Dynamic seal for rolling cutter drill bit

A dynamic seal is disclosed for sealing between a rotating cutter and a drill bit journal in an underground formation drilling bit, which seal utilizes a static elastomeric seal ring abutting a metal seal ring having a dynamic sealing face.

BACKGROUND OF THE INVENTION 
Normally, rolling cutter drill bits such as oil well bits, blast hole bits 
and mining bits, may be classified as either "sealed" or "unsealed" bits. 
The sealed bits, which are usually the premium line of bits, utilize 
elastomeric seals between the rotating cutters and the bearing journals to 
prevent intrusion of dirt, sand, rock cuttings, corrosive liquids and 
other contaminants into the bearing area. This reduction of detritus into 
the bearing area prolongs the life of the bearings and extends the 
drilling life of the bit. One such premium sealed bit having particularly 
good elastomeric journal bearing seals is that disclosed in U.S. Pat. No. 
4,037,673, granted to Daniel B. Justman on July 26, 1977, which patent is 
herein incorporated by reference. 
In the Justman patent, the drawing reveals a frustoconical rolling cutter 
15 which is rotatably mounted on a bearing shaft 14 by bearings 18 and 
19a. An elastomeric sealing ring 25 is located in an internal groove 24 in 
cutter 15 and sealingly engages shaft 14. The sealing ring can be an 
O-ring or be rectangular in cross-section, and is placed in hoop 
compression. The seal preferably is static with respect to the cutter and 
dynamic with respect to the shaft. 
Although the Justman drilling bit sealing system is an improvement over the 
seals that were conventional at that time, such as that disclosed in U.S. 
Pat. No. 3,765,495, it does suffer from one disadvantage also affecting 
the other known bit sealing systems. Conventional bit seals utilize a 
dynamic interface between the elastomeric seal member and either the 
bearing journal, the cutter, or both. As a result of the continuous 
movement of the elastomeric seal against one or both of the metal 
elements, a rapid wear and deterioration of the seal surface usually 
occurs. Efforts to slow this wear and deterioration have included the 
shielding type of structure disclosed in the aformentioned Justman patent 
and a polishing of the metal faces which contact the seal to a high 
surface smoothness. 
The present invention eliminates the elastomeric seal deterioration from 
sliding contact with metal surfaces by replacing the usual single 
elastomeric seal with a compound elastomeric and metal sealing system, 
with the metal component providing the dynamic seal against the rotating 
metal component in the bit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings, and more specifically, to FIG. 1, a sealing 
assembly 10 manufactured according to the present invention is disclosed 
in cross-sectional configuration. The assembly comprises a rigid metal 
ring 11 which is formed to have an L-shaped cross-section, and which abuts 
a circular elastomeric seal 12. Seal assembly 10 is particularly adapted 
for sealing the annular space between a rolling cutter 13 and a drill bit 
journal 14. Cutter 13 and journal 14 are illustrated in cross-sectional 
view with only the relevant portions being disclosed herein. It should be 
noted that the cutter 13 and bearing journal 14 may be of the typical 
cutter and journal construction utilized in conventional bits. In the 
present invention, journal 14 utilizes a bearing shaft 15 having a bearing 
surface 16 formed thereon. Adjacent the bearing surface 16 is a land or 
raised shoulder 17 formed at the base of shaft 15. A flange 18 adjoins 
land 17 and forms the outer barrier of the seal pocket. 
Cutter 13 has an inner bore 19 arranged for concentric location over shaft 
16 with a gap or annular space 20 therebetween. Cutter 13 has an enlarged 
annular bore 21 at the back face thereof to provide space for seal 
assembly 10. The perpendicular face 22 located annularly between bores 21 
and 19 forms the remainder of the seal pocket 23. Annular face 22 is a 
part of the dynamic sealing system associated with seal assembly 10. The 
metal ring 11, which has a cross-sectional L-shape, has an upper retainer 
leg 24 and a lower retainer leg 25. A raised seal shoulder 26 is formed on 
lower leg 25. The circular seal member 12 is located between flange 18 and 
shoulder 17 and is in abutment with the legs 24 and 25 opposite surface 
26. 
FIGS. 3 and 7 are cross-sectional side views of the metal ring 11 and the 
elastomeric seal 12. The seal 12 is essentially a circular elastomeric 
seal having an elongated cross-sectional area formed in basically a 
funnel, or conical, shape. The radially innermost portion 27 is located 
against bearing journal 14 while the radially outermost section 28 abuts 
seal ring 11. The seal ring 12 has the upper shoulders 28 and 27 bevelled 
as shown in FIG. 7 in order to more efficiently seal against the right 
angular surfaces 18 and 17, and the right angular legs 24 and 25. The 
engagement of the elastomeric ring 12 and the metal ring 11 is shown in 
cross-section in FIG. 8 and in expanded partial cross-section of FIG. 9. 
Referring now to FIG. 5, the L-shaped metal ring 11 is illustrated in an 
axial end view showing the means for preventing rotation of the metal ring 
on the bearing shaft 16. In FIG. 5 the L-shaped sealing ring 11 is shown 
having a pair of inner opposed tab sections 30 formed in the inner 
periphery of ring 11 and projecting radially inward. Likewise, a pair of 
opposed flats 29 are machined on shoulder 17 in bearing journal 14. Flats 
29 and tabs 30 are formed in complementary relationship to provide a 
locking arrangement of ring 11 on shoulder 17. Whereas FIG. 5 is an axial 
end view of locking ring 11 on journal 14, FIG. 2 is a cross-sectional 
side view of the sealing assembly located on journal 14. FIG. 2 is a view 
similar to that of FIG. 1, but taken at a point rotated approximately 90 
degrees from that of FIG. 1. The orientation of FIGS. 1 and 2 is 
illustrated in FIG. 5 by section lines 1--1 and 2--2. Section line 1--1 
represents the cross-sectional view of FIG. 1, and Section line 2--2 
represents the cross-sectional view of FIG. 2. 
In typical operation, the seal assembly of this invention is installed in a 
drilling bit by placing the elastomeric seal ring 12 over the bearing 
journal shaft 17 and onto snug fitting engagement on shoulder 17. Then the 
metal L-shaped dynamic seal ring 11 is slipped over bearing shaft 16 to 
abut elastomeric ring 12. After seal ring 12 and metal ring 11 are 
properly located on shaft 16 and shoulder 17, the cutter 13 is assembled 
on the journal. The smooth machined sealing surface 22 of cutter 13 is 
brought into engagement with complementary sealing surface 26 on arm 25 of 
ring 11. The abutment of ring 11 with seal 12 and between seal 12 and 
flange 18 provides the static seal between the cutter and the bearing 
journal. The abutment of surface 26 with surface 22 provides the dynamic 
seal therebetween. As shown in FIG. 5, metal ring 11 is prevented from 
rotating on bearing journal 17 by the provision of opposed inner tabs 30 
which mate with flats 29 formed on shoulder 17. The remainder of shoulder 
17, in conjunction with tabs 30, locks ring 11 onto journal 14 and 
prevents rotation of ring 11 while cutter 13 is rotating on the journal. 
Also, it should be noted that ring 11 and seal 12 are sized such that when 
cutter 13 is rotatably attached to bearing journal 14, seal member 12 is 
placed in compression sufficient to maintain ring 11 urged snugly against 
surface 22. The elastomeric nature of seal 12 along with its geometric 
configuration serves to act as a Belleville spring against ring 11 to keep 
it in tight contact with the sealing surface 22 in cutter 13. Likewise, 
the bevelled ends 27 and 28 of seal 12 maintain proper alignment of the 
ring between flange 18, shoulder 17 and the L-shaped portion of ring 11. 
This alignment also helps maintain ring 11 in proper alignment against 
surface 22. 
The materials from which the elastomeric seal and the metal ring are formed 
may be any of the conventional elastomers utilized in seals today for the 
seal ring; and any good alloy steel or chrome steel or copper beryllium 
material may be used in the metal ring. For example, one particularly good 
elastomer for use in the seal ring would be a silicone rubber having good 
temperature properties and poor dynamic deterioration resistance. Because 
of the static nature of the seal, there is no requirement for a high 
dynamic deterioration resistance, and the silicone rubber would make a 
very desirable seal. Because of the nature of the sealing system disclosed 
herein, i.e., the static nature of the elastomeric seal, properties of the 
elastomeric seal ring 12 can be selected without regards to any need for 
resistance to dynamic wear. Such properties which may be selectively 
enhanced might be high temperature resistance and/or high resistance to 
corrosive fluids. 
Although certain preferred embodiments of the invention have been herein 
described in order to provide an understanding of the general principles 
of the invention, it will be appreciated that various changes and 
innovations can be effected in the described rolling cutter drill bit seal 
system without departing from these principles. For example, whereas the 
elastomeric seal disclosed is shaped in a frusto-conical ring, it is clear 
that other geometric configurations of the elastomeric seal could be 
utilized. The invention, therefore, is declared to cover all changes and 
modifications of the specific example of the invention herein disclosed 
for purposes of illustration which do not constitute departures from the 
spirit and scope of the invention.