Abstract:
A shrink disc unit including a rotating body with a peripheral outer surface and a hub surrounding the rotating body with a peripheral inner surface. The peripheral inner surface and the peripheral outer surface form a separating line between the rotating body and the hub at an angle to a rotational axis of the rotating body. A fluid channel leads through the rotating body or the hub for pressurization of the separating line with a pressure fluid. A fixing device, formed from one of the rotating body or the hub, alone or in combination with the other, may be used to fix a tool for the assembly or disassembly of the hub at a given angular position on the rotating body and/or the hub.

Description:
This application is the U.S. national phase application of PCT International Application No. PCT/EP2004/014553, filed Dec. 21, 2004, which claim priority to German Patent Application No. DE 20 2004 001 530.7, filed Feb. 2, 2004. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The invention relates to a shrinkage disc unit which can in particular serve to connect two shafts. It further relates to a tool for establishing and/or releasing an interference fit assembly formed by the shrinkage disc unit. Lastly, it relates to an assembling and/or disassembling array, i.e. a combination of the shrinkage disc unit and the tool, for establishing and/or releasing the interference fit assembly. 
     2. Description of the Related Art 
     In many applications, two shaft ends are connected, for transferring torque, by a cylindrical interference fit assembly, wherein one shaft end is embodied as a hollow cylindrical shaft, into which the other shaft end, which is generally formed as a solid cylindrical shaft, is inserted. An additional sub-assembly is placed on the cylindrical outer surface of the hollow shaft and exerts a force directed radially inwards on the hollow shaft. This force causes the cylindrical inner surface of the hollow shaft to be pressed onto the cylindrical outer surface of the solid shaft, generating a frictional lock which can transfer torques and axial forces from one shaft end to the other. 
     Such a shrinkage assembly is for example used in wind power plants, to connect the rotor shaft to the input shaft of the gear system. Such an assembly is also a preferred example application of the invention. 
     A so-called shrinkage disc is then preferably used as the sub-assembly for generating the radial pressing, wherein a thick-walled, internally conical hub is mechanically or hydraulically pushed onto a thin-walled, externally conical tensioning sleeve. A cylindrical inner surface of the tensioning sleeve sits on the cylindrical outer surface of the hollow shaft. Pushing the hub onto the tensioning sleeve exerts the radially acting force described on the hollow shaft. 
     The two currently most common shrinkage disc designs comprise integrated devices which make external tools for assembling and disassembling substantially superfluous. Only spanners or hydraulic pumps are needed as external tools for assembling and disassembling the shrinkage discs. The axial force for pushing the hub onto the tensioning sleeve is generated either by tensioning screws or by a hydraulic chamber. 
     For disassembling one design, the tensioning screws are released. The conical surface assembly between the tensioning sleeve and the hub is embodied to not be self-locking, such that the hub slips from the tensioning sleeve by itself. In the other design, a second hydraulic chamber is installed which, for disassembling, generates an axial force, pointing towards the small diameter of the cone, onto the hub. The tensioning sleeve thus pushes the hub, against the self-locking in the conical joint between the hub and the tensioning sleeve. 
     Integrating the devices for generating the axial force for assembling and disassembling is very complicated and therefore leads to significantly higher production costs. Given that for a plant life of for example 20 years, the assembling and disassembling process shall only be performed once or twice, the complexity of integrating these devices is economically inappropriate. 
     Assembling a shrinkage disc of the first design on the hollow shaft is very time-consuming, since the tensioning screws distributed in large numbers on the circumference have to be screwed tight in stages, up to the maximum assembling torque, in order to prevent the shrinkage disc from being unevenly tensioned. In addition, intervals must be inserted which are necessitated by fitting processes of the screw connections and the necessary re-tensioning. Assembling the shrinkage disc is therefore considerably time-consuming. 
     A shrinkage disc of the second design has a significantly larger constructional length than the cone needed for generating the radial pressing, due to the integration of the hydraulic chamber for generating the assembling force. The larger constructional length also necessitates a longer hollow shaft, in order to provide the installation space for the shrinkage disc. The mass and the moment of inertia of the plant increase, which in many applications can result in a negative effect on operations. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a simple and therefore inexpensive design for an interference fit assembly, based on a shrinkage connection, for rotational bodies—referred to in the following as a shrinkage disc unit. The time needed for assembling and/or disassembling should nonetheless be short. The moment of inertia is preferably less than that of known shrinkage disc units. Another object is to prevent unimpeded axial movement between parts of the shrinkage disc unit while the shrinkage disc unit is being assembled and/or disassembled. 
     In accordance with the invention, the assembling axial force is applied by a separate tool which is preferably at least substantially annular and preferably divided, i.e. divided once or more than once into annular segments, and which can be detached from the shrinkage disc unit and is only fastened to the shrinkage disc unit or the hollow shaft during assembling and disassembling. Due to this configuration, it is possible to produce the shrinkage disc unit itself from comparatively simple and therefore inexpensive components. In addition, this achieves a reduction in the mass and the moment of inertia of the shaft connection. 
     The shrinkage disc unit comprises a hub having an axially widening circumferential inner surface which is pushed by the assembling axial force of the tool onto a circumferential outer surface of the rotational body which narrows at least substantially congruently with respect to the circumferential inner surface of the hub. The rotational body can in particular be a shaft, preferably a hollow shaft, or a tensioning sleeve arranged radially between the hub and the shaft. The circumferential surfaces form an inclined joint via which they are in frictional surface contact with each other. The circumferential surfaces, which can also be referred to as shrinkage surfaces, are preferably formed as conical surfaces. 
     The wedge or taper ratio of the shrinkage surfaces is preferably selected such that the friction in the joint between the surfaces achieves a self-locking against the hub axially slipping off the circumferential outer surface. In order, while assembling and disassembling the hub, to reduce or largely eliminate the axial holding forces resulting from this, the joint is preferably charged with a pressurized fluid during assembling and disassembling. 
     Due to the radial tensile stresses in the hub which build up during assembling as the hub body widens, the hub tends to slip in the direction of the slope of its circumferential inner surface. If the friction between the hub and the circumferential outer surface of the rotational body is reduced or eliminated by pressing pressurized fluid into the joint, there is a danger of the hub slipping off the rotational body abruptly. Due to the high kinetic energy of the hub released, this represents a great danger to the assembling staff and other parts of the plant if no additional securing elements—such as for example a shaft nut—are mounted on the rotational body in order to restrict the axial movement of the hub. 
     In a particularly preferred embodiment, the invention envisages the tool and the rotational body and/or hub being configured such that a pressurized fluid can only be pressed into the joint when the tool is mounted properly. This can be achieved by supplying the pressurized fluid via the tool or by separating the joint from the surroundings by sealing it off. The tool can also be configured to fulfill these two functions in combination. Further configuring the tool restricts the axial movement of the hub by itself. An axial movement of the hub on the circumferential outer surface of the rotational body is controlled by means of the tool. 
     The tool is connected to the rotational body, for example the tensioning sleeve or the free end of the hollow shaft, or to the hub in a positive and/or non-positive lock. A non-positive-lock connection is preferably achieved by tensile screws which are screwed into the frontal side of the tensioning sleeve, hollow shaft or hub and tighten the tool against the tensioning sleeve, hollow shaft or hub, thus securing it on the tensioning sleeve, hollow shaft or hub. A positive-lock connection is preferably achieved by a heel on a circumferential inner surface of the tool engaging with a counter heel which can in particular be formed by a radial, preferably circumferential groove in a circumferential outer surface of the rotational body or hub. 
     The assembling axial force is preferably applied by a number of hydraulic duty cylinders. Tensile screws, pressure screws, wedge mechanisms or lever mechanisms or combinations of these can, however, also alternatively be used. 
     The hub moves axially on the rotational body until the envisaged radial pressing of the interference fit assembly, preferably the pressing of a hollow shaft on a solid shaft, has been achieved. Due to the force-displacement ratios resulting over the joint, it is possible to determine the radial pressing via the shifting path of the hub or via the applied assembling forces. 
     The shrinkage disc unit is disassembled by shifting the hub on the rotational body in the direction of the slope of the joint and/or towards the smaller diameter of the preferably conical joint. If suitably designed, the assembling tool can also be used as a disassembling tool; alternatively, a separate disassembling tool can be used. 
     The self-locking of the hub against shifting on the circumferential outer surface allows an additional safeguard between the hub and the rotational body to be omitted during operations in certain applications. 
     In applications in which increased demands are made on the functional security of the shrinkage disc unit because of expected vibrations, the hub should be additionally axially secured on the circumferential outer surface. It is secured by means of at least one securing element which preferably establishes a positive-lock connection between the hub and the rotational body. 
     The hub is prevented from slipping off in an uncontrolled manner during assembling and disassembling processes, and the associated dangers are prevented, by configuring the pressure port for charging the joint—preferably hydraulically—with pressurized oil such that it can only be supplied through a counter piece which is a direct part of the tool; an autonomous port for the pressurized fluid is preferably not provided on the interference fit assembly via hydraulic screw connections or the like. Another configuration of the pressure port and the counter piece forces the tool to be properly mounted, in order to enable the pressure system of the shrinkage disc unit to be sealed off and the pressure to therefore build up. These measures ensure that if the hub slips off the rotational body in an uncontrolled manner, it is caught by the tool, such that there is no danger to persons or material. 
     The tool is preferably forced to be properly mounted because at least one portion of the tool and at least one counter portion of the rotational body or hub only interlock when the tool is properly mounted. Otherwise, the configuration of these portions prevents the tool from being mounted completely. 
     The embodiment of a shrinkage disc unit as described, in which the circumferential outer surface serving as the shrinkage surface is formed by a portion of a hollow shaft, is specifically appropriate for new constructions; by omitting a separate tensioning sleeve, the production and assembling costs, and therefore the overall costs of the plant manufacture, are reduced. 
     In existing plants, the shrinkage disc units used hitherto can be replaced by a shrinkage disc unit in accordance with the invention comprising a tensioning sleeve, since the port dimensions remain identical. 
     Preferred features of the invention are also described in the sub-claim and combinations of these. The features described in these, and those explained above, reciprocally complement each other in an advantageous way. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained below on the basis of example embodiments. Features explained by way of the example embodiments, each individually and in the disclosed combinations of features, advantageously develop the subjects of the claim. There is shown: 
         FIG. 1  a shrinkage disc unit according to a first example embodiment; 
         FIG. 2  a shrinkage disc unit according to a second example embodiment; 
         FIG. 3  a shrinkage disc unit according to a third example embodiment; 
         FIG. 4  a shrinkage disc unit according to a fourth example embodiment; 
         FIG. 5  a shrinkage disc unit according to a fifth example embodiment; 
         FIG. 6  a shrinkage disc unit according to a sixth example embodiment; 
         FIG. 7  a shrinkage disc unit according to a seventh example embodiment; 
         FIG. 8  a shrinkage disc unit according to an eighth example embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a first example embodiment of a shrinkage disc unit as described. 
     A preferably cylindrical inner surface  14  of a tensioning sleeve  2  is arranged on a congruent outer surface  15  of a hollow shaft  4 . A solid shaft  3  is inserted into the hollow shaft  4 , wherein a preferably cylindrical inner surface  22  of the hollow shaft  4  abuts a congruent outer surface  23  of the solid shaft  3 . The tensioning sleeve  2  comprises a conical outer surface  24  on which an inner surface  25  of a hub  1 , provided with a congruent cone, is supported. 
     A fixing structure of the assembling tool, formed as an annular body  7 , preferably comprises at least two radial divisions and is fastened in an annular groove  2   a  of the tensioning sleeve  2  in a positive lock via a stay directed radially inwards from the preferably cylindrical inner surface  7   d.    
     The axial assembling forces are generated hydraulically and applied by a plurality of duty cylinders which consist substantially of pistons  9  and cylindrical bores  26  comprising pressure ports  26   a . The cylindrical bores  26  are preferably worked directly into the annular body  7 . When the cylindrical bores  26  are charged with a pressurized fluid, the pistons  9  exert an axial force on the frontal side  1   a  of the hub  1  facing them, axially shifting it on the tensioning sleeve  2 . 
     The tensioning sleeve  2  preferably comprises a heel  2   b  having a smaller inner diameter than the cylindrical inner surface  14 . When assembling the shrinkage disc unit, the tensioning sleeve  2  is pushed far enough onto the hollow shaft  4  that the frontal surface  2   c  of the heel  2   b  comes to rest on the frontal surface  4   a  of the free end of the hollow shaft  4 . This defines the position of the tensioning sleeve  2  on the hollow shaft  4 . 
     In order to reduce the axial assembling and disassembling forces needed, it is preferably envisaged that a pressurized fluid is supplied to the joint  27  between the conical inner surface  25  and the conical outer surface  24 . 
     The pressurized fluid is supplied to the joint  27  via a system of bores  10   a ,  10   b ,  11 ,  12  and  13  which are preferably inserted directly into the annular body  7  and preferably directly into the tensioning sleeve  2 . The bore  11  is preferably embodied as a blind hole and arranged such that it is orientated from the cylindrical shell surface of the annular groove  2   a  radially with respect to the centre axis of the tensioning sleeve  2 . The bore  13 , formed as a blind hole, is preferably arranged such that it points from the conical outer surface  24 , substantially radially with respect to the centre axis of the tensioning sleeve  2 . The bore  12 , orientated substantially axially with respect to the centre axis of the tensioning sleeve  2 , connects the radial bore  11  to the radial bore  13 . The bore  12 , embodied as a blind hole, ports onto a frontal surface  2   d  of the tensioning sleeve  2  and is preferably sealed off against pressurized fluid escaping on the side of the frontal surface  2   d  by a suitable screw connection. The bore  10   a  in the annular body  7  is embodied as a blind hole and is arranged in the stay  7   a  such that it is orientated preferably flush with the radial bore  11  when the assembling tool is properly attached. The other bore  10   b  is embodied in the annular body  7  as a blind hole and is arranged substantially axially with respect to the centre axis of the annular body  7 . It connects a pressure port  10   c  on the frontal side  7   b  of the annular body  7  to the bore  10   a . A sealing element  28  seals off the stay  7   a , preferably radially, from the annular groove  2   a  at the point at which the pressurized fluid is conducted from the bore  10   a  to the bore  11 . When the shrinkage disc unit has been completely assembled and the tool removed, the bore  11  is sealed with a cover against contaminants entering. 
     The annular body  7  is for example forced to be properly mounted on the tensioning sleeve  2  by shrinking a cylindrical trunnion  5  into the cylindrical inner surface  7   d  of the annular body  7 , wherein when the annular body  7  is properly mounted, a preferably hemispherical end of the trunnion  5  protrudes into a radial bore  6  in a preferably cylindrical outer surface  2   h  of the tensioning sleeve  2 . The tensioning sleeve  2  is configured such that the trunnion  5  cannot be placed anywhere except in the bore  6 . It is therefore not possible to mount the annular body  7  on the tensioning sleeve  2  in a position other than the proper position. The inner diameter of the bore  6  is preferably only slightly larger than the outer diameter of the trunnion  5 , such that an angular offset between the bores  10   a ,  11  at the transfer point, caused by assembling, is minimized. 
     The tensioning sleeve  2  comprises a number of radial grooves  2   i  on its outer surface  2   h , into which securing elements  29  are inserted which are secured on the tensioning sleeve  2  with screws  30 . The securing elements  29  create the positive-lock connection between the radial grooves  2   i  of the tensioning sleeve  2  and the frontal side  1   a  of the hub  1  and so secure the hub  1  against slipping off the tensioning sleeve  2 . 
     When assembling the shrinkage disc unit, and when the joint  27  is charged with pressurized fluid, the hub  1  is axially pushed onto the tensioning sleeve  2  until the defined pressing between the hollow shaft  4  and the solid shaft  3  is achieved due to the radial widening of the hub  1 . The fluid pressure in the joint  27  is then reduced down to atmospheric pressure, such that the outer surface  24  of the tensioning sleeve  2  and the inner surface  25  of the hub  1  come to rest against each other. The radial tensile forces in the hub  1  then fixedly seat the hub  1  in a frictional lock on the tensioning sleeve  2 . 
     Once the hydraulic pressure in the joint  27  has been released, the securing elements  29  are mounted and fastened to the tensioning sleeve  2  using the screws  30 . Assembling the shrinkage disc unit is therefore complete. The pressure is then released in the cylindrical bores  26  of the assembling tool, and the assembling tool is removed from the tensioning sleeve  2 . The shaft connection is ready to be operated. 
     The component geometries and the pressures of the pressurized fluid in the joint  27  are preferably selected such that the axial frictional resistance force in the joint  27  after the pressurized fluid has been pressed in is less than the axial force which results over the angle of the conical joint  27  from the radial forces in the hub  1  and tries to drive the hub  1  from the tensioning sleeve  2 . In this way, pressing the pressurized fluid into the joint  27  causes the hub  1  to move axially by itself on the outer surface  24 , releasing the shrinkage disc unit. 
     The danger to the assembling staff of the hub  1  slipping off in an uncontrolled manner is prevented by the fact that the shrinkage disc unit cannot be disassembled without attaching the assembling tool to the tensioning sleeve  2 . Preferably, once the annular body  7  has been attached to the tensioning sleeve  2 , the pistons  9  are brought to rest on the frontal side  1   a  of the hub  1 , and a pressure is built up in the duty cylinders which corresponds to the pressure while assembling the shrinkage disc unit. This prevents the hub  1  from shifting axially on the tensioning sleeve  2  when the pressurized fluid is subsequently pressed into the joint  27 . Once the securing elements  29  have been removed, the hub  1  is shifted axially in the direction of the smaller cone diameter in a controlled manner, by slowly releasing the pressurized fluid from the duty cylinders, until the shrinkage disc unit is released, wherein it should be ensured that the pressure of the pressurized fluid in the joint  27  is largely maintained, in order to keep the axial shifting forces low and to prevent “scuffs” between the tensioning sleeve  2  and the hub  1  which can otherwise result due to the friction of the surfaces  24  and  25  when simultaneously moving relative to each other. 
       FIG. 2  shows a second example embodiment of a shrinkage disc unit. The design and function substantially correspond to the first example embodiment. Unlike the first example embodiment, however, the annular body  7  of the assembling tool is fastened to the hollow shaft  4  by means of a positive-lock connection. 
     The connection is preferably achieved by a radially encircling stay  7   a  of the annular body  7  engaging in a positive lock with a corresponding groove  4   b  in the preferably cylindrical outer surface  15  of the hollow shaft  4 . 
     The axial assembling forces are mechanically applied, in the example embodiment by a number of pressure screws  8  which are connected to the annular body  7  in axially orientated threaded bores  7   c . The threaded bores  7   c  are preferably worked directly into the annular body  7 . Screwing the pressure screws  8  into the threaded bores  7   c  applies an axial force to the frontal side  1   a  of the hub  1  facing them, axially shifting the hub  1  on the tensioning sleeve  2 . 
     The radial bore  6  for receiving the trunnion  5  when the annular body  7  is properly mounted is inserted into the outer surface  15  of the hollow shaft  4 . The axial portion of the hollow shaft  4  in question does not comprise any other notches or recesses which could receive the trunnion  5  so allow the assembling tool to be attached at an exact rotational angle. Only the bore  6  achieves this. 
     The frontal side  2   e  of the tensioning sleeve  2  preferably abuts a heel  4   c  of the hollow shaft  4 , and the tensioning sleeve  2  is thus axially positioned on the hollow shaft  4 . 
     The bores  11 ,  12  and  13  for supplying pressurized fluid to the joint  27  are—as opposed to the example embodiment according to FIG.  1 —inserted into the hollow shaft  4 . The bore  11  is preferably embodied as a blind hole and arranged such that it is orientated from the cylindrical shell surface of the annular groove  4   b  radially with respect to the centre axis of the hollow shaft  4 . The other bore  13  is preferably likewise embodied as a blind hole and is arranged substantially radially from the outer surface  15  of the hollow shaft  4  to the centre axis of the hollow shaft  4 . The bore  12 , orientated substantially axially with respect to said centre axis, connects the radial bore  11  to the radial bore  13 . 
     The cylindrical inner surface  14  of the tensioning sleeve  2  preferably comprises a radial annular groove  31  which is arranged such that when the tensioning sleeve  2  is mounted, the pressurized fluid can enter the annular groove  31  from the bore  13 . A bore  32  leads from the annular groove  31 , preferably radially with respect to the conical outer surface  24  of the tensioning sleeve  2 , such that the joint  27  can be charged with pressurized fluid. A circumferential sealing element  33   a ,  33   b  which seals the outer surface  15  of the hollow shaft  4  off from the inner surface  14  of the tensioning sleeve  2  is preferably arranged next to the annular groove  31  on both sides, in the direction of the longitudinal extension of the tensioning sleeve  2  in each case. In this way, the pressurized fluid is prevented from being able to escape through the joint  27  between the tensioning sleeve  2  and the hollow shaft  4 . 
     The bores  10   a  and  10   b , the pressure port  10   c  and the sealing element  28  preferably correspond in their arrangement in the annular body  7 , their embodiment and their function to the manner of the first example embodiment. 
     The shrinkage disc unit is assembled and disassembled as in the first example embodiment, except however that the axial forces onto the hub  1  are generated mechanically and not hydraulically. 
       FIG. 3  shows a third example embodiment of a shrinkage disc unit. The design and function substantially correspond to the second example embodiment. Unlike the second example embodiment, however, the conical outer surface  24  is formed by the hollow shaft  4 . The hub  1  is mounted directly on the hollow shaft  4 . Here, too, the joint  27  is charged with a pressurized fluid via a system of supply conduits  11 ,  12  and  13  which are connected to the bore  10   a  of the annular body  7  when the assembling tool is properly attached. Once completely mounted, the hub  1  is likewise axially secured on the hollow shaft  4  in a positive lock using securing elements  29 . 
       FIG. 4  shows a fourth example embodiment of a shrinkage disc unit. The design and function substantially correspond to the first example embodiment. Unlike the first example embodiment, however, the pressurized fluid for charging the joint  27  is supplied via the pressure port  35   b  and the longitudinal bore  35   a  of a screw-in lance  35  of the radial bore  11  in the tensioning sleeve  2 . Once the assembling tool has been attached to the tensioning sleeve  2 , an outer thread  35   d  of the screw-in lance  35  is screwed into the inner thread  7   e  of a substantially radial installation bore  7   g  of the annular body  7 , arranged flush with the bore  11 . This brings an externally conical trunnion  35   c  of the screw-in lance  35  to rest on the preferably congruent wall  36   a  of a conical bore  36  of the tensioning sleeve  2 . The conical bore  36  is arranged such that its centre line runs substantially flush with the centre line of the bore  11 , and such that it comprises a connection to the bore  11 . Since the trunnion  35   c  abuts the wall  36   a , the system of supply conduits  35   a ,  11 ,  12 ,  13  to the joint  27  is sealed off from the surroundings of the shrinkage disc unit. Two sealing elements  37  and  38  encircling on the trunnion  35   c  create an additional seal between the trunnion  35   c  and the wall  36   a . The torque for screwing in the screw-in lance  35  is introduced via a number of spanner flats  35   f.    
     The screw-in lance  35  comprises a tapered shaft  35   e  which allows elastic bending if and when the mounted annular body  7  is deformed by the axial assembling force of the tool. Since the maximum outer diameter of the conical trunnion  35   c  is smaller than the inner diameter of the portion  7   f  of the radial installation bore  7   g  not provided with an inner thread, the trunnion  35   c  can move freely relative to the annular body  7 . These configurations guarantee that the trunnion  35   c  remains resting on the wall  36   a  of the bore  36  if and when the annular body  7  is deformed and/or displaced during operations, so that the joint  27  is guaranteed to be reliably charged with pressurized fluid. 
     The screw-in lance  35  and the installation bore  7   g  are arranged between two cylindrical bores  26  lying next to each other in the annular body  7 . For simplicity, one of the cylindrical bores  26  and one of the pistons  9  are shown by dashed lines in  FIG. 4 . 
     The securing elements  29  are formed and arranged on the tensioning sleeve  2  such that they do not protrude into the space occupied by the pistons  9  while the shrinkage disc unit is assembled. 
     In order to position the screw-in lance  35  as exactly as possible with respect to the conical bore  36  when mounting the annular body  7 , they are preferably arranged in approximately the same radial plane as the trunnion  5  and the corresponding bore  6 . The bores  6  and  36  should be arranged as near to each other as possible. 
     The annular groove  2   a  of the tensioning sleeve  2  preferably comprises an externally conical wall  2   f  on its side facing the frontal side  2   d . The wall  2   g  facing away from the frontal side  2   d  is preferably embodied as a plane orientated perpendicular to the centre axis of the tensioning sleeve  2 . The stay  7   a  of the annular body  7 , which is directed radially inwards, comprises frontal surfaces  7   h ,  7   i  which are congruent with respect to the walls  2   f ,  2   g  of the annular groove  2   a  which they abut full-face when the annular body  7  is properly mounted. This configuration of the annular groove  2   a  and the stay  7   a  causes the annular body  7  to be supported by the tensioning sleeve  2 , which reduces deformation of the annular body  7  caused by the axial assembling force of the hydraulic cylinders. 
       FIG. 5  shows a fifth example embodiment of a shrinkage disc unit. The design and function substantially correspond to the example embodiment shown in  FIG. 4 . Unlike the example embodiment shown in  FIG. 4 , the pressurized fluid for charging the joint  27  is supplied via a preferably cylindrical tube  40  of the radial bore  11  in the tensioning sleeve  2 . 
     One end of the tube  40  is pressure-sealed and permanently connected to a preferably substantially spherical body  39  which radially envelopes the tube  40  but leaves its conduit channel  40   a  free. The spherical body  39  can alternatively be formed as a part of the tube  40  and can for example be formed from the tube  40  by a compression. 
     Once the annular body  7  has been attached to the tensioning sleeve  2 , the spherical body  39  is brought to rest on the wall  36   a  of the bore  36  in the tensioning sleeve  2 , which is again preferably conical. The conical bore  36  is arranged in the tensioning sleeve  2  such that its centre line runs substantially flush with the centre line of the bore  11 , and such that it comprises a connection to the bore  11 . 
     Screwing a pressure piece  43 , provided with an outer thread  43   c , into an inner thread  7   e  of the annular body  7  exerts a force on the spherical body  39  via a pressure sleeve  41  and preferably via a pressure spring  42 , said force pressing the spherical body  39  fixedly onto the wall  36   a  of the bore  36 . In the contact zone of the wall  36   a  and the spherical body  39 , this pressing preferably elastically deforms the contacting partners, achieving a seal between them. By a certain length equalization, the pressure spring  42  largely maintains the force on the spherical body  39  if the annular body  7  moves relative to the tensioning sleeve  2  due to deformation or displacement while the tool is operated. 
     The outer diameter of the spherical element  39  is smaller than the inner diameter of the portion  7   f  of the installation bore  7   g  not provided with a thread. The spherical element  39  and the annular body  7  can therefore move relative to each other without affecting the seal between the spherical body  39  and the conical bore  36 . 
     The pressure piece  43  and the pressure sleeve  41  comprise bores  43   b ,  41   a  through which the tube  40  is guided. The tube  40  is also guided through the axial opening of the pressure spring  42 . 
     The torque for screwing the pressure piece  43  into the inner thread  7   e  is introduced into the pressure piece  43  via a number of spanner flats  43   a.    
     As in the fourth example embodiment, the installation bore  7   g  and the sub-assembly consisting of the tube  40 , the pressure sleeve  41 , the pressure spring  42  and the pressure piece  43  are arranged between two cylindrical bores  26  lying next to each other in the annular body  7 . For simplicity, one cylindrical bore  26  and one piston  9  are also shown in  FIG. 5  by dashed lines. The securing elements  29  are also formed as in the fourth example embodiment. 
     The conduits for supplying the pressurized fluid to the radial bore  11  as shown in the example embodiments according to  FIGS. 4 and 5  can also be combined with the example embodiments according to  FIGS. 2 and 3 , in which the annular body  7  of the assembling tool is connected to the hollow shaft  4  in a positive lock. The conical bore  36  is then inserted into the hollow shaft  4 . 
       FIG. 6  shows a sixth example embodiment of a shrinkage disc unit in accordance with the invention. In terms of its essential design, the shrinkage disc unit corresponds to the third example embodiment, i.e. the hub  1  is shrunk directly onto the shaft  4 . A distribution system formed in the joint  27  for charging the joint  27  with pressure can be seen. The distribution system is formed by a number of circumferential grooves formed in the circumferential inner surface  25 , spaced parallel from each other along the rotational axis R. The circumferential grooves are connected to each other by at least one axial groove which is likewise formed in the circumferential inner surface  25 . 
     The sixth example embodiment differs from the first five example embodiments in that the joint  27  is supplied with the pressurized fluid by a fluid channel formed in the hub  1 . The fluid channel comprises a radial portion  16  and an axial portion  17  which is connected to the portion  16  and ports to the surroundings on the frontal side  1   a  of the hub  1  axially opposite the tool, such that when the port is not sealed off, there is free pressure equalization between the joint  27  and the surroundings. The two channel portions  16  and  17  are again formed as straight bores and directly intersect each other. 
     The fixing structure  7  of the tool again supports a number of pistons  9  arranged in even distribution around the rotational axis R, such that they can be moved axially against the frontal side  1   a . A single annular piston can be provided instead of a number of individual pistons  9 —as incidentally also in the other example embodiments. The pistons  9  correspond in their function and construction to the pistons  9  of the other example embodiments. 
     The fixing structure  7  supports another piston  19 , likewise such that it can be moved against the frontal side  1   a . The piston  19  acts as a sealing piston which separates the fluid channel  16 ,  17  from the surroundings, i.e. seals it off from the surroundings, when it presses against the frontal side  1   a . The sealing piston  19  is arranged in the fixing structure  7  such that when the tool—i.e. its fixing structure  7 —is properly mounted, the sealing piston  19  lies opposite the port of the fluid channel  16 ,  17 , such that it can be moved against the port region. The sealing piston  19  forms a fluid channel  20  through which the pressurized fluid is guided into the fluid channel  16 ,  17  and thus into the joint  27 , in order facilitate assembling and/or disassembling the shrinkage disc unit. A valve  21 —in the example embodiment, a pressure control valve—is arranged in the fluid channel  20  of the sealing piston  19 . The valve  21  seals the fluid channel  20  up until a predetermined supply pressure is reached, and releases it once the predetermined supply pressure has been reached or exceeded. 
     As in the other example embodiments, the pistons  9  are charged with pressure for assembling and/or disassembling the shrinkage disc unit, such that they are moved against the hub  1  and either push it onto the shrinkage surface  4   d  of the shaft  4  for the purpose of assembling or axially secure the hub  1  on the shaft  4  for the purpose of disassembling. At the same time as the pistons  9  are charged with pressure, the sealing piston  19  is also charged with the pressurized fluid in the direction of the hub  1 . The cylinder spaces of the piston or pistons  9  and of the sealing piston  19  can each be charged with the pressurized fluid and each charged with the same pressures. Up until the predetermined supply pressure in the cylinder space of the sealing piston  19  is reached, the valve  21  seals the fluid channel  20 , such that pressing pressurized fluid into the cylinder space of the sealing piston  19  initially results in the sealing piston  19  being drawn out. When the frontal side of the sealing piston  19  abuts the frontal side  1   a  of the hub  1 , the fluid channel  17  is sealed off from the surroundings and thus sealed-off against the pressurized fluid escaping. Further pressing the pressurized fluid in, and the associated increase in pressure in the cylinder space of the sealing piston  19 , opens the valve  21 , such that the pressurized fluid enters the joint  27  via the fluid channel  20  of the sealing piston  19  and the fluid channel  16 ,  17  of the hub  1 , and a fluid pressure is built up in the joint  27 . The sealing piston  19  moves together with the piston or pistons  9  and therefore remains in a sealing, pressing contact with the frontal side  1   a  of the hub during assembling and/or disassembling. 
       FIG. 7  shows a shrinkage disc unit in accordance with the invention, according to a seventh example embodiment, comprising a tensioning sleeve  2 , the mechanical design of which therefore corresponds to the first, second, fourth and fifth example embodiments. As in the sixth example embodiment above, the joint  27  can be charged with the pressurized fluid via the hub  1 . 
     Unlike the example embodiments described above, however, the shrinkage disc unit is provided with a port for the pressurized fluid, such that the tool is relieved of the function of supplying the pressurized fluid. During assembling and/or disassembling, however, it is given the function of sealing off the fluid channel of the hub  1  from the surroundings and therefore enabling pressure to be built up in the joint  27 . 
     The fluid channel  16 ,  17  of the hub  1  comprises a channel portion  16  which extends from the joint  27  up to a frontal side of the hub  1 —in the example embodiment, up to the frontal side radially opposite the joint  27 . An end portion of the channel portion  16  forms a port  18  for supplying the pressurized fluid. While the shrinkage disc unit is operated, the port  18  is sealed by means of a sealing element. For assembling and/or disassembling, a pressurized fluid supply is connected to the port  18  and the joint  27  is charged with pressure via the channel portion  16 . The channel portion  17  branching off from the channel portion  16  ports to the surroundings on the frontal side  1   a  of the hub  1 . When the port is open, a constant pressure equalization between the surroundings and the joint  27  is thus ensured. 
     For assembling and/or disassembling, the tool is positioned on the shrinkage disc unit at an exact rotational angle—as described above in the other example embodiments—and axially supported by the collar  2   f  of the groove  2   a . Once the tool has been properly fixed in this way, the pistons  9  are moved against the hub  1  in order to either push the hub  1  on for assembling or to secure it for disassembling while the joint  27  is charged with the pressurized fluid. As in the sixth example embodiment above, the fixing structure  7  supports a sealing piston  19  such that it can be moved against the frontal-side port of the fluid channel  17  in order to seal off the fluid channel  17  and therefore the pressure system of the shrinkage disc unit, for assembling and/or disassembling. Unlike the sixth example embodiment, however, the sealing piston  19  serves only to seal off the fluid channel  17  and does not also simultaneously serve as a pressurized fluid supply. 
       FIG. 8  shows an eighth example embodiment of a shrinkage disc unit in accordance with the invention, which differs from the seventh example embodiment only in that the hub  1  is shrunk directly onto the shaft  4 —as in the third and sixth example embodiments above. The shrinkage disc unit and the tool otherwise correspond to those of the seventh example embodiment. 
     With respect to the sixth, seventh and eighth example embodiments, it should also be noted that the functions of pushing on and/or securing the hub  1  on the one hand and the function of solely sealing off or of sealing off and supplying the pressurized fluid on the other hand are not necessarily performed by two systems of pistons, but can be performed by a single system of pistons or in principle by a single piston, as long as it is ensured that the function of supplying the pressurized fluid or alternatively the function of sealing off can only be fulfilled when the tool is properly fixed to the shrinkage disc unit. 
     In the foregoing description, preferred embodiments of the invention have been presented for the purpose of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise form disclosed. Obvious modifications or variations are possible in light of the above teachings. The embodiments were chosen and described to provide the best illustration of the principals of the invention and its practical application, and to enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claim when interpreted in accordance with the breadth they are fairly, legally, and equitably entitled. 
     REFERENCE SIGNS 
     
         
           1 : hub 
           1   a : frontal side 
           2 : tensioning sleeve 
           2   a : annular groove 
           2   b : heel 
           2   c : frontal side 
           2   d : frontal side 
           2   e : frontal side 
           2   f : collar 
           2   g : wall 
           2   h : outer surface 
           2   i : radial groove 
           3 : solid shaft 
           4 : hollow shaft 
           4   a : frontal side 
           4   b : annular groove 
           4   c : heel 
           4   d : circumferential outer surface 
           4   f : collar 
           5 : trunnion/protruding portion 
           6 : bore/retracted portion 
           7 : annular body 
           7   a : stay 
           7   b : frontal side 
           7   c : threaded bore 
           7   d : inner surface 
           7   e : inner thread 
           7   f : portion not provided with a thread 
           7   g : installation bore 
           7   h : frontal side 
           7   i : frontal side 
           8 : pressure screw 
           9 : piston(s) 
           10   a : bore 
           10   b : bore 
           10   c : pressure port 
           11 : radial bore 
           12 : axial bore 
           13 : radial bore 
           14 : inner surface 
           15 : outer surface 
           16 : fluid channel 
           17 : fluid channel 
           18 : port 
           19 : sealing means, sealing piston 
           20 : fluid channel 
           21 : valve 
           22 : inner surface 
           23 : outer surface 
           24 : circumferential outer surface 
           25 : circumferential inner surface 
           26 : cylindrical bore, bore 
           26   a : pressure port 
           27 : joint 
           28 : sealing element 
           29 : securing element 
           30 : screw 
           31 : annular channel 
           32 : bore 
           33   a : sealing element 
           33   b : sealing element 
           34 : joint 
           35 : screw-in lance 
           35   a : longitudinal bore 
           35   b : pressure port 
           35   c : conical trunnion 
           35   d : outer thread 
           35   e : tapered shaft 
           35   f : spanner flat 
           36 : conical bore 
           36   a : wall 
           37 : sealing element 
           38 : sealing element 
           39 : spherical element 
           40 : tube 
           40   a : conduit channel 
           41 : pressure sleeve 
           41   a : bore 
           42 : pressure spring 
           43 : pressure piece 
           44 : spanner flats 
           45 : bore 
           43   c : outer thread 
         R: rotational axis