Guard grid for a passageway

Abstract

A guard grid is used as protection in a ventilating shaft and similar passageways in structures with a considerable wall thickness, and the guard grid is particularly useful in nuclear power stations. In the passageway direction, the guard grid is divided into a number of grid-like members one following the other. The grid-like member on the outside of the structure has crossbars extending between opposite sides of the passageway and spacer bars extending perpendicularly to the crossbars. The crossbars and spacer bars form a honeycomb-like structure with a dimension in the direction of the passageway equal at least to the dimension of the spacer bars extending transversely of the passageway direction. An intermediate grid-like member is located next to the inner end of the outside grid-like member and it is made up of a curved framework formed of a number of parallel upwardly bent cross-members, the ends of the cross-members closer to the inside end of the passageway are spaced upwardly from the ends closer to the outside of the passageway. The curvature of the cross-members blocks the direct path of view through the passageway between the inside and the outside. The inside grid-like member is made up of a number of cross-plates with a row of spacer struts extending between each adjacent pair of cross plates. The cross plates and spacer struts form another honeycomb-like structure.