SUPPORT STRUCTURE OF A COVER

Abstract

The invention relates to a support structure of a cover of a structure capable of being inserted into the ground, for example of a shaft or a channel, wherein the cover (10) comprises a traversable surface (11) and the support structure (20) extends downwards under said cover into the structure and comprises beam-shaped supports (21-23) such that their under support side (24) facing away from the surface (11) experiences a tensile stress when the surface (11) is loaded. The invention is further characterized in that between two areas (A, A) a thickness (D) of the carriers with minimum tensile stress is configured substantially symmetrically in an increasing manner up to a maximum value and then, in turn, in a decreasing manner to form a ball shape when viewing the cover from below.

Claims

1-5. (canceled)

6. A support structure of a cover, wherein the cover comprises a traversable surface and the support structure extends downwards under the cover into a structure, and the support structure comprises beam-shaped supports such that a lower support side of the beam-shaped supports facing away from the traversable surface is subject to a tensile stress when a load is applied to the traversable surface, wherein between two areas (A, A) a thickness (D) of the beam-shaped supports is configured substantially symmetrically in an increasing manner up to a maximum value and then, in a decreasing manner, and the beam-shaped supports are configured to form a spherical shape at the bottom of the cover.

7. The support structure according to claim 1, the cover is formed as an integral cast part.

8. The support structure according to claim 2, the cover is a spherulitic cast iron part.

9. The support structure according to claim 1, the beam-shaped supports having side surfaces diverging towards the traversable surface and forming draft angles.

10. A process for dimensioning a support structure according to claim 1, the process comprising the steps of: a first thickness of the beam-shaped supports for bearing a predetermined load is determined by assuming a constant thickness over the length of the beam-shaped support; a second thickness of the beam-shaped supports in the areas of minimum tensile stress is determined for bearing the predetermined load based on a constant thickness over the length of the beam shaped support; and a maximum thickness of the beam-shaped supports is determined based on an increasing thickness from the second thickness to the first thickness and based on a decreasing thickness back to the second thickness.

Description

[0013] Below, two exemplary embodiments of the invention are explained in detail. In the figures:

[0014] FIG. 1 shows a plan view of a cover,

[0015] FIG. 2 shows a view along the line II-II of FIG. 1,

[0016] FIG. 3 shows a bottom view of the cover of FIGS. 1 and 2,

[0017] FIG. 4 shows an enlarged view of area IV in FIG. 3, and

[0018] FIG. 5 shows a plan view of a cover grating for a drainage channel designed according to the invention.

[0019] In the following description, the same reference numerals are used for identical and identically acting parts.

[0020] FIGS. 1-3 show a manhole cover made of ductile iron. This manhole cover comprises a support structure 20, which consists of eight radially extending supports 21, extending from an outer edge of the cover 10 inwards by an amount that is shorter than the radius. The height of the supports 21 risesas can be seen particularly in FIG. 2from the outer edge towards the inside and are interconnected at their inner ends by eight supports 23, arranged in a regular octagon. When a load acts vertically from above on the (built-in) cover 10, the inner supports 22 bear largely purely tensile loads transferred by the supports 21, in particular from their (in the installed state) bottom sides to the bottom sides 24 of the supports 22.

[0021] The relatively lowest tension acts on the supports 22 in the areas A, A, which are adjacent to the coupling areas at the ends of the supports 22. In a central area M between the areas A, A, the supports 21 now have a greater thickness D than in the areas A, A, adjacent to the ends of the supports 22. The side surfaces 25, 26 of the supports 21 (and also of the supports 22) have a uniform inclination angle relative to the vertical plane (or the plane perpendicular to the surface 11). Furthermore, corresponding radii are obviously provided in the transition areas to the plane forming the surface 11.

[0022] The same design principle is also used in the channel cover of FIG. 5. Again, supports 23 are provided, extending between side bearings 27, 27, which rest on an upper edge of a channel (or its frame). Slots 12 through which surface water can flow into a channel beneath the cover 10 are provided between the supports 23. The sphericity, i.e. the increased thickness D of the supports 23 in the center between the side bearings 27, 27, is magnified in FIG. 5. Again, the thickness D of the supports 23 increasing towards a central area M can once more be combined with an increased height of the supports 23, that is, a dimension perpendicular to the plane of the drawing in FIG. 5 and to the surface 11 of the cover 10.

[0023] For dimensioning the supporting structure 20, first the required thickness D of the supports 21 for a specified load of the cover 10 (largely perpendicular to the surface 11) is determined with the proviso that the support 21 has a constant thickness D. Then the load present in the areas A, A, i.e. in the area of the transitions to the radial supports 22 is determined, from which in turn the necessary thickness of a support (of constant thickness) is derived. Finally, a transition between the two thicknesses that is as uniform and crack-free as possible is derived. This results in material savings in the areas which do not have to have maximum thickness, a procedure that results in surprisingly substantial material savings.

LIST OF THE REFERENCE NUMERALS

[0024] 10 cover [0025] 11 surface [0026] 12 slot [0027] 20 supporting structure [0028] 21 support [0029] 22 support [0030] 23 support [0031] 24 bottom side of the support [0032] 25, 26 side surface of the support [0033] 27, 27 side bearing