 |
(1)The original glass, is moving in the direction of arrow A. (2)- Scanner Lamp (3)- 1st mirror. (4)- 2ed mirror. (5)-Depending on the machine could be a straight through lens that directs light directly to the drum or a CCD lens that converts light to electrical data. (6)-Drum (7)-Laser (digital copiers) (8)-Polygon Mirror (digital copiers) (9)-Imaging Lens (digital copier) |
** A Basic Copier **
SCANNING THE ORIGINAL: To keep it simple, glass or original moves past
the Scanning system, like fax machines. Most copiers (and flat bed
scanners for that matter) scan the original by moving the scanner lamp
and 1st mirror as one assembly.
1) Exposure- The original glass (fig 1 item 1) is illuminated by the Scanner (fig 1 item 2), and the reflected image through a series of mirrors (fig 1 items 3 and 4) is sent to the Lens or CCD (fig 1 item 5).
If the machine is an analog unit you can skip to step 2A.
In a digital machine the image information is sent to the laser assembly, the light coming from the laser (fig 1 item 7) is turned on and off by different means, by a shutter mechanism (not shown) or by digital on off circuit, there may be another mirror to reflect the light across the imaging lens but it is the Polygon mirror (fig 1 item 8) spinning at a high speed that reflects the light to the drum, the laser is timed to hit one of these mirror facets at a certain time and reflect it to a certain part of the drum. Although all of this is happening at a high speed to the laser its as if the spinning mirror and drum are standing still. Go to step 2B.
OKAY HERE COMES THE HARD PART:
2A) In an analog machine, where there were light areas in the original, light will strike the drum and remove the charge there. This results in high and low charges on the Drum in proportion to the scanned original. This results in an invisible electrical image on the Drum called 'The Latent Image".
2B) In a digital machine where there were light areas in the original, laser light will not strike the Drum (where no light strikes Drum, no toner will be attracted). Where there were dark areas on the original, laser light will strike the drum. This results in an invisible electrical image of high (no light on drum) and low charge areas (where light hit drum). This invisible image is called 'The Latent Image'. Go to DEVELOPING THE IMAGE.
Whew! Now that we got an idea of what the heck a latent image is lets develop it.
If you have an 80 copies per minute unit, imagine the following happening in less than one second!
DEVELOPING THE IMAGE: The machine is in standby and someone initiates the print cycle.
1) The Charge Corona (fig. 2
item 1) is energized with a high DC voltage. It ionizes the air
charging the Drum surface with an electro-static charge.
2) Light exposes the Drum and creates the Latent Image (fig 2-2).
Toner (in the Toner Hopper fig 2 item 3) moves into the Developer Unit (fig 2-4).
The Toner (which is a thermal plastic resin in powder form) mixes with the Developer powder in the Developer Unit (fig. 2 item 4). Developer powder is a metallic powder and will be held by the magnetic developer roller (fig. 2-5). Have you ever seen metal filings on a magnet- they stand up like a brush; well the Developer powder held by the magnetic roller creates the 'Magnetic Brush' (fig 2-5).
3) The Latent Image passes over the Magnetic Brush and Toner is attracted (by Static Charges) to the Latent Image. The Latent image is developed (becomes visible).
Paper is moving (arrow B) between the Drum and The Transfer corona (fig 2-6).
4)Transfer corona is energized and pulls Toner from Drum to the paper.
5)Separation corona (fig. 2-7) is energized and an AC charge nuetralizes the charge on the Drum and the paper falls off.
6)Lower Pressure Roller (fig 2-8) presses the paper against the Upper Heater Roller (fig. 2-9) that is hot (and by a lamp or heat element) Fixes (melts) the Toner to the paper. The paper exits.
7)Cleaning Blade (fig 2-10) scrapes the Drum clean of left over (residual) Toner (causing a slight residual charge on Drum).
8)Discharge Lamp (fig 2-11), (and or a discharge corona) illuminates the Drum surface with a low intensity lamp removing any remaining charge.
The machine is in standby.