Ammunition and explosives – Blasting – Detonation wave modifying
Reexamination Certificate
2000-06-08
2004-02-03
Nelson, Peter A. (Department: 3641)
Ammunition and explosives
Blasting
Detonation wave modifying
C102S331000, C102S323000
Reexamination Certificate
active
06684791
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to shaped charges and to the use of shaped charges in explosive blasting and in particular to the reduction of Nitrogen Oxides from explosive blasting in the mining industry.
The art of shaping a detonation charge to do work is a very well documented process. Explosions used to perforate well casings, heavy armor piercing shells and fireworks are all examples of shaping explosive energy.
In prior art blasting techniques a booster or primer is mainly used to further initiate a less sensitive blasting agent. The boosters usually range from one to five pounds in weight and are available in several compositions and shapes. During blasting a detonator or booster is used to provide a sufficient amount of energy to the blasting agent in order to initiate a sustained reaction in the blasting agent which travels from the point of initiation, usually the bottom of a bore-hole, through the entire column of blasting agent. The dynamics of the reaction in the blasting agent depend on the amount, shape and direction of the energy produced by the detonator or booster.
The direction of the initiation energy has many effects. Ideally the initiation energy produced by the detonator or booster directs the energy upward to the column of blasting agent and does not direct energy downward toward mineral strata. This protects the strata from damage yet accomplishes the initiation of the blasting agent column. In a shape charge booster the energy is also directed upward and not outward radially. If energy is directed radially outward, other bore-holes may be damaged.
The shape of the initiation energy has significant effects on the overall blast as well. The shape of the energy wave produced by the booster or detonator often determines the dynamics of the reaction of the column of blasting agent. As shown in U.S. Pat. No. 4,938,143, the increase in surface area of the contact between the blasting agent column and the booster partially determines whether the blast is overdriven or underdriven. This corresponds to the reaction dynamics and the overall effectiveness of the blast. The ideal reaction of the column of blasting agent is one that reaches hydrodynamic velocity or steady state velocity immediately at the point of initiation. By shaping the initiation energy wave a steady state velocity is reached more quickly and the efficiency or effectiveness of the blast is improved. Additionally, the initial shape of the energy wave produced assists in detonating the entire cross-section of the column of blasting agent. As opposed to a narrow lance of directed energy, by projecting the energy wave to encompass the sides of the blasting agent column the initiation energy initiates the entire cross-section of the column and produces a more desirable reaction traveling up the blasting agent column.
The amount of energy produced by a booster or detonator is also a concern for the efficient and sufficient detonation of the blasting agent column. The amount of energy produced by a booster should be enough to effectively initiate the column of blasting agent, but not so much as to affect the mineral strata, other bore-holes or the reaction of the column of blasting agent. Too much energy from the initiation may produce a blow-out or other effects that do not react the column of blasting agent. By controlling the amount shape and direction of the initiation energy a blast's efficiency and effectiveness is controlled for the desired results.
Often the conditions present in blasting greatly affect the efficiency of the blast. During blasting operations bore-holes are drilled and set with detonation means, booster means or both and then the blasting agent is supplied into the bore-hole before the detonation of the explosives. In some instances the blasting agent lies in the bore-holes for considerable time before the detonation. Often the blasting agent is adversely affected when allowed to sit for extended periods of time. The adverse effects are most profound near the bottom of the bore-holes where any water or other contaminants collect and the detonation or boosting means is located. The adverse effects seen in bore-holes may be wetting of the blasting agent, breaks or discontinuities in the basting column or other effects. When adverse conditions are present in blasting the use of prior art shaped boosters and detonators does not lead to the desired results that is the efficient initiation of the blasting agent. If the blasting agent surrounding and immediately atop the boosters or shaped charges is adversely affected by conditions present in the bore-hole, the shaped charge or booster directs a shock wave at blasting agent which does not sufficiently propagate the desired shock wave or reaction. The boosters in use may shape the energy wave correctly but the size of the initial detonation is normally not sufficient in order to overcome effects of the conditions present in the bore-holes.
When using blasting as a tool for mining or other industries the bore-holes are sometimes angled, to effectuate a desired use of the energy released during blasting. Often the angled bore-holes adversely affect the results of the blast. Blasting agent may settle to one side of the bore-holes. When using prior art type boosters the orientation of the booster is critical in obtaining efficient use of the explosives. In angled bore-holes the orientation of most prior art boosters are suspect. When a small shaped charge or booster is placed in a bore-hole, the booster or charge aligns with gravity forces and is often directed out of the perpendicular cross-section of the explosives column. While the prior art mentions the critical orientation of the shaped charge in relation to the cross-section of the blasting column it does not mention the means of achieving such orientation of the booster in the bore-holes and in particular the orientation in angled bore-holes.
Shaped charge detonation is a technique known to the mining industry, and almost all of the manufacturers of cast boosters sell a shaped booster for various applications. The art of shaping a charge is thoroughly explained in U.S. Pat. No. 4,938,143. U.S. Pat. No. 4,938,143 provides experimental proof that “steady state velocity” is reached as quickly as possible with shaped detonation. Though it is not explained in the patent, molten explosives were poured into a conical shaped mold and then solidified to make the shaped booster. U.S. Pat. No. 5,705,768 takes the invention in U.S. Pat. No. 4,938,143 one-step further by adding a shaped form on top of a cast booster. This invention fills the cylindrical end with inert material rather than explosive. The explosive incorporated into the design is a conical form at the top of the device. The explosive is conical shaped, and the resulting explosion is shaped because it takes the form of the cone through which the energy is broadcast. It also addresses the use of shaped charges to more effectively initiate the blast to remove overburden from mineral strata. In U.S. Pat. No. 5,705,768, the shaped charge directs energy with the use of a concave recess atop the shaped charge whereby the energy wave is broadened outwardly and up through the powder column. However, the arrangement disclosed in U.S. Pat. No. 5,705,768 does not solve orientation problems within bore-holes or address blast initiation of the entire cross section of the powder column to achieve faster steady state or hydrodynamic velocity. Though U.S. Pat. No. 5,705,768 does not have experimental findings it does reference U.S. Pat. No. 4,938,143 as the document to prove the value of the shaped charge. In fact, the technique of shaping a detonation is well known in the art. U.S. Pat. No. 4,938,143 is hereby incorporated by reference to demonstrate that shaped detonation is more efficient.
The present art is specific to casting explosive material in various shapes, the largest of which is 4 pounds. Research has demonstrated that a shaped booster is far more efficient in obtaining hydrodynamic velocity than the commo
LandOfFree
Shaped charge detonation system and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Shaped charge detonation system and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Shaped charge detonation system and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3302271