Abstract:
A securing element for securing the position of moving blades in slots, running at least mainly in the axial direction, of a rotor parent body of a turbomachine rotor is described, comprising a plate-shaped parent body, wherein the parent body has an approximately central recess which is formed between two end sections of the parent body and defines a center section, running between the two end sections, of the parent body, wherein the two end sections have bearing surfaces running parallel to one another.

Description:
The present invention relates to a securing element for securing rotor blades in position in grooves of a rotor base body of a turbine engine rotor. The present invention also relates to a method for mounting a securing element on a turbine engine rotor, in particular on a gas turbine rotor, and to a turbine engine rotor. 
     BACKGROUND 
     Rotors of a turbine engine, such as gas turbine rotors, have a rotor base body, as well as a plurality of rotor blades that rotate therewith. The rotor blades can either be an integral part of the rotor base body or be anchored via blade roots in one or a plurality of grooves of the rotor base body. Rotors having integral blading are referred to as blisks or blings, depending on whether a rotor base body is disk-shaped or ring-shaped. In the case of rotors where the rotor blades are anchored via blade roots in a groove, one differentiates between rotors whose blade roots are fastened in what are generally known as axial grooves of the rotor base body and those whose blade roots are fastened in what is generally known as a circumferential groove of the same. The present invention is directed to a rotor of a turbine engine, in particular a gas turbine rotor, where the rotor blades are fastened via their blade roots in grooves which extend at least predominantly in the axial direction of the rotor base body, thus in axial grooves. 
     In the case of gas turbine rotors where the rotor blades are anchored via their blade roots in such axial grooves of the rotor base body, plate-type elements, namely securing elements (also referred to as locking plates), and locking elements (also referred to as retaining plates) are used to axially secure the rotor blades. When assembling such a gas turbine rotor, the locking elements, respectively the retaining plates, are threaded into annular grooves of the rotor base body, as well as of the rotor blades, to this end, at least one of the rotor blades being axially displaced to allow the locking elements to be inserted into the annular grooves. For their part, the locking elements are secured in position in the annular grooves via at least one securing element, respectively one locking plate, the or each securing element being deformed to fit engagingly in the annular grooves of the rotor base body, as well as of the rotor blades, into a free space between two adjacent locking elements. 
     When working with the related art securing elements, the problem arises that, once they are fitted into the annular grooves, they spring back and then no longer engage abuttingly on the rotor base body in a predetermined manner. This degrades the function of the securing elements. 
     SUMMARY OF THE INVENTION 
     The securing element according to the present invention has a plate-shaped base member, the base member having an approximately centrally disposed recess which is formed between two end sections of the base member and which defines a middle section of the base member that extends between the two end sections, the two end sections having mutually in parallel extending bearing surfaces. 
     Once the securing element according to the present invention is fittingly mounted in the annular grooves of the rotor base body and rotor blades, it is ensured that it engages abuttingly by bearing surfaces formed on the end sections of the base member of the securing element, in a planar manner or flat on the rotor base body. The securing elements according to the present invention permit a very defined and reproducible mounting of the same in the annular grooves of the rotor base body and rotor blades. As a result, full functionality of the securing elements is ensured. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described in greater detail in the following on the basis of exemplary embodiments, without being limited thereto. Reference is made to the drawing, whose figures show: 
         FIG. 1 : a detail of a related-art gas turbine rotor in a perspective side view; 
         FIG. 2  another detail of a related-art gas turbine rotor in a front view; 
         FIG. 3   a - 3   b : views for illustrating the related-art procedure for mounting securing elements in the context of a gas turbine rotor according to  FIGS. 1 and 2 ; 
         FIG. 4  a securing element according to the present invention in a lateral view; 
         FIG. 5  the securing element according to the present invention in an intermediate position during assembly, namely following deformation of the same to fit into annular grooves of the rotor base body and rotor blades; 
         FIG. 6  the securing element according to the present invention in another intermediate position during assembly, together with a tool; 
         FIG. 7  the securing element according to the present invention in the installed position; and 
         FIG. 8  the securing element according to the present invention in the installed position. 
     
    
    
     DETAILED DESCRIPTION 
     Prior to describing the present invention in greater detail with reference to  FIG. 4 through 8 , a gas turbine rotor known from the related art, having roots of rotor blades that are guided in grooves that extend at least predominantly in the axial direction—so-called axial grooves—will first be discussed with reference to  FIG. 1 through 3 . 
       FIGS. 1 and 2  show details of a gas turbine rotor  10  known from the related art that has a rotor base body  11 , as well as a plurality of rotor blades  12 . Each of rotor blades  12  has a blade  13 , as well as a blade root  14 . A plurality of axially extending axial grooves  15  are introduced into rotor base body  11 , each rotor blade  12  being anchored by its blade root  14  in such an axial groove  15  in rotor base body  11 . Locking elements  16  and securing elements  17  are used to axially fix in position, respectively axially secure rotor blades  12  that are inserted into axial grooves  15 . Securing elements  17  are also referred to as locking plates; locking elements  16  as retaining plates. Rotor blades  12  are provided radially outwardly with segments of a shroud band  18 , rotor blades  12  being joined to one another in the region of shroud band  18  by a “Z” interlock. 
     In the assembled state of gas turbine rotor  10 , locking elements  16 , as well as securing elements  17  are guided in annular grooves, namely in an annular groove  19  of rotor base body  11 , as well as in an annular groove  20  of rotor blades  12 . 
     To be able to introduce locking elements  16  into annular grooves  19  and  20  of rotor base body  11 , as well as of rotor blade  12 , as may be inferred, in particular, from  FIG. 1 , some of rotor blades  12  are canted circumferentially in the direction of arrows  21 , allowing rotor blades  12  positioned therebetween to be axially displaced in the direction of arrows  22 . In this manner, the axially displaced rotor blades interrupt annular groove  20  of the same, respectively clear annular groove  20 , thereby allowing locking elements  16  to be inserted, respectively introduced into annular grooves  19  and  20 . Once locking elements  16  have been threaded in, securing elements  17  are deformed to fit engagingly in annular grooves  19  and  20  in accordance with  FIGS. 3   a  and  3   b  at selected circumferential positions (see  FIG. 2 ), into a free space between adjacent, respectively circumferentially spaced apart locking elements  16 , securing elements  17 , that have been deformed to fit engagingly, bent back as far as possible following the fitting deformation and, in the process, being straightened out to the greatest degree possible. In this context, under related art methods, the problem arises that securing elements  17  do not rest flat against rotor base body  11 , respectively blade roots  14 . To overcome this problem, a novel securing element has been devised in accordance with the present invention. 
       FIG. 4  shows a securing element  23  according to the present invention for securing rotor blades  12  in position in axial grooves  15  of rotor base body  11  prior to the assembly of the same. Securing element  23  according to the present invention has a plate-shaped base member  24 , base member  24  having an approximately centrally disposed recess  25 . Recess  25  is formed between two end sections  26  and  27  of base member  24  and delimits a middle section  28  of the same. In the region of the two end sections  26  and  27 , securing element  23  according to the present invention has mutually in parallel extending bearing surfaces  29  and  30 . Prior to assembly, bearing surfaces  29  and  20  of the two end sections  26  and  27  are in alignment. Prior to assembly, middle section  28  is uncambered. 
     A securing element  23  of this kind in accordance with the present invention may undergo elastic and plastic deformation in order to fit engagingly in between annular grooves  19  and  20  of rotor base body  11 , as well as of rotor blades  12 ; subsequently to its fitting deformation, securing element  23  assumes the position, respectively the shape shown in  FIG. 5 . Bearing surfaces  29  and  30  are cambered, as is middle section  28 . 
     For the further assembly of securing element  23  according to the present invention, a ram-type tool  33  is pressed against middle section  28  of securing element  23 , middle section  28 , as well as ram-type tool  33  being dimensioned to act on securing element  23  exclusively in middle section  28 , at a distance from end sections  26  and  27  thereof. Ram-type tool  33  bends securing element  23  in reverse, overbending it in middle section  28 , so that, following removal of ram-type tool  33 , securing element  23  assumes the position shown in  FIG. 7 . In the process, securing element  23  undergoes plastic deformation in middle section  28  in regions  34  and  35  where edge sections of ram-type tool  33  are effective, thereby forming portion  31  that has been subjected to extra bending stress shown in  FIG. 7 . Following removal of tool  33  and, thus, subsequently to the rebounding of securing element  23  that has been deformed to fit into, respectively that has been snapped into annular grooves  19  and  20  of rotor base body  11 , as well as of rotor blades  12 , bearing surfaces  29  and  30  of end sections  26  and  27  again extend mutually in parallel, and thereby realign after rebounding. Accordingly, subsequently to the rebounding of securing element  23 , bearing surfaces  29  and  30  of end sections  26  and  27  again assume the position shown in  FIG. 4 . On the other hand, the already mentioned, cambered portion  31  that has been subjected to extra bending stress remains following removal of ram-type tool  33 . 
     As may be inferred from  FIG. 4 through 8 , securing element  23  according to the present invention has a projection  36  in the region of end section  27 . As may be inferred from  FIG. 8 , this projection  36  may be threaded into annular groove  19  of rotor base body  11  when the securing element according to the present invention is fitted engagingly into annular groove  19 . In this context, projection  36  is dimensioned in such a way that a center-of-mass  37  of securing element  23  according to the present invention is displaced relative to a radial engagement  38  of end section  26  in the annular groove of blade root  12  in such a way that, during operation, centrifugal forces acting on securing element  23  press projection  36  against a sealing surface  32  in the region of annular groove  19  of rotor base body  11 . An optimized sealing action is hereby provided for securing element  23  according to the present invention.