A toner drum is a part of a xerographic copier. It is the part to which the toner adheres to before the image is transferred to the paper. It has a long life but will occasionally have to be replaced depending upon the volume of usage of the copier.
History
The toner drum was first patented in 1958. There were two patents issued that year for xerographic type toners. The first was issued to Vyverberg and the second to Wilson. Both were for corona type electrostatic devices. Since that time numerous improvements have been made to the toner drum, with subsequent patents being issued. One of the more modern versions of the toner drum was patented by the Xerox Company in 1991.
Process
When you place an article to be copied on the copier's surface, the beam of the printer's laser passes across the surface of the photo-receptive drum; this beam causes the area of the drum onto which it passes to take on a negative charge. This negative charge causes a reverse image of the document or image to be printed to be etched on the surface of the toner drum. The toner drum then rolls past the toner cartridge. The positive charged particles in the toner then stick to the negatively charged image etched on the toner drum.
Effects
The paper onto which the image is to be printed is passed under a corona wire. This corona wire has a strong negative charge and causes the paper to have a negative charge. When the toner drum passes over the paper, the strong negative charge of the paper draws the toner particles onto it. The toner particles contain iron particles that allow the particles to be drawn to the negative charge of the paper. Once the image is transferred to the paper, it passes under another corona wire, which gives it a positive charge. The paper then passes through heated rollers that fuse the image to the paper.
Final Process
After the image is transferred to the paper, the toner drum rotates under another corona wire, which gives the toner drum a total positive charge. Now the toner drum is ready to begin another image.
Benefits
Toner drums have a very long life. They are self-cleaning and require very little maintenance. They are constructed to be easily replaced by a copier technician. Old mimeograph-type copiers were extremely messy, requiring daily maintenance to clean the copying surface and use of hazardous chemicals for the image transferring process. Much progress has been made in the xerographic process in the past quarter century; you can only imagine the progress that will be made in the next.
