Abstract:
Suction openings in a rotating drum are alternately connected to or disconnected from the vacuum maintained inside the drum, when this is necessary to grip and transport a document, and to release it, respectively. Activation of a group of suction openings is effected by a diaphragm valve, supported by the drum in the interior thereof, with associated pneumatic logical switching means to operate the valve. The switching means have ports, connected to the high and low pneumatic feed levels, existing outside and inside the drum, respectively, and to a pneumatic signal line, providing a connection, insensitive to the drum rotation, with an external, fixed source of control signals for document transport. Other control signals may be generated by the presence or absence of a document on the drum. Various drums of this kind, rotating in opposite directions, are disposed closely together to form a high speed selective document transport system.