US4707688A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Detection of tool breaks that cause slowly decreasing cutting noise
Assignee: General Electric Co
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Filing: 1986-03-03
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Granted: 1987-11-17
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Expires: 2006-03-03
Abstract
Abstract Vibrations at the cutting tool-workpiece interface are sensed and the accelerometer output is preprocessed to yield a cutting noise vibration signal. Digital analysis of the sampled signal is performed to detect a gradual cutting noise signal level decrease tool break signature, either continuously decreasing or decreasing in a series of small abrupt steps. A tool break alarm is generated, without false alarming on metal-to-air tool path transitions, as the mean cutting noise signal level falls below an upper check limit and, after a preset time has elapsed, crosses a lower check limit.
Inventors
- 👤 Charles E. Thomas
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 01:16
CPC Classifications
G; G05; G05B; G05B19/00; G05B19/02; G05B19/18; G05B19/406; G05B19/4065; G01; G01H; G01H1/00
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
124 words
A machine tool monitor to detect gradually occurring cutting tool breakage comprising: a broadband vibration sensor which generates a signal corresponding to vibrations at the cutting tool-workpiece interface; an analog preprocessor having means to filter out lower frequency machinery noise and detect the signal energy, and output a cutting noise vibration signal in a frequency band below 100 kHz; a digital processor comprised of means for sampling the latter and converting samples to digital values, and for computing a mean cutting noise signal; and pattern recognition means to detect a gradual signal level decrease and generate a tool break alarm upon said mean cutting noise signal falling below an upper check signal level limit and, after a preset time, crossing a lower check limit.
Claim 2
Dependent Claim
124 words
A machine tool monitor to detect gradually occurring cutting tool breakage comprising: a broadband vibration sensor which generates a signal corresponding to vibrations at the cutting tool-workpiece interface; an analog preprocessor having means to filter out lower frequency machinery noise and detect the signal energy, and output a cutting noise vibration signal in a frequency band below 100 kHz; a digital processor comprised of means for sampling the latter and converting samples to digital values, and for computing a mean cutting noise signal; and pattern recognition means to detect a gradual signal level decrease and generate a tool break alarm upon said mean cutting noise signal falling below an upper check signal level limit and, after a preset time, crossing a lower check limit.
Claim 3
Dependent Claim
12 words
The monitor of claim 1 wherein said preset time is several seconds.
Claim 4
Dependent Claim
33 words
The monitor of claim 2 wherein said upper check limit is at about half the expected average cutting noise signal level and said lower check limit is about half the upper check limit.
Claim 5
Dependent Claim
49 words
The monitor of claim 1 wherein said pattern recognition means is reset to search for another downward crossing of said upper check limit in response to said mean cutting noise signal exiting the region between said upper and lower limits in either direction before said preset time has elapsed.
Claim 6
Dependent Claim
39 words
The monitor of claim 4 wherein said pattern recognition means includes a timer that is started as said mean signal falls below said upper check limit and is reset by the mean signal exiting before said timer is zero.
Claim 7
Dependent Claim
42 words
The monitor of claim 1 wherein said vibration sensor is an accelerometer and said analog preprocessor filters out machinery noise below 30 kHz and is further comprised of a full wave rectifier and low pass antialiasing filter serving as the energy detector.
Claim 8
Independent Claim
139 words
The method of acoustically detecting cutting tool breaks comprising the steps of: sensing vibrations at the tool-workpiece interface during a machining operation and generating an electrical signal; preprocessing said vibration signal to filter out low frequencies to reduce interference from machine tool noise sources and to detect the signal energy in a frequency band between 30 kHz and 100 kHz; sampling the preprocessed signal, converting samples to digitized values, and computing mean cutting noise signal samples; and detecting a gradual signal level decrease tool break signature by logic which analyzes the amplitude of said mean samples, performs a time duration check when the mean cutting noise signal level falls below an upper signal level check limit, and generates a tool break alarm only if the mean signal level crosses a lower check limit after a preset time has elapsed.
Claim 9
Independent Claim
139 words
The method of acoustically detecting cutting tool breaks comprising the steps of: sensing vibrations at the tool-workpiece interface during a machining operation and generating an electrical signal; preprocessing said vibration signal to filter out low frequencies to reduce interference from machine tool noise sources and to detect the signal energy in a frequency band between 30 kHz and 100 kHz; sampling the preprocessed signal, converting samples to digitized values, and computing mean cutting noise signal samples; and detecting a gradual signal level decrease tool break signature by logic which analyzes the amplitude of said mean samples, performs a time duration check when the mean cutting noise signal level falls below an upper signal level check limit, and generates a tool break alarm only if the mean signal level crosses a lower check limit after a preset time has elapsed.
Claim 10
Dependent Claim
46 words
The method of claim 7 further comprising the step of resetting the logic and searching for another downward crossing of said upper check limit in response to exiting the region between said upper and lower check limits in either direction before elapse of said preset time.
Claim 11
Dependent Claim
32 words
The method of claim 8 wherein said upper check limit is about half the expected average cutting noise signal level and said lower check limit is about half the upper check limit.
Claim 12
Dependent Claim
34 words
The method of claim 7 further comprising the step of detecting, in parallel, an abrupt signal level shift tool break signature and generating the tool break alarm upon detecting either type of tool break.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-11-16 | 1991-05-18 | 1991-11-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-11-16 | 1995-05-18 | 1995-11-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-11-16 | 1999-05-18 | 1999-11-17 | $7700.00 | Window Closed / Lapsed |