Abstract:
Various embodiments of an air spring end closure are disclosed. One has an outer part and an inner part joined together to provide a moment of inertia along an axis that is transverse to axial expansion and contraction of the air chamber that is greater than that of the outer part alone. Another has a part that is concave toward the chamber and contains one of a riser and a depression having a generally rectangular shape whose length runs transverse to the direction of expansion and contraction and that is widthwise centered on a diameter of the part. Still another has a part having an elliptical perimeter margin curled onto a similarly shaped axial end of a sleeve that provides the axial expansion and contraction.

Description:
TECHNICAL FIELD 
     The general subject matter of this disclosure relates to pneumatic springs that are used as components of suspensions in wheeled vehicles, such as suspensions for axles or bogies in large vehicles, a tractor-trailer being one example of such a vehicle. More particularly, the disclosure relates to top end closures of such springs that provide for attachment of the springs to an underbody of a vehicle, such as to a chassis frame of such a vehicle. 
     BACKGROUND OF THE DISCLOSURE 
     An example of a pneumatic spring (sometimes called an air spring because of the common use of air as the medium that fills the spring interior) comprises a top closure, a bottom closure, and a generally cylindrical flexible sleeve or bellows whose opposite ends are closed by the respective closures. The top closure is attached to an underbody component of a vehicle, such as a chassis frame rail or a structural floor rail that may be integrated with the vehicle body. The bottom closure is attached to a suspended component, such as an axle or bogie, containing wheels on which the vehicle travels. While various constructions for sleeves and bellows are known, they share a common characteristic of being gas-impermeable for containing a gas under pressure and retaining their general shape while contracting and expanding with motion of the closures toward and away from each other as the unsprung mass moves toward and away from the sprung mass. 
     Each closure is sealed to the respective end of the sleeve or bellows in a suitably appropriate fluid-tight manner to create a fluid-tight chamber that can expand and contract in length. The top closure typically contains a port through which a gas, such as air, can be introduced into or vented from the closed interior of the spring to set a suitable interior pressure. 
     It is known to fabricate closures from various materials that include metals and synthetics. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure relates to top closures of air springs that possess increased rigidity that allow an air spring to be fastened to a frame rail or other structural component of a sprung mass without additional external reinforcements, such as additional external brackets and/or plates for fastening the spring to the sprung mass. 
     The disclosed closures have increased cross sectional moments of inertia in certain planes by imparting an arch, cone, or domed shape to them for reducing the tensile loads and stresses in the closure material. 
     The closures may comprise any of various materials such as metals, plastics, composites, etc. and may be fabricated by any of various manufacturing processes (stamping, forming, molding, etc.). 
     A general aspect of this disclosure relates to a pneumatic spring comprising a pneumatic chamber comprising a cylindrical wall that is expansible and contractible along an axial direction and closed at opposite axial ends by respective closures, one of the respective closures comprising an outer part and an inner part joined to the outer part to endow the one of the respective closures with a moment of inertia along an axis transverse to the axial direction that is greater than that of the outer part alone. 
     Another general aspect relates to a pneumatic spring a pneumatic chamber comprising a cylindrical wall that is expansible and contractible along an axial direction and closed at opposite axial ends by respective closures, one of the respective closures comprising a part that is concave toward the pneumatic chamber and that comprises one of a riser and a depression having a generally rectangular shape whose length runs transverse to the axial direction and that is widthwise centered on a diameter of the part. 
     Another general aspect relates to a pneumatic spring comprising a pneumatic chamber comprising a cylindrical wall that is expansible and contractible along an axial direction and closed at opposite axial ends by respective closures, one of the respective closures comprising a part having an elliptical perimeter margin, and the axial end of the cylindrical wall that is closed by the one of the respective closures comprises a margin with which the perimeter margin of the part joins. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a pneumatic spring mounted on a chassis frame rail. 
         FIG. 2  is a perspective view of the chassis frame rail from a different direction showing a formed reinforcement embodiment of pneumatic spring top plate that is a subject of this disclosure attached to the rail. 
         FIG. 3  is a view lengthwise of the chassis frame rail showing an arched embodiment of pneumatic spring top plate that is the subject of this disclosure. 
         FIG. 4  is a perspective view of the chassis frame rail from still another direction showing a domed clamshell embodiment of pneumatic spring top plate that is the subject of this disclosure attached to the rail. 
         FIG. 5  is a top plan view of the formed reinforcement embodiment of top plate shown in  FIG. 2 . 
         FIG. 6  is a cross section view taken in the direction of arrows  6 - 6  in  FIG. 5 . 
         FIG. 7  is a cross section view taken in the direction of arrows  7 - 7  in  FIG. 5 . 
         FIG. 8  is a top plan view of the arched embodiment of top plate shown in  FIG. 3 . 
         FIG. 9  is a cross section view taken in the direction of arrows  9 - 9  in  FIG. 8 . 
         FIG. 10  is a cross section view taken in the direction of arrows  10 - 10  in  FIG. 8 . 
         FIG. 11  is a perspective view of the arched embodiment of top plate shown by itself. 
         FIG. 12  is a top plan view of one part of the arched embodiment of top plate shown by itself. 
         FIG. 13  is a cross section view taken in the direction of arrows  13 - 13  in  FIG. 12 . 
         FIG. 14  is a cross section view taken in the direction of arrows  14 - 14  in  FIG. 12 . 
         FIG. 15  is a perspective view of the part shown in  FIGS. 12-14 . 
         FIG. 16  is a top plan view of the domed clamshell embodiment of top plate shown in  FIG. 4 . 
         FIG. 17  is a cross section view taken in the direction of arrows  17 - 17  in  FIG. 16 . 
         FIG. 18  is a cross section view taken in the direction of arrows  18 - 18  in  FIG. 16 . 
         FIG. 19  is a perspective view of the domed clamshell embodiment of top plate shown by itself. 
         FIG. 20  is a top plan view of one part of the domed clamshell embodiment of top plate shown by itself. 
         FIG. 21  is a cross section view taken in the direction of arrows  21 - 21  in  FIG. 20 . 
         FIG. 22  is a cross section view taken in the direction of arrows  22 - 22  in  FIG. 20 . 
         FIG. 23  is a perspective view of the part shown in  FIGS. 20-22 . 
         FIG. 24  is a top plan view of an elliptical clamshell embodiment of top plate. 
         FIG. 25  is a cross section view taken in the direction of arrows  25 - 25  in  FIG. 24 . 
         FIG. 26  is a cross section view taken in the direction of arrows  26 - 26  in  FIG. 24 . 
         FIG. 27  is a perspective view of the elliptical clamshell embodiment of top plate shown by itself. 
         FIG. 28  is a top plan view of a flat elliptical embodiment of top plate. 
         FIG. 29  is a cross section view taken in the direction of arrows  29 - 29  in  FIG. 28 . 
         FIG. 30  is a cross section view taken in the direction of arrows  30 - 30  in  FIG. 28 . 
         FIG. 31  is a perspective view of the flat elliptical embodiment of top plate shown by itself. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a representative mounting of a pneumatic spring  40  on a chassis frame rail  42 . Spring  40  comprises a top closure  44 , a bottom closure  46 , and a flexible cylindrical sleeve  48  whose opposite lengthwise ends are closed by the respective closures  44 ,  46 . 
     Rail  42  comprises a vertical web  50  and inwardly turned top and bottom flanges  52 ,  54 . A central portion of top closure  44  is fastened to bottom flange  54 . A central portion of bottom closure  46  is fastened to a suspended vehicle component, such as an axle or bogie, containing wheels on which the vehicle travels, such component being depicted generically as an unsprung mass M. 
       FIGS. 5-7  disclose a formed reinforcement top closure of spring  40  that comprises a flat circular plate  60 , a formed reinforcement bar  62 , and fastening elements  64 ,  66 . The outer perimeter of plate  60  comprises an endless curled lip  68  that is initially flat but is subsequently curled sufficiently to secure plate  60  to the top perimeter margin of sleeve  48  with fluid-tight sealing. The top perimeter margin of sleeve  48  typically has an internal bead encased in elastomeric material so that the curled lip entraps the encased bead while compressing elastomeric material surrounding the bead to provide the fluid-tight sealing. 
     Bar  62  has a length that along the middle of the bar&#39;s width lies on a diameter of plate  60  but that stops short of lip  68 , ending at lengthwise ends in curved edges  70 ,  72  as shown in  FIG. 5 . Bar  62  comprises a top wall  74  whose top surface as viewed in  FIG. 6  is disposed flat against the flat bottom surface of plate  60  but is interrupted by respective depressions  76 ,  78  running lengthwise of the bar to either side of the middle of the bar that lies on a diameter of the plate to corrugate top wall  74  so that the top surface of the wall comprises three separate, parallel zones. The widthwise margins of bar  62  comprise flanges  80 ,  82  that as shown in  FIGS. 2 and 7 , are turned downward from top wall  74  at a right angle and have narrowing tapers at their lengthwise ends. 
     Fastening element  64  comprises a head  64 H and an externally threaded shank  64 S. Head  64 H is disposed against the inside of top wall  74  midway of the width of the bar near one lengthwise end. Shank  64 S extends from head  64 H through aligned through-holes in both top wall  74  and plate  60 . 
     Fastening element  66  comprises a head  66 H and an externally threaded shank  66 S. Head  66 H is disposed against the inside of top wall  74  midway of the width of the bar near the other lengthwise end. Shank  66 S extends from head  66 H through aligned through-holes in both top wall  74  and plate  60 . Fastening element  66  is hollow to provide for a gas such as air to pass into and out of the interior of the spring. 
       FIG. 2  shows the formed reinforcement top closure disposed against the bottom surface of bottom flange  54  and fastened to that flange. Shanks  64 S,  66 S pass through respective holes in flange  54 , and fasteners  84 ,  86  ( FIGS. 5 and 7 ) are threaded onto shanks  64 S,  66 S and tightened. With the length of bar  62  arranged transverse to the length of rail  42  as in  FIG. 2 , increased rigidity is imparted to the portions of the closure that overhang inboard and outboard limits of flange  54 . 
       FIGS. 8-15  disclose an arched plate top closure of spring  40  that comprises a circular arched plate  100  that is basically concave toward the interior of sleeve  48 , fastening elements  102 ,  104 , and a port element  106 . The outer perimeter of plate  100  comprises a curled lip  108  that is curled sufficiently to secure plate  100  to the top perimeter margin of sleeve  48  with fluid-tight sealing in a manner similar to that described above for plate  60 . 
     For increased rigidity beyond that provided by its arched shape alone, plate  100  has a generally rectangular depression  110  whose length at the middle of the depression&#39;s width lies on a diameter of plate  100  but stops short of lip  108 . Depression  110  comprises a flat rectangular bottom wall  112  and side walls  114 ,  116 ,  118 ,  120  that incline upward from bottom wall  112  to merge with a downwardly concave zone  122  that is responsible for the arched, or domed, exterior appearance of plate  100  in spring  40 . At its crest, zone  122  comprises a rectangular area  124  that is flat except at its corners near lip  108  where it blends with areas of zone  122  that form the concave shape by curving downwardly away. 
     Fastening elements  102 ,  104 , which are assembled to plate  100  prior to assembly of the plate to the sleeve, comprise respective heads  102 H,  104 H and externally threaded shanks  102 S,  104 S. Head  102 H is disposed against the inside of plate  100  in area  124  midway of that area&#39;s width near one lengthwise end. Head  104 H is disposed against the inside of plate  100  in area  124  midway of that area&#39;s width near the opposite lengthwise end. Shanks  102 S,  104 S extend from the respective heads through respective through-holes in plate  100 . 
     Port element  106  comprises a head  106 H disposed against the inside of bottom wall  112  near one lengthwise end and an externally threaded shank  106 S passing through a through-hole midway of the width of wall  112 . Port element  106 , which is also assembled to plate  100  prior to assembly of the plate to the sleeve, is hollow to provide for a gas such as air to pass into and out of the interior of the spring. 
       FIG. 3  shows the arched top plate disposed against the bottom surface of bottom flange  54  and fastened to that flange. Shanks  104 S,  106 S pass through respective holes in flange  54 , and fasteners  126 ,  128  ( FIGS. 8 and 9 ) are threaded onto shanks  104 S,  106 S and tightened. While the general concave shape of the arched top plate provides rigidity, the inclusion of depression  110  provides even more. With the length of depression  110  arranged transverse to the length of rail  42  as in  FIG. 3 , increased rigidity is imparted to the portions of the closure that overhang inboard and outboard limits of flange  54 . Port element  106  is present in  FIG. 3 , but not specifically shown. 
       FIGS. 12-15  show plate  100  by itself after it has been formed out of a metal, such as steel, by a metal forming process such as stamping. The perimeter margin is however shown having been curled instead of being flat as it would be after having been stamped but before assembly to sleeve  48 . 
       FIGS. 16-23  disclose a circular domed clamshell top closure of spring  40  that comprises a formed outer circular plate  130  and a formed inner circular plate  132  that are cooperatively associated. While plate  130  is formed to be basically downwardly concave, it is formed to include features that interrupt its basically domed shape. One feature is a depression  134  similar to depression  110  in plate  100 . Two additional features are elevated plateaus  136 ,  138 , which are located centrally in respective halves of the dome that are separated by depression  134 . 
     While plate  132  is formed to be basically slightly upwardly concave, it is formed to include a generally rectangular raised zone  140  whose shape approximately matches that of depression  134  so that when the two plates are assembled together to form the top closure of the spring, a top wall of raised zone  140  will abut the bottom wall of depression  134 . 
     Prior to assembly of the two plates to each other, and while the outer perimeter margin of each is still flat and not yet formed to final shape, fastening elements  142 ,  144  are assembled to outer plate  130  so as to place their respective heads  142 H,  144 H against the inside of the plate  100  near respective lengthwise ends of elevated plateaus  136 ,  138  with their shanks  142 S,  144 S extending through through-holes in the plate. 
     The two plates are then placed together with their flat perimeter margins in mutual abutment and with the top wall of zone  140  and the bottom wall of depression  134  also in mutual abutment. A head  146 H of a port element  146  is disposed against the bottom of the top wall of zone  140  with its threaded shank  146 S passing through aligned through-holes in the top wall of zone  140  and the bottom wall of depression  134 . A fastener  148  is threaded onto shank  146 S and tightened. The head  150 H of a fastening element  150  is placed against the inside of the top wall of raised zone  140  near the opposite lengthwise end from port element  146  with its shank  150 S extending through aligned through-holes in the two plates. A threaded fastener  151  is shown threaded onto shank  150 S. An auxiliary bracket (not shown) could be held secure on shank  150 S via fastener  151  at fastened to the chassis frame to provide added support and/or allow the closure to be made of thinner gauge material. 
     Then the abutted perimeter margins of the two plates are curled to form a two-lamina curled lip  152  securing the domed clamshell closure to the top end of sleeve  48 . Port element  146  is hollow to provide for a gas such as air to pass into and out of the interior of the spring. 
       FIG. 4  shows the domed clamshell top closure disposed against the bottom surface of bottom flange  54  and fastened to that flange. Shanks  142 S,  144 S pass through respective holes in flange  54 , and fasteners  156 ,  158  are threaded onto shanks  142 S,  144 S and tightened. Because the lengths of depression  134  and raised zone  140  are arranged transverse to the length of rail  42  as in  FIG. 4 , they, in conjunction with the two-plate domed structure, impart rigidity to the portions of the closure that overhang inboard and outboard limits of flange  54 . 
       FIGS. 24-27  disclose an elliptical domed clamshell top closure that comprises a downwardly concave outer elliptical plate  160  and an upwardly concave inner elliptical plate  162  cooperatively associated. Plate  160  is formed to be nominally downwardly concave as viewed along both major and minor elliptical axes, however its formation includes an elevated plateau  164  having a length that at the middle of the plateau&#39;s width is centered on the major elliptical axis. 
     Prior to assembly of the two plates to each other, and while the outer perimeters of each are still flat and not yet formed to final shape, fastening elements  166 ,  168  are assembled to outer plate  160  so as to place their respective heads  166 H,  168 H against the inside of the plate  160  near respective lengthwise ends of the top wall of plateau  164  with their shanks  166 S,  168 S extending through respective through-holes in the plate. Then a head  170 H of a hollow port element  170  is disposed against the domed portion of plate  160  to one side of plateau  164  and centered on the minor axis with its threaded shank  170 S passing through a through-hole in plate  160 . 
     The two plates  160 ,  162  are then placed together with their flat perimeter margins in mutual abutment. The abutted perimeter margins are then curled to form a two-lamina curled lip  172  securing them together as they cooperatively secure the closure to the top end of sleeve  48 . 
     Port element  170  is hollow to provide for a gas such as air to pass into and out of the interior of the spring by passing through the space bounded by the plates and one or more through-holes, such as through-hole  174 , in inner plate  162 . 
     The elliptical domed clamshell top closure is disposed against the bottom surface of bottom flange  54  and fastened to that flange. Shanks  166 S,  168 S pass through respective holes in flange  54 , and fasteners  176 ,  178  are threaded onto shanks  166 S,  168 S and tightened. The two-plate domed structure imparts rigidity to the portions of the closure that overhang inboard and outboard limits of flange  54 . 
       FIGS. 28-31  disclose a flat elliptical top closure of spring  40  that comprises a flat elliptical plate  180  and fastening elements  182  and  184 . The outer perimeter of plate  180  comprises an endless curled lip  186  that is curled sufficiently to secure plate  180  to the top perimeter margin of an elliptical sleeve  48  with fluid-tight sealing. 
     Fastening elements  182 ,  184  comprise respective heads  182 H,  184 H and externally threaded shanks  182 S,  184 S. Head  182 H is disposed against the inside of plate  180  on the major axis near one lengthwise end with shank  182 S extending through a through-hole in the plate. Head  184 H is disposed against the inside of plate  180  on the major axis near the opposite lengthwise end with shank  184 S extending through a through-hole in the plate. 
     A head  188 H of a hollow port element  188  is disposed against the inside of plate  180  to one side of the major axis centered on the minor axis with its threaded shank  188 S passing through a through-hole in the plate. 
     The flat elliptical top closure is disposed against the bottom surface of bottom flange  54  and fastened to that flange. Shanks  182 S,  184 S pass through respective holes in flange  54 , and fasteners  190 ,  192  are threaded onto the respective shanks and tightened. 
     While the illustrated embodiments are disclosed as being fabricated from a formable material, such as a steel, that allows their perimeters to be curled for attachment to an end of a sleeve or bellows, the basic shapes may have other perimeter geometries for enabling attachment to an end of a sleeve or bellows. Some of the disclosed embodiments, such as those shown in  FIGS. 2 ,  5 - 7  and  FIGS. 4 ,  16 - 19 , may avail themselves of the use of an auxiliary bracket (not shown) to attach to the chassis frame. In all embodiments, the attachment of the closure to the sleeve or bellows is properly sealed against air leakage, and any fasteners or vents passing through holes in a closure are also properly sealed to the closure.