Type printing telegraph
The type printing telegraph is a telegraph from the 19th century developed by David Edward Hughes in 1855 , which was also called "Hughser" by the post office at the time.
functionality
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The mechanism is less simple, but its efficiency is significantly greater than that of the Morse apparatus , over which it also has the advantage that the telegrams arrive in normal printed letters and are therefore legible for everyone without translation.
At the front of the table is the keyboard , consisting of 28 keys , which are described with letters , numbers and punctuation marks and which, when pressed, establish the connection between the battery and the cable; behind it, between the upright apparatus cheeks, is the moving carriage with a weight of 60 kg, connected to a braking device and the regulating lamella mounted in a cast-iron extension piece of the apparatus table; to the left of the drive is the electromagnetic system, and on the front wall of the machine you can see the printing device with the type wheel, which also includes the roll of paper attached to the right. The device on the left rear corner of the table top is a toggle switch that allows the direction of the telegraph current to be changed at will.
The electromagnetic system of the Hughes apparatus consists of a powerful steel magnet in the shape of a horseshoe, on the poles of which two hollow cores of soft iron surrounded by electromagnetic rollers are placed in such a way that they form the extension of the poles and have opposing magnetic poles themselves at their upper ends with pole shoes .
Opposite the pole pieces and resting on them when at rest, there is the flat iron anchor, which is easily rotatable between two brass stands around the tenon screws and is provided with two steel springs reaching downwards that rest against the adjusting screws.
With the help of these springs, the armature snaps off as soon as a current flows through the electromagnet from such a direction that its polarity is weakened. The armature strikes the lever of a locking device when it falls off, triggers it and thereby causes the coupling of the printing device with the drive and the imprint of the character that is at the lowest point of the type wheel at that moment.
Because the attractive force of the magnet is not sufficient to return the detached armature to the pole shoes by overcoming the opposing force exerted by the tension springs, Hughes transfers this work to the mechanics of the apparatus by using an eccentric attached to the pressure axis to move the arm on the right of the release lever G up again and thereby lets the armature press down onto the pole shoes, which then hold it in place until the next current pulse. At the same time, the coupling is automatically canceled again during this process, the pressure axis remains stationary and the release lever returns to its old position after it has returned the armature.
The pressure axis forms the front extension of the flywheel shaft. The latter carries on its free end a ratchet wheel provided with fine, crooked teeth and a pin onto which the pressure axis is pushed with its rear, correspondingly hollowed end. The two-armed cross-piece is attached to the rear end of the pressure axis and carries the rotatable pawl on the one hand and the spring pressing against the pawl on the other. At rest, an extension piece rests against the stop of the release lever, while a conical extension attached to the pawl rests on a prismatic piece of steel, the so-called inclined plane, attached to the angle.
If the right arm of the release lever lowers, the conical extension of the pawl slides down from the inclined plane, the pawl engages in the teeth of the ratchet wheel, and the coupling of the pressure axis with the flywheel axis, which constantly participates in the movement of the drive, occurs . After completion of one revolution, however, the locking cone meets the prismatic attachment m again from the right, rises on the same and thereby lifts the locking comb out of the teeth of the ratchet wheel; the coupling is therefore automatically canceled each time.
On its front part, located outside the apparatus housing and mounted in the brass bracket, the pressure axis is provided with several differently shaped lugs which activate the pressure device. The type wheel bears the letters, numbers and punctuation marks in raised engraving on its periphery; it sits with two other wheels, the correction wheel visible in the figure and the so-called friction wheel, on the same axis, but in such a way that only the friction wheel participates in the movement of the drive, while the front wheels, which are attached to a bushing, rotate freely move the axle and only participate in its revolutions if they are connected to the friction wheel by a similar engagement device as is used to couple the flywheel shaft to the pressure axle.
On the correction wheel with 28 sharp teeth is the figure change connected to the type wheel by a special socket. The latter consists of the two-armed lever, the arm of which plays within a round section of the steel disc. Depending on whether one or the other projection of this disk covers a tooth gap, the lever and thus the type wheel assume a position shifted by one field of the character string.
Since letters and digits or punctuation marks alternate with one another on the circumference of the type wheel, letters are printed in one case, and digits and punctuation marks in the other. Turning the lever causes a thumb of the pressure axis, which hits a tooth gap of the correction wheel with each rotation and corrects its position in such a way that it advances the correction wheel and with it the type wheel slightly through the pressure exerted on the rounded teeth of the same, if it lagged, and pushes back when it was advanced.
The gaps under the projections of the change lever correspond to two free fields of the type wheel, which are used to create the gaps. In the resting state, the correction thumb rests on the insulated spring attached to the ebonite angle and thereby creates a conductive connection between the body of the apparatus and the electromagnet. The printing of the characters takes place in such a way that the paper tape is thrown against the type disc, which is in full rotation, and of the types moistened with printer's ink, the one that is at the lowest point of the wheel at the moment in question is removed.
This uplifting of the paper tape guided over the pressure roller causes a thumb of the pressure axis, which hits against the upper nose of the rotating pressure lever; At the same time, the paper strip advances by a type width by pressing down the lever and with it the arm through another approach of the pressure axis, the hook-shaped approach engaging the teeth of a ratchet wheel connected to the pressure roller and thereby rotating the pressure roller.
The three-armed setting lever is used to bring the correction wheel and the type wheel out of connection with the drive and to hold them in the rest position. A pressure exerted on the button of the horizontal lever arm first brings the pin, which serves as a carrier, into contact with the leaf spring underneath, which is attached to the ebonite piece and which is directly connected to the line; only when the electromagnet is switched off, the lever follows the pressure downwards and causes the connection between the correction wheel to be broken by an extension of the arm, which brings the leaf spring with its steel extension into the area of a pin attached to the pawl of the correction wheel. and type wheel and the drive. The setting lever is triggered and the coupling with the ratchet wheel is released by striking a shoulder pin of the pressure axis against the extended end.
The current is generated in the Hughes apparatus by means of a keyboard of 28 keys, which are arranged in two rows one above the other; the top row is black, the bottom white. All keys, with the exception of the first and fifth white ones, starting from the left, are each marked with a letter and a number, respectively. Punctuation marks. The white keys are used to create the spaces; they correspond to the noses of the change lever and are therefore also struck when switching from letters to numbers or vice versa.
The key levers pivot on axes attached to the lower surface of a thick cast iron plate; on this plate rests by means of the flange-like approach, the pin sleeve, which is provided with vertical incisions at its lower edge. When a key is depressed, the free end of the key lever engaging through an incision in the pin socket lifts a contact pin resting above it with its upper, hook-shaped end along the inclined surface of the conical ring from the pin disk and brings it into the path of a vertical inside the steel sleeve Axis w mounted above the pin disc rotating carriage, which is given the same angular movement with the type wheel through conical toothing with the type wheel axis. When the button is released, the pen is pulled back into its rest position by the spring.
A steel bushing with protruding edges is pushed onto the slide axis. The fork-shaped brass piece is permanently attached to the axle, the middle protruding part of which carries a curved piece of steel, the so-called strop rail, at its lower end. The two outer arms serve as axle bearings for the moving part, the center piece of which, on the outside, contains the downward-facing, beveled steel strip, the lip. The other end of the movable part forms an angle lever, which rests with a steel pin attached to the side on the further edge of the bushing and presses it downwards when the lip moves upwards.
The brass angle is screwed on the left side of the front device cheek below the axis of the release lever; it forms the bearing for the two-armed contact lever. On the right, this lever carries a steel pin attached to the side, which grips under the upper protruding edge of the sleeve, so that when it is raised and lowered, the leaf spring attached to the left lever arm alternately touches the contact screws and, one of which with the battery, the other is connected to earth, while the lever itself is connected to the line through the body of the apparatus and the electromagnetic pulleys.
Every time the carriage passes a raised contact pin, the lowering of the socket and lever arm sends a current into the line, which causes the apparatus to respond to both the issuing and the receiving office and causes the relevant letter to be printed . The speed of rotation of the slide is 100-120 revolutions per minute.
See also
literature
- Sack: The Hughes Printing Telegraph (2nd ed.). Vienna 1884.
Individual evidence
- ↑ Deutsche Postzeitung, Volume VII (No. 22), November 16, 1896, p. 497