GB2087981A - Propeller blade root structure - Google Patents
Propeller blade root structure Download PDFInfo
- Publication number
- GB2087981A GB2087981A GB8135116A GB8135116A GB2087981A GB 2087981 A GB2087981 A GB 2087981A GB 8135116 A GB8135116 A GB 8135116A GB 8135116 A GB8135116 A GB 8135116A GB 2087981 A GB2087981 A GB 2087981A
- Authority
- GB
- United Kingdom
- Prior art keywords
- shell
- spar
- closure member
- blade
- root
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000000945 filler Substances 0.000 claims description 5
- 239000000463 material Substances 0.000 claims description 5
- 238000012423 maintenance Methods 0.000 claims description 2
- 238000000465 moulding Methods 0.000 abstract description 2
- 239000011257 shell material Substances 0.000 description 74
- 239000006260 foam Substances 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 239000002131 composite material Substances 0.000 description 3
- 239000004744 fabric Substances 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 230000002787 reinforcement Effects 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 239000004593 Epoxy Substances 0.000 description 1
- JOYRKODLDBILNP-UHFFFAOYSA-N Ethyl urethane Chemical compound CCOC(N)=O JOYRKODLDBILNP-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C11/00—Propellers, e.g. of ducted type; Features common to propellers and rotors for rotorcraft
- B64C11/16—Blades
- B64C11/20—Constructional features
Landscapes
- Engineering & Computer Science (AREA)
- Aviation & Aerospace Engineering (AREA)
- Structures Of Non-Positive Displacement Pumps (AREA)
- Toys (AREA)
Abstract
The blade is of the type having an airfoil shell 115 bonded to a spar 125 received within the interior of the shell and provided with a shell closure member 130 which covers the root end of the shell and includes an opening 135 therein which receives the spar. The closure member enhances the structural integrity of the shell, redistributing and minimizing stresses in the shell root. The closure member 130 may be formed integrally with the shell 115 as by molding and includes an upstanding collar 140, the spar being received through the collar and bonded to the inner surface thereof, thereby increasing the area of the shell-to-spar bond for stress reduction therein. <IMAGE>
Description
SPECIFICATION
Propeller blade root structure
Technical Field
This invention relates in general to propellers such as aircraft propellers and specifically to such propellers comprising an airfoil shaped shell fixed to and supported by an elongate structural spar received longitudinally within the interior of the shell.
Background Art
For purposes of weight minimization, various modern aircraft propellers comprise a lightweight shell filled with a foam such as methane foam for maintenance of the shape of the shell under operating conditions, and an elongate spar longitudinally received within the shell and attached thereto substantially along the entire length of the shell. For further enhancement of weight reduction, the shell is often formed from a lightweight composite such as an epoxy matrix provided with a plurality of glass fiber reinforcements disposed therewithin.
Operation and testing of such propellers have shown that the most highly stressed area is the bond joint between the shell and spar at the root end of the blade. It was recognized in the prior art that blade root stresses could be redistributed from the spar-to-shell bond area to other, less highly stressed areas of the shell and reduced in magnitude by the removal of portions of the shell from that bond area adjacent the bond area edges.
However, the criticality of precisely locating the removed shell portions with respect to the bond area, demands that such shell material removal be carried out subsequent to the bonding of the shell to the spar and therefore, to avoid damage to the shell, spar or foam filler, the removal of the shell material is carried out predominantly by hand, involving various hand scribing, cutting, grinding and sanding operations which are not only tedious for the operator but contribute substantially to the cost of the blade. Such a propeller shell structure is commonly known as a Biot shell structure after the originator thereof.Once the shell material is removed, to maintain the continuity of the airfoil surface at the blade root, the voids in the shell resulting from the removal of material therefrom are later filled, and a non-structural covering is applied to the shell root portion to seal the root end of the blade. Such filling and covering involves additional hand labor and therefore, is also inimical to the economy of blade manufacture.
Disclosure of Invention
It is therefore a principal object of the present invention to provide a propeller root structure wherein stresses at the interconnection of the shell and spar are minimized.
It is a further object of the present invention to provide such minimization of stresses at the interconnection of the shell and spar in an economical manner.
It is a further object of the present invention to provide such stress minimization without adversely affecting the airfoil shape or root end sealing of the blade.
These and other objects will become more readily apparent from the following detailed description taken in connection with the appended claims and accompanying drawings.
In accordance with the present invention, a propeller blade of the type comprising an airfoil shaped shell longitudinally receiving therewithin, and bonded to an elongate spar, is provided at the root end thereof with a closure member including an opening therein which accommodates a root portion of the spar. The spar is bonded along its length to the shell, and at its root end to the inner surface of the opening in the closure member for enhanced stress relief in the blade root. Preferably the closure member is provided with a collar portion upstanding therefrom in alignment with the closure member opening, the spar being bonded to the shell along the airfoil portion thereof and along the length of the sleeve inner surface.In the preferred embodiment, the shell, closure member and sleeve are integrally formed from a lightweight composite such as a matrix of epoxy resin having glass filament reinforcements disposed therewithin.
Brief Description of the Drawings
Fig. 1 is a fragmentary, perspective view of a prior art, Biot-type shell closure propeller blade root structure, portions of the blade root being broken away to show details of construction.
Fig. 2 is a fragmentary, perspective view of the propeller blade root structure of the present invention, portions of the blade root being broken away to show details of construction.
Best Mode for Carrying Out the Invention
Referring to Fig. 1, the root portion of a typical prior art, Biot-type shell closure propeller blade root is shown generally at 10 and comprises, an airfoil shaped shell 15 filled with a material such as urethane foam 20 to preserve the shell's shape during operation. The shell is carried by a structural spar 25 which is attached to the propeller's hub (not shown) by an elongate spar 25. The spar is received within the shell longitudinally thereof and is bonded thereto along the length of the spar, the bonded spar-to-shell joints being opposite each other generally centrally to the interior of the shell camber and face. Analysis of such prior art blades have indicated that the areas of highest shell stress exist in the shell root at the edge of the bonded connection between the shell and the spar.To reduce such blade stresses by redistributing the stresses to other less highly stressed portions of the shell, as discussed hereinabove, it has been the practice to remove those highly stressed shell portions subsequent to the bonding of the shell and the spar.
As shown in Fig. 1, removal of the highly stressed shell root portions results in two recesses 30 and 35 in mirror-image relation to one another.
The recesses are formed by hand by such hand processes as scribing,cutting, grinding, and sanding so as not to damage the spar and foam filler. Recesses 30 and 35 are shown for a blade having a lightweight composite shell. Were the shell to be formed from metal, inner oblique surfaces 40 and 45 of recesses 30 and 35 would extend outwardly to the leading and trailing edges of the shell whereby the leading and trailing shell root portions would be removed entirely. To preserve the airfoil shape of the shell, once the shell material is removed, recesses 30 and 35 are filled with a filler which is contoured to provide a smooth continuation of the airfoil surface.The root of the blade is then covered with a fabric covering and molded rubber boot shown together at 50 to seal the shell and protect the edge of the shell from damage due to, for example, handling and/or impact with foreign objects.
It will be appreciated that the manufacture of such a prior art Biot-type shell closure propeller blade, involving extensive handwork is therefore, expensive and time consuming. To reduce the amount of time and handwork, and therefore expense, in manufacturing a shell type propeller blade, and to enhance the reduction of shell root stresses, su'ch a blade may be manufactured in accordance with the present invention by providing the propeller shell with a root and closure member having an opening therein which receives the spar which is bonded to the inner surface of the opening for enhanced strength and stress reduction. Referring to Fig. 2, the propeller blade of the present invention is shown generally at 100 and as prior art blade 10, includes an airfoil shaped shell 11 5 filled with a filler such as methane foam 120 for preservation of the shell's shape under operating conditions.Likewise, the blade is provided with a structural spar 25 received longitudinally within the shell and bonded thereto along the length of the spar.
However, unlike the prior art Biot-type shell closure blade wherein the shell is closed by a fabric covering and rubber boot after removal of the highly stressed shell material, the shell of the present invention is formed with closure member 130 integral with the shell for sealing the root end of the shell. The closure member also enhances the structural integrity by integrally connecting the camber and face of the shell thereby reducing the stresses in those shell portions at the root thereof.
Closure member 130 is provided with an opening 135 therein, which receives the spar therethrough, the spar being bonded to the closure member about the inner surface of the opening. To increase the bonding area of the highly stressed shell-spar interconnection to lower stresses at that interconnection, closure member 130 is provided with a collar 140 upstanding from the closure member in alignment with opening 135. In the preferred embodiment, the height of the collar is approximately 0.3-0.5 times the blade thickness at the collar center although it will be understood that the invention is not so limited to such relative proportions.
It will be appreciated that enclosing the root end of shell 11 5 not only enhances the stress distribution within the shell but eliminates the necessity of substantial amounts of handwork associated with the manufacture of prior art Biottype shell closure propeller blades. Thus, wherein the Biot-type shell closure blade, recesses 30 and 35 were required to be formed by hand, in the present invention the shell with closure member 1 30 and, if desired, collar 140 is integrally molded in one molding operation about the spar 125 thereby requiring no removal of shell material by hand. Moreover, it will be recognized that closure member 130 provides an effective seal for the root end of the shell whereby the fabric covering and rubber boot 50 are no longer required.The collar substantially increases the area of bonding between the shell and spar thereby further contributing to the reduction of stresses in the blade root portion.
Although this invention has been shown and described with respect to detailed embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the claimed invention. Thus, it will be understood that the description herein of the materials employed in the blade root structure of the present invention is exemplary, the invention not being limited to such materials.
Likewise, the invention is not limited to aircraft propellers, but may be employed with equal utility in other types of propellers as well as in gas turbine engine fans. Furthermore, the invention is not limited to blades employing spars extending the entire length of the blade, but rather includes blades employing spars extending only partially into the shell interior.
Claims (3)
1. A propeller blade comprising:
an airfoil shaped shell;
a spar received longitudinally within said shell and fixed thereto along substantially the entire length of said spar;
filler material disposed within said shell for maintenance of the shape thereof;
said propeller blade being characterized by a closure member enclosing a root end of said shell, said closure member including an opening therein which accommodates a root portion of said spar, said spar being attached to said closure member about an inner surface of said opening.
2. The propeller blade of claim 1 wherein said closure member is integral to said shell.
3. The propeller blade of claim 2 wherein said closure member is provided with a collar outstanding therefrom and integral therewith, said collar being in alignment with said opening and attached to said spar along substantially the entire inner surface of said collar.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US20993980A | 1980-11-24 | 1980-11-24 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2087981A true GB2087981A (en) | 1982-06-03 |
| GB2087981B GB2087981B (en) | 1984-02-08 |
Family
ID=22780956
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8135116A Expired GB2087981B (en) | 1980-11-24 | 1981-11-20 | Propeller blade root structure |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS57114795A (en) |
| BR (1) | BR8107571A (en) |
| CA (1) | CA1165299A (en) |
| DE (1) | DE3146048A1 (en) |
| FR (1) | FR2494663B1 (en) |
| GB (1) | GB2087981B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2279114A (en) * | 1993-06-15 | 1994-12-21 | Nuaire Ltd | Fan impeller blade |
| US5660527A (en) * | 1995-10-05 | 1997-08-26 | The Wind Turbine Company | Wind turbine rotor blade root end |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2623599A (en) * | 1947-11-26 | 1952-12-30 | United Aircraft Corp | Propeller blade stress distributing means |
| GB659344A (en) * | 1948-05-04 | 1951-10-24 | United Aircraft Corp | Improvements in or relating to hollow aircraft propeller blades |
| US3161238A (en) * | 1962-07-05 | 1964-12-15 | Howard P Key | Helicopter rotor blade |
| US4169749A (en) * | 1977-09-21 | 1979-10-02 | The United States Of America As Represented By The Secretary Of The Navy | Method of making a hollow airfoil |
-
1981
- 1981-11-16 CA CA000390158A patent/CA1165299A/en not_active Expired
- 1981-11-20 BR BR8107571A patent/BR8107571A/en not_active IP Right Cessation
- 1981-11-20 GB GB8135116A patent/GB2087981B/en not_active Expired
- 1981-11-20 DE DE19813146048 patent/DE3146048A1/en not_active Ceased
- 1981-11-24 FR FR8121938A patent/FR2494663B1/en not_active Expired
- 1981-11-24 JP JP18904681A patent/JPS57114795A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2279114A (en) * | 1993-06-15 | 1994-12-21 | Nuaire Ltd | Fan impeller blade |
| US5660527A (en) * | 1995-10-05 | 1997-08-26 | The Wind Turbine Company | Wind turbine rotor blade root end |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3146048A1 (en) | 1982-08-19 |
| FR2494663B1 (en) | 1985-10-11 |
| FR2494663A1 (en) | 1982-05-28 |
| JPS57114795A (en) | 1982-07-16 |
| BR8107571A (en) | 1982-08-17 |
| GB2087981B (en) | 1984-02-08 |
| CA1165299A (en) | 1984-04-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19941120 |