Ammunition and explosives – Igniting devices and systems – Arming devices
Reexamination Certificate
2002-09-25
2003-08-12
Carone, Michael J. (Department: 3641)
Ammunition and explosives
Igniting devices and systems
Arming devices
C102S221000, C102S236000, C102S247000, C102S222000
Reexamination Certificate
active
06604467
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a safety system particularly for a small arms projectile for a small arms weapon.
BRIEF DESCRIPTION OF THE PRIOR ART
In our European Patent EP-B-0363079 there is described a small arms projectile for a smooth bore weapon preferably fired from a cartridge with a propellant charge therein, wherein the projectile comprises a generally cylindrical casing, a warhead assembly, said warhead being hollow to accommodate an explosive charge and an initiator therefor, the casing being formed with a firing pin spring biased to a safety position and locked in the safety position by at least one spring biased safety pin, wherein the spring biased safety pin is adapted to release on exit of the projectile from the muzzle of the small arm weapon.
EP-B-0363079 thus describes a projectile having a mechanical safety means for retaining the firing pin in the safety position. The mechanical safety means comprises at least one spring biased safety pin extending normal to the axis of the firing pin and located in a radial bore in the firing pin to prevent axial movement of the firing pin. The safety pin is radially retained by the cartridge.
There is a drawback associated with this arrangement. When the projectile leaves the muzzle of the small arms weapon there is a severe deceleration as it hits still air and this causes the projectile casing to decelerate and a deceleration force to be applied to the firing pin in the direction of the initiator. The shear force applied to the safety pin by the deceleration between the casing and the firing pin prevents ejection of the safety pin until the shear force is overcome by the spring biassing force acting on the pin. The firing pin is thus retained in its safety position by the safety pin. Only when the shear force has reduced will the safety pin release the firing pin. The effect of this is to delay the arming of the projectile by at least 0.1 seconds (or about 10 metres), or more reliably 0.2 to 0.3 seconds, which equates generally to about 20 or 30 metres down range. This means that targets at short range cannot be engaged and even targets of 25 to 30 metres cannot always be engaged reliably.
A further drawback with this arrangement is that there is only one safety means for retaining the firing pin in the safety position. There is a possibility therefore that the explosive charge could be initiated accidentally if the safety pin became dislodged from the firing pin due to the cartridge being damaged, for example.
In order to address these problems EP-B-0363079 suggests the use of a chemical safety means in addition to the mechanical safety means. The chemical safety means includes a layer of combustible adhesive material interposed between the firing pin and an adjacent hollow portion of the casing. The combustible adhesive material is connected to a bore at the rear of the casing adjacent a propellant charge so that it is activated by the explosion of the propellant charge when the projectile is fired.
In this arrangement the combustible adhesive material retains the firing pin in its safe position for a pre-determined period once the projectile has been fired. This prevents any shear forces being generated between the firing pin and the safety pin as the projectile decelerates on hitting still air. In this way ejection of the safety pin occurs immediately the projectile leaves the muzzle of the small arm. The time taken for the combustible adhesive material to release the firing pin and thus arm the projectile is determined by the characteristics of the combustible adhesive material.
A problem with this arrangement is that the combustible adhesive material may deteriorate and become unstable if stored for a prolonged period, particularly if the adhesive is in any way defective. This is a major drawback if a long shelf life is required as is usual for ammunition.
A further problem associated with this arrangement is that manufacturing constraints can result in the combustible adhesive material being insufficiently reliable to ensure that any delay in arming equates to about 3 metres from the user when the projectile is fired.
It is known, e.g. from FR-A-0 424 890, U.S. Pat. Nos. 2,537,855 and 2,564,797, that wholly mechanical contrivances can be used to effect safety latching of firing pins in projectile fuses, and that a firing pins can be used, whilst so latched, to hold an initiator in a safe condition, against forces urging it into an armed condition. None of these prior specifications, however, envisages the provision of increased safety in handling and in use, by means of plural, independently active mechanical safety latches which are designed and configured to be triggered in response to different events in the firing process.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a small arms projectile which has a safety means for retaining a firing pin in a safety position prior to firing and releasing the firing pin on application of acceleration forces consequent upon firing.
Another object of the present invention is to provide a small arms projectile which has at least two mechanically independent safety means for retaining a firing pin in a safety position prior to firing.
Another object of the present invention is to provide a small arms projectile which has a safety means for retaining a firing pin in a safety position prior to firing which operates to delay the arming of the projectile on firing in a more reliable manner than hitherto known safety means.
According to an aspect of the present invention there is provided a small arms projectile for a small arms weapon; the projectile comprising:
a generally tubular casing having an axially movable firing pin;
a compression spring providing a resilient force;
a warhead having an explosive charge; and
an initiator having safe and armed conditions and capable, when in its armed condition and when impacted with sufficient force by the firing pin, of detonating the explosive charge of said warhead;
wherein the casing also contains safety release means for releasably restraining the firing pin, against resilient force which tends to move the firing pin away from the initiator, in a safety position whereby said initiator is held by engagement with the firing pin in its safe condition, against an arming force tending to urge the initiator towards the armed condition;
wherein the safety release means comprise first and second mechanical means;
wherein said first mechanical means includes at least one component constructed to be frangible in response to the forces experienced on firing of the projectile, the strength of the frangible element being sufficient to withstand acceleration forces up to 500 g; and
wherein said second mechanical means includes at least one component disposed and configured so as to be ejected from the casing under the influence of said resilient force when the projectile leaves the weapon permitting said resilient force to move said firing pin away from said initiator to an extent allowing said initiator to be urged into its armed condition.
Accordingly, the initiator is movable between an unarmed position and a biased armed position, but is retained in the unarmed position by engagement with the firing pin in the safety position. In this way the initiator can not be armed until the firing pin is moved from the safety position and disengaged from the initiator.
It will be understood that the abbreviation “g” used herein represents the acceleration due to gravity. Typically a small arm projectile will experience an acceleration of between 10,000 g and 15,000 g when fired in the chamber of a small arms weapon. The safety release means retains the firing pin in the safety position on application of acceleration forces less than 500 g to prevent accidental arming of the projectile prior to firing. In this way the releasable safety means will protect the user if the projectile is accidentally dropped during handling since the acceleration forces applied to the projectile will generally be les
Alculumbre Michael
Sharp Frederick
Laubscher, Jr. Lawrence E.
Semunegus Lulit
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