Abstract:
A wedge unit for a braking device with brake lining carriers includes a wedge configured to be displaced in an actuation direction for spreading the brake lining carriers, and an adjusting element configured to displace the wedge, wherein the wedge is displaceable to the adjusting element.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention concerns a wedge unit for a braking device, and a braking device, in particular a drum brake, with a wedge unit. 
         [0002]    Wedge units for actuating brakes, in particular drum brakes, have been known for a long time in the prior art. In a wedge brake or wedge drum brake, to trigger the braking process, the brake lining carriers mounted pivotably on a brake carrier are pushed apart by means of a wedge. Thus the brake linings attached to the brake lining carriers make contact with the inside of the rotating brake drum and brake said brake drum. At their end facing the wedge, the brake lining carriers have so-called actuating pistons, the function faces of which are subjected to a pressure force by the wedge unit. 
         [0003]    In known wedges with floating mounted wedges, the wedge shifts and hence assumes an oblique position, since because of the floating mounting of the wedge, a force equilibrium occurs at the wedge faces, i.e. actuating forces which are identical over the wedge are transmitted to the leading and trailing brake shoes. In other words, the wedge is pushed to one side with an axial lift, which leads to an oblique position. The result of the oblique position is angular difference between the wedge faces and the function faces of the actuating pistons which are moved by means of the wedge. 
         [0004]    In former braking devices, this angular difference has not normally led to problems since a roller bearing is present between the wedge and the actuating piston, which compensates for the angular difference. The known roller bearings comprise a roller between each wedge face of the wedge and the corresponding adjacent function face of the actuating piston or brake lining carrier. 
         [0005]    Under higher input forces and/or a greater translation due to a reduction in the wedge angle, in particular to achieve a greater braking moment, a higher surface pressure is applied to the raceways and rollers, which may limit the service life of the rollers or actuating pistons and/or wedge. It must also be recalled that the rollers press into the piston running face and can hence block the brakes. 
         [0006]    The invention is based on the object of providing a wedge unit or actuating device for a braking device, and a corresponding braking device, which can also be configured for large braking forces. 
       SUMMARY OF THE INVENTION 
       [0007]    The wedge unit according to the invention for a braking device with brake lining carriers, in particular a wedge brake or wedge drum brake, comprises a wedge which can be shifted in an actuation direction, i.e. axial direction or lift direction, for spreading the brake lining carriers. The wedge unit furthermore comprises an adjusting element or lift element for shifting, in particular for performing a lift movement, of the wedge. According to the invention, the wedge is arranged displaceably or moveably relative to the adjusting element. 
         [0008]    The braking device or drum brake according to the invention comprises a brake drum, at least two brake lining carriers arranged in the brake drum for carrying brake liners, and a wedge unit for spreading the brake lining carriers. The wedge unit is configured in the manner of the invention. 
         [0009]    A first basic idea of the invention is to largely exclude or prevent an oblique position of the floating mounted wedge and hence an angle change of the wedge faces relative to the function faces of the actuating pistons which are actuated with the wedge. For this, the wedge unit is configured multi-piece and comprises a wedge and a separate adjusting element or lift element or actuating element for actuating the wedge. The wedge and the adjusting element are not rigidly connected together but are moveable relative to each other. Due to the multi-piece nature of the wedge unit and the movability between the wedge and the adjusting element, an axial shift of the wedge (in the actuation direction) can take place independently of a lateral displacement. The two movement directions, i.e. the axial direction or actuation direction firstly, and the lateral direction or transverse direction secondly, are thus decoupled from each other. 
         [0010]    The invention allows the use of a bearing with a particularly low surface pressure, e.g. a needle bearing or multi-roller bearing, i.e. a bearing with at least two rollers per wedge face, at the interface between a floating mounted wedge and an actuating piston. In this way, the load at the interface can be reduced to an acceptable level even under high input forces. The wedge unit according to the invention guarantees that the function faces of the wedge and the actuating piston always remain at least almost parallel, which allows the use of said bearing for the first time. 
         [0011]    A further basic idea of the invention may be regarded as the provision of a wedge unit, the wedge of which can be moved laterally, while retaining its angular position, at the same time as a lift movement (axial movement or displacement in the actuation direction). The lateral movement of the wedge may in particular take place independently of the movement of the adjusting element. It is preferably provided that the wedge, on an exclusively axial movement of the adjusting element, is moveable laterally or in the transverse direction, i.e. transversely to the lift direction or axial direction, while retaining its angular position. 
         [0012]    The wedge is preferably mounted on the adjusting element moveably, in particular displaceably, in a transverse direction or a lateral direction relative, in particular vertically, to the lift direction or axial direction or actuation direction. The lateral displaceability of the wedge relative to the adjusting element guarantees firstly a reliable transmission of lift from the adjusting element to the wedge, and secondly a reliable orientation in the lift direction or axial direction. Thus on a lift movement, the adjusting element and wedge remain oriented preferably parallel to each other, in particular in the lift direction. Particularly preferably, the wedge is mounted on the adjusting element displaceably in a plane vertical to the lift direction. It is of particular advantage here if the wedge is mounted rotationally fixedly or non-pivotably on the adjusting element. 
         [0013]    In principle, it is also conceivable that the wedge is mounted pivotably on the adjusting element, so that any oblique position of the adjusting element is not transmitted to the wedge. 
         [0014]    In a preferred embodiment of the invention, the adjusting element has a pressure face which extends transversely, in particular vertically, to the actuation direction and along which the wedge is mounted displaceably, in particular in the transverse direction. Preferably, the adjusting element comprises a pressure plate on which the pressure surface is formed. The pressure face is preferably an axial face which extends transversely, in particular vertically, to the actuation direction or lift direction. 
         [0015]    In a further preferred embodiment of the invention, the pressure face is a slip face for the wedge. In other words, the wedge is mounted sliding along the pressure face to give a lateral displaceability of the wedge relative to the pressure face. The pressure face thus serves to transmit the actuating forces or input forces or lift forces to the wedge. 
         [0016]    Furthermore, it is proposed that the adjusting element has a piston rod or is formed as a piston rod. Preferably, the one-piece adjusting element has a piston rod extending from the pressure plate. At its distal end opposite the pressure plate, the piston rod preferably has a connecting region, in particular for connection of a brake cylinder. 
         [0017]    To guide the wedge along the adjusting element, it is preferred that a guide structure, in particular a guide profile, is present at the interface between the wedge and the adjusting element. The guide structure or guide profile guides the wedge in the lateral direction. The guide structure is preferably configured such that an exclusively lateral movement of the wedge relative to the adjusting element is guaranteed. A lateral movement here means in particular a movement of the wedge in the direction of its opposing wedge faces. 
         [0018]    In a particularly preferred embodiment of the invention, the adjusting element or the wedge has a fork head which is configured to guide an engagement element of the corresponding other part (wedge or adjusting element) or mount this displaceably in the transverse direction or lateral direction. The fork head may in particular comprise two or more webs between which an engagement element of the corresponding other part (wedge or adjusting element) is guided displaceably in the transverse or lateral direction. The fork head may also be formed by a toothed structure, for example on the axial end face of the pressure plate and/or the webs. 
         [0019]    Furthermore, preferably a guide device is provided which guides the wedge in the transverse direction relative to the adjusting element. The guide device may in particular have a guide element which guides the wedge laterally along the adjusting element, and/or prevents or limits a movement of the wedge in the axial direction relative to the adjusting element. Preferably, the guide device is configured to allow a movement of the wedge exclusively in the transverse direction, i.e. the lateral shift direction. All other movement directions are preferably blocked or limited. The guide device may for example have a pin guided in an oblong slot. 
         [0020]    According to a further preferred embodiment, at least one stop is provided which limits the movement, e.g. the lateral displaceability, of the wedge in the transverse direction. This in particular allows an increase in installation comfort, wherein the wedge for example may be mounted captively on the adjusting element by the stop. 
         [0021]    The operational reliability may be improved if an axial guide is provided for the adjusting element, which guides the adjusting element in the actuation direction. The axial guide guides the adjusting element in particular such that this is moveable exclusively in the actuation direction. The axial guide thus prevents (within the limits of the predefined tolerances) a tilting or oblique positioning of the adjusting element. Since the adjusting element and the wedge are preferably always oriented parallel to each other, a tilting of the wedge element would be transmitted to the floating mounted wedge. The axial direction is in other words set and dimensioned in order to guarantee an exclusively axial movement of the adjusting element within the limits of the technical tolerances. 
         [0022]    In a further preferred embodiment, a bearing device is provided for mounting the wedge, which for example has at least two rollers on a wedge face of the wedge or is configured as a needle bearing. Due to the plurality of rollers per wedge face of the wedge, or the configuration as a needle bearing, the surface pressure can be reduced and hence the service life and/or load-bearing capacity of the bearing increased. 
         [0023]    As a whole therefore, one aspect of the invention may be that the wedge unit is constructed of multiple pieces and has a wedge and an adjusting element, wherein the adjusting element is arranged laterally displaceably relative to the wedge. The adjusting element preferably comprises a fork head with a large-area pressure plate and piston rod. The wedge element is e.g. mounted laterally displaceably via pins and linear recesses, i.e. floating, in the fork head, wherein the cylinder forces are transmitted axially via the large-area pressure plates to the wedge element, and from this via rollers or a needle bearing to the actuating pistons. The lateral displaceability of the wedge element may if required be limited so that a combination of a floating and rigid wedge results. The guidance of the pressure plate-piston rod is preferably dimensioned suitably to ensure an exclusively axial displaceability of the pressure plate with the fork head, since otherwise an angular difference could occur between the wedge faces and the actuating pistons. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    The invention is explained in more detail below with reference to preferred embodiments which are depicted in the attached diagrammatic figures. The drawings show: 
           [0025]      FIG. 1  is a lateral top view of a wedge unit according to the invention; and 
           [0026]      FIG. 2  is a diagrammatic view of a braking device according to the invention. 
       
    
    
       [0027]    The same or equivalent elements are marked with the same reference numerals in all figures. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]      FIG. 1  shows a wedge unit  10  according to the invention of a braking device  100 . The wedge unit  10  comprises a wedge  20 , the center plane (plane of symmetry) of which is oriented parallel to an actuation direction  12  (axial movement direction, lift direction). The multi-piece wedge unit  10  furthermore comprises an adjusting element  30  for moving the wedge  20  in the actuation direction  12 . The adjusting element  30  comprises a pressure plate  32  for moving the wedge  20  substantially in the actuation direction  12 , so that the braking device  100  can be brought from an idle position into a braking position. For this, the pressure plate  30  comprises a pressure face  34  which extends substantially vertically to the actuating direction  12 . The pressure face  34  cooperates with a corresponding opposite pressure face of the wedge  20 . 
         [0029]    The wedge  20  has opposing wedge faces  22  which are coupled via a bearing device  26 , in particular a roller bearing, to a brake lining carrier  82  or an actuating piston  84  for actuation of a brake lining carrier  82 . 
         [0030]    The wedge  20  is mounted on the adjusting element  30  displaceably in a transverse direction  14  which runs substantially vertically to the actuation direction  12 . The transverse direction  14  here in particular runs on a connecting line between the wedge faces  22  of the wedge  20 . In this way, on uneven loading of its two wedge faces  22 , the wedge may deviate laterally while the adjusting element  30  is guided in the actuation direction  12 . This prevents the wedge  20  together with the adjusting element  30  from being positioned obliquely because of the different loads. The lateral displaceability of the wedge  20  relative to the adjusting element  30  thus guarantees that the wedge faces  22  always remain oriented parallel to the corresponding rolling faces  86  of the actuating pistons  84  or brake lining carriers  82 , even if the actuating pistons  84  or brake lining carriers  82  are positioned differently on the two sides of the wedge  20 . This allows the use of a bearing with a reduced surface pressure, for example a multi-roller bearing as shown in  FIG. 1 . The bearing device  26  here comprises several, for example two, rollers  28  per wedge face  22 . 
         [0031]    At its end facing the wedge  20 , the adjusting element  30  has a guide contour  40  for guiding the wedge  20  in the transverse direction  14 . The guide contour  40  may in particular be configured such that it prevents or limits a movement of the wedge  20  along the pressure face  34  in a direction running vertically or transversely to the transverse direction  40 . The guide contour  40  may for example have one or more limiting walls  44  which extend in the transverse direction  14 . In the embodiment shown, the adjusting element  30  at its end facing the wedge  20  has a fork head  42  which mounts the wedge  20  displaceably. The fork head  42  comprises several limiting walls  44  running in the transverse direction  14 , between which the wedge  20  is mounted. The limiting walls  44  extend starting from the pressure plate  32 , and together with the pressure plate  32  form a slotted recess for the wedge  20 . 
         [0032]    Below the pressure plate  32 , a piston rod  50  is arranged which can be coupled to an actuating element, in particular a piston rod of a lift cylinder. 
         [0033]    To prevent the wedge  20  from becoming detached from the adjusting element  30 , a guide device  60  is provided which allows exclusively a movement of the wedge  20  in the transverse direction  14 . In the exemplary embodiment shown, the guide device  60  comprises a pin  62  mounted on the wedge  20  and guided in a recess  64  of the fork head  42 . In principle however the reverse arrangement is possible, i.e. the pin may be arranged on the fork head  42  or the adjusting element  30  and the linear recess on the wedge  20 . The linear recess  64  runs in the transverse direction  14 . End regions of the recess  64  each form a stop  66  which limits the movement of the wedge  20  in the transverse direction  14 . 
         [0034]    To ensure an exclusively axial movement of the adjusting element  30 , an axial guide  70  is provided for the adjusting element  30 . This is dimensioned and configured such that an oblique position of the adjusting element  30  is at least largely prevented. 
         [0035]      FIG. 2  shows, in heavily abstracted form, a braking device or drum brake  100  with a wedge unit  10 . The braking device  100  comprises a brake drum  80 , in the interior of which the brake pad carriers  82  are pivotably mounted on a brake carrier  90  via linkages  83 . The brake carrier  90  is attached to an axle element  88 . The brake lining carriers  82  are pressed apart via a wedge unit  10  according to the invention so that the brake linings mounted on the brake lining carriers  82  are pressed against the inside of the brake drum  80 . 
       REFERENCE NUMERALS 
       [0000]    
       
           10  Wedge unit 
           12  Actuation direction 
           14  Transverse direction 
           20  Wedge 
           22  Wedge face 
           26  Bearing device 
           28  Roller 
           30  Adjusting element 
           32  Pressure plate 
           34  Pressure face 
           40  Guide contour 
           42  Fork head 
           44  Limiting wall 
           50  Piston rod 
           60  Guide device 
           62  Pin 
           64  Recess 
           66  Stop 
           70  Axial guide 
           80  Brake drum 
           82  Brake lining carrier 
           83  Linkage 
           84  Actuating piston 
           86  Rolling face 
           88  Axle element 
           90  Brake carrier 
           100  Braking device