Patent Publication Number: US-2003234147-A1

Title: Piston rod seal for airlift damper

Description:
TECHNICAL FIELD OF THE INVENTION  
       [0001] This invention relates to an airlift shock damper having an inflatable air sleeve to adjust the riding height of the vehicle upon which the damper is mounted.  
       BACKGROUND OF THE INVENTION  
       [0002] Many motor vehicles have a suspension system that includes shock absorbers to control the relative movements of the vehicle chassis with respect to the vehicle body. These shock absorbers commonly include a housing and a piston assembly. The piston assembly includes a piston and a piston rod extending from the piston. The housing is commonly connected to a vehicle wheel end assembly. The housing is filled with a damping fluid, which is metered across the piston plate to dampen relative movement between the housing and piston assembly. The piston rod includes a portion extending from the top end of the housing, which is connected to the vehicle body through a conventional top mount. A jounce bumper is secured below the top mount to absorb the force of unusually large relative movement between the chassis and body. An airlift shock absorber includes an air sleeve that may be inflated to control the relative positions of the piston assembly and housing, to thereby control the riding height of the vehicle.  
       [0003] An airlift shock normally contains a seal to prevent air leak between the piston rod and the upper mount. A typical seal is achieved by machining a gland into the cylinder bore mating to the rod to retain an O-ring for the seal. The machining of an internal gland is difficult and costly, as is the installation of a small O-ring into an internal gland. Another approach is to machine an external gland on the tenon of the piston rod, which may weaken the tenon. A third option is an O-ring retainer to locate the O-ring during the assembly process as the mating part is pressed into place. U.S. Pat. No. 6,361,027, the disclosure of which is hereby incorporated by reference, shows a shock absorber with a flexible connection between an airlift component and the top mount.  
       SUMMARY OF THE INVENTION  
       [0004] This invention is a top mount for a damper having a piston rod tenon. The top mount comprises a mount insert and an o-ring. The mount insert is disposed on the tenon, and the o-ring is disposed on the tenon and within a cutout of the mount insert. A damper including the top mount, and a method of assembling a top mount, are also disclosed.  
       [0005] Accordingly, it is an object of the present invention to provide a top mount of the type described above that requires relatively little force to assemble.  
       [0006] Another object of the present invention is to provide a top mount of the type described above that is inexpensive and easy to assemble.  
       [0007] Still another object of the present invention is to provide a damper that includes a top mount of the type described above.  
       [0008] These and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments, read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0009]FIG. 1 is a cross-sectional view of a suspension damper according to the present invention; and  
     [0010]FIG. 2 is a cross-sectional view of a piston rod, mount insert and o-ring in a preassembled position.  
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS  
     [0011]FIG. 1 shows one embodiment of an airlift suspension damper  10  according to the present invention for a motor vehicle. The damper  10  includes a housing  12  defining a damping chamber  14 . A piston assembly  16  includes a damping piston  18  and a piston rod  20  that extends from the piston  18  through an upper end  22  of the housing  12 . Fluid within the chamber  14  is metered across the piston  18  in a manner well known to those skilled in the art to dampen the relative movement between the housing  12  and the piston assembly  16 . A gas cup  24  is slidably mounted within the housing  12 , and separates the damping chamber  14  from a compensating chamber  26 . The chamber  26  is charged with gas under pressure to move the gas cup within the housing  12  and compensate for the change in volume of the damping chamber  14  in response to extension and retraction of the piston rod  20  with respect to the housing  12 , and also to compensate for any change in volume of the damping fluid due to temperature changes, fluid loss, etc. A bottom mount  28  is secured to the lower end of the housing  12 , and is adapted to secure the housing  12  to a chassis component such as a vehicle wheel end assembly (not shown) in a conventional manner.  
     [0012] The piston rod  20  extends through a conventional jounce bumper  32 , which circumscribes the piston rod. The jounce bumper  32  is made of a resilient material, and absorbs the force of the housing  12  impacting upon the jounce bumper. These impact forces are due to especially large magnitude movements of the housing  12  which may be caused, for example, by movement of the vehicle upon which the shock absorber  10  is used over a particularly rough road at a relatively high speed.  
     [0013] The piston rod  20  includes a reduced diameter portion or tenon  33  that cooperates with the larger diameter portion of piston rod to define a shoulder upon which is disposed a washer  30 . The tenon  33  extends through a top mount  34  that abuts and attaches to the body  36  of the vehicle. The top mount  34  includes a top mount housing  38  having a radially outwardly projecting, circumferentially extending flange  40 , which joins the two halves of top mount housing sections  38 A and  38 B. A resilient force absorbing insert  42  engages the shoulder  31 , and is disposed around the tenon  33  of piston rod  20 . The piston rod  20  extends into the vehicle body  36  and is secured thereto by a conventional fastener.  
     [0014] The shock absorber  10  is provided with an airlift mechanism  58  including an inflatable air sleeve  46  and a pressure retainer  48 . The relative positions of the housing  12  and piston assembly  16  may be changed by altering air pressure within the air sleeve  46  to thereby change the riding height of the vehicle. This may be desirable, for example, to compensate for particularly heavy loads. A resilient force absorbing member  56  is bonded around the top mount housing  38 B and against the pressure retainer  48  to provide a seal and the flexibility required between those components. This resilient force absorbing member  56  also provides isolation from noise and impact harshness. Impact forces transferred through the jounce bumper  32  are also transferred through the resilient force absorbing member  56  through cooperating surfaces on the jounce bumper and the flexible force receiving member.  
     [0015] One end  60  of the air sleeve  46  circumscribes the upper end  22  of the housing  12  and is attached thereto by a conventional fastener to form a pressure retaining seal therebetween. The other end  62  of the air sleeve  46  circumscribes the pressure retainer  48  and is attached thereto by a conventional fastener to form a pressure retaining seal therebetween. Accordingly, the air sleeve  46 , the pressure retainer  48 , the upper end  22  of the housing  12 , and the top mount  34  cooperate to define a pressure retaining cavity  64 . Compressed air is introduced into, and released from, the cavity  64  through a conventional fitting (not shown).  
     [0016] In operation, the shock absorber  10  dampens relative movement between the body and chassis of the vehicle by metering the damping fluid within chamber  14  across the piston  18  to thereby dampen the relative movement between the piston rod  20  and housing  12 , which are respectively connected to the body and chassis of the vehicle. The dampening forces applied to the piston assembly  16  by this normal operation of the shock absorber  10  are transmitted through the force absorbing member  42  of the top mount  34  and from there to the vehicle body. As discussed above, the relative positions of the housing  12  and piston assembly  16  may be adjusted to control the riding height of the vehicle by introducing compressed air into, or releasing compressed air from, the cavity  64 . Accordingly, when compressed air is introduced into the cavity  64 , airlift forces are applied at the bottom of the top mount  34  through the resilient force absorbing member  56 .  
     [0017]FIG. 2 shows how the top mount insert  42  is sealed against the tenon  33  of the piston rod  20 . An o-ring  70  is initially piloted over the threads of the tenon  33  to a position around a neck  72  of the tenon, and a chamfered end  74  leading into a cutout  76  in the top mount insert  42  is situated against the o-ring. When the insert  42  is thereafter lowered, either manually or automatically toward the shoulder  30 , the o-ring  70  rolls down over the neck  72  and around a lower portion  78  of the tenon  33 . As shown in FIG. 1, the o-ring  70  is preferably ultimately disposed all the way up in the cutout  76  of the mount insert  42 . Relatively little force is required to roll the o-ring  70  into place, which reduces stress on the o-ring during assembly and reduces potential damage to the o-ring.  
     [0018] While the embodiment of the invention disclosed herein is presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. For example, the process described above is equally applicable for installing multiple o-rings. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.