EP0105653B1 - Method and assembly for hot consolidating materials - Google Patents

Method and assembly for hot consolidating materials Download PDF

Info

Publication number
EP0105653B1
EP0105653B1 EP83305446A EP83305446A EP0105653B1 EP 0105653 B1 EP0105653 B1 EP 0105653B1 EP 83305446 A EP83305446 A EP 83305446A EP 83305446 A EP83305446 A EP 83305446A EP 0105653 B1 EP0105653 B1 EP 0105653B1
Authority
EP
European Patent Office
Prior art keywords
elastomeric
medium
ram
cavity
pot die
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
Application number
EP83305446A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0105653A1 (en
Inventor
Walter J. Rozmus
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.)
Dow Chemical Co
Original Assignee
Dow Chemical Co
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 Dow Chemical Co filed Critical Dow Chemical Co
Priority to AT83305446T priority Critical patent/ATE31886T1/de
Publication of EP0105653A1 publication Critical patent/EP0105653A1/en
Application granted granted Critical
Publication of EP0105653B1 publication Critical patent/EP0105653B1/en
Expired legal-status Critical Current

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/1208—Containers or coating used therefor
    • B22F3/1216—Container composition
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/1208—Containers or coating used therefor
    • B22F3/1216—Container composition
    • B22F3/1241—Container composition layered
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/14—Both compacting and sintering simultaneously
    • B22F3/15—Hot isostatic pressing

Definitions

  • the subject invention is used for consolidating material of metallic and nonmetallic powder compositions and combinations thereof to form a predetermined densified compact. Consolidation is usually accomplished by evacuating a container and filling the container with a powder to be consolidated and thereafter hermetically sealing the container. Pressure is then applied to the filled and sealed container to subject the powder to pressure. Typically, heat is also applied to heat the powder to a compaction temperature. The combination of heat and pressure facilitates consolidation of the powder.
  • the powder to be compacted is encapsulated in a substantially fully dense and incompressible container providing a pressure-transmitting medium which maintains its configurational integrity while being handled both at ambient temperatures and at the elevated compaction temperatures, yet becomes fluidic and capable of plastic flow when pressure is applied to the entire exterior surface thereof to hydrostatically compact the powder.
  • the powder is hermetically encapsulated within the pressure-transmitting medium which is thereafter heated to a temperature sufficient for compaction and densification of the powder.
  • the pressure-transmitting medium with the powder therein may be placed between two dies of a press which are rapidly closed to apply pressure to the entire exterior of the pressure-transmitting medium.
  • the pressure-transmitting medium at least immediately prior to a selected predetermined densification, must be fully dense and imcompressible and capable of flow so that the pressure transmitted to the powder is hydrostatic and, therefore, from all directions, i.e., omnidirectional.
  • the pressure-transmitting medium defining the container must be removed from the compacted material and in so doing the integrity of the pressure-transmitting medium is lost whereby either the pressure-transmitting medium is no longer usable or must be completely recycled to fabricate a new container.
  • the subject invention is for consolidating material of metallic and nonmetallic compositions and combinations thereof to form a densified compact of predetermined density wherein a quantity of such material which is less dense than the predetermined density is heated and disposed in a cavity in a pressure-transmitting medium to which external pressure is applied to the entire exterior of the medium to cause a predetermined densification of the material by hydrostatic pressure applied by the medium in response to the medium being substantially fully dense and incompressible and capable of elastic flow at least just prior to the predetermined densification, the pressure-transmitting medium being an elastomeric medium.
  • the invention is characterised by encapsulating the material in a thermal insulating barrier means disposed within the cavity of the elastomeric medium to establish a thermal barrier between the material to be compacted and the elastomeric medium prior to applying pressure to the medium to limit heat transfer between the material and the elastomeric medium.
  • the press In order to effect compaction hydrostatically through a substantially fully dense and incompressible medium in a press, the press must provide sufficient force to cause plastic flow of the medium.
  • the material to be compacted is placed within a pressure-transmitting medium which is, in turn, placed in a press where it is subjected to forces rendering it fluid and capable of transmitting forces hydrostatically to the material to be compacted and in so doing the pressure-transmitting medium changes shape.
  • the pressure-transmitting medium totally encapsulates the material being compacted and loses its integrity upon being moved from the compacted material. Because the pressure-transmitting medium changes shape during the compaction and has its integrity destroyed by being removed from the compacted material, it either cannot be reused or must undergo significant processing for reuse.
  • the pressure-transmitting medium comprises an elastomeric medium which becomes fully dense and incompressible and capable of elastic flow just prior to the predetermined densification of the compact, yet is sufficiently elastic to return to its initial configuration for continued and repetitive reuse and compaction.
  • This may be accomplished in accordance with the instant invention by utilizing a thermal insulating barrier means between the elastomeric medium and the heated material to be compacted so that the integrity of the elastomeric medium is not degraded by the heat and may be used repetitively.
  • the subject invention may be utilized for consolidating various metallic powders and non- metallic powders, as well as combinations thereof, to form a densified compact.
  • the degree of density of the powder is increased to a predetermined or desired density which may be full density or densification or less than full density or densification.
  • the invention relates to a method for consolidating material of metallic and nonmetallic compositions and combinations thereof to form a densified compact of a predetermined density wherein a quantity of such material which is less dense than the predetermined final density is encapsulated in a pressure-transmitting medium to which external pressure is applied to the entire exterior of the medium to cause a predetermined densification of the encapsulated material by hydrostatic pressure applied by the medium in response to the medium being substantially fully dense and incompressible and capable of elastic flow, i.e., fluidic, at least just prior to the predetermined densification.
  • the medium transmits pressure hydrostatically like a liquid omnidirectionally about the material for compaction thereof.
  • a quantity of less than fully dense powder 10 fills and is encapsulated within a container 12.
  • the container 12 is evacuated as by a vacuum through a tube (not shown) and then is filled with the powder 10 under vacuum through the tube. After filling, the tube is sealed to hermetically seal the container 12 with the powder 10 under a vacuum therein.
  • the container 10 is a thin-walled and preferably of a sheet metal material.
  • the container 12 may be filled and sealed in accordance with the teachings of United States Patent 4,229,872 granted October 28, 1980 and assigned to the assignee of the subject invention.
  • the container 12 is circular in cross section to define a cylinder and has a fill tube (not shown) extending from one end thereof. It will be understood, however, that the configuration of the container 12 will depend upon the desired configuration of the end part or compact.
  • an assembly for implementing the subject invention includes a pot die 14 and a ram 16 which include attachment points 18 for attaching alignment keys for aligning the pot die 14 and ram 16.
  • the pot die 14 and the ram 16 also include bores 20 for receiving attaching bolts or pins to attach the pot die 14 and ram 16 to a press which may be one of any of a number of well-known types.
  • the ram 16 and pit die 14 are aligned during the opening and closing of the press between the open position shown in Figure 1 and the closed position shown in FIGURE 2.
  • a pressure-transmitting medium comprising first and second elastomeric components 22 and 24, defines a cavity for encapsulating the material to be consolidated.
  • the pot die 14 is made of an incompressible material such as steel and includes a pot die cavity 26.
  • the ram 16 is made of an incompressible material such as steel and includes a ram-cavity 28 therein.
  • the ram 16 includes a raised flange or ridge 30 surrounding the ram-cavity 28.
  • the pot-die cavity 26 has peripheral surfaces for receiving and sliding engagement with the exterior surfaces of the raised flange 30 of the ram 16.
  • the interior surfaces of the cavity 26 in the pot die 14 are aligned with the exterior surfaces of the flange 30 of the ram 16 so that they are in close sliding engagement with one another as the pot die 14 and ram 16 are closed.
  • the first component 22 of the elastomeric medium is retained in the pot-die cavity 26 as by being wedged therein or having small amounts of adhesive securing the elastomeric component to the cavity 26.
  • the second elastomeric component 24 is retained in the ram-cavity 28.
  • the first and second elastomeric components 22 and 24 define a cylindrical cavity for surrounding the material 10 for compaction thereof.
  • the elastomeric components 22 and 24 may, in addition to natural rubber, consist of elastomers such as neoprene, polysiloxane elastomers, polyurethane, polysulfide rubber, polybutadiene, buna-S, etc.
  • the elastomeric medium making up the components 22 and 24 is elastic in that it may be compressed and. yet returns to its original configuration. However, after the elastomeric medium defining the components 22 and 24 is compressed to a certain degree, it becomes substantially incompressible, yet fluidic, i.e., capable of elastic flow, so that at the point of compaction and the desired densification of the powder 10, it hydrostatically applies pressure omnidirectionally about the container 12 to compact the powder 10 therein.
  • the container 12 is of a material which is thin-walled and reduces in volume to compact the powder 10.
  • a thermal insulating barrier means establishes a thermal barrier between the powder material 10 and the elastomeric medium 22 and 24 prior to applying pressure to the medium 22 and 24 by the closure of the pot die 14 and ram 16 to limit the heat transfer between the material 10 and the elastomeric medium 22 and 24.
  • the thermal insulating barrier means includes a first thermal insulating jacket 32 completely surrounding the container 12 for limiting the heat loss from the material 10 and a second thermal insulating jacket 34 surrounding the first jacket 32 for protecting the elastomeric components 24 and 22 from heat emanating from the first jacket 32.
  • the jackets 32 and 34 are made of a ceramic material having a very low thermal conductivity.
  • the material of which the jackets 32 and 34 are made is fluidic or capable of flow at least just prior to the desired compaction of the powder 10 as pressure is applied thereabout hydrostatically through the elastomeric components 22 and 24.
  • the material of the jackets 32 and 34 may flow in the manner of quicksand just prior to compaction.
  • the container 12 has the first jacket 32 cast thereabout in a mold so that the jacket 32 completely encapsulates the container 12 and is a homogeneous material.
  • the first jacket 32 with the container 12 and the material therein is heated to an elevated temperature sufficient for compaction. During this heating, the jacket 32 becomes heated.
  • the jacket 32 With the container 12 and the material 10 therein, is placed within the second jacket 34 within the cavity defined by the elastomeric components 22 and 24.
  • the second jacket 34 is made of two complementary sections which mate together to completely encapsulate and surround the first jacket 32.
  • the second jacket 34 is also fluidic or capable of flow just prior to the desired densification of the powder 10.
  • the flange 30 enters the cavity 26 of the pot die 14 before the elastomeric components 22 and 24 contact one another and are compressed to create hydrostatic pressure as they become incompressible and fluidic for transmitting hydrostatic pressure omnidirectionally against the second jacket 34 which, in turn, transmits the hydrostatic pressure through the jacket 32 and the container 12 to compact and densify the powdered metal 10.
  • either or both of the jackets 32 and 34 may be made of a ceramic having reinforcing fibres therein which allow some contraction or expansion of the basic materials making up the jackets 32 or 34. In other words, either one of the jackets 32 and 34 may have fibers dispersed therein for reinforcement.
  • jackets 32 and 34 may be made of a crumbling material which may be crushed to become incompressible, but yet fluidic enough to transmit the pressure hydrostatically from the elastomeric components 22 and 24 to the container 12 and, thus, to the powdered metal 10.
  • a seal 36 of a harder material than the elastomeric medium defining the components 22 and 24 is disposed within and below the upper extremity of the cavity 26 of the pot die 14 so that after the flange 30 of the ram 16 enters the pot die 14 and applies pressure to the elastomeric components 22 and 24, the seal 36 is forced into sealing engagement with the interior surfaces of the cavity 26 in the pot die 14 at the juncture thereof with the exterior surface of the flange 30 of the ram 16 to prevent leakage of the elastomeric components 22 and 24 between the ram 16 and the pot die 14.
  • the seal 36 is of a higher durometer than the elastomeric components 22 and 24 and, therefore, is less capable of plastic flow albeit the seal material 36 is capable of plastic flow.
  • the elastomeric components 22 and 24 engage one another and begin to compress to a point at which they become incompressible and convey pressure hydrostatically in an omnidirectional fashion to compact the powdered metal 10.
  • the components 22 and 24, as well as the seal 36 include a plurality of lubrication grooves 38 and 40, respectively, in the exterior surfaces thereof to facilitate movement relative to the adjacent supporting surface of the cavities in which they are disposed.
  • a lubricant is disposed within the grooves 38 and 40 to allow the material to compress and slide relative to the adjacent surfaces.
  • the grooves are diminished in size so as to be imperceivable, yet the grooves exist to trap incompressible lubricant therein during full compression.
  • the powdered metal 10 fills a thin-walled container 12 which is, in turn, encapsulated within a first thermal insulating jacket 32 as by having the jacket 32 cast thereabout, after which they are heated to an elevated temperature sufficient for compaction of the powder 10.
  • a lower section of the second jacket 34 may be disposed within a cavity in the elastomeric component 22 of the pot die 14 and the first jacket 32 with the powder therein disposed within the lower section 34 of the outer jacket.
  • the upper half or section of the second jacket 34 is then disposed over the heated inner or first jacket 32 and the ram and pot die are moved together to the position shown in FIGURE 2 to densify and compact the powder into a densified compact 10'.
  • the elastomeric medium defining the components 22 and 24 may initially be compressible, but upon reaching a certain point of applied pressure becomes incompressible so as to hydrostatically transmit pressure in an omnidirectional fashion entirely about the jackets 32 and 34 to the powder 10 to compact and densify the powder into the compact 10' of the desired densification.
  • the pot die 14 and ram 16 may be opened to allow the elastomeric components 22 and 24 to return to their precompressed shape and to remove the comapct 10' so that thereafter the container 10 and the jackets 32 and 34 may be removed to expose the compact 10'.
  • the jackets 32 and 34 will be disposable and new jackets would be utilized on successive opening and closing of the pot die 14 and ram 16 for successively forming compacts 10'.
  • thermal insulating jacket may be utilized between the heated powdered material 10 and the elastomeric components 22 and 24. Additionally, the thicknesses of the thermal insulating barrier means may vary depending on the sizes, configurations, masses, etc. of the powder 10 to be compacted and densified.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Press-Shaping Or Shaping Using Conveyers (AREA)
  • Powder Metallurgy (AREA)
  • Press Drives And Press Lines (AREA)
  • Investigating Or Analyzing Materials Using Thermal Means (AREA)
EP83305446A 1982-09-20 1983-09-16 Method and assembly for hot consolidating materials Expired EP0105653B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT83305446T ATE31886T1 (de) 1982-09-20 1983-09-16 Verfahren und vorrichtung zum heissverdichten von material.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US41943582A 1982-09-20 1982-09-20
US419435 1982-09-20

Publications (2)

Publication Number Publication Date
EP0105653A1 EP0105653A1 (en) 1984-04-18
EP0105653B1 true EP0105653B1 (en) 1988-01-13

Family

ID=23662261

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83305446A Expired EP0105653B1 (en) 1982-09-20 1983-09-16 Method and assembly for hot consolidating materials

Country Status (11)

Country Link
EP (1) EP0105653B1 (ja)
JP (1) JPS5980701A (ja)
AR (1) AR231811A1 (ja)
AT (1) ATE31886T1 (ja)
AU (3) AU545852B2 (ja)
BR (1) BR8305054A (ja)
CA (1) CA1222152A (ja)
DE (1) DE3375286D1 (ja)
DK (1) DK160680C (ja)
MX (1) MX156866A (ja)
NO (1) NO164080C (ja)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63183104A (ja) * 1987-01-22 1988-07-28 Agency Of Ind Science & Technol 高強度・難加工粉末材の超塑性ウォ−ムダイ・パック鍛造法
JPH0528734Y2 (ja) * 1988-01-06 1993-07-23
JPH02140603U (ja) * 1989-04-25 1990-11-26
DE602004022171D1 (de) 2003-06-17 2009-09-03 Phibrowood Llc Teilchenförmiges holzschutzmittel und herstellungsverfahren dafür
US20050252408A1 (en) 2004-05-17 2005-11-17 Richardson H W Particulate wood preservative and method for producing same

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1338493A (fr) * 1962-08-13 1963-09-27 Desmarquest & Cie L Procédé et appareil de frittage de poudres
GB1087400A (en) * 1964-01-03 1967-10-18 Super Temp Corp Method and apparatus for consolidation of powdered materials and articles of manufacture produced therefrom
US3496425A (en) * 1968-02-23 1970-02-17 Trw Inc Art of forming powder compacts of uniform interconnected porosity
SE417580B (sv) * 1979-02-27 1981-03-30 Asea Ab Forfarande for framstellning av emnen fran pulver genom hogt allsidigt tryck
US4414028A (en) * 1979-04-11 1983-11-08 Inoue-Japax Research Incorporated Method of and apparatus for sintering a mass of particles with a powdery mold
SE426790B (sv) * 1980-04-25 1983-02-14 Asea Ab Forfarande for isostatisk pressning av pulver i en kapsel

Also Published As

Publication number Publication date
NO164080C (no) 1990-08-29
DK400583A (da) 1984-03-21
AU545852B2 (en) 1985-08-01
DK400583D0 (da) 1983-09-02
AR231811A1 (es) 1985-03-29
AU561135B2 (en) 1987-04-30
AU3982685A (en) 1985-09-12
JPS6239201B2 (ja) 1987-08-21
DE3375286D1 (en) 1988-02-18
ATE31886T1 (de) 1988-01-15
JPS5980701A (ja) 1984-05-10
AU3982585A (en) 1985-09-12
CA1222152A (en) 1987-05-26
EP0105653A1 (en) 1984-04-18
MX156866A (es) 1988-10-06
NO164080B (no) 1990-05-21
AU561136B2 (en) 1987-04-30
DK160680B (da) 1991-04-08
DK160680C (da) 1991-09-23
BR8305054A (pt) 1984-05-08
NO833160L (no) 1984-03-21
AU1896983A (en) 1984-04-19

Similar Documents

Publication Publication Date Title
US4596694A (en) Method for hot consolidating materials
US4597730A (en) Assembly for hot consolidating materials
EP0092992B1 (en) Pressure transmitting medium and method for utilizing same to densify material
US4547337A (en) Pressure-transmitting medium and method for utilizing same to densify material
KR900002123B1 (ko) 자동밀봉 유체 다이
US4526748A (en) Hot consolidation of powder metal-floating shaping inserts
EP0105653B1 (en) Method and assembly for hot consolidating materials
EP0145108B1 (en) A method for producing a clad alloy article and an assembly for use therein
WO2000006360A1 (en) Resin transfer molding using a double-chamber vacuum mold assembly
EP0278180B1 (en) Plastic foam containers for the densification of powder material
US5066454A (en) Isostatic processing with shrouded melt-away mandrel
US4478788A (en) Method of sealing a container
CA1090623A (en) Container for hot consolidating powder
US4255103A (en) Hot consolidation of powder metal-floating shaping inserts
EP0094164A1 (en) Method of consolidating material with a cast pressure transmitter
US4500009A (en) Sealed container
US5476268A (en) Seal assembly with a hard seal layer actuated through a silicone layer
US5234335A (en) Hydraulically, pneumatically or mechanically driven power unit
McEntire Dry pressing
US5470083A (en) Seal assembly with a hard seal layer actuated through a silicone layer
DE3047237C2 (de) Verfahren zum Herstellen kompliziert geformter Preßkörper mittels heißisostatischen Pressens
US7250131B2 (en) Method and a system for hot hydrostatic pressing
JPS61266204A (ja) 静水圧加圧成形用型並びにそれを用いた粉末成形方法
RU2044603C1 (ru) Пресс-форма для гидростатического прессования изделий из порошка
SU1349863A2 (ru) Устройство дл гидроэкструзии материалов в режиме гидродинамической смазки

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

Designated state(s): AT BE CH DE FR GB IT LI LU NL SE

17P Request for examination filed

Effective date: 19841010

17Q First examination report despatched

Effective date: 19860121

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: ROC-TEC, INC.

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: THE DOW CHEMICAL COMPANY

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT BE CH DE FR GB IT LI LU NL SE

REF Corresponds to:

Ref document number: 31886

Country of ref document: AT

Date of ref document: 19880115

Kind code of ref document: T

REF Corresponds to:

Ref document number: 3375286

Country of ref document: DE

Date of ref document: 19880218

ET Fr: translation filed
ITF It: translation for a ep patent 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
ITTA It: last paid annual fee
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19920605

Year of fee payment: 10

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 19920610

Year of fee payment: 10

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 19920629

Year of fee payment: 10

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: AT

Payment date: 19920710

Year of fee payment: 10

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: LU

Payment date: 19920716

Year of fee payment: 10

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19920930

Year of fee payment: 10

EPTA Lu: last paid annual fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

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

Effective date: 19930916

Ref country code: AT

Effective date: 19930916

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

Ref country code: SE

Effective date: 19930917

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

Ref country code: LI

Effective date: 19930930

Ref country code: CH

Effective date: 19930930

Ref country code: BE

Effective date: 19930930

BERE Be: lapsed

Owner name: THE DOW CHEMICAL CY

Effective date: 19930930

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

Ref country code: NL

Effective date: 19940401

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

EUG Se: european patent has lapsed

Ref document number: 83305446.3

Effective date: 19940410

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19980521

Year of fee payment: 16

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19980522

Year of fee payment: 16

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19980701

Year of fee payment: 16

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: 19990916

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

Effective date: 19990916

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

Ref country code: FR

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

Effective date: 20000531

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

Ref country code: DE

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

Effective date: 20000701

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST