Pantograph

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This page is about the duplication instrument. For the electricity pickup device used on trains, see Pantograph (rail). For the knife, see Pantographic knife.

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 they move in a fixed relationship to each other.

The first pantograph was constructed in 1630 by Christoph Scheiner, who used the device to re-create diagrams. One arm 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 eidograph was developed by William Wallace in 1831. Modern versions of pantographs can be found in many toy stores.

Thomas Jefferson built his own pantograph into his house, Monticello.

Another common use for the pantograph was to construct "drafting machines". In these devices the arms were arranged in such a fashion as to keep the "pen" arm at a specific angle in relation to the "pointer" arm - although the pointer and pen are missing. The "pointer" arm is fixed to the side of the table at a right angle, implying that that "pen" end is likewise at a fixed right angle no matter where it is moved. Typically a straight-edge is placed at the "pen" end, which can then be used to quickly draw a series of parallel lines. Drafting machines replaced the older system of t-square and triangles, speeding up drawing.

A type of pantograph was used in the early days of sound recording to duplicate phonograph cylinders in the late 19th century.

Also a type of windshield wiper arm that controls a wiper blade's orientation (usually vertical) throughout the entire motion across the windshield. The mechanism is most often a parallelogram, occasionally a trapezium with two equal sides, or rarely a trapezium with no equal sides. One long leg is rotated via a driven shaft, and the wiper blade is attached to a short leg. It is typically seen on large commercial vehicles such as buses, trucks, and tractors.

See also James Watt's parallel motion.

Another use for a device of this type sees it incorporated into a milling machine with a revolving cutter instead of a pen and a tray at the pointer end to fix pre cut lettered plates. In this way engineers can neatly and accurately engrave part numbers and such onto a part.

The pantograph design has more recently been used to create a 2-degree of freedom force-feedback device with very low inertia at McGill University's Center for Intelligent Machines.