|
| United States Patent
|
6,246,316 |
| Andsager |
June 12, 2001 |
Trailer tire pressure-monitoring system
Abstract
A tire pressure-monitoring system for use with a trailer. The
monitoring system includes an inductive proximity sensor mounted
adjacent each wheel. To activate the sensors, a target is mounted on
each brake drum. Rotational speed data for each wheel is relayed
from each sensor to a programmable logic controller which compares
the rotational speed of a wheel with another wheel. Sensitivity
parameters written into the program contained in the programmable
logic controller compares the input data and, if the data falls
outside the safe parameters, alerts the driver by activating and
audio or visual alarm mounted within the tow vehicle. The
sensitivity of the programmed logic may be optimized to
differentiate changes in a tire diameter due to turning versus an
actual loss in tire pressure.
| Inventors: |
Andsager; Richard L.
(Pahrump, NV) |
| Appl. No.:
|
09/511,558 |
| Filed: |
February 23, 2000 |
| Current U.S.
Class: |
340/444 ;
340/442; 340/443 |
| Current
International Class: |
B60C
23/06 (20060101); B60C 023/02 () |
| Field of
Search: |
340/444,442,443,448 |
References Cited
[Referenced By]
U.S. Patent
Documents
|
|
|
|
4119944 |
October 1978 |
Smith |
|
4777611 |
October 1988 |
Tashire et al. |
|
4807468 |
February 1989 |
Galan |
|
4816802 |
March 1989 |
Doerksen et al. |
|
5541859 |
July 1996 |
Inoue et al. |
|
5557552 |
September 1996 |
Naito et al. |
|
Primary Examiner: Hofsass; Jeffery
Assistant Examiner: Tang; Son
Attorney, Agent or Firm:
Stoneman; Martin L.
Claims
What is claimed is:
1. A low tire pressure alarm system for sensing abnormal rotational
speeds of a plurality of wheels on a trailer adapted for coupling to
a tow vehicle comprising, in combination:
a) a plurality of target means, each said target means being
constructed and arranged for mounting adjacent to each of at least
two of the wheels, for providing a sensing target rotating with each
of the wheels;
b) a plurality of sensing means, each said sensing means being
constructed and arranged for non-rotatable attachment to the
trailer, for sensing rotations of one said target means past one
said sensing means and for generating signals directly representing
rotational speeds;
c) a compilation means, coupled to each said sensing means, for
receiving said signals directly representing rotational speeds from
each said sensing means and for using said signals for computing and
comparing rotational speeds of the wheels; and
d) alarm indicator means, constructed and arranged for attachment to
the tow vehicle and for coupling to said compilation means, for
providing an indication of an abnormal rotational speed of a wheel.
2. The system of claim 1 wherein said compilation means is
constructed and arranged for attachment to the trailer.
3. The system of claim 2 wherein said compilation means comprises a
power means for assisting powering of said sensing means and said
compilation means.
4. The system of claim 3 wherein said compilation means comprises a
programmable logic controller.
5. The system of claim 4 wherein said compilation means further
comprises programming means for programming said programmable logic
controller for counting rotations of each of a plurality of the
trailer wheels within the same fixed time period in such manner as
to provide less sensitivity to rotational-count differences at lower
trailer speeds.
6. The system of claim 5 wherein:
(a) each said target means comprises a protuberance constructed and
arranged to extend from one of the wheels of the trailer;
(b) said alarm indicator means comprises an alarm constructed and
arranged for mounting in the tow vehicle; and
(c) each said sensing means is constructed and arranged for
attachment to an axle of the trailer.
7. The system of claim 6 wherein said target means is structured and
arranged for attachment to a brake drum of one of the wheels of the
trailer.
8. The system of claim 1 wherein each said target means comprises a
protuberance constructed and arranged to extend from one of the
wheels of the trailer.
9. The system of claim 8 wherein said protuberance comprises a
mechanical fastener constructed and arranged for attachment to
normally rotating parts of the wheel.
10. The system of claim 1 wherein each said sensing means comprises
an induction proximity sensor.
11. The system of claim 1 wherein said alarm indicator means
comprises an alarm constructed and arranged for mounting in the tow
vehicle.
12. The system of claim 11 wherein said alarm comprises an audio
alarm structured and arranged for mounting in the tow vehicle.
13. The system of claim 11 wherein said alarm comprises a visual
light structured and arranged for mounting in the tow vehicle.
14. The system of claim 1 wherein said sensing means is constructed
and arranged for attachment to an axle of the trailer.
15. A low tire pressure alarm system for sensing abnormal rotational
speeds of a plurality of wheels on a trailer adapted for coupling to
a tow vehicle comprising, in combination:
a) a trailer having at least two wheels;
b) a plurality of metal targets, each said target being mounted
adjacent to one of said wheels in such manner as to provide a
sensing target rotating with each of said wheels;
c) a plurality of sensors, each said sensor being attached
non-rotatably to said trailer in such manner as to sense rotations
of one said target past one said sensor and to generate signals
directly representing rotational speeds;
d) a computer mounted on said trailer and coupled to each said
sensor, said computer being structured and arranged so as to receive
said signals directly representing rotational speeds from each said
sensor and to use said signals to compare said direct
representations of rotational speeds of said wheels; and
e) a trailer coupler constructed and arranged to assist in system
coupling of said computer to an alarm indicator within a tow vehicle
of a type adapted to attach to said trailer.
16. The system of claim 15 further comprising:
(a) a tow vehicle of a type adapted to attach to said trailer; and
(b) an alarm indicator attached to said tow vehicle, said alarm
indicator being constructed and arranged for coupling to said
computer in such manner as to provide an indication of an abnormal
rotational speed of a said wheel.
17. The system of claim 15 wherein each said sensor is non-rotatably
attached to an axle of said trailer.
18. The system of claim 17 wherein each said sensor is a proximity
sensor.
19. The system of claim 18 wherein each said target comprises a
protuberance extending from and rotatably attached with one said
wheel.
20. The system of claim 19 wherein each said protuberance is
connected to a brake drum of one said wheel.
21. The system of claim 15 further comprising a programming means
for programming said computer for counting rotations of each of a
plurality of said wheels of said trailer within the same fixed time
period in such manner as to provide less sensitivity to
rotational-count differences at lower trailer speeds.
22. A method for sensing abnormal rotational speeds of a plurality
of wheels, each coupled to air-pressure-filled tires having an
optimal air pressure amount, on a trailer towable by a tow vehicle
traveling at a land speed, and alerting a driver of the tow vehicle
of the abnormal condition, comprising the steps of:
a) providing one proximity sensor for each of said wheels;
b) detecting each rotation of each said wheel by means of the
operation of each said proximity sensor;
c) computer-storing data directly associated with said rotations of
each said respective wheel for a selected time period;
d) computer-calculating the difference between the number of
rotations of at least two said wheels in said time period; and
e) producing a warning signal in said tow vehicle when said
differential achieves a selected value.
23. The method of claim 22 wherein said warning signal is indicated
when the value of said difference is at least 3 within a 10-second
period.
24. The method of claim 22 wherein said production of said warning
signal becomes less sensitive at progressively decreasing land
speeds, whereby the difference in rotational speeds of said wheels
on opposed sides of said trailer while said trailer is merely
turning does not produce a said warning signal.
25. A method of installing a low tire pressure alarm system for
sensing abnormal rotational speeds of a plurality of wheels on a
trailer adapted for coupling to a tow vehicle, comprising the steps
of:
a) providing a plurality of metal targets and a trailer having at
least two wheels;
b) preparing each said wheel with first attachment means for
attaching one said target with said wheel in such manner that said
target rotates with said wheel;
c) mounting each said target on one said wheel in such manner as to
provide a sensing target rotating with said wheel;
d) providing a plurality of proximity sensors;
e) preparing an axle area adjacent each said wheel with a second
attachment means for attaching one said proximity sensor;
f) mounting each said proximity sensor non-rotatably to said trailer
in such manner as to sense rotations of one said target past one
said proximity sensor and to generate signals directly representing
rotational speeds of said wheel;
g) providing a computer structured and arranged so as to receive
said signals from each said proximity sensor and to use said signals
to compare said representations of rotational speeds of said wheels;
h) mounting said computer on said trailer and coupling said computer
to each said proximity sensor; and
i) mounting on said trailer a trailer coupler constructed and
arranged to assist in system coupling of said computer to an alarm
indicator within a tow vehicle of a type adapted to attach to said
trailer.
26. The method of claim 25 further comprising the steps of:
(a) providing a tow vehicle of a type adapted to attach to said
trailer;
(b) providing an alarm indicator constructed and arranged for
coupling to said computer in such manner as to provide an indication
of an abnormal rotational speed of a said wheel; and
(c) mounting said alarm indicator within a cab of said tow vehicle.
27. The method of claim 25 wherein each said proximity sensor is
non-rotatably attached to an axle of said trailer.
28. The method of claim 25 wherein each said target comprises a
protuberance extending from and rotatably attached with one said
wheel.
29. The method of claim 28 wherein each said protuberance is
connected to a brake drum of said one wheel.
30. The method of claim 25 wherein said computer does said comparing
essentially by counting differences in number of rotations of each
said wheel.
31. The method of claim 30 further comprising the step of:
(a) using a programming means for programming said computer for
counting rotations of said wheels of said trailer within the same
fixed time period in such manner as to provide less sensitivity to
rotational-count differences at lower trailer speeds.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to providing a trailer tire pressure
monitoring system. More particularly, this invention concerns a
trailer tire pressure monitoring system for warning the driver of a
deflating tire on a trailer prior to tire failure. In addition, this
invention concerns the provision of a tire pressure monitoring
system which is capable of detecting a deflated tire by comparing
the rotational speed of several tires.
2. Description of the Prior Art
Typically, vehicle-coupled trailers are used to transport an
assortment of cargos such as, for example, goods, livestock, and
transient living quarters. Oftentimes, the driver of the towing
vehicle will be unaware of the occurrence of air pressure loss in
one or more of the trailers tires until it is too late and the tire
fails. For single axle trailers comprising only one tire on each
side of the trailer, a failure in a single tire may lead to
catastrophic consequences, such as trailer rollover or jackknifing,
which may not only damage the contents of the trailer but also
produce a traffic hazard to other motorists. Even for those
single-axle trailers having dual wheels per trailer side, or
multi-axle trailers comprising multiple wheels on each side of the
trailer, a single tire failure can still result in damage to the
trailer as well as collateral damage to other motorists caused by
flying tire debris. With these concerns in mind, if a device were
utilized to alert the driver of a possible hazardous tire condition,
preventive measures may be taken in time to minimize damage to not
only the affected tire but also to the remaining trailer components,
the trailer body, the tow vehicle, and the general public sharing
the road.
The current methods of detecting when a potentially abnormal air
pressure condition in a tire may be present typically fall into two
categories: direct air pressure detection and indirect air pressure
detection. Regarding the first category, direct air pressure
detection methods typically involve the use of air pressure
detectors within each individual tire which transmit a sensor signal
to a receiving unit for processing and interpretation. An example of
such a direct air pressure detection system can be found in the U.S.
Pat. No. 5,741,966 issued to Handfield et al. which teaches tire
pressure monitoring systems in which pressure detection units are
disposed within the tire and which sends signals relating to the
tire conditions, over an electromagnetic path, to a central receiver
unit. Although this system may be adequate for its intended uses
despite certain inefficiencies, the fact that signals are sent to
the central receiver unit via an electromagnetic path makes this
system susceptible to erroneous readings when used on a trailer due
to the fact that trailers are often equipped with electric brakes
which also generate magnetic fields.
With reference now to the second category, indirect air pressure
detection methods typically measure the rotational speed of each
tire and compare it with the rotational speed of the remaining
measured tires. The theory motivating indirect pressure measurement
being that upon losing air pressure, a tire's effective outer
diameter decreases, which results in a corresponding increase in the
rotational speed of the wheel in order to "keep up" with the land
speed of the vehicle. Upon detecting a tire rotating at a higher
speed than the remaining tires, the driver is alerted of a possible
abnormal tire condition. Those systems which utilize indirect air
pressure detection methods typically take advantage of existing
hardware which is currently available on passenger vehicles for
detecting the rotational speed of wheels. For example, many
passenger vehicles are currently equipped with 4 wheel ABS
(anti-lock braking system) devices and/or TRC (Traction Control)
devices which utilize tire revolution detection-type devices for
their respective operations. Examples of systems which utilize
existing ABS or TRC hardware can be found in U.S. Pat. Nos.
5,442,331, 5,218,862, and 4,876,528 issued to, respectively,
Kishimoto et al., Hurrell, II et al., and Walker et al. Although
such systems also may be adequate for their respective intended
uses, the fact that trailers typically are not provided with ABS or
TRC hardware makes the aforementioned prior art systems unsuited for
trailer applications.
Thus, the aforementioned systems and associated methods for
monitoring tire pressure for passenger vehicles do not adequately
address nor solve the above concerns with respect to trailers.
OBJECTS OF THE INVENTION
A primary object of the present invention is to fulfill the
above-mentioned need by the provision of a trailer tire pressure
monitoring system. A further primary object of the present invention
is to provide such a system which is efficient, inexpensive, easy to
use, and easy to install. In addition, it is a primary object of the
present invention to provide such a system which can differentiate
between relative changes in tire conditions due to vehicle-turning
versus changes in tire conditions due to actual air pressure loss.
SUMMARY OF THE INVENTION
In accordance with a preferred embodiment of the present invention,
this invention provides a low tire pressure alarm system for sensing
abnormal rotational speeds of a plurality of wheels on a trailer
adapted for coupling to a tow vehicle comprising, in combination: a
plurality of target means, each such target means being constructed
and arranged for mounting adjacent to each of at least two of the
wheels, for providing a sensing target rotating with each of the
wheels; a plurality of sensing means, each such sensing means being
constructed and arranged for non-rotatable attachment to the
trailer, for sensing rotations of one such target means past one
such sensing means and for generating signals representing
rotational speeds; a compilation means, coupled to each such sensing
means, for receiving such signals from each such sensing means and
for using such signals for computing and comparing rotational speeds
of the wheels; and an alarm indicator means, constructed and
arranged for attachment to the tow vehicle and for coupling to such
compilation means, for providing an indication of an abnormal
rotational speed of a wheel.
This invention also provides such system wherein the compilation
means is constructed and arranged for attachment to the trailer. It
also provides such system wherein the compilation means comprises a
power means for assisting powering of the sensing means and the
compilation means. Plus, it provides such system wherein each target
means comprises a protuberance constructed and arranged to extend
from one of the wheels of the trailer; and, also, wherein the
protuberance comprises a mechanical fastener constructed and
arranged for attachment to normally rotating parts of the wheel.
In addition, this invention provides such a low tire pressure alarm
system wherein each such sensing means comprises an induction
proximity sensor; and further, wherein such compilation means
comprises a programmable logic controller. It also provides such
system wherein the compilation means further comprises programming
means for programming the programmable logic controller for counting
rotations of each of a plurality of the trailer wheels within the
same fixed time period in such manner as to provide less sensitivity
to rotational-count differences at lower trailer speeds.
Furthermore, this invention provides such system wherein the alarm
indicator means comprises an alarm constructed and arranged for
mounting in the tow vehicle; and, also, wherein the alarm comprises
an audio alarm structured and arranged for mounting in the tow
vehicle. Still further, it provides such system wherein the alarm
comprises a visual light structured and arranged for mounting in the
tow vehicle.
This invention also provides such system wherein such sensing means
is constructed and arranged for attachment to an axle of the
trailer; and, also, wherein each target means comprises a
protuberance constructed and arranged to extend from one of the
wheels of the trailer, the alarm indicator means comprises an alarm
constructed and arranged for mounting in the tow vehicle, and each
sensing means is constructed and arranged for attachment to an axle
of the trailer. This invention also provides such system wherein
such target means is structured and arranged for attachment to a
brake drum of one of the wheels of the trailer.
In addition, this invention provides, in accordance with a preferred
embodiment thereof, a low tire pressure alarm system for sensing
abnormal rotational speeds of a plurality of wheels on a trailer
adapted for coupling to a tow vehicle comprising, in combination: a
trailer having at least two wheels; a plurality of metal targets,
each such target being mounted adjacent to one of the wheels in such
manner as to provide a sensing target rotating with each of the
wheels; a plurality of sensors, each sensor being attached
non-rotatably to such trailer in such manner as to sense rotations
of one target past one sensor and to generate signals representing
rotational speeds; a computer mounted on such trailer and coupled to
each sensor, such computer being structured and arranged so as to
receive signals from each sensor and to use such signals to compare
representations of rotational speeds of the wheels; and a trailer
coupler constructed and arranged to assist in system coupling of the
computer to an alarm indicator within a tow vehicle of a type
adapted to attach to such trailer.
Also, this invention provides such system further comprising: a tow
vehicle of a type adapted to attach to such trailer; and an alarm
indicator attached to such tow vehicle, such alarm indicator being
constructed and arranged for coupling to the computer in such manner
as to provide an indication of an abnormal rotational speed of a
such wheel. It also provides such system wherein each sensor is
non-rotatably attached to an axle of such trailer; and, further,
wherein each sensor is a proximity sensor. This invention also
provides such a system wherein each target comprises a protuberance
extending from and rotatably attached with one wheel; and also,
wherein each such protuberance is connected to a brake drum of one
wheel. Further still, this invention provides such system further
comprising a programming means for programming the computer for
counting rotations of each of a plurality of wheels of the trailer
within the same fixed time period in such manner as to provide less
sensitivity to rotational-count differences at lower trailer speeds.
Additionally still, this invention provides a method for sensing
abnormal rotational speeds of a plurality of wheels, each coupled to
air-pressure-filled tires having an optimal air pressure amount, on
a trailer towable by a tow vehicle traveling at a land speed, and
alerting a driver of the tow vehicle of the abnormal condition,
comprising the steps of: providing one proximity sensor for each of
the wheels; detecting the rotation of each wheel by means of the
operation of proximity sensors; computer-storing data associated
with such rotations of each respective wheel for a selected time
period; computer-calculating the difference between the number of
rotations of at least two wheels in such time period; and producing
a warning signal in the tow vehicle when the above described
differential achieves a selected value. Further, this invention
provides such method wherein such warning signal is indicated when
the value of such difference is at least 3 within a 10-second
period.
The invention also provides such method wherein the production of
the warning signal becomes less sensitive at progressively
decreasing land speeds, whereby the difference in rotational speeds
of the wheels on opposed sides of the trailer while the trailer is
merely turning does not produce a warning signal.
In addition, this invention also provides a method of installing a
low tire pressure alarm system for sensing abnormal rotational
speeds of a plurality of wheels on a trailer adapted for coupling to
a tow vehicle, comprising the steps of: providing a plurality of
metal targets and a trailer having at least two wheels; preparing
each such wheel with first attachment means for attaching a target
to each wheel in such manner that the target rotates with the wheel;
mounting each target on a wheel in such manner as to provide a
sensing target rotating with the wheel; providing a plurality of
proximity sensors; preparing an axle area adjacent each wheel with a
second attachment means for attaching one proximity sensor; mounting
each proximity sensor non-rotatably to the trailer in such manner as
to sense rotations of one target past one proximity sensor and to
generate signals representing rotational speeds of the wheel;
providing a computer structured and arranged so as to receive
signals from each proximity sensor and to use such signals to
compare representations of rotational speeds of the wheels; mounting
the computer on the trailer and coupling the computer to each
proximity sensor; and mounting on the trailer a trailer coupler
constructed and arranged to assist in system coupling of the
computer to an alarm indicator within a tow vehicle of a type
adapted to attach to a trailer. In addition, this invention provides
such method further comprising the steps of: providing a tow vehicle
of a type adapted to attach to a trailer; providing an alarm
indicator constructed and arranged for coupling to a computer in
such manner as to provide an indication of an abnormal rotational
speed of a wheel; and mounting an alarm indicator within a cab of
such tow vehicle. It also provides such method wherein each
proximity sensor is non-rotatably attached to an axle of such
trailer; as well as wherein each target comprises a protuberance
extending from and rotatably attached with one wheel. It further
provides such method wherein each protuberance is connected to a
brake drum of one wheel, and wherein the computer does such
comparing essentially by counting differences in number of rotations
of each wheel; and, also, further comprising the step of using a
programming means for programming the computer for counting
rotations of such wheels of such trailer within the same fixed time
period in such manner as to provide less sensitivity to
rotational-count differences at lower trailer speeds.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating a preferred embodiment of
the of the trailer tire pressure-monitoring system of the present
invention as installed on a trailer-tow vehicle combination.
FIG. 2 is an elevation view, in partial cross-section, illustrating
an preferred arrangement of the sensors and targets.
FIG. 3 is a flow chart representation which shows a preferred method
of detecting and communicating an abnormal tire condition.
FIG. 4A is a detail view taken from FIG. 1 (area 4), in partial
elevation, illustrating a preferred mounting arrangement for the
sensors and targets.
FIG. 4B is a partial cross-sectional view, taken through section
4B--4B of FIG. 4A, illustrating the separation distance between the
sensor and target.
FIG. 4C is an exploded perspective view, in partial cross-section,
illustrating the components comprising the sensor mounting assembly.
FIG. 4D is a partial elevation view, taken through section 4D--4D of
FIG. 4A, illustrating the sensor mounting assembly as attached to an
axle.
FIG. 5 is a detail view taken from FIG. 1 (area 5), in partial cross
section, illustrating a preferred mounting arrangement for the
module under the tow vehicle's dashboard.
FIG. 6 is a detail view taken from FIG. 1 (area 6), in partial
perspective, illustrating a preferred arrangement for coupling the
programmable circuit wiring to the tow vehicle.
FIG. 7 is a detail view taken from FIG. 1 (area 7), in partial
perspective, illustrating a preferred mounting arrangement for the
programmable logic controller (PLC) within the trailer.
FIG. 8A is a side elevation view showing an alternate preferred
attachment arrangement for attaching the target to the brake drum.
FIG. 8B is a detail view, taken from FIG. 8A, showing the relative
locations of the target and sensor.
FIG. 8C is a perspective view illustrating a clamp for use in
attaching the target to the brake drum in accordance with the
alternate preferred attachment arrangement of FIG. 8A.
FIG. 9 is a perspective view illustrating the use of a Hand Held
Programmer for programming the programmable logic controller.
FIG. 10 is a graph illustrating a typical example "alarm curve" for
a 16-inch wheel with attached 30-inch tire and showing the variable
sensitivity of the monitoring system for various tire conditions and
land speeds.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT AND THE BEST MODE OF
PRACTICE
Referring now to the Figures, shown in perspective (in dotted lines)
in FIG. 1 is a trailer 20 coupled, in well-known ways, to tow
vehicle 21. For example purposes only, trailer 20 is shown
comprising a dual-axle arrangement with the arrangement shown being
embodied by axles 24 having attached left and right wheel
arrangements 25 and 26, respectively. Although a dual-axle
arrangement is shown, it is to be understood that the trailer tire
pressure-monitoring system (herein monitoring system 28) of the
present invention may be effectively used with those trailers 20
comprising axles 24 numbering one or more. As will be appreciated by
those skilled in such art, the monitoring system 28 of the present
invention effectively ascertains when an abnormal tire condition is
present on the trailer 20 and alerts the driver of this condition
while there is time to correct the condition prior to catastrophic
failure.
Though the details of the monitoring system 28 of the present
invention will be discussed more fully as this disclosure
progresses, it is noted for now that the monitoring system 28
comprises at least one left-side sensor 29 and at least one
right-side sensor 30, with each of the sensors 29 and 30 being
preferably mounted to the trailer 20 adjacent, respectively, the
left wheel arrangement 25 comprising a left wheel 35, left tire 37,
and a left brake drum 38 (all as shown best in FIG. 2), and the
right wheel arrangement 26 comprising a right wheel 42, right tire
45, and right brake drum 46 (all as shown best in FIG. 2). Each of
the respective sensors 29 and 30 are coupled, by means of sensor
wiring 49, to a programmable logic controller (herein PLC 50) which
processes signals obtained from the sensors 29 and 30. A PLC (like
PLC 50) is a type of computer. The PLC 50 is preferably mounted in a
convenient and accessible place within trailer 20 and transmits the
processed information, also by means of suitable wiring 53, to
module 54 which may contain, for example, the activation and reset
components for the monitoring system 28 along with an audio or
visual means, or both, to alert the driver of an abnormal tire
condition. In the preferred embodiment described herein, the module
54 is preferably mounted within the tow vehicle 21. The details of
the module 54 and PLC 50 will be discussed more fully hereinafter
with respect to FIGS. 5 and 7, respectively.
Referring now to FIG. 2, shown is a preferred mounting arrangement
for sensors 29 and 30. As shown, the left-side sensor 29 is mounted
on the axle 24 adjacent the left brake drum 38, and the right-side
sensor 30 is mounted on the axle 24 adjacent the right brake drum
46. The method of attachment of the sensors depicted in FIG. 2 and
described herein, embodies herein a second attachment means for
attaching a proximity sensor. Each of the respective sensors 29 and
30 preferably comprise proximity sensors, more preferably 3-wire, 30
mm 9-30 volt DC (direct current) inductive proximity sensors of the
type commercially available from the Honeywell Corporation (992
series) and each having a maximum current consumption of about 15
milliamps. Applicant has discovered that the use of the inductive
proximity sensors 29 and 30 of the type described herein are not
susceptible to the magnetic fields generated by the electric brakes
common to many trailers 20, thereby minimizing erroneous readings
which the aforementioned magnetic fields may cause.
As utilized for the present invention, the sensors 29 and 30 detect
and then relay to the PLC 50 rotational speed information obtained
from the respective left and right wheels 35 and 42. In other words,
sensors 29 and 30 generate signals representing rotational speeds of
the wheels. To provide a "target" which will trigger a response from
the sensors 29 and 30, left and right protuberances or sensor
targets 57 and 58, respectively, are preferably provided. Sensor
targets 57 and 58 each herein embody a protuberance constructed and
arranged to extend from one of the wheels of the trailer. Sensor
targets 57 and 58 also embody herein a target means mounted adjacent
to at least two of the wheels. However, a target or target means
does not necessarily require a protuberance, and may be an already
existing rotating component of a wheel. A target is said to be
rotatably attached to the wheel. In other words, a target (or target
means) is attached to, or is part of, the wheel and rotates with the
wheel. Thus, sensor targets 57 and 58 each herein embody a sensing
target rotating with said wheel. In the preferred embodiment, the
targets 57 and 58 preferably comprise 8-32, 11/4-inch stainless
steel socket head bolts which are preferably attached to the inside
rim 61 of each respective brake drum 38 and 46 (as shown best in
FIG. 4B). Attachment of the targets 57 and 58 to each respective
inside rim 61 is preferably accomplished by tapping a suitably sized
opening in each inside rim 61 for threadably receiving, in
well-known ways, a respective target 57 and 58, as shown. This
method of attaching targets 57 and 58, embodies herein a first
attachment means for attaching a target with a wheel in such manner
that the target rotates with the wheel.
Referring further to FIG. 2 and introducing FIG. 3, the details of a
preferred method of using the monitoring system 28 to ascertain an
abnormal tire condition--and alerting the vehicle driver of such
abnormal condition--will now be discussed. For example purposes
only, the preferred method described herein is shown practiced with
a single axle 24, though it is to be understood that such a showing
is an example only and the preferred disclosed method may be
practiced, with reference to the teachings of this specification, by
those with skill in the art with multiple axles 24 without undue
experimentation. Shown in FIG. 2 is a partially deflated left tire
37 which, if not noticed in time, may lead to catastrophic failure
of the left tire 37, possibly resulting in damage to the trailer 20;
loss of control of the vehicle; injury to the driver, other
motorists, pedestrians, or bicyclists; or any combination of the
above consequences.
In operation, rotation of each respective brake drum 38 and 46
causes a corresponding rotation of the respective targets 57 and 58
past the corresponding sensors 29 and 30. This rotation of the
respective targets 57 and 58 past the corresponding sensors 29 and
30 causes sensors 29 and 30 to activate, thereby placing them in an
"ON" state. Conversely, upon each respective target 57 and 58
exiting the usable sensing distance D (as shown best in FIG. 4B) of
the corresponding sensors 29 and 30, the sensors 29 and 30
deactivate and return to an "OFF" state. As used herein, "usable
sensing distance" is defined as the nominal distance between a
respective target 57 and 58 and corresponding sensor 29 and 30 at
which the sensor 29 and 30 will turn on. As, for example, the left
tire 37 continues to deflate, the left wheel 35 (with coupled left
brake drum 38) will rotate at a faster rate in comparison to the
right wheel 42 (assuming the right tire 45 is properly inflated)
causing a disparity between the number of sensed ON states of
left-side sensor 29 in comparison with the right-side sensor 30.
In the preferred embodiment of the monitoring system 28 described
herein, applicant has discovered that a preferred distance of about
1/8-inch between the sensors 29 and 30 and their respective
corresponding targets 57 and 58 provides adequate results, and is
the best gap known to the applicant. However, it is to be understood
that the useable sensing distance defined herein is dependent on
such factors as the material comprising the target, target size, and
manufacturing tolerances for the sensors, to name a few. However,
one of ordinary skill in such art, upon reviewing the manufacturer's
instructions for the type of sensor used, will be able to ascertain
the optimal sensing distance for a particular application without
undue experimentation.
Referring now to the flow chart shown in FIG. 3, a preferred program
method to detect an abnormal tire condition will now be described.
With reference to block S21, upon activating the PLC 50, the PLC 50
is programmed to initiate a timed sweep beginning at time=0 seconds.
With reference now to blocks S22 and S23, for each aforementioned
timed sweep, the PLC 50 is preferably programmed to take a ten (10)
second sampling count of signals sent to PLC 50 from the left-side
sensor 29, of the rotational cycles of the left wheel 35 (for
example, wheel #1) and then store the data obtained in a separate
register for the left wheel 35. In a like manner, the PLC 50
(concurrently with the gathering of data as above stated for wheel
#1) takes a ten (10) second sampling count of signals sent to the
PLC 50 from the right-side sensor 30, of the rotational cycles of
the right wheel 42 (for example, wheel #2) and stores this data in a
separate data register assigned to the right wheel 42. Next, the PLC
50 compares the resulting revolutions of each respective wheel 35
and 42 for the aforementioned ten (10) second period, as shown in
block S24. The sensors 29 and 30 embody herein a sensing means,
being constructed and arranged for non-rotatable attachment to the
trailer, for sensing rotations of one target means past one sensing
means and for generating signals representing rotational speeds.
Referring to blocks S25 and S26, in the preferred embodiment, if the
revolution differential between the respective wheels 35 and 42 is
greater than or equal to three (3), the PLC 50 is instructed, by the
programmed logic, to activate an alarm (either audio or a visual
alarm light 62, as shown best in FIG. 5) which is part of the module
54 located within tow vehicle 21. As represented in block S27, upon
airing or replacing the left tire 37, the driver toggles a reset
switch 65 (shown best in FIG. 5), also comprising a component of
module 54, which extinguishes the alarm light 62 and resets the
aforementioned timed sweep at time=0 seconds. However, if the
aforementioned revolution differential between the respective wheels
35 and 42 is less than 3, the aforementioned timed sweep is
continuously repeated for the aforementioned ten (10) second
periods. The herein described method embodies herein a method
comprising the steps of: providing one proximity sensor for each of
the wheels; detecting each rotation of each wheel by such proximity
sensors; computer-storing data associated with such rotations of
each such respective wheel for a selected time period;
computer-calculating the differential between the number of
rotations of at least two wheels; and producing a warning signal
when such differential achieves a selected value. The herein
described method herein embodies a method for counting rotations of
each of a plurality of the trailer wheels within the same fixed time
period in such manner as to provide less sensitivity to
rotational-count differences at lower trailer speeds. In other
words, the method described herein embodies such computer comparing
essentially by counting differences in number of rotations of each
said wheel.
As will be appreciated by those skilled in such art, the PLC 50 of
the type described herein may be programmed in a number of ways in
order to perform the aforementioned comparisons of the revolutions
of the wheels 35 and 42. For those trailers 20 comprising multiple
axles 24, the PLC 50 may be programmed to randomly compare the
rotational information contained in a data register for a given
wheel with rotational data register information for any other wheel.
Alternatively, the PLC 50 may be programed to perform an averaging
algorithm of the data registers of all the wheels and compare each
wheel to that average. The details regarding the steps of
programming the PLC 50 will be discussed more fully herein with
respect to FIG. 9. The PLC 50 embodies herein a compilation means,
coupled to such sensing means, for receiving such signals from such
sensing means and for using such signals for computing and comparing
such rotations of the wheels. The PLC 50 also embodies a compilation
means, coupled to each sensing means, for receiving signals from
each sensing means and for using signals for computing and comparing
rotational speeds of the wheels.
Shown in FIGS. 4A-4D is a preferred of attaching each respective
sensor 29 and 30 to axle 24. For example purposes only, attachment
of the left-side sensor 29 will only be discussed herein, though it
is to be understood that the attachment of the right-side sensor 30
is accomplished in a substantially similar manner. The left-side
sensor 29 is preferably attached adjacent to the axle end 66 between
the axle flange 69 and any potential axle support or suspension
structure 70 such as a leaf spring 73, as shown best in FIGS. 2 and
4B. Actual attachment of the left-side sensor 29 to the axle 24 is
accomplished by means of a sensor attachment assembly 74, preferably
comprising a U-clamp 77 with attachable base member 78, both of a
well-known type and readily selectable by those skilled in such art
to match the diameter of the particular axle 24 encountered. The
base member 78, in turn, is provided, in a well-known manner, with a
pair of apertures (not shown) for receiving the threaded leg
portions 79 of U-clamp 77.
Attached to the bottom 81 of base member 78 is a sensor support
bracket 82, preferably comprising about a 3/32-inch thick rigid and
durable material, preferably aluminum, which is used to maintain the
left-side sensor 29 in a fixed, static relationship with respect to
the left brake drum 38. As shown, the sensor support bracket 82 in
the preferred embodiment comprises a planar portion 85 having a
plurality of apertures 86 for receiving the threaded leg portions 79
of U-clamp 77. The sensor support bracket 82 further comprises an
end portion 90 also having an aperture 93 sized to receive the
sensor body 94. Depending on such factors as the size of the axle
24, the end portion 90 may be required to form an angle .phi.
relative to the plane defined by the planar portion 85, as shown in
FIG. 4A. It is preferred that such angle .phi. be provided which
orients the longitudinal axis LA of the left-side sensor 29 in such
a manner that the longitudinal axis LA bisects the arc formed by the
sweep of the left target 57 at approximately a right angle (shown
best in FIG. 4A).
Referring further to FIGS. 4A-4D, the sensor support bracket 82 is
secured adjacent the bottom 81 of the base member 78 by use of two
threaded nuts 98 which, in turn, threadably engage, in well-known
ways, the threaded leg portions 79 of U-clamp 77. Likewise, each of
the sensors 29 and 30 of the type described herein also comprise a
threaded end portion 101 for threadably receiving two adjustment
nuts 102 which are used to secure, for example, the left-side sensor
29 to the sensor support bracket 82. As should be apparent to those
skilled in such art, the adjustment nuts 102 may be used to adjust
the aforementioned usable sensing distance D. Such adjustments are
accomplished in a well-known manner and consist of, for an example:
loosening the one respective adjustment nut 102 whose location,
relative to the body 94, needs to be adjusted, rotating the
adjustment nut 102 until it is at the desired location along the
body 94, sliding the body 94 through aperture 93 until the end
portion 90 abuts the adjusted nut, and then tightening both
adjustment nuts against the end portion 90.
It is to be understood that the dimensions of the sensor support
bracket 82 may be readily selected by those skilled in such art
depending on such factors as the dimensions of the relevant
components involved, such as, for example, the diameters of the left
brake drum 38 and of the axle 24, to name some such relevant
factors. Regardless of the above constraints, the longitudinal
length of the sensor support bracket 82 should be chosen so as to
afford a sufficient distance between the end portion 90 and the base
member 78 in order to accommodate the sensor wiring 49, as shown
best in FIG. 4A.
With reference now to FIG. 5, the details of the module 54 will now
be discussed. The module 54 preferably comprises (1) a plastic or
(2) a sturdy material such as steel, aluminum, or the like (formed,
in well-known metal bending ways, into an L-shaped member, as
shown). The module 54 comprises a front wall portion 105 on which
may be mounted, in well-known ways, such items as the PLC on/off
switch 106, a reset button 65 to reset the PLC 50 program, and an
alarm light 62 (embodying herein an alarm indicator means,
constructed and arranged for attachment to the tow vehicle and for
coupling to the compilation means, for providing an indication of an
abnormal rotational speed of a wheel) to provide the driver with an
indication of an abnormal tire condition. "Abnormal" as used herein
means the number or count of revolution difference between, e.g.,
wheel #1 and wheel #2, as programmed for alarm, e.g., in the
preferred embodiment a count difference of at least 3 (as
hereinbefore discussed in detail). Thus, abnormal rotational speeds
are any speeds sufficiently different than the rotational speeds of
other wheels to indicate a significant difference in tire pressure.
As shown, the module 54 is attached, preferably removably, to the
under portion 110 of the vehicle dashboard 111. The ability of the
module 54 to be removed is preferably accomplished by means of
well-known hook-and-loop type fasteners comprising a loop portion
115 and a hook portion 116. As is further shown in FIG. 5, the loop
portion 115, for example, may be attached, preferably adhesively, to
the top surface 119 of module 54. Likewise, the hook portion 116 may
be attached, preferably adhesively, to the under portion 110 of the
vehicle's dashboard 111. The PLC on/off switch 106, reset button 65,
and alarm light 62 are coupled, in well-known ways, to the tow
vehicle's 21 power supply (not shown) via power lead 120, and to the
PLC 50 via suitable electric wiring 53. A ground wire 121 and a fuse
124, preferably a 2 amp fuse incorporated into the power lead 120,
may also be used.
Shown in perspective, in partial cut-away, in FIG. 6 is a preferred
arrangement for coupling the electrical wiring 53 from the PLC 50 in
the trailer 20 to the electrical wiring 53 connecting to those
components found in the tow vehicle 21, such as the tow vehicle
power supply (not shown) and module 54. To conveniently detach the
electrical wiring 53 from the tow vehicle 21, it is preferred that
the tow vehicle 21 be provided with an electrical umbilical
connector 125, of a well-known type and which is attached in a
well-known manner, to the tow vehicle body 127, as shown. As will be
appreciated by those skilled in such art, the umbilical connector
125 of the type described herein allows for quick
coupling/uncoupling of the PLC 50 and other electrical components
such as, for example, trailer lights and electric trailer brakes
(neither shown) which may require the tow vehicle's power source
(not shown) for their power. As shown, the user may desire to have a
single umbilical connector 125 for coupling the electrical wiring 53
together, and a second umbilical connector 128 for connecting the
electrical wiring 129 for the aforementioned trailer electrical
components such as lights and brakes to the tow vehicle's 21 power
supply. Umbilical connector 125, electrical wiring 53, second
umbilical connector 128, and electrical wiring 129, alone or in any
combination thereof, herein embody a trailer coupler.
Shown in perspective, in partial cut-away, in FIG. 7 is a preferred
mounting arrangement of the PLC 50 within the trailer 20. Prior to
describing the details of the aforementioned preferred mounting
arrangement, the specific details of the PLC 50 should now be
discussed. The PLC 50 of the type disclosed herein preferably
comprises a Series 90(.TM.) 14-Point Micro PLC of the type
commercially available from GE Fanuc Automation North America, Inc.,
Charlottesville, Va. (catalog No. IC693UDR002). The herein described
PLC 50 operates on a 12-24 VDC (volts direct current) input power
and includes an internal central processing unit (CPU) as well as
input/output (I/O) and power supply functions. The internal power
supply (not shown) of PLC 50 comprises a 24 VDC power supply used to
provide power to the various input and output devices comprising the
monitoring system 28 such as, for example, sensors 29 and 30 and
alarm light 62. The internal power supply (along with the tow
vehicle's 21 power supply) embodies herein a power means for
powering such sensing means, such compilation means, and such signal
means. In addition, the PLC 50 comprises eight logic input circuits
and six relay output circuits.
The arrangement of field wiring the PLC 50 to the various I/O
devices comprising the herein described monitoring system 28 will
depend on such factors as number of sensors (e.g., 29 and 30),
additional/fewer components comprising the module 54 than those
aforementioned, etc. However, any such modifications to the field
wiring of the PLC 50 to accommodate, for example, the aforementioned
factors will be apparent to those skilled in such art and will not
be further discussed in detail herein. Rather, applicant
incorporates herein by reference the Series 90(.TM.) Micro PLC
User's Manual associated with the herein described PLC 50, published
by GE Fanuc Automation North America, Inc., Charlottesville, Va.
(Copyright 1994-1997) for further instruction.
Referring further to FIG. 7, the PLC 50 of the type described herein
is a compact unit having dimensions of about 31/5 inches.times.3
inches.times.41/2 inches, which allows the PLC 50 to be placed in a
convenient and out-of-the-way location in either the trailer 20 or
tow vehicle 21. As shown in FIG. 7, the PLC 50 is preferably mounted
to an upright wall 132 found in the trailer 20. The PLC 50 described
herein is provided with a channel 133 sized to receive, in a
well-known manner, a DIN rail 136, preferably a 35 mm DIN rail. The
DIN rail 136, in turn, is attached to the upright wall 132 by use of
fasteners 137, preferably threaded fasteners. Also shown is the PLC
50 coupled to the sensor wiring 49 and the electric wiring 53 for
the various components contained in the module 54, tow vehicle 21
power source, etc. Again, the specific manner in which the PLC 50 is
field wired will be apparent to those skilled in such art without
undue experimentation and will depend on a number of factors such
as, for example, the various I/O devices the user desires, the
number of sensors 29 and 30, etc.
With reference now to FIGS. 8A and 8B, the details of an alternate
preferred arrangement of attaching the targets (e.g., 57 and 58) to
a respective brake drum (e.g., 38 and 46) will be discussed. For
example purposes only, the herein alternate preferred attachment
arrangement will be shown and described as being practiced on the
left brake drum 38 though it is to be understood that the herein
disclosed will be substantially the same for the other similarly
arranged brake drums (e.g., the right brake drum 46). Thus, shown in
FIGS. 8A and 8B is the left brake drum 38 in which a dust cover 140
is provided. For those trailers 20 utilizing dust covers 140 of the
type described herein, the dust cover 140 typically is sized and
arranged to substantially overlay the inside rim 61 (as shown best
in FIG. 8B), thereby substantially preventing the aforementioned
disclosed preferred attachment location of the targets 57 and 58 to
the inside rim 61 (as in, e.g. FIG. 4B).
For these arrangements using a dust cover 140, the alternate
preferred described herein utilizes a band 141, preferably an
adjustable band of a well-known type and preferably made of rigid
and durable material such as, for example, a metal material, nylon,
or the like, and which is preferably attached to the outer periphery
144 of, for example, the shown left brake drum 38. A support 145,
preferably made of a rigid material such as metal, is attached,
preferably integrally, to the band 141. The support 145 is provided
with a threaded aperture 148 sized to threadably receive, for
example, left target 57 as shown. With reference to FIG. 8C, the
band 141 of the type described herein is typically adjusted by use
of a flat head screwdriver (not shown) to rotate screw 149. The
screw 149, in turn, is structured and arranged to engage slots 150
formed on the band body 153. Attachment of the band 141 to the axle
24 may be accomplished, for example, by progressively turning the
screw 149 in such a manner as to cause retraction of the band end
154 from the screw housing 155. The band 141 can then be placed
around, for example, the left brake drum 38 and the band end 154
reinserted into the screw housing 155 and the band 141 tightened
against, for example, the left brake drum 38 by turning the screw
149, in well-known ways.
As shown in the detailed view of FIG. 8B, it is preferred that the
band 141 be placed on, for example, the left brake drum 38 in such
manner as to position the target head 57a approximately along the
longitudinal axis LA (as shown in FIG. 4A) of sensor body 94, yet
with target 57 far enough way from the dust cover 140 so as to avoid
any potentially damaging contact between the support 145 and dust
cover 140. For this alternate preferred attachment arrangement
described herein, attachment of the sensors 29 and 30 to the axle 24
is as substantially illustrated and described previously with
respect to FIGS. 4A-4D and will not be discussed in any greater
detail herein.
Referring now to FIG. 9, shown is the PLC 50 of the type described
herein being programmed by use of a Hand-Held Programmer (herein HHP
159) also commercially available from GE Fanuc Automation North
America, Inc., Charlottesville, Va. (catalog No. IC693PRG300). To
assist in programming, the PLC 50 of the type described herein is
provided with a serial port 162 comprising a 15-pin D-type, female
connector which is structured and arranged to support those
protocols used with the herein described PLC 50 such as the SNP and
SNPX protocols as well as RTU Slave protocols. The HHP 159 and PLC
50 are coupled via a cable 163, also commercially available from GE
Fanuc Automation North America, Inc. (catalog No. IC693CBL303),
which comprises two 15-pin male D connector ends 166 with one such
end 166 adapted to interface, in well-known ways, with the serial
port 162, and the other such end 166 adapted to interface, in
well-known ways, with the HHP 159.
Alternatively, the PLC 50 may be programed using an MS-DOS
compatible personal computer (not shown) having a 386 or higher
microprocessor and at least 2 MB memory. It is noted that
Logicmaster(.TM.) 90-30/20 Micro software, also available from the
GE Fanuc Automation North America, Inc., will be required in order
to program the PLC 50 using a personal computer. The specific
details regarding the various steps of programming the PLC 50 using
either the HHP 159 or a personal computer should be apparent to
those skilled in such art and will not be elaborated on herein.
Rather, applicant again incorporates herein by reference the Series
90(.TM.) Micro PLC User's Manual associated with the herein
described PLC 50 for the specific programming s. The HHP 159 and the
personal computer described above each herein embody a programming
means for programming the PLC (computer).
FIG. 10 illustrates a representative "alarm curve" chart generated
for a trailer 20 having 16-inch diameter wheels 35 and 42 with
30-inch diameter tires 37 and 45. As shown, the left side of the
chart represents the effective diameter of the tire (with 30 inches
being the baseline tire diameter when tire's air pressure is at the
optimal, properly inflated level). The right side of the chart
represents the amount the tire has gone flat (in inches). For
example, a flat of 1.5 inches represents a decrease in tire diameter
of 3 inches yielding an effective tire diameter of 27 inches which
would cause the effective wheel to rotate at a faster rate in
comparison to the non-affected wheels (e.g., the rotational speed of
the wheels is directly related to the air pressure within the
tires). As is further shown, the bottom portion of the curve
represents the land speed of the trailer 20. All points falling upon
the generated curve 169 represents that land speed of the trailer
20, relative to the effective tire diameter, which will signal the
alarm light 62 that a potentially dangerous tire condition exists
(for the herein preferred alarm setting of at least three counts
difference in a ten-second interval, previously discussed). All
points falling below curve 169 will not trigger an alarm response;
and all points falling above curve 169, representing more of a
"flat", will trigger such alarm. As used herein, "land speed" refers
to the speed at which the trailer 20 is moving along the ground when
towed by the tow vehicle 21.
As will be appreciated by those skilled in such art, the programed
asymptotical relationship (e.g., curve 169) between the effective
tire diameter and the land speed yields a reduced sensitivity of the
monitoring system 28 at lower land speeds, thereby allowing the
monitoring system 28 to differentiate between those changes in tire
diameters due to turning versus similar changes resulting from an
actual loss in tire pressure (e.g., embodying herein such system
wherein at progressively decreasing land speeds, such warning light
is produced at air pressure amounts decreasing from such optimal
level). Likewise, the monitoring system's higher sensitivity at
higher speeds will likewise be appreciated by those skilled in such
art due to the fact that tire failure at higher speeds results in an
increased probability of more severe damage and/or injury (e.g.,
embodying herein such system wherein at progressively increased land
speeds, such warning signal is produced at air pressure amounts
approaching such optimal level). It should be understood that the
"alarm curve" disclosed herein is an example of one possible
generated curve for a particular wheel/tire diameter, and that
programming the desired sensitivity parameters into the PLC 50
should be apparent to those skilled in such art without undue
experimentation.
Although applicant has described applicant's preferred embodiment of
this invention, it will be understood that the broadest scope of
this invention includes such modifications as diverse shapes, sizes,
and materials. Such scope is limited only by the claims as read in
connection with the above specification. Further, many other
advantages of applicant's invention will be apparent to those
skilled in the art from the above descriptions and the below claims.
* * * * *
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