You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
RELATED U.S. APPLICATIONS  
       [0001]     Not applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       REFERENCE TO MICROFICHE APPENDIX  
       [0003]     Not applicable.  
       FIELD OF THE INVENTION  
       [0004]     The invention relates to a surface water drainage system, in particular a drainage channel.  
       BACKGROUND OF THE INVENTION  
       [0005]     A surface water drainage system of this kind is known, for example, from the documents CH 681 313 or DE 195 11 788 A1.  
         [0006]     The problems generally encountered with such drainage systems, in particular drainage channels, are associated with the fact that on one hand the cover lying on the structure installed in the ground must be fixed in position so firmly that even the impulse-like forces encountered when a vehicle travels over the covers cannot release them. On the other hand, the covers must be opened at regular intervals so that cleaning and maintenance work can be done.  
         [0007]     In the above-mentioned known surface water drainage systems a latch is attached to the undersurface of the cover, which bridges the cross section of the cover and/or the drainage channel equipped with said latch, and by way of lateral projections locks into undercut areas or recesses provided in the channel body.  
         [0008]     The structure of the known systems is relatively elaborate and hence costly.  
       BRIEF SUMMARY OF THE INVENTION  
       [0009]     It is the object of the invention to provide a surface water drainage system of the kind cited at the outset further, in such a way that manufacture and assembly are simplified while still ensuring at least equal durability and reliability of fixation.  
         [0010]     According to one aspect of the present invention a surface water drainage system comprises a structure adapted for installation in the ground such that it defines an upper edge and comprising a first locking means; a cover adapted for location on the upper edge of the structure and fabricated from sheet metal having edges forming U-shaped profiles with undercut sections that face toward one another and with a lower side forming a supporting rim; and fixation devices attached to said edges of the cover and comprising second locking means in the form of elastic hook elements that are mounted within said undercut sections and that are adapted for snapping engagement with said first locking means on the structure in order to retain the cover on the structure. According to another aspect of the invention a surface water drainage system comprises a structure adapted for installation in the ground such that it defines an upper edge and comprising a first locking means; a cover comprising a cast metal grating adapted for location on the upper edge of the structure and having edges defining recesses; and fixation devices attached to said edges of the cover and comprising second locking means in the form of elastic hook elements that are inserted into said recesses and that are adapted for snapping engagement with said first locking means on the structure in order to retain the cover on the structure.  
         [0011]     The essence of the invention resides in the fact that the locking means associated with the cover are constructed as elastic hook elements and are attached to the edges of the cover. This measure results in a considerable saving of material, because it eliminates regions of the latches provided in the known arrangements that are superfluous with respect to the actual purpose of fixation, being situated in the middle regions of the cover. An additional result is an increase in both durability and fixation performance. That is, whereas in the known systems releasing the snap engagement at one side of the latch or releasing the latch from the grid causes the entire cover no longer to be retained on the structure installed in the ground, in the arrangement according to the invention the locking means on the two sides, i.e. at the edges of the cover, are independent of one another. If one of the locking means is released, the other remains in place unaltered and can continue to perform its fixation function.  
         [0012]     The object cited above is thus achieved by a surface water drainage system, in particular a drainage channel, comprising a structure that can be installed in the ground, a cover that can be laid onto an upper edge of said structure, and fixation devices that are fixed to the cover. These fixation devices comprise locking means in the form of elastic hook elements fixed to the edges of the cover that can be brought into snap-on engagement with other locking means disposed on the installed structure to hold the cover onto said structure.  
         [0013]     Preferably the second locking means are detachably fixed to the cover. This makes it possible to exchange these locking means (individually) in case they exhibit material fatigue and/or are damaged in other ways.  
         [0014]     Exchanging of the locking means is facilitated by the fact that they are preferably fixed to the cover by a mechanism that does not require use of a tool.  
         [0015]     The second locking means preferably comprise fixation elements that can be deformed with less force when they are being fixed to the cover than when they are being removed from the cover. As a result, on one hand easy assembly is ensured (in the factory or during repair work), while on the other hand the fixation elements hold the locking means securely to the cover.  
         [0016]     The second locking means are preferably inserted into undercuts or recesses at the edge of the cover. Thus production of the cover no longer requires the additional expenditure that is otherwise necessary for separate devices with which to attach the locking means.  
         [0017]     The second locking means preferably comprise tensioning devices that brace them against the cover so as to ensure that they are fixed in position with no play. As a result, the cover is held to the structure installed in the ground so tightly that it does not rattle.  
         [0018]     In a first preferred embodiment the second locking means are constructed as springs, by bending strips of material. This makes their manufacture relatively inexpensive. In this case the second locking means are preferably fixed to undercut regions in the cover by means of tabs bent outward from the strip of material. As a result, on one hand easy manufacture with unaltered consumption of material is ensured, while on the other hand the attachment between locking means and cover is extremely durable. Furthermore, in this embodiment the cover is provided in its undercut sections with stamped-out areas or similar offsets, which can be engaged by the said tabs in order to fix the locking means to the cover. The durability of this arrangement is very high, and the effort of manufacture is low.  
         [0019]     In a second preferred embodiment the second locking means are constructed as elastomer bodies. Such bodies can be easily and economically produced, especially by injection molding, and exhibit great durability, which is very important in particular in view of the aggressive environmental influences (water, road salt, dirt) encountered in this area of application.  
         [0020]     Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]      FIG. 1  shows a first embodiment of the invention, including cover, in front view,  
         [0022]      FIG. 2  is a perspective drawing of part of the structure in the direction indicated by the arrow II in  FIG. 1 ,  
         [0023]      FIG. 3  shows a side view along the line III-III in  FIG. 1 ,  
         [0024]      FIG. 4  shows a partial view in the direction of the line IV-IV in  FIG. 1 ,  
         [0025]      FIG. 5  shows a side view of a locking device according to another embodiment of the invention,  
         [0026]      FIG. 6  shows a cross section through a drainage channel that can be installed in the ground,  
         [0027]      FIG. 7  shows a perspective view, from diagonally below, of another embodiment of the invention with a cast-iron grating as cover,  
         [0028]      FIG. 8  shows a partial plan view of the arrangement according to  FIG. 7 ,  
         [0029]      FIG. 9  shows a section along the line IX-IX in  FIG. 8 ,  
         [0030]      FIG. 10  shows a perspective view of a locking device according to  FIG. 7 ,  
         [0031]      FIG. 11  shows a side view of the locking device according to  FIG. 10 ,  
         [0032]      FIG. 12  shows a view along the line XII-XII in  FIG. 11 ,  
         [0033]      FIG. 13  shows a view along the line XIII-XIII in  FIG. 12 ,  
         [0034]      FIG. 14  shows a cross section through the cover, as well as locking element, in a third embodiment, and  
         [0035]      FIG. 15  shows an isometric partial view of the exemplary embodiment in  FIG. 14 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]     In the following description, the same reference numerals are used for identical parts and parts with identical actions.  
         [0037]     In the arrangement shown in FIGS.  1  to  4  the cover  20  has been shaped by bending sheet steel. The edges  21 ,  22  in this case form undercut sections  23 , each of which has a U-shaped profile with a supporting rim  29  on its lower side. The cover  20  is laid into a drainage channel such as is shown in  FIG. 6 , in such a way that the edges  21 ,  22  are apposed to inner surfaces of lateral folds  14 , which are formed by frames  12  that are attached to or poured into the upper edges  11  of a structure  10  that can be installed in the ground. The frames  12  additionally form bearing surfaces  13  on which the cover  20  rests, by way of its supporting rims  29 .  
         [0038]     Within the undercut sections  23  hook elements  30  are disposed, to serve as first locking means. In the region where they are situated the contour (in cross section) of the hook elements  30  is identical to the contour of the undercut section, i.e. it is likewise U-shaped, so as to ensure that the hook elements  30  formed from a strip of material make contact over their entire surface.  
         [0039]     Parts of the horizontal (in the assembled state) regions of the hook elements  30  are bent outward to form an upper tab  31  and a lower tab  32 , which thus project beyond the otherwise planar upper and lower horizontal surfaces of the hook elements  30 . Corresponding to these tabs, stamped-out areas are provided in the edges  21  and  22 , specifically on the surface  27  of the cover  20  and in the supporting rims  29 , so that in the assembled state the tabs  31 ,  32 , by way of their edges directed toward the interior of the channel, are firmly engaged with the corresponding edges of the stamped-out areas  25 ,  26 . To ensure that this engagement is maintained even if the cover is manufactured with relatively large tolerances, additional tabs are bent outward on the surfaces of the hook elements  30  that face toward the edges  21 ,  22 ; these act as tensioning tabs  33 . By pressing against the inner (vertical) surfaces of the undercut section  23 , these tensioning tabs press the hook elements  30  in the direction towards the interior of the channel.  
         [0040]     Each hook element  30  comprises a nose  34 , underneath which there is an insertion slope  35  and above which there is an unlatching slope  36 . Thus when a cover  20  with hook elements  30  mounted therein is set onto the structure  10 , at first the insertion slopes  35  slide along the inner edges of the frames  12  and bend the hook elements  30  inward. In the position in which the supporting rims  29  come to rest on the bearing surfaces  13 , the noses  34  are caught in notches  50  in the frames, which serve as second locking means. These notches  50  are formed in the frames  12  over the entire length of the latter, which enables particularly simple manufacture of the frames.  
         [0041]     The cover  20  is removed by simply pulling it upward, so that the unlatching slopes  36  slide along the inside edges of the frame  12  and bend the hook elements inward again.  
         [0042]     In the embodiment of the hook element  30  shown in  FIG. 5  the same basic functions are provided as in the embodiment previously described. However, the spring is somewhat slimmer and uses up less material.  
         [0043]     In the following another embodiment of the invention is explained with reference to FIGS.  7  to  13 . Here the cover  20  is a cast-iron grating constructed in the conventional way. At the edges of the grating recesses  24  are provided, into which can be inserted the first locking means  30 , which in this case are designed as elastomer bodies (in particular, injection-molded). So that these can be fixed within the recesses  24  of the cover  20 , the hook elements  30  on both edges are provided with guide slots  37 ,  38 , which engage closely with corresponding guide lugs  28  disposed at the inner edges of the recesses  24 . In addition catch elements (not shown) can be provided in order to ensure improved retention of the hook elements  30  in the recesses  24 .  
         [0044]     The hook elements  30  are dimensioned such that their surfaces  39  are flush with the surface  27  of the cover  20 .  
         [0045]     The remaining functional components of the hook element  30 , namely the nose  34 , the insertion slope  35  and the unlatching slope  36 , correspond to those in the previously illustrated embodiment of the invention.  
         [0046]     It is of course possible to replace the hook elements formed by bending strips of material, as explained with reference to FIGS.  1  to  6 , by elastomer elements according to FIGS.  10  to  13 . This is illustrated in  FIGS. 14 and 15  by another exemplary embodiment. Here, again, there is a cover  20  made by bending sheet steel. The edges  21 ,  22  each have undercut sections  23  with a U-shaped profile, the lower surface of which forms a supporting rim  29 . The cover  20  is now, as in the exemplary embodiments previously discussed, laid into a drainage channel according to  FIG. 6 , with hook elements  30  positioned in the undercut sections  23  to serve as first locking elements. In contrast to the first exemplary embodiment, these hook elements are made of elastomer or a similar flexible material. However, in the region where they are inserted the contour of the hook element  30  is nearly identical to the contour of the undercut section  23 , i.e. is likewise U-shaped, so as to ensure that the hook elements  30  make contact over their entire surface.  
         [0047]     The hook elements  30  comprise in the horizontal (in the mounted state) region a lower projection  60  that engages a correspondingly shaped recess  26  in the supporting rim  29  of the cover  20 . Furthermore, the insertion head  62  of the hook element  30  incorporates a slot  64 , which divides the insertion head  62  into a lower insertion head  61  and an upper insertion head  63 . In this case the height of the insertion head is somewhat greater than the vertical extent of the undercut section  23  formed in the cover  20 . As a result, after the hook element  30  has been put into place, the insertion head  62  is compressed, which is made possible because the slot  64  allows the upper insertion head  63  and the lower insertion head  61  to move towards one another. Because of the elastic construction of the hook element  30 , it becomes firmly wedged into the undercut section  23 . Even when the cover  20  is subjected to dynamic loads, this arrangement ensures a permanently firm fixation of the hook element  30  within the undercut section  23  of the cover  20 . Other advantages of a hook element  30  made of elastomer, of course, are its insensitivity to corrosion and the permanently fixed locking to the drainage channel. It is likewise possible in the case of a cast grating to employ hook elements that are correspondingly shaped by bending strips of material.  
       LIST OF REFERENCE NUMERALS  
       [0000]    
       
           10 . Underground structure  
           11 . Upper edge  
           12 . Frame  
           13 . Bearing surface  
           14 . Lateral fold  
           20 . Cover  
           21 . Edge  
           22 . Edge  
           23 . Undercut section  
           24 . Recess  
           25 . Stamped-out area  
           26 . Stamped-out area  
           27 . Surface  
           28 . Guide nose  
           29 . Supporting rim  
           30 . Hook element/2nd locking means  
           31 . Upper tab  
           32 . Lower tab  
           33 . Tensioning tab  
           34 . Nose  
           35 . Insertion slope  
           36 . Unlatching slope  
           37 . Guide slot  
           39 . Surface  
           50 . Notch/1st locking means  
           60 . Projection  
           61 . Lower insertion head  
           62 . Insertion head  
           63 . Upper insertion head  
           64 . Slot

Summary:
A surface water drainage system is provided that comprises a structure that can be installed in the ground, and a cover that can be laid onto an upper edge of said structure. Fixation devices are provided that are attached to the cover and comprise a locking means in the form of elastic hook elements fixed to edges of the cover that can be brought into snap-on engagement with other locking means on said structure in order to retain the cover on the structure.