Patent Publication Number: US-2023150074-A1

Title: Device for mounting/dismounting a connecting pin used for an end-to-end assembly of two frame elements

Description:
FIELD 
     The invention relates to a mounting/dismounting device to mount/dismount a connecting pin used for an end-to-end assembly of two frame elements of a structure. 
     The invention finds a preferred, and non-limiting, application for the mounting/dismounting of a connecting pin used for an end-to-end assembly of two frame elements of a crane structure, and preferably of a tower crane mast, of a crane boom or a counter-boom of a crane. 
     BACKGROUND 
     Conventionally, a tower crane mast is composed of a plurality of vertically stackable frame elements, called to be assembled together, end-to-end, during the mounting of the crane on its operating site, and to be separated from each other when dismounting the crane. 
     The frame elements, usually of square cross section, consist of four corner members (or vertical uprights) which are joined in pairs by lattice or triangulation structures, also called bracing, made up of diagonals and sleepers. During the vertical and end-to-end assembly of the frame elements, the ends of the corner members of two superimposed frame elements are rigidly connected to each other by connecting pins, generally associated with fish plates, as known for example from documents FR3014509A1, FR2781535A1 and FR2680813A1. 
     The connecting pins have enlarged heads extended by rods (often cylindrical in shape with a slightly frustoconical free termination), and they are usually tucked into the corner members from the outside to the inside. During dismounting, the connecting pins are conventionally ejected or driven out with a sledgehammer, by striking at the ends of the rods. 
     Patent EP0618047B1 suggests a tool for mounting/dismounting a connecting pin, implementing a pneumatic or hydraulic cylinder system. However, such a solution has the drawback of using dedicated tools, specially designed for such operations, thus limiting its use. Furthermore, it uses a hydraulic or pneumatic source connected to the tool by suitable hoses, limiting the range of use and involving risks inherent in the use of hoses liable to get stuck and increasing the load for the fitter. 
     SUMMARY 
     The invention suggests to respond to the problem of facilitating and securing the mounting/dismounting operations of the connecting pins, while offering a solution which is at once both practical and economical. 
     Thus, the invention suggests a mounting/dismounting device for mounting/dismounting a connecting pin used for an end-to-end assembly of two frame elements of a structure, such as for example a crane structure, this mounting/dismounting device comprising: 
     a mounting/dismounting rod having a longitudinal axis, a head adapted to cooperate with a screwdriver, and a rod body having a proximal portion prolonging the head and a threaded distal portion which terminates in a free end; 
     a base supporting a nut and having an abutment portion shaped to bear on any of the two frame elements, the threaded distal portion being provided to be screwed into the nut aligned on the longitudinal axis; 
     a proximal stop mounted freely in rotation on the proximal portion of the rod body around the longitudinal axis; 
     a bushing which is removable and mounted freely in translation along the longitudinal axis around the rod body between the nut and the proximal stop, such a bushing having a first open end and a second open end; 
     this mounting/dismounting device being configurable in: 
     a mounting configuration in which the bushing is in abutment against the proximal stop; and 
     a dismounting configuration in which the bushing is in abutment against the base or the nut. 
     Thus, the invention suggests a mounting/dismounting device which forms a mechanical assembly ready to be used with a screwdriver (also called power bolter) to mount/dismount the connecting pins, thus making it possible to operate with a commercial screwdriver, which is particularly economical because only the mounting/dismounting device is specially designed for such operations, whereas the actuator, namely the screwdriver, is conventional, and moreover is widely used by fitters who have to carry out numerous screwing/unscrewing operations. 
     In this way, the mounting and the dismounting of the connecting pin are done with the screwdriver and with the same mounting/dismounting device, but with different arrangements of the bushing depending on whether being in the mounting configuration or in the dismounting configuration. In both cases the screwdriver should simply perform screwing to carry out the operation and, once the operation is finished, it is enough to perform unscrewing to be able to remove the mounting/dismounting device. 
     Indeed, and as described below, the operations take place succinctly as follows, thanks to the invention: 
     during mounting, the mounting/dismounting rod is screwed into the nut, so that the nut pushes the connecting pin, the rotational forces being taken up on the structure by the abutment portion of the base and the bushing being wedged between the structure and the proximal stop, thus leading to a depression of the connecting pin through the two frame elements, said connecting pin finishing its depression by entering partially inside the bushing placed on the side of the screwdriver; 
     during dismounting, the mounting/dismounting rod is screwed into the nut, so that the proximal stop pushes the connecting pin, the rotational forces being taken up on the structure by the abutment portion of the base and the bushing being wedged between the structure and the nut, thus leading to extraction of the connecting pin from the two frame elements, said connecting pin finishing its release by entering partially inside the bushing placed on the side opposite that of the screwdriver. 
     Furthermore, the invention makes it possible to operate with a standalone battery-powered screwdriver, which avoids cable or hose problems, thus making mounting/dismounting operations safe. 
     It should be noted that, in the dismounting configuration, the bushing may be in abutment directly against the nut, or perhaps in abutment against the base in the alignment with the nut, so as to be in abutment against a portion of the base which is located between the nut and the bushing. In any case, in the dismounting configuration, the bushing is between the nut and the enlarged head of the connecting pin. 
     In an embodiment of the invention, the base comprises a support sleeve aligned on the longitudinal axis and having an open proximal end and an open distal end facing each other, this support sleeve internally supporting the nut, and wherein: 
     in the mounting configuration, the nut is blocked in rotation and is guided in translation along the longitudinal axis; 
     in the dismounting configuration, the nut is blocked in rotation and is blocked in translation along the longitudinal axis. 
     In this embodiment, the nut is movable between two distinct configurations, since during the mounting phase, it is the nut that moves axially along the longitudinal axis while the screwdriver remains axially fixed, whereas during the mounting phase it is the screwdriver which moves axially along the longitudinal axis while the nut remains axially fixed. 
     According to one possibility, at least one longitudinal groove is provided on the support sleeve, this longitudinal groove extending parallel to the longitudinal axis, and the nut is secured to at least one guide pin which, in the mounting configuration, is engaged in the corresponding longitudinal groove to block the nut in rotation and to guide the nut in translation along the longitudinal axis. 
     In this way, the nut can slide along the longitudinal groove, or longitudinal grooves, during mounting as the mounting/dismounting rod is screwed into the nut. 
     According to another possibility, the at least one longitudinal groove is prolonged, on the side of the open distal end of the support sleeve, by a circumferential groove which is followed by a locking groove having a generally “L” shape so that, in the dismounting configuration, the at least one guide pin is engaged in the locking groove to block the nut in rotation and in translation along the longitudinal axis. 
     Thus, when the guide pin is trapped in the bottom of the locking groove, it is blocked in rotation (possibly with an angular tolerance) and blocked in longitudinal translation, to allow the dismounting operation. 
     According to another possibility, the base comprises a proximal wall, secured to the proximal end of the support sleeve, such a proximal wall having a bearing relief which forms the abutment portion shaped to bear on any of the two frame elements. 
     Thus, bearing, and therefore taking up the rotational forces, on the structure is performed at the level of the proximal wall and therefore of the bearing relief. 
     Advantageously, the bearing relief is in the form of two linear stops facing each other, delimiting therebetween a notch into which the proximal end of the support sleeve opens. 
     This notch is sized to embed one of the two frame elements, and thus get trapped on the latter to block the base in rotation. It is of course possible to provide other types of bearing relief, such as for example a cantilever arm which will abut laterally on one of the two frame elements and thus block the base in rotation during the mounting/dismounting rod screwing phases. 
     According to another possibility, the base comprises a holding system mounted on the distal end of the support sleeve and cooperating with the free end of the rod body of the mounting/dismounting rod in the mounting configuration, to axially block the rod body along the longitudinal axis. 
     This holding system, which may for example take the form of a mechanical lock (such as a holding clip) has the function of holding the support sleeve (and therefore the base) on the mounting/dismounting rod during the mounting phase, the nut moving for its part inside the support sleeve which remains fixed. 
     According to another possibility, the base comprises one or several magnets disposed on the abutment portion for holding the base by magnetization on one of the two frame elements. 
     It is thus possible to provide one or several magnets on the abutment portion (or on the bearing relief described above), in order to allow the holding by magnetization of the base on one of the two frame elements, which also ensures that the base is held in place on the mounting/dismounting rod. 
     In one variant, the base comprises a cradle having a generally arched shape and provided with a proximal plate and a distal plate facing each other and connected by a spar, this spar forming the abutment portion shaped to bear on one of the two frame elements. 
     In this variant, the rotational forces are taken up at the level of the spar, which extends between the proximal plate and the distal plate which are arranged on either side of the two frame elements, and therefore on either side of the connecting pin. 
     According to one possibility, the proximal plate and the distal plate respectively comprise a proximal orifice and a distal orifice aligned on the longitudinal axis, this distal orifice being secured to the nut, and wherein the proximal stop and the bushing are adapted to pass inside the proximal orifice of the cradle. 
     According to another possibility, the proximal plate of the cradle supports a proximal tube internally defining the proximal orifice, the proximal stop and the bushing being adapted to slide inside said proximal tube. 
     This proximal tube thus forms an axial guide, for both the bushing (in the mounting configuration) and for the proximal stop, thus guiding the phase for screwing the mounting/dismounting rod. 
     According to another possibility, the distal plate supports, on an internal face opposite the proximal plate, a crown surrounding the proximal orifice and which is adapted to receive internally either an enlarged head of the connecting pin in the mounting configuration, or the open second end of the bushing in the dismounting configuration. 
     Such a crown makes it possible to block the connecting pin or the bushing radially, depending on whether being in a mounting or a dismounting operation. This crown, which may be attached to the nut, thus acts as a guide for the connecting pin during mounting and for the bushing during dismounting. 
     According to one feature, the bushing is secured to a radial extension arm adapted to be engaged in a window formed in the spar of the cradle, in order to block said bushing in rotation. 
     Such a radial extension arm thus provides torque recovery at the bushing. 
     According to another feature, the radial extension arm is provided with a free end cooperating with a locking member, such as a pin, to lock the radial extension arm in the window of the spar. 
     Thus, this locking member makes it possible to prevent the sleeve from falling, in particular during dismounting. 
     In a particular embodiment, the proximal stop is blocked in translation along the proximal portion of the rod body, against the head of the mounting/dismounting rod. 
     According to another possibility, the proximal portion of the rod body has a circumferential recess, and the proximal stop is blocked in translation by means of two pins which pass through said proximal stop to be engaged in the circumferential recess, for example in a diametrically opposite manner relative to the longitudinal axis. 
     Such pins make it possible to secure the proximal stop, without preventing the rotation of the rod body (preferably without friction due to play in the circumferential recess), and they also make it possible to remove the proximal stop if the latter is trapped in the structure. 
     In a particular embodiment, the proximal stop is guided in rotation by a running gear mounted around the proximal portion of the rod body. 
     Advantageously, the running gear is interposed between an annular stop, which bears against the head of the mounting/dismounting rod, and an inner shoulder provided in the proximal stop. 
     According to one feature, the annular stop has a concave rear face of hemispherical shape and which bears on a hemispherical bearing surface of the head of the mounting/dismounting rod. 
     The invention also relates to a mounting/dismounting system for mounting/dismounting a connecting pin used for an end-to-end assembly of two frame elements of a structure, such as a crane structure, this mounting/dismounting system comprising: 
     a mounting/dismounting device according to the invention; and 
     a screwdriver, for example an impact driver, equipped with a bit capable of cooperating with the head of the mounting/dismounting rod, in order to be able to rotatably drive said mounting/dismounting rod. 
     The invention also concerns an assembly kit for an end-to-end assembly of two frame elements of a structure, such as a crane structure, this assembly kit comprising: 
     a mounting/dismounting device according to the invention; and 
     at least one connecting pin adapted to pass through connecting holes provided in the two superimposed frame elements; 
     wherein the connecting pin has a tubular shape so that the mounting/dismounting rod can pass through it, and the connecting pin has an enlarged head. 
     According to one possibility, the first open end of the bushing is sized to allow the connecting pin to enter at least partially inside the bushing, in a first direction of insertion with the proximal end of the connecting pin which enters into the first open end of the bushing, and also in a second direction of insertion with the distal end and the enlarged head of the connecting pin entering the first open end of the bushing. 
     The invention also relates to a mounting method for mounting a connecting pin used for an end-to-end assembly of two frame elements of a structure, such as a crane structure, said assembly method comprising providing a mounting/dismounting device according to the invention wherein: 
     the connecting pin, of tubular shape, is positioned in a connecting hole passing through the two superimposed frame elements, and this connecting pin has a distal end provided with an enlarged head and a proximal end which are opposite to each other, said enlarged head being disposed on a first side of the structure, for example an outer side; 
     the bushing is mounted around the rod body, on a second side of the structure, opposite to the first side of the structure, while its second open end is placed in abutment against the proximal stop; 
     the base is placed on the structure with the nut being disposed on the first side of the structure in alignment with the connecting pin, the enlarged head of which is placed in abutment against the nut or the base; 
     the mounting/dismounting rod is pressed and passes through the two frame elements and the connecting pin until the threaded distal portion comes into contact with the nut supported by the base, and the bushing is in contact with one of the two frame elements on the second side of the structure; 
     the head of the mounting/dismounting rod is coupled to an bit of a screwdriver, for example an impact driver, which is located on the second side of the structure; 
     the screwdriver is activated to screw the threaded distal portion into the nut, leading to an axial displacement of the nut in a direction from the first side towards the second side of the structure, and therefore also to an axial displacement of the connecting pin which is engaged through the two frame elements, and wherein during screwing the abutment portion of the base bears against one of the two frame elements in order to block the base and the nut in rotation; 
     once the enlarged head of the connecting pin is in abutment against one of the two frame elements, the screwdriver is activated in the opposite direction to unscrew the threaded distal portion out of the nut and then remove the mounting/dismounting device. 
     The invention also relates to a dismounting method to dismount a connecting pin used for an end-to-end assembly of two frame elements of a structure, such as a crane structure, said dismounting method comprising providing a mounting/dismounting device according to the invention, wherein: 
     the connecting pin, of tubular shape, is mounted through the two superimposed frame elements in order to assemble them, and this connecting pin has a distal end provided with an enlarged head and a proximal end, which are opposite to each other, said enlarged head being disposed on a first side of the structure, for example an outer side; 
     the base is set up on the structure with the nut being disposed on the first side of the structure in alignment with the connecting pin, and with the sleeve which is mounted on the base, on the first side of the structure, and which is interposed between the nut and one of the two frame elements, the first open end of the bushing surrounding the enlarged head of the connecting pin; 
     the mounting/dismounting rod is pressed and passes through the connecting pin and the bushing until the threaded distal portion comes into contact with the nut; 
     the head of the mounting/dismounting rod is coupled to a bit of a screwdriver, for example an impact driver, which is located on a second side of the structure, opposite the first side of the structure; 
     the screwdriver is activated to screw the threaded distal portion into the nut, leading to an axial displacement of the proximal stop which comes into abutment against the proximal end of the connecting pin, thus pushing the connecting pin axially in one direction from the second side towards the first side of the structure, so that the connecting pin comes out at least partially from the two frame elements while entering inside the bushing; 
     once the proximal stop is in abutment against one of the two frame elements, the screwdriver is activated in the opposite direction to unscrew the threaded distal portion from the nut and then remove the mounting/dismounting device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present invention will become apparent upon reading the detailed description hereinafter of two non-limiting examples of implementation, made with reference to the appended figures in which: 
         FIG.  1    is a schematic perspective view of two frame elements of a crane structure, in this case a mast element and a fixed pivot element, with an illustration of connecting pins allowing their assembly; 
         FIG.  2    is a schematic perspective view of a first mounting/dismounting device according to the invention, in the dismounting configuration, coupled to a screwdriver; 
         FIG.  3    is a schematic perspective and axial section view of the first mounting/dismounting device, in the dismounting configuration, coupled to the screwdriver; 
         FIG.  4    is a schematic perspective view of a bushing, from two viewing angles, for the first mounting/dismounting device; 
         FIG.  5    is a schematic perspective view, from two viewing angles, of a base made in the form of a cradle for the first mounting/dismounting device; 
         FIG.  6    is a schematic view of a connecting pin suitable for the invention; 
         FIG.  7    is a schematic perspective and exploded view of an assembly comprising a mounting/dismounting rod, an annular stop, a running gear and a proximal stop, for the first mounting/dismounting device, and also for the second and third mounting/dismounting devices; 
         FIG.  8    is a schematic perspective view of the first mounting/dismounting device, in the mounting configuration, coupled to the screwdriver, and in position on the structure of  FIG.  1   ; 
         FIG.  9    is a schematic axial section view of the first mounting/dismounting device, in the mounting configuration and at the beginning of the mounting operation, in position on the structure with the connecting pin to be mounted; 
         FIG.  10    is a schematic view equivalent to that of  FIG.  9   , at the end of the mounting operation and with the connecting pin being mounted; 
         FIG.  11    is a schematic axial section view of the first mounting/dismounting device, in the dismounting configuration and at the beginning of the dismounting operation, in position on the structure with the connecting pin to be dismounted; 
         FIG.  12    is a schematic view equivalent to that of  FIG.  11   , at the end of the dismounting operation and with the connecting pin being partially dismounted; 
         FIG.  13    is a schematic perspective view of the first mounting/dismounting device which is stored on the underside of the fixed pivot element of the crane structure of  FIG.  1   , with several connecting pins; 
         FIG.  14    is a schematic perspective view of a second mounting/dismounting device according to the invention, in the dismounting configuration; 
         FIG.  15    is a schematic axial section view of the second mounting/dismounting device, in the mounting configuration and at the beginning of the mounting operation, in position on the structure with the connecting pin to be mounted; 
         FIG.  16    is a schematic view equivalent to that of  FIG.  15   , at the end of the mounting operation and with the connecting pin being mounted; 
         FIG.  17    is a schematic axial section view of the second mounting/dismounting device, in the dismounting configuration and at the beginning of the dismounting operation, in position on the structure with the connecting pin to be dismounted; 
         FIG.  18    is a schematic view equivalent to that of  FIG.  17   , at the end of the dismounting operation and with the connecting pin being partially dismounted; 
         FIG.  19    is a schematic perspective view of a third mounting/dismounting device according to the invention, in the mounting configuration; 
         FIG.  20    is a schematic perspective view of the third mounting/dismounting device according to the invention, in the mounting configuration, coupled to a screwdriver; 
         FIG.  21    is a schematic perspective view, from two viewing angles, of a base comprising a support sleeve, for the third mounting/dismounting device; 
         FIG.  22    is a schematic perspective view of a bushing, from two viewing angles, for the third mounting/dismounting device; 
         FIG.  23    is a schematic axial section view of the third mounting/dismounting device, in the mounting configuration and at the beginning of the mounting operation, in position on the structure with the connecting pin to be mounted; 
         FIG.  24    is a schematic view equivalent to that of  FIG.  23   , at the end of the mounting operation and with the connecting pin being mounted; 
         FIG.  25    is a schematic axial section view of the third mounting/dismounting device, in the dismounting configuration and at the beginning of the dismounting operation, in position on the structure with the connecting pin to be dismounted; and 
         FIG.  26    is a schematic view equivalent to that of  FIG.  25   , at the end of the dismounting operation and with the connecting pin being partially dismounted. 
     
    
    
     DESCRIPTION 
       FIGS.  2  to  5  and  7  to  13    relate to a first mounting/dismounting device  11  in accordance with the invention,  FIGS.  14  to  18    relate to a second mounting/dismounting device  12  in accordance with the invention and  FIGS.  19  to  26    relate to a third mounting/dismounting device  13  according to the invention. For the rest of the description, the same reference numerals will generally be used for the structural or functional elements which are identical or similar in the three mounting/dismounting devices  11 ,  12 ,  13 . 
     Each of the mounting/dismounting devices  11 ,  12 ,  13  has the function of making it possible to mount/dismount a connecting pin  2  used for an end-to-end assembly of two frame elements  91 ,  92  of a structure  9 , such as a crane structure. As described in more detail below, each of the mounting/dismounting devices  11 ,  12 ,  13  is configurable reversibly between two distinct configurations: 
     a mounting configuration used when mounting the connecting pin  2 ; and 
     a dismounting configuration used when dismounting the connecting pin  2 ; 
     so that an operator adapts the configuration according to the need. 
       FIG.  1    illustrates an example of a structure  9  which is in the form of a vertical structure, such as a mast (also called a tower or pylon) of a component assembly crane or a tower crane. One of the two frame elements  91 , the one below, is a mast element which comprises corner members (or vertical uprights) which are joined in pairs by lattice or triangulation structures made up of diagonals and sleepers. The other of the two frame elements  92  is a portion forming a fixed pivot, placed above the frame element  91  and therefore at the top of the mast, wherein this frame element  92  also comprises corner members (or vertical uprights). 
     During the vertical and end-to-end assembly of the two frame elements  91 ,  92 , the upper ends of the corner members of the frame element  91  and the lower ends of the corner members of the frame element  92  are superimposed and are rigidly connected to each other by connecting pins  2 , with for example two connecting pins  2  for each pair of superimposed corner members. 
       FIG.  6    illustrates an example of a connecting pin  2  which is adapted for each of the three mounting/dismounting devices  11 ,  12 ,  13 . Such a connecting pin  2  has a tubular shape, centered on a main axis  20 , and it has a distal end provided with an enlarged head  21  and a proximal end  22  which are opposite to each other. Due to its tubular shape, the connecting pin  2  has over its entire length an inner channel  23  which opens into both the enlarged head  21  and the proximal end  22 . The proximal end  22  may have a frustoconical shape, and the connecting pin  2  may have a cylindrical shape between the enlarged head  21  and the proximal end  22 . A transverse hole  24  may be provided at the level of the proximal end  22  to allow the passage of a safety stud. This hollow connecting pin  2  is made of a metallic material, for example of steel. 
     During its assembly, the connecting pin  2  is inserted into a connecting hole  90  which passes through the two superimposed frame elements  91 ,  92 , wherein it is the proximal end  22  of the connecting pin  2  which enters first. The connecting pin  2  is mounted when the enlarged head  21  comes into abutment against one of the two frame elements  91 ,  92 . During mounting, the connecting pin  2  is inserted from a first side of the structure  9 , for example an outer side in the example of  FIG.  1   , so that at the end of mounting the enlarged head  21  is disposed on this first side of the structure  9 , while the proximal end  22  protrudes on a second side of the structure  9 , opposite the first side, this second side therefore being an inner side in the example of  FIG.  1   . Thus, in the example of  FIG.  1   , the connecting pin  2  is inserted from the outside towards the inside; while being noted that alternatively it is possible to insert the connecting pin  2  from the inside to the outside. The first side and the second side are defined with respect to the axis of the connecting hole  90 , and are disposed on either side of the two frame elements  91 ,  92  along this axis of the connecting hole  90 . 
     Each of the mounting/dismounting devices  11 ,  12 ,  13  comprises a mounting/dismounting rod  3  which is illustrated alone in  FIG.  7   . This mounting/dismounting rod  2  is suitable for the three mounting/dismounting devices  11 , 
     This mounting/dismounting rod  3  has a longitudinal axis  30 , which will be the reference axis in the following description, and which defines the length of the mounting/dismounting rod  3 . In situation, this longitudinal axis  30  is coincident or substantially coincident with the axis of the connecting hole  90  inside which the connecting pin  2  is inserted, and therefore this longitudinal axis  30  is also coincident or substantially coincident with the main axis  20  of the connecting pin  2 . 
     This mounting/dismounting rod  3  has a head  31  adapted to cooperate with a screwdriver  8 , and a rod body  32  successively having along the longitudinal axis  30 : 
     a proximal portion  33  prolonging the head  31 ; 
     a smooth central portion  34 ; and 
     a threaded distal portion  35  which terminated in a free end  36 . 
     The proximal portion  33  has a circumferential recess  37 , axially offset with respect to the head  31 . The head  31  is shaped to be coupled to a bit  80  of the screwdriver  8 , for example by shape cooperation, so that the screwdriver  8  may rotatably drive the mounting/dismounting rod  3  around the longitudinal axis  30 . The head  31  is for example in the form of a hexagonal head, and the bit  80  of the screwdriver  8  is in the form of a hollow hexagonal bit. In the event of failure of the screwdriver  8 , it will thus be possible to use a manual wrench to turn the mounting/dismounting rod  3 . 
     The mounting/dismounting rod  3  is adapted to slide inside the connecting pin  2 , in its inner channel  23 , and even to pass right through, over its entire length, the connecting pin  2 ; the free end  36  of the mounting/dismounting rod  3  entering first the inner channel  23 . 
     Each of the mounting/dismounting devices  11 ,  12 ,  13  also comprises a proximal stop  4  mounted free in rotation on the proximal portion  33  of the rod body  32  around the longitudinal axis  30 . The proximal stop  4  is blocked in translation along of the proximal portion  33  of the rod body  32 , against the head  31  of the mounting/dismounting rod  3 . In other words, the proximal stop  4  remains in place against the head  31  and may only rotate. 
     The rod body  32  is passing through the proximal stop  4  over its entire length, and the proximal stop  4  has a distal end  43  forming a stopper as described below. This proximal stop  4  comprises a cylindrical proximal section  41  abutting against the head  31 , and a cylindrical distal section  42  which prolongs the proximal section  41  and which terminates in the distal end  43 . The distal section  42  has a diameter smaller than that of the proximal section  41 . 
     The proximal stop  4  is blocked in translation by means of two straight pins  44  which pass through the proximal stop  4 , and more precisely the proximal section  41 , to be engaged in the circumferential recess  37  of the proximal portion  33  of the rod body  32 , in diametrically opposite manner with respect to the longitudinal axis  30 . 
     Furthermore, the proximal stop  4  is guided in rotation by a running gear  45 , such as a roller thrust bearing, a ball thrust bearing or a needle thrust bearing, wherein this running gear  45  is mounted around the proximal portion  33  of the rod body  32 , inside an internal bearing provided in the proximal stop  4 , and more precisely in the proximal section  41 . This running gear  45  makes it possible to reduce the friction between the proximal stop  4  and the mounting/dismounting  3  when it rotates. 
     This running gear  45  is interposed between an annular stop  46 , such as for example a spherical thrust bearing, which bears against the head  31  of the mounting/dismounting rod  3 , and an inner shoulder provided in the internal bearing of the proximal stop  4 . This annular stop  46  has a concave rear face of hemispherical shape and which bears on a hemispherical bearing surface  38  of the head  31  of the mounting/dismounting rod  3 . 
     One or two anti-friction bearing(s)  47  may also be interposed between the distal section  42  and the proximal portion  33  of the rod body  32 , to reduce friction. 
     The pins  44  thus make it possible to secure the proximal stop  4 , the running gear  45  and the annular stop  46 , without preventing the rotation of the mounting/dismounting rod  3 , because the pins  44  are mounted with a clearance in the circumferential recess  37 . These pins  44  also make it possible to remove the proximal stop  4  if the latter is trapped in the structure  9 . 
     Each of the mounting/dismounting devices  11 ,  12 ,  13  comprises a base  5 ,  6  supporting a nut  59 ,  69  and having an abutment portion shaped to bear on one of the two frame elements  91 ,  92 . In situation, the threaded distal portion  35  of the rod body  32  of the mounting/dismounting rod  3  is designed to be screwed into the nut  59 ,  69  which is aligned with the longitudinal axis  30 . 
     There are differences between the bases  5 ,  6  of the different mounting/dismounting devices  11 ,  12 ,  13 : the first mounting/dismounting device  11  and the second mounting/dismounting device  12  each comprise a base  5  which extends from either side of the two frame elements  91 ,  92 , on both the first side and the second side of the structure  9 , while the third mounting/dismounting device  13  comprises a base  6  which is disposed only on the first side of the structure  9 . 
     In the first mounting/dismounting device  11  and in the second mounting/dismounting device  12 , the base  5  comprises a cradle  50  having a generally arched shape and which is provided with a proximal plate  51  and a distal plate  52  facing each other and connected by a spar  53 , this spar  53  forming the abutment portion shaped to bear laterally on one of the two frame elements  91 ,  92  and ensure a take-up of rotational forces. 
     The proximal plate  51  supports a proximal tube  54  internally defining a proximal orifice  55 , and the distal plate  52  comprises a proximal orifice  56  integral with the nut  59 , wherein the proximal orifice  55  and the distal orifice  56  are aligned on a central axis  500  which is, in situation, coincident or substantially coincident with the longitudinal axis  30 . More precisely, the nut  59  is secured to the distal plate  52 , and this nut  59  is centered on the longitudinal axis  30 . The nut  59  is therefore firmly fixed on the distal plate  52 , for example by welding. 
     Furthermore, the proximal stop  4  is adapted to pass inside the proximal orifice  55 , and more precisely the proximal stop  4  is adapted to slide inside the proximal tube  54 , as shown in  FIGS.  10  to  12  and  16  to  18   . 
     The distal plate  52  supports, on an inner face opposite the proximal plate  51 , a crown  57  surrounding the proximal orifice  55 . The spar  53  has windows  58 , for example of triangular shape in the first mounting/dismounting device  11  or of rectangular shape in the second mounting/dismounting device  12 . This base  5  is made of a metallic material, and for example of steel, for example by welding of its various components. 
     This crown  57  is adapted to receive internally: 
     either the enlarged head  21  of the connecting pin  2  in the mounting configuration, as shown in  FIGS.  9  and  15   ; 
     or a second open end  72  of a bushing  7  in the dismounting configuration, as will be described hereinbelow. 
     In position, and as shown in  FIGS.  8  to  12  and  15  to  18   , the proximal plate  51  is located on the second side of the structure  9  (inner side in the example of  FIG.  1   ) and the distal plate  52  is located on the first side of the structure  9  (external side in the example of  FIG.  1   ) opposite the enlarged head  21  of the connecting pin  2 , and the spar  53  extends on either side of the two structure elements  91 ,  92  between the two sides. 
     In the third mounting/dismounting device  13 , the base  6  comprises a cylindrical support sleeve  60 , centered on an axis which is, in position, coincident with the longitudinal axis  30 ; the axis of the support sleeve  60  will therefore be assimilated for the rest of the description to the longitudinal axis  30 . This support sleeve  60  thus forms a tube and has an open proximal end  61  and an open distal end  62  which are opposite to each other. The base  6  also comprises a proximal wall  63 , orthogonal to the longitudinal axis  30 , and which is secured to the proximal end  61  of the support sleeve  60 . 
     The support sleeve  60  internally supports the nut  69  which is secured to two guide pins  64  extending radially and disposed diametrically opposite with respect to the longitudinal axis  30 . Furthermore, the support sleeve  60  has two slots in which the two respective guide pins  64  are engaged, wherein these slots successively define, starting from the proximal end  61  towards the distal end  62 : 
     a longitudinal groove  651  extending parallel to the longitudinal axis  30 ; 
     a circumferential groove  652  which prolongs the longitudinal groove  651 , on the side of the distal end  62  of the support sleeve  60 ; and 
     a locking groove  653  which follows the circumferential groove  652  and which has a generally “L” shape. 
     Thus, two positions are possible for the nut  69  and the guide pins  64  depending on the configuration of the third mounting/dismounting device  13 : 
     in the mounting configuration, shown in  FIGS.  19  and  20   , the guide pins  64  are engaged in the corresponding longitudinal grooves  651 , so that the nut  69  is blocked in rotation around the longitudinal axis  30  and is guided in translation along the longitudinal axis  30 ; 
     in the dismounting configuration, shown in  FIG.  21   , the guide pins  64  are engaged in the corresponding locking grooves  653 , so that the nut  69  is locked in rotation around the longitudinal axis  30  and is blocked in translation along the longitudinal axis  30 . 
     The nut  69  passes from the mounting configuration to the dismounting configuration, and vice versa, by causing the guide pins  64  to pass from the longitudinal grooves  651  to the locking grooves  653 , and vice versa, via the circumferential grooves  652 . 
     The proximal wall  63  has a bearing relief  66  which forms the abutment portion shaped to bear on one of the two frame elements  91 ,  92  and ensure rotational forces take-up. This bearing relief  66  has a shape that is complementary to that of one of the two frame elements  91 ,  92 , and in the example illustrated this bearing relief  66  is in the form of two linear stops  67  facing each other, delimiting therebetween a notch into which the proximal end  61  of the support sleeve  60  opens. 
     Although not shown, it is possible to provide one or several magnets arranged on the bearing relief  66 , for example on the two linear stops  67  facing each other, in order to hold by magnetization the base  6  on one of the two frame elements  91 ,  92 . 
     The base  6  also comprises a holding system  68  mounted on the distal end  62  of the support sleeve  60  in order to cooperate with the free end  36  of the rod body  32  of the mounting/dismounting rod  3  in the mounting configuration, to axially block the rod body  32  along the longitudinal axis  30 . In the illustrated example, the holding system  68  is in the form of a mechanical lock of the holding clip-type, which passes transversely through the support sleeve  60  at its distal end  62 , and which has two elastically deformable lugs  680  shaped to be blocked in a circumferential locking recess provided for this purpose on the free end  36  of the rod body  32 . In the dismounting configuration, the holding system  68  is removed or moved so as to no longer cooperate with the free end  36  of the rod body  32 , and thus leave the rod body  32  free to translate along the longitudinal axis  30  with respect to the support sleeve  60 . 
     A handle  69  can also be secured to the base  6  to be able to manipulate and position it manually. In situation, and as shown in  FIGS.  23  to  26   , the base  6  is located on the first side of the structure  9  (external side in the example of  FIG.  1   ) with its proximal wall  63  facing the enlarged head  21  of the connecting pin  2 . 
     Each of the mounting/dismounting devices  11 ,  12 ,  13  comprises a bushing  7  which is removable and independent of the mounting/dismounting rod  3 , of the proximal stop  4  and of the base  5 ,  6 . In situation, this bushing  7  is mounted free in translation along the longitudinal axis  30  around the rod body  32 , between the nut  59 ,  69  and the proximal stop  4 . 
     The bushing  7 , of a generally cylindrical shape, has a first open end  71  and a second open end  72 . The first open end  71  has an opening diameter greater than that of the second open end  72 . Furthermore, the first open end  71  is sized to allow the passage of the enlarged head  21  of the connecting pin  2 , which allows the connecting pin  2  to enter at least partially inside the bushing  7  through its first open end  71 , whether in a first direction of insertion with the proximal end  22  of the connecting pin  2  which enters the first open end  71  of the bushing  7  (as shown in  FIGS.  9 ,  10 ,  15 ,  16 ,  23  and  24    during a mounting phase), and also according to a second direction of insertion with the distal end and the enlarged head  21  of the connecting pin  2  which enter the first open end  71  of the bushing  7  (as shown in  FIGS.  11 ,  12 ,  17 ,  18 ,  25  and  26    during a dismounting phase). 
     Two positions of the bushing  7  are possible depending on the configuration of the mounting/dismounting device  11 ,  12 ,  13 : 
     in the mounting configuration, visible in  FIGS.  9 ,  10 ,  15 ,  16 ,  19 ,  20 ,  23  and  24   , the bushing  7  is in abutment against the proximal stop  4  and more precisely the second open end  72  of the bushing  7  is placed in abutment against the proximal stop  4 ; 
     in the dismounting configuration, shown in  FIGS.  2 ,  3 ,  11 ,  12 ,  14 ,  17 ,  18 ,  25  and  26   , the bushing  7  is in abutment against the nut  59 ,  69  and more precisely the second open end  72  of the bushing  7  is placed in abutment against the nut  59 ,  69 . 
     In situation, once the mounting/dismounting device  11 ,  12 ,  13  is in place on the structure  9 : 
     in the mounting configuration, the bushing  7  is located on the second side of the structure  9 , interposed between the proximal stop  4  and one of the two structural elements  91 ,  92 , and wherein the first open end  71  of the bushing  7  bears against one of the two frame elements  91 ,  92  on the second side of the structure  9 , the first open end  71  of the bushing  7  being ready to receive the connecting pin  2  internally; 
     in the dismounting configuration, the bushing  7  is located on the first side of the structure  9 , interposed between the nut  59 ,  69  and one of the two frame elements  91 ,  92 , and wherein the first open end  71  of the bushing  7  bears against one of the two frame elements  91 ,  92  on the first side of the structure  9 , the first open end  71  of the bushing  7  surrounding the enlarged head  21  of the connecting pin  2  and being ready to receive the connecting pin  2  internally. 
     There are differences between the bushings  7  of the various mounting/dismounting devices  11 ,  12 ,  13 . 
     In the first mounting/dismounting device  11  and in the second mounting/dismounting device  12 , the bushing  7  has an outer diameter such that the bushing  7  is adapted to pass inside the proximal orifice  55  of the cradle  50  of the base  5 , and more precisely the bushing  7  is adapted to slide inside the proximal tube  54 , as shown in  FIGS.  9  and  15   . 
     In the first mounting/dismounting device  11  and in the second mounting/dismounting device  12 , the sleeve  7  is secured to a radial extension arm  73  adapted to be engaged in a window  58  made in the spar  53  of the cradle  50 , in order to block said bushing  7  in rotation in the dismounting configuration, as shown in  FIGS.  2 ,  3  and  14   ; this radial extension arm  73  allowing torque to be taken up during dismounting. Advantageously, the radial extension arm  73  is provided with a free end having a hole  74  in which is engaged a locking member  75 , of the pin type, to lock the radial extension arm  73  in the window  58  of the spar  50 , and thus avoid the fall of the bushing  7  during a dismounting phase. In the third mounting/dismounting device  13 , the bushing  7  does not have such a radial extension arm. 
     In the first mounting/dismounting device  11  and in the second mounting/dismounting device  12 , the second open end  72  of the bushing  7  has an external bearing  76  shaped to be internally received in the crown  57  provided on the proximal plate  51  of the base  5 , in the dismounting configuration, as shown in  FIGS.  3 ,  11  and  17   . 
     In the second mounting/dismounting device  12 , the second open end  72  of the bushing  7  has an internal bearing  77 , surrounded by the external bearing  76 , provided to internally receive the distal end  43  of the proximal stop  4  in the mounting configuration, as shown in  FIG.  15   ; this distal end  43  abuts against the second open end  72 . This internal bearing  77  thus makes it possible to guide or center the proximal stop  4  on the bushing  7 . In the first mounting/dismounting device  11 , the bushing  7  does not have such an internal bearing, the distal end  43  of the proximal stop  4  abuts against the second open end  72  without being received in such an internal bearing. 
     In the first mounting/dismounting device  11  and in the second mounting/dismounting device  12 , the second open end  72  of the bushing  7  is dimensioned so that, in the mounting configuration, this second open end  72  is in abutment against the distal section  42  of the proximal stop  4 . In the third mounting/dismounting device  13 , the second open end  72  of the bushing  7  is dimensioned so that, in the mounting configuration, this second open end  72  is in abutment against the proximal section  41  of the proximal stop  4 . 
     The rest of the description relates to the mounting method for mounting the connecting pin  2 , with reference to  FIGS.  9 ,  10 ,  15 ,  16 ,  23  and  24   . 
     Initially, the connecting pin  2  is positioned, on the first side of the structure  9 , in the connecting hole  90  passing through the two superimposed frame elements  91 ,  92 , its enlarged head  21  being at a distance from the two frame elements  91 ,  92 . 
     Then, the bushing  7  is mounted around the mounting/dismounting rod  3 , bringing its second open end  72  into abutment against the proximal stop  4 . 
     The base  5 ,  6  is placed on the structure  9  with the nut  59 ,  69  being disposed on the first side of the structure  9  in alignment with the main axis  20  of the connecting pin (therefore ultimately with the longitudinal axis  30 ), and the enlarged head  21  of the connecting pin  2  is placed in abutment against the base  5 ,  6 . 
     With the first mounting/dismounting device  11  and the second mounting/dismounting device  12 , the base  5  bears on the enlarged head  21 , by engaging the crown  57  around the enlarged head  21 , which allows centering the base  5 . With the third mounting/dismounting device  13 , the base  6  also bears on the enlarged head  21 , by engaging the support sleeve  60  around the enlarged head  21 , which allows the base  6  to be held in place. 
     Then the mounting/dismounting rod  3  is pressed and passes through the two frame elements  91 ,  92  and the connecting pin  2  until the threaded distal portion  35  comes into contact with the nut  59 ,  69  supported by the base  5 ,  6 , and the bushing  7  bears against one of the two frame elements on the second side of the structure  9 . 
     With the first mounting/dismounting device  11  and the second mounting/dismounting device  12 , it is possible to position the bushing  7  inside the proximal tube  54 , before inserting the mounting/dismounting rod  3  which will thus pass through the bushing  7  until the latter is in abutment against the proximal stop  7 . 
     The head  31  of the mounting/dismounting rod  3  is coupled to the bit  80  of the screwdriver  8  which is located on the second side of the structure  9 , opposite the connecting pin  2 . It is possible to make this coupling before or after having inserted the mounting/dismounting rod  3  through the two frame elements  91 ,  92  and the connecting pin  2 . 
     Then, the screwdriver  8  is activated to rotate the mounting/dismounting rod  3  (as schematically shown by the arrows T in  FIGS.  9 ,  15  and  23   ) and thus to screw the threaded distal portion  35  into the nut  59 ,  69 , leading to an axial displacement of the nut  59 ,  69  in a direction from the first side towards the second side of the structure  9  (as schematically shown by the arrows Al in  FIGS.  9 ,  15  and  23   ), and therefore also to an axial displacement of the connecting pin  2  (pushed by the nut  59 ,  69 ) which is engaged through the two frame elements  91 ,  92 . 
     During screwing, the abutment portion of the base  5 ,  6  (whether it is the spar  30  or the bearing relief  66 ) bears on one of the two frame elements  91 ,  92  in order to block the base  5 ,  6  and the nut  59 ,  69  in rotation around the longitudinal axis  30 , this abutment portion thus ensuring the torque take-up. 
     With the third mounting/dismounting device  13 , the screwdriver  8  is activated so that the free end  36  of the mounting/dismounting rod  3  may come to face the holding system  68 , then the screwdriver  8  is deactivated while the holding system  68  is set up to cooperate with this free end  36  in order to axially block the mounting/dismounting rod  3  along the longitudinal axis  30 . And then the screwdriver  8  is reactivated to finish screwing. 
     Finally, once the enlarged head  21  of the connecting pin  2  is in abutment against one of the two frame elements  91 ,  92  (therefore once the connecting pin  2  is mounted), the screwdriver  2  is activated in the opposite direction to unscrew the threaded distal portion  35  from the nut  59 ,  69  and then to remove the mounting/dismounting device  11 ,  12 ,  13 . 
     The rest of the description relates to the dismounting method for dismounting the connecting pin  2 , with reference to  FIGS.  11 ,  12 ,  17 ,  18 ,  25  and  26   . 
     Initially, the connecting pin  2  is mounted, so that the latter is mounted in the connecting hole  90  passing through the two superimposed frame elements  91 ,  92 , its enlarged head  21  being in abutment on one of the two frame elements  91 ,  92  on the first side of the structure  9 . 
     The base  5 ,  6  is placed on the structure  9  with the nut  59 ,  69  being disposed on the first side of the structure  9  in alignment with the main axis  20  of the connecting pin (therefore ultimately with the longitudinal axis  30 ), and with the bushing  7  which is mounted on the base  5 ,  6 , on the first side of the structure  9 , and which is interposed between the nut  59 ,  69  and one of the two frame elements  91 ,  92 , the first open end  71  of the bushing  7  surrounding the enlarged head  21  of the connecting pin  2 . 
     With the first mounting/dismounting device  11  and the second mounting/dismounting device  12 , the bushing  7  bears on the enlarged head  21 , having its first open end  71  engaged in an adjusted manner around the enlarged head  21 , and the base  5  bears on the second open end  72  of the bushing  7  with its crown  57  being engaged in an adjusted manner around the external bearing  76 , which allows centering of the base  5  and the bushing  7 . With the third mounting/dismounting devicel 3 , the bushing  7  bears on the enlarged head  21 , having its first open end  71  engaged in an adjusted manner around the enlarged head  21 , and the support sleeve  60  is mounted in an adjusted manner around the bushing  7 , which also allows centering the base  6  and the bushing  7 . 
     Then, the mounting/dismounting rod  3  is pressed and passes through the connecting pin  2 , entering the latter at the level of its proximal end  22 , and passes through the bushing  7  until the threaded distal portion  35  comes into contact with the nut  59 ,  69 . 
     The head  31  of the mounting/dismounting rod  3  is coupled to the bit  80  of the screwdriver  8  which is located on the second side of the structure  9 , opposite the connecting pin  2 . It is possible to make this coupling before or after having inserted the mounting/dismounting rod  3  through the connecting pin  2 . 
     Then, the screwdriver  8  is activated to rotate the mounting/dismounting rod  3  (as schematically shown by the arrows T in  FIGS.  11 ,  17  and  25   ) and thus to screw the threaded distal portion  35  into the nut  59 ,  69 , leading to an axial displacement of the proximal stop  4  which comes into abutment against the proximal end  22  of the connecting pin  2 , thus pushing the connecting pin  2  axially in a direction from the second side towards the first side of the structure (as schematically shown by the arrows A 2  in  FIGS.  11 ,  17  and  25   ), so that the connecting pin  2  comes out at least partially from the two frame elements  91 ,  92  while entering inside the bushing  7 . 
     Finally, once the proximal stop  4  is in abutment against one of the two frame elements  91 ,  92 , the screwdriver  8  is activated in the opposite direction to unscrew the threaded distal portion  35  from the nut  59 ,  69  and then remove the mounting/dismounting device  11 ,  12 ,  13 . Upon completion of these operations, the connecting pin  2  has come out sufficiently from the connecting hole  90 , to be able to easily finish pulling it out completely, in particular by hand. 
     Finally, it should be noted that, as illustrated in  FIG.  13   , the mounting/dismounting device  11 ,  12  or  13 , can be stored, with one or several connecting pins  2 , on one of the two frame elements  91 ,  92 , and for example on the frame element  92  which constitutes a portion forming a fixed pivot, in order to prevent the fitter from moving with the mounting/dismounting device and with the required connecting pin(s)  2 ; the fitter only having to carry the screwdriver  8 .