Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02216494 1997-10-01
Title: VEHICLE SAFETY MONITORING SYSTEM
FIELD OF THE INVENTION
This invention relates to a safety monitoring system for
vehicles such as transport trucks and trailers.
5 BACKGROUND OF THE INVENTION
Recently, considerable media attention has been given to
traffic accidents caused by a wheel or wheel assembly becoming detached
from a transport truck while the truck is in motion. Once separated from
the truck, a detached wheel or wheel assembly becomes an uncontrolled
10 projectile that has considerable weight and momentum. A number of
serious injuries and deaths have resulted from such incidents.
While there are requirements for periodic mechanical
inspections of transport trucks, generally, monitoring of the mechanical
condition and general roadworthiness of such vehicles relies on the
15 diligence and thoroughness of the truck operator and/or driver. Given
economic pressures to keep such vehicles in productive use, maintenance
and repairs are sometimes neglected. Random unpredictable component
failures can of course also be the cause of accidents.
An object of the present invention is to provide a safety
20 monitoring system for vehicles such as transport trucks and trailers.
SUMMARY OF THE INVENTION
In one aspect, the invention provides a safety monitoring
~yslem for the wheels of a vehicle in which each wheel rotates on a carrier
that is rotationally supported on the vehicle itself. The ~ysle~l~ includes
25 sensing means adapted to detect excessive axial movement of a wheel
outwardly of the vehicle, and rotational movement of a wheel with
respect to the associated wheel carrier, together with alarm means adapted
to provide a warning in the event of either excessive axial movement of a
wheel or rotation movement with respect to the associated wheel carrier.
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This aspect of the invention is based on the recognition that it
is possible to detect defects that could result in a wheel or wheel assembly
becoming detached from the vehicle by monitoring either of these two
eventualities. Excessive axial movement of a wheel can occur, for
5 example, in the event of catastrophic failure of a wheel bearing -- allowing
the entire wheel assembly to come off the axle. Rotational movement of a
wheel with respect to the associated wheel carrier will occur if the wheeI
studs that hold the wheel to the carrier shear.
In principle, the monitoring ~y~lelll of the invention can be
10 applied to a single wheel c~rrie-l by a hub, in which case the system detectsrotational movement of the wheel with respect to the hub. In the case of a
dual wheel vehicle having a pair of wheels mounted side-by-side coaxially
on the same hub, detection can be effected by sensing relative rotational
movement between the two wheels or between one wheel and the hub.
Preferably, of course, sensing means is provided on each
wheel of the vehicle, although sensing means could be used on only some
wheels of the vehicle, for example, only on the dual wheels where the
vehicle has both dual wheels and single wheels.
The alarm means may comprise a visual display panel to
20 alert the driver to a possible malfunction. The display panel can be
designed to identify which particular wheel A~s~mhly is defective.
In another aspect of the invention, the monitoring ~ysleln
may be applied to the brakes of the vehicle. This aspect of the invention
may be used in combination with the wheel monitoring ~yslell, discussed
25 previously, or separately. In this aspect of the invenlion, the monitoring
:iy:,le~l is applied to a vehicle having at each wheel a brake actuator
including an actuator element that is movable generally longitudinally at
each actuation of the vehicles brakes. The ~ystell~ includes means
associated with the actuator element of each brake actuator and responsive
30 to said generally longitudinal movement of the element beyond a
predetermined limit, together with alarm means adapted to provide a
warning if movement beyond the limit occurs at any of the actuators.
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In Ontario, the brakes of a transport truck are required to be
set so that the actuator element at each wheel has a maximum travel of
two inches. If travel beyond that amount is discovered during an
inspection of the vehicle, heavy fines are levied. In a vehicle equipped
5 with a monitoring system according to the invention, the ~yslelll may be
adjusted to respond and provide a warning if the travel of the actuator
element of any one wheel approaches that maximum. This will give the
opportunity to adjust the brakes to avoid contravention of applicable
regulations.
Different travel limits no doubt will apply in different
jurisdictions and the system preferably is adjustable so that the driver or
operator can maintain the brakes within whatever regulations apply or
within safety limits determined by the individual driver or operator.
In another aspect, the invention provides a safety monitoring
1~ ~ysle,n for the wheels of a vehicle in which each wheel is rotationally
supported on a chassis. The ~y~telll includes, in association with at least
one of the wheels, a sensor responsive to the presence of the wheel in a
defined operational position in relation to the chassis. The sensor is also
adapted to detect movement of the wheel beyond a pre-determined
20 amount from the defined position, such movement indicating a potential
wheel failure. The ~y~lem also includes an alarm means operationally
coupled to said sensor and adapted to provide a warning in the event that
movement beyond a predetermined amount is detected.
In this context, the word "chassis" is not be to i"t~l~reled as
25 rerelli.,g only to the frame of the vehicle, but as including any part of the vehicle between the frame and the wheels, e.g. axles and steering
components.
This aspect of the invention is based on the recognition that it
is possible to detect and anticipate the failure of wheels, bearings andlor
30 axles by monitoring any change in relative position of wheel with respect
to its normal operational position. It has been determined that even slight
changes in the position of the wheel can give an early warning of faults.
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The safety monitoring ~yslelll for the wheels of a vehicle
preferably includes a sensor mounting bracket which is mounted on the
chassis and designed to position the sensor such that it is adjacent to an
edge of a rim of the wheel. Further, the sensor is preferably an inductive
5 proximity sensor.
In one embodiment, the sensor is mounted on a drive axle.
In another embodiment, the wheel fault sensor is mounted
on a trailer axle.
In a further embodiment, the wheel fault sensor is mounted
10 on a kingpin cap.
In a still further embodiment, the wheel fault sensor is
mounted on a brake cam tube.
In another embodiment, the alarm means includes a display
panel adapted to provide audible and visual warnings to a driver of the
15 vehicle that the safety monitoring system has detected a wheel fault.
In another aspect of the invention, as applied to the brakes of
the vehicle described above, the vehicle brakes include, at each wheel, a
cam rod which is turnable about a longitudinal axis to operate a brake at
that wheel, and a slack adjuster mounted on the cam rod and having an
20 outer end coupled to the actuator element. The adjuster is adjustable
angularly with respect to the rod to compensate for travel of the actuator
element beyond a pre-determined limit as a result of brake wear. The
monitoring ~ysLem also includes means responsive to movement of the
actuator element beyond a pre-determined limit which comprises a sensor
25 responsive to the presence of the slack adjuster and adapted to detect
excessive travel of the slack adjuster as indicating excessive brake wear.
Preferably, the brake monitoring system has a sensor-
supporting bracket mounted on the ~h~si.s and designed to position said
sensor so that the slack adjustor will enter the sensing range of the sensor
30 once excess travel representing excessive brake wear has occurred. Further,
the sensor is preferably an inductive proximity sensor.
In one embodiment, the brake monitoring sensor is mounted
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on a cam tube.
In another embodiment, the brake monitoring sensor is
mounted on a kingpin cap.
In another embodiment, the brake monitoring system
includes an alarm means which comprises a display panel adapted to
provide audible and visual warning to a driver of the wheeled vehicle that
the sensing system has detected a brake actuator fault.
In a specific embodiment, the safety monitoring ~yst~
described immediately above, is provided to a transport vehicle
10 comprising a tractor unit and a trailer unit, each having a plurality of
wheels carried by at least two axles, wherein each wheel is associated with
a sensor responsive to the presence of said wheel and a means associated
with the actuator element of an associated brake actuator, and where an
alarm means is responsive to detection of a potential failure of any wheel
15 or excessive brake travel at any wheel.
In one embodiment, the brake monitoring aspect of the
invention may be applied to a vehicle such as an automobile having drum
or disc brakes. In this embodiment, a sensor wire is embedded within a
body of friction engendering material such as a brake lining or pad that is
20 applied against a rotating metal element such as a drum or disc when the
brakes are operated. When a predetermined amount of brake pad or
lining wear has occurred, the sensor wire contacts and forms an electrical
connection with the brake disc or drum and shorts to ground, providing a
warning signal.
25 BRIEFDESCRIPIIONOFTHE DRAWINGS
In order that the invention may be more clearly understood,
reference will now be made to the accompanying drawings which
illustrate a number of preferred embodiments of the invention by way of
example, and in which:
Pig. 1 is a partial perspective view of a transport tractor unit,
partly broken away to show a hub assembly of one wheel;
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Fig. 2 is an exploded perspective view of a typical such
assembly;
Fig. 3 is an elevational view of a sensor ring that may be used
in the assembly of Fig. 2;
5Fig. 4 is a simplified exploded view showing the sen~ing
means of the invention in association with the sensor ring of Fig. 3;
Fig. 5 is a diagrammatic elevational view corresponding to
Fig. 4, showing the two wheels assembled with the sensor ring and sensor;
Fig. 6 is an exploded perspective view showing an alternative
10wheel rim configuration;
Fig. 7 is a schematic illustration of a brake monitoring ~y~Le~
in accordance with the invention;
Fig. 8 is a block diagram illustrating the overall monitoring
~y~lem;
15Fig. 9 is a simplified illustration of a driver display panel that
may be used as part of the system showed in Fig. 8;
Fig. 10a is a cross-sectional view showing an alternative
wheel fault sensing means of the invention;
Fig. 10b is a perspective view showing how a sensor is
20mounted into a bracket using two sensor mounting rings;
Fig. 10c is a perspective view showing an alternative brake
fault sensing means of the invention;
Fig. 11a is a perspective view of an embodiment of the
alternative wheel and brake fault sensing means as adapted to a trailer
25axle;
Fig. 11b is a side view of the alternative wheel sensing means
as adapted to a trailer axle showing how rotatable bracket can variably
position sensor along the rim edge of a wheel;
Fig. 11c is a more detailed perspective view of the alternative
30brake fault sensing means as adapted to a cam tube;
Fig. 12 is a perspective view of an alternative embodint~nt of
the wheel fault sensing means as adapted to a drive axle;
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Fig. 13a is a perspective view of a dual purpose wheel and
brake sensing means as adapted to a steering axle kingpin cap;
Fig. 13b is a exploded view of a dual purpose wheel and brake
sensor bracket;
Fig. 13c is a cross-sectional view of a dual purpose wheel and
brake sensing means as adapted to a steering axle kingpin cap;
Fig. 13d is a cross-sectional view of a dual purpose wheel and
brake sensing means as adapted to a steering axle kingpin cap and showing
how brake actuator rod travel affects the relative position of the slack
10 adjustor;
Fig. 14 is a block diagram illustrating an alternative
embodiment of the overall monitoring ~y~lem of the present invention;
Fig. 15 is an alternative driver display panel that may be used
as part of the ~ysLelll shown in Fig. 14;
Fig. 16 is an another alternative driver display panel that may
be used as part of the system shown in Fig. 14;
Fig. 17 is an exploded view showing a brake shoe wear
monitoring system for use within automobile drum brake assembly in
accordance with the invention.
DESCRII~ION OF PREFERRED EMBODIMENTS
Referring first to Fig. 1, a tractor unit is generally indicated at
20 and is shown without ancillary components such, for example, as a fifth
wheel a~semhly. The cab is indicated at 22 and the chassis of the vehicIe at
24. Four rear wheel assemblies of the tractor unit are shown and are
individually denoted 26.
The frontmost wheel assembly at the left-hand side of the
tractor unit in Fig. 1 is shown broken away at 28 to reveal the brake and
hub assembly, generally denoted 30, on an axle 32 of the unit. A drum
brake assembly is shown at 34 and an actuator for the brake at 36.
Typically, the brakes are air-operated.
A typical truck wheel comprises a hub, a rim and a tire and
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tube assembly. A rim is attached to the hub and retained at the hub by
either single or dual nuts. The tire and tube assembly is then mounted on
the rim and inflated. It will be seen that each of wheel assemblies 26 is a
dual wheel assembly comprising two wheels disposed coaxially side-by-
5 side and carried by the same hub assembly. Fig. 2 shows a typical suchwheel and hub assembly in exploded form and without the tires. The rims
of the two wheels are indicated at 38 and 40 and are disposed outwardly of
the hub assembly 30.
Hub assembly 30 includes a brake drum 42 and a wheel carrier
10 in the form of a hub 44, which is rotationally supported on the axle 32 of
the vehicle by a wheel bearing (not shown). A series of studs 46 extend
through aligned holes in the hub 44, brake drum 42 and wheel rims 38 and
40 to clamp the whole assembly to the axle. Nuts for the studs are shown
at 48, outwardly of wheel rim 38.
Typically, each of the wheel rims 38 and 40 includes openings
such as those shown at 50. When the two wheel rims are clamped
together by the studs 46 and nuts 48, the openings in the respective rims
are aligned with one another.
The housing of axle 32 (Pig. 1) is diagrammatically indicated
in Fig. 2 at 52 and is fitted with a sensor 54 positioned to direct a sensing
beam 56 through the aligned openings 50 in the wheel rims 38 and 40. As
the wheel assembly rotates, beam 56 will be repeatedly interrupted by the
solid portions of the two wheel rims between the openings 50, providing a
pulsed signal. In the event that excessive relative rotation takes place
between the two wheel rims 38 and 40, the signal from sensor 54 will
change, or possibly be cut off if the two wheels turn with respect to one
another to an extent sufficient that the openings 50 are no longer aligned.
The sy~Lem will then provide an alarm to the effect that the wheel
assembly in question has developed a defect.
Sensor 54 is also sensitive to the distance of the inner wheel
rim 40 from the switch. For example, the sensor may be designed to in
effect "measure" that distance during the time when beam 56 is
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interrupted by the solid portions of the rim between the openings 50. The
sensor can then respond and give an alarm signal in the event that
distance exceeds a defined maximum value, indicating excessive axial
outward movement of the wheel assembly.
With certain types of wheel rims, it is conventional to
provide an annular ring between the two rims, primarily to protect the
rims against mechanical damage due to vibration and slight relative
movement when the vehicle is in motion. A typical such ring is indicated
at 58 in Fig. 2 and is shown in elevation in Fig. 3. The ring has openings 60
10 to receive the wheel studs 46. According to another aspect of the
invention, the ring 58 may be used as a re~er~l~ce that is sensed by sensors
of the monitoring ~y~lelll to detect abnormalities. It may be necessary to
radially enlarge the ring as compared with conventional protective rings.
Fig. 4 shows such an arrangement, in simplified exploded
15 form. Two wheels of a typical wheel assembly 26 are shown (with tires) in
exploded positions at 62 and 64 with a sensor ring 58 in between. A sensor
such as a proximity switch assembly 66 is carried at the distal end of an arm
68, the opposite end of which is secured to the axle housing 52 of the
vehicle. Arm 68 should be relatively rigid but may be adjustable or capable
20 of being bent so that its shape can be changed to fit different vehicles and
bring the proximity switch assembly 66 into appropriate relationship with
ring 58.
Fig. 5 is a diagrammatic illustration showing the two wheel
rims 38 and 40 (of the wheels 62 and 64) in their assembled condition, with
25 the sensor ring 58 between the two rims. The proximity switch assembly
66 is positioned adjacent the outer edge face of ring 58 as it rotates.
Assembly 66 is designed to be responsive to the axial position of ring 58
with respect to the longitudinal axis A-A of the wheel assembly, and to the
relative rotational positions of the two rims 38 and 40. For example, the
30 assembly may include a proximity switch, a signal from which is
represented by the arrow denoted 70 in Fig. 5, and which will respond to
any axial movement of ring 58 beyond a prescribed limit. A response to
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such movement beyond the limit will of course indicate excessive axial
movement of the wheel assembly and provide an alarm signal, indicating
possible hub bearing failure.
Assembly 66 will also include sensors that are responsive to
5 the relative rotational positions of the two rims 38 and 40, as indicated by
the arrows denoted 72 and 74. For example, these sensors may also be
proximity switches that respond to the presence or the absence of the
openings 50 in the wheel rims (see Fig. 2). These sensors will accordingly
provide timed pulses that will coincide as long as there is no relative
10 rotational movement between the two rims. When the sy~telll detects
that the pulses represented by the arrows 72 and 74 are out of phase, the
~y~lem will recognize that excessive rotational movement has taken place
between the two rims, for example indicating that the wheel studs have
sheared, and provide an alarm signal.
Fig. 6 shows an alternative style of wheel rim, the two rims
corresponding to the rims 38 and 40 of the previous views being denoted
38' and 40'. This style of wheel rim is designed so that each rim has
marginal flanges at each side, as indicated at F. When assembled together,
the marginal flange F at the outer side of the rim of the inner wheel (rim
40') confronts the corresponding flange at the inner side of the rim of the
outer wheel (rim 38'). A spacer 76 of short cylindrical form is fitted
between the two rims and is in effect clamped by the wheel studs and nuts.
Where this style of wheel rim is used, the spacer 76 can be used to provide
the ~eferellce for the sensor assembly such as assembly 66 in Figs. 4 and 5.
The proximity switch represented by the arrow 70 in Fig. 5 can be used to
"read" the spacer and respond to any deviation from its "datumn axial
location when the wheel assembly is fully tightened onto the hub (44 --
Fig. 2). If necessAry, openings or markings can be provided on the spacer to
be "read" by the sensor.
The previous description of course relates to aspects of the
monitoring system of the invention that are designed to detect and
respond to defects in a wheel assembly. Fig. 7 illustrates another aspect of
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the invention that relates to monitoring brake actuator travel. A typical
brake actuator is illustrated in simplified form and denoted as 78. As
mentioned previously, each wheel of the vehicle will be provided with
one of these actuators. The actuators are air-operated and are essentially
conventional. Reference numeral 80 denotes a housing for an air-
responsive piston of the actuator. A brake actuator rod 82 projects from
one end of the housing and has a clevis 84 at its distal end by which the
actuator is coupled to the actual brake mechanism (not shown). When the
driver applies the brakes, air is supplied to housing 80 to move rod
10 82 longitudinally with respect to housing 80 and apply the brakes.
According to this aspect of the invention, a sensor is
associated with the actuator rod 82 and is arranged to be responsive to
longitudinal movement of rod 82 at a predetermined threshold limit (e.g.
two inches). Fig. 7 shows two alternative arrangements. In one
15 arrangement, the housing 80 is provided with an opening 86 (not present
in a conventional brake actuator) and a sensor ~88 is fitted into the housing
so as to monitor longitudinal movement of rod 82 within the housing 80.
In an alternative arrangement, a sensor denoted 90 may be mounted on a
supporting bracket 92 so as to monitor movement of the rod externally of
20 housing 80.
For example, the sensors may be proximity switches or other
sensors responsive to longitudinal displacement of a rod. Sensors that
respond to markings or fittings on the rod (not shown) can be used.
Preferably, provision is made for adjustments so that the sensor can
25 respond to different extents of actuator rod travel, as determined by
applicable regulations or other safety criteria. If adjustability is required, it
may be desirable to use an external sensor such as sensor 90. Adjustability
may be provided by allowing for adjustment of the sensor position or
adjustment of fittings on the actuator rod.
In a simple alternative example, one or more limit switches
may be used, for example, a stationary limit switch co-operating with
adjustable stops on rod 82.
CA 02216494 1997-10-01
As mentioned previously, the brake monitoring aspect of the
invention described previously may be used in combination with or
separately from the wheel monitoring aspects described previously.
Conversely, the wheel monitoring aspect may be used without monitoring
5 the brakes.
Prererably, however, the system integrates both functions. Fig.
8 is a diagrammatic illustration of such an integrated ~yslem while Fig. 9
shows a corresponding display that may be provided within the driver's
cab of the vehicle.
The box indicated at 94 in Fig. 8 represents a plan view of the
tractor unit 20 of Fig. 1. The front wheel ~semblies 26 are shown as are
two rear wheel assemblies 96 (which may be single wheels). The display
panel shown in Fig. 9 is represented at 98 and an electronic signal
processor at 100. The various lines denoted 102 represent signals that are
15 fed to the processor from the wheel assembly sensors and from the brake
actuators described previously. Processor 100 may also receive signals
representing vehicle speed if n~c~s~ry. An output signal path to panel 98
is indicated at 104. The display panel shown in Fig. 9 includes
appropriately designated indicator lights for each wheel and for each of the
20 brakes of the tractor (in the upper portion of the panel denoted 98a). The
lower portion 98b of the panel includes corresponding indicator lights for a
three axle trailer (not shown).
In a further aspect of the present invention, wheel faults
and/or excessive brake actuator rod travel can be detected through the use
25 of specially mounted proximity sensors. Wheel faults can be detected by
using a proximity sensor to monitor the change in relative position of an
edge of a wheel (e.g. an inner wheel rim) with respect to its normal
operational position. Excessive brake actuator rod travel can be detected
using a specially mounted proximity sensor which determines when a
30 slack adjuster has experienced excessive rotation, as a result of excessive
brake rod travel, by monitoring whether an edge of the slack adjustor has
entered into its sensing distance.
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Wheel faults can be detected through the use of mounted
sensors which detect changes in the position of the wheel from a safe
operational position. The inventor has determined that even slight
changes in the position of the edge of a wheel with respect to the chassis
5 can provide an early warning of wheel bearing and/or axle faults. The
inventor has observed that if a wheel bearing is about to fail (e.g. due to
insufficient lubricant), the associated wheel assembly will begin to "play"
or move from its regular position prior to actual failure, for example, over
a period of roughly 15 minutes to an hour. The inventor has also observed
10 that if one or more of the wheel studs shear, the remaining studs will start
to agitate as a result of the centrifugal force on the unbalanced wheel. This
will cause the bearings to vibrate loose until the wheel breaks free from
the wheel assembly. Again, this phenomena will occur for period of, for
example, 15 minutes to an hour before a full catastrophic failure results.
By monitoring the axial movement of the wheel rim edge
beyond a predetermined amount from its normal operational position, the
present monitoring system can provide timely wheel fault detection to
assist in the pr~venLion of catastrophic wheel failure.
Figs. lOa to 16 illustrate a wheel and brake monitoring ~ysle
20 that can be used to monitor each wheel and associated brake assembly of a
transport truck comprising a tractor unit such as the unit 20 shown in Fig.
1, and an associated trailer (not shown).
Fig. lOa shows a wheel monitoring sensor and associated
mounting bracket in schematic form. The bracket (only a portion of it is
25 shown) is designated 150 and supports and locates a sensor 152 adjacent to
a wheel rim edge 154. Wheel rim are conventionally made out of either
steel or aluminum and reference will be made to both types of rims.
Bracket 150 is preLelably made from an aluminum and steel alloy and is
designed such that one end of bracket 150 can be secured to truck chassis 24
30 while the other end of bracket 150 positions sensor 152 adjacent to wheel
rim edge 154 within the sensing distance of sensor 152.
Sensor 152 is preferably an inductive proximity sensor for
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detecting the presence or absence of a conductive metal target within a
predetermined sensing range such that the movement of a wheel beyond a
pre-determined amount away from a defined operational position can be
detected. An inductive proximity sensor comprises a LC oscillating circuit,
5 a signal evaluator and a switching amplifier. The circuit's coil generates a
high frequency electromagnetic alternating field that is emitted at the
sensing face of the sensor. When a conductive metal target enters the field,
eddy currents are created within the sensor and a switching signal is
produced.
Sensor 152 is preferably a Honeywell SDS 30 millimetre
Cylindrical Proximity Sensor (Part No. SDS-C1-B4HM-A8N normally
open) with a maximum sensing distance of 16 millimetres and a weather
sealed and corrosion-proof jacket for heavy industrial application. It has
been determined that the detection distance for sensor 152 varies with the
15 type and thickness of the wheel rim being monitored. It has further been
determined that sensor 152 detects the presence of a typical aluminum
wheel rim within a sensing distance of 5 millimetres and detects the
presence of a steel wheel rim within a sensing distance of 9.5 millim.otres.
Alternatively, sensor 152 can be any suitable non-contact
20 sensing device which can detect the presence or absence of metallic or
rubber targets which would conventionally be present on a wheel within a
fixed range such that the movement of a wheel beyond a pre-determined
amount away from a defined operational position would be detected. For
example, the sensor could be selected to respond to the tyre rather than the
25 wheel rim.
As shown in Fig. 10b, sensor 152 is secured into bracket 150
(only a portion of it is shown) using sensor mounting rings 153 and 153',
which are moulded out of a material such as nylon. Sensor 152 has a
resilient plastic and metal housing with an outer metal threaded surface
30 which can engage with the inner threaded surfaces of mounting rings 153
and 153'. Sensor 152 is inserted into a hole in bracket 150 such that the
inner threads of ring 153 engage the outer threads of sensor 152 on one
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side of bracket 150 and the inner threads surface of ring 153' engage the
outer threads of sensor 152 on the other side of bracket 150. When the
threaded surfaces of rings 153 and 153' are completely engaged with the
threaded surface of sensor 152, sensor 152 is securely mounted within
bracket 150. This arrangement permits longitudinal adjustment of the
sensor for precise setting of sensing distance.
As described before, sensor 152 is positioned such that rim
edge 154 will be within the appropriate sensing distance while it is in its
normal operational position. As discussed earlier, the sensing distance is 5
10 millimetres for an aluminum rim and 9.5 millimetres for a steel rim.
Referring back to Fig. 10a, while the wheel is within a defined tolerance
from its normal operational position, rim edge 154 will be present within
the sensing distance of sensor 152. Once the wheel rim edge 154 moves
beyond a pre-determined amount away from its normal operational
15 position, rim edge 154 will no longer be within sensing distance of sensor
152. When this occurs, sensor 152 will output a switching signal indicating
that a potential wheel failure has occurred.
While the appropriate tolerance may vary, it has been
determined that a deviation of as little as .25 millimetres (or 10 thousands
20 of an inch) at the rim can be an indication of a potential wheel bearing or
stud failure in the case of transport truck wheel. Accordingly, for an
aluminum wheel rim, sensor 152 is positioned 4.75 millimetres from rim
edge 154 so that wheel rim edge 154 will pass out of monitoring range of
sensor 152 when it moves .25 millimetres or more away from its normal
25 operational position away from sensor 152. Similarly, for a steel wheel
rim, sensor 152 is positioned 9.25 millimetres from rim edge 154 so that
wheel rim edge 154 will pass out of monilo~ g range of sensor 152 when
it moves .25 millimetres or more away from its normal operational
position away from sensor 152.
Correct positioning is achieved using an appropriately
dimensioned metal spacer 151 which can have a thickness of either 4.75
millimetres or 9.25 millimetres depending on whether aluminum or steel
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wheel rims, respectively, are being used. When sensor 152 is so positioned,
movement of wheel rim edge 154 of .25 millimetres or more further away
from sensor 152 will cause sensor 152 to detect movement of wheel riIn
edge 154 out of its sensing distance indicating that a wheel fault has
5 occurred.
As the wheel assembly rotates, sensor 152 will detect the
presence of inner wheel rim edge 154 as long as the wheel remains
properly aligned with respect to its carrier means and consequently, as long
as no wheel faults are present. However, in the event that some form of
10 wheel fault occurs, movement of wheel rim edge 154, beyond the pr~
determined amount of .25 millimetres beyond its normal operating
position away from sensor 152, will be detected by sensor 152.
Since bearing or stud faults will cause both wheels of a dual
wheel assembly to "play", it is possible to monitor a dual wheel assembly
15 by monitoring the inner wheel alone.
Excessive brake rod travel can be detected using a specially
mounted proximity sensor to determine when a slack adjuster has
experienced excessive rotation due to excessive brake rod travel. The
inventor has observed that as the brake linings and brake drum are worn
20 down by frictional abrasion during repeated application of the brakes, the
slack adjuster will rotate further and further as the brakes are applied and
that a proximity sensor can be positioned to detect when the slack adjustor
rotates to a certain position signifying excessive brake rod travel.
Fig. lOc illustrates an embodiment of such a brake rod travel
25 monitoring ~yS~e~m. Truck brakes are applied by introducing pressurized
air through a tube into the brake chamber assembly 155 which in turn
extends a brake actuator rod 82. Brake actuator rod 82 acts on the end of a
slack adjuster 156 to turn a cam rod 158 which is housed within cam tube
160. Turning of cam rod 158 about its longitudinal axis causes the brake
30 linings to fictionally engage the inside surface of a brake drum (not
shown). Air brakes can fail if the brake linings or drum become excessively
worn, or if the brakes are not properly adjusted.
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Slack adjustor 156 is connected to a brake actuator rod 82 by a
clevis 84. When the brake actuator rod 82 moves longitudinally at each
actuation of the brake, slack adjustor 156 will rotate the cam rod 158, which
in turn urges the brake linings into engagement with the brake drum to
5 apply the brakes. In this way, the degree of rotation of slack adjustor 156
will vary in accordance with the distance that brake actuator rod 82 travels.
The brake rod travel monitoring system comprises bracket
150' (only a portion of it is shown) which mounts and locates sensor 152'
within the rotational path of slack adjustor 156. Bracket 150' is preferably
10 constructed from an aluminum and steel alloy and formed such that one
end of bracket 150' is adapted to be secured to truck chassis 24. The other
end of bracket 150' is used to position sensor 152' such that slack adjustor
156 of the brake mechanism will rotate into the sensing distance of sensor
152' when the associated brake actuator rod 82 has travelled beyond a pre-
15 deter~nined limit as a result of brake wear.
Sensor 152' is preferably secured into bracket 150' in the samefashion as described in respect of the wheel fault sensing ~ybtelll, using
sensor mounting rings 153 and 153'. Sensor 152' is preferably a Honeywell
Cylindrical Proximity Sensor (Part No. SDS-C1-B4HM-A8N normally
20 closed) with a max~mum sensing distance of 16 millimetres and a weather
sealed and corrosion-proof jacket for heavy industrial application. It has
been determined that sensor 152 detects the presence of the body of a
typical steel slack adjuster within a sensing distance of 11.1 millimetres.
Sensor 152' is positioned such that slack adjustor 156 comes
25 within 11.1 millimetres, or the sensing distance, of sensor 152' when slack
adjustor 156 has rotated through a distance corresponding to excessive
travel of brake actuator rod 82. It is generally desired to provide the driver
with advance waming that brake actuator rod 82 travel has exceeded 50.8
millimetres (or 2 inches). Accordingly, sensor 152' is positioned such that
30 slack adjustor 156 rotates into sensing distance of sensor 152' when the
brake adjustor rod 82 has travelled 44.45 millimetres (or 1.75 inches).
The wheel fault and brake travel monitoring ~ysLe~ is now
CA 02216494 1997-10-01
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described with respect to a left trailer wheel. Fig. 11a shows the design and
orientation of bracket 150 and sensor 152 assembly used to monitor a
wheel 40 attached to trailer axle 162 and bracket 150' and sensor 152'
assembly used to monitor excessive travel of brake actuator rod 82.
Bracket 150 of the wheel fault monitoring ~y~lem is mounted
on axle housing 52 of trailer axle 162 using a clamp 164. Clamp 164 may
either be square or round to accommodate a square or round trailer axle
162. Sensor 152 is shown secured into bracket 150 using sensor mounting
rings 153 and 153'. Bracket 150 is adjustable within clamp 164 about a pivot
10 point 166 (see Fig. 11b) so that bracket 150 can accommodate different rim
sizes. By suitably rotating bracket 150 about pivot point 166, alternatively
positioned sensor 152" can be placed adjacent to rim edge 154" of a smaller
wheel rim. It is also apparent that in this way, it is possible to mount
bracket 150 and clamp 164 such that sensor 152 is positioned at any angular
15 position about the centre of rotation of the wheel, although it is ~refe~ableto locate sensor 152 at a position on the left wheel conventionally known
as "3 o'clock on the wheel", or 90 degrees clockwise around the axle from
the top of the wheel when looking down the axle to the wheel.
As previously described, sensor 152 should be placed 4.75
20 millimetres from an aluminum rim edge 154 and 9.25 millimetres from a
steel rim edge 154 so that wheel rim edge 154 will pass out of monitoring
range of sensor 152 when it moves .25 millimetres or more away from its
normal operational position and sensor 152.
Now r.2f~ g to Figs. 11a and 11c, the brake rod travel sensor
25 bracket 150' is described. When the brakes are applied, brake chamber
~s~mhly 155 causes brake actuator rod 82 to travel longitudinally and slack
adjuster 156 to rotate as discussed above. Bracket 150' comprises a U-
shaped strap 168 and a sensor arm 170. Sensor arm 170 has at one end a
mounting flange 171. An elongate opening 173 extends longitudinally of
30 the arm. Strap 168 embraces a cam tube 160 which houses the brake cam
rod 158 (Fig. 10c). Strap 168 is placed around cam tube 160 and removably
secures sensor arm 170 onto cam tube 160 using nuts 169 that bear against
CA 02216494 1997-10-01
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flange 171 of sensor arm 170. Sensor 152' may be variably positioned
within opening 173 using sensor mounting rings 153 and 153'.
As discussed above, sensor 152' is positioned such that slack
adjustor 156 of the brake mechanism enters the sensing distance of sensor
5 152', when brake actuator rod 82 has travelled beyond a pre-determined
limit as a result of brake wear. Specifically, sensor 152' is positioned such
that slack adjustor 156 comes within 11.1 millimetres, or the sensing
distance, of sensor 152' when slack adjustor 156 has rotated through a
distance corresponding to excessive travel of brake actuator rod 82. Sensor
10 152' is positioned such that slack adjustor 156 rotates into sensing distance of sensor 152' when the brake adjustor rod 82 has travelled 44.45
millimetres (or 1.75 inches). Correct positioning can be achieved using an
appropriately dimensioned metal spacer 151 with length 11.1 millimetres
as previously described.
The wheel fault monitoring ~y~em is now described with
respect to a left drive wheel. Fig. 12 shows a side plate bracket 150" and
sensor 152 assembly used for monitoring wheels attached to a square drive
axle 174. Sensor 152 is shown located at 3 o'clock on the left drive wheel.
Bracket 150" fits closely to the drive wheel assembly and as a result does
20 not monitor axle faults to the degree that bracket 150' can on the trailer
axle as bracket 150' is mounted further along the body of the axle. It should
be noted that the bracket 150 and sensor 152 assembly for monitoring
wheels on the trailer axle can be also used on a drive axle just as side plate
bracket 150" can be used on a trailer axle. However, it is preferable to use
25 the rod shaped bracket 150 on a trailer axle where axle faults are more
common.
Bracket 150", comprises a U-shaped strap 168' and a sensor
arm 170'. Sensor arm 170' has a mounting flange 171' at one end and an
opening 176 at the other. Strap 168' is placed around drive axle 174 and is
30 used to removably secure sensor support arm 170' onto drive axle 174
using nuts 169' to engage the mounting flange 171 of sensor arm 170'.
Finally, sensor 152 is securely positioned within opening 176
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using sensor mounting rings 153 and 153'. Sensor 152 is positioned
adjacent and within sensing distance from the drive axle 174 wheel rim
edge 154 (not shown). In the event of a wheel fault, wheel rim 40 will be
caused to move beyond a pre-determined amount from its normal
5 operational position, which will in turn, cause sensor 152 to indicate a
change in the proximity of rim edge 154. As previously described, sensor
152 is positioned to detect the movement of rim edge 154 of .25
millimetres or more away from its normal operational position and
sensor 152. Correct positioning is achieved using an appropriately
10 dimensioned metal spacer 151 which can have a length of either 4.75
millimetres or 9.25 millimetres depending on whether aluminum or steel
wheel rims, respectively, are being used.
The brake rod travel monitoring system described in Pigs. 11a
and 11c can be installed on drive axle 174 in the manner described with
15 referellce to those figures, but using a U-shaped strap in place in place of
the curved strap 168 shown.
Figs. 13a, 13b, 13c and 13d show a dual purpose bracket 178
which is used to mount sensors 152 and 152' for monitoring wheel faults
and excessive brake actuator rod travel at a front steering wheel of a
20 vehicle. Since steering wheel rims turn with respect to their supporting
axle 32, it is not possible to use brackets of the form described previously.
Figs. 13a, 13b, 13c and 13d show the wheel fault and brake actuator rod
travel monitoring apparatus as applied to a right front steering wheel. It
should be noted that the wheel fault sensor 152 is positioned at 9 o'clock
25 on the right wheel, whereas it would be positioned at 3 o'clock on the left
wheel.
Bracket 178 is mounted on a kingpin cap 180 of a steerin~ axle
182. The wheel turns on a kingpin (not shown) below cap 180.
Bracket 178 is comprises a base 184 at one end of a first arm
30 186 (see Fig. 13b) and a separate second arm 187 and is preferably made
from an aluminum and steel alloy. Base 184 is attached to a kingpin cap
180 using metal screws inserted through screw holes 188. Alternatively,
CA 02216494 1997-10-01
base 184 may be welded onto kingpin cap 180 or can be designed to replace
kingpin cap 180 entirely. At its end opposite base 184, arm 186 has an
opening 190 through which sensor 152 can be mounted using sensor
mounting rings 153 and 153'. The second arm 187 is attached to arm 186
5 using a spacer bolt 191 and nuts 192. Sensor 152' is then mounted in an
opening 194 in arm 187 using sensor mounting rings 153 and 153'.
Referring now to Fig. 13d, it will be seen that bracket 178 is
designed so that the sensors 152 and 152' are positioned adjacent to the
wheel rim edge 154 and in the travel path of slack adjuster 156,
10 respectively.
As previously described, sensor 152 is positioned to detect the
movement of rim edge 154 of .25 millimetres or more away from its
normal operational position and sensor 152. Correct positioning is
achieved using an appropriately dimensioned metal spacer 151 which can
15 have a length of either 4.75 millimetres or 9.25 millimetres depending on
whether aluminum or steel wheel rims, respectively, are being used.
Further, sensor 152' is positioned such that slack adjustor 156
rotates into sensing distance of sensor 152' when the brake adjustor rod 82
has travelled 44.45 millinletres (or 1.75 inches). Correct positioning can be
20 achieved using an appropriately dimensioned metal spacer with a
thickness of 11.1 millimetres, similar to spacer 151 of Fig. lOa.
As previously described, when the brakes are applied, brake
chamber assembly 155 causes brake actuator rod 82 to travel longitudinally
and slack adjuster 156 to rotate from the positions shown in ghost outline
25 to the positions shown in full outline. Thus, when the brake actuator rod
82 moves longitudinally at each actuation of the brake, slack adjustor 156
will rotate the cam rod 158 and the amount of rotation will vary in
accordance with the distance that brake actuator rod 82 travels. Sensor 152'
is positioned such that when slack adjustor 156 rotates to compensate for
30 brake actuator rod 82 which has excessive travel, slack adjuster 156 will
come within the sensing range of sensor 152'.
While the above embodiments have been described with
CA 02216494 1997-10-01
respect to a conventional tractor-trailer, it should be understood that the
wheel fault and brake actuator rod travel monitoring ~y~lems can be
adapted to monitor wheel faults for any wheeled vehicle, including trucks,
trailers, cube vans and recreational vehicles. Further, bracket 150 may be
5 made of other metals or metal alloys such as iron or from other materials
such as kevlar, nylon or rigid petroleum products. Bracket 150 may be
constructed in a variety of shapes to negotiate around obstacles on truck
chassis 24. Sensor locations, sensing distances and the amount of
movement to which the sensor responds will of course vary according to
10 the type of sensor used and the particular vehicle to which the sy~Lelll of
the invention is applied.
Fig. 14 is a schematic plan view of a tractor unit 20 of the type
shown in Fig. 1 together with a typical trailer. Tractor wheel assemblies 26
are shown as are two trailer wheel assemblies 200 (which may be single
15 wheels). Further, a display unit is shown at 202, a tractor sensor unit is
shown at 204 and a trailer sensor unit is shown at 206. Display unit 202
consists of a display 208 and a microcontroller 210. Display 208 is mounted
within the cab. Microcontroller 210 receives and transmits data to and
from tractor sensor unit 204 and trailer sensor unit 206 and display 208 via
20 cables 212.
Cables 212 also run from monitoring sensors to their
appropriate sensor units. The portion of cables 212 running between the
trailer and the tractor is flexible and cables 212 are long enough to span the
distance between the tractor unit and the trailer unit no matter what
25 positions they assume relative to each other.
Microcontroller 210 includes a microprocessor 214 which
contains a read only memory (ROM) 216 to store instruction sets and a
random access memory (RAM) 218 to store dynamic data. Both memory
units 216 and 218 are controlled and accessed by microcontroller 210 in a
30 conventional manner. Microcontroller 210 continuously monitors the
~y~lem sensors using a well-known RS-485 network and controls LED
arrays, an audible alarm, and the push button inputs of display 208.
CA 02216494 1997-10-01
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The RS-485 network is a commonly used specialized data
interface which allows for the configuration of inexpensive local networks
that can support as many as 32 driver/receiver pairs and can operate in the
presence of electrically noisy environments.
Tractor sensor unit 204 and trailer sensor unit 206 each
contain dip-switches 220 and 222, respectively, which can be set to
determine the number of axles to be monitored, preferably between one
and five axles for each sensor unit. Each sensor is polled at an interval not
greater than lms. If a fault is detected by the appropriate sensor unit,
10 display unit 202 receives and latches a signal representing an alarm for the
appropriate axle wheel into RAM 218 of microcontroller 210. Display 208
will then visually and audibly alert the driver as to the relevant detected
~yslem faults.
Fig. 15 shows display 208, tractor sensor unit 204 and trailer
15 sensor unit 206. Display 208 provides visual and auditory warnings to the
driver indicating when wheel or brake faults have been detected by sensors
152 and 152', respectively, using a 3 by 8 bi-colour LED array 209 and a built-
in speaker (not shown). LED array 209 comprises 24 bi-colour LEDs which
indicate sensor status according to their colour. A green LED indicates that
20 no wheel or brake fault has been detected and a red LED indicates that a
wheel or brake fault has been detected. Each axle is provided with three
indicating LEDs, a left one indicating a left wheel fault, a middle one
indicating a brake fault, and a third right hand side one indicating a right
wheel fault. Display 208 provides eight indicating LED rows. In the case
25 where a tractor/trailer has more than eight axles, a single row of indicating LEDs can be further configured to indicate the status for two axles.
Display also incorporates three push buttons 211 to allow the
driver to interact with the wheel fault and brake travel monitoring ~y~le~
ACK allows the driver to acknowledge alarm conditions, RESET allows
30 the driver to reset the ~y~lem to see if a fault has been cleared and BRIGHT
allows the driver to adjust the brightness levels of the LEDs to adjust for
ambient light conditions.
CA 02216494 1997-10-01
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Referring now to Pigs. 14 and 15, when the monitoring
~yslem is powered-up or when the driver presses the RESET button,
display unit 202 performs a self-test of LED array 209 and the audible alarm.
Display unit 202 then begins polling tractor sensor unit 204 and trailer
5 sensor unit 206 using basic ASCII commands to determine the status of
sensors 152 and 152'. While sensors 152 and 152' do not detect wheel faults
or excessive brake travel, all LEDs relating to monitored axles will be green
and those LEDs not used will be off. When a fault occurs, the
corresponding LED will change from green to a blinking red and an
10 audible alarm will sound and continue until the driver presses the ACK
button. Once the ACK button is depressed, the audible alarm will stop and
the corresponding LED will cease blinking. The RESET button can be used
to reset the system or to check to determine whether a fault has been
cleared.
Specifically, upon initiation microcontroller 210 will send an
ASCII character "R" to tractor sensor unit 204 and trailer sensor unit 206.
Upon receipt of the character "R", tractor sensor unit 204 and trailer sensor
unit 206 initiate a read of their corresponding dip switches 220 and 222,
respectively to determine the number of axles which are required to be
20 monitored and commence monitoring procedure.
Microcontroller 210 then sends an ASCII character "A" to
retrieve status of the axles being monitored within tractor sensor unit 204
and then an ASCII character "B" to retrieve status of axles from the trailer
sensor unit 206. At this point, tractor sensor unit 204 and trailer sensor
25 unit 206 respond with a five digit code, with each digit representing the
particular status of an axle. The following table lists the codes and their
respective meanings.
DIGlT CONDITION
8 Axle not monitored
7 Axle not monitored, no-fault
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6 Right Wheel fault
5 Brake fault
4 Brake fault and Right wheel fault
3 Left Wheel fault
2 Left Wheel fault and Right Wheel fault
Brake fault and Left Wheel fault
0 Brake fault and Right Wheel fault and Left Wheel fault
Upon receiving the two five digit strings, microconllolIer 210
then determines the appropriate display for display 208. As an example,
when the five digit string 77588 is received from tractor sensor unit 204,
5 microcontroller 210 will determine that axle 1 and 2 are fault-free and that
axle 3 has a brake fault. Display 208 will then be provided with the
a~ro~iate data signals which will cause the middle LED in row 3 to turn
from green to a flashing red and the audible alarm to be sounded. In such a
fashion, the driver will be alerted to axle three's brake fault.
Microprocessor 210 also provides display unit 208 with a
signal which causes a separate visual warning when the trailer connection
has been disconnected. When a disconnection occurs, the LED array 209
will flash a distinct "X" pattern across LED array 209. This ensures that the
driver will be notified if the system is not in full operation.
Fig. 16 shows an alternative display 208 comprising a digital
display 224 and push buttons 226, display 208 being connected to the
monitoring ~y~teln using cables 212. Digital display 224 is a conventional
LCD display which allows display 208 to have a reduced width, height, and
thickness since the circuitry required to drive the LCD display is less buLky
than that required to drive the LED display panel described above.
Accordingly, the use of digital display 224 minimizes the space required to
mount display 208 within a truck cab. Digital display 224 provides driver
with a description as to whether a fault has been detected and if so, what
kind of fault has occurred and on which axle.
It should be noted that while this safety monitoring ~y~lelll is
CA 02216494 1997-10-01
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intended to be used to detect wheel faults and excessive brake travel, it is
also possible to use the system as a driving training ~yS~ by alerting a
trainee when they have made an inappropriate turn. When an
inappropriate turn is made which may lead to the jackknifing of the
5 tractor-trailer rig, it has been determined that the vehicle's trailer wheels
will turn so violently that the wheel rim edge 154 of each wheel will leave
the sensing range of wheel sensor 152 which will cause a wheel fault
indication to be given to the driver. The occurrence of such an in-lic~tion
will inform the driver that a dangerously narrow turn has been made.
Fig. 17 shows an exploded view of a brake monitoring ~y~lel~
for use in an automobile or other vehicle that uses a conventional drum
brake assembly. A sensor wire 228 is embedded into brake linings 229 on
shoes 230 and extends through backing plate 232 to a brake sensor unit (not
shown) which may be essentially of the form described previously in the
15 context of a truck brake monitoring system. Sensor wire 228 is positioned
a distance from the surface of brake linings 229 equivalent to the pre-
determined amount of brake lining wear desired to be detected.
When the brake linings 229 wear down by the pre-
determined amount, sensor wire 228 will be exposed along the surface of
20 brake linings 229 and will short to ground through the brake drum (not
shown). Even in the case of uneven brake pad wear, sensor wire 228 will
be exposed over certain areas of the approximately cylindrical surface of
brake linings 229. When sensor wire 228 makes electrical contact with the
brake drum, the brake sensor of the monitoring system will respond and
25 warn the driver that the brake linings should be replaced.
This technique can also be used in association with a disc
brake assembly. Por such an application, a sensor wire simil~r to 228 will
be embedded within at least one of the brake pads. When the pad wear
down to a pre-determined extent, the sensor wire will be exposed and will
30 make electrical contact with the brake disc causing the sensor wire to short. The brake sensor will then warn the driver to replace the pads.
It should of course be appreciated that the preceding
CA 02216494 1997-10-01
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description relates to particular preferred embodiments of the invention
only and that many modifications are possible within the broad scope of
the invention. While examples of sensor configurations and types have
been given, it should be noted in particular that applicant does not intend
5 to be limited to any particular one of these examples and that different
types of sensors and configurations may be used within the broad scope of
the invention. It may even be possible to provide sensor means in the
wheel rim itself, for example, in the form of a computer chip.
