(57) A multi-bladed propeller and shaft assembly is provided in which air can be fed to
the propeller blades to reduce the effects of cavitation. A shaft (10) leads to a
multi-bladed propeller (15) and carries a sleeve (18) formed with inlet passages (20)
and axial and radial passages (21, 24) leading to the respective blades (17). A slip
ring (45) supported in an anti-rotation device (62) allows the shaft sleeve (18) to
rotate within axially spaced bearings (46, 47) of the slip ring (45). Axially spaced
air seals (49, 50) together define with the body (48) of the slip ring an annulus
(51) within which inlet passages (20) rotate. Each seal (49 or 50) is formed as a
multiplicity of arcuate segments (80) resiliently biased towards the sleeve (18) and
having movably selaed end face portions (81, 82) to maintain pressure tightness. The
body (48) further has a radial flow passage (57) for admission of air under pressure
to the annular space (57) and a flexible fluid connector (56) connects the radial
flow passage (57) to an air supply line (54) leading from the hull structure. The
present shaft delivery slip ring avoids the need to feed air down the whole length
of the propeller shaft or to feed air into the hub through a slip ring making wiping
contact with the hub, which is structurally more complex.
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