Telescopic Strut for a Device for Lifting Loads

A telescopic strut, in particular for a device for lifting loads, in particular for a hanger for vehicles or vehicle parts, wherein the telescopic strut consists of an outer tube and an inner tube guided therein, wherein the inner tube is movable longitudinal direction in the outer tube, where a number of sliding shoes are attached to the outer tube to guide the inner tube, where the sliding shoes have each been introduced from the outside into an opening in the wall of the outer tube and protrude inwardly to guide the inner tube such that the telescopic strut, which is structurally simple and therefore inexpensive to produce, has good sliding properties, has little guide play and is easy to maintain.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a telescopic strut for a stabilizer for a device for lifting loads, in particular for a hanger for vehicles or vehicle parts.

2. Description of the Related Art

In order to stabilize conveying assemblies for lifting and lowering loads (so-called lifting mechanisms or “hangers”), use is often made of telescopic struts (referred to for short as telescopes). Here, an inner tube, which is moved in an outer tube, is retracted or extended during the lifting or lowering movement.

DE 10 2004 045 516 A1—Aßmann, “Vorrichtung zum Heben and Stabilisieren von Lasten” [“Device for lifting and stabilizing loads”] discloses telescopic struts of for stabilization in a device for lifting loads.

IT MO 20120019A1—Cosben, “Braccio Telescopico” [“Telescopic arm”] discloses the outer section of a telescopic arm of a crane with multi-part guide elements on the outer tube, which have a screw-based adjuster between a sliding piece and an upper part.

WO 2014/191561 A1 and EP 1 982 948 A2 disclose telescopic sections of a crane with such a design.

FR 2 759 687 A1 discloses guide elements inserted at an end side into an outer section of a telescopic crane arm.

Telescopes used for stabilizing conveying assemblies for lifting and lowering loads have hitherto been implemented with guide rollers. Here, the movement of the inner tube in the outer tube occurs via multiple, in part settable guide rollers. Here, the guide rollers are, for example, arranged horizontally and vertically on the outer tube of the telescope and serve for guiding the inner tube. Each guide roller is mounted rotatably in roller blocks, and these are in turn welded to the outer tube. The roller bearing arrangement is intended here to ensure as free and low-friction a movement as possible, and at the same time to guide the inner tube in the outer tube with the least possible clearance. This solution with rollers and bearings (for example, ball bearings) installed in the rollers is complex to manufacture and is therefore expensive. Furthermore, exchanging the rollers in the event of a defect or in the event of wear-induced damage is time-consuming and thus leads to long downtimes of the lifting mechanisms concerned. Moreover, in the case of the roller-based solution mentioned, the setting of the guide clearance of the telescopic struts is time-consuming.

SUMMARY OF THE INVENTION

In view of the foregoing, it is therefore an object of the present invention to provide a structurally simple, functional and low-maintenance configuration of telescopic struts.

A core concept of the solution in accordance with the invention to the problem is achieved by implementing the guidance of the inner tube in the outer tube of the telescopic strut using sliding shoes that are easy to manufacture. For the purposes of easy installation, the sliding shoes are plugged into corresponding openings in the outer tube from the outside, and guide the inner tube. The sliding shoes are preferably produced from a material with good sliding characteristics, for example plastic.

The foregoing and other objects and advantages are achieved in accordance with the invention by a telescopic strut, suitable for a stabilizer for a device for lifting loads, in particular for a hanger for vehicles or vehicle parts, where the telescopic strut is composed of an outer tube and of an inner tube guided in said outer tube, and where the inner tube is movable in a longitudinal direction in the outer tube. Here, a number of sliding shoes are attached to the outer tube for the purposes of guiding the inner tube, where the sliding shoes have each been introduced from the outside into an opening in the wall of the outer tube and protrude inwardly for the purposes of guiding the inner tube. This solution, which is simple in configuration and is inexpensive to produce, has good sliding characteristics, has a small guide clearance, and is easy to set and maintain.

The inner tube is advantageously composed of a metallic material, and the sliding shoes are composed substantially of plastic. Sliding shoes composed of plastic have good running characteristics, and a low rate of wear, on metallic surfaces.

A small tilting clearance of the telescope is achieved if the sliding shoes are grouped into two spaced-apart regions (guide regions) of the outer tube and, in each of the regions, at least four of the sliding shoes are arranged so as to be distributed annularly around the periphery of the outer tube.

In one particularly advantageous embodiment, the outer tube and the inner tube each have a substantially rectangular cross section, where, in each of the regions, two sliding shoes are arranged adjacent to one another at each of the wide sides of the outer tube, and where one sliding shoe is arranged at each of the narrow sides.

The sliding shoes advantageously have a bevel at least in a sliding direction at the contact surface with respect to the inner tube. This not only improves the running characteristics but also makes it easier for the outer tube equipped with sliding shoes to be assembled with the inner tube, such as after a disassembly operation.

In accordance with the invention, the sliding shoes have a substantially T-shaped cross section, where the small-area part of the sliding shoe is led through the opening of the outer tube from the outside, and where an overhanging wide part of the sliding shoe, as a bearing surface, bears against the outer tube from the outside and is connected, in particular screwed, to the outer tube in the region of the bearing surface. The sliding shoes can thus be installed or exchanged at any time, even when the inner tube has already been pushed into the outer tube. Furthermore, it is thus possible for the guide clearance to be set from the outside. For this purpose, in accordance with the invention, a spacer is introduced in each case between the outer side of the outer tube and the bearing surface of the sliding shoe, where, depending on the thickness or number of the spacers, the sliding shoe projects to a greater or lesser depth into the interior cross section of the outer tube, and can thus be exactly adapted to the dimensions (for example, width) of the inner tube. Here, the spacer is exchangeable for the purposes of setting a guide clearance of the telescopic strut and/or for the purposes of compensating for wear of the sliding block. Alternatively, setting screws, in particular grub screws, may be provided in additional threaded holes of the sliding shoes in the bearing region for the purposes of setting the penetration depth.

As a spacer, a metal sheet or a plastics plate is advantageously provided which, in one advantageous embodiment, is pushed in under the bearing surface of the sliding shoe from the side. The spacer is advantageously screwed to the sliding piece and to the outer tube, where, in a particularly advantageous embodiment, one and the same screws both fasten the sliding shoe to the wall of the outer tube and fix the spacer (distancing plate, “shim”). For this purpose, the spacer and the sliding shoe advantageously have identical bores or a corresponding bore pattern, where the screws used for fastening the sliding shoe to the outer tube are led through the bores of the spacer. In one embodiment, the spacer has no bores but has U-shaped cutouts, which are open to an outer edge, for the screws such that, even when the screws have already been installed, the spacer can be pushed in laterally under the bearing surface of the loosened sliding shoe. For the purposes of fixing, the spacer is then advantageously clamped between the bearing surface of the sliding shoe and the outer tube.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG.1shows a multi-sectional illustration of a telescopic strut T (“telescope”) in accordance with the invention having an outer tube AR and an inner tube IR, where sliding shoes are arranged annularly around the outer periphery of the outer tube AR in two guide regions FB1, FB2. The guide regions FB1, FB2are spaced apart from one another to a certain extent to prevent tilting of the inner tube IR in the outer tube AR. At the same time, however, both guide regions FB1, FB2are arranged close enough to the open end of the outer tube AR such that, even when the inner tube IR has been almost fully extended, the inner tube is guided in both guide regions FB1, FB2, and reliable, tilting-free guidance thus continues to be ensured.

FIG.2shows the telescopic strut in accordance with the invention in a perspective view, on the one hand from a first, upper side, and on the other hand from a second, lower side. The reference designations already introduced inFIG.1also apply toFIG.2and to all subsequent figures. In addition to the illustration fromFIG.1,FIG.2illustrates the sliding shoes G, which are fastened in the wall of the outer tube AR from the outside via in each case 6 screws. By contrast to FIG.1, in which the inner tube IR has been pushed into the outer tube AR from the left-hand side in the illustration, it is the case inFIG.2that the inner tube IR has been pushed into the right-hand end of the outer tube AR. Correspondingly, inFIG.2, the guide regions FB1, FB2with the sliding shoes G are situated at the right-hand, open end of the outer tube AR.

FIG.3shows a detail illustration of the installed sliding shoes G in the vicinity of the open end of the outer tube AR. Here, it is possible to see the substantially T-shaped cross section of the sliding shoes G, where the 6 screws via which the sliding shoe G is fastened are screwed into an overhanging region that bears against the outer tube AR from the outside, and where an integrally formed relatively small, cylindrical or rectangular part of the sliding shoe G projects through a corresponding opening of the outer tube AR in each case into the interior region of the outer tube AR and, via the bottom side, guides the inner tube IR.FIG.3also shows spacers D (distancing plates, “shims”) which, via their thickness, each define the depth to which the sliding shoe G penetrates into the interior region of the outer tube AR.

FIG.4shows a cross-sectional illustration, transversely with respect to the longitudinal direction of the outer tube AR, in the region of the installed sliding shoes G. The inner tube is not illustrated in this illustration. It can be seen here that the sliding shoes G are encirclingly beveled, in the region of their sliding surface, with a bevel F. Otherwise, the guide surfaces of the sliding shoes G, i.e., the contact surfaces with respect to the inner tube IR, are substantially smooth in this exemplary embodiment. In other embodiments, in which a (preferably PTFE-based) lubricant is additionally used, the sliding surface may also have a texture, in the depressions of which the lubricant can adhere.

FIG.5likewise shows a cross-sectional illustration of the outer tube AR in the region of six installed sliding shoes G, with the inner tube IR also being illustrated in this illustration. A guide clearance SP (clearance) is indicated at the sliding shoes G of the narrow sides of the outer tube AR. The guide clearance is set by virtue of spacers D of greater or lesser thickness being introduced to shim the bearing surfaces of the outer tube AR in the region of the contact surfaces of the sliding shoe G.

A plastic, in particular based on a pure, ultra-high-molecular-weight, low-pressure polyethylene, has proven successful as a material for the sliding shoes in interaction with an inner tube IR composed of metal.

The sliding shoes proposed here are easy to manufacture, for example, by cutting machining. By virtue of the fact that a roller configuration with roller blocks can be omitted, welding distortion of the outer tube during the production process is reduced. As a result, the outer tube can be manufactured more exactly and is less expensive to produce. The configuration proposed here has the effect that the sliding shoes can be easily set or adjusted and can also be easily exchanged.