Abstract:
A connection is provided whereby a first tube, which may be bent into an elbow, has at least one end flow drilled. During the flow drilling process the first end is shortened, reduced in thickness, and most importantly, the inner diameter is increased to accept a second tube. Before connecting the second tube, the first end is preferably tapped with threads which can receive a nut and the nut captures an end of the second tube, preferably entrapping one of at least one bead and a ferrel to provide a connection.

Description:
CLAIM OF PRIORITY 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/534,069 filed Sep. 13, 2011, incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a connection for connecting tubes or pipes together in fluid tight engagement, such as for special applications, and more specifically to connecting an aluminum pipe to a steel elbow which provides gas internally to a broiler element in a gas operated stove. 
     BACKGROUND OF THE INVENTION 
     Elbows for use in gas ovens with broiler elements have been used for a number of years. Some competitors provide brass castings for this part. Others, such as the applicant, provided stainless steel elbows which required numerous welding steps to form up components to be able to cooperate with an air shutter at one end internal to the oven as well as an aluminum pipe providing fuel to the elbow external to the heated space in the oven. Since many gas oven with broil elements are self-cleaning ovens capable of reaching temperatures exceeding 800-900 degrees Fahrenheit, the aluminum piping external to the oven is not normally located in the high temperature heated space. Furthermore, harsh cleaning chemicals are also not wisely applied to aluminum. 
     Machining and/or forming these prior art parts has been proven to be relatively expensive. In the prior art, a welded fitting is provided and fitting up with an outer thread fitting. This machined fitting provided male external threads which cooperated with internal female threads connected to a connector aluminum tube such as with a compression nut and sleeve or a ferrule style connection arrangement. The fitting was welded to the end of a steel tube forming the elbow. On the other end, external threads were machined into the outer surface of the pipe elbow to cooperate with internal threads of a brass orifice. 
     A need exists to find at least a simplified connector construction and/or elbow construction for the market place. 
     SUMMARY OF THE INVENTION 
     It is a present object of the present invention to provide an improved elbow and/or connection system for joining pipes or tubes together. 
     It is an object of the present invention to provide an improved connection such as from stainless steel to aluminum with a fluid tight connection. 
     It is a further object of many embodiments of the present invention to provide an improved elbow connection which provides improved connections connecting steel pipe to aluminum pipe at their respective ends in fluid tight engagement. 
     Accordingly, in accordance with the presently preferred embodiment of the present invention, an elbow connection commonly utilized with gas ovens such as those providing a broiler element is provided. In these style ovens, it is common to use aluminum tubing external to the oven chamber to direct the flow of gas received from a gas source to the stove whether natural gas or propane. However, when entering the oven heated area, the temperatures and environment internal to the oven, such as a self-cleaning oven, could be rather hostile to aluminum and thus a transition to stainless steel (or brass as provided by competitors) often occurs. In order to provide a component which can withstand the higher temperatures and/or harsh corrosive environment possibly contributed to by cleaning chemicals often utilized in ovens, a new elbow is contemplated with at least one improved connection. 
     In order to make the connection with a new elbow at an external oven connection, a stainless steel tube of a constant diameter is preferably flow drilled in the present instance from having an outer diameter of about ⅜ of an inch to having an outer diameter of about 0.616 inches which is almost doubling the outer diameter. In order to accomplish this flow drill process, a rapidly rotating drill bit expands the material while the end is compressed. In making this end, a tube is compressed by 0.075 inches. As it expands, its wall thickness changes from about 0.065 inches to about 0.040 inches. The inner diameter at the end thus increases relative to the diameter of the untreated section of the pipe by roughly doubling as well. 
     Within this larger open end, internal threads are tapped into an interior wall. A compression nut provided about an external portion of an inserted aluminum tube with external threads cooperates with the internal threads of the elbow connector portion. Between the compression nut and the end of the inserted tube is at least one of a single external bead, multiple external beads such as double bead, or a ferrule such as a brass ferrule which can compress against the tapering internal walls of the expanded end as the nut is screwed into the internal threads of the larger opening end. 
     An intermediate portions of the elbow can be flanged to cooperate with a connection of the oven wall and the other end of the elbow can have internal threads which can cooperate with external threads on a nozzle orifice which is preferably spaced from a conical section of the nozzle orifice which can then compress against an end surface of the pipe or tubing once installed to form a fluid tight seal. The nozzle orifice can then be connected to an air shutter to provide air gas mix to the boiler burner located downstream. A bend normally occurs between the two ends. This elbow construction provides advantages of prior art constructions and is believed to require fewer machining steps and/or provides simpler machining efficiency and/or a likely higher quality control capability than other designs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The particular features and advantages of the invention as well as other objects will become apparent from the following description taken in connection with the accompanying drawings in which: 
         FIG. 1  shows an external side plan view of the presently preferred embodiment of the present invention; 
         FIG. 2  shows a side partially cut-away view showing the connection of the construction of  FIG. 1  to a cooperating tube; 
         FIG. 3  shows a side partially cut-away view showing a first alternatively preferred embodiment showing connection of  FIG. 1  to a cooperating tube; 
         FIG. 4  shows a cross-sectional view of the elbow of  FIG. 1  prior to connecting to an orifice; and 
         FIG. 5  shows a cross-sectional view of an orifice connected to a second end of the elbow as shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a first presently preferred embodiment of the present invention in the form of an elbow  10  such as an elbow tube as utilized with broiler burners in a gas stove. As discussed above, the elbows, such as elbow  10 , are utilized to transition from external to internal to the oven compartment particularly for self-cleaning ovens with broiler elements which can often reach temperatures of about 900 degrees Fahrenheit or more and also be subjected to harsh chemicals such as oven cleaner chemicals inside the oven. An aluminum element would not fare well in such an environment. 
     Accordingly, the preferred embodiment is preferably made of steel such as cold-rolled steel which has been treated such as with a chrome plating process or other appropriate pre-selected material. Other appropriate materials may be utilized with other embodiments. Elbow  10  is comprised of a tube  12  having a first  14  and a second end  16 . Between first and second ends  14 , 16 , there is normally a bend  18  such as an elbow bend as illustrated. Flange  21  is also normally provided with bores  15 , 17  shown in phantom to connect to an internal oven wall (not shown) or other connection location. 
     First and second segments  20 , 22  on either side of the bend  18  and/or flange  21 , if provided, can be provided as required by manufacturers to accommodate particular styles of oven equipment. Other segments could be provided and/or other design criteria accommodated with other embodiments. First segment  24  of first tube  12  preferably provides an outwardly flared segment extending from first portion  20  to a second segment  26 . Second segment  26  is preferably provided with internal threads  28  which can be tapped to provide an internally threaded second segment  26  after providing the outwardly flared first segment  24 . 
     Internal or inner surface  30  of outwardly flared first segment  24  preferably is at least relatively smooth if not deburred, if necessary, so as to be in a proper condition as will be described in further detail below. The applicant has manufactured the elbow  10  by taking a straight segment of stainless steel tubing, bending it to provide bend  18 , and utilizing a flow drill to compress and expand the first end  14  to provide the outwardly flared segment  24  as well as the second segment  26 . Second segment  26  may then be tapped to provide internal threads  28 . Second segment  26  may have a relatively consistent inner and/or outer diameter as shown or taper like first segment  24  for other embodiments. 
     In performing the flow drill process, the 0.065 thickness of first pipe wall portion  32  is transitioned to about a 0.040 thickness at second pipe wall portion  34 . Thus, a wall reduction of somewhere between about 25% to 50% occurs, and more thoroughly about ⅓ of the thickness of the wall decreases at least in some portion of a first segment  24 , and second segment. Furthermore, as this process occurs, the length is shortened at the first end  14  as first end  14  is compressed towards the second end  16  during the flow drilling process. A shortening of about 0.075 has been measured during this process. Outwardly second segment  26  may have a relatively constant internal diameter particularly after tapping, such as about 0.58 which stands in contrast to the inner diameter of about 0.25 of tube segments  20 , 22 . The inner diameter increases from roughly doubles and preferably increases the fact of somewhere between about 1.5 times the original inner diameter to about three times, and more preferably, about two times the inner diameter. After tapping second segment  26  can cooperate with a 7/16 external threads shown as nut threads  36  provided a nut  40 . One will note that nut  40  is identically shown in the various embodiments as is the construction of the first end  14 . Other nuts  40  could be provided with other embodiments. 
     The difference in the embodiments of  FIG. 2  and  FIG. 3  is that the connections for other connected tube  42 , 44  are slightly different. A relatively straight segment of the tube  44  is illustrated for a first connection. A ferrule  46  is shown provided towards the first end  48  and then as the compression nut  40  is directed by screwing its threads relative to the second segment  26  and outwardly flared section  24  to provide a fluid tight seal against the inner surface  30  of the first section  24 . The ferrule  46  is simultaneously compressed against the exterior surface  43  of the tube  44 . The first end  48  of the tube  44  may also contact the internal surface  30  of the second segment  26  to assist in providing a fluted tight seal  24  as well. 
     In the presently preferred embodiment of  FIG. 2 , one or more beads illustrated as first and second beads  60 , 62  can be provided toward a first end  64  of tube  42 . More or fewer beads  60 , 62  may be provided in other embodiments. In this construction, the first tube  42  effectively provided with a built in ferrule. As the compression nut  40  is tightened with threads  36  relative to threads  28 , at least one bead  62  is placed in contact with the inner surface  30  of the outwardly flared first section  24  and possibly in combination with the first end  64  contacting internal surface  30  to provide a fluid tight seal. Other beads such as first bead  60  could also contact inner surface  30 . In this embodiment, the only possible source of fluid leakage is past the external portion of first bead  62 . In the embodiment of  FIG. 3 , a leakage could occur along internal surface  70  of the ferrule  52  as well as along an external surface  72  of the ferrule  52 . Providing one or more beads such as  60 , 62  is a process discussed in various other patents other than that of the applicant such as U.S. Pat. No. 5,573,285 and others. 
     The second end  16  may be machined to provide inwardly directed threads  81  which can then cooperate with a screw in orifice  80 . Orifice  80  may have outwardly directed threads which can provide a situation where the second end  16  is internally tapped such as to provide 5/16 threads internal to the inner bore. Then, a cooperating orifice  80  such as shown in  FIG. 5  can be screwed therein with outwardly directed threads  82 . The inwardly directed threads  84  at the second end  16 . 
     In addition to having the outwardly directed threads  82 , the outwardly directed threads  82  are preferably spaced by channel  86  from first row conical section  88  which may begin radially at the termination of the threads  82  and can extend radially outwardly preferably at least a substantial portion of the thickness of the tube portion  22 , if not past tube portion  22  so that when the orifice  80  is screwed on to the second section  22 , the first conical section  88  effectively forms a seal at the second end  16  as shown in  FIGS. 1 and 5  to form a fluid tight seal. The flats  90  can cooperate with a wrench to provide the appropriate amount of torque. The orifice  80  provides a measured flow path to a air shutter (not shown) internal to an oven and to provide a fuel/gas mixture to an internal broiler element for use by a gas oven. 
     Numerous alterations of the structure herein disclosed will suggest themselves to those skilled in the art. However, it is to be understood that the present disclosure relates to the preferred embodiment of the invention which is for purposes of illustration only and not to be construed as a limitation of the invention. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims.