ULTRASONIC EXTENSOMETER

• US 3,759,090 A
• Filed: 02/22/1971
• Issued: 09/18/1973
• Est. Priority Date: 02/22/1971
• Status: Expired due to Term

• Current Assignee: Donald C. Erdman, Evan B. Friedmann, Howard J. Mcfaul
• Original Assignee: Donald C. Erdman, Evan B. Friedmann, Howard J. Mcfaul
• Inventors: McFaul, Howard J., Erdman, Donald C., Friedmann, Evan B.
• Primary Examiner(s): Gill, James J.
• Application Number:
  US05/117,635
• Time in Patent Office: 939 Days
• Field of Search: 73/67.7,67.8,67.9,67.5,67.6
• US Class Current: 73/597
• CPC Class Codes: F16B 2031/022 using an ultrasonic transducer
• CPC Class Codes: G01L 5/246 using acoustic waves
• CPC Class Codes: G01N 2291/02827 Elastic parameters, strength or force

Abstract

An ultrasonic extensometer for measuring the elongation of a bolt or the like being tightened against structure which it fastens, the extensometer including a transducer magnetically coupled to one end of the bolt, a pulser/receiver for generating a periodic pulse signal which energizes the transducer that is subsequently energized by the echo pulse from the far end of the bolt to provide an echo signal which is received and amplified, indicating circuit means for detecting and providing a correct couple indication between the transducer and its associated bolt end, and measuring circuit means for displaying a variable duration meter signal responsively produced by the amplified echo signal and controlled in duration by a vernier signal responsively produced by the pulse signal after a predetermined delay which is adjustable to index the vernier signal a desired amount with respect to the meter signal so that when the bolt has been elongated the proper amount, the amplified echo signal then coincides with the indexing vernier signal and the duration of the meter signal is reduced to zero.

Claims

1. A method of establishing the position of a movable target point in a medium with respect to an indexed position thereof, which comprises the steps of:

generating a reference signal at a reference point in said medium, said reference signal traveling at a generally established velocity along a path therein to said target point;

producing a target signal in response to the arrival of said reference signal at said target point;

generating a marker signal at a predetermined occurrence relative to that of said reference signal;

measuring a substantially integral time multiple of the occurrence of said target signal following the generation of said reference signal relative to that of said marker signal;

indicating the measured difference between the substantially integral time multiple of the occurrence of said target signal and that of said marker signal on indicating means, said indicating means being calibrated in units to correspond with units of movement of said target point; and

varying the occurrence of said marker signal relative to that of said reference signal so that a predetermined index indication is provided by said indicating means whereby the position of said target point when moved from its indexed position in said medium is correspondingly indicated by said indicating means with respect to said index indication thereof.

2. The invention as defined in claim 1 wherein a plurality of uniformly spaced marker signals is generated, the beginning of which is generated at a predetermined occurrence relative to that of said reference signal and the ending is at an occurrence after that of said target signal, the substantially integral time multiple of the occurrence of said target signal is measured relative to a selected one of said marker signals and the measured difference therebetween is indicated on said indicating means, and the beginning of said plurality of uniformly spaced marker signals is varied relative to that of said reference signal so that a predetermined index indication is provided by said indicating means.

3. The invention as defined in claim 2 wherein said plurality of uniformly spaced marker signals are originally generated independently of said reference signal, and said target signal is an echo signal of said reference signal reflected back towards said reference point from said target point and its occurrence on arrival proximate said reference point is measured relative to the occurrence of a selected one of said marker signals.

4. Means for establishing the position of a movable target point in a medium with respect to an indexed position thereof, said position establishing means comprising:

means for generating a reference signal at a reference point in said medium, said reference signal traveling at a generally established velocity along a path therein to said target point;

means for providing a target signal in response to the arrival of said reference signal at said target point;

means for generating a marker signal at a predetermined occurrence relative to that of said reference signal;

means for measuring a substantially integral time multiple of the occurrence of said target signal following the generation of said reference signal relative to that of said marker signal;

means for indicating the measured difference between the substantially integral time multiple of the occurrence of said target signal and that of said marker signal, said indicating means being calibrated in units to correspond with units of movement of said target point; and

means for varying the occurrence of said marker signal relative to that of said reference signal so that a predetermined index indication is provided by said indicating means whereby the position of said target point when moved from its indexed position in said medium is correspondingly indiCated by said indicating means with respect to said index indication thereof.

5. The invention as defined in claim 4 wherein said marker signal generating means generates a plurality of uniformly spaced marker signals, the beginning of which is generated at a predetermined occurrence relative to that of said reference signal and the ending is at an occurrence after that of said target signal, the substantially integral time multiple of the occurrence of said target signal is measured by said measuring means relative to a selected one of said marker signals and the measured difference therebetween is indicated on said indicating means, and the beginning of said plurality of uniformly spaced marker signals is varied by said varying means relative to that of said reference signal so that a predetermined index indication is provided by said indicating means.

6. The invention as defined in claim 5 wherein said plurality of uniformly spaced marker signals are originally generated independently of said reference signal, and said target signal providing means includes a reflecting surface of said target point and said target signal is an echo signal of said reference signal reflected therefrom back towards said reference point, and its occurrence on arrival proximate said reference point is measured by said measuring means relative to the occurrence of a selected one of said marker signals.

7. Ultrasonic means for measuring changes in length of a bolt or the like, said ultrasonic means comprising:

an electromechanical transducer coupled to one end of said bolt;

a pulser/receiver for generating a periodic electrical reference signal which energizes said transducer to send a sonic reference signal down the length of said bolt to produce a sonic echo signal from the other end of said bolt, said sonic echo signal subsequently energizing said transducer to provide an electrical echo signal which is received and amplified by said pulser/receiver;

means responsive to said electrical reference signal to generate an electrical marker signal at a predetermined occurrence relative to that of said electrical reference signal;

means for measuring the occurrence of said electrical echo signal relative to that of said electrical marker signal;

means for indicating the measured difference between the occurrences of said electrical echo and marker signals, said indicating means being calibrated in units to correspond with units of change in length of said bolt; and

means for varying the occurrence of said electrical marker signal relative to that of said electrical reference signal so that a predetermined index indication is provided by said indicating means whereby changes in length of said bolt from its indexed length is correspondingly indicated by said indicating means with respect to said index indication thereof.

8. The invention as defined in claim 7 further comprising means for disabling said measuring means for a predetermined initial period whereby the spurious ringing portion of said electrical reference signal picked up by the receiver of said pulser/receiver during said initial period is prevented from affecting proper operation of said measuring means.

9. The invention as defined in claim 7 further comprising means for determining when a proper coupling of said transducer to the one end of said bolt is obtained.

10. The invention as defined in claim 9 wherein said proper coupling determining means includes means for sensing when said electrical echo signals are of at least a predetermined and sufficient magnitude which is obtainable with a proper coupling of said transducer to the one end of said bolt.

11. The invention as defined in claim 7 wherein said marker signal generating means generates a plurality of uniformly spaced electrical marker signals, the beginning of which is generated at a predetermined occurrence relative to that of said electrical reference signal and the ending is at a predetermined occurrence after that oF said electrical echo signal, the occurrence of said electrical echo signal is measured by said measuring means relative to a selected one of said electrical marker signals, the measured difference between the occurrences of said electrical echo signal and the selected one of said electrical marker signals is indicated on said indicating means, and the beginning of said plurality of uniformly spaced electrical marker signals is varied by said varying means relative to that of said electrical reference signal so that a predetermined index indication is provided by said indicating means.

12. The invention as defined in claim 11 wherein said measuring means includes a square wave generating means responsive to the occurrence of said electrical echo signal to initiate a square wave output signal and responsive to the occurrence of a next succeeding electrical marker signal to terminate said square wave output signal, said square wave output signal being adapted to be applied to said indicating means whereby an indication representative of the measured difference between the occurrences of said electrical echo and marker signals is obtained.

13. The invention as defined in claim 11 wherein said varying means includes a vernier delay pulse generator responsive to said electrical reference signal to provide a pulse output signal of a predetermined duration, the end of said pulse output signal initiating generation of said plurality of electrical marker signals, and said vernier delay pulse generator being adjustable to vary the duration of said pulse output signal whereby the occurrence of the beginning of said plurality of electrical marker signals can be varied relative to that of said electrical reference signal.

14. The inventions as defined in claim 11 wherein said marker signal generating means includes a controlled oscillator means for providing a plurality of oscillation signal cycles, and pulse former means for forming pulses from said oscillation signal cycles as said electrical marker signals.

15. The invention as defined in claim 14 wherein said oscillator means can be adjusted to vary its frequency of oscillation whereby the uniform spacing of said electrical marker signals can be varied according to changes in sonic velocity to provide correct indication of said indicating means for its calibration.

16. The invention as defined in claim 14 wherein said marker signal generating means further includes a frequency divider means connecting said oscillator means to said pulse former means.

17. The invention as defined in claim 11 wherein said varying means can be adjusted to vary the occurrence of the beginning of said plurality of electrical marker signals over a duration at least equal to that between two successive electrical marker signals.

18. The invention as defined in claim 17 wherein said varying means can be adjusted to vary the occurrence of the beginning of said plurality of electrical marker signals over a duration equal to two of the spaces between said electrical marker signals whereby greater ease of adjustment of said indicating means is obtained.

19. The invention as defined in claim 12 wherein said marker signal generating means includes a controlled oscillator means for providing a plurality of oscillation signal cycles and pulse former means for forming pulses from said oscillation signal cycles as said electrical marker signals, and said varying means includes a vernier delay pulse generator responsive to said electrical reference signal to provide a pulse output signal of a predetermined duration, the end of said pulse output signal initiating generation of said plurality of electrical marker signals and said vernier delay pulse generator being adjustable to vary the duration of said pulse output signal whereby the occurrence of the beginning of said plurality of electrical marker signals can be varied relative to that of said electrical reference signal.

20. The invention as defined in claim 19 wherein said marker signal Generating means further includes a frequency divider means connecting said oscillator means to said pulse former means, and said varying means can be adjusted to vary the occurrence of the beginning of said plurality of electrical marker signals over a duration at least equal to that between two successive electrical marker signals.