Patent Publication Number: US-11020759-B2

Title: System for controlling air shaping flow in spray cap of spray tool

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority to and benefit of U.S. Provisional Patent Application No. 62/325,061, entitled “SYSTEM FOR CONTROLLING AIR SHAPING FLOW IN SPRAY CAP OF SPRAY TOOL,” filed Apr. 20, 2016, which is herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The invention relates generally to spray devices, and, more particularly, to spray caps for spray tools. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described 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. 
     Spray coating devices are used to apply a spray coating to a wide variety of target objects. In order to achieve a desired finish quality of the spray coating, the spray coating devices may output a spray of coating material with a particular shape. Unfortunately, the shape may be non-uniform or less than optimal due to various factors, such as a non-uniform flow or distribution of air through the spray coating device. 
     BRIEF DESCRIPTION 
     Certain embodiments commensurate in scope with the originally claimed invention are summarized below. These embodiments are not intended to limit the scope of the claimed invention, but rather these embodiments are intended only to provide a brief summary of possible forms of the invention. Indeed, the invention may encompass a variety of forms that may be similar to or different from the embodiments set forth below. 
     In certain embodiments, a system includes a spray cap configured to couple to a spray tool, wherein the spray cap includes a body and an air shaping passage through the body. The air shaping passage includes a flow control passage, an expansion chamber downstream from the flow control passage, and one or more air shaping outlets downstream from the expansion chamber. 
     In certain embodiments, a system includes a spray tool including a body portion having a fluid passage and an air passage and a head portion fluidly coupled to the fluid passage and the air passage. The head portion includes a spray cap having a fluid nozzle receptacle, an air atomization passage, and an air shaping passage. The air shaping passage includes a flow control passage, an expansion chamber downstream from the flow control passage, and one or more air shaping outlets downstream from the expansion chamber. The head portion also includes a fluid nozzle disposed in the fluid nozzle receptacle. 
     In certain embodiments, a system includes a flow control insert configured to mount within a recess in a body of a spray cap of a spray tool. The flow control insert includes an air shaping passage having a flow control passage, an expansion chamber downstream from the flow control passage, and one or more air shaping outlets downstream from the expansion chamber. 
    
    
     
       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 cross-sectional side view of an embodiment of a spray tool having a spray cap with flow control features along an air shaping passage; 
         FIG. 2  is a partial cross-sectional side view of an embodiment of the spray tool of  FIG. 1  taken within line  2 - 2 , illustrating details of an air shaping passage having a flow control passage, an expansion chamber downstream from the flow control passage, and one or more air shaping outlets downstream from the expansion chamber; 
         FIG. 3  is a cross-sectional front view of an embodiment of the spray cap of  FIG. 2  taken along line  3 - 3 , illustrating an upstream portion of the air shaping passage leading up to the flow control passage; 
         FIG. 4  is a cross-sectional front view of an embodiment of the spray cap of  FIG. 2  taken along line  4 - 4 , illustrating a portion of the air shaping passage at the flow control passage; 
         FIG. 5  is a cross-sectional front view of an embodiment of the spray cap of  FIG. 2  taken along line  5 - 5 , illustrating a downstream portion of the air shaping passage at the expansion chamber downstream from the flow control passage; 
         FIG. 6  is a cross-sectional side view of an embodiment of the spray cap of  FIG. 1 , illustrating a flow control insert disposed in a recess in a body of the spray cap, wherein the flow control passage is disposed partially along the flow control insert, and the expansion chamber is disposed between the flow control insert and the recess; 
         FIG. 7  is a top view of an embodiment of the spray cap of  FIG. 6  taken along line  7 - 7 , illustrating an annular shape of the flow control passage, and a plurality of alignment features that facilitate alignment between the flow control insert and the recess in the body of the spray cap; 
         FIG. 8  is a cross-sectional side view of an embodiment of the spray cap of  FIG. 1 , illustrating a flow control insert disposed in a recess in a body of the spray cap, wherein the flow control insert includes inner and outer insert portions coupled together by one or more connecting portions, and the flow control passage is disposed between the inner and outer insert portions; 
         FIG. 9  is a top view of an embodiment of the spray cap of  FIG. 8  taken along line  9 - 9 , illustrating a substantially annular shape (e.g., segmented annular shape) of the flow control passage between the inner and outer insert portions, and the one or more connecting portions coupling the inner and outer insert portions; 
         FIG. 10  is a cross-sectional side view of an embodiment of the spray cap of  FIG. 1 , illustrating a one-piece construction of the air cap (e.g., one-piece structure) having an air shaping passage with a flow control passage, an expansion chamber, and one or more air shaping outlets; 
         FIG. 11  is a top view of an embodiment of the spray cap of  FIG. 10  taken along line  11 - 11 ; 
         FIG. 12  is a partial cross-sectional side view of an embodiment of the flow control passage of  FIG. 2 , wherein the flow control passage has a constant-width passage with a radial width that is constant in an axial direction along a central axis of the spray cap; 
         FIG. 13  is a partial cross-sectional side view of an embodiment of the flow control passage of  FIG. 2 , wherein the flow control passage has a converging-width passage with a radial width that increases or decreases in an axial direction along a central axis of the spray cap; 
         FIG. 14  is a partial cross-sectional side view of an embodiment of the flow control passage of  FIG. 2 , wherein the flow control passage has a converging passage portion, a throat portion, and a diverging passage portion, such that the radial width of the flow control passage decreases and then increases in an axial direction along a central axis of the spray cap; 
         FIG. 15  is a cross-sectional front view of an embodiment of the spray cap of  FIG. 2  taken along line  4 - 4 , illustrating another embodiment of a portion of the air shaping passage at the flow control passage, wherein the flow control passage has a radial width that varies in a circumferential direction about the central axis of the spray cap, such that the radial width increases toward air shaping horns of the spray cap; and 
         FIG. 16  is a cross-sectional front view of an embodiment of the spray cap of  FIG. 2  taken along line  4 - 4 , illustrating another embodiment of a portion of the air shaping passage at the flow control passage, wherein the flow control passage has a radial width that varies in a circumferential direction about the central axis of the spray cap, such that the radial width decreases toward air shaping horns of the spray cap. 
     
    
    
     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. 
     When introducing elements of various embodiments of the present invention, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     The present disclosure is generally directed to a spray tool, and, more particularly, to a spray cap or an air cap for spray atomization. The spray cap has a body and an air shaping passage to supply air to horns of the spray tool, wherein the air shaping passage may include a flow control passage or an annular gap, an expansion chamber downstream from the flow control passage, and one or more air shaping outlets downstream from the expansion chamber. In certain embodiments, the flow control passage, the expansion chamber, and the air shaping outlets may be integrally formed as part of the spray cap (e.g., a one-piece structure). In some embodiments, the flow control passage may be formed at least partially or entirely through a flow control insert, which fits within a recess in a body of the spray cap. The flow control passage and expansion chamber helps to regulate and distribute an air shaping flow more uniformly around the spray cap, thereby improving the shape of a spray of coating material and the quality of a coating by the spray. For example, the flow control passage may be a substantially annular passage (e.g., a continuous annular passage or a segmented annular passage), which restricts the air shaping passage before expansion in the expansion chamber. In this manner, the flow control passage and expansion chamber help to remove variations in the pressure, velocity, and flow rate of the air shaping flow caused by various upstream features (e.g., one or more discrete air supply passages upstream of the spray cap). The flow control passage, due to the substantially annular shape and flow restriction, thus helps to more uniformly distribute the air shaping flow to the air shaping outlets. As a result, the more uniform air shaping flow through the air shaping outlets helps to improve the shape of the spray and the quality of the coating applied by the spray. In addition, the flow control passage and expansion chamber may help to reduce noises created by the air shaping flow through the spray tool. 
       FIG. 1  is a cross-sectional side view illustrating an embodiment of the spray tool assembly  10  (e.g., spray coating gun) having a flow control section  11  in a spray tool  12 , wherein the flow control section  11  has a flow control passage  14  between an upstream chamber  16  (e.g., air shaping supply chamber) and a downstream chamber  18  (e.g., expansion chamber) leading to one or more air shaping outlets  20 . As discussed in further detail below, the flow control section  11  is configured to regulate and distribute an air shaping flow more uniformly to improve the shape of a spray of coating material and quality of a coating by the spray. 
     The spray tool assembly  10  includes an air supply  13  and a gravity fed container assembly  15  coupled to the spray tool  12 . As illustrated, the spray tool  12  includes a spray tip assembly  17  coupled to a body  19 . The spray tip assembly  17  includes a fluid nozzle or a liquid delivery tip assembly  22 , which may be removably inserted into a receptacle  24  of the body  19 . For example, a plurality of different types of spray tool devices may be configured to receive and use the fluid nozzle  22 . The spray tip assembly  17  also includes a spray formation assembly  26  coupled to the fluid nozzle  22 . The spray formation assembly  26  may include a variety of spray formation mechanisms, such as air, rotary, and electrostatic atomization mechanisms. However, the illustrated spray formation assembly  26  comprises a head portion  28  that is fluidly couple to fluid/liquid passage and air passage. The head portion  28  is removably secured to the body  19  via a retaining assembly  30  (e.g., threads, bolts and nuts, retaining ring, etc.). The head portion  28  includes a spray cap  29 , which includes a variety of air atomization orifices, such as one or more central air orifices or atomization outlets  32  disposed about a fluid tip exit or outlet  34  (e.g., liquid outlet) from the fluid nozzle  22  along a central portion of the spray cap  29 . The spray cap  29  may also have one or more air shaping outlets or orifices  20 , which use air jets to force the spray to form a desired spray pattern (e.g., a flat spray). The spray formation assembly  26  may also include a variety of other atomization mechanisms to provide a desired spray pattern and droplet distribution. 
     The body  19  of the spray tool  12  includes a variety of controls and supply mechanisms for the spray tip assembly  17 . As illustrated, the body  19  includes a liquid delivery assembly  38  having a liquid passage  40  extending from a liquid inlet coupling  42  to the fluid nozzle  22 . The body  19  also includes a liquid valve assembly  44  having a needle valve  46  extending movably through the body  19  between the fluid nozzle  22  and a liquid valve adjuster  48 . The liquid valve adjuster  48  is rotatably adjustable against a spring  50  disposed between a rear section  52  of the needle valve  46  and an internal portion  54  of the liquid valve adjuster  48 . The needle valve  46  is also coupled to a trigger  56 , such that the needle valve  46  may be moved inwardly away from the fluid nozzle  22  as the trigger  56  is rotated counter clockwise about a pivot joint  58 . However, any suitable inwardly or outwardly openable valve assembly may be used within the scope of the present technique. The liquid valve assembly  44  also may include a variety of packing and seal assemblies, such as packing assembly  60 , disposed between the needle valve  46  and the body  19 . 
     An air supply assembly  62  is also disposed in the body  19  to facilitate air-driven atomization and shaping at the spray formation assembly  26 . The illustrated air supply assembly  62  extends from an air inlet coupling  64  to the spray cap  29  via air passages  66  and  68 . The air supply assembly  62  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 tool  12 . For example, the illustrated air supply assembly  62  includes an air valve assembly  70  coupled to the trigger  56 , such that rotation of the trigger  56  about the pivot joint  58  opens the air valve assembly  70  to allow air flow from the air passage  66  to the air passage  68 . The air supply assembly  62  also includes an air valve adjustor  72  to regulate the air flow to the spray cap  29 . As illustrated, the trigger  56  is coupled to both the liquid valve assembly  44  and the air valve assembly  70 , such that liquid and air simultaneously flow to the spray tip assembly  17  as the trigger  56  is pulled toward a handle  74  of the body  19 . Once engaged, the spray tool  12  produces an atomized spray with a desired spray pattern and droplet distribution. 
     The gravity fed container assembly  15  and the air supply  13  provide a respective coating material (e.g., liquid or powder coating material) and air to the spray tool  12 . The air supply  13  enables the spray tool  12  to spray and shape the coating material exiting the gravity fed container assembly  15 . The air supply  13  couples to the spray tool  12  at the air inlet coupling  64  and supplies air via an air conduit  76 . Embodiments of the air supply  13  may include an air compressor, a compressed air tank, a compressed inert gas tank (e.g., nitrogen tank), or a combination thereof. In the illustrated embodiment, the gravity fed container assembly  15  is directly mounted to the spray tool  12  to supply a coating material (e.g., a solvent, paint, sealer, stain, etc.) to the spray tool  12 . The illustrated gravity fed container assembly  15  includes a spray coating supply container  78 , a lid  80 , a filter assembly  82 , and an adapter  86 . 
       FIG. 2  is a partial cross-sectional side view of an embodiment of the spray tool of  FIG. 1 , illustrating details of the spray formation assembly  26  of the spray cap  29 . As illustrated, the spray formation assembly  26  includes the head portion  26  with a mounting insert  101 , the fluid nozzle  22 , the spray cap  29 , and a retaining assembly  30 . The fluid nozzle  22  extends into a recess  102  (e.g., annular recess) in the body  19 , through a central bore  103  in the mounting insert  101 , through a central bore  104  in the spray cap  29 , and partially into the fluid outlet  34  in the spray cap  29 . The fluid nozzle  22  may be hand-inserted, press-fit, threadingly coupled, or otherwise fixedly or removably coupled into the recess  102  of the body  19 . Likewise, the mounting insert  101  extends circumferentially  124  around the fluid nozzle  22 , and may be removably or fixedly coupled to a recess  105  (e.g., annular recess) in the body  19 . For example, the mounting insert  101  may be press-fit or threadingly coupled to the recess  105  in the body  19 . The fluid nozzle  22  also includes an outer flange portion  106  (e.g., a tapered annular flange portion), which fits between the mounting insert  101  and the spray cap  29 . For example, the outer flange portion  106  may abut a tapered portion  107  (e.g., tapered annular surface) on a body  108  of the spray cap  29 . In the illustrated embodiment, the tapered portion  107  is disposed on an inner wall  109  (e.g., inner annular wall) of the body  108 . Thus, the outer flange portion  106  and the tapered portion  107  create a tapered interface (e.g., a compression fit interface) between the spray cap  29  and the fluid nozzle  22  upon complete assembly of the mounting insert  101 , the fluid nozzle  22 , the spray cap  29 , and the retaining assembly  30 . For example, the retaining assembly  30  may include a retainer nut  125 , which couples with an outer wall  111  (e.g., radially protruding outer annular flange) of the body  108  of the spray cap  29  and, also, couples with the mounting insert  101  (e.g., via a threaded interface  113 ). As the retainer nut  125  threads onto the mounting insert  101  via the threaded interface  113 , the retainer nut  125  pulls the spray cap  29  inwardly toward the body  19 , and axially  120  compresses the fluid nozzle  22  between the spray cap  29  and the mounting insert  101 . 
     In the illustrated embodiment, a coating material passage  112  (e.g., a fluid or liquid passage), an air atomization passage  114 , and one or more air shaping passages  116  extend through the body  19  of the spray tool  12 , the mounting insert  101 , and a body  108  of the spray cap  29 . During a spraying operation, the coating material (e.g., liquid or powder coating material such as paint) exits the spray tool  12  at the fluid outlet  34  when the needle valve  46  (see  FIG. 1 ) is actuated to retract away from the fluid outlet  34 . Simultaneously, air through the air atomization passage  114  is ejected from the air atomization outlets  32  to atomize the liquid coating material. Substantially simultaneously, air through the air shaping passage  116  is ejected from the air shaping outlets  20  to shape or force the spray (e.g., the atomized liquid coating material) to form a desired spray pattern (e.g., a flat spray). 
     The spray cap  29  may be described with reference to a central longitudinal axis  119 , an axial direction or axis  120 , a radial direction or axis  122 , and a circumferential direction or axis  124 . As illustrated, the spray cap  29  is configured to output the atomization air and liquid coating material in the axial direction  120 , and the air atomization passage  114  and the air shaping passage  116  are substantially annular passages extending circumferentially about the central axis  119 . In particular, the air atomization passage  114  and the air shaping passage  116  are concentrically disposed about the fluid passage  112  one after another in the radial direction  122 . The spray cap  29  includes a plurality of horns or axial protrusions  110  (e.g., 2, 3, 4, 5, 6, or more protrusions) extending downstream in the axial direction  120  away from a central region  31  having the outlets  32  and  34 , such that the air shaping passages  116  extend downstream beyond the outlets  32  and  34  to downstream portions  118  (e.g., tip portions) of the protrusions  110  at one or more downstream positions having the air shaping outlets  20 . Accordingly, the spray tool  12  outputs the atomization air and the coating material (e.g., liquid coating material) through the outlets  32  and  34  at the central region  31  to form a spray of the coating material upstream of the air shaping outlets  20 , such that the air shaping outlets  20  then direct air shaping flows (e.g., jets) from downstream portions  118  of the protrusions  110  inwardly toward the spray and the axis  119  to shape the spray into a desired spray pattern. 
     In the illustrated embodiment, the air shaping passage  116  includes the flow control passage  14  disposed between the upstream chamber  16  (e.g., air shaping supply chamber) and the downstream chamber  18  (e.g., expansion chamber), which leads to one or more air shaping outlets  20  (e.g., 2, 3, 4, 5, 6, or more outlets) in a downstream portion of each protrusion  110 . The flow control passage  14  may be disposed at an upstream region or base of the protrusions  110 , such as in an upstream portion  126  of the spray cap  29 . In certain embodiments, the flow control passage  14  may be disposed at least partially in or along a flow control structure  115  (e.g., an annular structural portion), which may be integral or separate from the spray cap  29 . For example, the flow control structure  115  and the flow control passage  14  may be an integral part of (e.g., one-piece with or fixedly coupled to) the spray cap  29 . By further example, the flow control structure  115  may be a flow control insert configured to couple with the spray cap  29 , wherein the flow control passage  14  may be disposed at least partially within or along the flow control insert (e.g., completely within the insert, or between the insert and the spray cap  29 . 
     The upstream chamber  16 , the flow control passage  14 , and the expansion chamber  18  may be substantially annular chambers or passages, which extend circumferentially  124  about the central axis  119 . The flow control passage  14  may be sized smaller (e.g., reduced or restricted cross-sectional area and radial  122  width) relative to both the upstream chamber  16  and the expansion chamber  18 . For example, the cross-sectional area or radial  122  width of the flow control passage  14  may be less than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 percent of the corresponding cross-sectional area or radial  122  width of the upstream chamber  16  and/or the downstream chamber  18 . By further example, the cross-sectional area or radial  122  width of the expansion chamber  18  may be equal to, less than, or greater than the corresponding cross-sectional area or radial  122  width of the upstream chamber  16 . In certain embodiments, the cross-sectional area or radial  122  width of the expansion chamber  18  may be at least approximately 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 90, or 100 percent greater than the corresponding cross-sectional area or radial  122  width of the upstream chamber  16 . Furthermore, the radial width  122  of the flow control passage  14 , the upstream chamber  16 , and the expansion chamber  18  may be uniform or varying in the circumferential direction  124  about the central axis  124 , thereby providing a desired regulation and flow distribution of the air shaping flow to the air shaping outlets  20 . 
     In operation, the flow control section  11  directs the air shaping flow to pass sequentially through the upstream chamber  16 , the flow control passage  14 , and the expansion chamber  18 . In this manner, the flow control section  11  forces the air shaping flow to spread out for better distribution in the upstream chamber  16 , squeeze through the reduced radial  122  width of the flow control passage  14  with a corresponding increase in velocity and reduction in static pressure for improved regulation and distribution of the air shaping flow, and then expand in the expansion chamber with a corresponding decrease in velocity and pressure recovery prior to delivery to the air shaping outlets  20 . As a result, at each outlet  20  and between different outlets  20 , the air shaping flow is more uniform (e.g., pressure, velocity, flow rate, etc.) as compared to a configuration without the flow control section  11 . In certain embodiments, the flow control section  11  may reduce turbulence in the air shaping flow and/or provide a more laminar flow to the air shaping outlets  20 . For example, air turbulence may be present in the air flow upstream of the flow control section  11  (e.g., due to fluctuations in the air supply  13 ; variations in the flow passages, such as bends, disruptions, intersections of passages, changes in geometry, etc.). However, the flow control section  11  (e.g., flow control passage  14  and chambers  16  and  18 ) may help to improve the air flow distribution (e.g., more uniform velocity, pressure, flow rate, etc.), which may help to reduce the turbulence generated upstream and/or provide a more laminar flow. In addition, the expansion chamber  18  may help to reduce noise created by the air flow upstream of the flow control section  11  and/or otherwise present in the spray tool  12  without the flow control section  11 . 
       FIGS. 3, 4, and 5  are cross-sectional front views of the head portion  28  of  FIG. 2 , further illustrating details of the air shaping passage  116  as it changes in cross-sectional area and radial  122  width through the upstream chamber  16 , the flow control passage  14 , and the expansion chamber  18  in the spray cap  29 .  FIG. 3  is a cross-sectional front view taken along line  3 - 3  of  FIG. 2 , illustrating an upstream portion (e.g., the upstream chamber  16 ) of the air shaping passage  116  leading up to the flow control passage  14 . The air shaping passage  116 , specifically the upstream chamber  16 , may be configured to receive the supplied air (e.g., from the air passage  68 ) via one or more discrete air holes  150  disposed in different discrete locations along the upstream chamber  16  (e.g., annular chamber). Given the discrete locations of the air holes  150 , the air is supplied to the upstream chamber  16  (e.g., annular chamber) in a non-uniform matter. Again, further downstream, the flow control section  11 , particularly the flow control passage  14  and the expansion chamber  18 , is configured to help regulate and control distribution of the air flow to the air shaping outlets  20 . 
     As illustrated in  FIG. 3 , the fluid passage  112  (e.g., annular fluid passage) is disposed circumferentially  124  about the needle valve  46  (e.g., coaxial arrangement). The fluid nozzle  22  (e.g., annular wall  128 ) is disposed circumferentially about the fluid passage  112  to help guide the fluid flow through the fluid passage  112  around the needle valve  46  to the fluid outlet  34 . The fluid nozzle  22  also includes a portion of the air atomization passage  114 , specifically a plurality of air atomization passages  114  disposed in a circumferential arrangement  130  in the annular wall  128  of the fluid nozzle  22 . The air atomization passages  114  are configured to feed an airflow to the central bore  104  of the spray cap  29 , and subsequently into the air atomization outlets  32 . The upstream chamber  16  (e.g., annular chamber or flow passage) of the air shaping passage  116  is disposed circumferentially  124  around the fluid nozzle  22  and the upstream portion  126  of the spray cap  29 . Thus, the fluid nozzle  22  and the upstream portion  126  of the spray cap  29  generally define an inner wall (e.g., inner annular wall) of the upstream chamber  16 . The retaining assembly  30  (e.g., the retainer nut  125 ) is disposed circumferentially  124  around the upstream chamber  16 , and thus defines an outer annular wall of the upstream chamber  16 . Again, the upstream chamber  16  (e.g., annular chamber) helps to direct the air flow into the flow control passage  14  for improved flow distribution and regulation or control of the air flow (e.g., pressure, velocity, flow rate, etc.). 
       FIG. 4  is a cross-sectional front view taken along line  4 - 4  of  FIG. 2 , illustrating a portion of the air shaping passage  116  at the flow control passage  14 . As illustrated, the flow control passage  14  has an annular cross-section (e.g., annular flow control passage), which has a radial width  132  that is less than a radial width  130  of the upstream chamber  16  (see  FIG. 3 ). For example, the radial width  132  (or the cross-sectional area) of the flow control passage  14  may be less than 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 percent of the radial width  134  (or the cross-sectional area) of the upstream chamber  16 . As a result, the flow control passage  14  restricts the air flow causing an increase in velocity and decrease in static pressure, thereby helping to regulate the air flow and better distribute the air flow into the downstream expansion chamber  18 . In certain embodiments, the flow control passage  14  and the flow control structure  115  may be an integral part of (e.g., one-piece with or fixedly coupled to) the spray cap  29 , or the flow control passage  14  may be disposed at least partially within or along a flow control insert (e.g., completely within the insert, or between the insert and the spray cap  29 ). 
       FIG. 5  is a cross-sectional front view taken along line  5 - 5  of  FIG. 2 , illustrating a downstream portion of the air shaping passage  116  at the expansion chamber  18  downstream from the flow control passage  14 . As illustrated, the air shaping passage  116  expands from the flow control passage  14  into the expansion chamber  18 , which is defined between two different portions (e.g., inner and outer walls  109  and  111 ) of the body  108  of the spray cap  29 . The expansion chamber  18  has an annular cross-section (e.g., annular chamber or passage), which has a radial width  136  that is greater than the radial width  132  of the flow control passage  14  (see  FIG. 4 ). For example, the radial width  136  (or the cross-sectional area) of the expansion chamber  18  may be at least approximately 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 90, or 100 percent greater than the radial width  132  (or the cross-sectional area) of the flow control passage  14 . As a result, the expansion chamber  18  expands the air flow causing a decrease in velocity and pressure recovery, thereby further helping to regulate the air flow and better distribute the air flow into the downstream protrusions  110  and air shaping outlets  20 . As the air flow exits the expansion chamber  18  and enters the protrusions  110 , the spray cap  29  directs the air flow through a plurality of air horn passages or bores  162  of the air shaping passage  116 . Each air horn or protrusion  110  includes at least one passage  162  of the air shaping passage  116 , which in turn leads to the air shaping outlets  20 . 
     As mentioned above, the flow control passage  14  may be integrally formed with or separate from the body  108  of the spray cap  29 . In  FIGS. 6-10  below, embodiments of the air shaping passage  116  shown in  FIG. 2  will be discussed in detail.  FIG. 6  is a cross-sectional side view of an embodiment of the spray cap  29  of  FIG. 1 . As illustrated, the spray cap  29  includes the body  108  having an outer wall  172  (e.g., outer annular wall  111 ), an inner wall  174  (e.g., inner annular wall  109 ), and a central end wall  176 . A fluid nozzle cavity  170  in the body  108  is configured to receive the fluid nozzle  22  that outputs a fluid through the fluid outlet  34  at the central end wall  176  for atomization into a spray. Circumferentially disposed about the fluid passage  112  within the fluid nozzle cavity  170  is the air atomization passage  114 , which feeds the air flow through the spray cap  29  and out through the air atomization outlets  32  at the central end wall  176  to help atomize the fluid exiting the fluid outlet  34 . Between the inner and outer walls  174  and  172 , the air shaping passage  116  is circumferentially disposed about the air atomization passage  114 . As discussed above, at least a portion of the air shaping passage  116  is a substantially annular passage (e.g., upstream chamber  16 , flow control passage  14 , and expansion chamber  18 ) extending circumferentially  124  about the central axis  119  of the spray cap  29 , while a downstream portion of the air shaping passage  116  extends axially  120  through the protrusions  110  (e.g., passages  162  shown in  FIG. 5 ). The air within the air shaping passage  116  flows through the protrusions  110  and exits the air shaping passage  116  (e.g., axial passages  162 ) at the one or more air shaping outlets  20  to shape the atomized fluid spray into a desired spray pattern (e.g., a flat spray). The body  108  of the spray cap  29  also includes a mounting flange  178  (e.g., along wall  111 ,  172 ), which is configured to couple the spray cap  29  to the head portion  28  of the spray tool  12  such that the spray cap  29  is removably secured via the retainer nut  125  (see  FIG. 2 ) via threads, bolts and nuts, retaining ring, etc. 
     In the illustrated embodiment, the flow control passage  14  is disposed or created between a flow control insert  180  (e.g., a removable embodiment of the flow control structure  115 ) and the body  108  of the spray cap  29 . The flow control insert  180  includes a first retainer portion  182  and a flow control portion  184 . The first retainer portion  182  is configured to couple with a second retainer portion  186  of the body  108  of the spray cap  29 , while the flow control portion  184  extends towards the inner wall  174  to form the flow control passage  14  (e.g., the flow control passage  14  is disposed between the flow control portion  184  and the inner wall  174 ). The first retainer portion  182  may include an annular protrusion  188  (e.g., outward radial protrusion) disposed on an outer surface  190  (e.g., outer annular surface) of the flow control insert  180 . The second retainer portion  186  of the body  108  may include an inner recess surface  192  (e.g., inner annular recess) along the inner wall  174  and an outer recess surface  194  (e.g., outer annular recess) along the outer wall  172 , thereby defining an annular recess or mounting region  195  configured to receive the flow control insert  180 . In addition, an annular recess  196  is disposed on the outer recess surface  194  and is configured to receive the annular protrusion  188  of the flow control insert  180 . Alternatively or additionally, the annular recess  196  may be disposed on the flow control inset  180  while the annular protrusion  188  is disposed on the body  108  of the spray cap  29 . Alternatively or additionally, the annular recess  196  and the annular protrusion  188  may be disposed at the interface between the flow control insert  180  and the spray cap  29  at the inner wall  174 . In some embodiments, the first retainer portion  182  of the flow control insert  180  and the second retainer portion  186  of the body  108  of the spray cap  29  may include snap-fit couplings, press-fit or interference-fit connections, or threaded connections (e.g., mating threads) to couple together the first and second retainer portions  182  and  186 . 
     The expansion chamber  18  is disposed downstream of the flow control passage  14  and the flow control insert  180 . In particular, the expansion chamber  18  is disposed between the flow control insert  180  and the annular recess  195  (e.g., the inner and outer recess surfaces  192  and  194 ) of the body  108 . As such, the air shaping passage  116  has a varying radial width (or cross-sectional area) along the axial direction  120 . In particular, the air shaping passage  116  has a radial width  132 ,  198  (or cross-sectional area) at the flow control passage  14 , a radial width  136 ,  200  (or cross-sectional area) at the expansion chamber  18 , and a radial width  202  (or cross-sectional area) through the protrusions  110 . In general, the radial width  132 ,  198  (or cross-sectional area) is smaller than the radial width  136 ,  200  (or cross-sectional area). However, radial width  202  may be equal to or less than the radial width  136 ,  200 , while the cross-sectional area  202  may be substantially less than the cross-sectional area  200  (e.g., due to the restriction of the air shaping passage  116  into axial passages  162  as shown in  FIG. 5 ). Furthermore, the radial width  132 ,  198  (or cross-sectional area) of the flow control passage  14  may be equal to or less than approximately 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 percent of an upstream radial width adjacent an upstream side of the flow control passage  14  (e.g., radial width or cross-section  134  of the upstream chamber  16  shown in  FIG. 3 ) and a downstream radial width of the expansion chamber  18  (e.g., radial width  136 ,  200 ). 
       FIG. 7  is a top view of an embodiment of the spray cap  29  of  FIG. 6  taken along line  7 - 7 . As illustrated, the flow control insert  180  may further include a first alignment feature  220  configured to interface with a second alignment feature  222  in the body  108  (e.g., the outer wall  172 ) as to ensure the correct alignment of the flow control insert  180  with the spray cap  29 . Specifically, the first alignment feature  220  may include a plurality of alignment protrusions  224  (e.g., radial tabs, keys, or projections), the second alignment feature  222  may include a plurality of slots  226  (e.g., radial recesses, keyways, or grooves), and the plurality of alignment protrusions  224  are configured/sized to be received by the plurality of slots  226 . In certain embodiments, the total number of the plurality of the protrusions  224  may be equal to or fewer than the total number of the plurality of slots  226 . The flow control insert  180  may be made of any suitable material (e.g., plastic, metal, etc.) such that the flow control insert  180  may also provide substantial sealing (e.g., water-tight and air-tight) to seal the air shaping passage  116  from the ambiance/atmosphere. For example, the flow control insert  180  may be a cast metal (e.g., aluminum), an injection molded plastic (e.g., nylon, PEEK, polymer, etc.), an elastomeric material (e.g., rubber or other elastomer), a composite material (e.g., hard particles distributed in a matrix material), or any combination thereof. 
       FIG. 8  is a cross-sectional side view of an embodiment of the spray cap  29  of  FIG. 1 , illustrating an embodiment of the air shaping passage  116  of  FIG. 2 , wherein the flow control passage  14  is disposed internally through the flow control insert  180 . In the illustrated embodiment, the flow control insert  180  includes an inner insert portion  240  (e.g., inner annular insert portion) and an outer insert portion  242  (e.g., outer annular insert portion) coupled together by a structural support or connecting portion  244  (see  FIG. 9 ) between axial end walls  246 , wherein the flow control passage  14  is disposed between the inner and outer insert portions  240  and  242 . Given that the inner and outer insert portions  240  and  242  are connected by the structural support  244  (e.g., circumferentially spaced radial arms, struts, linkages, or tabs), the flow control passage  14  may be described as a segmented annular flow control passage  14  and/or a substantially annular flow control passage  14  due to the insubstantial obstructions caused by the structural support  224 . This segmented or substantially annular configuration of the flow control passage  14  is further illustrated and described with reference to  FIG. 9 . 
     The outer insert portion  242  includes the first retainer portion  182  and the flow control portion  184 , which are configured to function in the same manner as discussed above in  FIG. 6 . For example, the first retainer portion  182  is configured to couple with the second retainer portion  186  of the body  108  of the spray cap  29  while the flow control portion  184  extends towards the inner insert portion  240  to form the flow control passage  14  (e.g., the flow control passage  14  is disposed between the flow control portion  184  and the inner insert portion  240 ). As set forth above, the first retainer portion  182  includes the annular protrusion  188  disposed on the outer surface  190  of the flow control insert  180 . The second retainer portion  186  of the body  108  includes the inner recess surface  192  along the inner wall  174  and the outer recess surface  194  along the outer wall  172 . The annular recess  196  is disposed on the outer recess surface  194  and is configured to receive the annular protrusion  188  of the flow control insert  180 . 
     The inner insert portion  240  has an inner insert wall or surface  248  that is configured to contact the inner recess surface  192  along the inner wall  174 . These surfaces  192  and  248  may be configured to couple together with an interference-fit or press-fit connection, a threaded interface (e.g., mating threads), or any combination thereof. In some embodiments, the inner recess surface  192  may include an annular recess or slot sized to receive the inner insert portion  240  along the inner insert wall  248  between the axial end walls  246 . In some embodiments, the first retainer portion  182  of the flow control insert  180  and the second retainer portion  186  of the body  108  of the spray cap  29  may include any retaining features to snap-fit, press-fit or interference-fit, or thread together the first and second retainer portions  182  and  186 . It may also be appreciated that each of the inner and outer insert portions  240  and  242  of the flow control insert  180  may include any appropriate retaining features to snap-fit, press-fit, interference-fit, or thread together with the second retainer portions  186  along the inner and outer recess surfaces  192  and  194 , respectively. 
     As set forth above, the expansion chamber  18  is disposed between the flow control insert  180  and the annular recess  195  (e.g., the inner and outer recess surfaces  192  and  194 ) of the body  108 . The air shaping passage  116  has a varying radial width along the axial direction  120 . As illustrated, the flow control passage  14  includes a first passage  250  and a second passage  252  disposed one after another through the flow control insert  180 . The first passage  250  is between the flow control portion  184  of the outer insert portion  242  and the inner insert portion  240 , and has a radial width (or cross-sectional area)  254 . The second passage  252  is between the first retainer portion  182  of the outer insert portion  242  and the inner insert portion  240 , and has a radial width (or cross-sectional area)  256 . As may be appreciated, the radial width (or cross-sectional area)  254  is smaller than the radial width  256 , which is smaller than the radial width (or cross-sectional area)  200  at the expansion chamber  18 . Furthermore, the radial width (or cross-sectional area)  254  of the first passage  250  of the flow control passage  14  may be equal to or less than approximately 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 percent of an upstream radial width adjacent an upstream side of the flow control passage  14  (e.g., radial width or cross-section  134  of the upstream chamber  16  shown in  FIG. 3 ) and a downstream radial width of the expansion chamber  18  (e.g., radial width  136 ,  200 ). 
       FIG. 9  is a top view of an embodiment of the spray cap  29  of  FIG. 8  taken along line  9 - 9 . As illustrated, the flow control insert  180  includes the alignment features  220 ,  222 ,  224 , and  226  to ensure the correct alignment of the flow control insert  180  with the spray cap  29  as discussed in detail above with reference to  FIG. 7 . In addition,  FIG. 9  further illustrates the construction of the inner insert portion  240  and the outer insert portion  242  coupled together by the structural support  244 . Since an insubstantial portion of the flow control passage  14  is blocked by the structural support  244  (e.g., non-continuous and discrete), the flow control passage  14  may be described as a substantially annular or segmented annular flow control passage  14 . For example, the flow control passage  14  (e.g., first and/or second passage  250  and  252 ) includes a plurality of passage portions  260  (e.g., first, second, third and fourth passage portions) circumferentially  124  spaced about the central axis  119  of the spray cap  29 , thereby defining a segmented or substantially annular passage. In certain embodiments, the spray cap  29  may include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more structural supports  244 , and thus may include 2, 3, 4, 5, 6, 7, 9, 9, 10, 11, or more passage portions  260 . The total cross-sectional area of the structural support  244  may be relatively small (e.g., less than 5, 10, 15, or 20 percent) compared to the total cross-sectional area of the plurality of passage portions  260 . For example, the flow control passage  14  may be at least 80, 85, 90, or 95 continuous to define a substantially annular flow control passage. Also, despite the flow control passage  14  being composed of the plurality of passage portions  260 , the flow control insert  180  may still provide substantial sealing (e.g., water-tight and air-tight) to seal the air shaping passage  116  from the other flow passages and the external environment. In some embodiments, the flow control insert  180  may include the inner and outer insert portions  240  and  242  without any intermediate structural support  244 , wherein each of the insert portions  240  and  242  is coupled to the body  108  of the spray cap  29  via a press-fit or interference fit, a threaded interface, a snap-fit or latch coupling, a retainer ring, or any combination thereof. In such embodiments, the flow control passage  14  may be a continuous annular passage rather than a segmented annular passage. 
       FIG. 10  is a cross-sectional side view of an embodiment of the spray cap  29  of  FIG. 1 , wherein the spray cap  29  is a one-piece structure  280  having the air shaping passage  116  with the flow control passage  14  and the expansion chamber  18 . In general, the one-piece structure  280  described herein may have the body  108  that conforms with any of the structural features/shapes of the spray cap  29  discussed above in  FIGS. 6-9  (e.g., the flow control insert  180  is integrally formed as part of the one-piece structure  280 ). For example, the one-piece structure  280  has the body  108 , including the outer wall  172  and the inner wall  172 , which generally define the air shaping passage  116 . In particular, the outer wall  172  extends around a passage portion  282  of the air shaping passage  116 . The outer wall  172  also includes the mounting flange  178  configured to couple with the retainer nut  125 . The spray cap  29  also includes a flow control portion  284 , similar to the flow control structure  115  and the flow control insert  180 , which defines the flow control passage  14 . The passage portion  282  extends from the mounting flange  178  along the protrusions  110  in the axial  120  direction, while the flow control portion  284  extends from the mounting flange  178  in the radial direction  122  towards the inner wall  174 . The flow control portion  284  ends at an inner annular surface  286 , such that the flow control passage  14  is disposed between the inner wall  174  and the inner annular surface  286  and is annular with respect the central axis  119  of the spray cap  29 . 
     Furthermore, the one-piece structure  280  also includes an annular recess or cavity  288  downstream of the flow control passage  14 , thereby defining the expansion chamber  18  (e.g., annular expansion chamber). Accordingly, the air shaping passage  116  of the one-piece structure  280  has the radial width  198  at the flow control passage  14 , the radial width  200  at the expansion chamber  18 , and the radial width  202  through the horns  100 . The radial widths (or cross-sectional areas)  132 ,  134 ,  136 ,  198 ,  200 , and  202  are generally the same as described in detail above. A top view of an embodiment of the spray cap  29  of  FIG. 10  taken along line  10 - 10  is shown in  FIG. 11 . As illustrated, the spray cap  29  includes the one-piece structure  280  with the flow control passage  14  disposed between the inner wall  174  and the flow control portion  284  of the outer wall  172 . 
     It may be appreciated that the spray  29  composed of the one-piece structure  280  can be built using an additive manufacturing technique such as a direct metal laser sinter (DMLS) process, wherein the spray cap  29  may include any suitable laser sintered metal material (e.g., stainless steel, nickel-chromium alloy, aluminum alloy, etc.). The structural features discussed above may be built in a layer-by-layer fashion. The one-piece structure  280  may also be built using any other additive manufacturing techniques, such as 3D-printing, wherein the spray cap  29  may include any suitable plastic or metal materials for the additive manufacturing technique. Regardless of the manufacturing technique at choice, the built spray cap  29  may provide substantial sealing (e.g., water-tight and air-tight) to seal the air shaping passage  116  from the other flow passages and the external environment. 
     In addition, while the flow control passage  14  discussed above in  FIGS. 1-11  may have a radial width (or cross-sectional area)  132 ,  198 ,  254  that is constant in the axial direction  120  along the central axis  119  of the spray cap  29 , some embodiments of the flow control passage  14  may have a radial width (or cross-sectional area)  132 ,  198 ,  254  that varies (e.g., increases and/or decreases) in the axial direction  120  along the central axis  119  of the spray cap  29  as shown in  FIGS. 12-14 .  FIGS. 12 to 14  each shows a cross-sectional side view of an embodiment of the flow control passage  14  of  FIGS. 1-11 . As illustrated in  FIG. 12 , the flow control passage  14  is a constant width passage  300  having a radial width (or cross-sectional area)  132 ,  198 ,  254 ,  302  that is constant along the axial direction  120 . In  FIG. 13 , the flow control passage  14  is a converging passage  304  having a radial width (or cross-sectional area)  132 ,  198 ,  254 ,  306  that decreases along the axial direction  120 . In  FIG. 14 , the flow control passage  14  includes a venture-type configuration with a series of a converging passage portion  308 , a throat portion  310 , and a diverging passage portion  312  disposed one after another. The converging passage portion  308  has a radial width (or cross-sectional area)  314  that decreases along the axial direction  120 , the throat portion  310  has a radial width (or cross-sectional area)  316  that is constant along the axial direction  120 , and the diverging passage portion  312  has a radial width (or cross-sectional area)  318  that increases along the axial direction  120 . Again, in each of the illustrated embodiments of  FIGS. 12-14 , the flow control passage  14  may be a continuous annular passage or a substantially annular or segmented annular passage as described in detail above. Furthermore, it may be appreciated that transitions between adjacent portions (e.g.,  308 / 310  and  310 / 312 ) may be rather smooth, e.g., curved transitions. 
     Furthermore, while the flow control passage  14  discussed above in  FIGS. 12-14  may have the radial width (or cross-sectional area)  132 ,  198 ,  254  that is constant or varies (e.g., increases and/or decreases) in the axial direction  120  along the central axis  119  of the spray cap  29 , some embodiments of the flow control passage  14  may also have the radial width  132 ,  198 ,  254  that is constant or varies in a circumferential direction  124  about the central axis  119  of the spray cap  29  as shown in  FIGS. 15-16 .  FIG. 15  is a cross-sectional front view of an embodiment of the spray cap  29  of  FIG. 2  taken along line  4 - 4 , illustrating another embodiment the flow control passage  14 . As illustrated, the radial width (or cross-sectional area)  132 ,  198 ,  254  of the flow control passage  14  varies (e.g., increases) in the circumferential direction  124  toward the air horn passages  162 , such that the radial width (or cross-sectional area)  132 ,  198 ,  254  is the largest around or adjacent the air horn passages  162  and the smallest between the air horn passages  162  (e.g., approximately midway between or 90 degrees relative to the air horn passages  162 ). Contrarily, in another embodiment, the radial width (or cross-sectional area)  132 ,  198 ,  254  of the flow control passage  14  in  FIG. 16  varies (e.g., decreases) in the circumferential direction  124  toward the air horn passage  162 , such that the radial width (or cross-sectional area)  132 ,  198 ,  254  is the smallest around or adjacent the air horn passages  162  and the largest between the air horn passages  162  (e.g., approximately midway between or 90 degrees relative to the air horn passages  162 ). In each of the illustrated embodiments of  FIGS. 15-16 , the flow control passage  14  may be a continuous annular passage or a substantially annular or segmented annular passage as described in detail above. Furthermore, the radial width or cross-sectional area (e.g.,  132 ,  198 ,  254 ) may gradually change or vary in a substantially smooth manner, e.g., curved transitions. 
     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.