Fluid reaction surfaces (i.e. – impellers) – Articulated – resiliently mounted or self-shifting impeller... – Nonmetallic resilient mounting
Reexamination Certificate
2001-03-05
2003-02-04
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Articulated, resiliently mounted or self-shifting impeller...
Nonmetallic resilient mounting
Reexamination Certificate
active
06514043
ABSTRACT:
The present invention relates to a hub assembly of a rotor for holding at least one wing, wherein the at least one wing is connected/mounted to the hub assembly in at least two suspension points. The hub assembly may be applied to any kind of either energy extracting devices such as wind turbines or the like or lift producing devices such as helicopter rotors or propellers.
The invention is suited for rotors in general and is able to enable coning movement of wings connected/mounted to the hub assembly, enable teetering movement of the rotor and enable alteration of the pitch angle of the wings connected/mounted to the hub assembly. The hub assembly according to the present invention provides a hub where all the pitching of the wings can occur synchronously/simultaneous due to an interconnection of the wings attached/mounted to the hub assembly and that coning of the wings may be applied at the same time with pitching of the wings and teetering of the rotor.
The usual approach to enable at least the pitching movement of the wings connected / mounted to the hub assembly is to mount the wings to the hub assembly by connecting the wing root to the hub via a ball bearing or similar bearing. This connection is usually centred close to the aerodynamic centre of the wing section, i.e. the point where the pitching moment resulting from the aerodynamic load on the wing is substantially zero.
The pitching of wings connected/mounted to the hub assembly in the usual manner is usually enabled by applying transmission system such as gearboxes, hydraulic pistons or the like to rotate the wings along theirs longitudinal direction. These gearboxes must some how be interconnect in order to assure synchronous/simultaneous pitching. Furthermore, the mounting/connection of the wings through wing root bearing or the like makes it very difficult to enable the wings to cone,.as this usually requires very expensive bearing and the application of springs and hydraulic systems to control the coning.
Furthermore, a teetering movement of the rotor is usually avoided even though such a motion is very desirable, as no workable solution has been found until now. A workable solution means that the solution should be strong, some how simple in order to avoid damages and reliable, so that operation of for instance a wind turbine is efficient even during high stress conditions and fatigue loads.
Thus, it is an aim of the present invention to provide a rotor comprising a hub assembly and at least one wing, where the pitch of the wing may be controlled by displacing at least one of at least two suspension point used for connecting I mounting at wing to the hub assembly.
From the prior art, hub assemblies allowing pitching and coning of the wings are known.
On such example is U.S. Pat. No. 4,131,391 which discloses a hub assembly for a helicopter where each wing is connected to the hub assembly via a serial connection comprising a bearing and a hinge. The bearing allows the wing to rotate around it longitudinal direction in order to adjust theirs pitch angle and the hinge allows the wing to cone. The pitch angle o the wings is adjusted by a rod connected to the bearing and acting at the periphery of the bearing in order to provide a lever used for rotating the blade.
A major problem of such known assemblies is that they do not allow the wings to be connected/mounted to the hub assembly in at least two suspensions point as the pitching of the wings is to be performed by rotating the wings in a bearing centred in the aerodynamic centre of the wings, which centering is crucial in the known hub assemblies as minimum pitching torque is indispensable in these cases.
U.S. Pat. No. 4,678,923 discloses a hub assembly for a wind turbine. The wings are connected to the hub by means of at least two resilient strips which are oppositely inclined both in the plane of rotation of the wings and in a plane extending through the rotational axis of the hub. In particular, each wing is connected to flanges of the hub by means of said two resilient strips in the sense that one strip connects the wing with a first flange and the other strip connects the wing with a second flange.
GB 2 029 911 discloses a connection arrangement for connecting a wing having a load bearing shell to a hub of a wind turbine. The arrangement comprises an inner sleeve connected to the hub and an outer sleeve connected to the wing. The wing is being connected to the hub by securing by bolts the inner and the outer sleeves to each other.
A major problem of such known assemblies and arrangements is that pitching of one wing of the rotor is de-coupled from pitching of another wing of the rotor (in the sense that pitching of one wing is not mechanically fed back to other wings) whereby each of the wing may be operating at its own pitch angle.
BRIEF DESCRIPTION OF THE INVENTION
The present invention provides a novel, simple and effective alternative to known rotors with hub assemblies. The present invention also provides a rotor with hub assembly that, besides from being cheaper than prior art rotors and hub assemblies, also allow the application of wings without the usual applied main spar extending inside wings in theirs entire length, whereby the weight of the wings and thereby the weight of the rotor may be smaller than usual which most often will provide a rotor more efficiently controlled.
Thus, in a first aspect, the present invention relates to a rotor having an axis of rotation said rotor comprising a hub assembly and at least one wing having a leading edge and a trailing edge, said at least one wing being connected/mounted to the hub assembly in at least two suspensions points so that the pitch of the wing may be controlled by displacing at least one of the suspensions points.
The at least one wing connected/mounted to the hub assembly extends from a root section to a tip section, and the wing is preferably connected/mounted to the hub assembly at the root section. By this way of connecting/mounting the wing to the hub assembly, a very advantageous way of controlling the pitch of the at least one wing is provided. As only one of the suspension points need to be displaced the wing does not have be connected I mounted to the hub assembly via a large and expensive ball bearing centred in the Aerodynamic centre of the wing. Furthermore, as only one suspension point needs to be displaced the need for a gearbox or the like used for turning the wing in a ball bearing is also not needed.
Furthermore, by having the two suspension points situated at or in the vicinity of the leading edge and the trailing edge of the wing shell, its torsional stiffness is effectively used to transfer driving torque loads.
A typical displacement of the at least one displacement point is a displacement substantially normal to the plane defined by the rotation of the wing, but the invention is not limited to this situation, as a change of the pitch of the wing may be accomplished by all possible displacements of at least one suspension point as long as such a displacement has a component in the direction normal to the plane defined by the rotation of the wing.
Preferably, the pitch of the at least one wing is controlled by a general mutual relative displacement of the suspension points.
In a preferred embodiment of the present invention, the at least two suspension points are situated/arranged on a circle having its centre in the centre of the axis of rotation of the rotor. In this preferred embodiment of the present invention, the suspension of the wing is neutral in the sense that substantially no interaction is present between a flap load (a load on the wing in the direction of the in going wind) and the pitching of the wing.
Furthermore, the suspension points are in a presently most preferred embodiment arranged in the vicinity of the leading edge and in the vicinity of the trailing edge of the wing. Covered by this situation is also the arrangement where the suspension points in arranged in the leading edge region and/or in the trailing edge region of the wing.
In another preferre
Ellebæk Preben
Johansen Bjørn
Petersen Jørgen Thirstrup
Rasmussen Flemming
Vølund Per
Birch & Stewart Kolasch & Birch, LLP
Forskningscenter Risø
Look Edward K.
McCoy Kimya N.
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