Appeal No. 2000-0181
Application No. 08/929,287
Appellants attribute these operating characteristics to
the inclusion of a friction brake, which is formed by thrust
bearing 23, constituted by engagement between downwardly
facing flange 8 in the housing 2 and washer 25 on turbine
shaft 17, both of which are made of a low-friction material
such as PTFE. According to page 2, lines 13 to 19 of the
specification (as amended):
Although it is not fully known as to how
the friction brake automatically limits the
rotational speed, it is possible that, at
low pressures, a liquid friction exists in
the axial gap of the two bearing surfaces
of the axial bearing as a result of the
liquid flowing through the nozzle. At
increasing pressures, the friction is
believed to convert into a dry friction by
reason of increased pressure forces acting
on upstream surfaces of the turbine that
act to increase braking action of the axial
bearing surfaces of the thrust bearing.
Claim 1, which is typical of the claims on appeal, recites the
operation of the claimed nozzle as (lines 25 to 33):
said friction brake formed by said axial
bearing surfaces [defined by a shoulder on
the shaft coupled to the turbine and by the
bearing bore] cooperating to brake
rotational movement of said shaft and
nozzle as a result of said axial bearing
surfaces being moved toward each other to
increase frictional resistance therebetween
in response to pressure in said chamber
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