FRAME FOR A NACELLE FOR A WIND TURBINE AND HATCH MEANS FOR A NACELLE
The present invention relates to a frame for a rear part of a nacelle for a wind turbine. The invention also relates to hatch means for shuttering an aperture in a bottom rear part of a nacelle for a wind turbine.
Wind turbines are equipped with a plurality of mechanical and electric components situated in the nacelle of the wind turbine. Initially, once the wind turbine is erected, these components have to be hoisted to the nacelle. However, subsequently during some time of functioning of the wind turbine, there may be a need for repairing these components.
Repair of the components may require lowering the components down to the ground or, in case the wind turbine is erected at sea, to a boat at the sea. It may even be necessary to exchange worn-out components with new component by initially lowering the worn-out components down from and subsequently hoisting new component up to the nacelle.
When components are to be installed in or removed from the nacelle, once the wind turbine is already erected, then the components may enter the nacelle through an aperture in the bottom of a rear part of the nacelle. However, when the wind turbine is functioning, the bottom of the nacelle must be closed. Accordingly, the bottom of the nacelle is provided with a hinged hatch, said hatch being capable of swinging downwards in order to reveal the aperture in the bottom of the nacelle, and through which aperture the components may be hoisted up into the nacelle or lowered down from the nacelle, when the hatch is open.
The size of the hatch is designed to be as small as possible, however of course in respect of the size of the components which are to be installed or which may need repair or exchange during use of the wind turbine. The size of the hatch is chosen in accordance with the largest of the components being installed or that largest of the components being expected to be repaired at ground or having to be exchanged some time during functioning of the wind turbine. However, the larger the hatch is, the greater is the risk of the hatch being torn off or in any other way impeding the durability and security precautions of the wind turbine, when having to open the hatch during repair, installation or exchange of components, perhaps in rough weather conditions or in other circumstances such as wind turbines erected at sea, and where working at the wind turbine is especially difficult.
Accordingly, the person skilled in the art will construct the size of the hatch as being as small as possible taking into consideration the needs and demands mentioned above. Thus, the size of the hatch is a compromise between a proper large size for installing and
removing components in the nacelle and a proper small size for ensuring that the hatch does not introduce constructional weakness and safety hazard when being open.
It is an object of the present invention to provide hatch means which fulfils the need for a proper large size of the aperture but without incorporating risks of the hatch means or the wind turbine as such suffering from an open hatch when being open in e.g. rough weather.
This object is obtained by a frame for a nacelle of a wind turbine, said frame constituting a bottom rear part of the nacelle and being mounted to a bed-plate of the nacelle, said frame comprising two girders running from the bed-plate of the nacelle and rearwards, said two girders running along a bottom and along outer side edges of the rear part of the nacelle, and said frame having an aperture being established between the girders, and said aperture having a width being substantially the same as a width of the bottom of the nacelle, and said frame comprising a plurality of hatch means being sufficient to shutter the entire width of the aperture.
By providing the rear bottom part of a nacelle with an aperture having a width being as large as possible, the ease by which components are hoisted up into the nacelle or lowered down from the nacelle is tremendously increased. Prior art hatches, which are hinged to one or both sides of the nacelle all lead to a severe limitation of the width of the possible free open area of the bottom of the nacelle, because the size of the hatches are limited due to safety reasons as discussed above. However, the safety precautions cannot be neglected.
By providing a plurality of hatch means, the size of each part of the plurality of hatch means can be much more limited than prior art hatches. This solution is not evident, because it is not obvious to a person skilled in the art how to have more than one or at the most two hatches. The skilled person will not be able to envisage the provision of more than two hatches, because to the skilled person the hatches must be hinged to the nacelle. Hinging of one or two hatches can only be accomplished by hinging the one or at the most two hatches to the one or to both sides of the nacelle.
In preferred embodiments, the aperture is capable of being closed by the plurality of hatch means, which are either fixedly attached to and permanently secured to the frame, or which are loosely detached and dismountably supported by the frame.
It is possible to select and provide hatch means which are connected to the frame by means of hinges or which are only supported by the frame. In order to maximise the size of the aperture, the hatch means must be constituted by a plurality of hatch means so that
the size of the hatch means are limited, independently of whether the firstly mentioned solution or the secondly mentioned solution is chosen.
The object of the invention may also be obtained independently of the frame according to the invention by providing hatch means for an aperture in the rear bottom part of a nacelle of a wind turbine, said hatch means being constituted by readily detachable hatch means being supported by the nacelle, said hatch means being divided into a plurality of partial hatch means so that the hatch means is capable of being only partly removed to reveal only a part of the aperture.
Hatch means only being supported and not actually fixed to the nacelle will enable sizing and constructing the hatch means in any suitable manner not being limited to any fixing of the hatch means to the nacelle, and only being dependent on the need for shuttering the aperture and being dependent on the demands set by the security precautions.
In a special embodiment, the hatch means are constituted by a number of plates, said plates being supported by a frame of the nacelle at opposite sides of the plates, and a centre part of the plates closing the aperture, when the plates are being supported by the frame of the nacelle.
The hatch means may have a size and extension resulting in the hatch means being plates rather than shutters. Then, opposite sides of a pair of sides of the plates are supported by the frame of the nacelle, and the other pair of opposite sides extend across the aperture. In a preferred embodiment, the plates are not fixedly attached to the frame of the nacelle, the plates are also readily detachable.
If the hatch means are constituted by plates, and if the plates have a length of one pair of opposite sides of the plates and a length of another pair of opposite sides of the plates being of an equal size, alternatively being of a substantially equal size, then the plates may be provided with means for grabbing the plates.
The plates, contrary to shutters, may be of a size making the plates less suitable for handling. If so, the plates may be provided with grabbing means making it easier to handle the plates, The grabbing means may be handles attached to the plates in any suitable manner at any suitable place. The grabbing means may also be holes or recesses provided in the plate itself and having a size and shape making the holes or recesses suitable as hand grips provided in the material of plate itself.
The object of the invention may, alternatively, also be obtained independently of the frame according to the invention by providing hatch means for an aperture in the rear bottom part of a nacelle of a wind turbine, said hatch means being constituted by fixedly attached means being permanently secured to the nacelle, said hatch means being divided into a plurality of partial hatch means, said partial hatch means being mutually hinged and foldable along the hinges, so that the hatch means are capable of being only partly folded to reveal only a part of the aperture.
Hatch means actually being fixed to the nacelle, but being constituted by a plurality of partial hatch means, will enable sizing and constructing the hatch means in a manner not being limited to only one or at the most two hatches having to shutter the aperture, and only being dependent on the need for shuttering only a limited part of the aperture being dependent on the demands set by the security precautions.
In a preferred embodiment of fixedly attached hatch means, the partial hatch means are being mutually hinged by providing at least one boundary hinge at a border of the entire number of hatch means, said boundary hinge being secured to the frame of the nacelle, and by providing at least one intermediate hinge at a centre part of the entire number of hatch means, said intermediate hinge being provided between neighbouring partial hatch means.
A plurality of hatch means being fixedly attached to the frame of the nacelle, but also maintaining the capability of revealing the aperture, is preferably mutually hinged. At least the one outer partial hatch means is hinged via a boundary hinge to the frame of the nacelle, and the other partial hatch means are individually hinged via intermediate hinges extending parallel with the boundary hinge. Thereby, the entire plurality of hatch means constitute a louvered closing, where the number of partial hatch means and accordingly the number of hinges may be chosen arbitrarily.
The folding of the hatch means may then take place in different ways depending on whether the hinges run longitudinally to or transversely to the nacelle.
As example, the folding of the mutually hinged hatch means may be effected transversely in relation to the nacelle by providing partial hatch means and intermediate hinges running longitudinally in relation to the nacelle, and where the folding of the mutually hinged hatch means is being effected by folding the partial hatch means partly or fully towards the rearmost end of the nacelle, alternatively by folding the partial hatch means partly or fully towards a position of the nacelle, where the nacelle meets the tower.
Alternatively, the folding of the mutually hinged hatch means may be effected longitudinally in relation to the nacelle by providing partial hatch means and hinges running transversely in relation to the nacelle, and where the folding of the mutually hinged hatch means is being effected by folding the partial hatch means partly or fully towards the one side of the nacelle, alternatively by simultaneously folding two individual sections of the partial hatch means partly or fully towards both sides of the nacelle.
According to a possible aspect of the invention, the hatch means may constitute not only closure means, but may alo constitute part of the overall structural integrity of the nacelle, i.e. constituting parts adding to the structural rigidity and strength of the nacelle. This aspect results in that the rigidity and the strength of the nacelle structure may be more or less decreased, when removing one or more of the hatch means. This of course is non- advantageous. However, contrary to teaching of the person skilled in the art, the inventor has recognised that, when one or more of the hatch means are removed, the wind turbine is not operating, and thus the forces acting on the structural parts of the nacelle are limited compared to when the wind turbine is operating. However, the teaching of the person skilled in the art says that if the hatch means constitute part of the structural integrity of the nacelle, which they may and preferably do, then the structural integrity of the nacelle will fail, when one or more of the hatch means are removed, and the nacelle will collapse. Thus, the hatch means according to the present invention will decrease the structural integrity of the nacelle in such a manner that the hatch means are not a possible solution to the problem of providing an opening in the nacelle being as large as possible. The invention will now be described with reference to the accompanying drawing, where
fig. 1 is a perspective view seen from below of a nacelle for a wind turbine and provided with an embodiment of hatch means according to the invention in place, fig. 2 is a perspective view seen from below of a nacelle for a wind turbine and provided with the embodiment of hatch means according to the invention removed, and fig. 3 is perspective view seen from above inside the nacelle for a wind turbine and provided with an embodiment of hatch means according to the invention in place.
Fig. 1 is a perspective view as seen from below the nacelle 1 of a wind turbine. The nacelle is situated at the top of the wind turbine tower 2. The nacelle 1 has an aperture 3 at a rear part 4 of the nacelle. The aperture 3 extends downwards from the nacelle 1 towards the ground or the sea, depending on where the wind turbine is erected. In the embodiment shown, the aperture 3 has a size extending in substantially the entire width of the rear part 4 of the nacelle 1. Also, in the embodiment shown, the aperture 3 extends substantially all the way from a rearmost end 5 of the nacelle to a bed-plate 6, where the nacelle 1 is connected to the tower 2 through the yaw mechanism (not shown). Thus, the
aperture 3 extends over substantially the entire extension of the bottom of the rear part 4 of the nacelle.
The length L of the aperture 3 is equal to a distance from the rearmost end 5 of the nacelle to the bed-plate 6, and the width W of the aperture is a distance between opposite sides of the aperture along sides 7,8 of the bottom of the rear part 4 of the nacelle. This results in the aperture 3 having its substantially largest possible size, when the aperture is provided at the bottom of the rear part of the nacelle. In the embodiment shown, the aperture 3 is substantially rectangularly shaped. However, it will be possible to give the aperture other shapes such as an oval or circular shape. Across the width W of the aperture, a carrying beam 9 is provided. This beam 9 is intended for assisting in carrying components in the rear part 4 of the nacelle 1, such as the generator 10 or any other components situated in or extending into the rear part of the nacelle. The beam 9 limits the overall free open size of the aperture, when the beam is mounted in the nacelle. However, the beam 9 might not be mounted until large components have been hoisted to the nacelle. Also, the beam 9 may be dismounted before large components are lowered down for repair or for being exchanged with other similar large components.
Fig. 2 and fig. 3 show the aperture, however shuttered by hatch means, and seen from beneath the nacelle and seen from inside the nacelle, respectively. In the embodiment shown, the hatch means are a plurality of shutters 11 extending transversely across the width W of the aperture from one side 7 of the aperture to an opposite side 8 of the aperture. Thus, the shutters 11 have a length 111 being equal to, or actually a bit longer than, the width W of the aperture. The shutters 11 have a width wll, which is substantially smaller than the length 111. The shutting up of the whole of the aperture is established by the plurality of shutters, the number of shutters being depend on the width of the shutters in relation to the length of the aperture. In the embodiment shown, more than ten shutters 11 are used to shutter the aperture. In the figure shown, before the aperture is fully shuttered, a final shutter 11 still has to be placed at a foremost end (see below), supported by the lateral surfaces 14 of the girders 13. More or less shutters may be used to shutter the aperture. Thus, the shutters are having the same length 111, but a smaller or larger width wll depending on whether more or less shutters are used to shutter the aperture.
As mentioned, the shutters 11 have a length 111 being a bit longer than the width W of the aperture. The shutters 11 are suspended by means of ends 12 of the shutters being supported on lateral surfaces 14 of two girders 13 running along the bottom sides of the rear part of the nacelle. A transverse distance between said girders 13 is defining the width W of the aperture. The girders 13 each have a substantially C-shaped cross section.
Alternatively, the girders may each have an L-shaped cross section. The main demands of the girders 13 are rigidity and the provision of a lateral surface 14 for supporting the ends 12 of the shutters 11. The girders 13 have a foremost end 15 being secured to the bedplate 6 (see fig. 1) of the nacelle, and the girders 13 have a rearmost end 16 being mutually connected by a transverse beam 17. As mentioned with reference to fig. 1, a supporting beam 9 is also provided between the girders 13 across the width W of the aperture. This beam is, also as mentioned, intended for supporting a rear part of the generator, when the generator as one of the components in the nacelle is in place in the nacelle. Along the girders 13 other supporting means are provided. These other supporting means are for different purposes, and are not related to the present invention as defined in the claims.
The ends 12 of the shutters 11 are supported on the lateral surfaces 14 of the girders 13. The ends 12 may be secured to the girders 13 by any convenient means. Longitudinal sides 18 of the shutters are provided with a profiling 19 shaped so that neighbouring shutters are mutually joined by the profiling along one side of the one shutter overlying a corresponding profiling along the adjacent side of an other neighbouring shutter. Also, profiling enhances the rigidity of the shutters. As shown, the shutters may be mutually secured along the longitudinal sides by joining the profiled sides of the shutters overlying each other. However, such mutual joining is optional and may be omitted if securing of each of the ends of the shutters is sufficient to keep the shutters in place. On the contrary, perhaps the mutual joining of the sides of the shutters may lead to the possibility of omitting the actual securing of the end of the shutters to the girders, just leaving the ends of the shutters supported by the girders. Still optionally, a combination of mutual securing of some or all of the sides of the shutters and securing of some or all of the ends of the shutters to the girders may be provided. The demand for safe securing of the shutters to the girders must be viewed in relation to the wish of an easy and fast removal of the shutters, when having to hoist components up to the nacelle or lowering components down from the nacelle.
Alternative embodiments of the hatch means comprises shutters having a width being larger and perhaps being substantially the same or even greater than the length of the shutters. Thereby, the shutters constitute one or more plates shuttering the aperture. If the plates have a magnitude making it difficult for a person to grab the plates along opposite sides of the plate, the plate may advantageously be equipped with handles or other gripping means for facilitating the lifting and lowering of the plates. The plates may be secured to girders as described above and/or may be mutually secured also as described above with reference to the description of fig. 2 and fig. 3.
Even alternative embodiments constitute a plurality of shutters or plates, which are mutually hinged and which may be removed fully or partly from the aperture. The shutters or plates are so hinged as to constitute a kind of louver closing. The hatch means constituting a louver closing may be opened in such a way that the mutually hinged shutters or plates open downwards underneath the bottom of the nacelle, or in such a way that the mutually hinged shutters or plates open upwards into the nacelle. The opening of the mutually hinged shutters or plates may take place longitudinally in relation to the nacelle, i.e. the hinges extend transversely and the folding is effected towards the rear part of the nacelle or towards the position where the nacelle meets the tower. Alternatively, the opening of the mutually hinged shutters or plates may take place transversely in relation to the nacelle, i.e. the hinges extend longitudinally and the folding is effected towards one of the sides of the rear part of the nacelle or towards both sides of the rear part of the nacelle.