The present invention relates to a sheet preform which can be used in the production of various framed pictures and which can be bent to the shape of a casing as a frame for the picture. The invention also relates to a method for framing a picture by using a sheet preform, as well as a frame for a picture.

The use of a photograph as a decorative product has become very common with digital photography and fabrication of pictures. Photographs and pictures used in interior decoration are normally framed. The frame can be made of, for example, wood or metal, or it can be bent of paperboard or cardboard, as disclosed, for example, in publications GB 1 401 844, DE 202 00 889 and FR 2 831 038. In some cases, a photograph can be printed out directly on a cardboard or paperboard which is bent into the shape of a frame, as dis- closed in publications GB 2 457 005, GB 2 430 362 and GB 2 104 278. Printing out on cardboard or paper in such a way that the quality of the picture is good requires a printer suitable for this purpose and may therefore be expensive. A solution that is technically and commercially easier to apply is to keep the frame and the picture separate, wherein the picture may be printed out on a normal, relatively thin substrate, such as photographic paper. When a separate frame is used to ensure the quality of the picture, it is important that the picture is stretched to the frame so that the picture has a surface as smooth and even as possible and thereby has a high quality appearance. Such a product is typically a photograph or an ink-jet printout stretched to an interior frame, and the product is generally known as a decor picture or a canvas picture. Two of the most common methods of manufacturing the product are the use of a stretcher in connection with a solid frame and the use of a wedge frame without a stretcher. Arrangements to be stretched to a solid frame are disclosed in publications GB 946 083, US 4,006,771 and US 4,635,700, whereas arrangements with wedges, screws and hinges to expand the frame are disclosed in publications US 3,133,357, US 5,271 ,171 , US 4,301 ,853, and US 3,529,563 The solid frame consists of wood strips sawn to a fixed length and notched at the ends. The frame is assembled, the picture is stretched with a stretcher and bent around the frame and fastened by stapling. The picture is removed from the stretcher, cut and finished. When a wedge frame is applied, the frame consists of wood strips sawn to a fixed length and notched at the ends, as well as wedges used for tightening them. The frame is assembled; the picture is placed on top of the frame, turned around it, and fixed by stapling. The picture is then stretched by spreading out the frame by means of wedges to be hit at the corners.

In bent frames of prior art, made of cardboard or another similar bendable material, the most significant disadvantage is the appearance. Because the picture (for example a photograph or a painting) is not stretched in a fixed frame, the picture contains surface roughness visible to the eye and therefore does not give an impression of good quality. Direct printing out of the image on a cardboard whose edge areas will later be bent to form a frame requires properties of the printing device which render such a printout expensive. Furthermore, even in this case the picture will easily remain slightly curved and does not give the impression of good quality. Moreover, such a method does not make it possible to sell and market the frame preform separately. Disadvantages in the stretching methods of prior art include the need for an expensive stretcher, the inflexibility caused by the use of wood strips of fixed length in the production of special sizes, the accuracy of shape in general (the frame must be measured to the cross-measure) and particularly in con- nection with the tightening of the wedge frame, and the sluggishness of the method in general. Yet another problem with the wood frame is the risk of twisting and warping of the frame, due to the properties of the material.

It has been discovered that when a separate picture is attached to a frame preform, the simultaneous bending of the preform and the picture to their form will construct the frame itself and stretch the picture to the frame. The method according to the invention is primarily characterized in that the picture is fastened to the sheet preform, and the picture is stretched to the frame by bending the sheet preform and the picture. The sheet preform according to the invention, in turn, is primarily characterized in that the sheet preform further comprises picture fixing elements for fastening the picture to the sheet preform, which picture fixing elements are provided in the sheet preform in such a way that at least one bending line is between a picture fixing element and the centre of the sheet preform. The picture frame according to the invention is primarily characterized in that the sheet preform also comprises picture fixing elements for fastening the picture to the sheet preform, which picture fixing elements are provided in the sheet preform in such a way that at least one bending line is provided between a picture fixing element and the centre of the sheet preform.

A significant advantage of the frame according to the invention to conven- tional stretching techniques is the ease and quickness of the production. The picture is simply fastened to a sheet in a planar shape, which sheet, at the stage of bending, automatically stretches the picture to the correct tension without auxiliary devices or tightening wedges. The structure of the frame itself enables a dimensionally accurate assembly even if the assembling per- son has no previous experience of said work. The frame is light in weight and inexpensive in terms of material and energy costs; it can also be made of recycled materials and, at the end of its life cycle, it can be recycled. The components of the frame are easy to transport and store when stacked in planar shape. Furthermore, the single preforms can be transported in straight shape, for example in an envelope, or rolled up, for example in a mail tube. In the same envelope or mail tube with the sheet preform, it is in many cases also possible to transport the picture to be framed in it. If necessary, the sheet preform can be cut to special measurements by simple tools at the production stage, wherein the manufacture of products of special sizes is flexible and cost-effective. Furthermore, a casing structure with open corners makes it possible to finish the corners of the product more accurately than when a conventional solid frame is used. Thus, the quality of the final product is also better. The casing structure is very strong and torsionally rigid, wherein the frame maintains it shape well and there is no risk of twisting or warping. The advantages of the separate frame and picture according to the invention, compared with the solutions of prior art, in which the edge areas of an image printed out on a relatively sturdy material are bent to form a frame for the rest of the image, include the cost-effectiveness of the printing, the planar image surface of high quality, and the possibility of mass production of the sturdy frame preform as a separate preform.

The product according to the invention can be utilized both in professional production, wherein the finished product is sold to the consumer, and as a do-it-yourself model to be assembled by the consumer, wherein its marketing can be expanded, for example, to convenience goods stores, interior decorating shops, etc. The product according to the invention can be utilized not only as a conventional decor picture but also in, for example, exhibition deco- rations, billboards, and message sign boards, both indoors and outdoors, according to the properties of the material used.

In the following, the invention will be described in more detail with reference to the appended figures, in which shows a sheet preform cut to shape, including the fixing elements and corner reinforcements, illustrates the fastening of the picture to the sheet preform, shows the bending of the casing of the frame and the mechanism for tightening the picture, shows the sheet preform of Fig. 1 bent into shape and the picture fastened to it, in a cross-sectional view of the picture along the line A-A of Fig. 1 , shows a corner reinforcement formed by bending of the sheet preform of Fig. 1 , and shows a finished product according to an advantageous embodiment of the invention.

In Figures 1 to 6, the same numerals or symbols are used for corresponding parts.

Figure 1 shows a preferred embodiment of a sheet preform to be used in the method according to the invention. The sheet preform 1 to be bent, consti- tuting the main component for the frame according to the invention, is either ready cut to size and shape, or it is cut to size and shape at the production stage by means of simple tools. The sheet preform can be made of, for example, cardboard, paperboard, plastic, or metal, or a combination of these, for example a laminate of two or more of such materials. The sheet preform is ready provided with the fixing elements 2 needed for fastening the picture K and forming the frame. Some of the fixing elements 2 are provided to fix the picture to the sheet preform. These fixing elements are indicated with the reference numerals 2a in the figure. Some of the fixing elements 2 are provided to keep the bent casing structure together. These are indicated with the reference numerals 2b. Some of the fixing elements 2 are provided to form a corner reinforcement in the bent frame structure. These are indicated with the reference numerals 2c. The fixing elements 2 may consist of, for example, tape, glue, self-adhesive tape, or various rivets, and all the fixing elements are not necessary similar to each other. Furthermore, the sheet preform is provided with bending lines 3 needed for bending. The bending lines can be made, for example, by creasing, wherein the bending line is formed by pressing the sheet preform at the bending line. The bending line can also be formed by scoring, wherein the bending line is scored on the surface of the preform. It is also possible to form the bending line by perforating. Furthermore, the bending lines can be formed by applying several of said methods, and not all the bending lines need to be formed by the same method. The bending lines 3a closest to the centre of the sheet preform determine the size of the frame and thereby also the part of the picture to be exposed. The width w _a of the part of the picture to be exposed is substantially the same as the length of the bending line 3a corresponding to the width. In a corresponding manner, the height h _a of the part of the picture to be exposed is substantially the same as the length of the bending line 3a corresponding to the height. In an embodiment of the invention, the sheet preform is provided with cuts 4 that separate corner reinforcement parts 5a and 5b from the part of the preform that constitutes the frame. In this embodiment, the corner reinforcement part 5a can be provided with a fixing element 2c for fixing the corner rein- forcement part 5b to the corner reinforcement part 5a. Furthermore, the preform can be provided with holes 6 to facilitate the hanging of the framed picture.

The fastening of the picture K to the sheet preform 1 is illustrated in Fig. 2. The picture K is fastened to the sheet preform by fixing elements 2a in such a way that the edges of the picture extend from the centre of the preform at least across the first bending lines 3a. Advantageously, each edge of the picture extends across at least the first two bending lines and most advantageously across the first two bending lines 3a and 3b. Because the picture extends across at least the first bending lines, at least the first bending lines 3a are provided between the picture fixing elements 2a and the centre O of the picture. Possibly also other bending lines 3 are provided between the picture fixing elements 2a and the centre O of the picture. In the embodiment of Fig. 1 , there are two picture fixing elements 2a on each side of the sheet preform. In some other embodiments of the invention, there may be only one picture fixing element 2a on each side, or there may be more of them. It is obvious that the width WK of the picture must be greater than the width w _a of the corresponding bending line 3a. In a corresponding manner, the height h _K of the picture must be greater than the length h _a of the corresponding bending line 3a. As an example, the invention can be applied in situations, in which the longer side w _a of the part of the picture to be exposed has a length of 210 to 840 mm, and in a typical photograph application, the shorter side h _a is 2/3 of the longer side. This example does not in any way restrict the invention from being applied to pictures of other sizes and other aspect ratios as well. The corners of the pictures are cut, for example, with scissors or other suitable cutting tools to a shape that is suitable for bending the picture and the preform, as illustrated in Fig. 2, in which the reference numerals 7 indicate the areas to be removed from the picture. For example, the corner of the picture K can be removed by a straight cut, as illustrated with the reference numeral 7a, or the corner K can be cut to correspond to the edge of the preform 1 , as illustrated with the reference numeral 7b.

Figure 3 illustrates the assembly of the frame. The edge areas of the frame are bent one by one into their correct form along the bending lines 3. The bending is performed by bending the preform along the bending lines towards that surface of the preform, to which the picture has not been attached. Thus, at each bending line, the outer surface of the sheet preform is stretched, and in the points where there is also the picture K at the bending line, the picture K is also stretched, thereby straining the picture. The extent of the straining can be adjusted by changing the material thickness of the sheet preform and the depth of the bending line as well as by selecting the point of fixing the picture, wherein an optimal relative stretch is always achieved in frames of different sizes, ensuring the high quality of the final product. A thick material will tighten the picture more than a thin one, a low bending line more than a deep one, and furthermore, the picture can be tightened the more, the greater the number of bending lines left between the fixing point of the picture and the centre of the picture. In an embodiment of the invention, the preform constitutes a frame whose edge has a rectangular cross-section. This embodiment is illustrated in Fig. 4. At each bending line 3, the preform has been bent to a substantially right angle, wherein a substantially rectangular hollow frame structure 8 has been formed. As discussed above, the bending stretches the outer surface of the preform 1 at the bending lines 3, simultaneously straining the picture K. For this reason, the picture K has a substantially flat surface, that is, the cross-section of the picture is substantially straight, but the preform 1 bends slightly, as shown in Fig. 4. In other embodiments of the invention, the cross- section of the edge of the frame may also be different in shape, for example a triangle or another polygon, or it may be solid and consist of bent preform layers on top of each other and a possible reinforcement. In some embodiments, the fixing means 2b for keeping the frame together may be provided on the reverse side of the preform, that is, on the side without any picture fixing means 2a. In other embodiments of the invention, the relative distances between the bending lines 3 will determine the shape of the frame to be formed. Thus, also the angle, where the picture and the frame are bent at the framing stage, will affect the extent of tightening the picture. A large bending angle will tighten the picture more than a small one.

In an embodiment of the invention, the corners are reinforced by using fixing means 2c to attach the corner reinforcement elements 5a and 5b which ensure the shape of the corner and reinforce the structure further. Figure 5 shows the corner reinforcement structure according to this embodiment. The figure shows the reverse side of a ready framed picture in a vertical view corresponding to the embodiment in which the picture K extends across the bending lines 3a and 3b and the frame structure has a rectangular cross- section, as shown in Fig. 4. For the sake of illustration, part of the picture K is omitted to show the fixing elements 2a. In the embodiment shown in the fig- ure, the fixing means 2c for the corner reinforcements are provided only in the corner reinforcement element 5a left under the corner reinforcement element 5b, wherein the fixing means 2c do not remain visible. In some other embodiments of the invention, the corner of the frame can be reinforced with separate corner braces to be placed inside the frame.

One embodiment of the method is to apply a sheet preform made of paper- board to frame a photograph printed out on ordinary photographic paper. A photograph framed according to this embodiment is shown in Fig. 6. In other embodiments, the material used for the preform can also be another bend- able material, for example plastic sheet, wherein the strength of the frame may be greater and its moisture resistance may also enable its application outdoors. Furthermore, in other embodiments, it is possible to fix pictures printed out on other materials, for example pictures printed out on a commonly used canvas material by the ink-jet technique, to the sheet preform, and to bend this into a framed canvas picture. Furthermore, a printed picture can be used as the picture. In particular, the picture to be used may be of a white reflecting material, wherein the sheet preform according to the invention can be used to make a framed projection screen. Furthermore, the sheet preform according to the invention can be used as a supporting frame structure for pictures in which a decorative frame is used outside the picture, wherein the external frame can be implemented in the form of a lighter structure than when conventional framing techniques are applied. The step of assembling the product can also be automated by relatively simple devices for production in larger scale.

It is obvious that the invention is not limited solely to the above-presented embodiments, but it can be applied within the scope of the appended claims.