ROCK DRILL SILENCING APPARATUS

APPAREIL DESTINE A ATTENUER LE BRUIT D'UNE PERFORATRICE DE ROCHE

English Abstract

The invention is concerned with a rock drill silencing apparatus that includes
a tubular housing (10) in which a pneumatic rock drill (12) can reciprocate.
The housing has an open mouth (50) at its forward end through which a drill
rod (58) attached to the rock drill can project. There is a seal (52) about
the open mouth and a thrusting arrangement to press the housing towards a rock
face (68) to be drilled such that the seal seals against that face. An air
motor (36) and feed screw arrangement drives the rock drill in a forward
direction in the housing during drilling. Air and flushing water conduits are
arranged to deliver compressed air and water from external sources to the rock
drill and air motor and there is an exhaust for conveying the rock drill
exhaust, drillings and flushing water out of the housing.

French Abstract

La présente invention concerne un appareil destiné à atténuer le bruit d'une perforatrice de roche, qui comprend une enveloppe (10) tubulaire dans laquelle une perforatrice de roche (12) pneumatique peut développer un mouvement de va et vient. Cette enveloppe possède une bouche (15) ouverte au niveau de son extrémité avant à travers laquelle une tige de forage (58) fixée à la perforatrice peut se projeter. Il existe un joint (52) autour de cette bouche ouverte et un agencement poussant destiné à presser l'enveloppe contre la face (68) d'une roche à forer de sorte que ce joint se scelle contre cette face. Un moteur pneumatique (36) et un agencement de vis d'avancement entraîne la perforatrice vers l'avant dans l'enveloppe pendant le forage. Des conduites d'air et d'eau de purge sont agencées de façon à apporter de l'air comprimé et de l'eau en provenance de sources extérieures à destination de la perforatrice et du moteur pneumatique et une évacuation permet de transporter les évacuations de la perforation, les éléments de forage et l'eau de purge hors de l'enveloppe.

Claims

CLAIMS:
1. A rock drill silencing apparatus comprising a tubular housing in which a
pneumatic
rock drill is reciprocable, an open mouth at a forward end of the housing
through which a drill
rod attached to the rock drill can project, sealing means about the open
mouth, thrust means
operable to press the housing towards a rock face to be drilled such that the
sealing means
seals against the rock face, air-powered drive means for driving the rock
drill in a forward
direction in the housing for drilling to take place, air delivery means for
delivering
compressed air from an external source to the rock drill and drive means,
water delivery
means for delivering flushing water from an external source to the rock drill,
and exhaust
means for conveying the rock drill exhaust, flushing water and drillings out
of the housing.
2. An apparatus according to claim 1 wherein the drive means is operable to
drive the
rock drill in a forward, drilling direction in the housing and also to
withdraw it in a rearward
direction after a drilling operation.
3. An apparatus according to claim 2 wherein the drive means comprises a
reversible air
motor in the housing, a feed screw arranged to be rotated by the air motor and
a feed nut on
the feed screw which is arranged to move axially in the housing along the feed
screw, when
the feed screw rotates, and to which the rock drill is attachable.
4. An apparatus according to claim 3 wherein the apparatus comprises brackets
which
are attached to the feed nut and engagable with the rock drill.
5. An apparatus according to any one of claims 1 to 5 comprising guide means
in the
housing for guiding movement of the rock drill therein.
6. An apparatus according to claim 5 wherein the guide means comprises a
series of
angularly spaced rollers arranged to support and guide the rock drill in the
housing.
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7. An apparatus according to any one of claims 1 to 6 wherein the sealing
means
comprises a resilient skirt secured about the open mouth.
8. An apparatus according to any one of claims 1 to 7 wherein the housing has
a
generally polygonal cross-section.
9. An apparatus according to claim 8 wherein the sides of the polygonal cross-
section
include thickened regions serving to reinforce those sides and the air and
water delivery
means includes conduits located internally in the thickened regions.
10. An apparatus according to claim 8 or claim 9 wherein the housing has a
generally
triangular cross-section.
11. An apparatus according to any one of claims 8 to 10 wherein the sides of
the housing
are formed integrally of plastics material.
12. An apparatus according to any one of claims 1 to 11 wherein the exhaust
means
comprises an exhaust conduit leading from the interior of the housing at a
position towards
the forward end thereof.
13. An apparatus according to claim 12 and comprising an exhaust receiver to
which the
exhaust conduit leads.
14. An apparatus according to claim 13 wherein the exhaust receiver includes
separator
means to separate liquid and solid components from the exhaust.
15. An apparatus according to any one of claims 1 to 14 wherein the thrust
means
comprises a pneumatic ram for acting between a fixed structure and the housing
in order to
press the housing towards the rock face.
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16. An apparatus according to any one of claims 1 to 14 and including a
support and
reaction device, anchorable in a mine working in which the rock drill is
deployed, to support a
rearward end of the housing.
17. An apparatus according to claim 16 wherein the thrust means comprises a
pneumatic
ram, actuable between the support and reaction device and the housing, to urge
the housing
towards the rock face.
18. An apparatus according to claim 16 or claim 17 wherein the support and
reaction
device comprises a prop anchorable at an upright attitude between a roof and
floor of the mine
working.
19. An apparatus according to claim 18 and including a forward support device
for
supporting the forward end of the housing.
20. An apparatus according to claim 19 wherein the forward support device
comprises a
prop anchorable between the roof and floor of the mine working and from which
the housing
is suspendable.
21. An apparatus according to any one of claims 1 to 20 and including a
pneumatic
percussive rock drill located in the housing and arranged to be driven back
and forth in the
housing by the drive means.
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Description

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"ROCK DRILL SILENCING APPARATUS"
BACKGROUND TO THE INVENTION
THIS invention relates to a rock drill silencing apparatus.
Pneumatic percussion drills are a major contributor to noise-induced
hearing impairment in mines. It is accordingly believed that it would be
highly advantageous to have a means whereby the operation of a
pneumatic rock drill could be silenced to an acceptable level.
One prior attempt to silence the operation of a rock drill is described in the
specification of South African patent 97/7248. Here a pneumatic rock drill is
located in a cylinder in the manner of a piston. Drilling thrust is provided
by
compressed air introduced into the cylinder behind the drill to drive the
drill
forwardly in the cylinder. Although the intention was that the enclosure of
the drill within the cylinder would reduce noise levels to an acceptable
value, the proposal suffered from a number of problems, not least of which
was that of ensuring a proper seal between the rock drill/piston and the
cylinder.
The present invention seeks to provide an alternative rock drill silencing
apparatus.
CONFIRMATION COPY

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SUMMARY OF THE INVENTION
According to the invention there is provided a rock drill silencing apparatus
comprising a tubular housing in. which a pneumatic rock drill is reciprocable,
an open mouth at a forward end of the housing through which a drill rod
attached to the rock drill can project, sealing means about the open mouth,
thrust means operable to press the housing towards a rock face to be
drilled such that the sealing means seals against that face, air-powered
drive means for driving the rock drill in a forward direction in the housing
for
drilling to take place, air delivery means for delivering compressed air from
an external source to the rock drill and the drive means, and exhaust
means for conveying the rock drill exhaust and drillings out of the housing.
Other advantageous features of the invention are defined in the appended
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail, by way of example only,
with reference to the accompanying drawings in which:
Figure 1 shows a perspective view of a rock drill silencing apparatus
according to the invention;
Figure shows a side view of the apparatus of Figure
2 1;
Figure shows a longitudinal cross-sectional view
3 of the housing of
the apparatus with a rock drill located
therein;
Figure shows a cross-section at the line 4-4 in
4 Figure 3; and
Figure shows a cross-section at the line 5-5 in
Figure 3.

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DESCRIPTION OF A PREFERRED EMBODIMENT
The rock drill silencing apparatus of the invention includes, as a major
component, an elongate rock drill housing 10 which is seen in Figures 1
and 2 and illustrated in more detail in Figures 3 to 5.
As will be apparent from Figures 4 and 5, the housing 10 is hollow with a
generally polygonal, in this case generally triangular, cross-section. It is
made of a composite plastics material, in this example an 80/20 weave
glass-fibre reinforced plastics material treated to have fire-resistant
properties consistent with underground mine usage. A conventional
pneumatic rock drill 12, in this case a SECOT"~ model S215T"" rock drill,
manufactured by The Steel Engineering Company (Pty) Limited of South
Africa, is located in the housing 10.
A U-shaped bracket 14 straddles and is connected to the body of the rock
drill towards the front end thereof. The bracket 14 carries three
equiangularly spaced rollers 16 which ride on central, thickened regions 18
of the walls 20 of the housing 10. These regions serve to reinforce the
housing walls. Another bracket 22 is connected to the body of the rock drill
towards the rear end thereof. Three further equiangularly spaced rollers 26,
carried by brackets attached to the backhead 28 of the rock drill, also ride
on the regions 18. It will be understood that the regions 18 act as rails for
the rollers, allowing the rockdrill to move backwards and forwards in the
housing 10 and that the rollers and regions 18 act to guide these
movements of the rock drill.
The numeral 30 indicates a threaded feed screw which is supported
rotatably by forward and rearward bearing assembles 32 which are
supported in the housing by brackets 34. A reversible air motor 36 is
located in the housing 10 to drive the feed screw.
An internally threaded feed nut 38 is engaged with the feed screw. The
feed nut has a flange 40 at one end and is externally threaded at the other

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end. The feed screw passes through the bracket 14 which is clamped
relative to the flange 40 by a locknut 42 on the threaded end of the feed nut
and an arrangement of spacers and washers 44, 46. The bracket 14 is
accordingly anchored to the feed nut. The bracket 22 is connected by a
bridging member 24 to the bracket 14 and is accordingly also anchored to
the feed nut.
With the air motor operational it will be understood that the feed nut will
move forwardly or rearwardly on the feed screw, the direction of such
movement being dependent on the direction of rotation of the feed screw.
Movement of the feed nut is accompanied by corresponding movement of
the rock drill itself.
The housing 10 has an open mouth 50 at its forward end. This is
surrounded by a resiliently flexible seal 52, in this made of a suitable grade
of polyurethane. Radial support arms 54 support a central eye 56 through
which extends a drill steel 58 chucked to the rock drill 12, as illustrated.
As
is conventional, the drill steel carries a drill bit 60 at its leading end.
Referring again to Figure 1, the apparatus of the invention also includes a
rear support and reaction device in the form of a prop 62. In the illustrated
case this is a simple telescopic prop which, as shown in Figure 2, can be
anchored between the hanging wall or roof 64 of a mine working in which
the rock drill 12 is to be used and the footwall or floor 66 of the working.
With a simple prop of this kind, wedges (not shown) can be used to anchor
the prop firmly in position at the correct distance from the mining face 68 in
which a hole is to be drilled. In other cases more sophisticated props which
include means to achieve firm anchorage can be used. Typical examples
are hydraulically actuated props or CAMLOCKT"" - type props could be
used in place of the simple prop 62.
The prop 62 carries transverse brackets 70 and 72 at different heights. In
the illustrated case, the piston 74 of a pneumatic ram 76 (Figure 3) is
attached to the upper bracket 70. The ram 76 is located at the rear end of

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the housing 10 and is actuable, with compressed air supplied to the ram
cylinder 78, to thrust the entire housing in a forward direction towards the
mining face 68.
In practice, the prop 62 is installed at a predetermined distance from the
face 68 and the ram is actuated to drive the housing 10 forwardly so that
the seal 52 is pressed firmly against the face. The resilience of the seal
enables it to make an effective seal even against a rough and uneven face.
It will be understood that the ram 76 could equally well be attached to the
lower bracket 72 if the rock drill is to operate at a lower level.
The housing is suspended at a position towards its forward end on a cable
80 carried by a transverse bracket 82 on another, similar support prop 84
anchored in position somewhat closer to the face than the prop 62. By
varying the length of the suspension cable it is possible to vary the
inclination of the housing 10 and hence of the rock drill 12, and to set the
height at which a hole will be drilled in the face 68.
The rearward end of the housing 10 is closed by an end cap 86.
Communicating with the interior of the housing, which is otherwise sealed
when the seal 52 is pressed against the face 68, is an exhaust port 88
leading through a control unit 90 to an exhaust conduit 92. As illustrated,
the exhaust port and control unit 90 are mounted on the housing 12
towards the forward end thereof. The exhaust conduit 92 leads to an
exhaust receiving unit 94.
As shown in Figures 1 and 2, water and compressed air supply hoses 96
and 98 extend from remote compressed air and water sources (not shown)
and are connected to the control unit 90. The control unit 90 includes valve
controls, either manually operable as exemplified by the control 91, or
automatic, for controlling the supply of air and water through delivery
conduits 93 located internally in the thickened regions 18 of the housing. Air
delivery conduits supply compressed air to the backhead 28 of the rock drill

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12 for operation of the drill motor, to the air motor 36 for operation of the
feed screw and to the ram 76. A water delivery conduit delivers water to the
backhead of the rock drill for flushing purposes during drilling. The internal
compressed air and water connections are omitted from the drawings in the
interests of clarity of illustration.
The operation of the apparatus is as follows. The props 62 and 84 are
installed at predetermined distances from the face 68. The housing 10 is
suspended from the props as shown in Figures 1 and 2. At this stage, the
rock drill 12 is completely retracted in the housing, such that the drill bit
60
does not extend past the seal 52. By appropriate valve operation at the
control unit 90, the ram 76 is extended to press the seal 52 against the
face. Compressed air is supplied to the air motor 36 to rotate the feed
screw in a sense to drive the rock drill forwardly and compressed air and
water are simultaneously supplied to the rock drill to operate it. The
arrangement is such that when the driving force applied by the air
motor/feed screw mechanism is equal to the resistance to drilling
experienced by the drill bit, the air motor stalls at the relevant air
pressure.
Drilling into the rock now commences with the air motor maintaining a
constant driving force to cause penetration of the drill bit into the rock.
The valve arrangement is such that when the full depth of the hole has
been drilled, the air motor is reversed, preferably automatically, to rotate
the feed screw in the opposite direction, thereby drawing the rockdrill
rearwardly in the housing and withdrawing the drill steel from the drilled
hole into the housing 10.
Throughout the drilling operation, the operator can stand away from the
apparatus. He may be equipped with a stand-off control for operating the
control unit and controlling the supply of water and air to the working parts
of the apparatus from a remote position. He may for instance be stationed
well away from the dangerous face area during the entire operation. In a
fully automated system he could in fact be setting up another apparatus to
drill a second hole while drilling of a first hole is still under way.

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The housing serves to contain and silence the operation of the rock drill. Air
exhausted by the rock drill, together with rock drillings flushed from the
drilled hole by the water, and the water itself, are removed from the housing
through the exhaust port 88 and are taken to the exhaust receiving unit 94
through the conduit 92.
Because the drilled hole is itself effectively sealed off during drilling,
drill
steel ringing and the noise generated by impacts of the bit against the
bottom of the hole are also diminished compared to conventional rock drills
in which the hole is exposed around the drill steel.
An added advantage is the fact that the operator is not required to hold the
rock drill during a drilling operation. This means that his hands are not
exposed to possibly injurious vibrations generated by the rock drill. The
vibrations of the rock drill are in any event damped to some extent by the
use of rollers 16, 26 of polyurethane.
In initial comparative testwork a prototype apparatus of the type described
and an unsilenced SECOT"' S215T"" rock drill were used to drill a series of
holes in a block of norite with a compressive strength in the range 210MPa
to 290Mpa. Noise levels were measured at the most likely position of the
ears of an operator. Drilling penetration rate was also measured. A rock drill
silenced in accordance with the invention was found to produce an average
noise level of 85dBA with a penetration rate of 500mm/min. The unsilenced
rock drill produced the same penetration rate but at an average noise level
of 110dBA. The tests showed that a rock drill silenced in accordance with
the invention is capable of producing comparable pentration rates but at far
lower noise levels.
The invention envisages that the exhaust receiving unit 94 will include
apparatus for separating liquid and solid components from the exhaust air.
The rock drillings may for instance be separated and collected to provide
real-time assay samples. Any oily contaminants arising from the operation

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of the drill could be also be separated from the water component, enabling
the water to be re-used if necessary.

Representative Drawing