Abstract:
A tool for servicing air brake systems. The tool includes a sliding bar locking mechanism. On one end of the bar is a movable, lockable tubular member; on the other end is a fixed hook member. The tool permits one person working alone to quickly replace an air brake diaphragm.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This patent application relates to air brakes and more particularly to a tool for holding air brake components in position on a vehicle during maintenance procedures. 
     2. Background Information 
     Air brake systems such as those used on semi-trailer trucks typically include one or more air brake assemblies at each wheel. Certain tools are already known for assembling or servicing brake chambers. U.S. Pat. No. 4,776,079 describes a clamping tool for supporting a handbrake while slowly releasing it against the action of a compression spring. This tool serves to securely hold together the brake can and brake drum during repair procedures. The tool includes a pair of handles that pivot with respect to one another and a pair of clamping arms carried by the handle members. One of the clamping arms includes an adjustable support leg. 
     U.S. Pat. No. 6,009,608 describes a device for reassembling a brake system. The device includes a pair of jaws extending outwardly from vice grip type pliers. The upper jaw section has a notch cut out of one end for supporting an upper end of a brake chamber casing. The lower jaw section has an aperture for receiving a lower end of a casing shaft. 
     U.S. Pat. No. 7,942,083 describes a C-clamp locking device especially adapted to depress brake drum springs while brake shoes are replaced. This tool includes a pair of opposing jaws, with a first jaw having a ring disposed perpendicular to a blunt second jaw. Vice-grip type handle portions are used. This tool, while useful in repairing drum brakes, is not particularly helpful in servicing air brake chambers. 
     It is recognized that the safety precautions must be taken when working on or around brake chambers. 
     The purpose of a service brake is to convert the air pressure force generated when the driver steps on the brake pedal into a mechanical push rod action to engage brake shoes or pads. 
     A typical air brake assembly includes a housing (or chamber) with a diaphragm arranged to activate a push rod when air enters the chamber from an inlet. Air pressure is hydraulically controlled via a brake pedal accessible to the driver. A return spring helps to expel the air and return the push rod to its withdrawn position when air pressure is released. A vehicle&#39;s front brake chamber thus includes a housing assembly and diaphragm enclosed within a two-piece housing, the push rod return spring, and a band clamp which holds the two-pieces of the housing together. 
     A rear brake chamber is similar, but can be more complicated, because it often has two chambers, one for the service brake and another for an emergency or parking brake. 
     The emergency/parking brake utilizes a spring brake mechanism. The spring brake mechanism is not controlled by the same compressed air system as the service brakes. The spring brake is applied when air pressure leaves the brake chamber and releases when air pressure builds up in the chamber. Spring brake chambers work by means of a large coil spring that provides enough force to hold the brakes in the applied position instead of air. The spring brake section is, in effect, piggybacked onto a service brake section but these two sections function as two separate systems. 
     SUMMARY 
     Statement of the Problem 
     Air brake systems typically provide little warning of the need for repair. Their demise is usually a sudden event, accomplished by agonizing sound of escaping air. While broken springs can seem to account for some catastrophic failures, it is more common for a leaking diaphragm to require immediate repair while the truck is on the road. Usually the air brake chamber failure starts when one of the internal springs, fatigued by repeated application and rust introduced by road chemicals, breaks into several pieces. This condition then goes unnoticed because the remaining brakes continue work just fine. Eventually, however, the jagged broken parts poke a hole in a diaphragm (also called a “pancake”). This can lead to an expensive and time consuming roadside repair. 
     Thus there is a need to replace an air brake diaphragm as quickly as possible while on the road, by one person working alone, and preferably without having to remove the air brake from the vehicle. Since opening the brake chamber can be hazardous, it can be quite awkward to service brake chambers outside of a workshop with standard tools. 
     Accordingly, there is presented herein a new tool used for servicing an air brake. The tool includes a sliding bar clamp having a movable jaw at one end. The movable jaw can be lockably positioned along the bar by activating a ratcheting handle. A tube is attached to the movable jaw and engages an anchor bolt on an outboard end of the air brake. A hook member is fixed to the other end of the bar to engage a push rod of the air brake. The hook end may be reversible by repositioning fasteners or via a swivel. With the tool in place, a band clamp can now be safely removed. Releasing the moveable jaw allows separating the parts of the housing to access and replace the diaphragm. Ratcheting the movable end closed again realigned the housing parts, enabling the band clamp to be refastened. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention description below refers to the accompanying drawings, of which: 
         FIG. 1  is a perspective view of an air brake diaphragm service tool. 
         FIG. 2  is a plan view of the tool being attached to a brake chamber on a vehicle. 
         FIG. 3  is another view of the tool and brake chamber after a jaw of the tool has been released to open a housing clamp to access the air brake diaphragm. 
         FIG. 4  is a view showing reassembly of the brake chamber. 
         FIG. 5A  is a detailed view of a tubular head end of the tool. 
         FIG. 5B  is a detailed view of the hook end. 
         FIG. 6  shows an embodiment with a swivel hook. 
         FIG. 7  is a more detailed view of the swivel hook components. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a perspective view of an air brake service tool. The tool is used to disassemble and then reassemble an air brake chamber while the air brake remains on the vehicle. The tool is especially adapted for orderly removal of a band clamp, housing disassembly, swapping out the pancake diaphragm, reassembly of the housing, and reattachment of the band clamp. The tool avoids the need to support an inboard end of the air brake camber with a second pair of hands or a jack or some other arrangement. 
     More particularly, the tool  10  consists of a Quick-Grip® style clamp mechanism  12 , including a head (or jaw)  14 , handle  18 , trigger  19 , and release  20 . Utilizing handle  18  and release  20  the head  14  is freed to slide back and forth along a bar  22 . Head  14  includes a structure  17  serving to support a tubular head  16 . 
     On the end of arm  22  opposite tubular head  16  is a reversible anchor hook assembly  30 . Hook assembly  30  consists of hook portion  25  and base portion  26 . Base portion  26  has a number of threaded holes  23  adapted to engage fasteners  24 . The holes  23  and fasteners  24  enable the hook  25  to be reversed 180° from the position shown in  FIG. 1 . Also on either side of hook  25  are standoffs  28 . The standoffs  28  help position the tool  10  on the brake chamber housing as will be shown in other figures and described below. 
     The position of the tubular head  16  can be adjusted left or right along bar  22  and locked into place by operating clamp handle trigger mechanism  19 . Clamp mechanism may operate in a manner such as a ratcheting clamp known as a Quick-Grip® clamp. Such clamps available from Irwin Tools®, or the E-Z Hold® clamps from Jorgenson®, or other similar products may be suitable. Still other types of bar clamps, pipe clamps and other may be used as long as they provide a jaw that can be moved along the bar and clamped in position. 
       FIG. 2  shows the tool  10  in an initial position after being attached to an air brake chamber  40 . The air brake chamber  40  remains in place on a vehicle such as attached to the vehicle by bracket  58 . The air brake assembly  40  consists of a housing base  41  and emergency and/or parking brake spring housing  47 . In operation of the service brake, a cam is rotationally activated when the brake pedal is depressed, to move a slack adjuster  56  and yoke  54  and in turn move push rod  52  outwards. This causes a diaphragm (positioned internal to housing  41  and not visible in  FIG. 2 ) to cause a shoe or pad to engage a service brake drum or disk (not shown). Return springs  32  and/or  33  return the diaphragm to its unloaded position when the brake pedal is released and push rod  52  retracted. 
     Also shown in  FIG. 2  is that a spring anchor safety bolt  48  has been inserted into the housing  44 . The anchor safety bolt  48  is used to pull back a coil spring portion  31  of the emergency brake during servicing. In particular, the anchor safety bolt  48  is threaded in the outboard end of housing  44  to engage the parking/emergency brake coil spring  31  thus releasing it from tension. This then enables service personnel to safely release fasteners  43  on service brake clamp  42  to access the diaphragm inside the housing. 
     To use the tool  10  to service the diaphragm, the tool  10  is placed on air brake  40  assembly such that the inner arch of hook  30  is placed over the top of push rod  52 . The tubular end  16  is then aligned with the anchor bolt  48 . The Quick-Grip® clamp  12  is then tightened by operating trigger  19  causing ratcheting head  14  to move tubular member  48  towards the left. This in turn causes tubular member  16  to enclose the anchor bolt  48  and eventually press against the outboard face  44  of spring brake housing  47 . 
     Thus with the tool  10  now firmly engaging the parts of air brake assembly  40 , the user can safely and easily access the inside of the housing by unfasten the two-piece band clamp  42  such as by loosening threaded fastener(s)  43 . 
     The ability to swap the hook from one orientation to the opposite orientation is useful since the orientation of the tool  10  needs to be different on the left and right sides of the vehicle. In particular, the hook end  30  is placed adjacent the push rod  52  portion of the air brake which is typically located on the inboard side of the air brake  40 . The tubular end  16  also engages an anchor bolt  48  that is always on the outboard end of the air brake regardless of the side of the vehicle being serviced. 
       FIG. 3  shows the tool  10  and air brake  40  after the two-piece clamp  42  is removed enabling the housing sections to be opened. Here the head  14  has been now disengaged from bar  22  using release handle  20  allowing the housing sections  40  and  46  to be separated. This allows the user to now remove and replace diaphragm  50 . In this position, with the standoff  28  held in place against the outward face of housing base  41 , push rod  52  still serves as a place to support hook  30 . The inner portion of tubular head  16  also still engages and supports the other side of air brake via anchor safety bolt  48 . This allows a single user of tool  10  to easily access diaphragm  50  while ensuring that the other relatively heavy components such as base  40 , housing midsection  46 , and so forth remain more or less aligned along an axis parallel to bar  22  for ease of reassembly. 
       FIG. 4  illustrates reassembly of the air brake chamber  40  using tool  10 . Diaphragm  42  is replaced in position between housing base  40  and midsection  46 . Trigger  19  is then again engaged to move ratchet head  14  to the left, causing tubular portion  16  to again fit snugly against face  44  of section  46 , and for hook  30  and inner standoff  28  to press against housing base  40 . The two pieces of the band clamp  42  can then be reattached to the housing sections by tightening fastener(s)  43 . 
     It can now be understood that while tools in the prior art may assist with assembly of air chambers on a workbench, they do not provide much assistance with an “on the truck” repair that might be necessary to complete by a person working alone. An on-truck repair requires disassembly, swapping out the pancake and reassembly of the various pieces of the brake chamber in position against housing base while the service brake clamp is reattached ideally by just one person. The tool  10  described herein achieves this end. 
     The tool can also be used for other procedures. For example, along with use for replacement of the pancake diaphragm, it should also be noted that the tool  10  can be used to engage the air brake assembly for the replacement of the parking brake chamber  46 . The parking brake subassembly is prone to fail independently of the service brake pancake. 
       FIG. 5A  is a detailed view of the tubular head  16 . It is typically implemented as a hollow cylinder having an inner diameter wide enough to slide over anchor bolt  48  and yet small enough to hold tool  10  in place while the housings of the air brake chamber  40  are disassembled. 
       FIG. 5B  is a more detailed view of the inner arch portion of hook end  30  placed against push rod  52 . Also seen is the inboard standoff  28  pressing against the inboard face of housing base  40 . 
       FIGS. 6 and 7  show an alternate embodiment of hook end  30  using a swivel arrangement to allow positioning the hook in either orientation. This swivel arrangement  72  consists of a pair of side plates  74  sandwiching either side of the bar  22 . Fasteners  76  hold the side plates  74  in position threading into holes in the side plates  74 . 
     A hollow tube  80  on the outboard end of side plates  74  holds shaft  70  with the attached hook  60 . The centerline of the hook  60  (that is, the peak of the inner arch where the hook contacts the brake pushrod) and the swivel post presented at the centerline of hollow tube  80  should be designed to be directly in line with each other. With these in alignment, even pressure is kept on the on the assembly when clamping force is applied by tool  10 . 
     Hook  60  is thus otherwise free to swivel about with shaft hollow tube  80 . Washer  82  and locking collar  78  hold the shaft  70  in vertical position in tube  80 . Standoffs  62  and  66  are placed on the swivel hook  60  serving the same function as the standoffs  28  in the fixed hook arrangement previously described in  FIG. 1 .