US20110002078A1 - Low-voltage-insensitive electro-pyrotechnic device - Google Patents

Low-voltage-insensitive electro-pyrotechnic device Download PDF

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Publication number
US20110002078A1
US20110002078A1 US11/811,568 US81156807A US2011002078A1 US 20110002078 A1 US20110002078 A1 US 20110002078A1 US 81156807 A US81156807 A US 81156807A US 2011002078 A1 US2011002078 A1 US 2011002078A1
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United States
Prior art keywords
bridge element
electrical input
input terminals
voltage
transient voltage
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
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US11/811,568
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David F. Lansburg
Gimtong Teowee
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Austin Star Detonator Co
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Individual
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Priority to US11/811,568 priority Critical patent/US20110002078A1/en
Assigned to SPECIAL DEVICES, INC. reassignment SPECIAL DEVICES, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: LANSBURG, DAVID F., TEOWEE, GIMTONG
Priority to PCT/IB2008/050557 priority patent/WO2008152529A1/en
Priority to CL2008001694A priority patent/CL2008001694A1/en
Assigned to WELLS FARGO FOOTHILL, LLC reassignment WELLS FARGO FOOTHILL, LLC ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SPECIAL DEVICES, INC.
Assigned to WAYZATA INVESTMENT PARTNERS LLC, AS AGENT reassignment WAYZATA INVESTMENT PARTNERS LLC, AS AGENT SECURITY AGREEMENT Assignors: SPECIAL DEVICES, INCORPORATED
Assigned to WELLS FARGO FOOTHILL, INC. reassignment WELLS FARGO FOOTHILL, INC. CORRECTIVE ASSIGNMENT TO CORRECT THE RECEIVING PARTY'S NAME NEEDS TO BE CORRECTED TO WELLS FARGO FOOTHILL, INC. ON THE RECORDATION COVER PAGE PREVIOUSLY RECORDED ON REEL 021709 FRAME 0708. ASSIGNOR(S) HEREBY CONFIRMS THE WELLS FARGO FOOTHILL,LLC IS NOT THE ASSIGNEE IN THE ORIGINAL ASSIGNMENT (SEE FIRST PARAGRAPH OF THE ASSIGNMENT). Assignors: SPECIAL DEVICES INCORPORATED
Assigned to SPECIAL DEVICES, INCORPORATED reassignment SPECIAL DEVICES, INCORPORATED NUNC PRO TUNC ASSIGNMENT (SEE DOCUMENT FOR DETAILS). Assignors: WELLS FARGO FOOTHILL, INC.
Publication of US20110002078A1 publication Critical patent/US20110002078A1/en
Assigned to AUSTIN STAR DETONATOR COMPANY reassignment AUSTIN STAR DETONATOR COMPANY ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SPECIAL DEVICES, INC.
Assigned to AUSTIN STAR DETONATOR COMPANY reassignment AUSTIN STAR DETONATOR COMPANY RELEASE BY SECURED PARTY (SEE DOCUMENT FOR DETAILS). Assignors: WAYZATA INVESTMENT PARTNERS, LLC
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F42—AMMUNITION; BLASTING
    • F42B—EXPLOSIVE CHARGES, e.g. FOR BLASTING, FIREWORKS, AMMUNITION
    • F42B3/00—Blasting cartridges, i.e. case and explosive
    • F42B3/10—Initiators therefor
    • F42B3/18—Safety initiators resistant to premature firing by static electricity or stray currents

Definitions

  • the present invention relates primarily to the field of electro-pyrotechnic devices, and more particularly, to a low-voltage-insensitive electro-pyrotechnic device.
  • Conventional electric detonators comprise hotwire initiators inserted into a metal shell with load charges.
  • the hotwire initiator is directly electrically exposed to external electrical input or stimulus from the legwires to the outside world, making it susceptible to stray electrical voltage or current entering the legwires, leading to possible inadvertent firing of the detonator.
  • Such electric detonators are likewise vulnerable to ESD strikes (either wire-to-wire or wire-to-shell), which can also lead to inadvertent firing.
  • hotwire resistance is typically in the range of 1 to 5 Ohm, significant current will flow through the hotwire at voltages of 1 to 5V without ESD protection. This makes electric detonators susceptible to low voltage sources such as watch batteries, etc.
  • a low-voltage-insensitive electro-pyrotechnic device comprises electrical input terminals, a bridge element connected to the electrical input terminals, and a transient voltage suppressor (“TVS”) connected between the bridge element and one of the electrical input terminals.
  • the device may utilize one bidirectional TVS on one side of the bridge element or two unidirectional TVSs on opposite sides of the bridge element, and may also include one or more resistors and/or an RF filter between the input terminals and bridge element.
  • FIG. 1 is a sectional view of a detonator according to a preferred embodiment of a low-voltage-insensitive electro-pyrotechnic device according to the present invention, and having a single bidirectional TVS.
  • FIG. 2 is a diagram of a suitable layout for the circuit board included in the embodiment of FIG. 1 .
  • FIG. 3 is an electrical schematic for the embodiment of FIG. 1 .
  • FIG. 4 is a schematic for an alternative embodiment having a single bidirectional TVS, but two parallel resistors rather than one.
  • FIG. 5 is a schematic for another alternative embodiment in which there are two unidirectional TVSs rather than a single bidirectional TVS.
  • FIG. 6 is a schematic showing an embodiment that further incorporates an RF filter.
  • FIGS. 1-3 depict a low-voltage-insensitive electro-pyrotechnic device according to a preferred embodiment of the present invention in which there is a single bidirectional TVS and a parallel resistor.
  • a hotwire initiator 20 is secured in the detonator 10 with an endplug 15 , with a TVS 22 placed before the hotwire initiator 20 and a parallel resistor 24 placed before the TVS 22 and between the two input terminals 26 from the legwires 28 .
  • FIG. 2 shows an example of a circuit board layout (with the positions where the TVS 22 and resistor 24 sit on the board depicted in dashed lines) using a 5.0 mm ⁇ 13.3 mm board 13 that can be accommodated inside the metal shell 30 of a common mining and blasting detonator as shown in FIG. 1 , with contact pads 21 provided for connection to the hotwire initiator 20 .
  • the TVS 22 blocks voltage applied across the legwires 28 until the clamping voltage is reached, at which point the TVS 22 starts conducting current to the hotwire initiator 20 .
  • the TVS 22 can be discrete axial or radial, preferably a surface mount component.
  • the TVS 22 is preferably chosen to conduct above 100V, more preferably 180V and most preferably above 200V but below 450V, typical voltage of electric blasting machines. Examples of such TVSs are smaj170ca, smaj190ca, p4sma200ca and p4sma220ca.
  • the assembly should block any DC input voltage up to 200V and will only start conducting at voltages above that (regardless of polarity since it is bidirectional).
  • the parallel resistor 24 placed before the TVS 22 and between the two input terminals 26 from the legwires 28 mitigates ESD charge buildup and also facilitates an electronic assembly continuity check performed at the downholes (to ensure there is electrical continuity between the legwires to the electric detonator below in the downholes).
  • the value of this resistor can be between 1 kOhm to 100 kOhm, most preferably 25 kOhm to 75 kOhm.
  • a combination of resistors in series or parallel can be used to achieve the desired final resistance (e.g., 1 kOhm to 100 kOhm).
  • two 150 kOhm resistors 25 can be employed in parallel to produce a circuit resistance of 75 kOhm.
  • an alternate embodiment could instead employ two unidirectional TVSs 23 .
  • Such an embodiment could also be used with a single resistor or a combination of resistors in series or parallel (not shown).
  • an RF filter 32 (comprising a pi(LC) filter, RC, RL networks, ferrite beads or chips, or a capacitor) can also be incorporated in the front of the assembly, to enhance blocking of higher frequency AC voltage such as from extraneous RF or EMI signals.
  • a TVS instead of a TVS, another means for upwardly shifting the all-fire voltage as measured at the input terminals could be used, such as a combination of (e.g., 100) forward voltage diodes (each producing a drop of 1 volt) connected in series between one of the input terminals and the hotwire initiator.
  • a combination of (e.g., 100) forward voltage diodes each producing a drop of 1 volt) connected in series between one of the input terminals and the hotwire initiator.
  • the detonator 10 is connected to an electric blasting machine (not shown) yielding an output of at least 250V from a 450 uF capacitive discharge, such as an REO Model CDJ 450J blasting machine with output of 500V 450 uF capacitance network.
  • an electric blasting machine not shown
  • the surge in voltage and current to the hotwire initiator 20 results in deployment of the detonator 10 within 20-30 us or .so.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

A low-voltage-insensitive electro-pyrotechnic device comprising electrical input terminals, a bridge element connected to the electrical input terminals, and a transient voltage suppressor connected between the bridge element and one of the electrical input terminals. The device may utilize one bidirectional TVS on one side of the bridge element or two unidirectional TVSs on opposite sides of the bridge element, and may also include one or more resistors and/or an RF filter between the input terminals and bridge element.

Description

    FIELD OF THE INVENTION
  • The present invention relates primarily to the field of electro-pyrotechnic devices, and more particularly, to a low-voltage-insensitive electro-pyrotechnic device.
    • BACKGROUND OF THE INVENTION
  • Conventional electric detonators comprise hotwire initiators inserted into a metal shell with load charges. The hotwire initiator is directly electrically exposed to external electrical input or stimulus from the legwires to the outside world, making it susceptible to stray electrical voltage or current entering the legwires, leading to possible inadvertent firing of the detonator. Such electric detonators are likewise vulnerable to ESD strikes (either wire-to-wire or wire-to-shell), which can also lead to inadvertent firing. Since hotwire resistance is typically in the range of 1 to 5 Ohm, significant current will flow through the hotwire at voltages of 1 to 5V without ESD protection. This makes electric detonators susceptible to low voltage sources such as watch batteries, etc.
    • SUMMARY OF THE INVENTION
  • A low-voltage-insensitive electro-pyrotechnic device according to an embodiment of the present invention comprises electrical input terminals, a bridge element connected to the electrical input terminals, and a transient voltage suppressor (“TVS”) connected between the bridge element and one of the electrical input terminals. The device may utilize one bidirectional TVS on one side of the bridge element or two unidirectional TVSs on opposite sides of the bridge element, and may also include one or more resistors and/or an RF filter between the input terminals and bridge element.
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • FIG. 1 is a sectional view of a detonator according to a preferred embodiment of a low-voltage-insensitive electro-pyrotechnic device according to the present invention, and having a single bidirectional TVS.
  • FIG. 2 is a diagram of a suitable layout for the circuit board included in the embodiment of FIG. 1.
  • FIG. 3 is an electrical schematic for the embodiment of FIG. 1.
  • FIG. 4 is a schematic for an alternative embodiment having a single bidirectional TVS, but two parallel resistors rather than one.
  • FIG. 5 is a schematic for another alternative embodiment in which there are two unidirectional TVSs rather than a single bidirectional TVS.
  • FIG. 6 is a schematic showing an embodiment that further incorporates an RF filter.
    •  DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
  • FIGS. 1-3 depict a low-voltage-insensitive electro-pyrotechnic device according to a preferred embodiment of the present invention in which there is a single bidirectional TVS and a parallel resistor. As seen in FIGS. 1 and 3, a hotwire initiator 20 is secured in the detonator 10 with an endplug 15, with a TVS 22 placed before the hotwire initiator 20 and a parallel resistor 24 placed before the TVS 22 and between the two input terminals 26 from the legwires 28. FIG. 2 shows an example of a circuit board layout (with the positions where the TVS 22 and resistor 24 sit on the board depicted in dashed lines) using a 5.0 mm×13.3 mm board 13 that can be accommodated inside the metal shell 30 of a common mining and blasting detonator as shown in FIG. 1, with contact pads 21 provided for connection to the hotwire initiator 20.
  • The TVS 22 blocks voltage applied across the legwires 28 until the clamping voltage is reached, at which point the TVS 22 starts conducting current to the hotwire initiator 20. The TVS 22 can be discrete axial or radial, preferably a surface mount component. The TVS 22 is preferably chosen to conduct above 100V, more preferably 180V and most preferably above 200V but below 450V, typical voltage of electric blasting machines. Examples of such TVSs are smaj170ca, smaj190ca, p4sma200ca and p4sma220ca. With the TVS 22 consisting of a bidirectional p4sma200ca, the assembly should block any DC input voltage up to 200V and will only start conducting at voltages above that (regardless of polarity since it is bidirectional).
  • The parallel resistor 24 placed before the TVS 22 and between the two input terminals 26 from the legwires 28, mitigates ESD charge buildup and also facilitates an electronic assembly continuity check performed at the downholes (to ensure there is electrical continuity between the legwires to the electric detonator below in the downholes). The value of this resistor can be between 1 kOhm to 100 kOhm, most preferably 25 kOhm to 75 kOhm. Alternatively, a combination of resistors in series or parallel can be used to achieve the desired final resistance (e.g., 1 kOhm to 100 kOhm). For example, as shown in FIG. 4, two 150 kOhm resistors 25 can be employed in parallel to produce a circuit resistance of 75 kOhm.
  • As shown in FIG. 5, an alternate embodiment could instead employ two unidirectional TVSs 23. Such an embodiment could also be used with a single resistor or a combination of resistors in series or parallel (not shown).
  • Optionally, as shown in FIG. 6, an RF filter 32 (comprising a pi(LC) filter, RC, RL networks, ferrite beads or chips, or a capacitor) can also be incorporated in the front of the assembly, to enhance blocking of higher frequency AC voltage such as from extraneous RF or EMI signals.
  • Also, instead of a TVS, another means for upwardly shifting the all-fire voltage as measured at the input terminals could be used, such as a combination of (e.g., 100) forward voltage diodes (each producing a drop of 1 volt) connected in series between one of the input terminals and the hotwire initiator.
  • In use, the detonator 10 is connected to an electric blasting machine (not shown) yielding an output of at least 250V from a 450 uF capacitive discharge, such as an REO Model CDJ 450J blasting machine with output of 500V 450 uF capacitance network. Upon arming and firing the blasting machine, the surge in voltage and current to the hotwire initiator 20 results in deployment of the detonator 10 within 20-30 us or .so.
  • Although the present invention has been described in detail in the context of a preferred embodiment of a detonator used in mining and blasting, one skilled in the art will appreciate that numerous variations, modifications, and other applications are also within the scope of the present invention. For example, although an embodiment of the invention for use in mining and blasting has been described, the invention could be used in other applications such as military, defense and aerospace applications where a low-voltage-insensitive electro-pyrotechnic device is needed. By using a TVS as high as 300V to 500V or even 1000V by having serially connected TVSs, it is possible to have all-fire voltage shifted to similarly high-voltage ranges. Further, in automotive applications such as airbags, such a low-voltage-insensitive electro-pyrotechnic device (for example, using a 45V TVS) can be used as an initiator that is impervious to typical automotive voltages of 12V to 42V. Thus, the foregoing detailed description is not intended to limit the invention in any way, which is limited only by the following claims and their legal equivalents.

Claims (20)

1. A low-voltage-insensitive electro-pyrotechnic device, comprising:
a) first and second electrical input terminals;
b) a bridge element connected to said electrical input terminals; and
c) a first transient voltage suppressor connected in series between said bridge element and said first electrical input terminal.
2. The device of claim 1, wherein the device is a detonator.
3. The device of claim 1, wherein the device is a detonator for use in mining and blasting.
4. The device of claim 1, wherein said bridge element is a hotwire initiator.
5. The device of claim 1, wherein said transient voltage suppressor is bidirectional.
6. The device of claim 1, further comprising a second transient voltage suppressor connected between said bridge element and said second electrical input terminal, wherein said first and second transient voltage suppressors are unidirectional.
7. The device of claim 1, further comprising a resistor connected between said electrical input terminals and said bridge element.
8. The device of claim 1, further comprising two or more resistors connected between said electrical input terminals and said bridge element.
9. The device of claim 1, further comprising one or more resistors connected between said electrical input terminals and said bridge element, and further comprising a second transient voltage suppressor connected between said bridge element and said second electrical input terminal, wherein said first and second transient voltage suppressors are unidirectional.
10. The device of claim 1, wherein the device is a detonator for use in mining and blasting and further comprises at least one resistor connected between said electrical input terminals and said bridge element.
11. The device of claim 10, wherein said transient voltage suppressor has a clamping voltage of at least 100V.
12. The device of claim 10, wherein said transient voltage suppressor has a clamping voltage greater than 100V and less than 450V.
13. The device of claim 10, wherein said transient voltage suppressor is a p4sma200ca.
14. The device of claim 10, wherein said resistor is connected in parallel between said input terminals and said bridge element and has a resistance greater than 1 kOhm and less than 100 kOhm.
15. The device of claim 14, wherein said resistor has a resistance greater than 25 kOhm and less than 75 kOhm.
16. The device of claim 14, further comprising an RF filter.
17. The device of claim 1, further comprising an RF filter.
18. A low-voltage-insensitive electro-pyrotechnic device, comprising:
a) first and second electrical input terminals;
b) a bridge element connected to said electrical input terminals; and
c) an upwardly voltage shifting means connected in series between said bridge element and said first electrical input terminal.
19. The device of claim 18, wherein said upwardly voltage shifting means comprises at least one transient voltage suppressor.
20. The device of claim 18, further comprising an RF filter.
US11/811,568 2007-06-09 2007-06-09 Low-voltage-insensitive electro-pyrotechnic device Abandoned US20110002078A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US11/811,568 US20110002078A1 (en) 2007-06-09 2007-06-09 Low-voltage-insensitive electro-pyrotechnic device
PCT/IB2008/050557 WO2008152529A1 (en) 2007-06-09 2008-02-15 Low-voltage-insensitive electro-pyrotechnic device
CL2008001694A CL2008001694A1 (en) 2007-06-09 2008-06-09 Low voltage insensitive electropyrotechnic device composed of a first and a second electrical input terminal, a bridge element connected to both terminals, and a transient voltage suppressor between the first terminal and the bridge element.

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US11/811,568 US20110002078A1 (en) 2007-06-09 2007-06-09 Low-voltage-insensitive electro-pyrotechnic device

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8166879B2 (en) * 2007-03-12 2012-05-01 Dyno Nobel Inc. Detonator ignition protection circuit

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4103619A (en) * 1976-11-08 1978-08-01 Nasa Electroexplosive device
US4967665A (en) * 1989-07-24 1990-11-06 The United States Of America As Represented By The Secretary Of The Navy RF and DC desensitized electroexplosive device
US5616881A (en) * 1995-05-30 1997-04-01 Morton International, Inc. Inflator socket pin collar for integrated circuit initaitor with integral metal oxide varistor for electro-static discharge protections
US5932832A (en) * 1996-04-15 1999-08-03 Autoliv Asp, Inc. High pressure resistant initiator with integral metal oxide varistor for electro-static discharge protection
US6272965B1 (en) * 1995-08-24 2001-08-14 Auburn University Method of forming radio frequency and electrostatic discharge insensitive electro-explosive devices
US6839097B2 (en) * 2000-04-12 2005-01-04 Lg.Philips Lcd Co., Ltd. Liquid crystal display with electrostatic protection circuits
US20080223241A1 (en) * 2007-03-12 2008-09-18 Dyno Nobel, Inc. Detonator ignition protection circuit

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4103619A (en) * 1976-11-08 1978-08-01 Nasa Electroexplosive device
US4967665A (en) * 1989-07-24 1990-11-06 The United States Of America As Represented By The Secretary Of The Navy RF and DC desensitized electroexplosive device
US5616881A (en) * 1995-05-30 1997-04-01 Morton International, Inc. Inflator socket pin collar for integrated circuit initaitor with integral metal oxide varistor for electro-static discharge protections
US6272965B1 (en) * 1995-08-24 2001-08-14 Auburn University Method of forming radio frequency and electrostatic discharge insensitive electro-explosive devices
US5932832A (en) * 1996-04-15 1999-08-03 Autoliv Asp, Inc. High pressure resistant initiator with integral metal oxide varistor for electro-static discharge protection
US6839097B2 (en) * 2000-04-12 2005-01-04 Lg.Philips Lcd Co., Ltd. Liquid crystal display with electrostatic protection circuits
US20080223241A1 (en) * 2007-03-12 2008-09-18 Dyno Nobel, Inc. Detonator ignition protection circuit

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8166879B2 (en) * 2007-03-12 2012-05-01 Dyno Nobel Inc. Detonator ignition protection circuit

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CL2008001694A1 (en) 2009-07-24
WO2008152529A1 (en) 2008-12-18

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