Abstract:
A fastening sheet assembly for attaching flat sheets to a backing panel has a releasable contact adhesive on its under-surface, and an integral disengaging member which is used to lift the low tack contact adhesive clear of the surface to which it is engaged.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation in part of application Ser. No. 09/095,695 filed Jun. 11, 1998 now abandoned, which was a continuation-in-part of Ser. No. 08/521,538, filed Aug. 30, 1995 now abandoned, which was a continuation in part of application Ser. No. 08/162,875, filed Dec. 8, 1993 now abandonded which was a continuation in part of application Ser. No. 08/059,374, filed May 12, 1993 now abandonded, and also a continuation in part of application Ser. No. 08/099,458, filed Jul. 30, 1993, all abandoned. Application Ser. No. 08/521,538, filed Aug. 30, 1995, above, was also a continuation in part of application Ser. No. 08/389,677, filed Feb. 14, 1995 now abandonded, which was a continuation in part of application Ser. No. 08/174,325, filed Dec. 30, 1993 now abandonded, and was also a continuation in part of application Ser. No. 08/059,374, filed May 12, 1993 now abandonded, and a continuation in part of application Ser. No. 08/162,844, filed Dec. 7, 1993, all abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention is an improvement to the adhesive fastener used for file folders of the type shown in U.S. Pat. No. 5,169,254, dated Dec. 8, 1992. 
     This type of fastener is typically mounted in a conventional file folder on a prong fastener along the top edge of the file folder panel. The adhesive fastener pieces are hole punched and fit on the prong fasteners of the file folder. They are small rectangular pieces each of which has a contact adhesive on its undersurface which engages the top edge of a paper to be secured in the file to hold it in place. The adhesive on each adhesive fastener is covered by a release paper which is removed when the fastener is to engage a paper sheet inserted in the file. All of the fasteners are flexible pieces. The adhesive fasteners are successively connected to paper sheets as they are inserted in the folder starting with the lowermost fastener. All of the unconnected adhesive fasteners are bent upwardly to provide an opening under the lowermost unconnected adhesive fastener. The paper sheet is inserted in this opening and aligned in position on the panel with previously inserted papers. 
     Removal of the adhesive covering on the fastener immediately above this newly inserted paper sheet will permit the adhesive on that fastener to adhere to that paper sheet when the upwardly bent fasteners are released and a slight rub or press applies a downward pressure to adhere the fastener to the paper sheet. 
     This unique type of file folder fastener piece allows papers to be inserted more quickly, and eliminates the two-hole punch operation. The adhesive fasteners are constructed of clear, flexible, plastic material, and the adhesive is a reusable type, so that the pages may be quickly removed, copied, and replaced, without disturbing the other pages in the file. The fastener provides greater holding power than an ordinary paper that is two-hole punched. Tapes will not tear out of the file. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     During the course of development of the adhesive fastener for file folders, limitations in materials, adhesives, and arrangement of the component parts were encountered. The adhesive fastener configuration of this application is an outcome of such development efforts. 
     The specific type of fastener material, for example, is of specific interest with respect to how fastened papers of the file fold back over the file during use. The type of adhesive and the substrate are important with respect to consistent holding power of the fastener, and also ability to separate the adhesive of the fastener from an inserted paper sheet. The width of the contact adhesive and its positioning affect both movability of the fastener attached paper sheets and also affect the hinge action provided by the fastener. 
     The lower free section with this configuration also provides a lifting section which is sufficiently wide to be grasped between the fingers of the user to separate the adhesive fastener from the paper to which it is attached. 
     Although a strong bond is provided by the adhesive to the paper, the paper can be quickly removed by pulling up the fastener from the paper. This combination of strength and releasability is not achieved with the holding power of ordinary contact adhesives. Their bond is either too strong, so that one cannot remove the bonded pieces, or, as in the case of the adhesive notes, the bond has no holding power. It has been found that in the setting of a file folder, a relatively small mid-range of adhesive strengths of sufficient holding power provided in the transverse direction parallel to the attached papers, is sufficient. Yet, the lower holding power or tack, than strong bonding adhesives, will permit the separation of the fastener from the paper, when the fastener is pulled upwardly away from the surface of the paper. The strength of the adhesive in the selected range is also great enough to resist papers being pulled away from the fastener when papers are folded back over the top of the file folder. 
     Consequently, the adhesive fastener of this invention provides the capability to quickly place a paper in a file, to hold it more securely than ordinary two-hole punched papers, and yet permits the paper to also be quickly removed, if desired, and subsequently replaced in the file folder. 
     Additionally, the contact adhesive on the file fastener provides a flexible hinge connection for a paper, so that it can be readily folded back over the top of the folder without the spring back problem encountered with ordinary two-hole punched paper fastening devices. This is accomplished by spacing the contact adhesive a distance from the prong fasteners so that a hinge area is provided. 
     The filed paper positioned anywhere in the file folder is readily separated from the fastener without requiring dismantling of the other papers in the file. This is not possible with conventional prong fastener mounted papers in a file folder. The fastener is easily pulled free of the paper to which it is attached, and the paper simply removed. If desired to reinsert the paper subsequently, the paper is merely inserted under the fastener as previously. To do this, a marking paper is placed underneath the paper to be removed from the file, so that the adhesive will then engage that paper during the time that the removed paper is absent from the file. To replace, the removed paper is merely placed in position underneath the marking or holding paper, and the making paper is removed, leaving the contact adhesive of the fastener now free to reengage the top surface of the removed fastener, as before. 
     The removal of a paper is a very simple operation. The fastener is simply pulled free. The positioning of the contact adhesive remotely from the lower edge of the fastener. The lower free area permits the user to grasp it and pull the fastener upwardly, this construction feature permits handy and quick disengagement of the fastener. 
     It has also been found that disengagement of the fastener can be substantially speeded, without reducing the holding power of the fastener. Surprisingly, it has been found that a reduction of approximately 50 percent in the width of the adhesive will allow quicker disengagement, without adversely effecting the holding power of the fastener. Apparently, because the larger force is ordinarily required up along a line parallel to the paper surface of the adhesive, and when the upward force is exerted, or when papers are folded over, the holding force required is substantially less, although transverse to the bonded surfaces, therefore a reduced adhesive width is possible. Also the reduction in peeling time (removal) is substantial and there is a substantial reduction in cost, since tape is expensive. 
     Use of two sided adhesive tape also is a major advance in providing a more reliable fastener, and one that does not require complex manufacturing techniques. Attempted production of fasteners with direct application of adhesive to the fastener surface presented quality control problems, as well as problems. economical production techniques. Purchasable commercial tapes, having high tack holding power on one side, providing a permanent bond to the fastener, and a lower tack releasable adhesive within the limits desired, were found and provided reliability, as well as simplified manufacturing techniques. However, finding a commercial tape having the quality control and reliability within the limits needed was difficult but was eventually found. 
     These and other features and advantages of this adhesive fastener invention will become apparent to those skilled in the art when taken with respect to the following detailed description of the preferred device. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a file folder showing adhesive fasteners in position. 
     FIG. 2 is a plan view of the adhesive fastener of this invention. 
     FIG. 3 is a sectional view along line  3 — 3  of FIG.  2 . 
     FIG. 4 is an enlarged perspective view of the adhesive fasteners of FIG.  1 . 
     FIG. 5 is a cross-section of a view of FIG.  4 . 
     FIG. 6 is a cross-sectional view similar to FIG. 5 showing a prior contact adhesive construction. 
     FIG. 7 is a side view of a file folder showing the manner in which the file sheets are folded back. 
     FIG. 8 is a side view of a file folder illustrating the manner in which the adhesive fasteners permit a file sheet to be folded back during use. 
     FIG. 9 is a plan view of another modification of adhesive fastener. 
     FIG. 10 is a cross sectional view along line  10 — 10  of FIG.  9 . 
    
    
     DESCRIPTION OF THE INVENTION 
     Referring particularly to the drawings, FIG. 1 discloses a plan view of a manila type file folder generally indicated at  10  having panels  12  and  14  a paper  16  shown on panel  14  with its upper edge  17  adjacent to the upper edge  15  of panel  14 . The securing prongs  18  and  19  of a prong type fastener mounted adjacent to the upper edge  15  are shown holding a plurality of adhesive fastener sheet generally indicated at  20  in position. FIG. 2 shows a plan view of the fastener sheet construction. The desired number of fastener sheets are placed on the prongs  18  and  19  to secure the paper sheet inserts in position in the file. 
     The fastener sheet  22  shown in FIGS. 2 and 3 is a bendable flexible piece of polypropylene which is approximately three and one half inches long and one and one half inches wide. It is approximately two mils in thickness. A strip of reenforcing tape  23 , one half inch wide, having an adhesive layer  23   a  is bonded to the underside of the longitudinally extending section of the fastener sheet provide strength around the punched holes  24  and  25  through which the prongs  18  and  19  are passed. The free area  26  is the hinge area which is five sixteenths inch wide and extends across adhesive fastener  22 . It is separated from the free edge grasping section  28  by a double-sided adhesive tape generally indicated at  30 , which is mounted on the underside of the fastener sheet element  22 . 
     The adhesive fastening strip  30  is a double-sided adhesive contact coated tape  34  having a non-removable type permanent adhesive layer  33  on the top side and a reusable removable type adhesive on its lower surface. The reusable adhesive layer  34  is covered by a release paper  36  which has a coating of silicone or similar type of coating to permit it to be removed from the adhesive layer  32 . The double coated tape  32  and the release covering paper strip  36  extend longitudinally across the entire length of the fastener piece  22  as shown in FIG.  2 . 
     It has high tack, permanent type adhesive up to 45 ounce peel value on its upper surface which permanently bonds it to the under surface of the fastener. The other side of the tape has medium (10 to 14 ounce peel value) tack, removable, reuseable adhesive for removably engaging the surface of paper sheet insert. 
     When the fastener is to be used to hold a paper in position the release strip  36  is peeled from the adhesive layer  34  of the lower-most unused fastener piece in the file folder. This is done after all the unused fastener pieces above the last inserted paper sheet are bent upwardly about the hinge areas  26  to provide an opening up to the prongs  18  and  19 . The paper sheet to be inserted, such as sheet  16  is then inserted into position under the lower-most fastener and aligned over the previously filed paper with the upper edge, such as edge  17  placed up against the prongs  18  and  19 . The upwardly bent fasteners are then released, placing the exposed adhesive strip of the lower most fastener into contact with the upper surface of the inserted sheet to hold it in position in the file. 
     FIG. 4 is an enlarged perspective in view of the super posed fasteners generally indicated in  20 , illustrated in the manner in which the paper sheet is held within the file. Of particular interest here, and for illustration purposes, the upper-most fastener sheet, in this case fastener sheet  22  has its lower right hand edge  29  bent upwardly to illustrate the simplicity of removal of the release cover paper strip  36  from the adhesive surface  34 . The release paper cover strip  36  is readily separated from the fastener sheet  22  at the corner  29  when it is bent back as shown. The release strip  36  is thicker and more rigid then the fastener material  22 , and therefore has a tendency to separate when the fastener edge  29  is bent backwardly. This permits the user to grasp the edge of the release paper cover strip  36  and easily remove it completely from the strip  34 , without the need of a grasping tab. As mentioned previously, this is accomplished with the lower-most unattached fastener, which is the fastener above the last-used fastener. For example, in FIG. 5 which is a side view of FIG. 4, the next fastener used would be fastener  44 . 
     FIG. 5 illustrates the removal of sheet  16 . The fastener  40  is lifted up and its adhesive layer  42  is pulled up and away from the sheet  16  and thereby separated from the top surface of sheet  16  to completely remove it. The adhesive on the under surface of the two side coated tape, as mentioned previously, is a releasable adhesive, which is strong enough to hold the papers in position, but also has the property of releasing or separating from the paper when the fastener strip is pulled upwardly along its lower edge as indicated by the arrow. In this respect, it has been found that a substantially narrower strip approximately {fraction (5/32)}&#39;s of an inch in width (about half that of prior widths) is sufficient to adequately secure the papers in the file. Surprisingly, slightly reducing the width has very substantially reduced the amount of time required to pull the fastener strip free from the paper to which it has been attached. The previous width, which was slightly more than one quarter inch, is illustrated in FIG. 6 at  30 ′ and  43 ′. Unexpectedly, the very narrow width of the adhesive strip provided both more than adequate holding strength, and simultaneously greatly reduced the peel time to remove the adhesive from an inserted paper. The time reduction is more than the fractional reduction in width, permitting the release to change from a slow steady peel, to a fast pull action. 
     FIGS. 7 and 8 illustrate the importance of the type of material used for the fastener  22  and its construction. 
     FIG. 7 is a side view of a folder assembly having a backing panel  50  and prong fastener  52  on which adhesive fasteners of the type described above are mounted. The sheet  54  is held in position by the adhesive fastener strip  57  on the under side of the fastener  56 . In this particular configuration, the file user has opened the file to review paper  54 . In doing so the papers above  54 , specifically papers  60  are folded back over the top of the panel as conventionally practiced. It should be noted then when the upper papers are folded back in this fashion, the adhesive fasteners permit them to lay back over the file, and to remain in that position, without having the springing back tendency of two-hole punched fastened papers. 
     Note in FIG. 7, that the sheet  60  when bent back has a tendency for its bottom edge  64  to move outwardly and away from the adhesive strip  59  on fastener  58  which is holding it in position. This is brought about by the sharp bending radius at  62 . The adhesive strength must be sufficient to resist separation. Note that the flexibility of the material of the upper most fasteners  66  permit a very sharp bend. This action takes place with the adhesive fastener material previously used, namely, polyethylene. It has been found that with the switch to the polypropylene material there is less bend. The difference in degree is considerable, since the polyethylene material thickness previously used was in the order of three to four mils. With the discovery that polypropylene material could be used, it was possible to eliminate the kick-out action of the piece  64 , with a material that was only half as thick. The kick out action of the upper edge of the pieces was annoying, since it required the user to tuck the upper edge  64  back into position under fastener  58  before the papers could be returned to their original position in the file. It also had a greater separation affect of the adhesive strip. 
     FIG. 8 illustrates the manner in which the pages lay back when using the polypropylene material of fastener  22 . The sheets are mounted on panel  70  with a top exposed sheet  74  held in position by the adhesive fastener  76 . The fastener  78  is bent upwardly but does not bend over as do the fasteners of FIG.  7 . This new fastener, and the other fasteners shown are more resistant to bending and have a tendency to bent upwardly to a more vertical position, as shown, without springing the paper back. The paper sheet  80  has a more gradual bend beyond the section  82  which is substantially upright. Note that the top section of  84  of sheet  80  does not come forward (kick out) and away from the prong  72 . Its slight inclination toward the prong  72  permits the section  84  to automatically return to its original position in engagement with the prong, without requiring the file user to tuck it back. The upper adhesive fasteners  86  and  88  provide some support and resistance to bending. 
     FIG. 9 is a plan view of a multiple section adhesive fastener  90 . FIG. 10 is a sectional view. Its general construction is similar to the fastener of FIGS. 2 and 3. The fastener  90  has an underlying reinforcing tape  92 , and is two hole punched at  93  and  94  to permit it to be mounted on prong fasteners. The double sided tape  95  mounted on the under side of the fastener piece  90  is identical with the two side coated tape of FIGS. 2 and 3. It has (high tack—45 oz.) permanent type adhesive on its upper surface which permanently bonds it to the under surface of the fastener  90 . The other side of the tape has the desired intermediate peel value range tack, removable, reusable adhesive for removably engaging the surface of paper sheet insert. While providing necessary holding power. 
     FIG. 10 is a cross sectional view of FIG. 9, along line  10 — 10  showing the reinforcing strip  92  in section, and an end view of the adhesive strip  95 . In this regard, it should be noted that it is possible to directly apply an adhesive strip directly to the surface of the fastener. Presently, however, quality control and manufacturing cost are limitations. But, in that event, the construction would simply be an adhesive layer  95  directly applied to the fastener surface, and covered by a removable silicon-coated release strip  95   a.    
     The economy of construction is a chief advantage of this configuration. But more importantly, the ease of attachment and release of a file paper, and its much greater flexibility were unexpected advantages. A hole  96  is made through the adhesive fastener  90  as shown. A connecting cut or slit  97  connects the lower free edge of fastener  90  to the hole  96 . This results in a two-piece member having individual engaging sections  98  and  99 . With this configuration, there is sufficient stability provided by each piece  98  and  99 . As a result of the cut  97  one fastener piece can hold two different paper sheets, thereby doubling capacity of the fastener piece. Unexpectedly, an upward pull on the fastener lower section gives an immediate, quick release from the file paper rather than a peel release. 
     Polypropylene, which is the material used for adhesive fastener  90  has less tear resistance then polyethylene. This has been the reason for using the reinforcing tape pieces  23  and  93  of the modifications shown. The tendency to tear is also a problem when the adhesive fastener is to be cut, as at  97 . It has been found necessary to end the cut line  97  in a pre-made opening  96  to avoid the tendency to tear. 
     With regard to the material used in the adhesive fastener, it has also been found preferable to provide a relatively rough surface having high surface tension at the maximum dyne level of 40 to 45 dynes. This will provide holding power between the permanent adhesive surface of a double coated tape and the under surface of the adhesive fastener  22 . Polypropylene film is a clear material having a coefficient of friction of between 0.30 to 0.60, a stiffness “secant modulus” of  115 , a yield strength of fifteen thousand square inch pounds. 
     The double coated adhesive tape has a polyvinyl chloride base which is approximately one mil thick. The adhesive is an acrylic adhesive. This is important, since it has been found that rubber based, and solvent based adhesives do not provide the necessary stability in the close range of 10-14 oz. peel value. A twelve ounce peel value is preferred. This provides holding strength without tending to peel, and yet to permit removal, the reusable adhesive coating must be of this type of adhesive. Too low a peel value will provide insufficient holding power to hold when file papers are folded back as shown in FIGS. 7 and 8, while too high a peel value will either take texture from the paper, or be non-removable. The peel value range must be accurately maintained generally between ten to fourteen ounce peel value. This required uniformity with good quality control, is the advantage of using a commercial tape product. 
     While this invention has been described as having a preferred design, it is understood that it is capable of further modifications, uses and/or adaptations of the invention following in general the principle of the invention and including such departures from the present disclosure as come within the known or customary practice in the art to which to invention pertains and as may be applied to the central features hereinbefore set forth, and fall within the scope of the invention and of the limits of the appended claims.