CA1071946A - Rock drill - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A percussive rock drill and more particularly a percussive rock drill having improved means for passing a flow of flushing fluid therethrough. The rock drill has a fluid motor including a body and a piston within the body. A fluid conveying tube extends within the body member and the piston, and a containment, including a pair of variable volume chambers connected by a pass-ageway has in the passageway a passage portion extending within the pistons such that the heat transfer medium contained in the passage portion is maintained in heat exchange relation with the tube. The piston includes means effective to induce a flow of heat transfer medium within the passage portion during the movement of the piston by increasing the volume of one of the variable volume chambers while decreasing the volume of the other of the variable volume chambers.

Description

10~:19~6 In the ar-t ol earth boring by percussive tool means such as in rock drilling it has long,been common -practice to direct a flow oE flushing fluid to the work ..
surface during ongoing drilling operations to flush detritus from the bore hole and to cool the drill bit. For example, . ~.
many known rock drills have included axially aligned com-municating bores in the hammer piston, striking element and drill steel whereby a desirably simple and compact :
means has been provided for direc-ting a flow of flushing fluid such as water to the bottom of the bore hole as well as for such additional purposes as the disslpation of heat generated within the drill. Although such flushing fluid arrangements have generally served the~ purposes intended, they have non~theless often been sub~ect to cert~i.n un-des.irable de.E.ic:iencies. For exampLe, the flow of flush-iny fluid throuyh the drill has not in all cases dissipated heat generated within the drill casinu as effectively as would be desirable. Furthermore, such arrangements have commonly included a water tube extending within the axial- .: :
ly aligned bores in the hammer pis-ton and striking element and having sealing means to protec-t internal drill portions from damage due to the entry o:E water the~reinto during operation. ~IeretoEore ther~ has been no ef:Eective back-up sealing means -to pro-tect the drill interior from water ..
damage in the event of primary water tube seal failure.
According to the present invention, there is ;.
provided a fluid motor having a body r,lember and a piston axially movable within the body member, the motor further ~ ~.
having motive fluid conducting means cooperable with a source of motive fluid flow for conducting motive fluid to the piston to drive the piston. An elonga-ted fluid :
conveying means extends wi-thin the body member and the -- 1 -- , .
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~ 46 piston, and a containment means is defined within the motor and is adapted to contain therein a quantity of heat transfer medium. The containment means includes :~
a pair of variable volume chambers and a passageway .
means communicating between the pair of variable volume chambers. The passageway means has a passage portion ex-tending within the piston such that the heat transfer :
medium contained in the passage portion is maintained in heat exchange relation with the fluid conveying means.
The piston includes means effective to induce a flow of such heat transfer medium within the passage portion during the movement of the piston by increasing the volume of on~ of the variable volume chambers while d~cre~asincJ the volume o:E the other of the variable volume chambers.
In a specific arrangement of the inven-tion, the fluid conveying means includes an elongated tube extending within a through bore formed in the piston.
I'he passage por-tion of the passageway may include a peripheral clearance between the bore and the tube. ~he chambers may be located adjacent spaced end por-tions oE the piston. Thus, the volume oE each o:E the chambers may be variable by the movement of the spaced end portions into and out of the respective chamber adjacent thereto `~
during the movement of the piston. .
These features and advantages of the present lnvention will become more readily apparent upon a reading :~
of the following description of the invention as shown in the sole accompanying figure which illustrates in side elevation and in partial longitudinal section a rock drill cons-truc-ted in accordance with the principles of the inven-tion described.

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There is generally indica-ted at 10 in the figure a percussive rock drill powered by fluid motor means which, it is to be understood from the outset, comprises but one of numerous fluid motor configurations adaptable for use in conjunction with the presen-t inven-tion. The drill 10 is illustra-ted in simplified ~orm solely for purposes ol clarity, and of course such simplification is not intended to unduly limit the scope of the invention described. Accordingly, as shown the drill 10 comprises an elongated, generally annular body member or rno-tor casing 14 disposed axially adjacent a generally annular chuck housing 15. The casing 14 and housing 15 are disposed axially intermediate a generally : :
disc-l.ike backhead 16 and a generally d.isc-li]ce ~ront head 18 ancl rig:id:l.y sccured therebetweel- as by a plu.ral:ity o:E lonyitucl:i.nally extending s.ide rods 20. ~s shown, rods 20 retain the casing 14 and housing 15 axially adjacent from each other and axially intermediate the respective ~ront head and backhead 18, 16 by means of threaded end . .:
portins 24 thereof which pass through suitably aligned . . .

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1~7~946 bores 22 in the Eront head and backhead and have cooper-ably threaded nut members 26 engaged thereupon to fixedly retain members 16, 14, 15 and 18 in the configuration described and in forceful compressive engagement with each other.
As noted hereinabove, the motor of drill 10 may take the form of any of various well kno~ designs com-prising generally a hammer piston element reciprocably carried for controlled repetitive impacting upon a strik-ing element. For purposes of illustrative simplicity the drill herein is shown as having a motor of the so-called "valveless distribution" type wherein a generally stepped cylindrical hammer piston 28 is carried :Eor reciprocal movement within an axial through bore portion 30 of a generally elongated annular liner 32 fixedly disposed with-in an axial through bore 34 in the casing 14 and substan-tially axially coextensive therewith. As shown the piston 28 includes axially spaced apart rearward and ~orward stem portions 28a, 28b, respectively, and an enlarged `~
int~rmediate portion 28c having lands as at 33 and adjac-ent grooves 35 disposed for reciprocal movement within an lntermediate,`generally stepped control portion 30a of bore 30. Bore portion 30a communicates via suitable pressure port means 36 and exhaust port means 38 with any suitable pressure fluid system (not shown) such as a hydraulic-fluid flow source whereby the reciprocal move-ment of the piston 28 causes lands 33 and grooves 35 to cyclically open and close the ports 36, 38 thus directing motive fluid flow to sustain piston reciprocation in the generally well known manner of valveless cycle fluid motors.
Inasmuch as such valveless motors are well known to those versed in the art, furtheF detailed description thereof is _~,, . .

~0~946 omitted herefrom. Suffice it to note in this regard that in operation the self-sustained reciprocal movement of piston 28 produces repetitive impacts of the forward stem 28b upon a striking element shown as a striking bar 40 which is rotatably carried in any suitable manner within housing 15 as by splined engagement at 42 within an annular chuck gear 44 which is journaled in bearings (not shown) for rotation within the housing 15. Any suitably adapted rotation means such as a fluid rotation motor 46 and cooperable gear train (not shown) carr:ied by housing 15 may be utilized to drive the gear 44 and striking bar 40 in rotation whereby a rotary impact dril].ing action i9 generated. A forward end portion ~Oa of striking bar 40 extends forwardly of ~ront head 18 through an axial through bore 50 in a front bushing member 52 and has a drill steel 54 axially, rigidly affixed thereto as by a known coupling sleeve 56. Drill steel 54 in turn has a drill bit 48 rigidly affixed adjacent a forwardmost end portion thereof whereby the rotary impact drilling action of drill 10 is transmitted directly to bit 48 or drilling into rock formations in the known manner.
The drill 10 includes means for delivering flushing liquid such as water to the drill bit 48 comprised of an axial through bore 58 extending within piston 28 and co~municating with an axially aligned through bore 60 extending within the striking bar 40.
Bore 60 in turn communicates with an axial through bore 62 extending within the drill steel 54 whereby flushing liquid may be directed to the bit 48 via a continuous axially extending path comprised of the respective bores 58, 60 and 62.

To protec~ internal components of drill 10 from the entry of flushing water thereinto, the waterpass-ing through bore 58 flows within a water tube 64 disposed within the bore 58 and extending forwardly into bore 60.
The tube 64 also extends rearwardly in~o a generally stepped, axial through bore 66 extending within backhead 16.
The tube 64 is provided with sealing means adjacent opposed longitudinal end portions thereof within bores 66 and 60 whereby the motor components contained within casing 14 are completely isolated from flushing water passed through the tube 64. The rearward sealing means is shown as comprising a suitably resilient annular seal 68 surrounding tube 64 within an enlarged portlon 66a of bore 66 and axially intermediate a radially inwardly extending shoulder 70 which defines the forward end of bore portion 66a, and a radially outwardly flared end portion 72 of tube 64. A water tube clamping membe~
74 is threadingly engaged within a rearwardmost threaded end`portion 66b of bore 66 whereby a forward end 74a o~
the member 74 forcefully engages flared end 72 to cap-tive-ly retain seal 68 intermediate shoulder 70 and the end portion 72 to effectively seal the annular space radially interemdiate tube 64 and bore 66.
Adjacent the forward end of tube 64 within bore 60 a suitable seal such as resilient wiping seal 76 is provided in a form of an annulus sealingly seated within an annular groove 78 spaced forwardly from the rearward-most end of bore 60. Seal 76 surrounds the tube 64 and extends in sealing engagement radially intermediate the tubo 64 and groove 78.

_ - , 10~946 I~ will be understood that flushing water may be introduced into the rearwardmost end of ~ube 64 in any conventional manner as through an inlet port 80 communica-ting with any suitable water pressure source (not shown) and further communicating via open passages 82 formed in backhead 16 with an enlarged annular bore portion 66c.
Bore portion 66c, in turn, communicates via suitable formed transverse passages 84 and a.forwardly extending axi.al passage 86 in member 74 with the tube 64 whereby in practice the ~lushing water is directed under pressure through tube 64 and thence to the drill bit 48.
To protect the drill components within casing l4 :
from water damage in the event of water tube seal failure, there is provided by the instant invention a fluid pressure sealing means wherein a pressurized charge of gas, air for example, is employed to back up the water tube seals as follows.
Within bore 30 in which piston 28 reciprocates there are formed chambers 88 and 90 adjacent opposed longitudinal ends thereof to receive respective piston . .
stems 28a, 28b, during the reciprocal travel of the p:iston 28 in operation. The chamber 88, shown as being Eormed :
wlthin a rearward enlarged end portion 30d oE bore 30 and an adjacent enlarged forward end portion 66d of bore : .
66, is sealed against fluid leakage therefrom by means .. ..
of the previously described rearward water tube seal 68 :
and additionally by such suitable sealing means as a ~.~ .... ..
me.tallic face seal formed intermediate adjacent surfaces :
of backhead 16 and liner 32 as at 92 radially outwardly adjacent the chamber 88, and an annular wiping seal 94 .
disposed within an annular groove portion 96 of bore 30 l forwardly of chamber 88 and surrounding piston stem 28a .
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~1946 in sealing engagement therewith. Accordingly, the chamber 88 is sealed against the escape of gas therefrom by any path except through an annular clearance 98 which is provided intermediate the exterior wal]. of tube 64 and the bore 58 and extends longitudinally to communicate intermediate chambers 88 and 90.
Chamber 9V is formed in a manner similar to chamber 88, being formed within a forward end portion 30e of bore 30, and within forwardly adjacent internal peri-pheral portions of the chuck gear 44 as a-t 100 radially intermediate the striking bar 40 and the internal periphery o~ gear 44. As shown, the chamber 90 may additionally comprise spaces axially intermediate bore portion 30e and space 100 as ~or e~ample space 102 extending a~ially inter-mediate the forward ends o~ casing 14 and liner 32, and the adjacent rearward end of gear 44, of further portions o~ the voidsj within the interior periphery o~ gear 44 as at 104 adjacent a forward end portion thereo~. It is to be understood that the components normally disposed within the gear 4b~ such as striking bar 40 and a rear bushing 41 for example, do not provide a sealing fit therewithin and clearances are thus maintained which provide for relative-ly free flow of gas throughout the entire chamber 90 intermediate the a~ial ends of the gear 44.
The chamber 90 is sealed against the escape of gas therefrom by the previously described forward water tube seal 76 and by additional seals shown as including:
an annular piston stem wiping seal 1~6 similar in all respects to the previously described seal 94; an annular wiping seal 108 interposed radially intermediate relatively rotating portions of gear 44 and casing l~
adjacent a rearward end o~ gear 44; an entirely similar .

~q~9~6 wiping seal 110 disposed radially intermediate a forward end portion of gear 44 and housing 15; an annular seal 112 disposed radially intermediate liner 32 and caslng 14 adjacent a forward end portion thereof; and an annular wiping seal 120 disposed radially intermediate striking bar 40 and chuck housing 52 within bore 50.
It will be seen that by means of -the sealing arrangements provided> chambers 88 and 90 are completely sealed against the exit o~ gas therefrom except that gas -~
may flow between chambers 88 and 90 via clearance 98 ex-tending therebetween within piston 28. Thus, a charge of pressurized gas may be maintained therewithin to pro-vide improved sealing according to one Eeature of the ins~an~ invention. In order to introduce such gas into the chambers 88 and 90 there may be provided gas inlet means sho~l as inlet passage 113 formed within backhead 16 and communicating with chamber 88, and having a gas ~ine connection 11~ whereby an external source of pressur-ized gas may be applied to introduce air or other gas into the chambers 88, 90 via passage 113. The connection ~ is shown as being sealingly closed by a cap 116 to preclude escape of contained gas to the atmosphere.
The gas introduced into the chambers 88 and 90 preferably is under positive pressure somewhat higher than the flushing water pressure whereby the large and undesirable extruding forces of the flushing water upon the water tube seals 68, 76 are effectively cancelled by the opposed gas pressure. In addition, the pressure differential by which the pressure of the gas within chambers 88, 90 exceeeds the flushing water pressure provides a small net outward pressure at all times across the respective water tube seals 76, 68 such that a failure .
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10719~6 of one or both o these seals will result in a flow of ,-gas outwardly from chambers 88, 90 thereby precluding ' any entry of flushing water thereinto.
According to an additional feature of the instant invention, as piston 28 reciprocates in operation and the stems 28a,and 28b alternately move into and out of the respective chambers 88 and 90~ some of the gas contained within the respective chambers 88,90 i5 cyclic-ally pumped therebetween through the clearance 98, the - , chamber 88 being partially emptied of gas and the chamber 90 being filled on piston upstroke, and the chamber 90 being partially emptied and chamber 88 being filled on the piston downstroke. This'pumping of gas between ' chambers 88 and 90 improves heat dissipation from the drill 10 and ensures uniform temperature of the piston 28 inasmuch as hea~ transfer from the piston 28 to the flowing gas occurs uniformly along the length thereof as the gas flows through passage 98 intermediate chambers ;' 88, 90. The heat is thence uniformLy conducted from the flowing gas to the flushing water through the wall o tube , 64 along substantially the entire length thereof. Further-.
more, by suitable sizing of chambers 88, 90 and clearance 98 the described cyclic p~lmping of gas may be made to create turbulent gas flow which further enhances heat transfer from the drill 10 to the flowing water. Such turbulent gas flow decreases the thermal insulating '' capability of the flowing gas as by breaking up the ' boundary gas layer adjacent the periphery of bore 60 and tube 64. ' ' ,:
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lOq~g~6 Of course it will be appreciated that ~he communicating passage 98 between chambers 88 and 90 need not take a form of a clearance around water tube 64. For example, the described heat transfer advantages may be .
provided for by a separate passage or plurality of passages extending within piston 28 and communicating .
with tube 64 in lie~ of or in addition to the clearance 98. Additionally, it should be appreciated that the described heat dissipation of gas pumping is operable with any number of gases over a wide range o~ gas pressures :
including air at atmospheric pressure.
According to the foregoing description, there is .:
provided novelmeans or dissipating heat from interior portions af a percussi~e rock drill and means for guarding against the en~ry of ~lushing liquid therein-to in the event of a seal ~ailure along the flushing liquid path there-through. Notwithstanding the reference herein to a specific preferred embodiment of the invention, it is of course to .
be appreciated that the invention being broadly conceived is subject to various modi~ications of the described embodi- .
ment. For example, the form of piston 28 may be varied withi~l a wide design latitude, chambers 88 and 90 ma~
be independentl~ pressurized and need have no commun-lcation therebetween for purposes of the described water tube sealing feature, chambers 88 and 90 may be adapted to communicate continuously with a reservoir of gas pressure, chambers 88, 90 might be supplemented by additional variable volume chambers and additional passageway means communi-cating between such additlonal chambers and chambers 88, 90, the striking element might be an anvil bloc~ in lieu of striking bar 40 and need not necessarily be rotatably carried, and the like. These and other embodiments and ~
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., l~ql9~6 modifications having been envisioned and anticipated by the inventor it is respectfully reques-ted that the inven-tion be interpreted broadly and limited only by ~he scope of the claims appended hereto.

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Claims (12)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A fluid motor comprising: a body member; a piston axially movable within said body member; said motor including motive fluid conducting means cooperable with a source of motive fluid flow for conducting motive fluid to said piston to drive said piston;
elongated fluid conveying means extending within said body member and said piston; containment means defined within said motor and adapted to contain therein a quantity of heat transfer medium; said containment means including a pair of variable volume chambers and passageway means communicating between said pair of variable volume chambers;

said passageway means including a passage portion extending within said piston such that the heat transfer medium contained in said passage portion is maintained in heat exchange relation with said fluid conveying means; and said piston including means effective to induce a flow of such heat transfer medium within said passage portion during the movement of said piston by increasing the volume of one of said variable volume chambers while decreasing the volume of the other of said variable volume chambers.

2. A fluid motor as claimed in claim 1 wherein said fluid conveying means includes an elongated tube extending within a through bore formed in said piston.

3. A fluid motor as claimed in claim 2 wherein said passage portion comprises a peripheral clearance between said bore and said tube.

4. A fluid motor as claimed in claim 1 wherein said chambers are located adjacent spaced end portions of said piston.

5. A fluid motor as claimed in claim 4 wherein the volume of each of said chambers is variable by the movement of said spaced end portions into and out of the respective chamber adjacent thereto during the movement of said piston.

6. A fluid motor as claimed in claim 1 wherein said heat transfer medium is a gas.

7. A fluid motor as claimed in claim 6 wherein said gas is pressurized.

8. A fluid motor as claimed in claim 1 wherein said motor is the motor of a fluid operable rock drill and said piston is a hammer piston reciprocally movable for repetitive impacting on an impact member of said drill.

9. A fluid motor as claimed in claim 1 wherein said contain-ment means is adapted to contain a predetermined fixed quantity of such heat transfer medium.

10. A fluid motor as claimed in claim 1 wherein said containment means is a constant volume containment means.

11. A fluid motor as claim in claim 1 wherein said containment means is isolated from said motive fluid conducting means in a manner to preclude fluid flow therebetween.

12. A fluid motor as claimed in claim 11 wherein said contain-ment means additionally is isolated from the environment exterior to said body member.