Arming Devices

This invention relates to arming devices for projectile warheads and is more particularly but not exclusively concerned with spin stabilised projectiles of the kind in which tail fin assemblies are free to rotate with respect to the projectile body.

It is usually desirable that a projectile warhead only becomes armed once the projectile has been launched and has covered a minimum `safe` distance from its launch-point.

According to a first aspect of the present invention, there is provided a warhead arming device for a missile having a rotatable tail fin assembly, the arming device comprising arming means, rotatable drum means operable for rotation from a first to a second position relative to said arming means, locking means for locking said drum means in said first position, control means connected to said tail fin assembly and operable to release said locking means after said tail fin assembly has completed a predetermined number of revolutions, thereby allowing said drum means to rotate to said second position to arm said warhead.

Preferably, said control means comprises shaft means attached to said tail fin asssembly and a flexible elongate element contained within said drum means, one end of said element being attached to said shaft means and the other end being attached to said locking means, the element being wound round said shaft means during said revolutions.

According to a second aspect to the invention, there is provided a control device for use in a weapon for initiating an output response, for example arming the weapon, the control device comprising first and second members mounted for relative rotation, and a flexible elongate element coupled between said first and second members for becoming wound onto said first member when said relative rotation occurs and, when the element has become so wound through at least a plurality of turns, for pulling the second member to move it and thereby initiate said response.

For a better understanding of the invention, reference will now be made, by way of example, to the accompanying drawings in which:

FIG. 1 is a partly sectioned side elevation of an arming device for arming a missile warhead, having a shutter forming part of the device, the shutter being shown in its `safe` position;

FIG. 2 is a plan view of the FIG. 1 devices in its `safe` position;

FIG. 3 is a partly sectioned side elevation of the FIG. 1 device shown in its `armed` position;

FIG. 4 is a plan view of the FIG. 1 device in its `armed` position;

FIG. 5 is a sectional view of a drum arrangement which may be used in the FIG. 1 device, the drum being in a locked position;

FIG. 6 corresponds to FIG. 5 but showing the drum arrangement in a release position;

FIG. 7 is a sectional view of another drum arrangement which may be used in the FIG. 1 device in its locked position;

FIG. 8 is a perspective view of the FIG. 7 arrangement with the drum and housing removed;

FIG. 9 corresponds to FIG. 7 but shows the drum arrangement in its released position;

FIG. 10 is a section on X--X in FIG. 9; and

FIG. 11 shows a part sectioned portion of the tail end of a missile having the arming device of the previous figures mounted on board.

FIGS. 1 to 4 show part of an arming device which is mounted on board a missile as shown in FIG. 11. An electrically-activated detonator 1 is mounted in a slidable shutter 2, which slides in grooves or guideways (not shown) from a `safe` position (FIGS. 1 and 2) to an `armed` position (FIGS. 3 and 4). In the `safe` position, a first pair of contact switches (not shown) complied between the missile fuse (not shown) and the detonator 1 are `open` while a second pair of contact switches (not shown) are closed so as to short-out the detonator by one pair of contact switches (not shown). Thus no electrical energy can be present in the circuit to fire the detonator 1 prematurely. Also, since the detonator is spaced from a stemming charge 3 leading to the actual missile warhead, the warhead is not set off even if the detonator 1 were to be prematurely fired. In the `armed` position, first contacts are opened while a second such pair of contact switches (not shown) are closed to complete a circuit leading from an electrical energy supply to the detonator 1 via the fuse. Meanwhile, the shutter 2 is driven from the `safe` to an `armed` position by a drive pin 4 which is attached to a rotatable drum 5. The drum is rotatable about axis 6, the missile axis, and is initially locked in the `safe` position. When released, the drum 5 is able to rotate, sliding the shutter 2 in its guideways to align the detonator 1 with the stemming charge 3 (mounted on the missile axis), the drum 5 rotating half a turn to move the shutter 2 from its `safe` to its `armed` position. Then, when the detonator 1 is fired, the firing sequence for the missile warhead (not shown) is initiated by the stemming charge 3. A spring latch 7 engages with the shutter 2 at a point 8 on its underside (FIG. 4) to prevent the shutter sliding out of the `armed` position.

FIGS. 5 and 6 illustrate one embodiment of the arrangement within the drum 5 ie the means for rotating the drum. The drum 5 is mounted for rotation with respect to a housing 9, but is locked to the housing when in the `safe` position, by means of a latch 10 which engages with a hole 11 formed in the wall of the drum 5 and the housing 9. The latch 10 is attached to a steel tape or ribbon 12 near one end 14 thereof which end is fixed to the wall of drum 5 and which is coiled within the drum 5 in the direction of rotation. Because of the elasticity of the steel ribbon 12, the coiled ribbon expands radially outwards and is constrained by the wall of the drum 5 as shown in FIG. 5. The other end of the ribbon 12 is attached to a central drive shaft 13 which is connected to the tail fin assembly of the missile (not shown). As the tail fin assembly rotates during flight of the missile, the shaft 13 rotates about axis 6 in the direction of arrow 15 thereby unwinding ribbon 12 from the wall of drum 5 and instead winding it onto the shaft 13 as shown in FIG. 6. When all the ribbon 12 is wound onto the shaft 13, the latch 10 becomes disengaged from the hole 11 and then further rotation of shaft 13 pulls the drum 5 with it, thereby sliding the shutter 2 into its `armed` position as previously described.

Depending on its detailed design, with the embodiment of FIGS. 5 and 6, there might be a tendency for the coiled ribbon 12 to fall away from the wall of the drum.

If so a second drum embodiment shown in FIGS. 7 to 10 may be preferred. Here, the ribbon 12 is coiled in the direction opposite to the direction of rotation of the shaft 13. Thus, between the drum 5 and shaft 13, the ribbon forms a rolling half loop 16 which tends to maintain the ribbon in place against the wall of the drum. The shaft 13 has a shoulder 17 formed on it which provides a mounting place for a pivot pin 18. The shaft end of the ribbon 12 is looped around the pin 18 and is able to turn with respect to it hence reducing any tendency for the ribon to break as it is wound onto the shaft 13. Also, a different drum latching arrangement is used in this embodiment. Here, a loop 21 formed at the drum end of ribbon 12 is pivotably engaged through an aperture 22 in a rectangular latch member 19.

Initially, this latch member is engaged in a slot 20 in the wall of drum 5 so as to extend into a corresponding slot 23 in the wall of the housing 9 when the ribbon has been fully wound onto the shaft 13, the latch member is pulled out of the slot 23 in the housing wall so releasing the drum for rotation relative to the housing and then the latch member catches in the slot 20 in the drum wall so that further rotation of the shaft pulls the drum with it.

The relative positions of the drum 5, shutter 2 and tail fin assembly on the missile are shown in FIG. 11. Items previously described are referenced similarly. The tail fin assembly 30 comprises four fins 31 (only three of which are shown) attached to a rotating hub 32, the hub 32 being connected to the shaft 13 to provide the drive for winding the tape or ribbon 12. As mentioned previously, the shutter 2 slides laterally ie in the direction of arrow 33, in guideways or grooves 34 to align the detonator 1 with the stemming charge 3, when the drum 5 rotates through 180.degree..

Instead of a rotating tail fin assembly, the missile could comprise some other member which rotates relative to the missile body as it is launched. For example, a wheel which extends from the body so as to be rotated by its engagement with the missile launching barrel. Such other member, could be used to rotate shaft 13 relative to the drum 5.

In both embodiments described, the length of the ribbon 12 determines how many revolutions of the tail fin assembly have to be executed before the warhead is armed.

Naturally, this invention is not limited to use on board missiles but may be used in any system which has a rotating member onto which the ribbon 12 may be wound in order to measure a given distance or time, both distance and time being related to the number of revolutions of the rotating member.

Instead of sliding the shutter 2 to align the detonator 1 with the stemming charge 3 when the drum 5 rotates, the rotation of the drum 5 itself can be used to make electrical switch contacts between the drum and the housing 9. In such a case, the making of the switch contacts may initiate arming, detonation or some other desired function, for example igniting a boost motor for the missile.