Anti-tip system, offshore crane boom, offshore crane

Abstract

The anti-tip system (8) for an offshore crane comprises a boom mounting portion (9) arranged for attachment to a boom (3) of an offshore crane (1) and a support structure mounting portion (10) to be attached to a support structure (2) for the offshore crane, the boom mounting portion comprising a frame having at least one longitudinally extending chord (16), the support structure mounting portion comprising a biasing element (14) biased towards an extended position, the boom mounting portion and the support structure mounting portion being configured to engage each other when a boom angle (a) of the boom exceeds a predetermined threshold.

Description

[Technical field]

[0001] The present invention relates to an offshore crane, and more particularly to an anti-tip system for an offshore crane. [Background technology]

[0002] Offshore cranes are widely known and are typically mounted on floating structures such as ships, barges, or jack-ups. Offshore cranes may be used for a variety of purposes, such as heavy lifting operations at offshore locations, for example, installing and removing heavy structures such as wind turbines, wind turbine foundations, platforms, platform tops, etc.

[0003] An offshore crane typically comprises a boom pivotally mounted to a support structure, at the tip of which a load may be hoisted. Various failure modes are known to crane designers, and offshore cranes are designed and constructed with such failure modes in mind. One such failure may be known as boom tipping. Boom tipping may occur, i.e., the boom may tip back beyond the vertical, due to swinging of the boom caused by any force or sudden loss of force, for example due to a mishap such as loss of load, failure of the rafter or hoist wires, vessel movement, failure of the lifting hook, etc. This results in structural damage or total loss of the boom and / or of structures near or behind the boom.

[0004] Various structures are known for limiting the position of the boom and / or defining the end position of the boom. The most commonly used structure is a boom stop, typically a hydraulic cylinder, typically mounted on an A-frame or similar structure, which engages the boom transverse to the longitudinal direction of the boom. When the boom reaches the end position, the boom stop engages a stopping surface. However, such boom stops have limited effectiveness and may not prevent the boom from tipping over or may not prevent structural damage to the boom. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an anti-tip system for an offshore crane. In particular, an object of the present invention is to provide an anti-tip system that can efficiently and / or effectively limit or prevent boom tipping. [Means for solving the problem]

[0006] To this end, the present invention provides an anti-tip system comprising a boom mounting portion and a support structure mounting portion, one of the boom mounting portion and the support structure mounting portion comprising a frame having at least one longitudinally extending chord, and the other of the boom mounting portion and the support structure mounting portion comprising a biasing element biased towards an extended position. The boom mounting portion may comprise a frame having at least one longitudinally extending chord, the distance of the at least one chord to the boom being greater near the base of the frame and smaller near the tip of the frame. In this case, the at least one longitudinally extending chord may have an angle with the main longitudinal axis of the boom, the angle being in the range of 1 to 30 degrees, more preferably in the range of 5 to 25 degrees, even more preferably in the range of 10 to 20 degrees, e.g. about 15 degrees. It has been found that such an angle may provide a particularly favorable combination of lateral and longitudinal anti-tip action on the boom, the lateral component being related to faster neutralization of adverse swing motions and the longitudinal component being related to boom loads along the longitudinal axis of the boom. Without wishing to be bound by theory, it is believed that such an angle may advantageously convert at least a portion of the momentum related to boom swing motions into boom loads along the longitudinal axis of the boom.

[0007] The frame may be embodied as a trussed or non-trussed frame, for example a box-shaped frame or a frame with plates and / or trusses. The frame with at least one chord may thus be triangular in side view with respect to the boom, with the chord extending obliquely towards the boom. The frame base of the frame may be located at the bottom end of the boom, i.e. at the boom base. At the boom base, the distance between the at least one chord and the boom may be greater than at a position further from the boom base, with the chord being oriented towards the boom. The at least one chord of the frame may be connected to the boom by a brace or a truss, at least at the bottom end of the chord and / or at the top end of the chord. The at least one chord of the frame may be connected to the boom directly or via a brace. In the latter case, the at least one chord may be said to be floating or to be supported only with respect to the boom by a brace. Preferably, the frame with at least one chord is attached to the boom and is permanently connected to the boom during normal operation. The trusses or braces of the frame can be connected to the trusses or braces of the boom and / or can be connected to the chords of the boom. In known designs, the boom may comprise or even consist primarily of such trusses, braces and / or chords. However, it will be appreciated that the boom may be partially or entirely designed without such elements, e.g., comprising one or more beams, plates, etc. It is possible to provide multiple trusses or braces over the length of the frame, which may be connected to the boom at various longitudinal and / or radial positions of the boom.Thus, over the length of the boom to which the boom attachment is connected, the connections between the trusses of the frame of the boom attachment on the one hand and the trusses or chords of the boom on the other hand are provided in a number of different positions, axially, i.e. in the longitudinal direction of the boom, and / or radially, i.e. transversely to the axial direction. Such multiple and / or various connections in different positions may allow advantageous load transfer from the anti-tip system to the boom in case of a disaster. The boom attachment embodied as a frame may typically be connected to the boom by welding and / or bolting, although hinged connections may also be considered.

[0008] One of the boom mounting portion and the support structure mounting portion may be hinged to an associated mounting base so as to follow movement of the boom when the boom mounting portion and the support structure mounting portion are engaged, and one of the boom mounting portion and the support structure mounting portion may be a compressible element, preferably biased towards an extended position, so as to follow movement of the boom when the boom mounting portion and the support structure mounting portion are engaged and / or to absorb energy in the event of a disaster.

[0009] The boom is pivotally connected to a support or base structure at the boom base. Such a support or base structure can be, for example, a swivel platform. The support structure mounting part of the anti-tip system is mounted to such a support structure. The support structure mounting part can comprise a biasing element biased towards an extended position. Typically, this biasing element can be a compressible element in that it can be compressed when contacted and / or subjected to a load. The biasing element can be, for example, a hydraulic cylinder, a pneumatic cylinder, or a spring-based system. The biasing element can be pivotally mounted at its lower end to the support structure and can be configured to engage at its outer free end with a frame of the boom mounting part. In this case, preferably, the lower end of at least one chord of the frame can be configured to engage with the outer end of the biasing element when the angle of the boom with respect to the horizontal becomes too large, i.e. above a safety threshold that can be predefined. The angle of the boom with respect to the horizontal is typically called the boom angle. The engagement between the frame and the biasing element is assumed at a boom angle of about 60 degrees, preferably at a boom angle between about 40 and 70 degrees. In this case, if the boom angle becomes larger, the biasing element is compressed against the biasing force of the frame. If the boom angle becomes larger, particularly rapidly, due to an unintended swing, the biasing element can absorb the kinetic energy, e.g., swing, while the force, e.g., tipping moment, can be transmitted to the boom string via the frame. Thus, the force can be directed in a direction that does not amplify the boom swing, and instead is directed to the boom string designed to bear such high loads. Thus, this tipping prevention system can effectively prevent the boom from tipping, and can also prevent damage to the boom due to swing. In addition, the provision of the truss frame makes it possible to realize a relatively lightweight structure that can effectively guide the load to the boom string in the event of a risk of boom tipping, thereby limiting or preventing failure.

[0010] Advantageously, the boom attachment portion and / or the support structure attachment portion are provided with engagement elements which engage with each other when the boom angle exceeds a predetermined angle.

[0011] A plurality of biasing elements may be provided that engage the frame of the boom mounting portion. For example, it may be envisaged that two biasing elements share a common engagement element, and thus the two biasing elements may be said to be positioned in parallel. Alternatively, the biasing elements may be positioned in series. Additionally, a combination of series and parallel configurations of multiple biasing elements is also possible.

[0012] It can further be understood that the compressible element as a biasing element may additionally comprise a damping element, such as a gas buffer or a crumple zone.

[0013] Alternatively, the support structure attachment portion may be a fixed element, such as a frame, and the boom attachment portion may be a compressible element, such as a biasing element, such that when the boom angle exceeds a certain threshold, engagement is triggered and the boom attachment portion is compressed while a load is directed to the support structure and / or boom.

[0014] Alternatively and / or additionally, in case of a disaster, when the boom may start to accelerate, the biasing element may be locked to stop further movement of the boom and thus prevent further acceleration of the boom. Locking of the biasing element may be performed at any position between the fully extended and fully compressed positions, including the fully extended and fully compressed positions. Locking of the biasing element may be achieved passively, for example when pressure in the biasing element increases suddenly. Locking may be performed mechanically, hydromechanically, hydraulically or by other means, for example to hold the biasing element or block fluid outflow. The biasing element may then be locked in a subsequent extended position, i.e. the subsequent extended position of the biasing element is fixed and the biasing element is blocked in that position. Parts of the biasing element that are extendable relative to one another between the fully extended and fully compressed positions of the biasing element may be blocked from moving relative to one another in the locked position. Locking of the biasing element may be performed when the boom attachment portion and the support structure attachment portion engage to allow pressure to build up in the biasing element. If the pressure on the biasing element becomes too great, e.g. greater than a predefined threshold, the biasing element may be locked. If this pressure becomes lower or may fall below the predefined threshold, the locking action may be released and the biasing element may remain engaged with the boom mounting support. Such thresholds for locking and unlocking may be the same, but are preferably different to prevent switching between locking and unlocking from being too abrupt. In other words, a hysteresis effect may be realized for locking and unlocking.

[0015] During normal crane operation, the support structure attachment portion and the boom attachment portion engage when the boom angle is greater than the predetermined boom angle. During normal crane operation, when the support structure attachment portion and the boom attachment portion engage, the support structure attachment portion and the boom attachment portion move with the movement of the boom. In normal operation, the support structure attachment portion and the engaged boom attachment portion move smoothly with the boom. In this case, in normal operation, the biasing element of the support structure attachment portion will be compressed and / or expanded to follow the movement of the boom. In normal operation, no or almost no additional load is induced and / or transferred to the boom by the anti-tip system. However, in the event of a disaster, the boom tip may accelerate and the engagement of the boom attachment portion and the support structure attachment portion occurs when the boom angle exceeds the predetermined boom angle if they are still not engaged. Furthermore, in this case, the engaged boom attachment portion and the support structure attachment portion move together while the additional acceleration energy of the boom tip is allowed to be absorbed by the biasing element and / or the biasing element is allowed to be locked. This allows loads to be applied longitudinally to the boom and / or to the support structure. The boom is capable of handling large loads via the chord. Thus, tipping of the boom can be effectively prevented without or with limited damage to the boom and / or its environment.

[0016] Because the biasing element is biased toward the extended position, when the boom mounting portion and the support structure mounting portion are engaged, this engagement may help maintain tension in the rafter wires of the rafter system, but may not prevent the wires from going slack.

[0017] In either case, when the boom angle is about 60 degrees, the lower end of at least one chord engages with an associated biasing element, which can follow the inclination of the boom. In normal operation, the boom can achieve an angle of about 83 degrees. At this point, the biasing element can be in a fully retracted position, in other words, fully compressed. When the boom is lowered, the biasing element can also follow the movement of the boom, and when the boom angle is less than about 60 degrees, the biasing element and the frame can disengage and the biasing element is again in an extended position.

[0018] An A-frame is often attached to a support structure, for example to guide the luffing and / or hoisting systems of a crane. Typically, such an A-frame has four connections to the support structure, which are arranged as two pairs of connections at a distance from each other. If the boom has two boom legs at its lower end, the boom base connection can be integrated into such a pair of A-frame connections, or the boom base can have its own support structure connection separate from the A-frame connection. In this latter example, the boom base connection is usually attached outboard of the A-frame connection. Also, if the boom is a single boom with a single boom leg, the boom base connection to the support structure can be separate from the A-frame or similar frame structure connection. Advantageously, a biasing element is also mounted on the support structure near the A-frame.

[0019] The boom mounting part of the tip-over prevention system is attached to the boom at the upper side of the boom, which may also be called the rear side of the boom, i.e. the side of the boom opposite to the side where the load to be lifted by the boom is usually positioned. In the side view, it can be seen that the boom has an additional triangular frame attached to such upper side of the boom, specifically near the base of the boom. Of course, this frame may be a rather prismatic three-dimensional structure with a larger base located at the base of the frame and the boom base, and a smaller tip where at least one chord of the frame crosses or nearly crosses one or more chords of the boom. In case the lower end of the boom is configured as two boom legs, each boom leg may comprise such a frame of the boom mounting part. Moreover, in that case, two biasing elements are arranged. It is envisaged that to each chord of the frame of the boom mounting part, a biasing element of the support structure mounting part is associated. For example, if the boom leg frame has two longitudinally extending chords trussed to the boom, there may be two chord lower ends configured to engage two corresponding biasing elements. Alternatively, these two chord lower ends may be joined to form one engagement element for the corresponding biasing elements.

[0020] In the rest position, the biasing element is preferably positioned so that it is not yet engaged and can optimally engage with the frame on the boom when the boom angle reaches about 50 degrees, preferably about 60 degrees. Thus, in the rest position, this biasing element has an angle with respect to the support platform so that it can engage with the frame at or about a boom angle of 50-70 degrees, preferably about 60 degrees. In order to hold the biasing element in the rest position, it is possible to provide a support arm that maintains the biasing element in the rest position and receives the biasing element again if it is disengaged from the frame. The support arm can be U-shaped to further limit excessive lateral movement of the biasing element. In practice, the biasing element is preferably hinged to the support structure, so that excessive lateral movement of the biasing element may result in failure of this hinge connection. This failure of the hinge connection can however be prevented by the support arm, in particular by a U-shaped portion, such as for example a U-shaped bracket of the support arm. Advantageously, in the rest position the biasing element is further biased towards the extended position. When engaged the biasing element may be compressed and / or expanded to follow the movement of the boom. Also, the angular position of the biasing element may be different from the rest position to allow it to follow the movement of the boom.

[0021] Furthermore, the invention relates to an offshore crane having a boom pivotally mounted to a support structure, the crane being equipped with such an anti-tip system, the boom side base being mounted to the boom and the support structure side base being mounted to the support structure, preferably pivotally mounted to the support structure.

[0022] In one example, as suggested elsewhere herein, at least one chord of the frame attached to the lower end of the boom is angled at between about 8-30 degrees relative to the longitudinal direction of the boom, preferably at between about 10-20 degrees, preferably at about 15 degrees. The frame may be attached to the lower 10-50% of the boom, such as the lower 10-40% of the boom, preferably the lower 12-35% of the boom length. The upper end of at least one longitudinal chord of the boom attachment may extend up to about 20-40% of the boom length, preferably up to about 25%.

[0023] More generally, the boom attachment is advantageously mounted on the lower end of the boom, preferably on the lower 10-50% of the boom chord. As indicated above, the boom attachment can be a frame or can be a compressible element, such as a biasing element.

[0024] These and other aspects are further described with reference to the following drawings, which comprise the figures of exemplary embodiments. [Brief description of the drawings]

[0025] [Figure 1a] FIG. 1 illustrates an offshore crane with the anti-tip system in a first position. [Figure 1b] FIG. 2 illustrates an offshore crane with the anti-tip system in a second position. [Figure 1c] FIG. 1 illustrates an offshore crane with the anti-tip system in a third position. [Diagram 2] FIG. 1 illustrates a boom of an offshore crane having a boom mounting for an anti-tip system. [Diagram 3] FIG. 3 is a detailed view of the boom mounting portion of FIG. 2. [Figure 4] FIG. 1D is a detailed view of the support structure mounting portion with the support arm in a position corresponding to FIG. 1C. [Diagram 5] 13A-13C illustrate alternative embodiments of the boom mounting portion of the anti-tip system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] It should be noted that these figures are provided by way of example and not as a limitation of the present disclosure. The figures may not be to scale. Corresponding elements are indicated by corresponding reference numerals.

[0027] FIG. 1a shows an offshore crane 1 mounted on a support or base structure 2. The offshore crane 1 comprises a boom 3 pivotally mounted to the support structure 2 and an A-frame 4 with, for example, a luffing and / or hoisting system 5. Here, a pair of connections of the A-frame 4 is positioned between the pivotal connections of the boom to the support structure 2, but it is understood that the pair of connections of the A-frame 4 and the pivotal connections of the boom to the support structure 2 can also coincide. The boom 3 has a boom base 6 and a boom tip 7. At the boom tip 7 a load can be lifted. The offshore crane 1 comprises an anti-tip system 8, which comprises a boom attachment part 9 and a support structure attachment part 10. Here, the boom attachment part 9 is shown in side view as a triangular truss frame 12 connected to the upper or rear side 11 of the boom. The lower or base end of the truss frame is provided with an engagement element 13 configured to engage with a support structure mounting portion 10, which in this case is provided as a biasing element 14, for example a hydraulic or pneumatic cylinder. The biasing element 14 is pivotally mounted to the support structure 2 and extends longitudinally. An outer end of the biasing element is provided with an engagement element 15 configured to engage with the engagement element 13 of the boom mounting portion 9. In the event of excessive loads and / or movements due to a disaster, the boom mounting portion 9 and the support structure mounting portion 10 cooperate together to prevent or limit tipping of the boom 3.

[0028] In Fig. 1a the boom 3 is shown in a first position, in which the boom attachment portion 9 is not restricted by the support structure attachment portion 10 and the boom attachment portion 9 is not engaged with the support structure attachment portion 10. Typically this corresponds to a boom angle of up to about 50-70 degrees, for example up to about 50-60 degrees. This boom angle α is taken as the angle between the longitudinal axis of the boom and the horizontal line as shown diagrammatically in Fig. 1a. The support structure side base 10, in particular the biasing element 14 of the support structure side base 10, is biased towards the extended position.

[0029] In FIG. 1b, it is shown that the boom mounting part 9 engages with the support structure mounting part 10 when the boom angle reaches a predetermined angle α1. This predetermined angle α1 can be set between about 50-70 degrees, or any value between about 50-70 degrees or about 50-70 degrees, for example about 60 degrees. To this end, the boom mounting part 9 can comprise a boom side base engaging element 13 and the support structure mounting part 10 can comprise a support structure side base engaging element 15. The boom side base engaging element 13 then engages with the associated support structure side base engaging element 15. For example, if the boom mounting part 9 has one chord 16 and the boom engaging element 13 is provided against the lower end 17 of this chord 16, this boom side base engaging element 13 has a corresponding and associated support structure side base engaging element 15 on the associated biasing element 14. In another example, the frame 12 may have two longitudinally extending chords 16 with boom-side base engagement elements 13 at their respective lower ends 17, in which case two associated support-side base engagement elements 15 are provided. These support-side base engagement elements 15 may be connected to two separate biasing elements or to one and the same biasing element. The biasing elements may be arranged in series, parallel, or a combination thereof. When the boom mounting portion 9 is engaged with the support mounting portion 10, the biasing element 14 is compressed against the biasing force. Thus, the biasing element 14 is able to follow the movement of the crane boom 3 until the biasing element 14 is fully compressed and the boom 3 is in its uppermost position as shown in FIG. 1c. In this case, the boom angle α2 may be as large as 83 degrees or even 85 degrees. In the event that a mishap causes unintended boom movement and / or boom acceleration, the anti-tip system 8 can absorb the energy resulting from such movement and can also direct excess loads towards the bowstring of the boom 3 and / or the support structure 2. Thus, tipping of the boom 3 can be limited or prevented.

[0030] As shown in Figures 1a, 1b, 1c and more particularly in Figure 4, the biasing element 14 is supported by a support arm 18. The support arm 18 holds the biasing element 14 in a neutral position as shown in Figure 1a, ready to engage with the boom mounting part 9. Preferably, the biasing element 14 is positioned at an angle β between about 30 degrees and about 65 degrees, depending on the angle α1 at which the engagement is envisaged when the boom 3 reaches the boom angle α1, for example at an angle similar to this angle α1, in order to optimally engage with the boom mounting part 9. When the biasing element 14 is engaged with the frame 12, the biasing element 14 can rotate with the rotation of the boom 3 and can be free from the support arm 18 at least with respect to such rotation. The support arm 18 can be provided with a U-shaped bracket at its outer end, which allows further limiting the lateral movement of the biasing element 14. In this sense, the support arm 18 can continue to cooperate with the biasing element 14 over the various rotational positions of the biasing element 14.

[0031] Figure 2 shows an example of a boom 3 of an offshore crane. Here, the boom 3 comprises two boom legs 19a, 19b at its boom base 6. Each boom leg 19a, 19b is hinged to a support structure, so that the boom 3 can only pivot about the axis of rotation of these hinges. Frames 12a, 12b are attached to the upper or rear side 11 of the boom 3.

[0032] In this case, the boom mounting part 9 comprises two frames 12a, 12b, which are connected to two legs 19a, 19b, in particular one each to each of these legs. Thus, an additional frame 12a, 12b is provided for each leg 19a, 19b. Each frame 12a, 12b comprises a chord 16a, 16b, respectively. These chords 16a, 16b extend in the longitudinal direction and are arranged obliquely relative to the boom 3, in particular to the longitudinal axis of the boom. Here, the angle θ (see FIG. 1c) between the chord 16 and said longitudinal axis is about 15°. At the lower ends 20a, 20b of the chords 16a, 16b, the distance between the chord 16 and the boom 3 is greater than the distance between the chord 16 and the boom 3 at the upper ends 21a, 21b of the chords. The chords 16a, 16b are connected to the boom 3 via a truss or brace 22. In the detailed view of FIG. 3, it can be seen that the upper ends 21a, 21b of the strings 16a, 16b are floating and are not connected to the boom themselves, but are connected to the boom via a truss 22. This ensures a smoother force transmission. At the lower ends 20a, 20b, the strings 16a, 16b are connected to the boom 3 via a truss 22. At that position, the truss 22 is connected to a position on the boom legs 19a, 19b. In FIG. 3, it can be seen that the boom side base engagement element 13 provided at the lower ends 20a, 20b of the strings 16a, 16b is embodied as a trumpet-shaped element. It is understood that other shapes of engagement elements are also possible. In this embodiment, the two frames 12a, 12b are connected to each other by an additional brace 33, which is optional. The brace 33 can also be omitted. The longitudinally extending frame chords 16a, 16b are connected to the boom 3, specifically to the boom base 6, via a number of trusses 22. The multiple trusses 22 may be connected to trusses 34 of the boom 3 or may be connected to a chord 35 of the boom 3. Connecting the longitudinally extending chords 16a, 16b to the boom 3 at a number of different locations allows loads to be transferred to the boom 3 in a distributed manner, thereby allowing for the transfer of relatively large loads before damage occurs.This allows for the transmission of relatively high loads of forces that may occur when the boom tip may swing and / or accelerate due to a disaster or other cause. Also, the chords 16a, 16b have a greater distance D1 from the boom 3 at their lower ends 20a, 20b, specifically from the upper side 11 of the boom 3, than a distance D2 from the boom 3 at their upper ends 21a, 21b. In instances where the frame chords 16 are directly connected to the boom 3, such as the boom chord 35, this distance D2 is zero. Therefore, at least one frame chord is oriented obliquely toward the boom 3, thereby effectively transmitting forces to the boom 3 or the boom chord 35.

[0033] It is noted that the frame 12 may have two strings instead of one, and these two strings may reach towards the two upper strings of the boom 3 or the boom leg 19.

[0034] FIG. 4 shows the boom base 6 hinged to the support structure 2 via boom connections 23a, 23b of the boom legs 19a, 19b, respectively. Here, the boom connections 23a, 23b are separate from the A-frame connections 24a, 24b. Here, the boom mounting structure 9 is shown engaged to the support mounting portion 10, with the respective engagement elements 13, 15 cooperating with each other. With the boom 3 in this position, the biasing element 14 of the support mounting portion 10 is almost fully compressed, which suggests that the boom 3 is in an up position or near an up position with a boom angle of about 83 degrees or 85 degrees. The biasing elements 14a, 14b, which engage the frames 12a, 12b of the boom mounting structure 9, respectively, are hinged to the support structure 2 via connections 25a, 25b, respectively. As explained above, each biasing element 14a, 14b of the support structure mounting part 10 is supported by a support arm 18a, 18b. The U-shaped ends 28a, 28b of the support arms 18a, 18b support each of the biasing elements 14a, 14b in a neutral position when not yet engaged with the boom mounting part 9. The U-shaped ends 28a, 28b also limit the lateral movement of the biasing elements 14a, 14b and ensure the integrity of the hinge connections 25a, 25b. Here, it can be seen that when the boom 3 is in the upper position, i.e. when the boom angle is large, the biasing elements 14a, 14b are located at a certain distance from the lower part of the U-shaped support ends 28a, 28b, but still between the arms of the U-shaped support ends 28a, 28b. In this example, the support arms 18a, 18b are connected to each other by a bar 29, which is optional.

[0035] FIG. 5 shows an alternative embodiment of the boom mounting part 9. The boom mounting part 9 is connected to the boom 3, in particular to the boom base 6. Here, the boom base 6 has two boom legs 19a, 19b. The boom mounting part 9 comprises at least one frame 12, where two frames 12a, 12b are provided for each leg 19a, 19b. Each frame has at least one longitudinally extending chord 16a, 16b, which is located at a distance from the boom 3 at its lower end and extends in a direction towards the boom 3. In this case, the longitudinally extending frame chord 16a, 16b branches into two chords 30a, 31a, 30b, 31b, which are directly connected to the respective boom chords of the boom legs 19a, 19b. In this embodiment, the frames 12a, 12b include multiple trusses 22 that connect to the boom chord at multiple different locations. In this way, forces can be transmitted to the boom 3 in a distributed manner.

[0036] In an alternative embodiment, the boom mounting portion 12 may be a compressible element that is advantageously biased towards the extended position. In this case, the support structure mounting portion 10 may be a frame or a frame-like structure. Such a frame-like structure may be hinged to the support structure 2 such that the boom mounting portion and the support structure mounting portion are able to follow the movement of the boom when engaged. Alternatively, the boom mounting portion is hinged to the boom such that the boom mounting portion is able to follow the movement of the boom when engaged with the support structure mounting portion.

[0037] The anti-tip system for an offshore crane comprises a boom mounting portion arranged for attachment to a boom of the offshore crane and a support structure mounting portion to be attached to a support structure for the offshore crane, the boom mounting portion comprising a frame having at least one longitudinally extending chord, the support structure mounting portion comprising a biasing element biased towards an extended position, and the boom mounting portion and the support structure mounting portion configured to engage each other when a boom angle of the boom exceeds a predetermined threshold.

[0038] Although features are described herein as part of the same or separate embodiments for clarity and ease of description, it will be understood that the claims and the scope of the disclosure may include embodiments having all or a partial combination of the features so described. Illustrated embodiments may be understood as having the same or similar components, unless each is described as being different.

[0039] In the claims, any reference signs placed in parentheses shall not be interpreted as limiting the claim. The word "comprises" does not exclude the presence of other features or steps than those recited in the claim. Moreover, the words "a" and "an" shall not be interpreted as being limited to "only one" but are used to mean "at least one" and do not exclude a plurality. If several measures are recited in mutually different claims, this fact alone does not indicate that these measures cannot be used in an advantageous combination. Numerous variations will become apparent to those skilled in the art, which are within the scope of the invention as defined in the appended claims. [Explanation of symbols]

[0040] 1. Offshore Crane 2 Support structure, base structure 3. Boom 4. A-frame 5. Winding System 6 Boom base 7 Boom tip 8. Anti-tip system 9 Boom mounting part, boom mounting structure 10 Support structure attachment portion, support structure side base 11 Upper side, rear side 12 Triangular truss frame 12a Frame 12b Frame 13 Boom side base engaging element, boom engaging element 14. Actuation elements 14a Biasing element 14b Biasing element 15 Support structure side base engagement element 16 Frame strings, longitudinally extending strings 16a string, longitudinally extending frame string 16b string, longitudinally extending frame string 17 Lower end 18 Support Arm 18a Support arm 18b Support arm 19 Boom leg 19a Boom Leg 19b Boom Leg 20a Lower end 20b Lower end 21a Upper end 21b Upper end 22 Trusses and braces 23a Boom connection part 23b Boom connection part 24a A-frame connection 24b A-frame connection 25a Connection, hinge connection 25b Connection, hinge connection 28a U-shaped end, U-shaped support end 28b U-shaped end, U-shaped support end 29 Bar 30a string 30b string 31a string 31b string 33 Brace 34 Truss 35 strings, boom strings

Claims

1. 1. An anti-tip system for an offshore crane, comprising: a boom mounting portion arranged to be attached to a boom of the offshore crane; a support structure mounting portion to be attached to a support structure for the offshore crane; Equipped with one of the boom mounting portion and the support structure mounting portion comprises a frame having at least one longitudinally extending chord; the other of the boom mounting portion and the support structure mounting portion includes a biasing element biased toward an extended position; The boom attachment portion and the support structure attachment portion are configured to engage each other when a boom angle of the boom exceeds a predetermined boom angle threshold.

2. 2. The system of claim 1, wherein the boom attachment portion comprises the frame having the at least one longitudinally extending chord, and the support structure attachment portion comprises the biasing element biased toward the extended position.

3. The system of claim 2 , wherein a distance of the at least one chord to the boom is greater near a frame base of the frame and less near a frame tip of the frame.

4. 4. The system of claim 2 or 3, wherein in a side view, the frame is triangular with respect to the boom and the at least one chord extends diagonally toward the boom.

5. 5. The system of claim 2, wherein the frame is permanently connected to the boom.

6. 6. A system as claimed in any one of claims 2 to 5, wherein over the length of the boom to which the boom mounting part is connected, connections between the trusses of the frame of the boom mounting part and the trusses or chords of the boom are provided at a number of different positions axially, i.e. in the longitudinal direction of the boom, and / or radially, i.e. transversely to the axial direction.

7. 7. A system as claimed in any one of claims 1 to 6, wherein the support structure mounting portion is intended to be mounted to a support structure to which the boom is pivotally connected, in particular at a boom base of the boom.

8. A system as claimed in any preceding claim, wherein the predetermined boom angle threshold is in the range of 40 to 70 degrees, preferably around 60 degrees.

9. The system of claim 1 , configured to automatically lock the biasing element in response to pressure on the biasing element exceeding a first predetermined pressure threshold.

10. 10. The system of claim 9, configured to automatically release a locked biasing element in response to a predetermined release criterion, in particular in response to the pressure on the biasing element falling below a second predetermined pressure threshold that is less than or equal to the first predetermined pressure threshold.

11. 11. The system of any one of claims 1 to 10, further comprising a support arm configured to hold the biasing element in a rest position having an angle relative to the support platform such that the biasing element is capable of engaging the frame at an angle of 50-70 degrees or approximately 50-70 degrees, preferably approximately 60 degrees.

12. The system according to claim 11 , wherein the support arm has a U-shape for limiting lateral movement of the biasing element, particularly in a rest position.

13. 13. An offshore crane having a boom pivotally mounted to a support structure, the crane being provided with an anti-tip system as claimed in any one of claims 1 to 12, the boom mounting portion being mounted to the boom and the support structure mounting portion being mounted to the support structure, preferably pivotally mounted to the support structure.

14. 14. An offshore crane as claimed in claim 13 when dependent on claim 2, wherein the at least one longitudinally extending chord of the frame has an angle of about 1 to 30 degrees with respect to a longitudinal direction of the boom.

15. An offshore crane as claimed in claim 13 or 14 when dependent on claim 2, wherein the frame is attached to the boom in a lower 10-50% of the boom length of the boom, preferably in a lower 12-40% of the boom length.

16. 16. The offshore crane of claim 15, wherein an upper end of the at least one longitudinal frame chord of the boom mounting portion extends up to about 10-50% of the boom length, preferably up to about 30% of the boom length.

17. Use of an offshore crane according to any one of claims 13 to 16 for lifting operations, in particular lifting heavy loads in offshore locations.

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