Patent ID: 7876186

Claim:
An electromagnetic actuator comprising: a coil assembly having a coil, which is energizable to generate a magnetic field, and a shell that is formed of a ferrous material, the shell defining an annular cavity into which the coil is received, the shell including an annular inner wall, first and second end walls, a first annular leg and a second annular leg, the annular inner wall being disposed radially inwardly of the coil, the first and second end walls extending radially outwardly from the inner wall and abutting opposite axial ends of the coil, the first annular leg being coupled to an end of the first wall opposite the annular inner wall and extending axially toward the second wall, the first annular leg defining a cylindrical guide surface, the second annular leg being coupled to an end of the second wall opposite the annular inner wall and extending axially toward the first wall; an armature that is formed of a ferrous material and which is movable relative to the coil assembly along a translation axis due to the magnetic field that is generated by the coil when the coil is energized, the armature having an annular mating guide surface that is matingly and slidably engaged to the guide surface formed on the first annular leg, the armature further having a rim that extends radially outwardly on a side of the armature opposite the annular mating guide surface; and a plunger mounted on the armature for movement therewith, the plunger abutting the rim, wherein the second annular leg includes a first frusto-conically shaped surface and the armature includes a correspondingly shaped surface that is drawn to the first frusto-conically shaped surface by the magnetic field when the coil is energized, and wherein the second end wall includes an annular rib that extends radially outwardly from the second annular leg, the annular rib being positioned to limit axial movement of the correspondingly shaped surface on the armature in a direction toward the first frusto-conically shaped surface on the second annular leg.