Abstract:
The present invention is directed to a releasable connection arrangement, with a non-positive and positive fit, for two rotationally symmetrical components at a connection point, especially for creating a leak-proof connection between closure elements on power plant valves.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to DE 102004013332.8 filed Mar. 17, 2004.  
       TECHNICAL FIELD  
       [0002]     The invention relates to a releasable connection arrangement, with a non-positive and positive fit, for two rotationally symmetrical components at a connection point, especially for creating a leak-proof connection between closure elements on power plant valves. A connection arrangement of this kind is known, for example, from the German Utility Model DE 298 22 922 U1.  
       BACKGROUND OF THE INVENTION  
       [0003]     In the known connection arrangement, each tensioning member has the force of a straining screw acting directly upon it, the screw acting between the tensioning members and one shoulder of the first component and bracing the tensioning member like a wedge along the wedge surfaces between the components.  
         [0004]     While a connection arrangement of this kind is beneficial from the point of view of the frictional contact connection, it nevertheless possesses the disadvantage that for installation or dismantling purposes, numerous straining screws have to be tightened evenly, which takes a relatively great amount of time. Uneven torque can lead to damage in operation. Apart from that, it is time-consuming and expensive to produce the numerous counter-bearings needed for the straining screws.  
         [0005]     The invention has set itself the objective of improving a connection arrangement of the generic kind, especially with regard to the disadvantages described above.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     The invention achieves this objective by means of a connection arrangement of the generic kind characterized in that an expanding ring is provided, abutting third wedge surfaces of the tensioning members with an outer expanding surface, and tensioning means are provided, acting between the expanding ring and one of the components, with which the expanding ring can be moved axially and the tensioning members can be moved radially or radially/axially.  
         [0007]     Thanks to the arrangement in accordance with the invention, with an expanding ring distributing the tensioning forces of the tensioning means over the circumference, fewer or different tensioning means can be provided than is the case in the state of the art, so that assembly or dismantling can be performed more easily and more quickly. Apart from that the flow of forces through the connection can be improved still further.  
         [0008]     It is preferably provided that the first and second bearing surfaces run radially. The groove can be formed in part of a radial portion of the first or second bearing surface so as to arrange the seal in parallel to the bearing surface proper.  
         [0009]     It is preferably provided that the first clamping surface should include a wedge angle with the second clamping surface, which is matched to a cone angle of the outer expanding surface in such a way that the expanding ring causes self-locking bracing of the components.  
         [0010]     It can be provided that the first clamping surface runs radially and the second clamping surface runs conically.  
         [0011]     Alternatively, it can be provided that the first clamping surface runs conically and the second clamping surface runs radially.  
         [0012]     In a further alternative, it can be provided that the first and second clamping surfaces run conically.  
         [0013]     The expanding ring can be formed continuously in the circumferential direction, or alternatively it can be provided that the expanding ring has radial expansion slots arranged spread out in the circumferential direction and a conically formed inner expanding surface with which it abuts a correspondingly conically formed third expanding surface disposed on the second component, and that it can be, radially expanded by axial displacement. In this context, it can be provided that the outer expanding surface and the third wedge surfaces of the tensioning members are in each case formed axis-cylindrically or conically.  
         [0014]     It can be provided that the expansion slots do not extend over an entire axial length of the expanding ring. Alternatively, the invention envisages that the expanding ring is provided with expansion slots arranged in an alternating way in the circumferential direction, in the manner of a collet.  
         [0015]     The expanding ring can be formed from separate expanding members disposed spread out over the circumference, and a thrust collar gripping round them.  
         [0016]     In a preferred embodiment of the invention, it is provided that there is a retaining ring releasably mounted on the first component, especially on the collar, adjacent to the first clamping surface, which retaining ring has a retaining surface running substantially axis-cylindrically and abutting a locking surface, which runs substantially axis-cylindrically, of the tensioning members and preventing the tensioning members and thus the connection arrangement from being released completely when the expanding ring is released.  
         [0017]     The tensioning means can be formed as straining screws distributed over the circumference. The straining screws can be located in a straining ring secured axially to the first component, especially by means of a circumferential groove and a sliding block.  
         [0018]     Alternatively, it can be provided that the straining screws engage through the expanding ring into the first component, especially into the collar.  
         [0019]     As a further alternative, it can be provided that the expanding ring has a flange ring formed integrally with it or resting on it, through which the straining screws engage in a circumferential portion of the second component located radially outside the tensioning members.  
         [0020]     Finally, it can be provided as an alternative that the tensioning means can be formed by a threaded nut acting on the expanding ring and co-operating with an external or internal thread of the first or second component.  
         [0021]     In a preferred embodiment of the invention, it is provided that the tensioning members consist of parts of a ring divided along two parallel secant planes which can be mounted, in a manner known per se, at mutual (circumferential) distances that are advantageously small compared to parts obtained by radial sections, i.e. they can be inserted between the first and second components.  
         [0022]     The invention also relates to a set of tensioning members for a connection arrangement according to the invention, formed from parts of a ring divided along two parallel secant planes and having first wedge surfaces formed radially or conically outwardly, second wedge surfaces formed radially or conically outwardly and internal third, axis-cylindrical or conical, wedge surfaces. Whereas the third wedge surfaces may be formed either axis-cylindrically or conically with any combination of angles in the first and second wedge surfaces, either the first wedge surfaces may be radial and the second wedge surfaces conical, or vice versa, or both may be conical. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     The invention will now be explained by means of various embodiments, reference being made to a drawing, in which  
         [0024]      FIG. 1  shows a longitudinal section view of a cover lock of a power plant valve with a connection arrangement in accordance with the invention,  
         [0025]     FIGS.  2  to  9  show further embodiments as variations on the connection arrangement shown in  FIG. 1 , and  
         [0026]      FIGS. 10 and 10   a  show a plan view and a sectional view of an expanding ring of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]     The invention will now be explained by reference to various embodiments relating to a novel cover lock of a power plant valve. In power plant valves for new conventional fossil-fuel thermal power plants, which are subject to high stresses, the operating pressures reach up to approx. 300 bar, while the operating temperatures can reach levels of 700° C. and more. The service lives of self-sealing graphite cover seals are not adequate in view of the extreme temperatures and pressures of the media. A graphite seal rapidly oxidizes to CO 2  when an operating temperature of 500° C. is exceeded, permitting atmospheric oxygen to enter.  
         [0028]     At operating temperatures on these levels, it is conceivable to use, among other things, a radially operative, high-temperature-resistant metal O-ring seal. From the structural point of view, the cover lock with a metal O-ring seal must be designed in such a way that the metal O-ring is placed in metal-to-metal contact. With conventional flange locks or self-sealing locks, this sealing method is of only limited feasibility or leads to disproportionately large dimensions of the housing and the lock member, which are not suitable.  
         [0029]     The construction of the invention makes it possible to design a cover lock for valves in an advantageous manner such that a metal O-ring seal is located in metal-to-metal contact and the pressure forces occurring can be absorbed by the twin action of a rotationally symmetrical cone system. According to the invention, the operating forces are intercepted by positive-locking ring segments provided with a plurality of conical lateral surfaces which are supported outwardly on the housing and inwardly on an expanding ring by means of cone envelope surfaces. If the angle of the cone is selected in the region of self-locking, i.e. the tangent of the angle of incline is smaller than the lowest static friction figure to be expected, this ensures that the axial reaction forces acting on the pre-tensioning members (tensioning means in the form of bolts) are small or virtually zero.  
         [0030]     Since the advantageous structural design means that only low pre-tensioning forces are required, which are independent of the operating pressure, relaxation and material fatigue do not occur in the tensioning means, and the dimensions relative to the magnitude of the forces which can be transmitted remain relatively small compared to conventional flange locks. The favorable flow of forces through the components connected to the twin-action, rotationally symmetrical cone system generates the lowest possible folding moments and bending moments and deformations in the housing and cover. In the outer tensioning members, which are in the shape of cone segments, mainly shearing strains occur, whereas in the expanding ring or supporting cone it is mainly tangential strains or, in the case of a slotted expanding ring supported on the inside, only compressive strains, which are easy to control.  
         [0031]      FIG. 1  shows a first embodiment of a connection arrangement of the invention, in which a first component, which is rotationally symmetrical at least at the connection point and is in this case a cover  2  of a power plant valve, has a collar  4  projecting radially outwards, on which are formed a first, radial clamping surface  6  and a first, likewise radial, bearing surface  8 .  
         [0032]     A second component  10 , in this case a housing of a power plant valve, which is likewise formed rotationally symmetrical in the region of the connection point shown at the top in  FIG. 1 , has at an open end a socket  12 , which surrounds and axially overlaps the collar  4  of the first component  2 . Formed in the socket  12  in order to co-operate with the first bearing surface  8  of the first component  2  there is a second bearing surface  14  likewise running radially, a groove  16  being formed in a radially inner region of the second bearing surface  14  to receive a metal O-ring seal  18 . The seal  18  is thus arranged in parallel to the bearing surface proper when the two components  2 ,  10  are fitted together and touching. Thus, the main axial forces are transmitted by the bearing surfaces and not by the seal which is thus subjected to a predetermined amount of axial compression.  
         [0033]     In the socket  12  there is formed, at an axial distance from the second bearing surface  14 , a hollowed out portion  20  and a second conical clamping surface  22 , which is opposite the first clamping surface  6  of the first component  2  when the components  2 ,  10  are fitted together as shown.  
         [0034]     A number of ring wedge-shaped tensioning members  24  are distributed over the circumference and are disposed with a first cone envelope or wedge surface  26  abutting the first clamping surface  6  and with a second wedge surface  28  abutting the second clamping surface  22 .  
         [0035]     An expanding ring  34  with an outer expanding surface  32  abutting third wedge surfaces  30  of the tensioning members  24  is placed in the axial direction  36  against the tensioning members  24 . Tensioning means are provided between the expanding ring  34  and the first component  2  (cover) in order to move the expanding ring  34  in the axial direction  36  and thus to move the tensioning members  24  along the second clamping surface  22 , i.e., in the embodiment according to  FIG. 1 , both in the axial direction  36  and also radially outwards. In the embodiment according to  FIG. 1 , the tensioning means are formed by straining screws  40 , which are screwed into threaded holes  42  of a straining ring  44 , which, for its part, is supported against a sliding block  48  inserted into a circumferential groove  46  of the first component  2 . Because of the relatively low axial forces that have to be applied through the straining screws  40 , neither the circumferential groove  46  nor the sliding block  48  need to be of any great size, unlike a conventional flange-like connection, in which the straining screws have to absorb the entire compressive force occurring in operation (operating pressure multiplied by the internal area of the cover). If the wedge and cone angles defined by the wedge surfaces  26 ,  28 ,  30  are selected such that self-locking occurs, the straining screws  40  merely have to apply the tensioning force needed for assembly, whereas no additional load occurs in operation, irrespective of the internal or operating pressure. Since the compressive forces between the cover and the housing (first and second components) are transmitted through compressive and frictional forces, the actual task of the straining screws  40  is only to immobilize the connection arrangement in its frictional connection and positive locking (first component  2 , second component  10 , tensioning members  24  and expanding ring  34 ), i.e. to prevent the expanding ring  34  from coming loose because of the inevitable vibrations, shocks and the like which occur in operation.  
         [0036]     In the region of the hollowed out portion  20  in the second component  10 , via holes  50  are inserted on the level of the tensioning members  24 , so that the tensioning members  24  can be knocked out in the event of dismantling. Using axial threaded forcing holes and corresponding forcing screws, not shown, the expanding ring  34  can be pressed out of the conical inner ring formed by the tensioning members  24 . This ensures that the connection arrangement can be dismantled with no difficulty.  
         [0037]     Essentially, the further embodiments shown in FIGS.  2  to  9  differ from the embodiment explained above merely with regard to the design of the expanding ring  34  and its bracing with different bracing means.  
         [0038]      FIG. 2  shows an expanding ring  34  with axial via holes  60 , through which stud bolts  64  are screwed and engage in blind threaded holes  62  in the first component  2 , the axial bracing of the expanding ring  34  being achieved by fastening nuts  66 . Because of the closed design of the expanding ring  34 , the stud bolts  64  are merely subjected to axial strain and not to bending.  
         [0039]      FIG. 3  shows a variant in which the expanding ring  34  is not formed in a continuous, or solid, manner in the circumferential direction, but instead has expansion slots running in the radial direction and spread out in the circumferential direction, one of which is indicated by  70  in  FIG. 3 . It is possible for there merely to be expansion slots inserted in an axial direction, e.g. from the lower side, each of which extends in accordance with the expansion slot indicated by  70  in  FIG. 3 , or alternatively the expanding ring  34  can formed like a collet, wherein successive expansion slots in the circumferential direction extend from alternately opposite axial directions into the expanding ring.  
         [0040]     In an alternative embodiment, which is not shown, it would also be possible for the expanding ring to be composed of separate expanding members spread out over the circumference.  
         [0041]     In all cases, it is appropriate for the expanding ring to be formed with a thrust collar, indicated by  72  in  FIG. 3 , gripping round the individual expanding members or the expanding portions subdivided by expansion slots. The thrust collar can be formed integrally, with expanding portions separated by expansion slots, or alternatively as a separate component.  
         [0042]     A feature common to all such embodiments according to  FIG. 3  is that the expanding ring  34  not only has an outer expanding surface  32 , but in addition an inner, conical expanding surface  74 , which co-operates with a corresponding conically formed third expanding surface  76  on the second component  2 . When the tensioning means (straining screws  40 ) are tightened, the thrust collar  72  thus moves in the axial direction  36  relative to the first component  2  in the direction of the collar  4 , while the inner expanding surfaces  74  of the slotted portion of the expanding ring  34  move outwards along the third expanding surface  76  both in the axial direction  36  and in the radial direction, i.e. the ring expands.  
         [0043]     Because of the above-mentioned radial expansion movement of the slotted portion of the expanding ring  34 , the third wedge surfaces  30 —which are shown conically in  FIG. 3 —of the tensioning members  24  and correspondingly also the outer expanding surface  32  of the expanding ring  34  could be formed axis-cylindrically, which simplifies manufacture.  
         [0044]      FIG. 4  shows a variant of the embodiment according to  FIGS. 1 and 2 , in which the expanding ring  34  has a flange portion or flange ring  80  formed integrally with it, through which stud bolts  64  are inserted, which for their part engage in blind threaded holes  62  in the second component  10 . As an alternative to the integral embodiment shown, the flange ring  80  could also be formed as a separate ring gripping over the actual expanding ring  34 , as will be explained in more detail below in connection with  FIG. 7 .  
         [0045]      FIG. 5  shows an embodiment in which the tensioning means are formed by a threaded nut  90  acting on the expanding ring  34 , the threaded nut  90  co-operating with an external thread  92  of the first component  2 . Alternatively, the threaded nut  90  could be provided with an external thread and the second component  10  with an internal thread in an open end portion of the socket  12  adjacent to the second clamping surface  22 , with a corresponding axial shortening of the expanding ring  34  or axial lengthening of the second component  10 .  
         [0046]      FIG. 6  shows a variant in which the expanding ring  34  is formed in accordance with  FIG. 4 , though in this case there is additionally a retaining ring  100  fixed to the collar  4  of the first component  2  by means of fastening screws  102 . The retaining ring  100  has a retaining surface  104  running axis-cylindrically, with which it abuts correspondingly formed locking surfaces  106 —which run axis-cylindrically—of the tensioning members  24 . The diameter of the retaining surface  104  is in this case selected such that the retaining ring  100  can be inserted when the connection arrangement is in its assembled but unbraced state, without already bracing the tensioning members  24 , but at the same time such that the tensioning members  24  cannot slip out of the hollowed out portion  20  when the retaining ring  100  is inserted. In other words, when the fastening nuts  66  are tightened, a radial gap, which is not shown in  FIG. 6 , appears between the retaining surface  104  and the locking surfaces  106 , since the tensioning members  24  are braced radially outwardly. If the fastening should come loose in operation, for whatever reason, it is still not possible for the cover  2  to be pressed out of the socket  12 ; instead, there may merely be a more or less slight leak in the connection point in the region of the seal  18 , because the tensioning members  24  still prevent any substantial axial movement of the components  2 ,  10  relative to one another.  
         [0047]      FIG. 7  shows a combination of the variants according to FIGS.  3  and  FIG. 4 , where a flange ring  80  is formed as a separate part and to a certain extent could also perform the function of a thrust collar, though this function, rather as in  FIG. 7 , is already performed by the thrust collar  72  as part of the expanding ring  34 .  
         [0048]      FIG. 8  shows a combination of  FIGS. 3 and 5 , in which, unlike  FIG. 3 , the tensioning means are formed by a threaded nut  90 .  
         [0049]      FIG. 9  shows a variant in which the tensioning members  24  do not (each) have, as has been the case so far, a first, radial wedge surface  26  and a second, conical wedge surface  28 , but rather a first, conical wedge surface  26  and a second, radial wedge surface  28 . It goes without saying that the first clamping surface  6  of the first component  2  corresponds to the second, conical wedge surface  28  and is thus likewise conically formed.  
         [0050]      FIG. 9  also shows that the retaining ring  100 , which was explained with reference to  FIG. 6 , can be replaced by a radial bearing collar  110  in the first clamping surface  6 , the design of the wedge surfaces in accordance with  FIG. 9  being particularly well-suited to this. In principle, however, even with a first clamping surface running radially in accordance with FIGS.  1  to  8 , it is still possible to provide a radial bearing collar in order to achieve the function of preventing the arrangement from coming completely loose.  
         [0051]      FIG. 10  shows a set of tensioning members  120  in accordance with the invention, consisting of four tensioning members  24  which are formed by dividing a rotationally symmetrical ring with a cross-section in accordance with  FIG. 10   a  along two parallel secant sections  124 ,  126 . Each individual tensioning member  24  has, similar to what is shown in  FIG. 1 , a first radial wedge surface  26 , which could also be formed outwardly conically ( FIG. 9 ), a second, outwardly conical wedge surface  28 , which could also be formed radially ( FIG. 9 ), and a third wedge surface  30 , formed inwardly conically, which could also be formed axis-cylindrically, as has been explained in connection with  FIGS. 3 and 7 .  
         [0052]     A major advantage of the set of tensioning members  120  according to the invention consists in the fact that the original ring is not divided into sectors along radial planes, but along parallel secant planes, which are spaced apart, so that the tensioning members can be assembled with the minimum spacing from one another.