Apparatus for Generating an Electrical Ignition Current in a Fuze of a Projectile

The present invention generally relates to weapon systems, and, more specifically, concerns a new and improved construction of apparatus for generating an electrical ignition current in the fuze of a projectile which is intended to be fired from a weapon or gun. Generally speaking the apparatus of this invention is of the type comprising an induction coil located in the projectile, a magnet for generating a magnetic field, a two-part or bipartite yoke, one part of which is located at the projectile and the other part of which is located at the weapon barrel, in order to generate a change in the magnetic flux upon passage of the projectile through the weapon barrel.

According to a state-of-the-art construction of apparatus of this type, as disclosed in U.S. Pat. No. 1,739,921, an electromagnet is arranged at the mouth or muzzle of the weapon barrel and the projectile fuze possesses an induction coil. Upon passage of the induction coil through the electromagnet there is induced a current in the induction coil which, on the one hand, is employed for charging a capacitor and, on the other hand, for switching-on a mechanical timing relay.

Disadvantageous with this prior art construction is the need to arrange an electromagnet at the muzzle at the region of the hot gases, and further, with such electromagnet there can only be induced a single current surge.

Furthermore, there is known to the art from U.S. Pat. No. 3,417,700 an apparatus where a number of induction coils containing permanent magnets are uniformly distributed at the circumference or periphery of the projectile body, and the coil axes are disposed radially with regard to the projectile body. The magnetic field produced by the permanent magnets is closed as long as the projectile is located within the weapon barrel and opens as soon as the projectile departs from the weapon barrel, resulting in a voltage being induced in the induction coil.

Yet this prior art apparatus is associated with the following drawbacks:

(a) such type arrangement of the induction coils cannot be employed with small caliber ammunition;

(b) the radial acceleration in the case of spinning ammunition does not allow for any such type arrangement of the induction coil; and

(c) there can only be generated a single pulse.

Therefore, with the foregoing in mind, it is a primary object of the present invention to provide an improved construction of apparatus for generating an electrical ignition current in the fuze of a projectile in a manner not associated with the aforementioned drawbacks and limitations of the prior art proposals.

Another and more specific object of the present invention aims at the provision of an apparatus of the previously mentioned type, by means of which, during passage of the projectile through the barrel of the weapon, there can be generated as large as possible energy, and which apparatus also is suitable for use with small caliber projectiles as well as spinning ammunition or projectiles.

Now in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the apparatus of this development is manifested by the features that according to one embodiment:

(a) the part of the yoke located at the weapon barrel possesses a number of ferromagnetic rings or ring members;

(b) paramagnetic rings or ring members are arranged between the ferromagnetic rings;

(c) the part of the yoke located at the projectile body comprises a substantially cylindrical body member having a substantially disc-shaped flange for the reception of the induction coil as well as a soft iron disc;

(d) the magnet in the form of a permanent magnet is arranged between this substantially cylindrical body member and the soft iron disc;

(e) the axis of the induction coil substantially coincides with the projectile axis; and

(f) the aforesaid ferromagnetic rings and paramagnetic rings are arranged at the end of the weapon barrel.

According to another embodiment of the invention, there is provided an arrangement wherein:

(a) the magnet comprises an electromagnet located at the mouth of the weapon barrel and composed of a number of ferromagnetic rings and paramagnetic rings arranged between the ferromagnetic rings;

(b) the part of the yoke at the weapon barrel comprises a three-arm yoke attached to said ferromagnetic rings;

(c) two electromagnetic coils polarized in opposite directions surround at least part of said three-arm yoke; and

(d) the axis of the induction coil substantially coincides with the axis of the projectile.

An advantageous construction of the modified embodiment comprises three such ferromagnetic rings connected to one another by two of the paramagnetic rings which are in the form of sleeves.

The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 is a longitudinal sectional view through an electronic projectile fuze arranged at the rear end of a projectile body equipped with a generator;

FIG. 2 is a longitudinal sectional view through the front end of a weapon barrel having a muzzle brake;

FIG. 3 is a longitudinal sectional view through a second exemplary embodiment of an electronic projectile fuze arranged at the rear end of a projectile body equipped with a generator;

FIG. 4 is a longitudinal sectional view of a third exemplary embodiment of an ignition current generator;

FIG. 5 is a cross-sectional view taken substantially along the line V--V of FIG. 4;

FIG. 6 schematically illustrates an exemplary embodiment of circuitry which can be used between the generator and capacitor with the apparatus of the invention;

FIG. 7 is a perspective view of the front end of a weapon barrel;

FIG. 8 is a longitudinal sectional view of a fourth exemplary embodiment of an electronic fuze arranged at the rear end of a projectile body equipped with an ignition current generator;

FIG. 9 is a diagram illustrating graphs of the magnetic flux and the induced voltage; and

FIG. 10 is a fragmentary longitudinal sectional view through an electronic fuze arranged at the rear end of a projectile body equipped with an ignition current generator according to a fifth exemplary embodiment of the invention.

At this point in the disclosure, it is mentioned that different ignition current generators for electronic projectile fuzes are known to the art, wherein both parts of the yoke are arranged in the projectile. With such type generators only the inertia forces can be utilized for generating the electrical energy.

In the case of spinning ammunition e.g. spinning projectiles, there can be employed, for instance, rotary generators wherein the rotational acceleration or a change in the moment of inertia can be utilized for generating the electrical energy. Friction forces appear between the rotor and the stator, and difficulties arise during the mounting of the rotor. Further, it is possible to use for spinning ammunition, for instance surge generators. Depending upon the construction of such surge generators the mode of operation is different. There are required different safety devices, for instance for providing the necessary safety during transport of the projectile.

In the case of fin-stabilized projectiles it is only possible to use surge generators or batteries.

Piezoelectric generators can be employed both for spinning ammunition as well as also for fin-stabilized projectiles. However, such type generators can only generate a very small amount of electrical energy per unit volume.

Now with the foregoing in mind the ignition current generators of the invention have been designed for the purpose of avoiding a number of such problems which are prevalent with the heretofore known prior art generators. Turning attention therefore initially to the embodiment shown in FIG. 1, it will be seen that a fuze housing 12 is attached at the rear end of a projectile body 10 which contains an explosive charge 11. This fuze housing 12 comprises a substantially pot-shaped threaded sleeve 13 and a tail screw 14 or equivalent structure which is threaded into the internal threading 15 of the sleeve 13. This sleeve 13 is also threadably connected with the internal threading 16 of the projectile body 10. Between the rear end surfaces or faces of the projectile body 10 and the sleeve 13 on the one hand, and the head 14a of the tail screw 14 on the other hand, there is arranged one part 17 of a yoke or equivalent structure. This yoke part 17 contains a permanent magnet ring 18 and a soft iron disc 19 as well as an induction coil 20. The induction coil 20 is surrounded by an insulating ring 21. Further, a guide ring 24 is secured to the outer periphery or circumference of the projectile body 10. Internally of the tail screw 14 there are located different components or elements of the fuze, which are not part of the subject matter of the invention and can be constructed in conventional fashion. One possible arrangement and operation of such elements, forming a fuze firing chain, has been disclosed for instance in the commonly assigned U.S. Pat. No. 3,994,228, granted Nov. 30, 1976 listing as the inventor "Walter Hurlimann", and entitled "Projectile Fuze for a Spinning Projectile Containing a Detonator Cap and an Electro-Magnetic Firing or Ignition Current Generator", to which reference may be readily had and the disclosure of which is incorporated herein by reference. Thus, in the description to follow there will only be considered enough of the structure of the elements located within the tail screw 14 to provide those skilled in the art with sufficient background information and a clear appreciation of the underlining concepts of the present invention. Hence, it will be appreciated that belonging to such elements is a charging capacitor 25 (see also FIG. 6) which can be charged by the inventive ignition current generator. Connected with the charging capacitor 25 is a detonator cap 26 which can be fired by the charge stored in the charging capacitor 25 as is well known. An electronic control element 27 ensures for the proper detonation of the detonator cap 26 at the correct moment in time. Located in front of the detonator cap 26 is a detonator or transfer element 28 which transmits the detonation or firing of the detonator cap 26 to a reinforcement charge 29. This reinforcement charge 29 is attached to the sleeve 13 and protrudes into the explosive charge 11. Further, the detonator 28 is located in a rotor 30 which can be rotated out of the illustrated armed position into a safety position. DDue to the spin of the projectile the rotor 30 moves out of the safety position into the armed or firing position.

Now as long as the projectile body 10 is located in the cartridge sleeve 23, then the cartridge sleeve 23 short-circuits the magnetic field produced by the permanent magnet 18. To ensure that the projectile can be reliably fired or exploded at the target there is also provided an impact switch 31.

Continuing, and looking to the arrangement shown in FIG. 2, it will be seen that a muzzle brake 33 is attached to the front end of a weapon barrel 32. Since this muzzle brake 33 does not constitute subject matter of the present invention, and its construction and mode of operation may be assumed to be part of the state of the art and not important for understanding the teachings of the present invention, no further discussion thereof is believed to be necessary. At the inner wall of the substantially sleeve-shaped muzzle brake 33 there is arranged the second part of the aforementioned yoke, which second part has been generally designed by reference character 70. This yoke part 70 will be seen to comprise rings or ring members 34 formed of a suitable paramagnetic material, for instance titanium. Now both between and in front of these titanium rings 34 there are secured the rings or ring members 35 formed of ferromagnetic material, for instance steel. The forwardmost ring 35 is threaded into or otherwise appropriately secured at the muzzle brake 33. The width of these rings is preferably somewhat greater than the width of the first part 17 of the yoke containing the soft iron disc 19 (FIG. 1).

The mode of operation of the apparatus described and illustrated in FIGS. 1 and 2 is as follows: When, upon firing the projectile, the projectile body or body member 10 departs from the cartridge sleeve 23, the magnetic field generated by the permanent magnet 18, and which magnetic field is located essentially at the yoke part 17, in the soft iron disc 18 and at the neck of the cartridge sleeve 23, remains shot-circuited by the weapon barrel 32. As soon as the projectile body 10, together with the fuze attached to its rear end, flies through the muzzle brake 33, then the magnetic field is opened by the paramagnetic rings 34 and is again short-circuited by the ferromagnetic rings 35. This opening and short-circuiting of the magnetic field in each case induces a voltage in the induction coil 20. Due to this induced voltage the capacitor 25 which is connected with the induction coil 20 can be charged. The control element 27 ensures that the capacitor 25, after the charging thereof, will not again discharge through the windings of the induction coil, for instance by using diodes or equivalent structures suitable for this purpose. Since during the movement of the projectile the direction of the induced voltage changes, it is advantageous to employ full wave rectifiers or a full wave rectifier arrangement, as generally indicated by reference character 75 in FIG. 6, at the control element 27.

At this point attention is directed to the modified version of fuze illustrated in FIG. 3 which differs from that shown in FIG. 1 essentially by the shape of the yoke part 17, the soft iron disc 19 and through the use of a suitable plastic ring 36.

The purpose of this modified version is especially seen in that the large forces, which are exerted by the propellent gas upon the tail screw 14, are transmitted to the projectile body 10 in such a manner that the ignition current generator, especially the induction coil 20, is not damaged. In all other respects this construction of fuze is like that considered above with regard to FIGS. 1 and 2, and therefore, the same reference characters have been generally used for the same or analagous components.

The ignition current generator depicted in FIGS. 4 and 5 will be seen to comprise a two-part sector-shaped yoke 37 and 38 which is attached or otherwise intergrated with an essentially rectangular plate 39. This yoke or yoke part 37 and 38 is surrounded by an induction coil 40, which in turn is arranged substantially coaxially with respect to the lengthwise axis of the projectile. At a second substantially rectangular plate 41 there is attached a permanent magnet 42, the shape of which corresponds to that of the yoke part or yoke 37, 38. The induction coil 40 is surrounded by a suitable plastic mass 43.

The mode of operation of this embodiment of ignition current generator does not differ from the embodiments of ignition current generators illustrated and considered above with regard to FIGS. 1 and 3.

The construction of muzzle brake shown in perspective view in FIG. 7 will be seen to comprise three ferromagnetic rings or ring members 44, 45 and 46 which are interconnected with one another by two paramagnetic sleeves or rings 47 and 48. The three ferromagnetic rings or ring members 44, 45 and 46 are further interconnected with one another by a triple-arm yoke or yoke part 49 formed of slightly magnetized material. This yoke part 49 is surrounded by two electromagnetic coils 50 and 51 polarized in opposite directions, by means of which the three ferromagnetic rings 44, 45 and 46 can be magnetized in such a manner that, for instance, the intermediate ring 45 forms a north pole and the outer rings 44 and 46 south poles. As best seen by referring to FIG. 7, bores 52 or equivalent structure are provided in the paramagnetic rings 47 and 48, and through such bores 52 there can escape the propellent gases. These bores 52 are directed such that they are effective in conventional manner as muzzle brakes.

Continuing, the projectile fuze shown in modified form in FIG. 8 merely differs from the construction of projectile fuze illustrated and discussed above in conjunction with FIG. 3 inasmuch as here there is not used any permanent magnet ring 18. This permanent magnet ring 18 is unnecessary if, as shown in FIG. 7, electromagnetic coils 50 and 51 are provided at the muzzle brake. These electromagnetic coils 50 and 51 together with the yoke part 49 and the three ferromagnetic rings 44, 45 and 46 generate a magnetic field upon passage of the projectile through the muzzle brake i.e. through the rings 44, 45 and 46. This magnetic field induces voltage pulses in the induction coil 20 (FIG. 8) which cause the capacitor 25 to charge.

The heretofore described embodiments of ignition current generators possess the following notable advantages:

The projectile does not contain any movable parts. A permanent magnet 18, preferably formed of a cobalt-samarium-alloy, is either secured to the yoke part 17 (FIGS. 1 and 3), or, electromagnets 50 and 51 are provided at the muzzle brake (FIGS. 7 and 8).

There can be produced a number of surge pulses or voltage pulses, since there can be arranged in the barrel or in the muzzle brake a number of ferromagnetic rings and a corresponding number of paramagnetic rings. As a result, the charge stored in the capacitor 25 can be increased.

These ignition current generators operate independently of the projectile spin and the firing acceleration. No inertia forces are required, rather there is utilized the relative movement between the weapon barrel and the projectile body for generating the charge.

The embodiments of ignition current generators disclosed herein are especially suitable for use with small caliber ammunition and also can be used with rockets where the firing acceleration and spin are relatively small.

The ignition current generators constructed according to the invention do not require any appreciable change in the construction of the weapon or gun, rather it is only necessary to appropriately construct the muzzle brake.

Now by turning attention to FIG. 9 there will be recognized the course of the magnetic flux .PHI. and the voltage. As soon as the yoke part 17 together with the induction coil 20 as well as the permanent magnet 18 and the soft iron disc 19 are located at the region of a paramagnetic titanium ring 34, then the magnetic flux .PHI. through the induction coil 20 is small, as indicated by point 1 in the graph shown at the top portion of FIG. 9. As soon as the yoke part 17 together with the induction coil 20 and the permanent magnet 18 and soft iron disc 19 are located at the region of a ferromagnetic steel ring 35, then the magnetic flux .PHI. through the induction coil 20 is large, as indicated by point 4 in the graph at the upper part of FIG. 9. Since the induced voltage U.sub.i is derived from the magnetic flux .PHI., this voltage U.sub.i assumes a negative value at point 4 upon decrease of the magnetic flux. The rectifier arrangement 75 of FIG. 6 ensures that the capacitor 25 also can be charged during the time that this alternating-current voltage is generated.

Finally, the projectile fuze illustrated in FIG. 10 differs from the heretofore described projectile fuze essentially by virtue of the fact that the generator will be seen to comprise in this case two induction coils 54 and 55. Between both of these induction coils 54 and 55 there is arranged a permanent magnet ring 56 which can be radially magnetized. This permanent magnet ring 56 is mounted upon a yoke or yoke part 57 which is formed by a sleeve 58 and two flanges 59 and 60.

The mode of operation of this modified version of generator is as follows:

Upon passage of the projectile through the weapon barrel 32, there is first opened the magnetic field about the first induction coil 54 by the paramagnetic rings 34 (FIG. 2) and thereafter the magnetic field about the second induction coil 55 is opened by the paramagnetic rings 34. By means of the ferromagnetic rings 35 there is firstly again closed the magnetic field about the first induction coil 54 and thereafter there is closed the magnetic field about the second induction coil 55 by the ferromagnetic rings 35.

In the event that one of these two magnetic fields is open and the other is closed, then the closed magnetic field ensures that the open magnetic field the magnetic flux .PHI. drops to null.

While there are shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto, but may be otherwise variously embodied and practiced within the scope of the following claims. Accordingly,