Patent Publication Number: US-6911170-B2

Title: Spray diffusers and method and mold for manufacture of same

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
   This application claims the priority of German Application No. 101 27 597.8 filed May 30, 2001, the disclosure of which is expressly incorporated by reference herein. 
   The invention relates to a method for manufacturing spray diffusers which have flow compartments and connected mouthpieces having a narrowed cross section for the discharge of the liquid to be diffused and which are manufactured using multi-part molds whose hollow spaces in their negative form correspond to the outer and inner dimensions of the spray diffusers and are filled with liquid or thixotropic manufacturing material that is then made to solidify. 
   In the manufacture of spray diffusers that are produced using a casting process, providing cores for the creation of the internal configuration is known, while the outer configuration, especially with the manufacture of ceramic nozzles, is produced using plaster molds. The cores are destroyed after the casting operation; the plaster molds can be used more often. 
     FIG. 2  schematically shows the appearance of a mold for the manufacture of ceramic nozzles according to the prior art. One can see that the interface between the core (not depicted here in detail) and a mouthpiece plug  50  lies within the area of the cross-sectional narrowing of flow chamber  51  to outlet channel  52  of mouthpiece  53 . A configuration of this type is selected in consideration of the finished moldability. The interface between outer mold part  54 , which is adjacent to mouthpiece  50 , which continues with a further upper molded part in a manner not shown in greater detail, is situated in the area of the outlet edge of mouthpiece  53 . Since the mold parts can never fit against each other exactly, mold parting seams result at these mold parting places because the manufacturing material runs into these parting gaps of the molds. At the two aforementioned places, at outlet edge  55  and at the transition on flow chamber  51  to the narrowed cross-section of mouthpiece  53 , thus at position  56 , mold parting seams are therefore produced which as a rule must be manually removed after extraction of the cast spray diffuser. Since these places  55  and  56  in spray diffusers are decisive for the quality and function of the spray diffuser because the flow path and interruption of the spray stream are affected here, the finishing work must be carried out thoroughly and at great expense. To explain this, reference is made in this connection to the fact that spray diffuser  57 , shown in  FIG. 2 , is a swirl spray diffuser for producing a hollow-cone spray stream, the liquid to be sprayed being fed in the direction of arrow  58 . The liquid that is fed in principle enters tangentially into flow chamber  51 , which as a rule is rotational symmetric, is set in rotation by the tangential entry so that a liquid film forms on the walls and then transitions into mouthpiece  53  at position  56  and, by reversal in the direction of rotation, transitions into a tangential and axial speed at outlet edge  55  and forms a liquid screen in the shape of a hollow cone that disintegrates into droplets just past outlet edge  55 . It therefore depends very much on the exact observance of the internal configuration. 
   An object of the present invention is to propose a manufacturing method, and a mold suitable for this method, with which it is possible to prevent to a great extent the expensive finishing work on the aforementioned critical areas. To achieve this objective, it is provided in a method of the type mentioned at the outset that the outlet edges of the mouthpiece and the transitional areas of the inner wall between flow chamber and mouthpiece are each formed out wall areas of one-piece molded parts that abut against the adjacent molded parts outside these wall areas. By this configuration, the two critical areas  55  and  56  are depicted in  FIG. 2  are produced without mold parting seams since there are no mold parting seams located within these areas. The mold parting places are situated at non-critical places, so that secondary machining does not require any great expense. 
   In a further development of certain preferred embodiments of the present invention, a mold for carrying out the method of the aforementioned type can be provided which is provided with a core and at least one mouthpiece plug, as is also the case for the state of the art. However, in contrast to the prior art, the mouthpiece plug is now provided with the negative in the shape of a circumferential groove and is configured in such a manner that it abuts against adjacent molded parts only outside this groove. 
   In a further development of certain preferred embodiments of the present invention, it is also advantageously possible to provide the mouthpiece plug with a ring whose perimeter corresponds to the transitional area of the inner wall between flow chamber and mouthpiece. This ring, which is adapted to the expanding inner contour of the flow chamber that is situated before the mouthpiece, can, as will be explained in greater detail below, be placed by the inner chamber of the mold onto the mouthpiece so that the mold release operation is not hindered. It is thus appropriate in a further development of the invention to place this ring on an axially projecting pin of the mouthpiece plug and hold it there, it being possible to provide this projecting pin with a non-circular cross-section in order to prevent the ring from twisting in relation to the mouthpiece plug. This projecting pin can also engage into the core, so that a twisting between mouthpiece and supplementary ring is safely avoided, and the manufacture of a cast spray diffuser is possible without problems. After mold release it is only necessary, as already mentioned, to remove the mold parting seams, which, however, are not located on the critical areas and therefore are relatively simple to remove without affecting the functional quality of the diffuser. 
   The present invention is described on the basis of embodiments in the drawing and is explained in the following. 
   Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic representation of the basic structure of a mold for carrying out the method of the invention; 
       FIG. 2  is the analogous representation to  FIG. 1  of a mold according to the state of the art for manufacturing a spray diffuser; 
       FIG. 3  is a longitudinal section through a complete mold for manufacturing a spray diffuser, constructed according to a preferred embodiment of the invention; 
       FIG. 4  is a cross-sectional view through the mold of  FIG. 3  taken in the direction of cutting plane IV; 
       FIG. 5  is a longitudinal sectional view through a spray diffuser manufactured using the mold and the manufacturing process according to  FIG. 3 ; and 
       FIG. 6  is a sectional view through the spray diffuser of  FIG. 5  taken in the direction of cutting plane VI—VI. 
   

   DETAILED DESCRIPTION OF THE DRAWINGS 
     FIG. 1  shows, analogously to  FIG. 2 , a part of a spray diffuser  7  that is to be manufactured using a casting process, for example in a ceramic or other type of material. This spray diffuser  7  is provided with an inlet channel  12  through which the liquid to be sprayed is introduced in the direction of arrow  8  into flow chamber  1 , which is a swirl chamber. The mold provided for manufacture of this spray diffuser  7  is comprised of a mouthpiece plug  10  that is inserted into a lower mold part  4  in order to accomplish the manufacture of mouthpiece  3  with the narrowed outlet channel  2  opposite flow chamber  1 . This mouthpiece plug  10 , in comparison to mouthpiece plug  50  in the state of the art (FIG.  2 ), is formed with a larger diameter and with a circumferential groove  13  that has the negative form of outlet edge  5  of spray diffuser  7 . This mouthpiece plug  10  formed in this way abuts at position  14  against outer molded part  4  (not shown), which naturally completely surrounds mouthpiece plug  10  and also continues upward in another mold. 
   This is explained again in detail with reference to  FIGS. 3 and 4 . A mold parting point therefore occurs at position  14  and not in the area of the outlet edge  5  of spray diffuser  7 . 
   Moreover, mouthpiece plug  10  is provided in its area that projects into subsequent flow chamber  1  with an axially projecting pin  11  on which is attached from within a ring  9  that lies on a support surface  15  of mouthpiece plug  10 . Ring  9  has a part of the inner contour of flow chamber  1 . However, it is also provided on its perimeter with the negative form of transitional area  6  from flow chamber  1  to mouthpiece  3 . This transitional area is therefore also arranged at a distance from the parting plane between ring  9  and mouthpiece plug  10 , which coincides with support surface  15 . Therefore, in the casting operation there end up being no mold parting seams at critical positions  5  and  6 . These, rather, are to be expected in the area of support surface  15  outside or at position  14 , likewise outside, where they can be removed relatively easily after the casting operation and after hardening of spray diffuser  7 , and this without affecting the dimensional accuracy of the spray diffuser. Expensive finishing work is therefore not required. 
     FIGS. 3 and 4  then show only schematically, and for the purpose of explanation, the overall mold structure that is necessary for carrying out the method according to the invention. The thing to be recognized here first is core  16 , which fills in inlet channel  12  and flow chamber  1  before the casting operation, and into which pin  11 ′ of mouthpiece plug  10 ′ projects. This pin  11 ′—just as pin  11  mentioned in relation to FIG.  1 —can have a non-circular cross-section that projects into the correspondingly non-circular recesses of ring  9 ′ or  9 , respectively, and into a corresponding recess of core  16 . This configuration namely ensures a twist-proof layering of mouthpiece plug  10 ′, ring  9 ′ and core  16 . Mouthpiece plug  10 ′ in this case is formed in the same way as mouthpiece plug  10  according to FIG.  1 . It therefore has circumferential groove  13 ′ from which outlet edge  5 ′ of the spray diffuser  7 ′ shown in  FIGS. 5 and 6  is later formed. 
   The core, which in other respects rests on the top surface  17  of ring  9 ′, is surrounded by two mold halves  4   a  and  4   b , which, together with core  16 , form a hollow chamber  18  in which spray diffuser  7 ′ ( FIGS. 5 and 6 ) is later formed. Mold halves  4   a  and  4   b  lie against each other in a parting plane  19  and between them form a circular opening  20  in which mouthpiece plug  10 ′ can be inserted. 
   For the manufacture of spray diffuser  7 ′, material in liquid or thixotropic form for production of the nozzle is filled in through an opening  21  at a suitable position into hollow space  18  and remains in this hollow space  18  until the structural constitution of the material has solidified. That can occur for example by cooling or also by drying. The air present in hollow space  18  can escape through openings  22  and  23  during the filling operation, i.e. in the casting operation. 
   Since, on the one hand, mold halves  4   a ,  4   b  and, on the other hand, also mouthpiece plugs  10 ′, ring  9 ′, which can be characterized as the inner mouthpiece plug, and the remaining molded parts never fit together smoothly and exactly, mold parting seams result at the parting places between these mold parts. In the embodiment shown, mold parting seams therefore result in parting plane  19  between the mold halves  4   a  and  4   b , but also in the plane of support surface  15 ′ between mouthpiece plugs  10 ′ and ring  9 ′ and in the plane of support surface  17  between ring  9 ′ and core  16 . However, all these parting planes lie within areas that are not decisive for the later dimensional and contour accuracy of the spray diffuser that is to be manufactured. The decisive areas of the later outlet edge  5 ′ ( FIGS. 5 and 6 ) or the transitional area  6 ′ have no mold parting seam, because with the manufacturing method using the corresponding mold form, one must make sure that the mold parting planes do not lie within these critical areas. 
   The result of this, as also becomes clear in relation to  FIGS. 5 and 6 , is that finishing work for the removal of mold parting seams is only necessary at the interfaces of planes  24  and  26  on the inner side of the spray diffuser and at the interface of plane  25  with the outer side of the spray diffuser, but which do not create any problems since these are essentially flat surfaces. 
   The new manufacturing method therefore permits spray diffusers to be manufactured in a simple manner. In this case the removal of the mold parting seams is the last work operation before a given needed surface treatment of the nozzle or before the firing. 
   The new manufacturing method has been described for a spray diffuser that is provided with a flow chamber  1  formed as a swirl chamber, which is narrowed down toward a mouthpiece  3 ′. The feeding of the liquid to be sprayed into swirl chamber  1  in this case occurs in an essentially tangential manner. 
   However, it is also completely possible to conceive of the idea of the present invention of moving mold parting seams out of the area of critical flow edges or reversing areas, even with other spray diffusers. Thus, even for a fan nozzle, the transitional area from the axial inlet to the crossover edge for the outlet slot and the break-off edge of this outlet slot itself, for the case that such nozzles are cast, can also be designed in mold areas at which no mold parting is carried out. Because of the considerably complex shaping of such fan nozzles, which do not always have rotationally symmetric flow guides, such fan nozzles nevertheless are manufactured as a rule via mechanical machining and not via a casting process. However, in the described embodiments of swirl nozzles with an essentially rotationally symmetric swirl chamber and mouthpiece outlet channel, the present invention offers decisive advantages. 
   The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.