Note: Descriptions are shown in the official language in which they were submitted.
CA 02645848 2008-12-04
PNEUMATIC LAUNCHER
FIELD OF THE INVENTION
The invention relates to pneumatic launchers for launching projectiles,
particularly but not exclusively to launchers for launching projectiles for
triggering
avalanches.
BACKGROUND TO THE INVENTION
In various circumstances it may be desirable to trigger an avalanche, usually
to
prevent the build up of material which could form an uncontrolled avalanche at
a
later time.
Various methods of triggering avalanches have been used. Explosive charges
can be placed by hand, although this requires a worker to travel close to the
avalanche zone, which is both time consuming and potentially dangerous.
Therefore various methods of triggering avalanches from a distance have been
developed. Explosive charges can be fired from a distance, for example using
some form of launcher such as a Howitzer.
Such launchers include the "Avalauncher", which delivers a projectile using
compressed gas. However, known pneumatic launchers perform poorly in a
number of areas. The launchers are generally inaccurate, which leads to poor
control of avalanche triggering. The launchers include valves which are prone
to
wear and are relatively difficult to replace.
It is an object of the invention to provide an improved pneumatic launcher, or
at
least to provide the public with a useful choice.
SUMMARY OF THE INVENTION
In a first aspect the invention provides a pneumatic launcher having:
a firing chamber configured to hold a projectile to be fired, a wall of the
firing
chamber having one or more apertures therein forming a flow path;
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a gas chamber for holding gas under pressure, the gas chamber communicating
via the flow path with the firing chamber; and
a firing valve having an open position and a closed position, and being
configured
to block the flow path in the closed position and, in the open position, to
allow gas
under pressure to flow from the gas chamber via the flow path into the firing
chamber, the firing valve including: a sliding valve body having one or more
operating surfaces angled with respect to a movement direction of the sliding
valve body, such that pressure acting on the operating surfaces forces the
valve
body to slide; and
a recess configured to receive, when the firing valve is in the closed
position, a
part of the sliding valve body including at least a first operating surface
such that
pressure in a region outside the recess is prevented from acting on the first
operating surface.
In a second aspect the invention provides a pneumatic launcher having:
a firing chamber configured to hold a projectile to be fired, a wall of the
firing
chamber having one or more apertures therein forming a flow path;
a valve chamber between the firing chamber wall and an outer valve chamber
wall, the valve chamber communicating via the flow path with the firing
chamber;
a gas chamber for holding gas under pressure and communicating with the valve
chamber; and
a firing valve positioned within the valve chamber, the firing valve having an
open
position and a closed position, and being configured to block the flow path in
the
closed position and, in the open position, to allow gas under pressure to flow
from the valve chamber via the flow path into the firing chamber, the firing
valve
including: a sliding valve body having: an inner surface which engages with an
outer surface of the firing chamber wall to close the flow path when the
firing
valve is in a closed position; one or more operating surfaces angled with
respect
to a movement direction of the sliding valve body, such that pressure acting
on
the operating surfaces forces the valve body to slide; and a protrusion
extending
outwards; and a valve wall positioned to the outside of the valve body and
engaging with the protrusion, such that a pressure difference can be
maintained
between the regions on each side of the protrusion.
In a third aspect the invention provides a pneumatic launcher having:
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a firing chamber configured to hold a projectile to be fired, a wall of the
firing
chamber having one or more apertures therein forming a flow path;
a gas chamber for holding gas under pressure, the gas chamber communicating
via the flow path with the firing chamber; and
a firing valve having an open position and a closed position, and being
configured
to block the flow path in the closed position and, in the open position, to
allow gas
under pressure to flow from the gas chamber via the flow path into the firing
chamber, the firing valve including: a sliding valve body having a range of
movement and cooperating with a part of the launcher to form a substantially
closed region ahead of the moving sliding valve body near an extremity of the
range of movement, thereby cushioning the motion of the sliding valve body.
In a fourth aspect the invention provides a pneumatic launcher having:
a firing chamber configured to hold a projectile to be fired, a wall of the
firing
chamber having one or more apertures therein forming a flow path;
a gas chamber for holding gas under pressure, the gas chamber communicating
via the flow path with the firing chamber;
a firing valve having an open position and a closed position, and being
configured
to block the flow path in the closed position and, in the open position, to
allow gas
under pressure to flow from the gas chamber via the flow path into the firing
chamber; and
wherein the firing valve is held in place by a fastening mechanism at one end
of
the valve and can be removed from the pneumatic launcher by releasing the
fastening mechanism and sliding the firing valve from the launcher.
In a fifth aspect the invention provides a pneumatic launcher having:
a breech; and
a breech plug configured to be inserted to close the breech during firing and
to be
removed from the breech to allow a projectile to be loaded into the launcher;
wherein the breech plug extends into a firing chamber of the launcher and is
shaped so as to produce a desired gas flow profile during firing, or is
adapted to
support an insert shaped so as to produce a desired gas flow profile during
firing.
In a sixth aspect the invention provides a pneumatic launcher having:
a breech;
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a breech plug configured to be inserted to close the breech during firing and
to be
removed from the breech to allow a projectile to be loaded into the launcher;
and
a breech seal configured to seal between the breech and the breech plug, when
inserted;
wherein the breech seal seals between a first face on the breech and a second
face on the breech plug, the first and second faces being substantially
transverse
to an insertion direction of the breech plug.
In a seventh aspect the invention provides a pneumatic launcher configured to
project a projectile using gas pressure and having a barrel with one or more
longitudinal ribs.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of example only, with reference to
the accompanying drawings, in which:
Figure 1 is a perspective view of a pneumatic launcher;
Figure 2 is a cut away view of a valve section in a pneumatic launcher,
showing the valve in an intermediate position;
Figure 3 is a cut away view similar to Figure 2, showing the valve in a
closed position;
Figure 4 is a cut away view similar to Figure 2, showing the valve in an
open position;
Figure 5 is a cut away perspective view of the sliding valve body of the
valve section in Figure 2;
Figure 6 is a cut away perspective view of the valve wall of the valve
section in Figure 2;
Figure 7 is a cut away view of a pneumatic launcher breech assembly;
Figure 8 is a perspective view of the breech assembly of Figure 7;
Figure 9 is a perspective view of one embodiment of a breech plug;
Figure 10 shows the breech plug of Figure 9, carrying a replaceable insert;
Figure 11 is an enlarged view showing the breech plug seal;
Figure 12 is a cut away perspective view showing the valve section and
breech assembly;
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Figure 13 is a cross-section of the pneumatic launcher barrel; and
Figure 14 is a schematic diagram showing external valves and conduits
used to operate the launcher.
DETAILED DESCRIPTION
Figure 1 shows a pneumatic launcher 1. The pneumatic launcher 1 may include
a base 2 which allows adjustment of the direction and elevation of the
launcher 1.
Adjustment of the direction may be achieved, for example, using a turntable 3
driven by a handle 4 via a suitable gear mechanism 5. Adjustment of the
elevation may be achieved, for example, using a hydraulic ram 6. The base 2
includes a number of supports 7, which support the main part of the pneumatic
launcher 1. Thus, the base 2 functions to support and direct the launcher 1.
Many different types of base or support may be used, or indeed the launcher
may
be used without a base or support.
The pneumatic launcher 1 includes a number of gas chambers 10, 11, 12 for
holding a compressed gas before the launcher is fired. These chambers may be
formed in any suitable manner, so long as they are capable of withstanding the
required pressures. Before firing, the chambers receive compressed gas from an
external source and hold the compressed gas until firing.
The chambers 10, 11, 12 communicate via conduits 13, 14, 15 with a valve
section 16, which is described in detail below. The valve section 16 in turn
communicates with a barrel 17. The back of the valve section 16 receives a
breech assembly 18, which again is described in detail below.
In use, a projectile is loaded into a firing chamber in the valve section 16,
through
the breech assembly 18. The breech is then closed. The valve contained in the
valve section 16 is operated to release compressed gas from the chambers 10,
11, 12 into the firing chamber, forcing the projectile from the firing chamber
through the barrel 17.
Figure 2 is a cutaway view of the valve section 16. The valve section 16 is of
generally cylindrical construction. The valve section 16 includes a barrel end
20
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and a breech end 21. The breech end 20 is configured to receive the barrel 17
(see Figure 1), while the breech end 21 receives the breech assembly 18 (see
Figure 1).
The valve section 16 includes a number of apertures 23, 24 which communicate
with the conduits 13, 15 shown in Figure 1. A further aperture which
communicates with the conduit 14 of Figure 1 is also provided but is not shown
in
Figure 2. The valve section 16 also includes a valve chamber 25 communicating
with the apertures 23, 24 formed in an outer wall of the valve chamber. The
valve chamber 25 also communicates via apertures 26, 27 with a firing chamber
28. The firing chamber 28 holds a projectile before firing and, in the
assembled
pneumatic launcher, communicates with the barrel 17.
Thus, a flow path is established from the chambers 10, 11, 12 through conduits
13, 14, 15 and apertures 23, 24 to the valve chamber 25. The flow path extends
from the valve chamber 25 via apertures 26, 27 to the firing chamber 28.
A firing valve operates to open and close this flow path and may be situated
within the valve chamber. In a closed position, the firing valve obstructs the
apertures 26, 27, such that compressed gas cannot flow from the valve chamber
into the firing chamber 28.
The firing valve may be formed as follows. A sliding valve body 30 may be
arranged with its inner surface 31 against the outer surface of the wall 32 of
the
25 firing chamber 28. The sliding valve body 30 slides along the length of the
valve
section 16 between a closed position (shown in Figure 3) and an open position
(shown in Figure 4).
In the closed position (see Figure 3) the sliding valve body 30 obstructs the
apertures 26, 27, preventing flow of compressed gas from the valve chamber 25
to the firing chamber 28. In the open position (see Figure 4), the sliding
valve
body is positioned out of the way, such that compressed gas can flow freely
from
the valve chamber 25 to the firing chamber 28.
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The sliding valve body 30 may be shaped to include a number of operating
surfaces 33, 34, 35, 36, 37. Each operating surface is oriented at an angle to
the
direction of motion of the sliding valve body 30 (i.e. each operating surface
is
non-parallel to the direction of motion). Therefore pressure acting on each
operating surface 33 - 37 creates a force tending to cause sliding motion of
the
sliding valve body 30. Motion of the sliding valve body 30 may be controlled
entirely by the action of gas pressure on these operating surfaces 33-37, as
described below.
The firing valve also includes a valve wall 40, which may be positioned to the
outside of the sliding valve body 30. The sliding valve body 30 includes a
protrusion 41, an outside surface of which engages with an inside surface of
the
valve wall 40. This means that a pressure difference can be maintained between
a region 42 on a first side of the protrusion 41 (where pressure acts on the
operating surface 33) and a trigger chamber 43 on a second side of the
protrusion 41 (where pressure acts on the operating surface 34). The chamber
43 communicates with the outside of the valve section 16 via a flow path 44.
Figure 5 is a perspective cut away view of the sliding valve body 30, while
Figure
6 is a similar view of the valve wall 40. Note that the L-shaped end section
45 of
the valve wall 40 consists of a number of protrusions 46 as shown in Figure 6,
rather than the continuous wall which could be incorrectly inferred from
Figures 2
to 4.
The operation of the firing valve over a complete firing cycle will now be
described with reference to Figures 2 to 4.
The valve chamber 25 begins in an unpressurised state. Pressure is introduced
via the flow path 44 into the trigger chamber 43, acting on the operating
surfaces
34, 35 to force the sliding valve body 30 into the closed position.
The valve section 16 includes a recess 50, which is configured to receive part
of
the sliding valve body 30, when the firing valve is in the closed position.
Figure 3
shows a part 51 of the sliding valve body 30 situated within the recess 50. In
the
closed position, pressure in the valve chamber 25 does not act on a first
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operating surface 37, situated at an end of the sliding valve body. Preventing
pressure from acting on this surface contributes to the stability of the
closed
position, since the pressure acting to force the sliding valve body 30 towards
the
open position is lessened.
With the firing valve in the closed position shown in Figure 3, pressurised
gas is
introduced into the chambers 10, 11, 12 and therefore into the valve chamber
25.
This pressurised gas may be drawn from the same source used to pressurise the
trigger chamber 43. Even though the pressure in the valve chamber increases,
acting on the operating surface 33, the combined area of the surfaces 34, 35,
36
is sufficient to create a force holding the sliding valve body 30 in the
closed
position.
When the chambers 10, 11, 12 and the valve chamber 25 have been sufficiently
pressurised, and an operator wishes to fire the pneumatic launcher, the
pressure
in the chamber 43 is released (preferably suddenly) to the outside of the
valve
section 16 via the flow path 44. The pressure in the trigger chamber 43 is now
much lower than the pressure acting to force the sliding valve body 30 towards
the open position. The sliding valve body 30 therefore moves rapidly from the
closed position to the open position, allowing compressed gas to flow from the
valve chamber 25 and chambers 10, 11, 12 into the firing chamber 28 to fire a
projectile.
The motion of the sliding valve body is rapid. This is beneficial for the
firing of the
pneumatic launcher 1, since it allows a rapid release of pressurised gas into
the
firing chamber 28. However, such rapid motion tends to damage the mechanism
of the firing valve, resulting in a short lifetime of these components and/or
a lack
of reliability. Therefore, the valve section 16 is designed to cushion the
motion of
the sliding valve body 30 so as to reduce any damage caused to the valve
components.
During firing, the sliding valve body 30 moves from the closed position of
Figure 3
through the intermediate position shown in Figure 2 to the open position shown
in
Figure 4. In the position of Figure 4, the end 53 of the sliding valve body 30
enters a narrowed passage 54 and the passage 54 is dimensioned to cooperate
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with the end 53 of the sliding valve body 30. This creates a substantially
closed
region 55 ahead of the protrusion 41 of the advancing sliding valve body 30,
near
the end of its range of movement. This closed region 55 cushions or slows the
motion of the sliding valve body 30, since the air within that region cannot
escape, or cannot escape fast enough to allow the sliding valve body 30 to
reach
the end of its range of motion unchecked.
A similar effect may be used to cushion motion of the sliding valve body 30
from
the open position to the closed position at the start of the firing cycle. For
example, a similar closed region could be created using the recess 50.
Alternatively, the pressure introduced through the flow path 44 could
initially be
fairly low, so that motion of the sliding valve body 30 into the closed
position is
relatively gentle.
The outer wall 57 of the valve chamber 25 is formed with an end plate 58 for
mounting of the firing valve into the valve chamber. A fastening mechanism,
which may be a top plate 59 is used to secure the valve wall 40 to the end
plate
58. A number of fasteners, for example threaded screws, engage with
cooperating apertures 60 in the top plate 59, valve wall 40 and end plate 58.
The
top plate may also be shaped to support the barrel in the assembled launcher.
Other fastening mechanisms may also be suitable. However, it is preferred that
the fastening mechanism should be situated at one end of the valve section 16,
such that when the fastening mechanism is removed the firing valve (including
the sliding valve body 30 and the valve wall 40) can be removed by sliding it
from
the end of the valve section 16.
The valve section 16 also includes a bottom plate 62 situated at the breech
end
21 and configured to receive a breech assembly as described below.
Finally, the valve section 16 includes a number of seals positioned to prevent
the
undesired flow of gas within the valve section. Figures 2 to 4 show the
grooves
provided to receive the seals, which may be o-rings formed from rubber,
composite material or any other suitable material.
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Thus, referring to Figure 4, a groove 63 is provided in the outer surface of
the
projection 41. The seal contained in this groove restricts gas flow between
the
first side 42 and the second side 43 of the projection 41. A seal 64 is
provided
between the outer surface of the firing chamber wall 32 and the inner surface
of
the sliding valve body 30.
A further seal 65 is provided near the end 51 of the sliding valve body 30, in
order
to seal within the recess 50, preventing pressure in the valve chamber 25 from
acting on the first operating surface 37. This seal is carried on the sliding
valve
body, for ease of replacement. However, a similar seal could be provided in or
near the recess 50. Two or more seals could be used to perform this function.
The above seals are all seals provided between moving components.
Furthermore, seals are provided between fixed components where those
components lie against each other in the assembled valve section 16. These
include a seal 67 between the outer wall 57 of the valve chamber and the
bottom
plate 62; and seals 68, 69, 70 at the joins between the outer wall 57 of the
valve
chamber, valve wall 40 and top plate 59.
Figure 7 shows the breech assembly 18 mounted to the bottom plate 62. The
breech assembly 18 includes a backplate 75 which is secured to the bottom
plate
62 by a number of fasteners. In the embodiment shown, the backplate 75 and
bottom plate 62 include a number of apertures 76 for receiving threaded
screws.
The breech assembly 18 also includes a locking ring 77 which rotates about the
axis of the breech assembly 18. A locking handle 78 is mounted to the locking
ring 77 to enable a user to operate the locking ring.
Finally, the breech assembly 18 includes a breech plug 79, which can be
removably inserted and locked into the breech by the locking ring 77. The
breech plug can be removed for loading of a projectile into the firing chamber
and
then inserted to close the breech during firing.
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Figure 8 is a perspective view of the breech assembly 18 mounted to the bottom
plate 62. This view shows the cooperating shapes of the breech plug 79 and
backplate 75. In use, the breech plug 79 can be inserted such that the lugs 80
situated on shoulders 81 pass through the cooperating aperture 82 in the
backplate 75. The inner surface (not shown) of the locking ring 77 is shaped
to
allow the lugs 80 to pass beyond the locking ring 77 when the locking ring is
in an
open position. The locking ring can then be rotated to a locked position, in
which
the inner surface of the locking ring 77 engages with the lugs 80, locking the
breech plug in place.
The breech plug 79 includes a protrusion 85 which sits within the firing
chamber
28, in order to position a projectile for firing. The breech plug 79 may also
be
shaped appropriately, so as to achieve desired flow characteristics within the
firing chamber 28. This may be achieved either by shaping the breech plug 79,
or by use of a shaped insert.
Figure 9 is a perspective view of an alternative breech plug which includes a
shaft 90 having a removable collar 91. Figure 10 shows the breech plug of
Figure 9, with a removable, shaped insert 92 arranged on the shaft 90 and held
in place by the collar 91 and fastener 93.
The shape of the breech plug 79, or the shape of the removable insert 92 can
be
adapted for any desired purpose, such as altering the range of the pneumatic
launcher, or adapting the pneumatic launcher for different types of
projectiles.
Furthermore, the breech plug operates to close or seal the breech during
firing.
For this purpose, a seal 95 may be provided, preferably between the breech
plug
and the bottom plate 62. Preferably, the seal 95 is situated between two
surfaces which lie against each other in a plane substantially transverse to
the
axis of the breech assembly 18 (where the axis of the breech assembly lies
along
an insertion direction of the breech plug). This orientation of the seal 95
provides
improved performance over prior systems, in which a seal has been provided
between circumferential faces. The seal 95 may be formed from rubber,
composite or any other suitable material.
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Figure 11 is an enlarged view of the breech plug 79 and bottom plate 62 (in
which the backplate 75 and locking ring 77 are not shown). This view clearly
shows the position of the seal 95.
Figure 12 is a cutaway perspective view of the valve section 16, with the
breech
plug 79 in place. Again, the backplate 75 and locking ring 77 are not shown in
this view.
Figure 13 is a cross-section of the barrel 17. The barrel 17 includes a
generally
cylindrical bore 100, through which the projectile is fired. However, the
barrel
also includes a number of ribs 101, which provide greater rigidity to the
barrel 17
without requiring a great deal of additional weight. The ribs may be external
ribs.
This improved rigidity provides significantly increased accuracy.
Figure 14 is a schematic diagram showing the various external valves and
conduits used to operate the launcher. Pressurised gas, preferably dry
nitrogen,
is held in a tank 105. This tank is connected by a conduit 106 with a three-
way
valve 107. In one position this valve 107 operates to feed pressurised gas
into
the trigger chamber 43 in the valve section 16 through conduit 108 in order to
close the firing valve. In a second position this valve 107 operates to feed
gas
through conduit 109 into the three gas chambers 10, 11, 12 to pressurise those
chambers. A one-way check valve 110 allows gas to flow from the conduit 109
into the conduit 108 but does not allow gas to flow in the opposite direction.
The chamber 43 is also connected via conduit 112 with a safety valve 113 and a
trigger valve 114. The safety valve is to be closed whenever the breech is
open,
and sensors and the like may be used to ensure that this is the case. When the
breech is closed, the safety valve 113 may be opened and the launcher may be
fired by opening the trigger valve 114 to release the pressure in the trigger
chamber 43 to the atmosphere.
Finally, various sensors and safety devices may be provided. Pressure release
or safety valves 115, 116 may be provided, and pressure gauges 118 may be
connected as required.
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The gas chambers may be pressurised for firing to a pressure in the range
about
40 to 600 pounds per square inch (psi), preferably in the range 100 to 400
psi.
the pressure chosen may depend on the desired range as well as the nature of
the projectile to be fired.
The firing chamber wall, sliding valve body, valve wall and the outer wall of
the
valve chamber may all be of generally cylindrical construction. This provides
for
ease of manufacture and alignment of the parts. In the assembled launcher,
these parts may be arranged substantially coaxially.
The outer valve chamber wall, bottom plate, top plate, valve wall, firing
chamber
wall, sliding valve body, breech assembly, breech plug and barrel may all be
formed from steel or any other suitable material.
The pneumatic launcher 1 has been described in general terms. However, while
the launcher is likely to have many and varied applications, it is expected to
be
particularly applicable to launchers used for triggering avalanches. Such
launchers generally fire a projectile having an explosive charge which
detonates
on or near a slope to trigger an avalanche.
The design of the valve section 16 provides improved reliability and a longer
lifetime for the various components. Furthermore, the valve section 16 is
easily
disassembled for removal or replacement of the firing valve.
While the present invention has been illustrated by the description of the
embodiments thereof, and while the embodiments have been described in detail,
it is not the intention of the Applicant to restrict or in any way limit the
scope of
the appended claims to such detail. Additional advantages and modifications
will
readily appear to those skilled in the art. Therefore, the invention in its
broader
aspects is not limited to the specific details, representative apparatus and
methods, and illustrative examples shown and described. Accordingly,
departures may be made from such details without departure from the spirit or
scope of the Applicant's general inventive concept.
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