Device for measuring the axial position of a piston rod relative to a cylinder housing

Device for measuring the axial position of a piston rod relative to a cylinder housing belonging to a cylinder-piston unit actuated by liquid pressure, with structures that constitute elevations and depressions formed in the cover surface of the piston rod, which structures form a material measure that runs in the axial direction, with a sensor device that is positioned on the cylinder housing and that employs sensors that are spaced in the axial direction to scan the structure in a contact-free fashion the purpose of position identification, and with an abrasion-proof cover for the purpose of guiding the structure inside the cylinder housing,

• wherein
• the structures are annular structures that enclose the piston rod concentrically, the cover is a tube coaxially slid onto the piston rod, and the annular structures form an absolutely coded material measure,
• and wherein
• annular measuring structures that are equidistantly positioned in the axial direction of the piston rod divide the material measure into segments that are absolutely scanned and that follow each other in periodic fashion, and an annular assigning structure is positioned within each segment, such that the axial position of the annular assigning structure within one segment is different from the axial position of the annular assigning structure in another segment and serves to clearly identify the given segment.