Patent ID: 7078833

Claim:
A force motor comprising: a shaped housing having: an internal wall: a cylindrical extension projecting from the internal wall; and a concave surface formed on the internal wall; a bobbin mounted in the shaped housing; a permanent magnet mounted in the bobbin, the bobbin isolating the magnet from the armature thereby Preventing contaminants from depositing on the armature; a cylindrical layer located between the bobbin and the armature, the cylindrical layer being made from an electric conductor and attached firmly on the armature, thus dampening the movement of armature due to vibration or shock; a shaped armature mounted in the shaped housing; wherein the shape of the armature and the housing cooperate to produce a flat F-S curve for the force motor, and wherein the shaped armature comprises: a cylindrical portion; a conical section, the large end of the conical section being larger than the cylindrical portion; and a cylindrical face formed at the junction of the cylindrical portion and the conical section, the cylindrical face extending from the outer surface of the cylindrical portion to the tip of the large end of the conical section, and wherein the cylindrical portion, the conical section and the cylindrical face at the junction of the cylindrical portion and the conical section are made from materials with different magnetic properties.