Drum printer
Drum printers (also: type roller or roller printer ) belong to the line and impact printers .
The most important component of the drum printer is the so-called type drum . On this there is a disc with all printable characters for each print position. There is a ribbon between the roller and the paper. This roller is rotated. As soon as the desired letter appears, it can be printed. However, since the roller is too heavy to be used to strike the letters, it remains in its position. Instead, small hammers (there is one for each printing position) hit the paper at the right moment and press the paper and ribbon against the roller.
However, since you rarely want to print a complete line with the same character, in the worst case (i.e. when every printable character occurs) a line is only completely printed when the roller has completely rotated once and thus the associated character at each printing position Hammer happened.
If the point in time at which the hammer is to hit the ribbon and paper is missed by even a millisecond, the roller with the letter in question has already moved on again. This causes some letters to "step out of line" up or down on the printout. This effect could only be reduced with chain and steel belt printers . Bold print and semi-graphic print could be achieved by multiple overprinting in the same place.
Drum printers reach speeds of several hundred lines per minute. It was printed on continuous paper. The noise of the little hammers was so loud that the printers were operated under noise protection hoods and the operators wore hearing protection .
Small drum printing units with rollers made of metal or plastic are used in table calculating machines , including types in which the drum is elastic and "bulges" from the inside. The first "mini printer" ever, the EP-101 from Shinshu Seiki , also had a drum printing mechanism.
Individual evidence
- ↑ Epson EP-101 (PDF; 209 kB)