Hybrid rotary actuator

Abstract

A rotary actuator ( 16 ) includes a rotor ( 48 ) which is disposed in a housing ( 34 ) between first and second pole pieces ( 42 and 44 ) of a stator ( 40 ). The rotor ( 48 ) is rotatable relative to the stator ( 48 ) between an unactuated position (FIG. 4 ) and an actuated position (FIG. 5 ). During rotation of the rotor ( 48 ), the axial extent of a first working air gap ( 66 ) between the rotor and a first pole piece ( 44 ) of the stator ( 40 ) remains constant. However, the axial extent of the working air gap ( 64 ) between the rotor ( 48 ) and the second pole piece ( 42 ) of the stator ( 40 ) decreases as the rotor moves from the unactuated position to the actuated position. In a preferred embodiment, the rotor lobes are made so that the net axial force of all of the rotor lobes is substantially zero thereby reducing stress on the rotor shaft support bearings.

1. A hybrid rotary actuator comprising:
 a housing;  
 a stator having first and second pole pieces disposed in said housing;  
 a rotor disposed in said housing between said first and second pole pieces of said stator, said rotor being rotatable relative to said stator between an unactuated position and an actuated position;  
 said first pole piece of said stator having a first stator surface which faces toward and is spaced from a first rotor surface on said rotor by a first working air gap, said first stator surface on said first pole piece of said stator and said first rotor surface on said rotor being spaced apart by the same distance when said rotor is in the unactuated position as when said rotor is in the actuated position so that the extent of the first working air gap along the axis of rotation of the rotor remains constant during rotation of said rotor between the unactuated and actuated positions;  
 said second pole piece of said stator having a second stator surface which faces toward and is spaced from a second rotor surface on said rotor by a second working air gap, said second stator surface on said second pole piece of said stator and said second rotor surface on said rotor being spaced apart by a smaller distance when said rotor is in the actuated position than when said rotor is in the unactuated position so that the extent of the second working air gap along the axis of rotation of the rotor decreases during rotation of said rotor between the unactuated and the actuated positions; and  
 a coil which is disposed in said housing and extends around at least a portion of said actuator, said coil being energizable to provide magnetic flux which passes across the space between said first stator surface and said first rotor surface and which passes across the space between said second stator surface and said second rotor surface during at least a portion of the rotation of said rotor between the unactuated position and the actuated position, said flux biasing said rotor to move from said unactuated position towards said actuated position,  
   wherein said first stator surface and said first rotor surface have flat configurations, said second stator surface and said second rotor surface have flat configurations and are inclined with respect to said first stator surface and said first rotor surface .  
 
     
     
       2. An apparatus as set forth in  claim 1  wherein said first stator surface and said first rotor surface are disposed in parallel planes which extend perpendicular to an axis about which said rotor is rotatable between the unactuated position and the actuated position, said second stator surface and said second rotor surface are inclined with respect to the parallel planes in which said first stator surface and said first rotor surface are disposed. 
     
     
       3. An apparatus as set forth in  claim 1  wherein said first stator surface and said first rotor surface have flat configurations, said second stator surface and said second rotor surface have flat configurations and are inclined with respect to said first stator surface and said first rotor surface. 
     
     
       4. An apparatus as set forth in  claim 1  further including a diverter gate connected with said rotor, said diverter gate being movable with said rotor during movement of said rotor between the unactuated and actuated position. 
     
     
       5. An apparatus as set forth in  claim 4  further including a spring connected with said diverter gate, said spring being effective to apply a force to said diverter gate to effect movement of said rotor from the actuated position to the unactuated position. 
     
     
       6. A method comprising the steps of:
 rotating a rotor relative to first and second stator pole pieces under the influence of a magnetic field conducted across a first working air gap between a first surface on the rotor and a surface on the first stator pole piece and across a second working air gap between a second surface on the rotor and a surface on the second stator pole piece;  
 maintaining the extent of the first working air gap along the axis of rotation of the rotor constant during rotation of the rotor; and  
 varying the second working air gap during rotation of the rotor wherein said first stator surface and said first rotor surface have flat configurations, said second stator surface and said second rotor surface have flat configurations and are inclined with respect to said first stator surface and said first rotor surface.  
 
     
     
       7. A hybrid rotary actuator, said actuator comprising:
 a stator having at least first and second pole pieces;  
 at least one rotor disposed between said at least first and second pole pieces of said stator, said at least one rotor being rotatable relative to said stator between an unactuated position and an actuated position, said at least one rotor having at least two rotor lobes generally disposed between corresponding stator lobes on each of said at least first and second stator pole pieces, each rotor lobe having upper and lower surfaces spaced apart from corresponding surfaces on said corresponding stator lobes of said at least first and second pole pieces of said stator;  
 said respective rotor lobe and stator lobe surfaces defining one of two possible configurations, each of said configurations comprising one of a fixed and variable rotor/stator surface spacing during rotation of said rotor; and  
 a coil which extends around at least a portion of said stator, said coil being energizable to provide magnetic flux which passes between said first and second stator pole piece and through said rotor during at least a portion of the rotation of said rotor between the unactuated position and the actuated position where at least one rotor lobe upper surface has a fixed rotor/stator surface spacing and at least one rotor lobe lower surface has a variable rotor/stator surface spacing.  
 
     
     
       8. A hybrid rotary actuator according to  claim 7 , wherein the fixed rotor/stator surface spacing is on only one of the upper and lower surfaces of said at least two rotor lobes. 
     
     
       9. A hybrid rotary actuator according to  claim 7 , wherein the fixed rotor/stator surface spacing is on both the upper and lower surfaces of at least one of said at least two rotor lobes. 
     
     
       10. A hybrid rotary actuator according to  claim 7 , wherein the fixed rotor/stator surface spacing is on one of the upper surface of at least one of said at least two rotor lobes and is on one of the lower surface of at least one of aid at least two rotor lobes. 
     
     
       11. A hybrid rotary actuator according to  claim 10 , wherein the fixed rotor/stator surface spacing is on the upper and lower surface of at least one of said at least two rotor lobes. 
     
     
       12. A hybrid rotary actuator according to  claim 10 , wherein the fixed rotor/stator surface spacing is on the upper surface of at least one of said at least two rotor lobes and is on one of the lower surface of an adjacent one of said at least two rotor lobes. 
     
     
       13. A hybrid rotary actuator according to  claim 7 , further including a housing, said coil and said at least one rotor disposed within said housing, said housing, said stator and said at least one rotor forming a generally toroidal magnetic circuit around said coil. 
     
     
       14. A hybrid rotary actuator according to  claim 13 , further including a shaft upon which said rotor is mounted for rotation therewith, wherein said housing includes a cylindrical housing portion and two endcap portions, each of said endcap portions mounting a respective pole piece. 
     
     
       15. A hybrid rotary actuator according to  claim 14 , wherein the fixed rotor/stator surface spacing is on only one of the upper and lower surfaces of said at least two rotor lobes. 
     
     
       16. A hybrid rotary actuator according to  claim 14 , wherein the fixed rotor/stator surface spacing is on both the upper and lower surfaces of at least one of said at least two rotor lobes. 
     
     
       17. A hybrid rotary actuator according to  claim 14 , wherein the fixed rotor/stator surface spacing is on one of the upper surface of at least one of said at least two rotor lobes and is on one of the lower surface of at least one of said at least two rotor lobes. 
     
     
       18. A hybrid rotary actuator according to  claim 17 , wherein the fixed rotor/stator surface spacing is on the upper and lower surface of at least one of said at least two rotor lobes. 
     
     
       19. A hybrid rotary actuator according to  claim 17 , wherein the fixed rotor/stator surface spacing is on the upper surface of at least one of said at least two rotor lobes and is on one of the lower surfaces of an adjacent one of said at least two rotor lobes. 
     
     
       20. A hybrid rotary actuator according to  claim 15 , wherein said stator comprises three lobes. 
     
     
       21. A hybrid rotary actuator according to  claim 16 , wherein said stator comprises four lobes and said fixed spacing is on two of said four lobes. 
     
     
       22. A hybrid rotary actuator according to  claim 18 , wherein said stator comprises four lobes and said fixed spacing is on the upper and lower surfaces of two of said lobes and said inclined spacing is on the upper and lower surfaces of two of said lobes. 
     
     
       23. A hybrid rotary actuator according to  claim 19 , wherein said stator comprises four lobes and said fixed spacing is on the upper surfaces and said inclined spacing is on the lower surfaces of a first two of said lobes and said inclined spacing is on the upper surfaces and said fixed spacing is on the lower surfaces of a second two of said lobes. 
     
     
       24. An apparatus as set forth in  claim 1 , further comprising:
   means for moving the rotor from the actuated position to the unactuated position.      
     
     
       25. An apparatus as set forth in  claim 24 , wherein the means for moving includes another rotary actuator.  
     
     
       26. A hybrid rotary actuator according to  claim 7 , further comprising:
   means for moving the rotor from the actuated position to the unactuated position.      
     
     
       27. An apparatus as set forth in  claim 26 , wherein the means for moving includes another rotary actuator.  
     
     
       28. Rotary actuator apparatus comprising:
   a first rotary actuator including:      a stator having first and second pole pieces;        a rotor disposed between said first and second pole pieces of said stator, said rotor being rotatable relative to said stator between an unactuated position and an actuated position;        said first pole piece of said stator having a first stator surface which faces toward and is spaced from a first rotor surface on said rotor by a first working air gap, said first stator surface on said first pole piece of said stator and said first rotor surface on said rotor being spaced apart by the same distance when said rotor is in the unactuated position as when said rotor is in the actuated position so that the extent of the first working air gap along the axis of rotation of the rotor remains constant during rotation of said rotor between the unactuated and actuated positions;        said second pole piece of said stator having a second stator surface which faces toward and is spaced from a second rotor surface on said rotor by a second working air gap, said second stator surface on said second pole piece of said stator and said second rotor surface on said rotor being spaced apart by a smaller distance when said rotor is in the actuated position than when said rotor is in the unactuated position so that the extent of the second working air gap along the axis of rotation of the rotor decreases during rotation of said rotor between the unactuated and the actuated positions; and        a coil which extends around at least a portion of said stator, said coil being energizable to provide magnetic flux which passes across the space between said first stator surface and said first rotor surface and which passes across the space between said second stator surface and said second rotor surface during at least a portion of the rotation of said rotor between the unactuated position and the actuated position said flux biasing said rotor to move from said unactuated position towards said actuated position,        wherein said first stator surface and said first rotor surface have flat configurations, said second stator surface and said second rotor surface have flat configurations are inclined with respect to said first stator surface and said first rotor surface, and          a second rotary actuator coupled to the first rotary actuator for moving the rotor in the first rotary actuator from the actuated position to the unactuated position.      
     
     
       29. Rotary actuator apparatus as set forth in  claim 28 , further comprising:
   a diverter gate connected with the rotor and movable with the rotor during movement of the rotor between the unactuated and actuated positions,        wherein the second rotary actuator is connected with the diverter gate and is energizable to effect movement of the rotor from the actuated position to the unactuated position.      
     
     
       30. Apparatus comprising:
   a first rotary actuator including:      a stator having at least first and second pole pieces;        at least one rotor disposed between said at least first and second pole pieces of said stator, said at least one rotor being rotatable relative to said stator between an unactuated position and an actuated position, said at least one rotor having at least two rotor lobes generally disposed between corresponding stator lobes on each of said at least first and second stator pole pieces, each rotor lobe having upper and lower surfaces spaced apart from corresponding surfaces on said corresponding stator lobes of said at least first and second pole pieces of said stator;        said respective rotor lobe and stator lobe surface defining one of two possible configurations, each of said configurations comprising one of a fixed and variable rotor/stator surface spacing during rotation of said rotor; and        a coil which extends around at least a portion of said stator, said coil being energizable to provide magnetic flux which passes between said first sand second stator pole piece and through said rotor during at least a portion of the rotation of said rotor between the unactuated position and the actuated position where at least one rotor lobe upper surface has a fixed rotor/stator surface spacing and at least one rotor lobe lower surface has a variable rotor/stator surface spacing, and          a second rotary actuator for moving the rotor from the actuated position to the unactuated position.      
     
     
       31. Apparatus as set forth in  claim 30 , further comprising:
   a diverter gate connected with the rotor and movable with the rotor during movement of the rotor between the unactuated and actuated positions,        wherein the second rotary actuator is connected with the diverter gate and is energizable to effect movement of the rotor from the actuated position to the unactuated position.