Patent Publication Number: US-2007102894-A1

Title: Caster adjustment apparatus and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of Provisional Application No. 60/734,074, filed on Nov. 7, 2005. 
    
    
     TECHNICAL FIELD AND BACKGROUND OF THE INVENTION  
      The present invention relates to the field of wheel caster adjustment. In particular, the invention relates to a caster adjustment apparatus, suspension member assembly, and method for selectively adjusting the caster of a wheel of a vehicle.  
      “Caster” is a term used to refer to the backward and forward tilt of the steering axis of a vehicle. Adjusting the caster of a wheel effects the way a vehicle handles. For example, adjusting the caster can maximize tire contact, improve turn-in, increase directional stability, and improve steering feel and self-center.  
      Various methods for adjusting caster have been developed and are employed on various types of vehicles. One such method is disclosed in U.S. Pat. No. 6,688,616. The method includes the use of cams and a fastener for adjusting the position of the control arm relative to a frame in the fore-aft direction. Other methods are complex and require a technician to perform the adjustment, require special tools, or require a substantial amount of time to perform the adjustment.  
      While most vehicles include some means for adjusting the caster of a wheel, some vehicles are manufactured with a preset caster that cannot be adjusted. For example, a conventional all-terrain vehicles (ATVs) are manufactured with a preset caster that cannot be adjusted. The suspension systems of the ATVs use upper and lower suspension members that are attached at one end to the frames of the ATVs and at the other end to the wheel hubs by ball joints. Thus, operators of the ATVs cannot adjust the caster to change handling characteristics. Such an adjustment would be beneficial in racing high-performance ATVs used under harsh conditions.  
      Accordingly, there is a need for a caster adjustment apparatus, suspension member assembly, and method that allows the caster of a wheel to be adjusted easily, in a short period of time without the use of special tools, and that can be used on vehicles that are manufactured without caster adjustment.  
     SUMMARY OF THE INVENTION  
      Therefore, it is an object of the invention to provide a caster adjustment apparatus that allows the caster to be easily adjusted.  
      It is another object of the invention to provide a caster adjustment apparatus that can be used with racing or high-performance vehicles used under harsh conditions.  
      It is another object of the invention to provide a caster adjustment apparatus that can be used on vehicles without a caster adjustment.  
      It is another object of the invention to provide a caster adjustment apparatus that allows the caster to be adjusted in the positive and negative directions.  
      It is another object of the invention to provide a suspension member assembly that allows the caster to be easily adjusted.  
      These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a caster adjustment apparatus for being positioned in a ball joint mount of a suspension member. The caster adjustment apparatus includes a flange having an aperture extending through the flange for receiving a ball joint therethrough, wherein a center of the aperture is offset from a center of the flange, and a plurality of openings positioned around a periphery of the flange at predetermined positions for engagement with an engagement member positioned on the ball joint mount. The caster adjustment apparatus also including a cylindrical sleeve extending from a bottom surface of the flange for being received in the ball joint mount.  
      According to another preferred embodiment of the invention, the openings are notches.  
      According to another preferred embodiment of the invention, the plurality of openings are spaced-apart in predetermined increments.  
      According to another preferred embodiment of the invention, the bottom surface of the flange is adapted to abut against the ball joint mount.  
      According to another preferred embodiment of the invention, the sleeve is adapted to be positioned within an aperture of the ball joint mount.  
      According to another preferred embodiment of the invention, the flange has a diameter greater than the diameter of the sleeve such that when the sleeve is positioned in the ball joint mount, the flange interferes with a top edge of the ball joint mount to provide a stop.  
      According to another preferred embodiment of the invention, a caster adjustment assembly includes a suspension member for being mounted between a vehicle frame and a vehicle wheel assembly. The suspension member includes a ball joint mount positioned for receiving a ball joint therein to connect the suspension member to the wheel assembly, and an engagement member positioned on the ball joint mount. The assembly also includes a first cam positioned in a fist side of the ball joint mount for receiving and adjusting the position of the ball joint. The cam includes a flange having an aperture extending through the flange for receiving the ball joint therethrough, and a plurality of openings positioned around a periphery of the flange at predetermined positions for engagement with the engagement member, wherein a center of the aperture is offset from a center of the flange, and a cylindrical sleeve extending from a bottom surface of the flange, the sleeve being received in the ball joint mount. At least one of the openings is engaged with the engagement member to secure the cam at a selected angular orientation relative to the ball joint mount.  
      According to another preferred embodiment of the invention, the engagement member is positioned on the first side of the ball joint mount.  
      According to another preferred embodiment of the invention, the plurality of openings are notches.  
      According to another preferred embodiment of the invention, a stud of the ball joint is positioned through the aperture.  
      According to another preferred embodiment of the invention, the assembly further includes a second cam positioned on a second side of the ball joint mount.  
      According to another preferred embodiment of the invention, the second cam includes a flange having an aperture extending through the flange for receiving the ball joint therethrough, and a plurality of openings positioned around a periphery of the flange at predetermined positions for engagement with an engagement member positioned on a second side of the ball joint mount, wherein a center of the aperture is offset from a center of the flange; and a cylindrical sleeve extending from a bottom surface of the flange, the sleeve being received in the ball joint mount.  
      According to another preferred embodiment of the invention, the plurality of openings are notches.  
      According to another preferred embodiment of the invention, the first cam and the second cam are positioned in opposing sides of the ball joint mount such that the apertures extending through the flanges are aligned to receive the ball joint therethrough.  
      According to another preferred embodiment of the invention, a method of adjusting the caster of a vehicle wheel includes the steps of providing a first caster adjustment apparatus having an aperture extending through a flange for receiving a ball joint therethrough; positioning the first caster adjustment apparatus in a ball joint mount; positioning the ball joint in the aperture; and securing the ball joint to the ball joint mount.  
      According to another preferred embodiment of the invention, the method further includes the step of removing a bushing from the ball joint mount.  
      According to another preferred embodiment of the invention, the method further includes the step of rotating the caster adjustment apparatus to a predetermined position such that an opening in a flange of the caster adjustment apparatus engages an engagement member on the ball joint mount.  
      According to another preferred embodiment of the invention, the method further includes the steps of providing a second caster adjustment apparatus having an aperture extending through a flange for receiving a ball joint therethrough; and positioning the second caster adjustment apparatus in a second opposing side of the ball joint mount.  
      According to another preferred embodiment of the invention, the method further includes the step of rotating the second caster adjustment apparatus such that the aperture of the second caster adjustment apparatus is aligned with the aperture of the first caster adjustment apparatus for receiving the ball joint therethrough.  
      According to another preferred embodiment of the invention, the method further includes the step of securing a wheel assembly to the ball joint. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:  
       FIG. 1  is a perspective view of an all-terrain vehicle;  
       FIG. 2  shows a prior art suspension system of the all-terrain vehicle of  FIG. 1 ;  
       FIG. 3  is a top view of a caster adjustment apparatus according to an embodiment of the invention;  
       FIG. 4  is a side view of the caster adjustment apparatus of  FIG. 3 ;  
       FIG. 5  shows the caster adjustment apparatus of  FIG. 3  and an upper suspension member of the suspension system of  FIG. 2 ;  
       FIG. 6  is a cross-section of the caster adjustment apparatus of  FIG. 3  inserted into a ball joint mount of the upper suspension member of  FIG. 5 ;  
       FIG. 7  shows the caster adjustment apparatus of  FIG. 3  used with the upper suspension member on the all-terrain vehicle of  FIG. 1 ;  
       FIG. 8  shows the caster adjustment apparatus of  FIG. 3  used with the upper and lower suspension members on the all-terrain vehicle of  FIG. 1 ; and  
       FIG. 9  is an exploded view of a suspension member assembly according to an embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE  
      While this discussion is limited to a suspension system of an all-terrain vehicle (ATV), the present invention is applicable to any vehicle where adjustment of caster is desired.  
      Referring now specifically to the drawings, a conventional all-terrain vehicle (ATV) having a suspension system with non-adjustable caster, is illustrated in  FIG. 1  and shown generally at reference numeral  10 . As shown in  FIG. 2 , the suspension system  11  of the ATV  10  uses upper  12  and lower  13  suspension members that are attached at one end to the frame  14  of the ATV  10  and at the other end to the wheel hub  16  by ball joints  17 A and  17 B. This type of suspension system does not allow adjustment of the caster, thereby forcing the operator to live with the preset handling characteristics mandated by the manufacturer.  
      Referring to  FIGS. 3 and 4 , a caster adjustment cam according to an embodiment of the invention is shown generally at reference numeral  20 . The cam  20  includes a flange  21  and a sleeve  22  extending from a bottom surface  23  of the flange  21 . The flange  21  includes an off-axis aperture  24 . A plurality of notches  26  are positioned around the periphery of the flange  21  and are spaced-apart in predetermined increments, for example, one-half degree, to allow minute adjustments of the cam  20 .  
      As shown in  FIGS. 5 and 6 , the cam  20  may be used with existing suspension members, such as upper suspension member  12  depicted in  FIG. 2 . As illustrated, suspension member  12  includes a ball joint mount  31  having a top surface  32 , a bottom surface  33 , and an aperture  34  extending through the ball joint mount  31  from the top surface  32  to the bottom surface  33 . The suspension member  12  is modified to include an engagement member  36  extending from the top and bottom surfaces  32  and  33  of the ball joint mount  31 .  
      The cam  20  is positioned such that a portion of the sleeve  22  is received in the aperture  34  of the ball joint mount  31 , thereby allowing the bottom surface  23  of the flange  21  to rest adjacent to the top surface  32 . The cam  20  is then rotated until a desired one of the notches  26  is aligned with the engagement member  36  extending from the top surface  32 . The cam  20  is then pushed further into the aperture  34  until the bottom surface  23  of the flange  21  comes into contact with the top surface  32 , thereby allowing the desired one of the notches  26  to engage the engagement member  36 .  
      A second cam  20  ′ is positioned such that a portion of a sleeve  22 ′ thereof is received in the aperture  34 , thereby allowing its surface  23 ′ to rest adjacent to the bottom surface  33 . The second cam  20 ′ is then rotated so as to align an off-axis aperture  24 ′ with the off-axis aperture  24 . The cam  20 ′ is then pushed further into the aperture  34  so that one of a plurality of notches  26 ′ engages the engagement member  36  extending from the bottom surface  33 . As illustrated in  FIG. 6 , a post  37  of the ball joint  17 A is then inserted through the off-axis apertures  24  and  24 ′ of the two cams  20  and  20 ′ and secured to the ball joint mount  31  by an attachment means, such as a nut  39 .  
      As shown in  FIG. 7 , the cams  20  and  20 ′ may be mounted in the upper suspension member  12  on the ATV  10 . The cams  20  and  20 ′ are initially installed on the ATV  10  with a center one of the notches  26  and  26 ′ engaging the engagement members  36 . This produces a neutral caster condition. When an operator wants to change the wheel caster of the ATV  10 , the nut  39  of the ball joint  17 A is loosened to allow the cams  20  and  20 ′ to disengage the engagement members  36 . The cams  20  and  20 ′ are then rotated either clockwise or counter-clockwise depending on the type of caster the operator desires. By rotating the cams  20  and  20 ′ clockwise, positive caster is attained, thereby reducing steering effort, increasing directional stability, and improving turn-in. This is particularly useful for younger riders who need an ATV that steers easily or for racers who desire specific steering characteristics for a particular race. By rotating the cams  20  and  20 ′ counter-clockwise, negative caster is attained, thereby increasing steering effort and increasing steering stability over rough terrain. Once the cams  20  and  20 ′ have been re-positioned, the ball joint  38  is re-tightened to secure the ball joint  17 A and cams  20  and  20 ′ in the desired position.  
      Referring to  FIG. 8 , the cams  20  and  20 ′ may also be mounted in both the upper  12  and lower  13  suspension members of the ATV  10 . By using the cams  20  and  20 ′ in the upper and lower suspension members  12  and  13 , not only can the wheel caster be changed as described above, but the wheelbase of the ATV  10  can be lengthened or shortened. By rotating the cams  20  and  20 ′ clockwise, the wheelbase is lengthened. Rotating the cams  20  and  20 ′ counter-clockwise shortens the wheel base.  
       FIG. 9  illustrates a suspension member assembly according to an alternative embodiment of the invention. The suspension member assembly  40  includes a suspension member  41  having a pair of elongate members  42  and  43  joined at an end  44 . The end  44  includes a ball joint mount  46  having a top surface  47 , a bottom surface  48 , an aperture  49 , and engagement members  50  extending from the top surface  47  and bottom surface  48  at predetermined locations. The suspension member assembly  40  also includes a pair of opposing cams  51  and  51 ′ for being inserted into the aperture  49  of the ball joint mount  46 . Like the cams  20  and  20 ′, the cams  51  and  51 ′ include flanges  52  and  52 ′, sleeves  54  and  54 ′ extending from bottom surfaces  56  and  56 ′, off-axis apertures  57  and  57 ′, and a plurality of notches  58  and  58 ′ for engaging the engagement members  50 . Each of the elongate members  42  and  43  include a frame mount  60  having an aperture  61  therethrough for accepting an insert  62  and bearings, such as roller bearings  63 , positioned on opposing ends of the insert  62 , thereby eliminating the need for bushings and increasing durability. As shown, the insert  62  includes a center section  64  and two bearing sections  66  and  67  positioned on opposing sides of the center section  64  for allowing a respective one of the bearings  63  to be supported thereon.  
      The suspension member assembly  40  is assembled by positioning a portion of the sleeves  54  and  54 ′ of the opposing cams  51  and  51 ′ within the aperture  49  until the respective flanges  52  and  52 ′ of each of the cams  51  and  51 ′ rest adjacent to respective top and bottom surfaces  47  and  48  of the ball joint mount  46 . The cam  51  adjacent to the top surface  47  is then rotated to a predetermined position so that a desired one of the notches  58  is aligned with the engagement member  50  extending from the top surface  47 . The cam  51  is then pushed further into the aperture  49  until the bottom surface  56  comes into contact with the top surface  47  of the ball joint mount  46 . The cam  51 ′ adjacent the bottom surface  48  is then rotated so that the off-axis apertures  57  and  57 ′ are in alignment with each other. The cam  51 ′ is then pushed further into the aperture  49  until the bottom surface  56 ′ comes into contact with the bottom surface  48  of the ball joint mount  46 . A post  70  of a ball joint  71  is then inserted through the off-axis apertures  57  and  57 ′ of the two cams  51  and  51 ′ and secured to the ball joint mount  46  by an attachment means, such as a nut  72 . Each of the inserts  62  are then positioned within a respective frame mount  60 . Once the inserts  62  are installed, each of the bearings  63  are positioned on respective bearing sections  66  and  67  of the inserts  62 . The suspension member assembly may be used as a replacement for the upper suspension member  12 , the lower suspension member  13 , or both.  
      A caster adjustment apparatus, suspension member assembly, and method are described above. Various details of the invention may be changed without departing from its scope. Furthermore, the foregoing description of the preferred embodiments of the invention and the best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation.