Abstract:
An artificial fingernail is formed to have thickness variations, and curvature, that aid in securely bonding the artificial fingernail to the natural nail, and also strengthen the artificial nail.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to the application and retention of artificial fingernails to natural fingernails; more specifically, it concerns a simple and rapid method of attaching artificial nails characterized by the elimination of prior problems and disadvantages. 
     It has been conventional practice to adhesively attach artificial fingernails directly onto the major extents of upper exposed surfaces of natural fingernails. This method not only risks damage to the natural nails as through promotion of fungus growth at the interface between the nails, but it also requires considerable time and effort and often results in an unsightly cumbersome and/or fake appearance. 
     If the artificial nail is attached to only the forwardmost extent of the vertical nail, as for example as described in U.S. Pat. No. 4,007,748, the desirably thin artificial nail tends to become too flexible, especially if it projects forwardly a considerable distance from the natural nail; also the undersides of the lateral edge portions of the artificial nail intended to bond to the natural nail tend to raise from the natural nail, undesirably reducing the strength of the bond. 
     SUMMARY OF THE INVENTION 
     It is a major object of the invention to provide an improved artificial fingernail characterized as overcoming the problems and difficulties referred to bove. Basically, the artificial nail comprises: 
     (a) a thin plastic sheet element sized to provide, when attached to the natural fingernail, a forward extension of the natural fingernail, 
     (b) said element having a generally U-shaped boundary region extending forwardly of the rearwardmost extent of the element, 
     (c) said element having an upper arch region with curvature such that the lateral sides of the element extend generally downwardly from the arch to be spread apart when said sides are pressed down on a natural nail, 
     (d) said lateral sides having thickness at said boundary region in excess of the thickness of the element at said arch region. 
     As will appear, substantially all of the boundary region, i.e. at least both lateral side portions of the nail, have thickness substantially in excess of the thickness of the element at the upper arch portion (which continues throughout the nail length), that differential thickness characterized as increasing the strength of the nail and also accommodating its flexure upon application to a natural nail, such flexure resulting in enhanced gripping of the natural nail by the thickened side portions of the nail. The result is a more stable, stronger, and more adherent artificial nail. 
     Further, the artificial nail may have a crescent shaped stop at its underside, to engage the forward edge of the natural nail and position the latter, upon application. 
     These and other objects and advantages of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following description and drawings, in which: 
    
    
     DRAWING DESCRIPTION 
     FIG. 1 is a top plan view of an artificial nail incorporating the invention; 
     FIG. 2 is an enlarged section on lines 2--2 of FIG. 1; 
     FIG. 3 is an enlarged section on lines 3--3 of FIG. 1; 
     FIG. 4 is a section on lines 4--4 of FIG. 1; 
     FIG. 5 is a top plan view showing application of the artificial nail to a natural fingernail; 
     FIG. 6 is a section on lines 6--6 of FIG. 5; 
     FIGS. 7 and 8 show the method of flexing the artificial nail to cause it to grip a natural nail; and 
     FIG. 9 is a view like FIG. 6, but showing a modification. 
    
    
     DETAILED DESCRIPTION 
     In the drawings, a solid artificial fingernail 10 is attachable to natural human fingernail 16 seen in FIGS. 5 and 6, for example. The artificial, plastic nail body 11 is longitudinally elongated; for example it may have a length greater than twice its width; however, less lengths are also contemplated. 
     The FIGS. 2 and 3 cross sections of nail body 11 show it to have in unflexed condition a generally semicircular, or circular section conformation, i.e. to have widthwise curvature substantially greater than that of a typical natural nail to which it is to be applied. Note in FIG. 7 that the unflexed width ω 1  of the artificial nail body is substantially less than the width ω 2  of the natural nail to which the artificial nail is to be applied. 
     FIGS. 1 and 5 show also that the artificial nail boundary along sides 11a and front 11b is generally U-shaped forwardly of the rearwardmost extent of the nail element, the two sides tapering in the direction toward front 11b. Further, the element has an upper arch region 11c with curvature such that the lateral sides 11a extend generally downwardly from the arch to be spread apart when the sides 11a are pressed down on the natural nail. Further, the arch region along the nail length is more flexible than the nail region at and adjacent the sides 11a by virtue of its reduced thickness t 1  as related to relatively greater thicknesses t 2  at and along the sides, whereby the center of the nail body may be flexed downwardly as in FIG. 8, while the sides being relatively less flexible tend to remain clamped down, or &#34;grip&#34; against the natural nail as they are spread apart laterally. This in turn facilitates a closely conforming gripping of the undersides of rear portions of the nail body to the natural nail, whereby a drop or two of glue initially applied at 50 to the nail underside as seen in FIG. 7 is spread apart during nail down-flexing, to impart a very good bond between the artificial and natural nails. 
     The thickness of the nail body, along its length, decreases from a maximum proximate each side 11a to a minimum near or at the top of the arch region 11c, medially of the nail (i.e along the intersection of the nail with a plane bisecting the nail, lengthwise thereof). Accordingly, substantially the entire boundary region of the nail (i.e. along and proximate edge portions 11a) exceeds substantially the thickness of the nail at the arch, these conditions prevailing substantially throughout the length of the nail and particularly at the nail region to be bonded to the natural nail, and contributing to the flexing and gripping characteristics referred to above. 
     The body 11 desirably has a generally concave rearward peripheral distal edge 13 forming a recess 14 to expose the main body of the natural (as for example human) fingernail 16, as better seen in FIG. 5. Accordingly, the illustrated body 11 forms two laterally spaced, rearwardly projecting cusps 17 at the points of locations where the lateral sides 11a meet the lateral extremities of the concave edge 13. The body 11 may consist of an acetate type, or other, flexible plastic material. 
     It will be noted that the molded plastic body has a stop shoulder or step 20a at the proximal underside juncture of the main extent of the nail with a reduced thickness top strip portion 30 of the nail. The stop or step is preferably located forwardly of edge 13 and has crescent shape, with lateral extremities which approach and terminate at the cusps 13. The shoulder 20a is forwardly spaced from rearward edge 13 at a maximum distance indicated at &#34;t&#34;, proximate the medial longitudinal axis 21 of the body. 
     Referring now to the method of attaching the thus provided artificial fingernail 10 to the natural nail 16, an abutting contact is effected between the stop shoulder 20a with the forward edge 15 of the natural nail, as seen in FIGS. 5 and 6 with force F applied (as in FIGS. 6 and 7) to flex the nail body 11 downwardly so as to &#34;grip&#34; the artificial nail as explained above. Preliminarily, the natural fingernail 16 may be trimmed as by scissors to provide and conform the blunt edge 15 thereof to the natural shape of edge 13; however, an exact match is not required. Also, a quick drying liquid adhesive is applied to an underside crescent shaped arc portion (designated at 25) of the artificial nail, near stop 20a and edge 13, as seen in FIG. 5, the glue or adhesive also indicated at 50 in FIG. 7. Portion 25 is translucent. 
     When the abutting contact is made as described, the liquid adhesive on crescent 25 is underlapped by a corresponding crescent shaped upper surface edge portion 25a of the natural fingernail, as seen in FIG. 5. Upon quick drying of the adhesive, the two narrow crescent shaped portions are firmly bonded together, and the main surface extent of the natural nail is not contacted by the liquid adhesive, or covered by the plastic nail, preserving the health of said main surface of the natural nail. 
     The crescent shaped portions of the two nails are retained together for the short period of time required for spreading and quick drying of the adhesive. After a few seconds, the artificial fingernail is completely and durably secured to the natural fingernail forward of blunt edge 15. One unusually advantageous adhesive is that sold under the trademark &#34;5-Second&#34; nail glue, a product of Toagosei Chemical Company, Tokyo, Japan. It is otherwise known as an alpha cyanoacrylate, and is capable of curing or drying in air in about 4-6 seconds. 
     Additional adhesive may be applied to the rearward edge 13 and to edge 15 (see FIG. 7) to strengthen the bonded attachment. Finally, the upper surface of the artificial nail adjacent edge 13 may be filed or buffed, and nail polish applied. 
     FIG. 9 shows a modification wherein the step shoulder 20a has been removed, and the rearward extent 30a of the artificial nail overlaps and is bonded to the top and forward surface 16a of the natural nail. Otherwise, the artificial nail body 111 is the same as body 11 described above, with thickness variations between regions 11a and 11c as referred to. 
     Elongated artificial nails, as shown, are strengthened by means of the present invention, so as to prevent unwanted flexing thereof, forwardly of the natural nails to which they are attached.