US3834181A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Aircraft engine flexible coupling
Assignee: Avco Corp
•
Filing: 1973-10-26
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Granted: 1974-09-10
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Expires: 1993-10-26
Abstract
Abstract An aircraft engine of the reciprocating type has a flexible coupling interposed in the drive train between the engine crankshaft and a propeller. The flexible coupling includes an elastomeric material having a predetermined stiffness or spring rate. This stiffness is selected so that the resonant frequency of the major order for the combined propeller flexible-coupling crankshaft system is at an R.P.M. above idle but substantially below the engine''s cruise R.P.M. The elastomeric compound has an internal damping factor of at least 0.2 to minimize the torsional oscillations during the resonant frequency condition.
Inventors
- 👤 R Strasburg
- 👤 E Critchlow
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 13:17
CPC Classifications
F; F16; F16D; F16D3/00; F16D3/02; F16D3/12; F16F; F16F15/00; F16F15/10; F16F15/12; F16F15/121; F16F15/124
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
147 words
In combination: a reciprocating internal combustion engine having a crankshaft rotatable at varying rates extending from an idle condition through a normal operating range to an upper limit of a maximum power condition; a propeller adapted to be driven by said crankshaft to produce a prime propulsive thrust; and means connectIng said crankshaft and said propeller and including an elastomeric coupling transmitting substantially all of the torque between said crankshaft and propeller to form a rotating system comprised of two masses interconnected by a spring, said elastomeric coupling having a predetermined stiffness producing a resonant frequency for the system at a given transient R.P.M. that is above the idle R.P.M. and substantially below the normal operating R.P.M. for said engine, said elastomeric coupling further having an internal damping factor C/Cc of at least 0.20 to limit the torsional oscillations of said coupling at the resonant frequency condition.
Claim 2
Dependent Claim
147 words
In combination: a reciprocating internal combustion engine having a crankshaft rotatable at varying rates extending from an idle condition through a normal operating range to an upper limit of a maximum power condition; a propeller adapted to be driven by said crankshaft to produce a prime propulsive thrust; and means connectIng said crankshaft and said propeller and including an elastomeric coupling transmitting substantially all of the torque between said crankshaft and propeller to form a rotating system comprised of two masses interconnected by a spring, said elastomeric coupling having a predetermined stiffness producing a resonant frequency for the system at a given transient R.P.M. that is above the idle R.P.M. and substantially below the normal operating R.P.M. for said engine, said elastomeric coupling further having an internal damping factor C/Cc of at least 0.20 to limit the torsional oscillations of said coupling at the resonant frequency condition.
Claim 3
Dependent Claim
20 words
Apparatus as in claim 1 wherein said elastomeric material transmits the torque from said crankshaft to said propeller in shear.
Claim 4
Dependent Claim
20 words
Apparatus as in claim 1 wherein said R.P.M. at which the resonant freqency occurs is between 1,400 and 1,800 R.P.M.
Claim 5
Dependent Claim
15 words
Apparatus as in claim 1 wherein the internal damping factor C/Cc is at least 0.25.
Claim 6
Dependent Claim
18 words
Apparatus as in claim 4 wherein the rotational spring rate of said elastomeric coupling is approximately 165,000 in.lb./rad.
Claim 7
Dependent Claim
39 words
Apparatus as in claim 1 wherein: said reciprocating internal combustion engine has an output reduction gear between said crankshaft and said propeller; said elastomeric coupling is interposed between said reduction gear and said crankshaft to transmit the torque therebetween.
Claim 8
Dependent Claim
20 words
Apparatus as in claim 6 wherein said elastomeric element transmits torque between said crankshaft and said reduction gear in shear.
Claim 9
Dependent Claim
102 words
Apparatus as in claim 7 wherein said connecting means comprises: an annular input member coaxial with and extending forward from said crankshaft, said input member having internal longitudinal splines; an output element telescoped into said input member forming an annular space therebetween, said output member having external splines around its periphery; a series of stacked input and output discs alternately having tabs received in the inward splines and in the external splines, and a series of elastomeric discs bonded to adjacent input and output discs whereby the torque is transmitted through said elastomeric discs between said input and output members in parallel.
Claim 10
Dependent Claim
51 words
Apparatus as in claim 8 wherein said input member has a notch in its open end extending for a portion of its circumference and said output member further comprises a radial tab aligned within said notch so that the rotation of the output member relative to the input member is limited.
Claim 11
Dependent Claim
82 words
Apparatus as in claim 1 wherein said engine crankshaft is adapted to directly drive said propeller and said connecting means comprises: an annular input disc secured to the end of said crankshaft; an output element comprising a shaft journaled in the end of said crankshaft and having an outer facing flange on which the propeller is secured, said flange being spaced from said disc; an elastomeric disc bonded to said input disc and said flange for transmitting the torque therebetween in shear.
Claim 12
Dependent Claim
19 words
Apparatus as in claim 10 wherein said elastomeric coupling has an internal damping factor C/Cc of at least 0.25.
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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) | 1977-09-09 | 1978-03-11 | 1978-09-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-09-09 | 1982-03-11 | 1982-09-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-09-09 | 1986-03-11 | 1986-09-10 | $7700.00 | Window Closed / Lapsed |