A cover for a road system device provided with a frame comprises: a blocking member and a base body defining a covering surface for the road system device, extending in a cover plane, and having a housing for receiving the blocking member. The housing and the blocking member are adapted for blocking the cover relative to the frame or to a neighboring cover. The housing is adapted to maintain the blocking member relative to the base body autonomously and to oppose a movement of the blocking member in a direction extending perpendicular to the cover plane and tending to move the blocking member away from the covering surface. The invention is applicable to access manholes for underground installations.

RELATED APPLICATIONS 
     This application is a U.S. National Phase of International Application No.: PCT/FR2010/050086, filed Jan. 20, 2010, designating the U.S., and published in French as WO 2010/086539 on Aug. 5, 2010 which claims the benefit of French Patent Application No. 09 50482 filed Jan. 27, 2009. 
     FIELD OF THE INVENTION 
     The present invention relates to a cover for a road system device provided with a frame, the cover being of the type comprising
         a blocking member,   a base body defining a covering surface for the road system device, extending in a cover plane, and having a housing for receiving the blocking member,       

     this housing and the blocking member being adapted for blocking the cover relative to the frame or to a neighboring cover, when the blocking member is in the housing. 
     It applies in particular to device for closing technical inspection chambers of an underground cabled network, such as hatches, and devices for closing access or inspection shafts for an underground water grid, such as manholes or sidewalks. 
     It more particularly applies to securing manholes or access hatches for telecommunications installations. 
     These road system devices generally comprise a frame durably sealed in the ground, in which one or more covers are inserted so that they can be released, arranged level with the surface of the ground. 
     In the case where the device has several covers, these covers are either a so-called slave cover, or a so-called master cover. A master cover can be removed from the frame independently of the potential presence of slave covers, whereas a slave cover cannot be removed from the frame when the master cover is in place. 
     BACKGROUND OF THE INVENTION 
     Document FR-A-2 765 256 describes a universal cover for a manhole for connecting chambers. 
     The cover comprises a base body that includes several attachment protrusions to which it is possible to fasten functional elements, such as hooks or a lock so as to form either a slave cover or a master cover. 
     Each attachment protrusion comprises surfaces for applying functional elements that are inclined towards each other. The functional elements have surfaces inclined in a manner complementary to those of the attachment protrusions. The functional elements must therefore be made specially for the cover and as a result are costly. 
     Furthermore, the functional elements are fastened by screws on the attachment protrusions. This fastening means is costly in terms of assembly time and logistics because a large number of components must be stored. Moreover, the screws can be released in an untimely manner. 
     Also, the functional elements are fastened on attachment protrusions that are not useful when no functional element is attached thereto. The cover is therefore costly in terms of material. 
     SUMMARY OF THE INVENTION 
     The present invention aims to propose a cover that allows reliable fastening of the functional elements using simple and economical means. 
     Other aims of the invention are to propose a cover that requires little material and has a low logistical cost. 
     To that end, the invention relates to a cover of the aforementioned type, characterized in that the housing is adapted to maintain the blocking member relative to the base body autonomously and to oppose a movement of the blocking member in a direction extending perpendicular to the cover plane and tending to move the blocking member away from the covering surface. 
     According to specific embodiments, the cover according to the invention includes one or more of the following features:
         the blocking member is a clamp having a core and two wings, in particular substantially U-shaped;   the blocking member comprises a blocking lug intended to come into contact with a neighboring cover or with the frame so as to block the cover;   the blocking lug protrudes from the core of the clamp on the side opposite the wings;   the blocking member is symmetrical relative to an axis of symmetry;   it has means for subjugating the blocking member on the base body;   the subjugation means cooperates with the blocking member by shape complementarity, and in particular comprises a pin;   at least one housing is delimited by a maneuvering recess of the cover, and the housing includes a frangible wall that must be broken so as to put the blocking member in place in the housing;   the cover includes guide means adapted to guide the blocking member during placement of the blocking member in the housing;   the base body and/or the blocking member is/are made from metal, in particular cast iron;   the blocking member is provided with an anti-closure means adapted to oppose closing of the cover when the latter is in an open position.       

     The invention also relates to a road system device, in particular a manhole, of the type comprising:
         a frame delimiting an access opening;   at least first and second covers adapted to cover the access opening, characterized in that   each of the covers is a cover as indicated above, the blocking member being an adaptation member, in that   each base body is provided with a first housing for receiving the adaptation member, and in that       

     when the adaptation member is in the first housing, the cover is a first type of cover among the even and odd slave covers, and when the adaptation member is outside the first housing, the cover is a second type of cover among master, even slave and odd slave covers, different from the first type of cover. 
     According to specific embodiments, the road system device includes one or more of the following features:
         the first housing is adapted to receive the adaptation member according to different first and second insertion directions, and when the adaptation member is received in the first insertion direction into the housing, the cover is the first type of cover, and when the adaptation member is received in the second insertion direction into the housing, the cover is a third type of cover among even and odd slave covers, this third type of cover being different from the first and second types of cover;   each of the base bodies includes a second housing, separate from the first housing and adapted to receive the adaptation member and when the adaptation member is in the second housing, the cover is a third type of cover among even and odd slave covers, this third type of cover being different from the first and second types of cover;   the base body includes a third housing, adapted to receive a second blocking member, and when the second blocking member is in the third housing, this blocking member is adapted to block one side of the cover relative to a side of the frame;   the base bodies of each of the covers are identical;   the two covers are of a different cover type, and the adaptation members of the two covers are identical.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood upon reading the following description, provided solely as an example and done in reference to the appended drawings, in which: 
         FIG. 1  is a perspective view of the outer side of a manhole according to the invention; 
         FIG. 2  is a perspective view of the inner side of the manhole of  FIG. 1 ; 
         FIG. 3  is a planar view of the inner side of the manhole of  FIG. 1 , the blocking members being in place; 
         FIG. 4  shows an enlarged and perspective view of part IV of  FIG. 3 ; 
         FIG. 5  is a perspective view of the inner side of part of the base body of the cover, before placing a blocking member; 
         FIG. 6  is a cross-sectional view through part of the manhole, the blocking member being located in the housing and subjugated, 
         FIG. 7  is a view identical to the view of  FIG. 6 , before the first placement of the blocking member; 
         FIG. 8  is a perspective view of the part of the manhole serving to block the slave cover relative to the master cover; 
         FIG. 9  is a view identical to that of  FIG. 8 , before the first placement of the blocking member; 
         FIG. 10  is a cross-sectional view of the part of the manhole shown in  FIG. 8 , and 
         FIG. 11  is a planar view of the inner side of an alternative of the manhole according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  shows a manhole according to the invention, designated by general reference  2 . 
     The manhole  2  is for example a manhole for a technical underground chamber containing telecommunications equipment. 
     The manhole  2  comprises a frame  4 , a slave cover  6  and a master cover  8 . 
     The frame  4  is sealed in the ground and delimits an access opening  10  ( FIG. 6 ), for example an underground chamber comprising telecommunications cables. In the present case, the access opening  10  is square-shaped. 
     The hole  2  defines a hole plane P-P that extends substantially parallel to the ground during installation. 
     The hole  2  defines an outer side E and an inner side I. The hole  2  also delimits a central axis X-X extending perpendicular to the hole plane P-P. 
     In the following, the expression “peripheral” designates the direction moving radially away from axis X-X and “central” designates the direction approaching the central axis X-X. 
     Moreover, the hole  2  includes, for each cover  6 ,  8 , a hinge (not visible) adapted to make the concerned cover tilt around a hinge axis Y-Y between open and closed positions. 
     The frame  4  includes a frame wall  12  extending substantially perpendicular to the hole plane P-P. 
     The frame includes a frame base  14  extending parallel to the hole plane P-P, and protruding radially towards the inside and towards the outside of the frame wall  12 . This frame base is intended to be embedded in a sealing material such as mortar. 
     The master cover  8  can be placed and removed from the frame  4  independently of the presence of a slave cover  6 , while the slave cover  6  cannot be removed from the frame  4 , or installed therein, when the master cover  8  is in place. Thus, after placement of the slave cover  6 , one need only lock the master cover  8  relative to the frame to lock the slave cover  6  in the frame  4 . 
     Each cover  6 ,  8  comprises a substantially triangular generic base body  16 , which covers about half of the surface of the access opening  10  and which extends along a cover plane T-T, which is parallel to the plane of  FIG. 3 . 
     The base body  16  is identical for each of the slave  6  or master  8  covers. As a result, a single base body  16  will be described below. 
     The base body  16  is made in a single piece by molding, preferably from cast iron. 
     The base body  16  comprises an inner surface  18 , visible in  FIG. 2 , and an outer surface  20 . The two surfaces  18 ,  20  are parallel to the cover plane T-T. The inner surface  18  corresponds to an inner side of the cover  6 ,  8  while the outer surface  20  corresponds to an outer side of the cover  6 ,  8 . 
     The base body  16  has stiffening ribs  24  on its inner surface  18 . Furthermore, the base body  16  includes maneuvering recesses  26  emerging on the outer surface  20 . Each maneuvering recess  26  is adapted to receive a maneuvering tool (not shown) intended to maneuver the cover  6 ,  8  when it is lifted or removed from the frame. 
     The inner surface  18  of the base body  16  includes a slave housing  28  (even) and a blocking housing  30 . 
     Each cover  6 ,  8  is also provided with at least one blocking member  32 . 
     The type of slave  6  or master  8  cover is defined by the presence or absence of the blocking member  32  in the slave housing  28 . When the blocking member  32  is present in the slave housing  28 , the cover constitutes a slave cover  6 , and when no blocking member  32  is present in the slave housing  28 , the cover is master cover  8 . The master cover  8  also has a bolt (not shown) adapted to lock the master cover  8  relative to the frame  4 . 
       FIG. 10  shows a transverse cross-sectional view parallel to axis X-X of the hole  2  at the slave housing  28  of the slave cover  6 . 
     The slave housing  28  includes a bottom wall  34  and two housing openings  36 ,  38  formed in side walls of the maneuvering recess  26 . 
     The bottom wall  34  extends parallel to the cover plane T-T. The housing openings  36 ,  38  extend substantially perpendicular to the cover plane T-T. 
     The slave housing  28  defines an insertion direction SI of the blocking member  32  in said housing  28  that is substantially parallel to the cover plane T-T. 
     The blocking member  32  is in this case a clamp with a core  40  and two wings  42 ,  44 , the clamp being substantially U-shaped. The blocking member  32  includes a blocking lug  46 , and in this case two blocking lugs  46 . The blocking lug  46  is intended to come into contact with the neighboring cover, in this case with the master cover  8 , so as to prevent the slave cover  6  from being lifted when the master cover  8  is in the frame  4 . Each blocking lug  46  protrudes from the core  40  of the clamp on the opposite side of the wings  42 ,  44 . 
     In the assembled state, one  42  of the wings is in the slave housing  28 , while the other wing  44  extends outside the slave housing  28 , on the other side of the bottom wall  34 . 
     Advantageously, the blocking member  32  is symmetrical relative to an axis of symmetry Z-Z. Thus, the blocking member  32  can be inserted into the housing  28  in the position indicated in  FIG. 10  or in a position rotated by 180° around the axis of symmetry Z-Z, which facilitates manipulation and assembly. In the latter case, the wing  44  is located in the slave housing  28  and the wing  42  is outside said housing  28 , on the other side of the bottom wall  34 . 
     The slave housing  28  is adapted to maintain the blocking member  32  relative to the base body  16  autonomously in a direction S extending perpendicular to the cover plane T-T and oriented away from the outer surface  20 . In other words, the slave housing  28  is adapted to oppose a movement of the blocking member  32  towards the inner side I relative to the base body  16  in the absence of any other maintenance means. Owing to the fact that the slave housing  28  is formed by the maneuvering recess  26 , the base body  16  only requires little material, and in any case, there is no superfluous material in the event the slave housing  28  is not used. 
     When the base body  16  is manufactured, the housing openings  36 ,  38  are not necessarily created. When these openings  36 ,  38  are not formed in a cover during its manufacture, each location of the housing openings  36 ,  38  is completely covered by a covering wall  50  having a thickness e substantially smaller than the wall thickness EP of the side walls of the maneuvering recess  26  of the base body  16 . Preferably, the thickness e is between 0.1 mm and 1 mm. These covering walls  50  form a sealing barrier of the maneuvering recess  26  relative to the inner side I of the manhole  2 . Thus, when the blocking member  32  is not placed in the slave housing  28 , given that the base body  16  is used for a master cover  8 , rainwater or various refuse cannot penetrate the maneuvering recess  26  inside the hole  2 . 
     The wall  50  is frangible and must be broken so as to put the blocking member  32  in place in the slave housing  28  for the first time. 
     The slave cover  6  also includes a subjugation means  60  of the blocking member  32  on the base body  16 . This subjugation means  60  is adapted to oppose removal of the blocking member  32  from the slave housing  28 . The subjugation means  60  cooperates by shape complementarity on the one hand with the blocking member  32  and on the other hand with the base body  16 . To that end, the blocking member  32  has a subjugation surface  62 , in this case delimited by a recess, while another subjugation surface  64  is delimited by the base body  16 . The subjugation means  60  also comprises a subjugation member, in particular a pin  66 , inserted between the subjugation surfaces  62  and  64 . 
     The slave cover  6  also has a guide means  70  adapted to guide the blocking member  32  relative to the base body  16  during insertion of said blocking member in the slave housing  28 . As emerges particularly from  FIG. 9 , the guide means  70  comprises a guide groove  72  in which the wing  44  of the blocking member  32  slides when the wing  42  is inserted into the slave housing  28 . 
     Preferably, the blocking member  32  is made from metal and more particularly cast iron. Preferably, the material of the base body  16  and the blocking member  32  are identical so as to avoid corrosion of either of said elements. 
       FIGS. 4 to 7  show the part of the hole  2  at the blocking housing  30 . The blocking housing  30  is adapted to receive a blocking member  32  so as to block one side of the cover  6  or  8  relative to a side of the frame  4 . The configuration and the operation of the blocking housing  30  and the blocking member  32  are similar to the operation of the slave housing  28  and the blocking member  32  previously described, and only differ therefrom by the following. 
     The blocking member  32  does not cooperate with a neighboring cover, but cooperates with the base  14  of the frame  4 . More precisely, a blocking lug  46  of the blocking member  32  is adapted to engage under a stop surface  74  of the frame forming a strike for the blocking member  32 . This stop surface  74  extends parallel to the hole plane P-P, is situated on the inner side of the base  14  and is delimited by a surrounding wall  76 . The surrounding wall  76  protrudes inwardly, parallel to axis X-X, thereby preventing sealing material from penetrating the frame at the location of the stop surface  74 . 
     As emerges from  FIG. 3 , the blocking element  32  is inserted into the housing  30 , both on the slave cover  6  and on the master cover  8 , and serves to prevent the slave cover  6  and the master cover  8  from lifting relative to the frame  4 . 
     Moreover, the bottom wall  34  has a stepped inner surface that leads to a low consumption of material and makes it possible to block the pin  66 . 
       FIG. 11  shows a manhole  2  according to an alternative of the invention. This manhole  2  differs from the manhole  2  previously described only in the following. 
     The frame  4  has a substantially rectangular shape. The manhole  2  has a master cover  8  and three slave covers. These three slave covers comprise two even slave covers  6 P and one odd slave cover  6 I. The two even slave covers  6 P are identical to the slave cover  6  previously described. 
     The even slave covers  6 P each comprise a base body  16  having an even slave housing  28 P identical to the aforementioned slave housing  28 . 
     In the case of even slave covers  6 P, the blocking member  32  is inserted in a first insertion direction SI 1  in the even slave housing  28 P, this insertion direction SI 1  being considered relative to said housing  28 P. When the locking member  32  is received in the even slave housing  28 P in this first direction, the cover  6  constitutes an even slave cover  6 P. 
     The odd slave cover  6 I is arranged between the two even slave covers  6 P. 
     The odd slave cover  6 I includes a base body  16  having an odd slave housing  28 I identical to the aforementioned slave housing  28  and in which a blocking member  32  extends. The blocking member  32  is inserted in a second insertion direction SI 2  in the odd slave housing  28 I, this insertion direction being considered relative to said housing  28 I. When the blocking member  32  is received in this second direction SI 2  in the housing  28 I, the cover constitutes an odd slave cover  6 I. It should be noted that the second insertion direction SI 2  is different from the first insertion direction SI 1 , and is in the present case a direction opposite the first insertion direction SI 1 . Thus, in  FIG. 11 , the two directions SI 1  and SI 2  are oriented in the same direction, given that the odd slave cover  6 I is rotated by 180° relative to the even slave covers  6 P. The even  28 P and odd  28 I slave housings are identical, their function is only defined by the insertion direction of the blocking member. 
     In other words, the type of cover, i.e. even slave cover  6 P or odd slave cover  6 I, is defined by the insertion direction of the blocking member  32  into the slave housing. 
     When the blocking member  32  is arranged in the slave housing in the second insertion direction SI 2 , the odd slave cover  6 I cannot be arranged on the frame  4  or removed from the frame  4  while the even slave cover  6 P adjacent to said blocking member  32  is in place. 
     Thus, in order to open the hole  2 , it is necessary first to remove the master cover  8 , then the even cover  6 P arranged between the master cover  8  and the odd cover  6 I, then the odd cover  6 I and finally the other even cover  6 P arranged opposite the master cover  8 . 
     It should be noted that the base body  16  of the odd slave cover  6 I is identical to the base body  16  of the master cover  8  and the even slave covers  6 P. 
     Moreover, the master cover  8  can include a bolt  80  adapted to lock the master cover  8  relative to the frame. 
     This alternative has a particularly low production cost, given that a single housing  28  is needed to define two types of cover. 
     One alternative not shown of a manhole  2  of  FIG. 11  includes the following features. This manhole  2  differs from the manhole  2  of  FIG. 11  only by the following. 
     The slave covers each comprise a base body  16  having a first slave housing, identical to the aforementioned slave housing  28 , as well as a second slave housing that is separate from the first slave housing. This second slave housing is for example arranged in the middle of a side of the slave cover. When the blocking member  32  is received in the first slave housing, the cover  6  constitutes an even slave cover. When the blocking member is arranged in the second slave housing, the cover  6  constitutes an odd slave cover. 
     When the blocking member  32  is arranged in this second slave housing, the odd slave cover cannot be arranged on the frame  4  or removed from the frame  4  as long as the even slave cover adjacent to this slave housing is in place. 
     It should be noted that the base body of the odd slave cover is preferably identical to the base body of the master cover and the even slave covers. 
     To that end, each of the base bodies of the covers includes an even slave housing, an odd slave housing and a blocking housing. When the blocking member is inserted into the even slave housing, the cover constitutes an even slave cover. When the blocking member is inserted into the odd slave housing, the cover constitutes an odd slave cover. When a blocking member is inserted neither in the even slave housing nor in the odd slave housing, the cover constitutes a master cover. 
     In this way, a single base body  16  can be used to constitute a master cover, an even slave cover or an odd slave cover. Likewise, a same blocking member  32  can be used to create the desired type of cover. The manhole  2  therefore has a low production cost. 
     In an alternative that is not shown, the blocking member  32  is provided with anti-closing means adapted to oppose the closing of the cover when the latter is in the open position. 
     This anti-closing means is for example made in the form of a rod fastened to the core  40  only when the cover is in the open position. This rod extends between the two lugs  46  and its free end bears against the wall of the underground chamber, thereby opposing the untimely closing of the cover. 
     Lastly, the fact that the blocking member is mounted parallel to the cover plane in the associated housing facilitates the strength of said member in the housing.