Appeal No. 1998-0402
Application No. 08/490,046
that is provided with a conductive coil so that the material
adjacent to the pipe can be heated. It is necessary to
determine, however, that a weld actually has been made and, as
acknowledged by the appellants, it was known at the time of
their
invention to do so by providing the sleeve with an indicator
stem that moved outward in response to the pressure developed
in the sleeve material by the heat of welding. The stem was
radially oriented and positioned in a recess in the sleeve so
that its free end was flush with the outer surface of the
sleeve
prior to welding, but was pushed outwardly by the sleeve
material as it expanded due to the heat of welding to a
position where it extended beyond the periphery of the sleeve.
However, according to the appellants, these indicating systems
could fail if thermoplastic material melted by the heat of
welding expanded outwardly around the stem through the recess
to an extent sufficient to escape to the peripheral surface of
the sleeve, which could weaken the connection and cause
overheating and burning (specification, page 2). The
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