CA2697299A1

CA2697299A1 - Profile shape for a crane jib

Info

Publication number: CA2697299A1
Application number: CA2697299A
Authority: CA
Inventors: Eckhard Wimmer
Original assignee: Individual
Current assignee: Palfinger AG
Priority date: 2007-09-05
Filing date: 2008-08-29
Publication date: 2009-03-12
Also published as: RU2010112864A; EP2185460A1; BRPI0816410A2; RU2497745C2; WO2009029965A1; MX2010002599A; CN101827774A

Abstract

The invention relates to a crane jib for a crane, having a longitudinal axis and an imaginary contour line that extends in a transversal plane relative to an axis of symmetry (s) in an at least approximately mirror-symmetric manner, the contour line intersecting the axis of symmetry (s) in a first and a second point of intersection (S1, S2) and the contour line having a straight section the imaginary extension of which in the direction of the second point of intersection (S2) intersects the axis of symmetry (s) and forms an acute angle therewith. The centroid (F) of the surface enclosed by the contour line in the transversal plane lies between the first point of intersection (S1) and a center (M) that is equally interspaced from the first and second point of intersection (S1, S2) on the axis of symmetry (s).

Description

Profile shape for a crane jib The present invention concerns a crane boom for a crane having a longitudinal axis and a notional contour line extending in a transverse plane relative to an axis of symmetry in at least approximately mirror-symmetrical relationship, wherein the contour line intersects the axis of symmetry at a first and a second intersection point and wherein the contour line has a straight portion whose notional extension in the direction of the second intersection point intersects the axis of symmetry and includes an acute angle therewith.

Such a crane is shown for example in Figure 13 of EP 583 552 B1.
In practice that crane boom is of a relatively large structural shape and is thus severely limited in its usability. For exaniple it is not suitable for the loading crane sector.
The object of the invention is to provide an improved crane boom.
That object is attained by a crane boom having the features of claim 1.
It will be appreciated that a real crane arm has both an outside contour and an inside contour by virtue of the material thickness of the components forming it. The 'notional contour line' refers to the outside contour of the crane boom.

The term centroid is used in the context of this disclosure to denote the center of gravity of the overall region enclosed by the notional contour line (the dash-dotted area in Figure l h). The term 'centroid' is therefore not to be interpreted in relation to the area enclosed between the outside and inside contours.

The choice of the configuration of the notional contour line such that the centroid of the region enclosed by the notional contour line is between the first intersection point and the center point provides that there is a free choice in respect of the sheet metal thickness of the crane boom enclosed by the notional contour line, in a relatively wide material thickness range. Unlike the situation in the state of the art (for example EP 583 552 Bi) the position of the zero crossing on the axis of symmetry (that position at which the tensile forces prevailing in the upper region of the crane boom change into the compression forces prevailing in the lower region of the crane boom) is set not by the selection of the sheet metal thickness but by the configuration of the notional contour line. Even with the same sheet metal thickness in all portions it is possible by means of the invention to shift the zero crossing into the lower region of the crane arm.

Further advantageous embodiments are defined in the appendant claims.
The invention further concerns a jib system for a crane, wherein at least one jib and/or jib extension is in the form of a crane boom as set forth in one of claims 1 through 26. Preferably there are provided between one and twenty, preferably between five or ten, jib extensions. It is particularly preferable for more than five jib extensions to be provided.

The invention further concerns a crane, in particular a loading crane, having a crane boom according to one of the aforementioned embodiments or a jib system of the aforementioned kind as well as a utility vehicle equipped with such a crane.
Further advantages and details of the invention will be apparent from the Figures and the related specific description. In the Figures:

Figure 1 a shows a first embodiment of the notional contour line of a crane boom according to the invention, Figures Ib and 1c show the construction of a contour line (Figure lb) and the corresponding sheet metal structure (Figure 1 c) of an embodiment in which the arcuate portion ki is approximated by a polygonal line, Figure ld shows a jib system having three jib extensions as shown in Figure lb, Figure 1 e shows the crane boom of Figures 1 a through 1 c, showing the position of the centroid, Figure 1f shows a jib system having a jib extension, showing the arrangement of mounting elements, Figure 1g shows a jib system with a jib extension, wherein the arcuate portion in the jib and the jib extension was approximated by different polygons, Figure 1 h shows the crane boom of Figures 1 a through 1 c and 1 e, wherein that area to which the centroid relates has been shown in dash-dotted lines representatively for all embodiments, Figure 2 shows a second embodiment of the notional contour line of a crane boom according to the invention, Figure 3 shows a third embodiment of the contour line of a crane boom according to the invention, Figure 4 shows a perspective view of a jib system as shown in Figure 1 d, and Figure 5 shows a utility vehicle with a crane according to the invention.
It will be presupposed that all Figures are true to scale insofar as the lengths of the individual contour portions and the illustrated angles are shown in the correct ratio to each other. All angle references relate to degrees, so that a full angle corresponds to 360 degrees. An angle of less than 1/4 full angle is interpreted as an acute angle. An angle of greater than 1/4 and less than V2 full angle is interpreted as an obtuse angle. An angle equal to '/4 full angle is identified as a right angle.
Figure 1 a shows a first embodiment of the configuration of the notional contour line of the crane boom in a transverse plane of the crane boom. In this respect the term transverse plane is used to identify a plane through which the longitudinal axis of the crane boom passes in orthogonal relationship. All crane booms according to the invention have an axis of symmetry s which is arranged in the transverse plane and in relation to which the contour line of the crane boom extends in the transverse plane in at least approximately mirror-image relationship. For the situation where the crane boom is of the same cross-sectional shape over a large part of or its entire longitudinal extent, that axis of symmetry s represents the straight section line of the transverse plane with the plane of symmetry extending along the longitudinal axis (median plane).
In all embodiments the contour line intersects the axis of symmetry s at first and second intersection points SI, S2. The center point M arranged on the axis of symmetry s equidistantly relative to the first and second intersection points SI, S2 represents the position of half the height of the crane boom in the transverse plane.
Starting from the center point M in the direction of the intersection point S2, that affords a region of the crane boom which, in operation, is predominantly subjected to a tensile loading. The region of the crane boom, that is between the center point M and the first intersection point SI, is substantially subjected to a compression loading in operation.

The configuration of the contour line of the crane boom shown in Figure 1 has four portions kl, gl, g2, g3 which can be distinguished from each other.

The portion k, which is arranged in the region of the compression loading that is greatest in operation is of an arcuate configuration since, as is known per se, that cross-sectional shape has reduced compression stresses and involves a reduction in the risk of buckling. It is sufficient if that portion is at least approximately arcuate in the sense that it can be approximated by a polygon, as is shown in Figures lb and lc.
Approximation of the arcuate portion kl by a polygon permits easier manufacture by folding of the metal sheets forming the crane boom. It will be appreciated however that an arcuate configuration can be implemented by means of a rolling operation.
The arcuate portion kl can also be only approximately arcuate in the sense that it can be formed for example by one or more ellipse portions of suitably slight eccentricity. It would also be possible to envisage a configuration for the arcuate portion ki by arranging in joining relationship suitably short straight, elliptical and/or arcuate segments.

As shown in Figure 1 it is particularly advantageous if the arcuate portion kl is in the form of a quarter-circle arc, that is to say it extends over an angle of about 90 degrees. It is possible in that way for the large part of the configuration of the contour line between the first intersection point S1 and the point M to be produced in the form of an arcuate portion kl. The variant shown in Figure 1 is particularly preferred, in which the center point of curvature K of the arcuate portion k, is in the proximity of or on the axis of symmetry s and the center point of curvature K of the arcuate portion ki is between the first intersection point S, and the center point M. Unlike the situation shown in Figure 1 the arcuate portion kl can certainly extend as far as the first intersection point Si. In that case therefore the entire contour line in the region of the intersection point SI and the center point M is in the form of an arcuate portion kl .
The embodiment shown in Figure 1 is particularly preferred however in which a third straight portion g3 tangentially adjoins the arcuate portion k, in the direction of the first intersection point S1, the third portion g3 including an angle y of less than 90 degrees with the axis of symmetry s (here the angle y is about 72 degrees).
That affords good weldability of the crane boom, better suitability for clamping for the welding operation by virtue of the portions which meet each other inclinedly and the possibility of producing a longitudinal weld seam without additional edge preparation.
Overall that affords a configuration which is more reliable in terms of process implementation.

The angle is preferably less than 80 degrees. Preferably the angle y is greater than 70 degrees.

In the Figure 1 embodiment the center point of curvature K of the arcuate portion kl is disposed directly on the axis of symmetry s between the center point M
and the first intersection point S1. Unlike the situation shown the center point of curvature K can also be arranged displaced somewhat relative to the axis of symmetry s. It should however always be in the region between the center point M and the first intersection point S1.
The first straight portion gi adjoins the arcuate portion kl in the direction of the second intersection point S2 tangentially to the auxiliary circle illustrated in Figures 1 a and lb, the first portion gl extending over the large part of the contour configuration between the center point M and the second intersection point S2. That straight configuration which is extended in length in the upper region of the crane boom and the resulting narrowing in cross-section forms a zone which is better suited than in the state of the art to carrying the tensile forces occurring here and the bearing and reaction forces which occur when arranged in a jib system. The notional extension gl' of the straight portion gi (see Figure lb) includes with the axis of symmetry s an acute angle (3 which in the illustrated embodiment is about 18 degrees. Quite generally the acute angle 0 can also be in a range of greater than 10 degrees, preferably greater than 15 degrees. In that respect an upper limit of 25 degrees is preferred in each case in order to exclude an excessively shallow configuration in respect of the straight portion gi.
In the embodiment shown in Figure 1 a second straight portion g2 directly adjoins the first straight portion gl, the second portion extending as far as the axis of symmetry s and intersecting it at the second intersection point S2. As can be seen in particular in Figure 1 c, for reasons relating to manufacturing technology it may be desirable if the second straight portion gZ (unlike the situation shown in Figure la) is connected to the first straight portion gi not directly but by way of a preferably curved further portion.

In the Figure 1 embodiment the second straight portion g2 includes with the axis of symmetry s an angle a which is smaller than 90 degrees (in the Figure 1 embodiment the angle a is about 65 degrees). A range for the angle a of less than 70 degrees is particularly preferred. The angle a in this embodiment should however be larger than 60 degrees.

In a further embodiment as shown in Figure 2 the second straight portion includes a right angle with the axis of symmetry s.
The second straight portion g2 affords the advantage that this arrangement, in the region around the tip of the crane boom, permits favorable local application of forces, as occurs for example when supporting slide packets between individual jib extensions. The short limb length affords a favorable relationship between the sheet metal thickness and the limb length so that deformation of the crane boom is prevented in the upper region.

It will be noted however that basically it would also be possible for the contour configuration in that region to be in the form of a second arcuate portion k2 (see Figure 3). That however only represents a special variant of a more general idea, namely the idea that the contour line ends in a rounded configuration at the line of symmetry s. As an alternative to the illustrated configuration of the rounded configuration in the form of an arcuate portion k2 the rounded configuration could for example also be in the form of an edge configuration 7.
In the embodiment of Figure 2 the notional contour line does not have an arcuate portion kl, but only straight portions gl, g2, g3, g4.
Quite generally it must be said in relation to all configurations of the crane according to the invention that the centroid F of the area enclosed by the contour line in the transverse plane lies in a region between the center point M and the first intersection point Si, that is to say below half the height of the crane boom.
That provides that the cross-section concentration of the crane boom is displaced as much as possible downwardly into the compression zone, thereby affording a lower compression stress component.
As can be seen from the Figures the contour line of all embodiments has, between the first intersection point S1 and the second intersection point S2, an extreme point E at maximum distance e from the axis of symmetry S. The spacing D
between the first intersection point and the second intersection point Si, S2 can in that case be at least twice as great as the distance e. Preferably the spacing D is at least two and a half times as great, particularly preferably 2.75 times as great, as the distance e. The spacing D can be in each case less than three times the distance e.

It can be provided that the spacing d of the contour line from the axis of symmetry s, at approximately a quarter of the spacing D between the first and second intersection points Si, S2, starting from the second intersection point S2, is less than or equal to 0.8 times the maximum distance e.

In the Figure 1 embodiment the extreme point E is between the center point M
and the first intersection point S1 approximately at the height of the center point of curvature K. In the Figure 1 a configuration the contour line has only one single extreme point E, that is to say the width of the crane boom decreases both in the direction of the first intersection point S, and also in the direction of the second intersection point S2, starting from the extreme point E. When the arcuate portion kl is approximated by a polygonal line, as shown in Figure 1 c, it will be appreciated that all points on the polygonal portion, by which the arcuate portion kl is approximated in the region of the extreme point E, involve that maximum distance e.
Starting from the auxiliary circle shown in Figure 1 a, of the radius r, the embodiment of Figure 1 involves a profile width b in accordance with b- 2r, a profile height D in accordance with D - 3r and a profile width upward bl in accordance with bl - r. Those particularly advantageous dimensions can be provided quite generally in crane booms according to the invention.

Figure 1 e shows for the embodiment of Figure 1 the position of the centroid F
between the center point M and the first intersection point S1 on the axis of symmetry s.
In this case the centroid F refers to the area shown in dash-dotted lines in Figure lh, that is to say the entire area enclosed by the notional contour line (corresponds to the outside contour).

Figure lf shows a jib system 5 with a jib extension, showing in addition the mounting of the jib system 5 by way of a mounting element 1 and mounting of the jib extension in the jib by way of mounting elements 2. It will be appreciated that the illustrated embodiment is intended purely by way of example in relation to the number of illustrated jib extensions. The same mounting elements can be used in jib systems having any number of jib extensions.

The embodiment of Figure 1 g shows two crane booms which involve for example a jib extension arranged in a jib. It is of significance that the arcuate portion ki is approximated by different polygons. The inwardly disposed cross-sectional profile has fewer edges in the region of the arcuate portion, which can be of advantage in particular when dealing with small profiles, in terms of manufacturing technology.
Production of a crane boom according to the invention can be effected for example in such a way that the crane boom is formed from two shells which are shaped in mirror image relationship with each other, wherein one of the shells respectively corresponds to one of the embodiments. The two shells can be joined together, for example welded, in the region of the first intersection point S1 and the second intersection point S2.

It will be noted however that it is particularly preferably provided that the crane boom is produced from a single metal sheet at least along a portion of its longitudinal extent, the metal sheet being suitably shaped and then closed along a single line (for example by welding). That line can extend for example in the region of the first intersection point S, or the second intersection point S2.
Shaping of the metal sheets can be effected in known manner or by folding or bending and/or rolling, and for example welding.

If different gauges are required, the outside contour should preferably remain the same and the sheet metal thickness should be applied inwardly.
Figure 4 shows by way of example a jib system 5 having a jib extension arranged in a jib.

Figure 5 shows by way of example a utility vehicle 3 on which a crane 4 according to the invention is arranged. The crane 4 has a jib system 5 according to the invention, in which case the individual jib extensions can be telescopically displaced relative to each other by way of thrust cylinders 6. It will be appreciated that telescopic displaceability can also be ensured by other drive means. A loading structure (not shown) could be arranged for example in the rearward region of the utility vehicle 3.

Claims

1. A crane boom for a crane having a longitudinal axis and a notional contour line extending in a transverse plane relative to an axis of symmetry in at least approximately mirror-symmetrical relationship, wherein the contour line intersects the axis of symmetry at a first and a second intersection point and wherein the contour line has a straight portion whose notional extension in the direction of the second intersection point intersects the axis of symmetry and includes an acute angle therewith, characterised in that the centroid (F) of the area enclosed by the contour line in the transverse plane lies between the first intersection point (S1) and a center point (M) arranged on the axis of symmetry (s) equidistantly relative to the first and second intersection points (S1, S2).

2. A crane boom as set forth in claim 1 characterised in that the acute angle (.beta.) is greater than 10 degrees.

3. A crane boom as set forth in claim 2 characterised in that the acute angle (.beta.) is greater than 15 degrees.

4. A crane boom as set forth in one of claims 1 through 3 characterised in that the acute angle (.beta.) is smaller than 25 degrees.

5. A crane boom as set forth in one of claims 1 through 4 characterised in that the contour line between the first intersection point (S1) and the center point (M) has at least partially an at least approximately arcuate portion (k1).

6. A crane boom as set forth in claim 5 characterised in that the arcuate portion (k1) is in the form of a quarter-circle arc.

7. A crane boom as set forth in claim 5 or claim 6 characterised in that the center point of curvature (K) of the arcuate portion (k1) is in the proximity of or on the axis of symmetry (s).

8. A crane boom as set forth in one of claims 5 through 7 characterised in that the center point of curvature (K) of the arcuate portion (k1) is between the first intersection point (S1) and the center point (M).

9. A crane boom as set forth in one of claims 5 through 8 characterised in that the straight portion (g1) is in the form of a tangential extension of the arcuate portion (k1).

10. A crane boom as set forth in one of claims 1 through 9 characterised in that the contour line, beginning with the second intersection point (S2) and extending away from the axis of symmetry (s), has a second straight portion (g2).

11. A crane boom as set forth in claim 10 characterised in that the second straight portion (g2) includes a right angle with the axis of symmetry (s).

12. A crane boom as set forth in claim 10 characterised in that the second straight portion (g2) includes an angle (.alpha.) of less than 90 degrees with the axis of symmetry (s).

13. A crane boom as set forth in one of claims 10 through 12 characterised in that the second straight portion (g2) is connected directly to the first straight portion (g1).

14. A crane boom as set forth in one of claims 10 through 12 characterised in that the second straight portion (g2) is connected by way of at least one -preferably curved - further portion to the first straight portion (g1).

15. A crane boom as set forth in one of claims 1 through 14 characterised in that the contour line between the first intersection point (S1) and the second intersection point (S2) has an extreme point (E) at maximum distance (e) from the axis of symmetry (s).

16. A crane boom as set forth in claim 15 characterised in that the spacing (d) between the first and second intersection points (S1, S2) is at least twice as great as the maximum distance (e) of the extreme point (E) from the axis of symmetry (s).

17. A crane boom as set forth in claim 14 or claim 15 characterised in that the spacing (d) of the contour line from the axis of symmetry (s) at approximately a quarter of the spacing (D) between the first and second intersection points (S1, S2) starting from the second intersection point (S2) is less than or equal to 0.8 times the maximum distance (e).

18. A crane boom as set forth in one of claims 15 through 17 characterised in that the extreme point (E) is between the first intersection point (S1) and the center point (M).

19. A crane boom as set forth in one of claims 5 through 18 characterised in that tangentially adjoining the arcuate portion (k1) in the direction of the first intersection point (S1) is a third straight portion (g3) which includes an angle (.gamma.) of less than 90 degrees with the axis of symmetry (s).

20. A crane boom as set forth in one of claims 1 through 19 characterised in that the arcuate portion (k1) is approximated by a polygon.

21. A crane boom as set forth in one of claims 1 through 20 characterised in that the crane boom is of the same cross-sectional shape at least over a large part of its longitudinal extent.

22. A crane boom as set forth in one of claims 1 through 21 characterised in that the contour line narrows in the direction of the second intersection point (S2) at least before the last third of the spacing (D) between the first and second intersection points (S1, S2).

23. A crane boom as set forth in claim 22 characterised in that the narrowing of the contour line continues to the second intersection point (S2) and ends in a rounded configuration at the line of symmetry (s).

24. A crane boom as set forth in one of claims 1 through 23 characterised in that the crane boom comprises at least one metal sheet and the metal sheet thickness of all portions (k1, k2, g1, g2, g3, g4) of the crane arm in the transverse plane is at least substantially equal in magnitude.

25. A crane boom as set forth in one of claims 1 through 24 characterised in that the crane boom comprises two shells which are shaped in mirror-image relationship with each other and are joined to each other - preferably in the region of the first intersection point (S1) and the second intersection point (S2).

26. A crane boom as set forth in one of claims 1 through 24 characterised in that the crane boom at least along a portion of its longitudinal extent comprises a single metal sheet which is closed along a single line which extends preferably in the region of the first intersection point (S1) or the second intersection point (S2).

27. A jib system for a crane characterised in that at least one jib and/or jib extension is in the form of a crane boom as set forth in one of claims 1 through 26.

28. A jib system as set forth in claim 27 characterised in that between one and twenty, preferably between five or ten, jib extensions are provided.

29. A jib system as set forth in claim 27 characterised in that more than five jib extensions are provided.

30. A jib system as set forth in one of claims 27 through 29 characterised in that the shapes of the contour line of the jib and the contour lines of all jib extensions are the same - possibly except for the degree of approximation of circular arcs by polygons.

31. A crane, in particular a loading crane, characterised by a crane boom as set forth in one of claims 1 through 26 or a jib system (5) as set forth in one of claims 27 through 30.

32. A utility vehicle (3) having a crane (4) as set forth in claim 31.