U.S. patent application number 14/390478 was filed with the patent office on 2015-06-25 for symmetrical bit for directional drilling tool.
This patent application is currently assigned to MINCON INTERNATIONAL LIMITED. The applicant listed for this patent is MINCON INTERNATIONAL LIMITED. Invention is credited to Joseph Purcell.
Application Number | 20150176334 14/390478 |
Document ID | / |
Family ID | 47901524 |
Filed Date | 2015-06-25 |
United States Patent
Application |
20150176334 |
Kind Code |
A1 |
Purcell; Joseph |
June 25, 2015 |
SYMMETRICAL BIT FOR DIRECTIONAL DRILLING TOOL
Abstract
A percussion drill bit for directional drilling tools. The drill
bit comprises a head portion formed with an axially extending
shank. The drill bit also comprises engagement means on the shank
engageable with complementary engagement means formed on a drive
chuck whereby rotational drive from the chuck may be transmitted to
the shank. The head portion of the drill bit is formed with a
plurality of slant faces arranged symmetrically about the head
portion.
Inventors: |
Purcell; Joseph; (Co. Clare,
IE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MINCON INTERNATIONAL LIMITED |
CO. CLARE |
|
IE |
|
|
Assignee: |
MINCON INTERNATIONAL
LIMITED
CO. CLARE
IE
|
Family ID: |
47901524 |
Appl. No.: |
14/390478 |
Filed: |
April 3, 2013 |
PCT Filed: |
April 3, 2013 |
PCT NO: |
PCT/EP2013/057046 |
371 Date: |
October 3, 2014 |
Current U.S.
Class: |
175/414 |
Current CPC
Class: |
E21B 4/06 20130101; E21B
7/067 20130101; E21B 10/36 20130101 |
International
Class: |
E21B 10/36 20060101
E21B010/36 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 5, 2012 |
IE |
S2012/0176 |
Claims
1. A percussion drill bit for directional drilling tools
comprising: a head portion formed with an axially extending shank
engagement means on the shank engageable with complementary
engagement means formed on a drive chuck whereby rotational drive
from the chuck may be transmitted to the shank; characterised in
that the head portion of the drill bit is formed with a plurality
of slant faces arranged symmetrically about the head portion.
2. The percussion drill bit of claim 1, wherein each of the slant
faces comprises a substantially planar surface angled with respect
to an elongate axis of the bit.
3. The percussion drill bit of claim 1, wherein each of the slant
faces comprises a plurality of contiguous planar surfaces and each
of the planar surfaces is angled with respect to the elongate axis
of the bit.
4. The percussion drill bit of claim 2, wherein each of the planar
surfaces is continuous.
5. The percussion drill bit of claim 2, wherein each of the planar
surfaces is non-continuous.
6. The percussion drill bit of claim 1, wherein the head portion of
the drill bit is formed with an odd number of slant faces.
7. The percussion drill bit of claim 6, wherein the head portion of
the drill bit is provided with three slant faces.
8. The percussion drill bit of claim 1, wherein the slant faces are
provided with a hard-wearing material to improve wear
resistance.
9. The percussion drill bit of claim 8, wherein the hard-wearing
material is provided in the form of flat wear carbides.
10. The percussion drill bit of claim 1, wherein the engagement
means comprises a plurality of axially extending splines on the
shank slideably engageable with complementary splines formed on the
drive chuck.
11. The percussion drill bit of claim 10, wherein the number of
splines is an integer multiple of the number of slant faces
provided on the bit.
12. A directional drilling tool comprising a locator housing
threadably connected to percussion hammer by means of a sub, and a
percussion drill bit disposed at a forward end of the hammer,
wherein the percussion drill bit is percussion drill bit as claimed
in any one of the preceding claims.
13-14. (canceled)
15. The percussion drill bit of claim 2, wherein each of the slant
faces comprises a plurality of contiguous planar surfaces and each
of the planar surfaces is angled with respect to the elongate axis
of the bit.
16. The percussion drill bit of claim 3, wherein each of the planar
surfaces is continuous.
17. The percussion drill bit of claim 3, wherein each of the planar
surfaces is non-continuous.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to horizontal directional
drilling and, in particular, to a drill bit for a directional
drilling tool.
BACKGROUND TO THE INVENTION
[0002] It is known to use directional drilling apparatus to form
substantially horizontal drill holes in the ground for installing
electrical or telephone cables, gas or water pipes, or HI the like.
The directional drilling equipment usually comprises a percussion
drill bit operable through a drill string and includes a steering
device so that the drill bit can be steered in a desired
substantially horizontal direction below and along the route of
roads and streets, and under river beds, roads and the like.
[0003] In a typical directional drilling system, a drill string
incorporating a percussion hammer, to apply axial impact forces to
the drill bit, is utilised to drill an initial pilot hole of a
smaller diameter (for example 133 mm) than the diameter of the
ultimate passage desired. The ultimate drill passage may have a
diameter of anything from 200 mm to 760 mm depending upon the size
of the cables, pipes or conduits to be inserted in the drilled
passageway. With the known horizontal drilling method, when the
percussion drill bit and hammer breaks through the surface after
having drilled the pilot hole, the percussion hammer system is
removed and a reamer bit is fixed to the protruding drill rod.
Using the drill string, the reamer bit is then pulled back against
the face of the drilled pilot hole. The present invention is
concerned with directional drilling tools for drilling the initial
pilot hole.
[0004] Steering of such horizontal directional drill tools is
typically carried out by providing a percussion drill bit having an
asymmetric chisel-shaped or slant-faced bit head. U.S. Pat. No.
4,867,255 discloses a technique for steering a downhole hammer. The
hammer has a forward most cutting bit, which is asymmetrically
configured with respect to the elongation axis of the hammer. In
order to cause the hammer to move along a straight path, the
asymmetrical cutting bit is rotated continuously either clockwise
or counter clockwise at a constant speed. To cause the hammer to
turn, rotation of the cutting bit is modulated in a particular way,
depending upon how the hammer is to turn.
[0005] Other directional drilling apparatuses having slant-faced
bit heads are described in U.S. Pat. No. 6,397,956, U.S. Pat. No.
6,454,025, U.S. Pat. No. 6,533,052 and U.S. Pat. No. 6,705,415.
[0006] One example of a known directional drilling apparatus using
a slant-faced bit head will now be described with reference to
FIGS. 1, 2, 5a, 5b and 6 of the accompanying drawings. As shown in
FIG. 6, the percussion drill bit has a head portion formed with an
axially extending shank. The head portion of the bit is similar to
that of a normal percussion drill bit, but with a portion machined
off one side of the bit to provide a slant face for steering
purposes. In the example shown, the slant face is provided with
flat-wear carbides, although these are not essential. FIGS. 1, 2,
5a and 5b show the slant-faced bit in assembly with the hammer and
a locating device known as a sonde. The sonde is located in a
locator housing in a fixed axial and angular location. The sonde
sends out a signal which provides data at the surface which
indicates depth, angle or pitch and angular position of the drill
tool. The locator housing is threadably connected to a hammer with
the slant-faced bit located at the end of the hammer. The
connection between the locator housing and the hammer can be made
using either a bent or a straight sub. A bent sub allows for more
aggressive steering of the tool. The bend is typically of the order
of 1 to 3 degrees. The bit is assembled so that the slant face is
located at the six o'clock position of the sonde.
[0007] In order to steer the hammer in an upward direction, the
sonde locator is checked so that its angular position reads six
o'clock, indicating that the slant face of the bit is at the six
o'clock position. The assembly is rocked about this point by about
60 degrees (or two "hours") either side of the initial point as the
hammer drills forward, causing the hammer to steer upwards. When
the required direction has been achieved, normal rotation is
applied and the system drills straight.
[0008] There are a number of disadvantages of this type of system.
In particular, all of the steering forces act on a single area of
the bit which can cause extreme bending stresses on the bit shank
and these stresses can lead to failure of the bit.
SUMMARY OF THE INVENTION
[0009] According to an aspect of the present invention, there is
provided a percussion drill bit for directional drilling tools
comprising:
[0010] a head portion formed with an axially extending shank;
[0011] engagement means on the shank engageable with complementary
engagement means formed on a drive chuck whereby rotational drive
from the chuck may be transmitted to the shank;
[0012] characterised in that the head portion of the drill bit is
formed with a plurality of slant faces arranged symmetrically about
the head portion.
[0013] The term "slant faces" is used herein to indicate that the
faces are angled with respect to an elongate axis of the bit.
[0014] The term "arranged symmetrically" is used herein to indicate
that the slant faces are arranged radially around the head portion
of the bit in such a way that the positioning of the slant faces is
symmetrical about at least one axis through the head portion of the
bit. Preferably, the slant faces are spaced at regular intervals
around the circumference of the head portion of the bit.
[0015] In one embodiment, each of the slant faces comprises a
substantially planar surface angled with respect to an elongate
axis of the bit. In another embodiment, each of the slant faces may
comprise a plurality of contiguous planar surfaces, wherein each of
the planar surfaces is angled with respect to the elongate axis of
the bit. Each of the planar surfaces may be continuous or
non-continuous.
[0016] The angle at which the slant faces are arranged with respect
to the elongate axis of the bit may be selected depending on how
aggressively the bit is required to steer. The less acute the angle
of the slant faces, the more aggressively the bit may be
steered.
[0017] An advantage of the present invention is that, because a
plurality of slant faces are provided, the forces on the bit due to
steering can be spread over the circumference of the bit by
indexing the bit in the chuck. In this way, each of the slant faces
may be used in turn to steer the bit, so that no one area of the
bit shank is subjected to extreme bending stresses, thereby
increasing the lifetime of the bit.
[0018] The head portion of the drill bit is preferably formed with
an odd number of slant faces. This allows the slant faces to be
arranged around the circumference of the bit such that carbides may
be provided diametrically opposite to each slant face to allow
cutting of material in the steering direction, while maintaining
symmetry of the bit. For example, if the tool is to be steered
upwards, the bit may be positioned such that one of the slant faces
is at the six o'clock position in the drill assembly, that is, at
the bottom of the assembly. In order to drill upwards, it is
preferable that carbides are provided at the top of the drill bit,
that is, at the 12 o'clock position, to allow the drill to move
upwards.
[0019] Ideally, the head portion of the drill bit is provided with
three slant faces.
[0020] The slant faces may be provided with a hard-wearing material
to improve the wear resistance of the slant faces. In one
embodiment, the hard-wearing material is provided in the form of
flat wear carbides. In another embodiment, a layer of a
hard-wearing material may be applied to the slant faces. In other
embodiments, strips of the material may be applied to the slant
faces.
[0021] In a preferred embodiment, the engagement means comprises a
plurality of axially extending splines on the shank slideably
engageable with complementary splines formed on the drive chuck.
Ideally, the number of splines is an integer multiple of the number
of slant faces provided on the bit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a side elevation of a known horizontal directional
drilling tool;
[0023] FIG. 2 is a side elevation of an alternate embodiment of a
known horizontal directional drilling tool;
[0024] FIG. 3 is a side elevation of a horizontal directional
drilling tool in accordance with an embodiment of the
invention;
[0025] FIG. 4 is a side elevation of a horizontal directional
drilling tool in accordance with an alternate embodiment of the
invention;
[0026] FIG. 5a is an isometric view of the drilling tool of FIG.
1;
[0027] FIG. 5b is an isometric view of the drilling tool of FIG.
2;
[0028] FIG. 5c is an isometric view of the drilling tool of FIG.
3;
[0029] FIG. 5d is an isometric view of the drilling tool of FIG.
4;
[0030] FIG. 6 is an isometric view of the percussion drilling bit
of the drilling tool of FIGS. 1 and 2;
[0031] FIG. 7 is an isometric view of a percussion drilling bit
according to an embodiment of the invention;
[0032] FIG. 8 is an isometric view of a percussion drilling bit
according to an alternate embodiment of the invention;
[0033] FIG. 9 is a plan view of the drilling bit of FIG. 7; and
[0034] FIG. 10 is a plan view of the drilling bit of FIG. 8.
DETAILED DESCRIPTION OF THE DRAWINGS
[0035] Referring first to FIGS. 7 and 9, there is illustrated a
percussion drill bit 1 for a directional drilling tool 10. The
drill bit 1 comprises a head portion 2 formed with an axially
extending shank 3. The head portion has a front cutting face 6,
which is provided with a plurality of carbide buttons or inserts 7.
Gauge row carbides 8 are provided at the periphery of the bit. The
drill bit further comprises twelve axially extending splines 4 on
the stub shank 3 slideably engageable with complementary splines
formed on a drive chuck. In accordance with the invention, the head
portion 2 of the drill bit 1 is formed with three slant faces 5
arranged symmetrically about the head portion 2. The three slant
faces 5 are equally spaced around the circumference of the head
portion 2 of the bit. Each of the slant faces 5 is provided with a
plurality of flat wear carbides 9.
[0036] As can be seen from FIG. 7, the slant faces 5 are inclined
at an angle with respect to the elongate axis X-X of the bit. Each
of the slant faces 5 comprises two contiguous planar surfaces 5a
and 5b, and each of the planar surfaces 5a, 5b is angled with
respect to the elongate axis of the bit. In the illustrated
embodiment, each of the planar surfaces is non-continuous, in the
sense that each of the surfaces is interrupted by a channel 15 in
the bit head 2.
[0037] As can be seen from FIG. 9, the slant faces 5 are arranged
radially around the head portion 2 of the bit 1 at regular
intervals in such a way that the positioning of the slant faces is
symmetrical about axis Y-Y.
[0038] Because the head portion 2 of the drill bit 1 is formed with
an odd number of slant faces, the slant faces can be arranged
around the circumference of the bit such that gauge row carbides 8
are provided diametrically opposite to each slanted face.
[0039] An alternate embodiment of the percussion drill bit of the
invention is shown in FIGS. 8 and 10. In this embodiment, a fewer
number of larger carbides 8 are provided on the gauge. This allows
larger slant faces 5 to be machined off the bit head 2, so that
each of the slant faces has a larger surface area.
[0040] FIGS. 3, 4, 5c and 5d show the percussion drill bit 1
according to the present invention in assembly with a hammer and a
locating device known as a sonde. A directional drilling tool 10
comprises a locator housing 11, a sub 12 and a hammer 13. The drill
bit 1 is disposed at a forward end 14 of the hammer 13. The sonde
is located in the locator housing 11 in a fixed axial and angular
location, as described above in relation to FIGS. 1 and 2. The
sonde sends out a signal which provides data at the surface which
indicates depth, angle or pitch and angular position of the drill
tool. The locator housing 11 is threadably connected to a hammer 13
with the symmetrical slant-faced bit located at the end 14 of the
hammer. The connection between the locator housing and the hammer
can be made using either a bent or a straight sub 12. A bent sub
allows for more aggressive steering of the tool. As shown in FIG.
3, the bend is typically of the order of 1 to 3 degrees. The bit is
assembled so that one of the slant faces 5 is located at the six
o'clock position of the sonde.
[0041] In order to steer the hammer 13 in an upward direction, the
sonde locator is checked so that its angular position reads six
o'clock, indicating that a slant-face is at the six o'clock
position. The assembly is rocked by about 60 degrees (or 2 "hours")
either side of this initial position as the hammer drills forward,
causing the hammer to steer upwards. When the required direction
has been achieved, normal rotation is applied and the system drills
straight. In order to distribute the forces on the bit 1 due to
steering, the bit may be indexed in the chuck. In this way, each of
the slant faces 5 may be used in turn to steer the bit, so that no
one area of the bit shank is subjected to extreme bending stresses,
thereby increasing the lifetime of the bit.
[0042] The words "comprises/comprising" and the words
"having/including" when used herein with reference to the present
invention are used to specify the presence of stated features,
integers, steps or components but does not preclude the presence or
addition of one or more other features, integers, steps, components
or groups thereof.
[0043] It is appreciated that certain features of the invention,
which are, for clarity, described in the context of separate
embodiments, may also be provided in combination in a single
embodiment. Conversely, various features of the invention which
are, for brevity, described in the context of a single embodiment,
may also be provided separately or in any suitable
sub-combination.
* * * * *