CA1047025A - Temperature-regulated, sealed bearing system afor rock drill bits - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention relates to an improved rock drill bit assembly primarily adapted for earth boring operations. In the conven-tional earth boring operation, a rock drill bit assembly is fastened axially to the boring and of a drill string. When a component element fails within the rock drill bit assembly during earth boring operations, it necessitates the costly operation of physically removing the entire drill string from the wellbore. Bearing failure is the major cause of rock drill bit assembly failure. The present invention provided a rock drill bit assembly having therewithin a temperature-controlled, sealed environ being adapted for the bearing means and the lubricant disposed between the relatively rotatable parts thereof.

Description

0~ 25i l'he pr~ erlt inv~rltion relates to a rock drlll blt assembly prlmarlly aclapted ~or earth boring operatlons, and more particularly, to an -lmproved rock drill bit a~sembly having thereln a temperature-controlled, sealed environ adapted ~or the bearing means and lubrlcant disposed between the relatively rotatable parts thereof.
In the conventlonal earth borlng operation, a rock drlll bit assembly is fastened axially to the boring end of a drll:L string. ~t ground surface-level, wlth the drlll string in the vex-tical position, torque is applied to the upper end of the drill string and transmitted vertically downward into the wellbore by the drill string and its rock drill bit assembly which cuts through the underlying geolog-ical formations wlth ea~h successive rotation of the drill string assembly.
; Generally, a rock drill bit assembly lncludes three basic components: a rock drill main body, at least one cone which is rotatably supported from a journal ~aclal surface of said rock drill main body, and bearing means wikh their 20 attendant lubricant posit~oned in the clearance space de- ~ ;
fined between the relatively rotatably opposed races of the rock drill main body and the cone.
When a component element fails withln the rock drill bit assembly during earth borlng operations, it neces-sitates the costly operation of physically removing ~he entire drill string from the wellbore in order to have access to the assembly so as to replace or repair the rock drill bit assembly at ground surface-level. Accordingly~ a conventional method used by the earth boring industry to 3 eoonomically evaluate rock drill bit assembly performance is to measure the linear footage bored prior to rock drill bit assembly failure.

Failure analysis of rock drill bit assemblle~ by cechnical expert~ ln the ea.rth b~r1rlg indu~try lndicates that bearing ~allure i3 the maJor aau~e of rock drlll bit asse~bly fallur~. Thelr studie~ further indicate that temperature extremes during the earth boring operatlon de stroy the lubricating properties of the lubrlcant or de~
~troy the bearing mean~ in a design where no lubrlcant is usedl and khat external contamlnants preaent ln the well-bore migrate -lnto the clearance space between the relatively rotatably oppos-lng ~aces of the rock drlll main body and the cone, and that these contamlnants being abraslve and corrosive in nature destroy the lubricant and bearing sur-facesg and thus cause the bearing component~ contained therein to eventually blnd, whereupon rock drill bit assem-bly ~allure occur~.
'~he~e ~ailure analysls results bear out baslc engin-eering theory that proper lubrication and correct temperature operating range are key ~actors ln ef~ectlng long bear-lng li~0 .
It was evident to the industry that a sy3tem using ~ealed lubricated bearing means would substantlally prevent lubricant and bearing eontaminationJ and that temperature-regulating means to protect the bearings and lubricant ~rom temperature degradation within the rock drill bit assembly would greatly increa~e rock drill bit assembly li~e, and thus increaæe the linear footage which can be drilled per rock drill bit assembly prior to ~ailure.
Thus, one conventional rock drill bit as~embly cur-rently in wide use and referred to as "u~eealed bearing con-struction", is designed w~h a pa3~ageway in the rock drill main body whlch communicatively connects downhole drilling fluid in the drill string hollow core wlth the bearing means positioned in the clearance ~pace de~ined between the rock drill main body ~ournal facial surface and the opposing :L~9L7~Z5 facla~ ~ur~ace of the cone. A portlon or the downhole drlll-lng fluld is forced through th-ls connectlng passageway into the clearance spac~ definlng the bearing means environ, wherein said fluid serve~ to lubr-lcats and cool the bear-ing elements, whereafter the spent ~`luid exits into the wellbore 'rhis method Or bearlng cooling and lubrication causes corros:lve and erosive action upon the bearln~ means and their respectlve ~ur~aces, and tends ko introduce debrls contaminant~ into the bearing envlron wherein these con-taminants eventually destroy the bearing means.
A second conventlonal rock drill bit assembly cur~rentl~ in wide use and referred to as "sealed bearing con-struction" is designed to provlde lubrication to the rock drill bik assembly bearing means by l~corporating an inter-nal reservoir cavlty within the core of the rock drill main body wlth an ingress connecting passageway thereto to accept and equalize pressure from the wellbore environ and transmit this equalization pressure to the reservoir cavity, and an egress connecting passageway from said reservoir cavity to the bearing means environ wherein lubricant ~rom the reservoir is transmitted to the bearing means. Lubricant stored in the reservoir ls pro~ressively -~
squeezed there~rom 50 as to provide lubrication to the bearing means and their contact sur~aces. In this system no direct provi~ion is made ~or dissipating ~rictional heat generated during earth borlng operations, said heat being conducted through the basically ~errous structure of the rock drill bit assembly to the bearing means and lubricant thereln, where exces~ive heat buildup eventually de~troys the lubricant and the bearing means.
Some earth boring operations are conducted in the hrctic relatively close to the surface level. Conditions exist ln these Arctlc climes where the bearing means and - . .

74~Jf~5 lubricant are thus sll~Jected to severe cold which lmpalrs thelr operation, and ~hortens their llfe expectancy unle~s temperature~regulation means are provlded thereto.
Accord~ng to the present lrlventl~n the temperature-regulated, sealed bearlng system ~or the rock drill blt assembly operates under temperature-elevated conditlons by the remotely located, control system communicatively 5ig-naling the heat exchanger to operate endothermically within the confines of the rock drill main bodys, as to induce heat transfer from the rock drill main body wall ma~s thereb~ cooling a journal facial surface thereon which is supporting the relatively rotatable cone, whereupon the relatlvely cooler supporting Journal racial ~urface induces heat transfer ~rom the bearing means and the lubricant in contact therewith, and from the sealing means peripherally disposed therear~und, thus cooling æame.
In the alternatlve J under frigid temperat~re con ditions, the heat exchanger is controlled to operate exothermically so as to induce heat transfer from itsel~
20 through the rock drill main body thereby heating a ~ournal ~ -facial surface thereon, whereupon the relatively warmer supporting ~ournal heats the bearing means, lubricant and seallng means in contact therewith.
The envlron, deflned by the fully enclosed clear-ance space bounded by the relatively rotatable oppo~in~
~aces of the ro¢k drill main body and the cone and said s ealing means, is thus temperature regulated internally 50 as to protect the bearing means, lubrlcant and sealing mean~ ~rom destructive temperature extreme~, and is thu~
sealed externallg ~o ~s to protect the bearing means and the lubricant from wellbore contamlnants.
The primary advantage o~ the present lnvention is that it increases the ll~e o~ the rock drill blt assembly ", . . .
, . . ~ .
~' ' ' ' , .

~ 3470Z5 by Lmproving the lubrication of bearing means positioned in a sealed clearance space defined between the relatively rotatable oppo3ing facial surfaces of the rock drill main body and the cone supported therefrom by maintaining the temperature of the bearing means and lubricant in said sealed clearance space within a defined temperat~re range by inducing heat transfer thereto or therefrom depending on boring conditions so as to prevent degradation of the lubricant, bearings and sealing means.
Another advantage of the present invention is that it provides a system for controlling said bearing and lubrication environ temperature by indirect means so that -the bearing means and the lubricant will not be contaminated by foreign deleterious substances. ;
A further advantage of the present invention is that it provides a system for temperature-regulation which does not require egress means through the bearing means area, thereby permitting the u~e of a peripheral boundary seal around said temperature-controlled environ which will prevent ingress of downhole boring contaminants, and which will prevent egress of lubricant.
Accordin~ to one broad aspect the invention relates to a rock drill bit assembly adapted for boring a cylindrical borehole in the earth, and comprising: a rock drill main body having at least one journal thereon; a cone disposed about said journal and adapted to rotate relative thereto, said journal and cone having opposing facial surfaces, portions of which mutually define a clearance space therebetween; sealed lubricated bearing means positioned within said clearance space for rotatably supporting said cone relative to said journal;
heat exchange mean~ for inducing ~he tran~fer of heat between ~, ~".' ' ~ ''. '' ' ', ~

:~~7~
, said journal and a moving fluid, said heat exchange means including a passageway extending within said journal and said rock drill main body for conducting said moving fluid from a .~
source outside said rock drill bit assembly through said ~ -journal, the portion of said passageway within said journal extending in close proximity to but physical-ly separated from ~ .
said opposing facial surfaces, the egress of said passageway ~.
opening into said bore-hole at a location remote from said journal.
Although the invention is described with particularity ~1 in the appended claims, a more complete understanding of the invention may be obtained from the following detailed description of various preferred embodiments.
Figure 1 is a pictorial schematic of the rock drill bit assembly connected to its supporting drill string, and ; said rock drill bit assembly being communicatively coupled to the remotely located control means; ~ ~
Figure 2 is a fragmentary cross-sectional view of , ~ :
.1 a rock drill bit assembly showing a remotely controllable I
heat exchange means thereln:

. 11 ,~ ' ~ .

~5A- , ' ~ ~' . ' , :

10~7~25 Figure 3 is a frag~erltary cross-sectional vlew of a rock drill bît as~.embly showing wlthin the rock drill ma:ln body a passageway clI-cult with ingress from the drill string for accepting downhole fluid and said passageway circuit coursing sa-.Ld downhole rluid through the rock drill main body so as to heat or cool a supportlng Journal facial surface thereof, and sald passageway circult egressing into the wellbore;
Figure 4 is simllar to Figure 3 except the egress 10 passageway is further adapted for both conventlonal con- ..
vection heat transrer coollng and for thermodynamic expan~ :
sion coollng of said supporting ~ournal facial ~urface;
Figure 5 ls a fragmentary cross-se¢tional v~ w of : a rock drill bit assembly ~howing wlthin the interior cavity of the rock drlll main body a diverter and deflecter means adapted ~or separating water ~rom the downhole fluid so that the fluid used for cooling the supportlng journal faclal surface has a relatively high water content;
Figure 6 i5 similar to Figure ~ except the egress passageway is further adapted for both conventional heat transfer cooling and for thermodynamic expanslon cooling of said supporting journal facial surface;
Figure 7 is a fragmentary cross-sectional view of a rock drlll bit asse~bly showing two independent pas~age- ~ :
w ay systems, one paasageway circuit adapted to conduct downhole drilling fluid, a~ the second passa~eway.¢ircult adapted to conduct a defined heat tran~fer fluid;
J~ Figure 8 is si~ilar to Figure 7 except the egress passageway for sald defined heat transfer fluid does not exit lnto the wellbore but has a return oonductlve passage-way adapted for coursing said defined heat transfer fluid baok to i'G8 ground ~urface-level ~ource.

Referring to F-lgures 1 through 4 -lnclusive, the 471~25 present inventi~rl relate~ to a rock drill bit assembly 10 generally comprising; a rock drill main body 100 havlng an internally confined heat exchanger means 20 thereln which is controlled ~rom a remotely located, control system 30, at least one cone 200 relatively rotatably ~upported f`rom a defined journal 151 facial surface 102 of sald rock drill main body 100, a peripheral seal 300 adapted for f'orming an enclosing boundary for the clearance space 700 defined between the relatively rotatable faces 102, 202 of said rock drill main body 100 and said cone 200, and bearing means 400 and lubrlcant 500 therebetween adapted ~or re-ducing rotatlonal friction.
The rock drill main bod~ 100 is substantially cylindrical ln form having an upper outer surfaoe configura-tlon adapted for cou~ling with the drlll string 50 and havlng a lower outer ~ournal facial sur~ace 102 adapted for relatlvely rotatably supporting a cone 200 thereon~ and said rock drill main body 100 having an inner cavlty 150 .
therewlthin adapted for conducting downhole fluld 600 for ~::
indirectly cooling or heating the bearing means 400, lubri-cant 500 and sealing means 300 and ~or conducting downhole fluid 600 for cleaning the cutting teeth 250 mounted in the cone 200 boring ~ace and ~or cleaning the wellbore bottom surface being bored.
The outer configuration of the rock drill main body 100 is constructed with an upper end adapted for oper-atively coupling with the drill string 50 by a threaded connection 120 or other equivalent means. An exterior wall sur~ac0 122 descend5 downwa~d from said threaded connection 120 so as to form the exterior sidewall 122 o~ the rock drill main body 100. The lower exterlor end of the rock drill main body has at least one ~upporting ~ournal 151 facial surface 102 which i~ adapted to relatively rotatably ' -7-` 310~7~S
~upport t;he cone 203 oppo~ing ~aclal ~urf'a~e 202 'chor~to.
'rh~ lnrler conrie;uratlon Or th~ rock dr~ll maln boq~
100 ¢an ba ~on~tru¢ted with ltwo indep~ndant pas~ageway clrcult~ 612, 62~ thereln branchir~ ~roDI the rock drlll maln body aavlty 150~ On~ pa8s~geway cir~ult 622 ha3 O~I'e8EI
~rom the drlll ætring 50 imm~d~ately above and 18 adapted to conduot downh~le drllling rluld 600 therethrou~h to ~- -Jet nozzle 640 p~sitionally lvcat~d inth~ bas~ area- of' said rock drill maln body lûO a~ to direc~ the nozzl~ ~low ont~
10 and~or pas'c the ¢uttlng te~th 250 mount~d in th~ ¢on~ 200 borlng racial surrac~.
Th~ 3econd pas~ageway clrault 612, 613, 614 feeds ~rom th~ ro~k drlll main body ~a~rlty 150 and OOUr~3eB th~
rluld 610 ther~ln throueh th~ aor~ o~ th~ rock drîll ~in bo~g 100 by a oontinuou~ ~sa~way comprl~ing thr~ ba~lc sectlons 612, 613, 614 w~lch induces heat trar~rer ~hrou~h th~ ro¢k dr~ll ~ body s~all 152 to a Journal 151 racial sur~a~ 102~ A~t~r th~ Plul~ 610 ha~ ~our~d throuEh th~
passag~a~ ~y~te~ 612, 613, 614, lt ~xits thr~ugh an ex~t 20 port 617 ~n th~ ~id~wall 122 o~ th~ ro~k drlll ma~r~ body 100 .
Dependi~g upon 'che ~ologloal PQrmat~n~ b~
an¢ount~rsd durlng ~p~cl~lc oar'ch borSn~ op~ratlonB~ di~er~ ::
tor 16t) and/or d~le¢tor 170 ~ans (Fl~uro~ 5 and 6~
~n~tall~d ~n the cavity 150 o~ th~ rock ~rlll maln body 00 B0 ao to a~para'c~ the d~ d eonstltuent o~ th~ down-hole drilling fluid 600, such as a mist of water and/or air, and dir~ct the d~sir~ s~parate~ ~at~r acou~ulat~Lon or ~lr through th~ ~e~ond pa~sageway ~ir~uit 612~ 613, 614 pr~-ousl~ d~crlb~d.
Tlw ~on~ ub~taEIt~ y ~olld 8truot~0 ha~lng a ~uppor~ad ~ao~ 202 in ~ub~tant~lly oppo~lng par~
allol r~lationshlp elith th~ o~po~ Jou~nal 151 ra~l ~ 4';'~ZS
surface 102 of the rock drill main body 100. An O~ring gland groove ~o8 is mach:Lned in~o the cone ~upported faclal surface 202 and is adapted to reta~n a sealing mean3 300 ~o that the clearance space 700 defined between the oppo-~ing face~ 102, 202 o* the rock drill main body 100 and the cone 200 is ~ully enclosed by an annular sealing ring 300 therearound. The remalning exterior faclal surface o~
the cone 200 is adapted to receivlngly accept cuttlng teeth lnserts 250 whlch contact the wellbore bottom surface and are adapted to cut through the underlying geological struc-ture.
The clearance space 700 between the relatively opposlng facial ~urfaces 102, 202 of the rock drill main body 100 and the cone 200, and which is peripherally en-closed by the sealing means 300 deflnes a temperature con-trolled envlron wherein the bearing means 400 and the lubrl-cant 500 are maintain~d at a tempera~ure level withln a desired temperature range by heat transfer lnduced by the heat exchange means.
Eearing means 400 may comprlse ball bearing~J
roller bearin.gs, bearing metals, or okher suitable bearing de~igns adapted to reduce ~rictlonal ~orces between rela-ti~ely rotatable surfaces 102, 202 of the rock drill main body 100 and the cone 200. l~e supporting ~ournal 151 faclal surfaoe 102 of the rock drill main body 100 and the parallel oppo~ing supported facial surface 202 of the cone 200 have mutuall~g opposing de~ned depressions 104, 204 wherein said roak drlll main body 100 faclal surface 102 retainingly confines one portion of the exterior surface of said bearing means 400 and wherein said cone 200 oppo-sing *acial surface 202 mutually retainingly confinoa a portion of the remaining exterlor sur*ace o~ said bearing mean~ 400.

7~
Lubrlca~ion mean~ have a x-e~2rvoir 504 po~ltloned ln the rock drill maln body 100 wherein lubrlcant 500 is retained. An ingress pressure equalizatlon passageway 502 from the wellbore, pressuri~e balances khe lubricant 500 in the reservolr 504. Lubrlcant 500 upon demand ~lows through the egress pa~sageway 506 from the lubrlcant reservoir 504 to the bearing ~eans 500 and their re~pective contact sur-.~aces, whereupon the rock drill m~in body 100 journal faclal ~ `ace 102 and the opposing cone 200 facial ~ur~ace 202 operating in conjunction with sealing mean~ 300 main-tain and con~ine the lubr-lcant 50Q within a defined enviro wherein the temperature is cont~olled within a deflned temperature range.
A remotely located control means 30 is po~itioned near the upper end of the drill skring 50 at ground ~urface-level. Depe~ding upon the earth boring conditions, coollng or heating fluid 600 is pumped downward through the hollow core of the drill string 50 to the interior cavity 150 of .
the rock drill main body 100, which is a component part of . ~:
the rock drill b~t assembly 10 which define~ the boring end of the drill string a~sembly. .:
The fluid 600 upon entering the rock drill main :~
body 100, i5 divided lnto tWQ stream~ 610, 620. One stream 620 enters a pa~ageway 622 defi~lng a courseway ror forcing the fluid 620 through noz~le 640 which directs the exiting nozzle flow against the cutting teeth 250 of the cone 200 and also direct~ the nozzle ~low against the boktom sur-face o~ the wellbore, thereby cleanin~ said teeth 250 and the wellbore bottom surface, and thus improvlng the boring action of the drill ~tr~ng a~sembly.
A second stream of fluid 610 is diverted from the .- rock drill main body 100 cavity 150 and i~ directed into a second passageway circult 612, 613, 614 wherein the ~luid ,, '' ~ .

contacts the wall mas~ 152 of the rock drill maln hody 100 Journal 151 ~upporting fac-lal surface 1O2J wherearter the spent fluld 616 ~lows out an exlt port 617 in the sidewall 122 o~ the rock drill main body 100.
If the earth boring operations are commenced in f`rlgid areas, the downhole drilllng fluid 600 is heated to be exothermic so that a9 a portion of the fluid 610 passes through the internally confined passageway 612, 613, 614 of the rock drill main body 100 in the area ad~acent to the supporting ~ournal facial surface 102, temperature gradients are generaked by the elevated temperature of the downhole fluld 610 whlch induces heat transfer from the circulating fluid 610 through the rock drill maln body 100 Journal wall 152 to the faci.al surface 102 de~inlng a boundary sur~ace of said temperature controlled environ. Gontrolled heat transfer to thi~ facial surface 102~and there~rom trans-mitted to the environ de~ined by the enclosed clearan~e space 700 between the respectively opposlng rotatable ~aclal surfaces 102, ?02 o~ the rock drill main body 100 and the cone 200, and the peripheral seal means 300 there-around J maintain the bearlng means 400 and the lubr~cant 500 therein enclosed withln a temperatu~e range which in-sures substantially long life ~r the lubricant 500 and for the bearlng means 400.
The ~ealing means 300 provides a dual functlon during the operation o~ the rock drill bit assembly 10.
One ~unction of the seal means 300 being to prevent well~
bore fluid from mlxing with the lubrlcant 500 or contam- :
inating the bear~ng contact sur~ace~ by de~ining an external barrier aga~nst these detrimental contaminants, and the second fun¢tlon of the seal means 300 being to retain the lubrlcant wi~hin said de~ined environ by defining an in-ternal ~arrier against lubricant loss, thereby insuring the ..~
' 7~5 lubricatlon of the bearing means l~oo and malntairllng the lubricant 500 within the deflned temperature range pre-viously forementloned.
It should be noted here-ln that the sealing means 300 i5 usually constructed of a material which is dele-teri.ously affe¢ted by temperature and thus said temperature controlled envlron serves also to protect and lncrease the life expectancy of seallng means 300 in rock drill bit assemblie3 employlng this type of ~eal.
In the alternatlve, ~here earth boring operation~
are commenced in geothermal areas or in many locales where excessive frictional heat buildup may occur in the rock drill bit assembly, the downhole fluid 600 is adapted t~ be endothermic and thus behave as a coolant so that heat trans- .
fer is induced from the defined temperature controlled ::
env~ron to the cooling oirculating fluid 610 flowlng within said passageway circuit 612, 613, 614 coursing through the .
rock drill main body 100 supporting ~ournal 151 and exiting 617 into the wellbore, :
Several alternate forms of the present invantion may be utilized to effect a temperature-regulated, sealed bearing system ~or the rock drill bit assembly 10. These alternate forms of the present invantion apply the same baslc methodology and prlnaiples as exemplifled in the detailed description of the preferred embodiment which was used by the lnventor to demon~trake the utility and lm~
proved performance of his present invention.
One alternate form of the preferred embodlment Figure 2 ls to use electrlcal heat exchanger 800 a~ the means for effecting heat transfer from or to the rock drill main body 100 so as to temperature regulate the environ defined as the clearance space 700 between the relatively opposlng faces 102, 202 of the rock drill main body 100 and .' .

7~ZS
the con~ 200. ~h~ electrical heat ex~ e rnean~ 800 ~rve~ th~ dual Gapnaity o~ b~lng able to lnduc~ h~atln~ or cooling Or th~ ~upport~ng Journal 151 ~a~ ao~ 10~ as earth borlng oondltlons ~o dlotate. qhe r~r~otsly locat0d control means 30 ~t ground ~ur~ce-levQl control~ 'che pow~r commungcat~d 'co the heat ~xchange nq~an~ 800 and the~by control~ the temperat~ Or ~ald ~nvlron withln th~ ~or~
m~ntloned da~lred temperatur~ range whlch 1~ conduci~2 to ln~urine long ll~e ~or the ~7earin~ mean~ 400 an~ th~ lubr~--10 ~ an~ 500 c~ntalned ther~ln, In ~ ~cond alt~rn2~te ~or~ o~ th2 pr~err~d ~mbod~-mont Flg. ~, tha pasaa~eway ~y~m 1~ adapted ~or oool~ng pUrpO3~311 by the ro~k drlll ma~n body 10~ havlr~; an en~arged holl~w cavlty 660 def'lning an e~ sag~way ~ as to p~rmlt ~xpan~on o~ th~ o~ol~ng rlu~ 610 upon contaet ~lth the r~latlvely ~armer internal wall 155 o~ 'che support~
J ourzu~l 151. mu~, t~ ~r~y abu~rb~d by the ~lui~ 610 in ~ontnct ~th sa~d wa~r l~upp~rt~n~; Journal ~Lnte~l ~11 ~urras~ 155 18 a~dltionally ~nhanced 'by th0rm~dynami~
xpan~ion coollng o~ said Journal Inl~ all ~ur~¢~ 155.
In a 'chird alternat~ ~orm o~ r~ d ~Dbodl-~ent Figuro 5, whlch ~ prlmarlly us~d w$~h a do~nholo rlu~
iys~om adapt~ ~or coollr4: pUrpO~ 3 d~v~rt~r means 1~ an~
d~Mect~r mean~ 170 ar~ ~nstall~d wlt~ ln th~ ~nt~rnal . cavl~,y 150 o~ tt~ r~c~c dr~ aln body 100 80 as tv s~par-ate liquid from said downhole fluid 600.
This separat~d ~a~2r î~ thon ~olloct~d in the botto~ Or ~aiA ~ntornal ca~ty 150 arllt 'c)un oour~d through ag~a~ 612, 613, 614 ror ~ool~Lr~ purpo~s, ~he2~upon ~t 30 ~xltls 617 lnt~ th~ ~llboro.
Coollng ~npaclty oan b~ ~ub~tant~lly ~r~a~ bg ~, u~lllz~ the lat~n~ hoat r~qu~ l to ~o~rt bllator ~ts llqul~ Bt~ to ~t0a~, ln lth~a3 s.n~9 otl~r a~rna~

s forms of' the pxeferr~d embodlment, and thi~ is a novel means :in itselr ~or providlng tempera'cure cooling regulatlon to bearing means 400 and lubricant 500 ln a rock drlll bit assembly 10.
It should be noted that thls method of cooling is further enhanced, if stlll additional coollng ls needed, by adding a thermodynamlc expanslon chamber 660 as shown in Figure 6.
A thermoskatic devi¢e can also be added at passag~-way 612 entry openlng 621 which is designed to open or closeat a de~ined temperature level so as to assi~t in control-ling the volume of ~luid flow in passageway 612, 613, 614 and thus effect the cooling effect of the ~luid flowlng therethrough.
A ~o~rth alternate ~orm of the pre~erred embodiment use~ a dual ~luid system Figure 7 which has two independent passageway circuits withln the drill string assembly wherein in one passageway circuit the downhole drilling ~luid 600 is coursed ~r~m a ~irst ground surface-level source through the dri}l strlng 50 into the rock drill maln bod~ 100 where -it performs only the ~unction of exiting through a nozzle 640 which is adapted to direct the flow there~rom to ¢lean the cone 200 cutting teeth 250 and to - clean the botto~ surface of the wellbore as it is bored.
In the second passageway circuit, a second ~luid 610 ls coursed ~ro~ ground surface-lev01 through a second lnde-pendent channel in the drill string 50 and then into the rock drlll main body 100 where it courses through passage-way 612, 613, 614 which is adapted to either cool or heat the supporting ~ournal surface 102 of the rock drill mainbody 100, and then e~lt into the wellbore. Sald ~econd circulatlng rluid 610 having characteristics pri~arily adapted ~or cooling or heating purpose~, while the ~irst fluid ~00 havirlg characterlstics primarily adapted ror cleanlng the cone 200 teeth 250 and the wellbore bottom sur-face durlng boring.
In a lif'th alternate o~ the pre~erred embodiment, Figu~ 8, the dual ~luid system in Figure 8 ls mod-l~ied in that within the second passageway system, the second ~luid 610 is coursed ~rom ground sur~ace-level through sald second independent channel ln the drill string 50 and then into -the rock drill main body 100 where it courses through said passageway 612, 613, 614 whlch is adapted to either cool or heat the supporting journal surface 102 o~ the rock drill main body lO0, but unlike the second alternate, the spent fluld is returned to the surface ground-level source through a connectlng return path 614a whlch conducts the ~luid back to the ground level-sur~ace for reuse.
It will of course be understood that various changes ma~ be made in the form, details, arrangement and propor-tions of the various steps o~ the method and the parts o~
the apparatus described in the embodiment herein, without departing from the spirit o~ the invention.

Claims (6)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A rock drill bit assembly adapted for boring a cylindrical borehole in the earth, and comprising: a rock drill main body having at least one journal thereon; a cone disposed about said journal and adapted to rotate relative thereto, said journal and cone having opposing facial surfaces, portions of which mutually define a clearance space therebetween; sealed lubricated bearing means positioned within said clearance space for rotatably supporting said cone relative to said journal;
heat exchange means for inducing the transfer of heat between said journal and a moving fluid, said heat exchange means in-cluding a passageway extending within said journal and said rock drill main body for conducting said moving fluid from a source outside said rock drill bit assembly through said journal, the portion of said passageway within said journal extending in close proximity to but physically separated from said opposing facial surfaces, the egress of said passageway opening into said bore-hole at a location remote from said journal.

2. The rock drill bit assembly as claimed in Claim 1, wherein said moving fluid is a circulating fluid, and further including an expansion chamber means for permitting the thermo-dynamic expansion of said circulating fluid to increase the cool-ing capacity of said heat exchange means,

3. The rock drill bit assembly as claimed in Claim 1, wherein said heat exchange means comprises a fluid circulation system including said passageway, for receiving said circulating fluid in close proximity to but physically separated from said facial surfaces, and further comprising means associated with said fluid circulation system for separating liquid from a mist of gas and liquid and supplying the resultant separated liquid to said internal passageway.

4. The rock drill hit assembly as claimed in Claim 17 wherein; said cone is an externally toothed cone, said heat ex-change means includes a first passageway system for conducting said circulating fluid into heat conducting relationship with the interior of said journal, said first passageway system in-cluding said passageway extending within said journal; and further comprising a second passageway system for conducting a drilling fluid into the vicinity of the exterior of said toothed cone; said first and second passageway systems being independent of one another so as to prevent the mixing of said circulating and drilling fluids within said systems.

5. The rock drill bit assembly as claimed in Claim 1, and further including means for remotely controlling the opera-tion of said heat exchange means.

6. The rock drill bit assembly as claimed in Claim 4, wherein said first passageway system includes a return passage-way which is adapted to conduct said circulating fluid away from said rock drill bit assembly.