Abstract:
A protective shield for a disc brake which includes a brake disc attached to a wheelshaft for a vehicle, and a brake yoke with a pair of brake supports. The protective shield is fitted close to one side of, and partly covers laterally, the brake disc. The protective shield has a protective plate and a fastening bracket portion which is designed to support and fasten the plate, and the fastening bracket portion is provided with end portions for fastening cooperation with fastening eyes in the brake supports.

Description:
TECHNICAL FIELD  
       [0001]     The present invention relates to a protective shield for a disc brake according to the preamble of claim  1  and a disc brake unit including such a protective shield.  
       STATE OF THE ART  
       [0002]     Disc brakes for road vehicles, and particularly for heavy utility vehicles, suffer from considerable problems due to fouling of disc brake units by dust, water and waterborne pollutants which contaminate, when the vehicle is in motion, both disc brakes and brake yokes with brake linings. This can have consequences in terms of effects on moving parts. Dirt and corrosion may in particular lead to functional impairment causing uneven or impaired braking effect as between different disc brake units.  
         [0003]     Moreover, differences in braking action and consequently uneven wear of brake linings may occur on the different sides of a disc if the linings are contaminated to different extents. All in all, in the state of the art, these problems reduce the usability of disc brakes and shorten service intervals, thereby increasing costs. This situation has also led to otherwise less efficient drum brakes being regarded as more reliable and as requiring less servicing.  
         [0004]     Various attempts at alleviating the problems of disc brakes have resulted in shaft-mounted protection surrounding the brake disc, but this has entailed problems of impaired cooling, inherent oscillations and extra unsprung weight.  
         [0005]     Another solution which has been proposed involves sheetmetal housings fastened by means of the brake unit&#39;s threaded connections. However, this latter solution has caused problems with regard to the stability of the fastening of disc brake units.  
       OBJECTS AND MOST IMPORTANT CHARACTERISTICS OF THE INVENTION  
       [0006]     One object of the present invention is to indicate a protective shield for a disc brake of the kind mentioned in the introduction, whereby the problems of the state of the art are reduced. A further object is to propose a protective shield which is economic to manufacture and fit and makes reduced weight possible while nevertheless maintaining efficient functioning.  
         [0007]     These objects are achieved in the case of a protective shield of the kind mentioned in the introduction by the features in the characterising part of claim  1 .  
         [0008]     The possibility is thus created of a light and stable structure in which the actual protective plate may be made thin and the fastening bracket portion ensures rigidity and effective fastening. This means that only two fastening points are needed, which is an advantage, inter alia from the assembly point of view. There is also the possibility of manufacturing the protective plate unit in such a way as to eliminate or at least minimise the risk of problems arising from inherent oscillations during the operation of a vehicle fitted with it. The fact that fitting involves only two fastening points means that the invention allows a configuration which allows cooling air to flow between the wheelshaft and the protective plate unit and on along the brake disc, so that sufficient cooling can be achieved.  
         [0009]     The fact that there is fastening cooperation with special fastening eyes in the brake supports is advantageous in that separate fastening is proposed, thereby avoiding any risk of impairing the fastenings of the disc brake unit itself.  
         [0010]     The invention results in reduced contamination in the region of the brake disc and hence a more even braking action and more even lining wear, with overall effects of greater functional reliability and longer service intervals for the brake disc units here concerned.  
         [0011]     The protective plate and the fastening bracket portion being separate elements means that these elements can each be optimised individually as regards material and design, so the protective plate may be made of thin sheetmetal material and the fastening bracket portion may have a rigid force-absorbing profile.  
         [0012]     In one aspect of the invention, the protective plate is provided with fastening regions for cooperation with a protective housing for creating an enclosing protective shield for the brake disc, which is appropriate for disc brake units which are freely mounted on a wheelshaft and are therefore not situated within the region of the rim of a vehicle wheel. In this aspect of the invention it is likewise advantageous that only two fastening points are needed, thereby simplifying fitting and affording freedom for the creation of gaps for flow of cooling air.  
         [0013]     Further advantages are indicated in the following detailed description of an embodiment with reference to the attached drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The attached drawings are as follows:  
         [0015]      FIG. 1  depicts schematically a section through a vehicle wheel with a disc brake unit according to the invention,  
         [0016]      FIG. 2  depicts parts of the disc brake unit in  FIG. 1  in a partly dismantled perspective view,  
         [0017]      FIG. 3  depicts a partly dismantled perspective view of an alternative embodiment of a disc brake unit according to the invention,  
         [0018]      FIG. 4  depicts a protective plate for a disc brake unit according to the invention, and  
         [0019]      FIG. 5  depicts in perspective a protective housing for a disc brake unit according to the invention.  
     
    
     DESCRIPTION OF EMBODIMENTS  
       [0020]      FIG. 1  thus depicts in section a vehicle wheel with a disc brake unit  1  placed within the circumference of a wheel rim  3  which supports a vehicle tyre  2 . Broken lines at  4  represent a wheelshaft to which the vehicle wheel is fastened.  
         [0021]     The disc brake unit  1  comprises a brake yoke  5 , a brake disc  6  fastened to the wheelshaft  4 , and brake linings  7  which are arranged on brake blocks and are for braking cooperation with the brake disc  6 . The brake yoke  5  comprises brake supports  8  (one depicted) for firm mounting of the brake yoke  5 . Each brake support  8  has its lower region lengthened so as to be designed to constitute a fastening point for a protective shield  9  which comprises a protective plate  10  and a fastening bracket portion  11 .  
         [0022]     The parts of the disc brake unit  1  which are of relevance for the invention are shown in more detail in  FIG. 2 , which depicts in perspective the brake yoke  5  with its brake supports  8 ,  8 ′, each of which is provided with a number of fastening holes  15  (shown in the brake support  8 ′) for accommodating fastening bolts for the brake yoke  5 . Ref. B denotes a brake disc.  
         [0023]     The outer extremity of the free end of each brake support  8 ,  8 ′ is provided with a fastening eye  13 ,  13 ′ with respective fastening holes  14 ,  14 ′ for fastening screws  12 ,  12 ′ intended to secure a unit comprising the protective plate  10  and fastening brackets  11 ,  11 ′ by cooperation with holes provided in the free end portions of the fastening brackets  11 ,  11 ′. The fastening brackets  11 ,  11 ′ have a flat U-shaped cross-sectional profile and are curved so that they together substantially describe a circular arc which is at a substantially radially even distance from a wheelshaft when the brake shield is in position. The contact surface between the protective plate  10  and the fastening brackets  11 ,  11 ′ is substantially planar.  
         [0024]     The radially innermost portion of the protective plate  10  is situated at a distance from the wheelshaft (ref.  4  in  FIG. 1 ) such that a cooling air flow can pass through the resulting gap and proceed radially along the brake disc. The radially outer periphery of the protective plate  10  is drawn somewhat inwards towards the brake disc so as to create a somewhat enclosing structure.  
         [0025]     The brake yoke  5  has in its upper portion an open recess  16  via which brake linings are intended to be extracted when they are being changed. The recess  16  is also used for other service operations relating to the disc brake unit, and for inspection purposes.  
         [0026]     A lining holder  18  in the form of a supporting U-bolt is placed transversely across the recess so as to extend substantially parallel with the wheelshaft. In a further aspect of the invention, this lining holder  18  is used for fixing a main cover  17  which is intended to provide dirt protection preventing the ingress of pollutants into the recess  16 . To this end, the main cover  17  substantially covers the adjacent outer arcuate section of the brake yoke. The main cover comprises a thin sheetmetal structure designed to cover said recess. The fastening of the main cover is by fastening cooperation with the lining holder  18  whereby fastening screws  20  are inserted in countersunk recesses  19  with holes running through the main cover  17  and are screwed firmly into the lining holder  18 .  
         [0027]     The main cover  17  is also provided with tabs  34  intended to cooperate with and protect indicating cables (not depicted) for indicating the state of wear of the brake linings.  
         [0028]     A multiplicity of ventilation slits  33  are arranged in the main cover to allow flow of air which has been used for cooling and which emanates from the region of the disc brake during operation of the vehicle. Cooling of the brake unit is thus promoted despite the presence of the main cover.  
         [0029]      FIG. 3  depicts another embodiment of the invention whereby fastening regions  23  distributed along the peripheral region of the protective plate  10  are used for fastening a protective housing  22 . The latter comprises a first portion  24  which runs substantially parallel with the protective plate  10 , and a second portion  25  which runs, in a manner surrounding the brake disc, substantially at right angles to the first portion  24  and the protective plate  10 . A structure enclosing both sides and the circumference of the brake disc is thus formed.  
         [0030]     The fastening regions  23  are matched by corresponding portions of the protective housing  22 , and joining together is done, for example, by spot welding or by upset riveting.  
         [0031]     Adding the protective housing  22  is applicable in the case of a single-mounted wheel, which means that the brake disc is protected from contamination in all directions, which is otherwise protected by the rim of a vehicle wheel.  
         [0032]     In its upper region directed towards the brake yoke  5 , the protective housing  22 , as also the protective plate  10 , is adapted to connecting closely adjacent portions of the brake yoke  5  while leaving a gap for flow of cooling air towards an adjacent wheelshaft (not depicted).  
         [0033]     At its upper portion, the brake disc unit in the case of a single-mounted wheel is supplemented by fitting an additional outer cover  26  outside the main cover  17 . This outer cover  26  is at a substantially even distance from the main cover  17  so as to leave an air gap  27  between the main cover  17  and the outer cover  26 . To this end, the outer cover  26  has a number of spacing portions  35  which help to maintain the continuity of the air gap  27 . The spacing portions  35  also serve as regions for joining together the main cover and the outer cover, e.g. by upset riveting.  
         [0034]     The object of the outer cover  26  is to protect the disc brake unit  1  from ingress of dirt, water etc. via the slits  33  in the main cover  17  (see  FIG. 2 ). The fastening of the outer cover  26  to a main cover is advantageously effected by the same fastening screws as for the main cover  17  as individual parts of the lining holder  18 . Advantageously, both the main cover  17  and the outer cover  26  are manufactured as pressed sheetmetal parts.  
         [0035]      FIG. 4  depicts the protective plate  10  in more detail with, pressed into it, a number of reinforcing grooves  31  which are distributed and differently aligned and contribute to the rigidity of the protective plate  10 . Ref.  30  denotes a substantially planar abutment surface  30  which is made by being pressed in a press tool and is for cooperation with the fastening brackets  11  and  11 ′ of the fastening bracket portion ( FIG. 2 ). This structure forming the abutment surface  30 , which moreover, as indicated above, describes substantially a circular arc, does of course also contribute to the rigidity of the protective plate  10 . Also depicted is a further abutment surface  32  for an undepicted additional part which relates to the special fitting of the device to certain wheelshafts.  
         [0036]      FIG. 5  shows the protective housing  22  in more detail with reinforcing grooves  29  running radially and with its first and second portions  24  and  25  respectively. Ref.  23 ′ denotes other fastening regions for cooperation with the fastening regions  23  on the protective plate  10  ( FIG. 2 ). Between these joining regions  23 ′ there are recesses  28  which, when the protective housing is fitted to a protective plate  10 , constitute apertures catering for the outflow of air which has been used for cooling a brake disc during vehicle operation.  
         [0037]     The invention may be modified within the scopes of the ensuing claims whereby the constituent parts may be configured otherwise, e.g. so that the bracket portion comprises a single fastening bracket which is permanently or detachably fastened to the protective plate. The brackets may also be configured otherwise, e.g. with some other cross-section or some other curvature, and be manufactured by some other appropriate production method.  
         [0038]     The invention represents a flexible solution which makes it possible to use the same protective shield on all the axles of a vehicle, which is a very great advantage in simplifying manufacture, assembly and stockholding and in reducing the overall cost of brake disc units which include the invention.  
         [0039]     It is preferable that the protective shield and the main cover be used in combination, but it is not excluded that either may be used without the other.  
         [0040]     Applying the invention to a disc brake results in significant improvements as regards service life and function. It also results in more even brake lining wear and consequently longer service intervals between brake lining changes.