Internal mix air atomizing spray nozzle

Abstract: The nozzle effects three stages of liquid atomization. The first stage is carried out by means of a single liquid orifice (20) and an expansion chamber (25) containing an impingement pin (21). A high velocity stream of liquid is discharged through the liquid orifice and is broken up into finely atomized particles upon striking the flat end (22) of the impingement pin. The second stage is produced by an air guide (30) which reduces in area to form jets of air into a high velocity annular air curtain, the curtain passing though the liquid orifice (33) in surrounding relation with the liquid stream and striking the atomized particles of the first stage to further atomize the particles. The mixture is then allowed to expand in the expansion chamber (23) to reduce the tendency of the liquid particles in the atomized mixture from commingling and reforming into larger particles. The third stage is effected by the expansion chamber and by multiple discharge orifices. The mixture is sprayed from the expansion chamber (23) through the multiple orifices (18) and, upon being discharged into the atmosphere, the particles are atomized further due to the release of pressure formed inside the expansion chamber.

Description: This invention relates generally to a nozzle for atomizing and spraying liquid and, more particularly, to a nozzle of the type in which the liquid is atomized by pressurized air which is mixed with the liquid internally of the nozzle. Internal mix air atomizing nozzles are known. Many of such nozzles, however, are not capable of effecting extremely fine atomization of the liquid when the liquid is supplied to the nozzle at a high flow rate. The term "nozzle" is used herein in the sense of the overall atomizing dispenser device or assembly. We are aware of EP-A-0225193 which forms the pre-characterising portion of claim 1. In EP-A-0225193 the outlet opening of the air supply means which increases the air velocity is located downstream of the expansion chamber, and a tapered side of the expansion chamber contracts the air supply. According to our invention in a nozzle for atomizing and spraying liquid, said nozzle comprising a body having a liquid passage which terminates in a single discharge orifice, an impingement pin having a generally flat end disposed in spaced opposing relation with said discharge orifice whereby a jet of pressurized liquid discharged through said orifice strikes the end of said pin and breaks up into a dispersed flow of the liquid, air supply outlet means for discharging air around said discharging orifice in an annular curtain around said liquid jet and for increasing the velocity thereof whereby said curtain of air will strike and further atomize the dispersed flow of the liquid into atomized particles, characterized by said air supply means having a discharge opening through which said curtain pass before said liquid jet strikes said pin, an expansion chamber communicating with said discharge opening, said chamber extending around said end of said pin and having a cross-sectional area substantially greater than the cross-sectional area of said discharge opening and said pin whereby the liquid discharged through said discharge opening expands in said chamber to restrict said atomized particles from commingling together and reforming into larger particles, and angularly spaced orifices leading from said chamber to ambient atmosphere to discharge said particles from said chamber and effect further atomization thereof, said air supply discharge opening being disposed downstream of said liquid passage discharge orifice, and said expansion chamber being disposed downstream of said air supply means discharge opening. With this arrangement because of the relative locations of the discharge openings, the discharge orifice, and the expansion chamber, we are able to provide an internal mix atomizing nozzle which effects atomization of the liquid in multiple stages so as to enable the nozzle to discharge a finely atomized spray at high flow rates. Specifically we provide a nozzle of the above character which mechanically atomizes the liquid, effects further atomization by means of a high velocity air stream, and then produces even finer atomization as an incident to spraying the liquid into the atmosphere. The invention also resides in a unique nozzle construction which reduces the tendency of atomized liquid particles to commingle and reform into larger particles prior to discharge of the particles into the atmosphere. These and other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. Brief Description of the Drawings FIGURE 1 is a cross-sectional view taken axially through a new and improved atomizing nozzle incorporating the unique features of the present invention. FIG. 2 is an enlarged cross-section taken substantially along the line 2-2 of FIG. 1. FIG. 3 is an end view of the nozzle as seen along the line 3-3 of FIG. 1. FIG. 4 is a cross-sectional view similar to FIG. 1 of another embodiment incorporating unique features of the present invention. FIG. 5 is a cross-section taken substantially along the line 5-5 of FIG. 4. FIG. 6 is an end view of the nozzle of FIG. 4 as seen along the line 6-6 of FIG. 4. While the invention is susceptible of various modifications and alternative constructions, a certain illustrated embodiment hereof has been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the scope of the invention, which is defined by the claims. Detailed Description of the Preferred Embodiment As shown in the drawings for purposes of illustration, the invention is embodied in a nozzle 10 for atomizing a stream of pressurized liquid and for discharging the liquid to atmosphere in the form of a finely divided spray. The nozzle includes a body 11 with an upwardly extending and externally threaded neck 12 which is adapted to be attached to a line 13 for delivering pressurized liquid to the nozzle. A second line 14 of larger diameter is coaxial with the line 13 and is suitably attached to the upper end of the body 11 below the neck 12. Pressurized air is supplied to the nozzle via the line 14. A nozzle tip 15 is positioned below the body 11 and is removably attached thereto by a coupling nut 16. The lower end 17 of the tip is generally frustoconical and is formed with a plurality (herein, eight) of discharge orifices 18 through which the liquid is sprayed. In this particular instance, the discharge orifices are perpendicular to the frustoconical end 17 of the tip but are angled outwardly relative to the axis of the nozzle 10 by virtue of the inclination of the end. Liquid introduced into the nozzle 10 is atomized into fine particles prior to being sprayed out of the discharge orifices 18. In accordance with the present invention, the nozzle atomizes the liquid in multiple stages so as to enable extremely fine atomization even when the flow rate through the nozzle is relatively high. More specifically, the body 11 of the nozzle 10 is formed with a central and axially extending liquid passage 19 which communicates with the line 13 and which terminates as an axially facing discharge orifice 20. Formed integrally with and projecting upwardly from the lower end 17 of the tip 15 is an impingement pin 21 having a substantially flat upper end 22 disposed in axially spaced and opposing relation with the orifice 20. The pin is located in a chamber 23 of circular cross-section defined within the tip 15. Upon being discharged from the orifice 20 and into the chamber 23, a high velocity stream of liquid strikes the upper end 22 of the pin 21 and is broken up into a thin sheet of small particles. Accordingly, the first stage of atomization is effected mechanically by virtue of the liquid striking the pin. Several (e.g., twelve) angularly spaced air passages 25 are formed through the body and preferably are inclined so as to converge upon progressing downwardly. At their upper ends, the passages communicate with the air line 14 through an annular manifold recess 38 and thus pressurized air is injected into the passages. The lower ends of the passages define air outlets 26 located upstream of and disposed in encircling relation with the single liquid orifice 20. That portion of the body 11 located downstream of the air outlets 26 defines a nose 28 having a generally frustoconical outer surface 29 which is inclined at approximately the same angle as the passages 25. The liquid discharge orifice 20 opens out of the lower end of the nose 28. In carrying out the invention, an air guide 30 is located within the tip 15 below the body 11 and contracts the jets of air from the outlets 26 into a tubular curtain which surrounds the liquid stream as the latter impinges against the pin 21. Herein, the air guide 30 is formed by an insert located within the upper end portion of the tip 15 and seated against an upwardly facing shoulder 31 formed around the wall of the chamber 23. The lower end portion of the insert 30 is formed with a cylindrical discharge opening 33 which is located between and is aligned with the orifice 20 and the pin 21. The cross-sectional area of the discharge opening 33 is substantially less than the cross-sectional area of the chamber 23. Formed in the insert 30 immediately above the discharge opening 33 is a chamber or bore 35 having a generals frustoconical wall 36. The upper end portion of the bore 35 is located immediately adjacent the air outlets 26 and its wall 36 tapers upon progressing downwardly. The air outlets 26 open generally axially into the annular space between the frustoconical surface 29 and the frustoconical wall 36. In this instance, the cone angle of the bore 35 is somewhat greater than the cone angle of the nose 28 and thus the annular space tapers upon progressing downwardly. With the foregoing arrangement, jets of air shooting from the outlets 26 are formed into an annular curtain by the wall 36 of the bore 35. The air curtain surrounds the stream of liquid discharged from the orifice 20 and, upon entering the discharge opening 33, undergoes a substantial increase in velocity. When the high velocity air emerges from the opening 33, it strikes the liquid particles previously atomized by the pin 21 and thus further atomizes those particles. Accordingly, the particles are subjected to a second stage of atomization which is effected pneumatically by the high velocity air. The open volume of the chamber 23 is substantial and thus the air/liquid mixture is permitted to expand in the chamber. As a result, there is little tendency for the atomized liquid particles to commingle and reform into larger particles prior to being sprayed through the orifice 18. A third stage of atomization occurs as the air/liquid mixture is sprayed from the chamber 23 through the orifices 18. As the mixture is discharged to atmosphere, the liquid particles are atomized even more finely as a result of being released from the pressure in the chamber. From the foregoing, it will be apparent that the present invention brings to the art a new and improved spray nozzle 10 in which the liquid is subjected to three stages of atomization as an incident to passing through the nozzle. Because the liquid is so thoroughly atomized, the nozzle is capable of producing a finely atomized spray even when the flow rate through the nozzle is large. The nozzle 110 illustrated in Figs. 4-6 is of substantially the same construction and mode of operation as the nozzle 10. Corresponding parts are identified by the same numbers in the 100 series without further discussion, except as may be appropriate to point out correlations and differences. In the main, the nozzle 110 provides an alternative design for conveying the pressurized liquid and air inputs from their supply connections to the air guide 130. In lieu of the one-piece multi-functional body 11 of nozzle 10, the nozzle 110 includes a manifold fluid supply tip body 111 which is of generally hollow cylindrical configuration. Body 111 includes an annular wall 140 which abuts the end of the nozzle tip 115 and has threaded connection with a coupling nut 116 at one end. The opposite end of the fluid supply tip body 111 includes an end wall 142 from which the threaded neck 112 extends. Wall 142 is formed with an annular manifold recess 138 and a plurality of short, straight passages 139 which extend from the manifold recess 138 to the open interior space 144 for passage of the compressed atomizing air from a supply line 114 into the space 144. The threaded neck 112 extends outward from the wall 142 for threaded connection with the supply line 113 which supplies pressurized liquid. In the embodiment of Fig. 4, both the liquid supply line 113 and the coaxial surrounding air supply line 114 are connected to a common coupler manifold member which threadably engages the neck 112. The member includes a central liquid passage and a ring of air passages which lead to an annular air manifold recess. A sealing gasket is disposed between the member and the body 111. The neck 112 also receives and supports a hollow cylindrical orifice insert 145. The orifice insert 145 includes the tapered nose 128 and a single discharge orifice 120 disposed within the air guide 130. An annular supply air guide 146 surrounds the insert 145. The guide 146 seats against a shallow shoulder 147 in the body 111 and is held in place by the end flange of the nozzle tip 115 and the coupling nut 116. The guide 146 is formed with an interior frustoconical surface 148 which leads from the up/stream end of this guide member 146 to a short cylindrical interior wall 150 which is generally parallel to and spaced from the outer wall of the orifice insert 145. The space 144 between the wall 142 and the air guide 146 serves as a manifold for the air supply between the inlets 138, 139 and the air supply passage defined between the outer surface of the liquid orifice insert 145 and the inner surface of the supply air guide 146. The impingement pin or pintel 121 is a separate pin element which is secured in position in the nozzle tip 115. The nozzle 110 atomizes liquid in substantially the same manner as the nozzle 10. That is, in each of them the liquid jet strikes the impingement surface 22, 122 and thereby is dispersed laterally as a film and/or small particles of water which fan out laterally beyond the impingement surface, moving outward generally normal to the extended axis of the nozzle and hence of the jet. The high pressure air travels at high velocity through the nozzle 10, 110. Its velocity is enhanced by the converging and constricting configurations of the air flow passages through the nozzle. The resulting high velocity air flows essentially parallel to the fluid jet, in an annulus or cylinder about that jet, through the cylindrical discharge opening 33, 133 and to the impingement surface 22, 122 where the air strikes the dispersed liquid on and around the impingement surface 22,122. In this regard, the discharge opening 33, 133 is somewhat larger in diameter than the circular impingement surface 22, 122. The high velocity air strikes the dispersing liquid around the impingement surface and atomizes the liquid being dispersed from its initial atomizing break-up against the impingement surface 22, 122. The substantial volume of the expansion chamber around and downstream of the impingement surface minimizes the commingling together and attendant reformation of the thus atomized liquid particles into larger particles prior to being sprayed through the discharge orifices 18, 118. This latter spraying further atomizes the liquid.

Claims: A nozzle (10) for atomizing and spraying liquid, said nozzle comprising a body (11) having a liquid passage (19) which terminates in a single discharge orifice (20), an impingement pin (21) having a generally flat end (22) disposed in spaced opposing relation with said discharge orifice (20) whereby a jet of pressurized liquid discharged through said orifice (20) strikes the end (22) of said pin (21) and breaks up into a dispersed flow of the liquid, air supply outlet means (14, 25, 30) for discharging air around said discharging orifice (20) in an annular curtain around said liquid jet and for increasing the velocity thereof whereby said curtain of air will strike and further atomize the dispersed flow of the liquid into atomized particles, characterized by said air supply means (14, 25, 30) having a discharge opening (33) through which said curtain pass before said liquid jet strikes said pin (21), an expansion chamber (23) communicating with said discharge opening (33), said chamber (23) extending around said end (22) of said pin (21) and having a cross-sectional area substantially greater than the cross-sectional area of said discharge opening (33) and said pin (21) whereby the liquid discharged through said discharge opening (33) expands in said chamber (23) to restrict said atomized particles from commingling together and reforming into larger particles, and angularly spaced orifices (18) leading from said chamber (23) to ambient atmosphere to discharge said particles from said chamber (23) and effect further atomization thereof, said discharge opening (33) being disposed downstream of said liquid passage discharge orifice (20), and said expansion chamber (23) being disposed downstream of said discharge opening (33). The nozzle as in claim 1 wherein said body (11) defines air passages (25) having outlets (26) spaced angularly around said liquid discharge orifice (20) for providing said annular curtain of air. The nozzle as in claim 2 in which said air passages (25) are inclined so as to converge toward said single discharge orifice (20). The nozzle as in claim 1 in which air passage outlets (26) are located upstream of said single discharge orifice (20). The nozzle as in claim 4 in which said body (11) includes an end portion (28) from which said single discharge orifice (20) opens axially, said end portion (28) having a generally frustoconical outer surface (29) which tapers inwardly upon progressing toward said single discharge orifice (20), said discharge opening (33) being defined by an air guide (30) having a chamber (35) with a generally frustoconical wall which tapers inwardly upon progressing axially toward said discharge opening (33). The nozzle as in claim 5 in which a portion of said frustoconical wall upstream of said discharge opening (33) encircles a portion of said frustoconical outer surface(29) in radially spaced relation thereto, said air passage outlets (26) opening generally axially into the space between said frustoconical wall and said frustoconical surface (29). The nozzle as in claim 6 in which the cone angle of said frustoconical wall is greater than the cone angle of said frustoconical surface (29).

Inventors: HUFFMAN DAVID C, HUFFMAN, DAVID C.
Applicants: SPRAYING SYSTEMS CO, SPRAYING SYSTEMS CO.
Application year: 1995
Main classification: B05B7
IPC codes: B05B7, B05B1