Abstract:
A repair kit for a vehicle brake slack adjuster provides C-shaped reinforcement plates that may be clamped on opposite sides of a damaged stabilizer anchor tab to repair the same without removal of the slack adjuster.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application 60/878,644 filed Jan. 5, 2007 hereby incorporated by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Background of the Invention 
     The present invention relates to vehicle brake systems and in particular to a repair kit for repairing a brake slack adjuster providing automatic brake adjustment. 
     Vehicle brakes work by frictional contact between a rotating element attached to the vehicle wheels, for example a brake drum or brake disk, and brake pads attached to the vehicle to press against this rotating element when a brake pedal is engaged. The mechanical advantage required to ensure sufficient braking force means that the movement of the brake pads is small with respect to movement of the brake pedal. As a result, small amounts of wear in the brake pads can result in substantial changes in height of the brake pedal even to the point where the brakes may no longer be operated. Accordingly it is known to provide for automatic adjustment of the brake “slack” or spacing between the brake pads and rotating element, through use of a “slack adjuster” mechanism. 
     Slack adjuster mechanisms and their operation are described generally in U.S. Pat. No. 4,484,665 entitled: “Brake Adjuster”; U.S. Pat. No. 5,327,999 entitled “Brake Lever For An S-Cam Automotive Drum Brake”; and U.S. Pat. No. 5,626,210 entitled: “Control Arm Arrangement For A Brake Lever” each hereby incorporated by reference. A common type of slack adjuster includes a slack adjuster body fitting about an S-cam shaft to rotate and S-cam when a lever of the slack adjuster is moved, for example, by a hydraulic cylinder. An internal mechanism of the slack adjuster may require a stationary reference point obtained, for example, by means of an anchor tab having an orifice receiving a locator pin attached to the vehicle frame. The orifice may include a wear reducing plastic insert. 
     The orifice of the anchor tab may be damaged or worn by constant use and the high forces associated with the braking mechanism. As the orifice enlarges, hammering between the orifice and the locator pin may generate mechanical noise as well as accelerate the failure of the orifice thus not allowing the slack adjuster to adjust properly. In these cases, the slack adjuster must be wholly removed from the brake assembly for repair or replacement at considerable expense. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a repair kit for slack adjusters that may be used when the orifice in the anchor tab of the slack adjuster has been enlarged or damaged by wear. The repair kit provides C-shaped elements that may fit about the anchor tab and locator pin without removal of the slack adjuster. Locator elements on the C-shaped elements securely engaged the anchor tab when the C-shaped elements are clamped together about the anchor tab. The present inventors have determined that the surface area and locator elements of the C-shaped elements provides a sufficient force transmission for reliable repair of these critical devices. 
     Specifically, the present invention provides a repair kit for a slack adjuster, the latter communicating with brake pads to provide for automatic slack adjustment of vehicular brakes, where the slack adjuster has a body fitting rotatably about a shaft and has a radially extending tab with an orifice for receiving a stationary locator pin. At the repair kit includes a first and second C-shaped element, the C-shaped elements defining a slot having a width corresponding to a width of the locator pin, each C-shaped element having opposable faces, at least one face including a locator element extending from the face to align the face with the anchor tab when the face is placed against the anchor tab. Clamp elements allows compression of the C-shaped elements together so that their faces contact corresponding opposed faces of the anchor tab with the locator element aligning the slot with the orifice. 
     It is thus one object of an embodiment of the invention to provide a method of repairing slack adjusters that does not require removing the slack adjuster from the locator pin and that may handle a wide variety of damaged anchor tabs by stabilization against the anchor tab face. 
     The locator element may be a lip fitting in part within the orifice when the C-shaped elements are clamped about the anchor tab. 
     It is thus an object of an embodiment of the invention to provide for resistance to movement of the C-shaped elements by positive engagement with an inner surface of the orifice. 
     Alternatively or in addition, the locator element may be a boss positioned outside of the anchor tab when the C-shaped elements are clamped about the anchor tab. 
     It is thus another object of an embodiment of the invention to provide guidance for the installation of the kit through surfaces flanking the anchor tab when the C-shaped elements are properly located. 
     The boss may separate the C-shaped elements when the C-shaped elements are clamped together. 
     It is thus an object of an embodiment of the invention to promote a parallel orientation of the C-shaped elements with respect to each other without bowing of the C-shaped elements. 
     The separation provided by the boss may be no greater than a thickness of the anchor tab measured in the direction of the separation when the C-shaped elements are clamped together about the anchor tab. 
     It is thus an object of an embodiment of the invention to ensure proper compression of the anchor tab between the C-shaped elements. 
     The clamp elements may be a set of machine screws received through bores in one C-shaped element and through corresponding threaded holes in the other C-shaped element so that tightening of the machine screws draws the C-shaped elements together. 
     It is thus an object of an embodiment of the invention to provide for a simple clamping mechanism that allows a large clamping force to be shared among multiple elements. 
     The width of the slot may be less than a corresponding width of the orifice. 
     It is thus another object of an embodiment of the invention to decrease play in the slack adjuster as may have been caused by wear or the loss of an insert. 
     These particular objects and advantages may apply to only some embodiments falling within the claims, and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective exploded view of a slack adjuster and the repair kit of the present invention showing its installation over a retaining pin without removal of the slack adjuster; 
         FIG. 2  is a front elevation of view of the slack adjuster anchor tab and one C-shaped element of the present invention showing corresponding dimensions of each; and 
         FIG. 3  is a cross-sectional view a long line  3 - 3  of  FIG. 2  showing locator elements for positioning the C-shaped elements about the anchor tab. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIG. 1 , a slack adjuster  10  may have a body  12  fitting about a brake actuation shaft  14  (S-cam shaft) to rock the brake actuation shaft  14  as indicated by arrows  16 . A lever portion  18  of the slack adjuster  10  may connect to a brake actuation arm (not shown) communicating with brake actuation hydraulics or air chambers. 
     An internal mechanism of the slack adjuster  10  described in the above referenced patents may connect to a radially extending anchor tab  20  having an orifice  22  that receives a locator pin  24 , the latter typically attached to the vehicle body to maintain a stationary position. During operation of the slack adjuster  10 , the orifice  22  may become enlarged or damaged. 
     The present invention permits the repair of the orifice  22  through the use of a first C-shaped plate  26  and second C-shaped plate  28  each having slots  30  extending upward part way through the plates  26  and  28  along a vertical (as shown) centerline through the plates  26  and  28 . The slots  30  allow the C-shaped plates  26  and  28  to be fit over the locator pin  24  on either side of the anchor tab  20  while the slack adjuster  10  is installed with the anchor tab  20  on the locator pin  24 . 
     A set of machine screws  32  may then pass through bores  34  in a front most C-shaped plate  26  to have their threaded shanks  40  received by tapped holes  36  in the rearmost C-shaped plate  28  clamping the plates  26  and  28  with their broad faces against corresponding broad faces of the anchor tab  20  with the slots  30  engaging the locator pin  24 . The machine screws  32 , when tightened in tapped holes  36 , pull C-shaped plate  26  toward C-shaped plate  28  the former as captured under the heads of the machine screws  32  resting outside of the bores  34 . 
     Referring now to  FIG. 2 , the slot  30  has a width that corresponds (i.e. is approximately the same width) as the width of the anchor tab  20  and smaller than a width of the orifice  22 . In this way the C-shaped plates  26  and  28  absorb the circumferential force of the locator pin  24  against the slack adjuster  10  communicating that force over a broad area to the anchor tab  20 . 
     Referring now to  FIGS. 2 and 3 , each C-shaped plate  26  and  28  may be substantially identical except for the bores  34  (which are sized to pass thread threaded shanks  40  of the machine screws  32 ) and a tapped holes  36  (which are sized to receive the threaded shanks  40  in engagement). In this way, tooling costs may be reduced. 
     Each of the C-shaped plates  26  and  28  has an inner face  42  that may abut corresponding broad faces  44  of the anchor tab  20  when the C-shaped plates  26  and  28  are clamped by the machine screws  32  to engage the same. 
     To assist in the retention and initial placement of the C-shaped plates  26  and  28  on the anchor tab  20 , the inner faces  42  may have locator elements extending inward from the inner faces  42  including lips  50  positioned about the slot  30  and sized to engage inner edges of the orifice  22 , and bosses  52  positioned between vertically opposed pairs of the bores  34  and tapped holes  36 , the bosses  52  abutting each other when the C-shaped plates  26  and  28  are clamped together about the anchor tab  20 . 
     Generally the bosses  52  extend inward from the inner faces  42  further than the lips  50  and thus hold the plates  26  and  28  in separation by an amount only slightly smaller than the thickness  56  of the anchor tab  20 . Thus, for example, the thickness of the anchor tab  20  may be 0.125 inches and the separation established by the bosses  52  may be 0.116 inches. In this way, the bosses  52  limit warping of the plates  26  and  28  under pressure by the machine screws  32 . The bosses  52  also abut outer edges of anchor tab  20 , thus allowing tighter engagement and rigidity. 
     The bosses  52  and lips  50  may be formed by a stamping metal plates  26  and  28  to deform them locally according to methods well known in the art. 
     The C-shaped plates  26  and  28  not only reinforce the existing orifice  22  but increase the surface area or contact area with the locator pin  24  from approximately ⅛″ to ½″. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.