Abstract:
The present disclosure relates generally to spray systems and, more particularly, to industrial spray coating systems for applying coatings of paint, stain, and the like. Specifically, the disclosed embodiments relate to a spray gun an air cap configured to produce air swirl. For example, in an embodiment, a system is provided that includes a spray coating device. The spray coating device has a liquid passage extending to a liquid outlet configured to output a liquid flow and an air passage extending to a plurality of air outlets configured to output an air flow. The plurality of air outlets is angled to swirl the air flow.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/435,737 entitled “HIGH SWIRL AIR CAP,” filed on Jan. 24, 2011, which is herein incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present system and techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     The invention relates generally to spray systems and, more particularly, to industrial spray coating systems for applying coatings of paint, stain, and the like. Spray coating devices are used to apply a spray coating to a wide variety of product types and materials, such as wood and metal. The spray coating fluids used for each different industrial application may have much different fluid characteristics and desired coating properties. For example, wood coating fluids (e.g., stains) are generally viscous fluids, which may have significant particulate/ligaments throughout the fluid. Existing spray coating devices, such as air atomizing spray guns, are often unable to breakup such particulate/ligaments to produce a desired coating. That is, the spray coatings that result from insufficient atomization usually have an undesirably inconsistent appearance, which may be characterized by mottling and various other inconsistencies in textures, colors, and overall appearance. 
     BRIEF DESCRIPTION 
     The present embodiments may provide improved atomization in spray devices to reduce the incidence of such undesirable particulates and/or ligaments. For example, in one embodiment, a system is provided that includes a spray coating device. The spray coating device has a liquid passage extending to a liquid outlet configured to output a liquid flow, and an air passage extending to a plurality of air outlets configured to output an air flow. The plurality of air outlets is angled to swirl the air flow. 
     In another embodiment, a system is provided with a spray head component having a plurality of air outlets. The plurality of air outlets has a plurality of air flow axes, wherein the plurality of air outlets is configured to output an air flow along the plurality of air flow axes. The plurality of air outlets is arranged at least partially around a liquid flow axis, and the plurality of air outlets is angled inwardly toward the liquid flow axis without intersecting the liquid flow axis. 
     In a further embodiment, a system is provided with a spray head component having a central surface with a central opening configured to allow output of a liquid flow along a liquid flow axis. The spray head component also includes a plurality of air atomization outlets disposed about the central opening along the central surface, and a first air horn protruding from the central surface at a first offset distance from the central opening. The first air horn has a first inner surface that curves circumferentially about the liquid flow axis, and the first inner surface has at least one first air shaping outlet. The spray head component also includes a second air horn protruding from the central surface at a second offset distance from the central opening. The second air horn includes a second inner surface that curves circumferentially about the liquid flow axis, and the second inner surface has at least one second air shaping outlet. 
    
    
     
       DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a plan view of an embodiment of a spray coating device having a spray head component configured to create air swirl for fluid atomization; 
         FIG. 2  is a cross-sectional side view of the spray coating device of  FIG. 1  illustrating various features for creating and shaping a spray coating; 
         FIG. 3  is a partial cross-sectional side view of an embodiment of the spray head component of  FIGS. 1 and 2  taken within line  3 - 3 ; 
         FIG. 4  is an exploded perspective view of an embodiment of the spray head component of  FIGS. 1-3  and separately illustrating embodiments of an air cap, a nozzle, and a pintle assembly of the spray head component; 
         FIG. 5  is a front axial view of an embodiment of a front face of the air cap taken along line  5 - 5  of  FIG. 3 , illustrating an air swirl created by a plurality of angled openings of the face; 
         FIG. 6  is a front axial view of the air cap taken along line  6 - 6  of  FIG. 3 ; 
         FIG. 7  is a partial cross-sectional view of an embodiment of an air horn of the spray head component taken along line  7 - 7  of  FIG. 4 ; 
         FIG. 8  is a partial cross-sectional view of another embodiment of an air horn of the spray head component taken along line  7 - 7  of  FIG. 4 ; 
         FIG. 9  is a cross-sectional side view of the spray coating device of  FIG. 1  illustrating an embodiment of an air cap having a removable liquid nozzle; and 
         FIG. 10  is an exploded perspective view of an embodiment of the spray head component of  FIGS. 1 and 9  and separately illustrating embodiments of an air cap, a nozzle, and a fluid seat of the spray head component. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
       FIG. 1  illustrates an embodiment of a spray coating device  10  that may incorporate various spray-shaping and atomization features in accordance with the presently contemplated embodiments. In the illustrated embodiment, the device  10  includes a spray head component  12  coupled to a body  14  of the spray coating device  10 . The spray head component  12  generally includes features for creating swirl in an air flow, as represented by arrows  16 . The swirled air flow  16  includes a first directional swirl  18  and a second directional swirl  20 . The first directional swirl  18  and the second directional flow  20  may be created by a plurality of angled orifices of the spray head component  12 , as will be discussed in detail below with respect to  FIGS. 2-6 . The first directional swirl  18  is created to improve atomization of a liquid flow  22  that is ejected from the spray coating device  10  along a liquid flow axis  24 . The first directional swirl  18  may induce some amount of swirling of the liquid flow  22 , which may cause a conical or vortical-shaped fluid ejection that diverges from the liquid flow axis  24 . To compensate for such induced swirl, and to create a regular spray shape, the second directional swirl  20 , which rotates in an opposing relationship to the first swirl direction  18  with respect to the liquid flow axis  24 , flattens the ejected fluid into a flat spray pattern. 
     It should be noted that the spray head component  12  in accordance with the present embodiments is presented in the context of a combination with the spray coating device  10  to facilitate discussion, and that the discussion of the spray coating device  10  and its components is not intended to limit the scope of the present approaches to air swirling to facilitate fluid atomization and spray shaping. Indeed, the spray head component  12  is combinable with a wide variety of spray coating devices including less than or more features than those presently disclosed. Therefore, keeping the operation of the spray head component  12  in mind, the spray coating device  10  also includes features that facilitate handling and spray triggering by a user, interface with various fluid sources (e.g., paint, water, lacquer, or other liquid coating sources, air sources, and so forth), fluid pressure adjustment, and storage, to name a few. 
     Specifically, in the illustrated embodiment, the spray coating device  10  includes a handle  26  to facilitate use of the spray coating device  10  by a user. The handle  26  is configured to allow gripping by the user&#39;s hand, and is disposed proximate a trigger  28  to allow the user to grip and trigger the spray coating device  10  as needed. The trigger  28  is generally configured to allow the liquid flow  22  to be ejected from the device  10  and also to allow air to flow through the spray head component  12  to form the swirled air flow  16 . As an example, the trigger  28  may be coupled to one or more valves that are internal to the spray coating device  10 , as will be discussed in further detail with respect to  FIG. 2 . The trigger  28  is coupled to the body  14  of the device  10  at a pivot joint  30 , which hinges the trigger  28  to allow rotational movement when the user pulls the trigger  28  towards the handle  26  and when the trigger  28  is released. 
     As noted above, the device  10  also includes a liquid adjustment assembly  32  for adjusting liquid flow through the device  10  and an air adjustment assembly  34  for adjusting air flow through the device  10 . The liquid adjustment assembly  32  may be coupled to the body  14  of the device  10  by a suitable connection, such as a press-fit, an interference fit, a snap fit, threads, and so on. The liquid adjustment assembly  32 , as illustrated, may include a fluid valve adjuster  36  that is configured to move a fluid needle valve  38  between positions to vary fluid flow within the body  14  of the device  10 . Similarly, the air adjustment assembly  34  may be coupled to the body  14  via press-fit, an interference fit, a snap fit, threads, and so on. The air adjustment assembly  34  also includes an air valve adjuster  40  that is configured to move an air needle between positions to vary an air flow through the body  14  of the device  10 , as will be discussed in further detail below with respect to  FIG. 2 . The device  10  also includes a fluid inlet coupling  42  for receiving liquid from a liquid source, as well as an air inlet coupling  44  for receiving air (e.g., compressed air) from an air source. When not in use or between sprayings, the device  10  may be stored (e.g., hung) using hook  46 . 
       FIG. 2  is a cross-sectional side view of the spray coating device  10  illustrating various internal features that result in the production of the swirled air flow  16  and the liquid flow  22  that is atomized by the swirled air flow  16 . As illustrated, the spray coating device  10  includes the spray head component  12  coupled to the body  14 . The spray head component  12  includes a fluid delivery tip assembly  50 , which may be removably inserted into a receptacle  52 . For example, a plurality of different types of spray coating devices may be configured to receive and use the fluid delivery tip assembly  50 . The spray head component  12  also includes a spray formation assembly  54  coupled to the fluid delivery tip assembly  50 . The illustrated spray formation assembly  54  includes an air atomization cap  56 , which in some embodiments may be removably secured to the body  14  of the device  10  via a threaded retaining nut  58 . In other embodiments, the air atomization cap  56  may be secured to the body  14  via a snap fit, an interference fit, a press fit, bolts, clamps, and so forth. 
     The air atomization cap  56  includes a plurality of air outlets  60  disposed in a curved arrangement about the liquid flow axis  24 . The plurality of air outlets  60  are generally configured to atomize and/or shape the spray exiting the spray coating device  10 . The plurality of air outlets  60  includes a first plurality of air outlets  62  and a second plurality of air outlets  64 . The first plurality of air outlets  62  are configured to create the first directional swirl  18  ( FIG. 1 ) to atomize the liquid flow  22  as the device  10  is activated (e.g., triggered). Embodiments of the first plurality of air outlets  62  are discussed in further detail below. The second plurality of air outlets  64  are disposed on air horns  66  that extend away from the body  14  of the spray coating device  14  and diverge away the liquid flow axis  24 . While the illustrated embodiment depicts the device  10  as including two air horns  66 , it should be noted that the number of air horns  66  may be increased or decreased, as will be discussed in further detail with respect to  FIG. 4 . In accordance with presently contemplated embodiments, the second plurality of air outlets  64  are configured to generate the second directional swirl  20  discussed above with respect to  FIG. 1 . The spray formation assembly  54  also may include other atomization mechanisms to provide a desired spray pattern and droplet distribution. 
     The body  14  of the spray coating device  12  includes a variety of controls and supply mechanisms for the spray head component  12 . As illustrated, the body  14  includes a fluid delivery assembly  68  having a fluid passage  70  extending from the fluid inlet coupling  42  to the fluid delivery tip assembly  50 . The fluid delivery assembly  68  also includes a fluid valve assembly  72  to control fluid flow through the fluid passage  70  and to the fluid delivery tip assembly  50 . The illustrated fluid valve assembly  72  includes the fluid needle valve  38  extending movably through the body  14  between the fluid delivery tip assembly  50  and the fluid valve adjuster  36 . The fluid needle valve  38  includes a tip portion  74  that protrudes into a removable nozzle and pintle assembly  76 . As will be discussed in further detail below, the nozzle and pintle assembly  76  includes features that, in conjunction with the tip portion  74 , control the flow of liquid through the fluid tip delivery assembly  50 . The fluid valve adjuster  36  is rotatably adjustable against a spring  78  disposed between a rear section  80  of the fluid needle valve  72  and an internal portion  82  of the fluid valve adjuster  36 . The fluid needle valve  72  is also coupled to the trigger  28 , such that the fluid needle valve  72  may be moved inwardly away from the fluid delivery tip assembly  50  as the trigger  28  is rotated in a first direction  84  (e.g., counterclockwise with respect to  FIG. 2 ) about the pivot joint  30 . However, any suitable inwardly or outwardly openable valve assembly may be used within the scope of the presently contemplated embodiments. The fluid valve assembly  72  also may include a variety of packing and seal assemblies, such as packing assembly  86 , disposed between the fluid needle valve  72  and the body  14 . 
     An air supply assembly  88  is also disposed in the body  14  to facilitate atomization at the spray formation assembly  54 . The illustrated air supply assembly  88  extends from the air inlet coupling  44  to the air atomization cap  56  via air passages  90  and  92 . The air supply assembly  88  also includes a variety of seal assemblies, air valve assemblies, and air valve adjusters to maintain and regulate the air pressure and flow through the spray coating device  12 . For example, the illustrated air supply assembly  88  includes an air valve assembly  94  coupled to the trigger  28 , such that rotation of the trigger  28  about the pivot joint  30  (e.g., in the first direction  84 ) opens the air valve assembly  94  to allow air flow from the air passage  90  to the air passage  92 . The air supply assembly  88  also includes the air valve adjustor  40  coupled to an air needle  96 , such that the needle  96  is movable via rotation of the air valve adjustor  40  to regulate the air flow to the air atomization cap  56 . As illustrated, the trigger  28  is coupled to both the fluid valve assembly  72  and the air valve assembly  88 , such that fluid and air flow in concert to the spray head component  12  as the trigger  28  is pulled toward the handle  26  of the body  14 . The air and the liquid (e.g., liquid paint or other coating) may flow through the body  14  substantially simultaneously, or one fluid may flow through the body  14  prior to the flow of the other fluid, for example using timing features incorporated into the trigger  28 . For example, in one embodiment, the fluid may begin flowing through the body  14  prior to the flow of air. Indeed, any timing configuration of the trigger  28  may be utilized in accordance with the disclosed embodiments. As discussed in detail below, once engaged (e.g., triggered), the spray coating device  12  produces an atomized spray with a desired spray pattern and droplet distribution. Again, the illustrated spray coating device  12 , as discussed herein, is provided as one embodiment of the disclosed air swirl features. Any suitable type or configuration of a spraying device may benefit from providing an atomizing and/or spray shaping air swirl in accordance with the presently contemplated embodiments. 
       FIG. 3  is a partial cross-sectional side view of an embodiment of the spray head component of  FIGS. 1 and 2  taken within line  3 - 3 . In particular,  FIG. 3  illustrates various features of the spray head component  12  that are configured to produce an atomizing and spray-shaping air swirl. As illustrated, the needle  96  of the air supply assembly  88  ( FIG. 2 ) and the fluid needle valve  38  of the fluid valve assembly  72  are both partially open, such that air and fluid passes through the spray head component  12  to generate an atomized spray. Specifically, turning first to the features of the air supply assembly  88 , the air flows through an air passage  110  about the needle  96  as indicated by arrow  112 . The air then flows through the body  14  and into a central air passage  114  that diverges to a first set of air passages  116  and a second set of air passages  118  that lead to the first plurality of air holes  62  and the second plurality of air holes  64 , respectively. The air then exits the first and second plurality of air holes  62 ,  64  to generate at least a first air flow, as depicted by arrows  120 , exiting the first plurality of air holes  62 , and a second air flow, depicted by arrows  122  exiting the second plurality of air holes  64 . In accordance with certain embodiments, the first air flow  120  generates the first directional air swirl  18  and the second air flow  122  generates the second directional air swirl  20 . The first directional swirl  18 , and thus the first air flow  120 , impinges on the liquid flow  22  radially inward and toward the liquid flow axis  24  at a first angle  121 . As an example, the first angle  121  may be between about 1° and about 65° relative to the axis  24  (e.g., 1°, 5°, 10°, 25°, 45°, 50°, 55°, or 65° from the axis  24 ) with respect to the oncoming liquid flow  22 . However, as discussed below, the first plurality of air holes  62  direct the first plurality of air flows  120  at an offset form the liquid flow axis  24  to generate the first directional swirl  18 . This results in swirling and atomization of the liquid flow  22  exiting the air atomization cap  56  (i.e., external to the spray coating device  10 ) to generate an atomized coating spray  124 . Because the first plurality of air holes  62  are angled so as to not intersect the liquid flow axis  24 , the atomized coating spray  124  may not be entirely flat (i.e., may be swirled). The second directional swirl  20 , and thus the second air flow  122 , impinges on the atomized coating spray  124  at a second angle  123  with respect to the liquid flow axis  24 . It should be noted that in some embodiments, the first and second angles  121 ,  123  may be the same, while in other embodiments, the first and second angles  121 ,  123  may be different. For example, the second angle  123  may be between about 1° and about 85° relative to and offset from the liquid flow axis  24  (e.g., 1°, 5°, 10°, 25°, 45°, 50°, 55°, 65°, 75°, or 85° from the axis  24 ) with respect to the oncoming atomized coating spray  124 . The second air flow  122  generates a flat coating spray  126 , as noted above, by swirling the second directional air flow  20  in an opposing relationship to the first swirled air flow  18 . However, in other embodiments, the second directional air flow  20  may be oriented in the same general direction as the first swirled air flow  18 . In some embodiments, the second air flow  122  may also provide further atomization of the atomized coating spray  124 . 
     Turning to the fluid flow through the device  10 , the fluid delivery tip assembly  50  includes the nozzle and pintle assembly  76 , which includes a sleeve  130  (e.g., a nozzle) disposed about a central member or pintle  132 . The illustrated pintle  132  includes a central fluid passage or preliminary chamber  134 , which leads to one or more restricted passageways or supply holes  136 . These supply holes  136  can have a variety of geometries, angles, numbers, and configurations (e.g., symmetrical or non-symmetrical) to adjust the velocity, direction, and flow rate of the fluid flowing through the fluid delivery tip assembly  50 . For example, in certain embodiments, the pintle  132  may have the supply holes  136  disposed symmetrically about the liquid flow axis  24 . In operation, when the needle valve  38  is open (i.e., the tip  74  is retracted away from an inner surface  137  of the nozzle and pintle assembly  76 ), a desired fluid (e.g., paint) flows through fluid passage  70 , about the needle valve  38  of the fluid valve assembly  72 , as indicated by arrows  138 . The fluid then flows into the central fluid passage or preliminary chamber  134  of the pintle  132 . As indicated by arrow  138 , the supply holes  136  then direct the fluid flow from the preliminary chamber  134  into a secondary chamber or throat  140 , which is defined as the space between a forward tip section  142  of the pintle  132  and an inner surface  144  of the sleeve  130 . The fluid flow  22  then exits the body  14  of the device  10  via a fluid tip exit  146  (e.g., a liquid outlet) of the nozzle and pintle assembly  76  along the fluid flow axis  24 . 
     In some embodiments, the sleeve  130  and the pintle  132  may have a configuration that results in a geometry of the throat  140  that diverges and converges toward the fluid tip exit  146 . During operation of such embodiments, these diverging and converging flow pathways may induce fluid mixing and breakup prior to air atomization and shaping by the air flows  120  and  122 . For example, successive diverging and converging flow passages can induce velocity changes in the fluid flow, thereby inducing fluid mixing, turbulence, and breakup of particulate that may be present in the liquid. Moreover, the fluid dynamics (e.g., viscosity, particulate concentration, and so on) of a given liquid may at least partially influence the particular configuration of the nozzle and pintle assembly  76 . Accordingly, the nozzle and pintle assembly  76  in accordance with presently contemplated embodiments is swappable (i.e., removable and replaceable) with other assemblies having differing sizes, shapes, and/or extents of the holes  136  and/or throat  140  to suit a particular coating application. 
       FIG. 4  is an exploded perspective view of an embodiment of the spray head component of  FIGS. 1-3  and separately illustrating various components of the spray head component  12 . Specifically, the air cap  56  configured to produce the air swirls, the sleeve  130 , and the pintle  132  are illustrated as separated along the liquid flow axis  24 . In accordance with presently contemplated embodiments, the air cap  56  and the nozzle and pintle assembly  76  may be removable from the body  14  of the device  10  without special tools or equipment due to their facile manipulation with widely available tools (e.g., wrenches or pliers). Alternatively, in some embodiments, the air cap  56  and/or the nozzle and pintle assembly  76  may be removed by hand. Accordingly, the illustration of  FIG. 4  depicts the separation of the components of the nozzle and pintle assembly  76  from the air cap  56  that may occur during cleaning or replacement operations. The air cap  56 , which is removable in addition to the nozzle and pintle assembly  76 , includes a central opening  150  oriented coaxially with the liquid outlet  146  of the sleeve  130 . This allows the liquid flow  22  to exit the device proximate and central to the plurality of first air holes  62  to facilitate atomization. In this way, the air flow is not collinear with the liquid flow, but rather impinges the liquid flow from a plurality of discrete locations (e.g., air holes  62  and  64 ) for atomization and spray shaping. The pintle  132  is illustrated as connected to a rear portion  152  of the spray head component  12 , and has the forward tip section  142  aligned coaxially with the liquid outlet  146  of the sleeve  130  and the central opening  150  of the air cap  56 . 
     The pintle  132 , as noted above, includes the plurality of orifices  136  and the forward tip portion  142  that interfaces with the liquid outlet  146  of the sleeve  130 , both of which allow liquid to flow through the nozzle and pintle assembly  76  and out of the device  10  in a controlled manner. In the illustrated embodiment, the liquid outlet  146  is a circular opening, as opposed to an ellipsoidal opening (e.g., a cat-eye opening). However, the use of a cat-eye opening as the liquid outlet  146  is also contemplated herein. Additionally, the pintle  132  includes a rear section  154  having a nozzle portion  156  extending through at least a part of the body  14  of the device  10 . The nozzle portion  156  is also removable from the body  14 , for example, by pulling on the nozzle portion  156  in a direction away from the body  14 . The rear section  154  also includes a plurality of air holes  158  that direct air towards the first plurality of air holes  62  of the air cap  56 . 
     The sleeve  130 , as illustrated, includes a first cylindrical section  160 , a tapered section  162 , and a second cylindrical section  164 . The first cylindrical section  160  is generally configured to receive the nozzle portion  156  of the pintle  132 , for example to secure the pintle  132  within the air cap  56  and/or the body  14  of the spray coating device  10 . The first cylindrical section  160  tapers to the second cylindrical section  164  via the tapered section  162 , which generally has a frusto-conical shape to reduce the inner diameter of the sleeve  130  to form a suitable size for the throat  140 , which, as noted above, is defined as the cavity between the sleeve  130  (i.e., the second cylindrical section  164 ) and the forward tip portion  142  of the pintle  132  when the nozzle and pintle assembly  76  is assembled. 
     As noted above, the air cap  56  includes a plurality of air holes, specifically a first plurality of air holes  62  configured to produce the first directional air swirl  18 , and a second plurality of air holes  64  disposed on air horns  66 , the second plurality of air holes  64  being configured to produce the second directional air swirl  20 . Specifically, in the illustrated embodiment, the air cap  56  includes a first air horn  166  and a second air horn  168  protruding away from the body  14  of the device  10  and having respective second pluralities of air holes  64 . The first air horn  166  and the second air horn  168  are disposed at opposite diametrical extents of the air cap  56  and face one another. Specifically, the first air horn  166  includes a first inner surface  170  (e.g., a concave surface) that curves circumferentially about the liquid flow axis  24  of the central opening  150 , which may be considered the liquid opening of the air cap  56 . Similarly, the second air horn  168  includes a second inner surface  172  (e.g., a concave surface) that curves circumferentially about the liquid flow axis  24  of the central opening  150 . The second plurality of air outlets  64  is disposed on the curved first and second inner surfaces  170 ,  172 . In accordance with certain presently contemplated embodiments, the curved geometry of the first and second inner surfaces  170 ,  172  may facilitate interaction with and/or flattening of the swirling, atomized coating spray  124 . For example, the curved surfaces  170 ,  172  help direct the second directional air swirl  20  radially inward towards the atomized coating spray  124  and against the first directional air swirl  18 . 
     The second plurality of air outlets  64  may be any size and/or shape to the extent that they are disposed on the respective inner surfaces of the air horns  66 . As will be appreciated with respect to the illustrated embodiment, the second plurality of air outlets  64  are angled relative to one another as a result of the concave shape of the surfaces on which they are disposed. However, as will be described in further detail with respect to  FIG. 6 , each of the second plurality of air outlets  64  may be angled non-perpendicular relative to its respective surface and/or the liquid flow axis  24 . In other words, the air flow  122  ( FIG. 3 ) is not normal to the surface at each of the air outlets  64 . In this way, each of the second plurality of air outlets  64  is angled with respect to the direction of the atomized coating spray  124  (i.e., the liquid flow axis  24 ), as well as angled relative to their respective surfaces. As an example, the air outlets  64  may be angled by between about 1° and about 85° relative to and offset from the liquid flow axis  24  (e.g., 1°, 5°, 10°, 25°, 45°, 50°, 55°, 65°, 75°, or 85° from their respective surfaces and relative to the liquid flow axis  24 ). As such each of the second plurality of air outlets  64  may be considered as having a compound angular geometry. 
     In a similar manner to the second plurality of air outlets  64 , the first plurality of air outlets  62  each have a compound angular geometry, and are disposed on a central surface  174  of the air cap  56 . That is, each of the first plurality of air outlets  62  are angled relative to their respective surfaces as well as angled relative to the liquid flow axis  24 . As an example, the air outlets  64  may be angled by between about 1° and about 85° relative to and offset from the liquid flow axis  24  (e.g., 1°, 5°, 10°, 25°, 45°, 50°, 55°, 65°, 75°, or 85° from their respective surfaces and relative to the liquid flow axis  24 ). The compound angular geometry of the first plurality of air outlets  62 , in accordance with present embodiments, creates a swirling action of atomizing air, which facilitates particulate breakup as well as homogenization of the liquid flow  22  exiting the device  10 .  FIG. 5  is a front axial view of an embodiment of the front surface  174  of the air cap  56  taken along line  5 - 5  of  FIG. 3 . 
     In the illustrated embodiment, the first plurality of air outlets  62  has a plurality of air flow axes, represented generally as arrows  180 . The first plurality of air outlets  62 , as noted above, are each configured to output an air flow along their respective air flow axes  180 . In the illustrated embodiment, the first plurality of air outlets  62  is arranged symmetrically and circumferentially about the liquid flow axis  24  such that the first plurality of air outlets  62  completely surround the central opening  150  of the air cap  56 . In other embodiments, the first plurality of air outlets  62  may be arranged partially about the liquid flow axis  24 . In other words, the first plurality of air outlets  62  may or may not completely surround the central opening  150 . In accordance with certain presently contemplated embodiments, the first plurality of air outlets  62  is angled radially inward toward the liquid flow axis  24  without intersecting the liquid flow axis  24 . 
     For example, the respective air flow axes  180  of the first plurality of air outlets  62  do not align with the center of the central opening  150 , which corresponds to the liquid flow axis  24 . In this way, the air flow axes  180  each do not bisect the central opening  150 . Indeed, to allow the first plurality of air outlets  62  to swirl air, and therefore the liquid flow  22 , each of the first plurality of air outlets  62  is offset at an angle  182  from a radius  184  of the central opening  150 . The respective angles  182  of each of the first plurality of air outlets  62  may be the same, or may be different, and may vary between about 1° and 25° offset from radii aligning the liquid flow axis  24  and the respective centers  186  of each of the air outlets  62 . For example, the angle  182  may be about 1°, 5°, 10°, 11.5°, 15°, 20°, or 25°, or any angle in between. Moreover, while the first plurality of air outlets  62  is illustrated as including 12 air outlets, in other embodiments the first plurality of air outlets  62  may include 2, 4, 6, 8, 10, 14, or more outlets. Indeed, any number of air outlets  62  configured to produce a swirling effect on the liquid flow  22  as it exits the device  10  is presently contemplated. 
     While any number of the first plurality of air outlets  62  may be used in accordance with the presently contemplated embodiments, it should be noted that the size of each first plurality of air outlets  62  may at least partially determine a suitable number of the air outlets  62 , in addition to the angle  182  that is used for air swirling. While the first plurality of air outlets  62  may each have the same or different dimensions, as an example of certain embodiments, the diameter of each of the first plurality of air outlets  62  may be between about 0.005 inches (in) and about 0.05 in (e.g., about 0.01 in, 0.02 in, 0.03 in, 0.04 in, or 0.05 in). Indeed, the total atomization area for the first plurality of air outlets  62  may be between about 0.01 in 2  and 0.05 in 2  (e.g., about 0.005 in, 0.01 in 2 , 0.02 in 2 , 0.03 in 2 , 0.04 in 2 , or 0.05 in 2 ). For example, in one embodiment wherein the air cap  56  has 12 of the first air holes  62 , the area of atomization may be about 0.015 in 2 , with each of the air holes  62  having a diameter of about 0.039 in. It should be noted that while  FIGS. 4-6  appear to present the air openings  62  in an ellipsoidal geometry, the orifices (the first plurality of holes  62 ) from which the atomizing air exits are indeed circular orifices when viewed from a perpendicular perspective with respect to the angled air flow  120  of each of the openings  62 . 
       FIG. 6  illustrates a front axial view of the air cap taken along line  6 - 6  of  FIG. 3 . Referring to the air horns  66  and the relative size of the first plurality of air openings  62  compared to the second plurality of air openings  64 , the first plurality of air openings  62  may each be smaller than each of the second plurality of air openings  64  by about 5%, 10%, 15%, 25%, 50%, 75%, 100%, 150%, 200%, or more. In some embodiments, the particular size relationship between the first air openings  62  and the second air openings  64  may also be determined by the number of first openings  62 , the number of second openings  64 , as well as the desired area of atomizing air for the first openings  62  and the desired area of spray shaping air for the second openings  64 . For example, the total area of the first openings  62  may be about the same as the total area of the second openings  64 , or may be about 1%, 5%, 10%, 15%, 20%, 50%, 100%, or more, larger than the second openings  64 . In other embodiments, the second openings  64  may be about 1%, 5%, 10%, 15%, 20%, 50%, 100%, or more, larger than the first openings  62 . 
     In some embodiments, the size, shape, and extent of the second plurality of air openings  62  may be at least partially determined by the extent to which the air horns  66  surround the central opening  150 . As noted above, the second plurality of air outlets  64  may be any size and/or shape to the extent that they are disposed on the respective inner surfaces of the air horns  66 . In the illustrated embodiment, the first air horn  166  protrudes from the central surface  174  of the air cap  56  at a first offset distance  191  away from the center of the central opening  150 . The second air horn  168  also protrudes from the central surface  174  and is disposed at a second offset distance  193  away from the central opening  150 . The first offset distance and the second offset distance  191 ,  193  may be substantially the same for both air horns  166 ,  168 , and may be substantially continuous from the central opening to the air horns  166 ,  168  due to their curved geometry. However, in other embodiments, the distances  191 ,  193  may be different. The extent that each of the curved air horns  166 ,  168  curve about the liquid flow axis  24  (or the central opening  150 ), as represented by arc  190 , may range from about 1° to about 180° (e.g., about 10° to about 160°, about 20° to about 140°, about 30° to about 100°, or about 40° to about 80°) around the circumference of the air cap  56 . In some embodiments, the arc  190  may be between about 25° to about 60° For example, the arc  190  may be 25°, 30°, 40°, 50°, 60°, or any angle in therein. 
     The extent of arc  190 , as well as the number, sizing, and angles of the second plurality of air outlets  64  may at least partially determine the manner in which the air flow  122  flattens the atomized coating spray  124  described above with respect to  FIG. 2 . For example, in the illustrated embodiment, the first and second air horns  166 ,  168  each include three air openings  192  that produce the air flow  122  along respective air flow axes, which is represented as arrows  194 . The air flow  122 , as noted above, produces swirled air that is countercurrent to the swirled air produced by the first plurality of air holes  62 . This results in the flattening effect described above, as well as additional atomization of the liquid. 
     Various configurations of air outlets of the air horns  66  may be further appreciated with respect to  FIGS. 7 and 8 , which are partial cross-sectional views of embodiments of an air horn of the spray head component taken along line  7 - 7  of FIG.  4 . Specifically,  FIG. 7  illustrates an embodiment of an air horn  200  having a curved inner surface  202  (e.g., a concave surface) with a pair of first spray shaping outlets  204  and a second spray shaping outlet  206 . As illustrated, the outlets  204  surround the outlet  206 . In accordance with the illustrated embodiment, the spray shaping outlets  204 ,  206  are not aligned with respect to their respective distances  201 ,  203 ,  205  away from a lower portion  208  of the air horn  200 , which is generally aligned with the liquid opening  146 . However, in other embodiments, the spray shaping outlets  204 ,  206  may be substantially aligned (i.e., have substantially the same distance  201 ,  203 ,  205  away from the lower portion  208 ). 
     In other configurations, the air outlets  64  of the air horns  66  may be replaced by one or more slots.  FIG. 8  illustrates a partial cross-sectional view of another embodiment of an air horn of the spray head component taken along line  7 - 7  of  FIG. 4 . Specifically,  FIG. 8  depicts an air horn  210  having a spray shaping air slot  212  disposed on a curved inner surface  214  (e.g., a concave surface). In a similar manner to the arrangement of the air outlets  64 ,  204 , and  206  described above, the air slot  212  extends in a crosswise direction  216  that is substantially parallel to the central surface  174  of the air cap  56 . In still further embodiments, the air horns  66  may include any number and/or combination of air slots and air openings having a variety of shapes and sizes. For example, the air openings on the air horns  66  may be ellipsoidal, rectangular, square, triangular, polygonal, and so on, with swirling occurring at least partially due to the curvature of the inner surfaces of the air horns  66 . Indeed, all such combinations are presently contemplated with respect to the formation of one or more swirled air flows to induce liquid atomization, or homogenization, or spray shaping, or any combination thereof. 
     As noted above, it may be desirable to incorporate feature that facilitate the use of the air cap configured to swirl air in conjunction with a variety of spray devices. For example, it may be desirable to provide an air cap in accordance with the presently contemplated embodiments that has the capability to receive a variety of geometries (e.g., shapes, and sizes) and configurations of valves, liquid outlets and internal flow patterns. One embodiment may include a relatively small liquid outlet for some spray coating applications (e.g., stains), while another embodiment may include a larger liquid outlet for other spray coating applications (e.g., epoxies), each of which may use different fluid seats. Accordingly, the disclosed embodiments provide interchangeable inserts configured for use with the air cap disclosed herein, which facilitates the use of different coating fluids. 
     With reference now to  FIG. 9 , a side cross-sectional view of an embodiment of the spray coating device  10  is provided with the air cap  56  having a removable fluid tip and seat assembly  220 . The fluid tip and seat assembly  220 , in a general sense, may be varied to allow a user to vary the size of a liquid outlet  222 . For example, the fluid tip and seat assembly  220  includes a removable tip housing  224  configured to abut the air cap  56 , as will be discussed below. The tip housing  224  interfaces with a removable insert  226 , which is disposed within an inner circumference of the tip housing  224  and is placed in abutment with the same. Although the tip housing  224  and insert  226  are separate pieces in the illustrated embodiment, the housing  224  and insert  226  may be provided as a single piece in some embodiments. 
     The insert  226  may be a generally annular structure configured to be disposed within the tip housing  224 , and may extend through the tip housing  224  to a certain offset, or may be flush with the tip housing  224 . The insert  226 , proximate the center of its annular structure, includes the liquid outlet  222 . The liquid outlet  222  is generally an opening of the insert  226  having a geometry (e.g., shape and size) tailored to a particular application. For example, as discussed above, the liquid outlet  222  may have a diameter that at least partially depends on the fluid that will be utilized for a particular spray coating application (e.g., stains, paints, epoxies). The insert  226  also includes an inner surface  228  that begins at an inner extent of the insert  226  and tapers into the liquid outlet  222 . The tapered inner surface  228  is configured to interface with the liquid needle valve  74 , which provides adjustability of liquid flow through the fluid tip and seat assembly  220 . Moreover, the tapered inner surface  228  enables the insert  226  to be used in conjunction with a variety of liquid needle valves. Additionally, the tapered liquid needle valve  74  may be used in conjunction with similar inserts having a variety of sizes of the liquid outlet  222 . The fluid tip and seat assembly  220  also includes an annular member  230  disposed in abutment with the insert  226 . The annular member  230  may facilitate the interface of the fluid tip and seat assembly  220  with the nozzle portion  156  described above with respect to  FIG. 4 . 
       FIG. 10  illustrates an exploded view of the components of the fluid tip and seat assembly  220 , each of the components being disposed along the liquid flow axis  24 . In the illustrated embodiment, the fluid tip and seat assembly  220  is exploded from the assembly  220  in an order of installation into the air cap  56 . For example, the air cap  56  may sequentially receive the tip housing  224 , the insert  226 , and the annular member  230 . The tip housing  224  can be made from any number of materials including stainless steel, tungsten carbide, delrin-type plastic, or any combination thereof. The tip housing  224  includes a forward tapered surface  232  having a frusto-conical shape extending from a first annular portion  234 . The tapered surface  232  opens to a central orifice  236  having a diameter  238  that facilitates an interface between the insert  226  and the tip housing  224 , as will be discussed below. The tip housing  224  also includes a second annular portion  240  disposed on an opposite side of the tip housing  224  from the tapered surface  232 . The second annular portion  240  includes a forward abutment surface  242  that abuts an inner surface  244  of the air cap  56  when the fluid tip and seat assembly  220  is placed into the air cap  56 . Moreover, the first annular portion  234  of the tip housing  224  has a diameter  246  that allows the forward portion of the tip housing  224  to extend through the central opening  150  of the air cap  56  while placing the forward abutment surface  242  against the inner surface  244  of the air cap  56 . 
     The insert  226  may be constructed from stainless steel, ultra high molecular weight (UHMW) or delrin plastic, tungsten carbide, or any combination thereof. The particular material or materials utilized for its construction may depend at least partially upon the particular coating application. For example, certain materials may be utilized for epoxies while others are used for paints or stains, and so on. The insert  226  includes a forward surface  248 , which is a curved surface in the illustrated embodiment. The forward surface  248  extends from a first annular portion  250  of the insert  226 , and has the liquid outlet  222  as a central opening. As noted above, the liquid outlet  222  may be varied by interchanging the insert  226  with another insert having a central opening of a different diameter. The forward surface  248  and the first annular portion  250  have a diameter  252  that allows the insert  226  to extend through the central opening  236  of the tip housing  224 . When the insert  226  is placed into the tip housing  224 , an abutment surface  254  of a second annular portion  256  of the insert  226  is placed against an inner surface  258  of the tip housing  224 , while the first annular portion  250  of the insert  226  extends through the central opening  236  of the tip housing  224 . As noted above, the insert  226  and the tip housing  224 , in some embodiments, may be a single piece. 
     The annular member  230 , as illustrated, includes a first abutment surface  260  that abuts a rear surface  262  of the second annular portion  256  of the insert  226 . A central orifice  264  of the annular member  230  allows a liquid needle valve, such as the needle valve  74  described above with respect to  FIG. 9 , to extend from an interior of the spray device  10  and through the fluid tip and seat assembly  220 . The annular member  230  also has a rear abutment surface  266  that abuts against a nozzle portion, such as the nozzle portion  156  described above with respect to  FIG. 9 . In an embodiment, the annular member  230  acts to seal the nozzle portion  156  against the fluid tip and seat assembly  220  to prevent fluid leakage. In this regard, the annular member  230  may be constructed from any material that is able to seal the nozzle portion  156  against the fluid tip and seat assembly  220 , for example synthetic and/or natural rubbers, plastics, ceramics, sintered materials, porous materials, malleable or soft metals, and so on. 
     While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.