Ultrasonic load indicating member, apparatus and method
First Claim
1. A method of making a load indicating fastener from a fastener having a head and a shank extending from the head, said shank being subjected to elastic deformation when stressed longitudinally such that one portion thereof moves relative to another portion thereof, said method comprising the steps of:
- forming a first flat surface on said head and a location remote from said shank, said first flat surface being normal to the longitudinal axis of said shank;
forming a piezoelectric sensor by applying a first and a second electrode means to opposite faces of a piezoelectric disk; and
permanently, acoustically, and mechanically interconnecting said piezoelectric sensor to said head of said fastener such as to electrically interconnect a first electrode of said piezoelectric sensor with said head and, further, such as to isolate said second electrode from said head.
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Abstract
A method of measuring the load in a member subjected to longitudinal stress, a load measuring device and a fastener tightening device using the method of measuring, a load indicating member and a load indicating fastener for use in conjunction with the method of measuring, a method of making the load indicating fastener, a method of tightening the load indicating fastener and a transducer for instrumenting a load bearing member are each disclosed and claimed. A thin piezoelectric sensor consisting of a piezoelectric film sandwiched between two thin electrodes is permanently mechanically and acoustically coupled to the upper surface of a member and is used to determine the length, tensile load, stress, or other tensile load dependent characteristic of the member by ultrasonic techniques.
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Citations
33 Claims
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1. A method of making a load indicating fastener from a fastener having a head and a shank extending from the head, said shank being subjected to elastic deformation when stressed longitudinally such that one portion thereof moves relative to another portion thereof, said method comprising the steps of:
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forming a first flat surface on said head and a location remote from said shank, said first flat surface being normal to the longitudinal axis of said shank; forming a piezoelectric sensor by applying a first and a second electrode means to opposite faces of a piezoelectric disk; and permanently, acoustically, and mechanically interconnecting said piezoelectric sensor to said head of said fastener such as to electrically interconnect a first electrode of said piezoelectric sensor with said head and, further, such as to isolate said second electrode from said head. - View Dependent Claims (2, 3, 4, 5)
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6. A load measuring device for use in conjunction with a load indicating member having a shank, a first flat surface formed adjacent one longitudinal end of said shank, and a piezoelectric transducer secured to said first flat surface, said load measuring device comprising:
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first contact means selectively engageable with said load indicating member; second contact means selectively engageable with said piezoelectric transducer; and measurement means responsive to the electronic differential between said first and second contact means such as to provide a measurement of a tensile load dependant characteristic of said shank when said shank is stressed longitudinally. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of tightening a load indicating fastener of the type having a shank subject to elastic deformation when stressed longitudinally, a head formed at one longitudinal end of said load indicating fastener, a first flat surface formed adjacent said head, tool engagement means formed on said head adjacent said first flat surface, piezoelectric sensor means permanently mounted on said first flat surface, and a second flat surface formed at the other longitudinal end of said shank, said method comprising the steps of:
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engaging a tightening tool with said tool engagement means; engaging contact means with said piezoelectric sensor; operating said tightening tool to tighten said load indicating fasteners; and measuring a signal representative of the time of flight of an ultrasonic wave along said shank by monitoring the differential electronic signal between said tool engagement means and said contact means such as to provide a continuous measurement of the tensile load of said shank during the operation of said tightening tool. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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Specification