Universal constant speed variable pitch boat propeller system

Abstract

A system that allows a boat propeller to maintain a constant blade speed by varying the pitch of the propeller in order to allow the boat's motor to operate at an optimum RPM. The system includes a governor that sends hydraulic fluid to an annular piston, which in turn controls the pitch of the boat propeller blades so that the torque experienced by the engine is kept approximately constant.

What is claimed is:  
     
         1 . An adjustable pitch boat propeller adapted for mounting on a drive shaft of a marine drive unit, the propeller comprising: 
 a hub, the hub adapted for mounting over the drive shaft of the marine drive unit, the hub having an external surface an internal surface and a piston;    a plurality of blades pivotally connected to said external surface of said hub;    at least one connector for pivoting said plurality of blades in response to movements of said piston; and    means for providing and maintaining a fixed amount of hydraulic pressure against said piston.    
     
     
         2 . A system according to  claim 1  wherein said connecting means comprises a substantially rigid link having a first end that is pivotally connected to said piston, and a second end that is pivotally connected to one of said blades.  
     
     
         3 . A system according to  claim 2  wherein said second end of each link comprises a plurality of independent connectors for attaching the link to one of the blades, so that the location of the connection of the link to the blade is varied by changing the attachment of the blade to the independent connector.  
     
     
         4 . A system according to  claim 1  and further comprising a governor for providing the fixed amount of pressure, the governor being responsive to a signal correlated to an operating speed of the marine drive unit.  
     
     
         5 . A method for adjusting the pitch on a boat propeller adapted for mounting on a drive shaft of a marine drive unit of a boat, the method comprising: 
 providing a propeller comprising: 
 a hub, the hub adapted for mounting over the drive shaft of the boat, the hub having an external surface and a piston housed within said external surface;  
 a plurality of blades pivotally connected to said external surface of said hub; and  
 a connector for pivoting at least one of said of blades in response to movements of said piston;  
 providing a desired amount of hydraulic pressure between the internal annular surface of said hub and said annular piston, so that the pitch is adjusted by moving the annular piston within the annular hub by varying the hydraulic pressure between the annular hub and the annular piston.  
   
     
     
         6 . A method according to  claim 5  wherein said means for providing a desired amount of hydraulic pressure comprises a constant speed governor with an adjustable pressure output.  
     
     
         7 . A method according to  claim 5  wherein said connector comprises a substantially rigid link having a first end that is pivotally connected to said annular piston, and a second end that is pivotally connected to one of said blades.  
     
     
         8 . A method according to  claim 7  wherein said second end of each link comprises a plurality of independent connectors for attaching the link to one of the blades, so that the location of the connection of the link to the blade is varied by changing the attachment of the blade to the independent connector.  
     
     
         9 . A method according to  claim 8  wherein said second end of each link includes means for accepting a connector, and a removable connector adapted for engagement with the means for accelerating a connector, the removable connector having a plurality of independent connectors for attaching the link to one of the blades, so that the location of the connection of the link to the blade is varied by changing the attachment of the blade to the independent connector.