Electricity: electrical systems and devices – Igniting systems
Reexamination Certificate
1999-12-02
2001-07-17
Leja, Ronald W. (Department: 2836)
Electricity: electrical systems and devices
Igniting systems
Reexamination Certificate
active
06262875
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns an ignition/firing element with a housing into which pass electrical connecting leads that are connected to an ignition bridge arranged on a chip, on which at least one ignition charge is placed.
An igniter for triggering detonators is disclosed in DE 38 83 266 T2. The igniter consists of an electrically operated igniter head or fuse head, a power source that is connected to the igniter head via a switching device, and an electronic unit. The electronic unit has at least one chip made from a semiconductor material and provided with a microcircuit. The chip supports an ignition head or an ignition bridge on its surface. The firing charge is placed directly onto the ignition bridge.
SUMMARY OF THE INVENTION
The object of the invention is to create an ignition/firing element, which due to its compact form of construction can be universally used and in which uncontrolled gas release on ignition of the ignition/firing element is prevented.
This object is achieved by the invention in that
the connecting leads are pins that are led into the housing through a glass bushing,
a metal body forms the base of the housing and this metal body has passages into which the glass bushings are inserted, and
the metal body is joined in a positive locking manner to a plastic body which covers the peripheral wall of the housing and which envelops the ends of the pins projecting from the glass bushing.
The mode of operation of the ignition/firing element is as follows: when an electrical voltage is applied to both pins this causes a current to flow through the ignition/firing element and the electrical energy is converted into thermal energy in the ignition bridge; the ignition bridge heats up. The firing charge placed on the ignition bridge is thereby triggered and the pressed base of the housing is ruptured by the gas pressure resulting from the conversion of the ignition charge or firing charges, respectively. The hot gases and particles can escape through this opening in order to ignite a following charge.
For permanent, stable coupling of the plastic body to the metal body, advantageously, the metal body has a reduced diameter with a peripheral groove at its end facing the ignition charge. At least two cut-outs are incorporated in this slot in the passages above the glass bushings. By injecting or integrally moulding the plastic body, this envelops the area of the reduced diameter of the metal body and penetrates the passages via the groove and the cut-outs and completely fills these passages above the glass bushings. An optimum connection is thus obtained.
Usefully, the housing is constructed in the form of a sleeve, the metal body forming the lower base plate. Advantageously, the housing encloses the plastic body and the metal body and is connected at the lower end of the metal body via a flange and a sealing composition.
In an advantageous development the chip rests on the metal body.
According to the invention, the chip has on its front side a conductive surface onto which is deposited at least one resistive track that is isolated from the conductive surface by laser cutting, so as to produce at least one ignition bridge having the necessary resistance values. The effect of laser cutting is to remove specific areas of the conductive surface.
To support the ignition and firing process it is advantageous to use an ignition bridge which initiates an exothermic reaction during ignition. For example, magnesium or zirconium or an alloy thereof is suitable for this purpose. The advantage of this is that the ignition charge no longer has to be permanently mechanically pressed onto the ignition bridge, since the ignition bridge itself produces an exothermic reaction after triggering.
One possibility for preventing unintentional triggering by noise pulses, high-frequency radiation, etc., is to connect a capacitor in parallel with the ignition circuit. Advantageously, the rear side of the chip is therefore metallized so that, in conjunction with the conductive surface on the front side, the chip forms a capacitor and this capacitor is connected in parallel with the ignition circuit. Other electronic components, such as resistors, coils, capacitors etc., can of course be additionally arranged on the chip.
REFERENCES:
patent: 5085146 (1992-02-01), Baginski
patent: 5431101 (1995-07-01), Arrell, Jr. et al.
patent: 5454320 (1995-10-01), Hilden et al.
patent: 3883266 (1988-08-01), None
Albrecht Uwe
Brede Uwe
Bretfeld Anton
Cornelius Heinz-Peter
Kraft Josef
Antonelli Terry Stout & Kraus LLP
Dynamit Nobel GmbH Explosivstoff-und Systemtechnik
Leja Ronald W.
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