Sheet delivery in a printing machine

摘要

A sheet delivery in a printing machine comprises a vacuum system for applying suction air and a sheet brake. The sheet brake is in the form of a brake roller which includes a carrier shaft having a longitudinal axis extending transversely to a sheet delivery direction. The carrier shaft includes a carrier pipe which communicates with the vacuum system. The carrier shaft has a control slit formed therein for the suction air. The control slit extends axially across the carrier pipe, corresponding approximately to a sheet width. A suction body pipe is coaxially supported on and surrounds the carrier pipe. The suction body pipe has a plurality of perforations formed therein and it is rotatably mouted on the suction body pipe. The suction body pipe is rotatably driven at a circumferential speed which is slower than a sheet delivery speed. Suction bodies are supported on the suction body pipe and they may be axially shifted thereon. The suction bodies are formed of radially assembled segments clamping the suction pipe. Bellows sealingly interconnect the suction bodies and seal the suction body pipe. Suction air is briefly applied to the suction nozzles in the sheet carrier surfaces of the suction bodies in phase with a working cycle of the sheet delivery.