US3718066A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tension indicating fastener
Assignee: IIT Research Institute
•
Filing: 1970-12-28
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Granted: 1973-02-27
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Expires: 1990-12-28
Abstract
Abstract A bolt having a shank and integral head has a strip of photoelastic material mounted on the head for manifesting in the form of photoelastic fringes linearly related to bolt tension the bending stresses created in the head during loading of the bolt. To determine the tension in the bolt during or after loading, polarized light is directed toward the photoelastic strip and reflected light from the strip is analyzed to measure fringe order. The fringe order is related to the amount of bending stresses in the head of the bolt by a predetermined calibration curve, the bending stresses being linearly related to bolt tension.
Inventors
- 👤 J Dally
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 16:01
CPC Classifications
F; F16; F16B; F16B31/00; F16B31/02; G; G01; G01B; G01B11/00; G01B11/16; G01B11/18; G01L; G01L5/00; G01L5/24
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
40 words
A combination according to claim 1 wherein said photoelastic member is rectangular in shape and wherein said side mounted to said head is a bottom side of said member and wherein vertical and top sides are spaced from said head.
Claim 2
Dependent Claim
117 words
A bolt comprising an externally threaded shank, a head integrally mounted to the end of said shank, said head having a depression formed in the upper surface thereof, a strip of photoelastic material having a side mounted on the bottom wall of said depression, said strip being adapted to manifest bending stresses in the form of photoelastic fringes linearly related to bolt tension during tensioning of said bolt, other sides of said strip being free of said head to reduce the effect of transverse stresses, and a layer of reflecting adhesive for mounting said strip within said depression, said layer of reflecting adhesive being adapted to permit the observation of said fringes on said strip by reflection.
Claim 3
Dependent Claim
16 words
A bolt according to claim 3 wherein said strip of formed of a birefringent polymeric material.
Claim 4
Dependent Claim
14 words
A bolt according to claim 4 wherein said polymeric material is an epoxy resin.
Claim 5
Dependent Claim
13 words
A bolt according to claim 4 wherein said polymeric material is a polycarbonate.
Claim 6
Dependent Claim
16 words
A bolt according to claim 3 wherein said head is provided with an undercut seating collar.
Claim 7
Independent Claim
107 words
A method of determining the amount of tension placed on a fastener, comprising the steps of: tensioning the fastener and applying tension to a shank connected to a head to cause bending stresses and strain in said head, directing polarized light toward a birefringent photoelastic material on said head such that the light is reflected by the photoelastic material and bending stresses are manifested in the form of fringes in the photoelastic material which are linearly related to the tension, analyzing the reflected polarized light to determine fringe order, and relating the fringe order to the amount of tension in the fastener by a predetermined calibration curve.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-02-27 | 1976-08-28 | 1977-02-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-27 | 1980-08-28 | 1981-02-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-27 | 1984-08-28 | 1985-02-27 | $7700.00 | Window Closed / Lapsed |