Abstract:
A brake plate ( 10 ) adapted for use in a wet brake system ( 24 ) having at least one disc rotatable about its axis through a volume of a liquid, said brake plate ( 10 ) including at least a plate body ( 12 ); a braking surface ( 14 ) on one radial face ( 16 ) of said plate scraper ( 18 ) extends axially beyond the braking surface ( 14 ) and a second position where said scraper ( 18 ) is retracted axially to lie substantially flush with or below the braking surface ( 14 ).

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a brake plate, and in particular, but not exclusively, to a brake plate for use in a wet brake system.  
         BACKGROUND OF THE INVENTION  
         [0002]    The Applicant is the proprietor of various inventions relating to wet brake systems and components thereof as described, for example, in International Application Nos. PCT/AU92/00540, PCT/AU95/00529 and PCT/AU97/00500, the contents of which are incorporated herein by way of reference.  
           [0003]    In broad terms, a wet brake system typically includes a disc fixed to rotate with a rotating component such as an axle, and a pair of brake pads, one on each side of the disc, with the disc and brake pads disposed within a seal housing containing a volume of oil.  
           [0004]    Wet brake systems enjoy various benefits over dry brake systems including: a substantially reduced rate of wear of brake pads; the ability to isolate contacting surfaces of the disc and pads from foreign matter and debris that may otherwise adversely effect performance or increase the rate of wear; and, the containment of dust from the brake pads.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the present invention to provide a brake plate that can further enhance the performance of a wet brake system.  
           [0006]    According to the present invention there is provided a brake plate adapted for use in a wet brake system having at least one disc rotatable about its axis through a volume of a liquid, said brake plate including at least:  
           [0007]    a plate body;  
           [0008]    a braking surface on one radial face of said plate body; and,  
           [0009]    at least one scraping means supported by said plate body and axially moveable between a first position where the scraping means extends axially beyond said braking surface and a second position where said scraping means is retracted axially to lie substantially flush with or below said braking surface.  
           [0010]    Preferably, said brake plate includes bias means for biasing said scraping means towards said first position.  
           [0011]    Preferably, each scraping means has a radial contact face for face to face contact with said disc, to scrape or wipe liquid from said disc.  
           [0012]    Preferably, said contact face is provided with a peripheral edge and at least one groove extending between and opening onto two spaced apart points on said peripheral edge, said at least one groove providing a flow path through which liquid can flow.  
           [0013]    Preferably, said peripheral edge includes opposite first and second lateral edges and opposite first and second radial edges extending between said first and second lateral edges, and said at least one groove includes one or more grooves extending between and opening onto any two of said lateral and radial edges.  
           [0014]    Preferably, said braking surface is divided into a plurality of spaced apart sectors disposed circumferentially about said one radial face of said plate body and wherein one scraping means is disposed between at least one set of mutually adjacent sectors.  
           [0015]    Preferably, each sector is provided with one or more grooves for providing corresponding flow paths for a liquid between two spaced apart points on a peripheral edge of said braking surface.  
           [0016]    According to another aspect of the present invention there is provided a wet brake system including at least:  
           [0017]    a disc adapted for coupling to a rotatable component to rotate with said component about an axis, said disc having first and second opposite radial faces;  
           [0018]    at least one brake plate in accordance with the first aspect of the present invention, said at least one brake plate fixed against rotation but linearly moveable relative to said disc parallel to said axis, said at least one brake plate disposed in facing relationship with one radial face of said disc;  
           [0019]    means for axially moving said brake plate relative to said disc between an engaged position where said braking surface is in engagement with a facing radial surface and a disengaged position where said braking surface is spaced from said facing radial surface; and,  
           [0020]    a sealed housing in which said disc and brake plate reside, said housing containing a volume of liquid through which said disc rotates.  
           [0021]    Preferably, said disc and said at least one brake plate are axially spaced when in the disengaged position, to the extent that said scraping means of said brake plate maintains contact with said facing radial surface of the disc. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0022]    [0022]FIG. 1 a  is a plan view of a brake plate in accordance with the present invention;  
         [0023]    [0023]FIG. 1 b  is a view of section  1 - 1  of FIG. 1 a ;  
         [0024]    [0024]FIG. 2 a  is a plan view of one embodiment of a brake pad incorporated in the brake plate;  
         [0025]    [0025]FIG. 2 b  is a view of section  2 - 2  of FIG. 2 a ;  
         [0026]    [0026]FIG. 3 is a plan view of a second embodiment of a brake pad incorporated in the brake plate; and  
         [0027]    [0027]FIG. 4 is a schematic representation of a wet brake system incorporating the brake plate depicted in FIG. 1 a.   
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0028]    Referring to the accompanying drawings and in particular, FIGS. 1 a  and  1   b , an embodiment of the brake plate  10  is shown as including a plate body  12  with a braking surface  14  on one radial face  16  of the plate body  12 . At least one (in this particular embodiment four) scraper or wiper means  18   a - 18   d  (hereinafter referred to in general as “scrapers  18 ”) is supported by the plate body  12 . The scrapers  18  are moveable axially between a first position where the scrapers  18  extend axially beyond the braking surface  14 , as depicted in FIG. 1 b , and a second position where the scrapers  18  are substantially flush with or below the braking surfaces  14 .  
         [0029]    Each of the scrapers  18  has a substantially planar contact face  20  for face to face contact with a disc  22  in a disc brake system (see FIG. 4). Contact face  20  has a peripheral surface which is made up of a first lateral (or an inner circumferential) edge  26 , a second lateral (or outer circumferential) edge  28 , and opposite first and second radial edges  30  and  32  extending between the edges  26  and  28 . A groove  34  is formed on the contact face  20  to provide a fluid flow path between two spaced apart points on thet peripheral edge of the contact face  20 . In this particular embodiment, the groove  34  extends between and opens onto respective points on the edges  26  and  28  of the contact face  20 .  
         [0030]    Each of the scrapers  18  is in the form of a generally rectangular shaped block  36  of a wear resistant, and preferably self-lubricating, material such as PTFE or PTFE impregnated with boron or manganese bronze. Each block  36  is housed within a respective cavity  38  formed between a back plate  40  and front plate  42  of the plate body  12 . The front plate  42  is provided with a plurality of apertures  44  through which the contact face  20  of respective scrapers  18  can extend. The width and breadth of the apertures  44  are smaller than the corresponding dimensions of the cavities  38 . Each block  36  is provided with a laterally extending peripheral skirt  48  which is configured and dimensioned so as to be able to slide axially within cavity  38  but unable to pass through aperture  44 . In this way, the scrapers  18  are retained to move axially within the cavities  38  of the brake plate  12 .  
         [0031]    Bias means in the form of one or more springs  50  are provided for biasing the scrapers  18  axially outwardly to a first position where the contact surface  20  extends axially beyond the braking surface  14 . Opposite ends of each spring are retained within blind holes  52  and  54  formed in the back plate  40  and block  36  respectively. The springs  50  are provided with a degree of pre-load in order to hold the scrapers  18  axially outwardly to the maximum extent.  
         [0032]    As seen most clearly in FIG. 1 b , each of the scrapers  18  is provided with opposite radially extending bevelled surfaces  56  and  58 . Bevelled surface  56  slopes away from the radial edge  30  and bevelled edge  58  slopes away from opposite radial edge  32 .  
         [0033]    Referring again to FIG. 1 a , the braking surface  14  is divided into a plurality of spaced apart sectors  60   a - 60   d  (hereinafter referred to in general as “sectors  60 ”). Typically, the sectors  60  would each comprise a separate brake pad that can be coupled or otherwise attached to the brake plate  10  and more particularly the front plate  42 . To this end, the front plate  42  is provided with a plurality of arcuate recesses (not shown) within which each sector  60  is seated.  
         [0034]    [0034]FIG. 2 a  and FIG. 2 b  depict one possible configuration of a sector/brake pad  60 . The braking surface  14  is formed on an upper face of the sectors  60  and is bound by a first lateral (or inner circumferential) edge  62 , second lateral (or outer circumferential) edge  64  and opposite radial edges  66  and  68  that extend between the inner and outer circumferential edges  62  and  64 . The edges  62 ,  64 ,  66  and  68  which bound the braking surface  14  constitute the peripheral edge of the braking surface  14 , and are all formed inboard of a laterally extending peripheral skirt  69  which seats in a corresponding recess (not shown) in the front plate  42 . A plurality of grooves  70  are formed in the braking surface  14  of each sector  60  to provide fluid flow paths between two spaced apart points on the peripheral edge of the braking surface  14 . For example, at least one groove  70   a  extends between inner circumferential edge  62  and outer circumferential edge  64 , at least one further groove, groove  70   b  extends between inner circumferential edge  62  and radial edge  68 , and at least one further groove  70   c  extends between the radial edge  66  and the outer circumferential edge  64 .  
         [0035]    When the brake plate  10  is used in a wet brake system the grooves  70  further assist in channelling oil or other liquid away from between the braking surface  14  and disc  22  during a braking operation.  
         [0036]    [0036]FIG. 3 depicts an alternative embodiment of the sector/brake pad  60 ′. This embodiment differs from the sector/brake pad  60  depicted in FIGS. 2 a  and  2   b  by the inclusion of four arcuate or circumferential extending grooves  72 . Each groove  72  follows a curved path extending between opposite radial edges  66  and  68 .  
         [0037]    [0037]FIG. 4 depicts in a schematic and general sense a wet brake system  24  incorporating the brake plate  10 . The system  24  includes a disc  22  mounted on a rotating component such as an axle  74 , and a sealed housing  76  which encloses the disc  22  and the brake plate  10 . The housing  76  would typically include a volume of fluid such as oil through which the disc  22  rotates as the axle  74  rotates, the disc  22  being fixed to rotate with the axle  74 . The brake plate  10  is juxtaposed relative to the disc  22  so that the braking surface  14  and contact face  20  of scrapers  18  face the radial surface  78  of disc  22 . The system  24  also includes an actuator (not shown) for axially moving the brake plate  10  relative to the disc  22 , between an engaged position where the braking surface  14  is in contact with the radial surface  78  and a disengaged position in which the braking surface  14  is spaced from the radial surface  78 . It is envisaged that the brake plate  10  would be spaced from the disc  22  so that in the disengaged position, the contact face  20  of the scrapers  18  would be in contact with the radial surface  78 . Thus, the scrapers  18  act to continually scrape, wipe or otherwise remove fluid from radial surface  78 . This substantially enhances the stopping power and efficiency of the brake system  24 .  
         [0038]    Now that embodiments of the present invention have been described in detail it will be apparent to those skilled in the relevant arts that numerous modifications and variations may be made without departing from the basic inventive concepts. For example, the brake plate  10  can be provided with any number of scrapers  18 . Further, it is not an absolute requirement that a scraper  18  be provided between each pair of mutually adjacent sectors  60 . Further, the contact face  20  of the scraper  18  can be formed without any groove or alternatively can be provided with multiple grooves in various patterns. The brake system  24  can also be provided with two brake plates  10 , one on each side of the disc  22  so as to clamp the disc  22  therebetween during a braking operation. In this embodiment, a pair of diametrically opposed callipers can be provided for moving the brake plates  10  into the engaged position.  
         [0039]    All such modifications and variations together with others that would be obvious to a person of ordinary skill in the art are deemed to be within the scope of the present invention, the nature of which is to be determined from the above description.