Abstract:
The invention relates to a pneumatic spring ( 1 ) comprising a roll bellow ( 3 ) which is secured to an unrolling tube ( 7 ) and which forms a spring space therewith ( 9 ). The unrolling tube ( 7 ) is connected to a base part ( 11 ) by means of a ball joint ( 13 ) which comprises a spherical bearing element ( 15 ) contained in the bearing shell. The bearing shell ( 17 ) can be adjusted in relation to the spherical bearing element ( 15 ) by means of a clamping element ( 25 ).

Description:
TECHNICAL AREA 
       [0001]    The invention pertains to a pneumatic spring according to the introductory clause of claim  1 . 
       PRIOR ART 
       [0002]    FIG. 6 of DE 199 59 839 A1 shows a pneumatic spring with a rolling bellows attached to a roll-down tube. A ball joint is installed between a base part—in this case, a vibration damper—and the roll-down tube. The ball joint consists of a spherical bearing element, which is located in a two-part bearing shell. A seal, which seals off the spring space of the pneumatic spring, is present between the two halves of the bearing shell. 
         [0003]    In this ball joint, dimensional deviations lead to increased internal friction or, in the other extreme case, in which the seal is not adequately pretensioned between the bearing shells, to the generation of noise and to leakage. 
         [0004]    The task of the present invention is to improve the ball joint especially intended for pneumatic springs in such a way that the problems familiar from the prior art with respect to friction and leakage are eliminated. 
       DESCRIPTION OF THE INVENTION 
       [0005]    According to the invention, the task is accomplished in that the bearing shell can be tightened onto the spherical bearing element by means of a clamping element. 
         [0006]    The bearing play between the bearing shell and the spherical bearing element can be adjusted precisely to the desired value, so that the friction problem is solved. 
         [0007]    In a concrete embodiment of the invention, the bearing shell has a conical gripping surface on the outside, against which the clamping element acts. The clamping element exerts an axial tensioning movement which reduces the diameter of the bearing shell. 
         [0008]    So that the bearing shell will be radially pretensioned in a uniform manner, the clamping element is formed by a tension ring. The clamping element is braced against a support sleeve and is itself therefore well centered. 
         [0009]    The spherical bearing element, the bearing shell, the tension ring, and the support sleeve form a closed structural unit, because the support sleeve cooperates with an additional gripping surface on the bearing shell, which, relative to the equator of the spherical bearing element, is opposite the first gripping surface. 
         [0010]    So that the bearing shell can be adjusted in a continuously variable manner, a threaded joint is present between the clamping element and the support sleeve. 
         [0011]    The bearing shell is elastic, so that the adjusting forces which must be exerted on the tension ring remain with limits. If, for example, the friction increases because of the heating of the ball joint, the tension ring can be loosened slightly. The bearing shell, because of its intrinsic elasticity, will assume an appropriately modified contour. 
         [0012]    The bearing shell, furthermore, is designed as a one-piece part. Making the shell in one piece offers a considerable advantage with respect to fabrication. The bearing shell is pushed over the spherical bearing element, and after this they cannot come apart. 
         [0013]    So that a basically inelastic material can also be used for the bearing shell, the bearing shell is slotted. Either one slot extending longitudinally or several slots, which proceed from one end of the bearing shell to a point past the equator of the spherical bearing element can be provided. 
         [0014]    In another advantageous embodiment, a seal separates the spring space from the bearing shell. The pretension of the bearing shell is therefore independent of the pretension of the seal, so that there can be no conflict between the goal of obtaining the desired bearing play and the goal of sealing the pneumatic spring effectively. 
         [0015]    The seal is designed as a lip seal, which is pretensioned onto the spherical bearing element as a function of the pressure inside the spring space. The seal is held in place axially between the roll-down tube and the support sleeve, so that there is no need to machine a separate sealing groove into the roll-down tube for the seal. 
         [0016]    The support sleeve is held in place radially by the roll-down tube and is held in place axially by a retaining ring on the roll-down tube. During assembly, the ball joint unit is simply pushed into the roll-down tube and attached by means of the previously mentioned retaining ring. 
         [0017]    According to an advantageous application, the base part is formed by a vibration damper, which passes through the spherical bearing element. 
         [0018]    The ball joint is simply set down on top of the base part. To prevent leaks, a seal is placed between the base part and the spherical bearing element. 
         [0019]    It should be possible to adjust the bearing play inside the ball joint quickly and easily, nor should any damage be thus caused. For this reason, the clamping element is provided with flats for a wrench. 
         [0020]    In certain applications of the ball joint with a pneumatic spring, it would be possible for dirt particles from the vehicle to intrude into the ball joint. So that this cannot occur with the inventive ball joint, it is covered by a protective bellows. 
         [0021]    If it is necessary to remove the ball joint to allow repairs, one end of the protective bellows, which is attached to the tension ring, can be removed very easily to provide free access to the ball joint. A simple spring clamp holds the end of the protective bellows firmly in place on the tension ring. 
     
    
     
       SHORT DESCRIPTION OF THE FIGURES 
         [0022]    The invention is to be explained in greater detail on the basis of the following description of the figures: 
           [0023]      FIG. 1  shows an overall view of a pneumatic spring with a vibration damper; 
           [0024]      FIG. 2  shows a transverse section of a ball joint assembly; and 
           [0025]      FIGS. 3 and 4  show views of the bearing shell of the ball joint. 
       
    
    
       [0026]      FIG. 1  shows a pneumatic spring  1  with a rolling bellows  3 , the upper end of which is supported on a connecting plate  5 . The other end of the rolling bellows is attached to a roll-down tube  7 . The rolling bellows and the roll-down tube form the boundaries of a spring space  9 , which is connected to a compressed air supply (not shown). Between the roll-down tube  7  and a base part in the form of a known vibration damper  11 , a ball joint  13  is provided, which is shown as an isolated assembly in  FIG. 2 . 
         [0027]    It can be seen in  FIG. 2  that the ball joint has a spherical bearing element  15 , which makes possible rotational movements in the circumferential direction in a bearing shell  17  and also makes it possible for the spherical bearing element to execute pivoting movements relative to a longitudinal axis  19 . The bearing shell  17  is designed as a one-piece part, as can be seen in  FIGS. 3 and 4 . The bearing shell, furthermore, is elastic especially in the radial direction, so that it can be pushed over the spherical bearing element  15  during installation. The bearing shell has slots  21 , which extend from the upper end to a point beyond the equator  23  (see  FIG. 2 ). Alternatively, it is also possible to provide a single continuous slot, such as that shown in broken line. 
         [0028]    The bearing shell  21  can be adjusted with respect to the spherical bearing element  15  by means of a clamping element  25 . The clamping element  25  is formed in part by a tension ring  27 , which is braced against a support sleeve  29 . Between the clamping element, i.e., the tension ring  27 , and the support sleeve  29  there is a threaded joint  31 , which makes it possible for the tension ring to be moved axially with respect to the support sleeve in a continuously variable manner. On the outside, the bearing shell has a conical first gripping surface  33  (see also  FIG. 4 ), on which the tension ring  27  acts. The support sleeve  29  cooperates with another gripping surface  35  on the bearing shell  17 , which, relative to the equator  23  of the spherical bearing element  15 , is opposite the first gripping surface  33 . 
         [0029]    The spherical bearing element  15 , the bearing shell  17 , the tension ring  27 , and the support sleeve  29  form a closed ball joint assembly, which can be adjusted after installation. For this purpose, the tension ring has flats  37  for a wrench to make it easier to turn the tension ring with respect to the support sleeve. The two gripping surfaces  33 ,  35  of the tension ring and the support sleeve are deformed toward the spherical bearing element  15 , as a result of which the ball joint can be adjusted precisely with respect to its bearing play. 
         [0030]    The spherical bearing element has a through-opening  39  to hold the vibration damper  11  ( FIG. 1 ). In the direction facing the vibration damper, the ball joint is covered by a protective bellows  41 , which is attached at one end to the tension ring  27  by means of a locking ring  43 . 
         [0031]    During the assembly of the pneumatic spring, the previously mentioned unit is threaded onto the vibration damper  11 . An angle ring  45  is attached to the vibration damper  11 , and a seal  47 , attached to the vibration damper, is provided between the spherical bearing element  15  and the base part  11 , i.e., the angle ring, to prevent leakage between the ball joint  13  and the vibration damper. In a further step of the assembly process, a seal  49  is mounted on the end surface of the support sleeve  29 ; this seal separates the spring space  9  from the bearing shell  17 . The seal  49  is designed as a lip seal, which is pretensioned onto the spherical bearing element  15  as a function of the pressure inside the spring space  9 . 
         [0032]    Then the roll-down tube  7  is pushed onto the support sleeve  29  from the direction of the piston rod  51  of the vibration damper  11 , so that the seal  49  is held in place axially between the roll-down tube  7  and the support sleeve  29 . The support sleeve in turn is held in place radially by the roll-down tube and is fixed axially by retaining ring  53 . 
         [0033]    So that the vibration damper  11  cannot fall out of the ball joint  13 , a retaining ring  55  is accommodated in a groove  57  ( FIG. 2 ) between the angle ring  45  and the spherical bearing element  15 . To remove the retaining ring  55 , an axial slot  59  is provided in the groove  57 ; this groove provides access for a tool, which can press the retaining ring out of the groove  57 . Then the protective bellows  41  is mounted and held in place by the locking ring. 
         [0034]    Because of the ball joint with optimal bearing play, the module consisting of the pneumatic spring and the vibration damper now present can be used to compensate for cardanic movements between, for example, a vehicle axle and a vehicle body, in a manner characterized not only by low friction but also by the absence of leakage.