Owners of igniter-fired stationary engines appreciate the need to periodically clean the contacts on their engines’ igniters. Although the contacts can burn a bit from electrical arcing, the real issue is carbon fouling, the electrodes becoming coated with non-conductive material to the point they’ll no longer contact to make a spark when they break.
To counter this issue, Edward R. Moffitt, working for Imperial Gas Engine Co. of San Francisco, designed a cleanable igniter for use on Imperial’s single-cylinder marine engines, an application where reliable spark could be the difference between making shore or not. Established circa 1903-1905, Imperial Gas Engine Co. manufactured engines until 1916 when it merged with another marine engine manufacturer, Atlas Gas Engine Co. in Oakland, just across the bay from San Francisco. The merged companies became Atlas-Imperial Engine Co.
To achieve his stated goal of an igniter whose contacts could be “readily cleaned … and restored to effective working condition without opening the chamber in which they are enclosed,” Moffitt designed an igniter whose movable stem and electrode could be pushed inward so that its contact foot could move back and forth longitudinally against the igniter’s fixed electrode.
In Moffitt’s design, a movable stem (d) in the igniter body (b) is rotated on its axis by a cam or pick arm acting on a rocker arm (h) fixed to the stem. The rocker arm rotates the stem against spring pressure (g), turning the stem to break contact between the movable stem’s contact foot (e) and the fixed electrode (a), thereby generating a spark.
What made Moffitt’s design novel was the simple expedient of a strong spring (s) pressing against the igniter body and the stem-mounted rocker arm. This spring tension sealed the larger bottom section of the stem tight against the igniter body while also allowing the stem to be stroked in and out so that the stem’s contact foot would draw back and forth across the helical shaped fixed electrode to “scrape and brighten each other,” Moffitt’s patent said.
A stop pin limited the movable stem’s rearward rotation, and the fixed electrode could be periodically loosened and given a small turn to present a fresh face to the stem’s contact foot. If the fixed igniter needed replacement, it could easily be renewed after removing the igniter from the engine.
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