Tower crane with automatic folding and unfolding stanchion

Abstract

A tower crane configured to fold and unfold between a working configuration and a transport configuration includes a boom hinged in rotation relative to a mast about a main axis of rotation. The tower crane includes a rear retainer fastened to a frame supporting the mast and to a stanchion. The stanchion extends the boom rearwardly of the main axis of rotation and is displaceable relative to the boom between a working position and a transport position. The tower crane further includes a lifting cable connected to a winding device exerting, on the lifting cable, a tension force applied on stanchion by a return system configured to cooperate with the lifting cable, so as to cause displacement of said stanchion from the working position to the transport position.

Claims

1. A tower crane configured to fold and unfold between a working configuration and a transport configuration, the tower crane having a boom hinged in rotation relative to a mast about a main axis of rotation, the tower crane comprising: a rear retainer fastened to a frame supporting the mast and to a stanchion, the stanchion extending the boom rearwardly of the main axis of rotation and configured to be displaceable relative to the boom between a working position and a transport position, wherein the tower crane further includes a lifting cable connected to a winding device configured to exert a tension force on the lifting cable, the tension force applied on the stanchion by a return system configured to cooperate with the lifting cable, so as to cause a displacement of the stanchion from the working position to the transport position.

2. The tower crane according to claim 1, wherein the return system includes at least one main return element in which the lifting cable is configured to be engaged, and the main return element is fastened on the stanchion.

3. The tower crane according to claim 1, wherein the stanchion is configured to be connected in rotation, about a secondary axis of rotation, to a first boom segment extending in a boom length direction, the stanchion displaceable between the working position and the transport position by a rotational movement relative to the first boom segment about the secondary axis of rotation.

4. The tower crane according to claim 3, wherein the stanchion has a stanchion body extending in a stanchion direction between a first end and an opposite second end, wherein the first end is configured to be connected to the first boom segment, and the main return element of the return system is disposed in the vicinity of the second end.

5. The tower crane according to claim 4, wherein the stanchion direction is parallel to the boom length direction when the stanchion is in the working position, and wherein the stanchion direction is orthogonal to the boom length direction when the stanchion is in the transport position.

6. The tower crane according to claim 5, wherein the first boom segment has at least one upper chord and one lower chord defining respectively, in a direction perpendicular to the boom length direction, an upper limit and a lower limit of the first boom segment, where the secondary axis of rotation is positioned at the lower limit, wherein the return system includes at least one secondary return element positioned in the vicinity of the upper limit, and the lifting cable is configured to engage successively in the secondary return element and then in the main return element, such that the tension force generates, on the main return element, a folding force directed towards the secondary return element and allowing a displacement of the stanchion from the working position towards the transport position.

7. The tower crane according to claim 6, wherein the secondary return element is fastened on the mast and connected to the winding device by a first portion of the lifting cable extending along the mast, wherein the secondary return element and the main return element are positioned, in the boom length direction, on either side of the secondary axis of rotation when the stanchion is in the working position.

8. The tower crane according to claim 7, wherein the return system includes one or several tertiary return element(s) fastened on the mast, the stanchion or the first boom segment, the lifting cable configured to engage the tertiary return elements, so as to transmit the tension force of the main return element to a second portion of the lifting cable, the second portion extending along the first boom segment.

9. The tower crane according to claim 1, wherein the winding device includes an actuator configured to vary an intensity of the tension force exerted on the lifting cable by the winding device.

10. The tower crane according to claim 9, wherein the lifting cable extends between a first cable end fastened to the boom and a second cable end connected to the winding device, and the winding device is secured to the mast, and wherein the actuator of the winding device is configured to vary a cable length of the lifting cable measured between the first cable end and the winding device, so as to vary the intensity of the tension force.

11. The tower crane according to claim 10, wherein the winding device includes a monitoring system configured to: determine a value of a characteristic quantity representative of the intensity of the tension force, compare the value to a previously defined threshold value, drive the actuator of the winding device so as to increase the cable length when the value is greater than the threshold value, and drive the actuator of the winding device so as to decrease the cable length when the value is less than the threshold value.

12. The tower crane according to claim 11, wherein the monitoring system is configured to determine the value of the characteristic quantity representative of the intensity of the tension force by at least the one of the following measurements: a direct measurement of the intensity of the tension force by a dynamometer, a measurement of an intensity of an electric current supplying the actuator of the winding device with electricity, or a measurement of a torque or a mechanical force internal to the actuator.

13. A method for unfolding and folding a tower crane in accordance with claim 1, the method including: an unfolding phase, during which the tower crane passes from the transport configuration to the working configuration, and during which the stanchion is displaced from the transport position to the working position under the action of the rear retainer configured to connect the stanchion to the frame supporting the mast, and a folding phase during which the tower crane passes from the working configuration to the transport configuration, and during which the stanchion is displaced from the working position to the transport position under the effect the tension force exerted by the winding device on the lifting cable.

14. The method according to claim 13, wherein, during the folding phase, the tension force generates, on the stanchion, a folding force causing a displacement of the stanchion from the working position to the transport position, the folding force opposing, in the vertical direction, the weight of the stanchion under the effect of gravity.

15. The method according to claim 13, wherein the winding device includes an actuator configured to vary an intensity of the tension force exerted on the lifting cable by the winding device, wherein the lifting cable extends between a first cable end fastened to the boom and a second cable end connected to the winding device, and the winding device is secured to the mast, wherein the actuator of the winding device is configured to vary a cable length of the lifting cable measured between the first cable end and the winding device so as to vary the intensity of the tension force, and wherein the folding phase includes a step of driving the actuator of the winding device so as to decrease the cable length so as to cause the displacement of the stanchion towards the transport configuration.

16. The method according to claim 15, wherein the winding device includes a monitoring system configured to: determine a value of a characteristic quantity representative of the intensity of the tension force, compare the value to previously defined threshold value, drive the actuator of the winding device so as to increase the cable length when the value is greater than the threshold value, and drive the actuator of the winding device so as to decrease the cable length when the value is less than the threshold value, wherein the unfolding phase includes at least one step during which the monitoring system compares the value of the characteristic quantity representative of the intensity of the tension force to a threshold unfolding value, and wherein the folding phase includes at least one step during which the monitoring system compares the value of the characteristic quantity representative of the intensity of the tension force to a folding threshold value, and wherein the folding threshold value is greater than said unfolding threshold value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the present invention will appear on reading the detailed description below, of several non-limiting examples of implementation, made with reference to the appended figures in which:

(2) [FIG. 1] is a view of a tower crane according to the invention in its working configuration;

(3) [FIG. 2] is a perspective detail view of a stanchion of a tower crane according to the invention;

(4) [FIG. 3] is a side view of a stanchion of a tower crane according to the invention;

(5) [FIG. 4] is a detail view of the return system of a tower crane according to the invention;

(6) [FIG. 5] is a view of a tower crane according to the invention in a first intermediate configuration, during a method for folding said tower crane;

(7) [FIG. 6] is a view of a tower crane according to the invention in a second intermediate configuration, during the method for folding said tower crane;

(8) [FIG. 7] is a detail view of a stanchion of a tower crane according to the invention in its working position;

(9) [FIG. 8] is a detail view of a stanchion of a tower crane according to the invention in an intermediate position, during a method for folding said stanchion;

(10) [FIG. 9] is a detail view of a stanchion of a tower crane according to the invention in its transport position; and [FIG. 10] is a view of a tower crane according to the invention in its transport configuration.

DESCRIPTION

(11) FIG. 1 represents a tower crane 1 according to the invention, in the working configuration.

(12) This tower crane 1 includes a boom 2 having a first boom segment 21, a second boom segment 22 and a third boom segment 23, hinged in pairs in rotation about a first axis of rotation of boom 221 and a second axis of rotation of boom 231.

(13) The tower crane 1 also includes a mast 3 having, for its part, a first mast segment 31 and a second mast segment 32, hinged in rotation relative to each other about an axis of rotation of mast 321.

(14) This mast is supported by a frame 4, intended to rest on the ground, the second mast segment 32 being hinged in rotation relative to the frame 4 about an axis of rotation of frame 41.

(15) The first boom segment 21 extends between a first end 211 and a second end 214 in a direction of arrow F, which may also be referred to as a boom length direction or a longitudinal direction of the boom or boom segment, and the first mast segment 31 extends in a direction of mast M.

(16) The first boom segment 21 and the first mast segment are moreover hinged in rotation relative to each other about a main axis of rotation 311.

(17) It should be noted that the first axis of rotation of boom 221, the second axis of rotation of boom 231, the axis of rotation of mast 321 and the axis of rotation of frame 41 are parallel relative to each other and also parallel to the main axis of rotation 311.

(18) This tower crane 1 can thus be folded and unfolded between:

(19) a working configuration (illustrated in FIG. 1), in which the first mast segment 31 and the second mast segment 32 extend in the same direction of mast M, this direction of mast M being vertical with respect to the ground on which the frame 4 is disposed (that is to say that the direction of mast M substantially coincides with the direction of the earth's gravity G), and in which the first boom segment 21, the second boom segment 22 and the third boom segment 23 all extend in the same direction of arrow F, i.e., the boom length direction, this direction of arrow F then being substantially perpendicular relative to the direction of mast M (and is then called «horizontal», and

(20) a transport configuration (illustrated in FIG. 10), in which the first mast segment 31 and the second mast segment 32 are stacked one on top of the other, and the first boom segment 21, the second boom segment 22 and the third boom segment 23 are also stacked on top of each other, the direction of arrow F and the direction of mast M then being substantially parallel and horizontal.

(21) In its transport configuration, the tower crane 1 has a very compact shape and is then very easily transportable.

(22) In its working configuration, the tower crane 1 is adapted to displace a load fastened to a hook C, itself connected to a block O designed to be displaceable along the boom 2.

(23) The block O is also connected to a lifting cable 5 including a first end 51 fastened on the third boom segment 23 and a second end 52 connected to a winding device 53 secured to the second mast segment 32.

(24) This winding device 53 (for example, consisting of a winch actuated by a motor) is designed to alternately increase or decrease a cable length of the lifting cable 5, which is measured between the first end 51 and the second end 52, (for example, by winding or unwinding said lifting cable 5), in order to respectively raise or lower the block O in the direction of mast M, and thus displace a load fastened to the hook C in the vertical direction when the tower crane 1 is in the working configuration.

(25) Thus, by increasing or decreasing the cable length of the lifting cable 5, the winding device 53 is therefore adapted to exert a tension force T of varying intensity on this same lifting cable 5.

(26) The tower crane 1 also includes a stanchion 6, hinged in rotation with the first end 211 of the first boom segment 21 about a secondary axis of rotation 61, and extending the boom 2 beyond the main axis of rotation 311.

(27) This stanchion 6 is also connected to a rear retainer 7, formed of several connecting rods 71, 72, 73 and 74 hinged to each other and connecting the stanchion 6 to the frame 4 by extending along the mast 2.

(28) In the working configuration of the tower crane 1, this rear retainer 7 allows, via the stanchion 6, maintaining the boom 2 in its horizontal position at the top of the mast 2.

(29) The following FIGS. 2 to 4 attempt to describe the geometry and the particular structure of the stanchion 6 and of the lifting cable 5.

(30) As shown in FIGS. 2 and 3, the stanchion 6 includes in particular two chords 62 hinged in rotation with the first boom segment 21 about the secondary axis of rotation 61 and joined at a junction point 63.

(31) In particular, these chords 62 are thus displaceable relative to the first boom segment 21 between a working position of the stanchion 6 (as illustrated in FIGS. 2 to 7) and a transport position (as illustrated in FIG. 9).

(32) As shown in these FIGS. 2 and 3, in the working position of the stanchion 6, the chords 62 define a plane parallel to the direction of arrow F.

(33) As visible in FIG. 9, in the working position of the stanchion 6, the chords 62 define a plane which is substantially perpendicular to the direction of arrow F.

(34) In its transport position, the stanchion 6 is in abutment against the first boom segment 6, thereby improving the overall compactness of the tower crane 1 in its transport configuration.

(35) In the remainder of this description, it will be said that the stanchion 6 follows a folding movement when it is displaced from its working position towards its transport position, and an unfolding movement when it is displaced from its transport position towards its working position.

(36) As previously mentioned, the stanchion 6 is connected, at the junction point 63 to the rear retainer 7: the junction point being located at a maximum distance from the main axis of rotation 311, this feature allows increasing the lever arm of the efforts exerted on the stanchion by the rear retainer 7.

(37) Thus, it is possible to drive the boom 2 in rotation about the main axis of rotation 311 by means of a minimum effort of the retainer 7 (in particular during the phases of folding and unfolding the tower crane 1, as described below).

(38) Moreover, it should be noted that the secondary axis of rotation 61 is positioned at a lower limit of the first boom segment 21 defined by lower boom chords 212.

(39) The tower crane 1 also includes a line of upper tie rods 64 joining the junction point 63 of the stanchion 6 to the first boom segment 21, at an upper limit of said first boom segment 21 defined by upper boom chords 213.

(40) It will also be noted that, as shown in particular in FIG. 3, the boom 2 is offset relative to the mast 3 in a transverse direction 33, orthogonal to the direction of mast M and to the direction of arrow F: this feature allows further increasing the compactness of the tower crane 1 when the latter is in its transport configuration.

(41) Consequently, the stanchion 6 extends obliquely with respect to the direction of arrow F, the junction point 63 being located (in the transverse direction 33) at the mast 3, while the hinge of the chords 62 with the first boom segment 21 is located at said first boom segment.

(42) Of course, other embodiments concerning the geometry and the relative positioning of the stanchion 6, of the first mast segment 31 and the first boom segment 21 can be considered.

(43) As shown in FIGS. 2 to 4, the stanchion cooperates with the lifting cable 5 via a return system 8.

(44) The return system 8 allows transmitting the tension force T exerted on the lifting cable 5 by the winding device 53 between a first portion 54 of the lifting cable 5, extending along the mast 3, and a second portion 55 of the lifting cable 5, extending along the boom 2.

(45) This return system 8 therefore cooperates with an intermediate portion 56 of the lifting cable, said intermediate portion 56 joining said first portion 54 and second portion 55.

(46) In particular, by raising the lifting cable 5 from its second end 52 (fastened to the winding device 53 «at the bottom» of the mast) towards its first end 51 (fastened to the boom 2), the lifting cable 5 is successively engaged in:

(47) a secondary return element 81, formed of two pulleys 811 fastened on the first mast segment 31 at the upper limit of the first boom segment 21;

(48) a main return element 82, formed of a pulley fastened on the stanchion 6 at the junction point 63; then

(49) four tertiary return elements 83, each formed of a pulley fastened alternately on the stanchion 6, the first boom segment 21 or the first mast segment 31.

(50) Thus, the return system 8 is well adapted to transmit the tension force T between the first portion 54 and the second portion 55 of the lifting cable 5.

(51) It should be noted that the pulleys of the secondary return element 81, of the main return element 82 and the tertiary return elements 83 are advantageously disposed so as not to introduce torsional efforts into the lifting cable 5.

(52) Indeed, the return directions of the latter are aligned two by two, such that no angle is generated between the cable 5 and each of the pulleys in which it is engaged.

(53) As previously, many other embodiments can be considered concerning this return system 8, whose structure is necessarily adapted to that of the tower crane 1.

(54) It is necessary, for reasons which will be described later, for this return system 8 to cooperate with the stanchion 6; in particular, it is necessary for the return system 8 to be configured to be able to transmit the tension force T, exerted on the lifting cable 5, to the stanchion 6.

(55) FIGS. 5 to 10 describe the different steps of a method for folding the tower crane 1 according to the invention, that is to say a method allowing shifting the latter from its transport configuration to its working configuration.

(56) This folding method begins with a step of folding the boom 2 on itself, by stacking (shown in FIG. 5) of the first boom segment 21, second boom segment 22 and third boom segment 23, by rotating about a first axis of rotation of boom 221 and of the second axis of rotation of boom 231.

(57) The mast is then also folded on itself, by a rotational movement of the first mast segment 31 about the axis of rotation of mast 321 and of the second mast segment 32 about the axis of rotation of frame 41.

(58) These rotational movements of the first mast segment 31 and the second mast segment 32 are carried out by means of a telescopic cylinder V, allowing exerting on them mechanical efforts tending to bring them closer or to move them away from each other.

(59) The rear retainer 7 being moreover connected in a hinged manner to the frame 4 (by means of a connecting rod 71, said connecting rod 71 also being telescopic) to the stanchion 6 (by means of a connecting rod 72), to the first mast segment 31 (by means of a connecting rod 73) and to the second mast segment 32 (by means of a connecting rod 74), this rear retainer is deformed under the effect of the folding movement of the mast 2: under the effect of the action of the cylinder V, the rear retainer allows monitoring the folding kinetics of the tower crane 1.

(60) In particular, during the folding of the mast 2 on itself, the forces exerted by the rear retainer 7 on the stanchion 6 decrease, causing a rocking movement of the boom 2 about the main axis of rotation 311: the boom 2 (itself already folded on itself) approaches the first mast segment 31 and the measurement of the angle between the direction of arrow F and the direction of mast M decreases.

(61) As shown in FIG. 6, at the end of this step of rocking the boom 2, the latter is positioned against the first mast segment 31 and the direction of arrow F and the direction of mast M are substantially collinear.

(62) Until then, the position of the stanchion 6 relative to the first boom segment 21 has not been changed: the stanchion 6 has remained in its working position, in which the chords 62 are substantially parallel to the direction of arrow F.

(63) Moreover, these steps of folding the boom 2 and the mast 3 cause the lifting cable 5 to loosen: during all previous steps, the winding device 53 has been driven, by means of a monitoring system whose operation will be described in more detail below, so as to reduce the cable length of the lifting cable 5, in order to compensate for the loosening of the lifting cable 5 and thus maintain a tension force in the lifting cable 5 of a relatively constant intensity.

(64) Once the configuration represented in FIG. 6 has been reached, the winding device 53 continues to be driven by the monitoring system so as to wind the lifting cable 5 (that is to say so as to decrease the cable length).

(65) Under the effect of the winding device 53, the lifting cable 5 exerts on the main return element 82 of the return system a tension force T directed towards the secondary return element 81.

(66) Due to the configuration of the return system 8, and in particular the relative positioning of the main return element 82, the secondary return element 81 and of the identified tertiary return element 83′ in this FIG. 7, the application of this tension force T on the main return element 82 results in the application of a folding force P on the stanchion 6, at the junction point 63.

(67) This folding force P has an intensity which depends in particular on the relative positioning of the main return element 82, the secondary return element 81 and of the tertiary return element 83′ (in particular, a positioning of the tertiary return element 83′ in the vicinity of the upper limit of the first boom segment 21 allows maximizing the intensity of the folding force P), and on the mechanical friction exerted by these same return elements 81, 82 and 83′ on the lifting cable 5.

(68) The folding force P thus exerts on the stanchion 6 a folding moment allowing driving the stanchion 6 in rotation with respect to the first boom segment 21 about the secondary axis of rotation 61.

(69) As shown in FIGS. 8 and 9, the stanchion 6 is thus displaced from its working position (in FIG. 7) towards its transport position (in FIG. 9) under the effect of the tension force T and the folding force P.

(70) It is important to note the positioning of the secondary return element 82, disposed in the vicinity of the upper limit of the first boom segment 21 (defined by the upper boom chords 213), relative to the secondary axis of rotation, disposed in the vicinity of the lower limit of the first boom segment 21 (defined by the lower boom chords 212), and relative to the main return member 82, disposed between said upper limit and said lower limit.

(71) Thanks to this positioning, the folding force P tends to bring the junction point 63 closer to this upper limit, that is to say, it tends to «lift» the stanchion 6 relative to the direction of arrow F.

(72) This direction of arrow F being, during the folding movement of the stanchion 6, substantially horizontal (as shown in FIG. 6), the folding force P is therefore opposed to the earth's gravity G: the folding movement of the stanchion is thus performed against the weight PO of the stanchion 6 and the rear retainer 7.

(73) It is therefore necessary for the tension force T to have a sufficient intensity for the folding force P to be significant enough to compensate for and overcome the weight PO tending to maintain the stanchion 6 in its working position.

(74) It will also be noted that the application of the folding force P at the junction point 63 allows maximizing the lever arm of this folding force P: it is thus possible to move the stanchion 6 by means of a tension force T of a moderate intensity.

(75) FIG. 8 illustrates an intermediate position of the stanchion 6, between its working position and its transport position, during its rotational movement about the secondary axis 61 under the effect of the tension force T.

(76) FIG. 9 illustrates this same stanchion 6 after it has reached its transport position: the stanchion 6 is then positioned in abutment against the first end 211 of the first boom segment 21, and the chords 62 are then substantially orthogonal to the direction of arrow F.

(77) Once the stanchion 6 is in its transport position, the folding of the mast 3 is completed under the effect of the cylinder V and the tower crane 1 is then in its transport configuration, illustrated in FIG. 10.

(78) In this transport configuration, the first mast segment 31 and the second mast segment 32 are folded over each another and both extend horizontally.

(79) Likewise, the boom 2 is folded back on itself in contact with the first mast segment 31 and also extends horizontally.

(80) Thus, the tower crane is in a very compact form and occupies a small volume, which makes it easily transportable by conventional means of transport.

(81) It should be noted that the fact of having displaced the stanchion 6 towards its transport position, in abutment against the first boom segment 21, allows reducing the space requirement of the tower crane 1 in its transport configuration: the folding of the stanchion 6 allows reducing a length L occupied by the tower crane 1 by a length L′ of the chords 62 (measured between the junction point 63 and the secondary axis of rotation 61.

(82) As previously mentioned, the tower crane 1 includes a monitoring system allowing driving the winding device 53 so as to control the intensity of the tension force T in the lifting cable 5 during the folding movement of the stanchion 6.

(83) More specifically, this monitoring system is capable of measuring a value of a characteristic quantity representative of the intensity of the tension force T, undergoing the same variations over time as the intensity of the tension force.

(84) For example, when the winding device is a winch actuated by a motor, the characteristic quantity may correspond to an intensity of the current for supplying this motor, or else a value of a resistive torque exerted on the motor shaft of the latter.

(85) This characteristic quantity can also correspond to the intensity of the tensile force T itself, for example measured by means of a dynamometer.

(86) The monitoring system is designed to regularly compare the value of this characteristic quantity with a pre-defined threshold value and to command the winding device 53 to increase the cable length when the value of this characteristic quantity is greater than this threshold value, and command the winding device 53 to decrease the length of the cable when the value of this characteristic quantity is less than this threshold value.

(87) It should be noted that an increase in the cable length automatically results in an increase in the intensity of the tension force T in the lifting cable 5, then in an increase in the value of the characteristic quantity.

(88) Conversely, a decrease in the cable length automatically results in a decrease in the intensity of the tension force T in the lifting cable 5, and then in a decrease in the value of the characteristic quantity.

(89) In this manner, the monitoring system allows automatically and continuously maintaining the value of the characteristic quantity approximately equal to the threshold value throughout the folding or unfolding movements of the tower crane 1, and therefore exerting, on the lifting cable 5, a tension force T of a substantially constant intensity.

(90) Consequently, thanks to the choice of the threshold value of the monitoring system, it is possible to monitor the intensity of the folding force exerted on the stanchion 6 and thus to control the kinematics of the displacements thereof.

(91) In particular, during the method for folding the tower crane 1 which are previously described, the stacking of the boom segments 21, 22 and 23 and the mast segments 31 and 32 tends to release the lifting cable 5 and to decrease the intensity of the tension force T.

(92) Consequently, the winding device 53 performs a regular winding of the lifting cable 5 in order to keep the intensity of the tension force T at a high level.

(93) In fact, as shown in FIGS. 7 to 9, the movement of the stanchion 6 towards its transport position is carried out against the force of the earth's gravity: the tension force T must therefore have a sufficiently significant intensity for the folding force P to be able to overcome the weight of the stanchion 6 and the rear retainer 7, in order to cause the folding movement of the stanchion 6.

(94) It is therefore necessary to choose for the threshold value of the monitoring system a sufficiently high value to be able to carry out a folding of the stanchion.

(95) A method for unfolding the tower crane 1, allowing the latter to pass from its transport configuration to its working configuration, can be carried out in a manner similar to the previously described folding method.

(96) This unfolding method can thus be described by the same FIGS. 5 to 10, navigated in the direction opposite to the folding method, that is to say the unfolding method begins with the transport configuration of the tower crane 1 illustrated in FIG. 10 and ends with the working configuration of tower crane 1 illustrated in FIG. 5.

(97) During this method for unfolding the tower crane 1, the mast is deployed by means of the cylinder V, driven so as to increase the distance separating the first mast segment 31 from the second mast segment 32.

(98) At the beginning of this unfolding method, the stanchion 6 is in its transport position, in abutment against the first boom segment 21.

(99) During the unfolding of the mast 3, the rear retainer 7 exerts mechanical efforts on the stanchion 6 at the junction point 63, resulting in the application, on the stanchion 6, of a mechanical torque allowing the initiation of an unfolding movement of the stanchion 6, towards its working position.

(100) The stanchion 6 is then subjected to the effects of its own weight, which tends to displace it towards its working position: the movement of unfolding of the stanchion 6 is thus carried out thanks to the rear retainer 7 and the weight of the stanchion 6.

(101) It should be noted that (as shown in particular in FIGS. 7 to 9), during the displacement of the stanchion 6 towards its working position, the lifting cable 5 always exerts, on the main return element 82, a tension force T, resulting in the application, at the junction point 63 of a folding force P opposing the weight PO of the stanchion 6: this folding force P thus allows compensating for the weight of the stanchion 6 and thus to slow down the «fall» of the stanchion 6 towards its working position under the effect of the earth's gravity.

(102) Consequently, the monitoring system of the winding device 53 allows, by continuously monitoring the value of the intensity of the tension force T during the unfolding movement of the stanchion 6, to control the kinematics of said stanchion 6.

(103) In particular, the unfolding of the stanchion 6 results in an increase in the cable length of the lifting cable 5: the monitoring system drives the winding device 53 so that the latter unwinds the lifting cable 5, gradually and in a controlled manner, in order to slow down the movement of the stanchion 6.

(104) Once the stanchion 6 has been unfolded and in its working position, the boom 2 is also driven in rotation (under the effect of the rear retainer 7 and via the stanchion 6) relative to the first mast segment 31 about the main axis of rotation 311 and displaced towards a horizontal position, until the tower crane 1 reaches its working configuration illustrated in FIG. 1, in which the boom 2 is perpendicular to the vertical mast 3.