WO2025093578A1 - System for anchoring a cable - Google Patents

Abstract

The invention relates to a system for anchoring a cable (3), comprising: - a frame (2); - a drum (1) rotatably mounted on the frame about an axis of rotation (X), the drum having a lateral surface (S) about an axis (Y) parallel to the axis of rotation (X), the drum being suitable for allowing the cable to travel by winding and/or unwinding the cable along a portion of the lateral surface, by rotation of the drum about the axis of rotation (X) in response to a variation in the mechanical tension of the cable; - at least one torsion spring (10a, 10b, 10c, 10d) arranged between the drum and the frame so as to compensate for the variation in the tension of the cable.

Description

Cable anchoring system

TECHNICAL FIELD

The invention relates to a system for anchoring a cable, a lifting device comprising such an anchoring system and a lifting machine comprising said anchoring system.

STATE OF THE ART

Container lifting and handling can be implemented using a gripping frame, commonly called a "spreader", connected by cables to a crane, typically a "Ship to Shore" (STS) crane, i.e. from the ship to the quay, for unloading containers from a ship or reloading containers onto a ship. Motors mounted on the crane allow the gripping frame to be raised or lowered by means of the cables. Hooking devices (commonly called "twist locks") are also attached to the gripping frame. Opening - or closing - the hooking devices allows a container to be secured - or released. To enable their opening or closing, the hooking devices are commonly powered by a hydraulic unit most often arranged on the gripping frame. The hydraulic unit may further be adapted to force the extension or contraction of the gripping frame in use, so as to adapt said gripping frame for handling containers of different sizes. The hydraulic unit is advantageously powered from the crane via a cable: a first end of the cable is wound around a reel mounted on the crane and a second end of the cable is connected to the gripping frame, advantageously via a chassis (commonly called a "head block") under which said gripping frame is mounted. Alternatively, the hooking members are entirely electric, and their power supply from the crane is also via such a cable. The cable may further comprise a data bus, for example a CAN bus (according to the English acronym "Controller Area Network"), responsible for transmitting the locking or unlocking information to the hooking members as well as any other information necessary for controlling the crane (weighing, lighting, etc.).

In order not to damage the cable, the unwinding and winding of the cable around the reel must allow the cable to be kept taut during all operations of lifting, unloading, loading, etc., of the containers. The unwinding and winding of the cable around the reel, so as to follow the movements of the gripping frame, are most often managed automatically by servo-control of the reel according to a model theoretical which calculates the torque to be applied to the reel depending on the operating phase and the position of the crane on its travel.

However, since the movement of the gripping frame is often managed manually by the crane operator, some movements of the gripping frame cannot be immediately compensated by the reel. This is particularly true in the event of sudden movements of the gripping frame when the frame is subjected to shocks, for example if the container misses the wedge and hits the container carrier's slides.

A cable anchoring system is therefore mounted on the chassis under which the gripping frame is mounted. This anchoring system may comprise a cylindrical drum advantageously mounted to rotate relative to the chassis by means of bearings, for example ball bearings. Under the effect of the tension of the cable, for example in the event of sudden movement of the gripping frame, said drum is rotated about its axis of rotation. The rotational movement of the drum causes the cable to be wound and/or unwound around said drum, thus providing a certain amount of clearance for the cable.

The anchoring system may further comprise a compression spring coupled to one or more dampers, for example hydraulic, metallic or elastic dampers (tensioners), adapted to dampen the movement of the cable. More specifically, when the reel pulls or pushes on the cable and the drum is rotated, the compression spring provides a return force on said drum proportional to the elongation of said compression spring under the effect of the rotation of the drum and the damper absorbs the shock.

However, such anchoring systems, whose footprint is limited by the size of the frame on which they are housed, do not allow sufficient cable movement, particularly in the event of impacts. In fact, the movement offered to the cable by the anchoring system is typically around 40 mm in the direction of cable unwinding when the reel pulls on the cable and 40 mm in the direction of cable winding when the reel releases the tension on the cable. This results in rapid wear of the cable, which requires frequent and costly maintenance operations.

In addition, the compression spring is subject to high stresses and consequently has a short lifespan which can be less than one year of use of the said spring at a rate of approximately 2000 hours of use of the spring per year. It is then necessary to change the anchoring system or replace the spring. The lifespan of the bearings is also less than what could be expected. Furthermore, the compression spring and/or other damping means that the anchoring system may include may prove cumbersome.

BRIEF DESCRIPTION OF THE INVENTION

An aim of the invention is to design a cable anchoring system, preferably adapted to be mounted on a crane chassis intended to support a gripping frame, making it possible to offer greater travel to the cable than the anchoring systems previously described and which remains compact and easy to manufacture.

To this end, the invention proposes a cable anchoring system comprising:

- a chassis,

- a drum rotatably mounted on the chassis around an axis of rotation, the drum having a lateral surface around an axis parallel to the axis of rotation, the drum being adapted to allow movement of the cable by winding and/or unwinding of said cable along a portion of the lateral surface, by rotation of said drum around the axis of rotation in response to a variation in the tension of the cable,

- at least one torsion spring arranged between the drum and the chassis so as to compensate for the variation in cable tension.

Under the effect of the rotational movement of the drum around the axis of rotation, the torsion spring generates a torsion angle around said axis of rotation to compensate for the variation in the cable tension. On the contrary, a compression spring generates an elongation, and to be able to compensate for the variation in the cable tension, said compression spring must be completed with yokes and/or pivot connections. In addition, torsion springs are compact and increasing the travel offered to the cable by winding and/or unwinding said cable around the lateral surface amounts to increasing the angular offset between the extreme torsion angles of said torsion spring, which does not induce any additional bulk or difficulties in the manufacturing of said torsion springs. On the contrary, increasing the travel offered to the cable with a compression spring amounts to increasing the length of said compression spring, therefore its size, and/or bringing said compression spring closer to the axis of rotation, which implies that said compression spring must be able to withstand much greater forces. Such a compression spring is difficult to manufacture. The anchoring system comprising the torsion spring(s) is therefore simpler to manufacture, more adaptable and less bulky.

According to other advantageous but optional features, considered alone or in combination: the at least one torsion spring comprises a first part mounted on the frame and a second part mounted on the drum, the second part being adapted to pivot relative to the first part; the anchoring system comprises at least two torsion springs arranged in series; a first portion of a first spring is mounted on the frame, a first portion of a second spring is mounted on the drum, and a second portion of the first spring is rigidly connected to a second portion of the second spring; each torsion spring comprises a rigid and hollow outer axis, a rigid central axis housed inside the rigid and hollow outer axis, and a damper configured to dampen a torsional movement of the rigid and hollow outer axis relative to the rigid central axis; the damper of the torsion spring comprises a plurality of elastomer elements arranged between the rigid central axis and the rigid and hollow outer axis; each torsion spring comprises a first hollow metal square-based prism forming the rigid and hollow external axis, a second prism forming the central axis arranged in the first prism with an angular offset relative to the first prism, and each elastomer element is a cylinder arranged between the first prism and the second prism, in each corner of the first prism; the anchoring system comprises two torsion springs in series, the second square-based prism of the first torsion spring being connected to the second square-based prism of the second torsion spring; the at least one torsion spring is configured to dampen the forces generated by the rotation of the drum about the rotation axis between a first stop position of the drum and a second stop position of the drum, the first stop position and the second stop position being angularly offset relative to the rotation axis by an angle between 0° and 90°, preferably between 0° and 60°; the anchoring system comprises at least two sets of torsion springs arranged in parallel, a first portion of each set of torsion springs being mounted on the frame and a second portion of each set of torsion springs being mounted on the drum; the anchoring system further comprises a compression spring and/or a tension spring comprising a first portion mounted on the frame and a second portion mounted on the drum.

Another object of the invention relates to a lifting device comprising:

- a gripping frame comprising at least one member for hooking a load to be lifted,

- a cable anchoring system as described above comprising a frame and a drum, the frame being fixed to the gripping frame and the drum being fixed to the frame,

- a reel suitable for being fixed to a lifting device, - a cable, a first end of the cable being anchored to the drum of the anchoring system by fixed winding of at least two turns around the lateral surface of the drum and a second end of the cable being wound around the reel.

Another subject of the invention relates to a lifting machine, such as a crane, a gantry or a forklift, comprising a lifting device as described above.

BRIEF DESCRIPTION OF THE FIGURES

Other characteristics and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings, in which:

- Figures 1A, 1B and 1C illustrate an example of application of a cable anchoring system according to the invention in which said system is fixed to a gripping frame itself mounted on a crane;

- Figures 2A, 2B and 2C represent a particular embodiment of the cable anchoring system according to the invention in which the lateral surface of the drum has a circular shape and an axis of rotation of the drum relative to the chassis passing through the center of the circle: Figure 2A represents the neutral position of the drum, Figure 2B represents the case of the application by the cable of a subtraction on the drum causing the rotation of said drum in the direction of winding of the cable, Figure 2C represents the case of the application by the cable of an overtraction on the drum causing the rotation of said drum in the direction of unwinding of the cable;

- Figures 3A, 3B and 30 represent a particular embodiment of the cable anchoring system according to the invention in which the lateral surface of the drum has a circular shape and an axis of rotation of the drum relative to the chassis offset from the center of the circle: Figure 3A represents the neutral position of the drum, Figure 3B represents the case of the application by the cable of a subtraction on the drum causing the rotation of said drum in the direction of winding of the cable, Figure 30 represents the case of the application by the cable of an overtraction on the drum causing the rotation of said drum in the direction of unwinding of the cable;

- Figures 4A, 4B and 40 represent a particular embodiment of the cable anchoring system according to the invention in which the lateral surface of the drum has an elliptical shape and an axis of rotation of the drum relative to the chassis offset from the center of the ellipse: Figure 4A represents the neutral position of the drum, Figure 4B represents the case of the application by the cable of a subtraction on the drum causing the rotation of said drum in the direction of winding of the cable, Figure 40 represents the case of the application by the cable of an overtraction on the drum causing the rotation of said drum in the direction of unwinding of the cable; - Figure 5 represents a cable anchoring system in which said system comprises a drum having an elliptical shape and an axis of rotation offset from the center of the ellipse as well as a compression spring adapted to dampen a movement of the cable by winding and/or unwinding the cable around a portion of the ellipse;

- Figure 6 represents a particular embodiment of a torsion spring comprising a first prism with a hollow metal square base, a second prism with a hollow metal square base housed inside the first prism with an angular offset relative to the first prism, and four elastomer cylinders arranged between the first prism and the second prism, in the corners of the first prism;

- Figures 7A, 7B, 7C and 7D represent a particular embodiment of the anchoring system of the invention in which said system comprises a drum having an elliptical shape and an axis of rotation offset from the center of the ellipse as well as two sets of torsion springs adapted to dampen a movement of the cable by winding and/or unwinding the cable around a portion of the ellipse and arranged along the axis of rotation of the drum so as to allow the rotation of said drum relative to the chassis, each set of torsion springs comprising two torsion springs mounted in series, Figure 7B representing the neutral position of the drum, Figure 7C representing the case of the application by the cable of a sub-traction on the drum causing the rotation of said drum in the direction of winding the cable, Figure 7D representing the case of the application by the cable of an over-traction on the drum causing the rotation of said drum in the direction of unwinding the cable;

- Figure 8 represents a particular embodiment of the anchoring system according to the invention in which the at least one torsion spring is a metal spring, the anchoring system further comprising a shaft and a bearing, the shaft and the bearing being configured to guide the rotation of the drum relative to the chassis around its axis of rotation.

For readability reasons, the drawings are not necessarily drawn to scale.

DETAILED DESCRIPTION OF EMBODIMENTS

The invention relates to a cable anchoring system comprising a frame and a drum, the drum being adapted to be mounted on the frame and anchor the cable on said frame.

With reference to Figures 1A, 1B and 1C, the chassis 2 is preferably a chassis adapted to be mounted on a gripping frame 4, said gripping frame 4 comprising one or more hooking members 5, said hooking members being adapted for gripping a load. The hooking members 5 of the gripping frame 4 may comprise, for example, four rotating locks adapted for gripping a container. When in use, the gripping frame 4 is connected to a lifting machine 6, for example a crane, by means 7 for lifting said gripping frame 4, said lifting means 7 being adapted to allow the movement of the gripping frame 4 relative to the lifting machine 6, typically the raising or lowering of said gripping frame 4, said movement being able to be controlled remotely by an operator, for example a crane operator positioned in the control cabin or in a control room from where he controls several cranes alternately. Alternatively, said movement can be managed completely automatically without the intervention of said operator. The lifting means 7 of the gripping frame 4 may comprise ropes and one or more motors mounted on the lifting machine 6.

According to an embodiment not shown in Figures 1A, 1B and 1C, a second gripping frame can be connected to the lifting machine 6 by means for lifting said second gripping frame, said lifting machine 6 further comprising an intermediate platform. Such a configuration is particularly advantageous when the lifting machine is an STS crane: the gripping frame 4 is used to move a container between the ship and the platform while the second gripping frame is used to move said container between the platform and the quay.

Cable 3 comprises one or more conductive links for the transfer of power and/or data. Each conductive link may be in the form of an electrically conductive wire, an optical fiber, or any other suitable form. Preferably, the cable comprises at least one conductive power supply link and one conductive control link for the attachment members 5 of the gripping frame 4. When the drum 1 is in use, that is to say when the drum 1 is mounted on the chassis 2, the chassis 2 mounted on a gripping frame 4 and the gripping frame 4 connected to a lifting machine 6, a first end of the cable is anchored to the chassis 2 via the drum 1 and a second end of the cable 3 is wound around a reel mounted on the lifting machine 6. More specifically, the drum according to the invention comprises a lateral surface (S) located around an axis (Y), so that when the drum 1 is in use, the first end of the cable 3 is wound around said lateral surface (S).

The reel mounted on the lifting equipment is typically an electronically controlled reel comprising a motor which winds or unwinds the cable so as to keep the cable taut whatever the operating phase of the gripping frame (for example during ascent, descent, start-up or stop phases). A control unit calculates a torque setpoint to be applied according to said operating phase. The torque value must be high enough to keep the cable taut without as much as damaging the cable. The torque setpoint is sent to a frequency converter which translates said torque setpoint into current to be imposed on the motor. A variation in the torque setpoint, for example when the position of the gripping frame changes or the operating phase changes, causes a variation in the motor current. Such a control loop has a non-zero reaction time which is the sum of at least one reaction time linked to the electronics and one reaction time linked to the transformation of the setpoint into current. The reaction time linked to the electronics is estimated to be around 75 ms. This reaction time does not allow the reel to respond quickly enough in certain situations, for example during sudden movements of the gripping frame, for example in the event of shocks or gusts of wind, thus generating tension in the cable.

The drum 1 is therefore adapted to be rotatably mounted on the chassis 2 around an axis of rotation (X) parallel to the axis (Y), so that when the drum 1 is in use, the drum 1 can be freely rotated around the axis of rotation (X) under the effect of a tension in the cable 3 not immediately compensated by the reel, thus allowing movement of the cable 3 by winding and/or unwinding said cable around the lateral surface (S) along a portion of the lateral surface (S).

More specifically, the drum, in a position described as neutral, may be subjected to a tensile force from the cable due to the torque imposed on said cable by the reel, allowing said cable to be kept taut. Mechanical tension of the cable is understood as a variation in the traction applied by the cable to the drum compared to the traction applied to said drum in the neutral position. This may be under-traction (configuration corresponding to a slack cable) or over-traction (configuration in which the reel pulls on the cable with a traction higher than the theoretical resultant of the setpoint). Such mechanical tension will cause a rotational movement of the drum around the axis of rotation (X) compared to this neutral position. In the case of under-traction, the rotational movement around the axis of rotation (X) will be in the winding direction to take up the slack cable until eventually reaching a first stop position. In the case of over-traction, the rotational movement around the rotation axis (X) will be in the direction of cable unwinding to release the cable until eventually reaching a second stop position.

For example, the first and second stop positions are angularly offset relative to the axis of rotation (X) by an angle between 0° and 60°, preferably by an angle between 0° and 90°. The lateral surface (S) of the drum in a plane (P) perpendicular to the axis of rotation (X) may have a circular shape. Alternatively, the lateral surface (S) may have in the plane (P) an ovoid or elliptical shape, or any other shape whose radius of curvature is not constant.

The axis of rotation (X) may intersect the plane (P) at the center of the circle of radius equal to the radius of curvature of the portion of the lateral surface along which the cable is wound and/or unwound and tangent to said portion. For example, if the lateral surface has a circular shape in the plane (P), the axis of rotation (X) may intersect the plane (P) at the center of the lateral surface.

Alternatively, the rotation axis (X) can intersect the plane (P) at any other point on the plane (P).

Figures 2A, 2B and 2C represent a particular example of a drum in use on a chassis, in which said drum has a circular shape in the plane (P) and the axis of rotation (X) intersects the plane (P) at the center of the circle. In particular, Figure 2A represents the configuration in which the drum is in a neutral position. Figure 2B represents the case of under-traction of the cable: the drum rotates from said neutral position in the direction of winding of said cable around the axis of rotation (X) to wind the slack cable. Figure 2C represents the case of over-traction of the cable: the drum rotates from the neutral position in the direction of unwinding of the cable around the axis of rotation (X) to unwind the cable.

Figures 3A, 3B and 3C represent another particular example of a drum in use on a chassis, in which said drum always has a circular shape in the plane (P) but the axis of rotation (X) does not intersect the plane (P) at the center of the circle. In particular, Figure 3A represents the configuration in which the drum is in the neutral position. Figure 3B represents the case of under-traction of the cable. Figure 3C represents the case of over-traction of the cable.

As another example, Figures 4A, 4B and 4C represent a case in which said drum has the shape of an ellipse in the plane (P) and the axis of rotation (X) does not intersect the plane (P) at the center of the ellipse, but at the center of the circle with a radius equal to the radius of curvature of the portion of the lateral surface (S) for winding and/or unwinding the cable and tangent to said portion. Figure 4A represents the neutral position of the drum, Figure 4B the case of under-traction of the cable and Figure 4C the case of over-traction of the cable. Preferably, the drum is arranged so that during use of said drum, a first part of the first end of the cable remains wound around said surface (S) in all phases of use of the chassis, and a second part of said cable in the extension of the first part winds and/or unwinds along the portion of the lateral surface (S) due to the rotational movement of the drum around the axis of rotation (X) between the first and second stop positions. By way of example, the first part of the first end of the cable has a length at least equal to two complete turns of the surface (S), preferably greater than two and a half turns. The first part of the first end is advantageously long enough to cancel the tension of the cable at the end of said cable by a so-called capstan effect. In a manner known per se, the capstan effect establishes the relationship between a holding force applied to one end of a cable wound around the lateral surface of a pad, for example a pad of circular section or a pad of non-circular section (for example an elliptical section), and a load force applied to an opposite end of said cable, which depends on the coefficient of friction of the cable on the lateral surface of the pad.

The anchoring system according to the invention further comprises at least one torsion spring arranged between the drum and the frame. When a sudden tension of the cable on the drum causes the drum to rotate around said axis of rotation (X) in the direction of winding or unwinding of the cable (where the sudden tension of the cable is understood as a variation in mechanical tension relative to the equilibrium tension making it possible to keep the cable taut), the torsion spring is configured to generate a return force on said drum which tends to compensate for said variation in tension. Thus, via the drum, the torsion spring makes it possible to limit the tensions in the cable and to keep the cable taut, and thus to avoid damage to the cable. Preferably, the torsion spring or the set of torsion springs generates all of the return forces on the drum. Alternatively, the anchoring system may further comprise a compression spring and/or a tension spring, such that said compression spring and/or said tension spring generate at least part of the return forces on the drum.

More specifically, under the effect of the mechanical tension of the cable and the resulting rotational movement of the drum around the rotation axis (X), each torsion spring deforms, generating a torsion angle and therefore a return force on the drum proportional to said torsion angle which tends to cancel said torsion angle and return the drum to its initial position. In the direction of winding the cable, the torsion spring can deform until it reaches a first limit torsion angle. In the direction of unwinding the cable, the torsion spring can deform until it reaches a second limit torsion angle. In a variant, the first limit torsion angle and the second limit torsion angle are limit torsion angle correspond respectively to a first stop position and a second stop position of the drum rotating around the axis of rotation (X). In other words, the rotation of the drum around the axis of rotation (X) is blocked in one direction by the torsion spring when the torsion spring has reached the first limit torsion angle and the rotation of the drum is blocked in the other direction when the torsion spring has reached the second limit torsion angle. In a preferred variant, the first stop position and the second stop position are reached by the drum rotating around the axis of rotation (X) slightly before the torsion spring reaches its first limit torsion angle and its second limit torsion angle. Such an embodiment advantageously makes it possible not to wear the torsion spring too quickly. In practice, the first stop position and the second stop position can be fixed by external mechanical stops, for example progressive rubber stops well known to those skilled in the art which will absorb the shock when the drum reaches its stop position. Typically, the first - respectively second - stop position and the first - respectively second - limit torsion angle are angularly offset by approximately 4°.

The arrangement of the torsion spring(s) between the drum and the frame may be such that each torsion spring is in the middle of its deformation range when the drum is in the neutral position. This provides equivalent travel in the direction of cable winding and in the direction of cable unwinding.

For example, if the first and second stop positions are angularly offset relative to the axis of rotation (X) by an angle of 90°, the middle of the deformation range of each torsion spring is preferably associated with a drum position at 45°. For example, if the first and second stop positions are angularly offset relative to the axis of rotation (X) by an angle of 60°, the middle of the deformation range of each torsion spring is preferably associated with a drum position at 30°.

A torsion spring advantageously has a smaller footprint than the compression spring conventionally used (see Figure 5 with the compression spring 8 comprising a first part fixed to the frame and a second part fixed to the drum), in particular when the torsion spring is arranged along the axis of rotation (X). Indeed, a compression spring has a limited elongation or compression length: increasing the travel offered to the cable therefore requires either, at a fixed distance between the compression spring and the axis of rotation (X), increasing the length of the compression spring and therefore the footprint of said spring, or bringing the spring closer to the axis of rotation (X). In the latter case, however, the compression spring must be able to withstand a very large force to counterbalance that of the cable. Indeed, the tension of the cable can be of the order of 2000 N in the axis of the cable and the tension on the spring, potentially even greater, is all the stronger the closer the spring is to the axis of rotation. In order to be able to withstand such a force, the compression spring will therefore have to have a greater wire thickness, which also significantly increases its length and therefore its size, but also poses problems with the manufacturability of said compression spring.

Furthermore, the compression spring, like any spring, must preferably be used in its linearity zone without reaching its stop positions in order not to excessively reduce the life of said spring, which requires further increasing the length of said compression spring.

As an example, consider a conventional anchoring system comprising a compression spring with a free length of 240 mm and an 86 mm extension range, in which the position of the compression spring is such that the compression spring must pivot slightly at each of its ends to follow the movement of the drum but where the ratio between the spring travel and the cable travel remains approximately 1:1. Such a cable anchoring system therefore provides a cable travel of around 86 mm. To increase the cable travel to 630 mm without changing the position of the compression spring, it would therefore be appropriate to replace the said 240 mm long compression spring with a compression spring of (240 x 630)/86 mm, or approximately 1.9 m.

Alternatively, if we wanted to maintain an actual spring length of 240 mm while providing a cable travel of 630 mm, we would have to position the compression spring approximately 7 to 8 times closer to the axis of rotation, which would multiply the forces experienced by the compression spring in the same proportions. In such a configuration, the compression spring would necessarily have to have a much larger wire diameter, and therefore ultimately a spring length probably greater than the desired 240 mm. A compression spring with such characteristics is not or very difficult to manufacture. In addition, all the fastening elements of the compression spring subjected to these significant forces would also have to be sized to withstand said significant forces, which would drastically increase the cost of the overall anchoring system. Finally, the risk of failure of such an anchoring system would be very high.

The force experienced by the torsion spring directly generates an angle of rotation and increasing the travel offered to the cable amounts to increasing this angle of rotation, which has no no effect on the space requirement. In addition, the torsion spring can easily be arranged along the rotation axis (X) inside the drum, which results in minimal space requirement.

As previously mentioned, the forces to which the compression spring or at least one torsion spring is subjected on the anchoring system are significant. In order to ensure that the service life of a compression spring used under such conditions is not reduced too much, it is advisable to use said compression spring only within its operating range and to increase the wire diameter of said compression spring. Thus, a compromise is required between the size of the compression spring and the service life of said compression spring. On the contrary, the torsion spring of the anchoring system according to the invention works exactly under the conditions for which it was designed, namely alternating torsions, so that an anchoring system comprising such a torsion spring can achieve longer service lives.

More specifically, in a first embodiment, the anchoring system comprises a torsion spring arranged along the axis of rotation (X). A first part of said torsion spring is mounted on the frame and a second part of said torsion spring is mounted on the drum, the second part being adapted to pivot relative to the first part.

Thus arranged, the first and second stop positions may correspond to the extreme pivoting positions of the second part of the torsion spring relative to the first part. According to a preferred alternative, the first and second stop positions are between the extreme pivoting positions of the second part of the spring relative to the first part (for example by means of external mechanical stops as previously mentioned). Not rotating until reaching the extreme positions in use of the drum advantageously makes it possible not to unnecessarily reduce the service life of the torsion spring.

In a second embodiment of the anchoring system according to the invention, the cable anchoring system comprises at least two torsion springs connected in series and arranged along the axis of rotation (X). In the variant where the anchoring system comprises two torsion springs connected in series, a first part of a first torsion spring can be mounted on the frame, a first part of a second torsion spring can be mounted on the drum, and a second part of the first torsion spring can be rigidly connected to a second part of the second torsion spring, the first part of the first torsion spring - respectively of the second torsion spring - being adapted to pivot relative to the second part of the first torsion spring - respectively of the second torsion spring. For a given lateral surface (S), the arrangement of two torsion springs in series advantageously makes it possible to double the angle between the first and second stop positions relative to the axis of rotation (X) and therefore to increase the length measured in the plane (P) of the portion of the lateral surface (S) along which the cable is wound and/or unwound. In other words, this makes it possible to increase the travel offered to the cable. Thus, if the angle between the first and second stop positions relative to the axis of rotation (X) with a torsion spring is between 0° and 30°, placing two torsion springs in series advantageously makes it possible to increase the angle between the first and second stop positions to an angle between 0° and 60°.

In other variants, the anchoring system comprises at least three torsion springs mounted in series, so as to further increase the angle between the first stop position and the second stop position, and thus the travel offered to the cable. However, in such variants, at least one torsion spring of the series mounting - called the middle torsion spring - is not embedded on either the drum or the frame, so that the torsion springs and the connecting pieces on either side of said middle spring must carry said middle torsion spring and withstand the forces generated by said middle torsion spring. The variant with only two torsion springs in series is therefore the preferred variant.

For example, a clearance angle between the first stop position and the second stop position of between 0° and 60° makes it possible to scan a portion of length of between 0 and approximately 630 mm measured in the plane (P) when the radius of curvature of the portion of the lateral surface (S) measures 575 mm, the diameter of the cable 50 mm and the distance d' measured in the plane (P) between the cable and the straight line of the plane (P) parallel to said cable which intersects the axis of rotation (X) is advantageously equal to the radius of curvature of said portion of the lateral surface (S). Indeed, the arc length of the portion of the cable I can be calculated as follows:

2 x (575 + 25) x 7T x 60 l = - = 628.32 mm = 630 mm

360

Such a length makes it possible to provide the cable with a travel of the order of 300 mm in the direction of winding the cable and 300 mm in the direction of unwinding the cable. Such a travel is considered by the inventors as the ideal travel for the cable from the neutral position. Indeed, the ideal travel allowing the cable to be kept taut so as not to damage it is equal to the product of the maximum speed of the gripping frame by the reaction time of the feedback loop of the electronically regulated reel. The maximum linear speed given by the motors to the gripping frame is typically between 150 m/min or 2.5 m/s and 240 m/min or 4 m/s and the reaction time The reaction of the electronically regulated reel being of the order of 75 ms, the ideal travel from the neutral position is therefore of the order of 300 mm in both the direction of unwinding and winding of the cable onto the drum. The series arrangement of two or more torsion springs advantageously makes it possible to offer the cable such travel while limiting the size. As mentioned previously, such a travel length is not reasonably achievable with a compression spring.

Each torsion spring may comprise a metal spring arranged along the axis (X). For example and as shown in Figure 8, the cable anchoring system comprises a single metal torsion spring 10, a first turn 11a of a first end of said metal spring being rigidly connected to the frame 2 and a second turn 11b of a second end of said spring being rigidly connected to the drum 1. In this configuration, the anchoring system may further comprise a shaft 12 rigidly connected to the frame 2 and oriented along the axis of rotation (X), and a bearing (not shown) rigidly connected to the drum 1. In this way, the bearing and the shaft 12 ensure the rotational guidance of the drum 1 relative to the frame 2 along the axis of rotation (X). Alternatively, the shaft may be rigidly connected to the drum and the bearing rigidly connected to the frame. The shaft 12 is for example arranged inside the turns of the metal torsion spring 10. Preferably, the anchoring system of figure 8 further comprises at least one shock absorber (not shown), for example a hydraulic, pneumatic, metal or elastic shock absorber (tensioners), which makes it possible to absorb shocks.

The first stop position and the second stop position of the drum may be fixed respectively by the first limit torsion angle and the second limit torsion angle of the metal torsion spring 10 (permanent deformation of said spring). Alternatively, the diameter of the shaft 12 may be judiciously chosen, so that the first stop position and the second stop position correspond to the torsion angles of the torsion spring 10 at which said torsion spring is "locked" by the shaft 12. In a preferred variant, the cable anchoring system further comprises at least two mechanical stops which block the rotation of the drum before the single metal spring 10 reaches the first limit torsion angle and the second limit torsion angle. Each mechanical stop comprises, for example, a first part secured to the chassis and a second part secured to the drum: when the drum rotates around the rotation axis (X), the second part of the mechanical stop comes to block against the first part of the mechanical stop, thus stopping the rotational movement of the drum in a stop position. Preferably, at least one mechanical stop is a progressive rubber stop well known to those skilled in the art. Alternatively and advantageously, each torsion spring may comprise a rigid and hollow external axis, a rigid central axis housed inside the rigid and hollow external axis, and a damper configured to dampen a torsional movement of the rigid and hollow external axis relative to the rigid central axis. On the anchoring system, the rigid central axis and the rigid and hollow external axis are oriented along the axis of rotation (X).

In the particular configuration where the anchoring system comprises a single torsion spring comprising a rigid and hollow external axis, a rigid central axis housed inside the rigid and hollow external axis, and a damper as previously described, the rigid central axis can be mounted on the drum and the rigid and hollow external axis can be mounted on the chassis, so that the twisting / pivoting of the rigid and hollow external axis relative to the rigid central axis along the axis of rotation (X) ensures the rotational guidance of the drum relative to the chassis along the same axis. In other words, the torsion spring plays in this configuration the dual role of bearing to guide the rotational movement of the drum relative to the chassis and of damper of the forces generated by said movement. Alternatively, the rigid central axis can be mounted on the chassis and the rigid and hollow external axis can be mounted on the drum.

Such a torsion spring comprising a rigid central axis housed inside a rigid and hollow external axis therefore advantageously makes it possible not to use other means of rotating the drum relative to the chassis such as rolling bearings or bushings (see Figure 5 in which rolling bearings 9 are used in conjunction with the compression spring 8, the rolling bearings 9 allowing the drum to rotate around the axis of rotation (X) and the compression spring damping said movement). Indeed, said rolling bearings or bushings are not suitable for the conditions of use of the anchoring system mounted on a gripping frame (permanent work on a limited angle of rotation without ever making complete turns, numerous vibrations) and wear quickly, limiting the service life of the anchoring system. Alternatively, the choice can be made to oversize the rolling bearings - in other words to use larger bearings with larger balls - so that said rolling bearings are able to withstand the high static loads to which they are subjected on the anchoring system in operation, due to working on a limited rotation angle, without excessively reducing the service life of the anchoring system. However, bearings thus oversized are more expensive and more bulky. On the contrary, torsion springs, conventionally used in vibratory mounts, are perfectly suited to such operating conditions. Preferably, the torsion spring damper comprises a plurality of elastomer elements arranged between the rigid central axis and the rigid external axis, for example four elastomer elements.

An elastomer is an elastic polymer material. Natural or synthetic rubber and neoprene are examples of elastomers within the meaning of the present invention.

Torsion springs with elastomer elements have several advantages over metal springs. For example, torsion springs with elastomer elements have been specifically designed to withstand and absorb permanent vibrations and shocks, which are the conditions typically encountered by the spring when mounted on the chassis in use on a lifting device. In comparison, steel springs, under the same conditions of permanent vibrations and shocks, quickly show their limitations: permanent stress induces cracks much more quickly on metal springs than on elastomer elements. Thus, the torsion spring with elastomer elements wears less quickly than steel springs.

Furthermore, elastomer elements have very low sensitivity to corrosion. Thus, springs comprising elastomer elements require very little maintenance and their service life is not reduced even when used in a corrosive atmosphere, for example at the seaside. In comparison, the metal spring, in particular the compression spring, is much more sensitive to corrosion and paint treatments are not sufficient to improve corrosion resistance satisfactorily: an impact, a notch or a lack of paint adhesion may be enough to initiate the corrosion phenomenon and cracking of the metal. Other known physicochemical processes aimed at increasing corrosion resistance, in particular processes involving heating, are prohibited so as not to harm the characteristics of the material, in particular its ability to withstand regular deformations in compression or elongation.

It is possible to dimension such a torsion spring with elastomer elements, in particular by the choice of the material and the dimensions of the elastomer elements, so as to obtain the angle between the first stop position and the second stop position desired, for example 30°, or even 45°, and so that said torsion spring is able to withstand the forces to which it will be subjected in use on the lifting equipment without impacting on the size of said torsion spring on the chassis and without harming the manufacturability of said torsion spring. In the case of the compression spring, increasing the strength of the spring compression involves increasing the diameter of the compression spring wire and therefore its size as well as its manufacturing difficulty.

Finally, unlike a metal spring, a torsion spring comprising elastomer elements is more resistant to overloads than a metal spring and the failure of an elastomer element allows it to continue operating in degraded mode, whereas the breakage of the metal spring of a torsion spring or a compression spring, which is unique, immediately stops the system. Operation in degraded mode allows it to continue operating, possibly at reduced speed, while the replacement of the faulty part is organized.

Each elastomer element not only serves as a spring generating a restoring force proportional to the torsion angle which compensates for the variation in forces in the cable, but also as a shock absorber generating a dissipative force proportional to the speed of the torsion movement which makes it possible to avoid reaching the stops at full speed. Thus, and unlike the compression spring and the metal torsion spring, the torsion spring comprising such elastomer elements advantageously makes it possible not to require the addition of another shock absorber such as a hydraulic, pneumatic, metal or elastic shock absorber (turnbuckles).

More specifically, with reference to Figure 6, each torsion spring 10 may comprise a first prism 11 with a hollow metal square base, a second prism 12 with a hollow metal square base housed inside the first prism 11 with an angular offset relative to the first prism 11 forming the central axis, and each elastomer element may be an elastomer cylinder 13 arranged between the first prism 11 and the second prism 12, in each corner of the first prism. In this case, the first prism 11 may be rigidly connected to the chassis - reciprocally to the drum - and the second prism 12 to the drum - reciprocally to the chassis. Such a configuration of the torsion spring comprising a second prism housed inside a first prism and an elastomer element in each corner of the first prism advantageously makes it possible to obtain a large angle of travel, of the order of 30° per torsion spring.

In the particular configuration in which two torsion springs are connected in series, the second inner prism 12 of the first torsion spring can be connected to the second inner prism 12 of the second torsion spring. The first outer prisms 11 of the first and second torsion springs can be connected to the drum and the frame respectively. Such a configuration of the first prisms 11 and second prisms 12 is particularly advantageous, since each first prism 11 can be very easily fixed to the drum, respectively to the frame, for example by means of a rider and two assemblies comprising bolts or rivets or a weld. Furthermore, the second prisms 12 can be easily connected by techniques known to those skilled in the art, for example by means of a square-based shaft and two axial stops.

Alternatively, the first prism 11 of the first torsion spring may be connected to the first prism 11 of the second torsion spring and the second prism 12 of the first torsion spring and the second prism 12 of the second torsion spring may be connected to the drum and the frame respectively.

Alternatively, the first prism 11 of the first torsion spring can be connected to the frame, respectively to the drum, and the second prism 12 of the second torsion spring can be connected to the drum, respectively to the frame, the second prism 12 of the first torsion spring being connected to the first prism 11 of the second torsion spring.

Torsion springs for both guiding the rotation of the drum around the axis of rotation (X) and compensating for variation in cable tension are not limiting to the scope of the invention. The invention extends to any anchoring system comprising a torsion spring configured to guide the rotation of the drum and compensate for variation in cable tension.

In addition to the embodiments of the cable anchoring system previously described, each spring may comprise two sets of springs mounted in parallel, a first part of the first set of springs and the second set of springs being connected to the frame and a second part of the first set of springs and the second set of springs being connected to the drum, each of the first and second sets of springs being able to be understood as a single spring or as at least two springs mounted in series. For the same rotation angle of the drum around the axis (X), the parallel mounting advantageously makes it possible to double the force of the springs. In addition, the parallel mounting makes it possible to distribute the forces taken up on the frame on either side of the drum and thus to minimize the shear forces on the springs.

As an example, Figures 7A to 7D show the particular configuration in which the spring comprises a first set of springs consisting of a first torsion spring 10a connected in series with a second torsion spring 10b and a second set consisting of a third torsion spring 10c connected in series with a fourth torsion spring 10d, the first set and the second set of springs being connected in parallel with each other. Furthermore, the four springs are arranged along the axis of rotation (X). In particular, Figure 7B represents the configuration in which the drum is in the neutral position. Figure 7C represents the case of under-traction of the cable. Figure 7D represents the case of over-traction of the cable.

In Figure 7A, such a configuration of torsion springs is shown in combination with a particular embodiment of the drum according to which said drum has in the plane (P) an elliptical shape and the axis of rotation (X) intersects said plane (P) at the center of the circle tangent to the winding and/or unwinding portion of the cable with a radius equal to the radius of curvature of said portion. Nevertheless, any combination of torsion spring in combination with a drum having any other shape remains within the scope of the invention.

As previously mentioned, the first stop position and the second stop position may correspond to the limit torsion angles of the torsion spring or of the set of torsion springs. Alternatively, the first stop position and the second stop position may be slightly offset so as to never reach the limit torsion angles of the torsion springs, for example by means of mechanical rubber stops as previously described.

The invention also relates to a lifting device comprising:

- a gripping frame,

- an anchoring system comprising a chassis and a drum as previously described, the chassis being fixed to the gripping frame and the drum to the chassis,

- a reel suitable for attachment to the lifting equipment,

- a cable, a first end of the cable being anchored to the drum of the anchoring system by fixed winding of at least two turns around the lateral surface of the drum and a second end of the cable being wound around the reel.

Finally, the invention relates to a lifting machine comprising a lifting device as previously described. According to a particular embodiment of the invention, the lifting machine is a crane, a gantry or a forklift. The lifting machine is for example a crane used for loading or unloading containers on a container ship.

According to a particular embodiment of the lifting machine, said lifting machine comprises, in addition to the lifting device as previously described, a second gripping frame and an intermediate platform. For example, the lifting machine is an STS crane and the gripping frame of the lifting device is used to move a container between the ship and the intermediate platform while the second gripping frame is used to move said container between the platform and the quay.

In a particular embodiment of the lifting device with two gripping frames, the second gripping frame is included in a second lifting device, said second lifting device being able to be produced according to any one of the lifting device embodiments previously described.

Alternatively, the lifting device does not include a second reel, so that the second gripping frame is not powered by a cable connected to a reel. For example, the second gripping frame is powered by a second cable deposited in a basket.

Claims

1. Cable anchoring system (3) comprising: - a chassis (2), - a drum (1) rotatably mounted on the chassis around an axis of rotation (X), the drum having a lateral surface (S) around an axis (Y) parallel to the axis of rotation (X), the drum being adapted to allow movement of the cable by winding and/or unwinding of said cable along a portion of the lateral surface, by rotation of said drum around the axis of rotation (X) in response to a variation in the mechanical tension of the cable, - at least one torsion spring (10, 10a, 10b, 10c, 10d) arranged between the drum and the chassis so as to compensate for the variation in the cable tension. 2. A cable anchoring system according to claim 1, wherein the at least one torsion spring comprises a first portion mounted on the frame and a second portion mounted on the drum, the second portion being adapted to pivot relative to the first portion. 3. Cable anchoring system according to claim 1, comprising at least two torsion springs arranged in series. 4. A cable anchoring system according to claim 3, wherein a first portion of a first spring is mounted on the frame, a first portion of a second spring is mounted on the drum, and a second portion of the first spring is rigidly connected to a second portion of the second spring. 5. Cable anchoring system according to one of claims 1 to 4, in which each torsion spring (10) comprises a rigid and hollow external axis (11), a rigid central axis (12) housed inside the external axis (11), and a damper configured to dampen a torsional movement of the rigid and hollow external axis relative to the rigid central axis. 6. Cable anchoring system according to claim 5, wherein the torsion spring damper comprises a plurality of elastomer elements (13) arranged between the rigid central axis (12) and the rigid and hollow external axis (11). 7. A cable anchoring system according to claim 6, wherein each torsion spring comprises a first hollow metal square-based prism forming the rigid and hollow outer axis, a second prism forming the central axis arranged in the first prism with an angular offset relative to the first prism, and wherein each element in elastomer is a cylinder arranged between the first prism and the second prism, in each corner of the first prism. 8. A cable anchoring system according to claim 7, comprising two torsion springs in series, the second square-based prism of the first torsion spring being connected to the second square-based prism of the second torsion spring. 9. Cable anchoring system according to one of claims 1 to 8, wherein the at least one torsion spring is configured to dampen the forces generated by the rotation of the drum around the axis of rotation (X) between a first stop position of the drum and a second stop position of the drum, the first stop position and the second stop position being angularly offset relative to the axis of rotation (X) by an angle of between 0° and 90°, preferably between 0° and 60°. 10. Cable anchoring system according to one of claims 1 to 9, comprising at least two sets of torsion springs arranged in parallel, a first part of each set of torsion springs being mounted on the frame and a second part of each set of torsion springs being mounted on the drum. 11. Cable anchoring system according to one of the preceding claims further comprising a compression spring and/or a tension spring comprising a first part mounted on the frame and a second part mounted on the drum. 12. Lifting device comprising: - a gripping frame (4) comprising at least one member for hooking a load to be lifted, - a cable anchoring system according to one of claims 1 to 11 comprising a frame (2) and a drum (1), the frame being fixed to the gripping frame and the drum being fixed to the frame, - a reel suitable for being fixed to a lifting device, - a cable (3), a first end of the cable being anchored to the drum (1) of the anchoring system by fixed winding of at least two turns around the lateral surface of the drum and a second end of the cable being wound around the reel. 13. Lifting machine (6), such as a crane, a gantry or a forklift, comprising a lifting device according to claim 12.