Mobile telescopic crane

Abstract

A mobile telescopic crane has a telescopic jib with at least three part-jibs. Each of the part-jibs is constructed from at least two part-jib portions so as to be telescopic in a longitudinal direction. Part-jib portions arranged at a spacing from one another transverse to the longitudinal direction each form a jib portion with at least one flexurally rigid connecting element. Respective adjacent jib portions are mechanically lockable with respect to one another in the longitudinal direction. A construction of this type of the jib means that an increase in the bearing load is easily achieved by increasing the area moment of inertia of the jib.

Claims

1. A mobile telescopic crane comprising: a movable undercarriage, a superstructure rotatably arranged on the undercarriage, a jib mounted on the superstructure wherein the jib is telescopic in a longitudinal direction, and is pivotable in a luffing plane, wherein the telescopic jib has at least three part-jibs, wherein each of the at least three part-jibs is constructed from at least two part-jib portions that are telescopic in the longitudinal direction, wherein the part-jib portions are arranged at a spacing from one another transverse to the longitudinal direction to form a jib portion with at least one rigid connecting element, wherein respective adjacent jib portions are mechanically lockable with respect to one another in the longitudinal direction, wherein the jib has three part-jibs which are arranged triangularly and symmetrically with respect to the luffing plane, and wherein one part-jib of the three part-jibs is arranged in the luffing plane and has a larger part-cross-sectional area than the other part-jibs.

2. A mobile telescopic crane according to claim 1, wherein the jib, perpendicular to the luffing plane, has a cross-sectional area A.sub.A produced by the at least three part-jibs and each of the at least three part-jibs, perpendicular to the luffing plane, has a part-cross-sectional area, wherein the ratio of the cross-sectional area A.sub.A to a sum A.sub.S of the part-cross-sectional areas is A.sub.A/A.sub.S1.

3. A mobile telescopic crane according to claim 1 wherein the jib, perpendicular to the luffing plane, has a width B.sub.A, and each of the part-jibs has a width B.sub.1 and B.sub.A/B.sub.i1.5.

4. A mobile telescopic crane according to claim 1, wherein the jib, parallel to the luffing plane, has a height H.sub.A and each of the part-jibs has a height H.sub.i, and the ratio H.sub.A/H.sub.i1.2.

5. A mobile telescopic crane according to claim 1, wherein respective adjacent part-jib portions of all the part-jibs are mechanically lockable with respect to one another in the longitudinal direction.

6. A mobile telescopic crane according to claim 1, wherein at least two adjacent part-jib portions are mechanically lockable with respect to one another by means of at least one locking bolt.

7. A mobile telescopic crane according to claim 1, wherein at least two adjacent part-jib portions are mechanically lockable with respect to one another by means of at least two locking bolts.

8. A mobile telescopic crane according to claim 1, wherein the jib has a width that changes perpendicular to the luffing plane, the width increasing from a lower part-jib facing the undercarriage up to two upper part-jibs remote from the undercarriage.

9. A mobile telescopic crane according to claim 1, wherein the part-jib arranged in the luffing plane is arranged on a lower side of the jib and the other part-jibs are spaced apart from the luffing plane and are arranged on an upper side of the jib.

10. A mobile telescopic crane according to claim 1, wherein the part-jibs arranged spaced apart from the luffing plane have the same cross-sections and the same cross-sectional areas.

11. A mobile telescopic crane according to claim 1, wherein the part-jib arranged in the luffing plane has a cross-section, at least in portions, which is selected from the group consisting of circular and oval.

12. A mobile telescopic crane according to claim 1, wherein the part-jib arranged in the luffing plane forms a receiving space, and a hydraulic cylinder is arranged in the receiving space to telescope the jib.

13. A mobile telescopic crane according to claim 1, wherein respective adjacent part-jib portions of the part-jibs arranged spaced apart from the luffing plane are mechanically lockable with respect to one another at an end.

14. A mobile telescopic crane according to claim 1, wherein the part-jibs define a cable guide channel.

15. A mobile telescopic crane according to claim 1, wherein a support cable is guided along the jib.

16. A mobile telescopic crane according to claim 1, wherein respective adjacent part-jib portions of the part-jibs which are spaced apart from the luffing plane are mechanically lockable with respect to one another at an end, and at least one locking bolt is provided to lock adjacent part-jibs and is mounted on a rigid connecting element.

17. A mobile telescopic crane according to claim 1, wherein a support cable is arranged in a cable guide channel in the jib.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a perspective view of a mobile telescopic crane according to a first embodiment with a telescopic jib, which is constructed from three part-jibs and is located in a transporting position.

(2) FIG. 2 shows a cross-section through the jib in FIG. 1 in the region of a connecting element.

(3) FIG. 3 shows a perspective view of the mobile telescopic crane in FIG. 1 with the jib located in a retracted operating position.

(4) FIG. 4 shows a perspective view of the mobile telescopic crane in FIG. 1 with the jib located in an extended operating position.

(5) FIG. 5 shows a cross-section through the jib in FIG. 4 in the region before the connecting element.

(6) FIG. 6 shows a cross-section through the extended jib in FIG. 5 in the region of a first jib portion to illustrate the arrangement of the part-jibs.

(7) FIG. 7 shows a perspective view of a mobile telescopic crane according to a second embodiment with a jib, which is constructed from three part-jibs and which is in an extended operating position.

(8) FIG. 8 shows a perspective view of a mobile telescopic crane according to a third embodiment with a jib, which is constructed from three part-jibs and is in a transporting position.

(9) FIG. 9 shows a perspective view of the mobile telescopic crane in FIG. 8 with the jib in an extended operating position.

(10) FIG. 10 shows a side view of the mobile telescopic crane in FIG. 9.

(11) FIG. 11 shows a cross-section through the jib in FIG. 10 along the section line XI-XI.

(12) FIG. 12 shows a cross-section through the jib in FIG. 10 along the section line XII-XII.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(13) A first embodiment of the invention will be described below with reference to FIGS. 1 to 6. A mobile telescopic crane 1 has a movable undercarriage 2, on which a superstructure 3 with a counter-weight 4 is arranged. The undercarriage 2 is configured in the conventional manner for travelling operation on public roads. For this purpose, the undercarriage 2 has a base frame 5, on which a plurality of axles 6 with wheels 7 arranged thereon, which can be driven and steered in the conventional manner, are mounted. The superstructure 3 and the counter-weight 4 arranged thereon are rotatably mounted on the undercarriage 2 about a rotational axis 8 running perpendicular to the base frame 5.

(14) Arranged on the superstructure 3 is a jib 9, which can be pivoted by means of a hydraulic cylinder 10 in a luffing plane W and is telescopic in a longitudinal direction L. The jib 9, for this purpose, has three jib portions 11 to 13, which can be retracted and extended telescopically by means of a hydraulic cylinder 14 and can thus be transferred from a retracted transporting position into an extended operating position. The first jib portion 11 is pivotably articulated to the superstructure 3 about a horizontal pivot axis 15 at the end. The jib 9 is pivoted in the luffing plane W by means of the hydraulic cylinder 10, which, proceeding from the superstructure 3 is articulated to the jib portion 11 spaced apart from the pivot axis 15.

(15) The jib 9 has three part-jibs 16, 17, 18, which are each constructed telescopically from three part-jib portions 19 to 21, 22 to 24 and 25 to 27. The hydraulic cylinder 14 is arranged within a receiving space of the part-jib 16, which is configured as a hollow cylinder to configure the receiving space. The part-jibs 16 to 18 are arranged transverse to the longitudinal direction L at a spacing from one another and connected to one another by four flexurally rigid connecting elements 28 to 31. The connecting elements 28 and 29 are in each case arranged at the end on the part-jib portions 19, 22 and 25 and form therewith the first jib portion 11. The connecting element is in turn arranged on the end of the part-jib portions 20, 23 and 26, which is remote from the first jib portion 11 and forms therewith the second jib portion 12. Accordingly, the connecting element 31 is arranged on an end of the part-jib portions 21, 24 and 27 remote from the second jib portion 12 and forms therewith the third jib portion 13.

(16) The jib 9 is constructed symmetrically with respect to the luffing plane W and has a jib centre longitudinal axis 32 designated the centroidal axis and located in the luffing plane W. The part-jibs 16 to 18 accordingly have associated part-jib centre longitudinal axes 33 to 35, which are arranged polygonally or triangularly and symmetrically with respect to the luffing plane W. The centre longitudinal axes 32 and 33 are located in the luffing plane W and have a spacing b.sub.1=0 perpendicular to the luffing plane W and a spacing h.sub.1 from one another parallel to the luffing plane W. In comparison to this, the centre longitudinal axes 34 and 35 have the same spacings b.sub.2 and b.sub.3 perpendicularly from the luffing plane W. Furthermore, the centre longitudinal axes 34, 35 have a spacing h.sub.2 and h.sub.3 with respect to the centre longitudinal axis 32 and parallel to the luffing plane W.

(17) The lower part-jib 16 arranged in the luffing plane W and facing the undercarriage 2 therefore form a lower side of the jib 9, whereas the upper part-jibs 17, 18 arranged spaced apart from the luffing plane W and remote from the undercarriage 2 form an upper side of the jib 9. The jib 9 perpendicular to the luffing plane W has a width B, which increases proceeding from the lower part-jib 16 in the direction of the upper part-jibs 17, 18 up to a maximum width B.sub.A. This is illustrated in FIG. 6.

(18) The part-jib portions 19 to 27 are configured as a hollow cylinder and have a circular cross-section. FIG. 6 illustrates the cross-sectional form of these part-jib portions 19, 22 and 25 of the first jib portion 11 and the position of the part-jib portions 19, 22, 25 relative to one another and with respect to the luffing plane W. The part-jib portion 19 has an external radius R.sub.1, which is greater than the respective external radius R.sub.2 and R.sub.3 of the part-jib portions 22 and 25. The part-jib portion 19 therefore has a height H.sub.1=2.Math.R.sub.1 parallel to the luffing plane W and a width B.sub.1=2.Math.R.sub.1 perpendicular to the luffing plane W. Accordingly, the part-jib portions 22 and 25 have associated heights H.sub.2=2.Math.R.sub.2 and H.sub.3=2.Math.R.sub.3 and associated widths B.sub.2=2.Math.R.sub.2 and B.sub.3=2.Math.R.sub.3. The jib 9 in the region of the jib portion 11 therefore has a height or a maximum height H.sub.A, which is produced from the sum of R.sub.1, R.sub.2, h.sub.1 and h.sub.2. Furthermore, the jib 9 in the region of the jib portion 11 has a width or a maximum width B.sub.A, which is produced from the sum of R.sub.2, R.sub.3, b.sub.2 and b.sub.3. The same is produced for the jib portions 12 and 13, the external radii R.sub.1 to R.sub.3 being correspondingly smaller because of the telescopic ability of the jib 9. To telescope the jib 9, respective part-jib portions 19 to 27, which are adjacent in the longitudinal direction L, of each part-jib 16, 17 18 are guided so as to be displaceable into one another.

(19) There applies to the ratio of the width B.sub.A to each of the widths B, wherein i=1 to 3: B.sub.A/B.sub.i1.5, in particular B.sub.A/B.sub.i2, and, in particular B.sub.A/B.sub.i2.5. Furthermore, there applies to the ratio of the height H.sub.A to each of the heights H.sub.i wherein i=1 to 3: H.sub.A/H.sub.i1.2, in particular H.sub.A/H.sub.i1.5, in particular H.sub.A/H.sub.i2, and, in particular H.sub.A/H.sub.i2.5. The same applies to the jib portions 12 and 13.

(20) The jib portions 19, 22 and 25, perpendicular to the luffing plane W, have part-cross-sectional areas A.sub.1, A.sub.2 and A.sub.3, which are, in each case, produced from the circular area with the associated external radius R.sub.1, R.sub.2 and R.sub.3. The part-cross-sectional areas A.sub.i therefore in each case comprise the associated material cross-sectional areas A.sub.Mi and the cavity cross-sectional areas A.sub.Hi limited by the material, wherein there applies i=1 to 3. Owing to the spaced apart arrangement of the part-jibs 16, 17 and 18 or the part-jib portions 19, 22 and 25, the jib 9, in the region of the jib portion 11, has a cross-sectional area A.sub.A, which is greater than a sum A.sub.S of the part-cross-sectional areas A.sub.1 to A.sub.3. The cross-sectional area A.sub.A is illustrated in FIG. 6 by the dotted lines, which in each case run tangentially between adjacent part-jib portions 19, 22, 25. The dotted lines together with the part-jib portions 19, 22, 25 form a peripheral line of the jib portion 11. The peripheral line limits the cross-sectional area A.sub.A. Speaking figuratively, the cross-sectional area A.sub.A is produced in that a cable forming the peripheral line is tightly tensioned about the part-jib portions 19, 22, 25. The same applies to the jib portions 12, 13.

(21) To the ratio of the cross-sectional area A.sub.A to the sum A.sub.S of the part-cross-sectional areas A.sub.1 to A.sub.3 there applies: A.sub.A/A.sub.S1, in particular A.sub.A/A.sub.S1.5, in particular A.sub.A/A.sub.S2, in particular A.sub.A/A.sub.S2.5, in particular A.sub.A/A.sub.S3, and, in particular A.sub.A/A.sub.S4. The same applies to the jib portions 12 and 13, wherein it is to be taken into account that the part-jib portions 20, 23, 26 or 21, 24, 27, because of the telescopic ability, correspondingly have smaller radii R.sub.1, R.sub.2 and R.sub.3.

(22) Owing to this construction, the jib 9, in comparison to conventional jibs, has a higher area moment of inertia I.sub.z,tot or I.sub.y,tot in relation to bending forces acting perpendicular to the luffing plane W and in the luffing plane W. The area moment of inertia I.sub.z,tot with respect to bending forces acting perpendicular to the luffing plane W, in other words upon a bend about the z-axis, is produced as:

(23) $\begin{array}{cc}{I}_{z,\mathrm{tot}}=\underset{i=1}{\overset{n}{.Math.}}\left[I_{z,i}+b_i^2.Math.A_{\mathrm{Mi}}\right],& \left(1\right)\end{array}$
wherein
i is a continuous index for the part-jibs,
I.sub.z,i is the part-jib i's own proportion,
b.sub.i is the spacing of the centroidal axis or centre longitudinal axis of the part-jib i from the centroidal line or centre longitudinal axis of the jib in the y-direction,
A.sub.Mi is the material cross-sectional area of the part-jib i,
b.sub.i.sup.2.Math.A.sub.Mi is the Steiner proportion of the part-jib i and n is the number of part-jibs.

(24) For the equation (1) there also applies n=3 and b.sub.i=0. Equation (1) describes the achievable area moment of inertia I.sub.z,tot in an ideally flexurally rigid jib 9. In the practical dimensioning of the jib 9, a reduction ratio is to be taken into account in the Steiner proportions and depends on the number of connecting elements 28 to 31 and their degree of flexural rigidity.

(25) Accordingly, the area moment of inertia I.sub.y,tot with respect to bending forces acting parallel to the luffing plane W, in other words in the case of a bend about the y-axis is produced as:

(26) $\begin{array}{cc}{I}_{y,\mathrm{tot}}=\underset{i=1}{\overset{n}{.Math.}}\left[I_{y,i}+h_i^2.Math.A_{\mathrm{Mi}}\right],& \left(2\right)\end{array}$
wherein
i is a continuous index for the part-jibs,
I.sub.y,i is the part-jib i's own proportion,
h.sub.i is the spacing of the centroidal axis or centre longitudinal axis of the part-jib i from the centroidal line or centre longitudinal axis of the jib in the z-direction,
A.sub.Mi is the material cross-sectional area of the part-jib i,
h.sub.i.sup.2.Math.A.sub.Mi is the Steiner proportion of the part-jib i and
n is the number of part-jibs.

(27) Corresponding with equation (1) a reduction ratio is to be taken into account in equation (2) in the Steiner proportions.

(28) The area moments of inertia are a measure of the rigidity of the jib 9 relative to the respective bending forces. Because of the Steiner fractions, the area moments of inertia are substantially increased relative to conventional jibs.

(29) The connecting elements 28 to 31 are substantially formed as triangular plates and in each case have two through-openings 36, 37 for the part-jib portions 22 to 27 of the part-jibs 12 and 13. Furthermore, the connecting elements 28 to 31 in each case have a rectangular through-opening 38 for the part-jib portions 19 to 21 of the part-jib 16, which extends approximately up to the centre longitudinal axes 34, 35. The through-openings 38 therefore form a cable guide channel 39 in the connecting elements 28 to 31 to guide a support cable 52. The support cable 52 is guided in the conventional manner from the free end of the jib 9 to a cable winch 53 arranged on the superstructure 3. The support cable 52 is guided on the free end of the jib 9 over two deflection rollers 54, 55, which are rotatably mounted on the free end of the jib 9 by means of a support frame 56.

(30) The part-jibs 17 and 18 can be displaced relative to the part-jib 16 parallel to the luffing plane W. For this purpose, two hydraulic cylinders 40 are rigidly arranged on the end facing the superstructure 3 on both sides of the part-jib portion 19 and connected to the connecting element 28. Accordingly, two hydraulic cylinders 41 are fastened at the end on the part-jib portion 19 and are connected to the connecting element 29. To displace the part-jibs 17, 18 or to fix these part-jibs 17, 18 relative to the part-jib 16, locking units 42 are provided. The locking units 42 are integrated into the part-jib portions 19 to 21 and the associated connecting elements 28 to 31. FIGS. 2 and 5, by way of example, show the locking unit 42 associated with the part-jib portion 19 and with the connecting element 29. The locking unit 42 has two locking bores 43, arranged in an opposing manner, opening into the through-opening 38 and running perpendicular to the luffing plane W. Locking and unlocking are possible owing to associated locking bolts 44, which can be guided through locking bores 45 of the part-jib portion 19 and the locking bores 43. The locking bolts 44 can be actuated, for example, hydraulically, pneumatically or electromechanically.

(31) The jib 9 can be transferred from a transporting position into an operating position and vice versa by the hydraulic cylinders 40, 41 and the locking units 42. In the transporting position, the cross-sectional area A.sub.A or the height H.sub.A of the jib 9 is reduced in comparison to the operating position, so the mobile telescopic crane 1 has a lower overall height. The reduction in the overall height is necessary, for example, to not exceed a maximally permissible height in road traffic.

(32) In addition, the locking units 42 belonging to the connecting elements 29 and 30 have locking bores 46, through which the locking bolts 44 can also be guided. The locking bores 46 are in each case configured in the inner part jib portion 20 or 21, so, in the locked state, the adjacent part-jib portions 19 and 20 or 20 and 21 are locked in the longitudinal direction L.

(33) For locking in the longitudinal direction L, locking units 47 and 48 are furthermore provided and are arranged in the region of the connecting elements 29 and 30. The locking units 47 and 48 are mounted or fastened directly on the respectively associated connecting element 29 or 30. The locking units 47, 48 in each case have locking bores 49, 50, which are configured in the adjacent part-jib portions 22 and 23, 23 and 24, 25 and 26 and 26 and 27. A respective locking bolt 51 can be guided through the locking bores 49, 50, so the desired mechanical locking of the jib portions 11 and 12 and 12 and 13 can be achieved. Alternatively, corresponding to the locking units 42, two locking bolts 51 can be provided, which are arranged opposing one another and can be displaced in respective associated locking bores 49, 50. The locking bolts 51 can be actuated, for example, hydraulically, pneumatically or electromechanically.

(34) FIGS. 1 and 2 show the mobile telescopic crane 1 in the state provided for travelling operation. The jib 9 is in a completely retracted transporting position. The locking units 42, 47 and 48 are unlocked and the jib portions 11 to 13 are retracted telescopically. Furthermore, the part-jibs 17 and 18 are completely lowered by means of the hydraulic cylinders 40, 41, so the part-jib 16 is completely arranged in the through-openings 38. In this state, the mobile telescopic crane 1 has the smallest possible overall height, so the maximally permissible height in road traffic is not exceeded. FIG. 2 illustrates the transporting position of the jib 9 with the aid of a cross-section through the connecting element 29.

(35) FIG. 3 shows the mobile telescopic crane 1 with the jib 9 in a telescopically retracted operating position. By means of the lifting cylinders 40, 41, the part-jibs 17, 18 and the connecting elements 28 to 31 have been extended relative to the part-jib 16 parallel to the luffing plane W. The locking units 42 belonging to the connecting elements 28 and 31 are then locked.

(36) The jib 9 is thereupon erected in the luffing plane W by means of the hydraulic cylinder 10 and telescopically extended by means of the hydraulic cylinder 14. FIG. 4 shows the mobile telescopic crane 1 in an operating position with the completely erected and telescopically extended jib 9. In this state, the locking units 42, 47 and 48 belonging to the connecting elements 29 and 30 are also locked, so the jib 9 has a high degree of rigidity. FIG. 5 shows a cross-section through the locking units 47, 48 adjacent to the connecting element 29.

(37) The jib 9 according to the invention, because of the high area moments of inertia, has a high degree of rigidity with respect to bending forces perpendicular and parallel to the luffing plane W. As a result, in relation to the weight of the jib 9, a substantial bearing load increase can be achieved. In particular, the jib 9, even without an increase in weight compared to conventional jibs, or with only a slight increase in weight, has a significant bearing load increase, which approximately corresponds to that of a conventional jib with anchoring supports. However, compared to a conventional jib with anchoring supports, no separate transportation and no laborious assembly are necessary.

(38) A second embodiment of the invention will be described below with the aid of FIG. 7. In contrast to the first embodiment, the part-jibs 17a, 18a are rigidly arranged by means of the connecting elements 28a to 31a on the part-jib 16a and not displaceable relative thereto. If, as a result, the maximally permissible height of the mobile telescopic crane 1a is not exceeded, simplification of the structure of the jib 9a is thus possible. Since the connecting elements 28a to 31a are rigidly arranged on the part-jib 16a, the locking bores 43 can be dispensed with. With regard to the further structure and the further mode of functioning, reference is made to the description of the first embodiment.

(39) A third embodiment of the invention will be described below with the aid of FIGS. 8 to 12. In contrast to the previous embodiments, the mobile telescopic crane 1b has a jib 9b with three part-jibs 16b, 17b and 18b, the part-jib 16b arranged in the luffing plane W having an oval cross-section. The connecting elements 28b to 31b accordingly have oval through-openings 38b. The cable guide channel 39b is configured in the connecting elements 28b to 31b above the part-jib 16b to guide the support cable 52. The part-jib centre longitudinal axis 33 of the part-jib 16b runs in the intersection point of the maximum height H.sub.1 and the maximum width B.sub.1 of the part-jib 16b.

(40) The part-jib 16b arranged in the luffing plane W has a maximum width B.sub.1 perpendicular to the luffing plane W and a maximum height H.sub.1 in the luffing plane W, wherein there applies: H.sub.1/B.sub.1>1, in particular H.sub.1/B.sub.11.2, and, in particular H.sub.1/B.sub.11.5. The part-jib 16b, in the direction of the luffing plane W, overlaps with the part-jibs 17b, 18b with an overlap amount h.sub.12 or h.sub.13, wherein there applies h.sub.12=h.sub.13. There applies, furthermore, h.sub.12<R.sub.2 and h.sub.13<R.sub.3. The part-cross-sectional area A.sub.1 is in each case greater than the part-cross-sectional area A.sub.2 and A.sub.3. There preferably applies A.sub.1/A.sub.21.5, in particular A.sub.1/A.sub.22, and, in particular A.sub.1/A.sub.22.5. The same applies to A.sub.1/A.sub.3. The jib 9b, in the region of the jib portion 11b, has a maximum height H.sub.A, which is produced from the sum of H.sub.1 and R.sub.2 less the overlap amount h.sub.12. Furthermore, the jib 9b in the region of the jib portion 11b has a maximum width B.sub.A, which is produced from the sum of R.sub.2, R.sub.3, b.sub.2 and b.sub.3. The same is produced for the jib portions 12b and 13b, the external radii R.sub.2 and R.sub.3 and the maximum height H.sub.1 and the overlap amount h.sub.12 being correspondingly smaller because of the telescopic ability of the jib 9b.

(41) The part-jibs 17b, 18b, corresponding to the second embodiment, are arranged at a fixed spacing from the part-jib 16b. Alternatively, the part-jibs 17b, 18b, corresponding to the first embodiment, can be displaced relative to the part-jib 16b. The hydraulic cylinder 14b is arranged within the part-jib 16b to telescope the jib 9b.

(42) The locking units 47b, 48b are fastened directly to the connecting elements 29b, 30b, so adjacent part-jib portions 22b and 23b, 23b and 24b, 25b and 26b and 26b and 27b are mechanically lockable with respect to one another at the end. The locking units 47b, 48b, in each case, have two opposingly arranged locking bolts 51b, which can be guided through respective associated locking bores 49, 50. The locking bolts 51b can be actuated, for example, hydraulically, pneumatically or electromechanically.

(43) The jib 9b has a high degree of flexural rigidity with respect to bending forces acting in the luffing plane W and bending forces acting perpendicular to the luffing plane W. The part-jib 16b, because of its oval cross-section and its part-cross-sectional area A.sub.1, can, in particular, absorb high bending forces, which act in the luffing plane W. With respect to the further construction and the further mode of functioning of the mobile telescopic crane 1b, reference is made to the preceding embodiments.

(44) The features of the jibs 9 to 9b can basically be combined in any way to form a jib according to the invention. Apart from the simple increasing of the bearing load by increasing the area moments of inertia, the jibs 9 to 9b according to the invention have further advantages compared to a conventional jib with anchoring supports. The jibs 9 to 9b according to the invention, in each jib portion 11 to 13b, can be optimized separately with respect to the acting bending forces, so these are continuously absorbed along the jib 9 to 9b and not only at the end of the jib. Moreover, both the transfer of the jibs 9 to 9b into the operating position and their operation are extremely simple. In particular, no laborious control of the pretensioning force of the anchoring cables is necessary, so the operation is simplified and the reliability is simultaneously increased, as no incorrect control of the pretensioning force is possible. A large number of optimizing parameters are provided by means of the number of part-jibs 16 to 17b and their arrangement and spacing with respect to one another, whereby the cross-sectional area A.sub.A is defined, and by means of the cross-sectional form and the part-cross-sectional areas A.sub.A so a jib 9 to 9b according to the invention can be optimized with respect to the capacity to absorb bending forces acting perpendicular to and in the luffing plane W and with respect to the weight. In total, the jibs 9 to 9b according to the invention allow a substantial increase in the bearing load at a predefined weight compared to conventional jibs. In particular, with the same bearing load, substantially easier handling of the jibs 9 to 9b is possible with respect to transportation and assembly or transfer into the operating position compared with conventional jibs with anchoring supports.