Abstract:
The caster angle of a unibody vehicle may be adjusted by securing a fixed frame member to the vehicle&#39;s rocker panel pinch weld to provide an anchor point for adjustment. An hydraulic porter power ram mounted between the forward end of the frame leg and the lower control arm of the steering assembly is used to push the lower control arm forward to the proper caster angle. A stabilizing bar attached to the fixed frame member minimizes twisting of the fixed frame member under hydraulic pressure.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to an automotive caster alignment tool and, in particular, to a tool to adjust and repair the caster angle of the right or left hand strut of unibody cars.  
           [0002]    In most unibody cars of today, the caster is not adjustable. “Caster” refers to the angle of the steering axis in relation to an imaginary, vertical line through the center of the wheel when viewed through from the side of the wheel. “Positive caster” is the term used when the vertical line is tilted toward the rear of the vehicle. “Negative caster” is the term used when the vertical line is tilted forward. The proper caster angle stabilizes the car for better steering and handling.  
           [0003]    When the caster is pushed back on the right hand side of the vehicle, for example, the vehicle will pull or drift to the right causing handling problems. This may be caused by bumping into a curb or a parking block in a parking lot. The automobile owner may bring his or her car into an alignment shop for a front end alignment. The alignment equipment is mounted to the front wheels of the car and various measurements are made such as camber, caster, toe and thrust. If a caster problem is found, all the alignment equipment is removed from the car and the car has to be transported to a frame shop.  
           [0004]    To repair or adjust the caster angle it is known in the art to use a frame machine to pull the caster to the proper angle. Typically, alignment shops do not have a frame machine because of the space requirements and cost of such equipment. Often because of inaccuracies at the frame shop, the car must be transported back and forth between the frame shop and the alignment shop multiple times at an increased cost to the alignment shop. The only way to pull lower control arm on one side of the car back into place using a frame machine is to compare its position to the position of the lower control arm on the other side of the car. If both control arms are out of position, then the adjustment made on the frame machine will be incorrect.  
         SUMMARY OF THE INVENTION  
         [0005]    It is therefore a primary object of the present invention to provide a caster adjustment tool, which may be used to adjust the caster to the proper angle without removing the front end alignment equipment.  
           [0006]    Another important object of the present invention is to provide a caster adjustment tool, as aforesaid, which may be used to repair or adjust the caster angle of the right or left hand strut of a unibody car.  
           [0007]    Still another important object of the present invention is to provide a caster adjustment tool, as aforesaid, which is relatively simple to use.  
           [0008]    Yet another object of the present invention is to provide a caster adjustment tool, as aforesaid, which is relatively inexpensive.  
           [0009]    These and other objects of the present invention are achieved by a caster adjustment tool which may be mounted to the pinch weld below the rocker panel along either side of the vehicle. A hydraulic jack or other means such as a jack screw may be used to push the lower pivoting point of the steering and suspension forward to achieve the proper caster angle for proper drivability of the vehicle.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a front elevation view of the caster adjustment tool of the present invention mounted to the rocker panel of a car shown as a partial view.  
         [0011]    [0011]FIG. 2 is a side elevation view of a steering and suspension for a right front wheel of a vehicle showing the caster angles.  
         [0012]    [0012]FIG. 3 is a plan view of the caster adjustment tool of the present invention.  
         [0013]    [0013]FIG. 4 is a side elevation view of the caster adjustment tool of the present invention.  
         [0014]    [0014]FIG. 5 is an enlarged perspective view of a vertical pinch weld clamp of a caster adjustment tool along line  5  shown in FIG. 4.  
         [0015]    [0015]FIG. 6 is an enlarged perspective view of a vertical pinch weld clamp of the caster adjustment tool along line  6  shown in FIG. 4.  
         [0016]    [0016]FIG. 7 is an enlarged perspective view of a horizontal pinch weld clamp of the caster adjustment tool of the present invention.  
         [0017]    [0017]FIG. 8 is an enlarged perspective view of the torsion bar attachment to the horizontal bar of the caster adjustment tool of the present invention along line  8  of FIG. 4.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    Referring initially to FIGS. 1 and 2, caster adjustment tool  10  is mounted to the vertical pinch weld  12  of automobile  14  (shown as partial view). Automobile  14  is supported on rack  16 . Hydraulic jack  18  extends from the end of caster adjustment tool  10  to the lower control arm  20  near the lower pivot point such as the lower ball joint of the steering and suspension  22  to which wheel  24  is mounted.  
         [0019]    Most roads have a crest or crown down the center of the road, which allows water to drain from the road. To offset road crown, the right front steering assembly has a more positive caster than the left front steering assembly. This unequal caster causes the vehicle to drift or pull to the side with the least positive caster. Thus, this unequal caster compensates for the road crown and allows the vehicle to travel straight down the road without drifting to the right. Typically, the caster angle  26  for passenger vehicles is between zero and five degrees positive.  
         [0020]    Referring to FIGS.  1 - 4 , caster adjustment tool  10  is generally T-shaped with a main rail  28 , a pair of clamps  30  and  32  secured near the opposing ends of main rail  28  and a pair of cup-shaped end caps  34  and  36  secured to the outside end of clamps  30  and  32 , respectively. A center stabilizing member or torsion bar  38  is secured to main rail  28  at approximately the midpoint and extends generally perpendicular from main rail  28 . When caster adjustment tool  10  is mounted to a vehicle  14 , center member  38  extends traversely under the vehicle  14  and is supported by a block or other support means (not shown) generally parallel to the lower plane of the vehicle. Center member  38  acts as a lever arm or torsion bar to limit rotation and twisting of main rail  28  when hydraulic pressure is applied to either end cap  34  or  36 .  
         [0021]    The proper caster for each side of the vehicle is determined by measuring from a vehicle manufacturer specified reference point (not shown) on the side of the vehicle such as a hole or bolt in the frame, to the lower control arm  20  on the steering and suspension assembly  22 . These measurements on each side of the vehicle are compared to the vehicle specification to determine if the left and right casters are within the proper range. If either the right or left caster is out of tolerance, caster adjustment tool  10  is clamped to the pinch weld  12  along the side of vehicle  14 .  
         [0022]    A reference mark  40  is made using a grease pencil or other marker along pinch weld  12  toward the front of the vehicle to aid in determining when caster angle  26  has been properly adjusted. Referring, for example, to right front wheel  24 , hydraulic jack  18  is placed between end cap  36  and lower control arm  20  and hydraulic piston  40  is extended until it contacts lower control arm  20 . With a tape measure or other measuring instrument in place, the distance between pivot point  20  and the reference mark is increased by applying hydraulic pressure through hydraulic jack  18  to piston  42  to push pivot point  20  forward relative to the vehicle until pivot point  20  has been properly adjusted.  
         [0023]    By way of example, the manufacturer-specified measurement for the right caster from the reference point (not shown) to the lower control arm  20  for the right caster may be 60 inches for a particular vehicle. When the right caster is measured at a front-end alignment shop, the measurement may be 58¾″. The difference between the manufacturer&#39;s specification and the actual measurement is 1¼″. Thus, the right pivot point  20  would need to be adjusted forward 1¼″.  
         [0024]    To make this adjustment using caster adjustment tool  10 , the crown end of piston  42  of hydraulic porter power ram  18  is placed against the lower control arm  20  with piston  42  in the retracted position. An extension (not shown) may be added to the piston  42  to extend the reach of reach of piston  42 . A reference mark  40  is made on pinch weld  28  at the other end of hydraulic jack  18 . Caster adjustment tool  10  is held in place with clamps  30  and  32  over pinch weld  28  approximately one-half inch forward of reference mark  40 . Clamps  30  and  32  are secured to pinch weld  40  by tightening bolts  48  to approximately 80 inch foot pound of torque. At the other side of the vehicle, stabilizer bar  38  is raised as high as possible to approximately parallel with the lower plane of vehicle  14  and supported in place with a block or other means. With caster adjustment tool  10  in place and a tape measure extending between lower control arm  20  and mark  40  on pinch weld  12 , lower control arm  20  needs to be adjusted 1¼″ forward relative to the mark placed on the pinch weld  12 .  
         [0025]    The base of porter power ram  18  is placed in cup  36  and the crown end of piston  42  is placed against lower control arm  20 . Hydraulic pressure is applied through hydraulic jack  18  extending piston  42 , which pushes lower control arm  20  forward to achieve the proper positive caster angle  26 . Stabilizing center member  38  prevents main rail  28  from twisting under the pressure of hydraulic jack  18  against end cap  36 . Once the proper caster angle  26  is achieved for the right steering and suspension assembly  22 , caster adjustment tool  10  is removed and the process is repeated for the other side of the vehicle to adjust the left caster, if necessary.  
         [0026]    Those skilled in the art will understand that only one clamp may be used to secure caster adjustment tool  10  to pinch weld  28  to adjust the caster angle. The clamp nearest the lower control arm  20  to be adjusted should be clamped to pinch weld  28 . The other end of main rail  28  may be supported on a block generally parallel to pinch weld  28 .  
         [0027]    Referring to FIGS. 5 and 6, a cut-away view of vertical pinch weld clamp  32  is shown. Clamp  32  includes a back plate  44  and a clamp plate  46 . Back plate  44  may be welded or otherwise fastened to main rail  28 . Clamp plate  46  is adjustably secured to back plate  44  with bolts  48  extending through apertures (not shown) and back plate  44  which are in axial alignment with apertures (not shown) in clamp plate  46 . Bolts  50  are prevented from rotation during adjustment of clamp  32  by bolt retaining blocks  52  when nuts  48  are turned. A plurality of tines or gripping points  54  extend from clamp plate  46  into the pinch weld channel  56  formed between back plate  44  in clamp plate  46 . Tines  54  are in axial alignment with generally coned-shaped recesses  58  in back plate  44 .  
         [0028]    An offset block  60  helps maintain the alignment of clamp plate  46  with back plate  44  when clamp  32  is adjusted. End cap  36  is welded or fastened generally perpendicularly to back plate  44  and main rail  28 . When caster adjustment tool  10  is clamped to pinch weld  10  (FIG. 1), bolts  48  are tightened until tines  54  securely grip pinch weld  12  to prevent clamps  30  and  32  from slipping when hydraulic pressure is applied.  
         [0029]    In the preferred embodiment, main rail  28  and center member  38  are constructed of square, steel tubing. End caps  34  and  36  may be made of steel or iron pipe. The components of clamps  30  and  32  may be constructed of three-eighths to one-half inch steel plate, steel bolts and tines.  
         [0030]    Referring to FIG. 7, a horizontal pinch weld clamp  62  is shown. Clamp  62  is generally the same as clamp  32  except that it is configured to grip a horizontal pinch weld which is used on some cars, such as Hondas. Clamp  62  is generally C-shaped with the lower portion  64  welded to main rail  28 . The upper portion  66  of clamp  62  includes a pair of apertures (not shown) in axial alignment with clamp plate  68  apertures (not shown). Clamp plate  68  is adjusted turning bolt  70  to tighten or loosen nut  72 .  
         [0031]    Referring to FIG. 8, a sectional perspective view of stabilizing center member or torsion bar  38  to main rail  28  is shown. End plate  74  is welded to the end of center member  38 . Nut retaining blocks  76  prevent nuts  78  from turning when bolts  80  (FIGS. 3 and 4) are turned.  
         [0032]    It should be appreciated from the foregoing disclosure that caster adjustment tool  10  may be used without effecting or interfering with front end alignment equipment which is known in the art.  
         [0033]    It is to be understood that while certain forms of this invention have been illustrated and described, it is not limited thereto, except in so far as such limitations and their equivalents are included in the following claims.