Note: Descriptions are shown in the official language in which they were submitted.
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CONNECTOR BLOCK CONFIGURED TO INDUCE A BEND IN SHOCK
TUBES RETAINED THEREIN
FIELD OF THE INVENTION
The present invention relates to connector blocks for positioning
shock tubes in signal transmission relationship with the percussion-actuation
end of a detonator. In particular, the present invention relates to connector
block designs that improve the efficiency of detonator to shock tube energy
transmission.
BACKGROUND TO THE INVENTION
Blasting operations frequently trigger a series of explosions in an
exact order, with precise timing. For this ptupose, blasting systems have
been developed that employ shoclc tubes (also known as signal transmission
lines) that transfer a blast initiation signal to an explosive charge. A
signal
from a single shock tube can be transferred to multiple shock tubes in a
blasting system via the use of connector block / detonator assemblies,
thereby permitting the initiation of multiple explosive charges in a
controlled
mazmer.
Safety and reliability are paramount for any blasting system, and
efficient sliock tube initiation is an important factor in this regard. Shock
tube initiation failure results in unexploded charges at the blast site, with
inevitable safety concerns. Moreover, the reliable iiiitiation of shock tubes
ensures that the required blasting pattern is effected.
The efficiency of shock tube initiation depends primarily upon
connector block design. Reliable initiation of shock tubes requires sufficient
energy to be transferred from the base charge of the detonator to the shock
tubes, thereby compressing the shock tubes extremely rapidly to initiate
thein.
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The shock tube retention means of a connector block holds one or
more shock tubes in contact with, or close proximity to, the percussion-
actuation end of the detonator retained within the block. Importantly, the
shock tube retention means ensures that the shock tubes are retained in signal
transmission relationship with the detonator. Several examples of comiector
block designs are known in the art, which comprise a shock tube retention
means for the arrangement of at least one shock tube adjacent to the
percussion-actuation end of the detonator. These examples generally
encoinpass the use of a clip-like member, integral with the connector block,
for retaining the shock tubes within a slot formed between the clip-like
member and the percussion-actuation end of the detonator. In this way, the
shoclc tubes are retained in signal transmission relationship with the end of
the detonator.
In one example, United States Patent 5,204,492, issued to ICI
Explosives USA Inc. on Apri120, 1993, discloses a detonator assembly for
initiating up to eight traiismission lines. The assembly comprises a
connector block that houses a low strength detonator. The connector block
comprises a confining wall surrounding the closed end of the low strength
detonator. One or more signal transmission lines can be inserted through a
gap in the confining wall and operatively confined adjacent to the
percussion-actuation (closed) end of the low strength detonator.
CoiTesponding United States Patents 5,171,935 and 5,398,611, issued
to the Ensign Biclcford Coinpany on December 15, 1992 and March 21, 1995
respectively, disclose a connector block having a housing with a channel
formed therein for receiving a low energy detonator. The coimector block
further comprises a tube engaging member for holding transmission tubes
adjacent an end of the chaiuiel, wherein the tube engaging member is
attached to the connector block via a resiliently deformable seginent.
Transmission tl.ibes may be inserted into a slot formed between the housing
and the tube engaging member.
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In another example, United States Patent 5,703,319, issued to the
Ensign Bickford Company on December 30, 1997, discloses a connector
block comprising a clip meinber. The clip member cooperates with the
signal transmission end of a body member to define a slot for receiving one
or more signal transmission lines in communication with the output end of a
detonator. The clip member is characterized in that it comprises a section of
continuously decreasing tliiclcness to facilitate lateral insertion of signal
transmission lines into the slot by deformation of the clip member.
United States Patent 5,499,581 issued to the Ensign-Biclcford
Compauy on March 19, 1996, discloses a connector block design for
connecting signal transmission lines in a blasting system. The patent
discloses improved means for securing a detonator within the connector
block via a displaceable locking member. The connector block may further
coznprise a flexible, cantilevered line retaining means to receive one or a
plurality of outgoing signal transmission lines.
In a final example, United States Patent 5,659,149 issued to the
Ensign-Bickford Company on August 19, 1997, discloses a connector block
including a slot configured to constrain just a single acceptor line retained
therein in an undulate configuration i.e. a configuration having consecutive
(multiple) bends or kinlcs including zig-zags. In this way the acceptor line
is
retained more securely within the slot by virtue of the multiple contortions
introduced into the acceptor line, thereby preventing unwanted sliding or
displacement of the connector block along the acceptor line.
The connector blocks disclosed by the prior art generally retain at
least one shoclc tube in signal transmission relationship with the percussion-
actuation end of a detonator by confining the shoclc tube(s) within a slot.
Preferably, the slot is dimensioned to retain the shock tubes in signal
transmission relationship with the detonator, without unduly squeezing the
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shock tubes. In this way, the energy of detonator actuation compresses the
shock tubes extremely rapidly, thereby resulting in their initiation.
The inventor of the present application has determined that optimal
energy transfer requires contact between the shock tubes and the surface of
the percussion-actuation end of the detonator (or the surface of a positioning
surface, which is in contact with the detonator). However, the inventor has
noted that dimensional tolerances in the manufacture of connector blocks and
shock tubes can result in poor shock tube / detonator contact. For this
reason, the insertion of an undersized shock tube into an oversized slot of a
connector block can result in poor shock tube / detonator contact, and
reduced transfer efficiency of actuation energy. Therefore, manufacturing
tolerances can contribute significantly to shock tube initiation reliability.
Furthermore, an undersized shock tube in an oversized slot would allow the
block to slide uncontrollably to other undesirable locations along the shock
tube.
In addition, plastic coxulector blocks comprising flexible shock tube
retention means can exhibit variations in slot dimensions. The connector
blocks of the prior art generally comprise flexible and resilient shock tube
retention means in the form of a clip, for holding the shock tubes in signal
transmission relationship with the percussion-actuation end of a detonator.
The flexibility of the shock tube retention means can permit facile shock tube
insertion. However, the inventor of the present application has detennined
that shock tube retention means of this kind may not properly reassume their
original shape after distortion, thereby affecting the width of the shock tube
retention slot. Moreover, the presence of one or more shock tubes within the
slot can alter the configuration of the shock tube retention means, thereby
affecting slot widtll for subsequent shock tube insertion. These factors may
further increase the risk of iinproper shock tube / detonator contact within
the
connector block.
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Accordingly, there is a need for improved connector block designs,
wherein shock tubes are positioned in efficient signal transmission
relationship with the percussion-actuation end of a detonator, and preferably
in inaterial contact with the detonator.
5
SUMMARY OF THE INVENTION
An object of the preseiit invention, at least in a preferred form
thereof, is to provide a connector block, wherein shock tubes are preferably
retained in firm contact with the percussion-actuation end of a detonator. In
this way, air gaps between the detonator and the shock tubes are essentially
eliminated, thereby increasing the energy transfer efficiency from the
detonator to the shock tubes.
It is a further object of the present invention, at least in a preferred
form thereof, to provide a comiector block wherein shock tubes are
positioned accurately in signal transmission relationship with the percussion-
actuation end of a detonator, wherein air gaps resulting from manufacturing
tolerances are virtually eliminated.
It is a further object of the present invention, at least in a preferred
form tliereof, to provide a comiector block, wherein the connector block is
substantially prevented from sliding along the shock tubes located within the
slot of the connector block.
Conventional connector block designs include a`straight' slot for the
retention of shock tubes. As will be apparent from the foregoing, a straight
slot presents significant disadvantages with regard to the security of shock
tube retention, and the possibility of the connector block being slidably
displaced along the tubes. Moreover, previous attempts to address these
issues have lead to the generation of comlector blocks configured to
constrain shock tubes in a contorted undulate configuration within the block,
in which multiple bends or lcinks are introduced into the shock tube(s) (see
United States Patent 5,659,149). However, the inventors have found that
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such contortions render the shock tubes difficult to insert into the connector
blocks, and
can present difficulties with maintaining optimal signal transmission.
The inventors unexpectedly found that the connector blocks of the present
invention, in which a single principle bend is introduced into the shock
tube(s), allows for
optimization of multiple connector block attributes. The connector blocks
disclosed herein
permit relatively facile shock tube insertion, excellent detonator-to-shock
tube signal
transfer efficiency, secure retention of shock tubes, and uptake of unwanted
tolerances in
connector block or shock tube manufacture. Moreover, unlike the connector
block designs
disclosed in US 5,659,149, the connector block of the present invention permit
insertion of
a plurality of shock tubes.
Therefore, in a first embodiment there is provided a connector block for
retaining at
least one shock tube in signal transfer relationship with a detonator, the
connector block
comprising: a housing having a bore formed therein for receiving a detonator
provided
with a percussion-actuation end; and a shock tube retention means defining
with said
housing a slot for receiving therein at least one shock tube and holding said
at least one
shock tube in sigrial transfer relationship with said percussion-actuation end
of said
detonator present in said bore, said slot having an entrance for allowing
insertion of said at
least one shock tube into said slot; wherein at least one of said housing and
said shock tube
retention means adjacent to said slot is configured to induce a single~,
shallow bend in said
at least one shock tube passing within said slot, said single, shallow bend
comprising a
non-reversing smooth arcuate curve within said slot, said curve having a
centre or focus
located outside the region of the slot.
In an alternative embodiment, there is provided a connector block for
retaining at least one
shock tube in signal transfer relationship with a detonator, the connector
block comprising:
a housing having a bore formed therein for receiving a detonator provided with
a
percussion-actuation end; and a shock tube retention means defining with said
housing a
slot for receiving therein at least one shock tube and holding the shock
tube(s) in signal
transfer relationship with the percussion-actuation end of the detonator
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present in the bore, the slot having an entrance for allowing insertion of the
shock tube(s) into the slot, characterized in that at least one of the housing
and the shoclc tube retention meaiis includes at least one projection facing
the
slot, which projection causes the shock tube(s) positioned in the slot to bend
in a region passing through the slot.
The invention also relates to a detonator assembly comprising a
connector block as defined above, a detonator positioned within the bore of
the connector block housing and at least one shoclc tube retained within the
slot of the connector block.
Preferably, the connector blocks of the present invention induce the
shock tubes to contact the percussion-actuation end of the detonator. In an
alternative embodiment, the colulector bloclcs of the present invention fiu-
ther
coinprise a positioning membrane for positioning the surface of the
percussion-actuation end of the detonator in signal transmission relationship
with the slot. In this way, the slot may be defined in part by the positioning
membrane. The corresponding connector blocks are preferably configured to
ensure the shock tubes contact the positioning surface, which contacts the
percussion-actuation end of the detonator. The positionh-ig membrane may
partially or conlpletely enclose the signal transmission end of the bore.
In an alternative embodiment of the present invention, at least one of
the housing or the shock tube retention means comprise two projections
configured to induce a bend in the shock tube or shoclc tubes deposited
witllin the slot of the connector block.
Preferably, the connector bloclcs of the present invention are suitable
for llousing a detonator with a hemispherical percussion-actuation end. In
this way, the shock tubes may be arranged and retained within the slot
equidistant from the initiation poirit of the heinispherical base charge
witliin
the percussion-actuation end of the detonator. In one einbodiment, the shock
tubes may be bent towards the percussion-actuation end of the detonator. In
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an alternative embodiment, the shock tubes may be bent away from the
percussion-actuation end of the detonator.
The present invention encoinpasses connector blocks that induce one
or more shock tubes positioned therein, to beiid either towards or away from
the detonator, whilst preferably contacting the percussion-actuation end of
the detonator (or a positioiiing membrane in contact with the percussion-
actuation end of the detonator).
The corulector block configuration of the present invention induces a
single principle bend (preferably a shallow arcuate curve) in one or several
shock tubes as they pass within the slot, to improve the signal transmission
and / or contact of the detonator with the shoclc tube(s). Advantageously, the
present invention inalces it possible to retain a plurality of shock tubes in
signal transinission relationship with a detonator.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a longitudinal cross-section of a connector block
according to a first preferred embodiment of the present invention;
Figure 2 is a longitudinal cross-section of a connector block
according to a second preferred embodiment of the present invention;
Figure 3 is a Iongitudinal cross-section of a connector bloclc
according to a third preferred embodiment of the present invention;
Figure 4 is a longitudinal cross-section of a connector block
according to the present invention, the longitudinal cross-section taken
perpendicular to the cross-sections shown in Figures 1, 2, or 3; and
Figure 5 is a longitudinal cross-section of a connector block
according to a fourth preferred einbodiment of the present invention.
DEFINITIONS
"Bore" - either a hole (preferably, but not necessarily, cylindrical)
rtulning though the interior of the coiuiector block of the present invention,
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or alternatively an open cliaiulel or groove formed in a side of the coimector
block, for the housing of a detonator therein.
"Bend" - a non-reversing smooth arcuate curve (as opposed to a
sharp angled kinlc or right-angle bend) positioned within a slot of a
connector
block in a region of a percussion-actuation end of a detonator. The center or
focus of the curve is generally located outside the region of the slot of the
connector block (i.e. in the direction of the longitudinal axis of the bore,
more distant than the nearest and furthest parts of the slot to the housing).
Preferably, the bend is so shallow that the bend defines a curve having a
centre or focus located a distance from the curve that is longer than half the
length of the comiector block. More preferably, the bend is even shallower,
such that the bend defines a curve having a centre or focus located a distance
from the curve that is longer than the connector block.
"Bend towards the percussion-actuation end of the detonator" - a
configuration of at least one shock tube, wherein the bend in the at least one
shock tube is orientated in accordance with the embodiment illustrated in
Figure 1.
"Bend away from the percussion-actuation end of the detonator" - a
configuration of at least one shock tube, wherein the bend in the at least one
shock tube is orientated in accordance with the embodiment illustrated in
Figure 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The connector block of the present invention is configured to
iinprove the positioning of shock tubes relative to the percussion-actuation
end of a detonator (most preferably, air gaps between the shock tubes and the
detonator, resulting from manufacturing tolerances, are substantially
eliminated). For this purpose, the present invention provides significant
improvements over existing coiulector block designs, by reducing the
possibility of improper shock-tube / detonator contact within the connector
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block. The connector blocks of the present invention are preferably adapted
to induce a single (or single principle) slight bend in the shock tubes
inserted
therein. In this way, the shock tubes are biased into signal transmission
relationship with the detonator, and are forced to adopt a configuration that
5 increases the possibility of optimal material contact and minimal separation
distance between the shock tubes and the detonator percussion-actuation
surface, despite variations in dimensions resulting from normal tolerances in
the manufacture of the connector blocks, shock tubes and detonators.
Shock tubes are manufactured to exhibit a degree of resilience to
10 bending forces, particularly over short distances of, for example, a few
centimeters in length. For this reason, a region of a shock tube inserted
within a connector bloclc will tend to be straight (unless a bending force is
applied). The comlector blocks of the present invention utilize the bending
resilience of shock tubes to improve the positioning of the shock tubes within
the connector block. For this purpose, the connector blocks of the present
invention comprise a slot, defined in part by a shock tube retention means on
one side of the slot, and the detonator housing on the other side of the slot,
wherein the slot is configured to induce a bend in one or more shock tubes
deposited therein. In this way the shoclc tubes are forced to bend against a
bias, and into an appropriate position adjacent the percussion-actuation end
of a detonator.
It is believed that any degree of bending will improve shock tube
positioning relative to the surface of the percussion-actuation end of a
detonator. However, the preferred degree of shoclc tube bending will depend
upon the expected degree of tolerance in the system. For example, if the
shock tubes are lazown to have a diameter of 3m1n 10% (due to tolerance)
then the slot should be configured to induce a sufficient bend in the shock
tubes so that a shock tube of (e.g. of 2.7mm diameter) is accurately
positioned adjacent the end of the detonator. Any degree of bending is
expected to improve both detonator to shock tube energy transmission, and
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shoclc tube retention within the connector bloclc. Preferably, the degree of
shoclc tube bending should zlot be so great as to substantially reduce the
diameter of (ox induce a kinlc into) the shock tube(s) since this may reduce
initiation efficiency. Hence, i.n certain embodiments the present invention
teaches away from United States Patent 5,659,149 by generally avoiding
connector block coiifigurations that cause contortions or other undulations in
the shoclc tubes retained tllerein.
The present invention encoinpasses any slot configuration that
induces a bend in the shoclc tubes inserted therein. Particularly preferred
embodiments of the present invention will be illustrated with reference to the
accompanying drawings.
Figure 1 illustrates a connector block I comprising a housing 2 with a
bore 3 ruluiing longiti.idinally througll the housing. The bore is configured
for receiving a detonator 4, the detonator having a percussion-actuation end 5
and a closure crimp 6. The bore is configured to position the percussion-
actuation end of the detonator in energy communicating relationship with a
slot 7 for retaining at least one shock tube 8 therein (note that only one
shoclc
tube is visible in Figure 1, but there would normally be several additional
shoclc tubes present in the slot 7 in front of and behind the plane of the
paper
- see Fig. 4). The slot is def.ned in part by a shock tube retention means 9,
and the adjacent housing 2. The shock tube retention meaiis 9 may coinprise
a flexible, resilient material, or may comprise a rigid material. Preferably,
the shock tLibe retention means 9 sliould be sufficiently rigid to bend the
shock tubes without suffering undue deformation itself.
The slot 7 is dimensioned and configured to receive at least one
shock tube in such a way that a bend 8a within the slot (as shown) is induced
in part in each shock tube located therein. The bend improves the contact
between the slioclc tubes and the percussion-actuation end 5 of the detonator.
In the embodiment shown in Figure 1, the bend 8a in the shock tube is
induced by two projections 10 and 11, integral with the shock tube retention
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means 9, and protruding into the slot 7 at each side thereof. In this way, the
shock tube is forced to bend towards the detonator against the bias of its own
stiffness, and exit the slot at positions 12 and 13. Importantly, a region 14
of
the shock tube adjacent the percussion-actuation end 5 of the detonator is
caused to contact the detonator, wliich protrudes slightly into the slot froni
the bore 3, thereby optimizing signal transmission in the event of detonator
actuation. Although less preferred, similar shock tube / detonator contact can
be attained with the provision of only one of projections 12 and 13 shown in
Figure 1.
A further embodiment of the present invention is illustrated in
Figure 2. The embodiment encoinpasses a connector block 20 comprising a
housing 21 witli a bore 22 running longitudinally through the housing. The
bore is configured to receive a detonator 23 having a percussion-actuation
end 24 aiid a closure crimp 25, and to position the percussion-actuation end
24 of the detonator in signal transfer relationship with a slot 26. The slot
is
dimensioiied for retention of at least one shoclc tube 27 in energy
communicating relationship with the percussion-actuation end of the
detonator (note that the cross-section of the connector block is parallel with
the longitudinal axis of the shock tubes located therein, and therefore only
one shock tube is shown in Figure 2). Furthermore, the slot is defined in part
by a shock tube retention zneans 28, and the adjacent parts of the housing 21.
The shock tube retention means inay comprise a flexible; resilient material,
or may comprise a more rigid material, as described for the embodiment
shown in Figure 1.
The slot 26 is dimensioned and configured to receive at least one
shock tube 27, and induce a bend 27a in each shock tube located tllerein. The
bend improves the contact between the shock tubes and the percussion-
actuation end 24 of the detonator. In the embodiment shown in Figure 2, the
bend 27a in the sllock tube is induced by two projections 29 and 30, integral
with the housiiig 21, and protruding into the slot 26. In this way, the shock
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tube is forced to bend away from the detonator against a bias, and exit the
slot at positions 31 and 32. Importantly, a region 33 of the shock tube
adjacent the percussion actuation end of the detonator is forced into
juxtaposition with the detonator, thereby optimizing signal transmission in
the event of detonator actttation. In an alternative embodiment, a region of
the shock tube may be induced to contact an outer surface 34a of a
positioning membrane 34 (shown in broken lines in the Figure). The inner
surface 34b of the membrane is in energy commtulicating relationship with
the percussion-actuation end 24 of the detonator. The positioning membrane
helps the user to insert the detonator into the bore 22 to the correct depth
as
the meinbrane acts as a stop. Altlzough less preferred, similar shock tube /
detonator contact can be attaiized with the provision of only one of
projections 29 and 30 shown ii1 Figure 2.
The embodiments illustrated in Figures 1 and 2 provide for
alternative shock tube configurations, wherein the shock tubes may bend
towards the surface of the detonator (Figure 1), or the shoclc tubes bend away
from the surface of the detonator (Figure 2). Either shock ttibe configuration
is suitable for reducing the presence of gaps between the detonator and the
shock tubes resulting from tolerances in the connector block and/or the shock
tubes. However, witllout wishing to be bound by theory it is believed that
the embodiment illustrated in Figure 1 may provide improved shock tube /
detonator contact over the embodiment shown in Figure 2. In this regard, by
bending the shock tubes towards (ratlier than away from) the detonator
surface the length of shock tube / detonator contact is increased, and the
average distance between the shock tube and the detonator stirface in the slot
is reduced. These factors are expected to provide improved efficiency of
detonator to shock tube energy transmission upon detonator actuation.
A fiirther embodiment of the present invention is illustrated in
Figure 3. In this regard, the slot has an arcuate shape in cross-section,
relative to the longitudinal axis of the shock tube or shoclc tubes. The
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embodiment encoinpasses a connector block 40 comprising a housing 41
with a bore 42 ruiming longitudinally through the housing. The bore is
configured to receive a detoi-iator 43 comprising a percussion-actuation end
44 and a closure crimp 45, and position the percussion-actuation end of the
detonator in signal transfer relationship with a slot 46. The slot is
dimensioned for retention of at least one shock tube 47 in energy
communicating relationship witll the percussion-actuation end of the
detonator (note that the cross-section of the connector block is parallel with
the longitudinal axis of the shock tubes located therein, and therefore only
one shock tube is showil in Figure 3). Furtllermore, the slot is defined in
part
by a shock tube retention means 48, and the housing 41. The shock tube
retention ineans may comprise a flexible, resilient material, or may comprise
a more rigid material, as described for the embodiment illustrated in
Figure 1.
The slot 46 is dimensioned and configured to receive at least one
shock tube, and induce a bend in each shoclc tube located therein. The bend
improves the contact between the shock tubes and the percussion-actuation
of the detonator. In the embodinient shown in Figure 3, the bend in the shoclc
tube(s) is induced by the shape of the slot in cross-section (relative to the
longitudinal axis of the shock tubes located in the slot). In this way, the
shock tube(s) are forced to bend towards the detonator against a bias, and
exit the slot at positions 49 aild 50. Importantly, a region of each shock
tube
51 adjacent the percussion actuation end of the detonator is forced into
juxtaposition witli the detonator, thereby optimizing signal transmission in
the event of detonator actuation. In ati alternative embodiunent, a region of
the shock tube znay be induced to contact a positioning surface, wherein the
positioning surface is in energy cominunicating relationship with the
percussion-actuation end of tlae detonator.
The present invention fi.irther encompasses a connector block similar
to the connector block illustrated in Figure 3, wherein the slot is of arcuate
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cross-section and induces the shock tube or shock tubes located therein to
bend away from the detonator, whilst inducing contact with the percussion-
actuation end of the detonator.
To clarify an arrangement of the shock tubes within the slot, a
longitudinal cross-section of a preferred connector block of the present
invention is illustrated in Figure 4. In this regard, the longitudinal cross-
section is taken perpendicularly to the cross-sections illustrated for the
embodiments of the invention shown in Figures 1, 2, and 3. Moreover,
Figure 4 illustrates a preferred embodiment of the invention, wherein the
percussion-actuation end of the detonator is hemispherical, and the shock
tubes are arranged in the slot around the surface of the percussion-actuation
end of the detonator, equidistant from the initiation point of the
hemispherical base charge. The connector block 60 comprises a plastic
housing 65 with a bore 61 running longitudinally through the housing for
receiving a detonator 62 therein, with the percussion-actuation end 63 of the
detonator in signal transmission relationship with a slot 64. The slot is
defined in part by the housing 65 and a shock tube retention means 66, and
is configured to retain at least one shock tube 67 in signal transmission
relationship with the percussion-actuation end 63 of the detonator 62. The
slot is configured to induce a bend in the shock tubes located therein (the
bend in the shock tubes is not visible in Figure 4, since the cross-sectional
view illustrates the shock tubes perpendicular to their longitudinal axis).
The slot comprises an entrance, which allows lateral insertion of one or
more shock tubes into the slot. Preferably, the slot is dimensioned to permit
insertion of up to six shock tubes.
A further preferred embodiment of the present invention is
illustrated in Figure 5. The embodiment provides for a connector block 80
that induces a bend in the shock tube(s) located therein, to retain the shock
tube(s) in energy transmission relationship with the percussion-actuation
end 82 of a detonator 83. The connector block comprises a housing 85 with a
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16
longitudinal bore 84 rumiing though the housing for locating the detonator
83 therein. The connector block further comprises a shock tube retention
means 86, which together with the housing 85 defines a slot 87.
In contrast to the embodiments illustrated in Figures 1 and 2, the
connector block comprises projections 88 and 89 on the housing, and
projections 90 and 91 on the shock tube retention means (90 and 91). In this
way, projections 90 and 91 bend the shock tube(s) towards the detonator and
push region 92 of the shock tubes onto the surface of the percussion-
actuation end of the detonator.
The improvement in the preferred embodiment illustrated in Figure 5
relates to the additional projections 88 and 89 present on the housing. The
projections 88 and 89 alter the configuration of the shock tube(s) as they
exit
the slot at positions 93 and 94. The projections 88 and 89 induce the shock
tubes to bend in a direction opposite to the bending influence of projections
90 and 91. In this way, the shock tubes are bent away from one another as
they exit the slot, thereby reducing the potential for interference of
crowding.
The potential for interference or crowding of shock tubes is best
illustrated by simultaneous coiisideration of Figures 1 and 4, which may be
considered alternative cross-sections though a similar connector block of the
present invention, at 90 to one another each along the main longitudinal axis
of the block. In this case, a detonator having a hemispherical percussion-
actuation end is inserted into the connector block. Due to the alternative
cross-section, Figure 1 illustrates only one of the upperinost shock tubes
shown in Figure 4. However, although not visible in Figure 4, each of the 6
shock tubes shown will also be retained in a bent configuration about the
hemispherical percussion-actuation end of the detonator. For this reason, the
plane of the bend for each shock tube will be offset relative to the plane of
the bend of every other shock tube in the assembly. The alternative bending
planes of each shoclc tube exiting the slot raises the potential problem for
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17
interference of the tubes. Tlie embodiment of the invention illustrated in
Figure 5 therefore aims to overcome such interference problems.
Importantly, by avoiding shock tube interference, the shock tubes can
be arranged in juxtaposition within the slot thus permitting insertion of a
maximal number of shock tubes into the slot (for example as illustrated in
Figure 4). In Figure 5, the shock tube illustrated is shown to exit the slot
at
positions 93 and 94 at an angle approximately perpendicular to the
longitudinal axis of the detonator. This configuration is expected to
substantially reduce the risk of interference between the shock tubes as they
exit the slot. However, in alternative embodiments, the projections 88 and
89 may induce only a minor deviation in the bend of the shoclc tubes, or
alternatively may bend the shock tubes away from the detonator as they exit
the slot. These embodiments are also expected to reduce the risk of
interference between the shock tubes as they exit the connector bloclc.
Although less preferred, similar shoclc tube I detonator contact can be
attained with the provision of only one of projections 90 and 91, together
with only one of projections 88 and 89 respectively.
It is also important to note that the projections 88 and 89 are
generally configured to avoid sllock tube crowding as multiple sliock tubes
exit the slot. The principle bend is introduced into each shock tubes as they
pass within the slot by projections 90 and 91. The additional bends in the
shock tubes induced by projections 88 and 89 occur generally on the
periphery of, or generally outside of, the slot. The embodiment illustrated in
Figure 5 therefore provides for a connector block that introduces more than
one bend into the shoclc tubes. However, only one principle bend is
introduced into each shock tube generally within the confines of the slot,
tllereby taking up virtually all of the tolerance in connector bloclc / shock
tube manufacture, and biasing the shock tube towards the percussion-
actuation end of the detonator.
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Only one shock tube is illustrated in Figure 5, due to the orientation
of the cross section. However, more than one shock tube may be arranged
around the detonator in accordance with the embodiment illustrated in
Figure 4.
The inventive concepts illustrated in Figure 5 may also be applied to
the shock tube configuration shown in Figure 2. In this regard, the shock
tube in Figure 2 is conf~igured to bend away from the end of the detonator by
the influence of projections 29 aiid 30, which are integral with the housing.
Additional projections may be provided on the shock tube retention means to
alter the bending configuration of the shoclc tube(s) as they exit the slot at
positions 31 and 32, tllereby reducing the risk of interference between the
shock tubes, as required.
Although the positioning membrane has been described in relation to
an embodiment of the invention shown in Figure 2, the use of a positioning
membrane can be applied to any of the embodiments and corresponding slot
configuratioiis illustrated herein. The positioning membrane is preferably
dimensioned and configured to position the detonator in efficient energy
communicating relationship with the slot, and shock tubes subsequently
inserted therein. The positioning membrane is preferably shaped for intimate
contact with the surface of the percussion-actuation end of the detonator. For
example, the positioning inembrane may be Ilemispherical in shape to
receive a hemispherical end of a detonator. In addition, the positioning
membrane preferably comprises a material of suitable properties and
thickness for efficient energy transmission from the base charge of the
detonator to the shock tubes contained in the slot. The positioning
meinbrane may partially or completely cover the end of the bore adjacent to
the slot. In this way, the slot may be defined in part by the positioning
membrane.
Without wishing to be bound by theory, it is believed that the
connector blocks of the present invention provide improved security of shock
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19
tube retention. In this way, the configuration of the slot is predicted to
increase the pull-out forces required to accidentally detach a shock tube from
the connector block. Moreover, the improved shock tube retention is
predicted to reduce the possibility of the connector block from sliding along
the shock ti,ibes located therein. Therefore, the connector blocks of the
present invention may have the additional advantage of improved security of
shoclc tube retention, with iinportant benefits to the safety and reliability
of
the system.
While the invention has been described with reference to particular
preferred embodiments thereof, it will be apparent to those skilled in the art
upon a reading and understanding of the foregoing that numerous connector
block designs that induce a bend in shock tubes located therein other than the
specific embodiments illustrated are attainable, which nonetheless lie within
the spirit and scope of the present invention. It is intended to include all
such
designs, and equivalents thereof within the scope of the appended claims.
Throughout this specification and the claims which follow, unless
the context requires otlierwise, the word "comprise", and variations such
as "comprises" and "comprising", will be understood to imply the
inclusion of a stated integer or step or group of integers or steps but not
the exclusion of any other integer or step or group of integers or steps.
The reference to any prior art in this specification is not, and should
not be taken as, an aclcnowledgment or any form of suggestion that that prior
art forms part of the common general lcnowledge.
