EP0450543B1 - Structural member with elements for reducing air resistance - Google Patents

Description

The invention relates to a box-shaped component with a polygonal box profile according to the preamble of claim 1.

It is known that such box-shaped components have a large drag coefficient because of their unfavorable flow and therefore a relatively high flow resistance.

It is already generally known to provide components with aerodynamically favorable claddings. However, such claddings are very complex in terms of production technology and assembly technology and are therefore expensive. In addition, in many cases it is not possible for functional reasons to completely clad such components. Examples are solid wall girders that are used in crane construction, bridge construction or in general in steel construction and, for example, certain surfaces of the girder must remain free as running surfaces for trolleys or the like. Another example is a driver's cab or engine house, which is arranged at a high height on a crane and which is exposed to considerable wind loads and is therefore considerably involved in the wind forces acting on the crane.

From DE-A-19 26 248 it is already known to equip edges of solid wall girders for crane bridges or conveyor belts with rounding elements which are intended to improve the flow around. These rounding elements essentially have the task of giving the edges of a solid wall girder a more favorable shape so as to reduce the formation of eddies at these edges. Relatively complicated cross-sectional profiles have therefore been developed for the known carriers, which on the one hand make such carriers complex in terms of production technology and therefore expensive, and on the other hand reduce the possible uses of such carriers. For example, it may be the case that the known rounding elements bring a reduction in the wind resistance of the carrier for a certain inflow direction, but this is paid for by the fact that the wind resistance is greater for ideal flow directions than for simple box profiles.

It is also known in the case of bodies which always have a specific orientation to a flow to effect a better fit of the flow in certain areas of a surface lying in the flow by means of slat-like guide surfaces (DE-U-82 02 119.8). However, such a device is only effective for a narrow range of the flow direction, so that it cannot achieve the object on which the present invention is based.

The magazine "De Ingenieur" year 83 / no. 38/24. Sept. 1971, page A 670 ff. Shows a box-shaped component of the type mentioned in the preamble of the new claim 1. It is a horizontally running bridge for which essentially only the two horizontal inflow directions or inflow components of transversely to the longitudinal direction of Meaning. The bridge can therefore be optimized for these two flow directions. For this purpose, it is clad on its lateral end faces with an approximately wedge-shaped profile, which is only aerodynamic, but not structural. In addition, a guide surface is assigned to each of the two upper transition surfaces between the profiles and the road. The transition surfaces are continuous surface transitions that the flow can easily follow. The guiding surfaces have the task of improving the laminarity of the flow in the area close to the roadway and thus reducing the incidence of fluttering. They do not have a flow control function.

As can be seen in particular from FIG. 4, the guide surfaces run only to the highest apex, so that a part of the guide surface that is particularly important for a possible guiding function and extends beyond the apex is missing.

It is the object of the present invention to create a component of the type mentioned in the preamble of claim 1, which is simple in terms of production technology and therefore inexpensive, which is versatile and which brings about a significant improvement in the flow resistance coefficient regardless of the respective flow direction.

This object is achieved according to the invention by the features contained in claim 1.

The shape of the component itself is not changed, but rather it retains its shape, for example, for manufacturing or functional reasons. All edges of the component exposed to a possible flow are each provided with guide surfaces running along these edges, which have a profile encompassing the edges and are arranged at a distance from the component walls. These guide surfaces have the effect that the flow in the critical area of the edges is kept largely turbulence-free, so that the dead water and vortex zone in the outflow area is narrow and the resistance therefore remains relatively low.

According to a proposed embodiment, the profile of the guide surfaces is essentially evenly curved and runs approximately parallel to the wall surfaces forming the respective edge of the component. As a result, the medium flowing around the component can flow largely smoothly into the space between the component wall and the guide surface; it is constantly deflected by the uniformly curved guide surface and in turn flows largely parallel to the wall surface of the component from the space between this wall and the guide surface.

According to the invention, the guide surfaces are assigned to all edges exposed to a possible flow, and they improve the flow around these edges in the manner described.

For a conventional solid wall girder with a rectangular box profile, it is provided according to the invention that all edges of this component which are exposed to possible flow are provided with guide surfaces. Such a solid wall girder has essentially the same good resistance for all flows directed transversely to the girder axis, compared to a girder without baffles, since both the flow in the inflow area and in the outflow area is guided through baffles and vortex formation is reduced or prevented. In the case of a component with an approximately cuboid structure, for example the driver's cab of a high crane, all edges of the component which are exposed to the flow are provided with guide surfaces.

According to the invention, the profiles of the guide surfaces can be quarter-circle profiles; these are therefore particularly suitable for the cladding of edges which are formed by walls at right angles to one another. Quarter-circle profiles of this type can be produced in a particularly advantageous manner from sections of longitudinally divided tubes. Such tubes are standard components that are common in many sizes; slitting is possible in a simple and inexpensive manner with relatively simple technical facilities.

In particular if obtuse-angled or acute-angled edges are to be clad, it may be more favorable, however, to use metal or plastic extruded profiles adapted to these edge profiles to manufacture. Another possibility is to manufacture the guide surfaces as bent sheet metal parts.

According to one embodiment of the invention, the guide surfaces are fastened to the respective components via connecting struts detachably connected to the guide surfaces on the one hand and / or the components on the other hand.

Fig. 1

schematisch ein Vollwandkastenprofil mit an den vier Längskanten angeordneten, viertelkreisförmigen Leitblechen und symmetrischer Anströmung;

Fig. 2

eine Anordnung gemäß Fig. 1 mit einer demgegenüber geänderten Strömungsrichtung;

Fig. 3

schematisch ein Kastenprofil mit Leitblechen etwa gemäß den Fig. 1 und 2 in einer perspektivischen Darstellung, wobei Verbindungsstreben zum Befestigen der Leitflächen am Vollwandträger zu erkennen sind;

Fig. 4

einen Vollwandträger mit dreieckigem Kastenprofil und mit zwei an bevorzugten Kanten angeordneten Leitblechen;

Fig. 5

ein Fahrerhaus für einen Hochkran mit an den Längskanten und einzelnen Querkanten angeordneten Leitflächen.

Several embodiments of the invention are shown in the drawing and described in more detail below. Show it:

Fig. 1

schematically a solid wall box profile with quarter-circular baffles arranged on the four longitudinal edges and symmetrical flow;

Fig. 2

an arrangement according to Figure 1 with a changed flow direction.

Fig. 3

schematically a box profile with baffles approximately according to Figures 1 and 2 in a perspective view, connecting struts for attaching the baffles to the solid wall support can be seen;

Fig. 4

a solid wall girder with a triangular box profile and with two guide plates arranged on preferred edges;

Fig. 5

a driver's cab for a high crane with guide surfaces arranged on the longitudinal edges and individual transverse edges.

1 and 2 each show a carrier 2 with a rectangular box profile. The longitudinal edges 3a to 3d of the profile beam 2 are each assigned guide surfaces 4a to 4d. The guide surfaces 4a to 4d each have a quarter circle profile which comprises the associated longitudinal edges of the profile carrier 2, the end edges of the quarter circle profile each running parallel to the wall surfaces of the profile carrier 2 forming the assigned longitudinal edges.

1, a portion 6 of the flow lines runs outside the guide surfaces, which have the effect of rounded edges for these flow lines 6 and therefore form a relatively low resistance. Another part 8 of the streamlines occurs between the two flow-side guide surfaces 4a, 4b and divides into two streams 10, 12, which flow between the flow-side guide surfaces 4a, 4b and the associated wall sections of the profile support 2 and then from the flow-side guide surfaces 4c , 4d are taken up again and passed around the rear edges 3c, 3d of the profile carrier 2 in the flow direction. In the outflow zone, the streams 10, 12 combine again with the streams identified by the streamlines 6.

FIG. 2 shows the arrangement according to FIG. 1 with a modified flow directed towards an edge 3b of the profiled beam 2. Here, too, the guide surface 4b assigned to the edge 3b of the profiled beam 2 that is exposed to the flow acts like a rounded edge that divides the flow into two inner streams 14, 16 with little resistance, which are divided by the two outer guide surfaces 4a, 4c are guided with low resistance around the associated edges 3a, 3c to the outflow zone, where they reunite with the outer streams identified by the streamlines 18.

Fig. 3 shows a perspective view of a profile beam 2 with a rectangular box profile, the four longitudinal edges 3 of the profile beam 2 each having guide surfaces 4 with a quarter circle profile. The guide surfaces 4 are each connected to the walls of the profile beam 2 via connecting struts 20. The connecting struts 20 are detachably connected to the guide surfaces 4 and / or the profile support 2 in a manner known per se and therefore not shown in detail, for example by screws, so that the guide surfaces e.g. can be attached or removed even after assembly of the structure formed from the supports.

Fig. 4 shows a profile carrier 22 with a triangular box profile. The two front edges 26, 28 in the direction of flow 24 are each assigned guide surfaces 30, 32, which also include the assigned edges again in such a way that their inlet and outlet edges run parallel to the walls forming the edges 26, 28 of the profiled support 22. In this exemplary embodiment, the rear edge 34 in the direction of flow 24 has no guide surfaces, since it itself represents a shape that is favorable for the outflow. An arrangement according to FIG. 4 is suitable, for example, for carriers which are preferably exposed to a constant flow direction 24. An application example is a bridge support or the like standing in a river.

5 shows a driver's cab 36 for a high crane which is exposed to high wind speeds. Are on the four vertical longitudinal edges of the cab 36 Guide surfaces 38 are arranged which act in horizontal wind directions as described with reference to FIGS. 1 and 2. The edges delimiting the ceiling wall of the driver's cab 36 are correspondingly assigned guide surfaces 40, the edges delimiting the bottom wall guide surfaces 42.

As already described, in particular the guide surfaces assigned to rectangular edges can be produced from tube profiles quartered in the longitudinal direction.

Claims (9)

1. A box-shaped member of polygonal box profile, with guide surfaces (4a, 4b, 4c, 4d; 4; 30, 32; 38, 40, 42) which are associated at least with individual regions (3a, 3b, 3c, 3d; 3; 26, 28) and which are arranged at a spacing relative to the walls of the member, characterised in that the individual regions are all edges (3a, 3b, 3c, 3d; 3; 26, 28) of the member which are exposed to a possible oncoming flow and each of said edges which are exposed to a possible oncoming flow have associated therewith a respective guide surface (4a, 4b, 4c, 4d; 4; 30, 32; 38, 40, 42) of a profile which embraces the edge (3a, 3b, 3c, 3d; 3; 26, 28).
2. A member according to claim 1 characterised in that the profile of the guide surfaces (4) is substantially uniformly curved and terminates substantially parallel to the wall surfaces forming the respective edge (3) of the member.
3. A member according to claim 1 or claim 2, in particular a solid-wall bearer of rectangular box profile, characterised in that at least all longitudinal edges of the member (2) are provided with guide surfaces (4).
4. A member according to claim 1 or claim 2 of a substantially parallelepipedic structure, characterised in that substantially all edges of the member (36) are provided with guide surfaces (38, 40, 42).
5. A member according to one of claims 1 to 4 characterised in that the profiles of the guide surfaces (4) are quarter-circle profiles.
6. A member according to one of claims 1 to 5 characterised in that the guide surfaces (4) comprise portions of longitudinally divided tubes.
7. A member according to one of claims 1 to 5 characterised in that the guide surfaces (4; 30, 32; 38, 40, 42) are produced in the form of drawn profiles from metal or plastics material.
8. A member according to one of claims 1 to 5 characterised in that the guide surfaces (4; 30, 32; 38, 40, 42) are produced in the form of bent sheet metal pieces.
9. A member according to one of claims 1 to 8 characterised in that the guide surfaces (4) are fixed to the member (2) by way of connecting struts (20) which are connected releasably to the guide surfaces (4) and/or the members (2).

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