DE9210902U1 - Telescopic boom for mobile cranes or similar - Google Patents

Abstract

A telescopic jib for cranes, preferably mobile cranes, consists of an outer articulation piece which is pivotably mounted on the vehicle or its superstructure and in which several telescopically retractable and extendable telescopic sections (Tele I, Tele II, Tele III, Tele IV) are held. Each section is provided with bearings for the section guided in it and can be locked to this section. A hydraulic pressure-medium piston/cylinder unit is provided for the extension and retraction of the individual sections. To provide sections which are simple to manufacture at high flexural strength, the articulation piece and the sections (Tele I, Tele II, Tele III, Tele IV) consist of profiles forming shells, of which each, in the horizontal position swung onto the vehicle, has a bottom, roughly round part (H1XBu) and a top, half-box-shaped part (H2XBo) whose legs directed towards one another are welded to one another. Each shell with a roughly round profile consists of strips (B4, B5, B6) folded relative to one another, of which successive strips in each case enclose obtuse angles (WI, W2, W3) with one another. <IMAGE>

Description

13 August 1992 92-2990 G/em

Liebherr-Werk Ehingen GmbH, 7930 Ehingen/Donau

Telescopic boom for mobile cranes or similar

The invention relates to a telescopic boom for mobile cranes or the like, consisting of an outer pivot piece pivoted on the vehicle or its superstructure, in which several telescopically collapsible and extendable telescopic sections are held, whereby each section is provided with bearings for the section guided in it and can be locked with this section, and whereby a hydraulic pressure medium piston-cylinder unit is provided for extending and retracting the individual sections.

In a telescopic boom of this type, known for example from DE-PS 21 48 966, the individual telescopic sections have a substantially box-like profile, with the lower chords of the individual sections having flat V-shaped profiles or flat channel-shaped profiles, which are formed by legs angled from a flat central web part. These lower chords are welded to the edge areas of the downward-pointing legs of U-shaped profile parts with rounded corner areas between their web parts and legs to form box-shaped profiles, with the area of the welds

In addition, stiffening strut-like sheets can be welded into the connections. The individual telescopic sections are supported one inside the other on the channel-shaped profiled lower chords according to the pressure distribution ratio known from DE-PS 21 48 966, whereby in the area of the upper rounded corners of the box profiles the bearing forces are transferred by rollers or correspondingly shaped bearing shoes. In order to protect the side walls of the U-shaped profile part against dents, U-shaped profiled buckling stiffeners are welded onto the inside or outside of the legs of the profile. The lower chord, which is mainly loaded by bending forces, is stiffened and protected against dents by its V-shape or the two longitudinal bends that form the channel shape.

Despite the welded-in buckling stiffeners and the bend lines, the well-known telescopic boom is not only sensitive to buckling, but also requires a lot of effort to manufacture due to its complicated cross-sectional shape. Telescopic booms are not only subjected to bending, but also to torsion. The bearing elements arranged in the lower chord with a grooved or V-shaped cross-section counteract any twisting. However, if the telescopic boom is equipped with a luffing needle, it is braced via a rear α-frame or similar using guy ropes, so that a guide that transmits torsional forces in the bearing elements of the V-shaped lower chords can be canceled out if the moment acting to the rear is equal to or greater than the moment acting to the front and resulting from the load and needle boom weight.

In order to give a telescopic boom sufficient torsional rigidity independent of its sliding bearing, it is known to bolt the individual boom sections together

and additionally provided with lateral guide bearings.

The object of the invention is to create a telescopic boom of the type specified at the outset, which is characterized by a simple and economically producible construction with high bending stiffness of its individual sections.

According to the invention, this object is achieved in a telescopic boom of the generic type in that the pivot piece and the sections consist of profiles forming shells, each of which in the horizontal position (pivoted towards the vehicle) has a lower, approximately round part and an upper, half-box-shaped part, the legs of which are directed towards one another and are welded together, and that each shell with an approximately round profile consists of tires bent relative to one another, of which successive ones enclose obtuse angles with one another.

Using figures la to 14h of the following figure description, linkages and sections have been described which have at least one lower shell with a round profile and which are the subject of European patent application 92 102 268.7. Such round profiles not only have favorable area inertia and section moments, so that they have a high bending stiffness, they also provide a high level of protection against dents due to their round cross-section, so that additional measures to protect against dents can be dispensed with.

However, the production of round or oval shells is relatively complex. For this reason, the lower shells of the pivot piece and the sections of the telescopic boom according to the invention are made by a series of successive bends in the

in such a way that an approximately round profile is achieved.

If a round profile of the shells is to be produced, the corresponding cut pieces must be rolled. Since rollers of lengths that correspond to the shot lengths are not available, long profiles cannot be rolled from one piece. It is therefore necessary to weld the individual sections together at their joints.

The production equipment required for bending is relatively simple and available in normal companies. Approaching round profiles by bending the blanks can therefore be achieved more economically than forming round shells by rolling.

The formation of the shells with an approximately round profile through multiple edging has the additional advantage that an even better buckling resistance can be achieved compared to a continuous rounding.

For practical purposes, the lower profile part has approximately the shape of a half ellipse with a vertex formed by the smaller radius.

The legs of the upper profile part can be at right angles to the straight web part forming the upper chord or can form an obtuse or acute angle with it.

An embodiment of the invention is described in more detail below with reference to the drawing.

In this shows:

Fig. 1 a - a telescopic boom in different extension states of its telescopic sections,

Fig. 2 a cross section through the telescope

leger according to Fig. 1 in a state in which all boom sections are telescoped in,

Fig. 3 a cross section through two interconnected

locked telescopic shots in the area of the end stiffening collar of the outer shot,

Fig. 3 a a cross section through two interconnected

locked telescopic sections in which the bearing segments are inserted from the front - the inner and outer shape of the bearing correspond to the elliptical shape of the inner and outer telescopic sections -,

Fig. 4 a top view of the collar-shaped

Locking area of two telescopic sections with each other according to Fig. 3,

Fig. 4 a is the top view corresponding to Fig. 3 a,

Fig. 5 shows a cross section corresponding to Fig. 2

cut through the pushed together telescopic boom sections,

Fig. 6 a cross section through the single-telescopic

copied boom sections with circular cross-section,

Fig. 7 a cross section through the outer

steering piece telescopic boom sections with similar elliptical cross-sections, without built-in guides for the supply chains,

Fig. 8 a longitudinal section through the bearing

two telescopic sections in the extended state or by storing the first telescopic section in the boom linkage in the extended state,

Fig. 9 a cross section through the inner bearing

along the line IX-IX in Fig. 8,

Fig. 10 and 11 are representations corresponding to Figures 8 and 9, but with a triangular anti-twist device ,

Fig. 12 a cross section through a telescope

shot or an outer link piece with a profile composed of a half-box-shaped part and a round part,

Fig. 12 a to 12 f

and 12 h the corresponding bending, bending tension, bending compression and composite stress diagrams,

Fig. 13 a cross section through a telescope

shot or an outer link piece with an upper half-box-shaped profile, the legs of which form obtuse angles with the web part, and a lower elliptical profile part,

Fig. 13 a to 13 f

and 13 h the corresponding bending, bending tension, bending compression and composite stress diagrams,

Fig. 14 a cross section through a telescope

shot or an outer link piece with a profile that is composed of an upper half-box-shaped profile, the legs of which form acute angles with the web part, and a lower elliptical profile,

Fig. 14 a to 14 f

and 14 h the corresponding bending, bending tension, bending compression and composite stress diagrams, and

Fig. 15 a corresponding to Figures 2 and 5

Cross section through the telescopic boom with the inventive profile of the pivot piece and the sections.

As can be seen from Fig. 1, the outer linkage piece 1 of the telescopic boom 2 is provided with a joint piece 3, via which

this is hinged to the upper carriage of a crane, crane vehicle or similar. The piston rod of a hydraulic piston-cylinder unit 5 is hinged to the part enclosed by the outer hinge piece 1 in the joint 4.

Parallel to the piston-cylinder unit 5, a square profile 6 is hinged above it to the boom linkage piece 4 in a torsion-proof manner.

The pivot piece and the other telescopic sections are provided with collar-like stiffeners 8 - 10 in the area of their ends, on which pressure medium piston cylinder units provided with locking bolts are arranged. The innermost telescopic section is provided with a roller head at its outer end, as can be seen from Fig. 1.

Fig. 2 shows an enlarged cross-section through the telescopic boom sections pushed together. The inner sections 12, 13, 14 can be telescoped out from the outer boom linkage piece 1, which has a circular cross-section in the embodiment shown, and have elliptical shapes, with the ratio of their long to their short axes increasing from the outside to the inside. By increasing this ratio, crescent-shaped spaces 16 are formed between the side walls of the telescopic sections, in each of which profile boxes 17 with longitudinal slots for caterpillar-like chains (not shown) can be arranged, which serve to guide and hold supply lines, for example hydraulic and electrical lines.

As can be seen from Fig. 2, the long axes of the elliptical profiles are reduced from shot to shot only by approximately equal and relatively small amounts, so that the bending stiffness of the

Shots only decrease by small amounts from shot to shot, since the area moment of inertia determining the bending stiffness is essentially determined by the long axes.

The piston rod of the single-stage hydraulic cylinder 18 is hinged to the lower fastening frame 3 of the boom linkage piece 1 in Fig. 1. The hydraulic cylinder is provided with a collar-like widening 19 in the area of its piston rod outlet end, from which the locking bolts 20 can be extended. These locking bolts move into receptacles 21 that are provided on each telescopic section. For a more detailed design of this arrangement, reference is made to Figures 1-3 and the associated description of the utility model G 19 13 210.6.

Parallel to the piston-cylinder unit 5, 18, the box profile 6 is pivotably but non-rotatably connected to the lower fastening frame 3 of the boom linkage piece 1. The individual telescopic sections 12 - 15 are provided with sliding bearings 24, which are arranged at the lower frame ends of all telescopic sections. The box profile 6 is guided in these sliding bearings. The sliding bearings 24 only have a relatively small axial length, so that when the telescopic sections are pushed in, they lie close to one another in the axial direction.

The individual sections are provided with all-round bearings in the manner shown in Figures 3 and 4 or Fig. 3a and 4a, which consist of individual bearing segments 26 adapted to the cross-sectional shape, which can consist of a suitable plastic, such as polyamide, or other suitable bearing materials or even of composite materials.

Instead of bearings made up of individual bearing segments, continuous all-round bearings can also be provided.

A peripheral bearing is arranged on the inside of the end collars 27 that close off the individual sections. Further bearings are located at the inner frame end of each telescoped section, as can be seen from Figures 8 and 9.

Furthermore, hydraulic cylinders 28, 29 are arranged on opposite sides of the upper half of each stiffening collar 27, the pistons 30, 31 of which form or carry locking bolts. The individual telescopic sections are provided in a known manner with holes for the locking bolts 30, 31.

Fig. 5 again shows a cross-section through the round profiles of the telescopic shots.

All telescopic sections could also consist of round profiles as shown in Fig. 6. However, these round profiles have the disadvantage compared to the elliptical profiles according to Fig. 5 that larger diameter gradations, which greatly reduce the bending stiffness, would have to be provided if supply lines were to be arranged in the annular spaces between the individual sections.

The single-stage piston-cylinder unit allows the individual sections to be extended to achieve the desired boom length. Regarding the adjustable different extension states of the individual telescopic sections, we refer to Figures 10 - 19 of the utility model G 90 13 210.6 and the associated description, which also apply to the telescopic boom described here.

With the telescopic boom described above, the individual sections can be stored in one another with almost no play due to their round design, which is advantageous for the operation of the crane.

When extending the telescopic boom with the single-stage hydraulic cylinder, only the telescopic section that is being extended or retracted is unbolted. The section to be extended or retracted is connected to the hydraulic cylinder in the manner described during the process.

If the hydraulic cylinder and its piston rod do not ensure sufficient anti-twisting protection, this is achieved by the parallel profile described. This anti-twisting profile is preferably a large-volume square tube or triangular tube, which has a large, polar area moment of inertia, so that the remaining torsional elasticity is negligible. Instead of a square tube, any other shape can be chosen, for example a triangular or hexagonal tube.

Shots made from round tubes can be manufactured inexpensively in the usual way. Elliptical cross sections can also be produced in a simple way, for example by subsequently pressing a round tube laterally using hydraulic presses so that the desired elliptical shape is created.

With the circular cross-sectional shape of the sections, which is the easiest to produce, the diameters of the sections are reduced relatively significantly if sufficiently large annular spaces are to be created for the arrangement of supply lines. This distance can be reduced to a favorable ratio.

This is especially useful when external cable drums are used, although these must also be protected against the effects of the weather.

The plastic bearings for the elliptical cross sections of the shots can be produced, for example, by copy milling. Circular bearings can be produced more easily by turning. The bearings can also be cast or pressed into molds.

The elliptical design of the individual shots also has the advantage that in the highly stressed lower and upper pressure areas, the buckling radius is smaller and thus the buckling resistance is greater. The larger buckling radius is in the middle, more neutral load zones.

As can be seen from Fig. 7, both the boom linkage and the sections that can be telescoped out from it can have similar elliptical profiles, so that elliptical annular spaces with the same width over their entire circumference are formed between the individual sections. If the individual sections are mounted so that they can be moved axially within one another using bearings of the type shown in Figures 3, 8 and 9, the required torsional rigidity is already ensured, so that the box profile used for guidance can be dispensed with. Due to the fact that the individual sections are guided in one another in a way that prevents them from twisting, locking the individual sections to one another is also not necessary with such a design.

Fig. 12 shows the cross-section through a telescopic section or an outer linkage piece of a telescopic boom, which consists of a lower semi-elliptical profile part 40 and an upper

The profile part 40 consists of a half-box-shaped profile part 41, the legs of which are welded together in a horizontal parting plane by weld seams 42, 43. The legs 44, 45 of the upper half-box-shaped profile part are connected to the upper web part 46 by curved areas 47, 48 with the bending radius RL. The lower profile part 40 is formed by a shell with a semi-elliptical cross-section, whereby the profile shape can be described by the three radii ri, Rmi and Ri, which is very close to an ellipse. For manufacturing reasons, a simplification can be made if the cross-sectional shape is only defined by the two radii ri and Rmi. The elliptical shape changes only slightly during production due to the simplifications described, although these can even be advantageous from a static point of view. This is because the area of the dent-resistant shell with the radius ri or the angle Ey2 becomes larger and the radius Rmi can be extended almost to the middle of the profile. This eliminates the larger and therefore less dent-resistant area with the radius Ri. This makes the lower shell 40 more dent-resistant overall, since the dent resistance decreases linearly with the increase in the radii.

The profile according to Fig. 13 differs from that according to Fig. 12 only in that the upper profile shell 41' has half-box-shaped profile legs 44' and 45', which enclose obtuse angles with the web part 46'.

The profile according to Fig. 14 has an upper shell 41'' consisting of a half-box-shaped profile, the profile legs 44'' and 45'' of which enclose acute angles with the web part 46''.

For the profiles according to Figures 12 to 15, the structural center between the dimensions Hl and H2 is the profile center. The lower part has the shape of a half ellipse, which at the same time

forms the lower structural profile shell. For manufacturing reasons, the lower part can be extended upwards by the dimension V, whereby the dimension H2 of the upper shell is shortened accordingly.

If the sheet thicknesses of the lower shell ti or t2 are matched to the thickness of the upper shell t3 and the profile heights Hl or H2 are adjusted so that the center of gravity is located near the center of the profile and the deviations B2 less than B or B2 greater than B of the profiles according to Figures 13 and 14 are not greater than shown, the following stress ratios result, which are shown in the diagrams with the letters a to h:

The compressive stress (-) is often the most critical stress in thin-walled hollow profiles due to the risk of buckling. The greatest bending compressive stress is caused by the main load on the boom around the X-X axis (X direction) at the lower vertex of the radius ri. This is the same for the three profiles shown in Figures 12 to 14.

The lateral loading or deflection of the boom around the Y-Y axis (Y direction) in both directions causes compressive or tensile stresses in the profile side walls, the magnitude of which is proportional to the distance to the Y-Y axis of inertia.

For all three profiles, these stresses are =0 at the lower vertex, so that there is no change in the compressive stress from the X direction. At the upper edge of the profile, the stresses from the Y direction are reduced due to the radii RL.

Along the side wall upwards, the tension and compression forces add up.

Compressive stresses from the Y-direction with the bending stresses from the X-direction.

These stress ratios are shown for each of the three profiles in the corresponding diagrams.

In the profile according to Fig. 12, the build-up of compressive stress in the upper side wall, which is susceptible to buckling, is the lowest due to the uniform, lateral stress distribution in the upper half of the profile or the upper shell. The manufacture of this profile is simpler than that of the profiles according to Figures 13 and 14, since the legs 44, 45 form right angles with the web part of the upper shell, which are easier to control in steel construction due to the available tools.

In the profile according to Fig. 13, the lateral stress distribution is highest in the middle of the profile, which results in an increase in the compressive stress in this area compared to the profile according to Fig. 12. However, since the radius Ri is continued upwards over the middle of the profile, the buckling resistance is improved, so that this is not disadvantageous.

In the profile according to Fig. 14, the lateral stress curve has the highest value at the point where the radius RL begins. As the curvature ends below the center of the profile due to the radius R, the flat profile side that is not buckling-resistant is larger and is also shifted downwards. This area receives higher compressive stresses due to these influences. The less favorable buckling behavior must therefore be compensated for by appropriate measures (larger sheet thickness or buckling stiffeners).

The profile shapes of the pivot piece and the sections according to the invention can be seen in Fig. 15. The profile shapes correspond to the profile shape described in Figs. 12e to 12h, but with the difference that the approximately semi-elliptical

see lower shells are formed by successive bending of the cuts.

Below Fig. 15 there is a table showing appropriate dimensions and angles of the individual profiles.

Claims (4)

13 August 1992 92-2990 G-fö Liebherr-Werk Ehingen GmbH, 7930 Ehingen/Donau Telescopic boom for mobile cranes or similar Protection claims: 1. Telescopic boom for cranes, preferably mobile cranes, consisting of an outer pivot piece pivoted on the vehicle or its superstructure, in which several telescopically collapsible and extendable telescopic sections are held, whereby each section is provided with bearings for the section guided in it and can be locked with this section, and whereby a hydraulic pressure medium piston cylinder unit is provided for extending and retracting the individual sections, characterized, that the pivot piece and the sections consist of profiles forming shells, each of which, in the horizontal position (swiveled towards the vehicle), has a lower, approximately round part and an upper, half-box-shaped part, the opposite legs of which are welded together, and that each shell with an approximately round Profile consists of strips bent relative to one another, successive strips of which form obtuse angles with one another. 2. Telescopic boom according to claim 1, characterized in that the lower profile part has approximately the shape of a half ellipse with the apex formed by the small radius. 3. Telescopic boom according to claim 1 or 2, characterized in that the legs of the upper profile part are at right angles to the straight web part forming the upper chord. 4. Telescopic boom according to claim 1 or 2, characterized in that the legs of the upper profile part form acute or obtuse angles with the straight web part.