Note: Descriptions are shown in the official language in which they were submitted.
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SELECTIVELY WEAKENED CORES FOR CORE WOUND PAPER PRODUCTS
FIELD OF TIIE INVENTION
This invention relates to a core for core wound products,
particularly to a core which has been flattened or compressed to
minimize its void space, and more particularly to a flattened core
having a means for rerounding the core to more nearly its
original condition.
BACKGROUND OF THE INVENTION
Core wound paper products, such as toilet tissue and paper
towels, are well known in the art and are highly useful consumer
products. Such products comprise a core about which layers of the
paper product are wound. The core may be, and frequently is,
inserted onto a spindle for convenient temporary storage of the
paper product and for removal of the paper product from the core
and from the balance of the roll on demand. The spindle is
inserted through the center of the core and, thus, requires the
core to be open, so that the spindle may fit therethrough without
encountering excessive friction or later causing difficulty in the
dispensation of the desired paper product.
A preferred core shape is a cylinder having a geometrically
round cross-section, so that the core (and the paper product wound
2~ thereon) freely rotates about the axis of the spindle and the
paper product is easily removed from the roll. One improvement to
rolls of core wound paper products is compression of the core, in
a direct~on normal to the ~axis of the core, to reduce the void
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space in the core. This arrangement provides for convenient
storage, handling and shipment of core wound paper products, due
to the products may be stored and shipped more economically and in
higher densities.
Several attempts have been made in the art to capitalize on
the benefits of compressed core wound paper products. For
example, U.S. Patent 4,762,061 issued August 9, 1988, to ~atanabe
et al. and U. S. Patent 4,909,388 issued March 20, 1990, to
Watanabe disclose rolls of paper product compressed to one-half to
one-fifth of the original diameter of the product. The cores of
these products are taught to be provided with a slight elasticity
to allow the cores to return from the flattened shapes, attained
under compression, to the original cylindrical shape. It is
generally desired, per these patents, that the flattened rolls be
easily returned to their original shape.
U.S. Patent 1,005,787 issued October 1911 to Sibley discloses
a flattened toilet paper package wound onto a hollow core made of
flexible and axially corrugated paper stock. The corrugated core
holds the fabric and results in an oscillatory motion as the paper
is removed from the roll. European Patent Specification 709,363
published May 19, 1954, to Samson discloses a web of paper or
pliable sheet material wound upon a core which is diametrically
flattened and is said to readily resume its tubular shape when the
roll is unpacked. The core consists of spirally wound strips of
kraft sheet material and is flexible. The flexibility is said to
permit the core to be flattened without cracking and to later
recover its cylindrical shape after flattening.
- U.S. Patent 4,886,167 issued December 12, 1989, to Dearwester
discloses unilaterally compressed toilet tissue having flattened
cores with little to no void space illustrated between the
metrically opposed faces of the flattened core cross-section. The Dearwester
patent shows particularly preferred compact, compressed rolls of toilet tissue
and paper towels.
The foregoing teachings suffer from the drawback that upon rerounding,
diametrically opposed creases frequently occur throughout the core and prevent
the desired cylindrical shape from
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being obtained. These creases frequently cause the core to fit
poorly on a spindle, and thereby, results in an inconvenience to
the user each time such a core is inserted onto, used whileon, or
removed from a spindle. Furthermore, the non-round cross-section
of such a core may prevent easy removal of the paper product from
the remainder of the roll, resulting in further inconvenience to
the user each time a sheet or a larger portion of the paper
product is desired. A core having a nonround cross section is
also typically noisier during dispensing.
One attempt to overcome the problems associated with core
flattening is to prevent such flattening, as disclosed in U.S.
Patent 2,659,543 issued November 17, 1953, to Guyer, which patent
suggests a way to maintain the original core shape. This patent
teaches a core for tape products having at least one axially
oriented groove or slot disposed along the outside of the core at
uniform intervals around its circumference. ~hen material is
tightly wound onto the core, the grooves slightly collapse,
providing relief of the compressive hoop stress induced by tight
winding of the tape about the core. However, this teaching
suffers from the drawback that the round cross-section of the core
is maintained and the aforementioned advantages of a flattened
core are lost.
~ hat is needed, therefore, is a core which can be flattened
as taught in the prior art, but more conveniently and accurately
rerounded after the compressive stresses applied to the paper
product are removed.
Accordingly, an object of an aspect of this invention is to provide a core
having a means for flattening and rerounding the core in a manner
more convenient to the user and which will precisely and
repeatedly cause the core to more nearly resume its original
shape.
BRIEF SUMMARY OE THE INVENTION
The present invention comprises a flattened core about which
a core wound paper product is wound to comprise a roll of the
paper product. The flattened core has an inner circumference, an
outer circumference, and two oppositely disposed ends defining a
longitudinal axis. The flattened core is capable of approximating
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a circular cross section, upon rerounding. The core further
comprises at least one axially oriented means for weakening the
resistance of the core to applied compressive forces. The
weakening means is disposed on at least one of the inner
circumference, the outer circumference, or may intercept both the
inner and outer circumferences by being through the entire
thickness of the core.
In one embodiment, the weakening means comprises a plurality
of axially oriented continuous score lines. In a second
embodiment, the weakening means comprises a plurality of axially
oriented perforations. In a third embodiment, the weakening means
comprises a plurality of axially oriented holes. The score lines,
perforations, or holes may either be blind - so that only one
circumference of the core is affected by the weakening means or
may pass through the entire thickness of the core to intercept
both the inner and outer circumferences of the core.
Other aspects of this invention are as follows:
A flattened core about which a paper product may be wound, and having
an inner surface, an outer surface, and two oppositely disposed ends defining a
longitu-lin~l axis, said flattened core being capable of approxim~ting a circular
cross-section, the improvement comprising: an axially oriented means for
we~k~ning the resistance of said core to applied radially compressive forces,
said we~k~ning means being disposed on at least one of said inner surface and
said outer surface of said flattened core and locally reducing the thickness
thereof.
A flattened core about which a paper product may be wound, and having
an inner surface, an outer surface, and two oppositely disposed ends defining a
longitudinal axis, said flattened core being capable of approxim~ting a circularcross-section, the improvement comprising: means for we~kPning the resistance
of said core to applied radially compressive forces, said we~kening means
comprising a plurality of axially oriented perforations on one said surface of
said flattened core.
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A flattened core about which a paper product may be wound, and having
an inner surface, an outer surface, and two oppositely disposed ends defining a
longitudinal alcis, said flattened core being capable of appro~cim~ting a circular
cross-section, the improvement comprising: means for we~k~ning the resistance
of the core to applied radially compressive forces, said weakening means
comprising at least one axially oriented score line disposed along at least one of
said inner surface and said outer surface of said flattened core.
BRIEF DESCRIPTION OF THE DRA~INGS
While the Specification concludes with claims particularly
pointing out and distinctly claiming the present invention, it is
believed the same will be better understood from the following
Specification taken in conjunction with the associated drawings
wherein like parts are given the same reference numeral, and:
Figure 1 is a perspective view of a flattened core and paper
product a~ording to the present invention;
Figure 2 is a perspective view of a core according to the
present invention prior to flattening, and having a plurality of
various types of axially oriented score lines disposed about the
inner and outer circumferences of the core;
Figure 3 is a schematic plan view of a core according to the
present invention when unfolded, and having five circumferentially
spaced axially offset holes;
Figure 4 is a schematic plan view of a core according to the
present invention when unfolded, and having five circumferentially
spaced holes inset from each end;
Figure S is a schematic plan view of a core according to the
present invention when unfolded, and having five lines of equally
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sized cuts and lands extending inwardly about one inch from each end of
the core;
Figure 6 is a schematic plan view of a core according to the
present invention when unfolded, and having five lines of equally sized
cuts and lands penetrating only abeut one half the thickness of
the core;
Figure 7 is a schematic plan view of a core according to the
present invention when unfolded, and having five lines of
perforations with cuts one-third the length of the lands;
Figure 8 is a schematic plan view of a core according to the
present invention when unfolded, and having five lines of cuts
tenminating before intercepting either end of the core;
Figure 9 is a schematic plan view of a core according to the
present invention when unfolded, and havi~ five lines of cuts and
lands, larger than those of either Figures 6 or 7;
figure 10 is a schematic plan view of a core according to the
present invention when unfolded, and having five lines of equally sized
cuts and lands smaller than those of the preceding figures; and
Figure 11 is a schematic plan view of a core according to the
present invention when unfolded, and having five lines of alternately
spaced cuts and lands with the cuts three times the size of the
lands.
DETAILED DESCRIPTION OF THE INVENTION
As illustrated in Figure 1 and as used herein, a ~core"
refers to a hollow tubular member about which another component is
wound in a spiral for later dispensing and removal. As used
herein, a "paper product" refers to a ce11ulosic base product
wound onto the core 20 and is removed, typically, in batch form,
i.e., one or more sheets at a time, for usage and eventual
discard. Used paper prodùct 24, when taken from the core 20, is
not returned. As used herein a "roll~ refers to the aggregation
of a "core" and a "paper product~ wound thereon. The roll 28 may
further comprise a wrapping 32 to maintain the configuration
illustrated by Figure 1.
A core 20, according to the present invention, may
advantageously be used for toilet tissue or for paper towels. The
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core 20 is generally cglindrical prior to compression and
flattening, has an axial length defined by two oppositely disposed
ends. The ends of the core 20 are circular in cross section prior
to flattening. The line connecting the centers of these circles
is the "longitudinal axis" of the core 20. As used herein ~axial~
refers to the longitudinal axis.
When toilet tissue is wound on the core 20, the resulting
roll 28 of toilet tissue typically has a diameter of about 10.2
centimeters to about 12.7 centimeters (4.00 to 5.00 inches) and a
length of about 11.4 centimeters (4.50 inches) between the ends.
If a core 20 embodying the present invention is used for paper
towels, the roll 28 of paper towels typically has a diameter of
about 10.2 to about 15.2 centimeters (4.00 to 6.00 inches) and a
length of about 27.9 centimeters (11.0 inches) for the embodiments
described herein.
The typical core 20 may be made of two layers of a paper
having any suitable combination of bleached krafts, sulfites,
hardwoods, softwoods, and recycled fibers. The core 20 should
exhibit uniform strength without weak spots. Preferably, the core
20 is not calendered, so that it is relatively stiff and retains
adhesive deposited thereon. The core 20 should have a mullen
strength of at least 60 and preferably at least 70 as measured
according to ASTM Test Method D2529. The core 20 may have a
thickness of about 0.5 millimeters (0.020 inch). The core 20
should be free of objectionable odor and impurities or
contaminates which may cause irritation to the skin.
The core 20 may be made of paper having a basis weight of
about 0.16 kilograms per square meter (0.032 pounds per square
foot) and a ring crush strength of at least 6.79 kilograms per
centimeter (38 pounds per inch) and preferably at least 8.93
kilograms per centimeter (SO pounds per inch) as measured
according to Tappi Standard T818 OM--87.
The core 20 according to the present invention is provided
with at least one means 36 for selectively weakening the
resistance of the core 20 to compressive forces, and more
particularly to diametrically applied compressive forces. The
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diametrically applied compressive forces may occur at any point
along, or throughout the entire axis of, the core 20.
As used herein, "diametrically applied compressive forces n
refer to opposed compressive forces applied at any diameter of any
cross section of the core 20. It is, of course, to be recognized
that compressive forces may be applied along a chord of the cross
section and not be coincident a diameter. However, the principles
involved in such application are substantially similar to those of
diametrically applied compressive forces and, will not be further
distinguished or repeated.
Upon application of the compressive forces, the core 20 will
collapse into the flattened condition of Figure 1. The cross
section of the flattened core 20 of Figure 1 has a major axis a-a,
and a mutually orthogonal minor axis i-i. The major axis a-a and
minor axis i-i of the cross section are transverse and orthogonal
the longitudinal axis of the core 20. The major axis a-a is
aligned with the longest dimension of the cross section of the
paper product 24 when flattened, and the minor axis i-i is the
perpendicular bisector thereto.
It has been found that at least one circumferentially
disposed means 36 for weakening the resistance of the core 20 to
applied compressive forces is required. Preferably, but not
necessarily, each means 36 for weakening the resistance of the
core 20 to applied compressive forces is equally circumferentially
spaced from the adjacent means 36 for weakening the resistance of
the core 20 to applied compressive forces, so that the cross
section of the core 20 more nearly approaches a circle than an
irregular polygon upon rerounding.
The azimuthal orientation of the major and minor axes a-a and
i-i of the flattened core 20 can be predetermined by the
circumferential disposition and spacing of the means 36 for
weakening the resistance of the core 20 to applied compressive
forces. If the core 20 is provided with two diametrically opposed
means 36 for weakening the resistance of the core ?0 to applied
compressive forces, and if the diameter along which the
compressive forces are applied is about 90- relative to the two
means 36 for weakening the resistance of the core 20 to applied
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compressive forces, the core 20 will generally flatten at the two
means 36 for weakening the resistance of the core 20 to applied
compressive forces.
The resulting flattened core 20 will have a major axis a-a
S with two vertices, one located at each end of the major axis a-a
and corresponding to the means 36 for weakening the resistance of
the core 20 to applied compressive forces. Therefore, preferably,
an even number of means 36 for weakening the resistance of the
core 20 to applied compressive forces is provided, so that each
means 36 for weakening the resistance of the core 20 to applied
compressive forces is diametrically opposed to another means 36
for weakening the resistance of the core 20 to applied compressive
forces.
However, upon rerounding the core 20 will not approximate its
original cylindrical shape, due to the two vertices maintain the
cross section of the core 20 in a somewhat doubly convex shape.
Additional circumferentially disposed means 36 for weakening the
resistance of the core 20 to applied compressive forces are needed
to provide additional vertices. Upon rerounding, the core 20 will
assume a polygonal cross section, corresponding in number of sides
to the number of vertices, each vertex corresponding to a
particular individual means 36 for weakening the resistance of the
core 20 to applied compressive forces.
As nQted above, at least one, and even a plurality of two
means 36 for weakening the resistance of the core 20 to applied
compressive forces is inadequate due to the resulting doubly
convex shape upon attempted rerounding. If four means 36 for
weakening the resistance of the core 20 to applied compressive
forces are provided, the core 20 rerounds to a generally square
cross section and has a hollow hexahedronal shape. Such a core
20, when attempted to be rerounded, suffers from excessive wobble
and noise on the spindle and is, therefore, generally not
preferred.
A core 20 having six means 36 for weakening the resistance of-
the core 20 to applied compressive forces, each equally
circumferentially spaced (on increments of about 60- or a multiple
thereof) from the adjacent means 36 for
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weakening the resistance of the core 20 to applied compressive
forces, works well. Two means 36 for weakening the resistance of
the core 20 to applied compressive forces occur at each end of the
major axis a-a of the core 20 when it is flattened. Two means 36
for weakening the resistance of the-core 20 to applied compressive
forces are disposed on each side of the flattened core 20,
straddling the minor axis i-i and juxtaposed with the two means 36
for weakening the resistance of the core 20 to apptied compressive
forces on the other side of the flattened core 20. This core 20
rerounds to a hexagonal cross section and exhibits less wobble and
noise during dispensing.
A core 20 having eight, ten, or twelve equally spaced means
36 for weakening the resistance of the core 20 to applied
compressive forces is undesirable due to--natura1 tendency of the
core 20 to reform to a quadrilaterally shaped cross section. Also
this structure requires two stages of rerounding, further
inconveniencing the user.
As illustrated in Figure 2, a particularly preferred means 36
for weakening the resistance of the core 20 to applied compressive
forces is a continuous axially oriented score line. the score
line is preferably parallel to the axis of the core 20, but
prophetically may wrap the core 20 in a helical shape, if desired.
A means 36 for weakening the resistance of the core 20 to applied
compressive forces is considered to be ~axially orientedH if a
line drawn through the weakening means 36 forms an included angle
less than + 45' of the longitudinal axis of the core 20.
The score lines may be disposed on either the inner or outer
circumference of the core 20. It will be apparent, that if a
plurality of score lines is provided, the plurality may be divided
between the inner and outer circumferences of the core 20.
As used herein, "score lines" are inclusive of lines of
compression, and, preferably, lines defined by material removed
from the core 20. The score lines may be made by a scoring rule
or a rotary die and preferably penetrate about 25 percent to about
3s 100 percent of the thickness of the core 20. The score lines
preferably extend between and to both ends of the core 20.
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If desired, the means 36 for weakening the resistance of the
core 20 to applied compressive forces, such as a score line, may
be continuous, discontinuous or intermittent and may resemble
discrete holes or perforations. The discrete holes or
s perforations may, but need not, extend to each end of the core 20
and may be axially offset from the ends of the core 20.
For example, referring to Figures 3-10, in turn, eight
nonlimiting examples are provided, illustrating various means 36
for weakening the resistance of the core 20 to applied compressive
forces. One sample of each example is tabulated in Table I, to
provide for easy comparison of the effect of the parameters listed
in Table I on the attempted rerounding.
Each row in Table I represents one sample, which was prepared
from commercially available Charmin brand toilet tissue made and
sold by the Procter & Gamble Company of Cincinnati, Ohio. The
cores 20 were removed from the roll 28 of paper product 24,
provided with the designated means 36 for weakening the resistance
of the core 20 to applied compressive forces, and inserted back
into the center of the paper product 24 to complete the roll 28.
Each roll 28 of paper product 24 was then diametrically compressed
along the minor axis i-i with a force of about 36 kilograms (80
pounds).
The rolled paper products 24 were then aged for a period of
about four weeks at about SOX relative humidity and 72-F. A
minimum two week aging period is considered necessary to allow any
memory or resiliency of the core 20 to be developed, so that
storage and shipping conditions are approximated and accurate data
are obtained when the sample is later rerounded. An aging period
of less than about two weeks is considered unsatisfactory, as the
results obtained may not approximate that seen in actual practice
when the product is made, warehoused, shipped to the point of
purchase, purchased, taken to the consumer's home, and finally
installed onto a spindle and used.
Each core 20 was made of the aforementioned materials and is
about 11.43 centimeters (4.5 inches) in length. The samples of
Figures 3-10 were provided with six equally spaced means 36 for
weakening the resistance of the core 20 to applied compressive
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forces, one through-cut far opening the core 20 and five means 36
for weakening the resistance of the core 20 to applied compressive
forces as described be~ow.
The first column of Table I provides a plan view illustration
of the described means 36 for weakening the resistance of the core
20 to applied compressive forces. In the second column of Table
I, the five means 36 for weakening the resistance of the core 20
to applied compressive forces are described. However, for these
samples the cores 20 had to be slit and opened as illustrated in
the plan views of Figures 3-10 to install the described weakening
means 36 for a total of six means 36 for selectively weakening the
resistance of the core 20 to applied compressive forces.
Whenever five described weakening means 36 were utilized with
one continuous through slit, the through slit was reclosed with
adhesive tape and the core 20 compressed, so that upon flattening
the major axis a-a intercepted the taped slit and one of the
described weakening means 36. In practice, the aforementioned
through slit would be replaced by a means 36 for weakening the
resistance of the core 20 to applied compressive forces which is
similar to the other five as described, so that all six means 36
for weakening the resistance of the core 20 to applied compressive
forces are identical.
The percentage of the perforated or cut surface area listed
in the third column of Table I is the percentage of axial linear
dimension affected by the means 36 for weakening the resistance of
the core 20 to applied compressive forces. Each core 20 had a
total linear dimension of about 68.8 centimeters (27.1 inches) (6
lines x 4.5 inches). In the fourth column the longitudinal axial
distribution of the weakening means 36 is listed as either
end-to-end and extending throughout the entire length of the core
20, centered and not intercepting the ends, or endwise and
starting at both ends, but not meeting in the center.
The vertex forming effect of the weakening means 36 in the
fifth column of Table I was judged to be low (~L~), medium (~M~),
or high (~H~), based upon subjective judgment when trying to
reround the core 20 to its original cylindrical condition. A
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sample was judged to be. low in vertex forming effect if no
distinct vertices were observed upon rerounding. A sample was
judged to be medium in vertex forming effect if a change in the
direction of curvature was apparent at one or more of the
vertices. A sample was judged to be high in vertex forming effect
if the vertices formed corners at the means 36 for weakening the
resistance of the core 20 to applied compressive forces.
The sample of Figure 3 was provided with five holes,
approximately 6.4 millimeters diameter (0.25 inches). Each hole
is axially offset from the circumferentially adjacent hole by
approximately one-fifth of the length of the core 20.
The sample of Figure 4 was provided with ten
circumferentially spaced holes having a diameter of approximately
6.4 mm (0.25 inch), five at each end of the core 20. Each of the
five holes was in the same plane, and inset approximately one inch
inward from the end of the core 20. The five holes at each end of
the core 20 were axially aligned with the mutually opposite five
holes at the other end of the core 20.
The sample of Figure 5 was perforated from each end towards
the center of the core 20 with alternating one millimeter (0.04
inches) cuts 40 and one millimeter (0.04 inch) lands 44. The
perforations extended inwardly about 2.54 centimeters (1 inch)
from each end of the core 20.
The_sample of Figure 6 was perforated with alternating one
millimeter (0 04 inch) cuts 40 and one millimeter (0.04 inch)
lands 44. The. cuts 40 are made from the inside circumference
through one half the thickness of the core 20. the percentage of
effective surface area for Figure 6 was halved, to account for the
fact that the perforation only affects one half of the total
thickness of the core 20.
The sample of Figure 7 was perforated with alternating two
millimeter (0.08 inch) cuts 40 and six millimeter (0.24 inch)
lands 44. The cuts 40 and lands 44 extend throughout the entire
length of the core 20.
The sample.of Figure 8 was proYided with double cuts 40 about
2.54 centimeters (1.0 inch) in length. The cuts 40 were axially
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terminated about 1.27 centimeters (O.S inch) inwardly from each
end.
The sample of Figure 9 was perforated with alternating 9.6
millimeters (0.38 inch) cuts 40 and 9.6 millimeters (0.38 inch)
lands 44. The perforations extend -entirely from end to end of the
core 20.
The sample of Figure 10 was perforated with alternating one
millimeter (0.04 inch) cuts 40 and one millimeter (0.04 inch)
lands 44. The perforations extend from end to end of the core 20.
The sample of Figure 11 was provided with alternating three
millimeter (0.12 inch) cuts 40 and one millimeter (0.04 inch)
lands 44. The perforations extend from end to end of the core 20.
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~ TABLE I
Percentage of Axial
Perforated Distribution Vertex
or Cut Axial of Weakening Forming
fiq.No. DescriDtion Dimension Means Effect
3 0.25 in. dia. 6 end-to-end L
axially offset
holes
4 Five 0.25 in. dia. 11 endwise L
holes, 1 in. in
from each end
lmm cut, 1 mm land 22 endwise M
extending
inwardly 1 in.
from ea. end
6 lmm cut, lmm land 25 end-to-end M
throughout one-half
the thickness of the core
7 2 mm cut, 6 mm land 25 end-to-end M
2S
8 Double 1 in. cuts 44 centered M
spaced inwardly 0.5
in. from ea. end
9 0.38 in. cut, 0.38 in. 50 end-to-end H
land
1 mm cut, 1 mm land 50 end-to-end H
11 3 mm cut, 1 mm land 75 end-to-end H
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As can be seen from Table I, generally as the samples had
less than about 2~% of the axial dimension effected by the means
36 for weakening the resistance of the core 20 to applied
compressive forces, the vertex forming effect was judged to be
low. As the percentage of perforated or cut area affected by the
means 36 for weakening the resistance of the core 20 to applied
compressive forces approaches 20% to 45X, the vertex forming
effect was judged to be medium, relative to the other samples. As
the percentage of perforated or cut area effected by the means 36
for weakening the resistance of the core 20 to applied compressive
forces increases above 50Z, the vertex forming effect was judged
to be high. However, all samples were placed on a spindle and
then dispensed. All samples were judged to be superior to a
control sample (having no means 36 for weakening the resistance of
the core 20 to applied compressive forces) in both noise and in
smooth, uninterrupted dispensing.
2~
