EP1061263A1

EP1061263A1 - Rotor with blades attached to a hub by bearings contained in a bush

Info

Publication number: EP1061263A1
Application number: EP00202051A
Authority: EP
Inventors: Riccardo Manisco
Original assignee: FBM Hudson Italiana SpA
Current assignee: FBM Hudson Italiana SpA
Priority date: 1999-06-14
Filing date: 2000-06-08
Publication date: 2000-12-20
Also published as: ITMI991321A1; EP1061264A1; ITMI991321A0

Abstract

A description is given of a twin-blade or multi-blade rotor (33) comprising a hub (30) on which is fixed for each blade (32n) a bush (31) containing in its interior one or more bearings whose outer races are integral with the said bush (31), and whose inner races are integral with a member which is fixed to the said hub (30) and which is connected to the said bush (31), the radially innermost end of a blade (32n) being fixed to the said bush (31), in which rotor the said bush (31) is provided with a hollow extension (31p) in which a cylindrical cavity (31c) is formed, and the end part (32c) of the said blade (32) is also cylindrical and complementary to the said cylindrical cavity (31c), the said bush (31) being provided with means (34, 44, 54, 64, 36n, 36p) for reversibly clamping the said end part (32c) of the blade (32) in the said cylindrical cavity (31c).

Description

The present invention relates to the technological field of propellers, fans or other twin-blade or multi-blade axial-flow rotors used in the aeronautical industry or for purposes of ventilation.
More specifically, it relates to the field of twin-blade or multi-blade axial-flow rotors in which the pitch angle of each blade can be varied while the rotor itself is in motion.
In the present state of the art, this result is achieved by causing bushes coaxial with the longitudinal axis of the various blades to rotate on a system of bearings.
Each of these bushes terminates at its radially outermost end in a flange set at right angles to its axis, and this flange is fastened face-on to another flange attached to the radially innermost end of the blade, whose longitudinal axis therefore coincides with that of the said bush and its bearings.
Blades for rotors fitted with a system for modifying their pitch angle while in motion have therefore to be built with different configurations from those used for blades in which the pitch angle can be modified only when the rotor is stationary.
These blades, as is known to those skilled in the art, terminate at their radially innermost end with a cylindrical part which is inserted into a clamp fitted to the rotor hub, which clamp, when tightened with bolts, keeps the blade locked in the position corresponding to the desired pitch angle.
In the technological sector in question, the costs of manufacture of the individual components of a rotor are very important, so the inventor of the present innovation set out to reduce these costs by devising a constructional solution for cases of in-motion variable-pitch blades that can also be used for producing blades for rotors in which the pitch is variable when the blades are stationary.
Using the solution provided by the invention, in other words, it is possible to build blades that can generally be used in both cases without further modification, and there are obvious savings achievable in the various processes when unifying the type of blade that can be adopted equally well for rotors with variable pitch angle when stationary or when in motion.
To obtain the advantageous results described above, the inventor of the present invention has modified the design of bearing bushes for the in-motion variable pitch angle mentioned above by extending radially outwards the part that does not contain bearings and constructing this part in such a way that it can be inserted into, and locked in, the cylindrical end part of a blade designed for rotors in which the pitch is variable when stationary.
The invention, which will be explained more fully in the continuation of this description, consists therefore of a rotor composed of a hub and two or more blades in accordance with the preamble of the accompanying Claim 1, characterized by the characterizing part of the same claim.
The construction of a rotor according to the invention will now be described in greater detail, purely by way of example and without implying any restriction or limitation as compared with other possible solutions.
In the course of the description reference will also be made to the appended drawings, which show:

in Fig. 1 a perspective view of the hub only of a rotor with in-motion variable blade pitch angle according to the current state of the art;
in Fig. 2 a front view of the hub only of a rotor with variable blade pitch angle when stationary, according to the current state of the art;
in Fig. 3 a side view of what is shown in Fig. 2;
in Fig. 4 an exploded perspective view of the detail of a hub and of one part of a rotor constructed in accordance with the present invention;
in Fig. 5 a longitudinal section through the detail shown in Fig. 4 in which the parts are assembled together.

Referring initially to Fig. 1, this shows the structure of a rotor hub 16 rigged in such a way that the pitch angle of the blades (not shown) can be varied even when the rotor is in motion: fixed to a disc 18 integral with the hub are a number of clamps 19, one for each blade; and in each clamp 19 there is fixed, in a radial direction, a member 17m containing in its interior a system of rolling-contact bearings (not visible in the drawing), the outer races of which are integral with a projecting portion 17s, usually of cylindrical shape, whose longitudinal axis coincides with the longitudinal axis of the blade that is to be attached.
The said projecting portion 17s then terminates at its radially outermost end in a flange 17f, perpendicular to the axis of the said member 17m, in which flange several holes are made.
The blade (not shown, as already mentioned) is therefore fixed to the said projecting part 17s (and, thanks to the abovementioned bearings, it can be rotated even when the rotor hub 16 is in motion) by means of another flange integral with the radially innermost end of the blade itself.
Basically, in order for the system to function, each blade must end in a flange in the vicinity of its root.
Figs 2 and 3, however, show a hub 18 in which the system of connection to the blades 20n is such as to allow the blade pitch angle to be varied only when the hub is stationary.
Each blade 20n has its own clamp 19n assembled on the discoidal hub 18: between the two opposite parts constituting a clamp 19n is a cylindrical cavity 21c of radial axis into which the end 20c of the blade 20n is inserted, close to its root, this end likewise being cylindrical.
When in the position corresponding to its desired pitch angle, the blade 20n is thus fixed by tightening pairs of bolts which hold the said two parts of the clamps 19n together.
In conclusion, the radially innermost end of each blade 20n must comprise a cylindrical portion 20c, so the type of blade 20n used for hubs 18 equipped for varying the blade pitch angle when the blades are stationary cannot be used for hubs equipped for varying the blade pitch angle when the blades are in motion.
Figures 4 and 5, however, show the detail of a hub 30 of a rotor 23 produced in accordance with the present invention: in this hub a bush 31, containing in its interior the abovementioned bearings that enable a blade 32n to be rotated about its axis, is provided with a hollow extension 31p in which is formed a cylindrical cavity 31c from whose outer walls a part 31i has been removed to create a space that will allow the assembly of a fixing plate 34 which is shaped towards the inside of the bush 31 in such a way as to press against the cylindrical end part 32c of a blade 32 inserted into the bush 31.
The said fixing plate 34 is fixed to the said extension 31p by a number of bolts 36n that connect it to another plate 64 arranged symmetrically on the outside of the bush 31. Tightening these up creates a pressure on the said end part 32c sufficient to hold the blade 32n fast when the rotor 33 is in motion.
In order to distribute the loads more effectively it is advisable to insert, between the cylindrical part 32c of the blade 32 and the two said plates 34, 64, two more shaped plates 44, 54, which again are more or less symmetrical and arranged on two opposite sides of the said cylindrical part 32c.
The plates 34, 44, 54, 64, the bush 31 and the cylindrical part 32c can all be fastened by other through bolts 36p of which there may be two, for example, as indicated in the figures.
There are many other possible ways of producing the said extension 31p of the bush 31 that is composed of two parts clamped reversibly together, and all these ways will still provide the advantage referred to earlier that it will be possible to use exactly similar blades and hubs both for rotors in which the pitch angle is variable when they are stationary and for rotors in which the pitch angle is variable when they are in motion.
The objects set by the inventor have therefore been achieved, together with a reduction in weight and a reduction in the complexity of manufacture of the end parts of rotor blades.

Claims

Twin-blade or multi-blade rotor (33) comprising a hub (30) on which is fixed for each blade (32n) a bush (31) containing in its interior one or more bearings whose outer races are integral with the said bush (31), and whose inner races are integral with a member which is fixed to the said hub (30) and which is connected to the said bush (31), the radially innermost end of a blade (32n) being fixed to the said bush (31), which rotor is characterized in that the said bush (31) is provided with a hollow extension (31p) in which a cylindrical cavity (31c) is formed, and the end part (32c) of the said blade (32) is also cylindrical and complementary to the said cylindrical cavity (31c), the said bush (31) being provided with means (34, 44, 54, 64, 36n, 36p) for reversibly clamping the said end part (32c) of the blade (32) in the said cylindrical cavity (31c).
Rotor (33) according to Claim 1, in which the said hollow extension (31p) of the abovementioned bush (31) is formed in two parts (31p, 34) that can be clamped together by threaded means (36n) exerting sufficient pressure on the cylindrical end part (32c) of the said blade (32) to keep it locked during the rotation of the said blade (32).
Rotor according to Claim 2, in which the wall of the said hollow extension (31p) of the bush (31) is laterally open, and one or more fixing plates (34, 44, 54, 64), which can be connected to it by threaded means (36n, 36p), are shaped so as to press against the said end part (32c) of the blade (32) when the blade is inserted into the cavity (31c) of the bush (31) so as to lock it when the said threaded means (36n, 36p) are tightened.