Note: Descriptions are shown in the official language in which they were submitted.
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B~CKGROUND OF TIIE INVF,~lTION
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This invention relates in general to earth boring
bits, and in particular to a bearincJ seal for earth
boring bits.
This inven-tion concerns particularLy the type o~
earth borincJ bit tha-t employs -three rotatable cutters
mounted on de~encling bear~nc~ shaE-ts. ~ach conical cut-
ter rotatcs on its bcarin~ shaEt as the drill bit is
rotated. The cutter las teeth of tun~sten carbicle in-
serts on its exterior for disintegrating th~ ear~h. The
bearings are usually either a journal type, or they may
employ roller hearings. ~rhe bearings are supplied with
lubricant and sealed by an elastomeric seal located in a
groove formed in the bearing shaft at its base.
Because o~ tolerances, particular]y with the roll-
er bearing type bearin~s, the cutter will have radial,
axial and an~ular movements relative to the bearin~
shaft. The seal, which usually is in sliding contact
with the c~ltter, wi11 experience var~ing degrees of pres-
sure because of this movernent, tending to cause leakacle.
There have been several proposals in the past to provide
a floatincJ seal that is able to move ra(lially to accommo-
date the cutter rnovement.
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1157~63
SUMMI~RY OY T~IE INVENTION
This invention provides an improved Eloating seal for
the bearings of an earth boring bit. In the preferred em-
bodiment, a groove for the seal is ~ormed in the shaft
near its intersection with the head section. ~ suppor-~ing
ring is located in this annular groove. PreEerably, the
supporting riny is a split ring tha~ can be expanded for
installation, however, has a minimum diameter. rrhe mini-
mum diameter is greater than the inner diameter of the
groove, providing an annular clearance on the inside of
the supporting ring to allow it to float.
~ n elastomeric ring is located on the outer circum-
ference of the supporting ring, and preferably is an O
ring. The supporting ring urges the elastomeric rin~ into
sealing and sliding contact with the cutter. Means are
provided to prevent the O-ring from moving along the axis
of the shaft and for providing sealing against the sides
of the O-ring. In the preferred embodiment, ~his consists
o~ a backup ring, which squeezes the O-ring agains-t 1,he
sides of the groove and also protects the O-ring from cut-
tlngs.
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1 1 5'74B3
RIEF DESCRIPTION F_THE DR~WINGS
Fig. 1 is a par-tial vertical sectional vie~w of an
earth boring bit constructed in accordance with this in-
vention.
Fig. 2 is an enlarge~ vertical sect.ional view of part
o the bearing seal of the earth boring bit of Fig. 1.
Fig. 3 is a sectional view of t}le earth boring bit
of Fig. 1, taken along the line III-III of FicJ. 1.
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SCRl:l"L`:lON ~ 1'EI~ ;O E~ML~ODlML~
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Fig. 1 illustrates an earth borincJ bit ll particular~
ly constructecl for drilling blast ho],es for minincJ. I'arth
borinc~ bit 11 has three heacl sections 13 (only one sho~n),
which are subsecluently welded together. Each heacl sec-tion
13 has a depe~ndi~J bearillcJ pin or shaEt lS. ~n annular
groove 17 is formecl in shat 15 at its intersection with
head section 13. Groove 17 is rcctangular in transverLie
cross-section, as shown in Fic~. 1, Witil a depth about the
same as its width. Groove 17 is formed normal to -the axis
of shaft 15.
Referrinc~ to Fig~ 2, groove 17 has a cylinclrical base
or inner diameter 19, and inner and outer sidewalls 21 and
22 tha-t are parallel with each other and normal to base 19.
A supporting ring 23 is placed inside groove 17 during as-
sembly. Supporting ring 23 is preferably metal, ancl is cut
into at a single point 25, as shown in Fig. 3, for installa-
tion. Although supporting ring 23 is stif, the separation
at point 25 enables ring 23 to be expanded for inser-tion
over shaft 15. Once over groove 17, the resiliency oE rinc,~
23 will cause the ends of support ring 23 at point 25 to
close toyether as shown in Fig. 3. ~fter installation, the
ends of ring 23 could be tack welded back together, if de-
sired. Once installedl ring 23 will be incontac-tlble, de-
fin:ing a rninimum diameter oE rincJ 23. ~ing 23 is cylinelrical
~nd has a width that is slightly less than the wiclth of <~roove
17 to allow it to rnove radially in groove 17. The inner dia-
meter of ring 23, when at its minimum ~iameter position shown
in Fig. 3, is c~rcater -than the diametcr of base 1~ by about
1/16 inch. This results in an empty annular space or clear-
ancc between ring 23 and base 19 Eor allowinc~ ring 23 to
float or move radially ~/ith respect to shaft ].5. The outer
diarlleter of ring 23 is less than the outer cliameter o groove
17 de~ining an annular cavity i.n groove 17 on the outer cir-
cumference oE rincJ 23~
A backup ring 27, preferably of an elastomeric rnater-
ial, is located in groove 17, with its inner circumEerence in
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contact wi.th thc~ outer ci.rculnerence oE rinc~ ~3~ tiaclcup
rincJ 27 is rectanc~ular in cross-section and haS a cross-
sectional width thcl~ is about one third the width of
c3roove 17. l~he cross-sectional heic3ht of backup ring
27 is selected so that its outer circu:mFerence cxtends
above groove l7.
Sidewall 21, supportincJ rinc~ 23 ancl backup rinc3 27
clefine an annular space Eor .receiving an elastomeric
rincJ, preferably a conventional O-rincJ 29. O-rinc~ 29 is
circular i.n transvers~ cross-sec-tion, as shown in Fi(~. 2.
The transverse cross-sectional diameter of O-rinc3 29 is
slightly greater than the cross-sectional width oE ~he
annular space provided be-twcerl backup ring 27 and sicle-
wall 21, to provide sealincJ and prevent axial movement
of O-rinc3 29. The outer diameter of O-riny 29 is select
ed so that it will extencl above the top of ~roove 17 a
selected amount~ The inner diameter of O-ring 29 is the
same as the outer diameter o supportin~ ring 23. In
the preferred embodiment, O-ring 29 is softer than bac~-
up ring 27, ~referah1y ahout 90 durometer Eor backup rin~J27 and 70--~0 durometer for O-ring 29.
ReerrincJ aga.in to Fig. l, a cutter 31 of clenerall.y
conical confic~uration i.s rnoun~ed ro~ata~ly on shaft 15.
Cutter 31. has a ~:lura:li.ty oE cutt.incJ ~lements, 5uch as
sintered tunc3sten c,arbide inserts 33 on its exterior.
Cutter 33 has a central, axial cavi.ty 35 that receives
shaft 15. An annular backface 37 surrounds ~he entrance
to cavity 35. nackface 37 is located in a plane ~hat
is normal to -the ~IY~i'i of bcaring pi.n 15.
In the cmbodiment shown i.n Fig. 1, a nose bu~ton 39
i~ moun~ecl in ~he l~ase oE cavit~ 35 for frictioncll con~
tact ~ith a matincJ inlay 40 mounted to the end o~ the
shaft 15. Nose button 3g and in]ay ~1 a.re o~ harder
metal than shaft 15 and cutter 31. A slot 41 formed in
inlay 40 leads from the center to the side o~ inlay ~0.
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l~ plu~a]i~y oE rvllel bear:ings 43, each c~lindric~l
:in shape, are mo-lnted be-tween a reduced d:iarneter p~L-tion
of shaft 15 and cavity 35. A second and lar~er diame-ter
set of roller bearings 45 are moun~ed between cavi-ty 35
and shaft 15 immediately inward from groove 17. Cutter
31 is re-tained on sha-Et 15 by a snap ring 47 located be-
tween -the roller ~earings 43 and 45. Snap ring 47 fits
within mating grooves of cutter 31 and shaf-t 15, as
taught in U.S. Patent No. 4,236,764, issued -to 1~dward
M. Galle on December 2, 1980, all oE which material is
incorporated by reference. Cutter 31 has a smooth, cv-
lindrical seat 49 formed in cavi-ty 35 between roller
bearings 45 and backface 37.
As shown in Fig. 2, O-ring 29 is sclueezed between
lS seat 4~ and the incontractible supporting ring 23.
O~ring 29 will also be under some axial pressure or
s~ueeze between backup ring 27 and groove 21. sac]cup
ring 27 wiLl be in contact with seat 49, but not under
any significant radlal compression. rrhe particular a- .
mount of radial and axial squeezc is selcctecl so as to
provide adequate radial sealing between O-rincJ 29 and
cutter seat ~9, and axial sealiny between O-ring 29,
groove 17 and backup ring 27. The squeeze, which is the
percent of deformation with respect to transverse cross
sectional dimension in the relaxecl condition, should be
as low as possible to avoid excessive friction and heat.
A pressure differen-tial of about 50-60 psi ~pounds per
square inch) across O-ring 29 between cavity 35 and the
bit exterior, and a temperature of about 200F (~hr.en-
heit) rnaxitnum ~lre cxpected. rrhe squeeze calculations
must consider that under this maximum ternperature O-rinfJ
29 ~till volumetrically e~.pand about six percent Alsv,
preferably the squeez~ is less than with prior art, O-
ring seals used in drill hits, such as tau~ht in U.S.
35 l'atent No. 3,397,928, which is currently about 17 percent.
The desired range of squeeze is calculated in a con-
ventional manner, taking into consideration manufac~urincJ
tolerances. In one embodiment the radial squeeze is in
the range from 9.6 to 10.2 percent, and -the axial squee~e
is ~3 to 6 percent bcfore assembly. After assembly, the
a~ial squeeze will incre.lse since the raclial in~erfeLence
will deform O-ring 2~, prcssing its sides outwarcl.
rrhe embodiment o~ Ficl. 1 has a c~lindrical reservoir
S1 sealed from ~he exterior by a cap r~3 retained in place
by a retaining r:incJ 55. ~ piston 57 is slidahly and re--
ciprocally carried inside reservoir Sl. Piston S7 is
sealed in reservoir 51 by an O-rinc3 59~ Piston 57 has a
cavity ox socket 61 on its upper side that mates witll a
socket 63 formed in cap 53. A coil spring 65 fits with-
in sockets 61 and 63 and urges piston 57 downward. Spring
65 is shown comE~ressed in ~iCJ. 1 and has the capacity to
push piston 57 cdownward into contact with the base of res-
ervoir 51.
A lubricant passage ~7 extends downward throucJh head
section 13 from the ~ase of reservoir 51. Another lubri-
cant passage 69 is iocated paralle1 with the axis o shaft
15 and extends from the bo-t~om oE passaye 67 to the end of
shaft lS ancl thr.ough the inlay ~0. ~n entrance port 71 ex-
tends from the exterior of head section 13 to passa~e 67
for introducing lubricant into the reservoir 51. Entrance
port 71 i5 sealed by a removable plucJ 73.
To assemble bit 11, supportinc3 rincJ 23 will be slipp-
ed over sha~t 15 and inserted into yroove 17. Backup riny
~7 will be placed in groove 17 agains~ outer sidewall 22.
Then, O-rinq 29 will be clrawn over sha~t 15 and inserted
into cJroove 17 between backup ring 27 and inner sidewall
21. Roller hea~inys 43 and ~5 will be placed in cavi~y 35
of cutter 31, and snap ring 47 will be placed in its ~Jroove
~ithin cutter cavit~ 35. Then -the cutter is pushecl over
shaft 15 until snap rin~ 47 snaps into its matiny groove in
shaft lS. C`utter backface 37 wil.l be 'located sli(Jhtly out-
ward from yroove 17. The seat 4g in cutter cavity 35 will
press and deform O-ring 29.
The three head sections 13 with assembled cu~ters 31
are then welded to~ether. Threads (not shown) are then
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mach:i.ned on the top of the bi-t for securing to dri:ll p:ipe.
Piston 57 .is placed in reservoi.r 51. Coil sprincJ 65 is
placed on top of piston 57 ancl cap 53 is securecl in place.
Io fill with lu~-icaIl~ normal:Ly a vacu~lm will be drawn on
the system through por-t 71. After th~ passages and spaces
have been evacuatecl lubricant is in-troduced through port
71 filling reservoir 51 passacJes 67 69 and the spaces
in cutter c:av.ity 35 }.ctwe~n roller bearinc3s ~3 roller
bearings 45 and shaEt 15. Sorne lubrican~ will be removed
h~fore runni.ncJ-to allow for volumetric expansion of th~
lubricant with temperature increase.
In operation ~he bi-t shown in the fiyures will be
secured tv a section of drill pipe and used to drill ~last
holes for mining purposes. ~ir will be puMped down the
drill string and throucJh the bit ou-t nozzles (not shown)
for coolin~ an~l removing cu~tings. The static pressure
surrouncling bi-t 11 at the bottom of the hole will be a-t-
mospIIeric. The bi.~ wil.l. be ro-ta-~ed with each cutter 31
rotating on each shaEt 15. Similar bits having similar
seal arranc~ements rnay b~ used in oil gas water ancl other
mi.neral exploration drilling and the drillinc3 fluid may
be a liquid instead of air.
The outer circurnference of O-ring 29 will be in slid-
ing contact with cutter seat 49. ~he pressure on the sides
25 of 0-rinc3 29 between sidewall 21 and backup riny 27 will
normally prevent supporting riny 23 O-ring 29 and backup
ring 27 from rotating with respect to shaft 15 although
some rotation may occur. If 50, the inner side of O-rincJ
29 would be in sliding contact with groove inner wall 21
30 and backup rinc3 27 in sliding contact with outer wall 22.
Backup ring 27 w.i:Ll prcvent cuttin~Js frorn enterillcJ and con-
tacting G-rinc3 29. ~s cutter 31 rota-tes supportinc3 ring
23 is ~rec to Inove radia].ly ~ .h respcct to the a:~is of
shaft 15 t~ accommodate radial and angular movement of cut-
ter 31 with respect to shaft 15. Ihis movement of support-
.iny ring 23 allows O-riny 29 co stay in substantially the
same amount of compression against seat 49 thus provid-
iny an effective seal ac]ai.nst the entrance of external
1 ~ 5'7'~S3
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materials ancl sea:linc3 the lu~ric.lnt.
Backup ring 21 cooperates with groove 17 ~o serve as
means for pressincJ agains-t the sides of O--ring 29 ~or seal~
i.ng and to prevent movemen-t o O-ri.ng 29 along the a~:is o-f
shaft 15. The backup riny 27 also helps prevent cuttings
damaye -to O-ring ?.9. ~iston 57 will maintain cl posi-tive
pressure on ~he lu~ri.cant in the ~eclr.Lng arear;. .~s lubri-
cant is depletecl because oE :rictional. heat, pi.ston 57 wil].
move downwarcl in reservoi:r 51 to mai.nE:ain a supply of lubri--
cant to the b~aring areas.
The i.nvention has significant advantacJes. The sealmeans floats with respect to the shaft to accommodate
0bbl.ing of the cu-tte.r on the shaft and maintain an ef-
ective seal. The seal is simple in construction.and
easy to install.
While the invention has been shown in only one oE
its forrns, it should be apparent to those ski].led in the
art that it is not so limited but is susceptible -to var-
ious changes and modi.fications without departinq from the
spirit of the invention.
