EP0511547B1 - Gesteinsbohrmeissel - Google Patents

Gesteinsbohrmeissel Download PDF

Info

Publication number
EP0511547B1
EP0511547B1 EP92106450A EP92106450A EP0511547B1 EP 0511547 B1 EP0511547 B1 EP 0511547B1 EP 92106450 A EP92106450 A EP 92106450A EP 92106450 A EP92106450 A EP 92106450A EP 0511547 B1 EP0511547 B1 EP 0511547B1
Authority
EP
European Patent Office
Prior art keywords
inserts
gage
insert
heel
borehole
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
EP92106450A
Other languages
English (en)
French (fr)
Other versions
EP0511547A2 (de
EP0511547A3 (en
Inventor
David P. Crockett
Michael E. Hooper
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.)
Smith International Inc
Original Assignee
Smith International Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Smith International Inc filed Critical Smith International Inc
Publication of EP0511547A2 publication Critical patent/EP0511547A2/de
Publication of EP0511547A3 publication Critical patent/EP0511547A3/en
Application granted granted Critical
Publication of EP0511547B1 publication Critical patent/EP0511547B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00—Drill bits
    • E21B10/08—Roller bits
    • E21B10/16—Roller bits characterised by tooth form or arrangement
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH DRILLING; MINING
    • E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B10/00—Drill bits
    • E21B10/46—Drill bits characterised by wear resisting parts, e.g. diamond inserts
    • E21B10/50—Drill bits characterised by wear resisting parts, e.g. diamond inserts the bit being of roller type
    • E21B10/52—Drill bits characterised by wear resisting parts, e.g. diamond inserts the bit being of roller type with chisel- or button-type inserts

Definitions

  • the present invention relates generally to a rock bit of the type as described in the preamble of claim 1.
  • Earth boring rock bits for drilling oil and gas wells typically have three rotatable cutters that roll over the bottom of a borehole as the bit rotates. Each cutter is generally conical and has a frustoconical heel surface that passes near the borehole sidewall as the cutter rotates.
  • One type of rock bit known as a tungsten carbide insert bit or TCI bit, has wear resistant inserts secured in holes formed in the cutters. Such inserts are usually made of tungsten carbide.
  • the inserts are arranged in circumferential rows on the conical surface of the rotatable cutter at various distances from the heel surface.
  • the row nearest, but not on the heel surface is known as the gage row.
  • the gage row of inserts cuts rock at the gage of the hole.
  • the heel surface extends upwardly along the wall of the hole drilled by the gage row.
  • certain cutters have gage row structure that includes staggered rows located thereon.
  • the staggered rows comprise two rows of inserts alternately spaced so that the grip portion of the inserts do not interfere.
  • the inserts on the gage row are oriented in such a manner to cause the cutting elements to cut both the borehole bottom and sidewall.
  • This combined cutting action compromises the insert because the cutting action operating on the borehole bottom is usually a crushing and gouging action while the cutting action operating on the sidewall is a scraping action.
  • the crushing action calls for a tough insert while the scraping action calls for a hard insert.
  • one grade of tungsten carbide cannot ideally perform both functions.
  • the inserts of the heel rows of these prior art bits cannot be as hard as that recommended for the sidewall scraping action because they must be tough enough to crush the bottom hole formation.
  • the gage row of inserts cannot be as tough as the interior rows of inserts because they must perform a large portion of scraping action on the borehole sidewall.
  • the present invention as defined in claim 1 minimizes the above-mentioned shortcomings by providing a rolling cone rock bit with a plurality of cutters each mounted on the body of the bit to rotate about an axis.
  • Each cutter has a generally frusto-conical support surface for rolling contact with the bottom of a borehole, and a heel surface at the base of the cutter adjacent to the sidewall of the borehole.
  • a plurality of wear resistant inserts positioned on the support surface are arranged in circumferential rows, each insert being generally cylindrical with a projected crown area profile and having a central axis.
  • each gage insert is oriented to have its axis extend partiallly radially outward to enable the gage insert to engage the borehole bottom.
  • Each gage insert defines a cutting surface projected crown area profile taken through a section through the centerline of the cone.
  • a plurality of heel inserts located near the gage inserts are at an acute angle with respect to the gage inserts in a direction away from the apex of the cone.
  • Each insert defines a cutting surface projected crown area profile taken through a section through the centerline of the cone. The crown area profile of a heel insert, when rotated around the cone to the same plane as a gage insert crown area profile, overlaps the gage insert crown area profile to enable the heel inserts to slidably engage the borehole sidewall.
  • the heel row inserts scrape against the wall, they are made of a harder grade of tungsten carbide than the gage row inserts, and the gage row inserts are tougher than the heel row inserts.
  • the heel row insert crown area profiles are located up the borehole sidewall within three millimeters of the gage row insert crown area profiles.
  • FIGURE 1 illustrates a drill bit or rock bit, generally indicated by an arrow 10, having a threaded pin section 11 for securing to the bottom end of a drill string.
  • the rock bit further includes a main body 12 having a plurality of legs 13, 14 and 15 extending downwardly therefrom. Each leg includes a bearing pin (not shown in FIGURE 1) extending toward the center of the bit.
  • Three cone shaped cutters 16 are rotatably mounted on the bearing pins and are adapted to roll along the bottom of a borehole as the bit is rotated.
  • the cutters 16 tend to roll along the hole bottom much like a wheel except that because the axes of the bearing pins are offset from the axis of the bit, and because of the geometry of the cones, a true roll of the cones is not possible. Therefore, in addition to the rolling motion, a small sliding motion is imparted thereto which would be analogous to the movement of an automobile tire that is out of alignment.
  • Each cutter cone 16 has a plurality of wear resistant inserts 20 interferingly secured by the insert grip 90 in mating holes drilled in the support surface of the cutter cone.
  • the inserts 20 are constructed from sintered tungsten carbide.
  • the inserts 20 are located in rows that extend circumferentially around the generally conical surface of each cutter. Certain of the rows are arranged to intermesh with other rows of the other cutters so that the entire bottom of the hole is drilled.
  • each cutter is generally conically shaped with a nose area 21 at the apex of the cone and a heel surface 22 at the base of the cone.
  • the heel surface 22 is frustoconical and is adapted to pass near the wall of the borehole as the cutters rotate about the borehole bottom.
  • the row of inserts 20 closest to the heel surface 22 is called the gage row 23.
  • the gage row inserts are further separated into a first row of gage inserts 24 and a second row of heel inserts 25.
  • each of the gage inserts 24 is oriented with its axis extending radially outwardly and downwardly to engage the borehole bottom.
  • the cutting profiles of the inserts are illustrated in a cross section as seen in FIGURE 3.
  • Each of the heel inserts 25, on the other hand, is with its axis oriented outwardly and downwardly at a greater angle from the centerline of the cone.
  • the heel inserts are oriented at an acute angle to the gage inserts in a direction away from the apex of the cutter cone to more closely face the sidewall of the borehole.
  • the inserts 20 must be made of an extremely tough grade of tungsten carbide.
  • gage row of inserts 24 also contact the hole bottom in a similar manner. However, prior to the present invention, these inserts 24 also performed a scraping action along the borehole sidewall before they make their imprint on the borehole bottom (see FIGURE 4). As mentioned previously, this necessitated making the gage row inserts harder to accommodate the scraping function and minimize wear which can cause the hole to be drilled under the desired gage or diameter. Unfortunately, when one makes a tungsten carbide insert harder, it necessarily becomes less tough.
  • the present invention minimizes such a problem by having the heel row inserts 25 interleaved between the the gage inserts with their cutting surface profiles being overlapped.
  • the crowns of the gage row inserts and heel row inserts are separated by only a distance D 1 in the cutting surface profile as illustrated in FIGURE 3. This enables the heel inserts 25 to engage the borehole sidewall at points much lower in the borehole and much sooner in the cutting cycle than previous heel inserts.
  • the distance D 1 is preferably within four millimeters in a 20 cm diameter rock bit.
  • the crown of the insert is the part of the projected area of the insert that contacts the intact rock formation, as illustrated in FIGURE 3.
  • the insert is a gage insert
  • the same planetary motion occurs except that the planetary orbit is the largest.
  • the same type of movement is involved, i.e. the insert rolls over the spot with a small sliding motion.
  • the gage insert would also contact a portion of the sidewall during a portion of its travel. This, of course, results in almost pure scraping, and the gage insert normally would have to be harder than an inner row insert because of the large abrasive forces acting thereon.
  • each alternate gage row insert 24 oriented toward the hole bottom to cut the hole bottom while the other of each alternate heel row insert 25 being oriented to the sidewall to cut the sidewall.
  • the first set can be made of a hard material and the second set of a tough material.
  • this is accomplished by two means, i.e. the orientation of the two inserts (one toward the hole bottom and the other toward the sidewall) and the close proximity of the insert projection profiles.
  • the closeness is shown by dimension D 1 in Figure 3, which is preferably less than four millimeters.
  • the heel row inserts 25 are restricted to mostly scraping, they can be made of a very hard tungsten carbide or they can also be coated with super hard abrasives such as polycrystalline diamond.
  • inserts 24 are shown as hemispherical, they can also be constructed of different conventional shapes such as chisels.
  • the heel row inserts 25 can have their abrasive surfaces be slightly spherical, flat, or some other configuration and still come within the invention.

Claims (9)

  1. Gesteinsbohrmeißel (10) zum Bohren eines Bohrloches mit einem Meißelkörper (12), einer Vielzahl von Schneidköpfen (16), die jeweils am Meißelkörper (12) zum Drehen um eine Achse montiert sind, wobei jeder Schneidkopf (16) eine im allgemeinen kegelstumpfförmige Tragfläche für einen rollenden Kontakt mit dem Boden eines Bohrloches aufweist, jeder Schneidkopf (16) ferner eine rückwärtige Oberfläche (22) an seiner Basis benachbart der Seitenwand des Bohrloches sowie eine Vielzahl von verschleißfesten Einsätzen (20, 24) aufweist, die an der Tragfläche positioniert und in Umfangsreihen angeordnet sind, wobei jeder Einsatz (20, 24) im wesentlichen zylindrisch mit einem vorstehenden, gewölbten Flächenprofil ausgebildet ist und eine zentrale Achse aufweist, wobei eine der Einsatzreihen benachbart der rückwärtigen Oberfläche (22) angeordnet ist und eine Reihe (23) von Kalibereinsätzen definiert, wobei jeder Kalibereinsatz (24) so ausgerichtet ist, daß seine Achse teilweise radial nach außen weist, damit der Kalibereinsatz (24) mit dem Boden des Bohrloches in Eingriff treten kann, wobei jeder Kalibereinsatz (24) ferner ein vorstehendes, gewölbtes Flächenprofil einer Schneidfläche definiert, bezüglich eines Schnitts durch die Mittellinie des Kegels, und mit einer Mehrzahl von rückwärtigen Einsätzen (25), die nahe den Kalibereinsätzen (24) unter einem spitzen Winkel bezüglich der Kalibereinsätze (24) in einer Richtung weg vom Scheitelpunkt des Kegels angeordnet sind, dadurch gekennzeichnet, daß jeder rückwärtige Einsatz (25) ferner ein vorstehendes, gewölbtes Flächenprofil der Schneidfläche im Schnitt durch die Mittellinie des Kegels aufweist, wobei das gewölbte Flächenprofil der rückwärtigen Einsätze (25), wenn sie um den Kegel zur gleichen Ebene wie ein gewölbtes Flächenprofil des Kalibereinsatzes gedreht wird, das gewölbte Flächenprofil des Kalibereinsatzes überlappt, so daß die rückwärtigen Einsätze (25) gleitend mit der Seitenwand des Bohrloches in Eingriff treten können.
  2. Gesteinsmeißel nach Anspruch 1, wobei die rückwärtigen Einsätze (25) zwischen die Kalibereinsätze (24) eingefügt sind.
  3. Gesteinsmeißel nach einem der vorangegangenen Ansprüche, wobei die Einsätze (20, 24, 25) aus Wolframcarbid hergestellt sind.
  4. Gesteinsmeißel nach Anspruch 3, wobei die Einsätze (25) der rückwärtigen Reihe aus einem Wolframcarbid eines höheren Härtegrades als die Einsätze (24) der Kaliberreihe hergestellt sind.
  5. Gesteinsmeißel nach Anspruch 4, wobei die Einsätze (24) der Kaliberreihe aus dem gleichen Hochleistungs-Wolframcarbid wie die anderen Reihen der Einsätze (20) hergestellt sind.
  6. Gesteinsmeißel nach einem der vorstehenden Ansprüche, wobei die gewölbten Flächenprofile der Einsätze der rückwärtigen Reihe bezüglich der Seitenwand des Bohrloches innerhalb von 4 mm höher angeordnet sind als die gewölbten Flächenprofile der Einsätze der Kaliberreihe.
  7. Gesteinsmeißel nach einem der vorstehenden Ansprüche, wobei die rückwärtigen Einsätze (25) mit einer äußeren Schicht aus polykristallinem Diamant beschichtet sind.
  8. Gesteinsmeißel nach einem der vorstehenden Ansprüche, wobei die Drehachsen der Schneidköpfe (16) jeweils gegenüber der Achse des Meißelkörpers (12) versetzt sind.
  9. Gesteinsmeißel nach einem der vorstehenden Ansprüche, wobei die Schneidköpfe (16) bei ihrer Drehung eine im wesentlichen flache Oberfläche, die dem Boden eines Bohrlochs entspricht, und eine im wesentlichen zylindrische Oberfläche definieren, die der Seitenwand eines Bohrlochs entspricht.
EP92106450A 1991-05-01 1992-04-14 Gesteinsbohrmeissel Expired - Lifetime EP0511547B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US69390091A 1991-05-01 1991-05-01
US693900 1996-04-29

Publications (3)

Publication Number Publication Date
EP0511547A2 EP0511547A2 (de) 1992-11-04
EP0511547A3 EP0511547A3 (en) 1993-04-14
EP0511547B1 true EP0511547B1 (de) 1996-12-11

Family

ID=24786590

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92106450A Expired - Lifetime EP0511547B1 (de) 1991-05-01 1992-04-14 Gesteinsbohrmeissel

Country Status (5)

Country Link
EP (1) EP0511547B1 (de)
CA (1) CA2066296A1 (de)
DE (1) DE69215746D1 (de)
MX (1) MX9201958A (de)
NO (1) NO921667L (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7729895B2 (en) 2005-08-08 2010-06-01 Halliburton Energy Services, Inc. Methods and systems for designing and/or selecting drilling equipment with desired drill bit steerability
US7860693B2 (en) 2005-08-08 2010-12-28 Halliburton Energy Services, Inc. Methods and systems for designing and/or selecting drilling equipment using predictions of rotary drill bit walk
US7860696B2 (en) 2005-08-08 2010-12-28 Halliburton Energy Services, Inc. Methods and systems to predict rotary drill bit walk and to design rotary drill bits and other downhole tools
US9493990B2 (en) 2004-03-02 2016-11-15 Halliburton Energy Services, Inc. Roller cone drill bits with optimized bearing structures

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5323865A (en) * 1992-09-23 1994-06-28 Baker Hughes Incorporated Earth-boring bit with an advantageous insert cutting structure
US5341890A (en) * 1993-01-08 1994-08-30 Smith International, Inc. Ultra hard insert cutters for heel row rotary cone rock bit applications
US5668092A (en) * 1993-04-07 1997-09-16 Smith International, Inc. Rock bit grease composition
US5542485A (en) * 1993-07-08 1996-08-06 Baker Hughes Incorporated Earth-boring bit with improved cutting structure
US5351768A (en) * 1993-07-08 1994-10-04 Baker Hughes Incorporated Earth-boring bit with improved cutting structure
US5819861A (en) * 1993-07-08 1998-10-13 Baker Hughes Incorporated Earth-boring bit with improved cutting structure
US5589443A (en) * 1995-12-21 1996-12-31 Smith International, Inc. Rock bit grease composition
SE523853C2 (sv) 1997-06-30 2004-05-25 Smith International Borrkrona med stora insatser
US20040045742A1 (en) 2001-04-10 2004-03-11 Halliburton Energy Services, Inc. Force-balanced roller-cone bits, systems, drilling methods, and design methods
ZA200104086B (en) * 2000-05-18 2003-02-18 Smith International Rolling cone bit with elements fanned along the gage curve.
US6374930B1 (en) * 2000-06-08 2002-04-23 Smith International, Inc. Cutting structure for roller cone drill bits
RU2473770C1 (ru) * 2011-10-05 2013-01-27 Дмитрий Юрьевич Сериков Буровое шарошечное долото

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2990025A (en) * 1958-06-16 1961-06-27 Dresser Ind Bit
CA938605A (en) * 1969-01-28 1973-12-18 Dresser Industries Soft formation insert bits
US3727705A (en) * 1972-01-21 1973-04-17 Hughes Tool Co Drill bit with improved gage compact arrangement

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9493990B2 (en) 2004-03-02 2016-11-15 Halliburton Energy Services, Inc. Roller cone drill bits with optimized bearing structures
US7729895B2 (en) 2005-08-08 2010-06-01 Halliburton Energy Services, Inc. Methods and systems for designing and/or selecting drilling equipment with desired drill bit steerability
US7778777B2 (en) 2005-08-08 2010-08-17 Halliburton Energy Services, Inc. Methods and systems for designing and/or selecting drilling equipment using predictions of rotary drill bit walk
US7827014B2 (en) 2005-08-08 2010-11-02 Halliburton Energy Services, Inc. Methods and systems for design and/or selection of drilling equipment based on wellbore drilling simulations
US7860693B2 (en) 2005-08-08 2010-12-28 Halliburton Energy Services, Inc. Methods and systems for designing and/or selecting drilling equipment using predictions of rotary drill bit walk
US7860696B2 (en) 2005-08-08 2010-12-28 Halliburton Energy Services, Inc. Methods and systems to predict rotary drill bit walk and to design rotary drill bits and other downhole tools
US8145465B2 (en) 2005-08-08 2012-03-27 Halliburton Energy Services, Inc. Methods and systems to predict rotary drill bit walk and to design rotary drill bits and other downhole tools
US8296115B2 (en) 2005-08-08 2012-10-23 Halliburton Energy Services, Inc. Methods and systems for designing and/or selecting drilling equipment using predictions of rotary drill bit walk
US8352221B2 (en) 2005-08-08 2013-01-08 Halliburton Energy Services, Inc. Methods and systems for design and/or selection of drilling equipment based on wellbore drilling simulations
US8606552B2 (en) 2005-08-08 2013-12-10 Halliburton Energy Services, Inc. Methods and systems for designing and/or selecting drilling equipment using predictions of rotary drill bit walk

Also Published As

Publication number Publication date
NO921667L (no) 1992-11-02
MX9201958A (es) 1992-11-01
DE69215746D1 (de) 1997-01-23
EP0511547A2 (de) 1992-11-04
EP0511547A3 (en) 1993-04-14
NO921667D0 (no) 1992-04-29
CA2066296A1 (en) 1992-11-02

Similar Documents

Publication Publication Date Title
US5353885A (en) Rock bit
CA2220679C (en) Rolling cone bit with gage and off-gage cutter elements positioned to separate sidewall and bottom hole cutting duty
EP0511547B1 (de) Gesteinsbohrmeissel
CA2288923C (en) High offset bits with super-abrasive cutters
US6439326B1 (en) Centered-leg roller cone drill bit
US5813485A (en) Cutter element adapted to withstand tensile stress
US5346025A (en) Drill bit with improved insert cutter pattern and method of drilling
US7686106B2 (en) Rock bit and inserts with wear relief grooves
US6651758B2 (en) Rolling cone bit with elements fanned along the gage curve
US20080060852A1 (en) Gage configurations for drill bits
GB2347957A (en) Cutter element adapted to withstand tensile stress
AU2725997A (en) Rolling cone bit with enhancements in cutter element placement and materials to optimize borehole corner cutting duty
CA2257934C (en) Cutter element adapted to withstand tensile stress
CA1046497A (en) Rotary rock bit with multiple row coverage for very hard formations
CA2257885C (en) Non-symmetrical stress-resistant rotary drill bit cutter element
GB2349405A (en) Rolling cone bit
GB2378725A (en) A roller cone drill bit for hard formations having a high offset
GB2373275A (en) Roller cone drill bit

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): DE FR GB IT NL

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): DE FR GB IT NL

17P Request for examination filed

Effective date: 19931008

17Q First examination report despatched

Effective date: 19950118

GRAG Despatch of communication of intention to grant

Free format text: ORIGINAL CODE: EPIDOS AGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAH Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOS IGRA

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): DE FR GB IT NL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRE;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.SCRIBED TIME-LIMIT

Effective date: 19961211

Ref country code: FR

Effective date: 19961211

Ref country code: NL

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 19961211

REF Corresponds to:

Ref document number: 69215746

Country of ref document: DE

Date of ref document: 19970123

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19970312

NLV1 Nl: lapsed or annulled due to failure to fulfill the requirements of art. 29p and 29m of the patents act
EN Fr: translation not filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19990318

Year of fee payment: 8

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20000414

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20000414