Lexmark International, Inc.

Gregrory Lawrence Ream

Benjamin Keith Newman

David Lee Merrifield

Phillip Byron Wright

Gary Scott Overall

James J Molloy

Thomas Campbell Wade

Steven L Applegate

Cyrus Bradford Clarke

Timothy P Craig

Thomas Gregrory Survant

An improved electrophotographic (EP) printer is provided having a detachable process cartridge that contains a non-volatile memory device, which is an EPROM that cannot be erased after a bit is burned. A 'toner wheel' mounted to the exterior of the toner reservoir of the process cartridge provides, in conjunction with an optoelectronic sensor, an electrical signal that the printer receives and uses to determine toner usage. A toner 'gas-gauge' is created which uses 'bucket levels' as discrete steps to indicate how much of the measured physical toner material actually remains within the toner reservoir. After a given amount of toner material has been dispensed through the developer unit, one of the bits of the EPROM memory device is irreversibly burned, thereby providing a permanent record on the process cartridge of a certain amount of toner usage. As with a normal automobile gas gauge, the toner gas-gauge reading should never increase unless the amount of toner material inside the toner reservoir has increased. Once the bucket level transitions begin to occur for the toner gas-gauge, the printer becomes aware that a majority of the toner material has been expended from inside the toner reservoir. If the number of bucket gradation levels then increases by more than the hysteresis amount, then the printer will 'lock out' the operation of a non-reusable process cartridge. When the lock-out mode occurs, a particular bit is burned on the EPROM mounted to the cleaner housing of the process cartridge. This ensures that this particular process cartridge cannot be removed, then simply placed back into the same (or a different) printer, and then begin supplying toner to a printer. Certain important 'machine data' also can be stored in the EPROM memory device on the process cartridge of the present invention. The present invention is also able to declare the 'end-of-life' of a process cartridge when the gas-gauge toner sensor is not functional (such as when it has been tampered with).

Method and apparatus for storing data in a non-volatile memory circuit

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Lexington, KY, United States of America

Gregrory Lawrence Ream