Telescopic boom of a crane

Abstract

The present invention relates to a telescopic boom (10) of a crane (1), extending along a longitudinal development direction (L) between a proximal end (11) and a distal end (12), and comprising a plurality of extensions (14', 14", ..., 14X), telescopically arranged inside each other and movable in translation with respect to each other along said longitudinal development direction (L), wherein each of said extensions (14', 14", ..., 14X) has, in a cross-section transversal to the longitudinal development direction (L), a polygonal profile, wherein, in at least one pair of consecutive extensions (14IX, 14X) of said plurality of extensions (14', 14", ..., 14X), the polygonal profile of the innermost extension (14X) of the pair of consecutive extensions has a number of sides less than the number of sides of the polygonal profile of the outermost extension (14IX) of the pair of consecutive extensions. The present invention also relates to a crane (1) comprising said telescopic boom (10).

Description

FIELD OF TECHNOLOGY

[0001] The present invention relates to a telescopic boom of a crane, such as a loader crane or a truck crane, particularly a telescopic boom provided with a large number of extensions.PRIOR ART

[0002] Cranes, such as articulated cranes, have one or more telescopic booms comprising extensions mutually movable in translation, such that they form an open kinematic chain with a plurality of translational degrees of freedom in space. In the case of loader cranes normally the only telescopic boom is a secondary boom, pivotally connected to a main boom, which in turn is pivotally connected to a column pivoting relative to a base. Sometimes the main boom may also be telescopic. There may then be one or more prolongation elements, connected in succession to the secondary boom, also made of telescopic booms. In the case of truck cranes, normally the telescopic boom provided with extensions is the main boom, which is connected in a rotating manner with respect to a column. At the end of the extensions there is typically an end-effector with a hook operated by a winch for lifting loads, or, for example, a platform for lifting objects or people.

[0003] In modern cranes, there is an increasing need to provide a large number of extensions in the telescopic boom (typically at least eight or more extensions) to increase the versatility of movement. At the same time, cranes are required to have the ability to lift increasingly high loads while maintaining adequate light weight. This feature, together with the large number of extensions and thus the high extension capacity of the telescopic boom, means that the telescopic boom must have a high resistance to bending (both in the longitudinal and transverse directions), which is achieved by using materials, particularly steels, with high strength and by adapting the polygonal profile section of the extensions, in particular by increasing, with the same thickness, the number of sides, which can be as high as ten or more, in equal numbers in all extensions. However, the large number of sides of the polygonal section of the extensions, together with the use of high-strength materials and the thicknesses required to achieve the desired bending strength, result in significant technological complications, in particular the impossibility of making a very large number of extensions, given the technological difficulty of providing a section with a large number of sides in the distal positions, that is, in the last extensions close to the end-effector, which have a reduced cross-section compared to the extensions in the proximal position, within which they are telescopically inserted.SUMMARY OF THE INVENTION

[0004] It is therefore an object of the present invention to provide a telescopic boom of a crane such that at least some of the limitations and problems mentioned with reference to telescopic booms according to the known technique are overcome.

[0005] Particularly, it is an object of the present invention to provide a telescopic boom of a crane that is capable of having a high number of extensions, and thus high extensibility, and that, at the same time, has high bending strength, thus being able to lift high loads even under high extension conditions.

[0006] This and other objects are achieved by a telescopic boom of a crane according to claim 1. Dependent claims define possible advantageous embodiments of the invention.BRIEF DESCRIPTION OF THE FIGURES

[0007] To better understand the invention and appreciate its advantages, some of its non-limiting embodiments will be described below, referring to the attached figures, in which: Figure 1 is a side view of an articulated crane including a telescopic secondary boom according to a possible embodiment of the invention; Figure 2 is a perspective view of a telescopic crane boom according to a possible embodiment of the invention; Figure 3 is a sectional view, along a plane orthogonal to the longitudinal development direction L, of the telescopic boom in Figure 2; Figure 4 is a sectional view, again along a plane orthogonal to the direction of longitudinal development, of a detail of the telescopic boom in Figure 2. DETAILED DESCRIPTION OF THE INVENTION

[0008] With reference to the attached Figure 1, by way of example, an articulated crane, more particularly a hydraulic loader crane, is shown as a whole under reference 1. It should be noted, however, that the present invention, in addition to loader cranes, may find application in cranes of any kind, articulated or non-articulated, for example in truck cranes. In the following description we will therefore refer to a hydraulic loader crane as shown in Figure 1, purely for sake of simplicity.

[0009] The crane 1 of the example in Figure 1 comprises a column 2 rotatable about its own axis, and two booms 9, 10, which are rotatably coupled to each other. In the crane of the figure 1 example, only the second boom 10 is extendable by a plurality of extensions 14 movable in translation relative to each other. Conventionally, in a crane of the type in Figure 1, the first boom 9, in this example case with no extensions, is referred to as the "main boom," while the second boom 10, provided with the extensions 14, is referred to as the "secondary boom." Main boom 9 is rotatable with respect to column 2.

[0010] The free end 5 of the last extension (i.e., of the telescopically innermost extensions) of the secondary boom 10 is commonly referred to as the end-effector. A hook 6, for example, can be provided at the end-effector 5, which can be handled, for example, by a rope winch (not shown in the figures).

[0011] Crane 1 includes a plurality of actuators to move the bodies forming its kinematic chain and support the related loads. In particular, there may be actuators 7, e.g., hydraulic, for moving the extensions 14, an additional actuator 8, e.g., hydraulic, for moving the main boom 9 relative to column 2, as well as an additional actuator (not visible in Figure 1) for relative rotation of the secondary boom 10 relative to the main boom 9.

[0012] It is an object of the present invention a telescopic boom provided with a plurality of extensions, such as, for example, the secondary boom 10 provided with the extensions 14 of the crane 1 of the example in Figure 1. It should be noted in any case that, as mentioned in the introductory part of the present description, the present invention finds equally application in telescopic booms of any cranes, for example of articulated cranes (main boom, secondary boom or prolongation elements), as well as of any other type of crane, for example in the main boom of a crane truck.

[0013] Referring now to Figures 2 and 3, they show the telescopic boom 10 according to a possible embodiment of the invention. The telescopic boom 10 extends longitudinally, along a longitudinal direction of development L, from a proximal end 11 to a distal end 12. Referring, for example, to the loader crane 1 in Figure 1, the proximal end 11 is where the secondary telescopic boom 10 is connected to the main boom 9, while the distal end 12 is where the end-effector 5 is positioned. The telescopic boom 10 comprises a plurality of extensions movable in translation with respect to each other along the longitudinal development direction L, so that the axial extension of the telescopic boom 10 itself can be changed, in particular the distance between the proximal end 11 and the distal end 12. In the example shown in Figures 2 and 3, ten extensions 14', 14", ..., 14 X< are specifically provided. Conventionally, the extension 14' closest to the proximal end 11 will be referred to as the "first extension," while the extension 14 X< closest to the distal end 12 will be referred to as the "last extension." The extensions 14', 14", ..., 14 X< are mutually arranged telescopically, i.e., positioned inside each other, starting from the first extension 14' (outermost) to the last extension 14 X< (innermost), and have sections of decreasing size from the first extension 14' toward the last extension 14 X< . The first extension 14', in turn, is telescopically positioned inside a proximal fixed element 15, through which, for example, the swivel coupling with the main boom 9 at the proximal end 11 in crane 1 of the type depicted in Figure 1 can be realized. Extensions 14', 14", ..., 14 X< and proximal fixed element 15 have an at least partially tubular conformation.

[0014] The telescopic boom 10 according to the embodiment shown in Figures 2-3 has a number of extensions equal to ten, but any number of extensions can alternatively be provided. However, the present invention finds particular advantageous application in telescopic booms with a large number of extensions, preferably at least 8 extensions, even more preferably 10 extensions or more, in addition to the proximal fixed element 15. Referring now to the section in a plane orthogonal to the longitudinal development direction L shown in Figure 3, each of the extensions 14', 14", ..., 14 X< , as well as the proximal fixed element 15, has a polygonal profile. The polygonal profile is closed or substantially closed since the extensions can be made, for example, by sheet metal bending.

[0015] The proximal fixed element 15 and most of the extensions 14', 14", ..., 14 X< have, in cross section, profiles having the same shape (i.e., the same number of sides of the polygonal profile), as well as a decreasing size from the first to the last extension. However, according to the present invention, in at least one pair of consecutive extensions (i.e., in a pair comprising two extensions arranged telescopically directly inside each other, without the interposition of additional extensions), the polygonal profile of the section of the innermost extension has a number of sides less than the number of sides of the polygonal profile of the section of the outermost extension. This condition is particularly advantageously realized in the pair of extensions formed by the penultimate 14 IX< and the last 14 X< extensions (the ninth and tenth extensions in the example of Figures 2 and 3), in which the polygonal profile of the section of the last extension 14 X< has a number of sides less than the number of sides of the polygonal profile of the section of the penultimate extension 14 IX< . For example, according to one possible embodiment, the penultimate extension 14 IX< , as well as preferably all the outermost extensions 14', 14", ..., 14 VIII< , as well as like the proximal fixed element 15, has a section with a decagonal profile, while the last extension 14 X< has a section with a hexagonal profile. Of course, conformations of the polygonal sections of the extensions with different numbers of sides than the above-mentioned decagonal and hexagonal profiles can be provided alternatively. Also, it should be noted that, in the same telescopic boom, several pairs of consecutive extensions can be provided in which the sides of the polygonal profiles of the sections are different. For example, according to a possible embodiment not shown in the figures, there may be a first pair of extensions intermediate or close to the end-effector (but not the last one) in which the number of profile sides changes from 10 to 6 and a further pair of extensions, for example the last one, i.e. the distal one, in which the number of profile sides changes from 6 to 4.

[0016] Sliding coupling between extensions having a polygonal cross-section and the same number of sides is achieved in ways known as such, for example by means of skids (not shown in the figures) having, for example, a rectangular or square cross-section. Such a solution, as will be clear to the skilled person, is not suitable, however, for sliding coupling between extensions having a polygonal section with a different number of sides, particularly between the penultimate extension 14 IX< and the last extension 14 X< . Therefore, advantageously, with reference to the detail illustrated in Figure 4, between the penultimate extension 14 IX< and the last extension 14 X< , the telescopic boom 1 comprises one or more skids 16 having the dual function of allowing the relative sliding of extensions 14 IX< and 14 X< , as well as of adapters for their mutual coupling, given the different profile conformation of their sections. Specifically, skids 16 are positioned at facing portions of the profiles of extensions 14 IX< and 14 X< having different numbers of sides. For instance, in the example in Figure 4, there is a total of four skids 16 in two upper portions and two lower portions, respectively, wherein the penultimate extension 14 IX< has two sides, while the last extension 14 X< has only one side. In particular, preferably, the skids 16 are placed at vertices between two successive sides of the profile of the section of the penultimate extension 14 IX< , to which a single side of the profile of the section of the last extension 14 X< corresponds. As will be clear to the skilled person, standard skids according to the known art, with a rectangular cross-section, would not be suitable for this function.

[0017] To this purpose, advantageously, the skids 16 comprise a flat inner surface 17 facing a flat outer surface 19 of the last extension 14 X< , and an outer surface 18 complementary to an inner surface 20 of the portion of the profile of the penultimate extension 14 IX< between two successive sides. For example, in the embodiment in Figure 4, the outer surface 18 of the skid 16, in cross section, has the trend of a polygonal chain having two successive sections connected at a vertex, like the inner surface 20 of the penultimate extension 14 IX< . In this manner, it is possible to make only the last extension 14 X< with a hexagonal profile, keeping all other extensions with a decagonal profile. This achieves a high overall bending strength of the telescopic boom and a simplicity of machining the last extension that allows the telescopic boom to be made with a large number of extensions.

[0018] To the described embodiments of the telescopic boom of a crane, the skilled person, in order to meet specific contingent needs, may make numerous additions, modifications, or substitutions of elements with functionally equivalent ones, without, however, departing from the scope of the attached claims.

Claims

1. Telescopic boom (10) of a crane (1), extending along a longitudinal development direction (L) between a proximal end (11) and a distal end (12), and comprising a plurality of extensions (14', 14", ..., 14X), telescopically arranged inside each other and movable in translation with respect to each other along said longitudinal development direction (L), wherein each of said extensions (14', 14", ..., 14X) has, in a cross-section transversal to the longitudinal development direction (L), a polygonal profile, wherein, in at least one pair of consecutive extensions (14IX, 14X) of said plurality of extensions (14', 14", ..., 14X), the polygonal profile of the innermost extension (14X) of the pair of consecutive extensions has a number of sides less than the number of sides of the polygonal profile of the outermost extension (14IX) of the pair of consecutive extensions, characterized in that it further comprises one or more skids (16) interposed between the extensions of said pair of consecutive extensions (14IX, 14X) for relative translation thereof, wherein said one or more skids (16) are conformed so as to form adapters between the different polygonal profiles of the cross-sections of the extensions of said pair of consecutive extensions (14IX, 14X).

2. Telescopic boom (10) according to the preceding claim, wherein said pair of consecutive extensions comprises the two extensions (14IX, 14X) of the plurality of extensions (14', 14", ..., 14X) closest to the distal end (12) of the telescopic boom (10).

3. Telescopic boom (10) according to any one of the preceding claims, wherein all of the extensions outer with respect to the outermost extension (14IX) of the pair of consecutive extensions (14IX, 14X) have, in a cross-section transversal to the longitudinal development direction (L), a number of sides equal to the number of sides of the polygonal profile of the cross-section of the outermost extension (14IX) of the pair of consecutive extensions (14IX, 14X).

4. Telescopic boom (10) according to any one of the preceding claims, wherein the polygonal profile of the cross-section of the innermost extension (14X) of the pair of consecutive extensions (14IX, 14X) is hexagonal and the polygonal profile of the cross-section of the outermost extension (14IX) of the pair of consecutive extensions (14IX, 14X) is decagonal.

5. Telescopic boom (10) according to any one of the preceding claims, wherein said plurality of extensions (14', 14", ..., 14X) comprises at least ten extensions.

6. Telescopic boom (10) according to any one of the preceding claims, wherein said one or more skids (16) are positioned at facing portions of said pair of consecutive extensions (14IX, 14X) in which the profiles of their cross-sections have different numbers of sides.

7. Telescopic boom (10) according to any one of the preceding claims, wherein said one or more skids (16) are positioned at vertices of the polygonal profile of the cross-section of the outermost extension (14IX) of the pair of consecutive extensions (14IX, 14X).

8. Telescopic boom (10) according to the preceding claim, wherein said skids (16) comprise a flat inner surface (17) and an outer surface (18) having, in a cross-section transversal to the longitudinal development direction (L), a profile trending as a polygonal chain with two successive sections connected at a vertex.

9. Crane (1) comprising a telescopic boom (10) according to any one of the preceding claims.

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