Abstract:
A fitting for connecting conduit. The fitting includes a plurality of electrical conductors running through the fitting and a sealing compound that has been expanded within the fitting to separate the electrical conductors from each other and sides of the fitting. In a further embodiment, the fitting includes a plurality of conductors running through the fitting and a sealing compound that has been expanded within the fitting to separate the conductors from each other and sides of the fitting. The fitting includes a first plug that is secured within a first opening in the fitting such that the first plug is inserted into the first opening after the sealing compound is added to the fitting through the first opening.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a Continuation of U.S. application Ser. No. 10/391,250, filed on Mar. 18, 2003, which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to sealing conduits, and in particular to an expanding conduit sealer. 
       BACKGROUND OF THE INVENTION 
       [0003]    Electrical conduit is used to mechanically protect electrical conductors. The U.S. National Electrical Code and Canadian Electrical Code require that explosion-proof enclosures housing arcing and sparking devices be sealed off to prevent propagation of flames or gases through the conduit system, and to minimize the explosion pressures. Such seals minimize the effects of pressure piling by acting as a barrier to stop burning gases from traveling through the conduit to other parts of the system. 
         [0004]    When sealing conduit fittings, past methods utilize a fiber material that is weaved around each electrical conductor in the conduit to separate them. The fiber material is also packed in to form a dam at each end of a horizontal fitting, and at the bottom of a vertical fitting. A Portland type cement is then mixed with water and poured in through a funnel, puddled with a stick to remove air bubbles and left to cure for at least 24 hours. 
         [0005]    The past methods were fairly labor intensive and error prone. Errors resulted when electrical conductors were not separated or fittings were not filled completely full with sealing compound. Further labor included obtaining clean water and mixing containers and the use of a stick to remove air bubbles. 
       SUMMARY OF THE INVENTION 
       [0006]    An expanding compound is used to seal conduit fittings. The compound is injected into the fitting, and expands to separate conductors within the fitting. In one embodiment, the compound expands to four times its size, and hardens within approximately one hour. In a further embodiment, the compound is a two-part product that is mixed in a self contained applicator and injected into the fitting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a cross section of a horizontal mount sealing fitting illustrating use of a sealing compound. 
           [0008]      FIG. 2  is a cross section of the sealing fitting of  FIG. 1  with expanded sealing compound. 
           [0009]      FIG. 3  is a cross section of a vertical mount sealing fitting illustrating use of a sealing compound. 
           [0010]      FIG. 4  is a cross section of the sealing fitting of  FIG. 2  with expanded sealing compound. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following description is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims. 
         [0012]      FIG. 1  shows a horizontal fitting  110  for joining two horizontally disposed conduits via mating sets of threads  115  and  120  at each end of fitting  110 . The length of the fitting is approximately the distance between the two sets of thread, and the width of the fitting is approximately equal to the outside diameter of the fitting. 
         [0013]    Multiple conductors  123  are disposed within the fitting. Two openings  125  and  130  are provided in the fitting  110 . Removable plugs are used to plug the openings. Opening  125  is shown without the plug installed, and a plug  135  is shown installed in opening  130 . Opening  130  is larger than opening  125  in one embodiment. An expanding sealing compound  133  is provided in a liquid state inside the fitting  110 . One of the plugs may be removed to allow injection of the sealing compound. In this example embodiment, the sealing compound is injected through opening  125 . 
         [0014]    In one embodiment, the sealing compound  133  is a two-part mixture that starts to expand once the two parts are mixed. When expanded, it fills the fitting  110  as shown at  210  in  FIG. 2 . The expanding compound works its way between conductors so that as it expands, the conductors are separated from each other. In one embodiment, the expanding compound expands four times its size immediately after being mixed. It is desired that when the compound is expanded, none of the conductors are touching either themselves, or sides of the fitting  110 , and the compound expands to fill the fitting  110  over at least a portion of the length of the fitting  110  referred to as a sealing chamber  137  which extends between the two ends of the fitting  110 . In one embodiment, the sealing chamber  137  extends approximately about and partly past the hub stops  140  and  145  on each end of the fitting. In a further embodiment, the sealing compound forms an explosion proof seal. 
         [0015]    In one embodiment, the expanding compound is provided in a cartridge with the two parts or materials separated by a barrier, such as a foil barrier partway between a top and bottom of the cartridge. The cartridge is squeezed to deform the foil barrier, and a mixing rod is coupled to a plunger in the cartridge. The plunger is then pushed to the bottom of the cartridge by the rod. The rod is then pushed and pulled between the top and bottom of the cartridge for approximately 40 to 50 strokes, where a stroke is one complete in and out cycle. The cartridge is rotated while the rod is pushed and pulled to ensure that the plunger is swiping all material in the cartridge. 
         [0016]    In one embodiment, mixing is done within 30 seconds of starting the mixing process, as pressure builds up on the inside of the cartridge as the material starts to expand. At the last stroke, the mixing rod is pushed all the way to the bottom of the cartridge. The rod is then pulled out, while the cartridge is squeezed to hold the plunger at the bottom. A nozzle is then attached to the top of the cartridge where the rod was removed, and then the rod is used at the bottom of the cartridge to push the plunger. This causes mixed liquid material, the expanding compound, to be injected through the nozzle. In one embodiment, the cartridge is marked with volumetric increments corresponding to one-ounce segments for measuring the amount of compound injected. The sealing fitting plug is promptly replaced and tightened to prevent the sealing compound from expanding outside the fitting and/or gelling around the threads in the fitting that mate with corresponding threads on the plugs. 
         [0017]    The term “compound” in one embodiment comprises the use of two or more materials that are mixed and start expanding. In further embodiments, the compound is a single material that may start expanding at a controlled time, such as by exposure to air or other gases or by electrical stimulation, heat, or any other controllable event. 
         [0018]    Typical applications are for sealing fittings in the ½ inch to 6 inch trade sizes. The temperature of the compound should be between 4° C. and 29° C. The compound in one embodiment will expand approximately 4 times its size following injection. The amount of compound for different size fittings may be established empirically, but is approximately one fourth of the volume of the sealing chamber. Some hazardous areas that the seals may be used in include, but are not limited to Class I, Division 1 &amp; 2 Groups A, B, C, D and Class I, Zones 0, 1 &amp; 2. 
         [0019]    In one embodiment, the compound used is Chem-Cast 637 sealing foam c/o Chem-Cast 637 isocyanate and Chem Cast 637 Polyol. Isocyanate is a dark brown liquid, insoluble in water with a boiling point of 392 degrees F. (200 degrees C.), a vapor density of 0.00016 (mm Hg) and a specific gravity of 1.2 g/ml. Polyol is a gray liquid, partially soluble in water with a specific gravity of 1.05 g/ml. When mixed together the resultant material is gray in color. It has a rise time of 1.5-2.5 minutes and a gel time of 4-5 minutes. When fully cured the foam density is 15-20 lbs./ft 3 . The compression strength is &gt;60 psi, porosity is &gt;90% closed cell and has a water absorption of &lt;1%. Chem-cast 637 is a fire resistant two-part rigid, polyurethane foam. It expands to fill voids inside of the sealing fitting and forms a dense, high strength foam. It has excellent adhesion to many surfaces without the use of primers. 
         [0020]      FIG. 3  shows a vertical fitting  310  for connecting two vertically disposed conduits via threads  315  and  320 . Multiple conductors  323  are disposed within the fitting. One or more openings  325  and  327  provide access to the inside of the fitting. Threaded plugs are used to plug the openings. One plug  328  is shown installed in opening  327 , which is a lower opening. In one embodiment, opening  325  is a top opening that provides access to the inside of the fitting  315  to inject the liquid compound. Opening  327  provides access to create a fiber dam  330  at a bottom of the fitting, referred to as a hub. In one embodiment, the fiber is a mineral fiber, such as Chico X® sealing compound provided by Crouse-Hinds and it is packed using a hardwood stick of other tool that will not damage the conductors. Hub sizes range from ½ inch to 6 inches. 
         [0021]    The fiber is first packed while the conductors are forced away from the hub opening and forced apart. The fiber is then packed between and around conductors in the hub to form the dam  330 . An area above the dam  330  is referred to as a sealing chamber  340 . The dam provides a means of blocking the un-gelled expanding compound  342  from leaking out of the sealing chamber. Care should be taken to ensure no shreds of fiber are left clinging to the side wall of the sealing chamber or to the conductors. Such shreds when imbedded in the sealing compound may form leakage channels. The completed dam should be even with an internal bushing  350 , also referred to as a conduit stop. For the horizontal fitting, no dams are required, but may be used if desired. 
         [0022]      FIG. 4  shows vertical fitting  310  with a plug  410  installed quickly after the compound is inserted, and it shows the compound in a fully expanded state at  420 . The compound works its way between conductors as it expands to ensure that none are touching each other when the compound is fully expanded. An explosion proof seal is formed. The term “explosion proof” refers to normally encountered explosive environments. It is not meant to cover environments not normally anticipated in environments where such fittings are utilized.