A D V E N T U R E S   in   C Y B E R S O U N D

The electrical researcher Heinrich D. Ruhmkorff, from Hannover, around the middle of the nineteenth century was able to improve Callan's two-winding induction spark-coils, on the basis of the research conducted in Paris by Masson and Breguet in 1842, in such a way that since then these devices bear his name.

The first patents date back to 1851 and follow one another introducing a few fundamental novelties. The iron core is still rectilinear and the primary winding, close to the iron, and the secondary winding, are arranged on it. The primary winding is fed by a storage battery, through a switch operated by the magnetized core. The current in the primary winding is pulsed, and the voltage on the secondary is alternating.

First of all, Ruhmkorff took particular care of the secondary insulation, using for the winding a lacquered copper wire, then inserting between one layer and the other a sheet of paper or varnished silk and finally separating the primary winding from the secondary one by a glass pipe.

Afterwards, by using an invention of the English E. and C. Bright, he divided the secondary winding into compartments, each one wound and insulated from the others; all were then connected in series. In this way the spots between which the highest difference in potential was to be found were at the greatest possible distance. The secondary wire could reach even tens of kilometers of total length.

Later Ruhmkorff improved the mercury switch by covering the mercury with alcohol to extinguish the spark and avoid oxidation. Finally, applying fizeau's device, he connected a capacitor between the terminals of the primary interruption bow, in order to increase the induced voltage. The frontal pawn is used to invert the primary current.

J. Fleming: The alternate current Transformer - "The Electrician" Company, London, 1892 - vol.II - p.35.

A. Ganot: Traité de Physique - Hachette, Paris, 1894 - p.1041.

Source: http://www.ien.it/museum/txt/rocch_ruhmkorff.html

Ruhmkorff coil by , J. Carpentier, Paris

"Made in or about 1896, this is an authentic, fully functional Ruhmkorff Induction unit. It throws a considerable spark from 2 dry cells, the gap being either heavy copper wire mounted in the binding posts atop the coil as shown, or running leads off to a separate spark gap.

On the left side of the coil is the adjustable vibrator, and on the right side, a current-reversing switch and 2 binding posts. The coil end plates are 1/2" circular glass slabs grooved to hold the 1/4" diameter twisted gut ropes that terminate in brass plates mounted to the wood base. The glass end slabs are cemented to the coil with hard red sealing wax. The coil's core is a bundle of iron rods with a total diameter of 1 1/4".

With the possible exception of the two binding posts on the right, every part on this device appears to have been hand-machined specifically for it. Nothing appears mass-produced. There is a box inside the base with contacts on top that meet spring leaf contacts in the base itself. This is a glass plate condensor, It is not the original, but it is correct size and fully functional. Weight is 28 pounds."

Nel 1851, H. D. Ruhmkorff, meccanico ed elettrotecnico tedesco, penso' di produrre correnti indotte in un rocchetto di grandi dimensioni dotato di due avvolgimenti separati Questa invenzione che porta il suo nome ebbe moltissime applicazioni pratiche in quanto rese disponibile una sorgente di alta tensione piu' comoda e potente delle macchine elettrostatiche in uso prima di allora.

Source: http://www.geocities.com/CapeCanaveral/Lab/3248/predecessori.html

Célèbre constructeur d'instruments de physique, né en Allemagne vers 1805. Il se rendit à Paris et travailla chez des fabricants d'instruments de précision, entre autres chez M. Chevalier, et, comme il était doué de grandes dispositions pour la mécanique, il devint en peu de temps un ouvrier d'une rare habileté.

Ayant réuni de l'argent, Ruhmkorff fonda à Paris une maison qui ne tarda pas à prospérer. Il construisit particulièrement des instruments électro-magnétiques, des galvanomètres, des appareils d'induction, etc, exécutés avec une perfection qui lui gagna tous les suffrages.

En 1851, il imagina de produire des courants d'induction dans une bobine de grande dimension et à deux fils, et cette belle invention, féconde en résultats pratiques, le rendit bientôt célèbre.

Ses produits envoyés à l'Exposition universelle de 1855 lui valurent, outre une médaille de première classe, la croix de la Légion d'honneur.

Lors du concours qui fut ouvert, en 1858, pour récompenser l'application la plus utile de l'électricité, Ruhmkorff obtint un prix de 50 000 francs, et, au concours de 1864, son appareil d'induction perfectionné lui fit donner le grand prix, qui n'avait pas encore été décerné.

Source: http://www.polytechnique.fr

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