GB2140136A - Folding fin assembly for missiles - Google Patents

Abstract

A missile includes a fin assembly having a fin member 13 unfoldable from a stowed position in which it lies alongside the missile body 10 and a deployed position in which it upstands therefrom. Deployment of the fin is effected by means of U-shaped member 21 driven by means of torsion spring 22 about an axis T transverse to the hinge axis H of the fin. The fin member 13 is locked in its deployed position by means of a resilient strip 17 engaging a rebate 19 on the fin member 13. <IMAGE>

Description

SPECIFICATION Folding fin assembly for missiles This invention relates to missiles of the type having a folding fin assembly which allows the fin to be movable from a stowed, inoperative position, and to a locking arrangement therefor.

Modern high speed weapons tend to be small and light and to have thin fins and control surfaces. Unless protected, these surfaces may be easily damaged during handling on the ground and during air carriage and the sharp edges can injure people handling the weapon. Because the weapons are light, it is possible to carry a large number on an aircraft, but if exposed to airflow the wings and fins of the large number of missiles may alter the aerodynamics of the aircraft.

Consequently the applicants propose to house the missile in a launch box which serves both to provide the missile with protection prior to launch and also to guide the missile during launch. In this instance however, the frontal area, and hence the drag attributable to the arrangement, is high if the launch box is to house the missile with its fins in an unfolded position. It is therefore an aim of this invention to provide a missile folding fin assembly which allows the frontal area of the missile prior to launch to be reduced, consequently allowing use of a launch box having a small frontal area.

According to one aspect of this invention, there is provided a missile including an elongate body portion, a fin assembly having a fin member hingedly mounted with respect to the missile body for folding movement about a generally chordwise hinge axis from a stowed position in which it lies generally alongside the missile body to a deployed position in which it upstands therefrom and deployment means for moving said fin member from its stowed position to its deployed position, said deployment means including arm means extending between the fin member and the missile body when the fin member is in its stowed position and mounted with respect to the missile body for turning movement generally within a longitudinal plane upstanding from said body portion and drive means for turning said arm means in the appropriate sense thereby to move said fin member from its stowed position to its deployed position.

Preferably, said drive means is in the form of a torsion spring, the arm means being initially maintained in its position intermediate the fin member and the missile body by releasable retention means.

Preferably, said drive means is provided within the missile body and the missile body includes recess means to receive the arm means when the fin has been deployed. This allows the drag due to the deployment means after deployment of the fin to be greatly reduced.

Preferably, said arm means is in the form of an elongate generally U-shaped member, the free ends of the member being attached to the drive means.

.In normal usage, the missile will be provided with a plurality of fin members spaced about the periphery of the missile body, each with associated deployment means. In this arrangement, where the drive means are each in the form of a torsion spring, each arm means is preferably held alongside the missile body by means of tie means encircling the missile body, there being cutting means adapted to cut the tie means and thereby simultaneously to allow deployment of the fins.

Preferably, the or each fin assembly includes locking means adapted to lock the fin member in its deployed position. Such locking means may comprise a recess in the fin member adjacent the hinge axis and associated spring strip means which is urged into locking engagement with the recess when the fin member is in its deployed position.

In another aspect of this invention, there is provided a missile including a fin member unfoldable from a stowed position to a deployed position, said fin member including lug means mounted for turning movement with respect to a relatively fixed member about a hinge axis, said lug means having an end region generally transversely disposed with respect to said hinge axis, and including rebate means associated with said end region, said fixed member carrying a resiliently flexible spring strip means resiliently biassed towards said end region and having a latch portion adapted to engage said rebate means when the fin member is in its deployed position.

Preferably, said fin member and said relatively fixed member each include lugs spaced alternately along the hinge axis in castellated fashion, each of the lugs associated with said fin member including rebate means, respective locking strip means being secured to said fixed member and being adapted lockingly to engage said rebate means when the fin member is in its deployed position.

For convenience, the term "fin member" has been adopted in this specification as a generic description to include any form of aerodynamic control surface which upstands from a body and the term should therefore be taken to include fins, wings, canards, foreplanes etc.

Further aspects will become apparent from the following exemplary description with reference to the accompanying drawings, in which: Figure 1 is an end view of a missile of this invention located in a launch box prior to launch, Figure 2 is a perspective view of the rear end of the missile of Fig. 1, Figure 3 is a detail view of a fin of the missile of Figs. 1 and 2 in its deployed position, and Figures 4a, 4b and 4c are detail views of the fin of Fig. 3, Fig. 4a being a side view of part of the hinge arrangement when the fin is stowed, Figs. 4b and 4c being views on arrows IV-IV of Fig. 4b when the fin is stowed and deployed respectively.

Referring to the drawings, the missile is provided with four fin assemblies equispaced about a rearward region of the missile body 10. Each fin assembly comprises an elongate fin base member 11 upstanding from the missile body and secured by means of stub shaft 1 2 to a control actuation mechanism (not shown) housed within the body for effecting control movements of the deployed fin and a fin member 1 3 hingedly attached to a fin base member 11 by means of hinge pin 14 for movement about a chordwise hinge axis H from the stowed inoperative position shown in Figs. 1 and 2 to the deployed operative position shown in Fig. 3. The hinge arrangement comprises alternate co-axial lugs 15, 16 respectively forming part of the fin member 1 3 and the fin base member 11.

Hinge pin 14 is secured in the arrangement by means of a threaded end portion which is threadedly engaged with a bore in the foremost lug 16.

Referring to Figs. 3 and 4a, b and c, each fin assembly includes a locking system arranged to lock the fin in its deployed position and which in the embodiment illustrated comprises three locking strips 17 located between adjacent pairs of lugs 1 5 and 16. Referring now in particular to Fig. 4 (a), lugs 1 5 and 1 6 to either side of the locking strip 1 7 are spaced slightly apart to accommodate strip 1 7 when the fin member 1 3 is in its stowed position. The locking strip is of spring material and is secured by welding or brazing its lower end in the base of a V-shaped slot 18 provided in fin base member 11.One half of the adjacent end face of lug 1 5 of the fin member is relieved so as to provide a diametral step 1 9 and the locking strip is arranged so that at ail times it bears against the end region of lug 1 5. The upper end of the spring strip is shaped to engage the relieved half of the lug 1 5 with an upper edge region 20 of the strip abutting diametral step 1 9 when the fin member 1 3 moves from its stowed position (Fig.

4b) to its deployed position (Fig. 4c) so as to lock it in the latter position.

The assembly includes a deployment mechanism arranged to effect deployment of the fin. The deployment mechanism comprises a generally U-shaped member 21 which extends around the periphery of the fin base member 11, the free ends of the Ushaped member 21 terminating in torsion springs 22 anchored within the missile body 10 so as to urge the U-shaped member 21 to move about turning axis T from the position shown in Fig. 2 through roughly 180 to be received in stowage cavity 23 located rearward of the fin member 1 3 below the surrounding surface of the missile body 10. The U-shaped member 21 carries two wiper rollers 24 on each limb to allow the member to be a loose fit around the fin member 1 3 and to space each limb sufficiently from the hinge axis of the fin thus to prevent the mechanism jamming.

The U-shaped members 21 of each fin assembly are held, prior to deployment of the fin members, against the surface of the missile body 10 by means of a wire 25 encircling the missile body and passing over each of the ends of the U-shaped member 21. The wire 25 also passes through a Duplex explosive wire cutter 26. The fin members themselves may be reieasably bonded by suitable adhesive to the missile body to prevent flutter of the fine members prior to launch.

In the embodiment shown in Fig. 1, the missile is located in a launch box 27, with the outboard ends of the fin base members 11 contacting associated sliders 28 of PTFE material located in the corners of the launch box.

On launch of the missile, it leaves the launch box 27 and at a predetermined instant thereafter the wire cutter 26 is actuated to allow release of the wire 25 holding down the U-shaped members 21. These members are then urged by means of the torsion springs 22 to turn in a plane upstanding from the surface of the missile about turning axis T. As this occurs, one of the limbs of each U-shaped member 21 rides up the side of the fin base member 11 and thence causes the fin member 1 3 to unfold about hinge axis 11 to its deployed condition. The U-shaped member 21 then continues until it is received in stowage cavity 23.

As each fin member 1 3 reaches its deployed position, it is locked there by the locking strip 1 7 as previously described.

The described arrangement allows the frontal area of the missile to be reduced as compared to missile arrangements not having a folding fin capability and this feature allows the launch box in which the missile is carried and*or launched to be of much smaller crosssectional size. Once the fin members have been deployed, the deployment mechanism is housed below the surface of the missile body and the drag associated therewith is minimised. The arrangement is also suitable for missiles which require a fin member which is free to turn after deployment of the control surface since the deployment mechanism is not engaged with the deployed fin member.

Although the span of the fin members shown in the drawings is equal to only a half of the diameter of the missile body, consideration of Fig. 1 will show that the arrangement could be used for fin members up to a span slightly greater than the diameter of the missile. Deployment of the fin members being initiated by an explosive wire cutter also allows the deployment of the fins to be delayed until a predetermined period after launch, and initiation of the wire cutter can be effected by electronic delay means.

The locking system employed in the illustrated embodiments prevents the fin member from returning to its stowed position; it would normally be necessary to break or crumple all three locking strips before the fin member could be folded once more. Of course if it were wished to return the fin member to its stowed position without damaging the locking strips, this could be achieved by unscrewing the hinge pin, removing the fin member, bending the plates back to the position shown in Fig. 4a and then reassembling the hinge.

Claims (9)

1. A missile including an elongate body portion, a fin assembly having a fin member hingedly mounted with respect to the missile body for folding movement about a generally chordwise hinge axis from a stowed position in which it lies generally alongside the missile body portion to a deployed position in which it upstands therefrom, and deployment means for moving said fin member from its stowed position to its deployed position, said deployment means including arm means extending between the fin member and the body portion when the fin member is in its stowed position and mounted with respect to the missile body for turning movement generally within a longitudinal plane upstanding from said body portion, and drive means for turning said arm means in the appropriate sense thereby to move said fin member to its deployed position.

2. A missile according to claim 1, wherein said drive means comprises a torsion spring, said arm means being initialiy maintained in its position between said fin member and the body portion by releasable retention means.

3. A missile according to claim 1 or 2, wherein said drive means is located within said body means, and the body portion includes recess means to receive the arm means when the fin member has been deployed.

4. A missile according to any of the preceding claims, wherein said arm means is in the form of an elongate generally U-shaped member, the free ends of which being attached to said drive means.

5. A missile according to claim 2, which includes a plurality of fin assemblies each having respective deployment means, said retention means comprising tie means encircling each of said arm means and cutting means adapted to cut said tie means.

6. A missile according to any of the preceding claims, wherein the or each fin assembly includes locking means adapted to lock the fin member in its deployed position.

7. A missile according to claim 6, wherein said locking means comprise recess means provided in the fin member adjacent the hinge axis and associated spring strip means which is urged into locking engagement with said recess when the fin member is in its deployed position.

8. A missile including a fin member unfoldable from a stowed position to a deployed position, said fin member including lug means mounted for turning movement with respect to a relatively fixed member about a hinge axis, said lug having an end region generally transversely disposed with respect to said hinge axis and including rebate means associated with said end region, said fixed member carrying a resiliently flexible spring strip means resiliently biassed towards said end region and having a latch portion adapted to engage said rebate means when the fin member is in its deployed position.

9. A missile according to claim 7, wherein said fin member and said relatively fixed member include lugs spaced alternately along the hinge axis in castellated fashion, each of the lugs associated with said fin member including rebate means, respective locking strip means being secured to said fixed 'member and being adapted lockingly to engage said rebate means when the fin member is in its deployed position.

1 0. A missile substantially as hereinbefore described, with reference to and as illustrated in, any of the accompanying drawings.