The Invention deals with marine propellers, in particular with contra rotating propellers featuring pitch control possibility.
It is well known that propulsive efficiency of contra-rotating propellers exceeds those of two separated propellers at the same conditions and also considerably exceeds efficiency of single propeller. However, majority of know contra-rotating arrangements is based on set of bevel gears engaged with two concentric shafts.
The proposed invention is supposed to be viable solution for application of medium speed four stroke engines for high efficiency propellers in contra rotating arrangement.
The invention combines advantages of variable pitch propeller and contrarotating propellers, former being well known as advantageous in terms of soft thrust reversing, engine load control and overload protection, possibility of maintaining constant RPM for an PTO generator drive and cleaner environment and later being known as propulsive device having proppeler efficiency far exceeding those inherent to single propeller, jet recuding the overall diameter to abt 80% of single propeller diameter.
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