CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is a Continuation of International Application No. PCT/EP2006/000071, filed Jan. 6, 2006, and which designates the U.S. The disclosure of the referenced application is incorporated herein by reference. 


   FIELD OF THE INVENTION 
   The invention relates to a tubular rotary joint, in particular tubular rotary joints for conducting a polymer melt. 
   BACKGROUND OF THE INVENTION 
   When laying and constructing pipelines, it is known to enable the rotatability of pipe sections by means of so-called tubular rotary joints. A tubular rotary joint of this type has been disclosed, for example, in DE 70 00 900 U. Here, a holder and a connection body, which is rotatably connected to the holder, interact in order to design a pipe section, which is connected to the connection body and can move in relation to the holder. Within the holder, a distribution chamber is provided, which is coupled to a distribution channel of the connection body. In the known device, a slide bearing is used in order to enable the rotary motion of the connection body. A system of this type can be used only for higher temperatures with average pressure load. However, in addition to high temperatures, high pressures also arise when conducting polymer melts. These high pressures lead to correspondingly high radial and axial forces. However, such high-pressure forces cannot be taken up by the slide bearing, particularly in the design disclosed in the prior art. 
   For this purpose, tubular rotary joints are likewise known from the prior art, in which the slide bearing is replaced by roller bearings. It is thus indeed possible to apply high pressures. However, according to the invention, roller bearings have a limited suitability for high temperatures. Another problem of the tubular rotary joints disclosed in the prior art is that a free rotatability of the connection body in the holder is not ensured at high pressures. In particular, forces acting only on one side of the connection body can be particularly detrimental. 
   It is an object of the invention is to further improve a tubular rotary joint of the known kind, particularly for conducting a polymer melt. In one embodiment, a secure operability is assured even at high temperatures of over 250° C. and high pressures of above 200 bar. 
   SUMMARY OF THE INVENTION 
   According to the invention, this objective is attained by means of a tubular rotary joint. 
   Advantageous refinements of the invention are defined by the features and combinations of features of the dependent claims. 
   A special advantage of the invention is that the connection between the holder and the connection body is formed by means of a shaft-hub connection. For this purpose, the connection body comprises a shaft journal, which is mounted in a bearing bore of the holder. The bearing bore penetrates the distribution chamber such that loads acting on one side of the connection body and resulting from the fluid pressures within the distribution chamber are avoided. 
   This improved version of the tubular rotary joint is particularly advantageous, in which the bearing bore completely penetrates the holder to form two bearing points so that approximately equal pressure forces act on the shaft journal in both the bearing points. The bearing bore is preferably designed in the bearing points such that its diameter is of equal size so that the pressures acting on the shaft journal are compensated. 
   Seals for sealing the distribution chamber are assigned advantageously to the bearing points between the holder and the shaft journal. 
   The seals in the bearing points can be formed using temperature-resistant packing glands. It is particularly advantageous if the packing glands are held by adjustable pre-tensioning means in order to enable a complete sealing of the distribution chamber. On the other hand, it is particularly advantageous when conducting a polymer melt if a small quantity of the polymer can be guided out of the bearing points on both sides of the distribution chamber in order to discharge, for example, any broken-down polymer material. 
   In conjunction with slide bearings, even gap seals are implemented preferably between the shaft journal and the holder. 
   The shaft journal is mounted preferably using a slide bearing support, so that it is possible to implement small shaft bearing clearances having a diameter of &lt;0.15 mm. 
   In order to ensure the connection between the distribution chamber of the holder and the distribution channel of the connection body in any position of the connection body, the distribution chamber according to an advantageous refinement is formed within the holder by means of a groove, which surrounds the shaft journal substantially concentrically. Thus, at the circumference of the shaft journal, there is sufficient quantity of fluid, which can reach the distribution channel inserted in the connection body. 
   However, the distribution chamber can also be designed using a circumferential recess on the shaft journal. Depending on the diameter of the shaft section with the recess, the distribution chamber can be designed concentrically to the bearing bore inside or outside the latter so as to ensure a constant uniform distribution and guidance of the melt when the shaft journal rotates. 
   The distribution channel can be designed advantageously in the connection body by means of a blind hole from the connection end up to the shaft journal. The closed end of the blind hole in the shaft journal is connected by means of a cross hole to the distribution chamber located outside. The shape of the cross hole and the blind hole can be designed such that there results the smallest possible pressure loss when the polymer melt flows through the tubular rotary joint. 
   According to an advantageous refinement of the tubular rotary joint, the distribution channel of the connection body can be formed by means of a through-hole from the connection end to a second opposite connection end, wherein the through-hole in the region of the shaft journal is connected by means of a cross hole to the distribution chamber. It is possible by means of this refinement of the invention to simultaneously supply fluid to two pipe sections connected to the rotary joint. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained below in more detail based on a few exemplary embodiments of the tubular rotary joint and with reference to the attached drawings, in which: 
       FIG. 1  schematically shows a longitudinal view of a first exemplary embodiment of the tubular rotary joint according to the invention 
       FIG. 2  schematically shows a cross-sectional view of the exemplary embodiment illustrated in  FIG. 1   
       FIG. 3  schematically shows a longitudinal view of another exemplary embodiment of a tubular rotary joint according to the invention 
       FIG. 4  and 
       FIG. 5  schematically show longitudinal views of additional exemplary embodiments of the tubular rotary joint according to the invention. 
   


   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1 and 2  show different views of a first exemplary embodiment of a tubular rotary joint.  FIG. 1  shows a longitudinal view of the exemplary embodiment, and 
     FIG. 2  shows a cross-sectional view thereof. The following description shall apply to both the figures unless there is explicit reference made to either of the figures. 
   The tubular rotary joint comprises a cuboid holder  1 . In the holder  1 , a distribution chamber  3  is formed, which is connected to a feeder  4 . The feeder  4  is designed at the upper side of the holder  1 , and is connected to a pipe section, which is not shown here. 
   In the holder  1  a bearing bore  5 , which is directed transversely to the feeder  4 , is formed in the middle region of the holder  1 . The bearing bore  5  penetrates the distribution chamber  3  and the adjoining sidewalls of the holder  1 . The distribution chamber  3  is formed by means of a circumferential groove  7  substantially concentrically to the bearing bore  5  within the holder  1 . A connection body  2  is rotatably mounted in the bearing bore  5  of the holder  1 . For this purpose, a bearing end  13  of the connection body  2  is designed as a shaft journal  9 , which is rotatably mounted in the bearing points  6 . 1  and  6 . 2  of the holder  1 . One connection end  14  of the connection body  2  protrudes laterally from the bearing bore  5  of the holder  1 . A pipe section  15  is coupled to the free end of the connection end  14 . Within the connection body  2 , a distribution channel  10  is formed by a blind hole  11  from the connection end  14  towards the bearing end  13 . In the region of the shaft journal  9 , the blind hole  11  comprises a cross hole  12 , by means of which the blind hole  11  is connected to the distribution chamber  3 . 
   As shown in  FIG. 2 , the groove  7  is designed substantially concentrically to the circumference of the shaft journal  9  to form the distribution chamber  3  in the holder  1  so that the distribution chamber  3  is always connected to the distribution channel  10  in any position of the shaft journal  9 . 
   Several heating elements  24  can be integrated into the holder  1 , which heating elements heat that region of the tubular rotary joint that conducts the melt. 
   It is clear from  FIG. 1  that seals  8 . 1  and  8 . 2  are disposed between the shaft journal  9  and the bearing points  6 . 1  and  6 . 2  of the holder  1  so that the distribution chamber  3  is sealed from the outside. In addition, means (not illustrated) act on the shaft journal  9  for securing it axially so as to avoid any impermissible axial movement of the connection body  2 . 
   In the exemplary embodiment shown in  FIGS. 1 and 2 , a high-temperature polymer melt is conveyed under high pressure by means of the feeder  4  into the distribution chamber  3 . From the distribution chamber  3 , the polymer melt flows through the cross hole  12  to the blind hole  11 . The distribution channel  10  thus formed guides the polymer melt thereafter to the connected pipe section  15 . The pipe section  15  can be rotated relative to the holder  1  about the shaft journal  9  acting as an axis. Rotation angles in the range of 360° and above are possible. 
   In this exemplary embodiment, the bearing points  6 . 1  and  6 . 2  are designed as sliding support or plain bearings, the diameters of the bearing clearances amounting to a maximum of 0.15 mm. It is thus possible to rotate the shaft journal  9  even at higher temperatures. 
   The bearing points  6 . 1  and  6 . 2  could also be designed to include a bushing or a roller bearing, if appropriate. In principle, it is particularly advantageous to provide the shaft journal with a symmetrical design in the two bearing points in the tubular rotary joint according to the invention since substantially compensated pressure forces act on the connection body  2 , thereby maintaining the free movement of the rotation of the shaft journal  9  even at higher pressures. The seal provided in the exemplary embodiment shown in  FIGS. 1 and 2  for sealing the distribution chamber is illustrated by way of example. The location and type of seal can be selected freely for sealing purposes. Thus, gap seals could also be designed between the shaft journal and the holder, thereby eliminating the necessity of additional sealing means. 
     FIG. 3  shows another exemplary embodiment of the tubular rotary joint according to the invention.  FIG. 3  shows a longitudinal view of the exemplary embodiment, the cross-sectional view of which is substantially identical to the exemplary embodiment shown in  FIG. 2 . 
   The tubular rotary joint comprises a holder  1  and a connection body  2  mounted in the holder  1 . The holder  1  is designed with a distribution chamber  3 , which can be connected by means of a feeder  4  to an external pipe section. The distribution chamber  3  is formed as a groove  7  and is concentric to the shaft journal  9 . The distribution chamber  3  is penetrated by a bearing bore  5 , which completely penetrates the walls of the holder  1 . In the bearing bore  5 , a shaft journal  9  is rotatably mounted in the bearing points  6 . 1  and  6 . 2  of the holder  1 . On each of its sides, the shaft journal  9  comprises a connection end  14 . 1  and  14 . 2 , to which a pipe section can be coupled. The connection body  2  thus formed is penetrated by a through-hole  21 , which together with a cross hole  12  forms the distribution channel  10  in the region of the shaft journal  9  within the distribution chamber  3 . 
   Packing glands  16 . 1  and  16 . 2  are disposed at the bearing points  6 . 1  and  6 . 2  respectively between the shaft journal  9  and the holder  1 . Pre-compressioning means  17 . 1  and  17 . 2  are designed concentrically to the shaft journal  9  on both the sides of the holder  1 , so that a pre-compressioning force is exerted on the packing glands  16 . 1  and  16 . 2 . In this case, since each of the pre-compressioning means  17 . 1  and  17 . 2  is designed identically, only the pre-compressioning means  17 . 1  is explained below in further detail. The pre-compressioning means  17 . 1  is formed by means of an annular straining collar  20 , which is molded to a ring flange  18 . The ring flange  18  is concentric to the shaft journal  9  and is coupled to the holder  1  by means of the straining screw  19 . The straining collar  20  acts on a front side of the packing gland  16 . 1 . The opposite inner side of the packing gland  16 . 1  is held by a portion  22  of the holder  1 . 
   The ring flange  18  can be fixed to the holder  1  by clamping the straining screws  19  depending on the desired preliminary compression of the packing gland  16 . 1 . Thus, the packing glands  16 . 1  and  16 . 2  can be adjusted so as to ensure a complete sealing of the distribution chamber  3  from the surroundings. However, even permissible leakages can be adjusted, in order to be able, for example, to continuously discharge the consumed polymer material from the distribution chamber  3 . In this respect, the adjustability of the packing glands  16 . 1  and  16 . 2  is particularly advantageous for ensuring the impermeability of the tubular rotary joint while conducting a polymer melt. 
   In the exemplary embodiment shown in  FIG. 3 , a polymer melt that is supplied by means of the feeder  4  can be uniformly guided during operation to the two connection ends  14  of the connection body  2 . To avoid an impermissible axial movement of the shaft journal, fixing collars  23  can each be assigned to the straining collars  20  outside the holder  1 . The position of the shaft journal in the axial direction is secured by means of the fixing collar  23 . The fixing collar  23  is shown using dashed lines in  FIG. 3 . 
     FIG. 4  schematically shows a longitudinal view of another exemplary embodiment of the tubular rotary joint according to the invention. 
   According to the exemplary embodiment shown in  FIG. 4 , the holder  1  is formed using several components, wherein a distribution housing  34  contains a penetrating bearing bore  5 , in which the bearing end  13  of the shaft journal  9  is mounted. On its front side and coaxially to the bearing bore  5 , the distribution housing  34  comprises a receiving hole  35 , in which a shaft shoulder  25  of the shaft journal  9  is guided. For connecting a pipe section, the distribution housing  34  comprises a feeder  4 , which is aligned substantially transversely to the bearing bore  5 . The feeder  4  opens into the receiving hole  35 . In the region of the feeder  4 , a circumferential recess  27  is inserted in the shaft shoulder  25 , which recess forms the distribution chamber  3  within the holder  1 . The recess  27  in the shaft shoulder  25  connects to a cross hole  12  at the groove base. This cross hole is connected to a middle blind hole  11  and thus represents the connection of the distribution chamber  3  to the distribution channel  10 . 
   For mounting the shaft journal  9 , a bearing plate  32  is provided on the connection end  14  of the shaft journal  9 . This bearing plate  32  is connected to the distribution housing  34  and contains a bearing bore  5  to form the second bearing point  6 . 2 . 
   A pipe section  15  for connecting a melt line is provided on the free connection end  14  of the shaft journal  9  that protrudes from the bearing plate  32 . 
   For sealing the distribution chamber  3  formed within the holder, seals  8 . 1  and  8 . 2  are disposed at both the sides of the shaft shoulder  25 , each of said seals extending concentrically to the bearing bore  5 . Furthermore, gap seals could also be designed between the shaft shoulder  25  and the receiving hole  35 . 
   However, in the exemplary embodiment shown in  FIG. 4 , it is also possible to design the distribution chamber by means of a circumferential groove, which extends concentrically to the receiving hole and opens directly into the receiving hole  35  and is connected to the feeder  4 . In this case, the shaft shoulder will not have any circumferential recess. 
     FIG. 5  shows another exemplary embodiment of a possible design of the tubular rotary joint.  FIG. 5  schematically shows a longitudinal view of the tubular rotary joint. 
   In this exemplary embodiment, the connection body  2  is likewise formed by means of a shaft journal  9 , which is mounted in a holder  1  by means of a bearing end  13 . The holder  1  comprises a penetrating bearing bore  5 , in which the shaft journal  9  is mounted in the bearing points  6 . 1  and  6 . 2 . Between the bearing points, the shaft journal  9  comprises a recess  27 . 1 , which is connected to a feeder  4  within the holder  1 . At the groove base of the recess  27 . 1  of the shaft journal  9 , a cross hole  12  is designed, which opens into a distribution hole  31 . 
   That free end  14  of the shaft journal  9  that protrudes from the holder  1  supports a movable holder  26 , which comprises a penetrating bearing bore  5  and is mounted by means of the connection end  14  of the shaft journal  9  in the bearing points  6 . 3  and  6 . 4 . Between the bearing points  6 . 3  and  6 . 4 , the connection end  14  of the shaft journal comprises a second recess  27 . 2 , which is connected in its groove base to the distribution hole  31  by means of a cross hole  12 . The movable holder  26  comprises a discharge outlet  29  for connecting a pipe section. This discharge outlet opens into the recess  27 . 2  of the shaft journal  9 . The recess  27 . 2  on the circumference of the shaft journal  9  forms a distribution chamber  36 . 
   Between the bearing end  13  and the connection end  14 , the shaft journal  9  comprises a circumferential separating web  30 , which secures the shaft journal  9  in the axial direction. The separating web  30  is designed outside the bearing bores  5 , between the holder  1  and the movable holder  26 . 
   At the bearing end  13  of the shaft journal, a drive adapter  28  is provided, by means of which a rotary drive can be connected to the shaft journal  9 . The shaft journal  9  is thus advantageously prevented from getting stuck inside the holder  1 . 
   The functioning of the embodiment of the tubular rotary joint shown in  FIG. 5  is substantially identical to the preceding exemplary embodiments. Thus, a polymer melt is supplied through the feeder  4  by means of a stationary melt supply line. The polymer melt flows through the distribution chamber  3  and the distribution channel  31  and reaches the discharge chamber  36  and the discharge outlet  29  connected thereto. The melt distribution takes places independently of the position of the shaft journal and the positions of the holder  1  and the holder  26  relative to each other. For sealing the distribution chamber  3  and the discharge chamber  36  designed at the connection end, gap seals  33 . 1  and  33 . 2  are designed between the shaft journal  9  and the holder  1 . Similarly, gap seals  33 . 3  and  33 . 4  are designed between the holder  26  and the shaft journal  9 . 
     FIG. 1  to  FIG. 5  show the structure and design of the individual components of the exemplary embodiments only by way of example. In principle, for example, the sealing concept of the exemplary embodiment shown in  FIG. 1  or  FIG. 3  can also be implemented in the exemplary embodiment shown in  FIG. 5 .
The invention relates to a tubular rotary joint, in particular for conducting a polymer melt, comprising a holder and a mobile connection body, which is rotatably connected to the holder by means of one bearing end. A distribution chamber with a feeder is configured in the holder, said chamber being connected to a distribution channel that is configured in the connection body. The distribution channel in the connection body leads to a connection end, to which a pipe section can be coupled. To guarantee the flexibility of the connection body at high pressure and at high temperatures, the bearing end of the connection body is configured as a shaft journal, which is rotatably mounted in a bearing bore that penetrates the distribution chamber in the holder.