Note: Descriptions are shown in the official language in which they were submitted.
~1~23~Ç~
This invention relates to alignment apparatus for indicating the
angular relationships of the vehicle wheels such as caster, camber, toe-
in, and steering axis cant and, in particular, relates to an apparatus
employing a line of sight alignment instrument.
Vehicles, such as cars, truck trailers and light trucks, typically
require periodic maintenance checks and adjustment of front end alignment.
Normally, alignment is correctly set when the vehicle is manufactured,
howelter, after extensive use, damage to the front end or hard usage, such
as occurs by hitting curbs, potholes and the like, misalignment may occur
and the vehicle will encounter handling difficulties, a poor ride and
excessive tire wear characteristics related to the incorrect alignment.
Such handling difficulties include vehicle wandering and pulling to one
side~ which requires constant and annoying steering wheel correction by
the driver, hard steering and front tire shimmy.
Front end alignment centers on the precise geometric relationship
of a number of parts, even when they are changing relative pOSitiOIIS,
; which provide front wheel stability and control. These geometric angles
include toe-in, camber~ caster, and steering axis cant (sometimes termed
king pin inclination).
Camber is the angle which the center line of the wheel makes with a
vertical axis. The top of the wheel tilts away from the car so that the
tire is inclined vertically. Closely related to camber is toe-in, which
is the amount that both wheels are closer together a-t the front than at
the rear of the wheel. Both camber and toe-in are related to vehicle weight
on the wheel and to compression forces occurring on the steering linkage
with forward speed. Normally, the greater the camber, the greater is the
toe-in.
Caster is the cant of the upper ball joint toward the rear of the car.
Caster moves the pivot point of the wheel forward of the tire's center and
provides yet another type of directional stahility by causing a drag on the
bottom of the wheel when it turns, there~y resisting the turn and ~ending
to hold the wheel steady in the directi.on of straight ahead vehicle moven-ent.
2;~
It will be appreciated that too slight a caster angle will cause the wheels
to wander or weave at high speed and steer erratically when the brakes are
applied. In contrast, too great a caster angle encourages hard steering
and low speed shimmy. Additionally, placing the weight of the car directly
over the pivot point allows the easiest possible steering and removes load
from the outside wheel race bearings.
Steering axis cant, or king pin inclination in vehicles having a king-
pinl is the angle Erom the vertical at which the steering knuckle is
attached to the upper and lower ball joints. The canted steering knuckle
lo controls wheel directional stability by forcing the wheel to lift the
chassis in order to turn from a straight ahead direction. As the steering
arm releases its force Oll the wheel, the wheel automatically tends to
return to its straight ahead position under the downward force of the
chassis weight.
Additionally, the vehicle must track properly to make for easier
steering and prevent excessive tire wear. Tracking is the condition whereby
the rear wheels of the car follow the front wheels in parallel relation.
Further, the dual rear wheels of truck tractors and trailers may be
out of alignment specification and trackingl toe and camber may need to
be properly set.
The present invention provides mean.s and a method of use thereof
whereby all of the above alignment checks can be accurately accomplished.
l`he principal objects of the present invention are: to
provide a wheel alignment apparatus utilizing a minimum of
.'~-,.
components; to provi~e a wheel alignment apparatus employing
an accurate sighting means for de-termining angular relationships;
to provide a wheel alignment apparatus using scaled targets
which are easy to read and located for the convenience of
the operator; to provide a wheel alignment apparatus which
is mobile and can be easily moved into and out of operational
position; to provide a wheel alignment apparatus which is
capable of a high degree of accuracy; to provide a wheel
alignment apparatus in which certain components thereof may
be conveniently stored after use in a relatively small area;
to provide a wheel alignment apparatus for checking caster,
camber/ toe-in and steering axis cant; to provide such a
wheel alignment apparatus which a method of use therefor is
easily and quickly learned by laymen; to provide a method
for the use of the wheel alignment apparatus which is re:Latively
easy and quickly accomplished whereby an operator may align
the vehicle in a reIatively short period of time; to provide
such an alignment apparatus utilizing laser beams wherein
the lasers are adjustably and movably mounted for accurate
positioning relative to a vehicle and targets located relative
thereto for alignment checks; to provide such alignment
apparatus usable on garage floors and the like whereby
special platforms and pits are not necessary; to provide
such alignment apparatus wherein laser support structure
permits variatation of spacing, elevational and -tilt to
accommodate different size and types of vehicles; to provide
such alignment apparatus with scaled targets and mountings
which are adjustable for accommodating different wheel and
tire sizes for accurate checking of substantially all vehicles;
and to provide a wheel alignment apparatus which is relati~ely
inexpensive, sturdy and efficient in use and i.n which a
method for use thereof is simply and easily accomplished.
Accordiny to one aspect of the invention there is
provided apparatus Eor checking wheel alignment of a wheeled
vehicle comprising: (a) a base structure having a surface
supporting a vehicle Eor alignment checks thereof; (b) target
structure mountable on the wheels of a vehicle and having scaled
targets located thereon in diametrically opposed relation and
laterally outwardly of the wheels; (c) laterally spaced laser
beam projecting members positioned longitudinally from and
aligned with the target structure and spaced generally laterally
from the longitudinal axis of the vehicle; (d) a support
structure for said laser beam members having spaced apart
standards and a shaft member extending therebetween; said shaft
having spaced arms; (e) means rotatably mounting said spaced
arms on said standards with said shaft radially outwardly from
said rotatable mounting means; (f) means adjustably rotating said
arms for raising and lowering said arms and the shaft thereon to
vary the spacing from the base surface; (g) means piutally
mounting the shaft on the arms for adjusting the angle of said
laser beams relative to ~he base surface; (h~ means movably
mounting the laser beam members on the shaft for adjusting the
lateral spacing thereof; and (i) means for positioning the
vehicle and laser beam members relative to the base surface for
the laser beam members to project beams parallel to the
longitudinal axis of said vehicle and equally spaced therefrom
for impingement on the scaled targets on the respective wheels
of said vehicle.
According to another aspect of the invention there is
provided a method for checking the alignment of the wheels of a
vehicle, which comprises: (a) establishing a line of sight from
a sighting instrument parallel to and longitudinally spaced from
a longitudinal axis of a vehicle; (b) mounting a target
structure on a wheel, said target structure having a target
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situated laterally of said wheel and spaced radially of the
axle of said wheel; (c) locating said target at a first cardinal
axial point of said wheel; (d) directing said line of sight to
impinge on said target at said first cardinal point; ~e) locat~
ing said target at a second cardinal axial point of said wheel;
(f) directing said line of sight to impinge on said target at
said second cardinal point; (g~ measuring the lateral difference
between the impingement of said line of sight on sa.id target in
said first cardinal position and in said second cardinal
position, the difference measurement corresponding to a measure-
ment of angular alignment of said ~heel.
Other objects and advantages of this invention will
become apparent from the following description taken in
connection with the accompanying drawings wherein are set orth,
by way of illustration and example, cextain embodiments of this
invention.
Figure 1 is a top plan view of a wheel alignment
apparatus
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3~
embod~ing the present invention and shown in connection with
an automotive vehicle.
Fig. 2 is a side elevational view of the wheel alignment
apparatus with target components thereof mounted upon front
wheel rims of the vehicle.
Fig. 3 is a diagrammatic, fragmentary, elevational view
of components of the wheel alignment apparatus positioned
adjacent rear wheels of the vehicle.
Fig. 4 is a front elevational view of sighting instruments
and support structure therefor comprisiny portions of the
alignment apparatus~
Fig. 5 is a side elevational view of the sighting
instrument and support structure therefor.
Fig. 6 is a fragmentary, rear elevational view of the
support structure for the sighting instruments and showing
details of an elevating mechanism therefor.
Fig. 7 is a side elevational view of a wheel engaging
and target support structure having sighting targets mounted
thereon.
Fig. 8 is a front elevational view of the wheel engaging
and target support structure and having portions broken away
to show engagment thereof with the wheel rim.
Fig. 9 is a diagrammatic, front elevational view of the
front wheels of the vehicle showing the wheels lifted from
ground support and with wheel engaging and target support
structures mounted thereon.
Fig. 10 is a diagrammatic front elevational view of the
vehicle front wheels in ground supporting contact and with
target structures mounted thereon.
Fig. 11 is a diagrammatic elevational view of a front
wheel with targets mounted thereon and shown with regard to
the measurement of camber, the angle of which is exaggerated
L ~
for purposes of illustration.
Fig. 12 is a diagrammatic, front elevational view
illustrating toe-in measurement, the angle of which is
exaggexated for purposes of illustration.
Fig. 13 is a diagrammatic, top plan view of a vehicle
axle and front wheels thereof and illustrating caster measurement.
Fig. 14 is a diagrammatic, front elevational view
depicting a measurement of caster in one turning direction
of the wheel.
Fig. 15 is a diagrammatic, front elevational view
showing caster measurement in the opposite turning direction
to that shown in Fig. 14.
Fiy. 16 is a diagrammatic, front elevational view
showing the vehicle front wheel lifted from ground contact
and turned in one direction to provide a measurement for
determining steering axis cant.
Fig. 17 is a diagrammatic, front elevational view of
the vehicle front wheel lifted from ground contact and
turned in the opposite direction to that shown in Fiy. 15 to
provide a second measurement for steering axis cant and
which, in combination with the measurement provided in Fig.
16, corresponds to the angle of steering axis cant.
Fig. 18 is an enlarged, fragmentary view of a sighting
instrument and movable support structure therefor.
Flg. 19 is a perspective view of a modified form of
sighting instrument support structure and showing a cabinet
enclosing same and providing storage space for tools and
components associated with the wheel aliynment apparatus.
Fiy. 20 is an elevational view of a front target used
in the measurement of toe-in and toe~out.
Fig. 21 is an elevational view of a rear target used in
the measurement of toe-in and toe-out.
;3~
Fig. 22 is an elevational view of a front target used
in the measurement of king pin inclination or steering axis
cant.
Fig. 23 is an elevational view of a rear target used in
the measurement of king pin inclination or steering axis
cant.
Fig. 24 is an elevational view oE a lower, or first
target used in the determination of camber and caster of the
vehicle's left front wheel.
Fig. 25 is an elevational view of an upper, or second
target used in the determination of camber and caster o the
vehicle left front wheel.
Fig. 26 is an elevational view of a lower, or first
target used in the determination of camber and caster of the
vehicle right front wheel.
Fig. 27 is an elevational view of an upper, or second
target used in the determination of camber and caster of the
vehicle right front wheel.
Referring to the drawings in more detail:
As required, detailed embodiments of the present invention
are disclosed herein, however, it is to be understood that
the disclosed embodiments are merely exemplary of the invention
which may be embodied in various forms, therefore, specific
structural and functional details as disclosed herein are
not to be interpreted as limiting, but merely as a basis for
the claims and as a representative basis for teaching one
skilled in the art to variously employ the present invention
in virtually any appropriately detailed structure.
The reference numeral 1 generally indicates a line of
sight wheel alignment apparatus embodying the present invention.
The apparatus 1 includes a movable support means 2 with
sighting instruments 3 mounted thereon from which lines of
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sight 5 are respectively dire,ted at dïscrete indicia or
scale marks on targets 4 mounted upon the wheels of a vehicle.
An automotive vehicle 7, such as a truck or car of
which the front end alignment is to be checked is positioned
50 that access is gained to the underside thereof, as by
raising on roller plates 6 movable on the flat surface of
the garage floor 8~ however, a ramp or other vehicle elevating
and supporting structure may be used ïn those situations where
a permanent or semi-permanent installation is desired. It
will be appreciated that the movable sighting instrument
support means 2 and the roller plates 6 permit vehicle align-
ment to be conducted on a ~are base or floor, that is, a floor
having no fixed or permanent mountings or structures. Therefore,
the alignment apparatus I requires a minimum of floor space and
is particularly suited for Erame and body shops, service
stations, or the like where there is little or no space avail-
able for permanent installations.
The support means 2 rests upon the garage floor 8, Figs.
4 and 5 and preferably has a frame or base 16 having sets of
front and rear casters or wheels 14 and 15 mounted on the
underside thereof Eor movement on the floor 8. Upright mounts
18 and 19 are secured to opposite ends of the base 16 and have
respective front and rear vertical legs 21 and 22 connected
by a top bar or arm 23 extending therebetween.
The elongate frame or base 16 is movable upon the floor
8 to locate, or "square", the longitudinal axis of the
support means 2 transversely to the longitudinal axis of the
vehicle 7. Once the frame or base 16 has been properly
positioned, as described below, the same is retained in
position by adjustable jack screws 26 adjacent each Eront
wheel 14 and having a lower floor engaging pad 27 and an
-8-
upper crank arm 28.
An elongate back beam 33 extends between the mounts 18
and 19 and has opposite ends connected to the respective
arms 23 by journal boxes 34 and 35 with interior, self-
aligning bearings permitting rotation of the back beam 33.
Transverse arms 36 and 37 are rigidly secured to the
back beam 33 spaced from and adjacent the journal boxes 34
and 35. Respective front ends 38 and 39 thereof are split
inwardly to bearing surfaces 40, Fig. 5, for receiving and
rotatably supporting an elongate sighting instrument supporting
front beam 41. Fasteners 32, such as bolts, extend through
the ends 38 and 39 and cause the same to clamp around ends
43 of the beam 41 ~or preventing excessive free rotation.
Means for rotating the back beam 33 and thereby moving the
front beam 41 upwardly or downwardly relative to the back
beam 33 are included and, in the illustrated example, Fig.
6. the arm 36 has a mid portion ~2 connected to a jack screw
4~ via a swivel connector 45 on the arm 42. A journal 46
affixed to the base 16 mounts the bottom end of the jack
screw 44 thereto. ~ hand wheel 47 facilitates rotation of
the jack screw 44 for moving the front beam 41 upwardly and
downwardly.
The front beam 41 supports the sighting instruments 3
such as telescopes, light beam projectors and the like. In
the illustrated example, the sighting instruments 3 comprise
low power lasers 50 and 51 which project respective lines of
sight 5 beams of coherent, collimated radiation capable of
great accuracy for alignment. The sighting instruments 3,
exemplified as by the lasers 50 and 51, are preferably
sufficiently sensitive to minor misalignment angles to
permit relatively precise alignment of front end parts. The
sighting instruments 3 are preferably sturdily mounted to
supports andl in the ill-lstrated example, the lasers 50 and
51 are mounted within respective housings 49 rigidly connecte~
to sleeves 52 and 53 selectively movable along the front
beam 41.
Preferably, the front beam 41 ls transversely polygonal,
such as square or rectangular and the sleeves 52 and 53 do
not rotate relative thereto. In the illustrated example,
the front beam 41 has cylindrical ends 43 which are rotatable
within the arm remote ends 3~ and 39 and thereby enable both
lasers 50 and 51 to rotate upwardly and downwardly together
and move lines of sight 5 respectively projected therefrom
in parallel vertical planes. The sleeves 52 and 53/ Fig.
18, each have a rectangular body portion 54 with front and
rear sides 55 and 56 spaced from the front and rear surfaces
of the beam 41. Ears 57 project outwardly from the front
side 55 and wheels 58 are mounted thereto, as by pin 59.
The front wheels 58 extend through an opening 55' in the
front side 55 for rolling engagement with the beam 41. A
rear tension wheel 60 is mounted to the rear side 56 by a
lever arm 61 pivotally connected to the rear side 56 by an
ear 57' and having a spring 61' held in compression at an
end of the arm 61. The rear wheel 60 contacts the beam 41
through an opening 56' in the rear side 56 of the body
portion 54 and permits rolling movement of the respective
sleeves 52 and 53 on the beam 41. The upper side of each
body portion 54 slides on the beam 41 and frictionally
inhibits free movement thereon while the rear tension wheels
60 inhibit wobbling movement or misalignment of the sleeves
53 and 52 thereon. Thus, the sleeves 52 and 53 and thereby
the lasers 50 and 51 are selectively movable on the beam 41
and are maintained in s-traight ahead posltion.
The sighting instruments 3, such as the lasers 50 and
--10--
2~3~6
5]., project respective lines of sight 5 toward targets 4
located on wheel~ 10 o the vehicle 7. In the illustrated
example, Figs. 7 and 8, an adjustable target supporting and
wheel engaging structure 62 is mounted to the inner surface
of the tire bead flange 63 of the wheel rim 64. The wheel
engaging structure 62 includes a vertical sha:Et 66, such as
formed of rectangular metal tubing, and a cross bar 67 rigidly
and normally connected thereto as by welding, at a structure
center 68. Movable up and down on the vertical shaft 66 are
a pair of upper and lower vertically curved legs 69 and 70
having respective thumbscrew secured sleeve ends 71 and 72
selectively slidable upwardly and downwardly on the vertical
shaft 66 relative to the center 68 to coaxially align the center
68 with the wheel hub center or vehicle axle. The upper and
lower legs 69 and 70 have respectïve stra.ight portions 69'
and 70' extending parallel to the vertïcal shaft 66 and spaced
laterally therefrom toward the rim 64. An upper rim engaging
post 7~ has a sleeve end 75 slidably connecting the post 74
to the upper leg straight portion 69'. A hi.nged tip end 76
2Q of the post 74 engages the interior surface of the tire bead
flange 63 and is tightly maintained in engagement by adjust-
ment of a primary thumb screw 77 extended through the sleeve
end 75 and a secondary thumb screw 78 extended through a lever
arm portion 79 of the hinged tip end 76 and contacting the
sleeve end 7~.
Extending outwardly .fron~ the lower leg 70 and inwardly
toward the wheel rim 64 are a pair of diverging, spaced
lower rim engaging posts 81 and 82 which have short, threaded,
shaft ends 83 and 84 extended horizontally and laterally
therefrom for engag:ing the tire bead flange 63. The posts
81 and 82 are connected to a central sleeve 85 through which
is extended a thumb screw 86 for selectively positioning the
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sleeve 85 along the stxaight portion 70'.
The targets 4 are mounted upon the wheel engaging
structure 62 and extend outwardly and horizontally from
portions of the vertical shaft 66 and the cross bar 67. It
will be appreciated that the vertical shaft 66 and the
horizontal cross bar 67 are of the same length and that
certain targets 4, described below, are located at cardinal
points, that is, along the horlzontal and vertical axis
thereof, relative to the front wheel 10, such as top,
bottom, front and rear with 90 spacing between each target
4. Further, placement of the center 68 of the wheel engaging
structure 62 is adjusted by the use of the various sleeves
and thumb screws and, when correctly adjusted, the center 68
should be aligned coaxially with t.he center of the wheel
axle shaft or hub cap of the vehicle to space certain
targets 4 equidistantly from the center 68 and at 90 angles
from each other.
The targets 4 are preferably laterally adjustable
toward and away from a respective vertical shaft 66 and
cross bar 67 so as to be the same distance from the wheel
rim 64. In the illustrated example, the targets 4 are
mounted upon shafts 91 having mid portions 94 which are
square in cross section and which have connector ends 90
rigidly mounted on sleeves 88 movable along the vertica:L
shaft 66 and the cross bar 67 and fixed in position therealong
by thumbscrews 89. Flanged nuts 92 on threaded free ends 96
of the bolt shafts 91 facilitate manual adjustment of the
: targets 4 inwardly and outwardly relative to the wheel rim
64. Coil springs 93 are sleeved on the shafts 91 between
the sleeve 88 and ends of target tubular members 9S sleeved
on the shafts 91 and urge the targets 4 laterally away from
a respective sleeve 88.
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When the wheel en~aging and target supporting structure
62 is mounted to the wheel rim 64, certain targets 4 are
spaced circumferentially and laterally of the wheel axle and
cardinally located at opposite vertical and horizontal
positions around the rim 64; these respective target positions
are hereafter designated as upper and lower targets 97 and
98 and front and rear targets 99 and lO0. Each of the
targets 4 have indicia thereon providing scale measurements
described below, for determining alignment angles of the
front wheels 10. The targets 4 are preferably comprised of
a sturdy, shatter resistant transparent material, such as
plexiglass, which permits a line of sight 5 from a sighting
instrument 3 to pass therethrough, as for example through
the front target 99 to the rear target 100 and thereby
visibly impinge upon a discrete scale mark thereof as described
below.
The targets 4 are individually illustrated in Figs. 20
through 26. Figs. 20 and 21 show targets which are used to
measure horizontal angular relationships, such as toe-in or
toe-out, and are consequently mounted upon the opposite ends
67' of the cross bar 67. A front target 99 has vertical and
horizontal lines 104 and 105 which cross at 106 and thereby
form a central aiming point for impingement of a line of
sight 5 thereon. rrhe transparency of the front target 99
permits the line of sight 5 to pass therethrough and impinge
upon the rear target lO0, Fig. 21 which may have a frosted
or lightly textured surface to better permit seeing the
point of impingement of the line of sight 5 thereon, as for
example, a laser light beam from the lasers 50 and 51.
The rear target lO0 includes an inch scale 108 showing
up to two inches of toe-out or toe-in and a metric scale lO9
with up to 4 1/2 cm of toe-out or toe-in and which are
13-
separated by a horizontal line 110. A vertical zero line 111
divides a toe-ollt side 113 and a toe-ïn side 114 of the
target 100.
Figs. 25 through 27 show left and rïght sets of targets
4 which are used to measure vertical angular relationships,
such as camber, and measurements which are predominately
vertical angular relationships, such as caster. The lower
targets 98 for the vehïcle left and right front wheels 10,
~igs. 24 and 26 respectively are preferably identical and
have horizontal and vertical lïnes 117 and 118 which cross
at point 119 and provïde an aiming point for the lïne of
sight S. A left front wheel upper target 971 Fig. 25 and a
right front wheel upper target 97, Fïg. 27 each have a lower
caster scale 120 showing caster in degrees from zero to
eight and an upper camber scale 121 showing camber in degrees
from zero to six and separated from the caster scale 120 by
a horizontal line 122. A vertical zero line 124 divides
positive and negative sides 125 and 126 of the camber and
caster scales 120 and 121. The positive and negative sides
125 and 126 accord with the wheels as the alignment apparatus
operator would look at them from the sighting instruments 3
and, for example, a positive camber measurement means that the
bottom of the wheel 10 tilts inwardly toward the longitudinal
axis, or center or the vehicle 7.
Figs. 22 ancl 23 show targets 4 which are used to measure
the predominately horizontal angular relationship of king
pin inclination or steering axis cant and which are positioned
along the cross bar 67 and preferably located radially
inwardly of the front and rear targets 99 and 100. A front
steering axis cant target 127, Fig. 22, has a horizontal line
128 extending thereacross and a central vertical line
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129 dividing the target 127 into equal left turn and right
turn aiming portions 130 and 131 for receiving the line of
sight 5 as the forward portion of the front wheel 10 moves
outwardly and inwardly about the vehicle turning axis. Each
portion 130 and 131 has a vertical line 132 for directing a
line o~ sight 5 therethrough when the front wheel 10 is
turned 20.
A rear steering axis cant target 135, Fig. 23, has left
turn and right turn aiming portions 136 and 137 oppositely
placed of the front steering axis cant target 127 left turn
and right turn aiming portions 130 and 131 and positioned
for receiving a line of sight 5 as the rearward portion of
the front wheel 10 moves outwardly and inwardly. The left
turn and right turn aiming portions 136 and 137 are separated
by a vertical dividing line 139 and each have a vertical
line 140 for indicating 20 of turn in the according direction.
A vertical scale 142 in each of the respective portions 136
and 137 shows the steering axis cant in degrees from five to
twenty for the direction of turn.
The steering axis cant targets 127 and 135 are each
located on the cross bar 67 between the ends 67' and the
center 68. Clips or sleeves 155 are open on the rear side
thereof for outward detachment from the cross bar 67 and are
mounted to the targets 127 and 135 as described in connection
with the sleeves 88 and the targets 97 through 100. To
maintain a set relationship to the center 68, the clips or
sleeves 155 are preferably connectible to the cross bar 67
only at 157 and 158 and have an interior pin insertable
within a bore (not shown) in the cross bar 67, the distance
of the bore from the center 68 being known and set to accord
with the degree scales 142 of the rear steering axis cant
target 135. The steering axis cant targets 127 and 135
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. . .
extend upwardly to not interfere with a line of sight 5
directed toward the front and rear targets 99 and 100 during
determination of toe-ln and toe-out. The steering axis cant
targets 127 and 135 are located at cardinal positions, that
is, along the horizontal cross bar 67, radially inward of
the front and rear targets 99 and 100.
Additionally, indicia bearin~ left and right rear wheel
targets 145 and 146 are positioned adjoining left and right
rear tires 147 and 148~ Fig. 3, during an initial or vehicle
positioning phase of alignment. In the illustrated example,
each rear target 145 and 146 includes an upright standard
150 for positioning the target by the wheel and having
supportive feet 151 spaced whereby the rear wheel targets
145 and 145 abut the rear tires 147 and 14~ and extend
normally therefrom. Preferably, each rear wheel target 145
and 146 has vertical scale lines spaced in centimeters or
inches, and with numbers thereof progressing serially toward
outside edges 152 thereof.
To use the alignment apparatus 1 the vehicle 7 is
lifted, as by power jacks 160 and the front wheels 10, and
pre~erably the rear wheels 145 and 146 are positioned atop
the roller plates 6. The vehicle 7 is aligned by the driver
as much as possible transversely to the front beam 41.
As is conventional, the vehicle front end is checked
for worn or loose fitting parts which must be replaced
before alignment. The mechanic uses a jack to raise the
~ront wheels above the roller plates 6 and shakes them both
horizontally and vertically to detect any looseness. The
mechanic spins the whee]s to test for deteriorated bearings.
30 Shock absorbers are checked for proper snubbing action by
lowering the front wheels 10 to the roller plates 6 and
bouncing the car up and down by hand. Frame damage which
;
~ -16-
would alter -tracking and turning characteristics is checked
by measuring carefully between common points, such as from
the rear edge of the front wheel rim to the rear edge of the
back wheel rim. A twisted or distorted chassis may make
front end alignment difficult if not impossible. Additionally,
the front tires should be equally worn and be equally inflated
for best alignment results.
Precise positioning of the vehicle 7 relative to the
sighting instrument support means 2 is accomplished by
placing the left and right rear wheel targets 1~5 and 146
against the rear wheels 147 and 148 so that they extend
normally therefrom. Wheel engaging and target supporting
structures 62 are connected to each of the front wheels 10,
as described in connection with Figs. 7 and 8, so that the
shaft 66 is vertical and the cross bar 67 is horizontal. A
bubble level (not shown) may be used for proper positioning
of the structure 62. Using a measuring tape or rule, the
targets 4 are adjusted toward or away from the vertical
shaft 66 and the cross bar 67 so that they are laterally
equidistant from the tire rim 64 and thereby aligned parallelly
to the side of the front wheel.
The sleeves 88 of the front and rear targets 99 and 100
are moved along the cross bar 67 until they are even with
the margins of the front wheel 10 so that the front and rear
targets 99 and 100 provide a true measurement of toe-in and
toe-out. Preferably, the sleeves 88 of the upper and lower
targets 97 and 98 are not moved as the scales thereof are
calibrated with respect to a set distance or radius between
the targets 97 and 98 and the structure center 68. Accordingly,
it is preferred that the upper target 97 be adjusted to
extend downwardly and the lower target 98 adjusted to extend
upwardly for equidistant spacing from the center 68.
x~
Using a rule to measure the radius of the front tire to
the floor 8, the jack screw 44 is rotated to adjust the
front beam 41 upwardly or downwardly until the lines of
sight 5 of the sighting instruments 3, such as the lasers 50
and 51, are horizontally directed through the axle or hub
center of the rim 64. The lasers 50 and 51 are selectively
moved inwardly or outwardly on the front beam 41 until the
lines of sight 5, such as laser light beams, extend parallel
to the sides of the vehicle 7 and laterally equldistant from
the front and rear wheels as determined by the left and
right rear wheel targets 145 and 146 and means such as the
front and rear targets 99 and 100 or a transparent ruled
card or plate (not shown) held manually against the front
wheel 10. If the car 7 i5 located properly with respect to
the front beam 41, the lines of sight will impinge at
points 162 and 163 on the left and right rear wheel targets
145 and 146 and equidistantly from the outside edges 152. If
the lines of sight 5 are not parallel to the vehicle sides,
the sighting instrument support means 2 is moved relative to
the vehicle 7 until the lines of sight 5 become parallel
thereto and then the floor engaging jack screws 26 are set
to maintain the elongate base 16 in fixed position. Additionally,
the front wheels 10 may be found to be turned relative to
the longitudinal axis of the vehicle 7. This will be detected
by comparing the position of impingement of the line of
sight 5 on the rear targets 100 relative to the front targets
99 for deviation, or difference of the scale markings.
Rotation of the steering wheel may be required to move the
front wheels 10 to a straight ahead position.
A twisted or distorted chassis, which would effect the
tracking characteristics of the vehicle, will become apparent
during this initial calibration and "setting-up" phase.
,:
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'
4~
Small deviations may be acceptable but certain conditions
may require frame straightening before front end alignment
can be accurately accomplished.
After the fron~ beam 41 is "squared", or aligned normally
to the front wheels 10 and the rear tires 104 and 105, each
of the front wheels 10 are checked for both lateral run-out;
i.e., misalignment in a plane perpendicular to the center
axis and radial run-out; i.e., misalignment or eccentricity
in the center axis. In this procedure, the front wheels 10
are raised from contact with the roller plates 6 by pneumatic
or hydraulic power jacks 160 so that the front wheels 10 are
substantially vertical Fig. 9. The front beam 41 is acljusted
either upwardly or downwardly until the line of sight 5 from
the sighting instrument 3 extends horiæontally through the
vehicle wheel center or axle. Next, the line of sight 5 is
rotated in a vertical plane toward either the upper target
97 or the lower target 98 to check for proper camber or
vertical run-out. The impingement of the line of sight 5,
such as the laser beam, with a scale mark on the target 97
20 or 98, as at point 164 is noted by marking with a grease
pencil, recording, or other means. Next, the wheel is
rotated 180 degrees and the impingement of the line of sight
5, as at point 165, noted upon the opposite target now in
the line of sight 5. The point of impingement of the line
of sight should be at the same lateral scale mark on both
targets. If there is deviation from proper vertical run-
out, suspension parts, such as the upper control arm, should
be adjusted until the points 164 and 165 lie in the same
vertical plane.
Next, horizontal or toe-in run-out is checked by
adjusting the front beam 41 until the line of sight 5 passes
through the horizontal front and rear targets 99 and 100.
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Horizontal run-out is checked by noting the point of line of
sight impingement upon the front target 99 as at point 166
and the reciprocal rear tar~et lO0. The point of impingement
upon the rear target 100 should be at the same lateral scale
marking as on the front target 99. If there is deviation,
suspension parts, such as the tire rod, should be adjusted.
Run-out checks are now complete and accordingly, the wheel,
when raised in the air and spun, should not wobble on its
axis.
The front wheels lO are then lowered onto the roller
plates 6, Fig. lO, or checking camber, illustrated in an
exaggerated angle thereof in Fig. ll or purposes of illustration.
First, the front beam 41 and the sighting instruments 3 are
adjusted so that the lines of sight 5 extend horizontally
and through the cross point ll9 of the bottom target 98.
The line of sight 5 in then moved upwardly in a vertical
plane to spot a point of impingement 167 on the camber scale
marks of the upper target 97, indicating, for example, 2 of
negative camber to the lower target 98. The deviation, or
degree of vertical angle~ appears as the difference from the
vertical between the line of sight impingement points of the
upper and lower targets 97 and 98 and the camber scale 121
provides a measurement corresponding to actual degrees of
camber. Adjustment of the suspension and steering parts may
be necessary to set in the manufacturer's specified camber
angle.
Measurement of toe-in or toe-out, Fig. 12, is accomplished
by procedures similar to camber measurement. Keeping the
front beam 41 in the same position as above, the sighting
instruments 3, such as the lasers 50 and 51 are located
thereon to direct the lines of sight 5 through the cross
point 106 of the front target 99. The line of sight 5
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extends through the front target 9~ and impinges the surface
of the rear target 100 on either the toe-in side 114 or the
toe-out side 113. As the front and rear targets 99 and 100
are adjacent the front wheel margins, the deviation, or
degree of horizontal angle from straight ahead~ indicated on
the rear target 100 is a true toe-in or toe-out measurement.
Here again, adjustment of the proper vehicle steering and
suspension parts, such as the tie rod, may be requiredO
Next to be checked is caster, Figs 13-15, which is the
cant of the upper ball joint toward the rear of the vehicle.
Caster, like car~er and toe-in, is measured with the weight
of the vehicle upon the front wheels. First, using the
degrees of turn scales of the front and rear steering axis
cant targets 127 and 135 for example, the wheels 10 are
turned 20 degrees either left or right from a s~ralgh~ ahead
direction Fig. 13. The lasers 50 and 51 are adjusted to
direct respective lines of sight 5 through cross points 119
of the lower targets 98 on the front wheels 10. The lines
of sight 5 are flipped upwardly and a point of impingement
168, for example, upon each caster scale 120 of the upper
targets 97 is noted, for example negative 2 ln a wheel
right turn, Fig. 14~ This is one direction of the angular
rotational deviation caused by the cant of the upper ball
joints. The wheels 10 are then turned 40 degrees in the
opposite direction or 20 degrees past the straight ahead
position, Fig. ]5 and using the same procedures as above,
the angular rotational deviation is noted upon the caster
scale 120 of the upper target 97, for example 3/4 degree
Fig. 15. The difference between the two measurements, for
example 1 1/4 degrees, is the angle of caster of the wheel
Steering axis cant, or kingpin inclination, is determined
with the weight of the vehicle 7 off the front wheels 10 and
3~
with the front end raised, as by the jacks 160, Figs. 16 and
17. The vehicle brakes are applied and held down to prevent
axial rotation of the front wheels 10. Next, the front beam
41 is adjusted upwardly so that a line of sight 5 extends
horizontally through the front and rear steering axis cant
targets 127 and 135. The sighting instruments 3 are adjusted
laterally to direc-t lines of sight 5 through the vertical
lines 132 of respective left and right turn portions 130 and
131 of the front steering axis cant target 127 and toward
the 20 turn lines 140 of left and right turn portions 136
and 137 of the rear steering axis cant target 135. The line
of sight 5 will align with one of the vertical lines 132 and
an opposite 20 turn line 140 when the front wheel is turned
20 from straight ahead posit.ion in either direction.
Using the above method to determine degrees of turn,
the front wheels 10 are turned right 20 degrees Fig. 16 and
the point of line of sight 5 impingement upon the vertical
scale 142 of the right turn portion 137 of the rear steering
axis cant target 135 no-ted, as for example lOU. The front
wheels 10 are turned left 40 degrees in the opposite direction,
or 20 degrees past the straight ahead position, Fig. 17, and
as determined the point of line of sight 5 impingement upon
the vertical scale 142 of the left turn portion 136 of the
rear steering axis cant target 135 noted, as for 8. The
angle of steering axis ~ant is then determined by the average
of tha right and left turn measurements for example 9.
A modified form of elongate base 16 of the sighting
instrument support 2 is shown in Fig. 19 whereby a cabinet
170 co~ers the base 16 and encloses the sight instruments 3
for providing a storage facility for the associated wheel
engaging and target support structures 62 and the rear wheel
targets 144 and 145. In the illustrated example, opposite
sides 172 and 173 and a back 174 extend upwardly from margins
of the base 16 and are covered by a top 175. Doors 177 and
178 are slidably mounted in a ~ront opening 179 of the
cabinet 170 and are movable thereacross to close o~f the
cabinet 170 and secure materials and tools therein.
It will be apparent from the preceeding description
that the wheel alignment apparatus of the present invention
has features which enable it to be easily and quickly used
by even a relatively inexperienced vehicle mechanic. Intensive
training is not required to enable the operator to understand
the theory and procedures of operation of the apparatus,
thus offering relatively few opportunities for error.
Further, relatively precise scale measurements are indicated
by a well defined, narrow beam of light for a readily
apparent visual display.
It is to be understood that while one form of this
invention has been illustrated and described, it is not to
be limited to this specific form or arrangement of parts
herein described and shown, except insofar as such limitations
are included in the following claims.
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