Ammunition and explosives – Igniting devices and systems – Electrical primer or ignitor
Reexamination Certificate
1998-01-20
2001-01-30
Tudor, Harold J. (Department: 3641)
Ammunition and explosives
Igniting devices and systems
Electrical primer or ignitor
C102S202900, C102S202140
Reexamination Certificate
active
06178888
ABSTRACT:
FIELD OF INVENTION
This invention relates to detonators and in particular to chip slapper type detonators and a method of making the same.
BACKGROUND OF INVENTION
Detonators are used to detonate a primary charge such as an explosive of an air to surface missile. Such detonators are also used to detonate explosives used in other tactical devices, construction explosives, rocket boosters, and the like. These types of detonators must be physically robust and of high integrity. For example, an air to surface missile may be designed to pierce a bunker or other building and only then detonate the primary explosive. The detonator must, therefore, survive the shock of the launch and the impact with the bunker.
Exploding foil initiator (“EFI”) detonators, (e.g. “chip slappers”), generally include a ceramic chip upon which is deposited two opposing conductive copper lands which taper to a narrow “bridge” portion therebetween. An electrical current is provided to the lands at the time of initiation and the bridge portion bursts sending a flying plate thereon into an explosive charge which, in turn, detonates the primary charge.
It is convenient to package the chip and the explosive charge within a standard electronics housing such as a “TO” type transistor package including a base with one or more electrical leads and a can which covers the base. Such detonator packaging techniques, however, are fraught with problems.
First, the lead posts of the transistor package base are typically connected to the lands of the chip slapper by individual wires. These wires tend to break in the harsh environment described above and/or burn under the application of high amperage current. In addition, securing the individual wires to the lands and lead posts involves a considerable amount of man hours.
One attempt at overcoming the breakage and burning problems includes interconnecting a number of individual wires from each lead to the lands thereby providing redundancy should any one wire break or burn. This solution, however, only adds to the complexity of the design and entails additional man hours required to interconnect each additional wire.
Another problem with present chip slapper detonator designs is that once the wires are in place, some kind of a mechanical spacer must be placed between the EFI and the explosive charge to optimize the spacing therebetween thereby assuring that the flying plate travels the correct distance before striking the explosive charge. These mechanical spacers must be carefully designed and selected—often involving additional man hours in the fabrication of the detonators resulting in higher costs.
Another important consideration is that the explosive charge must contact the inside top surface of the transistor package can in order to prevent energy losses.
Due to loose manufacturing tolerances, however, the length of the transistor can, the height of the header wall of the transistor base, the thickness of the explosive charge, and the thickness of the chip can all vary. To accommodate these variations and to ensure that the explosive charge is in intimate contact with the inside of the can, the prior art methods included forcing the total height of the components inside the can (e.g., the chip, the spacer, and the explosive charge) to always be greater than the length of the transistor can through the use of a resilient member or members disposed inside the can below the explosive charge. The resilient member is compressed by exerting pressure on the can and the rim of the can is then welded to the flange of the base.
One problem with this prior art design is the complexity involved in choosing the structure and orientation of the resilient member which often includes incorporating two explosive charges separated by the resilient member. And, these additional components add to the cost of the detonators and the man hours required for their fabrication.
SUMMARY OF INVENTION
It is therefore an object of this invention to provide an improved detonator.
It is a further object of this invention to provide such an improved detonator which is physically robust and able to withstand violent environmental conditions.
It is a further object of this invention to provide such an improved detonator which facilitates the use of standard, low tolerance, low cost transistor packages.
It is a further object of this invention to provide such an improved detonator which is easier to fabricate than prior art detonators.
It is a further object of this invention to provide such a detonator which eliminates the need for mechanical spacers and resilient members associated with prior art detonators.
It is a further object of this invention to provide such a detonator which is less expensive to manufacture than prior art detonators.
It is a further object of this invention to provide such an improved detonator which incorporates low resistance electrical connections.
It is a further object of this invention to provide a method of manufacturing a physically robust detonator.
This invention results from the realization that a more physically robust and optimized chip slapper type detonator can be made, not by soldering a number of individual wires between the lead posts of the base and the chip slapper and then using mechanical spacers to separate the flying plate of the chip slapper from the explosive charge, but instead by using a connecting barrel which simultaneously provides the proper spacing between the flying plate and the explosive charge (eliminating the need for mechanical spacers) and which also electrically interconnects the lead posts of the base with the lands of the chip slapper in a robust fashion thereby eliminating the fragile wires used in the design of prior art detonators.
This invention features a detonator comprising a base portion including electrical leads and an exploding foil initiator, typically a chip slapper, on the base portion. The exploding foil initiator includes two conductive lands separated by a bridge portion therebetween. A connecting barrel of a predetermined thickness resides on the exploding foil initiator for optimizing the spacing between the exploding foil initiator and an explosive charge and for robustly interconnecting the lands of the exploding foil initiator with the electrical leads of the base portion. The connecting barrel includes conductive plates extending between the leads of the base portion and the lands of the exploding foil initiator and an opening between the conductive plates. The opening is located over the bridge portion of the exploding foil initiator so that the flying plate of the chip slapper can pass through the opening.
The barrel typically includes a top insulating layer laminated to a bottom conductive layer, the conductive plate formed by etching away the conductive layer from selected portions of the insulating layer. The opening in the conductive plate of the barrel may extend through the top insulating layer. The insulating layer is preferably polyimide and the conductive layer is preferably copper. The conductive plate may have the shape of an annular sector with a broad distal end for simultaneously covering a plurality of leads on one side of the base portion and a tapered proximal end connected to a land of the exploding foil initiator.
The base portion may include a header wall terminating in a support surface. The connecting barrel is preferably disposed between the exploding foil initiator on the support surface and an explosive charge. The detonator may further include a cap having an interior top surface and an enclosure wall extending downward from the interior top surface and surrounding the exploding foil initiator and the explosive charge. The wall terminates in a rim secured at a location along the header wall corresponding to the thickness of the exploding foil initiator, the thickness of the barrel, the thickness of the explosive charge, plus an extra length necessary for welding (approximately 0.020″) thereby ensuring that the explosive charge is in communication with the interior top surface of
Adams John T.
Neyer Barry T.
Tomasoski Robert J.
EG&G Star City, Inc.
Iandiorio & Teska
Teska Kirk
Tudor Harold J.
LandOfFree
Detonator does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Detonator, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Detonator will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2472435