Multiple component in-line paint mixing system

Details Multiple component in-line paint mixing system Multiple component in-line paint mixing system

1999-04-23

2001-03-20

Walker, W. L. (Department: 1723)

Agitating

With flushing of mixing chamber

C366S152100, C366S160100, C366S182400

Reexamination Certificate

active

06203183

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to mixing systems, and more particularly, to paint mixing systems for producing relatively small industrial quantities of paint from two or more paint subcomponents.
BACKGROUND OF THE INVENTION
Known aircraft paint mixing methods include the batch method and the in-line method. In the batch method, containers of cure (catalyst), flow (reducer), and base (resin) are prepared separately and then poured into a large container where they are manually stirred. After an induction waiting period, required for some paint systems, the paint is transported to the point-of-use where it is sprayed using hand-held pressurized spray guns. The containers are rinsed with solvent, left to dry, and then disposed of as waste.
In the in-line method, mixing is limited to two subcomponents. Separate lines of base and cure are fed into a small mixing container. Prior to reaching the mixing container, each paint subcomponent passes through an adjustable valve (e.g., a needle valve or a pneumatic valve) its own flow meter. A control system tracks the flow and adjusts the valves as needed to ensure the proper mix ratio. The mixing container mixes the subcomponents by passing the fluid through a static baffling or other torturous path. After the subcomponents are mixed in the container, the paint travels along an output line to a spray gun, as in the batch method.
In the aircraft industry, both current batch and in-line mixing methods have disadvantages. In the batch method, any unused material must be properly disposed of according to government regulations. The waste therefore adds unnecessary expense to the cost of producing a painted plane and to the environment. In the current in-line method, the flow meter and adjustable valves must be both extremely accurate and responsive in order to ensure a proper mix ratio of the fluid components. Such equipment tends to be mechanically complex and expensive. The extra mechanisms required for each component line also make the current in-line systems expensive. Extra solvent is needed to flush the additional parts during cleanup, which further increases the system's total waste. In addition, current in-line systems are generally designed to mix only two components. Popular polyurethane/epoxy aircraft formulations, however, often consist of three components (base, flow, and cure). Thus, it is necessary to batch mix two of the three components (i.e., the flow and cure), and then add the third component (base) in-line—a system that therefore suffers the disadvantages of both methods.
Thus, a need exists for an improved system of mixing two, three and even four fluid subcomponents (in particular, paint subcomponents) which is capable of producing a paint of a proper ratio on demand and without having to overmix the amount for a particular job. The ideal system would preferably consistently yield a product with less than about ±2% error in mix ratio error, and would be capable of mixing two or more subcomponents in-line without the need for batch mixing. Such an ideal system would receive the benefit of reduced costs of material supplies, reduced waste to the environment, and reduced need for cleanup solvent. The present invention is directed to such an ideal system.
SUMMARY OF THE INVENTION
The present invention in-line mixing system is provided for mixing multiple fluid subcomponents, and particularly, for mixing paints having two or more fluid subcomponents. An in-line mixing system formed in accordance with the present invention includes multiple subcomponent input lines. Each line includes a valve having open and closed positions for allowing and prohibiting the flow of subcomponent through the input line. The mixing system further includes a reducing manifold including multiple input passages. One subcomponent input line is connected to each manifold input passage. The multiple input passages converge to form a single output passage. A flow meter is in communication with the manifold output passage and measures the flow of subcomponent through the output passage. During use, a slugwise line of subcomponents is formed by alternatingly opening and closing the input line valves. Mixing components connect to the output of the flow meter to combine the slugwise subcomponents into paint.
In accordance with other aspects of this invention, the preferred flow meter is a positive displacement gear-type flow meter. The mixing components preferably include an integrator connected to the output of the flow meter and a static mixer connected to the output of the integrator. A paint output line is connected between the static mixer and a spray gun. The paint within the output line may be optionally pressurized by an output pressure pump. The mixing system preferably further includes a control system having a controller in communication with the flow meter and the input line valves. The input line valves are switched between their open and closed positions by the controller. The control system monitors the flow meter, determines the amount of each subcomponent, and switches the valves accordingly to result in the appropriate subcomponent mix ratio. Where the input line valves are solenoid valves, the controller is capable of electrically switching the solenoid valves between their open and closed positions. A computer is provided for user interface in operating the control system.
In accordance with further aspects of the invention, one preferred embodiment of the mixing system includes three subcomponent input lines, with each line including a solenoid valve. The reducing manifold includes three input passages. One subcomponent input line is connected to each input passage, the input passages intersecting to form a single output passage. A flow meter is in communication with the manifold output. The output of the flow meter is connected to an integrator where partial mixing of the subcomponents occurs. The system further includes a static mixer that is connected to the integrator output. The static mixer more thoroughly mixes the components. The solenoid valves, manifold, flow meter, integrator, and static mixer are located in a first compartment of a housing.
In accordance with still other aspects of the invention, the first preferred embodiment further includes a check valve connected between each solenoid valve and the manifold. A control system is provided and includes a controller located in a second compartment of the housing. The second compartment is positively pressurized by an air purge unit. The amount of pressurization is in the range of about 0.6 inches of water to about 4 inches of water.
In accordance with still further aspects of this invention, a unique integrator is provided for use in mixing paint fluid subcomponents. The integrator includes a sealed container having an input port and an output port, an influent tube positioned within the container and connected to the input port, and an exfluent tube positioned within the container and connected to the output port. Both the influent and exfluent tubes include a series of longitudinal holes and one in the closed end of each. The sealed container is pressurized according to the supply pump outputs. To accommodate the pressure increase in fluid flowing along the influent tube to its closed end, the influent holes preferably decrease in size in going from the input port to the influent tube closed end. Likewise, the exfluent holes preferably increase in size in going from the output port to the exfluent tube closed end. Both the influent and exfluent holes decrease and increase nonlinearly in size, respectively. The integrator is sized to hold about ~250 cc of fluid.
In accordance with yet other aspects of this invention, a method of mixing paint from multiple paint fluid subcomponents is provided. The method includes forming a line of unmixed subcomponent slugs using a reducing manifold. The manifold includes multiple input passages that converge to form a single output passage. A single flow meter is in communication with the manifold outpu

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