Abstract:
The invention relates to a pneumatic brake cylinder including a piston for transferring the pneumatic pressure to a brake, and a device for automatic adjustment in the event of wear of the brake linings, the device comprising a spindle, an adjusting nut, and a control sleeve that can be engaged with the adjusting nut. According to the invention, the control sleeve is embodied as a composite part including a metallic coupling ring and a sliding sleeve of a plastic material.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of priority to International Patent Application No. PCT/EP2009/007185 filed 7 Oct. 2009, which further claims the benefit of German Patent Application No. 10 2008 051 678.3 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. During the normal braking operation, the adjusting nut is blocked in such a way that only a linear movement in the direction of the longitudinal 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, 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. 
         [0004]    A toothing system which can engage into a corresponding toothing system of the adjusting nut is usually provided on that side of the control sleeve which faces the adjusting nut. Since the control sleeve has to absorb high loadings, it is produced nowadays from a heavy metal continuous casting. Although this material ensures a high strength which is sufficient for this use, it permits only a relatively rough formation of the toothing system. This factor greatly limits the accuracy during the adjustment of the brake cylinder. 
       SUMMARY 
       [0005]    The disclosed embodiment configure a pneumatic brake cylinder in such a way that, in the case of wear of the brake linings, very exact adjustment of the brake cylinder can take place. The production costs for the brake cylinder are to be reduced despite the improved adjustment. 
         [0006]    According to the disclosed embodiments, the use of a control sleeve which is configured as a composite part which has a metallic coupling ring and a sliding sleeve made from plastic, the production costs can be reduced in comparison with the previously customary continuous casting. The metallic coupling ring can be configured, for example, as an extruded steel part. This makes the inexpensive production of a very fine and precise toothing system possible. The use of plastic for the sliding sleeve has likewise proven to be very inexpensive. The plastic of the sliding sleeve has a pronounced damping action during the absorption of the torque which is exerted by the adjusting nut. As a result, the wear of the toothing system, despite the higher degree of fineness, is reduced in comparison with the control sleeve made from a continuous casting. The weight of the pneumatic brake cylinder could also be reduced by the use of the novel control sleeve. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0007]    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: 
           [0008]      FIG. 1  shows a section through a pneumatic brake cylinder according to the disclosed embodiments, 
           [0009]      FIGS. 2 and 3  show detail illustrations of the brake cylinder which is shown in  FIG. 1 , 
           [0010]      FIG. 4  shows a three-dimensional illustration of one preferred exemplary embodiment of a control sleeve with inserted sliding blocks, 
           [0011]      FIG. 5  shows the control sleeve from  FIG. 4  in a sectioned illustration, 
           [0012]      FIG. 6  shows a section through the coupling ring of the control sleeve from  FIGS. 4 and 5 , 
           [0013]      FIG. 7  shows the coupling ring in a three-dimensional illustration, 
           [0014]      FIG. 8  shows a three-dimensional illustration of the preferred exemplary embodiment of the control sleeve without locking arms, 
           [0015]      FIG. 9  shows the coupling ring of the control sleeve from  FIG. 8  without a sliding sleeve, 
           [0016]      FIG. 10  shows a second exemplary embodiment of a control sleeve in a three-dimensional illustration with integrally formed locking arms, and 
           [0017]      FIG. 11  shows the coupling ring of the control sleeve from  FIG. 10  without a sliding sleeve. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    In accordance with disclosed embodiments, the coupling ring is particularly advantageously encapsulated using injection molding by the sliding sleeve or the sliding sleeve is injection molded into the coupling ring. In this way, a fixed connection is brought about between the sliding sleeve and the coupling ring, without it having been necessary to perform an additional mounting step. 
         [0019]    The coupling ring is advantageously provided with apertures in the region which is connected to the sliding sleeve. During the injection molding of the control sleeve, this leads to the apertures being filled with plastic. The connection between the coupling ring and the sliding sleeve is strengthened as a result. In particular, greater torques can be transmitted from the coupling ring to the sliding sleeve as a result. 
         [0020]    The coupling ring has a toothing system for the positively locking engagement into a toothing system of the adjusting nut. Since the toothing system of the coupling ring can be of very fine configuration, very precise adjustment of the brake cylinder is possible. As a result of the positively locking connection between the coupling ring and the adjusting nut, a great torque can be transmitted despite the fine toothing system. 
         [0021]    The toothing system is advantageously attached on the free end side of the coupling ring and is configured as an oblique internal toothing system. A great engagement surface area is thus ensured in conjunction with an oblique external toothing system on an end side of the adjusting nut. The oblique position of the two toothing systems also at the same time brings about a centering action, with the result that the toothing system of the control sleeve and the toothing system of the adjusting nut are in each case in engagement with one another over their full surface area. 
         [0022]    According to disclosed embodiments, a locking device is provided which prevents rotation of the control sleeve. In this way, the torque which is transmitted by the adjusting nut can be absorbed reliably. The locking device is configured in such a way that only the rotation of the control sleeve is prevented. In contrast, a displacement of the control sleeve in the direction of the longitudinal axis of the brake cylinder is permitted in a predefined range. 
         [0023]    A piston tube is advantageously provided which is actuated by the piston. Said piston tube has slot-shaped openings, through which the locking arms extend. The slot-shaped openings are dimensioned in such a way that the movement of the control sleeve can be decoupled from the movement of the piston tube. 
         [0024]    The locking arms engage with their free end into slot-shaped cutouts. The width of the slot-shaped cutouts is adapted to the width of the locking arms. In this way, rotation of the control sleeve is prevented reliably. 
         [0025]    The longitudinal extent of the slot-shaped cutouts is dimensioned in such a way that the cutouts act as a stop for the control sleeve and restrict a sliding movement of the control sleeve. Here, the permitted sliding section 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]    In one exemplary embodiment, the slot-shaped cutouts are provided in the housing of the brake cylinder or a part which is connected to the latter. The locking arms are connected fixedly to the sliding sleeve and are advantageously injection molded onto the latter. In this exemplary embodiment, the locking arms move together with the sliding sleeve. 
         [0027]    In another exemplary embodiment, the slot-shaped cutouts are provided in the sliding sleeve itself. In contrast, the locking arms are configured as sliding blocks and are connected fixedly to the housing of the brake cylinder, in particular are screwed to it. In this particularly advantageous exemplary embodiment, the sliding blocks do not have to be moved. As a result, the weight of the control sleeve can be reduced further. The lower weight of the control sleeve makes itself felt by reduced inertia during its movement. As a result, even higher precision is possible in the adjustment of the brake cylinder. 
         [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 design of the novel control sleeve can be gathered from  FIGS. 4-11 , one preferred exemplary embodiment being shown in  FIGS. 4-9 . The control sleeve  1  is constructed as a composite part, a coupling ring  4  having been connected to a sliding sleeve  2 . The coupling ring  4  is configured as an extruded steel part and comprises a toothed ring  9  and a connecting ring  10 . The connecting ring  10  and the toothed ring  9  have the same internal diameter, whereas the external diameter of the toothed ring  9  is dimensioned to be greater than the external diameter of the connecting ring  10 . As a result, the step  12  is produced in the outer contour of the coupling ring  4 . The free end side of the toothed ring  9  is provided with an oblique internal toothing system  5 . The connecting ring  10  has a number of round apertures  11 . 
         [0030]    Two sliding channels  3  which lie opposite one another are machined into the sliding sleeve  2 . The sliding blocks  6  engage into the sliding channels  3 . The width of the sliding blocks  6  is adapted exactly to the width of the sliding channels  3 , with the result that no rotational movement of the sliding sleeve  2  is possible if the sliding blocks  6  are fixed. In order for it to be possible to fix the sliding blocks  6 , the fastening holes  7  are provided which serve, in particular, to receive screws. The longitudinal extent of the sliding channels  3  is dimensioned in such a way that the feed gap  8  remains during engagement of the sliding blocks  6 . The significance of the feed gap  8  will be explained in greater detail further below during the functional description of the brake cylinder. 
         [0031]    During the production of the control sleeve  1 , the coupling ring is inserted into the injection molding die. During the injection molding of the control sleeve  1 , the plastic also fills the step  12  of the coupling ring  4  and enters the apertures  11  of the connecting ring  10 . As a result, an excellent connection is ensured between the coupling ring  4  and the sliding sleeve  2 . The plastic in the apertures  11  prevents the components from being able to rotate with respect to one another. 
         [0032]      FIGS. 10 and 11  show a further exemplary embodiment of a control sleeve. The coupling ring  15  which is used here has a stepless outer circumference. The step for receiving the sliding sleeve  14  is situated here on the inner side of the coupling ring  15 . While the coupling ring  4  is plugged in the sliding sleeve  2  in the first exemplary embodiment according to  FIGS. 4-9 , the sliding sleeve  14  is plugged in the coupling ring  15  in this exemplary embodiment. Here too, apertures are provided which, filled with the plastic of the sliding sleeve  14 , bring about an antirotation safeguard between the sliding sleeve  14  and the coupling ring  15 . 
         [0033]    In the exemplary embodiment according to  FIGS. 10 and 11 , locking arms  16  are injection molded directly onto the sliding sleeve  14 . The locking arms  16  have runners  17 , by way of which the locking arms engage into a stop ring which is screwed to the brake cylinder. Here too, recesses are provided in accordance with the sliding channels  3  of the first exemplary embodiment, with the result that a certain longitudinal displacement of the runners  17  is possible. The extent of the displacement corresponds to the feed gap  8  in the first exemplary embodiment. 
         [0034]    The use of the novel control sleeve will be explained using the pneumatic brake cylinder which is shown in  FIG. 1 . The fastenings  21  for a brake caliper are situated firstly on the yoke  20  and secondly on the housing  19 . 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 enlarged. 
         [0035]    The piston  22  is provided in the housing  19 . The pressure space  30  is situated between the piston  22  and the housing  19 . The compressed air connection, via which compressed air is fed to the pressure space  30 , cannot be seen in this illustration. The piston tube  23  is actuated by the piston  22 . However, the piston  22  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, with which the piston  22  presses onto the piston tube  23 . 
         [0036]    Slots are provided in the piston tube  23 , through which slots sliding blocks  6  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  31  on the inner wall of the housing  19 . The piston  22  and the piston tube  23  are held in their rest position by the piston return spring  26  which is supported on the housing  19  and the piston tube  23 . 
         [0037]    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 cone tube  23 . 
         [0038]    On its oblique end side, the adjusting nut  25  has an external toothing system  34  (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  5  of the control sleeve  1  is normally in engagement with the external toothing system  34  of the adjusting nut  25 . The control sleeve  1  is prevented from rotating via the sliding blocks  6  which are screwed to the housing  19 . As a result of the engagement of the internal toothing system  5  of the control sleeve  1  with the external toothing system  34  of the adjusting nut  25 , the latter is likewise prevented from rotating. The control sleeve  1  is prestressed via the locking spring  27  which is supported on the control sleeve  1  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  29 , with the result that rotation of the spindle  24  with respect to the yoke  20  is prevented. 
         [0039]    In the following text, the function of the brake cylinder  18  is to be described: 
         [0040]    The piston  22  is pressed to the left by an increase of the pneumatic pressure in the pressure space  30 . Here, it actuates the piston tube  23  and likewise presses it to the left, counter to the force of the piston return spring  26 . The control sleeve  1  which is prestressed by the locking spring  27  is pressed with its internal toothing system  5  onto the external toothing system  34  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  33  is not in engagement with the external toothing system of the adjusting nut  25 . This state is shown in  FIG. 2 . 
         [0041]    At the moment, at which the control sleeve  1  has been displaced so far to the left that the feed gap  8  between the sliding blocks  6  and the boundary of the sliding channels  3  is closed, 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 feed gap  8  has now been closed, the control sleeve  1  can no longer participate in a further movement of the piston tube  23 . 
         [0042]    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  34  of the adjusting nut  25  comes out of engagement with the internal toothing system  5  of the control sleeve  1 . At the same time, however, the external toothing system  34  comes into engagement with the piston tube toothing system  33 . 
         [0043]    In the case of a further build up of pressure in the pressure space  30 , 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  22  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  33  and transmitted to the piston tube  23 . The torque passes to the housing  19  via the sliding blocks  6 . 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  1  is shown in  FIG. 3 . 
         [0044]    When the brake is released, the piston tube toothing system  33  is also released again from the external toothing system  34  of the adjusting nut  25 . At the same time, the external toothing system  34  of the adjusting nut  25  comes into engagement again with the internal toothing system  5  of the control sleeve  1 . 
         [0045]    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. 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. 
         [0046]    The braking process is initiated as in the case of a normal braking operation. The piston  22 , piston tube  23  and control sleeve  1  move together to the left. The control sleeve  1  participates in this movement until the feed gap  8  is closed. The internal toothing system  5  of the control sleeve  1  is then decoupled from the external toothing system  34  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  33  does not yet couple into the external toothing system  34  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  34  of the adjusting nut  25  is coupled neither to the internal toothing system  5  of the control sleeve  1  nor to the piston tube toothing system  33 , 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 . 
         [0047]    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  33  to the external toothing system  34  of the adjusting nut  25 . 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. 
         [0048]    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  32  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. 
       LIST OF DESIGNATIONS 
       [0000]    
       
           1  Control sleeve 
           2  Sliding sleeve 
           3  Sliding channel 
           4  Coupling ring 
           5  Internal toothing system 
           6  Sliding block 
           7  Fastening hole 
           8  Feed gap 
           9  Toothed ring 
           10  Connecting ring 
           11  Aperture 
           12  Step 
           13  Further exemplary embodiment of a control sleeve 
           14  Sliding sleeve 
           15  Coupling ring 
           16  Locking arm 
           17  Runner 
           18  Brake cylinder 
           19  Housing 
           20  Yoke 
           21  Fastening for brake caliper 
           22  Piston 
           23  Piston tube 
           24  Spindle 
           25  Adjusting nut 
           26  Piston return spring 
           27  Locking spring 
           28  Conical spring 
           29  Disk spring 
           30  Pressure space 
           31  Sliding band 
           32  Return hexagon 
           33  Piston tube toothing system 
           34  External toothing system of the adjusting nut