Abstract:
A letter form, which serves as both letter and window envelope, wherein the address is reverse printed on the inside of the window cover film and does not dictate the arrangement and design of the printed text of the letter form and wherein the address is readable when inserts are included. Preparation of the letter form advantageously includes printing of text and address concurrently.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to production from a single, printable sheet of paper or the like, of a letter form, which serves as both letter and envelope. 
     2. Description of the Prior Art 
     Letter forms of this type consisting of a single sheet and, when folded, made up of two or several leaves lying one atop another, joined together to form a self-contained letter/envelope are known, for example, from Swiss Patent No. 609,634 and U.S. Pat. No. 3,482,780. In these types of letter form, the inner side of the sheet is printed with information and a mailing address. The sheet is then folded once or twice and the two or three sheet-parts are stuck together along their edges. With the exception of the address, the lettering on the inner side of the sheet is thus covered. The latter is visible through a window. The address area with the address of the addressee, located on one sheet-part, and the window which is to be provided on the other sheet-part must therefore be arranged in such a manner that they lie opposite one another when the sheet is folded. The consequence of this is a lack of freedom in the choice of where the address area and window are to be arranged, especially if the position at which the address is to appear on a letter is governed by existing postal regulations. 
     Furthermore, the known letter forms consisting of two parts have the disadvantage that it is impossible to insert an enclosure between the folded halves of the sheet since this would obscure the address area, unless the enclosure is both too small to cover up the address area and also is secured so that it cannot slip in front of the address area. 
     It is an object of the present invention to provide a letter form giving greater freedom in the arrangement of the address area and the window than with known letter forms and with which there is no risk of the address being unintentionally covered by any enclosures inserted. 
     It is a further object of the present invention to provide a process which permits the production, in a simple manner, of such letter forms. 
     These and other objects are achieved by the article and process described herein and illustrated by the accompanying drawings. 
     SUMMARY OF THE INVENTION 
     The letter form, according to the present invention, comprises a single printable sheet containing a pre-selected window opening bearing a cover. On the inside surface of the sheet is printed the letter or other information to be sent. On the inside of the window cover is reverse-printed the addressing information. When folded and sealed, the letter form provides a self-contained envelope with the addressing information readable through the window. 
     Since, according to the invention, the address or information relating to the recipient are no longer printed on one of the sheet-parts but on the rear side of the window cover and the address area thus lies on the rear side of the window cover, the provision of an address area on the other sheet part is unnecessary. The address area is therefore no longer a necessarily determining factor for the arrangement of the printed text, i.e., information to be printed on the inner side of the sheet. 
     Furthermore, the window can be arranged in any suitable position or, where applicable, in the prescribed position without this having any serious consequences for the arrangement and design of the imprint (text, tables and the like) to be applied to the inner side of the sheet. Further, the address or the recipient&#39;s identification code cannot be covered over by inserted enclosures. 
     The application of the address or the recipient&#39;s identification code in mirror writing to the rear side of the window ensures that the appearance of the lettering from the front side of the window is as normal and can therefore be read without difficulty. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a plan view of the inner side of a sheet of a single-fold embodiment of a letter form according to this invention. 
     FIG. 2 shows a perspective view of the sheet of FIG. 1, folded once and in the half-open condition, with an enclosure inserted. 
     FIG. 3 shows an oblique view, from the front, of the sealed letter form of FIG. 1. 
     FIG. 4 shows an oblique view of a three-fold embodiment of a letter form according to this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The letter form 1 shown in FIGS. 1-3 consists of a sheet 2, the inner side of which is designated 2a and the outer side of which is designated 2b. The sheet 2 has end edges 12, 13. The sheet consists of two halves 3 and 4, which are divided by a transverse fold line 5, applied in known manner. Both halves 3, 4 of the sheet are provided at the lateral edges 6, 7 with edge strips 8, 9 having sprocket holes (FIG. 1) for registered conveying, as is known to workers in the field. These edge strips 8, 9 can be torn off along separation lines 10, 11. There is a peripheral separation line 14, applied in known manner, at a distance from the lateral edges 6 and 7 as well as end edges 12 and 13. Together with the edges 6, 7, 12, 13 this defines a peripheral edge section 15. The part of the edge section 15 which is located in sheet-half 3 carries adhesive strip 16. 
     Sheet-half 4 is provided with an address window 17 which is formed by an opening 18 in sheet-half 4. This opening 18 is covered over by a cover film 19, the rear side of which corresponds to inner side 2a of sheet 2 and is designated 19a and the front side of which corresponds to outer side 2b of sheet 2 and is designated 19b. An address 20, which typically is a post office address but might be an addressee&#39;s identification code, for example, is applied in mirror writing, i.e., in a script which is the wrong way round, where right and left are reversed, to the rear side 19a of the cover film 19, as can be seen from FIG. 1. Cover film 19, when printed, is a see-through cover; that is, it is sufficiently transparent or translucent that addressing information 20 can easily be read through the film. In the area beyond the window 17, the inner side 2a of the sheet 2 is provided with an imprint 21, e.g., text, numbers, tables and the like. However, it is not necessary to provide an address area on sheet-half 3 since this is located on the rear side 19a of the cover film 19. 
     The production of the letter form 1 described above proceeds as follows. 
     Printing of address 20 advantageously is done concurrently with, that is, simultaneously with, or consecutively to, printing of all or at least a portion of imprint 21. The unfolded sheet, however, may have been preprinted on the outer side 2b and, at least to a certain extent, also on the inner side 2a. Typically, imprint 21 is provided on inner side 2a by means of an electronically controlled printer, e.g., a laser printer or an ink-jet printer. In addition, the address 20 is applied in mirror writing to the rear side of the cover film 19a covering window 17. Application of adhesive strip 16 may be performed by conventional means either before or after printing of imprint 21 and address 20. 
     Folding and sealing is performed after printing and after application of the adhesive strip. After the imprint 21 and address 20 have been applied, the hole-bearing edge strips 8, 9 are torn away, preferably prior to folding. The sheet 2 is then folded along the fold line 5. Prior to sealing, an enclosure 22 may be inserted between the sheet-halves 3, 4, which lie one on top of the other, as shown in FIG. 2. Finally, the two sheet-halves 3, 4 are stuck together along their edges 6, 7, 12, 13 by means of the adhesive strip 16. FIG. 3 shows letter form 1 folded, sealed and ready to be sent. 
     As shown in FIGS. 2 and 3, the address 20, which was applied beforehand in mirror writing to the rear side 19a of the cover film 19, is correct as seen from the front side 19b of the cover film 19, i.e., it is no longer the wrong way round. The enclosure 22 lying behind the window 17 does not hide the address 20. When the sheet halves 3, 4 are folded one on top of the other, the lettering 21 is covered and cannot be seen from outside. 
     To open the sealed letter form 1, the edge section 15 is torn away along the separation line 14. 
     As stated above, cover film 19 can be transparent or somewhat opaque, e.g., milky, just so that even in the latter case the address 20 can be read. The entire film 19 need not be transparent. It is required only that the address be readable. This can be achieved, for example, by use of an otherwise unacceptably opaque cover film 19 which becomes see-through, i.e., transparent or translucent, during printing at those points at which the address 20 is imprinted. Materials for such covers are known to workers in the field. It will be understood that use of an appropriate non-transparent cover film 19 will permit printing on that portion of inner side 2a which in the folded article will lie below cover film 19, without interfering with the readability of address 20. 
     Another embodiment of this invention is shown in FIG. 4. In this embodiment the letter form is folded twice to produce the final article. 
     In the case of a letter form 101 of this type (FIG. 4), the sheet 102 has two fold line 103, 104 running at some distance from one another and dividing the sheet 102 into three sections 105, 106, 107, namely a middle section 106 and two outer sections 105, 107. The window 17 with the address 20, which is applied in mirror writing to the rear side of the cover film 19 of the window 17, is here arranged in one of the outer sections 107. The sheet 102 is then folded in such a way that the sheet section 107 having the window 17 is laid above the other outer sheet section 105 so that the window 17 comes to rest on the unprinted rear side 105a of this other outer sheet section 105. 
     As will be noted from the embodiments described above, the folded sheet 2, 102 may consist of a single leaf or several leaves lying one on top of the other and connected to each other.