Type lever typewriter
The type lever typewriter is a typewriter whose types are attached to individual levers . After it was perfected by Franz Xaver Wagner , the construction became the most widely used from 1893. Further developments mainly concerned only an improved mechanism for the movement of the type lever and the electromotive support of the hand control. The type lever typewriter was replaced by models that had a compact type carrier instead of individual type levers, a ball head or a type wheel on which all types were housed together.
left: typing keys; behind and above large gear: type lever ; above: platen; in front of the platen: ink ribbon in a cylindrical housing
Type lever gear
A: button lever, B: intermediate lever, C: type lever, D: roller
All levers are rotatably mounted in the machine frame (the levers are connected to one another with a rotary slide joint (pin in fork)).
Rest position: lightly drawn levers;
Type stop: hatched lever
The characteristics of a type lever machine are the types that are individually attached to levers. This distinguishes it from other typewriters, especially those designed later, which use a type carrier on which all types are arranged together (type roller, ball head, type wheel). For each type carrier there is a separate type lever mechanism, with which it is hit on the paper lying on a roller by pressing the corresponding write key.
The success of the type lever typewriter was based, among other things, on the replacement of older type lever mechanisms with the Wagner gear . Wagner had improved the transmission between the key and the type lever by adding an intermediate lever. The three levers that swing back and forth in the machine frame form two coupled three-part gears: 1. gears with the links of the button lever, intermediate lever and frame; 2. Gearbox with the links intermediate, type lever and frame. Each lever is connected to the next one via a double joint (pin in fork, which both rotates and shifts in it).
In 1907, the Royal Typewriter Company of New Jersey launched the Royal 1 typewriter , which included an improved Wagner gearbox. The inventor Edward B. Hess replaced the double joints with coupling links with two swivel joints each, resulting in a six-link transmission with only swivel joints. The coupling links were relatively rigid pieces of wire, which is why the name pull wire gear (otherwise also Hess drive or Royal gear) became established. With this type lever gear, which has also been modified in terms of its geometry, a high stroke speed of the type lever with more ergonomic key movement was achieved (initially low, later higher key force). It was later adopted and retained by all manufacturers of lever type typewriters.
Since the type levers all have to hit the same point in the middle of the machine, Franz Xaver Wagner invented the so-called type lever segment . The bearing points of the type levers in the frame are arranged in a vertical semicircle with the stop point in the middle. This means that all type levers are of the same length and have the same drive conditions.
As a rule, there are two types of the same letter on top of each other on each type lever, one in lower case and the upper case letter above. Switching to capital letters is triggered using the shift key : Either the writing pad ( platen ) is raised or the type lever segment is lowered.
Platen
The platen is a steel cylinder covered with a thick rubber cylinder. In ordinary type bar typewriters it is little more than a DIN - A4 -Blatt is wide, so that it can be described in full width from the left to the right edge. Machines with wide carriage are intended for A4 crossways (corresponds to A3 lengthways ). This was the condition for a typewriter to be considered an office typewriter .
Rubber rollers wear out over time. The rubber becomes hard and, due to the fact that on machines with a fixed font width, the types repeatedly hit the same place on the platen, over time, groove-like depressions are formed. The rollers are cleaned and roughened during maintenance using suitable solvents (at the time trichlorethylene and perchlorethylene , after which other highly toxic halogen-containing compounds were later banned ) or denatured alcohol . In very bad cases, the roller can be sanded down by a few tenths of a millimeter on a lathe . If this does not help anymore, the rubber flooring has to be renewed. In the heyday of the typewriter, many car tire manufacturers, as specialists for rubber vulcanization, had such a platen service in their program, for example Continental AG .
Ribbon transport, lift and switching
With a type a character is printed with the help of a ribbon between the type and the paper . The tape made of natural silk, cotton or nylon releases some of the ink with which it is soaked onto the paper. So that the writing can be read immediately, the ribbon is only lifted with the ribbon fork while the type is being opened. Modern ribbons often have a different color in the upper half than in the lower half (mostly black above and red below) or, since the 1980s, often black and correction white to cover up false characters. The user of the appropriate typewriter selects the color by adjusting the stroke of the ribbon fork. When the hub is switched off, writing is carried out without color, for example on permanent stencils (so-called wax matrices ).
dare
In lever type typewriters, the segment with the type levers is firmly mounted, and the platen, which is attached to a carriage, the so-called carriage, moves with the writing paper against the direction of the line, i.e. one step to the left with each character stroke. The carriage is driven off with the help of a strong clock spring mechanism that winds up when the carriage is pushed to the right (beginning of the line in the middle of the segment).
Stepping of the car
After each stop, the carriage is moved to the next free space for the next stop. The step size of the type lever typewriter is normally fixed due to the design. There are models with 10, 12 and 15 characters per inch ( CPI ). Some machines have a switchable blocking function , with which each character triggers two steps. Step switching on machines with proportional font is rare and mechanically very complex . Each character triggers the appropriate step size.
Carriage return
At the beginning of a new line, the carriage is pushed back by hand using the line shift lever . The platen is also rotated by the line spacing to be set on the carriage beforehand . Single line spacing (DIN 5008) and 1.5 lines are common. With many machines, however, you can also advance up to 2.5 lines. When the carriage is pushed back, a clock spring is pulled up, which enables the carriage to write, which triggers the switch nose of the type lever when it hits the switch bracket behind the segment.
The platen can also be turned further independently of the line switch lever with the aid of one of the rotary knobs at its right and left end. After that, your line indexing gear will snap into place again after half a line spacing or several half lines. In the case of a so-called piercing roller , the coupling of the switching gear with the roller can be continuously adjusted and in this way, for example, a form with preprinted lines can be positioned at the appropriate height. The so-called roller grooving button for momentary release of the clutch is usually located in the center of the left roller turning button.
Edge settings
The edges of the writing surface are defined by markings that can be moved on the carriage. The left marking limits the carriage return for the beginning of the line. On the right-hand edge, the keys that trigger the carriage feed are already blocked, but this is announced mechanically with a bell before about 10 characters can be written. The margin lock can be released using the margin release button and a few characters can be continued or started with them before the left margin.
Paper feed lever
Most office typewriters have a special lever on the cart to quickly and easily pull a sheet of paper over the platen. A setting wheel can often be used to preselect the position up to which the sheet should be drawn in when the paper feed lever is fully lifted.
Paper release lever
The paper release lever releases the pressure springs that press the paper tray against the platen via small pressure rollers. This is used to gently remove a finished sheet of paper. It is often shown in films that the author of a typewritten document simply pulls on the paper and thus removes the sheet from the machine with a rattling noise in the line break. This type of paper removal “thanks” every typewriter in the long run with a line break that is defective due to wear and tear. In addition, the paper release lever is used to release a sheet of paper that has been clamped at an angle so that it can be aligned.
Switching
Switching between small and large letters (lowering the type lever segment or lifting the carriage with the platen) is done by pressing a toggle key. This is to be pressed simultaneously with the write key of the corresponding letter. There are two toggle keys for typing with the ten-finger system , one on the left and one on the right in the keypad. The shift lock to lock the capitalization is located above the left shift key . It enables progressive capitalization without the need to keep pressing a shift key.
Some older machines, which had a double-sized keypad (so-called full keyboard ) for separate upper and lower case, therefore did not have a shift key.
Special buttons
Space bar
The space bar moves the carriage one typing step further without a character being hit.
Dead keys
A dead key does not trigger step switching, but a character is written. The next character is then printed in the same place. Dead keys are used for accentuations ( accent aigu , accent grave , accent circonflexe ). To do this, you first hit the accentuating or dead key, and then the letter to be accented, which triggers a step sequence as usual. The accent circonflexe is composed of the accent aigu and the accent grave, which are on a common dead key. Press this key one after the other without and once with the shift key. In addition to the accented dead key, some Swiss keyboards have another dead key to display the umlauts written in German with a trema (two dots).
The type lever belonging to a dead key lacks the switching nose so that the switching bracket behind the segment is not hit.
Tabs
tab
With the help of a tab device ( tab key ), characters can be saved in columns, e.g. B. arrange them in lists and tables. With such a key, a so-called tab stop can be set and removed again at any point in a line . The tab stop is a small slider on the back of the carriage that is pushed into the working position or back into the rest position. It is also possible to push back all set tab stops together. If you press the tab key again, the step-by-step circuit is disengaged and the carriage moves to the next tab position. If no tab stop is set, the carriage drives to the right edge. In order to avoid excessive noise or even damage in the heavy trolleys of the office typewriters, a centrifugal brake is usually engaged when the step-by-step switch is disengaged, which prevents the trolley from being transported too quickly.
Decimal tab
The decimal tabulator is a further development of the tabulator (see above), with which it is usually also used. It enables decimal numbers to be spelled correctly one below the other for accounting purposes, that the decimal separator (in German a comma, in English a point) is in the same column below one another. There is a decimal tab key for 10, 100, 1,000, 10,000 and 100,000 digits. For example, if you want to write the number 12,345.67 under the number 678.90, you usually set the tab stop to the position of the ones place and approach the position for 678.90 with the 100 tabulator. The car now comes to a stop exactly at the position for the 6. In the second line, you then press the 10,000 tab, with which the car stops at the position of the 10,000 digit.
Electromechanical type lever typewriter
With the electromechanical type lever typewriter, “typing” is supported by a motor. The effort required to hit the keys is less than with the older, purely mechanical type lever typewriter. The type levers hit the paper with the same force, which results in an almost even typeface. However, the function of the electromechanical type lever typewriter is not fundamentally different from that of the fully hand-operated type lever typewriter.
Type lever drive
An electric motor is used as the drive, which drives a shaft lying transversely in the machine. In the original design, this is a toothed shaft, which can be thought of as a very wide gear. The actuation of a write button no longer acts directly on the type lever, but triggers a drive lever that is brought up to the splined shaft and taken along by it. The drive lever acts on an intermediate lever, which moves the type lever to the stop with the help of a pull wire. Immediately afterwards, the drive lever disengages and falls back into its starting position.
In some machines, instead of the largely wear-free splined shaft, a rubber roller is installed, which drives the respective type lever via a so-called slip or friction lever. This system is more susceptible to wear and maintenance than the splined shaft, but allows the respective stop force to be set separately for each individual type lever. The punctuation mark “point”, for example, does not have to be hit with the same force as the letter “W” in order to produce an imprint with the same density of color on the paper.
Some keys, such as the hyphen and the underscore as a toggled character, but also "double line", "point" and "X" can be pressed a little deeper against a slight resistance behind the normally defined pressure point of the keyboard and thus trigger an automatic repeat stroke ( Permanent function).
Better models have a key lock that prevents two type levers that are struck at the same time from jamming. If two keys are struck together, the entire keyboard is blocked for one revolution of the drive roller.
Carriage return
The carriage return takes place with the electrically operated type lever typewriter motorized. For this purpose, when the carriage return button is pressed for the first time in this type of machine, a clutch is triggered, which pushes the carriage back with the power of the motor and performs a line feed. In terms of its function, this key corresponds to the return or enter key used on computer keyboards in use today.
Switching
Switching between lowercase and uppercase letters is also supported by a motor in the electromechanical models.
literature
- Otto Lueger: Lexicon of the entire technology and its auxiliary sciences, Bd. 7 Stuttgart, Leipzig 1909, pages 808-813.
- Brockhaus' Kleines Konversations-Lexikon, fifth edition, volume 2. Leipzig 1911, p. 655
Remarks
- ↑ Sketch of a pull wire gear