Patent ID: 7513445

Claim:
A metering servo valve for a fuel injector of an internal-combustion engine, comprising: a shell having a cavity forming a shoulder in the shell; a valve body housed in the cavity of the shell; an open/close element; an armature being displaceable between a first arrest element and a second arrest element, axially spaced from the first arrest element, the second arrest element being fixed in the valve body, the first arrest element being displaceable to adjust the displacement of the armature; an electromagnet positioned to affect displacement of the armature; a casing rigidly housing the electromagnet and having an annular projection and a substantially cylindrical portion including an inner surface toward the cavity of the shell, an outer surface, opposed to the inner surface, an annular groove formed on the outer surface and configured to house an elastic o-ring, a resting surface, and an elastically deformable region toward the resting surface, the cylindrical portion at least partially extending between the annular projection and the resting surface, the resting surface having at least one planar region substantially perpendicular to an axis of the shell and a tapered region adjacent the resting surface and positioned internally toward the cavity of the shell with respect to the planar region, the elastically deformable region being positioned adjacent the tapered region and including a cross section having a reduced thickness designed to enable elastic deformation by bending of the elastically deformable region, the cross section being formed between the annular groove and the tapered region, the planar region having an inner diameter greater than the inner diameter of the groove, so that the cross section of the tapered region is in part set in cantilever fashion with respect to the groove; and a ring nut engaging the annular projection of the casing and threadedly coupled to the shell with a tightening torque to fixedly couple the casing to the shell and urge the resting surface of the cylindrical portion of the casing against the shoulder of the shell wherein the elastically deformable region of the cylindrical portion of the casing is designed to undergo elastic deformation as a function of the tightening torque.