Boom stabilization system for offshore cranes

Abstract

A boom stabilization system for an offshore crane, comprising: a boom mounting section configured to be attached to the boom of an offshore crane; and a support mounting section configured to be attached to a support structure for an offshore crane, wherein the boom mounting section comprises a frame having at least one longitudinally extending chord member; the support mounting section comprises a biasing element that is biased toward an extended position; and the boom mounting section and the support mounting section are configured to engage with each other when the boom angle of the boom exceeds a first predefined boom angle threshold. The system is configured to use the biasing element to limit and / or reduce the boom angle in order to suppress slack in the luffing wire of the offshore crane when the boom angle exceeds a second predefined threshold greater than the first predefined threshold.

Description

Technical Field

[0001] The present invention relates to an offshore crane. In particular, the present invention relates to a boom stabilization system for offshore cranes.

Background Art

[0002] Offshore cranes are widely known and are typically mounted on floating structures such as vessels, barges, or jack-up structures. Offshore cranes can be used for a variety of purposes, for example, lifting heavy loads at offshore locations such as the installation and removal of heavy structures like wind turbines, wind turbine foundations, platforms, and platform topsides.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Offshore cranes typically feature a boom pivotably mounted to a support structure. Loads can be hoisted at the tip of the boom. Crane designers are aware of various failure modes, and the design and manufacture of offshore cranes are carried out with such failure modes in mind. In some failure modes, excessive swaying motion of the boom, induced by certain forces caused by accidents such as load loss, breakage of the luffing or hoist wire, ship motion, or lift hook breakage, or by the sudden loss of force, can cause excessive destabilization of the boom. This can result in structural damage, or in some cases, the loss of the boom and / or other members of the crane and / or structures near the boom. Various structures are known for limiting the boom's position and / or defining the boom's end position. One commonly used structure is a boom stopper, which is a hydraulic cylinder typically mounted on an A-frame or similar structure that engages with the boom in a direction transverse to the boom's longitudinal direction. When the boom reaches its end position, the boom stopper engages with the stopping surface. However, the effectiveness of such boom stoppers is limited, and they may not prevent structural damage to the boom or other crane components if excessive boom instability occurs. A possible alternative or additional means to improve boom stability is to impose a relatively large minimum radius on the crane, also known as the minimum outreach, i.e., the horizontal distance from the base of the crane to the nearest possible position of the load being suspended from the crane. However, a large minimum outreach limits the versatility of the crane in terms of possible load positions and may also result in excessive space requirements for crane operations, which can be problematic, especially in confined environments such as ship decks or offshore platforms.

[0004] The object of the present invention is to provide a boom stabilization system for offshore cranes. In particular, the object of the invention is to provide a boom stabilization system that can effectively and / or effectively limit or prevent damage to a crane while allowing a relatively small minimum outreach for the crane. [Means for solving the problem]

[0005] In contrast, the present invention provides a boom stabilization system according to claim 1, comprising a boom mounting section and a support mounting section. One of the boom mounting section and the support mounting section comprises a frame having at least one longitudinally extending chord, and the other of the boom mounting section and the support mounting section comprises a biasing element that is biased toward the extended position. The boom mounting section 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. The at least one longitudinally extending chord may then have an angle with the longitudinal principal 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, and even more preferably in the range of 10 to 20 degrees, for example, about 15 degrees. Such angles can produce a particularly favorable combination of lateral and longitudinal stabilization effects on the boom, with the lateral component being associated with a more direct suppression of unfavorable swaying motion, while the longitudinal component can be associated with loads along the longitudinal axis of the boom. Without being bound by theory, it can be considered that such angles can thus favorably convert at least a portion of the momentum associated with boom sway into loads on the boom along its longitudinal axis.

[0006] The frame may be embodied as a truss frame or as a frame without a truss, for example, as a box frame or a frame with plates and / or a truss. Thus, a frame having at least one chord may, in a side view, have a triangular shape with respect to the boom, with the chord extending diagonally toward the boom. The frame base of the frame may be at the lower end of the boom, at the boom base. At the boom base, the distance between the at least one chord and the boom may increase as it moves away from the boom base, with the chord being guided toward the boom. At least one chord of the frame may be connected to the boom using braces or trusses at least at the lower and / or upper ends of the chord. At least one chord of the frame may be connected to the boom directly, or it may be connected to the boom via braces. In the latter case, at least one chord can be said to be floating, or to be supported by the boom only by braces. Preferably, the frame having at least one chord is attached to the boom and permanently connected to the boom even during normal operation. The trusses or braces of the frame can be connected to the trusses or braces of the boom, and / or to the chords of the boom. In known designs, the boom may have, and may even be composed primarily of, such trusses, braces, and / or chords. Nevertheless, it should be understood that the boom may be designed partially or entirely without such elements, for example, with one or more beams or plates. Multiple trusses or braces can be provided along the length of the frame, at various longitudinal and / or radial positions of the boom, to which the boom can be connected. Thus, along the length of the boom where the boom attachment is connected to the boom, the connections between the trusses of the frame at one boom attachment and the trusses or chords of the other boom are provided at multiple distinct positions in the axial direction, i.e., the longitudinal direction of the boom, and / or radial direction, i.e., the direction transverse to the axial direction.Multiple and / or different connections at different locations may provide beneficial load transfer from the stabilization system to the boom. The boom mounting section, which is embodied as a frame, can typically be connected to the boom by welding or bolting, but hinge connections may also be considered.

[0007] One of the boom mounting section and the support mounting section may be hinged to its associated mounting base to allow it to follow the movement of the boom when the boom mounting section and the support mounting section are engaged. Alternatively, one of the boom mounting section and the support mounting section may be a compressible element that is preferably biased toward the extended position to allow it to follow the movement of the boom when the boom mounting section and the support mounting section are engaged, and / or to absorb energy.

[0008] The boom is pivotably connected at its base to a support structure or base structure. Such a support structure or base structure may be, for example, a slewing platform. The support mounting portion of the boom stabilization system is attached to such a support structure. The support mounting portion may include a biasing element that is biased toward the extended position. The biasing element may typically be a compressible element in that it can be compressed when it is in contact with and / or when a load is applied. The biasing element may be, for example, a hydraulic cylinder or a pneumatic cylinder or a spring-based system. The biasing element may be pivotably attached to the support structure at its lower end and may be configured to engage with the frame of the boom mounting portion at its outer free end. The lower end of at least one chord of the frame is preferably configured to engage with the outer end of the biasing element when the angle of the bottom with respect to the horizontal is relatively large, i.e., greater than a first threshold that may be predefined. The angle of the bottom with respect to the horizontal is typically called the boom angle. The engagement between the frame and the biasing element is expected at boom angles of approximately 60 degrees, preferably between approximately 40 and 70 degrees. As the boom angle subsequently increases, the biasing element is compressed against the biasing force of the frame. In the case of unintended swaying motions that increase rapidly, the biasing element can absorb kinetic energy, such as the energy of the swaying motion, whereas forces, such as the overturning moment, can be transmitted through the frame to the boom's chords. Thus, the forces can be directed in a direction that does not amplify the boom's swaying motion, but instead directed to the boom's chords, which are designed to receive such high loads. Therefore, the boom stabilization system can effectively prevent excessive swaying of the boom, and thus prevent damage to the boom due to excessive swaying motion. Furthermore, by providing a truss frame, for example, a relatively lightweight structure can be provided that effectively guides the load to the boom's chords in the event of any possible excessive swaying of the boom, thereby limiting or preventing damage.

[0009] The boom mounting section and / or support mounting section are advantageously provided with engaging elements that engage with each other when the boom angle exceeds a predefined angle.

[0010] Multiple biasing elements may be provided that engage with the frame of the boom mounting section. For example, two or more biasing elements can be considered to share one common engaging element and therefore can be said to be positioned in parallel. Alternatively, the biasing elements may be positioned in series. Combinations of series and parallel configurations of multiple biasing elements are also possible.

[0011] Furthermore, the compressible element acting as a biasing element may also include additional damping elements such as a gas buffer or a crushable zone.

[0012] Alternatively, the support mounting portion may be a fixed element such as a frame, and the boom mounting portion may be a compressible element such as a biasing element. In this case, engagement occurs when the boom angle exceeds a first predefined threshold, and the boom mounting portion is compressed while the load can be directed to the support and / or boom.

[0013] In an optional, advanced explanation, for example, if a disaster occurs and the boom begins to accelerate, the biasing elements can be locked to stop further movement of the boom, thereby preventing further acceleration of the boom. Locking of the biasing elements can be performed at any position between the fully extended position and the fully compressed position, including their own positions. Locking of the biasing elements may also be achieved passively, for example, if the pressure within the biasing elements rises excessively rapidly. Locking can be performed mechanically, hydraulically, hydraulically, or by other means, for example, by holding the biasing elements or blocking the outflow of fluid. Then, in the subsequent extended position, the biasing elements can be locked; that is, the extended position of the biasing elements is fixed, and the biasing elements are constrained to that position. Members of the biasing elements that are extendable relative to each other between the fully extended position and the fully compressed position of the biasing elements may be constrained not to move relative to each other in the locked position. Therefore, optionally, the boom stabilization system may be configured to allow the biasing action of a biasing element to be stopped by locking the biasing element, thereby essentially fixing the normally variable length of the biasing element at least until the subsequent release of the lock. Locking of the biasing element can be performed when the boom attachment and support attachment are engaged, allowing pressure to accumulate within the biasing element. If the pressure on the biasing element is too high, for example, above a predefined threshold, the biasing element can be locked, and when the pressure can become lower or fall below a predefined threshold, the lock can be released so that the biasing element can remain engaged with the boom attachment. Such thresholds for locking and unlocking may be the same, but preferably different to prevent the locking and unlocking from switching too rapidly. In other words, a hysteresis effect may be provided with respect to locking and unlocking.

[0014] During normal crane operation, the support mount and boom mount engage when the boom angle exceeds a predefined boom angle. When the support mount and boom mount engage during normal crane operation, they move together with the boom. The movement of the boom and the boom, engaged with the support mount, is smooth during normal operation. In normal operation, the biasing element of the support mount is compressed and / or expands to follow the boom's movement. In normal operation, there is little to no additional load induced to and / or transmitted to the boom by the boom stabilization system. In some cases, if the boom mount and support mount are not yet engaged when the boom angle exceeds a predefined boom angle, the boom tip accelerates and engagement occurs between the boom mount and the support mount. Subsequently, the engaged boom mount and support mount move together, and the additional energy of the boom's acceleration may be absorbed by the biasing element and / or the biasing element may lock. This allows the load to be applied longitudinally to the boom and / or within the support structure. The boom can handle large loads through the chord members. Therefore, excessive boom swinging can be effectively prevented without or with limited damage to the boom and / or its environment.

[0015] Since the biasing element is biased toward its extended position, when the boom attachment and support attachment are engaged, this may help maintain tension on the luffing wire of the luffing system, and in some cases, in particular, it may be possible to suppress wire slack by ensuring that the biasing of the biasing element is large enough to limit or reduce the boom angle accordingly.

[0016] In either case, when the boom angle is approximately 60 degrees, the lower end of at least one chord engages with its associated biasing element, allowing the biasing element to follow the boom's inclination. Under normal operation, the boom angle can reach approximately 83 degrees. At this point, the biasing element may be in a fully retracted position, in other words, it may be fully compressed. When the boom is lowered, the biasing element may similarly follow the boom's movement, and when the boom angle falls below approximately 60 degrees, the biasing element and the frame may disengage, and the biasing element returns to its extended position.

[0017] In many cases, an A-frame may be attached to a support structure, for example, to guide the luffing system and / or hoisting system of a crane. Such an A-frame typically has four connections to the support structure, arranged as two sets of connections at a certain distance from each other. When a boom has two boom legs at its lower end, the boom base connection can be integrated into one of such sets of A-frame connections, or the boom base may have its own support connection separate from the A-frame connections. In the latter example, the boom base connection is usually attached outside the A-frame connections. Also, 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 A-frame or similar frame structure connections. Advantageously, biasing elements are similarly attached to the support structure alongside the A-frame.

[0018] The boom attachment of the boom stabilization system is attached to the boom on the upper side of the boom, which is also sometimes called the rear side of the boom, i.e., the side of the boom opposite to where the load hoisted by the boom is normally positioned. In a side view, it can be seen that the boom has an additional triangular frame attached to such an upper side of the boom, particularly near the base of the boom. Naturally, the frame may have a more prismatic shape, having a larger bottom at the base of the frame and the base of the boom, and a smaller tip where at least one chord of the frame intersects, or nearly intersects, with one or more chords 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 attachment. In this case, two biasing elements are also arranged. For each chord of the boom attachment frame, associated biasing elements of the support attachment are expected. For example, when a frame on a boom leg has two longitudinally extending chords that are truss-connected to the boom, there may be two lower ends of the chords configured for engagement with two corresponding biasing elements. Alternatively, the two lower ends of the chords may be joined to form a single engagement element with the corresponding biasing elements.

[0019] In the stationary position, the biasing element is not yet engaged, and is preferably positioned so that it can optimally engage with the frame on the boom when the boom angle reaches approximately 50 degrees, preferably about 60 degrees. In this way, in the stationary position, the biasing element has an angle with respect to the support platform, allowing it to engage with the frame at boom angles of 50 to 70 degrees or about 50 to 70 degrees, preferably around 60 degrees. To hold the biasing element in the stationary position, a support arm can be provided to maintain the biasing element in the stationary position and to receive the biasing element again when it is disengaged from the frame. The support arm can be U-shaped to 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 could lead to breakage of the hinge connection, which can be prevented by the support arm, in particular by a U-shape such as a U-shaped bracket on the support arm. Advantageously, in its stationary position, the biasing element is also biased toward its extended position. When engaged, the biasing element may be compressed and / or expanded to follow the movement of the boom. Also, the angled position of the biasing element may differ from its stationary position so that it can follow the movement of the boom.

[0020] The boom stabilization system is configured to use the biasing stiffness of a biasing element to limit and / or reduce the boom angle in order to suppress slack in the luffing wire of an offshore crane when the boom angle exceeds a second predefined boom angle threshold which is greater than a first predefined boom angle threshold. The second predefined boom angle threshold is in the range of 77 to 89 degrees, preferably in the range of 80 to 86 degrees, for example, about 83 degrees.

[0021] By using biasing elements in this manner to suppress slack, it is advantageous to promote the stability of the crane's base and overall rigidity, especially at relatively large boom angles. Conventionally, at such large boom angles, slack in the luffing wire is relatively common, resulting in reduced base stability and overall crane rigidity, particularly associated with the risk of excessive boom sway. For example, environmental factors such as wind and waves have traditionally caused boom instability, and relatively small disturbances can sometimes be amplified when the boom is essentially pulled back to a smaller boom angle, for example, by being limited by the luffing wire, leading to impacts in the crane structure. Such impacts, especially excessive ones, can then lead to damage to crane components such as the luffing wire and sheaves, and may even result in the boom detaching from its luffing wire and falling. In some cases, excessive swaying can even cause the boom to tip over, i.e., tilt backward beyond its vertical position.

[0022] In this regard, without adhering to theory, at relatively large boom angles, the so-called restoring force of the boom against uncontrollable rotation and swing is conventionally considered to be relatively low. In this context, the restoring force can be understood as the variation in the lateral component of the force exerted on the boom by the luffing wire due to changes in the boom angle. The initial equilibrium of this force is typically induced by the gravitational component acting on the boom, for example, directly and / or through the suspended load, and such a gravitational component tends to move the boom in a direction that decreases the boom angle, that is, it is the component of gravity that acts laterally with respect to the boom axis and exerts a downward moment on the boom. As the boom angle approaches 90 degrees, corresponding to the vertical boom axis, the direction of the gravitational and luffing wire forces becomes increasingly parallel to the boom axis, so the restoring force decreases more and more, and as a result the lateral force component becomes smaller and smaller, so that only a small moment associated with the distance between the boom axis and the luffing wire and / or hoist wire connected to the boom remains.

[0023] On the other hand, simply using a winch to reel in the luffing wire and reduce its slack is not effective and may even worsen the problem, because it only increases the lower limit of the boom angle imposed by the luffing wire, meaning the boom can still swing further to a larger boom angle.

[0024] In contrast, if the boom stabilization system is configured to limit and / or reduce the boom angle in order to suppress slack in the luffing wire of an offshore crane by utilizing the biasing stiffness of the biasing elements, the boom can be kept stable even at relatively large boom angles, and the restoring force can be increased, which is usually relatively small. In particular, while the luffing wire may impose a variable lower limit on the boom angle, the boom stabilization system may simultaneously impose a substantially corresponding upper limit on the boom angle, so that the boom is essentially continuously constrained to a very narrow range of possible boom angles, for example, a range of nearly zero, in terms of uncontrollable boom rotation, while still allowing controlled adjustment of the boom angle over a relatively wide range of possible boom angles, including, for example, boom angles up to about 90 degrees. Being able to safely operate the crane at such large boom angles improves the versatility of the crane and can reduce the minimum outreach of the crane in particular, which can relax requirements regarding free deck space around the crane, for example.

[0025] Optionally, at least selectively, and / or when the boom angle exceeds a second predefined boom angle threshold, the biasing stiffness of the biasing element is determined to be such that it maintains the boom angle at a variable lower limit imposed on the boom angle by the luffing wire, and in particular, the biasing stiffness is then determined to be such that, with respect to the boom angle, it dampens any possible environmental disturbances acting on the boom.

[0026] With reference to the above description, in this way, the boom may thus essentially be continuously constrained to a very narrow range of possible boom angles in terms of uncontrolled boom rotation, while still allowing controlled adjustment of the boom angle over a relatively wide range of possible boom angles. In general, such uncontrolled boom rotation may in particular be associated with such environmental disturbances, for example relatively irregular boom movements resulting from wind and / or waves, acting directly on the boom, acting via the vessel or offshore platform on which the crane is installed, and / or acting via a load suspended from the crane.

[0027] Thus, when the lower limit imposed on the boom angle by the luffing wire is fixed, the boom stabilization system is preferably configured to essentially limit or constrain the boom angle to said lower limit. When the lower limit imposed on the boom angle by the luffing wire increases, i.e. when the luffing wire is wound up, the limitation or constraint performed by the boom stabilization system preferably follows the lower limit in accordance therewith, i.e. the upper limit imposed on the boom angle also essentially increases correspondingly. When the lower limit imposed on the boom angle by the luffing wire decreases, i.e. when the luffing wire is extended, the limitation or constraint performed by the boom stabilization system preferably likewise follows the lower limit in accordance therewith, i.e. essentially correspondingly reduces the upper limit imposed on the boom angle, and in some cases, if such reduction exerted solely by gravity is not sufficiently realized, or is not stably realized, the boom stabilization system may also reduce the boom angle.

[0028] Optionally, the boom stabilization system is preferably configured to actively vary the biasing stiffness of the biasing element by utilizing a hydraulic or pneumatic control line operatively connected to the biasing element.

[0029] In this manner, the biasing stiffness can be increased for boom stabilization as needed, and the biasing stiffness can be reduced in other cases. Advantageously, such reduced biasing stiffness may lead to improved energy efficiency, for example with respect to the energy required to wind up the luffing wire. When the biasing stiffness is actively increased in this way, it may be preferable to perform appropriate active control of the luffing wire substantially simultaneously, for example via a winch associated with the luffing wire, and it should be understood that this is particularly to prevent situations where excessive opposing forces arise from the luffing wire on one hand and the biasing element on the other. Thus, for example, the speed and / or torque of the winch associated with the luffing wire may be synchronized with the action of the biasing element.

[0030] Optionally, the boom stabilization system is configured not to cause a limitation and / or reduction of the boom angle when the boom angle does not exceed a second predefined boom angle threshold.

[0031] In this way, the crane can be operated with greater energy efficiency, particularly in terms of the energy requirements for winding the luffing wire. On the other hand, when the boom angle does not exceed a second predefined boom angle threshold, the boom can still be sufficiently stabilized by the gravitational component, i.e., by a sufficiently large restoring force associated with such a smaller boom angle. Nevertheless, it should be understood that the biasing element may still have some effect on the boom angle at such smaller boom angles, in particular a damping effect that does not limit or reduce the boom angle. Such a smaller damping effect can advantageously contribute to the stabilization of the boom, for example, by preventing excessive swinging as described elsewhere in this specification. Thus, the biasing element may exhibit a greater biasing stiffness when the boom angle exceeds a second predefined boom angle threshold, and a smaller but non-zero biasing stiffness when the boom angle is between the first predefined boom angle threshold and the second predefined boom angle. Such angle-dependent differences in biasing stiffness may be realized in various ways, as further described elsewhere in this specification.

[0032] Optionally, the boom stabilization system includes one or more sensors arranged to generate signals indicating a possible need to suppress slack in the luffing wire for stabilizing the offshore crane.

[0033] For example, such a sensor may respond to changes in one or more of the following: boom angle, piston position of biasing element, luffing wire tension, hoist wire tension (associated with load loss), boom speed, and / or acceleration amplification. It should be understood that such parameters and other parameters can indicate, at least to some extent, a possible need to suppress luffing wire slack for crane stabilization. For example, a possible need to suppress slack may generally increase as the boom angle increases, as the wind strength increases, as the waves acting on the vessel or platform become stronger, and as the heavy crane load decreases. Where there is a possible need to suppress such slack, it may be particularly advantageous to utilize the boom angle limiting and / or reduction that may be provided by the boom stabilization system, while at other times, for example from the standpoint of energy efficiency, it may be preferable not to utilize, or to not utilize, effective limiting and / or reduction. To facilitate such a balance between safety and efficiency during crane operation, the generated signal or a signal derived therefrom may be presented to the crane operator, who may then take an appropriate response action, for example, through active control of the boom stabilization system and / or other components of the crane. In some cases, an automatic control device may be provided, configured to receive the signal and automatically take such a response action, for example, based on predefined criteria that can represent a desired balance between safety and efficiency. Advantageously, such a response action may include, among other possible actions, increasing the stiffness of the biasing element of the boom stabilization system to suppress slack in the luffing wire. The increase in stiffness may be achieved, for example, by increasing the pneumatic or hydraulic pressure in a pneumatic or hydraulic control line operably connected to the biasing element, for example, by increasing the pressure on one or more of the pneumatic or hydraulic cylinders.Correspondingly, if the need to suppress sag decreases or ceases to exist, the stiffness may be reduced, for example, when the boom angle is relatively low, environmental conditions are relatively mild, or the crane load is relatively heavy. Such increases and / or decreases in stiffness may be stepwise, for example, and may be switched between two, three, four, five, or more predefined stiffness levels depending on whether a threshold is exceeded, for example, a possible third and more predefined boom angle threshold and / or thresholds of other parameters referred to herein. Alternatively, such increases and / or decreases may be incremental, i.e., gradually adjusted in proportion to a stepwise change in the need to suppress sag. Correspondingly, the generated or derived instruction signals may be discrete or continuous. Furthermore, such signals may be one-dimensional or multi-dimensional and may be generated using one or more possible sensors. In some cases, the generated or derived instruction signal may be a composite signal indicating the overall need to suppress luffing wire slack, taking into account inputs from multiple sensors and / or evaluation of sensor data against multiple criteria such as thresholds. Furthermore, there is further possibility that the adjustment of the stiffness of the biasing elements, or more generally the adjustment of the operation of the boom stabilization system, may be jointly controlled by the operator and the automatic control device, in which case, for example, at a lower first risk level, the operator is advised to take a response action, and the decision is left to the operator, while at a higher second risk level, the system automatically takes such a response action. Further possibility is that the system may allow the operator to switch between different modes, namely manual mode and automatic mode. Switching to automatic mode may also be automatic in some cases, for example, when it is determined that the risk of luffing wire slack is relatively high.Therefore, many different variations of boom stabilization systems facilitate the safe operation of cranes at large boom angles, and in particular, they can be combined with appropriate energy efficiency. In this case, various related factors can be considered, and the degree of involvement of the crane operator may also vary.

[0034] The present invention further relates to an offshore crane having a boom pivotably attached to a support structure, the crane being equipped with such a boom stabilization system. The boom base is attached to the boom, and the support base is attached to the support structure, preferably pivotably attached to the support structure.

[0035] In one example, as suggested elsewhere in this specification, at least one chord of a frame attached to the lower end of the boom has an angle of about 8 to 30 degrees with respect to the longitudinal direction of the boom, preferably about 10 to 20 degrees, and preferably about 15 degrees. The frame may be attached at a position 10% to 50% below the boom, for example, at a position 10% to 40% below the boom, preferably at a position 12% to 35% below the boom. The upper end of at least one longitudinal frame chord of the boom attachment may extend to about 20% to 40% of the boom length, preferably about 25%.

[0036] More generally, the boom attachment is advantageously attached to the lower end of the boom, preferably 10% to 50% of the lower part of the boom chord. As noted above, the boom attachment may be a frame or a compressible element such as a biasing element.

[0037] These and other embodiments will be further illustrated with reference to drawings comprising illustrations of exemplary embodiments. [Brief explanation of the drawing]

[0038] [Figure 1a] This is a diagram of an offshore crane equipped with a boom stabilization system in the first position. [Figure 1b]This is a diagram of an offshore crane equipped with a boom stabilization system in the second position. [Figure 1c] This is a diagram of an offshore crane equipped with a boom stabilization system in the third position. [Figure 2] This is a diagram of the boom of an offshore crane equipped with a boom mounting section for a boom stabilization system. [Figure 3] Figure 2 is a detailed view of the boom mounting section. [Figure 4] This is a detailed diagram of the support mounting section with a support arm in the context corresponding to Figure 1c. [Figure 5] This is a diagram of one embodiment of an alternative boom mounting section for a boom stabilization system. [Figure 6] This is a diagram of an offshore crane equipped with a boom stabilization system in the fourth position. [Figure 7] This is a top view of a ship equipped with an offshore crane. [Modes for carrying out the invention]

[0039] Please note that the figures are provided as examples only and do not limit this disclosure. The figures may not be to their actual size. Corresponding elements are indicated by their corresponding reference numerals.

[0040] Figure 1a shows an offshore crane 1 attached to a support structure or base structure 2. The offshore crane 1 comprises a boom 3 pivotably attached to the support structure 2 and an A-frame 4 equipped with, for example, a luffing system 5 and / or a hoisting system. Here, a pair of connections of the A-frame 4 are positioned between the pivotal connections of the boom to the support structure 2, although it is understood that they may also be in the same position. The boom 3 has a boom base 6 and a boom tip 7. A load can be hoisted at the boom tip 7. The offshore crane 1 is equipped with a boom stabilization system 8 comprising a boom attachment section 9 and a support attachment section 10. The boom attachment section 9 is seen here in the side view as a triangular truss frame 12 connected to the upper or rear side 11 of the boom. The lower or bottom end of the truss frame is provided with an engagement element 13 configured to engage with the support attachment section 10. The support attachment section 10 is here provided as a biasing element 14, for example, a hydraulic or pneumatic cylinder. The biasing element 14 is pivotably attached to the support structure 2 and extends longitudinally. The outer end of the biasing element is provided with an engaging element 15 configured to engage with the engaging element 13 of the boom mounting portion 9. Both the boom mounting portion 9 and the support mounting portion 10 work together to prevent or limit excessive swinging of the boom 3, in particular, in the event of excessive load and / or motion.

[0041] In Figure 1a, the boom 3 is shown in a first position, in which the boom attachment 9 is free from the support attachment 10 and is not engaged with the support attachment 10. Typically, this applies to boom angles of approximately 50 to 70 degrees, for example, approximately 50 to 60 degrees. The boom angle alpha is considered to be the angle between the longitudinal axis and the horizontal axis of the boom, as schematically indicated in Figure 1a. The support base 10, in particular the biasing element 14 of the support 10, is biased toward the extended position.

[0042] Figure 1b shows that when the boom angle reaches a predefined angle alpha 1, which can be set to an angle between approximately 50 and 70 degrees, or any value within such an angle, or approximately such an angle, for example, approximately 60 degrees, the boom mounting portion 9 engages with the support mounting portion 10. For this purpose, the boom mounting portion 9 may be provided with a boom base engaging element 13, and the support mounting portion 10 may be provided with a support base engaging element 15. The boom base engaging element 13 then engages with its associated support base engaging element 15. For example, when the boom mounting portion 9 has a single chord member 16 with a boom engaging element 13 provided at its lower end 17, the boom base engaging element 13 has a corresponding associated support base engaging element 15 on an associated biasing element 14. In another example, the frame 12 may have two longitudinally extending chords 16, each having a boom base engagement element 13 at its lower end 17, in which case two associated support base engagement elements 15 are provided, which can be connected to two separate biasing elements or to the same single biasing element. Multiple biasing elements can be arranged in series, in parallel, or in combination thereof. When the boom mounting portion 9 engages with the support mounting portion 10, the biasing element 14 is compressed against the biasing force. Thus, the biasing element 14 can follow the movement of the crane boom 3 until the biasing element 14 is sufficiently compressed and the boom 3 reaches its uppermost position, for example, as shown in Figure 6. The boom angle alpha 3 can then be up to 90 degrees. If unintended boom motion and / or boom acceleration occurs, the boom stabilization system 8 can absorb the energy resulting from such motion and guide excessive loads toward the chords of the boom 3 and / or toward the support structure 2. Therefore, damage from excessive swinging of boom 3 can be limited or prevented. Figure 1c shows boom 3 at angle alpha 2, which is between angles alpha 1 and alpha 3. Angle alpha 2 may correspond to a second predefined boom angle, as will be further described elsewhere in this specification.

[0043] As can be seen in more detail in Figures 1a, 1b, 1c, and 6, and in Figure 4, 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 Figure 1a, where the biasing element 14 is ready to engage with the boom mounting section 9. For optimal engagement with the boom mounting section 9, when the boom 3 reaches boom angle alpha 1, the biasing element 14 is preferably positioned below angle beta, which is between about 30 and about 65 degrees, and where engagement is expected, depending on the angle alpha 1, for example, angle alpha 1. Once 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 also restrict the lateral movement of the biasing element 14 by providing a U-shaped bracket at its outer end. In this sense, the support arm 18 may continue to cooperate with the biasing element 14 through various rotational positions of the biasing element 14.

[0044] Figure 2 shows an example of a boom 3 of an offshore crane. Here, the boom 3 has two boom legs 19a and 19b at its boom base 6. Each boom leg 19a and 19b is hinged to a support structure, allowing only pivotal movement of the boom 3 around the axis of rotation of the hinge. Frames 12a and 12b are attached to the upper or rear side 11 of the boom 3.

[0045] The boom mounting section 9 here comprises two frames 12a, 12b, each connected to its respective legs 19a, 19b. In this way, an additional frame 12a, 12b is provided for each leg 19a, 19b. Each frame 12a, 12b comprises a chord member 16a, 16b. The chord members 16a, 16b extend longitudinally and are positioned obliquely to the boom 3, particularly obliquely to the longitudinal axis of the boom. Here, the angle theta (see Figure 1c) between the chord member 16 and the longitudinal axis is approximately 15 degrees. At the lower ends 20a, 20b of the chord members 16a, 16b, the distance between the chord member 16 and the boom 3 is greater than the distance between the chord member 16 and the boom 3 at the upper ends 21a, 21b of the chord members. The chord members 16a, 16b are connected to the boom 3 via a truss or brace 22. In detail in Figure 3, the upper ends 21a, 21b of the chord members 16a, 16b are floating and not connected to the boom by themselves, but are connected to the boom via the truss 22. This ensures a smoother force transfer. At the lower ends 20a, 20b, the chord members 16a, 16b are connected to the boom 3 via the truss 22, where the truss 22 is connected to a predetermined position on the boom legs 19a, 19b. The boom base engagement elements 13 provided at the lower ends 20a, 20b of the chord members 16a, 16b are embodied as trumpet-shaped elements, as seen in Figure 3. It is understood that engagement elements of other shapes are also possible. In this embodiment, the two frames 12a, 12b are connected to each other using additional braces 33, which is optional. The braces can also be omitted. The longitudinally extending frame chord members 16a, 16b are connected to the boom 3, and in particular to the boom base 6 via a plurality of trusses 22. Multiple trusses 22 can be connected to trusses 34 of boom 3, or to chords 35 of boom 3. By connecting longitudinally extending chords 16a, 16b to boom 3 at multiple different locations, the load can be distributed and transmitted to boom 3, making it possible to transmit relatively large loads before damage can occur. This allows for the transmission of relatively large loads of forces that may occur when the boom tip may swing and / or accelerate.Furthermore, the chord members 16a and 16b at the lower ends 20a and 20b are at a greater distance D1 from the boom 3, particularly from the upper surface 11 of the boom 3, than the distance D2 at their upper ends 21a and 21b. In cases where the frame chord member 16 is directly connected to the boom 3 using, for example, a boom chord member 35, the distance D2 becomes zero. Thus, at least one frame chord member is guided diagonally toward the boom 3, thereby guiding the force to be transmitted to the boom 3 or the boom chord member 35 in an effective manner.

[0046] It should be noted that the frame 12 may have two chord members instead of a single chord member, and these two chord members may reach either the two upper chord members of the boom 3 or the two upper chord members of the boom leg 19.

[0047] Figure 4 shows the boom base 6 hinged to the support structure 2 via boom connectors 23a and 23b of boom legs 19a and 19b, respectively. Here, the boom connectors 23a and 23b are separate from the A-frame connectors 24a and 24b. The boom mounting section 9 is shown here engaged with the support mounting section 10, with the respective engaging elements 13 and 15 shown cooperating with each other. At this position of the boom 3, the biasing element 14 of the support mounting section 10 is almost completely compressed, indicating that the boom 3 is in its upper position, or nearly in its upper position. In the specific example of Figure 4, the boom 3 has a boom angle of approximately 83 or 85 degrees in this case. However, in some variations, even larger boom angles of up to approximately 90 degrees are possible, as illustrated in the example of Figure 6. Returning to Figure 4, as an example applicable to the example in Figure 6, the biasing elements 14a and 14b, which engage with the frames 12a and 12b of the boom mounting section 9, respectively, are hinged to the support structure 2 via the connecting sections 25a and 25b. As described above, each biasing element 14a and 14b of the support mounting section 10 is supported by the support arms 18a and 18b. The U-shaped ends 28a and 28b of the support arms 18a and 18b support the biasing elements 14a and 14b in a neutral position when they are not engaged with the boom mounting section 9. The U-shaped ends 28a and 28b also restrict the lateral movement of the biasing elements 14a and 14b, which can ensure that the hinge connections 25a and 25b are intact. Here, with boom 3 in its upper position, i.e., at a large boom angle, we can see that the biasing elements 14a and 14b are at a certain distance from the bottom of the U-shaped support ends 28a and 28b, but are still between the arms of the U-shaped support ends 28a and 28b. In this example, the support arms 18a and 18b are connected to each other using a bar 29, but this is optional.

[0048] Figure 5 shows an alternative embodiment of the boom mounting section 9. The boom mounting section 9 is connected to the boom 3, and more specifically to the boom base 6. The boom base 6 here has two boom legs 19a and 19b. The boom mounting section 9 comprises at least one frame 12, here with two frames 12a and 12b provided on each of the legs 19a and 19b, respectively. Each frame has at least one longitudinally extending chord 16a, 16b at its lower end, located at a certain distance from the boom 3 and extending in one direction toward the boom 3. Here, the longitudinally extending chord 16a, 16b is divided into two chords 30a, 31a, 30b, 31b that connect directly to the respective boom chords of the boom legs 19a and 19b. In this embodiment, the frames 12a and 12b are provided with multiple trusses 22 that connect to the boom chords at multiple different positions. Thus, forces can be distributed and transmitted to the boom 3.

[0049] In an alternative embodiment, the boom attachment 9 may be a compressible element that is favorably biased toward the extended position. The support attachment 10 may then be a frame or a frame-like structure. Such a frame-like structure may be hinged to the support structure 2 so that, once engaged, the boom attachment and the support attachment can follow the movement of the boom. Alternatively, the boom attachment may be hinged to the boom so that, when engaged with the support attachment, it can follow the movement of the boom.

[0050] The boom stabilization system is configured to limit and / or reduce the boom angle by utilizing the biasing stiffness of the biasing element 14 in order to suppress slack in the luffing wire 5 of the offshore crane 1 when the boom angle exceeds a second predefined boom angle threshold, for example, corresponding to alpha 2 in Figure 1c, which is greater than a first predefined boom angle threshold, for example, alpha 1 in Figure 1b.

[0051] The boom stabilization system may be substantially passive, meaning its boom stabilization function may be independent of any active control, or at least capable of operating without any active control. Such a passive configuration greatly promotes reliable and safe operation of the system, in contrast to active systems, which may be relatively sensitive to various failures of associated active elements such as control devices or power supplies. In the case of a passive system, for example, the biasing stiffness of the biasing element 14 may be designed to be sufficiently large to stabilize the boom 3 under various conditions and at various boom angles, while still allowing the boom 3 to move by actively driving the luffing wire 5.

[0052] Alternatively, in some variations, the boom stabilization system may include one or more active elements and / or subsystems, which are complementary to the passive functions described above, for example, and therefore do not necessarily impair the passive functions. For example, the biasing element 14 or associated elements may be configured to actively extend the biasing element 14 toward an extended position in accordance with, for example, a pressure threshold or other threshold, thereby adding an active counterforce against the swing of the boom 3, as opposed to mere passive damping or restraint. In other words, the biasing stiffness of the biasing element 14 may be variable, and in particular controllable, in order to selectively increase or decrease the bias. Such active behavior not only further limits or prevents uncontrolled swinging of the boom 3, but may also allow for the selection of even larger boom angles, for example, up to about 90 degrees, as illustrated by angle alpha 3 in Figure 6. In particular, the active system may safely tolerate such large angles with limited or no disadvantage to energy efficiency. In contrast, if such a large boom angle is permissible using a passive system, although this is not necessarily excluded herein, the driving of the luffing wire 5 may be less energy efficient due to the continuous resistance resulting from the relatively high biasing stiffness of the non-variable wire as described above.

[0053] However, it is also conceivable to achieve variable biasing stiffness in a passive boom stabilization system, for example, depending on the boom angle. In that case, for example, a set of biasing sub-elements may be used to form passive biasing elements, where different biasing sub-elements have different, for example, linear or nonlinear stiffness. When such different biasing sub-elements are arranged in parallel, the sub-elements with higher stiffness may be arranged to engage at higher boom angles than the sub-elements with lower stiffness. Alternatively, or additionally, when such different biasing sub-elements are arranged in series, the resulting overall stiffness may be influenced by the sub-elements with lower stiffness at smaller boom angles and by the sub-elements with higher stiffness at larger boom angles.

[0054] This disclosure thus describes and illustrates an example of a boom stabilization system for an offshore crane, the boom stabilization system comprising a boom mounting section positioned to be attached to the boom of an offshore crane, and a support mounting section attached to a support structure for the offshore crane, wherein the boom mounting section comprises a frame having at least one longitudinally extending chord member, and the support mounting section comprises a biasing element biased toward an extended position, the boom mounting section and the support mounting section are configured to engage with each other when the boom angle of the boom exceeds a first predefined threshold, and the boom stabilization system is configured to limit and / or reduce the boom angle by utilizing the biasing stiffness of the biasing element to suppress slack in the luffing wire of the offshore crane when the boom angle exceeds a second predefined boom angle threshold greater than the first predefined boom angle threshold.

[0055] As illustrated in Figure 6, the boom stabilization system can advantageously enable the crane 3 to operate safely at boom angles up to approximately 90 degrees, particularly while suppressing slack in the luffing wire 5. For illustrative purposes only, a slack luffing wire 5s is shown as a dotted line in Figure 6, in which case it will be understood that the boom stabilization system can advantageously suppress such slack, and as a result the luffing wire 5 remains taut even at such a relatively large boom angle alpha 3, thereby continuing to contribute to the stabilization of the boom 3.

[0056] Here, a boom stabilization system installed on the ship 36, which allows the crane 3 to operate safely at a larger boom angle, can effectively reduce the minimum outreach of the crane 3 from a larger minimum outreach 37a to a smaller minimum outreach 37b, as illustrated in the top view of Figure 7. As a result, the usable space around the crane 3, here, the deck space of the ship 36 as illustrated in Figure 7 by the shaded area between 37a and 37b, is increased.

[0057] For clarity and conciseness, each feature is described herein as part of the same or distinct embodiment; 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. Furthermore, the embodiments shown may be understood to have the same or similar components, except for the parts described as different.

[0058] Reference numerals enclosed in parentheses within a claim should not be construed as limiting the claim. The term “comprising” does not exclude the existence of features or steps other than those enumerated in the claim. Furthermore, the terms “a” and “an” should not be construed as limiting to “only one,” but rather as meaning “at least one,” and do not exclude multiple. The fact that certain means are enumerated in different claims does not mean in itself that combinations of these means cannot be used advantageously. Many variations will become apparent to those skilled in the art, insofar as they fall within the scope of the invention as defined by the following claims. [Explanation of Symbols]

[0059] 1. Offshore crane 2 Support structure 3 Boom 4 A-frame 5. Roughing Wire 5s slack roughing wire 6. Boom base 7 Boom tip 8. Boom stabilization system 9. Boom mounting section 10 Support mounting section, support base section 11. Top side of the boom Frames 12, 12a, and 12b 13, 13a, 13b engaging elements 14. Encouraging Factors 15 Engaging elements 16, 16a, 16b string material 17 Lower end of the string 18, 18a, 18b Support arms 19, 19a, 19b legs 20a, 20b Lower end of the string 21a, 21b Upper end of the string 22 Truss 23a, 23b Boom connection section 24a, 24b A-frame connection section 25a, 25b connection section 28a, 28b U-shaped end, U-shaped support end 30a, 31a, 30b, 31b string material 34 Truss 35 Boom string material 36 Ships 37a Larger minimum outreach Minimum outreach smaller than 37b Alpha, 1, 2, 3 boom angle Beta angle is similar to alpha angle. The angle between the theta chord 16 and its longitudinal axis D1 Distance from the boom to the chord at the lower end D2 Distance from the boom to the chord at the upper end

Claims

1. A boom stabilization system for offshore cranes, - A boom mounting section configured to be attached to the boom of the aforementioned offshore crane, - comprising a support mounting portion attached to the support structure for the offshore crane, - The boom mounting portion and the support mounting portion are each equipped with a frame having at least one longitudinally extending chord member, - The boom mounting portion and the other support mounting portion are equipped with a biasing element that is biased toward the extended position. - The boom mounting portion and the support mounting portion are configured to engage with each other when the boom angle of the boom exceeds a first predefined boom angle threshold. - A boom stabilization system for an offshore crane, configured to limit and / or reduce the boom angle by utilizing the biasing stiffness of the biasing element in order to suppress slack in the luffing wire of the offshore crane when the boom angle exceeds a second predefined boom angle threshold which is greater than a first predefined boom angle threshold.

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

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

4. In a side view, the frame has a triangular shape with respect to the boom, and the at least one chord extends diagonally toward the boom, according to claim 2 or 3.

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

6. The system according to any one of claims 2 to 5, wherein, over the length of the boom at the location where the boom attachment is connected to the boom, the connections between the truss of the frame of the boom attachment and the truss or chords of the boom are provided at a plurality of distinct positions in the axial direction, i.e., the longitudinal direction of the boom, and / or in the radial direction, i.e., a direction perpendicular to the axial direction.

7. The system according to any one of claims 1 to 6, wherein the support mounting portion is attached to a support structure to which the boom is pivotably connected, particularly at the boom base of the boom.

8. The system according to any one of claims 1 to 7, wherein the first predefined boom angle threshold is in the range of 40 to 70 degrees, preferably about 60 degrees.

9. The system according to any one of claims 1 to 8, further comprising a support arm configured to hold the biasing element in a stationary position, wherein in the stationary position, the biasing element has an angle with respect to the support platform, so that engagement with the frame is possible at an angle of 50 to 70 degrees or about 50 to 70 degrees, preferably around 60 degrees.

10. The system according to claim 9, wherein the support arm is U-shaped, thereby restricting the lateral movement of the biasing element, particularly in the stationary position.

11. The system according to any one of claims 1 to 10, wherein the second predefined boom angle threshold is in the range of 77 to 89 degrees, preferably in the range of 80 to 86 degrees, for example, about 83 degrees.

12. The system according to any one of claims 1 to 11, wherein, at least selectively and / or when the boom angle exceeds the second predefined boom angle threshold, the biasing stiffness of the biasing element is determined to be such that it maintains the boom angle at a variable lower limit imposed on the boom angle by the luffing wire, in particular, the biasing stiffness is then determined to be such that it dampens any possible environmental disturbances acting on the boom with respect to the boom angle.

13. The system according to any one of claims 1 to 12, preferably configured to actively change the biasing stiffness of the biasing element by utilizing a hydraulic or pneumatic control line operably connected to the biasing element.

14. The system according to any one of claims 1 to 13, wherein the system is configured not to cause limitation and / or reduction of the boom angle when the boom angle does not exceed the second predefined boom angle threshold.

15. The system according to any one of claims 1 to 14, comprising one or more sensors arranged to generate a signal indicating a possible need to suppress slack in the luffing wire for stabilizing the offshore crane.

16. An offshore crane having a boom pivotably attached to a support structure, wherein the offshore crane is equipped with a boom stabilization system according to any one of claims 1 to 15, the boom mounting portion being attached to the boom, and the support mounting portion being attached to the support structure, preferably pivotably attached to the support structure.

17. The offshore crane according to claim 16, as referenced to 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 the longitudinal direction of the boom.

18. The offshore crane according to claim 16 or 17, as referenced to claim 2, wherein the frame is attached to the boom at a position 10% to 50% below the boom length of the boom, preferably at a position 12% to 40% below the boom length.

19. The offshore crane according to claim 18, wherein the upper end of at least one longitudinal frame chord of the boom mounting portion extends to about 10% to 50% of the boom length, preferably to about 30% of the boom length.

20. A vessel, such as a jack-up ship, equipped with an offshore crane as described in any one of claims 16 to 19.

21. Use of an offshore crane according to any one of claims 16 to 19 and / or a vessel according to claim 20 for lifting operations, particularly heavy lifting operations at an offshore location.

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