Rotary actuator

Abstract

A rotary actuator ( 100 ) having a reference structure ( 110 ), an output member ( 113 ) arranged for rotary movement relative to the reference structure, a first linear motor ( 116 ) arranged to selectively apply an output force urging a first motor member ( 119 ) and a second motor member ( 122 ) apart along a generally linear direction, in which the first linear motor is configured and arranged to cause a torque between the output member and the reference structure in a first direction, and second linear motor ( 137 ) arranged to selectively apply an output force urging a second linear motor first member ( 134 ) and a second motor member ( 137 ) apart along a generally linear direction, in which the second linear motor is configured and arranged to cause a torque between the output member and the reference structure in a direction opposite to the first direction.

1 . A rotary actuator comprising:
 a reference structure;   an output member arranged for rotary movement relative to said reference structure about an axis;   a first linear motor having a first member and a second member, said first linear motor configured and arranged to selectively apply an output force urging said first member and said second member apart along a generally linear direction;   said first linear motor first member coupled to said reference structure;   said first linear motor second member coupled to said output member and configured and arranged to cause a torque between said output member and said reference structure in a first direction about said axis when said first linear motor applies said output force;   a second linear motor having a first member and a second member, said second linear motor configured and arranged to selectively apply an output force urging said second linear motor first member and said second linear motor second member apart along a generally linear direction;   said second linear motor first member coupled to said reference structure; and   said second linear motor second member coupled to said output member and configured and arranged to cause a torque between said output member and said reference structure in a direction about said axis opposite said first direction when said second linear motor output force is applied.   
     
     
         2 . A rotary actuator as set forth in  claim 1 , wherein said first linear motor comprises a single acting hydraulic motor. 
     
     
         3 . A rotary actuator as set forth in  claim 2 , wherein said first linear motor first member comprises a prismatic chamber and said first linear motor second member comprises a piston. 
     
     
         4 . A rotary actuator as set forth in  claim 3 , wherein said prismatic chamber is a cylinder. 
     
     
         5 . A rotary actuator as set forth in  claim 3 , wherein said first linear motor comprises a piston link arranged between said piston and said output member. 
     
     
         6 . A rotary actuator as set forth in  claim 3 , wherein said first linear motor first member is rigidly mounted to said reference structure. 
     
     
         7 . A rotary actuator as set forth in  claim 5 , wherein said piston link and said piston are connected through a ball joint. 
     
     
         8 . A rotary actuator as set forth in  claim 5 , wherein said piston link and said output member are connected through a pivot joint or pin joint. 
     
     
         9 . A rotary actuator as set forth in  claim 1 , wherein said first linear motor and said second linear motor each have a direction of action which is generally parallel. 
     
     
         10 . A rotary actuator as set forth in  claim 1 , wherein said output member comprises a shaft and a first pivot bearing coupled to said first motor second member and a second pivot bearing coupled to said second motor second member. 
     
     
         11 . A rotary actuator as set forth in  claim 10 , wherein said first pivot bearing and said second pivot bearing are separated by an offset in a dimension parallel to said axis. 
     
     
         12 . A rotary actuator as set forth in  claim 10 , wherein said first pivot bearing, said second pivot bearing, and said axis are collinear. 
     
     
         13 . A rotary actuator as set forth in  claim 1 , wherein said first linear motor first member comprises a cylinder and said first linear motor second member comprises a piston, said piston comprising a first surface and a second surface, said first surface forming a first chamber with said cylinder and said second surface forming a second chamber with said cylinder. 
     
     
         14 . A rotary actuator as set forth in  claim 13 , wherein said cylinder comprises a generally cylindrical surface, and said cylindrical surface comprises a hole between said piston first surface and said piston second surface. 
     
     
         15 . A rotary actuator as set forth in  claim 14 , and further comprising a drive link coupled to said piston and traversing said hole. 
     
     
         16 . A rotary actuator as set forth in  claim 2 , wherein said second linear motor comprises a single acting hydraulic motor. 
     
     
         17 . A rotary actuator as set forth in  claim 16 , wherein said first linear motor and said second linear motor have an equivalent hydraulic fluid volume displaced for a given linear motor linear distance of actuation. 
     
     
         18 . A rotary actuator as set forth in  claim 16 , wherein said first linear motor and said second linear motor are hydraulically balanced. 
     
     
         19 . A rotary actuator as set forth in  claim 1 , wherein said output member is coupled to an aircraft control surface. 
     
     
         20 . A rotary actuator as set forth in  claim 1 , and further comprising a position sensor configured and arranged to measure an angle between said output member and said reference structure. 
     
     
         21 . A rotary actuator as set forth in  claim 20 , and further comprising a servo controller. 
     
     
         22 . An actuator for rotating a shaft about an axis, said actuator comprising:
 a housing;   a first single acting cylinder disposed in said housing and having a first piston and a first connecting link therein;   a crank disposed on said shaft;   a second single acting cylinder disposed in said housing and having a second piston and a second connecting link therein;   wherein said first and second connecting links are attached to different locations on said crank; and   wherein said actuator is configured and arranged such that actuation of said first single acting cylinder causes said crank to rotate in a first direction and actuation of said second single acting cylinder causes said crank to rotate in a second direction opposite said first direction.   
     
     
         23 . The actuator of  claim 22 , wherein said first and second cylinders are oriented substantially parallel. 
     
     
         24 . The actuator of  claim 22 , wherein said first and second cylinders are both configured and arranged to each have a pre-load to provide a force in the same general direction to remove a backlash. 
     
     
         25 . The actuator of  claim 22 , wherein said shaft rotates on a set of bearings disposed in said housing. 
     
     
         26 . The actuator of  claim 22 , wherein said shaft is connected to an aircraft control surface. 
     
     
         27 . The actuator of  claim 22 , wherein said actuator is configured and arranged to move said crank from a first position to a second position by applying an additional pressure to one of a first pressure chamber and a second pressure chamber. 
     
     
         28 . The actuator of  claim 27 , wherein said actuator is configured and arranged to be able to maintain a position of said crank by providing a substantially equal pressure inside said first and second pressure chambers. 
     
     
         29 . The actuator of  claim 27 , wherein said actuator is configured and arranged to maintain a position of said crank by not allowing hydraulic fluid to flow in or out of said first or second pressure chambers. 
     
     
         30 . The actuator of  claim 22 , wherein said first and second single acting cylinders have a cross section which is not circular. 
     
     
         31 . The actuator of  claim 22 , wherein said first connecting link is connected to said first piston through a ball joint. 
     
     
         32 . The actuator of  claim 22 , wherein said first connecting link and said output member are connected through a pivot joint or pin joint. 
     
     
         33 . The actuator of  claim 22 , wherein said first and second single acting cylinders are separated by an offset in a dimension parallel to said axis. 
     
     
         34 . The actuator of  claim 22 , wherein said first and second single acting cylinders share a common bore. 
     
     
         35 . The actuator of  claim 22 , wherein said actuator is configured and arranged such that said first single acting cylinder expels a substantially equal volume of hydraulic fluid to a volume of hydraulic fluid drawn in by said second single acting cylinder for a movement of said shaft. 
     
     
         36 . The actuator of  claim 22 , and further comprising a position sensor configured and arranged to measure an angle between said shaft and said housing. 
     
     
         37 . The actuator of  claim 36 , and further comprising a servo controller. 
     
     
         38 - 56 . (canceled)