Patent Publication Number: US-6216561-B1

Title: Method for manufacture of a razor head

Description:
This is a divisional application of patent application Ser. No. 09/102,138, filed Jun. 6, 1998 for INTRINSICALLY FENCED SAFETY RAZOR HEAD, now U.S. Pat. No. 6,032,372. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to safety razors of the type that have a plurality of adjacently mounted blades permanently mounted in the razor head. More particularly, this invention relates a method of manufacturing razor heads having a plurality of short blades having intrinsic fencing, mounted at a high slicing angle. 
     BACKGROUND OF THE INVENTION 
     The advantages of using blades with a slicing rather than chopping motion have been known for hundreds, perhaps thousands of years. One has but to cut a loaf of bread to immediately realize that a slicing motion cuts cleaner and with less tearing. The most immediate advantage for the blade is the reduction of force that is required for cutting, reducing wear and tear on the cutting edge. For a shaver, it is perhaps more important that the cutting force applied to the follicles be reduced, producing a less painful shaving experience. While it has been possible for the shaver to use straight razors, as well as disposable razor cartridges, in such a way as to create an oblique or slicing angle, this has always been hazardous, as the blade that easily slices follicles also easily slices the epidermis. Several patents have resulted from attempts to safely apply the advantages of a slicing angle to shaving. Gordon, (U.S. Pat. No. 3,964,160) and Copelan, (U.S. Pat. No. 5,526,568) patented razors which made manual oblique shaving easier, that is, the wrist did not have to be held at an awkward angle to maintain the slicing angle, but both lacked the concomitant stability of a razor head perpendicularly oriented to the shaving direction. Copeland teaches that, to obtain the advantages of oblique shaving while avoiding cutting of the skin, the oblique angle of a useable razor head should be restricted to between 10 and 26 degrees, and preferably to an angle of 18 degrees. Razors featuring adjustable slicing angles, such as Gordon&#39;s, have had an additional disadvantage, since the geometry of the razor head must be carefully balanced, and is unlikely to be optimum for variable slicing angles. Others have patented a variety of oblique arrangements, wherein a pair of blades are oriented in a “V” arrangement. Carroll (U.S. Pat. No. 1,241,921), Moody (U.S. Pat. No. 228,829), and Browning (U.S. Pat. No. 1,387,465) are typical of this approach, which suffers from excess stability. Because of the large footprint created by the two legs of the cutting zone, such a razor head has great difficulty in handling variations in facial geometry; a difficulty which only increases as the slicing angle, is increased. Savage (U.S. Pat. No. 4,663,843) patented a razor head using a conventional blade in tandem with blades angled at a slicing angle. He teaches that the slicing angle should lie between 15 and 30 degrees, in order to have some of the advantages of oblique cutting, while avoiding cutting of the skin. Savage does not appreciate the advantages arising from the use of intrinsic fencing, which would not only allow shaving at much higher slicing angles, but also make a tandem conventional blade unnecessary. 
     Fencing of razor blades is known. Dickenson (U.S. Pat. No. 1,035,548) teaches the use of wire wrapping of the blade edges, an approach that has been used by several others, such as Iten (U.S. Pat. No. 3,505,734), and Michelson (U.S. Pat. No. 3,750,285). Similarly, Ferrara (U.S. Pat. No. 3,263,330) discloses a fencing arrangement wherein the blade edge is wrapped with a flexible perforated sheet, and Auton (U.S. Pat. No. 4,252,837) patented a blade fenced with a vacuum deposited intermittent coating. Galligan et al. (U.S. Pat. No. 4,914,817) teaches the use of tape having parallel riblets covering parts of the blade edges. None have previously appreciated the advantages accruing from intrinsically fenced blades. 
     Foil blades are known. Ackerman (U.S. Pat. No. 2,794,252) patented a perforated foil blade arrangement claimed to enable omni-directional shaving. Brown (U.S. Pat. No. 5,153,992) patented a perforated blade wherein shaving could be accomplished with a “scrubbing action”. Perforated blades do not benefit from the advantages inherent in a single high slicing angle. 
     Ceramic blades are also known. Hahn (U.S. Pat. No. 5,048,191) teaches the production of ceramic blades using abrasive and sputtering steps, while Trotta (U.S. Pat. No. 5,018,274) patented a razor head produced from a obliquely sliced ceramic billet containing rectangular cells. The Trotta approach requires a considerable amount of polishing of small cut parts. 
     OBJECTS AND ADVANTAGES 
     Accordingly, I claim the following as objects and advantages of the invention: to provide a method for manufacturing a razor head having intrinsically fenced cutting means oriented at a high shearing angle which is capable of producing a smooth, safe shave with reduced pulling of follicles. 
     Further objects and advantages will become readily apparent as the specification proceeds to describe the invention with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above as well as other objects of the invention will become more apparent from the following detailed description of the preferred embodiment of the invention, when taken together with the accompanying drawings in which: 
     FIG. 1 is a perspective view of an assembled razor head with unitary blade means, according to the invention. 
     FIG. 2 is an exploded perspective view of the razor head assembly of FIG.  1 . 
     FIG. 3 is a perspective view of an assembled razor head of an alternative embodiment of the invention, with two sets of unitary blade means with opposing slicing angles. 
     FIG. 4 is an exploded view of the FIG. 3 razor head assembly. 
     FIG. 5 is a perspective view of a unitary blade billet being cut into unitary blades with high slicing angles, according to the invention. 
     FIG. 6 is a sectional view taken along  6 — 6  of FIG.  5 . 
     FIG. 7 is a perspective view of an assembled razor head of an alternative embodiment of the invention, with fenced blade means set at a high slicing angle. 
     FIG. 8 is a perspective view of a unitary blade billet being cut into unitary blades billet having fence ridges, according to another embodiment of the invention. 
     FIG. 9 is a partial perspective view of a composite unitary blade, according to the invention. 
     FIG. 10 is a partial perspective view of another composite unitary blade. 
     FIG. 11A is a side view of two adjacent blades in FIG.  10 . 
     FIG. 11B is a side view of an alternative embodiment of the two adjacent blades shown in FIG.  11 A. 
     FIG. 12 is an perspective view of an assembled razor head with a foil unitary blade, according to the invention. 
     FIG. 13 is an exploded perspective view of the razor head assembly shown in FIG.  12 . 
     FIG. 14A is a cross section taken at  14 — 14  of FIG. 13, prior to grinding, according to an embodiment of the invention. 
     FIG. 14B is a cross section taken at  14 — 14  of FIG. 13, subsequent to grinding, according to an embodiment of the invention. 
     FIG. 15A is an alternative cross section to that shown in FIG.  14 A. 
     FIG. 15B is an alternative cross section to that shown in FIG.  14 B. 
     FIG. 16 is an exploded perspective view of a razor head of an another embodiment of the invention. 
     FIG. 17 is a top plan view of a razor strip being cut into segments. 
     
       
         
           
               
             
               
                   
               
               
                 Drawing Reference Numerals 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 1 
                 razor head 
               
               
                 2 
                 blade base 
               
               
                 3 
                 cap 
               
               
                 4 
                 right flanking guard 
               
               
                 5 
                 blade platform 
               
               
                 7 
                 unitary blade 
               
               
                 8 
                 trailing guard 
               
               
                 9 
                 left flanking guard 
               
               
                 10 
                 right locating post 
               
               
                 12 
                 left locating post 
               
               
                 13 
                 recess 
               
               
                 16 
                 skin tensioning means 
               
               
                 18 
                 blade land 
               
               
                 19 
                 leading guard 
               
               
                 20 
                 handle 
               
               
                 21 
                 unitary blade base 
               
               
                 22 
                 cutting edge 
               
               
                 23 
                 blade 
               
               
                 24 
                 flat top 
               
               
                 25 
                 unground face 
               
               
                 28 
                 acute wall 
               
               
                 29 
                 vertical wall 
               
               
                 30 
                 oblique wall 
               
               
                 31 
                 flow channel 
               
               
                 32 
                 unitary billet 
               
               
                 34 
                 corner 
               
               
                 36 
                 corner 
               
               
                 38 
                 channel floor 
               
               
                 40 
                 projection 
               
               
                 42 
                 fenced unitary blade billet 
               
               
                 44 
                 fenced unitary blade 
               
               
                 46 
                 composite unitary blade 
               
               
                 48 
                 composite unitary blade 
               
               
                 50 
                 shaving direction 
               
               
                 51 
                 trim direction 
               
               
                 52 
                 blade base 
               
               
                 53 
                 blades 
               
               
                 54 
                 blades 
               
               
                 56 
                 gap 
               
               
                 57 
                 unitary blade 
               
               
                 60 
                 parallelogram form 
               
               
                 61 
                 parallelogram form 
               
               
                 62 
                 guard wedge 
               
               
                 63 
                 base 
               
               
                 64 
                 blade segment 
               
               
                 66 
                 perforation 
               
               
                 68 
                 blade support 
               
               
                 70 
                 lower leg 
               
               
                 72 
                 leg angle 
               
               
                 74 
                 upper leg 
               
               
                 76 
                 slot 
               
               
                 77 
                 unitary foil blade 
               
               
                 78 
                 raised slot edge 
               
               
                 79 
                 locating slot 
               
               
                 80 
                 inidividual blade 
               
               
                 81 
                 cut line 
               
               
                 82 
                 blade slot 
               
               
                 84 
                 blade strip 
               
               
                 85 
                 strip surface 
               
               
                 86 
                 score line 
               
               
                 88 
                 cutting line 
               
               
                 90 
                 shaving angle 
               
               
                 92 
                 leading flat 
               
               
                 93 
                 trailing flat 
               
               
                 94 
                 angle 
               
               
                   
               
            
           
         
       
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Specific terms are used as follows: “Shaving plane” means the ideally flat skin surface to be shaved. “Safety razor” means a razor having a leading guard, which is typically used with a lather or cream. “Razor head” is meant to include both razor cartridges adapted for use with a separate handle, as well as the upper, operative elements of a disposable razor with a permanently attached handle. “Shaving direction” signifies the direction in the shaving plane in which the razor head is intended to be moved. “Trim direction” signifies the direction in the shaving plane generally perpendicular to the shaving direction, that is, the direction taken when the razor head is moved sideways. “Cutting zone” refers to that area of the razor head containing blades, which is designed to cut follicles. The cutting zone has a width, which is generally perpendicular to the shaving direction, and a height considerably shorter than the width. “Span” means the distance between two adjacent edges in the cutting zone, measured in the shaving direction. “Leading span” means the span between the leading guard and the first encountered blade edge. “Trailing span” means the span between the trailing guard and the immediately preceding blade edge, while “intermediate span” means the span between two adjacent cutting edges. “Blade spacing” refers to the distance between two adjacent cutting edges measured in the direction perpendicular to the shaving direction. “Fencing” refers to any method of intermittently and positively breaking the contact of a blade edge with the skin, so that a long blade edge is effectively broken up into a series of shorter blade edges. “Effective cutting length” means the uninterrupted cutting edge, bounded by guards or fencing elements, which can contact the skin. “Shaving angle” is the angle the blades make relative to the shaving plane. “Slicing angle” is the angle in the shaving plane that the blade edges make relative to the trim direction. “Trim angle” is the angle in the shaving plane that the blade edges make relative to the shaving direction. “Guard” refers to one of the generally peripheral ridges that control the contact of the razor edges with the skin. “Leading guard” means the guard extending along the width of the cutting zone, which contacts the skin prior to the blades. “Trailing guard” means the guard extending along the width of the cutting zone, which contacts the skin subsequent to the blades, and “flanking guard” means either one of the two guards that keep the skin from contacting the cut edges of the blades along the height of the cutting zone. “Unitary blade” refers to a structure containing a plurality of blades oriented in a fixed spaced relationship. A unitary blade may be of the monolithic, composite, or foil types. 
     Principle of the Invention 
     The genesis of this invention began with the observation that fencing was effective even at high slicing angles, coupled with the realization that short sections of blades, bounded by leading and trailing guards, were functionally superior to single short blade segments between fencing elements. 
     An investigation was conducted to examine the relationship of slicing angle to perceived roughness, as it was expected that the sensation of roughness, as it reflects the tendency of the cutting edge to grab and release small protrusions on the surface, would provide a measure of the tendency of the blade to cut into the epidermis. A randomly textured rubber surface was used to simulate rough skin. A razor blade edge, oriented at a 90 degree shaving angle in order to eliminate the propensity to cut into the simulated skin, was loaded to simulate a light shaving pressure, and was pulled across the surface at various slicing angles. A measure of the subjective sensation of roughness was then created by force ranking the trial results obtained with a full width blade using slicing angles from 0 to 80 degrees, at 10-degree increments. This ranking runs from 1 to 9, with larger numbers indicating increasing roughness. The results appear in the column for the 39-mm length in the table below. The perceived roughness tended to increase steadily from 0 degrees to 80 degrees, with a small dip occurring at 10 degrees. The effective blade width was then reduced by partially covering the blade edge with thin metal tape. The trial was then repeated as before, this time rating the perceived roughness relative to the 9 level scale developed using the full width (39 mm) blade. 
     As the effective blade length was incrementally reduced, an unexpected inversion of the trend to increasing roughness was observed to occur at lengths of 8 mm and below, which is contrary to the teachings of others versed in the art. At 8 mm, the inversion occurs at 40 to 50 degrees, and at 6.5 and 4.5 mm, the inversion occurs at 30 degrees. The inversion is more pronounced at 6.5 mm and below, where the perceived roughness plummets to the lowest levels on the scale. Surprisingly, the best results were obtained at angles greater than 50 degrees. To check the effect of the total exposed blade length, another test was run with a blade fenced in 2 places to provide three lengths of exposed blade, each 4.5 mm long, which produced almost identical results to that tabulated for a single 4.5 mm section in the table below, indicating that this discovered effect is in the total length of the exposed blade. 
     
       
         
           
               
             
               
                 TABLE 
               
               
                   
               
             
            
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
            
           
         
       
     
     Shaving tests were performed using a conventional two-blade cartridge razor fenced to provide multiple exposed lengths corresponding to the blade lengths used in the Table above. It was found that exposed blade lengths of 9.5 mm and greater tended to cut the skin at slicing angles above 30 degrees. Using an exposed blade length of 8 mm produced a smooth shave at various shearing angles up to 85 degrees, with no noticeable cutting. However, several hours later, some reddening was observed, indicating that cutting of the epidermis did occur. For exposed lengths of 6.5 mm and below, no cutting or delayed skin response was observed at any slicing angle. Pulling of follicles during shaving was noticeably reduced at angles greater than 30 degrees, and this was particularly noticeable at angles greater than 45 degrees. Subsequent tests were performed using nine short blades arranged in a staggered relationship, and guarded with leading and trailing guards. Using blade lengths of 6.5 mm, and a slicing angle of 45 degrees, it was apparent that the same benefits of enhanced follicle cutting resulted, while at the same time epidermal damage was avoided, as was predicted from the previous tests. This general arrangement of short blades with leading and trailing guards at a high slicing angle is herein referred to as “intrinsic fencing”. The “high slicing angle” should be more than 30 degrees, preferably at least 45 degrees and most preferable at least 50 degrees. To control the flow of skin so that contact with the blades is limited to the effective blade length, the leading and trailing guards should rise approximately to the level of the cutting edge. The guards may also rise above this level, reducing the effective blade length, and may comprise skin tensioning means. Intrinsic fencing is superior to wire or thread fencing, which can break or become dislodged during use, and can trap or impede shaving debris. 
     For razor heads employing cutting edges at a slicing angle, skin flow control using short blade segments between leading and trailing guards is superior to that obtained by point fencing of the blades, such as that obtained by forming deposits on the blade edge. With leading and trailing guards, the skin is supported in the blade direction by the several blades, and also in the guard direction, while the skin can bulge further into the spaces between the blades when point fencing is used. 
     The arrangement of blades in the instant invention produces a variable span—a leading span which ranges from zero to the intermediate span, which is constant, and a trailing span, which ranges from the intermediate span to zero. To control the intermediate span so as to produce a smooth and continuous shave, the blade spacing should not exceed the effective blade length multiplied by the cosine of the slicing angle. Also, it is believed that the minimum effective blade length is about 1 mm, in order to provide sufficient cutting action. 
     In order to produce a clean trim line, the shaver may move the razor head of the instant invention against the skin in the trim direction. If, for instance, the blades are set at a slicing angle of 45 degrees, then the trim angle is also 45 degrees. As the slicing and trim direction are orthogonal, the slicing angle plus the trim angle equal 90 degrees. Trimming a clean line next to a mustache can be accomplished by moving the razor head down the face to the edge of the mustache, then moving the razor head sideways along the edge of the mustache. When moved sideways, the cutting means are arranged one behind the other. This not only produces a sharp trim line, but cuts the follicles many times over in one pass, so as to produce an unusually close shave. The razor head of the instant invention thus has two modes of operation, shaving and trimming, which in general can be accomplished without twisting the razor head or the wrist, but is accomplished simply by changing the direction of the stroke. If the razor head of the instant invention has bi-directional cutting means so as to allow shaving in both the forward and reverse shaving direction, then trimming may also be accomplished in the forward and reverse trim directions. 
     Monolithic Unitary Blades 
     While it is possible to construct a self-fenced blade arrangement using separate blade segments, it is preferable to employ a unitary blade, with each of the blade edges fixed in the proper relationship to its neighboring blade edges, so as to simplify the assembly of the razor head, and to insure that the placement of the blade edges relative to one another does not change. One embodiment of the invention wherein the cutting means are monolithic is illustrated in FIG. 1, where the assembled razor head  1   a  is mounted to a handle  20 . The shaving direction is indicated by the arrow  50 , and the trim direction is indicated by the arrow  51 . In FIG. 2, the razor head  1   a  is shown to comprise a blade platform  5   a,  a unitary blade  7 , and a cap  3   a.  The blade platform  5   a  further comprises a blade land  18  for locating the unitary blade, a leading guard  19  rising up to or slightly above the level of the cutting edges  22  of the unitary blade  7  when assembled, and having skin tensioning means  16 , a left flanking guard  9   a,  and a right flanking guard  4   a.  The unitary blade  7  comprises a blade base  2 , from which project a plurality of blades  23 , which have a substantially flat top  24 , and a cutting edge  22 . The cap  3   a,  comprises left and right locating posts,  12  and  10 , which enter into matching receiving notches (not shown) in the blade platform  5   a.  The cap  3   a  has a trailing guard  8 , which rises up to or slightly above the top of the unitary blade  7 , when assembled. The recess  13  allows passage of shaving debris channeled between the blades  23 , to exit the cutting zone, which comprises the top surface of the unitary blade  7 . 
     In another embodiment of the invention, more than one monolithic blade means may be employed to increase the size of the cutting zone, and to cut follicles with both left handed and right handed blade means, so as to maximize the potential for closely cutting every follicle in one pass of the razor head. In FIG. 3, the razor head is generally indicated by numeral  1   b,  the shaving direction is again indicated by the arrow  50 , and the trim direction by the arrow  51 . In FIG. 4, the razor head  1   b  is shown to comprise the same general elements as shown in FIG. 2, with the addition of a second unitary blade  57 , subsequent to the first unitary blade  7 . The unitary blade  57  has the same blade spacing, but the opposite hand of the unitary blade  7 , while the cutting length of the blades  54  may be different from that of the blades  23 . The unitary blade  57  comprises a blade base  52 , from which project a plurality of blades  54 , which have a substantially flat top  24 , and a cutting edge  22 . The blades  23 ,  54  are aligned so that shaving debris may pass continuously down the channels formed between the adjacent blades  23  of the cutting zone of the first blade  7  into the channels formed by adjacent blades  54  of the second unitary blade  57 , and thence into the recess  13 , which opens to the back of the razor head  1   b.  In order that the channels of the blade  7  match with the channels of the blade  57 , the blade spacing of each should be the same, although the slicing angles may differ. A gap  56 , shown in FIG. 3, may be provided to allow shaving debris to exit channels that intersect a flanking guard  9   b.  The unitary blades may be fixed to the blade land  18 , shown in FIG. 4, by means of an adhesive applied to the interface or, as one alternative, the unitary blades may be captured by means of an interference fit with the flanking guards  4   b  and  9   b,  or by means of an interference fit with the leading guard  19  and trailing guard  8 . 
     The unitary blades  7 ,  57  may be manufactured from an extruded ceramic billet  32 , shown in FIG.  5 . After extrusion to a near net shape, the cutting surface is ground to produce the cutting edges, and the billet is heat treated to produce the required hardness, followed by an optional polishing step. By extruding to near net shape, a minimum of grinding or polishing need be done to create the cutting edges. The next step in the preparation of the unitary blade is to divide the billet diagonally across the width at an angle to the long direction of the billet equal to the slicing angle. This may be accomplished by abrasive cutting, or by snapping along a score line  86 . The unitary blade may be used in this parallelogram form  60 , or the width may be trimmed to remove the corners  34 ,  36  to produce a rectangular form  7 . By sectioning the billet  32  after the cutting edges  22  have been prepared, handling and polishing of small parts is minimized. 
     In FIG. 6, a partial cross-section of the unitary blade  7  is shown, which comprises blades  23   a  and  23   b,  and unitary blade base  21 . For purposes of illustration, the blade  23   a  is shown in the near net extruded shape, prior to grinding, and the blade  23   b  is shown subsequent to grinding. The unground face  25  has been removed by the grinding step, forming the cutting edge  22  at the intersection of the flat top  24  and the acute wall  28 . Variation in the depth of grinding will not influence the angular geometry of the cutting edges  22  so long as the plane of the flat top  24  intersects within the blade  23   b  anywhere with the acute wall  28 . The blades additionally comprise an oblique wall  30 , and a vertical wall  29 . A land  38  separates the adjacent blades  23   a,    23   b.  The flow channel  31  defined by the walls  28 ,  29 ,  30  and the land  38 , channels shaving debris down the unitary blade  7  and allows shaving lubricant to similarly flow down the blade, where it can continue to lubricate the skin, instead of being removed immediately, as with conventional blade heads. 
     In another embodiment of the unitary construction, the billet  32 , in FIG. 5, and  42 , in FIG. 8, may be extruded of a relatively soft metal such as aluminum, magnesium, zinc, copper, tin or alloys thereof. It is believed that because of the reduced cutting pressures associated with high shear angles, the billet  32 ,  42  may even be extruded of a polymeric or resinous material. After milling, burnishing, or polishing the face to obtain sharp edges, a hard overlay may be bonded to the face of the billet for durability, corrosion resistance, and lubricity. Appropriate materials for hard facing would include stainless steel, chromium, titanium, metal oxides, nitrides, carbides, borides, mixtures of a metal carbide, tungsten carbide, titanium carbonitride, zirconium nitride, titanium aluminum nitride, chromium/boron carbide, chromium/diamond-like carbon, titanium diboride/chromium, titanium diboride/titanium carbonitride composite, ceramics containing binders, molybdenum, diamond, diamond-like material, silicon, silicon alloys, fluorotelomer, polytetrafluorethylene, chromium, boron carbide, titanium carbide, vanadium carbide, chromium carbide, titanium nitride, chromium nitride, boron nitride, hafnium nitride, carbon nitride, alumina, silicon dioxide, titanium dioxide, zirconia, chromium oxide, hafnium, tungsten, hafnium/diamond-like carbon, niobium/diamond-like carbon, molybdenum/diamond-like carbon, vanadium/diamond-like carbon, silicon/diamond-like carbon, tantalum/diamond-like carbon, silicon carbide/diamond-like carbon, or mixtures thereof. 
     The size of the cutting zone may be increased by employing extrinsic fencing, that is, actually breaking up the blade edge with projections. In FIG. 7, the razor head  1   c  comprises an extrinsically fenced unitary blade  44 , comprising projections  40 . In FIG. 8, a unitary blade billet  42  is illustrated. Unitary blades may be divided from the billet  42  along cutting line  88  to form a parallelogram form  61 , which may be further trimmed into a rectangular shape. By grinding the face of billet  42  in a segmented fashion, raised projections  40  may be allowed to remain, thereby limiting the maximum effective cutting length to the distance between two adjacent projections  40  on a cutting edge  22 . 
     Composite Unitary Blades 
     In another embodiment of the instant invention, strip blades may be bonded into a fixed position using the process of insert injection molding, pultrusion, welding, or by the use of adhesives, to fix the blades into a permanent geometrical relationship. An individual blade insert may be created, or preferably, a billet which is thereafter cut along a diagonal as in the case of the unitary construction. It is preferred that the blades are perforated so as to allow them to be mechanically locked in place. A composite unitary blade  46  is illustrated in FIG. 9, which comprises blades  64  with cutting edges  22 , bonded in a spaced relationship in a base  63  which has a triangular guard wedge  62  to avoid the use of short, difficult to handle blades. The blades  64  have perforations  66  in order to aid in mechanically trapping the blades  64  into the base  63 . 
     Another embodiment of the composite unitary blades is illustrated in FIG. 10, wherein the composite unitary blade, generally indicated by the numeral  48 , comprises blades  53 , individually bonded to blade supports  68 , which are in turn bonded to adjacent blade supports  68 . Bonding may be adhesive, or by means of welding. As shown in FIGS. 11A and 11B, the shaving angle  90  is related to the thickness of the blade  53 , the upper leg  74  and lower leg  70  of the blade support  68 , and the leg angle  72 . 
     Foil Unitary Blades 
     In another embodiment of the unitary construction, shown in FIGS. 12 and 13, a strip of metal may be slotted to produce substantially rectangular slots  76 , oriented at a high slicing angle, to produce a unitary foil blade  77 . The unitary blade is supported by insertion into a locating slot  79  in the cap  3   d,  and into a similar locating slot (not shown) in the blade platform  5   d,  when the cap  3   d  is mated to the blade platform  5   d  by means of left and right locating posts  12 ,  10  into matching notches (not shown) in the blade platform  5   d.  At least one of the longer sides of the slots  76  serves as a cutting edge. This cutting edge may be due to the thinness of the strip, or the subsequent grinding of the strip surface. One method of grinding an edge  22  into the strip is shown in FIGS. 14A and 14B, where the edge of the slot  76  has been bent upwards, so that the raised slot edge  78  lies above the plane of the strip surface  85 . Grinding the plane of the surface flat then removes the corner of the slot edge  78 , and produces a cutting edge  22 . In yet another embodiment, as shown in FIGS. 15A and 15B, both edges  78  of the slot  76  have been bent upwards and ground to produce cutting edges  22 , resulting in a bi-directional blade. The blade may be used flat, or may be used with a positive curvature as shown in FIGS. 12 and 13, with an axis of curvature parallel to the width of the cutting zone. In this case, the leading flat  92  of the cutting edge  22  may rise above the leading guard  19 , as the unslotted leading flat then serves the function of the guard  19 . In the same way, the trailing flat  93  serves the function of the trailing guard  8 . 
     While bi-directional blades have been discussed in the case of unitary foil blades, they may also be employed with other blade constructions, such as with monolithic unitary blades. 
     Assembled Blades 
     While the embodiments that have been described have all been directed to unitary constructions, it is also possible to assemble discrete blades. While a razor comprising discrete blades is more difficult to assemble compared to unitary blades, it does have several points in its favor. First, conventional blade technology may be used. Second, the weight of the razor head is minimized. And third, by supporting the blades fore and aft, allowing the center section to be unobstructed, flow of debris is channeled between the blades directly to the rear of the razor head. While there are conventional razor heads that direct the flow of debris between the blades, none allow for a completely free and unobstructed passage. 
     An embodiment of the invention wherein the cutting means are assembled is illustrated in FIG. 16, where the exploded razor head is generally indicated by the numeral  1   e.  The razor head  1   e  is shown to comprise a blade platform generally indicated by the numeral  5   e,  a plurality of individual blades  80 , and a cap  3   e.  The cap  3   e  comprises left and right locating posts  12 ,  10  which enter into matching receiving notches (not shown) in the blade platform  5   e.  The cap  3   e  has a trailing guard  8 , which rises slightly above the cutting edges  22  of the individual blades  80  when assembled. Blade slots  82  in the cap  3   e,  in cooperation with blade slots (not shown) in the platform  5   e,  capture and support the blades  80  therebetween when the cap  3   e  and platform  5   e  are mated. There is no blade land, as in the case of the unitary blades previously described, so as to allow free passage of shaving debris between adjacent blades  80 , exiting from the rear of the razor head  1   e.    
     In FIG. 16, the blade platform  5   e  further comprises a leading guard  19  rising slightly above the level of the cutting edges  22  of the blades  80  when assembled and having skin tensioning means  16 , a left flanking guard  9   e,  and a right flanking guard  4   e.  While skin tensioning means  16  have been illustrated in the several drawings as comprising triangular shaped riblets, any method of skin tensioning may be employed. 
     In FIG. 17, the individual blades  80  are shown to be cut into a parallelogram shape from a continuous blade strip  84 , with the angle  94  of the cut line  81  to the long axis of the strip  84 , approximately equal to the slicing angle, so as to minimize the required depth of the slots  82 . 
     While the invention has been described in connection with preferred embodiments, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.