U.S. patent application number 11/991428 was filed with the patent office on 2009-11-19 for one-piece drill bit for single-pass anchor bolting and single pass drilling apparatus.
Invention is credited to Aimo Helin, Christer Lundberg, Pierre Ravat.
Application Number | 20090285638 11/991428 |
Document ID | / |
Family ID | 37836097 |
Filed Date | 2009-11-19 |
United States Patent
Application |
20090285638 |
Kind Code |
A1 |
Lundberg; Christer ; et
al. |
November 19, 2009 |
One-piece drill bit for single-pass anchor bolting and single pass
drilling apparatus
Abstract
The present invention relates to a drill bit and a single pass
drilling apparatus. The one-piece drill bit has a connection
portion, adapted to be rigidly connected to a drill steel, a pilot
part and a reamer part. The pilot part has first rock machining
means. The reamer part has a first center line and second rock
machining means. The second rock machining means is provided
axially between said connection portion and said first rock
machining means and to one side of the pilot part. The drill bit
has a rotational direction. A side of the pilot part facing away
from the reamer part is provided with a wear resistant means. The
wear resistant means is integral with the first rock machining
means.
Inventors: |
Lundberg; Christer;
(Sandviken, SE) ; Helin; Aimo; (Tampere, FI)
; Ravat; Pierre; (Loyettes, FR) |
Correspondence
Address: |
DRINKER BIDDLE & REATH (DC)
1500 K STREET, N.W., SUITE 1100
WASHINGTON
DC
20005-1209
US
|
Family ID: |
37836097 |
Appl. No.: |
11/991428 |
Filed: |
June 26, 2006 |
PCT Filed: |
June 26, 2006 |
PCT NO: |
PCT/SE2006/000778 |
371 Date: |
May 22, 2008 |
Current U.S.
Class: |
405/259.1 ;
175/385 |
Current CPC
Class: |
E21D 21/004 20130101;
E21B 10/40 20130101 |
Class at
Publication: |
405/259.1 ;
175/385 |
International
Class: |
E21B 10/26 20060101
E21B010/26; E21D 20/00 20060101 E21D020/00; E21D 21/00 20060101
E21D021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2005 |
SE |
0501979-9 |
Claims
1. A one-piece drill designed for single-pass anchor bolting, said
drill bit having a connection portion, adapted to be rigidly
connected to a drill steel, a pilot part and a reamer part, said
pilot part having first rock machining means, said reamer part
having a first center line and second rock machining means, said
second rock machining means being provided axially between said
connection portion and said first rock machining means and to one
side of the pilot part, said drill bit having a rotational
direction, wherein a side of the pilot part facing away from the
reamer part is provided with a wear resistant means, said wear
resistant means being integral with the first rock machining
means.
2. The drill bit according to claim 1, wherein an imaginary line,
extending through the first rock machining means and being
perpendicular to the first center line of the reamer part, forms an
acute first angle with a normal to the first center line and
wherein the normal intersects a rock machining means that leads in
the rotational direction of the drill bit.
3. The drill bit according to claim 2, wherein the first angle is
not less than 0.degree. and not more than 20.degree..
4. The drill bit according to claim 2, wherein the leading rock
machining means in the reamer part is a button and wherein the
normal intersects its center line.
5. The drill bit according to claim 2, wherein the normal
intersects the forward most point of the leading rock machining
means in the rotational direction.
6. The drill bit according to claim 2, wherein the first rock
machining means is a chisel, and the second rock machining means is
at least three button.
7. The drill bit according to claim 1, wherein a middle line of the
pilot part forms an acute second angle with an axis extending
parallel to the first center line.
8. The drill bit according to claim 7, wherein the second angle is
-20.degree. to +20.degree., excluding 0.degree..
9. The drill bit according to claim 1, wherein the length of the
pilot part is defined as a distance between the forward most
portion of the pilot part and the forward most second rock
machining means, in a direction parallel to the first center line,
and wherein said length is at least 10 mm and not more than 60
mm.
10. A single pass drilling apparatus comprising drilling means and
an anchor bit wherein the apparatus comprises a one-piece drill bit
as defined in claim 1.
11. The drill bit according to claim 3, wherein the leading rock
machining means in the reamer part is a button and wherein the
normal intersects its center line.
12. The drill bit according to claim 3, wherein the normal
intersects the forward most point of the leading rock machining
means in the rotational direction.
13. The drill bit according to claim 3, wherein the first rock
machining means is a chisel, and the second rock machining means is
at least three button.
14. The drill bit according to claim 2, wherein a middle line of
the pilot part forms an acute second angle with an axis extending
parallel to the first center line.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a drill bit and a single
pass drilling apparatus according to the preambles of the
independent claims.
[0002] The installation of anchor bolts to reinforce excavations is
usually carried out in two distinct steps. Usually, a bore is
drilled and the drill steel and bit extracted before the bolt is
inserted into the bore and tightened or grouted. Single pass anchor
bolting involves carrying out these two steps simultaneously, with
the task of removing the drill steel to insert the bolt being
eliminated. The advantages of single pass bolting include
minimizing the time required for bolt installation, improving
safety for drilling equipment operators, when comparing with manual
or semi manual bolting, and enhancing prospects for full automation
of the process. A further advantage is improved quality and
precision of anchor bolt installation, when comparing with manual
or semi manual bolting. The diameter of the bore is critical for
anchor bolt performance in the case of friction, e.g. Split set
bolts. Still a further advantage with single pass bolting is that
the bore cannot collapse when retracting the drill bit since the
bolt is already in the bore. This leads to much better efficiency
as the bolt is always installed; i.e. there will be no lost
holes.
[0003] Prior attempts at single pass bolting have generally been
targeted at innovative anchor bolts, which also act as the drill
steel, having a drill bit provided about an end thereof. Such
apparatus are used via a rotational drilling method or a
rotary/percussive drilling method and are generally unsuitable for
hard ground conditions. Existing hard ground percussive anchor
bolts that do not reuse the drill bit suffer from cost problems. A
wide variety of roof bolts exist and one particular form is tubular
(e.g. split-sets, Swellex, etc.), having a central bore formed
lengthwise through the bolt. Drill bits adapted to be extracted
through a casing have been complex and accordingly expensive. Cost
competitiveness of drilling speed versus bit cost are complicated
in prior single pass anchor bolts due to the use of specialized
anchor bolts and the exclusive use of either complex retractable
bits. It nevertheless remains the case, that the installation
advantages of a self-drilling roof bolt outweigh those of the
non-self-drilling type.
OBJECTS OF THE INVENTION
[0004] The drill bit according to the present invention has as one
object to substantially overcome the above-mentioned problems
associated with the prior art, or at least to provide an
alternative thereto.
[0005] Another object of the present invention is to provide a
single pass drill bit.
[0006] Still another object of the present invention is to provide
a drill bit and a single pass drilling apparatus that are less
costly to use and so to make use of single pass bolting in the
mining industry more attractive.
[0007] Still another object of the present invention is to provide
a drill bit having good wear resistance.
[0008] Throughout the specification, unless the context requires
otherwise, the word "comprise", or variations such as "comprises"
or "comprising", will be understood to imply the inclusion of a
stated integer or group of integers but not the exclusions of any
other integer or group of integers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The attached drawings show an example embodiment of the
invention of the foregoing kind. The particularity of those
drawings and the associated description does not supersede the
generality of the preceding broad description of the invention.
[0010] FIGS. 1A-1G schematically show a sequence of single pass
roof bolting using a drill bit according to the present invention.
FIG. 2A shows the drill bit according to the present invention and
a rod portion in a side elevational view. FIG. 2B shows the drill
bit in a front view. FIG. 3A shows the drill bit during drilling of
a hole in the rock in a side elevational view. FIG. 3B shows the
drill bit in a front view during drilling of the hole in the
rock.
DETAILED DESCRIPTION OF THE INVENTION
[0011] FIGS. 1A-1G show a single pass drilling apparatus 10
according to the present invention using a drill bit 16 according
to the present invention and FIGS. 2A-3B more closely show the
drill bit 16 according to the present invention. The single pass
drilling apparatus 10 comprises several parts; e.g. an elongated
drill steel 11 having a leading end 12 and a trailing end, not
shown, reference being had to a drilling direction F. The leading
end 12 has a connection portion comprising a thread 15, a taper or
a bayonet connection, not shown. A one-piece drill bit 16 is
provided having rock machining means 17 and 18A, 18B, 18C. The
drill bit 16 is connectable to the drill steel via a connection
portion 20 comprising a thread, a taper or a bayonet connection
(not shown). The drill steel 11 and the drill bit constitute
drilling means. The single pass drilling apparatus 10 further
comprises an anchor bolt 21 adapted to at least partially enclose
the drill steel 11. The anchor bolt 21 has open ends. The greatest
diametrical dimension of the drill bit is smaller than the smallest
diameter of the anchor bolt 21.
[0012] The basic idea of the single pass drilling apparatus 10 is
to drill the bore while the bolt encloses the drill steel, and then
to retract the bit to be used again. There are no losses of bit
parts. The single pass drilling apparatus 10 has been more closely
described in Swedish Patent Application No. 0400597-1, the
disclosure of which is hereby incorporated by reference.
[0013] The drill bit 16 can be designed as follows, reference being
had to FIGS. 2A and 2B. The one-piece drill bit 16 has two integral
parts, i.e. a pilot part 14, long enough, i.e. the length L, to
guide the entire apparatus 10 properly, and a reamer part 19. The
center line or middle line CL1 of the pilot part 14 forms an acute
second angle .alpha. with an axis CL3 extending parallel to a first
center line CL2 of the reamer part. The angle .alpha. is
-20.degree. to +20.degree., excluding 0.degree., preferably not
less than +0.1.degree. and not more than +15.degree., index "+"
being shown in FIGS. 2A and 3A. The middle line CL1 will during
drilling substantially coincide with the axis of the bore 22. The
middle line CL1 of the pilot part 14 also substantially coincides
with the center line of the anchor bolt 21 during drilling, but not
during retraction of the drill bit. The center line or middle line
CL2 of the reamer part 19 and the center line of the drill steel 11
coincide when not drilling. It should be noted that neither the
pilot part 14 nor the reamer part 19 has to be circular or
symmetrical in radial cross-section, so the reference to lines CL1
and CL2 shall be understood as a reference to average middle lines
in the respective parts.
[0014] The one-piece rock drill bit 16 comprises a body 25 and
cemented carbide means, i.e. chisels and/or buttons 17, 18A, 18B
and 18C. The body of the drill bit is made of steel. The body 25
comprises the substantially cylindrical pilot part 14 and the
substantially conical reamer part 19. The pilot part 14 can have a
conical shape and the reamer part 19 can have a cylindrical shape.
The pilot part has a front face carrying a diametrically extending
chisel 17 or two or more diametrically substantially aligned front
buttons, not shown. The reamer part 19 can have a circular radial
cross-section. The reamer part has a front face carrying one or
more front buttons; in this case three front buttons 18A, 18B and
18C. The front faces may be convex or substantially planar. The
buttons 18A, 18B and 18C may form a peripheral arch on the reamer
part. The buttons 18A, 18B and 18C may project somewhat outside the
periphery of the reamer part in order to machine a bore 22 during
drilling which has a bigger diameter than the steel body 25. The
number of cemented carbide buttons in the reamer part can be varied
depending on how great the diameter of the drill bit is. Chipways
or recesses can be provided in areas between adjacent reamer
buttons, through which flush medium can pass. The rock drill bit 16
is to be coupled to the drill steel 11 by means of a connection
portion, so as to transfer rotational movement and percussion in
the usual manner. The drill steel 11 includes a channel for
conveying a flush medium. A main channel for flush medium is
provided inside the drill bit. This main channel communicates at
its forward end with a number of branch channels, which exit in the
front faces. The flush medium will in practice be water, cement or
air. The pilot part drills a pilot bore 22A of less diameter and
length in relation to the bore 22. The length L of the pilot part
14 is defined as the distance between the forward most portion of
the pilot part and the forward most reamer button 18A, 18B or 18C,
in a direction parallel to the reamer part center line CL2. The
length L is at least 10 mm and not more than 60 mm to provide good
guidance of and good service life for the drill bit. The reamer
buttons in this embodiment comprises a leading button 18A, an
intermediate button 18B and a trailing button 18C. During drilling,
the greatest reactional forces on the reamer 19 act on the leading
and intermediate rock machining means 18A, 18B. Therefore, an axial
plane through the chisel 17 is angled such that it passes between
the leading and intermediate rock machining means 18A, 18B. Stated
another way, an imaginary line S, preferably a midline through the
rock machining means or chisel 17 and perpendicular to the center
line CL2 of the reamer part 19, forms an acute first angle .beta.
with a normal N to the center line CL2. The normal N intersects the
rock machining means or button 18A that leads in the rotational
direction R of the drill bit 16. The angle .beta. is preferably not
less than 0.degree. and not more than 20.degree.. If the leading
rock machining means in the reamer part 19 is a button then the
normal N intersects its center line. If the leading rock machining
means in the reamer part 19 has another shape then the normal N
intersects its forward most point in the rotational direction R.
During drilling, the greatest reactional forces on the reamer 19
act on the leading and intermediate buttons 18A, 18B. The rock
machining means 17 will inter alia extend at least to the envelope
surface 50. Therefore, by positioning the rock machining means 17
in a certain relation to the leading button 18A the envelope
surface 50 of the pilot part the rock machining means 17 will form
a wear resistant means 17' during drilling at the position of the
reamer most subjected to wear. Said wear resistant means 17' is
thus integral with the first rock machining means 17. A tangent T,
touching the envelope surface 50 or a skirt 51 of the drill bit and
being parallel to the center line CL2, forms a radial distance X
with the periphery of the pilot part at its forward end. The
distance X is not zero and is preferably not less than -5 mm and
preferably not more than +5 mm.
[0015] The discussed shape gives good drilling results and a better
contact surface between the pilot hole 22A and the pilot part 14.
By having the pilot part inclined towards the reamer part by some
degrees better drilling results are achieved because the drill
steel always bends in the same direction when drilling, and the
bending of the drill steel 11 is limited by a contact at the
axially lower end 52 of the skirt 51 axially below the buttons
18A-18C. The lower end 52 of the skirt, where it is supposed to be
in contact with the rock, can be either harder than the rest of the
steel body 25 by means of surface treatment, or be provided with
hard inserts to reduce wear.
[0016] The operation of the single pass rock bolting apparatus 10
is shown in FIGS. 1A-1G. FIGS. 3A and 3B corresponds to for example
FIG. 1C. The degree of bending of the drill steel 11 is exaggerated
in FIG. 3A. The drill bit 16 is connected, for example threaded, to
the drill steel 11. A drilling machine such as a standard drill
jumbo holds the drill steel. The bolt 21 is preferably
automatically fed around the drill steel and positioned behind the
drill bit 16 in the drilling direction F. In FIG. 1A the pilot part
14 primarily will abut against the rock such that for a short while
it will machine the rock surface during circular interpolation.
Then the pilot part 14 will find its correct center and begin to
drill centrally while the drill steel 11 simultaneously starts
wobbling about the pilot part middle line CL1 1B. Then the reamer
part 19 gets in contact with the rock surface and begins to ream
the hole made by the pilot part 14. After a short while, the bolt
21 reaches the hole and is forced into the hole as shown in FIG.
1C. Usually the bolt 21 is spaced axially from the drill bit 16.
The bolt 21 diameter is preferably less than that of the bore 22.
The drill bit 16 will continue to drill and ream the bore 22, while
the bolt is pushed forwardly by a coupling sleeve 26 of the
drilling machine, see FIG. 1D, until feed of the different parts is
stopped. The depth of the bore 22 is substantially determined by
the length of the bolt 21, i.e. when a washer 23 positioned at the
trailing end of the bolt reaches the rock face or entrance of the
bore further feed will be stopped, see FIG. 1E. There is an anchor
bolt pusher on the drilling machine. The bolt pusher is a coupling
sleeve 26 or a dolly tool, which is driven by the drill steel. The
dolly tool usually rotates together with the drill steel and the
bolt during insertion. However, for instance the bolt may be held
such that it does not rotate during insertion, e.g. in the case of
a mechanical anchor bolt. The dolly tool can torque the anchor bolt
when fully inserted. The dolly tool can also slide along the drill
steel to allow an easier installation of mechanical shell bolts and
grouted bolts. FIG. 1E shows the anchor bolt 21 fully inserted,
with the drill steel and drill bit still in the anchor bolt. A
pusher pushes the plate to the rock face. The washer could be a
loose conventional plate having a central hole that cooperates with
a bulge 24 at the trailing end of the bolt. Then the drill bit is
retracted from the pilot hole 22A, see FIGS. 1F. It is preferable
that the axial space between the bolt and the drill bit is greater
than the depth of the pilot bore 22A such that the leading end of
the bolt does not interfere with the retraction of the drill bit.
The drill bit and the drill steel can be completely retracted and
can be reused for repeated drilling operations.
[0017] The machine driving the apparatus 10 can be a top hammer
drilling machine, a pure rotary machine or a down-the-hole
equipment.
[0018] The drill bit according to the present invention provides
good wear resistance since wear on its side facing away from the
reamer part is received by a wear resistant rock machining means
17' and provides favorable drilling results.
[0019] The invention described herein is susceptible to variations,
modifications and/or additions other than those specifically
described and it is to be understood that the invention includes
all such variations, modifications and/or additions which fall
within the scope of the claims.
* * * * *