Intelligent washer

Abstract

An intelligent fastener unit for fastening together structural members. The fastener unit includes a fastener with an externally threaded shank, an internally threaded mating member for threaded engagement with the fastener, and an intelligent washer having an RFID tag and an antenna mounted on one surface of a centrally aperture body member, and a pressure sensor mounted on the opposite surface for generating electrical signals representative of the compressive force applied to structural members captured by the fastener, the mating member and the washer. An air gap is formed in the washer body member between the outer periphery and the central aperture to reduce eddy current formation when the RFID tag is interrogated by an RFID tag reader using r.f. signaling. The RFID tag has a memory containing information specific to the fastener unit—such as fastener unit identification, specified torque value and other information Once installed, the existing torque on a collection of fastener units is measured by using the RFID tag reader to scan the information stored in the memory of each fastener unit washer.