CA1229476A - Razor blades - Google Patents
Razor bladesInfo
- Publication number
- CA1229476A CA1229476A CA000441437A CA441437A CA1229476A CA 1229476 A CA1229476 A CA 1229476A CA 000441437 A CA000441437 A CA 000441437A CA 441437 A CA441437 A CA 441437A CA 1229476 A CA1229476 A CA 1229476A
- Authority
- CA
- Canada
- Prior art keywords
- tip
- blade
- micrometers
- edge
- distance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B26—HAND CUTTING TOOLS; CUTTING; SEVERING
- B26B—HAND-HELD CUTTING TOOLS NOT OTHERWISE PROVIDED FOR
- B26B21/00—Razors of the open or knife type; Safety razors or other shaving implements of the planing type; Hair-trimming devices involving a razor-blade; Equipment therefor
- B26B21/54—Razor-blades
- B26B21/56—Razor-blades characterised by the shape
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B26—HAND CUTTING TOOLS; CUTTING; SEVERING
- B26B—HAND-HELD CUTTING TOOLS NOT OTHERWISE PROVIDED FOR
- B26B21/00—Razors of the open or knife type; Safety razors or other shaving implements of the planing type; Hair-trimming devices involving a razor-blade; Equipment therefor
- B26B21/54—Razor-blades
- B26B21/58—Razor-blades characterised by the material
Abstract
Abstract A razor blade edge tip has a cross-sectional shape defined, over up to 40 µm from the extreme edge by the equation w = adn, in which w is the tip chord thickness in µm at a distance d from the extreme edge; a is the factor of proportionality in the range 0.71 - 0.92, and n is an exponent having a value in the range of 0.65 to 0.75. This results in a tip shape which is relatively thick very close to the edge but whose overall cross-section is narrow, compared with known tip shapes.
Description
I
This invention relaxes to razor blades and is particularly concerned with the shaping of the cutting edge.
The invention and prior art will be considered in conjunction with the accompanying drawings in which:
Figure 1 is a greatly magnified view of a blade tip of typical, or average shape;
Figure 2 is a tip shape diagram illustrating the principle of "tlp-width~ measurement;
Figure 3 is a highly diagrammatic representation of lo the cutting of a facial hair;
Figures 4 to 7 are cross-sections of various respective blades currently marketed by a variety of manufacturers;
Figure 8 is a view, like Figures 4 to 7, of the tip shapes described in British Patent Specification 1465697.
The invention resides broadly in a razor blade having a cutting edge the cross-sectional shape of which within the first 40 em measured back from the extreme edge is defined by the formula w = awn wherein d is the distance from the tip in em; w = the tip width (or thiclcness) in em at a given distance d; a is a factor of proportionality of about 0.8 and n it an exponent having a value less than 0.75, and wherein the included angle between the tip facets in the region from 40 em to 100 em from the extreme edge is within the range 7- 14 and preferably 9 to 11 1/2.
In the case of a stainless steel blade n is in the range 0.65 to 0.75 and a is in the range 0.71-0.92.
It has been found that blades having these tip characteristics provide improved shaving on comparative shave testing, but are sufficiently strong to give a reasonable useful life.
In order to convey a proper understanding of the nature of the present invention, it is convenient to describe and illustrate the background prior art in some detail.
,. ..
oh By Cutting edges on razor blades are sharpened by grinding a succession of pairs of facets (usually three) of different included angles onto a strip of steel by means of suitably arranged abrasive wheels. The cross-section through such an edge is illustrated in Figure 1 with typical values for dimensions and angles shown, and its customarily described as a "3-facet edge. While the final pair of facets is being ground, (this stage is usually called "honing"), strip deflection in the sharpening machine together with the mechanical interaction between the steel and the abrasive particles of the wheel, produces final facets which are usually not planar but slightly convex. The curvature is a function of the type of steel and abrasive wheel used, as well as the sharpening machine setting parameters. Because of this convexity of the final facets, the blade tip cross-section in this region is customarily referred to as "Gothic arched. The curvature prohibits precise geometrical definition of this part of the blade tip by means of a single parameter so that it its usual to characterize the shape by defining tip thicknesses at various distances back from the edge. An alternative method is to ascribe a mathematical equation oh B
Lowe to fit the form of each half of the facet cross-~ection.
These method Are illustrated in ~igllre 2.
During use, a nor blade it held in the razor it angle of approximately 25, end with the edge in contact with the Yin, it it moved over the face Jo that when the edge encounters a beard hair, it enter and severs it by progre~i~e penetration, tided by a wedging action. It it believed that the cut portion of the heir (which it on overage bout 100~um diameter remain I pressed in contact with the blade facet remote from the facial Ruin surface for a penetration up to only bout half the hair diameter. Beyond this, the hair con bend and contract nay from the blade to relive the wedging force. The refastens to penetration through reaction between heir and blade facet therefore occurs only o'er about the first 50 em of the blade tip back from the edge and the geometry of the blade tip in this region lo regarded A being the ought important from the cutting point of view. This it ill~tr~ted it Figure 3.
It in slur that reduction in the included angle of the facet killed correspondingly reduce the resistance to continued penetration of the blade top into the hair. However, if the included angle eureka reduced too much, the strength of the blade tip Gould be inadequQt~ to withstand the resultant bending force on the edge during thy cutting prows and the tip would deform pl~tically or fracture in a brittle phony, depending on the mechanical properties Or the Motorola from which it it made) and Jo sustain permanent damage, which would impair it subsequent cutting p~rformAnceO
i.e. the edge Gould become 'blunt' or 'Doyle In order to Dunn nuitRble ape or thy blade tip which it Utah triune enough to prevent such bending induced dsmag~l on Tahitian ho been nude of the magnitude of the bending Starr imposed during the everyone of hair. From these values and knowledge of the yield trench of the steel from which the blade is made, minimum dimension con be calculated for the tip section. The trusses imposed during cutting were amid to Roy from the ~isoo-el~stic flow of saturated hair material past the blade tip.
lye currently produced have tip geometries with some dominion which ore below these minimum value and are known to become dulled by edge bendirlg during the normal shaving life (which it on average, approximately 10 days for a blade made from conventional razor blade stainless steel).
We have now found that by careful control of the tip geometry in specific regions 0 - I em from the edge the overall cro~s-~ection con be reduced Jo that cutting performance end shaving satisfaction are improved, while retaining Dakota strength to resist edge bending damage nod so maintain acceptably durability The tip shape of awry ~anuf~cturera blades currently on the market are one in Figures 4 to 7 7 sod Figure 8 illustrates b-lade tip forts as describe I
in British Potent 1465967.
These known blade tip shape I compared with the preferred blade tip shape of the prevent in mention in figures 10 and 1 ox .
In one for of the prevent invention, the blrlde tip cro~-section it first narrowed by grinding the three facet to smaller included ankles thin those typified in Figure 1. This produce blade tip whose cross-~ection it generally narrower throughout end, importantly, in the 0 -40 em doughtiness back from the ode which it us particular introit during her c~tti~go Such an edge it too weak to with tend Tracy during awing end must be further modified. This to achieved ~zz~
by adding what amount to a fourth sharpening age It is carried out using rotting interlocking disc or purl of leather or synthetic leather, (usually called "strops") with abrasive material nodded to their 5 peripheries. The sharpened blued pi between the fftropY, which polish the facet, removing a small amount of steel from their surface, and Jo changing the 'Gothic arch" dimension. Thief stage it culled "abrasive stropping". Buick of the flexibility of 10 the strop leather, allowing it to conform omit to the sharpened blade tip, abrasive stropping ionizes the curvature of the final facet, clove to the edge, while having let effect on the facet shape further back.
It has been found tint when blade ens 15 sharpened with suitably reduced facet included angle followed by nun appropriate abhorrer stropping treatment, B the tip shape it changed so that the width close to two edge become larger than those on conventionally ~hnrpened edge, utile the widths further away 20 from the edge remain smaller thin those on conventionally sharpened edge. This royalty in the blade tip close to the edge being stronger than normal, A tint it Can bettor Wright the bending actresses imposed on it during hair cumin Chile the reduced auction further back from 25 the edge, present lets resistance to penetration during bar cutting, so facilitating the Utahan process.
The ultimate tip radius of the edge should be conventional, with an average value of less than AYE
and preferably less than AYE as stated, for example in Patent Specification 1,378~550 ISSUE. 3,761,374), that is, withinthenormal range for conventionally sharpened edges.
Blades in accordance with the invention hut been wound to haze superior shaving performance when compared with conventional Lydia on a standard awing text.
~3L2~
One form of blonde in accordance with the invention and the manner in which it it formed are described in detail below by Jay of example, with reference to ire 9, 10 end 11, in which:
Figure 9 it diagrammatic illustration of n blade zip stropping Operation figures 10 and BOA are representation of blade tip forms in accordance with the invention, compared with the known blade tip forms teen in Figures 4 to 8. Fig. lo is a detail from Fig. 10 on a larger scale; and Figure 11 it a graph of width at different distances 'd' plotted on logarithmic scale.
Stainless steel razor blade trip, of nominal composition 13~ Or, owe C, Winnie hardened and tempered in nccordanse with conventional practice, and sharpened - by grinding and honing to produce edge of three facet configuration, a illustrated in Figure I, but with included Nile smaller than those conventionally manu~nctured. The blued were pled between rotting troupe of artirici~l leather, owe surface contained fine Alumina nbra~i~e, in the anywhere of con~ntional Brie stropping, where the angle jet on the troupe (which it the included angle between the tangent to the strops at their point of inter~ectiDn, shown it 25 ire 9) way in the range 30-34. The facet were provided with metallic c08ting of an alloy of cry end platinum (applied in accordance with Potent Us 3,829,969~ with a superimposed costing of fluorocarbon Metro ugh go described in British Potent owe ooze j 3 The prows of grinding, honing end stropping are well known in the art, but it Jill be understood that lo ronYention~1 ethos could be employed for sharpening the tip, e.g. during the strip button nppropri~tely ehap2d die or roller, or by electrolytic or shekel dissolution hung or by ion bombardment ` plan.
go The blade tip cros~-secti~n~ were measured using optical interf~rom~try. A blue it planed under thy objective lens of a m~tnllur~ic~l microscopy fitted with n Michelson type interferometer and viewed it a ma~nificntion of about 1000X. The interf~romcter is adjusted to produce fringes which are oriented it right Nile to the edge of the blade. The blade is tilted at an appropriate angle Jo that the fringes are dip-placed to reveal the topography of the blade facets.
The fringe spacing is adjusted so that fringe displace-Monet can be readily measured sty various distances back from the edge. Knowing the angle of tilt, the tip pow is calculated from the sum of these fringe displacements, measured it corresponding positions or. etch wide of the I blade.
The results of these measurements ore shown in Fire 10, in which the spread of profiles of the preferred blaze tips over the first 40 em ore shown by solid shaded bands, end the spread of profiles of known 20 blued is indicated by the crushed bud B In this specific example, the widths w at distances d from theextremeedgewereas set out below:-d sum) w sum) 3 0.25 .20 - .30 0.5 34 - 5 1.0 .71 .92
This invention relaxes to razor blades and is particularly concerned with the shaping of the cutting edge.
The invention and prior art will be considered in conjunction with the accompanying drawings in which:
Figure 1 is a greatly magnified view of a blade tip of typical, or average shape;
Figure 2 is a tip shape diagram illustrating the principle of "tlp-width~ measurement;
Figure 3 is a highly diagrammatic representation of lo the cutting of a facial hair;
Figures 4 to 7 are cross-sections of various respective blades currently marketed by a variety of manufacturers;
Figure 8 is a view, like Figures 4 to 7, of the tip shapes described in British Patent Specification 1465697.
The invention resides broadly in a razor blade having a cutting edge the cross-sectional shape of which within the first 40 em measured back from the extreme edge is defined by the formula w = awn wherein d is the distance from the tip in em; w = the tip width (or thiclcness) in em at a given distance d; a is a factor of proportionality of about 0.8 and n it an exponent having a value less than 0.75, and wherein the included angle between the tip facets in the region from 40 em to 100 em from the extreme edge is within the range 7- 14 and preferably 9 to 11 1/2.
In the case of a stainless steel blade n is in the range 0.65 to 0.75 and a is in the range 0.71-0.92.
It has been found that blades having these tip characteristics provide improved shaving on comparative shave testing, but are sufficiently strong to give a reasonable useful life.
In order to convey a proper understanding of the nature of the present invention, it is convenient to describe and illustrate the background prior art in some detail.
,. ..
oh By Cutting edges on razor blades are sharpened by grinding a succession of pairs of facets (usually three) of different included angles onto a strip of steel by means of suitably arranged abrasive wheels. The cross-section through such an edge is illustrated in Figure 1 with typical values for dimensions and angles shown, and its customarily described as a "3-facet edge. While the final pair of facets is being ground, (this stage is usually called "honing"), strip deflection in the sharpening machine together with the mechanical interaction between the steel and the abrasive particles of the wheel, produces final facets which are usually not planar but slightly convex. The curvature is a function of the type of steel and abrasive wheel used, as well as the sharpening machine setting parameters. Because of this convexity of the final facets, the blade tip cross-section in this region is customarily referred to as "Gothic arched. The curvature prohibits precise geometrical definition of this part of the blade tip by means of a single parameter so that it its usual to characterize the shape by defining tip thicknesses at various distances back from the edge. An alternative method is to ascribe a mathematical equation oh B
Lowe to fit the form of each half of the facet cross-~ection.
These method Are illustrated in ~igllre 2.
During use, a nor blade it held in the razor it angle of approximately 25, end with the edge in contact with the Yin, it it moved over the face Jo that when the edge encounters a beard hair, it enter and severs it by progre~i~e penetration, tided by a wedging action. It it believed that the cut portion of the heir (which it on overage bout 100~um diameter remain I pressed in contact with the blade facet remote from the facial Ruin surface for a penetration up to only bout half the hair diameter. Beyond this, the hair con bend and contract nay from the blade to relive the wedging force. The refastens to penetration through reaction between heir and blade facet therefore occurs only o'er about the first 50 em of the blade tip back from the edge and the geometry of the blade tip in this region lo regarded A being the ought important from the cutting point of view. This it ill~tr~ted it Figure 3.
It in slur that reduction in the included angle of the facet killed correspondingly reduce the resistance to continued penetration of the blade top into the hair. However, if the included angle eureka reduced too much, the strength of the blade tip Gould be inadequQt~ to withstand the resultant bending force on the edge during thy cutting prows and the tip would deform pl~tically or fracture in a brittle phony, depending on the mechanical properties Or the Motorola from which it it made) and Jo sustain permanent damage, which would impair it subsequent cutting p~rformAnceO
i.e. the edge Gould become 'blunt' or 'Doyle In order to Dunn nuitRble ape or thy blade tip which it Utah triune enough to prevent such bending induced dsmag~l on Tahitian ho been nude of the magnitude of the bending Starr imposed during the everyone of hair. From these values and knowledge of the yield trench of the steel from which the blade is made, minimum dimension con be calculated for the tip section. The trusses imposed during cutting were amid to Roy from the ~isoo-el~stic flow of saturated hair material past the blade tip.
lye currently produced have tip geometries with some dominion which ore below these minimum value and are known to become dulled by edge bendirlg during the normal shaving life (which it on average, approximately 10 days for a blade made from conventional razor blade stainless steel).
We have now found that by careful control of the tip geometry in specific regions 0 - I em from the edge the overall cro~s-~ection con be reduced Jo that cutting performance end shaving satisfaction are improved, while retaining Dakota strength to resist edge bending damage nod so maintain acceptably durability The tip shape of awry ~anuf~cturera blades currently on the market are one in Figures 4 to 7 7 sod Figure 8 illustrates b-lade tip forts as describe I
in British Potent 1465967.
These known blade tip shape I compared with the preferred blade tip shape of the prevent in mention in figures 10 and 1 ox .
In one for of the prevent invention, the blrlde tip cro~-section it first narrowed by grinding the three facet to smaller included ankles thin those typified in Figure 1. This produce blade tip whose cross-~ection it generally narrower throughout end, importantly, in the 0 -40 em doughtiness back from the ode which it us particular introit during her c~tti~go Such an edge it too weak to with tend Tracy during awing end must be further modified. This to achieved ~zz~
by adding what amount to a fourth sharpening age It is carried out using rotting interlocking disc or purl of leather or synthetic leather, (usually called "strops") with abrasive material nodded to their 5 peripheries. The sharpened blued pi between the fftropY, which polish the facet, removing a small amount of steel from their surface, and Jo changing the 'Gothic arch" dimension. Thief stage it culled "abrasive stropping". Buick of the flexibility of 10 the strop leather, allowing it to conform omit to the sharpened blade tip, abrasive stropping ionizes the curvature of the final facet, clove to the edge, while having let effect on the facet shape further back.
It has been found tint when blade ens 15 sharpened with suitably reduced facet included angle followed by nun appropriate abhorrer stropping treatment, B the tip shape it changed so that the width close to two edge become larger than those on conventionally ~hnrpened edge, utile the widths further away 20 from the edge remain smaller thin those on conventionally sharpened edge. This royalty in the blade tip close to the edge being stronger than normal, A tint it Can bettor Wright the bending actresses imposed on it during hair cumin Chile the reduced auction further back from 25 the edge, present lets resistance to penetration during bar cutting, so facilitating the Utahan process.
The ultimate tip radius of the edge should be conventional, with an average value of less than AYE
and preferably less than AYE as stated, for example in Patent Specification 1,378~550 ISSUE. 3,761,374), that is, withinthenormal range for conventionally sharpened edges.
Blades in accordance with the invention hut been wound to haze superior shaving performance when compared with conventional Lydia on a standard awing text.
~3L2~
One form of blonde in accordance with the invention and the manner in which it it formed are described in detail below by Jay of example, with reference to ire 9, 10 end 11, in which:
Figure 9 it diagrammatic illustration of n blade zip stropping Operation figures 10 and BOA are representation of blade tip forms in accordance with the invention, compared with the known blade tip forms teen in Figures 4 to 8. Fig. lo is a detail from Fig. 10 on a larger scale; and Figure 11 it a graph of width at different distances 'd' plotted on logarithmic scale.
Stainless steel razor blade trip, of nominal composition 13~ Or, owe C, Winnie hardened and tempered in nccordanse with conventional practice, and sharpened - by grinding and honing to produce edge of three facet configuration, a illustrated in Figure I, but with included Nile smaller than those conventionally manu~nctured. The blued were pled between rotting troupe of artirici~l leather, owe surface contained fine Alumina nbra~i~e, in the anywhere of con~ntional Brie stropping, where the angle jet on the troupe (which it the included angle between the tangent to the strops at their point of inter~ectiDn, shown it 25 ire 9) way in the range 30-34. The facet were provided with metallic c08ting of an alloy of cry end platinum (applied in accordance with Potent Us 3,829,969~ with a superimposed costing of fluorocarbon Metro ugh go described in British Potent owe ooze j 3 The prows of grinding, honing end stropping are well known in the art, but it Jill be understood that lo ronYention~1 ethos could be employed for sharpening the tip, e.g. during the strip button nppropri~tely ehap2d die or roller, or by electrolytic or shekel dissolution hung or by ion bombardment ` plan.
go The blade tip cros~-secti~n~ were measured using optical interf~rom~try. A blue it planed under thy objective lens of a m~tnllur~ic~l microscopy fitted with n Michelson type interferometer and viewed it a ma~nificntion of about 1000X. The interf~romcter is adjusted to produce fringes which are oriented it right Nile to the edge of the blade. The blade is tilted at an appropriate angle Jo that the fringes are dip-placed to reveal the topography of the blade facets.
The fringe spacing is adjusted so that fringe displace-Monet can be readily measured sty various distances back from the edge. Knowing the angle of tilt, the tip pow is calculated from the sum of these fringe displacements, measured it corresponding positions or. etch wide of the I blade.
The results of these measurements ore shown in Fire 10, in which the spread of profiles of the preferred blaze tips over the first 40 em ore shown by solid shaded bands, end the spread of profiles of known 20 blued is indicated by the crushed bud B In this specific example, the widths w at distances d from theextremeedgewereas set out below:-d sum) w sum) 3 0.25 .20 - .30 0.5 34 - 5 1.0 .71 .92
2.0 1.17 - 1-37 owe 1.86 - 2.16 owe 3-05 - 3.52 20.0 6.12 - 6.85 30.0 8.43 - 9.52 40.0 10.73 -12.~1 The gsometr~ of this profile was replated on a graph using }~r~hmi~ scales fur zip thickness I
as a function of distance from the edge and the resultant plot is shown in Figure 11, from which it is seen that a straight line can be fitted to the plotted points.
From the slope and intercept of the straight line, the tip shape can be defined by the equation w = awn in which a is a factor of proportionality of about 0.8 and n an exponent having a value of not more than 0.75, and more specifically within the range 0.65 - 0.75.
The known blades measured were found to have best fit straight lines with exponents (or gradients) within the range 0.76 -- 1Ø
The smaller gradient is a primary characteristic of the present invention and results in the fact that the blade tip of the present invention, compared with those of the prior art, is relatively thick and strongly arched close to the extreme edge, but relatively thin over the remainder of the typo The included facet angles in the region ~10 100 Lam from the tip are in the range 9 to 11 1/2 but making due allowance for manufacturing tolerances could be in the range 7 to 12 or even 7 to 14.
It must be appreciated that the tip shapes described above are for stainless steel blades and could be made substantially thinner for harder blade materials such as sapphire, titanium carbide or diamond.
To produce an equivalent tip shape from a material harder than stainless steel, we reduce the corresponding tip widths in inverse proportion to the square root of the yield strength of the harder material in comparison with stainless steel. In the case of diamond, for example, the tip widths would be approximately 40% of those calculated for stainless steel.
Furthermore, the tip region of a stainless steel blade may be coated with a material harder than stainless steel and having a higher yield strength. In such a case the chord oh widths given by the basic equation are reduced by adopting the modified formula: w _ on awn in which m is the ratio of the yield strength of the coating material to that of stainless steel.
Furthermore, in order to ensure the integrity of the steel substrate, the value for w must also satisfy the equation we' (wooden, where h is the thickness of the coating.
It will be understood by those skilled in the art that the blade tips may, in each case, be coated with materials such as pile which further enhance the cutting action.
The thicknesses of such coatings are, of course ignored for the purposes of calculating the tip chord widths `\
oh
as a function of distance from the edge and the resultant plot is shown in Figure 11, from which it is seen that a straight line can be fitted to the plotted points.
From the slope and intercept of the straight line, the tip shape can be defined by the equation w = awn in which a is a factor of proportionality of about 0.8 and n an exponent having a value of not more than 0.75, and more specifically within the range 0.65 - 0.75.
The known blades measured were found to have best fit straight lines with exponents (or gradients) within the range 0.76 -- 1Ø
The smaller gradient is a primary characteristic of the present invention and results in the fact that the blade tip of the present invention, compared with those of the prior art, is relatively thick and strongly arched close to the extreme edge, but relatively thin over the remainder of the typo The included facet angles in the region ~10 100 Lam from the tip are in the range 9 to 11 1/2 but making due allowance for manufacturing tolerances could be in the range 7 to 12 or even 7 to 14.
It must be appreciated that the tip shapes described above are for stainless steel blades and could be made substantially thinner for harder blade materials such as sapphire, titanium carbide or diamond.
To produce an equivalent tip shape from a material harder than stainless steel, we reduce the corresponding tip widths in inverse proportion to the square root of the yield strength of the harder material in comparison with stainless steel. In the case of diamond, for example, the tip widths would be approximately 40% of those calculated for stainless steel.
Furthermore, the tip region of a stainless steel blade may be coated with a material harder than stainless steel and having a higher yield strength. In such a case the chord oh widths given by the basic equation are reduced by adopting the modified formula: w _ on awn in which m is the ratio of the yield strength of the coating material to that of stainless steel.
Furthermore, in order to ensure the integrity of the steel substrate, the value for w must also satisfy the equation we' (wooden, where h is the thickness of the coating.
It will be understood by those skilled in the art that the blade tips may, in each case, be coated with materials such as pile which further enhance the cutting action.
The thicknesses of such coatings are, of course ignored for the purposes of calculating the tip chord widths `\
oh
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A razor blade having a cutting edge tip of stainless steel, the cross-sectional shape of which up to a distance of 40 µm from the extreme edge is defined by the equation:
w = adn in which w is the chord thickness in µm of the tip at a distance d in µm from the extreme edge of the blade; a is a factor of proportionality of about 0.8 and n is an exponent having a value in the range 0.65 to 0.75.
w = adn in which w is the chord thickness in µm of the tip at a distance d in µm from the extreme edge of the blade; a is a factor of proportionality of about 0.8 and n is an exponent having a value in the range 0.65 to 0.75.
2. A razor blade having a cutting edge tip of a material which has a higher yield strength than stainless steel, the cross-sectional shape of which up to a distance of forty micrometers from the extreme edge is defined by the equation:
w = adn in which w is the thickness in micrometers of the tip at a distance d in micrometers from the extreme edge of the blade; a is a factor of proportionality not greater than 0.8;
n is an exponent having a value in the range 0.65 to 0.75;
and the width w obtained from the said equation is reduced in inverse proportion to the square root of the ratio of the yield strength of said tip material to that on stainless steel.
w = adn in which w is the thickness in micrometers of the tip at a distance d in micrometers from the extreme edge of the blade; a is a factor of proportionality not greater than 0.8;
n is an exponent having a value in the range 0.65 to 0.75;
and the width w obtained from the said equation is reduced in inverse proportion to the square root of the ratio of the yield strength of said tip material to that on stainless steel.
3. A razor blade having a cutting edge tip of stainless steel, said cutting edge tip being coated with a material having a greater yield strength than stainless steel, the cross-sectional shape of said tip up to a distance of forty micrometers from the extreme edge being defined by the equation:
w = adn, (1) in which w is the thickness in micrometers of the tip at a distance d in micrometers from the extreme edge of the blade; a is a factor of proportionality not greater than 0.8;
and n is an exponent having a value in the range 0.65 to 0.75; and by the equation;
(2) in which m is the ratio of the yield strength of the coating material to that of stainless steel;
and by the equation:
w3 ? (w - 2h)a2d2n, (3) in which h is the thickness in micrometers of the coating.
w = adn, (1) in which w is the thickness in micrometers of the tip at a distance d in micrometers from the extreme edge of the blade; a is a factor of proportionality not greater than 0.8;
and n is an exponent having a value in the range 0.65 to 0.75; and by the equation;
(2) in which m is the ratio of the yield strength of the coating material to that of stainless steel;
and by the equation:
w3 ? (w - 2h)a2d2n, (3) in which h is the thickness in micrometers of the coating.
4. A razor blade having a cutting edge tip of stainless steel, the cross-sectional shape of which up to a distance of forty micrometers from the extreme edge is defined by the equation:
w = adn in which w is the thickness of micrometers of the tip at a distance d in micrometers from the extreme edge of the blade; a is a factor of proportionality not greater than 0.8 and n is an exponent having a value in the range 0.65 to 0.75; and wherein the blade tip is formed with facets at a distance between forty and one hundred mm from the extreme edge, which facets converge toward the edge at an included angle in the range 9° to 11-1/2°.
w = adn in which w is the thickness of micrometers of the tip at a distance d in micrometers from the extreme edge of the blade; a is a factor of proportionality not greater than 0.8 and n is an exponent having a value in the range 0.65 to 0.75; and wherein the blade tip is formed with facets at a distance between forty and one hundred mm from the extreme edge, which facets converge toward the edge at an included angle in the range 9° to 11-1/2°.
5. A razor blade having a cutting edge tip of gothic arch configuration, at least the tip of said blade including a material which have a higher yield strength than stainless steel, the cross-sectional shape of said blade up to a distance of forty micrometers from the extreme edge being defined by the equation:
w = adn, in which w is the thickness in micrometers of the tip at a distance d in micrometers from the extreme edge of the blade; a is a factor of proportionality not greater than 0.8; n is an exponent having a value in the range of 0.65 -0.75; and the blade tip is formed with facets at a distance between forty and one hundred micrometers from the extreme edge, which facets converge toward the edge at an included angle in the range 9° to 11-1/2°.
w = adn, in which w is the thickness in micrometers of the tip at a distance d in micrometers from the extreme edge of the blade; a is a factor of proportionality not greater than 0.8; n is an exponent having a value in the range of 0.65 -0.75; and the blade tip is formed with facets at a distance between forty and one hundred micrometers from the extreme edge, which facets converge toward the edge at an included angle in the range 9° to 11-1/2°.
6. A razor blade having a cutting edge, the cross-sectional shape of said cutting edge being such that the tip thicknesses w at distances d from the tip of said cutting edge lie within the following ranges:
7. A razor blade according to claim 6 wherein said cutting edge tip is of gothic arch configuration, the cross-sectional shape of said blade up to a distance of forty micrometers from the extreme edge being defined by the equation:
w = adn, in which w is the thickness in micrometers of the tip at a distance d in micrometers from the extreme edge of the blade, a is a factor of proportionality having a value in the range of 0.71 0.92, and n is an exponent having a value in the range of 0.65 - 0.75.
w = adn, in which w is the thickness in micrometers of the tip at a distance d in micrometers from the extreme edge of the blade, a is a factor of proportionality having a value in the range of 0.71 0.92, and n is an exponent having a value in the range of 0.65 - 0.75.
8. A razor blade according to claim 7 wherein the gothic arch configuration has been changed by removing a small amount of steel from the tip surfaces by abrasive stropping after the final facets of the blade have been formed by honing.
9. A method of forming the cutting edge of a razor blade comprising the steps of sharpening the edge of a stainless steel razor blade strip by grinding and honing to provide a sharpened (Claim 9 cont'd ....) edge of three-facet configuration, and then passing the sharpened razor blade strip between rotating strops of artificial leather which strops contain abrasive to provide a razor blade having a cutting edge tip, the cross-sectional shape of which up to a distance of forty micrometers from the extreme edge is defined by the equation:
w = adn in which w is the thickness in micrometers of the tip at a distance d in micrometers from the extreme edge of the blade; a is a factor of proportionality of about 0.8; and n is an exponent having a value in the range 0.65 to 0.75.
w = adn in which w is the thickness in micrometers of the tip at a distance d in micrometers from the extreme edge of the blade; a is a factor of proportionality of about 0.8; and n is an exponent having a value in the range 0.65 to 0.75.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8233014 | 1982-11-19 | ||
| GB8233014 | 1982-11-19 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1229476A true CA1229476A (en) | 1987-11-24 |
Family
ID=10534368
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000441437A Expired CA1229476A (en) | 1982-11-19 | 1983-11-18 | Razor blades |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0126128B1 (en) |
| JP (1) | JPS59502135A (en) |
| CA (1) | CA1229476A (en) |
| DE (1) | DE3372189D1 (en) |
| ES (1) | ES275817Y (en) |
| GB (1) | GB2130955B (en) |
| IN (1) | IN160884B (en) |
| MX (1) | MX161634A (en) |
| WO (1) | WO1984002104A1 (en) |
Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2234966A1 (en) * | 1997-06-10 | 1998-12-10 | Brian G. Balistee | Improved blade edge |
| KR100914866B1 (en) * | 2001-07-11 | 2009-08-31 | 코닌클리케 필립스 일렉트로닉스 엔.브이. | Cutting member, shaving head, and shaver |
| US7144403B2 (en) | 2003-07-29 | 2006-12-05 | Alcon, Inc. | Surgical knife |
| JP4575735B2 (en) * | 2004-09-27 | 2010-11-04 | フェザー安全剃刀株式会社 | Microtome blade |
| US9751230B2 (en) * | 2014-05-19 | 2017-09-05 | The Gillette Company | Razor blades |
| WO2016101990A1 (en) * | 2014-12-22 | 2016-06-30 | Bic-Violex Sa | Razor blade |
| WO2016015771A1 (en) | 2014-07-31 | 2016-02-04 | Bic-Violex Sa | Razor blade coating |
| US11230025B2 (en) | 2015-11-13 | 2022-01-25 | The Gillette Company Llc | Razor blade |
| US11654588B2 (en) | 2016-08-15 | 2023-05-23 | The Gillette Company Llc | Razor blades |
| EP3372361A1 (en) | 2017-03-08 | 2018-09-12 | BIC-Violex S.A. | Razor blade |
| EP3372362A1 (en) | 2017-03-08 | 2018-09-12 | BIC-Violex S.A. | Razor blade |
| JP6864034B2 (en) * | 2019-05-13 | 2021-04-21 | ビック・バイオレクス・エス・エー | Razor blade |
| KR20210039205A (en) * | 2019-10-01 | 2021-04-09 | 주식회사 도루코 | Shaving Blade |
| US20210276211A1 (en) * | 2020-03-05 | 2021-09-09 | John Robert Harris | Razor blade with improved asymmetric profile |
| KR102516887B1 (en) * | 2020-06-16 | 2023-03-31 | 주식회사 도루코 | Shaving Blade |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3461616A (en) * | 1966-10-14 | 1969-08-19 | Gillette Co | Methods and apparatus for sharpening razor blades or similar cutting tools |
| GB1258348A (en) * | 1969-10-15 | 1971-12-30 | ||
| GB1350594A (en) * | 1970-02-05 | 1974-04-18 | Gillette Industries Ltd | Sharpening cutting edges |
| US3761373A (en) * | 1971-07-09 | 1973-09-25 | Gillette Co | Process for producing an improved cutting tool |
| GB1465697A (en) * | 1973-06-20 | 1977-02-23 | Wilkinson Sword Ltd | Razor blades |
-
1983
- 1983-11-14 WO PCT/GB1983/000288 patent/WO1984002104A1/en active IP Right Grant
- 1983-11-14 JP JP58503810A patent/JPS59502135A/en active Granted
- 1983-11-14 DE DE8383903805T patent/DE3372189D1/en not_active Expired
- 1983-11-14 EP EP19830903805 patent/EP0126128B1/en not_active Expired
- 1983-11-15 GB GB08330432A patent/GB2130955B/en not_active Expired
- 1983-11-15 IN IN761/DEL/83A patent/IN160884B/en unknown
- 1983-11-18 MX MX19947083A patent/MX161634A/en unknown
- 1983-11-18 ES ES1983275817U patent/ES275817Y/en not_active Expired
- 1983-11-18 CA CA000441437A patent/CA1229476A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0126128A1 (en) | 1984-11-28 |
| IN160884B (en) | 1987-08-15 |
| JPH0532076B2 (en) | 1993-05-14 |
| JPS59502135A (en) | 1984-12-27 |
| ES275817Y (en) | 1984-12-16 |
| GB2130955A (en) | 1984-06-13 |
| EP0126128B1 (en) | 1987-06-24 |
| ES275817U (en) | 1984-05-16 |
| DE3372189D1 (en) | 1987-07-30 |
| WO1984002104A1 (en) | 1984-06-07 |
| MX161634A (en) | 1990-11-27 |
| GB8330432D0 (en) | 1983-12-21 |
| GB2130955B (en) | 1985-10-02 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |