Thrust enhancing propeller guard assembly

Abstract

A propeller guard assembly for watercraft that, in cooperation with a rotating propeller, creates a substantial increase in propulsive thrust and provides improved all around shielding of the latest state of the art propeller configurations such as wider propeller blades and contra rotating dual propeller systems.

I claim:  
     
         1 . A thrust enhancing propeller guard assembly for mounting on a housing of a motor for rotating the propeller about a longitudinal axis, the propeller functioning to propel a boat through the water, the thrust enhancing propeller guard assembly comprising: 
 (a) a first subassembly including: 
 (i) a first mounting means connected to the housing for connecting said first subassembly to the housing;  
 (ii) a first generally ring-shaped cowling of a first diameter connected to said first mounting means;  
 (iii) a second generally ring-shaped cowling of a second, larger diameter connected to said first mounting means, said second cowling circumscribing the propeller; and  
 (iv) a third generally ring-shaped cowling of a second diameter connected to said first mounting means, said third ring-shaped cowling circumscribing the propeller and arranged to create an annular space between said second and third ring-shaped cowlings for controlling the flow of water there between to create a venturi effect;  
   (b) a second subassembly connected to said first subassembly, said second subassembly comprising: 
 (i) a second mounting means connected to the housing; and  
 (ii) a fourth generally ring-shaped cowling of a first diameter connected to said second mounting means; and  
   (c) connector means operably associated with said first and second subassemblies for interconnecting said first and second subassemblies.    
     
     
         2 . The thrust-enhancing propeller guard assembly as defined in  claim 1  in which each of said first, second and third generally ring-shaped cowlings has a peripheral portion disposed within a plane that extends at an acute angle relative to the longitudinal axis.  
     
     
         3 . The thrust-enhancing propeller guard assembly as defined in  claim 1  in which each of said first, second and third generally ring-shaped cowlings are generally airfoil shaped in cross section.  
     
     
         4 . The thrust-enhancing propeller guard assembly as defined in  claim 1  in which the housing includes a cavitation plate and a skeg and in which said first mounting means comprises a first mounting member connected to the cavitation plate and a second mounting member connected to the skeg.  
     
     
         5 . The thrust-enhancing propeller guard assembly as defined in  claim 4  in which said second mounting means comprises an upper mounting member and a lower mounting member.  
     
     
         6 . The thrust-enhancing propeller guard assembly as defined in  claim 5  in which said connector means comprises: 
 (a) an upper connector plate for interconnecting said first mounting member and said upper mounting member; and  
 (b) a lower spanner member for interconnecting said second mounting member and said lower mounting member.  
 
     
     
         7 . The thrust-enhancing propeller guard assembly as defined in  claim 6  in which said upper connector plate is generally “U” shaped and in which said lower spanner member comprises an elongated connector plate.  
     
     
         8 . A thrust-enhancing propeller guard assembly for mounting on a housing of a motor for rotating the propeller about a longitudinal axis, the propeller functioning to propel a boat through the water, said housing includes a cavitation plate and a skeg, the thrust-enhancing propeller guard assembly comprising: 
 (a) a first subassembly including: 
 (i) a first mounting member connected to said cavitation plate;  
 (ii) a second mounting member connected to said skeg;  
 (iii) a first generally ring-shaped cowling of a first diameter connected to the housing at an axially spaced location from the propeller, said first cowling comprising first and second semicircular segments each having upper and lower extremities, each said segment being connected at its upper extremity to said first mounting member and each of said segments being connected at its lower extremity to said second mounting member;  
 (iv) a second generally ring-shaped cowling of a second, larger diameter connected to the housing at a spaced location from said first cowling, said second cowling circumscribing the propeller and being a generally airfoil shaped in cross section, said second cowling comprising first and second semicircular segments each having upper and lower extremities, each said segment being connected at its upper extremity to said first mounting member and each of said segments being connected at its lower extremity to said second mounting member; and  
 (v) the third generally ring-shaped cowling of a second diameter connected to the housing at a spaced location from said second ring-shaped cowling, said third cowling being generally airfoil shape in cross section, circumscribing the propeller and being arranged to create an annular space between said second and third ring-shaped cowlings for controlling the flow of water there between to create a venturi effect, said third cowling comprising first and second semicircular segments each having upper and lower extremities, each said segment being connected at its upper extremity to said first mounting member and each of said segments being connected at its lower extremity to said second mounting member;  
   (b) a second subassembly connected to said first subassembly, said second subassembly including: 
 (i) an upper mounting member;  
 (ii) a lower mounting member;  
 (iii) a fourth generally ring-shaped cowling of a first diameter connected to said housing at a location axially spaced from the propeller and axially spaced from said third generally range-shaped cowling, said fourth cowling comprising first and second semicircular segments each having upper and lower extremities, each said segment being connected at its upper extremity to said upper mounting member and each of said segments being connected at its lower extremity to said lower mounting member; and  
 (iv) connector means operably associated with said first and second subassemblies for releasably interconnecting said first and second subassemblies.  
   
     
     
         9 . The thrust-enhancing propeller guard assembly as defined in  claim 8  further including a pair of oppositely disposed torque bars connected to said first, second and third generally ring-shaped cowlings of said first subassembly.  
     
     
         10 . The thrust-enhancing propeller guard assembly as defined in  claim 8  in which each of said first, second, third and fourth cowlings is generally airfoil shaped in cross section.  
     
     
         11 . The thrust-enhancing propeller guard assembly as defined in  claim 8  in which said connector means comprises: 
 (a) an upper connector plate for interconnecting said first mounting member and said upper mounting member; and  
 (b) a lower spanner member for interconnecting said second mounting member and said lower mounting member.  
 
     
     
         12 . The thrust enhancing propeller guard assembly as defined in  claim 11  in which said upper connector plate is generally “U”-shaped and in which said lower spanner member comprises an elongated connector plate.