Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACRGROUND OF T~E INVENTION
The present invention relates to percussive drilling
equipment in which a hammer piston is repeatedly lmpacted
against a drill bit.
;~ 5 A conventional percussion drill depicted in FIG. 6
comprises a hollow cylindrical casing 100, a rear sub 102
threadedly attached to a rear end of the casing, and a driver
sub 104 threadedly attached to a front end of the casing.
A drill bit 106 is mounted in the driver sub 104 and is
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connected for common rotation therewith by longitudinal
splines. Disposed within the casing is an inner cylindrical
sleeve 108, a front end of which rests upon a rear edge of
the driver sub 104. Seated on a rear end of the inner sleeve
is a support body 110 wh~ch carries a forwardly extending
tube 112. Sand~iched between the support body and the
rear sub 102 is a valve guide member 114 in which a check
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`! valve 116 is spring-biased toward a closed position.
-~ Slidably mounted within the inner sleeve is a hammer
i, piston 118. Pre~surized air is conducted downwardly through
a passage formed within the rear sub 102, the valve guide
member, and the support body, and enters a channel
arrangement 117 ~efined by opposing surfaces of the inner
sleeve, the hammer piston, and the casing. The pressurized
air is conducted through the channel arrangement and is
directed alternately to front and rear ends of the hammer
piston for reciprocating the piston forwardly and rearwardly
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in a manner which i8 well known in the art. During its
forward stroke the piston strikes the drill bit. The reax
sub 102 pushes the support body 110 toward the sleeve 108
via a rubber make-up ring 115.
The make-up ring 115 is formed of a resilient
material to ensure that the rear sub can be completely
screwed onto the casing. ~owever, the ring 115 also makes
it possible for the inner 61eeve 108 to move longitudinally
relative to the casing in response to the percussive
vibrations during a drilllng operation. That movement of
the sleeve can cause galling on the outer circumference of
the inner sleeve and the inner circumference of the casing,
as well as ~eening on both ends of the inner sleeves and the
components against which they abut. Eventually, a costly and
time-consumi~g replacement of the damaged components is
required.
Furthermore, the inner sleeve has holes 120 formed
longitudinally along a rear end thereof for conducting
pressurized air. Those holes are difficult and expensive
to machine, and may crack due to the vibration and peening
of the inner sleeve. The holes terminate in radial ports 122
which are also expensive and difficult to machine and may
crack when stressed.
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Close tolerances are req~ired between the outer
diameter of the ~nner sleeve and the inner diameter of the
casing $n order to achieve a proper fit therebe~ween and to
minimize leakage between various air channels defined by
those parts. Such close tolerances are expensive to achieve
and promote the galling discussed earlier.
SU21t~ARY OF THE INVENTION
The present invention relates to a percussion drill
for drilling in subterranean formations. The drill comprises
a cylindrical arbor which includes inner and outer ~ircum-
ferences. The inner circumference defines a front-to-rear
extending longitudinal axis. The outer circumference has
a forwardly facing first lateral stop shoulder, and a
rearwardly facing ~econd lateral stop shoulder disposed ~-
rearwardly of the first stop shoulder. A casing arrangement
is secured to the arbor and ~8 disposed around the outer
circumference thereof. The casing arrangement includes a
rearwardly facing lateral stop face and a forwardly facing
stop face abutting the first and second stop shoulders,
respect~vely, for constraining the arbor against longitudinal
movement relative to the casing arrangement. A drill bit is
mounted to a front end ~f the ca~ing arrangement. A hammer
piston is di~posed within the inner circumference of the
arbor for longitudinal sliding movement relative thereto.
A rear sub is mounted to a rear end of the casing arrangement
and includes a conduit for conducting a forward flow of
pressurized air. The arbor includes a pa~age arrangement
for conducting a pressurized air alternately to oppos~te ends
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of the hammer piston for prod~cing rearward and forward
longitudinal reciprocation of the hammer piston. The ha~mer
piston applies impacts to a rear end of the drill bit during
forward strokes of the hammer piston while the arbor is
S constrained against longitudinal movement relative to the
casing arrangement by stop faces.
Preferably, the casing arrangement comprises
separate and front and rear casing sections secured to front
and rear ends, respectively, of the arbor. The front casing
section carries the rearwardly facing stop face, and the rear
casing section carries the forwardly facing stop face.
~ referably, the outer circumference of the arbor
includes a radially outwardly projecting flange disposed
intermediate front and rear ends of the arbor. That flange
carries the first and ~econd ~top surfaces.
It is preferred that a front portion of the rear
sub is telescopingly received in a rear end of the inner
circumference and engages that inner circumference in a
manner radially supporting a rear end of the arbor.
The present invention also pertains to a control
arbor, per se, which can be employed in a drill of the above-
described type.
BRIEF S~MMARY OF THE DRAWINGS
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The ob~ects and advantages of the invention will
`~ 25 become apparent from the following detailed description of
a preferred embodiment thereof in ~onnection with the
accompanying drawings, ln which like numerals designate
like elements, and in which:
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FIGURE 1 is a longitudinal sectional view of a
percussion drill according to the present invention, with
a hammer piston thereof disposed at the forward end of its
stroke.
FIGURE 2 i8 a v$ew ~imllar to FIG. 1 with the hammer
piston dlsposed at the end of a rearward stroke;
FIGURE 3 is a cross-sectional view taken along the :~
line 3-3 in FIG. 1;
FIG~RE 4 is a side elevational view of a control ~ -
arbor of the percussion drill;
FIGURE 5 is a side elevational view of a hammer
piston of the percussion drill; and
FIGURE 6 is a longitudinal sectional view taken
through a prior art percuQsion drill.
15 DETAI~ED DESCRIPTION OF A PREFERRED
EMBODIMENT OF T~E INVENTION
A percussion drill 10 according to the present
invention comprises a control arbor 12 which includes
inner and outer circumferential surfaces 14, 16. The outer
surface 16 includes an annular ~lange 18 projecting radially
outwardly at about a longitudinal midpoint o~ the control
arbor, and front and rear externally threaded surface
portions 20, 22 disposed on opposite sides of the flange 18.
Fxont and rear ends of the outer ~urface 16 are defined by
portions 24, 26 of reduced diameter, the portion 26 having
a chamfer 27.
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A circumferential row of radially extending,
circumferentially spaced ports 28 ic formed in the reduced
diameter front portion 2.4, which ports project completely
through the arbor. Another circumferential row of radial
S ports 30 i8 formed in the reduced diameter portion 24
long$tudinally rearwardly of the first row of ports 28.
An additional circumferential row of radial ports 32 is
formed in the reduced-diameter rear portion 26. : :
Threadedly connected to the front threads 20 of the
arbor i8 the internally threaded rear end of a cylindrical
front caclng section 34, and thxeadedly connected to the rear
threads 22 of the arbor is the internally threaded front end
of a cylindrical rear casing section 36. The casing sections
~;~ 34, 36 are threaded onto the arbor fiuch that a rear radial :
lS end face 38 of the front casing section 34 defines a stop
face which abutq a forwardly facing radial stop shoulder 40
of the flange 18, and a front radial end face 42 of the rear
casing section 36 defines a stop face which abuts a rear-
wardly facing radial stop shoulder 44 of the flange 18.
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Thus, the arbor 12 i6 securely constrained against longi-
tudinal movement relative to the casing sections 34, 36.
i~ The inner circumferences of the front and rear
casing sections 34, 36 define, together with the reduced
diameter portions 24, 26 of the outer circumference of the
arbor, front and rear annular chambers 43, 45. Those
. chambers are isola~ed from one another by the threaded
- connections between the arbor and casing ~ections, and
by the flange 18.
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Threadedly coupled to a rear end of the rear casing
section 36 is a rear 6Ub 46, and threadedly coupled to a
front end of the front casing section 34 is a driver sub 48.
Disposed in a rear end of the rear sub 46 is an internally
threaded hole 47 (or optionally an externally threaded post)
for connecting the rear sub to a drill string (not shown).
Disposed within the driver sub 48 is a drill bit 50 which
is connected for common rotation with the driver ~ub by
a conventional splined coupling 52 therebetween. The drill
bit 50 is afforded a slight amount of longitudinal movement
relative to the drive sub 48, but forward movement of the
drill bit terminates when a radial flange 51 of the drill
bit engages a bit retainer ring 53.
The rear sub 46 includes diagonal ports 55 for
conducting a flow of pressurized air from the hole 47 to an
annular chamber 57 disposed between the rear sub 46 and the
~ rear end of the arbor 12. That chamber 57 is contiguous with
J' the earlier described chamber 45. A spring-biased check
j valve 56 i8 disposed between the hole 47 and the ports 55 for
preventing a back flow of liquid to the hole 47. The check
valve 56 i8 mounted in a check valve guide 58 which can be
adjustable in the manner disclosed in ys ~atent Application :
Serial No. 07/317,865 to align bypass holes 60 of different
; diameter with a hole 61 in the rear sub 46.
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A rear ena portion 63 of the inner circumferential
surface 14 of the arbor 12 is of slightly enlarged diameter
and snugly telescopingly receives an outer circumferential
surface 64 of a front portion of the rear sub 46 so as
to be radially supported and stabilized by the rear sub.
A longitudinal gap 67 i8 disposed between the rear end of the
arbor 12 and the rear sub 46 to ensure that the rear sub can
be fully screwed onto the rear casing section 36.
Slidably disposed within the inner circumferential
surface 14 of the arbor is a reciprocable hammer piston 70
which has a central throughbore 72 and a plurality of
longitudinally extending, circumferentially spaced ribs 73
(FIG. 5) along its outer circumference. Formed between the
ribs 73 are longitudinal channels 74 which terminate short
of the piston ends so as to be closed off at their front and
rear ends 74F, 74R.
The drill bit 50 carries a rearwardly projecting
tube 76 which is receivable in the throughbore 72 of
the piston to communicate that throughbore 72 with a
throughbore 78 in the drill bit. A forwardly projecting
tubular portion 80 of the valve guide 58 is sized to be
received in a rear end of the throughbore 72 and contains
a passage 82 therein which interconnects the bypass hole 60
with the throughbore 72. In that way, surplus air can be
conducted from the chamber 57 and through the holes 61
'~ and 60, the passnge 82 and ehe throughboro~ 72 and 78 for
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~ ejection from a front ena of the arill bit for cleaning
- and cooling the cutting elements and conducting away the
cuttings.
~ he afore-described percucsion drill 10 is assembled
S by threadedly securing the front and rear casing ~ections
34, 36 to the arbor until the rear and front ends 38, 42 of
the casing sections abut the ~top shoulders 40, 44 of the
-`- flange 18. This en~ures that the arbor cannot move
longitudinally relative to the casing sectionQ. The rear
sub 46 is threadedly secured to the rear end of the rear
casing section 36, whereupon the front portion of the rear
sub enters the rear portion 63 of the arbor to provide radial
support therefor. The hammer piston 70 i~ slid into the
arbor, followed by the attachment of a unit comprised of
the drill bit 50, the driver ub 48, and the bit retainer
;, ring 53. That unit ls attached by ~crewing the driver
sub 48 to the front casing section 34.
In operation, the drill 10 i8 rotated by a drill
string while the hammer piston 70 is repeatedly reciprocated
to ~trike the drill bit. The hammer pi~ton i8 guided for
movement within the control arbor 12 which is constrained
against longitudinal movement relative to the casing sections
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34, 36. Furthermore, the rear end of the arbor i8 radially
braced by the front portion of the rear sub 46.
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Pressurized air for reciprocating the hammer piston
is conducted downwardly through the drill string and into the
hole 47 of the rear ~ub 46. The air pushes open the check
valve 56 and travels through the diagonal po~t8 55 to the
annular chamber 57 and from there to the annular chamber 45.
When the hammer piston is positioned at the end of its
forward stroke (FIG. 1), the pressurized air travels radially
inwardly through the radial ports 32, through the
longitudinal channels 74, radially outwardly through the
ports 30 and into the front chamber 43. From that chamber 43
the air flows radially inwardly through the ports 28 and acts
against the front surface of the hammer piston to displace
the latter rearwardly. As the front end of the rearwardly
traveling hammer piston travels rearwardly past the radial
ports 30, the pressurized air no longer communicates with the
front chamber 43. Instead, the pressurized air is able to
travel to a location behind the hammer piston 70 once the
rear ends of the longitudinal channels 74 of the hammer
-` piston co~municate with the enlarged diameter portion 63 of
the inner diameter of the arbor (FIG. 2). As this occurs,
the hammer plston is dlsplac~d forwardly by the air pressure.
`' It will be ~ppreciated that the arbor i~ not
susceptible to galling or peening ~ince the arbor cannot
move longitudinally relative to the casing sections 34, 36.
2S Furthermore, there are no longitudinally drilled ho~es in ~he ~ ~-
arbor, so the problem of holes cracking under stress is not
present. Since no longitudinal holes are disjposed in the
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arbor, there is no need to undertake the difficult and
expensive drilling of slots in the inner circumference
to communicate such longitudinal holes with the inner
circumference. The threaded connections between the arbor
and ca6ing sections effectively isolate the front and rear
chambers 43, 45 from one another, go there iB no need for to
establish close tolerances between the outer circumference of
the arbor and the inner circumferences of the casing sections
34, 36 to achieve such isolation.
Although the present invention has been described
in connection with a preferred embodiment thereof, it will
be appreciated by those ~killed in the art that additions,
modifications, substitutions, and deletions not specifically
described may be made without departing from the spirit and
scope of the invention as defined in the appended claims.
WHAT IS CLAIMED IS:
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