US 3606682 A
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n. CAMP EI'AL 7 3,606,682
RAZOR BLADES Original Filed Oct. 30, 1967 INVENTUR. OLD E. CAMP BY Es w. EVANS v ATTORNEY United States Patent 01 lice 3,606,682 Patented Sept. 21, 1971 3,606,682 RAZOR BLADES Harold E. Camp and James W. Evans, Corning, N.Y., assignors to Corning Glass Works, Corning, NY. Original application Oct. 30, 1967, Ser. No. 678,846, now
Patent No. 3,514,856, dated June 2, 1970. Divided and this application June 26, 1969, Ser. No. 862,548 Int. Cl. B26b 25/54 U.S. Cl. 30-34655 3 Claims ABSTRACT OF THE DISCLOSURE Razor blade construction having defined angular and dimensional limits of the converging surfaces forming the cutting edge and an effective recessed portion immediately adjacent thereto for improved cutting ease and shaving comfort.
CROSS-REFERENCE TO RELATED APPLICATION This application is a division of our co-pending application Ser. No. 678,846; filed Oct. 30, 1967 now Pat. No. 3,514,856.
BACKGROUND OF THE INVENTION The invention resides in the field of razor blade construction and particularly to the cutting edge configuration required to provide improved shaving comfort.
The prior art contains various chemical and mechanical procedures for preparing the cutting edge of razor blades; however, as a whole, the art lacks any criteria as to what is necessary to actually provide the ultimate in frictionless shaving. U.S. Pat. No. 2,262,588 to Mailman discloses a conventional V-shaped blade and a method of providing a double-edged hollow-ground blade which facilitates the formation of a keen cutting edge without excessive heat. However, the patent does not suggest any parameters or criteria necessary in order to produce a blade which provides a minimum amount of friction and discomfort during the shaving operation.
U.S. Pat. No. 3,071,858 to Alter sets forth the prior art concept of forming razor blades with multiple tapered facets. Although dimensions and angles are given with respect to the final converging facets which form the cutting edge, there is no indication as to the limits or parameters which provide improved shaving comfort, and in fact the patent leads one to believe that the only way to accomplish such result is to apply a coating to the blade.
The instant invention overcomes this void in the prior art by actually setting forth specific criteria for razor blade configurations to provide optimum shaving comfort based upon scientific investigations and experimental data.
SUMMARY OF THE INVENTION The present invention, in its simplest form, sets forth an optimum razor blade configuration for shaving comfort which not only includes a minimum and maximum included angle between the converging surfaces forming the cutting edge, but also the maximum length of such converging surfaces and the minimum length of an effective relief portion immediately adjacent such converging surfaces.
It thus has been an object of the present invention to provide an improved razor blade configuration having defined parameters which produce minimum whisker drag during shaving and accordingly afford the utmost in shaving comfort.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmental cross-sectional view of the cutting edge configuration of a preferred embodiment of the present invention.
FIG. 2 is a fragmental cross-sectional view in elevation of a further embodiment of the blade configuration shown in FIG. 1 but with one side extended for strength.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, a greatly enlarged blade portion 10 of a razor blade 12 is shown having a pair of converging surfaces or facets 14 forming a cutting edge 16. Immediately behind the converging surfaces 14 and communicating therewith are a pair of substantially parallel surfaces 18 of a shank portion 20 forming an effective relief area. The surfaces 18 are not only substantially parallel to each other, but also are substantially parallel to a cross-sectional axis of the blade which bisects the included angle between facets 14. A pair of tapered surfaces 22 extend rearwardly of the parallel surfaces 18 and join the shank portion 20 with the full body width of the razor blade 12.
The included angle a formed by and between the converging surfaces 14, which produce the cutting edge 16, must be between 10 and 35. Should the included angle a between the surfaces 14 exceed 35", the resulting tip or cutting edge 16 exhibited to the skin whiskers, is so blunt that virtually no cutting action is achieved. If, on the other hand, the included angle a is less than 10, the resulting razor blade tip is extremely weak and subject to failure. Further, the length of the converging surfaces of facets 14, which form a nose portion, should be maintained as short as economically and/or structurally possible, to reduce shaving friction by presenting a minimal surface area to the skin and whiskers. In order to obtain a comfortable shave the maximum length b of the facets 14 should not exceed .002 inch, or otherwise an excessive frictional area is presented to the beard hairs resulting in undesirable irritation.
The length of the substantially parallel surfaces 18 along shank portion 20, providing an effective relief area for the beard hairs, taken in conjunction with the length of the nose portion or point formed by facets 14 is critical for obtaining optimum shaving comfort. That is, shaving comfort is maximized by reducing the amount of drag or friction between the razor blade and the beard hairs during the actual cutting of the individual hairs. It has been found that the average thickness or diameter of a beard hair is between .004 and .006 inch, with about .005 being a median. Since our main criteria in devising a razor blade configuration for ultimate shaving comfort is to reduce the amount of razor blade surface area in contact with the beard hair as it is being cut, the blade length 0 as represented by the combined nose portion and shank between the cutting edge 16 and rear portion of the shank 20, must not be less than the thickness of an average beard hair, or about .005 inch, so that the blade will pass entirely through the beard hair before the hair engages tapered surface 22 of the blade. That is, as the blade passes through a beard hair, facet 14 of minimal length is the only surface which engages the hair, since the parallel surfaced shank portion 20, in effect, provides a relief area for the hair being cut, so that there is virtually no razor surface drag or friction created on the hair in the relief area.
Although the minimum blade length c between the cutting edge 16 and rear portion of shank 20 is about .005 inch, as determined by the size of the average beard hair, the maximum blade length c is determined by the thickness of the shank and the rigidity of the material utilized. We have found that when utilizing a glass blade with a shank thickness between parallel surfaces 18 of about .001 inch to about .0006 inch, the maximum blade length should preferably not exceed .01 inch in order to avoid an undesirable tendency of the blade length to flex and thus bow one of the relief surfaces 18 intoa friction sur 1 I face. However, the maximum length which can be utilized without obtaining a flexing or bowing of the relief area will, of course, vary with the thickness of the shank and the material utilized.
The maximum thickness of the shank is limited by the fact that the facets 14 must not exceed .002 inch and must define an included angle between 10 and 35. Accordingly, the maximum thickness of the shank is about .001 inch, since if made thicker, it would undesirably increase the length of the facets 14. Although very small minimum shank thicknesses are theoretically possible, in the case of glass, we have found that a practical minimum from a strength standpoint is about .0006 inch, since the blade becomes fairly weak below this thickness. Again, it is conceivable that lesser thicknesses would be feasible with other materials.
The particular angle formed by tapered surfaces 22 is not critical to shaving comfort, since it begins at a point where the beard hair has already been severed by the cutting edge, and accordingly such surfaces may be formed with virtually any desired angular configuration.
Referring now to FIG. 2, a further embodiment of a razor blade construction is shown which is similar in many respects to that illustrated in FIG. 1. That is, a blade portion 10 of a razor blade 12' is shown having a sloped facet 14', cutting edge 16', a fiat relief surface 18, and a tapered surface 22. Opposite facet 14' is an extended facet 24, which not only converges with facet 14' to form cutting edge 16, but which also extends rearwardly at a substantially constant angle to join the body portion of the blade 12.
Blade portion 10' is, in effect, one-half of blade portion 10, with the parameters of angle a and distances b and being the same as those specified for angle a and distances b and 0, respectively. The main difference between blade portion and blade portion 10 is the fact that either side of blade portion 10 may be presented to the skin for shaving since it has effective relief portions 18 on both sides thereof, whereas blade portion 10 may only have one surface thereof presented to the skin for shaving since it only has one relief area surface 18'. The main advantage derived from the configuration of blade portion 10 is the fact that added rigidity and strength is obtained by increasing the thickness dimensions of the shank portion 20'. Since the thickness of the shank portion 20' is increased, the relief surface area 18' may be slightly concave, if desired, as shown by the broken line in FIG. 2.
, between about 10 and 35, one of said facets having a maximum length rearwardly of said cutting edge of .002 inch, a short relief area having a thickness less'than said main body portion, one side of said relief area having a first surface communicating with said one facet and extending rearwardly thereof at an angle to a cross-sectional axis of said blade bisecting the included angle formed by said facets which is less than the angle to such axis formed by said one facet, a tapered surface communicating betweensaid first surface and said main body portion at an angle to said axis which is greater than that formed thereto by said first surface, the other of said facets extending rearwardly at a substantially constant angle and communicating with said main body portion, and the combined length of said one facet and said relief area as measured along said cross-sectional axis having a maximum length of 0.1 inch.
2. An improved razor blade configuration as defined in claim 1 wherein said first surface forming one side of said relief area is substantially parallel to said cross-sectional axis.
3. An improved razor blade configuration as defined in claim 1 wherein said first surface is slightly concave.
References Cited UNITED STATES PATENTS 2,555,214 5/1951 Wallach 30346.55X 3,349,488 10/1967 Craig 30-346.55X
FOREIGN PATENTS 428,172 5/1935 Great Britain 30346.55 494,391 5/1954 Italy 30-34655 ROBERT C. RIORDON, Primary Examiner J. C. PETERS, Assistant Examiner