US3362330A

US3362330A - Proximity fuze

Info

Publication number: US3362330A
Application number: US534066A
Authority: US
Inventors: Lagerstrom Karl Olof Gunnar; Hartmann John Fredrik Alf
Original assignee: Foersvarets Fabriksverk
Current assignee: Foersvarets Fabriksverk
Priority date: 1966-03-14
Filing date: 1966-03-14
Publication date: 1968-01-09
Anticipated expiration: 1985-01-09

Description

Jan. 9, 1968 K, o. LAGERSTRGM ET AL 3,362,330

PROXIMITY FUZE Filed March 14, 1966 INVENTORS KARL OLOFGU/V/VAR LAGERSTRUM 60574 WOLK JOH/VFREDR/ LF HART/MANN United States Patent Office 3,362,330 Patented Jan. 9, 1968 3,362,330 PROXIMITY FUZE Karl Olof Gunnar Lagerstriim, Eskilstuna, Giista Wolke,

Jakobsherg, and John Fredrilr Alf Hartmann, Steel;- liolm, Sweden, assignors to Forsvarets Fabriksverk, Eskilstuna, Sweden Filed Mar. 14, 1966, Ser. No. 534,066 6 Claims. (U. 102-702) ABSTRACT OF THE DISCLOSURE Proximity fuze in which an electrical circuit for determining the firing sensitivity of the proximity fuze includes a number of series or parallel connected impedance elements located inside the envelope of the fuze. Control conductors connected in the sensitivity circuit and to the impedance elements have continuous parts which penetrate the wall of the envelope through insulation members providing electrical insulation from the remainder of the envelope and from each other. The connection of each conductor and its associated impedance element in the sensitivity circuit provides a predetermined impedance influence or absence of such influence on the sensitivity circuit by the associated impedance element, which influence or its absence is changed by an interruption of the associated conductor. A part of each conductor is located at or just under the outer surface of the envelope insulation members and that part of each conductor can be broken, out or otherwise interrupted, e.g., by means of a knife or similar tool, to change the impedance and hence sensitivity setting of the sensitivity circuit without gaining access to the interior of the fuze.

Cross reference to related application Co-pending application Ser. No. 534,067, filed on Mar. 14, 1966 relates to a different construction and method for changing the influence of impedance elements on proximity fuze electrical sensivity circuits without gaining physical access to the interior of the fuze envelope.

Background The present invention relates to a proximity fuze for a projectile, such as a bursting shell, which makes the projectile detonate shortly before it hits the target. The proximity fuze radiates energy in the form of electromagnetic waves or sound waves. A part of the radiated energy is reflected from the target, returns to and is received by the proximity fuze. When the received energy reaches a predetermined level the fuze ignites the charge in the projectile.

The amount of received reflected energy is greatly dependent on the reflecting power of the target. If the ground is the target, the reflecting power depends upon the character of the terrain and therefore, the distance from the target at which a projectile with a pre-set proximity fuze detonates, will vary for different kinds of target terrain. The distance where detonation occurs is also influenced by the angle of the direction of movement of the projectile in conjunction with terrain surface, also by the speed of the projectile, and whether or not there is a wood or woods on the target terrain.

The distance from the target at which detonation should take place in order to obtain the best possible effect is dependent on the protecting level of the target on the angle between the direction of movement of the projectile and the target level and on the capacity of the terrain to prevent the spreading of projectile splinters. For each type of projectile the distance from the target at which detonation should occur, in order to cause maximum damage, has a specific value. The damage caused by the projectile when exploded at the desirable specific distance is frequently many times greater than if the projectile is exploded at other distances, which could be rather close to the specific distance.

Before each shot it may as a rule be possible to find out or to estimate the reflecting power and the character of the terrain, such as the presence of wood, and also the protecting level of the target. It may also be possible to know or estimate the speed of the projectile, the angle between the direction of movement of the projectile and the level of the target, and also the specific explosion distance for maximum damage. Therefore, it is possible to increase the effect of the expenditure of ammunition if the proximity fuze of each projectile is capable of being adjusted immediately before the firing, so that each projectile may explode at the desired specific distance and maximum damaging effect will be obtained.

The adjustability may be continuous or non-continuous. Generally the characteristics of the fuze may be changed by adjusting an impedance, such as a resistance, in the electric circuit of the proximity fuze, for example in its amplifier part. It is also possible to change the magnitude of the transmitted energy or to adjust the sensitivity of the receiving means. If a continuous adjustability is wanted, for example in the form of a continuously adjustable potentiometer, special steps have to be taken to ensure a good contact-making in consideration of the forming of oxide on the contact making parts during storage. Further, there should be way to effectively prevent the adjustment of the potentiometer from being influenced by the rotation of the projectile. There is a device known for this purpose (U.S. Patent 2,552,482) but it is rather complicated.

Summary Calculations have shown that it is sufiicient to provide an adjustability of the characteristics of the proximity fuze in ten steps or less, in order to obtain a correct adjustment of the distance at which detonation should take place for achieving the maximum damage.

One object of the present invention is to provide a proximity fuze which is adjustable in steps. This adjustability means that the characteristics of the fuze may be altered in steps, so that the desired distance from the target for detonation may be approximately obtained. By a stepwise adjustment a simpler and more rigid construction can be obtained than by a continuous adjustability.

Another object of the invention is to provide such a stepwise adjustability by enabling an impendance to be adjusted without any need for disassembling the fuze .or to make any incision in the fuze or to influence the aerodynamic characteristics of the projectile.

A further object resides in the provision of a proximity fuze according to the invention having a number of impedance elements connected in series or in parallel in a circuit for adjusting the sensitivity of the fuze, the impedance elements being located inside the envelope of the fuze and connected to conductors which penetrate the wall of said envelope and insulated from said envelope by means of an insulation member, the outer surface of which is in level with the outer surface of the envelope. A part of each of the conductors is located at or just beneath said outer surface of said insulation member. When the impedance elements are connected in series, each of the conductors is connected in parallel to one of the elements so as to provide a short circuit path for the latter. When the impedance elements are connected in parallel, each of the conductors is connected in series with one of the impedance elements. The part of each conductor which is located at or just beneath the outer surface of the insulation member can be cut off by means of a knife or a simi lar tool.

Further objects and features of the proximity fuze according to the invention will become apparent from the following description and claims and from the accompanying drawing, in which FIGS. 1 and 3 illustrate simplified circuit diagrams of two embodiments of the present invention, and

FIG. 2 illustrates a section through the envelope of a proximity fuze and shows how the conductor shunted across one of the impedance elements of FIGURE 1 can be situated adjacent the exterior surface of the fuze according to the invention.

In the embodiment according to FIG. 1 a number of impedance elements 1 are connected in series in an electrical circuit, such as a part of a potentiometer (not shown), by means of which the sensitivity characteristics of the proximity fuze are determined. Each impedance element 1 is shunted by a conductor 2. As illustrated in FIG. 2, where only one of the plurality of impedance elements is shown, each impedance element 1 is located inside an envelope 4 enclosing the fuze. Each conductor 2 penetrates the wall of said envelope 4 and is insulated from the latter by means of an insulating member 3. The outer surface of insulating member 3 is level with and follows smoothly the outer surface of the rest of the envelope 4. A part of each conductor 2 is located at or just under the outer surface of the insulating member 3. The insulating member 3 is preferably made from a soft material, such as a synthetic resin of a suitable kind. This makes it possible to cut through one or more of the shunting conductors 2 by means of a knife or a similar tool, which will influence the characteristics of the proximity fuze.

In the second embodiment according to FIG. 3 a number of impedance elements 5 are connected in parallel in an electrical sensitivity circuit within the proximity fuze of the same kind as described in connection with FIG. 1. Also, in this case, each impedance element 5 is located inside the envelope 4 of the fuze. Each conductor 6, leading to one of the elements 5, is, however, penetrating the wall of said envelope 4 and is insulated from the latter by means of an insulating member 3 of the kind illustrated in FIG. 2. A part of each conductor 6 is located at or just under the level of the outer surface of the insulating member 3 in a manner similar to the arrangement shown in FIG. 2.

The cutting off of or breaking of the exteriorly located part of one or more of the conductors 6 will influence the impedance characteristics and hence sensitivity of the sensitivity circuit of the proximity fuze in the way indicated above.

By cutting off the exterior parts of one or more of the conductors 2. or 6 before the shot is fired it is possible to adjust the distance from the target at which the explosion of the projectile is going to take place, in order to get the maximum damaging efiect of the explosion.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and no restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. In combination in a proximity fuze which comprises an envelope and an electrical circuit for determining the firing range sensitivity of the prox mity fuze, the improvement comprising: a plurality of interconnected impedance elements located inside of said envelope and connected in said sensitivity circuit; and a plurality of conductors, each of which is associated and connected in circuit with a specific one of said impedance elements in said sensivity circuit so that continuity of each of said conductors controls the effect of its associated impedance element on the impedance of the sensitivity circuit; each of said conductors having a portion, intermediate its connections to said sensitivity circuit, which penetrates said envelope so that a part of the conductor is disposed immediately adjacent the envelope exterior surface; the portions of said envelope penetrated by said conductors constituting electrically insulating means which insulate said conductor portions; said conductor portions providing exteriorally accessible control means by which the impedance effect of each of said impedance elements on said sensitivity circuit can be changed.

2. The combination as defined in claim 1 wherein said plurality of impedance elements are connected in series with each other in said sensitivity circuit; each of said conductors is shunt connected across an associated said impedance element; and an intermediate extent of each said conductor, between its shunt connections, passes into and back out of at least a part of said insulating means with a portion of said conductor disposed adjacent the exterior surface of the associated part of said insulating means.

3. The combination as defined in claim 1, wherein said plurality of impedance elements are connected in parallel with each other in said sensitivity circuit; each of said conductors is connected from one end of and in series with an associated said impedance to one side of said parallel connection; and an intermediate extent of each said conductor, between its series connections, passes into and back out of at least a part of said insulating means with a portion of said conductor disposed adjacent the exterior surface of the associated part of said insulating means.

4. The combination as defined in claim 1, wherein said conductor portions penetrate into and through said envelope and a part thereof is exterior of and is disposed against the exterior surface of said insulating means.

5. The combination as defined in claim 1, wherein said insulating means is made from soft material and conductor portions which penetrate said envelope are embedded in said insulating means with a part thereof closely adjacent but below the exterior surface of said insulating means.

6. The combination as defined in claim 1 wherein the exterior surface of said insulating means is smoothly contoured with the exterior surface of the remainder of said fuze envelope.

References Cited UNITED STATES PATENTS 1,791,606 2/1931 Ruhlemann 10270.2 2,552,482 5/1951 Ferris et al. 102-70.2 2,959,128 11/1960 Boykin 10270.2 3,048,136 8/1962 Holmes 102--70.2 X 3,166,015 1/1965 Tuve et a1. 102-702 V BENJAMIN A. BORCHELT, Primary Examiner.

W. C. ROCH, V. R. PENDEGRASS,

Assistant Examiners.