Measurement of motions of rotating shafts using non-vibrating contact potential difference sensor

• US 7,152,476 B2
• Filed: 07/23/2004
• Issued: 12/26/2006
• Est. Priority Date: 07/25/2003
• Status: Expired due to Fees

• Current Assignee: Qcept Investments, LLC
• Original Assignee: Qcept Technologies, Inc.
• Inventors: Hawthorne, Jeffrey Alan, Steele, M. Brandon
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): Miller, Rose M.
• Application Number:
  US10/897,758
• Publication Number:
  US 20050016279A1
• Time in Patent Office: 886 Days
• Field of Search: 736/50, 736/60
• US Class Current: 73/660
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence

Abstract

An apparatus having a non-vibrating contact potential probe. The non-vibrating contact potential probe is capable of measuring the chemical and geometrical irregularities on a rotating shaft. The chemical and geometrical information can be used to determine various properties of the rotating shaft.

Claims

1. An system for monitoring motion of a rotating shaft as part of a machine comprising:

at least one non-vibrating contact potential probe;

a source of historical data regarding performance of the shaft;

the historical data indicating whether the shaft is in a state selected from the group consisting of a normal state and an abnormal state;

a mechanism for measuring a contact potential difference between the rotational shaft and the at least non-vibrating contact potential probe; and

an output signal from the probe characteristic of the measured contact potential difference, said output signal compared to the historical data enabling at least one of controlling motion of the rotary shaft, monitoring for motion indicative of problems or potential failure and evaluating and optimizing performance of the machine.

2. The apparatus of claim 1 further comprising a system component for altering the signal output by the at least one non-vibrating contact potential probe.

3. The apparatus of claim 2, wherein the system component for altering the signal comprises a bias voltage source which applies a voltage to the at least one non-vibrating contact potential probe.

4. The apparatus of claim 1, wherein the at least one non-vibrating contact potential probe comprises a plurality of probes.

5. The apparatus of claim 4, wherein the plurality of probes comprise a first probe and a second probe located a fixed distance apart.

6. The apparatus of claim 1, wherein the abnormal state indicated by the data is torsional or lateral vibration.

7. The apparatus of claim 1 further comprising an electrical connection between the shaft and either the non-vibrating contact potential sensor or a ground point.

8. A method of measuring rotation of a rotating shaft component and its operating state, comprising the steps of:

providing a non-vibrating contact potential probe;

rotating the rotating shaft component with respect to the non-vibrating contact potential probe;

monitoring the relative motion between the non-vibrating capacitance probe and the rotating shaft component;

measuring the change in voltage and the change in current due to the relative motion; and

outputting a signal comprising voltage information and current information characteristic of an operating state of the rotating shaft component undergoing rotation.

9. The method of claim 8 further comprising the step of converting the signal to digital values.

10. The method of claim 8 further comprising the step of processing the signal in a domain to determine a frequency at which the signal repeats.

11. The method of claim 8 further comprising the step of altering the signal to make a capacitance portion of the signal much larger than a voltage portion of the signal which is characteristic of the chemical charge of a measured surface of the rotating shaft component.

12. The method of claim 11, wherein the step of altering the signal comprises applying a bias voltage to the non-vibrating contact potential probe wherein the magnitude of the capacitance portion of the signal is increased.

13. The method of claim 12 further comprising the step of comparing the altered signal with an unaltered signal to determine at least one of magnitude and frequency of lateral vibrations in the rotating shaft component.

14. The method of claim 8, wherein the step of providing a non-vibrating contact potential probe includes providing a first non-vibrating contact potential probe and a second non-vibrating contact potential probe.

15. The method of claim 14 further comprising the step of spacing the first non-vibrating contact potential probe a fixed distance from the second non-vibrating contact potential probe, wherein the change in the phase of repetition of the signal at the two locations indicates a twist.

16. The method of claim 8 further comprising the step of forming an irregularity on the surface of the rotating shaft component.

17. A process for using surface variations on a shaft to determine at least one characteristic of the shaft, the process comprising the steps of:

providing a non-vibrating contact potential probe;

rotating the shaft with respect to the non-vibrating contact potential probe;

outputting a signal caused by motion of the shaft relative to the non-vibrating contact potential probe;

interpreting the signal to determine at least one characteristic of the shaft; and

further comprising the step of altering the signal to make a capacitance portion of the signal much larger than a voltage portion of the signal which is characteristic of the chemical charge of a measured surface of the rotating shaft.

18. The process of claim 17, wherein the step of altering the signal comprises applying a bias voltage to the non-vibrating contact potential probe wherein the magnitude of the capacitance portion of the signal is increased.

19. The process of claim 17 comprising a first non-vibrating contact potential sensor and a second non-contact potential sensor and further comprising the step of spacing the first non-vibrating contact potential probe a fixed distance from the second non-vibrating contact potential probe, wherein the change in the phase of repetition of the signal at the two locations indicates a twist.