US3871297A

US3871297A - Percussion fuses with a tilting rotor for gyratory projectiles

Info

Publication number: US3871297A
Application number: US405301A
Authority: US
Inventors: Jean Claude Bayard; Louis Fournet; Jean Jacob; Bernard Pierre; Marcel Roux
Original assignee: Etat Francais
Current assignee: Etat Francais
Priority date: 1972-10-13
Filing date: 1973-10-11
Publication date: 1975-03-18
Anticipated expiration: 1992-03-18
Also published as: ES419494A1; IL43422A0; ZA737954B; IL43422A; FR2203500A5; DE2350915A1; CH579259A5; GB1413919A

Abstract

In the fuse body are mounted an upstream percussion element sensitive to impact and a tilting rotor arranged between said percussion element and a downstream element of the pyrotechnic chain of the fuse. In the tilting rotor a housing is formed traversing it from side to side and shielding a pyrotechnic charge intended to ensure the ignition of said downstream element. The tilting rotor is held temporarily, until the departure of the shot, by a locking device releasable by the action of the field of force generated by this departure, in an angular resting position for said housing is disaligned with respect to said upstream percussion element and to said downstream element of the pyrotechnic chain of the fuse. The tilting rotor, including the pyrotechnic charge that it carries, is arranged so as to have no imbalance. The pyrotechnic charge is entirely symmetrical with respect to the middle transverse plane of the housing. The rotor is arranged so as to have a principal axis of inertia, and the resting position of the rotor is such that its principal axis of inertia forms in resting position an angle of 90* with the axis of the fuse, said resting position being then a position of unstable equilibrium from which, on gyration of the fuse, the rotor seeks to reach its active position through an angular travel of 90*, in one direction or the other, by reason of the appearance of a restoring torque tending, in the field of centrifugal forces and as soon as the rotor is separated however little it may be from its resting position in unstable equilibrium, to merge, that is to say to align, the principal axis of inertia (XX) of the rotor and the axis of gyration (YY) of the fuse, the pyrotechnic charge housed in said rotor then being aligned with the upstream percussion element and the downstream element of the pyrotechnic chain of the fuse.

Description

United States Patent 1191 Bayard et a1.

[ Mar. 18, 1975 1 PERCUSSION FUSES WITH A TILTING ROTOR FOR GYRATORY PROJECTILES [75] Inventors: Jean Claude Bayard;L0uis Fournet; Jean Jacob, all of Bourges; Bernard Pierre, Lyon; Marcel Roux, Bourges, all of France [73] Assignee: Etat Francais, Paris, France [22] Filed: Oct. 11, 1973 [21] Appl. No.: 405,301

[301 Foreign Application Priority Data Oct. 13, 1972 France 72.36251 [52 US. Cl. 102/79 [51] int. Cl. F42c 15/26 [58] Field of Search 102/79, 80

[56] References Cited UNITED STATES PATENTS 2,155.100 4/1939 Scelzo 102/79 3,211,099 10/1965 Popovitch 102/79 3,353,489 11/1967 Berger 102/79 3.616.757 11/1971 Berger 102/79 Primary Examiner-Verlin R. Pendegrass Attorney, Agent, or Firm-Larson, Taylor and Hinds [57] ABSTRACT In the fuse body are mounted an upstream percussion element sensitive to impact and a tilting rotor arranged between said percussion element and a downstream element of the pyrotechnic chain of the fuse. In the tilting rotor a housing is formed traversing it from side to side and shielding a pyrotechnic charge intended to ensure the ignition of said downstream element. The tilting rotor is held temporarily, until the departure of the shot, by a locking device releasable by the action of the field of force generated by this departure, in an angular resting position for said housing is disaligned with respect to said upstream percussion element and to said downstream element of the pyrotechnic chain of the fuse. The tilting rotor, including the pyrotechnic charge that it carries, is arranged so as to have no imbalance. The pyrotechnic charge is entirely symmetrical with respect to the middle transverse plane of the housing. The rotor is arranged so as to have a principal axis of inertia, and the resting position of the rotor is such that its principal axis of inertia forms in resting position an angle of 90 with the axis of the fuse, said resting position being then a position of unstable equilibrium from which, on gyration of the fuse, the rotor seeks to reach its active position through an angular travel of 90, in one direction or the other, by reason of the appearance of a restoring torque tending, in the field of centrifugal forces and as soon as the rotor is separated however little it may be from its resting position in unstable equilibrium, to merge, that is to say to align, the principal axis of inertia (XX) of the rotor and the axis of gyration (YY) of the fuse, the pyrotechnic charge housed in said rotor then being aligned with the upstream percussion element and the downstream element of the pyrotechnic chain of the fuse.

10 Claims, 2 Drawing Figures PERCUSSION FUSES WITH A TILTING ROTOR FOR GYRATORY PROJECTILES The invention relates to percussion fuses with a tilting rotor, intended to equip projectiles actuated by a gyratory movement aroung their axis, especially projectiles of the small or medium calibre type (for example of a calibre comprised between and 50 mm).

It will be convenient firstly to specify that it is intended, by the expression percussion fuse with tilting rotor" to mean a fuse comprising a rotor, generally spherical, spheroidal, even if necessary cylindrical, arranged between an upstream percussion element (percussion member associated or not with the first primer) and an element downstream of the pyrotechnic chain of the fuse and comprising a housing traversing this rotor from side to side and containing a pyrotechnic charge (first primer or secondary relay) intended to ensure the ignition of said downstream element on intervention of the abovesaid percussion member, the abovesaid rotor being mounted in the body of the fuse so as to be able to pass by tilting from a rest position, for which the abovesaid housing is disaligned with respect to the upstream percussion element and to the downstream element of the pyrotechnic chain of the fuse (thus rendering impossible ignition of this downstream element in case of accidental intervention of the percussion member or accidental explosion of a first primer), to an active position for which the upstream percussion element, the housing contained in the pyrotechnic charge and the downstream element of the pyrotechnic chain of the fuse are aligned, thus enabling the firing of said downstream element, by means of the abovesaid pyrotechnic charge, in the case of intervention of the upstream percussion element.

In a fuse of this type, the tilting of the rotor on departure of the shot (tilting ensuring its passage from its rest position to its active position) is generally caused by the field of centrifugal forces generated by the gyration of the projectile around its axis and, of course, for safety reasons, before the departure of the shot (safety of storage, of handling and of supply) the rotor is held temporarily in resting position by a locking device arranged so as to be rendered inoperative by the forces brought into play on departure of the shot (generally by the abovesaid field of centrifugal forces).

It is known that the present tendency, in the matter of percussion fuses in general and of percussion fuses with a tilting rotor in particular, is to seek to increase the safety at the beginning of the trajectory, that is to say to increase the distance separating the emergence from the mouth of the barrel from the point of the projectory of the projectile from which the fuse becomes armed", that is to say capable of operating by percussion in case of impact.

It is understood that, in the case of percussion fuses with a rotor tilting under the effect of a field of centrifugal forces, the safety of the beginning of the trajectory varies in the same sense as the duration of total travel of tilting causing the rotor to pass from its rest position to its active position, this duration of travel being itself, all things being otherwise equal,

an increasing function of the angular amplitude of the total course of tilting, a longer course involving a more considerable duration of travel,

and a decreasing function of the intensity of the initial torque of tilting urging the rotor (assumed in rest position) towards its active position, an initial weaker tilting torque impressing less angular acceleration on the rotor.

It is seen, according to these theoretical considerations, that there would be advantage, in increasing the barrel mouth safety of such a fuse with a tilting rotor, to amplify the tilting course of its rotor and to reduce the magnitude of the initial tilting torque urging said rotor (assumed in rest position) towards its active position.

Now, specialists have not, hitherto, used these theoretical teachings, and for practical reasons it appears opportune to specify this here to establish better the originality and advantage of the invention.

In fact, in prior fuses with a tilting rotor, the rotor had a dissymetry with respect to the middle plane perpendicular to the axis of the housing containing the pyrotechnic charge, such a dissymmetry being manifested by the presence of an imbalance which, under the effect of the field of centrifugal forces, reached a stable position of equlibrium, that is to say a position for which it was separated to the maximum from the axis of the fuse.

Given the dissymmetric character of the tilting rotor of such fuses (here including its pyrotechnic charge), it was excluded that the rotor should be able to tilt in one direction or the other to enable its imbalance to occupy one or other of two possible stable equilibrium positions (diametrically opposite positions).

One is therefore necessarily obliged to adopt, for such a dissymmetric rotor, a rest position for which its imbalance was substantially separated from the axis of the fuse, which well defined the direction of tilting of the rotorbut which on the other hand only enabled an overall .tilting course less than the housing of the pyrotechnic charge then having, for the rest position of the rotor, an inclination with respect to the axis of the fuse.

When the rotor of such a fuse was in rest position, this rotor was urged, once the fuse was actuated with its gyratory movement, by a return force of appreciable value due to the fact that its imbalance was separated from the axis of the fuse, this state of affairs appearing also advantageous to the specialists, who desired that the return force exerted on the rotor should be capable of ensuring its starting and of overcoming resistance due to friction.

Thus, according to this prior art, on one hand, the total course of tilting of the rotor was far from having the maximum possible amplitude (90), and, on the other hand, the initial tilting torque was voluntarily adjusted to an appreciable value.

In other words, for constructional reasons, specialists were led towards solutions not enabling the obtaining of increased safety at the beginning of the trajectory given that they had been led to adopt a reduced tilting course and a considerable initial return torque.

Moreover, the existence of this considerable return torque risked, to a certain extent, the generation of frictional stresses disturbing the operation (on unlocking) of the locking system of the tilting rotor.

It is a particular object of the invention to overcome these drawbacks of the tilting rotor percussion fuses known hitherto, that is to say to provide a fuse of this type having increased safety at the beginning of its trajectory and comprising a locking system for its rotor whose operation is not disturbed, on unlocking, by return forces exerted on the above said rotor.

The percussion fuse according to the invention, for a gyratory projectile, comprises a fuse body in which are mounted an upstream percussion element (generally a percussion member is necessary associated with a first primer) sensitive to impact and a tilting rotor arranged between said percussion element and a downstream element of the pyrotechnic chain of the fuse, in which tilting rotor is formed a housing passing through it from side to side and shielding a pyrotechnic charge intended to ensure the ignition of said downstream element, the abovesaid tilting rotor being held temporarily, until the start of the shot, by a locking device releasable by the action of the fields of forces generated by this departure, in an angular lifting position over which the abovesaid housing is disaligned with respect to the abovesaid upstream percussion element and to the abovesaid downstream element of the pyrotechnic chain of the fuse, said fuse being characterized in that,

on one hand, its tilting rotor (here including the pyrotechnic charge which it bears) is arranged so as to have no imbalance,

on the other hand, the pyrotechnic charge housed in its rotor is entirely symmetrical with respect to the middle transverse plane of the housing shielding said charge.

on the other hand again, said rotary is arranged in addition to have a principal axis of inertia,

and, on the other hand lastly, the resting position of the abovesaid rotor is such that its principal inertia axis forms in this resting position an angle of 90 with the axis of the fuse, the abovesaid resting position then being an unstable equilibrium position from which, on gyration of the fuse, the rotor seeks to reach its active position through an angular travel of 90, in one direction or the other, by reason of the appearance of a return torque tending, in the centrifugal field of forces and as soon as the rotor has separated however little it may be from its resting position in unstable equilibrium, to merge, that is to say to align, the principal axis of inertia of the rotor and the axis of gyration of the fuse, the pyrotechnic charge housed in said rotor then being aligned with the percussion element upstream and the element downstream of the pyrotechnic chain of the fuse.

It should be noted that the disturbances undergone by the projectile in the barrel of the firearm and at its mouth (precession and nutation) are largely sufficient, taking into account the constructional tolerances, to separate the rotor slightly from its unstable equilibrium position as soon as the locking device has become inoperative, which then enables the appearance of the return torque previously mentioned.

Besides, being given the longitudinal symmetry of the pyrotechnic charge contained in the rotor, the direction of tilt of the latter is of little importance given that, whatever is the direction the abovesaid rotor will present itself in exactly the same manner, with respect to the upstream percussion element and the downstream pyrotechnic element, once it will have reached its active position through an angular travel of 90 in one direction or the other.

Such a percussion fuse, with a tilting rotor without imbalance keyed in resting position at 90 possesses, with respect to a conventional fuse ofthe same type but with an imbalanced tilting rotor keyed in resting position at about 45 with respect to the axis of the fuse, increased safety at the beginning of trajectory due to the fact,

on one hand, that the total travel of tilting of the rotor has a much greater amplitude (of the order of double),

and on the other hand, that the return torque ensuring the starting of the rotor as soon as the latter is slightly separated from its unstable resting position then has a very low value, the torque concerned starting from the value zero for the precise position of unstable equilibrium, then passing through a maximum and falling again finally to the value zero once the rotor arrives in active position.

Although it is possible to envisage attributing to the tilting rotor a cylindrical shape and then mounting it pivotally around an axis perpendicular to the axis of giration of the fuse, it is indead preferable to adopt, for this rotor, a spherical or spheroidal shape and to mount it then in a bearing of corresponding shape so that it possesses, once released, full liberty of movement, that is to say, in all azimuths.

ln fact, such a freedom is manifested, for the rotor, on its passage from its safety position to its armed position, by the possibility of progressive starting and longer routeing obtaining a corresponding gain in safety at the beginning of trajectory.

The gain realized in safety at the beginning of the trajectory due to the invention is very appreciable and can lead, all other things being equal, to a safety distance of the beginning of the trajectory multiplied by a high factor, which enables the envisaging of safety of the start of the trajectory comprised between 10 and 20 meters and even more, such safety values at the beginning of the trajectory, at present sought in military programs, not having been achievable with a conventional percussion fuse with an imbalanced rotor keyed at 45 and without a special time delay device.

Now it is interesting to note that the advance contributed by the invention results from an original concept of the construction and of the angular keying of the rotor of the fuse, the latter remaining particularly simple and inexpensive.

It is also appropriate to indicate that a rotor arranged and keyed angularly according to the invention could be perfectly well incorporated in percussion fuses with a conventional tilting rotor instead and in place of the rotor itself of these fuses whose safety at the beginning of the trajectory would be strongly enhanced due to the fact of this substitution.

It would be appropriate in addtion to indicate, as a benefit of the invention, that the low value of the tilting torque exerting on the rotor in rest position avoids any hesitation and any disturbance in the releasing operation of the locking device holding the abovesaid rotor in resting position.

It has been seen that the invention implies, for the rotor, the existance ofa principal axis of inertia, the existence of such being obtained very simply by constituting the housing of the pyrotechnic charge by diametric bore and by adopting a pyrotechnic charge of less density than that of the constituent material of the rotor, the principal axis of inertia of said rotor then being merged with the axis of the bore.

As to the absence of any imbalance in the rotor, it does not necessarily imply complete symmetry of shape of said rotor (a dissymmetry of shape can be compensated by a balancing weight), but it seems however simpler to adopt a rotor which is entirely symmetrical, including here its pyrotechnic charge, with respect to the middle transverse plane of the housing containing said pyrotechnic charge.

To this end and as already indicated, there is preferably adopted, for the rotor, a spherical shape (with or without a flat), said rotor then being guided by bearings in the shape of spherical domes.

As for the pyrotechnic charge housed in the rotor, which charge must by symmetrical with respect to the middle transverse plane of its housing in order that its behavior may be identical in active position for the two directions of the possible tilting of the rotor, it could be constituted, either by a single element, or by two elements separated one another and arranged symmetrically with respect to the abovesaid middle plane.

Lastly, it should be pointed out that it is possible advantageously, if it is desired to further increase the safety at the beginning of the trajectory of the fuse, in order to achieve values of the order of 40 to 50 meters and even more, to associate with the locking device of its rotor a complementary time-delay system, for example of a type (known in itself) with the unwinding ofa spiral ribbon in the field of centrifugal forces, the delay introduced by this time-delay system preceding the delay constituted by the duration of the travel of the tilting rotor by 90 and adding to this duration of travel.

To illustrate in more accurate manner the various features of the invention, there will now be described below two preferred embodiments, but which are in no way to be regarded as limiting, with reference to the accompany ing drawing, in which:

FIG. I shows, in elevation the partial axial section, a percussion fuse constructed according to a first embodiment of the invention, said fuse being mounted with its rotor in resting position,

FIG. 2 shows, under the same conditions as FIG. 1, another embodiment of a fuse of the same type according to the invention.

The fuse illustrated in FIG. I, intended for a gyratory projectile, comprises a fuse body I equipped rearwardly with a detonator 2 and comprising a threading la for its adaptation to the nose of the projectile.

Inside the rocket body 1 is arranged a spherical tilting rotor 3 free of any imbalance and comprising a diametric housing or passageway 4 in which are housed two elemental pyrotechnic charges 5a and 5b separated from one another and arranged symmetrically with respect to the middle transverse plane of the housing 4.

The rotor 3 is held and guided by spherical bearings 6 ensuring its positioning between the detonator 2 and the firing pin 7.

Such a tilting rotor has a principal axis of inertia XX merged with the axis of the housing 4.

A releasable locking device holds the rotor 3 in resting position with its principal axis of inertia XX oriented perpendicularly to the axis of gyration YY of the fuse. the abovesaid locking device being constituted by inclined pins 8 engaged in facing housings formed respectively in the rotor 3 and in the guide bearings 6 of this rotor, the abovesaid pins, which retract under the effect of the centrifugal force into housings 8a provided for this purpose. being temporarily held in active position by a ring 9 radially expandable under the effect of the field of centrifugal forces.

The operation of such a fuse is as follows.

' On the departure of the shot, the ring 9 separates radially, freeing the pins 8 which then -retract into the housings 8a, thus releasing the rotor 3; the latter immediately leaves its unstable equilibrium position under the effect of the disturbances to which the projectile is subjected, and it enters gradually into rotation whilst tilting by to gain, for a helicoidal track, a stable equilibrium position for which its principal axis of inertia XX is merged with the axis YY of the fuse.

Such a fuse has a safety at the beginning of the trajectory which is notable by reason of the relatively long helicoidal path (in one direction or the other) which its rotor must effect and the little importance of the return torque acting initially on said rotor.

Moreover, due to the fact of the weakness of this initial return torque, the withdrawal of the pins 8 operates without frictional or wedging stresses and the unlocking of the rotor does not risk giving rise to an accident, the rotor indeed gaining with a certain time delay the stable active position for which the elemental pyrotechnic charges 5a and 5b are aligned with the firing pin 7 and the detonator 2.

From this moment, the fuse is armed and, in the case of impact, the firing pin 7 ensures the firing of that of the two elemental charges 5a or 512 which occurs facing said firing pin (in the direction of tilting of the rotor 3) and plays then the role of primer, the other elemental charge playing the role of a relay with respect to the detonator 2.

There is shown, in FIG. 2, another embodiment of a percussion fuse with a tilting rotor according to the invention, the same reference numbers and letters denoting, in this FIG. 2, the same members or elements as in FIG. 1.

The fuse illustrated in FIG. 2 differs from that illustrated in FIG. 1,

on one hand, by the constitution of the pyrotechnic charge of this rotor, which pyrotechnic charge is constituted by a single element 5 extending symmetrically on both sides of the middle transverse plane of its housing,

and, on the other hand, by the constitution of the locking device of the rotor 3, which device is constituted by a radially expandable split ring 10, supported on a shoulder 10a arranged in the wall of the rotor, said ring being held temporarily in closed position by a spiral band 11, itself held wound by a radially expandable split ring 12 under the effect of the field of centrifugal forces.

On the departure of the shot, the ring 12 frees the spiral band ll, which unrolls with a certain time delay (which delay constitutes a safety at the beginning of the supplementary trajectory), after which the ring 10 opens radially thereby freeing the rotor 3, which then gains its active position by the same process as in the case of the fuse illustrated in FIG. 1.

We claim:

1. A gyratory percussion fuse comprising:

a fuse body having a longitudinal axis of gyration and adapted for movement along that said axis, and including an upstream percussion element sensitive to impact, a downstream element of the pyrotechnic chain of the fuse, and a tilting rotor arranged, longitudinally, between said percussion element and said downstream element,

said tilting rotor having a passageway extending therethrough from side to side, and a pyrotechnic charge in said passageway, said tilting rotor being entirely symmetrical with respect to a middle transverse plane through the center of said passageway, said rotor further having an axis of inertia, and the weight of said rotor including the pyrotechnic charge being equally balanced,

holding means including a locking device releasable in response to forces generated by a shot for bolding the tilting rotor in a rest position with respect to the fuse body prior to a shot, at which rest position said passageway is out of alignment with said percussion element and said downstream element so that the rotor blocks inadvertent movement of the percussion element toward the downstream element, and wherein at said rest position the said axis of inertia of the tilting rotor is at an angle of 90 to the said longitudinal axis of gyration of the fuse body, and said fuse body including means for mounting the tilting rotor so as to permit the tilting rotor to move in either direction from said rest position through a 90 angle to align the passageway with the percussion element and downstream ele ment and hence align the axis of inertia with the longitudinal axis of the fuse body to arm the fuse in response the action of a restoring force operating on the tilting rotor as the rotor is released by said holding means.

2. Percussion fuse according to claim 1, wherein the tilting rotor of said fuse has a spherical or spheroidal shape and comprises a diametric passageway receiving a pyrotechnic charge of a density less than that of the constituent material of the rotor, the principal axis of inertia of said rotor being merged with the axis of said diametric housing.

3. Percussion fuse according to claim 1, wherein said tilting rotor. including its pyrotechnic charge is entirely symmetrical with respect to the said middle transverse plane of the passageway containing said pyrotechnic charge.

4. Percussion fuse according to claim 3, wherein the pyrotechnic charge of its tilting rotor is constituted of two identical elemental charges, separated from one another and arranged symmetrically with respect to the middle transverse plane of the housing of said charge.

5. Percussion fuse according to claim 3, wherein the pyrotechnic charge of its tilting rotor is constituted by a single element comprising a plane of symmetry coinciding with the plane of symmetry of the housing containing this element.

6. Percussion fuse according to claim 1, wherein the locking device of its tilting rotor is equipped with a time delay system retarding the release of this locking device and thus conferring an additional barrel safety to the fuse.

7. Percussion fuse according to claim 2, wherein said tilting rotor, including its pyrotechnic charge is entirely symmetrical with respect to the middle transverse plane of the passageway containing said pyrotechnic charge.

8. Percussion fuse according to claim 2, wherein the locking device of its tilting rotor is equipped with a time delay system retarding the release of this locking device and thus conferring an additional barrel safety to the fuse.

9. Percussion fuse according to claim 3, wherein the locking device of its tilting rotor is equipped with a time delay system retarding the release of this locking device and thus conferring an additional barrel safety to the fuse.

l0. Percussion fuse according to claim 4, wherein the locking device of its tilting rotor is equipped with a time delay system retarding the release of this locking device and thus conferring an additional barrel safety to the fuse.

Claims

1. A gyratory percussion fuse comprising: a fuse body having a longitudinal axis of gyration and adapted for movement along that said axis, and including an upstream percussion element sensitive to impact, a downstream element of the pyrotechnic chain of the fuse, and a tilting rotor arranged, longitudinally, between said percussion element and said downstream element, said tilting rotor having a passageway extending therethrough from side to side, and a pyrotechnic charge in said passageway, said tilting rotor being entirely symmetrical with respect to a middle transverse plane through the center of said passageway, said rotor further having an axis of inertia, and the weight of said rotor including the pyrotechnic charge being equally balanced, holding means including a locking device releasable in response to forces generated by a shot for holding the tilting rotor in a rest position with respect to the fuse body prior to a shot, at which rest position said passageway is out of alignment with said percussion element and said downstream element so that the rotor blocks inadvertent movement of the percussion element toward the downstream element, and wherein at said rest position the said axis of inertia of the tilting rotor is at an angle of 90* to the said longituDinal axis of gyration of the fuse body, and said fuse body including means for mounting the tilting rotor so as to permit the tilting rotor to move in either direction from said rest position through a 90* angle to align the passageway with the percussion element and downstream element and hence align the axis of inertia with the longitudinal axis of the fuse body to arm the fuse in response the action of a restoring force operating on the tilting rotor as the rotor is released by said holding means.

3. Percussion fuse according to claim 1, wherein said tilting rotor, including its pyrotechnic charge is entirely symmetrical with respect to the said middle transverse plane of the passageway containing said pyrotechnic charge.

10. Percussion fuse according to claim 4, wherein the locking device of its tilting rotor is equipped with a time delay system retarding the release of this locking device and thus conferring an additional barrel safety to the fuse.