Note: Descriptions are shown in the official language in which they were submitted.
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ROCK BORING DEVICE
Technical Field
The present invention relates to a boring device for creating bore holes in
rock, or
removing rock from a surface. (For example the floor of a quarry).
Background Art
Boring of holes in rock faces can be conducted in a variety of ways. For
example,
explosive boring, as the name suggests, involves drilling in the rock face a
central
primary hole and a series of secondary holes about the primary hole. The
secondary
holes have a diameter suitable to receive an explosive charge, while the
primary holes
provides an opening in the rock towards which cracks that are formed in the
rock after
detonation of the explosive, can propagate. The primary hole is normally of a
greater
diameter than the secondary holes. Cracks that propagate from the secondary
holes to
the primary hole create rock chips or segments, that can be separated from the
rock
being bored and which are thereafter removed, leaving behind a bore hole. The
size of
the bore hole required determines the number of primary and secondary holes
needed,
while each explosive detonation can only remove a certain amount of rock, so
that the
above process may have to be repeated several times to form a bore hole of
sufficient
cross section and length. As can easily be appreciated this method of boring
can be
quite dangerous due to the use of explosive material, while it is also time
consuming
and complicated to prepare the primary and secondary holes in the rock face.
Additionally detonation of the explosives is a skilful exercise, as each
explosive is
detonated separately and at different times, to achieve the greatest extent of
crack
propagation.
A different form of rock boring involves the use of roller cutters that are
rotationally
forced into impact with the rock to again create cracks that propagate through
the rock.
The roller cutters employ a plurality of cutting tips, arranged at a variety
of different
diameters, which are forced into engagement with the rock surface adjacent one
another, so that cracks are formed by one cutting tip propagate and intersect
with
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cracks formed by an adjacent tip, thus created a rock chip or segment that can
be
separated from the rock under the impact of the roller cutter. Applying
immense
compressive forces to the rock creates the cracks, and eventually a balancing
tensile
failure occurs. Boring devices of this kind are subject to extensive impact
loading
because the cutting tips are forced into engagement with the rock under large
loads in
order to generate the cracks in the rock and thus the rock boring device is
required to
have facility for large impact absorption. The impact absorption is provided
by way of
a huge absorption mass attached to the device and the mass is of such a size,
that
known boring devices can weigh many hundreds of tonnes, a substantial
component of
which is for impact absorption. As a consequence, the weight and size of these
devices makes them expensive to construct and operate. Disclosure of the
Invention
It is an object of the following invention to overcome, or at least reduce one
or more of
the disadvantages associated with prior art boring devices. It is a further
object of the
invention to provide a mechanical device of a rotary cutting type, that
provides
improved rock removal from a rock face to form a rock bore and which is
relatively
economical to manufacture and operate. The cross section of this bore may be
circular, or a polygon, or a planar surface. (Longwall in Coal or a quarry
floor).
A rock boring device according to the present invention includes a rotary disc
cutter,
that in use, is either inserted into a pilot opening formed in the rock face,
or
approaches the rock face at an angle to enable entry.
For this cutting action to be initiated the tip of the disc should initially
contact the rock
at significant angle. (Probably in excess of 45 , but differing rock types or
conditions
may reduce or increase this requirement).
The boring device is characterised in that the disc cutter is driven in an
oscillating
manner, and also driven to nutate or free to nutate. The disc cutter is driven
to move
in this manner about separate or combined oscillating and nutating axes. The
nutation
angle may be varied or fixed from 0 to almost 90 (Most probably less than 5
). That
motion, when applied to the rock face, will cause the disc cutter to apply
force to the
rock that promotes cracks which propagate toward the rock face adjacent the
opening.
By this mechanism rock fragments or chips can be separated from the rock when
a
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crack propagates from the wall of the opening to the adjacent rock face. The
crack
will propagate from a pressure bulb created by the motion of the oscillation,
nutation
or combination of both motions. This cutting action enables the rock to fail
in tension
rather than the current traditional compressive first then tension technique.
This
phenomenon significantly reduces the supporting structure mass for the
proposed
technology. To insure that the cutting mechanism does not move away from the
rock
being cut, rather than cut the rock, a mass surrounding the cutter may be
necessary.
Brief Description of the Drawings
Several preferred embodiments of the invention will now be described with
reference
to the accompanying drawings, in which:
Figure 1 is a schematic view of the rock boring device of the preferred
embodiment of
the present invention and showing the manner in which it makes contact with a
rock
face,
Figure 2 is also a schematic view of the rock boring device showing the manner
in
which it acts to remove rock material,
Figure 3 is a detailed cross-sectional side elevational view of the rock
boring device,
Figure 4 is a schematic side elevational view of one example of how the device
may
be machine mounted to achieve the creation of a bore hole,
Figure 5 is a plan view of the machine mounted device of Figure 4, and
Figure 6 is a schematic view of another example of how the device may be
machine
mounted to achieve the creation of a bore hole.
Best Modes for Carrying Out the Invention
With reference to Figures 1 and 2 of the drawings, the rock boring device 10
according
to this preferred embodiment of the present invention includes a rotary disc
cutter 11,
that in use, is either inserted into a pilot opening formed in the rock face
R, or
approaches the rock face at an angle (a) to enable entry (see Figure 1).
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For this cutting action to be initiated the tip of the disc should initially
contact the rock
at significant angle. (Probably in excess of 45 , [a] but differing rock types
or
conditions may reduce or increase this requirement).
The boring device 10 is characterised in that the disc cutter 11 is driven in
an
oscillating manner, and also driven to nutate or is free to nutate. The disc
cutter 11 is
driven to move in this manner about separate or combined oscillating and
nutating
axes. The nutation angle (0) may be varied or fixed from 0 to almost 90
(Most
probably less than 5 ). That motion, when applied to the rock face, will cause
the disc
cutter to apply force to the rock that promotes cracks which propagate toward
the rock
face adjacent the opening (see Figure 2). By this mechanism rock fragments or
chips
12 can be separated from the rock when a crack 13 propagates from the wall of
the
opening to the adjacent rock face. The crack will propagate from a pressure
bulb 14
created by the motion of the oscillation, nutation or combination of both
motions.
This cutting action enables the rock to fail in tension rather than the
current traditional
compressive first then tension technique. This phenomenon significantly
reduces the
supporting structure mass for the proposed technology.
Advantageously, the nutating motion of the disc cutter also lends to promote
separation of the rock segments from the rock face and may assist sharpening
of the
contact point of the rotatably mounted disc. Because the disc is rotatably
mounted,
during each oscillation, the disc will precess. This action provides a new
portion of
the consumable portion of the disc to the rock and also will assist to
distribute the
temperature created due to the interaction of the disc and the rock. The
cutting action
of the tip 15 of the disc will require that the heel 16 of the disc does not
contact the
rock. To accomplish this a positive rake angle (Sl) must be achieved. This
angle may
be fixed or varied depending upon the operational mechanism. This angle may
also be
varied depending upon the rock type of characteristics. The variables being
monitored
by assessment of the forces within the drive mechanism and surrounding support
structure, and the results applied to algorithms in an allied computer control
system.
Depending upon the result of the interpretation of the data, the computer can
act to
alter angle SZ by providing a suitable signal to a electro-mechanical actuator
that can
provide the require force to alter the angle of the disc during the cutting
action.
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A rock boring device according to the invention principally will bore a groove
in the
rock at circa the diameter of the disc, and at the depth of plunge into the
rock. The
cutter excavates the rock by generating cracks in the rock and separating rock
segments formed by the cracks. However, rock normally will also be removed by
the
abrasive action of the cutting tips against the rock and the nutating motion
of the disc
cutter against the rock will also facilitate removal of rock in this manner.
However, the amount of rock removed by this mechanism is relatively small.
This
rock is in the zone referred to previously as the pressure bulb 14.
Currently the pressure bulb area or disc to rock contact zone is cooled and
airborne
dust is controlled by the addition of low pressure water (Less than 10 Bar)
applied
through the disc via a series of holes. This coolant could also be applied
from an
external source so that it is directed to contact the tip of the disc area. It
may be
possible to increase the performance of the system by directing high-pressure
water
(Probably above 200 Bar) at the pressure bulb area. This jet could be applied
either
perpendicular to the direction of travel, or in line with the axis of travel,
or any angle
in between. The water jet indicated as 17 in Figure 2 may enter the crack that
is
propagating from the pressure bulb and apply a force in equal and all
directions,
thereby forcing the rock chip to break to the free air side.
The disc cutter of the boring device preferably has a circular, rock engaging
periphery,
and may include a plurality of cutting tips which are removably connected to
the
cutter, but could be permanently connected.
Preferably, those tips extend from the disc cutter at or adjacent to the
circular
periphery thereof either radially, axially, or in a combination of both. The
cutting tips
can be formed of any suitable material, abrasion resistant, with inherent
toughness
such as tungsten carbide, alloy and hardened steel, possibly ceramic or other,
depending on the type of rock being bored. They can also have any suitable
shape and
can be fixed to the disc cutter in any suitable manner. The cutter may also be
contiguous and be produced of any or a combination of the materials mentioned.
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The oscillating movement of the disc cutter can be generated in any suitable
manner.
This motion may be direct mechanical means, or by poly-phase hydraulic pump
and
motor combination.
With reference to Figure 3 of the drawings the cutting device 10 includes a
mounting
assembly 17 as well as the rotary disc cutter 11. The mounting assembly 17
includes a
mounting shaft 18 which is rotatably mounted within a housing 19, that can
constitute
or be connected to a large mass for impact absorption. The housing 19 thus,
can be
formed of heavy metal or can be connected to a heavy metallic mass. The shaft
18 is
mounted within the housing 19 by a bearing 20, which can be of any suitable
type and
capacity. The bearing 20 is mounted in any suitable manner known to a person
skilled
in the art, such as against a stepped section 21.
The housing 19 can have any suitable construction, and in one form includes a
plurality of metal plates fixed together longitudinally of the shaft 18. With
one such
arrangement, the applicant has found that a plurality of iron and lead plates
provides
effective impact absorption based on weight and cost considerations.
The shaft 18 is mounted for rotating motion about a central longitudinal axis
AA. The
shaft 18 includes a driven section 21 and a mounting section 22. The driven
section 21
is connected to drive means 23 at the end thereof remote from the mounting
section by
any suitable connectors, such as heavy duty threaded fasteners 24, while a
seal 25 is
applied between the facing surfaces of the mounting section and the drive
means.
The drive means 23 can take any suitable form and the means shown in Figure 3
is a
shaft that may be driven by a suitable engine or motor. The drive means 23 is
mounted within the housing 19 by bearings 26, which are tapered roller
bearings,
although other types of bearings, either anti friction, plain hydrostatic, or
hydrodynamic, that provide radial and axial force reaction could also be
employed.
With one typical arrangement, the bearings 26 are mounted against a stepped
section
27 of the drive means 23 and against a mount insert 28 which is also stepped
at 29.
The mount insert 28 is fixed by threaded connectors 30 to the housing 19, and
fixed to
the mount insert 28 by further threaded connectors 31 is a sealing cap 32
which seals
against the drive means 23 by seals 33. The sealing cap 32 also locates the
outer race
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34 of the bearings 26 by engagement therewith at 35, while a threaded ring 36
locates
the inner race 37.
The mounting section 22 is provided for mounting of the disc cutter 11 and is
angularly offset from the axis A-A of the driven section 21, which generally
will be
approximately normal to the rock face being excavated. The axis B-B of the
mounting
section 22 is shown in Figure 3 and it can be seen that the offset angle 0 is
in the order
of a few degrees only. The magnitude of the offset angle 0 determines the size
of the
oscillating and nutating movements of the disc cutter 11 and the angle 0 can
be
arranged as appropriate. The angle 0 could be zero, but the axis of the
eccentric
section off-set from the A-A axis (Fig 3). This would provide oscillation but
no
nutation.
The disc cutter 11 includes an outer cutting disc 38 that is mounted on a
mounting
head 39 by suitable connecting means, such as threaded connectors 40. The
outer
cutting disc 38 could include a plurality of tungsten carbide cutting bits 41
which are
fitted to the cutting disc matrix in any suitable manner. Alternatively, a
tungsten
carbide ring could be employed. The outer cutting disc can be removed from the
cutting device for replacement or reconditioning, by removing the connectors
40.
The disc cutter 11 is rotatably mounted on the mounting section 22 of the
mounting
shaft 18. The disc cutter 11 is mounted by a tapered roller bearing 42, that
is located
by a step 43 and a wall 44 of the mounting head 39. An incline surface 45 of
the
mounting head 39 is disposed closely adjacent a surface 46 of a mounting
insert 47.
The surfaces 45 and 46 are spaced apart with minimum clearance to allow
relative
rotating movement therebetween and the surfaces have a spherical curvature,
the
centre of which is at the intersection of the axes A-A and B-B.
A seal 48 is located in a recess 49 of the surface 45 to seal against leakage
of
lubricating fluid from between the mounting shaft 18, and the housing 19 and
the disc
cutter 11. A channel 50 is also provided in the surface 45 outwardly of the
sea148 and
ducts 51 connect the channel 50 to a further channel 52 and a further duct 53
extends
from the channel 52 to a front surface 54 of the outer cutting disc 38.
Pressurised fluid
can be injected into the various channels and ducts through the port 55 and
that fluid is
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used to flush the underside of the cutting disc 38 as well as the relative
sliding surfaces 45
and 46.
The disc cutter 11 is rotatably mounted to the mounting section 22 of the
mounting shaft 18
by the tapered roller bearing 42 and by a further tapered roller bearing 56.
The bearing 56 is
far smaller than the bearing 42 for the reason that the large bearing 42 is
aligned directly in
the load path of the disc cutter and thus is subject to the majority of the
cutter load. The
smaller bearing 56 is provided to pre-load the bearing 42.
The bearing 56 is mounted against the inner surface of the mounting shaft 18
and the outer
sui-face of a bearing loading facility, comprising a nut 57 and a pre- loading
shaft 58a.
Removal of the outer cutting disc 38 provides access to the nut 57 for
adjusting the pre-load
of the bearing 56.
T he nutating movement of the disc cutter 11, occurs simultaneously with the
oscillating
motion and that nutating movement is movement in which a point on the cutting
edge of the
disc cutter is caused to move sinusoidally, in a cyclic or continuous manner
as the disc cutter
rotates. This movement of the disc cutter applies an impact load to the rock
surface under
attack, that causes tensile failure of the rock.
The direction of impact of the disc cutter against the rock under face is
reacted through the
bearing 42 and the direction of the reaction force is substantially along a
line extending
through the bearing 42 and the smaller bearing 56.
T'he boring device of the invention is not restricted to a single disc cutter,
but can include
more than one. For example, the boring device may include three disc cutters
arranged along
the same plane, but at approximately 45 to each other. Such an arrangement
can produce a
bore of a particular shape, while the speed at which rock is removed is
greatly increased. In
this arrangement, each of the three disc cutters can be driven by the one
drive means, or they
may be driven by separate drive means.
Alternatively with reference to Figures 4 and 5 the cutting device 10 may be
mounted on a
moveable boom 58 to enable the disc cutter 11 to be moved about the pilot
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opening as that opening is enlarged. In this arrangement the housing, and
impact
absorption mass (if provided) may also be mounted on the boom. The boom may be
elevated by an actuator 59 to tilt about a horizontal axis X and pivotable
laterally via a
turntable 63 about a vertical axis Z by extension and retraction of a pair of
rams 64 and
65 extending from cradle 66 to either side of the turntable 63 and mounted on
a chassis
70. The boom 58 has shaft 67 therethrough which in turn carries a connector 68
to
which the cutting device 11 is pivotably connected at W. The shaft 67 can
rotate about
its longitudinal axis Y. As a consequence of the pivot axes W, X, Y and Z, the
cutting
device can be positioned through a whole range of orientations including over
one arc
dictated by a short radius R1 about pivot axis W and an arc dictated by a
larger radius
R2 about pivot axes X and Z. The entire assembly would be anchored by a
clamping
means. This may be by vertical anchoring, horizontal anchoring or by
application of a
mass or adhesive mechanism to ensure the entire vehicle is in a finite
position prior to
commencing the first cut. Subsequent cuts at the rock face must be referenced
to the
previous cut to ensure a predetermined depth of cut is maintained. To increase
the
depth of cut beyond the design limit will cause the surrounding mechanism to
engage
the rock and stall or cease the cutting action.
This indexing and the geometry to cut the face can be composed by computer
control
in order to provide appropriate speed of operation.
With reference to Figure 6 of the drawings, in a still further arrangement, a
pair of
boring devices 10 may be mounted on separate booms 60 and the disc cutters are
swept in an arc across the rock face and about pivot points 69, to continually
remove
successive layers of rock from the face. The entire machine platform 61 must
be
securely anchored within the bore by gripping mechanisms 62.
The disc cutters of each device is arranged to sweep in an arc across the rock
face
being excavated in a first direction D1 and having completed that sweep,
return in the
reverse direction D2, with each sweep of the disc cutters removing a layer of
the rock
face. Entrance of the disc cutters into the rock for each successive pass, may
be at the
cusp C between adjacent concave sections formed by the sweep of each disc
cutter.
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The complete machine for the purpose of excavating a tunnel should be mobile
and
may be mounted on a crawler or on wheels. Providing the carrier or supporting
vehicle will fit into the hole size selected, the opening in the rock can be
from
completely circular at the minimum end of the cutting shape spectrum, to
somewhat
ovoid. However most customers currently prefer to have a flat floor to enable
them to
operate subsequent vehicles.
