Lifting device, in particular crane, and method for operating such a lifting device

Abstract

The invention relates to a lifting device (1), in particular a crane, which comprises a load hook (2) for attaching a load to be lifted, a rope (5, 6) connected to the load hook to raise or lower it, a deflection arrangement (3, 8) for deflecting the rope, and a rope drum (4) for winding or unwinding the rope, wherein the deflection arrangement divides the rope into a first rope section (5) extending from the deflection arrangement to the load hook and into a second rope section (6) extending from the deflection arrangement to the rope drum.The lifting device has a force determination unit () designed to determine a force of the first rope section, the first force, and a force of the second rope section, the second force, and a control unit designed to compare the first force and the second force and to stop a procedure of the load hook in the direction of the deflection arrangement when a ratio of the first force to the second force reaches a predetermined threshold.

Description

[0001] The present invention relates to a lifting device, in particular a crane, and a method for operating such a lifting device.

[0002] Lifting equipment such as cranes, rope excavators, and crawler cranes are essential tools in many industrial and construction applications. Their necessity stems from the ability to efficiently and safely lift, move, and position heavy loads, which would be impossible without mechanical assistance. They ensure that loads are moved safely and in a controlled manner and exhibit high precision in load positioning, which is particularly important in the construction and manufacturing industries.

[0003] The basic function of lifting devices is to move loads vertically, which is achieved by ropes, chains, or hydraulic systems (for the sake of simplicity, the term "ropes" will be used below, although the invention also includes chains or the like). Many cranes, such as traveling cranes or crawler cranes, can also move loads horizontally, which expands their range of applications. Cranes such as rope excavators, crawler cranes, and tower cranes offer the ability to rotate loads around a vertical axis, which is helpful when placing materials in confined or difficult-to-access areas. Furthermore, crawler cranes and rope excavators are generally specifically designed to move across uneven or difficult terrain, enabling their use on construction sites and in the mining industry.

[0004] Typical applications for lifting equipment include construction, for example, lifting and positioning building materials, steel beams, concrete, and other heavy components. In logistics and transportation, lifting equipment designed as cranes assists in loading and unloading containers and heavy goods, particularly in ports and warehouses. In mining, specialized lifting equipment, such as site-specific cable excavators, is used to move large quantities of earth and rock. In industry and manufacturing, lifting equipment supports the movement of heavy machine parts and raw materials in factories and production facilities. As can be seen from the above, lifting equipment is an indispensable tool that contributes to increased efficiency and smooth workflows in many industries.

[0005] However, with the known lifting device, there are limitations during operation to ensure that a load hook that has been pulled upwards on a rope (or chain or the like) can also be moved back into a lowered position.

[0006] Many lifting devices, especially crawler cranes or cable excavators, have a restriction that an "empty" load hook, which is not lifting a payload, must not be raised. This restriction, typically found in the operating instructions of a lifting device, serves to prevent a situation in which lowering the load hook from a raised position is no longer possible and, under certain circumstances, it may even become impossible to stop the load hook from moving away from the ground.

[0007] A lifting device typically comprises a rope (which can also include a chain or similar), a deflection mechanism for the rope, and a load hook connected to the rope. To raise or lower the load hook, a rope drum is provided at the end of the rope furthest from the load hook. This drum serves to wind or unwind the rope. The rope drum is typically connected to a motor that rotates it. In conventional lifting devices, the load hook is either unnecessarily heavy to ensure that even when raised, it can be lowered by its own weight, or operation is prohibited in which a load hook may be raised without a load attached.

[0008] However, since the provision of an excessively heavy load hook in the operation of the lifting device entails various disadvantages, for example in terms of poorer handling or a reduced maximum load weight, the aim of the present invention is to create an improved lifting device that mitigates or overcomes the disadvantages explained above and yet allows the load hook to be lifted without a load.

[0009] This is achieved with a lifting device that has all the features of claim 1 or with a method that has all the method steps according to claim 13. Further advantageous embodiments of the present invention are found in the dependent claims.

[0010] According to the invention, a lifting device is provided, in particular a crane, which comprises a load hook for attaching a load to be lifted, a rope connected to the load hook in order to raise or lower it, a deflection arrangement for deflecting the rope, and a rope drum for winding or unwinding the rope, wherein the deflection arrangement divides the rope into a first rope section extending from the deflection arrangement to the load hook and into a second rope section extending from the deflection arrangement to the rope drum.The lifting device according to the invention is characterized by a tensile force determination unit designed to determine a tensile force of the first rope section, the first tensile force, and a tensile force of the second rope section, the second tensile force, and a control unit designed to compare the first tensile force and the second tensile force and to stop a movement of the load hook towards the deflection arrangement when a ratio of the first tensile force to the second tensile force reaches a predetermined threshold value.

[0011] According to the invention, the first tensile force can be determined by the weight of the first rope section, the weight of the load hook, and optionally the weight of the load attached to the load hook. Similarly, the second tensile force is determined by the weight of the second rope section, i.e., essentially the length of rope extending from the deflection device to the rope drum.

[0012] According to the invention, it can be provided that the first tensile force and second tensile force each describe the tensile force acting on the deflection arrangement.

[0013] The lifting device therefore comprises a cable pulley system in which the cable is guided from a cable drum via a deflection arrangement, typically including a pulley or similar device, to a load hook connected to the cable. The pulling force determination unit serves to determine the pulling force of different cable sections, which are compared with each other and, upon reaching or approaching a predetermined threshold, stop further lifting of the load hook by winding the cable onto the cable drum.

[0014] According to the invention, the tensile force determination unit can be designed to determine a tensile force acting on the deflection arrangement, preferably to determine a tensile force acting on the deflection arrangement through the first rope section and a tensile force acting on the deflection arrangement through the second rope section separately from each other.

[0015] The rope is divided into a first rope section and a second rope section, whereby when the load hook is lifted, the first rope section is the part of the rope running towards the deflection arrangement and the second rope section is the part of the rope running away from the deflection arrangement.

[0016] It is clear to the expert that when the load hook is lowered, the first rope section is the part of the rope running away from the deflection device and the second rope section is the part of the rope running towards the deflection device.

[0017] Accordingly, the first rope section is the rope section that runs from the deflection device to the load hook, and the second section is the rope section that runs from the deflection device to the rope drum.

[0018] To ensure that releasing the rope drum always results in the load hook being lowered, the tension determination unit determines a tensile force on the first rope section (called the first tension force) and a tensile force on the second rope section (called the second tension force). Based on these values, the control unit defines a maximum lifting height for the load hook. This is done by comparing the first tension force with the second tension force to ensure that the second tension force does not exceed the first. If it did, the weight of the second tension force would cause the first rope section to be pulled further upwards towards the deflection mechanism, resulting in an uncontrolled collision of the load hook with the deflection mechanism.

[0019] The invention proposes using the tensile force determination unit to allow the lifting of a load hook only to the extent that the weight of the load hook itself (or the weight of the load hook plus the weight of the load attached to the load hook) and the first rope section allow it to be lowered again. The tensile force of the second rope section must also be taken into account, since (in a frictionless system) if the first tensile force decreases, for example by lifting the load hook and the resulting shortening of the first rope section, the first tensile force must not become less than the second tensile force, otherwise the load hook's movement towards the deflection arrangement can no longer be stopped.

[0020] The second pulling force depends primarily on the weight of the second rope section, taking into account that this weight remains constant even when the load is lifted. Finally, the weight of the second rope section from the deflection mechanism towards the rope drum is constant.

[0021] The control unit therefore compares whether there is at least an equilibrium between the first tensile force, which depends on the weight of the first rope section and the load hook (optionally also on the weight of the attached load), and the second tensile force, which depends on the weight of the second rope section, in order to ensure that the load hook can be lowered into the ground again. If the second tensile force is equal to or greater than the first tensile force, this is not possible.

[0022] According to an advantageous modification of the present invention, the control unit can further be designed to reduce a maximum speed when moving the load hook towards the deflection arrangement when the ratio of the first pulling force to the second pulling force reaches a predetermined further threshold value.

[0023] By implementing the additional threshold, a stepwise restriction is implemented. Initially, in a non-critical range, the load hook can move upwards towards the deflection mechanism at a maximum speed. Once the specified further threshold is reached, thus approaching a critical state, the maximum speed at which the load hook can move upwards towards the deflection mechanism is reduced. Finally, once the specified threshold that stops the load hook's movement towards the deflection mechanism is reached, the lever movement of the load hook is halted.

[0024] The limitations of the lifting device are therefore implemented in stages, with the maximum speed being reduced first and only then the lifting movement of the load hook coming to a complete stop.

[0025] Advantageously, it can be provided that the specified further threshold for limiting the maximum speed is greater than the specified threshold for stopping the process, so that when the load hook is moved towards the deflection arrangement, the maximum speed is first limited and only then is the process stopped.

[0026] According to a further optional embodiment of the present invention, the deflection arrangement may have at least one deflection roller, preferably wherein at least two deflection rollers are provided, the respective axes of rotation of which are spaced apart from each other.

[0027] Furthermore, the deflection arrangement may include at least two deflection pulleys lying in a common plane. The disc of one deflection pulley defines a plane in which the disc of the other deflection pulley is also located. The disc serves to deflect the rope connected to the pulley and typically has a groove on its outer circumference for guiding the rope.

[0028] According to a further optional modification of the present invention, the tensile force of the first rope section can be provided that it depends on the mass of the first rope section, the mass of the load hook, and the mass of any load attached to the load hook. It should be noted that the length of the first rope section, which is essential for its weight, varies when the load hook is raised or lowered.

[0029] Furthermore, the tensile force determination unit can be designed to determine the tensile force acting on a deflection arrangement of the first or second rope section. In the case of the second rope section, there is essentially no variation in weight, since the length of the second rope section from the deflection arrangement to the rope drum remains constant when the load hook is raised or lowered.

[0030] Furthermore, according to the present invention, it can be provided that the tensile force of the second rope section depends on the mass of the second rope section.

[0031] According to an advantageous embodiment of the present invention, it can be provided that the predetermined threshold value for stopping a movement of the load hook in the direction of the deflection arrangement is greater than or equal to 1, preferably greater than 1 (in particular greater than or equal to 1.1, preferably greater than or equal to 1.2) in order to take into account any friction losses that counteract the tensile force of the first rope section.

[0032] It is clear to those skilled in the art that any safety margins to compensate for friction losses and / or the inertia of the rope, for example 20%, preferably 35% or particularly preferably 50%, can be added to a ratio of 1 to the first tensile force and the second tensile force.

[0033] According to an optional modification of the present invention, it can be provided that the traction force determination unit is arranged in the deflection arrangement, in particular in a deflection roller of the deflection arrangement.

[0034] Furthermore, according to an advantageous embodiment of the present invention, the tensile force determination unit can be designed in multiple parts, preferably wherein the multi-part tensile force determination unit is arranged in several deflection rollers of a deflection arrangement in order to be able to determine the tensile force acting on a respective deflection roller.

[0035] According to the present invention, the tensile force determination unit can be designed to determine a force acting on a deflection pulley of the deflection arrangement, in particular a tensile force.

[0036] In particular, according to the present invention, it can advantageously be provided that the tensile force determination unit includes a sensor for determining a weight. High-quality force measurement sensors are readily available on the market and can be operated with very high accuracy, making them particularly suitable for implementing the present invention. Force measurement is usually carried out using so-called force-measuring lugs or force-measuring shafts, which are examples of such sensors.

[0037] According to the present invention, it can be provided that the first tensile force and / or the second tensile force is / are a force that acts on the deflection arrangement, in particular a roller of the deflection arrangement, perpendicularly downwards towards the ground.

[0038] The invention further relates to a method for operating a lifting device, in particular according to one of the preceding claims, comprising the steps of: determining a first tensile force from a first rope section of a rope which is connected from a rope drum via a deflection arrangement to a load hook, wherein the first rope section runs from the deflection arrangement to the load hook; determining a second tensile force from a second rope section of the rope, wherein the second rope section runs from the deflection arrangement to the rope drum; and stopping a movement of the load hook in the direction of the deflection arrangement when a ratio of the first tensile force to the second tensile force reaches a predetermined threshold value, preferably limiting a maximum speed of the movement of the load hook in the direction of the deflection arrangement when a ratio of the first tensile force to the second tensile force reaches a predetermined further threshold value.

[0039] Furthermore, in an optional modification of the method, the predetermined threshold for stopping the movement of the load hook towards the deflection arrangement can be greater than or equal to 1, preferably greater than 1 (in particular greater than or equal to 1.1, preferably greater than or equal to 1.2), in order to account for any friction losses that counteract the tensile force of the first rope section. As already explained above in connection with the lifting device, a safety margin of 1 (or greater than 1) is typically added to the ratio of the first tensile force to the second tensile force, which takes into account friction losses and the inertia of the rope.

[0040] Furthermore, the invention relates to a crane, in particular a crawler crane, or a cable excavator with a lifting device according to one of the previously described embodiments or with a control system for carrying out a method with the above discussed process steps.

[0041] Further features, details, and advantages of the invention will become apparent from the following description of the figures. These show: Fig. 1: a schematic representation of a lifting device according to the invention with a low-weight load hook for three different height strokes of the load hook, and Fig. 2: a schematic representation of a lifting device according to the invention with a higher-weight load hook for three different height strokes of the load hook.

[0042] Fig. 1Figure 1 shows a schematic representation of a lifting device 1 according to the invention with a low-weight load hook 2, wherein 3 different lifting heights of the load hook 2 are shown side by side. The weight of the load hook 2 is indicated as 40 weight units to the left of the mass symbol (labeled "m" in the figure).

[0043] The lifting device 1 shown depicts a cable pulley system, in which a cable 5, 6 is guided via a deflection arrangement 3 from a cable drum 4 to a load hook 2. The load hook 2 is connected to the end of the cable 5, 6 that is spaced away from the cable drum 4. The deflection arrangement 3 is located in a space spaced away from the ground, for example, by means of a boom 7 or the like. Of course, it is also possible for the deflection arrangement 3 to be attached to the ceiling of a hall or the like, so that a boom 7 in the strict sense is not necessary.

[0044] To facilitate understanding of the basic operating principle of the present invention, the mass of the load hook 2, as well as the mass of the first rope section 5 and the second rope section 6, are indicated next to the symbol for mass. Since, in this case, the first rope section 5 and the second rope section 6 are oriented vertically, the tensile force due to the mass is directly proportional to the weight of the first rope section 5 and the second rope section 6, respectively.

[0045] The first tensile force is composed of the first rope section 5 and the load hook 2, while the second tensile force is determined solely by the second rope section, which runs from the deflection arrangement 3 to the rope drum 4.

[0046] If one considers the left-hand representation of the Fig. 1It can be seen that the mass of the load hook 2 and the first rope section 5 equals 90 weight units, whereas the mass of the second rope section 6 is only 50 weight units. If the rope drum 4 is now released, i.e., not braked by a braking mechanism, the load hook 2 will therefore drop downwards, as indicated by the downward-pointing arrow. This occurs because the weight of the load hook 2 and the first rope section 5 is greater than the weight of the second rope section 6 and simply needs to be multiplied by the acceleration due to gravity of 9.8 N / kg.

[0047] However, it is clear to those skilled in the art that the tensile force of inclined leads of the rope 5, 6 to the deflection arrangement 3 can also be easily calculated and is likewise encompassed by the invention.

[0048] In the middle representation of the Fig. 1The load hook 2 was raised to approximately the midpoint of the maximum possible stroke of the lifting device 1. This shortens the first rope section by about half, which also means that the weight of the first rope section is roughly halved and therefore only amounts to 25 weight units. However, the combined weight of the load hook 2 and the first rope section 5 is still greater than the weight of the second rope section 6, so that when the rope drum 4 is released, the load hook 2 will again descend towards the ground.

[0049] This is different in the right-hand representation of the Figure 1, in which a state of the lifting device 1 is considered in which the load hook 2 has been raised to its maximum lifting position. The weight of the first rope section 5 is now reduced to 0, so that the first tensile force is determined only by the weight of the load hook 2 itself. However, since even in a fully raised state the second rope section still has 50 weight units, the second tensile force is greater than the first tensile force, which is now determined only by the load hook 2, so that when the rope drum 4 is released, in deviation from the left and middle representations of the Fig. 1 The load hook 2 does not descend towards the ground. On the contrary, a force is exerted that pushes the load hook 2 further towards the deflection device 3. This is because the weight of the load hook 2 (40 weight units) is less than the weight of the second rope section 6 (50 weight units).

[0050] The idea according to the invention is to determine the tensile force or weight of the first rope section, which depends on the load hook 2 and the first rope section 5, the length of which varies, and to compare it with the tensile force or weight of the second rope section 6. If the first tensile force (influenced by the weight of the load hook 2 and the first rope section 5) approaches or even reaches the second tensile force (influenced by the weight of the second rope section), further lifting of the load hook 2 in the direction of the deflection arrangement 3 is stopped.

[0051] It may also be provided that, even before reaching a value that leads to stopping the lifting of the load hook 2, a further predetermined threshold value is provided, upon reaching which the maximum travel speed for lifting the load hook is reduced.

[0052] Fig. 2 shows a to Fig. 1 similar configuration of a lifting device 1, wherein elements with identical reference numerals have the same meaning.

[0053] In contrast, the load hook 2 is now significantly heavier and weighs 75 weight units instead of 40.

[0054] Now, let's look at the right-hand image in Fig. 2It can be seen that even when the load hook 2 is raised to its maximum extent in the direction of the deflection arrangement 3, the first tensile force (in this position essentially defined only by the weight of the load hook 2) is still greater than the second tensile force, defined by the second rope section with a height of 50 weight units. Therefore, releasing the rope drum 4, even in such a position, will allow the load hook 2 to be lowered if a sufficiently massive load hook 2 is used. However, a heavy load hook 2 is disadvantageous in its handling and also reduces the maximum lifting capacity of a lifting device 1.

[0055] Lifting devices of the aforementioned type are also used, for example, in the auxiliary lifting of a special foundation engineering equipment with a piling rig, such as a pile driver or a drilling rig. Reference symbol list:

[0056] 1 Lifting device 2 Load hook 3 Deflection arrangement 4 Rope drum 5 First rope section 6 Second rope section 7 Boom 8 Pulley

Claims

1. Lifting device (1), in particular crane, comprising: a load hook (2) for attaching a load to be lifted, a rope (5, 6) connected to the load hook (2) for raising or lowering it, a deflection arrangement (3) for deflecting the rope (5, 6), and a rope drum (4) for winding or unwinding the rope (5, 6), wherein the deflection arrangement (3) divides the rope (5, 6) into a first rope section extending from the deflection arrangement (3) to the load hook (2) and into a second rope section extending from the deflection arrangement (3) to the rope drum (4), characterized bya tensile force determination unit designed to determine a tensile force of the first rope section, the first tensile force, and a tensile force of the second rope section, the second tensile force, and a control unit designed to compare the first tensile force and the second tensile force and to stop a procedure of the load hook (2) in the direction of the deflection arrangement (3) when a ratio of the first tensile force to the second tensile force reaches a predetermined threshold.

2. Lifting device (1) according to the preceding claim 1, wherein the control unit is further designed to reduce a maximum speed when moving the load hook (2) towards the deflection arrangement (3) when the ratio of the first pulling force to the second pulling force reaches a predetermined further threshold value.

3. Lifting device (1) according to the preceding claim 2, wherein the predetermined further threshold for limiting the maximum speed is greater than the predetermined threshold for stopping the method, so that when the load hook (2) is moved in the direction of the deflection arrangement (3), the maximum speed is first limited and only then is the method stopped.

4. Lifting device (1) according to one of the preceding claims, wherein the deflection arrangement (3) has at least one deflection roller (8), preferably wherein at least two deflection rollers (8) are provided, the respective axes of rotation of which are spaced apart from each other.

5. Lifting device (1) according to the preceding claim 4, wherein the deflection arrangement (3) has at least two deflection rollers (8) lying in a common plane.

6. Lifting device (1) according to one of the preceding claims, wherein the tensile force of the first rope section depends on the mass of the first rope section, the mass of the load hook (2) and the mass of any load possibly attached to the load hook (2).

7. Lifting device (1) according to one of the preceding claims, wherein the tensile force of the second rope section depends on the mass of the second rope section.

8. Lifting device (1) according to one of the preceding claims, wherein the predetermined threshold for stopping a movement of the load hook (2) in the direction of the deflection arrangement (3) is greater than or equal to 1, preferably greater than 1, to take into account any friction losses that counteract the tensile force of the first rope section.

9. Lifting device (1) according to one of the preceding claims, wherein the traction force determination unit is arranged in the deflection arrangement (3), in particular in a deflection roller (8) of the deflection arrangement (3).

10. Lifting device (1) according to one of the preceding claims, wherein the traction force determination unit is designed in multiple parts, preferably wherein the multi-part traction force determination unit is arranged in a deflection arrangement (3) in several deflection rollers (8).

11. Lifting device (1) according to one of the preceding claims, wherein the tensile force determination unit is designed to determine a tensile force acting on a deflection pulley (8) of the deflection arrangement (3).

12. Lifting device (1) according to one of the preceding claims, wherein the tensile force determination unit comprises a sensor, in particular in the form of a force measuring tab, for determining a weight.

13. Method for operating a lifting device (1), in particular according to one of the preceding claims, comprising the steps of: determining a first tensile force from a first rope section of a rope (5, 6) which is connected from a rope drum (4) via a deflection arrangement (3) to a load hook (2), wherein the first rope section runs from the deflection arrangement (3) to the load hook (2); determining a second tensile force from a second rope section of the rope (5, 6), wherein the second rope section runs from the deflection arrangement (3) to the rope drum (4); and stopping a movement of the load hook (2) in the direction of the deflection arrangement (3) when a ratio of the first tensile force to the second tensile force reaches a predetermined threshold value, preferably limiting a maximum speed of the movement of the load hook (2) in the direction of the deflection arrangement (3).when the ratio of the first tractive force to the second tractive force reaches a predetermined further threshold value.

14. Method according to the preceding claim 13, wherein the predetermined threshold for stopping a movement of the load hook (2) in the direction of the deflection arrangement (3) is greater than or equal to 1, preferably greater than 1, to take into account any friction losses that counteract the tensile force of the first rope section.

15. Crane, in particular crawler crane, or cable excavator with a lifting device (1) according to one of the preceding claims 1 to 12 or with a control for carrying out a method according to one of the preceding claims 13 to 14.

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