Abstract:
An air brake monitoring system which provides a warning signal, either visual or audible, to truckers informing them when their brake system needs corrective attention. More particularly, the system of the present invention permits the brake monitoring system to be easily adjusted to account for the needs and desires of the individual vehicle operator.

Description:
TECHNICAL FIELD OF THE INVENTION 
     The present invention relates to the general art of land vehicles, and to the particular field of brake systems for trucks, more specifically, the invention relates to air brake systems for trucks. 
     BACKGROUND OF THE INVENTION 
     Modern tractor-trailer combination vehicles require a properly functioning braking system in order to stop safely. If any portion of the braking system malfunctions, an unbalanced braking situation may result. For example, if a malfunction occurs in the trailer braking system while the tractor braking system functions normally, jack-knifing may occur. The problem is particularly acute if two or more trailers are involved in so-called “turnpike trains” in which a single tractor pulls two or three trailers. 
     Brake-related problems account for over half of all violations that can bring a highway transport vehicle into an out-of-service state during roadside inspections. Brake problems are also a common cause of transport vehicle accidents, and have been cited as a factor in nearly 30% of all truck related accidents by the Commercial Vehicle Safety Association. For vehicle owners or operators of these vehicles, brake problems can therefore lead to costly downtime and, in the event of an accident, possible liability and insurance expenses. In many cases, status of brake systems is assessed during roadside service inspections. These brake system inspections involve the measurement of the travel distance of the brake push rod to an accuracy level on the order of a fraction of an inch. However, it is estimated that 9% of vehicles that pass this test still have other brake issues that are difficult or impossible to detect without otherwise removing the wheel and/or dismantling the brake system and that warrant an out-of-service violation. 
     In the prior art, heavy duty trucks and other large vehicles are typically equipped with an air brake actuating system. The air brake actuating system applies air to a service chamber to move a diaphragm in a first direction. A push rod typically moves with the diaphragm, and the push rod is connected to a linkage that actuates the vehicle brakes. An emergency chamber is generally also attached adjacent to the service chamber, and is operable to move the push rod in the event that the air system fails. To this end, a high strength power spring is typically incorporated into the emergency chamber to actuate the push rod when there is a failure in the system air line. This spring also typically actuates the push rod when the vehicle is parked. 
     A brake actuator has a predetermined amount of available movement, or stroke, for the push rod. The amount of movement of the push rod required to fully actuate the brakes must be carefully monitored such that it is within the stroke of the brake actuator. The prior art has experienced situations wherein there has been an excessive amount of push rod movement for actuation of the brake system. This excessive required push rod movement can be created by any one of several factors. Typically, excessive movement is due to brake lining wear. As the brakes wear, more movement of the push rod is required to actuate the brakes. Further, as the linkages, connections, etc. between the members connecting the push rod to the brakes bend or become loose or excessively worn, additional push rod movement may be required to adequately stroke the brake. A combination of these several features may sometimes cause the amount of push rod movement required to actuate the brakes to approach the available push rod movement, or stroke, from the brake actuator. This is, of course, an undesirable situation. 
     The prior art has attempted to monitor the amount of push rod movement during actuation of the brake, and provide some indication to an operator of when there is excessive push rod movement. The determination of when there is excessive push rod movement is dependent upon the designed stroke, or rated stroke, of the brake actuator. In addition, an apparatus known as a slack adjuster is typically placed between the push rod and the foundation brake. The slack adjuster is incrementally adjusted to compensate for slack in the braking system and to decrease the required push rod movement. Automatic slack adjusters are now available which automatically adjust the foundation brake system. 
     Therefore, there is a need for a system which constantly monitors each of the brakes of a truck braking system and warns the operator when any brake is operating out of spec. 
     There is a further need for a system which constantly monitors each of the brakes of a truck braking system and warns the operator when any brake is operating out of spec and which identifies the brake in need of attention. 
     It is often uneconomical to change brakes as soon as they begin to operate out of spec. However, there must be a balance between economy and safety. Therefore, there is a need for a brake monitoring system that can be adjusted to account for the need to balance economy with safety. Such a system should warn the vehicle operator that the brakes are entering a range where they should be closely watched and change will be needed soon. Such a system should also be adjustable to be able to accommodate the capabilities and desires of the individual operator. 
     SUMMARY OF THE INVENTION 
     These and other objects are achieved by an air brake monitoring system which provides a warning signal, either visual or audible, to truckers informing them when their brake system needs corrective attention. More particularly, the system of the present invention permits the brake monitoring system to be easily adjusted to account for the needs and desires of the individual vehicle operator. 
     Specifically, the system of the present invention monitors each brake and each monitor includes an electronic microswitch that is activated via the slack adjustor to alert a driver that the truck/trailer brakes need adjustment. One monitor is installed to be associated with each wheel and is connected to a signal light located in the truck cabin. Each monitor is also connected to a signal light located on the outside of the truck. With this arrangement, truckers can automatically receive a warning signal informing them that the brake system needs attention. 
     Other systems, methods, features, and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views. 
         FIG. 1  shows a truck having the brake monitoring system embodying the present invention. 
         FIG. 2  shows a brake chamber assembly which includes a brake monitor embodying the teaching of the present invention. 
         FIG. 3  shows contact between the slack adjuster and the microswitch activating element to activate the system and generate an alert signal when the brake unit associated with the microswitch is not operating in a desired manner. 
         FIG. 4  shows an alternative form of the invention which includes two microswitch activating elements to generate a first alert when the brake unit is nearing an out-of-spec condition and a second alert when the brake unit is actually operating out of spec. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the figures, it can be understood that the present invention is embodied in a system which permits a vehicle operator to monitor the state of the brakes of a land vehicle, such as a truck in a manner which permits the monitoring system to be easily and efficiently customized to meet the particular needs and desires of the vehicle operator. 
     Specifically, the present invention is embodied in system  10  for monitoring the brakes of a truck  14  and generating a signal when a brake unit is in need of attention. System  10  includes a brake system which has a plurality of brake units, such as indicated by reference numeral  20  associated with the wheels of the truck, with each brake unit being associated with a brake of a wheel. 
     The brake units are identical and each brake unit includes a brake chamber assembly  30  which has a diaphragm unit  40  which is operably connected to an air supply via a brake pedal in the truck to be receive air when the brake pedal is actuated as will be known by those skilled in the art. Each brake unit further includes a push rod  50  connected to the diaphragm unit to be moved by the diaphragm unit in direction  52  when the diaphragm unit receives air. A slack adjuster  60  is connected to the push rod to move therewith in direction  62 . Connecting elements  70  connecti the slack adjuster to brake shoes (not shown) of the truck to move those brake shoes a distance which corresponds to the movement of the slack adjuster to slow and/or stop the truck in a manner known to those skilled in the art. 
     A brake unit monitor  80 , such as shown in  FIG. 2 , is associated with each brake unit. Each brake unit monitor includes a base plate  90  mounted on the brake chamber, a first microswitch  100  mounted on the base plate adjacent to the slack adjuster, and a first microswitch activating element, such as spring  110 , mounted on the base plate and connected to the first microswitch to operate the first microswitch when the first microswitch activating element is operated. 
     As indicated in  FIGS. 2 and 3 , the first microswitch activating element is located on the base plate spaced apart from the slack adjuster and in position to be contacted by the slack adjuster when it is operating to apply the brake associated therewith. The first microswitch activating element is located a distance  120  from the slack adjuster so normal operation of the slack adjuster will not have the slack adjuster contact the first microswitch operating element. As is understood by those skilled in the art, as brake elements become worn, the brake elements must be moved farther to engage sufficiently to slow or stop the vehicle. As the brake elements are required to move farther, the push rod, and hence the brake adjuster, must move correspondingly farther. This adjustment is indicated in  FIG. 2  by arrow  122  as being closer to the first microswitch activating element. Therefore, the distance  120  is selected so that when the slack adjuster moves during normal brake operation, there is no interference between the slack adjuster and the first microswitch activating element. However, as the brake elements become worn, the slack adjuster has to move in direction  122  farther to apply the brakes in the desired manner. This condition is indicated in  FIG. 3  by distance  124  which is greater than pre-set distance  120 . As will be understood from  FIG. 3 , the pre-set distance  120  is selected so that the slack adjuster will contact the first microswitch activating element to activate the first microswitch as soon as the brake units are no longer operating in the desired manner. Thus, normal operation of the brakes will not cause interference between the slack adjuster and the first microswitch activating element, but when the brake associated with the monitor is in need of attention, such as when the brake elements are worn, the push rod and hence slack adjuster will have to move farther than normal which allows the first microswitch activating element to be contacted by the slack adjuster when the slack adjuster has moved a pre-set distance to contact the first microswitch operating element and operate the first microswitch. In this manner, each brake unit is constantly monitored and as soon as the brake unit associated with a brake unit monitor begins to operate out of specification, the first microswitch will be activated. 
     A slot  140  is defined in base plate  90  adjacent to first microswitch activating element  110  and first microswitch  100  so the first microswitch activating element can be moved in directions  142  to adjust the pre-set distance. The slot extends from adjacent to plate  144  on which base plate  90  is mounted to adjacent to distal end  146  of base plate  90  so there is a great deal of flexibility in positioning the microswitch and the microswitch activating element with respect to the slack adjuster whereby the vehicle operator or other person in charge of the brakes of the vehicle will have great flexibility in customizing the brake monitoring system to his or her particular needs and desires, The preferred pre-set distance  120  is two inches. The slot is wide enough so the mounting element can be securely fastened to the base plate adjacent to the slot yet can be easily moved along the base plate in the slot. Mounting element  112  on the base plate using slot  140  permits the switch to be moved and customized to accommodate the particular needs and desires of the vehicle operator. That is, one operator may wish to replace the brakes later than another. The first operator may then position element  110  at a location spaced apart from the slack adjuster that differs from the spacing set by the second operator. In fact, an operator can easily change the spacing as his or her needs change. 
     System  10  further comprises a signal system  150  which alerts an operator or other person as soon as one of the brake units is not operating in the desired manner. System  150  includes a first signal element  160  located on a panel  162  located in the truck. First signal element  160  is electrically connected, as by conductors  170 , to the first microswitch of each of the brake unit monitors on the truck to be activated when the slack adjuster of any one of the brake unit monitors moves a distance at least equal to the pre-set distance and contacts the first microswitch activating element to operate the first microswitch. 
     System  150  further includes second signal, such as signal  180  located on the outside of the truck. Second signal  180  is associated with all of the brake units on the truck and is electrically connected to the first microswitch of each brake unit to be activated when the slack adjuster of one brake unit monitor moves a distance at least equal to the pre-set distance and contacts the first microswitch activating element to operate the first microswitch of the one brake unit associated therewith. Thus, when any of the brake unit monitors detects a brake unit operating out of spec, signal  180  will be activated. Signals  160  and  180  can be lights to generate a visible signal, or elements which generate an audible signal, or both as desired. 
     System  150  further includes a plurality of third signals, such as signals  200  and  202 , located on panel  162  inside the truck and which are similar to signals  160  and  180 . Each third signal has one brake unit monitor associated therewith. Each third signal is electrically connected to the brake unit monitor associated therewith to be activated when the slack adjuster of the associated brake unit monitor moves a distance at least equal to the pre-set distance and contacts the first microswitch activating element to operate the first microswitch of the associated brake unit. In this manner, a vehicle operator will be alerted when any of the brakes units is operating out of spec and will be alerted as to which brake unit is the unit in need of attention. 
     When all three signals are in use, an operator will be alerted from either inside or outside the vehicle when there is at least one brake unit in need of attention. When all three signals are in use, the operator can identify which unit is in need of attention. 
     An alternative form of the system is shown in  FIG. 4 . The alternative form of the system includes a warning microswitch activating element  220  near the first microswitch activating element but within the pre-set distance between the slack adjuster and the first microswitch activating element to generate a warning alert when the brake unit is nearing an out-of-spec condition and a second alert when the brake unit is actually operating out of spec. For example, if the pre-set distance  120  is two inches, warning microswitch activating element  220  could be set at one inch so it is activated prior to the activation of switch  100  and alert a vehicle operator that the brake system is close to operating out of spec, but is not yet out of spec. As with the embodiment discussed above, the switches  100  and  220 , and their associated switch activation elements, are mounted on the base plate using slot  140  so they can be moved and adjusted to customize the monitoring and alarms to the individual needs and desires of the vehicle operator. Thus, for example, one operator might be comfortable with the brakes of the vehicle actually out of spec whereas another operator may not be comfortable with the brakes of the vehicle operation within, but close to, spec. 
     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of this invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.