Electronic delay detonator

Details Electronic delay detonator Electronic delay detonator

1998-01-23

2000-07-04

Jordan, Charles T.

Ammunition and explosives

Igniting devices and systems

Ignition or detonation circuit

F23Q 702

Patent

active

060822651

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an electronic delay detonator for controlling an ignition delay time with high accuracy in blasting work for charging a plurality of explosives into an object of destruction (such as rock or a building) and sequentially detonating them, and particularly to an electronic delay detonator which is free of a misfire range and thereby provides extremely high safety.


BACKGROUND ART

An electronic delay detonator has heretofore been known which allows an energy charging circuit to store therein electrical energy supplied from a blasting machine, is activated in response to the stored electrical energy and performs switching after a lapse of a desired delay time.
Prior arts of the electronic delay detonator have been proposed as examples as follows: constant of an RC circuit as a reference is disclosed in Japanese Patent Application Laid-Open Nos. 83200/1983, 91799/1987, etc. accuracy by using a characteristic frequency of a solid oscillator such as a quartz oscillator as a reference is disclosed in U.S. Pat. No. 4,445,435, DE 3,942,842, Japanese Patent Application Laid-Open No. 79797/1993, WO95/04253, etc.
In general, each of these electronic delay detonators comprises an electronic timer 100 supplied with electrical energy from a blasting machine 10 and an electric detonator 200 as shown in FIG. 1. The electronic timer 100 includes an energy charging circuit 120, a delay circuit 30 and an electronic switching circuit 140. In blasting, the electronic timer 100 is supplied with the electrical energy from the blasting machine 10, stores the electrical energy in the energy charging circuit 120, and then, drives the delay circuit 30 based on the electrical energy stored in the energy charging circuit 120 after completion of the supply of the electrical energy from the blasting machine 10. After a predetermined delay time has elapsed, the delay circuit 30 closes the electronic switching circuit 140 so that the electrical energy stored in the energy charging circuit 120 is supplied to the electric detonator 200, whereby the electric detonator 200 is fired.
Thus, when the electronic timer 100 including the delay circuit 30 is deactivated for some causes, generally, damage by an impact, the electric detonator 200 is not fired. Therefore, structures for protecting the electronic timer against the impact grow in importance. As these techniques, there have heretofore been known ones disclosed in Japanese Patent Application Laid-Open Nos. 35298/1982, 290398/1988 and 158999/1987, Japanese Utility Model Application Laid-Open No. 31398/1989, etc., for example. The following structures have been disclosed in these gazettes. an electric detonator and sealed with epoxy or a composition of epoxy with elastomer; or polyethylene; plastic case and a vacant space is defined between the case and the electronic timer.
Major uses of the aforementioned electronic delay detonator are for reduction in ground vibration or noise produced due to blasting. As described in Japanese Patent Application Laid-Open No. 285800/1989, it is however necessary to meet the following condition in respect of the accuracy of an ignition time with a view toward achieving these objects: within 10 ms, the standard deviation .sigma. of the ignition time interval should be limited so as to fall within at most .+-.1 ms.
In actual blasting work, a plurality of explosives inserted in electronic delay detonators are used and charged into their corresponding explosive boreholes defined therein based on predetermined blasting patterns. Thereafter, the explosives are successively detonated to fracture such as rock with predetermined time differences. Therefore, these explosive boreholes are expected to be adjacent to each other at a much shorter distance according to the blasting patterns. It is also apprehended that the explosives and electronic delay detonators will be subjected to a violent blasting shock of the adjacent boreholes before their own firing. Particularly when the blasting work is carried out for tunnel d

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