CA1096851A - Earth boring drill bit with snap ring cutter retention - Google Patents
Earth boring drill bit with snap ring cutter retentionInfo
- Publication number
- CA1096851A CA1096851A CA304,706A CA304706A CA1096851A CA 1096851 A CA1096851 A CA 1096851A CA 304706 A CA304706 A CA 304706A CA 1096851 A CA1096851 A CA 1096851A
- Authority
- CA
- Canada
- Prior art keywords
- cutter
- shaft
- ring
- groove
- snap ring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/08—Roller bits
- E21B10/20—Roller bits characterised by detachable or adjustable parts, e.g. legs or axles
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B10/00—Drill bits
- E21B10/08—Roller bits
- E21B10/22—Roller bits characterised by bearing, lubrication or sealing details
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C43/00—Assembling bearings
- F16C43/02—Assembling sliding-contact bearings
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C2352/00—Apparatus for drilling
Abstract
Abstract of the Disclosure Disclosed herein is an earth boring bit of other-wise conventional construction except for the bearing and cutter retention. A snap ring is used to retain the cutter, the grooves that receive the ring and the ring construction being such that the ring is forced into the retainer groove when the cone is thrust inward. The ring cannot therefore accident-ally return to its assembly position to permit cutter loss.
This enables the use of exclusively frictional bearings and retainer means of exceptional strength and reliability.
This enables the use of exclusively frictional bearings and retainer means of exceptional strength and reliability.
Description
10~6851 sackground of the Invention 1. Field of the Invention: This invention relates in , general to earth boring drill ~its and in particular to improved bearings and means for retaining the rotatable cutters on such bits.
2. Prior Art: The success of rotary drilling enabled the discovery of deep oil and gas reservoirs. The rotary rock bit was an important invention which made that success possible.
Only the soft formations could be commercially penetrated with the earlier drag bit, but the two cone rock ~it invented by H.R.
Hughes, U.S. Patent No. 930,759, drilled the hard cap rock at the Spindletop Field near Beaumont, Texas with relative ease.
That distant invention, within the first decade of this century, could drill a scant fraction of the depth and speed of the modern rotary rock bit. If the original Hughes bit drilled for hours, the modern bit drills for days. Bits today sometimes drill for miles instead of feet. Many improvements contributed to the impressive improvement in the performance of rock bits.
The original bit of Hughes had rotatable cutters, frictional bearing surfaces and ring-type retainers generally threaded for retention in the cutter. Because of the difficulty in providing seals with long life, relatively large lubricant reservoirs were required. By the decade of the thirties, drill bits with anti-friction bearing that were unsealed became commercially successful and replaced the sealed and lubricated drill bits. This type drill bit may be seen in the U.S. patent to Lewis E. Garfield et al, Patent No. 2,030,442.
G.O. Atkinson et al obtained U.S. Patent No. 3,075,781 on a seal that minimized leakage and required only a small reser~
voir of lubricant. The pressure compensator is all improvement that minimizes the pressure differential across the seal and increases its reliability. A recent version of the pressure
Only the soft formations could be commercially penetrated with the earlier drag bit, but the two cone rock ~it invented by H.R.
Hughes, U.S. Patent No. 930,759, drilled the hard cap rock at the Spindletop Field near Beaumont, Texas with relative ease.
That distant invention, within the first decade of this century, could drill a scant fraction of the depth and speed of the modern rotary rock bit. If the original Hughes bit drilled for hours, the modern bit drills for days. Bits today sometimes drill for miles instead of feet. Many improvements contributed to the impressive improvement in the performance of rock bits.
The original bit of Hughes had rotatable cutters, frictional bearing surfaces and ring-type retainers generally threaded for retention in the cutter. Because of the difficulty in providing seals with long life, relatively large lubricant reservoirs were required. By the decade of the thirties, drill bits with anti-friction bearing that were unsealed became commercially successful and replaced the sealed and lubricated drill bits. This type drill bit may be seen in the U.S. patent to Lewis E. Garfield et al, Patent No. 2,030,442.
G.O. Atkinson et al obtained U.S. Patent No. 3,075,781 on a seal that minimized leakage and required only a small reser~
voir of lubricant. The pressure compensator is all improvement that minimizes the pressure differential across the seal and increases its reliability. A recent version of the pressure
- 3 ~
1~"6851 compensator and pressure relief system is æhown in the U.S.
Patent of stuart c. Millsapps, Jr., No.`3,942,596. E.M. Galle patented an 0-ring type seal, U.5. Patent No. 3,397,928, that ultimately made friction bearings once again feasible in drill bits. An illustration of a recent bearing con~iguration is shown in the U.S. Patent No. 3,922,038 issued to S.R. Scales. This bit has a cylindrical, friction bearing and a cutter retained by a ball bearing similar to that shown in the above patent to Lewis E. Garfield et al.
A ball bearing in a lubricated rock bit bearing has inherent disadvantages. A failure in an~ one o~ the numerous balls or the raceway in which they are positioned may permit metallic fragments to enter the friction bearing, with near certain damaging results. Metallic particles will often damage the seal ring, causing lubricant loss and rapid bearing failure. The necessity for a hole drilled into tIle ball race for introduction of the balls, retained by a welded plug, adds complexity to the bit that provides additional room for manufacturing error. The rock bit is the focal point of an expensive drilling process that has a low tolerance for failure.
There is shown in the prior art rock bit bearing and retainer means that are totally frictional; hat is, without anti-friction ball or roller bearings. The original Hughes bit had friction bearings exclusively. A few of the many bits with only frictional bearings will be mentioned briefly.
F.L. Scott in U.S. Patent No. 1,803,679 discloses a lubricated, tapered frictional rock bit bearing that retains its cutter by means of a resilient snap ring. J.C. Wrlght et al in ; ~ U.S. Patent No. 2,049,581 discloses a cutter rotatably secured with a snap ring to a bearing shaft releasa~ly connected to the legs or head sections of a hit. The U.S. Patent No. 2,814,465 to W.G. Green discloses a lubricated frictional bearing having
1~"6851 compensator and pressure relief system is æhown in the U.S.
Patent of stuart c. Millsapps, Jr., No.`3,942,596. E.M. Galle patented an 0-ring type seal, U.5. Patent No. 3,397,928, that ultimately made friction bearings once again feasible in drill bits. An illustration of a recent bearing con~iguration is shown in the U.S. Patent No. 3,922,038 issued to S.R. Scales. This bit has a cylindrical, friction bearing and a cutter retained by a ball bearing similar to that shown in the above patent to Lewis E. Garfield et al.
A ball bearing in a lubricated rock bit bearing has inherent disadvantages. A failure in an~ one o~ the numerous balls or the raceway in which they are positioned may permit metallic fragments to enter the friction bearing, with near certain damaging results. Metallic particles will often damage the seal ring, causing lubricant loss and rapid bearing failure. The necessity for a hole drilled into tIle ball race for introduction of the balls, retained by a welded plug, adds complexity to the bit that provides additional room for manufacturing error. The rock bit is the focal point of an expensive drilling process that has a low tolerance for failure.
There is shown in the prior art rock bit bearing and retainer means that are totally frictional; hat is, without anti-friction ball or roller bearings. The original Hughes bit had friction bearings exclusively. A few of the many bits with only frictional bearings will be mentioned briefly.
F.L. Scott in U.S. Patent No. 1,803,679 discloses a lubricated, tapered frictional rock bit bearing that retains its cutter by means of a resilient snap ring. J.C. Wrlght et al in ; ~ U.S. Patent No. 2,049,581 discloses a cutter rotatably secured with a snap ring to a bearing shaft releasa~ly connected to the legs or head sections of a hit. The U.S. Patent No. 2,814,465 to W.G. Green discloses a lubricated frictional bearing having
4 --10~685~
tapered and cylindrical portions joined ~y suitable means and secured to a cutter by a retainer ring. A lock ring is shown in Edward B. Williams, Jr.'s U.S. Patent No. 3,844,363 for retaining a cutter and shaft with frictional bearings to a rock bit. A frictional bearing with tapered and cylindrical portions is disclosed by E.M. Galle in his U.S. Patent No . 3,361,494, along with frictional plug lock and pin lock retaining systems.
A recent revival of the earlier seen threaded ring retainer is seen in U.S. Patent No. 3,971,60a of Murdoch et al. Notwith-standing this array of ideas, the only significantly successfulrock bit in commerce today uses a ball bearing retainer.
The threaded retainer ring has some disadvantage that - may have limited its success. The threads act as stress raisers and the ring must be secured against rotation while the cone is mated with it. This generally requires a drilled hole in the head section.
Snap rings may have stress raising groove configurations ; and exhibit a tendency to retract during drilling into the assembly groove and permit accidental cutter loss. When a cutter is thrust inward, as when reaming for example, the loading of the ring causes stresses that tend to urge the ring into the assembly groove, with the possibility of cutter loss.
Summary of the Invention The invention may be summarized as an improved friction bearing and snap ring retainer means for a rock bit of the type having rotatable cutters, with sealed and lubricated ~earings and a pressure compensation system. The preferred snap ring is circular in cross section for assem~ly within two registering snap ring grooves, one in the cutter and the other in the bearing shaft that supports the cutter. The grooves in the preferred form have circular or semi-circular ~ottoms, one being an assembly groove of a depth at least as great as the cross-:~L0~6851 sectional thickness of the ring. The other groove, the retainergroove, has a depth less than the cross-sectional thickness of the ring. When the cutter is thrust outward (toward the wall of the bore hole), there is clearance between the ring and assembly groove, but when the cutter is thrust inward, the ring is con-fined between the assembly groove and the retainer groove. The ring is forced outward into the retainer groove by either the offset edge of the assembly groove or an inclined wall ~or~ed on the edge of the assembly groove, either of which produces a conical force distribution. This urges the ring into the retainer groove and prevents accidental displacement of the ring into the assembly groove and loss of the associated cutter.
Further assurance of cutter retention is provided because the distance from the edge of the assembly groove to the opposing edge of the retainer groove is less than the thickness of the ring when the cone experiences thrust loading.
Additional objects, features and advantages of the invention will become apparent in the following description.
~0'~6851 In accordance with one broad aspect, the invention provides in combination with an earth boring bit having at least one cantilevered bearing shaft rotatably supporting a sealed and lubricated cutter, an improved cutter retention means comprising: friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft; one of said cutter and shaft having an assembly groove and the other having a registering, retainer groove; a snap ring positioned in the registering grooves; the retainer groove having a depth less than the cross-sectional thickness of the ring, the assembly groove having a depth at least equal to the cross-sectional thickness of the ring, an outer sidewall and an inner sidewall, with the inner sidewall having a frusto-conical surface inclined at a selected angle ~ relative to a plane perpendicular to the axis of the shaft to engage the snap ring and generate a force component oblique to said axis and urge the snap ring into the retainer groove when the cone is thrust inward and away from said thrust surface.
In accordance with another aspect, the invention provides in combination with an earth boring bit having at least one cantilevered bearing shaft rotatably supported to a sealed and lubricated cutter, an improved cutter retention means comprising: friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft; the shaft having an assembly groove and the cutter having a registering, retainer groove; a snap ring positioned in the registering grooves; the retainer groove having a depth less than the cross-sectional thickness of the ring; the assembly groove having a depth at least equal to the cross-sectional thickness of the ring and inner and outer sidewalls; the surface of the shaft and the inner sidewall of the assembly groove ~-6a-l~g6~1 intersecting at a corner; the inner sidewall having a frusto-conical surface inclined at a selected angle ~ relative to a plane perpendicular to the axis of the shaft to engage the snap ring and urge it into the retainer groove when the cone is thrust inward and away ~rom said thrust surface.
In accordance with a further aspect, the invention provides in combination with an earth boring bit having at least one cantilevered bearing shaft rotatabl~ supporting a sealed and lubricated cutter, and improved cutter retention means comprising: exclusively friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft; pressure adjustment means included in the lubrication system to control the pressure differential across said seal; one of said cutter and shaft having an assembly groove with a curved bottom and the other having a registering, retainer groove with a curved bottom; a snap ring having a cross-section with a curved boundary positioned in said grooves; the retainer groove having a depth at least equal to one-half the cross-sectional thickness of the ring and a curved outer wall to engage the snap ring; the assembly groove having a depth at least equal to the cross-sectiona thickness of the ring and inner and outer sidewalls; the inner sidewall of the assembly groove having a frusto-conical surface inclined at a selected angle ~ relative to a plane perpendicular to the axis of the shaft to urge the snap ring against the curved outer wall of the retainer groove when the cone is thrust inward and away from said thrust surface.
In accordance with yet another aspect, the invention provides in combination with an earth boring bit having at least one cantilevered bearing shaft rotatably supporting a sealed and lubricated cutter, an improved cutter retention means comprising: exclusively friction bearing means between ~-6b-cæ~,~.
?
10~68Sl said cutter and shaft, including an inwardly facing thrust surface on the shaft; pressure adjustment means included in the lubrication system to limit the pressure differential across the seal; one of said cutter and shaft having an assembly groove with a circular bottom and the other having a registering, retainer groove with a circular outer sidewall;
a snap ring with a circular cross-section positioned in said grooves; the retainer groove having a depth at least equal to one-hal~ the cross-sectional thickness of the ring; the assembly groove having a depth at least equal to the cross-sectional thickness of the ring and inner and outer sidewalls;
the surface of the shaft and the inner sidewall of the assembly groove intersecting at a corner; the inner sidewall having a frusto-conical surface inclined at a selected angle ~ relative to a plane perpendicular to the axis of the shaft to provide surface contact rather than edge contact with the snap ring.
This application is related to copending applications - 306,830 and 304,646 filed ~uly 5, 1978 and June 2, 1978 respectively. These applications share the disclosure of the present application but claim other embodiments of inventions disclosed in this case.
Application 306,830 generically claims the improved cutter retention means in combination with an earth boring bit and comprising the snap ring of circular cross-section, the retaining groove in the cutter or journal being - approximately half the thickness of the ring.
The present application specifically claims the improvement where the assembly groove has a depth at least equal to the cross-sectional thickness of the snap ring, the groove having an outer side wall and an inner side wall with the inner side wall having a frusto-conical surface inclined at a selected angle relative to a plane that is perpendicular to the axis of the shaft.
-6c-1096~S~
Brief Descrlption of the Drawings Fig. 1 is a fragmentary view, partially in section, of a rock bit which embodies the features of t~e inv~ntion.
Fig. 2 is a full view of a snap ring used to rotatably retain the cutter on the bearing shaft or pin of the rock bit of Fig. 1.
Fig. 3 is an enlarged, fragmentary view in longitudinal section of a portion of the cutter and the ~earing pin of Fig. 1.
Fig. 4 is a fragmentary view, in longitudinal section, of a region of the cutter and bearing pin around the cross-sectioned snap ring, of Fig. 1, the cutter being thrust outwardly on the bearing shaft.
Fig. 5 is, like Fig. 4, a fragmentary view, in longitudinal section but with the cutter thrust inwardly on the bearing shaft.
Fig. 6 is a fragmentary view, in longitudinal section, of a second construction with the cutter thrust inward.
Fig. 7 is a fragmentary view, in longitudinal section, of a third construction, with the cutter thrust inward.
Description of the Preferred Embodiment Portions of an earth boring drill bit 11 are shown in Fig. 1, including a body 13 formed of three head sections 15 that are typically joined by a welding process. Threads 17 are formed on the top of body 13 for connection to a conventional drill string (not shown). Each head section 15 has a cantilevered shaft or bearing pin 19 having its unsupported end oriented inward and downward. A generally conically shaped cutter 21 is rotatably mounted on each bearing pin 19. Cutter 21 has earth disintegrating teeth 23 on its exterior and a central opening or bearing recess 25 in its interior for mounting on the bearing pin 19. Friction bearing means formed on the bearing pin 19 and cutter bearing recess 25 are connected with lubricant passages 27. (See U.S. Patent Nos. 3,397,928 and 4,012,238 for bearing surface treatments.) A pressure compensator 29 and associated 10~6851 passages constitute a lubricant reservoir that limits the pressure differential bet~en the lubricant and the ambient fluid which surrounds the hit after flowing through the nozzle means 32. An O-ring seal 31 located between each bearing pin 19 and cutter 21 at the base of the bearing pin prevents egress of lubricant and ingress of borehole fluid. ~see U.S. Patent No. 3,397,928 for O-ring seal disclosure and U.S. Patent No.
3,935,114 for lubricant.) Referring to Figs. 3, 4 and 5, an annular assembly groove 33 is formed on the cylindrical surface 34 of the bearing pin 19. Groove 33 has a circular bottom portion 35 formed about a radius located on centerline 41. An outer and an inner side-wall designated respectively sidewall 37 or 39 extend from the semi-circular bottom portion 35 to the surface of the bearing pin 19, outer sidewall 37 being the one farther from the inner end or nose 43 of the bearing pin 19. Outer sidewall 37 is planar and perpendicular to the coaxis (not shown) of the bearing pin 19 and cutter 21.
Inner sidewall 39 is a conical thrust surface or inclined wall nonperpendicular to the axis of the bearing pin, oriented at an angle ~ of preferably 15 with respect to a plane perpendicular to axis of the bearing pin. This produces an entrance to groove 33 larger than the diameter of its circular bottom portion 35 and is a beneficial thrust surface as will be explained subsequently.
A registering retainer groove 45 is formed in the bearing recess 25 of cutter 21. Groove 45 has sidewalls 46 and 50, with outer sidewall 46 located farthest from nose 43 of bearing pin 19. As seen in section, sidewall 46 has the form of a circular arc equal to one quarter of a circle, with a radius substantially equal ~o the radius of the bottom portion 35 of the previously described groove 33. The depth of groove 45 is ~Oq~851 greater than the radius of the circular arc. As seen in section in Fig. 4, inner sidewall 50 consists of a straight line connected at one end by means of a s~all radius with the quarter-circular arc of sidewall 46 and its other end extends to form one surface of a tapered or conical frictional nose bearing 52.
Grooves 33 and 45 are located so that they register to define an irregularly shaped annular cavity with curved bottoms.
A snap ring 47 with a curved boundary and preferably circular cross-section is located in this cavity. It is formed of resilient metal, preferably piano wire, and contains a gap 49 (see Fig. 2) so that its annular diameter may be compressed or expanded. The annular diameter of ring 47 is selected so that it will expand tightly into groove 45 when relaxed. The cross-sectional diameter of 47 is substantially equal to the diameter of the circular portion 35 of groove 33.
The depth of assembly groove 33 is at least as large as the cross-sectional diameter of ring 47. This enables ring 47 to be stressed and retract ~ully into groove 33 for assembling cutter 21 over bearing pin l9. The depth of retainer groove 45 is greater than one-half the cross-sectional diameter of ring 47 but less than its cross-sectional full diameter. This depth is greater than the thickness of one-half the diameter of the cross section of ring 47 by an amount, conveniently called the "offset", which in the preferred form is in the range from .005 inch to .020 inch. This places the cross-sectional centerline 51 of ring 47 outside the cylindrical surface 34 of the bearing pin and also outside the edge of the retainer groove by the same quantity.
To assemble the cutter 21 over bearing pin l9, a tool (not shown) is used to compress ring 47 into groove 33. The cutter 21 is then inserted partially over the bearing pin 19 and the tool removed. Cutter 21 is ~hen forced outwardly and _ g _ 10~685~
against the bearing pin until engagement o~ the o~posing surfaces of the tapered nose bearin~ 52, as shown in Fi~. 4.
Groove 45 will be sufficiently aligned with groove 33 ~or ring 47 to snap into it. Ring 47 is shown in Fig. 4 against sidewall 46 of groove 45, and is not touching sidewall 50. Sidewall 39 of groove 33 also is separated from the ring by a clearance space Cl to assure movement into retainer groove 45. The center-line 51 of ring 47 is offset to a position outside the surface 34 of the bearing pin 19 by the preferred distances of .005 to 10 .020 inch.
Centerlines 41 and 51 do not lie on a common plane perpendicular to the bearing pin axis. Rather, centerline 51 is spaced closer to the nose 43 than centerline 41. Because of clearance Cl the cutter 21 may move inward on bearing pin 19 to the position shown in Fig. 5. Here, ring 47 is confined between sidewall 46 of groove 45 and the corner of sidewall 39 of groove 33. A clearance C2 appears between the opposing surfaces of conical or tapered thrust bearing 52.
The distance from the offset annular edge of wall 39 ; 20 of the assembly groove 33 to the opposite corner or outer wall 46 in retainer groove 45 is less than the thickness or diameter of snap ring 47 when the cutter i~ thrust inward to the position shown in Fig. 5. That is, the diameter of the snap ring in Fig. 5 is represented by the letter x ~ y. The distance from the edge of wall 39 to the opposite corner of groove 46 is a : lesser distance x. Hence, when the cone is thrust inward, the ring cannot be retracted into the assembly groove 33 but must remain in the retainer groove 45 to prevent accidental cutter loss.
In operation, the most normal drilling condition produces outward thrust of cutter 21 on bearing pin 19 as seen in Fig. 4. No external forces are exerted on ring 47 due to ~0"685~
engagement of the surfaces o tapered bearing 52 and the result-ing clearance C3 ~etween the ring 47 and wall 37 of gro~ve 33.
If thrust on the cutter is inward, as sometimes occurs when reaming an undersized hole, the tendency will be for the cutter 21 to be pushed inwardly and from the bearing pin 19. This tendency will be resisted by ring 47, which transmits the thrust between sidewall 46 and sidewall 39 as shown in Fig. 5. Inner sidewall 39 serves as a thrust surface, providing a compressive reacting ~orce.
The forming of inner sidewall 39 at an angle a generates a force component F ~see Fig. 6~ at the same angle ~ and in a direction oblique to the axis of rotation of the cutter 21. Thus, the configuration of the groove 33 produce~ a three dimensional conical force distribution F that expands the ring 47 outward into groove 45 in cutter 21. This prevents compression of ring 47 into the groove 33 of bearing pin 19 and the consequent loss of cutter 21.
Fig. 6 is a second construction from that shown in Figs.
4 and 5 in that the walls 37, 39 of assembly groove 33 are parallel and formed at the angle ~ . The "offset" is smaller in Fig. 6 and is not necessarily utilized since here the tapered wall 39 exerts a force component F normal to the surface of ring 47 to urge the ring into retainer groove 45.
In Fig. 7 is shown a third construction in which the walls 371 39 of assembly groove 33 are parallel and perpendicular the centerline of the bearing pin. Here the edge or outer wall 39 of groove 33 engages the ring 47 at a distance from the center-line 51 of the ring 47 equal to the "offset" from cylindrical bearing surface 34. A force component F is exerted obliquely against the ring, at an angle normal to the surface of ring 47, to urge the ring into the retainer groove 45 when the cone is thrust inward.
10~68S$
The preferred construction o~ Figs. 4 and 5 is a combination of the features of Figs. 6 and 7 in that ~all 39 (but not wall 37) of groove 33 is tapered and the "of~set" feature is also used. The quantity of offset in the specified preferred range is such that angle ~ of preferably 15 results in surface 39 contact with the ring rather than sharp edge contact. This provides a superior wear condition since a sharp edge will wear the ring more rapidly.
Each of the three constructions of Fig. 4 through 7 have a feature that further minimizes loss of a cutter, as previously explained in connection with Fig. 5. That is, the cross-sectional thickness x ~ y of the ring 47 is greater than the distance x from the edge of wall 39 to the opposite corner of groove 46 when the cutters are thrust inwardly on their bearing shafts.
It should be apparent from the foregoing that improve-ments having significant advantages have been made. The utilization of a ~earing structure which consists of lubricated frictional bearing surfaces, including a frictional retainer means, simplifies construction and increases reliability. The utilization of the disclosed snap ring and groove configuration minimizes the danger of loss of the cutter. The previously described offset position between the centerline of the ring and the surface of the bearing near the assembly groove results in an oblique force component that urges the ring into its retainer groove. The smooth angular thrust surface in the assem~ly groove to engage the ring when the cone is thrust inward provides an advantageous wear environment. Furthex, the inclined orientation of this surface, which acts as a thrust surface, also urges the retainer ring into its retaining groove when the cone is thrust inward. The ring configuration and thickness being lesser than the distance across the groove assures cutter retention.
~0~6851 While th.e inYention has ~een shown in only one of its forms, it should be apparent to. those skilled in the art that it is not thus limited ~ut is susceptible to various chanyes and modifications without departing from the spirit thereof.
tapered and cylindrical portions joined ~y suitable means and secured to a cutter by a retainer ring. A lock ring is shown in Edward B. Williams, Jr.'s U.S. Patent No. 3,844,363 for retaining a cutter and shaft with frictional bearings to a rock bit. A frictional bearing with tapered and cylindrical portions is disclosed by E.M. Galle in his U.S. Patent No . 3,361,494, along with frictional plug lock and pin lock retaining systems.
A recent revival of the earlier seen threaded ring retainer is seen in U.S. Patent No. 3,971,60a of Murdoch et al. Notwith-standing this array of ideas, the only significantly successfulrock bit in commerce today uses a ball bearing retainer.
The threaded retainer ring has some disadvantage that - may have limited its success. The threads act as stress raisers and the ring must be secured against rotation while the cone is mated with it. This generally requires a drilled hole in the head section.
Snap rings may have stress raising groove configurations ; and exhibit a tendency to retract during drilling into the assembly groove and permit accidental cutter loss. When a cutter is thrust inward, as when reaming for example, the loading of the ring causes stresses that tend to urge the ring into the assembly groove, with the possibility of cutter loss.
Summary of the Invention The invention may be summarized as an improved friction bearing and snap ring retainer means for a rock bit of the type having rotatable cutters, with sealed and lubricated ~earings and a pressure compensation system. The preferred snap ring is circular in cross section for assem~ly within two registering snap ring grooves, one in the cutter and the other in the bearing shaft that supports the cutter. The grooves in the preferred form have circular or semi-circular ~ottoms, one being an assembly groove of a depth at least as great as the cross-:~L0~6851 sectional thickness of the ring. The other groove, the retainergroove, has a depth less than the cross-sectional thickness of the ring. When the cutter is thrust outward (toward the wall of the bore hole), there is clearance between the ring and assembly groove, but when the cutter is thrust inward, the ring is con-fined between the assembly groove and the retainer groove. The ring is forced outward into the retainer groove by either the offset edge of the assembly groove or an inclined wall ~or~ed on the edge of the assembly groove, either of which produces a conical force distribution. This urges the ring into the retainer groove and prevents accidental displacement of the ring into the assembly groove and loss of the associated cutter.
Further assurance of cutter retention is provided because the distance from the edge of the assembly groove to the opposing edge of the retainer groove is less than the thickness of the ring when the cone experiences thrust loading.
Additional objects, features and advantages of the invention will become apparent in the following description.
~0'~6851 In accordance with one broad aspect, the invention provides in combination with an earth boring bit having at least one cantilevered bearing shaft rotatably supporting a sealed and lubricated cutter, an improved cutter retention means comprising: friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft; one of said cutter and shaft having an assembly groove and the other having a registering, retainer groove; a snap ring positioned in the registering grooves; the retainer groove having a depth less than the cross-sectional thickness of the ring, the assembly groove having a depth at least equal to the cross-sectional thickness of the ring, an outer sidewall and an inner sidewall, with the inner sidewall having a frusto-conical surface inclined at a selected angle ~ relative to a plane perpendicular to the axis of the shaft to engage the snap ring and generate a force component oblique to said axis and urge the snap ring into the retainer groove when the cone is thrust inward and away from said thrust surface.
In accordance with another aspect, the invention provides in combination with an earth boring bit having at least one cantilevered bearing shaft rotatably supported to a sealed and lubricated cutter, an improved cutter retention means comprising: friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft; the shaft having an assembly groove and the cutter having a registering, retainer groove; a snap ring positioned in the registering grooves; the retainer groove having a depth less than the cross-sectional thickness of the ring; the assembly groove having a depth at least equal to the cross-sectional thickness of the ring and inner and outer sidewalls; the surface of the shaft and the inner sidewall of the assembly groove ~-6a-l~g6~1 intersecting at a corner; the inner sidewall having a frusto-conical surface inclined at a selected angle ~ relative to a plane perpendicular to the axis of the shaft to engage the snap ring and urge it into the retainer groove when the cone is thrust inward and away ~rom said thrust surface.
In accordance with a further aspect, the invention provides in combination with an earth boring bit having at least one cantilevered bearing shaft rotatabl~ supporting a sealed and lubricated cutter, and improved cutter retention means comprising: exclusively friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft; pressure adjustment means included in the lubrication system to control the pressure differential across said seal; one of said cutter and shaft having an assembly groove with a curved bottom and the other having a registering, retainer groove with a curved bottom; a snap ring having a cross-section with a curved boundary positioned in said grooves; the retainer groove having a depth at least equal to one-half the cross-sectional thickness of the ring and a curved outer wall to engage the snap ring; the assembly groove having a depth at least equal to the cross-sectiona thickness of the ring and inner and outer sidewalls; the inner sidewall of the assembly groove having a frusto-conical surface inclined at a selected angle ~ relative to a plane perpendicular to the axis of the shaft to urge the snap ring against the curved outer wall of the retainer groove when the cone is thrust inward and away from said thrust surface.
In accordance with yet another aspect, the invention provides in combination with an earth boring bit having at least one cantilevered bearing shaft rotatably supporting a sealed and lubricated cutter, an improved cutter retention means comprising: exclusively friction bearing means between ~-6b-cæ~,~.
?
10~68Sl said cutter and shaft, including an inwardly facing thrust surface on the shaft; pressure adjustment means included in the lubrication system to limit the pressure differential across the seal; one of said cutter and shaft having an assembly groove with a circular bottom and the other having a registering, retainer groove with a circular outer sidewall;
a snap ring with a circular cross-section positioned in said grooves; the retainer groove having a depth at least equal to one-hal~ the cross-sectional thickness of the ring; the assembly groove having a depth at least equal to the cross-sectional thickness of the ring and inner and outer sidewalls;
the surface of the shaft and the inner sidewall of the assembly groove intersecting at a corner; the inner sidewall having a frusto-conical surface inclined at a selected angle ~ relative to a plane perpendicular to the axis of the shaft to provide surface contact rather than edge contact with the snap ring.
This application is related to copending applications - 306,830 and 304,646 filed ~uly 5, 1978 and June 2, 1978 respectively. These applications share the disclosure of the present application but claim other embodiments of inventions disclosed in this case.
Application 306,830 generically claims the improved cutter retention means in combination with an earth boring bit and comprising the snap ring of circular cross-section, the retaining groove in the cutter or journal being - approximately half the thickness of the ring.
The present application specifically claims the improvement where the assembly groove has a depth at least equal to the cross-sectional thickness of the snap ring, the groove having an outer side wall and an inner side wall with the inner side wall having a frusto-conical surface inclined at a selected angle relative to a plane that is perpendicular to the axis of the shaft.
-6c-1096~S~
Brief Descrlption of the Drawings Fig. 1 is a fragmentary view, partially in section, of a rock bit which embodies the features of t~e inv~ntion.
Fig. 2 is a full view of a snap ring used to rotatably retain the cutter on the bearing shaft or pin of the rock bit of Fig. 1.
Fig. 3 is an enlarged, fragmentary view in longitudinal section of a portion of the cutter and the ~earing pin of Fig. 1.
Fig. 4 is a fragmentary view, in longitudinal section, of a region of the cutter and bearing pin around the cross-sectioned snap ring, of Fig. 1, the cutter being thrust outwardly on the bearing shaft.
Fig. 5 is, like Fig. 4, a fragmentary view, in longitudinal section but with the cutter thrust inwardly on the bearing shaft.
Fig. 6 is a fragmentary view, in longitudinal section, of a second construction with the cutter thrust inward.
Fig. 7 is a fragmentary view, in longitudinal section, of a third construction, with the cutter thrust inward.
Description of the Preferred Embodiment Portions of an earth boring drill bit 11 are shown in Fig. 1, including a body 13 formed of three head sections 15 that are typically joined by a welding process. Threads 17 are formed on the top of body 13 for connection to a conventional drill string (not shown). Each head section 15 has a cantilevered shaft or bearing pin 19 having its unsupported end oriented inward and downward. A generally conically shaped cutter 21 is rotatably mounted on each bearing pin 19. Cutter 21 has earth disintegrating teeth 23 on its exterior and a central opening or bearing recess 25 in its interior for mounting on the bearing pin 19. Friction bearing means formed on the bearing pin 19 and cutter bearing recess 25 are connected with lubricant passages 27. (See U.S. Patent Nos. 3,397,928 and 4,012,238 for bearing surface treatments.) A pressure compensator 29 and associated 10~6851 passages constitute a lubricant reservoir that limits the pressure differential bet~en the lubricant and the ambient fluid which surrounds the hit after flowing through the nozzle means 32. An O-ring seal 31 located between each bearing pin 19 and cutter 21 at the base of the bearing pin prevents egress of lubricant and ingress of borehole fluid. ~see U.S. Patent No. 3,397,928 for O-ring seal disclosure and U.S. Patent No.
3,935,114 for lubricant.) Referring to Figs. 3, 4 and 5, an annular assembly groove 33 is formed on the cylindrical surface 34 of the bearing pin 19. Groove 33 has a circular bottom portion 35 formed about a radius located on centerline 41. An outer and an inner side-wall designated respectively sidewall 37 or 39 extend from the semi-circular bottom portion 35 to the surface of the bearing pin 19, outer sidewall 37 being the one farther from the inner end or nose 43 of the bearing pin 19. Outer sidewall 37 is planar and perpendicular to the coaxis (not shown) of the bearing pin 19 and cutter 21.
Inner sidewall 39 is a conical thrust surface or inclined wall nonperpendicular to the axis of the bearing pin, oriented at an angle ~ of preferably 15 with respect to a plane perpendicular to axis of the bearing pin. This produces an entrance to groove 33 larger than the diameter of its circular bottom portion 35 and is a beneficial thrust surface as will be explained subsequently.
A registering retainer groove 45 is formed in the bearing recess 25 of cutter 21. Groove 45 has sidewalls 46 and 50, with outer sidewall 46 located farthest from nose 43 of bearing pin 19. As seen in section, sidewall 46 has the form of a circular arc equal to one quarter of a circle, with a radius substantially equal ~o the radius of the bottom portion 35 of the previously described groove 33. The depth of groove 45 is ~Oq~851 greater than the radius of the circular arc. As seen in section in Fig. 4, inner sidewall 50 consists of a straight line connected at one end by means of a s~all radius with the quarter-circular arc of sidewall 46 and its other end extends to form one surface of a tapered or conical frictional nose bearing 52.
Grooves 33 and 45 are located so that they register to define an irregularly shaped annular cavity with curved bottoms.
A snap ring 47 with a curved boundary and preferably circular cross-section is located in this cavity. It is formed of resilient metal, preferably piano wire, and contains a gap 49 (see Fig. 2) so that its annular diameter may be compressed or expanded. The annular diameter of ring 47 is selected so that it will expand tightly into groove 45 when relaxed. The cross-sectional diameter of 47 is substantially equal to the diameter of the circular portion 35 of groove 33.
The depth of assembly groove 33 is at least as large as the cross-sectional diameter of ring 47. This enables ring 47 to be stressed and retract ~ully into groove 33 for assembling cutter 21 over bearing pin l9. The depth of retainer groove 45 is greater than one-half the cross-sectional diameter of ring 47 but less than its cross-sectional full diameter. This depth is greater than the thickness of one-half the diameter of the cross section of ring 47 by an amount, conveniently called the "offset", which in the preferred form is in the range from .005 inch to .020 inch. This places the cross-sectional centerline 51 of ring 47 outside the cylindrical surface 34 of the bearing pin and also outside the edge of the retainer groove by the same quantity.
To assemble the cutter 21 over bearing pin l9, a tool (not shown) is used to compress ring 47 into groove 33. The cutter 21 is then inserted partially over the bearing pin 19 and the tool removed. Cutter 21 is ~hen forced outwardly and _ g _ 10~685~
against the bearing pin until engagement o~ the o~posing surfaces of the tapered nose bearin~ 52, as shown in Fi~. 4.
Groove 45 will be sufficiently aligned with groove 33 ~or ring 47 to snap into it. Ring 47 is shown in Fig. 4 against sidewall 46 of groove 45, and is not touching sidewall 50. Sidewall 39 of groove 33 also is separated from the ring by a clearance space Cl to assure movement into retainer groove 45. The center-line 51 of ring 47 is offset to a position outside the surface 34 of the bearing pin 19 by the preferred distances of .005 to 10 .020 inch.
Centerlines 41 and 51 do not lie on a common plane perpendicular to the bearing pin axis. Rather, centerline 51 is spaced closer to the nose 43 than centerline 41. Because of clearance Cl the cutter 21 may move inward on bearing pin 19 to the position shown in Fig. 5. Here, ring 47 is confined between sidewall 46 of groove 45 and the corner of sidewall 39 of groove 33. A clearance C2 appears between the opposing surfaces of conical or tapered thrust bearing 52.
The distance from the offset annular edge of wall 39 ; 20 of the assembly groove 33 to the opposite corner or outer wall 46 in retainer groove 45 is less than the thickness or diameter of snap ring 47 when the cutter i~ thrust inward to the position shown in Fig. 5. That is, the diameter of the snap ring in Fig. 5 is represented by the letter x ~ y. The distance from the edge of wall 39 to the opposite corner of groove 46 is a : lesser distance x. Hence, when the cone is thrust inward, the ring cannot be retracted into the assembly groove 33 but must remain in the retainer groove 45 to prevent accidental cutter loss.
In operation, the most normal drilling condition produces outward thrust of cutter 21 on bearing pin 19 as seen in Fig. 4. No external forces are exerted on ring 47 due to ~0"685~
engagement of the surfaces o tapered bearing 52 and the result-ing clearance C3 ~etween the ring 47 and wall 37 of gro~ve 33.
If thrust on the cutter is inward, as sometimes occurs when reaming an undersized hole, the tendency will be for the cutter 21 to be pushed inwardly and from the bearing pin 19. This tendency will be resisted by ring 47, which transmits the thrust between sidewall 46 and sidewall 39 as shown in Fig. 5. Inner sidewall 39 serves as a thrust surface, providing a compressive reacting ~orce.
The forming of inner sidewall 39 at an angle a generates a force component F ~see Fig. 6~ at the same angle ~ and in a direction oblique to the axis of rotation of the cutter 21. Thus, the configuration of the groove 33 produce~ a three dimensional conical force distribution F that expands the ring 47 outward into groove 45 in cutter 21. This prevents compression of ring 47 into the groove 33 of bearing pin 19 and the consequent loss of cutter 21.
Fig. 6 is a second construction from that shown in Figs.
4 and 5 in that the walls 37, 39 of assembly groove 33 are parallel and formed at the angle ~ . The "offset" is smaller in Fig. 6 and is not necessarily utilized since here the tapered wall 39 exerts a force component F normal to the surface of ring 47 to urge the ring into retainer groove 45.
In Fig. 7 is shown a third construction in which the walls 371 39 of assembly groove 33 are parallel and perpendicular the centerline of the bearing pin. Here the edge or outer wall 39 of groove 33 engages the ring 47 at a distance from the center-line 51 of the ring 47 equal to the "offset" from cylindrical bearing surface 34. A force component F is exerted obliquely against the ring, at an angle normal to the surface of ring 47, to urge the ring into the retainer groove 45 when the cone is thrust inward.
10~68S$
The preferred construction o~ Figs. 4 and 5 is a combination of the features of Figs. 6 and 7 in that ~all 39 (but not wall 37) of groove 33 is tapered and the "of~set" feature is also used. The quantity of offset in the specified preferred range is such that angle ~ of preferably 15 results in surface 39 contact with the ring rather than sharp edge contact. This provides a superior wear condition since a sharp edge will wear the ring more rapidly.
Each of the three constructions of Fig. 4 through 7 have a feature that further minimizes loss of a cutter, as previously explained in connection with Fig. 5. That is, the cross-sectional thickness x ~ y of the ring 47 is greater than the distance x from the edge of wall 39 to the opposite corner of groove 46 when the cutters are thrust inwardly on their bearing shafts.
It should be apparent from the foregoing that improve-ments having significant advantages have been made. The utilization of a ~earing structure which consists of lubricated frictional bearing surfaces, including a frictional retainer means, simplifies construction and increases reliability. The utilization of the disclosed snap ring and groove configuration minimizes the danger of loss of the cutter. The previously described offset position between the centerline of the ring and the surface of the bearing near the assembly groove results in an oblique force component that urges the ring into its retainer groove. The smooth angular thrust surface in the assem~ly groove to engage the ring when the cone is thrust inward provides an advantageous wear environment. Furthex, the inclined orientation of this surface, which acts as a thrust surface, also urges the retainer ring into its retaining groove when the cone is thrust inward. The ring configuration and thickness being lesser than the distance across the groove assures cutter retention.
~0~6851 While th.e inYention has ~een shown in only one of its forms, it should be apparent to. those skilled in the art that it is not thus limited ~ut is susceptible to various chanyes and modifications without departing from the spirit thereof.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In combination with an earth boring bit having at least one cantilevered bearing shaft rotatably supporting a sealed and lubricated cutter, an improved cutter retention means comprising:
friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft;
one of said cutter and shaft having an assembly groove and the other having a registering, retainer groove;
a snap ring positioned in the registering grooves;
the retainer groove having a depth less than the cross-sectional thickness of the ring;
the assembly groove having a depth at least equal to the cross-sectional thickness of the ring, an outer sidewall and an inner sidewall, with the inner sidewall having a frusto-conical surface inclined at a selected angle a relative to a plane perpendicular to the axis of the shaft to engage the snap ring and generate a force component oblique to said axis and urge the snap ring into the retainer groove when the cutter is thrust inward and away from said thrust surface.
friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft;
one of said cutter and shaft having an assembly groove and the other having a registering, retainer groove;
a snap ring positioned in the registering grooves;
the retainer groove having a depth less than the cross-sectional thickness of the ring;
the assembly groove having a depth at least equal to the cross-sectional thickness of the ring, an outer sidewall and an inner sidewall, with the inner sidewall having a frusto-conical surface inclined at a selected angle a relative to a plane perpendicular to the axis of the shaft to engage the snap ring and generate a force component oblique to said axis and urge the snap ring into the retainer groove when the cutter is thrust inward and away from said thrust surface.
2. In combination with an earth boring bit having at least one cantilevered bearing shaft rotatably supported to a sealed and lubricated cutter, an improved cutter retention means comprising:
friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft;
the shaft having an assembly groove and the cutter having a registering, retainer groove;
a snap ring positioned in the registering grooves;
the retainer groove having a depth less than the cross-sectional thickness of the ring;
the assembly groove having a depth at least equal to the cross-sectional thickness of the ring and inner and outer sidewalls;
the surface of the shaft and the inner sidewall of the assembly groove intersecting at a corner;
the inner sidewall having a frusto-conical surface inclined at a selected angle .alpha. relative to a plane perpendicular to the axis of the shaft to engage the snap ring and urge it into the retainer groove when the cutter is thrust inward and away from said thrust surface.
friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft;
the shaft having an assembly groove and the cutter having a registering, retainer groove;
a snap ring positioned in the registering grooves;
the retainer groove having a depth less than the cross-sectional thickness of the ring;
the assembly groove having a depth at least equal to the cross-sectional thickness of the ring and inner and outer sidewalls;
the surface of the shaft and the inner sidewall of the assembly groove intersecting at a corner;
the inner sidewall having a frusto-conical surface inclined at a selected angle .alpha. relative to a plane perpendicular to the axis of the shaft to engage the snap ring and urge it into the retainer groove when the cutter is thrust inward and away from said thrust surface.
3. In combination with an earth boring bit having at least one cantilevered bearing shaft rotatably supporting a lubricated cutter and seal, an improved cutter retention means comprising:
exclusively friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft;
pressure adjustment means included in a lubrication system to control pressure differential across the seal;
one of said cutter and shaft having an assembly groove with a curved bottom and the other having a registering, retainer groove with a curved bottom;
a snap ring having a cross-section with a curved boundary positioned in s aid grooves;
the retainer groove having a depth at least equal to one-half the cross-sectional thickness of the ring and a curved outer wall to engage the snap ring;
the assembly groove having a depth at least equal to the cross-sectional thickness of the ring and inner and outer sidewalls;
the inner sidewall of the assembly groove having a frusto-conical surface inclined at a selected angle .alpha.
relative to a plane perpendicular to the axis of the shaft to urge the snap ring against the curved outer wall of the retainer groove when the cutter is thrust inward and away from said thrust surface.
exclusively friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft;
pressure adjustment means included in a lubrication system to control pressure differential across the seal;
one of said cutter and shaft having an assembly groove with a curved bottom and the other having a registering, retainer groove with a curved bottom;
a snap ring having a cross-section with a curved boundary positioned in s aid grooves;
the retainer groove having a depth at least equal to one-half the cross-sectional thickness of the ring and a curved outer wall to engage the snap ring;
the assembly groove having a depth at least equal to the cross-sectional thickness of the ring and inner and outer sidewalls;
the inner sidewall of the assembly groove having a frusto-conical surface inclined at a selected angle .alpha.
relative to a plane perpendicular to the axis of the shaft to urge the snap ring against the curved outer wall of the retainer groove when the cutter is thrust inward and away from said thrust surface.
4. In combination with an earth boring bit having at least one cantilevered bearing shaft rotatably supporting a lubricated cutter and seal, an improved cutter retention means comprising:
exclusively friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft;
pressure adjustment means included in a lubrication system to limit pressure differential across said seal;
one of said cutter and shaft having an assembly groove with a circular bottom and the other having a registering, retainer groove with a circular outer sidewall;
a snap ring with a circular cross-section positioned in said grooves;
the retainer groove having a depth at least equal to one-half the cross-sectional thickness of the ring;
the assembly groove having a depth at least equal to the cross-sectional thickness of the ring and inner and outer sidewalls;
the surface of the shaft and the inner sidewall of the assembly groove intersecting at a corner;
the inner sidewall having a frusto-conical surface inclined at a selected angle a relative to a plane perpendicular to the axis of the shaft to provide surface contact rather than edge contact with the snap ring.
exclusively friction bearing means between said cutter and shaft, including an inwardly facing thrust surface on the shaft;
pressure adjustment means included in a lubrication system to limit pressure differential across said seal;
one of said cutter and shaft having an assembly groove with a circular bottom and the other having a registering, retainer groove with a circular outer sidewall;
a snap ring with a circular cross-section positioned in said grooves;
the retainer groove having a depth at least equal to one-half the cross-sectional thickness of the ring;
the assembly groove having a depth at least equal to the cross-sectional thickness of the ring and inner and outer sidewalls;
the surface of the shaft and the inner sidewall of the assembly groove intersecting at a corner;
the inner sidewall having a frusto-conical surface inclined at a selected angle a relative to a plane perpendicular to the axis of the shaft to provide surface contact rather than edge contact with the snap ring.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US84664277A | 1977-10-28 | 1977-10-28 | |
| US846,642 | 1977-10-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1096851A true CA1096851A (en) | 1981-03-03 |
Family
ID=25298509
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA304,706A Expired CA1096851A (en) | 1977-10-28 | 1978-06-02 | Earth boring drill bit with snap ring cutter retention |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5471702A (en) |
| BR (1) | BR7804960A (en) |
| CA (1) | CA1096851A (en) |
| FR (1) | FR2407333A1 (en) |
| GB (1) | GB1599377A (en) |
| MX (1) | MX148805A (en) |
| NL (1) | NL7809267A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4577705A (en) * | 1984-04-23 | 1986-03-25 | Smith International, Inc. | Bellows lubricant pressurizer for sealed bearing rock bits |
-
1978
- 1978-05-31 GB GB24708/78A patent/GB1599377A/en not_active Expired
- 1978-06-02 CA CA304,706A patent/CA1096851A/en not_active Expired
- 1978-08-02 BR BR7804960A patent/BR7804960A/en unknown
- 1978-09-12 NL NL7809267A patent/NL7809267A/en not_active Application Discontinuation
- 1978-09-19 FR FR7826844A patent/FR2407333A1/en not_active Withdrawn
- 1978-09-26 MX MX175014A patent/MX148805A/en unknown
- 1978-10-24 JP JP13145278A patent/JPS5471702A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| GB1599377A (en) | 1981-09-30 |
| NL7809267A (en) | 1979-05-02 |
| FR2407333A1 (en) | 1979-05-25 |
| MX148805A (en) | 1983-06-22 |
| JPS5471702A (en) | 1979-06-08 |
| BR7804960A (en) | 1979-05-29 |
| JPS6128076B2 (en) | 1986-06-28 |
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |