Tuesday 5th December 1911
Warren Johnson (63), inventor of the electric thermostat and manufacturer of Johnson tracks since 1905 in Milwaukee, Wisconsin, US, died. Johnson had an inquisitive mind and was particularly interested in electricity. In 1883, he developed a thermostat, which he deployed at the State Normal School. He called the instrument an “electric tele-thermoscope” in the patent application. It was a bi-metal coiled thermostat with a mercury switch, which could be used to ring a bell to alert the fireman to open or close the heating damper. While not the first bi-metal thermostat, Johnson received a patent for the device and interested William Plankinton, heir to the Plankinton Packing Company, to provide financial backing to manufacture the device.
The Johnson Electric Service Company was established in 1885 in Milwaukee, Wisconsin. Johnson’s most notable contribution to temperature control was the automatic multi-zone temperature control system – a pneumatic system that used a bi-metal thermostat to control air flow through a nozzle and thereby operate a pilot regulator. The amplified air signal from the regulator was then used to control a steam or hot water valve on a heat exchanger, or to control a damper of a forced air system. He received a patent for the system in 1895.
Johnson continued to invent additional control devices, as well as products such as chandeliers, springless door locks, puncture-proof tires, thermometers, and a hose coupling for providing steam heat to passenger railcars. He also designed pneumatic tower clocks, one of which was built for the Milwaukee City Hall tower.
He experimented for a time with wireless communications, forming the American Wireless Telegraph Company. The company’s exhibit at the Paris Exposition Universelle of 1900 won second prize, beating out Guglielmo Marconi. A test tower was built several miles south of Milwaukee, but the tests were unsuccessful. For about three months, Lee de Forest who eventually went on to design the audio vacuum tube that provided the breakthrough for radio, worked on the project with Johnson.
Johnson also sought to form an automobile company, introducing first a steam-powered truck and then a line of automobiles using gasoline-powered engines. The company was among the first to receive a contract to deliver mail with a horseless carriage.
He is credited with more than 50 patents.