Ammunition and explosives – Igniting devices and systems – Laser or light initiated
Reexamination Certificate
1998-12-29
2001-03-13
Carone, Michael J. (Department: 3641)
Ammunition and explosives
Igniting devices and systems
Laser or light initiated
C102S201000
Reexamination Certificate
active
06199483
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns an installation designed for demolition or destruction of constructions, such as buildings, industrial buildings, bridges, rock and in general, any natural structure or constructed structure (buildings, public works, underground works, quarries, etc.) wherein the demolition of destruction of the constructions is accomplished using explosives.
2. Discussion of Background
When constructions, bridges, materials, etc., are destroyed using explosives, a large number of small explosive charges are placed in holes drilled in the structures of the works to be demolished.
At the present time, these small charges are primed by medium or high intensity electrical detonators that are electrically fired by means of firing apparatus.
More precisely, in order to limit nuisances such as vibrations, blast, noise, etc., the global explosion is broken down into a multitude of small explosions which occur at specific time intervals.
Electric detonators with micro-delays are usually used for this purpose and are grouped in series (for example twenty units). A time interval (for example 25 thousandths of a second) is provided between each detonator in the same series.
Sequential type exploders are also usually used, in which several lines of detonators are fired at time intervals. Several sequential firing apparatuses may then be coupled.
When designed to demolish a residential building, existing installations operating according to the above stated principle comprise 1500 to 2000 detonators for each firing. Firing may last for 3 to 4 seconds, due to the spacing of explosion initiated by the installation. This firing takes place after preliminary work to install charges and primers which may last for 3 to 4 days, or even a week.
With current installations, accidental priming or failures may occur throughout the duration of the prior work to install charges and primers.
The main risk of accidental ignition is due to stray currents that may occur around primed charges. These stray currents may originate from a number of causes, such as lightning, currents originating from overhead or underground electrical networks, currents originating from nearby electrical installations in operation (electrical transformers, e.g., railway or tramway catenary lines, lights, etc.), and natural currents circulating underground when boring tunnels.
Charges may also be fired accidentally due to the use of electronic devices, such as radios, walkie-talkies, portable telephones, etc., in the vicinity of these charges.
Accidental firing of the detonators may also occur during transport or during storage, for example, due to stray currents or accidents of various types.
Since the drilling work may last for 3 or 4 days or even a week, there is also a risk that the previously installed charges may be fired mischievously by means of a simple electric battery.
Furthermore, when the construction to be demolished concerns the nuclear industry, as is particularly the case for demolition of a nuclear power station, existing demolition installations cannot be used at the time of firing due to disturbances that exist in an intense radioactive environment.
Existing electrically fired demolition installations are also affected by failures that can affect the demolition work. One particular cause of these failures is broken electric wires or wires in contact with metal structures, such as protective grills, metal equipment in buildings to be demolished, etc. When the construction to be demolished is a large metal structure, such as a thermal power station, failures may also be caused by electric fields produced by the enormous mass of steel in the building.
Furthermore, electric detonators used in existing demolition installations may be stolen and easily reused, both during their transport or storage, and after being installed in the construction to be demolished.
Finally, note that when there are any problems in the circuits of this type of demolition installation, these problems are frequently very long and dangerous to detect. It is easy to find out which line is defective, but it is impossible to know the exact location of the break in the circuit.
SUMMARY OF THE INVENTION
The purpose of the present invention is a demolition installation, the original design of which enables it to eliminate all disadvantages of existing electrically controlled installations, and in particular, eliminates all risks of accidental or mischievous firing both during work to install charges and priming operations, and during prior storage and transport of components of the installation.
According to the present invention, this result is obtained by means of a demolition installation characterized by the fact that it comprises at least two independent groups, each including:
a control unit with several outputs, each comprising at least one laser source and at least one control switch for the said laser source, in which closure will cause the laser source to emit a laser beam at one or more of the said outputs;
optically controlled pyrotechnic initiators placed at determined locations in the structure to be demolished; and
optical fibers connecting each of the pyrotechnic initiators to one of the outputs of the control unit.
In an installation designed in this way, pyrotechnic initiators are only fired optically through the optical fibers. Therefore, firing is absolutely independent of stray currents. This procures optimum safety, particularly when the construction to be demolished is located in or close to electrical substations or under catenary lines. Furthermore, stormy weather has no influence on the work progress or safety.
The characteristic mentioned above also means that constructions located in large urban centers can be demolished at no risk, despite the large amount of electronic equipment present in these centers.
Furthermore, firing triggered by mischievous persons is impossible, since these persons would need a laser and the laser will have to be compatible with the precise frequency of the laser used in the installation.
Since firing is controlled optically, ignition cannot be disturbed by any metal mass. Safety during transport and during storage of components is also guaranteed.
Furthermore, optically controlled detonators cannot be used if they are stolen.
Finally, a computer can easily be used to determine the location of a break in the optical fibers.
In a first embodiment of the present invention, the laser sources are sources with a pumped solid rod operating in relaxed mode. Each control unit then comprises a single laser source and an optical divider coupler with an input that can receive the laser beam emitted by the laser source and several outputs forming control unit outputs.
Some or all of the optical fibers in each group then connect several pyrotechnic initiators to one of the outputs of the control unit through at least one second optical divider coupler.
Advantageously, each control unit comprises a secondary input and feedback means capable of aiming an additional laser beam penetrating into the control unit through its secondary input, towards the input of the optical divider coupler. A supplementary laser source common to all groups is then provided, so that the supplementary laser beam can be emitted whenever necessary following a failure of the laser source in one of the control units.
Each control unit may thus include an auxiliary control input and second feedback means capable of setting up a bypass optical path between the auxiliary input of the control and the input of the optical divider coupler for this control unit. In particular, this arrangement means that the integrity of optical fibers can be checked using a visible light source placed in front of the auxiliary control input.
Each control unit preferably comprises a retractable shutter that may be placed between the laser source and the input of the optical divider coupler.
The second feedback means are formed on this retractable shutter when it occupies an active shutte
Cardem Demolition S.A.
Carone Michael J.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Semunegus Lucit
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