Patent Publication Number: US-2005126867-A1

Title: Sealing device for a slack adjuster

Description:
FIELD OF THE INVENTION  
      The present invention relates to sealing boots and, more particularly, to sealing boots for slack adjusters used with vehicle braking systems.  
     BACKGROUND OF THE INVENTION  
      Slack adjusters are commonly used with vehicular braking systems to take up the excess spacing or slack that occurs between the parts of a braking system after a significant amount of use and wear. Braking systems including slack adjusters, however, are exposed to a variety of road and environmental conditions that can cause contamination of their inner workings and reduce their effectiveness. Various sealing devices have been used to attempt to inhibit contamination of the inner workings of slack adjusters. Such sealing devices often comprise several components. For example, some conventional sealing devices for slack adjusters include boots, seals, and connection brackets or other connection devices to connect the boots and seals to one another and to the slack adjuster. Often, one or more of the connections between the components or between the components and the slack adjuster is prone to mechanical failure or dislodgement, thereby allowing the inner workings of the slack adjuster to become exposed to road dirt or rust and thereby contaminated. Accordingly, there is a desire for a sealing device that effectively inhibits contamination of a slack adjuster.  
     SUMMARY OF THE INVENTION  
      The present invention provides a boot for a slack adjuster. The slack adjuster includes a link and a body that defines a cavity and a lip. The boot includes a plurality of expandable folds comprising a bellows and a first seal integrally formed with the bellows on a first end. The first seal is engageable with the link. The boot also has a boss and a second seal integrally formed with the bellows on a second end. The second seal is positionable in the cavity of the body and is engageable with the link. The boss is engageable with the lip of the body to inhibit removal of the second seal from the cavity.  
      The slack adjuster also has a radially inwardly extending lip that at least partially closes an opening of the cavity and a boot that includes a seal and a plurality of folds comprising a bellows. The seal has a boss and is positionable in the cavity. The boss is engageable with the lip to inhibit removal of the seal from the cavity.  
      The present invention further provides a method of assembling a slack adjuster, including providing a body of the slack adjuster, the body defining a cavity therein, providing a boot that includes a plurality of bellows and a seal integral with the plurality of bellows, inserting the seal of the boot into the cavity, and inserting a link through the boot and into the cavity after the seal is inserted into the cavity.  
      Additional features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a slack adjuster including a sealing device embodying the invention.  
       FIG. 2  is a partial exploded perspective view of the slack adjuster of  FIG. 1  including the sealing device.  
       FIG. 3  is a partial cross-sectional view taken along line  3 - 3  in  FIG. 1 , shown with the slack adjuster in a retracted condition.  
       FIG. 4  is a partial cross-sectional view similar to the cross-sectional view shown in  FIG. 3 , shown with the slack adjuster in an extended condition.  
      The invention is not intended to be limited in its application to the details of the construction and arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
    
    
     DETAILED DESCRIPTION  
      Referring to  FIGS. 1 and 2 , a slack adjuster  20 , including a sealing device or boot  56 , is useable with vehicular braking systems (not shown) to take-up the slack in the vehicular braking systems that occurs over time due to wearing of the brake pads, brake drums, and other components of the vehicular braking systems.  
      The slack adjuster  20  includes a body  24  with a shaft aperture  28  therethrough. A splined support  32  is positioned within the shaft aperture  28  to receive a camshaft or shaft (not shown) of the braking system. As will be known to those of skill in the art, the shaft may be an “S” camshaft, which refers to the manner in which the shaft brings about operation of the braking system. A yoke  36  is pivotally connected to the body  24  using a first pin connection  40  and is pivotally connected to a linking bar or link  44  using a second pin connection  48  to form a connection between internal slack adjusting components (not shown) of the slack adjuster  20  and the braking system (not shown). The braking systems and internal slack adjusting components are conventional and well known to those of ordinary skill in the art and, therefore, will not be discussed in greater detail herein except where reference thereto is necessary to describe the present invention.  
      With continued reference to  FIGS. 1 and 2 , the body  24  defines a cavity  52  into which the link  44  extends. The link  44  is axially movable within the cavity  52  and interacts with the internal slack adjusting components housed within the body  24 . The slack adjuster  20  also includes a sealing device or sealing boot  56  that inhibits contamination of the cavity  52 . The slack adjuster  20  may operate inappropriately or may be inoperable if contaminates, such as, for example oil, dirt, water, dust, etc., enter the cavity  52  and interfere with the internal slack adjusting components. Accordingly, the boot  56  inhibits such contaminates from entering the cavity  52  and contaminating the slack adjuster  20 .  
      Referring now to  FIGS. 2 and 3 , the boot  56  is a single integral piece that defines a boot cavity  60  therethrough and includes a plurality of folds comprising a bellows  64 , an upper seal  68  (as viewed in  FIGS. 2 and 3 ) and a lower seal  72  (as viewed in  FIGS. 2 and 3 ). The boot  56  is formed of a single material, which has a consistent hardness throughout. The boot  56  can be made of various types of elastic materials, and can have various hardnesses (e.g., 45 to 75 Shore A). In a preferred embodiment of the present invention, the boot  56  is made of Nitrile Butadiene Rubber (NBR), with a hardness of 45 to 65 Shore A. It should be understood, however, that the boot  56  can integrally be formed of a composite material that has portions of various hardnesses and still be within the spirit and scope of the present invention.  
      In the illustrated embodiment, the boot  56  includes five folds. The plurality of folds are expandable (see  FIG. 4 ) to allow movement of the upper seal  68  with the link  44  (discussed in greater detail below) relative to the lower seal  72 .  
      The upper seal  68  is positioned at an upper end (as viewed in  FIGS. 2 and 3 ) of the bellows  64  and is engageable with the link  44 . The upper seal  68  includes a lip  76  that is positionable within a recess  80  defined in the link  44  to connect the upper seal  68  to the link  44 . The resiliency of the upper seal  68  is sufficient to maintain the lip  76  in the recess  80  during normal operation, but allow an operator to disconnect the upper seal  68  from the link  44  when desired. Accordingly, the upper seal  68  moves with the link  44  (discussed in greater detail below) during normal operation of the slack adjuster  20 .  
      The lower seal  72  is positioned at a lower end (as viewed in  FIGS. 2 and 3 ) of the bellows  64 , within a seal cavity  84  defined in the body  24  between a lip  88  and a shoulder  92  of the body  24 . The lip  88  partially closes off the opening to the seal cavity  84 . The lower seal  72  includes a boss  96  that is positioned in the seal cavity  84  and engageable with the lip  88  of the body  24  to inhibit removal of the lower seal  72  from the seal cavity  84  when the link  44  is positioned within the boot  56 . The lower seal  72  also includes a pair of flanges or projections  100  that extend therefrom and engage the link  44  to form a seal with the link  44 . The engagement between the lower seal  72  and the link  44  inhibits contamination of the cavity  52 . The projections  100  are resilient, which allows them to maintain engagement with the link  44  as the link  44  moves axially within the cavity  52 . During axial movement of the link  44 , the projections  100  engage an outer surface of the link  44  and wipe the outer surface. In other embodiments of the present invention, the lower seal  72  may include any number of projections  100  to create a seal between the projection(s)  100  and the link  44  and still be within the spirit and scope of the present invention.  
      With particular reference to  FIGS. 2 and 3 , the slack adjuster  20  is assembled by inserting the lower seal  72  of the boot  56  into the seal cavity  84 . Depending on the exact configuration and type of material of the boot  56 , the lower seal  72  may need to be folded or twisted in order to insert it past the lip  88  of the body  24  and into the seal cavity. In some embodiments of the present invention, the lower seal  72  may be made of a material sufficiently resilient to allow insertion of the lower seal  72  past the lip  88  of the body  24  and into the seal cavity  84  solely by biasing the lower seal  72  downward against the lip  88 , without folding or twisting. The lower seal  72  may be inserted past the lip  88  and into the seal cavity  84  by deforming it in other manners and still be within the spirit and scope of the present invention.  
      Once the lower seal  72  is inserted into the seal cavity  84 , the link  44  is inserted through the boot cavity  60  and into the cavity  52  of the body  24 . As the link  44  is being inserted, the link  44  engages the lip  76  of the upper seal  68  and the projections  100  of the lower seal  72  and slides past the lip  76  and the projections  100 . When the link  44  is properly positioned relative to the body  24 , the lip  76  of the upper seal  68  engages the recess  80  and is maintained in the recess  80  due to the resiliency or press fit of the upper seal  68 , thereby connecting the upper seal  68  to the link  44 . The projections  100  engage the link  44  when the link  44  is properly positioned relative to the body  24  to create an effective seal with the link  44  and inhibit contamination of the cavity  52 . The link  44  is then interconnected with the internal slack adjusting components (not shown) and the yoke  36  of the slack adjuster  20 . With the link  44  positioned within the boot  56 , the boss  96  of the boot  56  is snuggly positioned against the body  24  and is prevented from collapsing in on itself and disengaging from the lip  88  of the body  24 . Therefore, the engagement between the lip  88  of the body  24  and the boss  96  of the lower seal  72  is ensured and inhibits removal of the lower seal  72  from the seal cavity  84 .  
       FIGS. 3 and 4  show the operation of the slack adjuster  20  as it relates to the boot  56 . The slack adjuster  20  can operate in a retracted condition (see  FIG. 3 ), in which the link  44  is in a downward position and the folds of the bellows  64  of the boot  56  are compressed or unexpanded, and in an extended condition (see  FIG. 4 ), in which the link  44  has moved from the downward position to an upward position and the upper seal  68  has moved upward with the link  44  to expand the folds of the bellows  64  of the boot  56 . The connection between the upper seal  68  and the link  44  and the engagement of the lower seal  72  and the lip  88  of the body  24  facilitate movement of the upper seal  68  with the link  44  and facilitate movement of the upper seal  68  relative to the lower seal  72 . In the illustrated embodiment, the five folds of the bellows  64  allow the boot  56  to expand approximately 0.25 inches per fold (approximately 1.25 inches overall). By including five folds in the bellows  64 , the boot  56  has a slimmer retracted profile P 1  (corresponding to the retracted condition of the slack adjuster  20 ) and a slimmer extended profile P 2  (corresponding to the extended condition of the slack adjuster 20 ) than a boot having fewer bellows and the same expansion capability. In other words, with all other variables being equal, a boot with fewer than five bellows and the same expansion capability will have retracted and extended profiles wider than the retracted and extended profiles P 1 , P 2  of the boot  56 .  
      When the slack adjuster  20  is initially connected to a new or relatively new braking system, the slack adjuster  20  is in the retracted condition because the braking system is not worn down and the slack adjuster  20  has no slack to take-up from the braking system. As the braking system begins to wear over time, the slack adjuster  20  takes up the slack in the braking system causing the link  44  to move upward and the slack adjuster  20  to move toward the extended condition. The two projections  100  continuously engage the outer surface of the link  44  in a “wiping” manner, sliding over the surface of the link  44 , as the slack adjuster  20  moves between the retracted condition and the extended condition to inhibit contamination of the cavity  52 . When the braking system has sufficiently worn down to the point that the slack adjuster can no longer function adequately, the braking system (or components of it) is replaced.  
      Although particular constructions of the present invention have been shown and described, other alternative constructions will be apparent to those skilled in the art and are within the intended scope of the present invention. Thus, the present invention is to be limited only by the claims.