Abstract:
A protective cover which is generally in the form of a flexible bellows construction secured at each end by collars in order to define an interior space includes vent means. Thus, when the cover is deformed, the volume within the interior is altered by aspiration or evacuation through the vent means. The vent means includes a vent element in order to allow air or fluid transfer into and out of the interior but prevent ingress of contaminants such as grit and water to the interior.

Description:
BACKGROUND TO THE INVENTION  
         [0001]    The invention relates to protective covers and more particularly but not exclusively to protective covers for protecting moving parts in a mechanism of motor vehicles.  
         SUMMARY OF THE INVENTION  
         [0002]    According to the invention, there is provided a protective cover for a motor vehicle joint, the cover having a deformable structure defining an interior space closed at both ends and including vent means coupled to the interior space, the vent means including a vent element adapted to allow fluid flow thereacross whilst stopping contaminant and/ or water entering into the interior space whereby excess fluid pressure within the interior can be reduced by fluid evacuation and aspiration through the vent means.  
           [0003]    Typically, the fluid will be air.  
           [0004]    Protective covers embodying the invention will now be described, by way of example with reference to the accompanying diagrammatic drawings in which: 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 is a schematic front elevation of a steering arrangement with protective covers;  
         [0006]    [0006]FIG. 2 is a schematic front elevation of the steering arrangement depicted in FIG. 1 turned to the right;  
         [0007]    [0007]FIG. 3 is a schematic front elevation of the steering arrangement depicted in FIGS. 1 and 2 turned to the right and subject to suspension articulation;  
         [0008]    [0008]FIG. 4 is a schematic front elevation of a transmission arrangement with protective covers;  
         [0009]    [0009]FIG. 5 is a cross-section through one of the protective covers embodying the invention;  
         [0010]    [0010]FIG. 6 is an enlarged view of the portion of FIG. 5 shown at II; and,  
         [0011]    [0011]FIG. 7 is an end view of part of a connector shown in FIG. 6, looking in the direction of the arrow III; 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    The protective cover arrangement  10  shown in FIGS. 5 and 6 comprises a small diameter sealing collar  12  at one end and a larger diameter sealing collar  14  at the opposite end, with a plurality of bellows turns  16  integrally extending between the two ends. In use, the two sealing collars are attached to two relatively movable parts of a mechanism (not shown) which is to be protected in a motor vehicle. The cover  10  protects the mechanism from ingress of water, dirt and other contamination.  
         [0013]    In one particular application of the protective cover shown in FIGS.  1  to  3 , two of them are respectively mounted to protect the ends of a steering rack of a steering arrangement  100  in a vehicle. Thus, the steering arrangement  100  may comprise a steering box  104  operated directly by the driver&#39;s steering wheel  105  or through the intermediary of a power steering arrangement. A steering rack extends outwardly in opposite directions from each side of the steering box  104  and is moved axially in one or the other direction by the steering box in response to steering action by the driver. The opposite ends of the rack are connected to turn the steerable wheels  103  of the vehicle. In use, a cover  110  extends from one side of the steering box  104 , with its larger diameter fixing collar  114  being secured to the steering box  104  where the steering rack extends outwardly therefrom. The smaller diameter collar  112  of the cover  110  is secured to the distal end of the rack.  
         [0014]    At the opposite side of the steering box  104 , from which the second end of the rack protrudes, a second cover  110  is secured, with its smaller diameter collar  112  fixed to that distal end of the steering rack.  
         [0015]    The two protective covers  110  thus protect the two end portions of the rack and the bellows flexibly accommodate axial movement.  
         [0016]    As the steering rack moves to and fro, in order to carry out desired steering action, the two protective covers  110  will be alternately compressed and expanded as will now be explained in more detail.  
         [0017]    It will be noted from FIG. 1 that the steering arrangement depicted has wheels  103  in a straight-ahead configuration. Thus, the steering box  104  is not displacing the steering rack either to the right or the left. In such circumstances, the protective covers  110  are not generally deformed (that is, not compressed or stretched), and so the interior volumes of these covers  110  will be substantially at their designed pressure, normally atmospheric. Thus, these covers  110  should not rupture, create noise problems or alter the function of the underlying steering mechanism.  
         [0018]    In FIG. 2, the steering arrangement of FIG. 1 has been turned to the right. Thus, cover  110   a  is compressed whilst cover  110   b  is expanded. The covers  110  are sealed by collars  112 ,  114  at each end. Therefore, the compressed cover  110   a  would normally be at an elevated pressure whilst the expanded cover  110   b  would be at a reduced pressure.  
         [0019]    Similarly, in FIG. 3, the covers  110  are respectively further expanded ( 110   b ) and compressed ( 110   a ) by suspension  111  movement to accommodate bumps as the vehicle including the steering arrangement moves.  
         [0020]    [0020]FIG. 4 shows how a similar problem can arise with a drive shaft or transmission arrangement. A drive shaft  201  extends between an outboard joint  230  and an inboard joint  231 . The outboard joint  230  is supported by a suspension  233  and the wheel  234 . In such circumstances, the protective covers  232  can be angled and the protective cover  236  can be compressed or expanded. The pressure variation appears only in the inboard joint  231 .  
         [0021]    It is necessary to accommodate the resultant changes in pressure in the protective covers. If this is not done, excessive pressure may rupture the protective covers. One known way of dealing with this problem, is to interconnect the interiors of the two covers used at respective ends of a steering rack. In this way, when one cover is contracted by movement of the steering rack, the increased pressure within the now deformed cover is transmitted to the interior of the other cover which will at the same time be expanded.  
         [0022]    In accordance with a feature of the covers being described, this interconnection between the two bellows at opposite ends of the steering rack is removed in order to allow easier assembly and to reduce costs.  
         [0023]    Referring to FIG. 5, the bellows  10  there shown has a vent arrangement  20  at one end. The vent  20  is L-shaped in form, comprising a relatively long hollow tubular part  22  and a relatively short hollow tubular part  24 . Each part  22 , 24  has an open end  22 A, 24 A. As shown in FIGS. 5 and 6, the vent  20  is secured in position on the cover  10  so that the end  24 A is attached to the wall of the bellows adjacent the larger diameter collar  14  and with the hollow interior of the part  24  thus open to the interior  25  of the cover  10 . The part  24  of the vent  20  thus extends radially of the major axis of the cover  10  and the part  22  of the connector extends in an axial direction.  
         [0024]    Such a bellows  10  can therefore be mounted at one end of a steering rack (for example, as shown in FIGS.  1  to  3 ) or at one end of a drive shaft (for example, as shown in FIG. 4). A similar bellows would then be mounted at the other end of the steering rack or drive shaft.  
         [0025]    The vent  20  of the bellows  10  at the other end of the rack or drive shaft would be mounted on the bellows in the same way.  
         [0026]    Each vent  20  is very firmly secured to the bellows  10 . A welding operation can be used to form a very strong welded bond between the material of the vent  20  and the material of the bellows  10 . In addition, a mechanical bond is formed between the vent  20  and the material of the bellows  10  where it enters the end  24 A of the vent  20 . However, the vent  20  could be mounted on the bellows  10  by a glueing operation.  
         [0027]    It will be appreciated that the vent  20  can be situated at any desired position on the external wall of the bellows.  
         [0028]    At the open end of  22   a  of each vent  20 , a vent element  21  is located. The purpose of this element  21  is to allow air to pass into and out of the bellows  10  whilst preventing ingress of contaminants and water to the interior volume  25 .  
         [0029]    In effect, the vent  20  and the vent element  21  adjust the volume of air within the interior so that it is consistent with air pressure. In such circumstances, the vent element  21  acts as a filter to prevent transfer of contaminants, such as grit, grease, etc. and water, into the interior, allowing relatively free movement of air to adjust the volume of the interior  25  as the cover  10  is deformed in extension or compression. In such circumstances, the vent  20  prevents excessive fluid (air) pressure build-up in the interior  25  and will normally maintain that interior at about atmospheric pressure. Furthermore, with a lubricant inside the protective cover  10  it will be understood this lubricant is prevented from escaping and so facilitating continued lubrication of a protected mechanism.  
         [0030]    The vent element  21  can be formed of a Teflon (Trade Mark) material of calibrated porosity to allow air movement but to prevent contaminants or water entering the interior  25 . Clearly, the specific material used is dependent upon the installation requirements; suitable other materials may be used.  
         [0031]    The vent  20  and vent element  21  remove the necessity of a connecting tube between the pair of protective covers  10 . Thus, installation and maintenance of the cover  10  is made less difficult and costly.  
         [0032]    In order to extend the operational life of vent element  21 , it will be understood that at least a proportion of any contaminants and/or water will be removed from the element  21  as air or fluids flow out of the interior  25 .  
         [0033]    This vent works also to avoid any variation of pressure due to external temperature or atmospheric pressure variation.