Abstract:
A cover for the grain tank of a combine harvester is disclosed that, when raised, is capable of acting as a tank extension to increase the storage capacity of the grain tank. The cover comprises side panels ( 10, 12 ) and end panels ( 14,   16 ) of which the edges interlock when the cover is raised. In the invention, each of the side and end panels ( 10, 12, 14, 16 ) is formed of a plurality of hollow extrusions ( 50 ). Each extrusion is of box section construction with parallel inner and outer walls ( 52, 54 ) separated from one another by two or more transversely extending webs ( 56, 57, 58 ). Formations ( 60, 62 ) on the side edges of the extrusions ( 50 ) permit each pair of adjacent extrusions to be interlocked with one another along their length.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a grain tank cover for a combine harvester. 
       BACKGROUND OF THE INVENTION 
       [0002]    It is known to provide a combine harvester with a cover for the grain tank which when raised can serve as a grain tank extension in order to increase its capacity. Examples of such covers are to be found in EP 1201112 and EP 1486109, which are imported herein by reference in their entirety. 
         [0003]    A typical cover, to which the present invention relates, has four or more panels, in particular front and rear end panels and two side panels. Each of the side panels may itself be formed of two separate pivotable sections, as shown for example in EP 1201112. 
         [0004]    In the closed position of the grain tank, the two side panels meet and overlap in the middle to cover the grain tank completely. The end panels lie beneath the side panels. A first of the end panels is connected to a hydraulic jack so that it may be raised and lowered, while the second of the end panels is connected to the first through a mechanical linkage, such as a torque tube, so that the end panels are raised and lowered in synchronism. 
         [0005]    As the end panels rise, tapering side edges of the end panels force the side panels to rise at the same time and this may be assisted by providing rollers on the end panels and arcuate tracks for the rollers on the side panels. In the fully raised position, the edges of the side and end panels interlock with one another to form a rigid structure capable of holding grain so as to increase the storage capacity of the tank. 
         [0006]    The tube through which the grain is delivered to the tank after it has been separated from the remainder of the crop material by the threshing and sieving system of the combine harvester, may have an articulated section that is raised as the tank cover is raised, so as to allow the grain tank to be filled up to its extended height. 
         [0007]    If the grain tank cover is to serve as an extension, it is imperative that its four panels be made of a rigid material capable of withstanding the weight of the grain without bending or buckling. In order to achieve this, the four panels may be formed of thick steel plates, but such panels are very heavy and unattractive. 
         [0008]    If made of thinner steel, it is necessary to strengthen the plates by riveting them to reinforcement bars or to a frame, but this both spoils the appearance of the panels and also makes it difficult to provide smooth guides on the inner surfaces of the side panels to act as tracks for the rollers on the end panels. 
       OBJECT OF THE INVENTION 
       [0009]    The present invention seeks therefore to provide a grain tank cover of which the panels are formed of a lightweight material that has sufficient strength to withstand the weight of the grain when the tank is full and that has flat surfaces on both sides both for aesthetic reasons and to permit smooth running of the rollers that are used in raising and lowering the side panels. 
       SUMMARY OF THE INVENTION 
       [0010]    In accordance with the present invention, there is provided a cover for the grain tank of a combine harvester, which cover is capable when raised of acting as a tank extension to increase the storage capacity of the grain tank, the cover comprising side panels and end panels of which the edges interlock when the cover is raised, characterised in that each panel is formed of a plurality of hollow extrusions, each extrusion having a box section with parallel inner and outer walls separated from one another by two or more transversely extending webs, and formations on the side edges of the extrusions to permit each pair of adjacent extrusions to be interlocked with one another along their length. 
         [0011]    Preferably, the material from which the extrusions are made comprises aluminium. 
         [0012]    Though it would be possible to interlock adjacent extrusions by sliding them into one another from one end, it is preferred to be able to place the adjacent extrusions side by side and to snap them into one another. 
         [0013]    In order to avoid the hollow section of each extrusion being exposed at the ends of the panels, it is desirable to provide end caps. In the preferred embodiment of the invention, the end caps of the side panels and the end panels are shaped to interlock with one another when the grain tank cover is in its raised position. 
         [0014]    It is further desirable to provide modified extrusions to serve as the edges of the side panels that overlap one another and as the edges that are hinged to the grain tank. 
         [0015]    It has been found that, by constructing the panels of a grain tank cover in this manner, the weight of the cover can be reduced significantly at the same time as improving both the aesthetic appearance of the cover and the ease with which the side panels and the end panels can be moved relative to one another as the cover is being raised and lowered. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: 
           [0017]      FIG. 1  is a perspective view of a known grain tank cover in a raised position in which it acts as an extension of the grain tank; 
           [0018]      FIG. 2  is a vertical central section through the grain tank extension of  FIG. 1 ; 
           [0019]      FIG. 3  is a perspective view of a grain tank cover comprising panels made of extrusions according to an embodiment of the invention; 
           [0020]      FIG. 4  shows a section through an aluminium extrusion used in the panels of  FIG. 3  in an embodiment of the invention; 
           [0021]      FIG. 5  shows in section how two extrusions of the kind shown in  FIG. 4  interlocked with one another to form a rigid structure; and 
           [0022]      FIG. 6  is a perspective view of the two extrusions in  FIG. 5  during at a stage in their assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]      FIGS. 1 and 2  show a grain tank cover comprising four panels  10 ,  12 ,  14  and  16 . The side panels  10  and  12  are hinged by means of hinges  18  to two opposite sides of a rectangular opening in the top of the grain tank of an agricultural harvester (not shown) while the front and rear end panels  14  and  16  are hinged to the other two sides of the opening by means of hinges  20 . The side panels  10  and  12  in  FIGS. 1 and 2  are each formed of two sections  10   a,    10   b,  and  12   a,    12   b  which are connected to one another by means of hinges  22 . In the closed position of the cover, the end panels  14  and  16  lie horizontally over the opening in the grain tank but they do not fully cover it because of their shape and because they do not meet in the middle. The side panels  10  and  12  close over the panels  14  and  16  and they do meet in the middle so as to close the opening fully and protect the contents of the grain tank from rain. In such a closed position of the cover, the tank has its normal volume and the vehicle can drive on public roads without any risk of it colliding with low bridges or footpaths. The harvester can also be used in this way when harvesting crops, the tank being filled from inside by a so-called bubble-up tube  24 . The operator can inspect the grain tank by manually pivoting open the sections  10   b  and  12   b  or it is possible to provide a small inspection hatch when the side panels are formed in one piece. 
         [0024]    In the raised position illustrated in  FIGS. 1 and 2 , the panels all come together to define an extension volume and an extension to the bubble-up tube  24  ensures that the grain tank continues to fill from the top. This allows grain to be stored both in the grain tank and within the extension volume bounded by the panels  10 ,  12 ,  14  and  16  thereby increasing its storage capacity. 
         [0025]    The design and operation of the grain tank extension has been described above to the extent necessary for an understanding of the present invention; it should however be mentioned that  FIGS. 1 and 2  correspond to  FIGS. 5 and 7 , respectively, of EP 1201112, which describes these figures in greater detail, and is imported herein by reference. In particular, the latter reference describes the mechanism, which comprises rollers on the end panels and arcuate guide rails on the side panels, for raising and lowering the panels, the manner in which the edges of the panels interlock when they are in the raised position, and the manner in which the bubble-up tube  24  is extended as the cover is raised. 
         [0026]    The present invention is not concerned with the design of the grain tank cover as such and is equally applicable to grain tank covers of other designs. The invention is instead concerned with the material from which the panels  10 ,  12 ,  14  and  16  of the cover are made. When the panels are made of a lighter material, as proposed in the present invention, it is possible and preferred for the side panels  10  and  12  to be formed in one piece. Such a construction is shown in  FIG. 3 , in which like components have been allocated the same reference numerals as in  FIGS. 1 and 2 . 
         [0027]    As previously mentioned, it is possible to form each panel from steel of sufficient thickness to provide the necessary strength. However, such panels are very heavy. If the panels are made of sheet steel or aluminium riveted to a support frame, then the rivets and buckling spoil the appearance of the panels. 
         [0028]    As shown in  FIG. 3 , the panels in the present invention are made of interlocking extrusions, preferably made of aluminium or an aluminium alloy. The preferred cross-section of the extrusions is shown in  FIGS. 4 to 6 . The extrusion  50  is of hollow box section having parallel inner and outer walls  52  and  54 , separated from one another by webs  56 ,  57  and  58 . Formations  60  and  62  along the side edges of the extrusions are shaped to allow two similar extrusions to snap fit into one another and, once assembled, the extrusions form a light, strong and attractive panel, which is flat on both sides. 
         [0029]    The geometry of the formations  60  and  62 , which will now be described in more detail, is preferred because it is easily assembled and extremely robust. 
         [0030]    Once snap fitted to one another, the extrusions  50  can only be separated by sliding them lengthwise relative to one another and even that can only be achieved by applying extremely high forces. It is however stressed that this extrusion profile is given only by way non-limiting example and that formations of a different shape can be used to achieve a strong interlock between adjacent extrusions. 
         [0031]    Such terms as up, down, left and right as used in the ensuing description, all refer to the extrusion as viewed in  FIGS. 3 to 5 . The formations  62  on the right side of the extrusion  50  in  FIG. 3  comprise a lower flange  62   a  that is coplanar extension of the wall  54  and terminates in an upwardly directed lip  62   b.    
         [0032]    An upper flange  62   c,  which extends laterally from the web  58  in a direction parallel to the walls  52  and  54 , terminates in an upstanding lip  62   d.  The flange  62   c  defines an upwardly facing channel, over the left side of which there protrudes an overhang  62   e,  which is a coplanar extension of the wall  52 . The formations  60  on the left side of the extrusion  50  comprise an upper flange  60   a  formed as a coplanar extension of the wall  52 . The end of the flange  60   a  is formed with a nose  60   b  that projects further to the left but is offset from the plane of the wall  52  by an amount equal to the thickness of the wall  52 . A rib  60   c  projects from the underside of the flange  60   a.  The formations  60  further include a hook-shaped lower flange  60   d,  which terminates in a ramped surface  60   e.    
         [0033]    The manner in which the formations  60  and  62  interlock, is clearly shown in  FIG. 4 . In particular, the nose  60   b  of the extrusion  50 R on the right in  FIG. 4  fits under the overhang  62   e  of the extrusion  50 L on the left to prevent the extrusion  50 R from moving upwards. The underside of the flange  60   a  contacts the upper surface of the lip  62   d,  and the hook-shaped lower flange  60   d  fits over the upstanding lip  62   b  on the lower flange  62   a  to prevent the extrusion  50 R from moving downwards relative to the extrusion  50 L. The abutment of the rib  60   c  against the lip  62   d  and the fitting of the hook  60   d  over the lip  62   b  serve to prevent the extrusions from being pulled apart. 
         [0034]    To assemble the extrusions  50 R and  60 L, the extrusion  50 R is tilted upwards. This allows the nose  60   b  to be slotted beneath the overhang  62   e.  When a force is then applied to push down on the extrusion  50 R to return it to a horizontal position, resistance is encountered as the ramped surface  60   e  rides over the lip  62   b  causing a slight deflection of the flange  62   a.  Once the hooked flange  60   d  has cleared the lip  62   b  the two extrusions snap into position and the rib  60   c  engages behind the lip  62   d.    
         [0035]    The central sections of the panels  10 ,  12 ,  14  and  16  are made of a plurality of identical extrusions, but different extrusions are required for the edges of the panels where they overlap one another and where they are hinged to the grain tank. It will be clear that such end extrusions will have along one edge formations identical with the formations  60  or  62  as described above and along the opposite edge a shape suited to their purpose, such as receiving a hinge or to form an upstanding ledge as a rain barrier where the side panels overlap. 
         [0036]    End caps are placed over the ends of the extrusions in order to conceal and close off the open box sections. The end caps are shaped in the manner described in EP 1201112 with reference to the  FIGS. 8 and 9  thereof, so that the edges of the side and end panels interlock with one another when the grain tank cover is raised to achieve an effective seal at the corners of the grain tank extension, as well preventing the side and end panels from splaying apart. The end caps may themselves be formed as aluminium extrusions defining a channel to fit over the exposed ends of the extrusions of each panel and formations projecting from the channel that fit one under the other when the ends of the side panels and the end panels meet in the raised position of the cover. 
         [0037]    If desired, as taught in EP 1486109, a blind may be secured to one of the side panels to cover the grain tank when the four panels are raised.