BACKGROUND

1. Field of the Invention 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.

2. Description of Related Art 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. Patent Nos. 2,365,688 to Dewey; 2,342,117 to Brown et al; 2,499,901 to Brown; 2,797,554 to Donovan; and 4,162,702 to Andersson. 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. Patent Nos. 5,251,693 and 5,311,661 to Zifferer, a heat exchange tube having a portion that includes corrugations is described. U.S. Patent Nos. 4,377,083 to Shepherd; 4,514,997 to Zifferer; 2,110,965 to Singer; 2,378,729 to Schmidt; 4,383,429 to Ceccacci; and 1,777,728 to A.D. Kumpf also describe modifications of cross-sectional shape and/or area of conduits. U.S. Patent No. 5,016,806 to Yapp et al. describes the use of rollers to impart a desired shape to a tubular member. 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. A pointing device may be used to form a conduit with a reduced diameter end. U.S. Patent No. 5,311,661 to Zifferer describes a pointing device for forming a reduced diameter end portion in a conduit. Some corrugated or fluted conduits may be used as columns and as pillars, posts, poles, standards, and the like. U.S. Reissue Patent 18,272 to Frahm et al. describes a corrugated or fluted sheet metal shaft and a method for making the same.

SUMMARY 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 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. 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. 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. 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 hi 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. 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. 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. 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. 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. 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 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: Figure 1 shows a perspective view of an unmodified conduit. Figure 2 depicts a conduit with reduced diameter end portions. Figure 3 depicts an embodiment of a corrugated conduit. Figure 4 depicts a cross section of a corrugated conduit embodiment taken substantially along line 4-4 of Figure 3. Figure 5 depicts an embodiment of a corrugated conduit. Figure 6 depicts a cross section of a corrugated conduit embodiment taken substantially along line 6-6 of Figure 5. Figure 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. Figure 8 depicts a cross-sectional view of an embodiment of a point reduction die. Figure 9 depicts a perspective view of an embodiment of a conduit modifier having a single set of rollers. Figure 10 depicts a perspective view of an embodiment of a conduit modifier having two sets of rollers. Figure 11 depicts an end view of an embodiment of a conduit modifier having two sets of rollers. Figure 12 depicts an embodiment of a roller for a conduit modifier. Figure 13 depicts an embodiment of a roller for a conduit modifier. Figure 14 depicts a cross-sectional representation of a conduit modifier taken substantially along line 14- 14 of Figure 11. Figure 15 depicts a perspective view of a conduit modifier during formation of a corrugated conduit. 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 Figure 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. 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, hi 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. Conduit 20 may have outer diameter 24. Conduit 20 may have an initial outer diameter in a range from about 1/2 inch to 12 inches or more. In an embodiment, a conduit has a nominal diameter of about 5 inches. 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. Figure 2 depicts a representation of pointed conduit 26 formed from conduit 20 of Figure 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. 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. Figure 3 depicts an embodiment of corrugated conduit 34 formed from a pointed conduit similar to the pointed conduit depicted in Figure 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. Figure 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. 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. Figure 5 depicts an embodiment of corrugated conduit 34 formed from a pointed conduit similar to the pointed conduit depicted in Figure 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. Figure 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. In some embodiments, one set of rollers of a conduit modifier may compress ridges formed by another set of rollers of the conduit modifier. For example, a distance from center 40 of corrugated conduit 34 to an outermost and/or innermost surface of a ridge of ridges 36 (or groove of grooves 38) established by a first set of rollers may be decreased by a second set of rollers. 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. 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. A pointing device may be used to form pointed conduit 26 (shown in Figure 2) from conduit 20 (shown in Figure 1). Figure 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. 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. Figure 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 Figure 2. Figure 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 Figure 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. Rollers 58 of conduit modifier 54, such as the conduit modifier depicted in Figure 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. Figure 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 Figure 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. In some embodiments, rollers 58, 58' may be arranged such that rollers 58 compress ridges formed by rollers 58'. In some embodiments, rollers 58, 58' may be arranged such that rollers 58' compress ridges formed by rollers 58. Compression of ridges by a second set of rollers may decrease a distance from a center of a corrugated conduit to an outermost and/or innermost surface of a ridge (or groove) established by the first set of rollers. As shown in Figure 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. Figure 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. Figure 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. 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. 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). 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. Figure 14 depicts pointed conduit 26 prior to insertion into conduit modifier 54. Pointed conduit 26 may be formed using pointing device 42 depicted in Figure 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. 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'. Figure 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. 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. 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.