Patent US3784322A successfully refreshed from Google Patents.
US3784322A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Propeller blade
Assignee: HOFFMANN GmbH and Co KG
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Filing: 1972-01-14
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Granted: 1974-01-08
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Expires: 1992-01-14
Abstract
Abstract A propeller blade of the kind having a light wood body, a root of harder wood, and a metal ferrule connecting the root to the propeller hub, is reduced in bulk without loss in mechanical strength or efficiency by using a special wood/resin lamination for the root and covering the whole of the body with a skin composed of a resin reinforced by one or more layers of fiber, e.g., woven glass fiber fabric. The application of a metal protection to the leading edge of the blade and the retention of this protection are also assisted by the aforesaid skin, and special forms of screw for anchoring the blade root to the ferrule, and special forms of ferrule, are also proposed.
Inventors
- 👤 R Erich
- 👤 H Hoffmann
- 👤 G Rudiger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 13:45
CPC Classifications
B; B64; B64C; B64C11/00; B64C11/16; B64C11/20; B64C11/22
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
222 words
A propeller blade comprising a body of longitudinally laminated light wood covered with a protective laquer covering and having a metal facing secured to its leading edge, said metal facing being soldered to a metallic fabric for its fixation to the blade body, a blade root of laminated wood of greater mechanical strength than that of the blade body forming a continuation of said body at the end thereof opposite to the body tip, and being detachably fixed within a hollow metal ferrule with a smooth inner surface by anchorage screws extending into the blade root in a direction parallel to the longitudinal axis of said blade for connecting said blade to the hub of the propeller, in which the protective covering of the blade body consists of a fiber-reinforced resin, in which said blade root is laminated in the longitudinal direction only of the propeller blade, the laminae of said root being of a highly compressed bonded resin wood composition, and in which that anchorage screw comprises a shank with an outer threading of saw tooth cross sectional shape, wherein the longer flank of said cross section defines an angle of less than 45* with the longitudinal axis of said shank, and the shorter flank of said cross section defines an angle of between 45* and 90* with said longitudinal axis.
Claim 2
Dependent Claim
222 words
A propeller blade comprising a body of longitudinally laminated light wood covered with a protective laquer covering and having a metal facing secured to its leading edge, said metal facing being soldered to a metallic fabric for its fixation to the blade body, a blade root of laminated wood of greater mechanical strength than that of the blade body forming a continuation of said body at the end thereof opposite to the body tip, and being detachably fixed within a hollow metal ferrule with a smooth inner surface by anchorage screws extending into the blade root in a direction parallel to the longitudinal axis of said blade for connecting said blade to the hub of the propeller, in which the protective covering of the blade body consists of a fiber-reinforced resin, in which said blade root is laminated in the longitudinal direction only of the propeller blade, the laminae of said root being of a highly compressed bonded resin wood composition, and in which that anchorage screw comprises a shank with an outer threading of saw tooth cross sectional shape, wherein the longer flank of said cross section defines an angle of less than 45* with the longitudinal axis of said shank, and the shorter flank of said cross section defines an angle of between 45* and 90* with said longitudinal axis.
Claim 3
Dependent Claim
35 words
A propeller blade as claimed in claim 1, in which the metallic fabric of said metal facing the leading edge of the blade body is engaged with said fiber-reinforced protective coating of the blade body.
Claim 4
Dependent Claim
45 words
A propeller blade as claimed in claim 2 in which the said metal facing secured to the leading edge of the blade is made of stainless steel which has been given a galvanic treatment to make it suitable for soldering to the aforesaid metallic fabric.
Claim 5
Dependent Claim
22 words
A propeller blade as claimed in claim 3 in which said blade body has a tip portion composed exclusively of fiber-reinforced resin.
Claim 6
Dependent Claim
36 words
A propeller blade as claimed in claim 4 in which the fiber-reinforcement of the said protective covering of the blade body is made up of one or more layers of a woven fiber fabric, preferably fiberglass.
Claim 7
Dependent Claim
62 words
A propeller blade as claimed in claim 4, in which said metallic fabric of the leading edge facing is provided exclusively at the location of said tip with incisions extending transversely to the longitudinal axis of the propeller blade to form laps of metallic fabric, and wherein said laps are engaged to different superimposed layers of the fiber reinforcement of said tip.
Claim 8
Dependent Claim
36 words
A propeller blade as claimed in claim 6, in which said laps of the metallic fabric are engaged to the different superimposed layers of the fiber reinforcement of said tip by a form of stitching seam.
Claim 9
Dependent Claim
51 words
A propeller blade as claimed in claim 1, in which the compression of the said laminae of the root of the blade is continuously attenuated, as regarded in the direction towards the tip of the blade, at the zone of the junction of said root with the body of the blade.
Claim 10
Dependent Claim
35 words
A propeller blade as claimed in claim 1, in which each said anchorage screw has a threaded shank which extends into the blade root to a depth substantially equal to that of said metal ferrule.
Claim 11
Dependent Claim
49 words
A propeller blade as claimed in clAim 9, in which the leading end of said shank of each anchorage screw is formed as a cutter tip to produce in the said root of the blade a longitudinal bore for cutting the threading of the shank of the anchorage screws.
Claim 12
Dependent Claim
63 words
A propeller as claimed in claim 10 in which the said hollow metal ferrule comprises a tubular body open at both ends and with a smooth cylindrical interior throughout said body having at one end only an external ring flange, and a bottom plate closing said flanged end of the tubular body and having holes to receive the heads of said anchorage screws.
Claim 13
Dependent Claim
48 words
A propeller blade as claimed in claim 1, in which the said hollow metal ferrule comprises a tubular body with a smooth cylindrical interior, said body having an internal annular flange at one end thereof, and said flange having holes to receive the heads of said anchorage screws.
Claim 14
Dependent Claim
33 words
A propeller blade as claimed in claim 12, in which said tubular body is conically flared outwards, at the end opposite to the flanged end, into a cylindrical section of enlarged internal diameter.
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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) | 1977-01-07 | 1977-07-09 | 1978-01-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-07 | 1981-07-09 | 1982-01-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-07 | 1985-07-09 | 1986-01-08 | $7700.00 | Window Closed / Lapsed |