Patents Show Birth of The Electronic Age
The Electronics Age began as far back as the late 1800’s and, like many major advances in civilization, was the result of the separate efforts of a number of individuals whose actions, collectively, set the stage for change.
In this case the stage for change was set primarily by 4 individuals whose creative actions took place on both sides of the Atlantic over a period of about 20 years.
On January 27, 1880 U.S. Patent No. 223,89 (PDF) was granted to America’s most famous inventor, Thomas Alva Edison, for an electric light bulb in which an electric current could be passed through a carbon filament in an evacuated glass bulb, heating the filament to incandescence.
In his research, Edison is reported to have tested 6,000 filament materials. (Since then, the drawing of the light bulb in this patent has become an icon for Edison and his inventive genius.)
After his patent issued Edison continued to work on improvements to his light bulb. In 1883 he inserted an extra electrode into one of his light bulbs and found that when the electrode was maintained at a positive potential an electric current flowed through the vacuum from the filament to the electrode.
Edison failed to understand the phenomenon, but following his usual practice, he recorded it in his notebook. He named it the Edison Effect.
Although he found a use for it and actually patented as an Electrical Indicator (U.S. Patent No 307,031 PDF), he missed the real significance of the unusual flow of current through a vacuum and soon directed his attention to other inventive pursuits.
As a result, for the next few years, the Edison effect remained primarily a little known laboratory curiosity. However knowledge of the Edison Effect gradually spread and triggered a chain of events in the U.S. and England, over the next 20 years, that significantly changed the world we live in.
In 1897, an English physicist, Joseph John Thomson, discovered the electron with its negative charge. In the next scene in this drama, details of Thomson’s discovery reached John Ambrose Fleming, formerly an assistant to Edison who, by the late 1890’s, had become a professor of Electrical Engineering at University College, London.
Knowledge of Thomson’s discovery of electrons suggested to Fleming that the nearly forgotten Edison Effect was the result of a discharge of electrons from the incandescent carbon filament, and the passage of the electrons across the vacuum to the extra electrode.
Based on his analysis of Edison’s work, and the knowledge of Thomson’s discovery, Fleming invented the vacuum tube diode, wherein the carbon filament was surrounded by a positively charged cylindrical metal plate electrode.
When the filament was heated to incandescence electrons were emitted and traveled through the vacuum to the metal electrode only if it was positively charged. This meant that Fleming’s vacuum tube diode could convert alternating current to direct current thus serving as a rectifier for the electronic devices yet to come.
The final episode in this saga was the contribution of an American inventor, Lee Deforest. Building on the work of Edison, Thomson, and Fleming, he added a metal grid of fine wire between the filament and plate of a Fleming diode to form a vacuum tube triode.
When the grid was positively charged it amplified the flow of electrons. It was the first electronic amplifier. In 1907 he was granted U.S. Patent No. 841,387 (PDF) for his invention.
DeForest was a prolific inventor. He received more than 300 patents, but none was as important as the “audion” (the name he gave to his vacuum tube triode).
With this episode the Electronics Age began.
