Adjustable-displacement gear pump

Abstract

A positive displacement fluid pump capable of an output flow rate can be varied from a maximum to zero at a given pump rotation speed. The pump is a variable-fluid-displacement-volume, gear pump having complement elements associated with pumping gears to provide end seals for a variable-length pumping chamber. A timing arrangement maintains both pumping gears always in synchronization, whether engaged or fully disengaged (zero pump output). And a follower provides effective sealing with a movable face of an axially-translating pumping gear.

What is claimed and desired to be secured by United States Letters Patent is:  
     
         1 . A pump having a positive displacement per cycle that is continuously variable between a maximum flow rate and a zero flow rate comprising: 
 a housing;    a first driven gear rotatably movable with respect to the housing;    a second gear rotatably movable with respect to the housing and meshing with the first gear, wherein the first and second gears are axially movable relative to each other;    a first complement, secured to rotate with and slide axially along the first gear;    a second complement, secured to rotate with and slide axially along the second gear;    a movable follower sealably engaged to the first complement and second gear, and slidably engaged with the first gear, wherein the first complement and second gear are configured to move continuously between a first position corresponding to the maximum flow rate and a second position corresponding to the zero flow rate;    a fixed follower sealably engaged with the second complement and slidably engaged with the second gear; and    a timing gear configured to rotate in correspondence with said first driven gear.    
     
     
         2 . The pump of    claim 1   , further comprising: 
 a drive shaft carrying said first driven gear in driving relation.    
     
     
         3 . The pump of    claim 2   , further comprising: 
 an idler axle carrying said second gear.    
     
     
         4 . The pump of    claim 3   , wherein the timing gear is spaced axially from the first driven gear by the stationary follower.  
     
     
         5 . The pump of    claim 4   , wherein the stationary follower further comprises: 
 a sleeve center positioned to cooperate with the second complement.    
     
     
         6 . The pump of    claim 5   , wherein the sleeve center has an axial length at least equal to a thickness of the second complement.  
     
     
         7 . The pump of    claim 6   , wherein the movable follower further comprises: 
 a sleeve positioned to slide axially over said sleeve center in a sealed relation, further adapted to travel with the movable follower.    
     
     
         8 . The pump of    claim 7   , further comprising a pump chamber having a continuously variable length defined by a distance between the first and second complements.  
     
     
         9 . The pump of    claim 8   , wherein said pump chamber length varies continuously between a maximum length corresponding to the length of said first driven gear less the length of the first compliment and a minimum length, including zero, corresponding with said zero flow rate.  
     
     
         10 . The pump of    claim 9   , further comprising: 
 an adjuster configured to continuously vary the length of said pump chamber between said maximum length and said minimum length.    
     
     
         11 . The pump of    claim 10   , wherein said adjuster comprises: 
 a mechanical linkage configured to displace the movable follower.    
     
     
         12 . The pump of    claim 10   , wherein said adjuster comprises: 
 a fluid applied to exert a differential pressure between a proximal piston face and a distal piston face, wherein the proximal piston face comprises a proximal end of the follower and a proximal end of the first complement, and wherein the distal piston face comprises a distal end of said first driving gear and a distal end of said sleeve.    
     
     
         13 . The pump of    claim 10   , further comprising a metering valve found between the movable follower and an output port, wherein said metering valve operates at reduced chamber length.  
     
     
         14 . The pump of    claim 11   , wherein the timing gear is configured to reduce energy applied to fluid within the housing.  
     
     
         15 . An improved pump, having axially translatable gears, to reduce energy applied to a working fluid during conditions of reduced pump output and full drive shaft speed, the improvement comprising: 
 a pump chamber comprising a sleeve and having a variable length to proportionally control pump output, the length variable between a maximum length and a minimum length, the minimum length corresponding to an effectively zero pump output;    the sleeve forming a pumping seal with a gear when the pump is configured to produce an output flow;    a timing arrangement adapted to keep a plurality of gears in constant synchronization, whether the gears are engaged or fully disengaged; and    an adjuster to vary the chamber length between the maximum and the minimum.    
     
     
         16 . The pump of    claim 15   , wherein the chamber length is a distance between a proximal seal and a distal seal.  
     
     
         17 . The pump of    claim 16   , wherein: 
 the distal seal comprises a stationary follower to form an effective axial seal with an axially fixed gear; and    the proximal seal comprises a movable follower to form an effective axial seal with an axially translating gear.    
     
     
         18 . The pump of    claim 17   , wherein the stationary follower comprises a portion of a gear complement, a sleeve center, and a housing bridge element.  
     
     
         19 . The pump of    claim 15   , wherein the sleeve is cantilevered from a movable follower and journaled in a housing for axial translation.  
     
     
         20 . The pump of    claim 19   , wherein a sleeve center, coaxial with the sleeve, axially spaces a timing gear from another gear.  
     
     
         21 . The pump of    claim 15   , wherein the adjuster comprises a mechanical linkage structured to translate a movable follower.  
     
     
         22 . The pump of    claim 15   , further comprising a metering valve between a movable follower and an output port, the metering valve operable during conditions of reduced chamber length.  
     
     
         23 . The pump of    claim 15   , the timing arrangement comprising: 
 a timing gear maintained in meshing agreement with a first gear, and axially spaced apart from the first gear.    
     
     
         24 . The pump of    claim 15   , wherein the adjuster comprises: 
 a working fluid applied to exert a differential pressure between a proximal piston face and a distal piston face; 
 the proximal piston face comprising a proximal end of a follower and a proximal end of a complement; and  
 the distal piston face comprising a distal end of a gear and a distal end of the sleeve.  
   
     
     
         25 . The pump of    claim 24   , wherein the working fluid is pressurized by a secondary pump between a gear and a timing gear.  
     
     
         26 . A method to vary a fluid output rate, between a maximum rate and essentially zero, during a constant operational speed for a positive displacement pump, the method comprising: 
 providing a pump comprising: 
 gears, including first and second pump gears, and a timing gear to maintain synchronization between the pump gears; with  
 the first pump gear in pump sealing relation to a sleeve cantilevered from a movable follower;  
 the pump gears arranged for meshing engagement and mounted for relative axial translation between a position of maximum length engagement to complete disengagement; and  
   axially translating the second pump gear relative to the first pump gear such that the engagement length therebetween correspondingly changes between a maximum length and zero.    
     
     
         27 . The method of    claim 26   , wherein the axial translation is effected by a mechanical linkage element arranged to translate the movable follower.