Abstract:
A blade unit for a razor comb which can be used equally in two hair cutting directions is disclosed. The blade unit comprises a blade and a blade holder partially housing the blade. The blade holder has two edges, both of which are provided with a plurality of protrusions for combing hair. The protrusions partially cover the blade edge, leaving a plurality of uncovered blade edge portions for cutting hair. The covered blade edge portions and uncovered blade edge portions have an equal length and are provided alternately. The blade unit can be additionally provided with an appropriate blade sliding means for exchanging the covered and uncovered blade edge portions to refresh the cutting portions of the blade.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to a razor comb. More particularly, this invention relates to a spare razor blade unit for a razor comb. The razor blade unit of the present invention can elongate the life of its blade by facilitating alternate utilization of blade portions. 
     2. Prior Art 
     In FIG. 14 is shown a conventional spare-type hair razor blade unit 1&#39; comprising a blade 3 and a blade holder 2. The blade 3 has two surfaces 3a and 3c and a blade edge 5. The blade holder 2 comprises two surfaces 2a and 2b connected with a backbone 2c, which is formed by bending a metal plate. The holder surface 2a has a straight edge 20a while the surface 2b has a wavy edge 20b having a plurality of parabolic protrusions 4b. The two edges 20a and 20b provide a slit therebetween for securely holding the blade 3. The blade edge 5 protrudes from the slit. The blade 3 is sandwiched between two holder surfaces 2a and 2b with the parabolic protrusions 4b for combing hair protruding beyond the blade edge 5. The parabolic protrusions 4b partially cover the blade edge 5 of the blade surface 3b while the blade edge 5 of the blade surface 3a is left uncovered, providing covered blade portions B and uncovered blade portions A for cutting hair. As can be seen in the figure, blade portions A and B appear on the blade edge 5 alternately. This razor blade unit 1&#39; can be attached to and detached from a blade unit holder not shown in this figure. 
     In FIG. 15 is shown another conventional spare-type razor blade unit 1&#34; disclosed in Japanese Patent Application No. 7-67847 filed by the present applicant, which is nearly identical with the foregoing razor blade unit 1&#39; except that this razor blade unit 1&#34; further comprises an elliptic window 6 provided in the holder surface 2a to receive a boss 3d fixedly provided on the blade surface 3a. The sliding of the boss 3d with a finger along the elliptic window 6 facilitates the blade 3 to slide within the blade holder 2 in the directions shown by arrows. Thus, this razor blade unit 1&#34; facilitates alternate use of blade portions A and B. The covered blade portions B turn into uncovered blade portions A. The blade edge 5 of the razor blade unit 1&#34; can be used theoretically twice as long as that of the razor blade unit 1&#39;. 
     As will be understood by a person skilled in the art, a razor comb incorporating either razor blade unit 1&#39; or 1&#34; can be appropriately used only by either a right-handed person or left-handed person since the razor blade units 1&#39; and 1&#34; can provide adequate cutting of hair in a single direction only because the cutting performance of the blade edge 5 is subtly different between the two cutting directions. Therefore, such conventional razor blade units are utilized &#34;reversely&#34; between left-handers and right-hander. Additionally, a single user, left-hander or right-hander, often wishes to use a razor comb in both directions to trim hair by reversing the attachment (to the blade unit holder) of the razor blade unit. Such a reversing of the blade unit when required often is very inconvenient and impractical. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a razor blade unit which eliminates difference in trimming performance between the two hair cutting directions. 
     It is another object of the present invention to further furnish such a razor blade unit with blade portion switching means and provide an elongated life to the blade. 
     A razor blade unit of the present invention comprises a razor blade and a blade holder. Unlike the foregoing conventional razor combs, both holder edges are provided with a wavy pattern and have parabolic protrusions appearing alternately. Accordingly, the functional difference between the two hair cutting directions has disappeared. The upper protrusions and lower protrusions partially cover the blade edge and provide a plurality of covered blade edge portions and a plurality of uncovered blade edge portions for cutting hair. 
     The razor blade unit of the present invention can be additionally provided with a blade sliding means for sliding the blade within the blade holder to convert the covered blade portions into uncovered blade portions, and vice versa, elongating the life of the blade about twice that of a blade unit without such a blade sliding means. 
     The blade sliding means utilizable in the blade unit of the present invention may be a combination of a window provided in the blade holder and a boss provided on the blade, a through opening formed in the blade holder and a through hole formed in the blade, or a cut or cuts formed in the blade holder and a cut or cuts formed in the blade. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a razor blade unit according to an embodiment of the present invention; 
     FIG. 2 is a perspective view of a razor blade unit according to another embodiment of the present invention having a blade sliding means; 
     FIG. 3(a) is a plan view of the razor blade unit of FIG. 2 showing a position of the blade within a blade holder; 
     FIG. 3(b) is a plan view of the razor blade unit of FIG. 2 showing the other blade position; 
     FIG. 4 is a perspective view of a blade unit holder; 
     FIG. 5 is a perspective view of another blade unit holder having a window to facilitate use of a blade sliding means; 
     FIG. 6(a) is a plan view of a blade unit according to another embodiment of the present invention, showing a blade position; 
     FIG. 6(b) is a plan view of the blade unit of FIG. 6(a) showing the other blade position; 
     FIG. 7 is a partial perspective view of another blade unit holder, partially in section; 
     FIG. 8 is a plan view of a blade unit according to another embodiment of the present invention; 
     FIG. 9 is a partial perspective view of another blade unit holder; 
     FIG. 10 is a plan view of a blade unit according to another embodiment of the present invention; 
     FIG. 11 is a perspective view of another blade unit holder incorporating a blade unit of the present invention having a blade sliding means; 
     FIG. 12 is an enlarged partial perspective view showing the mechanism of the blade sliding means of FIG. 11 in detail; 
     FIGS. 13(a) and 13(b) show two positions of the blade sliding means of FIG. 12; 
     FIG. 14 is a perspective view of a conventional blade unit; and 
     FIG. 15 is a perspective view of another conventional blade unit having a blade sliding means. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIG. 1 is shown a blade unit 1 according to an embodiment of the present invention, comprising a blade holder 2 and a blade 3 slidably held in the blade holder 2 with its blade edge 5 partially protruding from holder edges 20a and 20b. The blade holder 2 comprises a holder surface 2a and surface 2b connected with a backbone 2c. Generally, such a blade holder is provided by bending a metal plate roughly along a centerline or in half. The surface 2a has a plurality of parabolic protrusions 4a provided along its edge 20a and the surface 2b has a plurality of parabolic protrusions 4b provided along its edge 20b. The parabolic protrusions 4a and 4b are generally of an identical size having a width L. 
     Preferably, the protrusions 4a and protrusions 4b appear alternately and together cover about 50% of the blade edge 5, leaving the other blade portions (about 50% altogether) uncovered. Advantageously, the length of each uncovered blade portion is also L. The covered blade portions are indicated by &#34;B&#34; and the uncovered blade portions are indicated by &#34;A&#34; in the figure. It is preferred that the covered blade portions B and the uncovered blade portions A appear alternately. Unlike a conventional blade unit where only either protrusions 4a or 4b are provided, this blade unit of the present invention can be adequately used in both hair cutting directions since the difference in cutting performance between the two cutting directions is totally eliminated. 
     In FIG. 2 is shown another blade unit 1 of the present invention. This blade unit 1 is similar to the foregoing blade unit, the difference being a blade sliding means additionally provided in the blade unit 1, comprising an elliptic window 6 having a length of about L provided in the holder surface 2a and a boss 3d provided on the blade surface 3a, which is received within the window 6 when the blade 3 is attached to the blade holder 2. The boss 3d can be moved with a finger within the window 6 so that the blade 3 slidably held in the holder 2 can be moved together within the holder 2 in the directions indicated by broken arrows to convert the covered blade portions B into uncovered blade portions A, and vice versa. The life of the blade 3 or blade edge 5 can be elongated theoretically twice as long. FIGS. 3(a) and 3(b) show the two positions of the blade 3 within the holder 2. Together with the boss 3d, the blade 3 slides within the holder 2 in both directions indicated by broken arrows, where in FIG. 3(a) the blade 3 held at the left position shows the uncovered blade portions A for cutting hair and in FIG. 3(b) the blade 3 held at the right position shows the other fresh uncovered blade portions A for cutting hair which are formally the covered blade portions B in FIG. 3(a). 
     The window 6 can be a through opening 6 formed in the holder surfaces 2a and 2b. The boss 3d can be a through hole 3d formed in the blade 3. When a combination of such a through opening 6 and hole 3d is utilized, the sliding of the blade 3 within the holder 2 can be furnished with a pin by inserting the pin in the hole 3d. 
     In FIG. 4 is shown a blade unit holder 10 comprising a holder casing 11 and a grip 13. A blade unit 1 of the present invention is inserted into the holder casing 11 for use. The conversion of blade portions A and B of the blade unit 1 is performed as required before the insertion of the unit 1 into the holder casing 11. 
     FIG. 5 shows another blade unit holder 10 which is similar to the foregoing blade unit holder. The only difference is that the holder casing 11 has an opening 14 which is considerably larger than the window 6 and can receive the window 6 when the blade unit 1 is inserted in the holder casing 11. The blade 3 can be moved within the blade holder 2 after the blade unit 1 is inserted in the blade unit holder 10. Alternatively, the opening 14 can be a through opening 14 formed in the holder casing 11 and the window 6 can be a through opening 6 where a through hole 3d is utilized. 
     Another blade unit 1 is shown in FIGS. 6(a) and 6(b) prepared similarly with the foregoing blade units. This blade unit 1 is provided in place of the foregoing blade sliding means with parabolic cuts 8 each having a depth approximately corresponding to the width of each protrusion 4a or 4b on the distal and proximal ends of the blade holder 2. The blade 3 can be moved within the blade holder 2 for exchanging the blade portions A and B by pressing the blade portion in one of the cuts 8. FIG. 6(a) shows a position of the blade 3 within the blade holder 2 and FIG. 6(b) shows the other position of the blade 3. 
     FIG. 7 partially shows another type of blade unit holder 10, partially in section. A projection 12 whose size, configuration and position correspond to those of the cut 8 is provided within the holder casing 11 such that the blade portion in the corresponding cut 8 can be pressed by the projection 12 when the blade unit 1 is inserted into the holder casing 11. For exchanging the blade portions A and B, the blade unit 1 is removed from the casing 11 and reinserted into the casing 11. 
     In FIG. 8 is shown a modification of the blade unit 1 described above. This blade unit 1 has only one such a cut 8 on a distal or proximal end of the blade holder 2, which facilitates a single time renewal of blade portions A and B. 
     FIG. 9 shows a blade unit holder 10 additionally having a parabolic cut 15 whose shape, size and position correspond to those of the cut 8 on the distal end of the holder casing 11, though it is advantageous to provide the cut 15 slightly larger than the cut 8. A bolt 17 is also provided within the holder casing 11 as a stopper of the blade unit 1. The blade portion in the cut 8 received in the parabolic cut 15 is pressed for renewal of the blade portions A with the blade portions B. 
     Still another blade unit 1 according to the present invention is shown in FIG. 10. The blade unit 1 has a different type of blade sliding means, comprising a generally rectangular cut 9 having a length of about 2L or twice the width of a protrusion 4a or 4b on the backbone 2c and a rectangular cut 3e having a length of about L or the width of each protrusion 4a or 4b on the non-blade edge of the blade 3 which is positioned to be received within the cut 9 of the holder 2. The blade 3 in the blade holder 2 can be moved by pushing or pulling the cut 3e within the cut 9 for renewal of blade portions A with the blade portions B. 
     FIG. 11 shows another blade unit holder 10 and a blade unit 1 mounted in the holder 10. The blade unit 1 for this holder 10 may be the blade unit shown in FIG. 10. Here, however, the blade 3 can be moved within the blade holder 2 as held within the holder casing 11 by means of a press button 19. The press button 19 comprises a flat top 19a and a leg 19b which can engage the cut 3e of the blade 3 when pressed down with a finger as shown in FIGS. 12 and 13(a) and 13(b), FIG. 12 being an enlarged view and FIG. 13(a) and 13(b) respectively showing the engaged position and disengaged position of the press button 19. The leg 19b engaged in the cut 3e can be pushed or pulled with finger pressure as applied on the flat top 19a for sliding the blade 3 within the blade holder 2. 
     The foregoing embodiments are provided to illustrate the present invention. It is possible for a person skilled in the art to modify the present invention within the teaching and spirit of the invention. The true scope of the invention is given by the attached claims.