Process and assembly for identifying and tracking assets

Information

  • Patent Grant
  • 7014100
  • Patent Number
    7,014,100
  • Date Filed
    Friday, April 27, 2001
    23 years ago
  • Date Issued
    Tuesday, March 21, 2006
    18 years ago
Abstract
An assembly and process for identifying and tracking assets, particularly tubulars, equipment, tools and/or devices. An antenna is electrically connected to a responding device, such as a radio frequency identification device, and this assembly is connected to an asset. The antenna may be positioned about the exterior and/or the interior of the asset and significantly increases the range of signals that may be received and/or broadcast by the responding device. A transceiver may accordingly be positioned a greater distance from the asset without regard to the orientation of the asset and still permit communication between the transceiver and the responding device. In this manner, information that specifically identifies the asset may be compiled in a data base so as to maintain an accurate history of the usage of such assets as tubulars, equipment, tool and/or devices.
Description
CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to the following copending patent applications: U.S. patent application Ser. No. 09/586,648, filed on Jun. 1, 2000 and entitled “Method and System for Performing Operations and for Improving Production in Wells”; U.S. patent application Ser. No. 09/656,720, filed on Sep. 7, 2000 and entitled “Method and System for Performing a Casing Conveyed Perforating Process and Other Operations in Wells”; and U.S. patent application Ser. No. 10/032,114, filed on Dec. 21, 2001 and entitled “Method and Apparatus for Determining Position in a Pipe”.


BACKGROUND OF THE INVENTION

1. Field of the Invention


The present invention relates to processes and assemblies for identifying and tracking assets, such as tubulars, equipment and tools used in subterranean wells, and more particularly, to processes and assemblies for identifying and tracking such assets which facilitates accurate input of data into a data base.


2. Description of Related Art


Tubulars are commonly employed in subterranean wells. During drilling of a subterranean well bore, a drill bit is secured to one end of a drill string which is made up of individual lengths of drill pipe. These lengths are conventionally secured together by means of a threaded collar. After the drill bit is secured to a first length of drill pipe, the bit and first length of drill pipe are lowered to the ground and usually rotated to permit the bit to penetrate the earth. Drilling fluid is circulated via the interior of the pipe to the drill bit to lubricate the bit and to carry cuttings back to the drilling rig at the surface of the earth via the annulus formed between the bore hole being drilled and the drill pipe. As drilling progresses, additional lengths of drill pipe are secured to the uppermost length of drill pipe in the well bore. As this process continues, a drill string is formed that is made up of individual lengths of drill pipe secured together. Once the well bore is drilled to the desired depth, the well bore is completed by positioning a casing string within the well bore to increase the integrity thereof and provide a path for producing fluids to the surface. The casing string is normally made up of individual lengths of relatively large diameter metal tubulars which are secured together by any suitable means, for example screw threads or welds. Usually, each length of casing is provided with male screw threads at each end thereof and individual lengths of casing are joined together by means of a collar having female screw threads at each end thereof. Conventionally, after the casing string is cemented to the well bore face and perforated to establish fluid communication between the subterranean formation and the interior of the casing string, a production tubing string is positioned within the casing string to convey fluids produced into the well to the surface of the earth. Tubing strings are conventionally made up of individual lengths of relatively small diameter tubing secured together by collars in a manner as described above with respect to casing. Tubing strings may also be used to convey fluids to treat the well or a subterranean formation of interest or to convey tools or equipment, such as packers, plugs, etc., that are needed to complete or work over a well


Tubulars are transported to the well site in anticipation of an operation and are temporarily stored there until deployed into a well. At the well site, each length of tubular is measured or “tagged” to determine the exact length thereof. Because each tubular as manufactured usually varies in length, it is important to determine and know the exact length thereof so that the total length of a given tubular string that is positioned in a subterranean well is known. As the first tubular of a given string is positioned in a well, the tubular is designated with a first number, e.g. 1, and the length thereof is manually recorded at the well site into either a paper or computer data base. As each subsequent individual length of tubular is secured to the tubular string already positioned in the well, the next consecutive number that is assigned to that tubular and its exact length is also manually recorded into the data base at the well site. In this manner, the exact number of tubulars that make up a given string positioned in a subterranean well and the exact length of the string is known. The compilation of a data base in this manner is also desirable so as to maintain an accurate history of the usage of tubulars, equipment and/or tools. Such history of usage can be used to provide maintenance and predict potential problems. However, problems routinely occur with this procedure due to manual error(s) in entering into the data base tubular length(s) that are not part of the tubular string positioned in a well, in entering the wrong sequence of individual tubular lengths that make up a string, and/or in failing to enter an individual tubular length(s) that is part of a tubular string positioned in a subterranean well. Such errors lead to time consuming problem solving, while expensive rigs are often present at the well site, to determine the precise depth of the well, of a certain individual length of casing, and/or of a certain downhole tool. Further problems occur with this conventional method when tubulars are withdrawn from the well bore, temporarily stored on site and subsequently used in a different operation at that well or transported and used in a different well. In accordance with this conventional method, individual lengths of tubulars removed from a well are stacked at the well site without any consideration given to the number assigned to that tubular as run into the well. The individual length of tubulars are not actually physically marked with a designation number and marking such tubulars as they are being pulled from a well is not practical since the rig necessary for performing this operation is expensive. In some instances, individual lengths of drill pipe are provided with a unique serial number from the manufacturer which is entered into the data base as the drill string is being made up. However, such entry is expensive and plagued by manual errors, and often, the serial number of an individual length of drill pipe is not easily found or illegible if found due to rust, corrosion, wear, etc.


In an effort to automate the data input process and to provide a completely accurate information data base, a system has been developed to track asset inventory wherein an electronic tag, such as a passive radio frequency chip, is attached to articles of manufacture that are used in the oil & gas industry. A hand held wand is employed by field personnel to read such electronic tag and the code gleaned during such reading is transferred by cable to a hand held portable terminal. This information is then sent to a personal computer. This system is commercially available from Den-Con Tool Company. of Oklahoma City, Okla. under the trade name designation “Print System”. However, electronic tags, such as a passive radio frequency chip, do not transmit through steel, and therefor, require field personnel to position the hand held wand adjacent and close to the tag to read it. Thus, the use of this system at field locations, such as drilling and completion rigs, offshore platforms etc., has proved to be inefficient since field personnel must first locate the position of the electronic tag and then properly position the wand in extremely close proximity to the tag, sometimes repeating the procedure to ensure that the tag is properly read. This is time consuming and expensive.


Thus, a need exists for an identification and tracking method wherein individual lengths of tubulars, pieces of equipment or tools are accurately identified and inventoried prior to deployment in a given subterranean well, as positioned in a well and/or as stacked at a well site after being pulled from a well and awaiting deployment in the same or different wells. A further need exists for effectively eliminating errors in data base entry for information about individual lengths of tubulars, equipment and/or tools. A still further need exists for eliminating time delays associated with automated reading of radio frequency identification devices employed to identify and track tubulars or other tools or equipment.


SUMMARY OF THE INVENTION

To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, one characterization of the present invention may comprise an assembly is provided for identifying and tracking an asset. The assembly comprises a responding device adapted to be connected to an asset and an antenna electrically connected to said responding device.


In another characterization of the present invention, an assembly is provided for use as a fluid conduit. The assembly comprises a tubular, a responding device connected to the tubular, and an antenna electrically connected to the responding device.


In yet another characterization of the present invention, an assembly is provided for use as a fluid conduit. The assembly comprises a tubular, a collar releasably secured to one end of the tubular, the collar comprising a generally tubular body, a responding device connected to the generally tubular body, and an antenna electrically connected to the responding device.


In still another characterization of the present invention, a process for identifying and tracking assets is provided which comprises positioning a transceiver in proximity to an asset having a responding device and an antenna electrically connected to the responding device so as to permit communication between the transceiver and the responding device via the antenna.


In yet still another characterization of the present invention, a process for identifying and tracking tubulars is provided which comprises positioning a transceiver and a tubular having a responding device and an antenna electrically connected to the responding device in proximity to each other without regard to the rotational orientation of the tubular so as to permit communication between the transceiver and the responding device via the antenna.


In yet still another characterization of the present invention, a process is provided for identifying and tracking assets which comprises positioning an asset having a responding device connected thereto within a transceiver having a generally annular antenna so as to permit communication between the transceiver and the responding device via said antenna.





BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the invention.


In the drawings:



FIG. 1 is a partially cutaway, perspective view of one embodiment of the process and assembly of the present invention;



FIG. 1A is a blown up portion, as outlined in FIG. 1, of the embodiment of the process and assembly of the present invention that is illustrated in FIG. 1;



FIG. 2 is a partially cutaway, perspective view of another embodiment of the process of the present invention;



FIG. 2A is a blown up portion, as outlined in FIG. 2, of the embodiment of the process and assembly of the present invention that is illustrated in FIG. 2:



FIG. 3 is a partially cutaway, perspective view of still another embodiment of the present invention;



FIG. 3A is a blown up portion, as outlined in FIG. 3, of the embodiment of the process and assembly of the present invention that is illustrated in FIG. 3; and



FIG. 4 is a partially sectioned, perspective view of a responding device being read by a transceiver in accordance with the present invention.





DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As utilized throughout this specification, the term “asset” refers to any article of manufacture or device, which includes, but is not limited to, tubulars, equipment and tools designed to be run on, connected to and/or operated by tubulars. As utilized throughout this specification, the term “tubular” refers to an individual length of any generally tubular conduit for transporting fluid, particularly oil, gas and/or water in and/or from a subterranean well and/or transportation terminal. When referring to a “tubular” which is used in a subterranean well, tubulars are usually secured together by means of collars to form a string of tubulars, such as a tubing string, drill string, casing string, etc., which is positioned in a subterranean well as utilized, at least in part, to transport fluids. Environments other than a subterranean well in which tubulars may be used in accordance with the present invention, include, but are not limited to, pipelines and sewer lines.


Referring to FIG. 1, a portion of two tubulars are illustrated as 2 and 6. Each end of tubulars 2 and 6 may be provided with screw threads. As illustrated in FIG. 1, the outer surface of one end 3 and 7 of tubulars 2 and 6, respectively, are provided with screw threads 4 and 8. A collar 10 is utilized to secure ends 3 and 7 of tubulars 2 and 6 together. The internal surface of collar 10 is provided with screw threads 12 which threads 4 and 8 are mated with.


In accordance with the embodiment of the present invention as illustrated in FIG. 1, the outer surface of collar 10 is provided with a groove or trough 14 which extends about substantially the entire circumference or periphery of collar 10. A responding device 20, for example a radio frequency identification device (known as a “RFID”), is positioned in groove 14. This radio frequency identification device 20 may be in the form of a passive radio identification device (know as a “PRID”). Such PRIDs are conventional and are used for merchandise security in the retail industry, library security, etc., and generally comprise a solid state printed circuit which is configured to resonate upon receipt of radio frequency energy from a radio transmission of appropriate frequency and strength. Such devices do not require any additional power source, as the energy received from the transmission provides sufficient power for the device to respond with a weak and/or periodic reply transmission so long as it is receiving an appropriate transmission.


Alternatively, the responding device 20 may be in the form of an active device, requiring a separate source of electrical power (e.g., electrical storage battery or other electrical power means). Such devices are also conventional, and may be configured to draw practically no electrical power until a radio frequency signal is received, whereupon they are electrically energized to produce a responding transmission.


In accordance with one embodiment of the present invention, an antenna 24 is electrically connected to the responding device 20 by any suitable means, such as by silver solder or welds, and is positioned within groove 14 and extends about substantially the entire circumference or periphery of collar 10. Antenna 24 may be constructed of any suitable electrically conductive material as will be evident to a skilled artisan, for example suitable nickel based alloys such as INCONEL. Preferably, device 20 and antenna 24 are incorporated in a TEFLON ring which is positioned in groove 14 and forms a fluid tight seal through which an appropriate radio frequency signal may be transmitted and received.


A radio frequency transmitter and receiver (i.e. a transceiver) 40 is provided (FIG. 4). Transceiver may be in the form of a hand held portable terminal 42 connected to a hand-held wand 44 by means of cable 43. In operation, as a tubing string that comprises tubulars joined together, for example by collars, is being moved into position for use, wand 44 may be manually held adjacent the tubulars without regarding for the specific orientation of a responding device on a given tubular. Alternatively, where the process permits, wand 44 may be secured in a stationary position that is adjacent the tubulars and held in that position by any suitable mechanical means as will be evident to a skilled artisan. Transceiver 40 constantly transmits a radio frequency signal in the direction of the tubing string. As antenna 24 on a given collar 10 passes adjacent wand 44, the signal emanating from wand 44 is received by antenna 24 and transmitted to radio frequency identification device 20. Device 20 detects this signal and sends a radio frequency response that is transmitted through the antenna 24 so as to be received by transceiver 40. In this manner, each tubular joint and its position is identified. By using an antenna in accordance with the present invention not only is the orientation of tubulars (and therefor responding devices) as well as the corresponding transceiver irrelevant, but the antenna is able to receive and broadcast radio frequency signals at greater distances than by using only a radio frequency identification device, e.g. up to 15 inches or more with an antenna as compared to 3 inches for an RFID device alone.


In another embodiment of the present invention that is illustrated in FIG. 2, a bore or hole 11 is provided in collar 10 and a RFID 20 is positioned in bore 11 and is electrically connected to an outer antenna 24 by any suitable means, for example by silver solder or welds 25. In accordance with the embodiment of FIG. 2, a generally annular inner antenna 26 is positioned in a ring 18 that is provided with screw threads 19 on the outer surface thereof. Threads 19 are mated with threads 12 on collar 10 such that ring 18 is positioned in the gap between the ends 3, 7 of tubulars 2, 6, respectively, as mated with collar 10. Inner antenna 26 is electrically connected with RFID by any suitable means, for example a silver solder or welds 27. The operation of this embodiment with respect to use of a transceiver 40 that is positioned outside of the tubulars is identical to that described with respect to FIGS. 1 and 4 above. However, the embodiment of FIG. 2 may also be used in conjunction with a transceiver that is transported through the bores of the tubulars (not illustrated). As thus constructed and assembled, radio frequency signals from transceiver(s) may be received from the exterior of tubulars and adjoining collars by means of outer antenna 24 and/or from the interior of tubulars and adjoining collars by means of inner antenna 26 and information from RFID 20 may be transmitted via antenna 24 to transceiver(s) located external to the tubulars and adjoining collars and/or via antenna 26 to transceiver(s) located internal to the tubulars and adjoining collars. In this manner, information transmission can occur to and/or from the exterior and/or the interior of the tubulars.


While responding device 20 and antennas 24 and 26 have been described above as connected to a collar 10, it is within the scope of the present invention to connect responding device 20 and antennas 24 and/or 26 directly to a tubular and/or to tools, equipment and/or devices, especially those used in conjunction with tubulars, in a manner substantially similar with that described above with respect to collar 10. For tubulars, such direct connection is mandatory where collars are not utilize to secure individual tubulars together as is often the case with drill strings where individual tubulars are connected to each other.


It is also within the scope of the present invention to utilize a conventional responding device, for example a RFID, without an associated antenna. As illustrated in FIG. 3, a RFID 20 is positioned within a bore or hole 11 formed in the outer surface of collar 10. A commercially available epoxy is placed in the bore or hole 11 and cured thereby encapsulating RFID device 20 in a fluid tight seal through which an appropriate radio frequency signal may be transmitted and received. In this embodiment, a transceiver 50 is employed which is sized and configured to permit the passage of tubulars therethrough. As illustrated, transceiver 50 is configured in a ring like shape that has an annular groove 51 formed in the inner surface thereof. An antenna 52 for the transceiver is positioned within groove 51 and extends substantially the entire length of the groove. In this embodiment, tubulars equipped with a conventional RFID may be passed through transceiver 50 with the antenna 52 ensuring that radio frequency communication between the transceiver and the RFID occurs without regard to rotational orientation of the tubulars.


While the use of an antenna in accordance with the embodiments of the present invention has been described herein only in conjunction with tubulars, it will be evident to a skilled artisan that the antenna may be used in conjunction with equipment, tools, and other devices that are secured to tubulars or to any asset that is required to be identified and tracked by use of a transceiver. Examples of such equipment, tools and devices used in conjunction with tubulars used in pipelines, subterranean wells or other fluid transmission lines, are bits, packers, plugs, pigs, valves, landing nipples, profiles, disconnects, ported subs, perforated nipples and polished bore receptacles.


While the foregoing preferred embodiments of the invention have been described and shown, it is understood that the alternatives and modifications, such as those suggested and others, may be made thereto and fall within the scope of the invention.

Claims
  • 1. An assembly for identifying and tracking an asset comprising: a responding device adapted to be connected to an asset;a first antenna electrically connected to said responding device and extending along the outer periphery of said asset; anda second antenna electrically connected to said responding device and extending along the inner periphery of said asset.
  • 2. The assembly of claim 1 wherein said responding device is a radio frequency identification device.
  • 3. The assembly of claim 2 wherein said radio frequency identification device is passive.
  • 4. The assembly of claim 1 wherein said antenna extends substantially around the entire outer periphery of said asset.
  • 5. The assembly of claim 1 wherein said asset has a groove in the outer surface thereof and said responding device and said first antenna are positioned within said groove.
  • 6. The assembly of claim 5 wherein said responding device is a radio frequency identification device.
  • 7. The assembly of claim 6 wherein said radio frequency identification device is passive.
  • 8. The assembly of claim 5 wherein said groove extends substantially around the entire outer periphery of said asset.
  • 9. The assembly of claim 8 wherein said groove is generally annular.
  • 10. The assembly of claim 8 wherein said first antenna extends substantially around the entire outer periphery of said asset.
  • 11. The assembly of claim 5 further comprising: a sealant positioned in said groove so as to surround and secure said responding device and said first antenna in said groove.
  • 12. The assembly of claim 1 wherein said responding device is positioned within a hole in said asset.
  • 13. The assembly of claim 1 wherein at least a portion of the interior of said asset has screw threads.
  • 14. The assembly of claim 1 wherein said second antenna is embedded in a ring having a threaded outer surface that is mated with said screw threads of said interior of said asset.
  • 15. An assembly for use as a fluid conduit comprising: a tubular;a responding device connected to said tubular;a first antenna electrically connected to said responding device and extending along the outer periphery of said tubular; anda second antenna electrically connected to said responding device and extending along the inner periphery of said tubular.
  • 16. The assembly of claim 15 wherein said responding device is a radio frequency identification device.
  • 17. The assembly of claim 16 wherein said radio frequency identification device is passive.
  • 18. The assembly of claim 15 wherein said tubular has a groove in the outer surface thereof and said responding device and said first antenna are positioned within said groove.
  • 19. The assembly of claim 18 wherein said responding device is a radio frequency identification device.
  • 20. The assembly of claim 19 wherein said radio frequency identification device is passive.
  • 21. The assembly of claim 18 wherein said groove extends substantially around the entire outer periphery of said tubular.
  • 22. The assembly of claim 21 wherein said groove is generally annular.
  • 23. The assembly of claim 21 wherein said first antenna extends substantially around the entire outer periphery of said tubular.
  • 24. The assembly of claim 18 further comprising: a sealant positioned in said groove so as to surround and secure said responding device and said first antenna in said groove.
  • 25. The assembly of claim 15 wherein said responding device is positioned within a hole in said tubular.
  • 26. The assembly of claim 15 wherein at least a portion of the interior of said generally tubular body has screw threads.
  • 27. The assembly of claim 15 wherein said second antenna is embedded in a ring having a threaded outer surface that is mated with said screw threads of said interior of said tubular.
  • 28. The assembly of claim 15 wherein said tubular is drill pipe and the fluid conduit is a drill string for use in a subterranean well.
  • 29. The assembly of claim 15 wherein said tubular is tubing and the fluid conduit is a tubing string for use in a subterranean well.
  • 30. The assembly of claim 15 wherein said tubular is pipe and the fluid conduit is a pipeline.
  • 31. The assembly of claim 15 further comprising: a tool connected to said tubular; anda second responding device connected to said tool.
  • 32. An assembly for use as a fluid conduit comprising: a tubular;a collar releasably secured to one end of said tubular, said collar comprising a generally tubular body;a responding device connected to said generally tubular body;a first antenna electrically connected to said responding device and extending along the outer periphery of said generally tubular body; anda second antenna electrically connected to said responding device and extending along the inner periphery of said generally tubular body.
  • 33. The assembly of claim 32 wherein said responding device is a radio frequency identification device.
  • 34. The assembly of claim 33 wherein said radio frequency identification device is passive.
  • 35. The assembly of claim 32 wherein said first antenna extends substantially around the entire outer periphery of said generally tubular body.
  • 36. The assembly of claim 32 wherein said generally tubular body has a groove in the outer surface thereof and said responding device and said first antenna are positioned within said groove.
  • 37. The assembly of claim 36 wherein said responding device is a radio frequency identification device.
  • 38. The assembly of claim 37 wherein said radio frequency identification device is passive.
  • 39. The assembly of claim 36 wherein said groove extends substantially around the entire outer periphery of said generally tubular body.
  • 40. The assembly of claim 39 wherein said groove is generally annular.
  • 41. The assembly of claim 39 wherein said first antenna extends substantially around the entire outer periphery of said generally tubular body.
  • 42. The assembly of claim 36 further comprising: a sealant positioned in said groove so as to surround and secure said responding device and said first antenna in said groove.
  • 43. The assembly of claim 32 wherein said responding device is positioned within a hole in said generally tubular body.
  • 44. The assembly of claim 32 wherein at least a portion of the interior of said generally tubular body has screw threads.
  • 45. The assembly of claim 32 wherein said second antenna is embedded in a ring having a threaded outer surface that is mated with said screw threads of said interior of said generally tubular body.
  • 46. The assembly of claim 32 wherein said tubular is drill pipe and the fluid conduit is a drill string for use in a subterranean well.
  • 47. The assembly of claim 32 wherein said tubular is tubing and the fluid conduit is a tubing string for use in a subterranean well.
  • 48. The assembly of claim 32 wherein said tubular is pipe and the fluid conduit is a pipeline.
US Referenced Citations (63)
Number Name Date Kind
4023167 Wahlstrom May 1977 A
4572293 Wilson et al. Feb 1986 A
4630044 Polzer Dec 1986 A
4656463 Anders Apr 1987 A
4656944 Gonzalez Apr 1987 A
4698631 Kelly et al. Oct 1987 A
4808925 Baird Feb 1989 A
4827395 Anders et al. May 1989 A
5105742 Sumner Apr 1992 A
5142128 Perkin et al. Aug 1992 A
5160925 Dailey et al. Nov 1992 A
5202680 Savage Apr 1993 A
5206680 Dillow Apr 1993 A
5279366 Scholes Jan 1994 A
5354956 Orban et al. Oct 1994 A
5355957 Burleson et al. Oct 1994 A
5361838 Kilgore Nov 1994 A
5394141 Soulier Feb 1995 A
5457447 Ghaem et al. Oct 1995 A
5479860 Ellis Jan 1996 A
5495237 Yuasa et al. Feb 1996 A
5497140 Tuttle Mar 1996 A
5505134 Brooks et al. Apr 1996 A
5530358 Wisler et al. Jun 1996 A
5608199 Clouse et al. Mar 1997 A
5626192 Connell et al. May 1997 A
5629623 Sezginer et al. May 1997 A
5654693 Cocita Aug 1997 A
5680459 Hook et al. Oct 1997 A
5682099 Thompson et al. Oct 1997 A
5682143 Brady et al. Oct 1997 A
5720345 Price et al. Feb 1998 A
5836406 Schuh Nov 1998 A
5864323 Berthon Jan 1999 A
5877996 Krokstad et al. Mar 1999 A
5911277 Hromas et al. Jun 1999 A
5923167 Chang et al. Jul 1999 A
5931239 Schuh Aug 1999 A
5995449 Green et al. Nov 1999 A
6018501 Smith et al. Jan 2000 A
6025780 Bowers et al. Feb 2000 A
6078259 Brady et al. Jun 2000 A
6081729 Bauerschmidt et al. Jun 2000 A
6085805 Bates Jul 2000 A
6097301 Tuttle Aug 2000 A
6184685 Paulk et al. Feb 2001 B1
6243041 Mischenko et al. Jun 2001 B1
6257338 Kilgore Jul 2001 B1
6288685 Thomas Sep 2001 B1
6333700 Thomeer et al. Dec 2001 B1
6343649 Beck et al. Feb 2002 B1
6366089 Poitzsch et al. Apr 2002 B1
6429653 Kruspe et al. Aug 2002 B1
6476609 Bittar Nov 2002 B1
6531871 Hay et al. Mar 2003 B1
6536524 Snider Mar 2003 B1
6597175 Brisco Jul 2003 B1
6788263 Clark et al. Sep 2004 B1
20010013410 Beck et al. Aug 2001 A1
20010013411 Beck et al. Aug 2001 A1
20010042617 Beck et al. Nov 2001 A1
20010043146 Beck et al. Nov 2001 A1
20010054969 Thomeer et al. Dec 2001 A1
Foreign Referenced Citations (5)
Number Date Country
0 412 535 Feb 1991 EP
0 651 132 May 1995 EP
0 730 083 Sep 1996 EP
WO 0118357 Mar 2001 WO
WO 0173423 Oct 2001 WO
Related Publications (1)
Number Date Country
20020158120 A1 Oct 2002 US