Abstract:
An anchoring system in concrete having a predrilled hole with an undercut. The anchoring system includes a cylindrical rod that is threaded at one end and has a trunk conical head at the other end. A sleeve extends over the lower portion of the cylindrical rod above the trunk conical head. The cylindrical rod is inserted into the hole so that the sleeve is adjacent to the undercut. The sleeve is fixed against being subsequently withdrawn. The cylindrical rod is then rotated relative to the sleeve thereby lifting up the trunk conical head into the sleeve so as to press against and thereby expand the sleeve outward against the walls of the undercut.

Description:
BACKGROUND OF THE INVENTION 
     The present invention refers, as expressed by the title of this specification, to a series of improvements introduced in the anchoring systems through threaded bolts, intended to be installed in drilled holes previously made on blocks, tiles or walls of concrete or brick, stone blocks, etc. which drilled holes, at a certain depth, have a cavity of a diameter bigger than the drilled hole itself and on which cavity the axial fixation of the anchoring is made. These cavities may have any shape, though normally they are an annular hole which surface closer to the drilled hole has a trunk-conical shape. Not only the drilled hole but also the annular hole will be made by any conventional means and with the use of any adequate tool, and the performance of said drill is left out of the scope of the present invention. 
     SUMMARY OF THE INVENTION 
     In a more concrete mode, the improvements preconized are specially applicable to anchoring systems on concrete; for which hereinafter this material is to be cited as a constituent of the receiving element of the bolt, though, as previously said, it may be any other material. 
     The improvements preconized are especially applicable to anchoring bolts provided with a threaded sector in one of its ends, with which the corresponding tightening nut cooperates for the object to be fastened, assisted by a washer, such improvement being centered in the existence at the opposite end of the stud, of a trunk-conical head, longitudinally striated, divergent with respect to the body of the stud and as from same, being said head approximately coincident, from the dimensional point of view, and concretely in correspondence with its maximum diameter belonging to its bigger and free basis, with the drilled hole of the concrete in which the bolt is to be installed. 
     The smaller basis of said head presents a diameter which coincides with that of a first sector of the stud, which determines one neck, also longitudinally striated, which diameter is, in turn, lower than the rest of the stud. 
     On the said striated neck, several pieces are installed, which in their whole define a cylindrical bush with its internal surface striated, and with its external surface provided with a perimetral groove on which is located an elastic ring, which holds said pieces adapted against the neck of the stud, and which perimetral groove makes up, besides, a weakening line for said pieces, which permits that same, in the operational phase of fixation of the bolt, be obtusely bent outwards, until defining an angle which is determined by the conicity of the trunk-conical head of the stud. 
     Besides, these pieces show, also in their external face, at their end opposite to that of incidence over the cited head, an external perimetral offset, intended to the coupling of said pieces at the nozzle of a sleeve, in turn internally offset and which is adapted to the sector of bigger diameter of the stud, affecting it in all its length. 
     At the same time, this sleeve incorporates an external perimetral groove, close to its receptor end of the set of pieces cited, in which groove is installed an elastic nozzle which legs press the side surface of the stud through two diametrally opposite areas in which said groove perforates the walls of the sleeve, having said fork the end of, during the mounting of the bolt, moving along the stud until reaching the echeloning defined by the neck of same, at which situation it recuperates elastically, fixing this way the stud and the sleeve axially, and acting consequently as a link between these elements. 
     To attain this axial fixation between stud and sleeve at said stud, concretely at the linking point between its body and its neck, an abrupt echeloning is defined, preferably on a right angle, so that once the arms of the fork close elastically on the neck, there exists the possibility of uncoupling before an axial traction on the stud. 
     It should be highlighted as well, in accordance with another improvement preconized, that the length of the pieces associated to the neck of the stud, and more concretely the length of same defined between the folding groove and its end adjacent to the trunk-conical head of the stud, is the adequate one so that when folded they result laterally overlapping in a dimension determined by the transverse dimensions of the cavity of the drill in which the bolt is to be installed, whilst the length of said pieces, between the cited folding groove and the end opposite to the head of the stud, the adequate one for it to exert an internal pressure in the mostly tensioned area of the walls of the drill, avoiding its collaspe. 
     In a similar way, the folding groove existing in the external face of these pieces has the adequate dimension to allow that the folding to the outside be made with an angle equivalent to that of conicity of the head of the stud. 
     The transverse sections of the pieces grouped on the neck of the stud, define sectors of circular crown, which at the area comprised between the folding groove and the end opposite to the head of the stud, have constant and equal internal and external diameters, respectively, to those of the neck of the stud and to those of the bigger base of its head, so that all these elements make up a cylinder, while the other sector of said piece may have the same section as the rest of the piece or have diameters varying respectively, increasing towards its free end, with the same formula of variation as the diameters of the trunk-conical head of the stud and of the cavity of the drilled hole, for which when folding these areas of the pieces during the installation of the bolt, they show internal and external difficulties which constitute cone trunks equal to those which form the head of the stud and the cavity of the drilled hole in which the bolt is installed. 
     Another improvement preconized is centered in the fact that the end areas of the internal face of said pieces have longitudinal grooves which gear with others that exist at the head and neck of the stud, which may have been incised previously, but in a similar way, if the enveloping pieces are of a material softer than the stud and may be produced during the installation of the bolt by the pressure to which they are submitted. It has also been set forth that the cited offset end of these pieces be introduced between the sleeve and the neck of the stud, with the necessary adjustment to hinder the radial movement of said pieces, avoiding their ungearing. 
     Going back again to the elastic fork, same presents a separation between its arms equal to the diameter of the neck of the stud, for which it recuperates elastically upon reaching this area, closing on it when the folding of the group of pieces which surround said neck is completed, setting forth the axial retention previously cited. 
     In this sense, there also exists the possibility that the cited fork be housed in a groove made at the sine of the sleeve, in which case the latter will lack the two drillings of the sleeve. 
     As a complement of the structure described and like other of the improvements preconized, it has been set forth that for the folding of the said set of pieces which houses the neck of the stud, a complementary tooling be used, made up by a threaded cylindrical piece, threaded internally, in coincidence with the thread of the stud, and this piece, at one of its edges incorporates a polygonal head, to be driven through a key, and that on the other offers a plain frontal contact surface, through an axial bearing or anti-friction bush, on a second piece, the latter with two plain faces, one in which the contact cited with the first piece is established, and another from which overlaps a small neck which internal and external diameters are respectively the same to those of the sleeve, and these two pieces which make up the tooling are kept coupled through an elastic ring. 
     In this sense, the length of the neck of the second piece of such a tooling, is the adequate so that, by screwing the tooling to the stud until the neck makes contact with the sleeve and introducing the bolt in the drilled hole in which it must be installed, so that the piece which bears said neck makes contact with the surface of the body, the groove of the pieces associated to the neck of the stud, is opposed to the initial area of the cavity which exists in the drilled hole, being the total length of the tool the adequate one so that the end of the stud be at level with the end of the first piece of the tool, when the folding provided for the cited pieces which envelope the neck is completed. 
     To complement the description that is being made and in order to help to a better understanding of the characteristics of the invention, we enclose herewith as an integral part of the specification herein, a set of drawings in which, with an illustrative but not limitative character, the following has been represented: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1, shows a side elevation view and in section at one fourth of an anchoring threaded bolt, made in accordance with the object of the present invention. 
     FIGS. 2a and 2b, show a cross-sectional section of the bolt at level of the elastic nozzle, in accordance with the two possibilities provided to the purpose, one in which said fork is internal to the sleeve and another in which it is external to same all of it in accordance with the A--A cutting line of FIG. 1. 
     FIGS. 3a and 3b, show the same detail of the previous figure, in its two versions, at the end of the fastening of the anchoring, concretely when the cited fork has reached the neck of the stud. 
     FIG. 4 shows another cross-sectional view of the bolt, in this case made at level of the perimetral groove of the group of pieces which surround the neck of the stud, in which is located the elastic retention ring for same, as per the C--C cutting line of FIG. 1. 
     FIGS. 5a and 5b, show another cross-sectional view of the stud, in accordance with the B--B cutting line of FIG. 1, concretely at the level of the linking area between this group of pieces and the sleeve, having it been represented a considerably magnified view in which are noticed the complementary indentations between the cited group of enveloping pieces of the neck and the neck itself. 
     FIG. 6 shows a side elevation view and in section at one fourth of the tool set forth for the implantation and fixation of the anchoring. 
     FIG. 7 shows a side elevation view of an anchoring bolt, duly housed at a hole previously made at a concrete wall, being coupled to said bolt the tool represented in the previous figure, and all of it under conditions of starting the corresponding fixation. 
     FIG. 8 shows, as per a representation similar to that of FIG. 7, the location of the bolt at the end of said operational phase of fixation, concretely when the terminal sector of the pieces associated to the neck of the stud has been deformated, radially, but still the working tool associated to the stud is yet held. 
     FIG. 9 shows, finally, the same assembly of the previous figure after the elimination of said tool and its substitution for the piece to be fastened by the anchoring in question. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     On view of these figures, it can be noted how the improvements that are preconized are based in the following: 
     The stud (1) is a cylindrical rod that is threaded at one of its ends and on the other has a trunk-conical head. At the threaded area of the stud is installed the nut (2) and the washer (7), through which are fastened the elements that are to be fastened with the anchoring bolt to the concrete wall or tile, brick, etc. At the threaded end of the stud (1) there is a slot or similar thing, to fasten it with a screwdriver or with the corresponding key, when initiating the tightening of the nut. Close to the trunk-conical head of the stud (1) it has a neck, that is, a cylindrical area which diameter is less than that of the rest of the stud. The smaller base of the trunk-conical head has the same transverse section than the neck and is adjacent to it. The bigger base, which constitutes the end of the stud, is bigger than the transverse section of the rest of the stud and is approximately the same (with the necessary clearance) as the drilled hole in which the anchoring bolt is installed. 
     Around the neck of the stud (1) are located several pieces (3) equal among themselves and with a basically prismatic shape, which lengths are the same as that of the neck. These pieces (3) have at their two ends, longitudinal grooves at the internal face. At the end adjacent to the sleeve (5) they have, at the external face, an offset which allows that this offset end be introduced in the sleeve (5) being adjusted between it and the throat of the stud (1). 
     At the side surface of the trunk-conical head of the stud (1), there are longitudinal grooves which gear with those existing at one of the ends of the pieces (3), making up a system which hinders the rotation of the stud (1), during the tightening of the nut (2) for the same purpose, the neck of the stud has, at the area opposite the head of the stud, longitudinal grooves which gear with pieces (3) at their other end. The length of the grooves existing at the neck is enough for said gearing to be held after the movement of the stud (1) relative the bush (5), during the installation of the bolt, as hereinafter described. 
     This configuration constitutes, a double effect anti-rotation system: on one part, it hinders the parts (3) to rotate on themselves as their end is adjusted between the edge of the sleeve (5) and the neck of the stud (1) and on the other, it hinders the stud (1) to rotate when tightening the mounting tool or the nut (2), as said stud (1) is geared to the pieces (3) and these remain fixed in the concrete by the pressure they exert on it. The stud (1) cannot be ungeared from the pieces (3) as therefor these pieces should move radially towards the outside, which is hindered by the adjustment with which the edge of the pieces (3) is introduced between the sleeve (5) and the neck of the stud (1). 
     The gearing of the grooves of the pieces (3) in those of the neck and in those of the head of the stud (1) is favoured by the forces which are exerted between both when folding the pieces (3) during the installation of the bolt. 
     The grooves of the pieces (3) may be previously cut or, if the material of which they are made is softer than that of the stud (1) they form during the installation of the bolt, by the pressure which the stud (1) exerts on it, to fold them as hereinafter explained. 
     The double gearing of the pieces (3) with the neck and with the head of the stud (1) avoids these pieces (3) to be crossed regarding the axle of the stud (1) as it might happen if they were geared to it in only one of its ends. 
     The pieces (3) have, at their external surface, a transverse slot (see FIG. 4) which has a double task which serves as housing to the circular elastic ring (4) through which the pieces (3) are held in their position around the neck of the stud (1) and allows to fold the end of the pieces (3) towards the outside an angle the same as that of conicity of the trunk-conical heads of the stud, during the installation of the bolt (see FIG. 8). Therefor, this slot or groove A has the necessary depth and width. 
     The groove divides the pieces (3) in two different shape areas; as described hereunder. 
     The transverse section of the pieces (3) between the groove for folding and its end adjacent to the sleeve (5) is a circular crown sector, which internal and external diameters are respectively the same to that of the throat of the stud (1) and to that of the bigger base of the trunk-conical head of said stud (1). The circumferential dimension of the pieces (3) is such that, when installed around the neck of the stud (1), the perimeter of them all completes a cylinder. 
     The pieces (3) between the groove for folding and its end adjacent to the trunk-conical head of the stud (1) may have two alternative shapes: either a prismatic shape the same as the rest of the piece (3) or a shape such that, when the piece is folded through the groove of the angle set forth, the internal and external surfaces of this area form cone trunks, which conicity angles are the same respectively to that of the trunk-conical head of the stud (1) and to that of the cavity of the drilled hole in which the anchoring bolt is installed. To attain this, before making the cited folding, the transverse sections of the pieces (3) in this area are made up by sectors of circular crowns which diameters vary respectively along the length of the piece (3) with the same formula of variation as the diameters of the trunk-conical head of the stud and of the cavity of the drilled hole. In this latter alternative a total contact of the folded end of the pieces (3) is obtained, with the trunk-conical head of the stud and with the surface of the cavity of the drilled hole. 
     The length of the pieces (3) between the groove for folding and its edge adjacent to the trunk-conical head of the stud (1) is the adequate one so that, when folding said pieces, the angle previously cited, its ends overlap laterally a dimension that is determined by the width of the cavity existing in said drilled hole. 
     The area of the pieces (3) comprised between the groove for folding and its end adjacent to the sleeve (5) produces a radial pressure in the walls of the drilled hole made on the concrete, which avoids that said walls fall towards the inside as a consequence of the force that the rest of the pieces (3) exert on the cavity of the drilled hole. Therefore, its length is the adequate one so that they cause pressure in the area to which, in accordance with the theories of resistance of materials, are produced the greatest efforts. 
     The sleeve (5) is a cylindrical, hollow piece which internal and external diameters are respectively the same to the general diameter of the stud (1) and to the diameter of the bigger base of its trunk-conical head (and therefore it is also the same as the drilled hole in which the bolt is installed). Its length is the adequate one so that, when levelled with the surface of concrete (with the tolerance hereinafter indicated) the groove of the pieces (3) be opposed with the beginning of the cavity of the drilled hole. 
     The bush (5) on its external face, has a circumferential groove in which an elastic fork (wire or strap) (6) is housed, U shaped. The groove perforates the wall of the sleeve in two diametrally opposed areas through which the two legs of the fork (6) make contact on the stud (1). The task of this fork is that, when the stud (1) moves with respect to the sleeve (5), to fold the pieces (3) during the installation of the bolt, the two legs of the fork get closed around the neck of the stud (1) (see FIGS. 2 and 3) when the folding of the said pieces (3) is completed. This way, the stud (1) and the sleeve (5) are seized between themselves, and it is hindered that the stud (1) falls to the depth of the drilled hole (when the bolt is installed on floors) or that the sleeve (5) comes out of the drilled hole (when the bolt is installed on roofs) and it is avoided that the pieces be misplaced (3) once folded. The separation between the two legs of the U is deformed (see FIG. 2) when opposed to the normal area of the stud, and this deformation is elastically recuperated when opposed with the throad of the stud (see FIG. 3). 
     The groove is located at the bush (5) in the position necessary for the fork (6) to reach the beginning of the throat of the stud (1) when the folding of the pieces (3) is completed. 
     The echelon which the stud has at the initiation of the neck is abrupt (normally on a right angle) so that once the fork (6) has been closed, it may not open again. 
     In another alternative solution, the fork (6) could be installed in a groove located inside the bush. In this solution it would not be necessary that the groove perforated the walls of the sleeve (5). 
     The anchoring bolt made up as previously described is adequate to be installed in a drilled hole having a cavity in its depth (see FIG. 7) because and as previously stated and can be seen in FIG. 8, when the pieces (3) are folded during the installation of the bolt, its ends overlap laterally from the perimeter of the drilled hole, penetrating in said cavity. 
     For the folding of the pieces (3) the tool which can be seen semi-sectioned in FIG. 6 is used. 
     This tool is made up by a cylindrical piece (9) innerly threaded with the same thread as the stud (1) which, in one of its ends has an hexagonal head to be able to move with a key and in the other has a plain surface, which makes a frontal contact with the piece (10) through an axial bearing or an anti-friction bush (11). The pieces (9 and 10) are kept coupled through an elastic ring (12) Seger type or similar. The piece (10) has a plain frontal surface from which overlaps a small neck which internal and external diameters are respectively the same as that of the stud (1) and the external diameter of the sleeve (5). 
     During the installation of the bolt, the frontal surface of the piece (10) is supported on the surface of the concrete and its neck is introduced in the drilled hole made on the concrete. The neck of the piece (10) has a length adequate so that, in this position, the groove of the pieces (3) be opposed to the initiation of the cavity existing in the drilled hole. 
     In order to know that the pieces (3) have reached the folding angle set forth, the movement which the stud (1) has had during the installation is measured. Therefore, the total length of the tool is the adequate so that, when the installation of the bolt is completed, the end of the stud (1) be levelled with the end of the tool (or overlapping a pre-set length). 
     The installation procedure of the bolt in the drilled hole is the following: 
     The tool is screwed to the stud (1) until it stops with the sleeve (5) and is introduced along the drilled hole until the front part of the tool is stopped by the concrete surface. In this situation, the groove of the pieces (3) is opposed with the initiation of the cavity of the drilled hole. The tool is rotated, screwing it to the stud (1) with which same is moved towards the outside of the drilled hole (see FIG. 8) so that its trunk-conical head presses on the end of the pieces (3) forcing them to be folded along the groove and be introduced in the cavity of the drilled hole. 
     At the same time, due to the movement of the stud (1), the fork (6) is moved along it and reaches the throat of said stud (1) when the folding of the pieces (3) is completed, closing around it when it exceeds the echelon existing at the beginning of the throat. 
     At this stage, the bolt is installed in the drilled hole so that the pieces (3) be inserted inside the cavity of the drilled hole with a certain ease and the sleeve (5) remains, with respect to the surface of the concrete, resunk a depth the same as the length of the neck of the piece (10). 
     The tool is withdrawn and the piece to be fixed (8) is placed. The nut is tightened with the tightening pair set forth, with which the bolt is moved towards the outside, so that the folded area of the pieces (3) makes pressure in the frontal surface of the cavity. In this position, the sleeve (5) is approximately levelled with the surface of the concrete. 
     From the whole description previously made, it is understood that, once installed, the bolt makes up a true anchoring, as the axial loads to be supported are transmitted by the head of the stud (1) to the pieces (3) by direct contact. In turn, these pieces (3) transmit them also by direct contact to the frontal surface of the cavity existing in the drilled hole. In this, it differs from the usual expansion bolts in which the transmission of the loads is made by scraping with the concrete surface. 
     Each of the characteristics previously described participates alltogether with all the others in the operation of the bolt, as briefly described hereunder. 
     The neck existing in the stud allows the pieces (3) to have a big thickness, with which it is attained that these pieces (3) have the necessary rigidity to transmit the loads. 
     In turn, the great thickness of the pieces (3) hinders that the head of the stud (1) comes out sliding between said pieces (3) though these be nailed in the concrete, when the latter is smashed by the pressure they exert on it. 
     The existence of an echelon in the initiation of the neck of the stud (1) allows that once the pieces (3) have been folded, the elastic fork (6) be closed in said neck, uniting the bush (5) and the stud (1) in-between, and hindering that the whole of the bolt be disarmed and that the pieces (3) be displaced. 
     The gearing between the grooves of the pieces (3) and those of the head and the neck of the stud (1) sets forth an anti-rotation system which allows the tightening of the stud during the folding of the pieces (3). 
     The adjustment of the end of the pieces (3) between the stud (1) and the sleeve (5) hinders that these pieces, once geared, be ungeared. 
     The existence of an area of the pieces (3) which, once folded, adopts a trunk-conical shape, allows that a full contact with the head of the stud and with the surface of the widening of the drilled hole be established, with which it is attained a better transmission of the loads to be supported. 
     The remaining part of the pieces (3) exerts an internal pressure in the walls of the drilled hole, banding innerly the mostly stressed area of the concrete, with which it is hindered that said walls fall by the force exerted by the folded areas of the pieces (3). 
     It is not considered necessary to make this description more extensive so that any expert in the art understands the scope of the invention and the advantages derived from same. 
     The materials, shape, size and disposition of the elements will be susceptible from variation provided this means an alteration to the essentiality of the invention. 
     The terms under which this specification has been described must be always taken in a broad non limitative sense.