Lifting devices equipped with auxiliary devices to suppress boom tipping in the event of sudden loss of load

Abstract

A lifting device is described that includes a force-absorbing base to which a boom with a hoisting cable for lifting a load in a substantially vertical direction is tiltably connected. The lifting device includes an auxiliary device for suppressing overturning of the boom in the event of a sudden loss of the load. The auxiliary device is connected to the base of the lifting device, provides a contact surface that is in permanent contact with a contact surface of the boom or that will come into contact with the contact surface in the event of overturning, and further includes a drive and control system configured to stop movement of the boom when a predetermined force between the contact surfaces is exceeded as a result of the boom overturning. The described auxiliary device can be autonomous and can be located on the lifting device.

Description

[Technical Field]

[0001] The present invention relates to a lifting device comprising a force-absorbing base to which a boom with a hoisting cable for lifting a load in a substantially vertical direction is tiltably connected, the lifting device further comprising an auxiliary device for suppressing overturning of the boom in the event of a sudden loss of the load, for example due to a break in the hoisting cable. The present invention likewise relates to an auxiliary device for suppressing overturning of the boom in the event of a sudden loss of the load.

[0002] The present invention can in principle be applied to lifting any object, both on land (onshore) and at sea (offshore). However, the advantages of the present invention are most apparent when lifting objects offshore. For example, a typical application concerns the offshore installation of platforms for wind turbines. [Background technology]

[0003] Lifting devices for lifting loads generally comprise a force-absorbing base, for example a so-called A-frame, to which a tiltable boom about a horizontal axis is connected. The base is configured to transfer forces acting on the boom to a base surface, for example the deck and hull of a ship. The pivotal connection between the base and the boom allows the boom to be tilted in a vertical plane using a so-called pull cable between a fully raised position, in which the boom is positioned at a minimum angle to the vertical, and a fully lowered position, in which the boom is positioned at a maximum angle to the vertical. The boom's range of motion then lies between these two positions. Connected to the boom is a hoisting cable, which extends substantially vertically, to which a load can be attached in order to lift the load.

[0004] When lifting a load, the boom may suddenly tip backward and be forced beyond its highest raised position. Such boom tipping can occur in the event of a sudden load loss, for example, due to a break in the hoisting cable or if the load suddenly becomes disengaged from the hoisting cable. When a load is lifted, a force is exerted on the lifting device in response to the load's gravity. This force is exerted, particularly on the hoisting cable, boom, and retraction cable. Compared to the two cables, the boom is relatively stiff and does not deform significantly. However, the hoisting cable and retraction cable have increased elastic energy. In the event of such a so-called sudden load loss, the boom tends to "let go" of the load due to the sudden release of the increased elastic energy in the retraction cable. If the lifting device is located on a ship and the boom is projecting laterally, for example, to the starboard side (SB), water ballast can be placed on the opposite port side (PS) to restore balance. In that case, if the load is suddenly lost and the balance is disrupted, the vessel will begin to tilt away from the load, in this case in the PS direction. This will result in the boom tilting around its base and, as it were, being raised further. This will intensify the tipping action and the boom may then move beyond its vertical equilibrium point and even destroy itself. This situation is, of course, highly undesirable.

[0005] It should be noted that the term "tipping" is not limited to the aforementioned movement of the boom beyond the vertical point of equilibrium. Even if the boom does not "tip" in this way, but instead the retraction cable becomes slack due to a sudden rearward movement of the boom (away from the load), the retraction cable may subsequently be placed under tension again with a sudden force. The boom, likewise, may become overloaded with such a sudden load. This phenomenon is also classified as "tipping" and must also be avoided. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide an auxiliary device for suppressing tipping of the boom in the event of a sudden loss of load, and a lifting device equipped with the auxiliary device, thereby avoiding or at least reducing the risk of damage associated with tipping. [Means for solving the problem]

[0007] This object is achieved by providing a lifting device having the features of claim 1. The lifting device of the invention comprises a force absorbing base to which a boom comprising a hoisting cable for lifting a load substantially vertically is tiltably connected, and further comprises an auxiliary device for suppressing overturning of the boom in the event of a sudden loss of the load, for example due to a break in the hoisting cable, wherein the auxiliary device is connected to the base of the lifting device and provides a contact surface that is in contact with the contact surface of the boom or that will come into contact with the contact surface of the boom in the event of overturning, and further comprises a drive and control system configured to stop or block movement of the boom if a predetermined force between the contact surfaces is exceeded as a result of overturning of the boom.

[0008] In embodiments in which the contact surface of the auxiliary device is in contact with the contact surface of the boom, the boom will exert a force on the auxiliary device that is less than a predetermined maximum force during normal boom operation. The contact surface of the auxiliary device is then freely displaceable with the boom's movement. In the event of tipping, the force exerted on the auxiliary device will exceed the predetermined maximum force. The drive and control system then ensures that the movement of the contact surface is stopped, inhibited or blocked, for example by blocking means suitable for this purpose. In this way, tipping of the boom is prevented.

[0009] In the embodiment in which the contact surface of the auxiliary device contacts the contact surface of the boom in the event of tipping, the boom exerts substantially no force on the auxiliary device during normal boom operation. In this embodiment, the contact surface of the auxiliary device is free to displace with boom movement and follows the boom movement because it does not exceed a predetermined force, which may be zero or may otherwise have a different value from the previous embodiment. In the event of tipping, the boom will come into contact with the contact surface of the auxiliary device. The force applied to the auxiliary device then exceeds the predetermined force, which causes the drive and control system to ensure that the movement of the contact surface is stopped, inhibited, or blocked, for example, by a blocking means. This prevents the boom from tipping.

[0010] In an embodiment of the lifting device, the contact surface of the auxiliary device comes into contact with the contact surface of the boom by connecting the auxiliary device, more particularly its working part, to the boom, preferably at the outer end of the working part.

[0011] In another embodiment of the lifting device, the drive and control system is configured to hold the contact surfaces of the auxiliary device and the boom at a small mutual distance so that during tipping, only limited acceleration of the boom is possible.

[0012] The auxiliary device of the present invention can stop the boom immediately (or within a relatively short time) after a sudden loss of load. This prevents the boom from accelerating or building up kinetic energy. The auxiliary device is connected to the base so as to transmit forces resulting from the boom rebounding against a base connected to the base, such as the hull of a ship.

[0013] The lifting device can be used on land and also on any type of ship, where the advantages of the present invention are particularly apparent in its use on a monohull crane ship. The auxiliary device is further configured to stop the (accelerating) boom between its most raised and most lowered positions. According to the present invention, it is not necessary to stop the (accelerating) boom in all positions between the most raised and most lowered positions. It may be sufficient to provide only a part of this range, for example halfway from the most raised to the most lowered position.

[0014] According to an embodiment of the present invention, the contact surface of the auxiliary device is held at a small mutual distance from the contact surface of the boom by the drive and control system, so that the boom can only be accelerated to a limited extent during tipping. The auxiliary device is therefore not connected to the boom in this embodiment. This has the advantage that during normal use, any movement of the boom (e.g., twisting or bending) is not transmitted to the auxiliary device. The auxiliary device can thus be made relatively lightweight.

[0015] The small mutual distance can be selected within limits. A practical embodiment relates to a lifting device in which the mutual distance between the two contact surfaces is kept between a minimum distance and a maximum distance.

[0016] In a suitable embodiment, a lifting device is provided in which the minimum distance is between 1 mm and 10 mm and the maximum distance is between 5 mm and 30 mm. In normal use of the boom (i.e. in a situation where no tipping has occurred), the contact surfaces of the auxiliary devices are then kept at a distance which may be between 1 mm and 30 mm.

[0017] It is further advantageous to characterize the lifting device in such a way that the mutual distance between the two contact surfaces is kept constant by the drive and control system. For example, it is now possible to control it based on a vector distance. A further improved embodiment of the lifting device comprises a drive and control system configured to control the mutual distance horizontally, preferably keeping it within limits, even more preferably keeping it constant.

[0018] A suitable embodiment of the present invention provides a lifting device in which the boom has two legs and the auxiliary device provides two contact surfaces that come into contact with two corresponding contact surfaces on the boom in the event of tipping.

[0019] In an embodiment of the invention, it is further possible to characterize the lifting device such that the boom is tiltable about a tilt point and the contact surface of the boom is at least 2 / 5 of the length of the boom from the tilt point, more preferably at least halfway along the length, which makes it possible to limit the forces acting on the auxiliary device in the event of tipping.

[0020] In another embodiment, the base of the lifting device comprises an A-frame and the auxiliary device is connected to the A-frame of the lifting device, preferably to the upper side of the A-frame.

[0021] The assist device may take any suitable form so long as it provides a contact surface for the boom and is capable of stopping the boom in the event of a sudden rearward movement away from the load.

[0022] A practical embodiment relates to a lifting device, in which the auxiliary device comprises a frame to which is mounted a support beam which is horizontally displaceable between end positions by means of a drive system, the end faces of the support beam forming the contact surfaces.

[0023] In an embodiment, a particularly suitable drive system comprises a rack and pinion system comprising a gear rack driven by a pinion, the outer end of the gear rack providing a contact surface with the boom, the rack and pinion system being configured such that in the event of tipping, the forces acting on the auxiliary device by the accelerating boom can be absorbed, thus restricting boom movement.

[0024] In a suitable embodiment, the lifting device has a feature in which the pinion stops boom movement by action of a blocking means, for example, a brake acting on the pinion, when a predetermined maximum torque is exceeded as a result of the boom tipping. The pinion may be driven by an electric drive, for example, an electric motor. If, during tipping, the drive torque exceeds a predetermined torque (which results from a predetermined force), a brake on the electric drive is activated, stopping and blocking the drive. A suitable brake may, for example, comprise several plates held apart by electromagnets. Activating the brake turns off the electromagnet, causing a spring to "close" the plates against each other. It will be clear that multiple options exist and that the invention is not limited to this specific embodiment.

[0025] Rack and pinion systems are known per se and are used, for example, in jack-up platforms, in particular for moving the legs of such jack-up platforms upwards and downwards. Rack and pinion systems are capable of transmitting relatively large forces.

[0026] In order to be able to automatically adjust the mutual distance between the contact surfaces, the lifting device in an embodiment comprises a control system with measuring means for measuring the mutual distance between the two contact surfaces. In principle, any measuring means suitable for this purpose can be applied. The measuring means are preferably optical measuring means.

[0027] In an embodiment, the measuring means is provided at the location of the contact surface of the auxiliary device.

[0028] The auxiliary device provided on the lifting device can be integrated with the lifting device. However, according to another aspect of the invention, the auxiliary device can be provided autonomously and arranged on the lifting device. Such an auxiliary device for suppressing overturning of the boom in the event of a sudden load loss can be connected to the base of the lifting device and further comprises a drive and control system configured to provide a contact surface that comes into contact with the contact surface of the boom in the event of overturning and to hold the contact surface of the auxiliary device and the contact surface of the boom at a small mutual distance so that only limited acceleration of the boom is possible during overturning.

[0029] Possible embodiments of the auxiliary device have already been described in detail above, and reference to this description hereinafter will suffice.

[0030] When the auxiliary device is applied in combination with a lifting device for lifting loads at sea, for example for wind turbine components, the work is preferably carried out from a (floating) vessel or from a jack-up platform which provides more stability.

[0031] Further embodiments, as well as their features and further advantages, will be further explained with reference to the accompanying drawings. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is an isometric side view of a lifting device according to an embodiment of the present invention. [Figure 2] FIG. 2 is an isometric rear view of a detail of the lifting device of FIG. 1. [Figure 3] 1 is a schematic top view of a ship with a lifting device according to an embodiment of the present invention deployed thereon; [Figure 4A] 1A-1C are side views of a lifting device with an auxiliary device according to an embodiment of the present invention at different tilt angles; [Figure 4B]1A-1C are side views of a lifting device with an auxiliary device according to an embodiment of the present invention at different tilt angles; [Figure 4C] 1A-1C are side views of a lifting device with an auxiliary device according to an embodiment of the present invention at different tilt angles; [Figure 5A] 4B is a detail of the side view of FIG. 4A. [Figure 5B] 4C is a detail of the side view of FIG. 4B. [Figure 5C] 4D is a detail of the side view of FIG. 4C. [Figure 6] 1 is a cross-sectional view of an auxiliary device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The same or similar components are designated in the figures with the same reference numerals.

[0034] FIG. 1 shows a lifting device 1 according to the present invention. This embodiment consists, among other things, of a force-absorbing base, itself consisting of a bottom frame 11 and an A-frame 12. A boom 10 is tiltably disposed on the force-absorbing base. A retraction cable 13 is further disposed from the approximate height of the bottom frame 11, over the upper outer end of the A-frame 12, and to at least the upper outer end 14 of the boom 10, to lift the load substantially vertically. The retraction cable 13 can also be tensioned along other paths. The lifting device 1 is also optionally rotatable, either because the bottom frame 11 is a rotatable bottom frame or because the bottom frame 11 is disposed on another rotatable element.

[0035] Such lifting devices are susceptible to tipping over, which can occur if the load is suddenly lost, for example, when the hoisting cable breaks, when a hook or other connection means connecting the hoisting cable to the load breaks, or when the load itself collapses, either partially or totally.

[0036] Tipover involves any undesirable movement of the boom 10 resulting from the release of built-up tension in the boom 10. In a severe tipover, the boom 10 ends up in a fully upright position, and the remaining momentum may cause all or part of the boom 10 to tilt beyond this point, after which the portion of the boom 10 that tilted beyond this upright point may tip backward. This is also referred to as a complete tipover. In a less severe, but still dangerous, tipover, the boom 10 may only partially upright, thereby causing the retraction cable 13 to slacken. When the boom 10 then tips backward or forward, tension may be restored to the retraction cable 13 with a sudden force. This is also referred to as a snatch load. Like a complete tipover, a snatch load has damaging consequences.

[0037] FIG. 1 therefore further shows that the lifting device 1 comprises an auxiliary device 3, which in this embodiment is arranged at the upper outer end of the A-frame 12. It is also possible to attach the auxiliary device 3 below the A-frame 12 or to a different part of the force-absorbing base. The auxiliary device 3 consists, among other things, of a frame 31, on which a rack-and-pinion system 32 and an orientation device 34 are arranged. In this embodiment, the rack-and-pinion system 32 and the orientation device 34 form a drive and control system; in other embodiments, the drive and control system can also be composed of different components. A support beam 30 is arranged on each rack-and-pinion system 32. The outer end of the support beam 30, which is directed towards the boom 10, provides a contact surface 33. The support beam 30 can be displaced substantially horizontally between end positions by the drive and control system, in this embodiment by the rack-and-pinion system 32.

[0038] A corresponding number of contact surfaces 33' can be designated on the boom 10, which are the locations where the contact surfaces 33 will come into contact with the boom 10 in the event of a sudden loss of load.

[0039] The distance between the contact surfaces 33, 33' is kept small to prevent the boom 10 from gaining momentum during tipping, i.e., to prevent the boom 10 from accelerating excessively. In this embodiment, the drive system is able to displace the contact surface 33.

[0040] As soon as the contact surfaces 33, 33' contact each other, a portion of the momentum of the boom 10 is absorbed by the auxiliary device 3. This portion is proportional to the portion of the boom 10 that is below the contact surface 33'. The remaining portion of the momentum of the boom 10 that is not absorbed by the contact surface 33 distorts the integrity of the boom 10. If the remaining momentum is excessive for the integrity of the boom 10 despite the auxiliary device 3, the boom 10 may further tip over. Therefore, it is preferable that the contact surfaces 33' be located as high up on the boom 10 as possible. Thus, in certain embodiments, these contact surfaces on the boom 10 are located at least two-fifths of the way along the height of the boom 10, and preferably at least halfway up.

[0041] An orientation device 34 controls, from the frame 31, the angle of orientation of the support beam 30 relative to the boom 10. Orienting the support beam 30 in this manner allows the contact surface 33′ to be independent of the tilt angle of the boom 10, which has the advantage that, if it is desired to reinforce the contact surface of the boom 10, only a small portion of the boom 10 needs to be reinforced. A further advantage of orienting the contact surface 33 relative to the boom 10 in this manner is that, when the contact surfaces 33, 33′ contact each other, this surface is as large as possible immediately, or in other words, the contact surfaces 33, 33′ contact each other with the most forward facing possible orientation. This is desirable because if the support beam 30 contacts the boom 10 at an angle, it may result in poor absorption of the momentum of the boom 10 and / or may cause undesirable damage to the boom 10.

[0042] The illustrated embodiment of the auxiliary device 3 comprises two contact surfaces 33. It is also possible to provide only one or more contact surfaces. The desired number of contact surfaces is determined, for example, based on the number of legs of the boom 10. In the illustrated embodiment, the boom 10 has two legs, but a boom 10 consisting of only one leg is also possible.

[0043] In the embodiment shown, the base comprises an A-frame 12. The illustration shows two slightly angled posts and several beams connecting the posts. The A-frame optionally further comprises two rear legs that extend downward and further rearward from the top of the A-frame 12. Additional frame configurations that fulfill this function may also be provided.

[0044] Figure 2 shows details of the lifting device 1, again showing the boom 10, A-frame 12 and retraction cable 13. This figure further illustrates the configuration of the frames 31, on which in this case two support beams 30 rest. For each support beam, the frame 31 comprises a horizontal leg 31A and a diagonal leg 31B, which are attached to each other at a protruding outer end 31D and at opposite outer ends 31C, 31E, both of which are connected to the A-frame 12.

[0045] 1 and 2 both show that this embodiment of the lifting device 1 is suitable for lifting a load on its first side. In this embodiment, the boom 10 is arranged on the base so that it can tilt towards this first side of the lifting device 1. As can be seen from the boom 10, the side towards which it can tilt is also the first side, towards which the boom 10 is configured to lift. If the auxiliary device 3 were not provided, the boom 10 would be accelerated in the direction opposite to the direction in which it can tilt when the load is suddenly released.

[0046] In this embodiment, the auxiliary device 3 is therefore preferably arranged on a second side of the boom 10, located opposite the first side, and the auxiliary device 3, in particular the contact surface 33, is in the path that the boom 10 would move in the event of a sudden loss of load.

[0047] 3 shows a schematic top view of a ship 2 equipped with a lifting device 1 according to the invention. In this embodiment, the lifting device 1 can also rotate. In this embodiment, the boom 10 is therefore configured to lift a load in a region extending from an inner radius 40, where the boom 10 is positioned as upright as possible, to an outer radius 41, where the boom 10 is tilted as far forward as possible. The auxiliary device 3 makes it possible to avoid tipping of the boom 10 in the event of a sudden load loss during the lifting of this load, within a low-risk region 42. As indicated above, it is also possible to configure the boom 10 to tilt beyond the point where the auxiliary device 3 can prevent tipping, with the risk remaining as it is in region 43.

[0048] Figures 4A to 4C show side views of the lifting device 1 described above with reference to Figures 1 and 2. In particular, Figures 4A to 4C again show the boom 10, the A-frame 12, and the auxiliary device 3, this embodiment of which again consists of a frame 31, drive and control systems 32, 34, and a support beam 30 with a contact surface 33. Figures 5A to 5C show details of these side views, and figures with the same letter designation correspond to one another.

[0049] In the side view shown, the boom 10 has maximum outreach in FIG. 4A . In this case, the auxiliary device 3 can no longer keep the distance between the contact surfaces small when the boom 10 is tilted beyond this first tilt angle. The effectiveness of the auxiliary device 3 in preventing tipping of the boom 10 will therefore decrease in proportion to how far the boom 10 is tilted beyond this angle. A second tilt angle can therefore be specified, beyond which the auxiliary device 3 can no longer prevent tipping of the boom 10 if the boom experiences a sudden loss of load.

[0050] 5A shows in more detail that the support beam 30 is extended to its extreme position in order to keep the distance between the contact surface 33 and the contact surface of the opposing boom 10 small. In this case, the orientation device 34 points the support beam 30 downwards at the maximum possible angle.

[0051] In Figure 4B, the boom 10 has a smaller outreach than in Figure 4A. In a preferred embodiment, the mutual distance between the two contact surfaces remains constant whenever the boom 10 is adjusted, for example, when the boom 10 is adjusted from the tilt angle shown in Figure 4A to the smaller tilt angle shown in Figure 4B.

[0052] To achieve this, the lifting device 1 can be equipped with measuring means for measuring the mutual distance between the two contact surfaces. Such measuring means can, for example, comprise optical measuring means, which can be arranged in particular on the frame 31 or on the support beam 30. From the frame 31, the absolute tilt angle of the boom 10 can be measured, and it is possible to deduce how far the support beam 30 needs to protrude in order to keep the mutual distance between the contact surfaces small. From the support beam 30, the relative distance between the beam 10 and the measuring means can be measured. If these measuring means are fixedly arranged on the support beam 30, the distance between the contact surface 33 and the boom 10 can also be derived, so that the drive and control system 32, controlled by the measuring means, can displace the support beam 30 to keep the distance constant.

[0053] 5B shows in more detail that the support beam 30 is displaced together with the boom 10 to keep the distance between the contact surface 33 and the opposing contact surface of the boom 10 small. The angle at which the support beam 30 is oriented relative to the boom 10 is reduced by the orientation device 34.

[0054] In the side view shown in Figure 4C, the boom 10 has a minimum outreach. In each of these embodiments, the mutual distance between the two contact surfaces is kept between a minimum distance and a maximum distance. The minimum distance may be, for example, between 1 mm and 5 mm, and the maximum distance may be, for example, between 5 mm and 10 mm. This mutual distance primarily relates to the mutual distance in the horizontal direction.

[0055] 5C shows in more detail that the support beam 30 has again been displaced along with the boom 10 by the drive and control systems 32, 34 to keep the distance between the contact surface 33 and the opposing contact surface of the boom 10 small. The angle at which the support beam 30 is oriented relative to the boom 10 has also been reduced, and the support beam 30 is substantially horizontal in this position.

[0056] Figure 6 shows a cross-sectional view of an embodiment of an auxiliary device 3 according to the invention. Again, the lifting device 1 comprises a boom 10, an A-frame 12 as part of the force-absorbing base, and the auxiliary device 3. In this embodiment, the rack and pinion system 32 consists of a pinion 37 and a gear rack 36 arranged on the support beam 30. When the pinion 37 rotates, the support beam 30 is displaced in the desired direction via the gear rack 36. As mentioned above, this is done in order to keep the distance between the contact surfaces 33, 33' small.

[0057] However, in the event of tipping, it is desirable that the support beam 30 does not move, or moves very little, relative to the frame 31 connected to the force absorbing base. In a preferred embodiment, the rack and pinion system 32 is therefore provided with blocking means which, in the event of tipping, inhibit any movement of the support beam 30 relative to the horizontal leg 31A. It will also be appreciated that in this embodiment, the horizontal leg 31A takes on a heavier form than the diagonal leg 31B, and therefore the risk of crushing the horizontal leg 31A when the contact surfaces 33, 33' come into contact is minimized.

[0058] The blocking means can, for example, immediately block the movement of the support beam 30 when the support beam 30 is no longer being moved, i.e., when the boom 10 has a certain tilt angle. In this case, the support beam 30 is preemptively blocked and, in fact, will be blocked more frequently if it were to tip over. However, the tilt angle of the boom 10 is often not constant, and this is also due to reasons other than the boom 10 being tilted by the lifting device 1. For example, if the boom 10 is slightly tilted or twisted due to wind force, it is still desirable to keep the distance between the contact surfaces 33, 33′ small. Therefore, the support beam 30 is adjusted more frequently, thereby ensuring that the support beam 30 is not blocked as frequently. Therefore, in a preferred embodiment, the rack-and-pinion system 32 includes force detection means configured to detect whether an external force is being applied to the support beam 30, for example, in a direction away from the boom 10, and to control the blocking device to block the support beam 30. [Explanation of symbols]

[0059] 1 Lifting device 2 ships 3 Auxiliary Devices 10. Boom 11 Bottom frame 12 A-frame 13 Lead-in cable 14 Upper outer edge 30 Support beam 31 frames 31A horizontal leg 31B Diagonal Leg 31C Outer end 31D outer end 31E Outer end 32 Rack and pinion systems, drive and control systems 33 Contact surface 33' contact surface 34 Orientation Device 36 Gear rack 37 Pinion 40 inner radius 41 outer radius 42 Low-risk areas 43 areas

Claims

1. 1. A lifting device comprising a boom with a hoisting cable for lifting a load in a substantially vertical direction, the boom comprising a tiltably connected force absorbing base, the lifting device further comprising an auxiliary device for suppressing overturning of the boom in the event of a sudden loss of load, the auxiliary device being connected to the base of the lifting device and providing a contact surface which will come into contact with a contact surface of the boom in the event of overturning, and a drive and control system configured to stop movement of the boom when a predetermined force between the contact surfaces is exceeded as a result of overturning of the boom, the drive and control system is configured to maintain the contact surfaces of the auxiliary device and the boom at a small mutual distance so that the boom is only capable of limited acceleration during tipping; A lifting device, wherein the auxiliary device comprises a frame to which is mounted a support beam which is horizontally displaceable between end positions by means of the drive system, the end faces of the support beam forming the contact surfaces.

2. the mutual distance between the two contact surfaces is kept between a minimum distance and a maximum distance; 10. The lifting device of claim 1.

3. the minimum distance is between 1 mm and 10 mm and the maximum distance is between 5 mm and 30 mm; 3. A lifting device according to claim 2.

4. the mutual distance between the two contact surfaces is kept constant; A lifting device according to claim 2 or claim 3.

5. the mutual distance is the mutual distance in the horizontal direction; A lifting device according to any one of claims 2 to 4.

6. the drive and control system is configured to vertically displace the contact surface of the auxiliary device opposite the contact surface of the boom when the boom is tilted. A lifting device according to any one of claims 1 to 5.

7. the boom has two legs, and the auxiliary device provides two contact surfaces that are in contact with corresponding contact surfaces of the boom, or that will come into contact with the two corresponding contact surfaces of the boom in the event of tipping; A lifting device according to any one of claims 1 to 6.

8. The boom is tiltable about a tilt point, and the contact surface of the boom is at least 2 / 5 of the boom length from the tilt point. A lifting device according to any one of claims 1 to 7.

9. the base comprises an A-frame of the lifting device, and the auxiliary device is connected to the A-frame of the lifting device; A lifting device according to any one of claims 1 to 8.

10. The auxiliary device is connected to the upper side of the A-frame.

10. A lifting device according to claim 9.

11. the drive system comprises a rack and pinion system comprising a gear rack driven by a pinion; A lifting device according to any one of claims 1 to 10.

12. If a predetermined torque is exceeded as a result of the boom tipping over, the pinion stops the movement of the boom by applying a brake to the pinion. A lifting device according to claim 11.

13. the control system comprises measuring means for measuring the mutual distance between the two contact surfaces. A lifting device according to any one of claims 1 to 12.

14. 14. A lifting device according to claim 13, wherein the measuring means is provided at the location of the contact surface of the auxiliary device.

15. the measuring means comprises an optical measuring means; A lifting device according to claim 13 or 14.

16. An auxiliary device for suppressing tipping of a boom in the event of a sudden loss of load, said auxiliary device being connected to a base of a lifting device and providing contact surfaces which will come into contact with contact surfaces of said boom in the event of tipping, and further comprising a drive and control system configured to stop operation of said boom when a predetermined force between said contact surfaces is exceeded as a result of tipping of said boom; the drive and control system is configured to maintain the contact surfaces of the auxiliary device and the boom at a small mutual distance so that the boom is only capable of limited acceleration during tipping; The auxiliary device comprises a frame on which is mounted a support beam which is horizontally displaceable between end positions by means of the drive system, end faces of the support beam forming the contact surfaces.

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