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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an improvement in poles, markers and the like provided with a device for linking to the ground with breaking point, in particular anti-parking posts or vertical signalling markers used in road signalling. 
     2. Description of the Related Art 
     It is relatively expensive to replace markers and posts damaged further to a shock by a vehicle, insofar as not only must the damaged part be replaced, but it has to be unsealed and the replacement part sealed. 
     In the past, it has therefore been proposed to fix the signalling markers or posts with the aid of a ground-linking device comprising a breaking part, so that, in the event of shock by a vehicle, only the linking piece or one of its elements is deformed or broken. It follows that, in principle, only the linking piece and/or the corresponding element are to be replaced. 
     U.S. Pat. No. 3,340,531 in particular discloses such a linking device. This document provides fixing the pole to the ground via a sealed base having a hollow tube with the diameter of the pole, the link between this hollow tube and the pole being ensured by a linking piece which is placed, half in this hollow tube and half in the pole. This linking piece presents a median circumferential thin section intended to form the zone of deformation or of rupture. This linking piece may be pierced in its length so as to receive a sling intended to maintain the pole and the base together when the linking piece has broken. The major drawback of this device consists in the risk of damaging the opposite edges of the pole and the base. In effect, in the event of a considerable shock, bringing about complete rupture of the linking piece, the edges of the pole and of the base may violently strike one another or part of the linking piece. 
     U.S. Pat. No. 3,912,405 discloses another device of this type, comprising a linking piece of which a part is interposed between the pole and the tube sealed in the ground, having the same diameter as the latter but having a thinned rupture zone. Inside this linking piece there extends a flat iron element intended to maintain the sealed tube and pole together after rupture of the linking piece. The geometry of this flat iron element is not favourable to correct functioning of this device apart from a shock perpendicular to the plane of this piece. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved linking device fully performing its role while avoiding any damage of the pole and of the base. 
     Another object of the invention is to provide such a device which may be adapted to poles of different geometrical shapes. 
     A further object of the invention is to provide a device which may be used with a base not projecting above ground level. 
     Yet another object of the invention is to be able to propose such a device not having a part projecting with respect to the pole on inclined ground. 
     The present invention has for its object a pole, marker or the like formed by an anchoring post and a vertical member or upright, in particular a tube, the anchoring post and upright being linked together by a linking piece, preferably cylindrical, having a zone of lesser resistance to force. The assembly is arranged so that the opposite edges of the anchoring post and the upright have a space therebetween in which the zone of lesser resistance is provided. The linking piece, possibly having a central longitudinal bore, receives a sling or the like shaped to provide a link between the anchoring post and upright after rupture of the linking piece. The post and the upright each include a plate or block element, the two plates oppose one another and at least one has a surface sloping from its center towards its periphery such that the space between the two plates is greater at the periphery of the pole than at its center. 
     The linking piece is therefore centered on the median axis of the pole and of the anchoring post. 
     The linking device according to the invention, formed by the two plates and the linking piece, may be used for any street structure fixed to the ground by one or more uprights or poles. Without this being exhaustive, mention may be made of anti-parking posts or markers, barriers, benches, candelabra, signalling, in particular road-signalling masts, advertizing supports and panels, luminous markers, supports of all types, such as trashcan supports. The expression pole, marker or the like is therefore intended to cover all of the possibilities. 
     The inclined surface of the plate is preferably a surface of generally convex shape. Advantageously, the curvature or the angle of the inclined surface is chosen so that the linking piece breaks before contact between the plates. In any case, the curvature makes it possible to avoid any contact between the edges of the plates. Possible contacts will be made in resistant zones of the plates. In addition, the plates may advantageously be pieces which are solid or of thickness greater than the thickness of the poles, and therefore present a high resistance. 
     According to the invention, the plates may have an outer diameter identical to or different from that of the anchoring post or the upright which bear them. It will very advantageously be identical when plate and pole will be off-the-ground in order not to increase the dimensions and to avoid any projecting part. The plate or plates may be fixed definitively, for example by welding, or be made in one piece with the upright and/or the anchoring post, or be removably fixed by any means known per se. 
     According to a particularly advantageous modality, anchoring post and corresponding plate are removably fixed together and are arranged so as to be able to be placed below ground level or substantially at that level. A circular, preferably flat, supple joint is provided between the two plates, preferably on their periphery. This embodiment ensures a certain tightness and renders invisible the adaptation of the pole or marker while allowing the linking piece to be easily changed after a shock. The outer diameter of the joint is preferably larger than or equal to that of the upper plate or the upright, which advantageously makes it possible to preserve the seal and the plate in the event of rupture. In the event of rupture, the upper plate linked to the upright does not come into contact with the seal, but with the joint. The joints are preferably chosen to present a diameter greater than the diameter of the plates. 
     According to a particular embodiment, a supple, flat, circular joint is provided between the two plates and not projecting therebeyond, as well as a second circular joint coming into position on the periphery of the preceding one, this joint being shaped to be able to adapt itself substantially to the inclination of the ground. It may therefore be a question of a second flat joint, of a joint presenting an inclined surface or, preferably, of a flat joint cut into two parts along an inclined plane so that, in the case of horizontal or substantially horizontal ground, the joint is used in its flat form and, in the case of inclined ground, one of the two joints is turned through 180° so that the maximum thicknesses of the two joints coincide. In the latter case, a flat, unequally cut joint may be used, so as to propose to the user different possibilities from the same joint set, as a function of the inclination of the ground, the user being able simply to use one or the other of the two half-joints thus produced or the association of the two. 
     According to a preferred embodiment of the invention, particularly adapted to a location below ground level, the plate fixed to the anchoring post is formed by a first half-plate secured with the anchoring post and presenting a housing to receive, on the one hand, one end of the linking piece and, on the other hand, a second half-plate having the bore for the linking piece and means for removable fixation in the housing of the first half-plate, in that the linking piece presents the end (for example a flange) shaped to be positioned in the housing of the first half-plate and to be removably immobilized therein when the second half-plate is in place, and in that this half-plate preferably includes the inclined or convex surface. The removable link between the two half-plates may be produced by any known means, for example by means of screws or, better, of a bayonet or catch fixation system, preferably with a screw or like locking. 
     The anchoring post and corresponding plate may also be one and the same piece and includes means for fixation on a surface. This embodiment is adapted in particular, but not exclusively, for fixation on a vertical surface for the suspension of signs or signalling panels. 
     The linking piece preferably comprises a circular groove near at least one of its two ends and the plate comprises one or more bores intended to receive means, for example points or screws, inserted in the groove to maintain the linking piece in place, this groove further being separated from the outer surface of the linking piece by a zone of diameter which is constant or not, intermediate the diameter of the linking piece and that of the groove. 
     According to an advantageous modality of the invention, in its part intended to be fixed to the pole, marker or the like proper, the upper plate is arranged so as to be able to receive poles, markers or the like of different diameters. For example, two or more shoulders of different sections or diameters decreasing from the periphery of the plate may be provided to that end, each section or diameter being able to receive poles of corresponding section or diameter. 
     These shoulders may be inscribed in the same plane orthogonal to the median axis of the linking device or in different planes, preferably with the reduction of section or diameter being made in the direction opposite the location of the linking piece. The shoulders may be of any shape as a function of the geometrical shape of the pole, e.g. circular, oval, rectangular, square, etc. . . 
     The invention also relates to the linking device formed by the two plates and by the linking piece, as defined hereinbefore. This device generally comprises a linking piece including a zone of lesser resistance and two plates each including a central bore having an inner diameter slightly larger than the outer diameter of the linking piece. The two plates are adapted to be mounted on the linking piece and to face each other by opposite surfaces of which at least one is inclined, preferably of generally convex shape, the linking piece being designed to be able to be removably immobilized with respect to the two plates, so that, after immobilization of the three pieces with respect to one another, a space remains between the two surfaces, in which the zone of least resistance is located. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be described in greater detail with the aid of embodiments given by way of non-limiting examples and with reference to the drawings, in which: 
     FIG. 1 shows a view in partial section of a pole according to the invention. 
     FIGS. 2 and 3 show in partial section two other embodiments provided so that the anchoring post and its plate can be placed below ground level. 
     FIG. 4 shows in section a plate according to a particular embodiment. 
     FIG. 5 is a view in partial section of another embodiment, and 
     FIG. 6 schematically shows a mode of adaptation to inclined ground and an upper plate with shoulders. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a signalling pole  1  comprising an anchoring post or base  2  sealed in the ground  3  and the pole  4 . Pole and anchoring post are formed from a cylindrical metal tube. FIG. 1 shows that the pole and the anchoring post each comprise a plate or block elements  5 ,  6  respectively. Each plate is fitted in the pole or the corresponding post and fixed by a welding bead  7 ,  8  respectively; Of course, other fixing means may be provided for the plates. 
     The opposite surfaces of the plates or blocks  5  and  6  are referenced  9 ,  10  respectively. Surface  9  is plane while surface  10  presents a curvature so as to give surface  10  a generally convex form. 
     The two plates or blocks  5  and  6  include a central bore  11  of generally cylindrical shape, adapted to receive, tightly, a linking piece  12  having a circumferential groove  13 . When the linking piece is in place, it leaves a space  14  between the two surfaces  9 ,  10  of the plates  5 ,  6 , in which space the circumferential groove  13  is inscribed. It is clearly seen that the central bores  11  and the linking piece  12  are centered on the median axis of the post and the upright or pole proper. 
     In the vicinity of each of its two ends, the linking piece  12  has grooves  15 . Opposite these grooves, when the linking piece  12  is in place, each of the plates  5  and  6  has three threaded transverse bores  16  intended to receive threaded fasteners  17  of which the inner end engages in the groove to maintain the linking piece in place. It will be noted that groove  15  presents a complex form with a part intended to receive the point in position of fixation and a part  19  of diameter intermediate the outer diameter of the linking piece and the diameter of this groove, this part  19  being provided to allow easy dismantling, even in the case of shock of high intensity with risk of damage at the point of contact between point and groove. 
     The linking piece  12  comprises a longitudinal central orifice  20  receiving a sling or connection  21 , which may be a supple or more or less rigid sling, intended to maintain anchoring post and pole attached together after rupture of the linking piece. To that end, the ends of the sling are provided with stop pieces  22  with diameter greater than orifice  20 . 
     A rigid sling may be used, particularly for relatively high poles, designed to avoid the upright falling to the ground too quickly after rupture of the linking piece. 
     Reference numeral  23  designates a joint intended to obturate the space  14  for sealing and aesthetic purposes. It may be a joint made of plastics material or of a metallic joint. 
     Reference will now be made to FIG. 2 which shows an embodiment of the invention in which the rupture device is rendered invisible by the fact that it is located below ground level, this making it possible not to modify substantially the outer appearance of the pole. This is particularly interesting in the domain of anti-parking posts and in particular of markers or small posts performing, at the same time, a decorative role, made in particular of cast iron, stainless steel and presenting various shapes, namely of constant diameters or of irregular diameters, for example generally conical, triangular, or oval in shape. 
     The anchoring post  30 , sealed in the ground  3 , presents an inner thread  32  intended to cooperate with an outer thread  33  borne by the plate or block element  31 . A flat, circular joint  34  is provided between the plate and the anchoring post so as to ensure tightness with respect to the threading. 
     As in the preceding embodiment, the plate  31  or has block element three bores  16  intended to allow passage of the fastener points  17  intended for fixation of the linking piece  12  in the plate  31 . It will be noted that the access to the point of plate  31  can be effected only after screwing and withdrawal of the plate  31  with respect to the anchoring post  30 . 
     The anchoring post and the plate or block element  31  are placed in the ground so that the surface  35  of the plate  31  which, here, is a surface of generally convex shape, lies slightly below the level  3   a  of the ground. It will be noted that, in this embodiment, when the linking piece  12  is in place, the edge  36  of the linking piece  12  which upwardly defines the circumferential groove or area of reduced dimension  13 , lies substantially at ground level. 
     The pole  37  is, here, directly manufactured with the plate or block element  38 . Here a pole of cast iron essentially hollow, but presenting an initially solid part in which a blank may be formed in the foundry, allowing the subsequent machining of the bores intended to receive the linking piece  12  and the end of the sling  21 , and bores intended to receive the points of three fasteners  17 . 
     The lower surface  40  of the plate  38  is, here, a plane surface. When the assembly is mounted, it will be noted that this surface  40  lies substantially at ground level, in the plane of the edge  36 . During assembly, there is interposed between surfaces  40  and  35 , a supple, flat, circular joint  41  which, in the event of a shock, can deform under the effect of the deformation of the linking piece  12 , which will avoid any damage of the seal. 
     FIG. 3 shows a variant embodiment of FIG. 2, in which the fixation of the lower plate is made differently. 
     This plate or block elements  42  presents a peripheral flange  43  having bores  44  coming opposite corresponding bores  47 , threaded and made in the anchoring post  45 . It will be understood that the plate  42  is fixed on the anchoring post by screws  46 . 
     Of course, other variants of fixation of the lower plate may be envisaged, such as the embodiment of a bayonet system. 
     FIG. 4 shows the preferred embodiment in the case of a link below ground level. The plate fixed to the anchoring post  52  is formed by a half-plate  53  welded to the post and presenting in its upper part a circular housing  54  intended to receive the other half-plate  55 . This half-plate  55  has a bore  56  adapted to receive a linking piece  57 . The half-plate  55  presents a curvature  58  going from the bore  57  to the periphery of the half-plate  55 . In the region of this curvature  58 , it further has bores  59  for the passage of screws  60  intended to fix the two half-plates  55  and  53  together by screwing in corresponding threaded holes  61 . The half-plate  53  a central bore  62  with, in its upper part, a part  63  of larger diameter. The linking piece  57  presents a flange  64  which, on being housed in part  63 , may be immobilized in place by the fixation of the half-plate  55  on the other  53  by screws  60 . 
     As in the embodiments of FIGS. 2 and 3, this assembly is sealed below ground level  65 . The seal  66  proper stops, upwardly, at the upper end of the half-plate  53 . This is symbolized by the broken line in FIG.  4 . Two circular joints  67 ,  68  (or one single joint) are placed between this end and the surface  65 . It is seen that, as in FIGS. 2 and 3, the pole  69  will be in contact with this joint, which is deformable. 
     The space  70  between the surface  65  and the seal  55  is filled with an appropriate material such as stone, cement, asphalt, etc. . . 
     For the rest, the linking piece comprises, as before, the circumferential groove, the groove for the engagement of the fastener points for fixation to the pole and the longitudinal central bore with the sling. 
     An elastic means such as a spring  48  (FIG. 1) may be provided between the plate and the end of the linking piece, in order to facilitate withdrawal of the latter from its housing in the plate. 
     In the different embodiments, anchoring post and associated plate may have standard dimensions in order to be usable with poles and associated plates of various shapes and diameters. 
     Reference will now be made to FIG. 5, which shows a plate or block element  50  having presenting sealing flanges  51  allowing the plate  50  to be fixed on a vertical surface. Furthermore, the plate  50  presents the characteristics allowing it to accommodate a linking piece according to the invention. The plate  50  therefore performs the role, here, of anchoring post intended in particular for a mural signalling or for signs. 
     In any case, the linking device may be adapted for positioning on an inclined surface  80  (pavement, road), the pole with its upper plate or block element  81  remaining vertical (cf. FIG.  6 ). A set of 2 circular joints  82 ,  83  may in particular be used. One,  82 , is of constant section and is placed in the space between the two plates  81 ,  84  in which it is totally inscribed. The otherjoint  83  is a flat joint cut into two along an inclined plane  85  and giving two substantially equal parts. This joint  83  may be used in its flat form in the case of horizontal ground or, as shown in FIG. 6 (inclined ground), after turning one of the parts over through 180°, in its inclined form in order to follow the inclination of the ground. 
     In a variant, the inclined plane  85  may have two unequal parts, which allows a greater flexibility of use, the installer being able to place one or the other of the two parts of different inclinations or the two superposed, depending on the slope of the ground. 
     A specific set of joints  83  of different shapes may also be resorted to. 
     FIG. 6 also shows that, in its upper part, the upper plate  81  has two shoulders of different diameters enabling two diameters of pole to be accommodated. 
     Anchoring post, pole proper, plates, linking pieces may, of course, be made of different materials. The poles may generally be made of metal, such as iron, aluminium, cast iron, or of plastics material and even wood. The linking device according to the invention may be made of metal, particularly steel or brass, or of plastics material, particularly reinforced plastics material. The device according to the invention may of course be adapted to the different geometrical shapes that the poles may have in general. Similarly, the person skilled in the art may select the constituent materials as a function of the desired shock resistance.

Summary:
A pole or the like formed by an anchoring member and a vertical member which are linked by a linking piece having a zone of lower resistance to force. Block members are provided at the opposite ends of the anchoring member and the vertical member each of which has a central bore for receiving the linking piece and at least one of the block members has a surface slopping from its center towards it periphery such that a space between the opposite block members is greater at the periphery of the pole than at its center.