DE102014019466B4 - Lattice telescopic boom made of angle profiles - Google Patents

Abstract

Lattice telescopic boom for a crane, with at least one telescopic section (10), wherein the telescopic section (10) comprises corner posts (1) made of folded flat material, which are thinner in their bending areas (2) than in their outer areas.

Description

The present invention relates to a lattice telescopic boom for a crane, as well as a method for producing a corner post for a corresponding lattice telescopic boom.

From the EN 10 2011 115 355 A1 A boom element for a telescopic boom is already known in which the boom element has bowl-shaped corner posts and lattice bars and the bowl-shaped corner posts are connected to one another by means of the lattice bars. This design means that the boom element not only has the required stability but also a reasonable weight in order to be able to achieve the highest possible lifting height.

Furthermore, the DE 41 13 719 A1 a process for bending and folding sheet metal; in which the folding area protrudes as little as possible from the remaining surface of the folded part without any significant loss of strength, thus allowing the smallest possible folding radius to be used.

It is known from the state of the art to manufacture corner posts of telescopic lattice booms or lattice telescopic booms from angle profiles, pressed profiles or even welded constructions from angle profiles.

Angle profiles are made from folded flat material. The thickness of the flat material required for the telescopic lattice boom is at least 30mm, preferably 50mm or more. The thickness is required due to the buckling or bulging of the corner post. The telescopic sections of the lattice boom or the lattice telescopic boom can have a length of 23 - 27 meters or more.

According to the current state of the art, flat materials up to 50mm thick can only be bent with a length of up to 6 meters. The maximum available bending force plays a limiting role here. It should be noted that the material required is a high-strength fine-grain structural steel. This is very elastic and springs back strongly. It is also important for the manufacturing process that the bending radius and the bending allowance (or bending die width) depend on the thickness of the sheet being bent.

The bending radius is a function of the sheet thickness. For fine-grained structural steels with yield strengths of 960 MPa, the rule of thumb is: bending radius = 4 x sheet thickness. In practice, this formula is used for sheets over 20mm. For example, a sheet thickness of 50mm requires a bending radius of 200mm.

The bending die width is also a function of the sheet thickness. For fine-grained structural steels with yield strengths of 960 MPa, the rule of thumb is: bending die width = 10 x sheet thickness. For example, a sheet thickness of 50 mm requires a bending die width of approx. 500 mm.

The bending allowance is mainly determined by the bending die width, since after bending the folded sheet still has to be picked up by the support points.

The width of the finished corner post is therefore: width = sheet thickness + bending radius + bending allowance.

The bending allowance means an additional weight of the corner post. It is present twice on the corner post, to the left and right of the bent point, and the weight is not used at the point where it contributes optimally to increasing the area moment of inertia.

It is known to change the bending allowance mechanically or thermally after bending. However, this is an additional, cost-intensive work step. In addition, each corner post would have to be processed twice.

The static requirement for the area moment of inertia over the entire length of the telescopic or telescopic section or the first telescopic section would result in a need for a leg length of 140mm. In terms of manufacturing technology, however, 180mm is required in accordance with the conditions mentioned above due to the need for a corresponding bending allowance. This results in disruptive secondary factors such as higher weight and a shifted center of gravity of the corner post.

From the above-mentioned explanations, it can be seen that for a telescopic section with the required length, four so-called required joints would be required. A required joint is when two elements have to be connected to one another in order to achieve the required total length of the component. Required joints can therefore occur, for example, between two corner posts, each 6 m long, which are part of a telescopic section that is at least 12 m long. Welded seams are usually used in crane construction. However, any weld seam subject to tensile stress is an unfavorable factor for a boom, especially in a heavily stressed area such as the corner post. Required joints should therefore be minimized or avoided entirely.

The object of the present invention is therefore to provide an improved lattice telescopic boom for a crane, which comprises corner posts which are easy to manufacture and/or which requires a smaller number of required joints.

This object is achieved according to the invention by a lattice telescopic boom for a crane with the features of claim 1, with at least one telescopic section, wherein the telescopic section comprises corner posts made of folded flat material, which are thinner in their bending areas than in their outer areas.

The thinner design of the bending areas makes it easier to bend the flat materials, meaning that longer corner posts can be bent. At the same time, the outer areas are thicker than the bending areas, meaning that enough material remains on the corner post to ensure a high area moment of inertia of the lattice telescopic boom.

In a preferred embodiment, it is conceivable that a longitudinal recess is formed on the inside of the corner posts.

The arrangement of the recess on the inside of the corner posts ensures that there are no edges or other obstacles in the bending area of the flat material that could cause the flat material to jam or bend unevenly when it is pressed into the bending die. The inside of the corner post refers to the side that is part of the inside of the telescopic section.

In a further preferred embodiment, it is conceivable that the corner posts are divided into three regions, each with a substantially constant thickness, of which the first region has a smaller thickness than the second and third regions.

The first, thinner area can essentially correspond to the longitudinal recess. By forming the three areas with essentially constant thicknesses, a particularly simple design of the flat material is possible, which, as a folded corner post, has an essentially constant cross-section over its entire length.

In a further preferred embodiment, it is also conceivable that a telescopic section comprises at least two elements connected by a required joint. The elements can be corner posts. Since the thinned bending areas make it possible to bend longer corner posts overall, it is thus possible to produce correspondingly longer elements of the telescopic section. Due to the longer elements, a complete telescopic section can comprise fewer required joints than a telescopic section known from the prior art, which consists of several shorter elements and therefore comprises several required joints.

In a further preferred embodiment, it is conceivable that the corner posts are produced by primary shaping, and/or reshaping, and/or separating, and/or joining as well as by bending.

The present invention is also directed to a telescopic section for a lattice telescopic boom according to one of claims 1 to 5 and to a crane, in particular a mobile crane, with a lattice telescopic boom according to one of claims 1 to 5.

The invention is further directed to a method for producing the corner post of a telescopic section of a lattice telescopic boom according to one of claims 1 to 5, with the steps: primary shaping, and/or reshaping, and/or separating, and/or joining a flat material; and bending the flat material in an area with the smallest thickness of the flat material. It can advantageously be provided that the flat material is essentially rectangular and planar before bending and/or that the flat material is bent until two areas of the flat material are essentially perpendicular to one another after bending. A planar design of the flat material can mean that a first base area of the flat material runs essentially in one plane, while the side opposite the first base area has partial areas that run in two or more spaced-apart planes. The first base area and the partial areas of the side opposite it can run essentially parallel.

• 1: Flachmaterial vor Abkanten;
• 2: Flachmaterial nach Abkanten mit Schema Flächenschwerpunkte;
• 3: Eckstiel gemäß dem Stand der Technik; und
• 4: Schema eines Gitterteleskopauslegers.

Further details and advantages of the invention are shown in the figures.

• 1 : Flat material before bending;
• 2 : Flat material after bending with diagram of area centres of gravity;
• 3 : Corner post according to the state of the art; and
• 4 : Schematic of a lattice telescopic boom.

According to the invention, the corner post 1 is further designed as a bent construction according to 2 However, in contrast to the 3 The flat material required for this purpose is shown in the state of the art 1 in the bending area 2 is thinner than in the outer area, e.g. in the bending allowance 4, 4'. Possible manufacturing methods can be: primary forming, forming, separating, whereby material is removed in the bent area of the flat material, or joining, whereby material is applied in the outer area of the flat material, e.g. in the bending allowance 4, 4'. In 1 a cross-section of a flat material for producing a corner post 1 is shown. The cross-section can be essentially constant over the entire length of the corner post 1. However, embodiments are also conceivable in which the corner post 1 has a variable cross-section.

2 shows a preferred embodiment of the corner post 1 with a taper in the bent area, which was created, for example, by mechanical processing before bending. A corner post 1' according to the prior art and without a taper is shown in dashed lines.

As from 2 and 3 As can be seen, the bending radius 105 can be reduced according to the invention. Each corner post 1', 1 has 2 a center of gravity S1, S2. The four center of gravity S1, S2 of the corner posts 1', 1 of a telescopic section 10 influence the area moment of inertia of the entire telescopic section 10 via the distance to the center axis 100 of the cross section through the respective telescopic section 10 or telescopic section 10. If the distance is large, as in the case of the center of gravity S2, a larger area moment of inertia results than in the case of the center of gravity S1. Since the distance of the center of gravity is included in the calculation as a square, this is also an improvement with considerable practical effects. A higher area moment of inertia can be achieved with a boom with the same weight. The center of gravity S1 corresponds to the center of gravity of a corner post 1' according to the state of the art.

The area center of gravity S2 corresponds to the area center of gravity of a corner post 1 according to the invention. It can be seen that the area center of gravity S2 is further away from the central axis 100 than the area center of gravity S1. This results in a higher area moment of inertia for the entire telescopic section 10 according to the invention.

Furthermore, the force required for bending can be reduced according to the invention, so that lengths of up to 12 m or more can be bent with the existing bending force or with the existing bending devices. The number of required strokes for a telescopic section 10 can be reduced to two or a maximum of three.

Alternatively, the thickness of the flat material can be chosen to be larger in order to increase the total area moment of inertia of the boom without having to increase the bending force. The sheet metal in bending area 2 is tapered again by mechanical processing.

As mentioned above, a major advantage is the reduction of the bending die width, which allows the bending allowance to be reduced to the bare minimum.

3 shows a corner post 1' or a part of a corner post 1' according to the prior art. Bending radius 105 and bending allowance 4, 4' are larger than provided for in the invention.

4 shows a schematic representation of a lattice telescopic boom according to the prior art. Here, a single telescopic section 10 is partially mounted within a pivot piece 20. The lattice telescopic boom can of course comprise a larger number of telescopic sections 10. It is also conceivable that the pivot piece 20 itself comprises corner posts 1, as provided according to the invention for the telescopic sections 10.

Claims (10)

Lattice telescopic boom for a crane, with at least one telescopic section (10), wherein the telescopic section (10) comprises corner posts (1) made of folded flat material, which are thinner in their bending areas (2) than in their outer areas. Lattice telescopic boom according to Claim 1 , characterized in that a longitudinal recess is formed on the inner side of the corner posts (1). Lattice telescopic boom according to Claim 1 or 2 , characterized in that the corner posts (1) are divided into three regions, each with substantially constant thickness, of which the first region (2) has a smaller thickness than the second (4) and the third region (4'). Lattice telescopic boom according to one of the Claims 1 , 2 or 3 , characterized in that a telescopic section (10) comprises at least two elements connected via a demand joint. Lattice telescopic boom according to one of the preceding claims, characterized in that the corner posts (1) are produced by primary shaping, and/or reshaping, and/or separating, and/or joining, as well as by bending. Telescopic section (10) for a lattice telescopic boom according to one of the Claims 1 until 5 . Crane, in particular mobile crane, with a lattice telescopic boom according to one of the Claims 1 until 5 . Method for producing the corner post of a telescopic section (10) of a lattice telescopic boom according to one of the Claims 1 until 5 , comprising the steps of: primary forming, and/or reshaping, and/or separating, and/or joining a flat material; and bending the flat material in an area with the smallest thickness of the flat material. Procedure according to Claim 8 , characterized in that the flat material is substantially rectangular and planar before bending. Procedure according to Claim 8 or 9 , characterized in that the flat material is bent until two regions of the flat material are substantially perpendicular to one another after bent.

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