Abstract:
A boot-type seal having a seal and a valve. The seal has a first seal member, which is configured to sealingly engage a first surface, and a second seal member, which is configured to sealingly engage a second surface. The valve is coupled to the seal and is operable in a first condition, which inhibits fluid communication therethrough, and a second condition, which permits fluid communication therethrough. The condition of the valve changes from the first condition to the second condition in response to a fluid pressure exerted on a side of the seal that exceeds a predetermined threshold pressure. A brake assembly that incorporates the boot-type seal is also provided.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention generally relates to boot-type seals and more particularly to a pressure-bleeding boot-type seal that is especially suited for use in a brake assembly.  
         BACKGROUND OF THE INVENTION  
         [0002]    A typical brake assembly for a motor vehicle includes a caliper assembly and one or more brake pads. The caliper assembly includes a frame or body, which is mounted to the structure of the vehicle and a caliper piston. The caliper piston is movably mounted to the caliper body so as to be selectively engagable with the brake pads to cause the brake pads to frictionally engage an element, such as a vehicle rotor, to thereby slow or stop the vehicle.  
           [0003]    The caliper body includes a piston bore into which the piston is received. A boot-type seal is typically employed to seal around the perimeter of both the piston bore and the caliper piston to inhibit moisture, dirt, debris and other contaminants from entering the piston bore and potentially damaging the caliper body and/or caliper piston. Despite the widespread use of such boot-type seals, several drawbacks are known and thus, such boot-type seals are susceptible to improvement.  
           [0004]    One such drawback concerns the buildup of fluid pressure within such boot-type seals. As those of ordinary skill in the art will appreciate, heat generated during the operation of the brake assembly causes the air that is trapped by the boot-type seal to expand. In especially severe instances, it may be possible for the boot-type seal to expand and deleteriously contact another portion of the brake assembly, causing the boot-type seal to burn, melt, or otherwise undergo a shortening of its useful life as a result of thermal cycling at elevated temperatures. If severe enough, such damage may lead to a failure of the boot-type seal through which dirt, debris, moisture and other contaminants may be transmitted.  
         SUMMARY OF THE INVENTION  
         [0005]    In one preferred form, the present invention provides a boot-type seal for sealing a joint between a first surface and a second surface. The boot-type seal includes a seal having a first seal member, which is configured to sealingly engage the first surface, and a second seal member, which is configured to sealingly engage the second surface. The boot-type seal also includes a valve that is coupled to the seal. The valve is operable in a first condition, which inhibits fluid communication therethrough, and a second condition which permits fluid communication therethrough. The condition of the valve changes from the first condition to the second condition in response to a fluid pressure exerted on a side of the seal that exceeds a predetermined threshold pressure.  
           [0006]    In another preferred form, the present invention provides a brake assembly having a caliper body, a caliper piston and a boot seal. The caliper piston is at least partially disposed in a piston bore formed in the caliper body. The boot seal cooperates with the caliper body and the piston to define a cavity. The piston boot includes a first seal member, which sealingly engages the piston, a second seal member, which sealingly engages the caliper body, and a vent that is in fluid communication with the cavity. The vent includes a valve element that is operable in a sealed condition in which the valve element inhibits fluid communication between the cavity and the atmosphere. The valve element is further operable in an unsealed condition to vent at least a portion of a fluid within the cavity to the atmosphere. The valve element is normally maintained in the sealed condition but changes to the unsealed condition in response to a fluid pressure within the cavity in excess of a predetermined threshold pressure.  
           [0007]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0009]    [0009]FIG. 1 is a rear elevation view of a brake assembly constructed in accordance with the teachings of the present invention;  
         [0010]    [0010]FIG. 2 is a sectional view taken along the line  2 - 2  of FIG. 1;  
         [0011]    [0011]FIG. 3 is an enlarged portion of FIG. 2;  
         [0012]    [0012]FIG. 4 is similar to FIG. 3 but illustrates the valve in an open condition to vent the seal;  
         [0013]    [0013]FIG. 5 is a sectional view similar to that of FIG. 3 but illustrating a second brake assembly and boot-type seal constructed in accordance with the teachings of the present invention;  
         [0014]    [0014]FIG. 6 is a sectional view taken along the line  6 - 6  of FIG. 5;  
         [0015]    [0015]FIG. 7 is a sectional view similar to that of FIG. 3 but illustrating a third brake assembly and boot-type seal constructed in accordance with the teachings of the present invention;  
         [0016]    [0016]FIG. 8 is a sectional view taken along the line  8 - 8  of FIG. 7;  
         [0017]    [0017]FIG. 9 is a sectional view similar to that of FIG. 3 but illustrating a fourth brake assembly and boot-type seal constructed in accordance with the teachings of the present invention; and  
         [0018]    [0018]FIG. 10 is a sectional view similar to that of FIG. 3 but illustrating a fifth brake assembly and boot-type seal constructed in accordance with the teachings of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]    With reference to FIGS. 1 and 2 of the drawings, a brake assembly  10  is illustrated to include a caliper body  12 , a caliper piston  16  and a boot-type seal  20  constructed in accordance with the teachings of the present invention. Although the brake assembly  10  is illustrated to be of a type that is commonly utilized in automotive vehicles, those skilled in the art will appreciate that the boot-type seal  20  of the present invention has other uses. Accordingly, those skilled in the art will appreciate that the example provided herein should not be interpreted as limiting the scope of the present invention in any way.  
         [0020]    In the example provided, the caliper body  12  conventionally includes a piston bore  14 , which is sized to slidingly receive the caliper piston  16 , and an annular seal groove  15 , which is sized to receive an annular high-pressure piston seal  18 . The high-pressure piston seal  18  sealingly engages both the caliper body  12  and the caliper piston  16  in a conventional manner to inhibit a loss of a hydraulic fluid (not shown) that is employed to translate the caliper piston  16  relative to the caliper body  12 .  
         [0021]    The circumference of the caliper piston  16  is highly finished so as to effect a requisite level sealing between the caliper piston  16  and the high-pressure piston seal  18  through the range of the caliper piston&#39;s movement. Tight or close tolerancing of the piston bore  14  relative to the outer diameter of the caliper piston  16  also aids in the achievement of the requisite level of sealing.  
         [0022]    With reference to FIGS. 2 and 3, the boot-type seal  20  protects the joint that is defined by the intersection of the caliper body  12  and the caliper piston  16 , as well as protects the portion of the outer surface  16   a  of the caliper piston  16  that is located outwardly of the high-pressure piston seal  18 . The boot-type seal  20  is illustrated to include a seal portion  20   a  and a valve  20   b , which is coupled to the seal portion  20   a . The seal portion  20   a  includes a first seal member  22 , a second seal member  24  and a bellows  30 , which interconnects the first and second seal members  22  and  24 . The first and second seal members  22  and  24 , the bellows  30  and the valve  20   b  may be unitarily formed from a suitable material, such as silicone rubber.  
         [0023]    In the example provided, the first seal member  22  abuts and sealingly engages a wall  12   a  of a counterbore  12   b  that is formed into the caliper body  12  concentric with the piston bore  14 , while the second seal member  24  is disposed in and sealingly engages an annular groove  28  formed about the perimeter of the caliper piston  16 . An annular reinforcing member  26 , which is formed of a suitable material, such as spring steel, may be employed to reinforce the first seal member  22  and urge it into sealing contact with the caliper body  12 .  
         [0024]    The bellows  30  includes one or more convolutions  30   a  and as noted above, serves to interconnect the first and second seal members  22  and  24  to one another. The convolutions  30   a  are formed with a degree of flexibility that permits the first and second seal members  22  and  24  to remain sealingly engaged to the caliper piston  16  and the caliper body  12 , respectively, throughout the caliper piston&#39;s range of movement. In this regard, the convolutions  30   a  deflect (e.g., fold or unfold) in response to the translation of the caliper piston  16  within the piston bore  14 .  
         [0025]    The valve  20   b  includes a vent channel  34 , which is formed through the seal portion  20   a , and a valve element  38  that is employed to seal the vent channel  34 . In the example provided, the vent channel  34  is generally L-shaped, extending forwardly from a rearward surface of the first seal member  22  and thereafter radially outwardly through the perimeter of the first seal member  22 . The valve element  38  is an annular lip that is resiliently coupled to the first seal member  22 . The distal end of the valve element  38  engages an annular spot face  12   c , which is concentric with the counterbore  12   b , to thereby close the outlet of the vent channel  34 .  
         [0026]    With reference to FIG. 4, the pressure of the gas  40  trapped in the volume or cavity  32  that is defined by the counterbore  12   b , the boot-type seal  20  and the caliper piston  16  may increase during the operation of the brake assembly  10  due to heat. Since the vent channel  34  extends through the seal portion  20   a , the gas  40  exerts a force directly onto the valve element  38 . When the pressure of the gas  40  increases to a predetermined threshold, the force that acts on the valve element  38  is sufficient in magnitude so as to lift the valve element  38  out of contact with the spot face  12   c  to enable fluid communication between the cavity  32  and the atmosphere  42 . In this manner, a portion of the gas  40  that had been trapped in the cavity  32  is released through the valve  20   b  to the atmosphere  42  as indicated by the arrows A to thereby reduce the pressure of the gas  40  that remains in the cavity  32 . With the pressure of the remaining gas  40  in the cavity  32  having been reduced through the venting operation, the force acting on the valve element  38  is reduced and as such, the valve element  38  is able to return into abutment with the spot face  12   c  and seal the vent channel  34 .  
         [0027]    With reference to FIGS. 5 and 6, another brake assembly  110  is illustrated and includes a caliper body  112 , a caliper piston  116  and a second boot-type seal  120  that is constructed in accordance with the teachings of the present invention. The caliper body  112  and caliper piston  116  are generally similar to the caliper body  12  and caliper piston  16  of FIG. 2 and as such, will not be discussed in significant detail other than to note the manner in which they are coupled to the boot-type seal  120 , which is discussed in detail, below.  
         [0028]    The boot-type seal  120  is shown to include a seal portion  120   a  and a valve  120   b , which is coupled to the seal portion  120   a . The seal portion  120   a  includes a first seal member  122 , a second seal member  124 , a bellows  130 , and an auxiliary seal member  125 , which extends from the first seal member  122  and sealingly engages the caliper piston  116 .  
         [0029]    The first seal member  122  is disposed within an annular groove  127  formed in the caliper body  112  and sealingly engages the caliper body  112 . The second seal member  124  is disposed within an annular groove  128  in the caliper piston  116  and sealingly engages the caliper piston  116 . The bellows  130  includes a plurality of convolutions  130   a  and interconnects the first and second seal members  122  and  124  to one another.  
         [0030]    The valve  120   b  includes a vent channel  134 , which is formed through the seal portion  120   a , and a valve element  138  that is employed to seal the vent channel  134 . In the example provided, the vent channel  134  is generally Z-shaped, extending forwardly from a rearward surface of the second seal member  124 , jogging radially inwardly and thereafter outwardly through the front of the second seal member  124 . The valve element  138  is an annular lip that is resiliently coupled to the second seal member  124 . The distal end of the valve element  138  engages the outer perimeter of the caliper piston  116  to thereby close the outlet of the vent channel  134 .  
         [0031]    The pressure of the gas  140  trapped in the cavity  132  that is defined by the boot-type seal  120  and the caliper piston  116  may increase during the operation of the brake assembly  110  due to heat. Since the vent channel  134  extends through the seal portion  120   a , the gas  140  exerts a force directly onto the valve element  138 . When the pressure of the gas  140  increases to a predetermined threshold, the force that acts on the valve element  138  is sufficient in magnitude so as to lift the valve element  138  out of contact with the caliper piston  116 , which is illustrated in phantom, to enable fluid communication between the cavity  132  and the atmosphere  42 . In this manner, a portion of the gas  140  that had been trapped in the cavity  132  is released through the valve  120   b  to the atmosphere  42  to thereby reduce the pressure of the gas  140  that remains in the cavity  132 . With the pressure of the remaining gas  140  in the cavity  132  having been reduced through the venting operation, the force acting on the valve element  138  is reduced and as such, the valve element  138  is able to return into abutment with the caliper piston  116  and seal the vent channel  134 .  
         [0032]    With reference to FIGS. 7 and 8, a third brake assembly  210  is illustrated. The brake assembly  210  is generally similar to the brake assembly  110  of FIGS. 5 and 6, except for the construction of the caliper piston  216  and the valve  220   b  of the boot-type seal  220 . More specifically, the caliper piston  216  is formed with an annular groove  228  for receiving the second seal member  224 , and one or more vent grooves  250 , which are illustrated as being generally L-shaped in the particular example provided.  
         [0033]    The valve  220   b  includes a vent channel  234 , which is formed through the seal portion  220   a , and a valve element  238  that is employed to seal the vent channel  234 . In the example provided, the vent channel  234  extends radially outwardly from the second seal member  224  toward the caliper piston  216  and terminating at a point rearwardly of the second seal member  224 . The valve element  238  is an annular lip that is resiliently coupled to the second seal member  224 . The distal end of the valve element  238  engages the outer perimeter of the caliper piston  216  to thereby close the inlet of the vent channel  234 .  
         [0034]    The pressure of the gas  240  trapped in the cavity  132  that is defined by the boot-type seal  220  and the caliper piston  216  may increase during the operation of the brake assembly  210  due to heat. When the pressure of the gas  240  increases to a predetermined threshold, the force that acts on the valve element  238  is sufficient in magnitude so as to lift the valve element  238  out of contact with the caliper piston  216 , which is illustrated in phantom, to enable fluid communication past the valve element  238  and into the vent channel  234 . The gas exiting the cavity  132  into the vent channel  234  is able to pass through the vent grooves  250  and into the atmosphere  42 . In this manner, a portion of the gas  240  that had been trapped in the cavity  132  is released through the valve  220   b  to the atmosphere  42  to thereby reduce the pressure of the gas  240  that remains in the cavity  132 . With the pressure of the remaining gas  240  in the cavity  132  having been reduced through the venting operation, the force acting on the valve element  238  is reduced and as such, the valve element  238  is able to return into abutment with the caliper piston  216  and seal the vent channel  234 .  
         [0035]    With reference to FIG. 9, a fourth brake assembly  310  is illustrated. The brake assembly  310  is generally similar to the brake assembly  110  of FIGS. 5 and 6, except for the construction of the caliper piston  316  and the valve  320   b  of the boot-type seal  320 . More specifically, the caliper piston  316  is formed with a first annular groove  328  for receiving the second seal member  324 , and a second annular groove  350  that is positioned rearwardly of the first annular groove  328 .  
         [0036]    The valve  320   b  includes a vent channel  334 , which is formed through the seal portion  320   a , and a valve element  338  that is employed to seal the vent channel  334 . In the example provided, the vent channel  334  extends radially outwardly from the second seal member  324  toward the caliper piston  216 , extending forwardly therefrom through the second seal member  324  and radially inward at a point forwardly of the second seal member  324 . The valve element  338  is an annular lip that is resiliently coupled to the second seal member  324 . The distal end of the valve element  338  engages the outer perimeter second annular groove  350  to thereby close the inlet of the vent channel  334 . Operation of the valve  320   b  of the boot-type seal  320  is generally similar to the operation of the valve  220   b  of the boot-type seal  220  discussed above, except that the gas  340  is vented to the atmosphere  42  directly through the vent channels  334 .  
         [0037]    With reference to FIG. 10, a fifth brake assembly  410  is illustrated. The brake assembly  410  is generally similar to the brake assembly  310  of FIG. 9, except for the construction of the caliper piston  416  and the valve  420   b  of the boot-type seal  420 . More specifically, the caliper piston  416  is formed with a single annular groove  428  for receiving the second seal member  424 , while the valve element  438  sealingly engages the rear face  438   a  of the annular groove  428  to close the inlet of the vent channel  434 . Operation of the valve  420   b  of the boot-type seal  420  is generally similar to the operation of the valve  320   b  of the boot-type seal  320  discussed above.  
         [0038]    The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.