Fluid sprinkling – spraying – and diffusing – Processes – Including mixing or combining with air – gas or steam
Patent
1998-10-19
2000-05-23
Weldon, Kevin
Fluid sprinkling, spraying, and diffusing
Processes
Including mixing or combining with air, gas or steam
239412, 239434, 239571, B05B 714
Patent
active
060656859
DESCRIPTION:
BRIEF SUMMARY
This invention relates to spray nozzles, and more particularly those for use in the spraying of cementitious compositions such as concrete.
Spray nozzles for the purpose of applying cementitious compositions such as shotcrete, usually include a means of injecting a liquid into the composition. In the so-called "dry process" wherein a dry spraying mixture is conveyed to the nozzle, the liquid consists mainly of water, often with admixtures such as accelerators dissolved or dispersed therein. In the "wet process" wherein a wet mixture (with water already added) is conveyed to the nozzle, the liquid is generally a solution or dispersion of admixtures. This liquid injection is generally effected by a liquid supply pipe which injects liquid into the composition via a port in the nozzle. The amount of liquid to be added may be varied by means of a valve in the supply pipe. In such a case, the operation of the valve changes the injection pressure of liquid being supplied which varies the velocity of injection of the liquid while the cross section of the port remains the same, thus changing the depth of penetration of the liquid in the composition stream passing through the nozzle. This disturbs the homogenity of the composition as soon as the injection pressure is no longer high enough to moisten the composition homogeneously.
This problem is well known and a solution thereto has long been sought. One proposed apparatus comprises an annular port, the gap width of which can be changed only when the nozzle is dismantled, i.e. before the initial operation. A change of the gap width therefore involves a long interruption of the operation, so that neither fluctuations in the composition of the concrete, nor fluctuations of the liquid pressure can be balanced as soon as would be desirable.
A further development is represented by a construction with several ports, the outflow cross section of which may be adjusted externally during operation. This construction has its advantages, but also has disadvantages, one of which being the fact that the operator of the unit has to adjust the cross section of the port to provide the amount of liquid desired, which action requires a great deal of concentration during work as well as experience in operating such units. A still further disadvantage is the fact that the ports easily become clogged, thus changing the outflow velocity of the other ports due to the pressure increase, and as a result the whole unit has to be dismantled in order to clean the ports. A further disadvantage of this is that, since this unit only has a few ports of adjustable cross section, the composition flow is not continuously radially moistened and is therefore not homogeneous.
Another known spray nozzle comprises two coaxial tubes, one fixed and the other movable but resiliently urged against the first. The supply of liquid for injection into a sprayable composition forces the movable tube away from the fixed tube, thus defining an annular duct through which the liquid can enter the sprayable composition. As the pressure increases, so does the width of the duct, thus guaranteeing an almost constant outflow velocity. However, such a nozzle is complicated with many components, and it is expensive and too impractical to be generally acceptable. It has now been found that it is possible to make a spray nozzle which is substantially free from the disadvantages of the art. The invention therefore provides a spray nozzle of the type adapted to feed a liquid to a material being sprayed therefrom, which nozzle comprises a tubular spray conduit around the circumference of which, in a plane perpendicular to the direction of flow of the material, is disposed an annular liquid feed port which is fed from a pipe feed via an annular reservoir which surrounds the tubular spray conduit in the vicinity of the feed port, characterised in that the feed port is closed in a liquid-tight manner by resilient material openable by liquid pressure and whose degree of opening, and therefore the quantity of liquid fed to the material
REFERENCES:
patent: 2690901 (1954-10-01), McCormack
patent: 4093124 (1978-06-01), Morane et al.
patent: 4667884 (1987-05-01), Braziel
Database WPI, AN 94-239508, XP002031055 Copy of PCT International Search Report for PCT/EP97/05325 dated Jan. 15, 1998.
MBT Holding AG
O'Hanlon Sean P.
Weldon Kevin
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