Self-contained fluid-power servomechanism

Abstract

An example method of using a servomechanism can include controlling a reversible positive displacement pump that is located in a first chamber of a housing to push a fluid, via a first passage in the housing, against one side of a vane that is rotably disposed in a second chamber of a housing to rotate an output shaft that is coupled to the vane and controlling the reversible positive displacement pump to push a fluid, via a second passage in the housing, against another side of a vane to reverse rotation of the output shaft.

What is claimed is: 
     
         1 . A method of using a servomechanism, comprising:
 controlling a reversible positive displacement pump that is located in a first chamber of a housing to push a fluid, via a first passage in the housing, against one side of a vane that is rotably disposed in a second chamber of a housing to rotate an output shaft that is coupled to the vane; and   controlling the reversible positive displacement pump to push a fluid, via a second passage in the housing, against another side of a vane to revers rotation of the output shaft.   
     
     
         2 . The method of  claim 1 , comprising making up fluid in the first and second passages with fluid from a reservoir in the housing that is coupled via a third passage to each of the first passage and the second passage via one-way valves configured to flow into the first passage and the second passage. 
     
     
         3 . The method of  claim 1 , wherein controlling the reversible positive displacement pump includes controlling a gear pump. 
     
     
         4 . The method of  claim 3 , wherein controlling the reversible positive displacement pump includes controlling a gear pump using feedback from a transducer disposed in the housing. 
     
     
         5 . The method of  claim 4 , wherein controlling the reversible positive displacement pump includes controlling a gear pump using feedback from a transducer disposed in the housing that is coupled directly to the output shaft. 
     
     
         6 . The method of  claim 1 , wherein controlling the reversible positive displacement pump includes controlling an electric motor, disposed in the housing, to rotate the reversible positive displacement pump. 
     
     
         7 . A method of assembling a servomechanism, comprising:
 forming a housing by defining a first interior chamber and a second interior chamber, with a first passage extending between the first interior chamber and the second interior chamber and a second passage extending between the first interior chamber and the second interior chamber;   rotably disposing an output shaft in the housing with at least one end of the output shaft exposed through the housing;   coupling a vane to the output shaft rotably disposed in the first chamber of the housing for sealingly reciprocally rotating inside the first chamber around a vane axis, the vane dividing wherein the first chamber into a first variable volume portion, with a first face of the vane, parallel the vane axis, exposed to the first variable volume portion, and a second variable volume portion, with a second face of the vane, parallel the vane axis, exposed to the second variable volume portion, wherein the first passage opens to the first variable volume portion and the second passage opens to the second variable volume portion;   disposing at least one rotor of a reversible positive displacement pump in the second chamber of the housing, the at least one rotor for sealingly rotating inside the second chamber, wherein the first passage opens to a first side of a rotor-housing seal and the second passage opens to a second side of the rotor-housing seal;   disposing an electric motor inside the housing, the electric motor for rotating the at least one rotor; and   disposing an output shaft monitoring feedback transducer inside the housing in alignment with the housing and the output shaft, the output shaft monitoring feedback transducer for monitoring an orientation of the output shaft with respect to the housing.   
     
     
         8 . The method of  claim 7 , wherein disposing at least one rotor of a reversible positive displacement pump includes disposing a gear pump in the housing. 
     
     
         9 . The method of  claim 8 , wherein a first-gear-to-second-gear seal of the gear pump defines a gear pump interface chamber, and forming the housing includes forming a relief proximal the gear pump interface chamber to provide a leakage path out of the gear pump interface chamber into a remainder of a fluid-retaining portion of the housing. 
     
     
         10 . A servomechanism, comprising:
 a housing defining a first interior chamber and a second interior chamber, with a first passage extending between the first interior chamber and the second interior chamber and a second passage extending between the first interior chamber and the second interior chamber;   an output shaft rotably disposed in the housing with at least one end of the output shaft exposed through the housing;   a vane coupled to the output shaft and rotably disposed in the first chamber of the housing to sealingly reciprocally rotate inside the first chamber around a vane axis, wherein the vane divides the first chamber into a first variable volume portion, with a first face of the vane, parallel the vane axis, exposed to the first variable volume portion, and a second variable volume portion, with a second face of the vane, parallel the vane axis, exposed to the second variable volume portion, wherein the first passage opens to the first variable volume portion and the second passage opens to the second variable volume portion; and   at least one rotor of a reversible positive displacement pump disposed in the second chamber of the housing to sealingly rotate inside the second chamber, wherein the first passage opens to a first side of a rotor-housing seal and the second passage opens to a second side of the rotor-housing seal;   an electric motor coupled inside the housing to the at least one rotor to turn the at least one rotor; and   an output shaft monitoring feedback transducer coupled inside the housing and aligned to monitor an orientation of the output shaft with respect to the housing.   
     
     
         11 . The servomechanism of  claim 10 , wherein the reversible positive displacement pump is a gear pump and the at least one rotor is a first gear, and comprising a second gear disposed in the second chamber to sealingly rotate inside the second chamber, wherein the first passage opens to a first side of a first-gear-to-second-gear seal and the second passage opens to a second side of the first-gear-to-second-gear seal. 
     
     
         12 . The servomechanism of  claim 10 , wherein an exterior profile of the servomechanism is sized to be disposed in a space sized to receive a geared hobby servomechanism and wherein the at least one end of the output shaft is splined to mate with a servo horn. 
     
     
         13 . The servomechanism of  claim 10 , wherein the housing defines a third passage extending between the first passage and the second passage, with a first check valve disposed in the third passage between the first passage and the second passage. 
     
     
         14 . The servomechanism of  claim 13 , wherein the housing defines a fourth passage extending between the first passage and the second passage, with a second check valve disposed in the fourth passage between the first passage and the second passage, wherein the first check valve is oriented to permit flow from the first passage to the second passage, and the second check valve is oriented to permit flow from the second passage to the first passage, the first check valve and second check valve comprising a servosaver. 
     
     
         15 . The servomechanism of  claim 10 , wherein a fifth passage extends to each of a third check valve and a fourth check valve, with the third check valve oriented to permit flow from the fifth passage into the first passage, and the fourth check valve oriented to permit flow from the fifth passage to the second passage, the fifth passage in fluid communication with a reservoir. 
     
     
         16 . The servomechanism of  claim 15 , wherein the reservoir comprises a spring-loaded piston sealed to a piston cavity of the housing, with the spring disposed on an opposite side of a fluid-facing side of the piston. 
     
     
         17 . The servomechanism of  claim 15 , comprising a first output shaft seal disposed between a top portion of the output shaft and the housing and a second output shaft seal disposed between a bottom portion of the output shaft and the housing, wherein a top end of the output shaft and a bottom end of the output shaft are exposed to an exterior of the housing. 
     
     
         18 . The servomechanism of  claim 17 , comprising a first output shaft relief disposed between the first output shaft seal and the second output shaft seal and between a top portion of the output shaft and the housing and a second output shaft relief disposed between the first output shaft relief and the second output shaft seal and between a bottom portion of the output shaft and the housing, with each of the first output shaft relief and the second output shaft relief in fluid communication with a reservoir via a sixth passage. 
     
     
         19 . The servomechanism of  claim 18 , wherein the electric motor is coupled to the at least one rotor via a motor shaft, and comprising a motor shaft seal disposed between the motor shaft and the housing. 
     
     
         20 . The servomechanism of  claim 19 , wherein the sixth passage extends to the motor shaft between the at least one rotor and the motor shaft seal.