Importance

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Abstract

A length of envelope material adapted for being fed to an envelope-forming machine in which the material comprises a succession of envelope units in an unbroken row wound in the form of a roll with a succession of windings. Each envelope unit has a transverse fold line dividing the unit into two halves along which separated units can be respectively folded to form respective envelopes. Each envelope unit has a window opening and a transparent cover on the opening. First strings of glue are provided on each unit for joining the halves thereof together after folding along the fold line. Further strings of glue join the transparent cover to the unit. The strings of glue and the transparent cover are of respective thicknesses to form a uniform elevation at one side of the material of each unit. The diameter of the roll in which the length of material is wound corresponds to the dimensional length of each unit and the thickness of the glue strings and covers so that the roll is substantially cylindrical.

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First Claim