Measuring and testing – Specimen stress or strain – or testing by stress or strain... – By loading of specimen
Reexamination Certificate
2002-04-30
2004-12-28
Noori, Max (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
By loading of specimen
Reexamination Certificate
active
06834552
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a fibre optic strain-gauge of the kind using a mechanical construction providing a linear, strain-dependent relative movement of oppositely positioned spaced-apart first and second optical fibre-holding elements in a direction substantially perpendicular to the axial direction of the optical fibres, in which the varying transmission of light between the two fibres is used as an indication of the strain.
BACKGROUND ART
In strain-gauges of this kind it is known to position two optical fibres oppositely in order to transmit light from one fibre to the other and to provide a strain-dependent relative movement of the fibres, whereby the transmission of light is dependent on the strain. In such systems it is most common to use focusing lenses in order to have a relatively high transmission of light and the use of fibres without any optical elements is setting a high demand on the precisior of the positioning of the fibres which is at least expensive and difficult to achieve. In this connection both alignment and mutual distance between the fibres have to be controlled in an exact manner, in order to achieve a stable correlation between strain and transmission of light. One example of a fibre-optical strain-gauge of this kind is described in U.S. Pat. No. 4,611,378. This document describes a method for positioning optical fibres on fibre-holding elements in alignment about a mechanical quiescent point in the absence of strain. Due to the use of relatively thick fibres, e.g. 0.3 mm 0.6 mm and 1.0 mm in diameter, the demand on the precision of the positioning of the fibres is not very high and this document does not address any of the problems in connection with precise alignment and positioning of the fibres.
U.S. Pat. No. 4,300,813 describes a fibre-optic acoustical transducer. The fibre is mounted under tension to orient the fibre axis along a straight line and at thereafter. The mechanical construction maintains one fibre end face stationary and the other fibre and cantilevered and permits vertical displacement of its end face. The vertical displacement is induced by acoustical waves impinging on a membrane connected to move the cantilevered fibre end. There is no indication in this document suggesting any way of connecting the cantilevered fibre end to provide a measurement of stain in a mechanical construction and, furthermore, no suggestion of providing a movement of both fibre ends in opposite directions perpendicular to the axial direction of the fibres is provided.
Other types of fibre-holding strain-gauges use bending, stretching and compression of the light transmission passage between the optical fibre ends, and is e.g. described in U.S. Pat. No. 5,812,251. Due to the necessary relatively long distance between the optical fibre ends in the constructions described in this document, however, these types of strain-gauges require the use of lenses in order to achieve an acceptable output signal.
DISCLOSURE OF THE INVENTION
It is the object of the present invention to provide a fibre-optical strain-gauge of the kind referred to above, with which it is possible to achieve a very precise alignment and positioning of the two oppositely positioned optical fibres in the strain-gauge construction in a simple manner. With this arrangement an exact alignment of the two optical fibres is automatically achieved in a simple manner and the distance between the two fibre ends can be controlled by controlling the prestressing of the optical fibre, or the mechanical construction, i.e. controlling the applied force.
Preferred embodiments of the fibre-optical strain-gauge are revealed hereafter.
REFERENCES:
patent: 4204742 (1980-05-01), Johnson et al.
patent: 4293188 (1981-10-01), McMahon
patent: 4300813 (1981-11-01), Gravel
patent: 4359637 (1982-11-01), Perren
patent: 4611378 (1986-09-01), Caserta et al.
patent: 5140155 (1992-08-01), Carome
patent: 5224977 (1993-07-01), Anjan et al.
patent: 5245400 (1993-09-01), Anjan et al.
patent: 5338929 (1994-08-01), Douma et al.
patent: 5812251 (1998-09-01), Manesh
patent: 6184797 (2001-02-01), Stark et al.
Jackson Douglas E.
Noori Max
Stites & Harbison PLLC
Vestas Wind Systems A/S
LandOfFree
Fibre-optical strain-gauge does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fibre-optical strain-gauge, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fibre-optical strain-gauge will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3322440