Variable displacement hydraulic gear pump

Abstract

A variable displacement hydraulic gear pump has a housing having fluid inlet and fluid outlet ports; and first and second gears rotatable in the housing. The first gear and the second gear are positioned in gear tooth engagement for at least a portion of the axial length of each. At least one of the first gear and the second gear is axially moveable, to vary the axial length of gear tooth engagement.

1 . A variable displacement hydraulic gear pump comprising: 
 a housing having fluid inlet and outlet ports;    a first gear rotatably disposed in said housing, and having first gear teeth and a first gear teeth axial length;    a second gear rotatably disposed in said housing, and having second gear teeth and a second gear teeth axial length;    said first gear teeth and said second gear teeth positioned in gear tooth engagement for at least a portion of said first gear teeth axial length and a portion of said second gear teeth axial length; and    at least one of said first gear and said second gear being axially moveable.    
     
     
         2 . The gear pump of  claim 1 , one of said first gear and said second gear being a ring gear having internal teeth thereon.  
     
     
         3 . The gear pump of  claim 2 , the other of said first gear and said second gear having external teeth thereon.  
     
     
         4 . The gear pump of  claim 2 , one of said first gear and said second gear being axially restrained in said housing.  
     
     
         5 . The gear pump of  claim 2 , including a shaft axially translatable in said housing, and one of said first gear and said second gear disposed on said shaft.  
     
     
         6 . The gear pump of  claim 5 , the other of said first gear and said second gear axially restrained in said housing.  
     
     
         7 . The gear pump of  claim 1 , each said first gear and said second gear having external teeth thereon.  
     
     
         8 . The gear pump of  claim 7 , one of said first gear and said second gear being axially restrained in said housing.  
     
     
         9 . The gear pump of  claim 1 , one of said first gear and said second gear being axially restrained in said housing.  
     
     
         10 . The gear pump of  claim 1 , including a shaft axially translatable in said housing, and one of said first gear and said second gear disposed on said shaft.  
     
     
         11 . A method for operating a gear pump comprising the steps of: 
 providing a first gear and a second gear disposed in meshed relationship over a gear engagement axial length; and    adjusting said gear engagement axial length.    
     
     
         12 . The method of  claim 11 , including restraining one of said first gear and said second gear while axially positioning the other of said first gear and said second gear.  
     
     
         13 . The method of  claim 11 , including providing an internally toothed gear and an externally toothed gear, and sliding said externally toothed gear axially in said internally toothed gear.  
     
     
         14 . The method of  claim 13 , including restraining said internally toothed gear against axial movement while moving said externally toothed gear axially.  
     
     
         15 . The method of  claim 11 , including providing first and second externally toothed gears and moving at least one of said gears axially.  
     
     
         16 . The method of  claim 15 , including restraining one of said gears against axial movement.  
     
     
         17 . A hydraulic system comprising; 
 a hydraulic device having a variable input flow requirement;    a hydraulic fluid source; and    a variable displacement hydraulic gear pump in fluid flow relationship between said fluid source and said hydraulic device, said gear pump including; 
 a housing;  
 a first gear rotatably disposed in said housing, and having first gear teeth and a first gear teeth axial length;  
 a second gear rotatably disposed in said housing, and having second gear teeth and a second gear teeth axial length;  
 said first gear teeth and said second gear teeth positioned in gear tooth engagement for at least a portion of said first gear teeth axial length and a portion of said second gear teeth axial length; and  
   at least one of said first gear and said second gear being axially moveable.    
     
     
         18 . The hydraulic system of  claim 17 , one of said first gear and said second gear being a ring gear.  
     
     
         19 . The hydraulic system of  claim 17 , each said first gear and said second gear being externally toothed gears.  
     
     
         20 . The hydraulic system of  claim 17 , one of said first gear and said second gear being restrained against axial movement.