Apparatus and method for applying parallel flared elastics to disposable products and disposable products containing parallel flared elastics

A series of elastic break brakes are provided throughout a travel path of elastics in a machine operation. Elastic strands thread through each individual brake mechanism, and if an elastic strand breaks downstream, a natural snap back of the elastic, which ordinarily travels through the system under tension, drives an immediately upstream cam mechanism back, and holds the elastic thread in place at the elastic break brake immediately upstream of the break as to minimize rethreading required downstream of the elastic break brake.

BACKGROUND OF THE INVENTION

The invention relates to disposable garments, and more particularly, a pants-type diaper, which is equipped with elastic strips effectively encircling the leg-holes without traversing the crotch region and to a method for producing such diapers.

Disposable diapers of the children's training pant type, or of the adult incontinence type, are typically equipped with elastic strands, which encircle the leg-holes. These strands of elastic are typically captured with adhesive between two layers of non-woven materials. Various methods are used to position these elastic strands so that they produce the desired encircling effect.

In one method of manufacture, the diapers are produced in an orientation whereby product flow is in the form of a single continuous web and the direction of travel is at a right angle with respect to what would be described as the crotch line of the diaper, i.e., the normal direction of product flow is parallel to the waist as opposed to parallel to the crotch.

One method of creating the desired effect of encircling the leg holes of the pant with elastics is to interleave two swaths of elastic strands, each curving across the face of the traveling web, encircling about one half of the leg-hole areas and crossing the path of the other. As a pair, they create a boundary around each leg-hole cutout, which resembles a circle or ellipse. In practice, however, the lateral excursions of the elastic lay-down device are speed-limited. As the traveling web is moving at some speed in one direction, and as the elastic lay-down device has speed and acceleration limits in the cross-direction, there is a limit to the steepness of the oblique angle which it is possible to form between the two. The result of this limitation is usually seen in the form of apparent incompleteness in the formation of the leg-hole-encircling pattern, particularly at the crotch line, where the two swaths cross each other.

From the point on the web at which one leg-hole pattern has been completed to the point at which the next can be begun, the elastic laydown device must reposition itself to a favorable starting point. This period of repositioning occurs as the crotch region passes the laydown device. As a result, the elastic strands must also cross this region of the product, at which they may or may not be attached by means of adhesives to the carrier webs. Various means are used to control or limit the positional relationships of the elastic strands in this region. The two sets of strands may cross over each other, creating an “X” pattern, or, they may loop back over to their respective sides, creating an “O” at the center of the crotch region. Alternatively, they may be mechanically stopped and prevented from crossing each other, creating two sets of generally parallel lines at the crotch. The lay-down pattern used at the crotch will determine the final appearance of the product in this area.

The shirring effect created by elastic strands when laminated with any flexible fabric is well known. However, to have this shirring effect applied to the crotch of a pant-type garment can be undesirable. The elastics create a contractile force, which tends to distort the garment at this location, thereby reducing the garment's aesthetic appeal, effectiveness and comfort. Thus various methods of reducing or eliminating the effects of the elastic tension normally occurring at the crotch have been attempted. These methods include the elimination of the adhesive bond between the strands and the liner materials described in U.S. Pat. No. 5,745,922 as “unsecured space” as well as various methods of cutting the strands to eliminate their effects.

As mentioned, one method of eliminating the undesired effects of the elastic strands which cross the crotch region is to sever them. This method is described in U.S. Pat. No. 5,660,657. Unfortunately, such severing usually requires the introduction of a transversely extending cut, which can result in a loss of web tension in the severed part of the carrier web. This also creates an undesirable opening in the diaper backsheet. A proposed solution for this problem is taught in U.S. Pat. No. 5,707,470, wherein an ultrasonic device is used to sever the elastic members, while the carrier webs which encapsulate the elastics are left intact. See, also, U.S. Pat. No. 5,643,396. Another problem associated with such severing lies in the tendency of the unsecured severed ends of elastic to retract to some point beyond the limits of any adhesive pattern. Thus, the elastic strands are not controlled or anchored near the ends of the adhesion pattern and may snap back to further into the adhesive pattern. This results in an incomplete elastic pattern and poor product characteristics.

One method of compensating for the incompleteness of the encircling pattern entails insertion of an additional set of elastic strips, running parallel to the crotch line and transverse to the web path. See U.S. Pat. Nos. 5,634,917 and 5,660,657. Typical products of this type are provided with an outer laminate, which is formed of an inner liner material and an outer backsheet material, between which the leg-hole elastics are disposed.

Often, leg elastics or other types of continuous ribbons are applied to running webs in a sinusoidal pattern by a roll-fed web process. Roll-fed web processes typically use a constant infeed rate, which in the case of a sinusoidal ribbon application, can result in necking, or undesirable narrowing of the ribbon toward the inner and outer portions of the sine curve in the cross-machine direction. This is because the infeed rate of the ribbon web does not match with the velocity of the substrate it is being laid upon in the machine direction. Instead, the ribbon material is stretched somewhat at the extremities of the sine curve.

Roll-fed web processes typically use splicers and accumulators to assist in providing continuous webs during web processing operations. A first web is fed from a supply wheel (the expiring roll) into the manufacturing process. As the material from the expiring roll is depleted, it is necessary to splice the leading edge of a second web from a standby roll to the first web on the expiring roll in a manner that will not cause interruption of the web supply to a web consuming or utilizing device.

In a splicing system, a web accumulation dancer system may be employed, in which an accumulator collects a substantial length of the first web. By using an accumulator, the material being fed into the process can continue, yet the trailing end of the material can be stopped or slowed for a short time interval so that it can be spliced to leading edge of the new supply roll. The leading portion of the expiring roll remains supplied continuously to the web-utilizing device. The accumulator continues to feed the web utilization process while the expiring roll is stopped and the new web on a standby roll can be spliced to the end of the expiring roll. In this manner, the device has a constant web supply being paid out from the accumulator, while the stopped web material in the accumulator can be spliced to the standby roll. Examples of web accumulators include that disclosed in U.S. patent application Ser. No. 11/110,616, which is commonly owned by the assignee of the present application, and incorporated herein by reference.

Examples of curved elastic application are disclosed in U.S. Pat. No. 6,482,278, incorporated herein by reference. Other examples include U.S. Pat. Nos. 8,100,173 and 8,025,652.

During the use of elastics in manufacturing disposable products, a continuous web of elastic is often threaded through numerous pieces of machinery upstream of a deposition point and adhesion of the elastic to another running web, such as a nonwoven material. If for some reason an elastic strand breaks during machine operation, it is necessary to re-thread the elastic through all of the machinery both upstream and downstream of the break.

SUMMARY OF THE INVENTION

Provided are methods and an apparatus for applying parallel flared elastics to a substrate used to form a disposable product, and severing elastics contained in a laminate from a leg hole opening. Other novel laydown patterns of elastics are also disclosed.

A series of elastic break brakes are provided throughout a travel path of elastics in a machine operation. Elastic strands thread through each individual brake mechanism, and if an elastic strand breaks downstream, a natural snap back of the elastic, which ordinarily travels through the system under tension, drives an immediately upstream cam mechanism back, and holds the elastic thread in place at the elastic break brake immediately upstream of the break as to minimize rethreading required downstream of the elastic break brake.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first toFIGS. 1a, 1band 1c, one of the preferred embodiments of the process of this invention and related apparatus are illustrated. The process utilizes two main carrier webs; a non-woven web11which forms an inner liner web, while web12forms an outwardly facing layer in the finished diaper. In this embodiment, non-woven web11is slit, at slitter station15, by rotary knives14along three lines. One of these, line16, is on approximately the centerline of web11and two additional lines17and18are parallel to and spaced a short distance from centerline16. The effect is twofold, first, to separate web11into two halves, as also seen inFIG. 5b. One half,19, will become the inside of the front of the diaper50and the second half,20, will become the inside of the back of that garment. Second, two separate, relatively narrow strips22and24are formed which are subsequently used to cover and entrap portions of the leg-hole elastics25and26. Strips22and24are separated physically by an angularly disposed spreader roll23and aligned laterally with their downstream target positions on the inner edges of webs19and20.

This invention relates particularly to a variation in the way that leg elastics25and26(which can be ribbons) are applied. In particular, the infeed rate of leg elastics or ribbons25and26is sped up at the outer extremities of the sine curve in the machine direction so that the vertical component of the velocity of the ribbon placement is at or near the velocity of the substrate web20to which the ribbon is applied. This results in little to no tension upon the elastics or ribbons25and26.

Adhesive patterns are applied to the liner webs20in target areas for the leg-hole elastics26. A spray gun assembly29of a type known in the art is preferably used to apply the adhesive patterns. Two sets of leg-hole, elastic strands26are introduced through laydown guides30, which reciprocate from side to side past each other. The strands26are glued to the web sections20, their laydown patterns following a serpentine or sinusoidal path. Laydown guides30then apply the strands26, which form leg-hole elastics as the web sections20are carried along the face of a drum or roll32.

In a preferred embodiment of the present invention, the elastics25and26are laid down in a smooth repetitive oscillation, with a centerline along an line in the machine, and an amplitude in the cross-machine direction. In a preferred embodiment, the infeed velocity of the elastics is increased as the waveform reaches maximum amplitude, then decreases again until the laydown passes the centerline, increasing again until minimum amplitude. This variation decreases neckdown.

Elastic laydown guides28and30are provided with the ability to make side-to side excursions, and the infeed of elastic25and26is provided with the ability of variable infeed speed. Elastic laydown guides28and30can be provided with the ability to make side-to side excursions by an arm that generally travels side to side e.g., by a swinging motion, or slides side to side. The side-to-side excursions of the leg-hole elastic laydown guides28and30result in generally arcuate segments of elastic strands extending on each side of the web centerline. After the nonwoven strips22and24have been applied to cover and entrap those parts of the elastics26that run nearest to and parallel to the inner edges of the webs20, a second pair of slitter knives34is used to trim away a portion of the narrow nonwoven strips22,24, along with that part of the inner liner webs20to which they are laminated. This also removes those portions of the elastic strands26which are contained within the laminations. The resultant trimmed scrap strips36are removed from the process for disposal elsewhere.

The effect of the last-described step is to remove the cut away portions of the elastic, eliminating its corresponding unwanted gathering effect from the crotch region of the garments50. The remaining portions of the curved elastic strands create a gathering effect around the leg openings of the finished garments50.

Subsequent to the combining and trimming of the inner webs20and the cover strips22,24, the combining drum32carries the webs to a nip with a second combining drum38, where the web sections20, with their respective curved elastic patterns exposed, are transferred to and laminated adhesively against the inside face of outer liner web12. This process entraps the curved elastic patterns26between the inner liners20and outer web12thereby forming a composite web39.

The composite web39is then provided with a pattern of adhesive in preparation to receive an absorbent insert or patch46. The patch46is cut from a provided patch web40by a cooperation of a cutter41and an anvil surface on a vacuum roll42and rotated into position for transfer to the composite web39by a patch applicator105. If the patch46is to be applied to the web39, a determination explained more fully below, the patch applicator105forces the web39against the patch46, thereby adhering the patch46to the web39.

Leg-hole materials48, if not previously removed, are cut at a cutting station47, thereby removing the material48contained within an approximate perimeter defined by the curved pattern of the elastics26and defining one half of a leg opening (with the other half of a leg opening provided in an adjacent leg-hole opening). The running composite chassis web39is folded, before or after cutting out of the leg holes, longitudinally along its centerline, thereby generally aligning its front waist edge with its back waist edge. The regions53which are to become the side seams54of the garments50are then welded by a sealing device49either ultrasonically or by heat. Note that the leg holes are preferably cut out before this point, leaving only a narrow zone for welding. The weld pattern is preferably wide enough to extend into both the left side seam of one garment and the right side seam of the adjacent garment. The garments50are then separated by passing through a cut-off knife assembly55, which severs the web along the transverse axis of the side seam weld53.

As described above, the laydown guides30used to apply the leg-hole elastics26to the liner web20oscillate from side to side to apply the leg-hole elastic26to the liner web20in a generally wave-like pattern. It should be understood that due to the oscillating motion of the laydown guides28and30, it is desirable to change the rate at which the leg-hole elastic25and26is introduced to the liner web20. As shown inFIG. 5, the velocity of the leg-hole elastic26has both a vertical (machine direction) component Vy and a horizontal (cross-machine direction) component Vx. It is contemplated that the vertical component of the velocity of the leg-hole elastic25and26is equal to, and in the same direction as, the velocity of the liner web20on which the leg-hole elastic26is being applied.

The incoming ribbon has variable speed, with the incoming ribbon increasing in velocity as the incoming ribbon is deposited in the curved pattern from the centerline to the maximum amplitude (its greatest distance from the centerline in the cross-machine direction towards a first boundary of the web), decreasing as the incoming ribbon is deposited in the curved pattern from the maximum amplitude to the centerline, and increasing as the incoming ribbon is deposited in the curved pattern from the centerline to the minimum amplitude (its greatest distance from the centerline in the cross-machine direction towards the other boundary of the web).

In a preferred elastic laydown pattern such as shown inFIG. 5, two lanes of elastic25and26are laid down in separate lanes, with both minimum amplitudes in the same position in the machine direction.

At least one web accumulator (not shown) can be located upstream of, or before, the leg-hole elastic guides30, as shown inFIG. 1a. The accumulator can take any form, such as a servo driven roller that speeds up and slows down, an alternate roller configuration, a rocking roller configuration, or any different means of accumulating the web, such as a miniature accumulator, or a device similar to a diaper cross-folder, or a tucker blade.

In this manner, the rate at which the leg-hole elastics26are being fed to the liner web20can be altered while the rate at which the leg-hole elastics26is fed to a rate adjustment apparatus314(not shown) remains the same.

It is further contemplated that the system may include a tension control device (not shown). The tension control device is preferably sized and configured to eliminate tension in the leg-hole elastic26prior to applying the leg-hole elastic26to the liner web20. In this manner when the leg-hole elastic26is applied to the liner web20, the leg-hole elastic will not become misshapen as it would if the leg-hole elastic26were under tension. The tension control device can takes the form of a web accumulator, or any form known in the art capable of performing such a function.

In this manner, the leg-hole elastic26is accumulated in the tension control device when the rate of application of the leg-hole elastics26to the liner web20is slowed as described above. It is contemplated that the above-described system will provide active tension control and feed approach to change the feed of the leg-hole elastics26to the liner web20so that the leg-hole elastic is not under tension when it is applied to the liner web20. This will result in leg-hole elastics26that are applied to the liner web20in an undistorted manner.

Referring now toFIG. 6, a top view of an exemplary pair of swinging arms90for applying elastics25and26is shown. The swinging arms can be programmed or operated to apply the elastics in a wave pattern (see, e.g.,FIG. 5) on a running web such as shown inFIG. 1.

It should be understood that the above-described arrangement may be used to apply any type of material to a moving web in a curved pattern. In the illustrated example, the material is leg-hole elastics26taking the form of elastic strands; however it is contemplated that the material could take the form of elastic tape. It is further contemplated that the material could take the form of non-elastic strands or non-elastic tape.

Referring now toFIG. 7, a perspective view showing a preferred embodiment of an alternative embodiment of the present invention is shown. This embodiment is used to create a pant-type diaper with waist band elastics and curved elastics, with a portion of the curved elastics removed by a chip in a leg opening section of the pant-type diaper.

In this embodiment, two or more series of leg band elastics210and212are laid down. Preferably waistband elastics210run parallel to one another, while another sequence of leg and waist elastics212are laid down in a curved pattern inboard of the waistband elastics210. Preferably, the leg and waist elastics212are applied in a curved fashion. At what will become the leg hole opening of the diaper, the leg and waist elastics212are generally parallel, and each of the independent the leg and waist elastics212are then curved towards absorbent insert or patch46, and increasingly separated in distance from one another the closer the leg and waist elastics212get to the absorbent insert or patch46.

As described above, sliding laydown guides30can be used to apply the leg and waist elastics212to the liner web20, the laydown guides oscillates from side to side to apply the leg and waist elastics212to the liner web20in a generally wave-like pattern. Alternatively, a swing arm or series of swing arms90such as shown inFIG. 6can be used to apply the leg and waist elastics212. The swing arms28and30, or the sliding laydown guides30can be programmed to move in a predetermined fashion in order to lay down a straight line of elastics26in a machine direction by remaining in a constant position, or can lay down a patterned shape of elastics26by moving from side to side as desired.

Referring now toFIGS. 8 and 9, plan views of a pant-type diaper with parallel waist band elastics210and flared leg and waist elastics212is shown.

Similar to the configuration shown inFIG. 1b, leg-hole materials48, if not previously removed, are cut at a cutting station47(FIG. 7), thereby removing the material48and forming a leg opening contour216on both the left and the right sides of the product. Referring particularly toFIG. 9, it can be seen that the leg and waist elastics212do not occupy what later will become seam53, but instead pass through leg opening contours216for removal at cutting station47(FIG. 7).

Referring now toFIGS. 10-12, these figures show in-process top views of pant type diapers with varying applications of straight and curved elastics.

As shown inFIG. 10, in one embodiment, parallel waist elastics210are applied to both the front and the back, and a series of parallel leg and waist elastics212are provided on a front of the product, while curved leg and waist elastics212are provided on the rear of the product. The curved leg and waist elastics212of the rear of the product would cross a secondary leg contour216of the product, and those elastics would not be contained within the side seam bond53.

Referring toFIG. 11, parallel waist elastics210are applied to both the front and the back, and a series of parallel leg and waist elastics212are provided on a front of the product, while curved leg and waist elastics212are provided on the rear of the product. The curved leg and waist elastics212of the rear of the product would cross a secondary leg contour216of the product, and those elastics would not be contained within the side seam bond53. Similarly, a portion of the parallel leg and waist elastics212of the front of the product would enter a tertiary leg contour216, and some of those parallel leg and waist elastics212would be severed during chip removal.

In the embodiment shown inFIG. 12, curved leg and waist elastics220are provided on the front of the product, and curved leg and waist elastics212which do not enter the side seams53are provided on the rear of the product. These and other elastic lay down variations, including following the leg cut in a tight group, a combination of a flared feature on the back (or front); and the opposing sides with elastics are tightly grouped together following a leg cut die and going through the leg cut die; or no elastics in those portions, are all contemplated.

Referring now toFIGS. 13-16generally, a series of elastic break brakes300are provided throughout a travel path of elastics (such as elastic26) in a machine operation. Elastic strands thread through each individual brake mechanism300, and if an elastic strand breaks downstream, a natural snap back of the elastic, which ordinarily travels through the system under tension, drives an immediately upstream cam mechanism back, and holds the elastic thread in place at the elastic break brake300immediately upstream of the break as to minimize rethreading required downstream of the elastic break brake.

Referring generally toFIGS. 13-17, an elastic break brake300to allow downstream travel of an elastic thread during machine operation and to stop unwanted elastic travel is disclosed. A rotating weight310is carried by a pin308coupled to a base306. A base elastic retaining surface312spaced apart from said rotating cam weight310. The rotating cam weight310is rotatable by the force of elastic26traveling under tension between said rotating cam weight310and said base elastic retaining surface312. The force of the traveling elastic26causes the cam weight310to be slightly rotated in a downstream machine direction allowing passage of said elastic26during machine operation. If a break in the elastic26occurs, the elastic goes limp and therefore the force of the traveling elastic26is no longer enough to hold the rotating cam weight310in its slightly downstream rotated position. Instead, the cam weight310rotates back upstream due to gravity and the absence of the force from elastic26traveling under tension. The elastic26is then trapped between the cam weight310and the elastic retaining surface312. This prevents unwanted elastic26travel, and makes the task of re-threading the elastic26far shorter.

Referring now toFIG. 13, a perspective view of a representative elastic travel sequence is shown in somewhat diagrammatic fashion. A series of elastic break brakes300are provided throughout the travel path of introduced elastic webs, and through each elastic break brake300, the continuous web of elastic is threaded.

Referring toFIG. 14, a side view of elastic break brakes300of the present invention are shown carrying an elastic strand26. A securing mechanism(s)304holds the elastic break brakes300in place. The elastic is threaded between a rotating cam weight310and a base elastic retaining surface312, which is very closely spaced apart from the rotating cam weight310. The rotating cam weight310is carried by pin308coupled to a base back306generally depending from base302.

During routine operation, the elastic26is traveling under tension, and at speed, sufficient to cause the cam weight310to be slightly rotated in the downstream (machine) direction. Elastic26is allowed to and capable of passing between the cam weight310and the base elastic retaining surface312.

Referring now toFIG. 15, should a break in the elastic strand26occur upstream of a series of the elastic break brakes300, the elastic break brake immediately upstream of the break in the elastic would, due to gravity or otherwise (e.g., a spring mechanism, or motor controlled) rotate counterclockwise to cinch the elastic strand26between the cam weight310and the base elastic retaining surface312. By maintaining control of the elastic26just upstream of the break point of the elastic26, only re-threading downstream of the activated elastic break brake300is required.

Similarly, as shown inFIG. 16, should a break in the elastic strand26occur between two elastic break brakes300, the elastic break brake300immediately upstream of the break would due to gravity or otherwise (e.g., controlled) rotate counterclockwise to cinch the elastic strand26between the cam weight310and the base elastic retaining surface312. By maintaining control of the elastic26just upstream of the break point of the elastic26, only re-threading downstream (in the machine direction) of the activated elastic break brake300would be required.

Referring now toFIGS. 18-23, top views of pant type diapers with varying applications of straight and curved elastics are shown.

Referring toFIG. 18, a series of flared elastics400are provided on a front and a back of a pant type diaper. On the back side, a single straight elastic strand402is provided, which is crossed over by the flaring elastics400of the back side of the pant.

InFIG. 19, multiple straight elastic strands402are provided on the rear of the diaper, which are crossed over by the flaring elastics400.

Referring toFIG. 20, another novel elastic laydown pattern is shown. In this embodiment, the distance between successive strands of the flared elastics400on the rear side decreases towards the center of the diaper. A similar embodiment is shown inFIG. 21, but the flaring elastics400on the rear stop well short of a centerline CL of the product and are discontinued across the crotch portion of the product.

Referring toFIGS. 22 and 23, the elastics400do not fan, but instead are parallel to one another generally along a leg cutout216, and then run parallel to each other through the centerline CL of the product. This configuration is a flared configuration. In this arrangement, the elastics400run from near the disposable product side areas410(when worn about the waist of a user) and run parallel from there, toward the crotch portion of the diaper, and particularly toward the absorbent core46crossing the centerline CL. In this sense, the elastics400generally are running in a direction that is skew to the machine direction. Each of the elastics400eventually turns to the centerline CL and next runs in the machine direction for a segment. At the centerline. Throughout the elastic laydown sequence, elastics400will be parallel, but spaced apart based on the time the elastic departs from the generally parallel to the leg cutout216direction, to the machine direction. At the parallel to the leg cutout216direction, the plurality of elastic strands400are considered running in parallel skew to the machine direction, that is neither in the machine direction or the cross machine direction. Still running in parallel, the elastic400pattern is mirrored, and the elastics return the flare to a second side area410of the product, resulting in a parallel flared elastic pattern. Additionally, at least one of the front or back set of elastics400could run entirely curved and parallel along their traverse of the front or back panel.