CA2206578C - Knife - Google Patents

Abstract

A knife is disclosed for cutting a plurality of articles from a sheet or web of material.
The knife can be formed or secured to the outer surface of a rotary die cutter. 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 therebetween of from about 15°
to about 180°. Each of the second and third cutting members also has an arcuate section which intersects with the first cutting member to form a general wishbone configuration. This unique knife profile enables two adjacently arranged articles to be simultaneously cut from a sheet or web of material with zero clearance between at least a portion of the outer peripheries of the two articles.

Description

'~
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.

' - 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.

' - 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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Fig. 1, a rotary die cutter 10 is shown having an outer periphery 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.

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.

~

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 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.

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 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 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 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 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 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 ' - 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.

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.

' ~ 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.

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.

Claims (22)

1. A knife comprising:
a) a first cutting member having a first end;
b) a second cutting member having an arcuate section integrally joined to a linear section, said arcuate section of the second cutting member integrally joined to said first cutting member approximate said first end of the first cutting member;
and c) a third cutting member having an arcuate section integrally joined to a linear section, said arcuate section of the third cutting member integrally joined to said first cutting member approximate said first end of the first cutting member;
wherein said second and third cutting members are arranged relative to one another to form an angle therebetween of 180° or less, and said first end of the first cutting member cooperates with said arcuate sections of the second and third cutting members to form a wishbone configuration having a semicircular shaped inside edge formed from said second and third arcuate sections.

2. The knife of claim 1, wherein said first cutting member is linear.

3. The knife of claim 1, wherein said first cutting member is non-linear.

4. The knife of claim 1, wherein each arcuate section of the second and third cutting members has an outside edge and an arcuately shaped centerline, and when a rectangle is drawn about the point of intersection of said first, second and third cutting members, the area of the cutting surface of said knife is from between about 20% to about 70% of the total surface area of said rectangle, said rectangle being formed by drawing a first line through two points, each of said two points being located on one of said outside edges of said second and third cutting members, respectively, at a location where an individual arcuate section is joined to its corresponding linear section, a second line and a third line are then drawn perpendicularly to said first line at locations where said first line crosses said outside edges of said second and third cutting members, respectively, a fourth line is then drawn parallel to said first line such that it passes through a point where the centerline of said second cutting member joins the centerline of said third cutting member, and a fifth line is drawn parallel to said fourth line and at a distance from said fourth line which is equal to the distance between said first and fourth lines, said fifth line being drawn on the same side of the first line as is the fourth line, and said fifth line intersecting said second and third lines to form said rectangle.

5. The knife of any one of claims 1 to 4, wherein said first cutting member has a thickness of at least about .001 inches.

6. The knife of claim 5, wherein said first cutting member has a thickness of between about .001 inches to about .005 inches.

7. The knife of any one of claims 1 to 6, wherein said second and third cutting members each have a thickness of at least about .001 inches.

8. The knife of claim 7, wherein said second and third cutting members each have a thickness of between about .001 inches to about .005 inches.

9. A knife comprising:
a) a first cutting member having a first end;
b) a second cutting member having an arcuate section integrally joined to a linear section, said arcuate section of the second cutting member integrally joined to said first cutting member approximate said first end of the first cutting member;
and c) a third cutting member having an arcuate section integrally joined to a linear section, said arcuate section of the third cutting member integrally joined to said first cutting member approximate said first end of the first cutting member;
wherein, said second and third cutting members are arranged relative to one another to form an angle therebetween of from between about 15° to about 180°°; and the arcuate sections of said second and third cutting members cooperate with said first end of the first cutting member to form a general wishbone configuration.

10. The knife of claim 9, wherein said second cutting member has an interior edge and said third cutting member has an interior edge, both of said interior edges joining one another to form a circular arc between said second and third cutting members.

11. The cutting knife of claim 9, wherein said second cutting member has a linear section integrally joined to said arcuate section.

12. The cutting knife of claim 9, wherein said third cutting member has a linear section integrally joined to said arcuate section.

13. The cutting knife of any one of claims 9 to 12, wherein said first cutting member has a thickness equal to said second cutting member.

14. The knife of any one of claims 9 to 13, wherein said angle formed between said second and third cutting members is from between about 30° to about 150°.

15. The knife of claim 14, wherein said second and third cutting members are arranged relative to one another to form an angle therebetween of from between about 45 ° to about 120°.

16. The knife of claim 15, wherein each of said second and third cutting members each arcuate section has an outside edge and an arcuately shaped centerline.

17. The knife of claim 16, wherein when a rectangle is drawn about the point of intersection of said first, second and third cutting members, the area of the cutting surface of said knife is from between about 20% to about 70% of the total surface area of said rectangle, said rectangle being formed by drawing a first line through two points, each of said two points being located on one of said outside edges of said second and third cutting members, respectively, at a location where an individual, respective arcuate section is

18 joined to its corresponding linear section, a second line and a third line are then drawn perpendicularly to said first line at locations where said first line crosses said outside edges of said second and third cutting members, respectively, a fourth line is then drawn parallel to said first line such that it passes through a point where the centerline of said second cutting member joins the centerline of said third cutting member, and a fifth line is drawn parallel to said fourth line and at a distance from said fourth line which is equal to the distance between said first and fourth lines, said fifth line being drawn on the same side of the first line as is the fourth line, said fifth line intersecting and said second and third lines to form said rectangle.

18. The knife of claim 15, wherein said first cutting member has a thickness greater than said second cutting member.

19. The knife of claim 17, wherein the area of cutting surface of said knife is from between about 21% to about 69% of the total surface area of said rectangle.

20. The knife of any one of claims 1 to 19, wherein the first cutting member bisects the second and third cutting members.

21. The knife of claim 20, wherein the knife has a tuning fork shape.

22. The knife of any one of claims 1 to 20, wherein the first cutting member intersects the second cutting member at an offset angle, thereby forming a non-symmetrical arrangement with the second and third cutting members.