Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02636679 2008-07-02
1
SANITARY NAPKIN HAVING ZONES OF DIFFERENT HEIGHTS AND DENSITIES
FIELD OF THE INVENTION
The present invention relates generally to absorbent articles and more
particularly to the
field of sanitary napkins.
BACKGROUND OF THE INVENTION
Sanitary napkins of the prior art generally have a planar surface presenting
little relief.
This is even more frequent for ultra-thin sanitary napkins. When worn, these
napkins often
become shapeless by the pressure exerted by the thighs on the product, among
other
things. The outcome of this being that the napkin is no more in contact with
the body of
the user. When a sudden flow occurs, the blood is not captured instantly and
can be
conveyed in non desired locations of the napkin. This can cause leakages in
the front, the
rear or the sides of the napkin.
Therefore, one goal in the field of sanitary napkins is to produce sanitary
napkins that can
optimally fit the wearer's body while at the same time being able to rapidly
absorb the
menstrual flow. Another goal is to be able to direct or guide the menstrual
flow in order to
limit any leakages.
Many attempts have been made in the prior art, to develop sanitary napkins
with improved
absorbency. Some of these attempts disclose sanitary napkins with heightened
zones.
Among these, there is a first method which consists in adding an absorbing
mousse to
form a bump. This implies a complex fabrication method. Other drawbacks are
the
availability, the quality, and the cost of the absorbing mousse as a raw
material.
There are also US2006/0189954, US2006/0259002A1, US6448466B1, and
US6791005B2 which disclose a method where additional absorbing matter, which
is often
made of cellulose fibres, is added in different places of the napkin, to form
a bump. These
methods add steps to the fabrication process and/or do not allow for
controlling the
density of the bump.
CA 02636679 2008-07-02
2
Also a strongly marked bump makes the napkin more difficult to manufacture.
Indeed, the
bump prevents the napkin from being folded and from being packaged in an
individual
envelope. Even if the napkin is not folded, the stacking of this type of
napkins, in a bag, for
selling, becomes compromised.
US2006/0142725A1, US6114597, US6293931131, US6423043B1, US6866658B2,
US6887225B2, EP0983759B1 and CA2386014 present napkins having a mechanical
device for raising a part of the absorbent mattress of the napkin. The
addition of such a
device in the fabrication process is complex and the way it works or operates
is not very
well documented in the prior art. Furthermore, the comfort of such a napkin is
questionable.
US2006/0259022A1, US6425890B1, US6610902B1 and US6656170B2 present a napkin
having a rigid bump. Even though this method allows the napkin to preserve its
bump
when worn, this can also be very uncomfortable.
W02006/084304A1 and W02006/110067A1 present a napkin having a third segment to
form the bump. Again, this type of napkins can be uncomfortable to some
consumers.
In the art, the absorbent mattress is commonly composed of cellulose fibres,
to which
super absorbent powder can be added. The napkin is then formed by projection
of the
fibres in a cavity or a mould of predetermined shape and thickness or by
fibres dosage on
a conveyor in a continuous or an intermittent manner. The absorbent mattress
thus
formed moves on the fabrication line and is usually calendered with smooth
rollers so as
to give it a smaller thickness and to give it more firmness.
There is also known in the art that additional rollers can create canals of
diverse shapes
used as barrier and for directing the menstrual flow. The canals generally
formed have a
maximal width of 3mm and a maximal depth of 10mm. Various designs of such
canals are
present in the industry.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an improved sanitary napkin
that
CA 02636679 2008-07-02
3
overcomes at least one of the aforesaid drawbacks of the prior art.
In accordance with the present invention, that object is achieved with a
sanitary napkin
suitable for use in a crotch portion of an undergarment, the sanitary napkin
comprising a
main body made of an absorbent material extending on a longitudinal axis for
laying on an
upper side of said crotch portion of the undergarment, the main body
comprising:
- a central zone where the absorbent material has a given density and a given
thickness;
- a transition zone, surrounding the central zone, where the absorbent
material is
i0 denser and less thick than in the central zone, the transition zone being
obtained by
compression of the sanitary napkin; and
- an external zone surrounding the transition zone where the absorbent
material is
less dense and thicker than in the transition zone.
Thanks to the fact that the central zone has an increased height and a reduced
density as
compared to the transition zone and to the external zone, the napkin in the
central zone
provides a better contact with the wearer's body and the menstrual flow
absorbed thereon
rapidly flows out toward the transition zone. On its side, the transition zone
which has an
increased density and reduced height relative to the central zone and external
zone acts
as a canal directing the menstrual flow forward or rearward, thereby limiting
leakages via
the sides of the napkin.
In accordance with another aspect of the invention, an apparatus for producing
a sanitary
napkin as defined previously is provided. The apparatus comprises:
- a calender having a first roller and a second roller to laminate the
sanitary napkin,
the first roller having an external surface provided with a recess of desired
shape
surrounded by a projection;
whereby the central zone and transition zone of the sanitary napkin are shaped
by
means of the recess and projection respectively.
As can be appreciated, this apparatus can give to the absorbent mattress
various
thicknesses and accordingly different densities allowing the menstrual flow to
be directed
in strategic locations of the napkin, in order to avoid leakages.
CA 02636679 2008-07-02
4
Further features and advantages of the present invention will be better
understood upon
reading of preferred embodiments thereof with reference to the appended
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a napkin according to a first preferred
embodiment of the
invention.
Figure 2 is a top view of the napkin of figure 1.
Figure 3 is a perspective view of a napkin according to a second preferred
embodiment of
the invention.
Figure 4 is a top view of the napkin of figure 3.
Figure 5 is a top view of a calender design for the high density zone
(transition zone) of
the napkin of figure 1 or 3.
Figure 6 is a schematic side view of an apparatus for making a napkin,
according to the
invention.
Figure 7 is a schematic exploded perspective view of the apparatus of figure
6.
Figure 8 is a side view of the female roller of the apparatus of figure 7.
Figure 9 is a front view of the female roller of figure 8.
Figure 10 is a side view of a male roller of the apparatus of figure 7.
Figure 11 is a front view of the male roller of figure 10.
Figure 12 is a schematic exploded perspective view of the apparatus for making
the
napkin of figure 3.
CA 02636679 2008-07-02
Figure 13 is a side view of the male roller of the apparatus of Figure 12.
Figure 14 is a front view of the male roller of figure 13.
5 DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
In the present description, it should be understood that the expression
"sanitary napkins"
is used to designate any sanitary product adapted to be positioned in the
crotch section of
an undergarment irrespectively of its construction, its level of absorbency or
its shape,
including panty liners.
Referring to figures 1 to 4, the present invention provides a sanitary napkin
10 suitable for
use in a crotch portion of an undergarment. The sanitary napkin 10 comprises a
main
body 11 made of an absorbent material extending on a longitudinal axis for
laying on an
upper side of the crotch portion of the undergarment. The sanitary napkin 10
can have a
layer of permeable material, a layer of impermeable material and a layer of an
absorbent
material sandwiched between the layer of permeable material and the layer of
impermeable material. The absorbent material or absorbent mattress can be
made, for
example, of cellulose fibres andlor of super absorbent powder. The main body
11 of the
sanitary napkin 10 comprises a central zone 20 where the absorbent material
has a given
density and a given thickness. The main body 11 also has a transition zone 30,
surrounding the central zone 20, where the absorbent material is denser and
less thick
than in the central zone 20, the transition zone 30 being obtained by
compression of the
sanitary napkin. The main body 11 further has an external zone 40 surrounding
the
transition zone 30 where the absorbent material is less dense and thicker than
in the
transition zone.
As can be appreciated, the central zone which has a reduced density and an
increased
height with respect to the transition zone and the external zone and which is
located
directly under the vagina when the napkin is worn, allows a better contact
with the vulva's
wearer and a better scattering or flow of the blood towards the transition
zone. In other
words, thanks to the fact that the central zone has a low density, the blood
does not
remain in the central zone but rather flows outwardly toward the transition
zone which has
an increased density.
CA 02636679 2008-07-02
6
Still referring to figures 1 to 5, the sanitary napkin according to the
invention can be made
without changing the usual fabrication method, which is known in the sanitary
napkin field.
The present invention uses the fact that blood crosses rapidly zones of low
density, but
spreads and stays in zones of high densities.
As shown in figures 1 and 2, heightened zones 20, or bumps, allow to increase
the
contact between the napkin and the female body and to rapidly absorb the
menstrual flow.
to These bumps 20 have a lower density. This allows to absorb blood rapidly
and to bring it
to the bottom of the napkin 10. It is advantageous to surround this low
density zone 20
with a high density zone 30. Indeed, as soon as the flow reaches this high
density zone
30, this one will stay and travel therein.
Furthermore, if the high density zone 30 is also surrounded by a lower density
zone 40,
the flow tends to stay in the calendered zone 30 having a higher density. In
this case, the
exterior zone 40, having a lower density, acts as a barrier to stop the blood
from leaking
from the front, the rear or the sides of the napkin 10.
As shown in figures 3 and 4, according to another embodiment of the invention,
it is
possible to add other zones 50 of increased height and of lower density in the
front and
the rear of the absorbent mattress. These bumps 50 further limit the risks of
leakage from
the front or the rear of the napkin 10 and increase the area of the napkin
which is in
contact with the female body, particularly in the area between the buttocks.
This category
of products is preferred for night time products.
Preferably, the napkins 10 according to the preferred embodiments of the
invention have
the following dimensions, given for exemplification only. As it will be seen
below, the
invention can also be applied to maxi napkins
Napkin of Figures 1 and 2: ultra thin napkins
Zone Thickness
central zone 20 More than 4.0mm
CA 02636679 2008-07-02
7
transition zone 30 Less than 2.0mm
external zone 40 Less than 2.7mm, more than 2.0mm
Napkin of Figures 1 and 2: maxi napkins
Zone Thickness
central zone 20 More than 7.0mm
transition zone 30 Less than 2.5mm
external zone 40 Less than 6.0mm
Napkin of Figures 3 and 4: ultra thin napkins
Zone Thickness
central zone 20 More than 4.0mm
transition zone 30 Less than 2.0mm
external zone 40 Less than 2.7mm, more than 2.0mm
other zones of increased height 50 More than 2.7mm, preferably more than
4.0mm
Napkin of Figures 3 and 4: maxi napkins
Zone Thickness
central zone 20 More than 7.0mm
transition zone 30 Less than 2.5mm
external zone 40 Less than 6.0mm
other zones of increased height 50 More than 6.0mm, preferably more than
7.0mm
As apparent to an expert in the art, different configurations of heights could
provide similar
results and the invention is not intended to be limited to the dimensions
given
lo hereinabove. As also apparent to an expert in the art, the zones could have
many different
shapes and are not limited to the shapes shown in the figures.
When the napkin is calendered, the transition zone 30 is heavily compressed.
It is thus
possible to observe a hardening, or boarding, of the absorbent mattress in
this zone.
Indeed, the cellulose fibres being highly compressed can return to their
initial cardboard
CA 02636679 2008-07-02
8
form. This boarding creates rigidity in the napkin, which in turn can be
uncomfortable for
certain users. In order to avoid the boarding phenomenon and its
disadvantages, it is
possible to add a pattern 60 to the calendering rollers 100, 102, shown in
figures 6, 7, 8
and 12, which breaks the tensions in the transition zone 30 of the mattress
and which
gives it more suppleness. Figure 5 shows an example of a pattern 60 applied to
the
transition zone 30.
As apparent to an expert in the art, the pattern shown in figure 5 could
differ as long as it
brings similar advantages.
Referring now to figures 6 to 14, the present invention also provides an
apparatus for
producing a sanitary napkin 10 as defined previously. The apparatus comprises
a
calendar or having a first roller 100, 102 (also referred as a female roller)
and a second
roller 150, 152 (also referred as a male roller) to laminate the sanitary
napkin, the first
roller 100, 102 having an external surface 130 provided with a recess 120, 122
of desired
shape surrounded by a projection 110. The central zone 20 and transition zone
30 of the
sanitary napkin 10 are shaped by means of the recess 120, 122 and projection
110
respectively, whereas the external zone 40 is obtained by the external surface
130 of the
first roller 100, 102. As can be appreciated, the more the projection 110 is
high as
compared to the level of the external surface 130, the more the transition
zone 30 on the
sanitary napkin will be calendered and thus, the more dense it will be; and
the more the
recess 120, 122 is deep as compared to the level of the external surface 130,
the less the
central zone 20 will be calendered and thus, the thicker and less dense the
central zone
20 will be.
The second roller 150, 152, can be smooth or can have projections 160, 162,
164
extending on its external surface 170. The rollers 100 and 150 or 102 and 152
are spaced
from each other according to the heights and densities desired, so as to
produce with the
help of the recess 120, 122 and the projection 110, the sanitary napkin having
zones of
different heights and densities when a napkin is passed between the rollers
with its
permeable layer facing the first roller 100, 102. The role of the projections
160, 162, 164
on the male roller will be discussed further below.
Figures 6, 7 and 12 show the fabrication process of the absorbent mattress as
well as the
CA 02636679 2008-07-02
9
calendering step of the process.
Different views of the calender rollers 100, 102, 150, 152 are shown in
figures 7 to 11.
When the napkin passes between a male roller 150, 152 and a female roller 100,
102 or
between a female roller 100, 102 and a smooth roller, not shown, the absorbent
mattress
is calendered to different heights in predetermined locations according to the
projections
110, 160, 162, 164 and recesses 120, 122 of the rollers.
The desired heights of the napkin are obtained when the mattress is
calendered. The
cavities 120 in the rollers allow the bumps 20, 50 to be obtained on the
napkin, whilst the
projections 110 of the rollers allow thinner zones to be obtained on the final
product.
The calendering rollers 100, 102 of the invention have recesses or cavities
120 of a
predetermined shape which allow creating bumps 20, 50 on the mattress.
The rollers used for manufacturing the napkin 10 shown in figures 1 and 2 are
shown in
more details in figures 7 to 11. The female roller 100, 102 is preferably
installed under the
conveyer belt which conveys the napkins or can be installed over the conveyer
belt, as
shown in figure 7. A male roller or a smooth roller is preferably installed
over the
conveyer belt in order to allow applying a sufficient pressure on the product
in order to
obtain the desired pattern and zones but it can be installed under the
conveyer belt as
shown in the figures. Apparatuses having different configurations of conveyer
belts,
rollers and means for holding and rotating the rollers, for compressing
sanitary napkins
are well known in the art and will not be discussed herein.
If a smooth roller is used, the napkin 10 generally presents a bump on its
underneath
surface 180, figure 6. One could prefer to avoid such underneath bump. In
order to
minimize this phenomenon, a male roller 150, 152 having a projection 160, 162,
164 can
be used. This male roller 150, 152 is designed to fit together with its female
100, 102
counterpart. The male roller 150, 152 has projections 160, 162, 164
corresponding to the
areas where bumps are desired on the products. Figure 10, 11, 13 and 14 show
examples of male rollers.
Figures 7 to 11 show an embodiment of the apparatus and the rollers of the
invention, for
CA 02636679 2008-07-02
producing the napkin shown in figures 1 and 2, while figures 12 to 14 show an
embodiment of the apparatus and the rollers of the invention, for producing
the napkin
shown in figures 3 and 4.
s Although preferred embodiments of the present invention have been described
in detail
herein and illustrated in the accompanying drawings, it is to be understood
that the
invention is not limited to these precise embodiments and that various changes
and
modifications may be effected therein without departing from the scope or
spirit of the
present invention as defined in the appended claims.
