RU2263871C1 - Electric spark igniter - Google Patents

Abstract

FIELD: production of electric spark igniters for boulder blasting.

SUBSTANCE: the invention is pertaining to the field of the boulder blasting. The electric spark igniter with self-cutoff from a current source contains: a body 5, a small leading-in socket 4 with the built-in electric inputs 3, a fuse head 1 fixed on the electric inputs on their butts and igniting the ignitable (igniter) composition (on the drawing it is not displayed) made on the basis of a mix of a blasting explosive and a powder of the active metal built-up on the fuse head. The butts of the electrical leads are made at a flush with a surface of the small leading-in socket or dipped below the level of the surface of the small leading-in socket and coated, including the places of the fuse head fixation with the electroinsulating compound 2 made on the basis of an epoxide resin with an epoxy hardener and with add-on as a filling material of a fine powder of high-melting inorganic compounds (in mass %) from 25 up to 30. The technical result is a capability to self-cutoff from a source of current after actuation.

EFFECT: the invention ensures a capability to self-cutoff from a source of current after actuation.

2 cl, 1 dwg

Description

The invention relates to blasting operations, in particular to initiating devices, and can be used in igniter or explosive devices.

A known design of an electric detonator with an isolated incandescent bridge, consisting of a housing, an insert, a plug made of dielectric material, a filament bridge pressed against the plug by an insulating gasket, and a flammable composition deposited on top of the insulator. Due to the absence of physical contact of the sensitive initiating material with the incandescent bridge, the electric detonator is disconnected from the current source after the bridge burns out [1].

The disadvantage of this technical solution, selected as an analogue, is the following factors. Firstly, the device uses a very highly sensitive flammable substance, and secondly, during the combustion of flammable compositions or charges, the resulting conductive products, being under high pressure, penetrate the insulation strip and the interelectrode gap, which can lead to a short circuit. As a result, the effect of self-shutdown is leveled.

As a prototype for the execution of the claimed device, an electric bridge electric detonator according to the patent [2] is taken, comprising a housing, a shoe with built-in electric inputs, an igniter composition and an incandescent bridge isolated from a metal housing, the end sections of which, including the adjacent area around the attachment points with a connecting electrode, covered with an insulating composition, which consists of an insulating varnish flowing down from the center region of the curved bridge after the dipping process or is applied to the points drops mounts. The ends of the electrical inputs protrude above the surface of the pads. The insulating layer hides the sharp edges and protruding ends of the wire and prevents the discharge of static electricity between the metal casing and the attachment points of the incandescent bridge.

The disadvantage of the selected prototype is that the device is not intended for self-shutdown and does not provide it, since there are exposed sections of protruding current-carrying electrodes between which short circuit of conductive products of flammable compositions can occur after their combustion, in addition, the insulating varnish is destroyed by combustion of the ignition composition, which also contributes to an increase in the electrical conductivity of the interelectrode gap.

The objective of the invention is the achievement of self-disconnection from the current source when igniting pyrotechnic and powder charges.

The technical result achieved by using the invention is that when the electric igniter is activated by an electric current pulse with an amplitude of 2 A and a voltage duration of 10-30 ms on the electric inputs, after ignition of the ignition and working compositions, the electric igniter is disconnected from the current source with a probability of at least 0.999 . Self-shutdown is maintained upon ignition of the working charge of both generating gaseous products of combustion (pressure in the chamber up to 600 kgf / cm ² ) and solid slags.

The specified technical result is achieved due to the fact that in an electric igniter containing a housing, a shoe with built-in electrical inputs, an incandescent bridge attached to them, an igniting (igniting) composition, the ends of the electrical inputs are made flush with the surface of the shoe or buried relative to the surface of the shoe and are coated with a durable, fireproof epoxy resin insulating compound. The insulating composition contains from 25 to 30% by weight of the powder of an inorganic compound from the group of nitrides, carbides and stable oxides. In order to increase safety during handling, a mixture of blasting (secondary) explosive with active metal powder is used as an ignition composition.

The execution of the ends of the electrical inputs flush with the surface of the pads or with a recess facilitates coating them with an electrically insulating layer. The coating of the ends of the electrical inputs, including the attachment points of the incandescent bridge, with an insulating layer eliminates the physical and electrical contact of the electrical inputs with the igniter composition and combustion products of this composition after operation, thereby eliminating active electrical connection between the electrical inputs, i.e. self-disconnection from the current source is realized.

The addition of 25 to 30% by weight of a fine powder of refractory inorganic compounds, for example, covalent carbides or nitrides (in particular, boron) or stable oxides (in particular, silicon), gives the composition strength and fire resistance and contributes to the survivability of the coating during combustion of an igniter composition. The use of amorphous boron powder as a filler also allows to achieve the claimed technical result. The specified fraction of the filler provides optimal viscosity, when the content is less than 25%, the composition turns out to be easily flowing, when the content is more than 30%, the composition becomes non-technological in operation.

The use of a blasting explosive mixture with an active metal powder as an ignition composition, along with coating the ends with an insulating layer, significantly improves handling safety compared to devices with highly sensitive initiating explosives, in particular during fire or exposure to electrical factors.

The drawing schematically shows an electric igniter with self-disconnection from a current source, where it is indicated:

1 - glow bridge,

2 - insulating composition,

3 - electric inputs,

4 - block

5 - housing electric igniter,

6 - igniter composition,

7 - working charge.

For a specific design, the electric igniter included a thin-walled aluminum alloy sleeve, an AG-4C press material block, 0.5 mm diameter copper wire electrical inputs, an X20H80-VTs filament bridge of diameter 40 mm, an average resistance of 1, 2 ohms. Its fastening to electric inputs was carried out by soldering. A composition of ED-20 epoxy resin (40%), L-20 hardener (32%) and inorganic pigment (boron carbide powder, boron nitride or amorphous boron powder - 28%) were used as an insulating composition. The pyrotechnic composition of a mixture of a blasting explosive and a metal powder was used as an igniter, and octogen was used as a working charge.

The device operates as follows.

When the electric inputs 3 are connected to the current source, the glow bridge 1 heats up, ignites the composition 6, when it reaches a temperature of ~ 1400 ° C it melts and loses its continuity, the products of combustion of the ignition composition 6 and the main charge 7 contribute to the complete destruction of the bridge. After operation of the electric igniter, the ends of the electric inputs are electrically isolated from each other, there is no current between them, the electric igniter is disconnected from the current source.

Experimental verification of the claimed device has confirmed the high reliability of self-disconnection from the current source of an electric igniter in the most difficult conditions caused by exposure to gaseous and solid electrically conductive products of combustion after burning of the bridge. The electric igniter in the explosive device created a pressure of up to 600 atm. 28 experiments were carried out with electric igniters having an average resistance of 1.2 Ohms. The use of electric igniters was carried out by an electric current pulse with an amplitude of 1.9-2.0 A, the voltage maintenance time at the electric inputs was 13 or 30 ms. In all experiments, the pressure in the control volume was recorded, while the average time before the bridge burned out and disconnected from the power source was 7.6 ms with a standard deviation of 0.66 ms. Thus, the lifetime of the bridge always turned out to be shorter than the duration of maintaining the voltage at the electric inputs, i.e. implemented self-shutdown.

Sources of information

1. M.E. Gill, E. D. Iangley. An electric igniter with an isolated bridge // US Patent No. 3249047, cl. 102-28, published on 05/03/1966.

2. Diehl GMBH & Co. Bridge electric detonator // German patent No.DE 3613134, class. F 42 B 3/12, published 10/22/1987.

Claims (2)

1. An electric igniter comprising a housing, a block with built-in electric inputs, an igniter composition, an incandescent bridge attached to the electric inputs, wherein the attachment points and the end sections of the bridge are coated with an insulating composition, characterized in that the ends of the electric inputs are flush with the surface of the block or are buried and covered with an insulating composition, and the insulating composition is made on the basis of epoxy resin with the addition of a fine powder of refractory inorganic compounds from 25-3 as a filler 0% by weight. 2. The electric igniter according to claim 1, characterized in that a mixture of blasting explosive with an active metal powder is used as an igniter composition.