Note: Descriptions are shown in the official language in which they were submitted.
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llEAT SENSOR FOR TRACTOR TRAILER AXLE
This invention relates to a tractor trailer axle
heat sensor adapted to sense the temperature at a
rotating bearing interface disposed between a trailer
axle spindle and a hub-drum assembly which carries tire
rims and tires.
BACKGROUND TO TIIE INVENTION
In lorries; or, large tractor trailers commonly used
in North America, the trailers or semi-trailers
generally use tandem double wheels on either side, at
the rear; sometimes also in the centre.
Over the past short while wi~h the increase of cargo
loads carried by such trailers during transit across
the highway network throughout North America and
particularly in the Province of Ontario, Canada, many
accidents have occurred due to the fact that the drum-
hub assembly flies off the trailer axle spindle due to
fatigue of the studs or nuts holding the hub-drum
Z0 assembly to the axle spindle. Severe damages to other
vehicles occur and in some instances, even death to
motorists who travel behind, in front, or along the
opposite travelling lanes to the truck that is having
these difficulties.
THE INVENTION
It is an object of the invention to provide a
warning device, to the operator of the truck pulling a
trailer, of a temperature increase in the axle spindle-
bearing-hub and drum assembly interface for each wheel
on the trailer. The hub-drum assembly is secured onto
the axle spindle generally by a hub-drum locking
assembly which threadingly engages over a threaded
portion of the spindle end to hold the hub-drum sub-
assembly on the spindle. A pair of annular roller
bearings are provided between the hub-drum assembly and
the spindle to allow free rotation of that assembly
about the spindle during travel. Generally there are
two bearings, an inner larger bearing and an outer
smaller bearing. If either of these bearings are not
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adequately maintained, they tend to dry up and seize
and the temperature of the bearing region is increased,
as is the axle spindle itself and the rotational bore
define~ ~y the hub-drum assembly. When the temperature
at the bearing region increases beyond either the
fatigue temperature of the bearing itself or, of the
spindle axle, the whole hub-drum assembly dislodges and
can fly off and away from the trailer. This phenomenum
has been referred to in recent literature as "run-away
truck wheels". When the lorry is travelling at speeds
of lOOkmh or more, the momentum of such run-away truck
wheels will travel great distances, sometime cross the
meridian of the highway into oncoming traffic. In
other instances, the retaining nuts loosen or melt off
creating run-away truck wheels. Fatigue generally
occurs when the temperature of the bearing interface
rises above 270 F and when it reaches approximately
290 F, metal fatigue can set in to the adjoining
regions of the hub-drum assembly and of the axle
spindle.
It is an object of this invention to monitor the
temperature at the spindle-axle/hub-drum interface and
to provide the driver of the truck pulling the trailer
having such sensored wheels an indication that the
temperature has risen above 270 F so that the rig can
be taken off the road; then servicing take place.
The invention contemplates a method of measuring the
temperature at a bearing interface thermally in contact
with a spindle attached to at least one end of an axle
carrying with drum-hub assembly adapted for rotating
on the bearing, the assembly carrying tire rim and
tires by which the trailer is traversed with the ground
comprising the steps of placing a thermo couple in
thermal contact with the bearing, monitoring the
temperature of the bearing up to a predetermined upper
threshold temperature above which thermal metal fatigue
can ensue and, activating a warning indicator when the
threshold temperature has been reached.
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Additionally, the invention contemplates a
temperature responsive device adapted to monitor a
threshold temperature of a bearing region disposed
between an axle-s~indle and a hub and drum sub-
assembly, the sub-assembly carrying about its outer
perimeter tire rims adapted for engagement of tires
which traverse the ground and upon which a trailer
carried by the axle is traversed comprising an axle-
spindle defining, on its outer perimeter, an annular
bearing region, a hub and drum assembly defining an
inner bore adapted to rotatingly travel within the
annular bearing region, a thermal sensor thermally in
contact with the bearing region and, monitorin~ means
electrically attached to the thermal sensor and
responsive to a threshold temperature including an
indicator means therefor. Preferably, thermal sensor
is located within a bore defined by the axle-spindle
and co-axial with the bearing region, preferably
located between the diametrical plane of the ends of
the bearing region and as described in the preferred
embodiment in the diametrical plane of an outer annular
bearing where there are two annular bearings defining
the bearing region.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of
example and in reference to the accompanying drawings
in which:
Figure 1 is cross-sectional view of a portion
of an axle with spindle according to the invention;
Figure 2 is a block circuit diagramme of the
electronic circuit according to the invention for
measuring the temperature of each spindle axle-bearing
interface.
Referring to Figure 1, (10) is a cross-sectional
view of a modified conventional trailer hollow axle
with spindle that is generally used in North America
for the purposes of carrying hub-drum assemblies
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carrying wheels of a tractor trailer. It consists of a
hollow cylindrical shaft (11) that is the axle to the
trailer (not shown) and extends from one side of the
trailer to the opposite side, only the left-hand
portion of the hollow axle (11) is indicated. It is
welded, at its end, to a hollow, stepped cylindrical or
swaged member, referred to as an axle-spindle (12) by
an annular weld ( 13) . The spindle ( 12) has a first
outer annular step (14) to accommodate an inner larger
diameter cylindrical roller bearing ( 16) and then steps
into a smaller diameter outer annular step ( 15) which
accommodates an outer smaller annular roller bearing
(18). The end of the spindle ( 12) is outwardly
threaded at (17). The outer bearing (18) is held in
position by a double locking nut and washer assembly
(19,20,21) which is constrained by the threaded nuts
(19,21) into locking position over the outer threads
(17) against the outer surface of the outer smaller
bearing (18). Typically, a wheel hub and drum assembly
(30,35) has an outer radial flange ( 35) integral with a
hub drum portion (not referenced) which defines an
inner bore (36). The flange (35) carries rim (30) and
inner and outer tandem wheels ( 31) and ( 32) that are
attached to the peripheral of the flange ( 35) by
conventional means. The inner bore ( 36) is profiled in
a manner to allow the hub drum assembly ( 30,35) to
freely rotate over the bearings (16) and (18) in a
fashion conventionally known. The spindle (15) has an
internal bore (23) and is generally fitted with an
overcovering frost plug ( 24) to isolate contaminates
from entering into the bore ( 23) that may be partially
filled with a lubricant such as grease or oil.
Conventionally, the bore (23) terminates at an inner
end surface ( 26) but according to the invention, a
sealed aperture (27) is drilled therein to provide
access for the passage, in a sealing fashion, of an
electrical conducting wire (51), part of a circuit
(50), see Figure 2, serially connected to a battery (B)
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and an indicator (I) and a thermal sensor (S)
preferably located within the bore (23). The sensor
(S) is in the thermal contact with that bearing region
defined by the diametrical planes of the roller
bearings (16) and (18), thus preferably located co-
incident to the diametrical plane of the outer smaller
bearing (18) and confined within the bore (23).
Preferably, the indicator (I) is placed in the driver
cabin and is visible to the driver of the lorry and the
indicator (I) remains on when the temperature measured
by the sensor (S) is below the upper threshold
temperature range, 270 F to 290 F. Thus, any time the
ignition o~ the lorry is activated the indicator (I)
will light indicating that the sensor (S) is working
properly. When the threshold temperatures is exceeded,
the indicator light (I) extinguishes indicating that
the bearing region (16,18) temperature has exceed
threshold temperature. Although the preferred range is
270 F to 290 F, depending upon the materials used for
the hub and drum assembly (30,35) and their respective
physical properties, the threshold temperature range
can be varied.
