EP1184328B1 - Cable arrangement for tower crane - Google Patents

Description

The present invention relates to the technical field of tower cranes, with distributing boom, that is to say a crane boom provided with a raceway along which is mounted rolling a carriage, under which is located the hook of lifting, moved with this cart. The invention is more particularly concerned with a distribution cable circuit, with a device for tensioning this cable, for a crane of the type in question, the "distribution cable" being a motorized cable which, in this type of crane, ensures moving the carriage along the arrow.

In general, distribution cables for tower cranes must be tensioned with a properly controlled tension. In addition, in the case of folding arrows composed of two or more successive elements, articulated together, the circuits of the distribution cables must be compatible with the folding positions of the boom.

The distribution cable may be a single cable, describing a loop path. This cable can also be made in two parts, that is to say composed of a rear distribution cable and a front distribution cable.

In the known embodiments of distribution cables for tower cranes, there are among others devices for automatic tension and controlled cables, placed in the path of the rear distribution cable. These particular devices exert, on the distribution cable, a force of a determined value, independent of the position of the crane, via a specific pulley provided with a gas spring, mounted on the carriage.

Also known devices for compensation of the length of the distribution cable, by means of pulleys mounted on a linkage linkage between the foot of the boom and the arrowhead, with automatic and adjustable tension maintenance of the front distribution cable to using a mechanical spring (see EP 0 414 646 A2).

These existing systems have disadvantages. Thus, they are located at an intermediate point of the length of the arrow (possibly on the carriage, as in the first device mentioned above), so that their dead weight creates a moment that is added to the other moments s' exercising on the arrow. In addition, their adjustment is difficult.

• Le dispositif de compensation comporte un mouflage, dont le poids mort élevé crée un moment additionnel important sur la structure de la grue.
• Le ressort de type hélicoïdal délivre une force proportionnelle à son allongement, ce qui induit, pour une faible course, une variation d'effort importante sur le câble de compensation, et impose un réglage fréquent.
• Lorsque la grue travaille avec sa flèche relevée, la charge exerce un effort sur le chariot, dirigé vers l'arrière, qui détend le câble de distribution arrière.

More particularly, the device of the above-mentioned document EP 0 414 646 A2 has the following specific drawbacks:

• The compensation device comprises a haul, whose high dead weight creates an important additional moment on the structure of the crane.
• The helical type spring delivers a force proportional to its elongation, which induces, for a short stroke, a large force variation on the compensation cable, and requires frequent adjustment.
• When the crane works with its boom raised, the load exerts a force on the carriage, directed to the rear, which relaxes the rear distribution cable.

• au cours du montage de la grue, le maintien des câbles de distribution sous tension, avec un effort constant, tout en maintenant le chariot en position, avec compensation de la longueur du câble dans la région de l'articulation des éléments de flèche, quelle que soit la position relative de ces éléments, et avec possibilité de réglage de la pré-tension des câbles à hauteur d'homme ;
• au cours de l'utilisation de la grue, le maintien des câbles de distribution sous tension, avec un effort constant, sans nécessité de nouveaux réglages au cours de la vie des câbles pour compenser leurs allongements, et tout en minimisant les moments créés par le poids mort du dispositif.

The present invention aims to improve the distribution cable circuits with voltage device, so as to eliminate the disadvantages described above, the aims of the invention being, more particularly:

• during assembly of the crane, keeping the distribution cables under tension, with constant effort, while maintaining the carriage in position, with compensation of the length of the cable in the region of the articulation of the jib elements, which whatever the relative position of these elements, and with the possibility of adjusting the pretension of the cables at the height of man;
• during the use of the crane, the maintenance of the distribution cables under tension, with a constant effort, without need of new adjustments during the life of the cables to compensate for their elongations, and while minimizing the moments created by the dead weight of the device.

• un câble de distribution arrière dont une première extrémité est fixée sur un côté du tambour d'enroulement d'un treuil de distribution motorisé, et dont la deuxième extrémité est fixée sur le chariot de flèche, ce câble passant sur au moins une poulie portée par la partie arrière de l'élément de pied de flèche,
• un câble de distribution avant dont une première extrémité est fixée sur l'autre côté du tambour d'enroulement du treuil de distribution, et dont la deuxième extrémité est fixée sur le chariot de flèche, ce câble passant sur des poulies comprenant au moins une poulie portée par la partie avant de l'élément de pointe de flèche,
• un dispositif de tension agissant sur le câble de distribution arrière ou avant, pour le maintien en tension de ces deux câbles, et
• pour la ou chaque articulation entre deux éléments de flèche consécutifs, un système de compensation de longueur de câble, constitué par un ensemble de poulies portées par les extrémités adjacentes des deux éléments de flèche et/ou par des organes du dispositif d'articulation entre ces deux éléments de flèche,

cette grue étant essentiellement caractérisée par le fait que le dispositif de tension comprend un bras articulé sur l'élément de pied de flèche, ce bras articulé portant une poulie sur laquelle passe le câble de distribution arrière, et au moins un ressort à gaz monté entre un point de l'élément de pied de flèche et un point du bras articulé.To this end, the object of the invention is a folding crane tower crane composed of two or more successive elements articulated together, including an arrow foot element and an arrow tip element, along which moves a boom truck, the crane having a distribution cable circuit with:

• a rear distribution cable whose first end is fixed to one side of the winding drum of a motorized distribution winch and whose second end is fixed to the boom carriage, this cable passing over at least one pulley carried by the back part of the boom foot element,
• a front distribution cable whose first end is fixed on the other side of the winding drum of the distribution winch, and the second end of which is fixed on the boom carriage, this cable passing over pulleys comprising at least one pulley carried by the front part of the boom tip element,
• a tension device acting on the rear or front distribution cable, for maintaining these two cables in tension, and
• for the or each articulation between two consecutive jib elements, a cable length compensation system constituted by a set of pulleys carried by the adjacent ends of the two jib elements and / or by members of the articulation device between them. two arrow elements,

this crane being essentially characterized by the fact that the tensioning device comprises an articulated arm on the boom foot element, this articulated arm carrying a pulley on which the rear distribution cable passes, and at least one gas spring mounted between a point of the boom foot element and a point of the articulated arm.

Preferably, the tensioning device with articulated arm and gas spring is mounted in the rear part of the boom foot element.

According to another advantageous characteristic of the tower crane with distribution cable circuit object of the invention, the second end of the rear distribution cable, or the front distribution cable, is fixed on a tension drum located on the trolley arrow, this drum being provided with means for driving and locking in rotation, for the tensioning of this cable.

• une poulie montée en un point intermédiaire de la première bielle,
• une poulie montée à l'extrémité avant supérieure de l'élément de flèche arrière,
• une poulie montée devant la précédente, et
• une poulie montée sur la deuxième bielle.

According to one embodiment of the tower crane with distribution cable circuit object of the invention, in the case of a device for articulation between two consecutive deflection elements comprising a horizontal axis of articulation located substantially halfway. height of these two boom members, nestable into one another, a first link articulated on the lower front end of the rear boom member, and a second link articulated on the lower rear end of the element front boom, the two rods being hinged together and to a folding cylinder, the system of compensation associated with this articulation concerns the front distribution cable, and it comprises:

• a pulley mounted at an intermediate point of the first connecting rod,
• a pulley mounted at the upper front end of the rear boom member,
• a pulley mounted in front of the previous one, and
• a pulley mounted on the second connecting rod.

Overall, the tower crane with distribution cable circuit, object of the invention, has the following advantages:

The gas spring of the tension device develops a large stroke, with a constant thrust force, and it does not require any intervention to make up the elongations of the distribution cable throughout the life of the cable. In other words, the large stroke of the gas spring allows a "lifetime" adjustment of the tension of the rear and front distribution cables.

The tension device, which does not require hauling and is located on the foot of the boom, preferably in the rear part of the boom foot, induces only a weak moment due to its dead weight.

The tensioning drum located on the carriage, at one end of one of the rear or front distribution cables, makes it possible to pre-tension the distribution cables from the ground level without being imposed for this operation. , a defined position of the arrow carriage on the free part of the arrow.

Being mounted on the rear distribution cable, the tensioning device keeps it permanently energized, avoiding the relaxation of the cable under the effect of the raised load, when the crane works with his arrow up.

Finally, the technical solution according to the invention ensures the exact compensation of the length of the distribution cable, at the joint between two consecutive deflection elements, by adapting in particular to a two-link articulation device, such as described in the previous French patent application FR 2796632 A (or its equivalent EP 1072553 A1) in the name of the Applicant, in which case the path of the front distribution cable makes it possible to bypass the connecting axis of the upper chords of the boom element rear and the front boom element.

• Figure 1 est une vue d'ensemble, de côté, d'une grue à tour pourvue d'un circuit de câble de distribution conforme à la présente invention ;
• Figure 2 est un détail de l'extrémité avant de la pointe de flèche de la grue de la figure 1 ;
• Figure 3 est un détail de l'extrémité arrière du pied de flèche de cette grue, avec le dispositif de tension du câble de distribution ;
• Figure 4 est un détail de la région médiane de la flèche, en position alignée, avec représentation de l'articulation des deux éléments de flèche, et avec indication du chariot :
• Figure 5 est une autre vue de détail de la région médiane de la flèche, correspondant à la figure 4, mais en position repliée.

The invention will be better understood from the description which follows, with reference to the attached schematic drawing showing, by way of example, an embodiment of this tower crane with distribution cable circuit:

• Figure 1 is an overall side view of a tower crane provided with a distribution cable circuit according to the present invention;
• Figure 2 is a detail of the front end of the boom tip of the crane of Figure 1;
• Figure 3 is a detail of the rear end of the boom foot of this crane, with the tensioning device of the distribution cable;
• Figure 4 is a detail of the median region of the arrow, in aligned position, with representation of the articulation of the two arrow elements, and with indication of the carriage:
• Figure 5 is another detail view of the median region of the arrow, corresponding to Figure 4, but in the folded position.

FIG. 1 schematically represents a crane with foldable tower which comprises a fixed base frame 1 on which is mounted a rotating frame 2, orientable about a vertical axis 3. The crane comprises a mast 4, made in two elements 5 and 6 articulated together about a horizontal axis 7. The lower mast element 5 is articulated by its base, about a horizontal axis 8, to the front of the rotating frame 2. At the top of the upper mast element 6 is articulated around a horizontal axis 9, a distributing arrow 10 along which is movable a carriage 11, the arrow 10 being composed here of two elements, which are a rear element said foot of arrow 12 and a front element said Arrowhead 13. As shown in Figure 1, this crane further comprises struts 14 for training the mast 4, a device 15 for retaining the boom 10, and a ballast 16 carried by the rear portion of the rotating frame 2.

The boom foot 12 has a triangular section, and the boom tip 13 has a U-shaped section. This arrowhead 13 is articulated, by its rear part, to the front part of the jib 12, around a horizontal axis 17 located substantially halfway up the arrow 10. Thus, in the folded position of the arrow (see FIGS. 1 and 5), the two boom elements 12 and 13 are nested one inside the other, the triangular section of the boom foot 12 nesting in the section in " U "of the arrowhead 13 returned.

• dans la partie avant du pied de flèche 12, deux plaques latérales 19,
• dans la partie arrière de la pointe de flèche 13, deux plaques latérales 20, chacune avec une lumière en arc de cercle 21 (l'axe horizontal 17 traversant toutes les plaques latérales 19 et 20, sensiblement à mi-hauteur),
• un axe horizontal 22 situé à l'extrémité avant supérieure du pied de flèche 12, et traversant les lumières 21,
• une bielle double coudée 23, articulée en 24 sur l'extrémité avant inférieure du pied de flèche 12,
• une bielle double sensiblement rectiligne 25, articulée en 26 sur l'extrémité arrière inférieure de la pointe de flèche 13,
• un axe horizontal 27 de liaison articulée des deux bielles 23 et 25.

More particularly, in the example illustrated in the drawing, as shown in FIGS. 4 and 5, the jib foot 12 and the jib tip 13 are connected by a hinge device 18 which, in addition to the horizontal axis 17, comprises the following elements :

• in the front part of the jib foot 12, two side plates 19,
• in the rear part of the arrow tip 13, two side plates 20, each with an arcuate light 21 (the horizontal axis 17 passing through all the side plates 19 and 20, substantially at half height),
• a horizontal axis 22 located at the upper front end of the jib 12, and passing through the lights 21,
• a double cranked rod 23, hinged at 24 on the lower front end of the boom foot 12,
• a substantially rectilinear double rod 25 articulated at 26 on the lower rear end of the boom tip 13,
• a horizontal axis 27 of articulated connection of the two connecting rods 23 and 25.

The hinge device 18, previously described, is powered by a double-acting cylinder 28, whose body 29 is hinged, at its rear end, on the jib foot 12 at the upper chord 30, at a certain distance of the front end of this jib foot 12. The rod 31 of the cylinder 28 is articulated, by its front end, to the connecting axis 27 of the two connecting rods 23 and 25.

The elbow of the first connecting rod 23 leaves a free passage to the axis 22; the double rod configuration of this crank rod 23, as well as the second rod 25, leaves a free passage to the rod 31 of the cylinder 28.

The upper chord 30 of the jib foot 12 is connected, by trellis structures 32, to the two lower chords 33 of this jib 12 which constitute a section of the tread of the trolley 11. The jib tip 13 comprises two chords 34 connected, by lattice structures 35, two lower ribs 36 which constitute another section of the tread of the carriage 11.

The translational movement of the carriage 11, along its raceway on the boom 10, is controlled from a motorized winch of distribution, provided with a winding drum 37 and located, in the example illustrated, in the region of the mast foot 38 (see Figure 1, bottom). The movement control of the carriage 11 is effected by means of a rear distribution cable 39 and a front distribution cable 40.

The rear distribution cable 39 rises along the mast 4, and it passes over a pulley 41 (see FIG. 3) of horizontal axis, carried by the mast head 42, then on a pulley 43 of horizontal axis, carried by the rear part of the boom foot 12. Then, the rear distribution cable 39 passes over a pulley 44 of horizontal axis, mounted on an arm 45 hinged about a horizontal axis 46 on the foot of boom 12, then this cable 39 returns to a pulley 47 of horizontal axis carried by the rear end of the jib foot 12, the latter pulley 47 being located behind the previous pulley 44. Finally, the rear distribution cable 39 extends towards the before on a variable length, along the arrow 10 to the carriage 11 on which is fixed its second end.

Referring again to FIG. 3, the tensioning device, designated as a whole by reference numeral 48, is located on the circuit of the rear distribution cable 39, at the rear part of the boom foot 12. This device tension 48 includes the aforementioned pulley 44, mounted at the end of the articulated arm 45 on the boom foot 12. The tensioning device also comprises a gas spring 49, articulated between a point of attachment 50 on the boom foot 12 on the one hand, and the end of the articulated arm 45 on the boom foot 12, on the other hand. The gas spring 49, thus mounted, acts on the arm 45, and thus on the pulley 44, in the direction indicated by an arrow F, in other words, towards the front.

The front distribution cable 40 has a first end, fixed on the other side of the winding drum 37 of the distribution winch, while its other end is fixed on a tension drum 51 located on the carriage 11, the this cable 40 being the following (see FIGS. 1, 2, 3 and 4):

The front distribution cable 40 rises along the mast 4, and it passes over a pulley 52 of horizontal axis, carried by the masthead 42, then on a pulley 53 of horizontal axis, carried by the rear part The two pulleys 52 and 53 may be coaxial respectively with the two corresponding pulleys 41 and 43 on which the rear distribution cable 39 passes.

From the pulley 53, the front distribution cable 40 extends forward, along the boom foot 12 and over the entire length thereof, to a pulley 54 of horizontal axis, mounted on the bent rod 23 belonging to the articulation device 18 between the jib foot 12 and the tip arrow 13. The cable 40 then passes on a pulley 55 of horizontal axis, mounted at the upper front end of the jib 12, then on another pulley 56 of horizontal axis, mounted in front of the previous one and close to this one, always at the upper front end of the foot of arrow 12.

From there, the front distribution cable 40 passes on a pulley 57 of horizontal axis, mounted on the other connecting rod 25 of the articulation device 18, namely the connecting rod 25 articulated on the rear end of the tip of arrow 13. Then the cable 40 extends forward, along the arrowhead 13 and over the entire length thereof, to a pulley 58 of horizontal axis, carried by the front end of the arrowhead 13 (see detail in Figure 2).

Returned by the pulley 58, the front distribution cable 40 then extends rearward, along the arrowhead 13 and over the entire length thereof, to a pulley 59 of horizontal axis, located at the lower rear end of the boom tip 13 (this when the carriage 11 is on the boom foot 12, as shown in Figures 4 and 5).

The circuit of the front distribution cable 40 comprises a last pulley 60 of horizontal axis, carried by the lower front end of the jib 12.

At the hinge device 18 between the jib foot 12 and the jib tip 13, the two pulleys 54 and 57 respectively mounted on the two connecting rods 23 and 25 form, with the two other pulleys 55 and 56 mounted at the level of the upper chord 30 of the jib 12, a system for compensating the length of the cable. Passing on these two pulleys 55 and 56, the front distribution cable 40 bypasses the connecting pin 22 of the respective upper ribs 30 and 34 of the jib 12 and of the jib 13, this also in the aligned position arrow 10 (FIG. 4) only in its folded position (FIG. 5).

As indicated above, the second end of the front distribution cable 40 is fixed on a drum 51 carried by the carriage 11. The drum 51 is provided with a drive square of its axis of rotation, which can be moved to the using a key, locking means in rotation of the drum 51 are also provided. These means allow pre-tensioning of the cables 39 and 40 (as detailed below), as well as the possible storage of excess cable length, in the event of a decrease in the length of the arrow 10.

1. 1. Mise en pré-tension du câble :
   Cette opération est réalisée sur la grue repliée à l'horizontale, la flèche 10 elle-même étant soit repliée, soit alignée. Le chariot 11 est placé alors à l'extrémité avant du pied de flèche 12, si la flèche 10 est repliée, ou placé sur la pointe de flèche 13 en un point quelconque de la longueur de cet élément, si la flèche 10 est alignée.
   Le chariot 11 se situant ainsi à hauteur d'homme, l'opérateur enroule le câble de distribution avant 40 sur le tambour de tension 51 situé sur ce chariot 11, en s'aidant de la clé et du carré d'entraînement. Le chariot 11 est ainsi mû vers l'avant de la flèche 10, ce qui tend le câble de distribution arrière 39. Ce faisant, le câble de distribution arrière 39, passant entre autres sur la poulie 44 portée par l'extrémité du bras 45, fait pivoter ce bras 45 dans le sens opposé à la flèche F, autrement dit vers l'arrière. Le pivotement du bras 45 comprime le ressort à gaz 49, jusqu'à sa course de compression maximale.
   Lorsque cette manoeuvre est terminée, le ressort à gaz 49 exerce une poussée sur la poulie 44 portée par le bras 45. Le chariot 11 étant libre sur son chemin de roulement, le long de la flèche 10, la poulie 44 met en tension le câble de distribution arrière 39 et le câble de distribution avant 40, avec le même effort de tension pour les deux câbles 39 et 40.
2. 2. Maintien en tension pendant le travail de la grue :
   Les câbles de distribution arrière 39 et avant 40 s'allongent, en cours d'utilisation de la grue, sous l'effet des charges levées par le crochet 61 et distribuées par le chariot 11. Lorsque ces câbles s'allongent, le ressort à gaz 49 réagit sur le bras 45 avec un effort de poussée constant, qui maintient une tension permanente et de valeur constante dans les câbles de distribution arrière 39 et avant 40.
3. 3. Repliage de la flèche :
   Le repliage de la flèche 10, à partir de sa position alignée (figure 4), est commandé par le vérin 28 qui agit sur les bielles 23 et 25 du dispositif d'articulation 18 entre le pied de flèche 12 et la pointe de flèche 13. Le chariot 11 étant situé en un point du pied de flèche 12, cette opération de repliage fait seulement intervenir le câble de distribution avant 40, plus particulièrement au niveau du système de compensation.
   Lors du repliage de la flèche 10, avec passage de la position de la figure 4 à celle de la figure 5, le mouvement relatif des deux bielles 23 et 25, portant respectivement les poulies 54 et 57, raccourcit la longueur de la partie de câble située entre ces deux poulies 54 et 57 d'une distance égale à l'augmentation de la longueur de la partie de câble entre les deux poulies 59 et 60, situées en vis-à-vis lorsque la flèche 10 est alignée mais s'éloignant l'une de l'autre au cours du repliage. Par conséquent, la longueur de la partie du câble de distribution avant 40, entre la poulie 53 portée par le pied de flèche 12 et le tambour de tension 51 situé sur le chariot 11, ne varie pas, en particulier dans la région du dispositif d'articulation 18.
   Il y a donc compensation exacte de la longueur du câble et, en conséquence, le chariot 11 reste immobile et se maintient dans la position initialement occupée, au cours de cette opération de repliage de la flèche 10.
   En outre, pendant et après cette opération, les câbles de distribution arrière 39 et avant 40 restent tendus en permanence, avec le même effort de tension dû au ressort à gaz.
4. 4. Dépliage de la flèche:
   On considère maintenant l'opération, inverse de la précédente, qui consiste à déplier la flèche 10 à partir de sa position repliée (figure 5), cette opération étant aussi commandée par le vérin 28. La compensation de longueur du câble s'effectue alors de manière analogue, au niveau du dispositif d'articulation 18, et elle conduit aux mêmes résultats, c'est-à-dire au maintien de la position du chariot 11, ainsi que de la tension des câbles de distribution 39 et 40.
5. 5. Travail de la grue avec flèche partiellement repliée :
   L'amenée de la grue dans une telle position correspond à une partie de l'opération de repliage de la flèche 10, décrite au paragraphe 3 ci-dessus. Cette phase s'effectue, de la même manière, avec compensation de longueur pour le câble de distribution avant 40.
   Par ailleurs, au cours du travail de la grue avec la flèche 10 partiellement repliée, la tension des câbles de distribution arrière 39 et avant 40 est maintenue, selon la description donnée au paragraphe 2 ci-dessus.
   L'on ne s'éloignerait pas du cadre de l'invention, telle que définie dans les revendications annexées :
   • en remplaçant l'unique ressort à gaz 49, dans le dispositif de tension 48, par deux ou plusieurs ressorts à gaz, montés et agissant en parallèle ;
   • en modifiant la position du treuil de distribution sur la grue, ce treuil pouvant être placé aussi sur la tête de mât 42, ou sur le pied de flèche 12, ou encore à mi-longueur de la flèche 10 ;
   • en étendant l'application de l'invention à une grue avec flèche possédant un nombre d'éléments quelconque, par exemple trois éléments, ces éléments pouvant avoir une forme quelconque, avec un système de compensation de longueur de câble au niveau de chaque articulation entre deux éléments de flèche consécutifs ;
   • en adaptant le circuit de câble, en particulier dans sa partie constituant le système de compensation, aux particularités du dispositif d'articulation entre les éléments de flèche, ce dispositif d'articulation pouvant être de tout type.

The operation of the devices described above is as follows:

1. 1. Pre-tensioning the cable:
   This operation is performed on the crane folded horizontally, the boom 10 itself being either folded or aligned. The carriage 11 is then placed at the front end of the boom foot 12, if the boom 10 is folded, or placed on the boom tip 13 at any point along the length of this element, if the boom 10 is aligned.
   The carriage 11 is thus located at man's height, the operator winds the front distribution cable 40 on the tension drum 51 located on the carriage 11, with the help of the key and the drive square. The carriage 11 is thus moved forward of the boom 10, which tends the rear distribution cable 39. In doing so, the rear distribution cable 39, passing among others on the pulley 44 carried by the end of the arm 45 , rotates the arm 45 in the opposite direction to the arrow F, in other words to the rear. The pivoting of the arm 45 compresses the gas spring 49 to its maximum compression stroke.
   When this maneuver is completed, the gas spring 49 exerts a thrust on the pulley 44 carried by the arm 45. The carriage 11 being free on its raceway, along the arrow 10, the pulley 44 puts in tension the cable rear distribution cable 39 and the front distribution cable 40, with the same tensioning force for the two cables 39 and 40.
2. 2. Keep in tension during the work of the crane:
   The rear distribution cables 39 and 40 before lengthen, in use of the crane, under the effect of the loads raised by the hook 61 and distributed by the carriage 11. When these cables are elongated, the spring to gas 49 reacts on the arm 45 with a constant thrust force, which maintains a constant tension and constant value in the rear distribution cables 39 and 40 before.
3. 3. Folding the arrow:
   The folding of the boom 10, starting from its aligned position (FIG. 4), is controlled by the jack 28 which acts on the connecting rods 23 and 25 of the articulation device 18 between the boom foot 12 and the boom tip 13 The carriage 11 being located at a point of the jib foot 12, this folding operation only involves the front distribution cable 40, more particularly at the level of the compensation system.
   When folding the boom 10, with passage from the position of Figure 4 to that of Figure 5, the relative movement of the two connecting rods 23 and 25, respectively carrying the pulleys 54 and 57, shortens the length of the cable portion located between these two pulleys 54 and 57 by a distance equal to the increase in the length of the portion of cable between the two pulleys 59 and 60, located opposite each other when the arrow 10 is aligned but moving away from each other during folding. Therefore, the length of the portion of the front distribution cable 40, between the pulley 53 carried by the jib foot 12 and the tensioning drum 51 on the carriage 11, does not vary, particularly in the region of the delivery device. articulation 18.
   There is therefore exact compensation of the length of the cable and, consequently, the carriage 11 remains stationary and remains in the initially occupied position, during this folding operation of the boom 10.
   In addition, during and after this operation, the rear distribution cables 39 and 40 before remain stretched permanently, with the same tension force due to the gas spring.
4. 4. Unfolding the arrow:
   We now consider the operation, the inverse of the previous one, which consists in unfolding the boom 10 from its folded position (FIG. 5), this operation being also controlled by the jack 28. The compensation of the length of the cable then takes place similarly, at the hinge device 18, and it leads to the same results, that is to say the maintenance of the position of the carriage 11, as well as the tension of the distribution cables 39 and 40.
5. 5. Work of the crane with partially folded boom:
   The bringing of the crane in such a position corresponds to a part of the folding operation of the boom 10, described in paragraph 3 above. This phase is carried out, in the same way, with length compensation for the front distribution cable 40.
   Furthermore, during the work of the crane with the boom 10 partially folded, the tension of the rear distribution cable 39 and before 40 is maintained, as described in paragraph 2 above.
   One would not depart from the scope of the invention, as defined in the appended claims:
   • replacing the single gas spring 49 in the tensioning device 48 by two or more gas springs mounted and acting in parallel;
   • by modifying the position of the distribution winch on the crane, this winch being able to be placed also on the masthead 42, or on the foot of boom 12, or at half-length of the boom 10;
   • extending the application of the invention to a boom crane having any number of elements, for example three elements, these elements may have any shape, with a cable length compensation system at each joint between two consecutive arrow elements;
   • by adapting the cable circuit, in particular in its part constituting the compensation system, to the particularities of the articulation device between the jib elements, this articulation device being able to be of any type.

Claims (4)

1. A tower crane with folding delivery jib (10) made up of two or more successive elements (12, 13) articulated together, one of which is a jib root element (12) and one of which is a jib tip element (13), along which elements a jib crab (11) moves, the crane comprising a delivery cable circuit with:

   - a rear delivery cable (39), a first end of which is fixed to one side of the winding drum (37) of a motorized delivery winch and the second end of which is fixed to the jib crab (11), this cable (39) passing over at least one pulley (43) carried by the rear part of the jib root element (12),

   - a front delivery cable (40), a first end of which is fixed to the other side of the winding drum (37) of the delivery winch and the second end of which is fixed to the jib crab (11), this cable (40) passing over pulleys comprising at least one pulley (58) carried by the front part of the jib tip element (13),

   - a tensioning device (48) acting on the rear (39) or front delivery cable (40) to keep these two cables (39, 40) taut, and

   - for the or each articulation (18) between two consecutive jib elements (12, 13), a cable-length compensation system consisting of a set of pulleys (54, 55, 56, 57, 59, 60) carried by the adjacent ends of these two jib elements (12, 13) and/or of members (23,25) of the device (18) that articulates these two jib elements (12, 13) together,

   characterized in that in the tensioning device (48) comprises an arm (45) articulated to the jib root element (12), this articulated arm (45) carrying a pulley (44) over which the rear delivery cable (39) passes and at least one gas spring (49) mounted between a point (50) on the jib root element (12) and a point on the articulated arm (45).
2. A tower crane with a delivery cable circuit as claimed in claim 1, characterized in that the tensioning device (48), with articulated arm (45) and gas spring (49), is mounted in the rear part of the jib root element (12).
3. A tower crane with a delivery cable circuit as claimed in claim 1 or 2, characterized in that the second end of the rear delivery cable (39) or of the front delivery cable (40) is fixed to a tensioning drum (51) situated on the jib crab (11), this drum (51) being equipped with means for driving it and for preventing it from rotating, so as to tension this cable.
4. A tower crane with delivery cable circuit as claimed in any of claims 1 to 3, characterized in that in the case of a device (18) for articulating two consecutive jib elements (12, 13) together which comprises a horizontal articulation spindle (17) situated approximately mid-way up these jib elements (12, 13) which can be nested one inside the other, a first link rod (23) articulated to the lower front end of the rear jib element (13) and a second link rod (25) articulated to the lower rear end of the front jib element (13), the two link rods (23,25) being articulated together and articulated to a folding ram (28), the compensation system associated with this articulation involves the front delivery cable (40), and this system comprises:

   - a pulley (54) mounted at an intermediate point on the first link rod (23),

   - a pulley (55) mounted at the upper front end of the rear jib element (12),

   - a pulley (56) mounted in front of the previous one, and

   - a pulley (57) mounted an the second link rod (25).

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