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| | R-12 Retrofitting: Are we really doing it because DuPont’s patent for Freon® ran out? |
 | | Patent Number 1,833,847 was issued November 24, 1931 (reissued August 7, 1934) to Thomas Midgley, Jr., Albert L. Henne and Robert R. McNary, all of Ohio, for “Heat Transfer.” The original application was filed February 8, 1930. |
 | | Nor is the present invention limited to the examples set forth for a particular advance of the present invention resides in the fact that a great number of new refrigerants with graduated properties is rendered available, and that one is accordingly enabled to secure the most suitable refrigerant for varied purposes. |
 | | Patent Number 1,953,216, issued April 3, 1934 to Howard M. Elsey and assigned to Westinghouse Electric and Manufacturing Company appears to accidentally cover CFC refrigerants. |
| www.imcool.com /articles/aircondition/refrigerant_history.htm (1804 words) |
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