Note: Descriptions are shown in the official language in which they were submitted.
~ WO 96/10727 2 2 ~17 3 ~ PCTIGB95102340
TYRE SCANNING APPARATUS AND METHOD
This invention relates to apparatus for det~rrnining physical ~h~r~cteri~cti~s of
a tyre and to a method of determining physical characteristics of a tyre. The
invention is particularly useful for determining the depth of tread rPm~ining
on a tyre and/or for detscting defects in a tyre. The invention enables tyres
to be sc~nned in situ, that is to say when mounted on a wheel or rim fitted to
a vehicle.
According eo a first aspect of the present invention there is provided a~pal~tusfor determinin~ physical characteristics of a tyre mounted on a wheel fitted
to a vehicle, which a~alaLus comprises sc~nnin~ means ~ rte~l to scan a tyre
and to produce an output in~lic~tive of iLlfo~ ;<)n relating to tread depth, andin-lic~tor means responsive to the output of the sc~nnin~ means to provide an
in~ tion of tread depth.
According to a second aspect of the present invention, there is provided a
method for determining physical ~h~r~cteri.cti~s of a tyre, which method
comprises sc~nning a tyre mounted on a wheel fitted to a vehicle and
producing Lh~l~;Lolll an output inrlic~tive of information relating to tread
depth, and providing from said output an inrli~ ~tion of tread depth.
In order for the sc~nning means of the a~al~Lus of this invention to scan a
tyre, the sc:~nning means may be driven across the w~lth of the tyre, e.g. by
means of an electric motor. ~ltem~tively, or as well, the tyre itself may be
moved transversely of the scanner and/or may be rotated relative to the
scanner. In other embodiments the sc~nning means may incln~e a sufficient
number of scanner devices, which may be of the same or dir~lellL type, or a
Wo 96/10727 2 ~ 3 9 PCT/GBg5/02340 ~
r;?~
sufficiently wide sc~nning head to scan the width of the tyre without a
requirement for relative movement between the a~à~at~ls of this invention and
the tyre. In yet other embodiments a movable mirror may be used to scan the
tyre.
Any suitable sc~nning means may be employed in the ap~a~aLus of this
invention. Thus for example electrom~gnetic radiation, e.g. continuous or
pulsed laser light, may be directed onto the tyre and a reflection of that
radiation detected to provide tread depth il~o~ tion In other embo~limt-nrs
high frequency, e.g. ultrasonic, sound may be reflected from the tyre surface
to provide tread depth information. It is envisaged that other sc~nnin~ means
may be used, such as, for example, the direction onto a tyre of one or more
hydraulic or pn~nm~tic jets, with variations in jet pressure (either reflected
pressure or back pressure) being measured to obtain tread depth ~ ;on,
or that, for example one or more metal detectors could be used to derive tread
depth information, e.g by me~llring the changes caused by tread depth
variation, in the strength of a signal resnlting from th~ presence of metal in
the tyre. (In one embo~liment of the sc~nning apparatus of the present
invention, a succession of sc~nning means are arranged to lie beneath, e.g., in
the case of an optical sr~nning means, undemeath a panel of ~lallsparell~
material, a path of travel of a tyre to be tested; as the vehicle drives along said
path, the successive sr~nning means scan the region of the tyre presented to
the successive sc~nning means to provide the requisite tread depth
information. Where non-optical sc~nnirig means are employed, the sC~nninp
means may be embedded in the surface over which the tyre passes.
In a preferred embo~lim~rlt, pulses of visible or invisible laser light are
directed on to the tyre surface and the reflections of those pulses from the tyre
Wo 96/10727 2 = PcrlGss5lo234o
tread detected, the time delay in receiving the pulses being used to derive an
in-lir~tion of tread depth in respect of the tyre.
In another embo~limçnt, visible light reflected from the surface of the tyre, e.g
from an obliquely arranged light source, is recorded, e.g. by means of a
charge couple device (CCD), CMOS, video camera or the like, the image then
digitized, converted to, e.g., a grey scale, and the shades of grey used to
provide an estim~te of tread depth. The visible light employed may be ambient
light but preferably in these embo(1iments the apparatus in~ les a light source
providing a light output of known i~ ily and known spectral ~lo~G.Lies. It
will of course be possible to provide means for varying the ;~le~ y of the
light source or, e.g. by means of suitable filters, to vary the spectral ~u~el~ies
of the light.
It will be understood that if a CCD, CMOS or camera is used, whe~ as the
sc~nning means or as an adjunct to the sc~nning means, the CCD, CMOS or
camera may be arranged to prûduce an actual image of the tyre tread or a
portion thereof, which image may be printed or stored in any suitable storage
means, such as digitally on hard or floppy disk.
In yet another embo~lim~nt~ a stereoscopic image of the tyre tread is obtained,
e.g by use of a pair of spaced ç~msr~c or lenses, and information derived from
the stereoscope image (e.g. length ûf shadows, etc.) in respect of tread depth.
Although in a simple embodiment there may be no need to obtain tread depth
information from more than ûne region of the tyre, in general it is desirable
to obtain tread depth information for some or all of the tyre's circumference.
Although the a~p~a~us of this invention may be arranged to rotate about the
2~1739
WO 96/10727 PCT/GB95/02340
tyre, it is more convenient,~,to~rovide means for rotating the tyre to present
different regions of t~e~tyre's circumference to the a~para~us of this inventionfor sc~nning. Such tyre rotation means may comprise a pair of rollers for
receiving and supporting a tyre mounted on a wheel and fitted to a vehicle,
one or both of the rollers being drivable in rotation to rotate the tyre. It is to
be understood that the apparatus of this invention may be fitted, retro-fitted
or installed in other vehicle maintenance or inspection equipment, such as for
example a vehicle lift or hoist or a vehicle brake-testing apparatus such as a
rolling road, or a weighbridge. In such circllm~t~nres, it will may be possible
to use the wheel rotation facility provided in that other apparatus, provided
always of course that means can be provided to ensure that the tyre/wheel can
be rotated at a speed suitable for the apparatus of the present invention.
The output of the apparatus of the present invention will most suitably be in
the form of an electric signal, the voltage of which is proportional to tread
depth. If analogue, this signal may be converted to a digital signal and then
passed e.g. to a conl~u~er and VDU for processing and display.
The in-lic~trJr means responsive to the output of the sc~nning means need not
of course be a co~ u~el- and VDU and any suitable inrlir~tor means may be
employed. In a simple case the intlic~tor means may be no more than a
PASS/FAIL indicator, inrlicating for exarnple whether or not the depth of tread
rem~ ing at one region of the tyre is snfficient to comply with applicable law.
In other embodiments the display may show a profile of the tyre to reveal
tread depth variations, or may in~iic~te deviations from a standard tread
pattem. The in-lic~tor means may be audible rather than visible, e.g. to
provide a pleasing sound intended to in~ te a PASS, and a loud, unpleasant
noise intended to indicate a FAIL.
~ Wo 96110727 ~ - 2~ 01 739 PCT/GB95/02340
Furthermore, sl1cce~ive tread scans may be compiled to build a virtual 3-
~lim~n.~io l~l image of the tyre, which image may for çxample be mapped by
suitable software onto an image of a torus to create a picture of a tyre and
may for example be rendered in false colours to provide easily visible depth
information. Thus, for e~ample, pa;ts of the tyre which have s~ti~f~ctory tread
depth might be indicated in green while other parts of the tyre which do not
have s~ti~f~ctory tread depth might be indicated in red.
An advantage of using a computer as the in~ tor means of this invention is
that the il~o~ a~ion derived from the scanner means may be manipulated and
processed in many different and useful ways. Thus, for example, it may be
possible to 'zoom in' on a specific region of the tyre for a ~let~ fl inspectionof that region; it may also be possible to rotate on screen a 3-~iim~n~ional
image of the tyre or of a region of the tyre to e~mine it from di~c~c~L
aspects. It may also be possible to alter the relative scaling of the image to
provide, for example, an image with exaggerated depth of tread as co~ aled
to overall tread width.
In a preferred embodiment of the present invention, a tyre mounted on a
wheel fitted to a vehicle is rotated over or in front of a sc~nning a~a~us
according to the present invention. A con1~uLcr associated with the sc~nning
apparatus is progr~mm~l to obtain data from the sc~nning means in respect
of the ty;e tread and to process that data. Specifically, the program is
provided with predetermined m~xim11m and minim11m pçrmi~ible tyre
circumferences. The rotating tyre is scanned and data is obtained for the
entire width of the tyre and for several circumferential rotations of the tyre.
The software then scans through the data to find one or more ic1entifi~ble
marks, tread depth anomalies or other unique iclt-ntifiçrs on the tyre
Wo 96/10727 7 3 ~ ~ ~ PcTlGs95lo234
circumference. Using this identifier or set of identifiers the program then
scans the collected data to find one or more repetitions of that i~lentifier or set
of identifiers. Having achieved this, the program then checks that the
circumferential llict:~nre between the repeated identifier or set of i~lentifiers is
within the m~ximllm and miniml~m perrnitted tyre ~ u~ll[crcllces. If the
circumferential distance is between those limits then that circumferential
~ t~nce is taken as the cir~un~lcllce of the tyre. The software then
processes the data to obtain tread depth information for a complete revolution
of the tyre, i.e. for one circumference of the tyre to check whether the tread
depths measured comply with preprogrammed legal criteria. For example, in
the case of the United Kingdom, the central 75% of the width of the tyre tread
must have a tread depth of at least 1.6mm about the entire ~ ;ul~clcnce of
the tyre. The software compares the tread depth inform~tion derived from the
data collected with the preprogr~mme-l criteria and in-lis~tes by suitable meanswhether the tyre complies or not with the legal requirements.
The apparatus of the present invention may be capable not only of providing
tread depth information but also of providing other information about the
condition of the tyre. Thus, the a~paralus of this invention may be adapted
to reveal bulges in a tyre wall, nicks or notches in a tyre wall, uneven wear
caused by over-inflation, under-inflation, or vehicle suspension and/or steeringgeometry set-up errors. Indeed the a~ lus of this invention can under
certain circllm~t~nces be used as a diagnostic tool for assessing the correctness
of such suspension and/or steering geometry set-up.
The apparatus and method of the present invention may also be used to
measure other tyre parameters such as, for example, overall concentricity of
the tyre, or whether a side wall of the tyre lies adequately in or about a single
Wo 96/10727 PcTlGss5/o234o
plane. For this purpose it may be necessary to drive the wheel in rotation by
means other than rollers bearing upon the tyre itself, for example by driving
the wheel in rotation by a force applied to the wheel rim or to the axle of the
wheel, with the tyre out of contact with the ground or any other surface
imposing load upon the tyre itself.
The a~ Lus of this invention may also, for example, include detection
means for detecting the presence of metal, thus to reveal, for example,
whether or not the tyre has picked up a nail. Such detection means may
employ an mduction loop for detecting the presence of metal.
If a computer is used to process the results of the sc~nnin~, then other data
manipulation also becomes possible. For e~c~mrl~ on a conv~ntio~l tyre, the
tread pattern repeats about the circumference of the tyre at fixed intervals,
normally of 2 or 3 centim~tres in the case of a tyre for a private car. Thus,
by ex~minin~ only a few regions of the tyre (preferably at non-ul~ ,lnlly
spaced locations about the tyre, the overall tread pattern of the tyre may be
determined, since differences in tread depth will not signifi~ntly affect the
tread pattern. Once the repeat of the tread pattern has been i~entifiç~l (which
may, as will be recognised by one skilled in the art, be simply achieved by
means of appropriate software) the repeat can then be coln~alGd with other
sections of the tread about the cir~;ull~t,~nce of the tyre to reveal gross
differences between the portions of tread being compared such as the presence
of a bald patch, a piece of glass, a stone or a nail.
The inventor recognises that it may be useful to have a database of common
tyre tread pattems for tread i~le3~tifi~ticln and comparison purposes, and to
provide information which may be used for m~rketing and other purposes.
WO 96/10727 PCT/GB95/02340
2201739
;~
For example, it is illegal in the United Kingdom to drive a car on a public
highway with certain combinations of radial and cross-ply tyres; the ability
automatically to identify a tyre by its tread and thus to determine rapidly
whether it is radial or cross-ply is of great value to the police, garages and
others in a~es~ing the legality of any particular combination of tyres present
on a vehicle. Again, on trucks and heavy goods vehicles, it is fairly common
to find tyres of different sizes (diameter or width) being employed at the same
time. The apparatus of the present invention makes it possible readily to
identify the individual tyres present on the vehicle and thus to ~ietermine
whether the tyres meet legal requirements.
For marketing purposes, for example, the apparatus of the present invention
can, subject to the requirements of the United Kingdom Data Protection Act
1984, provide tyre sellers and m~nnf~c~lrers~ and car m~nnfactllrers, with
useful inform~tion about tyre popularities, by type of vehicle, by geogr~phi~l
region~ etc. In conjunction with .,~ ation relating to the vehicle (e.g. age
of vehicle, year of registration, mileage, body type, co~ ally/ personal car anddate of last test/inspection) and/or the address of its registered owner/keeper,it is possible for the police and others to send out remin-lers of the need to
replace tyres at intervals calculated from knowledge of the mak.e of the tyres,
of tyre wear rates and of the condition of the tyres on the vehicle.
The scanning apparatus may also include recorder means, e.g one or more of
a vid~o camera, a still camera or digitai storage device ( e.g. a hard disk,
floppy disk, magneto-optical disk or CD-Rom), and printout means to provide
a perm:lnent record, e.g on paper or on floppy disk, of a tyre and/or of the
vehicle to which the tyre is fitted, which record may be in a form suitable for
use e.g. by the police for evi-lenti~ry purposes.
WO 96110727 ~ t~ 4 PCTIGB95102340
~ 22~1 739
The sc~nnin~ a~ aluS of this invention may be adapted also to measure the
gross dimensions of the tyre under test, for example the cir~ull~fer~llce (and
hence the radius and ~ meter) of the tyre and its overall width, in order to
facilitate a more rapid and accurate i~lentific~tion of the tyre under test by
reference to a tyre tread ~i~t~b~ce, which ~i~t~ aee may be present either in anadjacent co~ uler or in a remote colll~uLel ~ccessible by modem, by digital
telephone or by any other suitable means.
The sc~nnin~ a~alus of this invention may also be provided with one or
more lateral support devices for supporting on the appal~Lus either a tyre per
se or a tyre mounted on a wheel but off a vehicle. With such a tyre suitably
supported, the tyre rotation means may drive the tyre in rotation to enable
sc~nning of the tyre. It is to be appreciated that such lateral ~.u~poll devicesare adjuncts to the a~LaLlls of the present invention. Suitable ~u~ull
devices include simple guide el~m~nts position~ble to support the tyre in an
upright po~ition, and guide elements equipped with one or more rollers or
other low-friction contact devices to support the tyre in an upright position
and yet permit rotation of the tyre, and means for supporting and rotating a
tyre about a vertical axis.
The apparatus of the present invention may include ~n~ ry means for
viewing one or both of the sidewalls of a tyre to enable an asse~m~-nt to be
made of the condition of the or each sidewall and to view information present
on one or both of the sidewalls of a tyre under test, e.g. the maker's name, thetyre ~limen~ions7 the recomme~ed pressures, the recommen(le~l use to which
the tyre is to be put, the const,-uction of the tyre, etc. For example, such
ancillary means may include one or more sc~nning means as discussed above,
the output of said sc~nnin~ means being delivered to a processor able to
WO 96/10727 2 2 U i 7 3 9 PCT/GB95/02340 ~
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t' ~
subject the output to optical character reading (OCR) thereby to read that
information and input it into a database or to print out the information in
conjunction with the tyre tread scan.
The apparatus of this invention may also include weight-mç~c-lring means to
determine the weight applied to the wheel by the vellicle and its load.
conjunction witn information that may be obtained from the sc~nning means
about the area of tyre in contact with the ground (the 'footprint' of the tyre)
it may be possible to calculate a numerical value for the tyre pressure. This
calculated tyre pressure may be compared with a l~t~b~ce of known or
recommended tyre pressures for specific tyre and/or vehicle combinations to
provide an in~lis~tion of whether the tyre is currently over- or under-infl~te-l
An embodiment of the sc~nning apparatus of the present invention will now
be described, by way of example only, by reference to the acco~ anying
drawings, in which:
Fig 1 is a diagr~mm~tic view of the elements of an
embodiment of apparatus according to the present
invention;
Fig 2 is a 2--limencional plot of the results of sc~nnin~
a tyre;
Fig 3 is a further 2-~limencional plot of the results of
sc~nning a tyre;
Fig.4 is a 3-~iim~n.cional plot of the results of sc~ ;.-g
s
~ WO 96/10727 PCTIGB95/02340
~2~1 ~3g
a tyre;
Fig S is a mapping of 3-~iim~ncion~l tyre tread depth
data onto a torus;
Fig 6 is a photograph of a region of a tyre which
in~ es both a stone and a nail in its tread;
Figs 7a to 7e are diagr~mm~tic illustrations of di[r~
tyre wear anomalies that may be detected and/or
diagnosed by means of embo~im~.nt~ of the present
invention;
Fig 8 is a perspective view of an embo~im~nt of
apparatus according to the ~l~selll invention in the
form of a 'drive through' system, with a vehicle in a
preliminary position;
Fig 9 is a second illustration of the embc!~1im~nt of the
apparatus according to the present invention which is
shown in Fig 8, with the vehicle in place for its front
tyres to be sc~nne~l
Fig 10 is an illustration of another embodiment of
apparatus according ~o the present invention, suitable
for in~t~ tion in, e.g., a garage or petrol filling station
envir -nmPnt and
Wo 96/10727 2 2 017 ~ 9 . ~ Pcr/Gss5lo234o ~
Fig l 1 is an illustration of another embodiment of
apparatus according to the present invention, in a form
capable of easy assembly and disassembly for road-side
use by the police for conrl~lcting spot-checks on tyre
condition.
Referring to the drawings, and particularly to Fig l, there is shown an
embodiment of a~pEl~Lus 1 according to the present invention. The a~ Lus
l consists of a frame 2 supporting a pair of slide rods or bars 3. Mounted on
the slide rods or bars 3 is a support 4 carrying a 12 volt laser analog sensor
5. This sensor 5, which in this embodiment is one available from M~tsll~hitz~
Electronics Inc. as part No. NAIS ANLl451RE, consists of a laser 6 adapted
to emit pulses of red light and a detector 7 for receiving reflected pulses. Thesupport 4 includes a clamp 8 carrying a toothed belt 9 which extends about
pulley lO supported by bracket 1 l. A 24 volt electric motor 12 is provided
with a drive 13 for driving the toothed belt 9 in rotation, thus to drive the
support 4 and its laser analog sensor 5 along the slide rods or bars 3. The
direction of rotation of electric motor 12 is controlled by suitable software tocause the support 4 to be driven back and forth along slide rods or bars 3 as
required. The frame 2, slide rods or bars 3, support 4, clamp 8, belt 9, pulley
lO, bracket l 1, electric motor 12 and dlive 13 are conveniently derived from
or obtained from a conventional inkjet printer such as is available from
companies such as Epson, Star Microelectronics and Hewlett Packard, whence
also can be derived the desired control software for driving the support 4 back
and forth along slide rods or bars 3. (It will be appreciated that any suitable
software, whether derived from existing drivers or custom-written may be used
for this purpose.)
WO 96/10727 - ' ~ t ~:' PCTtGB95/02340
A tyre 14, provided with a tread 15 is mounted on a wheel 16 and fitted to a
vehicle 17 (not shown in Fig 1). The tyre 14 is positioned over laser analog
sensor 5 and is supported upon rollers 1~, 19. At least one of rollers 18, 19
is rotatably drivable by means of a motor (not shown) to cause rotation of the
tyre 14. The tyre 14 is conveniently positioned at a distance of between
30mm and 50mm from sensor 5, although this rli~t~n~e. will vary in
accordance with the capability of the laser sensor selected for use in the
invention. (In order to minimi~;e any risk to the public or to an operative of
the apparatus, the laser is preferably selected to be of a power that complies
with relevant safety laws, e.g. as required by the British Health and Safety
E~xecutive. Suitable lasers are Class 1 or Class 2 lasers in accordance with
British Standard BSEN 60825-1, emitting visible light.)
With tyre 14 suitably positioned over laser analog sensor 5, the ~a~us is
driven to cause laser sensor S to scan the tyre tread 15.
When the system is initially activated the electronics resets its O~la~ g
memory to zero and runs a software routine which causes the motor (not
shown) to rotate the tyre.
The analogue output from sensor 5 is converted to a digital signal by means
of analogue-to-digital converter 20 and then passes to a computer 21 with
VDU 22. The sc~nnin~ may take place at a sc~nnin~ speed of approximately
lOcm/sec. With the laser pulsing at a rate of 1000 pulses/second and a
distance to be sc~nn~d of, say, 15 to 20 cm, this provides several thousand
individual measurements of the depth of the tread, with a resolution of
appro,Yimately 0.7 by 0.2mm per measurement (i.e. laser spot size) and a
depth accuracy of approximately 50}1m. The tyre may be driven in rotation
Wo 96/10727 PCrlGB95/02340
at a constant rate equivalent to a road speed of, say, up to S to 7 miles per
hour (224 to 312 cm/second). For the conver~ nse of the user, it is ~ r~ d
that the time taken to scan an entire tyre be no longer than approximately 90
seconds. It is to be understood that the manner and rate of rotation may be
selected in accordance with the drive means employed to drive the tyre in
rotation. Thus, if a stepper motor is used to rotate the tyre, the tyre may be
intermitt~tly rotated between scans effected on a moment~rily stationary tyre.
It is also to be ~lnclerctood that in other embo~lim~nts the tyre may be rotatedat a rate considerably greater than is in~ te~l above, e.g. at a rate equivalentto a road speed of approximately 25 kilometres/hour and an adequate number
of individual scans still be obtained to provide a s~ti~f~ctory quantity of datato enable useful tread depth inforrnation to be obtained about the tyre under
test.
Information corresponding to the image sc~nn~l by the detection device is
stored in the memory of the system and is analyzed to observe the tyre pattem
and to identify the cyclic pattem of the tyre; when it has identified what it
thinks is the pattem the system will then rotate the tyre again and this time
look for v~ri~n~es to this pattem.
As hereinbefore, the software identifies a point on the ci~;ulllfelcllce of the
tyre and takes this as a datum point; all comparisons are then made relative
to this point.
If a point of variance to the cyclic pattern is detected it marks this in its
memory (anomaly map) as a point to investigate further, it also scans the
surface at this region to measure the depth of tread pattem and records into
memory the depth memory map for the total ~;u- u~l~clcllce of the tyre under
14
~ wo 96llO727 PcT/Gss5/02340
22ol 73~
test.
The decision as to whether a tyre has passed or failed comes from the criteria
programmed into the software based upon the law of the land where the
system is used and upon judgements progr~mme~l into the system software
e.g. by trade bodies, by tyre associ~tior-~ m~n11f~ct11rers, by local equivalents
of the United Kingdom Department of Transport, or by other interested
parties.
It is to be noted that in normal circnm~t~nces, the a~alaLus of this invention
will be protected from e,Llvi-.llll,ental factors such as rain, dust, etc. by
ensu~ing that e.g. sensiLive parts of the a~dLus are screened, e.g. by a glass
panel or by providing a suitably, e.g. hori7ont~11y, directed air curtain.
An example of an output obtained by means of the ~aLuS and method of
this invention is shown in Fig 2. In Fig 2, a scale factor of l has been used
for the hori7Ont~1 scale but the vertical scale has been multiplied by a factor
of approximately 5. As may be seen from the output plot of Fig 2, which in
this case is taken from a Dunlop DM2 205x60 R9lV tyre, the tyre has along
the line of scan a tread depth of not less than approximately 4mm. The
results of another, similar scan are shown in Fig 3.
Successive sc~nnin~ measurements may be plotted on a 3_tlim~-n~ion~1 graph
or chart to build a 3-dimensional picture of the tread of the tyre. An example
of such a graph is shown in Fig 4. As may be seen, the elevated portions 23
of tread 15, as well as valley portions 24 of tread 15 and also minimllm tread
depth indicator bars 25, are clearly visible. (These miniml-m tread depth
indicator bars, if present, may be conveniently used to provide a depth datum
WO 96/10727 PcT/Gsg5/02340
2~û173~ ~ O
point from which to measure the tread depth variations.)
The 3-~,imen.ci,on~l tread depth data may be mapped, e.g. by using suitable
software such as 'Autocad', onto a torus to provide a clear visual in,~licz,tionof the tyre being scanned. An example of such a 3-f,lim~n~ionzl mapping is
shown in Fig c,, the tread shown in Fig S being an actual reproduction of the
tread on the tyre sc~nne~ It is possible to render this 3-dimensional mapping
in false colours in accordance with the depth of tread present at any particularregion of the tyre to provide an imm~r,,iztely recognizable in~i,rztion of
whether the regions of the tyre complies with applicable local law con~ernin~
minim~lm permissible tread depths.
As mentioned hereinbefore, the a~ us and method of the present invention
may be used to detect gross anomalies in or on the tyre. The system stores
in its memory the output from the scznning process and by taking szmp1ie s of
this is able to build-up an image of the actual tread pattem, compare various
points on the tyres surface where the tread pattem is found to repeat, and
detect differences in the pattem between the points. These anomalies could
be bald patches, nails stuck into the surface, cut tread, uneven wear or similardefects.
Figs 6 and 7 are pertinent to these purposes. Fig 6 shows a region 26 of a
tyre 27 which has embedded in it both a stone 28 and a nail 29. The presence
of both the stone 28 and the nail 29 can be detected by employing in the
computer 21 suitable tread i~lentifi~ti~ n and co~ hison software to draw the
attention of an operative to the differences which are manifested by the
presence of these intrusions. Of course, if the app~h~lus of the present
incorporates a metal detector as discussed above then this will detect the
16
Wo 96/10727 ! '" ' ' ' ' -' Pcr/Gss5/02340
1 7 3 9 . .
presence in the tyre of the nail. Fig 7, which is taken from 'Flln~1~m~nt~lc of
Motor Vehicle Technol-tgy', by V.A.W. Hillier, 4th edition, ISBN 0-7487-
~016-3, in-lic~tes how different con-litionc can affect the state of the tread of
a tyre. As shown in Fig 7a, under-inflation of a tyre will cause measurably
more wear on the shoulders of the tyre than on its centre portion. This pattem
of anomalous wear can be detected by the apparatus and method of the
present invention and can be used to diagnose a long-term under-infl~tion
condition. Similarly, as shown in Fig 7b, a long-term over-infl~te-l con~lition
of the tyre will result in relatively greater wear towards the centre of the tyre
than at the shoulders of the tyre. This pattern of anomalous wear too can be
detected by the a~al~lus and method of the present invention and can be used
to diagnose such a long-term over-infl~tion conrlition In Fig 7c, there is
illustrated a condition in which ;the tyre has suPfered asymm~--tric tread wear,which may well be due to the presence of excessive camber in the suspension/
steering geometry of the vehicle. Once again, the a~ a~-;Ls and method of
the present invention can detect this conr~itif n and offer a ~ n~si~ Fig 7d
illustrates a tyre condition in which the grooves of the treads of the tyre have'feathered edges'. This condition can be caused by an incorrect amount of
toe-in or toe-out of the tyre as mounted on the vehicle and once again the
apparatus and method of the presen~ invention can detect this condition and
offer a diagnosis. If by means of the appa~d~us and method of the present
invention there be detected a condition such as that illll~tr~te-l in Fig 7e (the
presence of one or more bald or relatively bald spots about the circumference
of the tyre), then the apparatus can suggest that this con-lition may be due to
other defects in the vehicle, such as steering sl~ckness~ brake drum or disc
wear or distortion, wom shock absorbers or dampers or road wheels
inadequately balanced in rotatiorl;
WO 96110727 ~ PCT/GB95102340~
22û1739
Referring now to Figs 8 and 9, there is shown an illustration for a right-hand
drive vehicle of an installation employing the apparatus and method of the
present invention. A vehicle 30 drives towards fixed ramps 31a and 31b,
p~l-sin~ to insert into slot 32 of pillar 33 a suitable coin, credit card, charge
card, jetton or token, to pay for the tyre tread analysis. AccepLa.,ce of the
payment is sign~lled to the driver on display 34 and the driver is instructed
to drive the vehicle slowly forwards until the front wheels travel up ramps 31a
and 3 lb and are supported by rollers 35 and 36. (N.B. The customer is kept
informed of the systems operation at all times via a variety of output devices.
These could be either a computer monitor screen, e.g. a Zenith Cruise Pad
wireless-linked computer display screen, a L~l ? or LCD display screen or
moving message device or via recorded mtos~ges played to the customer at
the a~,op.iate time.) A sc~nning apparatus according to the present invention
is located beneath and between each pair of rollers 35 and 36. Once a sensor
detects that the vehicle is in the correct position, the rotation of the wheels
and the sc~nning of the tread of the tyre is effected. Once this has been
completed the driver is instructed to drive the vehicle fulw~uds again to
position the rear wheels in a position on the rollers suitable for sc~nning The
sc~nning process is then once more carried out. Once the sc~nning is
complete, the results are processed and analyzed and a printout of the results
is produced, in readily understandable form and presented by means of slot 37
in pillar 38 to the driver for retention and inspection. (Additionally, the
apparatus looks for worn areas of the tyres' s~ res; if the system detects an
anomaly which it cannot resolve it wiil call for or in~lic~t~ that a visual
inspection by a suitable trained operative is required.) The display device 34,
which may be a LCD or LED moving mess~ge sign os TV screen, is used to
indicate to the vehicle driver or the operator the status of the test sc~nnin,~
unit, the rem~ining time needed to complete the testing and instructions to
18
~WO96/10727 G~l 73~ PCr/GB95102340
~; F~
proceed forwards, collect ~ loul, etc. The display device 34 can also
in~ te at which point on the tyre's surface the anomalies have been detecte~
In the case of a TV screen an actual picture may be displayed to show a bad
defect to the customer.
It will be appreciated that the operation of the apparatus of this invention canbe initiated via any suitable initiation circuit e.g. a push button, beeping of the
hom of the vehicle or fl~ching of its h~ ht~.
The arrangement shown in Fig lQ of the drawings is similar to that shown in
Figs 8 and 9 and shows how the apparatus of this invention might be in~t~ d
in a garage or petrol filling station, rather in the m~nner of a car-wash. The
wording on the panel 39 is an example of the display that might appear to a
motorist, displayed on display 34.
The apparatus illu~a~d in fig 1 l of tlle drawings is suitable for use by law
enforcement personnel, by the side of a road or elsewhere. In this
embo-limPnt, the ~ aLus is small, compact and portable and is arranged to
be easily set up and t1icm~ntlt~1 for temporary use. The ~ aLuS should be
capable of being easily assembled with the pairs of ramps arranged in parallel
and at a suitable spacing, and with the ramps fixed in position by any suitable
means for the duration of use. For example, the ramps may be linked together
and/or be of sufficient weight to remain in their proper position during usage.
The apparatus is c~ ect~d, e.g. by means of an RS232 cable or an infra-red
link to a portable computer e.g. a notebook or laptop co~ uler, which has
facilities for producing hard copy, eg by means of an inkjet or bubblejet
- printer. The power source for the apparatus of this invention may be the
onboard power supply of a vehicle, e.g. a police car, or may be provided by
19
WO 96/10727 PcrlGss5/o234o 0
220~39
electrical storage batteries or by an electricity generator. For evidentiary
purposes, the printer will normally produce a plurali~y of iclentir~l reports,
some for retention by the police and one for the vehicle driver.
The apparatus and method of this invention provide the ability to ~ L~llll fast,accurate and sophisticated investigations into the condition of a vehicle tyre,
and will be greatly welcomed by law enrolcelllent agencies, tyre fitting
org~ni7~tions~ tyre m~nllf~ctllrers and by motorists, truck drivers etc.
The invention may be pel~olllled otherwise than as has been particularly
described; the invention includes within its scope all modifications, alterations,
substitutions and improvements that would be a~e--L to one skilled in the
art.
