Fuze mechanism for a munition

Details Fuze mechanism for a munition Fuze mechanism for a munition

2001-06-13

2003-03-11

Carone, Michael J. (Department: 3641)

Ammunition and explosives

Igniting devices and systems

Arming devices

C102S254000, C102S251000, C102S244000, C102S235000, C102S229000

Reexamination Certificate

active

06530324

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to munitions, and more particularly to a fuze for a munitions such as a grenades adapted to be deployed from mortars, artillery and rockets, and more specifically to a fuze mechanism having a construction adapted to ensure detonation once the mechanism is armed.
2. Discussion
Fuze mechanisms are used in a variety of military applications in connection with grenades deployed from mortars, artillery and rockets. A typical arming mechanism for such a grenade is shown in
FIGS. 1 and 2
. This arming mechanism of the fuze
10
includes a fuze housing
11
having an arming screw
12
. The fuze housing
11
is secured to a grenade
32
. The arming screw
12
has a threaded portion
14
, which is engaged with a threaded opening
16
a
in an inertia weight
16
. When in the unarmed state shown in
FIG. 1
, the firing pin tip
18
of the arming screw
12
rests within a bore
20
formed within a slide member
22
. The slide member
22
is biased by a biasing spring
24
to the right in the direction of the drawing of FIG.
1
. In the unarmed state, the firing pin tip
18
of the arming screw
12
located inside the bore
20
of the slide member
22
holds the slide member
22
in the unarmed and safe position shown in FIG.
1
. Thus, the firing pin tip
18
is not able to engage a stab detonator
26
disposed in a recess
26
a
at the left end of the slide member
22
shown in
FIG. 1
, until the arming action of unthreading the arming screw threads
14
and the weight threads
16
a
occurs.
When the grenade is deployed, such as through a mortar shell, an artillery shell or a rocket payload, as the grenade falls to Earth, a drag ribbon
30
secured to the arming screw
12
unfurls and begins to vibrate and rotate. These drag induced dynamic movements of the drag ribbon
30
unthread the arming screw threads
14
from the weight threads
16
a
such that the firing pin tip
18
is withdrawn from the bore
20
in the slide member
22
. The said movements are illustrated in FIG.
3
. Upon release, the slide member
22
is urged to the right by the biasing force of the biasing spring
24
, as also shown in the drawing of FIG.
3
. This motion aligns the stab detonator
26
with the firing pin tip
18
of the arming screw
12
. In addition to initiating the arming mechanism, the unfurled drag ribbon
30
also orients the grenade
32
during the grenade
32
descent phase of the deployed cargo flight. During deployed flight, the drag ribbon
30
, lifts upward on the grenade
32
causing the grenade base
32
a
to be aimed at the surface of the ground
36
or target. When the base
32
a
of the grenade
32
strikes the ground surface
36
with the slide member
22
in the deployed and armed position, the inertial motions of the combination of the weight
16
and the arming screw
12
cause the arming screw
12
firing pin tip
18
to be driven into the stab detonator
26
, thereby initiating the stab detonator
26
and functioning the grenade
32
.
Owing to in flight oscillations of the drag ribbon
30
and the grenade
32
combined with irregularities in the ground surface
36
, the grenade
32
may impact the ground surface
36
in a plurality of attitudes. It has been recently discovered that for a discrete population of the family of impacts, that the arming and firing mechanism is subject to failure. The fault mechanism and envelope can be characterized in the drawings of
FIGS. 3 and 4
. When the grenade base
32
a
of the grenade
32
contacts the ground surface
36
or target at small angles, as shown in
FIG. 4
, the fuze
10
can be momentarily disarmed. More specifically, if the grenade body
32
lands at an angle defined by “&agr;”, as indicated in
FIG. 4
, an upper surface
32
b
of the grenade
32
moves in one direction, in this example to the right (indicated by arrow
27
) as the grenade
32
rotates about the contact point between the grenade base
32
a
and the ground surface
36
, while the slide member
22
moves in the opposite direction or to the left as also shown in the illustration of FIG.
4
.
This phenomena is a function of the spatial positioning between the ground
36
or target contact point, the grenade
32
center of gravity position at impact and the ability of the slide member
22
to move linearly relative to the fuze housing
11
and the top surface
32
b
of the grenade
32
. The vertical plane for the specified performance fault illustrated in
FIG. 4
thus lies between near zero degrees and &agr; degrees, where &agr; is the angle between the base
32
a
of the grenade
32
and a flat ground surface
36
which is perpendicular to the earth's gravity vector as represented by the line
40
shown in FIG.
4
. The fault envelope in the horizontal plane, as shown in
FIG. 5
, is zero degrees +/−“&bgr;” degrees, where &bgr; is the angle between the highest point on the grenade upper surface
32
b
when the grenade
32
is oriented at some angle &agr;, from the ground surface
36
or target, and the longitudinal axis
34
of the slide member
22
, and more specifically where the slide member
22
, once deployed, is directed upward and away from the grenade base
32
a
impact point on the ground surface
36
or target surface.
When the grenade base
32
a
strikes the ground
36
or target surface at an angle &agr; and the slide member
22
is positioned within the angle &bgr; on either side of the longitudinal axis
34
, as defined in
FIG. 5
, the top surface
32
b
of the grenade
32
and the bottom surface
22
a
of the slide member
22
move in opposite directions. More specifically, in the drawing of
FIG. 4
, the top surface
32
b
of the grenade body
32
moves to the right while the slide
22
momentarily overcomes the biasing force of the biasing spring
24
and moves to the left. The relative motion between the top surface
32
b
of the grenade
32
and the slide member
22
causes the stab detonator
26
to be momentarily moved out of axial alignment with the firing pin
18
as the firing pin
18
is carried down toward the slide member
22
by the inertia of the arming screw
12
and weight
14
. This momentary misalignment of the stab detonator
26
with the firing pin tip
18
of the arming screw
12
prevents the firing pin tip
18
from striking the stab detonator
26
or causes the firing pin tip
18
to strike the stab detonator
26
outside of its percussion sensitivity envelope, thus preventing initiation of the stab detonator
26
and detonation of the grenade
32
. Finally, after dissipation of the relative velocities between the bottom of the slide member
22
a
and the top surface of the grenade
32
b
which had arisen from the instantaneous contact of the grenade
32
with the target or ground surface
36
, the biasing force of the biasing spring
24
again causes the slide member
22
to be urged into its fully extended position shown in
FIGS. 3 and 4
. In this position the fuze
10
remains in an armed state, thus leaving the grenade
32
in a highly dangerous condition where external grenade
32
contact or vibration can cause the armed firing pin tip
18
to contact and initiate the stab detonator
26
, thereby involuntarily functioning the grenade
32
.
It is known, that in tactical maneuvers, large numbers of munitions incorporating a fuze mechanism
10
of the type illustrated in
FIGS. 1-5
are not detonated upon impact with a ground surface
36
or target due to the orientation at which the grenade
32
impacts the ground surface
36
or target. It is therefore a principal object of the present invention to provide an arming mechanism for a munition, such as a grenade
32
, which is not susceptible to spurious anomalies caused by the orientation at which the munition impacts a ground surface
36
or target when deployed.
It is still a further object of the present invention to provide an arming mechanism for a munition that incorporates a means to maintain the fuze mechanism in an armed state once the mechanism assumes an armed condition, rega

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