Ammunition and explosives – Igniting devices and systems – Ignition or detonation circuit
Reexamination Certificate
1999-01-19
2001-01-16
Jordan, Charles T. (Department: 3641)
Ammunition and explosives
Igniting devices and systems
Ignition or detonation circuit
C102S206000, C102S215000, C102S200000
Reexamination Certificate
active
06173651
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a detonator control method of the electronic ignition module type, as well as to an encoded firing control assembly and to a ignition module for its implementation.
In most works involving explosives, the bursters containing the detonators are caused to detonate according to a very accurate time sequence, in order to improve the working yield of the explosive and to better control its effects.
Conventionally, a pyrotechnic device at the level of the detonators themselves enables to obtain various delay times between the explosions of the bursters. The detonators are actuated simultaneously by an exploder which delivers a certain electric energy to a firing line linking the detonators, in series or in parallel. The combustion of retarding pyrotechnic compounds then generates the requested pyrotechnic delays.
However, these pyrotechnic delays often exhibit insufficient relative accuracy.
To overcome this shortcoming, it has been suggested to use integral delay detonator ignition devices of the electronic type. Such devices enable to take advantage of the accuracy of electronic systems to enrich and to fine-tune the delay time ranges obtained previously in a pyrotechnic manner.
The application for patent FR-2.695.719 suggests a detonator control method with an integral delay electronic ignition module in which the ignition modules can be programmed using a programming unit. They call for an accurate time basis at the level of each detonator.
It has also been suggested in the patent U.S. Pat. No. 4,674,047, to use detonators fitted with electronic means enabling them to establish a dialogue with an external control unit. Each detonator is fitted with a capacitor whose discharge actuates the burster. The delay times of each detonator can be programmed on-site, whereas an identification code has been ascribed previously to each detonator, for example when leaving the factory. During a firing sequence, the detonators receive from the control unit successive orders, first to discharge the capacitor above mentioned, then to fire. They send back to the control unit, pieces of information enabling this unit to check the firing sequence for correct operation. The detonators are fitted to this view with a microprocessor-based local intelligence. The delay times which have been ascribed to the said are stored on non-volatile memories in their microprocessors.
In this last known system, each of the detonators has an internal time basis enabling it to perform a countdown in relation to the delay time which it has been ascribed. At the time of programming the detonator, its time basis is compared to a reference time basis for the control unit. Any possible error is then compensated for by a delay time adjusted value, whereby this adjusted value is stored in a memory of the detonator.
SUMMARY OF THE INVENTION
The purpose of this invention is to provide a control method of the electronic ignition module type, as well as an encoded firing control assembly and a ignition module for its implementation, conferring to the detonators the advantages above mentioned of the integral electronic delay detonators, but also greater simplicity of manufacture and of operation, as well as increased safety.
More precisely, a purpose of the invention is to be able to use detonators having rudimentary internal clocks while enabling excellent accuracy of a firing sequence.
Another purpose of the invention lies in using as internal clocks, cheap and heavy-duty oscillators, incorporated into integrated circuits.
According to the invention, a detonator control method of the electronic ignition module type is provided, whereby each ignition module is associated with specific parameters comprising at least one identification parameter and one explosion delay time of the associated detonator. The ignition module comprises:
a firing capacitor designed, after loading, to discharge in a cartridge head of the detonator to generate an ignition,
a battery capacitor ensuring temporary operating autonomy,
a rudimentary internal clock with a local frequency,
a non-volatile identification memory designed for the storage of the identification parameters.
The modules are capable of establishing a dialogue with a firing control unit fitted with a reference time basis and designed for transmitting to them an order to load their firing capacitors, as well as an order to fire and to receive from the modules one or several pieces of information relevant to their states.
According to the method:
the specific parameters are stored in at least one information storage medium,
at least one programming unit is caused to enter the identification parameters,
using the programming unit, the identification parameters are stored in the modules,
the specific parameters are stored using the information storage medium in the firing control unit,
the modules are ordered using the firing control unit, to load the firing capacitors,
a firing order is sent to the modules using the firing control unit, triggering off a firing sequence synchronised to the local frequencies.
The control method according to the invention is characterised in that after storing the specific parameters in the firing control unit and before loading the firing capacitors, the local frequency of the internal clock of the module is measured, using the firing control unit and for each successive module, using the reference time basis, then this internal clock is calibrated taking this measurement into account, using an algorithmic correction value of the local frequency and finally, an associated delay time is sent to the module.
The word <<calibration>> must be here understood as the determination of the algorithmic correction value appropriate for each module, since we want to stress that we are not acting on the internal clock properly speaking and hence, we do not modify its local frequency.
The factory adjustable internal clocks are calibrated shortly before a firing sequence.
This calibration is the all the more important that the local frequencies of the modules are, at first, all distinct from one another and therefore lead to an algorithmic correction value which is different for each module.
The control method according to the invention can be singled out from the previous art by the roles played by the programming unit, the firing control unit and the information storage medium. It is particularly unique in that the internal clocks of the modules are first adjusted during manufacture, then calibrated shortly before a firing sequence, using the reference time basis of the firing control unit. The calibration stage of the internal clocks is dissociated from the programming of the delay times of the modules.
An obvious advantage of the method according to the invention lies in that it is now possible to use in the modules, rudimentary adjustable internal clocks, whereas solely the reference time basis contained in the firing control unit should be accurate. Such an internal clock may for instance be incorporated into an integrated circuit, such a usually denominated ASIC (Application Specific Integrated Circuit). To serve as a clock, a simple circuit comprising a resistor and a capacitor is thus perfectly suited, although a frequency recorded in this circuit is subject to noticeable alteration with the passing of time. It is however quite interesting to use internal clocks which are rather stable in the long run, in order to avoid any final resetting stage. The solution suggested in the method according to the invention reduces notably the cost of the circuit in relation to the use of a quartz, without detriment to the accuracy nor to the safety of a firing sequence.
Another advantage provided by the use of rudimentary oscillators lies in that they may be more vibration-proof and hence less fragile, than a quartz.
Identification parameters can be entered in two ways into the programming unit: either by inputting them manually or by letting the programming unit calculate them automatically following an incremen
Clot Philippe
Fivaz Eric
Pathe Claude
Trousselle Raphael
Davey Bickford
Jordan Charles T.
Semunegus Lulit
Young & Thompson
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