FIELD OF THE INVENTION The present invention relates to an air brake monitoring apparatus for use on an air braking system of a vehicle, and more particularly to an electronic air brake monitoring apparatus having wear sensors connected to a indicator in the vehicle.

BACKGROUND OF THE INVENTION Air actuated braking Systems used on large vehicles, such as trucks, buses, trains, and the like, include a separate and independent brake mechanism for each wheel, which brake mechanism is actuated by means of an air cylinder housing actuation mechanism that operates a brake clevis rod over a few centimeters of linear travel, from a rest position corresponding to the non-application of the vehicle's brakes to an actuated position corresponding to the application of the vehicle's brakes. As the vehicle's brakes wear, or possibly in the event of a fault with the brakes, the travel of the brake clevis rod increases until it travels beyond a safe range of operation, whereat sufficient force for fully applying the vehicle's brakes cannot be provided.

It is known in the prior art to mount a gauge defining two or more safe operating limit positions on the air cylinder housing by means of a suitable bracket and to fix a co-operating pointer on the brake slack adjuster pin for linear movement therewith, such that the pointer moves along the gauge between said operating positions. Thus, the gauge and indicator together provide a visual indication of the extent of travel of the brake clevis rod when the brake mechanism is actuated, thereby indicating whether the vehicle's brakes are within a safe range of operation, or not. A significant fault with this system is that an operator must visually inspect the indicator at each wheel to

determine the status of each brake, which is very inconvenient, time consuming, and potentially dangerous, and is therefore often not done.

U. S. Patent No. 5,253,735 issued October 19,1993, to Larson et al. teaches an Apparatus to Sense and Annunciate Truck Brake Condition, wherein the sensing of the travel of each brake mechanism is performed automatically. An annular sensor disk is mounted in fixed relation on the cam shaft of each brake mechanism and includes two Hall effect switches electrically connected by wires to an annunciator in the truck's cab. A cam shaft measuring disk carrying a magnet is mounted on the end of the cam shaft for rotation therewith such that the magnet has radial position similar to that of the two Hall effect switches. In use, operation of the brake pedal actuates each brake mechanism, thus causing the clevis to rotate the cam shaft. Accordingly, the magnet moves with respect to the two Hall effect switches, which movement is sensed by the two Hall effect switches and is indicated by the annunciator.

It can be seen that in the Larson et al. sensing system, the sensors are each separately mounted into the wheel hub. Such separate mounting of the sensors has a number of serious drawbacks associated with it. The most serious drawback is that the magnet and sensors are not independent of the wheel hub, but instead are an integral part of the wheel hub. Accordingly, a specific size of sensor must be used. Further, this sensing system cannot be installed on existing vehicle brake mechanisms, which is highly undesirable, and it is difficult to perform maintenance on integral type systems such as this.

Also, each sensor must be individually installed, or separately removed, if necessary. There is no provision for installing or removing the sensors as a modular sensor unit. Moreover, a specifically designed or adapted hub must be used, which would be prohibitively expensive when installing such a system on a multi-axle transport trailer.

Further, with such integral installation, it is very difficult to provide a suitable housing around the sensors for inducing a stronger magnetic field

around the sensors, thereby enhancing the sensitivity of the sensors to the magnet. Also, it is difficult to seal the sensors from the elements, which is also undesirable since the wheel hubs are exposed, under normal operating conditions, to a significant amount of water, dirt, salt, and so on.

Another disadvantage with the Larson et al. sensing system is that there is no supplementary indicator that is viewable by an operator to permit in situ visual verification of the position of the brake clevis rod.

Additionally, the sensing system disclosed in Larson et aL measures two positions only, which has been found to be insufficient for providing early warning of brake wear.

It is an object of the present invention to provide an air brake monitoring apparatus that indicates the travel of the brake clevis rod upon actuation of the brake mechanism.

It is an object of the present invention to provide an air brake monitoring apparatus that indicates whether a vehicle's brakes are within a safe range of operation, or not.

It is another object of the present invention to provide an air brake monitoring apparatus that is independent of the wheel hub.

It is yet another object of the present invention to provide an air brake monitoring apparatus wherein various sizes of sensors can be used.

It is a further object of the present invention to provide an air brake monitoring apparatus that can be installed on existing air brake systems.

It is yet a further object of the present invention to provide an air brake monitoring apparatus that is readily suited to perform maintenance thereon.

It is yet a further object of the present invention to provide an air brake monitoring apparatus wherein the sensors are installed modularly in a sensor unit for each brake.

It is yet a further object of the present invention to provide an air brake monitoring apparatus that is significantly less expensive to install onto a vehicle than are known prior art systems.

It is still a further object of the present invention to provide an air brake monitoring apparatus that is significantly less expensive to maintain than are known prior art systems.

It is still a further object of the present invention to provide an air brake monitoring apparatus having a magnet and co-operating sensor.

It is yet another object of the present invention to provide an air brake monitoring apparatus that provides a suitable housing around the sensors for inducing a stronger magnetic field around the sensors, thereby increasing the sensitivity of the sensors to the magnet.

It is still another object of the present invention to provide an air brake monitoring apparatus wherein the sensors are sealed off from the environment.

It is still a further object of the present invention to provide an air brake monitoring apparatus wherein the sensors measure more than two positions of the brake mechanism.

It is still a further object of the present invention to provide an air brake monitoring apparatus for use on truck trailers, buses, trains, and the like.

SUMMARY OF THE INVENTION In accordance with the present invention there is disclosed an air brake monitoring apparatus for use on a vehicle for indicating the wear condition of brakes on an air braking system of the type having a plurality of brakes, each brake having an air cylinder housing, an air actuated piston, and a brake clevis rod connected at one end to the piston and connected at its opposite end via a brake clevis pin to a brake slack adjuster that connects the brake

clevis rod to the operating cam of the brake mechanism. The piston, brake clevis rod, and brake clevis pin are movable along a longitudinal axis between a brake-of f position and a brake-on position. The air brake monitoring apparatus comprises an equal plurality of magnets and means for respectively operatively mounting each magnet on a selected one of the brake clevis rod and the air cylinder housing in fixed relation thereto. There is also an equal plurality of sensor units and means for respectively operatively mounting each sensor unit on the other one of the brake clevis rod and the air cylinder housing in fixed relation thereto, each sensor unit having a second plurality of magnetically responsive sensor elements mounted therein for sensing the relative longitudinal position of the magnet relative to a respective sensor unit, when the magnets and the sensor units are mounted in place, such that each the magnetically responsive sensor element produces an electrical signal in response to the relative longitudinal position of the respective magnet. An indicator means is mounted on the vehicle and operatively connected to the sensor units for receiving the electrical signals therefrom and providing an operator perceptible indication corresponding to the received signals, and indicative of the wear condition of the brakes.

Other advantages, features and characteristics of the present invention, as well as methods of operation and functions of the related elements of the structure, and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following detailed description and the appended claims with reference to the accompanying drawings, the latter of which is briefly described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS The novel features which are believed to be characteristic of the air brake monitoring apparatus according to the present invention, as to its structure, organization, use and method of operation, together with further objectives and advantages thereof, will be better understood from the following drawings in which a presently preferred embodiment of the invention

will now be illustrated by way of example. It is expressly understood, however, that the drawings are for the purpose of illustration and description only, and are not intended as a definition of the limits of the invention. In the accompanying drawings: Figure 1 is a side elevational view of a tractor trailer type truck having a preferred embodiment air brake monitoring apparatus according to the present invention installed thereon, with the wheels partially sectioned for ease of illustration ; Figure 2 is a perspective view of the preferred embodiment air brake monitoring system of Figure 1, with the brake clevis rod in a retracted position, thereby corresponding to the brakes not being applied ; Figure 3 is a perspective view similar to Figure 2, with the brake clevis rod in an extended position, thereby corresponding to the brakes being applied and indicating a safe operating range for the brake mechanism; Figure 4 is a perspective view similar to Figure 2, but with the parts of the tractor trailer type truck either removed or shown in phantom for the sake of clarity ; Figure 5 is a perspective view from an opposed direction as compared to Figure 4, showing the sensor and mounting bracket means only of the preferred embodiment air brake monitoring system; Figure 6 is an exploded perspective view of the sensor and mounting bracket means of Figure 5; Figure 7 is a partially sectional side elevational view of the preferred embodiment air brake monitoring system of Figure 2, with the brake clevis rod in an extended position and indicating a safe operating range for the brake mechanism ;

Figure 8 is a top plan view of the preferred embodiment air brake monitoring system of Figure 7; Figure 9 is a partially sectioned side elevational view taken along sight line 9-9 of Figure 8; Figure 10 is a partially sectional side elevational view taken along sight line 10-10 of Figure 8 ; Figure 11 is an enlarged perspective view of the sensor used in the preferred embodiment vehicle monitoring system; Figure 12 is an exploded perspective view of the sensor of Figure 11; Figure 13 is an enlarged sectional side elevational view taken along sight line 13-13 of Figure 11; Figure 14 is a side elevational view of the magnet mount shown in Figures 2-4 and 7-10; Figure 15 is a sectional side elevational view of the magnet mount of Figure 14; Figure 16 is an exploded sectional side elevational view of the magnet mount of Figure 15; Figure 17A is a front elevational view of a display panel used in the preferred embodiment air brake monitoring system of Figure 1, with a portion of the display panel cut-away to reveal enclosed circuitry, and with none of the light emitting diodes illuminated ; Figure 17B is a front elevational view similar to Figure 17A, but without the cut-away portion and with two columns of light emitting diodes illuminated to indicate that the brakes have been applied;

Figure 17C is a front elevational view similar to Figure 17B, but with two of the brake travel light emitting diodes illuminated, so as to indicate that the brake on the left wheel of the first axle is being monitored; Figure 17D is a front elevational view similar to Figure 17C, but with two other of the brake travel light emitting diodes illuminated, so as to indicate that the brake on the right wheel of the fifth axle is being monitored ; Figure 17E is a front elevational view similar to Figure 17D, but with two other of the brake travel light emitting diodes illuminated, so as to indicate that the brake on the left wheel of the ninth axle is being monitored ; Figure 17F is a front elevational view similar to Figure 17E, but with five of the brake travel light emitting diodes illuminated, so as to indicate that the brake on the right wheel of the first axle is being monitored and to further indicate that a yellow or red situation exists on an axle not being directly monitored; Figure 17G is a front elevational view similar to Figure 17A, but showing two of the four"specific conditions"light emitting diodes illuminated ; Figure 17H is a front elevational view similar to Figure 17G, but showing all four of the"specific condition"light emitting diodes illuminated ; Figure 18 is a front elevational view of a first alternative embodiment display panel ; Figure 19 is a front elevational view of a second alternative embodiment display panel ; Figure 20A is a top plan view of the preferred embodiment vehicle brake monitoring system of Figure 2, with the brake clevis rod in a retracted position; Figure 20B is a top plan view similar to Figure 20A, with the brake clevis rod in a slightly extended position corresponding to the brakes being

applied and indicating a safe operating range for the brake mechanism, thus indicating little or no brake wear; Figure 20C is a top plan view similar to Figure 20B, with the brake clevis rod in a partially extended position corresponding to the brakes being applied and indicating a safe operating range for the brake mechanism, thus indicating Some brake wear; Figure 20b is a top plan view similar to Figure 20C, with the brake clevis rod in a significantly extended position corresponding to the brakes being applied indicating a marginally safe operating range for the brake system, thus indicating significant brake wear; Figure 20E is a top plan view similar to Figure 20D, with the brake clevis rod in an overextended position corresponding to the brakes being applied and indicating that the brake mechanism is operating outside a safe operating range, thus indicating an unacceptable amount of brake wear or other brake mechanism failure; Figure 21A is a front elevational view of the display panel of Figure 17A1 corresponding to the brake clevis rod being a retracted position as shown in Figure 20A and with none of the light emitting diodes illuminated; Figure 21B is a front elevational view of the display panel similar to Figure 21A, but corresponding to the brake clevis rod being in a slightly extended position as shown in Figure 20B and with the appropriate light emitting diodes illuminated ; Figure 21C is a front elevational view of the display panel similar to Figure 21 B, but corresponding to the brake clevis rod being in a partially extended position as shown in Figure 20C and with the appropriate light emitting diodes illuminated ; Figure 21 D is a front elevational view of the display panel similar to Figure 21 C, but corresponding to the brake clevis rod being in a significantly

extended position as shown in Figure 20D and with the appropriate light emitting diodes illuminated ; Figure 21E is a front elevational view of the display panel similar to Figure 21 D, but corresponding to the brake clevis rod being in an overextended position as shown in Figure 20E and with the appropriate light emitting diodes illuminated ; and, Figure 22 is a side elevational view of a tractor trailer type truck having an alternative embodiment air brake monitoring apparatus according to the present invention installed thereon, with the wheels partially sectioned for ease of illustration.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Reference will now be made to Figures 1 through 17G, which show a preferred embodiment of the air brake monitoring apparatus according to the present invention, as indicated by the general reference numeral 20, for use on a vehicle such as a transport truck trailer 22, as can be seen in Figure 1, for indicating the wear condition of brakes as indicated by the general reference numeral 24, as best seen in Figures 1,2,3,7 and 10, on an air braking system as indicated by the general reference numeral 26 in Figures 1- 3 and 7-10, of the type having a plurality of brakes 24.

The air brake monitoring apparatus 20 may equivalently be used on the braking system of other types of vehicles such as buses, trains, and so on.

Each brake 24 has an air cylinder housing 28 containing an air actuated piston 30, as is best seen in Figures 7,9 and 10. A brake clevis rod 32 is securely connected at one end 32a, as best seen in Figure 10, to the piston 30 for linear movement therewith and, as best seen in place in Figures 2,3, and 7 through 10, is securely connected at its opposite other end 32b, as best seen in Figures 2,3,4,8 and 10, in pivotal relation to a brake slack adjuster 34 by means of a specially designed clevis pin 60, as shown enlarged in Figures 14 through 16. The clevis pin 60 is retained in place within co-

operating bore holes 33 (as best seen in Figure 8) in a"U"-bolt head portion 31 of the brake clevis rod 32. The devis pin 60 is thereby operatively mounted on the brake clevis rod 32 for longitudinal movement therewith. The brake slack adjuster 34 connects the brake clevis rod 32 to the operating cam 36 of the actual braking mechanism 38 within the wheel hub 39 via a cam rod 35 (see Figures 2,3,7 and 10). Thus, the piston 30 and the brake clevis rod 32 are movable along a longitudinal axis"L"between a brake-off position, as can be best seen in Figure 2, and a brake-on position, as can be best seen in Figure 3.

It should be noted that many of the wheels on large transport trucks and their trailers and on buses are double wheels or one mounted in and under on a side axle, such that two wheels are attached to a single brake 24.

With particular reference to Figures 4,8,10 and 14 through 16, it will be appreciated that the air brake monitoring apparatus 20 of a vehicle 22 comprises a plurality of permanent magnets 50, which plurality is equal to the number of individual brakes 24 that make up the air braking system 26 of the vehicle 22. The clevis pin 60 associated with each brake 24 provides the means for respectively operatively mounting each respective magnets 50 on the brake clevis rod 32 and the air cylinder housing 28 of that brake 24 in fixed relation to said cylinder housing 28. Thus, in the preferred embodiment illustrated, the magnets 50 are each mounted by means of a respective clevis pin 60 on a respective brake clevis rod 32.

As can be best seen in Figures 14,15, and 16, the clevis pin 60 has a first end 61, a second sensor-facing end 62, and an elongate main body portion 63 extending between the first end 61 and the second end 62.

Preferably, the elongate main body portion 63 is made from hard steel for the purpose of strength. A small diameter bore hole 64 is disposed in the elongate main body portion 63 adjacent the first end 61. A cotter pin 69 extends through the bore hole 64 to retain the clevis pin 60 in place in the"U"- bolt head portion 31 of the brake clevis rod 32.

An annular shoulder portion 65 is disposed along the elongate main body portion 63 a short distance from the second end 62. The elongate main body portion 63 terminates shy of the second end 62 50 as to define a reduced diameter post portion 66 which also terminates shy of the second end 66, as best seen in Figure-5. A stainless steel collar member 67 is pressed-fit over the post portion 66 and abuts at its proximal end against the annular shoulder portion 65. The distal end of the collar member 67 clevis pin 60 and also defines the second end 62 of the recess 68 disposed adjacent the second end 62 of the clevis pin 60. The recess 68 is shaped and dimensioned to receive and retain in frictional engagement a respective one of the magnets 50, which magnet 50 is press-fit into the recess 68.

There is also provided according to the invention a plurality of sensor units 70, which plurality of sensor units 70 is equal to the plurality of magnets 50, so that there will be a one-to-one correspondence of magnets 50 and sensor units 70. Each of the sensor units 70 comprises a unitary sealed sensor unit, as will be discussed in greater detail below.

There is also provided according to the invention a means 80 for operatively mounting each sensor unit 70 on the other one of the brake clevis rod 32 and the air cylinder housing 28 in fixed relation thereto (see especially Figures 4,5 and 6). In the preferred embodiment illustrated, each sensor unit 70 is mounted in adjustable removable and replaceable relation on the respective air cylinder housing 28 by said mounting means 80, which mounting means comprises a mounting plate 82, a horizontal arm bracket 84, a threaded fastener 86, a nut 87, a vertically adjustable"L--shaped mounting arm 90, threaded fastener 91, nut 94 and threaded post 29. More particularly, the sensor 70 is welded to the small mounting plate 82 having a pair of apertures 83 therein. The purpose of having two apertures 83 in the mounting plate 82 is to permit right-hand and left-hand mounting. The mounting plate 82, and therefore the sensor unit 70, is secured in longitudinally adjustable relation to the horizontal arm bracket 84 by means of a threaded fastener 86 extending through an elongate aperture 85 in the

horizontal arm bracket 84. The threaded fastener 86 is secured in place by the co-operating nut 87 and a washer 87a.

A visual alignment indicator 88 having an indicator arm 88a is also optionally mounted on to the mounting plate 82 by the threaded fastener 86.

The purpose of the visual alignment indicator 88 is to provide a visual indication of the location of the clevis pin 60, and therefore the magnet 50, in relation to the sensor unit 70 when the brake 24 is off, and the brake clevis rod 32 is in its retracted position. In this manner, the sensor unit 70 can be correctly positioned during installation by longitudinally aligning the clevis pin 60 and the indicator arm 88a.

The horizontal arm bracket 84 is mounted in vertically adjustable relation to the"L"-shaped mounting arm 90 by means of the threaded fastener 91 passing through an elongate aperture 92 in the vertical portion 90a of the mounting arm 90 and passing through an aperture 93 disposed near one end of the horizontal arm bracket 84, and secured in place by a co-operating nut 94 and washer 94a. The"L"-shaped mounting arm 90 is secured in place on the air cylinder housing 28 by means of a nut 29a securely threadably engaged on the co-operating threaded post 29. The threaded post 29 is internally anchored in the air cylinder housing 28 and extends through an elongate aperture 95 in the horizontal portion 90b of the"L"-shaped mounting arm 90.

As can be best seen in Figures 11 through 13, each sensor unit 70 has a second plurality of magnetically responsive sensor elements 72 mounted therein for sensing the relative longitudinal position of the respective magnet 50 relative to the sensor unit 70, Preferably, the plurality of magnetically responsive sensor elements 72 comprises at least three magnetically responsive elements, and in the preferred embodiment illustrated, the plurality of magnetically responsive sensor elements 72 comprises four magnetically responsive sensor elements : specifically a first magnetically responsive sensor element 72a, a second magnetically responsive sensor element 72b, a

third magnetically responsive sensor element 72c, and a fourth magnetically responsive sensor element 72d. The magnetically responsive sensor elements 72a, 72b, 72c, and 72d, are disposed in a substantially longitudinally aligned array along the longitudinal axis of each sensor unit 70. Each sensor unit 70 also comprises an additional magnetically responsive sensor element 72e, used to turn off the sensor unit when the respective magnet 50 moves away from the sensor unit 70. Preferably, the shut-off magnetically responsive sensor element 72e is also disposed in the substantially longitudinally aligned array with the other four sensor elements 72a through 72d.

In the preferred embodiment illustrated, each of the magnetically responsive sensor elements 72 comprises a Hall effect element, which are conventionally used in the art of sensing the proximity of magnets. The magnetically respective sensor elements 72a through 72e may alternatively comprise other types of magnetically responsive elements, if desired. It has been found that Hall effect elements are suitably sensitive for this application, can withstand the rigours of the jolting associated with being mounted on a vehicle braking system for a commercial vehicle or the like, and have also been found to be cost effective.

The magnetically responsive sensor elements 72a through 723 are mounted in sealed relation within their respective sensor unit 70. The unitary sealed sensor unit 70 has a first end 70a and a second end 70b, and comprises a substantially solid elongate outer housing 73 having a throughpassage 74. Preferably, the substantially solid elongate outer housing 73 and the throughpassage 74 are each substantially rectangular in cross- section. A sensor circuit board 75 is preferably disposed within the throughpassage 74 and has the magnetically responsive sensor elements 72a-72e mounted thereon disposed in a substantially longitudinally aligned array along the longitudinal axis"L"of the sensor unit. A ferrous metal bar 76 is preferably disposed within the throughpassage 74 adjacent the circuit board 75 such that the sensor circuit board 75 is disposed between the ferrous

metal bar 76 and the magnet 50 in the installed configuration illustrated in, for example, Figure 8, to thereby permit the ferrous metal bar 76 to draw the magnetic field of the magnet 50 through the magnetically responsive sensor elements 72a-72e (i. e, increase its magnetic flux), so as to thereby maximize the sensitivity of the sensor elements 72a-72e to the magnet 50.

The substantially elongate outer housing 73 is preferably made from a non-ferrous metal, such as aluminum, or from a suitable plastics material, or from other suitable materials, to permit full penetration of the magnetic field from the magnet 50 through the outer housing 73, thus maximizing the strength of the magnetic field activating the magnetically responsive sensor elements 72a-72e.

There is also provided according to the invention a means for sealing the ends of the throughpassage 74, preferably comprising an epoxy based material 77. During construction of the sensor unit, the sensor circuit board 75 and the ferrous metal bar 76 are put into place as illustrated within the throughpassage 74 of the elongate outer housing 73, and the epoxy based material is thereafter poured in a liquid state into an open end of the throughpassage 74, with the other end of the throughpassage 74 being blocked off by an appropriate barricade (not shown). The epoxy based material subsequently hardens to form the sealed sensor unit 70.

When the magnets 50 and the sensor units 70 are mounted in place on the vehicle 22 as shown in the Figures and as previously described, each of the magnetically responsive sensor elements 72a-72e produces an electrical signal in response to the relative longitudinal position of the respective magnet 50, which signal is, of course, representative of the relative portions of the clevis pin 60 and clevis rod 32, and hence, indicative of the wear condition of the brakes 24.

An indicator means comprising a visual display, and more specifically a visual display panel 100 is mounted in the truck 22, specifically within the cab

23 of the truck 22. A preferred embodiment of the visual display 100 is best seen in Figures 17A through 17H, and 21A through 21 E. The visual display panel 100 comprises a plastic housing 102 having a representative diagram of the truck 22 printed thereon, which representative display shows an outline of the cab 23a and frame 104, the front wheels 1061,106r on the front axles, the first set of wheels 1081,108r on the second axle, and the second set of wheels 1101, 11Or on the third axle.

The visual display panel 100 also comprises means for indicating which of at least three magnetically responsive sensor elements, and in the preferred embodiment illustrated the four magnetically responsive sensor elements 72a, 72b, 72c, and 72d, is producing an electrical signal in response to the position of the respective magnet 50.

The visual display panel 100 is operatively connected to the magnetically responsive sensor elements 72a, 72b, 72c, and 72d in each of the sensor units 70 for receiving the electrical signals from each of the sensor units 72a, 72b, 72c, and 72d, and providing an operator perceptible indication.

In the preferred embodiment, the operator perceptible indication is a visual indication comprising a plurality of light emitting diodes 112 through 146, and may also include an auditory indication corresponding to the received signals and indicative of the wear condition of the brakes 24.

In the preferred embodiment illustrated, the sensor units 72a, 72b, 72c, and 72d are connected in electrically conductive relation to the visual display panel 100 by means of wires 79, with a sheathed three-conductor wire 79 extending from each sensor unit 72a, 72b, 72c, and 72d to a common bundle 79a (as can be seen in Figure 1), which common bundle 79a runs to the cab 23 of the truck 22, whereat the wires 79 are connected to the visual display panel 100. In the preferred embodiment illustrated, the wires 79 are connected to a microprocessor 101 and to related circuitry 101 a within the display panel. 100, as are the light emitting diodes 112 through 146 (see

Figure 17A). The microprocessor 101 and related circuitry 101a control the operation of the visual display panel 100.

The visual display panel 100 can be seen in Figure 17A with none of the light emitting diodes 112 through 146 illuminated, and can be seen in Figures 17B through 17H with various ones of the light emitting diodes 112 through 146 illuminated. It should be understood that the pattern of light emitting diodes that are illuminated in Figures 17B through 17F do not necessarily represent patterns that would be encountered during everyday use of the air brake monitoring apparatus 20 but instead are illuminated to illustrate the particular functionality of the light emitting diodes being discussed.

Disposed immediately beside the outline of the cab 23a and frame 104 and wheels 106 through 110, are corresponding pairs of light emitting diodes 112 through 122 arranged in four vertical columns of three light emitting diodes in each vertical column. The inner two rows of diodes, or in other words the light emitting diodes closest to the outline of the cab 23a and frame 104 and wheels 106-110, has an upper light emitting diode 1121 on the left and an upper light emitting diode 112r on the right; a middle light emitting diode 1141 on the left and a middle light emitting diode 114r on the right; and a lower light emitting diode 1161 on the left and a lower light emitting diode 116r on the right. These light emitting diodes 112 through 116 in these inner two columns are electrically connected to the first magnetically responsive sensor element 72a in respective sensor units 70, and accordingly illuminate when the brakes 24 of the truck 22 are applied, as can be seen in Figure 17B.

Immediately juxtaposed each of these inner columns of light emitting diodes 112 through 116 is a corresponding outer column of tri-color (green, yellow, and red) light emitting diodes, 1181,118r, 1201,120r, 1221,122r.

The tri-color diodes 118 through 122 indicate how far the magnet 50 in the respective clevis pin 60 has travelled along the longitudinal axis"L"of the respective sensor unit 70. When the magnet 50 reaches the first magnetically

responsive sensor element 72a or the second magnetically responsive sensor element 72b, the light emitting diodes 1181,118r, 1201,120r, 1221,122r illuminate in a green color to indicate that the brakes 24 of the respective wheel are within a safe operating range. If the magnet 50 reaches the third magnetically responsive sensor element 72c, the light emitting diodes 1181, 118r, 1201,120r, 1221,122r illuminate in a yellow color to indicate that the brakes 24 of the respective wheel are within a marginally safe operating range. If the magnet 50 reaches the fourth magnetically responsive sensor element 72d, the light emitting diodes 1181,. 118r, 1201, 120r, 1221, 122r illuminate in a red color to indicate that the brakes 24 of the respective wheel are outside a safe operating range. Optionally, an audible alarm may sound to immediately alert the driver to this unsafe condition.

In the event that the truck 22 has more than the three axles indicated by the outline 104, the visual display panel 100 automatically switches to showing the condition of the fourth, fifth, sixth, and subsequent axles sequentially. For instance, as can be best seen in Figure 17C, when the visual display panel 100 is indicating the first, second and third axles, the light emitting diode 130a is illuminated (indicating mode 1), and another light emitting diode is illuminated to indicate which particular wheel on which particular axle is being indicated. As illustrated, light emitting diode 1181 is illuminated to indicate that the left wheel on the first axle is being indicated; as best seen in Figure 17D, when the visual display panel 100 is indicating the fourth, fifth and sixth axles, the second light emitting diode 132a is illuminated (indicating mode 2), and another light emitting diode is illuminated to indicate which particular wheel on which particular axle is being indicated. As illustrated, light emitting diodes 120 is illuminated to indicate that the right wheels on the fifth axle are being indicated; and, as is best seen in Figure 17E, when the visual display panel 100 is indicating the seventh, eighth and ninth axles, the light emitting diode 134a is illuminated (indicating mode 3), and another light emitting diode is illuminated to indicate which particular wheel on which particular axle is being indicated. As illustrated, light emitting

diode 1141 is illuminated to indicate that the left wheels on the ninth axle is being indicated. Further, light emitting diodes 130b, 132b, 134b indicate that there is a yellow or red indication in the associated mode, so that that mode can be checked. As can be best seen in Figure 17F, in addition to light emitting diode 132a being illuminated to indicate mode 2, the light emitting diode 132b is illuminated, thus indicating that one of the brakes 24 in either the fourth axle, the fifth axle, or the sixth axle is in either a yellow condition, corresponding to the brake 24 being within a safe operating range, but just marginally so, or is in a red condition, corresponding to the brake 24 being outside a safe operating range. Also, light emitting diode 122r would be correspondingly illuminated either yellow or red, to specify the particular wheel and the condition of the brake 24 for that wheel.

Disposed along the top of the visual display panel 100 there are preferably disposed a green light emitting diode 140, a green light emitting diode 142, a yellow light emitting diode 144, and a red light emitting diode 146. These four light emitting diodes 140 through 146 indicate the specific condition of the brakes 24 for each wheel, and accordingly are referred to henceforth collectively as the"specific condition"light emitting diodes. The green light emitting diode 140 is electrically connected to the first magnetically responsive sensor element 72a in the respective sensor unit 70; the green light emitting diode 142 is electrically connected to the second magnetically responsive sensor element 72b in the respective sensor unit 70; the yellow light emitting diode 144 is electrically connected to the third magnetically responsive sensor element 72c in the respective sensor unit 70; and the red light emitting diode 146 is electrically connected to the fourth magnetically responsive sensor element 72d in the respective sensor unit 70. In use, for example, as can be best seen in Figure 17G, light emitting diodes 140 and 142 are illuminated to indicate that the magnet 50 of the particular wheel being indicated has reached the second magnetically responsive sensor element 72b, which indication corresponds to the brake 24 being marginally within acceptable limits. Further, as can be best seen in Figure 17H, all four

specific condition light emitting diodes 140,142,144,146 are illuminated, thus indicating that the magnet 50 of the particular wheel being indicated has reached the fourth magnetically responsive sensor element 72d, which indication corresponds to the brake 24 being outside a safe operating range.

The light emitting diodes 112 through 146 all remain on for fifteen seconds after the brakes have been applied and released. This is important in the event that the parking brake of the truck 22 is applied, so that the light emitting diodes do not remain illuminated indefinitely..

The visual display panel 100 also comprises a selectively operable control means for selecting the sensor unit 70 to be monitored, and a feedback means for verifying the selected sensor unit. In the preferred embodiment illustrated, the selectively operable control means comprises a pushbutton 150 disposed near the bottom of the visual display panel 100, and the feedback means comprises various ones of the light emitting diodes 112 through 146. The pushbutton 150 permits the most recent status of the sensor units 70 to be recalled, and also permits sequential toggling from one sensor unit 70 to the next, either when the brakes 24 are applied or when recalling the most recent status of the display panel 100.

In addition to being useful during driving, it would be understood that the light emitting diodes 140,142,144,146 are also useful during a pre-trip inspection to display to the operator the specific condition of the brakes 24 on each wheel of the truck 22. For instance, the brakes 24 on one side of the truck 22 may be more worn, on an overall basis, than the brakes 24 on the opposite side of the truck 22. Such an imbalance in braking function between the left and right sides of the truck 22 would be apparent from the display panel 100, by consecutively displaying the status of each of the wheels 24 (using pushbutton 150). An operator could visually discern whether the yellow light emitting diode 144 and the red light emitting diode 146 become illuminated more frequently when checking the wheels 24 on the left. side of the vehicle or when checking the wheels 24 on the right side of the vehicle,

thereby indicating which side of the truck 22 has more brakes 24 that are either marginal or unsafe. Further, the tri-colour light emitting diodes 1181, 1201, and 1221 on the left side of the display panel 100 will illuminate as yellow or red more frequently if the brakes 24 on the left side of the truck 22 are either marginal or unsafe, and the tri-colour light emitting diodes 118r, 120r, and 122r on the right side of the display panel 100 will illuminate as yellow or red more frequently if the brakes 24 on the right side of the truck 22 are either marginal or unsafe.

Reference will now be made to Figure 18, which shows a first alternative embodiment visual display panel 180 for use in the air brake monitoring apparatus 20 of the present invention. The visual display panel 180 is similar to the visual display panel 100 shown in Figures 17A through 17H, except that the light emitting diode indicators for mode 1, mode 2, and mode 3 are not present and that there are four rows of light emitting diodes 182 for indicating the brake status of each wheel (labelled 1L, 1R, through 4R). More particularly, in use, the light emitting diodes 1811 are used to indicate the status of the air brake monitoring apparatus 20 mounted on the front wheel 1821; the light emitting diodes 181 r are used to indicate the status of the air brake monitoring apparatus 20 mounted on the front right wheel 182r ; the light emitting diodes 1831 are used to indicate the status of the air brake monitoring apparatus 20 mounted on the left wheels 1821 on the second axle ; the light emitting diodes 183r are used to indicate the status of the air brake monitoring apparatus 20 mounted on the right wheels 184r on the second axle ; the light emitting diodes 1851 are used to indicate the status of the air brake monitoring apparatus 20 mounted on the left wheels 1861 on the third axle ; the light emitting diodes 185r are used to indicate the status of the air brake monitoring apparatus 20 mounted on the right wheels 186r on the third axle ; light emitting diodes 1871 are used to indicate the status of the air brake monitoring apparatus 20 mounted on the left wheels 1881 on the fourth axle ; and light emitting diodes 187 are used to indicate the status of the

air brake monitoring apparatus 20 mounted on the right wheels 188 are on the fourth axle.

Reference will be now made to Figure 19, which shows a second alternative embodiment of the visual display panel 190 for use with the air brake monitoring apparatus 20 of the present invention. The visual display panel 190 is for use in a smaller vehicle, such as a delivery truck that might be used by courier companies and the like, and shows single left and right front wheels 192 and associated light emitting diodes 194, and one rear wheel axle having wheels 196 and associated light emitting diodes 198. More specifically, in use, the light emitting diodes 1941 are used to indicate the status of the breaks 24 mounted on the left front wheel 1921 ; the light emitting diodes 194 are used to indicate the status of the brakes 24 mounted on the right front wheel 192r; the light emitting diodes 1981 are used to indicate the status of the breaks mounted on the rear left wheel 1961; and the light emitting diodes 198r are used to indicate the status of the breaks 24 mounted on the rear right wheels 196r.

Reference will now be made to Figures 20A through 21 E to describe the air. brake monitoring apparatus 20 of the present invention in use. As can be best seen in Figure 20A, the brake clevis rod 32 is in a retracted position.

Accordingly, the clevis pin 60 is disposed adjacent the first end 70a of the sensor unit 70, and accordingly is not detected by any of the magnetically responsive elements 72a through 72e. Correspondingly, as can be best seen in Figure 21A, none of the light emitting diodes 112 through 146 on the visual display panel 100 are illuminated. However, when the brakes 24 of the truck 22 are applied, the six light emitting diodes 1121,112r, 1141,114r, 1161, and 116r are illuminated, as is best seen starting at Figure 21 B and continuing through Figure 21 E, to indicate that the brakes 24 have been applied and that the sensor units 70 are operational. As the brakes 24 are applied, the clevis pin 60 first moves past the shut-off sensor 72e; however, the presence of the magnet 50 at the shut-off sensor 72e is inconsequential since the microprocessor 101 and the electronic circuitry 101a already consider the

display for that particular sensor to be shut off. The clevis pin 60 then reaches alignment with the first magnetically responsive sensor element 72a, as can be seen in Figure 20B. Thereat, the first magnetically responsive sensor element 72a detects the proximity of the magnet 50 in the clevis pin 60 and sends a signal to the visual display panel 100 and, as best seen in Figure 21 B, the green light emitting diode 140 of the four"specific condition"light emitting diodes 140 through 146, illuminates so as to indicate that the brakes 24 have reached a first position at the beginning of the safe operating range.

If the truck brakes 24 are virtually unworn or perhaps slightly worn, at most, and are therefore well within a safe operating range, the brake. Clevis rod 32 will stop at this point and the light emitting diode 140 on the visual display panel 100 will be the only one of the four"specific condition"light emitting diodes 140 through 146 illuminated, thus indicating that the particular brake is safe.

In the event that the brakes 24 are moderately worn, the brake clevis rod 32 will continue to travel in the same direction. As the clevis pin 60 reaches alignment with the second magnetically responsive sensor element 72b, as can be seen in Figure 20C, the second magnetically responsive sensor element 72b detects the proximity of the magnet 50 in the clevis pin 60 and sends a signal to the visual display panel 100 and, as can be seen in Figure 21C, the two green light emitting diodes 140,142 of the four"specific condition"light emitting diodes 140 through 146, illuminate so as to indicate that the brakes 24 is still within a safe operating range. If the truck brakes 24 are moderately worn, and are therefore within a safe operating range, the brake clevis rod 32 will stop at this position and the light emitting diode 140 and the light emitting diode 142 will be the only ones of the four"specific condition"light emitting diodes 140 through 146 that are illuminated.

In the event that the brakes 24 are more worn, the brake clevis rod 32 will continue to travel in the same direction towards the opposite second end 70b of the sensor unit 70. As the clevis pin 60 reaches alignment with the third magnetically responsive sensor element 72c, as can be seen in Figure

20D, the third magnetically responsive sensor element 72c detects the proximity of the magnet 50 in the clevis pin 60 and sends a signal to the visual display panel 100 and, as can be seen in Figure 21 D, the yellow light emitting diode 144 on the visual display panel 100 illuminates in addition to the light emitting diodes 140,142/to indicate that the brake 24 on this particular wheel is within a safe operating condition, but just marginally so. If the brake 24 is marginally within a safe operating range, the brake clevis rod 32 will stop at this position, and the three light emitting diodes 140,142, and 144 of the four "specific condition"light emitting diodes 140 through 146 will remain illuminated.

If the brakes 24 are excessively, and therefore unacceptably worn, and therefore are outside a safe operating range, or perhaps if the brake mechanism 38 is malfunctioning or is broken, then the brake clevis rod 32 continues to a position as shown in Figure 20E, beyond the second end 70b of the sensor unit 70, whereat the clevis pin 60 reaches the fourth magnetically responsive sensor element 72d. The fourth magnetically responsive sensor element 72d detects the proximity of the magnet 50 in the clevis pin 60 and sends a signal to the visual display panel 100 and, as can be seen in Figure 21 E, the red light emitting diode 146 on the visual display panel 100 illuminates, in addition to the other three light emitting diodes 140, 142, and 144, to indicate that the brake 24 is outside a safe operating range.

Optionally, an audible alarm may sound to immediately alert the driver to the unsafe condition.

Other modifications and alterations may be used in the design and manufacture of the air brake monitoring apparatus according to the present invention without departing from the spirit and scope of the accompanying claims. For example, in an alternative embodiment, it is contemplated that he sensor units 70 could be connected in electrically conductive relation, as aforesaid, to the indicator means, namely the visual display panel 100, by means of an RF transmitter 200 operatively connected in signal receiving relation to the plurality of sensor units 70 and a co-operating RF receiver 202 operatively connected in signal providing relation to the indicator means, as can be seen in Figure 22.