Abstract:
A training tool for teaching the operation of the brake elements of a heavy duty air brake system is disclosed. Brake elements are replicated on a stand which also supports a compressed air tank and compressed air lines which couple compressed air to a brake chamber which is included in the air braking system of an air brake equipped vehicle. The brake drum of the training tool is partly cut away so that a trainee can observe the mechanical operation of the brake elements housed within the brake drum. A slack adjuster is carried on a simulated axle on which the brake drum is supported. A brake pedal is carried on the stand to activate the brakes and to facilitate a quick understanding of the interaction between the brake pedal and the brake shoes located within the brake drum. A dash valve is provided on a simulated dashboard segment so that operation of the parking brake system can be demonstrated to an observer.

Description:
CROSS REFERENCE TO PENDING APPLICATION  
       [0001]     This application claims priority from copending provisional patent application entitled “Air Brake Training Tool”, Ser. No. 60/605,050 filed Aug. 27, 2004. The disclosure of provisional patent application Ser. No. 60/605,050 is hereby incorporated in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention pertains to the adjustment of air powered brakes on trucks and other large vehicles, and particularly to training of drivers and mechanics for such vehicles, in the proper adjustment of the slack adjusters used to adjust the brakes.  
         [0003]     Large trucks and buses are typically equipped with air powered service brakes which are operated by compressed air. In addition, the parking brakes of such vehicles are engaged by complete release of compressed air from the air brake system. Due to wear, the brakes of such vehicles need adjustment of the spacing of the brake shoes from the brake drums so that application of the brake pedal of the vehicle will cause proper forcing of the brake shoes against the brake drums.  
         [0004]     The distance of brake shoes from each brake drum when no braking is applied is controlled by a member of the braking system known as the slack adjuster which is moved by a tie rod driven by an actuating member known in the industry as the brake chamber. The slack adjuster angularly positions cam elements which apply separating force to the brake shoes of a brake drum. The slack adjuster may be adjusted so that the brake shoes are properly separated from the brake drum when no braking force is needed and properly forced against the brake drum when braking is needed.  
         [0005]     The conventional method of adjusting the brake adjusters for each wheel is to crawl under the axles of the truck and to apply wrench force to an adjustment screw on the slack adjuster. Because proper brake adjustment is a regulatory requirement on United States highways, the brakes will be inspected by regulatory personnel at inspection opportunities. If a brake system of a wheel is found to be out of adjustment, the driver is forbidden to proceed until the brake system is brought into specification compliance. As a result it is quite useful for a driver of an air-brake equipped vehicle to know how to make the fairly straight forward adjustment of the slack adjusters.  
         [0006]     Conventionally, drivers may be trained to make proper slack adjuster adjustments on a one-on-one basis by crawling under a truck with an instructor to lie under the truck axle at the location of the slack adjuster. There the student driver may be shown the method to adjust the slack adjuster. Because of the inconvenience of such training techniques, frequently drivers operate trucks without the training to make proper brake adjustments, in which case the driver must wait for a service technician to arrive to adjust the brakes when they are found out of adjustment. This possibility leads to excessive down time for the truck and driver.  
         [0007]     No training tool exists to instruct a group of students at one time as to the adjustment of slack adjusters, nor to allow an instructor and one or more students to observe the operation of the brake shoes as the slack adjuster is adjusted without crawling under a truck axle.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention provides a training tool for teaching the operation of the brake elements of a heavy duty air brake system. Brake elements are replicated on a stand which also supports a compressed air tank and compressed air lines which couple compressed air to an actuator which is known in the industry as a “brake chamber”. The brake chamber is included in the air braking system of an air brake equipped vehicle.- The brake drum of the training tool is partly cut away so that a trainee can observe the mechanically operative elements of the brake equipment housed within the brake drum. A slack adjuster is carried on an axle on which the brake drum is supported. A brake pedal is also carried on the stand to provide the trainee with standard components in the truck cab and to facilitate a quick understanding of the interaction between the brake pedal and the brake shoes located within the brake drum. While standing, a trainee may practice operating the brakes and be instructed about the adjustment of the slack adjuster of the air brake system.  
         [0009]     A pull out control knob is provided on the training tool which replicates a “dash valve” found on the dashboard of an air-brake equipped truck which is used to set the parking brakes of the truck. When the control knob is pulled out, air is exhausted from the parking brake chamber causing the brake shoes to be maximally applied against the brake drum. The operation of the parking brake system may be understood by use of the replicated dash valve.  
         [0010]     It is a primary object of the present invention to provide a training tool to teach the operation of the brake system of a vehicle equipped with air brakes. It is also an object of the invention to provide a training tool which allows the instruction of a group of truck drivers about the adjustment of the slack adjuster components of a heavy duty air brake system. Further it is an object of the invention to facilitate the training of drivers of heavy trucks to be able to adjust the slack adjusters of the air braking system of a truck while in the field and without the assistance of a service technician. It is yet another object of the invention to provide a useful training tool for classroom teaching of student truck drivers and to train truck mechanics for proper brake adjustments.  
         [0011]     The foregoing and other objects of the present invention will be understood from a careful examination of the detailed description which follows. 
     
    
     DESCRIPTION OF THE DRAWING FIGS.  
       [0012]      FIG. 1  is a front elevation of the preferred embodiment of the invention with the air ducts shown schematically.  
         [0013]      FIG. 2  is an enlarged perspective of the simulated axle and brake drum assembly of the invention.  
         [0014]      FIG. 3  is a schematic diagram of the operational parts of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]      FIG. 1  discloses an air brake training tool  2  characterized by the present invention with the air lines thereof diagrammed schematically to assist in understanding of the disclosure. Training tool  2  comprises a frame  6  supporting a simulated truck axle housing provided by pipe segment  44  to which is mounted a brake drum assembly  52 . Brake drum assembly  52  comprises brake drum  28 , brake shoes  24 ,  26 , and cam followers  20 ,  22 . Frame  6  may be sized to position the brake drum assembly  52  at a height which may be comfortably viewed by a user while standing. Frame  6  supports compressed air tank  4  which may be substituted with a continuous supply of compressed air. Air tank  4  is coupled by pedal duct  64  to a pedal operated air valve  66  controlled by foot pedal  10  which is carried on pedal bracket  12 . Pedal operated air valve  66  is further coupled to first air duct  68  which is joined to a brake actuator which is known in the industry and shall be referred to in this disclosure as brake chamber  8 .  
         [0016]     Now referring additionally to  FIG. 2 , in the preferred embodiment, a segment of sidewall  29  of brake drum  28  is removed creating observation opening  32  through which the action of cam  18 , cam followers  20 ,  22 , and brake shoes  24 ,  26  may be examined. A second observation opening  33  is disposed in the opposing side of brake drum  28  to allow observation of brake drum components from the opposite side of the brake drum  28 . Brake chamber  8  comprises service brake chamber  30  and parking brake chamber  42 . Pedal operated air valve  66  is selectively operated by pedal  10  such that pressurized air in tank  4  may be transferred through first air duct  68  to service brake chamber  30  of brake chamber  8  as pedal  10  is depressed, while when pedal  10  is released to return to its rest position, air pressure in service brake chamber  30  of brake chamber  8  is exhausted through pedal operated air valve  66  into the atmosphere. Pedal operated air valve  66  regulates the air pressure present within service brake chamber  30  of brake chamber  8  releasing the air pressure as the pedal  10  is allowed to come to its rest position at which it is not depressed. It is to be understood that air pressure must be elevated in parking brake chamber  42  for the service braking system is to be operated, as is true for the prototype truck.  
         [0017]     Frame  6  is sufficiently tall to allow a user to comfortably observe the action of cam  18 , cam followers  20 ,  22 , and brake shoes  24 ,  26  while standing or sitting. A user may operate foot pedal  10  thereof while standing.  
         [0018]     Frame  6  may comprise fixed alignment casters  84  supporting first legs  58  of frame  6  and swivel casters  86  which support second legs  54  thereof, such that training tool  2  may be moved easily around a training facility. Lock mechanism  88  is provided on swivel casters  86  to allow the user to selectively prevent further movement of training tool  2  when it is in position to be used for training. First legs  58  and second legs  54  may be sufficiently tall to position brake drum assembly  52  at an easily viewed height, that is, at approximately three to five feet off a floor surface, and such that a user may operate foot pedal  10  with the user&#39;s foot while still observing the brake shoes  24 ,  26  and the slack adjuster  14  of training tool  2 .  
         [0019]     To simulate service air brake operation of a heavy motor vehicle such as a truck, depression of the brake pedal  10  causes elevation in air pressure in the service brake chamber  30  of brake chamber  8  which causes brake chamber  8  to extend push rod  46  which is hingedly coupled to lever arm  15  of slack adjuster  14 . Slack adjuster  14  is received on shaft  16  which is journaled in first bearing housing  48 . First bearing housing  48  is securely mounted to pipe segment  44  and supports shaft  16  allowing it to rotate with slack adjuster  14 . Shaft  16  is joined to actuator cam  18  which, when rotated forces cam followers  20 ,  22  to separate, thereby moving brake shoes  24 ,  26  outward to touch and frictionally interact with the inside surfaces of brake drum  28 . As air pressure in service brake chamber  30  of brake chamber  8  decreases, push rod  46  is retracted into brake chamber  8 , causing slack adjuster  14  to reversely rotate toward its rest position which in turn rotates shaft  16  resulting in brake shoes  24 ,  26  disengaging from their touching engagement with the interior of brake drum  28 .  
         [0020]     As brake pedal  10  is released, air pressure is bled from service brake chamber  30  into the atmosphere by pedal operated valve  66 . Thus as the air in first air duct  68  decreases in pressure, brake chamber  8  is caused to retract push rod  46  which causes slack adjuster  14  to rotate in a reverse direction about the centerline of shaft  16 . The reverse rotation of shaft  16  rotates cam  18  which allows cam followers  20  and  22  to approach each other, thereby reducing the outwardly directed force of brake shoes  24 ,  26  against brake drum  28 . Spring  50  assists in urging brake shoes  24 ,  26  to separate from brake drum  28 .  
         [0021]     In order to train truck mechanics or drivers who may be called upon to adjust slack adjusters on a truck, training tool  2  assists to elucidate the operation of air brake shoe operation and the proper adjustment of slack adjusters. Using training tool  2 , the effect of adjustment of adjustment bolt  34  of slack adjuster  14  may be demonstrated. A trainee may observe the movement of the brake shoes  24 ,  26  in relationship to brake drum  28  when the brake pedal  10  is depressed and released. Once this operation is understood, the trainee may be instructed on the proper separation of brake shoes  24 ,  26  from brake drum  28  when the brake pedal  10  is at rest, that is, not depressed. The proper gap between the shoes  24 ,  26  and brake drum  28  when the brake pedal is at rest is a matter of specification for a heavy duty air brake system. When the gap is excessive, an increase of air pressure in service brake chamber  30  from air tank  4  due to depression of brake pedal  10  will fail to adequately force the brake shoes  24 ,  26  against the brake drum  28  and insufficient braking will result.  
         [0022]     Adjustment to achieve the proper separation of brake shoes  24 ,  26  from brake drum  28  is accomplished by altering the relative position of rotation of slack adjuster  14  about shaft  16 . This adjustment is accomplished in the type of slack adjuster illustrated as slack adjuster  14  by manual rotation of the adjusting bolt  34 . As adjusting bolt  34  is rotated, slack adjuster  14  forces shaft  16  to be incrementally rotated which results in an altered rest position of cam  18 . Hence, when slack adjuster  14  is caused to rotate by extension of push rod  46  from brake chamber  8  in response to increasing air pressure within service brake chamber  30 , slack adjuster  14  will rotate shaft  16  and cam  18  will move brake shoes  24 ,  26  toward brake drum  28  a proper distance.  
         [0023]     The adjustment of slack adjuster  14  and the effect thereof is easily understood by use of training tool  2 . Training tool  2  allows a group of trainees to be instructed at the same time because the brake training tool  2  provides easy observation of the effect of adjustment of the slack adjuster  14 . Any trainee or user of training tool  2  may observe the operation of brake shoes  24 ,  26  relative to brake drum  28  while standing or sitting. Furthermore, a trainee or user may manually adjust adjusting bolt  34  of slack adjuster  14  while standing or even while sitting on an appropriately tall and closely located stool or chair. Training tool  2  allows an improvement in training technique over current training which necessitates both the instructor and trainee to crawl beneath a truck to view and adjust the slack adjuster in place on a truck axle.  
         [0024]     In the case of the operation of the parking brake system of an air brake equipped vehicle, a parking brake valve known as the “dash valve” is provided on the truck dashboard which is used to fully activate the brakes of the truck when it is parked. In the training tool  2 , parking brake operation is simulated by use of a dash valve knob  36  mounted upon a panel  38  which may simulate a truck dashboard. Also mounted to the panel  38  is an air pressure gauge  40  which is coupled to the air tank  4  to monitor air pressure present in the brake system. When the dash valve knob  36  is drawn out from the panel  38  to a “brake engaged” position, air pressure in the second air duct  80  is released, causing a spring (not shown) within parking brake chamber  42  of brake chamber  8  to extend push rod  46  thereby moving free end  17  of lever arm  15  of slack adjuster  14  and in response rotating shaft  16 , causing cam  18  to rotate and force brake shoes  24 ,  26  into positive frictional contact with brake drum  28 . When the parking brake is to be applied the abutment of brake shoes  24 ,  26  must be firm against brake drum  28  and will only be released when dash valve knob  36  is pushed in, that is, returned to “brake released” position. In that position, air pressure in air tank  4  will be coupled to parking brake chamber  42  of brake chamber  8  through parking brake supply duct  78 , causing the spring within parking brake chamber  42  to compress and retract push rod  46 .  
         [0025]     From observation of  FIG. 1  it can be seen that an inlet  60  including a ball valve may be included to allow addition of compressed air to air tank  4 . A pop-off valve may be placed in the wall of air tank  4  such as at the coupling of pedal duct  64  to air tank  4  for a safety relief valve in case of excessive pressure in air tank  4 .  
         [0026]     Because slack adjusters vary from vehicle to vehicle, hooks  56  may be provided on leg  54  of frame  6  to facilitate storage of alternative slack adjusters  55 ,  57  which may be interchanged with slack adjuster  14  as desired. Because the adjustment features of alternative slack adjusters  55 ,  57  vary from that of adjusting bolt  34 , the replacement of slack adjuster  14  with one of alternative slack adjusters  55 ,  57  permits the instruction of trainees as to methods to adjust more than only a first type of slack adjuster.  
         [0027]     Referring to  FIG. 3 , the operational system of the invention is shown schematically. A supply of compressed air may be introduced to air tank  4  through inlet  60  or a constant source of compressed air may be attached to inlet  60  when repeated operation of the simulator training tool  2  will deplete the supply of compressed air in the system. Gauge line  62  communicates compressed air from air tank  4  to pressure gauge  40  so that the residual compressed air pressure may be monitored. Pedal duct  64  supplies compressed air to pedal operated air valve  66  which is controlled by foot pedal  10  (see  FIG. 1 ). Pedal operated air valve  66  remains closed until foot pedal  10  is depressed, whereupon air under pressure in air tank  4  is permitted to pass from pedal duct  64  into first air duct  68  through first inlet port  70  and into service brake chamber  30  in which a diaphragm (not illustrated) is moved by the increasing air pressure. As foot pedal  10  is released to return to its undepressed position, compressed air in service brake chamber  30  is allowed to escape to the atmosphere via pedal exhaust port  74 . As air pressure in first air duct  68  declines, the diaphragm in service brake chamber  30  of brake chamber  8  retracts push rod  46  causing slack adjuster  14  to rotate shaft  16  in a clockwise direction as diagrammed in  FIG. 3 . As foot pedal  10  is released, pedal operated air valve  66  gradually opens the connection between first air duct  68  and pedal exhaust port  74  causing air pressure in service brake chamber  30  to decline, which allows push rod  46  to retract in response to bias of an internal spring (not shown), thereby rotating slack adjuster  14  in a clockwise direction (as viewed in  FIG. 3 ) and releasing the force of cam  18  against cam followers  20 ,  22  (see  FIG. 2 ).  
         [0028]     Parking brake valve  76  is controlled by dash valve knob  36  (see  FIGS. 1, 2 ). When dash valve knob  36  is pulled out, communication between parking brake supply duct  78  is interrupted from second air duct  80  and air in second air duct  80  is exhausted to the atmosphere through second exhaust port  82 . With no pressurized air in second air duct  80  which is coupled to parking brake chamber  42  of brake chamber  8  by second inlet port  72 , air cylinder  8  extends push rod  46  fully, causing slack adjuster  14  to activate the brake shoes  24 ,  26  (see  FIG. 2 ) fully. When parking brake dash valve knob  36  is pushed in, compressed air in parking brake supply duct  78  is once again allowed by parking brake valve  76  to pressurize spring brake chamber through second air duct  80 , causing brake chamber  8  to retract push rod  46  and thereby to rotate slack adjuster  14  and shaft  16  clockwise, releasing the grip of brake shoes  24 ,  26  on brake drum  28 .  
         [0029]     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.