Patent Number: US 0,334,823
Patent Title: Commutator for Dynamo Electric Machines
Patented on: 1886 January 26
Inventor: Nikola Tesla
Critical Features disclosed in this patent
1. Elements to prevent sparking on dynamo-electric machines
2. Drum-style with brushes
Note: Nikola Tesla was an inventor who obtained around 300 patents worldwide for his inventions. Some of Tesla’s patents are not accounted for, and various sources have discovered some that have lain hidden in patent archives. There are a minimum of 278 patents issued to Tesla in 26 countries that have been accounted for. Many of Tesla’s patents were in the United States, Britain, and Canada, but many other patents were approved in countries around the globe. Many inventions developed by Tesla were not put into patent protection.
Reference: https://en.wikipedia.org/wiki/List_of_Nikola_Tesla_patents