Note: Descriptions are shown in the official language in which they were submitted.
CA 02206578 1997-OS-14
'~
A KNIFE PATENT
FIELD OF THE INVENTION
This invention relates to a knife for cutting articles from a sheet or web of
material.
More specifically, this invention relates to a knife having a unique
configuration which can
be formed or secured to the outer surface of a rotary die cutter for cutting a
plurality of
articles from a sheet or web of material with zero clearance between at least
portions of the
outer peripheries of two adjacent articles.
BACKGROUND OF THE INVENTION
Many different kinds and types of articles are manufactured today which entail
cutting or stamping out a plurality of identically shaped articles from an
elongated sheet or
web of material. The sheet or web of material can be a single layer or a
laminate formed
from two or more layers. In producing such articles, trim.waste is usually
present and it is
beneficial from a cost standpoint to minimize such waste. Trim waste is
defined as all
material which does not make up a finished article. It includes waste located
adjacent to
the periphery of each article as well as waste cut out from the interior of an
article. Even
when the trim waste is kept to a minimum, its presence can still cause
problems in that it
has to be separated and conveyed away from the finished articles. The trim
waste also has
to be handled if it is to be properly disposed of, reGaimed or recycled.
For uniquely configured articles having at least one nonlinear edge, it is
very difficult
to completely do away with trim waste. However, it is possible to minimize the
amount of
trim waste and to design the waste to have a certain profile so that it can be
easier to
handle as it is separated from the finished articles.
One way to minimize trim waste is to design the cutting knife to have a
profile such
that the knife will simultaneously cut two adjacent articles from a sheet or
web of material.
By arranging two or more articles across and/or along a sheet or web of
material such that
two articles are joined by a common peripheral segment, a reduction in waste
can be
obtained.
1
' - CA 02206578 1997-OS-14
Now, a knife has been invented having a unique configuration and which can be
formed or secured to the outer surface of a rotary die cutter for cutting a
plurality of articles
from a sheet or web of material with zero clearance between at least a portion
of the outer
peripheries of two adjacent articles.
SUMMARY OF THE INVENTION
Briefly, this invention relates to a knife which can be formed or secured to
the outer
surtace of a rotary die cutter for cutting a plurality of articles from a
sheet or web of
material. The knife includes a first cutting member having a first end, and
second and third
cutting members joined to the first end of the first cutting member. The
second and third cutting
members are arranged relative to one another to form an angle therebeiween of
from about 15°
to about 180° . Each of the second and third cutting members also has
an arcuate section
which cooperates with the first cutting member to form a general wishbone
configuration. This
unique configuration enables two artiGes to be simultaneously cut from a sheet
or web of
material with zero clearance between at feast a portion of the outer
peripheries of the two
adjacent articles.
The general object of this invention is to provide a knife for cutting
articles from a
sheet or web of material. A more specific object of this invention is to
provide a knife
having a unique configuration which can be formed or secured to the outer
surface of a
rotary die cutter for cutting a plurality of articles from a sheet or web of
material with zero
clearance between at least a portion of the outer peripheries of two adjacent
articles.
Another object of this invention is to provide a knife which has a bifurcated
configuration which can simultaneously cut a portion of the outer peripheries
of two
adjacent articles.
A further object of this invention is to provide a knife which has at least
three cutting
members intersecting at a common location.
Still another object of this invention is to provide a knife which will
present a more
economical way of cutting a plurality of articles from a sheet or web of
material.
Still further, an object of this invention is to provide a die knife having a
thickness of
at least about .001 inches (about .025 mm).
Other objects and advantages of the present invention will become more
apparent
to those skilled in the art in view of the following description and the
accompanying
drawings.
2
' - CA 02206578 1997-OS-14
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic of a rotary die cutter showing a pair of knives each
having an
hourglass profile and arranged end to end such that a common section of the
knife can
simultaneously cut a portion of the outer peripheries of two adjacent
articles.
Fig. 2 is a cross-sectional view of one of the knives shown in Fig. 1 taken
along
line 2--2.
Fig. 3 is a top view of an absorbent article, such as a sanitary napkin or
panty liner,
and having a central longitudinal axis X-X which has been cut out by the
rotary die cutter.
Fig. 4 is a side view of the absorbent article shown in Fig. 3 depicting
several
distinct layers.
Fig. 5 is an exploded top view of the area within the dotted circled shown in
Fig. 1
depicting the bifurcation of the knife.
Fig. 6 is an exploded top view of the knife profile located within the area of
the
dotted circle shown in Fig. 5.
--Fig:-~ ~-a-portion-of-the-view shown in Fig. 8 depicting a rectangle drawn
about the
bifurcation point of the knife.
Fig. 8 is an exploded view of an alternative knife prot'ile located within the
area of
the dotted circle shown in Fig. 5.
Fig. 9 is a portion of the view shown in Fig. 8 depicting a rectangle drawn
about the
bifurcation point of the knife.
Fig. 10 is an exploded view of an alternative knife profile located within the
area of
the dotted circle shown in Fig. 5.
Fig. 11 is a portion of the view shown in Fig. 10 depicting a rectangle drawn
about
the bifurcation point of the knife.
Fig. 12 is an exploded view of still another alternative knife proi';le
located within the
area of the dotted circle shown in Fig. 5.
Fig...13 a portion of the view shown in Fig. 12 depicting a rectangle drawn
about the
bifurcation point of the knife.
3
- CA 02206578 1997-OS-14
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Fig. 1, a rotary die cutter 10 is shown having an outer periphery
12
which is circular in configuration. Secured to or mounted onto the outer
periphery 12 are
two or more knives 14 which are depicted having an hourglass configuration and
a central
longitudinal axis X-X which circumscribes the outer periphery 12 of the rotary
die
cutter 10. The knives 14 are arranged such that they abut one another and have
a
common edge 16 located therebetween. It should be noted that the knives 14 can
have
any type of configuration desired including: a square; a rectangle; a circle;
an ellipsoid; an
hourglass; an oval, etc. The knives 14 can be used to cut a sheet of material
which is
comprised of a single layer or a web of material which is comprised of two or
more layers.
For purposes of this invention, the knives 14 will be described as being
secured to or
mounted onto a rotary die cutter but as is known to those skilled in the art,
the knives 14
could be used by themselves or be attached to a movable member or to some
other type of
rotating or reciprocating mechanism.
For ease of understanding, the present invention will be described in relation
to
cutting out or stamping out a plurality of absorbent articles such as sanitary
napkins, panty
liners, incontinent garments, etc. from an elongated sheet or web of material.
Referring to Fig. 2, the knife 14 is shown as being integrally formed with the
rotary
die cutter 10 and extending outward in the radial direction from the outer
periphery 12. The
knife 14 includes a shank 18 which terminates into a knife blade 20. The knife
blade 20
has an inside edge 22 and an outside edge 24, one or both of which may be
tapered or
inclined toward one another so as to form an apex 28. The apex 26 can be a
sharp point
or it could be a flat surface as viewed under a microscope. The overall
thickness (t) would
be in the neighborhood of about .0012 inches to about .0018 inches (about
.0305 mm to
about .0460 mm) when used to cut an absorbent article, such as a panty liner.
As the knife
blade 20 wears from use, it is possible to regrind one or both of the surfaces
22 and 24 so
as to maintain the desired thickness (t) of the apex 26.
As mentioned above, although the knife 14 is shown as being integrally
attached to
the rotary die cutter 10, it is also possible for the knife 14 to be mounted
onto a plate which
is then screwed, bolted or somehow removeably attached to the rotary die
cutter 10.
4
CA 02206578 1997-OS-14
Referring to Figs. 3 and 4, the knife 14 is designed to cut an article 28 out
of an
elongated sheet or web of material. The sheet or web of material can be a
single layer of
material or it can be formed from two or more different, distinct or identical
layers which can
be vertically stacked, assembled, laminated or bonded together. When two or
more layers
are present, the layers can be laminated or bonded together by heat, pressure,
heat and
pressure, glue, adhesive, thermal bonds, mechanical bonds, chemical bonds,
etc. The
articles 28 can have almost any kind of configuration imaginable. For purposes
of
illustration, the article 28 is depicted as an elongated panty liner having a
central
longitudinal axis X-X. However, it should be noted that this invention is not
limited to this
particular shape. The materials which can be cut by the knife 14 include
paper, plastic,
film, thermoplastic films, absorbent fluff, coform, foam, wood pulp,
cardboard, wood, or any
other known material or combination thereof. Coform consists of a spunbonded
carrier
sheet with a mixture of pulp fibers and extnrded polypropylene which is
available from
Kimberly-Clark Corporation having an office at 401 N. Lake Street, Neenah,
Wisconsin 54956. For purposes of discussion only, the article 28 will be
described as an
absorbent article such as a sanitary napkin, a panty liner, or an incontinent
garment. It
should be noted that the knife 14 can cut both linear and nonlinear edges,
curves, arcuate
shapes, circles, etc. Articles having a straight or linear segment such as a
square,
rectangle or parallelogram profile tend to be easier to nest and die cut in a
line-to-line
fashion.
As shown in Fig. 1, two knives 14 are shown being formed in a portion of the
outer
periphery 12 of the solid shaft die cutter 10. The knives 14 are an-anged in
an end-to-end
configuration about the outer periphery 12 of the rotary die cutter 10 and
cooperate with
other knives 14 (not shown) which would form a row of knives 14 which extend
completely
around the outer periphery 12. The number of knives 14 which are present will
depend on
the length of the circumference of the die cutter 10 and the size and shape of
the individual
knives 14. The knives 14 can be machined into the shaft of the die cutter 10
such that they
appear in an offset and/or a side-by-side arrangement. Multiple knives 14 can
be
machined about the periphery 12 and across the width of the die cutter 10. For
example, 2,
3, 4, 5, etc., knives 14 can be formed about the periphery 12 and across the
width of the
rotary die cutter 10 so that a plurality of articles can be cut out for each
revolution of the die
cutter 10. It should be noted that when the knives 14 have an irregular
profile, it may be
advantageous to nest the knives 14 in a pattern across the width of the die
cutter 10, so as
to be able to cut out additional articles.
5
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CA 02206578 1997-OS-14
Referring again to Figs. 3 and 4, the absorbent article 28 is shown which is
designed to be adhesively attached to the inner crotch portion of a wearer's
undergarment.
Such articles normally consist of several layers of distinct materials which
are vertically
arranged. The layers, from top to bottom, can Include a liquid-pervious cover
30, an
absorbent 32, a liquid-impermeable baffle 34, a garment attachment adhesive 36
secured
to a lower surface of the baffle 34 and a removable peel strip 38. Other
layers, such as a
transfer layer, a wicking layer, a layer containing superabsorbent materials,
additional
absorbent layers, etc. can also be utilized. The various layers can be
vertically stacked,
assembled, laminated andlor bonded together to form a multilayer web of
material from
which the articles 28 can then be cut or stamped out. The various layers can
be bonded
together by using: heat, pressure, heat and pressure, construction adhesive, a
hot melt
glue, stitching with thread, ultrasonic bonding, mechanical bonding, thermal
bonding,
chemical bonding, or a combination of these and/or other means known to those
skilled in
the art.
The liquid-permeable cover 30 is designed to contact the body of the wearer
and
can be constructed of a woven or nonwoven material which is easily penetrated
by body
fluid. The liquid-permeable cover 30 can be fomned from either natural or
synthetic fibers.
Suitable materials include bonded carded webs of polyester, polypropylene,
polyethylene,
nylon or other heat-bondable fibers. Other polyolefins, such as copolymers of
polypropylene and polyethylene, linear low density polyethylene, finely-
perforated film webs
and net materials, also work well. A preferred material is a composite of an
apertured
thermoplastic film positioned above a nonwoven fabric. Such a composite
material can be
formed by extrusion of a polymer onto a web of spunbond material to form an
integral
sheet. One example of this is an apertured, thermoplastic polyethylene film
bonded to a
spunbond material. Spunbond is a nonwoven material which is manufactured and
commercially sold by Kimberly-Clark Corporation having an office located at
401 N. Lake
Street, Neenah, Wisconsin 54956. The apertured film/nonwoven laminate exhibits
a
smooth appearance and is soft to the touch. This material is relatively soft
and does not
irritate ~thte wearer's skin and Xet fias a cushioned feel because of its
bulk.
Another material useful as the liquid-permeable cover 30 is a spunbond web of
polypropylene. This spunbond web can contain from between about 1 percent to
about 8
percent of a whitening agent, such as titanium dioxide (Ti02) or calcium
carbonate (CaCOa)
to give it a clean, white appearance. A uniform thickness of spunbond is
desirable because
it will have sufficient strength, after being pertorated, to resist being tom
or pulled apart
6
CA 02206578 2004-06-08
during use. The most preferred polypropylene webs have a basis weight of
between about
18 grams per square meter (gsm) to about 40 gsm. An optimum weight is between
about
30 gsm to about 40 gsm.
The absorbent layer 32 can be present as a single layer or as two or more
layers.
The absorbent 32 can be formed from various natural or synthetic fibers such
as wood pulp
fibers, virgin cellulose fibers, regenerated cellulose fibers, cotton fibers,
peat moss, or a
blend of pulp and other fibers. The absorbent layer 32 could also be formed
from a fine
pore fabric such as wet-laid, ait:dried tissue or from an uncxeped through air-
dried (UCTAD)
tissue having a basis weight of from about 30 gsm to about 120 gsm. The UCTAD
tissue
can be prepared by a process disclosed in U.S. Patent No. 5,048,589 issued to
Crook et al.
on September 17, 1991. The UCTAD tissue is disdosed in U.S. Patent No.
5,399,412
issued to Sudall et al. on March 21, 1995. The absorbent layer 32 may also be
comprised of other well-known materials such as: cellulose fibers, rayon
fibers,
cellulose sponge, hydrophilic synthetic sponge, for example polyurethane, and
the like.
The liquid-impermeable baffle 34 is designed to permit the passage of air or
vapor
out of the absorbent article 28 while blocking the passage of body fluid. The
liquid-impermeable baffle 34 can be made from any material having these
properties. The
liquid-impermeable baffle 34 can also be constructed from a material that will
block the
passage of vapor as well as fluids, if desired. A good material from which the
baffle 34 can
be constructed is a micro-embossed, polymeric film, such as polyethylene or
polypropylene.
Bicomponent films can also be used. A preferred material is polyethylene film.
Most
preferably, the baffle 34 will be made out of a polyethylene film having a
thickness in the
range of from about 0.5 mm to about 2.0 mm.
It should be noted that construction adhesive can be used in the article 28 to
attach
and bond the various layers together. For example, construction adhesive can
be used to
bond the liquid-impermeable baffle 34 to the absorbent 32 or to bond the
absorbent 32 to
the liquid-permeable cover 30. The presence of such construction adhesive and
the
amount used will depend upon one's manufacturing specifications. Useful
construction
adhesives are commercially sold by National Starch and Chemical Company,
having an
office located at 10 Findeme Ave., B~dgewater, New Jersey 08807.
7
CA 02206578 1997-OS-14
The absorbent article 28 can also include one or more elongated strips or
areas of
garment attachment adhesive 38 which is secured to the bottom surtace of the
liquid-impermeable baffle 34. The garment attachment adhesive 36 functions to
attach the
article 28 to the inner crotch portion of the user's undergarment. The garment
attachment
adhesive 36 enables the absorbent article 28, particularly a sanitary napkin,
panty liner or
incontinent garment, to be properly aligned and retained relative to the
user's vaginal
opening so that maximum fluid protection can be obtained.
The garment attachment adhesive 36 can cover the complete bottom surtace of
the
liquid-impermeable baffle 34 or only a portion of it. The garment attachment
adhesive 36
can consist of a swirl pattern of adhesive or be one or more strips of
adhesive. The
garment attachment adhesive 36 can also consist of a plurality of adhesive
dots which are
randomly or uniformly arranged on the exterior surface of the baffle 34. When
in strip form,
the garment attachment adhesive 36 can be aligned along the central
longitudinal axis X-X
of the absorbent article 28. Alternatively, the garment attachment adhesive 36
can be
present as two or more spaced apart longitudinal strips. The garment
attachment
adhesive 36 is of such a nature that it will allow the user to remove the
absorbent article 28
and reposition it on the wearer's undergarment if needed. A hot melt adhesive
which works
well as the garment attachment adhesive is commercially sold by National
Starch and
Chemical Company having an office located at 10 Findeme Avenue, Bridgewater,
New
Jersey 08807.
In order to protect the garment attachment adhesive 38 from contamination
prior to
use, the adhesive 38 can be protected by a releasable peel strip 38. The peel
strip 38 can
be a white Kraft paper which is coated on one side so that it can be released
from the
adhesive 38. The coating can be a silicone coating, such as a silicone polymer
commercially available from Akrosil having an office located 206 Garfield
Avenue,
Menasha, Wisconsin, 54952. The peel strip 38 is designed to be removed by the
user prior
to attachment of the absorbent article 28 to the inner crotch portion of her
undergarment.
Referring to Fig. 5, an exploded top view of the knife 14 is shown depicting
the
common edge 18. °~he knife 14 includes a first cutting member 40 having
a first end 42.
The first end 42 is depicted as a dotted line simply for the purpose of better
understanding
the invention. The knife 14 also includes a second cutting member 44 which is
joined to
the first end 42 of the first cutting member 40. The knife 14 further inGudes
a third cutting
member 46 which is also joined to the first end 42 of the i'irst cutting
member 40. It should
be noted that by the word "joined° it is meant that the second and
third cutting members, 44
8
CA 02206578 1997-OS-14
and 46 respectively, can be integrally machined or formed out of material
which forms the
first cutting member 40. Additionally, the word °joined~ can include
the attachment of the
second and third cutting members, 44 and 46 respectively, to the first cutting
member 40 by
means of welding, mechanically bonding, thermally bonding, chemically bonding
or some
type of physical attachment known to those skilled in the art. For best
results, the second
and third cutting members, 44 and 46 respectively, should be machined out of a
single
piece of metal with the first cutting member 40. It should be noted that the
entire knife 14 is
machined out of the solid shaft of the die cutter 10.
The first cutting member 40 can be a linear or a nonlinear member formed from
ferrous or nonfen-ous metal. Preferably, the knife 14 is formed out of tool
steel. The first
cutting member 40 should have a thickness t~ of at least about .0010 inches +
.0002 inches
(.0254 mm +.0050 mm) and preferably has a thickness of between about .0010
inches +
.0002 inches to about .0050 inches + .0002 inches (at least about .0254 mm +
.0050 mm to
about .1270 mm + .0050 mm). The second and third cutting members, 44 and 48
respectively, can also be formed from ferrous or nonferrous metal and
preferably are
formed from tool steel. The second and third cutting members 44 and 48
respectively,
should have a thickness of at least about .0010 inches + .0002 inches (at
least about .0254
mm + .0050 mm). Furthermore, the second and third cutting members, 44 and 46
respectively, should have a thickness of between about .0010 inches + .0002
inches to
about .0050 inches + .0002 inches (about .0254 mm + .0050 mm to about .1270 mm
+
.0050 mm). The thickness tz of the second cutting member 44 and the thickness
t3 of the
third cutting member 46 can be equal to the thickness t~ of the first cutting
member 40. It
should be noted that, preferably, the first, second and third cutting members,
40, 44 and 48
respectively, will a!I have the same thickness within .0002 of an inch (.0050
mm), but may
have different thicknesses if desired. For example, the first cutting member
40 can have a
thickness t~ which is greater than, equal to, or less than the thickness t2 of
the second
cutting member 44 and/or of the thickness t3 of the third cutting member 46.
As shown in Fig. 5, the second and third cutting members, 44 and 46
respectively,
are arranged relative to one another to form an angle alpha (a) therebetween
of 180° or
less. Preferably, this angle is between from about 15° to about
180°, more preferably,
between from about 30° to about 150° and, most preferably,
between from about 45° to
about 120°. It should be noted that the angle alpha (a) can be measured
anywhere
9
- CA 02206578 1997-OS-14
between the second and third cutting members, 44 and 46 respectively, and may
vary as
the configuration of the second and third cutting members 44 and 46 diverge
from one
another.
The second and third cutting members, 44 and 46 respectively, each has an
arcuate
section 48 and 50, respectively, which cooperates with the first cutting
member 40 to form a
general wishbone configuration.
Referring to Fig. 6, one can see that each of the second and third cutting
members, 44 and 46 respectively, contain a linear section 52 and 54
respectively, which is
integrally joined to the arcuate sections, 48 and 50 respectively.
Furthermore, each of the
second and third cutting members, 44 and 46 respectively, has an interior
edge, 56 and 58
respectively. Both of the interior edges 56 and 58 can join one another to
form a circular
arc 60 between the second and third cutting members, 44 and 46 respectively.
The circular
arc 60 can be formed on any given radius and can be in the shape of a semi-
circular arc of
about 180° or be in the shape of an arc of less than 180°. When
the first, second and third
cutting members, 40, 44 and 46 respectively, are machined out of a single
piece of metal, it
is advantageous to form the arc 60 with an arc of about 180°.
Referring to both Figs. 6 and 7, the second and third cutting members, 44 and
46
respectively, also contain an outside edge, 62 and 64 respectively. Each of
the first,
second and third cutting members 40, 44 and 46, respectively, also contain a
centerline
A-A, B-B and C-C, respectively, see Fig. 7. The centerline for the first
cutting
member 40 will be a linear line while the centerline for the arcuate shaped
portions of the
second and third cutting members, 44 and 46 respectively, will be curved or
arcuate
shaped. The centerlines B-B and CSC of the second and third cutting members,
44 and
46 respectively, will join at a point "D" which is equal distance between two
vertically
aligned points located the outside edges 62 and 64 of the second and third
cutting
members, 44 and 46 respectively.
The unique configuration of the knife 14 can be described as a ratio of the
area of
the cutting surtace of the knife 14 to the total surtace area of a rectangle
formed about the
intersection of at least two of the first, second and third cutting members
40, 44 and 46,
respectively: The rectangle, can be drawn about the point of intersection
°D" using the
following procedure. A rectangle 66 is formed by drawing a first line 68
through two points.
Each of the points being located on one of the outside edges 62 and 64 of the
second and
third cutting members, 44 and 46 respectively, at a location where the
respective arcuate
section 48 and 50 are ~oin~d to the respective linear sections 52 and 54. By
doing so, a
- CA 02206578 1997-OS-14
point "E" is established on the outside edge 62 of the second cutting member
44 and a
point "F" is established on the outside edge 64 of the third cutting member
46. It should be
noted that point "D" is equal distance between points "E and F". A second line
70 and a
third line 72 are then drawn perpendicular to the first line 68 at locations
where the first
line 68 crosses the outside edges 62 and 64 of the second and third cutting
members, 44
and 46 respectively. In other words, the lines 70 and 72 perpendicularly
intersect the first
line 68 at points "E" and "F", respectively. A fourth line 74 is then drawn
parallel to the first
line 68 such that it passes through a point "G" (see Fig. 6). Point "G"
represents the center
of the smallest diameter circle which can be inscribed at the intersection of
the first cutting
members 40 with at least one of the second and third cutting members 44 and 46
respectively, while tangentially touching points "H", "I" and "J".
Point "H" represents a point on at least one of the arcuate sections 48 and 50
of the
second and third cutting members, 44 and 46 respectively. Point "H" is located
on at least
one of the interior edges 56 and 58 which forms the circular arc 60. Point "I"
represents the
intersection or meeting point of the outer edge 76 of the first cutting member
40 with either
the outside edge 62 of the second cutting member 44. If these two edges, 76
and 62, do
not form a straight line, then each is extended so that they will intersect as
is depicted in
Fig. 6. Point "J" represents the intersection or meeting point of the outer
edge 78 of the
first cutting member 40 with the outside edge 64 of the third cutting member
46. If these
two edges, 78 and 84, do not form a straight line, then each is extended so
that they will
intersect as is depicted in Fig. 6. The circumference of the circle will then
tangentially
contact points "H", "I" and "J" and the center of the circle will be point
"G". When only point
"J" is known, a circle is drawn so that its outer circumference touch point
"J" as well as
tangentially touching the outside edge 62 or 64 and the interior edge 56 or
58.
Whether the outer circumference of the circle actually contacts the outer
edges 76
and 78 of the first cutting member 40 or an extension of the outer edges 76
and 78 will
depend upon the angle and location at which the first cutting member 40
intersects the
second and/or third cutting members, 44 and 46 respectively. For example, in
Fig. 6, the
first cutting member 40 intersects the second and third cutting members, 44
and 46
respectively, at a location wherein the second cutting member 44 is identical
in length to
the third cutting member 46. In this configuration, it is necessary to extend
the outer
edges 76 and 78 such that they intersect the outside edges 62 and 64 at
locations whereby'
the circle having a center point "G" can be circumscribed. In contrast to
this, the
configuration shown in Fig. 8 depicts the first cutting member 40 being offset
relative to the
second and third cutting members, 44 and 46. In this configuration, point "I"
is located at
11
CA 02206578 1997-OS-14
the point where the outer edge 78 meets the outside edge 82 and point "J" is
located at a
point where the outer edge 78 intersects with the outside edge 64. The
establishment of
the circle should now be understood relative to the different configurations
which are
possible for the knife 14.
Referring again to Fig. 7, it should be noted that when the first cutting
member 40
equally bisects the second and third cutting members, 44 and 48 respectively,
it forms a
"mirror image" along the longitudinal center line A-A. By a "mirror image", it
is meant that
the upper half of the knife 14 is a reflection of the lower half of the knife
14. The entire
image of the knife 14 is very much like a tuning fork which can be used to
tune musical
instruments. In Fig. 7, the centerline A A of the first cutting member 40
intersects
point "D", the point where the centerlines B-B and C--C of the second and
third cutting
members, 44 and 46 respectively, meet.
Returning to the formation of the rectangle 66, the fourth line 74 will be
drawn
parallel to the first line 68 and will pass through the point "G". A fifth
line 80 is then drawn
parallel to the fourth line 74 and at a distance from the fourth line 74 which
is equal to the
distance between the first and fourth lines, 68 and 74 respectively. It should
be noted that
when forming the rectangle 66, both the fourth line 74 and the fifth line 80
will be located to
the same side of the first line 68. The fifth line 80 will be drawn such that
it intersects the
second and third lines, 70 and 72 respectively, to form points "K" and "L".
The rectangle 66
will then encompass an area bounded by the points "E", "F'°, "L" and
"K". This area is
referred to, for purposes of this invention, as the total surface area of the
rectangle 66. It is
important that the rectangle 66 be constructed according to the above method
so that the
total surface area for the rectangle 66 can be established. Once this is
accomplished, the
area of the cutting surtace of any knife configuration can be compared to the
total surface
area of the rectangle 86. The total surface area of any two rectangles, formed
by the
above method, do not have to be equal but should be fairly close in
dimensions. For
different knife configurations and different knife thicknesses, the total
surface area for the
rectangles 66 can be different when measured to the third or fourth decimal
place.
The total surtace area of the rectangle 66 can be calculated by multiplying
its length
times its width as is known to those skilled in the art. One will then measure
the area of the
cutting surtace of the knife 14 which is present within the total surface area
of the
rectangle 66 using common mathematical principles and formulas. It should be
noted that
12
' - CA 02206578 1997-OS-14
the area of the cutting surface area of the knife 14 can be readily calculated
using a
Cad-Cam program. Cad-Cam programs are commercially available and are known to
those
skilled in the art.
Referring to Table 1 below, several calculations have been performed by
varying
the thickness of the first, second and third cutting members, 40, 44 and 46
respectively.
For each calculation, all three cutting members 40, 44 and 46 have
approximately the same
thickness, that being either .001 inches (.025 mm), .002 inches (.050 mm) or
.005 inches
(.127 mm). For cutting absorbent articles, like sanitary napkins and panty
liners, it is not
recommended to use a knife thickness of greater than about .005 inches (about
.127 mm).
The total surface area of the rectangle 66 and the area of the cutting surface
of the
knife 14, in in2 and mm2 has also been calculated. One will see that the area
of the cutting
surface of the knife 14 as a percent of the total surtace area of the
rectangular 66 will vary
depending upon the thickness of the cutting members 40, 44 and 46, as well as
the angle
and the location of the intersection of the first cutting member 40 relative
to the second and
third cutting members, 44 and 46 respectively. It should also be realized that
the
thicknesses of the three cutting members 40, 44 and 46 do not have to be the
same.
TABLE 1
Total Surface Area of the Cutting
Thickness Area of Rectangle Surface of the Area of the
Knife
in inches Knife (inz) (mm~ as 90 of rectang
(mm) ~in2) le
(mm2)
-
,
.001 (.025) .00012 (.07742) .000025 (.016130) 20.83
.001 (.025) .00012 (.07742) .00002 (.01290) 30.77
.002 (.050) .00013 (.08387) .00004 (.02580) 30.77
.002 (.050).00013 (.08387) .00005 (.03226) 38.46
.005 (.127) .00018 (.10323) .0001 (.0645) 62.50
.005 (.127) .00016 (.10323) .0001 (.0645) 68.75
NOTE: 1 in 25.4 mm.
=
1 ina = 64.52 mm2
Referring again to Fig. 7, the area of the cutting surface of the knife 14
represents
30.7796 of the totat surfaox area of the rectangle 66. The 30.7790 was
obtained when each
of the first, second and third cutting members, 40, 44 and 46 respectively,
had a thickness
of approximately .001 inches (approximately .025 mm). As the thickness of the
knife 14
gets larger and as the angle changes at which the first member 40 intersects
the second
and third cutting members, 44 and 48 respectively, the area of the cutting
surface of the
knife 14 within the total surface area of the rectangle 66 wilt change.
13
' ~ CA 02206578 1997-OS-14
Referring to Figs. 8 and 9, the first, second and third cutting members, 40,
44 and
46 respectively, also have a thickness of .001 inches (.025 mm) but the first
cutting
member 40 intersects the second member 44 at an offset angle. The formation of
the
rectangle 82 is identical to that described above for rectangle 66, shown in
Fig. 7. In fact
the rectangle 82 has comer points "E", "F~, °LH and "Kp and lines 68,
70, 72 and 80. For the
knife profile shown in Fig. 9, the area of the cutting surtace of the knife 14
is 20.839'0 of the
total surtace area of a rectangle 82. The reason that the area of the cutting
surface of the
knife 14 is less in Fig. 9, than in Fig. 7, is that the first cutting member
40 is offset from the
second cutting member 44. This forms a non-symmetrical arrangement between the
second and third cutting members, 44 and 46 respectively. In this arrangement,
less
surtace area of the second cutting member 44 is included in the calculation
and hence a
lower ratio is obtained.
Similar calculations were made for the knife 14 when the thickness of the
first,
second and third cutting members, 40, 44 and 46 respectively, increased to
.002 inches
(.050 mm). In this case, the area of the cutting surtace of the knife
represented 30.7796 of
the total surface area of the rectangle when the knife 14 was similar in
appearance to that
shown in Fig. 6 and 38.4696 of the total surface area of the rectangle when
the knife 14
was similar in appearance to that shown in Fig. 8.
Referring now to Figs. 10 and 11, similar calculations were made by varying
the
2o thickness of the first, second and third cutting members, 40', 44' and 48'
respectively, such
that they all had a thickness of .005 inches (.127 mm). In Fig. 11, the area
of the cutting
surtace of the knife 14 was calculated to be 62.596 of the total surface area
of the
rectangle 84.
Referring to Figs. 12 and 13, calculations were made for the three cutting
members, 40' 44' and 46' respectively, when they each had a thickness of .005
inches
(.127 mm) and the first cutting member 40' was offset relative to the second
cutting
member 44'. The area of the cutting surtace of the knife 14 was calculated to
be 68.7596
of the total surtace area of the rectangle 86. The above calculations are all
listed in Table I
above.
It should be noted that the area of the cutting surtace of the knife 14 can
represent
from between about 2096 to about 7090 of the total surtace area of the
rectangle. More
particularly, the area of the cutting surtace of the knife 14 can represent
from between
about 219~o to about 69% of the total surface area of the rectangle.
14
CA 02206578 1997-OS-14
It has been found that such a knife 14 is extremely useful in cutting
absorbent
products because the commdn edge 16 decreases the amount of trim waste which
would
normally be present between two adjacent but non-abutting knives. By reducing
the
amount of trim waste, one can obtain a mope efficient operation using less raw
material.
The common edge 16 of the knife 14 is able to cut a portion of the outer
periphery of two
adjacent products with a single cut and therefore can increase production of
multiple
products.
While the invention has been described in conjunction with several specific
embodiments, it is to be understood that many alternatives, modifications and
variations will
be apparent to those skilled in the art in light of the aforegoing
description. Accordingly,
this invention is intended to embrace all such alternatives, modifications and
variations
which fall within the spirit and scope of the appended claims.
