Note: Descriptions are shown in the official language in which they were submitted.
021 99 452
The present invention relates to the trucking
industry in general, and in particular to a system for
detecting and signalling a possible failure of a rotating
wheel on a truck or a trailer.
R~R~PCUND OF THB INVENTION
There have been numerous incidents recently of wheels
or wheel sets catastrophically separating from a truck or a
trailer travelling at speed and then moving in a direction
away from the vehicle. In some cases the wheel sets, which
can weigh several hundred pounds and may be travelling at
more than 100 Kph, have struck vehicles travelling in the
immediate vicinity, causing severe damage and even death.
The trucking industry is being held accountable for these
tragic incidents and the maintenance practices of the
industry as a whole has come under close scrutiny. In some
instances wheel failure has been the result of improperly
tightened wheel bolts which have fractured, allowing the
wheel set to separate from its support. In other cases, the
vehicle has been consistently overloaded so as to place undue
stress and strain on the axle with the result that there has
been a structural failure at the end of the axle. Wheel
failures that occur on major arteries and result in tragic
accidents receive considerable media coverage and prompt much
outrage. The number of such reported incidents appears to be
rising, however, and there now appears to be a need for an
ineYr~n~ive system which can detect wheel problems and
communicate the unacceptable condition to the vehicle driver
so that he can take immediate action that will avoid the
catastrophic separation of wheel from vehicle.
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8UNMARY OF THE INVENTION
The present invention provides two relatively simple
and inexpensive systems that can be attached to new trucks or
trailers and which also can be retrofitted to existing
vehicles. Each system includes a plurality of magnets that
positioned about the inside of a wheel rim, with equiangular
spacing therebetween. The magnets are located close to the
outer edge of the rim on the side facing inwardly of the
vehicle and can be attached thereto in the same manner that a
wheel weight, used for balancing a wheel, might be attached.
Preferably four magnets are provided, spaced apart by 90~,
although more or fewer magnets could be used. If the vehicle
is provided with wheel sets made up of a pair of wheels, i.e.
dual wheels, then the magnets are located on the innermost
wheel of the wheel set.
In the case of a set of driven wheels the drive axle
therefor will be contained within a non-rotating axle tube or
support. In the case of non-driven wheels there will be a
non-rotating support carrying a wheel mounting assembly and
hub at the end thereof. For the present invention at least
one sensor is mounted to the non-rotating support for the
wheel, the sensor being positioned at the same distance from
the wheel axis as the magnet~ and also being positioned at a
predetermined distance or spacing from the plane containing
the magnet faces. The sensor is preferably in the form of an
induction coil such as might be used in the ignition system
of a two-stroke engine.
When subjected to a moving magnetic field, a signal
in the form of a train of electrical pulses is generated in
the coil. If the magnet members are rotating in a magnet
021 99 452
plane outside a predetermined acceptable distance from the
sensor the magnetic field generated thereby will not be
strong enough to create a signal at the sensor. If the magnet
members come close to the sensor, within the predetermined
acceptable distance, the magnetic field will generate a
signal at the sensor.
In its simplest form the present invention includes a
DC transformer connected to the sensor. When a signal from
the sensor, measurable in minivolts is passed to the
transformer it is stepped up considerably thereby so that the
stepped up signal may be used to activate an indicator in the
cab of the vehicle to which the invention is attached. In
another embodiment, if the predetermined distance is such
that the sensor will always generate a signal, the strength
of which is dependent on the spacing of the magnet plane from
the sensor, a discriminator connected to the sensor analyses
the signal to determine if it exceeds a threshold value and
if it does, the discriminator will activate an indicator to
signal the vehicle operator that an unsafe condition has been
detected. With each embodiment the signal to the operator
will preferably be in the form of a flashing light or a
beeping horn, in response to which the operator should slow
down and bring his vehicle to a halt so as to investigate the
situation which gave rise to the warning signal. The
indicator could also be tied into a computer programmed to
reduce the fuel supply to the vehicle's engine or to gently
apply the brakes, so as to start to slow the vehicle down,
should the operator fail to heed the warning signal after a
set period of time. The indicator, in addition to providing
a warning signal, would preferably include a chart or other
means to identify the wheel on the truck or trailer which is
generating the fault signal.
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The present invention is based on the premise that a
moving magnet can generate a signal through induction in a
suitable sensor. If the magnet faces are arranged in a plane
that is normal to the wheel axis, which axis coincides with
the axis of the axle, then any departure of the magnet plane
from normal relative to the axle axis will increase or
decrease the distance between the magnet plane and the sensor
as the wheel wobbles and the magnets pass the sensor. Wheel
wobble could be the result of loose wheel lug nuts, broken or
cracked lugs, a damaged wheel hub, or a bent axle caused by
overloading or impact. For any given wheel and axle
combination and vehicle load rating it should be possible to
determine an optimum spacing between the magnet plane and the
sensor and also to determine maximum acceptable and expected
wheel movement relative to the sensor. The maximum expected
and acceptable wheel movement will determine the maximum
distance or spacing of the magnet plane relative to the
sensor. As long as the rotating wheel maintains the magnet
plane beyond the maximum spacing the sensor will not generate
a train of pulses strong enough to generate a failure signal.
However, should for example one of the wheel lugs crack so
that the movement of the wheel exceeds the expected range
then the magnet plane will intrude into the acceptable
spacing, the sensor will generate the necessary train of
pulses threshold, and a failure signal will be transmitted to
the indicator adjacent the operator so that he is warned of
the possible failure of the wheel. He can then stop his
vehicle, inspect the problem wheel, and take appropriate
remedial action.
Generally speaking, the present invention in its
first embodiment may be considered as providing a system for
detecting and signalling a possible failure of a rotating
0 2 1 9 9 4 5 ~
wheel on a vehicle, which wheel includes a rim having a
central axis and a tire mounted to the rim and is affixed to
rotatable axle means carried by suitable non-rotating support
means, the system comprising: a plurality of magnetic
members equiangularly spaced apart on the wheel rim at a
uniform distance from the axis, defining a magnet plane
normal to the axis, and facing inwardly of the vehicle; at
least one sensor member mounted to the support means and
positioned relative thereto so as to be spaced from the plane
by a predetermined distance representing a safe operating
condition for the wheel, rotation of the wheel and the
magnets creating a rotating magnetic field which induces a
signal in the form of a train of electrical pulses in the
sensor member if the magnet plane is within the predetermined
distance; transformer means connected to the at least one
sensor member for increasing the strength of the signal; and
indicator means connected to the transformer means; whereby
should the sensor means generate a signal, the transformer
means will activate the indicator means to warn the vehicle
operator of a possible wheel failure.
In its second embodiment the present invention may be
considered as providing a system for detecting and signalling
a possible failure of a rotating wheel on a vehicle, which
wheel includes a rim having a central axis and a tire mounted
to the rim and is affixed to rotatable axle means carried by
suitable non-rotating support means, the system comprising:
a plurality of magnetic members equiangularly spaced apart on
the wheel rim at a uniform distance from the axis, defining a
magnet plane normal to the axis, and facing inwardly of the
vehicle, rotation of the magnet members with the wheel
creating a rotating magnetic field; at least one sensor
member mounted to the support means and positioned relative
0 2 1 9 9 4 5 2
thereto so as to be spaced from the plane by a predetermined
distance representing a safe operating condition for the
wheel, the rotating magnetic field inducing a signal in the
form of a train of electrical pulses in the sensor member,
the strength of the signal being dependent on the spacing of
the magnet members from the at least one sensor member;
discriminator means connected to the at least one sensor
member for analysing the signal; and indicator means
connected to the discriminator means; whereby should the
discriminator means detect a signal of a strength beyond a
threshold representing a safe operating condition, the
discriminator means will activate the indicator means to
warn the vehicle operator of a possible wheel failure.
BRIEF DE8CRIPTION OF THE DRAWINGD
Figure 1 shows schematically the system of the first
embodiment of the present invention.
Figure 2 shows a wheel rim face with a plurality of
magnets mounted thereto.
Figure 3 is an enlarged view of a mounting
arrangement for a sensor.
Figure 4 shows schematically the system of the second
embodiment of the invention.
n~A-pTpTIoN OF THE PREFERRED ENBODI~ENT
Figure 1 of the drawings illustrates schematically
the system 10 of the present invention. The system is
applicable to any type of wheeled vehicle but it has
particular relevance to transport vehicles such as trucks and
trailers. It will work on the driven wheels of a truck or on
the non-driven wheels of a truck or a trailer. The system 10
021 99 452
includes a 12 volt power supply 12, such as a vehicle
battery, which is connected to a step up transformer 1~. The
transformer 1~ is capable of transforming a weak input
signal, in millivolts, to a 12 volt, or so, signal which can
be utilized in the vehicle's electrical system. The signal
received by the transformer 1~ is provided by a sensor 16,
the sensor being fixedly mounted to a bracket 18 and the
bracket in turn being mounted to a non-rotating portion 20 of
the vehicle's suspension system. If the system of the
invention is being used with a driven wheel or wheel set of
the vehicle the bracket 18 is preferably connected to the
non-rotating tube or support that carries a rotating axle
therein. If the system is being used with a non-driven wheel
or wheel set then the bracket 18 is attached to the non-
rotating support member that carries the wheel hub or othermounting means at the outer end thereof.
The bracket 18 is attached to the non-rotating
support member adjacent the outer end thereof so that the
sensor 16 can be positioned close to a plane P defined
adjacent the inner edge or face of a wheel rim 22, the rim 22
mounting a tire 24 thereon. The rim 22 is provided with a
plurality of equiangularly spaced permanent magnets 26 facing
inwardly of the vehicle, the inwardly directed magnet faces
28 defining the plane P, which plane is normal to the axis A
of the axle and the wheel rim 22. As the wheel rim rotates
at speed the moving magnets will create a moving magnetic
field, the strength of which is dependent on the strength of
the magnets, the number of magnets, and the speed of wheel
rotation. Preferably, four magnets 26 are provided, at 90~
intervals around the edge of the wheel rim, although fewer or
more could be used. The magnets may be mounted to the wheel
rim 22 by an adhesive or they could be attached in the same
021 99 452
manner as the weights used when balancing a wheel, that is,
by way of small tangs which can be hammered between the
sidewall of the tire 2~ and the adjacent surface of the
rim 22.
The transformer 1~ is grounded as at 30 and it is
also connected to an indicator device 32 that is positioned
within the cab of the vehicle, close to the vehicle
operator's position and preferably within his field of
vision. The indicator can be provided with audible and/or
visual warning means to catch the attention of the operator
whenever the indicator is activated. The indicator 32
preferably is sectioned to include a plurality of zones 34,
each of which represents a particular wheel or wheel set of
the vehicle.
The present invention operates on the principles of
electrical induction, such that the sensor 16, being
subjected to a rotating magnetic field generated by the
rotating wheel rim, will be induced to generate a signal in
the form of a train of electrical pulses. The strength of
that signal will depend on the speed of the rotating wheel
and the proximity of the magnet plane P to the sensor. If
the magnet plane P lies outside a predetermined acceptable
distance D the magnetic field will not be capable of
generating a detectable signal at the sensor 16. If the
magnet plane P becomes tilted so as to bring the magnets
closer to the sensor in the vicinity thereof the magnetic
field will then induce a detectable train of electrical
pulses in the sensor.
For any vehicle and wheel combination it will be
possible to calculate an acceptable distance D that
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represents the maximum allowable inwards tilt of the magnet
plane P near the sensor. Some tilt of the plane can be
expected under normal operating conditions, due to impact of
the wheel with obstructions such as potholes or debris, or
minor permanent deflection or hen~ing of the axle or its non-
rotating support. If the allowable predetermined tolerance
for tilt of the magnet plane is exceeded, it is likely that
there is a problem with the wheel. Such a problem could be a
bent axle or axle support resulting from constant overloading
of the vehicle or a structurally damaging impact, or failure
of one or more of the wheel retaining lugs. Should such a
situation develop on a vehicle equipped with the present
invention, the magnet plane P will tilt inwards towards the
sensor 16 and the weak induced train of electrical pulses
will be stepped up by the transformer 1~ so that vehicle
electrical power flows to the indicator 32 and sets off a
warning signal that tells the operator that a failure
condition is imminent. As previously suggested, the warning
signal may be an audible one, such as a horn or a siren
sound, or it may be a visual one such as a flashing light.
Simultaneously with this primary warning signal the zone 3
on the indicator 32 that corresponds to the failing wheel
will light up so that the operator can immediately tell which
wheel is at fault.
In addition to activating the indicator 32 the
transformer could also be connected to the engine management
computer of the vehicle to signal that computer to reduce the
fuel flow to the engine so as to cause the vehicle to lose
speed. This option would only be exercised should the driver
fail to take appropriate action, as by stopping the vehicle
to investigate the problem giving rise to the failure warning
signal. Arbitrarily slowing the vehicle down is a drastic
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step and one which should only be activated after the driver
has been given ample opportunity to stop the vehicle on his
own volition. Certainly, a reduction in fuel flow would have
to be gradual in order to avoid a dangerous condition that
could easily affect following traffic.
As an alternative, the transformer could be connected
to the vehicle braking system and programmed to gently apply
the vehicle brakes in the event that the driver does not heed
the failure warning signal after a predetermined period of
time. Again, any non-operator controlled application of the
brakes would have to be very gradual in order to avoid sudden
braking manoeuvres that could affect following traffic. It
is hoped and expected that if fuel flow control or braking
control were exercised by the discriminator the operator
would sense these conditions, realise that some control is
being taken away from him, and take his own action to slow
the vehicle and bring it to a halt for inspection of the
problem wheel.
The magnets and the sensor will be located in areas
of the vehicle that are subjected to water, slush, snow, ice
and dirt. However, it is expected that centrifugal force
effects due to rotation of the wheel will tend to keep the
magnets clean. Should debris or other material, including
ferromagnetic material, accumulate on the magnets, it is
expected that the close proximity of the magnets to the
sensor and its mounting bracket will permit the bracket or
the sensor housing to skim such debris or material from the
magnets. Similarly, any buildup of debris on the sensor
should be removed by the rotating magnets close thereto.
Also, as seen in Figure 3, the sensor 16 should be recessed
slightly within a surrounding, non-magnetic housing 36
02199452
carried by the bracket 18 so as to reduce the risk of damage
or contamination.
If the present invention is used with a wheel set
that includes a pair of wheels affixed together, i.e. dual
wheels, the magnets would be attached to the innermost wheel
of the pair.
Because the present invention requires that the
distance between the magnet plane P and the sensor 16 be set
for the particular vehicle to which the invention is applied,
that distance should also be available to roadside vehicle
inspectors at vehicle inspection stations, presumably as part
of the vehicle documentation. An inspector, knowing that
distance, and equipped with a suitable gauge can slip the
gauge between the sensor and a magnet positioned opposite the
sensor. If the gauge slips easily between the sensor and the
magnet it is likely that there are no imminent problems
associated with the wheel being inspected. If the gauge does
not slip between the sensor and the magnet this is an
indication that there is a problem with the wheel and that
further investigation is necessary before the driver is
permitted to take his rig out on the road again. Of course,
all vehicle operators driving vehicles equipped with the
present invention would also be provided with the necessary
gauges so that they can check the wheel condition each time
that they perform their own inspection of the vehicle.
The second embodiment of the invention is illustrated
schematically in Figure 4, wherein it is seen that the
transformer 1~ of the first embodiment is replaced by a
discriminator 38. The discriminator is preferably a small
micro-computer which can analyse an incoming electrical
0 2 1 99 4 52
signal, in the form of a train of electrical pulses, and
determine whether the strength of the signal exceeds a
predetermined threshold value. The signal received by the
discriminator 38 is provided by the sensor 16, the sensor
being fixedly mounted as in the first embodiment.
The discriminator 38 is grounded as at ~o and it is
also connected to an indicator device 32 that is positioned
within the cab of the vehicle, close to the vehicle
operator's position and preferably within his field of
vision. The indicator is the same as is used with the first
embodiment .
With this embodiment, the sensor 16, being subjected
to a rotating magnetic field generated by the magnets on the
rotating wheel rim, will always be induced to generate a
signal in the form of a train of electrical pulses. The
strength of that signal will depend on the speed of the
rotating wheel and the proximity of the magnet plane P to the
sensor. The discriminator can be programmed to take into
consideration the component of the signal attributable to
wheel speed so that it can therefore determine whether any
increase in signal strength is attributable to the magnet
plane P being tilted so as to bring the magnets closer to the
sensor in the vicinity thereof.
For any vehicle and wheel combination it will be
possible to calculate a threshold signal strength that
represent the maximum allowable inwards tilt of the magnet
plane P near the sensor. If the allowable predetermined
tolerance for tilt of the magnet plane is exceeded, it is
likely that there is a problem with the wheel. Should such a
situation develop on a vehicle equipped with this embodiment
0 2 1 99 4 52
of the present invention, the magnet plane P will tilt
inwards towards the sensor lC and the induced train of
electrical pulses will be of such a strength to cross the
predetermined threshold established in the discriminator 38.
When that occurs the discriminator will close a relay therein
allowing vehicle electrical power to flow to the indicator 32
and set off a warning signal that tells the operator that a
failure condition is imminent. As previously suggested, the
warning signal may be an audible one, such as a horn or a
siren sound, or it may be a visual one such as a flashing
light. Simultaneously with this primary warning signal the
zone 3~ on the indicator 32 that corresponds to the failing
wheel will light up so that the operator can immediately tell
which wheel is at fault.
In addition to activating the indicator 32 the
discriminator 38 could also be connected to the engine
management computer of the vehicle and programmed to signal
that computer to reduce the fuel flow to the engine so as to
cause the vehicle to lose speed. As an alternative, the
discriminator could be connected to the vehicle braking
system and programmed to gently apply the vehicle brakes in
the event that the driver does not heed the failure warning
signal after a predetermined period of time.
The present invention provides inexpensive systems
for ensuring that heavy vehicles on our roads are safer than
they are now. Use of either warning system of this invention
should reduce the number of catastrophic wheel failures and
the dangerous effects of runaway wheels travelling at highway
speeds. While the preferred forms of the invention have been
described herein it is understood that persons skilled in the
art would be able to modify the invention without departing
021 99 452
from the spirit thereof and accordingly the protection to be
afforded the invention is to be determined from the claims
appended hereto.
