Crane comprising first mast with tiltable first mast upper part

Abstract

Provided is a crane with a main boom and a back mast, of which at least one comprises a first mast upper part comprising at least one mast section and a first mast lower part comprising at least one mast section, and a first mast tilting. The first mast tilting member is arranged between the first mast upper part and the first mast lower part, and has a straight hoisting state wherein the first mast upper part and the first mast lower part are essentially in line with each other, and a tilted hoisting state wherein the first mast upper part is tilted with respect to the first mast lower part.

Claims

1. A Crane, which crane comprises: a crane base; a first mast, which first mast comprises a plurality of first mast sections, wherein the first mast is one of the main boom and the back mast of the crane; and a second mast, wherein the second mast is the other of the main boom and the back mast, wherein the main boom is pivotable about a first pivot which is arranged at the crane base and has a horizontal pivot axis, wherein the first mast comprises a first mast tilting member which is arranged between two of the first mast sections, thereby defining a first mast upper part and a first mast lower part of the first mast, wherein the first mast upper part comprises at least one of the first mast sections and is arranged between the first mast tilting member and an upper end of the first mast, wherein the first mast lower part comprises at least one of the first mast sections and is arranged between the crane base and the first mast tilting member, and wherein the first mast tilting member: (i) comprises an upper connection part connected to the first mast upper part and a lower connection part connected to the first mast lower part, (ii) has a straight hoisting state in which the first mast upper part and the first mast lower part are essentially in line with each other, and a tilted hoisting state in which the first mast upper part is tilted with respect to the first mast lower part and away from the second mast, and (iii) is adapted to transfer forces from the first mast upper part to the first mast lower part in both the straight hoisting state and the tilted hoisting state.

2. The Crane of claim 1, wherein the first mast is the back mast; and wherein the second mast, which is pivotable about the first pivot which is arranged at the crane base and has the horizontal pivot axis, is the main boom.

3. The Crane according to claim 1, wherein a first cross section of the at least one first mast section of the first mast upper part that is connected to the first mast tilting member is of the same dimensions as a second cross section of the at least one first mast section of the first mast lower part that is connected to the first mast tilting member.

4. The Crane according to claim 1, wherein multiple of the plurality of first mast sections of the first mast, and the upper connection part and the lower connection part of the first mast tilting member, are adapted such that the first mast tilting member can be arranged between any two of the multiple first mast sections.

5. The Crane according to claim 1, wherein the crane further comprises a strut with a first strut end connected to the first mast and a second strut end attached to a first strut guywire, which first strut guywire is attached to the upper end of the first mast upper part for keeping the first mast upper part in a fixed position relative to the first mast lower part when the first mast tilting member is in the tilted hoisting state.

6. The Crane according to claim 5, wherein the crane further comprises a second strut guywire, which is attached to the second end of the strut, and to the first mast lower part or the crane base, wherein the crane further comprises a winch for winding one of the first strut guywire and the second strut guywire, wherein, when the first mast tilting member is in the tilted hoisting state, (a) a first distance between the second end of the strut and the upper end of the first mast upper part is determined by the first strut guywire, and (b) a second distance between the second end of the strut and the first mast lower part and/or crane base is determined by the second strut guywire, and wherein the first mast upper part is adapted to be moved in line with the first mast lower part to bring the first mast tilting member into the straight hoisting state, by winding one of the first strut guywire and the second strut guywire on the winch.

7. The Crane according to claim 5, wherein the strut has: (a) a functional position for keeping the first mast upper part in a fixed position relative to the first mast lower part when the first mast tilting member is in the tilted hoisting state, and (b) a non-functional position it in which the strut is essentially parallel with the first mast lower part and in which the first end of the strut is located above the second end, wherein the crane comprises a winch for winding a guywire which is attached to the strut, which is adapted to subject the strut to an upwards movement by winding the guywire on the winch, wherein the first mast lower part has a strut guide for guiding the strut parallel to the first mast lower part during the upwards movement, and wherein the first mast further comprises a strut positioning element, which is adapted to stop the upwards movement of the strut and force the strut to pivot, until the strut is in the functional position.

8. The Crane according to claim 7, wherein the second end of the strut is further attached to a second strut guywire, which second strut guywire is also attached to the first mast lower part or to the crane base, wherein the second strut guywire has a length which is adapted to maintain the strut in the functional position.

9. The Crane according to claim 1, wherein the first mast tilting member further comprises an extendable cylinder, which is adapted to move the first mast tilting member from the straight hoisting state to the tilted hoisting state.

10. The Crane according to claim 9, wherein the first mast tilting member is in the straight hoisting state when the extendable cylinder is extended and in the tilted hoisting state when the extendable cylinder is retracted.

11. The Crane according to claim 1, wherein a back length of the back mast is longer than 50% of a main length of the main boom, wherein the back length of the back mast is longer than 75% of the main length of the main boom, or wherein the back length of the back mast is approximately equal to the main length of the main boom.

12. The Crane according to claim 1, wherein the first mast tilting member has a tilting axis over which the first mast upper part is tilted relative to the first mast lower part, wherein the tilting axis is located in proximity of a neutral plane of the first mast tilting member.

13. The Crane according to claim 1, wherein the first mast tilting member comprises a first upper part locking device, which is adapted to lock the first mast upper part in a fixed position relative to the first mast lower part when the first mast tilting member is in the straight hoisting state.

14. The Crane according to claim 13, wherein the first upper part locking device comprises an extendable hydraulic cylinder, wherein the first mast upper part is locked in a fixed position relative to the first mast lower part when the extendable hydraulic cylinder is in the extended state, and wherein the first mast upper part is movable relative to the first mast lower part when the extendable hydraulic cylinder is in the retracted state, or vice versa.

15. The Crane according to claim 1, wherein the second mast also comprises a plurality of second mast sections, wherein the second mast comprises: a second mast upper part comprising at least one of the second mast sections; a second mast lower part comprising at least one of the second mast sections; and a second mast tilting member, wherein the second mast tilting member: (i) is arranged between the second mast upper part and the second mast lower part, and comprises an upper connection part connected to the second mast upper part and a lower connection part connected to the second mast lower part, (ii) has a straight hoisting state in which the second mast upper part and the second mast lower part are essentially in line with each other, and a tilted hoisting state in which the second mast upper part is tilted with respect to the second mast lower part, and (iii) is adapted to transfer forces from the second mast upper part to the second mast lower part in both the straight hoisting state and the tilted hoisting state.

16. The Crane of claim 1, wherein the first mast is the main boom; and wherein the second mast is the back mast.

17. A Method for operating a crane, the method comprising the following steps: arranging a crane at a hoisting location, which crane comprises a crane base, a first mast which comprises a plurality of first mast sections and is one of the back mast and the main boom, and a second mast which is the other one of the back mast and the main boom, wherein the first mast comprises a first mast tilting member which is arranged between two of the first mast sections, thereby defining a first mast upper part and a first mast lower part of the first mast; assembling the first mast with the first mast tilting member in a straight hoisting state in which the first mast upper part and the first mast lower part are essentially in line with each other; and moving the first mast tilting member from the straight hoisting state into a tilted hoisting state in which the first mast upper part is tilted with respect to the first mast lower part and away from the second mast.

18. The Method according to claim 17, wherein the method further comprises the following steps: prior to moving the first mast tilting member into the tilted hoisting state, attaching a first load to a hoisting wire connected to a hoisting mechanism arranged at an upper end of the main boom, and hoisting the first load with the main boom while the first mast tilting member is in the straight hoisting state; and after moving the first mast tilting member into the tilted hoisting state, attaching a second load to the hoisting wire connected to the hoisting mechanism arranged at the upper end of the main boom, and hoisting the second load with the main boom while the first mast tilting member is in the tilted hoisting state.

19. The Method according to claim 17, wherein the method comprises the steps of: prior to moving the first mast tilting member into the tilted hoisting state, attaching a third load to a hoisting wire connected to a hoisting mechanism arranged at an upper end of the main boom, and lifting the third load with the main boom while the first mast tilting member is in the straight hoisting state; while the third load is being lifted, moving the first mast tilting member from the straight hoisting state into the tilted hoisting state; and when the first mast tilting member is in the tilted hoisting state, bringing the third load to a ground surface and detaching the third load from the hoisting wire.

20. The Method according to claim 17, further comprising the steps of, when the first mast tilting member into the tilted hoisting state, attaching a fourth load to a hoisting wire connected to a hoisting mechanism arranged at an upper end of the main boom, and lifting the fourth load with the main boom while the first mast tilting member is in the tilted hoisting state; while the fourth load is being lifted, moving the first mast tilting member from the tilted hoisting state into the straight hoisting state; and when the first mast tilting member is in the straight hoisting state, bringing the fourth load to a ground surface, and detaching the fourth load from the hoisting wire.

21. The Method according to claim 17, further comprising the steps of prior to moving the first mast tilting member into the tilted hoisting state: pulling a strut upwards parallel to the first mast lower part along a strut guide comprised by the first mast lower part, by winding a guywire which is attached to the strut, on a winch, until the strut reaches a strut positioning element, wherein the guywire is a first strut guywire which is attached to a second end of the strut and connected to an upper end of the first mast upper part; pivoting the strut around the strut positioning element until the strut is in a functional position, by winding the guywire further on the winch; and winding the first strut guywire on a winch until the first strut guywire is tensioned for keeping the first mast upper part in a fixed position relative to the first mast lower part when the first mast tilting member is in the tilted hoisting state.

22. The Method according to claim 17, wherein the step of arranging the crane at the hoisting position includes arranging the second mast, which comprises a plurality of second mast sections, and a second mast tilting member which is arranged between two of the second mast sections, thereby defining a second mast upper part and a second mast lower part of the second mast, wherein the method further comprises the following steps: assembling the second mast with the second mast tilting member in a straight hoisting state in which the second mast upper part and the second mast lower part are essentially in line with each other, and moving the second mast tilting member from the straight hoisting state into a tilted hoisting state in which the second mast upper part is tilted with respect to the second mast lower part and away from the first mast.

23. A Method for operating a crane, the method comprising the following steps: arranging a crane at a hoisting location, which crane comprises a crane base, a first mast which comprises a plurality of first mast sections and is one of the back mast and the main boom, and a second mast which is the other one of the back mast and the main boom, wherein the first mast comprises a first mast tilting member which is arranged between two of the first mast sections, thereby defining a first mast upper part and a first mast lower part of the first mast; assembling the first mast with the first mast tilting member in a tilted hoisting state in which the first mast upper part is tilted with respect to the first mast lower part and away from the second mast; and moving the first mast tilting member from the tilted hoisting state into a straight hoisting state in which the first mast upper part and the first mast lower part are essentially in line with each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described in more detail below in reference to the figures, in which in a non-limiting manner exemplary embodiments of the invention will be shown. Across the various figures, the same reference numbers have been used to indicate the same features.

(2) In the figures:

(3) FIG. 1 shows a possible embodiment of a crane according to the invention, wherein the first mast tilting member is in the straight hoisting state.

(4) FIG. 2 illustrates a possible embodiment of a crane according to the invention, wherein the strut is pulled up until the strut positioning element.

(5) FIG. 3 illustrates a possible embodiment of a crane according to the invention, wherein the strut is pivoted into the functioning position.

(6) FIG. 4a shows the first mast tilting member in the straight hoisting state.

(7) FIG. 4b shows the first mast tilting member in the tilted hoisting state.

(8) FIG. 5 shows a possible embodiment of a crane according to the invention, wherein the first mast tilting member is in the tilted hoisting state.

(9) FIG. 6 shows a possible embodiment of the invention, wherein both the main boom and the back mast comprise a respective tilting part.

(10) FIG. 7a illustrates another possible embodiment of the first mast tilting member in the straight hoisting state.

(11) FIG. 7b illustrates another possible embodiment of the first mast tilting member in the tilted hoisting state.

DETAILED DESCRIPTION OF THE DISCLOSURE

(12) FIG. 1 shows a possible embodiment of a crane 1 according to the invention. The crane 1 has a first mast 2 and a second mast 3, both supported by a crane base 23. In the example of FIG. 1, the first mast 2 is the main boom and the second mast 3 is the back mast, and both are lattice masts. The first mast 2 is a lattice mast and comprises multiple mast sections 15.1-15.8. The first mast 2 has a first pivot 17, and the second mast 3 has a second pivot 18, both located at the crane base 23. Both pivots 17,18 have a horizontal pivot axis (not shown). In the shown example, the second mast 3 also is a lattice mast comprising multiple mast section 16.1-16.8.

(13) The first mast 2 comprises a first mast tilting member 6, which is arranged between mast sections 15.2 and 15.3. The first mast tilting member 6 divides the first mast 2 in a first mast upper part 4 and a first mast lower part 5. The first mast upper part 4 comprises two mast sections 15.1, 15.2, and extends from the first mast tilting member 6 to an upper end 13 of the first mast 2. The first mast lower part 5 is located between the crane base 23 and the first mast tilting member 6. The first mast lower part 5 comprises six mast sections 15.3-15.8. Mast sections 15.1-15.7 have similar cross sectional dimensions. Moreover, mast section 15.2 is identical to mast section 15.3, and mast section 15.1 is identical to mast sections 15.3-15.7. Only mast section 15.8 has different cross sectional dimensions, since this mast section 15.8 is adapted to be connected to the crane base 23.

(14) The first mast tilting member 6 is connected to the first mast upper part 4 by an upper connection part 7 and to the first mast lower part 5 by a lower connection part 8. The first mast tilting member 6 further comprises an extendable cylinder 32. In the situation shown in FIG. 1, the extendable cylinder 32 is in its extended position.

(15) In FIG. 1, the first mast tilting member 6 is in a straight hoisting state. In the straight hoisting state, the first mast upper part 4 and the first mast lower part 5 are essentially in line with each other. As can be seen in FIG. 1, in the straight hoisting state, the first mast 2 of the crane 1 according to the invention looks similar to a conventional crane with a conventional first mast, and it also functions similar. That is, in the straight hoisting state the crane 1 can hoist a load 24 with hoisting mechanism 21 comprising a hoisting wire 22. The hoisting wire 22 is connected to the first mast 2 at the upper end 13 of the first mast 2. The hoisting wire 22 is a main hoisting wire, meaning that it is adapted to hoist the maximum load the crane 2 is designed for. The crane 2 does not comprise an auxiliary hoisting wire.

(16) In the shown example, the first mast 2 is connected to the second mast 3 by a second mast guywire 14, which is also connected to a ballast weight 20. The forces that are present in the first mast upper part 4, are transferred to the first mast lower part 5 via the first mast tilting member 6. It should be noted that, depending on the location of the load, before hoisting in the straight hoisting state, both the first mast 2 and the second mast 3 may be pivoted about their respective pivots 17, 18, such that the first and second mast 2,3 are less vertical. Also the ballast weight 20 may be brought to a position further away from the crane base 23. Thus, the situation shown in FIG. 1 is not the most horizontal position in which the first mast 2 and second mast 3 can be arranged for hoisting.

(17) The crane 1 further comprises a first mast stop 46 and second mast stop 47 for the first mast 2 and the second mast 3 respectively. The first and second stop 46,47 are adapted to prevent the first and second mast 2,3 from falling backwards. Optionally, it is envisaged that when the back mast 3 it tilted further with respect to the horizontal, that is additional back mast stop (not shown) can be provided above the ballast 20 to prevent the back mast from falling down, since in such a situation the forces on the second mast stop 47 may be too large.

(18) According to the invention, the first mast tilting member 6 of the crane 1 also has a tilted hoisting state, wherein the first mast upper part 4 is tilted with respect to the first mast lower part 5. This will be explained in more detail with reference to FIGS. 4a-4b. The crane 1 comprises a strut 9 for keeping the first mast upper part 4 in a fixed position relative to the first mast lower part 5, when the first mast tilting member 6 is in said tilted hoisting state.

(19) In the situation shown in FIG. 1, the strut 9 is in a non-functional position. In the shown example said non-functional position entails that the strut 9 is parallel to the first mast lower part 5. The strut 9 has a second end 10 that is connected to a first strut guywire 34. As can be seen, the first strut guywire 34 is attached to the strut 9 on a location that does not fall on the centerline of the strut. The first strut guywire 34 is connected to a sheaf (not shown) at the upper end 13 of the first mast upper part 4. The first strut guywire 34 is further connected to a winch (not shown). The winch in the shown example is located in the upper part 4.

(20) By winding the first strut guywire 34 on the winch, an upwards pulling force is created on the strut 9, which causes the strut 9 to move upwards parallel to the first mast lower part 5. During this upwards movement, the strut 9 is guided by the first mast lower part 5, which has a strut guide 35. In the shown example, the outside of the first mast lower part 5 functions as the strut guide 35. The upwards movement is stopped when a first end 11 of the strut 9 reaches a strut positioning element 30. The strut positioning element 30 has a strut positioning hole 37. The strut 9 has at its first end 11 also a strut positioning hole 38. The strut positioning holes 37, 38 are aligned when the strut 9 reaches the strut positioning element 30, which is the situation shown in FIG. 2.

(21) In FIG. 2, the second end 11 of the strut 9 is in contact with the strut positioning element 30, which prevents the strut 9 to move further upwards parallel to the first mast lower part 5. A strut positioning pin is arranged through the aligned strut positioning holes 37,38. However, a rotational movement is not prevented. The second end 10 is attached to the first strut guywire 34. The second end 10 is also attached to a second strut guywire 36, which in turn is also attached to the bottom of the first mast lower part 5. The second strut guywire 36 is attached in a different attachment point than the first strut guywire 34. By maintaining the pulling force in the first strut guywire 34 on the first end 10 of the strut 9, the strut 9 is pivoted around the strut positioning element 30, until the strut 9 reaches a functional position, which is shown in FIG. 3. The pivoting of the strut 9 can be accomplished because the first strut guywire 36 is attached to the strut 9 on a location that is not on the centerline of the strut 9.

(22) In FIG. 3, the strut 9 is in the functional position. In the functional position, the first end 11 of the strut 9 is connected to the first mast 2, via the strut positioning element 30. The second strut guywire 36 is limited in length, which length is predetermined. Once the second strut guywire 36 is at its full length and tensioned, it prevents the strut 9 from moving further upwards or pivoting further. As such, the strut 9 is kept in the functional position. Once the strut 9 is in the functional position, the first mast tilting member 6 can be adapted into the tilted hoisting state.

(23) FIG. 4a shows a close-up of the first mast tilting member 6 in the straight hoisting state, and FIG. 4b in the tilted hoisting state. Also visible in these figures is the strut positioning element 30 which in this example is attached to the first mast tilting member 6, and the first end 11 of the strut 9 which has already been brought into the functional position.

(24) The first mast tilting member 6 comprises a first upper part locking device, comprising two positioning holes 40, 41 and a pin 42. In the straight hoisting state shown in FIG. 4a, the two positioning holes 40, 41, are aligned. In this position, the pin 42 is inserted into the positioning holes 40, 41. The pin 42 is connected to a hydraulic cylinder (not shown), which is controllable by an operator on the ground level. As such, the operator can insert or remove the pin 42 from the positioning holes 40,41. By this pin-hole connection, the first mast tilting member 6 is prevented from moving into the tilted hoisting state. Thus, the first mast upper part 4 is locked in a fixed position relative to the first mast lower part 5.

(25) The first mast titling section further comprises a hinge 43. The hinge 43 is located in the center of the cross section of the first mast tilting member 6, seen in a direction which in FIG. 4a goes from left to right. On the location of the hinge 43, the first mast tilting member 6 has a first tilting axis 44 which in FIGS. 4a-4b extends in a direction perpendicular to the paper. Thus, the first tilting axis 44 is also located in the center of the cross section. Since the mast sections of the first mast 2 are symmetrically, the neutral plane 45 of the first mast 2 is located on the central axis of the first mast 2. Hence, the first tilting axis 44 extends perpendicular to the neutral plane 45, and they have an intersection point. This enhances a symmetrical division of the forces that come from the first mast upper part 4, onto the first mast lower part 5.

(26) In the straight hoisting state shown in FIG. 4a, the extendable cylinder 32 is in the extended state. The extendable cylinder 32 is also a hydraulic cylinder, and also controllable by an operator on the ground level. In the straight hoisting state, the extendable cylinder 32 also prevents the first mast upper part 4 from tilting relative to the first mast lower part 5. To move the first mast tilting member 6 from the straight hoisting state to the tilted hoisting state, an operator first removes the pin 42 by operating the hydraulic cylinder attached to the pin 42. Thereafter, the operator controls the extendable cylinder 32 to retract it. The retracting movement of the extendable cylinder 32 results in a small pulling force on the first mast upper part 4, on the right side as shown in FIGS. 4a-4b, which causes the first mast upper part 4 to start tilting. Once the tilting has started, it is continued under the influence of gravity, until the first mast tilting member 6 is in the tilted hoisting state as shown in FIG. 4b. In the tilted hoisting state, the extendable cylinder 32 is without any internal pressure. Furthermore, essentially no forces are transferred from the first mast upper part 4 to the first mast lower part 5 though the extendable cylinder 32. Thus, essentially all those forces are transferred through the hinge 43 which is located on the neutral plane 45.

(27) During the tilting, i.e. the movement from the straight hoisting state to the tilted hoisting state, the length of the first strut guywire 34 (see FIG. 3) is controlled such that the tilting can be controlled. By slowly letting the length of the first strut guywire 34 increase, the first mast upper part 4 slowly tilts more with respect to the first mast lower part 5.

(28) FIG. 5 shows the crane 1 while hoisting a load 24, when the first mast tilting member 6 is in the tilted hoisting state. In the example shown in FIG. 5, a building 25 is in the close vicinity of the crane 1, and the crane 1 is used to hoist the load 24 onto the building 25. The building 25 being so close to the crane 1, prevents the first mast 2 from being in a relatively horizontal position. In the straight hoisting state, the first mast 2 would not be able to hoist the load 24 onto the building 25, because the first mast 2 would clash with the building 25. The crane 1 according to the invention comprising the first mast tilting member 6, made it possible to bring the first mast upper part 4 in a tilted position relative to the first mast lower part 5. As such, the horizontal reaching span of the first mast 2 is increased, as well as the flexibility and maneuverability of the crane 1.

(29) During the hoisting with the first mast tilting member 6 in the tilted hoisting state, the strut 9 is in the functional position, and the first strut guywire 34 locks the first mast upper part 4 in a fixed position relative to the first mast lower part 5. As explained above, the first strut guywire 34 is winded on a winch (not shown) for bringing the strut 9 in the functional position. Once the strut 9 is in the functional position, the second strut guywire 36 prevents the strut 9 from moving or pivoting further upwards. Thus, the end of the first strut guywire 34 at the strut 9 is essentially in a fixed position. By controlling the length of the first strut guywire 34, which can be accomplished by winding more or less on the winch, the distance between the upper end 13 of the first mast upper part 4 and the second end 10 of the first mast strut 9 is also controlled. By maintaining this distance constant, the first mast upper part 4 is locked in a fixed position relative to the first mast lower part 5.

(30) To bring the first mast tilting member 6 back into the straight hoisting state, the first strut guywire 34 can be winded further on the winch. By doing this, the distance between the strut 9 and the upper end 13 of the first mast upper part 4 is decreased. Since the strut 9 is prevented from moving further upwards by the second strut guywire 36, the upper end 13 is forced to move closer to the strut 9. Eventually, the first mast upper part 4 will be in line with the first mast lower part 5. The operator can then lock the first mast tilting member in the straight hoisting state with the pin 42, which was shown in FIG. 4a.

(31) In FIG. 5, the second mast guywire 14 connects the second mast 3 to the first mast 2 in the upper end 13 of the first mast upper part 4. The second mast guywire 14 absorbs forces directly from the upper end 13 to the second mast 3, meaning that the first mast upper part 4 is not subjected to those forces. This reduces all the forces in the first mast 2 considerably, and as such also the moments and stresses.

(32) FIG. 6 shows an embodiment a crane 1 according to the invention, wherein also the second mast 3 can be tilted. In the shown example, this is accomplished in a very similar way as for the first mast 2. However, it is also possible that there are differences between the two tiltable masts 2, 3, since the invention is not limited to the example shown in these figures.

(33) The second mast 3 in FIG. 6 comprises multiple mast section 16.1-16.7. A second mast tilting member 106 is arranged between mast sections 16.2 and 16.3. The second mast tilting member 106 is very similar to the first mast tilting member 6, and also comprises an extendable cylinder 132. The second mast tilting member 106 has a straight hoisting states and a tilted hoisting state. The second mast 3 is divided by the second mast tilting member 106 into a second mast upper part 104 comprising two mast sections 16.1, 16.2, and a second mast lower part 105 comprising six mast section 16.3-16.8. Mast section 16.2 is identical to mast section 16.3, and mast section 16.1 is identical to mast sections 16.4-16.7. The second mast titling part 106 further also comprises an upper connection part 107 connected to the second mast upper part 104 and a lower connection part 108 connected to the second mast lower part 105, as well as two positioning holes (not shown) and a pin (not shown) for locking the second mast upper part 104 in a fixed position relative to the second mast lower part 105, when the second mast tilting member 106 is in the straight hoisting state.

(34) The second mast 3 further comprises a second mast strut 109, which can be brought into a functional position in the same way as the strut 9. A first strut guywire 134 and a second strut guywire 136 are provided, with the same function as their counterparts at the first mast 2. By tilting the back mast, the outreach of the ballast weight 20 is increased.

(35) As can be seen, the tilting of the second mast 3 in the shown example is very similar as the first mast 2. All embodiments that are possible for the first mast 2, are also possible for the second mast 3. Furthermore, it is also possible that only the back mast can be tilted, and not the main boom.

(36) FIG. 7a and FIG. 7b show another possible embodiment of the first mast tilting member 206, in the straight hoisting state and the tilted hoisting state respectively. This first mast tilting member 206 also comprises an extendable cylinder 232. However, the extendable cylinder 232 in this case is not arranged directly between the first mast upper part 4 and the first mast lower part 5. Instead, it is arranged essentially perpendicular to the neutral axis 45 of the first mast 2 and connected to a hinge 209. To said hinge 209, there is also connected a first bar 208 which is connected to the first mast upper part 4 by hinge 210, and a second bar 207 which is connected to the first mast lower part 5 by hinge 211.

(37) In the straight hoisting state as shown in FIG. 7a, the extendable cylinder 232 is in a retracted state. By extending the extendable cylinder 232, the hinge 209 is pushed to a direction away from the first mast 2, which in FIGS. 7a-7b is to the right. The first and second bar 207,208 will thus also be pushed in that direction, and pivot about the hinges 210 and 211 respectively. As such, the tilting of the first mast upper part 4 relative to the first mast lower part 5 is initialized. Again, once initialized, the first mast upper part 4 will tilt further under the influence of gravity.

(38) In the tilted hoisting state as shown in FIG. 7b, the extendable cylinder 232 is in an extended state. The first mast tilting member 232 also comprises a hinge 243 which is located on a first mast titling axis 244, which again is in the neutral plane 45 of the first mast. In the tilted hoisting state, all forces are transferred from the first mast upper part 4 to the first mast lower part 5 through the hinge 243. Thus, the extendable cylinder 232 and the first and second bar 207,208, are subjected to essentially no forces.