US2133119A - Delay detonator - Google Patents

Description

a l! e /O J. B. SMITH r-:r AL 2,133,119

DELAY DETONATOR Oct. 11, 1938.

Filed April 5, 1935 Ill Il 'Il' lll? earch red UNITED STATES PATENT lOFFICE DELAY DETONATOR John B. Smith, Frederick R. Seavey, and Carl A.

Taylor, Alton, Ill., assignors to Western Cartridge Company, East Alton, Ill., a corporation of Delaware Application April 5,

Claims.

This invention relates generally to detonators, and particularly to electrically ignitable detonators of the delay type.

The object of the present invention, generally stated, is to provide an electrically ignitable delay detonator which is positive in operation, even though exposed to moisture, safe to handle and economical to manufacture.

Another object of this invention is to provide an explosive train in a delay detonator wherein the constituents of the charge are so selected and arranged that the detonator will be positive in operation and substantially immune to premature explosions.

A further object of this invention is to provide a method of securing the lead conductors in position in an electrically ignitable delay detonator. Other objects Will become apparent to those i drawing, in which:

Figure 1 is a View in longitudinal section of a delay detonator constructed in accordance with the present invention;

Figures 2 and 5 inclusive, illustrate respecy tively the successive steps of the method of securing lead conductors in accordance with the present invention; and

Figure 6 is a detail sectional view of a plug in which the lead conductors are secured.

Figure 7 is a detail view of the end. of the lead wire split in accordance with the present invention to receive a resistance bridge.

Figure 8 is a view showing a series of interchangeable delay charges with corresponding interchangeable parts to provide a coordinated gas cooling space.

In accordance with the present invention, generally stated, the explosive train of a detonator of the delay type is composed of a plurality of charges, the constituents of which are so selected that upon ignition of an initial chargethe remaining charges will be progressively ignited and burned with a minimum possibility of preme ture explosion and the maximum practical uniformity. In accordance with the present invention, the constituents of the respective charges are so selected as to secure positive ignition of the next succeeding charge without creating high gas pressures. More specifically the present invention contemplates, in a detonator having a delay charge adapted to burn for a predetermined period of time, a more sensitive charge disposed in position so as to ignite the delay charge ex- 1935, Serial No. 14,742

posed to be ignited by the delay charge and in turn to ignite the initiating detonator charge.

The present invention further contemplates a method of securing the lead conductors in the end of a delay detonator whereby the same are not only held positively against relative movement but whereby the arrangement lends itself particularly to water proong.

Referring now to the drawing, Figure 1 illustrates one embodiment of a detonator construction in accordance with the present invention.

Such a detonator may comprise a tubular housing I which may be formed of sheet metal or other suitable material into one end of which a pair of lead conductors 2 extend as shown. The lead conductors which are preferably of the insulated type may have their ends skinned as shown at 3 and about the skinned portion, a plug 4 of hard material such, for instance, as sulphur may be cast. The plug 4 is preferably so pro portioned as to be insertable in the end of the tubular housing I but to substantially fill the end thereof. The particular method of kinking and mounting the ends of conductors 2 in plug 4 will be more specifically described hereinafter.

Arranged across the ends of lead conductors 2 is a resistance lament 5 adapted to be energized from a suitable source of electrical energy il iV l to which the conductors 2 lead and surrounding the intermediate portion of the filament 5 may be a charge 6 of priming material adapted to be ignited by a heated filament.

The priming charge 6 may be of any suitable composition, such, for instance, as the following:

Per cent Nitro starch 20 Mercury fulminate 22.5 Lead sulphocyanate Potassium chlorate 15 Ferro silicon 10 Charcoal 2.5

but any other suitable composition may be used.

On the interior of housing I and in spaced relation to plug 4 may be a tube 'l of brass or other suitable material arranged to fit snugly within housing l and adapted to contain a delay charge or fuse 8. At the end of the delay charge 8 nearest the priming charge 6 may be an ignition charge 9 of more sensitive composition than the delay charge and adapted to be readily ignited by a flame from the primer charge B. For instance, the ignition charge 9 may be composed of 60% fast black powder and 40% slow fuse powder (such as 200 second) of approximately equal mesh. As pointed out above, however, the delay charge of fuse 8 may be of a less sensitive material but one, the burning rate of which is well known. For instance, such a. suitable charge may comprise smokless powder of a suitable type which may, if desired, be blended with a suitable amount of black powder. It will be understood, of course, that the length of the fus'e 8 and the loading density may be regulated in accordance with the delay desired for the particular detonator, it being understood that the parts may be made longer or shorter, in order to control the burning period and thereby control the length of the delay,

As clearly shown in Figure 1, considerable space is left on the interior of tube I between priming charge 6 and ignition charge 9. This intervening space provides expansion space for the gases generated upon combustion of both the priming and ignition charges, as well as the delay charge and thereby reduces the danger of premature explosions. In order to permit the escape of gases generated and thus prevent excessive pressures in the expansion space I0, an opening such as II may be formed in the wall of tube I. The opening II may, in accordance with the present invention be covered with a iilm I2 of suitable water prooiing material which is readily disruptable by the pressure set up in space Ill. A suitable composition is as follows:

Per cent Ethyl acetate z, 68 Nitrocellulose 17.5 Rosin f 10 Camphor 4.5

but other suitable compositions may be employed.

That portion of housing I in which vent II is situated may be enclosed within an auxiliary sleeve I3 extending entirely around the housing I and tightly fitting the latter at both of its ends. The sleeve I3 may be provided with one or more vent openings I4, preferably arranged on the opposite side of the assembly from vent I I, that is to say, in approximate diametrically opposed relation from vent I I. With the vents I I and I 4 thus arranged, it is apparent that gases escaping from vent II will be bailled by sleeve I3 and caused to pass around to the opposite side of housing I before they may escape through vent I4. Consequently, if any incandescent sparks should escape with the gases through vent II, they will be caused to travel for sufficient distance in the space between housing I and the sleeve I3 to permit them to cool sumciently that they will not prematurely ignite the charge to be exploded. Moreover, in such relation, the sleeve I3 operates to protect the water proofing film I2 from accidental puncture.

As remarked above, the period of delay may be varied by varying the length of fuse 8 and this may be accomplished by providing a series of tubes I of various lengths differing, for instance, as by intervals of approximately one second. In accordance with the present invention, sleeves I3 are coordinated with the delay charge, the longer the delay interval the greater the length of sleeve I3. Accordingly, a series of sleeves I3 differing in length by increments of about one-eighth inch per interval of delay, or, for instance, one corresponding to each length of tube I may be provided so that as the period of delay increases the volume of the gas cooling chamber within the sleeve I3 also increases and greater cooling is eiectcd due to the increase of metal surface.

This is clearly illustrated in Figure 8 which shows a series of delay tubes I, I0 and II with their charges and therebeneath a corresponding series of sleeves I3, 3D and 3|, the lengths of which are coordinated with the length of the charges in tubes 1, 'IIJ and II so as to eiiect proper cooling of the gases.

Disposed adjacent the end of delay fuse 8 opposite ignition charge 9 is another sensitive charge I5 which may be descriptively termed a flash charge, the composition of which may be such as to be readily ignitible by the delay fuse 8 and which, when ignited generates sufiicient heat and/or flame to properly ignite the detonating charge I6 and thereafter the base charge I'I of an ordinary blasting cap having a cartridge I8. Such a iiash charge as I5 may, for example, be composed of fast burning black powder which passes 24 mesh and is caught on 4B mesh. 'I'he detonating charge I6 may comprise mercury fulminate, trinitrotoluene, picric acid, tetryl, potassium chlorate and the like in various suitable combinations and proportions; but where the de- Vice is used as an igniter with blasting powder, the detonating charge may be replaced by black powder. In the embodiment shown in the draw ing, the flash charge I5 is disposed in the cartridge of the blasting cap, although it will be apparent that the flash charge I5 might, if desired, be positioned in the end of housing I or even in the end of delay tube 'I so as to be ignitible by the delay iuse 8. In the latter case, it will be understood that the end of the delay tube should be sealed with a suitable water proofing.

The open end of the cartridge I8 may, as shown in the drawing, be connected with the adjacent end of housing I. This connection may be accomplished by telescopng the respective parts, as shown in the drawing and corrugating the same to hold the same in position. When it is desired to employ the corrugation for holding the parts together, the exterior of delay tube 'I may be provided with a circumferential groove I9 into which the metal of the housing I and cartridge I8 may be crimped. Moreover, the end of cartridge I8 may be sealed to housing I using a suitable water proong such as that of film l2.

The end of housing I opposite the blasting cap or detonator may be suitably sealed after the insertion of plug 4 with the embedded lead wires 3 by depositing thereupon a small amount of a suitable water proofing material 20 which may, for instance, be of the following composition:

Per cent Pitch 60 Rosin 35 Linseed oil 5 Over the layer of water proong material may be poured suiiicient molten sulphur to fill up the end of housing I and hold the other parts in position. Such a sulphur iiller is designated as 2l.

If desired an additional kink may be formed in lead wires 2 so that the kink may be embedded in sulphur ller 2I so as to more firmly hold the wires against relative movement or displacement.

In preparing plugs 4 with the conductors 2 embedded therein, as hereinbefore described, a convenient procedure is illustrated more or less diagrammatically in Figures 2 to 5 inclusive. As shown in Figure 2 the wires 2 may be rst provided with kinks 3 and thereafter a suitable hard material, such, for instance, as sulphur may be cast about the same to form plugs 4 as shown in uns; uve/J. u .vu x uns Figure 3 so that the bare ends of conductors 2 extend slightly beyond the end wall of plug 4, as shown at 22. The extending ends 22 of the conductors 2 may then be bridged across by resistance filament 5. This may be accomplished in accordance with the procedure set forth in United States Patent No. 1,605,688 wherein the ends 22 ofthe lead conductors are first split and a resistance filament swaged in position.

After the resistance filament 5 has been secured to ends 22 of the lead wires, a suitable moldable substance such, for instance, as sulphur may then be cast about the connections between the filament 5 of the lead wires, as illustrated at 23. The auxiliary plug 23 may be so cast as to bond itself with plug 4 and thus provide a firm support for the entire assembly.

Preferably, the auxiliary plug 23 is so cast that the intermediate portion of filament 5 is left exposed, as shown at 24 in Figure 6. This may be accomplished by providing a recess 25 of suitable configuration in auxiliary plug 25. The recesses 25 may thereafter be filled with the priming mixture 6. From the foregoing description it is apparent that when the filament 5 is energized as by an electric current passing therethrough, the priming charge E in which the filament is buried becomes ignited due, either to the rise in temperature of filament 5 or a burning out of the same causing an are within the primer charge. The flame or flash produced by ignition of the priming charge is then effective to ignite ignition charge 9 which latter, being in contact with the end of the delay charge or fuse 8, ignites the delay charge. The delay charge then continues to burn for a predetermined interval.

The combustion of the ignition charge 9 creates a sufficient volume of gas to disrupt the water proofing film I2 across vent II so that the gases from the priming charge 6, ignition charge 9 and delay charge 8 are vented from the space I0 into the annular cavity between the exterior of housing I and the interior of sleeve I3. These gases are forced to travel forward for the length of the annular cavity and to travel through 180 in the annular cavity before they are released to the surrounding medium. It will be understood that the length of the path between openings I I and I4 will vary in accordance with the length of the delay fuse 8 and accordingly, in accordance with the length of the delay tube 1, the longer the delay the longer the travel between openings Il and I4.

The spiral travel of the gases just described, sufficiently cools the gaseous products of combustion that they are incapable of igniting the explosives with which the detonator is employed. As previously described, the sleeve I3 also operates as a baille and prevents premature ignition of the explosive to be detonated by sparks or hot slag from the detonator.

When the delay charge 8 has burned for the predetermined interval, the flash charge I5 is ignited and produces a sumcient flash to properly ignite the detonating charge IB.

From the foregoing description, it is apparent that many modifications of the delay detonator hereinbefore described will present themselves to those skilled in the art Without departing from the spirit of this invention. It is to be distinctly understood, therefore, that the embodiment hereinbefore specifically described and shown in the drawing, is for illustrative purposes only and that the invention is not limited to the specific details thereof. Such modifications and the use of such individual features and subcombinations of features as do not depart from the spirit of this invention are, although not specifically described herein, contemplated by and Within the scope of the appended claims.

Having thus described the invention, what is claimed is:

1. The method of making delay detonator connections comprising, forming kinks in a pair of lead wires, embedding the kinks in a plug of hard material with the ends of the Wires extending therebeyond, then connecting a resistance filament to the ends of the Wires, and surrounding the connections with hard material bonded ,to the plug.

2. The method of making delay detonator connections comprising, forming kinks in a pair of lead wires, casting a sulphur plug about the kinked portions of the wires with the ends of the Wires extending beyond the plug, splitting the ends of the wires, bridging a resistance filament between the split ends, and thereafter casting additional sulphur about the end portions of the Wires and filament and in bonded relation to the plug.

3. A delay detonator comprising in combination, a tubular housing, a series of tubes each containing a delay charge of different lengths and adapted to fit said housing, and sleeves corresponding to each tube of the series, said sleeves arranged to fit over said housing to provide a gas chamber thereabout having a Volume depending upon the length of the delay.

4. A delay detonator comprising in combination, a housing having a gas vent, a delay column in said housing, the length of said column depending upon the period of delay desired, and a sleeve about the vented portion of said housing, the size of said sleeve being coordinated with the length of the delay column.

5. A delay detonator comprising in combination, a housing, removable delay charge in said housing and a series of members selectively cooperating With said housing to provide a gas cooling chamber having a volume coordinated With the delay charge.

JOHN B. SMITH. FREDERICK R. SEAVEY. CARL A. TAYLOR.

"'7 J; V CERTIFICATE OF CORRECTION.,

Patent No., 2,l55,ll9 OctobeI1 ll, 1958.

JOHN B. SMITH, ET AL. Itis hereby certified that error appear-s in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 8, for the word "split" read notched; and that the said Letters Patent should be read with this'corr'ecton therein that the same my c/onform to the record of the case in the Patent Office j Signed and sealed this 27th day of December, A. D. 1958. l

Henry Van Arsdale (Seal) Acting Commissioner of Patents.

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