Abstract:
A conduit modifier may be used to corrugate at least a portion of a conduit. The conduit modifier may include at least a first plurality of rollers arranged in a first pattern around a passageway. The first plurality of rollers may form ridges and grooves lengthwise along a conduit passing through the passageway. A second plurality of rollers arranged in a second pattern around the passageway may compress ridges formed by the first set of rollers. The ridges may be formed such that a distance from a central axis of the conduit to a highest portion of an outer surface of a ridge is substantially equal to a distance from the central axis of the conduit to an outer surface of the un-corrugated portion of the conduit. The corrugated portion of the modified conduit may be expandable.

Description:
BACKGROUND  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to conduits. The present invention generally relates to a conduit having a corrugated portion with a distance from a center of the conduit to a highest portion of a ridge that is substantially the same as the radius of an un-corrugated portion of the conduit. The present invention also generally relates to an apparatus and method for forming a corrugated conduit having a corrugated portion and an un-corrugated portion.  
           [0003]    2. Description of Related Art  
           [0004]    The use of conduits, such as tubes and pipe, is well known. For example, elongated hollow tubes may be used as heat exchange tubes. The use of tubes in heat exchangers is disclosed in various U.S. patents, including U.S. Pat. No. 2,365,688 to Dewey; U.S. Pat. No. 2,342,117 to Brown et al.; U.S. Pat. No. 2,499,901 to Brown; U.S. Pat. No. 2,797,554 to Donovan; and U.S. Pat. No. 4,162,702 to Andersson, all of which are incorporated by reference as if fully set forth herein.  
           [0005]    In some applications, such as tube-in-shell type heat exchangers, tubes having a non-uniform outer surface have been proposed. For example, in U.S. Pat. Nos. 5,251,693 and 5,311,661 to Zifferer, both of which are incorporated by reference as if fully set forth herein, a heat exchange tube having a portion that includes corrugations is described. U.S. Pat. No. 4,377,083 to Shepherd; U.S. Pat. No. 4,514,997 to Zifferer; U.S. Pat. No. 2,110,965 to Singer; U.S. Pat. No. 2,378,729 to Schmidt; and U.S. Pat. No. 4,383,429 to Ceccacci, all of which are incorporated by reference as if fully set forth herein, also describe modifications of cross-sectional shape and/or area of conduits. U.S. Pat. No. 5,016,806 to Yapp et al., which is incorporated by reference as if fully set forth herein, describes the use of rollers to impart a desired shape to a tubular member.  
           [0006]    Conduits may be formed of many different materials. Some conduits may be made of materials that are relatively soft (e.g., copper or aluminum). Wall thickness of some conduits may be relatively thin. A conduit made of a relatively soft material and/or a conduit having a relatively thin wall thickness may be corrugated using blades to press indentions in the conduit. Some conduits may be made of relative hard materials (e.g., carbon steel, stainless steel, titanium). Some conduits may have relatively a relative large wall thickness. The use of blades to form a corrugated conduit from a relatively hard material and/or from a conduit having a relatively large wall thickness may be difficult.  
           [0007]    A pointing device may be used to form a conduit with a reduced diameter end. U.S. Pat. No. 5,311,661 to Zifferer, which is incorporated by reference as if fully set forth herein, describes a pointing device for forming a reduced diameter end portion in a conduit.  
         SUMMARY  
         [0008]    A conduit modifier may be used to form corrugations in a portion of a conduit so that the conduit has a corrugated portion and an un-corrugated portion. In an embodiment, a width of the corrugated portion of the conduit may be larger than a diameter of an un-corrugated portion of the conduit. In an embodiment, a width of the corrugated portion of the conduit may be substantially the same as the diameter of an un-corrugated portion of the conduit. The conduit may be made of a metal, metal alloy, or polymer. In some embodiments, the conduit may be made of a relatively hard metal. For example, the conduit may have a hardness equal or greater than the hardness of carbon steel. In other embodiments, the conduit may be made of a softer material (e.g., copper or aluminum). A conduit to be corrugated may have a diameter from about {fraction (1/2)} inch to 12 inches or more. In some embodiments, the conduit may have a relatively large wall thickness. For example, the conduit may be a schedule  40  pipe or heavier gage pipe. In other embodiments, the conduit may have a relatively thin wall thickness.  
           [0009]    In some embodiments, a conduit modifier may process a conduit that has at least one pointed end. A pointed end of a conduit may include a first portion having a first diameter, a tapered portion, and a second portion having a second diameter. The first diameter is smaller than the second diameter. A pointing device may be used to point an end of the conduit. In some embodiments, both ends of a conduit are pointed.  
           [0010]    A pointing device may include a die having a frustro-conical surface that ends in an opening having a desired diameter. An end of the conduit may be pressed into the die until the end emerges through the opening. The portion of the conduit pushed through the opening may have a diameter that is smaller than the original diameter of the conduit. The frustro-conical section of the die may form a tapered section in the conduit. The portion of the conduit that passed through the opening of the die and the tapered portion of the conduit may have a larger wall thickness than other portions of the conduit.  
           [0011]    A conduit modifier may include a first set of rollers arranged around a central axis of a passageway through the conduit modifier at a selected distance from the central axis of the passageway. The selected distance may allow a first portion of a pointed tube to pass through the passageway without contacting the rollers. The selected distance may be sufficient to allow the rollers to contact a tapered portion of a conduit. The first set of rollers may form a corrugated portion of conduit by forming indentions in the conduit. The rollers may form a series of ridges and grooves in the conduit. In some embodiments, each roller of the first set of rollers may have a convex shape.  
           [0012]    In some conduit modifier embodiments, the conduit modifier may include a second set of rollers. The second set of rollers may be staggered relative to the first set of rollers so that the second set of rollers contacts ridges formed by the first set of rollers. The second set of rollers may be arranged around the central axis at a selected distance from the central axis so that the rollers allow passage of a first portion of a conduit through the rollers. The rollers may contact a tapered portion of the conduit. The staggered relation of the second rollers to the first rollers may allow the second rollers to press ridges and grooves formed by the first set of rollers into the conduit. The second set of rollers may allow the formation of a conduit having a corrugated portion with a width that is substantially the same as the diameter of a first portion of the conduit. In some embodiments, each roller of the second set of rollers may have a concave shape.  
           [0013]    Rollers may be supported in roller holders. The roller holders may include bearings that allow for rotation of the rollers. The rollers may be made of a material harder than the material of the conduit. The use of bearings and rollers may allow for the formation of corrugations in conduits without the need to have rollers formed of very hard and expensive materials (e.g., tungsten carbide). The use of rollers may allow for the formation of a corrugated conduit in a short period of time.  
           [0014]    A method of modifying a conduit may include corrugating a portion of the conduit with a first plurality of rollers in a conduit modifier. Lengthwise ridges formed by corrugating the conduit with the first plurality of rollers may then be at least partially compressed with a second plurality of rollers, such that a distance from a central axis of the conduit to a high point of a ridge is reduced. Reducing the ridges may also move low points of grooves formed in the conduit towards the central axis of the conduit. In some embodiments, a distance from a central axis of the conduit to a high point of a ridge may be substantially the same as a radius of anun-corrugated end portion of the conduit.  
           [0015]    Modifying a conduit may include inserting a first end portion of a conduit into a first end of a passageway of a conduit modifier. The conduit modifier may include a first plurality of rollers surrounding a first portion of the passageway and a second plurality of rollers surrounding an adjacent portion of the passageway. Relative motion of the first end portion of the conduit and the conduit modifier may be achieved such that the first plurality of rollers engages the conduit in the first portion of the passageway. As the first plurality of rollers engages an angled or middle portion of the conduit, at least two sets of alternating grooves and ridges may be formed lengthwise along an outer surface of the conduit. The second plurality of rollers may engage the ridges formed by the first plurality of rollers upon continued relative motion of the conduit and the conduit modifier. As the ridges are engaged by rollers in the second plurality of rollers, the ridges, and the grooves between the ridges, may be pushed radially inwards.  
           [0016]    A system for modifying a conduit may include a pointing device and a conduit modifier. The pointing device may be used to form at least one pointed or reduced diameter end of a conduit. The conduit modifier may be used to form alternating ridges and grooves lengthwise along an outer surface of a pointed conduit. The conduit modifier may also at least partially compress the ridges so that a distance from a central axis of the conduit to a high point of a ridge is substantially equal to an outer diameter of a pointed end of the conduit. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    Advantages of the present invention will become apparent to those skilled in the art with the benefit of the following detailed description of embodiments and upon reference to the accompanying drawings in which:  
         [0018]    [0018]FIG. 1 shows a perspective view of an unmodified conduit.  
         [0019]    [0019]FIG. 2 depicts a conduit with reduced diameter end portions.  
         [0020]    [0020]FIG. 3 depicts an embodiment of a corrugated conduit.  
         [0021]    [0021]FIG. 4 depicts a cross section of a corrugated conduit embodiment taken substantially along line  4 - 4  of FIG. 3.  
         [0022]    [0022]FIG. 5 depicts an embodiment of a corrugated conduit.  
         [0023]    [0023]FIG. 6 depicts a cross section of a corrugated conduit embodiment taken substantially along line  6 - 6  of FIG. 5.  
         [0024]    [0024]FIG. 7 depicts a perspective view of an embodiment of a pointing device used to reduce an outer diameter of at least one end portion of a conduit.  
         [0025]    [0025]FIG. 8 depicts a cross-sectional view of an embodiment of a point reduction die.  
         [0026]    [0026]FIG. 9 depicts a perspective view of an embodiment of a conduit modifier having a single set of rollers.  
         [0027]    [0027]FIG. 10 depicts a perspective view of an embodiment of a conduit modifier having two sets of rollers.  
         [0028]    [0028]FIG. 11 depicts an end view of an embodiment of a conduit modifier having two sets of rollers.  
         [0029]    [0029]FIG. 12 depicts an embodiment of a roller for a conduit modifier.  
         [0030]    [0030]FIG. 13 depicts an embodiment of a roller for a conduit modifier.  
         [0031]    [0031]FIG. 14 depicts a cross-sectional representation of a conduit modifier taken substantially along line  14 - 14  of FIG. 11.  
         [0032]    [0032]FIG. 15 depicts a perspective view of a conduit modifier during formation of a corrugated conduit. 
     
    
       [0033]    While the invention may be susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. The drawings may not be to scale. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but to the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF EMBODIMENTS  
       [0034]    [0034]FIG. 1 depicts an embodiment of conduit  20 . Conduit  20  may be made of metal, metal alloy, or polymer. In some embodiments, the conduit may be made of a relatively hard metal. For example, conduit  20  may have a hardness equal or greater than the hardness of carbon steel. In some embodiments, conduit  20  may be formed of stainless steel, carbon steel, titanium, titanium alloys, or combinations thereof. In other embodiments, conduit  20  may be made of a softer material (e.g., copper, copper alloys, aluminum, or aluminum alloys). A length of conduit  20  may be chosen so that a corrugated conduit that is formed from conduit  20  has a desired length. In some embodiments, length of conduit  20  may about 40 feet. Shorter or longer lengths may be used to produce a corrugated conduit of a desired length.  
         [0035]    Conduit  20  may have thickness  22 . Thickness  22  of conduit  20  may be any desired thickness. In some embodiments, conduit  20  may be schedule  40  or heavier gage pipe. In other embodiments, the conduit may have a relatively thin wall thickness. For example, a conduit may be a 20 gage, 7 gage, or lighter gage pipe.  
         [0036]    Conduit  20  may have outer diameter  24 . Conduit  20  may have an initial outer diameter in a range from about {fraction (1/2)} inch to 12 inches or more. In an embodiment, a conduit has a nominal diameter of about 5 inches.  
         [0037]    A pointing device may be used to transform conduit  20  into a pointed conduit. A pointed conduit refers to a conduit with at least one end that has a smaller diameter than a diameter of a body of the conduit. FIG. 2 depicts a representation of pointed conduit  26  formed from conduit  20  of FIG. 1. Pointed conduit  26  may include body  28 , frustro-conical portions  30 , and end portions  32 . Outer diameter of body  28  may be the same as outer diameter of conduit  20 . End portions  32  may have outer diameters that are smaller than the outer diameter of body  28 . An outer diameter of a first end portion may be the same or different than an outer diameter of a second end portion. A length of a first end portion may be the same or different than a length of a second end portion. In some embodiments, a pointing device may be used to point only one end of a conduit. In an embodiment, outer diameter of end portions  32  may be about 3-6 inches (e.g., 4.25 inches) while outer diameter of body  28  may have a 4-8 inch (e.g., 5 inch) nominal diameter.  
         [0038]    A conduit may be corrugated. A corrugated conduit refers to a conduit having a number of indentions in a body of the conduit that form ridges and grooves in the conduit. Indentions in the conduit may change both an outer surface and an inner surface of the conduit. In some embodiments, grooves and ridges may be formed in a symmetrical pattern about a circumference of a conduit. In some embodiments, grooves and ridges may be formed in an asymmetric pattern about a circumference of a conduit. In some embodiments, grooves and ridges may be formed in a portion of the circumference of a conduit. Grooves and ridges may have shapes including, but not limited to, arcuate, semi-circular, rectangular, trapezoidal, or v-shapes. Certain grooves/ridges may have sizes and/or shapes that are different than the sizes and/or shapes of other grooves/ridges.  
         [0039]    [0039]FIG. 3 depicts an embodiment of corrugated conduit  34  formed from a pointed conduit similar to the pointed conduit depicted in FIG. 2. A conduit modifier used to form corrugated conduit  34  may have a single set of rollers. A “roller” is defined as a device that turns around an axis and in doing so can bend at least a portion of another piece, such as a conduit. Corrugated conduit  34  may include un-corrugated end portions  32 , ridges  36 , and grooves  38 . A “ridge” is defined as a raised strip on or in a piece, such as a conduit. FIG. 4 depicts a cross-sectional representation of corrugated conduit  34 . A distance from center  40  of corrugated conduit  34  to an outermost surface of a ridge of ridges  36  may be substantially the same distance as the radius to the outer surface of body  28  of pointed conduit  26 . In some embodiments, a distance from center  40  to a bottom of a groove of grooves  38  on an outer surface of corrugated conduit  34  may be substantially the same as the radius to the outer surface of end portion  32  of pointed conduit  26 .  
         [0040]    Ridges  36  and grooves  38  may have shapes including, but not limited to, arcuate, semi-circular, rectangular, trapezoidal, or v-shapes. In some embodiments, ridges  36  and grooves  38  may be evenly spaced around corrugated conduit  34 . In other embodiments, the spacing of grooves and ridges may be asymmetrical. The number of ridges  36  formed in conduit  34  may range from about 3 to about 20 ridges. In some embodiments, the number of ridges formed in a conduit may range from about 6 to about 10. In an embodiment, 8 ridges are formed in a conduit.  
         [0041]    [0041]FIG. 5 depicts an embodiment of corrugated conduit  34  formed from a pointed conduit similar to the pointed conduit depicted in FIG. 2. A conduit modifier used to form corrugated conduit  34  may have two or more sets of rollers. Corrugated conduit  34  may include un-corrugated end portions  32 , ridges  36 , and grooves  38 . FIG. 6 depicts a cross-sectional representation of corrugated conduit  34 . A distance from center  40  of corrugated conduit  34  to an outermost surface of a ridge of ridges  36  may be substantially the same distance as the radius to the outer surface of end portions  32 .  
         [0042]    Corrugating a conduit may result in a strong conduit that is more resistant to bending moments than an un-corrugated conduit used to form the corrugated conduit. A corrugated conduit may have an aesthetically pleasing shape. In some embodiments, a corrugated conduit may be used as a structural member. Corrugating a conduit may increase outer and inner surface areas of a conduit. Corrugations in a conduit may promote turbulent fluid flow in and/or around the conduit. Increased surface area and the promotion of turbulent flow may increase the desirability of using the conduit as a heat exchanger element. The conduit may be, but is not limited to being, a heat exchanger element of a co-current heat exchanger, a counter-current heat exchanger, or a baffled heat exchanger.  
         [0043]    In some embodiments, a corrugated conduit may be formed to serve as an expandable conduit. The corrugated conduit may be inserted into a tubular member to strengthen and/or seal the tubular member when the corrugated conduit is expanded in the tubular member. After inserting the corrugated conduit into the tubular member, the conduit may be hydraulically or otherwise expanded against walls of the tubular member. For example, conduits may be used to form linings in petroleum drill stems. Drill stems may have threaded ends to accommodate interconnections for deep hole drilling. The threaded ends may have an inner diameter smaller than an inner diameter of a middle portion of the drill stem. A corrugated conduit with ridges that are located a distance from a center of the conduit that is substantially the same as a radial distance of an un-corrugated portion of the conduit may facilitate insertion of the corrugated conduit into the drill stem. After insertion, the corrugated portion of the conduit may be expanded against the drill stem. In an embodiment, a corrugated conduit of extended length may be formed by coupling end portions of two or more corrugated conduits together. The extended corrugated conduit may be expanded hydraulically within the drill stem.  
         [0044]    A pointing device may be used to form pointed conduit  26  (shown in FIG. 2) from conduit  20  (shown in FIG. 1). FIG. 7 depicts an embodiment of pointing device  42  that may be used to form pointed conduit  26 . Pointing device  42  may include a pair of clamps  44 , point reduction dies  46 , and slidable die carriers  48 . In an embodiment, pointing device  42  may reduce an outer diameter of an end of conduit  20 . In another embodiment, pointing device  42  may simultaneously reduce outer diameters at both ends of conduit  20 . In some embodiments, a pointing device may be adjustable to accommodate conduits of differing lengths and diameters.  
         [0045]    Conduit  20  may be secured in clamps  44 . After conduit  20  is secured in clamps  44 , slidable die carriers  48  may be actuated to engage respective point reduction dies  46  with ends of conduit  20 . A drive system used to move die carriers  48  and/or conduit  20  may be a hydraulic drive system.  
         [0046]    [0046]FIG. 8 depicts an embodiment of reduction die  46  of a pointing device. Reduction die  46  may include frustro-conical section  50  and cylindrical section  52 . A wide end of frustro-conical section  50  may have a diameter that allows for insertion of a conduit that is to be pointed. As the conduit is forced into reduction die  46 , the diameter of the conduit may be reduced to a diameter of cylindrical section  52 . After a sufficient length of small diameter section of conduit has been formed, a force used to push the conduit into reduction die  46  may be removed, and the reduction die may be separated from formed pointed conduit  26 . Frustro-conical section  50  of reduction die  46  may form frustro-conical portion  30  of pointed conduit  26 , as shown in FIG. 2.  
         [0047]    [0047]FIG. 9 depicts an embodiment of conduit modifier  54  having a single set of rollers. The embodiment of conduit modifier  54  may be used to form a corrugated conduit such as corrugated conduit  34  depicted in FIG. 3. Conduit modifier may include back plate  56 . Back plate  56  may be mounted upon or included as part of a device (e.g., a draw bench). Conduit modifier may include a first set of rollers  58  surrounding a central passage. Rollers  58  may be mounted in roller housings. Rollers  58  may be supported by axles and bearings mounted in the roller housings.  
         [0048]    Rollers  58  of conduit modifier  54 , such as the conduit modifier depicted in FIG. 9, may be radially spaced around the central passage so that an end portion of a pointed conduit is able to pass through the central passage without touching rollers  58 . A frustro-conical portion and a body of the pointed conduit may contact rollers  58  when the pointed conduit is pushed and/or pulled through the central passage. Rollers may indent the conduit and form a series of grooves and ridges in the pointed conduit to produce a corrugated conduit.  
         [0049]    [0049]FIG. 10 depicts an embodiment of conduit modifier  54  having two sets of rollers. The embodiment of conduit modifier  54  may be used to form a corrugated conduit such as corrugated conduit  34  depicted in FIG. 5. Rollers  58  and rollers  58 ′ may surround a central passage. Rollers  58 ,  58 ′ may be mounted in roller housings. Rollers  58 ,  58 ′ may be supported by axles and bearings mounted in the roller housings.  
         [0050]    As shown in FIG. 11, rollers  58  may alternate with rollers  58 ′ around central passage  60 . When a pointed conduit is inserted into central passage  60  of conduit modifier  54 , rollers  58  may contact a frustro-conical portion and a body of the pointed conduit. Rollers  58  may indent walls of the conduit to form grooves and ridges in the conduit. Ridges formed by rollers  58  may then contact rollers  58 ′. Rollers  58 ′ may push the ridges towards an axis of central passage  60  (i.e., towards the longitudinal axis of the central passage). Grooves between ridges may also move towards the axis of central passage  60 .  
         [0051]    [0051]FIG. 12 depicts an embodiment of roller  58  of conduit modifier  54  having rollers  58  and rollers  58 ′. An outer surface of roller  58  may have a convex shape. FIG. 13 depicts an embodiment of roller  58 ′. An outer surface of roller  58 ′ may have a concave shape. The concave shape may conform better to a shape of a ridge formed by roller  58 .  
         [0052]    In an embodiment of conduit modifier used to form corrugated conduit from 5 inch nominal diameter pipe, rollers may be about 3 inches in diameter. Widths of the rollers may be chosen to form grooves and ridges of desired sizes. In an embodiment, a width of each roller is about 0.75 inches.  
         [0053]    In some embodiments, rollers may not need to be formed of very hard materials to indent conduits. Rollers may be made of material that is harder than the conduits being corrugated. A significant portion of force between the rollers and a conduit being corrugated may be borne by bearings supporting the rollers. Supporting a significant portion of load applied to the rollers on bearings may allow the rollers to be formed of relative inexpensive material and long lasting material (i.e., as compared to tungsten carbide rollers).  
         [0054]    In an embodiment, rollers may be designed to produce a desired surface geometry, outer diameter, and/or cross-sectional shape of a conduit. Diameter, face thickness, and shape of the rollers may be chosen to produce desired corrugations. In some embodiments, rollers may include roughened surfaces to form texturing in corrugations formed in a conduit. In some embodiments, texturing may be formed in a corrugated conduit after the conduit is formed. Texturing may be formed in a corrugated conduit by, but is not limited to being formed by, scoring, etching, and/or peening a surface or surfaces of the corrugated conduit. In some embodiments, a corrugated conduit may be chemically and/or mechanically polished to reduce the presence of texturing in surfaces of the conduit.  
         [0055]    [0055]FIG. 14 depicts pointed conduit  26  prior to insertion into conduit modifier  54 . Pointed conduit  26  may be formed using pointing device  42  depicted in FIG. 7. Pointed conduit  26  may be moved into central passage  60  of conduit modifier  54 . In some embodiments, a portion of the conduit that has passed through conduit modifier  54  may be grasped and a remaining portion of the conduit may be pulled through the conduit modifier.  
         [0056]    End portions  32  of pointed conduit  26  may pass through central passage  60  without contacting rollers  58  and rollers  58 ′. Frustro-conical section  30  and body  28  may contact rollers  58  and rollers  58 ′. FIG. 15 depicts a conduit modifier during formation of a corrugated conduit. Rollers  58  and rollers  58 ′ of conduit modifier  54  may form indentions in pointed conduit  26  to form corrugated conduit  34 . Rollers  58 ′ may push ridges  36  formed by rollers  58  inwards so that a height of the ridges in corrugated conduit  34  from a center axis of the conduit is about the same as the outer radius of un-corrugated end portion  32  of the corrugated conduit.  
         [0057]    The apparatus and method described herein may be used advantageously for forming modified conduits quickly and efficiently, without requiring frequent replacement of machine components. Large and/or heavy-duty conduits may be modified to form corrugated conduits. In some embodiments, a distance from a central axis to an outermost portion of a ridge of a corrugation may be substantially the same as a radius from the central axis to an outer diameter of an un-corrugated portion of the conduit.  
         [0058]    In this patent, certain U.S. patents, U.S. patent applications, and other materials (e.g., articles) have been incorporated by reference. The text of such U.S. patents, U.S. patent applications, and other materials is, however, only incorporated by reference to the extent that no conflict exists between such text and the other statements and drawings set forth herein. In the event of such conflict, then any such conflicting text in such incorporated by reference U.S. patents, U.S. patent applications, and other materials is specifically not incorporated by reference in this patent.  
         [0059]    Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims.