Patent ID: 8026781

Claim:
A solenoid comprising: a core having a junction surface; a plunger having a junction surface and located proximate to the core; a shading ring located proximate to an interface between the core junction surface and the plunger junction surface, the shading ring having an outside diameter slightly smaller than the diameter of the core, and operable to produce a concentration of magnetic attraction within an annular range of the interface between a center of the interface and a location of the shading ring; wherein one of the core junction surface or the plunger junction surface is substantially flat and the other of the core junction surface or the plunger junction surface has a concavity formed therein such that an annular contact region is formed at the interface between the core junction surface and the plunger junction surface which is substantially smaller than the respective junction surfaces and is located proximate to the annular range of the concentration of magnetic attraction.