US3524408A - Electrostatic discharge dissipator for a heater bridgewire circuit of an electro-explosive device - Google Patents
Electrostatic discharge dissipator for a heater bridgewire circuit of an electro-explosive device Download PDFInfo
- Publication number
- US3524408A US3524408A US699450A US3524408DA US3524408A US 3524408 A US3524408 A US 3524408A US 699450 A US699450 A US 699450A US 3524408D A US3524408D A US 3524408DA US 3524408 A US3524408 A US 3524408A
- Authority
- US
- United States
- Prior art keywords
- electro
- bridgewire
- heater
- explosive device
- circuit
- Prior art date
- 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.)
- Expired - Lifetime
Links
- 239000002360 explosive Substances 0.000 title description 41
- 239000004020 conductor Substances 0.000 description 28
- 239000000463 material Substances 0.000 description 19
- 239000007789 gas Substances 0.000 description 17
- 238000010304 firing Methods 0.000 description 15
- 229910052754 neon Inorganic materials 0.000 description 12
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 description 12
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 10
- 229910052756 noble gas Inorganic materials 0.000 description 6
- 230000001939 inductive effect Effects 0.000 description 5
- 239000002184 metal Substances 0.000 description 4
- 239000003990 capacitor Substances 0.000 description 3
- 238000009413 insulation Methods 0.000 description 3
- 230000003068 static effect Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 230000000977 initiatory effect Effects 0.000 description 2
- 238000004382 potting Methods 0.000 description 2
- 239000004593 Epoxy Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000012212 insulator Substances 0.000 description 1
- 238000010849 ion bombardment Methods 0.000 description 1
- 229910052743 krypton Inorganic materials 0.000 description 1
- DNNSSWSSYDEUBZ-UHFFFAOYSA-N krypton atom Chemical compound [Kr] DNNSSWSSYDEUBZ-UHFFFAOYSA-N 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- 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 heater bridgewire circuit of an electro-explosive device is rendered safe against unintentional firing resulting from electrostatic discharge by operatively associating with such circuit an electrostatic discharge dissipator of a gaseous electrical conductable type which includes electrodes arranged in a predetermined environment of an ionizable gas so that one electrode is electrically connected to a lead wire for the heater bridgewire and another electrode is electrically grounded.
- a typical electro-explosive device includes a pair of lead wires connected to a heater bridgewire embedded in a body of explosive material.
- the initiating phenomenon consists of an are which occurs between one bridgewire circuit and the outer case of the device or between bridgewire circuits when redundant circuitry is employed. Since the heater bridgewire is located in the initiating explosive material, it is presumed that any electrostatic discharge between circuits. or between circuit and case, involves a positive ion bombardment of the ignitable material in the path of the are.
- the human body is capable of building up a static charge of 810,000 ergs equivalent to a 500 mmf capacitor charged to 18,000 volts.
- the average electro-explosive device can be inadvertently fired if carried about while holding onto the lead wires or the case and at the same time contacting a grounded conductor such as a pipe or radiator, or contacting even an ungrounded conductive mass of comparatively large size with the case or lead wires not in direct contact with the person's body.
- a grounded conductor such as a pipe or radiator
- the fact that the lead wires may be twisted or fastened together does not alter the susceptibility of the device to electrostatic discharge firing.
- spark gaps of millimeter size either hermetically sealed or open to atmosphere have been used in an attempt to restrict the maximum potential that can be applied and maintained between the bridgewire circuit and the case of an electro-explosive device. But the use of such spark gaps has not been fully satisfactory. This is because in an uncontrolled vacuum or gaseous atmosphere, the gap breakdown voltage value can be very unpredictable unless the gap is built with extreme precision. Moreover, ionizing potentials may change with each discharge even though the gap length remains constant.
- gaseous electrical conductable means including two or more electrodes arranged in a controlled or predetermined environment of an ionizable gas and operatively associated with circuits to provide one or more preferential alternate electrostatic discharge paths rather than those that would discharge through the explosive material of the electro-explosive device.
- the gaseous electrical conductable means may be incorporated directly into the structure of the electroexplosive device or may be a separate component directly insertable by in-line series connections between the electrical connector of the device and the electrical connector on the firing circuit cable.
- Another advantage of the present invention is that it dissipates an electrostatic discharge other than through the explosive material in a simple manner which adds very little increase to the cost of the electro-explosive device.
- FIG. 1 is a longitudinal central sectional view, partly schematic, through an electro-explosive device equipped with electrostatic discharge dissipator means embodying one form of the present invention.
- FIG. 2 is a fully schematic view similar to FIG. 1 and showing another form of the present invention.
- FIG. 3 is another fully schematic view similar to FIG. 2 and showing still another form of the present invention.
- FIG. 4 is still another fully schematic view of protecting a redundant heater bridgewire circuit against electrostatic discharge and showing yet another form of the present invention.
- the numeral 10 represents a conductive metal case of any suitable configuration for housing the electro-explosive device. This case is shown as having an enlarged cavity 11 at one end and a smaller cavity 12 at the other end.
- the wall portion of case 10 between its cavities l1 and 12 is shown as having two holes 13 and I4.
- a squib or primer 15 containing an explosive material 16 of well known composition and in which a heater bridgewire I7 is embedded.
- a lead wire 18 is electrically connected to one end of bridgewire I7 and another lead wire 19 is electrically connected to its other end.
- These lead wires 18 and 19 are shown as extending exteriorly of the device to provide terminals 20 and 21, respectively.
- Explosive material 16 is intended to be ignited by bridgewire 17 when a low voltage firing signal is applied to terminals 20 and 21 to heat the bridgewire.
- Insulation between the aforementioned firing circuit and case is provided by a ceramic insulator 22 arranged in the base of case cavity 12 and through which lead wires 18 and 19 extend, and also by glass seals 23 and 24 arranged in case holes 13 and 14, respectively, and through which lead wires 18 and 19, respectively, also extend.
- gaseous electrical conductable means are shown incorporated in the electro-explosive device to provide an electrostatic discharge path alternate to spark discharge through explosive material 16. While a predetermined environment of any suitable ionizable gas may be employed as the gaseous electrical conductable means, it is preferred to use a confined body of an inert noble gas such as helium, neon, argon, krypton and xenon. An inert noble gas is preferred because of its relatively low ionization potential. Conveniently neon glow lamps are commercially avialable for this purpose. Accordingly, a neon glow lamp 25 is shown operatively associated with the firing circuit including lead wires 18 and 19 and heater bridgewire 17. This lamp and the associated circuitry are embedded in suitable insulative potting represented by the numeral 27. Epoxy insulation is a preferred potting material.
- Neon glow lamp 25 includes an envelope 28 filled with neon gas and a pair of metal electrodes 29 and 30.
- a conductor or wire 34 electrically connects electrode 29to lead wire 18.
- a conductor or wire 37 electrically connects electrode 30 to case 10.
- conductor or wire 37 includes in series a resistor 38 of a non-inductive type for limiting current flow. Case 10 is shown grounded at 39.
- a typical commercially available neon glow lamp suitable for use as lamp 25 has a breakdown potential of 70 to volts D.C. depending on ambient temperature and exclusion of light conditions. Such a lamp is rated for current operation of 2 milliamperes using a current limiting resistor at higher currents. sputtering of the'metal electrodes occurs and failure of the lamp can occur in milliseconds. When a 1500 mmf capacitor charged to 9000 volts is discharged into such a glow lamp with a 10 ohm series resistor. a peak current of I50 am peres has been recorded without damage to the lamp. This is probably explained by reason of the extremely low RC time constant of .075 micro s'econd.
- bleed-offof unwanted high voltage electrostatic charges by gaseous ionization can be reliably depended upon to initiate at 70 to 135 volts.
- the normal intended firing signal would be in the to 28 volt range. where no bleed-off occurs.
- Some of the electrostatic energy could be dissipated as heat in the bridgewire 17 if the discharge were applied to a single pin of the circuit and the lamp 25 were connected to ground by a path that included the bridgewire.
- the use of a ohm nominal non-inductive resistor 38 in the circuit is intended to assure distribution of the applied static energy so that it would be impossible for more than 109? ofthe total discharge energy to be dissipated directly in the heater bridgewire 17.
- resistor 38 is not essential, it is preferred because it permits much greater total electrostatic discharge dissipation ⁇ vithout ignition.
- the electrical circuit represented in FIG. 2 is similar to that depicted in FIG. 1 except for omission ol the resistor 38 and inclusion of a second net .i glow lamp 26.
- This lamp 26 includes an envelope 3
- the neon glow lamp corresponding to lamp is designated 25' having an envelope 28' and electrodes 29'and 30', and the bridgewire l7'shown embedded in explosive material l6'has lead wires I8'and 19 between which lamps 25'and 26 are arranged.
- Electrode 29' is electrically connected to lead wire 18 by conductor or wire 34'.
- Electrode 33 is electrically connected to lead wire 19' by conductor or wire 35.
- a conductor or wire 36 electrically connects electrodes 30' and 32 together.
- Ground conductor or wire 37' is shown as electrically connecting conductor or wire 36. externally of envelopes 28' and 31. to ground 39. It is pointed out that conductor or wire 37'has no resistor therein comparable to resistor 38 shown in FIG. l.
- the electrical circuit represented in FIG. 3 is similar to that dipicted in FIG. 2 except that only a single neon glow lamp 40 having three electrodes 4
- the electrical circuits depicted in FIG. 4 contemplate the use of neon glow lamp means to protect against electrostatic discharge in a redundant heater bridgewire electro-explosive device.
- the numeral 47 represents a heater bridgewire having lead wires A and B. and the numeral 48 represents a second heater bridgewire having lead wires C and D. Both bridgewires 47 and 48 are shown embedded in the same body ot'explosivc material 16a.
- a three-electrode neon glow lamp 54 is shown as having two of its electrodes 55 and 56 electrically connected by conductors or wires 57 and 58. respectively. to lead wires C and A. respectively. lts third electrode 59 is electri cally connected by conductor or wire 60 to ground 61. In this manner. neon glow lamp 54 protects against static discharge between circuit AB and ground. between circuit C-D and ground. and between circuit A-B and circuit C-D.
- an electro-explosive device having a circuit including a pair of lead wires connected by a heater bridgewire embedded in a body olexplosive material and to which lead wires a firing signal is applied to heat said bridgewire for exploding said material.
- the im rovement of an electrostatic dischar e dissipator independent of the means which applies sai firing signal which comprises gaseous electrical conduct-able means including electrodes arranged in a predetermined environment of an ionizable gas.
- first conductor means electrically connecting one of said electrodes to one of said lead wires.
- second conductor means electrically grounding another of said electrodes.
- An electro-explosive device which further comprises a third conductor means electrically connecting still another of said electrodes to the other of said leads.
- said gaseous electrical conductable means includes two separate confined bodies of ionizable gas and a pair of electrodes arranged in each such gas body.
- said first conductor means electrically connects one electrode in one gas body to one oi said leads.
- said second conductor means electrically grounds the other electrode in said one gas body and also electrically grounds. one electrode in the other gas body. and further comprises third conductor means electrically connecting the other electrode in said other gas body to the other of said leads.
- An electro-explosive device according to Claim 12 wherein said second conductor means includes a resistor.
- an electro-cxplosive device having a first heater bridgewire circuit including a first pair of lead wires con nected to a first heater bridgewire embedded in a body of explosive material and to which first pair of lead wires a firing signal is applied to heat said first bridgewire for exploding said material. and a second heater bridgewire circuit including a second pair of lead wires connected to a second heater bridgewire embedded in said body ofexplosivc material and to which second pair of lead wires a firing signal is applied to heat said second bridgewire for exploding said material.
- the improvement of an electrostatic discharge dissipator independent of the means which apply said firing signals which comprises gaseous electrical conductable means including electrodes arranged in a predetermined environment of an ionizable gas.
- first conductor means electrically connecting one of said electrodes to one lead wire of said first circuit.
- second conductor means electrically connecting another of said electrodes to one lead wire of said second circuit.
- third conductor means electrically grounding still another one of said electrodes
Description
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US69945068A | 1968-01-22 | 1968-01-22 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3524408A true US3524408A (en) | 1970-08-18 |
Family
ID=24809383
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US699450A Expired - Lifetime US3524408A (en) | 1968-01-22 | 1968-01-22 | Electrostatic discharge dissipator for a heater bridgewire circuit of an electro-explosive device |
Country Status (1)
Country | Link |
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US (1) | US3524408A (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3728967A (en) * | 1969-06-13 | 1973-04-24 | Us Navy | Tri-pri three contact primer |
US4261263A (en) * | 1979-06-18 | 1981-04-14 | Special Devices, Inc. | RF-insensitive squib |
EP0266783A1 (en) * | 1986-11-07 | 1988-05-11 | DIEHL GMBH & CO. | Ignition element |
EP0679859A2 (en) * | 1994-03-29 | 1995-11-02 | Halliburton Company | Electrical detonator |
US20070188540A1 (en) * | 2006-02-13 | 2007-08-16 | Lexmark International, Inc. | Actuator chip for inkjet printhead with electrostatic discharge protection |
US10066919B2 (en) | 2015-06-09 | 2018-09-04 | Owen Oil Tools Lp | Oilfield side initiation block containing booster |
EP3686395A3 (en) * | 2017-08-09 | 2020-10-21 | GeoDynamics, Inc. | Igniter system, downhole tool and method |
US10920544B2 (en) | 2017-08-09 | 2021-02-16 | Geodynamics, Inc. | Setting tool igniter system and method |
-
1968
- 1968-01-22 US US699450A patent/US3524408A/en not_active Expired - Lifetime
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3728967A (en) * | 1969-06-13 | 1973-04-24 | Us Navy | Tri-pri three contact primer |
US4261263A (en) * | 1979-06-18 | 1981-04-14 | Special Devices, Inc. | RF-insensitive squib |
EP0266783A1 (en) * | 1986-11-07 | 1988-05-11 | DIEHL GMBH & CO. | Ignition element |
EP0679859A2 (en) * | 1994-03-29 | 1995-11-02 | Halliburton Company | Electrical detonator |
EP0679859A3 (en) * | 1994-03-29 | 1996-07-03 | Halliburton Co | Electrical detonator. |
US20070188540A1 (en) * | 2006-02-13 | 2007-08-16 | Lexmark International, Inc. | Actuator chip for inkjet printhead with electrostatic discharge protection |
US7361966B2 (en) | 2006-02-13 | 2008-04-22 | Lexmark International, Inc. | Actuator chip for inkjet printhead with electrostatic discharge protection |
US10066919B2 (en) | 2015-06-09 | 2018-09-04 | Owen Oil Tools Lp | Oilfield side initiation block containing booster |
EP3686395A3 (en) * | 2017-08-09 | 2020-10-21 | GeoDynamics, Inc. | Igniter system, downhole tool and method |
US10914147B2 (en) | 2017-08-09 | 2021-02-09 | Geodynamics, Inc. | Setting tool igniter system and method |
US10920544B2 (en) | 2017-08-09 | 2021-02-16 | Geodynamics, Inc. | Setting tool igniter system and method |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: CONAX BUFFALO CORPORATION Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:COMAX CORPORATION;REEL/FRAME:004489/0469 Effective date: 19831003 Owner name: CONAX CORPORATION, A CORP. OF DE. Free format text: MERGER;ASSIGNORS:CONAX CORPORATION (MERGED INTO);2300 WALDEN CORP. (CHANGED TO);REEL/FRAME:004489/0471 Effective date: 19730629 |
|
AS | Assignment |
Owner name: CONAX FLORIDA CORPORATION, 2801 75TH STREET, NORTH Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:CONAX BUFFALO CORPORATION;REEL/FRAME:005108/0722 Effective date: 19881206 |