Variable pitch marine screw - with elastic mounting of blades to smooth out torque changes

摘要

The blades (1) of the marine screw are mounted in the hub (2) to rotate about a vertical axis (3) through the mounting in order to vary the blade pitch. The blade is arranged so that its centre of thrust is in front of the pivot axis w.r.t. water flow. The blade is elastically mounted so that increased torque causes the blade to feather more and hence reduce damage. The engine is thus able to run at its most optimum speed from start, with the blade pitch regulated automatically to prevent excessive torque. The system requires no complicated pitch control linkage, but only a simple torsional spring.