Patent ID: 7009477

Claim:
An actuator for generating a force in an axial direction, the actuator comprising: a hollow body ( 30 , 31 , 33 ) housing magnetic flux generating means ( 20 ); a core ( 50 , 51 , 52 ) arranged concentrically in said hollow body in fixed relationship thereto and forming an annular space ( 22 ) therebetween; and armature means ( 25 ) extending at least partially into said annular space and carrying two axially-spaced coil means ( 23 , 24 ); wherein said magnetic flux generating means ( 20 ) is arranged in said hollow body to lie in a position axially intermediate said two coil means for generating a magnetic flux path in said hollow body and said core and through said two coil means to generate said force between said hollow body and said armature when said coils are energized; and a bearing portion extending from an outer surface of the core ( 52 ); and wherein the armature means ( 25 ) comprises a low friction area ( 53 ) between the first and second coil means ( 23 , 24 ); wherein the bearing portion abuts the low friction area of the hollow member in order to form a bearing restricting lateral movement of the armature means ( 25 ) during operation and also forming an air seal between a cavity formed by the armature and the core.