Recirculating duplex documents copier

In the method of pre-collation copying of both sides of a set of duplex document sheets, by plurally circulating and serially copying said documents during said plural circulations, and by inverting said documents an odd number of total times during a circulation utilizing inverter means to copy opposite sides of the document, controlled by a control means, the improvement comprising:

• inhibiting the operation of said inverter means with said control means during a first succession of contiguous plural document circulations to copy only one side of said documents,
• actuating said inverter means with said control means to invert the document set during a document circulation after the document set has been circulated a number of times substantially equal to the quotient of a constant number divided by the number of document sheets in said document set,
• inhibiting the operation of said inverter means again to copy only the other side of said documents in a second succession of contiguous plural document circulations substantially equal to the number of documents set circulations in said first succession, and
• repeating said actuations and inhibitions of said inverter means and said first and second successions by a number of times determined by said control means.

In a method of pre-collation copying a set of a known number of duplex document sheets, wherein the documents can be inverted an odd total number of times during a circulation with inverter means, to copy opposite sides of the document in a subsequent circulation, controlled by a control means;

• the improvement comprising:
• actuating said inverter means with said control means to invert the document set during the first document set copying circulation;
• inhibiting the operation of said inverter means with said control means during successions of subsequent contiguous plural document copying circulations to copy only one side of said documents;
• actuating said inverter means again during only single document circulations at the end of each of said successions, which occurs each time after the document set has been circulated a number of times in succession equal to the quotient of a constant number divided by the number of document sheets in said document set, to copy opposite sides of said documents in alternate successions of equal numbers of plural document set circulations;
• said inverter means being so operated by a number of times determined by said control means from the total number of copies to be made;
• and
• wherein the copies made in alternate said successions of document circulations are temporarily stored in a buffer set of a pre-determined maximum copy sheet capacity, and wherein said constant number corresponds to said copy sheet capacity.