CA2547438A1 - Web stabilization on a slip and cut applicator - Google Patents

Abstract

This invention proposes a new, improved method and apparatus for applying web segments to a traveling web. Ears, or wings, are placed on a running web of disposable diapers. Because these webs are often asymmetrical or otherwise incompatible with the principle of slipping over the surface of a moving vacuum roll, the webs may float from side to side or otherwise be drawn out of square by asymmetrical forces. A vacuum groove is provided on a vacuum roll to counter these effects.
Alternatively, a ridge with vacuum about the ridge is provided, also to pull a machine direction line of material into the groove or over the ridge, thereby giving the web some degree of cross-directional stability.

Description

rttv. Docked Nc.: 1047.18&27 pdtent WEB STABILIZATION ON A SLIP AND CUT APPLICATOR
Background of the Invention The present invention relates to disposable undergarments and more specifically, to methods and apparatuses for processing disposable undergarments.
Various types of automatic manufacturing equipment have been developed which produce the desired results with a. variety of naateria,.~s and configurations.
This equipment generally includes slip-and-cut applicators to which this invention is principally directed.
This invention. is directed primarily at slip-and-cut applicators, which are typically compr~~.sed cf a cylindrical rotating vacuum anvil; a rotating kn~.te roll;
and a transfer device. In typical applicatior_s, a tape web or an ear web can be fed alor_g a vacuum face of the rotatv_ng anvil_. A knife-edge, mounted on the rotating knife roll, cuts subsequer:t ears from each other against the anv-_1 face. This kni=e-edge is pre=erably moving at a surface Veloci ty sin~~iia=- to that of t~~e anvil ' s ClrCL;m=eren Ce. OnCe Cut, tile Web Segment 1S .n°_d by Wa,~.1.:~: dravJn ':i_rCLlgr1 1101 eS on trle a_'?v~1' s face a5 -_ '.S
carried at '..he anv,~~'-'s spec: doW:~.s~ream to the transfer point where the web segment is trar_sfe=-red to the traveling web.

Atty. Docket Nc.: 10~'7.18E2%

A common problem associated with slip-and-cut applicators occurs at the point of cut. Since the Web being cut is traveling at a very low velocity compared to the anvil and knife velocity ;perhaps 1/20thi, the engagement of the knife with the ear web tends to induce a high tensile strain in the ear web. having been placed under such a high level of stress, the ear web can recoil violently when the cut is finally completed, causing loss of control of the ear web. This "snap-back" effect increases wits! the thickness ef the ear web. Th=~cker webs tend to prolong the duration of engagement with the knife before completion of the cut, thereby increasing the build-up of strain. This is a common process problem.
that is usually addressed by the provision of various shock-absorbing devices. One possible solution might have been t0 :_"eduCe t~'le SU.-'face VelOClty Of tile knife, but substantially different velocities between the knife and anvil result in rap id wear of the tcnife edge and/or anvil face, depending on relative r:ard_ness.
Continual improvements and competitive pressures have incrementally increased the operational speeds of disposable diaper converters. As speeds increased, the mechanical integrity and operatior~al capabilities of the applicators had to be improved accordingly. As a further complication, the compieyity of the web segments being attached has also increased.
S,,ip-and-cut apparatus' are we~_1 known for their db111ty t0 Cllt 2'elatl'Vely Sh0_"~ segments Of One Web anC place their? accurately On anOtCler, nigiler S~ee:~ web.
30 Cer~a,~n materials, hov,~ever, behave bad,-y in these th cu-~c;~ng ap-.":l lCatiCns . -'ile ter~s10r1 p'il Sa~iOri Ca;lSed by may cause she material tc snap baci:, ios~_ng its natural rack dov,~n the: mov=~ncT surface cf t:-le anvil roll. This is especia-'~ly common v:ith thick: we~~s. Other material s, such as nonwoven fa:rics, may b. difficu=t to control because Pt~v. Dcche~ No.: 1C!4?.1882?

they are very porous and provide little resistance to air flow to keep the material on track. Still ctner materials, sucl: as certain perforated films may possess texture qualities which tend tc be very unstable on the anvil surface, acting instead like a puck on an air hockey table.
These problems are further exacerbated by using materials with a very low modulus of elasticity.
Here, even very low levels of vacuum at the anvil surface may cause the material to stretch with the advancing movement of the anvil. The sudder_ change of tension seen when the knife cuts this over-stretched web car_ result in severe snap-back and complete loss cf position, relative to the intende;3 centerline. Likewise, webs with very high moduli may snap back violently when the web is cut.
An even more challenging requirement is to control an asymmetrical web, such as a diaper ear web as it passes through the slip-and-cut process. For instance, as described in co-pending application titled "High Speed Vacuum Porting" ~-led the same day as ~he present application, the ear web also encounters control difficulties. In such instances, the web has a very narrow continuous ribbon section along one edge, and carries with ~_t a chain of die-cut ears, which must be contrclled. This application does not 'rave lines of web tension in the ear section, and wrile vacuum is generally r ecrsired to maintain some con-:.ro-'_ of the ear s , any excessive draw produced by such vacuum w'11 tend to skew tine ear on the anvil as tn~: vacuum-~-nduced drag produced by the faster-moving anvil arLd felt by the ears is out of line w~~th the ribbon segment.
I t is k~ovTn in the pr;~o=- ar . to run a straight WeD entlr e-!! y wi ~~'lin a grOOVe , SllCY'_ aS ~il cOmmer ~1a1 embodiments o~ U.S. Fatent No. 5,~G7,513. However, This 3 '.', f a.,.. ~ o ~~ r ~ c - ~ n s ~ .~ ~ r c - ~ o ~- ~ ~i 5 r ~ior ~_ do__, not pros d' th~ d__.~r~~ os~ d'~r~~_--onG_ Attv, Docket No.: =,04?.18827 G -control of webs wider than the groove.
It is therefore, an object of this invention.
to maintain: cross-directional control of the ribbon segment, keeping it parallel to the target web.
Likewise, any web that might tend to stray from its natural parallel entry l~_ne might benefit from the invention..
Summary of the Invention Ears, or wings, are placed on a running web of disposab'~e diapers. Because these webs are often asymmetrical or otherwise incompatible with the princip~~e of slipping over the surface of a moving vacuum roll, the webs may float from side to side or otherwise be dravm out of square by asymmetrical forces. A vacuum groove is t~rovided on a vacuum roll to counter these effects.
Alternatively, a ridge with vacuum about the ~.~idge is provided, also to pull a machine direction line of material into the groove or over the ridge, thereby giving the web some degree of cross-directional stability.
In a typical configuration of a slip-and-cut applicator, ':.here is a pattern of vacuum holes distributed to evenly draw ~he entering web onto the anvil's surface and thence into the cut point where the knife edge e;=gages the anvil. The present irven~ion provides a solution by means of a machive-direc~ion groove along ~~ line of vacuum holes at a place where the main tension lines in the in-feeding ma~er~'~al are continuous. 7.'his groove, with its vacuum, will draw ti2e web into the groove, thereby provide a degree of axial stiffness and a corresponding obsrruc~ion and resistance to cress-d;~rectional movement.
Such a groove is norma':~ly v,-ider t:~ar_ the diameter of the vacuum holes, which fall into the groove, but is al so r..o~-rna~~~~:.y kepi narrow and s'r~allow sc as to Attv. Docket No.: 7.a4~.1862?
avoid producing a visible wrink-~.~e in the material. A
typical width and depth might be 3mm wide by 1 mm deep.
In another embodiment, the anv~~l may be provided with a series of circumferentia~_ grooves, thereby p~'oviding the material with a corrugated bed of parallel grooves on which the advancing material may ride.
Still another embodiment achieves similar results by means of a raised ridge, rather than a groove.
Such a ridge provides the material with the r_ecessary obstruction anal stiffness resistant to cross-directional movement. In such embodiments, vacuum holes are positioned on either side of su~h a ridge so as to better hold the material against said ridge.
Brief Description of the Drawings Fig. 1 is a diagrammatic side view of a Prior Art process;
Fia. 2 is a perspective view of an anvil roll of the present: invention carrying an ear web;
Fic~. 2a is a an ear carr,_ed by the anvil roll of the present: invention;
Fic; . 3 is a front view of an anvil roll of the present invent:ion;
Fic;. 3a is a partial cross sectional view of an anvil roll of the present invention;
Ficr. 4 is a front view of an alternate embodiment of an anvil roll of the present invention;
Ficr. 5 is a front view of a second alternate embodiment of an anvil roll of :.he present invention;
Fic~. 5a is a partial cross sectior~al view of a riche patter applied on ar_ anvil =~0~_1 of the present inver:ticr~.
Fiq. 5b is a partial c~~oss sectional view of an alterWa'e ;'1Q'yJe pattern JL 'bile present lnVen..l,~n.
Description of the Preferred Embodiment A-lt:hough the disclosure hereof is deta-_led and Atty~. Docket No.: 1D47,18B27 exact to enable those skilled in the art to practice the invention, the physical embodiments hereir_ disclosed merely exemplify the invention, which may be embodied in other specific structures. While the preferred embodiment r~as been described, the details may be changed without departing from the invention.
Referring more particularly to the drawings there is seen in Figure 1 a diagrammatic illustration of a prior art process for app'-ying tabs to webs in a diaper making process. The present invention can use this prior art method of affixing the tabs 12 to the web 10, with a different anvil, the new anvil 114 described below. Web 10 is a composite material used in formation of diapers which is generally formed of various layers of material such as plastic back sheets, absorbent pads and nonwoven topsheets. A series of ears 12 are applied to web 10. ;n the illustrated process a rotatabie vacuum anvil 14 is used to supply the ears 12 to web 10. Anvil 14 has internally reduced air pressure or vacuum (shown diagrammatically on Fig. 2), and a plurality of openings 24 are provided through its surface to enable suction of the tab segmer..ts 12 against. the anvil surface 14. A web of the ear tab forming material 16 is fed by rollers 20 and 22 against the anvil surface 14 where it is cut into segments bSr a rotary knife 18.
~n the prior art, the su=M ace of the anvil roll 14 has vacuum holes 24 on its smooth surface. In a typical configuration of a slip-and-cut applicator, there is a pattern of vacuum holes 24 distributed to evenly draw the e=;tering web onto the surface of anvil ,_4 and thence into the cut point where the ~:.nife edge 18 engages the anvil 14.
Referring now to Fig. 2, a perspective view of an anvvyl roll 114 is shown carrying an ear web, or forming material 1e. '='his material ~6 is comprises of Attv. Locket No.: 104?.18827 two portions, 12a and 12b as shown ir_ Fig. 2a. Segment 12a is more specifically referred to as the tab section of the ear 12, segment 12b is a ribbon section of the ear .l 2 .
The ear forming material 16 is cut intc individual ears 12 by the rotary knife 1B as shown in Fig. 1, along lines such as the dashed lines shown in Fig. 2.
Referring now to Fig. 3, a front view of an anvil roll 114 of the present invention is shown carp-ying an ear 12 in phantom. In this embodiment, a machine-direction groove 115 along a line of vacuum holes 24 is provided at a place where the main tension lines in the in-feeding material such as ear forming material 16 is continuous, such as the ribbon portion 12b. This groove 115, with its vacuum applied through holes 24 as shown, will draw the web into the groove 1'~5, and thereby p~~ovide a degree of axial stiffness and a corresponding obstruction and resistance to cross-directional movement.
It is preferred that vacuum holes 24 reside both v,~ithin the groove 115 and outside cf tile groove 115 on the surface o. the anvil roll 7.14 as shown.
Still referring to Fig. 3, anvil insert 140 is provided across the groove 1'~5 to provide a surface to engage rotary knife 18 at the desired locatior_. Insert 140 creates a bridge for the r,ibbor_ 12b to ride upon so that she =gibbon 12b can be introduced .r. a cutting position relat=ive to the knife 18 as the knife 18 ,is shown in Fig. .~. Alternatively, insert 140 could simply be machined in.tc the roll 1'.~4.
Referring now -~c Fig. 3a, .~ partial ~.ross SectlOnal vleW' Of the anVl1 rOi~ 1~4 a-'iOng 1=ne .5a - ~d~
from Fig. 2 _w shown. As can be seen, the groove 115 visible. A preferred embodiment of the groove 115 is that the groove 1,_5 is sliahtl~~ v,=_der than the diameter Atty. Docket Nc.: L047.18&2?
_ g _ of the vacuum holes 24, which fall ;.into the groove 115, but is also normally kept narrow and shallow so as to avoid producing a visible wrinkle -~.n the material. F.
typical width and depth might be 3mm wide by 1 mm deep.
It is also prF~ferred that she groove 115 be wider than the ribbon 12b of the ears ,~2.
In operation, the ears 12 are carried by the anvil 114. The ears 12, and preferably the ribbon portion 12b, are passed over the groove 115, and drawn slightly into the groove 115. The vacuum applied to the groove i15 slightly holds the ears 115 along the ribbon 12a of the ears thereby providing stability from either non-machine direction rotation, or nor_-machine direction pulling or pu~;hing.
Referring now to Fig. 4, a front view of an alternate embodiment of the anvil roll 114 of the present invention is shown. In tris embodiment, the anvi,~. 114 is provided with a series of radial grooves 1~~5 in the machine direction, thereby providing the material with a corrugated bed of parallel grooves 115 on which the advancing material (not shown) may ride.
Referring now to Fig. 5, a front view of a second alternG.te embodiment of the anvil roll 114 of the present invention is shown. This embodiment achieves the de sired obstruction and stiffness resistant to cross directional movement by means of a ra-.'used ridge 125 (or ser,_es of ridges 125, not shown.') , rather than a groove 115. The ridge 115 is prow--ided with vacuum holes 24 that are pesitionecL on either side of the ridge 125 so as to batter hold tr.e material's against said =-idge 125.
Referring now to Fia. 5a, a partial cross Se~tlOnal Vlew of err:°_ anV~l r01! 114 along _1ne 5a - :~c~
from Fic. 4 i_=~ shown. As c: an be seen, the ridge '~25 is visible. In '=his embodime_it, the ridge ,-25 provides a ,, r spine about wh~.~ch cross-dire..~_o_:al stabile ty is added to Atty. Docket Nc.: 1047.18827 - g _ the advancing ribbon.
Referring now to Fig. 5b, a partial cross sectional view of an alternate ridge pattern 125 is shown. In this embodiment, the ridge ,~25 may be dimensioned similarly to the g=-oove i15 described previously.
In operation, s__miia_- to that described with the groove system above, the die-cut ears are applied the moving web, a:Lso similar to that shown in Fig. 1. The ears are passed on top of the ridge 125, and drawn about the ridge 125 slightly by the vacuum holes provided near to the sides of the ridge 125. This vacuum a-~ong a length of the ears thereby also provides stability from either nor-machine direction rotation, or non-machine direction ~ul.!ing or pushing, similar to that described with the groove system and method above.
It can be seen that either the ridge or the groove/vacuum system described above can comprise means for maintaining cross-directional stability in an advancing in-feeding web, because the ir_-feeding web will be prov=.~ded w:_th a degree c>f resistance from ncn-machine directional movement by the slight fixation to the machine direction vacuum holes 24.
ThE: fCre'~OlnQ -iS CC?'1S-~dered aS i1111StratlVe r o ~ ' ' l o Cf +' c. ; A , -h en on,_y o_ th p.-lnclp s h.. _nv~ntior:. Fur_ more, since numerous modifications and changes wil-- _eadily OCCUr t0 thOSe 5~:111ed 1n t~"1°_ art, l t 1S not deSlred tC
limit the li.LVentlOn t0 the e};.act cCllStruCtlOn and operation. shown and described. tn~h=~le the preferred embodiment has been descr'_bed, the deta-_is may be charged without departing from the inver_tion.

Claims (10)

1. An anvil roll comprising:
a substantially cylindrical anvil body;
a source of vacuum coupled to said anvil body;
a plurality of vacuum holes provided on an outer surface of said anvil body, said holes communicative with said source of vacuum;
a groove provided on said outer surface of said anvil body, said groove oriented in a machine direction;
a plurality of vacuum holes provided in said groove;
an advancing in-feeding web positioned across said groove, a portion of said web drawn into said groove to provide the cross-directional stability.

2. An anvil roll according to claim 1, the anvil roll further comprising an insert across said groove for engaging a cutting structure.

3. An anvil roll according to claim 1, said anvil roll further comprising an integral cutting surface across said groove.

4. An anvil roll comprising:
a substantially cylindrical anvil body;
a source of vacuum coupled to said anvil body;
a plurality of vacuum holes provided or, an outer surface of said anvil body, said holes communicative with said source of vacuum;
a ridge provided on said outer surface of said anvil body, said ridge oriented in a machine direction;
a plurality of vacuum holes provided proximally to said ridge;
an advancing in-feeding web positioned across said ridge, a portion of said web drawn over said ridge to provide the cross-directional stability.

5. An anvil roll comprising:

a substantially cylindrical anvil body;
a source of vacuum coupled to said anvil body;
a plurality of vacuum holes provided on an outer surface of said anvil body, said holes communicative with said source of vacuum;
a means for providing cross-directional stability in an advancing in-feeding web.

6. A method of applying ribbon to a moving web, said method comprising:
providing an anvil roll with at least one groove;
applying vacuum to said groove;
passing an advancing ribbon over said groove;
drawing a portion of said ribbon into said groove;
whereby said vacuum and said groove provide cross-directional stability to said advancing ribbon.

7. The method of claim 6, further comprising the step of cutting said ribbon in a cross-machine direction after said ribbon is drawn into said groove.

8. A method of applying ribbon to a moving web, said method comprising:
providing an anvil roll with at least one ridge;
applying vacuum proximal to said ridge;
passing an advancing ribbon over said ridge;
passing said ribbon over said ridge with said vacuum;
whereby said vacuum and said ridge provide cross-directional stability to said advancing ribbon.

9. A method of applying ribbon like strips of material to a traveling web, said method comprising:
providing a ribbon like strip of material;
providing an anvil roll with at least one groove;

applying vacuum in said ridge;
allowing a part of the ribbon like strip of material to run in said groove.

10. The method of claim 9, the method further comprising cutting said ribbon in a cross-machine direction after said ribbon runs in said groove.