LATTICE PIECE, LATTICE BOOM, AND WORK MACHINE

Abstract

The present disclosure relates to a lattice piece for a lattice boom having four corner bars that are connected to one another by a plurality of posts and diagonals, wherein the lattice piece has a rectangular cross-section having two longer and two shorter sides. A cross-sectional section of the corner bars is designed as a hollow section that has a larger extent in the direction of the longer side of the lattice piece than in the direction of the shorter side of the lattice piece. At least one side of the corner bar section has a stabilization structure in the form of a joint, a kink, a bend, or a rounded portion. The present disclosure further relates to a lattice boom comprising at least one lattice piece in accordance with the present disclosure and to a work machine having such a lattice boom.

Claims

1. A lattice piece for a lattice boom having four corner bars that are connected to one another by a plurality of posts and diagonals, wherein the lattice piece has a rectangular cross-section having two longer sides and two shorter sides, wherein a cross-sectional section of the four corner bars is a hollow section that has a larger extent in a direction of the two longer sides of the lattice piece than in a direction of the two shorter sides of the lattice piece, with at least one side of the corner bar section having a stabilization structure in the form of a joint, a kink, a bend, or a rounded portion.

2. The lattice piece in accordance with claim 1, wherein adjacent corner bars that form the two shorter sides of the lattice piece are connected to one another over a larger number of diagonals than adjacent corner bars that form the two longer sides of the lattice piece, with the diagonals extending at the longer and/or at the shorter sides.

3. The lattice piece in accordance with claim 1, wherein the four corner bars have a greater area moment of inertia in the direction of the two longer sides of the lattice piece than in the direction of the two shorter sides of the lattice piece.

4. The lattice piece in accordance with claim 1, wherein the four corner bars have a cross-section differing from a rectangular shape.

5. The lattice piece in accordance with claim 1, wherein the stabilization structure extends substantially along a total length of the corner bar.

6. The lattice piece in accordance with claim 1, wherein the corner bar section has at least five kinks, bends, and/or rounded portions in total.

7. The lattice piece in accordance with claim 1, wherein the four corner bars are produced in one piece from a metal sheet.

8. The lattice piece in accordance with claim 1, wherein the four corner bars are produced from at least two metal sheets welded to one another.

9. The lattice piece in accordance with claim 8, wherein the at least two metal sheets have the same shape.

10. The lattice piece in accordance with claim 8, wherein the at least two metal sheets have different shapes.

11. The lattice piece in accordance with claim 1, wherein at least one stiffening element is attached within the corner bar section in a region of a connection point of a diagonal.

12. The lattice piece in accordance with claim 11, wherein the stiffening element extends in a longitudinal direction of the corner bar and is only attached inwardly in the corner bar at the side at which the diagonal is connected to the corner bar.

13. The lattice piece in accordance with claim 1, wherein each corner bar has a respective mount at two ends to or in which a connection element is attached or inserted and welded for connection to a complementary connection element of a different lattice piece.

14. A lattice boom having at least one lattice piece in accordance with claim 1.

15. A work machine having the lattice boom in accordance with claim 14.

16. The lattice piece in accordance with claim 2, wherein the lattice piece with the diagonals extending at the longer and/or at the shorter sides can be releasably fastened to the respective corner bars.

17. The lattice piece in accordance with claim 5, wherein the stabilization structure forms a change in direction of the outer contour of the hollow section transversely to the longitudinal axis of the corner bar.

18. The lattice piece in accordance with claim 9, wherein the at least two metal sheets are welded to one another such that the corner bar section has point or axis symmetry.

19. The lattice piece in accordance with claim 10, wherein the at least two metal sheets are welded to one another such that the corner bar section has axis symmetry.

20. The lattice piece in accordance with claim 13, wherein the connection element is a fork element and the complementary connection element is a counter-fork element, the fork elements having a layer design of a plurality of differently shaped metal sheets welded to one another.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0044] Further features, details, and advantages of the disclosure result from the embodiments explained in the following with reference to the Figures. There are shown:

[0045] FIG. 1: an embodiment of the lattice piece in accordance with the disclosure in a perspective view;

[0046] FIG. 2: a side element of the lattice piece of FIG. 1 in a perspective view;

[0047] FIG. 3: a perspective cross-sectional view of the corner bar of the lattice piece in accordance with the disclosure in accordance with an embodiment;

[0048] FIG. 4: the corner bar section of FIG. 3 in a schematic frontal view;.

[0049] FIGS. 5a-b: a plurality of embodiments for cross-sectional sections of the corner bar of the lattice boom in accordance with the disclosure in a schematic frontal view in each case;

[0050] FIG. 6: an enlarged view of a stiffening element at the connection point of two diagonals at a corner bar in accordance with an embodiment;

[0051] FIG. 7a: a corner bar having fork elements in accordance with an embodiment in a side view and in a top view;

[0052] FIG. 7b: a corner bar having fork elements in accordance with a further embodiment in a side view and in a top view;

[0053] FIG. 8a: a fork element and a counter-fork element of the corner bar of FIG. 7a in perspective single views; and

[0054] FIG. 8b: a fork element and a counter-fork element of the corner bar of FIG. 7b in perspective single views.

DETAILED DESCRIPTION

[0055] An embodiment of the lattice piece 10 in accordance with the disclosure is shown in a perspective view in FIG. 1. The lattice piece 10 comprises four parallel corner bars 12 that have connection elements 32 that are formed as fork elements at the ends and via which the lattice piece 10 is connectable to other lattice pieces 10 or boom parts to form a boom, such as a lattice boom, of a mobile crane or crawler crane. Two respective adjacent corner bars 12 are connected to one another via a plurality of posts 14 and diagonals 16.

[0056] The lattice piece 10 has a rectangular cross-section with a greater width than height. In this respect, the corner bars 12 are connected to one another along the long sides L of the lattice piece 10 via a smaller number of diagonals 16 than along the shorter side K of the lattice piece 10. In FIG. 1, the corresponding buckling lengths K.sub.K and K.sub.L are drawn that result from the respective distances of the connection points 18 of the diagonal elements 16 at the corner bars 12. As can be recognized, the corner bars 12 have different buckling lengths K.sub.L, K.sub.K for the diagonals 16 of the long and short sides L, K, with the buckling length K.sub.L being larger than the buckling length K.sub.K.

[0057] The diagonals 16 extending at the long sides L of the lattice piece 10 are releasably connected to the corner bars 12, while the diagonals 16 of the short sides K are fixedly welded to the corner bars 12. FIG. 2 shows a single side part that forms one of the short sides K of the lattice piece 10, with fastening elements 19 or pin points for the diagonals 16 attached to the corner bars 12 and to the fork elements 32 and the side parts forming the front faces of the lattice piece 10 being able to be recognized.

[0058] The lattice piece 10 has a higher lateral stiffness and a higher torsion stiffness due to the greater width, which results in a smaller deformation and a higher payload in crane operation. The divisibility of the lattice piece 10 in the vertical plane facilitates the transport of the lattice piece 10. The diagonals 16 and corner bars 12 are here optimally adapted to the geometry of the lattice piece 10. The smaller number of diagonals 16 at the long sides L cause a smaller installation effort, a smaller total weight, and fewer tolerances.

[0059] The larger buckling length K.sub.L at the long side L associated therewith is now compensated in accordance with the disclosure by an optimized section of the corner bars 12. FIGS. 3 and 4 show an embodiment of the corner bar 12 with an optimized cross-sectional section in a perspective view and in a schematic frontal view. The corner bar section in accordance with the disclosure differs from the typically used circular or square cross-sectional shapes in that it has a greater width than height, that is an aspect ratio not equal to one. The corner bar 12 has the greater extent in this respect in the direction of the long side L of the lattice piece 10 to compensate the greater buckling length K.sub.L in this plane by the higher area moment of inertia that results therefrom. The mass of the lattice piece 10 is optimally utilized in this process.

[0060] The corner bar 12 is assembled from two differently shaped metal sheet sections that are welded to one another by longitudinal seams 20′ (weld joints) and that form a hollow section. The metal sheets are each formed with axial symmetry and are joined together such that the resulting corner bar section also has axial symmetry (cf. FIG. 4, the vertical axis of symmetry divides the section at the center). The metal sheet sections of the corner bar 12 each have rounded portions or bends 20 (that can also be understood as “kinks”) that serve buckling stabilization and extend along the total length of the corner bar 12. The use of additional components such as welded transverse stiffening plates can be dispensed with due to these stabilization structures 20 that are easy to produce and that are implemented in the shaping of the section metal sheets themselves (i.e. the stabilization structures are formed by the shape and/or arrangement of the section metal sheets themselves that form the hollow section. The weld seams 20′ can also be understood as stabilization structures. The corner bar section substantially has the shape of a convex irregular polygon overall. In FIG. 4, a stiffening element 22 arranged within the hollow section can furthermore be recognized that will be described further below.

[0061] The embodiment shown in FIGS. 3 and 4 is, however, only one of many configuration possibilities of the corner bar section to implement a desired buckling stabilization and buckling length adaptation. Further examples are shown in FIGS. 5a and 5b in a frontal view in each case. In this respect, FIG. 5a shows examples having axial symmetry for sections produced in one piece (these shapes can naturally also be composed of two or more metal section sheets). The sections shown in FIG. 5b are substantially oval or ellipsoid, with the sections having a plurality of bends/rounded portions/kinds viewed close up. Except for the example at the far left, the sections of FIG. 5b are composed of two differently shaped metal sheets and likewise have axial symmetry. The section shown at the far left in FIG. 5b is, in contrast, assembled from two identically shaped metal sheets and has point symmetry overall, which inter alia simplifies the manufacture.

[0062] To stabilize the corner bars 12 even more against buckling, such as on the use of thin section metal sheets, additional stiffening elements 22 can be installed within the hollow section of the corner bars 12. An example for this is shown in FIG. 6 in which a detail of a connection point 18 of two diagonals 16 at the corner bar 12 is shown. In this respect, the stiffening element 22 that is arranged inwardly in the corner bar 12, that extends along the longitudinal direction of the corner bar 12, and that is fastened or welded to the inner side of the hollow section at the side facing the connection point 18 is shown dashed since it cannot be seen from the outside. The connection element 22 in this embodiment is bent along its middle axis in parallel with the longitudinal axis of the corner bar 12. FIG. 4 shows the stiffening element 22 in a frontal view.

[0063] Such an angular or half-shell shaped stiffening element 22 may be present per connection point 18 to stabilize the junctions 18. However, a variety of other designs are also conceivable here. Such stiffening elements 22 can be effected easily in the case of a corner bar 12 composed of two metal sheet sections since these longitudinal elements 22 can already be installed before the joining together or welding of the corner bar metal sheets.

[0064] The performance of the lattice piece 10 in accordance with the disclosure is expanded by an optimized fork/fork design. For this purpose, the corner bars 12 have connection elements 22 at the two ends that are designed as fork elements each having a bore for establishing a releasable pin connection between two lattice pieces 10 or between one lattice piece 10 and another boom part such as an articulated connection piece, boom head, or the like.

[0065] A corner bar 12 having the two fork elements 32 attached to both sides in accordance with a first embodiment is shown in FIG. 7a in a side view (upper illustration) and a plan view (lower illustration). FIG. 8a shows the individual fork elements 32 in a perspective view. The fork elements 32 are set at the ends or mounts of the corner bar 12 in this embodiment. The fork elements 32 have chamfers 38 at one side and are suitably designed on the oppositely disposed side to be able to affix the fastening elements 19 (cf. FIG. 2).

[0066] FIGS. 7b and 8b show a second embodiment in which the fork elements 32 are inserted into corresponding mounts or cutouts at the ends of the corner bar 12 and are welded thereto. This manner of construction enables a welding with minimal weld deformation and an omission of head plates at the ends of the corner bars 12 that are prone to breakage. The weld seams 30 between the fork element 32 and the corner bar 12 are shown as thick black lines in FIG. 7b and are loaded on shear in operation.

[0067] The fork and counter-fork element 32 have different designs in the two embodiments to enable a joining into one another and have a layer design or a sandwich structure comprising a plurality of welded lamellae 34, 36. The lamellae 34, 36 have different shapes or contours. Alternatively to the lamella design, thin metal connection sheets can e.g. also be used as spacers between the fingers of the fork elements 32. These prefabricated fork elements 32 can be subjected to a mechanical post-machining as a whole. Releasable connection points for post connections to the corner bars 12 can additionally be provided at the fork/fork packets.

[0068] The (“edged”) shape of the corner bars 12 in accordance with the disclosure provided with stabilization structures 20, 20′ provides some further advantages or properties in addition to those described above.

[0069] 1) Embodiment of the diagonal connection advantageous from a technical production aspect: Diameter of the diagonals 16 becomes smaller than the distance selected between two stabilization structures 20, 20′ at the corresponding side surface of the corner bar section 12.

[0070] 2) Statically advantageous embodiment of the diagonal connection: Diameter of the diagonals 16 becomes larger than the distance selected between two stabilization structures 20, 20′ at the corresponding side surface of the corner bar section 12.

[0071] 3) Advantageous arrangement of the weld joints 20′ within the corner bar section 12: Arrangement of the weld joints 20′ such that all the weld joints 20′ are located on one side of the corner bar section 12 (cf. FIG. 5b, third section from the left) so that the corner bar section 12 does not have to be rotated during welding. This means that the corner bar 12 can be assembled, for example, from two half-shell metal sheets, with one of the half shells having a somewhat larger width than the second half shell. Both weld seams can be produced from one side, optionally only rotated by a few degrees (and indeed also in a “downhand position”).

[0072] 4) Advantageous embodiment of the bends/edges 20 of the corner bar 12 with an inner radius that is as small as possible (e.g. 4× the sheet metal thickness). An even smaller radius can only be produced with difficulty from a technical production aspect. It must be noted that this radius also defines the minimal distance from adjacent bends/edges 20. The number of bends/edges 20 that can be technically produced in a corner bar 12 is thus also restricted.

REFERENCE NUMERAL LIST

[0073] 10 lattice piece [0074] 12 corner bar [0075] 14 post [0076] 16 diagonal [0077] 18 connection point [0078] 18 fastening element [0079] 20 stabilization structure (kink/bend/rounded portion) [0080] 20′ weld seam [0081] 22 stiffening element [0082] 30 weld seam [0083] 32 connection element (fork element) [0084] 34 metal sheet/lamella [0085] 35 metal sheet/lamella [0086] 38 chamfer [0087] K.sub.K buckling length, short side [0088] K.sub.L buckling length, long side [0089] K short side of the lattice piece [0090] L long side of the lattice piece