Note: Descriptions are shown in the official language in which they were submitted.
CA 02313840 2000-07-10
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates to mining and more particularly to the hoisting
of refuse
materials from a mine shaft work site.
2. DESCRIPTION OF THE RELATED ART
Shaft excavation in hard rock is carried out by drilling and loading the
drilled bores
with explosives which are then detonated. The broken rock must then be hoisted
to the
surface. This is typically done with large steel buckets.
For shafts less than one and one-half kilometers deep, a standard double dnun
mine
hoist is normally employed to hoist the shaft buckets up and to lower them
down. The same
hoist may later be employed for hoisting the ore from the mine, not with
buckets but with
rectangular-shaped conveyances called "skips". However, as the working depth
of recent
mines has exceeded two kilometers, the standard double drum hoist has been
found to be no
longer satisfactory, because it cannot handle the length of wire rope combined
with the weight
in the bucket.
One mining concern is known to have attempted to overcome the problem by using
a
multi-rope hoist known as the "Koepe" winder or friction hoist in a mine shaft
with a depth of
nearly two kilometers. However, this hoist was found to be unsatisfactory
because the "tail
ropes" had a tendency of tangling and the hoist rope was found to have a
severely short life
span (in some cases as little as six weeks).
Others have modified the double drum hoist by dividing each drum into two
separate
compartments and by winding identically sized ropes of standard diameter in
each
compartment. In this case, the ropes from one drum were attached to a single
conveyance
(skip). This type of hoist has enjoyed great commercial success and is known
today as the
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BMR (Bkair mukti-rope) hoist. The BMR hoist is in use at nearly all deep mines
in two
configurations, one using a mechanical coupling {double universal joint) to
connect a single
motor to the shafts of both hoist drums. The other makes use of an electric
coupling between
the single motor and the hoist drum shafts.
When a very deep shaft is to be sunk (or excavated) for a new mine it is
normal
practice to use a BMR hoist to remove the broken rock, since the BMR hoist can
later be
used when the mine is in operation to raise ore. However, during the shaft
sinking stage, the
8MR hoist is not fully utilized. The two ropes on each drum cannot be attached
to one shaft
sinking bucket, in view of the above mentioned tangling problem. In addition,
in order to
make the BMR hoist applicable for both shaft sinking and mine operation, the
hoist motor was
found to be severely over-sized for the shaft sinking phase. This meant that
the motor had to
run at reduced capacity {approximately one half the horsepower requirement for
which it was
designed. In addition, the e~ciency of an over-sized electricak motor is
reduced when
operating at a fraction of its design rating and this resulted in a waste of
about ten percent of
the ekectricak power fed to the hoist.
Mine shafts are cuirentky being excavated and contemplated for excavation to
even greater
depths (approximately 2 'f~ kilometers). Therefore, there remains an urgent
need for a practical
device which is capable of hoisting broken rock during a shaft sinking
procedure for extremely
deep mine shafts, with sufficient speed and economy.
SUMMARY OF THE INVENTION
Briefly stated, the present invention provides a device for excavating a mine
shaft,
comprising a pair of drums, each drum having a pair of regions, each region
wound with one
of a pair of hoist ropes; four refuse carriers, each attached to one of the
hoist ropes and drive
means for driving the drums to deliver two carriers at a time to a work site
in the shaft.
In another aspect of the present invention, there is provided a device for
removing
refiise material from a work site in a mine shaft, comprising a pair of drums,
each drum having
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a pair of regions, each region to engage one of a pair of hoist ropes; four
carriers for carrying
the refuse material, each carrier being attached to one of the hoist ropes,
drive means for
driving the drums, wherein the device is operable to deliver, in repetition,
two groups of two
carriers to the work site.
Preferably, the drive means includes at least one drive motor and a
transmission
arrangement for driving both of the drums and the hoist ropes on one drum are
wound
oppositely to the hoist ropes on the other drum. In this manner, one drum
lifts two loaded
refuse carriers while the other drum lowers the other two empty refuse
carriers.
In one embodiment, a positioning means positions the carriers at the work site
and
provides four paths, each of which guides a corresponding carrier. In one
example the
positioning means includes four guide regions, each to receive one carrier.
The carrier may be provided by a bucket or other suitable conveyance for
hoisting
broken rock from the work site.
In yet another of its aspects, there is provided a method for excavating a
mine shaft,
comprising the steps of
providing a pair of drums;
dividing each drum into a pair of regions;
winding each region with one of a pair of hoist ropes;
providing four refuse carriers and attaching each to one of the hoist ropes;
and
driving the drums in order deliver two carriers at a time to a work site in
the shaft.
Preferably, the driving step includes the step of coupling both of the drums
to a single
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drive motor and a transmission arrangement.
In one embodiment, the method includes the step of winding the hoist ropes on
one
drum opposite to the hoist ropes on the other drum, the step of positioning
the carriers at the
work site and the step of determining a difference in weight between the two
carriers at the
site. Preferably, the positioning step fiuther includes the step of providing
four guide regions,
each to provide a path for one carrier.
In yet another of its aspects, the present invention provides a device for
excavating a
mine shaft, comprising a drum having a pair of regions, each region wound with
one of a pair
of hoist ropes; a pair of refixse carriers, each of which is attached to one
of the hoist ropes and
drive means for driving the drum to deliver the carriers to a work site in the
shaft.
The present invention should significantly improve the rate of advance of
sinking very
deep shafts, with reduced electrical energy consumed to perform the task.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention will be provided, by way of
example
only, with reference to the appended drawings, in which:
Figure 1 is a plan view of a shaft excavation;
Figure 2 is a sectional view taken on line 2-2 of figure 1; and
Figure 3 is schematic view of a device for used in the excavation of figure 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the figures, there is provided a device 10 for removing refuse
material
from a work site in a mine shaft 12. The device has a pair of drums 14, 16,
each of which has
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a pair of regions 14a, 14b, 16a, 16b. One of four hoist ropes 18a, 18b, 20a
and 20b is wound
on each region. It can be seen from figure 3 that the hoist ropes on drum 14
are wound
oppositely to the hoist ropes on the other drum 16.
Four carriers 30a, 30b, 32a, 32b, in this case in the form of buckets, are
provided for
carrying refixse material between the work site and the surface. Each bucket
is attached to one
of the hoist ropes.
A drive means is provided for driving the drums, wherein the device is
operable to
deliver, in repetition, two groups of two buckets to the work site. The drive
means includes a
single drive motor 34 and a transmission arrangement 34a for driving both
drums. However,
more than one motor may be used and the transmission may include a mechanical,
electrical
or other suitable transmission unit. In this case, the axles of the drums are
joined by a
universal joint shown at 34b, for delivering power from the motor 34 to the
drum 16 via drum
14.
A positioning means shown generally at 40 positions the buckets at the work
site 12.
The positioning means includes a frame assembly 42 with four guide regions or
wells 44
which in turn provide four paths, each for a corresponding bucket.
Figure 2 shows a shaft excavation with one arrangement for two buckets at the
work
site, in this case the bottom of the shaft excavation in position where the
buckets may be
weighed before being simultaneously hoisted to the surface.
Thus, the device 10 utilizes the unused compartment of the drums of a
conventional
mufti-rope mine hoist by being wound with an additional wire rope, being
substantially
identical to the length, weight, construction and diameter of the wire rope
already wound in
the other compartment of each drum. The free end the wire ropes are each
fitted to a shaft
sinking bucket of substantially identical weight and volumetric capacity, that
is within about
three percent .
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During operation, one drum is driven by the motor in an opposite direction to
the other
drum. With two buckets, for example buckets 30a, 30b, filled with broken rock
at the work
site, the motor drives the drum 16 to wind up the wire ropes 20a, 20b and thus
hoist the
buckets upward toward the surface. Meanwhile, the buckets 32a, 32b (empty and
at the
surface) are lowered as a result of the unwinding of the wire ropes 18a, 18b.
Each bucket is also provided with a guidance device (known as a cross-head)
shown at
46, wherein each guidance device is of substantially identical weight and
dimension. The
guidance device is used to keep the shaft sinking bucket confined to its
designated travel path
as it rises and descends in the shaft.
When the two descending buckets reach the positioning means 40 near the shaft
bottom their cross-heads are automatically detached when they abut the frame
assembly 42
situated in their travel path. The two buckets are lowered further through the
wells 44 to a
point just beneath the frame assembly 40 called the "hanging mark". At this
point, when the
shaft men are ready for the buckets on the shaft bottom they "ring it down",
by sending a
message to the surface for the motor to be operated at reduced speed, so that
the buckets can
travel downward at reduced speed without guidance to a leveled area on the
pile of broken
rock. Here the buckets are filled with broken rock by a machine designed for
that purpose
and known to those skilled in the art.
When the buckets are full, a message is then conveyed to the surface and the
motor is
activated in reverse, causing the buckets to be hoisted to just clear the
broken rock pile. Here,
the wire ropes are allowed to "steady" themselves. The filled buckets may be
weighed by a
device that determines the rope-end load by measuring the hydraulic pressure
of compensating
support devices at the sheave wheel atop the head frame, or by other means
such as a simple
level made from a clear plastic hose filled with water. In this latter case,
if the filled buckets
hang to the same level, normally they are of equal weight. Once the shaft men
are suitably
trained, they may be able to judge, by eye, when the buckets have
substantially the same
weight, to make measurement otherwise unnecessary.
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Generally, the weights of the filled buckets should be within'f~ tonne {500
kilograms)
of one another. If not, broken rock is removed from the heavier bucket or
added to the lighter
bucket before both are hoisted simultaneously to surface.
A weighing system that can determine that the rope-end loads are nearly equal
is
desirable, in some cases, to ensure that the buckets reach the dump position
on surface
simultaneously. This is due to the fact that the wire ropes stretch under
load. As a
consequence, if the loading is not equal the buckets will reach surface one
ahead of the other.
To determine the allowable out of balance load the following formula may be
used:
a = FLIEA
where a is the difference in elevation of the buckets when they have reached
the surface dump
in the head frame, F is the rope-end load in Kilonewtons (kn.), L is the
length of wire rope
between the surface dump and the shaft bottom in meters, E is the modules of
elasticity of the
roper in Gigapascals (GPa) and A is the area of circle enclosing the wire rope
section in square
millimeters.
Thus for a difference in "end load" (weight of the bucket and its payload) of
500 kg,
will produce a force of 4.9 kn at the rope-end. With a length of 2.600
kilometers; a modukus
of 65 GPa; and a rope diameter of 51 millimeters, this weight difference will
produce a
differential rope stretch of 0.096 meters.
Thus, device 10 provides a method for hoisting or elevating shot ( or broken)
rock
more efficiently during the excavation of a deep mine shaft. This is done by
simultaneously
hoisting two shaft sinking buckets (or other conveyances) toward the surface
of the shaft,
while two others are lowered into the shaft. This allows the full capacity of
a mufti-rope
double drum winder (such as a BMR hoist, for example) to be utilized for shaft
sinking.
Moreover, it increases the efficiency of the electrical motors driving the BMR
hoist since it
may be run at near its design capacity.
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While the above device makes use of a pair of drums, each coupled with a pair
of
buckets, there may be some cases where a single drum can be used instead of
two. In this
case, the single drum would have a pair of regions, each region wound with one
of a pair of
hoist ropes. Each of a pair of refuse carrier may then be attached to one of
the hoist ropes and
drive means can be provided for driving the single drum to deliver the
carriers to a work site in
the shaft.
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