BOLT TENSION GAUGING SYSTEM
First Claim
1. A method for comparing the contours of an end surface of a fastener for identifying any different tension states of the fastener, the method comprising the steps of:
- (a) obtaining a first measurement which is a first contour map of an end surface of the fastener;
(b) obtaining a second measurement which is a second contour map of the surface of the fastener, said second measurement obtained at a period of time after the first measurement is captured; and
(c) comparing the first contour map with the second contour map for any differences.
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Accused Products
Abstract
An apparatus and method for measuring the tension in bolts, screws, rivets, and other fasteners, is disclosed wherein the deformation of the fastener head is measured (or the end of fastener in such cases as there is not a distinct formed head, for example stud bolts). The deformation generally is an analytic function of the tension in the fastener. The deformation is a continuous two-dimensional distribution over the surface of the fastener head, which allows redundant measurement and therefore more reliable measurement of fastener total axial tension, and also allows in some instances an evaluation of the bending stresses in the fastener from the distortion of the deformation pattern on the head. An advantage of the invention is that the length of the fastener or its temperature need not be known. The measurements can be determined by optical, capacitance, optical imaging, air gauging and piezoresistive techniques.
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Citations
16 Claims
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1. A method for comparing the contours of an end surface of a fastener for identifying any different tension states of the fastener, the method comprising the steps of:
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(a) obtaining a first measurement which is a first contour map of an end surface of the fastener;
(b) obtaining a second measurement which is a second contour map of the surface of the fastener, said second measurement obtained at a period of time after the first measurement is captured; and
(c) comparing the first contour map with the second contour map for any differences. - View Dependent Claims (2, 3, 4, 5)
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6. A method for comparing the contours of an end surface of a fastener for identifying any different tension states of the fastener, the method comprising the steps of:
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(a) obtaining a first measurement which is a first contour map of an end surface of the fastener;
(b) obtaining a second measurement which is a second contour map of the end surface of the fastener, said second measurement obtained at a period of time after the first measurement is captured; and
(c) comparing the first contour map with the second contour map for any differences;
wherein any found differences between the first contour map and the second contour map represent a change in tensions in the fastener;
wherein the obtaining of the first measurement and the second measurement is independent of a temperature or length of the fastener. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
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14. A method for comparing the contours of an end surface of a fastener for identifying any different tension states of the fastener, the method comprising the steps of:
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(a) obtaining a first measurement which is a first contour map of an end surface of the fastener;
(b) obtaining a second measurement which is a second contour map generated an amount of depression in the central portion of the end surface of the fastener, said second measurement obtained a period of time after the first measurement is captured; and
(c) comparing the first contour map with the second contour map for any differences;
wherein any found differences between the first contour map and the second contour map represent a change in tension in the fastener;
wherein the obtaining of the first measurement and the second measurement is independent of a temperature or length of the fastener;
wherein the first measurement and the second measurement are obtained by a micrometer indicator selected from mechanical micrometer indicators, electrical micrometer indicators, linear variable displacement transducers, inductance proximity sensors, piezoresistive sensors, strain gauge sensors, or capacitance gap sensors. - View Dependent Claims (15, 16)
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Specification