Appeal No. 2005-1173 Page 6
Application No. 10/134,793
component to be connected, onto the threaded seat, such as for example the threaded
seat of the cylinder head of the engine, in advance, before using the box spanner for
tightening, and make it possible to withdraw the component easily when unscrewing it,
in particular in cases of difficult access or close to sources of heat, such as the cylinder
head of an engine.
Bogni then teaches that one embodiment of the retaining device for a box
spanner, which is known from the prior art, consists of a permanent magnet of hollow
cylindrical shape fixed to the internal surface of the hollow space of the box spanner
above the polygonal seat for turning the plug. The permanent magnet of cylindrical
shape has a coaxial hole of a size which is necessarily smaller than the cavity of the box
spanner but large enough for the passage of the ceramic extension of the plug.
Retention of the plug is provided by the action of the permanent magnet on the metal
part of the plug, which is located at the bottom of the ceramic extension. The
disadvantage of this embodiment is that the cylinder of magnetic material forms a
projection which partially obstructs the hollow space of the box spanner. Insertion of the
plug in a manner which is not perfectly coaxial with the box spanner, which is highly
likely if the spanner is being used in a situation with difficult direct access to the
threaded member, brings about scraping of the very delicate surface of the ceramic
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