Apparatus for converting a stream of partly overlapping sheets into a stack

Apparatus for converting a stream of flexible sheets, particularly paper sheets, wherein the trailing portion of each preceding sheet is overlapped by the leader of the next-following sheet, into a stack of fully overlapping sheets, comprising a support for the stack of sheets, said support including a member against which the leaders of the sheets in the stack abut;

• at least one endless perforated conveyor having an elongated lower reach above said support;
• means for driving said conveyor to thereby move said lower reach in the direction from the one toward the other end thereof;
• a suction chamber disposed above said lower reach and having a foraminous bottom wall adjacent said lower reach;
• means for feeding the stream to said one end of said lower reach whereby the underside of said lower reach attracts the leaders of successive sheets of the stream and advances the thus attracted sheets toward a position of register with said support;
• and means for varying the effective length of that portion of said lower reach which attracts the leaders of successive sheets to said underside thereof, including a non-permeable sealing device disposed between said bottom wall and said lower reach and abutting against said bottom wall to seal the adjacent portion of said lower reach from the interior of said suction chamber, said sealing device extending beyond said member of said support toward said one end of said lower reach to overlie a portion of the stack adjacent to said member so that the leaders of successive sheets are free to become separated from said lower reach before such leaders reach said member of said support.