Shrouded propeller

Claim 1

A shrouded propeller arrangement for operation in ice-filled waters, which comprise: a propeller having a central axis, a nozzle which has a central axis and is mounted so that its central axis substantially coincides with the central axis of the propeller, the nozzle having first and second opposite ends and being substantially rotationally symmetrical about its central axis, and an ice breaker annulus mounted substantially coaxialy with the nozzle at said first end thereof and spaced therefrom, said ice breaker annulus defining a substantially unobstructed aperture and extending axially beyond said said first end of the nozzle, the radius of the aperture defined by the ice breaker annulus not being substantially less than the radius of the inner periphery of the nozzle, whereby a main flow path for water entering the nozzle passes through the aperture, and the radius of the outer periphery of the ice breaker annulus being less than the radius of the outer periphery of the nozzle at said first and thereof, whereby a secondary flow path for water entering the nozzle passes by way of the space between the ice breaker annulus and the nozzle, so that in the event that the main flow path is obstructed, the secondary path is available for water flow into the nozzle, the ice breaker annulus acting on ice chunks or floes moving against it so that said chunks or floes are crushed or held at a distance from said nozzle, whereby a free water flow path through said nozzle is maintained.