EP1408578B1 - Supporting arm of a radio control antenna for a lifting apparatus - Google Patents

Description

The present invention relates generally to the field of radio controlled hoisting devices. More particularly, this invention relates to a multi-position radio control antenna support arm for lifting apparatus. The invention applies in particular to the radio control tower cranes.

For the radio control of tower cranes, as known for example from the European patent application EP 1149796 A2 in the name of the Applicant, there are antennas for receiving or receiving-transmitting control or control signals. These antennas are either fixed antennas or removable antennas.

When they are fixed, the radio control antennas are directly fixed on a point of the frame of the crane, or they are incorporated in a unit of reception or reception-emission of the signals of control or control, unit which is itself mounted fixed on the crane. The fixed antennas thus have a unique, non-modifiable position.

• soit sur un boîtier de réception ou réception-émission des signaux de commande ou de contrôle, qui est lui-même positionnable sur la grue à divers emplacements, spécialement prévus à cet effet ou non ;
• soit sur une embase magnétique ou non, avec une longueur suffisante de câble de transmission ou avec des rallonges de câble amovibles, l'embase étant positionnable sur la grue à divers emplacements, spécialement prévus à cet effet ou non.

When they are removable, the radio control antennas are generally fixed:

• either on a receiving box or receiving-transmitting control or control signals, which is itself positionable on the crane at various locations, especially provided for this purpose or not;
• either on a magnetic base or not, with a sufficient length of transmission cable or with removable cable extensions, the base being positionable on the crane at various locations, especially provided for this purpose or not.

The radio control is always disturbed by the metallic obstacles between the transmitter and the receiver of the control or control signals, obstacles which reduce its range and create echoes. Moreover, the quality of the transmission of control or control signals is largely affected by the length of the cable that connects the antenna to the receiver, the connections related to the extension cables, and the quality of the electrical mass between the cable. antenna and its support, if it is removable.

More particularly, solutions with fixed antenna (s), single position, are dependent on metal obstacles and mainly the frame of the crane itself, especially during its rotation.

• difficulté de passage des câbles ;
• longueur importante du câble de transmission, qui doit être prévue pour la position la plus éloignée de l'antenne ;
• perturbations dues à la mauvaise qualité des connexions électriques, dans le cas de l'utilisation de rallonges de câble ;
• défauts fréquents de continuité de la masse électrique ;
• risque de détérioration du câble de transmission, lors du travail de la grue, par exemple en raison de projections, de chocs et des conditions climatiques.

Solutions with removable antenna (s) are dependent on even more diverse factors:

• difficulty in passing cables;
• large length of the transmission cable, which must be provided for the furthest position of the antenna;
• disturbances due to poor quality of electrical connections, in the case of the use of extension cords;
• frequent defects in electrical continuity;
• risk of deterioration of the transmission cable, when working the crane, for example due to projections, shocks and weather conditions.

US-A-3833898 shows a mobile crane, whose arrow carries, in particular at its free end, an antenna which serves as a proximity sensor, to serve as a safety system in case the boom of the crane is approaching dangerously d a live overhead power cable. This document is not related to the radio control of the cranes.

The present invention aims to avoid the disadvantages of the various current types of fixed or removable radio remote control antennas, related to their positioning, by providing a solution for optimally positioning a receiving antenna, or receiving-emitting, so to reduce the influence of metallic obstacles on electromagnetic waves, while protecting the cables and minimizing other disturbances, in order to optimize the operation of the radio control.

For this purpose, the subject of the invention is essentially a radiocontrol antenna support arm for a tower crane, the support arm being pivotally mounted around a vertical pivot axis, on a chassis or lower frame of the crane, so that it can be positioned in at least two distinct angular positions, the angular positions in which the support arm is immobilizable comprising a position folded against the crane, and at least one position away from the metal structure of the crane, the support arm being a tubular arm having a head offset vertically with respect to said pivot axis, on which at least one radio control antenna is mounted, and a transmission cable which leads to said antenna passing inside the tubular support arm.

In one embodiment of this steerable support arm, it comprises a base portion rotatably mounted on a fixed pivot, defining the aforementioned vertical pivot axis, a bent or bent tube extending the base portion, and at the end of the tube the base-shaped head, on which is mounted the radio control antenna.

• une première position, rabattue contre le châssis ou bâti inférieur de la grue, cette position étant utilisable pour le travail de la grue, et aussi pour son transport à l'état replié ;
• une deuxième position, écartée du châssis ou bâti inférieur de la grue, cette position étant utilisable pour le montage et démontage de la grue ; et
• au moins une troisième position, écartée du châssis ou bâti inférieur de la grue, cette position amenant l'antenne vers l'avant du châssis ou bâti inférieur, ou en avant de la base du mât de la grue.

The angular positions, in which the support arm or its tube are immobilizable, advantageously comprise a position folded against the hoist such as crane, and at least one position away from the metal structure of this hoist. In particular, in the case of a folding tower crane, the predefined angular positions of this support arm comprise:

• a first position, folded against the frame or lower frame of the crane, this position being used for the work of the crane, and also for its transport in the folded state;
• a second position, spaced from the frame or lower frame of the crane, this position being used for the assembly and disassembly of the crane; and
• at least a third position, spaced from the frame or lower frame of the crane, this position bringing the antenna to the front of the frame or lower frame, or in front of the base of the mast of the crane.

For example, the angular distance between the first position of the support arm and its second position is here about 60 °, and the angular distance between the second position of the support arm and its third position, and where appropriate between the positions. following, is also about 60 °, the support arm thus having for example an angular deflection of the order of 120 °.

For the positioning of the antenna support arm in its first position, folded against the frame or lower frame of the crane, it is provided, in a particular embodiment, an upper positioning pin retained on a plate attached to said frame or frame , this pin cooperating with another plate, provided with a hole, connected to the base-shaped head of the support arm.

For the positioning of this antenna support arm in its two or more other positions, separated from the frame or lower frame of the crane, it is provided for example, at the base portion and the fixed pivot of the support arm, a lower positioning pin connected to the base portion of the support arm and adapted to cooperate with one or the other of two or more holes drilled in a plate secured to a portion of the fixed pivot

This fixed pivot, serving for the orientation of the antenna support arm, is feasible in the form of a folded sheet-shaped "U", whose wings are positioned horizontally, one above the other, so as to form an upper bearing and a lower bearing, traversed by the base portion of the support arm, the aforesaid plate pierced with two or more holes being secured to the upper flange of the folded sheet which forms the upper bearing .

A radio-control antenna support arm is thus obtained, which makes it possible to position the antenna in an optimal reception or reception-transmission position (depending on the type of antenna concerned), opposite a portable radio unit. command used by the operator. In particular, the antenna can be brought into an optimal position which is that to reduce the influence of metal obstacles, forming part of the crane itself or the operating site of this crane, and may be between control unit carried by the operator, and the receiving unit or reception-transmission carried by the crane.

In particular, the spaced apart position of the frame or lower frame of the crane, and advanced relative to the base of the mast of the crane, is useful when the operator is himself in front of the mast, to proceed with the hooking or stalling loads on the hook of the crane.

The other intended positions of the support arm also respond, in the application of the invention to a folding tower crane, to other requirements which are to obtain a retracted position, for the transport of the crane, and a position particular in which the antenna support arm does not obstruct the movements of unfolding and folding, during assembly and disassembly of the crane.

In addition to the distance of the antenna from the metal masses of the crane, avoiding disturbances due to electromagnetic waves, the radio-control antenna support arm has other significant advantages.

• Le tube protège mécaniquement le câble contre tout type d'agressions extérieures, telles que projections, chocs et intempéries.
• Le câble, de longueur minimale et constante, ne risque ni d'être enroulé, ni d'être vrillé.
• Ce câble ne risque pas d'être détérioré lors d'un changement de position de l'antenne.
• Aucune déconnexion du câble, donc de l'antenne, vis-à-vis de l'unité réceptrice ou réceptrice-émettrice, n'est nécessaire lors d'un changement de position de l'antenne.

In particular, the bent or bent tube of the support arm provides effective protection of the connecting cable between the antenna and the receiving unit or transceiver, this cable passing inside the tube. The cable is thus electromagnetically protected against any parasitic emission, which guarantees the quality of the transmission-reception. In addition, the cable is mechanically protected, under various aspects:

• The tube mechanically protects the cable against any type of external attack, such as projections, shocks and bad weather.
• The cable, of minimum and constant length, does not run the risk of being twisted or kinked.
• This cable will not be damaged during a change of position of the antenna.
• No disconnection of the cable, therefore the antenna, vis-à-vis the receiving or receiving-transmitting unit, is necessary during a change of position of the antenna.

This results in an improvement in the quality of the electrical connection between the antenna and the receiving or receiving-transmitting unit.

Furthermore, the structure of the antenna support arm according to the invention makes it possible to carry out in a simple and rapid manner the positioning and the immobilization of the antenna, in the chosen position.

• Figure 1 est une vue en perspective, montrant partiellement une grue à tour équipée du bras-support d'antenne objet de l'invention, avec indication de deux positions de ce bras-support ;
• Figure 2 est une vue de côté de cette partie de grue, avec le bras-support en position rabattue ;
• Figure 3 est une vue en coupe, à échelle agrandie, suivant III-III de figure 2, montrant la partie supérieure du bras-support et les moyens de positionnement qui lui sont associés ;
• Figure 4 est une vue en plan par dessus correspondant à la figure 2, avec indication des trois positions du bras-support ;
• Figure 5 représente, en vue de dessus à échelle agrandie, le détail du pivot fixe de ce bras-support, avec les moyens de positionnement associés ;
• Figure 6 est une vue en coupe verticale de ce pivot fixe, suivant VI-VI de figure 5 ;
• Figure 7 représente, vue en plan par-dessus, une variante de ce bras-support d'antenne de radiocommande, avec indication de ses quatre positions.

The invention will be better understood with the aid of the description which follows, with reference to the appended diagrammatic drawing showing, by way of nonlimiting examples, two embodiments of this radiocontrol antenna support arm for apparatus for lifting:

• Figure 1 is a perspective view, partially showing a tower crane equipped antenna support arm object of the invention, with indication of two positions of the support arm;
• Figure 2 is a side view of this crane portion, with the support arm in the folded position;
• Figure 3 is a sectional view, on an enlarged scale, III-III of Figure 2, showing the upper portion of the support arm and the positioning means associated therewith;
• Figure 4 is a plan view from above corresponding to Figure 2, with indication of the three positions of the support arm;
• Figure 5 shows, in plan view on an enlarged scale, the detail of the fixed pivot of this support arm, with the associated positioning means;
• Figure 6 is a vertical sectional view of this fixed pivot, according to VI-VI of Figure 5;
• 7 shows, in plan view from above, a variant of this radiocontrol antenna support arm, with an indication of its four positions.

Figures 1, 2 and 4 show a rotating frame 2 of a folding tower crane, the rotating frame 2 being pivotally mounted on a fixed frame, not shown. On the rotating frame 2 is hinged around an axis horizontal 3, the base of the mast 4 of the crane. A support arm 5 for a radio remote control antenna 6 of the crane is mounted, in an adjustable manner, on the rotating frame 2, more particularly on one of the two lateral parts of this frame 2, between which the base of the mast takes place. 4.

The support arm 5 comprises a base portion 7 mounted on a fixed pivot 8 of vertical axis, a bent tube 9 which extends the base portion 7 upwards, and a head 10 carried by the upper end of the tube 9 .

The base portion 7 is in the form of a rectilinear tube section, of vertical axis 11, rotatably mounted in the fixed pivot 8 - see in particular FIG. 6.

The fixed pivot 8 is in the form of a "U" folded sheet, with a horizontal upper wing 12 and a horizontal lower wing 13, which respectively form an upper bearing and a lower bearing traversed by the base portion 7 of the support arm 5. The vertical part 14 of the folded sheet, which connects its two horizontal wings 12 and 13, is fixed, in particular welded, against the rotating frame 2 of the crane, on the inner side of a lateral part of this chassis 2.

The curved shape of the tube 9 brings its upper end, thus the head 10 of the support arm 5, in a position clearly offset relative to the vertical axis 11.

The upper head 10 of the support arm 5 is like a base or upper horizontal face, on which is fixed vertically the radio control antenna 6. It is a receiving antenna only, or a receiving and transmitting antenna .

The antenna 6 is connected, by a transmission cable 15, to a reception or reception-transmission unit, not shown. The cable 15 passes inside the bent tube 9, which provides mechanical and electromagnetic protection of this cable 15 - see FIG.

Due to its rotatable mounting by the fixed pivot 8, the support arm 5 can be brought into different angular positions, which correspond to different positions of the antenna 6 relative to the rotating frame 2 and the mast 4 of the crane. These positions are in particular illustrated in FIGS. 1 and 4. A first position indicated by A is distinguished here, in which the support arm 5 is folded against the rotating frame 2, and two other positions, designated B and C, in which the support arm 5 deviates from the rotating frame 2. The angular difference between the first position A and the second position B is about 60 °. Similarly, the angular difference between the second position B and the third position C is about 60 °. Thus, the angular displacement of the support arm 5 is about 120 °.

Means are provided for the positioning of the support arm 5 in the three positions A, B and C, previously defined.

For the positioning of the support arm 5 in the first position A, and as shown in Figures 2 and 3, there is provided an upper positioning pin 16, retained for example by screwing on a small horizontal plate 17 welded to the rotating frame 2 of the crane. The pin 16 cooperates with another plate 18, provided with an oblong hole 19, which is connected to the base-shaped head 10 of the support arm 5, the plate 18 being welded in the lower part of the head 10.

• sur la partie de base 7 du bras-support 5, une patte radiale 20 ;
• sur le pivot fixe 8, une plaque 21 qui prolonge l'aile supérieure 12 constituant le palier supérieur, et qui comporte deux trous 22 et 23, situés à égale distance de l'axe vertical 11 ;
• et un pion de positionnement inférieur 24 lié à la patte radiale 20 de la partie de base 7, et prévu pour coopérer avec l'un ou l'autre des deux trous 22 et 23 de la plaque 21.

For the positioning of the support arm 5 in the other two positions B and C, and as shown in FIGS. 4 to 6, provision is made for:

• on the base portion 7 of the support arm 5, a radial tab 20;
• on the fixed pivot 8, a plate 21 which extends the upper flange 12 constituting the upper bearing, and which has two holes 22 and 23, located equidistant from the vertical axis 11;
• and a lower positioning pin 24 connected to the radial tab 20 of the base portion 7, and provided to cooperate with one or the other of the two holes 22 and 23 of the plate 21.

• Dans la position A, le bras-support 5 est rabattu contre la partie latérale du châssis tournant 1 de la grue. Cette première position, maintenue au moyen du pion de positionnement supérieur 16, est notamment une position d'immobilisation du bras-support 5 utilisée pour le transport de la grue à l'état replié. Elle constitue aussi une position utilisable pour le travail de la grue.
• La deuxième position B, dans laquelle le bras-support 5 et l'antenne 6 sont écartés du châssis 2, est utilisable pour le montage et le démontage de la grue, car elle autorise le libre passage de la base du mât 4 lors de son dépliage ou de son repliage. Cette deuxième position est maintenue au moyen du pion de positionnement inférieur 24, introduit à cet effet dans le trou 22 de la plaque 21.
• La troisième position C, dans laquelle le bras-support 5 est écarté du châssis 2 et l'antenne 6 est amenée en avant de la base du mât 4, supprime la "zone d'ombre" éventuelle de la première position A, dans le cas d'un opérateur positionné, avec son unité de commande, à l'avant de la grue, à proximité de la charge levée. Cette troisième position est maintenue au moyen du pion de positionnement inférieur 24, introduit à cet effet dans l'autre trou 23 de la plaque 21.

The overall operation of the support arm 5 is as follows:

• In the position A, the support arm 5 is folded against the side portion of the rotating frame 1 of the crane. This first position, maintained by means of the upper positioning pin 16, is in particular a position of immobilization of the support arm 5 used for transporting the crane in the folded state. It is also a usable position for the work of the crane.
• The second position B, in which the support arm 5 and the antenna 6 are separated from the frame 2, is used for mounting and dismounting the crane, since it allows the free passage of the base of the mast 4 during its unfolding or folding. This second position is maintained by means of the lower positioning pin 24, introduced for this purpose into the hole 22 of the plate 21.
• The third position C, in which the support arm 5 is separated from the chassis 2 and the antenna 6 is brought forward of the base of the mast 4, eliminates the possible "shadow zone" of the first position A, in the case of a Operator positioned, with his control unit, at the front of the crane, near the lifted load. This third position is maintained by means of the lower positioning pin 24 introduced for this purpose into the other hole 23 of the plate 21.

Note that, for the passage from the first position A to the second position B, or vice versa, it may be necessary to lift a few centimeters the support arm 5, this firstly to clear the plate 18 of the positioning pin upper 16, and secondly to bypass the obstacle constituted by the upper edge of the frame 2 of the crane. For this purpose, the base portion 7 of the support arm 5 is slidably mounted along the vertical axis 11 in the fixed pivot 8, which makes it possible to raise the support arm 5 before turning it, then to lower it when he has reached his new angular position. A stop member, such as a safety pin 25, is provided on the base portion 7 of the support arm 5, to limit the lifting of this support arm 5 and thus prevent it from emerging from its pivot 8 , in particular during a change of position of the support arm 5. The lifting of the support arm 5 can from the second position B to the third position C, or vice versa.

As further shown in FIG. 2, the cable 15 forms, at its exit from the base part 7, a loop which is sufficient to allow the slight lifting of the support arm 5, necessary during the change of position of this support arm . Beyond this loop, the cable 15 enters through a through hole 27 in the rotating frame 2 which here constitutes the frame of the electrical cabinet of the crane.

FIG. 7, in which the elements corresponding to those previously described are indicated by the same references, represents a variant of this support arm 5 for a radio control antenna 6, which differs mainly from the preceding embodiment in that it has four positions, designated A to D, the structure of the support arm 5 itself not substantially changed.

In the first position A, the support arm 5 is folded against the side portion of the rotating frame 2 of the crane. This first position A, blocked as previously by an upper positioning pin, serves to immobilize the support arm 5 for the transport of the crane, and also constitutes a working position, particularly for the orientation of the crane 360 °

The second position B, located at an angular distance of about 60 ° from the previous one, is a preferred position for mounting and dismounting the crane.

The third position C, located at an angular distance of about 60 ° from the previous one, and therefore about 120 ° from the first position A, brings the antenna 6 to the front of the frame 2. This is a preferential position, when the operator is positioned at the front of the crane, near the raised load.

Finally the fourth position D, located at an angular distance of about 60 ° from the previous one, and therefore about 180 ° from the first position A, brings the antenna 6 to the front of the base of the mast 4. This last position D is preferential in the case where the operator is positioned in height, on the side of the crane opposite the antenna 6.

FIG. 7 also indicates, for each position A, B, C or D of the support arm 5, the limits of the corresponding zones covered without obstacles between the transmitter, namely the control unit 26, and the antenna 6 (FIG. receiver).

For the immobilization of the support arm 5 in the three positions B, C and D, all spaced from the frame 2, one always uses a single lower positioning pin, which in this case can be introduced into one of the three holes drilled in the integral plate of the fixed pivot 8, these three holes being drilled on the same circle centered on the vertical axis 11 of pivoting of the support arm 5.

• en modifiant le nombre des positions possibles du bras-support ;
• en répartissant ces positions sur une plage angulaire plus ou moins importante, et avec des distances angulaires plus ou moins grandes, le débattement angulaire du bras-support pouvant être quelconque, en allant jusqu'à une possibilité d'orientation de ce bras-support sur 360° ;
• dans la mesure où il s'agit d'un bras-support tubulaire, en le réalisant sous la forme d'un bras télescopique, avec système de compensation de la longueur du câble passant à l'intérieur ;
• en réalisant le bras-support comme un bras déformable, en plusieurs sections, cette variante comme la précédente permettant aussi un positionnement réglable en hauteur pour l'antenne ;
• en disposant deux ou plusieurs antennes, par exemple une antenne réceptrice et une antenne émettrice séparées, sur la tête du bras-support ;
• en modifiant les détails constructifs du pivot et des moyens de positionnement ;
• en appliquant ce bras-support d'antenne à des grues à tour de tous types.

One would not depart from the scope of the invention, as defined in the appended claims:

• modifying the number of possible positions of the support arm;
• by distributing these positions over a greater or lesser angular range, and with greater or smaller angular distances, the angular displacement of the support arm can be arbitrary, up to a possibility of orientation of this support arm on 360 °;
• in that it is a tubular support arm, in the form of a telescopic arm, with a compensation system of the length of the cable passing inside;
• realizing the support arm as a deformable arm, in several sections, this variant as the previous one also allowing a height-adjustable positioning for the antenna;
• arranging two or more antennas, for example a receiving antenna and a transmitting antenna separated, on the head of the support arm;
• modifying the constructive details of the pivot and the positioning means;
• applying this antenna support arm to tower cranes of all types.

Claims (11)

1. A radio-control antenna (6) support arm (5) for a tower crane, which it is able to be orientated about a vertical pivoting axis (11) on a lower frame or chassis (2) of the crane such that it can be positioned in at least two separate angular positions (A, B, C, D,), wherein the angular positions in which the support arm (5) can be immobilized comprise a position (A) folded back against the crane (2), and at least one position (B, C, D) separated from the metal structure of the crane, this support arm (5) being a tubular arm (9) comprising a head (10), radially offset with respect to the said pivoting axis (11), upon which is mounted at least one radio-control antenna (6) and a transmission cable (15) which ends at this antenna (6) passing through the inside of the tubular support arm (5, 9).
2. The radio-control antenna support arm as claimed in claim 1, characterized in that it comprises a base part (7) mounted such that it rotates on a fixed pivot (8), defining the said vertical pivoting axis (11), a curved or bent tube (9) extending the base part (7) and, at the end of the tube (9), a head (10) in the form of a mounting plate, upon which the radio-control antenna (6) is mounted,
3. The radio-control antenna support arm as claimed in claim 1 or 2, characterized in that, in the case of a folding tower crane, the predefined angular positions of this support arm (5) comprise:

   - a first position (A), folded back against the lower frame or chassis (2) of the crane, this position (A) being usable for the working of the crane and also for its transport in the folded state;

   - a second position (B), separated from the lower frame or chassis (2) of the crane, this position (B) being usable for raising and lowering of the crane; and

   - at least a third position (C), separated from the lower frame or chassis (2) of the crane, this position (C) bringing the antenna (6) towards the front of the lower frame or chassis (2), or in front of the base of the crane's mast (4).
4. The radio-control antenna support arm as claimed in claim 4, characterized in that the angular distance between the first position (A) of the support arm (5) and its second position (B) is about 60° and the angular distance between the second position (B) of the support arm (5) and its third position (C) and, if applicable, between the following positions (C, D), is also about 60°, the support arm (5) thus having, for example, an angular positional range of the order to 120°.
5. The radio-control antenna support arm as claimed in both of claims 2 and 3, characterized in that the means for positioning the support arm (5) in its first position (A), folded back against the lower frame or chassis (2) of the crane, comprise an upper positioning pin (16) held on a plate (17) fixed to the said frame or chassis (2), this pin (16) cooperating with another plate (18), provided with a hole (19), attached to the support arm's (5) head (10) in the form of a mounting plate.
6. The radio-control antenna support arm as claimed in both of claims 2 and 3, characterized in that the means for positioning of the support arm (5) in its other two or more positions (B, C, D), separated from the lower frame or chassis (2) of the crane, comprise, in the base part (7) and at the fixed pivot (8) of the support arm (5), a lower positioning pin (24) attached to the base part (7, 20) of the support arm (5) and provided for cooperating with one or other of two or more holes (22, 23) drilled in a plate (21) integral with a part (12) of the fixed pivot (8).
7. The radio-control antenna support arm as claimed in claim 6, characterized in that the fixed pivot (8), used for the orientation of the support arm (5), is produced in the form of a sheet, folded into a "U" shape, whose flanges (12, 13) are positioned horizontally, one above the other, in such a way as to form an upper bearing and a lower bearing, traversed by the base part (7) of the support arm (5), the said plate (21) drilled with two or more holes (22, 23) being integral with the upper flange (12) of the folded sheet which forms the upper bearing.
8. The radio-control antenna support arm as claimed in claim 7, characterized in that the two flanges (12, 13) of the sheet folded in a "U" shape are connected by a vertical section (14) which is fixed, and in particular welded, against the lower frame or chassis (2) of the crane.
9. The radio-control antenna support arm as claimed in any one of claims 5 to 8, characterized in that the base part (7) of the support arm (5) is mounted such that it slides along a vertical axis (11) in the fixed pivot (8), which makes it possible to raise the support arm (5) to allow its movement from one position to another position.
10. The radio-control antenna support arm as c in both of claims 5 and 9, characterized in that the raising of the support arm (5) is provided for releasing the plate (18) from the upper positioning pin (16) and for moving around the obstacle formed by the upper edge of the lower frame or chassis (2) of the crane during its movement from the first position (A) to the second position (B).
11. The radio-control antenna support arm as claimed in claim 9 or 10, characterized in that a stop device, such as a safety pin (25) is provided on the base part (7) of the support arm (5) to limit the raising of this support arm (5) and to prevent it from coming out of its pivot (8), particularly during a change of position of the support arm (5).

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