To ensure reliable and productive processing of printed sheets into stacks, a sheet stacker includes: a flipping device for flipping a sheet with respect to the sheet's orientation before being received by the flipping device onto a stack support or a stack of sheets on the stack support; a sensor assembly for detecting an out-of-plane deformation of a top sheet with respect to the underlying stack support or a stack of sheets on the stack support at least for each sheet added to the stack; and a controller configured to determine from data from the sensor assembly whether the top sheet was successfully flipped and stacked.

To prevent deformation to relatively stiffer sheets during flipping, while ensuring reliable holding of relatively weaker sheets, a method for stacking sheets received from a printer by a sheet flipping device includes at least one slot for receiving a leading portion of a sheet. The method includes determining a respective insertion depth parameter for a first and a second sheet, wherein the second sheet has a greater stiffness than the first sheet; inserting a length of the first sheet into the at least one slot in correspondence with its respective insertion depth parameter, followed by flipping said first sheet; inserting a length (D2) of the second sheet into the at least one slot in correspondence with its respective insertion depth parameter, followed by flipping said second sheet, wherein the inserted length of the first sheet is greater than that of the second sheet.

A sheet stacking apparatus includes a frame, a round member directly or indirectly connected to the frame, and an arm directly or indirectly connected to the frame. The arm is rotatable to rotate between a first position and a second position. The arm is positioned to bias sheets toward the round member when in the first position, and the arm is positioned to bias the sheets away from the round member when in the second position.

A sheet flipping device comprising: a flipping element rotatably disposed adjacent to a sheet receiving plane and having, in its outer periphery, at least two insertion slots for insertion of a respective leading edge of a sheet to be flipped; a sheet transport device configured for feeding sheets with their respective leading edges into the insertion slots; and a controller configured to control the sheet transport device and a rotary drive (54) for the flipping element such that each sheet the leading edge of which has been inserted into one of the insertion slots is temporarily restrained while the transport mechanism continues to feed the sheet, so that the sheet flips over, and the sheet is then dropped onto the receiving plane, wherein each insertion slot has a mouth defined between a peripheral surface of the flipping element and a flexible finger that extends tangentially from said peripheral surface, the controller is configured to move one of the insertion slots into a sheet receiving position regardless of whether or not a trailing edge of a preceding sheet has left the sheet transport device, and the flexible finger has sufficient flexibility to be deflected by a sheet which has its trailing edge still held in the sheet transport device.

A medium stacker includes a stacking portion, a rotary portion, a medium holder, a medium mover, and circuitry. The stacking portion has a stacking face to stack a sheet medium on which an image is formed. The rotary portion is configured to hold a leading end of the sheet medium in a sheet conveyance direction, reverse the sheet medium on the stacking face of the stacking portion, and convey the sheet medium. The medium holder is configured to hold the sheet medium when the sheet medium is conveyed by the rotary portion. The medium mover is configured to move the sheet medium to a predetermined position in a direction orthogonal to the sheet conveyance direction of the sheet medium while the sheet medium is held by the rotary portion. The circuitry is configured to control the rotary portion and the medium mover.

A sheet stacking apparatus includes a frame, a round member directly or indirectly connected to the frame, and an arm directly or indirectly connected to the frame. The arm is rotatable to rotate between a first position and a second position. The arm is positioned to bias sheets toward the round member when in the first position, and the arm is positioned to bias the sheets away from the round member when in the second position.

To ensure reliable and productive processing of printed sheets into stacks, a sheet stacker includes: a flipping device for flipping a sheet with respect to the sheet's orientation before being received by the flipping device onto a stack support or a stack of sheets on the stack support; a sensor assembly for detecting an out-of-plane deformation of a top sheet with respect to the underlying stack support or a stack of sheets on the stack support at least for each sheet added to the stack; and a controller configured to determine from data from the sensor assembly whether the top sheet was successfully flipped and stacked.

A single sheet handling device (14a to 14d, 30, 200, 252, 270, 350) for the input and the output of rectangular single sheets (38) respectively into and out of a container (12a to 12d). These rectangular single sheets can in particular be banknotes (38). The single sheet handling device (14a to 14d, 30, 200, 252, 270, 350) has a feeding device with feeding elements for the sheet-by-sheet feeding of single sheets (38) and for storing these single sheets (38) in a stack (36) of single sheets in the container (12a to 12d). Further, the single sheet handling device has a separating device with separating elements for the sheet-by-sheet removal of single sheets (38) of the stack (36) from the container (12a to 12d). The feeding elements and the separating elements are arranged separately from the container (12a to 12d).

To prevent deformation to relatively stiffer sheets during flipping, while ensuring reliable holding of relatively weaker sheets, a method for stacking sheets received from a printer by a sheet flipping device includes at least one slot for receiving a leading portion of a sheet. The method includes determining a respective insertion depth parameter for a first and a second sheet, wherein the second sheet has a greater stiffness than the first sheet; inserting a length of the first sheet into the at least one slot in correspondence with its respective insertion depth parameter, followed by flipping said first sheet; inserting a length (D2) of the second sheet into the at least one slot in correspondence with its respective insertion depth parameter, followed by flipping said second sheet, wherein the inserted length of the first sheet is greater than that of the second sheet.

A sorting machine (1) for sorting flat articles (100, 101) having non-uniform physical characteristics, the sorting machine having sorting outlets equipped with stackers (3) controlled by a monitoring and control unit in compliance with a plurality of programs, each of which is assigned to a predefined type of flat article (100, 101) having predetermined physical characteristics and setting predetermined operating parameters such as, in particular, the pitch between said flat articles (100, 101), and the speed at which said flat articles (100, 101) are conveyed, the sorting machine (1) having means for determining the predetermined physical characteristics of each incoming flat article (101) arriving in said stacker (3), said monitoring and control unit being arranged to act after said determination to assign a predefined type of flat article to said flat article (101) arriving in said stacker (3) and to activate the corresponding unstacking program so as to apply predetermined operating parameters while said incoming flat article (101) is being stacked.