WO1981002766A1

WO1981002766A1 - A wind mill rotor with an automatically adjustable angle of inclination

Info

Publication number: WO1981002766A1
Application number: PCT/DK1981/000030
Authority: WO
Inventors: F Jensen; S Olsen; B Jensen
Original assignee: F Jensen; S Olsen; B Jensen
Priority date: 1980-03-27
Filing date: 1981-03-25
Publication date: 1981-10-01
Also published as: DK144742B; DK144742C; EP0048252A1; DK131980A

Abstract

A wind mill rotor of the type where a rotor blade (5) is adjustable in dependence upon the speed of rotation and the wind load. With a view to obtaining simple and reliable means for regulating the angle of inclination of the rotor blade, a bracket (4) is provided which is journalled at the end of a main shaft (1) for rotation about an axis (A) substantially perpendicular to the main shaft (1). The bracket (4) is so arranged that when rotating about the main shaft (1) it produces a torque (MA) about the axis (A), and the rotor has means (9, 13, 14) for converting this torque (MA) to a torque (MC) about the axis of inertia (C) for the balanced rotor blade (5, 8), the torque (MC) causing the angle of inclination of the rotor blade (5) to be changed.

Description

A wind mill rotor with an automatically adjustable angle of inclination

The invention relates to a wind mill rotor with a single rotor blade which is connected to and balanced about a main shaft for transmitting usefull effect in the form of a torque to said shaft. More particularly, the invention relates to a rotor of the type where the angle of inclination of the rotor blade with respect to the rotor plane is automatically adjusted in dependence upon both the axial wind pressure on the rotor blade and the speed of rotation of the blade.

A rotor of the present type is known e.g. from the German Patent No. 805 388. By means of this known rotor the inclination of the rotor blade may be changed from a starting position to an operating position by means of a first centrifugal weight and can, by means of second centrifugal weight in connection with the wind pressure on the rotor, adjust the angle of inclination in a direction towards the starting position when the wind speed is too great. The scope of adjustment in the known mechanism is rather restricted and relies on a construction which is partly very complicated and partly impedes the coupling of additional regulating equipment for adjusting the angle of inclination.

The object of the invention is to provide a retor which in relation to the prior art comprises simpler and more reliable regulating means, which may easily be combined with additional regulating equipment

This object is achieved by arranging the rotor as defined in the characterizing portion of claim 1, as the shape of the bracket and the position of the rotor blade with respect to the bracket cause a torque produced by the centrifugal forces on the bracket to be converted very simply and reliably to a torque for regulating the angle of inclination.

Since, in operation, the rotor of the invention is in a balanced position which is not, like in the prior art, partly fixed by strong springs, the forces for adjusting the angle of inclination are so small that the rotor may be constructed in the simple manner defined in claim 2. It will be appreciated that the bearings used may also take the form of sleeve bearings. The arrangement also allows additional moments of force to be transmitted very easily to the rotor for adjust ing its position depending upon the operating conditions.

The invention will be explained more fully by the following description of some embodiments with reference to the drawing, in which

fig. 1 shows a sketch illustrating the principle of a wind mill rotor according to the invention,

fig. 2 shows another embodiment of the rotor according to the invention, while

fig. 3 shows certain parts of those shown in fig. 2, as seen to the left in fig. 2.

Fig. 1 illustrates the principle of the rotor of the invention. The figure shows a main shaft 1 which is rotatably journalled in bearing pedestals, such as the bearing pedestal 2, and connected, in a manner not shown in detail, to a load and mounted on a tower, as is generally known. The free end of the main shaft is connected to a rotor according to the invention and of the type which is adapted to the wind direction which is shown by the arrow V and which is substantially parallel with the main shaft when the swaying position is correct.

The free end of the main shaft 1 is rigidly connected to a fork 3 whose free arms have pins for journalling a bracket 4 so that the bracket is rotatable about an axis A, but so that a torque from the propeller blade 5 about the main shaft 1 is transmitted direct to the main shaft. The bracket 4 has attached to it; e.g. by welding, at least one arm 6 whose end carries a centrifugal weight 7,. the function of which will be explained later.

The rotor blade 5 is statically balanced around the main shaft 1 by means of a counterweight 8 and is rigidly connected to said weight by means of an angularly bent shaft section 9 comprising three straight sections 10, 11 and 12. The shaft section 11 is journalled in the bracket 4 by means of bearings 13, 14 so that the shaft section 11 and thus also the rotor blade 5 and the counterweight 8 are rotatable about an axis B. The axis designated C defines the axis of inertia of the rotor blade 5 and the counterweight 8.

The rotor of the invention causes in a very simple and reliable manner a torque on the bracket 4 about the axis A to be converted into a torque about the axis C. A torque about the axis C causes the rotor blade 5 to rotate about the axis B and the angle of inclination of the rotor blade in relation to the rotor plane to be changed. This conversion of torque will be appreciated by imagining that the tip of the rotor blade and the coτinterweight 8 are secured against rotation about the axis A, and when the bracket 4 is then rotated about the axis A, the angle of inclination of the rotor blade will be changed as a result of the radial forces from the bearings 13 and 14 acting outside the axis of inertia C, which may be characterized by the angle S. When the rotor rotates, the same will happen in fact, but the fixing, as previously mentioned, of the rotor blade and the counterweight about the axis A will be caused by the centrifugal force which attacks along the axis of inertia of the rotor.

With a view to the balancing of the rotor, its axis of inertia preferably intersects the imagined elongation of the main shaft 1. If the centre of gravity of the rotor blade 5 and the counterweight 8 lies in the imagined, elongation of the main shaft, the bracket 4 will preferably be balanced about the main shaft by means of the arm 6A and the centrifugal weight 7A, which are fitted symmetrically with respect to the arm 6 and the weight 7 so that the axis of inertia of the bracket goes through the centre of gravity of the rotor blade and the counterweight and intersects the imagined elongation of the main shaft at an angle other than 90°.

In operation, the bracket 4 is subjected to the action of the torque mentioned owing to the rotation of the centrifugal weights 7 and 7A about the main shaft 1, so that the bracket 4 is subjected to the action of a torque which is designated MA in the figure. This torque is converted, in accordance with the explanation given above, to the torque MC about the axis C shown in the figure. In addition to these torques, torques will of course occur in operation which are produced by the action of the wind on the rotor blade 5. It should be mentioned, however, that the point of action of the wind in the rotor may be varied, within certain limits, in relation to the axis B or C as the latter points of action depend upon the aerodynamic configuration of the rotor blade, while the conversion of moment, as explained in the foregoing, depends upon the angle S. To obtain ideal operation under all conditions, the rotor is therefore preferably provided with additional regulating equipment, as is illustrated by way of example in the embodiments shown in figs. 2 and 3.

Fig. 2 shows a side view of a preferred embodiment of the rotor of the invention, while fig. 3 shows the same rotor as seen to the left in fig. 2. The parts of figs. 2 and 3 which in principle correspond to parts shown in fig. 1 have been given the same reference numerals as in fig. 1. Thus, the main shaft 1, the fork 3, the bracket 4, the rotor blade 5, the arm 6, the centrifugal weight 7, the counterweight 8 and the shaft section 10 recur.

Instead of the bearings 13, 14 shown in fig. 1 the embodiment shown in figs. 2 and 3 has a single large bearing 20, whose outer ring 21 is secured to the bracket (fig. 3), and whose plane is perpendicular to the axis B from fig. 1. The inner ring of the bearing 20 carries the propeller blade 5 and the shaft section 10 with the counterweight 8, respectively, via a pair of flanges 22 and 23, which are each provided with a groove for receiving a wire, which will be described later. The rotor blade 5 and the shaft section 10 are moreover secured to the bearing 20 so as to produce the angle S, cf. the corresponding angle from fig. 1. Fig. 3 also shows pins 24, 25 on the bracket 4 for cooperation with the fork 3.

The embodiment shown has moreover some auxiliary feature for regulating the inclination of the propeller blade, where the angle of inclination of the propeller blade means the angle between the propeller blade and the actual rotor plane. The regulating features comprise a spring 26 whose one end is secured to a wire 27 that runs around pulleys 28, 29 and extends around the flange 23, to which the free end of the wire 27 is secured. A wire 30, 30A extends. around the flange 22 and runs about pulleys 31, 32 and is secured to the main shaft

1 in the fitting 33. A stop clip 34 is fitted on the wire section.30A. Further, another spring 35 is provided whose one end is secured to the arm 6. The other end of both springs 26, 35 is secured to a bracket 36 which is connected, via a bearing 37, to a pull rod 38, by means of which the bracket 36 may be axially displaced along the main shaft 1.

The mode of operation of the embodiment shown in figs.

2 and 3 will now be explained. When the rotor does not rotate, the spring 35 pulls, via the arm 6, the rotor blade 5 out to a relatively large cone angle, and as the pulleys 31, 32 are fitted on a holder which is rigid in relation to the bracket 4, the wire 30 will be tightened and pivot the rotor blade 5 to a large angle of inclination corresponding to a starting position. As the rotor gains speed the centrifugal force influences the cone angle so that the rotor blade 5 assumes a position more perpendicular to the main shaft 1 and the spring 35 is stretched at the same time. When the stop clip 34 engages the holder for the pulley 32, corresponding to a small cone angle, the wire section 30A will relax, but the spring 26 will pull the rotor blade 5 to a small angle of inclination by means of the wire 27, to thereby define the operating position of the rotor blade 5.

The conversion of moment explained in connection with fig. 1 does not affect the embodiment shown in figs. 2 and 3 until the rotor is spinning too fast. When the speed of rotation is too great, the centrifugal weight 7 causes, as previously explained, the angle of inclination to be increased, resulting in a reduction in the speed of rotation. In normal operation, the spring forces are counterbalanced by the pull in the wire 30, which defines the operating position, and by the forces from the moment conversion, but at a suitably great speed of rotation the forces from the moment conversion will exceed the spring forces so that the angle of inclination increases whereby the wire sections 30 and 30A are relaxed as the cone angle is maintained by the centrifugal forces. The embodiment shown in fig. 2 and 3 thus illustrates how the rotor of the invention acts as an overspeed brake. Another advantage obtained at the same time is that the function of the overspeed brake depends upon the mutual movement between machine parts, which also move in the normal operation of the rotor so that there Is no risk of the overspeed brake getting jammed.

The embodiment shown also permits the overspeed brake to be regulated manually by axial movement of the rod 38. If, e.g., the bracket 36 is displaced to the right in fig. 2, the speed of rotation will be reduced, because the effect of the centrifugal weight 7 overcomes the effect of the springs 26, 35 at a lower speed of rotation.

Claims

Pa t en t C l a i m s:

1. A wind mill rotor with a rotor blade which is connected to and balanced about a main shaft for transmitting useful effect in the form of a torque to the shaft, and with an arrangement for automatic adjustment of the angle of inclination of the rotor blade depending upon wind pressure and speed of rotation, c h a r a c t e r i z e d in that a bracket is provided which is joumalled on the main shaft for transmitting the torque and for free rotation about a first axis transversely to the main shaft, and that the axis of inertia of the bracket forms an angle other than 90° with the main shaft and is preferably substantially perpendicular to the first axis, said rotor blade being joumalled in the bracket for rotation about a second axis which is substantially perpendicular to the main shaft and the first axis and forms an acute angle with the axis of inertia of the balanced rotor blade.

2. A wind mill rotor according to claim 1, c h a r a c t e r i z e d in that the bracket comprises at least a ball or roller bearing whose plane is perpendicular to the said second axis, the inner ring of the bearing carrying the propeller blade and the outer ring of the bearing having a pair of diametrically opposite pins for the coupling of the bracket to the main shaft and being rigidly connected to a centrifugal weight which defines the axis of inertia of the bracket.