Patent ID: 7621517

Claim:
A sheet accumulator comprising: A. an in let feed path to an accumulation location; B. an outlet feed path; C. a non-circular sheet circulation path; D. sheet driving means associated with the sheet circulation path for selectively advancing a partial accumulation of one or more sheets at an accumulation location around the circulation path, and back to the accumulation location to accumulate a next sheet fed from the inlet feed path with the partial accumulation to form a final accumulation, and delivering an accumulation of sheets along said outlet feed path; and E. a control system for feeding and accumulation of sheets in the accumulator, the control system including; an inlet sensor arranged to detect the arrival of sheets into the sheet accumulator along the inlet feed path; a circulation sensor arranged to detect when a partial accumulation has been advanced around the circulation path and back to the accumulation location, and a deskew roller pair that is located across the accumulation location and defines a deskew nip between the rollers at the accumulation location for substantially aligning the leading edges of sheets simultaneously stopped at the accumulation location, wherein the control system is configured to accumulate the next sheet fed from the inlet feed path with a partial accumulation that has been circulated around the circulation path by detecting the arrival of the next sheet at the inlet sensor and the presence of the partial accumulation at the circulation sensor, and to feed the next sheet and advance the partial accumulation so that they arrive simultaneously at the accumulation location to accumulate the next sheet with the partial accumulation.