science · 16 November 1875 · 149 years ago
In 1875, the first U.S. patent for a dental mallet, or "Electro-magnetic Dental Pluggers" was issued to William G.A. Bonwill of Philadelphia, Pa. (No. 170,045). His tooth-filling device was used to drive gold into a tooth cavity. He derived the idea from observing the sounder of a telegraph key (while at the Continental Hotel in Philadelphia, 27 Feb 1867). The automatic tool was designed to be "manipulated as readily as the usual hand-tools." An electromagnet functions to drive a mallet, while also breaking the circuit to allow the spring-loaded mallet to return, at which point the circuit is closed, and the cycle repeated under the control of the operator.
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