Information
-
Patent Grant
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6431294
-
Patent Number
6,431,294
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Date Filed
Monday, June 5, 200024 years ago
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Date Issued
Tuesday, August 13, 200222 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 175 413
- 175 417
- 137 62413
- 137 62418
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International Classifications
-
Abstract
A percussion drill 10 has a tubular fluid transmitting body 14, with a drill bit 16 mounted on a drill bit support 20 itself mounted in body 14 via a spring 22 and salines 24. A mass 28 is spring mounted in the body 14 and is movable to impact on a face 26 of the support 20. Mounted to the mass 28 is a rotating valve 32 comprising two valve plates 34, 36. Each plate 34, 36 defines a slot 38, 40, such that rotation of one of the valve plates 36 relative to the other moves the slots 38, 40 into and out of alignment; the change in alignment of the slots 38, 40 alters the flow of drilling fluid through the valve 32, so altering the drilling fluid pressure force acting on the mass 28, so causing mass 28 to push against the spring 30, and impact on the drill bit support 20 providing a percussive act ion at the drill bit 16.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a percussive tool, and in particular but not exclusively to a percussive tool for use in drilling operations utilizing drilling fluid or “mud”.
2. Description of the Prior Art
It has long been appreciated that providing a percussive action to a drill bit can increase the drilling rate, particularly when drilling through hard rock. Air driven percussion drills have been used successfully for a number of years in the mining industry. Also, hydraulic fluid driven percussion tools are well established in the construction industry. However, attempts to provide a percussion drill utilizing drilling fluid or “mud” as the working fluid have met with difficulties; the evasive nature and high solids content of drilling fluid tends to damage the valve mechanisms necessary to provide the percussive effect.
It is among the objectives of embodiments of the present invention to provide a percussion drill which will operate successfully and reliably utilizing drilling fluid or mud as the working fluid.
SUMMARY OF THE INVENTION
According to the present invention there is provided a percussion drill comprising:
a fluid transmitting body;
a drill bit support;
a mass movable relative to the body for impacting on the drill bit support;
means associated with the mass for creating a fluid pressure force on said mass; and
a rotating valve for controlling flow of fluid through the body to produce a varying fluid pressure force on the mass and induce acceleration of the mass.
The use of a rotating valve facilitates use of the drill in applications where the working fluid contains solids, such as drilling fluid.
According to another aspect of the present invention there is provided a percussive drilling method comprising the steps:
providing a drill having a fluid transmitting body, a drill bit support, a mass movable relative to the body for impacting on the drill bit support and a rotating valve for controlling flow of fluid through the body; and
passing drilling fluid through the body to the drill bit support via the rotating valve to vary the flow of the fluid through the body and produce a varying fluid pressure force on the mass to induce acceleration of the mass.
Preferably, the valve rotates around a longitudinal axis, and most conveniently around the central longitudinal axis of the body. In other embodiments the valve may rotate around a transverse or lateral axis.
The valve may be provided separately of the means for creating fluid pressure force on the mass, or may be integral therewith.
Preferably also, the valve comprises two portions, each defining a fluid port, such that relative rotation of the parts varies the alignment of the ports and varies the flow area defined thereby. Most preferably, one portion is rotatable relative to the body. The valve ports may be in the form of slots on a common axis. In an alternative embodiment, one of the valve portions provides fluid communication with alternative fluid paths through the body, one of said fluid paths providing fluid communication with the means for creating fluid pressure force on the mass, and another of said paths by-passing said means.
Preferably also, the valve permits fluid flow through the body in all valve configurations, to assure a continuing supply of drilling fluid to the drill bit.
Preferably also, the mass is spring mounted in the body, to provide a return force; the fluid pressure force will tend to induce acceleration of the mass in one direction, and the return action of the spring will accelerate the mass in the opposite direction, when the spring force is greater than the fluid pressure force. In other embodiments, the return force may simply be gravity, or may be an opposing fluid pressure force.
The mass may define a flow passage therethrough, and the flow passage may define a restriction such that fluid flowing through the mass is subject to a pressure drop, creating a pressure force across the restriction.
The drill bit support will typically be adapted for mounting a drill bit to the body and the mass will impact directly on the support. However, in some embodiments the mass may not impact directly on the support; there may be an intermediate member or other force transmission means therebetween.
Preferably also, the drill bit support is spring mounted in the body, and is preferably splinted to the body.
Preferably also, the body is adapted for mounting to a drill string.
Preferably also, the drill includes means for driving the valve, such as a valve motor, and most preferably a drilling fluid driven positive displacement motor.
According to a further aspect of the present invention there is provided a percussion tool comprising:
a fluid transmitting body;
a bit support;
a mass movable relative to the body for impacting on the bit support;
means associated with the mass for creating a fluid pressure force on said mass; and
a valve for providing a continuing but varying flow of fluid through the body to produce a varying fluid pressure force on the mass and induce acceleration of the mass.
The use of a valve which is not required to stop flow through the body, that is the valve is not required to seal, facilitates use of the drill in applications where the working fluid contains abrasives or solids, such as drilling fluid; as the valve is not required to be fluid tight, clearances, materials and other aspects of the valve specification may be selected with the primary aim of withstanding operation using abrasive working fluid.
According to a still further aspect of the present invention there is provided a method of providing a percussive action in a downhole tool, the method comprising the steps:
providing a tool having a fluid transmitting body, a bit support, a mass movable relative to the body for impacting on the bit support and a valve for controlling flow of fluid through the body; and
passing drilling fluid through the body and the valve to provide a varying but continuing flow of fluid through the body and producing a varying fluid pressure force on the mass to induce acceleration of the mass.
The bit support may be integral with a bit, or may provide mounting or support for a separable bit. The bit may be a drill bit, a chisel or a hammer.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects of the present invention will now be described, by way example, with reference to the accompanying drawings, in which:
FIG. 1
is a sectional view of a percussion drill in accordance with a first embodiment of the present invention;
FIG. 2
is a sectional view of a percussion drill in accordance with a second embodiment of the present invention; and
FIG. 3
is a sectional view of a percussion drill in accordance with a third embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference is first made to
FIG. 1
of the drawings, which illustrates a percussion drill for mounting on the lower end of a drill string (not shown) The drill
10
is illustrated located in a drilled bore
12
, during a drilling operation.
The drill
10
has a tubular body
14
through which drilling fluid is pumped from the surface to exit at the drill bit
16
, the drilling fluid lubricating the drill bit and carrying drill cuttings up the bore annulus
18
to the surface.
The drill bit
16
is mounted on a drill bit support mandrel
20
, which is itself mounted in the lower end of the body
14
via a spring
22
and longitudinal salines
24
. The uppermost face of the mandrel
20
defines an anvil
26
, upon which impacts the lower end of an axially splinted reciprocating mass
28
. A spring
30
acts between the mass
28
and the anvil face
26
, and tends to lift the mass
28
within the body
14
.
Mounted at the upper end of the mass
28
is a rotating valve
32
including a valve plate
34
which is fixed relative to the mass
28
, and a valve plate
36
which is rotatable relative to the mass
28
. Each plate
34
,
36
defines a slot
38
,
40
positioned on the drill longitudinal axis
42
, such that rotation of the valve plate
36
moves the slots
38
,
40
into and out of alignment, to vary the flow area defined thereby. The rotatable valve plate
36
is coupled to a telescopic drive shaft
44
, the axially fixed portion of which is mounted in the body
14
by appropriate bearings
46
. The drive shaft
44
is coupled to the transmission shaft
45
of a positive displacement motor
48
which is driven by the flow of drilling fluid therethrough.
In use, drilling fluid is pumped through the drill string, while weight is applied to the string and at least the lower portion of the string is rotated. The passage of drilling fluid through the motor
48
results in rotation of the transmission shaft
45
and drive shaft
44
, and thus rotation of the upper valve plate
36
. As the valve plate
36
rotates to a position in which the slots
38
,
40
are misaligned and flow of drilling fluid through the valve
32
is restricted, a pressure differential is produced across the valve
32
, creating an unbalanced force across the axially splinted mass
28
, which force causes the mass
28
to move down and compress the spring
30
. When the mass
28
reaches the end of its stroke it impacts on the anvil face
26
, which impact is transferred directly to the drill bit
16
. As the valve plate
36
continues to rotate the slots
38
,
40
come into alignment and the valve
32
opens, reducing the restriction to flow through the valve
32
and reducing the pressure differential across the valve
32
. The mass
28
is then pushed upwards by the spring
30
until the valve
32
closes again and the cycle is repeated.
Thus, the mass
28
reciprocates within the body
14
, impacting upon the drill bit mandrel
20
, and providing a percussive action at the drill bit
16
. In many situations, particularly in hard rock drilling, this percussive action will dramatically increase the drilling rate.
Reference is now made to
FIG. 2
of the drawings, which illustrates a percussion drill
60
in accordance with a second embodiment of the present invention. The drill
60
includes many features which are similar to those of the drill
10
described above, and in the interests of brevity these features will not be described again in detail.
In the drill
60
the reciprocating mass
62
and the rotating valve
64
are mounted separately on the body, unlike the first embodiment in which the valve
32
is mounted on the mass
28
. A stationary valve plate
66
is fixed relative to the drill body
68
, and a rotating valve plate
70
is axially fixed relative to the body
68
, such that there is no need to provide a telescopic drive shaft linking the valve
64
to the positive displacement motor
71
.
The mass
62
defines a central through bore
72
incorporating a nozzle
74
to restrict fluid flow through the bore
72
and create a pressure drop across the mass
62
. In use, when the valve
64
closes, the flow downstream of the valve
64
is reduced and therefore the pressure drop across the reciprocating mass nozzle
74
is also reduced, and the mass
62
is moved upwards by a return spring
76
. When the valve
64
opens again, the flow downstream of the valve
64
increases and the mass
62
is forced down to impact on the bit mandrel
78
.
Reference is now made to
FIG. 3
of the drawings, which illustrates a percussion drill
90
in accordance with a third embodiment of the present invention. In this embodiment the spring loaded reciprocating mass
92
incorporates a nozzle
94
and is mounted below a rotating valve
96
which is axially fixed relative to the tubular drill body
98
. The valve
96
includes a stationary diverter valve plate
97
and a rotating diverter valve plate
99
. The stationary plate
97
includes two ports
100
,
101
, one port
100
providing fluid communication between the upper part of the tubular body
98
and a cylinder
102
in which the mass
92
is located, and the other valve port
101
providing communication with a bypass conduit
104
which carries drilling fluid past the reciprocating mass cylinder
102
.
Thus, in use, as the diverter valve plate
99
rotates, in a first position drilling fluid flows through the cylinder
102
causing a pressure drop across the nozzle
94
and forcing the mass
92
downwards to impact onto the bit mandrel
108
, and in a second position the valve
96
allows flow to bypass the cylinder
102
and flow through the conduit
104
, reducing the flow through the reciprocating mass
92
and allowing the return spring
110
to push the mass
92
upwards.
In an alternative arrangement, the rotating diverter valve plate
99
is replaced-by a plate defining a slot, in a similar manner to the first and second embodiments described above. Thus, as the slotted plate rotates, the stationary valve plate port
100
provides continuous fluid communication between the upper part of the tubular body
98
and the cylinder
102
in which the mass
92
is located, and the other valve port
101
provides selective fluid communication with the bypass conduit
104
which carries drilling fluid past the reciprocating mass cylinder
102
.
Thus, in use, as the slotted valve plate rotates, in a first position, in which the slot is out of alignment with the port
101
, drilling fluid flows through the cylinder
102
causing a pressure drop across the restriction
94
and forcing the mass
92
downwards to impact onto the bit mandrel
108
. In a second position, in which the slot is also aligned with the port
101
, the fluid will tend to follow the path of least resistance and will thus bypass the cylinder
102
and flow through the conduit
104
, reducing the flow through the reciprocating mass
92
and allowing the return spring
110
to push the mass
92
upwards.
In still further embodiments the form of the fluid bypass conduit
104
may be varied, for example a plurality of conduits may be provided, or an annular or part annular conduit may be provided.
It will be apparent to those of skill in the art that the above described arrangements provide a relatively simple means for producing a percussive drilling effect. Also, the use of a rotating valve facilitates reliable operation even when using an abrasive working fluid such as drilling fluid. Further, the configuration of the valves, which permits a continuing flow of fluid, allows the clearances between the moving parts and details of the valve specifications to be selected such that, for example, opposing moving surfaces exposed to drilling fluid may be formed of suitable wear resistant material.
Claims
- 1. A percussion drill comprising:a fluid transmitting body; a drill bit support coupled to the body; a mass movable relative to the body for impacting on the drill bit support; means associated with the mass for creating a fluid pressure force on said mass; a rotating valve located in the body for controlling flow of fluid through the body to produce a varying fluid pressure force on the mass and induce acceleration of the mass; and a valve motor for driving said valve.
- 2. A percussion-drill according to claim 1 wherein said rotating valve rotates around a longitudinal axis.
- 3. A percussion drill according to claim 2 wherein said longitudinal axis is the central longitudinal axis of said fluid transmitting body.
- 4. A percussion drill according to claim 1 wherein said rotating valve is provided separately of the means for creating a fluid pressure force on said mass.
- 5. A percussion drill according to any preceding claim 1 wherein said valve comprises two portions each defining a fluid port, such that relative rotation of the portions varies the alignment of the fluid ports and varies the flow area defined thereby.
- 6. A percussion drill according to claim 5 wherein one of said portions is rotatable relative to said body.
- 7. A percussion drill according to claim 5 wherein said fluid ports are in the form of slots on a common axis.
- 8. A percussion drill according to claim 5 wherein one of said valve portions provides fluid communication with alternative fluid paths through said body, one of said paths providing fluid communication with the means for creating fluid pressure force on the mass; and another of said paths bypassing said means.
- 9. A percussion drill according to claim 1 wherein said valve permits fluid flow through the body in all valve configurations.
- 10. A percussion drill according to claim 1 wherein said mass is spring mounted in said body.
- 11. A percussion drill according to claim 1 wherein said mass defines a flow passage therethrough.
- 12. A percussion drill according to claim 11 wherein said flow passage defines a restriction such that fluid flowing through the mass is subject to a pressure drop.
- 13. A percussion drill according to claim 12 wherein said mass impacts directly on said drill bit support.
- 14. A percussion drill according to claim 1 wherein said drill bit support is spring mounted in said body.
- 15. A percussion drill according to claim 1 wherein said drill bit support is splinted to said body.
- 16. A percussion drill according to claim 1 wherein said body is adapted for mounting on a drill string.
- 17. A percussion drill according to claim 1 wherein said valve motor is a drilling fluid driven positive displacement motor.
- 18. A percussion drill according to claim 1, wherein said body is adapted for rotation in a bore, rotation of the body causing rotation of the drill bit support and a drill bit mounted thereto.
- 19. A percussive drilling method comprising the steps:providing a drill having a fluid transmitting body, a drill bit support mounted to the body, a mass movable relative to the body for impacting on the drill bit support, a rotating valve in the body for controlling flow of fluid through the body and a valve motor for driving said valve; and passing drilling fluid through the body and the drill bit support via the rotating valve to vary the flow of the fluid through the body and produce a varying fluid pressure force on the mass to induce acceleration of the mass.
- 20. The drilling method of claim 19, further comprising rotating the body, rotation of the body causing rotation of the drill bit support and a drill bit mounted thereon.
- 21. A percussion tool comprising:a fluid transmitting body; a bit support coupled to the body; a mass movable relative to the body for impacting on the bit support; means associated with the mass for creating a fluid pressure force on said mass; and a valve located in the body and operable to provide a continuing but varying flow of fluid through the body to produce a varying fluid pressure force on the mass and induce acceleration of the mass.
- 22. A percussion drill according to claim 21, wherein said body is adapted for rotation in a bore, rotation of the body causing rotation of the drill bit support and a drill bit mounted thereto.
- 23. A method of providing a percussive action in a downhole tool the method comprising the steps:providing a tool having a fluid transmitting body, a bit support mounted to the body, a mass movable relative to the body for impacting on the bit support and a valve in the body for controlling flow of fluid through the body; and passing drilling fluid through the body and the valve to provide a varying but continuing flow of fluid through the body and producing a varying fluid pressure force on the mass to induce acceleration of the mass.
- 24. The method of claim 23, further comprising rotating the body, rotation of the body causing rotation of the drill bit support and a drill bit mounted thereon.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9756204 |
Dec 1997 |
GB |
|
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/GB98/03710 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO99/29996 |
6/17/1999 |
WO |
A |
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
3654961 |
Phillips |
Apr 1972 |
A |
4478248 |
DeVall et al. |
Oct 1984 |
A |
5415240 |
Mundjar |
May 1995 |
A |
Foreign Referenced Citations (2)
Number |
Date |
Country |
2 108 594 |
May 1983 |
GB |
WO 9744565 |
Nov 1997 |
WO |