GB2197256A

GB2197256A - Element for binding sheets

Info

Publication number: GB2197256A
Application number: GB08627198A
Authority: GB
Inventors: Guido Mugnai
Original assignee: Unibind Ltd
Current assignee: Unibind Ltd
Priority date: 1986-11-13
Filing date: 1986-11-13
Publication date: 1988-05-18
Also published as: GB8627198D0

Abstract

Element for binding sheets using heat-activatable adhesive, characterized in that the adhesive layer (4) is in contact with a heat conducting element (3). The element (3) may be a U-shaped metal strip having the adhesive layer (4) applied to the bottom inner surface (13) thereof. The element (3) is attached to the inner side (5) of a heat-insulating backing member (2). Alternatively the element (3) may be in the form of a flat strip attached to the backing member (2). <IMAGE>

Description

SPECIFICATION Element for binding sheets with inner gluing back for thermal gluing systems.

This invention relates to an element for binding sheets of paper more especially a back forming element coated on its inner side with a layer of a heat-activable adhesive. The element is preferably U-shaped and can be foreseen of a front cover sheet and a rear cover sheet.

The element according to this invention is used for binding a stack of documents such as printed or typed paper sheets into an unitary item, so that said stack is fixed between the front and rear cover sheets and the back portion spanning the rear edges of said front and rear cover sheets. The stack of documents is glued to said layer of heat-activable adhesive.

Files provided with such elements are already known. In these known files a layer of a hot-melt adhesive is applied on a back portion made of a heat-insulating material. The heatinsulating coefficient is almost so high that the hot-melt adhesive can only be heated and softened within a reasonable time into an active form if a heating source raised on a temperature much higher than the boiling point of the adhesive is used. This heating source can be for example a heating plate.

If such a file stays for too long time on the heating plate or similar heating device, the adhesive may be caused to boil and to be decomposed, damaged or evaporated. Such a degradation may not be immediately noticeable, but may appear after some time (for example a few weeks), so that the binding between the file and the papers or documents inserted therein is prematurely destroyed.

Moreover, the activation of the adhesive layer of said known files is obtained by maintaining the heating plate or similar heating device in contact with the outer surface of the back portion of the file, said back portion being usually made of a heat insulating material such as card board possibly reinforced with a wooden or non-woven fabric.

The heat transfer from the heating plate to the adhesive layer through the heat-insulating material of the back-portion is poor, so that high temperatures and/or long heating times are necessary.

According to the present invention a back forming element is used of which the arrangement or composition is such that the heat emitted by the heating plate is quickly transferred to the adhesive layer so that a lower temperature of the heating plate or similar device is sufficient for activating completely the adhesive layer within a short period of time (for example, less than 30 seconds), said temperature being lower than the boiling point of the adhesive.

The element for binding sheets of paper according the invention is essentially characterized in that the adhesive layer is in contact with a heat conducting element, this element being preferably a metal strip carrying the adhesive layer. In a preferred embodiment of the invention, the heat conducting element is a Ushaped metal strip having inner surfaces which are at least partially coated with the adhesive layer. The metal strip may be made of steel or another metal, such as aluminium. The element for binding sheets can exclusively be made of said heat conducting element carrying the adhesive layer, however in a preferred embodiment the element will also comprise a more classical backing member as well as cover sheets, said heat conducting element being connected to the backing member by any suitable means, e.g. by a thin layer of a thermo-hardening adhesive and the like.

The characteristics of the invention will become more clearly out of the following description of some preferred embodiments only given as an example and without any limitations, reference being made to the enclosed drawings in which.

Figure 1 is a cross-section of first embodiment of the element according to the invention, provided with a stack of paper sheets; Figures 2 to 6 are cross-sections showing other embodiments of the invention; Figure 7 is a perspective view of an embodiment almost similar to the embodiment of Fig. 6, free from paper sheets.

In these figures, the same elements are designated by the same reference numbers.

The element for binding sheets of paper according to the invention designated generally by 1 in Fig. 1 comprises a back portion or backing member 2 having a U-shape in crosssection; a heat conducting element 3 consisting in a longitudinal metal strip such as a steel strip and a layer 4 of an adhesive of the known hot-melt type, which is applied on the heat conducting element 3.

The metal strip 3 is connected by suitable means to the inner side 5 of the backing member 2. This connection may be obtained by welding or rivetting the metal strip 3 to the backing member 2.

The backing member 2 is made of a flexible material such as a synthetic polymer (for example soft polyvinyl chloride) having a melting point which is higher than that of the hotmelt adhesive. The flexibility enables the closing and opening of the file.

When a plurality of paper sheets 6, such as printed or typed sheets, must be bound, the adhesive layer 4 is molten by applying a heating plate (not shown) on the outer side 7 of the backing member 2 and the heat emmitted by the heating plate is transferred to the metal strip 3 through the backing member 2. The metal strip 3 is thereby uniformly heated to a temperature causing the melting of the adhe sive layer 4 while the edge 8 of the stack of sheets 6 is in contact wth the outer surface 9 of the adhesive layer 4, the inner side 10 of which being applied on the metal strip 3.

Due to the presence of the heat conducting element or metal strip 3 coated with the adhesive layer 4, the latter may be heated uniformly to the melting point, within a very short period of time, so that the proximal edge 8 of the stack of sheets 6 is correctly glued to the element 1.

The elements 1 according the invention and shown in Figs. 2 and 3 comprise also a front cover sheet 11 and a rear cover sheet 12, these sheets being connected to the backing member 2. These cover sheets 11 and 12 are preferably made of a hard synthetic material, such as transparent polyvinyl chloride.

As respectively shown in the Figs. 2 and 3, the cover sheets can be connected to the outer side 7 or the inner side 5 of the Ushaped backing member 2.

In the embodiment shown in Fig. 4 the element 1 for binding sheets only consists in said heat conducting element carrying the adhesive layer 4 of the known hot-melt type, the heat conducting element being made of a Ushaped metal strip 3.

According to the embodiments shown in Figs. 5 and 6 the U-shaped metal strip 3 is attached, e.g. glued or welded, to a backing member 2 made of a synthetic polymer, similarly as shown in Figs. 1 and 2. The layer 4 covers the inner side of the bottom 13 of the U-shaped metal strip 3. As shown in Fig. 7 the layer 4 can also cover partially the inner surface face of the legs 14 of said U-shaped metal strip 3.

Between the U-shaped metal strip 3 and the backing member 3 can be placed a heat-insulating material which may be made of synthetic material.

This heat insulating material, which is not shown in the figures, is preferably placed between the outer surface of the legs 14 of the U-shaped metal strip 3 and the inner surface of the sides 15 of the U-shaped backing member 2.

The component parts of the file according to this invention can be made of the following materials and have the following thickness: backing member 2 made of flexible polyvinyl chloride; bottom thickness 0, 1 mm -side thickness 0,2 mm metal strip 3 made of steel: thickness 0,1 to 0,2 mm, front and rear cover sheets made of transparent polyvinyl chloride: thickness 0,18 mm.

The use of a U-shaped metal strip procures a greater tear resistance tha a flat metal strip or bath particularly when rigid glossy paper is inserted between the stack of papers. The advantages offered by such a U-shaped strip are mainly that a quantity of sheets can be bound together in a stack which exhibits excellent holding capacities. Damage to the binding are avoided even when the bound assembly is entirely opened. Normally, when the U-shaped metal strip is not used each sheet of the stack pivots individually upon its glued edge during the opening of the assembly.

The pivotement movement of the sheets occurs easily for the first sheets and for the last sheets. When the bound assembly is of important thickness the inner sheets are hemmed in their pivotment movement, so that the reader is obliged to press the inner sheets by the hand in order to put aside on both sides of the separation line the swelled stack of sheets. When the sheet to which the reader wishes to have access, is a rigid glossy paper, the pivoting movement of the thickened sheet obout the convexity of the subjacent sheets likes to the swinging of a lever arm. The pivoting point of the lever is the bulge of the sheets and considerable tensible forces are applied on the adhesive layer.

Glossy paper is difficult to glue, because the adhesive is applied on a protective layer of the sheet which is not firmly bound with the paper and thus easily separated.

When a U-shaped metal strip 3 is used, the pivoting movement of the sheets upon the glaced edge thereof during the opening of the file is limited by the rigid legs 14 of the Ushaped metal strip 3.

If the sheets 8 of the stack are hemmed between the edges of the legs 14 of the Ushaped metal strip 3, the glued edge of the sheets is not subject to any tear forces because a sheet pivots upon a pivoting axis which is approximatively located in a plan containing the edges of the legs of the U-shaped metal strip 6.

If the sheets 8 are not hemmed between the edges of the sides of the U-shaped metal strip, the rigid legs 14 of the U-shaped metal strip counteract the pivoting movement upon the glued edge of the sheets, so that the compacting and tensible forces applied on the adhesive layer during the opening of the file are not able to destroy the adhesive binding between the sheets and the metal strip 3.

This latter case shows the additional advantage of using an U-shaped metal strip as heatconducting material.

The invention is, of course, not limited to the above described embodiments, which may be modified namely in respect with the shape of the component parts, within the scope of appended claims. The surface of the metal strip 3 may be treated so as to be rough or roughened in order to achieve an optimum tear resistance of the adhesive layer 4 applied thereon.

Further, the backing member 2, the front cover sheet 11 and the rear cover sheet 13 of the file according the invention, may be made of the same synthetic material. They may form a whole which is cutted out of the same sheet of synthetic material.

Claims

1. Element for binding sheets with inner gluing back for thermal gluing systems, characterized in that the adhesive layer (4) is in contact with a heat conducting element (3).

2. Element according to claim 1, characterized in that the heat-conducting element (3) is a metal strip carrying the adhesive layer (4).

3. Element according to claim 1 or 2, characterized in the that heat-conducting element (3) is a U-shaped metal strip having inner surfaces which are at least partially coated with the adhesive layer (4).

4. Element according to claim 3, characterized in that the adhesive layer (5) is applied on the inner surface of the bottom (13) of the U-shaped metal strip (3).

5. Element according to one of the preceeding claims, characterized in that it comprises also a backing member (2) of flexible material, the heat-conducting element (3) being attached to the inner side (5) of said backing member.

6. Element according to claim 5 characterized in that said backing (2) is made of a heat-insulating material.

7. Element according to claim 6, characterized in that the heat insulating material is flexible.

8. Element according to claim 5, 6 or 7 characterized in that the backing member (2) is made of a soft synthetic polymer having a melting point which is higher than that of the adhesive.

9. Element according to one of the preceeding claims, characterized in that it comprises a U-shaped backing member (2), a front cover sheet (11) and a rear cover sheet (12), said sheets (11, 12) being connected to the backing member (2) and the heat conducting element (3)being attached to the inner side (5) of said backing member.

10. Element according to claim 9, characterized in that the cover sheets (11, 12) are made of synthetic material.