Abstract:
An air spring ( 1 ) has a cylindrical flexible sleeve ( 2 ) secured at each end to form a fluid chamber ( 14 ). One end ( 6 ) of the sleeve ( 2 ) is secured to a retainer ( 8 ). The retainer ( 8 ) has a ribbed reinforcement structure ( 16 ) which allows the air spring ( 1 ) to be directly mounted to a moveable part of a vehicle or other machinery. The retainer ( 8 ) has an extending mounting structure ( 13 ) on one side of the reinforcement structure ( 16 ) and a bead-seating surface ( 12 ) adjacent to the reinforcement structure ( 16 ).

Description:
FIELD OF THE INVENTION 
     The present invention is directed toward a retainer for an air spring. More particularly, the present invention is a thermoplastic upper retainer for an air spring which provides for easy air spring assembly and mounting. 
     BACKGROUND OF THE INVENTION 
     Air springs have been used for motor vehicles and various other machines and equipment for a number of years. The springs provide cushioning between movable parts, primarily to absorb shock loads imparted thereon. The air spring consists of at least one flexible elastomeric reinforced sleeve extending between a pair of retainers, forming a pressurized chamber therein. The sleeve typically has a relatively inextensible bead core at each end for securing the sleeve to the retainers. Alternatively, the sleeve may be secured to the retainers by conventional crimping means. There may be one or more pistons associated with the air spring. The retainers also assist in securing the air spring on spaced components or parts of the vehicle or equipment by being secured to a mounting plate which is attached to the moveable part of the vehicle or machine. 
     The fluid in the pressurized chamber, generally air, absorbs most of the shock impressed upon or experienced by one of retainers. The retainers move towards and away from each other when the air spring is subjected to any forces. 
     Both upper and lower retainers are conventionally formed of stamped metal. If the air spring has a piston, the piston, upon which the lower retainer is secured, may be metal or thermoplastic. A bumper, mounted on either retainer and provided for impact absorption and transference, is usually thermoplastic or thermoelastic, depending upon the forces which will ultimately be acting on the air spring and the forces to which the bumper will be subjected. 
     When the air spring is mounted to a vehicle, a subassembly made from coated steel stampings and plumbing components are used to achieve the mounting attachment, air connection and airsleeve bead captivation. Such conventional mounting means are illustrated in the following U.S. Pat. Nos. 5,203,585; 5,464,245; 5,403,031, 5,346,247, and 4,733,876 (which has a two material upper retainer which has a mounting structure rising from two cojoined flat plates). Other known air springs and retainers are disclosed by U.S. Pat. No. 5,535,994 and EP 295,392. 
     SUMMARY OF THE INVENTION 
     The present invention is directed toward providing a lightweight, low cost means of easily attaching the air supply end of the air spring directly to a suspension frame rail of a vehicle. 
     The present invention is an improved air spring for absorbing and transmitting shock loads between parts moveable relative to one another. The air spring comprises a flexible cylindrical sleeve which is secured at each end to form a fluid chamber therein. One end of the sleeve is secured to a retainer. The retainer has a ribbed reinforcement structure which allows for direct mounting of the airspring to one of the moveable parts. 
     The ribbed reinforcement structure of the disclosed retainer is comprised of a plurality of ribs. In an alternative construction, the ribs may run the full length of the reinforcement structure. The ribs may also be at least two sets of ribs, with the ribs extending at different angles relative to each other. 
     The disclosed retainer has an axially extending mounting plate for directly mounting the air spring to the moveable part. 
     The disclosed retainer also has a bead seating surface. The bead seating surface is adjacent to the ribbed reinforcement structure. 
     The disclosed retainer is formed from a thermoplastic material having a tensile strength in the range of 1965 to 3165 kg/cm 2  (28,000 to 45,000 psi), and a flex strength in the range of 2810 to 4220 kg/cm 2  (40,000 to 60,000 psi). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described by way of example and with reference to the accompanying drawings in which: 
         FIG. 1  is a half cross-sectional view of an air spring with the inventive upper retainer; 
         FIG. 2  is a perspective view of the inventive retainer; 
         FIG. 3  is a side view of the upper retainer; 
         FIG. 4  is a top view of the retainer; 
         FIG. 5  is a bottom view of the retainer; and 
         FIG. 6  is a cross-section view of the retainer through line  6 — 6  of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is illustrated within an assembled air spring  1  in  FIG. 1 . The air spring  1  has a cylindrical elastomeric sleeve  2 . The elastomeric sleeve  2  is preferably comprised of at least 3 plies: an outer elastomeric ply  3 , at least one reinforcing ply  4  formed of elastomeric embedded reinforcing cords, and an inner elastomeric ply  5 . The upper end  6  of the sleeve  2  has a relatively inextensible bead  7  for securing the airsleeve  2  to the inventive upper retainer  8 . The bead core  7  is at least one continuous winding of wire, preferably steel. The configuration of the bead core  7  may vary as is conventionally known. The lower end  9  of the airsleeve  2  may also be defined by a bead core  10  for securing the lower end  9  of the airsleeve  2 . 
     The lower end  9  of the airsleeve  2  is secured to a piston  11 . The lower end  9  of the airsleeve  2  may be secured in any conventional manner, including, but not limited to, crimping the lower end  9  of the airsleeve  2  to the piston or to a conventional lower retainer or by securing the bead core  10  by a lower retainer. An internal bumper may be provided for absorbing impact forces. When the air spring  1  is in use, the upper retainer  8  moves in an axial direction and the sleeve  2  travels up and down the outside of the piston  10 . 
     The inventive upper retainer  8 , seen illustrated in  FIGS. 2 to 6 , is a unitary article, provided with both bead seating means  12  and mounting means  13 . The underside of the retainer  8  is defined by the bead seating surface  12 , see  FIG. 3 . At the axially innermost edge of the bead seating surface  12 , relative to the air chamber  14  formed within the air spring  1 , is a bead retention lip  15 . The bead retention lip  15  has a radial width of at most 10 mm, and is preferably in the range of 2 mm to 6 mm. The width of the bead retention lip  15  is greater than zero to prevent the bead  7  from dismounting and disengaging from the retainer  8  under low-pressure operation of the air spring  1 . If the bead retention lip  15  has a radial dimension greater than 10 mm, then the bead  7  cannot be press-fitted onto the retainer  8  without damage to either the airsleeve  2  or the bead  7  due to the highly inextensible nature of the bead. In mounting the bead  7  to the retainer  8 , the bead  7  is held onto the retainer  8  by the interference fit between the bead seating surface  12  and the air spring bead  7  to effect a seal. The radius of the bead seating surface  12  is less than the greatest radius of the retainer  8 , but greater than the radius of the air spring bead  7 . 
     The intermediate reinforcement section  16  of the air spring retainer  8  is defined by a plurality of ribs  17  which extend the length or width of the intermediate reinforcement section  16  of the retainer  8 . The ribs  17  are located between the outer plate  18  and the inner plate  19 . A preferred embodiment of the ribs  17  is illustrated in  FIGS. 2 ,  3  and  6 . As seen most clearly on  FIG. 6 , the ribs  17  extend the full length of the outer and inner plates  18 , 19 . The ribs  17  are substantially equal in width and are equidistant from each other, forming equiwidth cavities. The ribs  17  are blended at the point of connection with the upper and lower plates  18 , 19 . Also between the two plates  18 , 19  are two ribs  20  which extend perpendicular to the plurality of ribs  17 . These perpendicular ribs  20  assist in providing structural support to the retainer  8 . 
     As noted, the illustrated configuration is the preferred embodiment for the structural ribbing and air inlet means of the upper retainer  8 . The ribbing  17 ,  20  between the upper and lower plates  18 ,  19  is provided for structural integrity and impact resistance. The distance between the ribs  17 , and thus the relative widths of the cavities, may vary in accordance with the resulting impact forces to which the air spring  1  will be subjected. Both the ribbing  17  and perpendicular ribbing  20  may extend from either the top plate  18  or the bottom plate  19  without contacting the opposing plate. Additionally, all of the chambers may be formed with a more circular cross-section and more rounded radially inner end points than presently illustrated. The ribbing may also be provided in other configurations wherein the ribbing extends at angles relative to one another, such as in a herringbone or diamond pattern, to vary the retainer strength characteristics. The configuration of the ribbing pattern is limited solely by molding dictates. 
     Two adjacent air chambers  21  provide means for the flow of the pressurized fluid into and out of the pressurized chamber  14 . The chambers  21  are formed with a smaller width and a lesser extending depth than the formed cavities. At the radially inner most point  22  of the fluid admitting chambers  21 , the chambers  21  terminate in an orifice  23  which extends through the bottom plate  19 . The stepped-in configuration of the fluid admitting chambers  21  permit a push-in fitting to be secured in the retainer  8  during a post molding action. The walls of the fluid admitting chambers  21  are shaped to match the configuration of the push-in fittings. The orifice  23  may extend through the retainer  8  in an axial direction only, as opposed to the illustrated radial/horizontal access for fluid flow. For such a construction, the entire intermediate section  16  of the retainer  8  is defined by ribbing  17 ,  20  and two axial extending orifices for the insertion of air fittings pass through both the upper and lower plates  18 ,  19 . 
     On the axially outer side of the top plate  18 , means  13  are provided for securing the air spring  1  to any vehicle frame or bracket upon which it is desired to mount the air spring  1 . A unitary plate  24  is located off-centered on the top plate  18 . The location of the plate  24 , relative to the center of the top plate  18 , as well as the height and width of the plate  24  is dependent on the vehicle frame structure on which the air spring  1  is to be mounted. The plate  24  is supported by a set of braces  25 . The plate  24  and the braces  25  are formed as an integral part of the retainer  8  by molding the plate  24  with the retainer  8 , welding the plate  24  to the retainer  8 , or by bonding the plate  24  to the retainer  8 ; the plate  24  is preferably molded as an integral part of the retainer  8 . The plate  24  is provided with at least one mounting hole  26 . The holes  26  are reinforced with steel inserts  27  to strengthen the mounting of the air spring  1 . 
     The retainer  8  is injection molded from a resilient material, preferably thermoplastic. Examples of applicable material include, but are not limited to, fiberglass reinforced nylon, long fiber reinforced thermoplastic, commercially available as CELSTRAN, and short fiber reinforced thermoplastic, commercially available as ZYTEL. The tensile strength of the material should be within the range of 1965 to 3165 kg/cm 2  (28,000 to 45,000 psi), have a flex strength in the range of 2810 to 4220 kg/cm 2  (40,000 to 60,000 psi), and notched izod strength of 0.117–0.703 N-m/mm (2.0 to 12.0 ft-lb/in). 
     Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the fully intended scope of the invention as defined by the following appended claims.