US005347929A
`United States Patent 15
`Patent Number:
`5,347,929
`Lercheet al.
`Date of Patent:
`Sep. 20, 1994
`[45]
`
`[11]
`
`AACAA
`
`[75]
`
`[56]
`
`[54] FIRING SYSTEM FOR A PERFORATING
`GUN INCLUDING AN EXPLODING FOIL
`INITIATOR AND AN OUTER HOUSING FOR
`TEPConan WIRELINE CURRENT AND
`.
`Inventors: Nolan C. Lerche, Stafford; Clifford L.
`Aseltine, Houston, both of Tex.;
`Wallace E. Voreck, Jr., Sparta, N.J.
`1
`Assi
`.
`Assignee CompaenHoan“Fox
`[73]
`ao
`,
`[21] Appl. No.: 116,082
`.
`[22] Filed:
`Sep. 1, 1993
`5
`[51]
`Imt. C15 oeeccseseeseecssseceensresesses F42C 11/00
`[52] US. Ch. coeceecccccescssccsessssteccessseesereeesssees 102/202.14
`[58] Field of Search................ 102/202.14, 200, 202.5,
`102/202.7, 206
`
`Primary Examiner—Daniel T. Pihulic
`Attorney, Agent, or Firm—Henry N. Garrana; John H.
`Bouchard
`[57]
`ABSTRACT
`A firing head for a firing system adapted for use in a
`perforating gun includes an outer pressure bulkhead
`housing which simultaneously conducts two separate
`and independent currents: a wireline current from a
`wireline and a return current from an initiator embodied
`in the firing head.A fire set circuit provides a discharge
`pulse to the firing head, and a wireline conductorcable
`provides a wireline current to the fire set circuit. The
`firing head includes an outer pressure bulkhead housing
`adapted for conducting the wireline current from the
`wireline conductor cable to the fire set circuit, and an
`’
`:
`a
` ¢xploding foil
`initiator (EFI) responsive to the dis-
`Charge pulse from thefire set circuit for initiating the
`detonation of a secondary explosive. The discharge
`pulse energizing the firing head passes through the ex-
`ploding foil initiator (EFT and emerges from the EFI as
`References Cited
`an EFI return current. As a result, the outer pressure
`U.S. PATENT DOCUMENTS
`bulkhead housing of the firing head conducts two sepa-
`rate and independent currents: the EFI return current
`3,978,791
`9/1976 Lemieyet al... 102/202.14
`aes} Sri98e Barrett “hel 700 from the EFI to a ground potential, and the wireline
`
`81988 Barkeretal “e eeF027202.14
`4.762.067
`current from the wireline conductor cableto the fire set
`
`4,788,913 12/1988 Stroudet al... 102/202.5
`circuit.
`
`7/1990 Barker ......cccssssssseseeeseees 102/202.5
`4,944,225
`2/1992 Huberet al. oe eeeseees 102/200
`5,088,413
`
`22 Claims, 7 Drawing Sheets
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`TO FIRE
`FROM FIRE
`SET CIRCUIT
`SET CIRCUIT
`
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`24
`24
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`26a
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 001
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 001
`
`

`

`U.S. Patent
`
`Sep. 20, 1994
`
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`
`Sheet 1 of 7
`
`5,347,929
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`©Le~
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`n, Inc.
`Hunting Tita
`Ex. 1016
`Pg. 002
`
`NX
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 002
`
`
`
`
`
`
`

`

`U.S. Patent
`
`Sep. 20, 1994
`
`5,347,929
`
`Sheet 2 of 7
`
`
`
`
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 003
`
`

`

`U.S. Patent
`
`Sep. 20, 1994
`
`Sheet 3 of 7
`
`5,347,929
`
`
`
`
`
`
`
`
`
`
`
`
`
`TO FIRE
`SET CIRCUIT
`24
`
`FROM FIRE
`SET CIRCUIT
`24
`
`22¢
`
`22c2
`
`59c3
`\.\i
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`203A
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`22C2B
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`22cIA
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`22c1
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`7262Cc
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`22c2A
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`22c!lB
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`FIG.7
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`FIG.8
`
`22¢2D
`
`FIG.9 gTit
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 004
`
`

`

`U.S. Patent
`
`Sep. 20, 1994
`
`Sheet 4 of 7
`
`5,347,929
`
`FIG. 10
`
`
`FROM
`WIRELINE
`
`
`
`CABLE 16
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`2903
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`22c2
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`22d2 iT 22d1
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`FIG.11
`
`22¢3A "
`|
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`Z2cf
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` 22cTA
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`FIRE SET
`cit
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`CIRCUIT 24
`
`2262
`
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 005
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 005
`
`

`

`U.S. Patent
`
`Sep. 20, 1994
`
`Sheet 5 of 7
`
`5,347,929
`
`22al
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`22di 22e22f 22¢2B
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`FIG.14
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`FROM FIRE
`SET CIRCUIT
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`SE=2203
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`22¢2
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`22e
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`FIG.17
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 006
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 006
`
`

`

`U.S, Patent
`
`Sep. 20, 1994
`
`Sheet 6 of 7
`
`5,347,929
`
`FIG.15
`
`(PRIOR ART)
`
`FIG.16
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`itan,
`Ex. 1016
`Pg. 007
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 007
`
`

`

`U.S. Patent
`
`Sep. 20, 1994
`
`Sheet 7 of 7
`
`5,347,929
`
`NAHLGAF4
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`Hunting Titan, Inc.
`Ex. 1016
`Pg. 008
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`Hunting Titan, Inc.
`Ex. 1016
`Pg. 008
`
`
`
`

`

`1
`
`5,347,929
`
`FIRING SYSTEM FOR A PERFORATING GUN
`INCLUDING AN EXPLODINGFOIL INITIATOR
`AND AN OUTER HOUSING FOR CONDUCTING
`WIRELINE CURRENT AND EFI CURRENT
`
`5
`
`BACKGROUND OF THE INVENTION
`
`2
`gun. This prevents a gun from detonating when the gun
`is partially flooded. A bottom-up configuration again
`requires that the wireline pass through the bulkhead of
`the EFI detonating element in order for the wireline to
`be connected to the bottom side of the detonating ele-
`ment. However, such a pressure bulkhead is very ex-
`pensive to manufacture andis a short life part. In addi-
`tion, the conventional bulkhead electrical property does
`not lenditself well to conducting a rapid high energy
`discharge pulse. Usually, the parameters of a bulkhead
`electrical property that suffer are the effective series
`resistance (ESR) and the effective series inductance
`(ESD). Since typical values of ESR and ESIare quite
`large, the energy storage capacitor inside the EFI must
`also be large. In addition, however, a wireline feed-
`through for an EFI is difficult to fabricate for gun
`strings having small diameters.
`
`The subject matter of the present invention relates to
`a firing system adapted for use in a perforating gun
`connected to a wireline conductor cable in a wellbore,
`and more particularly,
`to an exploding foil initiator
`(EFD) firing system for use in the perforating gun, the
`EF]firing system including an outer housing adapted to
`function as an electrical conductor for conducting a
`return Current to ground potential from the EFIfiring
`system and a wireline current from the wireline conduc-
`tor cable.
`Exploding foil initiators (EFI) have been used for
`initiating the detonation of a secondary explosive. For
`example, U.S. Pat. No. 4,788,913 to Stroud et al dis-
`Accordingly, it is a primary object of the present
`closes a typical explodingfoil initiator. In addition, U.S.
`invention to providea firing system adaptedfor use in a
`Pat. No. 3,978,791 to Lemley et. al. and U.S. Pat. No.
`perforating gun having an outer housing pressure bulk-
`4,471,697 to McCormicket. al. also disclose exploding
`head which has a low effective series resistance and a
`foil initiator or “slapper” detonators. Furthermore, U.S.
`low effective series inductance and which provides an
`Pat. No. 4,441,427 to Barrett and U.S. Pat. No.
`electrical current signal conducting path for two sepa-
`4,762,067 to Barker et al disclose the use of Exploding
`rate and independent currents.
`Foil Initiators in a perforating gun for propelling a
`It is a further object of the present invention to pro-
`flying plate into a secondary explosive and detonating
`vide a firing system including an initiator adapted for
`the perforating gun. In addition, U.S. Pat. No. 5,088,413
`use in a perforating gun including an outer housing
`to Huberet. al. discloses an exploding foil bubble acti-
`pressure bulkhead which provides a conducting path
`vated initiator for use in a perforating gun, the Huberet.
`for two separate currents, one current being a return
`al. patent being incorporated by reference into this
`current conducting from the initiator to ground poten-
`specification. However, although theseinitiators per-
`tial, and another current being a wireline current con-
`form well, certain additional problems, associated with
`ducting from a wireline conductor cable to the initiator
`the use and/or performance of the EFI initiators in
`for purposes of detonatingtheinitiator.
`general and the exploding foil bubble activated initiator
`It is a further object of the present invention to pro-
`of the Huberet al. patent in particular, in a perforating
`vide a firing system adapted for use in a perforating gun
`gun wellbore environment, have yet to be solved.
`including an initiator for initiating detonation of the
`For example,initiation of a perforating gun string in
`40
`firing system, a fire set circuit electrically connected to
`a wellbore can be accomplished using secondary explo-
`theinitiator for providingafiring currentto theinitiator
`sives, such as HNS4. This explosive can be initiated
`and an outer housing enclosingtheinitiator for provid-
`using an EFIinitiator that receives a high energy pulse
`ing a conducting path for two separate currents, one
`from a fire set. Typically, the fire set consists of a high
`current being a return current from the initiator to
`voltage powersupply, an energy storage capacitor, and
`a switch that rapidly dumps stored energy into the EFI
`ground potential, and another current being a wireline
`through a high frequency connector. This connector
`current conducting from a wireline conductor cable to
`the initiatorin the firing system for purposes of detonat-
`must have a very low effective series resistance (ESR).
`ing the initiator.
`However, after detonation, the fire set must be con-
`tained in a protected housing whichis isolated from the
`In accordance with these and other objects of the
`well fluids and the pressures in the wellbore. Therefore,
`present invention, a firing head for a firing system
`a pressure bulkhead must be electrically and physically
`adapted for use in a perforating gun includes an outer
`connected to the fire set and the EFI for electrically
`pressure bulkhead housing which simultaneously con-
`connecting the fire set and the EFI to ground potential
`ducts two separate and independent currents, that is, a
`wireline Current from a wireline and a return current
`so that the EFI can ultimately detonate the secondary
`explosives in the perforating gun string. In addition,
`from an initiator embodiedin thefiring head. A fire set
`whenperforating oil wells, sometimesit is necessary to
`circuit provides a discharge pulse to the firing head, and
`selectively shoot multiple guns in the same gunstring.
`a wireline conductor cable provides a wireline current
`In order to detonate the gun selectively, the wireline
`to the fire set circuit. The firing head includes an outer
`voltage must pass through the upper guns in order to
`pressure bulkhead housing for enclosing the firing head,
`reach the lower guns in the gun string. Therefore, the
`and an exploding foil initiator (EFI) responsive to the
`pressure bulkhead which provides the EFI pulse must
`discharge pulse from thefire set circuit for initiating the
`also provide a means to transfer the wireline voltage
`detonation of a secondary explosive. The discharge
`through the guns in the gun string. Typically, this is
`pulse energizing the firing head passes through the ex-
`accomplished using a separate wireline feed through.
`plodingfoil initiator (EFI) and emerges from the EFI as
`Whenshooting perforating guns in a bottom up config-
`a return current. Due to the geometry of the outer
`uration, a detonating element must be placed on the
`pressure bulkhead housing of the firing head, the pres-
`bottom of the gun and the shaped charges are posi-
`sure bulkhead has a low Effective Series Resistance
`tioned above the detonating elementin the perforating
`(ESR)and a low Effective Series Inductance (ESI). As
`
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`SUMMARYOF THE INVENTION
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 009
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`Hunting Titan, Inc.
`Ex. 1016
`Pg. 009
`
`

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`5,347,929
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`3
`a result of this and a floating ground, the outer pressure
`bulkhead housing of the firing head is capable of effi-
`ciently conducting two separate and independent cur-
`rents: the return current from the EFI to a ground po-
`tential, and the wireline current from the wireline con-
`ductor cable to thefire set circuit.
`Further scope of applicability of the present inven-
`tion will become apparent from the detailed description
`presented hereinafter. It should be understood, how-
`ever, that the detailed description and the specific exam-
`ples, while representing a preferred embodimentof the
`present invention, are given by wayofillustration only,
`since various changes and modifications within the
`spirit and scope of the invention will become obviousto
`one skilled in the art from a reading of the following
`detailed description.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`A full understanding of the present invention will be
`obtained from the detailed description of the preferred
`embodiment presented hereinbelow, and the accompa-
`nying drawings, which are given by wayofillustration
`only and are not intended to belimitative of the present
`invention, and wherein:
`FIGS. 1 and2 illustrate a firing system adapted to be
`disposed in a perforating gun in accordance with the
`present invention;
`FIG.3 illustrates a cross section of FIG. 1 taken
`along section lines 3—3 of FIG.1;
`FIG.4 illustrates a firing head embodied within the
`firing system of FIG.1;
`FIG.5 illustrates a disassembled view ofthefiring
`head of FIG.4;
`FIG.6 illustrates a three-dimensional and enlarged
`view of a substantial portion ofthe firing head of FIGS.
`45;
`FIGS.7-13 illustrate views of various portions of the
`firing head of FIGS. 4-6;
`FIG.14 illustrates a longitudinal cross sectional view
`of the firing head shownin FIG.6 ina state whichexists
`prior to detonation of the EFI in thefiring head;
`FIGS. 15-16 illustrate longitudinal cross sectional
`views of the bubble activated detonator disclosed in
`US. Pat. No. 5,088,413 to Huberetal, the disclosure of
`which has been incorporated by reference into this
`specification;
`FIG.17illustrates a longitudinal cross sectional view
`ofthe firing head shownin FIG.6 in a state which exists
`after detonation of the EFIin the firing head; and
`FIG.18 illustrates the fire set circuit or power supply
`embodied in the firing system of FIGS.1-2.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`Referring to FIGS. 1 through 3, a firing system,
`adapted for use with a perforating gun,is illustrated.
`The perforating gun is adapted to be disposed in a well-
`bore,
`In FIGS. 1 and 2, a first housing 10 is threadedly
`connected to a second housing 12; however, a tie wrap
`14 prevents the second housing 12 from approaching
`and contacting the first housing 10 as long as the tie
`wrap 14is in place as shown in FIG. 1. The tie wrap 14
`is a safe-am device. It can easily be removed from its
`location shown in FIG.1; and, whenthe tie wrap 14is
`removed, the second housing 12 can be moved toward
`the first housing 10 thereby allowing the tip 12a of the
`second housing 12 to contact the tip 10a of thefirst
`
`4
`housing 10. When the tips 12a/10a of the first and sec-
`ond housings 10 and 12 contact each other, the firing
`system of FIGS.1-2 is armed. A detonating cord 16 and
`a wireline cable 18 are disposed adjacent one another
`within the interior of the first and second housings 10
`and 12. The wireline cable 18 runs, at its top end, to the
`surface of the wellbore; and the detonating cord 16 is
`connected, at
`its top end,
`to a plurality of shaped
`chargesin the perforating gun for detonating the shaped
`charges in a bottom-up firing sequence. The detonating
`cord 16 is connected,at its bottom end, to a booster 16a.
`The wireline cable 18 is disposed within a housing 20
`which encloses the booster 16a of the detonating cord
`16 andis further connected,at its bottom end,toa firing
`head 22 in accordance with the present
`invention.
`Whenthe firing head 22 of the present invention deto-
`nates, the booster 16a ignites and detonates whichiniti-
`ates the propagation of a detonation wavein the deto-
`nating cord 16. The detonation wave begins to propa-
`gate upwardly through the detonating cord 16 to the
`plurality of shaped charges in the perforating gun. The
`shaped charges of the perforating gun are disposed
`abovethefiring head 22 in FIG.1 (a bottom-up configu-
`ration);
`therefore the shaped charges detonate from
`bottom to top as described in the backgroundsection of
`this specification. As a result, when the shaped charges
`in the perforating gun detonate, a jet is formed from
`each shaped charge, starting with the lowermost shaped
`charge and ending with the uppermost shaped charge.
`The jets perforate a formation traversed by the well-
`bore, starting with a lowermost part of the formation
`and ending with an uppermost part of the formation.
`Well fluid begins to flow from the perforated formation.
`A power supply or fire set circuit 24 is electrically
`connected to the firing head 22. Thefire set circuit 24
`receives its energizing current from the wireline cable
`18. A wireline current conducting in the wireline cable
`18 energizes the fire set circuit 24 and, in response, the
`fire set circuit 24 provides the high energy discharge
`pulse to the firing head 22. In response, the firing head
`22 ignites and detonates the booster 16a as described
`above.
`FIG. 3 illustrates a cross section of FIG. 1 taken
`along section lines 3—3 of FIG.1.
`Referring to FIG.4, a three dimensional view of the
`firing head 22 of FIG.1 isillustrated.
`In FIG.4, the firing head 22 comprises an outer pres-
`sure bulkhead housing 22¢ and a pin 226 disposed
`within the interior of the pressure bulkhead 22a. Not
`shownin FIG.4 is an EFI bridge disposed on top of the
`pin 22b, an EFI barrel disposed on top of the EFI
`bridge, and a secondary (HE) explosive disposed on top
`of the EFI barrel. These components will be illustrated
`in FIG. 5. However, note in FIG. 4 that two separate
`and independentcurrents are flowing in the outer pres-
`sure bulkhead housing 22a. Thefirst current flowing in
`the pressure bulkhead 22a is the wireline current 18a
`conducting from the wireline cable 18, and the second
`current flowing in the pressure bulkhead 22a is the EFI
`return current 24a to EFI ground. The EFI ground
`potential is the same potential as to wireline power and
`is also floating in respect to all other potentials and, in
`particular, to tool ground.
`The EFT return current 24¢ is the return current to
`ground potential from an explodingfoil initiator (EFI)
`which is disposed on the top of pin 226. An EFI current
`246 originating from the fire set circuit 24 propagates
`upwardly through the pin 225 and moves toward to the
`
`15
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`Hunting Titan, Inc.
`Ex. 1016
`Pg. 010
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`Hunting Titan, Inc.
`Ex. 1016
`Pg. 010
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`5
`top of the pin 225 where it energizes the EFI disposed
`on the top of the pin 224. The EFIreturn current flows
`out of the EFI, into the outer pressure bulkhead housing
`22a, and downthe sides of the pressure bulkhead hous-
`ing 22a to ground potential. Simultaneously, wireline
`current 18a from wireline 18 flows down the sides of
`the pressure bulkhead housing 22a, and out the pressure
`bulkhead 22a on its way toward thefire set circuit 24.
`Due to the geometry (size, shape, volume) of the
`pressure bulkhead housing 22a,the housing 22a exhibits
`a low effective series resistance and a low effective
`series inductance. Asa result, the pressure bulkhead 22a
`will easily conducta rapid high energy discharge pulse
`from thefire set circuit 24.
`Referring to FIG.5, an exploded view ofthe flowing
`head 22 of FIG. 4 is illustrated.
`In FIG. 5, the outer pressure bulkhead housing 22a
`encloses the pin 22b. The pin 226 is madeofstainless
`steel (an electrically conductive material); however,
`substantially the entire surface area of the pin 22is
`coated with a polymide based insulating material 2243
`known as “PYRL-ML” manufactured by E. I. Dupont
`DeNemours (Dupont) Corporation. The PYRL-ML
`insulating coating 2253 covers the entire surface area of
`the pin 226 except for: (1) one circular area 226 1 dis-
`posed onthetop ofthe pin 228, and (2) the bottom 2252
`surface area of the pin. The circular area 22b1 on the top
`of the pin 226 appears to be a dot; however, the dot
`actually represents a conductive pad area for conduct-
`ing an electrical current from the pin 22b. The bottom
`2262 surface area of the pin 226 is not coated with the
`PYRL-MLinsulating coating 2253 because the bottom
`surface area 2262 of pin 226 is plugged into a female
`electrical connector which conducts a high energy
`discharge pulse to the pin 22d from the fire set circuit
`24. An EFI bridge 22c is disposed on the top of the pin
`226. The exact orientation of the EFI bridge 22c on the
`top of pin 22b is important, this orientation being dis-
`cussed with reference to FIG. 6 of the drawings. An
`EFIbarrel 22d is disposed over the EFI bridge 22c, the
`EFI barrel 22d having a hole disposed in the center.
`This hole and its function will discussed later in this
`specification. The outer pressure bulkhead housing 22a
`includes a top ground cap 22a]. A center bore 22a1A is
`disposed through the centerof the ground cap 22a1, and
`a secondary explosive in the form ofa cylindrical pellet
`22e (the secondary explosive being FIE) fits snugly
`within the center bore 22@1A of the ground cap 2201. A
`metal flyer 22/is disposed above the secondary explo-
`sive pellet 22e. Whenthe pellet 22e detonates, a flying
`plate is cut from the center of the flyer 22f, the flying
`plate flying across a space and impacting the booster
`16a of the detonating cord 16 in FIG.1 thereby initiat-
`ing the propagation of a detonation wavein the detonat-
`ing cord 16. The shaped charges in a perforating gun
`will detonate in response to the detonation wave. Fol-
`lowing detonation, O-rings 22g and 22h seal the pin and
`bulkhead thereby preventing fluid invasion beyond the
`bulkhead.
`Referring to FIG. 6, an enlarged three dimensional
`view of the pin 226, EFI bridge 22c, EFI barrel 22d,
`ground cap 221, secondary explosive pellet 22e and
`flyer 22f of FIG.5 is illustrated.
`In FIG.6, the pin 220 is coated with the PYRL-ML
`insulating coating 223 offigure except for a conductive
`pad area 226 1 disposed onthetop ofthe pin 22andthe
`bottom surface area 22b2 on the bottom ofthe pin. Since
`the pin 22d is madeofstainless steel, it can easily con-
`
`6
`duct an electrical current. The current is provided by
`the fire set circuit 24 which provides a high energy
`discharge pulse, the discharge pulse conducting from
`the bottom surface area 2262, up the center part of the
`pin 228, and toward the conductive pad area 2261. The
`EFTbridge 22c is comprised ofthree layers,a first layer
`22cl, a second layer 22c2, and a third layer 22c3. The
`first layer 22ci is 1 mil in thickness and is comprised of
`a polyimide material. One such polyimide material to
`use for the first layer 22c1 is a material known as “Kap-
`ton”. The Kapton polyimide material is manufactured
`by E. . DuPont De Nemours, Incorporated (Dupont).
`Thefirst layer 22cl includes a hole 22c1A whichisfilled
`with a conductive epoxy in orderto facilitate the con-
`ductance of an electrical current (the high energy dis-
`charge pulse from thefire set circuit 24) from the pin
`225, into the conductive pad area 2261, and into the
`conductive epoxy whichfills the hole 22c1A ofthe first
`layer 22c1. The second layer 22c2 of the EFI bridge 22c
`is approximately 170 micro-inch in thickness, is com-
`prised of a Copper material, and is electroplated to the
`first layer 22cl. The Copper material of the second
`layer 22c2 is an electrically conductive material and was
`selected to receive the high energy discharge pulse,
`from the conductive epoxy in hole 22c1A, into a first
`left hand portion of the copper second layer 22c2 and to
`further conduct the pulse through a center neck section
`22c2A of the copper second layer 22c2 toward a second
`right hand portion of the copper second layer 22c2
`where a crescent conductive pad area 22c2Bis disposed.
`The crescent conductive pad area 22¢2B on the second
`layer 22c2 of the EFI bridge 22c is electrically con-
`nected to a conductive epoxy which is disposed within
`a hole 22c3A of the third layer 22c3 of the EFI bridge
`22c, the conductive epoxy in the hole 22c3A being elec-
`trically connected to a shoulder X which is disposed
`around an interior of the ground cap 22a1 of the outer
`pressure bulkhead housing 22a. The high energy dis-
`charge pulse from the second right hand portion of the
`copper second layer 22c2 conducts into the crescent
`conductive pad area 22c2B and eventually conducts
`through the conductive epoxy in the hole 22c3A and
`into the ground cap 22c1ofthe outer pressure bulkhead
`housing 22a. The third layer 22c3 of the EFI bridge 22c
`is 1 mil in thickness and is comprised of the Kapton
`polyimide material. The third layer 22c3 includes the
`hole 22c3A, in which a conductive epoxy is disposed,
`which has a shape which conformsto the shape ofthe
`crescent conductive pad 22c2B ofthe second layer 22c2.
`The EFTbarrel 22d is actually a spacer layer made of
`a polyamide material. The EFT barrel 22d is 0.010
`inches in thickness and is 0.25 inches in diameter and
`includes a hole 22d1 which is 0.055 inches in diameter
`and is 0.010 inches in height. As will be explained fur-
`ther in this specification, when a bubble forms in the
`third layer 223 of the EFI bridge 22c, the hole 22d1 of
`the EFIbarrel 22d guides, forms, and shapes the bubble
`before the bubble impacts the secondary explosive pel-
`let 22e. As noted earlier, the outer pressure bulkhead
`housing 22a includes the ground cap 22a1 which is
`disposed above the EFI barrel 22d. The ground cap
`22a] includesa center bore in which a secondary explo-
`sive (HE) pellet 22e is disposed. The pellet 22e is posi-
`tioned directly above the hole 22d1 in the EFI barrel
`22d and directly above the neck section 22c2A of the
`copper second layer 22¢2 of the EFI bridge 22c. The
`flyer 22fis disposed directly above the ground cap 22a1.
`When the secondary explosive pellet 22edetonates, a
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. O11
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 011
`
`

`

`5,347,929
`
`25
`
`35
`
`45
`
`50
`
`20
`
`7
`8
`flying plate 22/1 is sheared off the flyer 22f As will be
`dot representing an electrically conductive pad area
`noted later in this specification, the flying plate 22/1 flys
`2261 for conducting an electrical current.
`across a space and impacts the booster 16a of the deto-
`Referring to FIG.13, the pin 224 is coated onits sides
`nating cord 16 in FIG. 1,
`(but not on its bottom 2262) with the PYRL-MLinsu-
`Referring to FIG. 7, a top view of the second layer
`lating coating 2263. As noted earlier, the pin 22d itself
`22c2 and the third layer 22c3 of the EFI bridge 22c of
`(without the coating) is madeof an electrically conduc-
`FIGS. 5 and6is illustrated. Note how the crescent
`tive stainless steel material; however, substantially the
`conductive pad area 22c2Bis electrically connected to a
`entire surface area is coated with the insulating coating
`2263 except for the bottom 2252(whichis adapted to be
`conductive epoxy disposed within the hole 22c3A in the
`third layer 22¢3 and how the conductive epoxy in hole
`connected to an electrical connector) and the dot con-
`ductive pad area 226 1 disposed on the top of the pin.
`22¢3A is electrically connected to the shoulder X of the
`Referring to FIG. 14, a longitudinal cross sectional
`outer pressure bulkhead housing 22.
`view ofthe firing head 22 shownin FIG.6 is illustrated
`Referring to FIG. 8, a top view ofthefirst layer 22cl
`in a state which exists prior to detonation of the explod-
`of the EFTbridge 22cis illustrated. Note the hole 22c1A.
`ing foil initiator (EFI)in the firing head 22. A functional
`in the first layer 22cl. As noted earlier, the hole 22c1A
`description of the operation of the firing head 22, prior
`is filled with a conductive epoxy 22c1B in order to
`to vaporization of the neck section 22c2A of the second
`facilitate the conductance of the discharge pulse from
`layer 22c2 and detonation of the secondary explosive
`the fire set circuit 24, through the pin 226, the conduc-
`pellet 22e, will be set forth in the following paragraph
`tive pad area 2261 and the epoxy 22c1B to the second
`with reference to FIG. 14.
`layer 22c2 of the EFI bridge 22c.
`In FIG. 14, the discharge pulse 24b from thefire set
`Referring to FIG. 9, the geometry associated with
`circuit 24 passes through the center of the pin 22). An
`the neck section 22c2A of the second layer 22c2 of the
`insulating coating 2253 coats substantially the entire
`EFIbridge 22c, before the neck section has vaporized in
`surface area of the pin; however, a hole in the coating
`responseto the discharge pulse from thefireset circuit
`exposes a conductive pad area 22b1. The discharge
`24, is illustrated. Before vaporization of the neck sec-
`pulse 245 passes through the conductive pad area 2251,
`tion, the first left hand portion 22c2C of the second
`through the conductive epoxy in the hole 22c1A in the
`layer 22c2 is integrally connected to the neck section
`first layer 22cl of the EFI bridge 22c, and into the sec-
`22c2A, the neck section being integrally connected to
`ond layer 22c2 of the EFI bridge 22c. The discharge
`the second right hand portion 22c2D ofthe second layer
`pulse current 24b propagatesfrom the left hand portion
`22c2 . Whenthe discharge pulse from thefire set circuit
`22c2C of the second layer 22c2 of the EFI bridge 22c,
`24 passes through the neck section 22c2A (of FIG. 6),
`through the neck section 22c2 A, and toward the right
`the neck section vaporizes and disappears. FIG.9 illus-
`hand portion 22c2D of the second layer (see FIG.9).
`trates the neck section 22c2A ofthe second layer 22c2 of
`The current which emerges from the neck section
`the EFI bridge 22c before the neck section vaporized
`22cZA of the second layer 22c2 of the EFI bridge 22cis
`and disappeared as a result of the discharge pulse cur-
`now Called the EFI return current 24¢. The EFI return
`rent passing through necksection.
`current 24a propagates from the right hand portion
`Referring to FIG. 10, the EFI barrel 22d is illus-
`22c2D of the second layer 22c2 into the crescent con-
`trated. The barrel 22d has a hole 22d1 disposed through
`ductive pad area 22c2B disposed on the second layer,
`its center, the hole guiding and forming a bubble from
`the EFT return current 24a continuing to propagate
`the third layer 22c3 during the passage of the bubble
`from the crescent conductive pad area 22c2B into the
`through the hole 22d1 toward the secondary explosive
`ground cap 22a1of the outer pressure bulkhead housing
`pellet 22e. The barrel 22dincludes a notch 22d2. The
`22a. The EFI return current 24a propagates from the
`notch 22d2 is needed to allow pressure to be applied to
`ground cap 22a1 downthe sides of the outer pressure
`the top of the conductive pad area 2201,via the conduc-
`bulkhead housing 22ato ground potential in the manner
`tive epoxy in hole 22c1A, during attachment of the EFI
`shownin FIGS.4 and 6 of the drawings.
`to the pin 228,
`Referring to FIGS. 15 and 16, a longitudinal cross
`Referring to FIG. 11, another view ofthefirst, sec-
`sectional view of the prior art bubble activated detona-
`ond andthird layers of the EFI bridge 22cis illustrated.
`tor disclosed in U.S. Pat. No. 5,088,413 to Huberet. al.
`Asnoted in FIG.6, the EFI bridge 22c includesa first
`is illustrated.
`layer 22c1, a second layer 22c2 and a third layer 22c3.
`In FIGS.15 and 16, from a functional point of view,
`The first layer 22c1A includes a hole 22c1A, and the
`when the neck section 22c2A ofthe second layer 22c2 of
`third layer 22c3 has a hole 22¢3A which correspondsto
`the EFI bridge 22c vaporizes in response to a current
`the shape ofthe crescent shaped conductive pad 22c2B
`flowing through the neck section, a turbulenceis cre-
`of the second layer 22c2 of the EFI bridge 22c. The hole
`ated immediately above the neck section. As a result of
`22c3A in the third layer 22¢3 allows the crescent pad
`the turbulence, a bubble 22c3B forms in a corresponding
`22c2B to electrically contact the shoulder X of the
`section of the third layer 22c3 of the EFI bridge 22c.
`ground cap 22a] of the outer pressure bulkhead housing
`The bubble 22c3B impacts the secondary explosive 22e,
`22a via the conductive epoxy in hole 22c3A.
`the secondary explosive 22einitiating the propagation
`Referring to FIG.12, the top of pin 22dis illustrated.
`of a detonation wave in detonating cord 16. See U.S.
`The top part of pin 226 is coated with a PYRL-ML
`Pat. No. 5,088,413 to Huberet. al. for further details.
`insulating coating 2263, where the PYRLML polyam-
`Referring to FIG. 17, a longitudinal cross sectional
`ide based dielectric insulating coating is manufactured
`view ofthefiring head 22 shownin FIG.6 is illustrated
`by Dupont Corporation. However, a small portion 2261
`in a state whichexists after detonation of the exploding
`of the top part of pin 228 is not coated with the insulat-
`foil initiator (EFI bridge 22c) in the firing head 22. A
`ing coating 2253 thereby allowing the electrically con-
`functional description of the operation ofthe firing head
`ductive material (stainless steel) of the