Razors and razor cartridges

A razor cartridge having a first blade proximal to a front of the cartridge and having one or more first coatings disposed thereon, a second blade proximal to a back of the cartridge, the second blade having one or more second coatings disposed thereon, wherein a thickness of at least one of the one or more first coatings disposed on the first blade is less than a thickness of at least one of the one or more second coatings disposed on the second blade.

FIELD OF THE INVENTION

This invention relates to razors and more particularly to razor cartridges and even more particularly to the razor blades and their coatings in the razor cartridges.

BACKGROUND OF THE INVENTION

In shaving, it is desirable to achieve a close shave, while also providing a comfortable experience during hair removal. It is desirable to provide a razor cartridge having a plurality of razor blades contained therein each of which has a sharpened edge. The sharpened edge is comprised of a substrate and one or more coatings deposited thereon which engage(s) the hair and provides shaving comfort. It has been found that even when using blades with coated sharpened edges, intended to provide both a close shave and good comfort, the overall shaving experience can still be uncomfortable to some users.

It is desirable to provide a razor cartridge having blades with coated sharpened edges that improve shaving comfort while not compromising on closeness or other shaving attributes.

SUMMARY OF THE INVENTION

A razor cartridge for a razor is provided. The razor cartridge comprises a guard, a cap, and at least two blades with parallel sharpened edges located between the guard and cap. A first blade defines a blade edge nearest to the guard and a second blade defines a blade edge nearest to the cap. The present invention also contemplates that the first blade is not the nearest to the guard but defines a blade nearer or closer to the guard than the second blade and also that the second blade is nearer or closer to the cap than the first blade is. In the present invention, the first blade has one or more coatings with a thickness less than the coating thickness of the second blade. The present invention also contemplates that in razor blades having multiple coatings, just one coating varies in thickness between the first and second blades. The present invention contemplates that the hard coating of the first blade is less thick than the hard coating of the second blade.

In a first embodiment, the present invention is directed to a razor cartridge comprising a first blade proximal to a front of the cartridge, the first blade having one or more first coatings disposed thereon, a second blade proximal to a back of the cartridge, the second blade having one or more second coatings disposed thereon, wherein a thickness of at least one of the one or more first coatings disposed on the first blade is less than a thickness of at least one of the one or more second coatings disposed on the second blade. The at least one of the one or more first coatings is a first hard coating and the at least one of the one or more second coatings is a second hard coating. The front of the cartridge comprises a guard area and the back of the cartridge comprises a cap area. The first razor blade is adjacent to the guard area. The second razor blade is adjacent to the cap structure. At least one of the one or more second coatings is at least two times as thick as the at least one of the one or more first coatings. The first hard coating ranges in thickness from about 150 Angstroms to about 1800 Angstroms. The second hard coating ranges in thickness from about 500 Angstroms to about 3500 Angstroms.

In another embodiment, the present invention is directed to a razor cartridge comprising a first razor blade having a first hard coating, a second razor blade having a second hard coating, the first blade disposed closer to a guard area of the razor cartridge than the second blade and the second blade disposed closer to a cap area of the razor cartridge than the first blade, wherein the second hard coating has a second thickness that is greater than a first thickness of the first hard coating.

The first hard coating or the second hard coating comprises a carbon containing material, chromium containing material, niobium containing material, boron containing material, titanium containing material, or any combination thereof. The first razor blade is adjacent to the guard area. The second razor blade is adjacent to the cap area. The razor cartridge further includes at least one third razor blade having at least one third hard coating, the at least one third razor blade disposed between the first and the second razor blade. At least one of the at least one third hard coating is substantially the same as the first hard coating. At least one of the at least one third hard coating is substantially the same as the second hard coating. The second hard coating is at least two times as thick as the first hard coating. A thickness of the first hard coating ranges in thickness less than about 800 Angstroms and a thickness of the second hard coating is greater than about 800 Angstroms. A ratio of the second thickness to the first thickness is about 1.5 to about 4.5. The first blade has one or more coatings of a thickness at least about 2.75 times less than the thickness of the second blade.

In another embodiment, a razor cartridge is provided comprising a plurality of razor blades disposed within the cartridge from a front area to a back area of the razor cartridge, each of the blades comprising a coating, wherein a thickness of the coatings increases from the front area to the back area.

In yet another embodiment, a razor cartridge is provided with coated razor blades, one of said coated razor blades disposed closer to a guard area of said cartridge and having a coating thickness that is lowest of all coating thicknesses of said coated razor blades in said cartridge.

Where a razor has multiple blades, one or more blades can be designed with coatings having reduced thicknesses while other blades can be designed to have thicker coating(s). This combination of different blades having differing coating thicknesses provides a shave having improved comfort while maintaining closeness.

DETAILED DESCRIPTION OF THE INVENTION

In the prior art even when using blades with coated sharpened edges, intended to provide both a close shave and good comfort, the overall shaving experience can still be uncomfortable to some users. The prior art includes commercially available razor cartridges, all of which have razor blades in each position of the razor cartridges such that each of the blade coatings on each blade in prior art razor cartridges are the same. It was realized surprisingly that having such an arrangement presents disadvantages, for instance, in shaving comfort, during shave strokes. It was discovered that while each blade is in a different position in the razor cartridge, each position engages the skin and hair differently.

For instance, in a position closer to the front of the cartridge or near or nearest the guard area, the blade or blades (e.g., primary blades or primary blade edges) are required to achieve a substantial amount of the cutting action as the bulk of the hair cutting is achieved by this blade or blades and most of the long hairs are cut by this blade or blades. In turn, this blade or blades near the front of the cartridge comprise minimal skin-management properties.

The blade or blades toward the back of the cartridge or near or nearest the cap area will be required to engage and cut remaining hairs (e.g., clean up) and will comprise substantial skin-management properties and as such will have blade edges with less propensity to engage the skin than those at the front of the cartridge, but will encourage gliding over the skin without nicking, cutting, or scraping the skin. This will reduce the likelihood of post-shave irritation and improves the comfort during and after shaving. These blade edges also may have higher strength and durability.

The blade or blades in the middle, a “third blade” or “third blades” as referred to herein, may vary between functioning similarly to those blades in front and those in back of the cartridge. In a razor cartridge with five blades, there are generally five slots or five positions, one for each blade. The first blade is generally disposed in the first slot nearest the guard and the second blade is generally disposed in the fifth slot nearest the cap, while the three third blades are generally disposed in the second, third, and fourth slots in between the first and fifth slots.

In a shaving stroke, hair and skin typically travels from the front of the cartridge to the back of the cartridge. The pressure is the force normal to the skin per unit area. This pressure (force per unit area) of each blade edge on the skin and hair can be different from a blade edge in the first position (in the front of the cartridge or guard area) to a blade edge in the last position (in the back of the cartridge or cap area). For instance, generally the pressure on a first blade is low and the pressure on the last blade in the razor cartridge is high. With this increasing blade to skin pressure realized from the first blade to the last blade, each shaving stroke with a razor cartridge having sharp blades can provide discomfort during shaving.

Unexpectedly, it has been determined that the comfort of a shave can be optimized if one or more of the coatings on the razor blades in a razor cartridge are different. The differences of the coatings of the present invention can comprise differences in overall coating thickness (e.g., all hard coating thicknesses taken together), different thicknesses of individual coating layers, and/or differences in type of materials utilized, whether between just two blades or across all blades within a razor cartridge.

Specifically, it has been determined that by increasing or decreasing a coating thickness of the blade edge, of even just one coating, in a deliberate manner based on position in the razor cartridge, skin management is greatly improved while the likelihood of skin engagement, which results in a scraping feel, nicks, cuts, and irritation is greatly reduced. Most razor blades have both hard and soft coatings disposed thereon. Even if only the hard coating thickness between two blades in particular positions is varied, this result is realized. Most preferably in the present invention, increasing the thicknesses of one or more of the coatings of the blade edges disposed towards the back of the cartridge (e.g., cap area) and/or reducing the thicknesses of one or more of the coatings of the blade edges disposed towards the front of the cartridge (e.g., guard area), shaving comfort is improved and closeness of the shave is not compromised.

In a razor cartridge of the present invention comprising a guard, a cap, and at least two blades with parallel sharpened edges located between the guard and cap, a “first blade” defines a blade edge nearest and a “second blade” defines a blade edge nearest to the cap. It should be noted that the present invention also contemplates that the first blade is not the nearest to the guard but defines a blade edge nearer or closer to the guard than the second blade and that the second blade is nearer or closer to the cap than the first blade.

Germane to the present invention, the first blade comprises one or more coatings and the second blade comprises one or more coatings wherein one or more coatings of the first blade have a thickness that is less than the thickness of the one or more coatings of the second blade.

The present invention also contemplates that in razor blades having multiple coatings, just one coating can vary in thickness, or two or more coatings can vary in thickness, between the first and second blades. Though any one or more of the multiple coatings may be varied in thickness, the present invention contemplates that one coating that may be varied may be the one or more layers of hard coating of both the first blade and the second blade such that the hard coating of the first blade has a thickness less than (e.g., thinner) that of the hard coating of the second blade, whether the hard coating is of the same type or not.

“Stress” as used herein is a force per unit area in a solid material resisting separation, compacting, or sliding, that tends to be induced by external forces. The solid material contemplated in the present invention is a substrate such as the skin or the skin surface.

“Pressure” as used herein, is defined as a type of stress exerted uniformly in all directions and its measure is also the force per unit area.

The term “blade load” as used herein signifies the force applied by an individual blade onto a substrate such as the skin. The stress on the skin resulting from the blade tip's contact on the skin is often referred to as “tip stress.”

A “hard” coating as used herein signifies a non-lubricious coating. Hard coatings contemplated in the present invention can be comprised from one or more of amorphous, fine-, micro-, or nano-crystalline materials which may or may not comprise carbon, carbon containing materials such as diamond, amorphous diamond, nano-crystalline, or diamond like carbon or DLC, nitrides (e.g., boron nitride, niobium nitride, chromium nitride, zirconium nitride, or titanium nitride), carbides (e.g., silicon carbide), chromium containing materials, boron containing materials, titanium containing materials, oxides (e.g., alumina, zirconia), metal or metal alloys (e.g., chromium, chromium platinum, titanium), or other ceramic materials (including nanolayers or nanocomposites), mixtures thereof, or stacking of multiple “hard” coatings. Any of the materials can be doped with other elements, such as tungsten, titanium, silver or chromium by including these additives, for example in the target during application by sputtering. The materials can also incorporate hydrogen, e.g., hydrogenated DLC. Thus, a hard coating of the present invention can be comprised of a carbon containing material, a chromium containing material, a boron containing material, a titanium containing material, or mixtures thereof, nitrides of Ti, Al, Zn, Cr, or mixtures thereof, including but not limited to, TiN, TiCN, TiAlN, ZrN, TiCN, and CrN.

A “layer” as used herein signifies at least one material on the blade edges satisfied by a variety of factors, including but not limited to, the composition, morphology or structure of the layer(s), the presence of a boundary between layers, whether the process used to make the product is expected to result in one or more layers, and whether there is a sufficient change in composition or morphology as to result in one or more layers. For instance, a change in density, stress state, or crystalline structure results in a substantially different layer. As such, while there may be only one type of material or composition disposed on a blade edge, there could be distinguishable layers if there is a change in the morphology of the material. This would section the material into layers, each layer having a different morphology. For instance, one layer may be more dense, more crystalline, or more columnar than another layer, despite being made of the same material.

A “coating” is often used interchangeably with “layer.” As used herein a “coating” can signify one or more layers of materials on a blade edge. Thus, the present invention “coating” may be defined by a single layer, such as a hard coating type layer, or similarly, multiple layers as multiple coatings. Most razors have at least one hard coating and at least one soft coating disposed on a blade edge. The present invention also contemplates the term “coating” to signify the “overall” or total coating which includes all the layers of hard coating materials disposed on a blade edge. Thus, while a finished blade edge may include a soft coating, for purposes of the present invention, the “overall” coating is generally meant to comprise only the hard coating layers and not any soft coating layers.

The “thickness” of the coating as the term is used herein generally signifies the width dimension of a particular material or materials. For a blade edge coating, a Scanning Electron Microscope (SEM) is used to visualize the thickness and obtain reasonable thicknesses over the blade edge or edge region (e.g., ranging from the ultimate tip to about 40 micrometers or more back from the tip). The thickness value at a distance from the ultimate tip is generally determined by the orthogonal distance along an orthogonal line from a point on the tangent line to the exterior surface of the hard coating at the distance from the tip to a point on a tangent line on the coating interface with the substrate. Effectively, the perpendicular distance across the coating between an exterior coating tangent line and a coating-substrate interface tangent line represents the thickness value at distance.FIG.23andFIG.24depict thicknesses of the hard coatings of the present invention at various distances from the ultimate tip.

While stainless-steel is the desired substrate of the razor blade of the present invention, as it is the common substrate for razor blades, blade substrates comprised of another metal or metals, ceramic, composite, plastic, glass, or any combination thereof, are also contemplated in the present invention. One substrate material which may facilitate producing an appropriately sharpened edge is a martensitic stainless-steel with smaller more finely distributed carbides. This type of steel may have similar overall carbon weight percent. A fine carbide substrate provides for a harder and more brittle after-hardening substrates, and enables the making of a thinner, stronger edge. An example of such a substrate material is a martensitic stainless-steel with a finer average carbide size with a carbide density of 90, 100, 200, 300, 400 carbides per 100 square micrometers, to 600, 800, 1000 carbides or more per 100 square micrometers as determined by Scanning Electron Microscopy, SEM 4000× or higher.

The term “about” as used herein generally signifies approximately or around. When a range of numerals are given, e.g., “about 4 to about 40” is disclosed herein, the present invention contemplates +/−10 percent of each number. Thus, for clarity, if a reference is described as being “about 4 to about 40” signifies the range of “3.6 to 44” as being encompassed by the present invention since the range of 3.6 to 4.4 represents +/−10 percent of 4 and the range of 36 to 44 represents +/−10 percent of 40.

Referring toFIG.1, a razor cartridge8includes a guard10, a cap12, and two blades14and16. The first blade14has a coating that is thinner than the thickness of the coating of the second blade16and as shown, the first blade14is positioned between the guard10and the second blade16. Thus, when the razor cartridge8is in use, the first blade14will contact the hair before the second blade16.

As used herein in both the text and the figures the term “first blade” refers to a blade having relatively thinner coating(s) or thinner hard coating(s), which requires a lower pressure on the first blade so that the skin is not negatively impacted than the blade referred to as the second blade. The first blade has good hair engagement and efficiency but does not sacrifice safety and comfort. Likewise, the term “second blade” refers to a blade having a relatively thicker coating or coatings, or thicker hard coating(s), which allows for greater pressure (i.e., force divided by area) on the second blade without negatively impacting the skin than the blade referred to as the first blade.

Referring toFIGS.2-4, other razor cartridges can include a guard10, a cap12, and multiple blades14,15,16(three, four, five or more blades respectively). In each instance a first blade14having thinner coating(s) than a second blade16which is positioned between a guard10and the cap12. As noted above, the second blade is the blade generally nearest or nearer to the cap12than the first blade.

As depicted inFIG.2, the razor cartridge8has three blades. The first blade14is the blade with the thinner coating(s) and positioned closest or adjacent to the guard10(i.e., in the principal position). The second blade16having the thicker coating(s) is positioned in the third position from the guard10, i.e., in the position nearest or adjacent the cap12. A third blade15is positioned between the first blade14and the second blade16. The third blade15may be identical to the first blade14, identical to the second blade16, or have a configuration different from the first blade14and the second blade16. Preferably, the third blade15is identical to the first blade14.

As depicted inFIG.3, the razor cartridge8can include four blades. The first blade14is the blade with thinner coating(s) and positioned closest to the guard10(i.e., the principal position). The second blade16having thicker coating(s) is positioned in the fourth position from the guard10, i.e., in the position nearest the cap12. Two third blades15are positioned between the first blade14and the second blade16. The third blades15may be identical to the first blade14, identical to the second blade16, or have a configuration different from the first blade14and the second blade16. Preferably, the third blades15are each identical to the first blade14though any configuration is contemplated as long as a first blade has a coating thickness less than a second blade.

As depicted inFIG.4, the razor cartridge8has five blades. The first blade14is the blade having thinner coating(s) and positioned closest to the guard10(i.e., the principal position). The second blade16having thicker coating(s) is positioned in the fifth position from the guard10, i.e., in the position nearest the cap12. Three third blades15(15′,15″, and15′″) are positioned between the first blade14and the second blade16. The third blades15′,15″, and15′″ may be identical to the first blade14, identical to the second blade16, have a coating thickness different from the first blade14and the second blade16, or have any number of different coating thicknesses amongst themselves. Further, each blade may have a different coating thickness relative to other blade coating thicknesses in the razor cartridge, as depicted inFIG.19.

FIG.5shows a cross-sectional image50of an actual razor cartridge8of the embodiment depicted inFIG.4taken at a substantial midpoint of the cartridge. As can be seen, first blade14is disposed in a first position or blade slot1proximal to the guard structure10towards the front of the cartridge50a, the second blade16is disposed in position or blade slot5proximal to the cap structure12towards the back of the cartridge50b, and third blades15are in the middle section of slots, namely blades slots or positions2,3, and4.

An illustrative diagram of a cross-section of representative blades of the present invention is shown inFIG.6. A first blade14of the present invention is shown inFIG.6depicting a substrate54and a first hard coating51deposited thereon. Hard coating51has an overall thickness53. Coating thickness51is determined at a location of about four to about forty micrometers from the coated blade tip57. Coating51may be comprised of one or more layers of the same or different materials, structures, or morphology. For instance,FIG.20, as described in detail below, depicts a finished first blade edge having both hard and soft coatings and with an overall coating51a(e.g., inclusive of the soft coating material) and with the hard coating51comprising several types of materials layered to form the thickness53of the hard coating51. These individual layers may each be of varying thicknesses.

A representative second blade16of the present invention is also shown inFIG.6having a substrate56and a hard coating52deposited thereon. Hard coating52may be comprised of one or more layers of the same or different materials, structures, or morphology. Coating52has an overall thickness55determined at a location of about 4 micrometers to about 40 micrometers from the tip58of the second blade16. The coating thickness53of the first blade is less than the coating thickness55of the second blade. As shown, coating52is thicker than coating51. As with the first blade coating51, coating52may be comprised of one or more layers of the same or different materials, structures, or morphology. For instance,FIG.21, as described in detail below, depicts a finished second blade edge having both hard and soft coatings and with an overall coating52a(e.g., inclusive of the soft coating material) and a hard coating52comprising several types of materials layered to form the overall thickness55of the hard coating52. These individual layers may each be of varying thicknesses. The various types of layers of the first and second blade coatings will be further described in conjunction withFIGS.20,21,21a, and22below.

In embodiments ofFIG.7-19all references to coating thicknesses are for hard coating thicknesses. In one embodiment of the present invention, the third blades15(15′,15″, and15′″) ofFIG.4are each identical to the first blade14. Specifically, the thickness of the coatings of the third blades15are each identical to the coating thickness of the first blade14.FIG.7depicts such an illustration of cross-sectional views of portions of the blade edges within the razor cartridge8showing coatings51,52on each blade14,16, and substrates54,56, respectively. As can be seen, the first blade14and the three third blades15(shown as first third blade15′, second third blade15″, and third third blade15′″ for clarity) have coatings of identical thicknesses53, all of which are thinner than the coating thickness55of coating52of the second blade16.

FIG.8depicts an illustration of cross-sectional views of portions of the blade edges within the razor cartridge8showing coatings51,52on each blade14,16, and substrates54,56, respectively. As can be seen, the second blade16and the three third blades15′,15″, and15′″ have coatings of identical thicknesses55, all of which are thicker than the coating thickness53of the first blade14.

FIG.9depicts an illustration of cross-sectional views of portions of the blade edges within the razor cartridge8showing coatings51,52on each blade14,16, and substrates54,56, respectively. As can be seen, the first blade14and an adjacent one, a first15′ of the three third blades15have coatings of identical thicknesses53, both of which are thinner than the coating thickness55of the second blade16and the remaining two third blades15″ and15′″.

FIG.10depicts an illustration of cross-sectional views of portions of the blade edges within the razor cartridge8showing coatings51,52on each blade14,16, and substrates54,56, respectively. As can be seen, the first blade14and two of the three third blades15′ and15″ have coatings of identical thicknesses53, all of which are thinner than the coating thickness55of the second blade16and the remaining one third blade15.

As noted above, the present invention contemplates that the first blade does not necessarily have to be the blade most proximal or nearest to the guard and can be defined as a blade edge nearer or closer to the guard when compared to the location of a second blade. Similarly, the present invention contemplates that the second blade does not necessarily have to be the most proximal or nearest blade to the cap and can be defined as a blade edge nearer or closer to the cap when compared to the location of the first blade.

Accordingly, the present invention contemplates a second blade16having a thicker coating disposed in a third blade position of the razor cartridge as shown inFIG.11which depicts an illustration of cross-sectional views of portions of the blade edges within the razor cartridge8showing coatings51,52on each blade14,16, and substrates54,56, respectively. Here, while the third blade15′″ and the second blade16are numbered as before, the thicker coating of the third blade15′″ renders it, functionally as a “second blade” of the cartridge for purposes of the present invention. The third blade15′″ and the second blade can be thought to have effectively swapped positions. The third blade15′″ (or the effective “second blade” in the third blade15′″ position) is still nearer or closer to the cap than the first blade14. InFIG.11, the first blade14and two of the three third blades15′ and15″ adjacent to the first blade14, along with the second blade16or effectively the third blade15′″ assuming a swap, which is, as shown, most proximal or closest to the cap12, have coatings of identical thicknesses53, all of which are thinner in dimension than the coating thickness55of the third blade15′″. Effectively, the “second blade” in this arrangement is in position4of the razor cartridge. In this embodiment, there are three blades (i.e. first blade14and adjacent third blades15′ and15″ and second blade16) which have a coating thickness that is thinner than the coating thickness of the third blade15′″. Alternately, one or both of the first and third third blades may have the same thickness as the third third blade15′″ as shown inFIG.12where both the first third blade and second third blade,15′ and15″ respectively, have the same thickness as the third third blade15′″ ofFIG.11, inFIG.13where only the first third blade15′ has substantially the same thickness as the third third blade15′″ ofFIG.11, and inFIG.14where only the second third blade15″ has substantially the same thickness as the third third blade15′″ ofFIG.11. In these embodiments, the second blade16closest to the cap has a thickness which is nearly identical to the first blade14. In such an arrangement, one or more of the third blades effectively acts as the “second blade” for the razor cartridge in that it is the blade which is closer to the cap structure and it has a thicker coating than the first blade.

In an alternate embodiment shown inFIG.15, an illustration of cross-sectional views of portions of the blade edges within the razor cartridge8is depicted showing coatings51,52on each blade14,16, and substrates54,56, respectively, where a first blade14is in the principal position nearest the guard10and a first third blade15′ is in the next position adjacent to the first blade14. The thickness of the coating of the first third blade15′ is substantially identical to that of the second blade16which is positioned closest to the guard10. The first blade14has a coating thickness53which is thinner than the coating thickness55of both the first third blade15′ and the second blade16. The other third blades15depicted, third blades15″ and15′″, have a coating thickness which is identical to the coating thickness of the first blade14.

Further still, the first and third third blade15′ and15′″, respectively, may have coating thicknesses that are substantially identical to that of the second blade16as shown in alternate embodiment ofFIG.16, the second third blade15″ may have a coating that is substantially identical to that of the second blade16with first and third blades15′ and15′″ having a coating substantially identical to that of the first blade14as shown in alternate embodiment ofFIG.17, and the first and second third blade15′ and15″, respectively, may have coating thicknesses that are substantially identical to that of the second blade16as shown in alternate embodiment ofFIG.18.

FIG.19depicts an illustration of cross-sectional views of portions of the blade edges within the razor cartridge8showing coatings on each blade and substrates20, respectively. As can be seen, the coating thicknesses increase incrementally across the razor cartridge from the first blade14to each of the third blades, and from the third blades to the second blade16. None of the coating thicknesses on the razor blades are identical. As shown, the first coating23of the first third blade15′ adjacent to the first blade14has a coating thickness24which is not identical to the coating thickness22of the coating21of the first blade14but rather thicker than coating21of the first blade14. The second third blade15′″ has a coating25with a thickness26which is not identical to that of the coating21of the first blade14or the coating23of the first of the third blades15′, but rather thicker than both coating21of the first blade and coating23of the first of the third blades15′. The third third blade15′″ has a coating27with a thickness28which is not identical to any of the coatings of the first blade14or first two third blades15′ or15″ (e.g., coatings21,23, and25, respectively), but rather is thicker than that of the first blade or first two third blades. Finally, the second blade16has a coating29with a thickness30. Thickness30is the thickest coating of all the blades14,15′,15″,15′″ as arranged in the razor cartridge (not shown).

As noted, one or more of the third blades can function as a “second blade” of the present invention. While razor cartridges have been described and shown supra with exemplary thicknesses, all permutations of varying coating thicknesses on the razor blade edges across a razor cartridge are within the scope and contemplated in the present invention. Also, while razor cartridges have been shown with two, three, four and five blades, razor cartridges having six or more blades may also be desirable.

Preferably, the blades of the present invention are arranged within the razor cartridge such that they have a progressive geometry. An example of a razor cartridges with blades arranged to have a progressive geometry is described in U.S. Pat. No. 6,212,777, incorporated herein by reference in its entirety.

In some instances, the first blade has a coating thickness at least 5% less than the coating thickness of the second blade. Preferably, the first blade has a coating thickness at least about 10% less than the coating thickness of the second blade, and up to about 50% less than the coating thickness of the second blade.

In general, the hard coating thickness of the first blade is between about 300 Angstroms and 1800 Angstroms, preferably about 500 to about 1000 Angstroms, and more preferably, about 600 to about 925 Angstroms. These ranges incorporate all hard coating materials, inclusive of all hard coating materials making up the overall hard coating of the first blade.

The hard coating thickness of the first blade is less than that of the second blade. Preferably, the first blade has a hard coating thickness of at least about two times less than that of the second blade.

Though not considered part of the overall hard coating, it should be noted that a soft coating applied to a finished first blade or a second blade can generally add about 200 Angstroms to about 5000 Angstroms to the overall hard coating.

In general, the hard coating thickness of the second blade is between about 500 Angstroms and about 3500 Angstroms, preferably about 1500 Angstroms to about 2700 Angstroms. The hard coating of the second blade is thicker than the hard coating of the first blade. These ranges incorporate all hard coating materials, inclusive of all hard coating materials making up the overall hard coating of the first blade. Accordingly, if more than one type of material makes up the hard coating layer, then the summation of thicknesses of each hard coating layer is utilized for the thickness of the overall hard coating.

In the present invention, a first blade has a coating thickness of at least about 500 Angstroms less than that of the second blade coating. In one embodiment, a thickness of the first hard coating has a thickness less than about 800 Angstroms and a thickness of the second hard coating is greater than about 800 Angstroms. In the present invention, the ratio of thicknesses of second coating to the first coating is about 1.5 to about 4.5, and more preferably the ratio is about 2.7. Preferably, in the present invention, a ratio of thickness of a second hard coating to a first hard coating is about 1.5 to about 4.5 times, preferably at least about 2, and most preferably about 2.7.

Providing a blade having thicker coating(s) can be accomplished by having one or more of the layers that make up the overall coating on the blade edge be thicker. For instance, referring toFIG.20, there is shown a finished first blade14including an overall coating51having a substrate54and multiple coating layers such as interlayer134, hard coating layer136, overcoat layer138, and outer layer130. The substrate54is typically made of stainless steel though other materials can be employed. An example of a razor blade having a substrate, interlayer, hard coating layer, overcoat layer and an outer layer is described in U.S. Pat. No. 6,684,513.

Interlayer134is used to facilitate bonding of the hard coating layer136to the substrate50. Examples of suitable interlayer material are niobium, titanium and chromium containing material. A particular interlayer is made of niobium greater than about 100 Angstroms and preferably less than about 500 Angstroms thick. The interlayer may have a thickness from about 150 Angstroms to about 350 Angstroms, and more preferably about 160 to 240 Angstroms. PCT 92/03330 describes use of a niobium interlayer.

Hard coating layer136provides improved strength, corrosion resistance and shaving ability and can be made from any of the materials described above. Preferably hard coating layer136is made of diamond, amorphous diamond or DLC. The hard coating136of blade14has a thickness137. A particular embodiment for the first blade14includes a hard coating comprised of DLC having a thickness137of between about 100 Angstroms to about 1,000 Angstroms, preferably from about 200 Angstroms to about 750 Angstroms, more preferably between about 300 Angstroms to about 600 Angstroms, and most preferably about 450 Angstroms to about 550 Angstroms. DLC layers and methods of deposition are described in U.S. Pat. No. 5,232,568. As described in the “Handbook of Physical Vapor Deposition (PVD) Processing, “DLC is an amorphous carbon material that exhibits many of the desirable properties of diamond but does not have the crystalline structure of diamond.”

Overcoat layer138is used to reduce the tip rounding of the hard coated edge and to facilitate bonding of the outer layer to the hard coating while still maintaining the benefits of both. Overcoat layer138is preferably made of chromium containing material, e.g., chromium or chromium alloys or chromium compounds that are compatible with polytetrafluoroethylene, e.g., chromium platinum. A particular overcoat layer is chromium about 100 to about 200 Angstroms thick. Overcoat layer may have a thickness of from about 50 Angstroms to about 500 Angstroms, preferably from about 100 Angstroms to about 300 Angstroms, and most preferably about 180 Angstroms to about 250 Angstroms. First blade14has a cutting edge that has less rounding with repeated shaves than it would have without such an overcoat layer.

Hard coating136is a hard coating whose thickness would be included in the overall hard coating thickness53. The interlayer134comprised of niobium is considered a hard coating layer and thus, its thickness would be included in the hard coating thickness53. The overcoat layer138comprised of chromium is also considered to be a hard coating and its thickness would be included in the hard coating thickness53.

Outer layer130is used to provide reduced friction. The outer layer130may be a soft coating of a lubricious material such as a polymer composition or a modified polymer composition. The polymer composition may be polyfluorocarbon. A suitable polyflourocarbon is polytetrafluoroethylene, sometimes referred to as a telomer. A particular polytetrafluoroethylene material is Krytox LW 1200 available from Chemours, formerly Dupont. This material is a nonflammable and stable dry lubricant that consists of small particles that yield stable dispersions. It is furnished as an aqueous dispersion of 20% solids by weight and can be applied by dipping, spraying, or brushing, and can thereafter be air dried or melt coated. The layer is preferably less than 5,000 Angstroms and could typically be 1,500 Angstroms to 4,000 Angstroms, but can be as thin as 100 Angstroms, provided that a continuous coating is maintained. Provided that a continuous coating is achieved, reduced telomer coating thickness can provide improved first shave results. U.S. Pat. Nos. 5,263,256, 5,985,459, and 10,118,304 which are hereby incorporated by reference, describe techniques which can be used to change the thickness of an applied telomer layer.

First blade14is made generally according to the processes described in the above referenced patents. A particular embodiment includes a niobium interlayer134, DLC hard coating layer136, chromium overcoat layer138, and Krytox LW1200 polytetrafluoroethylene outer coat layer130. Chromium overcoat layer138is deposited to a minimum of 100 Angstroms and a maximum of 500 Angstroms. It is deposited by sputtering using a DC bias (more negative than −50 volts and preferably more negative than −200 volts) and pressure of about 2 millitorr argon. The increased negative bias is believed to promote a compressive stress (as opposed to a tensile stress), in the chromium overcoat layer which is believed to promote improved resistance to tip rounding while maintaining good shaving performance. First blade14preferably has a tip radius ranging from about 200 to about 400 Angstroms, measured by SEM after application of overcoat layer138and before adding outer layer130.

Referring now toFIG.21, there is shown a finished second blade16including substrate56having a hard coating52and an overall coating52awhich includes the hard coating52and a soft coating such as outer layer135. The hard coating52may comprise individual layers, interlayer131, hard coating layer132a, and overcoat layer133which may comprise a portion of the hard coating52. The substrate56is typically made of stainless steel though other materials can be employed. An example of a razor blade having a substrate, interlayer, hard coating layer, overcoat layer and an outer layer is described in U.S. Pat. No. 6,684,513.

As with the first blade14, interlayer131can be used to facilitate bonding of the hard coating layer132to the substrate56. Examples of suitable interlayer material are niobium, titanium and chromium containing material. A particular interlayer is made of niobium having a thickness greater than about 100 Angstroms and preferably less than about 500 Angstroms. For instance, the interlayer may have a thickness from about 150 Angstroms to about 350 Angstroms, and more preferably about 160 to 240 Angstroms. PCT 92/03330 describes use of a niobium interlayer.

Hard coating layer132provides improved strength, corrosion resistance and shaving ability and can be made from any of the materials described herein. Preferably coating layer132is made of diamond, amorphous diamond or DLC. The hard coating132of blade16has a thickness139. In the present invention, hard coating thickness139is desirably about 1.5 to 4.5 times greater or thicker than the thickness137of the first blade, preferably at least about 2 times thicker than thickness137, and most preferably about 2.75 times thicker than thickness137of the first blade14. A particular embodiment for the second blade16includes hard coating or DLC thickness ranging from about 400 to about 3000 Angstroms, from about 900 Angstroms to about 2500 Angstroms, preferably greater than 1000 Angstroms, more preferably greater than 1200 Angstroms, and most preferably about 1700 to about 2500 Angstroms. DLC layers and methods of deposition are described in U.S. Pat. No. 5,232,568. As described in the “Handbook of Physical Vapor Deposition (PVD) Processing,” DLC is an amorphous carbon material that exhibits many of the desirable properties of diamond but does not have the crystalline structure of diamond.

Overcoat layer133is used to reduce the tip rounding of the hard coated edge and to facilitate bonding of the outer layer to the hard coating while still maintaining the benefits of both. Overcoat layer133is preferably made of chromium containing material, e.g., chromium or chromium alloys or chromium compounds that are compatible with polytetrafluoroethylene, e.g., chromium platinum. A particular overcoat layer is chromium about 100 to about 200 Angstroms thick. Overcoat layer may have a thickness of from about 50 Angstroms to about 500 Angstroms, preferably from about 100 Angstroms to about 300 Angstroms, and most preferably 180 Angstroms to about 250 Angstroms. Second blade16has a cutting edge that has less rounding with repeated shaves than it would have without the overcoat layer.

Hard coating132is a hard coating whose thickness would be included in the overall hard coating thickness55. The interlayer131comprised of niobium is considered a portion of overall hard coating52and thus, its thickness would be included in the hard coating thickness55. The overcoat layer133comprised of chromium is also considered to be a portion of the hard coating52and its thickness would be included in the hard coating thickness55.

Outer layer135is used to provide reduced friction. The outer layer135may be a soft coating of lubricious material such as a polymer composition or a modified polymer composition. The polymer composition may be polyfluorocarbon. A suitable polyflourocarbon is polytetrafluoroethylene sometimes referred to as a telomer. A particular polytetrafluoroethylene material is Krytox LW 1200 available from DuPont. This material is a nonflammable and stable dry lubricant that consists of small particles that yield stable dispersions. It is furnished as an aqueous dispersion of 20% solids by weight and can be applied by dipping, spraying, or brushing, and can thereafter be air dried or melt coated. The layer is preferably less than 5,000 Angstroms and could typically be 1,500 Angstroms to 4,000 Angstroms, and can be as thin as 100 Angstroms, provided that a continuous coating is maintained. Provided that a continuous coating is achieved, reduced telomer coating thickness can provide improved first shave results. U.S. Pat. Nos. 5,263,256, 5,985,459, and 10,118,304 which are hereby incorporated by reference, describe techniques which can be used to change the thickness of an applied telomer layer.

Second blade16is made generally according to the processes described in the above referenced patents. A particular embodiment of a second blade16includes a niobium interlayer131, DLC or carbon containing hard coating layer132, a chromium containing overcoat layer133, and a Krytox LW1200 polytetrafluoroethylene outer coat layer135. Chromium containing overcoat layer133is deposited to a minimum of 100 Angstroms and a maximum of 500 Angstroms. It is deposited by sputtering using a DC bias (more negative than −50 volts and preferably more negative than −200 volts) and pressure of about 2 millitorr argon. The increased negative bias is believed to promote a compressive stress (as opposed to a tensile stress), in the chromium overcoat layer which is believed to promote improved resistance to tip rounding while maintaining good shaving performance. Second blade16preferably has a tip radius of about 200 to about 400 Angstroms, measured by SEM after application of overcoat layer133and before adding outer layer135.

Referring now toFIG.21a, there is shown a finished second blade16including substrate56having a hard coating52and an overall coating52awhich includes the hard coating52and a soft coating such as outer layer135. The hard coating52may comprise individual layers, interlayer131, hard coating layer132a, and overcoat layer133. InFIG.21a, only one layer has a different thickness when compared toFIG.20. The hard coating layer132aof the second blade16inFIG.21ais thicker than hard coating136ofFIG.20, or thickness137is less than thickness139a. Hard coating layer132ais a portion of the hard coating52whose thickness would be included in the overall hard coating thickness55. However, an interlayer131comprised of niobium is considered a portion of the hard coating52and thus, its thickness would be included in the hard coating thickness55and the overcoat layer133comprised of chromium is also considered to be a portion of the hard coating52and its thickness would be included in the hard coating thickness55.

The present invention contemplates blades with any other feasible coatings. For instance, as depicted inFIG.22, an alternate embodiment of a first or a second blade60in a razor cartridge of the present invention has a substrate64where an overall coating61aincludes a first layer62comprised of any of a Chromium only material or a Chromium containing material such as Platinum Chromium material, Chromium Nitride, Chromium Carbide, or any other Chromium containing material, whether doped, mixed, or otherwise comprising, and a lubricious outer coat layer63such as polytetrafluoroethylene. Coating61amay also be comprised of any other feasible materials. The first layer62is the only hard coating in blade60and as such, the coating thickness65of first layer62accounts for the overall hard coating thickness.

It is also noted that the present invention contemplates that substrate54of the first blade14inFIG.20and substrate56of the second blade16ofFIG.21can be different. For instance, substrate56may have a smaller shape, sharper profile, or comprise a different material than substrate54or vice-versa. Similarly, substrate64ofFIG.22may have a different shape or profile or material than either of substrates54or56.

A diagrammatic view of a coated edge region141of the first blade14is shown inFIG.23. The first blade14includes stainless steel body portion or substrate54with a coating51disposed thereon as described herein. The coated wedge-shaped sharpened edge141has a tip146. Tip146preferably has a radius of from about 125 to about 300 Angstroms with facets A and B that diverge from tip146. The coating51has a thickness143of between about 300 Angstroms to about 1800 Angstroms when measured at a distance142of four micrometers from the blade tip146. The thickness143is determined by the orthogonal distance along line P1taken from a point T1at the distance142on a line tangent to the exterior surface51aof the hard coating51to a point T2on a line tangent to the coating interface51bwith the substrate54. A 90-degree angle is formed from exterior surface51aand the perpendicular line P1. Effectively, the perpendicular distance across the coating between T1and T2represents the thickness143at distance142.

The coating51has a thickness145of between about 300 Angstroms to about 1800 Angstroms when measured at a distance144of ten micrometers from the blade tip146. The thickness145is determined by the orthogonal distance along line P2taken from a point T3on a line tangent to the exterior surface of the hard coating at the distance144on the exterior surface51cof the coating51to a point T4on a line tangent to the coating interface51dwith the substrate54. A 90-degree angle is formed from exterior surface51cand the perpendicular line P2. Effectively, the perpendicular distance across the coating between T3and T4represents the thickness145at distance144. At distances beyond ten micrometers from the blade tip the coating51is substantially the same thickness. The coating51may taper down to lower thicknesses the further back from the tip (e.g., forty micrometers or more).

A diagrammatic view of a coated edge region151of the second blade16is shown inFIG.24. The second blade16includes stainless steel body portion or substrate56with a coating52disposed thereon as described herein. The coated wedge-shaped sharpened edge151has a tip156. Tip156preferably has a radius of from about 125 to about 300 Angstroms with facets A and B that diverge from tip156. The coating52has a thickness153of between about 600 Angstroms to about 3000 Angstroms when measured at a distance152of four micrometers from the blade tip156.

In order to provide a proper thickness value comparison, the thickness of the second blade is determined in the same manner, using the same technique, and at the same distance from the ultimate tip as the thickness of the first blade.

The thickness153is determined by the orthogonal distance along line P3taken at the distance152from a point T5on a tangent line on the exterior surface52aof the hard coating52to a point T6on a tangent line on the coating interface52bwith the substrate54. A 90-degree angle is formed from exterior surface52aand the perpendicular line P3. Effectively, the perpendicular distance across the coating52between T5and T6represents the thickness153at distance152.

The coating52has a thickness155of between about 600 Angstroms to about 3000 Angstroms when measured at a distance154of ten micrometers from the blade tip156. The thickness155is determined by the orthogonal distance along line P4taken at a distance154from a point T7on a tangent line on the exterior surface52cof the coating52to a point T8on a tangent line on the coating interface52dwith the substrate54. A 90-degree angle is formed between exterior surface52cand the perpendicular line P4. Effectively, the perpendicular distance across the coating52between T7and T8represents the thickness155at distance154. At distances beyond ten micrometers from the blade tip the coating52is substantially the same thickness. The coating52may taper down to lower thicknesses the further back from the tip (e.g., forty micrometers or more).

Due to the mechanical complexity of the skin in response to a load, simulation modeling can predict the mechanical behavior of skin during various dynamic loading situations, such as those found during a shaving stroke. One such simulation technique is a finite element analysis model. An example of a finite element analysis technique with skin, hair, and a shaving device is described in U.S. Pat. No. 8,306,753, assigned to the Assignee hereof and incorporated herein by reference in its entirety.

FIG.25shows a cross-sectional diagram70of razor cartridge80having blades84,85, and86of the prior art applied on a finite element analysis model of skin depicting the cartridge as it would press or load against the skin72.

The guard71and cap73are two areas of the razor cartridge80where the stress onto the skin may be the highest as indicated by the dark areas, red color, or hatching74. The blades of the prior art cartridge also exhibit stress on the skin in areas74and, in particular, the blades towards the cap, e.g., blades85′″ and86, are shown to comprise the most stress.

FIG.26depicts a 3-dimensional finite element model90illustrating the pressure areas A and B on the skin92of the five blades96,95′,95″,95′″, and94of a prior art cartridge such as that ofFIG.25. As withFIG.25, the razor blade96which is disposed nearest the cap92has the highest degree of pressure area A, as indicated by the dark area A, followed by blades95′″,95″, and95′ each with a slightly lower degree of pressure area B as compared to area A, while blade94nearest the guard structure95appears to have substantially no pressure as indicated in area C.

A representative graph of the individual blade load of each blade as a percentage of the total cartridge load in the prior art cartridges described herein can be seen inFIG.27. Blade5(e.g., blade96inFIG.26) has the highest blade load at about 7.6, blade4(e.g., blade95′″ ofFIG.26), has a load of about 5.9, blade3(e.g., blade95″ ofFIG.26) has a load of about 3.9, blade2(e.g., blade95′ ofFIG.26) has a load of about 0.3, and blade1(closest to the guard structure, blade94ofFIG.26) has no load.

One benefit of the present invention can be realized with an arrangement of blades (e.g.,FIG.7) in a particular razor cartridge, as shown inFIG.28, a representative graph depicting the reduction in individual blade load of each blade as a percentage of a total cartridge load. InFIG.28, the load on blade5(e.g., blade16inFIG.7) is significantly reduced to a load of about 5.7 from a load of about 7.6. While still the highest blade load, this reduction assists greatly in improved comfort and shave performance. Blade4(e.g., blade15′″ ofFIG.7), has a load of about 3, blade3(e.g., blade15″ ofFIG.7) has a load of about 3.5, blade2(e.g., blade15′ ofFIG.7) has a load of about 3, and blade1(closest to the guard structure, blade14ofFIG.7) has no load.

FIG.29shows four contour plots or maps300,310,320, and330depicting stress in a substrate (e.g., skin mimic) resulting from contact with a blade under shaving loads. Stress, defined as the force per unit area, as noted, can act in different directions upon a substrate. Razor cartridges are desirably designed to control blade loads at or below design load scenarios. Exceeding the load for which a blade is designed is undesirable as the excessive load may decrease comfort or cause nicks, cuts, or other injuries during shaving. The “design load” can be defined as a force applied to the blade whereby the location of greatest stress intensity and magnitude is desirably located at the shoulder of the blade versus its tip during contact. Forces applied to a blade at or below the design load result in more load support coming from the blade's shoulder (e.g., located at about 1 micrometer or less from the ultimate tip) as opposed to intense concentration of stress at the sharp tip when design load is exceeded.

A thicker coating on a second blade16as described herein, changes the shape as shown, and affects the design load such that the design load of the first blade14is lower than the design load of the second blade16. Accordingly, the first blade14having a thinner coating than a second blade16may be deemed to be more sensitive to conditions of higher load, such as nicks and cuts, than the second blade when the load is exceeded. The blades of different coating thicknesses can be arranged to ensure that, by position in the cartridge, the desired design load compliance is maintained. For instance, the second blade of the present invention having a thicker coating may be considered a “skin-safe” type blade providing comfort, skin management and less nicks and cuts versus a first blade having a coating of reduced thickness as compared to the second blade and which, may be required to optimally cut hair more closely and efficiently. Accordingly, the first blade is desirably arranged to be closer to the front of the cartridge (nearer or nearest to the guard structure) than the second blade.

Plots300and320depict blades shaving at design loads modeled at the same scale for the first and second blades14,16, respectively, of the present invention. The stress in the substrate (e.g., skin)305resulting from the blade contact is illustrated by contours302with generally darker areas307indicating a greater stress, and lighter areas314indicating less stress. As can be seen in plot300, the resulting distribution of stress from the first blade14contacting the substrate at design load includes a stress concentration301at the tip of the blade306and stress concentration307at a bevel or shoulder area308. Stress concentrations from blade14in plot300are indicated by dark areas with tightly arranged contours at the tip306of the blade and at the shoulder area308. These areas generally occur where the blade profile's curvature changes the most in contact with substrate305. Similarly blade16in plot320depicts contours302with stress concentrations303at the tip316and stress concentration309at the shoulder area318. When comparing the second blade16to the first blade14, the magnitudes of stress concentration at the tips306and316and the shoulders308and318of the first blade14and second blade16, respectively, are generally smaller or lower for the second blade than for the first blade14. Accordingly, at their respective design loads, the first blade14has a bit more stress on the substrate305than the second blade16. However, at their respective design loads, both blades14and16, as shown in plots300and320, have a higher magnitude of stress concentration at the shoulders308and318than at the tips306and316. Thus, at or below the design load, it is desirable, as shown in plots300and320to have most or all of the stress distributed at the shoulder and away from the tip.

It follows that, when the design load is exceeded, the first blade14will still have more stress on the substrate than the second blade16resulting from different coatings (e.g., different coating thicknesses). Plots310and330illustrate shaving loads exceeding desired design levels and show how the first and second blades of the present invention contact the substrate (e.g., skin). It is noted that the stress at design load scenarios of plots300and320is less than the stress in the exceeding design load scenarios of plots310and330. As above, the blades' contact with the substrate (e.g., skin)305are illustrated by contours302and generally darker areas of more tightly arranged contours like area311at the blade tip306, and area317at the blade's shoulder308of blade14which indicate regions with greater magnitude and concentration of stress. Similarly, concentrations of stress313and319from blade16in contact with substrate305are occurring at the tip316and shoulder318respectively. As can be seen in plot310, the stress of the first blade14upon the substrate305when exceeding the design load includes stress311at the tip306of the blade and stress317at a bevel or shoulder area308. Likewise, in plot330the stress of the second blade16upon the substrate305when exceeding the design load includes stress concentration313at the tip316and stress concentration319at the shoulder318. However, in the scenarios where the design load has been exceeded as in both plots310and330it can be observed that the magnitude and concentration of stress is greater at the tips306and316than at the shoulders308and318of both blades14and16respectively. When the design loads of both blades14and16have been exceed as in both plots310and330the stress is concentrated with greater intensity and magnitude at the tips306and316than at the shoulders308and318. Exceeding the design load concentrates a higher magnitude of stress at the tips306and316than at the shoulders308and318and is undesirable as the high intensity of stress at the tip may decrease comfort or cause nicks, cuts, or other injuries during shaving.

Plots310and330also show a bulge area315of the substrate (e.g., skin) in an area to the left of the blade tips in the diagram. This bulge area is not pronounced in plots300and300. The bulge area315generally is a response of the substrate to the excessive load being put on the substrate by the blades, whether it be the first or second blade. As this bulge is in front of the blade leading its direction of travel while shaving, it is generally desirable to minimize the bulge area315to avoid discomfort, nicks, cuts, or other undesirable effects from shaving.

As shown in plots310and330, when at the same load, which in these plots exceeds design load, the first blade14has more stress on a substrate both at the tip and the shoulder than the second blade16. When design load is exceeded, it is desirable to have less stress at the tip.

Desirably, stress is distributed evenly both at the tip and shoulder at or below design load whereas stress is more likely to be distributed at the tip when design load is exceeded with some stress at shoulder. More desirably, stress is distributed to support the skin at the shoulder in a way that the tip does not exceed a failure stress of the skin.

Turning now toFIG.30, a graph400of skin stress from a blade tip405as a function of blade load406values, e.g.,411,412,413,414,415of a representative razor cartridge (e.g.,FIG.25) is depicted. Shavers in the act of using a razor apply a force through the handle to the cartridge on the surface being shaved. This force varies by the shaver's preference for balancing closeness and comfort. Generally, the load applied by shavers can be in the range of about 50 gram-Force (gF) to about 1000 gram-Force (gF). Cartridges are designed to distribute some of this shaving load over the blades. Individual forces on the blade or blades result from this load distribution.

As shown by stress areas described supra, the loads on each blade generally increase from the first blade closest or closer to the guard being a minimum to a maximum on the second blade closest or closer to the cap than the guard. Individual blades loads can generally be in the range of about 0 gF to about 25 gF for average shaving loads (e.g., about 250 gF to about 375 gF).

Blade tip and edge designs, driven by the thickness of the coating of the present invention, provide a balance of cutting action and skin management properties in a razor cartridge. The blade load and thickness of the coating affect the stress exerted on the surface being shaved. As shown in graph400ofFIG.30, a range of stress is exerted on the shaved surface results when all blade loads are considered.

InFIG.30, the first blade14of the present invention, having a thinner coating, optimized to achieve a substantial amount of the cutting action, represented by curve420, exerts more stress as a function of blade load than the second blade16, which has a thicker coating optimized to achieve substantial skin management properties, represented by curve430and exerts less stress as a function of blade load.

Thus, while the first blade14exerts more stress, it can be positioned in the cartridge such that the load on the first blade is controlled below a threshold of discomfort. The second blade exerts less stress overall as a function of load and can be positioned in the cartridge to accommodate higher loading as desired for closeness. In the present invention, the first blade is positioned closer or closest to the guard structure and the second blade is positioned close or closest to the cap structure).

This graph indicates that, under high blade load values such as at413,414, and415, a second blade may be desirable since the second blade type (e.g., thicker coating) has less skin stress under the blade tip. It may also follow that under lower blade load values such as411or412of graph400, the first blade14of the present invention, may be selected.

Prior art curves440and450represent the stress upon two different prior art blades such as those found in commercial Gillette razors.

The prior art curves are based on two blades of prior art cartridges where one blade in the razor cartridge closer or closest to the cap does not have a thicker coating than that of another blade closer or closest to the guard. It is noted that blade tip stresses inFIG.30of both the first blade14and the second blade16of the present invention fall well outside the prior art curves440and450for prior art blades. This can be attributed to the second blade having a thicker coating than that of the first blade.

The present invention contemplates that the first blade14and the second blade16may also comprise different colors to distinguish their thicknesses. For instance, the first blade may be a blue colored blade and the second blade may be of no additional color (e.g., steel colored) or any different color other than the blue color of the first blade, such as green or gold or even a light hue of blue. The third blades of the present invention may also be any color, whether the same or different than that of the second blade. In this way, a user may be able to recognize a type of cartridge based on the colors of the blades as arranged in the cartridges. For instance, a color arrangement of the present invention with blade thicknesses based on any of the embodiments described or that feasibly could be arranged is possible. Thus, the cartridge500having a guard540and a cap530, representative of the thickness arrangement of the embodiment ofFIG.7, may have four blue blades as shown inFIG.31, as the color for the first blade540is and all third blades550in the first four blade positions and a gray color for the second blade560in the fifth blade position. These cartridges with different colored blades may be deemed to have recognizable attributes or be touted as such, e.g., an “efficient,” a “comfort” cartridge or a “sensitive” cartridge for a user.