US PATENT SUBCLASS 219 / 644
.~.~.~ Interior surface

Current as of: June, 1999
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219 /   HD   ELECTRIC HEATING

600  DF  INDUCTIVE HEATING {7}
635  DF  .~ Specific heating application {8}
643  DF  .~.~ Tube (i.e., pipe) {1}
644.~.~.~ Interior surface

DEFINITION

Classification: 219/644

Interior surface:

(under subclass 643) Subject matter wherein the heating is applied to an inner tube wall.