Abstract:
The invention relates to a pneumatic spring system which comprises a pneumatic spring cap and pneumatic cushioning bellows, a pneumatic spring piston with a lateral rolling surface and a base surface that is designed such that a multi-chamber system protrudes into the interior of the pneumatic spring piston. The aim of the invention is to provide a pneumatic spring piston that can be subjected to eccentric loads at a reduced weight and without a holding plate. The multi-chamber system and the fastening system are mounted in such a position that there is maximally one mirror plane perpendicular to the base surface of the pneumatic spring piston, in relation to the piston center axis, and that an eccentric rest surface of the pneumatic spring piston directly contacts the spring carrier.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Applicants claim priority under 35 U.S.C. §119 of German Application No. 199 31 198.6 filed Jul. 7, 1999. Applicants also claim priority under 35 U.S.C. §120 of PCT/DE00/02035 filed Jun. 23, 2000. The international application under PCT article 21(2) was not published in English. 
    
    
     DESCRIPTION 
     The invention relates to a pneumatic spring system comprising at least the following structural components, specifically 
     a pneumatic spring cover and a pneumatic spring bellows; 
     a pneumatic spring piston which in particular is made of plastic or aluminum, and which comprises a face area that is arranged opposite the pneumatic spring cover; a lateral roll-off surface for the pneumatic spring bellows to roll off on, and a base area that is designed in such a way that a multi-chamber system projects into the interior of the pneumatic spring piston; 
     a first fastening system, which is arranged within the base area of the pneumatic spring piston; as well as 
     a reinforcement, in particular a longitudinal guiding rod or element with which the base of the pneumatic spring piston is anchored by the means of the first fastening system as well as an additional second fastening system. 
     A pneumatic spring system of said type is described, for example in published patent document EP 0 501 043 B1 (FIG.  2 ). 
     The pneumatic spring piston, which is referred to also as the roll-off piston or immersion piston, is made of steel, plastic or aluminum, whereby the two last-mentioned materials are increasingly finding preferred use because of their lower weight as compared to steel. Furthermore, the multi-chamber system of the pneumatic spring piston comprises a ring chamber in most cases, which extends within the edge zone of the base area, forming an annular outer edge and an inner edge; and one or a plurality of core chambers defined by bridges, such core chamber or chambers being arranged within the inner edge of the ring chamber. In addition, the pneumatic spring piston has the largest diameter in most cases within the zone of its base area, so that a widening is formed in this way. 
     The pneumatic spring pistons known heretofore are constructed in such a way that they have a plurality of mirror planes in conjunction with a central support body. Pneumatic spring pistons that are rotation-symmetrical in relation to the center axis of the piston are known as well. 
     Now, two variations exist with respect to the stress acting on the pneumatic spring piston: 
     The pneumatic spring piston is stressed centrically. 
     The pneumatic spring piston is stressed eccentrically, which is the case in particular in conjunction with a longitudinal guiding rod serving as the spring support. This could be accomplished until now in conjunction with the piston construction described above only with the help of a holding plate made of steel, which is secured on the base of the pneumatic spring piston especially when a pneumatic spring piston made of plastic is used. 
     Now, the problem of the invention is to provide a pneumatic spring system of the type specified above, in conjunction with which the pneumatic spring piston can be stressed eccentrically while omitting a holding plate and achieving at the same time a reduction of the weight. 
     Said problem is solved according to the characterizing part of claim  1  in that 
     the multi-chamber system and the first fastening system are arranged in a way such that only one mirror plane at the most is present vertically in relation to the base of the pneumatic spring piston, namely with respect to the center axis of the piston, with formation of an eccentric support surface for the pneumatic spring piston with direct contact with the spring support. 
     Advantageous design variations of the pneumatic spring system as defined by the invention are specified in claims  2  to  27 . 
    
    
     Now, the invention is explained in the following with the help of exemplified embodiments and by reference to five drawings, in which: 
     FIGS. 1,  2  show two particularly advantageous construction variations of the multi-chamber system. 
     FIG. 3 shows a pneumatic spring piston made of plastic, with a metal insert cooperating with a spring support; 
     FIGS. 4,  5  show two different views of a metal insert consisting of a threaded component and a reinforcing rib. 
    
    
     The following list of reference numerals and symbols applies in conjunction with said figures: 
       1 , 1 ′, 1 ″ Pneumatic spring piston 
       2 , 2 ′, 2 ″ Base area of the pneumatic spring piston 
       3 , 3 ′, 3 ″ Face area of the pneumatic spring piston 
       4 , 4 ′, 4 ″ Roll-off surface of the pneumatic spring piston 
       5 , 5 ′, 5 ″ Ring chamber 
       6 , 6 ′, 6 ″ Outer edge of ring chamber 
       7 , 7 ′, 7 ″ Inner edge of ring chamber 
       8 , 8 ′, 8 ″ Core chambers 
       9 , 9 ′ Main bridge 
       10 , 10 ′ Fastening bridge 
       11 , 11 ′, 11 ″ First fastening system 
       12  Outer bridge (perpendicular to main bridge) 
       13  Inner bridge (perpendicular to main bridge) 
       14  Transverse bridge (parallel with main bridge) 
       15  Outer bridge (inclined relative to main bridge) 
       16  Inner bridge (inclined relative to main bridge) 
       17  Head chamber 
       18  Bridge (with curved shape 
       19  Spring arm (longitudinal guiding element) 
       20  Support surface 
       21  Bore drilled in spring arm 
       22  Longitudinal outer edge of spring arm 
       23  Threaded part of metal insert 
       24  Reinforcing rib of metal insert 
       25  Bores within the reinforcing rib 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 A, B, C, D 
                 Ring chamber segments 
               
               
                   
                 H 
                 Overall height of pneumatic spring piston 
               
               
                   
                 S 
                 Center axis of piston 
               
               
                   
                 X 
                 Mirror plane 
               
               
                   
                   
               
             
          
         
       
     
     FIG. 1 shows a pneumatic spring piston  1  with the base  2 , the face  3 , the latter being arranged opposite the pneumatic spring cover, as well as with the lateral roll-off surface  4 , on which the pneumatic spring bellows can roll off. Within the zone of its base area  2 , the pneumatic spring piston has its largest diameter, with formation of a widening. Furthermore, the base area  2  is designed in such a way that a multi-chamber system projects into the interior of the pneumatic spring piston. 
     The multi-chamber system comprises a ring chamber  5 , which is arranged within the marginal zone of the base area  2  with formation of a ring-shaped outer edge  6  and an inner edge  7 . Furthermore, several core chambers  8  are present, said core chambers being defined by bridges and being located within the inner edge  7 . 
     The base area  2  of the pneumatic spring piston has a through- and straight-extending main bridge  9 , which is connected with the center zone of the base area, but which does not extend through the center axis “S” of the piston. No central support body is provided within the direct zone of the center axis “S” of the piston. 
     Furthermore, the base area  2  of the pneumatic spring piston has the two fastening bridges  10  with an area size adequate for receiving the first fastening system  11 . The two fastening bridge connect in this conjunction the outer edge  6  and the inner edge  7  of the ring chamber  5 , specifically with inclusion of the main bridge  9 , forming in this manner the four ring segments A, B, C and D. 
     The main bridge  9  in turn is connected with a system of four bridges extending perpendicular to the main bridge, with formation of the two outer bridges  12  and the two inner bridges  13 . Said bridges are arranged in this conjunction with about the same spacing between each other and exclusively extend from the inner wall  7  to the inner wall of the ring chamber  5 . The two outer bridges  12  as well as the main bridge  9  each change in this conjunction with a wide surface area into the fastening bridge  10 . Furthermore, the two inner bridges  13  are connected by a transverse bridge  14 , which extends parallel with the main bridge  10 , clamping the center axis “S” of the piston. 
     The pneumatic spring piston  1  is constructed in such a way that one single mirror plane “X” is present perpendicular to the base area  2 , specifically as opposed to the designs known until now. 
     The pneumatic spring piston  1 ′ according to FIG. 2 is different from the pneumatic spring piston  1  according to FIG. 1 in that the core chambers  8 ′ are designed in another way. 
     A total of four bridges, specifically the two outer bridges  15  and the two inner bridges  16  extend within the inner edge  7 ′ of the ring chamber  5 ′ inclined in relation to the main bridge  9 ′, specifically with formation of a fan-shaped structure. Said four bridges extending in the form of a fan merge in this conjunction in the area of the inner edge  7 ′ of the ring chamber  5 ′ in the form of a common meeting point, whereby a head chamber  17  is present within said meeting point. Said head chamber is outwardly defined by the inner edge  7 ′ of the ring chamber  5 ′. Said head chamber is located about half way between the two fastening bridges  10 ′. 
     Furthermore, the bridges extending in the form of a fan are connected with each other by a bridge  18  extending in a curved manner. Said bridge extends in this conjunction from the fastening bridge  10 ′ to the fastening bridge. Within the area of the two outer bridges  15 , the curved bridge  18  furthermore extends through the main bridge  9 ′, with formation of a total of two areas of intersection. 
     Said pneumatic spring piston  1 ′, too, is constructed in such a way that one single mirror plane “X” is present perpendicular to the base area  2 ″. Furthermore, in the present case, too, no central support body is present within the immediate range of the center axis “S” of the piston. 
     FIG. 3 shows a pneumatic spring piston  1 ″ made of plastic, in particular from glass fiber-reinforced plastic, which rests with direct contact on the spring support  19 , which is referred to also as a rocking arm (or rocker). An eccentric support surface  20  is formed in this conjunction with respect to the center axis “S” of the piston, said support surface being part of the base area  2 ″. Said support surface is at the same time the fastening surface because the first fastening system  11 ″ is located within said area. Said first fastening system is connected in a fixed manner with a second fastening system (e.g. a screw) via a drilled hole  21  located in the spring arm  19 . 
     The main bridge  9  (FIG. 1 or  9 ′ (FIG. 2) extends in particular parallel with the longitudinal outer edge  22  of the spring support  19 , specifically in a way such that the main bridge is located within the support area  20  of the pneumatic spring piston  1 ″, whereby the edges of the main bridge and the spring support are substantially aligned with each other. 
     The depth of the core chambers  8 ″ amounts to at least ⅔ of the overall height “H” of the pneumatic spring piston  1 ″. 
     FIGS. 4 and 5 again show details of the first fastening system  11 ″ according to FIG. 3 viewed from two different aspects. 
     In the present case, the first fastening system  11 ″ is a metal insert, which in turn consists of a threaded part  23  and a reinforcing rib  24 . Furthermore, the reinforcing rib has a number of horizontally extending bores  25 . 
     The fastening system  11 ″ is particularly suited for a pneumatic spring piston made of plastic, whereby the plastic extends through the bores  25  in a material-locked matter. It is possible also to provide for holding ribs instead of using such bores. 
     The fastening system  11 ″ offers the advantage that the stress within the environment of the threaded part  23  is reduced. Furthermore, the reinforcing rib  24  provides for a reduction in the deformation of the piston, which is important when a plastic material us used. This assures a long useful life of the pneumatic spring system. 
     If necessary, it is possible also to employ as the first fastening system simple threaded bores or threaded bushes for receiving the second fastening system, especially when a pneumatic spring piston made of metallic materials is used.