US1964826A

US1964826A - Electric squib

Info

Publication number: US1964826A
Application number: US602811A
Authority: US
Inventors: Harold A Lewis; Clifford A Woodbury
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1932-04-02
Filing date: 1932-04-02
Publication date: 1934-07-03
Anticipated expiration: 1951-07-03

Description

July 3,1934. H. A. LEwls m; ,9 4, 26

ELECTRIC SQUIB Filed April 2, 1932 Patented July 3, 1934 UNITED STATES PATENT OFFICE ELECTRIC scum Application April 2, 1932, Serial No. 602,811

8 Claims.

Our invention relates to a new and improved form of electric squib and more, particularly to a waterproof squib adapted for use with pelleted black powder.

Electric squibs for the ignition of explosive compositions have been in general use for many years and are used with explosives such as black blasting powder, for example, where the initiation of the explosive is brought about by means of flame, as distinguished from high explosives such as dynamites, the explosion of which is caused by the sudden detonation of an explosive material contained in a cap shell. The use of the electric current for the firing of squibs is advantageous over the use of fuse for the reason that the squib can be placed in, intimate contact with the explosive, while the leading wires for conducting the electric current may be made sufficiently long so that the operator can be in a position of complete safety at the time of explosion.

In the electric'squibs commonly used at the present time, the leading wires pass through a mass of solid insulating material in such a way that they are held definitely in place and apart from one another. The ends of these wires extend a short distance beyond the plug of insulating material and are connected, one to the other, by means of a highly resistant wire of such diameter that it is heated to incandescence when the electric current passes through it. This fine connecting wire is surrounded by, embedded in, or cemented to a mass of readily ignitable material, such that the passage of the electric current through the wire causes the material to fire. This firing element is customarily enclosed in a tube of any desired material, closed at the rear end by a filling or fusible material. At the forward end of the squib the tube extends somewhat beyond the ignition charge, and may be-closed by a cork or cap, or by other loose fitting means, as desired. This capping is intended only for the protection of the ignition composition previous to use, both from the efiects of moisture and from'mechanical disturbance, and is to be removed before the squib is fired.

' While the electric squibs of the type described above have been generally satisfactory in the field, their use has been accompanied with certain disadvantages. When such a squib is used with pelleted powder for example, which comprises black powder compressed into -cylindrical form, with a small diameter hole longitudinally through the center for the introduction of the firing device, the squib has the disadvantage that the flame is projected straight ahead through the hole in the pelleted powder, and comes into contact with the walls of the powder only ina small degree. Attempts have been made to overcome this disadvantage by arranging small diameter holes in the side walls of the squib, preferably those of metal construction. This means is advantageous in bringing about ignition of the powder. However, both with this type of squib and with the type first described, there is the disadvantage that the ignition compositions are exposed to the action of atmospheric moisture, which frequently may cause rapid deterioration of the squib composition. a

The object of our invention is to provide an electric squib that will bring about more certain ignitionof the black powder. A further object of the invention is to provide an electric squib that is completely protected from atmospheric moisture effects. A still further object of our invention is to provide an electric squib having a considerable explosive effect on ignition, whereby the blasting powder in proximity to the squib charge is disintegrated and pulverized, so that ignition of the freshly exposed surface of the powder is more certain. Further objects will be disclosed as the description of the invention proceeds.

We find that these objects of our present invention may be accomplished provided the shell. of our electric squib is solid and completely closed at the end which contains the explosive charge. While the shell may be made of any suitable pressure-resistant material, we find metallic shells to be desirable, because of availability and ease of working. Various metals may be used for the construction of our shells, for example copper, steel, etc, but we prefer to use shells of aluminum, because of the favorable properties possessed by this metal.

Within, and at the base of, the metal shell described, an explosive charge is inserted. Variousv compositions are satisfactory for our ignition charge. For example, we may use black powder advantageously, or mixtures of -mercury fulminate and potassium chlorate, or like materials. Another composition that has given very satisfactory results has comprised a sulfocyanate, an oxidizing agent, and a low ignition point fuel or combustion accelerator.

While the compositions described above give favorable results when used in the closed metal shell described, we find that increased effectiveness is obtained if two different charges are introduced into the squib shell, namely an ignition charge and a base charge. The use of the two charges is desirable because of the two functions involved. In the case of the ignition charge, for example, it is important that it be capable of ready ignition by a low firing current. In theignition of pelleted black powden'however, by means of an electric squib, it is desirable that the main explosive charge be relatively slowburning and produce a considerable-flame.

We find a satisfactory arrangement to be the use of black powder as abase charge within theclosed end of the squib, this charge being pref- Various compositions may be used with satis faction for the ignition charge and the following desirable compositions are cited as representative:

The explosive charge used in our improved squib may be brought to ignition by various means. For example, an electric match-head may be used, spaced at the desired'distance from the explosive charge and adapted to be fired electrically, the flame from the match-head causing the ignition of the explosive charge. We may bring about ignition also by use of an ignition charge contained in the ordinary concave plug, the flame from this charge bringing about ignition of the main charge. We prefer, however, to have a small diameter bridge wire pass through the explosive charge, and to ignite said charge directly by this wire, when heated to incandescence by the passage of a current.

We find the use of a solid metal shell, of uniform wall thickness, and completely closed at the end containing the explosive charge, to give satisfactory results. We prefer, however, to have the wall of the electric squib weakened at one or more places. With such an arrangement, the firing of the explosive charge causes the rupture of the shell wall at the place of previous weakening. In this way the flame from the explosive at the time of firing can be directed as'desired, and brought with more certainty into immediate contact with the black powder charge to be fired.

Our new electric squib has many advantages in use. Because of the solid metal shell, the explosive charge is completely protected from the effect of moisture so that no deterioration on storage can result from this cause. A further advantage comes from the fact that the squib has a decided disruptive and explosive effect, so that the walls of the pelleted powder are pulverized and disintegrated in the neighorhood of the squib. This brings about the exposure of fresh dry powder surfaces in finely divided condition, so that instantaneous ignition of the black powder is made certain.

By way of example, we illustrate our new electric squib diagrammatically in the accompanying drawing. In this, Figure 1 represents a form of our electric squib containing only one explosive charge, which is ignited by the bridge wire and which also furnishes the flame for firing the black powder ouside thesquib. Figures 2 and 3 illustrate forms of our new squib containing a base charge, with a separate ignition charge superimposed thereon. In each of the forms illustrated, the leading wires B pass through, and are held inplace by, the conical plug E. The bridge wire D connects the leading wires and is surrounded by the ignition charge C. A waterproof composition G is above the concave plug, with a sulfur seal H on top. The whole is enclosed in the" metal shell A. The explosion is "brought about by the electric current heating the bridge wire D to incandescence, which in turn fires the ignition charge. In Figure 1, the ignition charge C disrupts the metal shell on explosion and brings about the ignition of the explosive outside the shell. In Figures 2 and 3, on the other hand, the ignition charge on burning brings about the explosion of the base charge F, consisting preferably of compressed black powder. This charge of slow-burning, flame-producing powder is effective in causing the ignition of the explosion to be fired. In Figures 1 and 2, the shell walls are of uniform thickness throughout. Figure 3, on the other hand, shows a squib in which a weakening of the wall has been caused at K, for example by a partial cutting or stamping of the metal wall.

While we have described our new electric squib in detail in the foregoing, it will be understood that many variations in minor details may be used without departing from the spirit of the invention. We intend to be limited in our invention only as indicated in the following patent claims:

We claim:

1. An electric squib comprising in combination a metallic shell having a closed end, a base charge of black powder within the closed end, an ignition charge comprising lead sulfocyanate, potassium chlorate and a combustion accelerator, and means for firing said ignition charge.

2. An electric squib comprising in combination a solid shell of pressure-resistant material, a base charge of slow-burning, flame-producing composition, an' ignition charge comprising lead sulfocyanate, potassium chlorate,-and a combustion accelerator, and means for electrically igniting the charge.

3. An electric squib comprising in combination a solid metallic shell, a loose deflagrating explosive and electric ignition means embedded in the loose explosive.

4. An electric squib comprising in combination a solid metallic shell, a loose defiagrating explosive comprising a sulfocyanate mixture, and electric ignition means embedded in the loose charge.

5. An electric squib comprising in combination a solid metallic shell, a loose defiagrating explosive comprising lead sulfocyanate, potassium chlorate, and'a combustion accelerator, and electric ignition means embedded in the loose charge.

6. An electric squib comprising in combination a solid metallic shell, an ignition means, a loose charge of a readily ignitable composition having the ignition means embedded therein, and a pressed charge of deflagrating explosive.

7. An electric squib comprising in combination a solid metallic shell, an ignition means, a loose defiagrating explosive comprising a sulfocyanate mixture having the ignition means embedded therein, and a pressed charge of defiagrating explosives.

8. An electric squib comprising in combination a solid metallic shell, an ignition means, a loose deflagrating explosive comprising lead sulfocyanate, potassium chlorate and a combustion accelerator having the ignition means embedded therein, and a defiagrating explosive comprising compressed black powder.

HAROLD A. LEWIS. CLIFFORD A. WOODBURY.