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US Patent: 132
Improvement in propelling machinery by magnetism and electro-magnetism
Thomas Davenport - Brandon, VT

USPTO Classifications:

Tool Categories:
electrical devices : electric motors : DC motors


Not known to have been produced

Charles A. Cook
W. W. Ayres

Patent Dates:
Granted: Feb. 25, 1837

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This is the first U.S. patent for an electric motor. Davenport's invention was the world's first DC commutator motor. Credit for the invention should go, in part, to Davenport's wife, Emily, who kept detailed notes and is generally believed to have been a significant contributor to the inventive process. Davenport's first attempt to obtain a patent for this motor, in 1834, was rejected because the Patent Office had not yet issued any patents related to electricity. Lack of money and then the 1836 patent-office fire led to further delays in patenting.

Davenport used a Voltaic battery, an electromagnet mounted on a wheel, and another magnet on a stationary frame. The interaction between magnets could rotate the first magnet up to half a turn. Reversing the wires to the first magnet would cause it to rotate another half turn. Davenport invented the brushes-and-commutator mechanism to perform the reversals automatically, causing the magnet to rotate indefinitely. (Actually, the first motor commutator was created by Hungarian physicist Anyos Jedlik in 1828, but it is very likely that Davenport's version was created independently.) His first application was for a model train that he hoped would lead to full-size electric trains. But Voltaic batteries were inadequate for a full-size train, and it was 20 years before it was fully understood that if Davenport's motor was forced to rotate by mechanical means then it would generate electricity. Davenport died at age 49 in 1851, long before his invention had come into its own.

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