Apparatus for transferring a discrete portion of a first web onto a second web

Abstract
This invention relates to an apparatus for transferring a discrete portion of a first web traveling at a first speed onto a second web traveling a second speed. The apparatus includes a converting mechanism capable of forming at least one discrete portion out of the first web. An anvil roll is positioned in close proximity to the converting mechanism and can travel at a rotational speed equal to the first speed. The anvil roll is a vacuum roll that is capable of directing the discrete portion away from the converting mechanism. A transfer roll is arranged in close proximity to the anvil roll and initially travels at a rotational speed equal to the first speed. The transfer roll forms a gap with the anvil roll through which the discrete portion can pass. The transfer roll is also a vacuum roll that is capable of directing the discrete portion away from the anvil roll. The transfer roll is capable of changing rotational speed to match the second speed during a single revolution. A backing roll is arranged in close proximity to the transfer roll and travels at a rotational speed equal to the second speed. The backing roll cooperates with the transfer roll to combine the discrete portion with the second web.
Description




FIELD OF THE INVENTION




This invention relates to an apparatus for transferring a discrete portion of a first web onto a second web. More particularly, this invention relates to an apparatus for transferring a discrete portion of a first web onto a second web even when the first and second webs are traveling at different speeds.




BACKGROUND OF THE INVENTION




In today's consumer market, there are numerous types of products which require that a discrete portion of a first web be transferred, aligned and/or attached to a second web to make a composite article. Many times, the first and second webs are traveling at different speeds and the transfer has to take place at high speeds. Disposable absorbent articles, such as diapers, training pants, sanitary napkins, pantyliners and incontinence products, including undergarments, briefs, pants and pads, are representative products which rely on the merging of discrete portions of one web with a second continuous web. Many times, it is necessary to transfer, align and/or attach a discrete portion of a first web to a second web at speeds exceeding 100 feet per minute (3048 cm/min.). The attachment of a discrete portion of a first web onto a second web can be by various means including an adhesive, a mechanical connection, by forming a bond using heat and/or pressure, by forming an ultrasonic bond, etc. Hot or cold melt adhesives and ultrasonic bonds are the most commonly used forms of attachment.




Some disposable absorbent articles, such as sanitary napkins and incontinence pads, also rely on a garment attachment adhesive to secure the article to the inside surface of the user's undergarment. The garment attachment adhesive can be applied to the bottom surface of the article and is normally covered by a releasable liner or backing material. The releasable liner will prevent the garment attachment adhesive from becoming contaminated prior to use. Prior to use of the article, the consumer will remove the releasable liner. The mating of the releasable liner to the article is another example where a discrete portion of a first web needs to be brought into registration and alignment with a second web.




Many articles found in today's retail outlets, supermarkets and grocery stores require a label that notifies the consumer of the product inside the container or package. The label can provide useful information to the ultimate consumer. Some labels are required by law to provide a description of the ingredients or to ensure the consumer that the product has not been previously opened. Many such labels are secured to an outside surface of the container or package using an adhesive. Many other kinds of labels, such as mailing labels, name tags, etc. need to be adhered to the container or package just prior to shipment. Most of these labels are adhered to an outer surface of the container or package by an adhesive or glue. Attachment of such labels by high-speed equipment can utilize the present invention.




It should be noted that the list of items requiring a discrete portion of a first web, layer of material or composite member to be brought into contact and perhaps be secured to a second web is endless. Consumer goods of all kind can possibly take advantage of the present invention. The discrete portion, which can be transferred to a second web, can be made of almost any kind of material.




The production machinery for attaching a discrete portion of a first web to a second web can generally be described as an apparatus having a cutting mechanism and various rolls or rollers. Typically, the first web is a continuous roll of material that is advanced to a converting mechanism. One or more feed rolls may be used to advance the first web. The speed of the feed rolls determines the speed at which the first web is supplied to the converting mechanism. The converting mechanism can be a cutter capable of slitting, cutting or severing a discrete portion from the first web. The discrete portion will have a desired shape and size. In many cases, the cutting is performed as the first web is advanced through a nip formed by a rotary knife that comes into close proximity or contact with an anvil or backup roll. The discrete portion of the first web is then carried via various rolls, typically vacuum rolls, to a location where the discrete portion can be transferred to the second web.




In general, such converting mechanisms and transfer rolls are designed to operate at a constant speed to cut a particular size discrete portion from a first web and transfer it to a second web. Mechanical mechanisms such as gears, belts and chains are conventionally used to synchronize the first web, the cutting mechanism, the transport rolls and the second web.




When the dimensions of the discrete portion are changed, it is generally required to change some of the components of the converting mechanism and transfer rolls. With each component change, large amounts of money can be lost due to the downtime required to make the change, in addition to the capital invested in multiple grade change components.




One method used to avoid having to reengineer the machinery for each change made to the product is to run the apparatus at different speeds depending on the size of the discrete portion needed to be transferred to the second web. For example, if a longer discrete portion is needed, the rate at which the first web is advanced to the converting mechanism is increased. However, by increasing the speed of the first web, the transfer of the discrete portion onto the second web Will no longer occur at the same speed and/or at the desired interval.




When two webs of materials are joined at different speeds, there is a tendency for the materials to experience shock loads, pulling, wrinkles and gaps. In most applications, joining two webs traveling at different speeds can have drastic effects on a fast moving, continuous process. Another problem caused by mismatched web speeds is that as the discrete portion of the first web contacts the second web, a jarring or shocking action may occur. This action can cause at least one of the webs to rip, tear, or wrinkle. A torn web generally requires stopping the machine and rethreading the incoming web around the guide rolls and through the various nips. In a worst case scenario, the machine may be damaged and certain parts may need to be repaired and/or replaced.




There have been a vast number of attempts made at bringing together two webs traveling at the same or at different speeds, and combining them to provide a single combined web. To date, most methods lack full acceptance for one or more reasons.




Now an apparatus has been invented which allows a discrete portion of a first web traveling at a first speed to be successfully transferred to a second web that is traveling at a second speed.




SUMMARY OF THE INVENTION




Briefly, this invention relates to an apparatus for transferring a discrete portion of a first web traveling at a first speed onto a second web traveling at a second speed. The apparatus includes a converting mechanism capable of forming at least one discrete portion out of the first web. An anvil roll is positioned in close proximity to the converting mechanism and can travel at a rotational speed equal to or greater than the first speed. The anvil roll is a vacuum roll that is capable of directing the discrete portion away from the converting mechanism. A transfer roll is arranged in close proximity to the anvil roll and initially travels at a rotational speed equal to the anvil roll. The transfer roll forms a gap with the anvil roll through which the discrete portion can pass. The transfer roll is also a vacuum roll that is capable of directing the discrete portion away from the anvil roll. The transfer roll is capable of changing rotational speed to match the second speed during a single revolution. A backing roll is arranged in close proximity to the transfer roll and travels at a rotational speed equal to the second speed. The backing roll cooperates with the transfer roll to combine the discrete portion with the second web.




The general object of this invention is to provide an apparatus for transferring a discrete portion of a first web onto a second web. A more specific object of this invention is to provide an apparatus for transferring a discrete portion of a first web onto a second web when the first and second webs are traveling at different speeds.




Another object of this invention is to provide an apparatus for making a matched speed transfer of a discrete portion of a first web traveling at a first speed onto a second web traveling at a second speed.




Still another object of this invention is to provide an apparatus for transferring and attaching a discrete portion of a first web onto a second web when the two webs are traveling at different speeds.




Still further, an object of this invention is to provide an apparatus for transferring a discrete portion of a first web traveling at a first speed onto a second web traveling at a second speed while greatly reducing induced stresses in the webs.




Still further, another object of this invention is to provide an economical and efficient apparatus for transferring and attaching a discrete portion of a first web onto a second web when the two webs are traveling at the same or at different speeds.




Other objects and advantages of the present invention will become more apparent to those skilled in the art in view of the following description and the accompanying drawings.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a schematic diagram of an apparatus for transferring a discrete portion of a first web onto a second web.





FIG. 2

is a side view of a stomper roll interacting with a transfer roll to form a nip therebetween.





FIG. 3

is a schematic diagram of an alternative apparatus for transferring a discrete portion of a first web onto a second web.





FIG. 4

is a graphic representation of the speed modulation of the transfer roll being driven by a servomotor during a single revolution.





FIG. 5

is a schematic diagram of an alternative apparatus for transferring a discrete portion of a first web onto a second web using a transfer roll which is not vertically aligned with the anvil roll and rotary cutter.





FIG. 6

is a schematic diagram of an alternative apparatus for transferring a discrete portion of a first web onto a second web using at least two transfer rolls vertically aligned with the anvil roll and the rotary cutter.





FIG. 7

is a schematic diagram of still another alternative apparatus for transferring a discrete portion of a first web onto a second web using at least two transfer rolls that are not vertically aligned with the anvil roll and the rotary cutter.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring to

FIG. 1

, a schematic is depicted for a method of transferring a discrete portion of a first web onto a continuous second web when the first and second webs are traveling at the same or at different speeds. The method uses an apparatus


10


that includes a supply roll


12


containing a first web


14


. The first web


14


can be almost any kind of material. Typical materials include paper, cellulose fibers, pulp, plastic film, cloth, non-woven materials including spunbond, and various synthetic and non-synthetic materials. Other materials can also be used. The first web


14


can also be a composite formed from two or more similar or different materials joined together. The first web


14


can also be a laminate formed from two or more layers of material. The first web


14


can be primed or treated with a coating. The first web


14


can also be flexed or otherwise manipulated to provide certain desirable properties. An adhesive can be applied to at least one side of the first web


14


, if desired. However, the adhesive should not have such a strong peel strength that it would stick to downstream equipment. Furthermore, the first web


14


can be a continuous thin sheet or strip or it can have a three dimensional profile. For example, the first web


14


can be flat, lofty or bulky and may vary in thickness in the longitudinal and/or transverse directions.




The first web


14


can have any width that will be accommodated by the equipment it is designed to run on. Typical widths for absorbent articles can vary from between about 1 inch to about 36 inches (about 25.4 mm to about 914.4 mm). Preferably, the width of the first web


14


will be equal to or less than about 24 inches (about 609.6 mm). More preferably, the width of the first web


14


will be equal to or less than about 18 inches (about 457.2 mm). The length of the first web


14


, measured parallel to the machine direction, is generally greater than the width of the first web


14


. The length of the first web


14


should be as long as practicably feasible so as to decrease the number of changeovers required. The first web


14


is generally considered “continuous” if it has only one beginning and one ending point on the supply roll


12


.




The first web


14


is advanced from the supply roll


12


around one or more guide rolls


16


(only one of which is depicted). The number of guide rolls


16


will vary depending on a number of factors, including the length and width of the first web


14


, the distance the first web


14


has to travel, the desired tension, etc. The first web


14


is advanced through a nip


18


formed by the contact between a pair of feed rolls


20


and


22


. One or both of the feed rolls


20


and


22


can be driven, that is, rotated by a motor, to advance the first web


14


. More than one pair of feed rolls


20


and


22


can be used if one wishes to stretch the first web


14


. Preferably, the pair of feed rolls


20


and


22


will be driven so as to pull or draw the first web


14


away from the supply roll


12


and toward a converting mechanism


24


.




The converting mechanism


24


can be any type of device needed to cut, slice, die cut, stamp, bond or form a discrete portion


26


of desired dimensions from the first web


14


. For example, the converting mechanism


24


can be a rotary cutter


28


having one or more knives


30


secured about its outer periphery. One knife


30


is shown secured to the rotary cutter


28


in FIG.


1


. The knife


30


can have a linear or a nonlinear configuration. The knife


30


can be designed to completely sever the first web


14


or it could be configured to form the discrete portion


26


into a desired shape, such as into a rectangle, square, circle, oval, hourglass or some other desired shape. Besides the knife


30


, other suitable cutting apparatuses could be used. Such devices include two or more blades, a die, a stamp, an ultrasonic device, or any other suitable device known to those skilled in the art.




When the converting mechanism


24


is a rotary cutter


28


, it should span across the width of the first web


14


. The rotary cutter


28


cooperates with and is positioned in close proximity to an anvil roll


32


and forms a gap


34


therebetween. However, the knife


30


will rotate into contact with or be aligned to be very close to the outer surface of the anvil roll


32


. The knife


30


will form a nip with the anvil roll


32


so that the first web


14


can be severed. In

FIG. 1

, the rotary cutter


28


is shown as rotating in a counterclockwise direction while the anvil roll


32


is rotated in a clockwise direction. Preferably, both the rotary cutter


28


and the anvil roll


32


can have the same outside diameter and will rotate at the same speed. However, the rotary cutter


28


and the anvil roll


32


do not have to have the same outside diameter and can be setup to rotate at the same or at different speeds.




As the first web


14


passes through the gap


34


and is contacted by the knife


30


, a discrete portion


26


will be formed for each 360-degrees of rotation of the rotary cutter


28


. It should be noted that when the rotary cutter


28


has more than one knife


30


attached to its outer surface, a discrete portion


26


will be formed for each partial rotation of the rotary cutter


28


. Sometimes, the shape of the discrete portion


26


is such that trim waste


36


will be present after the discrete portion


26


is formed and separated from the first web


14


. This trim waste


36


can be directed to a recycling hopper


38


where it can be collected and later reused to make new material. The trim waste


36


can be in the form of a single continuous strip or it can consist of a plurality of smaller individual pieces.




The size and shape of the discrete portion


26


can vary. Generally, the length of the discrete portion


26


will change depending on the type of product being produced by the manufacturer. For example, some manufacturers of disposable absorbent articles will produce similar pads that will vary only in overall dimensions. Typically, the length of the discrete portion


26


, when forming an absorbent article, can range from between about 1 inch to about 24 inches (about 25.4 mm to about 609.6 mm). Preferably, the length of the discrete portion


26


can range from between about 1 inch to about 16 inches (about 25.4 mm to about 406.4 mm), and most preferably, the length of the discrete portion


26


will be equal to or less than about 12 inches (about 304.8 mm). In some methods, a plurality of discrete portions


26


may be cut and transferred simultaneously. For example, two parallel strips may be cut from the first web


14


. There may be a large amount of space between the two strips, or there may be little or no spacing. The length of the discrete portion


26


is controlled by the rotational speed of the feed rolls


20


and


22


, the placement of the knife or knives


30


on the rotary cutter


28


, as well as other factors known to those skilled in the art.




In

FIG. 1

, the discrete portion


26


that is formed by passing the first web


14


under the knife


30


is immediately transferred onto the outer surface of the anvil roll


32


. As the anvil roll


32


is rotated, the discrete portion


26


is carried away from both the rotary cutter


28


and from the trim waste


36


. To assist in holding the discrete portion


26


on the outer surface of the anvil roll


32


, a vacuum can be used. The vacuum or suction needed to draw the discrete portion


26


against the outer surface of the anvil roll


32


can be adjusted to meet one's needs depending on the size, shape, weight, dimensions and material characteristics of the discrete portion


26


. Typically, the anvil roll


32


is constructed of a strong material, such as steel, cast iron, aluminum, hard rubber or a hard thermoplastic material. It is also possible to harden the outer surface of the anvil roll


32


to prolong its life since it will match up with the knife


30


on the rotary cutter


28


. In addition, the outer surface of the anvil roll


32


can be coated to make it smooth and/or slick. Alternatively, the outer surface of the anvil roll


32


could be treated or machined to form a non-skid surface, a textured surface or a surface of high friction. The formation of grooves or a serrated configuration could be beneficial in certain instances.




It should be noted that the outside diameter of the anvil roll


32


could be made to almost any desired dimension. A typical outside diameter for an anvil roll


32


used to make disposable absorbent articles would range from between about 2 inches to about 26 inches (about 50.8 mm to about 660.4 mm). More preferably, the outside diameter of the anvil roll


32


will range from between about 4 inches to about 13 inches (about 101.6 mm to about 330.2 mm). Most preferably, the outside diameter of the anvil roll


32


will be equal to or less than about 12 inches (about 304.8 mm). It should be noted that the outside diameter of the anvil roll


32


could be smaller, equal to or larger than the outside diameter of the rotary cutter


28


.




The rotational surface speed of the anvil roll


32


can be slower than, equal to or greater than the rotational surface speed of the rotary cutter


28


. Preferably, the rotational speed of the rotary cutter


28


and the anvil roll


32


are the same. Furthermore, the anvil roll


32


should travel at a rotational speed at least equal to the speed of the first web


14


and preferably at a faster speed. In some instances, depending on the length of the discrete portion


26


, the discrete portion


26


will be at least partially located on the outer surface of the anvil roll


32


when the knife


30


is cutting the opposite end of the discrete portion


26


. In some situations, the discrete portion


26


will slip on the anvil roll


32


since the feed rate of the first web


14


is slower than the surface speed of the rotary cutter


28


or the anvil roll


32


. To ensure a smooth slip of the discrete portion


26


on the outer surface of the anvil roll


32


with decreased binding, gapping and pulling, it may be desirable to size the gap


34


to have a minimal clearance. The discrete portion


26


can then continue to slip on the anvil roll


32


until it is completely cut by the knife


30


. The actual severance of the discrete portion


26


from the first web


14


will release the discrete portion


26


and allow it to be completely transferred to the anvil roll


32


.




The discrete portion


26


will adhere to the outer surface of the anvil roll


32


because of the vacuum being pulled from within the anvil roll


32


. Generally, the outer surface of the anvil roll


32


will have a plurality of small holes formed therein that are connected to a source of vacuum. The force of the vacuum can range from between about 0.1 inches (about 2.54 mm) of water pressure to about 50 inches (about 1270 mm) of water pressure. Preferably, the force of the vacuum will be less than about 30 inches (762 mm) of water pressure, and most preferably, the force of the vacuum will be less than about 15 inches (about 381 mm) of water pressure. The vacuum is pulled from the center of the anvil roll


32


so that the discrete portion


26


will adhere to the outer surface of the anvil roll


32


. The amount of vacuum that will be needed will also be dependent upon the porosity of the material from which the discrete portion


26


is formed. The surface area of the discrete portion


26


over which the vacuum will act will also change and should be taken into consideration when calculating the amount of vacuum needed.




It should be noted that the discrete portion


26


, when completely severed from the first web


14


, should adhere to the outer surface of the anvil roll


32


and should travel at the rotational speed of the anvil roll


32


.




Still referring to

FIG. 1

, one will notice that the discrete portion


26


is transferred from the anvil roll


32


onto a transfer roll


40


. The two rolls


32


and


40


are positioned in close proximity to one another and are arranged to form a gap


42


therebetween. The gap


42


isolates the transfer roll


40


from vibrations and stresses induced in the anvil roll


32


by its interaction with the rotary cutter


28


. The gap


42


should be sized to permit the discrete portion


26


to be transferred onto the outer surface of the transfer roll


40


without being unduly compressed. The transfer roll


40


can have a diameter that is smaller than, equal to or larger than the diameter of the anvil roll


32


. Preferably, the transfer roll


40


will have the same diameter as both the anvil roll


32


and the rotary cutter


28


. The transfer roll


40


is a vacuum roll. The transfer roll


40


can be constructed of similar materials as the anvil roll


32


. Typical materials include steel, aluminum, hard rubber or a hard thermoplastic material. Alternatively, the transfer roll


40


can be constructed from low inertia materials like composite materials, graphite, a polycarbonate material, carbon fiber, KEVLAR® or nylon. KEVLAR® is a registered trademark of E. I. DuPont de Nemours & Company that has an office at 1002 Market Street, Wilmington, Del. 19801.




As the weight of the transfer roll


40


decreases, the faster it is capable of changing speed within a single rotational cycle. The outer surface of the transfer roll


40


can also be rubber-coated, treated or machined, similar to what has been previously described with reference to the anvil roll


32


. The type of surface utilized on the transfer roll


40


will depend upon one's preference, as well as on the material from which the discrete portion


26


is formed.




An adjustable, variable speed servomotor


44


drives the transfer roll


40


via a connector


46


. The transfer roll


40


is depicted as being driven in a counterclockwise direction. The connector


46


can be a coupling that joins two rotational shafts together. One shaft extending out of the servomotor


44


and the other shaft supports the transfer roll


40


. A gearbox


47


can also be positioned across the connector


46


and will function to change the torque requirements of the servomotor


44


. The gearbox


47


can be a low inertia gearbox that can increase or decrease the torque output of the servomotor. Preferably, the gearbox


47


will reduce the torque output of the servomotor


44


by a factor of at least about 5 to 1, and more preferably, by a factor of at least about 3 to 1.




The function of the transfer roll


40


is to transport the discrete portion


26


toward a second web


48


. Because of this, the transfer roll


40


will initially be traveling at the same speed as the anvil roll


32


. The speed of the transfer roll


40


can then be changed to match the speed of the second web


48


. Like the first web


14


, the second web


48


can be unrolled from a supply roll


50


. The second web


48


can be almost any kind of material. Typical materials used to manufacture an absorbent article include paper, cellulose fibers, pulp, plastic film, cloth, non-woven materials including spunbond, as well as various synthetic and non-synthetic materials. Other materials can also be used. The second web


48


can also be a composite formed from two or more similar or different materials. The second web


48


can also be a laminate formed from two or more layers of material. The second web


48


can be primed or treated with a coating. The second web


48


can also be flexed or otherwise manipulated to provide certain desirable properties. Furthermore, the second web


48


can be a continuous thin sheet or strip or it can have a three dimensional profile. For example, the second web


48


can be flat, lofty or bulky and may vary in thickness in the longitudinal and/or transverse directions.




The purpose of this invention is to be able to transfer a discrete portion


26


of a first web


14


, which is travelling at a first speed, onto a second web


48


, which is travelling at a second speed. The first and second speeds will most likely be different although they could be the same. In manufacturing disposable absorbent articles, the second speed will generally be faster than the first speed.




The second web


48


may be a virgin web. A virgin web is a web that has no additional layers, attachments or modifications thereto. Alternatively, and most usually, the second web


48


will have been at least somewhat processed, for example, scored, slitted, or had other discrete portions applied thereon. For example, for a disposable absorbent article, several discrete portions of elastic or some other material may have already been applied to the second web


48


before the discrete portion


26


is added.




The second web


48


can have any width that will be accommodated by the equipment it is designed to run on. Typical widths for manufacturing disposable absorbent articles can vary from between about 1 inch to about 36 inches (about 25.4 mm to about 914.4 mm). Preferably, the width of the second web


48


will be equal to or less than about 24 inches (about 609.6 mm). More preferably, the width of the second web


48


will be equal to or less than about 18 inches (about 457.2 mm). The length of the second web


48


, measured parallel to the machine direction, is generally greater than the width of the second web


48


. The length of the second web


48


should be as long as practicably feasible so as to decrease the number of changeovers required. The second web


48


is generally considered “continuous” if it has only one beginning and one ending point on the supply roll


50


.




It should be noted that an adhesive


52


could be dispensed from a mechanism


54


, such as a spray nozzle, a slot coater, a bead applicator, etc. onto at least one surface of the second web


48


. Preferably, the adhesive


52


is applied to an upper surface


56


of the second web


48


. Alternatively, the adhesive


52


can be in the form of a liquid bath that is retained in a container


58


. A roller


60


can be positioned relative to the container


58


so as to apply the adhesive


52


onto one surface of the discrete portion


26


while the discrete portion


26


is held by vacuum onto the outer surface of the transfer roll


40


. Alternatively, the adhesive


52


could be applied by other means known to those skilled in the art.




The second web


48


is advanced from the supply roll


50


around one or more guide rolls


62


(only one of which is depicted). The number of guide rolls


62


will vary depending on a number of factors, such as the length and width of the second web


48


, the distance the second web


48


has to travel, the desired tension, as well as other factors known to those skilled in the art.




The second web


48


is advanced between a gap


64


formed between the transfer roll


40


and a backing roll


66


. The backing roll


66


is positioned in close proximity to the transfer roll


40


and cooperates therewith. The backing roll


66


can have a diameter larger than, equal to or smaller than the diameter of the transfer roll


40


. Preferably, the transfer roll


40


has a larger diameter than the backing roll


66


. The backing roll


66


can have a rotational speed equal to that of the second web


48


. The second web


48


is advanced by a feed mechanism


68


that is located downstream of the gap


64


. The feed mechanism


68


can consist of various equipment including a pair of feed rolls, one or more process rolls, a vacuum conveyor, die rolls, functional rolls, S-wrapped rolls, nip rolls, etc. The purpose of the feed mechanism


68


is to pull or draw the second web


48


along at a steady speed. Preferably, the feed mechanism


68


is a process roll.




In

FIG. 1

, the backing roll


66


is rotating in a clockwise direction and is arranged in close proximity to the transfer roll


40


. The gap


64


formed between these two rolls


40


and


66


should be large enough to enable the discrete portion


26


and the second web


48


to pass therebetween without being unduly compressed. Preferably, the gap


64


will be dimensioned to provide a passage for the discrete portion


26


and the second web


48


with limited compression.




Referring to

FIG. 2

, the backing roll


66


can be replaced by a stomper roll


70


having a protruding section


72


. When the stomper roll


70


is used with the transfer roll


40


, a nip


74


is formed between the two rolls


40


and


70


. The stomper roll


70


is used to squeeze or press the discrete portion


26


against the second web


48


and form an attachment therebetween. For example, the stomper roll


70


can assist in squeezing any adhesive


52


present on the upper surface


56


of the second web


48


against the discrete portion


26


to form a secure bond therebetween.




Either the backing roll


66


or the stomper roll


70


can be used to help position, attach or secure the discrete portion


26


to the second web


48


. Usually both the backing roll


66


and the stomper roll


70


are driven rolls that can be rotated by a motor or a belt drive. If the material forming the second web


48


is stiff, the backing roll


66


does not have to be driven but could be freely rotatable. It should also be noted that for some methods, the backing roll


66


or stomper roll


70


could be replaced by a vacuum screen, a belt, a vacuum conveyor, a movable web or some other device. One requirement is that the substituted device be capable of providing the necessary compression to produce the pressure necessary to attach or secure the discrete portion


26


to the second web


48


.




Once the discrete portion


26


has been brought into contact with the second web


48


and is either positioned thereon or is attached or secured thereto, a combination web


76


is formed. This combination web


76


can be a continuous strip or be cut into individual segments. The combination web


76


can be wound on a roll, converted to a desired form, or be transported to another process where it can be utilized to make a finished product. The combination of all the discrete portions


26


, adhesives


52


and other items applied to the second web


48


can produce a finished disposable absorbent article.




Returning to the discussion on the method of driving the transfer roll


40


, one skilled in the art will quickly recognize some of the advantages of driving the transfer roll


40


with the variable speed servomotor


44


. A first advantage of driving the transfer roll


40


with a variable speed servomotor


44


is that it enables the transfer roll


40


to accelerate and/or decelerate quickly within a single revolution. The transfer roll


40


should be able to increase and/or decrease its speed during each 360-degree rotation. The variable speed servomotor


44


can be either an alternating current (AC) motor or a direct current (DC) motor. Preferably, the servomotor


44


is an AC motor. The actual horsepower produced by the variable speed servomotor


44


should be sufficient to provide enough torque and speed to drive the transfer roll


40


without any lagging or hesitation. A computer can be used to control the output of the servomotor


44


. Servomotors are commercially available from various equipment vendors. One such vendor is Rockwell Automation having an office at 1201 South Second Street Milwaukee, Wis. 53204-2496.




A second advantage of using the variable speed servomotor


44


for controlling the torque and speed of the transfer roll


40


is that a smooth speed transition is obtainable. Since the transfer roll


40


is independently driven by the servomotor


44


and is isolated from the anvil roll


32


by the gap


42


, the other moving parts will not be influenced by it. This independent aspect of the servo-driven transfer roll


40


provides a smoother and more stable speed change, and decreases any vibrations or frequencies which may be created by the other mechanisms. A decrease in vibrations corresponds to a decrease in the amount of errors or mistakes (such as wrinkles, puckers or tears) when applying the discrete portion


26


to the second web


48


. Also, as the discrete portion


26


is positioned on or applied to the second web


48


, the amount of shock created on the second web


48


is decreased.




A third advantage of the variable speed servomotor


44


is that it is an electronically controlled mechanism. This eliminates the need for a mechanical mechanism controlled by gears, chains, or manual switches. The electronically controlled mechanism allows for a smoother transfer of power to the transfer roll


40


.




It is preferred that the speed of the transfer roll


40


be changed from a first speed to a second speed after the entire discrete portion


26


is transferred from the anvil roll


32


to the transfer roll


40


. This will provide a smooth transfer and will reduce any shock, gapping, or pulling on the discrete portion


26


. However, depending upon the length of the discrete portion


26


and the diameter of the transfer roll


40


, this may not be possible. Sometimes, the physical set up of the apparatus as well as other factors, may require the speed of the transfer roll


40


to be changed while the discrete portion


26


is positioned on the outer surface of both of the rolls


32


and


40


. The present apparatus


10


and method allows for this.




The speed of the transfer roll


40


can be controlled by “step” inputs, that is, a sudden and immediate change from a first speed to a second speed or it can be controlled by “ramp” inputs. The actual curve of the input will be dependent upon the drive capabilities and the tuning parameters that can be programmed into the controlling computer by the user. The first speed of the transfer roll


40


will usually correspond to the speed of the anvil roll


32


and the second speed of the transfer roll


40


will correspond to the speed of the second web


48


.




It is foreseen that the apparatus and method of this invention can operate at high speeds to produce a plurality of absorbent articles per minute. Thus as little time as possible should be used to accelerate or decelerate the speed of the transfer roll


40


. When manufacturing absorbent articles, the servomotor


44


should be capable of completing at least 100 cycles per minute. More preferably, the servomotor


44


should be capable of completing at least 250 cycles per minute. Most preferably, the servomotor


44


should be capable of completing at least 400 cycles per minute.




Referring now to

FIG. 3

, an alternative embodiment is depicted for a method of transferring the discrete portion


26


from the first web


14


, travelling at a first speed, onto the second web


48


, travelling at a second speed. The numerals used in

FIG. 3

are the same as those used in

FIG. 1

to denote identical elements. The method uses an apparatus


10


′ that is similar to that shown in

FIG. 1

except that a non-vacuum anvil roll


78


is used along with an intermediate transfer roll


80


. The non-vacuum anvil roll


78


cooperates with the rotary cutter


28


to form the discrete portions


26


. However, each discrete portion


26


is not carried onto the outer surface of the anvil roll


78


. Instead, each discrete portion


26


moves downstream and contacts the outer circumference of an intermediate transfer roll


80


. The intermediate transfer roll


80


is a vacuum roll and will rotate at the same surface speed as the adjacent anvil roll


78


. The outside diameter of the intermediate transfer roll


80


can be smaller than, equal to or larger than the diameter of the transfer roll


40


. The diameter of the intermediate transfer roll


80


can also be smaller than, equal to or larger than the diameter of either the rotary cutter


28


and/or the non-vacuum anvil roll


78


. Preferably, the intermediate transfer roll


80


will have an outside diameter that is equal to the outside diameter of the transfer roll


40


. Most preferably, the rotary cutter


28


, the non-vacuum anvil roll


78


, the intermediate transfer roll


80


and the transfer roll


40


will all have the same outside diameter.




A plate


82


can be positioned downstream of the non-vacuum anvil roll


78


to assure that each discrete portion


26


that is cut will not fall between the non-vacuum anvil roll


78


and the intermediate transfer roll


80


. The plate


82


can also function to prevent the discrete portion


26


from physically staying on the outer surface of the non-vacuum anvil roll


78


. The plate


82


can be formed from different materials, for example, steel or aluminum, and can be closely aligned with the two rolls


78


and


80


.




Alternatively, the arrangement shown in

FIG. 3

will work equally well when the discrete portion


26


is attached to the trim waste


36


by one or more narrow fingers. The fingers can be designed to be easily broken as the discrete portion


26


comes into contact with the vacuum of the intermediate transfer roll


80


. The fingers will assure that each discrete portion


26


will not fall down between the non-vacuum anvil roll


78


and the intermediate transfer roll


80


. Instead, the discrete portion


26


will be urged onto the outside surface of the intermediate transfer roll


80


by the vacuum. The fingers will be easily broken by the force of the vacuum pulling on the discrete portion


26


thereby allowing the discrete portion


26


to move away from the trim waste


36


.




Referring now to

FIG. 4

, a graphic representation of the speed modulation for the servo-driven transfer roll


40


is shown. The speed of the transfer roll


40


, in seconds, is plotted along the x-axis and the velocity, in inches per second, is plotted along the y-axis. The transfer roll


40


was sized to have a circumference of about 30 inches (about 762 mm) and was operated at about 325 cycles per minute. The profile of the speed of the transfer roll


40


was measured when the speed of the second web


48


was traveling at about 1,085 feet per minute (about 33,070 cm/min) and the first web


14


was traveling at about 325 feet per minute (9,906 cm/min.). It should be noted that this invention would work when the speed of the first web


14


is less than, equal to or greater than the speed of the second web


48


.




The transfer roll


40


was set up as is depicted in FIG.


1


and the discrete portion


26


had a length of about 12 inches (about 304.8 mm). One complete revolution of the transfer roll


40


occurred every 360-degrees. It was assumed that the acceleration and deceleration of the transfer roll


40


could begin after at least one half of each discrete portion


26


was positioned on the transfer roll


40


. Starting at a time t


0


and continuing until time t


1


, the initial speed of the transfer roll


40


was constant at about 163 inches per second (about 4,140 mm/sec.), denoted by reference numeral A. During this time, the discrete portion


26


was being transferred from the outer surface of the anvil roll


32


to the outer surface of the vacuum transfer roll


40


while both rolls


32


and


40


were rotating at the same speed. At time t


1


, the speed of the transfer roll


40


began to accelerate and continued to accelerate until time t


2


when it reached a speed of approximately 490 inches per second (about 12,446 mm/sec.), denoted by reference numeral B. The speed of the transfer roll


40


was then decreased from time t


2


to time t


3


Starting at time t


3


, the transfer roll


40


was maintained at approximately 217 inches per second (approximately 5,512 mm/sec.) for a time period extending to time t


4


, denoted by reference numeral C. The approximately 217 inches per second (approximately 5,512 mm/sec.) was based on a web speed of about 1,085 feet per minute (about 33,070 cm/min.). At this point, the discrete portion


26


was transferred from the transfer roll


40


to the second web


48


. The transfer of the discrete portion


26


onto the second web


48


occurred while both the discrete portion


26


and the second web


48


were travelling at the same speed. The transfer roll


40


was then accelerated, starting at time t


4


, to a speed of approximately 490 inches per second (approximately 1,245 cm/sec.) which was attained at time t


5


, denoted by reference numeral D. Subsequently, the speed of the transfer roll


32


was decelerated back to the original speed of approximately 163 inches per second (approximately 4,140 mm/sec.) from time t


5


to time t


6


.




It should be noted that the transfer roll


40


will begin to accelerate prior to the time when the entire discrete portion


26


is attached to the second web


48


. This could cause wrinkles to form on the discrete portion


26


. The severity of the wrinkles will vary depending upon materials and this should be evaluated on a case by case basis. The wrinkles could be reduced or eliminated depending on the size of the gap


64


.




Once the discrete portion


26


has been transferred to the vacuum transfer roll


40


, the discrete portion


26


may be transferred to one or more additional transfer rolls or it can be positioned onto or be secured to the second web


48


. The apparatuses


10


and


10


′ and the methods using the apparatuses


10


and


10


′ are especially useful in manufacturing disposable absorbent articles. It is important that when the discrete portions


26


and the second web


48


are combined, their surface speeds be matched to within at least about 5% of each other. Preferably, the surface speeds will be matched to within at least about 3% of each other. More preferably, the surface speeds will be matched to within at least about 1% of each other. By matching the speeds of the discrete portions


26


and the second web


48


, shock loading can be reduced and wrinkles, gaps, and other defects can be eliminated. When the discrete portions


26


are combined with the second web


48


at different speeds, registration problems can occur. Furthermore, other downstream problems in the converting and/or in the packaging operations can occur when the speeds are not matched.




Once the discrete portion


26


is at least partially transferred from the transfer roll


40


onto the second web


48


, the servo-driven transfer roll


40


can be accelerated and decelerated back to a first speed that will match the speed of the anvil roll


32


. This will enable the transfer roll


40


to accept another incoming discrete portion


26


from the anvil roll


32


while rotating at the same speed as the discrete portion


26


.




When the second web


48


is travelling faster than the first web


14


, the discrete portion


26


can be severed from the first web


14


by the rotary cutter


28


. The discrete portion


26


is then attracted to the outer surface of the anvil roll


32


by a vacuum. The transfer of the discrete portion


26


onto the outer circumference of the transfer roll


40


can occur when at least half of the discrete portion


26


is on the transfer roll


40


. This can be accomplished by adjusting the vacuum levels between the transfer roll


40


and anvil roll


32


, as well as the surface roughness of the rolls


32


and


40


. As long as the transfer roll


40


has a greater surface force, the discrete portion


26


will slip on the anvil roll


32


. The transfer roll


40


is first accelerated and then decelerated to match the speed of the second web


48


. The reason the transfer roll


40


is accelerated and then decelerated is because of the distance the discrete portion


26


has to travel on the outer circumference of the transfer roll


40


in a given period of time. As the transfer roll


40


rotates, the remainder of the discrete portion


26


is pulled from the slower moving anvil roll


32


. As the discrete portion


26


enters the gap


64


, it is transferred onto the second web


48


and can be secured thereto, if desired. Once at least half of the discrete portion


26


is transferred onto the second web


48


, the servo-driven transfer roll


40


is decelerated so as to be at the proper speed to pick up another incoming discrete portion


26


from the anvil roll


32


. Likewise, the discrete portion


26


will be transferred after half of the discrete portion


26


is transferred by adjusting the vacuum levels.




Referring to

FIGS. 5-7

, three alternative arrangements are shown for arranging the various rolls. In addition, the use of more than one servo-driven transfer roll is also depicted. In

FIG. 1

, the rotary cutter


28


, the anvil roll


32


, the transfer roll


40


and the backing roll


66


are shown as being vertically aligned. In

FIG. 5

, the servo-driven vacuum transfer roll


40


is vertically offset from the anvil roll


32


and the rotary cutter


28


. This offset can reduce the amount of time the discrete portion


26


is present on the outer circumferences of both the anvil roll


32


and the transfer roll


40


. In some instances, because of the length of the discrete portion


26


and the diameters and rotational speeds of the rolls


32


and


40


, this arrangement will be more efficient.




In

FIG. 6

, a vertical arrangement is shown similar to

FIG. 1

except that a second servo-driven, vacuum transfer roll


84


is present. In

FIG. 6

, the first web


14


is directed into the gap


34


from the right side and the rotary cutter


28


is rotated clockwise while the anvil roll


32


is rotated counter-clockwise. The discrete portion


26


is cut and is transferred to a first transfer roll


40


at gap


42


. The discrete portion


26


is then transferred from the transfer roll


40


to the second transfer roll


84


at gap


86


. The first transfer roll


40


rotates in a clockwise direction while the second transfer roll


84


rotates in a counter-clockwise direction. From the second transfer roll


84


, the discrete portion


26


is transferred onto the second web


48


.





FIG. 7

shows an arrangement of rolls similar to that shown in

FIG. 6

except that in

FIG. 7

, the anvil roll


32


and the first and second transfer rolls,


40


and


84


respectively, are vertically offset from the rotary cutter


28


. This offset arrangement may be advantageous when the lengths of the discrete portion


26


change or when the diameters and speeds of the various rolls


32


,


40


and


84


need to be changed. The offset arrangement also can be used when less vertical spacing is present between the first and second webs,


14


and


48


, respectively.




The invention will be further described by way of the following theoretical example.




EXAMPLE 1




Calculations were completed using a rotary cutter


28


, a vacuum anvil roll


32


and a servo-driven vacuum transfer roll


40


arranged according to the schematic depicted in

FIG. 1

to produce a disposable absorbent article. Even though this example is a theoretical model, it does outline the steps one should follow to build a prototype. The size, shape and construction of the disposable absorbent article as well as the diameters, nips and gaps of the various rolls can be sized to accommodate the particular article that one desires to manufacture. The circumference of the rotary cutter


28


, the anvil roll


32


, and the transfer roll


40


could be selected to be about 30 inches (about 762 mm). The rotary cutter


28


could be made of steel and have a single knife


30


secured to its outer periphery. The knife


30


can have a cutting blade with a width of about 6 inches (about 152.4 mm). The knife


30


can be constructed from M2 tool steel that is commercially available from Kinetic Co. Inc. having an office at 6775 W. Loomis Road, Greendale, Wis. 53129-0200. The anvil roll


32


can be a solid roll constructed from D2 tool steel. Alternatively, the anvil roll


32


can be a constructed roll having a wall thickness sufficiently strong to withstand the accepted deflection forces. The constructed roll can allow an easier way to add vacuum to the roll. The surface of the construction roll should be made of D2 tool steel. The transfer roll


40


should be constructed of polycarbonate or lightweight plastic materials. These materials are commercially available from Cadillac Plastic & Chemical Co. having an office at 2803 Packerland Drive, Suite 17, Green Bay, Wis. 54313.




The vacuum in both of the anvil roll


32


and in the transfer roll


40


should be approximately 20 inches of water (approximately 508 mm of water). A 3,000 to 4,000 revolutions per minute (rpm) servomotor


44


with a torque capability of about 33 foot-pounds could be selected to power the servo-driven transfer roll


40


. The servomotor


44


can be purchased from Indramat, a Division of The Rexroth Corporation having an office at 5150 Prairie Stone Parkway, Hoffman Estates, Ill. 60192-3707. The servomotor


44


can be connected to a 3 to 1 low inertia gear box. Such a gearbox is commercially available from Wisconsin Bearing, a Division of Motion Industries having an office at 565 Enterprise Drive, Neenah, Wis. 54956.




The transfer roll


40


is a vacuum roll that can be driven by the servomotor


44


. The transfer roll


40


could be made from various lightweight materials, including a composite of aluminum, steel and engineered plastics. The surface of the vacuum transfer roll


40


could be coated, if desired, and finished to have a predetermined surface roughness. The gap


42


formed between the anvil roll


32


and the transfer roll


40


could be sized to be from between about 0.125 inches to about 0.188 inches (about 3.17 mm to about 4.77 mm) so as to allow the discrete portion


26


to easily pass therebetween. The exact dimension of the gap


64


will depend upon the material that is being transferred, the size of the transfer roll


40


, the rotational speed of the transfer roll


40


and the dimensions of the discrete portion


26


, as well as other factors.




A first web


14


of high loft, airlaid material can be fed horizontally through the nip


18


formed between the pair of feed rolls


20


and


22


. The first web


14


would be advanced through the gap


34


formed between the rotary cutter


28


and the vacuum anvil roll


32


. The discrete portions


26


can be individually cut from the first web


14


and be transferred onto the vacuum anvil roll


32


. The transfer of the discreet portions


26


can occur at the speed of the first web


14


. Each discrete portion


26


can be conveyed clockwise around the vacuum anvil roll


32


to the gap


42


. At the gap


42


each discrete portion


26


can be transferred onto the outer surface of the servo-driven, transfer roll


40


. While on the outer surface of the transfer roll


40


, each discrete portion


26


can be rotated counterclockwise and the speed of the transfer roll


40


can be changed to match the speed of the second web


48


. The speed of the second web


48


can be controlled by the feed mechanism


68


. The second web


48


can be made of polypropylene spunbond and can be fed into the gap


64


at a speed of about 217 inches per second (about 5,512 mm/sec.)




The discrete portion


26


, after being cut, can be passed from the anvil roll


32


to the transfer roll


40


. The anvil roll


32


and transfer roll


40


are set up with a minimal gap


42


therebetween to allow the passage of the discrete portion


26


from the anvil roll


32


to the transfer roll


40


. At a point between the transfer roll


40


and the backing roll


66


, the discrete portion


26


can be brought into contact with the second web


48


and the discrete portion


26


can be adhered to the second web


48


. The backing roll


66


will assure that the discrete portion


26


is firmly attached or positioned on the second web


48


to form the combination web


76


.




It should be noted that the discrete portion


26


can be cut out of the first web


14


so as to have a desired length and width, for example, a length of about 12 inches (about 305 mm) and a width of about 2 inches (about 51 mm). To produce about 325 discrete portions per minute (about 5.4 products per second, or one discrete portion every 0.18 seconds), the speed of the incoming first web


14


can be regulated at about 3,900 inches per minute (about 9,906 cm/min.). It is desirable to cut one discrete portion


26


per each rotation of the rotary cutter


28


. The rotary cutter


28


can rotate at 325 rpm which, in turn, requires the surface speed of the rotary cutter


28


and the anvil roll


32


to be about 9,750 inches/minute (about 24,765 cm/min.).




In Example 1, the first web


14


can be directed into the gap


34


where the discrete portion


26


will be cut from the first web


14


by the rotary cutter


28


cooperating with the anvil roll


32


. As the discrete portion


26


is being cut or immediately after being cut, it is transferred onto the outer circumference of the anvil roll


32


, which is rotating at the speed of the rotary cutter


28


. To correct for any mismatch in speeds between the rotary cutter


28


and the anvil roll


32


, while the discrete portion


26


is in contact with both, the discrete portion


26


is allowed to slip over the outer surface of the anvil roll


32


. After the discrete portion


26


has been released from the rotary cutter


28


and has been transferred onto the outer surface of the anvil roll


32


, the speed of the discrete portion


26


will match the speed of the anvil roll


32


.




The discrete portion


26


is carried by the anvil roll


32


and is transferred to the servo-driven transfer roll


40


. As soon as at least half the length of the discrete portion


26


has been transferred onto the surface of the transfer roll


40


, the transfer roll


40


is accelerated and then decelerated to a constant speed of about 13,020 inches/minute (about 33,070 cm/min.). This represents the same speed at which the second web


48


is traveling. The discrete portion


26


is transferred from the servo-driven transfer roll


40


to the second web


48


and firmly pressed in place by the backing roll


66


. The pressure at the nip point between the servo-driven transfer roll


40


and the backing roll


66


is about five pounds per linear inch.




While the invention has been described in conjunction with several specific embodiments, it is to be understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the aforegoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope of the appended claims.



Claims
  • 1. An apparatus having a machine direction for transferring a discrete portion of a first web traveling at a first speed onto a second web traveling at a second speed, comprising:a) a pair of feed rolls capable of advancing said first web through a gap formed by a converting mechanism and an anvil roll, said converting mechanism capable of forming at least one discrete portion out of said first web; b) a vacuum roll positioned downstream of said converting mechanism and said anvil roll by a distance greater than said discrete portion in the machine direction, said vacuum roll traveling at a desired rotational speed and capable of directing said discrete portion away from said converting mechanism; c) a transfer roll positioned in close proximity to said vacuum roll and initially traveling at a rotational speed at least equal to said rotational speed of said vacuum roll, said transfer roll forming a gap with said vacuum roll through which said discrete portion can pass, said transfer roll being capable of directing said discrete portion away from said vacuum roll, and said transfer roll being driven by a servomotor such that said transfer roll can change rotational speed to match said second speed during a single revolution; and d) a backing roll positioned in close proximity to said transfer roll and traveling at a rotational speed equal to said second speed, said backing roll cooperating with said transfer roll to combine said discrete portion with said second web.
  • 2. The apparatus of claim 1 further comprising a plate located between said anvil roll and said vacuum roll adapted to supporting said discrete piece.
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