Abstract:
A safety device, for ensuring the safety of an operator, is arranged in a rotor, in particular of a wind turbine. The device has a platform with a number of standing surfaces, at least one of the standing surfaces being substantially horizontal when the safety device is used as intended, and also having a securing system for securing the platform to a hub of the rotor and/or to an inner face of a rotor housing of the rotor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US National Stage of International Application No. PCT/EP2013/056683 filed Mar. 28, 2013, and claims the benefit thereof. The International application claims the benefit of European Application No. EP13150842 filed Jan. 10, 2013. All of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates to a safety device for ensuring the safety of an operator for an arrangement in a rotor, more particularly a wind turbine. It furthermore relates to a method for ensuring the safety of an operator for an arrangement in a rotor, more particularly a wind turbine. 
       BACKGROUND OF INVENTION 
       [0003]    By “rotors” are meant for example the drive propellers of aircraft, hovercraft and ships as well as also the wind and water wheels serving for obtaining energy. Wind turbines, more particularly industrial scale wind turbines, have a nacelle which is mounted on a tower, as well as a rotor which is mounted on the nacelle. The rotor represents a movable part of the wind turbine. It is connected by means of a shaft on the drive train to the interior of the nacelle in which typically the generator as well as further electrical and electronic elements are located. Within the scope of the invention by “rotor” is understood the complete unit of a hub, rotor blades fastened on the hub, and a rotatable substantially horizontally lying rotor axis. When the rotor is used as intended the rotor blades drive the hub and the rotor axis and thus the generator. 
         [0004]    The rotor of the wind turbine is normally fitted with a plurality of rotor blades, by way of example two, three or more rotor blades, which are mounted protruding radially away from the substantially horizontal centre axis of the rotor. During operation the rotor blades are often turned continuously in the wind by means of an adjusting mechanism so that an optimum energy yield can be obtained from the existing wind. This can be achieved for example by means of a rotation of the nacelle (yaw drive) and/or by means of a blade angle adjustment (pitch drive) of the rotor blades. 
         [0005]    The rotor represents a highly complex system in which in particular numerous movable elements such as the rotor blades and the corresponding adjusting mechanism are arranged. It is therefore necessary from time to time to carry out maintenance work and when required even repairs to the rotor. In particular, the hub of the rotor, that is a rotatable centre piece on which the rotor blades are fastened (a hub with a pitch drive is furthermore also termed a “rotor head”, however in the following the term “hub” is used as the standard form), represents a region in which it is particularly difficult and risky for the service personnel to operate. By way of example here bolts which are used to fasten the rotor blades on the hub have to be regularly checked and/or retightened. 
         [0006]    The said service works are nowadays normally carried out by a person who is secured by mobile frames and/or safety belts. The service workers thereby have to climb around at a mostly great drop height in the region of the open hub (i.e. provided with an access to the nacelle) in the end region of the rotor. Such procedures are very risky and furthermore complicated since the service workers have to be secured in the optimum possible way at all times. 
       SUMMARY OF INVENTION 
       [0007]    Starting from the problem illustrated here an object of the invention is to provide the possibility for an improved safety of an operator for working in the hub region of a rotor. More particularly importance is to be placed on a simpler possibility for safety, and/or such safety, which is equipped with a higher safety standard. 
         [0008]    This is achieved by a safety device and by a method according to the independent claims. 
         [0009]    According to this a safety device of the type mentioned at the beginning comprises at least the following elements: a platform having a plurality of standing surfaces of which when the safety device is used as intended at least one lies substantially horizontal, fixing device for fixing the platform on a hub of the rotor and/or on an inside of a rotor housing of the rotor. 
         [0010]    The invention offers the user an at least temporarily fixedly installed platform with several surfaces which are configured and measured so that he can stand on them on two legs. These surfaces are called “standing surfaces” within the scope of the invention. According to the invention in at least one position of the rotor one standing surface of the platform lies substantially horizontal. This position of the rotor is characterised as being specific for the use of the safety device. A horizontal surface offers the advantage that it minimizes the danger of the user slipping off. 
         [0011]    Within the scope of the invention the term “rotor housing” is to mean the entirety of all the housing segments of the rotor which surround the hub and connecting flanges of rotor blades on the hub. The rotor housing comprises in particular also a nose or cap, i.e. a hood-like cover of the hub against the wind direction. 
         [0012]    In order to configure the platform so that an operator can work safely thereon, it is fixed on the hub and/or on the inside of the rotor housing of the rotor by means of the fixing device. Thus in the installed state inside the rotor the platform is a part of the outermost end of the rotor. 
         [0013]    A platform of this kind can be attached fixedly or detachably in the region of the hub of the rotor by means of the fixing device. With a solid fixing the platform is in the end a fixed constituent part of the rotor or hub. In the case of a detachable fixing the platform or the safety device can also be formed as an add-on solution or as a mountable and in turn demountable device. The fixing device can comprise by way of example a screw, rivet, bolt or adhesive connection. 
         [0014]    By means of the platform which is fixed by the fixing device in the region of the hub of the rotor, in addition to a usually curved surface of the hub a number of standing surfaces are produced which provide the operator at any time with defined paths and handling regions during the intended use. The maintenance personnel are furthermore clearly better protected against a fall from a great height and can operate freely on the platform, more particularly unimpeded by security harnesses or corresponding security ropes. Drop paths are shortened since the platform also functions at the same time as a type of room divider of the interior space between the hub and the rotor housing. Overall maintenance and repair works are thereby easier in the region of the hub of the rotor, by way of example to renew a seal or to inspect and tighten bolts which fasten the rotor blades on the hub. 
         [0015]    The invention furthermore comprises a rotor, more particularly a rotor of a wind turbine having a safety device according to the invention as well as a wind turbine having a safety device according to the invention. 
         [0016]    The invention furthermore comprises a method of the type mentioned at the beginning wherein at least one standing surface of a platform of the safety device when the safety device is used as intended is positioned substantially horizontal wherein the platform is fixed on a hub of the rotor and/or on an inner side of a rotor housing of the rotor. 
         [0017]    The method according to the invention can be achieved by means of the safety device according to the invention. 
         [0018]    Further particularly advantageous configurations and developments of the invention are apparent from the dependent claims as well as from the following description wherein the independent claims of one claim category can also be developed analogously to the dependent claims of another claim category. 
         [0019]    The platform can fundamentally be suspended or mounted floating on the hub or on the rotor housing so that it is aligned each time in the properly designated position for use. In this case at least one standing surface of the platform thus always stands horizontal. The platform can have by way of example a weight which draws it always into the horizontal position and an additional locking device so that it reliably remains in this position during maintenance work. According to a configuration the safety device is mounted fixed on the hub of the rotor and/or on the inside of the rotor housing. The platform thus automatically turns during a rotational movement of the rotor or hub and the rotor housing, i.e. in the right direction and angle. More advantageously standing surfaces of the platform are arranged at different angles to one another so that the safety device provides a horizontal standing surface not only in the case of one single position of the rotor. 
         [0020]    According to an embodiment of the invention the platform is arranged relative to each two connecting flanges of rotor blades on the hub so that a standing surface on one side of the platform facing the rotor housing lies substantially parallel to a vertex face of the hub. By “vertex face” is meant a region of the curved surface of the hub which lies between two adjoining connecting flanges of the hub. With a rotation of the hub about the rotor axis the vertex faces arranged radially around the rotor axis are therefore aligned substantially horizontal alternately on a top side and an underneath side of the hub. “Substantially horizontal” hereby means that the curved vertex face stands symmetrical relative to a substantially flat standing surface. A three-vane rotor has by way of example three vertex faces. 
         [0021]    The maintenance worker normally stands for a particularly long time on the vertex faces of the hub for example since in the event of a substantially horizontal alignment these faces represent a safe, because comparatively less precipitous, standing site and offer a comfortable access to the adjoining connecting flanges of the rotor blades. A substantially parallel position of the standing surfaces on the outsides of the platform relative to the respective corresponding vertex faces of the hub has proved particularly favourable since it clearly becomes easier for the operator to climb from one standing surface to the next vertex face. This then plays a role particularly when the operator sets up for example a mobile ladder on the standing surface and where applicable leans against an end face of the hub and then climbs up the ladder in the direction of the vertex face. 
         [0022]    The platform of the safety device is advantageously arranged relative to the main extension directions of the rotor blades of a wind turbine so that a standing surface always lies substantially horizontal on an outer side of the platform when a rotor blade points downwards along a tower of a wind turbine towards a ground surface. This provides the possibility that a rotor blade mobile maintenance unit can be moved along the rotor blade between the hub and a rotor blade tip (for example for inspection and maintenance work) and at the same time an operator can carry out inspection and/or maintenance work inside the maintenance chamber between the hub and the rotor housing. 
         [0023]    The safety device is particularly configured so that the platform divides a hollow chamber between the hub and the inside of the rotor housing into essentially at least two hollow chamber regions separated from one another. The rotor housing can stand at such a distance from the hub which is measured so that an operator can move by crawling, kneeling or semi-upright therein. The hollow chamber can be formed like a dish and is penetrated by at least three rotor blades which are fitted on the hub. The platform can extend between a surface on the outside of the hub and a surface on the inside of the rotor housing. Dividing up the hollow chamber has proved advantageous since the drop path of an operator when falling down or sliding down in the hollow chamber along the surface of the hub is significantly reduced. It is particularly advantageous if the platform is therefore designed so that it divides the hollow chamber into a plurality of separated hollow chamber regions. 
         [0024]    Basically the platform of the safety device can have any shape, for example a polygonal or circular configuration. According to another embodiment the platform comprises three platform elements each with at least one standing surface to form a triangle. The platform elements can be formed circular or angular, e.g. rectangular or square. They can have the form of a frame, grid or scaffold, and be of the same or different size. The platform elements can form a triangle where they are connected to one another at the ends or at the edges running substantially parallel to the rotor axis. A chamber which is enclosed or defined by the insides of the platform elements directed towards the rotor axis is thus likewise triangular-shaped. It is called a “central chamber” within the scope of the invention. The platform elements of the triangle are particularly dimensioned sufficiently large so that the triangular-shaped central chamber can shelter an operator, e.g. a maintenance technician. 
         [0025]    A triangular shape of the platform offers the advantage that an alignment of the standing surfaces can be coordinated particularly simply with a position of the rotor blades when the rotor of the wind turbines has three rotor blades. If the platform is formed as an equilateral triangle, then it can be positioned relative to the hub so that during a rotor rotation about 120° a change always takes place from a first standing surface in a horizontal position to a second standing surface in a horizontal position. The platform according to the invention thus reduces the dependency of the horizontal position of a standing surface on a position of the rotor blades. 
         [0026]    Advantageously at least one of the platform elements comprises at least one opening as access for an operator. It is advantageous if all the platform elements comprise an opening. The opening(s) can advantageously have a dimension, or in the case of a circular opening, a diameter, which is large enough so that an operator can pass from any hollow chamber region through the opening into another hollow chamber region. The operator can pass from a chamber inside the hub into the hollow chamber between the hub and the rotor housing. He can then step from the chamber first into a region inside the triangular platform, the “central chamber”. From there the opening according to the invention in one or in each platform element allows access to one or any further hollow chamber region, wherein the access leads each time through a hollow chamber region inside the platform respectively to the “central chamber”. 
         [0027]    In principle an opening in the platform element can be opened permanently during operation of the safety device. In particular the safety device comprises a closing element for closing the opening. The closing element can be a flap, a sliding door, or a roller shutter which allows an opened and a closed state of the opening. It can also be formed as a removable cover. An operator can cover the opening by means of the closing element after passing through. The closing element is particularly designed so that it can be loaded with a weight of the operator without opening automatically. 
         [0028]    The further development according to the invention thus contributes to the safety of the operator. It reduces the risk of injury if the operator slides or falls down, for example starting from the vertex face. 
         [0029]    According to a configuration of the safety device the platform comprises bridging elements which span the contact points of the platform elements on the inner sides of the platform elements facing a rotor axis. By “contact point” is meant a place or spatial area where the ends of two platform elements meet one another at an angle and are for example welded to one another. By “inner sides” of the platform elements are meant those sides which in the case of a three-dimensional shape of the platform face one another and at the same time towards the rotor axis. The bridging elements can be set up at any points of the inner sides. They can have the configuration of a frame, grid or scaffold, and can be of the same or different size. They can be fastened on the platform elements by means of screw connections, adhesive connections, bolts or rivets. The bridging elements may each comprise at least one standing surface on which an operator can stand. When fitting a for example triangular-shaped platform with for example three bridging elements according to the invention, at least one doubling of the standing surfaces on an inside of the platform to six standing surfaces can be achieved by the bridging elements. With a rotation of the rotor around 360° an operator can consequently use in six different positions of the rotor a horizontal standing surface in an inner hollow chamber region of the platform. 
         [0030]    The bridging elements can basically each stand at any angle to the platform elements. The platform elements may stand on their inner sides facing the rotor axis at an angle of 120° to inner sides of each adjoining bridging elements likewise directed to the rotor axis. When the platform is designed as an equilateral triangle it results therefrom that each bridging element stands parallel to each opposite platform element. Thus with a rotation of a rotor about 120° in a starting and in an end position of the rotational movement, two parallel floors of the platform i.e. a platform and a bridging element, lie horizontal. Thus by way of example it becomes clearly easier to set up a ladder on a bridging element. The ladder can help the operator to pass from a space inside the triangular-shaped platform to an opening arranged above same, and then through it to a standing surface of a platform element lying parallel above same. Consequently during a rotation of the rotor about 60° a change takes place from one standing surface to an adjacent standing surface which then each lie horizontal and offer the operator a safe standing surface. The configuration according to the invention can significantly simplify the work of a maintenance technician in the hollow chamber, for example on the connecting flanges of the rotor blades. 
         [0031]    In principle the platform can be fastened solely on the hub of the rotor. According to a configuration the safety device comprises strut elements as a fixing device which connect the platform at contact points of the platform elements to an inner side of the rotor housing. The strut elements can be placed at any points on the inside of the rotor housing. They can have the form of a frame, grid or scaffold, of the same or different size. Furthermore they can be fastened to the platform or on the inside of the rotor housing by means of screw connections, adhesive connections, bolts or rivets. The strut elements can furthermore be designed so that they divide the hollow chamber between the hub of the rotor and an inside of the rotor housing into separate hollow chamber regions. 
         [0032]    The strut elements can basically be anchored at any points of the rotor housing which surrounds the hub and connecting flanges of the rotor blades on the hub. They are particularly fastened in the region of interfaces of segments of the rotor housing. The strut elements mounted on the platform thus connect the segments of the rotor housing to one another. The platform can serve by way of the strut elements as a reinforcement element of the rotor housing insofar as through its shape it absorbs the tensile forces acting on a housing segment of the rotor much more effectively than an adjacent housing segment. Fastening the strut elements on interfaces of the housing segments furthermore offers the advantage that fastening means, for example flat angle plates, are usually already provided at the interfaces which the strut elements can use for connection. Furthermore a single strut element can thereby be fitted at the ends of two housing segments of the rotor and stabilize them. 
         [0033]    The platform is particularly likewise also mounted on the hub so that the segments of the rotor housing not only support one another, but ultimately are fastened on the hub of the rotor. The strut elements can thereby replace or support any other reinforcement elements which connect the hub, a rotor housing as well as a rotor hood, structurally to one another. The configuration according to the invention thus serves as a structural element of a rotor and stabilises the rotor housing which increases its resistance for example to acute wind loads. The safety device thus offers a valuable synergy effect. 
         [0034]    The strut elements can run substantially parallel to a longitudinal axis of a blade of the rotor between interfaces of segments of the rotor housing and the platform. The safety device with the elements of the platform elements, the bridging elements and the strut elements can be constructed symmetrically, e.g. three-fold radially symmetrically. Such a design can enhance the working safety of the operator since the safety device has the same configuration each time in three different positions of the rotor. The operator is thus not forced to get used to or adapt to different forms and sizes of plates, standing surfaces, openings, which can take up part of his attention and in some circumstances can lead to a loss of time or accidents. Rather he discovers a uniformly configured working environment. 
         [0035]    The platform elements, bridging elements and strut elements can basically each have a quite different shape. By way of example the platform elements can be designed flat, whilst the strut elements can on the other hand be grid-like structures. The platform elements and/or the bridging elements and/or the strut elements are particularly designed as flat plates. The flat plates can be by way of example metal plates, for example made of corrosion-resistant stainless steel or aluminium. Alternatively they can be made of plastics, e.g. of glass fibre reinforced plastics, of wood or of carbon fibre. 
         [0036]    It is advantageous if the platform elements, bridging elements and strut elements are formed solely as plates. They each provide smooth standing surfaces which guarantee a particularly high working safety by not offering any engagement points for catching or clamping on an operator, which can lead for example to tripping and falling. The plates according to the invention can thereby provide the platform elements, bridging elements and strut elements with two standing surfaces lying parallel to one another on a front and a rear side. 
         [0037]    The plates may extend continuously or substantially without any gaps between an outer side of the hub and an inner side of the rotor housing so that they pass through the entire hollow chamber. The plates thus ensure that an operator in the event of falling down, for example from a vertex face, does not unintentionally pass from one hollow chamber region into another hollow chamber region or becomes jammed in an interspace. The same advantage is produced for tools or spare parts which an operator may be carrying loose with him; should they become undesirably lost or dropped they are prevented from slipping through into another hollow chamber region and can be quickly found again by the operator. 
         [0038]    Furthermore the plates offer the advantage that they can connect a rotor hood to the hub and can thus additionally strengthen a structure of the rotor housing. The plates therefore may have fastening elements for fastening the rotor hood on the platform. The fastening elements can comprise for example angle plates which are fixed on the plates or the rotor hood by means of rivets or screw connections. 
         [0039]    According to a configuration of the safety device an extension of the platform elements in a direction substantially transversely or vertically to the rotor axis comprises at least 1 m, particularly at least 1.3 m and more particularly at least 1.5 m as well as at most 5 m, particularly at most 4 m and more particularly at most 3 m. This extension permits an optimum adaption of the safety device to rotors, more particularly of wind turbines which have a different size and power performance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0040]    The invention will now be explained below once more in further detail with reference to the accompanying drawings and using embodiments. The same components in the different figures are thereby provided with identical reference numerals. The drawings show: 
           [0041]      FIG. 1  a perspective illustration with a partial section of a rotor housing according to the prior art; 
           [0042]      FIG. 2  a perspective partial section from the right of a rotor housing with an embodiment of the safety device according to the invention; 
           [0043]      FIG. 3  a side view from the right of the rotor of a wind turbine with the safety device; 
           [0044]      FIG. 4  a front view of a rotor housing with the safety device; and 
           [0045]      FIG. 5  a diagrammatic front sectional view of a rotor housing with the safety device. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0046]      FIG. 1  shows a section of a rotor  1  of a wind turbine with a hub  3  which is surrounded by a rotor housing  12 . The rotor  1  is formed with three vanes, i.e. it has three rotor blades (not shown in  FIG. 1 ) protruding radially from the hub  3 . Inside the hub  3  there is a tunnel-shaped hollow chamber (not shown) which serves as access from a tower (not shown) or a nacelle (not shown) of a wind turbine to connecting flanges  7  of the rotor blades  5  on the hub  3 . An exit  9  connects the tunnel to a dish-like maintenance chamber  21  between the hub  3  and the rotor housing  12 . Three two-prong ladder sections  10  protrude from an edge of the exit  9 . An operator  16 , e.g. a maintenance technician, climbs over an upper ladder section  10  in the direction of a vertex face  4  of the hub  3 . The vertex face  4  forms a region of the curved surface of the hub  3  which lies between the two circular connecting flanges  7  of the rotor blades  5  of the rotor  1 . In the illustrated position of the hub it offers a favourable, because substantially horizontally aligned, standing site for the operator  16  in order to inspect or tighten bolts for example by which the rotor blades  5  are mounted on the hub  3 . According to the prior art an operator  16  can rope himself by means of safety harness or belts onto security points which lie on an inner side  14  of the rotor housing  12  and/or on an outer surface of the hub  3  so that the operator  16  is protected against sliding or falling down. 
         [0047]      FIG. 2  shows a safety device  19  according to the invention on the rotor  1 . A platform  20  is mounted at the front on the hub  3  of the rotor  1  and is supported by three feet as strut elements  28  or a fixing device on the inner side  14  of the rotor housing  12 . The platform  20  is fixed on the hub  3  so that it turns automatically during a rotational movement of the rotor  1 . The rotor housing  12  includes three housing segments  13  which enclose the hub  3 , the connecting flanges  7  of the rotor blades  5  and the platform  20 . The rotor housing  12  has a front circular opening which during operation of the rotor  1  is covered by a rotor hood (not shown). The strut elements  28  of the platform  20  connect at interfaces  17  between the housing segments  13 . The platform  20  and the strut elements  28  are made substantially of metal. 
         [0048]    The platform  20  has three oblong platform elements  24  of identical length which are brought together in the form of an equilateral triangle. The platform elements  24  stand at internal angles α of 60° relative to one another. Each platform element  24  has an extension of 2 m in a direction perpendicular to a rotational axis R. At the inner sides  34  of the platform elements  24  facing the rotor axis R webs acting as bridging elements  26  span the tips of the triangle, i.e. the seam points between two adjoining platform elements  24 . The tips are formed from contact points  25  of the platform elements  24 . Each bridging element  26  thereby stands at an angle of 120° to an adjacent platform element  24 . Each bridging element  26  thereby also lies parallel to a platform element  24  which is opposite it on the other side of a central chamber  23  (as hollow chamber region). The platform elements  24  furthermore each have an opening  29  or an aperture which is covered here each time by a removable circular cover  30  as a closing element. The covers  30  have a diameter b which is large enough so that an operator can slip through the opening  29 . The platform  20  is measured so that the central chamber  23  is large enough so that an operator can stop and move about therein. 
         [0049]    Whilst the bridging elements  26  offer an operator a standing surface  32  for standing up, the platform elements  24  each have two potential standing surfaces  32 . An inner one of these standing surfaces  32  thereby points towards the rotor axis R, an outer standing surface  32  points towards the rotor housing  12 . In the central chamber  23  of the platform  20  there are therefore six potential standing surfaces  32 . When any one standing surface  32  is located in a horizontal position each rotation of the rotor  1  around 60° causes a horizontal position of an adjacent standing surface  32 . 
         [0050]    The strut elements  28  are seated on the outside at the tips of the triangle of the platform  20 . Each strut element  28  extends substantially parallel to a longitudinal axis L of an adjacent rotor blade  5 . Since the strut elements  28  are formed as flat plates they divide together with the platform elements  24  a maintenance chamber  21  between the hub  3  and the rotor housing  12  (as hollow chamber) into three outer partial chambers  22  (as hollow chamber regions) and a central chamber  23  (as hollow chamber region), which lies inside the platform  20 . 
         [0051]    Several angle plates  38  are mounted on the platform elements  24  and fasten the platform  20  on one side on the hub  3  and on the other side on the rotor hood (not shown). 
         [0052]    The platform  20  according to the invention offers the advantage that its in total nine potential standing surfaces  32  and its openings  29  provide an operator with defined paths and handling regions inside a maintenance chamber  21 . The triangular design of the platform  20  offers on its outer side during a rotor rotation about 120° a horizontally lying standing surface  32 , and even on its inner side facing the rotor axis R during a rotor rotation about 60°. It can thus assist or even replace a conventional safety fitting of an operator, such as safety harness and belts. The platform  20  furthermore considerably shortens the fall paths of an operator, e.g. from a vertex face (not shown) of the hub  3  starting in the direction of a connecting flange  7  of a rotor blade  5  which in this situation points directly downwards. The safety device  19  furthermore functions as a structural element of the rotor  1  and serves for a reinforcement and thus stabilizing of the rotor housing  12  with the rotor hood (not shown). 
         [0053]      FIG. 3  shows, in contrast to  FIG. 2 , an operator  16 , e.g. a maintenance technician who is moving forwards in an outer partial chamber  22  on a curved surface of the hub  3  in the direction of a vertex face  4  of the hub  3 . A horizontally aligned platform element  24  as well as the strut elements  28  which adjoin the ends of the platform element  24  and run inclined relative to the platform element  24  close off an upper outer partial chamber  22  from further partial chambers  22 ,  23 . A fall path of the operator and his equipment, e.g. loosely carried spare parts and/or tools, is thereby clearly shortened. A continuous extension of the platform elements  24  and the strut elements  28  between the hub  3  and the rotor housing  12  reliably prevents the operator and smaller elements from becoming jammed or slipping through. 
         [0054]      FIG. 4  shows, in contrast to  FIGS. 2 and 3 , the safety device  19  according to the invention in a front view. The operator  16  stands facing the viewer on a horizontal standing surface  32  of a bridging element  26  and has in front of him a mobile ladder  40  which is likewise standing on the bridging element  26 . A spacing between the bridging element  26  and the platform element  24  is here greater than a body size of the operator  16 . The mobile ladder  40  extends up to an open opening  29 . The operator  16  when climbing up the ladder  40  can pass through the opening  29 . He can then move on a horizontal standing surface  32  of the platform element  24 . An opening of the rotor housing  12  released by the housing segments  13  is covered by a disc-like rotor hood  15 . The platform elements  24  have angle plates  38  which run along an extension of the platform elements  24  between the strut elements  28 , and fasten the platform  20  additionally on the hub  3 . 
         [0055]      FIG. 5  shows, in contrast to  FIG. 4 , more particularly the three-fold radially symmetrical construction of the safety device  19  according to the invention. Each of the three strut elements  28  aligns flush with a longitudinal axis L of one of the three rotor blades  5  or stands parallel to it. The platform  20  with its platform elements  24  forms an equilateral triangle. A longitudinal axis L of each rotor blade  5  stands perpendicular to an opposing platform element  24 . The strut elements  28  are mounted by means of bolts  18  as fixing device on interfaces  17  of the segments  13  of the rotor housing  12 . 
         [0056]    It is finally pointed out once more that the devices described in detail above are only examples of embodiments which can be modified by one skilled in the art in the most varied of ways without departing from the scope of the invention. Furthermore the use of the indefinite article “a” and “an” does not rule out that the relevant features can also be present in several numbers.