FIELD OF THE INVENTION  
       [0001]     The invention relates to a railway bogie comprising at least one hydraulic spring having a housing being required for a functionality of the hydraulic spring and an axlebox.  
       BACKGROUND DISCUSSION  
       [0002]     From UIC standard a bogie with helical springs is well known, whereby the axlebox suspension consists of helical springs in combination with friction damping. Thereby the springs rest on support arms integral with the lower part of the axlebox housing and are connected with the bogie frame using caps integral with the bogie frame for taking up the top of the springs.  
         [0003]     US 2002-0089102 A1 discloses a hydraulic spring comprising a membrane. This document also discloses that the hydraulic spring is for use in rail vehicles especially as a primary spring.  
         [0004]     Further the catalogue of the company ContiTech Luftifedersysteme GmbH in Hannover, Germany, “Air Spring Systems for Modem Rail Vehicles”, printed and distributed in October 1998 discloses the use of hydraulic springs comprising a membrane in two-axle bogies.  
         [0005]     One object of the present invention is to provide an improved railway bogie comprising at least an axlebox and a hydraulic spring, so that the railway bogie has a simplified build-up and is therewith cheaper to produce.  
       SUMMARY  
       [0006]     According to one aspect, a railway bogie comprises at least one hydraulic spring having a housing required for operativeness of the hydraulic spring and an axlebox, wherein at least a part of the axlebox forms at least a part of the housing.  
         [0007]     By the fact that an existing part of the axlebox is designed and used to form a part of the housing of the hydraulic spring, the number of components is reduced in total so that a lower fault liability and a more favorable cost position can be achieved. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0008]     Further advantages, features and details of the invention are described with respect to one preferred embodiment of the invention with reference to the accompany drawings.  
         [0009]      FIG. 1  is a longitudinal cross section in the region of one wheel of a bogie.  
         [0010]      FIG. 2  is a sectional view along the line B-B of  FIG. 1 . 
     
    
     DETAILED DESCRIPTION  
       [0011]      FIG. 1  shows a longitudinal cross section in the region of one wheel  2  of a bogie of the so-called Y 25 type, whereby the cut is directed along a plane defined by the axes of rotational symmetry of a first and second hydraulic spring. The pictured section of the bogie comprises an axlebox  10  with a rolling bearing  4  mounted in a middle region of the axlebox  10 . The rolling bearing  4  supports one end of one of the two axles of the bogie.  
         [0012]     A base of the axlebox  10  is extended to the left and the right side forming a cup shaped region  12  at each of the sides. Each of the hydraulic springs comprises a spring element  20 , which is attached to each of the cup shaped regions  12  of the axlebox  10 . A metallic centerpiece  26  is located in the centre of each of the spring elements  20 .  
         [0013]     These two centerpieces  26  are attached to one bridging adapter  50 . Therefore the centerpieces  26  and the bridging adapter  50  have bores for connecting the centerpieces  26  with the bridging adapter  50  via two bolts  52  pictured uncut in  FIGS. 1 and 2 . In other embodiments, the bolts  52  can be integral parts of the centerpieces  26  or of the bridging adapter  50 , or the centerpieces  26  can be connected to the bridging adapter  50  by any other connecting means.  
         [0014]     The bridging adapter  50  is attached to a longeron of a frame  6  of the bogie. This longeron extends in a longitudinal direction parallel to the rails and is pictured uncut in  FIG. 1 . Preferably the bridging adapter  50  is connected to the bogie frame  6  by welding.  
         [0015]     In the following description, just the left cup shaped region  12  in connection with the left spring element  20  is described in detail, because the same applies to the right cup shaped region  12  in connection with the right spring element  20 . Therefore  FIG. 2  shows a sectional view along the line B-B of  FIG. 1 . The spring element  20  comprises sleeve shaped elastomeric elements  22  and intermediate sleeve shaped metallic elements  24  in an alternating succession, whereby the elastomeric and the metallic elements  22  and  24  are connected by way of vulcanization. Also the centerpiece  26  is connected by way of vulcanization to its adjacent elastomeric element  22 .  
         [0016]     The spring element  20  is secured to the respective cup shaped region  12  of the axlebox  10  via a sealing ring  42 , which is attached to the axlebox  10  via screws  44 . In other embodiments the spring element  20  also can be directly vulcanized to the cup shaped region  12 . The spring elements  20  forms together with the respective cup shaped region  12  of the axlebox  10  a volume for a fluid  30  particularly a hydraulic fluid. This volume is at least partly filled with the fluid  30 . The centerpiece  26  is prolonged into the volume forming a plunger shaped region  28 . Thereby at least a disk shaped region at the end of the plunger shaped region  28  is dipped into the fluid  30 , so that this arrangement fulfils the function of a damper. The cup shaped region  12  of the axlebox  10  together with the respective spring element  20  and the fluid  30  form together the hydraulic spring.  
         [0017]     In another embodiment of the invention, a hydraulic spring can be used, e.g. according to the already cited US 2002-0089102 A1, comprising a membrane instead of the plunger shaped section  28  of the centerpiece  26 , whereby the cup shaped region  12  of the axlebox  10  is then also one part of the housing of the hydraulic spring.
An axlebox-spring-unit of a railway bogie includes at least one hydraulic spring having a housing required for functionality of the hydraulic spring, and an axlebox. At least a part of the axlebox forms at least a part of the housing.