Overturn-preventing system of offshore crane, suspension arm and offshore crane

Abstract

An overturn prevention system (8) for an offshore crane, comprising: a boom mounting member (9) arranged to be mounted to a boom (3) of an offshore crane (1); a support mounting member (10) mounted to a support structure (2) for the offshore crane; wherein the boom mounting member comprises a frame having at least one longitudinally extending chord member (16); wherein the support mounting part comprises a biasing element (14) biased towards an extended position, and wherein the boom mounting part and the support mounting part are configured to engage with each other when a boom angle (alpha) of the boom exceeds a predetermined threshold.

Description

Technical Field

[0001] The present invention relates to an offshore crane. In particular, the present invention relates to an anti-capsize system for an offshore crane. Background Art

[0002] Offshore cranes are well known and are typically mounted on a floating structure, such as a ship or barge or a jack-up platform. Offshore cranes may be used for various purposes, such as for heavy lifting operations at offshore locations, such as installing and decommissioning heavy structures, such as wind turbines, wind turbine infrastructure, platforms, platform topsides, etc.

[0003] An offshore crane typically comprises a boom pivotally mounted to a supporting structure. At the top of the boom, a load can be hoisted. Crane designers are aware of various failure modes and will design and build offshore cranes with these failure modes in mind. One such failure may be referred to as boom capsizing. The swinging motion of the boom caused by one or another force or a sudden lack of force or by a disaster (e.g. loss of load, or failure of the luffing or hoisting cables, vessel motion, hook failure) will cause the boom to capsize, i.e. the boom tilts backwards beyond the vertical. This will result in structural damage or total loss of the boom and / or structures near or behind the boom. Various structures are known to limit the position of the boom and / or define the end position of the boom. The most commonly used structure is a boom stop: typically a hydraulic cylinder mounted on an A-frame or similar structure, which engages the boom in a direction transverse to the longitudinal direction of the boom. When the boom reaches the end position, the boom stop engages a stop surface. However, the effectiveness of such a boom stop is limited and will not prevent the boom from capsizing or prevent structural damage to the boom. Summary of the invention

[0004] An object of the present invention is to provide an anti-capsize system for an offshore crane. In particular, an object of the present invention is to provide an anti-capsize system that can efficiently and / or effectively limit or prevent the capsizing of a boom.

[0005] To this end, the present invention provides an anti-overturning system, comprising a boom mounting part and a support mounting part. One of the boom mounting part and the support mounting part comprises a frame having at least one longitudinally extending chord, and the other of the boom mounting part and the support mounting part comprises a biasing element biased towards an extended position. The boom mounting part may comprise a frame having at least one longitudinally extending chord, wherein the distance of at least one chord to the boom is greater near the base of the frame and smaller near the top of the frame. Then, the at least one longitudinally extending chord may comprise an angle with the longitudinal main axis of the boom, wherein the angle may be in the range of 1 degree to 30 degrees, more preferably in the range of 5 degrees to 25 degrees, even more preferably in the range of 10 degrees to 20 degrees, for example about 15 degrees. It has been found that such an angle may produce a particularly advantageous combination of lateral and longitudinal anti-overturning effects on the boom, wherein the lateral component may be associated with more direct counteracting of adverse swinging motions, while the longitudinal component may be associated with loading of the boom along its longitudinal axis. Without wishing to be bound by theory, it is believed that such an angle may thereby advantageously convert at least a portion of the momentum associated with the boom swing into a load on the boom along its longitudinal axis.

[0006] The frame can be implemented as a truss or non-truss, such as a box frame or a frame including plates and / or trusses. Thus, in a side view, the frame with at least one chord can be triangular relative to the boom, wherein the chord extends obliquely towards the boom. The frame base of the frame can be located at the bottom end of the boom (boom base). The distance between the at least one chord and the boom can be greater at the boom base than at a distance away from the boom base, wherein the chord is towards the boom. At least one chord of the frame can be connected to the boom at least at the bottom end of the chord and / or at the top end of the chord by a support or truss. At least one chord of the frame can be directly connected to the boom or can be connected to the boom by a bracket. In the latter case, the at least one chord can be considered floating or can be considered to be supported on the boom only by the bracket. Preferably, the frame including at least one chord is mounted to the boom and is permanently connected to the boom, also during normal operation. The trusses or brackets of the frame can be connected to the trusses or brackets of the boom and / or can be connected to the chords of the boom. In known designs, the boom comprises such trusses, brackets and / or chords, or may even consist mainly of such trusses, brackets and / or chords. However, it should be understood that the boom may be designed partially with such elements or completely without such elements, for example including one or more beams, plates, etc. Over the length of the frame, a plurality of trusses or brackets may be provided, which may be connected to the boom at various longitudinal and / or radial positions of the boom. Thus, over the length of the boom where the boom mounting part is connected to the boom, the connection between the trusses of the frame of the boom mounting part on the one hand and the trusses or chords of the boom on the other hand is provided at a plurality of different positions in the axial direction (i.e. in the longitudinal direction of the boom) and / or in the radial direction (i.e. transverse to the axial direction). Such a plurality and / or different connections at different positions may advantageously transfer loads from the anti-overturning system to the boom in the event of a disaster. The boom mounting part implemented as a frame may usually be connected to the boom by welding and / or bolts, but an articulated connection is also conceivable.

[0007] One of the boom mounting member and the support mounting member may be hingedly mounted to its associated mounting base to allow following the movement of the boom when the boom mounting member and the support mounting member are engaged. Furthermore, one of the boom mounting member and the support mounting member is a compressible element, preferably biased toward an extended position to allow following the movement of the boom when the boom mounting member and the support mounting member are engaged and / or absorbing energy in the event of a disaster.

[0008] The boom is pivotally connected to a support structure or base structure at the boom base. Such a support structure or base structure may be, for example, a slewing platform. The support mounting part of the anti-overturning system is mounted to such a support structure. The support mounting part may include a biasing element biased towards the extended position. The biasing element may generally be a compressible element, in that it may be compressed when in contact and / or under load. The biasing element may be, for example, a hydraulic cylinder, or a pneumatic cylinder, or a spring-based system. The biasing element may be pivotally mounted to the support structure at its lower end, and may be configured at its outer free end to engage with a frame of the boom mounting part. The bottom end of at least one chord of the frame is then preferably configured to engage with the outer end of the biasing element when the angle of the boom relative to the horizontal becomes too large, i.e., greater than a safety threshold, which may be predetermined. The angle of the boom relative to the horizontal is generally referred to as the boom angle. It is envisaged that the engagement between the frame and the biasing element is at a boom angle of about 60 degrees or at a boom angle of about 60 degrees, preferably at a boom angle of between about 40 degrees and about 70 degrees. When the boom angle changes larger, the frame compresses the biasing element against the biasing force. In the event of an unexpected swinging motion where the boom angle increases, in particular increases rapidly, the biasing element can absorb the energy of the motion (e.g., the swinging motion), and the force, such as the overturning moment, can be transmitted to the chord of the boom via the frame. In this way, the force can be directed to a direction in which the force does not amplify the swinging motion of the boom, but is directed to the chord of the boom, which is designed to receive such high loads. Therefore, the anti-overturning system can effectively prevent the overturning of the boom, and can also prevent damage to the boom due to the swinging motion. In addition, by providing a truss, a relatively light structure can be provided, which can effectively guide the load to the chord of the boom in the event of a potential overturning of the boom, thereby limiting or preventing failures.

[0009] Advantageously, the boom mounting member and / or the support mounting member are provided with engagement elements which engage with each other when the boom angle exceeds a predetermined angle.

[0010] A plurality of biasing elements may be provided that engage with the frame of the boom mounting member. For example, two biasing elements may be considered to share a common engagement element and thus may be considered to be positioned in parallel. Alternatively, the biasing elements may be positioned in series. Moreover, combinations of series and parallel configurations of the plurality of biasing elements are possible.

[0011] Furthermore, it will be appreciated that the compressible element as a biasing element may also include a damping element, such as a gas buffer or a corrugated zone.

[0012] Alternatively, the support mounting member may be a fixed element such as a frame and the boom mounting member may be a compressible element such as a biasing member. Additionally, when the boom angle exceeds a certain threshold, engagement occurs and the boom mounting member is compressed and loads may be directed to the support and / or boom.

[0013] Alternatively and / or additionally, in the event of a disaster, when the boom begins to accelerate, the biasing element can be locked to stop further movement of the boom, thereby preventing further acceleration of the boom. The locking of the biasing element can be performed at any position between the fully extended position and the fully compressed position (including the fully extended position and the fully compressed position). For example, when the pressure in the biasing element increases too quickly, the locking of the biasing element can be passively obtained. The locking can be performed mechanically, hydro-mechanically or hydraulically, or by other means (for example to maintain the biasing element, or to block the outflow of fluid). Then, in this extended position, the biasing element can be locked, that is, this extended position of the biasing element is frozen and the biasing element is blocked in this position. In the locked position, the portions of the biasing element that are extendable relative to each other between the fully extended position and the fully compressed position of the biasing element can be prevented from moving relative to each other. The locking of the biasing element can be performed when the boom mounting member and the support mounting member are engaged so that pressure in the biasing element may accumulate. If the pressure on the biasing element becomes too great, for example greater than a predetermined threshold, the biasing element may be locked; when the pressure may become lower or may drop below the predetermined threshold, the lock may be released so that the biasing element may remain engaged with the boom mounting support. Such thresholds for locking and releasing may be the same, but are preferably different to prevent too rapid switching between locking and releasing. In other words, a hysteresis effect with respect to locking and releasing may thus be provided.

[0014] During normal crane operation, when the boom angle becomes greater than a predetermined boom angle, the support mounting member and the boom mounting member engage. During normal crane operation, when the support mounting member and the boom mounting member engage, the support mounting member and the boom mounting member move together with the movement of the boom. In normal operation, the movement of the support mounting member and the engaged boom mounting member with the boom is smooth. Then, in normal operation, the biasing element of the support mounting member is compressed and / or extended to follow the movement of the boom. In normal operation, the anti-overturning system does not or hardly introduces and / or transfers any additional load to the boom. However, in the event of a disaster, the boom top may accelerate, and when the boom angle exceeds the predetermined boom angle, engagement occurs between the boom mounting member and the support mounting member if the boom mounting member and the support mounting member are not yet engaged. In addition, the engaged boom mounting member and the support mounting member move together, and the additional energy of the accelerated boom top can be absorbed by the biasing element and / or the biasing element can be locked. Thereby, loads can be introduced into the longitudinal direction of the boom and / or the supporting structure. The boom is capable of handling large loads via the chord. In this way, the boom can be effectively prevented from overturning without causing damage or causing limited damage to the boom and / or its environment.

[0015] Because the biasing element is biased toward its extended position, it may help maintain tension on the luffing cables of the luffing system when the boom mounting member and the support mounting member are engaged, but may not prevent the cables from slacking.

[0016] In any case, when the boom angle is about 60 degrees, the bottom end of at least one chord and the biasing element associated therewith are engaged, and the biasing element can follow the tilt of the boom. In normal operation, a boom angle of about 83 degrees can be reached. The biasing element can then be in a fully retracted position, in other words, the biasing element can then be fully compressed. When lowering the boom, the biasing element can also follow the movement of the boom, and when the boom angle becomes less than about 60 degrees, the biasing element and the frame can be disengaged and the biasing element is again in its extended position.

[0017] Typically, an A-frame may be mounted to a support structure, for example to guide a luffing system and / or a hoisting system of a crane. Such an A-frame typically has four connections to the support structure, which are arranged in two pairs of connections at a distance from each other. When the boom has two boom legs at the lower end, the boom base connection may be integrated into a pair of such connections of the A-frame, or the boom base may have its own support connection independent of the A-frame connection. In the latter example, the boom base connection is typically mounted on the outside of the A-frame connection. Furthermore, when the boom is a single boom with a single boom leg, the boom base connection to the support structure may be separate from the connection to the A-frame or similar frame structure. Advantageously, biasing elements are also mounted on the support structure on the sides of the A-frame.

[0018] The boom mounting part of the anti-overturning system is mounted to the boom at the upper side of the boom, which upper side may also be referred to as the rear side of the boom, i.e. the side of the boom opposite to the side where the load lifted by the boom is usually located. In a side view, it can be seen that the boom has an additional triangular frame mounted on such an upper side of the boom, in particular close to the boom base. Of course, the frame can be a three-dimensional structure with a more prismatic shape, with a larger bottom at the frame base and the boom base, and a smaller top end where at least one chord of the frame intersects or almost intersects with the chord of the boom. When the lower end of the boom is configured as two boom legs, each boom leg may be provided with such a frame of the boom mounting part. Then, two offset elements are also arranged. For each chord of the frame of the boom mounting part, an associated offset element supporting the mounting part is envisaged. For example, when the frame on one boom leg has two longitudinally extending chords (trusses connected to the boom), there may be two chord lower ends, which are configured to engage with two corresponding offset elements. Alternatively, the two chord lower ends may be joined to form one joined element with corresponding biasing elements.

[0019] In the rest position, the biasing element is not yet engaged, and the biasing element is preferably positioned so that the biasing element can optimally engage with the frame on the boom when the boom angle reaches about 50, preferably about 60 degrees. Therefore, in the rest position, the biasing element has an angle relative to the support platform so that it can engage with the frame at a boom angle of (or about) 50 degrees to (or about) 70 degrees, preferably about 60 degrees. In order to keep the biasing element in the rest position, a support arm can be provided, which holds the biasing element in the rest position and also accommodates the biasing element when the biasing element is disengaged from the frame. The support arm can be U-shaped to limit excessive lateral movement of the biasing element. In fact, the biasing element is preferably hingedly mounted to the support structure, so that excessive lateral movement of the biasing element may lead to failure of the hinge connection, which can be prevented by the support arm, in particular by the U-shape of the support arm (e.g. U-shaped bracket). Advantageously, in the rest position, the biasing element is also biased towards its extended position. When engaged, the biasing element can be compressed and / or extended to follow the movement of the boom. Furthermore, the angular position of the biasing element may be different from the rest position in order to be able to follow the movements of the boom.

[0020] The invention also relates to an offshore crane having a boom pivotably mounted to a supporting structure, wherein the crane is provided with such an anti-capsize system.The boom-based component is mounted to the boom and the support-based component is mounted to the supporting structure, preferably pivotably mounted to the supporting structure.

[0021] In one example, as mentioned elsewhere herein, at least one chord of the frame mounted to the lower end of the boom has an angle of about 8 to 30 degrees, preferably about 10 to 20 degrees, preferably about 15 degrees, relative to the longitudinal direction of the boom. The frame may be mounted to the lower 10% to 50% of the boom, such as the lower 10% to 40% of the boom, preferably the lower 12% to 35% of the length of the boom. The upper end of at least one longitudinal frame chord of the boom mounting member may extend up to about 20% to 40% of the length of the boom, preferably up to about 25%.

[0022] More generally, the boom mounting member is advantageously mounted at the lower end of the boom, preferably at the lower 10% to 50% of the boom chord.As described above, the boom mounting member may be a frame, or may be a compressible element, such as a biasing element. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] These and other aspects will be further explained with reference to the accompanying drawings, which include diagrams of exemplary embodiments, in which:

[0024] Figure 1a is an offshore crane having an anti-capsize system in a first position;

[0025] Figure 1b is an offshore crane having an anti-capsize system in a second position;

[0026] Figure 1c is an offshore crane having an anti-capsize system in a third position;

[0027] Figure 2 The boom of an offshore crane is a boom-mounted component having an anti-capsize system;

[0028] Figure 3 yes Figure 2 Details of the boom mounting components;

[0029] Figure 4 is with Figure 1c Details of the support mounting components with support arms in corresponding cases;

[0030] Figure 5 is an alternative embodiment of a boom mounted component of an anti-overturn system.

[0031] It should be noted that the drawings are provided by way of example and are not intended to limit the present disclosure. The drawings are not drawn to scale. Corresponding elements are indicated by corresponding reference numerals. DETAILED DESCRIPTION

[0032] Figure 1a An offshore crane 1 mounted on a support structure or base structure 2 is shown. The offshore crane 1 comprises a boom 3 pivotally mounted to the support structure 2 and an A-frame 4 comprising, for example, a luffing system and / or a hoisting system 5. Here, a pair of connections of the A-frame 4 are located between the pivotal connections of the boom to the support structure 2, but it will be appreciated that they may also coincide. The boom 3 has a boom base 6 and a boom tip 7. At the boom tip 7, a load may be hoisted. The offshore crane 1 is provided with an anti-overturning system 8 comprising a boom mounting part 9 and a support mounting part 10. Here, the boom mounting part 9 is shown in a side view as a triangular truss 12 connected to the upper or rear side 11 of the boom. At the lower or base end of the truss, an engagement element 13 is provided, which is configured to engage with the support mounting part 10. Here, the support mounting part 10 is provided as a biasing element 14, such as a hydraulic cylinder or a pneumatic cylinder. The biasing element 14 is pivotally mounted to the support structure 2 and extends in the longitudinal direction. An engagement element 15 is provided at the outer end of the biasing element, which engagement element 15 is configured to engage with the engagement element 13 of the boom mounting member 9. In the event of a disaster causing excessive loads and / or movements, the boom mounting member 9 and the support mounting member 10 cooperate together to prevent or limit overturning of the boom 3.

[0033] exist Figure 1aIn FIG. 1 , the boom 3 is shown in a first position in which the boom mounting member 9 is disengaged from the support mounting member 10 and the boom mounting member 9 is not engaged with the support mounting member 10. Typically, this applies to boom angles of up to about 50 to 70 degrees, for example, up to about 50 to 60 degrees. The boom angle α is considered to be the angle between the longitudinal axis of the boom and the horizontal plane, such as Figure 1a The support-based component 10, in particular the biasing element 12 of the support-based component 10, is biased towards the extended position.

[0034] Figure 1b It is shown that the boom mounting member 9 engages with the support mounting member 10 when the boom angle reaches a predetermined angle α1, which can be set between about 50 degrees and 70 degrees or can be set to any value between about 50 degrees and 70 degrees (for example, about 60 degrees). To this end, the boom mounting member 9 can be provided with a boom-based engagement element 13, and the support mounting member 10 can be provided with a support-based engagement element 15. Then, the boom-based engagement element 13 and the support-based engagement element 15 associated therewith engage. For example, when the boom mounting member 9 has a chord 16, wherein the boom engagement element 13 is provided at the lower end 17 of the chord 16, the boom-based engagement element 13 has a corresponding and associated support-based engagement element 15 on the associated biasing element 14. In another example, the frame 12 may have two longitudinally extending chords 16, each chord having a boom-based engagement element 13 at its lower end 17, and then two associated support-based engagement elements 15 are provided, which engagement elements 15 may be connected to two separate biasing elements or may be connected to the same single biasing element. The multiple biasing elements may be arranged in a series configuration or in a parallel configuration or in a series-parallel combination. Once the boom mounting member 9 is engaged with the support mounting member 10, the biasing element 14 is compressed against the biasing force. In this way, the biasing element 14 may follow the movement of the crane boom 3 until the biasing element 14 is fully compressed and the boom 3 is in its most upward position, such as Figure 1c As shown. At this time, the boom angle α2 can be as large as 83 degrees or even 85 degrees. In the event of a disaster resulting in unexpected boom movement and / or boom acceleration, the anti-overturning system 8 can absorb the energy generated by such movement and can direct the excess load to the chord of the boom 3 and / or to the support structure 2. Therefore, the overturning of the boom 3 can be limited or prevented.

[0035] from Figure 1a , Figure 1b , Figure 1c And more detailed Figure 4 As can be seen in FIG. 1 , the biasing element 14 is supported by a support arm 18. The support arm 18 holds the biasing element 14 in its neutral position, as shown in FIG. Figure 1a 1, in which the biasing element 14 is ready to engage the boom mounting member 9. To optimally engage the boom mounting member, when the boom 3 reaches the boom angle α1, the biasing element 14 is preferably positioned at an angle β, wherein the angle β is between about 30 degrees and about 65 degrees, depending on (e.g., similar to) the angle α1 at which engagement is envisioned. Once the biasing element 14 is engaged with the truss 12, the biasing element 14 can rotate with the rotation of the boom 3 and can be disengaged 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 to limit lateral movement of the biasing element 14. In this sense, the support arm 18 can continue to cooperate with the biasing element 14 at various rotational positions of the biasing element 14.

[0036] Figure 2 An example of a boom 3 of an offshore crane is shown. Here, the boom 3 comprises two boom legs 19a, 19b at its boom base 6. Each boom leg 19a, 19b is hingedly mounted to a support structure to allow pivoting movement of the boom 3 only about the axis of rotation of the hinge. A frame 12a, 12b is mounted to the upper or rear side 11 of the boom 3.

[0037] Here, the boom mounting part 9 comprises two frames 12a, 12b, which are connected to two legs 19a, 19b, in particular each frame is connected to a respective leg. Thus, each leg 19a, 19b provides an additional frame 12a, 12b. Each frame 12a, 12b comprises a chord 16a, 16b, respectively. The chords 16a, 16b extend longitudinally and are arranged in an inclined direction with respect to the boom 3, in particular with respect to the longitudinal axis of the boom. Here, the angle θ between the chord 16 and said longitudinal axis (see Figure 1c ) is about 15 degrees. The distance between the chord 16 at the lower end 20a, 20b of the chord 16a, 16b and the boom 3 is greater than the distance between the chord 16 at the upper end 21a, 21b of the chord and the boom 3. The chords 16a, 16b are connected to the boom 3 by trusses or brackets 22. Figure 3 As can be seen from the details, the upper ends 21a, 21b of the chords 16a, 16b are floating and are not connected to the boom itself, but are connected to the boom via the truss 22. This ensures a smoother transfer of forces. The chords 16a, 16b are connected to the boom 3 at the lower ends 20a, 20b via the truss 22. There, the truss 22 is connected to the positions on the boom legs 19a, 19b. Figure 3As shown, the boom-based engagement element 13 disposed at the lower ends 20a, 20b of the chords 16a, 16b is implemented as a trumpet-shaped element. It should be understood that the engagement element may also be of other shapes. In this embodiment, the two frames 12a, 12b are interconnected to each other by an additional bracket 33, but this is optional. The bracket 33 may also be omitted. The longitudinally extending frame chords 16a, 16b are connected to the boom 3, in particular to the boom base 6, through a plurality of trusses 22. The plurality of trusses 22 may be connected to the trusses 34 of the boom 3, or may be connected to the chord 35 of the boom 3. By connecting the longitudinally extending chords 16a, 16b to the boom 3 at a plurality of different locations, the load may be transferred to the boom 3 in a dispersed manner, thereby allowing a relatively large load to be transferred before damage may occur. In this way, when the boom top swings and / or accelerates due to a disaster or other reasons, it is allowed to transfer the forces that may be generated with a relatively large load. Furthermore, the distance D1 between the chords 16a and 16b and the boom 3 (particularly, the upper side 11 of the boom 3) at the lower ends 20a and 20b, respectively, is greater than the distance D2 between the chords 16a and 16b and the boom 3 at the upper ends 21a and 21b. In the example where the frame chord 16 is directly connected to the boom 3 (e.g., to the boom chord 35), the distance D2 even becomes 0. In this way, at least one frame chord is inclined toward the boom 3, thereby guiding the force transmission to the boom 3 or the boom chord 35 in an effective manner.

[0038] It should be noted that the frame 12 may be provided with two chords instead of a single chord, which may extend towards the two upper chords of the boom 3 or the boom legs 19 .

[0039] Figure 4The boom base 6 is shown hingedly mounted to the support structure 2 via the boom connections 23a, 23b of the boom legs 19a, 19b, respectively. Here, the boom connections 23a, 23b are separated from the A-frame connections 24a, 24b. Here, the boom mounting structure 9 is shown engaged with the support mounting part 10, the respective engagement elements 13, 15 cooperating with each other. In this position of the boom 3, the biasing element 14 of the support mounting part 10 is almost fully compressed, which indicates that the boom 3 is in or almost in its upper position with a boom angle of about 83 degrees or 85 degrees. The biasing elements 14a, 14b, respectively engaged with the frames 12a, 12b of the boom mounting structure 9, are hingedly connected to the support structure 2 via connections 25a, 25b, respectively. As explained above, each biasing element 14a, 14b of the support mounting part 10 is supported by a support arm 18a, 18b. In the case where it has not yet been engaged with the boom mounting part 9, the U-shaped ends 28a, 28b of the support arms 18a, 18b support the biasing elements 14a, 14b, respectively, in a neutral position. In addition, the U-shaped ends 28a, 28b limit the lateral movement of the biasing elements 14a, 14b, which can ensure the integrity of the hinge connection 25a, 25b. Here, the boom 3 is in an upward position, i.e. at a large boom angle, and it can be seen that the biasing elements 14a, 14b are at a distance from the bottom 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 interconnected to each other by a rod 29, but this is optional.

[0040] Figure 5 An alternative embodiment of a boom mounting part 9 is shown. The boom mounting part 9 is connected to the boom 3, in particular to a 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, here two frames 12a, 12b are provided, one for each boom leg 19a, 19b. Each frame has at least one longitudinally extending chord 16a, 16b, which chord 16a, 16b is at its lower end at a distance from the boom 3 and extends in a direction towards the boom 3. Here, the longitudinally extending frame chord 16a, 16b is divided into two chords 30a, 31a and 30b, 31b, which are directly connected to the respective boom chords of the boom legs 19a, 19b. In this embodiment, the frames 12a, 12b comprise a plurality of trusses 22 connected to the boom chords at a plurality of different positions. In this way, forces can be transferred to the boom 3 in a distributed manner.

[0041] In an alternative embodiment, the boom mounting member 12 may advantageously be a compressible element biased towards the extended position. The support mounting member 10 may then be a frame or frame-like structure. Such a frame-like structure may be hingedly mounted to the support structure 2 to allow the boom mounting member and the support mounting member to follow the movement of the boom once engaged. Alternatively, the boom mounting member may be hingedly mounted to the boom so that it may follow the movement of the boom when engaged with the support mounting member.

[0042] An anti-capsize system for an offshore crane, comprising: a boom mounting member arranged to be mounted to a boom of the offshore crane; a support mounting member mounted to a support structure for the offshore crane; wherein the boom mounting member comprises a frame having at least one longitudinally extending chord; wherein the support mounting member comprises a biasing element biased toward an extended position, wherein the boom mounting member and the support mounting member are configured to engage each other when a boom angle of the boom exceeds a predetermined threshold.

[0043] For the purpose of clarity and concise description, features are described herein as being part of the same or separate embodiments, however, it should be understood that the scope of the claims and disclosure may include embodiments having all or some combinations of the described features. It is understood that the embodiments shown have the same or similar components unless they are described as different.

[0044] In the claims, any reference signs placed in brackets shall not be construed as limiting the claim. The term "comprising" does not exclude the presence of other features or steps than those listed in the claims. Furthermore, the terms "a" and "the" shall not be interpreted as being limited to "one", but are used to mean "at least one", and do not exclude a plurality. The fact that certain measures are cited in mutually different claims does not mean that a combination of these measures does not have advantages. Many variations will be apparent to those skilled in the art, as long as they are included within the scope of the invention as defined in the appended claims.

Claims

1. An anti-capsize system for an offshore crane, comprising: - a boom mounting member arranged to be mounted to a boom of said offshore crane; - a support mounting member mounted to a support structure for said offshore crane; - wherein one of the boom mounting member and the support mounting member comprises a frame having at least one longitudinally extending chord; - wherein the other of the boom mounting member and the support mounting member comprises a biasing element biased towards the extended position; - wherein the boom mounting member and the support mounting member are configured to engage with each other when a boom angle of the boom exceeds a predetermined boom angle threshold.

2. The system according to claim 1, wherein: The boom mounting member includes the frame having the at least one longitudinally extending chord, wherein the support mounting member includes the biasing element biased toward the extended position.

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

4. The system according to claim 2 or 3, wherein: In a side view, the frame is triangular in shape relative to the boom, and the at least one chord extends obliquely toward the boom.

5. The system according to any one of claims 2 to 4, wherein: The frame is permanently connected to the boom.

6. A system according to any one of claims 2 to 5, wherein: The connection between the truss of the frame of the boom mounting assembly and the truss or chord of the boom is arranged at a plurality of different positions along the length of the boom where the boom mounting assembly is connected to the boom, in an axial and / or radial direction, i.e. in the longitudinal direction of the boom and in a radial direction, i.e. transverse to the axial direction.

7. A system according to any one of the preceding claims, wherein: The support mounting member is mounted to a support structure to which the boom is pivotally connected, in particular at a boom base of the boom.

8. A system according to any one of the preceding claims, wherein: The predetermined boom angle threshold is in the range of 40 degrees to 70 degrees, preferably about 60 degrees.

9. A system according to any one of the preceding claims, configured to automatically lock the biasing element in response to the pressure on the biasing element exceeding a first predetermined pressure threshold.

10. A system according to claim 9, which is configured to automatically release the locked biasing element in response to a predetermined release criterion, in particular in response to the pressure on the biasing element dropping below a second predetermined pressure threshold, the second predetermined pressure threshold being equal to or less than the first predetermined pressure threshold.

11. The system of any of the preceding claims, further comprising a support arm configured to hold the biasing element in a stationary position wherein the biasing element has an angle relative to the support platform such that the biasing element is engageable with the frame at an angle of or approximately between 50 and 70 degrees, preferably approximately 60 degrees.

12. The system according to claim 11, wherein: The support arm is U-shaped to limit lateral movement of the biasing element, particularly in the rest position.

13. An offshore crane having a boom pivotably mounted to a support structure, wherein: The crane is provided with an anti-overturning system according to any one of the preceding claims, wherein the boom mounting member is mounted to the boom and the support mounting member is mounted, preferably pivotably mounted, to the support structure.

14. An offshore crane according to claim 13 as appended to claim 2, wherein: The at least one longitudinally extending chord of the frame has an angle of about 1 degree to about 30 degrees relative to a longitudinal direction of the boom.

15. An offshore crane according to claim 13 or 14 as appended to claim 2, wherein: The frame is mounted to the boom at the lower 10% to 50% of the boom length of the boom, preferably at the lower 12% to 40% of the boom length.

16. The offshore crane according to claim 15, wherein: The upper end of the at least one longitudinal frame chord of the boom mounting member extends for about 10% to about 50% of the length of the boom, preferably for about 30% of the length of the boom.

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

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