Springfield, MA-To make laser printers as reliable as possible, engineers group critical wear items with the consumable toner. Every time you change the cartridge, you replace the print and developer drums too.
Of course, this design choice makes laser toner cartridges relatively expensive, so manufacturers have tried various means of extending the unit's life. Increasing the size of the toner hopper, for example, has been tried, but often results in caking that makes the toner unusable.
In contrast, the Perfect cartridge from RTI Corp. promises a twofold increase in throughput without a problematic increase in toner-hopper volume. "The design lets us guarantee increased yield," explains Peter Trotter, RTI's president.
Compatible with the ubiquitous Cannon SX print engine, two features distinguish the Perfect cartridge. The first is a variable-position magnetic element in its developer cylinder. Second is a proprietary change in the organic photoconductor (OPC) that coats the cartridge's imaging drum.
In a laser printer, modulated laser light strikes the rotating OPC-coated drum, creating a latent image as regions of unequal electrical potential. Adjacent to the imaging drum, the developer cylinder rotates at the lower opening of the toner hopper, transferring toner particles from the hopper to the latent image on the drum.
Ferro-plastic toner particles adhere to the developer because of a non-rotating magnetic member within the rotating cylinder. The alignment of the poles of this member with the toner-hopper opening and with the drum surface greatly affects the uniformity of toner transfer.
RTI's research showed that toner cartridges exhibited a wide deviation from optimal alignment in units where the magnetic member was held by fixed mounts. The company's solution: adjustable developer-cylinder endcaps that fit within the profile of standard cartridges.
The endcaps allow free movement of the magnetic member within the rotating developer cylinder. One endcap features a tab for manual rotation of the magnet and the other has a set screw for securing the magnet's position. Once the cartridges are completed, assemblers set and fix optimum magnetic-pole alignment. The resulting more-uniform toner distribution delivers better print quality and virtually complete emptying of toner from the hopper, i.e., longer life.
Trotter estimates that the performance improvement by the Perfect cartridge can be attributed 75% to the adjustable magnetic design and 25% to improvements in the OPC drum coating. "It's a longer-life drum than standard," he says. "We found that we needed it."
Additional details...Contact James Mokhiber, RTI Corp., Box 400, Oakland, NJ 07436, (201) 337-5501.