Patent Publication Number: US-9844790-B2

Title: Spray nozzle assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/317,802, filed Oct. 28, 2011, which will issue as U.S. Pat. No. 9,027,861 on May 12, 2015, which application is a continuation-in-part of U.S. patent application Ser. No. 12/989,130, filed Oct. 22, 2010, which is a national phase entry under 35 U.S.C. §371 of International Patent Application PCT/AU09/00502 filed Apr. 22, 2009, published in English as International Publication WO 2009/129571 A1 on Oct. 29, 2009, which claims the benefit under Article 8 to Australian Patent Application Serial No. 2008902000 filed Apr. 22, 2008, the entire contents of each of which are incorporated herein by reference. 
    
    
     FIELD 
     This invention relates in general to spray nozzle assemblies and, in particular, to the type of spray nozzle having a check valve that is specifically adapted to be used with spray drying nozzles, but could also be used in association with other nozzles. 
     BACKGROUND 
     The following references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the following prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the present invention of which the identification of pertinent prior art proposals is but one part. 
     For ease of description, we shall refer to such a spray nozzle assembly in terms of one associated with spray drying of milk. 
     In general, spray nozzles that are provided with swirl chambers and orifice discs have these components manufactured from tungsten carbide or the like, which is very hard, but also brittle and prone to damage when dropped or otherwise roughly treated during assembly and disassembly. 
     When ordinary spray nozzles are used for spray drying milk, a certain percentage of the liquid simply falls as drops from the nozzles, without being atomized, and this material can well lead to spoiling of the product. 
     To avoid this problem, a unitary check valve was developed for spray drying nozzles, and other nozzles, which caused little restriction in the flow through the nozzle and which, at the same time, did not have any parts, or break-off parts thereof, likely to be passed into the fluid stream. 
     Conventional check valves, however, have sealing problems when operated at high pressures and are not necessarily as compact as would be desirable. 
     Prior art nozzles generally have stepped annular shoulders that ensure coaxial alignment and concentricity of respective, axially aligned wear parts. However, because the flow material (like proteinous milk products) can set or dry to a viscous or glue-like consistency, it is necessary to build in clearance gaps including radial gaps (lateral gaps to the side of the wear parts) or axial gaps (longitudinal gaps between the wear parts and the nozzle components axially containing them). These gaps between the wear parts and the nozzle cylinder need to provide sufficient play or movability of the respective parts relative to each other to facilitate removal for replacement, cleaning and repair. Also, normal manufacturing tolerances dictate a gap requirement to prevent component jams axially and radially. Therefore, the prior art designs inherently lack accurate concentricity, which has adverse affects on spray nozzle performance, predictability of spay patterns and/or spray line production. Stepped annular shoulders in the internal wall of the nozzle cap mean prior art caps are structurally weak and introduce stress concentrations at the sharp angled corners within these steps. 
     DISCLOSURE 
     It is an object of the invention to ameliorate the above problems associated with spray nozzles and particularly those used in association with check valves, and to provide general improvements in the assembly and construction of spray nozzle components. 
     The invention in one aspect provides one or more housings within a spray nozzle assembly for protecting one or more wear components, such as the swirl chamber and orifice disc, from damage. 
     It is preferred that the housing is manufactured from a durable material such as stainless steel. However, any appropriate material is included within the scope of the invention. 
     In another aspect of the invention, there is provided a spray nozzle assembly including at least one wear part made from a hard and abrasion-resistant material and a protective housing made from a strong and resilient material and having a downstream chamber adapted to receive one or more of the wear parts in releasably trapped relationship, the downstream chamber having a wall including an arm or post adjacent at least one slot in the downstream chamber wall, the post including an protuberance extending inwardly towards the center of the housing, the protuberance at or near the end of the arm or post and adapted to prevent the wear part from escaping from the downstream chamber. 
     Hereinafter, reference to the post will include reference to the arm or post. 
     The housing and the downstream chamber are preferably generally cylindrical, but may include a number of symmetrical or irregular cross-sectional shapes, particularly to prevent axial rotation of the wear parts. The downstream chamber is preferably open-ended. 
     The housing may be a generally hollow cylinder. The housing may have shoulders for seating the wear parts. 
     Preferably, the present housing provides tapered seats for wear parts and the wear parts have complementary annular tapered or beveled edges. The tapering of the edges and corners enables the wear parts to cooperate with the housing seats to achieve self-alignment and concentricity as the parts are axially compressed into axial alignment on assembly. The wear parts naturally coaxially align with the housing and, as they are axially compressed in the housing, they align in fixed concentric and coaxial alignment. This arrangement provides for accurate alignment of orifices, apertures and openings for maximum efficiency and predictability of flow and spray characteristics. Concentricity is achieved by providing tapered surfaces, such as angular, radiused, curved, chamfered or beveled surfaces, over short axial or longitudinal distances, whereas prior art arrangements provided large longitudinal sections to locate parts axially. Concentricity is achieved via angular-type interfaces over a short distance, rather than the longer longitudinally radial location of the prior art steps, thus reducing adhesion surfaces at points or concentricity, which determine concentricity of the wear parts. One could provide shorter longitudinally aligned radial walls, but still need gaps to prevent adhesion. Full concentricity may be achieved only once the housing is compressed by an axial load in the cap to achieve full alignment. The tapered surfaces may be identical in angle or the tapered surfaces may be different, for example, concentricity may be provided thus:
         Radius to radius   Radius into taper engagement about a radius   Parallel taper-to-taper engagement   Varying taper angular point engagement       

     This provides a multiple step alignment: the clasp first aligns, followed by axial compression via an O-ring concentrically arranged in the top surface of an orifice disk, which forces the lower tapered surfaces into alignment. Concentricity is, therefore, achieved via an angular type interface over a short distance, rather than the longer longitudinally aligned radial location of the steps, thus reducing adhesion surface at points that determine concentricity of the wear parts. 
     Another aspect of the invention is that the nozzle component parts are screw fitted for axial engagement. This provides a particular functional advantage over other wear part installations that are not screw fitted, because in prior versions, a certain amount of longitudinal radial gap is required to enable removal and replacement of wear parts to be facilitated. In the present arrangement, the wear parts enclosed in the housing are compressed into a tightly fitting axial alignment. Prior art arrangements require an arbor press, such as a manually levered mandrel press, to disengage thickly bound parts glued together by sticky, viscous or dried materials. The axial screw engagement of the housing to the nozzle component, such as the nozzle cap, assists concentricity of the component parts, achieves a tight-fitting arrangement for better flow and predictability of spray properties, and provides an in-built arbor press or means to apply high torque to the component parts to break the adhesion caused by the dried material and enable replacement of the parts. The internal wall of the nozzle cap includes an annular guide to keep the housing wall and the post radially inwardly supported against flexing until the housing is partially removed from the nozzle cap. The internal wall of the nozzle cap includes an annular stress-relieving radiused recess. The bottom edge of the recess forms a radially inward clasp or grip retention diameter or annular guide to stop the post, arms or claws  145  from releasing grip of the wear parts until the “glue” is broken and the housing has been at least partially removed from the nozzle cap. 
     Moreover, the protective housing extends the life of the wear parts considerably. Excessive eccentricity affects a spray nozzle&#39;s performance. The geometry is off center, making a nozzle less efficient and requiring greater pressure of the flow material to deliver adequate flow of the product through the nozzle vortex, including the swirl chamber and the cavities defined by the nozzle. 
     Because concentricity of the component parts is achieved, the nozzle barrel components, such as the nozzle cap, may be engineered differently to avoid the sharp angles required in the prior art to achieve concentricity and the nozzle cap structures are not required to achieve alignment of the housing or wear parts. The nozzle head internal structures close to the orifice may be radiused in profile to minimize the concentration of stress areas or points associated with sharp edges by distributing the stress load over a wider surface area of the radiused or curved annular concave structure. 
     The wear part may include an orifice disc and/or a swirl chamber. The wear parts may be seated, trapped, fixed or otherwise located in the downstream chamber. The swirl chamber may be adjacent the orifice disc, which is preferably aligned axially therewith. The orifice disc may be sized to be trapped immediately under the retaining edge or protuberance. 
     The post is preferably resiliently deflectable to permit the wear part to enter or be removed from the downstream chamber upon application of sufficient force, but be retained against axial displacement at rest. The base of the post may be located intermediate the height of the chamber wall or may extend down to the base. 
     A longitudinally aligned key may extend along part or all of the length of the chamber wall. The key preferably cooperates with a complementary feature on the side wall of the wear part to prevent the wear part, particularly the swirl chamber, from rotating axially in the downstream chamber. The key advantageously provides structural reinforcement of the post and may extend beyond the post along the inside chamber wall down to or toward the base. 
     The complementary feature may be a longitudinally aligned groove. The key may be one or more protrusions protruding from the inner surface of the post toward the axial center of the downstream chamber and aligned longitudinally and parallel to the chamber axis. The key is preferably a ridge. The ridge may extend the full length of the post and down to a base of the downstream chamber. 
     The downstream chamber base may be an annular ledge or circumferentially spaced radially inwardly extending protrusions or any other seat device that prevents axial displacement of the wear part away from the retaining edge or protuberance to below the seat device within the housing. The top surface of the outer surface of the top of the post  137  and the inner chamber wall may be a radius-to-radius engagement or abutment relationship. 
     The chamber wall may include a side opening. The side opening may define one side of the post. However, to protect the post, the post may be defined by a slot either side of the post. The chamber wall may extend further to the opening from a slot adjacent the arm or post. The side opening may register with a mouth of a cavity of the swirl chamber. The side opening may provide flow communication between an intermediate chamber  114  of the housing  110  and the swirl chamber  150  via the cavity of the nozzle encompassing the housing. 
     The housing may include a wall having at least one opening, such as a slot, providing access to the intermediate chamber below the downstream chamber. The slot may be accessed by a cam tool. The cam tool may have a disc cam intermediate a shaft to enable the disc cam to be rotated and to bear against the one or more wear parts. The cam may overcome a retaining force of the protuberance by urging the wear part to bear against the retaining edge, thereby deflecting the post to allow the at least one wear part to be removed. The slot preferably provides flow communication between a lower chamber and the intermediate chamber. 
     It is further preferred that the orifice disc and the swirl chamber be retained in one or more housings by means of a peened or machined retaining edge about its periphery, thus making these parts and respective housing a unitary assembly. The retaining edge preferably extends radially inwardly. 
     The invention in a second aspect provides a clasp device used to locate and secure the swirl chamber and orifice disc components within the spray nozzle retainer cap. 
     The arrangement is such that the wear parts and housings clip in to the clasp device in which they are retained by means of the arm members. The precise means whereby this is effected is not restricted in the invention. A preferred means, however, is the engagement of the terminal ends of the arms with corresponding lugs on the engaging flats of the wear parts. 
     The invention in a third aspect is the provision within a spray nozzle assembly of a first O-ring that seats within a lance adapter and is held compressively by the retainer cap when assembled and a second O-ring within the retainer cap that compressively seals under the load applied by a clasp used to locate the swirl chamber and orifice disc components. 
     The arrangement is such that each O-ring is compressed independently of the other. 
     Previously, such sealing had been effected by means of flat washers or axial gland seals, both of these being less effective at high pressures. This could be partially addressed with support backup rings, however, these are difficult to install on a regular basis and expensive to replace and have limitations at elevated pressures. The use of the O-rings as described here addresses these problems and are highly effective in such a static arrangement at much higher pressure levels than previously possible. 
     In a further aspect of the invention, wear parts in a spray nozzle are provided with durable housings into which they are located. 
     It is preferred that these housings be applied to parts such as swirl chambers and orifice discs. 
     In a further embodiment of the invention, a swirl chamber or orifice plate can be provided that is smaller in diameter than that which would be conventionally used such that, when a housing is applied about their peripheries, the resulting diameter of each is then that of such conventional devices. 
     It is, therefore, preferred that these be able to be retrofitted to existing spray nozzle assemblies. 
     In an embodiment of the invention in which a check valve is included, the perforated sleeve covering the valve is provided with locating pins positioned at the end of the sleeve furthest from the nozzle in order to minimize the length of the spray nozzle assembly. 
     The invention in a fourth aspect provides a threaded end on the retainer cap that engages with an internal thread in the lance adapter, such that no exterior threads are provided on the assembled spray nozzle assembly and as such, damage to external threads cannot occur. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Possible and preferred features of the present invention will now be described with particular reference to the accompanying drawings. However, it is to be understood that the features illustrated in and described with reference to the drawings are not to be construed as limiting on the scope of the invention. In the drawings: 
         FIG. 1  shows an exploded diagram of the components of a first aspect of the invention; 
         FIG. 2  shows an assembled cross-sectional view of the nozzle assembly shown in  FIG. 1 ; 
         FIG. 3  is a perspective view of a component of the clasp device shown in  FIG. 1  with an arm member shown from additional partial side and top plan perspectives; 
         FIG. 4 a    is an exploded perspective view of part of the assembly shown in  FIG. 1  with the orifice disc shown from top plan and side perspectives; 
         FIG. 4 b    is a top plan view of an orifice disc shown in  FIG. 4 a    in its housing; 
         FIG. 5 a    is a side view of a cylindrical housing according to a second embodiment of the invention; 
         FIG. 5 b    is another side view of the cylindrical housing shown in  FIG. 5 a    rotated about 90 degrees; 
         FIG. 6 a    is a top plan view of a swirl chamber according to the second embodiment; 
         FIG. 6 b    is a side view of the swirl chamber shown in  FIG. 6   a;    
         FIG. 6 c    is a top plan view of an orifice disc according to the second embodiment; 
         FIG. 7  is an exploded view of a spray nozzle assembly according to the second embodiment; 
         FIG. 8 a    is a front elevation of a cam tool according to the second embodiment; 
         FIG. 8 b    is a side elevation of the cam tool shown in  FIG. 8   a;    
         FIGS. 9 a  and 9 b    are cross-sectional views of a spray nozzle made according to a third embodiment similar to the second embodiment; 
         FIG. 10  is an exploded perspective view of the spray nozzle made according to the third embodiment; and 
         FIG. 11  is a cross-sectional view of a spray nozzle assembly according to a fourth embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In a first embodiment, a spray nozzle  10  is shown in  FIGS. 1 through 4 , including a lance adapter  20  and retainer cap  30  components, with a spring valve  101 , a clasp device  40  and swirl chamber  50 . 
     The clasp device  40  has a first end, corresponding to a clasp base  41 , seats compressively against an O-ring  60  located against an annular shoulder  25  in sealing arrangement within the generally cylindrical lance adapter  20 . 
     The clasp device  40  comprises a generally cylindrical body  45 , extending rearward to the concentric base  41  that is generally concentric therewith and narrower in diameter, having an annular step down to the base  41 . An opposing end of the cylinder  45  has a seat  43  for a swirl chamber  50  and orifice disc  70  assembly. The seat  43  comprises a pair of opposed raised co-planar partial discs  46  that define therebetween a broad aperture  42  with parallel straight sides and radiused ends following the contours of the radiused forward end walls of the cylinder body  45 . The clasp  40  further includes arm members  44 , which each comprise an elongate arm  47 , that have a radiused or arced outer surface in cross-section following the contour of the cylinder body  45  and an internal planar surface that cooperates with a corresponding pair of opposed flats  51  extending the full length of the housing  55  outer body. The arms  47  of the arm members  44  each terminate in a shallow radially inwardly extending hook  48  that is adapted to clamp or pass over the upper edge  52  of the opposed flats  51  of the housing  55 , thereby preventing rotation of the housing  55  and importantly, therefore, the swirl chamber  50 , within the cylindrical body  45 . Limitation of rotation of the wear parts  50 ,  70  minimizes wear and enables the design of a predictable flow path and consistency of flow. Prior art swirl chambers have traditionally been cylindrical and permitted rotation within the cap. 
     The swirl chamber  50  characteristically has an entrance  53  defining a converging pathway into the cavity  56  of the swirl chamber  50 . A flat wall  54  of the housing  55  immediately below the entrance  53  allows a sufficient gap between it and the upper wall of the cylindrical body  45  to allow good flow communication between the central bore  33  of the cylindrical body  45  and cavity  56  via a gap  32  defined by the cylindrical body  45  and the lower edge of the flat wall  54 . The housings  55 ,  75  are loosely fitted within the clasp arms  44  to permit some slack, allow high tolerances and primarily to facilitate the removal of the wear parts after use has gummed them up with the cementitious or gluey flow material. 
     The orifice disc  70  compressively abuts an O-ring  80  against and with the retainer cap  30 . This provides an excellent seal between the orifice disc  70  and the retainer cap  30  because the O-ring  80  is captured in an upwardly facing circular groove  71  concentrically set in the upper face of the orifice disc  70 . The compression of the O-ring  80 , rather than using a traditional annular seal, significantly improves seal performance, longevity and wear resistance, and improves the tightness of the fit of the relative components. In this high-wear application, the compressive seal arrangement is advantageous. 
     In  FIGS. 3 a  and 3 b   , the profiles of the clasp arms  44  are shown. In  FIG. 3 a   , the clasp arms are shown to have a flat internal wall  44   b , which cooperates with the pair of flat walls  51  of the housing  55  to prevent rotation of the housing  55  about the longitudinal axis of the clasp device  40 . 
     During use of such a spray nozzle  10 , it is common for the material being sprayed to adhere to the contacting components. Wear parts that are exposed to the high abrasion and pressure of the flowable material are ideally made from costly, extremely hard and abrasion-resistant materials, preferably Tungsten-carbide or the more rudimentary iron-carbon steels. However, because of their hardness, such materials are generally brittle, lacking in strength. Therefore, advantageously, the wear parts  50 ,  70  of the present invention are separately formed using extremely hard materials, and then encased or pressed into tightly fitting cases, shrouds or housings  55 ,  75  made of stronger and more workable materials, such as 300 series stainless steel. Moreover, with the device  10  of the invention, the provision of the clasp  40  permits wear parts  50 ,  70  to be simply removed. The clasp device  40  has a threaded outer surface  41   a  on its base  41  above a pair of opposed flats  49 , which facilitate its removal by rotation using a suitable spanner, the threads  41   a  of the clasp base  41 . Upon rotation of the clasp  40  relative to the retainer cap  30 , damage to the wear parts is avoided that is caused by the conventional pressing out of the wear parts by an arbor press or other such means. 
     The swirl chamber  50  is located within the housing  55  made of stainless steel to provide a strong swirl chamber assembly with a strong outer casing but hard internal wear surfaces. Similarly, the orifice disc  70  is surrounded by the stainless steel housing  75 , which protects it from any damage that might otherwise result from dropping or handling during assembly and disassembly. 
     The swirl chamber and the orifice disc are retained in their housings as unitary devices by the peening or machining of a peripheral edge of each housing over these devices. Of course, other means of providing an annular inwardly radially extending flange or lip known to the skilled person can achieve satisfactory trapping or encasing of the hard wear item  50 ,  70  in the respective housing casing  55 ,  75 . 
     These wear items  50 ,  70  are manufactured typically from tungsten carbide, which is relatively expensive and brittle. However, they permit the production of a narrower, more accurate orifice  72  and greater precision in machining and other working of the material. By providing smaller diameter orifice discs  70  and swirl chambers  55 , expense is spared because less material is used in their manufacture, as well as the devices  50 ,  70  being protected from damage by their stainless steel housings  55 ,  75 . Pressing the wear items  50 ,  70  into their housings  55 ,  75  by peening or machining has proved efficacious and has overcome problems of relative movement of these components  50 ,  70 ,  55 ,  75 , which is problematic in this high-pressure, high-wear application where components out of alignment adversely affect performance and the duration between forced replacement of consumable products  50 ,  70 ,  55 ,  75 . This may be distinguished with the relative looseness of the fit of the consumables  50 ,  70 ,  55 ,  75  in the clasp device  40 , which permits some axial movement to facilitate removal and replacement. 
     It is also envisaged that these wear items  50 ,  70  be provided in situ in their housings  55 ,  75  at the same size as such conventional items that also permit them to be retrofitted to existing spray nozzle assemblies and used as wear part consumables therein. 
     With reference to  FIGS. 4 a  through 4 c   , there is shown the orifice disc  70  and housing  75  in greater detail. The orifice disc  70  is a circular thin disc shape that is 1 mm to 2 mm in height and about 14 mm to 20 mm in diameter, but noting that these dimensions are merely suggestive and the invention is not limited to orifices having particular dimensions. On the sides of the housing  75  corresponding to the position where the clasp hook  48  overhangs the housing  75 , the housing  75  has opposed flat sides with a recessed section  74  having a narrow and shallow ledge inclining upwardly toward the orifice  72 . The recess  74  provides a resting position in which the hook  48  is adapted to nest and includes a pair of spaced knobs or small ramps  77 , one at each end of the recess  74 , that laterally retain the hook, overhang or catch  48  and provides a ramp over which the ends of the hook  48  may ride on insertion or removal, noting that there is some play purposely incorporated in the fit of the component parts  40 ,  44 ,  55 ,  75 . 
     The orifice  72  is centrally located in the orifice disc  70 . Concentrically placed around the periphery of the disc  70  on its upper surface is a circular groove  71  adapted to receive an O-ring  80  as previously described. The groove is sufficiently deep to retain the O-ring  80 , but sufficiently shallow to allow the O-ring  80  to sit partially proud of the upper disc  70  surface. The orifice  72  is finely machined or otherwise formed to low tolerance, which is made possible by the use of hard and workable alloys. The orifice  72  has a flare mouth or inlet  72   a  located centrally on the orifice&#39;s  70  underside surface to facilitate pressurized flow into and through the orifice  72 . Different applications will require different sized apertures for the orifice  72 . 
     The orifice disc upper surface  78  includes an annular peripheral beveled or cammed edge  79  over which the upper inner walls of the housing  75  are peened or worked to provide a smooth transitional surface from the housing upper peripheral surface to that of the orifice disc  70  and ensure a good mating relationship. The lower side walls are similarly beveled or radiused to facilitate peening or working of an inward extending radial flange of the housings  55 ,  75  to extend over the upper and lower peripheries of the orifice disc  70 . 
     Although the materials described are preferred, they are not restricted in the invention. 
     In a second aspect of the invention shown in  FIG. 2 , a check valve is provided within the spray nozzle assembly. In this embodiment, the first end  41  of the clasp passes generally over the perforated sleeve  90  covering the valve spring  100 . This first end of the clasp in turn seats compressively against an O-ring  60  located against a shoulder  25  within the lance adapter  20  to form a seal. 
     The lance adapter  20  and end cap  30  engage by means of a screw thread  31  located within one end of the lance adapter and the exterior of one end of the end cap, the arrangement being such that when screw connection of these components has been effected, no external thread is present that could be damaged by contact. 
     Another embodiment of the inventive clasp arrangement is shown in  FIGS. 5 a  through 6 c   , a smaller (so-called “mini”) spray nozzle arrangement compared to the “maxi” embodiments shown in  FIGS. 1 and 3 through 4   c.    
     In  FIGS. 5 a  and 5 b    there is shown a substantially cylindrical protective shell or casing in the form of a housing  110  having a central bore  112  that is axially continuous through lower, intermediate and upper chambers  114 ,  116 , and  118 . The lowermost chamber  114  is the inlet for the clasp arrangement and receives incoming flow material into the nozzle. The lower outer surface of the housing  110  includes a threaded portion  120  that is adapted to engage the internal thread in a nozzle cap  30 . Similar to the valve arrangement  101  shown in  FIG. 2 , the lower chamber  114  receives the perforated sleeve  90  of valve  101  and telescopically the other valve  101  components, including the spring  100 . 
     The arrangement includes a swirl chamber  150  that may be identical to that shown in  FIGS. 1 and 2 , or may be dimensioned differently to give the chamber  150  different characteristics of atomization and spray pattern, velocity of spray and density of application, etc. The swirl cavity  156  in this case is very shallow and the broad wall  154  immediately below the mouth  53  is high, relative to the broad wall  54  of the housing  55  in  FIG. 1 . 
     However, the swirl chamber  150  further includes a longitudinal groove key  157  machined or otherwise formed the full height of the predominantly cylindrical wall  158  of the swirl chamber  150 . The groove key  157  provides a lock on axial rotation of the swirl chamber  150  when housed in the cylindrical housing  110 . The orifice disc  70  may be identical to that shown in  FIG. 1  or may be varied with respect to the orifice size  72 . There is bulk economy in providing swirl chambers  150  and orifice discs  70  of identical outer dimensions so that one size fits all arrangements. The orifice disc  70  is shown in  FIG. 6 c    with the O-ring  80  seated in the circular groove  71 . 
     The invention enables the same sized swirl chambers  150  and orifice discs  70  to be used in spray nozzles  10  of different sizes and capacities, such as mini and maxi spray nozzles, while advantageously protecting wear parts  50 ,  70 ,  150  made from hard and correspondingly brittle materials with housings  55 ,  75 ,  110  made from strong and resilient materials, irrespective of the spray nozzle bore sizes in the cap  30  and lance adapter  20 . 
     The cylindrical housing  110  is adapted to house both the swirl chambers  150  and orifice discs  70  in axial relationship in the chamber  118  in a snug fit but allowing a small amount of play to facilitate removal and replacement of the consumable wear parts  70 ,  150  when gummed up by dried flowed material, such as proteinous milk. 
     The flow path from the lance adaptor  20  through to the central bore  112  occurs through a pair of opposed large slots  132  formed in the cylindrical wall  134 , which provide the entrance for the flow material into the intermediate chamber  116 . 
     Immediately above the intermediate chamber  116  is an annular ledge providing a seat on which the swirl chamber  150  may rest when inserted into the upper chamber  118 . The cylindrical wall  134  includes a large generally rectangular opening  136  that is adapted to be in registration with the cavity mouth  153  of the swirl chamber  150 . 
     Circumferential registration of the swirl chamber  150  is achieved by providing a registration arm or post  137  defined by two spaced longitudinal slots  138  in the wall  134 , the post  137  having a key ridge  139  extending down a substantial portion of its length on the post&#39;s  137  inside surface. 
     The ridge may be two or more longitudinally aligned protrusions, but is preferably a continuous ridge starting immediately underneath the position that the orifice disc  70  takes up above the swirl chamber  150  in the upper chamber  118  to ensure that a standard circular disc  70  may be used, and depending down to the ledge  135 . The cylindrical housing  110  includes an open top  140  through which the swirl chamber  150  is first axially inserted by an operator, its beveled peripheral lower edge  159  assisting the lower edge&#39;s  159  passage past the upper end of the post, which includes a shallow detent, clasp, catch or stop  141  comprising a protrusion extending radially inwardly to trap the orifice disc  70  in place once inserted after the swirl chamber  150 . The post  137  is resiliently deflectable radially outwardly due to its narrow width, despite the strengthening properties of the ridge  137 , so that the orifice disc  70  may ride past the catch  145  and nest in the very top of the upper chamber  118 . The catch  145  forms part of a radially inwardly extending lip  146  that continues along the inner upper surface of the cylindrical wall  134  and gradually tapers off. The cylindrical shape of the orifice disc  70 , albeit shallow as it is and its tight axial fit in the downstream or upper chamber  118 , means that it is difficult to tilt out of axial alignment and is so held by the nonsymmetrical detent  145  on one side of the upper chamber  118 . 
     Once the spray nozzle has been used and the wear parts  70 ,  150  need replacing, the nozzle cap  30  and housing  110  are unthreaded from the lance adapter  20  and cap  30 , respectively. A special cam tool  160  may be used to lever the wear parts  70 ,  150  out of the housing  110  when required. The cam tool includes a central shaft and a crucifix handle  162  for manipulating the tool  160 . The remote end of the shaft  161  terminates in a cam device comprising a cam disc  164  intermediate a spindle  165 . In use, the cam device  163  is inserted into one of the large slots  132  and through to the opposed slot  132 , so that the cam disc  134  is located immediately underneath the swirl chamber  150  with the cam disc substantially in alignment with the slots  132 . On rotation of the tool  160 , the cam disc  163 , supported by the spindle  165  bearing against the lower edges of the slots  132 , rides up against the underside  166  of the swirl chamber  150 , whereby to apply upward force against the swirl chamber  150  so that the orifice disc  70  is forced passed the catch  145  and out of the upper chamber  118 . 
     Turning to  FIGS. 9 a    through  10 , there is shown an assembled nozzle  210  similar to the second embodiment shown in  FIGS. 5 a  through 8 b   . The nozzle  210  includes a nozzle cap  230  threadably engaged to a lance adapter  220 . The nozzle  210  includes a wear parts housing  240  threadably engaged to the nozzle cap  230  by an outer threaded surface  241   a  of the housing  240  engaging an internally threaded bore  241   b  in the nozzle cap  230 . The housing  240  traps the wear parts, a swirl chamber  250  and an orifice disc  270 , in concentric relationship by providing a self-aligning combination of beveled or tapered edges  259  and  273  that cooperate with similarly tapered annular surfaces within the housing  240  to ensure that as the orifice disc  270  is pressed past the claw  245  at the top of the arm  237 , the respective tapered surfaces of the wear parts  250 ,  270  and the internal surfaces of the housing  240 , cooperate to concentrically align part in the housing  240  in a fixed arrangement with minimal play between the wear parts  250 ,  270  and the housing  240 . 
     The provision of an axially compressed seal  280  in the upper surface  278  of the orifice disc  270  enhances the axial alignment and compression of the various parts  250 ,  270 ,  240  in the cavity defined between the nozzle cap  230  and the lance adapter  220 . Whereas a radial O-ring might fail and be forced through the orifice  285 , the compression seal  280  is much less likely to fail and its effectiveness is improved by the axial compression of the overall arrangement. The components  250 ,  270 ,  240  can be secured in a tight fit with negligible play because the axial engagement of the nozzle cap  230  and the housing  240  means that a large amount of torque can be applied to each component requiring disassembly to overcome the adhesive forces of the dried spray material. This also means that standard spanners can be used for disassembly of the threadably engaged parts  220 ,  230 ,  240  rather than an arbor press or other specialist disassembly device. Lands or flats  249   a  through  249   c  are provided for engagement by a spanner. 
     The upper end of the housing wall  234  slopes downwardly toward an opening  235  in the housing wall  234 , the opening  235  being for the purpose of registration with the mouth  253  of the swirl chamber  250 . The inclination downward of the upper edges  287  of the wall  234  protect the edges from damage and wear to which the upper opening  286  of the housing is exposed with the entry and removal of the wear parts  250 ,  270 . The retaining edge  245  extends substantially around the upper edge  287  for about 180 to 270 degrees. The arm  237  is sufficiently resiliently deflectable to permit the entry of the wear parts into the housing by manual force, although a special tool  160  is required to remove the wear parts  250 ,  270  from the housing as described with reference to  FIGS. 8 a    and  8   b.    
     In  FIG. 11 , there is shown a spray nozzle assembly similar to that shown in  FIGS. 9 a  and 9 b   , but showing the respective taper lower periphery  359  of a swirl chamber  350  that cooperates with a corresponding and parallel internal annular angled corner forming a seat  360  in the internal wall surface of the housing  340 . This enables a multi-stage procedure for achieving concentricity and axial alignment of the wear parts  350 ,  370  in which the wear parts may be eccentrically aligned once initially inserted into the housing  340 , the housing  340  comprising claws  345  that grip the upper chamfered edge  373  of an orifice disc  370 . However, on application of axial compressive force occasioned by the threaded engagement of the housing  340  in a nozzle cap  330 , an O-ring  380  in the orifice disc  370  symmetrically bears down of the orifice disc  370  and forces the self-alignment of the wear part  350  by the operation of the cooperation of the angled annular surfaces  359 ,  360 . 
     “Comprising”: Throughout the specification and claims, the word “comprise” and its derivatives are intended to have an inclusive rather than exclusive meaning unless the contrary is expressly stated or the context requires otherwise. That is, the word “comprise” and its derivatives will be taken to indicate the inclusion of not only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is expressly stated or the context requires otherwise. 
     Orientational Terms: Orientational terms used in the specification and claims such as vertical, horizontal, top, bottom, upper and lower are to be interpreted as relational and are based on the premise that the component, item, article, apparatus, device or instrument will usually be considered in a particular orientation, typically with the nozzle cap downstream and the lance adapter upstream. 
     While we have in this specification described one general form of a spray nozzle and one particular arrangement of the nozzle with a check valve, it will be understood that other spray nozzle forms, which operate in the same manner as that described, can readily be utilized in the invention. 
     All such modifications and applications are deemed to be within the spirit and scope of the invention. It will be appreciated by those skilled in the art that many modifications and variations may be made to the embodiments described herein without departing from the spirit and scope of the invention.