Firing pin assembly for a warhead detonator

A firing pin assembly for mechanically igniting a warhead detonator of a projectile by being accelerated in a forward direction by inertia upon impact, includes a firing pin having a rearward firing pin part and a frontal firing pin part arranged in series with the rearward firing pin part as viewed in the forward direction. The assembly further has a firing pin spring urging the firing pin in a direction opposite to the forward direction, and a mechanical device positioned between the rearward firing pin part and the frontal firing pin part. The mechanical device includes a transmission arrangement for transmitting a forward motion of the rearward firing pin part to the frontal firing pin part with a stepped up transmission ratio whereby a forward motion of the rearward firing pin part through a first distance results in a forward motion of the frontal firing pin part, against the force of the firing pin spring, through a second distance which is greater than the first distance.

CROSS REFERENCE TO RELATED APPLICATION
 This application claims the priority of German Application No. 198 48 356.2
 filed Oct. 21, 1998, which is incorporated herein by reference.
 BACKGROUND OF THE INVENTION
 This invention relates to a firing pin for mechanically igniting a warhead
 detonator situated in the bottom region of the projectile carrying the
 warhead. The firing pin is mechanically guided in a firing pin housing.
 The purpose of detonators is to ignite (detonate) the explosive of the
 warhead of a projectile or an explosive charge at the target or at a
 desired moment. Detonators of the mechanical type are provided with a
 firing pin to initiate the detonation.
 A firing pin of the above-outlined type is disclosed in German
 Offenlegungsschrift (application published without examination) No. 38 35
 888. The firing pin is integrated in a mechanical bottom detonator. As the
 projectile hits the target, the firing pin is, by inertia, accelerated
 forward against the force of a firing pin spring into a detonator charge
 causing ignition thereof to thus ignite a hollow charge of the projectile.
 It is a disadvantage of such a prior art arrangement that the mechanical
 bottom detonator may be used only in projectiles of low impact speed and
 thus short range because the response time of the firing pin after impact
 of the projectile is excessively long for igniting the hollow charge.
 Therefore, a mechanical detonator cannot be used as a bottom detonator for
 hollow charge projectiles and thus for projectiles of greater muzzle and
 traveling velocity. Therefore, an electric bottom detonator has been
 conventionally used to ensure a very short response time in
 high-performance projectiles. Such an electric bottom detonator, however,
 is more complex and more expensive than mechanical bottom detonators.
 SUMMARY OF THE INVENTION
 It is an object of the invention to provide an improved mechanical
 detonator which may be used in projectiles of high impact velocity
 requiring short response times.
 This object and others to become apparent as the specification progresses,
 are accomplished by the invention, according to which, briefly stated, the
 firing pin assembly for mechanically igniting a warhead detonator of a
 projectile by being accelerated in a forward direction by inertia upon
 impact, includes a firing pin having a rearward firing pin part and a
 frontal firing pin part arranged in series with the rearward firing pin
 part as viewed in the forward direction. The assembly further has a firing
 pin spring urging the firing pin in a direction opposite the forward
 direction, and a mechanical device positioned between the rearward firing
 pin part and the frontal firing pin part. The mechanical device includes a
 transmission arrangement for transmitting a forward motion of the rearward
 firing pin part to the frontal firing pin part with a stepped-up
 transmission ratio whereby a forward motion of the rearward firing pin
 part through a first distance results in a forward motion of the frontal
 firing pin part, against the force of the firing pin spring, through a
 second distance which is greater than the first distance.
 The invention is based on the principle to significantly reduce the
 response time between impact and detonation by dividing the firing pin of
 the mechanical detonator into several parts and placing a step-up
 mechanism between the divided parts. As a result, even at higher speed,
 the time lapse from the moment of impact of the projectile to the moment
 of detonation is sufficiently short. The divided firing pin preferably is
 composed of two parts which are spaced from, and mechanically coupled to,
 one another preferably by three balls.

DESCRIPTION OF THE PREFERRED EMBODIMENT
 FIG. 1 shows a grenade projectile 10 whose rear portion is secured in a
 propellant case 11. The grenade projectile 10 which may have a caliber of,
 for example, 40 mm, is a three-part structure, composed of a particularly
 structured frontal stand-off cap 12, a mid part formed of a projectile
 sleeve 13 and a rearward detonator housing 14 which accommodates the
 firing pin 20 structured according to the invention.
 The propellant case 11 defines a central bottom cavity 15 which receives a
 propellant charge 16 for accelerating the grenade projectile 10.
 The frontal part of the projectile comprises the warhead which, in addition
 to the pre-fragmented projectile sleeve 13, includes an explosive charge
 17, a hollow charge 18 and the frontal cap 12. The hollow charge 18 is
 preferably of trumpet shape for increasing its effectiveness in the target
 area, that is, in the region of its central cone tip 19, the opening angle
 of the hollow charge 18 is the smallest and it gradually increases
 forwardly. To ensure a minimum distance (stand-off) of the hollow charge
 18 from an armor plate representing the target and to provide for a secure
 support of the hollow charge 18 and the explosive charge 17, the cap 12
 has, at least internally, a specially downstepped shape in the forward
 direction. As a result, a deformation of the cap 12 may occur only in the
 frontal hollow hemispherical portion thereof, so that the rearward,
 form-stable, essentially cylindrical part of the cap 12 ensures at all
 times a minimum ignition distance for an optimal jet formation of the
 hollow charge 18.
 The firing pin 20 according to the invention is arranged in the rearward
 detonator housing 14 and will be described in further detail in
 conjunction with FIGS. 2a and 2b.
 The firing pin 20 according to the invention is composed preferably of a
 frontal firing pin part 20.1 and a rearward firing pin part 20.2 spaced
 from the part 20.1. The two firing pin parts 20.1 and 20.2 are held and
 guided mechanically in a bore 22 of a firing pin housing 21. Both firing
 pin parts 20.1 and 20.2 are preferably cylindrical and are spaced from one
 another by mechanical means 24, for example, by three balls 24 (only two
 balls are visible). The frontal firing pin part 20.1 has a firing pin tip
 20.11 and a guiding region 20.12 adjoined by a socket region 20.13. A
 firing pin spring 23 positioned about the guide region 20.12 engages with
 one end a collar of the socket region 20.3 and is held at its other end by
 a shoulder 21.1 of the firing pin housing 21. The socket 20.13 has a
 frustoconical outer face 20.131 having a forwardly open cone angle .beta..
 The frustoconical outer face 20.131 supports preferably three
 circumferentially uniformly distributed balls 24 between the firing pin
 parts 20.1 and 20.2. The rearward firing pin part 20.2 has a greater outer
 diameter than the frontal firing pin part 20.1. The housing 21 has, in the
 region between the rearward firing pin part 20.2 and the frontal firing
 pin part 20.1, that is, in the region in which the balls 24 are arranged,
 a funnel-shaped (frustoconical) surface 21.2 which tapers forwardly at a
 cone angle a. The length of the surface 21.2 depends from the length of
 surface 20.131 of the frontal firing pin part 20.1. In the zone of the
 firing pin tip 20.11 the housing 21 has an inner stepped-down frontal
 terminal portion bordered by the inner shoulder 21.1 which, as noted
 before, counter supports the firing pin spring 23.
 As the grenade projectile 10 impacts on the intended target, the rearward
 firing pin part 20.2 is pressed by inertia against the balls 24 which
 then, together with the rearward firing pin part 20.2 move in the
 direction of the frontal firing pin part 20.1 as shown in FIG. 2b. During
 this occurrence, the balls 24 run on the tapered (oblique) faces 21.2 of
 the housing 21 and the tapered (oblique) faces 20.131 of the socket 20.13
 and press the socket part 20.13 by camming action forward, thus pushing
 the frontal firing pin part 20.1 against the force of the firing pin
 spring 23 outwardly of the housing 21. The balls 24, in cooperation with
 the oblique surfaces 21.2 and 20.131 produce an upstepped mechanical
 transmission ratio which affects the response time (that is, the delay of
 detonation from the moment of impact on the target). The frontal firing
 pin part 20.1 with its firing pin tip 20.11 is accelerated and penetrates
 in a known manner into a non-illustrated detonator charge whereby an
 ignition is effected. The formation of an undisturbed hollow charge beam
 and an optimal splintering effect occur in a known manner. Also, the
 explosive charge 17 is ignited which, in turn, accelerates the copper
 particles of the hollow charge 18. The copper particles form, in a known
 manner, a hollow charge "jet" which pierces the target and thus penetrates
 the same.
 It has been found in practice that the selection of the angle
 .alpha.=.beta.=90.degree. provides for a transmission ratio of 1:1.58,
 whereby a secure and rapid detonation may be achieved. Stated differently,
 the time it takes for the rearward firing pin part 20.2 to travel a
 distance of 1 mm, the frontal firing pin part 20.1 is displaced 1.58 mm.
 It is, however, feasible to select the angles .alpha. and .beta. in an
 angular range between 80.degree. and 120.degree.. It will be understood
 that an angle greater than 90.degree. results in a greater transmission
 ratio whereas a flatter angle (less than 90.degree.) provides for a
 smaller transmission ratio. The smaller transmission ratios have the
 advantage that a secure detonation is achieved but have the disadvantage
 of a larger reaction time, while the converse result is achieved for large
 transmission ratios.
 The firing pin 20 according to the invention provides that mechanical
 bottom detonators may be used in faster and thus longer-range hollow
 charge grenade projectiles 10 than it has possible heretofore.
 The above-described exemplary arrangement according to the invention may be
 modified, for example, in that the firing pin 20 may be divided into three
 or more parts in case an even more rapid reaction time is required. In
 such a case force-transmitting spacer balls 24 are positioned between each
 adjoining firing pin parts. Also, the divided firing pin 20 may be
 directly integrated into the projectile detonator without the provision of
 a firing needle housing 21. The firing needle parts 20.1 and 20.2 may be
 of polygonal cross-sectional shape; in such a case the firing pin housing
 21 has no bore hole but an inner configuration which conforms to the
 peripheral outline of the firing pin parts 20.1 and 20.2.
 It will be understood that the above description of the present invention
 is susceptible to various modifications, changes and adaptations, and the
 same are intended to be comprehended within the meaning and range of
 equivalents of the appended claims.