(under subclass 451) Devices for automatically controlling flow of feed-water to a boiler by thermal responsive means, usually a thermostat of the expanding-solid type, which is exposed more or less to the steam as the water-level varies.
SEE OR SEARCH THIS CLASS, SUBCLASS:
504.2, for thermal means which operate a valve, on drop of
water-level below a certain limit, to operate an alarm or indicator.
