US PATENT SUBCLASS 138 / 148
.~ Spaced

Current as of: June, 1999
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138 /   HD   PIPES AND TUBULAR CONDUITS

140  DF  DISTINCT LAYERS {8}
148.~ Spaced

DEFINITION

Classification: 138/148

(under subclass 140) Device wherein at least one layer is spaced from an adjacent layer to form an enclosing chamber therearound.

SEE OR SEARCH THIS CLASS, SUBCLASS:

113, for radially spaced plural ducts.