Road structure – process – or apparatus – Pavement – Modules or blocks
Patent
1996-12-06
1999-07-13
Lisehora, James
Road structure, process, or apparatus
Pavement
Modules or blocks
404 42, E01C 506
Patent
active
059217057
DESCRIPTION:
BRIEF SUMMARY
The invention relates to blocks which are used principally in the paving of surfaces, for example the surfaces of roads, pavements, driveways and courtyards and in particular to the paving of surfaces subjected to high forces. The invention also relates to clusters of blocks and to blocks for use in the clusters.
Paving, consisting of a plurality of surfacing blocks, should be able to withstand large forces acting upon it. Forces to be withstood include both those caused when heavy loads are placed directly on the paving and those caused by turning loads, for example a turning vehicle. Usually the paving is laid as individual blocks on a bed of sand with joints between the blocks filled with sand or other suitable filling material. On loading, the blocks are able to move small amounts relative to other blocks thereby decreasing the risk of cracking of the blocks. However, blocks laid in that way may be displaced vertically under loading or may creep horizontally under traffic due to the sandfilled joints.
There are improved paving blocks having interlocking surfaces. The interlocking projections and recesses which help to provide "lock up" between blocks, allow an array of blocks to perform as a united load-bearing surface resisting both vertical and horizontal movement of the blocks. The term "lock up" is used for the purpose of this specification to describe a condition in which blocks in the paving become progressively wedged together when the paving is under traffic or subjected to loads thereby increasing the stiffness of the paving. However, in some cases in which the blocks are subjected to large loads, the "lock up" together with other factors have been found to be insufficient to avoid failure of the paving. Failure may take the form of areas of the paving sinking or of blocks creeping horizontally by an undue amount.
It is therefore an object of the invention to provide a block which mitigates the above problems.
According to the invention, there is provided a surfacing block having upper and lower surfaces bounded by walls extending between the surfaces wherein the surfaces are of a generally cruciform shape having four arms each of which extend in a direction substantially parallel to the lower surface and substantially perpendicular to two of the other arms of the block, wherein the block has around the boundary of its surface projections and/or recesses for interlocking engagement with recesses and/or projections of a neighbouring block.
The cruciform blocks have been found to have improved resistance to movement when laid from that of, for example, a rectangular block having a similar distribution of projections and recesses. The arms of the cruciform block stabilise the block and if, for example, a heavy load is exerted unevenly on the block there is increased resistance to lifting compared with a known block since, if an arm of the block begins to lift from the ground, the opposite arm is forced to interlock further with adjacent blocks thus hindering further movement of the block. Resistance to movement of the block, in the form of rotation about an axis perpendicular to the surfaces, is increased when the block is interlocked with other blocks due to the projections and recesses on the arms of the cruciform interlocking with projections and recesses of adjacent blocks and hindering such motion.
Advantageously, the projections and recesses extend through the entire thickness of the block so that the shape of the upper surface is substantially the same as the shape of the lower surface.
Advantageously, the shape of the blocks is such that a number of identical blocks as defined above can be laid with their upper surface uppermost such that there is a substantially constant spacing between the walls of adjacent blocks. In that way, a continuous surface may be formed with each block interlocking with an adjacent block thereby forming a substantially united load-bearing surface.
Advantageously, all of the arms of the cruciform are of substantially the same length. While it is envisaged that b
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patent: 5251997 (1993-10-01), Brock
patent: 5449245 (1995-09-01), Glickman
patent: 5645369 (1997-07-01), Geiger
SYMETRY brochure, Interpave Corporation, Cincinnatti, Ohio. (1989).
Hodson Christopher Douglas
Hodson Douglas Basil
Lisehora James
U.P.S. Limited
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