WO1994015254A1

WO1994015254A1 - Improved hinge for transparency envelope

Info

Publication number: WO1994015254A1
Application number: PCT/US1993/010824
Authority: WO
Inventors: Annette Marie Kiehne
Original assignee: Minnesota Mining And Manufacturing Company
Priority date: 1992-12-18
Filing date: 1993-11-10
Publication date: 1994-07-07

Abstract

A transparency envelope (2) for use with an overhead projector (1) is provided with a flap (7, 8) which may be unfolded to block unwanted light from shining past the transparency. The flap (7, 8) is connected to the envelope (2) by a hinge strip (9) which is free of adhesive or other attachment means in the center of its width so that the hinge remains flexible, and adhesive, if used, is not exposed when the flap (7, 8) is open.

Description

IMPROVED HINGE FOR TRANSPARENCY ENVELOPE

Technical Field

This invention relates generally to a hinge construction for attachment of one planar sheet to another and particularly to the construction of an envelope for transparencies for overhead projectors and like projecting apparatuses, the envelope comprising a substantially rectangular pocket of transparent plastic sheet material which is open at least along one side edge for insertion of the transparency to be presented.

Background Art

It is previously known, particularly in giving lectures and in teaching, to make use of transparencies which are presented to the viewers on a screen by means of an overhead projector. To realize a professional presentation of these transparencies there have been developed various types of envelopes for storage and presentation of the transparencies. In one type of envelope, see for example U.S. Patent No. 3,875,693, the transparency is framed with cardboard, paperboard or like material. The frame is meant to mask the illumination gaps formed about the periphery of the transparency proper. The frame can also be used for making notes and other memoranda needed by the lecturer. The disadvantage of these framed transparencies is that they will be bulky and therefore difficult to store and transport since they do not fit standard binders, files or shelves. Moreover, it is troublesome to attach the transparencies to the frames.

In another type of envelope, for example Swedish printed patent application no. 382,266, the envelope is a plastic sheet pocket with punched holes along one side, said plastic packet being open at the top for insertion of the transparency to be presented. These envelopes are simple to handle, store and transport as the outer dimensions of the plastic sheet packet are conformed to those of standard binders or files. Moreover the transparency is protected by the envelope, and after the lecture the envelope can be replaced by another one. However, this envelope is disadvantageous in that peripheral illumination is not masked and that the lecturer can not make written notes on the envelope without these notes being also shown on the screen. Further, the contours of the punched holes are also shown on the screen. This envelope therefore yields a total picture on the screen which in no way satisfies the requirements placed on a professional presentation of transparencies on overhead projectors.

Further examples of covers or envelopes for storage of transparencies for overhead projectors are disclosed by U.S. patents nos. 3,253,358; 3,264,936; 3,438,702; 3,438,703; 3,524,703; 3,536,393; 3,537,792; 3,544,211 and 3,600,079 and Swedish patent application no. 346,166. The covers and envelopes according to these publications are complicated to handle and include many of the drawbacks mentioned above. Also, most of those patents presuppose that the transparencies shall be presented on a definite sequence and the covers of most transparencies are difficult to exchange. U.S. patent no. 4,402,585, assigned to the assignee of the present invention and incorporated by reference herein, provides an envelope of the type mentioned in the introduction, while eliminating the disadvantages of the prior art envelopes and being simple to handle, store and transport and also of reliable design and function.

The envelope disclosed by U.S. patent no. 4,402,585 includes at least one opaque flap attached in a foldable manner along one of the longitudinal side edges of the pocket, the flap being attached to and spaced a distance from the longitudinal edge such that holes may be punched in the sheet material along the side edge between the flap and the edge and such that in the unfolded position the flap covers the longitudinal side edge and in the folded position it exposes the longitudinal side edge and any holes to permit storage in a binder, file or the like. The advantages gained by the envelope according to that invention are numerous. In the inwardly folded position of the flaps the envelope fits all standard file systems, ensuring simple storage and transport; it is easily and efficiently handled at the presentation as the flaps are preferably formed from firm plastic or paperboard; The insertion of the transparency is facilitated in that the envelope is preferably open along two sides, one of the sides being the longitudinal side having the punched holes. This will give a better retention of the transparency in the envelope, when stored in a file or binder. Moreover, the lecturer has the possibility of making notes and other important memoranda on the outwardly foldable flaps which also permit a professional presentation in that when outwardly folded they mask the peripheral illumination which would otherwise arise around the transparency and be projected on a screen. By being enclosed in a pocket envelope the transparency is protected from dirt and dust, and during the lecture the lecturer can make notes on the envelope which can then be exchanged for another one before the next presentation. The envelope is usable in many counties since the holes punched in the envelope may be of international standard or the holes may be punched separately for each user. Being antistatic and antiadhesion treated, it does not attract dust, does not adhere to other envelopes and does not pick up text from the transparency.

Unfortunately, there is one particular drawback associated with the commercial version of an envelope constructed according to the teachings of U.S. patent no. 4,402,585. The hinges which connect the flaps to the main portion of the envelope are formed of strip(s) of a nonwoven polymeric material which is coated with an adhesive and applied to the junction of the flaps and the envelope. The adhesive causes the hinges to be relatively stiff. This may cause the flaps to spring back to the folded position if the envelope is positioned on the projector with the flaps above the envelope or causes bowing of the transparency if the transparency is positioned such that the flaps are below the envelope prior to unfolding. This bowing is caused by tension in the hinge portion which results in the hinge area lifting off the projector and the transparency being supported at its center and the edges of the flaps. In this configuration, the projected image is out of focus except where the center of the transparency is in contact with the projector. Another problem with the hinge construction is that adhesive is exposed at the junction of the flaps and the envelope when the flaps are unfolded. This may result in transfer of the adhesive to the projector surface or sticking of the envelope to the projector surface.

Disclosure of the Invention

The present invention overcomes the problems associated with the commercial version of an envelope constructed according to the teachings of U.S. patent no. 4,402,585 by providing an improved hinge in the form of a strip of material which is attached to the envelope and the flaps only adjacent the longitudinal edges of the hinge strip so that the center of the hinge strip is free of attachment to either the envelope or the flaps. If the hinge strip is attached by means of an adhesive, the center of the hinge strip is kept free of adhesive so that the hinge portion does not stiffen and adhesive is not transferred when the flaps are unfolded. If the hinge strip is attached by means of heat sealing or welding, the center is likewise kept free of attachment so that the hinge remains flexible. Brief Description of the Drawings

The present invention will be more thoroughly described with reference to the accompanying drawings, wherein like numbers refer to like parts in the several views, and wherein:

Figure 1 is a perspective view of an overhead projector on which is positioned a transparency envelope in the unfolded position; Figure 2 is a plan view of the envelope of

Figure 1 in the folded position;

Figure 3 is a cross-sectional view taken generally along the line III - III of Figure 2;

Figure 4 is a plan view of a second embodiment of a transparency envelope;

Figure 5 is a cross-sectional view taken generally along the line V - V of Figure 4;

Figure 6 is a plan view of a third embodiment of a transparency envelope; Figure 7 is a partial cross-sectional view taken generally along the line VII - VII of Figure 6;

Figure 8 is a partial cross-sectional view of a fourth embodiment of a transparency envelope; and Figure 9 is an enlarged, partial cross- sectional view of the hinge portion of the transparency envelopes.

Description of the Preferred Embodiment

Figure 1 shows an overhead projector 1 of the kind used for educational and lecturing purposes for the projection of images on a screen. An envelope 2 according to the invention is placed on the horizontal stage of the overhead projector 1 and the envelope 2 encloses a transparency 3 to be presented. The position of the transparency 3 in the envelope 2 is shown in Figure 3. The envelope 2 and the transparency 3 are substantially rectangular and the envelope 2 is slightly larger than the transparency 3 both in width and preferably also in length. In the embodiment shown in Figures 1, 2 and 3, the envelope 2 comprises a pocket which consists of two sheets 4 and 5 of transparent plastic material, preferably approximately 0.5 mm polyester (PET), the sheets 4, 5 being joined together at least along one side or formed by folding a large sheet to form the faces of the envelope. Preferably, the plastic material is antistatic and antiadhesion treated in order not to attract dust and in order that text on the transparency 3 should not be picked up by the sheets 4, 5 of the envelope 2. Along one longitudinal side, preferably the longitudinal side not joined together, the envelope may be provided with punched holes 6 to permit storage in a binder, file or the like.

Two opaque, substantially rectangular, elongated flaps 7 and 8 are attached in a foldable manner to the outer side of one sheet 5 of the envelope 2. The flaps 7, 8 are made from a material which accepts text written by conventional writing instruments. Preferred materials for the flaps 7, 8 are polyvinyl chloride, paper or paper card stock. Further, the flaps 7, 8 are connected to the sheet 5 of the envelope 2 such that they are readily folded from the unfolded position shown in Figure 1 to the folded position shown in Figures 2 and 3 and vice versa. The flaps 7, 8 are attached to the sheet 5 by a hinge strip 9 of flexible adhesive tapes or a strip of material heat sealed or welded to the sheet 5 and the flap 7, 8. The construction of the hinge 9 will be more completely discussed below with reference to Figure 9.

As will appear from Figure 2, the flap 7 at that longitudinal side edge which may be provided with punched holes 6, is connected to the sheet 5 spaced from the longitudinal side edge so that the punched holes 6 are exposed in the folded-together state of the flaps 7, 8 to permit storage of the envelope 2 in a binder, file or the like. In the unfolded state the flap 7 covers these punched holes 6 so that they are not projected onto the screen during presentation.

In the unfolded state the envelope has a surface greater than the stage of the overhead projector so that the stage is entirely covered by the expanded envelope. Also in the unfolded state, the exposed surface portion of the envelope is smaller at least in width than the transparency to be inserted therein. This will prevent illumination gaps from arising on one or both sides of the transparency when it is projected onto the screen.

The embodiments described above relates to an envelope which has two flaps each of which is attached to one longitudinal side of the envelope. In another embodiment the envelope has but one flap which is attached to that longitudinal side edge which may be provided with punched holes and which is so large that in the unfolded state the envelope covers the stage of the overhead projector. For presentation, an envelope of this embodiment is placed in such a manner on the stage of the overhead projector that the longitudinal side edge of the envelope which is devoid of a flap is aligned with or protrudes outside the adjoining boundary edge of the stage. With the envelope placed in this manner on the stage, the larger flap also masks the illumination gap at the longitudinal side edge having the punched holes therein. This will result in a professional presentation of the transparency, the projected image being slightly laterally offset to the image obtained by means of the first described embodiment having two flaps. This lateral offset of the image however results in an equally good presentation of the transparency as seen from the perspective of the viewer.

An embodiment of an envelope having but one flap is shown in Figure 4 and 5. This envelope 2 ' , in which a transparency 3 is inserted, consists of a double- folded transparent plastic sheet 4' , the superposed longitudinal side edge portions of which may be provided with punched holes 6. On one side of the envelope 2' there is attached an opaque, substantially rectangular flap 7' by means of an adhesive tape 9' so that the flap 7' can be laterally unfolded. Figures 6 and 7 illustrate a further embodiment of the envelope of the invention. The envelope 2 ' ' shown in Figures 6 and 7 comprise two plastic sheets 4'', 5" between which a transparency 3 can by inserted. Provided along one of the longitudinal side edges is a flap 8''. On the other longitudinal side edge, in which punched holes 6" may be provided, there is arranged a flap means 7 ' ' consisting of two flaps 10" and ll". The flaps 8", 10" and 11" on the two longitudinal side edges of the envelope 2 ' ' are connected at 9" to the envelope 2' ' and each other in the manner described below. The flap 10' ' which is one of the two flaps 10", 11" constituting the flap means 7" and which is attached to the envelope 2 ' ' may be provided with punched holes 6 ' ' which correspond to the holes 6 punched in the envelope 2 and 2' and which will be placed straight opposite the holes in the envelope 2 ' ' when the two flaps 10' ', 11' ' are folded in as shown in Figure 6. When the flap means 7 ' ' is moved to the unfolded position used for projection the flap 10" is folded out so that when used the flap 10" will cover that portion of the stage which is outside the envelope 2 ' ' . The flap 11" will be folded in towards the envelope 2" and in the unfolded position of the flap means 7" the flap 11" will cover the longitudinal side edge provided with the punched holes 6". An essential advantage of this embodiment is that notes made on the flap 11" can be read by the lecturer in the unfolded and folded positions of the flap means 7" without making it necessary for the lecturer to fold the flap means 7". In still another embodiment of the present invention, which is shown in Figure 8, that longitudinal side edge which is not to be provided with holes, is open. In this case, the opaque flap 8" is attached to one sheet 4 ' ' of the envelope whereby the flap 8", when the envelope is to be stored in a binder, file or the like is foldable over the opening between the two sheets toward the front side of the other sheet 5", and will thus provide a satisfactory locking-up of the transparency 3" inserted in the envelope during said storage.

Figure 9 illustrates the hinge strip 9 as it is used to attach the flap 7 of the embodiment of Figures 1 - 3 to the sheet 5 of the envelope 2. As illustrated, the hinge strip 9 is a length of material, preferably a polymer such as polyester, which is attached to the flap 7 by means of an adhesive 12, preferably a pressure sensitive adhesive. In the commercial version of an envelope according to the teachings of U.S. patent no.

4,402,585 the adhesive completely covered the hinge strip 9 and causes the hinge strip 9 to be very stiff. This stiffness resulted in the flap 7 being biased toward the folded position and in some case even folding by itself after being unfolded. It will be seen from Figure 9 that if the hinge strip were completely coated with adhesive, the adhesive would be exposed if the flap were unfolded. This exposed adhesive could then transfer to the projector or cause the envelope to stick to the projector.

To overcome these problems the adhesive is located in two strips adjacent the edges of the hinge strip 9 and the center of the hinge strip 9 is left free of adhesive. Since the center of the hinge strip is free of adhesive, the folding portion of the hinge 9 does not become stiff and no adhesive is exposed when the flap 7 is unfolded. The construction shown in Figure 9 is applicable to all embodiments discussed above. Such a construction is also applicable if the hinge strip 9 is attached to the flap 7 and the sheet 5 by means other than an adhesive 12. If the hinge strip 9, the flap 7 and the sheet 5 are suitable polymeric materials, they may be attached to each other by means such as heat sealing or solvent or ultrasonic welding. In such a case, it will still be desirable to limit positioning of the weld to the limited areas shown in Figure 9 so that the hinge strip 9 does not become stiff. Although the hinge configuration of the present invention has been described with respect to an envelope designed for use with transparencies for projection, it should be apparent that the hinge construction could be used wherever it is desired to attach and hinge one edge of one sheet to the edge or body of another sheet.-

The flaps according to the proposed embodiments of the invention may of course be arranged either on the front side of the envelope as shown in the drawings, or the flaps may be arranged on the back side of the envelope. If the flaps are positioned on the back side or bottom side of the envelope when on the projector it is possible that the flaps of an envelope according to the first embodiment will unfold themselves to their developed position by dropping the envelope at some distance from the stage whereby the air resistance will cause the flaps on either side of the envelope to unfold automatically and expose the transparency inserted between the sheets 4 and 5.

The punched holes 6 should be of the international type to fit most of the conventional file systems. They may of course also be adapted to a certain file system without departing from the scope of the present invention.

Moreover, the shape of the flaps can be modified within the scope of the invention. It is essential that they mask the illumination gaps which would otherwise occur on one or both sides of the pocket.

Claims

Clai s :

1. In an improved envelope for viewing transparencies on overhead projectors, said envelope comprising a substantially rectangular pocket of transparent plastic sheet material having two longitudinal side edges connected by shorter side edges, said envelope being open at least along one side edge for insertion of the transparency to be presented, at least one opaque flap attached by a hinge to one of the longitudinal side edges of the pocket, said flap being attached to and spaced a distance from the longitudinal edge such that in the unfolded position the flap covers the longitudinal side edge and in the folded position it exposes said longitudinal side edge, the improvement comprising a length of material forming said hinge between said opaque flap and said envelope, said hinge being attached to said envelope and said flap at positions adjacent the longitudinal edges of said hinge material with the center of said hinge material being free of attachment to said envelope or said flap.

2. The improved envelope of claim 1 wherein said hinge material is a length of tape attached to said envelope and said flap by adhesive disposed adjacent the longitudinal edges of said tape, with the center of said tape being free of said adhesive.

3. The improved envelope of claim 2 wherein said adhesive is continuous along the length of said longitudinal edges of said hinge material.

4. The improved envelope of claim 1 wherein said hinge material is heat sealed or welded to said envelope and said flap along the longitudinal side edges of said hinge material and wherein said hinge material is not heat sealed or welded to either said envelope or said flap at the center of said hinge.

5. A hinge for attaching an edge of one sheet of material to another sheet of material, wherein both sheets of material are planar in the area of attachment, the hinge comprising a length of material having one longitudinal edge attached to said one sheet and the other longitudinal edge attached to the other of said sheets, said hinge being free of attachment to either of said sheets in the center area of said length of material.

6. A hinge according to claim 5 wherein said hinge is attached to said sheets by an adhesive disposed between said hinge and said sheets at the longitudinal edges of said hinge and wherein the center of said hinge is free of said adhesive.

7. A hinge according to claim 5 wherein said hinge and said sheets are polymeric materials and said hinge is attached to said sheets by heat sealing or welding along the longitudinal edges of said hinge and wherein the center area of said hinge is free of attachment to either of said sheets.