles right triangle 52, but rather is wrapped tightly thereabout by means of the tension employed to draw the ply through the folding board 50. Furthermore, there is no interruption of the fiber forming zone in the leading portion 13 of the. fiber deposition chute 12, since the vertical support member 57 may be located adjacent the edge of the fibrous web 21. Accordingly, it is feasible to obtain a uniform cross-machine direction basis weight and profile in the fibrous airfelt web 21 formed adjacent the lowermost surface of. the ply 20'. The embodiment illustrated in Figure 6 does, however, require greater overhead clearance at the fiber deposition chute 12 due to the fact that the ply 20' is not folded upon itself, as in the case of the embodiment illustrated in Figures 1-3.
In a particularly preferred embodiment of the present invention, the outermost tissue plies 23 and 24 illustrated in Figures 1 and 2 may be somewhat wider than the tissue ply 20 and the airfelt web portions 21 and 22. In such an embodiment the lateral edge portions of plies 23 and 24 may be secured to one another by folding, by adhesives, or by other means well known in the art to form a continuous encapsulating envelope. If desired, a continuous layer of moisture-pervious topsheet material may be secured in superposed relation to the continuous envelope. Absorbent pad segments of predetermined length are thereafter cut from the continuous envelope. The absorbent pad segments are preferably rotated 90° prior to securement to a continuous web of moisture-impervious backsheet material about their periphery to form a continuous web of disposable absorbent bandages, such as diapers. Individual diapers are thereafter cut from the continuous web intermediate the absorbent pad segments. U.S. Patent 3,952,745 issued to Duncan on April 27, 1976 and incorporated herein by reference is generally representative of such a construction. Aligning the machine direction of the tissue plies 20, 23 and 24 parallel to the waistband portions of the diaper in this manner is generally desirable since it aligns the tissue's direction of maximum strength with the direction in which the greatest tensile loads are typically applied in use.
It is noteworthy that the invention disclosed herein may be utilized to provide plies which are perforate or imperforate and which are either continuous or discontinuou in the cross machine_.direction intermediate a pair of fibrous webs in a single fiber deposition zone. Furthermore, multiple plies may be simultaneously fed utilizing an embodiment of the present invention, or multiple stages of the present invention may be employed to provide multiple reinforcing plies within a single structure, each ply being separated from the next by a fibrous layer. In addition, it should be noted that although in the embodiment illustrated in Figures 1-3 it is preferable to align the centerline of the ply 20 with the altitude of triangles 2, 4 to minimize overall height requirements in the deposition chute 12, the lateral positioning of the ply 20 may be altered as desired relative to the apex of the triangle and will maintain the selected position until manually reposLtioned. This is due to the fact that the laterally imposed forces introduced on the ply by the illustrated system remain in total balance with one another as the ply is tracked through the folding board. Thus, there is nothing to disturb the equilibrium established once the desired position of the web relative to the aL the triangle or triangles has been established.
While the present invention has been described in particular detail with reference to several preferred eabodiments, it is not intended to hereby limit to the particular embodiments shown and described. Many other variations of the present invention will be apparent to those skilled in the art.

Claims

1. A continuous, in-line mothed for forming an airlaid fibrous fluff web adjacent the uppermost and lowermost surfaces of a substantially planar rcinforoing·ply having substantially the same width as said fibrous web in a continuous fiber deposition zone, characterised in that it comprises the steps of:

(a) continuously feeding said substantially planar reinforcing ply in a.first direction in a first plane:

(b) introducing said moving reinforcing ply to a fiber deposition zone while oriented so that the direction of fiber flow is substantially parallel to the width of said ply to vacuum form the portion of said airlaid fibrous fluff web adjacent the lowermost surface of said reinforcing ply;

(c) guiding said moving reinforcing ply into contact with a first equal length leg portion of the trailirig surface of a planar isoceles right angled triangle, said first equal length leg portion being oriented perpendicular to said first direction of travel of said ply;

(d) wrapping said moving reinforcing ply about opposite surfaces of said planar right triangle by passing said ply about the hypotenuse thereof;

(e) restoring said moving ply to said first direction of travel by passing said moving ply about the second cqual length leg portion of said triangle, thereby causing said ply to assume a plmar condition in a second plane perpendicular to said first plane, said ply being posit ioned immedintely adjacent said first airlaid fibtons fluff web portion;

(f) exposing the uppermost surface of said moving reinforcing ply to said fiber deposition zone while in a planar condition to vacuum form the portion of said airlaid fibrous fluff web adjacent the uppermost surface of said reinforcing ply; and

(g) removing said ply and said airlaid web portions from said fiber deposition zone.

2. A method according to Claim 1 characterised in that said planar isosceles right angled triangle is located in a plane perpendicular to said first direction of travel of said substantially planar reinforcing ply and said ply to abruptly restored to said first direction of travel prior to exit thereof from said fiber deposition zone.

3. A method according to either one of Claims 1 and 2 characterised in that the relative thickness of the airlaid fibrous fluff web portions adjacent the uppermost and lowermost surfaces of said internal reinforcing ply is controlled by adjusting the machine direction position of said isosceles right angled triangle within said fiber deposition zone.

4. A method according to any one of Claims l.to 3 characterised in that a greater level of suction is applied to vacuum form the airlaid fibrous fluff web portion located adjacent the uppermost surface of said internal reinforcing ply than to vacuum form the air laid fibrous fluff web portion located adjacent the lowermost surface of said internal reinforcing ply to offset the added resistence to airflow created by said ply and said lowermost web portion.

5. ' A method according to anyone of Claims 1 to 4 characterised in that the airlaid fibrous fluff web portion located adjacent the lowermost surface of said internal reinforcing ply is vacuum formed directly over a second continuously moving tissue ply having a width at least as great as that of said internal reinforcing ply directly over the uppermost surface of the airlaid fibrous fluff web portion located adjacent the uppermost surface of said internal reinforcing ply upon exit thereof from said fiber deposition zone.

6. A method according to Claim 5 characterised in that said second and third tissue plies have a width greater than that of said internal reinforcing ply and the lateral edges of said second and third tissue plies are secured together by folding upon one another to form a continuous tissue envelope about the internal reinforcing ply and the uppermost and lowermost airlaid fibrous fluff web portions adjacent thereto.

7. A method according to Claim 6 characterised in that absorbent pad segments of predetermined length are cut from said continuous tissue envelope and thereafter secured intermediate a moisture-impervious backsheet and a moisture-pervious topsheet which are secured in superposed relation to one another, thereby forming a disposable absorbent bandage.

8. A continuous, in-line method for forming an airlaid fibrous fluff web adjacent the uppermost and lowermost surfaces of a substantially planar, fiber-impervious reinforcing ply having substantially the same width as said fibrous web in a continuous fiber deposition zone, said method comprising the steps of:

(a) continuously feeding said substantially planar reinforcing ply in a first direction in a first plane;

(b) guiding said moving reinforcing ply about a first direction changing means and into contact with the leading surface of a first planar isosceles triangle having an included angle of approximately 90 degrees at its apex, said triangle having its altitude oriented perpendicular to said first direction of travel of said ply;

(c) wrapping said moving reinforcing ply about opposite surfaces of said first planar triangle; -

(d) restoring said moving ply to its first direction of travel by directing said ply about the apex of said first triangle and the lateral edge portions of said moving ply in contact with the leading and trailing surfaces of said first triangle, thereby causing said ply to fold about itself in a second plane perpendicular to said first plane;

(e) introducing said moving reinforcing ply to said fiber deposition zone while in a folded configuration to vacuum form the portion of said airlaid fibrous fluff web adjacent the lowermost surface of said moving reinforcing ply in said first plane;

(f) wrapping said moving reinforcing ply about opposite surfaces of a second isosceles triangle identical to and longitudinally aligned with said first triangle and having its altitude oriented perpendicular to said first direction-of travel such that the lateral edges of said moving ply are guided on opposite sides of the apex of said second triangle as said moving ply is directed about the apex thereof, the lateral edges of said moving ply being maintained in contact with the leading and trailing surfaces of said second triangle, thereby restoring said ply to a planar condition;

(g) directing said moving reinforcing ply about a second direction changing means to restore it to said first direction of travel;

(h) exposing the uppermost surface of said moving reinforcing ply to said fiber deposition zone while in a planar condition to vacuum form the portion of said airlaid fibrous fluff web adjacent the uppermost surface of said reinforcing ply; and

(i) removing said ply from said fiber deposition zone.

9. The method of Claim 8, wherein the centerline of said moving reinforcing ply is caused to coincide with the altitidues of said first and said second isosceles triangles as said ply is drawn across the surfaces thereof, thereby causing said'ply to assume an inverted U-configuration about its centerline as it moves intermediate said first and said second triangles.

10. The method of Claim 8, wherein said first and second isosceles triangles are in parallel planes which are perpendicular to said first direction of travel of said substantially planar reinforcing ply, whereby said ply is restored to said first direction of travel prior to exit thereof from said fiber deposition zone.

11. The method of Claim 3, wherein the relative thickness of the airlaid fibrous.fluff web portions adjacent the uppermost and lowermost surfaces of said internal reinforcing ply is controlled by adjusting the machine direction position of said second isosceles triangle within said fiber deposition zone

12. The method of Claim 8 wherein a greater level of suction is applied to vacuum form the airlaid fibrous fluff web portion located adjacent the uppermost surface of said internal reinforcing ply than to vacuum form the airlaid fibrous fluff web portion located adjacent the lowermost surface of said internal reinforcing ply to offset the added resistance to airflow created by said ply and said lowermost web portion.

13. A continuous, in-line method for forming an . airlaid fibrous fluff web adjacent the uppermost and lowermost surfaces of a substantially planar, fiber-impervious reinforcing ply having substantially the same width as said fibrous web in a continuous fiber deposition zone, said method comprising the steps of:

(c) wrapping said moving rcinforcing ply about opposite surfaces of said first planar triangle such that the centcrline of said moving ply coincides with the altitude of said triangie along its leading surface;

.(d) restoring said ply to said first direction of travel by directing said ply about the apex of said first triangle while maintaining the lateral edge portions of said moving ply in contact with the leading and trailing surfaces of said first triangle, thereby causing said ply to assume an inverted U-shape about its centerline in a second . plane perpendicular to said first plane;

(e) introducing said moving reinforcing ply to said fiber deposition zone while in an inverted U-shape to vacuum form the portion of said airlaid fibrous fluff web adjacent the lowermost surface of said moving reinforcing ply directly on the surface of a second moving tissue ply having a width at least as great as said reinforcing ply;

(f) wrapping said moving reinforcing ply about opposite surfaces of a second isosceles triangle identical to and longitudinally aligned with said first triangle and having its altitude oriented perpendicular to said first direction of travel such that the centerline of said moving ply is caused to coincide with the altitude of said second triangle along its trailing surface and the lateral edges of said moving ply are maintained in contact with the leading and trailing surfaces of said second triangle, thereby restoring said ply to a planar condition;

(h) exposing the uppermost surface of said moving reinforcing ply to said fiber deposition zone while in a planar condition to vacuum form the portion of said airlaid fibrous fluff web adjacent the uppermost surface of said reinforcing ply;

(i) removing said ply and said airlaid web portions from said fiber deposition zone; and

(j) superposing a third tissue ply having a width at least as great as said reinforcing ply upon the uppermost portion of said airlaid web, thereby encapsulating said reinforcing ply and said airlaid web portions intermediate said second and third tissue plies.

14. The method of Claim 13, wherein said second and third tissue plies have a width greater than that of said internal reinforcing ply and the lateral edges of said second and third plies are secured together by folding upon one another to form a continuous tissue envelope about the internal reinforcing ply and the uppermost and lowermost airlaid fibrous fluff web portions adjacent thexreto.

15. The method of Claim 14, wherein absorbent pad segments of predetermined length are cut from said continuous tissue envelope and thereafter secured intermediate a moisture-impervious backsheet and a moisture-pervious topsheet which are secured in superposed relation to one another, thereby forming a disposable absorbent bandage.

16. An in-line fiber deposition apparatus for continuously vacuum forming an airlaid fibrous fluff web adjacent the uppermost and lowermost surfaces of a substantially planar internal reinforcing ply having substanially the same width as said web, said apparatus comprisirg:

(a) fiber disintegration means;

(b) a continuous fiber deposition chamber interconnected to said fiber disintegration means;

(c) a continuously moving foraminous support member passing through said deposition chamber in a plane substantially perpendicular to the direction of fiber flow;

(d) suction means located adjacent the surface of said foraminous support member opposite said fiber disintegration means;

(e) means for introducing said reinforcing ply to said deposition chamber in a first direction identical to that of said foraminous support member while said ply is oriented in a first plane such that its width .is substantially parallel to the direction of fiber flow within said chamber to facilitate vacuum forming the portion of said airlaid fibrous fluff web adjacent the lowermost surface of said reinforcing ply on said foraminous support member;

(f) guide means extending perpendicular to said first direction of travel within said fiber deposition chamber for abruptly reorienting said reinforcing ply to a second plane perpendicular to said first plane while restoring said ply to said first direction of travel to facilitate vacuum forming the portion of said airlaid fibrous fluff web adjacent the uppermost surface of said reinforcing ply; and

(g) means for removing said ply and said airlaid web portions from said fiber deposition chamber.

17. The apparatus of Claim 16, wherein said guide means for abruptly reorienting said reinforcing ply is comprised of a planar isosceles right triangle having one. of its.equal length leg portions oriented perpendicular to said first direction of travel of said reinforcing ply and the other of.its equal length leg portions in a second plane perpendicular to said first plane, said second plane being parallel to the plane of said foraminous support member.

18. The apparatus of Claim 16, wherein the position of said guide means for abruptly reorienting said reinforcing ply is adjustable in the machine direction within the fiber deposition chamber to vary the relative thickness of the uppermost and lowermost airfelt web portions.

19. The apparatus of Claim 16, wherein the suction means located adjacent the surface of said foraminous support member is comprised of a vacuum chamber having a length.at least equal to that of said fiber deposition chamber, said vacuum chamber having an internal partition member oriented perpendicular to the direction of travel of said.-ply, said partition member being adjustable in the machine direction to facilitate alignment thereof with said guide means for abruptly reorienting said reinforcing ply within said chamber and thereby facilitate the application of a higher level of suction during formation of the airlaid fibrous fluff web portion adjacent the uppermost surface of said reinforcing ply.

20. The apparatus of Claim 16, including means for feeding a second tissue ply having a width at least as great as said reinforcing ply into superposed relation with said foraminous support member prior to entry thereof into said fiber deposition chamber and means for feeding a third tissue ply having a width at least as great as said reinforcing ply into superposed relation with the uppermost surface of said uppermost airlaid fibrous fluff web portion upon exit thereof from said fiber deposition chamber.

21. An in-line fiber deposition apparatus for continuously vacuum forming an airlaid fibrous fluff web adjacent the uppermost and lowermost surfaces of a substantially planar reinforcing ply having substantially the same width as said web, said apparatus comprising:

(a) fiber disintegration means;

(e) means for continuously feeding said reinforcing ply in the same direction as said foraminous support member while oriented in a first plane parallel to that of said foraminous support member;

(f) first guide means extending in a direction perpendicular to said direction of travel for abruptly causing said reinforcing ply to invert and fold about itself in a second plane perpendicular to said first plane;

(g) means for introducing said reinforcing ply to said fiber deposition while in a folded configuration to facilitate vacuum forming the airlaid fibrous fluff web portion adjacent the lowermost surface of said reinforcing ply;

(h) second guide means extending perpendicular to the direction of travel of said reinforcing ply within said fiber deposition chamber for abruptly reorienting said ply from a folded configuration to a planar configuration in said first plane while restoring said ply to said first direction of travel to facilitate vacuum forming the portion of said airlaid fibrous fluff web adjacent the uppermost surface of said reinforcing ply; and

(i) means for removing said ply and said airlaid web portions from said fiber deposition chamber.

22. The apparatus of Claim 21, wherein said first and second guide means are comprised of identical planar isosceles triangles located in parallel planes and secured in longitudinal alignment with one another, said triangles having an included angle of approximately 90 degrees located at their apexes.

23. The apparatus of Claim 22, wherein said identical planar isosceles triangles are secured to one another by a planar member connecting their respective altitudes.

24. The apparatus of Claim 23, wherein said identical planar isosceles triangles and said connecting planar member are adjustable as a unit in the machine direction to vary the relative thickness of the uppermost and lowermost airlaid fibrous fluff web portions located on opposite surfaces of said reinforcing ply.