US3717905A

US3717905A - Air laying apparatus

Info

Publication number: US3717905A
Application number: US00174092A
Authority: US
Inventors: W Furbeck
Original assignee: International Paper Co
Current assignee: International Paper Co
Priority date: 1971-08-23
Filing date: 1971-08-23
Publication date: 1973-02-27
Anticipated expiration: 1990-02-27

Abstract

A stream of air carries loose fibers through enclosed ducts and deposits them in a series of equally spaced, substantially identical pads on a continuously moving web as it moves through a generally enclosed chamber. The web and now formed pads exit the chamber through an opening which is sealed by a unitary seal roll. The seal roll is provided with a circumferential cavity corresponding to the contour of the individual pads and is of a circumference equal to the distance between leading edges of successive pads. The seal roll is rotated at a tangential velocity equal to the linear velocity of the web moving under the roll so that a pad passing under the roll mates in the cavity in the roll surface thereby sealing against air leakage into the generally enclosed chamber and compacting the fibers of the pad in a controlled manner.

Description

[ 51 Feb. 27, 1973 AIR LAYING APPARATUS [75] Inventor: Warren R. Furbeck, Knoxville,

Tenn.

[73] Assignee: International Paper Comapny, New

York, N.Y.

[22] Filed: Aug. 23, 1971 [21] Appl. No.: 174,092

I A Related US. Application Data [63] Continuation-in-part of Ser. No. 26,002, April 6, 1970, abandoned, which is a continuation-in-part of Ser. No. 672,477, Oct. 3, 1967, Pat. No. 3,509,604.

[56] References Cited UNITED STATES PATENTS 3,518,726 Banks ..19/144.5

Primary ExaminerDorsey Newton Attorney-Fitch, Even, Tabin & Luedeka [57] ABSTRACT A stream of air carries loose fibers through enclosed ducts and deposits them in a series of equally spaced, substantially identical pads on a continuously moving web as it moves through a generally enclosed chamber. The web and now formed pads exit the chamber through an opening which is sealed by a unitary seal roll. The seal roll is provided with a circumferential cavity corresponding to the contour of the individual pads and is of a circumference equal to the distance between leading edges of successive pads. The seal roll is rotated at a tangential velocity equal to the linear velocity of the web moving under the roll so that a pad passing under the roll mates in the cavity in the roll surface thereby sealing against air leakage into the generally enclosed chamber and compacting the fibers of the pad in a controlled manner.

6 Claims, 8 Drawing Figures PATENTED FEB 2 7 I973 SHEET 1 OF 3 VACUUM INVENTOR Warren R. Furbeck PATENTED FEBZ 7 I975 SHEET 2 OF 3 INVENTOR Warren R. Furbe ck PATENIE mm mm SHEET 30F 3 FIG? INV'ENTOR Warren R. Furbe-ck 1 Ant LAYING APPARATUS This application is a continuation-in-part of copending application Ser. No. 26,002, filed Apr. 6, 1970 now abandoned, entitled Air Laying Apparatus, which in turn is a continuation-in-part of application Ser. No. 672,477, now U.S. Pat. No. 3,509,604 entitled Air Laying System Having a Seal Roll.

This invention relates to an air-laying system for producing a contoured web or pad from a quantity of loose fibrous'material and more particularly to an improved apparatus including a seal roll sealing against leakage of air thereby preventing an undesirable movement of fibers by the leaking air.

In an air-laying process, a stream of air carries fibers through suitable, enclosed ducts and deposits them on a continuously moving permeable web as it is carried through a generally enclosed forming chamber. The

fibers are filtered from the air stream by the web and may be formed by appropriate methods into a predetermined contour on the traveling web. In one example, a

I diaper pad may be formed by impinging a stream of airborne fibers of wood pulp onto a continuous web of creped tissue moved in a horizontal path beneath a forming chamber. The web is moved into and out of the chamber through slots or openings in opposite walls of the chamber, the sealing of at least one of such openings being an objective in the present invention. Flow of air for carrying the fibersmay be established by appropriate blowers disposed upstream of the web or by suction devices disposed downstream of the web or by a combination of these. In either event, the stream of air and fibers impinges upon the web and the fibers are filtered from the air stream as the air passes through the permeable web. The filtered fibers are retained on the web in the form of a mat or pad of loose fibers. The web preferably is disposed horizontally; the pad also lying in a-horizontal plane.

Because creped tissue and other webs frequently cannot withstand the pressure exerted thereagainst by the impinging flow of air and fibers, such webs are usually supported from beneath by a permeable carrier. Through either partially or completely'blocking the permeability of portions of such carrier, it ispossible to control the peripheral outline of the pad and to also control the thickness of the pad over one or several areas thereof.

U.S. Pat. No. 3,509,604, issued May 5, 1970 to Furbeck and U.S. Pat. No. 3,501,813, issued Mar. 24, 1970 to Lee et al., describe a process in which fibers of wood pulp are laid on a web formed by a continuous web of creped tissue as part of a process of fabricating a disposable diaper pad which has a central portion thicker than adjacent flanking or side portions. U.S. Pat. No. 3,501,813 describes three separate rolls, one for eachof the respective flanking portions and one for the central portion of the pad, extended to the fibrous pad and slightly compacted the pad traveling beneath I the respective rolls. All of these three rolls were the same diameter and separately driven at the same speed providing a tangential velocity equal to the linear velocity of the pad and the carrier. Although the adjacentends of the respective rolls were disposed close to one another, air leaked between them. Also, fibers were pinched between the adjacent roll ends and began to gather in the space between the roll ends. This impeded the free turning of the rolls. Eventually these fibers accumulated tothe point where it was necessary to remove them.

The seal roll described in U.S. Pat. No. 3,509,604, comprises a unitary roll having selected circumferential grooves conforming to the contour of the pad passing beneath the roll. The mating relation between the pad and roll contours effects a seal against air flow therebetween. Appropriate end seals are provided to preclude air leakage in theareas of the roll ends where they are joined to the enclosed forming chamber. Since the grooves in the roll extend uniformly and continuously around the entire circumference of the roll, it is possible to also seal against air leakage at the top of the roll by disposing an appropriately contoured doctor blade contiguous to the top of the roll, such doctor blade being sealably joined to the enclosed forming chamber. In this manner, the moving web carrier can pass into or out of the enclosed forming chamber through openings in the chamber without air leakage, such leakage being precluded by the sealing relationship between the roll, the web, the pad, if any, on the web and chamber itself;

In a disposable diaper pad, relatively large quantities of fluid must be quickly distributed and absorbedto prevent flooding and leaking from the diaper. To

achieve maximum absorption and distribution in an inand other prior art known to the present inventor provide suitable sealing in those instances where the moving pad is continuous and uninterrupted along its length and of constant width. No known provision has been made in seal rolls for nonuniform width in the pad, nor for interruptions in the length of the pad.

It is therefore a general object of the present invention to provide an improved air-laying apparatus for continuously forming a series of fibrous pads each having a predetermined shape. It is another object to provide an air-laying apparatus for continuously forming a series of fibrous pads of nonuniform width. It is another object to provide a novel construction for a seal roll.

Other objects and advantages of the invention will become apparent from the detailed description taken in connection with the accompanying drawings in which:

FIG. 1 is a representation of an air-laying apparatus depicting various novel features of this invention;

FIG. 2 is an elevational view of an air-laying apparatus embodying various novel features of the present invention;

FIG. 3 is an enlarged, elevational and fragmentary view of the seal roll shown in FIGS. 1 and 2;

FIG. 4 is a fragmentary sectional view taken substantially along the line 4-4 of FIG. 3;.

FIG. 5 is a fragmentary, partially sectioned view of a seal roll constructed in accordance with another emfor sealing the top of the seal roll;

FIG. 6 is a fragmentary view of a further embodiment for sealing the top of the seal roll;

FIG. 7 is a view of the fibrous pad made by the apparatus of FIG. 1; and

FIG. 8 is an enlarged fragmentary view of a further embodiment of the seal roll shown in FIGS. 1 and 2 and depicting multiple circumferential cavities on the seal roll.

As shown in the drawings for purposes of illustration, the invention'is embodied in an air-laying apparatus 11 (FIG. 1) which forms a series of pads 13 (FIGS. 1 and 7) of a predetermined shape from loose fibrous material such as wood pulp fibers. In this instance, each of the fibrous pads is formed with an hour-glass perimeter. In one diaper of 17 inches length, the wide end portions 15 may be l4 inches in width and the necked portion 14 may be 5 inches in width. The thickness of the pad may be uniformly about one-half inch. The present invention, however, is not limited to any particular size of diaper or pad perimeter or thickness as the dimensions, perimeter, or thickness may vary with different embodiments of the invention, except, however, the present invention is directed toward pads, .each of which is of uniform length and may also be nonuniform in width or thickness.

Very generally, the illustrated apparatus employs an air-laying unit 11 (FIGS. 1 and 2) which forms the fibrous pads 13. In this instance, a creped tissue web 16 is continuously dispensed from a roll 17 and fed through an enclosed chamber 18 through openings in the

chamber walls

19, 20. The opening in chamber wall 19 serves as an entrance for the web and a carrier 33 into the chamber. This opening may be rectangular and made sufficiently small as will permit the web and its carrierto pass therethrough but will not permit sufficient air leakage to disrupt the pad forming operation within the chamber. If desired, flexible skirts (not shown) may be provided around the periphery ofthis entrance toincrease the seal against air leakage. Within the chamber 18, fibers are deposited upon the web to produce a series of pads 13 upon the moving web. The present invention is concerned with the production of several individual pads separated one from another along the length of the web by a preselected constant distance. The pads are to be substantially identical. Their width may be constant or it may vary along the pad length as is depicted by the hour-glass" pad 13 shown in FIGS. 1 and 7.

The air-laying unit 11 is provided with a shredder 23 connected by a duct 27 to a refiner mill 25 which combines its action with that of the shredder to defibrate felted webs of wood pulp (not shown) into individual fibers or as close thereto as possible. The individual fibers are carried by an air stream down through a duct 28 to the upper endof an enclosed, forming chamber 18 through which travels a web 16 of creped tissue on an endless meshed belt carrier 33. A vacuum box 35 is disposed beneath the upper run of the carrier 33 and is connected in a suitable manner to a vacuum source to pull the air through the creped tissue web and the meshed belt. The fibers in the air stream are filtered onto the upper surface of the creped tissue web 16 as the air passes through the web and carrier and into the 'vacuum boxes. Portions of the openings through the meshed belt 33 are blocked, as indicated at 24 in FIG. 1, to limit air flow through the belt to those areas of the belt where the openings 26 are left unblocked. As the belt moves through the forming chamber 18, air flows out of the chamber through the tissue web 16 and the belt 33 through the unblocked openings so that fibers are filtered onto the web 16 in those areas of the web which overlie the unblocked openings 26 in the meshed belt. The shape of each pad of collected fibers as well as the distance between succeeding pads is thus determined by selectively blocking certain of the openings in the belt. The web and pad move longitudinally from right to left (FIG. 1) through suitable slots, such as the slot 32 (FIG. 3) in each of the end walls of the enclosed chamber 18. Slot 32 is sealed by a suitable seal roll 37 having a formed surface as will be described in detail.

The present invention is of particular utility in producing air-laid, wood pulp fiber pads which have a controlled density and cross-sectional thickness so as to provide a lightweight, soft and highly absorbent pad. If the fibrous material is too heavily compacted, the pad will not quickly absorb fluids and distribute them with the result that the pad and the diaper may be overloaded with fluid which will leak or strike through the pad. Also, desirably the. fibers are concentrated in those areas where they are most effective in distributing and absorbing body exudates. If the pad has portions which are thicker or wider than that required, an excess of fibers is provided beyond that needed for absorbency and this results in an unnecessary increase in cost of the pad. Hence, a controlled cross-sectional thickness and density is desired.

In accordance with the present invention, the air-laying apparatus is provided with an apparatus which provides a controlled thickness and compaction for the pad by serving as a revolving female die into which the pad is fitted as it exits the forming chamber. Such apparatus further seals the slot in the chamber wall through which the formed pads leave the air-laying unit 11. To limit the amount of compacting, the seal roll may be lifted as by springs or air cylinders. To assist pad formation and seal the exit slot, the seal roll is provided with a circumferential cavity corresponding to the contour of a pad. In a preferred embodiment, it further is of a circumference equal to the distance between the leading edges of successive pads and is rotated at a tangential velocity equal to the linear velocity of the continuously moving web passing beneath the roll and carrying successive pads under the roll and away from the air-laying unit. The roll also is rotated in registry with the progressing pads so that each successive pad mates with the circumferential cavity of the roll as the pad passes under the roll.

Proceeding now with a more detailed description of the invention and with particular reference to FIGS. 2 and 3, the forming unit 11 is supported by a main frame 39 with the shredder 23 disposed on upper beams and over the refiner 25. A felted wood pulp (not shown) of a predetermined moisture content is fed to the shredder 23 which chops the webs into postage-stamp size pieces which are then fed through a vertically disposed duct 27 leading down to the. refiner mill 25 which then grinds, breaks, or separates the pieces into individual wood pulp fibers or as close thereto as possible. A stream of moving air carries the fibers through a duct 28 and into the interior of the generally boxedshaped, enclosed chamber 18. The latter is generally hollow with an open, lower end disposed across and closely adjacent to the creped tissue web 16 and carrier 33 which pass through inlet and outlet slots 32 formed in the respective vertical end walls 19, 20 (FIG.3) of the chamber. The slot 32 extends considerably above the web 16 and its upper edge is defined by a wall 44 (FIG. 3). Each of the chamber side walls is sealed and connected toa vacuum box 35 below. The vacuum box 35 is a duct connected to a suitable source of suction (not shown). Preferably, the vacuum box 35 is formed by a vertical sidewall 46 (FIG. 3) defining a box-like chamber beneath the forming chamber 18. At the top of the vacuum box is a carrier support 48 in the from of an expanded metal screen having very wide openings to allow the air to pass easily without disturbing the fiber deposition of the web. As noted hereinbefore, selected ones of the openings through the thickness of the metal screen are blocked to define shaped areas through which the air flows out of the chamber. Such blocking is accomplished by any suitable means such as overlaying a blind belt over the screen with the blind belt having spaced apart, appropriately contoured openings cut therein. The screen openings alternatively may be blocked by plugging selected openings with a resin or latex. The seal roll is aligned over the end wall 46 of the vacuum chamber to provide a better sealing action with 1 the vacuum chamber and with the supported pad disposed on and supported by the wall 46 at the sealing roll.

The entrained fibers are filtered by the creped tissue web 16 from the air moving into the vacuum boxes. The web 16 is drawn from a large supply roll 17 and is disposed over the upper surface of the top run of the endless carrier belt 33 and moves with the latter through the chamber and then leaves the carrier to move to the next station (not shown) for further processing in forming the disposable diapers. In this instance, the web 16 is approximately 14 inches in width and the endless mesh belt 33 is of substantially equal width. The belt 33 is trained about a drive roll 49 rotatable about a generally horizontal axis and driven by a chain 51 extending to a gear unit 53 which in turn is driven by a drive shaftof the diaper-making machine (which is not shown). The mesh belt 33 extends from the drive roll 49 to an idler roll 55 and the upper run of the belt is disposed in a generally horizontal plane for travel through the air-laying unit. A pair of belt tension rolls 57 hold the endless carrier belt 33 at the proper tension. Fibers commence collecting on the web 16 as each portion of the screen having unblocked openings enters the chamber 18 underneath the continuously moving web'. As the web and carrier move together through the chamber, more fibers are collected on the web to form a pad of the desired thickness. Upon the web and screen leaving the chamber, the web carries the pad forward for further processing and the screen passes through a lower run and returns to the chamber entrance.

To seal slot 32 against the entry of air into the chamber, which is .below atmospheric pressure, an outlet seal roll is provided for the enclosed chamber 18. As best seen in FIGS- 3 and 4, seal roll 37 is mounted for rotation by stub shafts 61 disposed in a pair of bearings 63 carried by support arms 65. The rotational axis of the seal roll is disposed generally horizontally above and parallel to the web 16 and is disposed normal to the path of the web travel.

Adjacent the respective ends of the seal roll 37 are end seals 69 (FIGS. 3 and 4) of generally L-shaped configuration each with a vertically extending leg 70 fastened to the housing wall 20 adjacent the vertical sides of slot 32. The end seals 69 project outwardly from the housing wall20 to positions closely adjacent the radial end walls of theseal roll 37. Extending across the top of the seal roll 37 is a resilient roll 71. The resilient roll extends outwardly from the wall 20 into rolling engagement with the surface of the rotating seal roll and is fixedly biased against the seal roll so as to force a portion of the resilient roll into the circumferential cavity formed in the seal roll. The top of the resilient roll' 71 may be sealed against air flow into the forming chamber by a doctor blade or skirt, preferably flexible to accommodate vertical movement of roll 71, sealably joined to the chamber wall 20 and in sliding contact with the top of roll 71. Thus, the resilient roll and the end seals prevent sideways and overhead entrance of air or the loss of fibers from the slot 32. Because the lower surface of the roll 37 is in contact with the pad and web, it alleviates the loss of air pressure at the interface of the seal roll and the pad reduces any inward flow of ambient air to a volume and flow rate which will not disturb the velocity profile of the air stream within the forming chamber 18. That is, a large leakage of ambient air beneath the seal roll and into the chamber could roll fibers from the pad back into the chamber and also disrupt the air stream profile within the chamber and thereby disrupt the pad contour.

I In the preferred embodiment of the invention, the seal roll also functions as a web feeding roll in that the web 16 is gripped in the nip between the seal roll and the belt 33 and they combine to strip the web from its supply roll 17 and pull the web through the air-laying unit. To feed the creped tissue web 31 without wrinkling or tearing, the seal roll may be formed with a resilient layer 77 (FIG. 5) for pressing against the web 16 and belt 33. More specifically, the seal roll may have a layer of rubber one-eighth inch thick' fixed about a cylindrical metallic sleeve 78 for the seal roll.

The axial end portions of the seal roll are of equal diameter and are rotated at the same peripheral speed to feed the web 16. To rotate the roll 37, there is provided a drive train which includes a sprocket 79 (FIG. 4) fixed to stub shaft 61 and a driving chain 81 extending from the sprocket 79 to another sprocket 83 fixed to a support shaft 85 journaled in bearings 87 (FIG. 4) on the lower end of vertical frame member 89. The free end of support shaft 85 is provided with a worm gear 91' which is meshed with a suitable gear 93 carried on a horizontal drive shaft 95 extending longitudinally of the carrier 16. The shaft 95 is connected to and driven by a gear box 96 (FIG. 2) driven by a chain 97 extending to the drive sprocket for the carrier drive roll 49. Because the carrier 33 and the seal roll 37 are both driven by the gear unit 53, the speed of the carrier may be correlated with the rotational speed of the seal roll such that the tangential velocity of the seal roll engaging the web 16 matches the linear velocity of the carrier 33, hence the linear velocity of web 13.

In accordance with the preferred embodiment of the invention, the seal roll 37 is in the: form of a unitary roll having a circumferential cavity of about one-half inch uniform depth and an arcuate length equal to the linear dimension of the pad 13. A land 22 on the roll circumference defines the beginning and end of cavity 21. The arcuate length of this land corresponds to the linear spacing between successive pads 13 deposited on the web 16 so that as the seal roll is rotated at a tangential velocity equal to the linear velocity of the web 16 and in registry with the pads passing beneath the seal roll, one pad passes beneath the seal roll per each rotation of the roll, such pad mating with the cavity 21 inthe roll.

It has been found that the cavity 21 in the roll surface is particularly effective in shaping the pad fibers and establishing a controlled thickness. The slight compaction of the fibers by the roll assures a smoother upper surface and enhances the coherence of the fibrous pad which is of primary importance to the absorption characteristic of the pad and also of importance in providing a diaper which does not deposit fibrous matter upon the body of an infant.

In this instance, the pressure of the seal roll on the pad is regulated by biasing means which are in the form of individual attached scales 107 such as the common grocery scales comprising an elongated housing encasing an internal spring having an external load indicator means. The scales are fastened at their lower ends to the pivotally mounted bracket arms 65 for the seal rolls and attached at upper ends to a horizontally disposed, stationary frame member 108 (FIG. 2). The scales are adjustably mounted so that the force with which the roll engages the pad can be limited to a predetermined portion of the weight of the roll 37 and its pivot arm 65. In the preferred embodiment of the invention,,the seal roll applies a light even pressure to the pad 13 just sufficient to embed the pad in the roll cavity, therebystopping any large volume of ambient air from moving under the roll and imparting the desired degree of compaction to the pad.

To prevent pickup of fibers on the seal roll from the fibrous pad, the roll may have an outer layer of plastic material disposed on the resilient layer 77. A film of 0.0005 inch of polytetrafluoroethylene as sold under the trademark Teflon has been applied to the outer surface of the roll and has worked satisfactorily.

To control the amount of pressure exerted by the roll on the pad and thereby the amount of fiber compaction by seal roll 37, the seal roll is pivotally mounted for pivoting about a support shaft 85 and is lifted upwardly by an associated spring scale 107. The latter lifts a predetermined portion of the weight of the roll so that the roll engages the pad with a light yet predetermined force.

It will be appreciated that the seal roll may be provided also at the entrance opening of chamber 18. Because this entrance seal roll seals against the web 16 only, it is not provided with a cavity and has an uninterrupted cylindrical surface and a uniform diameter across its full length.

As an aid to understanding the invention, a brief description of the operation of the invention is provided. The creped tissue web 16 is disposed in the nip between the seal roll 37 and the upper surface of the continuous carrier 33. The seal roll engages the outer side edges of the creped tissue web and as the roll rotates, it and the carrier 33 strip the web from the supply roll 17.

As the web 16 passes through the unit 11, air-borne fibers move through the duct 27 into the enclosed chamber 29 and deposit on the web to form a pad of fibers. The air stream carrying the fibers moves through the web 16 and the meshed carrier 33 into the vacuum box 35 beneath the web and carrier.

The seal roll 37 is driven by shaft which, in turn, is driven by the drive 53 for the carrier 33 so that the seal roll portions engaging the web 16 have a tangential speed equal to the linear speed of the carrier 33.

The seal roll extends into engagement with the fibrous pad 13 on the web 16 to provide a lower seal preventing the loss of air pressure and fibers along the carrier and web from the slot 32 in the housing 29. At the opposite ends of the seal roll, end seals 69 are fixed to the enclosing chamber wall 20 and extend to the radial end faces of the roll. The slot 32 is further sealed at the top of the roll by the resilient roll 71 engaging the seal roll 37. The top of the resilient roll 71 is sealed by a doctor blade 68, preferably flexible, sealably joined to the wall 20 and extending outwardly from the wall to contact the resilient roll 71.

Best results are obtained by the direct positive driving rotation of the seal roll 37 by the shaft 95. Less satisfactory, but adequate results have been obtained without using such a positive drive. For instance, the seal roll may be rotated solely by the carrier 33 against which the roll is biased. Thus, the roll will, except for any slippage, have a tangential velocity equal to the linear velocity of the carrier 33.

From the foregoing it will be seen that the airlaying apparatus provides a pad with an improved outer surface, a controlled cross-sectional thickness, and a controlled degree of compaction. Also, the seal roll construction may be greatly simplified and easily driven through a simple driving arrangement. Although the seal roll 37 is shown and described in connection with a single air-laying unit, it will be appreciated that this roll could be also employed in a tandem air-laying apparatus where the pad is formed by sequential air-laying operations performed by a pair of tandem units rather than by a single unit.

Because the circumference of roll 37 is provided with both a cavity and a land, it will be recognized that the top of the roll cannot be sealed by a rigid member having a leading edge contoured to sealably engage the rotating seal roll. Accordingly, in the present invention, the top of the roll preferably is sealed by a further roll 71 formed of a resilient material or having a resilient surface coating or layer. This latter roll is rotatably mounted adjacent the uppermost portion of the slot 32 and with its axis of rotation parallel to the rotational axis of the seal roll 37. The resilient roll 71 is fixedly biased against the seal roll and rotated therewith conveniently by frictional engagement between the rolls. As the rolls rotate together, the resilient surface of roll 71 expands into the cavity 21 in the circumference of the seal roll and yields to accommodate the land 22 as well as the end portions of the seal roll surface, thus maintaining continuous sealing engagement with the rotating seal roll along a line extending between the opposite ends of the seal roll 37. The opposite ends of the resilient rolls are sealed by plates 63 as described for sealing the ends of the seal roll 37. The top portion of this resilient roll 71 is sealed against air flow into the forming chamber by means of a doctor blade 68, sealably joined to chamber wall 20 and extending outwardly therefrom to engage the top of the roll 71 in sliding and sealing contact. Preferably, the doctor blade 68 is flexible so as to accommodate slight vertical movements of the seal roll 37 as discussed hereinbefore.

In a further embodiment (FIG. 6) for sealing the top of the seal roll 37, there is provided an elongated plate 30 secured to the wall 20 of the chamber 18 and having a plurality of fingers 31, which are preferably flexible,

depending from its leading edge to slide over the outer surface of the rotating seal roll. These fingers are spaced very close to one another along the edge of the plate so as to prevent air flow between fingers. As the seal roll rotates, individual ones of these fingers may fall into the cavity 21 in the seal roll surface due to gravitational pull or be forced therein by biasing means (not shown). In either event, the fingers slide upon the seal roll surface, either in or out of the cavity as the case may be, and seal against air leakage into the chamber 18 through the slot 32.

It will be appreciated that the seal roll may be provided with two or more circumferential cavities as distinguished from a single cavity. A sea] roll 37 having multiple cavities 21a and 21b is shown in FIG. 8. A multiple-cavity seal roll may possess a circumference equal to the linear distance between the leading edges of successive pads passing beneath the rotated roll and be rotated at an appropriate tangential velocity as will cause successive pads to mate with successive cavities in the seal roll. For example, for a given linear velocity of pads passing beneath the seal roll, a three-cavity roll having a circumference equal to the linear distance between the leading edges of successive pads may be rotated with a tangential velocity one-third of that of a single-cavity seal roll having the same diameter. Alternatively, a three-cavity seal roll could be made with a circumference three times the linear distance between the leading edges of successive pads and be rotated with a tangential velocity equal to that of a single-cavity seal roll having a circumference equal to the linear distance between the leading edges of successive pads, assuming a given linear velocity of the pads.

While a preferred embodiment has been shown and described, it will be understood that there is no intent to limit the invention by such disclosure but, rather, it is intended to cover all modifications and alternative constructions falling within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. in an apparatus for continuously air laying a series of substantially identical fibrous pads each of uniform length spaced one from another a preselected constant distance on a moving carrier, said apparatus including at least one chamber in which fibers are carried by an air stream and are deposited on said carrier, said chamber having an opening through which said carrier and pads leave said chamber, the improvement com prising a unitary seal roll mounted for rotation about an axis disposed transversely of the movement of said pads and disposed to seal said opening by engaging successive ones of said ads and closing said opening at least one crrcumferen ral cavity in said roll extending less than completely around the roll circumference which when laid flat corresponds to the contour of individual ones of said pads, at least one land on the circumference of said roll defining the beginning and end of said cavity, and means for rotating said roll about its axis at a tangential velocity relative to the linear velocity of said pads on said carrier whereby said cavity is in registry with successive forwardly moving pads and successive pads mate with and enter said cavity as said roll is rotated and said pads are moved forwardly.

2. The apparatus of claim 1 wherein the circumference of said seal roll equals the linear distance between the leading edges of successive pads on said carrier and the tangential velocity of said seal roll equals the linear velocity of said pads on said carrier.

3. The apparatus of claim 1 wherein said seal roll includes multiple substantially identical circumferential cavities separated by substantially identical lands on the circumference of said roll.

4. The apparatus of claim 1 wherein said circumferential cavity of said seal roll is of nonuniform width.

5. The apparatus of claim 1 and including elongated resilient sealing means having its longitudinal axis parallel to said seal roll axis and disposed contiguous to and in sealing engagement with said seal roll in a region of said seal roll other than the region where said seal roll sealably contacts said pads to preclude air leakage between said seal roll and said chamber in such other region.

6. The apparatus of claim 5 wherein said elongated resilient sealing means comprises a. roll having at least a resilient surface and disposed in rolling contact with said seal roll.

Claims

1. In an apparatus for continuously air laying a series of substantially identical fibrous pads each of uniform length spaced one from another a preselected constant distance on a moving cArrier, said apparatus including at least one chamber in which fibers are carried by an air stream and are deposited on said carrier, said chamber having an opening through which said carrier and pads leave said chamber, the improvement comprising a unitary seal roll mounted for rotation about an axis disposed transversely of the movement of said pads and disposed to seal said opening by engaging successive ones of said pads and closing said opening, at least one circumferential cavity in said roll extending less than completely around the roll circumference which when laid flat corresponds to the contour of individual ones of said pads, at least one land on the circumference of said roll defining the beginning and end of said cavity, and means for rotating said roll about its axis at a tangential velocity relative to the linear velocity of said pads on said carrier whereby said cavity is in registry with successive forwardly moving pads and successive pads mate with and enter said cavity as said roll is rotated and said pads are moved forwardly.

6. The apparatus of claim 5 wherein said elongated resilient sealing means comprises a roll having at least a resilient surface and disposed in rolling contact with said seal roll.