Note: Descriptions are shown in the official language in which they were submitted.
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A device, charging unit and method of filling a borehole with an
explosive material
FIELD OF INVENTION
The invention relates to a device, in particular a device for
receiving an explosive material.
Beyond this, the invention relates to a charging unit.
Furthermore, the invention relates to a method of filling a borehole
with an explosive material.
BACKGROUND OF THE INVENTION
Explosive cartridges may be used in many technical fields for any
type of rock, rock mass, concrete or comparable material fragmentation.
GB 1,281,946 discloses an explosive cartridge comprising a casing
with electrically conductive end zones. An exploding wire or an electric
arc is provided for igniting the explosive charge. The wire or arc can be
short circuited by placing a length of removable metal foil between the
conductive zones. Individual cartridges can be connected together by
interlocking, screwing, by means of a sleeve, or by a bayonet connection.
The casing comprises plastics, cardboard or a wound paper strip. The
zones comprise metal foil; varnish containing conductive metal, graphite
or carbon black powder; or metal deposited chemically, electrolytically,
by evaporation in vacuum, or by cathodic projection.
When detonating in a borehole an explosive cartridge is creating
cracks and fragmentation in all directions around the hole. In typical rock
production blast this does not cause big problems as the bench face after
blasting can be scaled down with mechanical equipment and in that way
is made safe for the next blast.
However, in those situations where a blast is carried out along a
final rock wall or where in underground blasting the aim is to create
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(leave behind) a drift side wall as competent as possible, the strong
radial fragmentation all around the borehole is a problem. The amount
and length of cracking an explosive charge is creating in a borehole
depends amongst other factors on the pressure generated during
detonation.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a device and a method
enabling a smooth blasting in surface and underground applications.
In order to achieve the object defined above, a device, a charging
unit and a method of filling or partly filling a borehole with an explosive
material according to the independent claims are provided.
According to an exemplary embodiment of the invention, a device
for receiving an explosive material comprises a receptacle unit for
receiving the explosive material, and an anchoring unit, wherein the
receptacle unit is adapted to be flIled with explosive material from outside
of a borehole, wherein the anchoring unit is arranged on an outer surface
of the receptacle unit, and wherein the anchoring unit is adapted to
anchor the flexible receptacle unit in a borehole. In particular, the
explosive material may be used in the form of a bulk material or in the
form of so-called explosive cartridges.
According to an exemplary embodiment of the invention, a
charging unit comprises a device according to an exemplary embodiment
and an elongated container, wherein the device is arranged in the
elongated container. In particular, the elongated container may have a
cylindrical shape and/or may comprise or may be made of steel or hard
plastic.
According to an exemplary embodiment of the invention a method
of filling or partly filling.a borehole with an explosive material comprises
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introducing a device according to an exemplary embodiment into a
borehole, and filling the device with an explosive material from outside of
the borehole. In particular, the filling may be done by pumping or
blowing in the explosive material, like bulk explosives or explosive
cartridges. Thus, the explosives may be flexibly chosen from a wide
range of possible explosives. For this pumping an additional tube or pipe
may be used.
According to an exemplary embodiment of the invention a method
of filling a borehole with an explosive material comprises introducing a
charging unit according to an exemplary embodiment into a borehole,
and charging the device of the charging unit with an explosive material
and removing the elongated container. In particular, the method may
further comprise fixing the explosive charging element to the elongated
container. For example, the charging element fixing unit may be used to
fix the explosive charging element to the elongated container. In
particular, the charging or filling of the device may be made while the
elongated container is removed, i.e. at the same time, and/or the
charging itself may cause that the elongated container is removed or that
the filled device is removed (pressed) out of the elongated container, e.g.
by pumping the explosives into the device under application of a
relatively high pressure.
By providing a device having an anchoring unit it may be possible
to anchor the receptacle unit at a given predetermined distance to the
wall of the borehole, e.g. a centrally positioning may be possible, so that
the receptacle unit is arranged centred with respect to the borehole. In
particular, the receptacle unit and the anchoring unit may be formed by
two distinct units. For example, the anchoring unit may be formed by an
element which can be put over or pulled over the receptacle unit and may
be attached to the same, e.g. glued. Furthermore, the anchoring unit
may be adapted to decouple the explosive material and a borehole wall.
That is, the anchoring unit may be used to ensure that a gap is provided
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between the borehole wall and a filled receptacle unit efficiently
decoupling the same from each other. In particular, it may be ensured
that a wand of the receptacle unit may not come in direct contact with
the borehole wall. Since investigations have shown that leaving a gap,
e.g. an annulus gap, between the explosive charge, the receptacle can be
filled with, and the borehole wall may strongly reduces the damage or
fragmentation the explosives is creating, the anchoring of the receptacle
unit in the borehole may enable a smooth blasting in surface and
underground applications, like mining, tunnel construction, or tunnel
driving. The use of a receptacle unit, which may be adapted to receive an
explosive material and having an anchoring unit attached thereto, may
be an efficient way to enable a smooth blasting in surface and
underground applications even in strongly inclined boreholes or even in
vertical boreholes. In particular, the use of a device according to an
exemplary embodiment may possibly be advantageous over a partly
filling of the borehole with bulk explosives, i.e. explosives not filled into
receptacle units or cartridges, which filling with bulk explosives may be
done by pulling an explosive charging hose during charging out of a
borehole quicker than the filling with explosives is done, since this can be
done in general only with horizontal or slightly inclined boreholes. In
particular, the use of a device according to an exemplary embodiment
may possibly be even advantageous over the use of small diameter
explosive cartridges of about 20 mm to 25 mm which are charged into
boreholes of 40 mm to 50 mm, which also leads to the fact that the
boreholes are just partly filled with explosives. The use of a device
according to an exemplary embodiment of the invention may possibly be
more efficient to ensure that the borehole is just partly filled with
explosives to reduce the detonating pressure inside the borehole and
thereby possibly reducing the fragmentation around the boreholes. In
particular, according to an exemplary embodiment it may be possible to
build a continuous column charged with explosive material.
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Furthermore, the use of a device having an anchoring unit may
enable that the receptacle unit, e.g. explosive cartridge, string emulsion
or a tubular member filled with bulk explosives, may not be in contact
with parts of the borehole wall, and may even enabling that the
receptacle unit filled with an explosive charge is centred inside the
borehole, which may improve a decoupling of the explosive charge and
the borehole wall. Additionally, it may be possible to ensure a more
constant degree of a borehole filling by using a device according to an
exemplary embodiment, even under difficult and varying conditions, so
that a more constant decoupling may be enabled. Furthermore, the cross
section of the explosive may be more constant when using a device
according to an exemplary embodiment compared to the conventional
use of a bulk explosive. Thus, a detonating condition may be more
constant as well, so that the risk that the detonation stops in the
borehole due to a not constant cross section may be reduced when using
a device according to an exemplary embodiment.
In particular, the provision of at least one anchoring unit may
reduce the risk that the explosives the receptacle unit is filled with and/or
the receptacle unit itself is washed out, when the device is used in water
bearing strata.
Additionally, the use of an device according to an exemplary
embodiment may reduce the risk that small diameter receptacle units in
larger boreholes are overlapping, which possibly would reduce the
decoupling effect, or the risk of a gap between the receptacle units,
which possibly would produce a stop of the detonation, since the device
according to an exemplary embodiment comprises the anchoring unit
which may fix the positions of receptacle with respect to each other.
The term "receptacle unit" may particularly denote a unit which is
adapted to be charged with explosives. That is, an explosive cartridge
may not be called a "receptacle unit" in this sense, since an explosive
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cartridge is already filled with explosives, but may be used to fill or
charge a receptacle unit.
Next, further exemplary embodiments of the device will be
explained. However, these embodiments also apply to the charging unit,
and the methods of filling a borehole with an explosive material.
According to another exemplary embodiment of the device the
receptacle unit is a flexible receptacle unit. In particular, the flexible
receptacle unit may be a foldable receptacle unit.
A flexible receptacle unit may be in particular suitable to be filled
with an explosive material while ensuring that a borehole can be evenly
filled with the flexible receptacle unit. In particular, the provision of a
foldable receptacle unit may enable that the device is folded in a
container which can be easily introduced into a borehole and which can
be removed after the device is placed into the borehole while by
removing the folded receptacle unit will be unfolded.
According to another exemplary embodiment of the device the
anchoring unit is a centring unit. In particular, the device may comprise a
plurality of centring units. The centring unit(s) may be adapted to centre
the receptacle unit in a hole, borehole or the like. Furthermore, the
centring unit(s) may be glued, welded or vulcanized to an outside of the
receptacle unit, e.g. a flexible hose.
By centring the receptacle unit in the centre of the borehole it may
be possible to ensure that the decoupling between the receptacle unit
and the wall of the borehole may be maximized so that fragmentation
and damage around the borehole may be reduced.
According to another exemplary embodiment of the device the
receptacle unit is formed as a flexible hose, in particular as a plastic
hose. Specifically, the flexible hose may be formed by a thin plastic
material which is adapted to withstand a pressure of several bars, e.g.
between 5 bar and 15 bar, in particular about 10 bar, and/or to withstand
a force of gravity of the filled hose itself, e.g. in case the filled hose is
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arranged in a vertical borehole, which force may be up to 20 kN, in
particular, about 10 kN. A suitable thickness of a plastic hose or plastic
foil may be some tenth of a mm, e.g. a plastic foil having a thickness
between 0.1 mm and 2 mm, in particular about 0.5 mm. A length of the
receptacle unit, e.g. a plastic hose or any other suitable hollow or tubular
member, like a tube or a hollow cylinder, may be chosen in such a way
that it is about 20 cm longer than a borehole that is to be charged by the
plastic hose. For example, the length may be between 0.1 m and 100 m,
in particular the length may be between 1 m and 30 m. Due to the great
possible length of the receptacle unit the receptacle unit may also be
called an endless or continuous receptacle unit. In case a plastic hose is
used the hose may be stored on a barrel from which the hose may be
unwinded by pumping the explosives into the hose.
According to another exemplary embodiment of the device the
anchoring unit is formed as a springlike element. In particular each
anchoring unit may comprise a central annular part, which is adapted in
such a way that the receptacle unit is accomodatable into the annular
part, and may further comprise a flexible part, which is adapted in such a
way that the flexible part is able to fix the receptacle unit in a borehole.
Suitable materials, for the springlike element may be steel or plastic with
an elastic deformation behaviour which is high enough so that the
springlike elements really act like a springlike element, i.e. after a
deformation return to the state before the deformation. In particular, a
plurality of anchoring units or elements may be arranged or fixed on the
receptacle unit, e.g. a plastic hose. The anchoring units may have a
distance from each other which is chosen to be between 5 cm and 2 m, in
particular between 10 cm and 1 m.
According to another exemplary embodiment of the device the
flexible part is formed by a plurality of rod like elements. In particular,
the rod like elements may be formed by stiffeners, springs, legs or small
bars comprising and/or made of metal or plastic. In general, the term
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"flexible part" may particularly denote every element which is adapted to
have a pre-tension which is releasable in order to fix the receptacle unit
in a borehole. For example, each anchoring unit may comprise between
three and ten legs, in particular a minimum of three or six legs, wherein
the legs may be arranged in an equidistant arrangement along a
circumferential of the annular part, e.g. the angle distance between
neighboring legs is constant, e.g. in the case of three legs between each
pair of legs an angle of 1200 is provided.
According to another exemplary embodiment the device further
comprises an explosive booster unit, wherein the explosive booster unit is
attached to the receptacle unit. In particular, the explosive booster unit
may be attached to an end of the receptacle unit in such a way that this
end is sealed by the explosive booster unit. For example, the explosive
booster unit may be glued in such a way to one end of a receptacle unit,
which is formed by a hose, that this end is sealed by the explosive
booster unit. In particular, the explosive booster unit may have a
detonator hole which is adapted to receive a detonator. The explosive
booster unit may comprise or may be made of a highly explosive material
like TNT or PETN explosives. The provision of such an explosive booster
unit may be suitable measure to already provide an ignition mechanism
so that no additional preparation of the explosive charge may be
necessary. This may lead to the fact that the application of such a device
is simple so that even a non-expert person may be able to use it.
According to another exemplary embodiment of the device the
anchoring unit is adapted for decoupling the explosive material and a
borehole wall.
Next, further exemplary embodiments of the charging unit will be
explained. However, these embodiments also apply to the device, and
the methods of filling a borehole with an explosive material.
According to another exemplary embodiment of the charging unit
the elongated container comprises two walls which are arranged
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concentrically with each other, and the device is substantially placed
between the two walls. In particular, the two walls may be cylindrical.
More specifically, the receptacle unit and the anchoring units or anchoring
elements are arranged in a space built between the two walls. That is, an
outer one of the two walls has a greater diameter while an inner one of
the two walls has a smaller diameter so that a space between the outer
and the inner wall is formed into which the device can be placed. The wall
thickness of the container, which may also be called a protection
container, may be in the range between 0.1 mm and 10 mm, in
particular, between 0.5 mm and 5 mm and more particular in the range
between 1 mm and 3 mm. Preferably, an outside dimension or diameter
of the elongated container is sufficiently smaller than the borehole to be
charged with a decoupled charge so that it can be easily inserted into the
borehole.
According to another exemplary embodiment of the charging unit
the device is placed between the two walls, in such a way that the
anchoring unit is pre-tensioned. In particular, the term pre-tensioned
may denote that the anchoring or centring unit or units, e.g. the flexible
part, like springs or small elastic bars, has a pre-tension when arranged
between the walls which pre-tension will be released when the elongated
container is removed and thus the centring unit vacate or leave the space
between the two walls. In particular, the pre-tensioned state may be
distinguishable from a neutral state or released state.
According to another exemplary embodiment the charging unit
further comprises an explosive charging element, wherein the explosive
charging element is adapted to fill the device with an explosive material.
In particular, the explosive charging element may be an explosive
charging hose. The explosive charging hose may be adapted to be
insertable into the device or in a space formed by the inner wall of the
cylindrical container.
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According to another exemplary embodiment the charging unit
further comprises a charging element fixing unit, wherein the charging
element fixing unit is adapted to fix the charging element to the
elongated container.
Summarizing an exemplary aspect of the invention may be seen in
the fact that a possibly more efficient smooth blasting process is
proposed in which process bulk explosives is charged inside a charging
unit, which may be called a continuous blast charging unit (CONT-BLAST
charging unit). The CONT-BLAST charging unit may comprise a foldable
plastic hose, expandable centring units, an explosives booster, and a
cylindrical protection container. When charging bulk explosives with the
help of the CONT-BLAST charging unit into a borehole, in particular from
outside of the borehole, a continuous cylindrical 100% decoupled
explosives column which may be automatically centred in the borehole
may be formed. The diameter of the charge formed in the borehole may
be easily adapted to the desired decoupling ratio by just changing the
diameter of the foldable plastic hose. The foldable plastic hose may be
made of any type of thin plastics, able to withstand a charging pressure
in the range of several bars and the pulling forces acting on the hose in
vertical holes. The length of the plastic hose may be about 20 cm longer
than the borehoie charged, between 1 m and 30 m, for example. The thin
plastic hose may carry on its outside at distances between 10 cm and
100 cm small expandable centring units, which may centre the plastic
hose charged with explosives inside the borehole. The expandable units
may be of such a nature that the plastic hose may be kept from pulled
out of the borehole during the charging process and from sliding down
inside the borehole due to gravity forces. At the bottom the CONT-BLAST
charging unit may carry an explosives booster with a small hole in it for
putting in a detonator before charging. The explosives booster may be
attached, e.g. glued, to the foldable plastic hose. The foldable plastic
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hose and the expandable centring units may be stored inside a protection
container before charging.
The aspects defined above and further aspects of the invention are
apparent from the exemplary embodiment to be described hereinafter
and are explained with reference to this exemplary embodiment. It
should be noted that elements described in association with different
embodiments or aspects may be combined.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in more detail hereinafter with
reference to examples of embodiment but to which the invention is not
limited.
Fig. 1 schematically illustrates an explosives charging unit
according to an exemplary embodiment of the invention.
Fig. 2 schematically illustrates expandable centring units which
may be used in an exemplary embodiment of a device.
Fig. 3 schematically illustrates a borehole charged with an
explosives charging unit according to an exemplary embodiment of the
invention.
DESCRIPTION OF EMBODIMENTS
The illustration in the drawing is schematically. In different
drawings, similar or identical elements are provided with similar or
identical reference signs.
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In the following, referring to Fig. 1, an explosives charging unit
100, according to an exemplary embodiment is described. Fig. 1
schematically shows a cross-sectional view of the explosives charging
unit 100 which comprises a cylindrical protection container 101. In the
cylindrical protection container 101 a device 102 is arranged, comprising
a foldable plastic hose 103, expandable or elastic centring units 104 and
an explosives booster 105. The expandable centring units 104 and the
explosives booster 105 are attached, e.g. glued, to the foldable plastic
hose 103. Into the explosives booster 105 a detonator hole 106 is formed
which is adapted to accommodate a detonator for ignition of the
explosives booster 105. As shown in Fig. 1 the foldable plastic hose 103
and the expandable centring units 104 are arranged between two walls of
the cylindrical protection container 101 in such a way that the
expandable centring units 104 are compressed and pre-tensioned.
Furthermore, an explosives charging hose 107 is shown in Fig. 1 which is
attached to the cylindrical protection container 101 by a charging hose
fixing unit 108. The explosives charging unit 104 is introduced between
inner walls 109 shown in the cross-sectional view of Fig. 1 and which are
formed by an inner cylinder of the cylindrical protection container 101.
The explosives charging hose 107 can be used to charge the foldable
plastic hose 103 with explosives, which is indicated by the arrow 110.
Fig. 2 schematically shows an expandable centring unit 104 in an
enlarged view. Fig. 2a shows a cross-sectional view of the expandable
centring unit 104. The expandable centring unit 104 comprises a central
annular part 211 and a plurality of legs 212 which are sticking out from
the central annular part 211. In Fig. 2a three legs 212 are shown,
however in principle any suitable number is possible like six or even more
than six. Preferably, the minimum number of legs is three. Fig. 2b shows
a schematic longitudinal sectional view of an expandable unit 104, which
also shows the central annular part 211 and a plurality of legs 212. The
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legs 212 are glued, welded or vulcanized to the foldable hose 104 and
may be made of steel or plastic with high elastic deformation behavior.
In Fig. 3, the explosives charging unit 100 of Fig. 1 is shown after
being introduced in a borehole and charged with explosives. Thus, Fig. 3
shows a borehole 313 in a rock mass 314. Into the borehole 313 the
explosives charging unit 100 is introduced, however since the device 102
is already charged with explosives the cylindrical protection container 101
of Fig. 1 is removed. The foldable plastic hose 103 of the device 102 is
charged with an explosive 315. Since the cylindrical protection container
101 of Fig. 1 is removed the compressed expandable centring units 104
of Fig. 1 are expanded and fixing the device into the borehole 313. In
particular, the foldable plastic hose 103 is centred in the borehole 313.
Furthermore, a detonator 316 is introduced in the detonator hole 106 of
the explosives detonator 105. For ignition of the detonator an electric
cable or a so-called non electric shock tube 317 is attached to the
detonator 316.
In the following some geometrical dimensions and material
properties of the charging unit 100 are explained. The outside diameter
of the protection container 101 is sufficiently smaller than the borehole
313 to be charged with a decoupled charge, so that it can be easily
inserted into the borehole. The wall thickness of the protection container
is in the range of 1 mm to 3 mm and may be made of steel or hard
plastic. Preferably, the explosives booster consists of a cast PETN
explosives or TNT or any other type of high explosives. It has a slightly
smaller diameter than the inner diameter of the protection container. So
it can be inserted into the bottom of the protection container. The
booster is glued to the foldable plastic hose.
The diameter of the foldable plastic hose is in minimum around
10 mm smaller than the inner diameter of the protection container. The
actual size depends both on the diameter of the borehole and the
decoupling ratio desired, e.g. ration between borehole diameter and
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charge diameter. The foldable plastic tube may be made of a strong thin,
e.g. some tenth of a mm, plastic foil, which is able to withstand a
pumping pressure of the explosives in the range of several bars and able
to withstand also the pulling forces of the weight of the explosives when
charged into a vertical hole.
The expandable centring units are glued, welded or vulcanized
outside on the foldable plastic hose at distances sufficient to centre it in
the borehole during charging. The expandable centring units work like
springs. They may be made of steel or plastic with a high elastic
deformation behavior. They are of such a nature that they can be
compressed and stored inside the protection container. When they are
pulled out of the protection container they bounce up and tight
themselves against the borehole wall. Typically they have in minimum
three or six legs, looking into one or two directions after bouncing up.
Furthermore, the explosives charging hose is small enough to be
inserted into the Continuous-Blast charging unit (CONT-BLAST charging
unit). It is attached to the CONT-BLAST charging unit through a small
detachable fixing unit.
In the following some working principles of the CONT-BLAST
charging unit will be explained in more detail.
1. Putting a detonator, e.g. electric, non electric or electronic,
into the small hole in the booster at the bottom of the CONT-BLAST
charging unit.
2. Inserting an explosives charging hose, which is connected to
an explosives charging/manufacturing unit (for site sensitized or site
mixed emulsion explosives or cartridges) into the CONT-BLAST charging
unit and fixing the explosives charging hose to the charging unit by a
fixing unit.
3. Inserting the explosives charging hose with the CONT-BLAST
charging unit at the front end into a borehole until it reaches the bottom
of the borehole.
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4. Pumping bulk emulsion explosives through the charging hose
into the CONT-BLAST charging unit by the explosives manufacturing unit.
5. The pumping pressure pushes first the booster out of the
protection container and at the same time the foldable plastic tube is
continuously pulled out of the protection container while being filled with
explosives.
6. Every 10 cm to 100 cm one centring unit is pulled out of the
protection container by the foldable plastic tube and bounces up centring
the foldable plastic tube full with explosives inside the borehole.
7. When the explosives charging reaches the end of the
borehole, the foldable plastic tube carrying at the end one last centring
unit is completely pulled out of the protection container. The borehole is
now filled with a centred decoupled explosive charge, ready to be fired.
8. Detaching the charging hose from the empty protection
container, which might be re-used.
Summarizing a device for receiving an explosive material according
to an exemplary embodiment may enable that a decoupled continuous
explosives charge is centred automatically in the borehole and is not in
contact with borehole walls so that the decoupling may be ideally.
Furthermore, a decoupled charge with a continuous cylindrical cross
section may be formed which may be also formed in vertical and inclined
holes. In particular, the device may enable that the degree of borehole
filling, which corresponds to the decoupling ration, under production
conditions may be realized precisely. Additionally, the cross section of the
explosives may be cylindrical and constant and therefore the detonating
conditions may be constant as well, thus possibly also reducing the risk
that the detonation stops in the borehole. Moreover, the contact between
the initiation booster and the decoupled charge may be full and ideal for
a good initiation or ignition. Due to the anchoring or centring units of the
device the explosives may not be washed out of the borehole when
working in water bearing strata and there may be no risk of a gap in the
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explosives column. Beyond this, the system may be easily used with
existing emulsion explosives and charging units while the system itself
may be manufactured at low cost.
It should be noted that the term "comprising" does not exclude
other elements or features and the "a" or "an" does not exclude a
plurality. Also elements described in association with different
embodiments may be combined. It should also be noted that reference
signs in the claims shall not be construed as limiting the scope of the
claims.
