Expanding envelope with built-in divider

An expanding envelope with built-in dividers comprising an expansive base sheet and an expansive divider sheet, both formed of a resilient, stiff material, characterized in that said base sheet is folded transversely to form a base sheet center fold and counter folded transversely on both sides of said base sheet center fold to form a pair of base sheet bottom folds parallel to and spaced from said base sheet center fold so that said base sheet is collapsible at said base sheet center fold and thereby also delineating front and rear envelope panels from said base sheet that project upwardly from said bottom folds, and said base sheet further defines laterally projecting side panels that extend between and permanently secure said front and rear envelope panels together in mutually facing relationship, and said side panels are folded inwardly toward each other and are doubled back to delineate bifurcating side panel folds perpendicular to said base sheet center fold, whereby said side panels are collapsible at said bifurcating side panel folds, and further characterized in that said divider sheet is folded transversely to form a divider sheet center fold parallel to and in registration with said base sheet center fold and said divider sheet is counterfolded to form divider sheet bottom folds parallel to and spaced from said divider sheet center fold, thereby delineating front and rear divider panels located between and respectively facing said front and rear envelope panels and said divider sheet center fold lies adjacent and parallel to said base sheet center fold, and said base sheet and said divider sheet are permanently secured together between said center folds and said bottom folds.

A method of fabricating an expandable envelope with built-in dividers utilizing an expansive base sheet having opposing side panels and an expansive divider sheet, both formed of a resilient, stiff material comprising:

• positioning said divider sheet atop said base sheet in contact therewith,
• permanently securing said divider sheet and said base sheet together along a pair of mutually parallel, transverse front and rear lines of attachment
• folding said base sheet and said divider sheet upwardly together parallel to and between said transverse lines of attachment to create transverse, collapsible center folds therein,
• counterfolding said base sheet and said divider sheet together in both front and rear mutually parallel transverse bottom folds so that said front line of attachment resides between said center folds and said front bottom folds and so that said rear line of attachment resides between said center folds and said rear bottom folds, thereby creating from said base sheet front and rear cover panels, each having a top and a bottom, and thereby also creating from said divider sheet a pair of divider panels between said front and rear cover panels, and whereby said side panels project outwardly from a first one of said front and rear cover panels,
• folding both of said side panels of said base sheet toward each other to span the distance of separation between said front and rear cover panels,
• folding each of said side panels longitudinally back upon itself so as to form a longitudinal, center fold in each of said side panels, and
• permanently securing said side panels to a second one of said front and rear cover panels longitudinally from said top to said bottom thereof.