Fluid reaction surfaces (i.e. – impellers) – Sustained ancillary movement of rotary working member – Lead-lag type rotor blade movement
Reexamination Certificate
1998-10-21
2001-03-13
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Sustained ancillary movement of rotary working member
Lead-lag type rotor blade movement
C416S140000, C416S24400R
Reexamination Certificate
active
06200097
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hub for the rotor head of a rotary-wing aircraft, as well as to a rotor head including such a hub.
2. Description of the Related Art
A hub for the rotor head of a rotary-wing aircraft is already known from French patent FR-A-2 671 049, the rotor comprising at least two blades each of which is linked radially to said hub by a blade root provided with a rigid loop constituting the attachment of the blade onto said hub, said hub carrying laminated spherical stops, each of which is associated with one blade and comprises, between an outer armature rigidly linked to said hub and an inner armature linked to the root of said blade, an alternating stack of rigid cups and layers of an elastic material in the form of spherical portions having a common center, each laminated spherical stop, for the associated blade, constituting an element for retaining on said hub and a single articulation in flapping, drag and pitch, and said rigid loop of a blade surrounding the associated laminated spherical stop and being integral with the inner armature of this latter stop.
In the above document, said hub takes the form of a single-piece cage provided with a thin sidewall, of substantially cylindrical shape, including at least as many apertures as there are blades, each aperture having dimensions which are sufficient for at least the passage and the flapping of the laminated spherical stop of the corresponding blade.
Hence, with such a known hub, in the production of the rotor head, it is necessary to integrate each spherical stop of a rigid loop with the associated blade, then to insert the stops, thus integrated with their blades, through said apertures into said cage and, finally, to fix the stops to the hub. It can easily be imagined that this gives rise to difficult handling, adjustment and assembly operations.
In order to facilitate these operations, thought has already been given to providing intermediate linking sleeves between said stops and said blades, each of said sleeves, at one end, carrying the rigid loop, and, at the other end, carrying fixing means for the root of a blade. Hence, the blades can be mounted on the rotor head only after the linking sleeves have been mounted in the hub, which facilitates the complete mounting of the rotor head, but entails the supplementary components which are said linking sleeves.
SUMMARY OF THE INVENTION
The purpose of the present invention is to remedy these drawbacks of the prior art. The present invention relates to a hub of the type reiterated above, facilitating mounting of the rotor head, but without requiring linking sleeves between the hub and the blades.
To this end, according to the invention, the hub for a rotor head of a rotary-wing aircraft, of the type reiterated above, is noteworthy in that it comprises an upper plate and a lower plate forming two separate components assembled to one another with the outer armatures of the spherical stops being interposed, in such a way that said plates are spaced from one another and define between them a space in which the spherical stops are housed, said outer armatures being arranged at the periphery of said plates and being traversed by fixing means integrating together said plates and said spherical stops.
Hence, by virtue of the present invention, a hollow hub is obtained, without a sidewall with apertures, the internal space of which is accessible from the top, when the upper plate is dismantled, in order to facilitate the mounting and/or removal of the blades and of the spherical stops which are associated with them. That being so, it is possible to dispense with the linking sleeves and to use blades which are of a single piece with the blade root loop.
It will be noted moreover that, by virtue of the present invention, a particularly compact and particularly light hub is obtained, in which the spherical stops can be brought as close as possible to the center of the hub, since no drive shaft is located within the latter.
Advantageously, provision is further made for spacers arranged at the periphery of said plates, between said outer armatures, and made integral with said plates.
In the particular case in which the hub in accordance with the present invention is intended for a 3-blade rotor head, it is advantageous for said plates each to exhibit the general shape of a triangle with cut-off corners, and for each of said outer armatures to be located in the vicinity of a cut corner, while said spacers are arranged along the sides of said triangles.
In order to allow the spherical stops to flap downward, as well as to make available a very strong rigid part for fixing the hub to the shaft of the rotor, it is advantageous for said lower plate to include a bowl-shaped central part open toward said upper plate, and a peripheral rim on which said outer armatures of said stops, and possibly said spacers, are mounted.
This central bowl-shaped part may be substantially frustoconical.
Likewise, in order to allow upward flapping of the inner armatures of the spherical stops while avoiding giving said hub too great a height, it is advantageous for said upper plate to be hollowed out centrally, opposite said lower plate.
The upper and lower plates may be produced from light alloy or a composite material.
The present invention also relates to a rotor head for a rotary-wing aircraft including a hub in accordance with the invention, as mentioned above.
In such a hub head, it is advantageous for each blade lever to consist of two plates arranged on either side of said blade root and fixed thereto.
In a known way, the rotor head in accordance with the invention may include drag dampers. The latter may be mounted either between two consecutive blades or between each blade and said hub.
In the first case, it is advantageous for each drag damper to be mounted between the blade levers of the two consecutive blades. In the second case, it is advantageous for said spacers to include an attaching lug for such a drag damper, so that each of said dampers links the lever of a blade to one such attaching lug integral with the hub.
REFERENCES:
patent: 4732540 (1988-03-01), Mouille et al.
patent: 5116209 (1992-05-01), Anglade et al.
patent: 5267833 (1993-12-01), Mouille
patent: 5906476 (1999-05-01), Arlton
patent: 3510073 (1986-09-01), None
patent: 2671049 (1992-07-01), None
patent: 2689483 (1993-10-01), None
D. Braun, et al.: “FEL—A New Main Rotor System” Vertica, vol. 14, No. 1, Jan. 1, 1990, pp. 47-60, XP000099607, see p. 48-p. 49, see figures 2,23.
Look Edward K.
Rodriguez Hermes
Stevens Davis Miller & Mosher L.L.P.
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