Note: Descriptions are shown in the official language in which they were submitted.
This invention is gener'ally directed to methods and apparatus
for non-destructive inspection of rubber tires. Such inspection
techniques may also be combined' with conventional tire buffing
operations in accordance with this invention.
The invention here'claimed is directed to certain mechanical
features of the prefer'red embodiment. The electrical features,
se, are'tha'sol'e invention of Morris D. ~o and are disclosed
and claimed' in United' States Patent No. 4,266,428 dated ~ay 12,
' 1981. The'combination of mechanical and electrical features is
the joint invention of Doyle L. Dugger and Morris D. Ho and is
disclosed and claimed in United States Patent No. 4,275,589 dated
June 30, 1981.
There has long been an urgent need for cost effective,
efficient, non-destructive'inspection (NDI~ of rubber tire casings.
- There are'obvious safety benefits to be had by such techniques
if they can be efficiently and rapidly practiced. There are also
potential economic benefits. For example, during tire retreading
operations, a de~ective tire carcass can be discarded before
wasting further expenditures of time and money if it can be
accurately, efficiently and quickly detected.
In fact, the need for improved NDI methods and apparatus
relating to the testing of tire casings is so great that the U.S.
Army Materials and Mechanics Research Center has sponsored special
symposia devoted entirely to this subject in 1973, 1974, 1976 and
1978. The'proceedings of the first three of these symposia have
now been published and
.~
(
-- 2 ~
are available from the National Techniczl In.orma-
tion Se~vice~ They each include a complete chap-
ter on ultrasonic tire testing as well as other
. chapters devoted to different tire testing pro-
cedures ~e.g. holographic, infrared and X-ray~.
There are also many prior art patents relating
generally to the use of ultrasonic waves ko
non-destructively test pneumatic tire casings.
For example:
U.S. Patent No. 2,345t679 - Linse (1944)
" " " 2,378,237 - Morris (1945)
" " " 3,336,794 - Wysoczanski
et al (19673
" " " 3,604,249 - Wilson (1971?
" " 3,815,407 - Lavery (1974)
" " " 3,882/717 - McCauley (1975
" " " 4,059,989 - Halsey (1977)
There are also several prior art patents
- relating to mechanical structures for chuck;ng or .
otherwise physically handling pneumatic tire casings
during various types of non destructi~e testing or
manufacturing processes; For`example:
U.S. Patent No. 2,695,520 - Karsai (1954)
" " " 3,550,443 - Sherkin (I970)
" " " 3,948,094 - Honlinter (1976)
4,023,407 - Vanderzee tl977)
Although a wide variety of no~-destructive
ultrasonic tests have been performed on tires in the
past as shown by these prior art patents, they have
each suffered serious deficiencies and have failed
to achieve wid~spread acceptance in commercial prac-
tice.
- 3 -
Prior tire chucking mechanisms in gen~-al
hzve included axially movable tire mounting rims Lor
quickly mounting and inflating a test tire. ~rior
NDI machines have located an ultrasonic ~rans~itter
inside a rotatable inflated, tire, albeit such have
been only fixed or manually adjustable mounting ar-
rangements~ Othex NDI machines have included arti-
culated transmitter mounting arrangement in conjunc~
tion with a spread-open non-inflated test tire.
However, there has not yet ~een a commercially via-
ble mechanism arrangement for quickly positioning
ultrasonic transducers about an inflated test tire
wall while at the same time facilitating ~uick
tire mounting/de mounting procedures and also pro~
tecting the transducers from physical harm.
It has been discovexed that these
earlier attempts at ultrasonic non-destructive
in~pection of tire casings can be considerably im-
proved and madè more commercially viable.
In accordance with the present invention a non-
destructive tire testing apparatus having an ultrasonic acoustic
transmitter and an ultrasonic acoustic réceiver opposingly mounted
on the inside and outside respectively of a relatively movable
inflated tire wall and spaced therefrom by predetermined distances
so as to achieve acoustic coupling therebetween through a gaseous
medium interrupted by said tire wall and including electronic
circuits connected to said transmitter and receiver so as to obtain
and display a measurement of the condition of the thus tested
portion of the tire wall, said apparatus being characterized by:
opposing circular rings adapted to sealingly engage
_ 3a -
the corresponding rims of the tire when placed therebetween;
and
adjustable transmitter mounting means mechanically mounted
between said rings for retracting said transmitter radially
toward the center of the circular rings while mounting and
~e-mounting the tire from between said rings and for extending
said transmitter radially away from the center of the circular
rings and toward the t;re tread wall to a fixed active position
during a testing cycle.
A further aspect of the invention includes, a non-destructive
tire testing method comprising mounting an ultrasonic acoustic
transmitter and an ultrasonic acoustic receiver opposingly on the
inside and outside respectively of a relatively movable inflated
tire wall and spaced therefrom by predetermined distances so as
to achie~e acoustic coupling therebetween through a gaseous
medium interrupted hy said tire wall, co~necting electronic
circuits to said transmitter and receiver so as to obtain and
display a measurement of the condition of the thus tested portion
of the tire wall,
sealingly engaging the corresponding rims of the tire
with opposing circular rings when placed therebetween; and
retracting said transmitter radially toward the center
of the circular rings while mounting and de-mounting the
tire from between said rings and extending said transmitter
radially away from the center of the circular rings and toward
the tire tread wall toa fixed active position during a testing
cycle.
- 3b
The use of an inflated tire in the pre-
ferred embodiment has been discovered to assist in
maintaining a true running tire surface and thus
avoids signal variations that might otherwise be
caused by wobbling or other relative axial motions
of the tire walls during rotating. The inflated
tire is also useful in helping to at least par-
tially stress the tire walls, as they will be
stressed during normal use, and to open up leakage
passageways through the tire walls so that they may
be detected by ultrasonic detection of air passing
therethrough. Approximately only ~ive psi is needed.
to maintain a stable inflated tire stxucture. ~ow,
ever, it has been discovered that improved signal
-- 4 --
transmission and overall performance occurs i~ the
tire is inflated within the range of approximately
15-18 psi.
Although it may not be required, it is
preferred that the outer treadwall of the tire
under inspection first be buffed to present a uni-
form surface thus minimizing spurious defect in-
dications that might otherwise be caused by tread
patterns and/or by uneven wear spo s or patterns
in the outer treadwall surface of the tire. In
this connection, the tire buffing apparatus and
method may ~e advantageously employed in combina-
tion with the ultrasonic non-destructive testing
method and apparatus to present a unified, conven-
ient and efficient overall operation. Since such
a buffing operation is necessarily involved in
tire retreading operations anyway, this combina-
tion is particularly attractive where the tire
carcasses are being inspected in preparation for
retreading.
The preferred exemplar~ embodiment of
this invention includes special mechanical features
for automatically moving the acoustic transducers
into and out of operative position with respect to
the inflated tire walls. During tire mounting and
demounting operations, the acoustic transmitters are
retracted inwardly both radially and axia}ly with
respect to at least one tire mounting ring or flange
so as both to facilitate the tire mounting and de-
mounting operations and to protect the acoustictransmitters from possible physical damage. During
-- 5 --
or after ti~e inflation, these acoustic .ransmitters
are moved radially outwardly inside the infla~ed tire
in~o an operative position with respect to the inside
tire walls. At the same time, the array of acous~ic
5 receivers is moved radially inwardly towards the
outer inflated tire walls to a desired operative
position~
In the preferred exemplary embodiment,
the relative axial movement of the acoustic trans-
mitters with respect to a tire mountiny flange orring is achieved by spring loading the tire ring so
that it axially moves away from the acoustic
transmitters thereby uncovering t~em during the tire
mounting operation and thus providing prope~.clear-
ance for subseguent radially outward movement into
the inflated tire carcass. Such spring loading also
. helps in properly seating the tire rims with the
mounting flanges or rings during mounting and in-
flation operations.
' Thesa and other objects and advantages
o this invention will be better appreciated by
r.eading the following detailed dèscription of the
presently'preferred exemplary embodiment in con-
junction with the accompanying drawings, of which:
FIGURES 1 and 2 are pexspective views
of a combined NDI/buffer machine constructed in
accordance with this invention;
FIGU~E 3 is a block diagram o~ the inven-
tlon shown in FIGURES 1 and 2;
FIGURE 4 is a block diagram of the ultra-
sonic NDI circuits which may be used in the NDI~bu~f~r
machine of FIGURES 1~3 or in a machine having,only
N~I capabilities; and
.
~s~
( - 6
FIGURE 5 is a detailed cut-away cross-
sectional view of the fixed spindle and transmit-
ter mounting arrangement used in ~he embodiment
of FIGURES 1 and 2.
! ~ 7 -
Referring to FIGUP~S 1 znd 2, two per-
spective views of the presently preferred exemplary
combined tire buffer and NDI machine are shown. As
will be apparent, the N3I features of the machine
may be provided, if desired, without including the
tire buffing capability.
The major mechanical components of the
machine are mounted to an open frame 100 having
a fixed spindle 102 and an axially movable spindle
104 opposingly aligned along horizontal axis 106.
Conventional circular tire mounting rings or flanges
108 and llO are attached to the outer rotatable ends
of spindles 102 and 104 for mounting an lnrlated tire
112, therebetween. A conventional pneumatically opera-
ted tire lift mechanism 114 is conveniently provided
so as to assist the human operator in lifting and
swinging a tire into and out of place between rings
108 and 110 during tire mounting and demounting opera-
tions.
Ring 108, and hence tire 112, is driven by
a two horsepower d.c. motor 116 thxough reducing gears
118. A tire surface speed of approximately 600 feet
per minute is preferred for buffing operations while
a much lower speed o~ approximately 40 feet per minute
is preferred for NDI operations. Spindle 104, and
hence ring 110, is axially extended and retracted by
pneumatic cylinder 120. During tire mounting opera-
tions, ring 110 is retracted by cylinder 120 so as
to permit the tire 112 to be li~ted into place on
ring 108 by lift 114. Thereafter, ring 110 is ex~
tended against the corresponding rim of tire 112 and
(
-- 8 --
the tire is inflated to a desirec se'_ point pressure
by compressed air passed through the center o spin-
dle 102.
A conventional rotating tire buffing xasp
200 is mounted on a vertical pedestal 202 situated
on the backside of the machine as seen in FIGURE
2. The rasp 200 is controlled via a conventional
panel 204 to move laterally along a desired buff-
-ing path 206 and horizontally towaxds and away ~rom
the tire by conventional control mechanisms in-
cluding a "~oy stick" used to control
lead screws and associated drive motors
and the like. The buffer rzsp 200 is rotated by a
separate motor mounted on ped~stal 202. The buffer
mechanism, ~ se, is of a conventional type as
marketed by Bandag, Inc., e.g. Buffer Model No. 23A.
An array of 16 ultrasonic acoustic receiv-
ing transducers 210 is disposed above and around the
outer walls of tire 112. The receivers 210 prefer-
ably include a conically shaped collimator and/or
focusing tube to help limit the field of view for
each individual transducer to a relatively sm~ll
and unique area across the tire wall. The receivers
210 may be conveniently potted either individually
or in groups in a polyurethane foam or the like to
help mechanically fix the receivers in their re-
spective desired positions, to help protect the xe-
ceivers and to help i~olate the rec~ivers from
spurious ambient acoustic signals. The array of
receivexs Z10 is radially adjusted into operative
position by an air cylinder 212 having a coupled
5?¢
g
hydraulic control cylinder so as ~o define a radi-
ally extended operative position Lor the receivers
210
A block diagram of the combined tire
buffer/NDI machine and its associated electrical
and pneumatic circuits is shown in ~IGUXE 3. The
electrical motor and pneumatic cylinder controls
300 are of entirely conventional design and thus
not shown in detail. Opexator inputs depicted at
the left of FIGURE 3 are made directly or indirectly
by the operator via conventional electrical switches,
relays, air valves and/or liquid control valves.
In operation, a tire is placed on lift 114
and raised into position between the rings 108 and 110.
Preferably, a predetermined index position on the tire
is aligned with a physical index position on flange
108. Thereafter, the chucking apparatus is engaged
by causing flange 110 o move into the tire 112 so
as to pinch the tire beads together in preparation
for tire inflation. The tire is then inflated to a
desired set point pxessure~ As will be explained
in more detail below, the flange 108 is spring-loaded
such that durins chuck engagement and tire infla-
tion, it is caused to move axially outwardly against
the spring-loading (e.g. by approximately 2 inches).
This facilitates the tire inflation process and
simultaneously uncovers an ultrasonic transmitter
located within the tire from a relatively protec~ed
position so that it may subsequently be extended into
an operative position under the axray of receivers
210. An interlock switch activated by air pressure
and/or by the physical movement of flange 108 may
(
-- 10 --
be used to prevent any premature extension o~ the
transmitter before it is uncovered from its pro-
tected position.
In the buffing mode, the transmitter need
not be extended. The buffing rasp drive motors
are conventionally activated and controlled (e.g.
with a "joy stick" and conventional push button
controls) to buff the tire tread surface as de-
sired. Although it may not be required, it is
0 presently preferred to have the tire buf~ed to a
substantially uniform outer treadwall surface be~
fore NDI operations are performed. Such buf~ing
is believed to avoid possibIe spurious indications
o~ defects caused by normal tread patterns and/or
by uneven wear about the tire surface.
When the operator selects the NDI mode
of operation, an ultrasonic transmitter located
inside the in lated tire 112 is extended into opera-
tive position and the array of receivers 210 is
lowered into operati~e position by respectively asso-
ciated pneumatic cylinders~ The same 2-horsepower
d.c. motor which drives the tire` at approximately 600
surface feet per minute during buffing opera~ions may
be reduced in speed by conventional electrical circuits
so as to drive the tire at approximately 40 surface
feet pex minute during the NDI mode. After t~e tire
motion has reached a steady state, the operator may
activate the scan request input switch to the ultra-
sonic NDI cixcuits 302. Thereafter ~he walls o~ tire
112 will be ultrasonically inspected duri~g one or
` more complete tire revolutions to produce a display
304 which can be humanly interpreted directly or
5'~
11 --
îndirectly to reveal the condition of the tire (e.g.
satisfactory for further buffing and retreading,
doubtful or unsatisfactory). If questionable con-
dition is indicated, the tire may be discarded or
may be additionally buffed and retested.
The ultrasonic NDI circuits 302 are shown
in greater detail at ~IGURE 4. The outputs ~rom the
16 ultrasonic receivers 210 are amplified and multi-
plexed onto eight signal processing cha~nels A-H by
circuits 402. Each signal processing channel then pro-
vides AGC amplification, rectification, integration
and analog-to-digital conversion with the signal pro-
cessing circuitry 404. The resulting digitized outputs
are presented to a conventional eight bit data bus 406
which is interconnected to a conventional micro-computer
CPU (e.g. an 8080 type of eight bit computer~ 408. The
CPU 408 is also connected via a conventional address
bus 410 and data bus 406 to a data mem~ry 412, to a
programmable read-only memory (PROM) 414 and to a sys-
tem interface circuit 416. A display intex~ac~ 418 is
directly connected to the data memory banks 412 to pro-
vide a CRT type of oscilloscope display.
The system interace 416 provides the
necessary gating and other control signals to the
signal processing circuitry 404 and also provides
HIGH CHAN multiplexing signals to the preamplifier
circuits 402 as we}l as to the transmitter ~rivers
and multiplexing ci ~ itry 422 used to drive plural
ultrasonic transmitters. The operation of ~he en-
tire system is synchronized to the rotational move-
ments of tire 112 through a rotary pulse generator
424 directly driven with the tire (e.g. geared to
the reducer gears). The rotary pulse generator 4~4
.5~e
- 12 -
provides 1,024 pulses per revolu~ion a~ terminal ~GX
znd 1 pulse per revolution at terminals RPGY.
Ultrasonic acoustic transmitting crystals
500 and 502 are disposed inside inflated tire 112,
which is chucked between xings 108 and 110, rotatably
secured to spindles 102 and 104, respectively. The
elec~rical leads ~eeding transmitters 500 and 502 are
fed out through the fixed spindle 102 to the trans-
mitter activation circuits. Inflation air is likewise
fed in through the center of spindle 102 as are pneu-
matic lines and~or other control connections for ex-
tending and retracting the ~ransmitters.
The exemplary ul~rasonic t~ansmitters S00
and 502 have a radiation field which substantially
illuminates a sector o~ approximately 90. Hence,
they are mo~nted at 90 with respect to one another
on block 504 which may, for example, be formed from
polyvinyl chloride plastic materials. It has been
found that acceptable operation will not result
2Q if the ~ransmittexs are too close to the inside
tire surfaces or too far away from these surfaces.
In the preferred exemplary embodiment, trans~itting
crystals 50Q and 502 are approximately two inches
from the inner tire wall surfaces although this
optimum distance of separation may be varied by z
considerable amount (e.g. plus or minus approximately
one inch).
The arrayed receiving transducers 210 are
located about an arc generally corresponding to the
outside shape o the tire wall. Hexe again, it has
been found that acceptable operation does not result
if the receivers are too close or too far away from
- 13 -
the outer tire w211s . Prererably, ~he receivers are
no closer than a?pr~ximately 1 inch to the outer
tire surface b~ are preferably within 5.5 to 8.5
inches of the opposingly situAted trznsmitting
crystal. The receivins transducers 210 pre~erably
each employ a conically shaped collimator and/or
focusing tube. These
tubes are preferably machined from polyvinyl chloride
plastic material a~d also help to match the impedance
of the actual transducer crystal surface to the sux-
rounding ambient air acoustic impedance.
A moderately high ul~rasonic frequency is
employed so as to help avoid interference from spurious
ambient acoustic si~nals and to obtain increased resolu-
tion by using shorter waveleng~h acoustic signals while.
at the same time avoiding ultra-high frequency acoustic
signals and the pro.~lems associated therewi~h. ~re-
quencies above 40 ~z are desirable with 75 kHz
being chosen 2S the presently preferred optimum
frequency.
Greater de~ail of the fixed spindle 102
and of the associa.~d transmitter mounting arrange-
ment is shown in the cross-section of FIGURE 5~
The transmitti~g crystals 500 and 502 are d~rected
at 90 with respect to one another ~rom the face
of a PVC moun~ing block 1500. The block 1500 is,
in turn, attached to a retractable rod 1502 con-
nected to the pisto~ of a pneuma~ic cylinder 1~04.
As shown in FIGURE 5, the pneumatic
cylinder lS04 has retracted the transmitting cxy-
stals 500 and 502 into a protected area de~ined by
54L
-14-
an annular plate 1506 attached to the tire mounting
ring or flange 108. The tire mounting ring 108
is rotatably secured to the fixed spindle 102 through
ball-bearing assemblies 1508 and 1510. This rota-
table connection is maintained airtight by rotating
seal assembly 1512. The center of the spindle 102
is hollow so as to permit passage of pneumatic con-
trol line 1514 and of the transmitter electrical
leads there~hrough.
~0 The rotating ring 108 and its connected
assembly is spring-loaded via spring 1517 to its
axially extended position,
However, the ring 108 may be moved axially to the
position shown in dotted lines against the spring
force. In the preferred exemplary embodiment,
such motion begins to occur when the ring 108 has
approximately 1500 lbs. of lateral force applied
thereto. The sliding joint which permits such mo-
tion,is also maintained a~rtight by "O" ring 1516.
In the exemplary embodiment no more ~han approxi-
mately two inches of axial movement are permitted
before the spring force is sufficient to xesist
further movement even when the tire is inflated
to approximately 15-18 psi.
When the ring 108 is axially moved to
the left as shown by dotted lines in FIGURE 5
against the force of spring 1517, transmittexs
500 and 502 are then exposed and the pneumatic
cylinder 1504 can be activated to extend the trans-
mitter into the position shown by dotted lines inFIGURE 5 for an operative measurement cycle. Suit-
able interlocking switches activated by the internal
- 15 -
pressure of the inflated tire and/o~ by t'ne ~hysical
axial posi.ion of ring 108 can be employed to insuxe
that pneumatic cylinder 1504 is not orroneously
extended and damaged while the transmitters 500 and
502 are still enclosed and pxotected by the flange
1506.
While only a few exemplary embodiments
and only a few variations thereof have been ex-
plained in detail, those in the art will appreciate
that many other modifications and variations may be
made without departing from the no~el and advan-
tageous features of this invention. Accordingly,
all such modifications and variations are intended
to be included within the scope of this invention
as defined by the appended claims.
