(19)
(11) EP 0 298 663 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
03.01.1990 Bulletin 1990/01

(43) Date of publication A2:
11.01.1989 Bulletin 1989/02

(21) Application number: 88305962.8

(22) Date of filing: 29.06.1988
(51) International Patent Classification (IPC)4: E21B 37/02, E21B 37/04, E21B 10/32
(84) Designated Contracting States:
DE FR GB IT

(30) Priority: 08.07.1987 GB 8716040

(71) Applicant: Tri-State Oil Tool (UK), a division of Baker Hughes Limited
Aberdeen AB2 OES (GB)

(72) Inventor:
  • Doig, Thomas
    Scotland (GB)

(74) Representative: Pacitti, Pierpaolo A.M.E. et al
Murgitroyd and Company 373 Scotland Street
Glasgow G5 8QA
Glasgow G5 8QA (GB)


(56) References cited: : 
   
       


    (54) Downhole cutting tool


    (57) The tool, for example an underreamer for descaling a casing (46), has an upper body (10) telescoped within a lower body (12) on which are pivoted operating arms (22). The arms (22) are deployed from a retracted to an extended position by the hydraulic pressure of drilling mud pumped through a through-bore (18) against a shoulder (26) causing the upper body (10) to move within the lower body (12), which movement pivots the arm (22) via camming surfaces (28,29).
    In the fully extended position, an outer surface (44) of the arm (22) acts as a locating pad, and the arm is mechanically locked by mating surfaces (34,36).







    Search report