Abstract:
A special fitting for installing a flanged nipple from the exterior of a duct. The threaded nipple has a handling stem formed integrally therewith, which is used to hold the nipple and flange inside the duct while a flexible cup seal washer is deformed and passed through the space between the handling stem and the duct. Thereafter, the fitting is drawn up with a nut and the handling stem cut off to provide a nipple.

Description:
This invention relates generally to duct fittings, and more particularly to a fitting for installation of a nipple from the exterior of a duct, and method of installing same. 
     Industries of all types use ducting to conduct gaseous fluids. These include process piping systems and fume exhaust systems for various industries including the semi-conductor, pharmaceutical, pulpit paper, metals mining, chemical processing, petrochemical and hazardous waste disposal industries. For conducting corrosive fumes and chemically active gases, stainless steel duct and pipe coated with chemically resistant material such as Teflon is often used. 
     Occasionally, it is desirable to install a nipple into the duct after the duct system is already connected and in place, for the purpose of extracting samples or inserting sensors into the fluid passing through the duct. This poses a formidable problem, since the fitting cannot be welded without destroying the integrity of the duct internal coating. In the past, it has been necessary to either crawl into the duct to insert a flanged nipple with sealing gasket from the inside through a hole in the duct, or to resort to various special fittings and methods to install the nipple from the outside of the duct. 
     A number of authors have suggested schemes for installing a nipple from the exterior of a duct, these being listed below as follows, which list is not all-inclusive. 
     
       
         
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Pat. No. 
                 Inventor 
                 Issue Date 
                 Title 
               
               
                   
                   
               
             
             
               
                   
                   244,869 
                 Watson 
                 9/21/48 
                 Connector 
               
               
                   
                 2,398,041 
                 Russell 
                 4/9/46 
                 Fitting 
               
               
                   
                 1,542,645 
                 Saucke 
                 6/16/25 
                 Pipe Fitting 
               
               
                   
                 1,530,099 
                 Youngman 
                 3/17/25 
                 Tank Coupling 
               
               
                   
                 1,334,072 
                 Bennett 
                 3/16/20 
                 Boiler Connection 
               
               
                   
                   
               
             
          
         
       
     
     It would be desirable to have a simple fitting for installation of a nipple from the exterior of a duct which is comprised of simple parts and which can be installed from the outside of the duct. It would also be desirable to provide an externally installable nipple, which is compatible with a stainless steel duct coated internally with a protective layer of Teflon. 
     Accordingly, one object of the present invention is to provide an improved fitting for installation of a nipple from the exterior of a duct. 
     Another object of the invention is to provide an improved method for installation of such a nipple through a round hole in the duct. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the invention comprises a fitting for installation of a nipple from the exterior of a duct having a wall with an aperture therein for receiving a nipple comprising a nipple installation member having a hollow externally threaded nipple portion, a flange disposed on one end thereof and dimensioned so as to pass through the aperture, and an elongated handling stem extending from the other end of the nipple portion; a flexible cup seal washer having an outer dimension greater than that of the aperture and adapted to cooperate with the flange to seal the nipple portion in the aperture, the washer being sufficiently flexible and so dimensioned to enable passage over the elongated handling stem and through the aperture; and a nut with threads matching the externally threaded nipple portion, whereby the nipple portion may be installed from the exterior of the duct and the elongated handling stem then removed to provide a nipple sealed in the duct wall. 
     In its preferred form the nipple portion, flange and elongated handling stem comprise a single plastic member, wherein the elongated handling stem is a solid extension integral with the nipple portion and closing off one end of the nipple portion. The method includes the steps of inserting the flange and nipple portion through the aperture while holding the nipple installation member by the elongated handling stem from outside the duct, passing the flexible sealing washer around the stem and through the aperture, tightening the nut around the nipple portion to compress the washer between the duct wall and the flange to seal the nipple portion in the aperture, and removing the elongated stem member to provide a nipple in the duct wall. 
    
    
     DRAWING 
     The invention will be better understood by reference to the following description, taken in connection with the accompanying drawing, in which: 
     FIG. 1 is a drawing of a prior art nipple suitable for installation from the interior of a duct, 
     FIG. 2 is an exploded perspective view of a fitting according to the present invention, showing the major components making up the fitting, 
     FIG. 3 is an elevational view, taken in cross-section through the centerline of a nipple installation member, 
     FIG. 4 is an elevational view, taken in cross-section through the center line of a cup seal washer, and 
     FIGS. 5 through 8 are elevation drawings illustrating the method of installation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1 of the drawing, a prior art nipple is shown installed from the interior of a section of duct, having a duct wall  10  with an aperture  12  therein. A nipple fitting comprising a threaded hollow nipple portion  14  and an integral flange  16  had to be inserted from the interior  18  of the duct. A seal was accomplished by compressing a die cut gasket  20  against the wall of the duct with a jam nut  22 . The present invention does not require installation from inside of the duct  10 . 
     Referring to FIG. 2 of the drawing, the invention comprises a fitting indicated by bracket  24  comprising three elements: a nipple installation member  26 ; a cup seal washer  28 ; and a conventional threaded nut  30 . The nipple installation member  26  is made up of a hollow, externally threaded nipple portion  32 , a flange  34  on one end thereof, and an elongated handling stem  36  extending from the other end. The nipple installation member  26  is preferably an integral plastic member resistant to corrosion and compatible with the coating, if any, on the duct work. This plastic member may be molded, machined or built up from components joined by suitable techniques. A preferred material is Teflon®. The cup seal washer  28  is made of flexible elastomeric material, preferably Viton®. Teflon and Viton are registered trademarks of E.I. Du Pont de Nemours and Company. 
     Referring to FIG. 3 of the drawing, an enlarged cross-sectional view of the nipple installation member  26  details the aforesaid nipple portion  32 , flange  34  and elongated handling stem  36  in cross-section. Nipple portion  32  has a cylindrical bore  38  and external threads  40  joined by a smooth gasket sealing surface  42 . Flange  34  has a diameter selected to just pass through a circular aperture of a selected diameter which is cut in the wall of the duct from outside the duct. The flange  34  includes a beveled surface  44  to facilitate insertion of the member into the aperture in the duct and a radial sealing surface  46  for receiving the base of the cup seal washer. 
     The elongated handling stem  36  is of a lesser diameter than the nipple portion  32 , solid and of sufficient length to firmly hold the nipple portion inside the duct while the cup washer is being inserted through the aperture in the duct in a manner to be described. 
     Referring to FIG. 4 of the drawing, a cross section through the flexible cup seal washer  28  shows that it has a beveled periphery  48  tapering from a smaller diameter sealing surface  50  to a greater diameter sealing surface  52 . Sealing surface  50  is dimensioned to rest on the flange radial surface  46  (FIG.  3 ), and the inner diameter of the cup seal washer indicated at  54  fits closely about the smooth cylindrical surface  42  on the nipple portion (FIG.  3 ). 
     The upper sealing surface  52  is selected to be of a greater dimension than the diameter of the aperture in the duct work. A circular recess  56  provides additional flexibility for deforming the cup seal washer to pass through the aperture in the duct work, and sealing the interior of the duct. 
     Referring now to FIGS. 5-8 of the drawing, the method of installing a nipple from the exterior of a duct may be clearly followed through the successive steps shown in the drawings. First, a circular aperture  58  is cut into duct  60  from the outside. The nipple installation member  26  is inserted through aperture  58  by holding the elongated handling stem  36  and inserting the flange  34  and nipple portion  32  through the aperture. Next, the cup seal washer is threaded over the stem  36  and deformed to pass it through the aperture in the space between the stem  36  and the edge of the aperture, as seen in FIG.  5 . 
     Referring to FIG. 6, the assembly is located and centered, so that the outer edges of washer  28  cover the aperture, in order to seal the nipple with the sealing surface  52 . 
     In FIG. 7, the assembly is shown partially withdrawn from the aperture, until the flange  34  engages the lower surface of cup seal washer  28 , seating the lower sealing surface  50  on the flange surface  46  of the installation member  26 . The nut  30  is threaded over the stem  36  and screwed on to the externally threaded nipple portion  32 . The nut is tightened to compress washer  28  to provide a seal. 
     At this point, the fitting may be left in place until needed, since the stem  36  seals off the bore of the nipple portion  32 . If the nipple is to be used immediately, the stem  36  and a small length of the nipple portion  32  are removed by severing, as shown in FIG.  8 . 
     The foregoing invention provides a very simple fitting for installing a nipple from the exterior of a duct. It is especially useful for coated stainless steel duct used in corrosive atmospheres, because the materials of the nipple are compatible with the duct coating and cause no damage to the duct coating during installation. It is also useful for fiberglass reinforced plastic ducts, which also need to have penetrations sealed from corrosives. 
     While there has been disclosed what is considered to be the preferred embodiment of the invention, other modifications will occur to those skilled in the art, and it is desired to secure in the appended claims all such modifications as fall within the true spirit and scope of the invention.