Patent ID: 7326164

Claim:
An apparatus for making a window envelope in which a clarifying agent is applied to a portion of paper that makes up the envelope to provide the envelope with a transparent window, wherein the apparatus comprises: an envelope making means for acting on a continuous paper while the continuous paper is traveling along a continuous path of travel so that the continuous paper is successively folded, pasted and cut to form the envelope; and a clarifying agent applying means disposed upstream of said envelope making means and comprising: (a) a plurality of drying cylinders disposed in a path along which the continuous paper travels; (b) a looped drying path positioned to surround said drying cylinders to cause the continuous paper to travel around said drying cylinders with only one face of the continuous paper being brought into contact with said drying cylinders, and (c) a clarifying agent applicator means disposed mostupstream of said drying path for applying a water-soluble clarifying agent to an area on the other face of the continuous paper that is not brought into contact with said drying cylinders, said area being adapted to become the transparent window in the envelope, whereby the continuous paper that has traveled past said clarifying agent applicator and said drying path in said clarifying agent applying means is allowed to advance into said envelope making means.