Road structure – process – or apparatus – Apparatus – With in situ means for both comminuting and treating – e.g.,...
Patent
1998-05-21
2000-04-18
Lillis, Eileen Dunn
Road structure, process, or apparatus
Apparatus
With in situ means for both comminuting and treating, e.g.,...
404 92, 404108, 111178, E01C 1920, A01C 1700
Patent
active
060507438
DESCRIPTION:
BRIEF SUMMARY
This invention relates to spreaders which enable soil to be treated, more particularly by spreading onto it products intended to improve its characteristics, notably its mechanical characteristics, in order, in particular, to allow other work to be carried out on top of it.
It is known that in order to construct a road or a car park, for example, it is very uncommon to be able to lay down the necessary materials directly onto the rough ground. Apart from the laying out and grading operations, it is often necessary to treat the soil by spreading onto it a product such as lime or cement and then mixing these materials with the original material of the soil. These soil treatment techniques have largely been developed in recent years. They have brought an important development to prominence, in particular in temperate, humid areas, because they enable the moisture content of soils to be corrected, for example by supplying quicklime. Furthermore, and possibly in addition to this additive, in areas where aggregates are rare it is more economical to add cement, which allows a foundation layer to be produced straight away.
Currently known materials for carrying out this type of treatment are described in particular in European patent application No. 0462899, as well as in French standard NFP98-712. By way of example, a known spreader comprises a tank which acts as a silo, extraction means enabling a hopper situated at the end of this tank to be supplied, and a metering device receiving the product from the hopper and spreading it on the soil. This assembly is integral with a supporting chassis which can be either towed or self-propelled. Rubber skirts placed around the material outlet opening allow wind effects to be limited to a greater or lesser extent.
Despite numerous attempts to improve these devices, of which the afore-mentioned French standard gives a fair summary, these machines have undergone limited development. Consequently, and in spite of these improvements, the spreading technique has a long way to go before achieving a satisfactory level of development, and the defects concerning in particular the non-uniformity of longitudinal and transverse dispersion are always present at a level which is frequently dissuasive.
Because of the change in attitudes, one drawback which is becoming increasingly important concerns the dispersal of dusts, which adversely affect the protection of the environment and the well-being of persons working on the site or living in the vicinity. This drawback is now considered so important that it frequently causes site work to stop, for example in the presence of wind, which carries the dust over fairly large distances. This dust dispersal occurs when the spreader is filled by pulsed air transfer. Moreover, during spreading, in spite of the basic protection afforded by the above-mentioned skirts, the powdery spread product often drops from an appreciable height--necessitated by the need for an adequate clearance between the outlet of this product and the ground due to irregularities in this ground. The kinetic energy accumulated during this fall by the particles is dissipated by rebounding on contact with the ground, causing a cloud of dust.
Furthermore, the mass of the product contained in the spreader has irregularities in the density, which can be large, in particular when the spreader is loaded by pulsed air transfer. The product thus contains irregularly occluded air and its grains are furthermore charged with static electricity, which increases the irregularities in the density. This effect is even more marked when the product is delivered warm, which is also frequently the case.
Moreover, the product is extracted from the silo where it is contained by mechanical processes, such as a screw or a conveyor belt, to be transported to the metering device and distributor which in the majority of cases are situated at the rear of the spreader. This causes an additional change in the density of the product by compression and/or bulking. In certain cases extraction is effected by
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Addie Raymond W.
Lillis Eileen Dunn
LandOfFree
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