Permanent magnet linear actuators

Abstract

An electromagnetic actuator including: a core comprising a material having a high magnetic permeability relative to air; an array of coils sequentially arranged on the core, each coil of the array of coils being wound around the longitudinal axis of the core; and a magnet assembly movably mounted along the array of coils, the magnet assembly having a coil side facing the array of coils and an opposite side facing away from the array of coils and including an array of permanent magnets sequentially arranged along the array of coils in a direction parallel to the longitudinal axis, wherein the magnetic moments of the plurality of magnets are selected and arranged to augment the magnetic field produced on the coil side of the magnet assembly and to reduce the magnetic field produced on the opposite side of the magnet assembly.

What is claimed is: 
     
         1 . An electromagnetic actuator comprising:
 a core having a longitudinal axis, said core comprising a material having a high magnetic permeability relative to air and defining a hollow inner region extending the length of the core;   an array of coils sequentially arranged on the core, each coil of the array of coils being wound around the longitudinal axis of the core;   a magnet assembly movably mounted along the array of coils, said magnet assembly having a coil side facing the array of coils and an opposite side facing away from the array of coils, said magnet assembly comprising an array of permanent magnets sequentially arranged along the array of coils in a direction parallel to the longitudinal axis; and   a plurality of drive circuits located within the hollow region of the core and proximate to the coils.   
     
     
         2 . The electromagnetic actuator of  claim 1 , wherein each drive circuit of the plurality of drive circuits is located proximate to and is arranged to drive a corresponding different coil among the array of coils. 
     
     
         3 . The electromagnetic actuator of  claim 2 , wherein each drive circuit of the plurality of drive circuits is located within and arranged to drive a corresponding different coil of the array of coils. 
     
     
         4 . The electromagnetic actuator of  claim 1 , wherein the core comprises two longitudinal segments made of an electrically conductive material, and wherein the two segments function as power buses for the plurality of drive circuits. 
     
     
         5 . The electromagnetic actuator of  claim 1 , further comprising a circuit board on which the plurality of drive circuits are mounted, said circuit board located within the hollow inner region of the core. 
     
     
         6 . The electromagnetic actuator of  claim 5 , wherein the circuit board includes a control bus for carrying control signals for operating the plurality drive circuits. 
     
     
         7 . The electromagnetic actuator of  claim 1 , wherein the core comprises two segments each of which extends down the length of the array of coils, the two segments serving as electrically conductive lines for delivering power to the plurality of drive circuits and the coils in the array of coils. 
     
     
         8 . The electromagnetic actuator of  claim 1 , wherein the array of coils is a linear array of coils. 
     
     
         9 . The electromagnetic actuator of  claim 1 , wherein the magnet assembly comprises a plurality of arrays of permanent magnets, said first-mentioned array of permanent magnets being one of said plurality of arrays of permanent magnets, said plurality of arrays of permanent magnets being arranged about the array of coils to form a plurality of magnetic rings, each of which surrounds the array of coils. 
     
     
         10 . The electromagnetic actuator of  claim 1 , wherein the array of permanent magnets is an array of permanent ring magnets, each one encircling the coil array and the longitudinal axis of the core. 
     
     
         11 . The electromagnetic actuator of  claim 1 , wherein the core comprises a plurality of core segments and wherein each core segment of the plurality of core segments is associated with a different coil of the array of coils. 
     
     
         12 . The electromagnetic actuator of  claim 1 , further comprising a sleeve surrounding the array of coils, wherein the magnet assembly rides along and outside of the sleeve. 
     
     
         13 . The electromagnetic actuator of  claim 12 , wherein the sleeve is cylindrically shaped. 
     
     
         14 . The electromagnetic actuator of  claim 1 , wherein the core comprises iron and/or steel. 
     
     
         15 . The electromagnetic actuator of  claim 1 , wherein the coils in the array of coils are cylindrically shaped. 
     
     
         16 . The electromagnetic actuator of  claim 1 , wherein the core is cylindrically shaped.