Thread forming fasteners for ultrasonic load measurement and control

• US 20060144157A1
• Filed: 09/19/2003
• Published: 07/06/2006
• Est. Priority Date: 09/19/2002
• Status: Active Grant

• Current Assignee: Innovation Plus, LLC
• Original Assignee: Innovation Plus, LLC
• Inventors: Kibblewhite, Ian E, Molsbergen, Robert
• Granted Patent: US 8,037,772 B2
• Time in Patent Office: Days
• US Class Current: 73/761
• CPC Class Codes: F16B 2031/022 using an ultrasonic transducer
• CPC Class Codes: F16B 31/02 for indicating the attainment of a particular tensile load or limiting tensile load apparatus for, or method of, determining value of torque or twisting moment for tightening a nut or other member similarly stressed G01L5/24
• CPC Class Codes: G01L 5/246 using acoustic waves

Abstract

An ultrasonic load measurement transducer (14) is mated with a thread-forming fastener (12) to provide a load indicating thread-forming fastener (10) that can be used for precise and reliable assembly of critical bolted joints, such as those in the automobile and aerospace industries, among others. Steps can then be taken to accurately measure and control the load in the thread-forming fastener (10) during tightening, and to inspect the load in the thread-forming fastener (10) after assembly. A similar result can be achieved for a thread-locking fastener by mating an ultrasonic transducer with the thread-locking fastener assembly.

Claims

1. An apparatus comprising:

a thread-forming fastener including a head for engagement by a tool for applying a torque to the fastener, and a body portion extending from the head and including thread-forming portions; and

an ultrasonic transducer coupled with the fastener, for making ultrasonic load measurements in the fastener.

2. The apparatus of claim 1 wherein the ultrasonic transducer is coupled with the head of the fastener.

3. The apparatus of claim 1 wherein the ultrasonic transducer is permanently attached to the fastener.

4. The apparatus of claim 3 wherein the ultrasonic transducer is comprised of a piezoelectric polymer film permanently attached to the head of the fastener.

5. The apparatus of claim 3 wherein the ultrasonic transducer is comprised of an oriented piezoelectric thin film, vapor deposited directly on the head of the fastener.

6. The apparatus of claim 3 wherein the ultrasonic transducer is chemically grafted on the head of the fastener.

7. The apparatus of claim 1 wherein the ultrasonic transducer is temporarily attached to the fastener.

8. The apparatus of claim 1 wherein the ultrasonic transducer further includes an information storage medium applied to the ultrasonic transducer, wherein the information storage medium includes markings corresponding to data associated with the fastener.

9. The apparatus of claim 8 wherein the information storage medium is a bar code applied to the ultrasonic transducer.

10. A method of making a load indicating, thread-forming fastener, comprising the steps of:

providing a fastener having a first end including a surface for receiving an ultrasonic transducer, for making ultrasonic load measurements in the fastener, a shank extending from the first end and including thread-forming portions for tapping a hole, and a second end, opposite the first end and including a surface for reflecting an ultrasonic wave back to the first end; and

attaching an ultrasonic transducer to the first end of the fastener.

11. The method of claim 10 which further includes the step of attaching the ultrasonic transducer to a head associated with the first end of the thread forming fastener, for engagement by a tool for applying a torque to the fastener.

12. The method of claim 10 which further includes the step of permanently attaching the ultrasonic transducer to the fastener.

13. The method of claim 12 which further includes the step of permanently attaching an ultrasonic transducer comprised of a piezoelectric polymer film to the first end of the fastener.

14. The method of claim 12 which further includes the step of vapor depositing an ultrasonic transducer comprised of an oriented piezoelectric thin film directly onto the first end of the fastener.

15. The method of claim 12 which further includes the step of chemically grafting an ultrasonic transducer onto the first end of the fastener.

16. The method of claim 10 which further includes the step of temporarily attaching the ultrasonic transducer to the fastener.

17. The method of claim 10 which further includes the step of applying an information storage medium to the ultrasonic transducer, wherein the information storage medium includes markings corresponding to data associated with the fastener.

18. The method of claim 17 which further includes the step of applying a bar code to the ultrasonic transducer.

19. A method of measuring a load in a fastener, comprising the steps of:

providing a thread-forming fastener including a head for engagement by a tool for applying a torque to the fastener, and a body portion extending from the head and including thread-forming portions;

coupling an ultrasonic transducer with the fastener, for making ultrasonic load measurements in the fastener;

electrically connecting an apparatus to the ultrasonic transducer for supplying signals to the ultrasonic transducer and for receiving signals from the ultrasonic transducer;

monitoring the signals received from the ultrasonic transducer, providing an accurate measurement indicative of the load in the fastener; and

adjusting the measurement indicative of the load to compensate for effects of heating of the fastener resulting from forming a thread in a mating component during installation.

20. The method of claim 19 which further includes the step of imparting torque to the fastener and removing torque from the fastener in response to the measurement of the load in the fastener.

21. The method of claim 19 which further includes the step of determining a zero-load ultrasonic measurement, using the measurement indicative of the load in the fastener.

22. The method of claim 21 which further includes the step of measuring a torque in conjunction with the measurement indicative of the load in the fastener to determine the zero-load ultrasonic measurement.

23. The method of claim 21 which further includes the step of measuring an angle of rotation of the fastener in conjunction with the measurement indicative of the load in the fastener to determine the zero-load ultrasonic measurement.

24. The method of claim 21 which further includes the step of measuring time in conjunction with the measurement indicative of the load in the fastener to determine the zero-load ultrasonic measurement.

25. The method of claim 21 which further includes the step of taking measurements for determining the zero-load ultrasonic measurement prior to a load-inducing stage of the installation.

26. The method of claim 21 which further includes the step of taking measurements for determining the zero-load ultrasonic measurement during a load-inducing stage of the installation.

27. The method of claim 19 which further includes the step of placing markings on the ultrasonic transducer corresponding to data associated with the fastener.

28. The method of claim 27 which further includes the step of marking a bar code on the ultrasonic transducer.

29. A method of measuring a load in a fastener, comprising the steps of:

providing a thread-locking fastener assembly including a bolt having a head for engagement by a tool for applying a torque to the fastener assembly and a body portion extending from the head, and a nut for cooperating with the body portion of the bolt, wherein portions of the fastener assembly include resistance-inducing threads;

coupling an ultrasonic transducer with the bolt, for making ultrasonic load measurements in the fastener assembly;

electrically connecting an apparatus to the ultrasonic transducer for supplying signals to the ultrasonic transducer and for receiving signals from the ultrasonic transducer;

monitoring the signals received from the ultrasonic transducer, providing an accurate measurement indicative of the load in the fastener assembly; and

adjusting the measurement indicative of the load to compensate for effects of heating of the fastener assembly resulting from prevailing torque associated with the thread-locking fastener assembly.

30. The method of claim 29 which further includes the step of imparting torque to the bolt and removing torque from the bolt in response to the measurement of the load in the fastener assembly.

31. The method of claim 29 which further includes the step of determining a zero-load ultrasonic measurement, using the measurement indicative of the load in the fastener assembly.

32. The method of claim 31 which further includes the step of measuring a torque in conjunction with the measurement indicative of the load in the fastener assembly to determine the zero-load ultrasonic measurement.

33. The method of claim 31 which further includes the step of measuring an angle of rotation of the fastener in conjunction with the measurement indicative of the load in the fastener assembly to determine the zero-load ultrasonic measurement.

34. The method of claim 31 which further includes the step of measuring time in conjunction with the measurement indicative of the load in the fastener assembly to determine the zero-load ultrasonic measurement.

35. The method of claim 31 which further includes the step of taking measurements for determining the zero-load ultrasonic measurement prior to inducing the load in the fastener assembly.

36. The method of claim 31 which further includes the step of taking measurements for determining the zero-load ultrasonic measurement while inducing the load in the fastener assembly.

37. The method of claim 29 which further includes the step of placing markings on the ultrasonic transducer corresponding to data associated with the fastener assembly.

38. The method of claim 37 which further includes the step of marking a bar code on the ultrasonic transducer.