Patent ID: 8307700
Filing Date: 2012-11-13
Classification: G01M

Abstract:
1. A sensor for sensing the translation or position of a reciprocating free piston in a free piston Stirling machine having an outer pressure vessel for containing a working gas and at least one power piston freely reciprocatable in a cylinder within the pressure vessel at a nominal designed maximum stroke along an axis of reciprocation, the sensor comprising: (a) a disk mounted to an end face of the piston coaxially with the cylinder and reciprocating with the piston, the disk including a rim around its outer perimeter formed of an electrically conductive material, the disk having a thickness in the axial direction of no more than 30 percent of the nominal designed maximum stroke and radial dimensions perpendicular to the axis greater than its thickness in the axial direction; and (b) a coil wound coaxially with the cylinder, spaced outwardly from the outer perimeter of the disk and mounted in fixed position relative to the pressure vessel, the coil having conductor leads for connection to a detector circuit.