Recirculating documents duplex copier

A method for recirculatively copying a set of simplex original documents in a copier onto both sides of copy sheets to form pre-collated duplex copy sets comprising the steps of:

• circulating the documents in reverse (descending) serial page (N to 1) order beginning with the last sheet (N) in the document set and ending with the first sheet (1) in the document set,
• automatically determining whether there are an odd or even number of original documents in said document set by counting the documents as they are so circulated before they are copied,
• copying only the next-to-last (N minus 1) and subsequent alternate documents on the first copying circulation of said document set in said N to 1 order automatically in response to said determination that there are an odd number of original documents in said set, or alternately automatically copying only the last (N) and alternate subsequent documents on the first copying circulation of said document set in said N to 1 order in response to said determination that there are an even number of said original documents in said set, and
• copying all of said documents in said N to 1 order in all intermediate copying circulations of said document set, and
• on the last copying circulation, copying the alternate documents not copied on the first copying circulation,
• to provide properly collated output duplex copy sets with consistent copy sheet output inversion.

In the method of recirculatively copying a set of original documents in a copier onto both sides of copy sheets to form pre-collated duplex copy sets, including circulating the document set in reverse (descending) (N to 1) serial page order beginning with the last sheet (N) in the document set and ending with the first sheet (1) in the document set, the improvement comprising the steps of:

• automatically determining whether there are an odd or an even number of simplex original documents in said document set by counting the simplex documents as they are so circulated before they are copied,
• in the first copying circulation of the document set, copying in said N to 1 order only the last (Nth) and subsequent alternate simplex documents or alternatively only copying the next-to-last (N minus 1) and subsequent alternate simplex documents automatically in response to said determining of whether there are an odd or even number of simplex documents in said set, and
• in all intermediate copying circulations of the document set, copying all of said simplex documents in said N to 1 order, and
• in the last copying circulation of the document set, copying the alternate simplex documents not copied on said first copying circulation,
• to provide a properly collated output of duplex copy sets having consistent copy sheet output inversion.