EP0979922B1 - Bohrgestänge mit Innenrohr - Google Patents

Bohrgestänge mit Innenrohr Download PDF

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Publication number
EP0979922B1
EP0979922B1 EP99305930A EP99305930A EP0979922B1 EP 0979922 B1 EP0979922 B1 EP 0979922B1 EP 99305930 A EP99305930 A EP 99305930A EP 99305930 A EP99305930 A EP 99305930A EP 0979922 B1 EP0979922 B1 EP 0979922B1
Authority
EP
European Patent Office
Prior art keywords
diameter
rod
tube
tube rod
female
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP99305930A
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English (en)
French (fr)
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EP0979922A2 (de
EP0979922A3 (de
Inventor
Nigel Roberts
James Yao
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Boart Longyear Ltd
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Boart Longyear Ltd
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Filing date
Publication date
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Publication of EP0979922A2 publication Critical patent/EP0979922A2/de
Publication of EP0979922A3 publication Critical patent/EP0979922A3/de
Application granted granted Critical
Publication of EP0979922B1 publication Critical patent/EP0979922B1/de
Anticipated expiration legal-status Critical
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Classifications

    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
    • E21B17/02—Couplings; joints
    • E21B17/04—Couplings; joints between rod or the like and bit or between rod and rod or the like
    • E21B17/042—Threaded
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
    • E21B17/02—Couplings; joints
    • E21B17/04—Couplings; joints between rod or the like and bit or between rod and rod or the like
    • E21B17/042—Threaded
    • E21B17/0426—Threaded with a threaded cylindrical portion, e.g. for percussion rods

Definitions

  • This invention relates to a tube rod for rotary/percussive rock drilling, and in particular to the way two tube rods are connected one to the other by threads.
  • Tube rods are conventionally connected end to end by threads which allow rods to be screwed together (and unscrewed) to form a drill string which may consist of a large number of connected rods.
  • Tube rods, and drill strings made up from tube rods operate in a harsh environment. Considerable stresses are built up in the rods, and these usually manifest themselves in cracking of the rods in the area of the threaded joints. This cracking usually leads to failure of the respective rod. It is therefore desirable to design the threaded ends of the rods in a way which will minimise stress build up at any particular point, in particular to minimise stress build up at the bottom of the female threads.
  • Document EP 0 220 147 relates to a thread coupling for percussion drilling.
  • the drill rods comprise a male thread and a co-operating female thread.
  • Document GB 2 285 645 relates to a stress relief groove for a drill pipe. The grove is located in the weld neck.
  • a tube rod for percussion rock drilling having threaded ends, the tube rod having a hollow bore and at least one of the ends having a female thread, the major part of the tube rod length between the threaded ends having an outside diameter (the first diameter) and at least part of the or each female threaded end having an outside diameter (the second diameter) which is larger than the first diameter, and an annular groove between the female threaded end and the major part of the tube rod length, the annular groove having a root diameter (the third diameter) which is less than both the first and the second diameter, the hollow bore of the rod having a region between the female threaded end and the major part of the tube rod length where the internal diameter is less than at either side of this region.
  • the groove preferably has an asymmetrical profile when seen in cross section parallel to the tube axis, and the flank nearest the threaded end is preferably steeper than the opposite flank.
  • the female end is of the second diameter from its end up to the annular groove.
  • the female end is preferred for the female end to be of the second diameter only in a region surrounding the bottom of the threaded end which is where the major stress concentration occurs, or for the female end to be of the second diameter on both sides of the annular groove.
  • the rod will have one male threaded end and one female threaded end.
  • rods with two female threaded ends are conceivable, to be joined end to end by a tubular connector with two male threaded ends.
  • the hollow bore of the rod may be reduced in internal diameter at the inner end of the female threaded socket to form a neck, and the bore diameter tapers outwards from the neck to the full bore diameter of the major part of the tube rod length.
  • the internal diameter of the rod has a region between the female threaded end and the major part of the tube rod length where the internal diameter is less than at either side of this region.
  • the internal diameter of the tube rod can taper from the major part of the tube rod length down to this region of lesser internal diameter.
  • the internal diameter of the tube rod can also taper from the female threaded end down to this region of lesser internal diameter.
  • the female threaded end can have an internal shoulder at right angles to the tube axis, with the internal diameter of the tube rod tapering down from the shoulder to the region of lesser internal diameter.
  • the taper of the internal diameter can be a conical taper but is preferably a radiused taper.
  • the neck or region of lesser diameter of the internal bore preferably lies on substantially the same cross-section of the rod as the third (external) diameter of the rod.
  • the third (external) diameter of the rod lies on a cross-section of the rod which is offset from the centre of the neck or region of lesser diameter in the direction towards the major part of the tube rod length.
  • the threaded ends can be initially separate from the rod and can be joined to a length of constant cross section tube by friction welded joints, the length of constant cross section forming the major part of the tube rod length. This is a particularly expedient method of manufacturing which allows standard tube stock to be used for the major part of the rod, with only the ends requiring machining.
  • the threaded region of the male end can extend from an annular shoulder, the shoulder being adapted to abut against the end of the female threaded end of another rod when the two rods are screwed together.
  • the male threaded region is preferably shorter than the female threaded recess so that when the male threaded end is screwed into the female threaded end of another rod until the shoulder abuts the end of the other rod, the male end does not reach the bottom of the female recess. This helps to avoid tensile pre-loading of the joint.
  • the annular shoulder can be stepped and the mating end of a female threaded end section of another rod can have a shoulder such that when the rods are screwed together, the shoulders interengage to prevent substantial radial movement of one shoulder relative to the other. This helps to prevent relative radial movement at the shoulder which in turn helps to reduce bending of the assembled string of rods.
  • a tube rod assembly for percussion rock drilling including a plurality of rods connected end to end by joints comprising interengaging male and female threads wherein when the joints are assembled, an end of a female threaded component is in contact with an external shoulder on the adjacent male threaded component, the external shoulder having a circumferentially extending stepped land, with part of the end of the female threaded component fitting around the land to hinder relative radial movement between the two ends at the position of the shoulder.
  • a tube rod having threaded ends, at least one of the ends having a female thread, the major part of the tube rod length between the threaded ends having an outside diameter (the first diameter) and the or each female threaded end having an outside diameter (the second diameter) which is larger than the first diameter, wherein between the female threaded end and the major part of the tube rod length there is an annular groove having a root diameter (the third diameter) which is less than both the first and the second diameter, and the internal diameter of the rod having a reduced diameter neck, the narrowest part of which coincides with the location of the third diameter.
  • a tube rod having threaded ends, at least one of the ends having a female thread, the major part of the tube rod length between the threaded ends having an outside diameter (the first diameter) and the or each female threaded end having an outside diameter (the second diameter) which is larger than the first diameter, wherein between the female threaded end and the major part of the tube rod length there is an annular groove having a root diameter (the third diameter) which is less than both the first and the second diameter, and the internal diameter of the rod having a reduced diameter neck, the internal diameter of the rod tapering into the neck from both sides of the neck.
  • the invention also extends to a female threaded tube rod end for joining to a length of tube to contribute to the formation of a tube rod as set forth above.
  • Figure 1 shows a rod which has a central section 10, a female threaded end section 12 and a male threaded end section 14.
  • the central section 10 will typically be 1.5 to 2 metres in length (but can be up to 6 metres long), whilst the male and female threaded end sections will typically each have a length of about 250 millimetres.
  • the central section 10 is a tube having a constant cross section over its length. Typically the outside diameter will be about 80 to 90 millimetres, and the inside diameter about 65 to 75 millimetres, leaving a wall thickness of about 15 millimetres.
  • the end sections 12 and 14, both of which have a through bore, will be welded to the centre section 10 at 16 and 18. This welding can appropriately be achieved through a friction welding process.
  • the female threaded end section 12 shown in Figure 2 will normally be machined from solid material. Suitable steels are a 3% NiCrMo grade steel or a 3% CrMo grade steel.
  • the section 12 has an internally threaded end 20, and a tube end 22 which is to be welded to the centre section 10 at 18.
  • the external and internal diameters of the section 12 at the tube end 22 will be substantially the same as those of the centre section 10.
  • the end 20 of the section has an abutment shoulder 24, a mouth 26 into which the male threaded end of another rod will be introduced, a threaded region 28 and a relieved region 30 at the inner end of the thread section.
  • Figure 2 illustrates the thread which will be formed on the inner walls of the region 28.
  • This thread will be a double start trapezoidal thread, of the type well known in connecting tube rods for use in rotary/percussion rock drilling.
  • the root diameter of this thread will be substantially the same as that of the relieved portion 30.
  • the bore has a narrow neck at 32, and a tapered transition at 34 from the relieved portion 30 to the neck, and a further conically tapered portion 36 from the neck to the tube end 22.
  • the tapered transition 34 is shown in the form of a conical taper, but may alternatively be a radiused taper (see Figure 6).
  • the external surface of the female portion has a diameter in the region 38 which can be the same as that of the central portion 10 or can be larger.
  • the diameter at the end portion 40 is slightly larger than that of the central portion, for example 2% - 6% larger, and when the diameter at the region 38 is larger than the central portion, it can also be 2 - 6% larger.
  • annular groove 42 which has a root diameter substantially less than either the first or the second diameters.
  • This groove is bounded by a smooth curve, one flank of which closest to the end 24 is steeper than the other flank. Although not shown in this figure, the transition between the steep flank and the surface 24 can be radiused, rather than the sharp edge shown.
  • the base of the groove lies in a cross-sectional plane which incorporates the neck 32.
  • the radius of the base part of this groove 42 can, for example, be 12.5 millimetres.
  • the female threaded section 12 has a greater wall thickness than at any other region of its length.
  • the male threaded end section 14 (see Figure 3) has a threaded boss 44 extending from an unthreaded collar 46.
  • the diameter of the collar 46 is the same as that of the female end (the second diameter) so that when the male end is screwed into a female end, there is no step in the external diameter at the joint.
  • the male end could be of the first diameter and/or could have a diameter ramp at the end to blend into the external diameter of the female end without a step.
  • the collar 46 has externally a flat at 48 on which serial numbers or other information can be stamped.
  • the right hand end of the portion 14 (as seen in Figure 3) has a tube end 50 which will match the tube end 22 of the female threaded portion and will match the cross section of the central section 10.
  • the section has a through bore 52.
  • the threaded portion 44 will have external threads to match the internal threads 28.
  • the male end 14 of one rod is screwed into the female end 12 of another rod.
  • the two are screwed together until the shoulder 54 of one male end comes into contact with the shoulder 24 of the female end. There is no contact between the extreme end 56 of the male end and the internal shoulder 58 of the female end.
  • Figure 4 shows a male threaded end section 114 which differs from the section shown in Figure 3 by the introduction of a land 155 which engages, when the rods are screwed together, inside the mouth 26 of the adjacent female threaded end section, and forms a close fit in that mouth so as to prevent any significant radial movement between the shoulders 24 and 54. This minimises any tendency to bending in the assembled drill rod string.
  • Figure 5 shows an embodiment where both the neck 132 and the groove 142 are elongated as compared with the embodiment shown in Figure 2. This assists in reducing the stress level at the inner end of the threaded region 28, particularly in the part of the threaded region closest to the neck 132.
  • Figure 6 shows an embodiment similar to that of Figure 2, but where the tapered transition 34 is replaced by a radiused transition 234.
  • A represents the external diameter of the central section 10
  • B represents the maximum external diameter of the female threaded end section 14
  • C represents minimum external diameter of the female threaded end section 14 (at the groove 42)
  • D represents the smallest internal diameter of the threaded section 14 (at the throat 32)
  • E represents the core diameter of the female thread 28.
  • the external surface of the rod can be provided with external helically fluted portions 60, 62 ( Figure 7). These fluted portions help to enhance the straightness of holes being drilled, by maintaining some contact with the walls of the hole while allowing flow of drilling fluid and drilling debris past the rod up the hole. The rod is thus held straight in the hole, so that the drill bit is always presented to the rock ahead in the correct orientation.
  • annular groove 42 helps to reduce stress concentrations in the female threaded end, these concentrations otherwise arising in the area of the last thread root and internal recess of the threaded region 28.

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  • Engineering & Computer Science (AREA)
  • Geology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Mining & Mineral Resources (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Earth Drilling (AREA)
  • Vessels And Coating Films For Discharge Lamps (AREA)
  • Particle Accelerators (AREA)
  • Fluid-Damping Devices (AREA)

Claims (20)

  1. Bohrgestänge mit Innenrohr für Gesteinsschlagbohren mit Gewindeenden (12, 14), bei dem das Bohrgestänge mit Innenrohr eine Hohlbohrung und mindestens eines der Enden (12) ein Innengewinde hat, wobei der größere Teil (10) der Länge des Bohrgestänges mit Innenrohr zwischen den Gewindeenden (12, 14) einen Außendurchmesser (den ersten Durchmesser) und mindestens ein Teil des Innengewindeendes oder jedes Innengewindeende einen Außendurchmesser (den zweiten Durchmesser) hat, der größer als der erste Durchmesser ist, dadurch gekennzeichnet, daß das Bohrgestänge mit Innenrohr eine ringförmige Nut (42) zwischen dem Innengewindeende und dem größeren Teil (10) der Länge des Bohrgestänges mit Innenrohr beinhaltet, wobei die ringförmige Nut (42) einen Wurzeldurchmesser (den dritten Durchmesser) hat, der kleiner als der erste und der zweite Durchmesser ist, wobei die Hohlbohrung des Bohrgestänges einen Bereich (32, 24, 26) zwischen dem Innengewindeende und dem größeren Teil (10) der Länge des Bohrgestänges mit Innenrohr aufweist, wo der Innendurchmesser kleiner als auf jeder Seite dieses Bereichs ist.
  2. Bohrgestänge mit Innenrohr nach Anspruch 1, bei dem der zweite Durchmesser um 2% bis 6% größer als der erste Durchmesser ist.
  3. Bohrgestänge mit Innenrohr nach Anspruch 1 oder Anspruch 2, bei dem die Nut (42), im Querschnitt parallel zur Rohrachse betrachtet, ein asymmetrisches Profil hat.
  4. Bohrgestänge mit Innenrohr nach Anspruch 3, bei dem die dem Gewindeende am nächsten liegende Flanke der Nut (42) steiler als die gegenüberliegende Flanke ist.
  5. Bohrgestänge mit Innenrohr nach einem der vorstehend aufgeführten Ansprüche, bei dem eines der Enden (12, 14) ein Innengewinde (28) und das andere Ende ein Außengewinde (44) hat.
  6. Bohrgestänge mit Innenrohr nach einem der vorstehend aufgeführten Ansprüche, bei dem die Hohlbohrung des Bohrgestänges am inneren Ende des Innengewindes (28) einen reduzierten Innendurchmesser hat, um einen Hals (32) zu bilden, und der Bohrungsdurchmesser vom Hals (32) aus nach außen bis zum vollen Bohrungsdurchmesser des größeren Teils der Länge des Bohrgestänges mit Innenrohr kegelig verläuft.
  7. Bohrgestänge mit Innenrohr nach einem der vorstehend aufgeführten Ansprüche, bei dem der Innendurchmesser des Bohrgestänges mit Innenrohr vom größeren Teil (10) der Länge des Bohrgestänges mit Innenrohr aus nach unten zum Bereich mit dem kleineren Innendurchmesser kegelig verläuft.
  8. Bohrgestänge mit Innenrohr nach einem der vorstehend aufgeführten Ansprüche, bei dem der Innendurchmesser des Bohrgestänges mit Innenrohr vom Innengewindeende (28) aus nach unten zum Bereich mit dem kleineren Innendurchmesser kegelig verläuft.
  9. Bohrgestänge mit Innenrohr nach einem der vorstehend aufgeführten Ansprüche, bei dem das Innengewindeende (28) eine in rechten Winkeln zur Rohrachse vorgesehene Innenschulter (58) hat und die Innenrohrbohrung von der Schulter (58) aus nach unten zum Bereich mit dem kleineren Innendurchmesser kegelig verläuft.
  10. Bohrgestänge mit Innenrohr nach einem der Ansprüche 7 bis 9, bei dem die oder jede kegelige Ausbildung des Innendurchmessers eine konische Kegelausbildung ist.
  11. Bohrgestänge mit Innenrohr nach einem der Ansprüche 7 bis 9, bei dem die oder jede kegelige Ausbildung des Innendurchmessers eine gerundete Kegelausbildung ist.
  12. Bohrgestänge mit Innenrohr nach einem der vorstehend aufgeführten Ansprüche, bei dem der Hals (32) oder Bereich mit dem kleineren Durchmesser der Innenbohrung im wesentlichen im gleichen Querschnitt des Bohrgestänges wie der dritte (äußere) Durchmesser des Bohrgestänges liegt.
  13. Bohrgestänge mit Innenrohr nach Anspruch 12, bei dem der dritte (äußere) Durchmesser des Bohrgestänges in einem Querschnitt des Bohrgestänges liegt, der vom Zentrum des Halses (32) oder Bereichs mit dem kleineren Durchmesser aus in der Richtung zum größeren Teil (10) der Länge des Bohrgestänges mit Innenrohr hin versetzt ist.
  14. Bohrgestänge mit Innenrohr nach einem der vorstehend aufgeführten Ansprüche, bei dem die Gewindeenden (12, 14) zunächst vom Bohrgestänge getrennt sind und durch reibverschweißte Verbindungen zu einer Rohrlänge mit konstantem Querschnitt verbunden werden, wobei die Länge mit konstantem Querschnitt den größeren Teil der Länge des Bohrgestänges mit Innenrohr bildet.
  15. Bohrgestänge mit Innenrohr nach Anspruch 5, bei dem das Außengewindeende (14) einen sich von einer ringförmigen Schulter (54) aus erstreckenden Gewindebereich (44) hat, wobei die Schulter (54) so ausgeführt ist, daß sie an das Ende (24) des Innengewindeendes (12) eines anderen Bohrgestänges stößt, wenn die beiden Bohrgestänge miteinander verschraubt werden, wobei der Außengewindebereich (44) kürzer als der Innengewinderücksprung ist, so daß, wenn das Außengewindeende (14) in das Innengewindeende (12) eines anderen Bohrgestänges hineingeschraubt wird, bis die Schulter an das Ende des anderen Bohrgestänges stößt, das Außengewindeende nicht den Boden des Innengewinderücksprungs erreicht.
  16. Bohrgestänge mit Innenrohr nach Anspruch 15, bei dem die ringförmige Schulter am Außengewindeendeabschnitt (14) stufenförmig ausgebildet ist und das passende Ende eines Innengewindeendeabschnitts (12) eines anderen Bohrgestänges eine Schulter aufweist, so daß, wenn die Bohrgestänge miteinander verschraubt werden, die Schultern ineinandergreifen, um eine wesentliche radiale Bewegung einer Schulter im Verhältnis zur anderen zu verhindern.
  17. Bohrgestänge mit Innenrohr nach einem der vorstehend aufgeführten Ansprüche, bei dem das Bohrgestänge mindestens einen außen gerippten Abschnitt hat, wobei der Außendurchmesser an den Kronen des gerippten Abschnitts gleich groß oder größer als der zweite Durchmesser ist.
  18. Bohrgestänge mit Innenrohr nach Anspruch 17, bei dem der außen gerippte Abschnitt den Außendurchmesser des Innengewindeendes bildet, das den zweiten Durchmesser aufweist.
  19. Bohrgestängeeinheit mit Innenrohr zum Gesteinsschlagbohren, bei der die Einheit mehrere Bohrgestänge mit Innenrohren nach Anspruch 1 beinhaltet, deren Enden durch Verbindungen miteinander verbunden sind, die ineinandergreifende Außen- und Innengewinde (44, 28) umfassen, wobei, wenn die Verbindungen hergestellt sind, ein Ende (24) eines Innengewindebauteils in Kontakt mit einer Außenschulter (54) am angrenzenden Außengewindebauteil steht, wobei die Außenschulter einen sich am Umfang erstreckenden, stufenförmig ausgebildeten Ansatz hat, wobei ein Teil des Endes des Innengewindebauteils am Ansatz anliegt, um eine relative radiale Bewegung zwischen den beiden Enden an der Position der Schulter zu verhindern.
  20. Bohrgestänge mit Innenrohr nach einem der vorstehend aufgeführten Ansprüche, bei dem A den ersten Durchmesser repräsentiert; B den zweiten Durchmesser repräsentiert; C den dritten Durchmesser repräsentiert; D den kleinsten Innendurchmesser des Innengewindeabschnitts repräsentiert; und E den Kerndurchmesser des Innengewindes im Innengewindeende repräsentiert;
    und wobei:
    A kleiner als B ist;
    B bis zu 150% von E beträgt;
    C 100 bis 130% von E beträgt; und
    D 45 bis 60% von E beträgt.
EP99305930A 1998-07-30 1999-07-26 Bohrgestänge mit Innenrohr Expired - Lifetime EP0979922B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9816494A GB2340148B (en) 1998-07-30 1998-07-30 Tube rod
GB9816494 1998-07-30

Publications (3)

Publication Number Publication Date
EP0979922A2 EP0979922A2 (de) 2000-02-16
EP0979922A3 EP0979922A3 (de) 2001-01-17
EP0979922B1 true EP0979922B1 (de) 2004-01-28

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EP99305930A Expired - Lifetime EP0979922B1 (de) 1998-07-30 1999-07-26 Bohrgestänge mit Innenrohr

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EP (1) EP0979922B1 (de)
AT (1) ATE258645T1 (de)
CA (1) CA2278987A1 (de)
GB (1) GB2340148B (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE60221414T2 (de) 2001-10-22 2008-04-10 Ion Peleanu Verfahren zur bohrloch-flüssigkeitsbehandlung und pumpengestänge dafür
SE524155C2 (sv) 2002-05-22 2004-07-06 Atlas Copco Secoroc Ab Gängförband för borrsträng för slående bergborrning
CN102926673A (zh) * 2012-12-02 2013-02-13 中国石油化工股份有限公司 防失稳油管接头
EP4386247A2 (de) * 2015-05-22 2024-06-19 Sandvik Intellectual Property AB Bohrstange oder adapter mit verstärkter stutzenkupplung

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3067593A (en) * 1960-08-29 1962-12-11 American Iron & Machine Works Integral tool joint drill pipe
US4601491A (en) * 1983-10-19 1986-07-22 Vetco Offshore, Inc. Pipe connector
SE8504842L (sv) * 1985-10-17 1987-04-18 Santrade Ltd Borrstang for slaende bergborrning
US5358285A (en) * 1992-12-03 1994-10-25 Prideco, Inc. Stress relief groove for drill pipe
US5355968A (en) * 1993-05-20 1994-10-18 Grant Tfw, Inc. Tool joint stress relief groove
US5535837A (en) * 1994-07-05 1996-07-16 Grant Prideco, Inc. Helical stress relief groove apparatus and method for subterranean well drill pipe assemblies

Also Published As

Publication number Publication date
ATE258645T1 (de) 2004-02-15
EP0979922A2 (de) 2000-02-16
CA2278987A1 (en) 2000-01-30
GB9816494D0 (en) 1998-09-23
GB2340148A (en) 2000-02-16
GB2340148B (en) 2002-12-31
EP0979922A3 (de) 2001-01-17

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