U.S. patent application number 12/266501 was filed with the patent office on 2010-05-06 for percussion rock drilling bit with more efficient flushing.
Invention is credited to Dongmin Niu.
Application Number | 20100108398 12/266501 |
Document ID | / |
Family ID | 42130053 |
Filed Date | 2010-05-06 |
United States Patent
Application |
20100108398 |
Kind Code |
A1 |
Niu; Dongmin |
May 6, 2010 |
Percussion Rock Drilling Bit with More Efficient Flushing
Abstract
A design of crown of drill bit for percussive rock drilling with
big "V" shape front flushing grooves, small central "dead" area
will reduce the repeatedly crushing of broken rock cuttings. It
will not only improve the rate of penetration, but also decrease
the hole deviation, as well as the erosion to the outer surface of
drive sub and case tube of DTH hammer.
Inventors: |
Niu; Dongmin; (Mississauga,
CA) |
Correspondence
Address: |
DONGMIN NIU
3125 FIFTH LINE W., UNIT 76
MISSISSAUGA
ON
L5L-3S8
CA
|
Family ID: |
42130053 |
Appl. No.: |
12/266501 |
Filed: |
November 6, 2008 |
Current U.S.
Class: |
175/418 |
Current CPC
Class: |
E21B 10/38 20130101 |
Class at
Publication: |
175/418 |
International
Class: |
E21B 10/38 20060101
E21B010/38; E21B 10/56 20060101 E21B010/56 |
Claims
1. A crown of rock drill bit for percussion rock drilling,
comprising at least three fluid passages or flushing holes 1 which
emerge in the vicinity of the front face 8 of the crown; each
flushing hole connecting to a radially extending front groove 3
formed in the front face; the outer end of each front groove
connecting to a side groove 6 which extend axially rearward;
wherein each land formed between the grooves carries at least one
gauge insert 2 and one front insert 9.
2. The bit crown, according to claim 1 has only one button in the
central area 5, the area within the inner edge of the flushing
holes/grooves of the front head.
3. According to claim 1, the shape of each front groove 3, when
looking at the bit front face, is "V" shape, the width of the front
grooves, when measuring across the center of the flushing hole, is
bigger than its diameter, getting wider outwards, to minimum 1.3
times wider towards the outer edge 7 of bit front head.
4. According to claim 3, the sides 3a and 3b of front grooves 3,
when looking at the bit front face 8, can be straight and/or
curved; the opening width of side grooves 6 is the same or bigger
than that of front grooves 3.
Description
THE APPLICATION AREA
[0001] The present disclosure relates to bore holes drilling of an
earth formation by top hammer hydraulic drilling and down-the-hole
(DTH) drilling with a hammer that is driven by pressurized air or
other fluids.
THE BACKGROUND
[0002] The button bit technology was mainly focused on increasing
the rate of penetration, deviation improvement, better materials
and bit skirt design since their first introduction. There are not
significant changes in the designs to improve the flushing
efficiency.
[0003] However, the actual rate of penetration is determined by the
efficiency of both impacting and flushing. The broken rock debris
should be removed via flushing medium immediately so buttons will
hit fresh solid rock surface with each impact. Otherwise, a portion
of the impact energy will be consumed by crushing the broken
debris, eventually slow down the penetration.
[0004] An example of prior art of design is shown in FIG. 1, the
flushing holes located at the distance about half of the bit front
head radius to the center. They are connected via grooves 3 in the
front face to the side grooves 6 of bit head respectively. The
front head grooves 3 have straight parallel edges and the width of
them is about the same as the diameter of flushing hole.
[0005] From fluid dynamics, the majority of flushing medium at the
bottom of a hole will flow through the grooves 3 in the front face
of bit, which are bigger passages therefore have less restriction
to flushing medium. Broken rock chips within the areas will be blow
away by the flushing medium immediately. The blowing out force of
flushing medium is not as high in the areas without flushing
grooves because of the restriction and/or resistance of inserts and
bit body steel. Furthermore, the big rock chips are very likely
clamped and/or blocked by the bit front face, inserts and rock
surface. They will also block smaller chips. Therefore, the
majority of broken rock debris could not be blown away on time.
They get crushed repeatedly, and then are blown out by flushing
medium when meet the flushing grooves as the bit rotating.
[0006] Moreover, the central area of bit front head is a "dead
area", the area within the inner edge of the flushing
holes/grooves. There is theoretically no flushing force to blow
rock debris out from the area. They get crushed repeatedly.
[0007] All of the left over rock cuttings act as a cushion between
the bit and solid rock surface. The "cuttings cushion" prevents the
inserts from penetrating the solid rock. Therefore, large portion
of impact energy is consumed by crushing the cuttings and the rate
of penetration is slowed down; the body steel of bits front face
gets worn away fast.
[0008] The "cutting cushion" also prevents the buttons of bit from
grasping the solid rock, keeping the drill bit in a floating state.
Therefore, bit tends to move sidewise if it encounter side force,
causing the holes' deviation.
[0009] With the prior art of design, the width of the front grooves
3 is small on the edge of bit head. So the velocity of the flushing
medium and the cuttings is very high when moving out of the grooves
3, especially for DTH air hammer. Severe erosion will be created on
the behind outer surface of drive sub and hammer case tube.
THE DESCRIPTION OF THE INVENTION
[0010] As is shown in FIG. 2 and 3, there is only one insert 4 in
the central area 5 of the front head of the bit, so that the
flushing holes 1 can be close to the center as much as possible to
minimize the central dead area 5.
[0011] The width of front flushing grooves 3 becomes wider towards
the edge 7 of bit crown forming "V" shape front flushing areas as
viewed in the direction perpendicular to the front face 8. Each of
the front grooves 3 connects to a side groove 6 respectively, which
is in the surface of the cylinder and/or cone of bit crown. The
rock debris in the areas can be blown away by flushing medium
immediately. The inserts 2 moving into this area will hit the fresh
solid rock surface.
[0012] The opening size of groove 3 along edge 7 should be as wide
as possible so the total area of the grooves 3 is much bigger than
that of the conventional straight grooves, which means much less
re-crushing of the rock debris under the bit front face 8.
Therefore, more impact energy will be used to break solid rock
surface. Also the wider openings will significantly reduce the
velocity of the out moving flushing medium and the cuttings, which
results in much less erosion on the outer surface of drive sub and
hammer tube.
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