Note: Descriptions are shown in the official language in which they were submitted.
~31~
DEVICE FOR ADJI~STING CASTER
_
BACKGROUND OF THE INVENTION
_
1 Field of the Invention
The present invention relates to devices for
; adjusting caster of a vehicle wheel, and in
particular, it relates to a device that adjusts the
caster in a suspen~ion 6ystem having a rod member
that affects caster with the rod member having a
portion disposed in a bushing attached to the vehicle.
2 Description of the Prior Art.
.
Certain suspenQion systems, such as are used
in a Ford pick-up with a twin I-beam frame
construction, have a radius arm that extends from an
I-beam rearwardly to a radius arm bushing that i8
attached to a vehicle frame member. Both left and
right front suspension systems contain such a radius
arm. The radius arm bushing i8 typically made of a
hard rubber. At first, the bushing fits snugly and
holds the radius arm in the position selected by the
manufacturer of the automobile. However, due to the
action of the end of -the radius arm against the
bushing over a period of time along with the coil
spring settling, a small amount of play develops in
the end o~ the arm, which results in the caster of
the wheel and handling of the vehicle being affected.
Other vehicles with stabilizer bars that are
held with bushings have similar correction problems.
The prior art method of corre~ting this play is to
replace the bushing. This requires a good deal of
labor since the radius arm ha~ to be disconnected and
removed from the bushing and the bushing replaced.
1 3 1 6 1 ~ 5
SUMMARY OF THE INVENTION
The present invention includes a method and
a device for correcting caster of a vehicle suspension
system having a rod member that affects the c~ster of
the wheel with a portion of the rod member being
disposed within a bushing attached to the vehicle.
The device includes a curved longitudinal member for
insertion between the portion of the rod member
disposed within the bushing and the bushing.
In one case, where the rod member is a radius
arm, the device is inserted between an end of the
radius arm within the bushing and the bushing. In
another case, where the rod member is a stabilizer
bar having a portion retained within the bushing, the
device is inserted between the stabili~er bar and the
bushing.
The method of the pre~ent invention in the
case of the radius arm includes removing the nut,
washer and insulati~n, retaining the end of the
radius arm within the bushing, and inserting between
the end of the radius arm and the bushing, a
longitudinal main body portion being curved along a
longitudinal axis, either above the end of the radius
arm or below the end of the radius arm to adjust the
caster of the vehicle wheel. The insulator, washer
and nut are attached bacX to the radius arm.
The method of the present invention in the
case of a stabilizer bar is to remove a stabilizer
bar bracket that retains the bushing against the
stabilizer bar body bracket and insert the device of
the present invention either in front of or rearward
, i, :
, ,
~ ~L3161~5
of the stabilizer bar to correct ca~ter in the manner
desired. The stabilizer bar bracket i8 then
reattached to the stabili~er bar body bracket.
BRI~F_DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspectiYe view of an example
of a suspen6ion system in which the device of the
present invention i8 used.
Figure 2 is a cross-sectional view of the
device of the present invention, the radius arm
bushing and an end portion of the radius arm.
Figure 3 is a perspective view of the device
of the present invention.
Figure 4 is a diagrammatical view of a radius
arm illustrating how ca~ter is changed using the
present invention.
Figure 5 i~ an exploded perspective view
illustrating how the device of the present invention
is inserted between an end portion of the radius arm
and the radius arm bushing using a tool of the
present invention.
Figures 6, 7 and 8 are end views illustrating
the different thicknesses of the device of the
present invention.
Figures 6a, 7a and 8a are front views showing
different thicknesses of the device of the present
invention.
Figure 9 is an end view of the tool of the
present invention.
Figure 10 is a cross-sectional view of the
tool of the present invention, the bushing with an
end portion of the radius arm and a drill bit shown
~ 3 ~
whole illu~trating how the guide holes of the tool
are used.
Figure 11 is a perspective view of a suspen-
sion system having a portion of a ~abilizer bar
disposed within a bushing that is ~ecured to the
vehicle.
Figure 12 is an exploded perspective view of
the stabilizer bar, stabilizer bar bushing,
stabilizer bar bracket and stabilizer bar body
bracket and the device of the present invention.
Figure 13 is a plan view o~ an alternative
embodiment of the tool o~ the pre~ent invention.
Figure 14 is still another alternative
embodiment of the tool of the present invention.
DETAILED DESCRIPTIO~ OF THE PREF~RRED EMBODIMENTS
The present invention i5 used to adjust
cacter of a vehicle wheel in a suspension system such
as is generally indicated by 10 in Figure 1. Only
the left front wheel suspension system is ~hown with
it being understood that a right front wheel
suspension system is a mirror image of the left
suspension system illustrated in Figure 1. The
suspension system 10 is connected to a frame member
12 of a vehicle (not shown). The suspension system
10 includes an I-beam cross member 14. An axle 16 to
which a vehicle wheel (not shown) is rotatably
attached thereto is pivotally connected to the cross
member 14 by a steering knuckle 17 having an axis
20. A steering system 18 through a series of tie
rods pivots the axle about axis 20 through steering
knuckle 17.
-~"
' " .' ' `' ' ' ~ ' ' ,' ' .
., . - . j, .
~ 1 3 ~
The cross member ]4 is suspended from the
frame member 12 by a coil spring 22 and shock
absorber 24. A radiu~ arm 26 also holds the cross
member 14 at one end portion 28 and is attached to
the frame member 12 at another end portion 30.
The radius arm 26 is connected at the end
portion 30 to the frame member 12 through a radius
arm bushing 32 disposed in an arm bushing housing 34
that is securely welded or riveted to the frame
member 12. Referring to Figure 2, the bushing 32
typically has a greater diameter forward section 36
and a smaller diameter rearward section 38 that iB
disposed within the bushing housing 34. The bushing
contains an inner bore 40 through which the radius
arm end portion extends. The radius arm end portion
has a threaded end section 42 that extends beyond the
bushing 32. The radius arm is retained in position
by a nut 44 engaging the threaded end section 42. A
wa4her 46 and an insulator 48 are disposed between
the nut and the bushing. A spacer 50 is also
disposed between the insulator 48 and the bushing
housing 34. A retainer 52 is positioned adjacent a
front end of the bushing section 36~ The bushing 32
is made of a hard rubber for securely attaching the
radius arm to the frame member while dampening any
shocks that may be transmitted ~rom the wheels to the
body of the vehicle.
Since the radius arm end portion 30 is
riding within the bushing 32, the bushing 32 will
wear over a period of time resulting in a certain
amount of play developing. One primary cause for
bushing wear is that the spring 22 sags over an
:~ 3:~ 6~l~5
extended period of time. The sagging of æpring 22
causes accelerating wear in the bushing. The play
caused by the sagging spring through t'he worn bushing
32 results in a deviation in caster. ~aster is the
angle, as measured in degrees, that the steering
knuckle axis i8 inclined from the vertical toward the
front or rear of the vehicle. A small degree of
positive caster improves directional stability and
increases resistance to crosswinds or road surface
deviation.
The device of the pre~ent invention,
illustrated in Figure 3, eliminates the play
developed between the radius arm end portion 30 and
the bus'hing 32 and adjusts the caster angle. As
illustrated in Figure 4, the axis 20 of the steering
knuckle is 0 caster. Inclining the steering knuckle
axis toward the front of the ve'hicle to line 20a
provides a negative caster angle. Inclining the
steering knuckle axis toward the rear of the vehicle
provides a positive caster angle as identified by
reference character 20b.
The device 52 of the present invention
includes a longitudinal main body portion 54 being
curved about a longitudinal axis 55. The main body
portion 54 is generally arcuate in cross section. A
lip 56 is attached at one end and extends generally
perpendicular to the longitudinal axis 55. The main
body portion 54 of the device 52 has an inwardly
curved surface area 60 that generally conforms to the
outer curvature of the end portion 30 of the radius
armO
As illustrated in Figure 2, the device 52 of
the present invention adjusts caster without having
:~ 3 ~ L S
to disconnect the radius arm from the bushing. The
device 52 also eliminates any play that has developed
due to wear of the bushing 32 ~rom contact between
the bore 40 surfaces and the end portion 30 of the
radius arm.
~ 8 best illustratecl in Figure 5, the nut 44
is threadably disengaged from the threaded end 42 of
the end portion 30 of the radius ar~. The washer 46
and insulator 48 are also removed from the end
portion 30. The device 52 is then ins~rted on an
upper or a lower surface, depending on the caster
adjustment required of the end portion 30.
Positioning the device below the end portion 30 moves
the steering knuckle axis forward or to the position
20a of Figure 4. Positioning the device on a top
surface of the end portion 30 moves the steering
knuckle axis to the position 20b of Figure 4. The
lip 56 acts as a stop and retaining means fox
retaining the main body portion 54 in a selected
position. In addition, the lip 56 may be used to
facilitate removal of the device 52, if needed.
As illustrated in Figures 6, 7 and 8 (and
also Figures 6a, 7a and 8a), the thickness of the
longitudinal body 54, as depicted by arrows 62, 64
and 66 in Figures 6a, 7a and 8a, all respectively,
can be varied. Varying the thickness of the
longitudinal body 54 will vary the distance that the
end of the radius arm is moved thereby varying the
amount that the caster can be adjusted. The device
52 of the present invention is preferably provided as
a set of devices with different thicknesses so that a
device with the proper thickness is inserted to
adjust the caster the desired degree.
13~611~
To facilitate insertion of the device 52 of
the present invention, a tool 70, as illustrated in
Figures S and 9 i8 provided. The tool 70 includes a
front portion 72 and a rear portion 74 separated by a
flange portion 88. The front portion 72 and the rear
portion 74 are interchangable. The front portion 72
is inserted between the bushing 32 and the end
portion of the radius arm 30, as illustrated in
Figure 2, abutting the flange 88 against the
bushing. Both the front portion 72 and the rear
portion 74 have an inner curvature conforming to the
outer surface curvature of the radius arm 30, and an
outer surface curvature con~orming to the curvature
of the inner surface of the bushing bore.
The tool 70 is provided with a plurality of
guide holes 85 disposed within the Elange portion
88. If the space between the radius arm end portion
30 and the surface of the bore of the bushing 32 is
not sufficient to accept a device 52 having a
particular thickness, the guide holes 86 of the tool
70 are used to guide a drill bit 90 run by a drill 92
to remove amounts of rubber in the bushing. A series
of holes are drilled on a diametrically opposite side
from the point of insertion of the device 52 which
permits the drilled bushing section to be compressed
so that the device 52 is insertable between the end
portion 30 and the bushing 32, as illustrated in
Figure 10.
After the holes have been drilled in the
bushing, the device 52 is inserted between the end
:: .
portion 30 and the bushing 32. The lip 56 will
prevent the device ~rom being inserted further than
lS necessary.
After the device 52 is placed in position
and the caster adjusted to the desired angle, the
insulator 48 is placed against the spacer 50 and the
washer 46 is placed against the insulator 48 and the
nut 44 i5 threaded onto the threaded end section 42
of the radius arm.
The device of the present invention is also
useful in correcting caster where ca~ter i~ affected
by play developing between a stabilizer bar and
bushing retaining the stabilizer bar and weakening of
coil spring on strut. One such suspension i~
generally indicated at 100 in Figure 11. The
suspension system shown in Figure 11 is a suspension
system found in the Ford Escort. The suspension
system includes a MacPherson strut 102 including coil
spring 103 supporting each wheel on either side of
the vehicle. The wheels are attached to steering
knuckles 106 (only one being shown)~ The steering
knuckle, in turn, i9 supported at one point by a
control arm assembly 108 (only one being shown)~ The
control arm as~emblies are connected by a stabilizer
bar 110 that is secured to the vehicle by stabilizer
bar body brackets 112.
Referring to Figure 12, the stabilizer bar
110 extends through a stabilizer bar bushing 114.
The stabilizer bar bushing 114 is held in place by a
stabilizer bar bracket 116 that is attached to the
stabilizer bar body bracket 112 by bolts 118 and 120
engaging nuts 122 and 124.
:
.
6 ~
-- 10 --
It will be appreciated that if play develops
between the bushing 114 and the stabilizer bar 110,
such that caster was affected, the bushing 114 had to
be replaced. This required removing 'bracket 116,
cutting the bushing 114 80 that the bushing is
removed from the stabilizer bar and installing a new
bushing that is provided in two halves (hereinafter
referred to as a ~plit bu~hing). After the split
bushing is put on a stabilizer bar, th~ bracket 116
is then reattached to the stabilizer bar body bracket
112 to hold the split bushing in place.
Using a device 126 of the present invention
provides a simple method for eliminating the play
between the stabilizer bar and the stabilizer bar
bushing 114 and adjusting caster to a desired value.
The method of the present invention includes
loosening bolts 118 and 120 enouyh so that the device
126 can be inserted between the bushing 114 and the
stabilizer bar 110, either forward of the stabilizer
bar 110 or rearward of the stabilizer bar 110.
Placing the device 126 in front of the stabiliæer bar
110 reduces caster. Placing the device 125 rearward
of the stabilizer bar 110 increases caster.
After the device 126 i~ inserted in the
desirad position, the bolts 118 and 120 are
retightened, attaching the stabilizer bar bracket 116
once again to the stabilizer bar body bracket 112.
An alternative embodiment of the tool of the
present invention is generally indicated at 130 in
Figure 13. The tool 130 is a relatively flat plate
132 having at one end an aperture 134 with a diameter
sufficient to accept, for example, the end portion of
the radius arm 30 which is typically a 7/8 inch
' ~3~
11 --
diameter. In diametrically oppo~ite sides of the
aperture 134 are two sets of a series of 1/8 inch
guide holes 136 and 138, respectively. The tool 130
is used in a similar manner to ~he tool 70
illustrated in Figures 5, 9 and 10. The end portion
30 of the radius arm is inserted into the aperture
134 and then either guide holes 136 or guide holes
138 may be used to drill the bushing 32 as needed.
On an oppo~ite end of the tool 130 i8
located a curved Rlot 140 having a 7/16 inch radius
with a plurality of 1/8 inch guide holes 142 located
along the periphery of the slot 140. The slot 140
along with guide holes 142 is used to guide drilling
holes in the bushing when the device of the present
invention is used to adjust a stabilizer bar. The
edge surface of the slot 140 is placed against the
stabilizer bar along side the bushing, and the guide
holes 142 are used to guide a drill bit to drill the
bu hing, in a similar manner as shown in Figure 10.
One end of the tool 130 is used as a handle while
utilizing the other end to guide drilling holes in
the bushing.
In still another alternative ~mbodiment of
the tool generally indicated at 144 in Figure 14, the
tool 144 is a flat plate that includes an aperture
146 similar to aperture 134 of the tool in Figure
13. The apertur~ 146 includes two serie~ of guide
holes positioned on diametrically opposite sides of
the aperture 146. In addition, the tool 144 includes
a series of curved slots 152, 154 and 156. Each
curved slot has a plurality of 1/8 inch ~uide holes
associated therewith. The curved slot 152 has guide
~31611~
- 12 -
holes 15~ disposed along the periphery of the slot.
Similarly, the curved slot 154 has a plurality of
guide holes 160 disposed along the periphery of the
slot 154. The slot 156 also has a plura~ity of guide
holes 162 as~ociated therewith. The slots 152~ 154
and 156 each have a different radius and are used for
a stabilizer bars of differe!nt diameters, in the same
manner that curved slot 140 is used of Figure 13. In
the working embodiment, the slot 152 will accept a
bar of 1 inch diameter, the slot 154 will accept a
bar of 7/8 inch diameter, and the slot 156 will
accept a bar of 1 l/2 inch diameter.
In summary, the present invention provides a
solution for easily correcting caster in a vehicle
wheel having either a radius arm or stabilizer bar
retained within a bushing that can be worn. In
addition, the present invention provides a method for
correcting caster due to a worn bushing without
having to disconnect the radius arm or the stabilizer
bar.
Although the present invention has been
described with rPference to preferred embodiments,
workers skilled in the art will recognize that
changes may be made in form and detail without
departing from the spirit and scope of the invention.
.
.
