Fluid sprinkling – spraying – and diffusing – Processes – Including mixing or combining with air – gas or steam
Reexamination Certificate
2001-08-27
2004-11-30
Ganey, Steven J. (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Processes
Including mixing or combining with air, gas or steam
C239S011000, C239S290000, C239S296000, C239S300000, C239S413000, C239S422000, C239S526000
Reexamination Certificate
active
06824071
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to plural component spray-up manufacturing methods and apparatus, and more particularly to methods and apparatus for the application of gel-coat to molds and preforms.
BACKGROUND OF THE INVENTION
Plural component spraying systems are used in manufacturing plastic articles by applying resinous materials to a mold or preform for an article. In such systems, a liquid resin and a catalyst for the resin are mixed and directed to a substrate where the catalyst and resin react and harden to form the article. For example, in manufacturing articles with polyester resin, a catalyzing agent for the polyester resin is mixed with the resin; and the resin-catalyst mixture is applied to the substrate. In internal mix systems, the resin and catalyst are mixed within the spraying apparatus, and the mixture is directed by a nozzle onto the substrate. In external mix systems, the resin and catalyst are mixed externally of the apparatus and directed onto the substrate.
Many “plastic” articles, such as boat hulls, shower stalls, bathroom sinks and other shell-like articles of manufacture, are formed from liquid plural component materials, including a liquid polymer resin and a catalyst that converts the liquid polymer resin to a solid state. The manufacture of such articles is frequently performed by the “spray-up” method, that is, by directing a flow of the catalyzed liquid plural component material at a mold or preform for the article to provide an initially liquid coating that subsequently hardens in the form of the article. To provide strength and toughness to the article, reinforcing fibers, preferably glass, are combined with the catalyzed liquid plural component material as one or more layers of the catalyzed liquid plural component material are applied to the mold or preform. Curing and hardening of the catalyzed plural component material with the incorporated reinforcing fibers forms a more durable plastic article.
Because many such articles, for example, boat hulls, must have an attractive outer surface to provide a saleable article, a common method of providing such an attractive outer surface is to provide the mold or preform with a smooth polished surface and to apply, as the first step of the spray-up method in manufacturing the article, a liquid catalyzed plural component “gel coat” material. Gel coat materials are expensive and include catalyzable polymer resins and constituents such as pigments and particulate fillers that can cure on the smooth, polished surface of a mold or preform and provide, as the outer surface of the resulting article, an attractive, smooth, polished and colored, if desired, layer that hides the underlying layered reinforcing structure of the article.
Because the smooth, polished surface of the mold or preform forms the outer surface of the article, it is not necessary that the liquid plural component gel-coat material, or for that matter, the plural component materials used to form the structural layer of the article, be finely atomized, or formed into small particles, for deposition on the mold or preform. In such spray-up operations, and particularly in gel-coat operations, the formation of a uniform coating on the mold or preform is of the most importance, and it is desirable that the liquid gel-coat material be deposited uniformly, regardless of the particulate nature of the gel-coat material being deposited on the mold or preform.
In some spray-up systems, large quantities of pressurized air are used to atomize the liquid components. Such systems are expensive to operate and have a number of operational inadequacies. It is expensive to compress air, and the large quantities of compressed air used by existing systems impose a significant operating cost on the system. In addition, the blast of compressed air used to atomize the liquid components carries a significant quantity of spray particles away from the substrate, wastes the expensive resin and catalyst, creates an unclean spray area and sometimes requires over-spray collection systems, and can contribute to the problem of operating such manufacturing operations safely. Furthermore, the use of large quantities of air during operation of the system can create an undesirable spread of fumes.
In order to overcome some of the inadequacies attending the use of pressurized air to atomize components dispensed from a spraying apparatus, spraying systems have been developed which incorporate airless application techniques.
In prior airless application devices, an airless nozzle has been used to atomize liquid materials which are pumped at high pressure, that is, pressures generally exceeding 300-500 p.s.i. The most commonly used airless nozzle includes an internal, hemispherical passage termination, which is cut through by an external, V-shaped groove to form an elongated, elliptical-like orifice. Liquid material pumped at high pressures through such a spray nozzle is forced by the hemispherical termination of the passageway to converge in its flow at and through the elongated orifice. Because of the converging flow at the orifice, the liquid material is expelled through the orifice into a substantially planar, expanding, fan-like film with stream-like edges, forming particles, which are carried by their momentum to the article target. Such fan-like films, because they are formed by the convergence of the fluid, include heavy streams at their expanding edges, which are referred to as “tails.” Because of the heavy stream-like flow in the “tails,” the deposited layer of liquid formed by these edge portions of the expanding, fan-like film includes a disproportionate quantity of resin and produces a non-uniform deposit with stripes when the spray pattern is swept across a substrate by a gun operator, as shown in FIG.
10
. The non-uniform deposit and resulting stripes make the blending of deposited material into a film of uniform thickness difficult and can lead to a wasteful, excessively thick gel-coat layer.
Compressed air has also been used to solve the problem of tails created by airless spray nozzles. See, for example, U.S. Pat. Nos. 3,202,363; 3,521,824; 3,635,400; 3,843,052; 4,386,739 and 4,967,956.
Nevertheless, a need remains for an inexpensive, conveniently controllable means for uniform gel-coat application to molds and preforms.
SUMMARY OF THE INVENTION
The invention provides an apparatus and method by which a spray-up operator may conveniently control the application of a gel-coat material to a mold or preform to achieve a uniform coating.
Systems of the invention include a first source of gel-coat resin, a second source of catalyst for the gel-coat resin, means for delivering gel-coat resin and catalyst from the first and second sources to an application means, and air delivery means to provide a flow of compressed air to the application means, wherein the application means comprises a mixer for gel-coat resin and catalyst, and a manipulatable nozzle and air control assembly including a liquid nozzle for forming the catalyzed gel-coat material into a fan-like film with substantially flat faces and expanding stream-like edges extending from a liquid orifice, and an air nozzle assembly for directing independently controllable flows of compressed air at the substantially flat faces and at the expanding stream-like edges of the fan-like film.
Apparatus of the invention include an application means manipulated by a workman, such as the apparatus commonly referred to as a “spray gun,” comprising, as its forward end, a nozzle and air control assembly including a liquid nozzle forming the liquid coating material into an expanding fan-like film having opposed, generally flat faces between expanding stream-like edges, an air nozzle assembly carrying the liquid dispensing nozzle and including a pair of compressed air nozzles for directing an expanded flow of compressed air at each of the opposed, generally flat faces of the expanding fan-like film of coating material and a pair of air outlets for directing jets of compressed air at the expanding, stream-like edg
Brinks Hofer Gilson & Lione
Ganey Steven J.
Glas-Craft, Inc.
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