Automatic variable pitch marine propeller with mechanical holding means

A variable pitch marine propeller comprising a hub case;

• drive securing means designed to secure the propeller to a rotating drive shaft on a boat, such that the propeller rotates with the drive shaft;
• a plurality of blades extending transversely outwardly from the hub case and rotatably secured to the hub case about a blade pivot axis transverse to the axis of the drive shaft, for pivotal movement about the blade pivot axis between two extreme angular pitch positions, a first lower, pitch position and a second, higher, pitch position;
• each blade comprising a hydrodynamic surface, having a leading edge, and a blade shaft extending from the hydrodynamic surface along the blade pivot axis to the hub case;
• the hydrodynamic surface being so formed, and the blade axis and hydrodynamic surface being so juxtaposed to each other and to the hub case, that the center of pressure of the blade during initial acceleration from low boat velocity, is located intermediate the pivot axis and the leading edge, such that the resultant hydrodynamic torque vector initially generated upon such acceleration of the propeller acts so as to tend to cause pivotal movement of the blade towards the higher pitch position;
• bias means operably connected between a blade and the hub case, tending to retain the blades in the first lower pitch position;
• centrifugal mass means, secured to the blades, the centrifugal mass means being located in such a position relative to the blades, that upon rotation of the propeller a centrifugal force is imparted to the blades tending to pivot the blades from the first, lower, pitch position to the second, higher, pitch position;
• and mechanical holding means operably connected to the blades to hold the blades against pivoting towards the second pitch position;
• such that the blades are caused to pivot towards the second higher pitch position when the net effect of the centrifugal force effect and the hydrodynamic torque effect is sufficient to overcome the bias means and the mechanical holding means.