Type wheel
The daisy wheel (. English daisy wheel , literally daisy-wheel ) is next to Type lever and ball head of the most common types of carriers of electromechanical typewriters .
A type carrier in the form of a wheel is used for the manual production of embossed labels .
Mechanical cash registers each had 1 type wheel per column, which carried the types on the face.
Drum printers have type rollers.
General
The typewriter types are on a type wheel on resilient radial, i. H. arms arranged in a star shape. By turning the wheel, the desired character is brought into position and struck against the ribbon and paper with an electromagnetically operated pen . The font can be easily changed by exchanging the type wheel . Some manufacturers (e.g. Brother ) used a type wheel surrounded by a housing ( cartridge ) so that it remained protected even when changing and storing.
Type wheel printing with PC
In the early days of the personal computer, typewriter manufacturers offered not only an RS-232 connection to the computer but also separate printers with a type wheel as computer peripheral devices. The type wheel printers achieved the significantly better typeface compared to the dot matrix printers common at the time , especially in connection with carbon ribbons . They were therefore suitable for business correspondence, but were limited to the character set of the type wheel.
The manufacturer-specific character wheel character set did not always match the PC character set. In such cases driver or TSR programs were used, which carried out the necessary conversion during printing in the background.
history
Around a hundred years ago there were already two type carriers who combined all types on a single body. They were the forerunners of modern ball heads and type wheels.
- In the case of the type cylinder (also known as type roller), the types were arranged on a cylinder surface in several circles (planes) . The AEG Mignon pointer typewriter had a type cylinder with twelve types each in seven levels . The slightly curved 7 × 12 control panel of this typewriter was the flattened cylinder surface.
- A shorter type cylinder with a larger diameter is also called a type wheel in the older specialist literature, although the types were arranged in at least two, mostly three levels . It made it possible to control the most common types from the buttons with less mechanical effort. The type wheel of the Blickensderfer typewriter had 30 types each in three levels , so it had a significantly larger cylinder diameter than the type carrier of the Mignon.
- Different typewriter models were developed for both type carriers, which solved the operation and motion transmission in different ways. From these type carriers the modern ball head emerged, which differs from the historical type cylinder by the spherical shape and the tilting movement (instead of axial movement).
- The modern type wheel has only one level , or with it the types are arranged in a geometric level . As a result, the axis of rotation is not oriented transversely, but perpendicular to the surface of the sheet. Although it appears to be a step backwards, the modern type wheel is considered to be a technical advancement of the ball head, which for a long time was considered unsurpassable. The more filigree wheel is only about half as heavy as the more massive head (around 5 instead of 10 grams), it only needs one axis of movement (no planes ) and thus enables a simpler mechanical control that is much cheaper to manufacture than the spherical head technology and which remains almost maintenance-free over the entire service life. This makes it the only remaining whipping method for typewriters, mainly for economic reasons.
- In the summer of 1978, Olivetti launched the TES 401 memory typewriter and the ET 101 (basic model without memory function), the world's first type wheel typewriters. Other manufacturers did not follow until 1980, IBM held on to their ball head technology until 1994.
Drive technology
In an electromechanical typewriter with a type wheel, it is not the carriage with the platen, but the type wheel and its drive motor that move in the line direction.
When rotating the type wheel, two different construction principles are used, there are two different type wheel printing units.
Endurance printing unit
In the so-called endurance runner , the earlier and now obsolete technology, the type wheel rotates constantly at a constant speed. In the simplest version, one of the type carrier rods is extended. With each turn, his nose briefly passes a forked light barrier and generates an impulse. The fixed time intervals between the impulse and the writing position of the types are electronically stored so that the pen can hit the stick with the selected type at the right moment. The stop pin strikes very quickly and quickly returns to its starting position, so that the type wheel does not have to stop and the imprint is nevertheless sufficiently clear. Instead of an extended type bar with a forked light barrier, other sensors for generating a synchronization pulse are also possible. In order to save energy, the "endurance runner" can also be switched off in a time-controlled manner during writing breaks. This technology was only used on very early type wheel printers.
Inverting printing unit
While still used today change direction printing unit one is with most manufacturers stepping motor used for rotating the type wheel located on its axis by the shortest route forward or backward to the next required type. When Olivetti was used instead in some models DC motors with encoders, where the angle of rotation is monitored via a slotted wheel and a light barrier; the motor is then held in position by a high-frequency alternating voltage. Even rotational movements of the user when changing the type wheel can be recognized and corrected in this way. At the US manufacturer Exxon, the type wheel was the rotor of a linear motor; The print head was also the moving part of a linear motor, which enabled high printing speeds to be achieved. Since the type wheel stands still with each print, the stop pin can strike more slowly. The speed of this type of printer was increased by placing frequently used types next to each other on the type wheel. The type wheel is also designed to generate a pulse that is only required once for calibration (zeroing) after switching on the typewriter. Newer type wheels from Olivetti have small reflective surfaces on the inside, which have a different coding depending on the font. When you insert a new type wheel, the machine reads out this coding with one turn and recognizes the font type, velocity depending on the font size, nationality and step size of the font and automatically sets them, or refuses to use a type wheel that does not match the Keyboard matches.
Remarks
- ↑ Werner von Eye: History of the typewriter and machine writing. H. Apitz, Verlagbuchhandlung, Berlin 1941, Figures 17 and 23.
- ↑ Werner von Eye, 1941, p. 16
- ↑ Ernst Martin : The typewriter and its development history. Johannes Meyer, Pappenheim 1949, pp. 554–56.
- ↑ Werner von Eye, 1941, Figure 20
- ↑ www.stb-betzwieser.de: Selection of historical typewriters with type cylinder or type wheel