EP0499208B1 - Telescopic jib for mobile cranes or the like - Google Patents

Abstract

A telescopic jib for cranes consists of an outer articulation piece which is pivotably mounted on the vehicle or its superstructure and in which several retractable and extendable telescopic sections are held. Each section is provided with bearing arrangements 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. In order to provide a telescopic jib which has considerable flexural rigidity in its individual sections and is simple and economical to manufacture, the articulation piece and the sections have round profiles.

Description

The invention relates to a telescopic boom for mobile cranes, consisting of an outer link piece pivotally mounted on the vehicle or its superstructure, in which a plurality of telescopically collapsible and extendable telescopic sections are held, each section being provided with bearings for the section guided therein and with this section is lockable and a hydraulic pressure medium piston-cylinder unit is provided for extending and retracting the individual shots.

In a telescopic boom of this type, known from DE-B-21 48 966, for example, the individual telescopic sections have a substantially box-like profile, the lower straps of the individual sections having flat V-shaped profiles or flat channel-shaped profiles that pass through from a flat one middle web part angled legs are formed. These lower belts are welded to the edge areas of the downward facing legs of U-shaped profile parts with rounded corner areas between their web parts and legs to form box-shaped profiles. The individual telescopic sections are mounted one inside the other on the trough-shaped lower chords according to the pressure distribution ratio known from DE-PS 21 48 966, the bearing forces being transmitted in the region of the upper rounded corners of the box profiles by rollers or appropriately shaped bearing shoes. In order to protect the side walls of the U-shaped profile part against dents, bulge stiffeners with U-shaped profiles are welded onto the inside or outside of the legs of the profile. The lower flange, which is mainly subjected to bending forces, is stiffened by its V-shape or the two longitudinal bends that form the channel shape and secured against dents.

The known telescopic boom is not only sensitive to bulges despite the welded-in buckling stiffeners and the buckling lines, it can also be produced only with increased effort because of its complicated cross-sectional shape. Telescopic booms are not only subjected to bending, but also to torsion. In this case, the bearing elements arranged in the lower flange with a channel-shaped or V-shaped cross section counteract rotation. But if the telescopic boom is provided with a luffing needle, this is or the like via a rear A-frame. anchored by guy ropes so that a torsional force-transmitting guide in the bearing elements of the V-shaped lower chords can be canceled if the moment acting backwards is equal to or greater than the moment acting forward and resulting from the load and the jib weight.

In order to give a telescopic boom sufficient torsional rigidity regardless of its sliding bearing, it is known to bolt the individual boom sections to one another and additionally to provide them with lateral guide bearings.

The object of the invention is to provide a telescopic boom of the type specified, which is characterized by a simple and economically producible construction with great bending stiffness and resistance to buckling of its individual shots.

According to the invention, this object is achieved in that the articulation piece and the shots consist of profiles, each of which has a lower round and an upper half-box-shaped part in the horizontal position (pivoted onto the vehicle), the opposing legs of which are connected to one another. In the profile according to the invention, an upper semi-box-shaped profile is thus connected to a lower round profile in a horizontal parting plane. The lower round profile can for example be a semicircular profile. The lower profile part preferably has approximately the shape of a half ellipse with the apex formed by the small radius. The profile according to the invention thus consists of different profile parts with respect to its horizontal axis, while it is symmetrical about its vertical axis.

The profile according to the invention meets the requirements for a telescopic boom in a particularly favorable manner. The profiles of the individual shots of a telescopic boom are primarily subjected to tension in their upper area and to pressure in their lower area during operation, so that the lower area is highly susceptible to buckling. In the case of conventional profiles, which either had a box shape or, starting from a box shape, were provided with a lower V-shaped profile part, stiffening sheets were welded into the profile on the inside and / or outside to increase the buckling stiffness. The profile according to the invention meets the demands of a telescopic boom in a particularly favorable manner, because the lower region, which is highly sensitive to buckling, consists of a round profile which is much less sensitive to buckling than box-shaped profiles.

The buckling sensitivity of the lower profile part increases with the increasing compressive stress, i.e. in the direction of the lower apex line. It is therefore particularly advantageous to design the lower profile part in the form of a semi-ellipse, because this their apex region has the smallest radius of curvature and therefore has the least sensitivity to buckling in the region with the greatest compressive stress.

The legs of the upper profile part can be at right angles to the straight web part forming the upper chord. Since the upper profile part is subjected to tension, the risk of buckling is low, so that the straight profile legs are accepted.

According to an advantageous embodiment, the legs of the upper profile part form an obtuse angle with the straight web part. Due to this obtuse angle, the round profile part extends into the upper area of the overall profile, so that in particular the middle profile part is also less sensitive to dents. The lateral stress curve is highest in the middle of the profile, which increases the compressive stress in this area. If the curvature continues upwards over the center of the profile, the buckling stiffness in this area is improved.

According to a further embodiment it is provided that the legs of the upper profile part enclose acute angles with the straight web part. This embodiment takes into account the lateral stress curve, the corresponding risk of buckling in the lateral area, if necessary, being taken into account by appropriate measures. For example, larger sheet thicknesses can be selected or buckling stiffeners can be welded in.

The obtuse and acute angles of the profile shapes described above need only deviate slightly from 90.

In order to achieve a smooth transition of the two profile parts, the legs of the lower round profile part connect tangentially to the straight legs of the upper profile part.

The legs of the upper profile part are expediently connected to the straight web part by rounded regions. This embodiment makes it possible to arrange bearings for guiding and holding the telescopic shots in the rounded areas.

The top shell of each shot can be folded in one piece over its entire length, so that there are no weld seams and in particular no transverse weld seams in the pull zone.

During the manufacture of the boom sections, the upper shell can be placed on a straight plate and does not need to be held in special facilities, as with a complete oval boom profile.

In practical crane operation, the semi-box-shaped upper profile part creates additional advantages, which consist in the fact that the hoisting rope can lay down on the wide top chord without slipping sideways. Furthermore, the flat upper web part of the upper profile part is also useful for maintenance purposes, since it can be walked on safely. The upper profile part can also be sprayed with a rough covering, so that the necessary sliding security is given when walking on.

The arrangement of the bearings in the rounded area between the upper straight web part and the legs of the upper profile part makes it possible to keep the straight side profile walls free of bearings, so that they can be painted for corrosion protection and labeled.

According to one embodiment, it is provided that all boom sections are locked to one another in the extended and retracted state and that only one pressure medium piston cylinder unit articulated at one end with the boom linkage piece of the outer shot is provided, which extends and retracts only one shot that was previously unlocked . This configuration ensures that the individual shots are torsionally rigidly connected to one another by their constant locking. If a lock is released for the purpose of extending and retracting a shot, these two shots are secured against rotation by this connecting pressure-piston cylinder unit, the pressure-piston cylinder unit being provided with a suitable anti-rotation device.

To lock the individual shots together and to extend and retract them, an arrangement can be selected as is known from the older, but not previously published utility model G 90 13 210.6. Expediently, the piston rod of the piston-cylinder unit can therefore be articulated on the boom link piece and a driver device for the individual shots can be arranged in the region of the end of the cylinder from which the piston rod emerges. In this embodiment, only such a large length of the telescopic cylinder is buckled that corresponds to the extended part of the piston rod plus the necessary clamping length. Furthermore, the receptacles for the coupling pieces of the driver device can be arranged at the inner ends of the telescopic shots. To extend and retract a shot, only this is always coupled to the driver device, so that the control of the bolts is easier and more manageable overall. The receptacles for the coupling pieces of the driver device are expediently on ring-shaped frame parts at the inner ends of the telescopic sections intended. These recordings are expediently arranged in pairs opposite one another. They can consist of holes or bushings for retractable bolts. The receptacles can advantageously be arranged in common planes parallel to the center line of the shots. This configuration allows that the coupling pieces of the driver device on the telescopic cylinder, which will usually be bolts, only have to be extended by the same amount to couple each of the shots, so that the driver device can be made more uncomplicated overall and that Couplings or bolts can be closer together for opposite shots. For a more detailed description of the devices for locking and unlocking the shots with one another and for extending and retracting the shots, reference is made to the older utility model DE-U-90 13 210.6.

In order to lock the individual shots to one another, bolts which can be actuated hydraulically or by compressed air and suspension are expediently provided on their collar-like thickened end regions.

The bolts can be provided with cone-like or beveled centerings, which correct slight twists during the extension and retraction of individual shots when locking.

• Fig. 1 a - n einen Teleskopausleger in unterschiedlichen Ausfahrzuständen seiner Teleskopschüsse,
• Fig. 2 einen Querschnitt durch einen Teleskopschuß bzw. ein äußeres Anlenkstück mit einem aus einem halbkastenförmigen Teil und einem runden Teil zusammengesetztem Profil,
• Fig. 2 a bis 2 h die zugehörigen Biege-, Biegezug-, Biegedruck-und die zusammengesetzten Beanspruchungen darstellenden Diagramme,
• Fig. 3 einen Querschnitt durch einen Teleskopschuß bzw. ein äußeres Anlenkstück mit einem oberen halbkastenförmigen Profil, dessen Schenkel mit dem Stegteil stumpfe Winkel einschließen, und einem unteren elliptischen Profilteil,
• Fig. 3 a bis 3 h die zugehörigen Biege-, Biegezug-, Biegedruck-und die zusammengesetzten Beanspruchungen darstellenden Diagramme,
• Fig. 4 einen Querschnitt durch einen Teleskopschuß bzw. ein äußeres Anlenkstück mit einem Profil, das aus einem oberen halbkastenförmigen Profil, dessen Schenkel mit dem Stegteil spitze Winkel einschließen, und einem unteren elliptischen Profil zusammengesetzt ist,
• Fig. 4 a bis 4 h die zugehörigen Biege-, Biegezug-, Biegedruck-und die zusammengesetzten Beanspruchungen darstellenden Diagramme.

Embodiments of the invention are described below with reference to the drawing. In this shows

• 1 a - n a telescopic boom in different extension states of its telescopic sections,
• 2 shows a cross section through a telescopic section or an outer link with a profile composed of a half-box-shaped part and a round part,
• 2 a to 2 h the associated bending, bending tension, bending pressure and the composite stress diagrams,
• 3 shows a cross section through a telescopic section or an outer link piece with an upper semi-box-shaped profile, the legs of which form obtuse angles with the web part, and a lower elliptical profile part,
• 3 a to 3 h the associated bending, bending tensile, bending pressure and the composite stress diagrams,
• 4 shows a cross section through a telescopic section or an outer link with a profile which is composed of an upper semi-box-shaped profile, the legs of which form an acute angle with the web part, and a lower elliptical profile,
• 4 a to 4 h the associated bending, bending tension, bending pressure and the composite stress diagrams.

As can be seen from Fig. 1, the outer link 1 of the telescopic boom 2 is provided with a joint piece 3, by means of which it is attached to the superstructure of a crane, crane vehicle or the like. is articulated. The piston rod of a hydraulic piston-cylinder unit 5 is articulated in the joint 4 on the part enclosed by the outer articulation piece 1.

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

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

From Fig. 2 the cross section through a telescopic section or an outer link of a telescopic boom can be seen, which consists of a lower semi-elliptical profile part 40 and an upper semi-box-shaped profile part 41, the legs of which are welded together in a horizontal parting plane by welds 42, 43. The legs 44, 45 of the upper half-box-shaped profile part are connected to the upper web part 46 by curved regions 47, 48 with the bending radius RL. The lower profile part 40 is formed by a shell with a semi-elliptical cross-section, the profile shape being able to be described with a great approximation to an ellipse by the three radii ri, Rmi and Ri. For manufacturing reasons, a simplification can be made if the cross-sectional shape is defined only by the two radii ri and Rmi. The shape of the ellipse changes only slightly as a result of the simplifications described in the production, although from a static point of view these can even be favorable under certain circumstances. This is because the area of the bulge-resistant shell with the radius ri or the angle Ey2 becomes larger and the radius Rmi can be guided almost to the middle of the profile. This eliminates the larger and therefore less dent-proof area with the radius Ri. As a result, the lower shell 40 is overall more rigid, since the buckling security decreases linearly with the increase in the radii.

The profile acc. Fig. 3 differs from that of FIG. 2 only in that the upper profile shell 41 'with semi-box-shaped profile legs 44' and 45 ', which include obtuse angles with the web part 46'.

The profile acc. Fig. 4 has an upper shell 41 "consisting of a semi-box-shaped profile, the profile legs 44" and 45 "including acute angles with the web part 46".

2-4, the constructive middle between the dimensions H1 and H2 is the middle of the profile. The lower part usually has the shape of a half ellipse, which also forms the lower structural profile shell. For manufacturing reasons, the lower part can be extended upwards by dimension V, which means that dimension H2 of the upper shell is shortened accordingly.

• Die Druckspannung (-) ist wegen der Beulgefahr häufig die kritischste Beanspruchung bei dünnwandigen Hohlprofilen. Die größte Biege-Druckspannung entsteht durch die Hauptbelastung des Auslegers um die Achse X-X (X-Richtung) im unteren Scheitelpunkt des Radius ri. Dieses ist bei den drei Profilen gem. den Fig. 2 bis 4 gleich.

If the sheet thicknesses of the lower shell t1 or t2 are matched to the thickness of the upper shell t3 and the profile heights H1 or H2 so that the center of gravity axis is close to the profile center and the deviations B2 smaller B or B 2 greater B the Profiles acc. 3 or 4 is not larger than shown in the ratio, the following tension ratios result, which are each shown in the diagrams with the letters a to h below:

• The compressive stress (-) is often the most critical stress for thin-walled hollow profiles due to the risk of buckling. The greatest bending compressive stress results from the main load of the boom around the axis XX (X direction) in the lower vertex of the radius ri. This is according to the three profiles. 2 to 4 the same.

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

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

Along the side wall upwards, the tensile or compressive stresses from the Y direction add up with the bending stresses from the X direction.

These tension relationships are shown for each of the three profiles in the associated diagrams.

With the profile acc. Fig. 2 is the least by the uniform, lateral stress curve in the upper profile half or the upper shell, the build-up of the compressive stress in the upper bulge-sensitive side wall. The production of this profile is easier than that of the profiles acc. 3 and 4, since the legs 44, 45 form right angles with the web part of the upper shell, which are easier to control in steel construction because of the existing aids.

With the profile acc. 3, the lateral stress curve 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 continues upward beyond the center of the profile, the buckling stiffness is thereby improved, so that this is not disadvantageous.

4, the lateral stress curve has the highest value at the point at which the radius RL begins. Since the curvature by the radius R has already ended below the center of the profile, the flat profile side, which is not stiff against bulging, is larger and also shifted downwards. This area receives higher compressive stresses due to these influences. The less favorable buckling behavior may have to be compensated for by appropriate measures (larger sheet thickness or buckling strips).

Claims (10)

1. A telescopic jib (2) for cranes, preferably mobile cranes, consisting of an outer articulation component (1) pivotably mounted on the vehicle or its upper chassis, wherein there are mounted several telescopically retractable and extendable telescopic sections, in which arrangement each section is provided with bearing means for the section carried therein and is lockable with this section, and wherein provision is made for a hydraulic pressure medium piston-cylinder unit for the outward movement and retraction of the individual sections,
characterized in that
the articulation component (1) and the sections consist of profiles each of which has in the horizontal position pivoted onto the vehicle, a lower round part (40) and an upper half-box shaped part (41), and whose sides (44, 45) directed towards each other are welded together.

2. A telescopic jib according to claim 1, characterized in that the lower profile part (40) approximately has the shape of a half ellipse with the apex formed by the small radius.

3. A telescopic jib according to claim 1 or 2, characterized in that the sides of the lower round profile part (40) are tangentially joined to the straight sides (44, 45) of the upper profile part (41).

4. A telescopic jib according to one of claims 1 to 3, characterized in that the sides (44, 45) of the upper profile part (41) are disposed at right angles to the straight web part (46) which forms the upper boom.

5. A telescopic jib according to one of claims 1 to 3, characterized in that the sides (44', 45') of the upper profile part (41) form obtuse angles with the straight web part (46').

6. A telescopic jib according to one of claims 1 to 3, characterized in that the sides (44, 45) of the upper profile part (41) are joined to the straight web part (46) by rounded zones (47, 48).

7. A telescopic jib according to one of claims 1 to 6, characterized in that all the jib sections are locked to each other in their extended and retracted state, and that provision is made for only one pressure medium piston-cylinder unit articulated at one end on the articulation component of the outer section, which moves out or retracts in each case only one section that has been previously unlocked.

8. A telescopic jib according to one of the preceding claims, characterized in that in the sections, there is mounted parallel to the pressure medium piston-cylinder unit, a freely running- out profiled tube secured against rotation which is articulated on the articulation component, the length of which tube corresponds to the length of the outer section and whereon the inner sections are carried for longitudinal displacement by means of sliding bearings, but being secured against rotation.

9. A telescopic jib according to claim 8, characterized in that the profiled tube is a rectangular or triangular tube.

10. A telescopic jib according to one of the preceding claims, characterized in that for locking the sections, provision is made in their end zones thickened in the manner of collars, for pins that are actuable hydraulically or by compressed air and spring action.

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