AC Solenoid apparatus of the armature in tube type

Claim 1

An AC solenoid apparatus for operating a valve comprising: a relatively thin pressure proof tube made from nonmagnetic material, said tube having a longitudinal axis; an armature slidably positioned within said tube for movement along said longitudinal axis in contact with the inner face of said tube; a stationary core secured to one end of said pressure proof tube, said core having an axial bore along which oil can circulate between said valve and the interior of said pressure proof tube; an end member sealingly attached to the other end of said pressure proof tube; a pin positioned within the axial bore of said stationary core and engageable with said armature; and an exciting assembly including; a coil surrounding said pressure proof tube, said armature moving axially within said tube when said coil is energized by current flowing therethrough; a generally rectangular yoke having a pair of longitudinal side faces with openings therein surrounding said coil, said yoke having slots in each of said longitudinal side faces connecting said openings with the outside of said yoke; and a slotted annular ring made from magnetic material, said ring being interposed between said pressure proof tube and at least one opening of said yoke, the slot in said ring being in alignment with a slot in said yoke, said ring having an annular length greater than the thickness of said yoke.