Damped automatic variable pitch marine propeller

A self-actuating variable pitch marine propeller comprising a hub case;

• drive securing means designed to secure the propeller to a rotating drive means on a boat propulsion system, such that the propeller is caused to rotate, about a propeller axis, by the drive means;
• a plurality of blades which extend radially outward from, and are pivotally connected to, the hub case, about a blade axis extending transverse to the propeller axis, each blade comprising a hydrodynamic surface, and a blade shaft extending from the hydrodynamic surface along the blade axis, the center of pressure of the hydrodynamic surface being distant from the blade axis, such that rotation of the propeller by the drive shaft generates a hydrodynamic force torque about the blade axis tending to move the blade towards a higher pitch position;
• inertial mass means operably connected to the blade and designed to generate an inertial force torque, tending to cause each blade to pivot about the blade axis towards a higher pitch angle as the rotational speed of the propeller increases;
• and restricted viscous flow damping means mechanically, operatively connected to a blade, and designed to reduce the rotational velocity of such blade as the blade pivots about the blade axis in response to the hydrodynamic force torque and inertial force torque;
• whereby the blade is automatically movable between a first lower angle of pitch operational position, and a second higher angle of pitch operational position, as the rotational speed of the propeller increases, and whereby the blade rotatably moves between angular pitch positions slowly and without flutter.

A self-actuating variable pitch marine propeller comprising a hub case;

• drive securing means designed to secure the propeller to a rotating drive means on a boat propulsion system, such that the propeller is caused to rotate, about a propeller axis, by the drive means;
• a plurality of blades which extend radially outward from, and are pivotally connected to, the hub case, about a blade axis extending transverse to the propeller axis, each blade comprising a hydrodynamic surface, and a blade shaft extending from the hydrodynamic surface along the blade axis, the center of pressure of the hydrodynamic surface being distant from the blade axis, such that rotation of the propeller by the drive shaft generates a hydrodynamic force torque about the blade axis;
• inertial mass means operably connected to the blade and designed to generate an inertial force torque, tending to cause each blade to pivot about the blade axis towards a higher pitch angle as the rotational speed of the propeller increases;
• and restricted viscous flow damping means mechanically, operatively connected to a blade, and designed to provide a level of damping at least equal to the critical damping value of the rotating propeller blade relative to the fundamental mode of rotational displacement oscillation, so as to substantially reduce the rotational velocity of such blade as the blade pivots about the blade axis;
• whereby the blades are automatically movable between a first lower angle of pitch operational position, and a second higher angle of pitch operational position, as the rotational speed of the propeller increases, and whereby the blade rotatably moves between angular pitch positions slowly and without flutter;
• the center of pressure of the hydrodynamic surface being so juxtaposed relative to the blade axis that the hydrodynamic force torque generated about the blade axis when the propeller is rotated, at least during initial acceleration of the propeller, tends to move the blades towards a lower pitch position, such that the blades cannot move towards a higher pitch position until the propeller rotational speed is sufficiently great that the centrifugal force effect is sufficient to overcome the hydrodynamic force effect.

A self-actuating variable pitch marine propeller comprising a hub case, drive securing means designed to secure the propeller to a rotating drive shaft on a boat propulsion system such that the propeller rotates with the drive shaft;

• a plurality of blades extending radially outward from the hub case, each blade comprising a hydrodynamic surface, and a blade shaft extending from the hydrodynamic surface along a blade axis extending transverse to the drive shaft axis, said blade shaft being movably connected to the hub case, both pivotally about and linearly along the blade axis, such that rotation of the propeller by the drive shaft generates a centrifugal reaction force tending to cause each blade to move linearly outwardly along the blade axis;
• motion-direction means, operatively connected between the hub case and a blade shaft, designed to cause such blade to move pivotally about the blade axis, when the blade moves linearly along its blade axis;
• and a plurality of restricted flow damping means, each such damping means being mechanically, directly connected to one blade shaft, and designed to reduce the velocity of linear outward movement of such blade as the blade moves linearly and pivots about the blade axis in response to the motion-directing means;
• whereby the blades are automatically movable between a first lower angle of pitch operational position, and a second higher angle of pitch operational position, as the rotational speed of the propeller increases, and wherein the blade pivots slowly and without flutter.

A self-actuating variable pitch marine propeller comprising a hub case, drive securing means designed to secure the propeller to a rotating drive shaft on a boat propulsion system such that the propeller rotates with the drive shaft;

• a plurality of blades extending radially outward from the hub case, each blade comprising a hydrodynamic surface, and a blade shaft extending from the hydrodynamic surface along a blade axis extending transverse to the drive shaft axis, said blade shaft being movably connected to the hub case, both pivotally about and linearly along the blade axis, such that rotation of the propeller by the drive shaft generates a centrifugal reaction force tending to cause each blade to move linearly outwardly along the blade axis;
• motion-direction means, operatively connected between the hub case and a blade shaft, designed to cause such blade to move pivotally about the blade axis, when the blade moves linearly along its blade axis;
• coordination means operatively connected to each of the blades, such that movement of any one of the blades causes a proportional movement of the coordination means, whereby the movement of all of the blades is synchronized;
• and a restricted flow damping means, mechanically, operatively connected between the coordination means and the hub case, designed to reduce the rotational velocity of the blade as each blade pivots about the blade axis in response to the motion-directing means, and comprising a surface defining an enclosed fluid-containing chamber and having a fluid flow orifice extending through such surface into the chamber, at least a portion of such surface being movable relative to the hub case, such that the movement results in a change in the size of the chamber;
• connecting means between the coordination means and the movable portion of the surface, the connecting means being so designed that rotational movement of the blades result in a proportional movement of the movable portion of the surface, and wherein movement of the surface is limited by the flow of a viscous fluid relative to the chamber through the orifice;
• whereby the blades are automatically movable between a first lower angle of pitch operational position, and a second higher angle of pitch operational position, as the rotational speed of the propeller increases, and wherein a level of damping is provided at least sufficient to reduce by at least about fifty percent relative to an undamped such propeller, the rate of change in angular pitch operational position of the blades.

A self-actuating variable pitch marine propeller comprising a hub case, drive securing means designed to secure the propeller to a rotating drive shaft on a boat propulsion system such that the propeller rotates with the drive shaft;

• a plurality of blades extending radially outward from the hub case, each blade comprising a hydrodynamic surface, and a blade shaft extending from the hydrodynamic surface along a blade axis extending transverse to the drive shaft axis, said blade shaft being movably connected to the hub case, both pivotally about and linearly along the blade axis, such that rotation of the propeller by the drive shaft generates a centrifugal reaction force tending to cause each blade to move linearly outwardly along the blade axis;
• motion-directing means, operatively connected between the hub case and a blade shaft, designed to cause such blade to move pivotally about the blade axis, when the blade moves linearly along its blade axis;
• and restricted flow damping means, mechanically, operatively connected to a blade shaft, and designed to reduce the rotational velocity of such blade as the blade pivots about the blade axis in response to the motion-directing means;
• whereby the blades are automatically movable between a first lower angle of pitch operational position, and a second higher angle of pitch operational position, as the rotational speed of the propeller increases, and wherein the blade pivots slowly and without flutter, the restricted flow damping means comprises a surface defining an enclosed fluid-containing chamber and having a fluid flow orifice opening into the chamber, at least a portion of such surface being movable relative to the hub case, such that the movement results in a change in the size of the chamber;
• a valve seat, surrounding the orifice and secured to the defining surface, and a valve, movable relative to the valve seat, between a first position sealably closing the orifice and a second position away from the valve seat, so as to open the orifice, as the sped of the propeller increases;
• and feed-back means operably connected between the blades and the valve and directly responsive to the hydrodynamic torque generated by the blades, the feedback means tending to bias the valve against the valve seat with increasing force as the hydrodynamic torque increases;
• whereby an increase in the hydrodynamic torque increases the bias effect forcing the valve to seat against the valve seat, and thus requiring a greater centrifugal force effect torque to move the valve from the closed position.

In a variable pitch marine propeller comprising a plurality of blades, the blades being rotatably secured to the propeller, a self contained blade actuating and positioning mechanism for automatically causing rotational movement of the blade between a low pitch blade angular position and a high pitch blade angular position in response to forces generated as a result of a change in a boat operating parameter, and sensing means operably connected to the self-contained mechanism and designed to respond to such change in operating parameter;

• the improvement which comprises means to generate, sense and transmit, to the blade actuating and positioning mechanisms, centrifugal and hydrodynamic forces acting on the blade and which tend to change the blade pitch in the same direction, and restricted viscous fluid flow damping mean operably connected to the blade to control rotational movement and to reduce the rotational velocity of the blade during any such rotational movement, the damping means comprising an orifice and control means to open and close the orifice, and feedback means operatively connected to the control means and to the blade to apply any hydrodynamic force to the control means so as to close the orifice, whereby the damping means acts to restrain pitch change movement of the blade until the feedback force is overcome and to reduce the rate of change in the angular position of the blade, when movement is permitted.