Patent Publication Number: US-8979004-B2

Title: Pneumatic atomization nozzle for web moistening

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 12/400,146, entitled “Pneumatic Atomization Nozzle for Web Moistening”, filed Mar. 9, 2009, which is herein incorporated by reference. 
    
    
     BACKGROUND 
     The invention relates generally to a pneumatic atomization nozzle for web moistening. 
     Magazines, books and other publications are frequently produced on heatset web offset printing presses. Offset printing involves transferring images to a web (e.g., roll of paper) via rotating drums. These drums have an inked impression of images which are transferred to the web as it travels across the rotating drums. In heatset printing, ink may be dried by blowing hot air over the web after the images have been imprinted. However, the hot air may reduce web moisture content, resulting in broken fibers, page growth and/or a wrinkled publication. 
     To prevent this detrimental wrinkling, some printing presses employ a web remoistening system. For example, a web remoistening system may be used to spray the web with water after the drying process to remoisten the web. Current web remoistening systems utilize hydraulic atomization to achieve the desired web moisture content. In hydraulic atomization, a liquid is forced through a small orifice at high pressure to create droplets. Systems that employ hydraulic atomization are expensive because they must be constructed to withstand high liquid pressure. In addition, they require expensive high pressure pumps, liquid manifolds and solenoid valves. Furthermore, because the orifice is small, it tends to get clogged by impurities in the water. Therefore, hydraulic atomization systems typically spray de-ionized water, increasing operational costs. Moreover, hydraulic atomization systems are not well suited for web moistening at low flow rates because they tend to produce smaller droplets, thereby causing poor remoistening efficiency. 
     BRIEF DESCRIPTION 
     A system, in certain embodiments, includes a nozzle. The nozzle includes a liquid passage, a first pneumatic passage, and an exit surface. The exit surface includes at least one recirculation inducing feature configured to reduce deposits adjacent to the first pneumatic passage. 
    
    
     
       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 process flow diagram of a printing process in accordance with certain embodiments of the present technique; 
         FIG. 2  is a block diagram of a web moistening system in accordance with certain embodiments of the present technique; 
         FIG. 3  is a perspective view of a web moistening system in accordance with certain embodiments of the present technique; 
         FIG. 4  is a perspective view of a modular web moistening assembly taken within line  4 - 4  of  FIG. 3  in accordance with certain embodiments of the present technique; 
         FIG. 5  is a cross-sectional side view of a manifold having a thermally isolated liquid passage taken along line  5 - 5  of  FIG. 4  in accordance with certain embodiments of the present technique; 
         FIG. 6  is a partial cross-sectional front view of the manifold having a thermally isolated liquid passage taken along line  6 - 6  of  FIG. 5  in accordance with certain embodiments of the present technique; 
         FIG. 7  is an exploded perspective view of the modular web moistening assembly of  FIG. 4  showing certain web moistening modules separated from the manifold in accordance with certain embodiments of the present technique; 
         FIG. 8  is an exploded top perspective view of a module of the modular web moistening assembly taken within line  8 - 8  of  FIG. 7  in accordance with certain embodiments of the present technique; 
         FIG. 9  is an exploded bottom perspective view of a manifold and spray device assembly taken within line  9 - 9  of  FIG. 8  in accordance with certain embodiments of the present technique; 
         FIG. 10  is an exploded perspective view of multiple layers of a manifold that may be used in the module of  FIG. 8  in accordance with certain embodiments of the present technique; 
         FIG. 11  is a top view of three spray devices that may be employed in the web moistening system of  FIG. 3  in accordance with certain embodiments of the present technique; 
         FIG. 12  is a perspective view of a spray device that may be employed in the web moistening system of  FIG. 3  in accordance with certain embodiments of the present technique; 
         FIG. 13  is a schematic diagram of a front view of a spray device that may be employed in the web moistening system of  FIG. 3  in accordance with certain embodiments of the present technique; 
         FIG. 14  is an exploded view of a spray device that may be employed in the web moistening system of  FIG. 3  in accordance with certain embodiments of the present technique; 
         FIG. 15  is a top view of a first layer of the spray device represented in  FIG. 14  in accordance with certain embodiments of the present technique; 
         FIG. 16  is a top view of a second layer of the spray device represented in  FIG. 14  in accordance with certain embodiments of the present technique; 
         FIG. 17  is a top view of a third layer of the spray device represented in  FIG. 14  in accordance with certain embodiments of the present technique; 
         FIG. 18  is a top view of a fourth layer of the spray device represented in  FIG. 14  in accordance with certain embodiments of the present technique; 
         FIG. 19  is a top view of an alternative embodiment of the third layer of the spray device represented in  FIG. 14  in accordance with certain embodiments of the present technique; 
         FIG. 20  is a top view of an alternative embodiment of the fourth layer of the spray device represented in  FIG. 14  in accordance with certain embodiments of the present technique; 
         FIG. 21  is a detailed top view of the liquid and pneumatic orifices of the alternative embodiment of the fourth layer of the spray device represented in  FIG. 14  in accordance with certain embodiments of the present technique; 
         FIG. 22  is a top view of a second alternative embodiment of the third layer of the spray device represented in  FIG. 14  in accordance with certain embodiments of the present technique; 
         FIG. 23  is a top view of a second alternative embodiment of the fourth layer of the spray device represented in  FIG. 14  in accordance with certain embodiments of the present technique; 
         FIG. 24  is a detailed top view of the liquid and pneumatic orifices of the second alternative embodiment of the fourth layer of the spray device represented in  FIG. 14  in accordance with certain embodiments of the present technique; and 
         FIG. 25  is a top view of a third alternative embodiment of the fourth layer of the spray device represented in  FIG. 14  in accordance with certain embodiments of the present technique. 
     
    
    
     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. Any examples of operating parameters and/or environmental conditions are not exclusive of other parameters/conditions of the disclosed embodiments. 
     Embodiments of the present disclosure may reduce the cost of web moistening systems and provide enhanced moistening performance by employing pneumatic web moistening nozzles. For example, compared to hydraulic atomization, pneumatic systems may achieve effective web moistening with lower liquid pressures. Lower pressure operation may significantly reduce the production and/or operational costs associated with web moistening systems. For example, manifolds and nozzles may be constructed from less expensive materials such as aluminum, stainless steel or plastic. In addition, as compared to the machined components of hydraulic atomizers, the manifolds and nozzles may be constructed from laminated layers including internal passages that are secured together to form complete structures. Because these internal passages may be formed using less expensive techniques (e.g., laser cutting, water jet, plasma cutting, etching, etc.), the overall cost and production time of web moistening systems may be reduced. In addition, smaller and less expensive liquid pumps (e.g., gear pumps, peristaltic pumps, etc.) may be employed for pneumatic web moistening systems. In certain embodiments, these pumps may be configured to regulate the flow of liquid without utilizing expensive pressure regulating valves. 
     In further embodiments, the web moistening system may employ a modular design configured to reduce construction costs by enabling faster assembly of the system. Specifically, modules may include preassembled nozzles, valves, manifolds, and associated electronic devices. When a customer orders a web moistening system, an appropriate number of modules may be readily mounted to the system. This construction technique may significantly reduce assembly time compared to individually mounting each nozzle, manifold, valve and electronic component to the web moistening system. In addition, each module may include a protective hood configured to block water from entering the module and interfering with operation of the valves and/or electronic components. Furthermore, pressurized air may be routed to each module to increase the pressure under the hood such that the internal pressure is greater than the external air pressure. This arrangement may prevent humid outside air and/or debris from entering the module. In certain configurations, the hood may be constructed from a transparent or semi-transparent material, such as a translucent plastic, for example. Such a configuration may enable an operator to visually determine which nozzles are in operation via lights mounted within the module. 
     Further embodiments may include a manifold configured to provide air and liquid to the pneumatic nozzles. The manifold may include an air tube disposed about a water tube. This arrangement may limit the formation of condensation on the manifold. Specifically, the flow of air may thermally insulate the surface of the manifold from the cooler water. Maintaining the manifold at a warmer temperature may limit the formation of condensation. In certain configurations, the manifold may be positioned above a web. In such arrangements, limiting condensation on the manifold may prevent excess water from contacting and being absorbed by the web. 
     In certain embodiments, the pneumatic web moistening nozzle includes a liquid orifice and a pair of pneumatic orifices disposed on opposite sides of the liquid orifice. In this configuration, liquid droplets emitted from the liquid orifice may form a substantially flat fan-shaped pattern in a plane of the orifices. Furthermore, in certain embodiments, the pneumatic web moistening nozzle may be configured to reduce a buildup of salt and/or other minerals that may interfere with gas flow through the pneumatic orifices. Specifically, in one embodiment, a surface defining each pneumatic orifice may include an angled portion configured to provide a point adjacent to each pneumatic orifice. Due to the small surface area of the point, any collected minerals may be dislodged by gas flow through the pneumatic orifices and/or vibrations of the pneumatic web moistening nozzle, thereby reducing the accumulation of minerals that may obstruct gas flow. In a second embodiment, each pneumatic orifice may include an expansion portion disposed on a side opposite from the liquid orifice. It is believed that the expansion portions may induce recirculation, causing deposits to accumulate on an angled portion and/or within a corner of each expansion portion. Any collected minerals may be dislodged by gas flow through the pneumatic orifices and/or vibrations of the pneumatic web moistening nozzle, thereby reducing the accumulation of minerals that may obstruct gas flow. 
     As discussed in detail below, pneumatic web moistening nozzles may utilize larger liquid orifices and provide higher droplet velocities than hydraulic atomizers. The larger liquid orifice may be less prone to clogging because small particles may simply pass through instead of becoming lodged and obstructing liquid flow. Because the liquid orifice may be able to accommodate particles in the liquid, tap water may be used as the moistening liquid, instead of the more expensive de-ionized water. In addition, the larger liquid orifice may facilitate spraying other liquids, including silicone emulsions and lotion. Moreover, the higher droplet velocities may increase liquid deposition efficiency. 
       FIG. 1  presents a process flow diagram of heatset web offset printing  10  using a unique web remoistening system in accordance with certain embodiments of the invention. First, as represented by block  12 , ink is applied to a web. The web may be paper, for example, or any other substrate to which ink may be applied. In alternative embodiments, the web  102  may be a metal sheet to which oil may be applied, for example. The web is stored in rolls, which are unwound as the web travels through the printing process  10 . In offset printing, ink is first applied to a rotating plate cylinder by ink rollers. The ink is then transferred to an offset cylinder or rubber blanket cylinder which is in contact with the plate cylinder and rotating in the opposite direction. Finally, ink is applied to the web as it travels across the rotating offset cylinder. 
     However, the ink is still wet at this point in the printing process  10 . Therefore, the process  10  may proceed to dry the ink in an oven, as represented by block  14 . Web drying ovens generally circulate hot air over the web to dry the ink before it runs or smudges. Because the drying process  14  may leave the web excessively hot, the web may be cooled on a series of chilled rollers, as represented by block  16 . 
     Heating the web in the oven, as represented by block  14 , may have the undesirable effect of reducing web moisture content. If the web becomes too dry, wrinkling, broken fibers and/or page growth may occur during or after the binding process. Therefore, the printing process  10  may employ a liquid spray system to remoisten the web, as represented by block  18 . For example, the web remoistening system may employ a series of nozzles which spray a liquid onto the web as it travels through the system. In the disclosed embodiments, the web remoistening system may include pneumatic web moistening nozzles that provide high droplet deposition efficiency and substantially uniform spray patterns, while reducing mineral buildup that may interfere with the spray patterns. This configuration may provide increased web speed through the web remoistening system. Once the proper moisture content has been established, the web may be bound into its final publication form, as represented by block  20 . For example, the web may be folded, cut and bound into books, magazines or brochures. 
       FIG. 2  shows a block diagram of one embodiment of a web moistening system  100  using a unique configuration to enhance droplet deposition efficiency, reduce mineral buildup and provide uniform droplet distribution in accordance with certain embodiments of the invention. As previously discussed, a web  102  may enter the moistening system  100  after it has been cooled by the chilled rollers. The web  102  may then pass over a grounded reversing roller  104  and be charged by a corona-charging electrode  106 . The corona-charging electrode  106  bombards the web  102  with ions (charged particles), inducing a positive charge on the surface of the web  102 . This positive charge is represented by plus signs located on the side of the web  102 . To ensure that the maximum possible charge is applied, the reversing roller  104  may be grounded. 
     The web may then pass between a pair of spray devices  108 . While only two spray devices  108  are depicted in  FIG. 2 , each spray device  108  may represent a series of spray devices  108  extending along the width of the web  102  (e.g., perpendicular to the page). Also, additional spray devices  108  may be positioned along the direction of travel of the web  102 . The number and configuration of spray devices  108  may be selected to achieve proper web moisture content. Each spray device  108  may be grounded. During atomization, the positively charged web  102  may induce a negative charge on the liquid droplets. In alternative embodiments, the corona-charging electrode  106  may be configured to induce a negative charge on the surface of the web  102 , which may impart a positive charge on the liquid droplets. As the droplets approach the web  102 , they may then be electrostatically attracted to the web  102 , resulting in enhanced atomization and/or increased liquid penetration. 
     The spray devices  108  in the present embodiment may be pneumatic atomizers. As discussed in detail below, pneumatic atomizers may utilize large liquid orifices and provide high droplet velocities. The large liquid orifice may be less prone to clogging because small particles may simply pass through instead of becoming lodged and obstructing liquid flow. For example, an area of the large liquid orifices may be approximately 0.03 to 10, 0.1 to 5, 0.15 to 1, or about 0.2 square millimeters. In contrast, an area of the smaller hydraulic orifices may be less than approximately 0.005 to 0.01 square millimeters. For example, in certain configurations, pneumatic orifices may be approximately 25 times larger than hydraulic orifices. Moreover, the high droplet velocities may increase liquid deposition efficiency. In addition, spray devices  108  employing pneumatic atomization may propel droplets a greater distance than hydraulic atomizers. Specifically, as air pressure to a pneumatic atomizer is increased, droplets may be propelled a greater distance. In contrast, increasing liquid pressure in a hydraulic atomizer decreases droplet size, thereby reducing the distance a droplet may travel. For example, hydraulic atomizers may propel droplets approximately 1 foot, while pneumatic atomizers may propel droplets approximately 1.5 to 3, 2 to 4, or about 2 feet. Spray devices  108  may use both a gas source and a liquid source. Gas may be supplied by pneumatic supplies  110 , such as low pressure, high volume blowers, for example. Liquid may be supplied by liquid supplies  112 . In this embodiment, a low liquid flow rate may be desired. Therefore, the liquid supplies  112  may include gear pumps or peristaltic pumps. For example, gear pumps may be configured to provide a constant flow of liquid to the spray devices  108 . In addition, flow rate may be easily adjusted by varying gear speed, gear size and number of teeth on each gear. 
     In certain embodiments, the liquid supply  112  may include a storage tank configured to provide water, or other liquid, to the spray devices  108 . In such configurations, the tank may be elevated relative to the spray devices  108  to deliver an appropriate water pressure for web moistening. For example, in certain embodiments, the hydraulic head alone (i.e., without a pump) may be used to deliver the liquid (e.g., water) to the spray devices  108 . Alternatively, or in combination with an elevated tank, a pump (e.g., gear pump or peristaltic pump) may be coupled to the tank to deliver liquid to the spray devices  108  at a desire pressure and/or flow rate. In certain embodiments, the pump may be configured to pressurize the liquid to less than approximately 5, 4, 3, 2, or 1 bar, or approximately 0.1 to 1 bar, 0.2 to 0.9 bar, 0.3 to 0.8 bar, 0.4 to 0.7 bar, or about 0.5 bar. As appreciated, these liquid pressures are significantly lower than those used for hydraulic atomization. For example, hydraulic atomizers may operate at liquid pressures between approximately 5 to 100 bar. Lower pressure operation may significantly decrease the production and operational costs of the web moistening system  100  compared to higher pressure hydraulic atomization systems. For example, manifolds and nozzles for hydraulic atomizers are typically machined from solid blocks of material to eliminate joints that may leak at the higher pressures. Brass is generally employed for such pneumatic components because it is well suited for complex machining operations. However, machining components is both expensive and time consuming, thereby increasing production costs. In addition, to prevent corrosion of the brass components, caustic soda may be added to the liquid, thus increasing operational costs. In contrast, due to the lower pressures associated with pneumatic atomization, the manifolds and nozzles may be constructed from less expensive materials such as aluminum, composites (e.g., fiberglass), stainless steel or plastic, for example. In certain embodiments, the manifolds and/or nozzles may be constructed from extruded aluminum having an anti-corrosion coating. In addition, as compared to machining components, the manifolds and nozzles may be constructed from laminated layers including internal passages that are secured together to form complete structures. Because these internal passages may be formed using less expensive techniques (e.g., laser cutting, water jet, plasma cutting, etching, etc.), the overall cost and production time of the web moistening system  100  may be reduced. 
     As discussed above, certain embodiments may employ a gear pump to supply a liquid to the spray devices  108 . A gear pump may include a housing containing a drive gear interlocked with an idle gear. The housing may be configured such that a minimum gap exists between an interior surface of the housing and teeth coupled to each gear. The drive gear may be coupled to a shaft that extends outside of the housing and is driven to rotate by an electric motor, for example. A liquid inlet and liquid outlet of the housing may be positioned perpendicular to the direction of gear rotation and aligned with the interlocking portion of the gears. As the drive gear rotates, the idle gear may be induced to rotate and liquid may be pumped from the inlet to the outlet via motion of the gear teeth. Specifically, as the teeth of the drive gear and idle gear rotate, liquid becomes trapped within a space defined by the gear teeth and the interior surface of the housing. As the gears rotate, the trapped liquid is transported from the inlet side of the housing to the outlet side. In this manner, the gear pump may provide a constant liquid flow. 
     Further embodiments may employ a peristaltic pump. A peristaltic pump may include an annular flexible conduit and a rotor configured to compress a portion of the conduit. The flexible conduit may be disposed adjacent to an interior surface of a substantially rigid annular structure, and the rotor may be disposed adjacent to the conduit on an opposite side from the annular structure. The rotor may be connected to a shaft disposed within the center of the annular structure and driven to rotate by an electric motor, for example. As the shaft rotates, the rotor compresses the flexible conduit against the rigid annular structure. The rotor then moves along the entire circumferential extent of the flexible conduit, thereby establishing a pressure differential between liquid at an entrance to the conduit and the liquid exiting the conduit. This pressure differential induces liquid to flow through the pump in discrete pulses. As appreciated, flow rates for both the gear pump and the peristaltic pump may be varied by adjusting the speed of the driving motor to achieve a desired liquid pressure within the web moistening system  100 . 
     Alternative embodiments may utilize water provided by a public utility (i.e., tap water). However, the tap water may be supplied at greater than 3 bar, for example. Therefore, the liquid supply  112  may be configured to reduce the liquid pressure prior to the liquid entering the spray devices  108 . For example, the liquid supply  112  may include a flow rate controller and/or a pressure regulator. The flow rate controller may be configured to selectively open and close a valve to allow a precise quantity of liquid to flow from the water source (e.g., public utility) to the spray devices  108 , thereby establishing a desired liquid pressure. Similarly, the pressure regulator may be configured to reduce the incoming pressure to a desired level, while accounting for pressure variations in the supplied liquid. The flow rate controller and/or the pressure regulator may ensure that the spray devices  108  receive an appropriate liquid pressure (e.g., approximately 0.5 bar) such that a desired quantity of liquid is delivered to the web  102 . 
     The corona-charging electrode  106 , the pneumatic supplies  110  and the liquid supplies  112  may be controlled by a control system  114 . The control system  114  may include an electrostatic controller  116 , a liquid supply controller  118 , a pneumatic supply controller  120 , a computer system  122  and a user interface  124 . For example, the electrostatic controller  116  may adjust the voltage and/or current supplied to the corona-charging electrode  106  based on a desired web charge. Similarly, the liquid supply controller  118  and the pneumatic supply controller  120  may adjust the output of the liquid supply  112  and the pneumatic supply  110 . For example, if the liquid supplies  112  include gear pumps, the liquid supply controller  118  may adjust the speed of each gear pump based on a desired liquid flow rate. The liquid supply controller  118  may be described as a continuous flow controller, and may continuously adjust the gear pump to maintain accurate control of the flow rate. Each of the individual controllers may be regulated by the computer system  122  coupled to the user interface  124 . The user interface  124  may allow an operator to adjust parameters of the web moistening system  100  through a graphical user interface. 
       FIG. 3  is a perspective view of a web moistening system  100  having a unique atomization mechanism in accordance with certain embodiments of the invention. In this embodiment, the web (not shown) may enter along the reversing roller  104 . The web may then pass between two rows of spray devices  108 , one on each side of the web. Each spray device  108  may spray a fan shaped stream of liquid onto the web, establishing the desired moisture content. Because the present embodiment utilizes pneumatic atomizers, the liquid stream may have a greater velocity than web moistening systems  100  employing hydraulic atomizers. This higher velocity stream may increase liquid deposition efficiency. 
     As illustrated, a mechanical/electrical enclosure  126  is disposed adjacent to the web moistening section of the system  100 . In certain embodiments, the enclosure  126  may be covered by one or more panels to protect the electrical and mechanical components disposed within the enclosure  126 . The enclosure  126  includes a control cabinet  128  that may include elements of the control system  114  previously described with regard to  FIG. 2 . Furthermore, the enclosure  126  includes a high-voltage electrical supply  130  that may provide electrical power to the corona-charging electrode  106 . Components of the pneumatic supply  110  and the liquid supply  112  are also contained within the enclosure  126 . 
     In the present embodiment, the liquid supply  112  includes a liquid inlet  132 , an inlet pressure controller  134 , a liquid filter  136 , a flow rate controller  138 , and liquid outlets  140 . For example, water from a public utility may enter the liquid supply  112  through the liquid inlet  132 . The water may then flow into the inlet pressure controller  134  (e.g., pressure regulator). The inlet pressure controller  134  may be configured to reduce the pressure of the incoming water to a desired level appropriate for web moistening. The inlet pressure controller  134  may also monitor incoming water pressure to ensure the pressure is sufficient for web moistening. The water may then flow into the liquid filter  136  to remove contaminants that may be present within the tap water. Specifically, the liquid filter  136  may be configured to collect particulate matter within the water such that the particulates do not obstruct flow paths downstream from the filter  136 . The water flows from the filter  136  to the flow rate controller  138 . As previously described, the flow rate controller  138  may be configured to provide continuous liquid flow regulation, i.e., accurate control and/or precise adjustment of liquid flow rates. In certain embodiments, the flow rate controller  138  may include a flow meter coupled to a low pressure controller configured to monitor and continuously adjust liquid flow to achieve a desired level. For example, pressure may be adjusted such that the spray devices  108  provide approximately 2 grams of water for each square meter of the web  102 , thereby establishing a proper web moisture content. As appreciated, the flow rate may be higher or lower depending upon the configuration of the web  102  (e.g., initial moisture content, material properties, binding operations, etc.). For example, the flow rate controller  138  may be configured to enable the spray devices  108  to provide approximately 0.5, 1, 1.5, 2.5, 3, 3.5, 4, 5, 6, 8, 10, or more grams of water for each square meter of the web  102 . The water from the flow rate controller  138  then flows to the liquid outlets  140 . A hose (not shown) or other suitable fluid connector may couple the flow rate controller  138  to the liquid outlets  140 . 
     Alternative embodiments may include a gear pump or peristaltic pump to flow the liquid from the liquid inlet  132  to the liquid outlets  140 . For example, if the liquid pressure entering the liquid inlet  132  is lower than a desired pressure for web moistening, the pump may increase the pressure to the desired level. In addition, the pump may be configured to precisely regulate the pressure and/or flow rate of liquid provided to the spray devices  108 . In certain embodiments, the pump may have sufficient control of liquid flow to obviate the pressure regulating functions of the inlet pressure controller  134  and/or the flow rate controller  138 . In such embodiments, these controllers  134  and/or  138  may be omitted. However, as appreciated, a peristaltic pump may provide uneven flow due to the pulsating nature of the pumping system. Therefore, configurations employing a peristaltic pump may also include the flow rate controller  138  downstream from the pump to provide a substantially constant liquid pressure to the outlets  140 . The liquid outlets  140 , in turn, may provide liquid to a liquid inlet  142  within the web moistening section of the system  100 . A hose or other fluid connector (not shown) may couple the outlets  140  to an inlet  142  on each row of spray devices  108 . 
     The pneumatic supply  110  may include a blower  144  and pneumatic outlets  146 . As previously discussed, the blower  144  may be configured to provide low-pressure, high-volume air to the spray devices  108 . For example, the blower  144  may provide air at a flow rate of about 1 to 20, 2 to 10, or approximately 2 to 5 standard cubic feet per hour. This configuration may enable the spray devices  108  to properly atomize the liquid provided by liquid supply  112 . In certain embodiments, the spray devices  108  may be configured to utilize a constant pneumatic flow rate. In such embodiments, the blower  144  may be a constant speed blower, thereby reducing the cost of the web moistening system  100 . In further embodiments, the constant speed blower may be coupled to a valve configured to vent a portion of the air to the outside. By adjusting the position of this valve, variable pneumatic flow rates may be achieved with a constant speed blower. Air may be transferred from the pneumatic outlets  146  to a pneumatic inlet  148  disposed on each row of spray devices  108 . A hose or other pneumatic connector (not shown) may couple the outlets  146  to the inlets  148 . 
     In addition, the web moistening system  100  includes a series of cables  150  that link the control cabinet  128  with spray devices  108 . In certain embodiments, the cables  150  are configured to provide both electrical power and control signals to the spray devices  108 . Alternatively, separate control and power cables  150  may be employed. As discussed in detail below, the spray devices  108  may be organized into modules, with each module including a circuit board. A valve associated with each spray device  108  may be coupled to the circuit board within each module. A cable  150  electrically couples the control cabinet  128  to a first module. Another cable  150  then couples the first module to a second module. Further cables  150  are provided such that each module is linked to a successive module. Control signals from the control cabinet  128  flow through the cables  150  to each successive module. For example, the web moistening system  100  may employ the controller-area network (CAN or CAN-bus) standard to facilitate communication between the control cabinet  128  and each module. This standard may enable various components of the web moistening system  100  to communicate with one another without a host computer. Further embodiments may utilize the CANopen standard, which is an open protocol and may be better suited for web moistening systems  100 . In certain embodiments, a single cable  150  may connect with multiple modules, e.g., a single cable may include multiple connectors to plug into the multiple modules. For example, the system may include a single cable  150  for each row of modules or a single cable  150  for all modules. Using the one or more cables  150 , the control system  114  may control the operation of each spray device  108 . For example, certain webs  102  may not extend along the entire width of the web moistening assembly. In such situations, certain spray devices  108  (i.e., those not adjacent to the web  102 ) may be deactivated by closing valves associated with those spray devices  108 . This configuration may conserve water by only activating spray devices  108  adjacent to the web  102 . In certain embodiments, web width and position may be determined automatically via sensors in the web moistening system  100 . The control system  114  may then activate the appropriate spray devices  108  based on the detected web width and position. 
       FIG. 4  is a perspective view of a modular web moistening assembly taken within line  4 - 4  of  FIG. 3 . As illustrated, three modules  152  are positioned on each row of spray devices  108 . More or fewer modules  152  may be employed in alternative embodiments. For example, certain configurations may include 1, 2, 4, 5, 6, 7, 8, 9, 10, or more modules  152  positioned along each side of the web  102 . The number of modules  152  may be selected based on web width. For example, web moistening systems  100  configured to accommodate narrower webs  102  may include fewer modules than those configured to accommodate wider webs  102 . In addition, while 8 spray devices  108  are coupled to each module  152 , more or fewer spray devices  108  may be included in alternative embodiments. For example, certain embodiments of the modules  152  may include 2, 3, 4, 5, 6, 7, 9, 10, 12, 14, 16, or more spray devices  108  per module  152 . 
     This modular configuration may reduce construction costs by enabling faster assembly of the web moistening system  100 . For example, a number of modules  152  may be assembled and stored. Each module  152  may include preassembled spray devices  108 , valves, manifolds, and associated electronic devices. When a customer orders a web moistening system  100  configured to accommodate a particular web width, an appropriate number of modules  152  may be readily removed from storage and mounted to the system  100 . This construction technique may significantly reduce assembly time compared to individually mounting each spray device  108 , manifold, valve and electronic component to the web moistening system  100 . Reduced construction time may facilitate lower manufacturing costs and faster deliver times. 
     In addition, each module  152  includes a protective hood  154  disposed on an opposite side from the spray devices  108 . In alternative embodiments, the hood  154  may be disposed on the same side of each module  152  as the spray devices  108 . The hood  154  may serve to block water from the spray devices  108  from entering the module  152  and interfering with operation of the valves and/or electronic components. This configuration may further reduce construction costs compared to individually sealing each valve/electronic assembly associated with each spray device  108 . Pressurized air from the pneumatic supply  110  may be routed through a conduit within a manifold  156  to each module  152 . The pressurized air may increase the pressure under the hood  154  such that the internal pressure is greater than the external air pressure. This arrangement may block or oppose entry of external debris or humid outside air into the module  152  without employing expensive hood sealing devices. For example, the moisture content of the outside air may be greater than approximately 80% relative humidity due to the presence of water droplets from the spray devices  108 . This moist air may interfere with operation of the valves and/or electronic components within the module  152 . Therefore, blocking outside air from entering the module  152  via internal pressurization may ensure proper operation of the components within module  152 . 
     In certain configurations, the hood  154  may be constructed from a transparent or semi-transparent material, such as a translucent plastic, for example. Such a configuration may enable an operator to visually determine which spray devices  108  are in operation via lights mounted within the module. As previously discussed, each spray device  108  may have an associated valve configured to regulate the flow of liquid and/or air into the spray device  108 . These valves may be coupled to a common circuit board disposed within each module  152 . The circuit board may include a series of lights corresponding to the position of each valve. For example, the circuit board may include one light emitting diode (LED) for each valve. The LED may be configured to illuminate when the valve is open (i.e., the associated spray device  108  is in operation). In certain embodiments, a green light may indicate operation, a red light may indicate no operation, and/or a yellow light may indicate a problem. Any configuration of lights and colors may be used to indicate operational characteristics of the valves and other components of the modules  152 . In this configuration, an operator may determine the position of each valve by visually inspecting the LEDs through the transparent or semi-transparent hood  154 . This hood configuration may reduce construction costs compared to configurations employing opaque hoods  154  with lights mounted on the surface. Specifically, the transparent or semi-transparent hood  154  may obviate additional components and operations associated with sealing passages for wires and/or connectors coupled to external lights. 
     As illustrated, the cable  150  connects the mechanical/electrical enclosure  126  to a first module  152 . In certain embodiments, the cable  150  is configured to electrically couple to the circuit board within the first module  152  via a first connector mounted on the bottom of the module  152 . A second connector on the bottom of the first module  152  may couple the circuit board to a second cable  150  that electrically couples the first module  152  to a second module  152 . Similar configurations may be employed to link each of the modules  152  together. This configuration may reduce construction costs compared to systems employing one or more cables linking each spray device  108  to the enclosure  126 . Furthermore, because the cable  150  does not pass through the hoods  154 , the hoods  154  may be manufactured without holes and/or sealing devices (e.g., grommets), thereby reducing the cost of hood construction. 
       FIG. 5  is a cross-sectional side view of the manifold  156  including a thermally isolated liquid passage taken along line  5 - 5  of  FIG. 4 . The manifold  156  includes an outer structure defining a pneumatic passage  158  configured to provide air from the pneumatic supply  110  to the spray devices  108 . The manifold  156  also includes an inner structure defining a liquid passage  160  configured to provide liquid from the liquid supply  112  to the spray devices  108 . As illustrated, the liquid passage  160  is nested within the pneumatic passage  158 . In other words, the pneumatic passage  158  circumscribes the liquid passage  160 . In the present embodiment, both the liquid passage  160  and the pneumatic passage  158  are rectangular. Alternative embodiments may employ other cross-sectional configurations, such as circular, polygonal or elliptical, for example. In addition, the liquid passage  160  of the present embodiment contacts the pneumatic passage  158  along two surfaces. In further embodiments, the liquid passage  160  may contact 0, 1 or 3 surfaces. As illustrated, the air inlet  148  is coupled to the pneumatic passage  158 , while the liquid inlet  142  is coupled to the liquid passage  160 . This coaxial configuration may reduce the formation of condensation on the surface of the manifold  156 . 
     As previously discussed, evaporation of liquid droplets may increase air moisture content to approximately 80% or higher relative humidity. Therefore, if the liquid passing through a liquid passage is colder than the surrounding air, condensation may form on the liquid passage. As seen in  FIG. 4 , one row of spray devices  108  is positioned directly above one of the rollers. Therefore, any condensation that forms on a liquid passage may potentially fall onto the web  102 . In addition, because the web may be positively charged, a negative charge may be induced on the falling droplets. In certain configurations, the charge may be sufficient to attract droplets toward the web  102  even if a row of spray devices  108  is not positioned directly above a roller. The opposite charge may cause the droplets to be readily absorbed into the web  102 , thus resulting in excessive and non-uniform web moisture content. Furthermore, the water droplets may stain the web, thereby rendering a portion of the web unacceptable for publication. Therefore, limiting the formation of condensation on the surface of the manifold  156  may reduce the possibility of excessive and non-uniform web moisture and/or staining of the web. 
     As appreciated, increasing air pressure also increases air temperature. Therefore, pressurized air from the blower  144  may be warmer than the outside air. As illustrated in  FIG. 5 , this warm air flowing through the air passage  158  may at least partially surround the liquid passage  160 , thereby thermally insulating the liquid from the outside air. Specifically, the warm air within the air passage  158  may increase the surface temperature of the manifold  156  such that significantly less condensation forms on the manifold  156 . In other words, the warm air may thermally isolate the liquid passage  160  from the surface of the manifold  156 , thereby reducing condensation. In certain embodiments, the system may include a heater to elevate the temperature of the air, the manifold  156 , or a combination thereof. 
       FIG. 6  is a partial cross-sectional front view of the manifold  156  taken along line  6 - 6  of  FIG. 5 . The liquid flowing in direction  162  may cause condensation to form on the liquid passage  160 . However, because the liquid passage  160  is completely circumscribed by the pneumatic passage  158 , any condensation that forms on the surface of the liquid passage  160  may be contained within the pneumatic passage  158 . Furthermore, condensation may be dislodged and captured by air flow in direction  164 , and ultimately expelled through the spray devices  108 . 
       FIG. 7  is an exploded perspective view of the modular web moistening assembly of  FIG. 4  showing certain web moistening modules  152  separated from the manifold  156 . As previously discussed, this configuration may reduce construction costs by facilitating decreased assembly time of the web moistening system  100 . As illustrated, the manifolds  156  may serve to support the modules  152  in addition to providing liquid and air to the spray devices  108 . Specifically, each module  152  may be secured to the manifold  156  by bolts  166 . While four bolts per module are illustrated in  FIG. 7 , alternative embodiments may include more or few bolts, such as 2, 3, 5, 6, 7, 8, or more bolts  166 . In addition, manifold  156  includes four liquid passages  168  and two pneumatic passages  170  for each module  152 . As appreciated, more or fewer passages  168  and/or  170  may be employed in alternative embodiments. For example, the manifold  156  may include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more passages  168  and/or  170  for each module  152 . As discussed in detail below, each module  152  includes corresponding orifices configured to align with the passages  168  and  170  within the manifold  156 . In this configuration, both liquid and air may flow into the modules  152  and ultimately to the spray devices  108 . The modules  152  also include fasteners  172  configured to secure to bolts  166 , thereby coupling the modules  152  to the manifold  156 . In the illustrated embodiment, the modules  152  are arranged in two parallel rows with three modules  152  per row. In other embodiments, each row may include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more modules  152  per row depending on the size and nature of the web moistening system  100 . 
       FIG. 8  is an exploded top perspective view of a module  152  of the modular web moistening assembly taken within line  8 - 8  of  FIG. 7 . As illustrated, the hood  154  has been separated from the remainder of the module structure. The module  152  includes stand-off posts  174  configured to secure the hood  154  to the module  152  via bolts  176 . Specifically, three bolts  176  may pass through openings  177  in the hood  154  and secure to the stand-off posts  174 , thereby coupling the hood  154  to a manifold  178 . More or fewer bolts  176 , openings  177  and stand-off posts  174  may be employed in alternative embodiments. For example, the module  152  may include 1, 2, 4, 5, 6, 7, 8, or more bolts  176 , openings  177  and stand-off posts  174 . 
     As previously discussed, the hood  154  may serve to protect a circuit board  180  and valves  182  from external moisture and other contaminants. As illustrated, the circuit board  180  is mounted perpendicular to the manifold  178 . In alternative configurations, the circuit board  180  may be mounted parallel and adjacent to the manifold  178  (i.e., between the manifold  178  and the valves  182 ), or above the valves  182 . In the present embodiment, each valve  182  is positioned directly opposite the manifold  178  from each spray device  108 . As discussed in detail below, the manifold  178  is configured to direct a flow of liquid through each valve  182  prior to directing the liquid into the spray device  108 . Each valve  182  includes a connector  184  that may be coupled to the circuit board  180 . As previously discussed, the cable  150  may couple to the circuit board  180  to control the operation of the valves  182 . Control signals from the cable  150  may pass through the circuit board  180  to each of the valves  182  via the connectors  184 . Such an arrangement may reduce construction costs compared to providing each valve  182  with an individual electronic control unit. In certain embodiments, the connectors  184  may be configured to plug directly into the circuit board  180 . This configuration may reduce construction costs due to decreased assembly time and fewer parts (e.g., connecting wires). In addition, LEDs  185  may be mounted to the circuit board  180  to indicate the operation of each spray device  108 . For example, a control signal may direct a valve  182  to open. The circuit board  180  may include circuitry configured to detect the position of each valve  182  and illuminate an LED associated with the valve  182  to indicate valve position (e.g., lit LED indicates valve is open). 
     In further embodiments, the circuit board  180  may include additional circuitry configured to directly control valve operation based on input pressures or flow rates. For example, the control system  114  may output a desired liquid flow rate to each of the modules  152  via the cables  150 . Circuitry within each circuit board  180  may then adjust the liquid flow through each spray device  108  to achieve the desired flow rate. This configuration may facilitate an even distribution of liquid droplets across the web  102 . 
     In certain embodiments, the manifold  178  may be composed of multiple layers. These layers may be stacked to form a complete structure including internal liquid and pneumatic passages. As illustrated, the manifold  178  includes an orientation guide  187  to ensure proper orientation (e.g., stacking) of the multiple layers. In certain embodiments, the guide  187  may be a diagonal mark  187  on one side or edge of the multiple layers. Specifically, if any layer is not in the correct order, the mark  187  may not appear as a diagonal line. This configuration may serve to ensure proper flow of air and liquid through the manifold  178 . The mark  187  may be located at any suitable position about the circumference of the manifold  178 . The mark  187  may be etched into the structure of the manifold  178  or marked on the surface. In alternative embodiments, the orientation guide  187  may include an arcuate line, a series of indents, a series of notches, or the like, wherein these indicia indicate a proper order of the layers. As discussed in detail below, a similar orientation guide may be used on multiple layers of the spray devices  108 . 
       FIG. 9  is an exploded bottom perspective view of a manifold  178  and associated spray devices  108  taken within line  9 - 9  of  FIG. 8 , showing a spray device  108  removed from the manifold  178 . As illustrated, the manifold  178  includes 4 openings  186  configured to facilitate passage of bolts  166  through the manifold  178  such that the bolts  166  may couple with fasteners  172  to secure the manifold  178  to the manifold  156 . In addition, manifold  178  includes four liquid inlets  188  and two air inlets  190 . These inlets  188  and  190  are configured to provide liquid and air, respectively, to each of the spray devices  108 . 
     The spray devices  108  are each secured to the manifold  178  by four bolts  191  configured to pass through the spray device  108  and secure to the manifold  178  via four corresponding bolt holes  192 . The manifold  178  also includes a liquid outlet  194  and two pneumatic outlets  196  for each spray device  108 . As discussed in detail below, each spray device  108  includes corresponding pneumatic and liquid inlets. This configuration may facilitate the passage of air and liquid from the pneumatic and liquid inlets  188  and  190 , through the pneumatic and liquid outlets  194  and  196 , to the spray devices  108 . 
     As discussed in detail below, the spray devices  108  may include multiple layers secured together by the bolts  191 . However, these layers may be pre-assembled prior to delivery to a customer. For example, if a spray device  108  is not functioning properly, it may be removed for maintenance. However, once the bolts  191  are removed the layers may separate from one another, thereby increasing the possibility that the layers may be reassembled in an incorrect order. Therefore, each spray device  108  may include one or more bolts or rivets that secure the layers together. This configuration may facilitate enhanced removal and attachment of spray devices  108 . In certain embodiments, the securing bolt or rivet may be located in a corner of the spray device  108  such that each layer may rotate with respect to the next. In such a configuration, passages within the spray device  108  may be cleaned without creating a possibility that the layers may be reordered. 
     Furthermore, as illustrated, the spray devices  108  are secured below the manifold  178  (i.e., along the direction of travel of the web  102 ). This configuration reduces the possibility that dirt and/or other contaminants may clog passages within the spray devices  108  during operation and/or while removing and reinstalling spray devices  108 . For example, due to high web speeds, contaminants attached to the web  102  may be dislodged and impact the modules  152 . However, because the spray devices  108  are positioned below the manifold  178 , any debris from the web  102  may be deposited on an opposite surface from the spray devices  108 . This configuration may increase the time between maintenance cycles, thereby reducing the operational costs associated with the web moistening system  100 . 
       FIG. 10  is an exploded view of a manifold  178 , showing individual layers that comprise flow paths within the manifold  178 . Specifically, manifold  178  includes a first layer  198 , a second layer  200 , a third layer  202 , a fourth layer  204  and a fifth layer  206 . The first layer  198  corresponds to the portion of the manifold  178  coupled to the spray devices  108 , while the fifth layer  206  corresponds to the portion coupled to the valves  182 . As previously discussed, the first layer  198  includes bolt holes  186  configured to couple the manifold  178  to the manifold  156 . The first layer  198  also includes liquid inlets  188  and pneumatic inlets  190 , configured to receive air and liquid from the manifold  156 . Furthermore, the first layer  198  includes liquid outlets  194  and pneumatic outlets  196  configured to provide the spray devices  108  with liquid and air, respectively. 
     As illustrated, the bolt holes  186  extend through each layer  198 ,  200 ,  202 ,  204  and  206 . This configuration enables the bolts  166  to pass through the entire manifold  178  and engage the fasteners  172 . Liquid entering liquid orifices  188  may pass through liquid passages  208  in the second layer  200 . Similarly, air from the pneumatic orifices  190  may pass through pneumatic passages  210 . As illustrated, the diameter of the liquid passages  208  is smaller than the diameter of the liquid inlets  188 , and the diameter of the pneumatic passages  210  is smaller than the diameter of the pneumatic inlets  190 . The difference in diameters may facilitate insertion of O-rings within the liquid passages  208  and/or the pneumatic passages  210 , thereby providing a seal between the manifold  178  and the manifold  156 . In alternative embodiments, diameters of the passages  208  and/or  210  may be substantially the same or larger than the diameters of the respective inlets  188  and/or  190 . 
     The air and liquid may then pass into passages within the third layer  202 . Specifically, the third layer  202  includes liquid passages  212 ,  214 ,  216 ,  218  and  220 , and pneumatic passages  224 ,  226  and  228  that extend within the plane of the layer  202 . Liquid from the liquid passage  208  may enter a first planar liquid passage  212 . As illustrated, the width of the first planar liquid passage  212  is smaller than the diameter of the liquid passage  208 . As appreciated, alternative embodiments may employ a liquid passage  212  having a width substantially similar to or greater than the diameter of liquid passage  208 . A second planar liquid passage  214  and a third planar liquid passage  216  branch off from the first planar liquid passage  212 . In this configuration, substantially equal quantities of liquid may be directed to each passage  214  and  216 . Furthermore, liquid passing through liquid passage  214  flows into a smaller width planar liquid passage  218 , while liquid passing through liquid passage  216  flows into a smaller width planar liquid passage  220 . The width of passages  218  and  220  may be configured to facilitate proper liquid flow into each spray device  108 . In other words, the passages  218  and  220  may ensure a substantially equal pressure drop between each spray device, each module  152  and generally across the web moistening system  100 . 
     In a similar arrangement, air from the air passage  210  flows into the planar air passage  224  in the third layer  202 . The air flow is then split between two planar air passages  226  and  228  that extend in a substantially perpendicular direction to the air passage  224 . As illustrated, the width of the branched passages  226  and  228  is smaller than the width of the air passage  224 . This configuration may establish a substantially even air flow to each of the spray devices  108 . 
     Returning to the liquid flow path, liquid from planar liquid passages  218  and  220  may flow through liquid passages  230  in the fourth layer  204  and exit the manifold  178  through liquid outlets  232  in the fifth layer  206 . As illustrated, the diameters of the liquid passages  230  and the liquid outlets  232  are substantially similar to the widths of the planar liquid passages  218  and  220 . Alternative embodiments may include liquid passages  230  and/or liquid outlets  232  having smaller or larger diameters than the widths of the liquid passages  218  and  220 . As best seen in  FIG. 8 , valves  182  are disposed on the manifold  178  adjacent to the fifth layer  206 . Specifically, one valve is positioned directly adjacent to each liquid outlet  232 . In this configuration, liquid exiting the manifold  178  through liquid outlet  232  may enter the valve  182 . If the valve  182  is in a closed positioned, the path of the liquid terminates at the valve. However, if the valve  182  is in an open position, liquid may pass through the valve  182  and reenter the manifold  178  through a liquid inlet  234 , also disposed adjacent to the valve  182 . The liquid may then flow through a liquid passage  236  in the fourth layer  204  and enter a planar liquid passage  238  in the third layer  202 . Finally, the liquid may pass through a liquid passage  240  in the second layer  200  before exiting the manifold  178  through the liquid outlet  194 . As illustrated, the diameter of the liquid passage  240  may be substantially smaller than the width of the planar liquid passage  238 . This configuration may serve to maintain a substantially even pressure drop across the manifold, while supplying a proper quantity of liquid to the spray devices  108 . 
     In contrast to the liquid flow path, air from the two planar air passages  226  and  228  may be directed back to the second layer  200 . Specifically, because the fourth layer  204  does not include pneumatic passages, air flow may be restricted to layers  198 ,  200  and  202 . Therefore, air from the passages  226  and  228  may flow through air passages  242  within the second layer  200  and exit the manifold  178  through the pneumatic orifices  196 . Similar to the liquid configuration, the diameter of the passages  242  may be configured to maintain a substantially even pressure drop across the manifold, while supplying a proper quantity of air to the spray devices  108 . As appreciated, the thickness of each layer may be configured to establish a suitable flow of air and liquid through the manifold  178 . Furthermore, each illustrated layer may be representative of multiple layers. For example, in certain embodiments, layer  202  may include 2, 3, 4, 5, 6, 7, or more layers to establish an appropriate thickness. 
     The arrangement of air and liquid passages described above may be configured to provide a substantially equal air and liquid pressure to each spray device  108 , thus establishing an even flow of water droplets across the web  102 . As previously discussed, the layers  198 ,  200 ,  202 ,  204  and  206  may be composed of aluminum or stainless steel, and secured together by bolts  166 . Alternative configurations may employ plastic layers that may be laser welded together to form the manifold  178 . For example, the layers may be composed of a plastic that is semi-transparent to infrared radiation. After the layers are aligned, an infrared laser may project a beam into the layers, inducing the layers to fuse together. Such a configuration may provide reduced construction costs compared to aluminum or stainless steel layers, while providing enhanced sealing between layers. This enhanced sealing may enable higher pressure operation compared to bolted layers. Alternatively, aluminum, composite or stainless steel layers may be sealed using various welding, soldering, brazing, diffusion bonding, or adhesion techniques (e.g., via adhesives). Thus, the layered construction of the manifolds  178  may include one or more material bonds along seams between the layers. The material bonds may be along edges, faces, or both, of the adjacent layers. As appreciated, in addition to the multi-layered assembly described above, other embodiments of the manifold  178  may be constructed using alternative techniques. For example, the manifold  178  may be machined from solid blocks of material. 
       FIG. 11  is a top view of three spray devices  108  that may be employed in the present embodiment. As illustrated, each spray device  108  may project a fan-shaped droplet pattern  304  from a liquid orifice  302 . The fan-shaped droplet pattern  304  may be substantially flat and oriented in a direction perpendicular to the direction of travel of the web. The liquid streams  304  depicted in  FIG. 11  overlap each other as they expand, thereby providing substantially uniform water distribution across the web. In other embodiments, the spacing of the spray devices  108  and/or the angle of each fan-shaped droplet pattern  304  may be varied to alter the amount of overlap. Adjustment of these parameters may be based on a desired level of web moistening. 
       FIG. 12  is a perspective view of a spray device  108  having a unique atomization mechanism in accordance with certain embodiments of the invention. As discussed in detail below, the spray device  108  may be composed of layers, with each layer bolted together to form a complete apparatus. In the present embodiment, spray device  108  includes an orientation guide  401  to ensure proper orientation (e.g., stacking) of the multiple layers. In certain embodiments, the guide  401  may be a diagonal mark  401  on one side. Specifically, if any layer is not in the correct order, the mark  401  may not appear as a diagonal line. This configuration may serve to ensure proper flow of air and liquid through the spray device  108 . The mark  401  may be located at any suitable position about the circumference of the spray device  108 . The mark  401  may be etched into the structure of the spray device  108  or marked on the surface. In alternative embodiments, the orientation guide  401  may include an arcuate line, a series of indents, a series of notches, or the like, wherein these indicia indicate a proper order of the layers. After the layers have been properly aligned (i.e., a diagonal line is visible), bolts may pass through holes  402  to secure the layers. These bolt holes  402  may pass through the entire spray device  108 . 
     A liquid inlet  404  may serve to deliver liquid from the liquid supply  112  to the liquid orifice  302 . Similarly, pneumatic inlets  406  may facilitate gas flow from the pneumatic supply  110  through the spray device  108  to pneumatic orifices  408 . Both the liquid orifice  302  and the pneumatic orifices  408  are components of the nozzle  410 . 
     Liquid exiting the liquid orifice  302  may be separated into droplets by pneumatic atomization. The liquid orifice  302  may emit liquid at a relatively low flow rate, while the pneumatic orifices  408  may expel gas at a relatively high flow rate. Interaction between the high flow rate gas and the low flow rate liquid may cause the liquid to break up into droplets. Furthermore, some of the energy from the gas may be transferred to the liquid, increasing liquid droplet velocity. Because droplet velocity is a function of gas flow rate, pneumatic atomization may produce high velocity droplets while maintaining a low liquid flow rate. In other words, pneumatic atomizers may vary droplet velocity independently of the liquid flow rate. This configuration, unattainable with hydraulic atomization, may be well-suited for web moistening where greater droplet velocity and lower liquid flow rates are desired. 
     As seen in  FIG. 12 , the liquid droplets emitted from liquid orifice  302  form a substantially flat fan-shaped pattern  304 . This pattern  304  may include vacillating droplets established by gas streams emanating between the pneumatic orifices  408 . Specifically, two gas streams emanating from the pneumatic orifices  408  may converge near the liquid orifice  302 . These high velocity gas stream may induce a liquid stream emitted from liquid orifice  302  to form vacillating droplets.  FIG. 12  shows an exemplary droplet  412  as it vacillates in space between boundaries  414 . This droplet  412  is merely representative of droplets formed through the pneumatic atomization process. The frequency and amplitude of this vacillation may be controlled by varying the liquid and/or gas flow rates, the liquid and/or gas velocities, and/or the spacing between the liquid orifice  302  and the pneumatic orifices  408 . Adjusting the parameters of droplet vacillation is described in more detail in U.S. Pat. No. 5,902,540, which is herein incorporated by reference in its entirety. 
     Droplet vacillation may not be visible in the fan-shaped streams  304  depicted in  FIG. 11  because each droplet may vacillate at a high frequency. A combination of this high frequency vacillation and a large number of droplets may create the appearance of the relatively flat fan-shaped droplet pattern  304 . The particular fan-shaped pattern  304  created by this vacillation may result in uniform web moistening. 
     The flow rates of both liquid and gas are particularly adjusted to maintain the fan-shaped droplet pattern  304 . Specifically, if the gas flow rate is too high relative to the liquid flow rate, liquid droplets may not properly vacillate to form the fan spray pattern  304 . Without proper vacillation, the flattened fan-shaped pattern  304  may rotate approximately 90°, resulting in ineffective web moistening due to uneven liquid distribution across the web. For example, in certain embodiments, the liquid flow rate may be about 2 to 100, 5 to 70, 10 to 50, or approximately 10 to 30 cubic centimeters per minute. For example, if the liquid flow rate is approximately 10 to 30 cubic centimeters per minute, a gas flow rate of about 1 to 20, 2 to 10, or approximately 2 to 5 standard cubic feet per hour may produce proper droplet vacillation. 
     The liquid orifice  302  depicted in  FIG. 12  protrudes from the front face of the spray device  108  such that the liquid orifice  302  is positioned downstream from the gas flow of pneumatic orifices  408 . As illustrated, the protrusion is both rectangular and tapered. Alternative embodiments may employ a liquid orifice  302  having a non-tapered protrusion and/or a non-rectangular configuration. For example, in certain embodiments, the protrusion may have a circular, elliptical or triangular cross-section. This protrusion may facilitate automatic unclogging of the liquid orifice  302 . A portion of the gas emitted from each pneumatic orifice  408  may pass over the liquid orifice  302 . In this configuration, if an object or liquid on the surface obstructs the flow of liquid, the gas flow may dislodge it. 
       FIG. 13  is a schematic diagram of a front view of the nozzle  410  component of the spray device  108 . The nozzle  410  depicted in this figure contains a rectangular liquid orifice  302  and rectangular pneumatic orifices  408 . Experimentation has determined that rectangular orifices may produce effective spray patterns for web moistening. Furthermore,  FIG. 13  shows that the pneumatic orifices  408  are longer than the liquid orifice  302 . In particular, pneumatic orifices  408  have a length  409 , whereas liquid orifice  302  has a length  303 . In certain embodiments, length  409  may be at least 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 3, 4, 5, or more times length  303 . For example, length  409  may be more than approximately 20 percent longer than length  303 . Furthermore, liquid orifice  302  may be positioned such that pneumatic orifices  408  extend past opposite ends of liquid orifice  302  along a vertical axis  411 . This overlapping, or sandwich, configuration may reduce tails by confining liquid droplets to the plane of the fan-shaped stream. Tails are undesirable components of a spray pattern that are formed when a small number of droplets travel outside of the desired flow pattern. Confining these droplets to the fan-shaped stream may provide a more uniform liquid distribution across the web  102 . Alternative embodiments may employ pneumatic orifices  408  that extend past only one end of liquid orifice  302  along the vertical axis  411 . 
     Dimensions of both the liquid orifice  302  and the pneumatic orifices  408  may be varied based on the desired liquid spray configuration. For example, if a greater gas velocity is desired, the size of the pneumatic orifices  408  may be reduced. In addition, larger droplets may be formed by increasing the size of the liquid orifice  302 . However, as previously discussed, the disclosed embodiments may maintain the rectangular shape of orifices  302  and  408 , where the pneumatic orifices  408  are longer than the liquid orifice  302 . Therefore, a width  415  of liquid orifice  302  and a width  417  of pneumatic orifices  408  may be varied to adjust the size of orifices  302  and  408 , respectively. In the present embodiment, the width  415  of liquid orifice  302  is substantially similar to the width  417  of pneumatic orifices  408 . However, widths  415  and  417  may vary in alternative embodiments. In addition, the length  303  of liquid orifice  302  may be approximately two times the width  415 , as illustrated in  FIG. 13 . Alternatively, the length  303  may be about 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8 or more times the width  415  of liquid orifice  302 , for example. Similarly, as illustrated in  FIG. 13 , the length  409  of pneumatic orifices  408  may be four times the width  417 . In alternative embodiments, the length  409  may be about 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5 or more times the width  417  of pneumatic orifices  408 , for example. 
     Furthermore, orifice spacing may be varied to alter the frequency and/or amplitude of droplet vacillation, for example. As illustrated, pneumatic orifices  408  are spaced a distance  419  from liquid orifice  302  along lateral axis  413 . As presented in  FIG. 13 , spacing  419  is approximately 1.5 times the width  415  of liquid orifice  302 . In alternative embodiments, the spacing  419  may be about 0.5, 1, 1.5, 2, 2.5 or more times the width  415  of liquid orifice  302 . Further embodiments may enhance droplet formation by minimizing the spacing around liquid orifice  302 , such that spacing  419  approaches zero. By adjusting dimensions of nozzle components, spray patterns may be configured for particular applications. 
     One advantage of the present embodiment is that the liquid orifice  302  may be larger than the liquid orifice of a hydraulic atomizer. Hydraulic atomizers generally require a small liquid orifice to sufficiently accelerate the liquid linearly and/or rotationally such that it atomizes. In contrast, pneumatic atomizers use gas flow to atomize liquid. Therefore, a larger liquid orifice  302  may be employed. Larger liquid orifices may be less prone to clogging because small particles may simply pass through instead of becoming lodged and obstructing liquid flow. Because the liquid orifice  302  may be able to accommodate particles in the liquid, tap water may be used as the moistening liquid, instead of the more expensive de-ionized water typically utilized in hydraulic atomizers. In addition, the larger liquid orifice  302  may facilitate spraying other liquids, including silicone and lotion, that may induce clogging and/or be too viscous to flow through the smaller orifice of a hydraulic atomizer. 
     Furthermore, pneumatic atomization may utilize substantially less water than hydraulic atomization, thereby reducing operational costs. Specifically, to achieve proper atomization using a hydraulic system, a high water flow rate may be utilized. For example, a flow rate of approximately 1 liter per hour through each nozzle may be employed to achieve proper droplet formation via hydraulic atomization. However, desired flow rates may be significantly less than 1 liter per hour for proper web moistening. Therefore, a shield may be partially disposed within the spray pattern to block a portion of the liquid from contacting the web  102 . For example, if a flow rate of 0.3 liters per hour is desired, the shield may redirect 0.7 liters per hour. Because the redirected water may not be recovered and reused, 0.7 liter per hour of water may be wasted for each nozzle. In contrast, because pneumatic atomization utilizes air flow to achieve proper atomization, liquid flow rates may be decreased without adversely affecting droplet formation. For example, pneumatic atomization may enable the web moistening system  100  to vary flow rates between approximately 0.1 to 3.0, 0.2 to 2.5, or 0.3 to 2.0 liters per hour for each spray device  108 . In other words, the web moistening system  100  in the present embodiment may include a flow rate ratio (minimum to maximum) of approximately 1:20. 
     Moreover, pneumatic atomization may facilitate increased droplet size compared to hydraulic atomization, thereby further reducing water consumption. For example, hydraulic atomizers may produce droplets between approximately 20 to 100 microns in diameter. In contrast, pneumatic atomizers may produce droplets between approximately 100 to 1000, 200 to 800, or 300 to 500 microns in diameter. The larger droplets may experience less evaporation as they travel from the spray device  108  to the web  102 . Specifically, for a given quantity of water, larger droplets yield a smaller total surface area than smaller droplets because fewer larger droplets are formed. As appreciated, evaporation rate is dependent on surface area. Therefore, larger droplets may experience less evaporation, thereby reducing the quantity of water emanated from the spray devices  108  to achieve a desired web moisture content. In addition, larger droplets may result in a greater deposition efficiency compared to smaller droplets because the larger droplets may penetrate farther into the web  102 . In certain embodiments, deposition efficiency may increase between approximately 20% to 50%. Finally, water consumption may be reduced because a greater percentage of the larger droplets may overcome the web boundary layer. As appreciated, due to high web speeds through the system  100 , the web  102  may develop a boundary layer that may redirect the flow of droplets away from the web  102 . Due to the greater mass associated with larger droplets, more droplets may overcome this boundary layer and contact the web  102 . The combination of the mechanisms described above may decrease water consumption, thereby reducing operating costs. 
       FIGS. 14-18  show layers  602 ,  604 ,  606 ,  608 ,  610 ,  612  and  614  of an exemplary embodiment of the spray device  108 . As previously discussed, the spray device  108  may be formed from multiple layers of material. All of the layers,  602  through  614 , for one embodiment are depicted in  FIG. 14 , while  FIGS. 15-18  show a top view of the individual layers. As discussed in detail below, gas and liquid enter the spray device  108  along the vertical axis  411  generally perpendicular to layers  602  through  614 . The spray device  108  then expels the gas and liquid in a plane defined by a horizontal axis  617  and lateral axis  413 , generally in the plane of layers  602  through  614 . 
     Layer  602  is the top layer of the spray device  108 . A top view of this layer may be seen in  FIG. 15 . As illustrated, liquid from the liquid supply  112  may enter the liquid inlet  404  along vertical axis  411 . Similarly, gas from the pneumatic supply  110  may enter pneumatic inlets  406  along vertical axis  411 . As previously discussed, layer  602  includes bolt holes  402  configured to facilitate securing layers  602  through  614  together with bolts. 
     A top view of the second layer  604  may be seen in  FIG. 16 . This layer contains a vertical liquid conduit  616  which may facilitate liquid flow from the liquid inlet  404  to the liquid orifice  302 . Similarly, two vertical pneumatic conduits  618  are located in layer  604 . These conduits enable gas to travel through the spray device to the pneumatic orifices  408 . The vertical pneumatic conduits  618  are configured to control gas flow under a given pressure drop. Specifically, smaller conduit size reduces gas consumption under the same pressure drop. As can best be seen in  FIGS. 15 and 16 , a diameter  619  of the vertical pneumatic conduits  618  is smaller than a diameter  407  of the pneumatic inlets  406 . For example, the diameter  407  may be more than approximately 1.5, 2, 2.5, 3, 3.5, 4, or more times the diameter  619 . Furthermore, a diameter  405  of the liquid inlet  404  may be substantially similar to or larger than a diameter  621  of the vertical liquid conduit  616 . However, the diameter and shape of the vertical conduits  616  and  618  within this layer may be varied in alternative embodiments based on desired flow properties. 
       FIG. 17  depicts a top view of the third layer  606 . This layer includes another section of the vertical liquid conduit  616 . Layer  606  also contains two horizontal pneumatic conduits  620  which redirect gas from the vertical pneumatic conduits  618  to the pneumatic orifices  408 . As can be seen in  FIG. 14 , an initial width  623  of the horizontal pneumatic conduits  620  is substantially similar to the diameter  619  of the vertical pneumatic conduits  618 . However, the horizontal pneumatic conduits  620  narrow as they approach the pneumatic orifices  408 . Specifically, width decreases from the initial width  623  to a width  417  at the pneumatic orifices  408 . For example, the width  623  may be more than about 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8 or more times the width  417 . 
     A top view of the fourth layer  608  is shown in  FIG. 18 . This layer contains the two horizontal pneumatic conduits  620 , as seen in layer  606  ( FIG. 17 ). In addition, layer  608  contains a horizontal liquid conduit  622  that transfers liquid from the vertical liquid conduit  616  to the liquid orifice  302 . As best seen in  FIG. 14 , an initial width  627  of the horizontal liquid conduit  622  is substantially the same as the diameter  621  of the vertical liquid conduit  616 . Furthermore, the width of the horizontal liquid conduit  622  progressively decreases to correspond to a width  415  of the liquid orifice  302 . As with the horizontal pneumatic conduits  620 , the configuration of the horizontal liquid conduit  622  affects liquid flow properties. 
       FIG. 18  also depicts an angle, α, between each horizontal pneumatic conduit  620  and the horizontal liquid conduit  622 . This angle may be adjusted between approximately 0° and 90°. For example, in certain embodiments, α is about 10°, 20°, 30°, 40°, 50°, 60°, 70° or 80°, or an angle therebetween. As depicted in  FIG. 18 , α is approximately 10°. Experimentation has determined that an angle α of approximately 30° may be well-suited for certain web moistening applications. Varying α may affect both the configuration of the fan-shaped stream and the ability of the gas streams to dislodge obstructions in the liquid orifice  302 . 
     As previously discussed, liquid orifice  302  may protrude in a downstream direction from the gas flow of the pneumatic orifices  408 . As illustrated, liquid orifice  302  is positioned a distance  625  from the face of spray device  108 . In certain embodiments, distance  625  may be approximately 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more times the width  415  of liquid orifice  302 . As described above, the protrusion of liquid orifice  302  is tapered at an angle α and has a generally rectangular shape. Positioning the liquid orifice  302  downstream from the pneumatic orifices  408  may serve to dislodge obstructions in the liquid orifice  302 . However, in alternative embodiments, liquid orifice  302  may be positioned substantially flush with the face of spray device  108 . 
     Layer  610 , as depicted in  FIG. 14 , is substantially similar to layer  606 , and layer  612  is substantially similar to layer  604 . As can be seen in  FIG. 14 , the top and bottom of the horizontal liquid conduit  622  is formed by layers  606  and  610 , respectively. In other words, liquid flowing through the horizontal liquid conduit  622  is confined to a path through layer  608 . Therefore, the length  303  of the horizontal liquid conduit  622 , and liquid orifice  302 , along vertical axis  411  is equal to a thickness  609  of layer  608 . 
     In addition, layers  604  and  612  serve to confine the flow of gas to the horizontal pneumatic conduits  620 . Unlike the horizontal liquid conduit  622 , the length  409  of horizontal pneumatic conduits  620 , and pneumatic orifices  408 , along vertical axis  411  is equal to the thickness  609  of layer  608  combined with thicknesses  611  of layers  606  and  610 . As a result of this layering, the length  409  of the pneumatic orifices  408  is greater than the length  303  of the liquid orifice  302 . Layer  612  serves to provide symmetry to the spray device  108  between layers  604  and  612 . In this configuration, layers  604  to  612 , as a stack, may be rotated 180 degrees about horizontal axis  617  and sandwiched between layers  602  and  614 . Alternative embodiments may omit layer  612  such that layer  614  serves to confine the flow of gas to the horizontal pneumatic conduits  620 . 
     The final layer of the spray device  108  is layer  614 . This layer serves as an end cap for both the vertical pneumatic conduits  618  and the vertical liquid conduit  616 . By capping these conduits, both gas and liquid are forced to exit their respective orifices. The layered configuration described above may enable the spray devices  108  to be reconfigured for varying droplet sizes and/or spray patterns by replacing individual layers. Furthermore, as appreciated, in addition to the multi-layered assembly described above, other embodiments of the spray device  108  may be constructed using alternative techniques. For example, the spray device  108  may be machined and/or molded from solid blocks of material. 
       FIGS. 19-21  represent an alternative embodiment of spray nozzle  108  that is configured to reduce a buildup of salt and/or other minerals that may accumulate adjacent to pneumatic orifices  408  during operation of the spray device  108 . For example, the liquid supply  112  may provide the spray device  108  with “softened” water. Softened water is formed by passing tap water, for example, through a reverse-osmosis filter. However, this process may add small amounts of salt to the water. During operation of the web moistening system  100 , liquid droplets from the liquid orifice  302  may impact various regions of the spray device  108 , including areas adjacent to pneumatic orifices  408 . As these droplets evaporate, salt and/or other minerals within the water may be deposited within the flow path of the pneumatic orifices  408 . Over time, these deposits may accumulate, eventually interfering with gas flow and resulting in a non-uniform spray pattern. The alternative embodiment described below is configured to reduce the buildup of salt and/or other minerals within the flow path of the pneumatic orifices  408 . 
       FIG. 19  is a top view of an alternative embodiment of a third layer  702  of the spray device  108 . Layer  702  may replace layer  606  of the embodiment described above with regard to  FIGS. 14-18 . Layer  702  includes certain features configured to reduce a buildup of salt and/or other minerals that may accumulate within the flow path of pneumatic orifices  408  during operation of the spray device  108 . Specifically, layer  702  includes a point  703  forming an angle  704  and a curved portion  705  having a depth  706  and a width  708 . As discussed in detail below, the curved portion  705  is configured to direct a flow of gas toward the point  703  such that water droplets impact the point  703  and/or are redirected away from the spray device  108 . Any salt and/or mineral buildup on the point  703  may be dislodged by gas flow and/or vibration of the spray device  108 . In this manner, salt and/or mineral buildup within the flow path of the pneumatic orifices  408  may be reduced. 
     The angle  704  of the point  703  relative to the horizontal pneumatic conduits  620  is configured to provide a reduced surface area for the accumulation of salt and/or other minerals. As appreciated, deposits may be extricated from a smaller surface area with a reduced force. Therefore, the sharper the point  703 , the more likely a given force may dislodge the mineral buildup. Consequently, force provided by gas flow from the horizontal pneumatic conduits  620  may remove salt and/or other minerals from the point  703  due to the reduced surface area. For example, in certain embodiments, the angle  704  may be less than approximately 30°. Alternative embodiments may include angles  704  from 0° to 45°, 2° to 40°, 4° to 35°, 6° to 30°, 8° to 25°, 10° to 20°, and 12° to 15°, for example. Further embodiments may include angles  704  less than about 30°, 25°, 20°, 15°, 12°, 10°, 8°, 6°, 4°, or 2°. 
     Furthermore, the curved portion  705  is configured to redirect a flow of gas toward the point  703  and/or in a direction away from the spray device  108  (i.e., in the downstream direction). Specifically, the depth  706  of the curved portion  705  may be approximately two times the width  417  of the pneumatic orifices  408 . Further embodiments may include a depth  706  of greater than approximately 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or more times the width  417 . The width  708  of the curved portion  705  may be approximately seven times the width  417  of the pneumatic orifices  408 . Further embodiments may include a width  708  of greater than approximately 0, 2, 4, 6, 8, 10, 12, 14 or more times the width  417 . 
       FIG. 20  is a top view of an alternative embodiment of a fourth layer  710  of the spray device  108 . Layer  710  may replace layer  608  of the embodiment described above with regard to  FIGS. 14-18 . As illustrated, the point  703  and the curve portion  705  are substantially similar to the point  703  and curved portion  705  of layer  702 . Therefore, a thickness of the point  703  and the curved portion  705  is at least partially defined by the thickness of layers  702  and  710 . In alternative embodiments, the angle  704  of the point  703  and/or the depth  706  and/or the width  708  of the curved portion  705  may vary between layers  702  and  710 . 
     As illustrated, layer  710  includes a first pneumatic passage  620  extending directly along the liquid passage  622  to a first pneumatic orifice  408  disposed between a first surface  707  and a second surface  709 . The second surface  709  includes the point  703  and the curved portion  705  configured to reduce salt and/or other mineral buildup along the flow path of the first pneumatic orifice  408 . Specifically, the curved portion  705  forms a C-shape, U-shape, concave recess or curved recess within the second surface  709  and extends to the first pneumatic passage  620 . In other words, the curved portion  705  is directly adjacent to the first pneumatic orifice  408 . The interface between the curved portion  705  and the first pneumatic passage  620  forms the point  703 . The point  703  may also be considered a tip, peripheral edge, peak, protruding tip, or angled protrusion of the second surface  709  with respect to the first pneumatic passage  620 . As illustrated, the point  703  is positioned along the first pneumatic passage  620 , directly adjacent to the first pneumatic orifice  408 . Layer  710  also includes a liquid passage  622  extending to a liquid orifice  302  disposed between the first surface  707  and a third surface  711 . Furthermore, layer  710  includes a second pneumatic passage  620  extending directly along the liquid passage  622  to a second pneumatic orifice  408  disposed between the third surface  711  and a fourth surface  713 . The fourth surface  713  includes the point  703  and the curved portion  705  configured to reduce salt and/or other mineral buildup along the second pneumatic orifice  408 . 
     In certain configurations, an alternative embodiment of the fifth layer may be included. The alternative fifth layer may be substantially similar to layer  702 . Layers  702 ,  710  and the alternative fifth layer may be sandwiched between layers  604  and  612  of the spray device  108  presented in  FIG. 14 . Thus, the thickness of the expansion portion  703  may be defined by the combined thicknesses of the layers  702 ,  710  and the fifth layer. In this configuration, the alternative embodiment may function in a similar manner to the previously described embodiment, while limiting buildup of salt and/or other minerals in the flow path of the pneumatic orifices  408 . 
       FIG. 21  is a detailed top view of liquid orifice  302  and pneumatic orifices  408  of the alternative embodiment of the fourth layer  710 , showing the flow path of gas (e.g., air) around the pneumatic orifices  408 . As previously described, the point  703  and the curved portion  705  are configured to reduce the buildup of salt and/or other minerals that may interfere with the flow of gas from pneumatic orifices  408 . As illustrated, gas emitted from pneumatic orifices  408  may flow in a downstream direction  712 . As appreciated, the flowing gas may establish a region of low pressure, drawing surrounding air toward the flow. The curved portion  705  is configured to direct the air flow toward the point  703 . Specifically, the curved portion  705  converges with an inner surface of the horizontal pneumatic conduit  620  in the downstream direction, thereby forming the point  703  and directing air along the surface of the curved portion  705  in a direction  714 . Water droplets may be captured by the air flow and directed toward the point  703 . A portion of the water droplets may adhere to the point  703 , while other droplets remain in the air flow. Over time, the droplets that adhere to the point  703  may evaporate, causing an accumulation of salt and/or other minerals on the point  703 , as represented by buildup  716 . However, due to the small surface area associated with the point  703 , air flow from the surface of the curved portion  705  and/or gas flow from the pneumatic orifices  408  may dislodge the buildup  716  from the point  703 . Specifically, the flows may apply a shear force along the point  703  in a direction away from the spray device  108 . As previously discussed, the small surface area of the point  703  increases the likelihood that a given flow pressure may dislodge the buildup  716 . Therefore, the flows may remove the buildup  716  from the point  703  and carry it in a downstream direction  712 . In addition, the spray device  108  may vibrate during operation, providing an additional force to extricate the buildup  716 . Therefore, the quantity of salt and/or other minerals deposited adjacent to the pneumatic orifices  408  may be minimized. 
     In addition, buildup  716  on the point  703  may be further reduced because a portion of the water droplets captured by the air flow along the surface of the curved portion  705  may remain in the air flow. As illustrated, water droplets captured by air flowing in direction  714  may bypass the point  703  and flow in a direction  718 . For example, more than 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80% of the water droplets may remain in the flow. Because some of the water droplets do not adhere to the point  703 , less buildup  716  may be formed. In certain embodiments, the direction  718  may be substantially similar to the downstream direction  712  of the gas flow from the pneumatic orifices  408 . In this configuration, the air flow from the curved portion  705  may combine with the gas flow from the pneumatic orifices  408 . In addition, a portion of the air and/or gas flow may return to the curved portion  705 , thus establishing a recirculating flow in direction  714 . The combination of directing water droplets away from the spray device  108  and the small surface area of the point  703  may reduce salt and/or mineral buildup that may interfere with gas flow from the pneumatic orifices  408 , thereby maintaining a substantially uniform spray pattern  304 . 
       FIGS. 22-24  represent an second alternative embodiment of spray nozzle  108  that is configured to reduce a buildup of salt and/or other minerals that may accumulate adjacent to pneumatic orifices  408  during operation of the spray device  108 .  FIG. 22  is a top view of an alternative embodiment of a third layer  802  of the spray device  108 . Layer  802  may replace layer  606  of the embodiment described above with regard to  FIGS. 14-18 . Layer  802  includes certain features configured to reduce a buildup of salt and/or other minerals that may form adjacent to pneumatic orifices  408  during operation of the spray device  108 . Specifically, layer  802  includes an expansion portion  803  within each horizontal pneumatic conduit  620 , forming recesses within an exit surface  805 . The expansion portions  803  are configured to induce recirculation within the recesses and/or adjacent to the exit surface  805 . As discussed in detail below, recirculation within the expansion portion  803  may deposit salt and/or other minerals outside of the flow path of gas emitted from horizontal pneumatic conduits  620 . In addition, recirculation adjacent to the exit surface  805  may deposit salt and/or other minerals on a point or angled tip of the expansion portion  803  having a small surface area. Air flow and/or vibrations of the spray device  108  may dislodge the deposits from the point, thereby reducing buildup within the flow path of the pneumatic orifices  408 . 
     As illustrated, the expansion portion  803  has a depth  804  and a width  806  configured to induce recirculation within the expansion portion  803 . In the present embodiment, the depth  804  is approximately 3 times the width  417  of the pneumatic orifice  408 . Alternative embodiments may include a depth  804  of greater than approximately 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or more times the width  417 . Furthermore, the width  806  is approximately 2 times the width  417  of the pneumatic orifice  408 . Alternative embodiments may include a width  806  of greater than approximately 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or more times the width  417 . 
     The illustrated embodiment includes a substantially rectangular expansion portion  803 . Further embodiments may include alternative configurations such as substantially circular, triangular, elliptical or polygonal, among other configurations. In addition, the expansion portion  803  forms a point  808  along the exit surface  805  of the spray device  108 . The point  808  is configured to provide a reduced surface area for the accumulation of salt and/or other minerals. As appreciated, deposits may be extricated from a smaller surface area with a reduced force. Therefore, the sharper the point  808 , the more likely a given force may dislodge the mineral buildup. Consequently, force provided by gas flow from the horizontal pneumatic conduits  620  may remove salt and/or other minerals from the point  808  due to the reduced surface area. 
       FIG. 23  is a top view of an alternative embodiment of a fourth layer  810  of the spray device  108 . Layer  810  may replace layer  608  of the embodiment described above with regard to  FIGS. 14-18 . As illustrated, the depth  804  and the width  806  are substantially similar to the depth  804  and the width  806  of layer  802 . In addition, the thickness of the expansion portion  803  is at least partially defined by the thickness of layers  802  and  810 . In alternative embodiments, the depth  804 , the width  806  and/or the geometric configuration of the expansion portion  803  may vary between layers  802  and  810 . 
     The point  808  represents an exterior angled tip at an interface of the exit surface  805  and an interior wall  812  of the expansion portion  803 . As illustrated, the interior wall  812  extends toward the point  808  in a direction substantially parallel to the horizontal pneumatic conduit  620 . The intersection between the interior wall  812  and the exit surface  805  forms the point  808  which may also be considered an angled projection, external peak, or angled tip. As appreciated, an angle  814  of the point  808  may be varied by adjusting the geometric configuration of the expansion portion  803 . Furthermore, an interior corner  816  is defined by an interior angle between an interior ledge or step  818  and the interior wall  812 . As illustrated, the ledge  818  extends substantially perpendicularly outward from the horizontal pneumatic conduit  620 , i.e., away from the horizontal liquid conduit  622 . The interior wall  812  extends between the point  808  and the ledge  818 , forming the interior corner  816 . As appreciated, an angle  820  of the corner  816  may be varied by adjusting a length of the ledge  818  and/or the wall  812 . 
     In certain configurations, an alternative embodiment of the fifth layer may be included. The alternative fifth layer may be substantially similar to layer  802 . Layers  802 ,  810  and the alternative fifth layer may be sandwiched between layers  604  and  612  of the spray device  108  presented in  FIG. 14 . Thus, the thickness of the expansion portion  803  may be defined by the combined thicknesses of the layers  802 ,  810  and the fifth layer. In this configuration, the alternative embodiment may function in a similar manner to the previously described embodiment, while limiting buildup of salt and/or other minerals in the flow path of the pneumatic orifices  408 . 
       FIG. 24  is a detailed top view of liquid orifice  302  and pneumatic orifices  408  of the alternative embodiment of the fourth layer  810 , showing the flow path of gas (e.g., air) around the pneumatic orifices  408 . As previously described, expansion portion  803  is configured to reduce the buildup of salt and/or other minerals that may interfere with the flow of gas from pneumatic orifices  408 . As illustrated, gas emitted from pneumatic orifices  408  may flow in a downstream direction  821 . As appreciated, the flowing gas may establish a region of low pressure, drawing surrounding air toward the flow. Specifically, gas from the pneumatic orifices  408  and/or surrounding air may recirculate in a direction  822 . Water droplets may be captured by the air flow and directed toward the point  808 . A portion of the water droplets may adhere to the point  808 , while other droplets remain in the air flow. Over time, the droplets that adhere to the point  808  may evaporate, causing an accumulation of salt and/or other minerals on the point  808 , as represented by buildup  824 . However, due to the small surface area associated with the point  808 , recirculating air flow along direction  822  and/or gas flow from the pneumatic orifices  408  may dislodge the buildup  824  from the point  808 . Specifically, the flows may apply a shear force along the point  808  in a direction away from the spray device  108 . As previously discussed, the small surface area of the point  808  increases the likelihood that a given flow pressure may dislodge the buildup  824 . Therefore, the flows may remove the buildup  824  from the point  808  and carry it in a downstream direction  821 . In addition, the spray device  108  may vibrate during operation, providing an additional force to extricate the buildup  824 . Therefore, the quantity of salt and/or other minerals deposited adjacent to the pneumatic orifices  408  may be minimized. Furthermore, the buildup  824  on the point  808  may be substantially outside of the flow path of gas emitted from the horizontal pneumatic conduits  620 . Consequently, flow conditions may be generally uniform over extended use of the spray device  108 . 
     In addition, buildup  824  on the point  808  may be further reduced because a portion of the water droplets captured by the recirculating air may remain in the air flow. As illustrated, water droplets captured by air flowing in direction  822  may bypass the point  808  and flow in a direction  826 . For example, more than 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80% of the water droplets may remain in the flow. Because some of the water droplets do not adhere to the point  808 , less buildup  824  may be formed. In certain embodiments, the direction  826  may be substantially similar to the downstream direction  821  of the gas flow from the pneumatic orifices  408 . In this configuration, the recirculating air flow may combine with the gas from the pneumatic orifices  408 . In addition, a portion of the air and/or gas flow may return to the exit surface  805 , thus establishing the recirculating flow in direction  822 . Further embodiments may include a curved recess in the exit surface  805  adjacent to the expansion portion  803  and configured to direct the air flow toward the point  808 . The combination of directing water droplets away from the spray device  108  and the small surface area of the point  808  may reduce salt and/or mineral buildup that may interfere with gas flow from pneumatic orifices  408 , thereby maintaining a substantially uniform spray pattern  304 . 
     It is believed that a second recirculation zone may be formed within the expansion portion  803 . Specifically, a portion of the gas flowing through the horizontal pneumatic conduits  620  may flow in a direction  828  prior to exiting the pneumatic orifices  408 . Water droplets may be captured within the recirculating flow and deposited in the interior corner  816  of the expansion portion  803 . As the water evaporates, a buildup  830  may be formed within the corner  816 . As illustrated, the buildup  830  may be substantially outside of the flow path of gas emitted from the horizontal pneumatic conduits  620 . In this manner, the buildup  830  may not interfere with the gas flow from pneumatic orifices  408 . Over time, the buildup  830  may expand as additional salt and/or other minerals are deposited in the corner  816 . However, once the buildup  830  reaches a critical size, it may become dislodged by the gas flow from the horizontal pneumatic conduits  620 . Therefore, the size of buildup  830  may be limited to prevent interference with the gas flow. The combination of features described above may reduce salt and/or mineral deposits within and/or surrounding pneumatic orifices  408 , thereby maintaining a substantially uniform spray pattern  304 . 
       FIG. 25  is a top view of a third alternative embodiment of a fourth layer  902  of the spray device  108 . Layer  902  may replace layer  608  of the embodiment described above with regard to  FIGS. 14-18 . As illustrated, layer  902  includes a curved portion  904  similar to the curved portion  705  described above with regard to  FIGS. 19-21 . The curved portion  904  is configured to direct a flow of gas toward a point  905  such that water droplets impact the point  905  and/or are redirected away from the spray device  108 . Any salt and/or mineral buildup on the point  905  may be dislodged by gas flow and/or vibration of the spray device  108 . In this manner, salt and/or mineral buildup within the flow path of the pneumatic orifices  408  may be reduced. In addition, layer  902  includes an expansion portion  906  within each horizontal pneumatic conduit  620 . The expansion portions  906  are configured to induce recirculation within the recesses and/or adjacent to an exit surface  908 . As previously discussed, recirculation within the expansion portion  906  may deposit salt and/or other minerals outside of the flow path of gas emitted from horizontal pneumatic conduits  620 . In contrast to the rectangular expansion portions  803  described above with regard to  FIGS. 22-24 , the expansion portions  906  of layer  902  form a curved shape. This configuration may provide enhanced reduction of deposits adjacent to the pneumatic orifices  408 . In addition, the combination of the curved portions  904  and the expansion portions  906  may serve to reduce mineral deposits to a greater extent than either feature alone. Therefore, the present embodiment may enable the spray device  108  to maintain a substantially uniform spray pattern  304 . 
     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.