Abstract:
A fitting for tube and/or pipe includes two legs formed at a nominal included angle that is other than a right angle. An example would be a nominal included angle of about 2°±.5° from a right angle. A fitting is also provided that is drainable under the influence or force of gravity. Methods of forming such fittings are also provided including various combinations of steps of bending, cutting and welding.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/426,695, filed Nov. 15, 2002, the entire disclosure of which is fully incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     In industries that require high purity in fluid delivery systems, such as, for example, the biopharmaceutical and semiconductor industries, it is often a requirement that the fluid system be drainable. For example, a run of tubing may need to be joined to a flow control device such as a valve or other piece of tubing in such a manner that the tubing is non-horizontal, thereby allowing gravity to drain fluid from the tubing. Known tube fittings, for example, elbow fittings and T-fittings, have a nominal 90° angle between the centerlines of the tube legs. This right angle is typically held to tight manufacturing tolerances so that the end face is square and true for welding among other purposes. However, in order to join such a tube fitting to a non-horizontal tube that is angled (sloped) for drainability, it is known to miter cut the end of the fitting to produce an end face that extends at the desired angle (with respect to the horizontal centerline of the fitting end). However, the non-squared end face precludes the use of orbital welding equipment, which is commonly used for joining tube ends. Therefore, mitered tube ends must be manually welded, which increases cost and time and which lower repeatability of welds.  
         [0003]     Thus, there is a need for a fitting that can be used in a drainable fluid system such as one that has non-horizontal runs so as to drain under the influence of gravity, with a fitting that can be conveniently welded such as by orbital welding for example,  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention contemplates a fitting for tube and/or pipe conduits or other fluid components that is drainable under the influence or force of gravity so as to conveniently be installed in a drainable fluid system. In one embodiment, a fitting is provided that has two legs that form an included nominal angle between their centerlines other than a nominal right angle. In a specific embodiment the included nominal angle may be, for example, different from a right angle by two degrees ±.5 degrees. Since all known prior fittings are manufactured to a nominal right angle within conventional tolerances, the invention contemplates a drainable fitting such as, for example, a fitting that forms an included nominal angle other than a right angle that otherwise would be formed within conventional manufacturing tolerances.  
         [0005]     In accordance with another aspect of the invention, a fitting is provided that has two legs that form an included nominal angle other than a right angle and wherein one or more of the end faces of the legs are generally normal or square to a central axis of the leg. This arrangement facilitates conventional welding techniques such as orbital welding for fittings that are not right angle fittings.  
         [0006]     The invention also contemplates various techniques for manufacturing or forming fittings of the aforementioned variety. The invention is applicable to tube as well as pipe.  
         [0007]     These and other aspects and advantages of the invention will be readily appreciated and understood by those skilled in the art based on the following description of the exemplary embodiments in view of the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The foregoing and other features of the present invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the following description of the invention with reference to the accompanying drawings, in which:  
         [0009]      FIG. 1  is an illustration of a fitting in accordance with the invention, shown connected with a schematically illustrated fluid system portion;  
         [0010]      FIG. 2  is an enlarged view, partially in section, of the fitting of  FIG. 1 ;  
         [0011]      FIG. 3  is a view similar to  FIG. 2  of a fitting with the same bend angle as the fitting of  FIG. 1  but constructed in accordance with a second embodiment of the invention;  
         [0012]      FIG. 4  is a view similar to  FIG. 2  of a fitting with a different bend angle than the bend angle of the fitting of  FIG. 1 ;  
         [0013]      FIG. 5  is a view similar to  FIG. 3  of a fitting with the same bend angle as the fitting of  FIG. 4  but constructed in accordance with the second embodiment of the invention;  
         [0014]      FIG. 6  is an illustration of a portion of a fluid system including several fittings of the present invention;  
         [0015]      FIG. 7  is an illustration of a portion of another fluid system including several fittings of the present invention;  
         [0016]      FIG. 8  is an illustration of a portion of another fluid system including one fitting of the present invention; and  
         [0017]      FIG. 9  is an illustration of a portion of still another fluid system including one fitting of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     The invention provides a fitting for conduits such as tube and pipe that is drainable under the influence or force of gravity, so as to be conveniently installable in a drainable fluid system. Still further the invention provides a drainable fitting that can be welded by convenient techniques such as orbital welding. While the exemplary embodiments described herein relate to described nominal angles and exemplary tolerances, those skilled in the art will readily appreciate that the invention may be used for a fitting with a wide variety of included nominal angles and desired tolerances but that differ from a nominal right angle otherwise manufactured within conventional manufacturing tolerances. As used herein the term conduit includes tube and pipe.  
         [0019]     By nominal herein is meant the desired or preferred value, in this case of the included angle.  
         [0020]      FIG. 1  illustrates schematically a fitting  10  in accordance with the present invention. The fitting  10  is illustrated as being disposed below a fluid component or system portion indicated schematically at  12 . The component or portion  12  may be a valve, a container, a conduit or any portion of a fluid system. Together, the fitting  10  and the component  12  form a drainable assembly  14 . As described below in detail, the fitting  10  has a leg portion that extends at an angle to the horizontal so that a conduit section  16  connected with the fitting can drain the component or portion  12 , as well as the fitting  10  itself. Although the invention finds particular application for drainable fluid systems, the invention may also be used in fluid systems where drainability is not required, for example, a system having difficult plumbing angles.  
         [0021]     The fitting  10 , shown in more detail in  FIG. 2 , is illustrated as being an elbow type tube fitting. The present invention is applicable to pipe fittings as well as to tube fittings. The present invention is also applicable to fittings other than the elbow fitting shown in  FIGS. 1 and 2 . Thus, the term “fitting” as used herein is intended to be broad in scope, encompassing all types of tube fittings and pipe fittings, for example and not by way of limitation, T-fittings, as well as tube stubs on fluid flow equipment.  
         [0022]     Fittings in accordance with the present invention may be made from differing materials and are not limited to any particular material. For example, one preferred material is stainless steel. Other metals are suitable. Plastics may also be used.  
         [0023]     The fitting  10  ( FIG. 2 ) includes a wall  20  having coextending, inner and outer major side surfaces  22  and  24 . The inner surface  22  defines a fluid flow passage  26  that extends through the fitting  10 .  
         [0024]     The fitting  10  has a first straight section  28  and a second straight section  30  that are joined by a bend section  32  which in this example is a curve. The geometric contour of the fitting is exemplary and may be of any suitable form, fit and function for a specific application. The first straight section  28  terminates in a first end portion  34  of the fitting  10  that has a first end face  36 . The first end face  36  extends generally perpendicular to the centerline C 1  of the first straight section  28  of the fitting  10 .  
         [0025]     The second straight section  30  terminates in a second end portion  38  of the fitting  10  that has a second end face  40 . The second end face  40  extends generally perpendicular to the centerline C 2  of the second straight section  30  of the fitting  10 . The inner and outer surfaces  22  and  24  of the fitting  10  extend between and terminate at the first and second end faces  36  and  40 .  
         [0026]     In accordance with a feature of the invention, the curved section  32  of the fitting  10  has an angular extent or bend to form an included angle (designated “alpha” in  FIG. 2 ) that is nominally other than a right angle or ninety degrees. Prior art fittings are manufactured to a nominal ninety degrees within a conventional manufacturing tolerance. Thus, the invention contemplates a fitting having leg portions with an included nominal angle between their centerlines other than ninety degrees outside conventional manufacturing tolerances of a nominal ninety degree fitting. In particular, the curved section  32  has a nominal included angle that is selected to enable the fitting  10  to be self-draining (drainable), and to enable a conduit or other fluid flow device that is connected with the fitting (for example, the added conduit section  16  shown in  FIG. 1 ) to be drainable or self-draining under the influence or force of gravity although the exemplary embodiments herein illustrate the included angle as being formed by a curved portion or bend in the flow path, those skilled in the art will readily appreciate that the invention may be used with a wide variety of flow path geometry. Thus, the invention is directed to the use of an included angle other than a right angle and not limited by the geometry or profile of the flow path.  
         [0027]     In the illustrated embodiment, the curved section  32  has a nominal included angle of 88°. The fitting  10  is made with a manufacturing tolerance, for the included angle, of plus or minus one half degree, for example, but other tolerances may be used. Thus, an exemplary angular range of the included angle for the fitting  10 , may be 88°±½°. The invention contemplates nominal included angles greater than 90° and less than 90° or both depending on the particular application.  
         [0028]     Because the nominal included angle of the fitting  10  is other than 90°, the second straight section  30  of the fitting does not extend horizontally when the first straight section  28  is vertical, as shown for example in  FIG. 1 . Rather, the second straight section  30  of the fitting  10  extends (slopes) downward from the horizontal, as it extends away from the curved section  32 , when the first straight section  28  is vertical. As a result, the added section  16  ( FIG. 1 ) extends (slopes) downward from the horizontal, as it extends away from the fitting  10 , as shown in  FIG. 1 .  
         [0029]     Because the added section  16  extends downward from the horizontal, as it extends away from the fitting  10 , the added section is drainable. That is, fluid such as a liquid which flows into the section  16  from the fitting  10  has a tendency to flow downhill, away from the fitting, thus draining the fitting.  
         [0030]     In addition, the fitting  10  itself is drainable, or self-draining. That is, fluid such as a liquid which flows into the fitting  10  from a fluid device  12  has a tendency to flow downhill, out of the second straight section  38  of the fitting, and out of the fitting altogether, thus draining the fitting. A fluid droplet, placed into or flowing along the interior passage  26  of the fitting, flows to a plurality of successively lower surface points along the inner surface  22 , under the force of gravity, until leaving the fitting. The invention thus provides a fitting that is drainable and therefore usable in drainable fluid systems, but those skilled in the art will understand that a fluid component can meet the definition or requirement of drainability without requiring that the flow surfaces be completely clean or devoid of all fluid when the component is drained. Especially with shallow included angles of two degrees from normal for example, surface tension alone may prevent complete elimination of fluid from a fitting.  
         [0031]     Fittings made in accordance with the present invention, thus have an intentional deviation from a right angle in the curved section of the fitting. This guarantees that a fitting that falls anywhere within its manufacturing tolerance range, will drain.  
         [0032]     In contrast, a prior art fitting discussed above is made to a nominal angle of 90° in accordance for example with ASME specification BPE-2002. Thus, if a prior art fitting is, for example, used in place of the fitting  10  in the assembly of  FIG. 1 , the lower end of the fitting might extend horizontally, or might slope downward at an angle of up to one degree below horizontal, or might even slope upward at an angle of up to one degree above horizontal. Therefore, the prior art fitting is not per se usable if it is required that the fitting be drainable or that a fluid device connected with the lower end of the fitting be drainable.  
         [0033]     In accordance with another feature of the invention, the fitting  10  is easily connected with the section  16  by a preferred but not required orbital welding technique. Specifically, the second end face  40  of the fitting  10  extends generally at a right angle to the centerline of the second straight section  30  of the fitting. When the fitting  10  is installed with the first straight section  34  vertical, the centerline of the second straight section  30  of the fitting extends at an angle of 88° to the first straight section, that is, at an angle of two degrees down from the horizontal. Because the second end face  40  of the fitting  10  extends at a right angle to the centerline of the second straight section  30  of the fitting, the second end face of the fitting thus extends at an angle of two degrees from the vertical. Accordingly, there is no bend or interruption in the cylindrical nature of the joined pieces and orbital welding can be conveniently used. This aids in welding a section to the fitting  10  when the section is to be drainable, that is, sloped downward.  
         [0034]     As an example, the added section  16  shown in  FIG. 1  has an end face  44 , for connection with the fitting  10 , that extends at a right angle to the centerline of the pipe section. Therefore, when the end face  44  of the added section  16  is secured to the second end face  40  of the fitting  10 , the section extends parallel to (and is concentric with) the second straight section  30  of the fitting. The cylindrical outer surface of the second straight section  30  of the fitting  10  is therefore concentric with, and extends parallel to, the cylindrical outer surface of the section  16 . As a result, the two pieces  10  and  16  can be orbitally welded.  
         [0035]     For prior art right angle fittings, this is not possible if, for example, the tube section needs to extend two degrees off horizontal from the fitting, but the fitting straight section is horizontal—a proper weld can not be guaranteed. Therefore, having the second straight section  28  of the fitting  10  extend at a non-right angle to the horizontal not only provides a self-draining capability for the fitting, but also enables use of the desired automatic orbital welding process and equipment to connect the fitting in its fluid system. Where squareness of ends is required to allow for orbital welding, the present invention provides fittings that meet such a requirement.  
         [0036]     The fitting  10  that is shown in  FIGS. 1 and 2  is manufactured with the desired nominal included angle of 88° plus or minus one half degree. Thus manufacturing process can be used on any size tube or pipe, from as small as one half inch or less to as large as 4 inches or more. As discussed below, certain manufacturing considerations arise which might limit the applicability of this manufacturing process and suggest that other manufacturing processes, as also described below, are more suitable for certain tube and pipe sizes.  
         [0037]     The preferred first step in manufacturing the fitting  10  with this process is to take a relatively long piece of stock of the desired diameter, for example, one inch. The stock may be, for example, a twenty-foot length of tube stock. This piece is then compound bent to form a plurality of fittings  10  each having the desired bend angle, all interconnected as one piece in a generally serpentine form. The individual fittings  10  are then cut from the stock piece and finished.  
         [0038]     The finishing process may include cutting the straight sections  28  and  30  of the fittings  10  to the proper length; ensuring that the end faces  36  and  40  are square; and polishing the inner surface  22  of the fitting. The finishing process may also include treating the fitting  10  to remove stresses in the wall  20  that may have built up from the bending process. This treating may take the form of heat treating, for example, annealing. The annealing step can relieve internal stresses arising from bending. Heat treating might not be needed for some pieces, for example, smaller diameter fittings.  
         [0039]     An alternative manufacturing process may be used, for example, if the needed volume of fittings is not sufficient to warrant investing in the machinery needed to perform the preferred compound bending process. Two such alternative processes are described below.  
         [0040]     The first such process is preferably used with relatively small conduit sizes, for example, tubing sizes up to about one inch. This process starts with a fitting that is already manufactured with a nominal right angle (90°) curved section between two straight sections. The fitting is then bent to the desired off angle, for example, 88°±½°. The inner surface of the fitting is preferably polished, either before the bending step, or both before and after the bending step. The fitting can, if desired, be annealed to relieve stresses.  
         [0041]     The second alternative process is preferably used with relatively large conduit sizes, for example, tubing sizes over two inches. The fitting  50  shown in  FIG. 3  is an example of a fitting made by this process.  
         [0042]     The fitting illustrated in  FIG. 3  has a curved section  52  located between two straight sections  54  and  56 . The curved section  52  has a nominal bend angle alpha with a measurement of 88°±½°. The first straight section  54  is welded on one end of the curved section  52 . The second straight section  56  is welded on the opposite end of the curved section  52 . The lengths of the two straight sections  54  and  56  are selected to ensure that the resulting fitting  50  has the proper overall dimensions between its end faces  58 .  
         [0043]     This process starts with a manufactured nominal right angle (90°) curved section. An end portion of the curved section of the fitting is then cut off the remainder. Enough of the curved section is cut off to ensure that the remaining part of the curved section has the desired nominal included angle. For example, two degrees may be cut from a 90° curved section to provide a nominal 88° curved section. First and second straight sections are then secured to opposite ends of the curved section, preferably by welding, to provide a fitting that has the proper overall dimensions.  
         [0044]     In the resulting fitting  50 , the two straight sections  54  and  56  extend at a nominal angle to each other than is other than a nominal right angle. In the illustrated embodiment, the two straight sections  54  and  56  extend at a nominal angle of 88°±½° to each other.  
         [0045]     Another possible manufacturing process for these larger sized fittings involves starting with a manufactured right angle (90°) fitting including a curved section and two straight sections. One straight section and a small portion of the curved section of the fitting are then cut off the remainder. Enough of the curved section is cut off to ensure that the remaining part of the curved section has the desired angular extent. For example, two degrees may be cut from a 90° curved section to provide an 88° curved section. A new straight section is then secured to the cut end of the curved section, preferably by welding, to provide a fitting that has the proper overall dimensions.  
         [0046]      FIG. 4  illustrates another fitting  60  that is constructed in accordance with the present invention. The fitting  60  has a curved section  62  that extends between two straight sections  64  and  66 . The fitting  60  is manufactured with a nominal included angle, denoted “alpha”, that is other than ninety degrees. Specifically, the fitting  60  has a nominal included angle of 92°±½°. The fitting  60  is usable in fluid systems in a manner as described below with reference to  FIGS. 6-8 , for example.  
         [0047]     The fitting  60  is a one-piece fitting, as is the fitting  10  ( FIGS. 1 and 2 ). The one-piece fitting  60  may be manufactured with any of the processes described above that are used for manufacturing one-piece fittings.  
         [0048]      FIG. 5  illustrates a similar but multi-piece fitting  70  that is constructed in accordance with the present invention. The fitting  70  has a curved section  72  that extends between two straight sections  74  and  76 . The fitting  70  has a nominal included angle, denoted “alpha”, that is other than ninety degrees. Specifically, the fitting  70  is manufactured with a bend angle of 92°±½°. The fitting  70  is usable in fluid systems in a manner as described below with reference to  FIGS. 6-8 , for example. The fitting  70  is a two-piece fitting, as is the fitting  50  ( FIG. 3 ). The fitting  70  may be manufactured with any of the processes described above that are used for manufacturing two-piece fittings.  
         [0049]      FIG. 6  illustrates a portion of a fluid system  80  that provides an example of use of fittings in accordance with the present invention. In the fluid system  80 , liquid flows generally in a right to left direction as viewed in  FIG. 6 , as indicated by the arrow  82 .  
         [0050]     The system  80  includes a conduit that includes two co-axial sections  84  and  86 . The sections  84  and  86  are sloped downward so that their centerlines  88  and  90 , respectively, extend at an angle of about 92 degrees to the vertical, or two degrees downward from horizontal (horizontal is indicated by the line  92 ). The two sections  84  and  86  are joined by a drainage section  94  as described below. This configuration allows the sections  84  and  86  to be run in a ceiling, hidden from view, with the drainage section  94  dropping down into the room below—a typical setup in a pharmaceutical manufacturing plant.  
         [0051]     The drainage section  94  of the system  10  includes an 88° fitting  100  that is connected to the outlet (downhill) end  102  of the pipe section  84 . The lower end  104  of the 88° fitting  100  extends vertically. A 92° fitting  106  is connected to the inlet (uphill) end  108  of the section  86 . The lower end  110  of the 92° fitting  106  extends vertically.  
         [0052]     Because the lower ends  104  and  110  of the two fittings  100  and  106 , respectively, are vertical, they can easily be connected by nominal 90° elbows  112  and  114  and a valve  116 . The valve  116  can be used for tapping the flow of liquid through the section  88  to obtain a sample, or for use in processing. The valve  116  can alternatively be used for draining the system  80 . Liquid in the system  80  that is upstream of the valve  116 , in the fitting  100  and in the section  84 , drains downhill into the valve and can be let out through the valve. Liquid in the system that is between the valve  116  and the downstream (upper) end of the 92° fitting  106  also drains downhill into the valve and can be let out through the valve. Other liquid in the system portion  80  shown in  FIG. 6  drains down the section  86 .  
         [0053]      FIG. 7  illustrates a portion of another fluid system  120  that provides an example of use of fittings in accordance with the present invention. In the fluid system  120 , liquid flows in a right to left direction as viewed in  FIG. 7 , as indicated by the arrow  122 .  
         [0054]     The system  120  includes a section  124  that is sloped downward at two degrees below the horizontal. An 88° fitting  126  is connected to the outlet end of the pipe section  124  to provide for connection of a vertical drop  128 . From the lower end of the vertical drop  128 , another 88° fitting  130  is connected to another section  132  that again is sloped downward at two degrees below the horizontal. Thus, the two nominal 88° fittings  126  and  130  can be used to provide for a vertical drop between two sloped sections.  
         [0055]     The inlet end  134  of a nominal 92° fitting  136  is connected to the outlet end of the sloped section  132 . The outlet end  138  of the 92° fitting  136  extends vertically. Because the upper (outlet) end  138  of the fitting  136  is vertical, it can easily be connected to a pump  140  having a standard vertically mounted inlet  142 . Alternatively, another vertically extending system component can be connected with the outlet end  138  of the 92° fitting  136 . Thus, the nominal 92° fitting  136  can be used to provide a vertical outlet from a sloped pipe section.  
         [0056]      FIG. 8  illustrates a portion of a fluid system  150  that provides another example of use of fittings in accordance with the present invention. The system  150  includes a fitting  152 . The fitting  152  has a generally Y-shaped configuration including a lower leg  154  and two upper legs  156  and  158 . The upper legs  156  and  158  extend transverse to the lower leg  154 . At least one of the upper legs  156  and  158  extends at a nominal angle, other than a right angle, to the lower leg  154 . In the illustrated embodiment, both of the upper legs  156  and  158  extend at a nominal angle other than a right angle to the lower leg  154 . Specifically, both of the upper legs  156  and  158  extend at a nominal angle of 92° to the center axis of the lower leg  154 . As a result, both of the upper legs  156  and  158  drain into the lower leg  154  when the lower leg is mounted vertically. The fitting  152  is useful in draining two tube sections or pipe sections (not shown) that are attached to the upper legs  154  and  156  and that slope downward at an angle of two degrees below the horizontal.  
         [0057]      FIG. 9  illustrates a portion of a fluid system  160  that provides another example of use of fittings in accordance with the present invention. The system  160  includes a fitting  162 . The fitting  162  has an upside down generally T-shaped configuration including an upper leg  164  and two lower legs  166  and  168 . The lower legs  166  extend transverse to the upper leg  164 . At least one of the lower legs  166  and  168  extends at an angle, other than a right angle, to the upper leg  164 . In the illustrated embodiment, both of the lower legs  166  and  168  extend at an angle other than a right angle to the upper leg  164 . Specifically, one of the lower legs  166  extends at an angle of 88° to the upper leg  164 , and the other lower leg  168  extends at an angle of 92° to the upper leg. As a result, the lower leg  168  drains both the upper leg  164  and the other lower leg  166  when the upper leg is mounted vertically. The fitting  162  is useful in draining a device or other system portion (not shown) attached to the upper leg  164 , into a line that slopes downward and that includes, in the illustrated embodiment, the two lower legs  166  and  168 .  
         [0058]     It is important to note that while the exemplary embodiments herein are described in terms of exemplary nominal values and ranges of the included angle, these are not intended to be limiting in scope, other than being different from a nominal right angle and conventional tolerances. For example, it is contemplated that a nominal included angle of 87°±0.4, or 88.5±0.5 or 91.5±0.5 and so on are within the scope of the invention as is the exemplary range of 88°±0.5. Thus, one skilled in the art may select any desired nominal value and tolerance range other than a nominal 90° or right angle to assure drainability of the fitting.  
         [0059]     From the above description of the invention, those skilled in the art will perceive improvements, changes, and modifications in the invention. Such improvements, changes, and modifications within the skill of the art are intended to be included within the scope of the appended claims.