Abstract:
A tool for attaching and disengaging a return spring in a truck brake assembly comprises a handle, a shaft, and an arm with a hook and a smaller reverse hook. The hook provides leverage around the spring retainer and the reverse hook engages the spring end to move it into place.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application 61/463211, filed Feb. 11, 2011. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to servicing of the brakes on large trucks, primarily tractor-trailer configurations. It provides a convenient tool for the disassembly and reassembly of the wheel-mounted portion of the brake mechanism when the unit must be serviced 
         [0003]    A typical configuration for truck/trailer air brakes is a pair of approximately semi-circular components called “shoes,” each contacting half of a circular brake drum surrounding the axle of the vehicle. Brake pads, which may be metal or ceramic composites designed to withstand the heat and pressure of substantial friction, are attached to the outer surface of the shoes. When a brake pedal is depressed, a compressed air delivery network causes a cam to turn, which pushes the brake shoes outward, causing the pad to frictionally engage the surrounding drum as it rotates, slowing its motion to a stop. 
         [0004]    The brake shoes are attached to a spider, a round plate on the end of the axle, by anchor pins or other components. The brake shoes are movably secured to each other by springs, so that after the brake pedal is released, the shoes and pads withdraw from contact with the drums. Most brake assemblies have one or two retainer springs on one side of the axle and a return spring on the side of the axle adjacent the cam. The return spring must quickly pull the shoe away from the drum when the brake is released, and such springs are very strong, often 100 lb tension or more. When truck brakes are serviced, the shoes must be removed to replace the pads, and this entails stretching the retainer and return springs to remove them from their anchor positions. These springs are usually replaced as part of the service. The return spring, in particular, is difficult to stretch, and service personnel must find a way to carefully apply leverage to accomplish this. When standard tools, such as screwdrivers, pry bars or pliers are used, frustration and injuries can result as the spring slips from the tool. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The present invention provides a tool for removing and for reattaching the return spring on the most common air brake configuration in the industry, the Q and Q Plus brake systems made by the Arvin Meritor Corporation. It may also be useful in handling the return spring in other systems. The tool incorporates a handle, a shaft, and a double curved hook that enables a mechanic to engage and release the return spring with a twist of the device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0006]      FIG. 1  is a depiction of a truck air brake assembly; 
           [0007]      FIG. 2  is a diagram showing a step in removal of a brake assembly; 
           [0008]      FIG. 3  is a diagram showing a second step in removal of a brake assembly; 
           [0009]      FIG. 4  is a diagram showing the first step of installing a brake assembly; 
           [0010]      FIG. 5  is a diagram showing the second step of installing a brake assembly; 
           [0011]      FIG. 6  is a view of an embodiment of the invention; 
           [0012]      FIG. 7  is another view of the embodiment of  FIG. 6 ; 
           [0013]      FIG. 8  is a view of the distal end of an embodiment of the invention; 
           [0014]      FIG. 9  shows a step in attaching a return spring; 
           [0015]      FIG. 10  shows a step in attaching a return spring; 
           [0016]      FIG. 11  shows a step in attaching a return spring; 
           [0017]      FIG. 12  shows a step in attaching a return spring; 
           [0018]      FIG. 13  shows a step in attaching a return spring 
           [0019]      FIG. 14  shows a step in attaching a return spring. 
       
    
    
     DETAILED DESCRIPTION  
       [0020]    The configuration of the Q and Q Plus brake assemblies is shown in  FIG. 1 . Brake shoes  10  with attached pads  11  are on top and bottom halves of a circular configuration. Cam  14 , when rotated by the air pressure system activated by the driver&#39;s brake pedal, forces the shoes outward so the pads contact the surrounding drum (not shown) and slow the rotation of the wheel. A pair of retaining springs  15 , hooked through apertures  13  in the web  12  of the shoe  10  on the opposite side from the cam  14 , and a return spring  30  hooked over upper and lower return spring retainers  35 ,  36  hold the shoes together. 
         [0021]    The recommended method for disassembly of the brake involves releasing the return spring  30  first, then the retaining springs  15 . See  FIGS. 2&amp;3 . Similarly, on assembly the retaining springs  15  are set, the return spring retainers  35 ,  36  are inserted, and the return spring  30  is attached. See  FIGS. 4&amp;5 . Because of the strength of the return spring, particularly when a heavy duty spring is used, a tool is needed to stretch the spring over the retainer. Mechanics may use a long screwdriver, a pry bar or long-handled pliers to pull the spring end over the retainer. These tools sometimes slip, resulting in frustration and occasional hand injuries. 
         [0022]    The present invention is a tool configured to stretch a return spring onto or off of the retainer bar. One embodiment of the tool is shown in  FIGS. 6-8 . It comprises a handle  21 , an extended shaft  22 , a short arm  23  at approximately a right angle  24  from the shaft  22 , a first hook  25  in a plane approximately perpendicular to the plane of the shaft  22  and a short reverse hook  26 . An embodiment of this type may be fabricated by bending a single ⅜ inch steel rod into the appropriate shape. In one embodiment, the extended shaft is about 6 inches long, the arm of the first hook is about 2½ inches with a ½ inch curvature radius at its end and the short hook has a ¼ inch reverse curvature radius extending in a plane parallel to that of the shaft and rotated at an angle  27  of about 45 degrees in a direction away from the handle. 
         [0023]    The reverse hook  26  may be in the same plane as that of first hook  25 , meaning that angle  27  is zero degrees, or it may be rotated as much as about 90 degrees away from the handle  21 . Preferably the rotation angle  27  is between about 5 degrees and about 65 degrees, and more preferably it is about 45 degrees. The handle  21  is for grasping and operating the tool with sufficient leverage to extend the return spring  30 , and may be of any configuration, including a simple extension of the shaft  22 . 
         [0024]    Using the tool to attach the heavy duty return spring is illustrated in  FIGS. 8-12 . With the shoes set in place on the spider and the retaining springs in position, the lower return spring hook  31  is hooked over the lower return spring retainer  35  and the upper return spring hook  32  is placed next to the in-place upper return spring retainer  36 . The first hook  25  of the tool is hooked around the retainer  36  and the short hook  26  of the tool engages the upper return spring hook  32 . Rotating the tool about the retainer  36  as a fulcrum stretches the spring and pulls its hook end toward the retainer. With a twist of the tool, the spring hook is pulled over the retainer and can be released onto the retainer, completing the installation. To remove the return spring, the steps are reversed. The tool&#39;s first hook is hooked over the retainer and the short hook engages the spring hook. The retainer is used as a fulcrum to stretch the spring, and twisting the tool moves the upper hook of the spring away from the retainer, thereby releasing the spring. 
         [0025]    The foregoing description has been presented and is intended for the purposes of illustration and description. It is not intended to be exhaustive nor limit the invention to the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application and to enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed for carrying out the invention.