IL311372B2 - Double protection fuse - Google Patents

Description

MULTI-SAFETY FUZE ARRANGEMENT AND PROJECTILES IMPLEMENTING SAME TECHNOLOGICAL FIELD The invention generally contemplates safety fuzes and projectiles implementing same.

BACKGROUND Point Detonating (PD) fuzes are designed to detonate a mortar bomb upon impact. The PD fuze has a striking pin that is positioned so that when the explosive device impacts a surface, the firing pin is driven into a detonator. This type of a fuze poses a problem in transportation and storage where an accidental jostling or a drop could detonate the explosive device. Therefore, fuzes have been provided with safety features, which main purpose is to avoid unintentional explosion.As a single safety feature is typically inadequate to anticipate accidents, multiple safety features have been proposed. However, even with such multi-safety features once a safety feature status is changed from safe to armed, the device remains armed, therefore increasing the risk of an accident.Numerous solutions have been proposed. One of such a solution is disclosed in International Publication WO23/046327 which discloses a mechanical self-percussion fuze for a non-spinning round, which remains in a safe state until at least two mutually independent physical phenomena linked to the firing of the round occur.

REFERENCES [1] WO23/046327 GENERAL DESCRIPTION In light of the malfunctions associated with fuze arrangements of the art, the inventors of the technology disclosed herein have developed an improvement in the safety of arming and deploying projectiles.The technology subject of the present application generally concerns a mechanical percussion fuze having a mechanism involving at least two independent safety features.

The two (and sometime more) independent physical features operate in different environments to prevent accidental detonation of an explosive device implementing the fuze of the invention. Each safety feature has an Armed state and a Safe state. Each of the safety features must be mechanically changed from the safe state to the armed state within a predetermined period of time for the explosive device to be armed and ready to detonate upon impact.As further disclosed herein, the fuze of the invention may be configured as a dual- safety fuze wherein both launch inertia forces and air velocity criteria must be met for secured detonation to occur.The percussion fuze of the invention is generally fully mechanical and is free of any electronic elements or circuits. It is configured for mounting at a fore end of an artillery projectile configured to detonate on impact. The fuze generally comprises a striker pin having a laterally projecting arresting shoulder, a rotor assembly comprising a rotor having a striker pin arresting chamber and a timer mechanism that is articulated with the rotor and configurable for timed rotation thereof.The fuze is configurable between a "safe position" at which the striker pin is received within the striker pin arresting chamber; and a "launch position" that is initiated upon sensing launch inertia forces and which may evolve into a flight position or a safe position depending on whether an air velocity threshold is met. The "flight position" is initiated only upon meeting or crossing an air velocity threshold, whereupon the striker tip axially withdraws from the striker pin arresting chamber, facilitating rotation of the rotor by the timer mechanism to a position at which a detonator is disposed below the striker tip. Whereupon the launch inertia forces cascade to cause the striker pin to axially displace upwardly freeing the rotor to rotate, and within a predetermined period the air velocity threshold is met, the fuze becomes armed.Thus, in a first of its aspects, there is provided a percussion fuze for a projectile, the fuze comprising a striker pin coaxially positioned with respect to a shaft of said fuze and having a top portion slidingly engaging with a bottom end of the shaft, a bottom striker tip, and a laterally projecting arresting shoulder intermediating said top portion and the striker tip; a rotor assembly comprising a rotatable rotor and having a striker pin arresting chamber blocked at its bottom and formed with a striker pin arresting bracket or groove for selective arresting the arresting shoulder of the striker pin, and a throughgoing detonator cavity angularly offset from said arresting chamber for accommodating a detonator explosive; and a timer mechanism articulated with the rotor and configurable for timed rotation thereof.The laterally projecting arresting shoulder is a laterally projecting element that is an integral part of the striker pin or which is mounted thereon and which extends the diameter of the pin or the width of the pin at a predesigned location that is between the top portion of the striker pin and the striker tip. The shoulder may extend to one lateral side of the striker pin. The shoulder is not provided in a form of a gear tooth and is not intended to mesh with a cog wheel. Typically, the projecting should is a single structural element that may be provided in a variety of shapes.The fuze is provided within a housing configured to be connectable at a fore end of the projectile. In some configurations, the housing forms an integral part of the projectile body. In other cases, the housing may be screw couplable at a front end of the projectile. Irrespectively, a cap assembly is provided at a top end of the housing and comprising a cap with a shaft extending therefrom along a longitudinal axis. The cap assembly is axially displaceable between a closed position at which it bears over the housing, and an open position at which it axially shifts from the top end. An air velocity sensor is provided below said cap and is configurable and operable for determining or measuring an air velocity threshold. In some cases, the air velocity sensor is received within an air pressure sensor chamber. In some cases, at the open position the cap axially displaces to expose the air velocity sensor to ambient air pressure. At the closed position, the cap assembly sealingly conceals the pressure sensor chamber.In some cases, the air velocity sensor is received within an air pressure sensor chamber.The cap assembly is further provided with one or more restraining pins or arresting pins. The one or more pins are positioned to avoid accidental or unwanted rotation of the air velocity sensor when launch inertia forces have not exceeded a predetermined inertia threshold. Preventing the air velocity sensor from rotating, prevents cap assembly from displacing into the open position, as disclosed above, and further prevents the striker pin from axially displacing upwardly. The one or more pins extend downwardly from the cap assembly and are positioned to the side or sides of the shaft extending from the cap assembly. The number of pins may vary. In some configurations, the cap assembly comprises two such pins.

The striker pin is positioned coaxially with the shaft and its top portion is configured to slidingly engage with a bottom end of the shaft. The striker pin may coextend at a bottom end of the shaft and may be axially displaceable with respect thereto.The rotor is rotatable within the housing about a rotor axis that is offset of the shaft or fuze longitudinal axis.The fuze also comprises a detonator that is disposed in a detonator chamber of the housing, and is positioned coaxially below the rotor striker pin. A booster charge may also be disposed in the hosing below the detonator and received within a booster container. The explosive container typically projects from the bottom end of the housing.In another aspect there is provided a percussion fuze for a projectile, the fuze comprisinga striker pin coaxially positioned with respect to a shaft of said fuze and having a top portion slidingly engaging with a bottom end of the shaft, with a bottom striker tip, and a laterally projecting arresting shoulder intermediating said top portion and the striker tip;a rotor assembly comprising a rotatable rotor and having a striker pin arresting chamber blocked at its bottom and formed with a striker pin arresting bracket for selective arresting or locking (irreversibly) the arresting shoulder of the striker pin, and a throughgoing detonator cavity angularly offset from said arresting chamber for accommodating a detonator explosive; anda timer mechanism articulated with the rotor and configurable for timed rotation thereof;wherein the fuze is configurable between a safe position at which the striker pin is received within the striker pin arresting chamber; a launch position initiated upon sensing launch inertia forces, upon which the striker pin axially displaces upwardly and the rotor is released to rotate about a rotor axis, wherein when an air velocity remains within a predetermined time period under a predetermined air velocity threshold, the striker pin arresting shoulder irreversibly locks within the striker pin arresting bracket, or wherein when the air velocity meets the predetermined air velocity threshold within the predetermined time period a flight position is initiated, whereupon the striker tip axially withdraws from the striker pin arresting chamber, facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator, wherein the fuze is armed.

In some configurations, the striker pin arresting chamber is a two-level cavity, having a first level chamber for receiving a bottom portion of the striker pin at the safe position, and a second level chamber, shallower than said first level chamber and configured for receiving a bottom portion of the striker pin at a launch position.In some cases, the striker pin arresting chamber is crescent-shaped.Also provided is a fuze or a fuze arrangement comprising a housing connectable at a fore end of a projectile;a cap assembly is provided at a top end of the housing and comprising a cap with a shaft extending therefrom along a longitudinal axis; said cap assembly being axially displaceable between a closed position at which it bears over the housing, and an open position at which it axially shifts from the top end, and an air velocity sensor provided below said cap and configured for determining an air velocity threshold;a striker pin coaxially aligned with the shaft and having a top portion slidingly engaged with a bottom end of the shaft, with a bottom striker tip, and a laterally projecting arresting shoulder intermediate to said top portion and the striker tip;a rotor assembly comprising a rotor rotatable within the housing about a rotor axis offset of said longitudinal axis, and having a striker pin arresting chamber blocked at its bottom and formed with a striker pin arresting bracket (or cavity) for selective arresting the arresting shoulder of the striker pin, and a throughgoing detonator cavity angularly offset from said chamber and configured for accommodating a detonator explosive; anda timer mechanism articulated with the rotor and configurable for timed rotation thereof;wherein the fuze is configurable between a safe position at which the striker pin is received within the striker pin arresting chamber; a launch position initiated upon sensing launch inertia forces, upon which the striker pin axially displaces upwardly and the rotor is released to rotate about a rotor axis, wherein when an air velocity remains within a predetermined time period under a predetermined air velocity threshold, the striker pin arresting shoulder irreversibly locks within the striker pin arresting bracket (whereby the fuze is locked or inoperable to cause detonation), or wherein when the air velocity meets the predetermined air velocity threshold within the predetermined time period a flight position is initiated, whereupon the striker tip axially withdraws from the striker pin arresting chamber, facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator, wherein the fuze is armed.In some configurations, at the safe position of the fuze, as disclosed herein, the cap assembly is disposed at a normally closed position. The cap assembly may be biased by a preloaded spring into the open position.As disclosed herein, to arm the fuze, certain preconditions must be met. These criteria are: sensing of launch inertia forces greater than a predetermined inertia threshold and sensing of air velocities greater than a predetermined air velocity threshold, such that a time period between the sensing of inertia forces greater than the predetermined inertia threshold and the sensing of air velocities greater than the air velocity threshold is smaller than a predetermined time threshold. In other words, where the inertia threshold is met, but the air velocities do not exceed the predetermined threshold, the fuze will lock and not be armed. In case the inertia threshold is met, but the time threshold is exceeded before the air velocity threshold is met, the fuze will lock and not be armed. Only when the two mutually independent physical criteria are met; namely the inertia threshold is met, and the air velocities exceed the predetermined threshold within the time threshold, will the fuze arm.The launch inertia force may result from any accelerated movement of the projectile, which movement may be accidental (fall of the projectile) or planned or intentional (launching of the projectile). The acceleration causes the striker pin to axially displace upwardly, permitting the rotor to rotate about a rotor axis. The inertia threshold may thus be defined as any change in the projectile velocity. A drop movement of the projectile does not amount to a launch inertia force and thus remains below the inertia threshold. Without limitation, the launch inertia threshold is characteristic of a flight g- force that is at least 600 G, experienced in a direction opposite to the direction of flight and occurring over a time period of at least several milliseconds (between 1 and 5 msec).The projectile air velocity may be determined by a velocity sensor that is provided below the cap of the fuze arrangement, as disclosed herein, and is configured for determining the projectile’s air velocity and for determining whether the air velocity exceeds or is lower than a predetermined velocity threshold. The velocity threshold is typically characteristic of flight velocities (such velocities linked to the firing of the projectile) and as such is of a value that excludes velocities characteristic of accidental or non-flight movements (being of smaller velocities than flight velocities). Without limitation, the air velocity threshold is 50 m/sec. Projectile air velocities greater than m/sec meet the velocity threshold. Projectile air velocities lower than 50 m/sec do not cause arming of the fuze.The projectile air velocity threshold may vary based on the projectile use and other parameters determined by the operator. The air velocity threshold is at least 50 m/sec. In some cases, it may be 60, 70, 80 m/sec or higher.The projectile air velocity may be determined by any velocity sensor, as known in the art. Such a velocity sensor is a mechanical sensor which may be in a form of an revolvable element, e.g., a turbine, an impeller, arranged such that it can be driven by the displacement of air during projectile flight to generate the torque required for withdrawal of the striker pin. Putting it differently, revolution of the element, i.e., impeller, at a speed corresponding to the projectile’s air velocity that exceeds the threshold, causes axial withdrawal of the striker tip from the striker pin arresting chamber, facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator.The timer mechanism is articulated with the rotor and configurable for timed rotation thereof. The timer mechanism is configured to measure or time a time difference between the inertia threshold criterium and the air velocity threshold criterium, such that the time difference resulting in the arming of the fuze does not exceed a certain time threshold characteristic of a projectile firing. The time threshold defining a time difference between the inertia threshold criterium and the air velocity threshold criterium is typically a time period of less than 1 second, or less than 0.9 or 0.8 or 0.7 or 0.6 second, or is between 0.3 and 1 sec.The timer mechanism is a mechanical timer. The timer mechanism may comprise a cogwheel portion at a top portion of the rotor, which is configured to revolve back and forth in a precise time interval that is determined on the cogwheel dimension and structure and on a timekeeping element that engages the cogwheel.Generally, the timer mechanism may comprise a spring which is preset to deliver a force to a weighted wheel capable of oscillating back and forth at a constant rate. The mechanism comprises an escapement that releases the weighted wheel to move forward at a constant rate. Each movement releases a tooth of the wheel, such that the full movement defines the time period as defined.Further provided is a fuze as disclosed herein further comprising a detonator that is disposed in a detonator chamber of the housing, coaxially below the rotor striker pin; anda booster charge disposed in the hosing below the detonator and received within a booster container, said explosive container projecting from a bottom end of the housing.In some cases, the booster container extends below a screw-threaded portion of the housing and is configurable for screw coupling at a front end of the projectile.The invention further provides a projectile implementing, incorporating or generally comprising a fuze according to the invention.The invention further provides a fuze for a projectile, the fuze comprising a striker pin coaxially positioned with respect to a shaft of said fuze and having a top portion slidingly engaging with a bottom end of the shaft, a bottom striker tip, and a laterally projecting arresting shoulder intermediating said top portion and the striker tip; a rotor assembly comprising a rotatable rotor and having a striker pin arresting chamber blocked at its bottom and formed with a striker pin arresting bracket or groove for selective arresting the arresting shoulder of the striker pin, and a throughgoing detonator cavity angularly offset from said arresting chamber for accommodating a detonator explosive; and a timer mechanism articulated with the rotor and configurable for timed rotation thereof.In some configurations, the fuze is provided in a housing configured to be connectable at a fore end of the projectile.In some configurations, the housing forms an integral part of the projectile body.In some configurations, the housing is screw couplable at a front end of the projectile.In some configurations, the fuze is provided with a cap assembly at a top end of the housing and comprising a cap with the shaft extending therefrom along a longitudinal axis.In some configurations, the cap assembly is axially displaceable between a closed position at which it bears over the housing, and an open position at which it axially shifts from the top end.In some configurations, an air velocity sensor is provided below said cap and is configurable and operable for determining or measuring an air velocity threshold.In some configurations, the air velocity sensor is received within an air pressure sensor chamber.

In some configurations, at the open position the cap axially displaces to expose the air velocity sensor to ambient air pressure and at the closed position, the cap assembly sealingly conceals the pressure sensor chamber.In some configurations, the air velocity sensor is received within an air pressure sensor chamber.In some configurations, the air velocity sensor is a revolvable element arranged to be driven by displacement of air during projectile flight to generate torque required for withdrawal of the striker pin.In some configurations, the revolvable element is a turbine or an impeller.In some configurations, revolution of the element at a speed corresponding to the projectile’s air velocity exceeding a preset threshold, causes axial withdrawal of the striker tip from the striker pin arresting chamber.In some configurations, the rotor is rotatable within the housing about a rotor axis that is offset of the shaft or fuze longitudinal axis.In some configurations, the fuze comprises a detonator disposed in a detonator chamber of the housing, and is positioned coaxially below the striker pin.In some configurations, the fuze comprises a booster charge disposed in the hosing below the detonator and received within a booster container.In some configurations, the fuze comprisesa striker pin coaxially positioned with respect to a shaft of said fuze and having a top portion slidingly engaging with a bottom end of the shaft, with a bottom striker tip, and a laterally projecting arresting shoulder intermediating said top portion and the striker tip;a rotor assembly comprising a rotatable rotor and having a striker pin arresting chamber blocked at its bottom and formed with a striker pin arresting bracket for selective arresting or locking (irreversibly) the arresting shoulder of the striker pin, and a thoroughgoing detonator cavity angularly offset from said arresting chamber for accommodating a detonator explosive; anda timer mechanism articulated with the rotor and configurable for timed rotation thereof;wherein the fuze is configurable between a safe position at which the striker pin is received within the striker pin arresting chamber; a launch position initiated upon sensing launch inertia forces, upon which the striker pin axially displaces upwardly and the rotor is released to rotate about a rotor axis, wherein when an air velocity remains within a predetermined time period under a predetermined air velocity threshold, the striker pin arresting shoulder irreversibly locks within the striker pin arresting bracket, or wherein when the air velocity meets the predetermined air velocity threshold within the predetermined time period a flight position is initiated, whereupon the striker tip axially withdraws from the striker pin arresting chamber, facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator, wherein the fuze is armed.In some configurations, the striker pin arresting chamber is a two-level cavity, having a first level chamber for receiving a bottom portion of the striker pin at the safe position, and a second level chamber, shallower than said first level chamber and configured for receiving a bottom portion of the striker pin at a launch position.In some configurations, the striker pin arresting chamber is crescent-shaped.The invention further provides a fuze arrangement comprising a housing connectable at a fore end of a projectile, wherein a cap assembly is provided at a top end of the housing and comprising a cap with a shaft extending therefrom along a longitudinal axis; said cap assembly being axially displaceable between a closed position at which it bears over the housing, and an open position at which it axially shifts from the top end, and an air velocity sensor provided below said cap and configured for determining an air velocity threshold;a striker pin coaxially aligned with the shaft and having a top portion slidingly engaged with a bottom end of the shaft, with a bottom striker tip, and a laterally projecting arresting shoulder intermediate to said top portion and the striker tip;a rotor assembly comprising a rotor rotatable within the housing about a rotor axis offset of said longitudinal axis, and having a striker pin arresting chamber blocked at its bottom and formed with a striker pin arresting bracket (or cavity) for selective arresting the arresting shoulder of the striker pin, and a throughgoing detonator cavity angularly offset from said chamber and configured for accommodating a detonator explosive; anda timer mechanism articulated with the rotor and configurable for timed rotation thereof;wherein the fuze is configurable between a safe position at which the striker pin is received within the striker pin arresting chamber; a launch position initiated upon sensing launch inertia forces, upon which the striker pin axially displaces upwardly and the rotor is released to rotate about a rotor axis, wherein when an air velocity remains within a predetermined time period under a predetermined air velocity threshold, the striker pin arresting shoulder irreversibly locks within the striker pin arresting bracket, or wherein when the air velocity meets the predetermined air velocity threshold within the predetermined time period a flight position is initiated, whereupon the striker tip axially withdraws from the striker pin arresting chamber, facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator, wherein the fuze is armed.In some configurations, at a safe position of the fuze, the cap assembly is disposed at a normally closed position and is optionally biased by a preloaded spring into the open position.In some configurations, the fuze is configurable between a safe position at which the striker pin is received within the striker pin arresting chamber; a launch position initiated upon sensing launch inertia forces, upon which the striker pin axially displaces upwardly and the rotor is released to rotate about a rotor axis, wherein when an air velocity remains within a predetermined time period under a predetermined air velocity threshold, the striker pin arresting shoulder irreversibly locks within the striker pin arresting bracket, or wherein when the air velocity meets the predetermined air velocity threshold within the predetermined time period a flight position is initiated, whereupon the striker tip axially withdraws from the striker pin arresting chamber, facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator, wherein the fuze is armed.In some configurations, the launch inertia forces are greater than a predetermined inertia threshold characteristic of a projectile flight g-force.In some configurations, the flight g-force is at least 600 G, in a direction opposite to a direction of flight.In some configurations, the projectile air velocity is greater than a predetermined air velocity threshold characteristic of a projectile flight velocity.In some configurations, the air velocity threshold is 50 m/sec.In some configurations, the timer mechanism is articulated with the rotor and configurable for timed rotation thereof.In some configurations, the timer mechanism is configured to measure or time a time difference between an inertia threshold criterium and an air velocity threshold criterium, such that a time difference resulting in the arming of the fuze does not exceed a preset time threshold characteristic of a projectile firing.In some configurations, the time difference defines a time threshold being less than 1 second.In some configurations, the timer mechanism comprises a cogwheel portion at a top portion of the rotor, which is configured to revolve back and forth in a time interval that is determined on the cogwheel dimension and structure and on a timekeeping element that engages the cogwheel.In some configurations, the fuze is configurable between a safe position at which the striker pin is received within the striker pin arresting chamber; a launch position initiated upon sensing launch inertia forces of at least 600 g for at least 1 to 5 milliseconds, upon which the striker pin axially displaces upwardly and the rotor is released to rotate about a rotor axis, wherein when an air velocity remains within a predetermined time period under a projectile air velocity of 50 m/sec, the striker pin arresting shoulder irreversibly locks within the striker pin arresting bracket, or wherein when the air velocity is greater than 50 m/sec within the predetermined time period- a flight position is initiated, whereupon the striker tip axially withdraws from the striker pin arresting chamber, facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator, wherein the fuze is armed.In some configurations, the fuze is provided with a cap assembly at a top end of the housing and comprising a cap with the shaft extending therefrom along a longitudinal axis, the cap assembly further provided with one or more restraining pins or arresting pins to prevent the air velocity sensor from rotating when launch inertia forces have not exceeded a predetermined inertia threshold.

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Fig. 1 illustrates a projectile fitted with a fuze according to some embodiments of the present disclosure.

Fig. 2 is an enlarged view of a fuze according to some embodiments of the present disclosure. Figs. 3A-Bprovide enlarged views: Fig. 3Ais an enlarged view of a striker pin sub-assembly, as depicted in the fuze of Fig. 2. Fig. 3Bis an enlarged view of a striker pin and a rotor sub-assembly, as depicted in the fuze of Fig. 2. Figs. 4A-Fprovide: Fig. 4Ais an isometric view of a rotor used with a fuze of the present disclosure; Fig. 4Bis a planar top view, partially sectioned, of the rotor of Fig. 4A; Fig. 4Cis a vertical section along line C - C depicted in Fig. 4B; Fig. 4Dis a vertical section along line D-D depicted in Fig. 4B; Fig. 4Eis a vertical section along line E - E depicted in Fig. 4B;and Fig. 4Fis a vertical section along line F - F depicted in Fig. 4B. Figs. 5A-Dillustrate the fuze of Fig. 2at different operative positions thereof.

DETAILED DESCRIPTION OF EMBODIMENTS Reference is now made to the Figures in which certain non-limiting embodiments are exemplified. As generally stated, the present disclosure provides a unique multi-safety fuze systems which ensure arming of a projectile only when two or more mutually independent physical criteria are met within an extremely short predetermined period of time. Unlike multi-safety fuze systems of the art, the safety mechanism unique to the present disclosure ensures arming of the fuze only when proper flight conditions are met immediately following launch inertial forces are determined. Thus, arming of the projectile may occur in close proximity and immediately following launch. The safety mechanism avoids detonation or arming in case of accidental drop or under non-launch conditions.In comparison, in a fuze arrangement disclosed in publication [1 ], the multi-safety arrangement does not ensure arming only when the mutually independent physical criteria are met within an extremely short predetermined period of time, but rather the projectile is armed when inertial forces are detected and after a certain time has passed. Fig. 1illustrates a projectile fitted with a fuze according to some embodiments of the present disclosure. A fuze 10is fitted in a projectile 100.The fuze 10comprising a housing 12connectable at a fore end 102of the projectile 100.A cap assembly 14at a top end 16of the housing 12comprises a cap 18with a shaft 22extending therefrom along a longitudinal axis 24.The cap assembly 14is further detailed in Fig. 2.The cap assembly 14is axially displaceable between a closed position (as depicted in Fig. 5A)at which it bears over the housing 12,and an open position at which it axially shifts from the top end (as depicted in Fig. 5Band 5C),and an air velocity sensor 26,e.g., in a form of a turbine or an impeller, below said cap for determining an air speed threshold.In some cases, the housing 12is screw couplable at a front end 102of the projectile 100. A striker pin 30 is provided coaxial with the shaft 22 and has a top portion slidingly engaged with a bottom end 34 of the shaft 22, with a bottom striker tip 36, and a laterally projecting arresting shoulder 38depicted in Figs. 2, 3Aand 3B.The arresting shoulder 38 is intermediate (not necessarily provided midlength) to the top portion 32 and the striker tip 36. The striker pin 32 may be axially displaceable with respect to the shaft 22.A rotor assembly 44is depicted in Fig. 1, Fig. 2, Fig. 3B, Figs. 5A-D,and specifically in Figs. 4A-F.As depicted, the rotor assembly 44comprises a rotor 48 rotatable within the housing 12 about a rotor axis 50 offset of the longitudinal axis 24, as illustrated in Figs. 3and 4.The rotor 48having a striker pin arresting chamber 54blocked at its bottom and formed with a striker pin arresting bracket 56 for selective locking or arresting the arresting shoulder 38 of the striker pin 30. A throughgoing detonator cavity is angularly offset from said chamber 54 and is configured for accommodating a detonator explosive 62shown in Figs. 5B-D. A timer mechanism 70is shown in Fig 2.The timer mechanism is articulated with the rotor 48and configurable for timed rotation of the rotor. The timer mechanism 70is a mechanical timer, which may be of any form. In some cases it may include or may be a cogwheel element (not shown) at a top portion of the rotor 48.A transferring charge 74may be disposed in a detonator chamber 76of the housing, coaxially below the rotor striker pin 30.A booster charge 76may be disposed in the hosing below the transferring charge 74and received within a booster container 78. The booster container projects from a bottom end of the housing 12,as depicted in Figs. 5A-D.As illustrated in Figs. 5A-D,fuze 10is configurable between a safe position at which the striker pin 30 is received within striker pin arresting chamber 54 (Fig. 5A);a launch position initiated upon sensing launch inertia forces, upon which the striker pin axially displaces upwardly and the rotor is released to rotate about a rotor axis, wherein when an air velocity remains within a predetermined time period under a predetermined air velocity threshold, the striker pin arresting shoulder irreversibly locks within the striker pin arresting bracket (Fig. 5B),or wherein when the air velocity meets the predetermined air velocity threshold within the predetermined time period a flight position is initiated, whereupon the striker tip axially withdraws from the striker pin arresting chamber (Fig. 5C),facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator, as shown in Fig. 5D. An air velocity sensor 26 is provided in the cap assembly 14. In some cases it may be an impeller. The air velocity sensor 26 may be received within an air pressure sensor chamber 27 provided in the cap assembly. At the open position of the cap assembly, the cap 18 axially displaces to expose the air velocity sensor 26 to ambient air pressure. At the closed position, the cap assembly 14 sealingly conceals the pressure sensor chamber 27. The cap assembly 18 may be biased by a preloaded spring 21 into an open or a closed position.The striker pin arresting chamber 54,depicted in Fig. 3B,is a two-level cavity, having a first level chamber 82 for receiving a bottom portion of the striker pin 30 at the safe position, and a second level chamber 84, shallower than said first level chamber and configured for receiving a bottom portion of the striker pin 30 at a launch position. In some cases, the striker pin arresting chamber 54is crescent-shaped as illustrated in Figs. 4A-B. As further depicted in the figures, the cap assembly 14 is provided with one or more restraining pins or arresting pins 95Aand 95B.As depicted in the figures, two pins are positioned to the sides of the shaft 22 and provide an additional securing means to avoid accidental or unintentional rotation of the air velocity sensor 26 at any time prior to launch, whereupon inertia forces increase above a predetermined inertia threshold and cause the cap assembly from displacing into the open position, and the striker pin from axially displacing upwardly. The pins are positioned to avoid manual rotation of the sensor when the projectile is stationary or when the projectile is handled or moved.

Claims (33)

1. - 16-

2. CLAIMS: 1. A fuze for a projectile, the fuze comprising a striker pin coaxially positioned with respect to a shaft of said fuze and having a top portion slidingly engaging with a bottom end of the shaft, a bottom striker tip, and a laterally projecting arresting shoulder intermediating said top portion and the striker tip; a rotor assembly comprising a rotatable rotor and having a striker pin arresting chamber blocked at its bottom and formed with a striker pin arresting bracket or groove for selective arresting the arresting shoulder of the striker pin, and a throughgoing detonator cavity angularly offset from said arresting chamber for accommodating a detonator explosive; and a timer mechanism articulated with the rotor and configurable for timed rotation thereof. 2. The fuze according to claim 1, provided in a housing configured to be connectable at a fore end of the projectile.

3. The fuze according to claim 2, wherein the housing forms an integral part of the projectile body.

4. The fuze according to claim 2, wherein the housing is screw couplable at a front end of the projectile.

5. The fuze according to any one of the preceding claims, provided with a cap assembly at a top end of the housing and comprising a cap with the shaft extending therefrom along a longitudinal axis.

6. The fuze according to claim 5, wherein the cap assembly is axially displaceable between a closed position at which it bears over the housing, and an open position at which it axially shifts from the top end.

7. The fuze according to claim 5 or 6, wherein an air velocity sensor is provided below said cap and is configurable and operable for determining or measuring an air velocity threshold.

8. The fuze according to claim 7, wherein the air velocity sensor is received within an air pressure sensor chamber.

9. The fuze according to any one of claims 6 to 8, wherein at the open position the cap axially displaces to expose the air velocity sensor to ambient air pressure and at the closed position, the cap assembly sealingly conceals the pressure sensor chamber.

10. The fuze according to any one of claims 7 to 9, wherein the air velocity sensor is received within an air pressure sensor chamber. - 17-

11. The fuze according to claim 10, wherein the air velocity sensor is a revolvable element arranged to be driven by displacement of air during projectile flight to generate torque required for withdrawal of the striker pin.

12. The fuze according to claim 11, wherein the revolvable element is a turbine or an impeller.

13. The fuze according to claim 11 or 12, wherein revolution of the element at a speed corresponding to the projectile’s air velocity exceeding a preset threshold, causes axial withdrawal of the striker tip from the striker pin arresting chamber.

14. The fuze according to any one of the preceding claims, wherein the rotor is rotatable within the housing about a rotor axis that is offset of the shaft or fuze longitudinal axis.

15. The fuze according to any one of claims 1 to 14, comprising a detonator disposed in a detonator chamber of the housing, and is positioned coaxially below the striker pin.

16. The fuze according to any one of the preceding claims, comprising a booster charge disposed in the hosing below the detonator and received within a booster container.

17. The fuze according to claim 1, the fuze comprisinga striker pin coaxially positioned with respect to a shaft of said fuze and having a top portion slidingly engaging with a bottom end of the shaft, with a bottom striker tip, and a laterally projecting arresting shoulder intermediating said top portion and the striker tip;a rotor assembly comprising a rotatable rotor and having a striker pin arresting chamber blocked at its bottom and formed with a striker pin arresting bracket for selective arresting or locking (irreversibly) the arresting shoulder of the striker pin, and a thoroughgoing detonator cavity angularly offset from said arresting chamber for accommodating a detonator explosive; anda timer mechanism articulated with the rotor and configurable for timed rotation thereof;wherein the fuze is configurable between a safe position at which the striker pin is received within the striker pin arresting chamber; a launch position initiated upon sensing launch inertia forces, upon which the striker pin axially displaces upwardly and the rotor is released to rotate about a rotor axis, wherein when an air velocity remains within a predetermined time period under a predetermined air velocity threshold, the - 18- striker pin arresting shoulder irreversibly locks within the striker pin arresting bracket, or wherein when the air velocity meets the predetermined air velocity threshold within the predetermined time period a flight position is initiated, whereupon the striker tip axially withdraws from the striker pin arresting chamber, facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator, wherein the fuze is armed.

18. The fuze according to any one of the preceding claims, wherein the striker pin arresting chamber is a two-level cavity, having a first level chamber for receiving a bottom portion of the striker pin at the safe position, and a second level chamber, shallower than said first level chamber and configured for receiving a bottom portion of the striker pin at a launch position.

19. The fuze according to claim 18, wherein the striker pin arresting chamber is crescent-shaped.

20. A fuze arrangement comprising a housing connectable at a fore end of a projectile, wherein a cap assembly is provided at a top end of the housing and comprising a cap with a shaft extending therefrom along a longitudinal axis; said cap assembly being axially displaceable between a closed position at which it bears over the housing, and an open position at which it axially shifts from the top end, and an air velocity sensor provided below said cap and configured for determining an air velocity threshold;a striker pin coaxially aligned with the shaft and having a top portion slidingly engaged with a bottom end of the shaft, with a bottom striker tip, and a laterally projecting arresting shoulder intermediate to said top portion and the striker tip;a rotor assembly comprising a rotor rotatable within the housing about a rotor axis offset of said longitudinal axis, and having a striker pin arresting chamber blocked at its bottom and formed with a striker pin arresting bracket (or cavity) for selective arresting the arresting shoulder of the striker pin, and a throughgoing detonator cavity angularly offset from said chamber and configured for accommodating a detonator explosive; anda timer mechanism articulated with the rotor and configurable for timed rotation thereof;wherein the fuze is configurable between a safe position at which the striker pin is received within the striker pin arresting chamber; a launch position initiated upon sensing launch inertia forces, upon which the striker pin axially displaces upwardly and the rotor is released to rotate about a rotor axis, wherein when an air velocity remains - 19- within a predetermined time period under a predetermined air velocity threshold, the striker pin arresting shoulder irreversibly locks within the striker pin arresting bracket, or wherein when the air velocity meets the predetermined air velocity threshold within the predetermined time period a flight position is initiated, whereupon the striker tip axially withdraws from the striker pin arresting chamber, facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator, wherein the fuze is armed.

21. The fuze according to any one of claims 1 to 19 or a fuze arrangement according to claim 20, wherein at a safe position of the fuze, the cap assembly is disposed at a normally closed position and is optionally biased by a preloaded spring into the open position.

22. The fuze according to any one of claims 1 to 16, configurable between a safe position at which the striker pin is received within the striker pin arresting chamber; a launch position initiated upon sensing launch inertia forces, upon which the striker pin axially displaces upwardly and the rotor is released to rotate about a rotor axis, wherein when an air velocity remains within a predetermined time period under a predetermined air velocity threshold, the striker pin arresting shoulder irreversibly locks within the striker pin arresting bracket, or wherein when the air velocity meets the predetermined air velocity threshold within the predetermined time period a flight position is initiated, whereupon the striker tip axially withdraws from the striker pin arresting chamber, facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator, wherein the fuze is armed.

23. The fuze according to claim 22, wherein the launch inertia forces are greater than a predetermined inertia threshold characteristic of a projectile flight g-force.

24. The fuze according to claim 23, wherein the flight g-force is at least 600 G, in a direction opposite to a direction of flight.

25. The fuze according to claim 22, wherein the projectile air velocity is greater than a predetermined air velocity threshold characteristic of a projectile flight velocity.

26. The fuze according to claim 25, wherein the air velocity threshold is 50 m/sec.

27. The fuze according to any one of the preceding claims, wherein the timer mechanism is articulated with the rotor and configurable for timed rotation thereof. -20-

28. The fuze according to claim 27, wherein the timer mechanism is configured to measure or time a time difference between an inertia threshold criterium and an air velocity threshold criterium, such that a time difference resulting in the arming of the fuze does not exceed a preset time threshold characteristic of a projectile firing.

29. The fuze according to claim 28, wherein the time difference defines a time threshold being less than 1 second.

30. The fuze according to claim 28 or 29, wherein the timer mechanism comprises a cogwheel portion at a top portion of the rotor, which is configured to revolve back and forth in a time interval that is determined on the cogwheel dimension and structure and on a timekeeping element that engages the cogwheel.

31. The fuze according to any one of claims 1 to 16, configurable between a safe position at which the striker pin is received within the striker pin arresting chamber; a launch position initiated upon sensing launch inertia forces of at least 600 g for at least to 5 milliseconds, upon which the striker pin axially displaces upwardly and the rotor is released to rotate about a rotor axis, wherein when an air velocity remains within a predetermined time period under a projectile air velocity of 50 m/sec, the striker pin arresting shoulder irreversibly locks within the striker pin arresting bracket, or wherein when the air velocity is greater than 50 m/sec within the predetermined time period- a flight position is initiated, whereupon the striker tip axially withdraws from the striker pin arresting chamber, facilitating rotation of the rotor at a speed or rate preset by the timer mechanism to a position at which the striker pin is disposed coaxially above a detonator, wherein the fuze is armed.

32. The fuze according to any one of the preceding claims, provided with a cap assembly at a top end of the housing and comprising a cap with the shaft extending therefrom along a longitudinal axis, the cap assembly further provided with one or more restraining pins or arresting pins to prevent the air velocity sensor from rotating when launch inertia forces have not exceeded a predetermined inertia threshold.

33. A projectile implementing a fuze according to any one of claims 1 to 32.