Method of designing a roller cone bit

(19)

(11)

EP 1 500 781 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	12.04.2006 Bulletin 2006/15

(43)	Date of publication A2:
	26.01.2005 Bulletin 2005/04

(21)	Application number: 04025560.6

(22)	Date of filing: 31.08.1999

(51)

International Patent Classification (IPC):

(84)	Designated Contracting States:
	GB IT

(30)

Priority:

31.08.1998 US 98442 P

(62)	Application number of the earlier application in accordance with Art. 76 EPC:
	03021139.5 / 1371811
	99945376.4 / 1117894

(71)	Applicant: HALLIBURTON ENERGY SERVICES, INC.
	Carrollton, TX 75006 (US)

(72)	Inventor:
	Chen, Shilin The Woodlands, Texas 77385 (US)

(74)	Representative: HOFFMANN EITLE
	Patent- und Rechtsanwälte Arabellastrasse 4 81925 München 81925 München (DE)

(54)	Method of designing a roller cone bit

(57) Disclosed herein is a method of designing a roller cone bit, comprising the steps of:

calculating the curved trajectory of a non-axisymmetric tooth through formation material at the cutting face, as the bit and cones rotate;

calculating a straight line approximation to said curved trajectory; and

orienting said tooth with respect to said approximation, and not with respect to said curved trajectory.