US PATENT SUBCLASS 137 / 213
.~.~ With liquid level responsive gas vent or whistle

Current as of: June, 1999
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137 /   HD   FLUID HANDLING

154  DF  DIVERSE FLUID CONTAINING PRESSURE SYSTEMS {7}
206  DF  .~ Gas pressure storage over or displacement of liquid {5}
213.~.~ With liquid level responsive gas vent or whistle {1}
214  DF  .~.~.~> Combined high and low level responsive

DEFINITION

Classification: 137/213

(under subclass 206) Apparatus wherein a gas vent or whistle is opened in response to a predetermined liquid level.

(1) Note. An example of such apparatus is a low water level steam exhaust and signal for a boiler.

SEE OR SEARCH THIS CLASS, SUBCLASS:

197+, for discriminating gas outlets or vents which may be liquid level responsive.

386+, for liquid level responsive or maintaining systems.

558, for liquid level indicators involving release of a separate gas for their operation, or of internal gas pressure when gas is the only fluid in the system. The use of whistles with gas exhaust devices as found in diverse fluid containing pressure systems is so common in the art that no cross reference is made of patents involving such subject matter to subclass 558. The search note under subclass 558 directs that search be made in subclasses 213+.

SEE OR SEARCH CLASS 116, Signals and Indicators,

137+, for whistles, per se.

222, Dispensing,

39, for audible signals for dispensers and subclass 69 for float controlled vents for dispensers.

446, Amusement Device: Toys,

204+, for a sounding toy comprising a whistle.