US1821608A - Blasting cap - Google Patents

Description

Sept. l, 1931. H. Kl 'BABBlT-r 1,821,608

lBLASTING CAP Filed June l, 1929 Bq his aHorneLl Patented Sept. l, 193i HENRY K. BABBITT, OF WILMINGTON,

ISTATES PATENT FFICE DELAWARE, ASSIGNOR T0 E. I. DU PON'Jl' DE tantos NEMOURS & COMPANY, 0F WILMINGTON, DELAWARE, A CORPORATION 0F DEL- AWARE IBLASTING CAI Application led June 1, 1929. Serial No. 367,805.

This invention relates to delay electric.

blasting caps, and more particularly to means for releasing the pressure of the gaseous products of combustion of the priming charge in order to prevent pre-ignition of the explosive charge.

Delay action caps for use in mining and blasting operations have heretofore comprised essentially a shell containing a suitable explosive substance, such as fulminate of mercury, or tetryl at its inner end, a plug of sulphur or like substance at the outer end, through which insulated conducting wires for the shot firing circuit pass to the igniting compound, and a retarding means containing a core or train of slow burning powder interposed between and spacing the A fuse end of the cartridge and the detonating end.

Various methods have been suggested for the escape of the gases and avoidance of pressure within the shell, such as providing vent holes in the shell wall, and it has been proposed to carry a rubber jacket over the perforations' for the purpose of excluding moisture. Closable vents laterally to the fuse which open automatically under the action of the generated pressure have been suggested by Eschbach (UQS. Patent N o. 1,57 0,- 733). Eschbach furthermore provides a free-air space between the fuse cartridge and the retarding means and an air vent conimunicating with the space within the fuse for the escape of the gases and pressure resulting from the ignition of the match head in order to prevent-pre-ignition of the shot.

An object of the present invention is to provide a means whereby the heated gases and pressure produced within the cartridge at the time of initial ignition may be allowed to escape at as low a temperature as possible so as to avoid premature ignition of the explosive material in which the blasting cap is embedded or surrounded.

Another object of mv invention is a means whereby the gas is diffused in order to provide greater cooling effect of the gases than has heretofore been the practice.

A further object lof this invention is a device having the foregoing and other advantages and at the same time may be more simply constructed than devices of the prior art.

Other objects tion proceeds.

These objects may, be accomplished by means of an outer sleeve adapted to fit over the electric detonator and engage the casing at a point below the ventvin the wall.` This sleeve should be slightly larger than the shell of the fuse cartridge and spaced therefrom to permit ready exit of the gases. For this purpose spacing means inside the sleeve are essential, andin my preferred form I propose to provide an inner bead which, besides serving as a spacing means between the sleeve and the shell of the fuse will appear as the descrip-v cartridge, will also form a spiral channel v through which the escaping gases may pass. In this manner the desired cooling effect may be produced due to the extreme length of the channel and the diffusion of the gases that occurs. Where the spiral bead is not desired, pointed or oblong beads may be provided. I

My invention is illustrated by way of ex* ample in the accompanying drawings in which:

Figure 1 is a view of one4 form of my proy .ings it will be seen that 1 represents the in-v sulated conducting wiresof the shot firing circuit, 2 the sleeve member, 3 the ignition head, 4 spacing means for the sleevev member, 5 the spiral bead forming a channel for the escape of the gaseous products of combustion, 6 the gas vent, communicating with the free air space within the electric detonator, 7 the cap load, 8 and 9 sulphur plugs, 10 the'waterproofing compound, 11

the ignition (match) in place. In Figure 3 1s fled form ofthe sleeve Without the spiral bead,

this form being a plain sleeve vwhich fits over the detonator and is spaced therefrom by means of the pointed bead shown at 4b. This bead may, of course, lbe provided on either the sleeve or the shell of the detonator as desired as it will serve the same function equally well since it acts merely as a spacing means. This bead may also take an oblong form such as that shown at 4a in Figure 4;, in which case it may likewise be produced on the lshell of the detonator; v y

It will be understood that the foregoing parts are those conventionally used in this type of detonator. My improvement conslists principally in providing the sleeve W ich may be inserted over the detonator and adapted to engage the shell of thesame below the exit vent for the gases. f

rlhe sleeve may becombined with the detonator in various ways. Preferably, l pose to crimp thelower end of the sleeve so as to engage the grooves inthe retarding element, together with the shell of the blasting cap. The retarding agent may consist ofl any one of several materials such as black powder, fuse, or other slow burning materials. y lln somel cases it will be found desirableto have the gas vent closed at the exit from the air chamber, and for this purpose l propose to provide a low melting wax, lacquer or pyroxylin covering for the vent to prevent undue moisture or water from entering the air chamber., Other suitable means for closing the vent may be used, such as low melting solder, -but l prefer to use a pyroxylin material because of its quick response toincrease in temperature.

vAs many changes may be made in the above construction, and as apparently many Widely .dierent embodiments o'f my invention may be made without departi from the spirit or scope thereof, it is inten edthat all matter contained in the .accompanying specification 'and drawings shall be interpreted as illustrative merely, and that my invention shall not be limited exceptas stateduin the following claims.:

l claim: v

Y 14. Al delay el tric'detonator comprising in combination an ignition head,3an explosive load, a retardingmeans interposed between the ignition head and theload means, a free air-space between the ignition head and the retarding means, a vent .in vcommunication -with `the free air space fox-,exit of the gases formed during initial firing, a filler of lo'w fllsiblev Ar'naterial covering the vent,-l andy a sleeve surrounding the detonatorand spaced therefrom, and provided with aninner spiral air-space between retardmg means, a vent 1n communication with the free air-space for exit of the' gases vformed during initial firing, fusible materialicovering the vent, a sleeve surrounding the detonator, said sleeve having a spiral rib adapted to space the sleeve from they detonator and form a spiral channel for thedifusion and exit of the gases of combustion formed during initial ring so as to a illerof low prevent pre-ignition of the detonator charge'.

In testimony whereof, I aflx my signature.

v HENRY K. BABBITT.

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