CA1082087A - Method and apparatus for continuously attaching discrete, stretched elastic strands to disposable absorbent products - Google Patents

Abstract

ABSTRACT

A method is described for continuously attaching discrete lengths of elastic ribbon to a moving, substantially inelastic web, particularly for a disposable diaper. The method comprises the steps of feeding a heat-sealable elastic ribbon to an assembly station in a stretched condition; feeding a web of substantially inelastic material to said assembly station; adhering discrete lengths of said heat-sealable elastic ribbon to said web at said assembly station by elevating the surface temperature of said ribbon only in predetermined areas along the length of said elastic ribbon; maintaining said elastic ribbon in a stretched condition until the temperature of said ribbon has been lowered sufficiently to bond said ribbon to said web; cutting said elastic ribbon transversely in an area which is not adhered to said web, thereby forming severed unadhered ends of elastic at both ends of each discrete length of stretched elastic ribbon adhered to said web; and allowing the severed unadhered ends of said elastic ribbon to relax and contract to their unstretched state, whereby the presence of the unadhered ends does not interfere with the performance of the web or the discrete length of adhered elastic ribbon to which said unadhered ends are attached.

Description

i.08Z0~7 This invention relates to a method and apparatus for secur-ing an elastic ribbon in stretched condition to a continuously moving web, e.g. in the manufacturing of disposable absorbent diapers It is a divisional of Canadian application Serial No.
262,296, filed September 29, 1976 and is related to Canadian applications 341,393 and 341,394 filed concurrently herewith.
Method and apparatus for securing an elastic ribbon in stretched condition to a continuously moving web in the manu-facture of garments and the like is well known in the art.
This may be done either by sewing, by the use of a heat-activated coating on the elastic or by the use of a separate adhesive. It is also known that this process can be carried out in such a way that the elastic is joined in spots, i.e., not continuously secured to the moving web.
- U.S. Patent 3,828,367 which issued to Bourgeois on August 13, 1974 is representative of such prior art processes. The patent to Bourgeois is directed to a method for the continuous manufacture of disposable panties. The disclosure of Bourgeois teaches the adherence of a stretched elastic element to a mov- - -ing web in which the entire length of elastic is attached, said entire length of elastic being functional in the finished articles cut from the web. Bourgeois further suggests that the ; elastic may be adhered at all points of contact with the fabric web, or alternatively at spaced points along the entire length of elastic.
U.S. Patent 3,560,292 which issued to Butter on February

2, 1971 and which is also typical of the prior art, discloses a non-continuous process for fastening a tensioned elastic band to a textile sheet by fusion bonds or welds at least at the ends of the band and preferably at uniformly spaced spots throughout the entire extent of .., ``` 108Z087 the band. In the disclosed embodiment, baby pants made of a textile sheet of cellulose or the like have elastic bands secured to the leg opening and waistband portions thereof. During the welding step, the elastic bands are spot welded or fusion bonded at their ends by appropriate tools to the cut-to-size material positioned therebeneath by means of heat and pressure. After the welding spots have cooled off, the preliminary tensioning of the elastic bands is released and the projecting ends of the elastic bands are severed and discarded to facilitate assembly of the garment.
U.S. Patent 3,616,770 which issued to Blyther et al. on November 2, 1971 discloses apparatus for separating garments to which a continuous band of elastic has been sewn along the entire length thereof. In a preferred embodiment, a continuous band of elastic material is fed -from a reel under tension and the band and the garments are drawn through the sewing machine by suitable feed means which also serve to maintain the tension in the elastic. A pneumatically operated cutting device positioned immediately after the feed means cuts the elastic band between the garments, thereby separating the elasticated articles.
The prior art completely fails, however, to teach means for continuously joining elastic bands in discrete, -spaced areas while in a stretched condition at pre-determined points along a continuously moving, substant-ially inelastic web, said web thereafter severed in the areas where said elastic is unjoined to said web so that ~-the unadhered areas of the elastic bands become relaxed, inactive, and non-functional.

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In accordance with one feature of the present invention, there is provided a method for continuously attaching discrete lengths of elastic ribbon to a moving, substantially inelastic web, comprising the steps of:
feeding a heat-sealable elastic ribbon to an assembly station in a stretched condition; feeding a web of substantially inelastic material to said assembly station;
adhering discrete lengths of said heat-sealable elastic ribbon to said web at said assembly station by elevating the surface temperature of said ribbon only in predetermined areas along the length of said elastic ribbon; maintaining said elastic ribbon in a stretched condition until the temperature of said ribbon has been lowered sufficiently to bond said ribbon to said web; -cutting said elastic ribbon transversely in an area which is not adhered to said web, thereby forming severed unadhered ends of elastic at both ends of each discrete length of stretched elastic ribbon adhered to said web; and allowing the severed unadhered ends of said elastic ribbon to relax and contract to their unstretched state, whereby the presence of the unadhered ends does not interfere with the performance of the web or the discrete length of adhered elastic ribbon to which said unadhered ends are attached.
According to a further feature of the invention, there is provided an apparatus for continuously attaching discrete lengths of elastic ribbon to a moving, substantially inelastic web, said apparatus comprising:
means for feeding a heat-sealable elastic ribbon to an assembly station in a stretched condition; means for feeding a web of substantially inelastic material to said . ~ .: . . .: -- . ~ - . . . .

1(~8Z0~7 assembly station; means for adhering discrete lengths of said heat-sealable elastic ribbon to said web at said assembly station by elevating the surface temperature of said ribbon only in predetermined areas along the length of said ribbon; means for maintaining said heat-sealable elastic ribbon in a stretched condition until the temperature of said ribbon has been lowered sufficiently to bond said ribbon to said web; and means for cutting said elastic ribbon transversely in an area which is not adhered to said web, thereby forming severed unadhered ends of elastic at both ends of each discrete length of ~ :
stretched elastic ribbon adhered to said web.
In the following description, the preferred embodiments of this invention are described in conjunction ~ -with the preferred embodiments of the inventions described and claimed in Canadian applications 262,296, 341,392 and 341,393 . This includes the attached drawings in ~:
; which:

~' ,' ~082V~7 Figure 1 is a simplified sectional side elevation view showing the assembly of a web of disposable diaper material having stretched elastic bands secured thereto at regularly spaced locations along its length, said web being thereafter C-folded and cut at predetermined points along its length to form individual disposable diapers having discrete elastic leg bands;
Figure 2 is a simplified plan view of the disposable -diaper web illustrated in Figure 1, taken along view line 2-2 in Figure 1, illustrating the outline of the discrete absorbent pad, the positioning of the side notches and the location of the continuous, stretched elastic strands in the assembled web throughout web assembly, C-folding and cutting operations.
Figure 3 is a simplified plan view of the assembly station shown in Figures 1 and 2, illustrating a preferred drive mechanism for the apparatus;
Figure 4 is an enlarged, simplified, cross-sectional view of a diaper taken at a point corresponding to that of section line 4-4 of Figure 2, said diaper being illustrated ".

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~08~087 in a planar condition for purposes of clarity, said view illus-trating a preferred relationship between the moisture-impervious backsheet, the moisture-pervious topsheet, the absorbent pad and the stretched elastic leg bands in a diaper which has been severed from the web, but which is still being :
maintained in tension;
Figure 5 is an enlarged view taken along view line 5-5 in Figure 1, illustrating a preferred adhesive pattern applied to the stretched strands of elastic;
10Figure 6 is an enlarged cross-sectional view taken along section line 6-6 in Figure 2, illustrating a preferred relationship between the moisture-impervious backsheet, the moisture-pervious topsheet and the adhesive utilized to secure the stretched elastic bands to the backsheet after they have been combined by the laminating rolls;
Figure 7 is an enlarged cross-sectional view taken along section line 7-7 in Figure 2, illustrating a preferred relationship between the moisture-impervious backsheet, the moisture-pervious topsheet and the stretched elastic bands in those portions of the web where the elastic bands are unsecured to the web;
; Figure 8 is an enlarged, simplified, cross-sectional view taken along section line 8-8 of Figure 2, illustrating the ; tendency of the web guides to cause the outermost portions of the diaper web to wrap themselves about the board folder located at the infeed to the rotary drum; and : :

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: ~ , ; . . ': ' ~08Z087 Figures 9 - 11 are views similar to that of Figure 5, illustrating alternative adhesive patterns which may be employed in the practice of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS

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U. S. Patent 3,860,003 which issued to Buell on January 14, 1975, discloses a number of disposable diaper embodiments employing elastically contractible, flexible side portions to which the method and apparatus of the present invention are particularly well suited. It will be readily apparent to those skilled in the art, however, that although the following description of the present invention is in connection with disposable diaper structures having discrete elastic leg bands secured at predetermined locations along their length, the present invention may be practiced with equal facility and at high ; speed on any continuously moving web of interconnected articles having discrete elastically contractible bands secured thereto at predetermined locations along their length.
Referring to Figures 1 and 2, there is shown a ; continuous web 1 comprised of a plurality of inter-connected disposable diapers 2, each diaper being comprised of an absdorbent pad element 3, a pair of continuous, stretched elastic bands 4 secured to the web ; at predetermined spaced locations, said absorbent pad and :-said stretched elastic bands being located intermediate a moisture-impervious backsheet 5 and a moisture-pervious topsheet 6. The elastic bands 4 are preferably adhered to the moisture-impervious backsheet 5 intermediate the opposing - 8 -. .

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~082087 end portions of the hourglass-shaped absorbent pad elements 3 by means of beads of adhesive 7' applied at predetermined points along the length of the continuous stretched elastic bands 4.
This is most clearly illustrated in Figures 4 and 6. The components utilized to form the disposable diaper web 1 are maintained in tension throughout the web assembly, C-folding and transverse cutting operations illustrated in Figures 1 and 2.
Accordingly, the stretched elastic bands 4 are not allowed to gather or pucker the assembled web 1 until tension on the individual diapers 2 cut therefrom has been released.
The web forming or laminating operation is illustrated schematically in Figures 1 and 2. The hourglass-shaped absorbent pad segments 3 are fed into the nip between a pair of combining or laminating rolls 23 and 24 at regularly spaced intervals by means of an infeed conveyor 21 operating about discharge roll 22. For purposes of clarity, the pad infeed conveyor 21 and roll 22 are not shown in Figure 2. In a preferred embodiment the absorbent pad elements 3 are preferably comprised of airfelt confined within a cellulosic tissue envelope to provide pad integrity in use. A continuous web of moisture-impervious backsheet material 5 is directed about the uppermost combining roll 23, while a continuous web of moisture-pervious topsheet material 6 is directed about the lowermost combining roll 24.
As can be seen from Figures 2, 4, 7 and 8, the moisture-impervious backsheet material 5 is coated on portions of its -innermost surface with a flexible adhesive 7. It should be noted, however, that those portions of the moisture-impervious web 5 which are laterally aligned with the continuous stretched bands of elastic 4 are preferably not coated with adhesive 7 prior to entry into the nip between combining rolls 23 and 24.
_ g _ 1(~82087 In yet another embodiment of the present invention the flexible web laminating adhesive 7 may be applied directly to the moisture-pervious topsheet 6 rather than the moisture-impervious backsheet 5. In the latter embodiment, the flexible adhesive 7 must be applied in such a manner that the moisture-pervious characteristic of the topsheet is not impaired, or the adhesive must be so located that it will not adversely affect the finished structure's ability to absorb body exudates, or both.
The continuous bands of elastic 4 are preferably fed without any residual tension into a low-pressure nip formed between a pair of metering rolls 17 and 18. In a preferred embodiment, the low-pressure nip contacts opposite surfaces of the elastic bands, but exerts only slight pressure thereon to minimize deformation of the bands since deformation of the bands adversely affects the system's ability to match the velocity of the bands to the peripheral velocity of the metering rolls. The continuous bands of elastic 4 are wrapped almost completely about the periphery of metering rolls 18 and are thereafter fed almost completely about the periphery of an additional pair of identical metering rolls 19, as shown in Figures 1 and 2. The continuous bands of elastic 4 are thereafter directed into the nip formed between combining .

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1(~8Z087 rolls 23 and 2a intermediate the web of backshee. material 5, the absorbent pad elements 3 and the web of topsheet material 6. The rolls 17, 18 and 19 act to me~er the elas~ic being fed into the combining nip formed between rolls 23 and 24 at an extremely accurate and predetermined rate. The accurate metering is provided by minimizing slippage of the elastic bands relative to the surface of the metering rolls ~nd by minimizing deformation of the elastic bands. The low-pressure nip formed between rolls 17 and 18 and the relatively large contact area between the elastic bands 4 and the surface of rolls 18 and 19 function well in both regards. Furthermore, the low-pressure nip and the S-wrap arrangement of rolls 17, 18 and 19 minimize deformation of the bands, which would otherwise adversely affect the system's metering accuracy. The S-wrap metering system utilized in a preferred embodiment of the present invention provides a relatively constant resistance on the elastic so that when the peripheral velocity VD of the metering rolls 17, 18 and 19 is lower than the infeed velocity VB of the substantially inelastic moisture-impervious backsheet 5 and the infeed velocity Vc of the substantially inelastic moisture-pervious topsheet 6 at the combining nip formed between rolls 23 and 24, the continuous bands of elastic 4 are uniformly stretched and maintained under constant tension along that portion of their length between metering rolls 19 and combining `` rolls 23 and 24. In yet another embodiment of the present -, invention, a second low-pressure nip may be formed between metering rolls 18 and metering rolls 19, and the elastic bands may be fed directly about metering rolls 18 into said second nip. The latter arrangement is, however, less pre- -ferred due to the tendency of the nip to exert pressure on the elastic bands and cause deformation thereof.

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1()8Z087 The incoming veloci~y VA ol t:he uniformly spaced absorbent pad elements 3 is approximately equal to the incoming velocity VB of the moisture-impervious backsheet 5 and the incoming velocity Vc of the moisture-pervious topsheet 6.
~he difference between the surface or peripheral velocity ~D of metering rolls 17, 18 and 19 and the velocity of in-coming web 5, incoming web 6 and the incoming pad elements 3 at the nip between the combining rolls 23 and 24 thus determines the amount of draw or stretch in the continuous elastic bands 4.

As is illustrated in Figures 1 and 2, a pair of glue applicators 20 is preferably employed to apply a pre-determined amount of adhesive 7' at a predetermined spaced - intervals along the length of the continuous bands of elastic :

4. Because the degree of tension in the continuous elastic bands 4 between the metering rolls 19 and the nip formed between the combining rolls 23 and 24 is uniform, the discrete adhesive beads 7' can be accurately controlled both as to length and spacing so as to precisely align the adhesive 7' with the moisture-impervious backsheet 5 in an area intermediate -:
the opposing end portions of each hourglass-shaped absorbent pad segment 3 at the combining nip between rolls 23 and 24.
In yet another embodiment of the present invention, the entire surface of the elastic ribbon could be coated with ~ a heat-activated adhesive prior to the web assembly station, ; and suitable heating means provided at the assembly station to activate the adhesive only in the desired areas of securement of the web. In still another embodiment of the . ~
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1~8Z087 present invention, a heat-sealable elastic ribbon may be employed, and suitable heating means provided prior to or at the assembly station to raise the surface temperature of the ribbon sufficiently high in the desired areas of securement that the ribbon may be adhered to the web at said areas when it passes through the assembly station.
One heat-sealable elastic material from which such a ribbon may be extruded is available from Shell Chemical Company, Polymers Division, of Cleveland, Ohio under the trademark Kraton G Thermoplastic Rubber.
Attaching the stretched elastic bands 4 to the moisture-impervious backsheet 5 in the manner described herein eliminates adhesive bleed-through on the wearer contact surfaces of the diaper, particularly in situations wherein the adhesive 7' is subjected to compression, as in the nip between laminating rolls 23 and 24. Since many adhesives exhibit a degree of surface tackiness after set up, thus producing a higher coefficient of friction against the wearer's skin, the prolonged adhesive-to-skin contact which would likely occur due to the presence of the stretched elastic leg bands could result in chafing or rubbing and consequent wearer discomfort if the adhesive 7' were secured to the moisture-pervious topsheet 6 rather than the moisture-impervious backsheet 5. Accordingly, the former embodiment is generally preferred over the latter embodiment in the practice of the present invention. To avoid such wearer discomfort problems, the moisture-pervious topsheet 6 could, however, be precoated prior to securement of the elastic to render it non-porous within the area of elastic/adhesive .;

.--attachment, thereby permitting joinder of the elastic bands 4directly to the moisture-pervious topsheet 6 by means of adhesive 7' without creating an adhesive bleed-through problem. In yet another embodiment, a narrow, moisture-impervious film strip could be laminated between the elastic band and the moisture-pervious topsheet.
In a particularly preferred embodiment of the present invention, a fixed-gap clearance is maintained between the uppermost combining roll 23 and the lowermost combining roll 24. In the alternative, a variable-gap nip employing constant force either alone or in combination with a minimum fixed-gap clearance might be employed. The uppermost combining roll 23 preferably has a recessed portion 23' in its outermost surface designed to accept the hourglass-shaped absorbent pad segments 3 so that uniform pressure may be applied to secure the remaining portions of the diaper web together. As is ~-illustrated in the cross-section of Figure 6, the adhesive 7' applied to the continuous elastic bands 4 is preferably ~;
- extruded laterally by the action of the combining rolls 23 and 24 so as to produce the maximum feasible contact area between the moisture-impervious backsheet 5 and the elastic bands 4.
This is desirable not only from the standpoint of maximinizing the degree of securement between the elastic bands 4 and the backsheet 5, but also from the standpoint of minimizing any -inhibiting effect that the adhesive might have on the ability of the elastic bands to expand and contract after the adhesive has set up and tension has been removed therefrom.
As is illustrated in Figures 2 and 7, the moisture-pervious topsheet 6 is preferably adhered to those portions of the coterminous moisture-impervious backsheet 5 with which .~.... -, . : ' -. ' :
~ :. -, . : . ~ .

~08'~087 it comes in c,ontact by means of any suitable flexible adhesive 7. Those portions o~ the el~stic bands 4 which overlap the absorbent pad elements 3 and interconnect one diaper to another ~re preferably unsecured to the diaper web 1, as will be described in greater detail hereinafter. It is therefore preferable that no adhesive 7 be provided in the areas of the diaper through which the unsecured portions of the continuous ~tretched elastic bands 4 pass. Thus, the web of backsheet material 5 is preferably supplied to the combining nip with a striped pattern of adhesive such as is illustrated in Fi~ures 2, 6, 7 and 8 applied to its innermost surface. The hourglass-shaped, semi-rigid absorbent pad elements 3 are held relatively immobile with respect to the topsheet 6 and the backsheet 5, since their lowermost surface is adhered' , directly to the backsheet by means of the s'tripes of adhesive 7. In addition, they are tightly sandwiched between the , ~opsheet 6 and the backsheet 5 which are adhered to one another about most of the periphery of the pad elements 3.

,. After passing through the combining nip between rolls 23 and 24, the web is passed onto a perforated vacuum laminating belt 25 operating about rolls 26 and 27, as illustrated in Figure 1. The vacuum laminating belt 25 is operated at a velocity VE equal to that of the incoming webs '5.and 6 and the incoming pad elements 3 to maintain unifo~m . tension in the continuous stretched elastic bands 4. Suction is drawn on the web through the perforated belt 25 by means o~ a suction box 28 located intermediate rolls 26 and 27 just , beneath the innermost surface of the perforated conveyor belt.

Since the moisture-impervious backsheet 5 is located on the ~, 30 uppermost surface of the web 1, suction applied from the moisture-,, pervious topsheet side of the web tends to secure the web together , -~ - . .

108~087 until the adhesive 7 securing ~he various components of the diaper web together and the adhesive 7' securing the stretched elastic bands 4 to the moisture-impervious backsheet 5 have had an opportunity to set up.

- From the vacuum la~inating belt 25, the assembled diaper web 1 is preferably passed between a rotating trim ~nife 29 and an anvil table 30 which trims a portion of :--~ the excess topsheet and backsheet material from the web in : an area adjacent the recessed portions of the hourglass-shaped pad segments 3 to produce a ~eb having the general outline illustrated in Figure 2. The vacuum laminating belt 25 assists in maintaining proper register of the web 1 and the -~
i absorbent pad elements 3 contained therein with respect to the , trim knife 29 and anvil table 30 so that the excess material is i removed precisely at the desired point. The trim knife 29 and - :
anvil table 30 orm no part of the present invention, and, accordingly, may be of any conventional design well known in the axt. The excess topsheet and backsheet material severed from the web 1 are preferably remo~ed by vacuum means which are also well . ~ -20 known in the art. -From the trim knife 29 and anvil table 30, the continuous web 1 of interconnected disposable diapers 2 is fed onto a ,~ perforated vacuum hold-down belt 10 operating about rolls 9 and 11, as illustrated in Figure 1. Suction is drawn on the web 1 through the perforated belt 10 by means of a suction box 12 located intermediate rolls 9 and 11 just beneath the innermost surface of the perforated conveyor belt, The --purpose of the vacuum hold down belt 10 is to grip the lowermost ~ 16 -surface of the web 1 and thereby provide suf~icient resistance to slippage so that tension can be applied to those portions of the web located downstream from the vacuum hold-down belt.
Since there is essentially no movement between the lowermost surface of the web 1 and the uppermost surface of the vacuum hold-down belt 10, the web travels at substantially the same velocity as the belt, which for purposes of illustration will be referred to hereinafter as VF. In order to maintain the con,tinuous web 1 and the continuous elastic bands 4 contained therein in a stretched condition, the velocity VF of the vacuum hol,d-down belt 10 is preferably equal to ~he velocity VE of the - vacuum laminating belt 25.

' Figure 3 is a simplified schematic illustration of a ~; preferred driv,e system employed to power ~he web combining ,rolls 23 and 24, the elastic metering rolls 17, 18 and 19, the pad infeed conveyor belt 21, the vacuum laminating conveyor ' belt 25, t,he t,rim knife 29, and the vacuum hold-down conveyor , belt 10,. In a, pr,e~erred embodiment, all of the aforementioned ,,~ $q,u,ipment is driven ,by means of a lineshaft 40. The vacuum ` 20 hold-aown belt 10 'is driven by means of a right-angle power ''~ take-off 67 w,h,ich supplies power to the head pulley 11 of the o,o,nveyor by me,ans of çonne,cting shaft 66, ~no~her right-angle powe,r take-off 68 ,is ut,ili2ed to ,drive thç xota~ing trim knife 29 by means of connectin,g shaft 65. Right-angle power take-off 69 which co,nnects to the ,h,ead pulley 27 of the laminating t co,n,veyor belt ~,25 ,supplies power thereto by means of connecting s,haft 64. The lowermost combining roll 24 is also dri~en ,by the lineshaft ,by means of right-angle power ~ake-off 41 and ,, connecting shaft 62, while the uppermost combining roll 23 '~ 30 is driven in synchronization therewith by means of right-angle -: power take-off 59 and connecting shaft 61. As is a~parent,from . ~, , ~ 17 ~
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" 1(~8Z01~7 Figure 3, right-angle power take-off 59 is connected to the line-shaft 40 by means of right-angle power take-offs 55 and 57 and connecting shafts 56 and 58. Right-angle power take-off 42 is utilized to drive both the pad infeed conveyor 21 rotating about head pulley 22 and the S-wrap metering rolls 17, 18 and 19 utilized to feed the elastic bands 4 to the web laminating station. This is accomplished, in a preferred embodiment of the present invention, by providing a chain drive comprising sprocket 43 secured to shaft 63, sprocket 45 secured to shaft 46 and chain 44 connecting the two sprockets. Metering rolls 19 which are fixedly mounted on shaft 46 are thus driven in synchronization with, but at a lower peripheral velocity than the laminating rolls 23 and 24 by means of the chain drive system described above. Since each of the S-wrap metering rolls 17, 18 and 19 must operate at the same peripheral velocity VD, mating gears 49 and 50 (Figure 3) mounted on shafts 46 and 48 respectively are preferably utilized to drive the rolls 19 and 18 fixedly mounted thereon, while mating gears 51 and 52 (Figure 3) mounted ~ -on shafts 48 and 47 respectively are preferably utilized to drive the rolls 17 fixedly mounted on shaft 47. The degree of stretch or draw in the elastic bands 4 can thus easily be controlled by altering the drive speed of S-wrap metering rolls 17, 18 and 19 in relation to the speed of the upper and lower combining rolls 23 and 24. In the illustrated embodiment, this is easily - accomplished by changing sprocket 43 and/or sprocket 45.
; After passing over the vacuum hold-down belt 10, the web 1 is preferably directed about idler roll 60 and onto the surface of a conventional board folder 13. As is illustrated in Figure 2, the board folder 13 tapers from an infeed width substantially equal to the maximum width of the diaper web 1 in its unfolded condition to a discharge width substantially equal to the overall width of the diaper web after C-folding. -- 18 - ~-.: .

108Z0~7 The lateral edge portions of the diaper web are directed about board folder 13 by means of cooperating between a pair of infeed guiderails 14, as illustrated in Figures 1 and 2, and a slight change in direction of the board folder just prior to entrance of the C-folded web onto the surface of a rotary drum 15. The cross-sectional configuration of the web at this particular point is illustrated in Figure 8.
A particularly preferred means for C-folding the continuous, elasticized diaper web 1 and transversely cutting the discrete disposable diapers 2 from the continuous web while said web and the diapers cut therefrom are maintained in tension is described in greater detail in Hooper ~ Weber, U.S. Patent 4,022,456, granted May 10, 1977. The C-folded diaper web 1 is fed onto the periphery of the rotating drum 15 so that each diaper segment 2 is in register with one of the transverse cutting and transverse folding stations located about the periphery of the drum. The drum 15, as explained in detail in U.S. Patent 4,022,456, preferably has a peripheral velocity VG slightly greater than the ; incoming velocity VF of the continuous web 1. The drum preferably has four diaper cutting and transverse folding stations, shown generally at 70, 71, 72 and 73, equally spaced about its periphery. The web 1 and the individual diapers 2 cut therefrom are preferably secured to the periphery of the drum by means of spring-loaded gripping elements which compensate for the difference in the - velocity VG of the rotary drum 15 and the infeed -~
velocity VF of the web 1, said spring-loaded gripping --elements functioning .
~ 19 .

ff ' ' ~ . : - :

1(~8Z087 to maintain both the web and the individual diapers cut therefrom in tension until completion of the transverse folding operation of the individual diapers, which occurs downstream of the transverse cutting station. In preferred embodiment, the individual diapers 2 are cut from the web 1 at a predetermined point intermediate the absorbent pad elements 3 by the interaction of a rotary knife having one or more blades secured to its periphery, i.e., blade 16 in Figure 1, and one of the cutting anvils 86, 87, 88 or 89 associated with each of the diaper handling stations on the periphery of the drum.
Figures 1 and 2 illustrate the condition of the web 1 and an individual diaper 2 at the instant the transverse cut has been effected. As can be seen from Figures 2 and 4, the unsecured portions 4' of the elastic bands 4 which are not adhered to the backsheet 5 by means of adhesive 7' are non-functional after the individual diapers 2 have been severed from the web 1. Accordingly, when the individual diapers 2 are cut from the web 1, the non-functional portions 4' of the elastic bands 4 are allowed to relax and retract to their-free length without inhibiting the functioning of those portions of the bands which are adhered to the backsheet 5 by means of adhesive ' 7'.
Figure 6, which is a cross-sectional view taken along section line 6-6 of Figure 2, illustrates a preferred condition of the adhesive 7' after the web has passed between the combining rolls 23 and 24. It is desirable in the practice of the present invention to ; 30 compress the bead of adhesive 7' to the extent feasible so as to maximize the contact area between - 20 - ~-. . .

~' ' ~.. , , . ~ :, - ,. -1~8~087 the backsheet 5 ~nd th~ ~lastic b~nd 4. ~ thin layer oS adhesive is also generally preferable to a thicker layer of adhesive due to the fact that i~ has a lesser tendency to inhibit the gath--ring and stretch characteristics of the elastic ba~ds 4 in their areas of a & erence to the web. Figure 5 is illustrative of one preferred adhesive application pattern prior to assembly of the laminated web. Figures 9 - 11 are representative of alternative preferred embodiments of adhesive patterns which may be employed in the practice of the present invention. The em~odiment of Figure 9 is particularly desirable when it is desired to uniformly gather the elasticized article throughout the area of adherence between the elastic bands 4 and the backsheet 5. The reduced amount of adhesive applied in the centermost areas of the.elastic bands 4 has a lesser tendency to restrict expansion or contraction of ~he elastic, while thc grcater quantities of adhesive at the end points act to firmly secure the elastic bands 4 to the backsheet 5. The embodiment of Figure 10 may be employed in situations where the adhesive 7' is not particularly flexible after set up, yet it is desirable to gather the elasticized article with at least some degree of uniformity along the elasticized portions thereof. Figure 11, on the other hand, is illustrative of an embodiment wherein uniform gathering of the elasticized article along the elasticized portions thereof is not critical. If desired, the adhesive 7' may, of course, be applied to opposite surfaces of the stretched elastic bands 4 to facilitate securing them to both the backsheet 5 and the topsheet 6.
In a particularly preferred embodiment of the present ; 30 invention, the a & esive 7' used for adhering portions of the stretched elastic members 4 to the moisture-impervious backsheet

5 is comprised of a hot-melt adhesive which is so formulated , .:
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108~2087 that it is ~l~s~om~ric aIter it h~s set up. This allows essentially uninhibited ~athering of the diaper side flaps and subsequent stretching of the elastic members adhered thereto without any substantial separation therebetween. As should be apparent from the foregoing,the adhesive 7' utilized in the practice of the present invention must set up prior to the time at which tension is released in the non-functional end portions 4' of the elastic bands 4. The use of a hot- --melt adhesive in a preferred em~odiment of the present invention permits utilization of high speed product manufacturing techniques without introducing the inherent speed limitations or complexity of more traditional elastic attaching methods such as sewing, conventional adhesives, etc. One stretchable --elastomeric hot-melt adhesive which has been found particularly suitable for use in the practice of the present invention is a high viscosity, ethylene vinyl acetate based material available from Findley Adhesives, Inc., of Milwaukee, Wisconsin under Formula No. 691-336-20. However, any fast setting adhesive having the desired elastomeric and adhesion properties upon set up could be utilized with equal facility.
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Thus, it is apparent that there has been provided, in accordance with the present invention, method and apparatus for intermittently attaching a continuous, stretched elastic ribbon to a continuously moving web at discrete, predetermined locations along the length of said web, and .'~' , .

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108'~087 thereafter severing said elastic ribbon in a portion of its length which is not adhered to the web so that the severed unadhered ends of the elastic ribbon are allowed to relax and become non-functional. It should be noted, however, that while the invention has been described in conjunction with specific preferred embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations that fall within the spirit and broad scope of the appended claims.

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Claims (8)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for continuously attaching discrete lengths of elastic ribbon to a moving, substantially inelastic web, comprising the steps of:
(a) feeding a heat-sealable elastic ribbon to an assembly station in a stretched condition;
(b) feeding a web of substantially inelastic material to said assembly station;
(c) adhering discrete lengths of said heat-sealable elastic ribbon to said web at said assembly station by elevating the surface temperature of said ribbon only in predetermined areas along the length of said elastic ribbon;
(d) maintaining said elastic ribbon in a stretched condition until the temperature of said ribbon has been lowered sufficiently to bond said ribbon to said web;
(e) cutting said elastic ribbon transversely in an area which is not adhered to said web, thereby forming severed unadhered ends of elastic at both ends of each discrete length of stretched elastic ribbon adhered to said web; and (f) allowing the severed unadhered ends of said elastic ribbon to relax and contract to their unstretched state, whereby the presence of the unadhered ends does not interfere with the performance of the web or the discrete length of adhered elastic ribbon to which said unadhered ends are attached.

2. An apparatus for continuously attaching discrete lengths of elastic ribbon to a moving, substantially inelastic web, said apparatus comprising:
(a) means for feeding a heat-sealable elastic ribbon to an assembly station in a stretched condition;
(b) means for feeding a web of substantially inelastic material to said assembly station;
(c) means for adhering discrete lengths of said heat-sealable elastic ribbon to said web at said assembly station by elevating the surface temperature of said ribbon only in predetermined areas along the length of said ribbon;
(d) means for maintaining said heat-sealable elastic ribbon in a stretched condition until the temperature of said ribbon has been lowered sufficiently to bond said ribbon to said web; and (e) means for cutting said elastic ribbon transversely in an area which is not adhered to said web, thereby forming severed unadhered ends of elastic at both ends of each discrete length of stretched elastic ribbon adhered to said web.

3. The apparatus of Claim 2, wherein said means for feeding said elastic ribbon to said assembly station in a stretched condition is comprised of a low-pressure nip formed between first and second metering rolls and a third metering roll independent of said first and second metering rolls, said elastic ribbon being passed into said nip in an unstretched state, partially about the periphery of said second metering roll directly to said third metering roll, partially about said third metering roll, and from said third metering roll to said assembly station, said metering rolls being operated at a uniform peripheral velocity less than that of the incoming webs at said assembly station.

4. The apparatus of Claim 2, wherein said means for feeding said elastic ribbon to said assembly station in a stretched condition is comprised of a first low-pressure nip formed between a first metering roll and a second metering roll and a second low-pressure nip formed between said second metering roll and a third metering roll, said elastic ribbon being passed into said first nip in an unstretched state, partially about the periphery of said second metering roll directly into said second low-pressure nip, and from said second nip to said assembly station, said metering rolls being operated at a uniform peripheral velocity less than that of incoming webs at said assembly station.

5. The apparatus of Claim 2, wherein said means for adhering said discrete lengths of stretched elastic to said web at said assembly station in the discrete areas having adhesive applied thereto is comprised of a nip formed between a pair of combining rolls.

6. The apparatus of Claim 5, wherein said nip has a fixed gap clearance small enough to apply pressure to said web, said elastic ribbon, and the adhesive joining said ribbon to said web as they pass therethrough.

7. The apparatus of Claim 5, wherein said nip has a variable-gap clearance, and a constant force is applied thereto as said web and said elastic ribbon pass therethrough.

8. The apparatus of Claim 2, wherein said means for cutting said elastic ribbon transversely in an area which is not adhered to said web functions to simultaneously cut discrete articles from said web at a predetermined point along the length of said web.