Fluid sprinkling – spraying – and diffusing – With selectively preset flow cutoff or initiating means – By programming means
Patent
1995-01-19
1997-06-03
Morris, Lesley D.
Fluid sprinkling, spraying, and diffusing
With selectively preset flow cutoff or initiating means
By programming means
239301, B05B 130
Patent
active
056345933
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to the production of a spray of atomized particles and subsequently to imparting direction to the spray, and might find application in the production of either a layer or coating on a substrate, billet, tube or irregular section article.
The usual procedure is to atomize a stream of liquid by means of a high pressure gas to form a stream of atomized droplets that is directed onto a substrate or former, but it is also possible, especially with metals, to use wire or powder as the feedstock for producing a stream of droplets.
A wide range of such processes and materials have been proposed, but the process has been applied particularly advantageously to the sprayforming of metals. This process was devised in 1968 and has the capability of making a wide range of semi-finished products having improved properties. The products comprise plate, sheet and strip e.g. of high silicon steel, hollow and solid billets, tubes and rings as well as laminated products and matrix composites. In order to produce the particular shapes required it is usually necessary to move the substrate or former in an appropriate manner and at the same time to deflect the stream of atomized particles. The latter procedure is particularly important in ensuring that the process is operated with the highest efficiency with the lowest possible overspray and that the product is as near as possible to the final shape required.
We have found that the most efficient and reliable way of deflecting the stream of atomized particles is by pneumatic means i.e. using a secondary stream or streams of gas, usually inert gas, to deflect the primary atomized spray causing it to assume the required position. This procedure is herein referred to as `scanning`. Ways of carrying out this procedure are described in GB 1455862 and GB 2129249.
Turning firstly to the external programming of pneumatic scanning atomizers embodying rotary valves for programming.
SUMMARY OF THE INVENTION
The function of pneumatic scanning atomizers generally is to vary gas flow cyclically through a set of fixed scanning nozzles facing in a direction inclined downward and towards the axis of a metal stream contained within a stream of gas, known as the atomizing gas. Deflection can occur before, during or after atomization. In practical pneumatic scanning atomizers the angle of deflection is often varied during each cycle by restricting the flow of deflecting (or scanning) gas to a degree depending on the position of the rotor of a rotary valve. A periodic function relating scanning gas flow (and consequently deflection angle) to rotor position provides a preset program. It has been found possible with our earlier designs of scanning atomizers to use preset programs, to control two variable, namely the areas of the several constrictions which successively restrict gas flow during each cycle, and the fractions of cycle time for which each of these constrictions is operative. Convenient methods for generating precise preset programs using rotary valves are described in our International Patent Application No. PCT/GB92/01128.
Two alternative arrangements of gas path have been used in our earlier devices, to both of which arrangements the present invention can be applied. FIG. 15 of the accompanying drawings shows the first of these in diagrammatic form. It is a serial arrangement in which the rotor short-circuits parts of a chain of constrictions, depending on the magnitude of the gas flow required at different parts of the cycle. FIG. 16 of the accompanying drawings shows an alternative arrangement in which the rotor selects alternative paths also depending on the gas flow required at different points in the cycle. This is called the parallel system. It is important to note that in both cases there is a unique relationship between scanning gas flow and rotor position.
It has been found possible to relate mathematically the thickness profiles formed by a pneumatic scanning atomizer with the fractions of cycle time when successive constr
REFERENCES:
patent: 4064295 (1977-12-01), Singer
Gordon David P.
Morris Lesley D.
Sprayforming Developments Ltd.
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