US3861040A

US3861040A - Plural edge blade unit

Info

Publication number: US3861040A
Application number: US287335A
Authority: US
Inventors: Jr Francis W Dorion
Original assignee: Gillette Co LLC
Current assignee: Gillette Co LLC
Priority date: 1972-09-08
Filing date: 1972-09-08
Publication date: 1975-01-21
Anticipated expiration: 1992-01-21
Also published as: CA990492A

Abstract

A plural edge blade unit for insertion into a razor having cap and guard structures includes two identical blade members, each of which has a cutting edge offset outwardly from the center of the blade. The two blade members are permanently secured together with their cutting edges positioned parallel to each other and in a plane inclined with respect to the planes of the blade members.

Description

United States Patent [191 Dorion, Jr.

[4 1 Jan. 21, 1975 PLURAL EDGE BLADE UNIT [75] Inventor: Francis W. Dorion, Jr., I-lingham,

Mass.

[73] Assignee: The Gillette Company, Boston,

Mass.

[22] Filed: Sept. 8, 1972 [21] Appl. No.: 287,335

[52] U.S. Cl 30/346.58, 30/50, 30/62 [51] Int. Cl B62b 21/54, B26b 21/22 [58] Field of Search 30/32, 50, 346.55, 346.57,

[56] References Cited UNITED STATES PATENTS 2,151,265 3/1939 Clausen 30/346.58 X

2,319,980 5/1943 Des Jardins 30/50 X 2,715,267 8/1955 Force 30/50 3,262,206 7/1966 Tomek 30/346.59 3,514,856 6/1970 Camp 30/34655 X 3,786,563 1/1974 Dorion et al 30/50 FOREIGN PATENTS OR APPLICATIONS 478,290 2/1953 Italy 30/346.57 739,501 1/1933 France... 30/346.55 1,039,546 5/1953 France 30/50 973,077 9/1950 Francc 30/50 Primary ExaminerAl Lawrence Smith Assistant Examiner-Gary L. Smith [57] ABSTRACT A plural edge blade unit for insertion into a razor having cap and guard structures includes two identical blade members, each of which has a cutting edge offset outwardly from the center of the blade. The two blade members are permanently secured together with their cutting edges positioned parallel to each other and in a plane inclined with respect to the planes of the blade members.

2 Claims, 4 Drawing Figures PATENTEO M21 mm FIG 3 w\ AY FIG 4 PLURAL EDGE BLADE UNIT BACKGROUND OF THE INVENTION This invention relates to shaving and more particularly to replaceable plural edge blade units for use in shaving.

It is known that a plural cutting edge shaving system can provide superior shaving characteristics. Such a shaving system includes at least two cutting edges disposed parallel to one another in spaced relation to provide leading and following cutting edges so that both cutting edges are successively active with respect to the hair elements being cut during a single shaving stroke.

The relationships of components of a plural edge blade unit are conveniently discussed in terms of certain parameters defined as follows. The blade tangent angle (BTA) of an edge is the angle between the plane bisecting the two planes or facets defining the edge and the plane through the edge and tangent to the skin engaging surface next forward of the edge. The portion of the bisecting plane external to the material of the edge and the portion of the tangent plane forward of the edge are conventionally used in defining the angle so that a blade tangent angle less than 90 is obtained in any practical shaving geometry. The span (S) of an edge is the distance from the edge to the next forward skin engaging surface measured in the plane through the edge and tangent to the next forward skin engaging surface. The exposure (E) of an edge is the distance of the edge from a plane tangent to both the next forward and the next rearward skin engaging surfaces. The exposure may be positive or negative and is reckoned positive when the edge lies on the skinward side of the doubly tangent plane.

In a plural edge blade unit having, for example, two edges, the leading edge will be itself the skin engaging surface next forward of the following edge, so. that its position will in part determine the blade tangent angle and the exposure of the following edge. Further, the following edge will itself be the next rearward skin engaging surface of the leading edge, so that its position will in part determine the exposure of the leading edge.

It will therefore be readily appreciated that the several geometric parameters discussed above are interrelated, and in devising a plural edge blade unit it is necessary to consider the interrelationship in order to advantageously combine the optimum values of the several parameters.

It has been found advantageous in a plural edge shaving system to establish a blade tangent angle in the range to 32; a span in the range of 0.03 inch to 0.08 inch; and an exposure of each cutting edge in. a range of 0.002 inch to +0.004 inch.

Providing a commercially acceptable replaceable plural edge blade unit for use with a conventional razor involves a number of problems. These problems relate primarily to the facts'that the guard and cap structures, together with the blades between them, define the geometry of a shaving system and that the guard and cap structures of conventional razors cannot be changed, except for certain spacing adjustments in adjustable razors. This is distinguished from the tandem blade cartridge in which the cap and guard elements were designed de novo. Given the fixed relationships between cap and guard portions of existing razors, the disposition of a plural edge blade unit between those elements has proven to be incompatible within optimum geometrical relationships so long as conventional cutting edges are employed.

SUMMARY OF INVENTION It is therefore an object of the present invention to provide a novel and improved plural edge blade unit for use with conventional razors.

A further object of the invention is to provide such a blade unit in which the cutting edges cooperate with the razor guard and cap portions to define critical geometric relationships within desirable ranges.

Other objects of the present invention include establishing and permanently maintaining advantageous geometric relationships between the edges of a plural edge blade unit, reducing the cost of such a unit, and providing such a unit that is easily dispensed and used using conventional equipment. The invention features a plural edge blade unit including a leading blade member and a following blade member, each blade member having the form of a plate bounded by first and second flat faces, and each member having a straight, sharpened cutting edge thereon parallel to the faces and outwardly offset from the center of the plate. The bisecting plane of each edge is parallel to the faces. The two members are permanently affixed with their cutting edges positioned parallel to each other and in a plane inclined to the second faces. A particular embodiment features. two identical members each of which has an edge of chisel configuration and has passages therethrough to facilitate removal of shaving debris from the vicinity of the cutting edge and are permanently affixed to each other as by bonding or spot welding to maintain the distance (span) between the edges at a value in the range 0.03 inch to 0.08 inch and the blade tangent angle of the following edge at a value in the range 20 to 32. Other objects, features, and advantages will appear from they following description of a particular embodiment of the invention, in conjunction with the drawing, in which:

FIG. 1 shows a shaving system including a razor and a blade dispenser and employing a plural edge blade unit according to the invention;

FIG. 2 shows in plan view the blade unit used in the shaving system of FIG. 1;

FIG. 3 shows a cross sectional view of the blade unit shown in FIG. 2, the cross section being taken along the line 3-3 of FIG. 2; and

FIG. 4 shows in cross section a portion of the shaving system to reveal details in the vicinity of the cutting edges, the cross section being taken along the line 44 of FIG. 1.

DESCRIPTION OF PARTICULAR EMBODIMENT The shaving system 10, shown in FIG. 1, includes a conventional razor 12 of the injector type and a blade dispenser 14. A plural edge blade unit 16 according to the invention is supported in razor 12 for shaving; and replacement blade units are stored in and dispensed from dispenser 14 in a conventional manner. As shown particularly in FIGS. 2 and 3, each blade unit I6 is composed of two

identical members

18 and 20. Each

member

18, 20 has the general form of a thin plate several times longer than it is wide, bounded by flat

parallel faces

22, 24. (In a particular embodiment, dimensions are 1.495 X 0.315 X 0.010 inch.) A sharp cutting edge 26 is formed along one of the longer sides of member 18. Edge 26 is unsymmetrically formed with respect to a median plane through the plate so that it is parallel to faces 22 and 24 but closer to face 24 than to face 22. In the particular embodiment, edge 26 is 0.002 inch from face 24 and 0.008 inch from face 22. As shown particularly in FIG. 4, the

facets

28, 30 defining edge 26 are oriented at the same angles to face 24 so that the bisector plane 32 bisecting edge 26 is parallel to face 24. A number of debris removal slots 34 pierce blade member 18 as does elongated slot 36 used to facilitate holding of the blade unit in razor 12. Member 20, with

faces

42 and 44 and edge 46, is identical in all respects with blade member 18, and in particular edge 46 is parallel to

faces

42 and 44 while lying closer to face 44, and bisector plane 48 associated with edge 46 is parallel to face 42. Members 18 and are permanently affixed to each other by spot welds 50, to form plural edge blade unit 16, the position of the members relative to each other being staggered and such that faces 22 and 42 are contiguous and

edges

26 and 46 are permanently maintained parallel to each other at a distance of 0.041 inch and in plane 52 inclined at an angle of 23 to contiguous

flat faces

22 and 32. Member 18, with its edge 26, thus becomes the leading member in structure 16 while member 20, with its edge 46, becomes the following member. The angle between bisector plane 48 of edge 46 and plane 52, containing both edges, is the blade tangent angle of the following edge and in the described structure has the value 23. As shown particularly in FIG. 4, blade structure 16 is held in razor 12 with the two

edges

26 and 46 intermediate between guard element 60 and cap element 62. The span (S1) and blade tangent angle (BTA of leading edge 26 is established by the position of edge engaging projections 64 in razor 12. The span (S2) and blade tangent angle (BTA of trailing edge 46 is established by blade unit 16 without reference to the razor, the values being 0.041 inch and 23, respectively.

This plural edge blade unit is received into razors of the injector type originally designed for holding single edge structures and provides excellent shaving results. The permanent affixing of the blade members is advantageous in that it simplifies handling and dispensing of the blade unit while ensuring that the desired relationship between the edges is not impaired. In manufacturing, the blade members are advantageously stamped and sharpened before being joined together. The use of identical members is advantageous in simplifying manufacturing operations.

While a particular embodiment has been shown and described it will be understood that various modifications can be made without departing from the spirit and scope of the invention. For example blade members of other or different thicknesses may be used; the blade members may be secured together in a variety of ways including the use of suitable bonding agents to maintain the established geometry; and/or the blade edges may be sharpened to other or different configurations. Therefore, it is not intended that the invention be limited to the disclosed embodiment or to details thereof but departures may be made therefrom within the spirit and scope of the invention.

What is claimed is:

1. A plural edge blade unit for insertion into a razor of the injector type that has cap and guard structures, said blade unit including a leading plate member and a following plate member, each of said plate members being bounded by first and second flat faces, and each said member having a straight, sharpened cutting edge thereon parallel to said faces, each said cutting edge being offset outwardly from the center of the member at least about one-third the distance from the center of the member to its said first face, each of said members having passages penetrating therethrough for facilitating removal of shaving debris from the vicinity of said cutting edge, the second faces of said leading and following members being permanently spot welded together in position'to maintain a fixed distance between said cutting edge of said leading member and said cutting edge of said following member, said distance being in the range of 0.03 inch to 0.08 inch, and said cutting edges positioned parallel to each other and in a plane inclined to said second faces, each said cutting edge being offset outwardly from the center of the member and being defined by two facets, each facet being inclined with respect to the immediately adjacent face and the bisector of the angle defined by said two facets being parallel to said faces, the angle between said bisector of the edge of said following member and a plane passing through the edge of both said members being fixed and in the range of 20 to 32, and the perpendicular distance between said angle bisectors being less than 0.02 inch.

2. The blade unit as claimed in claim 1 wherein said fixed distance is about 0.04 inch and the angle between said bisector of the edge of said following member and a plane passing through the edges of both said members is fixed and about 23.

Claims

1. A plural edge blade unit for insertion into a razor of the injector type that has cap and guard structures, said blade unit including a leading plate member and a following plate member, each of said plate members being bounded by first and second flat faces, and each said member having a straight, sharpened cutting edge thereon parallel to said faces, each said cutting edge being offset outwardly from the center of the member at least about one-third the distance from the center of the member to its said first face, each of said members having passages penetrating therethrough for facilitating removal of shaving debris from the vicinity of said cutting edge, the second faces of said leading and following members being permanently spot welded together in position to maintain a fixed distance between said cutting edge of said leading member and said cutting edge of said following member, said distance being in the range of 0.03 inch to 0.08 inch, and said cutting edges positioned parallel to each other and in a plane inclined to said second faces, each said cutting edge being offset outwardly from the center of the member and being defined by two facets, each facet being inclined with respect to the immediately adjacent face and the bisector of the angle defined by said two facets being parallel to said faces, the angle between said bisector of the edge of said following member and a plane passing through the edge of both said members being fixed and in the range of 20* to 32*, and the perpendicular distance between said angle bisectors being less than 0.02 inch.

2. The blade unit as claimed in claim 1 wherein said fixed distance is about 0.04 inch and the angle between said bisector of the edge of said following member and a plane passing through the edges of both said members is fixed and about 23*.