US4389891A
Expired / Lapsed
US
⏱️ 0.0 years remaining
System for measuring resonance frequencies in turbine and compressor vanes and propeller blades
Assignee: Safran Aircraft Engines SAS
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Filing: 1981-06-24
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Granted: 1983-06-28
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Expires: 2001-06-24
Abstract
Abstract A system for measuring resonance frequencies in turbine and compressor vanes and propeller blades in which a vane or blade is excited at its base by a vibration generator and the phase of the excitation signal coming out of an acoustic transducer placed at the base is compared to that of the signal coming from a displacement transducer placed at the blade tip. The resulting phase error signal serves to pilot a variable-frequency oscillator which itself feeds the vibration generator, the frequency of which is noted by a frequency meter.
Inventors
- 👤 Jacques M. A. Fournier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 10:05
CPC Classifications
G; G01; G01H; G01H13/00
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
168 words
A system for measuring resonance frequencies in at least one rotatable blade rigidly attached at a base thereof to a base, comprising: an excitor for generating sound waves in the vicinity of said blade; at least one acoustic transducer placed in the vicinity of the base of said blade for generating a phase signal, the phase of which can be used as a blade excitation reference; a displacement transducer placed in the vicinity of the tip of said blade for generating a second signal based on blade tip displacement; a phase discriminator which receives the signals from said at least one acoustic transducer and said displacement transducer and produces an error signal based on the phase difference therebetween; an oscillator coupled to the discriminator for producing a variable frequency output in dependence on said error signal, said variable frequency output applied to said excitor; and a frequency meter coupled to the variable frequency output of said oscillator for measuring the oscillator frequency when the system has reached equilibrium.
Claim 2
Independent Claim
168 words
A system for measuring resonance frequencies in at least one rotatable blade rigidly attached at a base thereof to a base, comprising: an excitor for generating sound waves in the vicinity of said blade; at least one acoustic transducer placed in the vicinity of the base of said blade for generating a phase signal, the phase of which can be used as a blade excitation reference; a displacement transducer placed in the vicinity of the tip of said blade for generating a second signal based on blade tip displacement; a phase discriminator which receives the signals from said at least one acoustic transducer and said displacement transducer and produces an error signal based on the phase difference therebetween; an oscillator coupled to the discriminator for producing a variable frequency output in dependence on said error signal, said variable frequency output applied to said excitor; and a frequency meter coupled to the variable frequency output of said oscillator for measuring the oscillator frequency when the system has reached equilibrium.
Claim 3
Dependent Claim
29 words
A system according to claim 1, comprising: a phase converter selectively provided between the displacement transducer and the phase discriminator for selecting various modes of oscillation of the blade.
Claim 4
Dependent Claim
21 words
A system according to claim 1, wherein the acoustic transducer is placed in a median plane of excitation of the blade.
Claim 5
Dependent Claim
52 words
A system according to claim 1, comprising: two acoustic transducers arranged on opposed sides of the blade in the median plane of excitation thereof; and means coupled to the two acoustic transducers for producing a reference signal which is equal to the average of the two signals from the two acoustic transducers.
Claim 6
Dependent Claim
18 words
A system according to claim 1, further comprising: an integrator connected between the phase discriminator and the oscillator.
Claim 7
Dependent Claim
42 words
A system according to claim 1, further comprising: a filter and an amplifier inserted between said oscillator and said excitor, the gain of said amplifier being controlled by the output signal from the displacement transducer placed near the tip of the blade.
Claim 8
Dependent Claim
30 words
A system according to claim 5, further comprising: the displacement transducer and the amplifier feeding the excitor being connected in series to another amplifier and an automatic gain control device.
Claim 9
Independent Claim
23 words
A system according to claims 1, 3 or 7, comprising: an amplifier for amplifying the acoustic transducer signal fed to the phase discriminator.
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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) | 1986-06-27 | 1986-12-27 | 1987-06-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-06-27 | 1990-12-27 | 1991-06-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-06-27 | 1994-12-27 | 1995-06-28 | $7700.00 | Window Closed / Lapsed |