Patent ID: 7116097
Filing Date: 2006-10-03
Classification: F15B

Abstract:
1. A method of detecting a position of a movable member associated with a cylinder, the method comprising: providing a shaft having a core, a first hardened metallic region from a surface of the shaft to a first radial depth from the surface at a first longitudinal position, and a second hardened metallic region from the surface of the shaft to a second radial depth at a second longitudinal position; the second radial depth different from the first radial depth, the hardened metallic regions overlying the core and formed from at least one of case hardening and inductive hardening of a metal or an alloy of the shaft; sensing an eddy current or induced electromagnetic field to detect an alignment of at least one of the first hardened metallic region and the second hardened metallic region with a fixed sensing region at a respective time; and determining a longitudinal position of the shaft with respect to a cylinder at the respective time based on the sensed eddy current.