Note: Descriptions are shown in the official language in which they were submitted.
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A DOWN-THE-HOLE HAMMER DRILL ASSEMBLY
FIELD OF THE INVENTION
This invention relates to down-the-hole hammer drill assembly well known in
the
rock drilling industry particularly in the drilling into the earth from the
surface.
BACKGROUND TO THE INVENTION
These hammer drills are high energy consuming items of equipment and they are
also subject to heavy wear. There is thus a combining need for equipment
having
reduced wear and reduced down time which need is accentuated by the depths
to which holes are drilled at the present time.
OBJECT OF THE INVENTION
It is the object of the invention to provide improved equipment of the kind
referred
to with particular reference to the protection of the drill head components
against
damage from the operating environment while also ensuring a simplicity of
assembly and dissassembly.
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SUMMARY OF THE INVENTION
According to this invention there is provided a down-the-hole drill assembly
comprising an assembly of a bit and co-operating chuck including a bit
mounting
with an external sleeve surrounding the bit mounting, the sleeve during
operation
of the drill being clamped between the chuck and the bit head.
Further features of this invention provide for the sleeve to provide a shield
against the ingress of debris into the bit and chuck assembly during use and
to
provide a control for the exhaust of operating fluid from the lower chamber.
The invention further provides for the control of the operating fluid exhaust
from
the assembly to flow through the wall of the chuck and provide reverse
circulation
through pick up holes in and through the bit.
Further features of this invention provide for the assembly to include splines
in
the chuck engaging with splines on the bit and both sets of splines engaging
with
splines in the sleeve.
The invention also provides for the splines in the sleeve to be equal in
length to
the sum of the lengths of splines in the chuck and those on the bit and for
the
lengths of the splines in the chuck and on the bit to be equal or unequal
depending on the particular application of the drill assembly.
The invention further provides for the sleeve to provide control of a pin
releasably
engaging the bit to the chuck.
Further features of the invention provide for the assembly to comprise a
stepped
drill bit engageable with its narrow end within a drill chuck and having a
transverse retaining pin engaged through the chuck and a slot in the bit with
a
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sleeve slidably mounted on the chuck to be operatively held on the chuck
against
the step on the bit.
Yet further features of the invention provide for the chuck to be stepped to
enable
the sleeve to slide on a reduced diameter end of the chuck to be clamped
between the chuck or the end of the wear sleeve and the bit head.
According to further features of this invention there is provided a down-the-
hole
drill bit assembly comprising a drill bit having a shank engageable in the end
of a
chuck adapted to be retained in the end of the drill casing, the shank and
chuck
provided with alignable longitudinally extending transverse slots and means to
releasably retain a pin on which the shank can be reciprocated.
Further features of the invention provide for the pin to be flat and have a
shaped
head on each end, for the chuck and drill shank to have a series of mating
splines and for a head on the bit to seat on the end of the drill chuck which
is
securable in the end of a drill string wear sleeve.
The invention also provides for the heads of the pin to be offset on the ends
of
the pin.
These and still further features of the invention will become more apparent
from
the following description of some embodiments of the invention where reference
is made to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of this invention are described with reference to the
accompanying drawings, in which:
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Figure 1 shows a longitudinal cross-section through a hammer
drill
assembly;
Figure 2 shows a hammer assembly with a sleeve used as a
coupling. Both engaged and disengaged conditions of the
assembly are shown;
Figure 4 shows the coupling in use with venting exhaust passages
for
a hammer drill;
Figure 4A a modification to Figure 4 showing a foot valve tube;
Figure 5 shows an alternative construction of a drill assembly;
Figure 6 shows the assembly modified to provide for reverse air
circulation through the bit for sample collection;
Figures 7 & 8 show the invention applied to an alternative bit and
chuck
assembly; and
Figure 9 & 10 show a modification of the embodiments in Figures 7 & 8.
DETAILED DESCRIPTION OF THE INVENTION
The use of making screwthreads on contiguous components in down-the-hole
drill assemblies has been described in my co-pending PCT Application No.
PCT/IB2010/053549 filed on August 05, 2010. That disclosure is included in
this
specification by reference and should be read together with this specification
particularly for an understanding of the use of the expression "stopping
threads".
This means making screwthreads which may be screwed through each other so
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that the components are prevented from relative longitudinal co-axial movement
in one direction while being free for such movement in the opposite direction.
This movement is used, to permit direct striking of the piston on the bit and
providing a simple method of releasing the bit from the chuck.
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A first embodiment of the invention is described with reference to Figure 1
which
illustrates the operation of one form of hammer drill utilizing the present
invention.
This is disclosed in the specification and priority document for patent
application
2010/07703.
One feature required to make a hammer more efficient and increase the
performance is by increasing the frequency of the piston blows whilst
maintaining
the same stroke. A larger surface area at the bottom of the piston for the
compressed air to act on will propel the piston in the upward stroke away from
the bit faster thereby increasing the blows per minute. The outside diameter
of
the hammer is restricted according to the confined diameter of the hole that
is
being drilled and to maintain a reasonable wall thickness on the wear sleeve
it is
not possible to simply increase the piston diameter to achieve this end. The
wall
of the wear sleeve becomes too thin if the hole size is maintained.
When using a stepped piston with continuous pressure on the stepped shoulder
as in my SA Patent 2009/04814 included herein by reference, cutouts (47) on
the
piston shown in Figure 2 and, the cut out (57) shown in the bore of the
cylindrical
extension of the back head in Figure 3, are replaced in the present invention
with
porting through the piston wall and no cut out in the cylindrical bore of the
back
head. The specification of this patent is also included in this specification
by
reference only as background to the present invention.
As shown in Figure 1, (which is extracted from the specification of South
African
patent application 2010/07703 referred to above, a priority document of this
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application), compressed air enters and opens the check valve (1) downwardly.
This air then passes through ports A, into cutout B between the cylindrical
portion
of the back head (2) and the bore (3) of the wear sleeve (4) through ports C
into
space D around the piston stepped head (5) thus applying pressure on the
shoulder surface area (6), passes the major piston diameter (7) at cutout E
into
lower chamber F where it acts on the bottom surface area of the piston (8).
This
causes the piston to lift away from the bit (9) and the piston stem (10)
disengages
from the piston stem bush (11) for lower chamber F to exhaust through the
axial
bore G in the bit (9). The piston (8) continues traveling upward and ports I,
through the wall of the piston (8), communicate with ports H in the
cylindrical
lower part (12) of the back head (2).
Compressed air then flows through ports I into upper chamber J above the
piston
(8). At this stage the major diameter (7) of the piston is a well up the bore
(3) of
the wear sleeve (4) and the lower chamber is sealed off.
The pressure, that is now on the shoulder surface area, combined with the
pressure on the surface area of the piston exposed to the upper chamber J, the
axial exhaust passage K through the piston (8) is sealed off by the control
rod
(14). This will propel the piston (8) towards the bit (9) to strike the bit.
The control
rod (14) has now disengaged from piston passage K and upper chamber J
exhausts through K and then G through the bit (9). E has opened again and
compressed air is reintroduced into chamber F to repeat the cycle.
The back head as described is in one piece with the cylinder (the cylindrical
extension of the back head) but could be in two pieces.
When the hammer is lifted off the bottom of the hole the bit (9) drops forward
for
a limited travel. With the piston following the bit and port H is exposed to
chamber J allowing the compressed air to flow freely down K and G to the
atmosphere. Lower chamber F is shut off by the piston major diameter (7)
sealing
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off against the land L in the bore of the wear sleeve (4) thus rendering the
hammer inoperative and in flushing mode.
Of particular importance to the present invention is the sleeve (15) mounted
on
the shoulder (16) of the bit (9). In the operative position shown the sleeve
(15)
has splines (17) which move through splines (18) on the outside of the chuck
(19)
which forms an extension to the piston sleeve bush (11).
This sleeve (15) is held during operation of the drill between the stepped end
of
the chuck (19) and the shoulder (16) of the bit (9) and where it shields
components within it from debris generated by the drilling operation.
This feature of the invention will become clear from the description of the
further
embodiments described below.
Referring now to Figure 2 the operatively lower end of a down-the-hole drill
assembly (21) is shown in the operative position (22) on the right hand side
of the
drawings and in flushing mode (23) on the left hand side.
The components illustrated are the chuck (24) and bit (25) carrying splines
(26)
and (27). The splines (26) on the chuck (24) are longer than those (27) on the
bit
(25).
Stopping threads (28) and (29) are provided on the outer end of the bit (25)
shank and on the inside of the operatively lower end of the chuck (24). Those
threads (28) and (29) are shown disengaged so that the bit shank may slide in
the chuck (24) but prevent the shank from being withdrawn from the chuck. This
release can be achieved by engaging the threads and unscrewing the bit shank
out of the chuck (24).
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A locking sleeve (30) is located around the external splines (26) and (27).
The
locking sleeve (30) has internal splines (31) which mate with the splines (26)
and
(27) to slide relative thereto and the length of the sleeve (30) is
substantially the
same as the combined length of the splines (26) and (27).
Thus, in the flushing mode of the drill the locking sleeve (30) slides with
the bit
(25) down into the bit position shown in the left hand side of Figure 2. In
this
position the free ends (32) of the splines (26) are still in contact with the
splines
(31) in the sleeve (30) and the bit (25) can be driven to rotate by a
conventional
rotary motion mechanism for the drill.
To enable the bit (25) to be unscrewed from the chuck (24) the sleeve (30) is
moved upwardly on the splines (26) into the position shown on the right hand
side of Figure 2. Because of the difference in the length of the splines (26)
and
(27) the splines (31) in the sleeve (30) will no longer engage the splines
(27) and
the bit (25) can be unscrewed.
With the bit (25) removed the sleeve (30) can also be removed from the chuck
(24).
This engagement enables the sleeve to be assembled onto the chuck (24) and
the bit to be screwed into the chuck (24) releasing the thread engagement and
the drill will be in the flushing mode and ready to be operational.
This condition of the assembly with the bit hanging but not removed from the
chuck is a useful condition. It enables the drill operator to use the bit in a
grinding
manner, for example, in drilling operations through collapsed sections in a
borehole. The assembly thus enables hammer operations to be conducted when
both bit and chuck splines are fully engaged by the sleeve and grinding to be
effected when the bit and sleeve are hanging with the assembly in flushing
mode
described above and the ends of the bit and chuck threads in contact.
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Referring back to Figure 2, when it is necessary to remove the bit the drill
is
raised with the components in the flushing condition. Once on surface the
sleeve
can be manually lifted into the position shown on the right hand side of
Figure 2
and the bit screwed out of the stopping threads as described.
The arrangement of the splines on the bit and chuck and within the sleeve can
conveniently be about twelve splines on each component with a minimum of two
opposite each other for even load distribution.
A further modification to the hammer assembly utilizes the sleeve for
alternative
or additional purposes.
Shown in the right hand side of Figure 3 the hammer assembly piston (40),
locking sleeve (41) and bit (42) are pushed up into the drilling position. In
this
position the locking sleeve (41) is sealing venting holes (43) and the lower
chamber (44) can receive compressed air to drive the piston (40) upwards away
from the bit (42). When the bit (42) drops forward, shown in the left hand
side of
Figure 3, the piston (40) follows and the indicated sealing surfaces (45) and
(46)
on the piston (40) and in bore (47) of the wear sleeve (48) will seal and
prevent
compressed air from entering lower chamber (44). At this time the locking
sleeve
(41) will uncover the venting holes (43) in order for the air cushion which
has built
up beneath the piston (40) to escape via the open venting holes (43). As the
piston (40) drops further the slot (49) in the piston (40) is uncovered and
locates
opposite cutout (50) in the sleeve. This will allow compressed air to flow
down the
splines to clear them of rock cuttings and abrasive dust.
Those skilled in the art can create the sealing of the venting holes between
any
two of the parts moving relevant to each other. For example, between
stationary
wear sleeve and chuck or a moving locking sleeve and bit.
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Figure 4 shows an alternative way of sealing off as well as unsealing the
venting
ports (65) by the threaded bit anvil end (66). When the bit is in drilling
mode the
anvil head is opposite the undercut (67) and seals the opening (68) of the
venting
holes (69). As the bit drops forward, the undercut (67) is exposed and venting
of
5 the lower chamber (63) can take place through the bore (69) of the bit.
There is a
second undercut (70) which is connected to the bottom of the splined chuck end
(71) by ports (72) which would receive air from the uncovered venting ports
(65)
and provide air pressure to the bore of the locking sleeve (73) from where it
can
exhaust through the splines (74) to clear them from debris as well as
lubricate the
10 splines.
Referring to Figure 4A this shows a modification to that shown in the right
hand
side of Figure 4. It illustrates the inclusion of a foot valve tube (64B)
which
engages with the bore (61) of the piston (62) for sealing of the lower chamber
(63) instead of the alternative of the piston stem sealing within the piston
stem
bush. The clearance gap (64A) demonstrates that there is no sealing between a
piston stem bush and the piston stem as shown in Figure 4. The same bit
(fitted
with a foot valve tube) and chuck could be used on the same hammer as for one
without the foot valve.
The locking sleeve (73) acts in similar manner to that described with
reference to
Figure 3 to provide rotation of the bit, sealing and enmeshing of venting
passages of the lower chamber and clearing of the connecting splines.
Figure 5 shows a different bit (80) and chuck (81) arrangement and shows how
the bit splines (82) and chuck splines (83) engage directly into each other.
The
drilling position is on the right hand side with the bit dropped forward on
the left
hand side and with a replaceable cover sleeve (84) around the splines to
protect
them from outside abrasive wear. Once the bit (80) has been screwed through
the stopping thread (85) in the chuck (81), the splines (83) will be in
position to
enter into engagement with each other. When the bit (80) is pushed up into the
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splines (83), the cover sleeve (84) will be clamped between the bit (80) and
chuck (81) and at the same time seal the venting holes (not shown).
When the bit (80) drops forward the venting holes (not shown) will be unsealed
for the same purpose as described above.
Referring now to Figure 6 the sleeve (90) is shown used as a shroud around the
bit shank to direct the exhaust air between the sleeve (90) and bit shank (91)
to
the bottom of the borehole and thus force the rock sample cuttings up the
centre
of the bit.
Exhaust ports (92) are provided between the air passage (93) through the chuck
(94) into the splined area (95) between the chuck (94) and a cutout (96) to
the bit
face (97).
In use when the piston stem (not shown) pulls out of the piston stem bush and
the sample tube is in centre bore A, the exhaust air will flow through the
exhaust
ports (92) past the splined area of the chuck and bit and down exhaust cutout
(96) in the bit to the bit face (97) where it picks up the drilled cuttings
and
conveys them to the bore A in the bit and then through the sample tube and up
the centre pipe of the dual tube drill string to the surface where the
cuttings are
then collected for inspection. The sleeve (90) will direct the exhaust air to
finally
reach the bit face.
The assembly using the sleeve also affords protection of the sliding surfaces
of
the bit and chuck during drilling operations.
Referring to Figures 7 and 8 there is illustrated a conventional drill bit
(101) which
is slidable in a chuck (102) which has a stepped shoulder (103) to locate the
free
end of a sleeve (109) during drilling operations. The chuck has internal
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longitudinally extending splines (104) slideably engaged with complementary
splines (105) on the shank (106) of the drill bit (101).
The free end of the chuck (102) is screw threaded for engagement in the end of
the drill wear sleeve (not shown).
The chuck (102) also locates a diametrically extending pin (107) which engages
in a longitudinally extending slot (108) through the drill shank (106).
The drawings show in Figure 7 the pin (107) in the upper end of the slot where
the drill assembly is in the flushing mode.
A sleeve (109) slides on the outer reduced diameter surface of the chuck
(102).
Figure 7 shows the assembly in flushing mode with the bit dropped forwardly to
extend out of the chuck (102) and the sleeve extending forwardly to rest on
the
shoulder (110) on the drill shank (106).
In this condition the pin (107) can be moved through the slot (108) and out of
the
assembly to release the bit from the chuck.
Figure 8 shows the assembly in the drilling mode in which the pin (107)
engages
the opposite end of the slot (108) to that described above and the sleeve
(109) is
trapped between the shoulders (110) on the bit and (103) on the chuck. The pin
(107) is trapped within the sleeve (109) which also acts to prevent the
ingress of
debris between the splines on the bit shank (106) and in the chuck (102).
The drill assembly is simple and prevents binding of the bit in the chuck
during
use.
Figures 9 and 10 illustrate yet a further embodiment utilizing a sleeve in the
bit
assembly. This assembly (120) has a chuck (121) which can be engaged in the
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end of a drill string wear sleeve (not shown). A longitudinally extending
series of
engaging splines (122) are formed on the bit shank (123) and in the chuck
(121)
to provide the connection to provide a rotary drive for the drill bit (124).
Transverse longitudinally extending slots (125) are provided through the chuck
(121) at (126) and through the shank (123) at (127) to extend diametrically
through the assembly.
A flat pin (128) with a head (129) at each end fits through the slot at (125)
so that
the heads (129) are located in the wall of the chuck (121) and the body of the
pin
(128) is slidable in the bit shank (123) between the ends of the slot (125).
It will be appreciated that the pin (128) can be removed from the assembly
only
when the holes through the shank (123) and chuck (121) are aligned. This
configuration must be obtained with the assembly removed from the drill hole.
The slot (125) and pin (128) are dimensioned to permit movement of the bit
(124)
in the chuck (121) between drilling and flushing positions.
Further the body of the pin (128) may be offset between the heads (129)
towards
the operatively forward end of the bit head. This facilitates obtaining a
sufficient
length of movement between drilling and flushing positions of the bit (124) in
the
chuck (121).
In use the bit (124) is inserted into the chuck (121) and located so that one
head
(129) of the pin (128) can be threaded through the wall of the chuck (121) and
the bit shank (123) into the wall of the chuck (121) diametrically opposite
the
point of insertion. The heads (129) of the pin (128) will be captured in the
wall of
the chuck (121). Operation of the drill in the drill hole will prevent any
longitudinal
movement of the pin (128) and rotation of the chuck (121) will together with
the
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engaging splines on the bit shank (123) and chuck (121) provide the necessary
drive for rotation of the bit head.
Impacts on the bit head do not cause binding of the bit (124) in the chuck
(121)
because of the free movement available for the bit (124) in the chuck (121) on
the pin. All the impact power transfers directly onto the bit (124) to provide
maximum drilling effect.
The assembly is also effective and avoids the well know difficulties in
replacing
the bit in an operating drill assembly (120) while ensuring firm retension
during
drilling operations.
A sleeve (130) is clamped between the shoulder (131) on the bit head (124)
against a cut away section (132) of the head (129) of pin (128) and within a
recess (133) formed in the bottom end of the chuck (121).
When the bit drops into flushing mode the sleeve (130) is released from
engagement with the pin head (129) and can be manipulated through the chuck
(121) to release the bit (124).
The sleeve (130) also acts to prevent the ingress of debris through the chuck
(121) into the bit assembly.
