Patent Grant
7220457
1. Field of the Invention
The present invention relates generally to a spray head air atomizing assembly and more specifically to an air atomizing assembly to control the flow of atomizing air in a fluid spray or other delivery device such as an air sprayer for spraying paints, adhesives, coatings, and other semi-liquid materials. The invention also relates to a method and system of spraying or applying such materials by using the atomizing air or air stream as a vehicle for delivering catalyst, an agent, moisture or other component to the application fluid and of conditioning the application fluid.
2. Description of the Prior Art
Two common types of spray or delivery devices exist for spraying or delivering a fluid to a substrate. One such device is a so-called airless type sprayer or delivery device in which an application fluid is forced through one or more nozzle openings at high pressure. With this type of device, the fluid is atomized or disbursed into tiny droplets as a result of the pressurized fluid passing through the nozzle opening.
A second such device is an air or air atomized spray gun or delivery device in which the application fluid passes through a nozzle orifice, at pressures usually much lower than the pressures employed with airless spraying, in combination with atomizing air flowing through a plurality of air orifices surrounding the nozzle opening. The atomizing air functions to atomize or disperse the application fluid after its exit from the nozzle opening.
While many of the air atomizing assemblies of the prior art are generally acceptable when being used to atomize relatively low viscosity materials such as paint which , because of their physical characteristics, are broken up and atomized easily, the performance of such assemblies is limited and less than satisfactory when used to atomize high viscosity materials (in excess of about 3,000 centipoises) and materials which have a high surface tension such as epoxies, urethanes, polyureas and other adhesives. These high viscosity and high surface tension materials are difficult to atomize and thus tend to “string” a lot as the application material travels from the spray nozzle to the substrate.
Further, in prior art air atomizing sprayers or application systems, the atomizing air has been used primarily as a means to atomize or disperse the application fluid, with the introduction of secondary reaction components or other agents, catalysts and components being accomplished via other conventional means.
Accordingly, there is a need in the art for an improved air atomizing assembly, and more particularly a need for an air atomizing nozzle assembly which provides improved atomization of both conventional low viscosity materials such as paints as well as materials which have a relatively high viscosity and/or a high surface tension such as adhesives and the like. There is also need in the art for improved methods and systems of conditioning the application fluid and introducing and mixing secondary reaction components, agents and catalysts with the application fluid.
The present invention provides an improved spray head and air atomizing assembly which overcomes many of the limitations of the prior art. This atomizing assembly is applicable to conventional low viscosity materials such as paint, but is particularly applicable to atomizing materials which have a relatively high viscosity and a high surface tension such as adhesives.
In general, the air atomizing assembly in accordance with the present invention may be used with a conventional air sprayer or other application device having a nozzle opening. Such air sprayer or application device may be provided with an application fluid supply tube or conduit for a single component material or with an elongated mixing tube for a two component material. In one embodiment, the air atomizing assembly of the present invention includes an air atomizing tip which has a generally outer conical or frustoconical surface that converges in the direction of the nozzle opening and a corresponding atomizing assembly cap which includes an inner conical or frustoconical surface that mates with a portion of the exterior conical or frustoconical surface of the atomizing tip. One of these conical or frustoconical surfaces is provided with a plurality of atomizing air flow paths or grooves which spiral along such surface as it converges. When the atomizing tip and cap are assembled so that their respective conical or frustoconical surfaces mate with one another, a plurality of air passages defined by the grooves are formed between the respective conical or frustoconical surfaces. The cross-sectional configuration of these air passages as they exit from the atomizing assembly have a generally flattened configuration and most preferably, a configuration in which the circumferential dimension of the passages is at least about twice the depth or radial dimension of such passages. Because of the generally flat shape of the air passages at the exit end of the assembly, the airflow has a shear effect on the exiting application fluid. This shear effect tends to break up and shear portions of the application fluid from adjacent portions and results in significantly improved atomization of the application fluid. This is particularly true for materials having a high viscosity and/or high surface tension.
In a further embodiment, the nozzle assembly includes means in combination with the above atomizing assembly or other atomizing assemblies for breaking up the stream of applied material prior to atomization to provide for more thorough atomization and to facilitate higher flow rates. In the preferred embodiment, this means includes providing a diverter orifice or other structure within the application fluid flow stream and/or providing a portion of the atomizing air within the application fluid flow stream itself.
In a still further embodiment, the atomizing tip and atomizing cap have exterior and interior mating surfaces, respectively, which are provided with surfaces of other than conical or frustoconical configurations to shape or control the spray pattern of the application fluid. One such other shaped surface comprises, in cross section, an elliptical configuration or a generally flattened configuration with radiused ends to provide a wider spray pattern.
The method aspect of the present invention includes utilizing the atomizing air in a conventional air atomizing sprayer or application device, or in an air atomizing sprayer or application device as described above, to provide a curing agent such as moisture, a catalyst or a secondary reaction component to the application material or to condition the application fluid. Such a method is particularly applicable to one part or two part materials which are moisture cured or which require other curing catalysts or agents. In such an application, the present invention involves introducing such moisture or other catalyst or agent as part of the atomizing air stream. Preferably, a quantity of such moisture, catalyst or agent is provided to sufficiently cure the application fluid.
A further aspect of the method in accordance with the present invention is to condition the application fluid by heating or cooling the atomizing air stream for the purpose of controlling the viscosity and/or the cure rate of the application fluid.
Details of the above and other embodiments of the apparatus and method in accordance with the present invention will become apparent with reference to the drawings, the description of the preferred embodiment and method and the appended claims.
One aspect of the present invention relates generally to a spray head and an air atomizing assembly incorporated therein. As will be described in greater detail below, the spray head of the present invention may be used with an application fluid mixing assembly which in turn is designed for use with an application fluid spray or delivery device such as an air atomized paint sprayer or an air atomized spray or application device. Such sprayers or other application devices are used to deliver application fluids such as paints, adhesives, sealants, semi-liquids and the like, to a substrate. In describing this aspect of the present invention, the preferred embodiment will be described with respect to an air atomized paint or other application fluid sprayer.
A further aspect of the present invention relates to a method of spraying and more specifically to a method of spraying which utilizes the atomizing air or air stream as a vehicle for providing the application fluid with a curing agent, a curing catalyst, a reaction component or other secondary material or to condition the application fluid such as by heating or cooling the atomizing air to better control the viscosity, cure rates and/or other characteristics of the application fluid. The method aspect of the present invention is usable with the specific air atomizing assembly of the present invention as well as conventional air atomizing spraying and application assemblies of the prior and future art.
A further aspect of the present invention relates to a means for breaking up the stream of applied material prior to being atomized. This aspect of the invention is also used with the specific preferred atomizing assembly of the invention as well as conventional atomizing assemblies.
Both the method and apparatus aspects of the present invention have applicability to the deliverance of both single component materials as well as two or multiple component materials to a substrate. Two or multiple component materials are commonly applied through a mixing tube or the like to thoroughly mix the components prior to application. In contrast, thorough mixing is generally not required for single component materials which are commonly cured with moisture, light or other means. Thus no mixing tube is required for single component materials, although such materials can be applied through a mixing tube, if desired. The preferred embodiment for the embodiment of
In the description of the present invention, terms such as forward end or rearward end may be used to describe surfaces or ends of particular elements of the invention. Accordingly, unless otherwise stated, the forward end of an element as used herein shall be considered as the end facing or closest to the nozzle outlet end of the mixer assembly, while the rearward end of an element will be considered as the end or portion of an element which faces or is closest to the pressurized fluid inlet end of the mixer assembly.
With reference first to
The mixer tube 12 is an elongated tubular member having an exterior cylindrical surface 28 with dimensions approximating those of the inner cylindrical opening 20. The mixer tube 12 also includes a rearwardly positioned annular surface portion 29 and a frustoconically configured exterior surface portion 27. The forward end of the tube 12 includes a narrowed, nozzle end 31 and an application fluid nozzle opening or orifice 30.
The interior of the tube 12 is generally hollow, except for internal baffle means 32 which causes the application fluid to flow in a turbulent circuitous path from its rearward end to the forward end of the nozzle opening 30. The mixer tube 12 is designed to be positioned within the mixer body so that the outer cylindrical surface 28 engages the inner cylindrical surface of the opening 20 and so that the outer frustoconical surface 27 seats against the inner frustoconical surface 24. Mixing tubes of the type illustrated in
Although these elements can be constructed from conventional materials such as stainless steel, brass and other metals, they may also be constructed via injection molding or the like from various plastics such as nylon, polyethylene, polypropylene or various ultra high molecular weight (UHMW) materials. This is particularly true for elements of the atomizing assembly such as the tip 16 and the cap 18.
The air atomizer assembly which is comprised of the air nozzle body 15, the mixer or atomizing tip 16, the air atomizing cap 18 and the retaining nut 19 is illustrated in exploded or combined form in
With specific reference to
The interior of the mixer tip 16 as shown by the broken lines in
With continuing reference to
A feature of the preferred embodiment of the present invention is that the cross-sectional configuration of the recess 42 or the groove 40 as measured at the forward end 34 has a generally flat configuration in which the circumferential dimension “cd” is greater than the radial dimension “rd”. More preferably, the circumferential dimension “cd” is at least twice the radial dimension “rd” and most preferably the circumferential dimension “cd” is at least three times the radial dimension “rd”. In the embodiment shown in
In addition to the cross-sectional configuration of the recess 42 shown in
The air atomizing cap 18 is shown best in
As shown best in
When the air atomizing cap 18 is assembled in operational position with the mixer tip 16 as shown in
Because the angle which the frustoconical surface portion 58 forms with the axis 13 is significantly larger than the angle “B”, the surface portion 58 and surface 59 are spaced outwardly from the corresponding area of the surface portion 36 of the tip 16 (
The rearward end 55 of the atomizing cap 18 is generally annular and is perpendicular to the axis 13. When the device of the present invention is assembled, the surface 55 seats against the forward end of the air nozzle body 15 as described below. The exterior surface of the atomizing cap 18 is provided with a retaining shoulder 60 which mates with corresponding structure of the retaining nut 19 to retain the atomizing cap 18 in an assembled position relative to the air nozzle body 15 and thus the mixture body 11.
The air nozzle body 15 which is shown generally in
The retaining nut 19 (
When assembled in this manner as shown best in
As application fluid or material is discharged through the nozzle tip 30 from a pressurized source, the flat, converging and spiraling streams of atomizing fluid contact the discharged application fluid stream and dispenses or atomizes the stream into tiny droplets. Although applicant does not wish to be bound by any particular theory, it is believed that because of the generally flat shape or configuration of the atomizing air flow streams as they exit the atomizing nozzle assembly, the application fluid stream is subjected to shear forces and thus provides more thorough and complete atomization, particularly for fluids which are highly viscous and/or exhibit a high tensile strength. Preferably, the circumferential dimension “cd” of the recesses 42 (and thus passageways 43) at the forward end of the tip 16 is greater than the radial dimension “rd”, more preferably twice as great and most preferably about three times as great.
A further embodiment of a spray head and mixer assembly is shown in
The nut 76 is a retaining nut which includes a rearward cylindrical portion 81 having a diametrical dimension approximating or slightly larger than the exterior diameter of the tube 12. Immediately forward of the portion 81 is an interior surface designed to seat against a retaining member in the form of the O-ring grommet 78. The forward end of the nut 76 includes internal threads for connection to the air cap assembly 77.
The O-ring grommet 78 is slipped onto the mixing tube 12 after the nuts 75 and 76 have been slipped on and preferably has an internal diameter slightly smaller than that of the tube 12. When applied to the tube 12, the grommet 78 has sufficient stiffness and there is sufficient friction between the grommet 78 and the tube 12 to retain the nut 76 when tightened against the air cap assembly 77. If needed or desired, a second O-ring grommet or other retaining member can be provided. The grommet 78 or other retaining member is preferably selectively removable from the tube 12 and functions to retain the nut for the purpose intended.
The embodiment of
The air cap assembly 77 includes inner conical surfaces 86 and 88 similar to the conical surfaces 56 and 58 of
When connected with the mixer tube 12, the nut 76 and the assembly 77 define an atomizing air chamber 92 to provide atomizing air to the passages between the tip 16 and the conical surfaces 86 and 88. This embodiment provides a spray head construction in which the body 11 can be eliminated and in which the atomizing assembly comprised of the nut 76, the assembly 77 and the tip 16 can be easily changed for cleaning or for replacement or the like. Further, all of the air atomizing components of the embodiment of
In addition to the air atomizing assembly of the preferred embodiment and related equipment illustrated in
In the embodiment of
The present invention contemplates, however, that such grooves could be formed either in the outer frustoconical surface of the atomizing tip or the inner frustoconical surface of the atomizing cap and that the surfaces in which the grooves are formed could comprise configurations other than conical or frustoconical and that the grooves could be straight, spiraled or curved and could be of a variety of configurations. For example, the grooves that define the atomizing air channel could be straight, non-spiraled grooves and could be formed in surfaces that are not conical or frustoconical. Further, unlike the embodiment of
Further, although the preferred embodiment shows the outer and inner surfaces of the tip and cap as frustoconical, there is no requirement that such surfaces be limited to that shape. As described below with respect to
Thus, a feature of the present invention can be characterized as comprising a first atomizing member having an outer surface portion and a second atomizing member having an inner surface portion of a size and configuration substantially matching that of the outer surface portion, with one of the inner and outer surface portions having a plurality of grooves extending from its rearward end toward its forward end to define passageways or flow channels when such surfaces are assembled into engagement with one another.
The embodiment of
In the embodiment of
The flow channels 100 of
In general, the shape of the outer and inner surfaces of the first and second atomizing members in accordance with the present invention can assume a variety of shapes and configurations. Preferably, however, such inner and outer surfaces should preferably have complimentary dimensions and configurations for a length at least equal to the diameter of the nozzle opening. Further, such inner and outer surfaces should preferably have a cross-sectional configuration similar to the shape of the orifice. Specifically, if the orifice is elongated, the cross-sectional configuration of the inner and the outer surfaces should be elongated.
In certain spray application environments, the flow stream of the application fluid is relatively large due to the nature of the application fluid itself or the desire to increase the efficiency of the application process, among others. Such large flow streams, particularly flow streams of high viscosity fluids or high surface tension fluids such as epoxies, urethanes, polyureas and other adhesives, are difficult to spray or break up with atomizing air alone and often require relatively large application pressures. In many spray environments, this necessarily limits the maximum flow rate of fluid that can be satisfactorily atomized and applied and the equipment with which such fluid can be satisfactorily applied.
In the embodiment of
In
Thus, a further feature of the present invention includes means in the form of a flow breakup member positioned within the application flow stream and preferably at or near the orifice opening, but anywhere upstream of such opening, for breaking up the flow stream into smaller, more easily atomized flow streams. In some cases, particularly with the embodiment of
In
The method aspect of the present invention relates to a method of utilizing the atomizing air as a vehicle for introducing a curing agent, catalyst or other component into the application fluid or to otherwise condition the application fluid.
Many application fluids, and in particular adhesives and other high viscosity and high surface tension materials, are moisture cured. For example, most one-part silicon adhesives and most one-part urethane adhesives are moisture cured. This means that the presence of moisture in contact with the application fluid initiates the curing process. In the current art, it is common to apply the application fluid to a substrate and then apply moisture to the surface thereof to initiate the curing process. This has drawbacks, however, in that the moisture is not thoroughly mixed with the applied fluid and a skin comprised of cured application fluid tends to form on the surface of the applied fluid. However, by introducing moisture into the atomizing air, such moisture becomes thoroughly mixed with the application fluid, resulting in more complete and uniform curing. Introduction of moisture into the atomizing air also eliminates the extra step of applying the moisture to the substrate after application of the fluid.
Further, some resin systems require a curing catalyst or agent other than moisture to initiate the curing process. In accordance with the present invention, such curing catalysts or other agents can also be introduced via the atomizing air stream. This thoroughly mixes the catalyst or other agent with the application fluid and initiates the curing process immediately upon application.
Still further, for two-part application fluid systems, the atomizing air stream can be used to introduce and mix one part or component of the system with the other part or component of the system which is applied through the nozzle outlet.
A still further method in accordance with the present invention is to utilize the atomizing air to condition the application fluid. For example, in some application fluid systems, the viscosity of the application fluid and the cure rate of the application fluid can be controlled by controlling the temperature of the application fluid. This is commonly done by providing heating and/or cooling means in the application fluid supply line to heat the fluid to the desired temperature. In accordance with the present invention, however, the atomizing air is heated or cooled. This results in corresponding heating or cooling of the application fluid during atomization, thereby providing a means for controlling the viscosity and/or cure rate of the application fluid.
The system for performing the method aspect of the present invention described above is shown in
Such system also includes an inline heater/cooler means 115 for selectively heating or cooling the atomizing gas or fluid in the line 116 to a desired temperature. Thus, via the heater/cooler means 115, the atomizing gas or fluid can be conditioned to the desired temperature to thereby control the viscosity and/or the rate of cure of the application fluid. Appropriate control means 113 may be included in the system of
Although the description of the preferred embodiment has been quite specific, it is contemplated that various modifications could be made without deviating from the spirit of the present invention. Accordingly, it is intended that the scope of the present application be dictated by the appended claims rather than by the description of the preferred embodiment.
This application is a continuation-in-part of U.S. patent application Ser. No. 10/164,738 filed Jun. 6, 2002 now U.S. Pat. No. 6,951,310.
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| Number | Date | Country | |
|---|---|---|---|
| 20050023376 A1 | Feb 2005 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10164738 | Jun 2002 | US |
| Child | 10881014 | US |
