Patent Publication Number: US-9849474-B2

Title: Dense phase or dilute phase delivery through a powder gun

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a national phase entry under 35 U.S.C. §371 of, and claims priority to, pending International Application No. PCT/US2013/030199 filed Mar. 11, 2013, for DENSE PHASE OR DILUTE PHASE DELIVERY THROUGH A POWDER GUN, which claims the benefit of U.S. Provisional patent application Ser. No. 61/672,037 for DENSE PHASE OR DILUTE PHASE DELIVERY THROUGH A POWDER GUN filed on Jul. 16, 2012, the entire disclosures of which are fully incorporated herein by reference. 
     RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional patent application Ser. No. 61/672,037 for DENSE PHASE OR DILUTE PHASE DELIVERY THROUGH A POWDER GUN filed on Jul. 16, 2012, the entire disclosure of which is fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD OF THE DISCLOSURE 
     The inventions relate generally to material application devices that are used for spraying powder coating material onto a work piece or object. More particularly, the inventions relate to material application devices, for example powder spray guns, that can be configured to receive powder coating material in dense phase and dilute phase. 
     BACKGROUND OF THE DISCLOSURE 
     A material application device is used to apply powder coating material to an object, part or other work piece or surface. A material application device is also referred to herein as a spray gun. The powder coating material can be delivered from a powder pump to a spray gun in dilute phase or dense phase. Dilute phase refers to a powder flow or stream that is a lean mixture, or in other words has a high ratio of flow air to powder. Dilute phase powder pumps are most commonly used in the form of a Venturi style pump that uses a large volume of air to draw powder from a supply and push the powder to the spray gun. Dense phase refers to a powder stream that is a rich mixture, or in other words has a low ratio of flow air to powder. Dense phase pumps are commonly used in the form of a pump chamber that uses pressure to fill and empty a pump chamber but with a low flow air volume, referred to hereinafter as flow air. Because dense phase systems use less flow air, the powder hoses can be made smaller in diameter compared with powder hoses used with dilute phase systems. 
     SUMMARY OF THE DISCLOSURE 
     In an embodiment of the disclosure, a spray gun is presented that can be selectively configured to operate with a dilute phase powder delivery or a dense phase powder delivery. For example, the spray gun can be selectively configured to receive powder coating material from a Venturi powder pump or a dense phase powder pump. 
     In another embodiment presented herein, a configurable spray gun may include a gun body comprising a selectable forward section and a rearward section. The rearward section may be connected with either of two selectable forward sections so as to configure the spray gun to operate either with a dense phase powder supply or a with dilute phase powder supply. In another embodiment, the rearward section may include a selectable powder flow path that is connectable at an inlet end to a source of dense phase powder and at an outlet end to a selectable spray nozzle in the selectable forward section that may optionally include a diffuser. In still a further embodiment, an adapter assembly may be used to connect the rearward section with the selectable spray nozzle having an optional diffuser. 
     The disclosure also presents the concept of a spray gun that can be selectively configured, converted or re-configured to operate from a dilute phase powder pump or a dense phase powder pump as the case may be, while using many common components in the selectable configurations, for example, the same rearward section. Additional embodiments are disclosed herein. 
     In another embodiment, an adapter assembly provides an interface or connection between one of the selectable powder flow paths and a selectable spray nozzle. For example, the adapter assembly may provide an interface or connection between a reduced diameter selectable powder tube and a selectable spray nozzle. The reduced diameter selectable powder tube may be inserted through the rearward section by sliding the reduced diameter powder tube through a larger diameter selectable powder tube that is provided with the rearward section when the spray gun is to be assembled with a different selectable configuration. For example, the reduced diameter powder tube may be of a size that is useful with dense phase powder delivery from a dense phase pump, while the larger diameter powder may be of a size that is useful with a dilute phase pump, such as a Venturi pump to name one example. In another embodiment, the adapter assembly may provide continuity for an electrode. 
     In another embodiment, a spray gun that can be selectively configured to operate with a Venturi pump or a dense phase powder pump includes a gun body comprising a selectable forward section and a rearward section, with the selectable forward section including a selectable spray nozzle, an optional member for adding air to the powder flow, and an optional electrode. The rearward section may be used to support a selectable powder flow path, so that the rearward section is joinable with either of two selectable forward sections so as to form either of two selectable spray gun configurations. 
     In another embodiment, a first selectable spray gun configuration may include a first selectable spray nozzle and a first selectable powder flow path, with the first selectable powder flow path comprising a first cross-sectional area. A second selectable spray gun configuration may include a second selectable spray nozzle and a second selectable powder flow path, with the second selectable powder flow path comprising a second cross-sectional area, with the first cross-sectional area being different from said second cross-sectional area. In another embodiment, the second cross-sectional area is smaller than the first cross-sectional area. 
     In another embodiment, a spray gun that can be selectively configured to operate with a Venturi pump or a dense phase powder pump includes a gun body comprising a selectable forward section and a rearward section, with the selectable forward section further including two selectable configurations, for example, a spray nozzle or an air cap. Therefore, the spray gun may have three selectable configurations, for example, a dilute phase delivery spray gun, a dense phase delivery spray with a spray nozzle and a dense phase delivery spray gun with an air cap. 
     Another benefit of the selectively configurable spray gun concept is that for the second spray gun configuration, it will be noted that the second selectable flow path includes a second powder tube and an adapter tube which is part of an adapter assembly. This allows the adapter tube material to be selected based on the type of powder coating material being delivered through the second powder tube and sprayed through a spray nozzle, be it organic powder or porcelain enamel powder or other powder material. The powder flow does not impact surfaces as would occur when a spider is used, so the adapter support housing  106  will not exhibit wear. 
     In another embodiment, a spray gun includes a gun housing having a forward section and a rearward section, the forward section comprising a spray nozzle; the spray nozzle comprising an air diffuser for adding air to powder coating material when powder coating material is flowing through the spray nozzle, and a powder flow path extending through the spray gun from the rearward section to the forward section. The powder flow path comprises a first powder tube that extends through the rearward section and that is adapted to receive powder from a dense phase pump, and the rearward section includes a second powder tube of larger cross-sectional area than the first powder tube, the first powder tube extending through said second powder tube. 
     In all the embodiments, the spray guns may optionally have a bar mount configuration or a tube mount configuration. The spray guns also optionally may have a manual configuration or an automatic configuration. The spray guns may also optionally provide a charging electrode that is connectable to a high voltage source for applying electrostatic charge to the powder coating material during a coating operation. 
     These and other aspects and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description of the exemplary embodiments in view of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is schematic representation of a first selectable spray gun configuration or first spray gun that operates with dilute phase powder; 
         FIG. 2  is a schematic representation of a second selectable spray gun configuration or second spray gun in accordance with the teachings and inventions in this disclosure; 
         FIG. 3  is an elevation view of a first spray gun in a bar mount configuration; 
         FIG. 4  is an elevation view of the first spray gun of  FIG. 3 , in longitudinal cross-section; 
         FIG. 5  is an enlarged view of the circled portion of  FIG. 4 ; 
         FIG. 6  is an elevation view of a second spray gun in a bar mount configuration; 
         FIG. 7  is an elevation view of the first spray gun of  FIG. 6 , in longitudinal cross-section; 
         FIG. 8  is an enlarged view of the circled portion of  FIG. 7 ; 
         FIG. 8A  is an exploded perspective of the selectable forward section of the second spray gun of  FIG. 6 ; 
         FIG. 9  is a schematic drawing of an exemplary dense phase pump that may be used with the present inventions; 
         FIG. 10  is another embodiment in elevation of a selectable spray gun configuration for a dense phase delivery and using an air cap; 
         FIG. 11  is a longitudinal cross-section of a forward section of the spray gun of  FIG. 10  noted by the circled region of  FIG. 10 ; 
         FIG. 12  is another embodiment of a selectable forward section for a dense phase delivery and using a spray nozzle; 
         FIG. 13  is an isometric view of a manual spray gun for dense phase delivery and using an air cap; 
         FIG. 14  is a longitudinal cross-section of the manual spray gun of  FIG. 13 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Although the inventions are described in terms of exemplary embodiments of spray guns with specific configurations, those skilled in the art will readily appreciate that the inventions will find application and use with many different types of spray gun designs. For example, automatic sprays guns may have mounting configurations other than bar mount or tube mount, and manual guns can have many different configurations. An automatic spray gun is one that is typically mounted on a support structure that can move the spray gun into position for a coating operation, with the spray gun actuation (for example, trigger on and off times for controlling spraying) being controlled electronically. A manual spray gun has a handle and is usually manually gripped by the operator and triggered manually to start and stop a coating operation. The exemplary embodiments also use an electrode that is connectable to a high voltage supply, for example a multiplier, so as to apply electrostatic charge to the powder coating material, but the inventions also may be used with spray guns that are not corona discharge type electrostatic spray guns. For example, the inventions may be used with tribo-charging electrostatic spray guns or non-electrostatic spray guns. Specific embodiments of various components used with the spray gun are exemplary and may be changed depending on the particular spray gun design. 
     A powder coating operation or coating operation for short as used herein refers to the common method of using a powder spray gun to produce a cloud of powder coating material that is directed at an object being coated. Powder coating operations may be electrostatic or non-electrostatic as is well known. 
     Those skilled in the art will appreciate that powder flow passages, such as provided by powder tubes, are typically cylindrical in shape, but that non-cylindrical conduits may alternatively be used. Such powder tubes have an internal cross-sectional area but not necessarily an inside diameter. For the cylinder shaped powder tubes, the diameter is an adequate reference for comparing powder tubes of different size or different cross-sectional areas. Therefore, although in the disclosure herein we generally refer to diameter of exemplary powder tubes, we do not exclude from the scope of the inventions the alternative use of non-tubular powder conduits. 
     Although the exemplary embodiments are described in terms of use with dilute phase delivery system, such as for example, using a Venturi pump that produces a dilute phase powder flow input to a spray gun, and a dense phase delivery system, such as for example, using a dense phase pump that produces a dense phase powder flow input to a spray gun, such terminology should not be construed as limiting the use and scope of the inventions. Precise definitions of dilute phase and dense phase are not critical to the present inventions because the inventions allow for spray guns that can operate with dilute phase powder flow, dense phase powder flow or powder flow densities across a continuum of air/powder ratios in between dense phase and dilute phase. But for description purposes, a dilute phase powder flow is the type of powder flow that is produced by a dilute phase delivery system, for example a Venturi style powder pump, in which the powder flow has a leaner mixture of powder to air due to the high volume or amount of flow air (when compared with a dense phase powder pump) that is generated by the Venturi pump. A dense phase powder flow is the type of powder flow that is produced by a dense phase delivery system, for example a dense phase pump in which the powder flow has a richer mixture of powder to air due to the low volume or amount of flow air (when compared with a Venturi pump) that is generated by the dense phase pump. Dense phase pumps have smaller diameter powder hoses that provide dense phase powder flow to the spray gun as compared to the powder hoses that provide dilute phase powder flow from Venturi pumps due to the use of less flow air. For the basic concepts and embodiments herein, a dense phase powder flow is a powder flow produced by a dense phase pump that has a richer mixture of powder to air as compared to a dilute phase powder flow produced by a Venturi pump. The term “delivery system” is used interchangeably with the terms powder supply and powder pump. 
     By way of introduction, the present disclosure illustrates and describes a number of inventions and inventive concepts as embodied in the examples illustrated in the drawings and explained in the specification. One such inventive concept contemplates a first selectable spray gun configuration for powder delivered to the spray gun in dilute phase, and a second selectable spray gun configuration for powder delivered to the spray gun in dense phase. 
     In another embodiment, a spray gun can be selectively configured, converted or re-configured to operate from a dilute phase powder pump or a dense phase powder pump as the case may be, while using many common components in the two configurations, for example, the same rearward section. Additional embodiments are disclosed herein. 
     In a further embodiment of this concept, a spray gun with a first selectable configuration has a first selectable forward section that may be used to spray a lean mixture powder flow that is delivered from a dilute phase pump, for example a Venturi style pump. The dilute phase powder is input or supplied to a rearward section of the spray gun. The spray gun may then optionally be configured with a second selectable spray gun configuration in which a second selectable forward section may be used to spray a lean mixture powder flow, with the spray gun being supplied with powder coating material as a dense or rich mixture powder flow from a dense phase pump to the rearward section of the spray gun. Additional embodiments of this concept are presented herein. 
     The spray gun in the dense phase pump configuration or second selectable configuration provides a second selectable forward section that can be joined to the rearward section. The selectable forward section may include a second selectable spray nozzle and an adapter assembly that facilitates connecting or interfacing the second selectable spray nozzle to a forward portion or end of the rearward section. A second selectable powder flow path may be used that is connectable at an inlet end to a dense phase powder supply, and at an outlet end with the adapter assembly to be in fluid communication with the second selectable spray nozzle. Because the powder coating material in this second configuration is being supplied in dense phase, the second selectable forward section may include a member for adding air to the powder coating material when the powder coating material flows through the second selectable spray nozzle. The member for adding air may be disposed, for example, in the second selectable spray nozzle. An example of the member is a diffuser that comprises air porous material. 
     Another inventive concept of the present disclosure contemplates a configurable spray gun that uses many common components for two or more configurations, wherein one or more selectable configurations is for powder from a dense phase supply and the other configuration is for powder from a dilute phase supply. In an embodiment of this concept, it is to be noted that the configurable spray gun concept takes advantage of the simplicity of the selectable configurations so that the same rearward section may be used with a selectable forward section and selectable powder tube to provide either a dilute phase supply powder spray gun or a dense phase supplied powder spray gun. Additional embodiments of this concept are presented herein, including embodiments for a manual spray gun and automatic spray guns that may be selectively configured to use either a slot type spray nozzle or an air cap, all of which may use dense phase delivery to the spray gun. 
     In another embodiment of the configurable spray gun, in order to change over or select one of the selectable configurations with dense phase delivery, the assembler easily slides a smaller dense phase powder tube (the second selectable powder tube) through the larger dilute phase powder tube (the first selectable powder tube) that extends through the rearward section. The second selectable spray nozzle and adapter, or alternatively an air cap, are then installed on the forward end of the rearward section to complete a second selectable spray gun configuration. The second selectable spray nozzle or the air cap may alternatively be used to select the location of an electrode tip. For the second selectable spray gun configuration (spray nozzle or air cap), the electrode tip may optionally be disposed outside the second selectable spray nozzle, while for the first selectable spray gun configuration the electrode tip may optionally be disposed inside the first selectable spray nozzle. 
     Another inventive concept contemplates a spray gun for a dense phase powder supply that has a selectable forward section that is adapted to spray dilute phase powder. In an embodiment of this concept, a first powder tube having a first cross-sectional area extends through a second powder tube having a second cross-sectional area that is larger than the first cross-sectional area. The smaller cross-sectional area powder tube is connectable to a dense phase powder supply, and a first selectable forward section may include a spray nozzle or an air cap that dilutes the dense phase powder. When the smaller cross-sectional powder tube is removed, the larger cross-sectional powder tube is connectable to a dilute phase powder supply, and a second selectable forward section may be used that is adapted to operate with a dilute phase powder supply. Additional embodiments of this concept are disclosed herein. 
     In another embodiment, a spray gun for use with a dense phase powder supply is configurable using a selectable forward section that is adapted to spray dilute phase powder. In an embodiment of this concept, a first powder tube having a first cross-sectional area extends through a second powder tube having a second cross-sectional area that is larger than the first cross-sectional area. Additional embodiments of this concept are disclosed herein. 
     In another embodiment, the selectable forward section may have at least two selectable configurations, for example a spray nozzle or an air cap. And in a further embodiment, the selectable forward section includes structure for adding atomizing or dilution air to the dense phase powder flow delivered to the spray gun from a dense phase delivery system. In another embodiment, the selectable forward section is used with a rearward section that may be though need not be the same rearward section for all the selectable configurations of the spray gun, but using a selectable powder tube depending on whether the spray gun is configured for dense phase delivery or dilute phase delivery. 
     While various aspects and features and concepts of the inventions are described and illustrated herein as embodied in various combinations in the exemplary embodiments, these various aspects, features and concepts may be realized in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present invention. Still further, while various alternative embodiments as to the various aspects and features of the invention, such as alternative materials, structures, configurations, methods, devices and so on may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the aspects, concepts or features of the various inventions into additional embodiments within the scope of the present inventions, even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the inventions may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present inventions however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated. Additionally, even though some features and aspects and combinations thereof may be described or illustrated herein as having a specific form, fit, function, arrangement or method, such description is not intended to suggest that such descriptions or illustrated arrangements are required or necessary unless so expressly stated. Those skilled in the art will readily appreciate additional and alternative form, function, arrangement or methods that are either known or later developed as substitute or alternatives for the embodiments and inventions described herein. 
     With reference to  FIG. 1 , a first selectable spray gun configuration  10  may be realized using a first spray gun  10  which may be an automatic or alternatively manual spray gun. We will use the numeral  10  to refer generally to the first selectable spray gun configuration or first spray gun  10  for short, it being realized that the embodiment of the first spray gun  10  is but one example of many different spray gun designs that may be used. The first spray gun  10  may include a gun body  11  that includes front gun body  12  and a rear gun body  13  that house and support various components of the spray gun. The embodiments of a tube mount configuration and a bar mount configuration relate to automatic spray guns as is known in the art. Although we illustrate an automatic gun in a bar mount configuration herein, the inventions herein may also be used with a tube mount configuration and a manual spray gun configuration in a straightforward manner as described hereinbelow. The gun bodies  12 ,  13  may have multiple portions or pieces as needed. The housed components may include, for example, a first selectable powder flow passage, which may be realized as a first selectable powder tube  14  that defines a powder flow path P through the first spray gun  10  from a powder flow path inlet  16  to a powder flow path outlet  18 . The first spray gun  10  typically also includes a first selectable spray nozzle  20  having a spray outlet  22 . Powder flows from the powder flow path outlet  18 , into the first spray nozzle  20  and then out the spray outlet  22 . 
     The selectable spray gun configurations disclosed herein are noted as being a first selectable spray gun configuration and a second selectable spray gun configuration (there also is a third selectable configuration as described below). Each selectable spray gun configuration includes a selectable spray nozzle or air cap, a selectable powder flow path or selectable powder tube, and a selectable forward section. For ease of reading we oftentimes will use a shorthand reference to the “first” and “second” parts, without repeating the word “selectable” every time, it being understood that reference to first and second parts refer to the parts as used in the first and second selectable spray gun configurations respectively. 
     Although  FIG. 1  shows a distinct line between the powder flow path outlet  18  and the first spray nozzle  20 , this is for convenience only in the schematic diagrams. For example, it is common although no required that powder will flow into an expansion chamber  23  before the powder flows out the spray outlet  22 . Whether the expansion chamber  23  is considered to be part of the powder flow path, the first spray nozzle (as shown in  FIG. 1 ) or some separate flow section is not important to the present inventions. Oftentimes, the expansion chamber  23  bridges the space between the powder flow path outlet  18  and the first spray nozzle  20 . For the disclosure herein of both embodiments, it is sufficient to understand that the selectable powder flow path, which may be typically realized in the form of a powder tube, has an outlet end  18  that provides powder flow into the selectable spray nozzle. The selectable powder tube is optionally fully disposed in the rearward section  28  after the spray gun is fully assembled. 
     An exemplary embodiment of a first selectable spray gun configuration as represented in  FIG. 1  is an ENCORE® model spray gun which is available commercially from Nordson Corporation, Westlake, Ohio. However other dilute phase delivery spray guns may be used for the first selectable spray gun configuration  10 . The first spray gun  10  commonly uses a first selectable powder flow path P that may have a constant inside diameter D1 of a first powder tube  14 , or more precisely a powder tube with a constant transverse cross-sectional area from the inlet end  16  to the outlet end  18 . This promotes better flow characteristics and allows the powder tube cross-sectional area to be designed with the first spray nozzle  20  and spray outlet  22  to obtain desired spray patterns. Having a single size powder tube also facilitates purging and color change. However, a constant cross-sectional area for the powder flow path or first powder tube  14  is not a requirement. 
     A spray gun may be designed to function as a dilute phase delivery spray gun using dilute phase powder flow from a dilute phase pump, for example, a Venturi pump. Alternatively, a spray gun may be separately and distinctly designed as a dense phase delivery spray gun that receives a dense phase powder flow from a dense phase pump. There are significant differences between the two spray gun designs due to the characteristics of the powder flow received from the delivery system, and therefore the spray gun designs, and especially the spray nozzles and the powder tubes and hoses, are different for dense phase and dilute phase delivery, spraying and coating operations. This has resulted in the need for having spray gun parts inventory for both style spray guns. In the exemplary embodiment of  FIG. 1 , because the ENCORE® model spray gun uses dilute phase powder supplied from a dilute phase pump  24 , the first powder tube  14  may be, although need not be, a tube, for example a single piece tube, having a constant diameter D1 or cross-sectional area from the powder flow path inlet  16  to the powder flow path outlet  18 . Because the first spray gun  10  is used for spraying dilute phase powder flow, a frusto-conical portion  25  of the flow path may be provided at or very near or within the first spray nozzle  20 . This frusto-conical portion  25  serves as the expansion chamber  23  which allows the dilute phase powder flow to decelerate and further diffuse to facilitate spray pattern shaping from the first spray nozzle  20 . The dilute phase spray gun does not add air into the dilute phase powder flow because a dilute phase pump like a Venturi pump produces a high ratio and high velocity flow air in the powder flow. 
     The first spray gun  10  can be thought of as having a first selectable forward section  26  and a rearward section  28 . The first selectable forward section  26  includes the first spray nozzle  20 , and may also include an optional charging electrode  30  that receives electrical energy from a high voltage multiplier  32  that is electrically connected with the electrode  30 . In typical spray guns, the multiplier  32  may be located in the rearward section  28 . In  FIG. 1  the location of the multiplier  32  is shown schematically. In a conventional dilute phase spray gun such as the first spray gun  10 , the electrode tip  30   a  may be disposed within the first spray nozzle  20  interior volume. 
     We present herein the concept of a configurable spray gun that can have two or more selectable spray gun configurations. More configurations may be used as desired, but for purposes of this disclosure we present three exemplary selectable spray gun configurations. An important benefit of the configurable spray gun is to realize significant savings and use of common parts which can reduce having different parts inventories for different spray guns. Not only can there be selectable configurations when putting a spray gun together, but the spray guns can be easily and conveniently configured, re-configured or converted between the selectable configurations. In the exemplary embodiments, we start with a known design for a dilute phase spray gun  10  that operates with a dilute phase powder flow that is input to the rearward section from a dilute phase pump as a first selectable spray gun configuration. We further provide the ability to easily and conveniently convert or configure the dilute phase spray gun  10  into a second selectable spray gun configuration  40 , or second spray gun  40  for short ( FIG. 2 ), that can receive a dense phase powder input flow from a dense phase pump. In accordance with our inventions, the configuration or conversion is accomplished by providing a second selectable forward section that may include a second selectable spray nozzle (or an air cap as another selectable configuration) with an optional electrode, and an adapter assembly. Both spray guns  10 ,  40  may utilize the same rearward section  28 ′ as will be apparent from the descriptions below, but the second spray gun  40  may include a second selectable powder tube in the rearward section that is connectable to a dense phase pump. 
     It is important to note that although the exemplary embodiments herein illustrate a prior art spray gun  10  as one of the selectable spray gun configurations, such is for convenience and is not required. The configurable spray gun concept of the present disclosure may be realized by providing a first selectable spray gun configuration that is operable with a dilute phase powder flow input, even if it is a wholly new design, and also providing a second selectable spray gun configuration with structure to convert or alternatively configure or re-configure the first spray gun configuration to operate with a dense phase powder flow input, in accordance with the teachings herein. Also, the reference as to which selectable configuration is “first” or “second” or “third” is arbitrary and is used simply as a convenient reference to distinguish the selectable spray gun configurations. 
     In accordance with this inventive concept of the present disclosure, and in reference to  FIG. 2 , we illustrate an embodiment of a second selectable spray gun configuration  40  or second spray gun  40  for short, that may share many of the same components as the first spray gun  10  of  FIG. 1 , but with several different features. Parts that may be but need not be the same, are given the same reference numerals as the embodiment of  FIG. 1  but with a prime (′) marker. Accordingly, the second spray gun  40  may include a rearward section  28 ′ that may be the same as or have many of the same components as the rearward section  28  in the first spray gun  10 . For example, the rearward section  28 ′ may include the first powder tube  14 ′ and the multiplier  32 ′. 
     It is a significant feature and benefit of the present inventions, although not necessarily required, that the selectable spray gun configurations  10 ,  40  of  FIGS. 1 and 2  can share the same rearward section  28 ,  28 ′ configuration, with the configuration of  FIG. 2  only using a few quick and convenient modifications to convert between the two configurations. In particular, the rearward section  28 ′ may include a second selectable powder tube ( 48 ) that has a smaller diameter than the powder tube  14  of the first spray gun  10 . The second spray gun  40  may further include a second selectable spray nozzle  42  (or alternatively an air cap) that is provided as part of a second selectable forward section  44  that can be joined with the rearward section  28 ′. 
     The second selectable forward section  44  of the second spray gun  40  may include the second selectable spray nozzle  42  having a spray orifice  42   a  and an electrode  46 . Because the powder flow must dilute over a shorter distance as compared with the first spray gun  10 , it may be desirable to dispose the electrode tip  46   a  outside the spray nozzle  42 . In the first spray gun  10  of  FIG. 1 , the electrode tip  30   a  may be disposed inside the first spray nozzle  20 , for example, using a spider as is known in the art. The electrode  46  in the second spray gun  40  may be supported by the second spray nozzle  42  as needed. 
     Powder coating material P will be supplied to the second selectable forward section  44 , including the second selectable spray nozzle  42 , through a second selectable powder tube  48 . The second powder tube  48  includes an inlet end  48   a  connectable to a dense phase pump  50 , for example, using a dense phase powder supply hose  52 . The powder flow at the outlet end  48   b  of the second powder tube  48  will be dense phase. In order to spray the dense phase powder, air may be added to the powder flow. The second spray nozzle  42  may include a diffuser  54 . The diffuser  54  may be, for example, a frusto-conical body that is made of a material that is porous to air. The diffuser  54  therefore acts as both an expansion chamber and a member for adding air to the powder flow. The diffuser  54  may be disposed within the second spray nozzle  42 . Alternative structure as needed may be used for adding air into the dense phase powder other than a diffuser  54 . 
     The second powder tube  48  for the second spray gun  40  may have a smaller diameter D2 as compared to the first powder tube  14  of the first selectable spray gun configuration. As part of the configuration of the second spray gun  40 , the second powder tube  48  may be inserted into the second spray gun  40  through the back end of the rearward section  28 ′. The second powder tube  48  can be pushed forward through the inside space of the larger diameter first powder tube  14  in a telescoping manner as illustrated in  FIG. 2 . 
     It should be noted that when we refer herein to a dense phase pump, we refer to a pump that produces a powder flow that has a higher ratio of powder to flow air as compared with a dilute phase pump, for example a common Venturi style powder pump. As it pertains to the present disclosure, a dense phase powder flow will use a powder hose from an outlet of a dense phase pump to an inlet end of the spray gun, as well as a powder flow passage within the spray gun, that have a smaller diameter or cross-sectional area than the powder hose and the powder flow passage in the spray gun used with a Venturi or other dilute phase pump. 
     With reference to  FIGS. 3, 4 and 5 , we illustrate an embodiment of the first spray gun  10  in a bar mount configuration. A tube mount configuration and a manual spray gun configuration will be basically the same as far as the forward section of the spray gun is concerned. The rest of these types spray gun may be conventional. This is another significant benefit of the present inventions in that the configurable gun concepts may be utilized with bar mount, tube mount and manual gun designs because it is primarily the front end of these spray guns that gets configured. The back end of the spray guns are modified only as to which selectable powder tube is to be used and how to connect the powder tube to the associated pump via the feed hose. 
     The first spray gun  10  may be but need not be realized in the form of the ENCORE® model spray gun which is commercially available from Nordson Corporation, Westlake, Ohio, and is well known to those in the art. Therefore, a detailed description of that spray gun is not required to understand and practice the inventions of the present disclosure. We provide the description of the spray gun  10  as it pertains to the parts that are associated with the selectable configurations. 
     The first spray gun  10  may include the first selectable forward section  26  and the rearward section  28  which includes a bar mount assembly  60 . The bar mount assembly includes a mount bracket  62 . A rear gun body  64  (which may correspond to the rear gun body  13  in  FIG. 1 ) may be connected to a bulkhead  66  that is also connected to a front gun body  68  (which may correspond to the front gun body  12  in  FIG. 1 ). The first powder tube  14  may be a single piece powder tube that extends through the spray gun  10  and has a front end  14   a  ( FIG. 5 ) that is received in a spider  70 . Because the first spray gun  10  is designed for dilute phase powder spray, the first powder tube  14  may be of a larger diameter as is known. The first spray nozzle  20  is attached to a forward end of the front gun body  68  using a threaded nozzle nut  72 . The spider  70  supports the electrode  30 . The first powder tube  14  extends out the back end of the first spray gun  10  and can be connected to a dilute phase powder supply hose  74  with an appropriate hose connector  75  assembly. The powder supply hose  74  is connectable to an output of the dilute phase pump  24  ( FIG. 1 ) such as a Venturi pump, for example. An electrical connector  76  is connectable to an electrical energy source (not shown) for supplying power to the multiplier  32 . The multiplier  32  is electrically connected to the electrode  30  as described herein below. 
     With reference to  FIG. 5 , the first selectable forward section  26  may be the same for the tube mount configuration or a bar mount configuration, or a manual spray gun configuration as needed. The first forward section  26  includes an electrode support assembly  78 . The electrode support assembly  78  may include an electrode holder  80  that has the electrode  30  disposed within a passage  80   a  in the electrode holder  80 . The electrode tip  30   a  extends outside the electrode holder  80 . The electrode holder  80  has a first end that is received in the spider  70 . The electrode  30  includes a coiled end  30   b  that extends into a blind bore  82  in the spider  70 . Two angled ducts  84 ,  86  are provided in the spider  70  and extend outward through a flange  88 . In one of the angled ducts  84 , a current limiting resistor  90  is disposed and has a first lead  92  that extends down to contact the electrode coiled end  30   b . A second lead  94  of the resistor  90  contacts a conductive ring  96  that is supported on a back side of the flange  88 . The multiplier  32  is connected to an output contact pin  98  that contacts the conductive ring  96 . In this manner, high voltage electrical energy from the multiplier  32  is electrically connected to the electrode  30 . The spider  70  includes flow passages (not shown) that allow powder to flow past the spider  70  and into the spray nozzle  20 . Note that an air tube ( 132  described below) receives pressurized air from an air source (not shown). The pressurized air flows from the air tube ( 132 ) through an air fitting ( 134 ,  FIG. 8 ) into the spider ducts  84 ,  86  to serve as electrode wash air. 
     We note here that although the exemplary embodiments disclose various designs for the spray nozzles and air caps used for spraying the powder coating material, whether received as dense phase or dilute phase powder flow, these are but a few examples of many known or later developed spray nozzle and air cap designs that may be used to carry out the present inventions. 
     At this point, some of the differences between a dilute phase spray nozzle and a dense phase spray nozzle are useful to understand. In a spray gun for powder that is supplied with dilute phase delivery, for example from a Venturi or other dilute phase powder pump, for example the ENCORE® model spray guns discussed herein, the spray nozzle may be designed to provide a desired spray pattern through a slot or other spray outlet  22  in the spray nozzle  20 . The powder flow into the spray nozzle tends to have a high velocity and a large volume of flow air, thus providing a lower powder/flow air ratio or in other words a lean mix. The spray nozzle typically then does not have atomizing air or dilution air added because the powder flow is already dilute. The spray nozzle will tend to dissipate some of the energy of the powder flow as it exits the powder tube, and then form a desired spray pattern, often like a cloud of powder coating material. Typically the electrode tip will be disposed within the spray nozzle. 
     For a dense phase spray gun used with a dense phase delivery, the powder tube can serve as the spray outlet because the dense phase powder flow may appear as a liquid-like or stream-like flow. In this case, and air cap may be used to apply pressurized air to atomize or dilute the powder flow and to shape the spray pattern just forward of the powder tube outlet end, with the electrode tip typically being disposed exterior the front end of the spray gun. In other cases, a dense phase spray nozzle may include a source of atomizing or dilution air in the nozzle for diluting the spray powder flow before it exits the spray nozzle and is exposed to the electrode. 
     Again referencing  FIG. 5 , the spider  70  may include a tapered channel  100  (which may correspond to the frusto-conical path portion  25  in  FIG. 1 ) adjacent the front end  14   a  of the first powder tube  14 . This tapered channel  100  may be frusto-conical in shape and is used in a dilute phase spray gun to allow the high flow powder stream to dissipate some energy as it enters the first spray nozzle  20  and also to further diffuse so that the powder can be electrostatically charged more efficiently. 
     The first powder tube  14  may be positioned and held adjacent to the spider  70  by a retaining seal member  102 . The spider  70  is captured between the spray nozzle  20  and a front end of the front gun body  68  when the spray nozzle nut  72  is tightened onto the front gun body  68 . This also applies an axial load against the first powder tube  14  to help seat the spider  70  in the retaining seal  102 . 
     It should be noted at this time that the exemplary embodiments herein illustrate components that are of a selected shape and size as needed for particular spray gun designs. However, in terms of providing a spray gun design that can selectively be configured to operate with a dilute phase or dense phase spray gun, the choice of which parts may be the same and which parts are swapped may be determined based on the overall spray gun functionality desired. 
     A basic embodiment then for the configurable spray gun concept presented herein is the use of a selectable powder tube, a selectable spray nozzle and an adapter member that facilitates a configuration change when needed. The configuration change between a dilute phase powder tube and a dense phase powder tube allows the dense phase powder tube to be slid through the larger diameter dilute phase powder tube, thus allowing for minimal change in the rearward section  28 , which is the common section of the two selectable spray gun configurations. 
     This also emphasizes that a spray gun that is connectable to a dense phase supply into a spray gun that is otherwise configured to spray powder from a dilute phase supply, is embodied in a basic form by providing a powder tube of a smaller diameter being inserted through a powder tube of a larger diameter up to the spray nozzle. 
     With reference next to  FIGS. 6-8 , the second selectable spray gun configuration as realized in an exemplary embodiment of the second spray gun  40 , includes the rearward section  28 ′ and the second selectable forward section  44 . Since the second spray gun  40  may optionally share the same rearward section  28 ′ design as the first spray gun  10 , with the exception of the second selectable powder tube  48 , the description of that portion of the second spray gun  40  need not be repeated. But as shown in  FIG. 6 , the second spray gun  40  uses a supply hose  52  that connects to the dense phase pump  50 . Therefore, the second spray gun  40  may use a different hose connector  104  to connect the second powder tube  48  to the powder supply hose  52 . But this is an external connection and easily made without changing the rearward section  28 ′ design. From  FIG. 7  it is apparent how the second powder tube  48  can telescope through the first powder tube  14 . 
     The second forward section  44  is best illustrated in  FIGS. 8 and 8A . In contrast to the first forward section  26  of the first spray gun  10 , the spider  70  is replaced with an adapter tube holder  106 . Because the powder being fed to the second spray nozzle  42  is dense phase, it is preferred to add air to the powder flow as the powder passes through the forward section  44 . Air may be added using a member in the second spray nozzle  42  as will be further described below. Additionally, the dense phase powder is preferably diffused with added air before the powder flow is exposed to the electrode tip  46   a . Accordingly, the electrode tip  46   a  may be disposed outside the second spray nozzle  42 . Therefore, there is no need for a spider as is used with the first spray gun  10 , but a structure may be provided to accommodate adding air to the powder flow. 
     The adapter tube holder  106  may be shaped similar to the spider  70  and is held in place between the second spray nozzle  42  and the front end portion  109  of the front gun body  68 . The retaining seal  102  may join the back end of the adapter tube holder  106  with the first powder tube  14  in a manner similar to the spider  70  in the first spray gun  10 . Note that the front gun body  68  may be the same as is used for the first spray gun  10  as part of the rearward section  28 ,  28 ′ that is common to both selectable spray gun configurations. An adapter tube  108  is supported inside the adapter tube holder  106 . The second powder tube  48  includes a forward portion  110  with an open end. A back end  108   a  of the adapter tube  108  may be snugly seated in the forward portion  110  of the second powder tube  48 . For example, the second powder tube  48  may comprise an elastic material that allows a barbed end  112  to be inserted into the open end of the forward portion  110  of the second powder tube  48 . The elastic material may assist the second powder tube  48  to conform to the shape of the barbed end  112 . The adapter tube  108  and the adapter tube holder  106  comprise a selectable adapter assembly  107  that interfaces the second powder tube  48  and the second spray nozzle  42 . 
     A diffuser support  114  is disposed in the second spray nozzle  42 . The diffuser support  114  seats in a passage  116  in the second spray nozzle  42 . A seal  118 , such as an o-ring seal, is provided to form a seal interface between the passage  116  wall and the diffuser support  114 . The forward end of the diffuser support  114  provides a first recess or cavity  120 . An optional member  122 , also referred to herein as a diffuser (also see the discussion regarding a diffuser  54  with respect to  FIG. 2 ), for adding flow air to the powder flow P is disposed in the cavity  120  of the diffuser support  114 . The diffuser support  114  includes a wall  124  with a passage  126  therethrough. The member  122  has a back end that abuts a forward surface of the wall  124 . The diffuser support  114  includes a second cavity  128  that is axially separated from the first cavity  120  by the wall  124  but with the passage  126  therebetween. The forward end of the adapter tube  108  is disposed in the second cavity  128  and abuts a rearward surface of the wall  124 . In this manner, powder can flow from the second powder tube  48  outlet end  18 , through the adapter tube  108 , through the air diffused cavity ( 146 ) provided by the member  122  and out the spray orifice  22 . 
     The member or diffuser  122  may be provided as a hollow frusto-conical wall  130  that is made of an air permeable material, such as sintered polyethylene for example. An air tube  132  extends from a back end of the second spray gun  40  and is connectable to a supply of pressurized air (which for the ENCORE® model spray gun is used for electrode wash air). The forward end of the air tube  132  is attached to an air fitting  134 . The air fitting  134  opens to a cavity  136  that is provided between the front end of the front gun body  68  and the adapter tube holder  106 . In the first spray gun  10 , the pressurized air through the air tube  132  may be used as electrode wash air as is known. The adapter tube holder  106  includes one or more air passages  138  that open to an adapter tube holder socket  140  that receives the back end  142  of the diffuser support  114 . The diffuser support  114  also includes one or more air passages  144  that open to the first cavity  120  of the diffuser support  114 . By this arrangement, pressurized air that is applied to the air tube  132  passes through the air fitting  134  into the air cavity  136 , through the air passages  138  into the socket  140 , and from the socket  140  through the air passages  144  and into the first cavity  120  of the diffuser support  114 . The pressurized air flows through the air pervious material of the diffuser  122  and into the interior volume  146  of the diffuser  122  to mix with the powder flow for dilution or atomizing air. Note that the electrode coiled end  154  sits in a passage  156  which is in fluid communication with the socket  140 , so that pressurized air from the air tube  132  still may be used to provide electrode wash air. Therefore, the pressurized air from the air tube  132  may serve both as electrode wash air and also as the atomizing or dilution air for the dense phase powder flow that enters the second spray nozzle  42 . 
     The second spray nozzle  42  will typically be somewhat longer than the first spray nozzle  20  because of the diffuser  122 . Because the spider  70  is not used in the second spray gun  40 , a modified electrical connection between the multiplier  32  and the electrode  46  is provided. The multiplier output contact pin  98  makes contact with a conductive disk  148 . An extension spring  150  is provided in contact with the conductive disk  148  at one end and a conductive ring  152  at the other. The conductive ring  152  also makes electrical contact with a coiled spring end  154  of the electrode  46 . The electrode  46  extends through a passage  156  to the front of the second spray nozzle  42  so that the electrode tip  46   a  is disposed outside of the second spray nozzle  42 . 
     An adapter key  158  arrangement, for example, a pin and slot configuration, may be used to key the adapter tube holder  106  to the front gun body  68 . This key arrangement  158  can be used to assure that the conductive disk  148  is aligned with the extension spring  150  during assembly. Also, the key arrangement  158  may be used prevent a torsion or twist from being applied to the second powder tube  48  when the second spray nozzle  42  is assembled onto the second spray gun  40 . This twist could occur if the adapter tube holder  106  is not keyed to the front gun body  68  because of the connection between the adapter tube  108  and the second powder tube  48 . 
     A comparison of  FIGS. 5 and 8  illustrates how the selectable spray gun configurations can be used or changed as the case may be. In order to change over the first spray gun  10  to the second spray gun  40  configuration, or alternatively to configure the second spray gun  40  based on the first spray gun  10 , it will be noted that the assembler may remove the first spray nozzle  20  and the spider  70 , and remove any hose connection at the back end of the first powder tube  14 . Then the assembler can insert the second selectable powder tube  48  up through the first selectable powder tube  14  and snugly seat the open end  110  of the powder tube  48  onto the barbed end  112  of the adapter tube  108 . The adapter tube  108  and the adapter tube holder  106  comprise the adapter assembly  107  that provides an interface or connection between the second powder tube  48  and the second spray nozzle  42 . The adapter assembly  107  is installed onto the front gun housing  68  with the optional key  158  aligned properly. The adapter tube holder  106  and the adapter tube  108  therefore cannot rotate during further assembly of the second spray nozzle  42 . The second spray nozzle  42  may be preassembled with the diffuser holder  114  already installed. After the adapter assembly  107  is installed, the second spray nozzle  42  can be installed by inserting the front end  108   b  of the adapter tube  108  into the second cavity  128  of the diffuser holder  114 , and then the second nozzle nut  160  can be tightened onto the front gun body  68 . Note that the second nozzle nut  160  need not be the same as the first nozzle nut  72  for the first spray gun  10 . 
     It should be noted that the differences between the first selectable spray gun configuration  10  and the second spray gun configuration  40  all relate to easily accessible components on the outside front end of the spray gun, with the exception of inserting the second selectable powder tube  48  up through the first selectable powder tube  14  when the second spray gun configuration is to be used. The selectable forward sections are readily configured by removing the spray nozzle and the associated spider or adapter assembly and installing the alternative selectable parts for the desired configuration. 
     Another benefit of the selectively configurable spray gun concept is that for the second spray gun  40 , it will be noted that the second selectable flow path includes the second powder tube  48  and the adapter tube  108  which is part of the adapter assembly  107 . This allows the adapter tube material to be selected based on the type of powder coating material being sprayed, be it organic powder or porcelain enamel powder. The powder flow does not impact surfaces as would occur when a spider is used, so the adapter support housing  106  will not exhibit wear. 
     With reference to  FIGS. 10-12  we illustrate additional embodiments of the spray gun  40  in  FIG. 2  which is an embodiment of the second selectable configuration. The second selectable spray gun configuration is a spray gun that may be connected to a dense phase powder supply but produces a spray pattern using a dilute phase spray nozzle, and an optional electrode. Such a spray gun  200 , therefore, shares most of the features described hereinabove for the embodiments of  FIGS. 6-8A , but the second selectable forward section  44  has been modified so that the spray gun  200  may be not only selectively configured as a dilute phase delivery spray gun or a dense phase delivery spray gun, but additionally for the dense phase delivery spray gun configuration may further be optionally configured with a slot style spray nozzle ( FIG. 12 ) or an air cap ( FIGS. 10 and 11 ). A difference between a slot style spray nozzle and an air cap is that the air cap may be used to add dilution air to the powder flow that exits the powder tube  48  ( FIG. 2 ). With the slot style spray nozzle, dilution air is added using a diffuser  54  or other structure within the spray nozzle, as was described herein with reference to  FIGS. 2 and 8 . Thus, the second selectable forward sections of  FIGS. 8, 11 and 12  are installed in place of the first selectable forward section  26  of the spray gun of  FIGS. 1 and 5  (which may be but need not be an ENCORE® model) in order to configure the spray gun for dense phase delivery. 
     In order to provide a second selectable forward section that accommodates either an air cap or a slot style spray nozzle, we illustrate additional embodiments and modifications to the second selectable forward section  44  as compared with the embodiments of  FIGS. 3-8A . But the rest of the features and options already presented herein may be used and so need not be repeated, and like reference numerals are used for like components for clarity. For example,  FIGS. 10-12  show a bar mount configuration but a tube mount configuration may alternatively be used. The spray gun  200  may also use electrostatic or non-electrostatic coating processes. 
     The air cap style configurable spray gun  200  of  FIGS. 10 and 11  may include a second selectable forward section  202 , as well as the same rearward section  28 ′ as used with the spray gun  10 . The second selectable forward section  202  differs from the second selectable forward section  44  of  FIGS. 6-8A  in that it facilitates use of a selectable third configuration, for example, a PRODIGY® model air cap  204  available from Nordson Corporation. The PRODIGY® model spray gun is fully disclosed in U.S. Pat. No. 7,793,869 to Mater, et al for PARTICULATE MATERIAL APPLICATOR AND PUMP, the entire disclosure of which is fully incorporated herein by reference. 
     In order to further realize the benefit of being able to provide multiple selectable spray gun configurations that share many common components, the second selectable forward section  202  has the benefit that the spray gun  200  may have either an air cap configuration or a slot style spray nozzle configuration by simply selecting which front end to use. Moreover, with the modified second selectable forward section  202 , the forward section can now accept or support spray nozzles and air caps that were previously designed and are in use with the PRODIGY® model spray guns available from Nordson Corporation, Westlake, Ohio. This further enhances the savings of not needing special parts and inventory for different spray gun configurations because now a spray gun, for example an ENCORE® model spray gun, that is capable of spraying dilute phase powder from a dilute phase powder supply like a Venturi pump, can be selectively configured to spray dense phase powder from a dense phase powder supply and spray the powder through a spray nozzle or air cap that is otherwise usable with dense phase spray guns, for example a PRODIGY® model spray gun. 
     With reference then to  FIG. 11 , it should be noted that many of the components in the second selectable forward section  202  may be the same as the embodiment of  FIG. 8  herein and therefore like reference numerals are used and the description need not be repeated. Only the different components will be described as needed. The second selectable forward section  202  includes a modified adapter tube holder  206  as compared to the adapter tube holder  106  of  FIG. 8 . The main difference is that the modified adapter tube holder  206  has a truncated front end  208  rather than the front cylinder portion of the adapter tube holder  106 . The modified adapter tube holder  206  front end engages the back end of a conductive ring  210 . 
     The conductive ring  210  includes one or more air passages  212  so that pressurized air that is supplied from the air tube  132  passes through the air passages  138  in the adapter tube holder  206 , through a space  140  between the air passages  138  and the conductive ring  210 , and then through the conductive ring air passages  212  and out the air cap  204 . The air cap  214  includes horns  216  with air passages  218  that are in fluid communication with the air passages  212  in the conductive ring  210 . This allows the atomizing air to diffuse the dense phase powder as the powder flow exits the outlet end  108   b  of the adapter tube  108 . A seal  214  such as an o-ring for example may be used to force the pressurized air that passes through the adapter holder  206  into the air cap  204 . In this way, the pressurized air from the air tube  132  may be used as both electrode wash air and as the dilution or atomizing air for the dense phase powder that exits the adapter tube  108  into the air cap  204 . 
     With this modified adapter tube holder  206  then, a conventional PRODIGY® model air cap may be used with the second selectable forward section  202 . Of course, other air caps may be used as needed for particular applications. Note that when the air cap  204  is used, there is no need for the air diffuser support  114 . In order to couple electrical energy to the electrode  46 , we provide a hollow insert  220  in a cavity  222  of the air cap  204 . This insert  220  receives the powder flow that exits the adapter tube end  198   b , and may further optionally be used to support the electrode  46  for electrostatic coating operations. The electrode  46  is received in a passage  156  and has a coiled spring end  154  that makes contact with the conductive ring  210 . In addition, the insert  220  may be provided with an inwardly tapered, for example frusto-conical, forward opening  223  that helps to shape the powder flow pattern and keep the powder directed toward the centerline P of the powder flow path as the powder exits the air cap  204 . This directed flow can improve the ability to electrostatically charge the powder. 
     With reference to  FIG. 12 , the modified adapter tube holder  206  may also be used with a slot style spray nozzle to provide yet another (third) selectable spray gun configuration that can receive dense phase powder flow and spray the powder through a dilute phase nozzle. As noted above, the modified adapter tube holder  206  allows a spray gun, which in one configuration may be a dilute phase spray gun, for example a spray gun like the ENCORE® model spray gun, to be configured for a dense phase powder supply but with a front end that sprays the powder in dilute phase, for example spray nozzles and air caps used with a PRODIGY® model spray gun. 
     The selectable second forward section  224  for the third configurable spray gun may include the same adapter tube holder  206 , conductive ring  210 , air passages  212 , and seal  214  as the embodiment of  FIGS. 10 and 11 . The diffuser support  114  and the diffuser  122  may be the same as in the  FIG. 8  embodiment. The primary difference then between the embodiment of  FIG. 8  and the embodiment of  FIG. 12  is that the modified adapter tube holder  206  allows use of a conventional PRODIGY® model spray gun spray nozzle  226  and diffuser  122  to be used rather than the spray nozzle  42 . Of course, other spray nozzles may alternatively be used as needed for particular applications. 
     Therefore, the modified adapter tube holder  206  in  FIGS. 11 and 12  facilitates two additional selectable spray gun configurations using an air cap or spray nozzle that may also be useable with a PRODIGY® model spray gun. 
     With reference to  FIGS. 13 and 14 , we illustrate an exemplary embodiment of a manual spray gun that may also have three selectable configurations. The manual spray gun  230  for the most part may be, for example, an ENCORE® model manual spray gun, which is designed for use with dilute phase powder from, for example, a Venturi pump. However, alternatively, other manual spray guns with dilute phase delivery may be used. The ENCORE® model manual spray gun is well known and commercially available from Nordson Corporation, Westlake, Ohio and therefore need not be described in detail. This manual spray gun is also fully disclosed in United States Published Patent Application number 2009/0107397 A1 for APPARATUS AND METHODS FOR PURGING MATERIAL APPLICATION DEVICE, the entire disclosure of which is fully incorporated herein by reference. A manual ENCORE® model spray gun therefore is an embodiment of one of the three selectable manual spray gun configurations. 
     The manual spray gun  230  illustrated in  FIGS. 13 and 14  includes a manually gripped handle  232 , a barrel  234  and a forward section or nozzle assembly  236  at the front end. For a manual ENCORE® model spray gun using a dilute phase powder supply, the nozzle assembly  236  may be the same as the first selectable forward section  26  described herein with respect to  FIG. 5 . However, by configuring the nozzle assembly  236  to have the same selectable forward section  44  in  FIG. 8  or alternatively the same selectable forward section  202  as illustrated in  FIG. 11  or alternatively the same selectable forward section  226  in  FIG. 12  (each of which may be used in place of the forward section  26  of  FIG. 5  for an automatic or manual spray gun), the spray gun  230  may be used with dense phase delivery; and conveniently may be used with a conventional PRODIGY® model spray gun air cap  204 , as is shown with the  FIG. 11  embodiment or a PRODIGY® model spray gun spray nozzle  226  as is shown in  FIG. 12 . In addition, a smaller diameter powder hose  240  which is connectable to a dense phase pump  48 , can be inserted through the larger dilute phase powder path  242  that is already present in an ENCORE® model spray gun. The smaller diameter powder hose  240  can be inserted through the handle  232  and the barrel  234  to be attached to the back end of the adapter tube  108 . Thus, the spray gun  230  of  FIG. 14  is a manual spray gun otherwise designed for dilute phase powder delivery, that may optionally be configured to receive dense phase powder delivery and to spray that powder through a PRODIGY® model spray gun air cap  238 , or other air cap as needed. 
     The nozzle assembly  236  may use the same adapter tube holder  206  and related components as the embodiments of  FIGS. 11 and 12 , which allows the manual spray gun  230  to be used with an air cap  204  ( FIG. 11 ) or alternatively a slot type spray nozzle  226  ( FIG. 12 ), for example the PRODIGY® model spray gun air cap or spray nozzle, as the second and third selectable configurations, in a manner similar to the automatic spray gun configurations of  FIGS. 11 and 12 . Moreover, the manual spray gun  230  may have a fourth selectable configuration in that the second selectable forward section  44  of  FIG. 8  may be used for the nozzle assembly  236 . 
     It will be also noted that in a manner similar to the automatic spray gun embodiments herein ( FIGS. 8, 11 and 12 ), the atomizing air for the nozzle assembly  236  may be provided through the air inlet  244  that is used for electrode air wash for the ENCORE® model spray gun. Therefore, the embodiments of  FIGS. 11, 12 and 14  may use the modified adapter tube holder  206 , which includes air passages  132 , in a like manner with the adapter tube holder  106  in  FIG. 8 . Therefore, all these embodiments ( FIGS. 8, 11, 12 and 14 ) may use the pressurized air via the air tube  132  for both electrode wash air and for atomizing/dilution air. 
     We have referred to a dense phase powder pump  50  in the above disclosure, which is also commonly known as high density powder pumps. There are many different dense phase pumps available commercially, and one such pump is described in U.S. Pat. No. 7,997,878 issued on Aug. 16, 2011, to Terrence M. Fulkerson for DENSE PHASE POWDER PUMP WITH SINGLE ENDED FLOW AND PURGE; and U.S. Pat. No. 7,150,585 issued on Dec. 19, 2006, to Kleineidam et al. for PROCESS AND EQUIPMENT FOR THE CONVEYANCE OF POWDERED MATERIAL, the entire disclosures of which are fully incorporated herein by reference. With reference to  FIG. 9 , an exemplary dense phase pump  400  may use at least one or more pump chambers  402  in the form of a hollow cylinder  404  made of an air porous material  406 . The material  406  for the pump chamber  402  may be but need not be similar to the air diffuser  58  described herein, for example sintered polyethylene. Each pump chamber  402  is disposed in a pressure chamber  408  such that powder is drawn into a pump chamber volume  410  from a powder supply  411  through a feed hose  412  when the pressure chamber  408  has negative pressure applied from a vacuum source  414 , and powder is pushed out of the pump chamber  408  to a supply hose  418  when positive pressure is applied from a pressure source  416  to the pressure chamber volume  410 . Control of powder into and out of the pump chambers may be accomplished with powder flow control valves, for example, pneumatic pinch valves  420  (powder in) and  422  (powder out) respectively, which open and close out of phase with respect to each other as is known. Pressure control valves, for example vacuum control valve  424  and positive pressure control valve  426  may also be used to control the timing of when negative and positive pressure cycles occur. The low flow air for dense phase powder flow arises from the use of pressure to move the powder, as opposed to high velocity air as used in a dilute phase powder pump such as a Venturi pump. Different dense phase powder pump designs may produce powder flows that vary in the powder/air ratio or in other words how rich the powder flow is into the spray gun, and similarly different Venturi pump designs may produce different levels of lean powder flows. For this reason we do not limit the disclosure herein to a definition of what is dense phase versus dilute phase. But a dense phase powder flow will typically be used with smaller diameter or cross-sectional powder flow paths as compared to a dilute phase powder flow path due to the lower flow air volume in the powder flow. The schematic of  FIG. 9  shows an embodiment of the inventive concept of the second selectable spray gun configuration  40  that uses a dense phase powder flow into the second spray gun  40  and sprays the powder from a dilute phase selectable forward section  44 . 
     The inventions have been described with reference to the exemplary embodiments. Modifications and alterations will occur to others upon a reading and understanding of this specification and drawings. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.