EP2025637A1 - Method and device to facilitate weathervaning a tower crane in a disturbed wind - Google Patents

Abstract

The method involves exerting braking torque on a rotating part (2) of a tower crane when the tower crane is out of service. The braking torque is calculated from an expression Cfr2=Cfl2-Ccf2-Ccou, where Cfr2 represents the braking torque, Cfl2 represents the torque applied to an arrow (3) by wind with speed lower than maximum speed that is authorized for working of the crane, Ccf represents the torque applied to a camber (4) by the wind with speed lower than the maximum speed, and Ccou represents friction torque of an orientation crown (5) of the rotating part. An independent claim is also included for a device for assisting tower crane in a disturbed wind.

Description

The present invention relates, in general, to the technical field of tower cranes. More particularly, this invention is directed to a method and apparatus for facilitating the weathering of a tower crane in a disturbed wind.

A tower crane is usually composed of two main parts, which are on the one hand a non-rotating vertical pylon also designated as mast, and on the other hand a rotating part composed of an arrow and a counter-beam equipped with a ballast, the rotating part being mounted at the top of the mast being made orientable about a vertical axis.

To achieve the assembly of the rotating part, is interposed between the arrow and the counterfleche an orientation ring, comparable to a large ball bearing, which is composed of two concentric rings, including a fixed ring connected to the top of the mast and a movable ring connected to the rotating part, rings between which cylindrical balls or rollers roll.

To control the rotation of the rotating part of the crane, an electric gear motor integral with this rotating part rotates a pinion, which meshes with a toothed wheel cut into the fixed ring of the ring gear. If the power to be transmitted to rotate the rotating part is too important for a single motor, two or more geared motors can be mounted on the rotating part. The ring is designed to allow rotation of the rotating part with minimal drive torque; nevertheless, it is necessary to exert between the considered parts of the crane a sufficient torque to overcome the friction of the balls or rollers interposed between the fixed ring and the movable ring of the crown. The friction torque of the crown is here designated by Ccou.

The orientation geared motor has a brake composed of: an electromagnet, a spring, a plate movable in translation and fixed in rotation, provided with a coating of material with a high coefficient of friction, and a turntable connected to the motor shaft. When the motor is stopped, the coil of the electromagnet is not electrically powered, and the movable plate exerts via the spring a pressure on the turntable, so a braking torque on the geared motor . On the other hand, when the motor is electrically powered, the electromagnet attracts the mobile plate by compressing the spring, which frees the turntable which can then rotate freely. The setting of the spring, that is to say the force it exerts according to the displacement it undergoes, makes it possible to adjust the braking torque as well as exerted on the mechanism of orientation of the crane. In the case of a plurality of orientation geared motors, at least one of them is equipped with such a brake.

dans laquelle :

• Cfr₁ représente le couple de freinage à exercer pour freiner la partie tournante de la grue avec une vitesse de vent V1,
• Cfl₁ représente le couple appliqué à la flèche par un vent de vitesse V1,
• Ccf₁ représente le couple appliqué à la contreflèche par un vent de vitesse V1,
• Ccou représente le couple de frottement de la couronne.

In operation, the crane must be able to work up to a wind speed defined by standards, for example a speed of 72 km / h, this speed limit being designated by V1. It is therefore necessary that the brake of the steering mechanism takes up the difference in torque between the arrow and the counterpart of the rotating part, taking into account the friction torque of the crown. In other words, the braking torque must check the following inequality: $${\mathrm{cf.}}_1>{\mathrm{cfl}}_1-{\mathrm{ccf}}_1-\mathrm{Ccou}$$

in which :

• Cfr ₁ represents the braking torque to exert to brake the rotating part of the crane with a wind speed V1,
• Cfl ₁ represents the torque applied to the boom by a wind speed V1,
• Ccf ₁ represents the torque applied to the counterfleche by a wind speed V1,
• Ccou represents the friction torque of the crown.

Outside working periods, so when they are "out of order", tower cranes are usually put in wind vane, that is to say that we let the rotating part to move freely according to the wind direction in which case the counterfleche is placed against the wind and the arrow is moving in the direction of the wind. The weather vane crane ensures stability when exposed to storm winds, that is to say winds above the speed limit V1 previously mentioned.

To allow the crane to go into a wind vane, the crane operator disengages the engine brake from the steering mechanism when he leaves his workstation. French patent FR 2135689 describes such a brake and its control suitable for the weather vane of a tower crane.

dans laquelle :

• Cfl₁ représente le couple appliqué à la flèche par un vent de vitesse V1,
• Ccf₁ représente le couple appliqué à la contreflèche par un vent de vitesse V1,
• Ccou représente le couple de frottement de la couronne.

In order for the rotating part of a tower crane to necessarily turn into a wind vane, as soon as the wind speed exceeds the maximum value allowed by the standards for the use of the crane (speed V1), it is necessary that the torque exerted by the wind on the boom, reduced by the torque exerted by the wind on the counterfleche, is greater than the friction torque of the crown. In other words, the inequality should be verified: $${\mathrm{cfl}}_1-{\mathrm{ccf}}_1>\mathrm{Ccou}$$

in which :

• Cfl ₁ represents the torque applied to the boom by a wind speed V1,
• Ccf ₁ represents the torque applied to the counterfleche by a wind speed V1,
• Ccou represents the friction torque of the crown.

If this inequality is not verified, increase the area of the boom exposed to the wind, for example by adding vertical plates in the boom.

When the tower crane is installed in a non-built site and the wind is steady, the boom and the counter-baffle are exposed to the same wind speed. The surface of the arrow exposed to the wind being greater than that of the counterfleche (by construction or by adding plates in the arrow if necessary), when the rotating part is allowed to evolve freely, it turns in the wind bed. , the arrow moving in the direction of the wind.

Nevertheless, when the tower crane is installed in a disturbed environment, the speed of the wind striking the counterfleche can be very different from the speed of the wind simultaneously striking the boom. The difference between the torque applied to the boom and the torque applied to the counterfleche then becomes much greater than the friction torque of the crown, so that the rotating part of the crane, instead of getting into the wind bed, is to turn in a certain direction, without stopping. As a result, the crane fails to prop up properly, and its rotating part is driven in an uncontrolled rotation. Under such conditions, there is a risk of falling of the crane, especially if a gust of wind hits the rotating part when it is oriented perpendicular to the direction of the wind.

Such disturbed conditions may occur, in particular, if the crane is installed in an urban environment that creates an influence of neighboring buildings, or near a cliff, or in a valley, or near central cooling towers. electric, etc.

The present invention therefore aims to prevent the uncontrolled rotation of the rotating part of a tower crane, when it is installed on a site subject to disturbed winds, corresponding in particular to the implantations previously listed, this for avoid any risk of falling of the crane, the proposed solution consisting of an improved control of the crane's weather vane.

dans laquelle :

• Cfl₂ représente le couple appliqué à la flèche par un vent de vitesse V2 inférieure à la vitesse maximale V1 autorisée pour le travail de la grue,
• Ccf₂ représente le couple appliqué à la contreflèche par le même vent de vitesse V2 inférieure à la vitesse maximale V1,
• Ccou représente le couple de frottement de la couronne d'orientation de la partie tournante.

To this end, the subject of the invention is a method for facilitating the weather vane of a tower crane in a disturbed wind, the tower crane comprising a rotating part composed of an arrow and a counterfleche, and a rotation mechanism of the rotating part including at least one geared motor with a deactivated brake when the crane is turned off, to then allow the free orientation of the rotating part in the direction of the wind, this method being characterized by the fact that when the crane is put out of service, it is exerted on its rotating part a braking torque (Cfr ₂ ) given by the formula: $${\mathrm{cf.}}_2={\mathrm{cfl}}_2-{\mathrm{ccf}}_2-\mathrm{Ccou}$$

in which :

• Cfl ₂ represents the torque applied to the boom by a wind speed V2 lower than the maximum speed V1 allowed for the work of the crane,
• Ccf ₂ represents the torque applied to the counterfleche by the same wind speed V2 lower than the maximum speed V1,
• Ccou represents the friction torque of the turning ring of the rotating part.

Thus, the idea underlying the invention is to avoid the uncontrolled rotation of the rotating part of the tower crane, limiting the speed of winding of this rotating part by a specific braking system entering into action only when the crane is put out of service, and then creating a permanent braking torque, which opposes a possible significant difference in torque between the boom and the counterflash.

The invention also relates to a device for implementing the method defined above, this device being a rotation mechanism of the rotating part of the crane, with at least one geared motor, mechanism essentially characterized by the fact that the geared motor of the rotation mechanism of the rotating part, or at least one geared motor in the case of a plurality of geared motors, is equipped with a brake which is activated when the crane is put out of service, this brake then exerting the braking torque Cfr ₂ given by the formula: $${\mathrm{cf.}}_2={\mathrm{cfl}}_2-{\mathrm{ccf}}_2-\mathrm{Ccou}\mathrm{.}$$

Thus, the device of the invention consists of a rotation mechanism of which the orientation geared motor, or at least one of the geared motors, is equipped with a specific brake which controls the setting wind vane, for example by slowing down from a wind speed of 55 km / h, which in all cases must be less than the maximum speed allowed for the work of the crane.

In one embodiment of the device of the invention, in particular in the case of a rotation mechanism with a single geared motor orientation of the rotating part of the crane, with internal brake to this geared motor and deactivated when the crane is put when not in use, the additional brake activated when the crane is put into service to exert the braking torque Cfr ₂ , is an external brake, interposed between the output of the reduction gear of the geared motor, on the one hand, and a pinion which is in taken with a gear wheel of the slewing ring, on the other hand. The device thus remains a simple and compact structure, and it does not require any modification of the gearmotor itself with its integrated master brake.

According to another embodiment of this device, in the case of a plurality of geared motors for orienting the rotating part of the crane, only one of these geared motors of the rotation mechanism comprises an internal brake deactivated when the crane is put out of service, and at least one other geared motor orientation of the same rotation mechanism comprises the aforesaid brake which is activated when the crane is put out of service, the latter brake then exerting the braking torque Cfr ₂ . This solution can avoid the use of an external brake, the unused brake of one of the orientation geared motors being used to brake the rotating part in order to control the wind vane, according to the method of the invention.

• Figure 1 est un schéma illustrant, en vue en plan par-dessus, l'action du vent sur la partie tournante d'une grue à tour ;
• Figure 2 est une vue partielle, de côté, de la partie tournante d'une grue à tour équipée du dispositif de l'invention ;
• Figure 3 représente, très schématiquement, le dispositif de l'invention associé à un motoréducteur d'orientation.

The invention will be better understood with the aid of the description which follows, with reference to the attached schematic drawing showing, by way of example, an embodiment of this device to facilitate the weather vane of a tower crane. in a disturbed wind:

• Figure 1 is a diagram illustrating, in plan view over, the action of the wind on the rotating part of a tower crane;
• Figure 2 is a partial view, from the side, of the rotating part of a tower crane equipped with the device of the invention;
• Figure 3 represents, very schematically, the device of the invention associated with an orientation geared motor.

Referring to figures 1 and 2 , the rotating part 2 of a tower crane consists of an arrow 3 and a counter-flange 4, aligned on either side of an orientation ring 5 of vertical axis which overcomes the vertex 6 of the mast (not shown itself) of the crane. The ring 5 itself consists of two rings, a fixed ring connected to the top 6 of the mast, and a movable ring connected to the rotating part 2, the fixed ring forming an outer gear 7. An electric geared motor 8, secured of the rotating part 2, is coupled to a pinion 9 of vertical axis, which meshes with the toothed wheel 7.

In a known manner, as shown by figure 3 , the geared motor 8 comprises an electric motor 10, a gear reducer 11 and an internal brake 12, which is automatically actuated when the motor 10 is not powered, but is disabled when the crane is not in use.

According to the invention, an external additional brake 13 is interposed between the output of the gearbox 11 and the pinion 9 which is in engagement with the toothed wheel 7 of the ring gear 5. This external brake 13 comes into action only when the crane is set out of order, to exercise a minimal braking torque on the rotating part 2, and thus avoid an uncontrolled weather vane in case of disturbed wind. In practice, at the end of his working day, the crane operator puts the crane in a wind vane by disabling the internal brake 12 of the geared motor 8 and then activating the external brake 13 to allow it to exert its braking torque.

• un couple Cfl appliqué par le vent sur la flèche 3, et
• un couple Ccf appliqué par le vent sur la contreflèche 4.

Referring again to the figure 1 , a wind of a certain speed and direction, indicated by the arrow V, exerts on the rotating part 2 of the tower crane two pairs of opposite directions, namely:

• a torque Cfl applied by the wind on the arrow 3, and
• a Ccf couple applied by the wind on the counterfleche 4.

In addition, a Ccou friction torque is to be considered at the orientation ring 5 of the rotating part 2.

dans laquelle Cfl₁ et Ccf₁ représentent les couples appliqués par un vent de vitesse V1 respectivement à la flèche 3 et à la contreflèche 4.The internal brake 12 must take the difference in torque between arrow 3 and counterflash 4, taking into account the friction torque, up to a maximum wind speed V1 defined by the standards, for example a speed of 72 km / h. Thus, the braking torque Cfr ₁ for such a wind speed V1, torque to be exerted by this brake 12, must satisfy the relation: $${\mathrm{cf.}}_1>{\mathrm{cfl}}_1-{\mathrm{ccf}}_1-\mathrm{Ccou}$$

in which Cfl ₁ and Ccf ₁ represent the couples applied by a wind of speed V1 respectively to the arrow 3 and to the counterfleche 4.

dans laquelle :

• Cfl₂ représente le couple appliqué à la flèche par un vent d'une certaine vitesse V2 inférieure à la vitesse maximale V1,
• Ccf₂ représente le couple appliqué à la contreflèche 4 par le même vent d'une certaine vitesse V2 inférieure à la vitesse maximale V1,
• Ccou représente comme précédemment le couple de frottement de la couronne 5.

As for the braking torque noted Cfr ₂ , exerted by the external brake 13 to prevent the uncontrolled rotation of the rotating part 2 of the crane in a disturbed wind, it is given by the following formula: $${\mathrm{cf.}}_2>{\mathrm{cfl}}_2-{\mathrm{ccf}}_2-\mathrm{Ccou}$$

in which :

• Cfl ₂ represents the torque applied to the deflection by a wind of a certain speed V2 lower than the maximum speed V1,
• Ccf ₂ represents the torque applied to the counterfleche 4 by the same wind of a certain speed V2 lower than the maximum speed V1,
• Ccou represents as previously the friction torque of the crown 5.

The wind speed V2 is for example equal to 55 km / h (whereas, in the case taken here for example, the speed V1 is equal to 72 km / h).

To obtain the braking torque Cfr ₂ respecting the indicated relationship, it is sufficient to use an external brake 13 provided with a spring whose expansion force gives the desired torque value.

In the case of a crane equipped with two or more rotational geared motors of the rotating part, it is provided, contrary to the foregoing description, that only one of these geared motors comprises an internal brake used to brake the rotating part 2 of the rotating part. crane during crane service, when the rotating part is not rotated, this brake being deactivated when the crane is not in use. At least one other of the orientation geared motors comprises, in place of such a brake, another internal brake which is designed, in particular by the choice of the force of sound or its springs, to create the braking torque Cfr ₂ (which corresponds to the torque created by the external brake 13 in the previous example). In other words, it is only when the crane is equipped with a single geared orientation that must be inserted an external brake.

• en modifiant le nombre des motoréducteurs du mécanisme de rotation de la partie tournante de la grue ;
• en associant, au motoréducteur ou à chaque motoréducteur d'orientation, un ou des freins d'un autre type ;
• en dimensionnant ces freins pour d'autres valeurs critiques de la vitesse du vent, les vitesses de 72 km/h et 55 km/h n'étant que des exemples donnés à titre explicatif.

It is not departing from the scope of the invention, as defined in the appended claims:

• by modifying the number of geared motors of the rotation mechanism of the rotating part of the crane;
• by associating, with the gearmotor or with each orientation gearmotor, one or more brakes of another type;
• sizing these brakes for other critical values of the wind speed, speeds of 72 km / h and 55 km / h are just examples given for explanatory purposes.

Claims (4)

A method for facilitating the vane weathering of a tower crane in a disturbed wind, the tower crane comprising a rotating part (2) consisting of an arrow (3) and a counter-flech (4), and a rotation mechanism rotation of the rotating part (2) including at least one geared motor (8) with a brake (12) deactivated when the crane is put out of service, to then allow the free orientation of the rotating part (2) in the direction of the wind ( V), characterized in that, when the crane is put out of service, it is exerted on its rotating part (2) a braking torque (Cfr ₂ ) given by the formula: $${\mathrm{cf.}}_2>{\mathrm{cfl}}_2-{\mathrm{ccf}}_2-\mathrm{Ccou}$$

in which : - Cfl ₂ represents the torque applied to the boom (3) by a wind speed (V2) lower than the maximum speed (V1) allowed for the work of the crane, - Ccf ₂ represents the torque applied to the counterfleche (4) by the same speed wind (V2) lower than the maximum speed (V1), - Ccou represents the friction torque of the slewing ring (5) of the rotating part (2). Device for carrying out the method according to claim 1, in the form of a rotation mechanism of the rotating part (2) of the crane, with at least one geared motor (8), characterized in that the geared motor (8) of this rotation mechanism of the rotating part (2), or at least one geared motor in case of plurality of geared motors, is equipped with an additional brake (13) which is activated when the crane is put out of service, the brake (13) exerting then the braking torque (Cfr ₂ ) given by the formula $${\mathrm{cf.}}_2>{\mathrm{cfl}}_2-{\mathrm{ccf}}_2-\mathrm{Ccou}$$

Device according to claim 2, characterized in that, in particular in the case of a rotation mechanism with a gearmotor (8) for single orientation of the rotating part (2) of the crane, with brake (12) internal to this geared motor (8) and deactivated when the crane is put out of service, the additional brake (13), activated when the crane is put out of service to exercise the braking torque (Cfr ₂ ), is an external brake interposed between the output of the crane. gearbox (11) of the geared motor (8), on the one hand, and a pinion (9) which is in engagement with a gear wheel (7) of the slewing ring (5), on the other hand. Device according to Claim 2, characterized in that, in the case of a rotation mechanism with a plurality of geared motors for orienting the rotating part (2) of the crane, only one of these geared motors of the rotation mechanism comprises a internal brake deactivated when the crane is put out of service, and at least one other geared motor has the aforementioned brake which is activated when the crane is put out of service, this brake exerting then the braking torque (Cfr ₂ ).

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