Abstract:
A master-cylinder seal housed in a groove around a piston has a core connected to three annular and concentric lips. The core rests against a side of the groove and has: a surface provided with an interior edge followed by a peripheral platter cut by at least one channel, and an exterior crown provided with a connection zone formed by an interruption in the crown and deformable due to pressure within the seal to recreate the crown&#39;s continuity and impermeability while facilitating purging the brake system when there is no pressure in the channel and the connection zone.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a divisional application of U.S. patent application Ser. No. 13/995,413, which is the U.S. national stage of international patent application no. PCT/EP2011/072420, filed Dec. 12, 2011, and which claims priority to French patent application no. 100 50 10, filed Dec. 21, 2010, the entire contents of each of which is hereby incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a brake system master-cylinder seal having a generally annular shape, housed in a groove of the master cylinder around the piston, the seal being of a type comprising a core connecting three lips appreciably annular and concentric, respectively internal, intermediate, and concentric, each of which is equipped with a free end and an end connecting with the core, at least one portion of the free end of the intermediate lip creating an axial protrusion with respect to the free ends of the internal and external lips, the intermediate lip being interrupted along its periphery in such a way that it has several circumferentially spaced portions forming support areas and passages with the wall opposite that against which the surface of the core rests. 
       BACKGROUND 
       [0003]    There exist seals, notably described in European patent document EP 2,080,939, known as resupply seals, of the type described above, but under certain conditions, it is difficult to purge the master cylinder or, at least, to purge it effectively and completely. 
       SUMMARY 
       [0004]    An object of the invention is to provide a seal, e.g., a brake system master-cylinder resupply seal, that facilitates purging the brake system before it is filled with brake fluid and constitutes a supplementary sealing element for pressures on the order of 1 to 3 bars. 
         [0005]    According to the invention the surface of the core of the seal comprises:
       a peripheral platter,   a raised exterior crown, externally bordering the platter and having: at least one connection zone, open and deformable from the effect of the interior pressure of the seal to recreate the continuity of the exterior crown,   a heel beyond the crown and in the extension of each interruption formed by the connection zone of the crown,   at least one channel realized in the platter and issuing from the interior edge that does not emerge at the exterior terminating ahead of the connection zone of the crown.       
 
         [0010]    A channel that does not emerge at the exterior of the surface of the core of the seal is sufficient to constitute a passage to effectively purge the brake system when it is put in service. This also allows for the realization of a complementary sealing surface for certain pressures, notably, pressures comprised between 1 and 3 bars. 
         [0011]    According to another advantageous characteristic, the platter terminates ahead of the exterior crown and forms, with the exterior crown, a passage constituting a supplementary sealing chamber, especially if the connection zone consists of a cavity made in the exterior crown. 
         [0012]    According to another characteristic, the connection zone consists in the suppression of the exterior crown along a certain peripheral length. The material of the core near this connection zone can, thus, be deformed through the effect of the interior pressure of the seal to constitute a sealing zone in the extension of the exterior crown and on either side of it near the connection zone. 
         [0013]    According to another advantageous characteristic, the peripheral platter is separated from the exterior crown by a passage near the channel and the interior edge. As indicated above, this passage, especially when the exterior crown has a connection zone consisting of a cavity, can form an intermediate chamber, promoting, on the one hand, the deformation of the connection zone from the effect of internal pressure and, on the other hand, constituting a sealing chamber. 
         [0014]    The channel realized in the peripheral platter is preferably radially directed. This channel may be unique or several channels may be provided in the peripheral platter. 
         [0015]    The invention also concerns a brake system master cylinder having a body with a pressure chamber receiving a piston, the bore hole of the pressure chamber having a groove receiving a seal providing a seal for the piston in the body of the master cylinder, wherein the groove separates the pressure chamber from a supply chamber connected to the hydraulic fluid supply channel, characterized in that the groove accommodates a resupply seal of generally annular shape having a core connecting three appreciably annular and concentric lips (x-x axis of the master cylinder), respectively internal, intermediate, and external, each of which is equipped with a free end and a connection end with the core, wherein at least one part of the free end of the intermediate lip protrudes axially (x-x direction) with respect to the free ends of the internal and external lips, the intermediate lip being circumferentially interrupted so as to have several spaced portions in the peripheral direction, forming support areas and passages with the wall opposite the wall against which the surface of the core rests, the surface of the core comprising:
       a peripheral platter   a raised exterior crown, externally bordering the platter, the exterior crown having a connection zone that can be deformed by internal pressure on the seal to recreate the continuity of the exterior crown,   a heel beyond the crown and in the extension of each interruption formed in the crown by the connection zone,   at least one channel issuing from the interior edge not emerging at the exterior, terminating before the connection zone of the exterior crown.       
 
         [0020]    According to another advantageous characteristic of the invention, the master cylinder is a simple master cylinder with a piston and a groove receiving a resupply seal or a tandem master cylinder with a principal piston and an auxiliary piston, each of which cooperates with a resupply seal housed in a groove of the body of the master cylinder. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]      FIG. 1  shows a partial axial section of a brake system master cylinder according to the invention near a seal. 
           [0022]      FIG. 2  shows a perspective view of the seal of  FIG. 1 . 
           [0023]      FIGS. 3A and 3B  show respectively, and very schematically, illustrate the seal supports between the seal, the groove in the body of the master cylinder, and the piston, in the absence of pressure ( FIG. 3A ) and in the case of high pressure ( FIG. 3B ). 
           [0024]      FIG. 4  shows a section of the seal according to the invention. 
           [0025]      FIG. 5  shows a perspective view of a part of the rear face of the core of the seal of  FIG. 4  with a first embodiment of the seal means. 
           [0026]      FIG. 5A  shows a straight developed view of a portion of the surface of the core of the seal. 
           [0027]      FIG. 5B  shows a side view corresponding to  FIG. 5A , illustrating the different reliefs on the face of the core. 
           [0028]      FIG. 5C  shows a view similar to that of  FIG. 4A , displaying the deformable zone of the face of the core, 
           [0029]      FIG. 6  shows a partial perspective view of the rear face of the core of the seal, illustrating a second embodiment of the seal means. 
           [0030]      FIG. 6A  shows a straight developed view of a portion of the surface of the core, illustrating a second embodiment of the seal means. 
           [0031]      FIG. 6B  shows is a side view corresponding to  FIG. 6A  illustrating the relief of different portions of the surface of the core. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    According to  FIG. 1 , seal  22 , still referred to as a resupply seal, for brake system master cylinder  10  is shown. Body  12  of master cylinder  10  delimits pressure chamber  14  and brake fluid supply chamber  16 , itself connected to supply channel  18 . Body  12  has internal groove  20 , which is annular, with back wall  20 C and two opposed faces  20 A,  20 B. This groove  20  receives seal  22 , which cooperates with piston  24  to separate chambers  14  and  16 . Piston  24  is movable between a rest position, in which chambers  14  and  16  communicate, and an active position, when piston  24  is actuated by the brake pedal (movement to the left in  FIG. 1 ) to transmit braking forces. At this moment chambers  14  and  16  are separated. 
         [0033]    Seal  22  ( FIGS. 1 and 2 ) consists of core  25  bearing exterior lip  26 E, interior lip  261 , and intermediate lip  26 M. Intermediate lip  26 M has raised portions separated by intervals. Intermediate lip  26 M is intended to be applied to face  20 B to hold seal  22 , applied imperviously by its interior lip  261 , against piston  24 . 
         [0034]    The passage of brake fluid from supply chamber  16  to pressure chamber  14  occurs by bypassing seal  22  connected imperviously to piston  24 . This bypassing occurs between core  25  and face  20 A of groove  20 , then between exterior lip  26 E and back wall  20 C of the groove, then in intervals of the raised portions  30  of intermediate lip  26 M, because neither exterior lip  26 E nor interior lip  261  rest imperviously on groove  20 . 
         [0035]      FIGS. 3A ,  3 B illustrate, respectively, the state of seal  22  in the absence of pressure ( FIG. 3A ) and when pressure is applied in pressure chamber  14  ( FIG. 3B ). 
         [0036]    According to  FIG. 3A , in the absence of pressure on seal  22 , the latter is applied against piston  24  by its interior lip  261 , creating an impervious seal under low pressure on zone A 1  of piston  24  because of the specific, frustoconical, shape of piston  24  at this location. This low pressure allows brake fluid to flow for ESP regulation. Core  25  rests only weakly against side  20 A of groove  20 , as illustrated schematically by point A 2 . The same holds for exterior lip  26 E, which only lightly touches back wall  20 C of groove  20  (point A 3 ). As already indicated, side  20 B of groove  20  is not affected by the seal but simply serves as a support for median lip  26 M. 
         [0037]    According to  FIG. 3B , whenever pressure is generated, for example, by piston  24 , in pressure chamber  14 , this pressure is exercised in cavity  27  of seal  22 , creating a significant impervious zone B 1  with piston  24  and also an impervious zone B 2 , extending appreciably over first face  20 A of groove  20 , which accommodates the face of core  25 . A seal is also created at exterior lip  26 E, which presses against back wall  20 C of groove  20 . This seal is realized through the particular structure of the surface of core  25  according to the invention. 
         [0038]      FIG. 4  shows the section of the shape of revolution of seal  22  when it is not housed in groove  20 , revealing the shape of core  25 , the shape of exterior branch  26 E, equipped with protrusions, the shape of intermediate lip  26 M, with its raised parts and hollows, serving as a support against wall  20 B of groove  20  and allowing brake fluid to flow. 
         [0039]    Two embodiments of the surface of core  25  of seal  22  will be described below by means of  FIGS. 5 and 6 . These surfaces are respectively assigned reference numbers  100  and  200 , and analogous or equivalent elements will be assigned similar reference numbers in the 100 and 200 series. 
         [0040]      FIG. 5  illustrates a portion of a first embodiment of surface  100  of core  25  of the seal, which corresponds to a relief pattern and a hollow pattern distributed along the periphery of core  25  following a uniform distribution pattern, even following a unique pattern. 
         [0041]    Surface  100  consists of platter  102 , raised with respect to interior peripheral edge  101 . Platter  102  is traversed by channel  103 , non-emergent, issuing from interior edge  102  and blocked at its externally directed end. Platter  102  is capped by discontinuous exterior crown  104 , with interruption interval  105  in the direction of channel  103 . Interruption interval  105  forms connection zone  105 , which, when deformed under pressure, as will be described below, provides a seal due to the effect of the pressure. Beyond this connection zone  105 , heel  106  appreciably occupies the width of the interval. Heel  106  is bordered by exterior edge  107 . The direction of channel  103  is preferably radial, although this direction is not imperative. It can also be inclined with respect to the radial direction of the seal. 
         [0042]    The shape of the pattern of surface  100  is shown in the plan view of  FIG. 5A , which is a straight development of the circular shape.  FIG. 5B  is a side view of the straight development corresponding to  FIG. 5A  and illustrating the various levels of the elements composing surface  100 . 
         [0043]      FIG. 5B  shows the relation between the various levels in the radial direction with respect to an unspecified origin: the height, HO, of interior edge  101 , the height, HI, of platter  102 , and the height, H 2 , of interrupted crown  104 . The channel has a back wall with height H 0 . In this view, heel  106  has the same height, HI, as platter  102 . 
         [0044]      FIGS. 5 and 5A  illustrate, using a dashed line, the sealing line (L) of seal  100  when it is applied to face  20 A of groove  20  ( FIG. 1 ). The seal is realized by deformation under pressure of the interior of seal  100 . The deformation involves zone ZD, drawn on  FIG. 5C , which, when under pressure, is raised and flattens the surface of platter  102  in the interruption interval or connection zone  105  against face  20 A of groove  20 . Heel  106  serves to support this deformation force and constitutes a supplementary sealing surface when heel  106  is applied to side  20 A. 
         [0045]      FIGS. 6 ,  6 A,  6 B illustrate a second embodiment of surface  200  of core  25  of seal  22 . Surface  200  consists of a pattern consisting of platter  202  beyond interior edge  201 . Platter  201  is divided by channel  203  near interior edge  201 . Channel  203  emerges beyond platter  202  in the exterior peripheral direction, in peripheral passage  208 . 
         [0046]    Beyond the passage bordering platter  202  is exterior crown  204 , equipped with cavity  205 , which bars the extension of channel  203  and serves as a connection zone. Beyond cavity  205  is heel  206  with, on either side, exterior edge  207 . Heel  206  is also situated in the extension of channel  203 , extending on either side of this extension and there occupying a significant portion of the peripheral length of cavity  205 . 
         [0047]    When there is pressure inside seal  22 , cavity  205  is deformed outwardly, closing the passage it forms in the absence of pressure. A seal is thereby ensured at exterior crown  204  and the surface of cavity  205 , brought to the level of the exterior surface of crown  204 , that is to say, connection zone  205 . 
         [0048]    The invention concerns the realization of a simple or tandem master cylinder such as the one partly shown in  FIG. 1 . Such a master cylinder has a single piston  24  or a primary piston and an auxiliary piston, and the impermeability between pressure chamber  14  and supply chamber  16  with supply channel  18  is provided by resupply seal  22 , whose core has a sealing surface  100 ,  200 , similar to those described above.