GB2119036A - Dynamic seal for rolling cutter drill bit - Google Patents

Abstract

A seal assembly for sealing the bearings of a rolling cutter drill bit comprises a rigid ring 11 of generally L-shaped cross-section and having a land 26 to engage face 22 of the rotating cutter 13, and a resilient ring 12 providing a static seal between the ring 11 and the journal 14 and urging the ring 11 axially against the cutter. Inner tabs on the ring 11 engage flats on the journal 14 to prevent relative rotation therebetween. <IMAGE>

Description

SPECIFICATION Dynamic seal for rolling cutter drill bit This invention relates to rolling cutter drill bits.

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 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 ofthe bearings and extends the drilling life of the bit. One such premium sealed bit having particularly good elastomericjournal bearing seals is that disclosed in U.S. Patent 4,037, 673 (Daniel B. Justman) which patent is herein incorporated by reference.

In the aforesaid U.S. Patent No.4,037,673, there is described a frusto-conical rolling cutterwhich is rotatably mounted on a bearing shaft by bearings. An elastomeric sealing ring is located in an internal groove in the cutter and sealingly engages the bearing shaft. The sealing ring can bean O-ring or be rectangular in cross-section, and in placed in hoop compression. The seal preferably is static with respect to the cutter and dynamic with respect to the shaft.

Although the drilling bit sealing system of U.S.

Patent No.4,037,673 is an improvement overthe seals thatwereconventional atthattime,such asthat disclosed in U.S. Patent 3,765,494, it does sufferfrom one disadvantage also effecting the other previously proposed bit sealing systems. Conventional bit seals utilize a dynamic interface between the elastomeric seal member and eitherthe 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 ofthe seal surface usually occurs. Efforts to slowthis wear and deterioration have included the shielding type of structure disclosed in the aforementioned U.S.Patent No.4,037,673 and a polishing of the metal faces which contact the seal to a high surface smoothness.

An objectofthe present invention isto obviate or mitigate the aforesaid disadvantages.

According to the present invention there is provided a rolling cutterdrill bit of the type having a plurality of downwardly extending legs, each leg having a cylindrical journal extending therefrom, with a cutter body rotatably mounted on each said journal by bearing means, and a seal between said cutter and said journal outwardly of said bearing means, characterised in that: Said seal comprises a compound seal assembly having a rigid circular ring with a generally L-shaped cross-sectional configuration and having a sealing face formed externally thereon; and a resilient seal ring adapted for snug-fitting relationship on said journal and against said rigid ring; means are provided on said rigid ring and said journal to prevent relative rotation between said rigid ring and said resilient seal ring; and said cutter has a counterbore surface therein arranged to engage rotatably and sealingly said sealing face on said rigid ring.

According to a further aspect of the present invention there is provided a compound static dynamiccircularseal assemblyforsealing the bearing structure of a rolling cutter drill bit against intrusion of foreign detritus from outside the drill bit, said seal assembly being adapted to be located between the cutter and bearing journal of a rolling cutter drill bit, and said assembly comprising: a rigid dynamic ring having a generally L-shaped cross-sectional configuration, an external sealing face, and means thereon for enabling locking engagement on the bearing journal; and, a resilient static seal ring adapted for static peripheral sealing abutment between a bearing shaft and said rigid ring, and further adapted to provide resilient biasing of said rigid ring axially on a bearing shaft againstthe cutter.

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 againstthe rotating metal component in the bit.

Embodiments ofthe present invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig. is a tangential cross-sectional view of a portion of drill bit containing one embodiment of the invention; Fig. 2 is a tangential cross-sectional view of a portion of drill bit illustrating the embodiment of Fig. 1 rotated through 90 degrees; Fig. 3 is a cross-sectional radial view of a typical metal component ofthe present invention; Fig. 4 its a close-upviewofa portion of Fig. 3; Fig 5 is an axial view of the metal ring of Figs. 3 and 4; Fig. 6 is an axial view of the elastomeric ring of the invention;; Fig. 7 is a cross-sectional radial view of the elastomeric ring of Fig. 6; and Figs. 8 and 9 are cross-sectional and partial crosssectional views, respectively, of the seal system of thins invention.

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 prise a rigid metal ring 11 which is formed to have an L-shaped crosssection, and which abuts a circular elastomeric seal ring 12. Sealing assembly 10 is particularly adapted for sealing the annular space between a rolling cutter 13andadrill bitjournal 14.Cutter13and journal 14are illustrated in cross-sectional view with only the relevant portions being disclosed herein. It should be noted thatthe cutter 13 and bearing journal 14may 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.Aflange 18 adjoinsshoulder 17 and forms and outer barrieroftheseal 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 backface thereof to provide spaceforseal assembly 10. An annular face 22 is located annularly between bores 21 and 19 and is perpendicularthereto so as to form the remainder of the seal pocket 23. Annularface 22 is a part of the dynamic sealing system associated with seal assembly 10. The metal ring 11 which is of L-shape in cross-section, has an upper retainer leg 24 and a lower retainer leg 25. A raised seal land 26 is formed on lower leg 25. The circular seal 12 is located between flange 18 and shoulder 17 and is in abutment with the legs 24 and 25 opposite land 26.

Fig. 3 and 7 are cross-sectional side views of the metal ring 11 and the elastomeric seal ring 12. The seal ring 12 is essentially a circular elastomeric seal formed in basically a funnel, or conical, shape and having an elongated cross-section. The radially innermost portion or shoulder 27 is located against bearing journal 14 while the radially outermost portion or shou Ider 28 abuts ring 11. The seal ring 12 has the upper shoulders 28 and 27 bevelled as shown in Fig. 7 in orderto seal more efficiently against rig ht-ang led surfaces of flange 18 and shoulder 17, and the right-angled legs 24 and 25 of metal ring 11. The engagement of the elastomeric seal ring 12 and the metal ring 11 is shown in cross-section in Fig. and in enlarged partial cross-section in 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. Sthe L-shaped 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 sideviewofthesealing assembly located on journal 14.Fig. 2 is a view similarto that of Fig. 1, buttaken at a point rotated approximately 90 degress 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 piacing the elastomericseal ring 12 overthe bearing journal shaft 15 and into snug fitting engagement on shoulder 17.

Then the metal L-shaped dynamic ring 11 is slipped over bearing shaft 15 to abut elastomeric seal ring 12.

After seal ring 12 and metal ring 11 are properly located on shaft 15 and shoulder 17, the cutter 13 is assembled on the journal. The smooth-machined annular face 22 of cutter 13 is brought into engage mentwith complementary sealing land 26 on arm 25 of ring 11. The abutment of ring 11 with seal ring 12 and between seal ring 12 and flange 18 provides the static seal between the cutter and the bearing journal.

The abutment of land 26 with face 22 provides the dynamic seal therebetween. As shown in Fig 5, metal ring 11 is prevented from rotating on bearing journal 14 by the provision of opposed innertabs 30 which mate with flats 29 formed on shoulder 17. The remainder ofshoulder 17, in conjunction with tabs 30, locks ring 11 onto journal 14and prevents rotation of ring 11 while cutter 13 is rotating on the journal. Also, itshouldbenotedthatring 11 and seal ring 12are sized such that when cutter 13 is rotatable attached to bearing journal 14, seal ring 12 is placed in compress- ion sufficientto maintain ring 11 urged snugly against face 22.The elastomeric nature of seas ring 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 face 22 in cutter 13. Likewise, the bevelled ends 27 and 28 of seal ring 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 againstface 22.

The materials from which the elastomeric seal ring 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 elastomerfor use in the seal ring would be a silicone rubber having good temperature properties and poor dynamic deterioration resistance. Because ofthe static nature oftheseal ring,thereis no requirementfora high dynamic deterioration resistance, and the silicone rubber would make a very desirable seal.Because of the nature ofthesealing system disclosed herein, i.e., the static nature ofthe elastomericseal ring, 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 hightemperature resistance and/or high resistance to corrosive fluids.

Although certain preferred embodiments ofthe invention have been made herein described in order to provide an understanding ofthe general principles of the invention, itwill 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, where as the elastomeric seal ring disclosed is shaped in the form of a frusto-conical ring, it is clearthat other geometric configurations of the elastomeric seal ring could be utilized.

Claims (14)

1. Carolling cutter drill bit ofthetype having a plurality of downwardly extending legs, each leg having a cylindrical journal extending therefrom, with a cutter body rotatably mounted on each said journal by bearing means, and a seal between said cutter and said journal outwardly of said bearing means, char acterised in that: said seal comprises a compound seal assembly having a rigid circular ring with a generally L-shaped cross-sectional configuration and having a sealing face formed externallythereon; and a resilient seal ring adapted for snug4itting relationship on said journal and against said rigid ring; means are provided on said rigid ring and said journal to prevent relative rotation between said rigid ring and -said resilient seal ring; and said cutter has a counterbore surface therein arranged to engage rotatably and sealingly said sealing face on said rigid ring.

2. A drill bit as claimed in Claim 1 wherein said rigid ring is formed of metal and said resilient seal ring is formed of an elastomer.

3. A drill bit as claimed in Claim 1 or2, in which said seal ring is of generallyfrusto-conical form.

4. Adrill bit as claimed in any of Claims 1 to 3, wherein said resilient seal ring is selected from a material which exhibits good static sealing qualities and good resistance to high temperature deterioration.

5. A drill bit as claimed in any preceding claim, wherein said resilientseal ring is selected from a material which exhibits good static sealing qualities and good resistance to corrosive fluids.

6. A drill bit as claimed in any preceding claim, in which the resilient seal ring is of silicon rubber.

7. A drill bit as claimed in any preceding claim, wherein said metal ring is formed from a hard metal selected from cast metal, cast iron, steel, steel alloy, aluminium alloy, and copper-beryllium alloy.

8. Acompoundstatic-dynamiccircularseal assemblyforsealing the bearing structure of a rolling cutter drill bit against intrusion of foreign detritus from outside the drill bit, said seal assembly being adapted to be located between the cutter and bearing journal of a rolling cutterdrill bit, and said assembly comprising: a rigid dynamic ring having a generally L-shaped cross-sectional configuration, an external sealing face, and means thereon for enabling locking engagement on the bearing journal; and, a resilient static seal ring adapted for static peripheral sealing abutment between a bearing shaft and said rigid ring, and further adapted to provide resilient biasing of said rigid ring axially on a bearing shaft against the cutter.

9. A sealing assembly as claimed in Claim 8, wherein said resilient seal ring is formed of an elastomerexhibiting good static sealing ability and good high temperature deterioration resistance.

10. A seal assembly as claimed in Claim 8 or 9, wherein the seal ring isofsilicon rubber.

11. Aseal assembly as claimed in any of Claims8 to 10, wherein the seal ring is of frusto-conical form.

12. A seal assembly as claimed in any of Claims 8 to 1 1,wherein said rigid ring is formed of a hard metal selected from cast metal, cast iron, steel, steel alloy, aluminium alloy and copperberyllium alloy.

13. A rolling cutter drill bit substantially as hereinbefore described with reference to Fig. 1 and Figs.

3 to 9 or Fig. 2 and Figs. 3 to 9 of the accompanying drawings.

14. A seal assembly for a rolling cutter drill bit, substantially as hereinbefore described with refer enceto Fig. 1 and Figs. 3to 9 or Fig. 2 and Figs. 3to 9of the accompanying drawings.