Apparatus and methods for securing elastic to a carrier web

Abstract

Apparatus and methods are provided to allow for creation of an elastic laminate. Non-stretched elastic can be laid at peaks over a nonwoven layer contained in valleys and atop peaks. Stretched elastic can be laid over tented nonwoven to create nonwoven tunnels when a second nonwoven is laid atop the first nonwoven and elastic, and the tunnels resist un-stretching of stretched elastic strands by frictional or obstruction forces. An elastic assembly or structure comprising a first and second layer of material bonded at spaced apart bond sites is disclosed, with a plurality of elastic strands disposed in a non-linear manner between said first and second layer of material, so that said strands meander in a cross-machine direction and traverse a machine direction line, restraining movement of the strands by frictional forces between the strands and the non-woven layers.

Claims

1. An elastic assembly comprising: a first layer of material having a lengthwise direction and a crosswise direction; a second layer of material having a lengthwise direction and a crosswise direction; a plurality of first bond points bonding the first and second layers of material together and being formed in a first rectilinear column, the first bond points being spaced apart from one another in the lengthwise direction of the layers of material, each first bond point having a first crosswise side and an opposite second crosswise side; a first elastic strand disposed between the first and second layers of material, wherein the first elastic strand is positioned on the first crosswise side of a first one of the first bond points and is positioned on the second crosswise side of a second one of the first bond points; and wherein the plurality of first bond points trap the first elastic strand between the first and second layers.

2. The elastic assembly of claim 1 wherein a frictional force between the first elastic strand and the first and second layers of material retains the first elastic strand in place.

3. The elastic assembly of claim 1 further comprising a plurality of second bond points bonding the first and second layers of material together and being formed in a second rectilinear column which is offset in the crosswise direction of the layers of material from the first rectilinear column, the second bond points being spaced apart from one another in the lengthwise direction of the layers of material, each second bond point having a first crosswise side and an opposite second crosswise side; and a second elastic strand disposed between the first and second layers of material, wherein the second elastic strand meanders around the second bond points.

4. The elastic assembly of claim 1 wherein the first elastic strand is laid down on the first layer of material in a tensioned state.

5. The elastic assembly of claim 1 wherein the first elastic strand further comprises a straight segment generally extending in the lengthwise direction.

6. The elastic assembly of claim 1 wherein the first layer of material and the second layer of material are formed from a single web of material, with the first layer of material comprising a first portion of the single web of material and the second layer of material comprising a second portion of the single web of material that is folded over the first portion.

7. An elastic assembly comprising: a first layer of material having a lengthwise direction and a crosswise direction; a second layer of material having a lengthwise direction and a crosswise direction; a plurality of first bond points bonding the first and second layers of material together and being formed in a first rectilinear column, the first bond points being spaced apart from one another in the lengthwise direction of the layers of material, each first bond point having a first crosswise side and an opposite second crosswise side; a plurality of second bond points bonding the first and second layers of material together and being formed in a second rectilinear column which is offset in the crosswise direction of the layers of material from the first rectilinear column, the second bond points being spaced apart from one another in the lengthwise direction of the layers of material, each second bond point having a first crosswise side and an opposite second crosswise side, the first crosswise sides of the second bond points being adjacent to the second crosswise sides of the first bond points; a first elastic strand disposed between the first and second layers of material, wherein the first elastic strand is positioned on the first crosswise side of a first one of the first bond points and is positioned on the second crosswise side of a first one of the second bond points; and wherein the plurality of first and second bond points trap the first elastic strand between the first and second layers.

8. The elastic assembly of claim 7 wherein a frictional force between the first elastic strand and the first and second layers of material retains the first elastic strand in place.

9. The elastic assembly of claim 7 further comprising a plurality of third bond points bonding the first and second layers of material together and being formed in a third rectilinear column which is offset in the crosswise direction of the layers of material from the second rectilinear column, the third bond points being spaced apart from one another in the lengthwise direction of the layers of material, each third bond point having a first crosswise side and an opposite second crosswise side, the first crosswise sides of the third bond points being adjacent to the second crosswise sides of the second bond points; and a second elastic strand disposed between the first and second layers of material, wherein the second elastic strand meanders around the first and second bond points.

10. The elastic assembly of claim 7 wherein the first layer of material and the second layer of material are formed from a single web of material, with the first layer of material comprising a first portion of the single web of material and the second layer of material comprising a second portion of the single web of material that is folded over the first portion.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a side view of an apparatus and method of forming an elastic laminate;

(2) FIG. 2 is a side view of an elastic laminate with an unstretched elastic and a slack base layer;

(3) FIG. 3a is a side view of an elastic laminate with a tensioned elastic layer and a stretched or tensioned base layer;

(4) FIG. 3b is a side view of an elastic laminate with a tensioned elastic layer and a stretched or tensioned base layer, and a second material layer coupled to the elastic layer;

(5) FIG. 4a is a side view of an elastic laminate with a tensioned elastic layer and a stretched or tensioned base layer, and a second material layer coupled to the base layer (or first material layer) at discrete bond points, with the elastic layer positioned between the first and second material layers;

(6) FIG. 4b is a side view of an alternate embodiment of the present invention, with pins (or anvil bond points) placed about an anvil roll and carrying the first material layer, and elastic strands laid atop the first non-woven layer tented by the pins, with a second material layer laid over the elastic strands and first material layer, and the trilaminate bonded together and passed downstream for further processing;

(7) FIG. 4c is a perspective view of the machine of FIG. 4b, with elastic strands laid down atop the first material layer, and the elastic strands allowed to or encouraged to wander about the anvil bond points to be laid down and the first and second layers bonded at the bond points to secure the elastics therebetween in meandering fashion;

(8) FIG. 4d is a side view of a machine for joining the elastic and first material layer at bond points, bringing first material layer to a taut condition, and bonding a second material layer to the laminate during a second bonding operation;

(9) FIG. 5 is a side view of the unit of FIG. 4c, showing the trilaminate formation, with the meandering elastics trapped between the bond points of the first and second layers;

(10) FIG. 6 is an alternate embodiment of the pinned anvil arrangement, with slots provided about the anvil.

(11) FIG. 7 is an alternate anvil bond point configuration;

(12) FIG. 8 is a second alternate anvil bond point configuration encouraging circuitous path of the elastic strands about the anvil bond points, the spaces between the anvil bond points (where the first and second material layers will become bonded, creating short tunnels to encourage the lacing action of the elastics between these tunnels to limit creep);

(13) FIG. 9 is a third alternate anvil bond point configuration;

(14) FIG. 10 is a perspective view of elastic material contained in a single material hem;

(15) FIG. 11 is a perspective view of elastic material contained between two materials to create a trilaminate;

(16) FIG. 12 is a fourth alternate anvil bond point configuration;

(17) FIG. 13 is a fifth alternate anvil bond point configuration.

DESCRIPTION OF THE PREFERRED EMBODIMENT

(18) Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention.

(19) It is noted that the present techniques and apparatus are described herein with respect to products such as diapers, but as previously mentioned, can be applied to a wide variety of processes in which discrete components are applied sequentially.

(20) Referring now to FIG. 1, a side view of an apparatus and method of forming an elastic laminate is shown. A base support structure 18 is provided with peaks and valleys, which can be a “V” shape. A preferably non-woven layer 12 is laid into the valleys. Atop the nonwoven 12 is laid an unstretched or relatively unstretched elastic layer 14, which can comprise strands or a web of elastic. This elastic 14 is bonded to the non-woven layer 12 at bond points 16. Such bonding could be done with, but not limited to, adhesives, ultrasonics, or pressure.

(21) FIG. 2 is a side view of an elastic laminate with an unstretched elastic 14, and a slack base layer 12, shown just after bonding the two layers together.

(22) After bonding, the carrier web 12 is returned to its unaccumulated state thereby elongating the elastic(s) 14 in the process, as shown in FIG. 3a. If considered mathematically, a relationship between the amount of material accumulated within the valleys, and the distance between the peaks determines the final elongation or strain (ε) of the elastics. Twice the distance from peak to valley, divided by the distance between peaks, defines (ε) of the elastics. Put another way, twice the distance from peak to valley will measure the distance between bond points of nonwoven 12 in a non-accumulated state.

(23) If desired, as shown in FIG. 3b, a second material layer 20 (preferably nonwoven) can be coupled to the elastic 14, or in an alternate configuration, coupled to the first material layer (FIG. 4a).

(24) In an alternative embodiment of the present invention as shown in FIG. 4b, the forming technique described with reference to FIG. 4a is shown in side view in FIG. 4b. Pins or protrusions or anvil bond points 52 are placed about an anvil roll 50, and elastic strands 14 laid atop a nonwoven layer 12 tented by the pins 52. Adjacent tented nonwoven 12 peaks create somewhat of a tunnel when coupled with top nonwoven 20, and elastic 14 is carried in the tunnel in circuitous or meandering ways as shown in FIG. 4c. The result is that the elastic 14 is restrained from lateral (or cross-machine direction) movement by encountering bond points between the first and second material layers 12 and 20 respectively, created by points 52 acting against ultrasonic horn 54. Alternatively, adhesives can be used in bonding.

(25) Still referring to FIG. 4c, and also to FIG. 5, protrusions 52 on an anvil roll 50 carry nonwoven 12, and create a tenting effect by raising the portions of the nonwoven 12 carried by the protrusions 52. It is between and about these adjacent and downstream bond points that the elastic 14 is allowed to, or encouraged to, meander generally in the machine direction as opposed to traveling linearly in the machine direction. Elastic 14 is laid down with tension in a circuitous path over and about the protrusions 52. The elastic 14 forces the nonwoven 12 down around protrusions 52 and the protrusions 52 are used to ultrasonically bond a second, top nonwoven layer 20 to the first nonwoven 12. The elastic 14 experiences a fairly high frictional force against the bonded segments of the nonwoven layers 12 because of the serpentine (meandering) path of the elastic 14 about the bond points and against the material layers 12 and 20 themselves, keeping the elastic 14 from creeping.

(26) Referring now to FIG. 4d, a forming technique described with reference to FIG. 3b is shown in side view in FIG. 4. In particular, after joining initially relaxed elastic 14 and initially relaxed first material layer 12 at bond points 16 by bonding unit 54, first material layer 12 and elastic layer 14 can be brought taut by elongating elastic 14. After first material layer 12 is sufficiently taut, second material layer 20 (preferably non woven) is introduced to the laminate 12/14, and a second bonding operation occurs between material layer 20 and laminate 12/14. This bonding can be performed by adhesive (not shown) or by an ultrasonic horn 54 operating against drum 70.

(27) Referring now to FIG. 6, an alternate embodiment of the pinned anvil arrangement of FIGS. 4 and 5 is shown, with slots 55 provided about the anvil roll 50. First nonwoven layer 12, and atop that layer, the elastic 14 is laid down in slots 55, and a top nonwoven layer 20 is laid down and bonded to first nonwoven layer 12. This creates a tunnel of nonwoven, and the tight elastic 14 is resistant to creeping as described previously.

(28) In addition to the techniques described above, modifications to the physical properties of the elastic 14 can assist providing the desired frictional resistance between the elastic 14 and nonwoven 12. For instance, ultrasonic force applied to the strands can cause the strands to unravel; those unraveled ends would choke any created tunnels in the nonwoven. Alternatively or additionally, the nonwoven layers 12 could be bonded through the unraveled strands 14, or could be unraveled without bonding.

(29) Still alternatively or additionally, a polymer coating such as Ethylene Vinyl Acetate (EVA) could be intermittently applied on the stretched elastic strands 14, to create rings or collars of eventually solidified polymer. The eventually solidified polymer on the elastic strands 14 would provide a physical barrier on created or improvised tunnels and might even get bonded into the nonwoven bonds that form the tunnel.

(30) Still alternatively or additionally, two or more elastic strands 14, can be twisted together, those entwined fibers 14 also physically resist travel through the created tunnels as the elastic 14 tries to relax. Additionally, a single elastic strand 14 can be rolled to make a bulky twisted structure that resists creep through the tunnel more effectively than elastic 14 that is simply stretched. Alternatively or additionally, the elastic 14 can be frayed or nicked with a rough surface such as sandpaper; it may pull the individual fibers apart or roughen the surface to fatten it up.

(31) Referring now to FIG. 7, an alternate anvil bond point 52 configuration is shown. Bond points 52 are spaced apart in the machine direction by spacing y, and spaced apart in the cross-machine direction by spacing x. X and y can both vary and be variable between adjacent bond points 52. That is, the points can be closely spaced apart in the cross-machine or machine directions, or more distantly spaced apart, and the spacing can vary from one row to the next, and from one column to the next.

(32) For instance, as shown in a second alternate anvil bond point configuration of FIG. 8, the bond points 52 can be spaced to encourage a circuitous path of the elastic strands 14 about the anvil bond points (noting that in a preferred embodiment that a nonwoven will be draped over the bond points 52 and the nonwoven is not shown in FIG. 8). In this configuration, a cross machine direction spacing x′ offset is provided in a column of bond points 52. The spaces between the anvil bond points 52 (where the first and second material layers 12 and 20 will become bonded) creating short tunnels to encourage the lacing action of the elastics 14 between these tunnels to limit creep.

(33) Referring to FIG. 9, third alternate anvil bond point 52 configuration varies machine direction spacing y′, y″ and y″ by an offset provided between adjacent rows of bond points 52. As such, both y and x can be varied to encourage tunnel formation and encourage meandering elastics 14. Alternatively as shown in FIG. 9, the protrusions can be staggered such that protrusions of a first series of adjacent rows are not staggered in the cross machine direction. This would encourage a straight run of elastics (at the top of FIG. 9), and downstream in the machine direction, a second series of adjacent rows can be staggered or offset by a distance x′ to encourage a curved run (middle portion of FIG. 9), or the staggering of x′ and y′ can be more random resulting in a meandering pattern of elastics 14.

(34) Referring now to FIG. 10 elastic material 14 can be used in the present invention by single material hem of material 12. In this manner, the meandered elastic will be captured between a laminate of the first material 12 portions after folding over an outboard portion of web 12, for instance by a folding plow (not shown).

(35) Referring now to FIG. 11, a perspective view of elastic material 14 contained between two materials 12 and 14 to create a trilaminate is shown. As can be seen, the elastic 14 meanders around bond points between material layers 12 and 14.

(36) Referring now to FIG. 12 is a fourth alternate anvil bond point configuration is shown. A series of curved protrusions 56 can be used instead of or in addition to pins or protrusions 52 placed about an anvil roll 50 shown on FIGS. 4 and 5. In this embodiment, material layer 12 is introduced atop the roll 50, and carried in part by curved protrusions 56. Material layer 12 will somewhat drape over and about protrusions 56 to create channels encouraging elastic 14 to be laid down in a somewhat meandering pattern, such that when material layers 12 and 20 are bonded (see, e.g., FIG. 4a), the bond points between material layers 12 and 20 will result in friction between elastic 14 meandering through the bond points of material layers 12 and 20. This friction prevents elastic 14 from sliding or creeping, i.e., elastic 14 is generally retained by frictional forces in its laid down meandering pattern.

(37) Referring now to FIG. 13, shaped protrusions 58, generally having preferably rounded corners to prevent material defects as a result of machine processing, can be used. The shape of protrusions 58 can be changed, with the spacing between shapes, and the shapes of the protrusions 58 themselves changed to accommodate the creation of frictional holding forces between elastic 14 and material layers 12 and 20, specifically between elastic 14 and bonding points between material layers 12 and 20 which elastic 14 is sandwiched between. This configuration shows a larger surface area bond point, and a patterned profile of protrusions 52 is used to provide increased frictional resistance between elastic 14, the surrounding layers 12 and 20 and their bond points. In essence, a maze is provided for the elastic 14 to go through during manufacture, and rounded corners of protrusions 52 can urge the elastic 14 to be laid down in those maze patterns during the elastic laydown and bonding processes previously described.

(38) The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.