Silicone Rubber Heater In High Speed Laser Printer

Problem:

Computers can store and manipulate great quantities of data. However, the information output speed is often limited by the printer's capabilities.

Solution:

A new computer printer style uses Watlow silicone rubber heaters in a process capable of printing 43 full size sheets per minute - complete with forms, headings and graphics. This printer eliminates the need to stock standard forms, thereby reducing inventory costs.

Within the printer, a computer-controlled laser scans the image onto a photo-conductive drum. This drum contacts blank paper and attracts a dry toner onto its surface. The paper is then drawn across a heated Teflon^® coated plate (with a Watlow silicone rubber heater vulcanized to the inside) to cure the toner onto the paper's surface.

This application required quick thermal response for fast-paced changes in paper flow. To achieve this, a very thin etched foil heater was vulcanized to a light aluminum plate, to produce a low thermal mass. Thin silicone rubber insulation provided excellent thermal conductivity while maintaining electrical isolation to withstand a 2000 volt hi-pot test. Built-in thermocouples sense the plate temperature and thermal fuses eliminate the possibility of thermal runaway.

The heater must be capable of providing uniform surface temperatures for a variety of paper widths. To accomplish this, our heater features multiple, individually controlled, circuits including several with distributed watt densities. The assembly is perforated with dozens of small holes, which are part of a vacuum system in the final installation. The foil circuits were carefully laid out to clear each hole while minimizing no-heat areas.

The resulting system represents a significant advance in computer hardware technology.

Teflon^® is a registered trademark of DuPont.