US PATENT SUBCLASS 432 / 92
Current as of: June, 1999
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(under the class definition) Apparatus having in combination with the basic heating structure, additional structure; said additional structure (1) having a function other than the application of heat to material, or (2) serving to perfect the basic heating structure as a whole for its intended purpose.
(1) Note. Basic heating structure includes means holding or manipulating the work during heating, means for feeding work into a heating chamber, and means for returning escaping heat to the heating zone.
(2) Note. The additional structure required by this definition must be added to the basic heating structure elements. A detail of an essential element that perfects the element rather than the combination is classified below. For example, a heating apparatus element having protective cooling structure in classified in subclasses 233+ and a heating chamber structure having expansion relieving or absorbing means is classified in subclass 251.