US 3164917 A
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R. C. HARPER Jan. 12, 1965 INDEX TAB Filed May 3, 1962 United States Patent This invention relates to index tabs for use upon file dividers, cards and sheets of a variety of thicknesses and in particular to an improved index tab which operates on the clamping principle.
Index tabs fall into a number of different types. The
type in which the tab is permanently positioned on a file divider requires special riveting or gluing steps, cannot be shifted and has to be discarded with the file divider. The type in which the tab slidably interlocks with a specially formed edge of a file divider requires the added expense and inconvenience of the special divider and is diihcult to apply.
A third type of index tabs works on the clamping principle and is the type which this invention concerns. It can be applied to a plain file divider at any desired location and can be shifted from place to place. One construction of the clamp-type tab, suggested years ago, was a single piece of material bent in the form of a U, with flat depending legs contacting over a substantial area at their lower extremities forming a so-called flat nip. One disadvantage was that the fiat legs were hard to separate for insertion of a sheet. In an effort to improve this construction, it was suggested to indent the upper part of one of the legs against the other. Squeezing together of the legs between the indentation and the flap nip could open the lower part of the nip to receive thin papers. Nevertheless, the tab remained difficult to apply to thick file dividers, and it did not have an adequate grip on them. Consequently, this tab is unsatisfactory, and is not made today.
Another prior art clamp-type tab comprised two separate legs contacting at a line at their lowest extremities to form a so-called line nip. The legs were forced tightly together and pressure at the nip line deformed the body of a file divider so that a ridge of file divider material on either side ofthe nip opposed dislodging movement. When this tab was constructed to exert on thick dividers such as cardboard an adequate grip to withstand the roughness of treatment which those members encountered,
the nip was so tight that ledger bond, onionskin and similar thin papers and cards were torn when an attempt was made to apply the tab to them. Also, on applying and removing the tab from thick members, the nip grated the material and sometimes tore it. Therefore, this tab also lacked versatility and was difficult to use.
If a simple and inexpensive clamp-type index tab were produced which could be easily attached to cards and papers of a wide range of thicknesses and could grip each thickness to the appropriate degree, such atab would oifer numerous advantages over both the prior art clamp-type tabs and the other types of tabs. It is one object of the present invention to provide a new tab construction which meets this need.
The invention also concerns an index tab having an angular magnifying index tab head formed of a massive cylindrical lens of plastic or the like. Where the protruding head of an index tab is massive, it does not yield when it receives forces such as arise with the dragging of files over it. Rather, the head resists these forces and imposes a substantial strain on its fastening, so a firm and secure fastening is needed. In the practical art only permanent fastenings have been employed for these massive magnifying heads. The present invention provides a simple and economical clamp supported magnifying index tab which avoids the objectionable features of permanent fastenings.
3,164,91 Patented Jan. 12,1965
These and other objects of the invention will be more fully described in connection with the accompanying drawings, wherein:
FIG. 1 is a perspective view of one preferred embodi- 1rlnent of the invention having a massive magnifying index ead;
FIG. 2 is an exploded view on a magnified scale of parts of the embodiment of FIG. 1;
FIG. 3 is a cross-section of the tab taken on line 33 of FIG. 1;
FIG. 4 is a front view showing the various positions of the index tab as it is applied to a thick sheet such as a file divider;
FIG. 5 is a cross-sectional view similar to FIG. 3 of the tab applied to the thick sheet of FIG. 4;
FIG. 6 is a view similar to FIG. 3 showing the application of the tab to a thin sheet whose thickness is shown exaggerated for purposes of illustration; and
FIG. 7 is a view, similar to FIG. 1, of another embodiment of the invention. 7
Referring to the preferred embodiment of FIGS. 1-6, the index tab comprises a head member 12 and two leg members 14 and 16. The head member has a downwardly extending neck portion 13 and a massive integral head 20 set at an angle to the neck. The head is formed of an extruded transparent plastic and has a slot 21 for receiving a printed card. Its upper surface 22 is in the form of a convex, cylindrical lens, and serves to magnify the printing on the card, making it easy to read. Heretofore an expensive casting was thought necessary for such heads, but I have found an extruded form which is much less expensive has suitable optical properties.
Referring to FIGS. 1 and 2, the leg members are preferably identical, each being separate from the other, punched from a steel strip having an original uniform thickness. Each leg comprises an upper plate portion 24 for joining to the neck portion 13 of the head member, an upper projection 26 struck inwardly towards the other leg member, an elongated, preferably straight lever portion 28 extending downwardly from projection 26, and a lower, preferably straight projection portion 39 extending inwardly. For ease of manufacture, the plate and lever portions 24 and 23 in unstressed condition preferably lie in the same plane. As shown in FIG. 2, the upper projection 26 extends inwardly relative to the plate 24 an amount designated by the letter A and the lower projection 30 extends inwardly relative to the portion of the lever next adjoining it a greater amount, indicated by the letter B. The thickness of the neck portion 18 of the head member exceeds the sum of the distances that the two projections 26 extend inwardly of their supporting portions 24, and this neck thickness is less than the sum of the distance the two projections 35% extend inward 1y from their supporting portions 28; that is 2A C 2B.
Referring to FIG. 3, the leg members 14 and 16 are aligned and their plate portions 24 are secured to oppositely directed sides of the neck portion 18 by rivets 32. The projections 30 converge, edges 31 being in line contact under pressure. The elongated lever portions 28 are slightly flexed outwardly relative to the plates 24 and diverge continually from the projections 26 to a maximum opening D from which the projection 30 converge. The upper projections 26 he immediately below the plate portion 24 and the neck portion 18 of the head member. They oppose each other but are held out of contact.
In preferred embodiments, the elongated lever portion 28 of each leg member is more than twice the length of the material forming the upper projection 26, preferably about three times that length. The lower projection 30 is about the same length as the material forming the upper projection.
In manufacture, the leg members are preferably made from inch width, .012 inch thick, tinned, coldrolled steel. The steel strip in the form of a roll is fed into a punch press which has a die adapted to form the various portions of the leg members. In punching, the die forming the projection 26 thins the material at that point, as shown in FIG. 2, providing, in effect, a hinge of lesser torsional resistance to movement than the other portions of the leg member, lessening the resistance to movement of the tips 31. The degree to which the strip is so thinned provide a means for controlling the amount of pressure of the tips 31 at the nip line.
After the leg members are formed, they are tumbled to eliminate rough edges, and are riveted into position with brass rivets onto the neck 18.
Where the heads are of plastic that can be softened as by dielectric heating or by solvent, the leg member may be bonded to the base portion by the inherent adhesiveness of the plastic of the head member as well a with rivets.
The magnifying angle head member 20 is preferably formed of thermoplastic in an extrusion die, and cut, while soft, to the desired length.
Referring to FIG. 4, in application of the index tab to a thick file divider 29, the tab first is turned at a substantial angle to the margin of the divider at position 1. The ends of the projections 30 are rounded at 36 so that the tips 31 are cut away. Since the space between the diverging lever portions is Widest at the bottom, the edge of the thick divider can be inserted slightly between the leg members, and engage the converging portions 30, as shown in position 1, without pressure being applied. Then by rotating the tab while pressing it towards the divider, the tips 31 are progressively separated by camming action of the divider 29 and the legs move successively through positions 2, 3 and 4. The edge of the divider 29 is inserted wholly into the line nip between leg tips 31 at position 4 without engaging projections 26. Then with a final vertical movement, the divider is thrust upwardly between the projections 26, position 5.
Referring to FIG. 5, the index tab is thus removably secured to file divider 29 which is comprised of heavy stock on the order of .050 inch thickness. The stock is thicker than the separation between the two projections 26, so the projections are forced slightly apart. Since the projections 26 are supported from above by a small free length of the leg member, slight outward movement of the projections requires that the supporting upper leg portion be bent in a correspondingly small arc. Since resistance to resilient bending of a leg member, for a given increment of outward movement, is inversely proportional to the radius of curvature to which it is bent, the projection members 26 grip this file divider with great force, even though the file divider thickness does not greatly exceed the original separation of the two projections 26.
Simultaneously, the tips 31 of the leg members supported by the elongated lever arms 28 also grip the file divider. Since the projections 26 accomplish some of the i gripping on thick sheets, the force of this nip line of tips 31 is less from what would be required if it alone did the fastening. But this lesser force with which the leg tips grip is sufficiently concentrated because of the extremely small area of contact so the pressure resiliently deforms the material to a degree sutficient to provide a substantially greater opposition to dislodgment than that offered by a fiat nip. Thus, on the heavy-duty file dividers two spaced-apart, elongated grips are applied to the material which together enable the index tab to resist rough treatment.
Because the force of the lower nip line at 31 is less than that required in the prior art, a lesser force is needed to separate the file tabs when applying the tab to the margin i of the file divider which makes application very easy and the edges 31 of the nip can have a lesser grating effect on the material.
Referring to FIG. 6, due to the relatively relaxed force at the tips 31, the tab also can be easily applied to a thin divider 29', e.g. onionskin or ledger bond less than .012 inch thick. These materials are thinner than the space between projections 26 so they slide easily between them without opposition. When applied, the tips 31 indent the material in a single line to a degree sufficient to withstand the forces to which such thin materials are normally subjected.
Therefore, it will be appreciated that one and the same index tab is easy to apply and adequately grips file divider cards and sheets of an extremely wide range of thicknesses.
Referring to the embodiment of FIG. 7, the leg members are the same as described above, but the head member 40 is formed of a flexible material which foregoes the magnifying feature, but has the advantages of firm fastening and easy application to a wide range of thicknesses of sheet material.
It will be appreciated that numerous modifications to the specific details of the index tab can be made within the spirit and scope of the invention.
What is claimed is:
1. An index tab of the type wherein two opposed metal leg members are secured by their upper portions to the lower part of an index head member, said upper portions of said leg members spaced apart by said head member, the leg members extending downwardly freely from said head member to tips which define a line nip, the freely extending leg members providing a passage through which the edge of a sheet can be moved upwardly through said nip to said head member, the index tab characterized in that the freely extending portion of each of said leg members has an indentation at a point adjacent to but spaced below the point of securement of said leg members, each of said indentations defining a projection, said projections being opposite each other and extending toward each other, said projections having a combined inward extent less than the spacing between said upper portions so that said projections do not normally contact each other, said indentations enabling the flexing apart of the tips of said leg member by a paper sheet inserted therebetween and enabling movement of said sheet relative to said index head member, and said projections defining a restricted passage for relatively thick sheets whereby said projections can be pressed outwardly thereby, increasing the grip of said leg members on said relatively thick sheets.
2. The index tab of claim 1 wherein each of said leg members below its inward projection has a straight portion extending downwardly, diverging relative to the opposed leg member, and a straight lower inward projection defining the tip of said leg member converging relative to the opposed leg member, the combined inward extent of the lower projections of said two leg members exceeding the spacing between the upper portions of said leg members.
References Cited in the file of this patent UNITED STATES PATENTS 1,258,263 Smith Mar. 5, 1918 1,478,896 Ferency Dec. 25, 1923 1,807,100 Gratf et al May 26, 1931 1,826,614 Gratf et a1. Oct. 6, 1931 2,248,355 Jones July 8, 1941 2,513,127 Wolters June 27, 1950 3,062,217 Woodhouse Nov. 6, 1962 FOREIGN PATENTS 1,123,291 Germany Feb. 8, 1962