U.S. patent application number 09/933486 was filed with the patent office on 2002-06-20 for low-energy shock tube connector system.
This patent application is currently assigned to Austin Powder Company. Invention is credited to Capers, John, Jidestig, Goran.
Application Number | 20020073870 09/933486 |
Document ID | / |
Family ID | 26759254 |
Filed Date | 2002-06-20 |
United States Patent
Application |
20020073870 |
Kind Code |
A1 |
Capers, John ; et
al. |
June 20, 2002 |
LOW-ENERGY SHOCK TUBE CONNECTOR SYSTEM
Abstract
A shock tube connector system comprises a substantially
cylindrical detonator having a longitudinal axis a block body
receiving the detonator therein, and an end cap. The detonator
includes an axisymmetric exterior shell including a cylindrical
main section, a cylindrical explosive end portion having a diameter
less than the diameter of the main section, and a transition
portion connecting the main section and the explosive end portion
of the shell. An explosive charge is contained within the explosive
end portion of the shell and is distributed along the longitudinal
length of the explosive end portion. The explosive charge
preferable comprises two portions of lead azide or a first charge
portion of lead azide and PETN and a second charge portion of PETN.
An initiating shock tube is operatively connected to the explosive
charge via a delay element. The block body includes a housing
within which the main section of the detonator is received. A tube
holder connected to one end of the housing includes a base member
having a bore within which the explosive end portion of the
detonator is received. The tube holder is T-shaped and includes a
pair of engaging flanges spaced from the base member on laterally
opposite sides of the base member to define therebetween pair of
engaging slots extending parallel to the longitudinal axis of the
detonator and alongside the explosive end of the detonator received
in the bore. Each engaging slot is adapted to frictionally grip at
least four shock tubes alongside the explosive end of the detonator
with the longitudinal axes of the shock tubes substantially
orthogonal to the longitudinal axis of the detonator. The end cap
is connected to the other end of the housing and secures the
detonator within the block body.
Inventors: |
Capers, John; (McArthur,
OH) ; Jidestig, Goran; (Athens, OH) |
Correspondence
Address: |
Philip J. Moy Jr.
FAY, SHARPE, FAGAN, MINNICH &McKEE, LLP
Seventh Floor
1100 Superior Ave.
Cleveland
OH
44114-2518
US
|
Assignee: |
Austin Powder Company
|
Family ID: |
26759254 |
Appl. No.: |
09/933486 |
Filed: |
August 16, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09933486 |
Aug 16, 2001 |
|
|
|
09260818 |
Mar 2, 1999 |
|
|
|
60077427 |
Mar 9, 1998 |
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Current U.S.
Class: |
102/318 |
Current CPC
Class: |
C06C 7/00 20130101; C06C
5/06 20130101; F42D 1/043 20130101 |
Class at
Publication: |
102/318 |
International
Class: |
C06C 005/04; F42B
003/00 |
Claims
We claim:
1. A connector block for transmitting a detonation signal to one or
more shock tubes from a detonator having a longitudinal axis and an
explosive end portion containing an explosive charge, the connector
block comprising: a. a housing having a first end and a second end,
said housing being adapted to receive a detonator therein with the
explosive end of the detonator disposed adjacent said first end of
said housing; b. a tube holder connected to said first end of said
housing, said tube holder including at least one engaging slot
extending parallel to the longitudinal axis of the detonator and
alongside the explosive end of the detonator when the detonator is
received in said housing, said engaging slot being adapted to grip
at least four shock tubes alongside the explosive end of the
detonator with the longitudinal axes of the shock tubes
substantially orthogonal to the longitudinal axis of the
detonator.
2. The connector block of claim 1, wherein said tube holder
includes a pair of said engaging slots.
3. A connector block for transmitting a detonation signal to one or
more shock tubes from a detonator having a longitudinal axis and an
explosive end portion containing an explosive charge, the connector
block comprising: a. a housing having a first end and a second end,
said housing being adapted to receive a detonator therein with the
explosive end of the detonator disposed adjacent said first end of
said housing; b. a tube holder connected to said first end of said
housing, said tube holder including a base member having a bore
adapted to receive the explosive end of the detonator therein and
at least one engaging flange spaced from said base member to define
between said base member and said engaging flange an engaging slot
extending parallel to the longitudinal axis of the detonator and
alongside the explosive end of the detonator when the detonator is
received in said housing, said engaging slot being adapted to
frictionally grip a plurality of shock tubes alongside the
explosive end of the detonator with the longitudinal axes of the
shock tubes substantially orthogonal to the longitudinal axis of
the detonator.
4. The connector block of claim 3, wherein said base member of said
tube holder has a thickness substantially greater than the diameter
of the explosive end of the detonator and a width substantially
less than said thickness of said base member.
5. The connector block of claim 4, wherein said bore of said base
member has a diameter greater than said width of said base member
measured at said bore, whereby said bore opens into said engaging
slot and permits direct contact between the explosive end of the
detonator and the one or more shock tubes gripped in said engaging
slot.
6. The connector block of claim 3, wherein said engaging slot has a
length of at least about 12 mm.
7. The connector block of claim 3, wherein said base member has a
width of about 4 mm at said bore and a thickness of about 15-25
mm.
8. The connector block of claim 3, wherein said base member has a
width of about 4 mm at said bore and a thickness of about 20
mm.
9. The connector block of claim 3, wherein said engaging flange has
a width of about 5-7 mm and a thickness of about 15-20 mm.
10. The connector block of claim 3, wherein said engaging flange
has a width of about 6 mm and a thickness of about 17 mm.
11. The connector block of claim 3, wherein said engaging flange
includes a convex gripping surface facing said engaging slot.
12. The connector block of claim 3, wherein said engaging flange
includes a gripping surface facing said engaging slot and a ridge
projecting from said gripping surface into said engaging slot.
13. A connector block for transmitting a detonation signal to one
or more shock tubes from a detonator having a longitudinal axis and
an explosive end portion containing an explosive charge, the
connector block comprising: a. a housing having a first end and a
second end, said housing being adapted to receive a detonator
therein with the explosive end of the detonator disposed adjacent
said first end of said housing; b. means for securing a plurality
of shock tubes in proximity to the explosive end portion of the
detonator, said securing means being adapted to frictionally grip
at least eight shock tubes alongside the explosive end of the
detonator with the longitudinal axes of the shock tubes
substantially orthogonal to the longitudinal axis of the
detonator.
14. A connector block for transmitting a detonation signal to one
or more shock tubes from a detonator having a longitudinal axis and
an explosive end portion containing an explosive charge, the
connector block comprising: a. a housing having a first end and a
second end, said housing being adapted to receive a detonator
therein with the explosive end of the detonator extending beyond
said first end of said housing; b. a tube holder connected to said
first end of said housing, said tube holder including a base member
adapted to receive the explosive end of the detonator therein and a
pair of engaging flanges disposed on substantially laterally
opposite sides of said base member, each of said engaging flanges
being spaced from said base member to define between said
respective engaging flange and said base member an engaging slot
extending parallel to the longitudinal axis of the detonator and
alongside the explosive end of the detonator when the detonator is
received in said housing, each of said engaging slots being adapted
to frictionally grip a plurality of shock tubes alongside the
explosive end of the detonator with the longitudinal axes of the
shock tubes substantially orthogonal to the longitudinal axis of
the detonator.
15. The connector block of claim 14, wherein each of said engaging
slots has a length sufficient to grip at least four shock
tubes.
16. The connector block of claim 14, wherein said tube holder is
substantially T-shaped and includes a cross member connecting said
base member to said engaging flanges.
17. The connector block of claim 14, wherein said tube holder is
substantially fork-shaped and includes a cross member connecting
said base member to said engaging flanges adjacent said first end
of said housing.
18. A connector block for transmitting a detonation signal to one
or more shock tubes from a detonator having a longitudinal axis and
an explosive end portion containing an explosive charge, the
connector block comprising: a. a housing having a first end and a
second end, said housing being adapted to receive a detonator
therein with the explosive end of the detonator extending beyond
said first end of said housing; b. a tube holder connected to said
first end of said housing, said tube holder including: a base
member having a bore adapted to receive the explosive end of the
detonator therein, said base member having one end connected to
said first end of said housing and a distal end; a cross member
connected to said distal end of said base member and extending
substantially orthogonally with respect to the longitudinal axis of
the detonator; and a pair of engaging flanges depending from said
cross member and extending toward said housing on substantially
laterally opposite sides of said base member, each of said engaging
flanges being spaced from said base member to define between said
respective engaging flange and said base member an engaging slot,
each of said engaging slots being adapted to frictionally grip a
plurality of shock tubes alongside the explosive end of the
detonator with the longitudinal axes of the shock tubes
substantially orthogonal to the longitudinal axis of the
detonator.
19. The connector block of claim 18, wherein each of said engaging
slots has an entry opening adjacent said first end of said housing
to permit placement of shock tubes therein.
20. The connector block of claim 19, wherein: each of said engaging
flanges has a terminal end defined by a substantially planar
surface; and said housing includes an enlarged portion at said
first end of said housing, said enlarged portion of said housing
including a pair of converging surfaces, each of said converging
surfaces facing said terminal end of one of said engaging flanges
and defining therebetween an entrance slot communicating with said
entry opening of said associated engaging slot.
21. The connector block of claim 20, wherein the spacing between
said engaging flange and said converging surface of each of said
entrance slots is at a minimum adjacent said entry opening.
22. The connector block of claim 21, where said entry opening has a
width of about 1.5-2.0 mm.
23. A connector block for transmitting a detonation signal to one
or more shock tubes from a detonator having a longitudinal axis, an
explosive end portion containing an explosive charge, and an
opposite signal end for receiving an initiation signal, the
connector block comprising: a. a housing having a first end and a
second end, said housing being adapted to receive a detonator
therein with the explosive end of the detonator extending beyond
said first end of said housing; b. a tube holder connected to said
first end of said housing, said tube holder including a base member
adapted to receive the explosive end of the detonator therein and
at least one engaging flange spaced from said base member, said
base member and said engaging flange defining therebetween an
engaging slot extending parallel to the longitudinal axis of the
detonator and alongside the explosive end of the detonator when the
detonator is received in said housing, said engaging slot being
adapted to frictionally grip a plurality of shock tubes alongside
the explosive end of the detonator with the longitudinal axes of
the shock tubes substantially orthogonal to the longitudinal axis
of the detonator; and c. an end cap connected to said second end of
said housing, said end cap adapted to contact the signal end of the
detonator received in said housing.
24. The connector block of claim 23, wherein said housing includes
locking tabs at said second end of said housing, and said end cap
includes a ledge engageable by said locking tabs.
25. A shock tube connector system, comprising: a. a substantially
cylindrical detonator having a longitudinal axis, said detonator
including: an exterior shell, said shell including a cylindrical
main section, a cylindrical explosive end portion having a diameter
less than the diameter of said main section, and a transition
portion connecting said main section and said explosive end portion
of said shell, said shell being substantially axisymmetric with
respect to said longitudinal axis of said detonator, and said main
section having a signal end longitudinally opposite said explosive
end portion, an explosive charge contained within said explosive
end portion of said shell, said explosive charge being distributed
along the longitudinal length of said explosive end portion, and an
initiating shock tube operatively connected to said explosive
charge, said initiating shock tube entering said detonator at said
signal end of said main section of said shell and being adapted to
transmit an ignition signal to said detonator causing said
explosive charge to ignite; b. a block body including: a housing
having a first end and a second end, said main section of said
detonator being received within said housing and said explosive end
portion of said detonator extending beyond said first end of said
housing, and a tube holder connected to said first end of said
housing, said tube holder including a base member having a bore,
said explosive end portion of said detonator being received within
said bore, said tube holder including at least one engaging flange
spaced from said base member, said base member and said engaging
flange defining therebetween an engaging slot extending parallel to
said longitudinal axis of said detonator and alongside said
explosive end of said detonator received in said bore, said
engaging slot being adapted to frictionally grip a plurality of
shock tubes alongside said explosive end of said detonator with the
longitudinal axes of the shock tubes substantially orthogonal to
said longitudinal axis of said detonator; and c. an end cap
connected to said second end of said housing, said end cap securing
said detonator within said block body.
26. The shock tube connector system of claim 25, wherein said
engaging slot has a length sufficient to grip at least four shock
tubes.
27. A shock tube connector system, comprising: a. a substantially
cylindrical detonator having a longitudinal axis, said detonator
including: an exterior shell, said shell including a cylindrical
main section, a cylindrical explosive end portion having a diameter
less than the diameter of said main section, and a transition
portion connecting said main section and said explosive end portion
of said shell, said shell being substantially axisymmetric with
respect to said longitudinal axis of said detonator, and said main
section having a signal end longitudinally opposite said explosive
end portion, an explosive charge contained within said explosive
end portion of said shell, said explosive charge being distributed
along the longitudinal length of said explosive end portion, and an
initiating shock tube operatively connected to said explosive
charge, said initiating shock tube entering said detonator at said
signal end of said main section of said shell and being adapted to
transmit an ignition signal to said detonator causing said
explosive charge to ignite; b. a block body including: a housing
having a first end and a second end, said main section of said
detonator being received within said housing and said explosive end
portion of said detonator extending beyond said first end of said
housing, and a tube holder connected to said first end of said
housing, said tube holder including: a base member having a bore,
said explosive end of said detonator being received within said
bore, said base member having one end connected to said first end
of said housing and a distal end, a cross member connected to said
distal end of said base member and extending substantially
orthogonally with respect to said longitudinal axis of said
detonator, and a pair of engaging flanges depending from said cross
member and extending toward said housing on substantially laterally
opposite sides of said base member, each of said engaging flanges
being spaced from said base member to define between said
respective engaging flange and said base member an engaging slot,
each of said engaging slots being adapted to frictionally grip a
plurality of shock tubes alongside said explosive end of said
detonator with the longitudinal axes of the shock tubes
substantially orthogonal to said longitudinal axis of said
detonator; and c. an end cap connected to said second end of said
housing, said end cap securing said detonator within said block
body.
28. A detonator for a shock tube connector system, comprising: a.
an exterior shell including a cylindrical main section, a
cylindrical explosive end portion having a diameter less than the
diameter of said main section, and a transition portion connecting
said main section and said explosive end portion of said shell,
said main section having a signal end longitudinally opposite said
explosive end portion, b. an explosive charge contained within said
explosive end portion of said shell, said explosive charge being
distributed along the longitudinal length of said explosive end
portion, and c. an initiating shock tube operatively connected to
said explosive charge, said initiating shock tube entering said
detonator at said signal end of said main section of said shell and
being adapted to transmit an ignition signal to said detonator
causing said explosive charge to ignite.
29. The detonator of claim 28, wherein said explosive end portion
of said shell has an outer diameter of about 3-5 mm and an axial
length of about 9-15 mm.
30. The detonator of claim 28, wherein said explosive end portion
of said shell has an outer diameter of about 4.2 mm and an axial
length of about 11 mm.
31. The detonator of claim 29, wherein said explosive charge
comprises lead azide.
32. The detonator of claim 28, wherein said explosive charge
comprises about 175-240 mg of lead azide.
33. The detonator of claim 28, wherein said explosive charge
comprises about 210 mg of lead azide.
34. The detonator of claim 28, wherein said explosive charge
comprises lead azide and PETN.
35. The detonator of claim 28, wherein said explosive charge
comprises a first charge portion of about 100 mg of lead azide and
about 20 mg of PETN and a second charge portion of about 55 mg of
PETN.
36. The detonator of claim 28, further comprising a delay element
disposed between said explosive charge and said initiating shock
tube.
37. The detonator of claim 36, wherein said delay element includes
a delay tube having a frusto-conical end mating with said
transition portion of said shell.
38. The detonator of claim 28, wherein said shell is formed of
metal.
39. The detonator of claim 28, wherein said shell is formed of
aluminum.
40. The detonator of claim 39, wherein said shell has a thickness
of about 0.5 mm.
Description
[0001] This application claims priority from U.S. Provisional
Patent Application Ser. No. 60/077,427, filed Mar. 9, 1998.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a system for transmitting
an ignition signal from a single detonator to a plurality of
transmission lines connected to other detonators for the purpose of
producing a predetermined, timed blasting pattern. In particular,
the present invention relates to a system for controlling the
ignition of a series of non-electrical detonators.
[0003] In non-electrical detonation of explosives, signals are
transmitted between lengths of detonator cord, known as "shock
tubes," by employing connector blocks. A connector block typically
includes a detonator receiving the detonation signal from its own
shock tube, a housing to contain the explosive effect of the
detonator and limit the production of shrapnel, and a mechanism for
securing a plurality of shock tubes adjacent the charge within the
detonator. Upon ignition of the charge within the detonator,
signals are generated within the shock tubes held with the securing
mechanism. Examples of conventional detonator blocks include those
described in U.S. Pat. Nos. 5,171,935, 5,204,492, 5,423,263,
5,458,611, and 5,499,581, 5,703,319, and 5,792,975, which are
incorporated herein by reference.
[0004] Conventional shock tube connector systems are limited in a
number of ways. For example, they generally can hold a maximum of
four to six shock tubes, which limits the number of circuits that
can be initiated from a given connector block. Moreover, most
connector blocks create a variety of spatial relationships between
the explosive charge within the detonator and the several shock
tubes held by the block, which often results in inconsistent signal
transmission to the individual shock tubes. In addition, to the
extent more powerful detonator charges are employed to ensure
adequate signal transmission to all shock tubes, not only does the
cost of the system increase, but increased shrapnel may result.
[0005] It is the intention of this invention to provide a connector
block that can hold up to eight shock tubes and effect signal
transmission between the detonator and all eight shock tubes.
[0006] It also is the intention of this invention to provide a
shock tube connector system that utilizes a modified detonator to
transmit detonation signals efficiently and consistently to a
plurality of shock tubes.
[0007] Additional advantages of the present invention will be set
forth in part in the description that follows, and in part will be
obvious from that description or can be learned by practice of the
invention. The advantages of the invention can be realized and
obtained by the apparatus particularly pointed out in the appended
claims.
SUMMARY OF THE INVENTION
[0008] The present invention overcomes the problems of prior art
shock tube connector systems and accomplishes its purpose by
providing a mechanism to secure up to four shock tubes in each of
two parallel rows positioned on laterally opposite sides of the
explosive end of a detonator so that the longitudinal axes of the
shock tubes are substantially orthogonal to the longitudinal axis
of the detonator. The explosive end of the detonator preferably has
a reduced diameter and extended length and has an explosive charge
distributed longitudinally within it to provide the appropriate
energy blast to the rows of shock tubes.
[0009] To overcome the problems of the prior art shock tube
connector systems, and in accordance with the purpose of the
invention, as embodied and broadly described herein, the connector
block of this invention is for transmitting a detonation signal to
one or more shock tubes from a detonator having a longitudinal axis
and an explosive end portion containing an explosive charge and
comprises a housing having a first end and a second end and a tube
holder connected to the first end of the housing. The housing is
adapted to receive a detonator therein with the explosive end of
the detonator disposed adjacent the first end of the housing. The
tube holder includes at least one engaging slot extending parallel
to the longitudinal axis of the detonator and alongside the
explosive end of the detonator when the detonator is received in
the housing. The engaging slot is adapted to frictionally grip at
least four shock tubes alongside the explosive end of the detonator
with the longitudinal axes of the shock tubes substantially
orthogonal to the longitudinal axis of the detonator.
[0010] Preferably, the tube holder includes a base member having
one end connected to the first end of the housing with a bore
adapted to receive the explosive end of the detonator therein, a
cross member connected to the distal end of the base member and
extending substantially orthogonally with respect to the
longitudinal axis of the detonator, and a pair of engaging flanges
depending from the cross member and extending toward the housing on
substantially laterally opposite sides of the base member. Each of
the engaging flanges is spaced from the base member to define
between the respective engaging flange and the base member an
engaging slot, and each of the engaging slots is adapted to
frictionally grip a plurality of shock tubes alongside the
explosive end of the detonator with the longitudinal axes of the
shock tubes substantially orthogonal to the longitudinal axis of
the detonator.
[0011] In another aspect of the invention, the shock tube connector
system comprises a substantially cylindrical detonator having a
longitudinal axis, a block body receiving the detonator therein,
and an end cap. The detonator includes an exterior shell including
a cylindrical main section, a cylindrical explosive end portion
having a diameter less than the diameter of the main section, and a
transition portion connecting the main section and the explosive
end portion of the shell. The shell is substantially axisymmetric
with respect to the longitudinal axis of the detonator, and the
main section has a signal end longitudinally opposite the explosive
end portion. An explosive charge is contained within the explosive
end portion of the shell and is distributed along the longitudinal
length of the explosive end portion. An initiating shock tube is
operatively connected to the explosive charge. The initiating shock
tube enters the detonator at the signal end of the main section of
the shell and is adapted to transmit an ignition signal to the
detonator causing the explosive charge to ignite. The block body
includes a housing having a first end and a second end, with the
main section of the detonator being received within the housing and
the explosive end portion of the detonator extending beyond the
first end of the housing. A tube holder is connected to the first
end of the housing. The tube holder includes a base member having a
bore, with the explosive end portion of the detonator being
received within the bore. The tube holder includes at least one
engaging flange spaced from the base member, with the base member
and the engaging flange defining therebetween an engaging slot
extending parallel to the longitudinal axis of the detonator and
alongside the explosive end of the detonator received in the bore.
The engaging slot is adapted to frictionally grip a plurality of
shock tubes alongside the explosive end of the detonator with the
longitudinal axes of the shock tubes substantially orthogonal to
the longitudinal axis of the detonator. The end cap is connected to
the second end of the housing and secures the detonator within the
block body.
[0012] The accompanying drawings, which are incorporated in and
which constitute a part of this specification, illustrate at least
one embodiment of the invention and, together with the description,
explain the principles of the invention.
DESCRIPTION OF THE DRAWINGS
[0013] FIGS. 1A and 1B are perspective views of the shock tube
connector system of this invention holding eight shock tubes;
[0014] FIG. 1C and 1D are perspective views of the shock tube
connector system of this invention with the end cap removed.
[0015] FIG. 1E is a perspective view of the shock tube connector
system of this invention partially cut away to show the detonator
contained within;
[0016] FIG. 2 is a cross-sectional view of the shock tube connector
system of this invention taken along line 2-2 of FIG. 1E and
showing four shock tubes held on one side of the connector;
[0017] FIG. 3 is a cross-sectional view of the shock tube connector
system of this invention taken along line 3-3 of FIG. 1E;
[0018] FIG. 4 is a cross-sectional view of the shock tube connector
system of this invention taken along line 4-4 of FIG. 2, showing
two shock tubes held in place by the connector;
[0019] FIG. 5 is a cross-sectional view of the shell of the
detonator of the shock tube connector system of this invention;
[0020] FIG. 6 is a cross-sectional view of one embodiment of the
explosive end portion of the detonator of the shock tube connector
system of this invention; and
[0021] FIG. 7 is a cross-sectional view of a second embodiment of
the explosive end portion of the detonator of the shock tube
connector system of this invention.
DESCRIPTION OF THE INVENTION
[0022] Reference now will be made in detail to the presently
preferred embodiments of the invention, examples of which are
illustrated in the accompanying drawings.
[0023] As shown generally in FIGS. 1A-1E and in the cross-sectional
views of FIGS. 2-4, the shock tube connector system of this
invention comprises block body A, detonator B, and end cap C.
Detonator B is held within block body A and secured in position by
end cap C. Block body A and end cap C together comprise a connector
block and preferably are formed by injection molding techniques
from polyethylene, polypropylene, or a combination thereof. As
shown in FIGS. 1A, 1B, 2, and 4, a plurality of shock tubes D are
held in place by the connector of this invention.
[0024] Detonator B is a generally cylindrical metallic shell of
circular cross section preferably formed from aluminum about 0.5 mm
thick and shaped as shown in FIG. 5. The detonator is comprised of
a main cylindrical section 10, a smaller-diameter cylindrical
explosive end portion 12, and a transition portion 14. The shell of
detonator B preferably is axisymmetric with respect to its
longitudinal axis 15. The main explosive charge of detonator B is
located in explosive end portion 12 and is distributed along the
axial length of end portion 12 so that the explosive force of the
ignited main charge will ignite the shock tubes D held in place
alongside end portion 12. An initiating shock tube 16 connected to
the opposite signal end 18 of detonator B (see FIGS. 1E, 2, and 3)
provides the ignition signal to ignite the main charge within
explosive end portion 12. In the presently preferred embodiment,
main cylindrical section 10 has an outer diameter of about 7.5 mm;
explosive end portion 12 is about 9-15 mm in axial length, most
preferably 11 mm, and has an outer diameter of about 3-5 mm, most
preferably about 4.2 mm; and transition portion 14 accomplishes the
reduction in shell diameter over an axial length of about 4 mm. The
angle between opposite sides of the transition portion 14
preferably is about 50.degree..
[0025] Block body A includes housing 20, which has a cylindrical
bore sized to accommodate main cylindrical section 10 of detonator
B. Housing 20 preferably has a circular cross section over most of
its length, with grooves 22 formed in its surface to assist the
user in gripping the connector. A pair of prongs 24, each with a
locking tab 25, are formed at one end of housing 20 for engaging
with end cap C. A pear-shaped enlarged portion 26 is formed at the
other end 27 of housing 20. The distal end of pear-shaped enlarged
portion 26 includes a pair of surfaces 28 that converge toward one
another. Preferably, converging surfaces 28 are defined by a
frustum of a cone.
[0026] Connected to end 27 of housing 20 (at the distal end of
enlarged portion 26) is means for securing a plurality of shock
tubes in proximity to the explosive end portion of the detonator,
that is, adjacent the detonator's main charge. The securing means
of this invention, shown in the perspective views of FIGS. 1A-1E,
comprises a T-shaped tube holder 30 that includes base member 32
connected to enlarged portion 26 of housing 20, cross member 34
intersecting base member 32 orthogonally, and a pair of engaging
flanges 36 depending from the lateral ends of cross member 34 and
extending back toward main housing section 20. Each engaging flange
36 is disposed substantially parallel to base member 32 and is
spaced therefrom to define an engaging slot 38 on each lateral side
of base member 32. Each engaging slot 38 has an entry opening 37
adjacent end 27 of housing 20 to permit placement of shock tubes D
therein.
[0027] Each engaging slot 38 should be less than 3 mm in width,
preferably about 2.9 mm, to permit shock tubes of nominal 3 mm
diameter to be frictionally gripped by the surfaces of base member
32 and engaging flange 36 facing the slot. The engaging slot
preferably is at least about 12 mm in length (parallel to the
longitudinal axes of housing 20 and detonator B) to permit at least
four shock tubes D to be held in each slot with the longitudinal
axes of the tubes orthogonal to the longitudinal axis of the
detonator (see FIG. 2, showing four shock tubes held in one of the
engaging slots 38. The gripping surfaces 39 of engaging flanges 36
that face engaging slots 38 preferably have a slightly convex
shape, as shown in FIG. 4, and provide maximum gripping of shock
tubes D adjacent plane E passing through the lateral center of
block body A. Furthermore, a ridge (not shown) can be provided in
the lengthwise direction of engaging slot 38 (into the plane of
FIG. 4) on the gripping surface 39 of engaging flange 36,
preferably where it intersects with plane E, to provide additional
frictional securement of the shock tubes within engaging slot
38.
[0028] Base member 32 includes a cylindrical bore dimensioned to
accommodate explosive end portion 12 of detonator B. The width W of
base member 32 preferably is less than the diameter of explosive
end portion 12 of detonator B at the bore within base member 32, so
that the bore is exposed to slots 38 (as shown in FIGS. 1C and 1D),
and the end portion 12 extends laterally into slots 38. For
example, W preferably is about 4 mm at the bore when the outer
diameter of end portion 12 is 4.2 mm . As a consequence, shock
tubes D are gripped between the exposed detonator end portion and
the adjacent engaging flange 36. The thickness of base member 32
(orthogonal to width W in the plane of FIG. 4) is substantially
greater than width W, preferably about 15-25 mm and most preferably
about 20 mm, to provide containment of shrapnel upon the ignition
of detonator B and assist in directing the explosive force of
detonation toward the engaging slots. If desired, the width W of
base member 32 can be increased away from the bore area to provide
additional strength. Each engaging flange 36 preferably is about
5-7 mm wide and most preferably about 6 mm (measured in the same
direction as width W) and about 15-20 mm thick, most preferably 17
mm. The engaging flanges also assist in shrapnel containment..
[0029] The terminal ends 40 of engaging flanges 36 preferably are
substantially planar surfaces spaced from the adjacent surfaces 28
of enlarged portion 26 to define converging entrance slots 42 that
communicate with entry openings 37 of engaging slots 38. The
spacing within each entrance slot 42 preferably varies from about
4mm at its widest to about 1.5-2.5 mm, most preferably about 2.0
mm, at the entry opening 37. Because this smaller dimension is less
than the nominal diameter of a standard shock tube, the user should
sense resistance to the insertion of a shock tube into either of
engaging slots 38.
[0030] End cap C preferably has a hat-shaped exterior comprising a
flange 50 and a sleeve member 52. End cap C also includes a
circular ledge 54, recessed from the flange 50, that engages with
locking tabs 25 to secure the end cap in place. Preferably, a cross
member 56 spans ledge 54 and supports cylindrical spacer 58, which
is sized to contact with the signal end 18 of detonator B when the
latter is encompassed within block body A and ensure that detonator
B is inserted filly into block body A. Spacer 58 includes an axial
bore to allow shock tube 16 attached to detonator B to pass out of
the block body. The configuration of end cap C disclosed herein
provides a secure engagement of the end cap with block body A.
Other configurations may be used where it is desirable to provide
an end cap that is easier to disengage.
[0031] Typical methods for loading explosive charges in detonators
must be modified when using detonator B of this invention with the
reduced diameter at its end portion. In the preferred method of
loading the detonator, a number (typically one hundred) of empty
shells first are placed in a holder with the end portion 12
directed downwardly. Then the end portion of each of the shells is
loaded with the main charge, preferably by a volumetric dosing
process in which predetermined fractions of the charge are loaded
into the shell. Where an intermediate compression step is desired
for a given fraction, compression of the charge fraction preferably
is performed with press pins using a hydraulic press.
[0032] In one embodiment of the detonator of this invention, shown
in FIG. 6, the main charge consists of lead azide that is
dextrinated to make it less sensitive to detonation when undergoing
compression during this loading process. The charge is loaded in
two steps, each requiring the supply of approximately one half the
total charge. Initially, a first main charge portion 62A of
dextrinated lead azide is loaded into the end portion 12 and the
charge portion is pressed using a force between 100N and 3000N per
detonator, most preferably less than 1000N. A second main charge
portion 62B of dextrinated lead azide then is loaded on top of
first portion 62A. The total amount of dextrinated lead azide in
the main charge of this first embodiment preferably is 175-240 mg,
most preferably 210 mg loaded in two dosages of 105 mg each. If
desired, a thin layer of PETN (approximately 20 mg ) can be loaded
on top of first portion 62A prior to pressing to help guard against
the lead azide detonating during compaction. In addition, the main
charge can be loaded in more than two dosages.
[0033] To protect against explosion of the charges during
subsequent loading operations, a small, fast-burning pyrotechnic
charge 64, preferably about 50 mg of a zirconium/red lead mixture,
then is placed on top of the main lead azide charge. A delay
element 65 then is inserted into the shell and is compressed on top
of the main charge with press pins operated by a hydraulic press.
Press force for this step of the operation preferably is between
300 N and 3000 N per detonator. The delay element preferably
comprises a delay tube 66 filled with a charge 68 of delay powder,
such as a silicon/red lead mixture, and has a predetermined height
within main cylindrical section 10 of detonator B associated with
the desired time delay. The inside diameter of delay tube 66
preferably is about 3 mm, and delay tube 66 preferably is formed
from steel, aluminum, or zincalloy. The delay element typically
provides a relatively tight fit with the inner diameter of the
detonator shell and, in this instance, preferably has a
frusto-conical end to complement the transition portion 14 of the
detonator. If desired, a starter charge 70 can be pressed on top of
the delay powder 68 to transfer the ignition pulse from the
initiating shock tube to the delay powder. Finally, the detonator's
initiating shock tube is connected to delay element 65 in
accordance with conventional practice.
[0034] In an alternative embodiment, shown in FIG. 7, the main
charge comprises a first main charge portion 72A of about 100 mg of
dextrinated lead azide followed by a thin layer 74 of about 20 mg
of PETN to protect the lead azide during subsequent compression.
This material then is pressed with a pressing force of about 700N
to a height of about 5 mm. A second main charge portion 72B of
about 55 mg of PETN is then loaded but not pressed. The second
embodiment of the detonator for this invention also includes a
delay element 75, which preferably is formed by filling delay tube
66 with a dose 80 of delay powder, such as a silicon/red lead
mixture, up to about 5 mm short of the conical end (using, e.g.,
pins inserted in the conical end to provide the desired clearance).
Delay tube 66 then is turned conical end up and is filled with a
charge 78 of about 50 mg of dextrinated lead azide and an charge 80
of about 35 mg of inert powder, such as talc or a delay powder
substance. The lead azide charge 78 and inert powder charge 80 then
are compressed with a pressing force preferably about 700N.
Finally, the delay element 75 is inserted in the shell in a manner
similar to that described above with respect to delay element 65
(preferably without compressing the PETN of second main charge
portion 72B), and the detonator's initiating shock tube is
connected to delay element 75 in accordance with conventional
practice. If desired, a starter charge (not shown) can be loaded on
top of delay element 75.
[0035] The detonation/signal transmission system of this invention,
as described above, differs from that of conventional shock tube
connector blocks, which employ a detonator having a main charge
disposed at its extreme end and configured to ignite longitudinally
out of the detonator end to transmit the ignition signal to shock
tubes positioned at the extreme end. The system of this invention
employs a detonator having a main charge disposed along a
preselected axial length and configured to ignite laterally in
order to transmit the ignition signal to shock tubes arranged
alongside the main charge. The configuration of the connector block
of this invention increases the effective length over which the
detonator's ignition signal can be transmitted and, accordingly,
increases the number of shock tubes that can be ignited by a single
detonator. Other explosive substances, such as lead styphnate,
DDNP, or mixtures thereof can be used instead of lead azide as the
primary explosive charge within explosive end portion 14, and RDX,
HMX Tetryl, TNT, or mixtures thereof can be used in place of the
PETN in the embodiments described above. Irrespective of which
explosive compounds are used, however, the energy of the main
charge within end portion 12 should be as low as practicable while
reliably initiating up to four pairs of adjacent shock tubes. The
reduced diameter of end portion 12 is a result of minimizing the
size of the main charge and distributing the charge
longitudinally.
[0036] It will be apparent to those skilled in the art that
additional modifications and variations can be made in the
disclosed connector block, detonator, and shock tube connector
system without departing from the scope of the invention. For
example, the tube holder can be rotated by 180.degree. so that it
is fork-shaped, with the cross member connecting the engagement
flanges to the base member adjacent the enlarged portion of the
housing and the entry openings of the engagement slots being
disposed at the extreme end of the connector block opposite the end
cap. The invention in its broader aspects is, therefore, not
limited to the specific details and illustrated examples shown and
described. Accordingly, it is intended that the present invention
cover such modifications and variations provided that they fall
within the scope of the appended claims and their equivalents.
* * * * *