Loosening detection structure, loosening detection system and method

Patent metadata

Field	Value
Publication number	US-11976993-B2
Application number	US-201917774670-A
Country	US
Kind code	B2
Filing date	Nov 8, 2019
Priority date	Nov 8, 2019
Publication date	May 7, 2024
Grant date	May 7, 2024

Abstract

A loosening detection structure used to detect loosening of a bolt includes a material that is disposed between a fixing subject steel plate and a head portion of a metal bolt for fixing the steel plate and either attached to a seating surface of the head portion of the bolt or attached to a washer disposed between the steel plate and the head portion of the bolt, and that has electrical characteristics that vary in response to variation in a force for fastening the bolt to the steel plate.

First claim

The invention claimed is:

1. A loosening detection structure used to detect loosening of a bolt, comprising:
a material that is disposed between a fixing subject steel plate and a head portion of a metal bolt for fixing the steel plate and either attached to a seating surface of the head portion of the bolt or attached to a washer disposed between the steel plate and the head portion of the bolt, and that has electrical characteristics that vary in response to variation in a force for fastening the bolt to the steel plate; and
an antenna for wireless receiving an electromagnetic wave used to detect loosening of the bolt and wireless transmitting an electromagnetic wave that has passed through the material,
wherein the material is a hygroscopic resin material that takes in moisture from the air through an exposed surface in response to a reduction in the force for fastening the bolt.

2. A loosening detection structure used to detect loosening of a bolt, comprising:
a material that is disposed between a metal inner layer formed in the interior of the bolt and a metal outer layer formed on the exterior of the bolt and has electrical characteristics that vary in response to variation in a force for fastening the bolt to a fixing subject steel plate; and
an antenna for wireless receiving an electromagnetic wave used to detect loosening of the bolt and wireless transmitting an electromagnetic wave that has passed through the material,
wherein the material is a hygroscopic resin material that takes in moisture from the air through an exposed surface in response to a reduction in the force for fastening the bolt.

3. A loosening detection system comprising:
a loosening detection structure used to detect loosening of a bolt and a loosening detection device that detects loosening of the bolt,
wherein the loosening detection structure comprises either a material that is disposed between a fixing subject steel plate and a head portion of a metal bolt for fixing the steel plate and either attached to a seating surface of the head portion of the bolt or attached to a washer disposed between the steel plate and the head portion of the bolt, and that has electrical characteristics that vary in response to variation in a force for fastening the bolt to the steel plate, or a material that is disposed between a metal inner layer formed in the interior of the bolt and a metal outer layer formed on the exterior of the bolt and has electrical characteristics that vary in response to variation in the force for fastening the bolt to the fixing subject steel plate, wherein the material is a hygroscopic resin material that takes in moisture from the air through an exposed surface in response to a reduction in the force for fastening the bolt, and
the loosening detection device comprises:
an output unit for outputting an electromagnetic wave that is used to detect loosening of the bolt;
an input unit for receiving an electromagnetic wave returning through the material; and
a determination unit for comparing a measurement value of the received electromagnetic wave with a measurement value of an electromagnetic wave measured when the bolt is fastened, and determining loosening of the bolt on the basis of whether or not a resonance frequency has shifted or whether or not the resonance frequency is within a predetermined frequency range.

Assignees

• Nippon Telegraph & Telephone

Inventors

• Matsunaga Eri
• Minotani Tadashi
• Nakamura Masahito
• Tsuda Masayuki

Classifications

• G01L5/243 Primary

  using washers · CPC title

• G01L1/20

  by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids (of piezo-resistive materials G01L1/18); by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress · CPC title

• G01L1/2231

  the supports being disc- or ring-shaped, adapted for measuring a force along a single direction · CPC title

• G01L5/24

  for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed · CPC title

• G01N22/00

  Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more (G01N3/00 - G01N17/00, G01N24/00 take precedence) · CPC title