Note: Descriptions are shown in the official language in which they were submitted.
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ROCK DRILLING APPARATUS AND MECHANICAL CONVEYOR FOR DRILL
CUTTINGS
[0001] The invention relates to a rock drilling apparatus comprising
a movable base, a feeding beam, a rock drill arranged movably in the feeding
beam for drilling holes, means for conveying drill cuttings broken off the
rock
during drilling by means of a flushing agent to the mouth of a drill hole, and
a
system for collecting drill cuttings that comprises a funnel to be placed
around
the mouth of a drill hole, ducts for conveying the drill cuttings from the
mouth of
the drill hole, and at least one mechanical conveyor provided in connection
with said ducts for conveying the drill cuttings to a predetermined dumping
site.
[0002] The invention further relates to a mechanical conveyor for
drill cuttings, which is to be placed in a rock drilling apparatus, the
conveyor
comprising a conveyor mechanism for conveying drill cuttings from the inlet
end of the conveyor to the discharge end thereof, an actuator that drives the
conveyor, and a control unit for controlling said actuator.
[0003] During rock drilling, rock dust and stones of different sizes
break off the rock. Such drill cuttings can be flushed by means of a drilling
fluid, which is usually water, or alternatively, the drill cuttings can be
flushed by
means of compressed air or a mixture of compressed air and a fluid. The
flushing agent is typically conducted via a duct formed in a drill rod to a
drill bit,
which comprises a second set of ducts, via which the flushing agent is
supplied
to a space provided between the drill rod and the drill hole, so that as the
flushing agent flows upwards out of the drill hole, it also pushes out of the
hole
the rock material the drill bit has broken off the rock.
[0004] The drill cuttings must be removed from the site of drilling.
Especially drilling of long holes, i.e. holes of up to 60 meters, with a
rather
large diameter produces a great deal of drill cuttings, which can amount to as
much as 1 to 2 cubic meters per drill hole. Drilling is usually carried out
according to a predetermined drilling plan, which means that holes are located
very close to each other. Especially when drilling is directed downwards,
drill
cuttings cannot remain near the drill hole since they could flow down to the
adjacent hole already drilled. Piles of drill cuttings remaining at the site
of
drilling also hinder the movement of the rock drilling apparatus. For example
US 4,434,861 discloses a rock drilling apparatus, which comprises a tubular
element arranged at the mouth of the drill hole and connected via a hose to a
system for collecting drill cuttings, which draws rock material from the mouth
of
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the hole. However, heavy rock material cannot usually be conveyed a long
distance by means of a partial vacuum. Therefore, the collecting system
comprises different separators and filters arranged at the front of the
drilling
apparatus for distinguishing solid particles from the flushing agent. The
separated particles are forwarded from the separators by means of a
mechanical conveyor. The drill cuttings do not constitute a homogenous
material, but they contain even rather large stones and other pieces with
shapes that are difficult to process. A problem with mechanical conveyors is
that at times the inlet ends of the conveyor receive stones, which get caught
in
the conveyor mechanism and jam the conveyor. In such a case the conveyor
must be stopped and opened to remove the stone that got caught. It is
difficult
to restore the conveyor to working order. Furthermore, drilling must be
interrupted since the apparatus cannot be used for drilling when the conveyor
has been stopped.
[0005] At present, quarrying is carried out more and more often by
means of unmanned mining vehicles, which are remote-controlled for example
from an overground control room or even controlled fully automatically by a
navigation and control system provided in the apparatus itself. People are not
allowed to enter an unmanned mine due to danger of collision, and therefore
all maintenance and repair operations always require that quarrying be
interrupted in the entire closed area. Alternatively, a drilling apparatus
that
does not work properly must be driven to a specific repair site outside the
actual area where quarrying is carried out. Furthermore, since mine galleries
intended for unmanned devices are not always supported so as to be safe
enough for people, it is not possible to repair the apparatus in the actual
site of
quarrying. Naturally an unmanned mine is not productive if different
breakdowns, such as jamming of the conveyor for drill cuttings, prevent the
rock drilling apparatus from being used continuously and efficiently in the
area.
[0006] An objective of the present invention is to provide a new and
improved conveyor arrangement for conveying drill cuttings.
[0007] The rock drilling apparatus according to the invention is
characterized in that the conveyor is provided with means for detecting when
the conveyor has jammed and for forwarding the detection data to a control
unit of the conveyor, and that when the conveyor has jammed, the control unit
of the conveyor is arranged, on the basis of said detection data, to drive the
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conveyor for a predetermined period of time in a direction that is opposite to
the normal direction of conveyance.
[0008] Further, the mechanical conveyor according to the invention
is characterized in that the conveyor is provided with at least one sensor for
detecting when the conveyor has jammed, and means for forwarding the
defection data from the sensor to the control unit, and that after the
conveyor
has jammed, the control unit of the conveyor is arranged to drive the
conveyor,
on the basis of said detection data, for a predetermined period of time in a
direction that is opposite to the normal direction of conveyance.
[0009] A basic idea of the invention is that rock material that has
broken off the rock, i.e. drill cuttings, is flushed out of a drill hole to
the mouth
thereof by means of air or some other corresponding flushing agent, and it is
conducted forward for further processing by means of a collecting system.
Drill
cuttings are preferably separated from the flushing agent by means of
separators arranged at the front end of the rock drilling apparatus, and the
cuttings are conveyed from the separators by one or more mechanical
conveyors to the rear end of the apparatus or to some other suitable dumping
site that is sufficiently far away from the site of drilling. The conveyor for
drill
cuttings is provided with means for detecting when the conveyor jams.
Furthermore, a control unit of the conveyor is arranged to drive the jammed
conveyor in a direction opposite to the normal direction of conveyance for a
predetermined period of time. In such a case the stone that jammed the
conveyor moves towards the inlet end thereof, simultaneously changing its
position such that when the conveyor is again driven in the normal direction
after the predetermined period of time, the stone that caused the jamming
moves easily through the entire conveyor mechanism to the outlet end thereof.
An advantage of the invention is that a failure situation of the conveyor can
be
eliminated automatically without a need for repairmen to step in. This is
particularly important in connection with unmanned rock drilling apparatuses.
In such a case a jammed conveyor can be quickly restored to operation and no
one has to enter the closed operating area of an unmanned mining vehicle, nor
is it necessary to drive the vehicle out of the working area to the repair
site.
Therefore the jamming of the conveyor interferes as little as possible with
efficient use of the rock drilling apparatus. Furthermore, rapid detection of
jamming prevents the conveyor from being damaged.
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[0010] Further, a basic idea of a preferred embodiment of the
invention is to monitor, by means of a suitable sensor, an actuator that
drives
the conveyor. It is thus possible to measure the input power of the actuator.
When the input power exceeds a predetermined threshold value, it is
concluded that the conveyor has jammed. On the other hand, it is possible to
measure the torque generated by the actuator, or to monitor the movements of
the actuator or the conveyor mechanism by means of a movement sensor.
[0011] The invention will be described in more detail in the
accompanying drawings, in which
Figure 1 is a schematic side view of a rock drilling apparatus
according to the invention,
Figure 2 is a schematic sectional side view of a part of a mechanical
conveyor for conveying drill cuttings,
Figures 3 and 4 show schematically arrangements according to the
invention for monitoring the operation of the conveyor,
Figure 5 is a sectional view of the structure of a conveyor, and
Figure 6 shows schematically a rock drilling apparatus.
Like reference numerals denote like parts in the figures.
[0012] Figure 1 shows, in a simplified form, a rock drilling apparatus
according to the invention comprising a movable base. In this case the
apparatus is provided with frame steering, i.e. a front frame 1 and a rear
frame
2 are pivoted during steering with respect to one another. The front frame 1
is
usually provided with one or more booms. The figure shows a working boom 5,
which is provided with a feeding beam 6 and a rock drill 7, which constitute a
drilling unit 40. Alternatively, the drilling unit is supported on the base
without a
boom. A working plane 8 for the operator of the apparatus is typically also
arranged in the front frame 1. On the other hand, the rock drilling apparatus
can be unmanned, which means that it is steered by remote control or by
means of a specific navigation system. The rear frame 2 in turn comprises a
power unit 9, power transmission and units required to produce hydraulic
pressure, compressed air, electric power etc.
[0013] In Figure 1, thicker lines denote the components that are
related to the system for collecting drill cuttings. For the sake of clarity,
the
system components are shown in a simplified form. Arrows indicating flow
directions illustrate the operating principle. A pneumatic compressor 10,
which
is either external or preferably situated in the apparatus, generates the
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pressure for the compressed air, which is conducted via a pressure conduit
10a to the rock drill 7. Via ducts provided in a drill rod 11 and a drill bit
12 the
compressed air is conducted to a space between the rod and a drill hole, the
air thus carrying out of the hole the rock material the drill bit has broken
off the
5 rock. The system also comprises a tubular suction funnel 13 arranged at the
mouth of the drill hole and intersected by the drill rod 11. The suction
funnel is
connected via a first hose 14 to a first separator 15, which is in turn
connected
via a second hose 16 to a second separator 17. The second separator is
provided with a fan 18 or the like for producing a partial vacuum in the
system.
In such a case, the suction funnel 13 draws the drill cuttings away from the
mouth of the drill hole to the first separator 15, which separates the drill
cuttings into coarse and fine matter. The fine matter or dust is conveyed via
the
second hose 16 to the second separator 17, which comprises preferably
replaceable filter elements for filtering the flow. The pure air that has
passed
the filters is returned to the surrounding space via a pipe 19. The coarse
matter
from the first separator and the finer particles from the second separator are
conveyed by means of a first mechanical conveyor 20 and a second
mechanical conveyor 21 to the back of the rock drilling apparatus, which can
comprise a container 22, either connected to the apparatus or separate
therefrom, for colleting the drill cuttings. Alternatively, the drill cuttings
are
discharged from the back of the apparatus into a pile on the ground and
removed therefrom later on. The mechanical conveyors 20 and 21 are
preferably screw conveyors, which take only a little space. For example, a
belt
conveyor shown in Figure 4, or any other mechanical conveyor that is suitable
for the purpose, can also be used.
[0014] The coarse separator and the fine separator can also be
arranged side by side, or they can be combined into a single unit, unlike in
the
case shown in Figure 1. Furthermore, in some cases it is sufficient to have
only
one separator and to separate the matter into only one fraction of drill
cuttings.
Also the number of the conveyors for drill cuttings can vary depending on the
structure of the rock drilling apparatus and the system for collecting drill
cuttings.
[0015] Figure 2 illustrates the operating principle of a conveyor. The
inlet end of the conveyor comprises a feeding funnel 41 or the like. The drill
cuttings are usually drawn by means of a partial vacuum into the separator,
where the flushing medium and the drill cuttings are separated from one
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another. The drill cuttings 50 thus fall to the lower part of the separator,
which
acts as a kind of feeding funnel. The lower part of the feeding funnel is
provided with a conveyor 20, in this case a screw conveyor, which comprises
an outer pipe 27 and a conveyor screw 28 arranged rotatably therein. The
conveyor is open at its inlet end, such that the drill cuttings directed to
the
feeding funnel finally end up in the conveyor screw. The rotating spiral or
screw conveys the stones 50 in direction A towards the discharge end of the
conveyor. A stone 51 that is of an unsuitable size and/or shape can get caught
between the conveyor screw 28 and the beginning of the outer pipe 27, thus
causing the conveyor to jam. Correspondingly for example in a belt or a chain
conveyor, a stone can be caught between the conveyor device and the casing
that surrounds the conveyor. When the conveyor is driven according to the
invention in the direction opposite to the normal direction of conveyance for
a
predetermined period of time, for example 5 to 20 s depending on the
conveyor, the stone that jammed the conveyor travels towards the inlet end.
Naturally the stone does not leave the system, but it must be reconveyed when
the conveyor is again driven in the normal direction. However, the stone
probably returns to the conveyor in a different position and therefore it will
no
longer get caught between the conveyor and the outer pipe, but it will travel
to
the discharge end of the conveyor without problems. Particularly wedge-
shaped stones have been found to cause problems in all kinds of conveyors.
[0016] Figure 3 shows an arrangement for monitoring the operation
of a screw conveyor 20 driven by a pneumatic actuator 31. A pumping unit 60
forms the pressure of the pressure medium that is supplied via a duct 61 to a
directional control valve 62. The valve is shown in the figure in its
intermediate
position. The duct 61 is also provided with a pressure relief valve 63. When
the
valve 62 is moved to its upper position, pressure is able to reach the
actuator
31 via the duct 64, thus making the actuator rotate the conveyor screw in the
normal direction of conveyance D. Furthermore, the pressure medium that
leaves the actuator is able to flow via ducts 65 and 66 into a tank 67. If the
conveyor jams, the pressure in the duct 64 leading to the actuator rises, and
the rising pressure is detected by means of a sensor, in this case a pressure
switch 68, connected to the duct 64. The pressure switch 68 converts the data
about the rising pressure into electric detection data, which is transmitted
via a
connection 69 denoted by a broken line in the figure to a control unit 70 of
the
conveyor. The control unit can consist of programmable logic or any other
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device suitable for the purpose, such as a computer or a unit operating by
means of a pressure medium. In the control unit, desired threshold values can
be set for the detection data, and the unit also comprises an adjustable timer
and other necessary means for processing the detection data. On the basis of
the detection data obtained from the sensor 68, the control unit 70 provides
the
electrically controlled directional control valve 62 with a control signal via
a
connection 71, the directional control valve thus changing to the lower
position.
The pressure from the duct 61 is thus able to flow via the duct 65 to the
actuator 31 and via the ducts 64 and 66 to the tank. The conveyor is thus used
in a direction that is opposite to the normal direction of conveyance. The
control unit 70 changes the directional control valve to the upper position
after
a period of time determined in the timer of the control unit, and the drill
cuttings
are thereafter conveyed as usual.
[0017] In the arrangement shown in Figure 4, the operation of the
mechanism in a belt conveyor is monitored by means of a movement sensor
72. The sensor transmits data about the operation of the conveyor mechanism
via a connection 73 to the control unit. If the control unit detects that the
conveyor has stopped, it gives a control signal via a connection 74 to an
electric motor 75 that drives the conveyor, the motor thereafter changing its
direction of rotation. Alternatively, it is possible to measure the electric
power,
torque or speed of rotation of the electric motor 75 by means of a sensor 76
provided in connection with the motor. This measurement data can thereafter
be supplied via a connection 77 to the control unit, which processes the data
and compares it with a set threshold value.
[0018] Figure 5 shows, in a very simplified form, a screw conveyor,
which comprises an outer pipe 27 provided with a conveyor screw 28 that is
placed inside the pipe and rotated around its longitudinal axis in direction
D. In
this arrangement, the conveyor screw is formed of a spirally coiled band-like
material 29, such that the screw corresponds substantially to the inner
diameter of the outer pipe. Inside the conveyor screw there is an open space
30 that intersects the spiral. Such a structure enables longitudinal
elasticity of
the conveyor screw in direction E. Furthermore, the outer pipe 27 can be
flexible, so that the conveyor fits more easily into the structures of the
drilling
apparatus. A further advantage of the structure is that the conveyor screw
conforms to the shapes of large stone blocks, thus preventing the conveyor
from jamming and the mechanism from being damaged.
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[0019] Figure 6 shows yet another rock drilling apparatus according
to the invention. The apparatus is otherwise similar to the one shown in
Figure
1, except that it does not comprise any separators. For example when drilling
overhead holes, the flushing agent can be a fluid, in which case the mixture
of
the flushing agent and the drill cuttings is collected by means of the funnel
13
and conducted via the hose 14 to the inlet end of the first conveyor 20. In
the
situation shown in the figure, the mixture of a flushing fluid and drill
cuttings
travels in the hose 14 due to gravity, but in some cases the travel can be
further improved by means of a partial vacuum. It should be noted that the
rock
drilling apparatus shown in Figure 6 is unmanned, which means that it is
controlled by wireless data transmission from an outside control room or by
means of a specific navigation apparatus.
[0020] The drawings and the related description are only intended
to illustrate the inventive idea. The details of the invention can vary within
the
scope of the claims. Therefore the operation of the conveyor can be monitored
by different sensors depending on the structure and use of the conveyor. In
the
present application, 'sensors' also refer to measuring means suitable for the
purpose.
