Abstract:
The present invention relates to a disc brake with hydraulically operable brake pads and a mechanical actuating which includes an actuating shaft that is rotatably and sealedly mounted in a bore of a brake housing and acts upon at least one of the brake pads. The present invention focuses on that at least in the area of a shaft duct, a sealing element is provided which is fixed to the actuating shaft so as to rotate along with it and cooperates with at least one associated sealing element and/or mating sealing surfaces in a radial direction. The sealing element bridges a portion of the actuating shaft which is different from the shape of a circle.

Description:
TECHNICAL FIELD 
     The present invention relates to brake systems and more particularly relates to disk brake systems having integrated, mechanical actuating mechanisms. 
     BACKGROUND OF THE INVENTION 
     German patent application No. 34 38 209 discloses a disc brake of this type. The actuating shaft is cylindrically and rotatably mounted in a slide bearing, and a shaft sealing ring is placed in the area of a shaft duct which has a sealing lip that abuts on the periphery of the actuating shaft. 
     The manufacture of disc brakes of this type necessitates great effort and structure because the actuating shaft necessitates the provision of a cylindrical abutment surface in the area of the shaft sealing ring, on the one hand. On the other hand, a recess must be provided in the area of a pressure member, which is principally carried out by metal-cutting processes. In general, profile bars are meanwhile employed as actuating shafts having a recess which extends over the total overall length of the actuating shaft. This eliminates at least the need to manufacture the recess. However, no satisfactory solution has been found until now for sealing the mounting support of such actuating shafts against the ingress of dirt and moisture from outside. This frequently results in actuating shafts stuck with corrosion and, hence, defective disc brakes. 
     Therefore, an object of the present invention is to provide a reliable and also inexpensive sealing of the mounting support of profiled actuating shafts which permits reliable functioning over the total useful life of the disc brakes and, in addition, and minimizes losses due to friction. 
     This object is achieved by the brake system of the present invention wherein, in the area of a shaft duct, a sealing element is provided which is fixed to the actuating shaft so as to rotate along with it and cooperates with associated sealing elements and/or sealing surfaces in a radial direction. Another advantage is achieved because the sealing element that is movable along with the actuating shaft cooperates with an associated supplementary sealing element and/or an associated sealing surface also in an axial direction. 
     The present invention contemplates the combination of profiled actuating shafts with conventional and customary sealing elements or, respectively, with easy-to-make sealing surfaces. This minimizes the necessary costs. 
     Costs may be reduced even further by configuring the sealing element as a bushing, which can be manufactured of sheet metal or plastics material by way of deepdrawing processes, for example. A bushing provided as a snap-in element can be fitted to the actuating shaft easily and at low cost. 
     A functional advantage related to sealings can be achieved by forming a collar to the bushing on the side of the shaft end. Additionally, the collar includes a sealing surface for the axial abutment of a sealing element. 
     The sealing element has a disc-shaped configuration and includes radially outside and axial sealing lips which serve to abut on mating sealing surfaces. This produces together with axial sealing lips a prechamber in front of the radial seal which additionally improves the sealing effect of the sealing element. 
     In a preferred aspect of the present invention, the sealing element includes at least one recess into which a carrier element of the actuating lever is engaged. This achieves an improved connection of the sealing element to the shaft for rotation therewith. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a mechanical actuating mechanism of a disc brake according to the state of the art. 
     FIG. 2 is a cross-sectional view of a sealing arrangement of a mechanical actuating mechanism according to the present invention in a view like in FIG.  1 . 
     FIG. 3 is a cross-sectional view of a further development of a sealing arrangement of the mechanical actuating mechanism. 
     FIG. 4 is a cross-sectional view of another variation of the sealing arrangement. 
     FIG. 5 shows details of a modified embodiment in a view like in FIG.  2 . 
     FIG. 6 is still another modified embodiment of the present invention. 
     FIG. 7 is a view of a disc-shaped sealing element. 
     FIG. 8 is a cross-section through a disc-shaped sealing element taken along the line VI—VI in FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a partial cross-sectional view of a disc brake  1  with a mechanical actuating mechanism  2  for hydraulically operable brake pads (not shown). The mechanical actuating mechanism  2  includes an actuating lever  3  and an actuating shaft  4  which is unrotatably connected to lever  3  and is in operative connection to a non-illustrated pressure member. The actuating shaft  4  is rotatably mounted in a bore  5  of the brake housing  6  within a slide bearing  7  and has, at least in part, a cross-section different from the shape of a circle. Provided at end  8  of the actuating shaft  4  is a collar  9  which serves to abut on an intermediate wall  10  and secures the actuating shaft  4  in position in the brake housing  6  in an axial direction  11 . The other end  12  of the actuating shaft  4  extends out of the brake housing  6  in the area of a shaft duct  13 . In a radial direction  14  with respect to the actuating shaft  4 , a shaft sealing ring  15  is installed which protects the slide bearing  7  against the ingress of dirt and moisture from the outside. A sealing lip  16  of the shaft sealing ring  15  which is unrotatably mounted in the brake housing  6  bears against the circumference  17  of the actuating shaft  4 . Assisted by a spring  18 , the actuating lever  3  with the shaft  4  is constantly urged into an end position where the actuating lever  3  with an arm  19  moves to abut a pin  20 . 
     According to the present invention, as is shown in FIG. 2, a sealing element  21  in the form of a bushing is associated with the actuating shaft  4  and adapted to rotate with it. Element  21  extends over a recess  22  of the actuating shaft  4  at least in part. Thus, the bushing ensures a circular circumference  17  in the area of the shaft duct  13  which cooperates in a radial direction  14  with an associated sealing element  23  in the form of a sealing ring. On the end close to the lever, the bushing includes a collar  24  which bears against a mating sealing surface  26  of the actuating lever  3 , and a packing washer  25  is interposed there between. It should be noted that collar  24  and packing washer  25  are not absolutely necessary when the sealing element  21  is attached to the mating sealing surface  26  in a directly sealing fashion. On its other end, the bushing is positively engaged into a groove  27  which is arranged on the circumference of the actuating shaft  4 . To this end, at least one projection  28  is provided on the bushing which extends radially inwardly and ensures an attachment of the bushing to the actuating shaft  4  for rotation therewith. In addition, each projection  28  ensures that the bushing is axially secured in position with respect to the actuating shaft  4 . Of course, other types of attachment of the bushing to the actuating shaft  4  may also be provided. The type of attachment depends especially on which material is chosen for the bushing. For example, bushings made of sheet metal can be caulked, cemented or soldered to the actuating shaft  4 . It is also possible to solder or cement the bushing directly to the mating sealing surface  26  of the actuating lever  3  so that the groove  27  becomes unnecessary. Such a solution is shown in FIG.  6 . Further, combinations of the above-mentioned possibilities are appropriate which ensure an increased reliability in operation due to improved sealing or fastening arrangements. 
     Besides, the embodiment of FIG. 2 shows that the sealing element  23  is arranged in a bore  29  of the brake housing  6  formed fast with the housing. The sealing element  23  has a first sealing lip  30  which elastically abuts on the circumference  17  of the sealing element  21  in a radial direction  14 , and a second sealing lip  31  which elastically abuts on the mating sealing surface  26  of the actuating lever  3  in an axial direction  11 . This produces a chamber  32  between the first and second sealing lips  30 ,  31  which isolates the inside space  33  from gross contaminants. Especially the second sealing lip  31  protects the roller bearings  34 ,  35  against small-size contaminants and moisture. The advantage of the roller bearings  34 ,  35  is that they involve low losses due to friction, on the one hand, and that they are insensitive to corrosion, on the other hand. Principally, however, slide bearings may also be used without departing from the basic idea of the present invention. Moreover, it is self-explanatory that the sealing element  23  according to the present invention may have any desired configuration, for example, with a reinforcing ring  36  shaped in it. 
     The embodiments of FIGS. 3 and 4 are improvements of the sealing arrangement for a mechanical actuating mechanism corresponding to FIG.  2 . Especially the sealing element  21  configured as a bushing has a design different from the one in FIG.  2 . Exactly as in the variation described hereinabove, the bushing  21  at one end is positively engaged in a groove  27  of the actuating shaft  4  and is thereby reliably retained thereon. To improve the sealing effect, the bushing  21  has a deflected collar  24  at its end close to the shaft end. Advantageously, collar  24  has such a radial extension that it provides a sealing surface  60 . A sealing lip  31  of the sealing element  23  bears axially against the sealing surface  60 . It is preferred that the bushing  21  is made of stainless steel, and the collar  24  is produced by sheet-metal shaping, for example, in a punching operation. Similarly, the bushing may of course also be made of any other suitable material, such as plastics. Due to the appropriate material selection for the bushing, especially when it is made of stainless steel, the desired surface quality of the sealing surface  60  is achieved. The result is a particularly effective sealing joint between the bushing  21  and the sealing lip  31 . To ensure a sealing between the bushing and the actuating lever  3 , an additional packing washer  25  is enclosed between the collar  24  and the actuating lever. This additional provision prevents the ingress of dirt between the bushing and the actuating lever  3 . According to FIG. 3, the annular packing washer  25  can be safely positioned by a step  61  in the bushing and pressed against the actuating lever with the pressure needed. 
     In the sealing arrangement according to FIG. 4, the packing washer  25  has a larger extension in a radial direction and is interposed axially under preload between the bushing  21  and the actuating lever  3 . This eliminates the need for the step  61  on the bushing shown in FIG. 3, and the result is a simplified bushing design. Similarly to the arrangements described hereinabove, the collar  24  of the bushing is extended in a radial direction so far that it provides a sealing surface  60  for the axial abutment of the associated sealing lip  31 . 
     FIG. 5 shows a design wherein the sealing element  21  has the shape of a bushing and engages into groove  27  with fingers  38  arranged on the end of resilient arms  37 . On the end close to the lever  3 , an O-ring  39  is interposed between the sealing element  21  and the mating sealing surface  26 . Its purpose is to seal a gap  40  between the actuating shaft  4  and the sealing element  21 . The sealing element  21  is squeezed virtually elastically between the mating sealing surface  26  and the groove  27  by way of the elastic O-ring  39 . The sealing element  21  may thus be provided as a plastics component and, with locking engagement in groove  27 , slipped onto the actuating shaft  4 . This arrangement achieves advantages in terms of assembly. 
     According to FIG. 6, the bushing-shaped sealing element  21  is soldered or cemented to the mating sealing surface  26  of the actuating lever and further has a step  41  used to press an O-ring  42  against a roller bearing  34 , with a spacer ring  43  interposed. A sealing element  23  having a V-shaped cross-section bears against the circumference  17  of the sealing element  21  in a radial direction  14 . Sealing lips are provided on each leg of the sealing element  23  and bear against the mating sealing surface  26  respectively against the brake housing  6 . The sealing element  23  is generally used as a primary seal, while the O-ring  42  has the purpose of a main seal. It is principally possible to design the primary seal and the main seal integrally by shaping the O-ring  42  acting as a main seal directly to the primary seal. 
     The embodiment of FIG. 7 depicts a disc-shaped sealing element  21  which is slipped on a profiled actuating shaft  4 . The sealing element  21  is arranged on the actuating shaft  4  in positive engagement therewith because the projection  56  is engaged in the recess  44 . Recess  44  cooperates with a pressure member (not shown). The embodiment of FIG. 8 shows in a cross-sectional view a sealing element  21  arranged in a brake housing  6  and attached to an actuating shaft  4 . The sealing element  21  includes two radially external sealing lips  45 ,  46  and two axial sealing lips  47 ,  48 . The sealing lips  45 ,  46 ,  47 ,  48  are adapted for abutment on associated mating sealing surfaces  49 ,  50 ,  51  which are arranged on the actuating lever  3  or the brake housing  6 . Thus, the sealing element  21  provides a sealing both in an axial direction  11  and a radial direction  14 . Recesses  53 ,  54  for engagement by cam-shaped carrier elements  55  of the actuating lever  3  are provided on each end surface  52 . This achieves an unrotatable connection of the sealing element  21  and the actuating shaft  4 , and prevents the sealing element  21 , which is preferably made of an elastic material such as EPDM, for example, from being deformed in the area of the recess  44  to an unacceptable degree. 
     It should be noted that many variations of the sealing element  21  are possible without departing from the basic idea of the present invention.