US3874705A

US3874705A - Apparatus for binding sheets and product

Info

Publication number: US3874705A
Application number: US331293A
Authority: US
Inventors: William H Abildgaard; Iii Charles T Groswith
Original assignee: VeloBind Inc
Current assignee: VeloBind Inc
Priority date: 1969-10-29
Filing date: 1973-02-09
Publication date: 1975-04-01
Anticipated expiration: 1992-04-01

Abstract

A bookbinding is provided by plastic studs which fit through holes vicinal one margin of each sheet and strips which are fixed to the ends of the studs. Both strips may be apertured and the studs inserted through the holes in the strips and interposed sheets, both ends of the studs being headed. To facilitate handling, strips may be assembled in cartridges or coils, and studs in rods or coils. For thicker books, strips are formed with flanges fitting behind the page margins. Spine concealing tapes and caps fit over or around the spine edges of the sheets.

Description

United States Patent 1 1 1111 3,

Abildgaard et al. Apr. 1, 1975 APPARATUS FOR BINDING SHEETS AND 3,164,250 l/l965 Paxton 206/56 A B PRODUCT 3,260,264 7/1966 McKowen 281/25 R 3,285,404 11/1966 Spinney 206/56 A B Inventors: William Abildgaard. L08 Altos 3,334,918 8/1967 Pigna et 111., 11/1 A x Hills; Charles T. Groswith, Ill, Los 3,452,376 7/1969 lto III] R Altos, both of Calif, 3,475,775 ll/l969 Staats ll/l A C [73] Assignee: Velo-Bind, lnc., Sunnyvale, Calif. FOREIGN PATENTS R APPLICATIONS [22] Filed: Feb. 99 9 214,914 5/l941 Switzerland 402/52 [21] Appl. No.: 331,293 Primary Examiner-Lawrence Charles Related us. Application Data Attorney, Agent, or FirmJulian Caplan [60] Division of Ser No. 872,l34, Oct. 29, l969, which is a continuation-in-part of Ser. No ,799,045, Feb. [57] AFSTRACT 1969 p NO 3596929. A bookbmdmg 1s provided by plastic studs which fit through holes vicinal one margin of eachsheet and 52 us. c1. 281/21, 281/29, 206/56 AB Strips Whieh are fixed to the ends of the studs- Both 151 1m. (:1. B24d 1/00, B42d 3/00 Strips may be apertured and the Studs inserted through [58] Field 61 Search 251/21, 25; the holes in the Strips and interposed Sheets, both ends 2102 524 49 5 20 5 2 2 3 p5 of the studs being headed. To facilitate handling, strips may be assembled in cartridges or coils, and studs in 5 References Cited rods or coils. For thicker books, strips are formed with UNITED STATES PATENTS flanges fitting behind the page margins. Spine concealing tapes and caps fit over or around the spine edges l,()93,835 4/1914 Crump 281/25 R of the sheets. l,l89,826 7/l9l6 Jenkins 281/25 R 1,569,058 l/l926 Wigginton 281/25 R X 9 Claims, 26 Drawing Figures FUZTENTEU H975 SHLET 3 BF 5 FIG. /5.

APPARATUS FOR BINDING SHEETS AND PRODUCT This application is a division of Ser. No. 872,134, filed Oct. 29, I969, which was a continuation-in-part of copending application Ser. NO. 799,045, filed Feb. 13, 1969, now US. Pat. No. 596,929 issued Aug. 3, 1971.

This invention relates to a new and improved binding for books and a method for forming same.

Heretofore various means have been used to bind books. One commonly used method is to sew the sheets together using sewing machines of various types. Such method is inherently slow and expensive. Another method has been the glueing of the spine ends of the sheets together and preferably to a tape. One disadvantage of such methodis the fact that it requires time for thcglue to set-and further, that the binding is weak. A still further method has been stapling the sheets together with metal staples. Deficiencies of this method are the fact that the staples are only passed through sheets of limited thickness and cover only limited areas of thespinc edges of the sheets and further, that the pages tend to tear. Rigid metal posts have been used in such books as accounting books of account but these have been very heavy and expensive books for looseleaf purposes. The present invention provides a binding which eliminates all the defects of previous systems which have heretofore been set forth. One of the ad-' vantages of the present invention is the fact that the binding may be used to accommodate considerable variations in thickness of sheets and works as effectively whether the book bound is thin or thick.

Another advantage of the present invention is the fact that the binding operation may be performed with very simple equipment and with relatively unskilled labor. Pre-punehed sheets receive studs which are inserted through the holes in the sheets and through holes in strips which lie along the spine edges of the sheets.

The equipment used merely shears off the excess length of the studs depending upon the thickness of the book i and then forms a head on the severed end of the stud which retains the assembled book in position.

The present invention is adapted for use with a simple, desk-type piece of office equipment. Use of such equipment is relatively rapid and accommodates wide flexibility in the design of the treated book depending upon the choice of the customer. Thus color, decor of cover pages, and the design of the covering of the spine of the book may be varied depending upon the taste of the customer.

A still further advantage of the invention is the fact that the studs, which are made of various types of plastic, may be sufficiently flexible to permit the binding to curve as do the highest grade sewn book bindings and this facilitates exposure of the portions of the sheets which lie close to the spine.

Although the binding is, as has been stated, adapted to simple office equipment, nevertheless it is also adapted to more sophisticated equipment involving repetitive operations and higher speeds. Thus, the strips may be assembled and packaged in cartridges to fit into a machine without the necessity of manually positioning each individual strip. Alternatively, the strips may he formed in coils of a length sufficient to bind a number of books and such coils fit into the binding machine and are cut to length as required. Further, although in a simple form ofthe invention one of the binding strips is formed with studs which penetrate the holes in the sheet and also corresponding holes in the opposing strip, nevertheless both strips may be formed with holes and the connecting members furnished from rods or coils of plastic material fed into the machine manually or by mechanical means. Accordingly, although the present invention has a considerable advantage in that it is usable with very simple equipment, nevertheless it is also adaptable to commercial production of books.

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 is a perspective view showing two strips used in accordancewiththe present invention;

FIG. 2 is a schematic view showing steps in the compression of the strips, the shearing of the excess length of the studs, and the forming of a head on the end of the stud;

FIG. 3 is a schematic plan view of a book formed in accordance with the invention opened outwardly, the details of the book being shown in dot and dash lines;

FIG. 3A is an enlarged sectional view taken substantially along the line 311-311 of FIG. 3;

FIG. 4 is a side elevation of modified strips;

FIG. 5 is a side elevation of a pair of apertured strips and portions of rod material forming the studs;

FIG. 6 is a plan view of a cartridge of strips joined side-by-side by connecting gate material;

FIG. 7 is a plan view of a cartridge of strips formed by temporarily causing the strips to adhere to a web;

FIG. 8 is a view of a cartridge of strips joined end-toend by gate material;

FIG. 9 is a plan view of a cartridge of strips formed by temporarily causing the strips to adhere to a web of material;

FIG. 10 is a schematic view showing strips which have been prepared from coils of strip material severed to length with rods of stud material inserted through aligned holes in the strips;

FIG. 10A is a view similar to FIG. 10 showing the studs previously formed on one of the strips;

FIG. 11 is a fragmentary plan view of a book formed in accordance with the present invention showing intermittent placement of strips and also showing the application of a bound spine cover of channel shape;

FIG. 12 is an end elevation of the structure of FIG.

I l: FIG. I3 is an end elevation showing use of a tape to seal the spine edges of the sheets and strips;

FIG 13A is a modification of the structure of FIG. 13;

FIG. 14 is a perspective view similar to FIG. I of a modified strip construction used particularly with thick books;

FIG. 15 is an end elevation, partly broken away in section, of a book formed of the strip material shown in FIG. 14 and showing foam tape used to fill the space between strips;

FIG. 16 is a view showing a modified stud construction wherein the studs are rectangular rather than round;

FIG. 17 19. inclusive, are fragmentary sectional views similar to FIG. 15 of modified. constructions;

FIGS. 20 to 20C, inclusive are schematic fragmentary perspective views showing sequentially steps in the formation of a book in which the sheets have been notched rather than punched.

Directing attention to FIGS. l-3A, in one form of the invention there is provided a first strip 21 of plastic material having at equally spaced intervals along one side thereof a plurality of integral studs 22 each formed with a point 23. A matching plastic strip 24 is of approximately the same width and thickness as 21 and is formed at spaced intervals with holes 26. The spacing between holes 26 is the same as that between studs 22 and the size of holes 26 is sufficient to receive the studs with a sliding fit. In using the

strips

21, 24, sheets of paper are formed with holes along one margin, preferably inward of said margin, the spacing between said holes being equal to the distance between studs 22. Apertured cover sheets (not shown) which may be specially colored and/or textured may be placed on the top and bottom of a stack of sheets. The sheets are assembled with the holes therein aligned and the studs 22 are inserted through the holes until the strip 21 is in close contact with the outermost sheet or cover. As shown at the left hand end of FIG. 2, stud 22 penetrates the hole 26 in strip 24 and its end projects beyond strip 24. Pressure is applied to compress

strips

21 and 24 toward each other and thereby to compress the sheets through which the stud 22 extends together as well. As shown in the middle of FIG. 2, hot knife 27 or knife blade cuts off the excess length of stud 22 so that there is a slight protrusion thereof beyond the outer surface of strip 24. As shown in the right hand end of FIG. 2, pressure and- /or heat is applied to the end of stud 22 to form a head 28 which locks the strips and the sheets therebetween in assembled position. In copending application Ser.

No. 799,045, one form of apparatus forming the steps illustrated schematically in FIG. 2, is shown, but it will be understood that the particular mechanisms in said application are not exclusive.

In the phantom view shown in FIG. 3, the

strips

21, 24 and studs 22 form a ladder-like assembly with the rungs or studs 22 penetrating the holes in the sheets. The binding is secure and also has certain flexibility as is shown in FIG. 3A. When the pages of the book are opened out, the studs 22 flex in an arc and the

strips

21, 24 diverge outwardly-upwardly from straight parallelism while the spine edges of the sheets likewise curve upwardly. Thus, this binding method permits opening of the sheets in a manner similar to high class sewn binding.

FIG. 4 is a variation of the structure of FIG. 1 and illustrates that some of the studs 2241 may be formed on one of the strips 210 and other studs 22a on the companion strip 24a and that matching holes 2611 may be formed in each of the strips.

FIG. 5 illustrates a further modification of the invention. Two apertured strips 2412 are each formed with spaced holes 26b. The stud material 2212 is supplied in rods or coils of sufficient length to accommodate fabrication of several books. The strips 2417 are assembled on the outside of the stack of sheets with the holes 26b aligned with the holes in the sheets. Thereupon the stud material 22h is runthrough the hole 26b in the nearest strip 24h, thence through the aligned holes in the sheets and thence through the holes 2617 in the farthest strip 24b. Thereupon heads (this is not shown) similar to heads 28 of FIG. .2, are formed on both ends of that portion of the stud material 22b which is cut to size,

one head on the top of one strip 24b and one on the bottom thereof.

FIG. 6 shows a cartridge arrangement for strips 210. Actually these strips 210 may resemble the

strips

21 or 24 of FIG. 1 or the

strips

21a or 24a of FIG. 4 or the strips 24!; of FIG. 5. The strips 21c are parallel to each other and are connected to each other by gate material 31 of the type commonly produced in plastic molding operations. The cartridge of FIG. 6 may be installed in a machine for performing the operations illustrated schematically in FIG. 2, it being understood that one of the strips 210 is used to bind one book and then the next strip used to bind the next book, the gate material 31 being discarded as each strip is used.

FIG. 7 shows a cartridge similar to FIG. 6 except that a web 32 of paper or the like, having a tacky upper surface is used to hold the strips 21d in assembled position until they are used in binding a particular book. The strips 21d may be of the same type as the strips 210 of FIG. 6. It is to be understood that although in FIGS. 6 and 7, there are six strips shown, the number is subject to wide variation.

FIG. 8 shows strips 210 similar to strips 210 joined end to end by gate material 310. These strips are fed longitudinally rather than transversely as in the two preceding modifications.

FIG. 9 shows a tape 32fof paper similar to the paper of FIG. 7 and has a series of strips 21f applied thereto in end to end relation. The strips 2lfare similar to the strips 210. The number of strips 210 or 2lfwhich may be arranged end to end is likewise subject to variation.

FIG. 10 illustrates still another variation of the invention. Long coils of

plastic material

33, 34 each formed with spaced holes 36 are fed lengthwise into a machine and located with their holes 36 aligned and also in alignment with the holes of the sheets to be bound. Corresponding numbers of stud material 37 in the form of rods or coils of material are fed by means forming no part of this invention through the holes 36 in the top strip 33, thence through the holes in the sheets and out through the holes in the bottom strip 34. The strips 33. 34 are cut off by knives 38 or other means so that their overall length corresponds to the length of pages being bound. Heads may be formed on the stud material 37 in the same manner as described with reference to FIG. 5.

In FIG. 10A the bottom strip 34a is similar to the strip 34 of FIG. 10 and is formed with holes 360 at spaced intervals. The mating strip 41 is formed at equally spaced intervals with integral or previously assembled studs 42 similar to studs 22 of FIG. 1. Blades 38a cut the strips 34a, 41 to length and the excess length of studs 42 are sheared off as in the preceding modification of FIG. 2 and heads (not shown) are formed on the ends of these studs to secure the parts in assembled position.

In the preceding modification it has been assumed that the strips extend continuously from top to bottom of the book being formed. FIG. 1 I, however, illustrates that, by any of the means previously described, intermittent strip sections 24g may be spaced along the length of a cover or sheet 43. As shown here, there are three stud heads 28g formed in conjunction with each strip 24g, but it will be understood that this number is subject to wide variation and that the relative proportion of strip length 24g to the gaps 44 therebetween is likewise subject to variation. Although not shown,

, 5 there is a corresponding strip 21g of the same length as strip 24g on the bottom of the stack of sheets shown in FIG. 11. To finish off and make more secure and rigid the structure of FIG. 11. a channel shaped plastic spine cap 46 is slid endwise over the assembled book. As shown in FIGv 12, cap 46 has a base 47 spanning the distance between the outer surfaces of strips 21g. 24g,

has inturned sides 48 ofthe width of strips 21g. 24g and inturned lips 49 of the thickness of strips 21g. 24g. Various means may be used to retain the cap 46 in position such as an adhesive. The width of space 47 will accommodate a variation in book thicknesses and may be beat shrunk to size after assembly, if desired.

Directing attention to FIG. 13, a book comprising sheets 43 held together by

strips

21 and 24 with studs 22 passing through apertures in the sheets may be finished off at the spine by means of a strip 51 of a tape such as pressure-sensitive tape which adheres to the exposed edges of the sheets 43 and also to the edges of the

strips

21 and 24. In FIG. 13A, the tape 51a lies along the spine of the book but is of a sufficiently greater width so that edges 52 thereof may be folded over to cover

strips

21 and 24. The folded over portions 52 conceal the heads of the studs and may be preferred for additional reasons by some customers. The cap 46, tape 51 or 51a may be marked with various ornamentations and lengends such as book titles, if desired.

FIGS. 14 and 15 show modified strip constructions and spine finishing means particularly useful for thick books such as books which are more than approximately one inch thick. Strip 56 is molded with a flat outside flange 57 and an inward directed flange 58 extending at right angles thereto. Studs 59 which are similar to but longer than studs 22 of FIG. 1 and also preferably more flexible, project from flange 57 about midway between flange 58 and the inner edge of the strip. Studs 59 may be formed with points 61 to facilitate penetration of the holes in the sheets 60 which are to be bound. The matching strip 62 has an outside flange 63 dimensioned similar to flange 57 and an inward projecting flange 64 at right angles thereto which is similar to flange 58. Countersunk holes 66 are formed in flange 63 complementary to the positions of studs 59. When the book is assembled as shown in FIG. 15. the

flanges

58 and 64 lie against and help to support the spine edges of sheets 60. Studs 59 penetrate the holes in the sheets 60 and also holes 66 and a head 67 is formed on the severed end of the stud filling the countersunk hole substantially the same as in the preceding modification. To finish off the spine edge, a first strip 68 of a foam-type pressure-sensitive tape is slit to a width equal to the distance between the inner edges of

flanges

58 and 64 and adheres to the exposed spine edges of the sheet 60. To further finish the spine binding, a second piece 69 of tape similar to the piece 68 but of a width equal to the distance between

flanges

57 and 63 is applied as shown in FIG. 15. Suitable decorations and legends may be applied to the exposed surface of tape 69. It will be seen that the thickness of tape 68 is equal to the thickness of

flanges

58 and 64 while the thickness of tape 69 is equal to the distance between the outer edge of flange 58 and the outer edge of strip 57. As shown. these two thicknesses are the same. although this is not necessary to the invention.

Tapes

68 and 69 may be formed integral.

It will be understood that the arrangement ofstuds 59 and holes 66 on the

strips

56 and 62 is subject to varia- 6 tion as will be understood from an examination of FIGS. 4 to 10A inclusive. Studs 59 may initially be sep arate from flange 57 and installed as in FIGS. 5 and 10.

A modification of the form of the invention of FIGS. 14 and 15 is shown in FIG. 17. It will be understood that the structure of FIG. 15 may be modified by omitting the

tape sections

68 and 69 but if this is done, then the spine edge of the completed book is unsightly. To eliminate such unsightliness without requiring the use of tape, strip 56a is molded with inward directed flange 57a and an outside flange 58a of extended length which is formed at the outer edge of flange 57a. Appropriate studs 590 are connected to strip 56a. Because of the difficulty of molding the

flanges

57a, 58a and studs 59a all in one piece, it is preferable, although not essential, that the strip 561: initially be formed with holes 81 at spaced intervals along its length and preferably that said holes be forward with counterbore 82 on the outside surface of flange 57a. Rod-like stud material 83 is then inserted through hole 81., such material preferably having a head 84 formed thereon which seats in counterbore 82. It will be understood, however. that head 84 may be formed on the rod-like stud 83 after the latter has been inserted through hole 81 or that the head may be formed at the time that the stud is locked through the opposite strip 62a when the book is in the course of fabrication.

Matching strip 62a is formed with a series of holes 86 which are complementary to studs 83., said holes preferably being formed with counterbores 87 on the outside surface for the formation of heads 88 during the course of fabrication of the book. A notch 89 is formed on the outer edge of the inside surface of strip 62a to receive the, end of flange 58a. Thus, in the assembly of the book, each stud 83 is inserted through a hole 86 in strip 62a, the excess stud material being cut off and a head 88 formed filling the counterbore 87. At the same time, the end of flange 58:: is trimmed to appropriate length so as to seat in notch 89.

As shown in FIG. 18, strip 5612 is similar to that of the preceding modification. The outer flange 58b is spaced slightly inward from the outside edge of flange 58b. The matching strip 62b is formed with a groove 91 in the inside surface spaced inward from the edge of said strip to receive the end of flange 5811. In other respects, the

modification of FIG. 18 resembles that of the preceding modification of the same reference numerals followed by the subscript h are used to designate corresponding parts.

In the modification of FIG. 19. the outside flange 586 is positioned at the outer edge of flange 58: and is considerably extended length. Strip 62c is not formed with grooves or notches corresponding to the

elements

89 or 91 of the preceding modification. When the book is assembled, flange 580 is bent over the outside of the strip 620 and turned inward to lock against the inner edges of strip 621'. This arrangement finishes off the structure of FIG. 19. Much of the structure is similar to that of the two preceding modifications and the same reference numerals followed by the subscript c are used to designate corresponding parts.

The

studs

22 and 59 have been illustrated and described as being small diameter round members. However, FIG. 16 shows that the cross section of the studs 22/1 of strip 21h may be rectangular and, of course, the holes in the mating strip are similarly rectangular. A commonly used binding system punches rectangular holes along one margin of the sheets to be found using a quite different plastic comb" to penetrate the holes and bind the sheets together. By forming strip 21/1 with studs 22/1 the system of the present invention may be used with sheets punched with rectangular holes. Although the studs 22/1 are shown projecting from strip 2111, it will be understood from examination of FIGS. 1-10A and FIGS. 14 and 15, that the positioning of the studs and the construction of the strips is subject to considerable variation. Studs 22 11 may initially be separate from strips 21/1 and may be installed therein by means and method similar to FIG. 5, I0 and 20-20C.

In the preceding description it has been assumed that pages 60 are punched with round holes faced inward from the edge of the sheet. However, as shown in FIG. 20C notches 71 may be formed in the edges of 60a. Such notched sheets are currently used extensively in looseleaf accounting forms. Strip 73 and the corresponding stud-carrying strip 74 when pressed firmly together with head 77 formed on the severed ends of the studs will securely retain sheets 60a in place even though the notches 7] permit the sheets to be slid into the out of engagement with the studs prior to binding. In this version of the invention, a pressure-sensitive tape 51 may be applied to the spine edge of the completed book for identification purposes, and to further secure the notched pages from sliding free. This makes the system particularly adapted to use by accountants wherein ledger sheets are initially looseleaf while the books of account are open" and then are securely bound together once the books are closed."

An adaptation of this system is shown in FIG. 20 to 20B. A comb is initially provided for use with sheets 60b formed with notches 71h at one margin. Comb 72 may consist of two

apertured strips

73, 74. the distance between the apertures therein equalling the distance between notches 71b, and a plurality of rods 76 to penetrate the apertures in both strips and project outward on either side therethrough. The strips 73 slide relative to rods 76 with a fairly close fit so that rods do not fall out of the strips, but when sufficient pressure is applied, the

strip

73 or 74 slips along the rods. When the sheets 60h are ready to be bound, they are slid endwise so that the rods 76 enter the notches 71h. Until heads are formed on the rods 76, the comb functions as a looseleaf holder for sheets 60b since strip 73 may be slid toward and away from strip 74 to increase or diminish the pressure tending to hold the sheets in place. This is illustrated schematically in FIG. 20A. When it is desired to bind the sheets together, strips 73, 74 are pressed tightly together and the ends of rods 76 which project beyond the strips are cut off and formed with heads 77 permanently locking the sheets 60!: in place. A tape 51h inscribed with suitable legend to identify the sheets or for other purposes may be applied to the exposed spine edges.

It will be understood, although not shown in detail, that the rods 76 need not project through both

strips

73 and 74 but may be formed integrally and projecting only from one side of one of the strips as in FIG. 1 and that the arrangement of studs and the shape of the strips is subject to wide variation asis shown in FIGS. l10A, l4 and 16.

What is claimed is:

1. In combination for use in binding books, a plurality of first strips each having a plurality of studs projecting from one surface thereof, said studs spaced apart in intervals, a plurality of second strips of substantially the same length as said first strips formed with apertures spaced apart the same intervals as said studs, said apertures dimensioned to receive said studs when said studs are pushed through said apertures, each plurality of said strips being arranged in juxtaposition and which further comprises thin, discardable frangible members of plastic gate-like material to form a cartridge of strips joining adjacent strips.

2. The combination of claim 1 in which said strips are joined side-by-side.

3. The combination of claim 1 in which said strips are joined end-to-end.

4. The combination of claim I in which each said strip is of extended length, several times the length of a book to be bound, said strip severable into shorter lengths each approximately equal to the height of a book to be bound.

5. In combination for use in binding books, a first strip of a width to overlie one marginal edge of said book and being of substantially lesser width than the width of said book formed with a plurality of first apertures spaced apart in intervals, a second strip of substantially the same width as said first strip formed with a plurality of second apertures corresponding in spacing to said first apertures, and a plurality of rods or coils of stud material dimensioned to fit through both said apertures, said stud material severable into lengths and deformable to form heads to secure several lengths of stud material to said strips.

6. The combination of claim 5 in which each of said strips are formed in extruded lengths, said strips severable into lengths corresponding to the heights of books to be bound.

7. The combination of claim 5 in which each said strip is formed with a flange adjacent one longitudinal edge thereof perpendicular to the broad surfaces of said strips.

8. The combination of claim 5 which further comprises a stack of sheets formed with notches formed extending inward from one marginal edge of said sheets said first strip overlying said notches on one side of said stack, said second strip overlying said notches on the other side of said stack and compressed toward said first strip, said stud material extending through said notches, and fastening means formed on said stud material on the outside of each said strip to hold said strips assembled tight against opposite sides of said one margm.

9. The combination of claim 8 which further comprises a tape extending along said one margin of said stack having adhesive to cause said tape to adhere to said stack and to close off the exposed outer ends of said notches.

Claims

2. The combination of claim 1 in which said strips are joined side-by-side.

3. The combination of claim 1 in which said strips are joined end-to-end.

4. The combination of claim 1 in which each said strip is of extended length, several times the length of a book to be bound, said strip severable into shorter lengths each approximately equal to the height of a book to be bound.

8. The combination of claim 5 which further comprises a stack of sheets formed with notches formed extending inward from one marginal edge of said sheets said first strip overlying said notches on one side of said stack, said second strip overlying said notches on the other side of said stack and compressed toward said first strip, said stud material extending through said notches, and fastening means formed on said stud material on the outside of each said strip to hold said strips assembled tight against opposite sides of said one margin.