FIELD OF THE INVENTION 
     This invention relates to a new and improved bookbinding strip and method of binding books. A popular bookbinding uses a pair of strips, one strip having relatively rigid thermoplastic studs projecting therefrom, the other having holes to receive the studs. Paper formed with holes complementary to the studs is clamped between the pair of strips, the excess stud lengths are cut off and the ends of the studs preferably formed with rivet heads, completing the bind. The present invention uses flexible studs and grooves are formed in the second strip to receive the bent over stud lengths. Thus the excess stud length is not cut off. 
     DESCRIPTION OF THE PRIOR ART 
     As has been stated, pairs of plastic strips such as those shown in U. S. Pat. No. 4,369,013 are widely commercially available for use in binding machines. The present invention differs from such strips in two respects: First, the studs are flexible and, second, grooves are formed in the female strip to receive the studs. 
     Flexible metallic studs have also commonly been used primarily for non-permanent binding of papers into file folders. The commercially available binders of this type sold under the trademark ACCOPRESS, are either used without a second strip or, when used with a second strip, the latter has been of a complicated type having movable slides which hold the bent over binding strips in place. 
     Long, flexible studs have also been used for binding computer paper and the like, but such binding strips also require complicated means for holding the bent over studs in place. 
     OBJECTS OF THE INVENTION AND SUMMARY THEREOF 
     The present invention provides a female strip formed with grooves and latching means of the type hereinafter described in detail, to receive flexible studs of the opposite member. An extremely secure bind is accomplished without the use of complicated machinery or complicated bent stud retaining means. 
     More particularly, it is an object of this invention to provide a pair of strips, one have longitudinally spaced flexible plastic studs and the other having holes complementary to the spacing of the studs adjacent one or more grooves into which the bent over studs may be inserted and also provided with retaining means of a very simple nature holding the studs in bent over position. 
     A further object of the invention is to provide a binding means which does not require cutting or heading of the studs. The bind may be accomplished either manually or with apparatus which is relatively simple as compared with that previously used. 
     Mechanical simplicity of the strips is a further object of the invention. The locking means is built into the strip. No rivetting is required. 
     Since it is unnecessary to cut off excess scrap length, disposal of scrap is not a problem. 
     Another object of the invention is that the use of flexible studs permits unsnapping the bent stud ends from the retaining means, removing the female strip, adding or subtracting sheets and then rebinding the book. If a permanent bind is desired, the stud ends or strip may be permanently deformed. 
     Among the advantages of the invention is the final appearance of the book. The bent over stud ends resemble stitched bindings. 
     The strength of the bind is highly satisfactory. Failure occurs by breakage of the studs (a function of their cross-section area) rather than by reason of the ends of the studs pulling out of the retaining means. 
     Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views. 
    
    
     In the drawings: 
     FIG. 1 a fragmentary perspective view of a book formed in accordance with one modification of the present invention; 
     FIG. 2 is an enlarged sectional view take substantially along the line 2--2 of FIG. 1; 
     FIG. 3 is a sectional view taken substantially along the line 3--3 of FIG. 2; 
     FIG. 3A is a view similar to FIG. 3 of a modification; 
     FIG. 4 is more or less schematic view showing one means whereby the studs may be bent over; 
     FIGS. 5, 5A and 6 are plan views of the strips of modifications of the present invention; 
     FIG. 7 is a cross-sectional view through the stud of FIG. 1; 
     FIG. 8 is a view similar to FIG. 7 of a modification; 
     FIG. 9 is a view similar to FIG. 2 of a further modification; 
     FIG. 10 is a sectional view taken substantially along the line 10--10 of FIG. 9; 
     FIG. 11 is a view similar to FIG. 7 of a further modification; 
     FIG. 12 is a view similar to the modification of FIG. 3, showing use of a stud in accordance with FIG. 11; 
     FIGS. 13, 14, 15 and 16 are views similar to FIG. 12 of further modifications; 
     FIG. 17 is a plan view of a modified female strip; 
     FIGS. 18 and 19 are sectional views taken substantially along the lines 18--18 and 19--19 of FIG. 17; 
     FIG. 20 a view similar to FIG. 5 of a further modification; 
     FIG. 20A is a sectional view taken along line 20A--20A of FIG. 20; 
     FIG. 21 is a view similar to FIG. 2 of a still further modification; 
     FIG. 22 is a view similar to FIG. 2 of still another modification. 
     FIG. 23 is a view similar to FIG. 5 of another modification; 
     FIG. 24 is an enlarged sectional view taken substantially along the line 24--24 of FIG. 23; 
     FIG. 25 is a cross-section taken substantially along the line 25--25 of FIG. 24; 
     FIG. 26 is a view similar to FIG. 23 of still another modification; 
     FIG. 27 is a fragmentary perspective view showing unbending of a stud of the modification of FIG. 23. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     In the form of the invention shown in FIGS. 1-4, there is provided a male strip 21, preferably of a thin narrow plastic material. Either integral therewith or inserted therein at spaced intervals along the strip 21 are flexible plastic studs 22 having pointed ends 23. The material of the studs 22 may be of polypropylene, polyethelene, K-resin and any of a group of thermoplastic elastomers. The stud length 24 which is in excess of the length necessary to accommodate the pages being bound is bent over. The flexible nature of the plastic material of which the studs 22 is formed makes it possible to bend the studs at a relatively abrupt angle, specifically 90°. 
     The female strip 26 is likewise preferably of plastic and is formed with spaced holes 27 complementary to the spacing of the studs 22. To facilitate the tips 23 being inserted in holes 27, the bottom surface of strips 26 is preferably formed with a counterbore 28, or countersink. The top surface of strip 26 is formed with one or more longitudinally extending grooves 29 to receive the bent portions 24. In the form of the invention shown in FIGS. 1-4, the grooves 29 are formed with overhangs 31 along each upper edge. Thus the bent over portion 24 snaps between the overhangs 31 and is retained in place thereby. 
     The book of the present invention is used to bind a plurality of sheets 33 formed with holes 34 complementary to the spacing of the studs 22. Referring to FIG. 4, the strip 21 is placed with studs 22, projecting upright. Sheets 33 are then assembled on the studs 22. Thereupon the second strip 26 is installed over the studs 22, the counterbores 27 facilitating entry of the pointed ends 23. Thereupon the studs 23 are bent over at a right angle into the grooves 29. As shown schematically in FIG. 4, a roller 36 may cause the studs to be bent. The excess stud lengths 24 snap between the overhangs 31. 
     Directing attention to FIG. 1, it will be seen that the right end-most bent over portion 24 is directed in the groove 29 in an opposite direction from the other bent over portions; however, other arrangements, some of which are hereinafter set forth in detail may be employed. 
     In order to conceal the top of the strip 26 shown in FIG. 1, the alternate of FIG. 3A may be used. In this form of the invention, longitudinal grooves 41 may be formed in the side edges of the strip 26a. A channel 42 having inward extending projections 43 fit into the grooves 41. The channel 42 may be snapped into place or slid lengthwise from one end of the strip 26. 
     FIG. 5 shows pairs of bent over portions 24b turned toward each other inserted in grooves 46 rather than being in the same direction as shown in FIG. 1. FIG. 5A shows the bent over portions 24c overlapping, the grooves 47 being of extended width and of a length approximately equal to the grooves 46 of FIG. 5. 
     FIG. 6 shows a groove 47 of considerable width to accommodate the bent over portions 24d pointing in the same direction but overlapping adjacent bent over portions 24d. 
     FIG. 7 shows a circular cross-section stud 22. In FIG. 8 it is shown that the stud 22e could be square in cross-section or other convenient shape. 
     Directing attention to FIGS. 9 and 10, studs 22f may be formed with a longitudinal split 51, extending from the tip 23f to approximately the point where the stud 22f joins the strip 21f. The halves of the stud 22f may be bent in opposite directions so that the bent halves 52 seat in the grooves 29. Thus, the stud 22f functions similarly to a cotter pin. 
     As an alternate to the round cross-section configuration of FIG. 7, FIG. 11 shows stud 22g with a fluted configuration 56. As shown in FIG. 12, the flutes 56 dig into the sides of the channel 29g in female strip 26g, making the overhangs of the modification of FIG. 3 unnecessary. The flutes 56 stud 22g is pushed into the groove 29g, thereby holding the bent over portion 24g in place by friction. 
     FIG. 13 shows a female strip 26h wherein flutes 58 are formed in the groove 29h. The bent over portion 24h of the stud 22h may be round in cross-section. In FIG. 14, the stud 22h is shown square in cross-section. It will be understood that other cross-sectional shapes of studs may be used. 
     In FIG. 15, the overhangs 31 of the modification of FIG. 3 have been eliminated. Adhesive 61 may be used to retain the bent over portion 24j in place in groove 29j. FIG. 16 shows a weld or brazing 62 holding the bent over portion 24k in the channel 29k. 
     The grooves 29 of the previous modification are either intermittent or continuous. FIG. 17 shows a modification wherein the strips 66 are extruded, there being a continuous channel or extended groove 67 formed therein. At spaced intervals, holes 68 to accommodate the studs (not shown) are formed by punching or other means. 
     FIG. 20 shows a modification wherein one or both of the opposed sides of the groove 29n is formed with flexible inward extending tips 71. The bent over portion 24n stud 22n snaps under the tips 71 and is held in place. 
     FIG. 21 shows a female strip 26p similar to strip 26 of FIG. 2. Instead of a male strip, a second female strip 76 is provided substantially identical to strip 26p A length of stud material 27 havin9 two pointed ends 23p is inserted through one of the strips 26p, 76, through the holes 34 in the sheets 33 and through the hole 27p in the other strip 26p, 76. The strips are compressed together and then the ends 78 and 79 of the stud material 77 are bent over into the grooves 29p of both strips. The bent over portions 78, are retained in place by any of the means shown in the preceding modifications. A channel 42p having projections 43p fitting into grooves 43p in the side edges of each strip 26p, 76 may conceal grooves 29p and bent portions 78, 79 as in FIG. 3A. 
     As shown in FIG. 21, the stud material 77 is bent in U-shape. As shown in FIG. 22, the stud material 77q, is bent in a general Z-shape, so that the end 78q and 79q are disposed in opposite directions. 
     In the form of the invention shown in FIGS. 23-25 there is no stud 22 in the middle of the first strip 21r nor is there a hole 27 in the second strip 26r. Each stud 22r at the left hand side of the book as viewed in FIG. 23 is bent toward the middle, and each stud 22r on the right hand side is bent toward the middle. Such bending may be accomplished manually or by an appropriate tool. 
     Directing attention to the cross-section shown in FIG. 25 it will be seen that each groove 29r in strip 26r is formed substantially complementary to the shape of a stud 22r. On either outer longitudinal edge of the groove 29r is an overhang 31r (which may be approximately 3 mil. in width). When the stud end 24r is bent, the overhangs 31r spring apart sufficiently to permit the stud end 24r to enter the groove 29r and the overhangs 31r retain the same in place. 
     In FIG. 23 there are individual grooves 29r for each hole 27r. In FIG. 26 there is a single groove 67s extending longitudinally of strip 26s. 
     It may be desirable, from time to time, to add or subtract sheets 33 from the stack of sheets bound. As shown in FIG. 27 by appropriate tool 81, the ends 24r, 24s of the studs may be bent back to upright position. Thereupon the strips 26r, 26s may be removed and appropriate punched sheets 33 removed from or added to, or rearranged in position in the stack of sheets. Thereafter, the strips 26r, 26s may be replaced and the studs 22r, 22s bent to snap into the grooves 29r, 29s. 
     The modifications of FIGS. 3A, 5, 5A, 6, 8, 9, 11, 13, 14, 15, 16, 17, 20, 21, 22, 23 and 26 in many particulars resemble the structure of preceding modifications and the same reference numerals followed by subscripts a, b, c, d, e, f, g, h, j, k, m, n, p, q, r and s, respectively, are used to represent corresponding elements.
A first plastic strip has longitudinally spaced studs each of which can be bent over at a 90deg angle. A second strip has holes through which the studs fit and grooves which receive and secure the bent over studs. Several stud shapes and bent stud retaining grooves are described. Paper punched to receive the studs is clamped between the two strips. The studs are then bent over into grooves in the second strip and held in bent position. The paper is thus securely bound. A channel may be slipped over the outside of the second strip to conceal the bent studs and further secure them in place.