pantograph

Drawing of a pantograph, showing linkages of Sorenson's engraving pantograph (1867).

A pantograph (from Greek roots παντ- 'all, every' and γραφ- 'to write', from their original use for copying writing) is a mechanical linkage connected in a special manner based on parallelograms so that the movement of one specified point is an amplified version of the movement of another point. If a line drawing is traced by the first point, an enlarged (or miniaturized) copy will be drawn by a pen fixed to the other.

History

The first pantograph was constructed in 1603^[1] by Christoph Scheiner, who used the device to copy and scale diagrams, but he wrote about the invention over 27 years later, in "Pantographice" (Rome 1631).^[2] One arm of the pantograph contained a small pointer while the other held a drawing implement, and by moving the pointer over a diagram, a copy of the diagram was drawn on another piece of paper. By changing the positions of the arms in the linkage between the pointer arm and drawing arm, the scale of the image produced can be changed. A more complicated version called the eidograph was developed by William Wallace (1768–1843) in 1831.

Uses

Drafting

The original use of the pantograph was for copying and scaling line drawings. Modern versions are sold as toys.

Acoustic cylinder duplication

One advantage of phonograph and gramophone discs over cylinders in the 1890s—before electronic amplification was available—was that large numbers of discs could be stamped quickly and cheaply. In 1890, the only ways of manufacturing copies of a master cylinder were to mold the cylinders (which was slow and, early on, produced very poor copies), to record cylinders by the "round", over and over again, or to acoustically copy the sound by placing the horns of two phonographs together or to hook the two together with a hollow rubber tube (one phonograph recording and the other playing the cylinder back). Edison, Bettini, Leon Douglass and others solved this problem (partially) by mechanically linking a cutting stylus and a playback stylus together and copying the "hill-and-dale" grooves of the cylinder mechanically. When molding improved somewhat, molded cylinders were used as pantograph masters. This was employed by Edison and Columbia in 1898, and was used until about January 1902 (Columbia brown waxes after this were molded). Some companies like the United States Phonograph Co. of Newark, New Jersey, supplied cylinder masters for smaller companies so that they could duplicate them, sometimes pantographically. Pantographs could turn out about 30 records per day and produce up to about 150 records per master. In theory, pantograph masters could be used for 200 or 300 duplicates if the master and the duplicate were running in reverse and the record would be duplicated in reverse. This, in theory, could extend the usability of a pantograph master by using the unworn/lesser worn part of the recording for duplication. Pathé employed this system with mastering their vertically-cut records until 1923; a 5-inch diameter/4 or 6-inch long master cylinder, rotating at a high speed, would be recorded on. This was done as the resulting cylinder was considerably loud and of very high fidelity. Then, the cylinder would be placed on the mandrel of a duplicating pantograph that would be played with a stylus on the end of a lever, which would transfer the sound to a wax disc master, which would be electroplated and be used to stamp copies out. This system resulted in some fidelity reduction and rumble, but relatively high quality sound. Edison Diamond Disc Records were made by recording directly onto the wax master disc.

Other uses

In another application similar to drafting, the pantograph is incorporated into a milling machine with a revolving cutter instead of a pen, and a tray at the pointer end to fix precut lettered plates. In this way machinists can neatly and accurately engrave numbers and letters onto a part.

The device which maintains electrical contact with the contact wire and transfers power from the wire to the traction unit, used in electric locomotives and trams, is also called a "pantograph".

Herman Hollerith's "Keyboard punch" used for the 1890 US Census was a pantograph design and sometimes referred to as "The Pantograph Punch".^[3]

An early 19^th century device employing this mechanism is the polygraph, which produces a duplicate of a letter as the original is written.

See also

• Autopen
• James Watt's parallel motion
• Polygraph (duplicating device)

Notes

External links

• Pantograph Java applet
• Pantograph at mathworld.wolfram.com
• How to build a pantograph