EP2435781B1

EP2435781B1 - Mortar projectile fuse

Info

Publication number: EP2435781B1
Application number: EP09787742.7A
Authority: EP
Inventors: Antonio Gatti
Original assignee: Simmel Difesa SpA
Current assignee: KNDS Ammo Italy SpA
Priority date: 2009-05-28
Filing date: 2009-05-28
Publication date: 2015-12-16
Anticipated expiration: 2029-05-28
Also published as: EP2435781A1; KR20140073596A; WO2010137045A1; KR101560434B1

Description

The present invention relates to fuses for projectiles, and particularly to mechanical fuses suitable to be mounted on mortar projectiles, and controlled by time mechanisms.
More specifically, the invention focuses on the safety systems which are an integral part of said fuses, and perform the very important function of avoiding explosions under conditions other than the desired ones, particularly protecting the safety of whoever operates directly or indirectly on such fuses, on the projectiles on which they are mounted, or on the mortars which launch them.
Given the definition of mechanical time fuse; it has to include timer means, for example, a time-control mechanism (timer), capable of carrying out a chronometric activity of measuring time, the function of which is to activate the fuse at a given activation instant, i.e., after a pre-settable and preset time interval (the fuse "operation time"), starting at a given instant in which the timer begins to operate. The timer itself can be considered, under some aspects, a safety system, in the sense that it prevents the activation of the fuse, and the consequent explosion of the projectile, until the activation instant mentioned above. However, timer means having such a functionality as the one outlined above cannot be considered as totally independent safety means, since they need further safety means suitable to start the chronometric activity of the timer means not before a proper instant (thus starting, in other words, a "countdown"). The presence of mere timer means does not provide a complete solution to the problem of the fuse safety, but it diverts the said problem on the further means that are necessary to inhibit the functioning of the timer means.
Solutions to the above-mentioned problem are known to those of ordinary skill in the art. For example, means can be provided to block the timer when the fuse is "under rest conditions" (i.e., before assembling the fuse on the projectile, before inserting the projectile in the mortar). Such safety means "under rest conditions" can be, for example, outer "pullwire pins", connected to internal lock mechanisms to the fuse, which are "immobilized" until the pullwire pin is torn off by an operator, for example, immediately before the projectile is inserted within the mortar.
The mechanisms which allow setting, by graduation, the fuse operation time only under particular conditions (for example, after removing a fuse "protection cap") also belong to the category of the safety systems "under rest conditions".
In addition to such safety means "under rest conditions", "inertial" safety means are known, i.e., such as to remain active also after the mentioned safety means "under rest conditions" have been disabled, until the projectile reaches a given acceleration value, which typically occurs during the launching phase, and desirably shortly before the exit of the projectile from the mortar barrel. Such inertial safety means can be, for instance, latches (comprising for example set-back pins) associated to a sleeve which is movable, counteracting the force of a spring, only in the presence of a predefined acceleration. In the safety position, such latches lock an oscillating system of the timer, implementing the chronometric activity of the timer itself. In this manner, they prevent the "countdown" from starting, until the movement of the sleeve which they are associated to, caused by the acceleration, causes the displacement of the same latches and the unlocking of the timer, which begins to operate, and will determine the fuse activation with a predetermined delay
An example of such solution can be found in U.S. patent No. 3,286,634 .
It shall be noted that, in such type of solutions, there is a cooperation between inertial safety means and timer means; and, furthermore, there is an action "in sequence" of safety means "under rest conditions", "inertial" safety means, and timer means.
Solutions of the type outlined above are widely used, but in turn do not fully overcome the safety problems. In fact, the action "in sequence" of the several safety means can be caused by an individual initial accidental event. Let us figure a fuse from which the remaining safety pullwire pin has been removed, because the fuse is being inserted in a mortar; let us suppose that such fuse accidentally falls from a given height, such as to cause an acceleration comparable to the threshold one for the inertial safety means. In such a case, the timer begins to operate, and there are no more lines of defense before the explosion, except for the delay which is determined by the timer (which is generally of only a few seconds or a few tens of seconds).
A more efficient safety strategy consists in imposing a further safety mechanism relating to the so-called "fire chain misalignment" (i.e., "pyric axis misalignment"). This means that, under rest conditions, and until predefined conditions occur, the detonator (the task of which is to cause the explosion of the projectile charge by means of the detonation thereof, and which is embedded, for example, in a movable housing), is misaligned relative to percussion means (for example, with respect to the axis of a percussion shaft), controlled by the timer, intended to activate the fuse. The detonator is further misaligned with respect to the projectile charge, the explosion of which follows the detonation of the detonator, so that even an accidental detonation of the detonator cannot cause the explosion of the projectile.
Only in the presence of predefined conditions, the detonator housing moves, brings the detonator exactly under the percussion shaft, along a same axis, thereby creating the basis on which the activation can take place.
The misaligning of the pyric axis is a "strong" safety measure, due to the mentioned reasons.
Such method is, in turn, known, and it can be well illustrated by reading the U.S. patent 3,286,634 mentioned herein.
However, it shall be noted that even with this solution, considerable drawbacks remain about the safety level that can be obtained. In fact, the problem is once again diverted on the means suitable to control and start the aligning process of the pyric axis, and the processes related thereto.
In U.S. patent 3,286,634 , the detonator is housed within a cylinder that is hold by (and contained in) a rotor, the rotation of which is prevented by a rotor locking shaft, under safety conditions. The locking shaft is displaced after a given preset period of time by the action of the above-mentioned timer (e.g., after 1 sec from the countdown start). The locking shaft displacement disengages the rotor, which rotates, thus aligning the pyric axis, before the same timer determines the detonation which causes the explosion.
The problem, which makes the safety level insufficient, will be appreciated from the following considerations.
In this solution, the timer has a dual function, which it performs "in parallel", which produces two different "effects" occurring "in sequence": the control of the mechanism (locking shaft) which locks the rotor, and the control of the movement of the percussion shaft, which causes the detonation.
However, this means that, once the timer has started, both effects will certainly occur. Therefore, in some scenarios, among which the accidental scenario such as the one described before (a fall of the projectile before it is inserted in the mortar, capable of starting the timer), the explosion occurs all the same, and the measure shown in US 3,286,634 does not determine any improvement as regards safety.
More generally, the timer is a "single point of failure", i.e., a system which, in case of malfunctioning, nullifies the whole chain of safety devices.
The U.S. patent 2,449,170 (J.B. MacLean et al. ), which forms a basis for the preamble of claim 1, relates to bomb fuses, and particularly to fuses for aerial drop bombs, arranged to detonate at a predetermined time interval after having been dropped, and provided with a safety system.
The U.S. patent US 2,498,043 (Lauritsen ) relates to fuses, and particularly to a propeller-armed, impact-fired fuse which is reliable in operation.
It is the object of the present invention to devise and provide an improved synergic assembly of safety means for a fuse, particularly for a mechanical time fuse, capable of obviating the above-described drawbacks with reference to the prior art.
Such object is achieved by a fuse provided with a safety means assembly, formed in accordance with claim 1.
Such a fuse for projectile comprises detonation means, capable of assuming a detonation means safety condition and a detonation means armed condition; actuating means, suitable to detonate said detonation means, and capable of assuming an actuating means safety condition, an actuating means armed condition, and an actuating means active condition in which the actuating means detonate the detonation means; a timer, suitable to actuate the actuating means.
The fuse also comprises speed sensor means independent from said timer, operating on the basis of parameters depending on the projectile speed; said speed sensor means are safety means suitable to control the transition of the actuating means from the safety condition thereof to the armed condition thereof.
In the fuse, said speed sensor means are further configured to control the transition of the detonation means from the safety condition thereof to the armed condition thereof; and said timer is allowed to cause the transition of said actuating means from the armed condition thereof, to the active condition thereof, only if the detonation means have assumed the armed condition thereof, after being enabled by said speed sensor means.
A fuse with a safety means assembly such as those included in the present invention allows a remarkable improvement of the safety level of the fuse itself, while maintaining constructive simplicity conditions.
Said speed sensor means are suitable to control the transition of both the detonation means and the actuating means, from the respective safety condition to the respective armed condition.
According to an illustrative example, said timer is suitable to control the transition of the detonation means from the detonation means safety condition to the detonation means armed condition.
According to an illustrative example, said timer is suitable to control the transition of the actuating means from the actuating means safety condition to the actuating means armed condition.
In accordance with an illustrative example, the fuse further comprises first inertial safety means, suitable to inhibit the transition of the actuating means from safety condition thereof to the armed condition thereof, until said first inertial means detect a first predefined acceleration value; and to allow the transition of the actuating means from the safety condition thereof to the armed condition thereof, when said first predefined acceleration value is detected.
In accordance with an illustrative example, the fuse further comprises second inertial safety means, suitable to inhibit the transition of the detonation means from the safety condition thereof to the armed condition thereof, until said second inertial means detect a second predefined acceleration value; and to allow the transition of the detonation means from the safety condition thereof to the armed condition thereof, when said second predefined acceleration value is detected.
In accordance with an illustrative example, said first and second inertial safety means coincide.
According to an illustrative example, the timer is capable of carrying out a chronometric activity of measuring time, and of controlling said transition of the actuating means from the armed condition to the active condition at an activation instant t1, delayed by a preset amount of time relative to a start instant t0 of said chronometric activity.
In accordance with an illustrative example, the fuse further comprises third inertial safety means, suitable to inhibit said chronometric activity of the timer until said third inertial means detect a third predefined acceleration value; and to allow the start of said chronometric activity of the timer at an instant t0 in which said third predefined acceleration value is detected.
In accordance with an illustrative example, said third and second inertial safety means coincide.
According to an illustrative example of said actuating means, they comprise: percussion means, suitable to hit the detonator, through a movement thereof, in order to detonate it; and a locking/unlocking mechanism of said percussion means, capable of assuming a locking position and an unlocking position.
According to an illustrative example, said percussion means are capable of assuming a percussion means safety condition and a percussion means armed condition. In other words, the percussion means have a safety condition thereof and an armed condition thereof; and this concurs to determine the conditions of the fuse actuating means as follows:

the actuating means are in the actuating means safety condition if the percussion means are in the safety condition thereof and the locking/unlocking mechanism is in the locking position thereof;
the actuating means are in the actuating means armed condition if the percussion means are in the armed condition thereof and the locking/unlocking mechanism is in the locking position thereof;
the actuating means are in the actuating means active condition if, being the percussion means in the armed condition thereof, and being the locking/unlocking mechanism in the unlocking position thereof, the movement of the percussion means which is suitable to hit the detonator takes place.

According to an illustrative example, said percussion means comprise a percussion shaft and a striking mass.
In accordance with an illustrative example, the movement of the percussion means comprises a movement of the striking mass and a movement of the percussion shaft, being the movement of the percussion shaft capable of hitting the detonator.
According to an illustrative example, said locking/unlocking mechanism, in the locking position, is suitable to inhibit said movement of the striking mass, while, when it is in the unlocking position, it is suitable to allow said movement of the striking mass.
According to an illustrative example, the percussion shaft is capable to assume a percussion shaft safety position and a percussion shaft armed position. In other words, the percussion shaft has a safety position thereof and an armed position thereof; such that the percussion means safety condition occurs if the percussion shaft is in the safety position thereof; and the percussion means armed condition occurs if the percussion shaft is in the armed position thereof.
In accordance with an illustrative example, the transition from said safety position to said armed position of the percussion shaft corresponds to an axial movement of the percussion shaft.
In accordance with an illustrative example, the percussion means further comprise a preloaded spring, suitable to provide the necessary kinetic energy to the striking mass to perform said movement of the striking mass, if it is not otherwise locked.
According to an illustrative example of the locking/unlocking mechanism, it comprises a leverage system.
According to an illustrative example, the timer determines the transition of the actuating means from the armed condition thereof to the active condition thereof by acting on the locking/unlocking mechanism, so as to cause the transition from the locking position thereof to the unlocking position thereof.
In accordance with an illustrative example of said detonation means, the detonation means comprise a detonator, suitable to detonate, and a movable housing of the detonator.
According to an illustrative example, the movable housing is capable to determine a detonator safety position and a detonator armed position. In other words, said movable housing has a safety position of the detonator, in which the detonator cannot be activated by the actuating means; and an armed position of the detonator, in which the detonator can be activated by the actuating means.
According to an illustrative example, the detonation means safety condition occurs if said movable housing is in the safety position of the detonator; and the detonation means armed condition occurs if the movable housing is in the armed position of the detonator.
In accordance with an illustrative example, the safety position of the detonator is ensured by a misaligning of the detonator relative to the percussion shaft axis; and the armed position of the detonator is determined by the alignment of the detonator with respect to the percussion shaft axis.
According to an illustrative example of the movable housing of the detonator, the latter is composed of a rotor, capable of rotating around an axis thereof parallel to the percussion shaft axis, and it is suitable, as a consequence of the rotation thereof, to angularly displace the detonator from an axially misaligned position to an axially aligned position with respect to the percussion shaft axis.
According to a an illustrative example of the fuse according to the present invention, the actuating means are capable of exerting a mechanical action on the detonation means, so that the actuating means safety condition implies the detonation means safety condition; and the transition of the actuating means towards the actuating means armed condition implies the transition of the detonation means towards the detonation means armed.
In accordance with an illustrative example, the percussion shaft, in its safety position, exerts, through a second end thereof, a mechanical constraint on the detonator movable housing, so as to prevent the movement of said housing from the detonator safety position to the detonator armed position; and the percussion shaft, in the armed position of the percussion shaft, ceases to exert, through a second end thereof, said mechanical constraint on the detonator movable housing, so as to allow the movement of said housing from the detonator safety position to the detonator armed position.
According to an illustrative example, said mechanical constraint of the percussion shaft on the detonator movable housing results from the fact that said percussion shaft second end, in the safety position, is inserted in a hole which is drilled in said detonator movable housing; and the releasing of said mechanical constraint results from the fact that said percussion shaft second end, in the armed position, exits said hole drilled in the detonator movable housing.
According to an embodiment of the fuse, defined in the dependent claim 2, the speed sensor means comprise a turbine system. The turbine system comprises an impeller capable of rotating under the action of a predetermined air flow level relative to the projectile, related to a predetermined projectile speed value in air; and also comprises inertial locking/unlocking means of the turbine system, capable of preventing the rotation of the impeller until they detect a predefined value of acceleration for unlocking the rotation of the impeller.
According to such embodiment, the rotation of the impeller remains inhibited even after the action of said inertial locking/unlocking means of the turbine system has ceased, until the projectile reaches a predefined speed.
According to an illustrative example of said mechanical coupling means, they comprise:

a turbine shaft, connected to the impeller, capable of performing, as a consequence of the movement of the impeller, a movement of the turbine shaft, being said movement of the turbine shaft suitable to bring said turbine shaft from an engaging position of the turbine shaft, in which said shaft keeps at least one of said actuating means and detonation means in the safety condition, to a disengaging position, in which said shaft allows the transition of at least one of said actuating means and detonation means to the respective armed condition.

In accordance with an illustrative example, the turbine system further comprises a support of the turbine system, characterized by an internal thread; and the turbine shaft has a first end connected and integral to the impeller, a threaded stem suitable to be screwed to said thread of said support, and a second end.
In accordance with an illustrative example, the engaging position of the turbine shaft comprises the fact that said second end of the turbine shaft is connected to a first end of the percussion shaft of said percussion means of said actuating means, constraining it in its safety position. Further, said movement of the turbine shaft is an axial displacement movement, deriving from the unscrewing in the longitudinal direction of said turbine shaft along the turbine system support, being said unscrewing capable of converting into an axial movement the rotary movement imparted by the impeller to the turbine shaft. Furthermore, the turbine shaft disengaging position comprises the fact that the turbine shaft second end has moved away, due to said movement of the turbine shaft, from said percussion shaft first end, allowing the movement of the percussion shaft towards its armed position.
According to an alternative illustrative example, the turbine shaft engaging position comprises the fact that said turbine shaft second end exerts a mechanical constraint on the detonator movable housing, so as to prevent the movement of said housing from the detonator safety position to the detonator armed position. Furthermore, said turbine shaft movement is an axial displacement movement, deriving from unscrewing in the longitudinal direction the turbine shaft along the turbine system support, being said unscrewing capable of converting into an axial movement the rotary movement imparted by the impeller to the turbine shaft. Furthermore, the turbine shaft disengaging position comprises the fact that the turbine shaft second end, due to said movement of the turbine shaft, ceases to exert said mechanical constraint on the detonator movable housing, so as to allow the movement of said housing from the detonator safety position to the detonator armed position.
In accordance with another illustrative example, the mechanical constraint of the turbine shaft on the detonator movable housing results from the fact that said turbine shaft second end, in the engaging position, is inserted in a hole which is drilled in the detonator movable housing; and the releasing of said mechanical constraint results from the fact that the percussion shaft second end, in the disengaging position, exits said hole drilled in the detonator movable housing.
According to an illustrative example, the turbine shaft disengaging position comprises the fact that it allows both the percussion shaft movement towards the armed position thereof, and the movable housing movement from the detonator safety position to the detonator armed position.
According to an illustrative example, said turbine system further comprises an air conveyor, comprising respective air inlet and outlet openings, suitable to convey the air flow on the impeller.
In accordance with an illustrative example, said turbine system further comprises inertial locking/unlocking means of the turbine system, capable of preventing the rotation of the impeller until they detect a predefined value acceleration for unlocking the rotation of the impeller.
According to a particular an illustrative example of the inertial locking/unlocking means of the turbine system, they comprise: a turbine locking disk, arranged under the impeller, fitted to the turbine system support, having a saw tooth structure capable of preventing the rotation of the impeller; and a turbine locking/unlocking spring, capable of forcing said turbine locking disk against the impeller, until a predefined value acceleration for unlocking the rotation of the impeller is detected; such that said turbine locking disk is suitable to move, overcoming the force exerted by said turbine locking/unlocking spring, so as to move its saw tooth structure away from the impeller and to unlock the impeller.
According to an illustrative example, the rotation of the impeller remains inhibited even after the action of said inertial locking/unlocking means of the turbine system has ceased, until the projectile reaches a predefined speed.
According to an illustrative example, said inhibition of the rotation of the impeller depends on the friction between the turbine shaft thread and the turbine system support thread.
In accordance with an illustrative example of the fuse, it further comprises

a cap, suitable to protect the fuse under rest conditions;
a fuse body;
a fuse ogive, rotatable with respect to said fuse body;
a graduated scale (30) reported on the fuse body outer part, suitable to indicate a fuse safety position (S), i.e., a number corresponding to a graduation time.

According to an illustrative example, said cap comprises:

projections suitable to facilitate a grip and a manual rotation of the same cap;
two arms, capable of being inserted within corresponding recesses of said fuse body;
a protrusion inwardly projecting to the cap upper part;
a pin projecting within the cap so as to engage a corresponding notch which is provided on the surface of said fuse ogive, so that a rotation of the cap around a longitudinal axis thereof causes a corresponding rotation of the ogive relative to the fuse body.

In accordance with an illustrative example, said cap is suitable to allow the graduation of the fuse operation time, where the graduation comprises the definition of the time interval between said start instant t0 of the chronometric activity of the timer and said activation instant t1.
In accordance with an illustrative example, the cap allows the graduation of the fuse operation time, determinating said rotation of the fuse ogive relative to the fuse body, following the manual rotation of the cap.
In accordance with an illustrative example, the cap rotation determines a relative angular position of the ogive relative to the fuse body, such that said graduated scale indicates the graduation time in seconds.
In accordance with an illustrative example, the cap is suitable to ensure an overall safety of the fuse under rest conditions, being said cap extractable from the fuse only after the graduation of said fuse operation time.
In accordance with an illustrative example, the cap is suitable to ensure an overall safety of the fuse under rest conditions.
According to an illustrative example, the extraction of the cap from the fuse is prevented by a constraint existing between the cap arms and the corresponding recesses on the fuse body.
According to an illustrative example, the cap arms are of an asymmetrical length, so that they engage with the respective recesses only after a 360° rotation of said cap.
According to an illustrative example, the cap is watertight.
In accordance with an illustrative example, the fuse ogive is integral to the locking/unlocking mechanism of the actuating means; furthermore, the timer comprises a fixed disk and a movable disk, relative to the fuse body, said movable disk being immobile, before the start of the chronometric activity of the timer, and rotating, after the start of the chronometric activity of the timer, and being the angular rotation of said movable disk of the timer proportional to the time; furthermore, the ogive rotation relative to the fuse body determines a corresponding rotation of the locking/unlocking system of the actuating means relative to both the fixed disk and the movable disk of the timer.
According to an illustrative example, said movable disk of the timer is provided with a radial slot on the inner cylindrical surface thereof, suitable to receive the end of a first lever of said locking/unlocking mechanism; in the locking condition, said end of the first lever of the locking/unlocking mechanism is constrained to the inner surface of said movable disk of the timer. The rotation of the locking/unlocking system of the actuating means, relative to the movable disk of the timer which occurs in the graduation step, determines a graduation angular displacement of said radial slot of the movable disk relative to said end of the first lever of the locking/unlocking mechanism. The rotation of said movable disk of the timer, which occurs by the action of the timer, causes said radial slot of the movable disk to be positioned at said end of the first lever of the locking/unlocking mechanism after a given time which is proportional to said graduation angular displacement initially set. The presence of the radial slot of the movable disk at said end of the first lever of the locking/unlocking mechanism causes said end to enter the radial slot of the movable disk, thereby determining a movement of the second end of the first lever of the locking/unlocking mechanism, so that also the further levers comprised in the locking/unlocking mechanism move; thereby driving the transition of said locking/unlocking mechanism from its locking condition to its unlocking condition.
Thanks to the features of the invention mentioned herein, relevant technical advantages can be obtained.
For example:

the further safety means provided (speed sensors) operate "in parallel" with respect to the timer;
the further safety means are operated by other causes than those governing the timer itself, though operating therewith within a synergic sequential chain;
the further safety means exert their action while the projectile, with which the fuse is associated, is in flight; under conditions i.e., in which all the "under rest conditions" and "inertial" safety means have already been disabled;
the further safety means act through "strong" measures, such as, for example: the above-mentioned process of alignment of the fire chain (for example, by controlling the movement of the detonator housing); or the possibility of providing a safety position for the percussion shaft, in which the percussion shaft itself cannot however hit the detonator, even when the timer should wrongly "command" this action; or, the combination of the two mentioned measures;
according to an illustrative example, such further safety means, advantageously, act either in replacement of or in addition to any other systems for controlling the alignment of the fire chain;
according to an illustrative example, such further safety means are preferably as simple as possible, such as to avoid for example the addition of a second timer in the fuse, which besides being complicated, would leave the problem of defining how to drive this possible second timer still unresolved.

Further characteristics and advantages of the device according to the invention will result from the preferred exemplary embodiments thereof, with reference to the annexed figures, in which:

Fig. 1 shows a front view of a fuse according to the present invention, with the cap inserted;
Fig. 2 shows a perspective view of the same fuse, with the indication of the section planes I, II, III, used in the following figures;
Fig. 3 shows said fuse mounted to the corresponding projectile;
Fig. 4 shows a perspective view of the same fuse after the extraction of the cap;
Fig. 5 shows a perspective bottom view of the same fuse after the extraction of the cap;
Fig. 6 shows a partial longitudinal section, along the plane I of Fig. 2, of the fuse with cap;
Fig. 7 shows a longitudinal section of the fuse, along the plane I in Fig. 2, after the extraction of the cap, but still under safety conditions;
Fig. 8 shows a further longitudinal section of the same fuse, under the same conditions as in Fig. 7, sectioned along the plane II of Fig. 2;
Fig. 9 shows an exploded view of the same fuse, as seen from a bottom side point of view;
Fig. 10 shows an exploded view of the fuse, as seen from an upper side point of view;
Fig. 11 shows the turbine system comprised in a fuse according to the present invention;
Fig. 12 shows a front view of the fuse in safety rest condition, with the cap being inserted;
Fig. 13 shows the perspective view of a partial section of the upper part of the fuse, in which said turbine system under safety conditions is detailed;
Fig. 14 shows a cross-section along the plane III of the fuse of Fig. 2, in which the locking mechanism of the striking mass in locking conditions, under rest conditions is visible ;
Fig. 15 shows a section of a latch inertial safety system, comprised in some embodiments of the fuse;
Fig. 16 shows a partial perspective view of the interior of the fuse, and particularly the timer and the latch inertial safety system;
Fig. 17 shows a partial bottom perspective view of the interior of the fuse, and particularly the rotor housing the detonator, in the safety position;
Fig. 18 shows a section along the plane I of Fig. 2 of several elements of the fuse under safety conditions;
Fig. 19 shows a front view of the fuse, after the fuse operation time has been set, and ready for the extraction of the cap;
Fig. 20 shows a cross-section along the plane III of the fuse of Fig. 2, in which the locking mechanism of the striking mass after the graduation, but still in the locking condition is visible;
Fig. 21 shows a perspective view of the fuse after the extraction of the cap;
Fig. 22 shows the perspective view of a partial section of the upper part of the fuse, in which the turbine system is detailed, after the extraction of the cap, but still under safety conditions;
Fig. 23 shows a section of a latch inertial safety system, after the effect of the launch acceleration of the projectile;
Fig. 24 shows a partial perspective view of the interior of the fuse, and particularly the timer, after the chronometric activity has started, which has been released from the constraint caused by the latch inertial safety system;
Fig. 25 shows a partial perspective view of the interior of the fuse, and particularly the rotor housing the detonator, released from the constraint of the latches, but still locked by the locking shaft;
Fig. 26 shows the perspective view of a partial section of the upper part of the fuse, in which the turbine system, with the impeller being free of rotating, is detailed;
Fig. 27 shows the perspective view of a partial section of the upper part of the fuse, in which the turbine system is detailed, after the rotation and the related axial upward movement of the projectile have been completed;
Fig. 28 shows a section, along the plane I of Fig. 2, of several elements of the fuse (particularly the percussion shaft and the detonator) in armed conditions;
Fig. 29 shows a partial bottom perspective view of the interior of the fuse, and particularly the rotor housing the detonator, after the rotation which has brought the latter in the armed position thereof;
Fig. 30 shows a transversal section along the plane III of the fuse of Fig. 2, in which the locking mechanism of the striking mass in unlocking conditions is visible;
Fig. 31 shows a partial longitudinal view of the fuse along the plane I of Fig. 2, in which the actuating means active condition, in which the detonation occurs is visible;
Fig. 32 shows an exploded view of the fuse, in which several macro-blocks (particularly, actuating means, detonation means, speed sensor means, timer) comprised therein are identified.

In the following, through the more detailed illustration of the above-listed figures, several illustrative examples of the present invention will be described, which are to be considered as non-limiting examples.
In the exploded view in Fig. 32 several elements comprised in a preferred embodiment of the fuse 1 are illustrated:

speed sensor means 1000;
actuating means 2000, comprising, in turn, percussion means 2100 and a locking/unlocking mechanism 114 (further illustrated in the subsequent figures);
detonation means 3000;
timer 117.

In Fig. 32 a cap 2, an air conveyor 8, the outer part of the fuse ogive, 9, and of the fuse body, 3; a container of the explosive charge 160 are further illustrated.
In accordance with an illustrative example, the outer part of a fuse is designated with reference 1 (Fig. 1). A multi-function cap 2, which can be for example substantially frustoconical, covers the fuse ogive, under rest conditions.
In accordance with an illustrative example, such cap serves both to cover and protect the fuse, under rest conditions, and to allow setting the fuse operation time, i.e., the delay with which it is operated, starting from a given instant.
This cap is per se a safety system under rest conditions.
In accordance with an illustrative example, the cap 2 has projections 20 suitable to facilitate the grip and the rotation of the cap. Advantageously, the cap is provided with two arms 21, 22, capable of being inserted within corresponding recesses (not shown in Fig. 1) of the fuse body 3.
In accordance with an illustrative example, the arms have different lengths for reasons that will be explained below.
In accordance with an illustrative example, the outer part of the fuse body 3 has a graduated scale 30 thereon. An indication notch indicates under rest conditions a safety position (S), whereas after the graduation, corresponding to a rotation of the ogive relative to the fuse body (according to a procedure described herein below) such notch will designate a number in the graduated scale, corresponding to the operation time being set, expressed in seconds. The further notch 4 serves as the reference point for the proper assembly of the fuse.
In accordance with an illustrative example, a threaded part 5 serves to screw the fuse to the corresponding projectile. A lower part 6 of the fuse is a container of the explosive charge.
In Fig. 2, the same fuse is shown, seen from a different angle, in which sectional planes I, II, III are illustrated, which will be used in several subsequent figures.
In accordance with an illustrative example, a hole 7 serves as a key socket for screwing the fuse to the corresponding projectile (Fig. 2).
Fig. 3 shows the fuse 1 assembled with the corresponding projectile 300, ready for the launch, for example from a mortar.
Fig. 4 shows the fuse after the extraction of the cap 2. The air conveyor 8 serves to allow the inflow and outflow of the air, through the corresponding openings 81 and 82, while the projectile is in flight, causing the rotating movement of an underlying turbine (not seen in this figure). The outer part of the ogive 9 includes a notch 91, in which a pin (23 in Fig. 5) is engaged, which is provided within the cap, so that a given rotation manually imposed to the cap in a manner which can be graduated, before it can be extracted, causes a corresponding rotation of the ogive with respect to the fuse body; this implies that the fuse operation time can be set in a manner which can be graduated.
Fig. 5 shows a perspective view from below of the fuse and of the interior of the cap.
Fig. 6 shows a partial section of the fuse along the plane I, while the cap is mounted, which implies that all the fuse safety devices are in safety position. A section of the ogive 9, a section of the fuse body 3, and a section of the cap 2 should be particularly noted. In this section, the protrusion 24 projecting inwardly of the upper part of the cap should be noted, such as to hold the underlying turbine 10 in the "lowered" position, which, as illustrated below, corresponds to a safety position. This ensures that, when the cap is mounted, the turbine-based inner safety devices are operating.
Fig. 7 shows a complete section of the fuse, after the cap has been extracted, along the plane I of Fig. 2, in which the safety means provided are still under safety conditions. This figure shows:

the air conveyor 8, and the corresponding air inlet/ outlet openings 81, 82, described above in Fig. 4;
the fuse ogive 9 and body 3;
speed sensor means (generally designated with 1000, in Fig. 32), which, in the preferred embodiment described herein control both the actuating means and the detonation means of the fuse, as illustrated below.

In accordance with an embodiment, such speed sensor means comprise a turbine system, 10, illustrated herein in the engaging position thereof (i.e., in the example shown in Fig. 7, in the lower axial position thereof) corresponding to a safety condition both of said actuating means and said detonation means.
In accordance with an embodiment, such turbine system 10 comprises:

an impeller 100, suitable to rotate under the effect of an air inflow through said conveyor;
mechanical coupling means, comprising in the present embodiment a turbine shaft 101, with a first end 102 connected to the impeller 100, a stem 103 screwed by means of a thread 104 to a corresponding thread 105 provided on the support 106 of the turbine; and a second end 107;
inertial locking/unlocking means of the turbine system, comprising in the present embodiment a locking disk 108 of the turbine, arranged under the impeller 100, fitted on one side to the support 106 and capable, in the safety position shown herein, of locking the impeller, thereby preventing the latter from rotating, through a saw tooth structure.

The fuse shown in fig. 7 further comprises actuating means (generally designated with the reference 2000, in Fig. 32). In accordance with an illustrative example, the actuating means comprise:

percussion means (generally designated with the reference 2100, in Fig. 32) of the actuating means of the fuse, comprising, in the embodiment herein:
a percussion shaft 109, with a first end 110 connected to the end 107 of the turbine, and a second end 111; such shaft 109 being capable of axially moving and taking an axially lower safety position thereof (as that illustrated in Fig. 7) and an axially upper armed position thereof;
a striking mass 112, which is suitable to hit, if and when it is unlocked, the underlying percussion shaft 109, pushed by the action of a preloaded spring 113 thereof;
a locking/unlocking mechanism 114 of the actuating means, suitable to act, in the example considered herein, on the striking mass; and particularly, capable of maintaining the striking mass locked until the locking action of the locking/unlocking mechanism has been disabled by the action of a timer 117, described below;
detonation means (generally designated with 3000, in Fig. 32), comprising a movable housing 115 of the detonator; in the embodiment shown, such movable housing comprises a rotor, capable of taking a safety position of the detonator (as in Fig. 7) in which the detonator (not shown) keeps an axially misaligned position relative to the percussion shaft 109; and an armed position of the detonator, in which the detonator is in an axially aligned position relative to the percussion shaft 109.

It should be purposely observed that in the preferred embodiment of the invention, as considered herein, the safety position of the actuating means (therefore, the safety position of the percussion shaft) also implies the respective safety condition of the detonation means. In fact, the rotor 115, in the condition shown in Fig. 7, is locked in the safety position of the detonator (misaligned relative to the percussion shaft) by the end 111 of the percussion shaft 109, which, being inserted in a hole 116 (eccentric relative to the detonator) drilled on the rotor 115, prevents the latter from rotating towards the armed position of the detonator.
The fuse according to an illustrative example reported in Fig. 7 further comprises:

a timer 117, capable of carrying out a chronometric activity of measuring time, suitable to control the locking mechanism of the striking mass, allowing the unlocking therof only after a given activation instant t1, delayed by a preset time interval with respect to a start instant t0 of said chronometric activity of the timer. It shall be noted that, in accordance with an embodiment, said time interval is presettable, and corresponds to the fuse operation time (already mentioned while illustrating Figs. 2 and 4) which can be set and graduated through the mentioned rotation of the cap 2. It shall be further noted that, according to the present embodiment of the invention, such timer has also the further function of controlling, through a locking shaft 118, the movement of the rotor 115, allowing the rotation thereof only at a given instant t2, preset in such a way to precede t1;
a further latch inertial safety mechanism, 119, performing the functions of said second and third inertial safety means of the fuse;
an explosive charge 160;
the container of the explosive charge 6.

In accordance with an illustrative example, Fig. 8 shows a different longitudinal section of the fuse, along the plane II of Fig. 2, once the cap has been extracted.
In accordance with an illustrative example, the timer 117 includes a movable disk 120, in the shape of a rotating barrel, characterized by a radial slot present on the inner cylindrical surface thereof, intended to cooperate, as it will be illustrated herein below, with the locking/unlocking mechanism 114 of the striking mass; the timer 117 includes further elements, a fixed disk, and further an oscillating anchor, a toothed wheel, and other gears, which can be manufactured according to solutions known to those of ordinary skill in the art and are not essential to understand the present invention.
The latch inertial safety mechanism 119 comprises:

a central sleeve 121;
two safety side set-back pins 122, shown herein in the rest position thereof, in which they remain until a predefined acceleration threshold has been detected; in such rest position, the respective upper ends 123 of the set-back pins prevent the functioning of the timer 117, by locking an oscillating anchor thereof, while the respective lower ends 124 of the set-back pins engage the underlying rotor 115 of the detonator, by preventing the rotation thereof;
two locking spheres 125,
a spring 126.

In accordance with an illustrative example, Figs. 9 and 10 show, respectively, an exploded view of the fuse, as seen from a lower side point of view, and an exploded view of the fuse, as seen from an enlarged upper side point of view. In such exploded views, the components of the turbine-based non-inertial safety system 10 are particularly highlighted:
The Figures illustrate:

the air conveyor 8, of a substantially frustoconical hollow shape, with an air inlet upper opening 81 and side holes acting as openings 82 for the air escape; such conveyor serves to promote the action of the air pressure, which is related to the air flow hitting the impeller, which is related to the relative speed between the air and the moving projectile, in flight;
the impeller 100, shown in Fig. 10 in the upper part thereof, and in Fig. 9 in the lower part thereof, which shows a saw tooth lower structure 1001;
the turbine shaft 101, with a first end 102 suitable to be connected to the impeller 100, a stem 103 with a thread 104 suitable to be screwed to a corresponding thread 105 provided on the inner surface of the support 106; and a second end 107;
the locking disk 108 of the turbine, suitable to be inserted between the impeller 100, to which it is constrained in the safety position through the engagement of the toothed structure 1081 with the saw tooth structure 1001 of the impeller; and the underlying support 106, to which it is fitted; in order to facilitate a proper assembly, the disk 108 is provided with a central opening 1082, of a squared shape, for example, in which the pin 1061 having a corresponding squared shape is inserted; the disk 108, thanks to the structure described herein, can exert the function thereof of preventing the rotation of the impeller, under safety conditions;
a disk-shaped spring washer 1100, interposed between the disk 108 and the support 106, suitable to force the disk against the impeller, under rest conditions, and to allow, on the contrary, the withdrawal of the disk 108, under the action of the launch acceleration, upon reaching a given predefined acceleration level, so as to unlock the impeller and to allow the subsequent rotation thereof, under the action of the air pressure;
the support 106, with the above-mentioned pin 1061 suitable to the assembly of the disk 108; such support 106 is, in turn, mounted to the fuse ogive 9.

Fig. 11 shows the turbine in an enlarged and detailed form.
The operation of the fuse described in the preceding Figures, in an illustrative example of the invention, is described herein below, where a series of subsequent steps is highlighted throughout Figs. 12-31.

(1) CONDITIONS OF SAFETY UNDER REST CONDITIONS

1 A) As shown in Fig. 12, the fuse, under rest conditions, has to be with its cap 2 inserted thereon. In the embodiment shown herein, the cap is designed as to have, when mounted, a position that is constrained to the fuse, through two arms 21, 22 of different length, which are inserted within corresponding recesses (or cavities), for example emispherical, obtained at corresponding different heights on the fuse body outer part. Such constrained position, of safety "under rest conditions", also implies a defined angular position of the ogive relative to the fuse body, which involves, as illustrated herein below, that all the described safety devices internal to the fuse are operative. This condition is signalled for the sake of convenience on the graduated scale 30, which shows a preset position ("S").
In the rest conditions indicated herein, the cap cannot be extracted directly. In order to extract it, it is necessary to rotate the cap by at least a given angle with respect to the fuse body. This requires manually applying (being aided by the projections 20) a torque which is greater than the sum of the friction torque inherent to the fuse and the torque deriving from the force necessary to deform the arms so that they exit the two respective cavities.
Beside allowing the extraction thereof, the mentioned manual rotation of the cap allows setting a fuse operation time (which will be implemented by the action of the timer), proportional to the rotation angle according to what is indicated by the graduated scale 30. The angular range allowing the extraction of the cap determines the range of allowed time setting values, which in the shown example ranges between 6 and 54 seconds. Suitably, the allowed rotation angle is larger than 180° thanks to the already mentioned asymmetry of the arms 21, 22, which makes sure that they cannot insert again in the recesses on the fuse body after a rotation of 180°.
1B) In the step under examination, as shown Fig. 13, the turbine system 10 has to necessarily be in the condition in which it imposes both to the percussion shaft, and to the rotor the respective safety position. In fact, when the cap is mounted, the cap protrusion 24, which projects inwardly of the air conveyor, ensures that the turbine shaft is in the lower axial position thereof, and further prevents any upward unscrewing of the turbine. Vice versa, the cap could not be mounted, if the turbine shaft were not completely screwed, i.e., in presence of risks that the turbine shaft and the rotor were not in the respective safety position.
1C) During the step under examination, as shown in Fig. 14, the locking mechanism 114 of the striking mass is in the locking position thereof. The mechanism, comprising in this embodiment an assembly of a first lever 1141 and a second lever 1144, integral to the fuse ogive, and therefore to the cap. When the angular position of the cap corresponds to the indication S on the graduated scale, the position of said levers is the one shown in the Figure. The arm 1142 of the first lever 1141 is locked to a protrusion 1501 of a fixed disk 150 belonging to the timer, which prevents the rotation of the first lever 1141. The first lever 1141 locks, in turn, the second lever 1144, which it is coupled to through the arm 1143; and the second lever 1144, in turn, locks the striking mass (not shown in Fig. 14).
1 D) The latch inertial safety mechanism is, in this step, in the safety position too. Fig. 15 shows such mechanism, extrapolated from the rest of the fuse, in a condition equivalent to the one shown in Fig. 8 and in the subsequent Fig. 16. The mentioned safety position provides that the sleeve 121, forced upwardly by the spring 126, causes the two locking spheres 125 to move such a position as to preclude any longitudinal movement of the two set-back pins 122. In such conditions, the upper ends 123 of the set-back pins preclude the functioning of the timer, by locking the oscillating anchor 1171 thereof (visible in Fig. 16), and therefore they prevent the timer chronometric activity from starting. Furthermore, the lower ends 124 of the set-back pins preclude the rotation of the rotor 115, by being inserted within a notch 1151 (also visible in Fig. 17) provided on the edge of the rotor 115.
1E) The detonator movable housing, which is in the example herein a rotor 115, is, in turn, in the detonator safety position. This implies that the detonator is misaligned relative to the percussion shaft, which means that the fire chain is misaligned. As already discussed herein, this is a "strong" safety measure, which prevents the trigger of the pyric parts downstream of the detonator even in the case of an accidental burst of the detonator. In the exemplary embodiment under examination in Fig. 18 (longitudinal partial section of the fuse), the rotor 115 is locked in the safety position by three "inhibition elements":
- the already mentioned lower ends 124 of the set-back pins;
- the locking shaft 118, which locks the rotor by imposing a mechanical constraint of geometric radial type on a notch 1153 of the edge of the rotor; such locking shaft begins to rotate after the chronometric activity of the timer has started, being connected to a gear 1175 of the latter, and it disengages the rotor after a given time interval, at an instant t2, preceding the instant t1 in which the timer itlsef allows the movement of the striking mass on the percussion shaft, and of the latter on the detonator; it shall be noted that the sequentiality of the instants t1 and t2, indicated above, can be obtained as a consequence of a proper dimensioning of the mechanical parameters of the turbine system 10, according to standard design criteria;
- the lower end 111 of the same percussion shaft, inserted in the hole 116 of the rotor 115, being the percussion shaft in the safety position thereof, constrained by the safety turbine system.

It is further noted that, as already discussed herein, in accordance with an illustrative example, the essential safety functionality is just ensured by this third safety element, which is guaranteed by the speed sensor means (turbine system), which therefore act as further safety means. In fact, the first of the mentioned inhibition elements is inertial, and it will cease the action thereof when the launch acceleration ceases, as soon as the projectile comes out from the mortar barrel. The second inhibition element, depending on the timer, does not offer protection from any accidental start of the countdown, or from any malfunctioning of the timer itself.
According to an illustrative example of the invention, only the third safety means are provided. According to further distinct illustrative examples, also the first, or the second, or the first and the second of such elements are additionally provided.

(2) STEP OF GRADUATION AND PREPARATION TO THE LAUNCH
2A) By manually rotating the cap 2, the underlying fuse ogive rotates, as shown in Fig. 4. By rotating the ogive, the fuse operation time is set. Fig. 19 shows, for example, the fuse as set on 15 seconds.
2B) Within the fuse, the ogive rotation involves a corresponding rotation of the locking/unlocking mechanism 114, and particularly of the leverage system of the locking/unlocking mechanism, relative both to the fixed disk 150 and the movable disk 120 of the timer (as shown in Fig. 20, if compared to Fig. 14). The levers remain locked by the timer movable disk, in the safety position. What is different is the relative position of the lever 1141 arm 1142 with respect to a radial slot provided on the inner surface of the movable disk 120.
2C) Once the rotation has been performed, the two arms have moved out from the respective recesses on the fuse body, and the cap can be separated from the fuse (Fig. 21).
2D) The extraction of the cap releases the fuse ogive and the conveyor 8 of the air on the turbine. One of the constraint elements on the turbine is no longer active, but the turbine impeller 100 cannot be unscrewed, since it is locked by the underlying locking disk 108, pushed by the spring washer 1100. As illustrated above, the impeller-disk coupling occurs by means of a saw toothing, so as to allow the rotation of the impeller relative to the disk for clockwise rotation (screwing) but to prevent corresponding counter-clockwise rotations (unscrewing). The locking disk is fitted on the support so as not to be able to rotate relative to the support. Therfore, the impeller also cannot unscrew relative to the support until the locking disk is coupled thereto (see Fig. 22).
(3) LAUNCH (in-barrel step)
3A) Upon launching the bomb, the axial acceleration performs an action on the inertial safety means, shown in Fig. 23 in the condition in which the inhibition action on the timer and on the detonator rotor has ceased. The axial acceleration makes to go back first the central sleeve 121, and immediately after the two side set-back pins 122 against the respective helical springs 1221. The withdrawal of the side set-back pins causes:
3B) the release of the small anchor 1171 of the timer 117, which, pushed in a known manner by an escape wheel and a gear train, begins to count the time, i.e., the chronometric activity thereof. Then the set-back pins remain locked in a back position by a further spring (see Fig. 24);
3C) the releasing of the constraint imposed by the set-back pins on the rotor, since the ends 124, pushed downwards, have a lower diameter cylindical part, 1241, which releases the mechanical constraint of the set-back pins on the rotor; the rotor remains in any case locked in the safety position by the locking shaft 118 controlled by the timer (see Fig. 25);
3D) the axial acceleration also affects the turbine system (as illustrated in Fig. 26): the locking disk 108 goes back due to the acceleration against the spring washer thereof, unlocks the impeller and allows the potential rotation thereof. However, the latter does not begin to immediately rotate, being the driving torque generated by the air lower than the resisting torque produced by the friction between the thread 104 of the support 106 and the thread 105 of the turbine shaft 101, due to the weight of the shaft and of the impeller for the launch acceleration.
(4) LAUNCH (in flight step)
4A) Upon exiting the launch barrel, the axial acceleration ceases. The only forces which are exerted on the projectile are the aerodynamic drag to the advancement of the bomb in the air and the weigth force. The air pressure entering the conveyor keeps the locking disk backed and unconstrained from the impeller. Furthermore, the relative speed of the projectile in flight relative to the air, upon exiting the barrel, is above a preset minimum speed value, and it is such as to determine an air flow, between the inlet and outlet openings, capable of generating a driving torque sufficient to rotate the impeller 100. The latter, upon rotating, unscrews from the support 106 until stopping at the conveyor 8 top, thus obstructing the air inlet hole 81.
As shown in Fig. 27, the turbine shaft 101, by unscrewing, converts the rotary movement to an axial upward movement. This, in turn, allows the percussion shaft 109 to be lifted, by moving towards the armed position of the percussion shaft. Then the percussor end 111 exits the hole 116 of the rotor, which is now locked only by the locking shaft 118.
4B) Meanwhile, the timer continues its chronometric activity of counting time. Depending on this, through a gear assembly, it controls the movement of the locking shaft 118, which, at a given instant t2 (for example, about 1 sec. after the start of the time count) exits the corresponding notch 1153 in the rotor (as shown in Fig. 29). Therefore, the rotor 115 is free to rotate, under the bias of a spring thereof, and to align on the fuse central axis the detonator 1150 (in Fig. 28) with the percussion shaft 109 being thereover.
(5) FUNCTIONING
5A) As shown in Fig. 30, the timer movable disk 120, after rotating by an angle corresponding to the set operation time (for example 6° per second) has a slot thereof facing the lever 1141 arm 1142 of the locking mechanism 114. The arm 1142 enters the slot, the first lever 1141 can therefore rotate and unhook the second lever 1144, which releases the striking mass 112.
5B) As illustrated in Fig. 31, the preloaded spring 113 strongly pushes the striking mass 112 against the underlying percussion shaft 109, the end 111 of which penetrates in the underlying detonator 1150, which is meanwhile aligned thereto, axially, thus detonating it.

Claims

A fuse (1) for projectile (300), comprising:
- detonation means (3000), capable of assuming a detonation means safety condition and a detonation means armed condition;

- actuating means (2000), suitable to detonate said detonation means, said actuating means (2000) being capable of assuming an actuating means safety condition, an actuating means armed condition, and an actuating means active condition, in which said active condition the actuating means (2000) detonate the detonation means (3000);

- a timer (117), suitable to actuate said actuating means;

- speed sensor means (1000) independent from said timer (117), operating on the basis of parameters depending on the projectile speed, said speed sensor means being safety means suitable to control the transition of the actuating means (2000) from the safety condition thereof to the armed condition thereof;
characterized in that:
- said speed sensor means are further configured to control the transition of the detonation means (3000) from the safety condition thereof to the armed condition thereof;

- said timer (117) being allowed to cause the transition of said actuating means (2000) from the armed condition thereof, to the active condition thereof, only if the detonation means have assumed the armed condition thereof, after being enabled by said speed sensor means.
The fuse (1) according to claim 1, wherein the speed sensor means (1000) comprise a turbine system (10), said turbine system (10) comprising:
- an impeller (100) capable of rotating under the action of a predetermined air flow level relative to the projectile (300), related to a predetermined projectile (300) speed value in air, and

- inertial locking/unlocking means of the turbine system, capable of preventing the rotation of the impeller until they detect a predefined value of acceleration for unlocking the rotation of the impeller,
and wherein the rotation of the impeller remains inhibited even after the action of said inertial locking/unlocking means of the turbine system has ceased, until the projectile (300) reaches a predefined speed.
A projectile (300) comprising a fuse (1) according to any preceding claim.
A system comprising a projectile according to claim 3, wherein the projectile (300) is a mortar bomb.
A fuse (1) functioning method for a projectile (300), according to claim 3 comprising the steps of:
- driving detonation means (3000) from a detonation means safety condition to a detonation means armed condition;

- activating actuating means (2000) by a timer (117);

- detonating said detonation means by the actuating means (2000);

- driving the actuating means (2000) from an actuating means safety condition to an actuating means armed condition to an actuating means active condition, in which the actuating means (2000) detonate the detonation means (3000);

- measuring parameters depending on the projectile speed by speed sensor means (1000) independent from said timer (117), and

- controlling by said speed sensor means the transition of the actuating means (2000) from the respective safety condition to the respective armed condition;
characterized in that the further steps are provided of:
- enabling the transition of the actuating means (2000) from the armed condition to the active condition thereof, by controlling, by means of said speed sensor means, the transition of the detonation means from the respective safety condition to the respective armed condition;

- after said step of enabling, controlling by said timer (117) the transition of said actuating means (2000) from said armed condition thereof to said active condition thereof.