Note: Descriptions are shown in the official language in which they were submitted.
CA 02667876 2009-04-29
WO 2008/054302 PCT/SE2007/050709
Device and method for automatic change of a drill bit and
rock drilling equipment provided with the device
TECHNICAL FIELD
[0001] The present invention relates to a device for use in equipment for rock
drilling
and specifically in the replacement of a drill bit on a drill rod. The
invention also relates
to a method for replacing said drill bit on the drill rod.
STATE OF THE ART
[0002] Tunnelling and drifting operations in underground work and construction
activities increasingly involve the use of specifically adapted mining
machines.
[0003] The number and length of the drilled holes required in such operations
vary with
the cross-sectional area of the tunnel or drift and the type of rock. Drilling
is now
usually carried out with hydraulic drilling machines and there is a great deal
of use of
extension rods or pipes to form a longer drill rod with a replaceable drill
bit at its tip.
[0004] Drill bits become worn and have to be replaced. The amount of drilling
for
which a given drill bit can be used before it has to be replaced depends on
the
characteristics of the rock. When the drill bit loses sharpness, its so-called
drilling rate
decreases. Achieving high productivity in drilling therefore involves taking
into account
the cost of replacing and/or regrinding drill bits and the amount of time
required for
changing a drill bit.
[0005] The changing of drill bits is generally carried out manually and is a
time-
consuming and troublesome operation. Moreover, it may also take place in
unsafe
rock which is liable to fall, making the operation not only time-consuming but
also
dangerous or unsafe. Sometimes the dimensions of a drilling unit may be such
that it
is difficult for operators from their normal working position to reach the
place where the
drill bit changing operation has to be done.
[0006] It would of course be an advantage if drill bits could be replaced
automatically
by means of some form of equipment. A solution involving an automatic bit
changer
has been tried on the market. Specification US 3 976 149 refers to an example
of such
an automatic bit changer. The type of bit changer therein presented has proved
to
have disadvantages because of comprising too many moving components and
CA 02667876 2009-04-29
29312-68
2
therefore failing to withstand for long enough the very demanding environment
in
which it is used.
According to one aspect of the present invention, there is provided a
device for automatic changing of a drill bit on a drill rod for a drilling
machine
supported by a feeder, wherein it comprises: a bracket for fastening to a
forward
portion of the feeder, a magazine for drill bits, and a separate basket for
gathering
up replaced drill bits, attached to the bracket, a clamping means for firmly
clamping the drill rod and the respective drill bit during a change of drill
bit.
According to still another aspect of the present invention, there is
provided a method for automatically replacing a worn drill bit on a drill rod
belonging to a drilling machine disposed on a feeder provided with the device
as
described above, comprising the steps of: the feeder drawing the drill rod
back so
that the worn drill bit is located in the clamping means, raising the
pivotable
element up against the forward portion of the feeder, the clamping means
firmly
gripping the worn drill bit, the drilling machine rotating the drill rod so
that the worn
drill bit is unscrewed, the feeder feeding the drill rod forward so that the
worn drill
bit falls into the basket, feeding the drill rod further forward until it
abuts against
and is aligned with a drill bit in a delivery position in the magazine,
rotating the drill
rod so that the new drill bit is screwed firmly onto the drill rod, lowering
the
pivotable element away from the feeder.
According to yet another aspect of the present invention, there is
provided a computer readable medium having computer executable instructions,
for controlling a change of drill bit, stored thereon for execution by one or
more
computers, that when executed implement the method described above.
According to a further aspect of the present invention, there is
provided a rock drilling rig equipped with a feeder provided with the device
described above.
[0007] An object of embodiments of the present invention is to
provide a
solution to the difficulties described above.
CA 02667876 2009-04-29
29312-68
2a
DESCRIPTION OF THE INVENTION
[0008] One aspect of the invention presents a device which has the
characteristics as described above.
[0009] A further aspect of the invention is presented in the
independent
method claim.
[0010] Further embodiments of the invention are described in the
dependent claims.
[0011] The device according to embodiments of the invention has very
few
moving parts, which makes it easy to use, robust and operationally reliable.
It can
tolerate powerful impacts and shocks without jeopardising its operational
reliability.
[0012] Further advantages are of course that bit changing operations
become considerably safer than previously in that the operator does not need
to
go to where the drill bit is situated. A further advantage is that used drill
bits are
automatically gathered up and can thereafter be passed on, e.g. for grinding.
LIST OF DRAWINGS
Fig. 1 depicts schematically a general view of a drilling rig with
feeder, with a drilling machine mounted on it, and a circle indicating the
location
for the device depicted in the other drawings.
Fig. 2 depicts in perspective a device according to the invention
fitted to the forward end of a feeder for a drilling machine, with the
device's
magazine for drill bits and a basket for replaced bits depicted in a lowered
position.
Figs. 3a and 3b depict in perspective the device according to Fig. 1,
but with the magazine and the associated basket in a raised position.
CA 02667876 2009-04-29
WO 2008/054302 PCT/SE2007/050709
3
Fig. 4 depicts in perspective a clamping cylinder pertaining to the device
according to
Fig. 1, separated from the rest of the device.
DESCRIPTION OF EMBODIMENTS
[0013] A number of embodiments of the invention are described below with
reference
to the attached drawings.
[0014] A bit changer 1 of the kind according to the invention for automatic
changing of
a drill bit 2 on a drill rod is depicted in perspective in Fig. 2. The bit
changer 1 is fitted
to the forward end of a feeder 3 which supports a rock drilling machine 4 to
which a drill
rod 5 is connected, as illustrated in Fig. 2. The feeder 3 may itself be
articulatedly
suspended from a boom 101 fitted to a drilling rig 100, as illustrated in
general terms in
Fig. 1. The bit changer 1 is built around a bracket 6 which is adapted to
being
connectable to the forward end of the feeder 3.
[0015] The bracket 6 supports in its lower portion a shaft 7 running
transversely
relative to the direction of the drill rod 5. Two arms 8 situated on their
respective sides
of the bracket 6 are arranged for rotation relative to said shaft 7. These two
arms 8 are
each attached to diametrically opposite sides of a basket 9 which in this
example is
cylindrical. The function of the basket 9 is, as described below, to catch and
temporarily store worn and replaced drill bits 2. The base surface of the
basket, which
faces outwards (i.e. in the drilling direction) from the feeder 3 when the bit
changer is in
a raised position, is in this example planar and serves as support for a
magazine 10 for
drill bits 2. The basket's walls may otherwise be perforated, as illustrated
in the
drawings. The basket 9 is thus separate from the magazine and comprises no
moving
parts.
[0016] New or reground drill bits 2 are intended to be stored in the magazine
10 in a
straight column, i.e. in line, which means that the structure of the magazine
10 may
closely resemble a rectangular parallelepiped in which drill bits 2 are acted
upon by a
spring urging them towards one end of the magazine 10, which means that the
magazine 10 closely resembles a straight magazine of the type used with
machine
guns. The result is that a drill bit 2 out of a possible plurality of drill
bits present in the
magazine 10 will be constantly available for delivery at a short end of the
magazine.
i
CA 02667876 2009-04-29
WO 2008/054302 PCT/SE2007/050709
4
When a drill bit 2 is drawn from the magazine during a bit change, another
drill bit 2, if
there is one, is immediately caused to occupy the vacated position by the
spring urging
towards said short end all the drill bits 2 remaining in the magazine 10. This
is
illustrated in Fig. 3a.
[0017] The basket 9 and the magazine 10 are thus joined together by the arms 8
to
form a rotatable element, herein called the pivotable element In Figs. 3a and
3b the
pivotable element is raised and abuts against the front of the bracket 6. In
Fig. 2, in
contrast, the pivotable element is lowered to be out of the way during
drilling and also
be better protected from damage. When the pivotable element is raised, an
inner base
surface of the basket 9 will abut against a mounting 11 fitted to the front of
the bracket
and preferably made of rubber, although it may of course be made of other
material,
e.g. steel. The outer and inner base surfaces of the basket 9 are each
provided with a
central hole larger in diameter than the drill bit 2 so that a drill bit from
the magazine 10
can pass in through the outer base surface and proceed on through the inner
base
surface. A sleeve 13 extending outwards from the basket 9 connects to the hole
in the
inner base surface. When the pivotable element is raised up against the
bracket 6, the
basket 9 will be centred in the axial direction of the drill rod 5 by the
sleeve 13 being
accommodated and supported in a recess 12 in the mounting 11 which is adapted
to
the dimensions of the sleeve 13.
[0018] A clamping means 14 is mounted on the inside of the bracket. The
clamping
means 14 is intended to clamp the drill rod 5 and the respective drill bit 2
during a drill
bit replacement operation. The clamping means 14 is depicted separately in
Fig. 4.
[0019] The process of replacing a drill bit is described below:
1) When a drill bit 2 is worn and the operator intends to replace it, it is
released
when it is at the bottom of a drilled hole. If the striker hits the drill
without
rotation and the drill with the drill bit is pressed against the rock, the
threaded
connection between the drill bit and the drill will be loosened.
2) The drilling machine 4 is drawn back on the feeder 3 so that the drill bit
2
does at least not appreciably protrude outside the bracket 6. The drill rod 5
is
gripped firmly by the clamping means 14. Rotating the drill rod 5 relative to
the
drilling machine 4 draws it firmly against the drilling machine.
CA 02667876 2009-04-29
WO 2008/054302 PCT/SE2007/050709
3) The pivotable element comprising the basket and the magazine is raised up
against the mounting 11 so that the sleeve 13 and a drill bit 2 which is at
delivery position in the magazine 10 are aligned axially with the drill rod 5.
4) The drilling machine 4 is drawn back further on the feeder 3 so that the
worn
5 drill bit 2 is in line with the clamping means 14, followed by the drill
bit 2 being
clamped firmly by this clamping means. Rotation of the drill rod 5 by the
drilling
machine 4 in the opposite direction as compared with step 2) unscrews the
drill
bit.
5) The drill rod 5 is fed forward and hence pushes the worn drill bit 2 down
so
that the latter falls into the basket 9. A fallen worn drill bit 2 is
illustrated inside
the basket 9 in Fig. 3b.
6) The drill rod 5 continues to move forwards and meets a waiting drill bit 2
which is situated in the magazine 10 in a deliverable position and axially
aligned
with the drill rod 5. The drill rod 5 is rotated so that the new drill bit in
the
magazine 10 is screwed onto the drill rod.
7) The drill rod 5 with the new drill bit 2 is drawn back until the drill bit
2 is
within the bit changer 1.
8) The pivotable element comprising the basket 9 and the magazine 10 is
lowered to its lowered position.
9) The drilling machine 4 is ready for drilling with the new drill bit 2.
[0020] During the axial movements of the drill rod 5 which are involved in the
above
process, it is necessary to be able to control the drill rod's position in the
axial direction.
This is achieved by providing a longitudinal position sensor which measures
the drill
rod's position in the axial direction relative to a fixed point on the feeder
3, thereby
enabling an operator to control the axial feed of the drill rod. It is of
course possible
with a drilling rig which has a control programme for not only the various
steps
described above involved in a drill bit change but also the detection and
control of the
drill rod's longitudinal movement to be programmed in the form of a drill bit
change
programme which may be initiated by an operator and thereafter automatically
executes the various sequences of the bit change operation.
CA 02667876 2009-04-29
WO 2008/054302
PCT/SE2007/050709
6
[0021] The bit changer 1 according to the description may take the form of a
separate
unit which can be mounted on existing feeders for drilling rigs on the market
or be
integrated with the feeder and be already available for a drilling rig at the
time of
supply.
