Fluid reaction surfaces (i.e. – impellers) – Specific working member mount – Turbo machine
Reexamination Certificate
1999-05-05
2001-10-23
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Specific working member mount
Turbo machine
C416S226000, C416S22900R
Reexamination Certificate
active
06305905
ABSTRACT:
TECHNICAL FIELD
This invention is directed to propeller systems and blades, and more particularly, to a propeller blade which is designed to be bolted onto and removed from a propeller system without disturbing the blade retention bearing preload.
BACKGROUND ART
Modem propeller blades typically include root portions which extend into the hub arm of the hub of the propeller system and which are secured to and rotatable relative to the hub arm via a retention assembly. Typically the retention assembly includes one or a plurality of ball bearing assemblies which permit the rotation of the blade in the hub arm for accomplishing pitch change of the blade for altering the speed of the propeller and accordingly, the aircraft. Typical propeller blade systems using this type of arrangement include the system shown in U.S. Pat. Nos. 3,637,323, 2,248,590, 4,921,403 and 5,415,527. As can be seen from the drawings of each of these systems, the root of the propeller blade extends into the hub arm and thereby is connected to the inner surface of the hub arm via a retention mechanism, typically in the form of ball bearing assemblies and fastening elements. As can be seen from observing these figures, the removal of the blade from the hub arm for maintenance, repair or for other reasons, is a cumbersome task, involving the breakdown and disassembly of the retention assembly as well as the draining of the lubricating fluids. Accordingly, while such systems offer advantages with regard to blade preload, and blade retention, in addition to the above, the root portion of the blade is typically complex in design since it must be formed to have its outer surface interact with the retention mechanism.
The prior art does include blades of the bolt-on variety which have been designed, in part, to defeat the shortcomings of the aforementioned designs. Several systems of this variety are shown in U.S. Pat. No. 5,074,754, directed to rotor blades, and U.S. Pat. No. 3,734,642, , which is directed to a helicopter or aircraft rotor or blade. While the blade of U.S. Pat. No. 5,074,754 is bolted on via the application of retention plate 16 fastened to retention member 12 with blade 10 locked therebetween, this design suffers from various defects. For one, the blade is not directly retained by the fastening means or fasteners 18, but is indirectly retained via retention plate 16. In this manner, a level of protection is lost since failure of the plate as opposed to failure of multiple fasteners can lead to blade failure. In addition, the blade shown in this patent is apparently not a composite blade typical of current propeller systems and thereby has the disadvantages associated with not being formed from composite.
The blade in U.S. Pat. No. 3,734,642 is formed from a spar 18, 18′ a primary outer sleeve 24 and a secondary inner sleeve or cuff 38 located inwardly of the spar. The spar in this case is formed from a composite material, but as shown in the FIG. 1 and FIG. 2 embodiment, the spar 18 or 18′ does not extend to the base portion of the blade for fastening to the retention assembly or hub arm 14 since the composite, at the time of this patent, was not able to withstand the compressive forces of the fastening mechanisms. This is indicated in the background section where the author points out that the composite material cannot be bolted directly to the hub or other parts thereof because due to its fibrous nature, the composite material has a low shear strength at the bolt holes. Thereby, a rupture of the bonding connection between the composite blade or spar and the metallic cuff could progress so rapidly that adequate warning of impending blade failure could not be provided to the pilot in order for him to land the aircraft. Accordingly, the inventor for this patent set out to form a composite blade with an outer and inner sleeve for supporting the composite spar at the fastening interface. However, since the composite spar 18 does not extend to the base portion of the blade and accordingly is not directly fastened to the hub via fasteners 28, a level of security of the blade is lost. Reliability of securement is based solely on an adhesive holding the primary sleeve and cuff to the composite spar and thus, the composite spar to the propeller.
There exists a need, therefore, for a bolted-on composite propeller blade, which propeller blade is primarily formed from a composite spar, wherein the composite spar forms the elongated and base portion of the composite blade such that the blade is fastened to the retention assembly or hub arm by fastening the composite spar to the retention assembly or hub arm, thereby creating a strong, safe and easily removable composite propeller blade which does not disturb any preload of the retention assembly thereof.
DISCLOSURE OF THE INVENTION
The primary object of this invention is to provide a composite propeller blade formed in part from a composite spar, which blade includes fasteners used as the means for fastening the blade to a retention receiver member in a propeller hub, wherein the composite spar is mechanically captured by the fasteners when the blade is installed.
Another object of this invention is to provide a composite propeller blade which includes a bolt-on flange and an elongated body, wherein the body and flange of the blade is formed primarily from a composite spar.
Still another object of this invention is to provide a bolted-on propeller blade which is formed from a composite spar, wherein the composite spar forms the elongated portion of the blade as well as a flange portion of the blade, wherein the flange portion is adapted to receive fasteners for fastening the blade to the retention member in a propeller hub.
And still another object of this invention is to provide a bolted-on propeller blade, wherein the elongated portion of the blade is formed from a composite spar and a flange portion of the blade is also formed from the composite spar, wherein the flange portion includes openings for receiving fasteners for fastening the blade to a retention receiver member in a hub of a propeller, and wherein the blade further includes an inner and outer sleeve for protecting the composite flange from frictional and compressive force damage.
The foregoing objects and following advantages are achieved by the propeller blade of the present invention for attachment to a receiving member of a hub of a propeller. The blade comprises a composite spar having an elongated portion formed in the shape of an airfoil. The elongated portion has a base end and a tip end, and a base portion for attachment to the receiving member. The base portion extends substantially transverse to the elongated portion and includes openings for receiving fasteners for fastening the spar to the retention receiving member. The blade also preferably includes an inner and outer sleeve for protecting the spar from frictional and compressive force wear in the base portion from fasteners. Preferably, the blade also includes an outer fiberglass or Kevlar® shell and an inner weight tube for optionally adding more weight to the blade. The composite spar is preferably formed from a composite wall defining an interior space, which space is preferably filled with foam.
REFERENCES:
patent: 3554664 (1971-01-01), Cheeseman et al.
patent: 3637323 (1972-01-01), Chilman et al.
patent: 3734642 (1973-05-01), Dixon
patent: 4260332 (1981-04-01), Weingart et al.
patent: 4915590 (1990-04-01), Eckland et al.
patent: 4921403 (1990-05-01), Poucher et al.
patent: 5022824 (1991-06-01), Violette et al.
patent: 5074754 (1991-12-01), Violette
patent: 5222297 (1993-06-01), Graff et al.
patent: 5415527 (1995-05-01), Godwin
patent: 289647 (1991-05-01), None
patent: 502409 (1939-03-01), None
patent: 1560829 (1980-02-01), None
Nagle David P.
Violette John A.
Look Edward K.
Nguyen Ninh
United Technologies Corporation
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