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Expired European patentEurope

Method and apparatus for reducing field filter cake on sponge cores

EP 0132020 B1 · Applicant: Diamond Oil Well Drilling Co.

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Listed from its EPO record in Patent Yard's archive of European patents past their term. Its claims, description and drawings are in the EPO PDF and on Google Patents, and the Claude kit works from them.

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Why it's free to use

  • Filed March 27, 1984 and granted September 16, 1987. A European patent lasts at most 20 years from filing, so its term ended March 27, 2004.
  • A supplementary protection certificate, which can extend a medicine or crop-protection patent, adds at most five and a half years, so even that would have ended by September 27, 2009.
  • We check European rights only. A US or other national patent in its family could still be in force: check its family on Espacenet or Google Patents.
FiledMarch 27, 1984
PublishedJanuary 23, 1985
GrantedSeptember 16, 1987
Term endedMarch 27, 2004
Application numberEP 84302058
Classification (CPC)E21B25/08

Timeline

Timeline From EPO dates

1985198719891991199319951997199920012003Application filedMarch 27, 1984PublishedJan 23, 1985Patent grantedSep 16, 1987Term endedMarch 27, 2004

Sources & verification

Official EPO records

Full published documentClaims, description and drawings as a PDF.EPOEuropean Patent RegisterProcedure, status, file inspection and legal events.EPOLinked open EP data recordThe bibliographic record this page is built from.EPO

Cross-check elsewhere

Google PatentsFull text, worldwide family, citing patents and legal events.patents.google.comEspacenetNational family members and their legal status.European Patent Office

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