GB2121147A

GB2121147A - Missile fin assemblies

Info

Publication number: GB2121147A
Application number: GB08315131A
Authority: GB
Inventors: Laurence Goodwin
Original assignee: British Aerospace PLC
Current assignee: BAE Systems PLC
Priority date: 1982-06-02
Filing date: 1983-06-02
Publication date: 1983-12-14
Also published as: GB2121147B

Abstract

A missile includes a fin member 1 hingedly mounted for hinging movement about hinge axis H between a stowed position and a deployed position. The fin member 1 includes a transverse lever arm 4 which pivotally carries one end of a link 5. The other end of the link 5 is pivotally coupled to a cylindrical shell 3, which is relatively rotatable with respect to hinge axis H about a rotation axis R to move the other end of the link along a circular path thus to move the fin member to its deployed position. In a preferred arrangement, when the fin member is in its deployed position, the lever arm 4 extends tangentially to axis R and link 5 extends radially with respect thereto to provide a geometric lock. <IMAGE>

Description

SPECIFICATION Missile fin assemblies This invention relates to missiles which include one or more fin members movable between a stowed and deployed condition.

According to this invention, there is provided a missile including a fin member, link means and drive means, said fin member being hingedly mounted for hinging movement about a generally longitudinal hinge axis from a stowed position in which it lies generally alongside a region of the missile body and a deployed position in which it projects therefrom, said fin member including lever arm means extending generally transversely of said hinge axis, said link means being pivotally coupled at one end to said arm means and having its other end region constrained to move along a generally circular arc centred on a rotation axis, said drive means being arranged to move said other end region of the link means along the generally circular arc to effect movement of the fin member from its stowed position to its deployed position, The fin member and the link means are preferably so configured that when the fin member is in its deployed position, said link means is aligned substantially radially with respect to said rotation axis and said lever arm means is aligned substantially tangentially with respect thereto. This deployed configuration provides a geometric lock against movement of the deployed fin member and, furthermore, ensures that for a given rate of movement of said other end of the link means, the rate of deployment of the fin member decreases as it approaches its deployed position.This is because the lever arm means and the link means are in a dead centre position when the fin member is in its deployed position.

Conveniently, said fin member is hingedly attached to an outer shell member and said drive means includes an inner shell member arranged concentrically within said outer shell member, the inner and outer shell members being relatively rotatable with respect to said rotation axis.

Preferably, abutment means are provided to restrain movement of said link means when the fin member is in its deployed position. The missile preferably is provided with a piurality of fin members around its periphery and each fin member is provided with associated link means, each of these link means being coupled to a common drive member.

By way of example only, certain specific embodiments of missile will now be described in detail, reference being made to the accompanying drawings, in which: Figure 1 a, 1 b and 1 c are transverse sectional views of the tail unit of a missile and show a fin assembly in stowed, intermediate and deployed conditions respectively; Figure 2 is a longitudinal sectional view of part of a tail unit of a missile showing a fin assembly in its deployed condition; and Figure 3 is a transverse sectional view through a further form of tail unit for a missile.

Referring initially to Figure 1, this shows a single fin member 1 which is hingedly attached to outer cylindrical shell 2 for pivotting movement about hinge axis H for movement between a stowed configuration (Figure 1 a) and a deployed condition (Figure 1 c). The fin member 1 is curved to lie ciosely adjacent shell 2 when stowed. The cylindrical shell 2 is fixed to, or forms an extension of, the missile body. An inner drive shell 3 is arranged coaxially within shell 2 for turning movement about rotation axis R. The fin member 1 includes a lever arm 4 extending transversely of hinge axis H and which is pivotally coupled to a point on the inner shell 3 by means of link 5. The drive shell 3 is biassed in the clockwise direction by means of a spring device (not shown) and is latched in the stowed configuration by latch means (not shown).On release of the latch means, the drive shell is urged clockwise thereby causing the arrangement to pass through the intermediate configuration (Figure 1 b) to the deployed condition (Figure 1 c). The arrangement is configurated so that when in the deployed condition, link 5 is aligned radially with respect to rotation axis R, abutting abutment region 6 of the cylindrical shell 2. The radial alignment provides a geometric lock to prevent inertial or aerodynamic loads on the fin member 1 causing hinging movement thereof. Link 5 is further prevented from angular movement with respect to the drive shell 3 in on sense by abutment region 6 and in the other sense by the bias of the spring.

Moreover, the lever arm is configured so that when the fin member is erected, it lies substantially perpendicular to link 5; this configuration means that any turning moment imparted to the fin member 1 when erected results in a substantially wholly axial load on link 5. As a yet further precaution against movement of the erected fin member, the drive shell includes an abutment region 7 so that when in the erected condition link 5 is clamped between abutment regions 6 and 7.

Turning to Figure 2, each fin member is provided with three lever arms 4 arranged in tandem along the hinge axis H, each lever arm being coupled to the drive shell 3 by means of an associated link 5. Three lever arms 4 are preferred in the case shown, but other cases could involve more or less arms.

The arrangement of Figure 2 also differs from that of Figure 1 in that outer cylindrical shell 2 is rotatably mounted with respect to the missile body whilst inner shell 3 is fixed with respect thereto. In this case, erection and stowage movement will be imparted to the outer shell 2.

In another case, both outer and inner shells 2 and 3 may be free from constraint with respect to the missile body. In this latter case, inner shell 3 must be located by outer shell 2 in rotational relationship therewith, bearings being provided as shown between the missile body and shell 2 or between the body and shell 3.

Referring now to Figure 3, a typical arrangement employing four fin members is shown. In this arrangement each fin member 1 is moved in the same manner as in the arrangements of Figures 1 or 2 via a common inner drive shell 3.

In this arrangement, any transient load imparted to one of the fin members will be transmitted to the other fin member, so that transient forces acting on different fins at the same time will be balanced to some extent by the opposing forces transmitted to the drive shell 3.

Furthermore, for a given rate of rotation of shell 3 relative to shell 2, the rate of hinging of the fins to their deployed positions decreases as link 5 approaches its radially aligned position with respect to rotation axis R. The deployment motion of the fin is therefore arrested with reduced shock load on any part of the mechanism compared to previous arrangements in which the fin member itself is urged by a spring to meet the abutment stop when the fin member reaches its deployed position. Consequently, the internal forces acting during fin erection and locking may be reduced and regulated, thereby reducing the loads transmitted through the hinge and locking arrangement of the fin assembly. This may enable lighter and more compact arrangements to be designed.

Claims

1. A missile including a fin member, link means and drive means, said fin member being hingedly mounted for hinging movement about a generally longitudinal hinge axis from a stowed position in which it lies generally alongside a region of the missile body and a deployed position in which it projects therefrom, said fin member including lever arm means extending generally transversely of said hinge axis, said link means being pivotally coupled at one end to said arm means and having its outer end region constrained to move along a generally circular arc centred on a rotation axis, said drive means being arranged to move said other end region of the link means along the generally circular arc to effect movement of the fir' member from its stowed position to its deployed position.

2. A missile according to Claim 1, wherein the fin member and the link means are so configured that when the fin member is in its deployed position, said link means is aligned substantially radially with respect to said rotation axis and said lever arm means is aligned substantially tangentially with respect thereto.

3. A missile according to Claim 1 or Claim 2, wherein said fin member is hingedly attached to an outer shell member, and said drive means includes an inner shell member arranged concentrically within said outer shell member, the inner and outer shell members being relatively rotatable with respect to said rotation axis.

4. A missile according to any of the preceding Claims, wherein abutment means are provided to at least restrain movement of said link means when the fin member is in its deployed position.

5. A missile according to any of the preceding Claims, wherein a plurality of fin members are provided around the periphery of the missile, each fin member having associated link means and each link means being coupled to a common drive member.

6. A missile substantially as hereinbefore described with reference and as illustrated in any of the accompanying drawings.