Note: Descriptions are shown in the official language in which they were submitted.
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
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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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108Z087
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
. ~ .: . . .: -
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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:
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~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
. _ . . _ .
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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;J
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
.;
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108Z087
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
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~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
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-~ - . .
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
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108Z087
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
. ~, ,
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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. -
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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
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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
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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.
.',, ~' ','.
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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