Static structures (e.g. – buildings) – Openwork; e.g. – truss – trellis – grille – screen – frame – or... – Three-dimensional space-defining
Patent
1991-02-26
1993-12-14
Friedman, Carl D.
Static structures (e.g., buildings)
Openwork; e.g., truss, trellis, grille, screen, frame, or...
Three-dimensional space-defining
526532, 52680, 52686, E04H 1200
Patent
active
052691136
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a spacer suited for being embedded in concrete, for use with wire reinforcements placed in the walls of concrete pipes cast in molds, wherein radially projecting mounting elements for connecting the basic body with the wire reinforcement are provided on one side of a basic body, the radially opposite other side of the basic body being equipped with a spacer element projecting in radially opposite direction relative to the mounting element and terminating by an inclined surface which extends substantially in axial direction for assisting the sliding movement when mounting the mold.
A spacer of the type described above has been known from U.S. Pat. No. 4,741,143. The spacer disclosed by this publication serves for securing a reinforcing cage inside a cylindrical hole at a certain distance from the walls of the hole, which is to be filled completely with casting concrete, for the production of a solid column.
The side of the spacer where the latter is to be joined with the wire reinforcement displays mounting elements in the form of projecting wires which must be wound around the wire reinforcement for establishing the connection. The wall of the hole which is to be filled with casting concrete practically constitutes the mold for the solid cylindrical block to be produced. In order to enable the reinforcing cage, with the spacers fixed thereon, to be introduced in the axial direction and in well-centered relationship into the cylindrical opening to be filled with the casting concrete, the side of the spacer opposite the wire mounting elements is equipped with an oblique surface which extends in the axial direction and which is intended to facilitate the sliding movement.
However, it is a drawback of the spacer of the type described above that handling is extremely arduous, i.e. that mounting the spacer on the reinforcement is extremely time-consuming. The reason is that the wires have to be bent around the reinforcing bars and to be joined with the latter by twisting. The spacer as such consists of concrete in which the mounting elements are embedded. In spite of the oblique sliding surface provided, it cannot be excluded that gripping or jamming may occur between the relatively rough concrete material and a rough mold material, which may then lead to parts breaking off the spacer. In addition, a spacer of this type is not capable of resisting stresses in the circumferential direction. In the case of heavy circumferential stresses it cannot be excluded that the spacer may tilt laterally so that it can no longer guarantee the correct spacing in the radial direction, even if it may perhaps be caught by the reinforcement.
However, the described kind of stress, i.e. a force component acting in the circumferential direction, in fact is encountered in the production of cast concrete pipes. The mold used for such concrete pipes consists of an outer cylindrical mold and an inner central core which two elements define between them an annular space which is then filled with concrete. In contrast to the process of casting solid columns, where the concrete can be introduced centrally and where the poured concrete rises slowly, thus producing predominantly radial flow phenomena, pouring concrete into an annular cylindrical space gives rise also to a circumferential flow component. This is so because when concrete is poured at one point into the hollow mold of a concrete pipe, the concrete spreads uniformly in a substantially circumferential direction. The required spreading motion and compacting of the concrete is assisted by the use of vibrators, with the result that the wire reinforcement is likewise set into vibrating movement. This gives rise to forces acting in the circumferential direction which tend to displace the reinforcing cage in the circumferential direction, relative to the mold. In the presence of such stresses, a spacer of the type described above would tilt laterally so that there would be a risk of the reinforcement being embedded in the pipe in non-coaxial alignment.
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Friedman Carl D.
Mai Lan M.
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