| 摘要 |
A boat propeller has a housing adapted to be fixed to a boat, a hub rotatable about a main axis on the housing, a plurality of generally radially projecting vanes pivotable on the hub, and an operating core shaft coaxially received in the hub, rotatable about the main axis but axially nondisplaceable relative thereto, and having a rear end projecting axially from the hub and a front end. A yoke is fixed to the rear core-shaft end and respective rods fixed to the yoke are connected to the vanes for pivoting the vanes on angular movement of the core shaft about the main axis. A cylinder axially fixed in the housing at the front core-shaft end holds an axially displaceable piston. A nut element having a nonbinding internal screwthread is threaded on a screw element. One of the elements is axially coupled to the piston and the other of the elements is axially coupled to the core-shaft front end. The cylinder can be pressurized to axially displace the piston and, by axial-to-rotary conversion via the elements, rotate the core shaft.
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