Patent Publication Number: US-10329991-B2

Title: Thin foil encapsulated assemblies

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 14/467,907, filed Aug. 25, 2014, which claims the benefit of U.S. Provisional Application No. 61/869,841, filed Aug. 26, 2013, the disclosures of which are incorporated by reference herein. 
    
    
     BACKGROUND 
     This application discloses an invention which is related, generally and in various embodiments, to thin foil encapsulated insulation assemblies. 
     In various technologies, effective insulation for providing heat retention is an important design component. One example of a technology in which effective insulation is desired is the field of exhaust after-treatment systems for treatment of harmful exhaust emissions from internal combustion engines. Typical exhaust after-treatment systems are configured to reduce the level of undesirable exhaust byproducts such as nitrogen oxides. Accordingly, conventional exhaust after-treatment systems include a decomposition tube and fitting for an injector designed to inject a urea based diesel exhaust fluid or reductant, which is capable of decomposing into gaseous ammonia and carbon dioxide in the presence of exhaust gas within the tube under certain conditions. After exiting the decomposition tube, exhaust gas flows through a selective catalytic reduction (SCR) system where the ammonia reacts with nitrogen oxides to produce nitrogen and water. The catalytic conversion of nitrogen oxides is highly dependent on temperature, making heat retention through effective insulation a critical design requirement for decomposition tubes. 
     Insulating both the decomposition tube and the junction with injector module is possible using double walled tubes with insulation disposed in the annular space between an inner tube and an outer tube. Such a junction typically includes the decomposition tube with an integral injector tube to which an injection flange is joined for mounting the injector module. Insulating the junction between the decomposition tube and the injector tube is possible using relatively thick outer tubes and insulation housings that can be welded together at the junction to provide the necessary support and structural rigidity required to transfer loads between the decomposition tube and the injector tube. Nonetheless, double-walled tubes are expensive and add weight to the overall system. To avoid using double-walled systems, foil is used to surround the tube insulation on both the decomposition tube and the injector tube, but little or no insulation is used at the junction between the decomposition tube and the injector tube because there is no outer tube on which to support an insulated junction housing. 
     Thus, there is a need for a tube junction that can be insulated at relatively low cost and maintain light weight of the assembly. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the deficiencies of prior tube junctions by providing a tube junction housing having; a receptacle portion defining an insulation space; a receptacle portion lip joined to the injector housing and defining an injector flange opening; and a base flange joined to the receptacle portion and including a thin-walled connection surface. 
     The receptacle housing portion can define an injector tube axis through the injector flange opening and the base flange is substantially arcuate to define a receiver tube axis spaced apart from the base flange, and the injector tube axis and the receiver tube axis are disposed to define an angle of less than 90°. 
     The receptacle portion lip can define connector openings to allow for screws or bolts to connect an injector tube to a receiver tube. Also, the base flange can extend outwardly from the receptacle portion. 
     The tube junction housing can further include an injector flange disposed in the tube junction housing adjacent to and substantially co-planar with the injector flange opening. 
     The tube junction housing can also include insulation disposed in the insulation space. 
     In another aspect of the invention, an injector tube assembly is provided that includes: a receiver tube defining a longitudinal axis; tube insulation substantially surrounding the receiver tube; and a thin foil spaced apart from the receiver tube and substantially surrounding the tube insulation; an injector tube joined to the receiver tube at a tube junction and defining an injection tube axis; and a tube junction housing at least partially surrounding the tube junction and having; a receptacle portion defining an insulation space, and a receptacle portion lip joined to the receptacle portion and defining an injector flange opening, and a base flange joined to the receptacle portion and including a thin foil connection surface joined to the thin foil and the base flange rests on the tube insulation and is spaced apart from the receiver tube. Junction insulation is preferably disposed in the insulation space and an injection flange can be disposed in the tube junction housing adjacent to the injector flange opening. 
     The tube junction housing base flange can be substantially arcuate and spaced apart from the receiver tube axis. 
     The tube junction assembly receptacle portion lip preferably defines connector openings for access by screws, bolts or other connectors to secure an injector module to the injection flange. The base flange can extend outwardly from the receptacle portion to a distance that minimizes bearing pressure on the tube insulation. The assembly can also include an injector flange disposed in the receptacle portion adjacent to and substantially co-planar with the injector flange opening. Preferably, the tube junction assembly also includes insulation disposed in the insulation space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a side view of a decomposition tube and injector module assembly with a tube junction housing in accordance with the present invention; 
         FIG. 2  shows a perspective view of the embodiment of  FIG. 1 ; 
         FIG. 3  shows a cross-sectional view of the embodiment of  FIG. 1 ; 
         FIG. 4  shows a partial cross-sectional perspective view of the embodiment of  FIG. 1 ; 
         FIG. 5  shows a partial cross-sectional view of an embodiment of a curved decomposition tube assembly; 
         FIG. 6  shows a perspective view of a tube junction housing of the embodiment of  FIG. 1 ; 
         FIG. 7  shows a cross-sectional view of the tube junction housing of  FIG. 6 ; 
         FIG. 8  shows a perspective view of hydroformed tube junction housing used for affixing thin foil around an injector port in a different configuration according to an alternative embodiment of the invention; 
         FIG. 9  shows a perspective cross-sectional view of an insulated aspirator tube assembly with thin foil encapsulation according to an alternative embodiment; 
         FIG. 10  shows a perspective view showing the assembly of  FIG. 9  with a tube junction housing around the aspirator tube for affixing thin foil; and 
         FIG. 11  is a partial perspective view of an embossed thin foil used in conjunction with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It is to be understood that at least some of the figures and descriptions of the invention have been simplified to illustrate elements that are relevant for a clear understanding of the invention, while eliminating, for purposes of clarity, other elements that those of ordinary skill in the art will understand without illustrations. 
     In particular, and by reference to  FIGS. 1 through 4 , there is illustrated a partial embodiment of an exhaust after-treatment system  10 , which is coupled to an internal combustion engine (not shown). Referring to  FIG. 1 , part of an after-treatment system  10  is illustrated, which is capable of receiving and treating exhaust gas generated by the engine as indicated by directional arrow  12 . After being treated by the after-treatment system  10 , exhaust gas flows out of the, through a decomposition tube outlet end  45  of the after-treatment system  10  and through an SCR assembly (not-illustrated). The embodiments described herein are used in conjunction with an exhaust-after-treatment system, but the present invention is useful in any heat-sensitive system having a receiver tube  14  and an injector tube  15  joined at a junction  17  ( FIGS. 3 and 4 ) to merge or separate two fluid flows. 
     The after-treatment system  10  includes a receiver tube  14 , in this case a decomposition tube, an injector tube  15 , and a tube junction housing that in the illustrated embodiment is a reductant injector housing  16 . A reductant injector module  13  (seen in  FIG. 1 , but only the injector flange  18  is shown in  FIGS. 2 through 4  for clarity) is coupled to a reductant supply source (not shown) and injects reductant past the injector flange  18 , through the injector tube  15 , and into the decomposition tube  14 . The injector flange  18  is either welded directly to the injector tube  15  or is integral with and cast from the same material as the injector tube  15  and the decomposition tube  14 . In the straight decomposition tube  14  embodiment shown in  FIGS. 1  through  4 , the decomposition tube  14  is substantially cylindrically shaped with an elbow at the outlet end  45 , but other shapes, particularly different cross-sectional shapes are possible. Referring to  FIG. 2 , the decomposition tube  14  includes an inlet  20  to the tube, an inlet tube  22  and an outlet tube  23 . The injector tube  15  defines an injector tube axis  25  ( FIGS. 2 and 3 ) that extends outwardly at an angle relative to a receiver tube axis  27 . Preferably, an angle a between the two axes  25  and  27  is less than 90°, but other angles can be used, as seen in  FIGS. 9 and 10 , for example. 
     As shown in  FIGS. 1 through 7 , the reductant injector housing  16  includes a base flange  24  and receptacle portion  26  extending outwardly at an angle from the base flange  24 . The receptacle portion  26  at least partially surrounds the junction  17  and includes a through-hole portion  28  sized and shaped to expose the injector flange  18  to allow connection of the injector module  13 . A receptacle portion lip  29  lays over, but is not connected to the injector flange  18 . Cut-outs  31  allow access for bolt holes  37  in the injector flange  18  to be exposed for connecting. While the illustrated embodiment depicts a three bolt hole arrangement, any suitable number of bolt holes can be used, and other suitable connectors and arrangements are possible. 
     Referring to  FIGS. 3 and 4 , the decomposition tube  14  is surrounded by a layer of tube insulation  30  which is then encapsulated by a layer of thin foil  32 . Junction insulation  34  is preferably provided between the reductant injector housing  16  and the receiver tube  14 . The injector housing  16  is held against the junction insulation  34  by the layer of thin foil  32 . The reductant injector housing  16  is preferably hydroformed or stamped, and is thicker than the thin foil layer  32  that is welded, adhered to, or otherwise joined to the upper connection surface  33  of the base flange  24 . The reductant injector housing  16  is preferably between about 0.8 mm thick and about 2.7 mm thick, and preferably 1.2 mm thick and made of stainless steel, which is relatively thick and rigid compared to the thin foil  32 , as used in this invention. The thin foil  32 , on the other hand, is less than about 0.8 mm [0.031″], and preferably between about 0.17 mm [0.006″] and about 0.20 mm [0.008″] thick and made of stainless steel, or other formable metal. Embossment and other manufacturing processes can reduce or increase the foil thickness, particularly in localized areas, so the term “about” in reference to thin foil thickness, as used herein, refers to the dimensions of the foil  32 , but subject to changes from manufacturing processes. For example, embossment of thin foil  32  as seen in  FIG. 11 , can thicken the foil to about 0.35 mm [0.014″] to about 0.41 mm [0.016″] at the embossments. 
     The base flange  24  of the reductant injector housing  16  is not directly connected to the decomposition tube  14 , the injector tube  15 , or the junction  17 . Instead, it bears on the tube insulation  30 , and is spaced apart from the receiver tube  14 . The base flange  24  is wide enough to distribute loads on the tube insulation  30  and further provides a connection surface  33  (optionally on the upper or lower side of the base flange  24 ) to which the layer of thin foil  32  can be welded, preferably by resistance welding. Alternatively, this connection between the base flange  24  and the thin foil  32  could be done with other types of welds utilizing filler materials, brazing, or adhesives. The reductant injector housing  16  provides rigidity to prevent denting during service and installation of the reductant injector  13 , for example. The injector housing  16  also includes a receptacle portion  26  that defines an insulation space  35  into which junction insulation  34  can be packed to insulate around the injector junction  17 , thus minimizing the temperature drop across the injector tube  15  and the junction  17  with the decomposition tube  14  to improve performance. Additionally, the housing  16  eliminates the need for stamp tooling the thin foil layer  32  to specific contours around the injector, so it can be universally implemented for a specific tube injection configuration. 
     A curved decomposition tube assembly  100  is illustrated in  FIG. 5 . In this embodiment, the tube junction housing/reductant injector housing  116  is provided on the outer bend of a receiver tube/decomposition tube  114  where the injector tube  115  joins the receiver tube  114  at a junction  117 . Like the embodiment of  FIGS. 1 through 4 , the assembly  100  includes a layer of tube insulation  130  around receiver tube  122  and additional junction insulation  134  is provided between the reductant injector housing  116  and the receiver tube  122 . The reductant injector flange  118  is either welded directly to the injection tube  115  or is integral with and cast from the same material as the injection tube  115  and the decomposition tube  114 . Like the embodiment of  FIGS. 1 through 4 , the curved decomposition tube assembly  100  also includes a layer of thin foil  132  substantially surrounding the tube insulation  130 . Like the previously described embodiments, the injector housing  116  is not connected directly to the decomposition tube  114 , the junction  117 , or the injector tube  115 , and instead bears on the tube insulation  130  and/or the thin foil  132 , and is joined to the thin foil  132 . 
     As stated above, the injector housing  16 ,  116  connection surface  33 / 133  can be on the top or the bottom of the base flange  24 / 124 , so that the base flange  24 / 124  can be placed above the thin foil  32 / 132  rather than below the thin foil  32 / 132 . The injection housing  16 / 116  can also be used in conjunction with other insulation enclosures, such as foil tapes, elastic wraps, or woven/knitted materials for encapsulating insulation. 
     As stated above, the embodiments illustrated in  FIGS. 1 through 5  are related to exhaust after-treatment systems, but the present invention is not limited to this field. The present invention of a stamped pad/housing could be used in conjunction with thin foil to insulate around any complex geometry. For example, the present invention can be implemented with sensor couplings, hydrocarbon injectors, bracketed tubes, aspirator tubes or other complex shapes into which thin foil cannot be stamped, or attached. 
     Examples of additional alternative embodiments are illustrated in  FIGS. 8 through 10 . 
       FIG. 8  shows a perspective view of hydroformed pad system  300  having a hydroformed housing  316  used for affixing thin foil  332  around an injector port  319  in the injector flange  318 , and a different configuration that does not completely cover or insulate the junction  317  between the merging tubes  314  and  315 , but provides a base to which the thin foil  332  can be joined. Also, illustrated in  FIG. 8  are: a base flange  324  on the housing  316  and an injector axis  325  defined by the injector tube  315 . 
       FIG. 9  shows a cross-sectional view of an insulated aspirator tube system  200  having an aspirator tube  215  joined to a receiver tube  214  at a junction  217 . Thin foil  232  encapsulation is provided around the receiver tube  214 .  FIG. 10  shows the assembly  200  from  FIG. 9  prior to insulation to illustrate the use of pad/housing  216  around the aspirator tube  215  to aid in affixing thin foil  232  around the tube insulation  230 . The housing  216  is not directly affixed to the receiver tube  214 , aspirator tube  215 , or the junction  217 , but instead is able to slide (“float”) relative to the aspirator tube  217  while bearing on the tube insulation  230 . Such an arrangement permits the housing  216  to be secured to the thin-foil  232  and bear on the tube insulation  230  to improve the insulation properties around the junction  217 . 
     Nothing in the above description is meant to limit the invention to any specific formulation, calculation, or methodology. Many formulation, calculation and methodology substitutions are contemplated within the scope of the invention and will be apparent to those skilled in the art. The embodiments described herein were presented by way of example only and should not be used to limit the scope of the invention. 
     Although the invention has been described in terms of particular embodiments in this application, one of ordinary skill in the art, in light of the teachings herein, can generate additional embodiments and modifications without departing from the spirit of, or exceeding the scope of, the described invention. Accordingly, it is understood that the drawings and the descriptions herein are proffered only to facilitate comprehension of the invention and should not be construed to limit the scope thereof.