Abstract:
A damper assembly is provided including a telescopic damper having a piston rod extending from a first end. A mount assembly is mounted on the piston rod. A dust tube is provided the damper assembly including a substantially closed end, the closed end positioned between the telescopic damper and the mount assembly. The closed end of the dust tube includes an opening for receiving the piston rod and a rate surface for contacting a bumper portion of the mount assembly when the damper assembly contracts.

Description:
TECHNICAL FIELD  
         [0001]    This invention related to vehicle suspensions, and more particularly, to a dust shield for use with a damper.  
         BACKGROUND OF THE INVENTION  
         [0002]    Dampers, e.g., shock absorbers or struts, for suspension systems in automotive vehicles are well known. Some dampers are provided with a mechanism by which the damper serves as a component of a vehicle leveling system. In such a damper, an air chamber is provided that is operatively connected to a source of pressurized air for increasing or decreasing the air pressure within the chamber. The air chamber can be formed between a dust shield and an air sleeve attached to the damper. The dust shield further protects the damper and its seals from contaminants such as dust, dirt, gravel, and so on. Generally, a dust shield is a molded or formed member including a hollow cylindrical body. The dust shield can be formed of metal or plastic, for example, and is positioned over an upper end of the damper, such as a monotube damper.  
           [0003]    The air-adjustable damper is typically attached to the vehicle body by a rubber and steel shear mount. A stud holds the shear mount to the damper by threading onto an end of a piston rod. A rate washer portion of the stud or a bump plate is positioned between the rubber portion of the mount and the dust tube. The rate washer or bump plate contacts the rubber portion of the mount when the damper is fully compressed. The configuration of the rate washer determines the deflection rate of the rubber and steel shear mount. The rate washer also functions to hold the dust tube on the damper.  
           [0004]    However, the rate washer or bump plate is a steel part that requires a coating for rust protection and adds unwanted mass to the damper. Also, the rate washer is expensive because the shape requires that the washer be machined. Further, threading the rate washer onto the damper piston rod requires an amount of assembly time.  
           [0005]    It would be desirable to provide a damper assembly that overcomes these disadvantages.  
         SUMMARY OF THE INVENTION  
         [0006]    One aspect of the present invention provides a dust tube for use with a damper including a tubular member having a hollow cylindrical body portion and a substantially closed end. The closed end includes a contoured rate surface on an outer portion thereof.  
           [0007]    Other aspects of the present invention provide a dust tube with the closed end including a central opening. The rate surface extends from the central opening to the hollow cylindrical body portion. The rate surface can include a concave profile. The rate surface can include a contoured portion.  
           [0008]    Another aspect of the present invention provides a damper assembly including a telescopic damper having a piston rod extending from a first end. A mount assembly is mounted on the piston rod. A dust tube includes a substantially closed end with the closed end being positioned between the telescopic damper and the mount assembly. The closed end can include an opening for receiving the piston rod and a rate surface for contacting a bumper portion of the mount assembly when the damper assembly contracts.  
           [0009]    Other aspects of the present invention provide first and second washer members, the first and second washer members respectively positioned adjacent an inner and an outer surface of the closed end adjacent the central opening. The first and second washer members are spaced apart by a spacer member, the spacer member positioned within the central opening of the closed end. A pair of o-ring seals are respectively disposed between an outer diameter of the piston rod and an inner diameter of the spacer and between an outer diameter of the spacer and an inner diameter of the central opening. The first washer member is positioned to contact a shoulder feature of the piston rod. The mount assembly includes a central cylinder disposed on the piston rod. One end of the central cylinder contacts the second washer member and the other end of the central cylinder contacts a retaining member. A fastener member can secure the retaining member against the central cylinder. The fastener member can be threadably engaged to the piston rod. An elastomeric member can be disposed on the central cylinder. A bumper portion can form a portion of the elastomeric member, the bumper being positioned adjacent the rate surface and being drawn into engagement with the rate surface upon contraction of the assembly. The assembly can include at least a pair of mounting studs provided in the elastomeric portion of the mount assembly. The rate surface can be a contoured surface. The rate surface can be a concave surface.  
           [0010]    Another aspect of the present invention provides a damper assembly including a telescopic damper having a rod extending from a first end. A mounting means can be mounted on the rod and a dust tube is positioned on the damper, the dust tube including a substantially closed end, the closed end including contacting means formed thereon for contacting a bumper portion of the mounting means when the damper assembly contracts.  
           [0011]    The foregoing 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  
       [0012]    [0012]FIG. 1 illustrates an embodiment of a damper assembly of the present invention.  
         [0013]    [0013]FIG. 2 illustrates an enlarged cross-sectional view of a portion of the assembly of FIG. 1. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]    Referring to FIG. 1, a damper assembly, illustrated generally at  10  is provided for a vehicle. The damper assembly  10  includes a dust tube  12  with an integrated rate washer profile or surface  14 . The assembly  10  can generally include a damper body tube or reservoir tube  16  with an attaching portion  18  for attaching a lower end of the damper assembly to a vehicle (not shown). Opposite the attaching portion  18  a mount assembly  20  for attaching the other end of the assembly  10  to the vehicle can be provided. An air sleeve  22  can extend between the dust tube  12  and the damper body tube  16  to form an internal air chamber (not shown) therebetween for changing the ride characteristics and ride height of the vehicle as is conventional. A fixture  24  can be provided in the dust tube  12  to allow filling or venting of air in and out of the chamber.  
         [0015]    Referring to FIG. 2, a portion of the damper assembly  10  of FIG. 1 is illustrated. The damper assembly  10  includes a dust tube  12 . A piston rod  30  can extend through a piston rod opening  32  in an upper portion  34  of the dust tube  12 . A shear mount assembly  20  can be attached to the end of the piston rod  30 .  
         [0016]    The dust tube  12  can be formed from plastic, a composite material, or any suitable material. As will be shown, forming the dust tube  12  from plastic, or the like, provides an inexpensive, durable element, the rate profile of which can be easily modified for purposes of providing differing compression rates of the mount assembly  20  by, for example, varying the molds in which the dust tubes are formed. The dust tube  12  can take the shape of a cylindrical sleeve with a closed end or upper portion  34  positioned adjacent the mount assembly  20 . The closed end  34  can include a central opening or piston rod opening  32 . A rate surface  14  for contacting the shear mount assembly  20  can be formed on an outer surface  40  of the closed end  34  of the dust tube  12 . In the illustrated embodiment shown, the rate surface  14  is an annular, gently concave surface adjacent to and surrounding the central opening  32 . The rate surface  14  can extend from the central opening  32  radially outwardly to the dust tube sidewall portion or sleeve  42 .  
         [0017]    It will be understood that the rate surface  14  can include various configurations or cross-sectional profiles. The configurations can include contoured surfaces, for example curved, angled or other configurations. As will be discussed in more detail below, different configurations of the rate surface  14  will provide different rate of compression properties to the damper assembly  10  when in a fully compressed state.  
         [0018]    A piston rod  30  of the damper assembly  10  can extend axially through the central opening  32  and the shear mount assembly  20 . The piston rod  30  can include a shoulder  36 . An inner washer  38  can be positioned on the piston rod  30  contacting the shoulder  36 . The inner washer  38  can be positioned in an inner groove  44  formed adjacent the opening  32  on an inner surface  46  of the closed end  34  of the dust tube  12 . A spacer  48  can be disposed on the piston rod  30  in contact with the inner washer  38 . The spacer  48  can be positioned within the central opening  32  of the dust tube  12 . An outer washer  50  can be positioned adjacent the spacer  48  and positioned within an outer groove  52  formed on the outer surface  40  of the closed end  34  of the dust tube  12 .  
         [0019]    An inner o-ring seal  54  can be disposed between the outer diameter of the piston rod  30  and the inside diameter of the spacer  48 . An outer o-ring seal  56  can be disposed between the outer diameter of the spacer  48  and the inner diameter of the opening  32 . The inner and outer o-ring seals  54 ,  56  prevent leakage of air from the interior of the damper  10 .  
         [0020]    A distal portion  58  of the piston rod can extend outwardly from the opening  32  in the dust tube closed end  34 . Attached to the distal portion  58  of the piston rod is a shear mount assembly  20 . The shear or upper mount assembly  20  isolates the piston rod  30  from the vehicle body (not shown) so that vibrations are not transmitted to the interior of the vehicle. Further, upon compression of the damper, the shear mount assembly  20  contacts the rate surface  14  of the dust tube  12 .  
         [0021]    The mount assembly  20  can include a metal tube or cylinder  60 . The metal cylinder  60  can be positioned on the distal portion  58  of the piston rod  30 . One end of the cylinder can be positioned on the outer washer  50  and can be held in place by a cup shaped retainer  62  at the other end. The cup shaped retainer  62  can be secured to the end of the piston rod  58  by a threaded nut  64 , or the like, to secure the retainer  62  against the metal cylinder  60 , and thus, retain the mount assembly  20  to the damper  10 .  
         [0022]    The shear mount assembly  20  further includes an elastomeric portion  66  surrounding the cylinder. The elastomeric portion  66  can include a skirt portion or bumper portion  68  positioned adjacent the rate surface  14  of the dust tube  12 . A pair of mounting studs  70  are secured within the elastomeric portion  66  for fastening the shear mount assembly  20  to a vehicle frame or member (not shown).  
         [0023]    On compression of the damper, which occurs when the damper  10  contracts or collapses, the elastomeric bumper portion  66  of resilient foam material, urethane, natural rubber or an other suitable material is compressed after the piston (not shown) strokes into the reservoir (not shown) and the piston rod  30  draws the elastomeric portion, skirt or bumper portion  68  of the shear mount  20  into contact with the rate surface  14  of the upper portion  34  of the dust tube  12 . The rate surface  14  engages or deflects the elastomeric bumper portion  68  of the shear mount  20  in a manner to moderate the impact or moderate the rate of compression of the shear mount with the dust tube upper portion  34 . In effect, if the rate surface  14  were formed strictly perpendicular to the piston rod axis A, the impact of the elastomeric bumper portion  68  would be sudden. In this case, the compression of the elastomeric bumper portion  68  and the “bottoming” characteristics of the damper would depend on the compressive characteristics of the elastomeric portion of the shear mount  20  alone. If the rate surface  14  is angled away from the perpendicular, the engagement of the elastomeric bumper portion  68  and the rate surface will be more gradual and the bottoming characteristics of the damper will be “softer.” Thus, it will be understood that the profile of the rate surface  14  can be changeable to control and cushion the compressive response characteristics or final compressive action of the damper  10 . It will be understood that the term “contoured” in application to the rate surface  14 , will refer to a surface which is not a flat surface formed at a perpendicular orientation with respect to the axial A direction. In other words, the surface  14 , for contacting the bumper  68  can include an angled or curved surface or a combination of an angled or curved surface or profile.  
         [0024]    In this manner, a surface is provided for controlling a last portion of the compressive response characteristics of a damper while eliminating an expensive headed and machined steel stud/rate washer component, eliminating the need for rust protection of the stud/rate washer, eliminating the threaded joint between the stud and piston rod, reducing the overall mass and cost of the damper assembly, and which is easily changeable to different configurations.  
         [0025]    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. 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.