United States Patent
`
`[19]
`
`[11] Patent Number:
`
`5,347,929
`
`Lerche et al.
`[45] Date of Patent: Sep. 20, 1994
`
`
`
`llllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllIIIIHIII
`Usoos347929A
`
`[54]
`
`FIRING SYSTEM FOR A PERFORATING
`GUN INCLUDING AN EXPLODING FOIL
`INITIATOR AND AN OUTER HOUSING FOR
`CONDUCTING WIRELINE CURRENT AND
`EFI CURRENT
`
`‘
`
`[75]
`
`Inventors:
`
`Nolan C. Lerche, Stafford; Clifford L.
`Aseltine, Houston, both of Tex.;
`Wallace E. Voreck, Jr., Sparta, NJ.
`
`[73]
`
`Assignee:
`
`Schlumberger Technology
`Corporation, Houston, Tex.
`
`[21]
`
`App1.No.: 116,082
`
`[22]
`
`Filed:
`
`Sep. 1, 1993
`
`[51]
`[52]
`[58]
`
`[56]
`
`Int. Cl.5 .............................................. F42C 11/00
`US. Cl. ................................................ 102/202.14
`Field of Search ................ 102/202.14, 200, 202.5,
`102/202.7, 206
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`9/1976
`4/1984
`9/1984
`8/1988
`12/1988
`7/1990
`2/1992
`
`................. 102/202.14
`Lemley et a1.
`Barrett ......................... 102/202.6
`McCormick et al.
`....... 102/200
`
`Barker et a1.
`.......
`102/202.l4
`
`Stroud et al. ......... 102/202.5
`
`Barker .............. 102/202.5
`Huber et a1.
`........................ 102/200
`
`3,978,791
`4,441,427
`4,471,697
`4,762,067
`4,788,913
`4,944,225
`5,088,413
`
`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 conductor cable
`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
`exploding foil
`initiator (EFI) responsive to the dis-
`charge pulse from the fire set circuit for initiating the
`detonation of a secondary explosive. The discharge
`pulse energizing the firing head passes through the ex-
`ploding foil initiator (EFI) and emerges from the EFI as
`an EFI return current. As a result, the outer pressure
`bulkhead housing of the firing head conducts two sepa-
`rate and independent currents: the EFI return current
`from the EFI to a ground potential, and the wireline
`current from the wireline conductor cable to the fire set
`circuit.
`
`22 Claims, 7 Drawing Sheets
`
`220
`
`’—
`
`
`
`
`
`
`
`
`
`
`
`-
`
`‘
`
`
`
`
`
`
`
`
`TO FIRE
`FROM FIRE
`
`
`
`SET CIRCUIT
`SET CIRCUIT
`
`
`
`24
`24
`
`
`
`
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 001
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 001
`
`

`

`US. Patent
`
`Sep. 20, 1994
`
`Sheet 1 of 7
`
`5,347,929
`
`H
`
`
`
`I4
`
`76
`
`
`
`lflfllmwwfl-
`
`
`
`
`WW-(7%..Amy/«f
`aN_Iamps.
`
`
`
`W.
`
`Fm
`
`FIG. 7
`
`FIG.2
`
`1
`Hunting Titan, nc
`1016
`E
`Pg. 002
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 002
`
`
`
`
`

`

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

`

`US. Patent
`
`Sep. 20, 1994
`
`Sheet 3 of 7
`
`5,347,929
`
`
`
`
`
`
`
`
`
`
`
`24
`
`SET CIRCUIT
`24
`
`FROM FIRE
`SET CIRCUIT
`
`FIG. 7
`
`FIG. 8
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 004
`
`

`

`US. Patent
`
`Sep. 20, 1994
`
`Sheet 4 of 7
`
`5,347,929
`
` FIG. IO
`
`FROM
`WIREL INE
`
`
`
`CABLE 76
`
`
`
`
`
`FIRE SET
`
`CIRCUIT 24
`
` I
`3.1"!"
`22b2
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 005
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 005
`
`

`

`US. Patent
`
`Sep. 20, 1994
`
`Sheet 5 of 7
`
`5,347,929
`
`
`
`”nu‘—-'
`
`n‘\+\‘¢§§§‘,
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`mmmanWAI
`«3...;
`
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`
`~§“““““ “‘wm‘wm“ 5“
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`
`
`
`
`FIG. 74
`
` FROM FIRE
`
`SE7 CIRCUIT
`
`
`
`22e
`
`22”]
`
`
`2.2:r
`
`
`may"
`
`
`
`f‘k‘ 5‘
`
`22c]
`
`22/
`
`
`
`22M
`
`FIG. 77
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 006
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 006
`
`

`

`US. Patent
`
`Sep. 20, 1994
`
`Sheet 6 of 7
`
`5,347,929
`
`FIG. 75
`
`(PRIOR ART)
`
`
`
`FIG. 76
`
`76
`
`x
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`III
`In? 3““!
`1"...
`d
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`40..."...
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`
`nnnnnnn
`1111111
`000000
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 007
`
`

`

`US. Patent
`
`Sep. 20, 1994
`
`Sheet 7 of 7
`
`5,347,929
`
`
`
`
`
`
`q\\xOKMEG.
`
`AQ20>IMy.3:
`
`ovm
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 008
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 008
`
`

`

`1
`
`5,347,929
`
`2
`
`FIRING SYSTEM FOR A PERFORATING GUN
`INCLUDING AN EXPLODING FOIL INITIATOR
`AND AN OUTER HOUSING FOR CONDUCTING
`WIRELINE CURRENT AND EFI CURRENT
`
`BACKGROUND OF THE INVENTION
`
`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
`(EFI) firing system for use in the perforating gun, the
`EFI firing system including an outer housing adapted to
`function as an electrical conductor for conducting a
`return current to ground potential from the EFI firing
`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 a1 dis-
`closes a typical exploding foil initiator. In addition, U.S.
`Pat. No. 3,978,791 to Lemley et. al. and U.S. Pat. No.
`4,471,697 to McCormick et. al. also disclose exploding
`foil initiator or “slapper” detonators. Furthermore, U.S.
`Pat. No. 4,441,427 to Barrett and U.S. Pat. No.
`4,762,067 to Barker et a1 disclose the use of Exploding
`Foil Initiators in a perforating gun for propelling a
`flying plate into a secondary explosive and detonating
`the perforating gun. In addition, U.S. Pat. No. 5,088,413
`to Huber et. a1. discloses an exploding foil bubble acti-
`vated initiator for use in a perforating gun, the Huber et.
`al. patent being incorporated by reference into this
`specification. However, although these initiators per-
`form well, certain additional problems, associated with
`the use and/or performance of the EFI initiators in
`general and the exploding foil bubble activated initiator
`of the Huber et al. patent in particular, in a perforating
`gun wellbore environment, have yet to be solved.
`For example, initiation of a perforating gun string in
`a wellbore can be accomplished using secondary explo-
`sives, such as HNS4. This explosive can be initiated
`using an EFI initiator that receives a high energy pulse
`from a fire set. Typically, the fire set consists of a high
`voltage power supply, an energy storage capacitor, and
`a switch that rapidly dumps stored energy into the EFI
`through a high frequency connector. This connector
`must have a very low effective seriesresistance (ESR).
`However, after detonation, the fire set must be con-
`tained in a protected housing which is isolated from the
`well fluids and the pressures in the wellbore. Therefore,
`a pressure bulkhead must be electrically and physically
`connected to the fire set and the EFI for electrically
`connecting the fire set and the EFI to ground potential
`so that the EFI can ultimately detonate the secondary
`explosives in the perforating gun string. In addition,
`when perforating oil wells, sometimes it is necessary to
`selectively shoot multiple guns in the same gun string.
`In order to detonate the gun selectively, the wireline
`voltage must pass through the upper guns in order to
`reach the lower guns in the gun string. Therefore, the
`pressure bulkhead which provides the EFI pulse must
`also provide a means to transfer the wireline voltage
`through the guns in the gun string. Typically, this is
`accomplished using a separate wireline feed through.
`When shooting perforating guns in a bottom up config-
`uration, a detonating element must be placed on the
`bottom of the gun and the shaped charges are posi-
`tioned above the detonating element in the perforating
`
`5
`
`10
`
`15
`
`20
`
`25
`
`3O
`
`35
`
`45
`
`50
`
`55
`
`65
`
`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 and is a short life part. In addi—
`tion, the conventional bulkhead electrical property does
`not lend itself 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
`(ESI). Since typical values of ESR and E81 are 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.
`
`SUMMARY OF THE INVENTION
`
`Accordingly, it is a primary object of the present
`invention to provide a firing system adapted for use in a
`perforating gun having an outer housing pressure bulk-
`head which has a low effective series resistance and a
`low effective series inductance and which provides an
`electrical current signal conducting path for two sepa-
`rate and independent currents.
`It is a further object of the present invention to pro-
`vide a firing system including an initiator adapted for
`use in a perforating gun including an outer housing
`pressure bulkhead which provides a conducting path
`for two separate currents, one current being a return
`current conducting from the initiator to ground poten-
`tial, and another current being a wireline current con-
`ducting from a wireline conductor cable to the initiator
`for purposes of detonating the initiator.
`It is a further object of the present invention to pro-
`vide a firing system adapted for use in a perforating gun
`including an initiator for initiating detonation of the
`firing system, a fire set circuit electrically connected to
`the initiator for providing a firing current to the initiator
`and an outer housing enclosing the initiator for provid-
`ing a conducting path for two separate currents, one
`current being a return current from the initiator to
`ground potential, and another current being a wireline
`current conducting from a wireline conductor cable to
`the initiator in the firing system for purposes of detonat-
`ing the initiator.
`In accordance with these and other objects of the
`present invention, a firing head for a firing system
`adapted for use in a perforating gun includes an outer
`pressure bulkhead housing which simultaneously con-
`ducts two separate and independent currents, that is, 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 conductor cable provides a wireline current
`to the fire set circuit. The firing head includes an outer
`pressure bulkhead housing for enclosing the firing head,
`and an exploding foil initiator (EFI) responsive to the
`discharge pulse from the fire set circuit for initiating the
`detonation of a secondary explosive. The discharge
`pulse energizing the firing head passes through the ex-
`ploding foil initiator (EFI) and emerges from the EFI as
`a return current. Due to the geometry of the outer
`pressure bulkhead housing of the firing head, the pres-
`sure bulkhead has a low Effective Series Resistance
`(ESR) and a low Effective Series Inductance (1381). As
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 009
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 009
`
`

`

`5,347,929
`
`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 the fire 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 embodiment of the
`present invention, are given by way of illustration only,
`since various changes and modifications within the
`spirit and scope of the invention will become obvious to
`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 way of illustratiOn
`only and are not intended to be limitative of the present
`invention, and wherein:
`FIGS. 1 and 2 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 of the firing
`head of FIG. 4;
`FIG. 6 illustrates a three-dimensional and enlarged
`view of a substantial portion of the firing head of FIGS.
`4—5;
`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 shown in FIG. 6 in a state which exists
`prior to detonation of the EFI in the firing head;
`FIGS. 15—16 illustrate longitudinal cross sectional
`views of the bubble activated detonator disclosed in
`US. Pat. No. 5,088,413 to Huber et al, the disclosure of
`which has been incorporated by reference into this
`specification;
`FIG. 17 illustrates a longitudinal cross sectional View
`of the firing head shown in FIG. 6 in a state which exists
`after detonation of the EFI in 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 14 is 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, when the tie wrap 14 is
`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 the first
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`4O
`
`45
`
`50
`
`55
`
`60
`
`65
`
`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
`charges in 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 and is further connected, at its bottom end, to a firing
`head 22 in accordance with the present
`invention.
`When the firing head 22 of the present invention deto-
`nates, the booster 16a ignites and detonates which initi-
`ates the propagation of a detonation wave in 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
`above the firing head 22 in FIG. 1 (a bottom-up configu-
`ration);
`therefore the shaped charges detonate from
`bottom to top as described in the background section 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 thing head 22. The fire 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
`thing head 22 of FIG. 1 is illustrated.
`In FIG. 4, the firing head 22 comprises an outer pres-
`sure bulkhead housing 22a and a pin 22b disposed
`within the interior of the pressure bulkhead 22a. Not
`shown in 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 independent currents are flowing in the outer pres-
`sure bulkhead housing 220. The first 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 240 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 EFI return current 24a is the return current to
`ground potential from an exploding foil initiator (EFI)
`which is disposed on the top of pin 2217. An EFI current
`24b originating from the fire set circuit 24 propagates
`upwardly through the pin 22b and moves toward to the
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 010
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 010
`
`

`

`5
`
`5,347,929
`
`6
`
`top of the pin 22b where it energizes the EFI disposed
`on the top of the pin 22b. The EFI return current flows
`out of the EFI, into the outer pressure bulkhead housing
`220, and down the sides of the pressure bulkhead hous-
`ing 220 to ground potential. Simultaneously, wireline
`current 180 from wireline 18 flows down the sides of
`the pressure bulkhead housing 220, and out the pressure
`bulkhead 220 on its way toward the fire set circuit 24.
`Due to the geometry (size, shape, volume) of the
`pressure bulkhead housing 220, the housing 220 exhibits
`a low effective series resistance and a low effective
`series inductance. As a result, the pressure bulkhead 220
`will easily conduct a rapid high energy discharge pulse
`from the fire set circuit 24.
`
`Referring to FIG. 5, an exploded View of the flowing
`head 22 of FIG. 4 is illustrated.
`
`In FIG. 5, the outer pressure bulkhead housing 220
`encloses the pin 22b. The pin 22b is made of stainless
`steel (an electrically conductive material); however,
`substantially the entire surface area of the pin 220 is
`coated with a polymide based insulating material 22b3
`known as “PYRLML” manufactured by E. I. Dupont
`DeNemours (Dupont) Corporation. The PYRL-ML
`insulating coating 22b3 covers the entire surface area of
`the pin 22b except for: (1) one circular area 22b 1 dis-
`posed on the top of the pin 22b, and (2) the bottom 22b2
`surface area of the pin. The circular area 22b1 on the top
`of the pin 22b 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
`22b2 surface area of the pin 22b is not coated with the
`PYRL-ML insulating coating 22b3 because the bottom
`surface area 22b2 of pin 22b is plugged into a female
`electrical connector which conducts a high energy
`discharge pulse to the pin 2217 from the fire set circuit
`24. An EFI bridge 22c is disposed on the top of the pin
`22]). 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
`EFI barrel 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 220
`includes a top ground cap 2201. A center bore 2201A is
`disposed through the center of the ground cap 2201, and
`a secondary explosive in the form of a cylindrical pellet
`22c (the secondary explosive being FIE) fits snugly
`within the center bore 2201A of the ground cap 2201. A
`metal flyer 22f is disposed above the secondary explo-
`sive pellet 22e. When the pellet 22a detonates, a flying
`plate is cut from the center of the flyer 22f, the flying
`plate flying across a space and impacting the booster
`160 of the detonating cord 16 in FIG. 1 thereby initiat-
`ing the propagation of a detonation wave in 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 22]: seal the pin and
`bulkhead thereby preventing fluid invasion beyond the
`bulkhead.
`
`5
`
`10
`
`15
`
`2O
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`Referring to FIG. 6, an enlarged three dimensional
`view of the pin 22b, EFI bridge 22c, EFI barrel 220’,
`ground cap 2201, secondary explosive pellet 22e and
`flyer 22f of FIG. 5 is illustrated.
`In FIG. 6, the pin 22b is coated with the PYRL-ML
`insulating coating 22b3 of figure except for a conductive
`pad area 2217 1 disposed on the top of the pin 22b and the
`bottom surface area 22b2 on the bottom of the pin. Since
`the pin 22b is made of stainless steel, it can easily con-
`
`65
`
`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 22b2, up the center part of the
`pin 22b, and toward the conductive pad area 22b1. The
`EFI bridge 22c is comprised of three layers, a first layer
`22c1, a second layer 22c2, and a third layer 22c3. The
`first layer 22c1 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. I. DuPont De Nemours, Incorporated (Dupont).
`The first layer 22c] includes a hole 22c1A which is filled
`with a conductive epoxy in order to facilitate the con-
`ductance of an electrical current (the high energy dis-
`charge pulse from the fire set circuit 24) from the pin
`22b, into the conductive pad area 2212], and into the
`conductive epoxy which fills the hole 22clA of the 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 22c1. 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 22c2B is disposed.
`The crescent conductive pad area 22c2B 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 2201 of the outer
`pressure bulkhead housing 220. 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 2201 of the outer pressure bulkhead
`housing 220. The third layer 22c3 of the EFI bridge 220
`is 1 mil in thickness and is comprised of the Kapton
`polyimide material. The third layer 22c3 includes the
`hole 2203A, in which a conductive epoxy is disposed,
`which has a shape which conforms to the shape of the
`crescent conductive pad 22c2B of the second layer 22c2.
`The EFI barrel 220’ is actually a spacer layer made of
`a polyamide material. The EFI barrel 22d is 0.010
`inches in thickness and is 0.25 inches in diameter and
`includes a hole 22:11 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 22c3 of the EFI bridge 22c, the hole 22071 of
`the EFI barrel 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 220 includes the ground cap 2201 which is
`disposed above the EFI barrel 22d. The ground cap
`2201 includes a center bore in which a secondary explo-
`sive (HE) pellet 22c is disposed. The pellet 22e is posi—
`tioned directly above the hole 201 in the EFI barrel
`22d and directly above the neck section 22c2A of the
`copper second layer 22c2 of the EFI bridge 22c. The
`flyer 22fis disposed directly above the ground cap 2201.
`When the secondary explosive pellet 22edetonates, a
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 011
`
`Hunting Titan, Inc.
`Ex. 1016
`Pg. 011
`
`

`

`5,347,929
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`65
`
`7
`flying plate 22f1 is sheared off the flyer 22f As will be
`noted later in this specification, the flying plate 22f1 flys
`across a space and impacts the booster 16a of the deto-
`nating cord 16 in FIG. 1,_
`Referring to FIG. 7, a top view of the second layer
`22c2 and the third layer 22c3 of the EFI bridge 22c of
`FIGS. 5 and 6 is illustrated. Note how the crescent
`conductive pad area 22c2B is electrically connected to a
`conductive epoxy disposed within the hole 22c3A in the
`third layer 22c3 and how the conductive epoxy in hole
`22c3A is electrically connected to the shoulder X of the
`outer pressure bulkhead housing 22:2.
`Referring to FIG. 8, a top view of the first layer 22cl
`of the EFI bridge 22c is illustrated. Note the hole 22c1A
`in the first layer 22c1. As noted earlier, the hole 22c1A
`is filled with a conductive epoxy 22c1B in order to
`facilitate the conductance of the discharge pulse from
`the fire set circuit 24, through the pin 22b, the conduc—
`tive pad area 2261 and the epoxy 22clB to the second
`layer 22c2 of the EFI bridge 22c.
`Referring to FIG. 9, the geometry associated with
`the neck section 22c2A of the second layer 22c2 of the
`EFI bridge 22c, before the neck section has vaporized in
`response to the discharge pulse from the fire set circuit
`24, is illustrated. Before vaporization of the neck sec-
`tion, the first left hand portion 22c2C of the second
`layer 22c2 is integrally connected to the neck section
`2202A, the neck section being integrally connected to
`the second right hand portion 22c2D of the second layer
`22c2 . When the discharge pulse from the fire set circuit
`24 passes through the neck section 22c2A (of FIG. 6),
`the neck section vaporizes and disappears. FIG. 9 illus-
`trates the neck section 22c2A of the second layer 22c2 of
`the EFI bridge 22!: before the neck section vaporized
`and disappeared as a result of the discharge pulse cur-
`rent passing through neck section.
`Referring to FIG. 10, the EFI barrel 22d is illus-
`trated. The barrel 22d has a hole 22dl disposed through
`its center, the hole guiding and forming a bubble from
`the third layer 22c3 during the passage of the bubble
`through the hole 22d] toward the secondary explosive
`pellet 22e. The barrel ZZJmcludes a notch 22:12. The
`notch 22d2 is needed to allow pressure to be applied to
`the top of the conductive pad area 22b1, via the conduc-
`tive epoxy in hole 22c1A, during attachment of the EFI
`to the pin 22b.
`Referring to FIG. 11, another view of the first, sec-
`ond and third layers of the EFI bridge 22c is illustrated.
`As noted in FIG. 6, the EFI bridge 22c includes a first
`layer 22c1, a second layer 22c2 and a third layer 22c3.
`The first layer 22c1A includes a hole 22c1A, and the
`third layer 22c3 has a hole 22c3A which corresponds to
`the shape of the crescent shaped conductive pad 22c2B
`of the second layer 22c2 of the EFI bridge 22c. The hole
`22c3A in the third layer 22c3 allows the crescent pad
`22c2B to electrically contact the shoulder X of the
`ground cap 2201 of the outer pressure bulkhead housing
`22a via the conductive epoxy in hole 22c3A.
`Referring to FIG. 12, the top of pin 22b is illustrated.
`The top part of pin 22b is coated with a PYRL-ML
`insulating coating 22b3, where the PYRLML polyam-
`ide based dielectric insulating coating is manufactured
`by Dupont Corporation. However, a small portion 22b1
`of the top part of pin 22b is not coated with the insulat-
`ing coating 22b3 thereby allowing the electrically con-
`ductive material (stainless steel) of the pin 22b to show
`therethrough, this small portion 22b I forming a dot, the
`
`8
`dot representing an electrically conductive pad area
`22b1 for conducting an electrical current.
`Referring to FIG. 13, the pin 22b is coated on its sides
`(but not on its bottom 2262) with the PYRL-ML insu-
`lating coating 22b3. As noted earlier, the pin 22b itself
`(without the coating) is made of an electrically conduc-
`tive stainless steel material; however, substantially the
`entire surface area is coated with the insulating coating
`22b3 except for the bottom 22b2(which is adapted to be
`connected to an electrical connector) and the dot con-
`ductive pad area 22b 1 disposed on the top of the pin.
`Referring to FIG. 14, a longitudinal cross sectional
`view of the firing head 22 shown in FIG. 6 is illustrated
`in a state which exists prior to detonation of the explod—
`ing foil initiator (EFI) in the thing head 22. A functional
`description of the operation of the firing head 22, prior
`to vaporization of the neck section 22c2A of the second
`layer 22c2 and detonation of the secondary explosive
`pellet 22e, will be set forth in the following paragraph
`with reference to FIG. 14.
`
`In FIG. 14, the discharge pulse 24b from the fire set
`circuit 24 passes through the center of the pin 22b. An
`insulating coating 22b3 coats substantially the entire
`surface area of the pin; however, a hole in the coating
`exposes a conductive pad area 22b1. The discharge
`pulse 24b passes through the conductive pad area 22b1,
`through the conductive epoxy in the hole 22c1A in the
`first layer 22c] of the EFI bridge 22c, and into the sec-
`ond layer 22c2 of the EFI bridge 22c. The discharge
`pulse current 24b propagates from the left hand portion
`22c2C of the second layer 22c2 of the EFI bridge 22c,
`through the neck section 2202 A, and toward the right
`hand portion 22c2D of the second layer (see FIG. 9).
`The current which emerges from the neck section
`22c2A of the second layer 22c2 of the EFI bridge 22c is
`now called the EFI return current 24a. The EFI return
`current 240 propagates from the right hand portion
`22c2D of the second layer 22c2 into the crescent con-
`ductive pad area 22c2B disposed on the second layer,
`the EFI return current 24a continuing to propagate
`from the crescent conductive pad area 22c2B into the
`ground cap 22a1 of the outer pressure bulkhead housing
`22a. The EFI return current 24a propagates from the
`ground cap 22a1 down the sides of the outer pressure
`bulkhead housing 220t0 ground potential in the manner
`shown in FIGS. 4 and 6 of the drawings.
`Referring to FIGS. 15 and 16, a longitudinal cross
`sectional view of the prior art bubble activated detona-
`tor disclosed in US. Pat. No. 5,088,413 to Huber et. al.
`is illustrated.
`
`In FIGS. 15 and 16, from a functional point of view,
`when the neck section 22c2A of the second layer 22c2 of
`the EFI bridge 22c vaporizes in response to a current
`flowing through the neck section, a turbulence is cre-
`ated immediately above the neck section. As a result of
`the turbulence, a bubble 22c3B forms in a corresponding
`section of the third layer 22c3 of the EFI bridge 22c.
`The bubble 22c3B impacts the secondary explosive 22e,
`the secondary explosive 22e initiating the propagation
`of a detonation wave in detonating cord 16. See US.
`Pat. No. 5,088,413 to Huber et. al. for further details.
`Referring to FIG. 17, a longitudinal cross sectional
`