(19)

(11)

EP 3 902 974 A1

(12)

(43) Date of publication: 03.11.2021 Bulletin 2021/44 (21) Application number: 19918702.2 (22) Date of filing: 26.12.2019

(51) International Patent Classification (IPC):  E21B 23/04(2006.01) E21B 29/02(2006.01) E21B 27/00(2006.01) E21B 43/263(2006.01) (52) Cooperative Patent Classification (CPC): E21B 29/02; F23D 2201/30; F23B 99/00 (86) International application number: PCT/US2019/068609 (87) International publication number: WO 2020/185285 (17.09.2020 Gazette 2020/38)

(84) Designated Contracting States: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR Designated Extension States: BA ME Designated Validation States: KH MA MD TN (30) Priority: 28.12.2018 US 201862785893 P 23.12.2019 US 201916725555 (71) Applicant: Robertson Intellectual Properties, LLC Arlington, TX 76001 (US)	(72) Inventors: ROBERTSON, Michael C. Arlington, TX 76001 (US) GRATTAN, Antony F. Arlington, TX 76001 (US) STREIBICH, Douglas J. Arlington, TX 76001 (US) HUGGINS, Cory L. Arlington, TX 76001 (US) (74) Representative: Barker Brettell LLP  100 Hagley Road Edgbaston Birmingham B16 8QQ Birmingham B16 8QQ (GB)