Method and apparatus having a single coil with embedded magnets

A solenoid assembly comprising:

• a ferromagnetic core tube having a longitudinal axis, a radial exterior surface and a radial interior surface surrounding a cavity, the ferromagnetic core tube comprising a first channel and a second channel disposed on the radial exterior surface of the ferromagnetic core tube, the first channel and the second channel circumscribing the ferromagnetic core tube along a given portion of the longitudinal axis, wherein the first channel and the second channel are spaced from one another along the longitudinal axis, the first channel comprising a plurality of radial exterior surfaces, the second channel comprising a second plurality of radial exterior surfaces, wherein a first portion of the ferromagnetic core tube between the plurality of radial exterior surfaces of the first channel and the radial interior surface of the ferromagnetic core tube define a first thin wall portion of the ferromagnetic core tube, wherein a second portion of the ferromagnetic core tube between the second plurality of radial exterior surfaces of the second channel and the radial interior surface of the ferromagnetic core tube define a second thin wall portion of the ferromagnetic core tube, the first channel comprising a first magnetic ring radially spaced apart from the first thin wall, the second channel comprising a second magnetic ring radially spaced part from second thin wall;
• an armature maintained with the cavity, the armature operable to move through the longitudinal axis of the cavity in response to a current passing through the coil;
• a coil located radially outward of the ferromagnetic core tube, wherein the ferromagnetic core tube comprises a uniform single piece material, wherein the first channel maintains a filler material between an inner radial surface of the first magnetic ring and the outer radial surface of the first thin wall, and wherein the second channel maintains a filler material between an inner radial surface of the second magnetic ring and the outer radial surface of the second thin wall.

A method comprising:

• (a) providing a ferromagnetic core tube having a longitudinal axis, a radial exterior surface and a radial interior surface surrounding a cavity, the ferromagnetic core tube comprising a first channel and a second channel disposed on the radial exterior surface of the ferromagnetic core tube, the first channel and the second channel circumscribing the ferromagnetic core tube along a given portion of the longitudinal axis, wherein the first channel and the second channel are spaced from one another along the longitudinal axis, the first channel comprising a plurality of radial exterior surfaces, the second channel comprising a second plurality of radial exterior surfaces, wherein a first portion of the ferromagnetic core tube between the plurality of radial exterior surfaces of the first channel and the radial interior surface of the ferromagnetic core tube define a first thin wall portion of the ferromagnetic core tube, wherein a second portion of the ferromagnetic core tube between the second plurality of radial exterior surfaces of the second channel and the radial interior surface of the ferromagnetic core tube define a second thin wall portion of the ferromagnetic core tube, the first channel comprising a first magnetic ring radially spaced apart from the first thin wall, the second channel comprising a second magnetic ring radially spaced part from second thin wall;
• and
• (b) providing a coil located radially outward of the ferromagnetic core tube, wherein the ferromagnetic core tube comprises a uniform single piece material.