Bearing sealing means of earth boring bits

Details Bearing sealing means of earth boring bits Bearing sealing means of earth boring bits

1998-11-30

2001-01-23

Bagnell, David (Department: 3672)

Boring or penetrating the earth

Bit or bit element

Rolling cutter bit or rolling cutter bit element

C175S359000, C384S094000

Reexamination Certificate

active

06176331

ABSTRACT:

Reference is hereby made to Chinese Application No. 98113483.1 filed Mar. 25, 1998.
BACKGROUND OF THE INVENTION
The invention relates to a bearing sealing means of earth boring bits used in well drilling, the petroleum industry, geologic surveys and the like.
Because of limited space in bearings of earth boring bits, an O-ring has been used as a radial seal for such bearings due to its simple structure and safe property. Such radial seals for bearings of earth boring bits are described in U.S. Pat. No. 3,397,928. In general, clearances of bearings in earth boring bits are greater (usually 0.08 to 0.23 mm) since the working temperature of such bits is higher. However, the greater clearance brings unfavorable effects when O-rings are used as radial seals. Significant compressive deformation is required to fit with the eccentric rotation of a loaded cone, however this causes increased heat generation due to the sliding friction of the O-ring. If the temperature becomes too great, the O-ring can be permanently deformed. For these reasons, an O-ring made of rubber cannot be used, otherwise its working life will be shortened when the bit is operated at high speed.
Attempts have been made to improve the sealing structures of bearing in earth boring bits, however none have been satisfactory. For example, a sealing assembly is disclosed in U.S. Pat. No. 4,623,028, which comprises a static and softer O-ring, a dynamic and harder O-ring and a rigid supporting ring. A smaller compressive deformation is designed for the dynamic O-ring, while a greater compressive deformation is designed for the static to compensate the eccentric rotation of the cone. Due to this structure, the sealing assembly can be used at high operating speed. Unfortunately, use of the assembly was limited because of its complex structure and large volume. A floating seal for earth boring bits is disclosed in U.S. Pat. No. 4,428,687. The seal comprises a groove formed on the bearing shaft of a head section. A split supporting ring is located in the groove. An O-ring is provided in an annular space defined by sidewalls of the groove, the outer circumference of the supporting ring, and the circumferential surface of the shaft so that a seal structure comprising radial and axial seals is formed. After forming the axial seal on the sidewall of the groove, there is air in the floating clearance between the inner circumference of the supporting ring and the bottom of the groove; and the floating clearance has been closed. During drilling, the pressure of drilling liquid is much greater than that of air located in the floating clearance. This causes the O-ring to be pressed partially into the groove, and thus deforms the supporting ring. This will cause the seal to no longer function. In practice the technical solution of the above patent is not satisfactory.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a bearing seal for earth boring bits which can be used at high rotating speed. During drilling, the pressure in the floating cavity balances with that of drilling liquid. The bearing sealing means according to the invention is simple in structure and safe in property.
The object of the invention is attained to provide:
an annular groove at the entrance of a bearing hole, having a passage opened to the bottom of the annular cavity of the groove and connected with outside (for example, drilling liquid or grease lubricant filled in the bearing clearance);
a supporting ring located in the groove having an outer diameter being than the outer diameter of the groove;
an O-ring located in an annular space defined by the inner circumference of the supporting ring and the sidewalls of the groove.
After insertion of the bearing shaft into the bearing hole, the O-ring is squeezed in four directions so as to form a radial seal between the O-ring and the outer circumference of the bearing shaft and an axial seal between the O-ring and the sidewalls of the groove. Since the sliding frictional force produced between the O-ring and the sidewalls of the groove is significantly less than the radial compressive force acting on the O-ring. The O-ring and the supporting ring are completely coaxial with the bearing shaft even if the cone is eccentrically rotated. Thus, compressive deformation of the ring in the loaded direction of the bearing, and inadequate deformation in the non-loaded direction are avoided. The compression deformation of the O-ring can thereby be decreased by design so that it can be used at high rotating speeds. A passage connected with the outside is opened to the bottom of the groove so as to balance the pressure in the floating annular cavity with that of the outside and to maintain the safety of the seal. Drilling liquid filled into the floating annular cavity can cool the O-ring so that the bearing seal has a longer working life.
Compared to the prior bearing seals, the invention provides a number of advantages. First, because of the smaller compressive deformation and less heat produced by sliding friction, the O-ring can be used at a high rotating speeds. Second, the contact area between the O-ring and drilling liquid is larger so as to cool the O-ring effectively and to prolong its workinglife. Third, the bearing seal according to the invention is simple and compact in the structure and low in cost.


REFERENCES:
patent: 4074922 (1978-02-01), Murdoch
patent: 4168868 (1979-09-01), Shields
patent: 4256351 (1981-03-01), Langford, Jr.
patent: 4277109 (1981-07-01), Crow
patent: 4394020 (1983-07-01), Oelke
patent: 4410284 (1983-10-01), Herrick
patent: 4428687 (1984-01-01), Zahradnik
patent: 4429854 (1984-02-01), Kar et al.
patent: 4466622 (1984-08-01), Deane et al.
patent: 4516641 (1985-05-01), Burr
patent: 0 472 809 A1 (1992-03-01), None
patent: 941534 (1982-07-01), None
patent: 1317-090A (1987-06-01), None

Affiliated with

Also associated with

Rating

Bearing sealing means of earth boring bits does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Bearing sealing means of earth boring bits, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bearing sealing means of earth boring bits will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2476346