Abstract:
The invention relates to a pneumatic brake cylinder including a housing, a piston that can be moved in the housing and is used to transfer the pneumatic pressure to a brake, and a device for automatic adjustment in the event of wear of the brake linings, the device including a spindle, an adjusting nut, and a piston tube that can be engaged with the adjusting nut. According to the invention, a torque applied to the piston tube by the adjusting nut is introduced by the piston tube directly into elements connected to the housing in a fixed manner.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of priority to International Patent Application No. PCT/EP2009/007186 filed 7 Oct. 2009, which further claims the benefit of German Patent Application No. 10 2008 051 679.1 filed 15 Oct. 2008, the contents of which are incorporated herein by reference in their entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]    Disclosed embodiments relate to a pneumatic brake cylinder. 
       BACKGROUND 
       [0003]    Brake cylinders of this type are used, inter alia, in rail vehicles. There, they are frequently used to actuate a brake caliper, with the aid of which brake linings are pressed onto a brake disk. Here, the piston stroke is to always be approximately equally great, independently of the wear of the brake linings. For this purpose, an adjusting device is usually provided which has a spindle which is guided in a piston tube and an adjusting nut. An axial force is exerted on the spindle by a spring, which axial force attempts to pull the spindle out of the adjusting device. Since the spindle and the adjusting nut are connected to one another via a thread which is not self-locking, a torque acts on the adjusting nut as a result of the spring force. 
         [0004]    During the normal braking operation, the adjusting nut is blocked in such a way that only a linear movement together with the spindle in the direction of the longitudinal center axis of the brake cylinder is permitted, but not a rotational movement. A rotation of the adjusting nut may only be permitted for the adjusting operation when a certain wear of the brake linings has taken place. In order to control the rotational movement of the adjusting nut during the initiation of a braking operation, what is known as a control sleeve is used which is arranged within the piston tube such that it can be displaced on the spindle. The torque is transmitted from the control sleeve to the piston tube via integrally formed locking arms which are guided in open slots of the piston tube. During the braking operation, in contrast, the torque of the adjusting nut is transmitted directly to the piston tube. 
         [0005]    The piston tube is connected fixedly to the piston, with the result that the torque is transmitted from the piston tube to the piston. The torque is introduced into the housing via guide pins which are attached to the piston and which correspond with appropriate guides in the housing. This force transmitting connection between the piston and the piston tube leads to a complicated and expensive component which is difficult to mount. The dismantling, mounting and the components to be replaced are relatively expensive even in the case of reconditioning of the pneumatic cylinder. 
         [0006]    In the case of another known brake cylinder, the locking arms of the control sleeve are supported on a stop ring which is screwed into the cover of the cylinder. Here, the torque which acts on the adjusting nut is transmitted via the locking arms into the housing of the brake cylinder not only in the rest position but also during the braking operation, since the piston tube is also supported on the locking arms via the open slots. The control sleeve and the integrally formed locking arms therefore have to be of very solid and stable configuration. 
         [0007]    In the case of two previously known brake cylinders, the adjusting device cannot be premounted as one unit on account of the locking arms which are integrally formed onto the control sleeve. 
       SUMMARY 
       [0008]    Disclosed embodiments are based on the concept of configuring a pneumatic brake cylinder in such a way that the costs for the components can be reduced and the mounting can be made cheaper, both during the production and during reconditioning of the brake cylinder. This is achieved by a pneumatic brake cylinder. 
         [0009]    As a result of the fact that a torque which is applied by the adjusting nut to the piston tube is introduced by the piston tube directly into elements which are connected fixedly to the housing, no particularly solid control sleeve has to be used. Furthermore, a stop ring which is screwed into the cover of the housing is neither necessary, nor are guide pins needed which are attached to the piston and correspond with appropriate guides in the housing. The adjusting device can be premounted as one unit, since a control sleeve without locking arms can be used. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0010]    Further details and advantages of the disclosed embodiments result from the description of one exemplary embodiment which will be explained in detail using the drawing, in which: 
           [0011]      FIG. 1  shows a section through a pneumatic brake cylinder according to the invention, 
           [0012]      FIGS. 2 and 3  show detail illustrations of the brake cylinder which is shown in  FIG. 1 , 
           [0013]      FIG. 4  shows a view of a closed piston tube with inserted sliding blocks, 
           [0014]      FIG. 5  shows the illustration from  FIG. 4 , in which the piston tube, the adjusting nut and the piston return spring have been sectioned, and 
           [0015]      FIG. 6  shows a section through the illustration from  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The elements which are connected fixedly to the housing are advantageously configured as sliding blocks. It is normally sufficient to provide two sliding blocks of this type and to screw them fixedly to the housing. This connection ensures a reliable introduction of the torque from the piston tube directly into the housing during the braking operation. 
         [0017]    Since the piston tube has to be mounted such that it can be displaced axially in the housing, the connection between the sliding blocks which are connected fixedly to the housing and the piston tube also has to be of corresponding design. For this purpose, the sliding blocks slide in slots of the piston tube. In the case of the use of the control sleeve which is known from the prior art with the integrally formed locking arms, via which the torque was transmitted from the piston tube into the housing, open slots were necessary in the piston tube, in order for it to be possible to mount the control sleeve at all. The upwardly and downwardly closed slots which are then possible ensure substantially higher stability and security against deformation. 
         [0018]    In order to transmit the torque from the piston tube into the housing, the piston and guide pins which are attached to it no longer have to be used. A connection between the piston and the piston tube can therefore be dispensed with completely. The piston is therefore inserted loosely into the cylinder and has no fixed connection to the piston tube. 
         [0019]    Since, according to the invention, the torque is transmitted directly from the piston tube to the sliding blocks which are screwed to the housing, no torque has to be transmitted via the piston. As a result, the forces to be absorbed by the piston are restricted to compressive forces in the axial direction. The piston can therefore be produced as an inexpensive deep drawn part. The required stability is achieved by a deep drawn part made from steel. 
         [0020]    A sealing ring is advantageously vulcanized onto the edge of the piston. In contrast to a sealing ring which is fastened on the piston with the aid of a vulcanized steel ring, the mounting is simplified considerably both during the production of the brake cylinder and during the reconditioning of the brake cylinder, as a result of which the mounting costs can be reduced. The complete piston can be replaced in a simple way during the reconditioning of the brake cylinder. 
         [0021]    The adjusting nut advantageously has an oblique external toothing system on one end side. This ensures a large engagement area. The oblique position of the external toothing systems also brings about a centering action at the same time. 
         [0022]    During the braking operation, the torque which acts on the adjusting nut has to be introduced into the piston tube. For this purpose, the piston tube has a piston tube toothing system which can be brought into engagement with the external toothing system of the adjusting nut. The piston tube toothing system is configured as an oblique internal toothing system, with the result that the piston tube toothing system can engage completely into the toothing system of the adjusting nut. 
         [0023]    A control sleeve is also provided in the piston tube. The torque which acts on the adjusting nut is also to be introduced into the housing via the control sleeve in the case of the initiation of the braking operation. 
         [0024]    For this purpose, the sliding blocks engage with their free end into sliding channels of the control sleeve. In this way, no integrally formed locking arms are necessary. The sliding blocks achieve the object of introducing both the torque of the piston tube and the torque of the control sleeve into the housing. To this end, they protrude through the slots which are provided in the piston tube and in this way are connected at the same time to the piston tube and the control sleeve. 
         [0025]    The sliding channels of the control sleeve are dimensioned in such a way that they act as a stop for the sliding blocks and restrict an axial movement of the control sleeve. Here, the permitted sliding path of the control sleeve corresponds to the spacing of the brake linings from the brake disk plus the elastic deformation of the parts which transmit the braking force between the brake cylinder and the brake linings. 
         [0026]    The control sleeve is advantageously produced as a composite part with a sliding sleeve made from plastic and an injection molded coupling ring made from metal. The sliding channels are provided in the sliding sleeve. The use of plastic is sufficient for stability reasons, since no locking arms which have to transmit the torque from the piston tube to the housing are integrally formed on the control sleeve. The production costs for the control sleeve can therefore be reduced in comparison with the previously usual continuous casting. The metallic coupling ring can be configured, for example, as an extruded steel part. The use of plastic for the sliding sleeve has likewise proved to be very inexpensive. The weight of the pneumatic brake cylinder has also been able to be reduced by the use of this control sleeve. 
         [0027]    At its free end, the coupling ring has an oblique internal toothing system which can be brought into engagement with the external toothing system of the adjusting nut. The production of the coupling ring as an extruded steel part makes the inexpensive production of a very fine and precise toothing system possible. The plastic of the sliding sleeve has a pronounced damping action during the absorption of the torque which is applied by the adjusting nut via the internal toothing system. As a result, the wear of the toothing system is reduced in comparison with the control sleeve made from a continuous casting, despite the higher degree of fineness. A centering action which ensures the engagement of the two toothing systems over as full a surface area as possible also results again in the case of the engagement of the oblique internal toothing system of the control sleeve into the oblique external toothing system of the adjusting nut. 
         [0028]    It should be noted, that the disclosed embodiments may have been described above and below with respect to different subject-matter. In particular, some embodiments may be described with reference to apparatus components, whereas those or other embodiments have been described with reference to methodologies. However, a person skilled in the art will gather from the above and the following description that, unless notified otherwise, in addition to any combination features belonging to one type of subject-matter also any combination between features relating to different subject-matter, in particular between features of apparatuses and features of methodologies, is considered to be disclosed with this application. 
         [0029]    The fastenings  21  for a brake caliper are situated firstly on the yoke  20  and secondly on the housing  19  which is assembled from a cylinder  19   a  and a cover  19   b . In order to actuate the brake, the brake caliper (not shown here) has to be pressed apart; this means that the spacing between the yoke  20  and the housing  19  has to be increased. 
         [0030]    The piston  1  is provided in the housing  19 . The pressure space  17  is formed by the piston  1  and the cylinder  19   a  of the housing  19 . The compressed air connection, via which compressed air is fed to the pressure space  17 , cannot be seen in this illustration. The piston tube  23  is actuated by the piston  1 . However, the piston  1  is not connected fixedly to the piston tube  23 , but rather is inserted loosely into the brake cylinder. The actuation of the piston tube  23  takes place merely via an annular bearing face of conical configuration, with which the piston  1  presses onto a spring collar  11  which is screwed to the piston tube  23 . 
         [0031]    Slots  27  (see  FIG. 6 ) are provided in the piston tube  23 , through which slots  27  sliding blocks  8  extend which are screwed to the housing  19 . This measure prevents rotation of the piston tube  23  with respect to the housing  19 , but in contrast permits a longitudinal displacement of the piston tube  23 . In the case of the longitudinal displacement, the piston tube  23  is supported by the annular sliding bands  16  on the inner wall of the housing  19 . The piston  1  and the piston tube  23  are held in their rest position by the piston return spring  12  which is supported on the cover  19   a  of the housing  19  and the spring collar  11  of the piston tube  23 . 
         [0032]    The spindle  24  is situated in the piston tube  23 . The position of the spindle  24  is controlled by the adjusting nut  25 . The adjusting nut  25  and spindle  24  are connected to one another via a thread which is not self-locking, with the result that a force in the direction of the longitudinal axis of the spindle  24  exerts a torque on the adjusting nut  25 . This force is exerted on the spindle  24  by the conical spring  28  which is supported on the yoke  20  and the piston tube  23 . The conical spring  28  therefore exerts a force which attempts to pull the spindle  24  out of the piston tube  23 . 
         [0033]    A control sleeve  3  is provided in the piston tube  23 . The control sleeve  3  is constructed as a composite part, a coupling ring  6  (see  FIG. 5 ) having been connected to a sliding sleeve  4 . The coupling ring  6  is configured as an extruded steel part. The free end side of the coupling ring  6  is provided with an oblique internal toothing system  7 . Two sliding channels  5  which lie opposite one another are machined into the sliding sleeve  4 . The sliding blocks  8  engage into the sliding channels  5 . The width of the sliding blocks  8  is adapted exactly to the width of the sliding channels  5 , with the result that no rotational movement of the control sleeve  3  is possible if the sliding blocks  8  are fixed. In order for it to be possible to fix the sliding blocks  8 , fastening holes  9  (see  FIG. 4 ) are provided which serve to receive screws. The longitudinal extent of the sliding channels  5  is dimensioned in such a way that the setting stroke  10  (see  FIG. 6 ) remains during engagement of the sliding blocks  8 . The significance of the setting stroke  10  will be explained in greater detail further below during the functional description of the brake cylinder. 
         [0034]    On its oblique end side, the adjusting nut  25  has an external toothing system  14  (see, in particular,  FIGS. 2 and 3  which illustrate the part denoted by A in  FIG. 1  on an enlarged scale and in different working states). The internal toothing system  7  of the control sleeve  3  is in engagement with the external toothing system  14  of the adjusting nut  25  in the release position of the brake. The control sleeve  3  is prevented from rotating via the sliding blocks  8  which are screwed to the housing  19 . As a result of the engagement of the internal toothing system  7  of the control sleeve  3  with the external toothing system  14  of the adjusting nut  25 , the latter is likewise prevented from rotating. The control sleeve  3  is prestressed via the locking spring  13  which is supported on the control sleeve  3  and on the piston tube  23 . A toothed ring which is connected to the spindle  24  is pressed into a toothing system of the yoke  20  with the aid of the disk spring  26 , with the result that rotation of the spindle  24  with respect to the yoke  20  is prevented. 
         [0035]      FIGS. 4 to 6  show a premounted adjusting unit. The adjusting unit substantially comprises the piston tube  23 , the adjusting nut  25 , the control sleeve  3  and the locking spring  13 . The loosely inserted sliding blocks  8  (likewise shown) do not belong to the premounted adjusting unit and are inserted into the brake cylinder only after the mounting of the adjusting unit. 
         [0036]    When the housing  19  is open, the completely premounted adjusting unit is introduced into the cover  19   b . The sliding blocks  8  are inserted through the slots  27  of the piston tube  23  into the sliding channels  5  of the control sleeve  3  and are fastened to the cover  19   b  with the aid of screws only when the adjusting unit is situated in the correct position. The piston return spring  12  can then be pushed over a guide on the cover  19   b , the spring collar  11  can be screwed to the piston tube  23 , the piston  1  can be inserted and the cylinder  19   a  can be attached. An assembly having the spindle  24  and the yoke  20  is subsequently screwed into the adjusting unit and a folding bellows  29  which is already mounted on the yoke  20  is fastened to the cover  19   b.    
         [0037]    In the following text, the function of the brake cylinder  18  is to be described: 
         [0038]    The piston  1  is pressed to the left by an increase of the pneumatic pressure in the pressure space  17 . Here, it actuates the piston tube  23  and likewise presses it to the left, counter to the force of the piston return spring  12 . The control sleeve  3  which is prestressed by the locking spring  13  is pressed with its internal toothing system  7  onto the external toothing system  14  of the adjusting nut  25  and likewise moves to the left together with the piston tube  23 , spindle  24 , adjusting nut  25  and yoke  20 . In contrast, the piston tube toothing system  15  is not in engagement with the external toothing system  14  of the adjusting nut  25 . This state is shown in  FIG. 2 . In this state, a torque is exerted on the adjusting nut  25  by the spindle  24 . This torque is transmitted to the control sleeve  3  and from there to the housing  19  via the sliding blocks  8 . 
         [0039]    At the moment, at which the control sleeve  3  has been displaced so far to the left that the setting stroke  10  between the sliding blocks  8  and the boundary of the sliding channels closes, the brake linings (not shown here) come into contact with the brake disk. From this point in time, a counterpressure is built up via the yoke  20 . Since the setting stroke  10  has now closed, the control sleeve  3  can no longer participate in a further movement of the piston tube  23 . 
         [0040]    The piston tube  23  is then displaced further to the left by a small amount, counter to the force of the conical spring  28 , while the yoke  20 , spindle  24  and adjusting nut  25  remain at the same location. As a result of this displacement of the piston tube  23  with respect to the adjusting nut  25 , the external toothing system  14  of the adjusting nut  25  comes out of engagement with the internal toothing system  7  of the control sleeve  3 . At the same time, however, the external toothing system  14  comes into engagement with the piston tube toothing system  15 . 
         [0041]    In the case of a further build up of pressure in the pressure space  17 , the brake linings are pressed against the brake disk, the piston tube  23  being pressed with great force against the adjusting nut  25 . As a result of these forces which are directed counter to one another of the piston  1  and piston tube  23  on one side and of the yoke  20 , spindle  24  and adjusting nut  25  on the other side, a torque is exerted on the adjusting nut  25 . This torque is absorbed by the piston tube toothing system  15  and transmitted to the piston tube  23 . The torque is transmitted from the slots  27  in the piston tube  23  to the sliding blocks  8 . The torque passes to the housing  19  via the sliding blocks  8 . The housing  19  is connected to the brake caliper via the fastenings  21  in such a way that the torque is finally absorbed here. This state of the piston tube  23 , adjusting nut  25  and control sleeve  3  is shown in  FIG. 3 . 
         [0042]    When the brake is released, the piston tube toothing system  15  is also released again from the external toothing system  14  of the adjusting nut  25 . At the same time, the external toothing system  14  of the adjusting nut  25  comes into engagement again with the internal toothing system  7  of the control sleeve  3 . 
         [0043]    Whereas no rotation of the adjusting nut  25  is permitted during a normal braking operation, the adjusting nut  25  has to be able to rotate when an adjustment becomes necessary on account of wear of the brake linings and/or brake disk. If a certain amount of wear of the brake linings has taken place, the gap between the brake linings and the brake disk has also increased. As a result, a greater piston stroke is necessary, in order to bring the brake linings into contact with the brake disk again. 
         [0044]    The braking process is initiated as in the case of a normal braking operation. The piston  1 , piston tube  23  and control sleeve  3  move together to the left. The control sleeve  3  participates in this movement until the setting stroke  10  is closed. The internal toothing system  7  of the control sleeve  3  is then decoupled from the external toothing system  14  of the adjusting nut  25 . In contrast with a normal braking process, however, no counterpressure is then built up, since the brake linings are not yet in contact with the brake disk. As a result, the piston tube toothing system  15  does not yet couple into the external toothing system  14  of the adjusting nut  25 . A force is exerted via the conical spring  28  on the yoke  20  and spindle  24 , which force attempts to pull the spindle  24  to the left out of the piston tube  23 . Here, a torque acts on the adjusting nut  25 . Since, in this state, the external toothing system  14  of the adjusting nut  25  is coupled neither to the internal toothing system  7  of the control sleeve  3  nor to the piston tube toothing system  15 , the adjusting nut  25  can yield to the torque and rotates on the spindle  24 . As a result of this rotation of the adjusting nut  25 , the spindle  24  can be pulled out to the left relative to the adjusting nut  25 . 
         [0045]    The rotation of the adjusting nut  25  continues until the brake linings have come into contact with the brake disk. At this moment, a counterpressure is built up again which brings about coupling of the piston tube toothing system  15  to the external toothing system  14  of the adjusting nut  25 . The torque which acts on the adjusting nut  25  is then introduced again via the piston tube  23  directly into the sliding blocks  8  which are connected fixedly to the housing  19 . The adjusting operation is therefore finished and further braking processes take place again without adjustment until a certain amount of wear of the brake linings has occurred once again. 
         [0046]    If an adjustment is no longer possible, the brake linings have to be changed. Here, the brake cylinder  18  also has to be reset into its original state again. To this end, force is applied to the return hexagon  22  and the spindle  24  is turned completely into the piston tube  23  again. During the first braking process, after the mounting of the new brake linings, an adjustment takes place again, with the result that here too the predefined spacing between the brake linings and the brake disk is automatically set correctly. 
         [0047]    List of Designations: 
         [0048]      1  Piston 
         [0049]      2  Sealing ring 
         [0050]      3  Control sleeve 
         [0051]      4  Sliding sleeve 
         [0052]      5  Sliding channel 
         [0053]      6  Coupling ring 
         [0054]      7  Internal toothing system 
         [0055]      8  Sliding block 
         [0056]      9  Fastening hole 
         [0057]      10  Setting stroke 
         [0058]      11  Spring collar 
         [0059]      12  Piston return spring 
         [0060]      13  Locking spring 
         [0061]      14  External toothing system of the adjusting nut 
         [0062]      15  Piston tube toothing system 
         [0063]      16  Sliding band 
         [0064]      17  Pressure space 
         [0065]      18  Brake cylinder 
         [0066]      19  Housing 
         [0067]      19   a  Cylinder 
         [0068]      19   b  Cover 
         [0069]      20  Yoke 
         [0070]      21  Fastening for brake caliper 
         [0071]      22  Return hexagon 
         [0072]      23  Piston tube 
         [0073]      24  Spindle 
         [0074]      25  Adjusting nut 
         [0075]      26  Disk spring 
         [0076]      27  Slot 
         [0077]      28  Conical spring 
         [0078]      29  Folding bellows