US3509604A

US3509604A - Air laying system having a seal roll

Info

Publication number: US3509604A
Application number: US672477A
Authority: US
Inventors: Warren R Furbeck
Original assignee: International Paper Co
Current assignee: International Paper Co
Priority date: 1967-10-03
Filing date: 1967-10-03
Publication date: 1970-05-05
Anticipated expiration: 1987-05-05

Description

May 5, 1970 w. R. FURBECK AIR LAYING SYSTEM HAVING A SEAL ROLL 2 Sheets-Sheet 1 Filed Oct. 5; 1967 lNVENTOIZ v WW7? 2 I a/666% BY WW W dik, ATTvs.

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l l l |L| I. I. llrlllllllllmlll United States Patent 3,509,604 AIR LAYING SYSTEM HAVING A SEAL ROLL Warren R. Furbeck, Knoxville, Tenn., assignor, by mesne assignments, to International Paper Company, New York, N.Y., a corporation of New York Filed Oct. 3, 1967, Ser. No. 672,477 Int. Cl. D0lg 25/00 US. Cl. 19--156.3 7 Claims ABSTRACT OF THE DISCLOSURE A stream of air carries loose fibers through enclosed ducts and deposits them on a continuously moving carrier as it moves through a generally enclosed chamber. The carrier and now formed fibrous pad exit the chamber through an opening which is sealed by a unitary seal roll. The seal roll is provided with a groove corresponding to the contour of the pad and is slightly embedded in the pad to seal against air leakage which would cause an undesirable movement of the fibers in the chamber. The seal roll is rotated so that its walls defining the groove have a tangential velocity which differs from the linear velocity of the pad and carrier whereby the fibrous surface of the pad is brushed and worked by the 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 for working the fibrous material while 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 carrier as it travels through a generally enclosed} forming chamber. The fibers are filtered from the air stream by the carrier and may be formed by appropriate methods into a predetermined contour on the traveling carrier. For example, in copending application S.N. 507,089, entitled Forming Apparatus, a process is described in which fibers of wood pulp are laid on a carrier 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. Three separate seal rolls, one for each of the respective flanking portions and one for the central portion of the pad, extended to the fibrous pad and slightly comp-acted the pad traveling beneath the respective rolls. All of these three rolls were of 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 adjacent ends 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 to the point where it was necessary to remove them.

In a disposable diaper pad, relatively large quantities of fluid must be quickly absorbed and distributed to prevent flooding and leaking from the diaper. To achieve maximum absorption and distribution in an inexpensive manner, the air-laid pads are formed with a predetermined contour, a uniform cross-sectional thickness and a predetermined fiber compaction. Under the present invention, the air-laying apparatus forms a pad with such qualities and includes a novel seal roll construction which engages the pad with a light pressure and which gently screeds the fibers to provide a uniform cross-sectional thickness at least over the thicker and more absorptive part ice of the pad. The seal roll gently combs the fibers at the surface of the pad to provide a relatively smooth outer surface on the pad. The seal roll, as its name implies, performs the function of sealing the apparatus against air leakage and thereby prevents a resulting deleterious movement of fibers by ambient air rushing into the forming chamber. The invention also provides a much simpler construction of seal roll and the drive therefor, using but a unitary seal roll to provide the sealing previously requiring three rolls.

Accordingly, a general object of the invention is to provide an improved air-laying apparatus for forming a fibrous web having a controlled density and shape.

Another object of the invention is provide a simpler and more economical construction for a seal roll and the drive therefor.

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

FIGURE 1 is an elevational view of an air-laying apparatus embodying the novel features of the present invention;

FIGURE 2 is an enlarged, fragmentary view of a seal roll shown in FIGURE 1;

FIGURE 3 is a fragmentary sectional view taken substantially along the line 33 of FIGURE 2;

FIGURE 4 is a fragmentary, partially sectioned view of a seal roll constructed in accordance with another embident of the invention; and

FIGURE 5 is a transverse, cross-sectional view of the fibrous pad made by the apparatus of FIGURE 1.

As shown in the drawings for purposes of illustration, the invention is embodied in an air-laying apparatus 11 which forms a continuous web or pad 13 (FIGURE 5) of a predetermined shape from loose fibrous material such as wood pulp fibers. In this instance, the fibrous pad is formed with a central longitudinally extending portion 15 which is thicker than adjacent, longitudinally extending flanking or side portions 17. In a typical diaper, the central wide portion 15 may be 3 inches in width and about A inch in depth while the overall width of the pad is approximately 14 inches. The depth of the side portions is about A: of an inch. The present invention, however, is not limited to any particular size or contour of pad as the dimension and contours may vary with different embodiments of the invention.

Very generally, the illustrated apparatus employs a pair of air-laying units 19 and 21 (FIGURE 1) each of which forms a part of the fibrous pad 13. In this instance, the first unit 19 deposits a narrow 3 inch strip of fibrous material slightly more than of an inch in depth and the second unit 21 overlays on this strip a 14 inch wide layer of fibers slightly more than A; of an inch in depth. After passing the second unit 21, the small, thick central portion 15 is about inch deep and the wide, thin flanking side portions 17 are about /3 inch deep as the pad leaves the outlet end (the right hand side in FIGURE 1) 0f the airlaying apparatus 11.

Each of the

tandem units

19 and 21 is generally the same except for its seal rolls, as will be explained later. Thus, each unit is provided With a shredder 23 and connected refiner mill 25 which defibrate felted webs of wood pulp (not shown) into individual fibers or as close thereto as possible. The individual fibers are carried by an airstream down through a duct 27 to the upper end of an enclosed, forming chamber 29 through which travels a web 31 of creped tissue on an endless meshed belt carrier 33. Vacuum boxes 35 are disposed beneath the upper runs of the carrier 33 and are 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 31 as the air passes through the web and into the vacuum boxes. The web and pad move longitudinally from left to right (FIGURE 1) through suitable slots, such as the slot 32 (FIGURE 2) in each of the end walls of the enclosed chamber 29. These slots are sealed by

suitable seal rolls

37a, 37b, 37c and 37d, which may have different contours as will be described in detail.

The present invention is of particular utility in producing air-laid, wood pulp fiber pads which have a substan' tially uniform density and cross-sectional thickness in each of several portions and 17 so as to provide a lightweight, soft and highly absorbent pad. If the fibrous mate rial 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, if some of the portions 15 or 17 are formed with less than the prescribed cross-sectional thickness, there may not be enough fibers to absorb and distribute the fluid being received by the diaper. On the other hand, if the pad has portions which are thicker 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 uniform cross-sectional thickness and density is desired within the respective center and flanking portions 15 and 17 of the pad.

In accordance with the present invention, the air-laying apparatus is provided with an apparatus which provides a more uniform thickness for the pad, particularly at the thicker portion of the pad, by gently screeding the fibrous pad as it leaves the seal roll 37d at the outlet end of the forming unit 21. To limit the amount of compacting, the seal roll is lifted by springs. To screed the pad, the portions of the seal rolls engaging the pad have a tangential velocity which is less than the linear speed of the pad whereby the roll exerts a retarding force on the fibers it engages and causes a gently combing or brushing of the top of the pad. As a result, fibers at the high points and the thicker areas of the pad are redistributed to lower points in the pad and a smoother surface is obtained. As will be explained in greater detail, another feature of the invention is a simplified, unitary seal roll and a drive for the roll.

Proceeding now with a more detailed description of the invention, the

tandem forming units

19 and 21 are supported by a main frame 39 with the shredders 23 disposed on upper beams and over the refiners 25. A felted wood pulp web (not shown) of a predetermined moisture content is fed to each of the shredders 23 which chop the webs into postage-stamp size pieces which are then fed through vertically disposed ducts 41 leading down to the refiner mills 25 which then grind and break the pieces into individual wood pulp fibers or as close thereto as possible. Streams of moving air carry the fibers through the ducts 27 and into the interior of the generally boxedshaped, enclosed chambers 29. The latter are generally hollow with an open, lower end disposed across and closely adjacent to the creped web 31 and carrier 33 which pass through inlet and outlet slots 32 formed in the respectively vertical end walls 43 (FIGURE 2) of these chambers. These slots extend considerably above the web 31 and their upper edges are defined by a wall 44 (FIG- URE 2) which is adjacent the periphery of one of the seal rolls 37a-37d. Each of the chamber side walls is sealed and connected to a vacuum box below. The vacuum boxes 35 are ducts connected to suitable sources of suction (not shown). Preferably, the vacuum boxes 35 are formed by vertical side walls 46 (FIGURE 2) defining a box-like chamber beneath the forming chamber 29. At the top of the vacuum box is a carrier support 48 in the form of an expanded metal screen having very wide openings to allow the air to pass easily without disturbing the fiber deposition on the carrier. The seal rolls are aligned over the end walls 46 of the vacuum chamber to provide a better sealing action with the vacuum chamber and with the supported pad disposed on and supported by the walls 46 at the sealing rolls.

The entrained fibers are filtered by the creped tissue web 31 from the air moving into the vacuum boxes. The web 31 is drawn from a large supply roll 47 (FIGURE 1) and is disposed over the upper surface of the top run of the endless carrier belt 33 and moves with the latter through the respective chambers 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 31 is approximately 30 inches in Width and the endless mesh belt 33 is slightly larger in 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 shaft of 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 tandem units. A pair of belt tension rolls 57 hold the endless carrier belt 33 at the proper tension.

To seal the slots 32 against the entry of air into the chamber, which is below atmospheric pressure, an inlet and outlet seal roll are provided for each of the enclosed chambers 29. Each of the seal rolls 37a37d is mounted in an identical manner, therefore, the mounting of only one seal roll 370 is illustrated and discussed in detail. As best seen in FIGURES 2 and 3, seal roll 37c is mounted for rotation by stub shafts 61 disposed in a pair of bearings 63 carried by support arms 65. The rotational axes of the seal rolls are disposed generally horizontally above and parallel to the web 31 and are disposed normal to the path of web travel.

Adjacent the respective ends of the seal roll 370 are end seals 69 (FIGURES 2 and 3) of L-shaped configuration with vertically extending legs fastened to the housing wall 43 adjacent the vertical sides of the slots 32. The end seals 69 project outwardly from the housing wall 43 to positions closely adjacent the radial end walls of the seal roll 37c. Extending across the top of the seal roll 37c and disposed between the end seals 69 is flexible doctor or seal blade 71 which is fixed to the wall 43 above the slot opening 32. The doctor blade extends outwardly from the wall 43 into engagement with the rotating, upper peripheral surface of the seal roll. Preferably, the doctor blade is contoured along its free edge 73 to fit into grooves formed in the seal roll 37c. Thus, the doctor blade and the end seals prevent sideways and overhead entrance of air or the loss of fibers from the slot 32. As the lower surface of the roll 37c is embedded in the pad, it alleviates the loss of air pressure at the interface of the seal roll and the pad and 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 29. 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.

In the preferred embodiment of the invention, the seal rolls also function as web feeding rolls in that the web 31 is gripped in the nip between the seal rolls and the belt 33 and they combine to strip the web from its supply roll 47 and then feed the web through the tandem units. To feed the creped tissue web 31 without wrinkling or tearing, the seal rolls may be formed with a resilient layer 77 (FIGURE 4) for pressing against the web 31 and belt 33. More specifically, the seal rolls may have a layer of rubber inch thick fixed about a cylindrical metallic sleeve 78 for the seal roll.

The axial end portions of each seal roll are of equal diameter and are rotated at the same peripheral speed to feed the web 31. To rotate the rolls 370, there is provided a drive train which includes a sprocket 79 (FIG- URE 3) 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- URE 3) on the lower end of vertical frame member '89. The free end of each support shaft 85 is provided with a worm gear 91 which is meshed with a suitable gear 93 carried on a common, horizontal drive shaft 95 extending longitudinally of the carrier 33 between the seal rolls. At its left end (FIGURE 1) the shaft 95 is connected to and driven by a gear box 96 driven by a chain 97 extending to the drive sprocket for the carrier drive roll 49. Because the carrier 33 and the seal rolls 37a37d are all driven by the gear unit 53, the speed of the carrier web may be correlated with the rotational speed of the seal rolls such that the tangential speed of the seal rolls engaging the web 31 matches that of the linear speed of the carrier 33.

While the seal rolls 37b and 370 function to shape the inner portion of the central area of the pad, it is the last seal roll 37d which does the final contouring and fiber combing for the finished pad 13. In accordance with the preferred embodiment of the invention, this seal roll 37a is in the form of a unitary roll having a central groove 101 about three inches wide (FIGURE 4) with a diameter which is about inch less than the diameter of outer end portions 102 of the roll. The central groove 101 is flanked by grooves 105 which are inch deep and extend laterally about five and one-half inches from the groove 101 to an annular shoulder 106. The tangential speeds of the roll at the

grooves

101 and 105 are deliberately designed to be slower than the linear speed of the web 31 and the pad 13 so that these smaller diameter portions exert a retarding force on the pad fibers they contact. The retarding force causes a screeding of fibers on the upper surface of the pad.

It has been found that the smaller diameter portion at the groove 101 is particularly effective in providing a gentle combing or screening of pad fibers where the pad is relatively thick. This assures a smoother upper surface, a more uniform thickness and a more uniform density for the central portion of the pad which is of primary importance to the absorptive characteristic of the pad.

As these seal rolls are of unitary construction, the more complicated arrangement of separate drives for each of the flanking and central portions has been eliminated. Also, the pinching of fibers between rolls as previously employed, is avoided as well as the loss of any air between the radial faces of those adjacent rolls.

In this instance, the pressure of the seal rolls on the pad is regulated by biasing means which are in the form of individual springs having attached scales 107. The springs 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 (FIGURE 1). The springs are adjustably mounted so that the force with which the rolls engage the pad can be limited to a predetermined portion of the weight of the rolls 37a-37b and their respective pivot arms 65. In the preferred embodiment of the invention, the seal rolls apply a light even pressure to the pad 13 just sufiicient to embed the roll in the pad and stop any large volume of ambient air from moving under the roll.

To prevent pickup of fibers on the seal rolls from the fibrous pad, the rolls may have an outer layer of plastic material disposed on the resilient layer 77. A film of .0005 inch of polytetrafluoroethylene as sold under the trademark Teflon has been applied to the outer surface of the roll and has worked satisfactorily.

It will be appreciated that the various seal rolls 37b- 37d are configured with annular groove of a depth and width to correspond to the particular shape of the pad at the line of its passing beneath the roll. Thus, the seal rolls at the outlet side of the first tandem unit 19 and the inlet side of the second tandem unit 21 have only a3 inch wide central groove 113 (FIGURE 3) which is about inch in depth. Because the inlet seal roll 37a for the first tandem unit 19 seals against the web 31 only, it is not provided with any annular groove 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 31 is disposed in the nip between the seal rolls 37a-37d and the upper surface of the continuous carrier 33. The seal rolls engage the outer side edges of the creped tissue web and as they rotate they strip the web from the supply roll 47.

As the web 31 passes through the first tandem unit 19, air-borne fibers move through the duct 27 into the enclosed chamber 29 and deposit on the web to form a pad of fibers three inches wide. The air stream carrying the fibers moves through the web 31 and the meshed carrier 33 into the vacuum box 35 beneath the web and carrier.

Simultaneously, at the other tandem unit 27, a 14 inch wide pattern of fibers is being overlaid on the incoming 3 inch strip.

Each of the seal rolls 37a37d is driven at the same speed by a common shaft 95 which, in turn, is driven by the drive 53 for the carrier 33 so that the seal roll portions engaging the web 31 have a tangential speed equal to the linear speed of the carrier 33.

To control the amount of pressure exerted by the roll on the pad and thereby the amount of fiber compaction and embedding by each seal roll 37b37d, each seal roll is pivotally mounted for pivoting about a support shaft and is lifted upwardly by an associated spring having a 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.

The last three of the four seal rolls, namely, 37!), 37c and 37d extend into engagement with the fibrous pad 13 on the web 31 to provide a lower seal preventing the loss of air pressure and fibers along the carrier and web from the slots 32 in the housing 29. At the opposite ends of the seal rolls, end seals 69 are fixed to the enclosing chamber wall 43 and extend to the radial end faces of the rolls. The slots 32 are further sealed at the top of the roll by the flexible blades 71 extending from the housing wall 43 to engage the respective rolls.

The smaller diameter portions of the seal rolls, particularly seal roll 37d, effectively screed and comb the pad while compacting the same to provide an improved air-laid fibrous pad 13. Because the tangential speed of the smaller diameter portion 101 of the seal roll 37d is less than the linear travel speed of the pad 13 with which it is in contact, this roll portion exerts a drag or retarding force on the upper fibers of the pad tending to screed off any excess fibers and to fill in any areas Where the pad is relatively thinner in cross-sectional dimension.

Best results are obtained by the direct positive driving rotation of the seal rolls 37a-37d by the line shaft 95. Less satisfactory, but adequate results have been obtained without using such a positive drive. For instance, the seal rolls may be rotated solely by the carrier 33 against which the rolls are biased. Thus, the rolls 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 air-laying apparatus provides a pad with an improved outer surface, a more uniform density and a more uniform crosssectional thickness. Also, the seal roll constructionsmay be greatly simplified and easily driven through a simple and less complicated driving arrangement. Although the seal roll 37d is shown and described in connection with a pair of tandem air-laying units, it will be appreciated that this roll could be also employed in a non-tandem airlaying apparatus where the entire pad is formed in one unit rather than in a pair of units.

While a preferred embodiment has ben 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 fibrous material on a moving carrier and forming a pad of nonuniform cross sectional thickness including a longitudinally extending portion having a thickness significantly greater than the thickness of an adjacent flanking portion extending in the same direction, said apparatus comprising means for forming said pad and 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 pad leave said chamber, a unitary'seal roll mounted for rotation about an axis disposed transversely of said pad movement and disposed to seal said opening by engaging said pad and closing said opening, adjacent portions of said roll having different diameters to define a first groove aligned with said longitudinally extending thicker portion of said pad and having a depth to accommodate the same while engaging the surface thereof and second groove aligned with said flanking portion of said pad and having a depth to accommodate the same While engaging the surface thereof, and means for rotating said roll about its axis with the smaller diameter portions of the roll having a tangential velocity less than that of the linear velocity of said pad whereby said smaller diameter portions brush fibrous mate rial on the surface of said pad.

2. An apparatus in accordance with claim 1 in which said fibrous material is deposited onto a creped tissue web carried by said carrier through said chamber, and in which larger diameter portions on said roll engage said web and cooperate with said carrier to feed the web without wrinkling or tearing the same.

3. An apparatus in accordance with claim 1 in which means are provided to mount said seal roll to limit the pressure with which the seal roll engages the fibrous pad and said carrier.

4. An apparatus in accordance with claim 3 in which said mounting means includes means to mount said seal roll for pivotal movement toward and from said pad and biasing means for the pivotal movement of said seal roll and the pressure with which the roll engages the pad.

5. An apparatus in accordance with claim 1 in which 8 said seal roll includes an inner shaft, a layer of resilient material on said shaft for cushioning the compressive force of said seal roll, and an outer surface layer of plastic on said resilient layer to limit the amount of fibers picked up by the seal roll.

6. An apparatus for continuously air laying a fibrous material to form a pad of non-uniform cross sectional thickness including a longitudinally extending portion having a thickness significantly greater than the thickness of an adjacent flanking portion extending in the same direction, said apparatus comprising a moving carrier for receiving and carrying a fibrous material along a predetermined path of travel at a predetermined velocity, means including first and second substantially enclosed chambers spaced along said path of travel for conducting air streams bearing fibrous material to said carrier, each of said chambers having inlet and outlet openings through which said carrier may travel as it moves along said path, seal rolls mounted for rotation at each of said inlet and outlet openings, said seal rolls at the inlet slot of the second chamber and at outlet slot of both of said chambers each having grooves therein to accommodate said portions, said seal roll at the outlet opening of said second chamber having a first groove aligned with said longitudinally extending thicker portion of said pad and having a depth to accommodate the same while engaging the top surface thereof and a second groove aligned with said flanking portion of said pad and having a depth to accommodate the same while engaging the surface thereof, and means to rotate said seal roll at the outlet of said second chamber so that at least one of the grooves therein has a velocity different than said predetermined velocity of said carrier.

7. An apparatus in accordance with claim 6 in which each of said seal rolls is a unitary roll and in which the outlet seal roll for the first chamber and the inlet seal roll for the second chamber each have an identical groove lo cated centrally of the roll, and in which said outlet seal roll for the second chamber has a similar groove and is flanked by additional side grooves.

References Cited UNITED STATES PATENTS 2,057,167 10/1936 Sherman 161l24 XR FOREIGN PATENTS 23,675 1894 Great Britain.

DORSEY NEWTON, Primary Examiner