Abstract:
An elastomeric bearing arrangement for the reduction of machine vibrations caused predominantly by externally acting forces. The bearing, due to its special design and construction symmetry, is capable of processing the forces occurring in all spatial directions with optimal material protection. The bearing is preferably suitable for a rotational connection of rotor/gearbox units to the support plate in wind turbines. The bearing has a sandwich element ( 5 ), a cone element ( 3 ), a cone piece ( 4 ) and a cylinder piece ( 4   a ) which interact with one another.

Description:
[0001]    This application is a National Stage completion of PCT/EP2009/008044 filed Nov. 12, 2009, which claims priority from European Patent application serial no. 08019999.5 filed Nov. 17, 2008. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to an elastomeric bearing arrangement for the reduction of machine vibrations caused predominantly by externally acting forces. Owing to its special design and construction symmetry, it is capable of processing the forces occurring in all spatial directions with optimal material protection. The bearing according to the invention is preferably suitable for a connection, arranged in a circular manner, of rotor/gearbox units to the bedplate in wind turbines. 
       BACKGROUND OF THE INVENTION 
       [0003]    Diverse bearings are described for these purposes in the prior art. A solution which is already very usable is described in EP 1 593 867 B1, but this uses a special coupling. A bearing of this type is formed by the tensioning of two cone elements lying against one another and is depicted diagrammatically in  FIG. 1 . The force transmission in the case of this double-cone bearing takes place from the gearbox flange ( 2 ) to the bedplate ( 1 ) via the two tensioned diametrical cone bearings ( 10 ), which are supported unilaterally and pre-tensioned by the cone pieces ( 8 ) and ( 9 ). The pre-tensioning is carried out by means of the screw ( 7 ). The system allows perfect force transmission, but still has the following disadvantage: on introduction, for example, of a torsion moment around the rotor shaft axis, which is transmitted by all bearings in each case by a radial force in these bearings—the radial force acts in the case of the cone elements ( 10 ) in the center of the respective cone bearing, so that the resultant radial force acts approximately in the center between the two cones ( 8 ,  9 ). This results in a bending moment, which must be transmitted between the two cones ( 8 ,  9 ) and the machine flange ( 1 ). The transmission of this moment takes place via the separating surface ( 11 ) and the separating surface between cone ( 8 ) and the flange ( 1 ), and the screw connection ( 7 ). In order that the connection is not damaged, the resultant loading of the separating surfaces and the screw connection requires sufficiently large dimensioning of the contact surfaces and the screw connection. This may have the consequence that the physical size of the system as a whole increases significantly. 
       SUMMARY OF THE INVENTION 
       [0004]    The object was thus to provide a bearing for the said purposes which avoids or at least significantly reduces the said disadvantages, in particular the bending moments occurring in the region of the screw connection ( 7 ) and the cones ( 8 ,  9 ), but at the same time ensures the advantages of optimized vibration reduction, as described in EP 1 593 867 B1. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    This object has been achieved by means of the present invention, as described below and specified by the claims. The bearing arrangement according to the invention is depicted graphically in the Figures in which: 
           [0006]      FIG. 1  Conventional elements arranged in a circular manner; 
           [0007]      FIG. 2  Circular arrangement of the elements in accordance with the invention; and 
           [0008]      FIG. 3  Section through a bearing in accordance with the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0009]    The invention thus relates to an elastic machine or gearbox bearing for the transmission of the forces and moments occurring in all spatial directions, in particular axially and radially, and for the reduction or isolation of vibrations occurring, which comprises an axially oriented elastomeric sandwich element ( 5 ) and an elastomeric cone element ( 3 ), which is installed above or below the former and whose axis is oriented perpendicular to the sandwich element ( 5 ) and whose tapered end is positioned against this sandwich element ( 5 ), where the elements ( 3 ) and ( 5 ) are connected to one another by a cone piece ( 4 ), which is surrounded centrally by the cone element ( 3 ), and a cylinder piece ( 4   a ), which is surrounded centrally by the sandwich element ( 5 ), and each of the elements ( 3 ), ( 5 ), ( 4 ), ( 4   a ) has a central axially oriented hole for the accommodation of a clamping bolt or a clamping screw ( 7 ) for clamping a machine part ( 2 ), which is introduced between the elastomeric elements ( 3 ) and ( 5 ) and generally functions as clamping flange, to the machine part ( 1 ), which is installed below the element ( 3 ) and functions as attachment flange. 
         [0010]    In accordance with the invention, the elastic force-transmission moment now consists of an elastic cone element ( 3 ) and an elastic sandwich element ( 5 ), which is axially clamped thereto. Whereas the cone element ( 3 ) transmits axial forces and radial forces, the sandwich element ( 5 ) transmits virtually exclusively axial forces. The resultant total force acting on the bearing according to the invention now acts in the region of the cone piece ( 4 ) with a widened cross section, so that the bending moment formed no longer acts on the narrow connecting piece ( 4   a ) or the clamping means ( 7 ) to this extent and no longer results in a loosening of the attachment or in material fatigue. 
         [0011]    The stiffness of the sandwich element ( 5 ) is, in accordance with the invention, approximately a factor of 2-100, preferably 10-100, in particular 50-100, smaller than the radial stiffness of the cone element ( 3 ). 
         [0012]    The radial force transmission in the bearing also takes place in accordance with the radial stiffness ratio. Thus, about 2-100 times as much radial force is transmitted in the cone element ( 3 ) as in the sandwich element ( 5 ). The radial force transmission in ( 5 ) is thus negligible. This has the consequence that a large bending moment does not have to be transmitted in the cone piece ( 4 ), which results in alleviation of the load on the cylinder piece ( 4   a ), which is adjacent to the cone piece ( 4 ) and through which the clamping means ( 7 ) is also passed, so that this and also the clamping means merely have to be dimensioned for the tensile and compression forces arising. 
         [0013]    The introduction of load from the cone piece ( 4 ) into the attachment flange ( 1 ) is also simplified by the fact that virtually pure shear has to be transmitted here and the bending moment is significantly smaller than in the prior-art design in accordance with  FIG. 1 . In an embodiment of the invention, cone piece ( 4 ) and attachment flange ( 1 ) can also be integral constituents of a single component. 
         [0014]    In principle, the cone piece ( 4 ) and the cylinder piece ( 4   a ) can also be a single workpiece. 
         [0015]    The two elements are thus clamped to one another in the axial direction. The two elements may have the same stiffness in the axial direction, but this is not absolutely necessary. However, the cone element ( 3 ) has significantly greater stiffness in the radial direction than the sandwich element ( 5 ). 
         [0016]    The pre-tensioning and axial force transmission in the case of the sandwich element preferably take place via a pressure plate ( 6 ), which is provided with a hole which is able to accommodate the clamping bolt or the clamping screw ( 7 ). 
         [0017]    The invention thus relates to a corresponding bearing which has a pressure plate which is in direct or indirect contact with the sandwich element ( 5 ). 
         [0018]    In a particular embodiment, the pressure plate ( 6 ) and the sandwich element ( 5 ) form a constructional unit. 
         [0019]    It has furthermore been found that the force distribution over the entire bearing element is particularly advantageous if the fixed, non-elastic, conical cone piece ( 4 ) is not formed by a simple cone surface, but instead has convex curvature. The effect can be reinforced further if the elastomeric cone element ( 3 ) furthermore also has corresponding concave curvature on the inside and preferably also on the outside, so that its inside surface can come to rest on the outside surface of the cone piece ( 4 ) with an accurate fit. 
         [0020]    In a further embodiment, the cone piece ( 4 ) with the cylinder piece ( 4   a ) can form a constructional unit. 
         [0021]    The invention thus relates to a corresponding bearing in which the cone piece ( 4 ) has a surface with convex curvature on which the inside surface of the cone element ( 3 ) lies. In a further embodiment, the components ( 3 ) and ( 4 ) may again in accordance with the invention be combined to form a single constructional unit. 
         [0022]    The invention also relates to a corresponding bearing in which the inside surface of the cone element ( 3 ) has concave curvature, and preferably also in addition the outside surface of the cone element ( 3 ) has concave curvature. 
         [0023]    The elastomer elements ( 3 ) and ( 5 ) have 1 or more elastomer layers. In general, they essentially consist of at least two elastomer layers, which are separated by a stiff interlayer, usually a metal plate. The elements preferably consist of three to five elastomeric layers with corresponding intermediate plates or interlayers. The elements are terminated on the outside by likewise stiff layers/plates. 
         [0024]    The elastomer materials used for the bearings according to the invention essentially consist of a natural rubber, a natural rubber derivative or of a suitable elastic polymeric plastic or plastic mixture. In accordance with the invention, the elastomer layer may have different hardness (“Shore hardness”) and different damping properties, corresponding to the desired requirements. Elastomers having a hardness of 20 to 100 Shore A, in particular 30 to 80 Shore A, are preferably used. The preparation of such elastomers of different hardness is known from the prior art and is adequately described in the relevant literature. 
         [0025]    In accordance with the invention, the stiff intermediate plates or interlayers are made from materials having high stiffness, high strength and low compressibility. These are preferably metal sheets, but other materials, such as hard plastics, composite materials or carbon fiber-containing materials, can also be employed. The intermediate metal sheets and the elastomer materials are generally connected to one another during vulcanization. 
         [0026]    The cone element ( 3 ) of the bearing according to the invention should have a cone angle of 10-50° with respect to machine axis (a) or to the axis of the clamping element ( 7 ) against or in the screw-in direction. It preferably has a cone angle of 25-50°. 
         [0027]    The bearing according to the invention is versatile and can be employed in different ways. As a so-called unilateral bearing arrangement, it is particularly suitable for wind turbines in order to produce, in particular, a rotational elastic connection between the rotor shaft, the gearbox or a rotor/gearbox unit and the bedplate. 
         [0028]    However, it can also be employed in couplings as described in EP 1 593 867 B1 instead of the elastomer bearings mentioned therein. 
         [0029]    The bearing according to the invention can also be employed as tower decoupling in wind turbines, as described in EP 1 065 374 B1, which additionally results in simplification. 
         [0030]    It is likewise possible to improve machine feet in accordance with EP 1 065 374 B1 in that the bending moment between the flanges having the design described can be reduced and the screw forces can thus be decreased. 
       REFERENCE NUMERALS 
       [0000]    
       
           1  Attachment flange 
           2  Clamping flange 
           3  Elastomeric cone element 
           4  Cone piece 
           4   a  Cylinder piece 
           5  Elastomeric sandwich element 
           6  Pressure plate 
           7  Clamping means (screw/bolt) 
           8  Cone piece clamping side 
           9  Cone piece supported unilaterally 
           10  Symmetrical elastomeric cone bearing 
           11  Separation between the cones