Abstract:
An arrangement for axial locking of rotating blades in a rotor is provided. The arrangement includes a shaft collar, a projection, plate-like sealing elements, and a blocking element. The sealing elements are provided for axially securing the rotating blades. At least one sealing element has an opening for securing the sealing elements against displacement in the circumferential direction. The blocking element is inserted in a recess from the end side of the shaft collar and blocks the displacement path of the sealing element. In order for the blocking element to be secured against unintentional releasing, the blocking element is fastened on the rotor disk using plastic deformation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US National Stage of International Application No. PCT/EP2008/053271, filed Mar. 19, 2008 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 07007088.3 EP filed Apr. 4, 2007, both of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The invention refers to an arrangement for axial locking of rotor blades in a rotor, with a shaft collar, on the outer periphery of which provision is made for rotor blade retaining slots which extend in the axial direction of the rotor and in which rotor blades, with blade roots which correspond to the rotor blade retaining slot, are arranged in each case, with a projection which is arranged on an end-face side surface of the shaft collar in the region of the retaining slots, in which projection a radially outwardly open encompassing slot is provided and with radially inwardly open locking slots which are arranged in each rotor blade and which lie radially opposite the encompassing slot in each case, wherein for axial locking of the rotor blades provision is made for plate-like sealing elements which in each case engage in the encompassing slot and in the locking slot, forming an end-face sealing ring in the circumferential direction, wherein at least one of the sealing elements has a means for securing the sealing elements against displacement in the circumferential direction. In addition, the invention refers to a gas turbine with such an arrangement. 
       BACKGROUND OF INVENTION 
       [0003]    Rotors of gas turbines are known in which turbine rotor blades, which are arranged on the outer periphery in rotor blade retaining slots, are secured against axial displacement by means of sealing plates. In this case, to fasten these sealing plates on the rotor by means of riveting is known for example from U.S. Pat. No. 3,957,393. 
         [0004]    Furthermore, an arrangement according to  FIG. 1  is known. It shows a generic-type arrangement in a plan view, and  FIG. 2  shows an arrangement in a cross section according to the line of intersection II-II in  FIG. 1 . For each rotor blade  14  which is to be secured against axial displacement inside its rotor blade retaining slot  12 , two slightly overlapping sealing plates  16  are provided as sealing elements which in each case cover by half the end-face opening of the rotor blade retaining slot  12 . Each sealing plate  16  by its radially inner end  18  is inserted in an encompassing slot  20  which is provided on a rotor disk  19  on the end face, and by its radially outer end  22  is inserted in a locking slot  24  which is provided on the underside  26  of a platform  28  of the rotor blade  14 . In order to secure each sealing plate  16  against displacement in the circumferential direction U, a rectilinear metal strip  30 , which extends essentially in the radial direction of the rotor  23 , is fastened on each sealing plate. Each metal strip  30  terminates at its radially outer end  32  in a uniformly converging point  34 . Chamfered edges  36  are provided on the platforms  28  of the rotor blades  14 , wherein two oppositely disposed edges  36  of directly adjacent turbine rotor blades  14  form in each case a recess  38  which tapers to a point and into which the point  34  of the metal strip  30  can project and abut for securing the sealing plate  16  against displacement in the circumferential direction U. 
         [0005]    The sealing plates  16  furthermore cater for separation of two regions  37 ,  39  in which on the one hand cooling air can enter and on the other hand some of the hot gas can possibly enter. 
         [0006]    For fastening the metal strip  30  on the sealing plate  16 , two parallel slots  40  are provided in the last-named, through which the metal strip  30 , which is already pre-bent into a U-shape, is inserted. Before installing the sealing plate  16  on the rotor disk  19 , the end  41  of the metal strip  30  opposite the point  34  is already bent into the position which is shown in  FIG. 2  for the fastening of the metal strip  30 . 
         [0007]    After installing the rotor blades  14  in the rotor disks  19 , the sealing plates  16  with the pre-installed metal strips  30  are threaded one after the other into the endlessly encompassing slot  20  which is arranged on the rotor disk  19 , and into the locking slot  24  which is arranged on the underside  26  of the platform  28 . The sealing plates  16  are positioned along the circumference of the encompassing slot  20  so that each metal strip  30  lies opposite a recess  38 . The points  34  of the metal strips  30  are then bent into the recesses  38  in order to exclude displacement of the sealing plates  16  in the circumferential direction U. 
         [0008]    Since the metal strips may be bent only once on account of the enormously high mechanical requirements, when exchanging a rotor blade in the event of a service the metal strip which is then bent up is to be replaced by a new metal strip. Furthermore, the slots which are provided for accommodating the metal strips in the sealing plates weaken the said sealing plates. 
       SUMMARY OF INVENTION 
       [0009]    It is the object of the present invention to disclose an alternative arrangement for securing the sealing elements against a rotating displacement in the circumferential direction, in which the installation and removal times are improved. The provision of a gas turbine with such an arrangement is a further object of the invention. 
         [0010]    The object which is focused upon the arrangement for axial locking of rotor blades in a rotor is achieved by means of the features of the claims. 
         [0011]    The invention provides that in the case of the generic-type arrangement the means for securing the sealing elements against displacement in the circumferential direction comprise an opening which is provided in the sealing element and also a recess which is provided in the side surface of the shaft collar and approximately aligns with the opening, and a positionally locked blocking element which is seated in the recess and in the opening. The invention avoids the previous configuration in which a metal strip which is hooked into the sealing element engages in a form-fitting manner in a recess. Instead of the metal strip, a blocking element is now provided which can be inserted into the recess which is provided on the shaft collar on the end face. The blocking element blocks displacement of the sealing element in the circumferential direction since, being arranged in the region of the sealing element, it extends transversely to the encompassing slot in which the sealing element is seated and in the process engages in the opening which is provided on the sealing element. A negligible and tolerable clearance of the sealing element along the encompassing slot is possible only insofar as the width of the opening as seen in the circumferential direction is larger than the width of the blocking element which is to be considered in the circumferential direction. 
         [0012]    By using a blocking element which engages in the opening of the sealing element and is fastened on the end face on the shaft collar by means of caulking which plastically deforms the blocking element, a particularly reliable and simple axial securing of the sealing element against displacement in the circumferential direction can be achieved. Furthermore, installation is to be accomplished quickly and simply. For this purpose, the blocking element is to be plastically deformed on the end face with a suitable caulking tool, for example a tool in the style of a hammer and chisel, so that it abuts in the recess under tension. As a result, an exceptionally reliable frictional engagement between the wall of the recess and the blocking element is brought about, which reliably prevents the unwanted loosening of the blocking element during operation of the gas turbine. For removing the blocking element, the deformed region of the blocking element can be removed by grinding and in this way the frictional engagement is loosened for removal. 
         [0013]    In addition, with the construction according to the invention the slots which were provided for fastening the locking plate on the sealing element and previously weakened the sealing element are dispensed with. The rigidity of the sealing element is subsequently further increased, also its sealing effect. 
         [0014]    Advantageous developments are disclosed in the dependent claims. 
         [0015]    In an advantageous development of the invention, the blocking element, with regard to its installed position, is formed in the shape of a wedge in cross section in the region of the recess and moreover comprises a bolt which projects on the end face and which can be inserted into the opening of the sealing element. As a result of the wedge shape of the blocking element and of the recess which corresponds to the wedge shape a defined position of the blocking element in the rotor is predetermined. Furthermore, the orientation of the wedge shape of the recess is selected so that the converging side walls point outwards, in the same way as the flanks of the blocking element which correspond to them. As a result, the wedge-shaped blocking element is braced outwards under centrifugal force action and in the process wedges or jams further in the recess which further increases the frictional engagement between the flanks and the side walls and makes an unwanted loosening of the blocking element more difficult. Consequently, a particularly reliable arrangement can be disclosed as a result of this. 
         [0016]    According to an alternative development of the invention, the recess which accommodates the blocking element is open as seen in the radially outward direction. In this case, the blocking element which is inserted therein can be plastically deformed on the circumferential side, with regard to the rotor, instead of the end-face deformation. As long as provision is then still made for pockets which are additionally arranged in the sidewalls of the recess on the circumferential side, into which parts of the deformed material of the blocking element can deflect, a form-fit for positional locking of the blocking element can additionally also be provided in addition to the caulking of the blocking element. As a result of this, the blocking element is especially reliably safeguarded against loss. 
         [0017]    According to a further advantageous development, the recess, extending in the axial direction of the rotor, is arranged in the side surface of the shaft ring in such a way that it extends right into the encompassing slot. Weakening of the shaft collar or of a rotor disk which preferably forms the shaft collar is avoided in this case. Therefore, the opening which is provided on the sealing element is then provided on the radial inner end of the sealing element. This region of the sealing element heats up the least during operation so that the rigidity and the temperature resistance of the sealing element are not impaired as a result of the opening. 
         [0018]    It has been proved to be especially advantageous if every other sealing element, or each sealing element, has the means for securing the sealing elements against displacement. The arrangement is expediently provided on a rotor of a stationary gas turbine which is exposed to throughflow in the axial direction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The invention is explained based on a plurality of exemplary embodiments which are shown in a drawing. Further advantages and features result from the explanation. In the drawing: 
           [0020]      FIG. 1  shows the arrangement for axial locking of rotor blades in a rotor according to the prior art, 
           [0021]      FIG. 2  shows the cross-sectional view according to  FIG. 1  along the line of intersection II-II, 
           [0022]      FIG. 3  shows the detail of a plan view of a rotor disk with a rotor blade arranged thereupon as an arrangement for axial locking of the rotor blade by means of a sealing element, 
           [0023]      FIG. 4  shows a perspective view of a blocking element according to the invention, and 
           [0024]      FIG. 5  shows a perspective view of a blocking element which is inserted into the recess of the rotor according to a second development. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0025]      FIG. 3  shows a detail of the end-face plan view of the shaft collar  21 , which is formed by a rotor disk  19 , of a rotor  23  of a gas turbine. The rotor  23 , which is rotatable around the rotational axis  50 , has rotor blade retaining slots  12  which are distributed on its outer periphery  52  along the circumference U and extend in the axial direction, into which slots a rotor blade  14 , with a blade root  54  which is constructed corresponding to the rotor blade retaining slot  12 , in each case can be inserted. A rotor blade  14  is already inserted in the rotor blade retaining slot  12  which is shown in the middle in  FIG. 3 . As in the case of the prior art which is shown in  FIG. 1  and  FIG. 2 , a projection  58  or widening, with a radially outwardly open encompassing slot  20  therein, which extends in the axial direction, is arranged on an end face of the rotor disk  19  or on an end-face side surface  56  of the shaft collar  21 . The encompassing slot  20  for example is arranged radially further inwards than the rotor blade retaining slots  12 . The rotor blade  14  has a platform  28  which is arranged between blade root  54  and the profiled blade airfoil and on the underside of which provision is made for a locking slot  24  which is open towards the encompassing slot  20  and in this case lies opposite this. In a similar manner to the prior art, a sealing element  42  is inserted into the endlessly encompassing slot  20  and in the locking slot  24  and secures the rotor blade  14  against displacement along the rotor blade retaining slot. 
         [0026]    In contrast to the nearest prior art, the sealing element  42  completely covers the end-face opening of one of the rotor blade slots  12 . In this way, only one of the rotor blades  14  is secured in each case by one of the sealing elements  42  against displacement along the rotor blade retaining slot  12 . 
         [0027]    The sealing elements  42 , however, as in the case of the prior art, can be distributed over the circumference so that two directly adjacent sealing elements engage by half in the locking slot  24  of the rotor blade  14  in each case. Then two adjacent sealing elements secure one of the rotor blades  14  against axial displacement. 
         [0028]    Similar to the prior art, a completely installed ring of sealing elements  42 , which slightly overlap in each case, forms a sealing ring which separates a region  37  which is exposed to throughflow by a cooling medium from a further region  39  in which a hot gas can possibly be encountered ( FIG. 2 ). 
         [0029]    In order to secure the sealing element  42  itself against displacement in the circumferential direction, an opening  63 , which can be a cutout but also a hole, is provided on the radially inner end  61  of the sealing element  42 . 
         [0030]    Furthermore, a recess  65 , which extends essentially in the axial direction of the rotor  23 , i.e. parallel to its rotational axis  50 , is provided on the side surface  56  of the shaft collar  21  in the region of the projection  58  in each case. Each recess  65  has two oppositely disposed side surfaces  66  which, as seen in the outward direction, extend towards each other in a wedge-like manner, but do not touch, forming a gap. 
         [0031]    Instead of an outwardly open recess  65 , an outwardly closed recess can also be provided. In this case, the two side walls  66  which extend towards each other meet in a rounded point. 
         [0032]    The blocking element  67  which is perspectively shown in  FIG. 4  can be inserted into the recess  65 . The blocking element  67  comprises a section with a wedge shape which corresponds to the recess  65 , with flanks  70  which extend towards each other, and a bolt  69  which is arranged on the wedge-shaped section on the end face. With the blocking element  67  inserted in the recess  65 , its bolt  69  engages in the opening  63  of the sealing element  42 . 
         [0033]    In total, therefore, the means for securing the sealing element  42  against displacement in the circumferential direction U comprises the opening  63  in the sealing element  42 , the recess  65  which is arranged in the end face of the rotor disk  19 , and also the blocking element  67  which can be inserted into the recess. 
         [0034]    A negligible and tolerable clearance of the sealing element  42  along the encompassing slot  20  is possible only insofar as the width of the opening  63  as seen in the circumferential direction is larger than the width or the diameter of the bolt which is to be considered in the circumferential direction. In order to achieve an especially impermeable separation of the region  37  from the region  39 , the width of the opening  63  preferably corresponds essentially to the diameter of the bolt  69 . 
         [0035]    After inserting the blocking element  67  in the recess  65 , the blocking element is slightly plastically deformed by means of a caulking process. The blocking element  67  in this case is plastically deformed in the region  71 . As a result of this, the still existing, but negligible, clearance for inserting the blocking element  67  is removed so that a secure seating of the blocking element  67  results. As a result of removing the clearance, the flanks  70  are pressed onto the sidewalls  66 . As a result of this, a reliable frictional engagement is created between the walls  66  of the recess  65  and the flanks  70  of the blocking element  67  which reliably prevents the unwanted loosening of the blocking element. 
         [0036]    The caulking process can be carried out by means of a suitable chisel which is slightly rounded at the point, which when placed on the blocking element in the region  71  is provided with a hammer blow. For controlled positioning of the chisel the blocking element has an end-face premachined depression  71  in which the chisel is to be placed. 
         [0037]    An alternative development of the invention is shown perspectively in  FIG. 5 . In this case, the blocking element  67  which is shown from  FIG. 4  is inserted in the recess  65  with only a slight alteration. Instead of the end-face depression  71  the blocking element  67  which is to be used for  FIG. 5  has two depressions  71  on the generated surface side (circumferential side), with regard to the rotor, as an aid for the caulking process and which, providing the blocking element  67  is inserted in the recess  65  according to  FIG. 5 , in each case lie opposite a pocket  72  which is provided in the sidewalls  66  on the circumferential side. By means of a caulking process according to the aforesaid manner the material of the blocking element which is adjacent to the depressions  71  can be introduced into the pockets  72  so that a form-fit results for secure positioning of the blocking element  67  in the recess  65 . 
         [0038]    In all, an arrangement is disclosed by the invention in which the disadvantages which are known from the prior art are eliminated by a blocking element, which is inserted from the end face of the shaft collar into a recess, blocking the displacement path of the sealing element. So that the blocking element itself is secured against unwanted loosening this is fastened on the rotor disk by means of plastic deformation.