Wire mounting for an electric fuze of a shaped-charge projectile

March 19, 1968

3,373,687

Β. Η. O. SIMMONS WIRE MOUNTING FOR AN ' A SHAPED-CHARGE Filed April

ELECTRIC FUZE OF PROJECTILE

6, 1965

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ATTORNEYS

United States Patent Office ^{3373 687} wilt WH1VV Patented Mar. 19, 1968

3,373,687

WIRE MOUNTING FOR AN ELECTRIC FUZE OF _... „^A SHAPED-CHARGE PROJECTILE Bjorn Herman. Olof Simmons, Karlskoga, Sweden, assignor to Aktiebolaget Bofors, Bofors, Sweden, a corporation of Sweden

Filed Apr. 6,1965, Ser. No. 446,006

Claims priority, application Sweden, Apr. 7,1964 4,260/64

Claims. (Cl. 102—56)

The present invention relates to an explosive .projectile, and particularly to an explosive projectile of the hollow charge or shaped-charge type, which is detonated by activating an electric fuze.

There are. known projectiles of the general kind above referred to in which the fuze proper is mounted in the rear end of the projectile and a contact member is provided at the nose end or in the forward portion of the ^pr.°2^e?^de: ^{The contact} member is electrically connected with the fuze by a conductor wire, and the circuitry of the ¹⁸ that when the contact member is ought into contact with another metal component of trie projectile, an energizing circuit for the fuze is closed In actual practice, one terminal of the energizing circuit is usually connected to the outer metal shell castog of the toctme^ ‘ v ?^{ther terminal is COnnected} ‘θ he com tact member, which is mounted within the casing spaced ^f iⁿn ^he °,^{Uter Casing}- ^When the outer casing is ^{dUe t0 t1e} P^roJ^ectile striking a target the easins and the contact member are forced into engafeient thereby closing the energizing circuit. B^enr, mere

/.n3^he/^mOUni^ting-^{Of the conduct}or wire connecting the with th ^m_f^embe.^r t^ile forward portion of the projectile with the fuze m the rear end of the projectile presents several problems, some of which are due Io thelpecific requirements of a shaped or hollow charge as will be pointed out more fully hereinafter. ^S ’ ^{11 b}

The conductor wire must be electrically well insulated from the metal casing of the projectile^ since as nre duTtoI A« ““d ?^as.^ing.^is generally used ’as a con1^A h’gh grade insulation is of particular importance since the voltage for activating the fuze is gen” ally sun instance ^{&amp; Capacitor which} is charged, for eludes a to h ^a generator. This generator inoperated hv h r I'^{ng a magnetic field}’ which is operated by the forces of acceleration to which the projectile is subjected when propelled toward its target Arrangements of this kind are well known in the art ’ The accordingly It ^{Capacitor is usuaII}y finite small, Sd accordingly, it is important to reduce leakage losses to a minimum so that the charge in the capacitor will be suffi cient to activate the fuze when the energizing circuit thereof is closed as previously described. Obviously all the components in the activating arrangement for the fuze should be kept as small as possible for reasons of space In other words, maximal utilization of the capacitor charge is highly important. ⁸

Attempts have been made to mount the conductor wire substantially centric, that is, in the lengthwise axis of the hollow charge in the projectile. However, such central location of the. wire interferes to a considerable extent with the formation of the high velocity jet of hot particles which is generated by the shaped charge and which is the purpose of such charge. Tests have shown that the capability of the jet to penetrate the armored or other surface struck by the projectile was reduced to about half of the normal value due to the effect of a centrally ar10 ranged conductor wire, even though the wire was made as thin as was compatible with the required strength of the wire.

A further problem is caused by the rapid acceleration to which the wire is subjected when the projectile is launched. The difficulties encountered in this connection are particularly great when the wire is long, since the length of the wire determines the mass of the wire, and hence the effect of the high acceleration or inertia forces acting upon the wire. The high acceleration forces also create difficulties with respect to the mounting of the wire on the contact member, since the point of attachment inherently constitutes a somewhat weakened point.

It has been attempted to solve the problem by embedding at least part of the wire in the charge. However, the charges generally used have some electric conductivity, which makes it difficult to maintain a high grade insulation, and. the resulting leakage current jeopardizes the safe functioning of the fuze.

It is a broad object of the invention to provide a novel and improved wire mounting of the general type above referred to which holds the wire in a strong and electrically satisfactory fashion without adversely interfering with the jet stream generated when the charge of the projectile is detonated.

A more specific object of the invention is to provide a novel and improved wire mounting of the general type above referred to which permits a reduction of the mass of the wire to a minimum value and places the major part of the wire out of the path of the jet stream.

Another more specific object of the invention is to provide a novel and improved wire mounting in which the attachment of the wire to the afore referred to contact member of the energizing circuit of the fuze is such that the wire is fully capable of withstanding the powerful acceleration forces to which it is subjected when the projectile is propelled toward its target.

Other and further objects, features and advantages of the invention will be pointed out hereinafter and set forth m the appended claims constituting part of the application.

In the accompanying drawing a preferred embodiment of the invention is shown by way of illustration, and not by way of limitation.

In the drawing:

FIG. 1 is a perspective view, partly in section, of an explosive projectile of the shaped or hollow charge type in which is incorporated the wire mounting according to the invention; and

FIG. 2 is a detail view on a larger scale showing the attachment of the conductor wire to the contact member in the projectile.

Referring now to the figures in detail, the exemplified projectile is illustrated as an antitank projectile or missile. The front portion of the projectile comprises a substantially conical outer shell 1 which is mechanically and electrically connected to a rear casing 2 which is filled with a shaped explosive charge 3 of suitable composition. The rear end of casing 2 mounts an electric fuze 4 of conventional design. One terminal of the energizing circuit of this fuze should be visualized as being connected to the outer shell 1 through casing 2. A second terminal of the fuze is connected through a conductor wire 5 to a forward contact member 6. This contact member is shown in the form of an inner shell substantially duplicating the conical configuration of the outer shell 1. It is mounted spaced apart from the outer shell and electrically insulated therefrom. The circuitry of the fuze is arranged in a con3,373, 3 ventional manner, so that an energizing circuit for the fuze is closed, causing activation thereof, when the outer shell 1 and the inner shell 6 are brought into electric contact with each other, which occurs when the outer shell or both shells are deformed by the impact of the projectile on 5 a target.

The charge 3 is separated from the forward space in the projectile by a generally conical copper liner 7 for the charge, the apex of which faces the fuze. Assuming now that the energizing circuit of the fuze is closed by engage- ₁₀ment of the outer shell 1 and the inner shell 6 due to the projectile striking a target, and that the capacitor of the fuze is discharged as a result, the fuze causes ignition of charge 3. As the detonation front proceeds forwardly through the charge, particles of the copper liner 7 are _lgthrown off substantially perpendicularly in reference to the surface thereof, and such particles will join to form a jet including extremely hot molten metal particles which move at a high velocity along the lengthwise axis of the projectile. It is known and well understood that the jet 20 defines approximately a cone which has at each transverse plane a diameter of approximately 10% of the diameter of the cavity defined by the liner at the respective plane. The purpose of the jet is to strike and pierce the target at the point where the penetrating force is at a maximum. 25 Such function of hollow or shaped-charge projectiles is well known and understood as such, and does not constitute part of the invention.

As appears from the previous brief explanation of the formation and the path of a jet, a conductor wire cen- 30 trically disposed in liner 7 is bound to interfere considerably with the formation of the jet. As mentioned before, the penetrating force of the jet may be reduced by about 50%.

By arranging wire 5 eccentrically in reference to the 35 center axis of liner 7, that is, eccentrically in reference to the path of the jet, the wire will not appreciably interfere with the formation of the jet, and is also less exposed to the damaging forces of the jet.

It has been found that the eccentric disposition of the 40 wire in accordance with the invention permits the safe use of blank or uninsulated copper-coated piano wire having a thickness of 0.10 to 0.15 mm.

As is shown in FIG. 1, the wire extends from the fuze through a tube 8 inserted into the charge. The tube may be made of brass or a suitable plastic, but in many instances, a simple bore through the charge is sufficient. A guide disk 9 made, for instance, of insulation material, at the forward end of tube or bore 8 guides the wire which is extended through a hole 6a in the inner contact shell 6. A protective sleeve 10, made, for instance, of plastic, is preferably provided to prevent damage to the wire at the edge of the hole. The portion of the wire protruding between the inner shell 6 and the outer shell 1 is secured to contact shell 6 in strong mechanical and electrical contact therewith. While the wire may be attached by soldering, a rivet 11, such as is shown, has been found to be preferable. To protect the wire further, a strain relief means 12 is preferably provided between the point of attachment of the wire to contact shell 6 at rivet 11 and the hole 6a through which the wire is extended. The strain relief means may be in the form of a headed pin 12 upon which the wire is wound with several turns.

As pointed out before, the diameter of the cone formed by the jet occupies about 10% of the diameter of liner 7 at each transverse plane. As is evident from FIG. 1, the eccentric or slanted mounting of the wire assures that the wire will be outside the jet cone for practically its entire length.

The wire should be kept as short as possible to reduce its mass as much as possible. To this end, the mounting of the wire on inner contact shell 6 is placed as close to the rear end of contact shell 6 as is practical. Obviously, a small mass of the wire, in conjunction with the aforedescribed mounting thereof, and the provision of strain

687 relief means, make the wire capable of withstanding even very high forces of acceleration. It is also essential that the wire be stretched taut so that it offers a minimum basis for attack by the forces of acceleration and that it is safely eccentric for practically its entire length with respect to the path of the jet stream.

While the invention has been described in detail with respect to a certain now preferred example and embodiment of the invention, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and it is intended, therefore, to cover all such changes and modifications in the appended claims.