Abstract:
A low pressure foaming nozzle assembly having a modular construction for permitting the ready interchange of nozzle tips. The foaming nozzle assembly may be constructed of two pieces, with a first configuration employing a flow body and an engaging nozzle tip and a second configuration employing a pair of mating halves, wherein each mating half includes a portion of a venturi, a throat and a nozzle tip. The assembly cooperatively engages a foaming liquid source such as a wand, and upon pressure on the foaming liquid source, a foam is generated.

Description:
RELATED APPLICATIONS 
     The present application is a continuation in art of U.S. Ser. No. 09/114,766 filed Jul. 14, 1998 now U.S. Pat. No. 6,015,100, naming Mario J. Restive as the inventor which claims priority to U.S. Ser. No. 60/052,585 filed Jul. 15, 1997. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to nozzles for aerating a relatively low pressure liquid stream to produce a sprayable foam, and more particularly, to a nozzle assembly which permits ready interchangeability of a nozzle tip for creating different foam spray application patterns. 
     BACKGROUND OF THE INVENTION 
     Foams are typically produced by the mixing of a chemical, water and a gas under certain conditions. The particular chemicals employed depends upon the desired use of the foam. For example, in the agricultural arena foams are often used to apply pesticides and are often preferable to liquid application. 
     The application of chemicals in a foamed condition offers a number of benefits. The foam application permits the chemicals to be used with lower supply rates and active chemical content, thereby reducing costs. Further, the use of a foam composition reduces health and safety hazards caused by the splashing or drift of tiny droplets or a fine mist. Because a foam is readily visible it also provides a convenient way for visually determining coverage. 
     Generally, two basic methods have been utilized to generate foams. One method is the use of a chemical foaming agent which is added to the solution, and the solution is then foamed. The other method is the introduction of gas such as air into the liquid to form minute bubbles, thereby collectively forming the foam. The application of agricultural chemicals by foam generating equipment traditionally includes a nozzle unit which mixes air with liquid chemicals. 
     The type and consistency of foam created by particular foam generating nozzles is a function of a number of factors, including the chemicals to be applied, the pressure of the material when applied to the nozzle unit and the design of the nozzle unit. A resulting consistency of the foam is often dictated by the anticipated application. That is, for applications requiring prolonged retention on a vertical or downward facing surface, it is usually desirable to apply the material as a thick foam. Such foams often follow a 1:10 ratio, that is for each unit volume of liquid, 10 unit volumes of foam are produced. Alternatively, if penetration of a porous surface is desired, the foam is preferably formed with a minimally sized bubbles in a ratio of approximately 1:2. 
     It has been found that at the relatively low operating pressures, it is difficult to obtain sufficiently small particle size and hence sprayable foam generation. Therefore, prior systems have relied upon relatively high fluid pressures for foam generation. The prior foam generating devices are relatively high pressure units requiring 40 psi or more. The mechanisms required to generate these relatively high pressures and the inability of the foaming nozzles to efficiently use the available energy at low pressures have prevented relatively low pressure foaming technology in a truly portable, human transportable foaming apparatus. 
     Further, in view of the relatively complicated structure required for the passage of a liquid, introduction of air, generation of foam and application of the foam, a given foaming nozzle unit traditionally creates only a single type foam. That is, if alternative chemical compositions, or application patterns are desired, the nozzle unit must be completely removed and an entirely new nozzle unit applied. This increases the cost of the foam applicators. 
     Therefore, a need exists for a foaming nozzle assembly which is easily reconfigured to create a variety of foams. Further, the need exists for a foam generating nozzle which may be readily disassembled, cleaned and reassembled. The need also exists for such a nozzle assembly which may be reconfigured with interchangeable components. A similar need exists for a foaming nozzle assembly that can employ interchangeable nozzle tips or be constructed at cost that allows interchangeability. A further need exists for a foam generating nozzle that can be used in relatively low pressure applications, such as less than approximately 35 psi and still generate sufficient quantities of foam. 
     SUMMARY OF THE INVENTION 
     The present invention provides a foaming nozzle assembly for generating a sprayable foam at relatively low fluid pressures, below approximately 35 psi. Preferably, the foaming nozzle produces foam at pressures as low as 25 psi. The present foaming nozzle assembly may be readily attached to a wand. The foaming nozzle may also be disconnected from the wand and disassembled to allow for the ready interchangeability of the components, including a nozzle tip. Thus, the present invention allows a modification of the foam characteristics and application pattern without requiring the use of an entirely new assembly. The sprayable foam formed by the present foaming nozzle assembly reduces wind drift, lowers the required chemical concentration and allows for visual confirmation of both the spray path and the treated areas. 
     Generally, the present foaming nozzle assembly includes an elongate housing with a first end configured to releasably engage a conduit or wand, and a second end defining an outlet aperture. The housing further includes a stop and a radially directed air inlet port. The foaming nozzle assembly further includes a nozzle tip having a shoulder for cooperatively engaging the stop. The nozzle tip is constructed to be slideably disposed within the housing from the first end so as to seat against the stop and substantially occlude the outlet aperture. The foaming nozzle assembly further includes a throat having a divergent end and a convergent end, the throat being sized to be slideably disposed within the housing and contact the divergent end with the nozzle tip. Finally, the foaming nozzle assembly includes a venturi nozzle/deflector sized to be disposed within the housing such that the deflector portion operably aligns with the air inlet port in the housing and the venturi nozzle/deflector contacts the convergent end of the throat. 
     In an alternative configuration, the foaming nozzle assembly is constructed of two pieces. The two piece design may be formed in at least two configurations. In a first configuration of the two piece design, the foaming nozzle assembly is constructed of a flow body and a nozzle tip. The flow body includes structure corresponding to the venturi nozzle/deflector, the throat and a portion of the housing of the first embodiment. The flow body is an integrally formed single piece construction that includes structure corresponding to the venturi nozzle/deflector, the throat and a portion of the housing of the first embodiment. The nozzle tip is mechanically engaged the flow body to control the desired spray pattern and assist with foam generation. As the nozzle tip can be releasably attached to the flow body, the nozzle tip can be readily interchanged without requiring extensive downtime. 
     In the second configuration of the two piece embodiment, the foaming nozzle assembly is formed of mating halves along the flow path or longitudinal axis of the assembly. That is, each mating half includes a portion of the housing, the venturi nozzle/deflector, the throat and the nozzle tip. In this construction, the nozzle tips are not interchangeable with the remainder of the foaming nozzle assembly, but rather the entire foaming nozzle assembly is readily interchangeable with respect to the wand. 
     The present invention also contemplates a method of assembling a foaming nozzle assembly including slideably disposing a nozzle tip within an elongate housing, such that motion of the nozzle tip through the housing is limited by contact between the nozzle tip and the housing; disposing a diverging throat within the housing to be operably disposed with respect to the nozzle tip; disposing a venturi nozzle/deflector within the housing to operably align with the throat, thereby providing fluid communication through the venturi nozzle/deflector, the throat and the nozzle tip, and providing fluid access from a radial port in the housing to a convergent end of the throat. 
     Alternatively, the present invention contemplates a method of assembling a foaming nozzle assembly by engaging a nozzle tip with a body having a venturi nozzle/deflector and a throat to define a flow path therethrough. A further method encompasses assembling a foaming nozzle assembly by mating a pair of assembly halves, each half including a portion of a venturi nozzle/deflector, a throat and a nozzle tip. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational partial cross sectional view of a foaming nozzle assembly operably connected to a liquid source. 
     FIG. 2 is a cross sectional view of the foaming nozzle assembly. 
     FIG. 3 is a cross sectional view of a venturi nozzle/deflector for the foaming nozzle assembly. 
     FIG. 4 is an end view from downstream of the venturi nozzle/deflector of FIG.  3 . 
     FIG. 5 is a cross sectional view of a throat for the foaming nozzle assembly. 
     FIG. 6 is an end view from upstream of the throat of FIG.  5 . 
     FIG. 7 is an end view from downstream of the throat of FIG.  5 . 
     FIG. 8 is a cross sectional view of a housing for the foaming nozzle assembly. 
     FIG. 9 is an end view of a housing for the foaming nozzle assembly. 
     FIG. 10 is a perspective view of a two piece foaming nozzle assembly. 
     FIG. 11 is a side elevational view of the foaming nozzle assembly of FIG.  10 . 
     FIG. 12 is a cross sectional view of the two piece foaming nozzle assembly of FIG. 11 taken along lines  12 — 12 . 
     FIG. 13 is a perspective view of the flow body of the two piece foaming nozzle assembly of FIG.  10 . 
     FIG. 14 is a side elevational view of the flow body of FIG.  13 . 
     FIG. 15 is an end view of the upstream end of the flow body of FIG.  14 . 
     FIG. 16 is an end view of the downstream end of the flow body of FIG.  14 . 
     FIG. 17 is a cross sectional view of the flow body taken along lines  17 — 17  of FIG.  14 . 
     FIG. 18 is an enlarged detail view of the area  18  of FIG.  17 . 
     FIG. 19 is an enlarged detail view of the area  19  of FIG.  17 . 
     FIG. 20 is a perspective view of a nozzle tip for the foaming nozzle assembly of FIGS. 10-12. 
     FIG. 21 is a side elevational view of the nozzle tip of FIG.  20 . 
     FIG. 22 is an end view of the upstream end of the nozzle tip of FIG.  20 . 
     FIG. 23 is an end view of the downstream end of the nozzle tip of FIG.  20 . 
     FIG. 24 is a cross sectional view taken along lines  24 — 24  of FIG.  21 . 
     FIG. 25 is an enlarged detail view of the area  25  of FIG.  24 . 
     FIG. 26 is a perspective view of a component of an axially separated two piece construction of the foaming nozzle assembly. 
     FIG. 27 is a side elevational view of the component of FIG.  26 . 
     FIG. 28 is an end view of the upstream end of the component of FIG.  27 . 
     FIG. 29 is an end view of the downstream end of the component of FIG.  27 . 
     FIG. 30 is a top plan view of the component of FIG.  26 . 
     FIG. 31 is a cross sectional view taken along lines  31 — 31  of FIG.  30 . 
     FIG. 32 is an enlarged detail view of the area  32  of FIG.  30 . 
     FIG. 33 is a cross sectional view taken along lines  33 — 33  of FIG.  30 . 
     FIG. 34 is an enlarged detail view of the area  34  of FIG.  30 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a foaming nozzle assembly  10  of the present invention is shown. The foaming nozzle assembly  10  operably connects to a source  12  of the liquid to be foamed. Typically, an interface between the foaming nozzle assembly  10  and the source  12  is a rigid self supporting wand  14 . The wand  14  may include threads, snap fits or other mechanical connection configurations for operably connecting to the foaming nozzle assembly  10 . However, it is understood that any of a variety of interfaces to the source  12  may be employed. 
     The foaming nozzle assembly  10  includes a housing  20 , a nozzle tip  40 , a throat  60  and a venturi deflector/nozzle  80 . 
     The Housing 
     The housing  20  is a substantially tubular elongate member having an upstream wand engaging end  22  and a downstream nozzle end  24  disposed along a longitudinal axis. Preferably, the housing  20  is a cylindrical member having an interior and an exterior. A length of the interior adjacent the wand end  22  includes a plurality of threads  26 . The nozzle end  24  includes a nozzle port  25 , and a stop  28 . The stop  28  is a collar projecting radially inward toward the longitudinal axis of the housing  20 . The collar forms an annular seating surface  30 . A plurality of ribs or fins  32  project from the housing  20  to form levers for assisting in the connection of the nozzle assembly  10  to the wand  14 . The housing  20  includes at least one and preferably a plurality of air inlet ports  33  intermediate the wand end  22  and the nozzle end  24 . 
     The housing  20  may be formed by any of a variety of materials that are inert to the compositions to be foamed, such as wear resistant polymers. A preferred material for construction of the housing is Delran as manufactured by E. I. DuPont. 
     The Nozzle Tip 
     The nozzle tip  40  is configured to be slideably received within the housing  20 . The nozzle tip  40  is disposed in the nozzle end  24  of the housing  20  to provide an exit passage of the foaming composition from the foaming nozzle assembly  10 . The nozzle tip  40  is sized to be slideably received within the wand end  22  of the housing  20  and slide to the nozzle end  24 . The nozzle tip  40  has a through passage  43  from an upstream inlet  42  to a downstream foam spray outlet  44 . The particular foam spray outlet  44  of the nozzle tip  40  is selected for producing the specific foam pattern and may be any of a variety of constructions. The foam spray outlet  44  defines an area through which the pressurized liquid area mixture exits the nozzle assembly  10 . The nozzle tip  40  includes a shoulder  46  sized to contact the stop  28  and preclude further travel of the nozzle tip  40  with respect to the housing  20 . Preferably, contact between the shoulder  46  and the seating surface  30  substantially precludes fluid flow therebetween under operating pressures. The upstream end  42  of the nozzle tip  40  forms an upstream seating surface  48  for contacting the throat  60 . 
     The nozzle tip  40  may be formed of any of a variety of materials such as brass, wear resistant polymers or plastic. Alternatively, the nozzle tip may be one of a commercially available style. 
     The Throat 
     The throat  60  defines a central passage  63  and has a convergent upstream end  62  and a divergent downstream end  64 . The throat  60  is also sized to be slideably received within the housing  20 , passing through the wand end  22  to slide towards the nozzle end  24 . The throat  60  includes peripheral flanges to locate, or center, the throat with respect to the housing  20 . The downstream, divergent end  64  of the throat  60  includes a downstream seating surface  66  sized to cooperatively engage the upstream seating surface  48  of the nozzle tip  40 . The convergent end  62  includes contact surfaces  68  for abutting the nozzle tip  40 . 
     The upstream end  62  of the throat  60  includes at least one locating recess  69 . The locating recess  69  is in the form of an annular recess in an upstream face of the throat  60 . 
     In a preferred embodiment, the throat  60  has a total passage length approximately of 0.9 inches, and a convergent end diameter of approximately 0.078 inches. The convergent end diameter extends along the longitudinal axis for a length of approximately 0.3 inches, then flares at an angle of approximately 6 (12 conical angle) to a divergent end diameter of 0.3 inches. It has been found the same configuration of the throat  60  may be employed for a 0.1 and a 0.2 gallon per minute flow rate through the nozzle assembly  10 . 
     The throat  60  may be formed of a plastic wear resistant polymer. 
     The Venturi Deflector/Nozzle 
     The venturi deflector/nozzle  80  is sized to be slideably received within the housing  20 , passing from the wand end  22  toward the nozzle end  24 . The venturi deflector/nozzle  80  defines a converging, funnel shaped central passage  83  extending along the longitudinal axis from an upstream open end  82  to a downstream restricted venturi end  84 . The venturi deflector/nozzle  80  is sized to operably align the convergent end of the central passage  83  with the convergent end  62  of the throat  60 . The venturi deflector/nozzle  80  may also include a pair of peripheral flanges to locate, or center the nozzle with respect to the housing  20 . The downstream end  84  of the venturi deflector/nozzle  80  includes a plurality of locator bosses  86 . The locator bosses  86  are located at an equal radius from the longitudinal axis and are sized to be received or registered within the locating recesses  69  of the throat  60 . The locator bosses  86  of the venturi deflector/nozzle  80  and locating recesses  69  of the throat  60  thereby form a space between the venturi deflector/nozzle and the throat. 
     The locator bosses  86  and locating recesses  69  are sized to dispose a length of the venturi end  84  within the convergent end  62  of the throat  60 . That is, a portion of the venturi deflector/nozzle  80  and the throat  60  overlap along the longitudinal axis, with the throat having the larger diameter and the restricted end of the venturi deflector/nozzle having the smaller diameter. An outer surface of the restricted end  84  of the venturi deflector/nozzle  80  and the convergent end  62  of the throat  60  define an introduction annulus  89  therebetween. The introduction annulus  89  is fluidly connected to the radial ports  33  in the housing  20 . 
     Preferably, the outer surface  88  of the venturi end  84  of the venturi deflector/nozzle  80  forms deflector surfaces which redirect a radially inward air flow substantially parallel to the longitudinal axis. 
     The upstream, open end  82  of the venturi deflector/nozzle  80  includes a seating surface  92  for contacting the wand or an assembly seal. 
     The venturi deflector/nozzle  80  thus defines a primary flow control surface defined by the central passage  83  for directing liquid from the source  12  to the throat  60 . The venturi deflector/nozzle  80  also defines a secondary flow control surface defined by the outer surface  88  for introducing air from the radial port to the liquid flow passing from the primary flow control surface substantially parallel to the longitudinal axis. 
     The venturi deflector/nozzle  80  may be configured to provide a variety of flow rates. For example, in a 0.2 gallon per minute configuration, the venturi deflector/nozzle  80  defines a central passage  83  having a length of 0.54 inches, with an open end  82  diameter of approximately 0.36 inches and a restricted end  84  inner diameter of 0.04 inches. The outer surface  88  of the restricted end  84 , which defines a portion of the introduction annulus  89  has a diameter of 0.059 inches. The venturi deflector/nozzle  80  converges from the open end  82  to the restricted end  84  at an angle of approximately 20° from the longitudinal axis (conical angle of approximately 40°). In a 0.1 gallon per minute configuration, the restricted end  84  of the venturi deflector/nozzle defines an inner diameter of approximately 0.32 inches. 
     At least one of the seating surface  30  of the stop  28  and the shoulder  46  of the nozzle tip  40 , and the upstream seating surface  48  of the nozzle tip  40  and the downstream divergent end  64  of the throat  60  include a raised bead which may be made in the formation process. The raised bead increases the effective seating pressure between the relative components, thereby increasing the sealing and reducing fluid flow therebetween. 
     The ratio of the area of the venturi end  84  and the area of the nozzle tip foam spray outlet  44  defines a balance between the need to have a sufficient flow velocity exposed to the radial air inlet ports  33  and a sufficient back pressure to induce turbulent mixing in the throat  60 . The venturi end  84  and the foam spray outlet  44  act as a pair of resistors in series which are balanced to draw in sufficient air and generate foam from the air-liquid mixture. If the foam spray outlet  44  is sized too small, then the back pressure is too great and insufficient air is drawn through the ports  33  into the nozzle assembly  10 . Conversely, if the foam spray outlet  44  is too large, then the air-liquid mixture does not mix in the throat  60  and no foam in generated. 
     Similarly, a sufficient flow rate through the venturi nozzle/deflector  80  is required to generate a usable quantity of foam. Further, the present design must accommodate the relatively low flow rate of less than 0.5 gallons per minute and often between 0.1. and 0.2 gallons per minute. Such a small flow rate requires a small orifice sizing at the foam outlet  44 . However, small orifices create significant pressure drops across the orifice. The present design is selected to retain a sufficient pressure differential across the foam spray outlet  44  to permit ejection of a foam spray on the order of 5 to 10 feet from an initial liquid pressure of approximately 20 to 25 psi. The venturi nozzle/deflector  80  may also be formed of a wear resistant plastic polymer. 
     The present nozzle assembly  10  is selected to provide a liquid to generated foam volume of approximately 1:2. 
     Assembly 
     To assemble the foaming nozzle assembly  10 , a nozzle tip  40  is disposed within the housing  20  such that the nozzle shoulder  46  contacts the collar of the stop  28  and passage of the nozzle tip through the nozzle port  25  in the housing is precluded. The throat  60  is then slideably disposed within the housing  20  such that the downstream, divergent end  64  of the throat  60  contacts the upstream end  42  of the nozzle tip  40 . 
     The venturi deflector/nozzle  80  is then slideably disposed within the housing  20  to dispose the locator bosses  86  within the locator recesses  69  on the upstream end  62  of the throat  60 . 
     An O-ring seal  94  is then disposed in the wand end of the housing. The O-ring is sized to retain the nozzle tip  40 , the throat  60  and the venturi deflector/nozzle  80  within the housing  20 . Thus, the components are operably aligned within the housing  20  and unintended separation of the component from the housing is substantially precluded. 
     The wand  14  is then threadingly engaged with the housing  20  until the end of the wand contacts the O-ring  94 . Contact of the wand  14  and the O-ring  94  slightly compress the components thereby forming a sealed relation, as well as retaining them in their operable position. The present invention is directed to low pressure foaming devices and particularly those devices operating below approximately 35 psi. In particular, the present invention is directed to such low pressure systems operating at 25 psi or less. 
     Two Piece Foaming Assembly 
     Referring to FIGS. 10-12, the foaming nozzle assembly  10  can be formed of two pieces, a flow body  220  and a nozzle tip  240 . The flow body  220  is connected to the source  12  of the liquid to be foamed. Typically, an interface between the foaming nozzle assembly  10  and the source  12  is a rigid self supporting wand  14 . The wand  14  may include threads, snap fits or other mechanical connection configurations for operably connecting to the foaming nozzle assembly  10 . However, it is understood that any of a variety of interfaces to the source  12  may be employed. As shown in FIGS. 10-12, a threaded retainer  210  having a capture flange  212  is used to operably locate the foaming nozzle assembly with respect to the wand  14 . 
     The flow body  220  includes a venturi portion  280 , a throat portion  260  and at least one air inlet port  233 . The flow body  220  includes a retaining flange  213  sized to contact the retainer  210  and specifically the capture flange  212  to be located intermediate the threads of the wand and the capture flange  212  of the retainer. Preferably, the flow body is a one piece integral construction, formed by molding, such as injection molding. However, the flow body may be machined or tooled. 
     The venturi portion  280  defines a converging, funnel shaped central passage  283  extending along the longitudinal axis from an upstream open end  282  to a downstream restricted venturi end  284 . 
     The venturi deflector/nozzle  280  thus defines a primary flow control surface defined by the central passage  283  for directing liquid from the source  12  to the throat portion  260 . 
     The venturi deflector/nozzle  280  may be configured to provide a variety of flow rates. For example, in a 0.2 gallon per minute configuration, the venturi deflector/nozzle  280  defines a central passage  283  having a length of 0.54 inches, with an open end  282  diameter of approximately 0.36 inches and a restricted section  284  inner diameter of 0.04 inches. The venturi deflector/nozzle  280  converges from the open end  282  to the restricted section  284  at an angle of approximately 20° from the longitudinal axis (conical angle of approximately 40°). In a 0.1 gallon per minute configuration, the restricted section  284  of the venturi deflector/nozzle defines an inner diameter of approximately 0.32 inches. 
     The throat portion  260  defines a length of the central passage  283  and has a convergent upstream end  262  and a divergent downstream end  264 . 
     In a preferred embodiment, the throat portion  260  has a total passage length of approximately 0.9 inches, and a convergent end diameter of approximately 0.078 inches. The convergent end diameter extends along the longitudinal axis for a length of approximately 0.3 inches, then flares at an angle of approximately 6° (12° conical angle) to a divergent end diameter of 0.3 inches. It has been found the same configuration of the throat portion  260  may be employed for a 0.1 and a 0.2 gallon per minute flow rate through the nozzle assembly  10 . 
     As shown in FIGS. 17 and 18, the air inlet ports  233  intersect the central flow passage just downstream of the smallest diameter of the flow passage. A shoulder may be formed in the central passage  283  adjacent the intersection of the air inlet ports  233  to assist in foam generation. 
     Referring to FIGS. 12,  13 ,  14 ,  17  and  19 , an outer surface of the downstream end of the flow body  220  includes a structure for frictionally engaging and retaining the nozzle tip  240 . The structure may be flanges, tabs, fingers detents or ribs as shown. This structure is sufficient to retain the nozzle tip  240  relative to the flow body  220 . Although a secondary seal such as a gasket may be disposed intermediate the nozzle tip and the flow body, it has been found that a plurality of ribs  222  may be formed on the flow body  220 . The ribs  222  circumscribe the flow body and are sized to engage a corresponding portion of the nozzle tip. By employing a plurality of ribs  222 , the nozzle tip can be sealed relative to the flow body  220  for intended operating parameters. 
     As shown in FIGS. 20-25, the nozzle tip  240  for operably engaging the flow body  220  is shown. The nozzle tip  240  provides an exit passage of the foaming composition from the foaming nozzle assembly  10 . The nozzle tip  240  has a through passage  243  from an upstream inlet  242  to a downstream foam spray outlet  244 . The particular foam spray outlet  244  of the nozzle tip  240  is selected for producing the specific foam pattern and may be any of a variety of constructions. The foam spray outlet  244  defines an area through which the pressurized liquid area mixture exits the nozzle assembly  10 . 
     The nozzle tip  240  includes an inwardly projecting shoulder  246  sized to contact the ribs  222  on the flow body  220 . The shoulder  246  and the ribs  222  are selected to cooperatively and releasably engage the nozzle tip  240  and the flow body  220 . It is understood that a variety of configurations for the ribs and the shoulder may be employed such as recesses, channels or sockets. Preferably, contact between the shoulder  246  and the ribs  222  substantially precludes fluid flow therebetween under operating pressures. 
     Alternatively, and partially depending upon cost considerations, the flow body  220  and the nozzle tip  240  may include complimentary threads for threaded engagement. 
     The nozzle tip  240  may be formed of any of a variety of materials such as brass, wear resistant polymers or plastic. Alternatively, the nozzle tip may be one of a commercially available style. 
     Referring to FIGS. 26-36, an alternative configuration of the two piece foaming nozzle assembly is shown. In this configuration, the two pieces are mating pieces  310  separated along the flow path through the foaming nozzle assembly. Each mating half  310  includes a portion of the venturi, the throat and the nozzle tip. 
     Although the mating halves  310  may be formed as male and female, it is intended for ease of manufacturing that only a single half be formed such that two of the halves  310  may be cooperatively engaged to form the foaming nozzle assembly  10 . Specifically, as shown in FIGS. 26 and 30, the mating half  310  includes a projecting rib  312  and a channel recess  313  sized to receive the rib on mirror positions about the longitudinal axis of the assembly. 
     Thus, each mating half includes an air inlet port  333 , a venturi portion  380  a throat portion  360  and a nozzle portion  340 . Each mating half  310  also includes a portion of a retaining flange  323  for operably connecting the assembly to the wand  14 . The mating halves  310  may be operable joined by adhesives, thermal bonding or ultrasonic welding. 
     It is intended that the performance parameters of the mating halves  310  match the remaining embodiments of the foaming nozzle assembly  10 , and hence the dimensions are applicable to the mating halves configuration. 
     Operation 
     In operation, the relatively low pressure is applied to the liquid source  12 , thereby urging liquid from the source toward the nozzle tip  40  which is at ambient or atmospheric pressure. As the fluid flow is converged in the venturi deflector/nozzle  80 , the velocity increases as it passes through the restricted end  84  and into the convergent end  62  of the throat  60 . The increased velocity, pursuant to Bernoulli&#39;s equation, reduces the local pressure thereby drawing air in from the radial ports  33  through the housing  20 , between the venturi deflector/nozzle  80  and the upstream end  62  of the throat  60  through the introduction annulus  89  and into the convergent end of the throat. The fluid stream and the introduced air then mix as the flow becomes turbulent and passes toward the divergent end  64  of the throat  60 . The produced foam is then urged into the nozzle tip  40  where it is ejected through the orifice port  44  the pattern determined by the geometry and construction of the nozzle tip. 
     In the flow body  220 -nozzle tip  240  configuration, the retainer  210  is threaded onto the wand to dispose the retaining flange  213  intermediate the capture flange  212  and the wand or an O ring gasket. 
     The nozzle tip  240  may be selected and snapped or threaded onto the flow body  220 . As liquid passes through the flow body  220 , air is drawn into the flow via the air inlet ports  233  and the turbulent characteristic of the flow induces mixing and foam generation as the mixture exits through the attached nozzle tip. 
     In the mating halves configuration, the halves are joined prior to use so that an operator merely engages the mated halves with the wand and operates as in the remaining embodiments. 
     The present invention and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the true spirit and scope of the invention or sacrificing all of its material advantages, the form herein before described being merely preferred or exemplary embodiments thereof.