Telescoping jib comprising a rod guying system for a mobile crane and guying method therefor

Abstract

A telescoping jib of a mobile crane includes sections that telescope out of a jib housing from a transport position into an operating position. A guying system has successively connected tension rods extending from the jib housing to at least one of the extended telescoping jibs by at least one guying support. The mobile crane provides a lighter construction and improved road handling, and an increased load capacity for unchanged telescoping jib measurements. To this end, a guide holder arranged on the jib housing receives the tension rods in the transport position and, in the operating position, at least one movable tension rod on one of the guying supports is respectively securely connected to the outer end of a telescoping section head in an articulated manner and can be secured to a holding mechanism on the opposite end on an adjacent guying support of an adjacent telescoping section head.

Claims

1. A telescoping jib of a mobile crane comprising: a plurality of telescoping sections configured to be telescoped out of a jib basic box from a transport position to an operating position; and a guying system comprising a plurality of successively mutually connected tension rods which extend from the jib basic box via at least one guying support to at least one of the telescoping sections; wherein a guide holder for the tension rods is arranged on the jib basic box and receives the tension rods in the transport position of the telescoping jib and, in the operating position, in each case at least one of the displaceable tension rods on one of the guying supports is fixedly articulated in each case to an outer end of a telescoping section head and can be fixed to a rod holder on an opposite end on an adjacent guying support of an adjacent telescoping section head.

2. The telescoping jib as claimed in claim 1, wherein each guying support is arranged in each case at an outer end of a jib basic box head or an outer end of the telescoping section head of the telescoping sections.

3. The telescoping jib as claimed in claim 2, wherein a one of the guying supports is arranged on a head of the jib basic box and is guyed to the jib basic box in the region of a foot of the jib basic box via left and right, positionally fixed tension rods.

4. The telescoping jib as claimed in claim 1, wherein the at least one guying support comprises a plurality of guying supports with the jib basic box and each telescoping section each including a respectively one of the guying supports arranged thereon.

5. The telescoping jib as claimed in claim 4, wherein each guying support has an opening for the displaceable tension rods to be guided there through and the rod holder for the respective displaceable tension rod is arranged in a region of the opening.

6. The telescoping jib as claimed in claim 4, wherein a one of the guying supports is arranged on a head of the jib basic box and is guyed to the jib basic box in the region of a foot of the jib basic box via left and right, positionally fixed tension rods.

7. The telescoping jib as claimed in claim 5, wherein the rod holder comprises a movable locking bar via which the respective displaceable tension rod in the opening can be fixed in the operating position by engagement into a recess in the respective displaceable tension rod.

8. The telescoping jib as claimed in claim 7, wherein each guying support comprises two limbs which are arranged on the telescoping jib to the right and left of a center of the telescoping jib, as seen in the longitudinal direction of the telescoping jib, and form an angle of 45 degrees to 135 degrees.

9. The telescoping jib as claimed in claim 8, wherein at least one of the displaceable tension rods is fixedly articulated to each limb of each guying support and/or can be fixed to the rod holder.

10. The telescoping jib as claimed in claim 1, wherein the successive telescoping sections and the jib basic box can be secured to one another.

11. The telescoping jib as claimed in claim 1, wherein via an erector that connects the guide holders of the guying system to the jib basic box via one of the guying supports, the guide holders can be erected from a transport position to an operating position and, in the operating position, the guide holders and the displaceable tension rods resting thereon extend in parallel with a longitudinal direction and above the telescoping jib.

12. The telescoping jib as claimed in claim 11, wherein the guide holders can be pivoted from the transport position to the operating position via articulation points, the articulation points are arranged over the course of the guide holders and adjoining the guying support, the displaceable tension rods in the transport position on the guide holders have articulation points which are aligned with the articulation points of the guide holders.

13. The telescoping jib as claimed in claim 1, wherein the at least one guying support comprises a plurality of guying supports the jib basic box and each telescoping section each including a respective one of the guying supports arranged thereon.

14. The telescoping jib as claimed in claim 1, wherein each guying support comprises two limbs which are arranged on the telescoping jib to the right and left of a center of the telescoping jib, as seen in the longitudinal direction of the telescoping jib, and form an angle.

15. The telescoping jib as claimed in claim 14, wherein at least one displaceable tension rod is fixedly articulated to each limb of each guying support and/or can be fixed to the rod holder.

16. The telescoping jib as claimed in claim 1, wherein each guying support has an opening for the displaceable tension rods to be guided there through and the rod holder for the respective displaceable tension rod is arranged in a region of the opening.

17. The telescoping jib as claimed in claim 16, wherein the rod holder comprises a movable locking bar via which the respective displaceable tension rod in the opening can be fixed in the operating position by engagement into a recess in the respective displaceable tension rod.

18. A method for guying a telescoping jib of a mobile crane, wherein the telescoping jib comprises a plurality of telescoping sections configured to be telescoped out of a jib basic box from a transport position to an operating position, and a guying system comprising a plurality of successively mutually connected tension rods which extend from the jib basic box via at least one guying support to at least one of the extended telescoping jibs, wherein a guide holder for the tension rods is arranged on the jib basic box and receives the tension rods in the transport position of the telescoping jib and, in the operating position, in each case at least one of the displaceable tension rods on one of the guying supports is fixedly articulated in each case to an outer end of a telescoping section head and can be fixed to a rod holder on an opposite end on an adjacent guying support of an adjacent telescoping section head, such that the tension rods are guyed between the jib basic box and at least one adjoining telescoping section, said method comprising: successively extending the individual telescoping sections from the jib basic box together with in each case extending one of the displaceable tension rods from a respective guide holder from transport position to the operating position and fixing each displaceable tension rod in the operating position to the guying support of the adjacent telescoping section via the respective rod holder.

19. The method of claim 18, wherein the rod holder comprises a movable locking bar via which the respective displaceable tension rod in the opening can be fixed in the operating position by engagement into a recess in the respective displaceable tension rod.

20. The method of claim 19, wherein each guying support is arranged in each case at an outer end of a jib basic box head or an outer end of the telescoping section head of the telescoping sections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a perspective view of a mobile crane with a telescoping jib,

(2) FIG. 2 shows a perspective partial view of a mobile crane according to FIG. 1 with a partially extended telescoping jib,

(3) FIG. 3 shows a perspective plan view of a completely extended telescoping jib,

(4) FIG. 4 shows a detailed view of a guying support on a jib basic box of the telescoping jib, and

(5) FIG. 5 shows a detailed view of the guying supports on the telescoping jib in the position according to FIG. 2 with open locking bar elements.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) FIG. 1 shows a perspective view of a mobile crane designated by 1. The mobile crane 1 comprises essentially a lower carriage 2 and a superstructure 3. The lower carriage 2 supports counterweights 4 and comprises four vehicle axles 5 each with two wheels 6 suitable for road travel. Of course, the lower carriage 2 can also be equipped with more or fewer than four vehicle axles 5. Furthermore, the lower carriage 2 supports the superstructure 3, which can pivot with respect to the lower carriage 2 about a substantially vertically orientated axis of rotation D The superstructure 3 and lower carriage 2 can naturally also be rigidly mounted one on another. Arranged on the superstructure 3 is a combined driver's and crane operator's cabin 7 which can be pivoted about a vertical axis K from the front—as seen in the forwards travel direction F of the mobile crane 1—to the rear and vice versa. The combined driver's and crane operator's cabin 7 is thus located behind the superstructure 3 in the driving position and to the side next to the superstructure 3 in the crane operating position. Moreover, the superstructure has a luffable telescoping jib 8 mounted thereon which, for road travel, is completely retracted and, in the direction opposite the forwards travel direction F of the mobile crane 1, is stored on the lower carriage 2 in a downwardly inclined manner at a shallow angle proceeding from a horizontal, so that guying supports 15 arranged on the telescoping jib 8 and protruding upwards do not increase the construction height during travel of the mobile crane 1. It is naturally also possible to form the driver's and crane operator's cabin 7 separately from each other.

(7) The telescoping jib 8 typically consists of a jib basic box 9 and a plurality of extendible and retractable telescoping sections 10a-h and has a guying system 11 in order to achieve an increase in the bearing load with the telescoping jib 8 remaining otherwise unchanged. With this guying system, it is also possible to produce telescoping jibs 8 with smaller diameters or cross-sections whilst maintaining the bearing load. The guying system 11 consists substantially of a multiplicity of tension rods 16, 16′, 16a-16h, 16a′-16h′, of which the displaceable tension rods 16a-h, 16a′-h′ can be retracted and extended in parallel with the telescoping sections 10a-10h. In FIG. 1, the tension rods 16a-16h, 16a′-16h′ are completely retracted for road travel and rest above the jib basic box 9 in left and right guide holders 13a, 13b. Also, for road travel the left and right guide holders 13a, 13b are pivoted together with the tension rods 16a-16h, 16a′-16h′ to a rest position in order not to increase the construction height of the mobile crane 1.

(8) The jib basic box 9 is typically connected at its foot to the superstructure 3 via a horizontal luffing axle W and can be pivoted up and down via a luffing cylinder 12 (see FIG. 2). The jib basic box 9 receives the telescoping sections 10a-h within it in a conventional manner, these each being arranged one inside another and being retractable and extendible. In the respectively extended condition, the telescoping sections 10a-h are connected to one another via bolts, not illustrated. The foot of the inner, and therefore smaller, telescoping section 10a-h is in each case bolted, by means of a fitting bolting position hole, to the next outer and larger telescoping section 10a-h in each case or to the jib basic box 9. In FIG. 2, the foot of the telescoping section 10h is therefore connected to the head 10 of the telescoping section 10g via the bolts, not illustrated.

(9) FIG. 2 illustrates a perspective partial view of the mobile crane 1 according to FIG. 1 with a partially extended telescoping jib 8. The innermost and therefore uppermost telescoping section 10h is extended, the remaining telescoping sections 10a-g are still retracted. For crane operation, the superstructure 3 is pivoted out of the position for road travel (see in this respect FIG. 1) by 180° and so the telescoping jib 8 points in the forwards direction of travel F and creates space for arranging counterweights 4 on the rear side of the superstructure 3. The driver's and crane operator's cabin 7 has now been displaced laterally next to the superstructure 3 for crane operation.

(10) It is also apparent from FIG. 2 that, as seen in the longitudinal direction L of the telescoping jib 8, a lifting mechanism 14 having a cable drum is arranged on the jib basic box 9 for the purpose of lifting and lowering the crane loads. The cable drum of the lifting mechanism 14 points upwards and its rolling axis is arranged at a right angle to the longitudinal direction L of the telescoping jib 8 (see also FIG. 3). A lifting cable 18 is wound and unwound by the lifting mechanism 14 and extends from the lifting mechanism 14 along and above the telescoping jib 8 to the end of the last telescoping section 10h. Located at the end of the last telescoping section 10h are a deflecting roller 19 and a guide roller 31 (see FIG. 3), over which the lifting cable 18 is guided.

(11) In addition to the multiplicity of tension rods 16, 16′, 16a-16h, 16a′-16h′, the guying system 11 comprises substantially v-shaped and fork-shaped guying supports 15 which are arranged on the outer end—as seen in the longitudinal direction L of the telescoping jib 8—of a head 9a of the jib basic box 9 or a head 10 of each telescoping section 10a-h. Each v-shaped and fork-shaped guying support 15 comprises a left limb 15a and a right limb 15a′. Each of the left and right limbs 15, 15a′ consists of a lower part 15b, 15b′ and an upper part 15c, 15c′. The two lower limbs 15b, 15b′ adjoin one another—as seen with the telescoping jib 8 orientated horizontally—on the outside and at the top in the region of corners of the telescoping sections 10a-h, which have a substantially four-sided cross-section, or of the jib basic box 9, which has a substantially four-sided cross-section, and extend upwards and outwards in an inclined manner at approximately an angle of 45°. The upper free ends of the lower parts 15b, 15b′ are adjoined as one piece by the upper parts 15c, 15c′ in an inclined manner at approximately an angle of 45° so as to extend vertically upwards.

(12) The telescoping jib 8 is guyed by the positionally fixed jib basic box-tension rods 16, 16′ on the jib basic box 9 and the displaceable tension rods 16a-h, 16a′-h in each case in conjunction with the guying supports. The left and right positionally fixed tension rods 16, 16′ extend in a transport position at a shallow angle to the longitudinal direction L of the telescoping jib 8 and are each fastened at one end to the associated guying support 15 in the transition region between its lower and upper limbs 15b, 15b′, 15c, 15c′ and are connected to the other end in the lateral region of the foot of the jib basic box 9. Therefore, the tensioning forces acting upon the first guying support 15 of the jib basic box 9 are introduced into the jib basic box 9 via the positionally fixed tension rods 16, 16. In the retracted condition, the displaceable tension rods 16a-h, 16a′-h′ are stored on left and right guide holders 13a, 13b. Each of these guide holders 13a, 13b is designed as a flat, u-shaped profile which is open at the top and has u-shaped guide tracks for each of the displaceable tension rods 16a-h, 16a′-h′ and serves as a magazine for the displaceable tension rods 16a-h, 16a′-h′ when the telescoping jib 8 is retracted. The guide holders 13a, 13b are articulated at the upper end of the limb 15a, 15a′ of the guying support 15 on the head of the jib basic box 9a in each case at the head so as to be pivotable about an articulation point H, H′ having a horizontal axis. At the opposite foot, the guide holders 13a, 13b are mounted with an erecting mechanism 30 on the foot of jib basic box 9. Prior to luffing up and extending the telescoping jib 8, the guide holders 13a, 13b are pivoted upwards from their transport position to an operating position with the displaceable tension rods 16a-h, 16a′-h′ by means of the knee lever-like erecting mechanism 30 via an auxiliary cylinder. In this operating position, the displaceable tension rods 16a-h, 16a′-h′ and the guide holders 13a, 13b extend in parallel and above the telescoping jib 8.

(13) In order to permit the previously described movement of the guide holders 13a, 13b from the transport position to the operating position and also to benefit from the advantage of the reduced construction height in the transport position, not only the guide holders 13a, 13b but also the displaceable tension rods 16a-h, 16a′-h′ have to be designed in an articulated manner with articulation points H, H′. Each of the displaceable tension rods 16a-h, 16a′-h′ is thus designed at least in two parts with an articulation point H, H′. These articulation points H, H′ of all of the displaceable tension rods 16a-h, 16a′-h′ and also the guide holders 13a, 13b lie on a common, notional, horizontal axis in the transport position of the guide holders 13a, 13b and the telescoping jib 8. In relation to an extended pair of the first or uppermost displaceable tension rods 16h, 16h′, it is apparent from FIG. 2 that the displaceable tension rods 16h, 16h′ have an articulation point H, H′ in the vicinity of the uppermost guying support 15. The spacing between the articulation point H, H′ and the fixed connection of the displaceable tension rods 16h, 16h′ on the uppermost guying support 15 corresponds to the spacing between the uppermost guying support 15 and the articulation point H, H′ of the guide holders 13a, 13b in the transport position of the telescoping jib 8. Corresponding articulation points H, H′ and associated spacings can also be found in the case of all of the other displaceable tension rods 16h, 16h′, even though they are not illustrated in the drawing.

(14) The displaceable tension rods 16a-h, 16a′-h which, in the extended condition of the telescoping cylinder 8, are each connected to one another via the guying supports 15 thus form a cable-like, flexible construction, similar to a link chain, via the multiplicity of articulation points H, H′.

(15) FIG. 3 shows a perspective plan view, at an angle from above, of a completely extended telescoping jib 8. The guying supports 15 are arranged on each telescoping section head 10 and on the jib basic box head 9a and therefore spaced apart from one another. The limbs 15a and 15a′ of the guying support 15 are arranged on the telescoping jib 8 laterally to the right and left. The opposite upper parts 15c, 15c′ of the guying supports 15 have a spacing b with respect to one another. In relation to the displaceable tension rods 16h, 16h′, the associated articulation points H, H″ are illustrated in the vicinity of the uppermost guying support 15. Each of the displaceable tension rods 16a-h, 16a′-h′ is thus designed in two parts.

(16) It is also apparent from FIG. 3 that the lower parts 15b, 15b′ have a first length I and the upper parts 15c, 15c′ have a second length I′. Since the displaceable tension rods 16a-h, 16a′-h′ in the operating position are arranged substantially aligned with one another along the telescoping jib 8, the first and further lengths I, I′ are to be adapted accordingly because the diameters of the telescoping sections 10a-h decrease from the jib basic box 9 and therefore this is compensated for by an associated increase in the lengths I, I′.

(17) FIG. 4 shows a detailed view of a guying support 15 on a jib basic box 9 of the telescoping jib 8. Since, in the present case, no displaceable tension rods 16a-h, 16a′-h′ are stored in the guide holder 13a, 13b, all of the telescoping sections 10a-10h are at least partially extended. It is also evident that an opening angle a of the two limbs 15a and 15a′ amounts to approximately 45° to 135°, preferably 90°. In this case, both limbs 15a and 15a′ lie in a common notional plane which is orientated at a right angle to a longitudinal direction L of the telescoping jib 8. The lower parts 15b, 15b′ of the two limbs 15a, 15a′ themselves have a stretched triangle-like shape with the respectively adjoining vertical upper part 15c, 15c′, wherein a base side of the triangle lies against the telescoping section 10a-h or against the jib basic box 9.

(18) Arranged in each case in the upper parts 15c, 15c′ of the limbs 15a, 15a′ is an actuatable holding mechanism 17 for securing the displaceable tension rods 16a-h, 16a′-h′. As already previously described, the displaceable tension rods 16a-h, 16a′-h′ are each fixedly arranged on the associated upper part 15c, 15c′ of a guying support 15. An articulation point H, H′ permits pivoting of the displaceable tension rods 16a-h, 16a′-h′, which are retracted into the guide holders 13a, 13b, to the transport position. At the opposite end, the displaceable tension rods 16a-h, 16a′-h′ are fixed to the upper ends of the upper parts 15c, 15c′ of the limbs 15a, 15a′ via the respective holding mechanism 17. Each of the holding mechanisms 17 consists substantially of a left or right locking bar element 24a, 24b which can be brought into engagement with a left or right recess 23a-c, 23a′-c′, which is additionally formed corresponding thereto in a form-fitting manner, in the displaceable tension rods 16a-h, 16a′-h′ (see in this respect also FIGS. 3 and 5). For each displaceable tension rod 16a-h, 16a′-h′, three recesses 23a-c, 23a′-c′ are each arranged in the longitudinal direction thereof at a spaced interval and successively: A first recess 23a, 23a′ at the beginning of the displaceable tension rods 16a-h, 16a′-h′ for fixing in the retracted condition of the respective telescoping section 10a-h, a second recess 23b, 23b′ in the centre of the displaceable tension rods 16a-h, 16a′-h′ for fixing in a respective half-extended telescoping section 10a-h and a third recess 23c, 23c′ at the end of the displaceable tension rods 16a-h, 16a′-h′ for fixing in a respective fully extended telescoping section 10a-h.

(19) It is also evident in FIG. 4 (see also in this respect FIG. 5) that for each displaceable tension rod 16a-h, 16a′-h′ on the guying supports 15 left and right running rollers 27a-g, 27a′-g′ are arranged in and next to the upper limb 15c, 15c′ in order to assist the extension and retraction movement of the respective displaceable tension rod 16a-h, 16a′-h′ on each guying support 15.

(20) FIG. 5 shows a detailed view of seven of the total of eight guying supports 15 in the retracted condition of the telescoping sections 10a-g. In this predominantly retracted condition of the telescoping jib 8, the displaceable tension rods 16a-g, 16a′-g′ are likewise retracted and are received by the guide holder 13a, 13b. When the telescoping jib 8 is being extended, the displaceable tension rods 16a-h, 16a′-h′ run on running rollers 27a-g, 27a′-g′ which are arranged in and next to the upper limbs 15c, 15c′ of the limbs 15a, 15a′. In this case, the upper part 15c, 15c′ of the limbs 15a, 15a′ is provided in each case with an opening 32a-g, 32a′-g′, in which the displaceable tension rods 16a-h, 16a′-h′ are guided during the retraction and extension movement thereof. These openings 32a-g, 32a′-g′ are defined at the bottom by the running rollers 27a-g, 27a′-g′ and are defined at the top by the locking bar elements 24a, 24b. Said openings are defined laterally by walls of the upper parts 15c, 15c′.

(21) FIG. 5 also shows the function of the holding mechanism 17 for fixing the displaceable tension rods 16a-h, 16a′-h′ in the opening 32a-g, 32a′-g′ to the desired extension length. In the preferred embodiment, the respective locking bar element 24a, 24b can be displaced in a sliding direction s′ and thus in the longitudinal direction of the respective upper part 15c, 15c′ from a lower locking position to an upper unlocking position. In the locking position, the locking bar element 24a, 24b is in engagement with the respective recess 23a, 23a′ of the respective displaceable tension rod 16a-h, 16a′-h′. In the unlocking position, the locking bar element 24a, 24b is displaced upwards in the sliding direction s′ until the locking bar element 24a, 24b is moved out of the respective recess 23a, 23a′ and is thus located above the respective displaceable tension rod 16a-h, 16a′-h′. Moreover, the locking bar elements 24a, 24b are each pretensioned into the locking position via an upper spring element 28a′ which acts downwards in the sliding direction s′ and so a drive is required for movement into the unlocking position.

(22) This drive for moving the locking bar elements 24a, 24b is configured as follows. Each of the locking bar elements 24a, 24b is adjoined laterally by a left or right upper sliding element 25a′, 25b′ which extends downwards to the beginning of the upper part 15c, 15c′. At this location, it lies on left and right wedge pieces 22a, 22b which each serve as a sliding link for a movement of the upper sliding elements 25a′, 25b′ in the sliding direction s′ and mechanical force deflection. The left and right wedge pieces 22a, 22b are each fastened to upper ends of the right and left lower sliding element 25a, 25b. These sliding elements 25a, 25b have, at the lower end, a sliding roller 26a, 26b, are displaceable in a longitudinal direction of the lower parts 15b, 15b′ in a sliding direction s and end at the lower end of the lower parts 15b, 15b′ and thus face towards the surface of the respective telescoping section 10a-h. Like the upper sliding elements 25a′, 25b′, the lower sliding elements 25a, 25b are also pretensioned in each case via a lower spring element 28a, 28b in the direction of the lower end of the lower parts 15b, 15b and therefore in the locking direction of the locking bar elements 24a, 24b. In order to be able to move the respective lower sliding element 25a, 25b upwards in the sliding direction s and thus to move the locking bar elements 24a, 24b from the locking position to the unlocking position, a drive having a left and a right sliding cylinder 29a, 29b is provided. Attached to a free end of the piston rod of the sliding cylinder 29a, 29b is a respective sliding wedge 21a, 21b (see also in this respect FIG. 4), on which a lower end formed in the manner of a ramp is provided. The sliding wedges 21a, 21b are displaced below the left and right sliding roller 26a, 26b by extending the sliding cylinders 29a, 29b in order thus to raise the lower sliding element 25a, 25b, which is acted upon by the sliding rollers 26a, 26b, in the sliding direction S. The sliding cylinders 29a, 29b are arranged on the right and left in the region of the upper corners of the jib basic box 9 and can be retracted and extended in a sliding direction S.

(23) Since, at the time of actuation of the respective locking bar elements 24a, 24b from the locking position to the unlocking position, the respective guying supports 15 still locally adjoin the head 9a of the jib basic box 9, all of the locking bar elements 24a, 24b can be actuated one after the other by the same sliding cylinders 29a, 29b via the sliding wedges 21a, 21b.

(24) The function of the guying system 11 will be explained hereinafter with the aid of FIGS. 1 to 5. In a first step, the innermost telescoping section 10h of the telescoping jib 8 is extended together with its guying support 15. Since the displaceable tension rods 16h, 16h′ are fastened to the guying support 15 in the rod fixed points 20h, 20h′ of the limbs 15a, 15a′ of the guying support 15, they are entrained simultaneously in the longitudinal direction L of the telescoping jib 8 and thus drawn out of the guide holders 13a and 13b. In this case, the displaceable tension rods 16h, 16h′ are guided through the openings 32g, 32g′ and on the running rollers 27a, 27a′ of the guying supports 15 of the respectively next telescoping section 10g not yet extended in the longitudinal direction L. Upon reaching a desired bolting position of the innermost telescoping section 10h, the displaceable tension rods 16h, 16h′ are fixed to the limbs 15a, 15a′ by means of the two holding mechanisms 17 of the adjacent telescoping section 10g typically at half and full extension length. It is fundamentally possible to provide different bolting positions for each telescoping section 10a-h, these bolting positions then fixing a telescoping section 10a-h in a full or half or otherwise preselected extension path of the telescoping section 10a-h. In a similar manner, the displaceable tension rods 16a-g, 16a-g′ are then successively tensioned in portions between the respective guying supports 15 of the telescoping sections 10a-f and of the jib basic box 9 in parallel with the extension and bolting of the further telescoping sections 10a-f.