| (19) |
 |
|
(11) |
EP 0 237 359 A3 |
| (12) |
EUROPEAN PATENT APPLICATION |
| (88) |
Date of publication A3: |
|
23.11.1988 Bulletin 1988/47 |
| (43) |
Date of publication A2: |
|
16.09.1987 Bulletin 1987/38 |
| (22) |
Date of filing: 13.03.1987 |
|
|
| (84) |
Designated Contracting States: |
|
BE DE FR GB IT NL |
| (30) |
Priority: |
13.03.1986 US 839434
|
| (71) |
Applicant: SMITH INTERNATIONAL, INC. |
|
() |
|
| (72) |
Inventors: |
|
- Fyfe, George
()
- Jones, Kenneth William
()
|
|
| |
|
(57) A rotary drag bit (11) has cutters (19) rotatably mounted to fixtures (21) with journals.
The cutters (19) are constantly forced to rotate or precess by the interaction between
the earth formation and the cutter (19). The cutters (19) are fixed in skewed or offset
positions on a cutting face (17) of a rotary drill bit head (11). These cutters (19)
act as drag or shear cutters when they are operated in an earth formation.