US3825370A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Pitch varying mechanism for variable pitch fan
Assignee: Rolls Royce PLC
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Filing: 1972-12-06
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Granted: 1974-07-23
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Expires: 1992-12-06
Abstract
Abstract The blades of a variable pitch fan of a gas turbine engine are rotated about their longitudinal axes as well as about the axis of the engine by a gear system which comprises a stationary actuator which initiates the pitch varying movement by producing a rotary output corresponding to the degree of pitch change required, an epicyclic differential gear driven by this output and the engine main shaft, and arranged to produce an output corresponding to the sum of the rotary output and the shaft rotational speed, and a pitch changing gear adapted to be driven by the output of the differential gear and to produce relative rotation of two annulus gears connected to rotate the fan blades about their own axes.
Inventors
- 👤 Murtry D Mc
- 👤 M Agg
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 00:19
CPC Classifications
F; F04; F04D; F04D29/00; F04D29/26; F04D29/32; F04D29/321; F04D29/322; F04D29/323; F01; F01D; F01D7/00; F02; F02C; F02C7/00; F02C7/36; F02K; F02K3/00; F02K3/02; F02K3/04; F02K3/06; F05; F05D; F05D2220/00; F05D2220/30; F05D2220/36; F05D2260/00; F05D2260/40; F05D2260/403; F05D2260/4031; F05D2260/40311; F05D2260/70; F05D2260/74; F05D2260/79; Y; Y02; Y02T; Y02T50/00; Y02T50/60
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
206 words
A pitch varying mechanism for a variable pitch fan in which a plurality of fan blades are mounted on a rotor and a rotational shaft is provided for driving the rotor and wherein the mechanism comprises in combination: an actuator which is mounted stationary relative to the rotor and which is operable to produce a rotational output corresponding to the degree of pitch change required in the blades; an epicyclic differential gear having two input gears one of which is driven by the shaft and the other of which is driven by said rotational output, and having an output corresponding to the sum of the shaft rotational speed and the actuator rotational output; a pitch changing reduction gear having a pair of output gears and an input, the input corresponding to the output of the epicyclic differential gear, the output from the pitch changing reduction gear being in the form of relative rotation of the two output gears; and a plurality of fan bevel gears one connected to each of the blades of the fan, and which are driven by the two output gears of the pitch changiNg reduction gear, and which cause rotation of the fan blades about their longitudinal axes to vary their pitch.
Claim 2
Dependent Claim
206 words
A pitch varying mechanism for a variable pitch fan in which a plurality of fan blades are mounted on a rotor and a rotational shaft is provided for driving the rotor and wherein the mechanism comprises in combination: an actuator which is mounted stationary relative to the rotor and which is operable to produce a rotational output corresponding to the degree of pitch change required in the blades; an epicyclic differential gear having two input gears one of which is driven by the shaft and the other of which is driven by said rotational output, and having an output corresponding to the sum of the shaft rotational speed and the actuator rotational output; a pitch changing reduction gear having a pair of output gears and an input, the input corresponding to the output of the epicyclic differential gear, the output from the pitch changing reduction gear being in the form of relative rotation of the two output gears; and a plurality of fan bevel gears one connected to each of the blades of the fan, and which are driven by the two output gears of the pitch changiNg reduction gear, and which cause rotation of the fan blades about their longitudinal axes to vary their pitch.
Claim 3
Dependent Claim
77 words
A pitch varying mechanism according to claim 1 and wherein the pitch changing reduction gear comprises a sun gear driven by the output of the epicyclic differential gear, a plurality of planet wheels driven by the sun gear, and a pair of annulus gears which mesh with the planet wheels and which have different numbers of teeth, the difference between the number of teeth on the two annulus gears being equal to the number of planet wheels.
Claim 4
Dependent Claim
60 words
A pitch varying mechanism according to claim 2 and in which a sun wheel provides the output of the differential epicyclic gear and carries a gear which acts as the sun gear for the pitch changing reduction gear and which meshes with a gear on each planet wheel which is axially offset from annulus gears associated with the differential gear.
Claim 5
Dependent Claim
29 words
A pitch varying mechanism according to claim 3 and wherein each planet wheel is carried in a cage which is of open channel section and made in one piece.
Claim 6
Dependent Claim
67 words
A pitch varying mechanism according to claim 1 and wherein the epicyclic differential gear includes two annulus gears, a plurality of planet wheels, two sun wheels and a cage for supporting the planet wheels such that the teeth of alternate planet wheels are axially offset and mesh with different ones of the sun wheels and annulus gears to form two gear trains connected only through the cage.
Claim 7
Dependent Claim
63 words
A pitch varying mechanism according to claim 5 and wherein means are provided for holding the annulus gear of one of the gear trains stationary with its corresponding sun wheel being driven by the shaft, the annulus gear of the second gear train being driven by the output from the actuator and its corresponding sun wheel providing the output from the differential gear.
Claim 8
Dependent Claim
45 words
A pitch varying mechanism according to claim 1 and wherein the two annulus gears mesh with opposite sides of a gear connected to the root of each fan blade so that relative rotation of the annulus gears rotates the fan blades about their longitudinal axes.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-07-22 | 1978-01-21 | 1978-07-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-07-22 | 1982-01-21 | 1982-07-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-07-22 | 1986-01-21 | 1986-07-23 | $7700.00 | Window Closed / Lapsed |