US2877708A - Detonating fuse - Google Patents

Description

` March 17, 1959 M. REY

DETONATING FUSE I Filed June 22, 1956 /lmecEL PEV United States Patent- DETONATIN G FUSE Marcel Rey, Paris, France, assiguor. to Etablissements gey Freres & Cie., Paris, France, a corporation of rance Application June 22, 1956, Serial No. 593,081

Claims priority, application France July 8, 1955 1 Claim. (Cl. 102-27) The present invention relates to the priming of explosives for mines. y

The simultaneous priming of several charges of explosives or thepriming of deep charges or immersed charges is often effected by means of a detonator fuse of the exible type arranged in contact with the explosive charges to be primed. This method gives the priming'a large degree ofsafety due to the fact that the detonator itself (or the cap) utilised for the priming of the detonator fuse is generally located on the outside of the explosive charge proper and is not in contact with it. The detonating fuse fixed over the whole length of the charge of explosive ensures a complete and simultaneous detonation of the whole charge and enables a maximum speed of detonation to be obtained, or in other words a perfect utilization of the explosive.

A flexible detonating fuse usually comprises a core charged with explosive such as penthrite, hexogene or fulminate, enclosed in aprotective casing of textile material or of paper. This casing is itself covered by a coating of external protection which gives it a resistance to external shocks or to humidity. This external protection is obtained by means of impermeable coatings, such as bitumen, tar, pitch, gutta-percha, rubber or synthetic resins of diierent kinds. The detonating fuse protected in this wayy can withstand a large amount of handling, fairly large tractive efforts, and it can be handled without any danger.

,However, whenrit is desired to employ large charges of explosives, users have the habit, as a measure of safety, to prime the explosive charges not with a single detonating fuse but with two detonating fuses. In the latter case, these two fuses are independently accommodated along the whole length of the charges of explosive and are primed simultaneously, either by means of a master detonating fuse, or directly by a detonator or an electric fuse. This method of procedure enables the priming of the charge to be carried out by the second detonating fuse if one of these detonating fuses were to misfire for any reason whatever (deterioration, faulty manufacture).

However, this method of operation constitutes a new drawback due to the fact that it is necessary to fix the two fuses to the charge, and that the placing of this charge in position is made more ditlicult.

The present invention has for its object a detonating fuse which, whilst it gives the additional guarantees of the double priming, is much more convenient to handle.

The detonating fuse in accordance with the present invention is characterised in that it combines in a single fuse two separate explosive charges which are parallel to each other and are enclosed in a common casing.

This casing may either maintain the primary casings of the two charges in close contact, or it may keep them slightly spaced apart but separated only by a thin and narrow coupling strip formed by the mass of the coating. The two explosive charges preferably belong to two elementary fuses manufactured separately and then joined together in a twin fuse by simultaneous coating faice fuse of standard type, whilst at the same time giving,

from the point of view of detonation, a guarantee greater than that which is given by the use of two simple fuses.

In fact, not only can one of the charges compensate for the failure of the other, but in addition, the two charges normally contribute to the detonation by combining their effects, due to the fact of their etective proximity at a constant interval.

be primed just the same through the intermediary of the adjacent elementary fuse, the continuity of the charge of this latter ensuring the transmission of the explosivey wave to the two sections of the charge separated by the gap in the explosive in the rst. The same thing would apply if one of the elementary fuses were damaged on one of its sides due to an external cause (pulling out, tearing). Thus, in all cases, the detonating fuse in accordance with the invention will ensure the detonation of the charge of explosive which it is to control. Finally, it is to be observed that a twin detonating fuse of this kind has a resistance to tensile force which is definitelyv greater than the tensile strength of two single independent detonating fuses; the tractive effort is necessarily distributed in fact over the unit formed by the two elementary,

fuses of the twin fuse.

With a view to electric firing by priming, it has been proposed, especially in the lower part of deep mines, to'

incorporate in a detonating fuse two conducting wires intended to be connected to an electric fuse. This arrangement has been described in the French Patent No.`

1,109,173 of July 16, 1954, for Improvements in Detonating Fuses With a View to Electrical Firing. It s quite clear that in a twin fuse in accordance with the invention, it is possible to incorporate, still more easily than in a simple fuse, wires intended for electric ring,

these wires being held in the mass of the coating and.y passing along the elrnentary fuses in the space comprised In Fig. 4, a form of construction of a fuse in accordance with the invention, and incorporating conductive wires for electrical firing.

As can be seen in Fig. l, a fuse in accordance with the invention is shown as having two separate charges 1-1, parallel under a single external casing. Each charge 1 composed of a normal type of explosive such as penthrite, is preferably the core of a single distinct elementary fuse of the usual type, enclosed in a casing 3 of the usual type, gutta-percha or lapping for example, the two elementary fuses being joined together under the common casing 2. This casing 2 is preferably of plastic material and is moulded over the simple fuses. During manufacture, this can be obtained by passing the two juxtaposed fuses through an extrusion press, the crosssection of which corresponds to the transverse profile of Patented Mar. 17, 1959 Thus, if one of the elementary fuses has a discontinuity in its charge of explosive, it would germes the twin fuse to be obtained (see Figs. 2 and 3). The plastic material 3 of the coating encloses the unit formed by the two elementary fuses with a constant thickness over the whole section. It passes into the interstice of these fuses if they are contiguous (see Fig. 2), or lls the space between them if they are slightly separated (see Fig. 3), forming in both cases a thin and narrow coupling strip 4.

A fuse in accordance with the invention will be ernployed in the same way as a single fuse: it will be attached to the explosive cartridges which form the mining charge over the whole length of this charge and it will be lowered with this charge into the shot-hole. The priming will be carried out by fixing a detonator, for example an electric detonator to the extremity of the fuse. For this purpose, one of the single fuses only may be engaged in the cap after cutting the strip 4 with a knife and removing the protective casing 2 over the length of fuse introduced into the cap. It is also possible, after cutting the strip 4 over the length necessary, to remove the interior halves of the two single fuses and to join the exterior halves one against the other in the form of a single fuse, which will be engaged in the cap. Whatever method may be employed for fixing the cap, the firing of the latter will be transmitted to the two charges 1, thus producing their simultaneous detonation and the detonation of the explosive cartridges; in case of failure of one of the charges 1, the detonation will be ensured by the other charge. There is thus obtained the guarantee sought by miners when they use two single detonating fuses for priming a single charge of cartridges, but without any complication of the priming operation, and above all without running the risk of additional difficulty in the introduction of the primed charge of cartridges into the shot-hole.

It will be observed that the presentation of a detonating fuse in the form described of a twin fuse with two separate charges does not necessarily imply the simultaneous use of the two charges, since the fuse can be divided into two single fuses by cutting the strip 4 if it is desired to employ a fuse with a single charge.

As can be seen from Fig. 4, the fuse with two charges in accordance with the invention may have incorporated in it conducting electric wires 5 and 6, intended to be connected to an electric fuse at the end of the fuse. This arrangement is only an application of that which formed the object for the usual single detonating fuse of the French patent application of July 16, 1954 Improvements in Detonating Fuses With a View to Electrical Firing. In this case, as shown in Fig. 4, the two electrical conductors are preferably passed in the space comprised between the two elementary fuses, but on opposite sides of the twin fuse, which ensures their insulation by a certain mass of the coating which separates them. Any other arrangement of these conductors could furthermore he adopted.

The juxtaposition of two detonating fuses of the single p elementary type to form a twin fuse with a double charge,

which constitutes the essential feature of the invention, does not pre-suppose any particular form of construction of the coupling of the two elementary fuses. It is only necessary that this coupling should be permanent, or continuous, in order that the two charges may be close to gether over their whole length, and that they detonate simultaneously.

It will of course be understood that the invention is not in any way limited to the forms of construction shown and described, since these have only been given by way of example. t

What I claim is:

A twin detonating fuse comprising two separate, similar, parallel explosive charges, an inner casing individually enclosing each charge, an outer unitary plastic casing molded over the entire surfaces of the inner casings with a constant thickness of material thereover and with a narrow coupling strip therebetween, and a pair of electricity conducting wires embedded in the narrow coupling strip and insulated from each other.

References Cited in the file of this patent UNITED STATES PATENTS 1,982,288 Evans Nov. 27, 1934 2,239,052 Pearsall et al. Apr. 22, 1941 2,334,414 Klotz Nov. 16, 1943 2,445,032 McFarland July 13, 1948 2,511,005 Pool June 13, 1950 2,663,755 McBride Dec. 22, 1953 FOREIGN PATENTS 938,665 France Apr. 12, 1948 441,654 Italy Nov. 6, 1948 728,240 Great Britain Apr. 13, 1955

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