WO2015135074A1

WO2015135074A1 - Brake chamber with proximity sensor

Info

Publication number: WO2015135074A1
Application number: PCT/CA2015/050164
Authority: WO
Inventors: Dieter Albert SCHMIDT
Original assignee: Schmidt Dieter Albert
Priority date: 2014-03-12
Filing date: 2015-03-04
Publication date: 2015-09-17

Abstract

A brake adjustment monitoring apparatus for an air brake system comprises a non-contact proximity sensor mounted on a wall of a brake chamber so as to produce a signal when the push rod back plate comes within the proximity sensor's sensing distance.

Description

TITLE OF INVENTION

BRAKE CHAMBER WITH PROXIMITY SENSOR FIELD OF THE INVENTION

This invention relates to brake systems, and in particular to a device for monitoring the adjustment of air brake systems.

BACKGROUND OF THE INVENTION

Air brake systems exert a greater force to apply the brakes compared to hydraulic brake systems. Air brake systems are also more tolerant to leaks than hydraulic brake systems. For these and other reasons, air brake systems are commonly used with heavy commercial vehicles instead of hydraulic brake systems.

Nevertheless, to properly function, air brake systems must be properly adjusted. In many jurisdictions, drivers of vehicles using air brake systems are required by law to inspect brake adjustments daily. Drivers may also be required to inspect the adjustment of their vehicle's brakes before driving down steep gradients.

The adjustment of the brakes is usually determined by measuring push rod travel. Excessive push rod travel indicates that a brake needs to be adjusted. Brake inspections generally require the driver to exit from the cab of a vehicle and to crawl underneath the vehicle where the brake systems are located. As many drivers find brake inspections to be arduous, brake systems are often not inspected as frequently as required. This may result in brake failure causing damage to the vehicle or to the load or loss of life. To reduce the incidence of crashes caused by brake failure, it is known in the art to provide systems that monitor brake adjustment and alert drivers to the possibility that a brake may be out of adjustment. The types of monitoring devices can be divided into two broad groups: those measuring changes outside a brake chamber and those measuring changes inside a brake chamber. Given the harsh conditions that the underside of heavy commercial vehicles are exposed to, such as rocks, dirt, and moisture, monitoring devices that measure changes within a brake chamber are preferred since the interior of a brake chamber is relatively protected.

U.S. Patent No. 7,624,849 to Goncalves et al. discloses a number of alternative brake adjustment monitoring devices, including devices to measure changes occurring within a brake chamber. In one embodiment, a Hall-effect ratiometric sensor is used within a brake chamber to sense the position of a push rod back plate. The Hall-effect sensor is configured with two smaller springs and a magnet mounted on magnet housing between the two smaller springs. When the brakes are applied, the two smaller springs compress and the magnet is brought in closer to the Hall-effect sensor. In order to function properly, the Hall-effect sensor must be calibrated in relation to the effect of the smaller springs and the magnet.

Goncalves also discloses the general idea of a brake adjustment monitoring system that utilizes electromagnetic radiation within a brake chamber to sense the position of a push rod back plate. Goncalves' disclosed embodiment involves the use of radar waves that are bounced off a push rod back plate towards a radar receiver located on the brake chamber wall that the push rod back plate moves towards during brake application. However, it is anticipated that the presence of a return spring within the brake chamber is likely to lead multiple uncoordinated returns and difficulties calibrating the system. The compression and expansion of the return spring during brake applications is likely to lead to additional radar clutter.

Accordingly, a need exists for an improved brake adjustment monitoring device that overcomes the deficiencies noted above. It is therefore an object of this invention to provide a device that reliably detects when an air brake system is out of adjustment. It is a further object of the invention to alert the driver to a potential problem with a vehicle's brake adjustment.

These and other objects of the invention will be better understood by reference to the detailed description of the preferred embodiment which follows. Note that the objects referred to above are statements of what motivated the invention rather than promises. Not all of the objects are necessarily met by all embodiments of the invention described below or by the invention defined by each of the claims.

SUMMARY OF THE INVENTION

In one aspect, the invention comprises a monitoring system for an air brake comprising a brake chamber, a push rod and push rod back plate. The brake chamber is fitted with a non-contact proximity sensor, preferably an inductive sensor, mounted to the wall that the push rod back plate travels towards during brake application. The sensor is configured to generate an output in response to the push rod back plate coming within a predetermined distance of the proximity sensor and the signal may be relayed to the cab of a vehicle to alert the driver that one of the vehicle's brakes may be out of alignment.

In another aspect, the non-contact proximity sensor may be mounted to extend through the brake chamber wall that the push rod back plate travels towards during a brake application. In yet a further aspect, the depth that the non-contact proximity sensor extends through the wall can be adjusted by manipulation from the outside of the brake chamber.

In another aspect, a spring is attached to the push rod back plate of a brake chamber and a non-contact proximity sensor mounted on a wall of the brake chamber is configured to generate an output in response to the spring coming within the sensing distance of the proximity sensor.

In another aspect, the invention comprises a method of using or installing a non-contact proximity sensor on a brake chamber.

In a further aspect, a method of installing an air brake monitor system comprises creating a hole in the wall of a brake chamber, securing a threaded element over the hole, and securing a proximity sensor into the first threaded element. The method further comprises adjusting a slack adjuster connected to the push rod such that the push rod travel distance during a full brake application is the maximum allowable push rod travel distance, adjusting the depth that the proximity sensor extends through the wall such that the proximity sensor is just triggered, and re-adjusting the slack adjuster such that the push rod travel distance during a full brake application is under the maximum allowable limit.

In a further aspect, the method of installing an air brake monitor system further comprises disassembling the brake chamber, attaching a spring on a push rod back plate at a location to be in line with the hole in the wall, and reassembling the brake chamber.

The foregoing was intended as a summary only and of only some of the aspects of the invention. It was not intended to define the limits or requirements of the invention. Other aspects of the invention will be appreciated by reference to the detailed description of the preferred embodiments. Moreover, this summary should be read as though the claims were incorporated herein for completeness.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by reference to the detailed description of the preferred embodiment and to the drawings thereof in which:

Fig. 1 is a partially cut away side view of an air brake chamber showing the use of a proximity sensor according to one embodiment of the invention.

Fig. 2 shows a portion of a brake chamber wall prepared to receive a proximity sensor.

Fig. 3 shows the proximity sensor prior to being installed on the brake chamber.

Fig. 4 shows the proximity sensor of Fig. 3 installed on the portion of the brake chamber wall of Fig. 2.

Fig. 5 is partially cut away side view of the air brake chamber of Fig. 1 during a full brake application.

Fig. 6 is a partially cut away side view of an air brake chamber showing the use of a proximity sensor according to an alternate embodiment of the invention;

Fig. 7 is a partially cut away side view of the air brake chamber of Fig. 6 during a full brake application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Figure 1 shows a typical air brake chamber used with heavy commercial vehicles. Referring to Figure 1 , the air brake chamber 2 comprises a flexible diaphragm 4, a push rod 6 with push rod back plate 8 and a return spring 10. The air brake chamber 2 shown in Figure 1 is a service brake chamber. It will be appreciated that the invention may also be used in the service brake section of a spring brake chamber.

On one side of the diaphragm 4 is a compressed air space 12 and on the opposite side is an atmospheric air space 13 (typically vented through vent holes). During the application of the brakes by the driver, compressed air enters the compressed air space 12 and exerts a force against the diaphragm 4. The force causes the back plate 8 to compress the return spring 10, resulting in the movement of the diaphragm 4, push rod 6, and push rod back plate 8 in the direction shown by the arrow 14 towards wall 21 . The dotted outline 9 shows the maximum position that the push rod back plate 8 may travel to during a full brake application when the brakes are properly adjusted. Once the driver releases the brakes, compressed air is released from compressed air space 12, allowing the return spring 10 to return the push rod back plate 8, the push rod 6, and the diaphragm 4 back to their resting state (as shown in solid lines).

As the push rod 6 travels in the direction 14, a portion of the push rod 6 that was previously inside the brake chamber moves outside the brake chamber through an opening in wall 21 . The slack adjuster 30 also rotates in the direction 32 to activate the brake assembly (such as an s-cam brake, a wedge brake, or a disc brake).

Brake adjustment is normally inspected by measuring push rod travel. A brake is out of adjustment when the push rod travel exceeds the predetermined allowable limit for the particular type and size of brake chamber.

According to the invention, a non-contact proximity sensor 20 is mounted on a wall of the brake chamber 2. In the preferred embodiment of the invention, the proximity sensor 20 is mounted on the wall 21 that the push rod back plate 8 travels towards during brake application. Typically, this is also the wall that the push rod 6 travels through.

In the preferred embodiment, the proximity sensor is an inductive sensor. In inductive sensors, an oscillator circuit generates an electromagnetic field. When a metal object, such as the push rod back plate 8, disrupts the electromagnetic field, an eddy current is induced in the metal object which in turn causes a voltage drop in the oscillator. The drop in voltage is sensed by a detector, which generates an output signal. One suitable example of an inductive proximity sensor is IGS204 from ifm efector, inc. which has an 8 mm sensing range. It will be appreciated that inductive sensors with smaller or larger sensing ranges may also be used.

The proximity sensor 20 produces an electrical output when a metal object comes within its sensing distance. According to the invention, when the push rod back plate comes within the sensing distance of the proximity sensor 20, the output is produced.

The proximity sensor 20 may be mounted by various means. Referring to Figures 2-4, according to the preferred embodiment, a threaded proximity sensor 20 is used. A hole 40 is drilled into the wall 21 of the brake chamber and a receiving nut 42 is welded to the wall 21 over the hole 40. The proximity sensor 20 may then be screwed into the receiving nut 42 such that the sensing face 46 of the proximity sensor 20 enters the brake chamber first. A counter nut 44 may be placed on the proximity sensor 20 prior to screwing the proximity sensor into the receiving nut 42. Once the proximity sensor 20 is in place, the counter nut 44 may be rotated against the receiving nut 42 to secure the proximity sensor 20 in place.

The precise distance that the proximity sensor 20 will need to be inserted into the brake chamber 2 depends on the sensing range of the proximity sensor and on the type of brake chamber and its allowable push rod travel distance. According to the preferred embodiment, that is done as follows.

Referring again to Figure 1 , when the brakes are released, a spot 52 on the push rod 6 may be marked at the location that the push rod 6 leaves the wall 21 of the brake chamber 2. When the brakes are applied, the push rod moves in the direction 14. Referring now to Figure 5, during a brake application, the spot 52 will have moved in the direction 14 relative to the wall 21. The distance 54 between the spot 52 and the wall 21 is the push rod travel distance. An adjusting bolt 50 located on the slack adjuster may be turned until the distance 54 equals the maximum allowable push rod travel distance during a full brake application. For example, the air pressure during a full brake application may be between 620 - 690 kPa (90 - 100 p.s.i).

Once the brakes are adjusted to the maximum allowable push rod travel distance, the proximity sensor may be mounted. The proximity sensor 20 is screwed into the receiving nut 42 over the hole 40 and inserted into the brake chamber. The objective is to mount the proximity sensor 20 to a depth that just triggers an output from the sensor when the brakes are at the maximum allowable push rod travel. The depth that the proximity sensor 20 extends through the wall 21 can be adjusted by manipulation from outside the brake chamber 2. The activation of the proximity sensor 20 may be monitored using a sensing light connected to the output lines 22 of the proximity sensor. As the proximity sensor 20 is being screwed into the receiving nut 42 and into the brake chamber 2, it will eventually reach a position where the proximity sensor 20 detects the push rod back plate 8, causing the sensing light to turn on. The proximity sensor 20 may then be secured at this depth using the counter nut 44. At the secured depth, when the distance 54 equals the maximum allowable push rod travel distance of the particular brake chamber, the push rod back plate 8 comes within the sensing distance of the proximity sensor 20 triggering the proximity sensor's output. It will be appreciated that for a given brake chamber, a proximity sensor with a shorter sensing range will need to be secured at a greater depth within the brake chamber than a proximity sensor with a longer sensing range.

After the proximity sensor 20 is secured, the slack adjustor 30 must then be reset by turning the adjusting bolt 50 to ensure that the push rod travel distance 54 during a full brake application is under the maximum allowable limit.

Referring again to Figure 5, once secured at the correct depth in the brake chamber 2, the proximity sensor 20 detects whether the push rod back plate 8 comes within its sensing range. If the push rod back plate 8 comes within the sensing range of the proximity sensor 20, the proximity sensor is triggered. The triggering sends a signal through the output lines 22 to the cab of the vehicle to sound a warning buzzer or display a warning light to the driver. In the alternative, the signal may be sent wirelessly to the vehicle cab.

Figures 7 and 8 show an alternate embodiment of the invention. In the alternate embodiment, the proximity sensor 20 is not inserted into the brake chamber 2 as deeply as shown in Figures 1 and 5. Additionally, a compression spring 60 is attached to the push rod back plate 8 such that the compression spring 60 is substantially in line with the proximity sensor 20. In this embodiment, when the tip 62 of the compression spring 60 that is opposite the push rod back plate 8 comes within the sensing range of the proximity sensor 20, the proximity sensor is triggered. Effectively the presence of the compression spring 60 reduces the depth to which a given proximity sensor 20 must be inserted the proximity sensor is triggered by the tip 62 of the compression spring 60 rather than the push rod back plate 8 (as described for the embodiment shown in Figures 1 and 5).

The compression spring 60 also protects the proximity sensor 20. If the brakes are not properly aligned or if there is a mechanical failure in the brakes, the push rod back plate 8 may overextend in the direction 14. If the back plate 8 comes into contact with the proximity sensor 20, this could damage the proximity sensor. The compression spring 60 prevents the push rod back plate 8 from directly contacting the proximity sensor 20. Additionally, since the proximity sensor 20 senses the tip 62 of the compression spring 60 rather than the push rod back plate 8, the proximity sensor 20 may not need to extend through wall 21 into the brake chamber 2. In other words, no part of the proximity sensor 2 may need to extend into the atmospheric air space 13 and in such instances, it would be impossible for the push rod back plate 8 to directly contact the proximity sensor.

For the embodiments shown in Figures 7 and 8, the compression spring 60 must be attached to the push rod back plate 8 before the proximity sensor 20 is configured. To install the compression spring 60, the brake chamber 2 must be disassembled. This may be done by using a caging bolt or other means as known in the art. Once the brake chamber is disassembled and the push rod back plate 8 is exposed, the compression spring 60 may be attached to the push rod back plate such as by welding, adhesives or other means. Preferably, the compression spring is attached on a position on the push rod back plate 8 that will be in line with the hole 40 (shown in Figure 2) created in the wall 21 for the proximity sensor 20.

Once the compression spring 60 is attached to the push rod back plate 8, the brake chamber may be reassembled. The proximity sensor 20 may then be inserted to a depth that just senses the tip 62 of the compression spring 60 and triggers an output from the sensor when the brakes are at the maximum allowable push rod travel.

While new air brake systems may be manufactured according to the present invention, it will also be appreciated that the present invention may be retrofitted on a vehicle's current air brake system.

In the foregoing specification, the invention has been described with reference to specific embodiments thereof. However, the scope of the claims should not be limited by the preferred embodiments set forth in the examples, but should be given the broadest interpretation consistent with the description as a whole. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.

Claims

1. An air brake monitoring system comprising: a brake chamber comprising: a push rod; a push rod back plate; a wall that said push rod back plate travels towards during brake application; and a non-contact proximity sensor mounted on said wall wherein said proximity sensor is configured to generate an output in response to said push rod back plate coming within the sensing distance of said proximity sensor.

2. The air brake monitoring system of claim 1 wherein said non-contact proximity sensor is mounted to extend through said wall.

3. The air brake monitoring system of claim 2 wherein the depth that said non-contact proximity sensor extends through said wall can be adjusted by manipulation from the outside of said brake chamber.

4. The air brake monitoring system of claim 1 , 2, or 3 wherein said non- contact proximity sensor is an inductive proximity sensor.

5. An air brake monitoring system comprising: a brake chamber comprising: a push rod; a push rod back plate; a spring attached to said push rod back plate; a wall that said push rod back plate travels towards during brake application; and a non-contact proximity sensor mounted on said wall wherein said proximity sensor is configured to generate an output in response to said spring coming within the sensing distance of said proximity sensor.

6. The air brake monitoring system of claim 5 wherein said non-contact proximity sensor is mounted to extend through said wall.

7. The air brake monitoring system of claim 6 wherein the depth that said non-contact proximity sensor extends through said wall can be adjusted by manipulation from the outside of said brake chamber.

8. The air brake monitoring system of claim 5, 6, or 7 wherein said non- contact proximity sensor is an inductive proximity sensor.

9. A method of installing an air brake monitor system comprising: creating a hole in the wall of a brake chamber; securing a first threaded element over said hole; screwing a proximity sensor into said first threaded element; adjusting a slack adjuster connected to said push rod such that the push rod travel distance during a full brake application is the maximum allowable push rod travel distance; adjusting the depth that said proximity sensor extends through said wall such that the proximity sensor is just triggered; and re-adjusting said slack adjuster such that the push rod travel distance during a full brake application is under the maximum allowable limit.

10. The method of claim 9 wherein the push rod back plate triggers the proximity sensor when the push rod travel distance during a full brake application is the maximum allowable push rod travel distance.

11. A method of claim 9 further comprising: disassembling said brake chamber; attaching a spring on a push rod back plate at a location to be in line with said hole in said wall; and reassembling said brake chamber.

12. The method of claim 11 wherein the spring triggers the proximity sensor when the push rod travel distance during a full brake application is the maximum allowable push rod travel distance.

13. The method of any one of claims 9, 10, 1 1 , or 12 further comprising: threading a second threaded element on said proximity sensor before screwing said proximity sensor into said first threaded element; and securing said proximity sensor in place using said second threaded element after adjusting the depth that said proximity sensor extends though said wall.