Patent Publication Number: US-2023134041-A1

Title: Slack adjuster assembly for heavy-duty vehicles

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 63/275,629, filed Nov. 4, 2021. 
    
    
     BACKGROUND OF THE INVENTION 
     FIELD OF THE INVENTION 
     The present invention relates generally to the art of braking systems. In particular, the present invention relates to braking systems for heavy-duty vehicles that utilize drum brakes. More particularly, the present invention relates to a slack adjuster assembly for use in heavy-duty vehicle drum brake systems that measures S-cam rotation utilizing a sensor arrangement mounted within an inboard sealing assembly of the slack adjuster, thereby providing a sensor arrangement that is protected from water, chemicals, and/or debris and minimally disruptive to assembly and maintenance of the drum brake system. 
     BACKGROUND ART 
     The use of braking systems on heavy-duty vehicles is well-known. For the purposes of clarity and convenience, reference is made to a heavy-duty vehicle with the understanding that such reference includes trucks, tractor-trailers or semi-trailers, trailers, and the like. Common types of braking systems for heavy-duty vehicles typically include disc brake systems and drum brake systems. 
     Drum brake systems are generally incorporated into an axle/suspension system and typically include a brake drum mounted on a wheel hub of a wheel end assembly rotatably mounted on an outboard end of the axle. The brake drum typically includes a pair of brake shoes housed within the brake drum. Each brake shoe has a sacrificial, high coefficient of friction brake lining that is mounted on a metal backing plate, or shoe table, and maintained in a radially-spaced relationship from an interior braking surface of the brake drum. An S-cam attached to the outboard end of a camshaft of a cam shaft assembly of the drum brake system engages a pair of rollers, each roller being connected to an end of a respective brake shoe. 
     Drum brake systems also include a prior art slack adjuster assembly. Prior art slack adjuster assemblies typically include a slack adjuster attached to the inboard splined end of the camshaft. The slack adjuster establishes a rotation reference point for an automatic adjustment mechanism, such as a control arm operatively connected to the axle/suspension system, as is known. The automatic adjustment mechanism of the prior art slack adjuster assembly indexes the camshaft rotation from the rotation reference point in order to maintain a preset distance or clearance between the brake lining of the brake shoes and the interior braking surface of the brake drum, regulating the stroke and mechanical force of a brake air chamber necessary to slow or stop the heavy-duty vehicle. 
     During operation when the drum brake system is actuated, compressed air is communicated from an air supply source, such as a compressor and/or air tank, through air conduits or lines to a brake chamber, as is known. The brake chamber converts the air pressure into mechanical force and moves a pushrod. The pushrod, in turn, moves the slack adjuster of the prior art slack adjuster assembly, which causes rotation of the camshaft and S-cam. The S-cam forces the brake shoes radially outward such that the brake linings contact the interior braking surface of the brake drum, creating friction and slowing or stopping the heavy-duty vehicle. The prior art slack adjuster assembly indexes the rotation of the camshaft when the drum brake system is actuated. Once the drum brake system is released or no longer actuated, the camshaft, and thus the S-cam, rotates back, allowing the radially-spaced relationship between the brake lining and interior braking surface of the brake drums to be re-established. The slack adjuster rotates back to a new position based on the indexed rotation of the cam shaft, thereby maintaining the preset distance or clearance between the brake lining and the interior braking surface of the brake drum. 
     In order to facilitate maintenance, increase efficiency, and provide information regarding potential problems or issues of the drum brake system related to the slack adjusters, brake air chambers, and/or other components, prior art slack adjuster assemblies may incorporate one or more prior art sensor arrangements. Prior art sensor arrangements utilize sensors that may alert a fleet or operator of the heavy-duty vehicle to potential brake actuation issues. In particular, prior art sensor arrangements have utilized sensors that provide information allowing prediction of maintenance and/or replacement of slack adjusters, brake air chambers, air system components, worn brake shoes and/or drum linings, and/or other components before the condition potentially impacts safety or performance of the drum brake system. 
     More particularly, prior art sensor arrangements have been utilized to measure the stroke of the brake air chamber or, because rotation of the S-cam is proportional to the brake air chamber stroke, rotation of the camshaft. Prior art sensor arrangements generally utilize external components attached to the slack adjuster or the camshaft or internal components incorporated into and disposed within the slack adjuster. In particular, numerous types of slack adjusters from numerous manufacturers have been designed to be compatible with the splined interface on the inboard end of the camshaft. More particularly, some manufacturers of slack adjusters incorporate proprietary sensors into the slack adjuster. In addition, third-party sensors are available that can be adapted to fit with specific commercially available slack adjusters. Alternatively, prior art sensor arrangements have used components attached to the head of the S-cam and disposed within the brake drum. Some prior art sensors may even attach directly to a modified inboard end of a camshaft or may be attached to the axle or other components of the suspension system using commercially available brackets. 
     Prior art slack adjuster assemblies with prior art sensor arrangements, while adequate for the intended purpose, have potential disadvantages, drawbacks, and limitations. For example, prior art sensor arrangements are generally located or positioned in areas exposed to potential impacts and/or harsh environmental conditions, such as extreme temperatures, water, chemicals, and/or debris. As a result, prior art sensor arrangements may potentially be damaged or experience reduced accuracy and/or service-life, requiring more frequent maintenance and/or replacement, thereby increasing cost. In addition, prior art sensor arrangements are located or positioned in areas that interfere with or add complexity to maintenance, assembly, disassembly, and reassembly of the drum brake system and heavy-duty vehicle. As a result, use of prior art sensor arrangements with prior art slack adjuster assemblies may potentially increase heavy-duty vehicle down-time and cost of maintenance and assembly of the drum brake system. 
     Thus, there is a need in the art for an improved slack adjuster assembly that provides a sensor arrangement for monitoring camshaft rotation that can be utilized without regard to slack adjuster manufacturer; is minimally disruptive and/or does not add complexity to maintenance and assembly of the drum brake system; and provides an inboard sealing assembly that maintains lubrication of the slack adjuster and camshaft while protecting the sensor arrangement from potential impact damage, extreme temperatures, water, chemicals, and/or debris, thereby increasing the maintenance interval and service-life of the sensor arrangement and slack adjuster assembly and reducing heavy-duty vehicle down time. 
     SUMMARY OF THE INVENTION 
     Objectives of the present invention include providing a slack adjuster assembly with a sensor arrangement that monitors camshaft rotation and can be utilized without regard to slack adjuster manufacturer. 
     A further objective of the present invention is to provide a slack adjuster assembly with a sensor arrangement that monitors camshaft rotation and is minimally disruptive and/or does not add complexity to assembly and maintenance of the drum brake system. 
     Yet another objective of the present invention is to provide a slack adjuster assembly with an inboard sealing assembly that maintains lubrication of the slack adjuster and protects the sensor arrangement from potential impact damage, extreme temperatures, water, chemicals, and/or debris. 
     These objectives and advantages are obtained by the slack adjuster assembly, according to the present invention, for use in a heavy-duty vehicle drum brake system, the slack adjuster assembly comprising a slack adjuster, an inboard sealing assembly, and a sensor arrangement. 
     The slack adjuster is mounted on an inboard end of a camshaft of the drum brake system. The inboard sealing assembly sealingly engages with an inboard side of the slack adjuster. The sensor arrangement measures rotation of the camshaft and is at least partially disposed within the inboard sealing assembly to protect the sensor arrangement from impact damage, water, chemicals, and debris. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The preferred embodiments of the present invention, illustrative of the best mode in which applicants have contemplated applying the principles, is set forth in the following description, shown in the drawings, and particularly and distinctly pointed out and set forth in the appended claims. 
         FIG.  1    is a fragmentary elevational view, in section, of an exemplary embodiment slack adjuster assembly, according to the present invention; 
         FIG.  2    is an elevational view, looking axially outboard, of a portion of the slack adjuster assembly shown in  FIG.  1   , showing an inboard surface of a target of the sensor arrangement; 
         FIG.  3    is an elevational view, looking axially outboard, of a portion of the slack adjuster assembly shown in  FIG.  1   , showing an inboard surface of an alternative configuration of the target of the sensor arrangement; 
         FIG.  4    is a fragmentary elevational view, in section, of another exemplary embodiment slack adjuster assembly, according to the present invention; 
         FIG.  5    is a fragmentary elevational view, in section, of yet another exemplary embodiment slack adjuster assembly, according to the present invention; and 
         FIG.  6    is a fragmentary elevational view, in section, of still yet another exemplary embodiment slack adjuster assembly, according to the present invention. Similar reference characters refer to similar parts throughout. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An exemplary embodiment slack adjuster assembly  100  ( FIGS.  1 - 3   ), according to the present invention, may be incorporated into any drum brake system (not shown), including those utilizing a cam tube assembly (not shown). More specifically, slack adjuster assembly  100  may be mounted on a camshaft  86  (partially shown) of a drum brake system. Slack adjuster assembly  100  includes a slack adjuster  102 , an inboard sealing assembly  110 , and a sensor arrangement  150 . Slack adjuster  102  includes a body  104  having an internal spline  108  for receiving an external spline  87  of an inboard end  84  of camshaft  86 , as is known. 
     Inboard sealing assembly  110  abuts and/or is sealingly engaged with the inboard side of slack adjuster  102 . Inboard sealing assembly  110  includes one or more washers  112  and a snap ring or E-clip  114 . Washers  112  may be disposed about inboard end  84  of camshaft  86  and located adjacent slack adjuster  102  and outboardly of a groove  85  formed into the camshaft, as is known. E-clip  114  is snapped onto, or disposed about, inboard end  84  of camshaft  86  inboardly of washers  112 . More particularly, E-clip  114  mechanically engages inboard end  84  of camshaft  86  such that the E-clip is disposed within groove  85 . E-clip  114  acts as a retaining ring to limit the amount of axial movement of washers  112 , slack adjuster  102 , and camshaft  86 . 
     In accordance with an important aspect of the present invention, inboard sealing assembly  110  also includes a seal  130  disposed over inboard end  84  of camshaft  86  and in contact with body  104  of slack adjuster  102  to form a 360-degree seal on the inboard side. Seal  130  is formed from a flexible elastomeric material, such as rubber, with a generally bell- or cup-shape forming an inboardly extending recess or concavity  132  having a central opening  136  at the extremity of the concavity. An annular flange or projection  138  may be formed about and extend axially inboard from opening  136  of seal  130 . In addition, a large-diameter flap or lip  134  is formed about the outboard edge of concavity  132  and is in contact with a coverplate (not shown) or body  104  of slack adjuster  102  to form a 360-degree seal about the inboard side of the slack adjuster. As a result, pressurized grease may pool within concavity  132  as it flows between internal and external splines  108 ,  87  of slack adjuster  102  and camshaft  86 , respectively, and through washers  112  and E-clip  114  to form a grease reservoir about and adjacent to sensor arrangement  150  and components of slack adjuster assembly  100  to protect the sensor arrangement and other components from water, chemicals, and/or debris and to prevent wear and corrosion. The large diameter of lip  134  combined with the flexible elastomer of seal  130  allows the lip to be displaced or deflected away from body  104 . More specifically, in the event grease overfills concavity  132 , lip  134  may deflect radially outwardly and inboardly away from slack adjuster  102 , allowing excess grease to be purged from the concavity. The bell- or cup-shape of seal  130  combined with the flexible elastomer material of the seal also prevents the seal from pulling a vacuum on concavity  132  or pressurizing the concavity in the event axial movement of camshaft  86  occurs during braking. More particularly, in the event of axial movement of camshaft  86  during braking, seal  130  may flex, compensating for any volume changes within concavity  132 , thereby preventing suction of water, chemicals, and/or other debris past lip  134  into the concavity as well as preventing increased pressure from purging the grease out of the concavity. 
     Inboard sealing assembly  110  also includes a cover  120  disposed over or at least partially about seal  130 . Cover  120  may be formed with any suitable shape, such as tubular, stepped or graduated, from any suitable material, such as steel, plastic, or composite, using any suitable process, such as stamping. In particular, cover  120  may be formed with a generally tubular outboard section  122  and an inboard flange  124 . Outboard section  122  may mechanically engage with the inboard side of slack adjuster  102 . More specifically, outboard section  122  may be press-fit into an annular recess  106  formed into a coverplate (not shown) or the inboard side of body  104  of slack adjuster  102 . It is contemplated that any other suitable means of connection or attachment may be used between cover  120  and slack adjuster  102 , such as a threaded connection. Inboard flange  124  extends radially inward from outboard section  122 . An annular flange or collar  128  may be formed continuous with and extending axially-inboard from inboard flange  124  such that the collar is radially offset from and concentric with or parallel to outboard section  122 . Collar  128  includes a central opening  126  extending through the collar of cover  120 . The inner diameter of collar  128  generally corresponds to and is greater than or equal to the outer diameter of projection  138  of seal  130 . It is contemplated that cover  120  may also include a plurality of vents (not shown) formed through flange  124  and/or outboard section  122  and having a suitable size and/or shape to provide protection to seal  130  and sensor arrangement  150  from damage potentially caused by power washers while also allowing pressure equalization between the interior and exterior of the cover. As a result, air and/or grease may be purged from concavity  132  of seal  130  without creating back pressure, and water, chemicals, and/or debris may drain from cover  120 , preventing collection inside the cover. 
     Cover  120  may be connected to or engage with seal  130 . In particular, at least a portion of projection  138  of seal  130  may be disposed at least partially within and/or through opening  126  and/or mechanically engage collar  128  of cover  120 . More particularly, projection  138  may include a radially-outward extending lip  139  that mechanically engages the inboard edge of collar  128  of cover  120  to prevent relative axial movement between seal  130  and the cover, securing the seal within the cover. It is also contemplated that any other suitable method may be used to connect or engage seal  130  with cover  120 , such as adhesive. Engagement of seal  130  to cover  120  may facilitate control and adjustment of the contact pressure of lip  134  against the inboard side of slack adjuster  102 , as described in detail below. 
     Inboard sealing assembly  110  also includes a retaining ring  140  formed as a generally tubular structure from any suitable material, such as metal, using any suitable method, such as stamping. Retaining ring  140  includes an inboard flange  142 , a cylindrical body  143 , and an outboard flange  144 . Inboard flange  142  extends radially-inward from the inboard end of body  143  and has an inner diameter that is less than the inner diameter of the body. The outer diameter of body  143  generally corresponds to and is less than or equal to the inner diameter of projection  138 . Outboard flange  144  extends radially-outward from the outboard end of body  143  and has an outer diameter that is greater than the outer diameter of the body and the inner diameter of projection  138 . Retaining ring  140  may engage with or be disposed through opening  136  of seal  130  and at least partially within projection  138  such that outboard flange  144  contacts or mechanically engages the inner surface of concavity  132  of the seal, limiting or preventing axially-inboard movement of the retaining ring. 
     In accordance with another important aspect of the present invention, sensor arrangement  150  is at least partially mounted within seal  130  inboardly of slack adjuster  102  and engages inboard end  84  of camshaft  86  of the drum brake system. As a result, sensor arrangement  150  is disposed away from the brake drum (not shown) of the drum brake system in an area that is not exposed to extreme temperatures. Sensor arrangement  150  includes a detector, such as an eddy current sensor  152 , and a non-magnetized target  154 . Sensor  152  may be powered using any suitable method, such as a battery, direct wired transmission, and/or local energy harvesting, as is known. Sensor  152  may send and receive information via electronic signals using any suitable method, such as direct wired transmission or wireless RF, to or from a central processing unit or nearby receiver in communication with a remote management system, as is known. Sensor  152  is disposed within retaining ring  140  such that the outer surface of at least a portion of the sensor contacts or forms an interface with the inner surface of the retaining ring. In particular, the inner diameters of inboard flange  142  and body  143  of retaining ring  140  generally correspond to the outer diameter of at least a portion of sensor  152  such that the inboard flange limits or restricts axially-inboard movement of the sensor but allows relative rotation between the sensor and the retaining ring during braking. 
     Target  154  may be mounted on or attached to inboard end  84  of camshaft  86  in any suitable manner, such as a press-fit connection. More specifically, target  154  may mechanically engage with, such as by press-fit, a central opening  88  extending outboardly into camshaft  86  from inboard end  84 . Target  154  may have any suitable angular or rotational orientation, such as relative to a narrow point starting location, or throat, or a maximum radial point location, or tips, on an S-cam (not shown) of the drum brake system. Target  154  may be formed with an inboard surface  156  ( FIG.  2   ) having any suitable shape and/or may include any suitable pattern (see, e.g.,  FIGS.  2 - 3   ). Inboard surface  156  may be oriented to face inboardly such that the inboard surface interacts or forms an interface with the outboard end of sensor  152 , allowing the sensor to detect and determine the degree of angular rotation of camshaft  86 . A low-force spring  158  may be disposed about sensor  152  and between the sensor and inboard flange  142  of retaining ring  140 . Spring  158  maintains sensor  152  within a minimum distance of target  154  during operation of the heavy-duty vehicle in the event camshaft  86  and slack adjuster  102  potentially experience axial movement. Sensor arrangement  150  also includes a reference arm  160  formed from any suitable material, such as metal, by any suitable method, such as stamping. Reference arm  160  may be relatively straight or may be formed with one or more bends or joints, as is known. Reference arm  160  may connect sensor  152  to an anti-rotation pin  90  of the drum brake system or axle/suspension system. More particularly, reference arm  160  may be formed with an opening  162  at one end of the reference arm that aligns with an opening  153  formed in the inboard end of sensor  152 . A fastener  163  may be disposed through the aligned openings  162 ,  153  of reference arm  160  and sensor  152 , respectively, to attach the reference arm to the sensor. Reference arm  160  may be formed with another opening  164  formed through another, opposite end of the reference arm. A suitable anti-vibration structure, such as rubber or plastic grommet  166 , may be disposed within and about opening  164 , engaging reference arm  160 . Anti-rotation pin  90  may be disposed through grommet  166  and opening  164  in a slip-fit manner to connect reference arm  160 , and thus sensor  152 , to the pin, preventing rotation of the sensor relative to target  154  and slack adjuster  102 . Anti-rotation pin  90  may be rigidly mounted to a component (not shown), such as a beam (not shown) of an axle/suspension system (not shown) or any other suitable structure on an axle (not shown) or other component of the drum brake system. It is contemplated that anti-rotation pin  90  may also be used by a reference control arm (not shown) of slack adjuster  102 , as is known. 
     It is also contemplated that sensor  152  may be adjustable relative to reference arm  160  in order to allow setting of a reference point relative any other angular position suitable for determining rotation of the S-cam. 
     Alternatively, it is contemplated that sensor arrangement  150  may not include reference arm  160 . In such a configuration, sensor  152  may be disposed within retaining ring  140 , as described above, such that relative axial movement, but not relative rotation, may occur between the sensor and the retaining ring. In addition, retaining ring  140  may be disposed through opening  136  of seal  130  and at least partially within and affixed to projection  138  such that relative rotation between the projection and the retaining ring cannot occur. Similarly, at least a portion of projection  138  may be disposed within and/or mechanically engage opening  126  of cover  120  and be fixed using any suitable method, such as adhesive, within collar  128  such that relative rotation between the collar and the projection, and, therefore, between seal  130  and the cover, cannot occur. As a result of this configuration, the reference point of sensor  152  relative to the S-cam of the drum brake system may be set by rotating cover  120  relative to slack adjuster  102  prior to attachment of the cover to the slack adjuster to maintain the selected orientation. 
     During assembly of slack adjuster assembly  100 , target  154  of sensor arrangement  150  is oriented relative to the S-cam and attached to inboard end  84  of camshaft  86 . Projection  138  of seal  130  is inserted through opening  126  in flange  124  of cover  120  such that the projection is at least partially disposed within and/or engages collar  128  and lip  139  mechanically engages the inboard end of the collar. It is also contemplated that projection  138  may be attached to collar  128  using any suitable method, such as adhesive, to prevent relative rotation between the projection and the collar. Spring  158  is disposed about sensor  152  before the sensor is disposed within retaining ring  140 . Inboard flange  142  of retaining ring  140  contacts spring  158  to restrict axially-inboard movement of sensor  152 . It is also contemplated that sensor  152  may be attached to or engage retaining ring  140  such that the retaining ring limits axial movement while allowing rotation of the sensor relative to the retaining ring. Retaining ring  140  with sensor  152  may then be disposed within concavity  132  of seal  130  and inserted through opening  136  such that the retaining ring is at least partially disposed within projection  138  and outboard flange  144  limits further axially-inboard movement of the retaining ring. It is contemplated that projection  138  may be attached or connected to retaining ring  140  to prevent relative rotation between the retaining ring and the projection. Alternatively, retaining ring  140  may be installed in seal  130  prior to insertion of sensor  152  and spring  158  into the retaining ring. Inboard sealing assembly  110  with sensor  152  of sensor arrangement  150  is then attached to slack adjuster  102 . More specifically, outboard section  122  of cover  120  is inserted into recess  106  of the coverplate (not shown) or body  104  on the inboard side of slack adjuster  102  such that lip  134  of seal  130  is in contact with the slack adjuster. 
     Cover  120  may then be rotated in order to orient sensor  152  in a particular angular orientation before the cover is press-fit or attached to slack adjuster  102  using any other suitable manner. It is also contemplated that a threaded connection may be utilized between cover  120  and slack adjuster  102  to facilitate adjustment of the relative axial distance between lip  134  of seal  130  and the inboard side of body  104  of the slack adjuster independent of axial movement of camshaft  86  in order to maintain the 360-degree seal during braking. 
     Grommet  166  may be disposed in opening  164  of reference arm  160 . Anti-rotation pin  90  may then be slidably disposed through grommet  166  and opening  164  until opening  162  of reference arm  160  is aligned with and adjacent to opening  153  of sensor  152 . Fastener  163  may then be disposed through the aligned openings  162 ,  153  of reference arm  160  and sensor  152 , respectively, to attach the reference arm to the sensor. Alternatively, reference arm  160  may not be utilized, as described above. Grease is then typically added to slack adjuster  102  using a pressurized grease gun (not shown) in order to lubricate internal and external splines  108 ,  87 , respectively, of the slack adjuster and inboard end  84  of camshaft  86 . Grease is injected into slack adjuster  102  such that the grease passes through internal and external splines  108 ,  87 , respectively, and fills concavity  132  of seal  130 , protecting the internal and external splines, sensor  152 , and target  154  against the intrusion of water, chemicals, and/or debris, thereby reducing maintenance and extending the service-life of components of sensor arrangement  150 , slack adjuster assembly  100 , and the drum brake system. 
     Thus, slack adjuster assembly  100 , according to the present invention, provides sensor arrangement  150  for monitoring rotation of camshaft  86  that can be utilized without regard to slack adjuster manufacturer and is minimally disruptive and/or does not add complexity to maintenance and assembly of the drum brake system. In addition, slack adjuster assembly  100  provides inboard sealing assembly  110  that maintains lubrication of slack adjuster  102  and camshaft  86  while protecting sensor arrangement  150  from potential impact damage, extreme temperatures, water, chemicals, and/or debris, thereby increasing the maintenance interval and service-life of the sensor arrangement and slack adjuster assembly and reducing heavy-duty vehicle down-time. 
     Another exemplary embodiment slack adjuster assembly  200  ( FIG.  4   ), according to the present invention, may be incorporated into any drum brake system (not shown). Slack adjuster assembly  200  is similar in construction and arrangement to slack adjuster assembly  100  described above. As a result, the description below will be primarily directed to the differences between slack adjuster assembly  200  and slack adjuster assembly  100 . 
     Slack adjuster assembly  200  includes inboard sealing assembly  110 , described above, and a sensor arrangement  250 . Sensor arrangement  250  is at least partially mounted within seal  130  of sealing assembly  110  and engages inboard end  84  of a camshaft  86  of the drum brake system. 
     As a result, sensor arrangement  250  is disposed away from the brake drum (not shown) of the drum brake system in an area that is not exposed to extreme temperatures. Sensor arrangement  250  includes a detector, such as a Hall effect sensor  252 , and a diametrically-polarized target  254 . Sensor  252  may be powered using any suitable method, such as a battery, direct wired transmission, and/or local energy harvesting, as is known. Sensor  252  may send and receive information via electronic signals using any suitable method, such as direct wired transmission or wireless RF, to or from a central processing unit or nearby receiver in communication with a remote management system, as is known. Sensor  252  is disposed within retaining ring  140  such that the outer surface of at least a portion of the sensor contacts or forms an interface with the inner surface of the retaining ring. In particular, the outer diameter of at least a portion of sensor  252  generally corresponds to and is less than or equal to the inner diameter of body  143  and/or inboard flange  142  of retaining ring  140  such that the inboard flange limits or restricts axially-inboard movement of the sensor. Sensor  252  may be disposed within retaining ring  140  such that relative rotation between the sensor and the retaining ring can occur during braking. 
     Target  254  may be indirectly mounted on or attached to inboard end  84  of camshaft  86  using any suitable means, such as a press-fit connection. In particular, target  254  may be slidably disposed within and form an interface with a generally cylindrical receptacle  274 . More particularly, receptacle  274  may be formed with an outboard plate  276  having a surface feature or projection  278  that extends axially outboard to mechanically engage with, such as by press-fit, opening  88  of inboard end  84  of camshaft  86 . Receptacle  274  and/or target  254  may be formed with any suitable shape or surface feature along the interface between the target and receptacle to prevent relative rotation and may permit only one rotational orientation or two symmetrical rotational orientations between the target and the receptacle. Receptacle  274  may have any suitable angular or rotational orientation, such as relative to a narrow point starting location, or throat, or a maximum radial point location, or tips, on an S-cam (not shown) of the drum brake system. A low-force spring  258  may be disposed within receptacle  274  between plate  276  and target  254  to maintain close proximity between the target and sensor  252  during operation of the heavy-duty vehicle in the event camshaft  86  and slack adjuster  102  potentially experience axial movement. 
     Sensor arrangement  250  also includes a reference arm  260  formed from any suitable material, such as metal, using any suitable method, such as stamping. Reference arm  260  may be relatively straight or may be formed with one or more bends or joints, as is known. Reference arm  260  connects sensor  252  to anti-rotation pin  90  of the drum brake system. More particularly, an opening  262  at one end of reference arm  260  aligns with an opening  253  formed in the inboard end of sensor  252 . A fastener  263  is disposed through the aligned openings  262 ,  253  of reference arm  260  and sensor  252 , respectively, to attach the reference arm to the sensor. Reference arm  260  includes another opening  264  at another, opposite end. A rubber or plastic grommet  266  or other suitable anti-vibration structure may be disposed within and about opening  264  for engaging reference arm  260 . Anti-rotation pin  90  is disposed through grommet  266  and opening  264  in a slip-fit manner to connect the reference arm, and thus sensor  252 , to the pin, preventing rotation of the sensor relative to target  254  and slack adjuster  102 . It is contemplated that sensor  252  may be adjustable relative to reference arm  260  in order to allow setting of a reference point relative any other angular position suitable for determining rotation of the S-cam. 
     Alternatively, sensor arrangement  250  may not include reference arm  260 , as described above. In such a configuration, sensor  252  may be disposed within retaining ring  140  such that relative rotation between the sensor and the retaining ring does not occur. In addition, retaining ring  140  may be disposed through opening  136  of seal  130  and be disposed at least partially within and affixed to projection  138  such that relative rotation between the projection and the retaining ring cannot occur. Similarly, at least a portion of projection  138  may be disposed within and/or through opening  126  and/or mechanically engage or be fixed using any suitable method within collar  128  of cover  120  such that relative rotation between the collar and the projection, and, therefore, between seal  130  and the cover, cannot occur. Thus, in such a configuration, cover  120  may be rotated relative to slack adjuster  102  to set the reference point of sensor  252  relative to the S-cam of the drum brake system prior to attachment of the cover to the slack adjuster to maintain the selected orientation. It is also contemplated that, in such a configuration, inboard sealing assembly  110  may not include retaining ring  140  such that sensor  152  may instead be disposed within projection  138  of seal  130 . 
     Thus, slack adjuster assembly  200 , according to the present invention, provides sensor arrangement  250  for monitoring rotation of camshaft  86  that can be utilized without regard to slack adjuster manufacturer and is minimally disruptive and/or does not add complexity to maintenance and assembly of the drum brake system. In addition, slack adjuster assembly  200  utilizes inboard sealing assembly  110  that maintains lubrication of slack adjuster  102  and camshaft  86  while protecting sensor arrangement  250  from potential impact damage, extreme temperatures, water, chemicals, and/or debris, thereby increasing the maintenance interval and service-life of the sensor arrangement and slack adjuster assembly and reducing heavy-duty vehicle down time. 
     Yet another exemplary embodiment slack adjuster assembly  300  ( FIG.  5   ), according to the present invention, may be incorporated into any drum brake system (not shown). Slack adjuster assembly  300  is similar in construction and arrangement to slack adjuster assemblies  100 ,  200  described above. As a result, the description below will be primarily directed to the differences between slack adjuster assembly  300  and slack adjuster assemblies  100 ,  200 . 
     Slack adjuster assembly  300  includes inboard sealing assembly  310  and sensor arrangement  350 . Inboard sealing assembly  310  is sealingly engaged with the inboard side of slack adjuster  102 . Inboard sealing assembly  310  includes one or more washers  312 , a snap ring or E-clip  314 , a seal  330 , and a cap or cover  320 . Washers  312  may be disposed about inboard end  84  of camshaft  86  outboardly of groove  85 . E-clip  314  is snapped onto, or disposed about, inboard end  84  of camshaft  86  inboardly of washers  312 . More particularly, E-clip  314  mechanically engages inboard end  84  of camshaft  86  such that the E-clip is disposed within groove  85  and acts as a retaining ring to limit the amount of axial movement of washers  312 , slack adjuster  102 , and the camshaft. 
     Seal  330  is disposed over inboard end  84  of camshaft  86  and is in contact with body  104  of slack adjuster  102  to form a 360-degree seal on the inboard side of the slack adjuster. Seal  330  is formed from a flexible elastomeric material, such as rubber, with a generally tubular shape forming a generally cylindrical opening or cavity  332 . A large-diameter flap or lip  334  is formed about the outboard end of seal  330  and is in contact with a coverplate (not shown) or body  104  of slack adjuster  102  to form a 360-degree seal about the inboard side of the slack adjuster. An annular rib  372  is formed adjacent lip  334  and projects radially-inward from the outer surface of seal  330 . As a result, lip  334  may extend radially outwardly and axially outboard toward body  104  of slack adjuster  102  at an oblique angle. Rib  372  of seal  330  combined with the flexible elastomer material of the seal prevents the seal from pulling a vacuum within cavity  332  or pressurizing the opening in the event axial movement of camshaft  86  occurs during braking. More particularly, in the event of axial movement of camshaft  86  during braking, rib  372  allows seal  330  to flex, compensating for any volume changes within cavity  332 , thereby preventing suction of water, chemicals, and/or other debris past lip  334  into the concavity as well as preventing increased pressure from purging grease past the lip and out of the cavity. Seal  330  may also be formed with an annular inner groove  392 , an annular outer groove  394 , and an inboard flange or lip  339 . Inner groove  392  is formed into and extends radially outward from the inner surface of seal  330  axially adjacent rib  372 . Outer groove  394  is formed into and extends radially inward from the outer surface of seal  330  axially adjacent inner groove  392 . Generally, the outer diameter of outer groove  394  may be less than the outer diameter of inner groove  392 . The inner diameter of outer groove  394  may be less than the inner diameter of inner groove  392 . Inboard lip  339  extends radially outward from seal  330  and is formed about the inboard end of cavity  332  of the seal axially adjacent outer groove  394 . 
     Cover  320  of inboard sealing assembly  310  is formed with a stepped or graduated shape from any suitable material, such as steel, plastic, or composite, using any suitable process, such as stamping. Cover  320  may be formed with a generally cylindrical outboard section  322  and an inboard flange  324 . Outboard section  322  may mechanically engage with the inboard side of slack adjuster  102 . More specifically, outboard section  322  may be press-fit into annular recess  106  formed into a coverplate (not shown) or body  104  on the inboard side of slack adjuster  102 . It is contemplated that any other suitable method of connection or attachment may be used between cover  320  and slack adjuster  102 , such as a threaded connection. Inboard flange  324  extends radially inward from the inboard end of outboard section  322 . An annular flange or collar  328  is formed continuous with and extends axially-inboard from inboard flange  324  such that the collar is radially offset from and concentric with or parallel to outboard section  322 . Collar  328  defines an opening  326  extending through cover  320 . The inner diameter of collar  328  generally corresponds to and is greater than or equal to the outer diameter of outer groove  394  of seal  330 . It is contemplated that cover  320  may also include a plurality of vents (not shown) formed through flange  324  and having a suitable size and/or shape to provide protection to seal  330  and sensor arrangement  350  from damage potentially caused by power washers while allowing pressure equalization between the interior and exterior of the cover. As a result, air and/or grease may be purged from within seal  330  without creating back pressure, and water, chemicals, and/or debris may drain from cover  320 , preventing collection inside the cover. 
     Seal  330  may be connected to or engage with cover  320 . More specifically, at least a portion of seal  330  may be disposed within and/or through and/or mechanically engage with opening  326  and/or collar  328  of cover  320  such that outer groove  394  may be in contact with the inner surface of the collar. Lip  339  may mechanically engage the inboard edge of collar  328  to secure seal  330  to cover  320 . It is also contemplated that any other suitable method may be used to connect or engage seal  330  with cover  320 , such as adhesive. Engagement of seal  330  to cover  320  may facilitate control and adjustment of the contact pressure of lip  334  against the inboard side of slack adjuster  102 , as described in further detail below. 
     Inboard sealing assembly  310  also includes a retaining ring  340  formed as a generally tubular structure from any suitable material, such as metal, using any suitable method, such as stamping. The outer diameter of retaining ring  340  generally corresponds to and is less than or equal to the inner diameter of outer groove  394  of seal  330 . Retaining ring  340  includes an outboard flange  344  that extends radially-outward from the outboard end of the retaining ring. The outer diameter of outboard flange  344  is greater than the inner diameter of outer groove  394 . 
     Retaining ring  340  may also be formed with an inboard flange  342  that extends radially inward from the inboard end of the retaining ring to form a central opening  346 . Retaining ring  340  may engage with or be at least partially disposed within cavity  332  of seal  330  such that outboard flange  344  contacts or mechanically engages inner groove  392  of the seal, limiting or preventing axially inboard movement of the retaining ring while allowing relative rotation between the seal and the retaining ring. 
     In accordance with another important aspect of the present invention, sensor arrangement  350  is at least partially mounted within seal  330  and engages inboard end  84  of a camshaft  86  of the drum brake system. As a result, sensor arrangement  350  is disposed away from the brake drum (not shown) of the drum brake system in an area that is not exposed to extreme temperatures. Sensor arrangement  350  includes a detector, such as a rotary sensor  352 . Sensor  352  may be powered using any suitable method, such as a battery, direct wired transmission, and/or local energy harvesting, as is known. Sensor  352  may send and receive information via electronic signals using any suitable method, such as direct wired transmission or wireless RF, to or from a central processing unit or nearby receiver in communication with a remote management system, as is known. Sensor  352  may be attached to inboard flange  342  of retaining ring  340 . More specifically, a portion of sensor  352  may be disposed inboardly of and piloted into opening  346  of retaining ring  340 . Sensor  352  may be attached, such as by a plurality of fasteners  363  to the inboard side of inboard flange  342  of retaining ring  340 , as described in detail below. 
     Sensor arrangement  350  also includes a D-shaft  354  that is indirectly attached to inboard end  84  of camshaft  86  and engages with sensor  352 . In particular, D-shaft  354  may be slidably disposed within and form an interface with a generally cylindrical receptacle  374 . More particularly, receptacle  374  is formed with an outboard plate  376  having a surface feature or projection  378  that extends axially outboard to mechanically engage, such as by press-fit, opening  88  of inboard end  84  of camshaft  86 . Receptacle  374  and/or D-shaft  354  may be formed with any suitable shape or circumferential surface feature along the interface between the D-shaft and the receptacle to prevent relative rotation and may permit only one rotational orientation or two symmetrical rotational orientations between the D shaft and receptacle. Receptacle  374  may have any suitable angular or rotational orientation, such as relative to a narrow point starting location, or throat, or a maximum radial point location, or tips, on an S-cam (not shown) of the drum brake system. D-shaft  354  may also be formed with an inboardly projecting extension  356  that is disposed within and/or engages with a bore  355  of sensor  352 . A low-force spring  358  may be disposed within receptacle  374  between plate  376  and D-shaft  354  to ensure extension  356  remains disposed within bore  355  of sensor  352  during operation of the heavy-duty vehicle in the event camshaft  86  and slack adjuster  102  potentially experience axial movement. 
     Sensor arrangement  350  also includes a reference arm  360  formed from any suitable material by any suitable method. Reference arm  360  may be relatively straight or may be formed with one or more bends or joints, as is known. Reference arm  360  may connect sensor  352  to anti-rotation pin  90  of the drum brake system. More particularly, one or more openings  362  may be formed through one end of reference arm  360  and align with one or more openings  353  formed through sensor  352 . Openings  353  of sensor  352 , in turn, align with one or more openings  341  formed through inboard flange  342  of retaining ring  340 . Fasteners  363  are disposed through the aligned openings  362 ,  353 ,  341  of reference arm  360 , sensor  352 , and retaining ring  340 , respectively, to attach the reference arm to the sensor and the retaining ring. Reference arm  360  includes an opening  364  formed through another, opposite end. A rubber or plastic grommet  366  or other suitable anti-vibration structure may be disposed within and about opening  364  for engaging reference arm  360 . Anti-rotation pin  90  is disposed through grommet  366  and opening  364  in a slip-fit manner to connect the reference arm, and thus sensor  352  and retaining ring  340 , to the pin, preventing rotation of the sensor and retaining ring relative to slack adjuster  102 . Anti-rotation pin  90  may be rigidly mounted to a component (not shown), such as a beam (not shown) of an axle/suspension system (not shown) or any other suitable structure on an axle (not shown) or component of the drum brake system. It is contemplated that anti-rotation pin  90  may also be used by a reference control arm (not shown) of slack adjuster  102 , as is known. It is also contemplated that sensor  352  may be adjustable relative to reference arm  360  in order to allow setting of a reference point relative any other angular position suitable for determining rotation of the S-cam. 
     Alternatively, sensor arrangement  350  may not include reference arm  360 . In such a configuration, sensor  352  may be attached to retaining ring  340  such that relative axial movement, but not relative rotation, may occur between the sensor and the retaining ring. In addition, retaining ring  340  may be affixed to seal  330  such that relative rotation between the seal and the retaining ring cannot occur. Similarly, at least a portion of outer groove  394  of seal  330  may be fixed using any suitable means, such as adhesive, within collar  328  of cover  320  such that relative rotation between the collar and the outer groove, and, therefore, between the seal and the cover, cannot occur. Thus, in such a configuration, cover  320  may be rotated relative to slack adjuster  102  to set the reference point of sensor  352  relative to the S-cam of the drum brake system prior to attaching the cover to the slack adjuster to maintain the selected orientation. 
     Thus, slack adjuster assembly  300 , according to the present invention, provides sensor arrangement  350  for monitoring rotation of camshaft  86  that can be utilized without regard to slack adjuster manufacturer and is minimally disruptive and/or does not add complexity to maintenance and assembly of the drum brake system. In addition, slack adjuster assembly  300  utilizes inboard sealing assembly  310  that maintains lubrication of slack adjuster  102  and camshaft  86  while protecting sensor arrangement  350  from potential impact damage, extreme temperatures, water, chemicals, and/or debris, thereby increasing the maintenance interval and service-life of the sensor arrangement and slack adjuster assembly and reducing heavy-duty vehicle down time. 
     Another exemplary embodiment slack adjuster assembly  400  ( FIG.  6   ), according to the present invention, may be incorporated into any drum brake system (not shown). Slack adjuster assembly  400  is similar in construction and arrangement to slack adjuster assembly  300  described above. As a result, the description below will be primarily directed to the differences between slack adjuster assembly  400  and slack adjuster assembly  300 . 
     Slack adjuster assembly  400  includes an inboard sealing assembly  410  and sensor arrangement  350 , described above. Inboard sealing assembly  410  is sealingly engaged with the inboard side of slack adjuster  102  and includes one or more washers  412 , a snap ring or E-clip  414 , a seal  430 , and a cap or cover  420 . Washers  412  may be disposed about inboard end  84  of camshaft  86  outboardly of groove  85 . E-clip  414  is snapped onto, or disposed about, inboard end  84  of camshaft  86  inboardly of washers  412 . More specifically, E-clip  414  mechanically engages inboard end  84  of camshaft  86  such that the E-clip is disposed within groove  85  and acts as a retaining ring to limit the amount of axial movement of washers  412 , slack adjuster  102 , and the camshaft. 
     Seal  430  is disposed over inboard end  84  of camshaft  86  and is in contact with body  104  of slack adjuster  102  to form a 360-degree seal on the inboard side. Seal  430  is formed from a flexible elastomeric material, such as rubber, with a generally tubular, frustoconical shape forming an opening or cavity  432 . An inboard flange  439  may be formed about the inboard end of cavity  432  and extend radially outward from seal  430 . In addition, a large-diameter flap or lip  434  is formed about the outboard edge of cavity  432  and is in contact with a coverplate (not shown) or body  104  of slack adjuster  102  to form a 360-degree seal about the inboard side of the slack adjuster. As a result, pressurized grease may pool within cavity  432  as it flows between internal and external splines  108 ,  87  of slack adjuster  102  and camshaft  86 , respectively, and through washers  412  and E-clip  414  to form a grease reservoir about and adjacent to sensor arrangement  350  and components of slack adjuster assembly  400  to prevent wear and corrosion. The large diameter of lip  434  combined with the flexible elastomer of seal  430  allows the lip to be displaced from cavity  432 . More specifically, in the event grease overfills cavity  432 , lip  434  may deflect radially outwardly and inboardly away from slack adjuster  102 , allowing excess grease to be purged from the cavity. The frustoconical shape of seal  430  combined with the flexible elastomer material of the seal also prevents the seal from pulling a vacuum on cavity  432  or pressurizing the cavity in the event axial movement of camshaft  86  occurs during braking. More particularly, in the event of axial movement of camshaft  86  during braking, seal  430  may flex, compensating for any volume changes within cavity  432 , thereby preventing suction of water, chemicals, and/or other debris past lip  434  into the cavity as well as preventing increased pressure from purging grease past lip  434  and out of the cavity. 
     Cover  420  of inboard sealing assembly  410  is formed from any suitable material, such as steel, plastic, or composite, using any suitable process, such as stamping, as a generally cylindrical shape having an outboard section  422  and an inboard flange  424 . Outboard section  422  may mechanically engage with the inboard side of slack adjuster  102 . More specifically, outboard section  422  may be press-fit into annular recess  106  formed into a coverplate (not shown) or body  104  on the inboard side of slack adjuster  102 . It is contemplated that any other suitable method of connection or attachment may be used between cover  420  and slack adjuster  102 , such as a threaded connection. Inboard flange  424  extends radially inward from the inboard end of outboard section  422  and includes a central opening  426 . Inboard flange  424  also includes a plurality of openings  421  for receiving fasteners  363  to attach sensor  352  to cover  420 . It is contemplated that cover  420  may also include a plurality of vents (not shown) formed through flange  424  or outboard section  422  and having a suitable size and/or shape to provide protection to seal  430  and sensor arrangement  450  from damage potentially caused by power washers while allowing pressure equalization between the interior and exterior of the cover. As a result, air and/or grease may be purged from concavity  432  of seal  430  without creating back pressure and water, chemicals, and/or debris may drain from cover  420 , preventing collection inside the cover. 
     Seal  430  may be connected to, or mechanically engage with, cover  420 . More specifically, inboard flange  439  of seal  430  may be attached, such as by adhesive, to the outboard side of inboard flange  424  of cover  420 . Alternatively, inboard flange  439  and the outboard side of inboard flange  424  of cover  420  may have any suitable, reciprocal formations (not shown) that allow the inboard flange of the seal to be molded to or otherwise mechanically engage with the inboard flange of the cover. It is also contemplated that any other suitable method may be used to connect or engage seal  430  with cover  420 . Engagement of seal  430  to cover  420  may facilitate control and adjustment of the contact pressure of lip  434  against the inboard side of slack adjuster  102 . 
     Thus, slack adjuster assembly  400 , according to the present invention, provides sensor arrangement  350  for monitoring rotation of camshaft  86  that can be utilized without regard to slack adjuster manufacturer and is minimally disruptive and/or does not add complexity to maintenance and assembly of the drum brake system. In addition, slack adjuster assembly  400  utilizes inboard sealing assembly  410  that maintains lubrication of slack adjuster  102  and camshaft  86  while protecting sensor arrangement  350  from potential impact damage, extreme temperatures, water, chemicals, and/or debris, thereby increasing the maintenance interval and service-life of the sensor arrangement and slack adjuster assembly and reducing heavy-duty vehicle down time. 
     It is contemplated that slack adjuster assemblies  100 ,  200 ,  300 ,  400  according to the present invention, could be formed from any suitable material, including but not limited to composites, metal, and the like, without changing the overall concept or operation of the present invention. It is also contemplated that slack adjuster assemblies  100 ,  200 ,  300 ,  400  of the present invention could be utilized in drum brake systems on heavy-duty vehicles having more than one axle and/or one or more than one wheel per wheel end assembly, without changing the overall concept or operation of the present invention. It is further contemplated that slack adjuster assemblies  100 ,  200 ,  300 ,  400  of the present invention could be utilized with all types of heavy-duty vehicle drum brake systems without changing the overall concept or operation of the present invention. 
     It is contemplated that different arrangements and materials of inboard sealing assemblies  110 ,  310 ,  410 , other than those shown and described, could be utilized without changing the overall concept or operation of the present invention, so long as they achieve a 360-degree seal on the inboard side of slack adjuster  102  that prevents grease back pressure while providing protection for sensor arrangements  150 ,  250 ,  350  from impact damage, extreme temperatures, water, chemicals, and/or debris. Similarly, inboard sealing assemblies  110 ,  310 ,  410 , including seals  130 ,  330 ,  430  and covers  120 ,  320 ,  420 , could have different configurations without changing the overall concept or operation of the present invention. It is also contemplated that sensor arrangements  150 ,  250 ,  350  could utilize other types of angular or rotation sensors, other than those shown and described, such as anisotropic magnetoresistance sensors, variable resistant sensors, or potentiometers, without changing the overall concept or operation of the present invention. 
     Accordingly, the slack adjuster assemblies of the present invention are simplified; provide an effective, safe, inexpensive, and efficient structure and method, which achieve all the enumerated objectives; provide for eliminating difficulties encountered with prior art slack adjuster assemblies; and solve problems and obtain new results in the art. 
     In the foregoing description, certain terms have been used for brevity, clarity, and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. Moreover, the description and illustration of the invention is by way of example, and the scope of the invention is not limited to the exact details shown or described. 
     Having now described the features, discoveries, and principles of the invention; the manner in which the slack adjuster assemblies are used and installed; the characteristics of the construction, arrangement, and method steps; and the advantageous, new, and useful results obtained, the new and useful structures, devices, elements, arrangements, process, parts, and combinations are set forth in the appended claims.