WO1983001094A1

WO1983001094A1 - A windmill having automatic pitch control means

Info

Publication number: WO1983001094A1
Application number: PCT/DK1982/000084
Authority: WO
Inventors: Hans Joergen Lundgaard Laursen
Original assignee: LAURSEN, Hans, Jorgen, Lundgaard
Priority date: 1981-09-16
Filing date: 1982-09-16
Publication date: 1983-03-31
Also published as: DK411581A; EP0088778A1

Abstract

For adjusting the pitch of the wings of a windmill according to the wind and thus for stabilizing the wing rotation both in gusty wind and by general changes of the wind pressure the wings are mounted on wing spindles (10) rotatably held in wing bushings (1) on the wing hub (4), these bushings (12) being mounted pivotally about an axis (16) tangential to the path of rotation of the hub (4), such that the single wing (8) can yield rearwardly by sudden gusts, whereby the end of the wing spindle (10) will be moved slightly forwardly. On the end of the spindle (10) is eccentrically provided a pin (18), which is fixed relative the hub (4), such that said forward movement of the spindle end results in a rotation of the spindle (10) and therewith in a relevant adjustment of th wing pitch by gusts of wind. By a generally increasing wind a steadily reduce pitch will be desirable for stabilizing the speed of the wing rotor, and this is obtained by adjusting the position of the eccentric pin (18) by means of a mechanical servo mechanism comprising a roller (42) which is affected by the centrifugal force so as to react to an increased rotor speed by being forced against an annular track wall portion (46) on the mill housing (2), whereby the rotation of the roller (42) itself is utilized to produce the required displacement of the eccentric pin (18) for a relevant adjustment of the wing pitch

Description

A windmill having automatic pitch control means

The present invention relates to a windmill having wings, which are, during their operation, adjustable relative the wing hub for adaption of the wing position according to various operational conditions. Of primary relevance is the so-called pitch, as it may be desirable to decrease the pitch in two different situations, viz. both in connection with sharp gusts and if the mill tends to run too fast in strong wind. Both of these situations are easy to registrate by suitable servo mechanisms. Taking the necessary security in account, however, such regulation systems tend to be very expensive, and they are not to be further considered here, because the invention is confined to practically feasible and simple systems, in which the forces acting on the wing system are utilized, in a direct mechanical manner, to produce the desired adjustment.

For effecting a pitch reduction of the wings in response to gusts it has been proposed to use a special wind plate mounted laterally projecting from each single wing in a manner so as to cause the wing to rotate about its own axis, when it is subjected to a high wind pressure, whereby the wing plate will of course also generally seek to reduce the pitch of the wing in strong wind and thus counteract undue high speed ^"of the mill. The use of such a wind plate, however, shows the dis¬ advantage that the plate will necessarily disturb the aerodynamic conditions about the wing, and a large plate will thus reduce the efficiency of the wing considerably, while a small plate can only produce a correspondingly small adjustment force. A satisfactory compromise will be almost inachievable.

As far as the pitch adjustment at.high speed of the mill is concerned it is possible to utilize the existing centrifugal forces in the wing system for controlling the pitch in a direct manner. It has already been proposed that an outermost section of the wing be connected with an inner section through a screw thread, which forces the outer section to be rotated towards a reduced pitch in response to this section being subjected to a high centrifugal force, but such an arrangement is difficult to provide with sufficient sensivity and efficiency.

It is the purpose of the invention to provide a wind mill, in which the pitch adjustment of the wing is effected in a both simple and efficient manner. As far as the sudden gusts of wind are concerned the invention builds on the basic idea that the wing itself will be an excellent sensor, when the single wing blades or at least one of them are mounted so as to be rearwardly yieldable relative the wing hub, in the direction of the wind, and so as to produce the desired pitch reduction by virtue of this yielding or pivoting movement through a suitable mechanical control connection with the hub, whereby such a mechanical or direct connection may be provided in a simple manner. Thus, there will be no need to make use of any separate sensor plate for the wind pressure, i.e. the wing system as a whole may show an optimal aerodynamic form under all operational conditions.

At a generally high wind pressure the-mill according to the invention may hereby show a pitch of the wings as suitable for the moment of resistance at which the wing is driven. If the wing is easy-running it may, as mentioned, be desirable to reduce the pitch of the wing blades according to the speed of the wing, and for conditioning a simple and robust design it will here be attractive to utilize the centrifugal forces to effect the control. The invention, however, aims at a highly improved utilization of these forces for the said control as compared with the said known arrangement, and this is achieved with the use of a preferably mechanical servo system operated by a power derived from the rotary movement of the wing system relative the stationary surroundings, while the servo system is actuated in response to the speed of rotation, preferably by means of a weight body as influenced by the centrifugal force and connected with a coupling device for forcing a pitch control driving wheel against a circular driving path on the stationary wing bearing. Thus it is not the centrifugal forces themselves which effect the very pitch adjusting movement of the wings, as these forces should just act controllingly on the transmission of the much larger effect which is available when the adjusting movement is effected by a driving engagement between the rotating wing and the stationary bearing of the wing' rotor. The servo control will show a certain inherent tardiness or inertia, because a changed centrifugal force will require a certain rotation of the wing system for the completion of an associated change of the wing pitch, but such an inertia may constitute a good security against undesired cyclic variations, and besides very sudden changes of the wing speed will occur highly exceptionally only.

Thus, the invention makes use of two different control systems for the pitch adjustment, ^"actuated by the rearward "rocking" of the wings by sudden gusts and by the very speed of rotation of the wing system, - respectively. In practice, however, these control systems may be partly integrated in that the single wing, adjacent its root^", may have a fixed point located radial¬ ly spaced from the axis of rotation of the wing blade itself and spaced from the crosswise oriented "rocking axis" of the wing, whereby a rocking of the wing will

0?PL_. automatically produce a pitch adjusting rotation of the wing, while the location of the said fixed point can be adjustable depending of the operation of the said servo mechanism, whereby a change^' of location of the fixed point relative the axis of rotation of the wing blade itself will result in a pitch changing rotation of the wing blade.

In the following the invention is explained in more detail with reference to the accompanying drawing, in which:-

Fig. 1 is a top view of a wind mill according to the invention,

Fig. 2 is a perspective view of one of the mill wings, seen from inside the wing hub, ^* Fig. 3 is a perspective view of the wing hub, and Fig-.. 4 is a front view of a modified wing hub. The mill shown in Fig-. 1 comprises a mill housing 2 carried by a mast (not shown) and carrying a mill shaft 4, which is provided with a wing hub 6 for a number of wing blades 8; in Fig. 1 four such blades are ^'- indicated, while only two are indicated in Figs., 2-4. Each wing blade has a wing spindle 10 which is secured in a rotatable and non-displaceable manner in a wing bushing 12, whic "is itself pivotally suspended in a holding frame 14, mounted rigidly on the hub 6, by means of a pair of cardan pins 16, the common axes of which extend tangentially to the hub periphery, whereby the bushing 12 and therewith the wing 8 is tiϊtable in the axial plane of the mill through the concerned wing spindle 10, as indicated in dotted lines in Fig. 1.

The wing, however, is not freely pivoted, inasfar there is provided, at a point of the end surface of the wing spindle 10, a pin 18 which is secured to an eye member of a rod 20, which can so far be presumed to be a fixed rod, whereby the pin 18 cannot be moved in the direction of the rod 20 by some tilting force applied to the wing bushing 12.

However, the pin 18 is provided excentrically on the end surface of the wing spindle 10, and the rod 20 is somewhat laterally displaceable, whereby a pivoting of the wing bushing 12 about the pins 16 is not prevented, but will result in the wing spindle 10 being rotated in the bushing 12 corresponding to the relative displacement of the "fixed" pin 18. This, in turn, will result in a corresponding pitch adjusting rotation of the wing blade 8.

In operation of the mill the centrifugal forces on the wings will seek to hold the wings projecting perpendicularly from the mill shaft 4, while the wind pressure will seek to pivot the wings rearwardly. The system is so adapted that the pitch of the wings will be reduced the more they are rearwardly pivoted, but under stable wind conditions the centrifugal forces will generally hold the wings perpendicular to the mill shaft. By a sudden gust of the wind the mill will be influenced to accelerate with a certain inertia, and in the meantime the wings could get overloaded; the described system, however, provides for security against such overload in that the gust will cause an immediate rearward pivoting of the wing blade and a directly associated rotation of the wing towards a reduced pitch, which will weaken the effect of the gust on the wing. By a gust of short duration the rotational^'speed of the wings will not get time to be considerably changed, and the wing•blade positions will thus be reestablished by virtue of the centrifugal forces. In the case of a more durable change of the wind, though such a change seldom being initiated gustwise, other adjustment mechamisras might be provided for adjusting the wing pitch. The arrangement as so far described primarily serves to protect the wings against strong bending forces resulting

O.-'PI from sudden gusts of wind.

The illustrated wing bearing arrangement, however, is well suited for use in an additional adjustment mechanism, because a compulsory axial displacement of the rod 20 will result in a rotation of the wing spindle 10 and therewith in a pitch adjustment of the wing. Hereby an adjustment to changed operational conditions may be effected, whereby the centrifugal forces will still hold the wings projecting perpendicularly from the mill shaft, such that a change of position of the pin 18 will result in a pitch change and not in a permanent forward, or rearward pivoting of the wing. Even in its changed pitch position, therefore, the wing will still be protected against overloading due to gusts in the arrangement so far described, when care is taken that the pin 18 be stationarily fixed in its new position. This is achievable with the use of a screw spindle or another self locking device in the adjustment system of or for the rod 20. For such purpose a considerable gear ratio will be a normal requirement, „ which, however, is difficult to achieve if it should be produced directly by a change of the centrifugal force as resulting from a generally changed speed of the wing system. The invention provides for the solution that an occuring change of the centrifugal forces is caused to affect a coupling mechanism, by the aid of which the power as necessary for causing the pitch adjustment of the wings is taken from the wing system as driven by the wind, namely by actuation of an actuator system as cooperating with the stationary mill housing 2, whereby any desired gear ratio will be achievable.

Such an arrangement is shown in Fig. 3, in which the holding frames 1 of the wing blades are shown as consisting of opposed end portions of a through-going square tube 22 secured to the mill shaft 4 and constitut-

r ing the essential part of the wing hub 6. The above mentioned holding rod 20 of the pin 18 on the wing spindle 10 is shown as projecting through a hole in the side of the square tube 22 at the respective opposite ends thereof. Each of the rods 20 is connected with an angular lever 24 as pivotally mounted on the tube 22 and operable to transfer to the rod 20 a thrust or pull action by the influence from a rod 26, which is pivotally connected with the opposite end of the angular lever 24 and extends substantially parallelly with the square tube 22 inwardly towards a rotational fastening on a radial arm 28, which projects from a rotary cup member 30 as mounted on the square tube 22 centrally outside the end of the mill shaft 4. The rotary cup 30, which is rotat- able relative the square tube 22, is provided with a radial arm 32 connected via a rod 34 with a telescopic screw spindle mechanism 36, which is at one end secured to the square tube by means of a console 38. This console acts as a rotation bearing for a shaft 40, which extends perpendicularly towards the end surface of the •.. mill housing 2 and is rearwise in a wormlike driving engagement with the spindle mechanism 36.

At its end facing the mill housing 2 the shaft 40 is provided with a friction roller 42, which during the rotation of the wing system will run in or along the circular space between to rigid circular ribs 44 and 46 as protruding from the end surface of the mill housing 2. In the shaft 40 is inserted a tilt link 48 allowing for the outer end of the shaft as provided with the roller 42 to pivot slightly outwardly and inwardly in the radial direction of the wing hub under retainment of the rotary connection with the telescopic spindle 36. The pivotable end of the shaft 40 is guided in a slide guide 50, which extends in the said radial direction and is connected with a spring housing 52 containing a compression spring seeking to hold the shaft 40 swung inwardly.

In a stable operational situation the centrifugal forces acting on the roller 42 and the shaft 40 will counteract the spring force^' from the spring housing 52 such that the roller 42 assumes' a free position in the space between the two circular ribs 44 and 46. If the mill speed increases the roller 42 is thrown outwardly, whereby it will roll against and along the outer rib 46 and thus cause the shaft 40 to rotate. This rotation in turn will produce a length adjustment of the tele¬ scopic spindle 36, whereby the rod 34 causes a relative rotation of the hub cup member 30. Hereby the rods 26, via the angular levers 24, cause the adjustment rods 20 to get axially displaced, i.e. so as to forcibly displace the pins 18 (Fig. 2) as located on the ends of the wing spindles 10. Thus, because of the driving engagement between the roller 42 and the rib 46 the pitch of the wings will be adjusted, and the system is designed such that the pitch is hereby reduced, whereby the mill as here desired will be caused to slow down. - By the reduced speed the centrifugal forces on the roller 42 will get reduced, and soon the roller 42 will be forced inwardly by the spring and thus get out of its driving engagement with the rib 46. Should the speed decrease to below the desired speed range, then the spring in the housing 52 will force the roller 42 against the inner rib 44, whereby the described adjustment procedure will be repeated, now^* invertedly for enabling the mill speed to increase as ^"desired. In the event of wind or load changes some cyclic variations may occur in the adjustment procedure, but with a suitably low gear ratio between the shaft 40 and the telescopic spindle 36 an almost total tempering of the adjustment is achievable, e.g. if the roller 42 has to drive through several entire revolutions of the wing hub for effecting an appreciable change of the pitch

of the wing blades.

With the said gearing through the telescopic spindle 36 the pin 18 as seen from the associated wing will be a fixed point, i.e. the above mentioned momentary pitch change in the case of gusts (Figs. 1 and 2) will still be produceable, in practice even within a rather wide adjustment range for the location of the pin 18.

Due to the connections via the rotary hub cup member 30 it is sufficient to make use of a single ^' adjustment roller 46 for both or all of the wing blades. As indicated in Fig. 4 a corresponding connection may advantageously be. established between the wing bushings 12, such that the pivoting of these bushings about the cardan pins 16 will take place in a coordinated manner for maintaining the balance of the system. To this end it will be sufficient for each^"bushing 12 to be provided with a radial arm 54 adjacent the outer end of the bushing, this arm extending parallel with the mill shaft 4 past the end edge of the hub tube 22 and by means of a connector rod 56 being connected with a radial arm 58 on an additional, individually rotatable hub cup or disc 60, the two wing bushings being connected thereto in a symmetrical manner.

When by decreasing wind the mill slows down and perhaps finally stops, the roller 42 will be in engagement with the innermost rib 44, and it will thus seek to increase the wing pitch as far as possible, until the wings abut some suitable adjustment stop. For preventing the roller 42 from thereafter being driven further in sliding engagement with the rib 44 the pitch adjusting mechanism or one of the wing spindles can be connected with a movable abutment, which, at the end of the pitch increasing adjustment, is moved to force the roller shaft 40 outwardly to thereby lift the roller 48 out of engagement with the rib 44. When the wing rises again the mill will soon speed up, because of

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the high wing pitch, and as the roller- 42 is hereby forced outwardly against the rib 46 the pitch adjust-, ment procedure will be restarted; the first result will be a retraction of the- said movable abutment, whereafter operational adjustment in both directions will again be possible.

It will be appreciated that the power for operating the servo mechanism of the pitch adjusting system is derivedpractically directly from the wind power, as the entire mechanism is mounted stationarily on the rotating wing system and is in driving connection with a system, viz. the fixed mill housing, which in wind manifests itself as rotating relative the servo mechanism. However, exactly the same circumstances can be created with the use of an auxiliary wing system, which rotates independently about the mill shaft with a velocity different from that of the main wing system or opposite thereto, whereby the servo control power is derivable from the auxiliary- wing system. Besides, it will be understood that the very power transfer to the adjustment mechanism may take place otherwise than by a rolling engagement between a single roller and two ribs. Thus, the system may comprise a permanent driving engagement, whereby a coupling and reversing device as controlled by the^' centrifugal forces may be arranged in the connection to the wings. The drive co^'nnection may even comprise hydraulic elements.

In connection with Figs. 1 and 2 it has been mentioned that the axis (20) , about which the root of the wing is pivotal, extends tangentially to the wing rotor, and it should just be added that an exact tangential orientation is no condition, as the wings may even advantageously be arranged to pivot with a certain component in their plane of rotation.

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Claims

CLAIMS :

1. A windmill having a mechanism for adjusting the pitch of the wings in response co changes of the speed of rotation thereof, said mechanism comprising a corotat- ing weight body (42) operable to sense the speed of rotation by the action of the centrifugal forces and to effect a change of the wing pitch for counteracting a change of the centrifugal forces, characterized in that the adjustment mechanism is a mechanically powered servo mechanism (20,24,26,30,36,40,42,44,46), the driving power of which is being derived locally from the rotation of the wing hub (4) relative the fixed mill housing (2) or relative an auxiliary wind driven motor.

2. A windmill according to claim 1, characterized in that the weight body is constituted by or is connected" with a roller (42), which is biased inwardly in the radial direction of the wing hub (4) by means of a spring force (52) , whereby for increasing or decreasing centrifugal forces the roller (42) will be moved out¬ wardly or inwardly, respectively, said roller (42) by a desired speed of rotation of the wing hub running freely in a stationary annular track (44,46) on the end of the mill housing (2) as facing^' the wing hub (4) , and being in driving connection with the adjustment mechanism in such manner that the roller (42) , when "forced outwardly against the outer wall (46) of the track, rolls therealong for effecting a reduction of the pitch of the wings, and correspondingly causes an increase of the pitch when forced inwardly against the inner wall (44) of said track.

3. A windmill according to claim 1, characterized in that the wings (8) are arranged rearwardly pivotable in the direction of the wind, such that by wind gusts they are rearwardly pivotable against the action of the centrifugal forces, and that means (10,12,18,20) are provided for effecting a reduced pitch of the wings in direct response to such rearward pivot movement.

4. A windmill according to claim 3, in which the wings (8) with wing spindles (10) are- rotatably secured in wing bushings (12) on the wing hub (4) , characterized in that the wing- bushings (12) are pivotally mounted in the wing hub (4) about a tangential axis (16) extending in the direction of rotation, and that the wing spindles (10) are fixed to the wing hub at a point (18) , which is eccentric relative their own axis of rotation, in such a manner that a pivoting of the wing bushing (12) immediately results in a rotation of the wing spindle (10) for adjustment of the pitch of the wing.

5. A windmill according to claims 1 and 4, character¬ ized in^"-.that the eccentric point (18) of the wing spindle (10) is connected with the pitch adjusting mechanism as controlled by the centrifugal forces such that said mechanism effects the pitch adjustments by producing a displacement of the point (18) along a path concentrical with the axis of rotation of the wing spindle (10) itself.