Moving coil motor

Claim 1

Linear positioning apparatus comprising: a magnetic structure including an outer magnetic circuit and an inner magnetic circuit, at least one of which includes a source of magnetic flux, said inner magnetic circuit including a cylindrical core of magnetic material having an axial bore therein and being supported at one end thereof on said outer magnetic circuit, and said outer magnetic circuit including a front plate having an aperture therein larger than the diameter of said cylindrical core for forming therewith an air gap for supporting a radial magnetic field thereacross; shuttle means mounted with respect to said magnetic structure for lineally slidable motion through the air gap, in a direction normal to the radial magnetic field therein, said shuttle means having a conductor wound thereon for producing in response to applied electrical signal a magnetic field which interacts with the radial magnetic field in the air gap of said magnetic structure to produce linear motion of the shuttle means; transducer means including a pair of windings disposed on a bobbin having an internal bore therein and being disposed within the axial bore of said core recessed therein from the ends thereof, said transducer means including a source of magnetic flux slidably disposed within the bore of the bobbin and rigidly coupled to said shuttle means, the windings of said transducer means being disposed on the bobbin with winding densities that decrease substantially linearly with length along the bobbin from opposite ends thereof; circuit means connected to the winding of the transducer means for applying electrical signal to said conductor wound on said shuttle means to control the linear motion thereof; and a magnetic shunt disposed within the axial bore of said core adjacent the bobbin therewithin and having an aperture for passage therethrough of the rigid coupling between the shuttle means and the source of magnetic flux for said transducer means.