Note: Descriptions are shown in the official language in which they were submitted.
c~
The methods and systems utilized by the prior
art to eliminate the vibrations generated in vehicular
tires are basically modifications of balancing devices
utilized in industry to balance industrial components,
such as rotors, for the elimination of vibrations. The
terms "balance" and "unbalance" are popularly used to
indicate whether or not the part is free from vibration
as it is rotated. In this context, the term "balance"
denotes a condition wherein the rotor or the like is
rotating about its principal axis and coincident with its
supporting bearing.
In the case of a rotor, irrespective of its
configuration, the unbalancing forces always occur once
per revolution, which is the fundamental frequency of the
rotating rotor. In the case of long flexible rotors,
balancing is performed in multiple planes along the axis
of the rotor. In all cases, however, the rotor, once
balanced, has it principal axis of rotation rotating in
coincidence with its bearings. Balancing can be readily
accomplished since a rotor is effectively a homogenous,
non-flexible mass, and it is always sùpported in bearings
while freely rotating in space, whether durin~ balancin~
or in actual use.
A rubber tire, on the other hand, although it
is intended to be geometrically round, is not round when
in use since it does not freely rotate in space. Rather,
a tire must support a portion at least of the weight load
of the vehicle, and while supporting the load radially,
the tire is vertically in contact with the road. Unlike
a rotor, which is effectively a solid mass, a tire is flex-
0~
ible and expands and contracts in use. The radius of atire in the srea of vertical contact with the road is
always smaller than its radius at any other angle about
the tire due to the load it carries. The area in contact
with the road i3 known as the "tire patch" and it is this
area which is vertically loaded (referred to as the "loaded
radius"), the tire being deflected inwardly from 1/4 - 1/2
inch in the patch area under normal load and tire inflation.
Consequently, as the tire revolves about the vehicle's
wheel axle and bearings, which the tire also supports, the
physical geometric center of the tire is never coincident
with its principal bearing axis due to its constantly
changing supporting radius. This condition creates a con-
stantly changing dynamic disturbance which is directly
related to the velocity (revolutions per minute) of the
tire.
As a tire revolves, centrifugal forces are generated
which increase dramatically with increases in velocity;
and as the centrifugal forces increase, the tire tread
gradually expand~ radially outwardly - literally it grows -
and it also hardens due to the centrifugal outward forces
acting on the tread rubber as well as on the fabrics or
other reinforcement incorporated in the tire tread. As
the tire tread diameter grows, its over-all structure
stiffens and the size of the tire patch is reduced, along
with a reduction in side wallbulginess, resulting in an
increase in the loaded radius of the tire which acts to
raisé the vehicle. In addition, there are many variables
which enter into tire construction, including variations
caused by $he various splices in the tire; variations in the
10~3~
materials from which the tire is constructed, including
variations in their composition; dimensional irregularities
and inaccuracie~ both in the tire building equipment and in
curing; and, of course, human error. The net result is the
generation of a complexity of randomly distributed vibra-
tion producing forces which are transmitted to the vehicle
through its wheel hubs and axles. These vibration producing
forces manifest themselves as non-circular areas (non-
uniformities) extending around the periphery of the tire.
These non-uniformities vary in both location and magnitude
depending upon velocity, the velocity of particular concern
being the cruising speed at which the vehicle normally will
be operated. At cruising speeds the resiliency of the tire
is greatly reduced, which amplifies the stiffness of the non-
circular areas as they roll along the road. Since the sizeof the tire patch is also reduced, the unit load is greater,
which magnifies the reaction between the non-uniformities
and the road sorface. This reaction results in a rapidly
changing loaded ratius which generates a complex up and down
movement of the wheel hub and axle for each revolution of the
tire as the non-uniformities come into contact with the road
surface, and these movements are transmitted as vibrations to
the vehicle.
Although the terms "balance" and "unbalance" also have
been extenxively used in the tire manufacturing and correction
art, the terms are misleading and generally apply only to a
sm~ll spectrum of the vibration producing forces, usually being
confined to the forces produced by lack of tire symmetry which
occur only once per revolution of the tire and are variable in
magnitude, depending upon velocity. It may be flatly stated
1~.'30~30~
that all tires leaving t~e tire manufacturer's plant are in
an over^all self-exciting condition, that is, they are not
free from vibration when in use. Even though various
"balancing" steps may be performed by the automobile
manufacturer or by the seller or user of the tires which
may improve their "balance", the corrected tires are not
free from vibration causing forces which are centrifugally
generated either at the fundamental frequency or at fre-
quencies of higher order. While certain prior art processes
have included the honing of the outside periphery (tread)
of the tire to improve its roundness and concentricity, the
areas of the tread to be honed are determined under essen-
tially static conditions, usually without loading to simu-
late the weight load placed on the tire in use. Even in
prior art systems wherein the tire is loaded and revolved
at speeds of approximately one to five miles per hour, the
physical eccentricity, if any, generated in the tire at
these low Rpeeds is quite different from the centrifugally
generated eccentricity encountered when the tire is re-
volved under true environmental-like conditions, i.e., under
load and at cruising speed. Suffice to say that the prior
art, while recognizing the existence of lateral and radial
force variations when a tire is revolved in space and the
desirability of compensating for these variations, has
totally failed to understand the true nature of the centri-
fugally developed forces and their effect on tire performance,
much less how to effectively correct the tire to reduce these
forces to an acceptable low level. The centrifugal forces
developed in a tire at relatively slow speeds, ~uch as 50 or
even 100 revolutions per minute, are normally neglible and
. . .
~o~
have no real effect on either tire non-uniformity or dynamic
unbalance. The vibration producing ~orces which cause the
real problem are those which occur at relatively high speeds,
normally cruising speed, and it is these forces which have
been wholly neglected by the prior art.
Prior art systems are known wherein "balancing" is
effected by adding weights to the wheel rim, or by adding
counterbalancing weights to the tire itself. Some add the
weights to the inside and others to the outside of the tire.
In one system the weight is added internally to the entire
crown of the tire and then removed as required. In all
instances, however, the correction attempted is not dictated
by realistic changes in tire configuration caused by high
angular centrifugal forces; rather, it is dictated by forces
encountered when the tire is in a static or near-static con-
dition. It may be additionally noted that where the weight
is added internally to the crown of a tire, the performance
characteristics of the tire are altered. As in the case
where material i8 honed from the periphery of the tire when
in a static or near-static condition, the location and ampli-
tude of the generated forces will change with changes in velo-
city; consequently the addition or subtraction of materi.al
from the crown of the t:ire may worsen rather than improve
vibration when the tire is operated at cruising speed.
In order to correct the tire both for peripheral non-
uniformities and for lack of symmetry, it is essential to
locate and measure, as well as segregate, the vibration pro-
ducing forces. To this end, the present invention utilizes
the measuring system disclosed in co-pending United States
Patent No. 3,862,570, dated January 28, 1975, in the name of
the present inventor. In accordance with the teachings of
o~cj
this patent, both the dynamic unsy~letrical forces and the
centrifugally generated forces which are ~he result of
radially loaded peripheral non-uniformities are simulta-
neously measured and recorded so that the appropriate cor-
rective measures may be taken.
The present invention relates to a system and proce-
- dures for correcting tires for both lack of symmetry and
vibrations created by dynamic non-uniformities which are
centrifugally developed in the tire when under load and at
crusing speed.
The measuring system of the aforementioned United
States Patent 3,862,570 is utilized to determine under
simulated load and cruising speed conditions simultaneously
and independently both the magnitude and location of all the
generated vibration producing forces. The dynamic un-
symmetrical forces, whether radial or lateral, create a
fundamental frequency signal once per revolution of the tire
irrespective of its velocity, whereas the signals which are
the result of centrifugally amplified peripheral non-uniform-
ities vary in frequency and distribution about the peripheryof the tire in accordance with its velocity. Two sets of
sensors are utilized to measure the generated forces, the
fir~t 8et being positioned to measure and locate peripheral
non-uniformities, with the second ~et positioned to measure
and locate unsymmetrical forces on opposite sides of the
tire. All of the generated force signals are fed to an all
purpose digital computer where they are recorded and stored.
The computer, in turn, controls the action of correcting
mechanism which acts on the tire in accordance with the
recorded data.
0~
The tire is corrected in two stages, the first stage
comprising the honing of the outside periphery of the tire
by means of one or more honing or grinding devices which
remove rubber from the tread of the tire in the amounts and
at the places to reduce the centrifugally generated non-
uniformlties to an acceptable low level, preferably to a
level where the generated forces are effectively zero.
After the tire has been first corrected to reduce or
eliminate its centrifugally generated non-uniformities, it
is then subjected to a second stage corrective step during
which weights are effectively added to the opposite sides
of the tire at the places and in the amounts necessary to
counterbalance the dynamic unbalance forces detected and
located by the measuring system. Preferably this is accom-
plished by bonding a pair of annular rubber rings to theinsides of the tire beads prior to testing - usually as an
incident of the manufacture of the tire - and in the second
stage corrective procedure portions of these rubber rings
are removed except in those locations and in those amounts
2~ necessary to counterbalance the tire so that it will be
symmetrical (dynamically in balance) when operated at cruising
speed. The removal of the designated portions of the rubber
rings is accomplished by a second stage honing or grinding
device which coacts with an oscillating tire cradle, the
cradle serving to bring the designated areas of the rings into
contact with the honing device. The portions of the rubber
rings which remain after the second stage honing operation
are tho~e necessary to dynamically counterbalance the tire to
eliminate both radial and lateral vibrations resulting from
lack of symmetry. The second stage honing device, together
with the oscillating tire cradle, are controlled by the com-
:~0~3~ 0~
puter in accordance with the stored signals indicative ofthe lack of symmetry. Alternatively, the signals indicating
the location and magnitude of unsymmetrical forces may be
utilized for the addition of counterbalancing amounts of weight
at the proper locations about the inner surfaces of the tire
beads or adjoining sidewall areas of the ti.re, as by the bonding
of strips or patches of rubber material of the required weight
and length to the tire at the proper locations.
In accordance with the present invention there is
lQ provided a method of correcting a rubber tire for yibration
producing forces generated in the tire whenioperated under
load and at cruising speed, which comprises the steps of:
revolving the tire at a cruising speed equal to from
50-9Q m.p.h. under a load simulating the weight load supported
by the t;re in normal use to develop centrifugally generated
forces in the tire,
measuring the magnitudes and locations of the centrifugally
generated forces developed in the revolving tire, said measured
forces compri.sing (:al forces generated by peripheral non-
2Q uniformities, and Cbl forces developed by lack of tiresymmetry, and
correcting the tire for both the (al and Ub~ forces in
t~o stages, the first stage comprisi.ng correction for the
(:al forces ~y remoYing rubber from the periphery of the tire
in accordance with the magnitude and location of the non-
uniformities w.hile the tire is rotating at cruising speed, and
the second stage comprising correction for the (b~ forces by
selecti.vely adding to or removing rubber from the tire in the
areas at or adjacent the tire beads in accordance with the
magnitude and location of the o~ forces.
lV'~
It is a principal object of the present invention
to provide a, new tire yibxation correcting procedure which
eliminates all types of vifirations in a tire as encountered
in use at highway cruising speeds.
It is another o~ject of the present invention to
provide a new tire correcting procedure which insures a uniform
supporting radius (loaded radius~ maintained by the axis of
rotation of the tire in reLation to the tire patch at cruising
speeds.
lQ It i5 another object of the present inYentiOn to
provide a new tire vibration correcting procedure wherein a
counterbalancing material, preferably rubber, is added to, or
subtracted from the inner surface of the side walls of the
tire itself at or immediateIy adjacent the tire beads.
A further ob;ect of the present invention is to
provide a new tire vibration correcting system which utilizes
the measuring system of the aforementioned United States Patent
3,862,570 and includes correction of the tire both for cen-
trifugally generated non-uniformities and for lack of symmetry
as determined and measured by the said measuring system.
Still another object of the present invention is to
correct the tire in a two stage corrective procedure, the
-8a-
1090.~
first sta~e co~.prising the honing of the periphery of the
ti~e at cruising speed to effectively eliminate centrif-
ugally generated non-uniformities, with the second stage
procedure comprising the effective addition of weights to
the inside of the side walls in a manner to counterbalance
the tire for lack of symmetry without in any way adversely
affecting the performance characterlstic of the tires pre-
viously corrected outer periphery.
Further objects and features of the present invention
will become apparent from the following detailed descrip-
tion when taken in conjunction with the accompanying draw-
ings.
FIGURE 1 is a schematic diagram illustrating the pre-
ferred embodiment of the present invention.
FIGURE 2 illustrates in cross-section a typical tire
with counterbalancing rubber rings secured to the inside
of the tire beads.
FIGURE 3 i8 a fragmentary perspective view of the
tire shown in FIGURE 2.
FIGURE 4 is a diagrammatic elevational view of a tire
in cross-section illustrating the oscillation of the tire
to effect honing of the rubber balancing rings.
Referring first to FIGURE 1 of the drawings, the
system and procedures of the present invention comprise the
provision of a supporting base 10 having a pair of rigid
upstanding frame members 11 and 12 which support pillow
blocks 13 and 14 in which the axle 15 is rotatably journaled.
A test wheel 16 is secured to the axle and the tire 17 to
be corrected is mounted on the test wheel and inflated to
normal pressure. A shaft 18 rotatably journaled in pillow
blocks 19 and 20 is also supported by the frame members 11
- and 12, the shaft 18 being driven by drive means 21 through
a suitable flexible coupling 22, which may comprise a uni-
1~)9~''30~
versal join~. rhe shaft 18 drives a road-simulating drum
23 positioned to contact and drive the tire 17.
Lifting means 24 and 25, which may comprise twin
screw means, or hydraulic or pneumatic lifters, adapted
to be raised and lowered in unison act hrough pillow
blocks 19, 20 and drive shaft 18 to cause the drum 23 to
bear against the tire 17 to simulate the weight load which
will be borne by the tire under normal conditions of use.
To this end, the axles 15 and 18 lie in parallel relation
to each other and in a common vertical plane. In addition,
the drive means 21 will be of sufficient capacity to
revolve the drum 23 and hence the tire 17 at cruising speeds
equivalent to from 50-90 miles per hour under load.
Sensors 26 and 27 are mounted between pillow blocks
19 and 20 and their underlying lifters 24 and 25, respec-
tively. The sensors 26 and 27 thus lie beneath the axle
18 in a vertical plane passing through its axis of rotation
where they serve to measure the dynamic centrifugal forces
generated by the tire which are indicative of peripheral
non-uniformities uneffected by forces resulting from dynamic
unbalance. The sensors 26 and 27 will preferably comprise
piezoelectric quartz crystals capable of withstanding extreme
forces without fracturing. It may be pointed out that in the
application of load to the tire being corrected through the
lifters 24 and 25, a monetary force is applied t~ the sensors
26 and 27, but the sensors will immediately return to a zero
reading position once the load is applied and fixed, and
thereafter the sensors will react only to the dynamic forces
generated by non-uniformities developed in the portion of
the tire in contact with the drum. As the tire revolves,
l~JO~
the sensors 26 and 27 continuousl~ asure the forces gener-
ated by peripheral non-uniformities throughout the full width
of the tread and throughout the f~ll 36C circumference of
the tire. The sensors 26 and 2t generate force signals
indicative of the magnitude and loca~ion of the generated
forces and these signals are fed to the computer 28.
The computer 28 is an all-purpose digital computer
programmed to determine the areas on the tire where the
vibration producing forces appear as well as the amount of
rubber which must be removed from the outside periphery of
the tire to reduce the force generating non-uniformities to
at least an acceptable low level.
The honing of the periphery of the tire is accomplished
by the honing device 29, which may comprise a tire grinding
disc of known construction. The computer 28, acting through
controller 30 and drive means 31, controls a movable car-
riage 32 to initially position the honing device 29 in close
proximity to the periphery of the tire but free from contact
with its highest non-uniformity. In practice, the honing
device 29 will be moved to a position in which it lies approx-
imately twenty-thousandths of an inch (.020") from the point
of highest growth by means of the carriage 32. The controller
30 further serves to actuate a valve 33 mounted on the car-
riage 32 and operatively connected to the honing device 29,
the valve having a jet-like mpvement effective to move the
honing device into and out of honing engagement with the tire
17.
The recorded information concerning the location and
magnitude of the non-uniformities is converted by the com-
puter 28 to corrective signals which are fed to the controller
3~31~~omentarily acti~ates the valve 33 to fGrce the honing device
into engagement with the tire at the precise location of the
non-uniformity being corrected, such engagement being re-
peated for as many revolutions of the tire as required to
effectively remove the non-uniformîty. It will be understood
that where multiple non-uniformities are encountered, a
separate honing operation will be performed for each non-
uniformity. While in the embodiment illustrated in FIGURE 1
only a single honing device 29 has been illustrated, it will
be understood that a plurality of honing devices may be pro-
vided at spaced intervals relative to the periphery and the
tread width of the tire so that multiple honing operations
may be simultaneously performed on different aréas of the
tire during each honing cycle.
It may be noted that there are currently no uniform
standards for tire acceptability. Standards vary from manu-
facturer to manufacturer and are constantly changing. A
typical concentricity limit of acceptability is forty-thou-
sandths of an inch (.040") at the unrealistic road speed of
one to five miles per hour. In other words, by current com-
mercial standards, a tire is deemed acceptable if its peri-
pheral eccentricities do not exceed .040" under near static
conditions. It also may be noted that an eccentricity on a
tire of one-thousandths of an inch (.OOl") when rotated at
sixty (60) miles per hour will generate a force of 1.4 lbs.,
which means that an eccentricty of .040" will generate a
vibration producing force of 64 lbs. When it is further con-
sidered that a peripheral eccentricity in a tire of .040"
when operated at one to fi~e miles per hour may be substan-
tially magnified at sixty (60) miles per hour, the magnitude
109~9V~
of vibration producing forces inherent in currently available"balanced`' tires becomes readily apparent. It should be made
clear however, that there is no direct correlation between
the lack of concentricity of the first order encountered at
low speeds as opposed to centrifugally ger.erated non-uniform-
ities encountered at high speeds; they are not necessarily at
the same locations or of the same magnitude~ and they may
either increase or decrease in magnitude in accordance with
velocity. However, the figures given are indicative of the
problem.
Since the non-uniformities to be corrected are those
which are generated at cruising speeds, the corrective honing
of the tire must take place at the cruising speed for which
the tire is being corrected, whether it be at fifty, sixty
or ninety miles per hour. Honing the tire at these high
speeds requires extremely rapid movement of the honing device.
For example, a standard size tire running at sixty miles per
hour is revolving approximately 12 revolutions per second;
and to cause the honing device to move into and out of con-
tact with the tire once per revolution requires a systemcapable of movement on the order of twenty four times per
second (12 times in and 12 times out, or once per revolution).
Valve systems have been developed which are capable of operat-
ing within the parameters noted, and may be utilized to effect
the required movement of the honing device 29.
As the periphery of the tire is being honed, a second
set of sensors 34 and 35 operatively connected to pill~w
blocks 13 and 14 supporting wheel axle 15, measure for the
lack of symmetry in the tire. The sensors 34 and 35 also
may comprise piazoelectric crystals and they are mounted at
lOgO~
right angles with respect to the sensors 26 and 27; that is,
whereas the sensors 26 and 27 underlie and are effectively
contacted by the opposite ends o axle 18 (through its pillow
blocks) in a vertical plane, the sensors 34 and 35 are mounted
on one side of the axle 15 and lie in a horizontal plane pass-
ing through the axis of rotation of the axle where they are
effectively contacted by the opposite ends of the axle. In
this position, the sensors 34 and 35 detect lack of symmetry
(dynamic unbalance) on both sides of the tire, i.e., its
right and left sides. It may be pointed out that tires
are manufactured from strip stock and the lack of symmetry
will vary within each side of the tire and often at different
angular locations. It has been found that these vibrations
occur in two planes, known as a "couple", and they produce
both radial and lateral vibrations. The weights added to
the inside of each tire side wall in the area of the tire
beads, i.e., to the bead itself or to adjacent portions of
the ~ide walls, will effectively correct for vibrations in
each plane of the couple, lt being remembered that the un-
symmetrical force~ vibrate at a fundamental frequency onceper revolution of the tire irrespective of its velocity.
The force signals generated by the sensors 34 and 35
are also fed to the computer 26 where they are recorded and
stored. This stored information is utilized to control the
second stage corrective operation, which in the preferred
embodiment comprises the honing of portions of rubber rings
bonded to the inside of the tire in the area of the beads.
Thus, with reference to FIGURES 2 and 3, annular rings of
rubber 36 and 37 are added to the inside surfaces of the con-
ventional beads 38 and 39, respectively, of the tire 17. The
14
~30i~O~
beads of the tire are those portions which make contact with
the r~m of the wheel on which the tire is mounted; and in
the case of tubeless tires, the beads are configured to make
airtight contact with the wheel rim. The rubber rings 36
and 37 may be integrally molded as an incident of the manu-
facture of the tire, or they may comprise separately applied
rings or strips of rubber vulcanized or otherwise permanently
bonded to a conventional tire carcass.
The adding of weight in the form of rubber rings or
strips to the insides of the tire beads or to the adjacent
inside areas of the side walls in no way affects the--character-
istics of the tire tread under dynamic operating conditions;
that is, the added weight, being remote from the periphery
of the tire, does not contribute to or alter the centrifug-
ally induced non-uniformities inherent in the tire as manu-
factured. The added weights only affect tire symmetry, the
weights when properly honed serving to effectively counter-
balance the non-symmetrical forces present in the tire. It
will be understood that initially the size and weight of the
annular rings will be proportional to the size and weight
of the tire; generally speaking, the larger and heavier the
tire, the larger and heavier the rubber rings.
When the first stage honing operation is completed,
the tire is preferably removed from the wheel 16 and trans-
ferred to a second corrective device where the second stagecorrecting operation is performed. However, before the tire
is removed from the wheel 16, it is marked so that when
positioned in the second corrective device and properly
aligned, it will lie in the exact same relative position it
occupied when mounted on the wheel 16, and consequently in
lU~30~
its aligned position the tire will be calibrated with respect
to the data stored in the computer relating to lack of
symmetry as measured by the sensors 34 and 35.
The second stage corrective device, also shown in
FIGURE 1, comprises cradle 40 in which the tire 17 is seated,
together with a honing device 41 mounted on a carriage 42
by means of which the honing device 41 is selectively moved
into and out of contact with each of the rubber rings 36
and 37. The honing device 41 is moved into engagement with
the rubber ring being honed by the carriage 42 under the
direction of controller 43 which receives correcting signals
from the computer 28 based on stored data relating to lack
of tire symmetry. The cradle 40 is mounted for oscillatory
movement relative to the honing device 41 and is oscillated
by means of an oscillator 44 in accordance with corrective
signals supplied by the computer 28 to the controller 45
which controls oscillating movement of cradle 40 through
oscillator 44.
The tire 17 will be positioned in the cradle 40 with
the mark applied to the tire prior to its removal from the
wheel 16 in accurate registry with a reference point on
the cradle, thereby pocitioning the tire in the same rela-
tive position it occupied when mounted on the wheel 16. The
tire is thus indexed with respect to corrective signals from
the computer 28 based on the data stored in the computer
relating to the magnitude and location of the forces generated
by lack of tire symmetry. Once the tire has been properly
positioned in the cradle 40, the honing spindle 41 is moved
to a position in which it will contact one of the rubber
rings at the point of unbalance for the side of the tire on
16
1~0~0~
which the rin~ ~ei.g honed is located. The point of un-
balance will be determined by the computer in accordance
with the data supplied by the sensors 34 and 35, the point
of unbalance being the mean resultant point of the unsym-
metrical forces measured by sensors 34 and 35. There willbe two such points of unbalance, one for each side of the
tire.
The honing device 41 will be brought into alignment
with one of the points of unbalance by effecting relative
movement between the carriage 42 mounting the honing device
and the ~ire cradle. The honing device is then moved via
its carriage 42 into honing engagement with the rubber ring.
These movements are effected by the controller 43 in accord-
ance with the corrective signals from the computer 28. The
controller 43 will also control the depth to which the
rubber ring is to be removed. Concurrently with the movement
of the honing device 41 into honing engagement with the
rubber ring, the cradle 40 will be oscillated equally about
the resultant point of unbalance, the cradle moving back
and forth by equal distances on opposite sides of the
resultant point of unbalance, carrying the tire with it.
The distance traversed by the cradle 40 and the tire 17
will be determined by the computer and controlled by the
controller 45 which is operatively connected to oscillator
44. In this way each annular ring is honed to remove a
portion of the ring in amounts and over an area to leave
the proper amount of the ring to counterbalance the un-
symmetrical forces on that side of the tire. When the hon-
ing of one of the rings is completed, the honing device
will be shifted to the ring on the opposite side of the tire
17
lV9~
and the hon~ng operation repeated in acc,ordance with the
corrective signals supplied by the comp~ter as to the
location and magnitude of the unsymmetrical forces on the
remaining side of the tire.
With reference to FIGUR~ 4 which diagrammatically
illustrates one side of the tire 17, the resultant point
of unbalance is indicated by the point P7 and the honing
device is initially aligned to coincide with point P.
The distance in either direction from point P in which
the ring must be honed to remove the required amount of
rubber is also determined by the computer in accordance
with the stored data, and the computer acts through
oscillator 44 to oscillate the tire in opposite directions
from the point P to remove the required amount of rubber.
In the example illustrated, rubber is removed from the
ring throughout the areas A and B, which areas are effec-
tively counterbalanced by the complimentary areas C and D
on the opposite side of the ring. The remaining areas E
and F are in balance and effectively cancel each other.
It has been found that up to 45 removal of rubber on each
side of the unbalanced point P is the most effective for
counterbalancing. Beyond 45 in either direction from the
point of unbalance the effect is negligible. It will be
understood that the amount of rubber removed, both in terms
of length of cut and depth, will be determined by the com-
puter in accordance with the magnitude of the unsymmetrical
forces encountered.
As an alternative to the honing of rubber rings or
strips previously applied to the inside of the tire, strips
of rubber of the required length and thickness may be bonded
18
o~
to the i~ ne tire beads on the adjacent areas of
the side walls ~lS a part of the second stage corrective
operatior~, the weight and location of such strips being
determined by the computer from the stored data. In this
case, the compu~er will be progra~ed to indicate the
weight and location of the strips to be added, and the
resultant points of unbalance may be m~rked on the tire
in accordance with locations deter~ined by the computer,
whereupon the balancing strips will be applied in accord-
ance with the marks. In the case of the example illus-
trated in FIGURE 4, if corrective strips are to be added
instead of effecting balancing by honing pre-applied rings,
the resultant point of unbalance would be at the point ~',
which is diametrically opposite to the point P, and the
strips would be added in the areas C and D, being centered
at point P'.
As should now be apparent, the instant invention
provides an integrated system for eliminating the vibrations
generated in vehicular tires by correcting the tire both
for peripheral non-uniformities and for lack of symmetry.
The outside periphery of the tire is first honed in the
radially protruding force generating areas, which are the
areas that physically prevent the tire from maintaining a
constant loaded radius as it moves along the highway at
~5 cruising speed. Once the tire has been corrected for these
peripheral non-uniformities it is then corrected for lack
of symmetry, which is accomplished by either honing portions
of annular rubber rings or Qtrips added to the inside of the
tire in the areas of the tire beads, or by bonding separate
strips of rubber to the inside of the tire in the areasof the
1~0~0~
~eads at .ne .~_~tions and in amounts sufficient to counter-
balance the unsymmetrical forces. In either event, the
outward appearance of the tire does no'- s~ow that it has
had weights added, but each tire once corrected is free
from vibration producing forces when operated at its
intended cruising speed.
It has been found that when a tîre has been corrected
in accordance with the present invention, the magnitude
of vibration producing forces which may be generated at
less than cruising speed, as when the vehicle is being
operated at low or medium speeds, are of insufficient
magnitude to be objectionable and lie well within accept-
able parameters. The forces which pose the real problem
are those encountered at cruising speed, and it is these
forces which are corrected and reduced to an acceptable low
level.
By utilizing the system and method of the present
invention, the tire manufacturer may provide the customer
with tires especially designed for use at predetermined
cruising speeds, which in large measure will be governed
by the laws limiting speed of vehicles operated on the
highways.
Although a single preferred embodiment of a method
and system has been described and illustrated, it is to be
understood that modifications can be made without depart-
ing from the true spirit and scope of the invention. Numer-
ous such modifications have already been set forth and
others will undoubtedly occur to the worker in the art.
For example, the specific nature of the honing devices does
not conxtitute a limitation on the invention, the essential
~o~o~ux
factor beil~g le ~emoval of the centrifugally generated
peripheral ~aon-un~formites and, in the case of the added
rubber ringst the removal of sufficient portions of the
rings to effectively counterbalance the tire for lack of
symmetry. The progra~ming of the computer to convert the
measured force signals into corrective signals for the
operation of the honing devices and oscillator is within
the skill of the computer programmer, and numerous programs
may be devised in accordance with the desired parameters
for corrective action. It also will be evident that the
device which hones the annular rubber rings may be oscil-
lated relative to the tire rather than oscillating the
tire cradle or other tire support. Accordingly, it is
not intended that the invention be limited other than in
the manner set forth in the claims which follow.
