The folding pocket device for a buckle folding machine includes a folding pocket having a feed-in aperture enabling a sheet to run therethrough in a running-in direction into a pocket space of the folding pocket. A sheet stop device includes a sheet stop extending essentially transversely to the running-in direction in the pocket space, which is displaceable in the running-in direction and in the opposite direction. A sheet directing device includes a diverting device, which is displaceable from a clearance position in which the diverting device opens up the way to the feed-in aperture into the folding pocket to a diverting position in which the diverting device blocks the feed-in aperture in order to divert a sheet. In order to achieve quick switching from the clearance position to the diverting position, the diverting device can be displaced from the clearance position to the diverting position by the sheet stop when the sheet stop is displaced opposite to the running-in direction.

A process for the production of books (22) with digital printing from signatures, in which the book comprises signature groups (33), each formed with basic sheets (34), are parts of respective signature sheets (42). The process employs a manufacturing system (21) which includes a transversal cutting equipment (41) for cutting transversally the signatures sheets, and transversal and longitudinal folding equipment (46) for the formation of respective signatures (48). For a book with at least a sheet section devoid of text and/or figures in a last signature group, the method provides: a) identify a reduced signature group (59) including a number of sheet sections having at least a page with text and/or figures; b) cut the paper strip (23) to separate the reduced signature group as reduced signature group; c) actuate the transversal folding equipment (46) limited to the sheet sections having at least a page with text and/or figures and skipping the actuation of the transversal folding equipment (46) for a single sheet section; and d) actuate the longitudinal folding equipment (47) for folding longitudinally the reduced signature group.

A process for the production of books (22) with digital printing from signatures, in which the book comprises signature groups (33), each formed with basic sheets (34), are parts of respective signature sheets (42). The process employs a manufacturing system (21) which includes a transversal cutting equipment (41) for cutting transversally the signatures sheets, and transversal and longitudinal folding equipment (46) for the formation of respective signatures (48). For a book with at least a sheet section devoid of text and/or figures in a last signature group, the method provides: a) identify a reduced signature group (59) including a number of sheet sections having at least a page with text and/or figures; b) cut the paper strip (23) to separate the reduced signature group as reduced signature group; c) actuate the transversal folding equipment (46) limited to the sheet sections having at least a page with text and/or figures and skipping the actuation of the transversal folding equipment (46) for a single sheet section; and d) actuate the longitudinal folding equipment (47) for folding longitudinally the reduced signature group.

Folding information and printing surface information, included in content information of a sealed letter creation job, are compared with content printing conditions stored in a storage section, and an appropriate condition (a conveyance path after printing, execution/non-execution of image rotation, and printing page order) is selected such that the position of a window of a windowed envelope is aligned with the position of specifying information printed on a print sheet P to be a content when the print sheet P is enclosed in the envelope. A convey section and a printing section are controlled based on the selected content printing condition.