Sheet feeder having improved sheet extraction

A sheet feeder (10) has a supply station (16) wherein signatures fresh from the printing press are stacked. The stack is supported such that the signatures are in an arched, non-planar configuration. A sheet stripper (18) extracts signatures successively from the stack and feeds them in a constant stream to a transfer conveyor (20). The stripper grips the sheets with a suction device which applies a constant but locally intermittent vacuum. The transfer conveyor carries the signatures to a delivery station (22). The delivery station includes fingers (116) which arch the signatures. Arching the signatures in the supply and delivery stations prevents rolling of the signatures.