US3938762A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Rotor blade force track sensing system and automatic span tracking system
Assignee: Bell Helicopter Textron Inc
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Filing: 1974-05-20
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Granted: 1976-02-17
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Expires: 1994-05-20
Abstract
Abstract In eliminating one-per-rev vibration in a helicopter due to rotor unbalance, a one-per-rev vibration signal manifestation of rotor unbalance is generated and sampled when the rotor blades are successively in alignment with a reference direction during each cycle of rotation of said rotor. A difference signal is generated from the samples to represent by magnitude and phase the character of the unbalance. The rotor is modified in magnitude proportional to the magnitude of the signal and in direction dependent upon the span and chord components of the signal. In one aspect the force track error signal is applied to the input of a cyclic pitch control actuator system dynamically to automatically correct span unbalance forces.
Inventors
- 👤 Milford R. Murphy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:17
CPC Classifications
B; B64; B64C; B64C27/00; B64C27/001; Y; Y10; Y10S; Y10S416/00; Y10S416/50
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
87 words
The method of minimizing one-per-rev vibration in a helicopter due to rotor unbalance which comprises: generating a one-per-rev vibration signal for at least two blades of the rotor as a manifestation of rotor unbalance, sampling said signals when each of the rotor blades are successively in alignment with a reference direction during each cycle of rotation of said rotor, and generating a difference signal by comparing samples of said signals from each of the rotor blades to represent by magnitude and phase the character of said unbalance.
Claim 2
Independent Claim
87 words
The method of minimizing one-per-rev vibration in a helicopter due to rotor unbalance which comprises: generating a one-per-rev vibration signal for at least two blades of the rotor as a manifestation of rotor unbalance, sampling said signals when each of the rotor blades are successively in alignment with a reference direction during each cycle of rotation of said rotor, and generating a difference signal by comparing samples of said signals from each of the rotor blades to represent by magnitude and phase the character of said unbalance.
Claim 3
Dependent Claim
23 words
The method of claim 1 including displaying the generated difference signal to provide a guide for required correction of vibration inducing rotor unbalance.
Claim 4
Dependent Claim
27 words
The method of claim 1 in which a span component of said unbalance difference signal drives an actuator on the helicopter swashplate dynamically to minimize one-per-rev vibration.
Claim 5
Dependent Claim
49 words
The method of claim 1 in which said vibration signal is sampled four times per revolution of said rotor at quadrature points one of which is with one of said blades at said reference direction and samples taken at 180° points are compared to indicate chordwise and spanwise unbalances.
Claim 6
Independent Claim
93 words
The method of minimizing one-per-rev vibrations in a helicopter due to a rotor unbalance which comprises: generating a one-per-rev vibration signal manifestation of rotor unbalance, sampling said signal when the rotor blades are successively in alignment with a reference direction during each cycle of rotation of said rotor, generating a difference signal from said samples to represent by magnitude and phase the character of said unbalance, and resolving the signal into span and chord components to isolate out of track conditions and provide a guide for required adjustment of vibration inducing rotor unbalance.
Claim 7
Independent Claim
93 words
The method of minimizing one-per-rev vibrations in a helicopter due to a rotor unbalance which comprises: generating a one-per-rev vibration signal manifestation of rotor unbalance, sampling said signal when the rotor blades are successively in alignment with a reference direction during each cycle of rotation of said rotor, generating a difference signal from said samples to represent by magnitude and phase the character of said unbalance, and resolving the signal into span and chord components to isolate out of track conditions and provide a guide for required adjustment of vibration inducing rotor unbalance.
Claim 8
Dependent Claim
32 words
The method of claim 5 wherein the one-per-rev vibration signal is generated with the helicopter on the ground with the rotor at a normal speed with zero thrust to measure inertial unbalance.
Claim 9
Dependent Claim
24 words
The method of claim 5 wherein the one-per-rev vibration signal is generated with the helicopter hovering at normal rotor speed to measure aerodynamic unbalance.
Claim 10
Independent Claim
138 words
The method of minimizing one-per-rev vibration in a helicopter airframe when supported by a mast driven rotor which comprises: a. rotating said rotor at normal rotor speed and zero lift, b. generating a signal representative of unbalance force on said mast due to displacement of the center of gravity of the rotor from the mast axis, c. modifying the rotor in magnitude proportional to the magnitude of said signal and in direction dependent upon the span and chord components of said signal, d. hovering said helicopter at normal rotor speed, e. generating a signal representative in phase and magnitude of unbalance moments on said mast due to aerodynamic forces on said mast, and f. modifying the aerodynamics of said rotor in magnitude proportional to the magnitude of said signal and direction dependent upon said components of said signal.
Claim 11
Independent Claim
138 words
The method of minimizing one-per-rev vibration in a helicopter airframe when supported by a mast driven rotor which comprises: a. rotating said rotor at normal rotor speed and zero lift, b. generating a signal representative of unbalance force on said mast due to displacement of the center of gravity of the rotor from the mast axis, c. modifying the rotor in magnitude proportional to the magnitude of said signal and in direction dependent upon the span and chord components of said signal, d. hovering said helicopter at normal rotor speed, e. generating a signal representative in phase and magnitude of unbalance moments on said mast due to aerodynamic forces on said mast, and f. modifying the aerodynamics of said rotor in magnitude proportional to the magnitude of said signal and direction dependent upon said components of said signal.
Claim 12
Independent Claim
146 words
A system to aid in minimizing one-per-rev vibration in a helicopter airframe when supported by a mast driven rotor which comprises: a. means to generate a signal representative of unbalance force on said mast due to displacement of the center of gravity of the rotor from the mast axis when rotating at normal rotor speed and zero lift, whereby the rotor may be modified in magnitude proportional to the magnitude of said signal and in direction dependent upon the span and chord components of said signal, and b. means to generate a signal representative in phase and magnitude of unbalance moments on said mast due to aerodynamic forces on said mast when hovering said helicopter at normal rotor speed whereby the aerodynamics of said rotor may be modified in magnitude proportional to the magnitude of said signal and direction dependent upon said components of said signal.
Claim 13
Independent Claim
146 words
A system to aid in minimizing one-per-rev vibration in a helicopter airframe when supported by a mast driven rotor which comprises: a. means to generate a signal representative of unbalance force on said mast due to displacement of the center of gravity of the rotor from the mast axis when rotating at normal rotor speed and zero lift, whereby the rotor may be modified in magnitude proportional to the magnitude of said signal and in direction dependent upon the span and chord components of said signal, and b. means to generate a signal representative in phase and magnitude of unbalance moments on said mast due to aerodynamic forces on said mast when hovering said helicopter at normal rotor speed whereby the aerodynamics of said rotor may be modified in magnitude proportional to the magnitude of said signal and direction dependent upon said components of said signal.
Claim 14
Dependent Claim
32 words
The system of claim 7 wherein the motion of the mast relative to the airframe is continuously sensed and the resulting signal is synchronously sampled and stored to produce said unbalance signal.
Claim 15
Dependent Claim
24 words
The system of claim 10 in which said resulting signal is multiply sampled for each mast revolution to produce span and chord unbalance signals.
Claim 16
Dependent Claim
26 words
The system of claim 11 in which the phase at which said resulting signal is sampled is in quadrature and is sampled four times per revolution.
Claim 17
Dependent Claim
38 words
The system of claim 12 in which said phase lags the blade alignment with a reference direction by the phase lag of a two bladed rotor system to produce said resulting signal representative of displacement of said mast.
Claim 18
Independent Claim
198 words
A system for sensing and comparing unbalanced vibrational forces exerted by rotor blades of a rotary wing aircraft which are transmitted through its mast to a rotor support mounting, comprising: a. generator means to generate a first position signal when a first rotor blade is aligned with a reference direction fixed with respect to said mounting structure and a second position signal when a second rotor blade is aligned with said reference direction, b. vibration sensing means responsive to said unbalanced forces exerted in said reference direction for providing a vibration signal, c. first sampling means connected to said vibration sensing means and responsive to the first position signal for selecting as a first force signal sample the value of the vibration signal when the first blade is aligned with the reference direction, d. second sampling means connected to the vibration sensing means and responsive to the second position signal for selecting as a second force signal sample the value of the vibration signal when the second blade is aligned with the reference direction, and e. means connected between the first and second sampling means for comparing the first force signal sample with the second force signal sample.
Claim 19
Independent Claim
198 words
A system for sensing and comparing unbalanced vibrational forces exerted by rotor blades of a rotary wing aircraft which are transmitted through its mast to a rotor support mounting, comprising: a. generator means to generate a first position signal when a first rotor blade is aligned with a reference direction fixed with respect to said mounting structure and a second position signal when a second rotor blade is aligned with said reference direction, b. vibration sensing means responsive to said unbalanced forces exerted in said reference direction for providing a vibration signal, c. first sampling means connected to said vibration sensing means and responsive to the first position signal for selecting as a first force signal sample the value of the vibration signal when the first blade is aligned with the reference direction, d. second sampling means connected to the vibration sensing means and responsive to the second position signal for selecting as a second force signal sample the value of the vibration signal when the second blade is aligned with the reference direction, and e. means connected between the first and second sampling means for comparing the first force signal sample with the second force signal sample.
Claim 20
Dependent Claim
26 words
The system according to claim 14 wherein the comparing means comprises: a meter connected to indicate the algebraic difference between the first and second force signals.
Claim 21
Dependent Claim
28 words
The system according to claim 14 wherein the vibration sensing means comprises: a sensor on said mounting structure and having a sensitive axis aligned with said reference direction.
Claim 22
Dependent Claim
82 words
The system according to claim 14 wherein the means for providing a first and second position signal comprises: a. position sensing means for providing a single pulse when the first blade is aligned with the reference direction and a double pulse when the second blade is aligned with the reference direction, and b. means to render said generator means responsive to each said single pulse and to each said double pulse to produce two output signals for each revolution of said mast.
Claim 23
Dependent Claim
95 words
The system according to claim 17 wherein the position sensing means comprises: a. a single ferrous element affixed to said mast adjacent said mounting structure in alignment with one of said blades, b. a pair of ferrous elements affixed to said mast adjacent said mounting structure in alignment with the second blade, and c. a magnetic sensor mounted on said mounting structure adjacent said mast and in alignment with the reference direction and responsive to the single ferrous element and the pair of ferrous elements to provide, respectively, the single pulse and the double pulse.
Claim 24
Dependent Claim
51 words
The system according to claim 17 wherein said sensor is connected to two generators a first of which includes counting means for providing a first triggering signal in response only to the double pulse, and a first one-pulse generator responsive to the first triggering signal for producing the second position signal.
Claim 25
Dependent Claim
69 words
The system according to claim 17 wherein said first generator includes triggering means connected between said sensor and the second generator for providing a second triggering signal, arming means in said second generator operable in response to the second position signal to fire in response to the single pulse from said sensor and a second one-pulse generator responsive to the second triggering signal for producing the first position signal.
Claim 26
Dependent Claim
117 words
A system according to claim 20 wherein the triggering means comprises: a. a charge storage device connected to the input of the second one-pulse generator to actuate said second one-pulse generator upon discharge thereof, b. a first unidirectional current flow controlling device interposed between the first one-pulse generator, c. means to charge said storage device through the first unidirectional current flow controlling device in response to said second position signal, d. a second unidirectional current flow controlling device interposed between said position sensing means and said current storage device, and e. means to discharge said current storage device through the second unidirectional current flow controlling device in response to the single pulse from the position sensing means.
Claim 27
Dependent Claim
28 words
The system according to claim 21 wherein: a. the current storage device is a capacitor, and b. the first and second unidirectional current flow controlling devices are diodes.
Claim 28
Dependent Claim
72 words
A sensing and comparing device in accordance with claim 14 wherein said first and second sampling means comprise: a. first and second storage means for accepting and storing samples of said vibration signal, and b. first and second gate means connected respectively to the first and second storage means and actuated respectively by the first and second position signals for applying said vibration signal respectively to said first and second storage means.
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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) | 1979-02-16 | 1979-08-18 | 1980-02-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-02-16 | 1983-08-18 | 1984-02-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-02-16 | 1987-08-18 | 1988-02-17 | $7700.00 | Window Closed / Lapsed |